Atmospheric Ozone

PROGRAM COMMITTEE:

C.L. Mateer, C.S. Zerefos (co-chairmen) J.J. Barnett, R. Bojkov, G. Brasseur, J. Chang, H. U. Dutsch, P. Fabian, A. Ghazi, R. Hudson, I. Isaksen, K.F. Kunzi, J. London, H. Mantis, G. Megie, J.A. Pyle, C.D. Walshaw.

LOCAL ORGANIZING COMMITTEE:

Honorary Chairman: E.G. Mariolopoulos Chairman: C.S. Zerefos A. Anagnostopoulos, A. Ghazi, H.T. Mantis, D. Metaxas, C.C. Repapis, G. Vassilikiotis.

CO-SPONSORS. American Meteorological Society Commission of the European Communities IAMAP

HOSTS:

World Meteorological Organization Ministry of Northern Greece Chemical Industries of Northern Greece

Academy of Athens, Laboratory of Atmospheric Physics,

Thessaloniki and University of loannina, Greece

Publication arrangements: P.P. Rotondo,

Directorate-General Information Market and Innovation,

Commission of the European Communities, Luxembourg

International Ozone Commission (IAMAP)

Atmospheric Ozone

Proceedings of the Quadrennial Ozone Symposium held in Halkidiki, Greece, 3-7 September 1984

Edited by

c. s. ZEREFOS Laboratory of Atmospheric Physics, University of Thessaloniki, Greece

and

A. GHAZI Commission of the European Communities,

Directorate-General for Science, Research and Development, Brussels, Belgium

D. REIDEL PUBLISHING COMPANY ... 411

A MEMBER OF THE KLUWER " ACADEMIC PUBLISHERS GROUP

DORDRECHT/BOSTON/LANCASTER

for the COMMISSION OF THE EUROPEAN COMMUNITIES

Library of Congress Cataloging in Publication Data Main entry under title:

Ozone Symposium (1984 : Chalkidiki, Greece) Atmospheric Ozone.

At head of title: International Ozone Commission, IAMAP. Co-sponsors: American Meteorological Society and others. 1. Atmospheric ozone-Congresses. 1. Zerefos, C. S. (Christos S.)

II. Ghazi, A., 1940- III. Commission of the Europe}1D Communities. IV. American Meteorological Society. V. Title. QC879.7.G74 1984 551.5'112 85-1731

ISBN-13 :978-94-0 I 0-8847-3 DOI:IO.1007/978-94-009-5313-0

Publication arrangements by

e-ISBN-13:978-94-009-5313-0

Commission of the European Communities Directorate-General Information Market and Innovation, Luxembourg

EUR 9574 © 1985 ECSC, EEC, EAEC, Brussels and Luxembourg Softcover reprint of the hardcover 1 st edition 1985

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INTRODUCTION

This volume contains progress papers in atmospheric ozone research which were presen­ted at the Ouadrennial Ozone symposium held in Greece from 3 to 7 September, 1984. These pa­pers are grouped in nine chapters corresponding to the nine sessions of the symposium. The Editors proVide the following summary of the highlights for each chapter; this summary has been prepared after consulting the papers submitted for publication as well as session summa­ries kindly provided by the following session chairmen: R. Bojkov, H. DOtsch, P. Fabian, J. Hai­gh, I. Isaksen, L. Kaplan, K. KOnzi, J. London, H. Mantis, C. Mateer, A. Matthews, G. Megie and J. Russell.

Chapter 1 entitled: Chemical - radiative - dynamical model calculations includes results from recent developments in modeling techniques. The chapter begins with the results from a two - dimensional model using isentropic coordinates. With prescribed diabatic heating rates and a judicious choice of eddy diffusion coefficients this method can produce realistic fields of several stratospheric species. Three dimensional model simulations come next which demon­strate ozone transport by the stationary and transient components of the flow and emphasize the role of wave transport of ozone during a sudden stratospheric warming.

The problem of chemical model validation is addressed in several different approaches. The trajectory method allows a direct comparison of the change in concentration of ozone but the coverage of satellite ozone observations is such that ozone concentration in the same mass of air are obtained only at 8 to 10 day intervals. Validation of model predictions is of course dependent on the accuracy of computed trajectories. The other methods compare point calculations with measurements. Using the same set of reaction rates, all three methods prod­uce lower values for ozone than are measured, indicating inconsistencies in the derived fields of other species (particularly of the NOy family) and suggesting that some of the reaction rates might be reassessed. In addition to the chemical model validation, two new approaches to cal­culating photochemical acceleration coefficients are given.

In a two - dimensional analysis of the quasi-biennial oscillation (OBO) of ozone it was as­sumed that the ozone OBO is forced by the tropical stratospheric OBO wind circulation which is modeled from observations. The derived amplitude and phase of the ozone qBO compares well with satellite observations. Another presentation shows how inclusion of a representation of the semi-annual oscillation in a two - dimensional model improves the derived fields of CH. and Np. A study of the effect of EI Chichon volcanic cloud on ozone and temperature demon­strates that the inclusion of volcanic aerosol in a two - dimensional model can produce tempe­rature increases in the lower stratosphere with strong latitudinal gradients and hence implica­tions for changes in zonal wind structure. The model predicts an approximate 2% depletion of globally averaged total ozone following the eruption.

The chapter includes two other groups of papers; diagnostic methods and applications of the 'Limb Infrared Monitor of the Stratosphere' (LlMS) data and analysis of past and future trends in atmospheric ozone changes. The need for simultaneously measured data on multiple species, for evaluating the theory of ozone chemistry is emphasized and it is shown that to a large extent the LlMS data set is consistent with current photochemical theory. There remains the difficulty of explaining the low level of HN03 in the upper stratosphere as observed by LlMS and other in situ measurements, and the need for better understanding of polar winter dyna­mics.

The first chapter concludes with papers concerned with estimating ozone trends both past and present and projectiAg man's impact on future trends via multiple scenarios. The choices of estimated trends for CD2, CH., NP, NOx and CFC's are the dominating factors in these ana­lyses. Trends in both the total ozone amount and its vertical distribution are reported to be in a­greement with the most recent statistical analysis of ground - based data, although upper stra­tospheric temperature changes appear to be smaller than observed. The nonlinear dependence of ozone column to changes of CIO an NO are also studied in multiple scenarios. Future ozo­ne trends depend heavily on the assumedXtrends in many trace species, especially nitrogen containing species. It is clear that projections of future trends in the trace species are required. Another nonlinear effect predicted with large chlorine increases is a significant long-term ozo­ne decrease, although near term changes may be small.

Ozone Symposium - Greece 1984 -v-

Chapter 2 includes recent results on the climatic effects of secular changes in trace spe­cies as estimated from one - dimensional model calculations with radiative - convective ad­justments and fixed cloudiness_ The importance of taking into account coupling effects of tem­perature, trace gas concentrations, photochemistry and radiation, which has largely been igno­red in recent impact simulation studies, is stressed. The combined calculated effects on sur­face temperature of expected anthropogenic increases in CH 4, Np and Freon II and 12 in­cluding the resultant redistribution of ozone between the years 1980 and 2010 are found to be equal to that calculated for expected increases in CO 2, The approximate equality between the greenhouse effect from CO 2 increase and that of the other combined anthropogenic gases is stressed in all three papers in this chapter.

Details of the differences between the results of various models could be attributed to their different scenarios and differences in their physical parameterizations. Feedback interac­tions with clouds, include the possibility that the effect of increased cloudiness can be to red­uce the net heating, rather than enhance it, as generally believed. In addition to the feedback coupling of the various physical processes, it is shown that volcanic aerosols can affect the ozone indirectly by altering the atmospheric temperature structure and thus the photochemical coupling. The resulting radiative effects would in turn modify the initial temperature changes due to increased CO2 and volcanic aerosols.

Chapter 3 includes the results of measurements on key stratospheric constituents obtai­ned by different observational systems in ground - based, balloon, rocket and satellite experi­ments. There have been a number of recent extensive intercomparison campaings namely the MAP - Globus in southwestern Europe and the Balloon Intercomparison Campaign (BIG) in the U.S. Although the data from the MAP-GLqBUS compaign have become available only recently, initial inter comparisons show agreement of NP, CH 4 and CFCI 3 from cryogenic samplers. The time variability of nitric oxide from several experiments which are remarkably consistent over several hours, suggest that the variability is real. The next MAP-GLOBUS campaign. in 1985 will be a smaller effort focused on NO compounds.

Ne;"" results, based on cry~genic in-situ sampling of stratospheric halocarbon com­pounds, show a very rapid decrease of chlorinated compounds with altitude between 20 and 30 km. This large decrease is not predicted in model calculations and may be due to a problem ei­ther in I-D model calculations of vertical transport or to instrummental bias. The latter is less likely since the same results are reported independently by different groups. An additional no­teworthy cryogenic sampler result is the observation that molecules with higher flourine con­tent decrease less rapidly with altitude than those with less flourine, suggesting that these mo­lecules reside for longer times in the stratosphere.

In addition to the results from the international campaigns, the LlMS experiment on board Nimbus 7 spacecraft provided the basis for constructing a stratosphere - mesosphere climato­logy of N02 in both hemispheres for the period November 1978 through May 1979. Column N02

amounts are considerably larger in the summer than in the winter hemisphere Steep latitudinal gradients occur in winter high latitudes in situations where the height field is dominated by wave number one. Results are next given from recent flights with the Oxford balloon - borne pressure modulator radiometer which measures stratosphere NO and N02 by sensing emission from the atmospheric limb.

The global distribution of NO is retrieved from whole spectrum scans of the SBUV in­strument on board Nimbus 7. The NO vertical column above the 1 mb level is almost constant in the summer hemisphere and increases towards the winter pole. Another paper estimates that a thermospheric NO source of up to 50 ppbv at the 2 mb level is required to match rocket ozone profiles observed in the upper stratosphere and mesosphere. New measurements on N02 and N03 provided satisfactory comparison with modelled diurnal variation of these important spe­cies. In another paper an unknown N03 sink in the lower stratosphere was proposed to explain the rapid decrease of N03 below 30 Km.

New ground - based microwave data of stratospheric chlorine monoxide (CIO) show that CIO disappears faster in the lower stratosphere than in the upper stratosphere. This variation and its magnitude is in good agreement with current models suggesting that to first order the chemistry is quite well understood.

The chapter also includes reports of several campaigns of intercomparisons of measure­ments of trace species by various observational techniques.

-vi -

Chapter 4 deals with the analyses of ozone observations from various data sets and on va­rious times scales. It seems that backscattered UV measurements will be the major source of long term global information on total ozone and on ozone profiles. There are now about 15 years of satellite ozone data available which need proper interpretation. In general, the agree­ment between different satellite ozone measurements is good and a further improvement in such agreement is expected from reprocessing of satellite data incorporating new absorption coefficients.

Analyses of ozonesonde, umkehr and of satellite ozone data show evidence of stratosphe­ric ozone decrease following the erruption of EI Chichon. In fact the behaviour of total ozone at mid - latitudes is shown to be anomalous after the volcanic eruption and the first half of 1983 is probably a period of extremely low values of total ozone over middle and high latitudes of the northern hemisphere. However, there is no convincing physical explanation for this anomalous ozone behaviour. In addition to these real ozone decreases there are also errors caused by the volcanic cloud to ozone measurements by the Umkehr method. New evidence has been present­ed on a strong anticorrelation between the volcanic aerosol and columnar S02 amounts its phy­sical explanation being presently under study.

Periodic and long-term variations of ozone and temperature are examined in two papers. A homogeneous ozonesonde data set does not show any statistically significant trends in strato­spheric column ozone above 15 mb in the 1970's. During the same period significant upward trends in tropospheric ozone are observed in agreement with model predictions. Important ad­dition to the worldwide effort in monitoring the vertical ozone distribution are the new ozone­sonde sounding programme in the equatorial region and the rocket ozone soundings program­me in the tropics.

Stratosphere fields of temperature and ozone are examined in this chapter. In a compari­son between these two fields from independent satellite observations the coefficient of varia­tion between the two parameters is used to diagnose the relative importance of transport and photochemistry in determining the ozone distribution.

The development of ground-based Lidar for detailed vertical ozone profiles is used to provi­de examples of stratospheric ozone intrusions into the troposphere. A detailed discussion of the sources of error and their correction for the electrochemical ozsmesonde are next dis­cussed as well as the relative quality and performance of GOp.S. The chapter concludes with the development of a European climatology of ozone as derived from the Nimbus - 7 Total Ozone Mapping Spectrometer.

Chapter 5 includes recent developments in observational techniques and begins with the implementation of a 7 - station network of automated Dobson spectrophotometers which will allow routine measurements of the ozone vertical profile using the Umkehr technique for the purpose of detection of long term ozone trends in the 40 km altitude range. The importance of calibration level, statistical evaluation, operating mode and data analysis for the Dobson spec­trophotometer network is emphasized in subsequent papers with special attention being paid to possible interferences due to aerosol particles or S02.

The state of development of the performance of the automated Brewer spectrophotometer has been reviewed in routine comparisons with the Dobson instrument which confirm its high quality. This instrument is gradually being introduced in the world ozone network. The develop­ment of a new instument to replace the M-83 in the USSR network (the M-124) was also repor­ted.

Results of measurements of ozone and water vapour in the stratosphere and mesosphere with microwave radiometers are also presented in addition to the Lidar measurements. Poten­tialities for a spaceborne instrument (UARS) are also underlined and calibration and validation in both the UV and the IR wavelength ranges give an insight as to the accuracy'Of such mea­surements.

Ozone profiles obtained with Brewer-Mast ozonesondes are in good agreement with the profiles by differential absorption Lidar. On the other hand however the comparison of results obtained from different instruments shows much larger differences than is to be expected from the quoted errors of individual instruments. It is therefore most important that more intercom­parison campaigns similar to BOIC, MAP-GLOBUS and WINE, be continued in order to establish the absolute accuracy of different sensors.

- vii-

Results of new UV-absorption ozone in situ sensors, in situ mass spectrometry and spec­trophotometry in other regions of the spectrum are presented together with a modification of ECC ozonesondes for operation to 40 Km altitude. The chapter also includes measurements of me­sospheric ozone from satellite observation of the 1.27 11m airglow emission and a gas-gas che­miluminescent technique for measuring 0 and 0 3 in the middle atmosphere.

Chapter 6 includes studies concerned with the interaction of ozone and circulation using ozone and temperature data derived from satellites and 1 or the Global Air Sampling Program (GASP). Radiative damping coefficients derived from SAGE indicate coupling between ozone and temperature which can produce significant variations in the damping rate which in turn, critically depends on the vertical structure of the planetary waves. Data from the same satellite confirm that while in the lower stratosphere temperature and ozone waves are nearly in-phase, they are out-of-phase in the upper stratosphere with an in-between transition region, confirm­ing the results of earlier Umkehr analyses. Furthermore tracking the extremes of the ozone field derived from satellites can give a measure of the displacement of the winds. It is also demon­strated that over tropical latitudes very low ozone values occur in the upper troposphere (less than 20 ppbv) associated with the rising arm of the Walker circulation. While the transport due to the meridional circulation driven by diabatic processes is nearly constant during the winter, the portions due to transient waves and the uncompensated transport by eddies vary rapidly with time the effects of transport being in moderate agreement with the observed ozone chan­ges.

Large ozone variations (4 to 10 ppm) have been observed during the month of January pre­ceeding sudden stratospheric warming and the efficiency of the northward ozone transport by the flow pattern can be examined from combined ground-based and satellite soundings. It is al­so shown that the seesaw structure of the aBO can be explained by the modulation of tropo­spheric dynamical forcing associated with the location of the zero zonal wind critical surface. In addition the meridional and vertical transport of ozone by planetary waves depends on their vertical structure, their orientation and magnitude. Considering the effect of temperature wa­ves it is estimated that a 20% enhancement of the zonal mean ozone in the photochemical equilibrium region of the upper stratopshere can be produced by temperature wave of 15° K am­plitude which is typical of winter conditions.

Finally, three days of aircraft sampling in spring over Scotland indicate the presence of turbulent mixing processes which suggest that the exchange between the stratosphere and troposphere is not confined only to tropopause folding.

Chapter 7 contains new results and recommendation concerning the ultraviolet absor­ption cross-section of ozone. The chapter starts with a detailed description of the temperature dependence of the UV ozone absorption spectrum and the magnitude of resulting correction to ozone measurements based on previous cross section data. The impact of using the recom­mended ozone cross - sections on BUV satellite and Dobson total ozone measurements is also reported. For the SBUV satellite experiment, which gives total ozone values about 8% lower than the Dobson with presently - used cross - sections, the difference is essentially reduced to zero with the new coefficients. The Dobson values are reduced by 4% and the SBUV satelltie values are increased by 4%. However concerning the BUV and TOMS satellite experiments, for which the calibration is not as well determined as the SBUV calibration, differences up to 2-3 % still exist. The chapter includes also other interesting new results including an evaluation of collision broadened and oxygen as the perturbing gases and the result from a newly developed air-borne actinometer to measure the photolYSis frequency of Np at various heights and zenith angles.

Chapter 8 begins with results of recent measurements of solar spectral irradiance from So­lar Mesosphere Explorer (SME) satellite. It is shown that solar UV irradiance variations for the two year period 1982/83 were about + 15% at Ly-a, + 4% at 175-190 nm and less than + 1 % for the spectral interval 240-260 nm. The accuracy of present methods of solar irradiance measure­ments in the spectral interval 290-450 nm is next reviewed.

-viii-

Various aspects of solar activity and ozone variations are also discussed including the evi­dence of a short period (27 days) and long period solar cycle relationship between solar UV and ozone. The importance of solar proton events and solar faculae areas in solar activity - ozone relationships are also discussed.

Two papers deal with applications of the Brewer spectrophotometer to measurements of the solar UV radiation at the earth's surface. The zenith sky is (in contrast to the situation of vi­sible wavelengths) brighter than the horizon. The sulfur dioxide concentrations in an urban env­ironment are found to significantly deplete the solar UV beam so as to alter estimates of increa­sed UV-B with projected anthropogenic decrease in ozone. The extent of the influence of strato­spheric aerosols on ozone is also examined through the sensitivity of the ozone photodissocia­tion rates, the radiative energy budgets and the perturbed thermal structure. Finally calcula­tions are given of the variability of Ly-a absorption in the mesosphere and atmospheric tran­smittances.

The last chapter deals with recent results on the processes governing the background ozo­ne concentration in the troposphere. Nitrogen oxides and hydrocarbons transported to the higtl latitudes during wintertime in the northern hemisphere seem to play an important role for tro­pospheric ozone production over middle and high latitudes during springtime. Furthermore, in­creases in the release rate of the precursors may lead to an ozone increase at mid and high la­titudes of the order of 1 % per year.

Increasing trends in troposphere ozone are of major concern both because of their possi­ble influences on climate via alteration in the IR radiation field and in the transmission of U\t-B. However there is considerable disagreement in the papers of this chapter as to the rate of in­crease of tropospheric ozone (which so far seems to be confined to the northern hemisphere) because of unresolved problems with the observing systems (differences between ozone son­des and the information content of Umkehr observations with respect to troposphe­ric ozonej. The observed increase is undoubtedly a consequence of the anthropog~nic emis­sion of trace gases leading to photochemical ozone production. Therefore the ozone increase is greatest in the boundary layer around the main industrial centers and appears to be sprea­ding over the whole northern hemisphere.

In addition to photochemical processes, ozone transport from the stratosphere and dry de­position at the ground play an important role in the tropospheric ozone budget. In this context the increase of dry deposition over mountainous terrain due to the effect of local wind system is of importance both with respect to ozone itself and certain other trace substances.

These proceedings are published by the sponsorship of CEC in the framework of its R&D programme Environment.

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The Editors Christos S. Zerefos

Anver Ghazi

CON TEN T S

Introduction The Editors, Christos S. ZEREFOS, Anver GHAZI

Pres i dent i a 1 address

C.L. MATEER

Sir Charles Normad - In Memoriam C.D. WALSHAW, Department of Atmospheric Physics, Clarendon Laboratory, Oxford, UK

Implementation of the WMO ozone project (1980-84) R.D. BOJKOV, Member of the Ozone Commission-1 i ai son with WMO

C HAP T E R CHEMICAL-RADIATIVE-DYNAMICAL MODEL CALCULATIONS

Simulation of 03 distribution using a two-dimensional zonal-mean model in isentropic coordinate

M. KO, D. WEISENSTEIN and NIEN OAK SZE Atmospheric and Environmental Research Inc.; Massachusetts, USA, KA-KIT TUNG, Department of Mathematics, Massachusetts Institute of Technology, Cambridge, USA

A GCM study of the transport of heat, momentum and ozone in the stratosphere

D. CARIOLLE and M. DEQUE, Centre National de Recherches Meteorologiques, EERM, Toulouse, France

Ozone during sudden stratospheric warming: a three­dimensional simulation

K. ROSE, Institut fUr Meteorologie Freie Universitat Berlin - FRG; G. BRASSEUR, Institut d'Aeronomie Spatiale, Brussels, Belgium

A matrix method for calculating photochemical acceleration J.D. HAIGH, Centre for Remote Sensing, Imperial College of Science and Technology, London, UK

Photochemical acceleration C. GAY, Centro de Ciencias de la Atmosfera; J.L. BRAVO, Instituto de Geofisica, U.N.A.M., Ciudad Uriversitaria, Mexico

~ xi-

v

3

9

11

19

24

28

33

38

Budgets of stratospheric trace gases from 2-D-Model calculations and satellite observations

U. SCHMAILZL and P.J. CRUTZEN, Air Chemistry Division, Max-Planck-Institute for Chemistry F.R. Germany

A study of the ozone photochemistry in the upper stratosphere using lims data

M. NATARAJAN, Systems & Applied Sciences Corporation, Hampton, Virginia, USA: L.B. CALLIS, J.M. RUSSELL III, and R.E. BOUGHNER, NASA Langley Research Center, Hampton, Virginia, USA

A theoretical study of the quasi-biennial oscillation in the tropical stratosphere

X. LING and J. LONDON, Department of Astrophysical Planetary and Atmospheric Sciences, University of Colorado, USA

Study of the effect of El Chichon Volcanic Cloud on the stratospheric temperature structure and ozone distribution in a 2-D-Model

R.K.R. VUPPUTURI, Canadian Climate Centre, Downsview, Ontario, Canada

Aspects of the comparison of stratospheric trace species measurements with photochemical models

P.S. CONNELL and D.J. WUEBBLES, University of California, Lawrence Livermore National Laboratory, Livermore, California, USA

Derivation of OH concentrations from lims measurements

J.A. PYLE, A.M. ZAVODY, J.E. HARRIES, P.H. MOFFAT Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, UK

Lims data: Inferred stratospheric distribution of NO and

43

48

53

59

61

66

HO trace constituents and the calculated odd nitroge~ budget 72 x L.B. CALLIS, J.M. RUSSELL and R.E. BOUGHNER, NASA Langley Research Center, Atmospheric Sciences Division; M. NATARAJAN, Systems and Applied Science Corporation, Hampton, Virginia, USA

The distribution of ozone and active stratospheric species: results of a two-dimensional atmospheric model

D. CARIOLLE, Centre National de la Recherche Meteorologique, Toulouse, France: D. BRARD, Office National d'Etudes et de Recherches Aerospatiales, Chatillon, France

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77

Multiple scenario ozone change calculations: The subtractive perturbation approach

A.J. OWENS, C.H. HALES, D.L. FILKIN, C. MILLER and M. McFARLAND, Experimentaf Station, E.I. du Pont de Nemours & Co., Inc., Wilmington, Denver, USA

Trends in ozone and temperature structure:

82

Comparison of theory and measurements 87 D.J. WUEBBLES, Lawrence Livermore National Laboratory, University of California, Livermore, California, USA

Ozone in the 21st century: increase or decrease? 92

A. DE RUDDER and G. BRASSEUR, Institut d'Aeronomie Spatiale de Belgique, Brussels, Belgium

C HAP T E R II OZONE-CLIMATE INTERACTION

Climatoloqical effects of atmospheric ozone: a review WEI-CHYUNG WANG, Atmospheric and Environmental Research, Inc. Cambridqe, Massachusetts, USA

The climatic effects of ozone and trace qases

J.T. KIEHL, National Center for Atmospheric Research Boulder, Colorado, USA

The effect of ozone photochemistry on atmospheric and surface temperature changes due to increased CO2, N20, CH4 and volcanic aerosols in the atmosphere

R.K.R. VUPPUTURI, Canadian Climate Centre, Downsview, Ontario, Canada

C HAP T E RIll OBSERVATIONS OF RELEVANT TRACE CONSTITUENTS AND THEIR BUDGETS

98

103

104

Map-Globus in 1983 115 W.A. MATTHEWS, Service d'Aeronomie du CNRS, Verrieres le Buisson, France

Vertical profiles of chlorinated source qases in the midlatitude stratosphere 117

D. KNAPSKA, U. SCHMIDT, C. JEBSEN, G. KULESSA and J. RUDOLPH, Institut fUr Chemie 3: Atmospharische Chemie der Kernforschunqsanlage JUlich GmbH, JUlich, F.R. Germany: S.A. PENKETT, Environmental and Medical Sciences Division, AERE Harwell, Oxon, UK

-~-

A laboratory test of cryogenic sampling of longlived trace gases under simulated stratospheric conditions

D. KNAPSKA, U. SCHMIDT, C. JEBSEN, F.J. JOHNEN, A. KHEDIM and G. KULESSA, Institut fur Chemie 3; Atmospharische Chemie der Kernforschungsanlage Julich GmbH, Julich, F.R. Germany

The vertical distribution of halocarbons in the stratosphere P. FABIAN, R. BORCHERS, D. GOEMER, B.C. KRUEGER and S. LAL, Max-Planck-Institut fur Aeronomie (MPAE), Katlenburg-Lindau, F.R. Germany; S.A. PENKETT, Environmental & Med.Sci.Div. AERE Harwell, UK

Structures in the vertical profile of nitrous oxide measured over a mi d 1 at itude st at i on

S. LAL, R. BORCHERS, P. FABIAN, Max-Planck-Institut fur Aeronomie (MPAE), Katlenburg-Lindau, F.R. Germany

Global lower mesospheric water vapor revealed by lims observations

L.L. GORDLEY, Systems and Applied Sciences Corporation, Hampton, Virginia, USA; J.M. RUSSELL III and E.E. REMSBERG, National Aeronautics and Space Administration, Langley Research Center, Hampton, Virginia, USA

Intercomparison of stratospheric water vapor profiles obtained

122

129

134

139

during the balloon intercomparison campaign 144 D.G. MURCRAY, A. GOLDMAN and J. KOSTERS (DU), Physics Department, University of Denver, USA; R. ZANDER (ULG), Institut d'Astrophysique, University of Liege, Belgium; W. EVANS (AES), Atmospheric Environment Service, Canada; N. LOUISNARD and C. ALAMICHEL (ONERA), Office National d'Etudes et de Recherches Aerospatiales, France; M. BANGHAM and S. POLLITT (NPL), Laboratoire de Photophysique Mole­culaire, CNRS, France; B. CARLI, B. DINELLI, S. PICCIOLI, National Physical Laboratory, UK; A. VOLBONI (IROE), Istituto di Ricerca sulle Onde Elettromagnetiche del CNR, Italy; W. TRAUB and K.CHANCE (SAO), Smithsonian Astrophy-sical Observatory, USA

Intercomparison of stratospheric measurements of NO and N02 149 H.K. ROSCOE, B.J. KERRIDGE, Dept. of Atmospheric Physics, Oxford University, UK; S. POLLITT, M. BANGHAM, National Physical Laboratory, UK; M. LOUISNARD, ONERA, C. ALAMICHEL, CNRS, France; J.-P. POMMEREAU, CNRS, France: T. OGAWA, N. IWAGAMI, Geophys.Research Lab., Univ. of Tokyo, Japan; M.T. COFFEY, W. MANKIN, NCAR, Boulder, USA; J.M. FLAUD, C. CAMAY-PERET, CNRS, France; F.J. MURCRAY, A. GOLDMAN, Dept. of Physics, Univ. of Denver, USA: W.F.J. EVANS, T. McELROY, A.E.S., Toronto, Canada

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Intercomparative Measurements of Stratospheric Nitric Acid 151

S. POLLITT, National Physical Laboratory, Teddington, UK; M. COFFEY, W.G. MANKIN, National Center for Atmospheric Research, Boulder, Colorado, USA: W.F.J. EVANS, Atmos-pheric Environment Service, Downsview, Ontario, Canada; A. GOLDMAN, J.J. KOSTERS, D.G. MURCRAY, W.J. WILLIAMS, University of Denver, Denver, Colorado, USA; N. LOUISNARD, Office National d'Etudes et de Recherches Aerospatiales, Chatillon, France

Spatial and temporal variability of the N02 total content based on annual observation data 157

N.F. ELANSKY, A. Va. ARABOV, A.S. ELOKHOV and I.A. SENIK, Institute of Atmospheric Physics, Academy of Sciences of the USSR

Southern hemisphere nitrogen dioxide R.L. McKENZIE and P.V. JOHNSTON, PEL Atmospheric Station, DSIR, Omakau, Central Otago, New Zealand

The climatology of upper atmosphere nitrogen dioxide

163

revealed by lims observations 168 J.M. RUSSELL, NASA Langley Research Center, Atmospheric Sciences Division, Hampton, Virginia, USA; E.E. REMSBERG, L.L. GORDLEY, Systems and Applied Science Corporation, Hampton, Virginia, USA; J.C. GILLE, National Center for Atmospheric Research, Boulder, Colorado, USA

Comparisons of measured and predicted diurnal changes in stratospheric NO and N02 173

H.K. ROSCOE, B.J. KERRIDGE, L.J. GRAY, R.J. WELLS, Department of Atmospheric Physics, Clarendon Laboratory, Oxford University, UK: J.A. PYLE, Rutherford Appleton Laboratory, UK

Nitric oxide profile from 7 to 32 KM 175 W.A. MATTHEWS, PEL Atmospheric Station, DSIR, Lauder, Central Otago, New Zealand; Y. KONDO, M. TAKAGI and A. IWATA, Research Institute of Atmospherics, Nagoya University, Toyokawa, Japan

Measurement of oxides of nitrogen in the free troposphere over Japan 180

Y. KONDO, A. IWATA, Y. MORITA and M. TAKAGI, Research Institute of Atmospherics, Nagoya Unversity, Toyokawa, Japan: W.A. MATTHEWS, PEL Atmospheric Station, DSIR, Lauder, Central Otago, New Zealand

Measurements of atmospheric nitric oxide from nimbus 7 SBUV ultraviolet spectral scan data 184

R.D. McPETERS, Laboratory for Atmospheres NASA, Goddard Space Flight Center, Greenbelt, Maryland, USA

-xv-

Evidence for a thermospheric source of stratospheric NOX 188 A.J. KRUEGER, Planetary Atmospheres Branch, Goddard Space Flight Center, Greenbelt, Maryland, USA

Measurements of nighttime N0 1 and N02 in the stratosphere by matrixisolation and ESR spectroscopy 196

M. HELTEN, W. PAETZ, Institut fur Chemie 2: Chemie der belasteten Atmosphare; D.H. EHHALT, Institut fur atmos­pharische Chemie 3: Atmosphaische Chemie der Kernfor­schungsanlage Julich GmbH, Julich, F.R. Germany; E.P. ROETH, Gesamthochschule Essen, F.R. Germany

Variabilite temporelle du N03 stratospherique 201 J.P. NAUDET, P. RIGAUD, Laboratoire de Physique et Chimie de l'Environnement, Orleans, France; D. HUGUENIN, Obser-vatoire de Geneve, Sauverny, Switzerland

Quantitative observations of stratospheric chlorine monoxide as a function of latitude and season durinq the period 1980 - 1983 206

R.L. DE ZAFRA, A. PARRISH, P.M. SOLOMON and J.W. BARRETT, State University of New York, Stony Brook, New York, USA

Trace species in the stratosphere precision and variability 210 C. ALAMICHEL, Laboratoire de Photophysique moleculaire, Universite de Paris-Sud, France: N. LOUISNARD, Office National d'Etudes et de Recherches Aerospatiales, Chatillon, France

Trace constituents measurements deduced from spectrometric observations onboard spacelab

J. LAURENT, M.P. LEMAITRE, J. BESSON, A. GIRARD, Office National d'Etudes et de Recherches Aerospatiales, Chatillon, France; C. LIPPENS, C. MULLER, J. VERCHEVAL, M. ACKERMAN, Belgium Institute for Space Aeronomy, Brussels, Belgium

Simultaneous measurements of stratospheric trace gases as deduced

212

from air-borne infra-red spectrometry 216

M. AMODEI, B. DUFOUR, G. FROMENT, F. KARCHER, J.P. MEYER, Centre National de Recherches Meteorologiques, Toulouse, France; J. MARCAULT, Office National d'Etudes et de Recherches Aerospatiales,.Chatillon, France

The determination of stratospheric nitrogen dioxide concentrations from limb brightness measurements 222

C.T. McELROY, Atmospheric Environment Service, Downsview, Ontario, Canada

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C HAP T E R IV ANALYSIS OF OZONE OBSERVATIONS

Backscattered ultraviolet measurements of ozone 1970-200G an overview 229 A.J. FLEIG, Laboratory for Atmospheric Science Goddard Soace Flight Center, Greenbelt, Maryland, USA; W.G. PLANET, National Environment Satellite, Data and Information Service NOAA/NESS, Suitland, Maryland, USA; P.K. BHARTIA, Systems and Applied Sciences Corporation, Hyattsville, Maryland, USA

Global total ozone from TIROS measurements : 1979-1983 W.G. PLANET, J.H. LIENESCH and M.L. HILL, National Environmental Satellite, Data, and Information Service, National Oceanic and Atmospheric Administration Washington, USA

The observation of atmospheric structure with Toms and some potential advancements

A.J. KRUEGER, Planetary Atmospheres Branch, Goddard Space Flight Center, Greenbelt, Maryland, USA

Standard profiles of ozone from ground to 60 km obtained by combining satellite and ground based measurements

P.K. BHARTIA, D. SILBERSTEIN and B. MONOSMITH, Systems and ~pplied Sciences Corporation, Hyattsville, Maryland, USA; A.J. FLEIG, Laboratory for Atmospheric Sciences, NASA, Goddard Space Flight Center, Greenbelt, Maryland, USA

Annual and semiannual oscillations of stratospheric ozone K. MAEDA, Laboratory for Planetary Atmospheres NASA/Goddard Space Fliqht Center, Greenbelt, Maryland, USA

An evaluation of the performance of umkehr stations by solar

234

239

243

248

backscattered ultraviolet (SBUV) experiment 253 P.K. BHARTIA, C.K. WONG, Systems and Applied Sciences Corooration, Hyattsville, Maryland, USA; A.J. FLEIG, Laboratory for Atmospheric Sciences, NASA, Goddard Space Flight Center, Greenbelt, Maryland, USA

Intercomparison of satellite ozone profile measurements 258 A.J. FLEIG, Laboratory for Atmospheric Sciences, NASA~ Goddard Space Flight Center, Greenbelt, Maryland, USA, J.C. GILLE, National Center for Atmospheric Research; M.P. McCORMICK, NASA Langley Research Center; D.W. RUSCH, University of Colorado; J.M. RUSSELL III, NASA Langley Research Center; J.M. LINDSAY, Systems and Applied Sciences Corporation

Total ozone trend in the light of ozone soundings, the impact of El Chichon 263

H.U. DUETSCH, Atmospheric Physics ETH, Zurich, Switzerland

-~-

variability of the vertical ozone distribution

C.S. ZEREFOS, J.C. ZIOMAS, A.F. BAIS, Physics Dept., Lab. of Atmospheric Physics, University of Thessaloniki, Thessaloniki, Greece

An ozone soundings program at the eastern equator: preliminary results

M. ILYAS, School of Physics, University of Science of ~lalaysia, Penang, Malaysia

Mean vertical distribution of atmospheric ozone over Cagliari-Elmas (390 15'N - 090 03'E)

G. PIBIRI, P. RANDACCIO, A. SERRA, A. SOLLAI Istituto Fisica Medica - Universita Cagliari, Italy

A special ozone observation at Syowa station, Antarctica from February 1982 to January 1983

S. CHUBACHI, Meteorological Research Institute Yatabe, Tukuba-Gun, 305 Ibaraki, Japan

A comparison of ozone profiles derived from standard umkehr and short umkehr measurements from fifteen stations

C.L. MATEER, Atmospheric Environment Service, Downsview, Ontario, Canada; J.J. DELUISI, Geophysical Monitoring for Climatic Change NOAA/ERL, Air Resources Laboratory, Boulder, Colorado, USA

Rocket measurements of the vertical structure of the ozone field in the tropics

B.H. SUBBARAYA, A. JAYARAMAN and SHYAr1 LAL, Physical Research Laboratory, Ahmedabad, India

Time-periodic variations in ozone and temperature

A.D. BELMONT, Control Data, P.O.Box 1249, Minneapolis, Minneapolis, USA

Results of umkehr, ozonesonde, total ozone, and sulfur dioxide observations in Hawaii following the eruption of El Chichon volcano in 1982

W.D. KOMHYR and S.J. OLTMANS, NOAA Air Resources Laboratory, Boulder, Colorado, USA; A.N. CHOPRA and R.K. LEONARD, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA; T.E. GARCIA and C. McFEE, NOAA, Mauna Loa Observatory, Hilo, Hawaii, USA

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269

274

279

285

290

295

300

305

On the correspondence between standard umkehr, short umkehr and SBUV vertical ozone profiles 311

J.J. DELUISI, Geophysical Monitorinq for Climatic Chanqe NOAA/ERL, Air Resources Laboratory, Boulder, Colorado, USA; C.L. MATEER, Atmospheric Environment Service, Downsview, Ontario, Canada: P.K. BHARTIA, Systems and Applied Sciences Corporation, Hyattsville, Maryland, USA

Effects of the El Chichon stratospheric aerosol cloud on umkehr measurements at Mauna Loa, Hawaii 316

J.J. DELUISI, Geophysical Monitoring for Climatic Chanqe NOAA/ERL, Air Resources Laboratory, Boulder, Colorado, USA: C.L. MATEER, Atmospheric Environment Service, Downsview, Ontario, Canada; W.D. KOMHYR, Geophysical Monitoring for Climatic Change NOAA, ERL, Air Resources Laboratory, Boulder, Colorado, USA

Ozone-temperature relationships in the stratosphere A.J. MILLER, R.M. NAGATANI, NOAA/NMC/Climate Analysis Center; J.E. FREDERICK, NASA/Goddard Space Flight Center, USA

Lidar ozone measurements in the troposphere and stratosphere at the observatoire de.Haute Provence

J. PELON and G. MEGIE, Service d'Aeronomie du C.N.R.S. France

Vertical ozone distribution over Uccle (Belgium) after correction for systematic distortion of the ozone profiles

D. DE MUER, Meteorological Institute of Belgium

On the relative quality and performance of G.030.S. total ozone measurements

R.D. BOJKOV and C.L. MATEER, Atmospheric Environment, Service of Environment, Canada

321

325

330

335

Atmospheric ozone in map-qlobus 341 W.A. MATTHEWS, Service d'Aeronomie du CNRS, Verrieres le Buisson, France

One year European total ozone daily maps from Nimbus 7 and Dobson data 344

J.I. CACHO, M. GIL, M.J. SAINZ DE AJA, Comision Nacional de Investigacion del Espacio. Grupos Cientificos. Madrid, Spain

Une appellation commune du nom des grandeurs utilisees pour designer les quantites d'ozone dans l'air : 1 'ozonite

P. AIMEDIEU, Service d'Aeronomie du CNRS, Verrieres le Buisson, France

-x~-

349

Decreases in the ozone and the SO columns following the appearance of the El Chichon aero~ol cloud at midlatitude

A.F. BAIS, C.S. ZEREFOS, I.C. ZIOMAS, N. ZOUMAKIS Physics Dept., Lab. of Atmospheric Physics, Univ. of Thessaloniki, Greece; H.T. MANTIS, School of Physics and Astronomy, Univ. of Minnesota, USA: D.J. HOFMANN, Department of Physics and Astronomy. Univ. of Wyoming, USA; G. FIOCCO, Istituto di Fisica-Universita di Roma, Italy

Correlative studies of total ozone content with tropospheric properties - results from Indian stations

O.K. CHAKRABARTY, P. CHAKRABARTY and G. BEIG. Physical Research Laboratory, Ahmedabad, India

A qlobal climatology of total ozone from the Nimbus-7 total ozone

353

357

mapping spectrometer 363

K.P. BOWMAN, Laboratory for Atmospheres, Code 613. Goddard Space Flight Center, Greenbelt, Maryland, USA

C HAP T E R V RECENT DEVELOPMENTS IN OBSERVATIONAL TECHNIQUES

Umkehr observations with automated Dobson spectrophotometers 371

W.D. KOMHYR and R.D. GRASS, NOAA, Air Resources Laboratory, Boulder, Colorado, USA; R.D. EVANS and R.K. LEONARD, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA: G.M. SEMENIUK, U.S. Environmental Protection Agency, Washinqton, USA

Travelinq standard lamp calibration checks on Dobson ozone spectrophotometers during 1981-1983 376

R.D. GRASS and W.D. KOMHYR, National Oceanic and Atmospheric Administration, Air Resources Laboratory, Boulder, Colorado, USA

Recalibration of Dobson Field Spectrophotometers with a travelling Brewer spectrophotometer standard 381

J.B. KERR, W.F.J. EVANS and I.A. ASBRIDGE, Atmospheric Environment Service, Downsview, Ontario, Canada

Review of the Dobson spectrophotometer and its accuracy 387

R.E. BASHER, New Zealand Meteorological Service

- xx-

A study of scattered light from zenith at low sun in the near UV region where the ozone absorption changes rapidly 392

S.H.H. LARSEN, Institute of Physics, University of Oslo Norway

The automated Brewer spectrophotometer 396 J.B. KERR, C.T. McELROY, D.I. WARDLE, R.A. OLAFSON and W.F.J. EVANS, Atmospheric Environment Service Downsview, Ontario, Canada

Experiences with a Brewer spectrophotometer and intercomparison measurements with a Dobson spectrophotometer 402

U. KOEHLER, R. HARTMANNSGRUBER and W. ATTMANNSPACHER OWO Meteorologisches Observatorium Hohenpeissenberg Hohenoeissenberg, F. R. Germany

Ozone profiles derived from umkehr observations obtained with the Brewer ozone spectrophotometer 407

C.L. MATEER, J.B. KERR and W.F.J. EVANS, Atmospheric Environment Service, Downsview, Canada

Nimbus 7 SBUV/TOMS calibration for the ozone measurement H. PARK, Systems and Applied Sciences Corporation, Hyattsville,.Maryland, USA; D.F. HEATH, Laboratory for Planetary Atmosphere, NASA/Goddard Space Flight Center, Greenbelt, Maryland, USA

Ground-based microwave observations of mesospheric ozone at the

412

Bordeaux observatory 417 J. DE LA NOE, C. TURATI, A. BAUDRY, Observatoire de Bordeaux, France; N. MONNANTEUIL, J.M. COLMONT, Laboratoire d'Optique Ultra-Hertzienne, Universite de Lille, France; P. DIERICH, Observatoire de Paris-Meudon, France

Ozone and water vapor in the middle atmosphere measured with an airborne microwave radiometer 423

R. GYGER, K.F. KUENZI, Institute of Applied Physics, University of Berne, Switzerland; G.K. HARTMANN, Max-Planck-Institute for Aeronomy, Lindau (Harz), F.R. Germany

Vertical profiles and column density measurements of ozone from ground-based MM-wave spectroscopy at Mauna Kea, Hawaii a demonstration of capabilities

J. BARRETT, A. PARRISH, R.L. DE ZAFRA and P. SOLOMON, State University of New York, Stony Brook, New York, USA

- xxi-

428

Validation of a fast line-bv-line transmittance/radiance alqorithm against TIROS-N series channel 9 (ozone) 432

N.A. SCOTT, A. CHEDIN and N. HUSSON, Laboratoire de Meteorologie Dynamique du CNRS, Ecole Poly technique, Palaiseau, France

Information contained in satellite meteor spectra on the vertical ozone distribution 438

U. FEISTER, Meteorological Service of the GDR, Main Meteorological Observatory, Telegrafenberq, Potsdam, G.D.R.

High resolution infrared spectroscopic studies of atmospheric ozone and related trace constituents

A. GOLDMAN, D.G. MURCRAY and F.J. MURCRAY, Department of Physics, University of Denver, Denver, Colorado, USA; A. BARBE and C. SECROUN, Laboratoire de Physique Moleculaire, Equipe de Recherche Associee au CNRS, Faculte des Sciences, Reims, France

Measurements of the ozone profile up to 50 km altitude by

442

differential absorption laser radar 446 J. WERNER, K.W. ROTHE, Sektion Physik der Universitat Munchen, Garching, F. R. Germany; H. WALTHER, Max-Planck-Insitut fur Quantenoptik, Garching, F.R. Germany

Intercomparison of. ozone profiles obtained by Brewer/Mast sondes and differential absorption laser radar 450

W. ATTMANNSPACHER, R. HARTMANNSGRUBER, f'leteoro 1 ogi sches Observatorium Hohenpeissenberg des Deutschen Wetterdienstes, Hohenpeissenberg, F.R. Germany; J. WERNER, K.W. ROTHE, Sektion Physik der Universitat Munchen, Garching, F. R. Germany: H. WALTHER, Max-Planck-Institut fur Quantenoptik, Garching, F.R. Germany

Results from the balloon ozone intercomparison campaign (BOIC) 454

E. HILSENRATH, NASA/Goddard Space Flight Center, Greenbelt, Maryland, USA; J. AINSWORTH, A. HOLLAND, J. MENTALL, A. TORRES, NASA/Goddard Space Flight Center, USA; W. ATTMANSPACHER, Hohenpeissenberg Observatory, F.R. Germany; A. BASS, National Bureau of Standards; W. EVANS, Canada/Atmospheric Environment Service, W. KOMHY~, NOAA/Geophysical Monitoring for Climatic Change; K. MAUERSBERGER, University of Minnesota, USA; A.J. MILLER, NOAA/National Meteorological Center, USA; M. PROFFITT, NOAA/Aeronomy Laboratory, USA; D. ROBBINS, NASA/Johnson Space Center; S. TAYLOR, Systems and Applied Sciences Corporation; E. WEINSTOCK, Harvard University, USA

-xxii-

Balloon in-situ measurements of ozone with the NASA-JSC UV photometer

D.E. ROBBINS, NASA-Johnson Space Center, Houston, Texas, USA

460

Ozone intercomparisons from the balloon intercomparison campaign 465 D. ROBBINS, NASA-Johnson Space Center, Houston, Texas USA; W. EVANS, Atmospheric Environmental Services, Canada" N. LOUISNARD, ONERA, France; S. POLLITT, National Physical Lahoratory, UK; W. TRAUB, Smithsonian Astrophysical Observatory, USA; J. WATERS, Jet Propulsion Laboratory, USA

Ozone measurement from a balloon payload using a new fast-response UV-absorption photometer 470

M.H. PROFFITT, Aeronomy Laboratory, National Oceanic and Atmospheric Administration, and Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, USA

An in-situ multipass UV-absorption ozone sensor designed for stratospheric applications 475

E.M. WEINSTOCK, C.~. SCHILLER and J.G. ANDERSON, Center for Earth and Planetary Physics and Department of Chemistry, Harvard University, Cambridge, Massachusetts USA

Measurement of the vertical profile of ozone from the ascent of a balloon borne ultraviolet spectrophotometer

J.B. KERR and W.F.J. EVANS, Atmospheric Environment Service, Downsview, Ontario, Canada

Spectrum measurement techniques for rocket, balloon and satellite experiments

A. MATSUZAKI, Y. NAKAMURA, and T. ITOH, The Institute of Space and Astronautical Science, Tokyo, Japan

481

486

Precise ozone measurements using a mass spectrometer beam system 493 K. MAUERSBERGER, S. ANDERSON, D. MURPHY and J. MORTON School of Physics and Astronomy, University of Minnesota Minneapolis, Minnesota, USA

Performance characteristics of high-altitude ECC ozonesondes 499 W.D. KOMHYR, S.J. OLTMANS, NOAA Air Resources Laboratory, Boulder, Colorado, USA; A.N. CHOPRA, P.R. FRANCHOIS, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA

-uili-

Error performance of electrochemical ozone sondes OSR 504 U. FEISTER, P. PLESSING, K.-H. GRASNICK, Meteorological Service of the GDR, Main Meteorological Observatory, Telegrafenberg, G.D.R.

G. PETERS, Meteoroloqical Service of the GDR, Aerological Observatory, Lindenberg, G.D.R.

Mesure de la repartition verticale de l'ozone atmospherique par spectrophotometrie d'absorption dans le visible 509

P. RIGAUD, J.P. NAUDET, Laboratoire de Physique et Chimie de l'Environnement, Orleans, France D. HUGUENIN, Observatoire de Geneve, Sauverny, Switzerl and

Un cataloque de precautions instrumentales a prendre pour faire l'etude in situ de la variation crepusculaire ou diurne d'une espece stratospherique, presentation d'un cas particulier, l'ozone 514

P. AIMEDIEU, Service d'Aeronomie du CNRS, Verrieres le Buisson, France; P. RIGAUD, Laboratoire de Physique et Chimie de l'Environnement, Orleans, France; A. MATTHEWS, Departement of Scientific and Industrial Research, P.E.L. Atmospheric Station, Omakau, Central Otago, Nouvelle Zelande

Measurements of the ~tratospheric ozone by indigo decoloration 519 J.M. CISNEROS, CONIE, Madrid, Spain

Satellite measurement of mesospheric ozone from the 1.27 m Airglow emission

H. YAMAMOTO, T. MAKINO, H. SEKIGUCHI and I. NAITO Department of Physics, Rikkyo University Toshima-ku, Tokyo, Japan

A rocket gas-qas chemiluminescent technique for measurement of

522

atomic oxygen and ozone concentrations in the 15-95 km region 52i

S.P. PEROV and S.V. TISHIN, Central Aerological Observatory, USSR State Committee for Hydrometeorology and Control of Natural Environment, Moscow, USSR

Constructing emperical zenith ozone charts and tables using the multiple linear regression technique 532

G.K.Y. HASSAN, Meteorological Authority, Cairo, Egypt

Total-ozone measuring instruments used at the USSR station network 543 G.P. GUSHCHIN, S.A. SOKOLENKO, V.A. KOVALYOV, Main Geophysical Observatory, Leningrad, USSR

- xxiv-

C HAP T E R VI INTERACTION OF OZONE AND CIRCULATION

Simultaneous measurements of carbon monoxide and ozone in the NASA global atmospheric sampling program (GASP) 548

R.E. NEWELL, Department of Earth, Atmospheric and Planetary Sciences, Institute of Technology, Cambridge, Massachusetts, USA; HAO-FOU WU, Atmospheric Chemistry Branch, Goddard Space, Flight Center, Greenbelt, Maryland USA

The interannual variations of the global total ozone as a reflection of the general circulation changes in the stratosphere 553

F. HASEBE, Laboratory for Climatic Change Research Geophysical Institute, Kyoto University, Kitashirakawa,

Japan

Dependency of ozone transport on the vertical structures of planetary waves 558

K. KAWAHIRA, Geophysical Institute of Kyoto University, Japan

Ozone concentration data applied for studying mesoscale wave processes in the atmosphere 563

A.N. GRUZOEV·and N.F. ELANSKY, Institute of Atmospheric Physics, Academy of Sciences of the USSR

The effect of temperature waves on the zonal mean ozone content 568

K. KAWAHIRA, Geophysical Institute of Kyoto University, Japan

Aircraft measurements near jet streams 572 G. VAUGHAN, A.F. TlICK, Meteorological Office, Bracknell, Berkshire, UK

Wavenumber spectra of ozone from GASP aircraft measurements 580

G.D. NASTROM, W.H. JASPERSON, Control Data Corporation, Minneapolis, Minnesota, USA: K.S. GAGE, Aeronomy Laboratory, NOAA, Boulder, Colorado, USA

Measures of stratosDheric displacements from satellite data 585 S. MULLER, F.R. CAYLA and J.P. JULLIER, Etablissement d'Etudes et de Recherches Meteorologiques, Toulouse, France

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Variations of radiative heating/cooling in the stratosphere as revealed by satellite observations 589

P.-H. WANG and A. DEEPAK, Institute for Atmospheric Optics and Remote Sensing (IFAORS), Hampton, Virginia, USA; A. GHAZI, Commission of the European Communities, Brussels, Belgium

Observation of strong ozone variations during a prestage of the sudden stratospheric warming in January / February 1979

Sage near

W. BRAUN and H.U. DUETSCH, Atmospheric Physics ETH, Honqgerbera, ZUrich, Switzerland

studies of the waves and eddy fluxes of ozone and temperature 550 durinq the late February 1979 stratospheric warming

PI-HUAN WANG, Institute for Atmospheric Optics and Remote Sensing (IFAORS), Hampton, Virginia, USA

C HAP T E R VII LABORATORY MEASUREMENTS OF ABSORPTION CROSS-SECTIONS AND OF CHEMICAL RATE CONSTANTS

The ultraviolet cross-sections of ozone: I. The measurements A.M. BASS,.NBS, Washington, District of Columbia, USA R.J. PAUR, EPA, Research Triangle Park, North Carolina, USA

The utraviolet cross-sections of ozone: II. Results and

594

600

606

temperature dependence 611

R.J. PAUR, EPA, Research Triangle Park, North Carolina, A.M. BASS, NBS, Washington, District of Columbia, USA

New values of ozone absolute cross-sections in the ultraviolet spectral range at 298 and 228 K, by a method based upon pressure measurements at constant volume 617

J. MALICET, J. BRION, D. DAUMONT, Unite Associee au CNRS 776, Spectrometrie Moleculaire et Atmospherique, U.E.R. Sciences - Reims, France

Absolute absorption cross section measurements of ozone

D.E. FREEMAN, K. YOSHINO, J.R. ESMOND and W.H. PARKINSON Harvard-Smithsonian Center for Astrophysics

Absorption coefficients of ozone for the backscattered UV

622

instruments - SBUV, TOMS, and BUV - and for the Dobson instrument 625

K.F. KLENK, B. MONOSMITH and P.K. BHARTIA, Systems and Applied Sciences Corporation, 5809 Annapolis Road, Hyattsville, Maryland 20784

- xxvi-

Mesure de 1 'absorption par la haute atmosphere dans le domaine de lonqueurs d'onde de la "Fenetre atmospherique" au voisinage de 200 nm

M. PIRRE, Universite d'Orleans; P. RIGAUD, Laboratoire de Physique et Chimie de l'Environnement, Orleans, France; D. HUGUENIN, Observatoire de Geneve, Sauverny, Switzerl and

Theoretical N2-, 02-, and Air-broadened halfwidths of ozone calculated by quantum fourier theory with realistic collision dynamics

R. R. GAMACHE, The Center for Atmospheric Research, The University of LowelT, Lowell, Massachusetts, USA; R.W. DAVIES, GTE/Sylvania Laboratories, Waltham, Massachusetts, USA; L.S. ROTHMAN, Air Force Geophysics Laboratory. Hanscom, AFB, Bedford, Massachusetts, USA

630

635

Altitude resolved measurements of the N20 photolysis frequency in the stratosphere 640

W. HANS, C. KESSLER and U. SCHURATH, Institut f. phys. Chemie der Universitat Bonn, Bonn, F.R. Germany

C HAP T E R VIII RADIATION TOPICS RELEVANT TO ATMOSPHERIC OZONE

Solar irradiance and its spectral distribution through the terrestrial atmosphere

M. NICOLET, Space Aeronomy Institute, 3 Avenue Circulaire, Brussels, Belqium

Solar ultraviolet irradiance 1982 and 1983 G.J. ROTTMAN, Laboratory for Atmospheric and Space Physics University of Colorado, Boulder, Colorado, USA

A review of solar irradiance measurements between 270 and 480 nanometers

K. MOE, Department of Geoloqical Sciences, California State University, Fullerton, California, USA

The global response of stratospheric ozone to ultraviolet solar flux variations

D.F. HEATH, NASA/Goddard Space Flight Center, Laboratory for Atmospheres

B.M. SCHLESINGER, Systems and Applied Sciences Corporation

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646

656

661

666

Ozone and sunspots: why can we not find a direct correlation? 671

M. SCHMIDT, Max-Planck-Institute fur Aeronomie, Katlenburg-Lindau, F.R. Germany

Ozone depletion during solar proton events in solar cycle 21 676 R.D. McPETERS and C.H. JACKMAN, Laboratory for Atmospheres NASA, Goddard Space Flight Center, Greenbelt, Maryland, USA

Ultraviolet im~gery of the sky 680

W.F.J. EVANS, J.B. KERR and 0.1. WARDLE, Atmospheric Environment Service, Downsview, Ontario, Canada

Monochromatic UV-magnification factors and total ozone C.S. ZEREFOS, A.F. BAIS, I.C. ZIOMAS, Physics Dept .• Lab. of Atmospheric Physics, University of Thessaloniki, Greece

Ozone concentration and aurora frequency in relation to solar-terrestrial indices

R. PETROPOULOS and Y. LIRITZIS, Research Center for Astronomy and Applied lv1athematics, Academy of Athens, Greece

Calculations of Lyma~ Alpha absorption in the mesosphere J.L. LEAN, Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado/NOAA, Boulder Colorado, USA

Radiative interactions of stratospheric ozone and aerosols in the solar spectrum

V. RAMASWAMY, National Center for Atmospheric Research, Boulder, Colorado, USA

A sensitivity study of calculation of atmospheric ozone transmittances

F. MISKOLCZI and I. LASZLO, Department of Physics University of Calabar, Calabar, Institute for Atmospheric Physics, Budapest, Hungaria

C HAP T E R IX NON-URBAN TROPOSPHERIC OZONE

The role of isoprene oxidation in the tropospheric ozone budget in the tropics

D.A. BREWER, Systems and Applied Sciences Corp. Hampton, Virginia, USA; J.S. LEVINE, NASA Langley Research Center, Hampton, Virginia, USA

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686

691

697

702

708

715

Methane oxidation in aerosol-containing atmosphere

V.L. TALROSE, A.I. POROIKOVA and E.E. KASIMOVSKAYA Institute of Chemical Physics of the Academy of Sciences of the USSR; S.G. ZVENIGORODSKY and S.P. SMYSHLYAEV, Hydrometeorological. Institute, Leningrad, USSR

Hydroxt3 rgdical concentration in ambient air estimated from C n oxidation

J. HJORTH, G. OTTOBRINI, F. CAPPELLANI, G. RESTELLI, H. STANGL. Commission of the European Communities, Joint Research Center - ISPRA Establishment, ISPRA (VA) Italy C. LOHSE, University of Odense, Chemistry Dept. Odense, Denmark

Tropospheric ozone: transport or chemistry?

H. LEVY II, Geophysical Fluid Dynamics Laboratory/NOAA Princeton, New Jersey, USA

Effect of stratospheric intrusions on the tropospheric ozone

K. MUNZERT, R. REITER, H.-J. KANTER and K. POETZL, Fraunhofer Institute for Atmospheric Environmental Research, Garmisch-Partenkirchen, F.R. Germany

Vertical ozone profiles in the lower atmosphere and their relation

720

725

730

735

to long-range transport 740

F.L. LUDWIG, Atmospheric Science Center, SRI International, Menlo Park, California, USA

Cumulus cloud venting of mixed layer ozone

J.K.S. CHING, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, S.T. SHIPLEY and E.V. BROWELL, National Aeronautics and Space Administration, Langley Research Center, Hampton, Virqinia, USA; D.A. BREWER, Systems and Applied Sciences Corp., Hampton, Virginia, USA

Sources and budget of tropospheric ozone at a rural site in north west England

I. COLBECK and R.M. HARRISON, Department of Environmental Sciences, University of Lancaster, Lancaster, UK

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745

750

Seasonal behaviour of the tropospheric ozone in Japan

T. OGAWA and A. MIYATA, Geophysics Research Laboratory, University of Tokyo, Japan

Photochemical oxidants at Niwot Ridge, Colorado

M. TRAINER, J.M. ROBERTS, D.O. PARRISH, D.W. FAHEY, S.C. LIU, D.L. ALBRITTON, C. FEHSENFELD, Aeronomy Laboratory, NOAA Environmental Research Laboratories, Boulder, Colorado, USA

Diurnal variation of ozone in fine weather situations over hilly terrain

H.A. GYGAX and B. BRODER, Atmospheric Physics ETH, Honggerberg, ZUrich, Switzerland

Opposite behaviour of the ozone amount in the troposphere and lower stratosphere during the last years, based on the ozone measurements at the Hohenpeissenbergobservatory from 1967 - 1983

R. HARTMANNSGRUBER, W. ATTMANNSPACHER and H. CLAUDE DWD Meteorologisches Observatorium Hohenpeissenberg Hohenpeissenberg, F.R. Germany

Trends in tropospheric ozone concentration

R.D. BOJKOV, Atmospheric Environment Service of Environment Canada; G.C. REINSEL, Dept. of Statistics, University of Wisconsin at Madison, USA

754

759

765

770

775

Long-term surface ozone increase at Arkona (54,680 N, 13,430 E) 782

U. FEISTER, Meteorological Service of the GDR, Main Meteorological Observatory, Telegrafenberg, Potsdam; W. WARMBT, Meteorological Service of the GDR, Meteorological Observatory, Radebeul, GDR.

A neglected long-term series of ground-level ozone

E.G. MARIOLOPOULOS, C.C. REPAPIS, C.S. ZEREFOS, C. VAROTSOS, I. ZIOMAS, A. BAIS, Academy of Athens and Laboratory of Atmospheric Physics, University 'of Thessaloniki, Greece

- xxx-

788

Surface ozone near the equator

M. ILYAS, School of Physics, University of Science of Malaysia, Penang, Malaysia

Tropospheric ozone at four remote observatories

S.J. OLTMANS, Geophysical Monitoring for Climatic Change Air Resources Laboratory, ERL, NOAA, Boulder, Colorado, USA

Diurnal variations of non-urban ozone concentrations in Israel

E.H. STEINBERGER, Department of Atmospheric Sciences, The Hebrew University, Jerusalem; R. LEVY, Environmental Protection Service, Ministry of the Interior, Ben Gurion City, Jerusalem, Israel

Differences in tropospheric ozone profiles obtained by Mast (Brewer) and EEC (Komhyr) Sondes

R.D. BOJKOV, Atmospheric Environmental Service of Environment, Canada

Uncertainties in surface ozone measurements in clean air

C. M. ELSWORTH, I. E. GALBALLY and M. D. DOUGLAS CSIRO Division of Atmospheric Research, Mordialloc. Victoria, Austral i a

L'ozone serait-il l'oxydant principal du sulfure de dimethyle en milieu oceanique

P. CARLIER, Laboratoire de Physico-Chimie Instrumentale Universite, Paris, France

Ozone production and transfer in the FOS-BERRE basin area

C. TOUPANCE ana P. PERROS, Laboratoire de Physico­Chimie de l'Environnement, Universite de Paris Val de Marne, Creteil, France

LIST OF PARTICIPANTS

LIST OF AUTHORS

~ xxxi-

791

796

803

808

809

815

820

825

839

OPE N I N G

- Presidential address

- Sir Charles Normad - In Memoriam

- Implementation of the WMO ozone project (1980-84)

PresidentiaL Address

By C.L. MATEER

This morning, I want to make a few remarks on the state of atmospheric

ozone science and on the program for this symposium. In recent years, there

have been a number of reports which summarize the state of our science in

varying degrees of detaiL. These reports have been prepared in both Europe

and North America. The two most recent reports that I am aware of were

reLeased earLy this year, one by the u.s. NationaL Research CounciL, the

other by NASA. A carefuL reading of either of these reports, or even their

summaries aLone, gives one a reasonabLy baLanced view of our knowLedge of

atmospheric ozone science as of sometime Late in 1983.

~he fieLd of atmospheric ozone science draws together severaL discipLines

from the physicaL, mathematicaL, and bioLogicaL sciences. WhiLe we are

concerned this week excLusiveLy with the physicaL and mathematicaL sciences,

there have been some fairLy major recent advances on the bioLogicaL side

about the effects on humans of increased exposure to UV-B radiation. For

those of you not famiLiar with them, I shaLL take a few minutes to summarize

very briefLy the most important of these. My source is the u.S. NationaL

Research CounciL update released earLy this year. The report first points

out that increased Lifetime exposure of humans to UV-B radiation may occur

for reasons quite unreLated to decreases in totaL atmospheric ozone. These

reasons incLude changes in Life styLe or fashions, for exampLe, the urgent

need to have a good suntan over the entire body, as weLL as popuLation shifts

to sunnier cLimates, and the generaL increase in Longevity of the popuLa­

tion. The two most rapidLy advancing cLinicaL fieLds deaL with maLignant

meLanoma and photoimmunoLogy. The first of these, maLignant meLanoma in

humans, has become a major heaLth probLem with the rate of increase in

mortaLity for maLignant meLanoma being exceeded onLy by that for Lung cancer.

I quote directLy: 'new data support the hypothesis that the risk of deveLop­

ment of some types of maLignant meLanoma is reLated to exposure to sunLight.'

However, to quote further: 'evidence that UV radiation (or UV-B) is reLated

to maLignant meLanoma is onLy circumstantiaL.'

-3-

The advances in photoimmunoLogy are more specific to UV and UV-B. Studies

with Laboratory animaLs have indicated a decrease in the effectiveness of

the immune response system in there animaLs foLLowing exposure to UV-B.

Moreover, this suppression of the immune response is systemic, that is to

say, the effectiveness is reduced not onLy at the exposed site, but aLso

at distant unexposed sites. The foLLowing is a very strong statement and

again I quote directLy: 'recent studies have demonstrated unequivocaLLy

that systemic immunoLogicaL changes produced as a resuLt of UV-B irradiation

are an important factor in the deveLopment of primary skin cancers induced

in mice by UV radiation.' Furthermore, and again I quote: 'it has now been

demonstrated that at Least some of these immunoLogicaL changes aLso occur

in humans exposed to naturaL or artificiaL UV radiation'. In summary, these

new findings support the importance of a strong research effort in atmosphe­

ric ozone and timeLy representations to our gevernments if and when it

becomes cLear that controL action, or further controL action, is needed to

protect the ozone Lawer.

In many ways, the purpose of ozone research to-day is to improve our

knowLedge and understanding of the processes that govern the formation,

destruction, and transport of ozone in the atmosphere. This improved under­

standing Leads, in turn, to the formuLation of better mathematicaL-physicaL­

theoreticaL modeLs for the prediction of Long-term future ozone trends. For

this reason, the predictive modeL has become the centraL focus for ozone

research. ALthough there have been enormous advances in ozone science over

the past five or si~ years, and there have been reLativeLy Large changes in

modeL predictions, the uncertainty which must be attached to the modeL pre­

dictions of Long-term ozone trends has not decreased. What has come about

is the reaLization that the overaLL picture is much more compLex than origi­

naLLy beLieved. Moreover, to the scientific compLexities of predicting ozone

trends, we must add the imponderabLe of predicting future LeveLs of gLobaL

economic activity, which controL, to some considerabLe extent, the reLease

rates of those substance affecting ozone and coming from anthroposenic

activities. The expert economists are unabLe to make such predictions with

any certainty, even for reLativeLy short periods of time. Can we in the

ozone science community expect to do better?

We have known for over haLf a century that Large changes in totaL coLumn

ozone occur with the passage of surface weather systems. We have known for

-4-

over 30 years that atmospheric transport must be invoked, as weLL as

photochemistry, in order to expLain the gLobaL distribution of ozone. It is

equaLLy true that meteoroLogicaL processes pLay an important roLe in the

determination of future ozone trends. The prediction of some months ago in

the two U.S. reports that LittLe change in ozone coLumn was to be expected

over the next severaL decades was based on the counter-baLancing of opposing

effects. These were a Large percentage decrease in ozone concentration

centred about 40 km aLtitude where ozone concentrations are smaLL, a smaLL

percentage increase beLow the main ozone maximum where ozone densities are

large, and fairLy Large percentage increases in the upper troposphere

where ozone densities are reLativeLy smaLL. In other words, the overaLL

'LittLe change' prediction depends not onLy on the accuracy of the photoche­

micaL modeL, but aLso on the accuracy of parameterizing the compLex meteoro­

LogicaL processes of the Lower stratosphere in the one- and two-dimensionaL

modeLs used in making the predictions.

But we must go one step further. The ozone probLem to-day is over-shadowed

by the C02 cLimate prob~em. It is caLLed the C02 cLimate probLem because

C02 is the Largest singLe contributor. However, potentiaL changes in ozone,

especiaLLy tropospheric ozone, pLus changes in the concentrations of others

minor constituents which are invoLved in the ozone photochemistry, have a

potentiaL impact on surface temperature approximateLy equaL to that of C02.

It shouLd now be cLear that it is most unwise, if not impossibLe, to compLe­

teLy unbundLe the cLimate probLem and the ozone probLem. Ozone changes, and

the changes in minor constituents which must accompany the ozone changes

wiLL have an impact on cLimate. It is equaLLy true that cLimate change wiLL

have an important effect on ozone, not onLy through the effect of temperature

changes on reaction rates, but aLso potentiaLLy throuth the effects of

changed patterns of atmospheric circuLation and transport, especiaLLy in the

Lower stratosphere. The currentwisdom seems to be that reaL advances on this

compLete cLimate-ozone probLem wiLL come from studies with three-dimensionaL

modeLs which wiLL in some way effect a marriage of the compLexities of the

photochemicaL and meteoroLogicaL processes.

The best verification of a theoreticaL prediction is, of course, the

observation of the ~redicted effect. WhiLe many other aspects of the

theoreticaL predictions of ozone depLetion have changed over the past

-5-

severaL years, one aspect has remained reLativeLy constant, nameLy: a

fairLy Large percentage depLetion in a broad Layer centered near 40 km.

One of the important resuLts of the past 4 years, has been the detection

of a statisticaLLy significant ozone depLetion in Umkehr Layer 8 which is

centered about 40 km, in good agreement with current modeL predictions.

Because of the Large amount of noise inherent in most Umkehr data, and

bacause of the significant opticaL effects of voLcanic aerosoLs in the

stratosphere, this statisticaLLy significant resuLt was obtained onLy by

the use of advanced statisticaL methods and the incLusion of a variabLe

expressing the opticaL depth of the aerosoLs. It was aLso necessary, in the

statisticaL anaLysis, to aLLow for step functions in the data record at

severaL stations to coincide with either changes of instrument, recaLibra­

tion of an existing instrument, or a perceived accidentaL bLow to an instru­

ment. These Latter events were first detected in the anaLysis and Later con­

firmed with the principaLs invoLved. This anaLysis showed us how Large Umkehr

profiLe data step functions couLd be. The paper by Mr Komhyr wiLL indicate

how smaLL differences between Dobson instruments used in Umkehr observations

can become with proper care and attention.

In many respects, the atmosphere is our Laboratory. OccasionaLLy, it presents

us with unique opportunities for the advancement of our science. There have

been at Least two such opportunities since our Last quadrenniaL symposium.

The first of these was the eruption of the E1 Chichon voLcano in ApriL of

1982, the second was the E1 Nino which occurred during the subsequent nor­

thern hemisphere winter. These two events provided us with opportunities to

study the impact of voLcanic 502 on ozone observations, both surface based

and sateLLite, as weLL as the impact of stratospheric aerosoLs on both

Umkehr and BUV-type sateLLite observations. Measurements of the spread of

the voLcanic aerosoL cLoud provide fresh insights into Long-range stratos­

pheric transport processes. FinaLLy, the major minimum in totaL column ozone

in 1983, which I understand is gLobaL in nature, shouLd form the subject of

several studies over the next few years. This major ozone anomaLy was undoub­

tedLy reLated to the concurrent cLimate anomaLy, but a fuLL expLanation may

aLso have to invoke photochemistry, because ozone depLetion, near 30 km at

Least, seems aLso to have been present, at Least in 1982. Because it is

often difficuLt to assess the fuLL impact of events such as these untiL the

atmosphere has recovered to normaL, there appears to be very LittLe in this

symposium on the 1983 ozone anomaLy.

-6-

Another matter about which I wish to say a few words is the gLobaL ozone

observing system (GOOS). The first major step in having such a system of

practicaL use is to understand and quantify the differences between the

various components of the system. In the past, we have aLways bLamed diffe­

rences between, for exampLe, the Dobson network and the BUV type sateLLites,

on ozone absorption coefficient inconsistencies. For most ~pers presented

at this symposium, that is stiLL possibLe. However, we now have a good set

of reLative ozone absorption coefficients through most of the uLtravioLet

region used in ozone measurements and there is a poster paper by KLenk and

coLLeagues indicating the extent to which BUV-Dobson differences may be

resoLved by the use of these new coefficients.

ALso on the subject of inter-system differences, the"re have been recent

extensive campaigns on both sides of the AtLantic intercomparing various

methods for measuring the verticaL ozone profiLe up to 30-40 km. ResuLts

from these campaigns, nameLy MAP-GLOBUS in Europe and the BaLLoon Ozonesonde

Intercomparison Campaign (BOle) in North America are to be presented this

week.

In addition, we have a poster paper which intercompares ozone profiLe

resuLts from 4 separate sateLLite experiments, nameLy: LIMS, SAGE, SBUV,

and SME. This is an important paper because the sateLLites cLearLy provide

the best system for gLobaL ozone monitoring. I recaLL a Letter I received

from Professor Dobson severaL years ago in which he recognized that sateLLite

systems wouLd be the most important ozone observing systems in the future

and that the surface-based Dobson network wouLd be mainLy important for

providing ground truth for the sateLLite systems. Dobson's vision of the

sateLLite systems was quite correct for day-to-day and seasonaL and annuaL

mapping. UnfortunateLy, the probLem of Long-term drift in sateLLite instru­

ments has not yet been fuLLy resoLved and the ground-based network,sparse as

it may be, has stiLL to be used for estimating gLobaL trends. The SBUV expe­

timent on Nimbus 7 with nearLy six years of operation compLeted is perhaps

approaching the necessary LeveL of stabiLity after aLLowance for the known

deterioration of the diffuser pLate, and the foLLow-on SBUV-2 series on the

NOAA sateLLites wiLL, we hope, provide a soLution to this probLem incLuding

the shuttLe SBUV.

In organizing the program for this symposium, we recognized the importance

-7-

of the predictive modeLs by pLacing the modeLLing session at the beginning,

foLLowed by the much-too- short session on ozone-cLimate interaction. Because

measurements of the trace constituents are so very important in diagnosing

the vaLidity of the modeLs, we have scheduLed a fuLL day of oraL sessions,

pLus a Large number of poster papers, on this subject. Some of these trace

constituents are extremeLy difficuLt to measure. The first time one is

measured, history is made. With the second measurement comes the quandary,

because the two resuLts are virtuaLLy never the same. The questions foLLow

is this reaL naturaL atmospheric variabiLity? Has the instrument changed?

Or if two different instruments were used, are the two instruments that much

different? Therefore, we have to recognize the great importance of the

* BaLLoon Intercomparison Campaign (BIC) organized by NASA (Dr. Watson) to

intercompare the various trace constituent measurement methods. These resuLts

from BIC both the overview by Dr. Watson and the poster papers with the

detaiLs, are a key part of to-morrow's session.

It is interesting that the reviews of atmospheric ozone usuaLLy refer to

ozone changes in the stratosphere or the upper atmosphere in their titLes.

One reason for this is that one wishes at aLL costs to avoid becoming invoL­

ved in ozone as an urban poLLutant. NevertheLess, tropospheric ozone pLays

a key roLe to-day, for increasing tropospheric ozone is predicted to par­

tiaLLy canceL the predicted ozone decreases caused by chLorofLuorocarbons

in the upper stratosphere. We have aLso found in the recent past that

radiation matters are not perfectLy kno~n and shouLd not be negLected. The

position of the radiation session with Prof. NicoLet's review and the

tropospheric ozone session on the Last day of the symposium is that of the

anchor man in the oLympic reLay. We aimed for a strong start and a strong

finish.

In summary, and my Last 'finaLLy', many advances have been made in the past

4 years, and we have an even better reaLization of how much further we have

to go. Four years from now I hope we shaLL see some resuLts from the fuLLy­

coupLed cLimate-ozone probLem and the reaLization of a true gLobaL ozone

observing system, as weLL as strong advances in the other areas of atmos­

phe~~c ozone service.

* co-sponsored by C.E.C., CMA and National Institutions.

-8-

SIR CHARLES NORMAND IN MEMORIAM

C. D. WALSHAW Department of Atmospheric Physics,

Clarendon Laboratory, Oxford OXl 3PU, U.K.

When he retired from the Indian Meteorological Depart­ment in 1944, at the age of 55 years less one day, the Director-General, Dr. Charles Normand, C.I.E., had intended to settle down quietly in Cambridge. He had gone out tD India in 1913 almost in desperation at failing to obtain a teaching appointment in Chemistry, his favourite and best subject at Edinburgh University. His time in India was remarkable for his outstanding qualities of leadership and administration, for the priority he gave to unrelenting scientific activity and critical thought, and for the respect and affection felt for him by his staff. A visitor to Pune today will find this respect and affection still very much alive, and if the visitor has known Sir Charles he cannot fail to be deeply moved by the experience.

Among the attractions of Cambridge as a place of retire­ment was undoubtedly the fact that Sir Gilbert Walker, from whom he had learnt so much in his early days in India, was living in retirement there. Sir Charles did indeed arrive in Cambridge in the spring of 1945, having been honoured in the meantime both by the award of the Symons Gold Medal of the Royal Meteorological Society and by his Knighthood. But the settling down was not to be, because he soon received a warm invitation from Dobson to join him in his ozone work at Oxford. (He had visited Dobson in 1939 to make arrangements for new Indian spectrophotometers.) By October 1946 he was in Oxford, and so began that remarkably harmonious and fruitful collabor­ation which so greatly advanced our science. The situation at that moment seemed just ready for Sir Charles's particular talents and inclinations. Dobson's photoelectric instrument was in use at several stations, but it could use only one wavelength pair and was at the mercy of the unpredictable and delicate sodium-cathode photocells. Now the photomultipliers developed in World War II were in commercial production and promised great increases in sensitivity and reliability. Normand also realized the advantages of using more than one pair of wavelengths, as indeed Dobson's original photographic instrument had done. The carrying out of these improvements and the development of better methods of calibration and routine control of the instrument gave full play to Sir Charles's interest in such matters. The work was done in very close collaboration with Dobson and was assisted by Roy Kay, who joined them in 1948.

Then there were the problems of the network, at that time a purely voluntary set of collaborators, ma~y in universities, who must be kept informed of new developments or their inter­est Nould cool off. Sir Charles well knew how to solve prob­lems of this kind. It was at this time, 1948, that our Comm-

Ozone Symposium - Greece 1984 -9-

ission was set up, with Dobson as President and Normand at Secretary. These operations culminated in the special efforts for the I.G.Y. in 1958, and by the time the Travelling Physicist was appointed the techniques for adjustment and calibration of the instrument had been brought almost to the state they are in today.

Sir Charles's time at Oxford was clouded by the death of Lady Normand in 1953 and by the death of one of his two sons in a car accident. Following a serious attack of bronchitis he left Oxford in 1959, joining his son, Colin, and his family in Winchester. Here he kept up an active interest in all aspects of the atmosphere until his death on 25 October 1982.

To conclude I would like to quote some words written by the later Peter Sheppard at the end of his article in the Dictionary of National Biography on Sir Gilbert Walker, as I can think of none more fitting: 'These and other honours Walker wore lightly and ever remained modest, kindly, liberal minded, wide of interest and a very perfect gentleman'.

-10-

IMPLEMENTATION OF THE WMO OZONE PROJECT (1980-84)

Rumen D. Bojkov* Member of the Ozone Commission - liaison with WMO

Summary The WMO Global Ozone Research and Monitoring Project

continued to serve as a focal point for international action on ozone related initiatives and studies. successfully integrating the efforts of a large number of interested scientists located in various countries devoting time to the implementation of the numerous tasks. The Ozone Project continued the fruitful collaboration with the Ozone Commission of IAMAP and was assisted by UNEP. As it has become customary at each Symposium. besides conveying the good wishes for continued success on behalf of the Secretary General of WMO. the highlights of developments and achievements in this field. as far as WMO is concerned. are revie"led.

1. Introduction Ozone studies. like all other atmospheric research. are

truly global in character and can not be developed successfully, without active international collaboration in the fields of data exchange, research analysis and last. but not least. in the dissemination of results and review of knowledge.

The formal involvement of the World Meteorological Organization in this field. as a few of you will recall. began at the time of preparation for the International Geophysical Year. when WMO accepted responsibility to stimulate application of uniform observing practices. as well as to collect and publish the ozone data. After the IGY a formal resolution of the Third WMO Congress initiated further actions. namely: to improve the density of the ozone network and. at the same time. the reliability of observations; to stimulate methods for vertical ozone distribution measurements; to establish Regional centers responsible for standardisation; to set up a World Ozone Data Center (which has been operated on behalf of WMO by A.E.S.-Environment Canada since 1962); to assist countries in establishing ozone research programmes and to render support for meetings and symposia to disseminate the knowledge gained.

Therefore, when in the early 1970's public concern was expressed over the possible destruction of ozone as a result of human activities. WMO was in a strong position. in terms of expertise and international mandate. to provide appropriate advice to its Member States. It became increasingly clear that more concentrated efforts, encompassing observational and research analysis aspects needed to be internationally encouraged. As a consequence in 1975, WMO published the first authoritative statement on the modification of the ozone layer due to human activies, and also established the WMO Ozone Project. This project continues to successfully serve as a focus for international activities in this field. It is being executed

* Currently with the A.E.S.-Environment Canada

Ozone Symposium - Greece 1984 -11-

in collaboration with a number of interested countries, international bodies such as the UNEP and the Ozone Commission of IAMAP, and by a large number of individual scientists.

2. Main tasks since last Ozone Symposium During the past four years the WMO Ozone Project has

concentrated primarily on the following activities: - improving the various aspects of the Global Ozone

Observing System (G030S); - clarifying physical processes and phenomena which

possibly affect ozone photochemistry and ozone trends; - studying potential climatic effect of ozone and other

radiatively active minor trace gases, and - studying the effect of aerosol contamination -of the

stratosphere on Umkehr evaluation.

An all-encompassing meeting, which reviewed all available information on the State of the Stratosphere-1981 was jointly organized with NASA, NOAA and FAA. It drew on the expertise of 109 scientists from 13 countries and its report published as #11 of the Ozone Project series will remain a reference text in this field for years to come. Based on the conclusions of this meeting, the WMO Statement on modification of the ozone layer was revised and released in January 1982.

A concurrence of views on the performances and the needs of the G030S achieved at a WMO meeting in Boulder in 1980 (WMO Ozone Project Report #9) helped in establishing priorities for international ozone activities. Obviously, fundamental to the success of photochemi~al, dynamical and radiatve research of the ozone layer, is the overriding need for high quality compatible data and scientific assessments. Some details on these acttivities executed within the Ozone Project follow.

3. Total ozone The Dobson spectrophotometer is the mainstay instrument in

the global ozone network. WMO has been able to improve this network by a combination of upgrading, and intercomparing Dobson instruments.

reactivating, relocating In the last four years

more than 25 instruments have been improved with international support. Some of the stations involved are: Bracknell, Buenos Aires, Cachoeira Paulista, Cairo, Huancayo, Invercargill, Karachi. Manila, Messina, Mexico City. Mont-Louis. Nairobi. Naples, Natal, Perth, Potsdam. Guetta, Seoul. Seychelles. Sestola, Shiangher. Singapore, St.Helena and Vigna Di Valle.

An innovative exercise to provide information on the relative stability of performances of the Dobson instruments by using seven travelling standard lamps was implemented in collaboration with the World Dobson Ozone Spectrophotometer Central Laboratory operated by NOAA. The first cycle of standard lamp calibrations, completed in 1983, revealed that about two thirds of the Dobson stations require correction of less than 2%. However, about a dozen stations are particularly "noisy". As a result a comparison will be held later this year in Australia, to compare instruments from Japan, Aust~alia and a few other Far East stations.

Complementary to these efforts, the WMO arranged for and published an "Operational Handbook" on Dobson observations by Mr.W.D. Komhyr (WMO Ozone Project Report #6), and a most detailed

- 12-

review Basher

of the accuracy of the Dobson spectrophotometer by Dr.R.E. (WMO Ozone Project Report #13).

4. Vertical ozone distribution Although the importance of continuous and reliable

measurements of the vertical ozone distribution is well recognized, progress in this field has been very slow. Two new stations in Europe have initiated weekly ozone soundings and WMO assisted in the training of the operators. Requests urging all Dobson stations to initiate, when weather permits. standard or multiwavelength "short" Umkehr observations have been made on several occasions without much success. However. one important improvement in the frequency of Umkehr measurements is now being achieved through a joint venture of the EPA. NOAA and CMA to automate seven Dobsons located at: Boulder, Poker Flat-Alaska. Mauna Loa, southern Africa, Haute Provence. Huancayo. and Perth. WMO's assistance was instrumental for the last three stations. In most cases collaboration of nearby lidar operating institutions was assured to allow for, data permitting, aerosol correction of the Umkehr evaluation.

WMO cosponsored the participation of experts at a few field measurement experiments of vertical ozone distribution. using various techniques (e.g. Umkehr, MAST-Brewer, ECC-Komhyr,DASIBI). in Gap(Fr-ance) in 1981, t",ice in Palestine(Texas) in 1983 and again in France in 1983. The data from these campaigns are being reported at this Symposium. The more elaborate NASA-Texas experiments will, in particular, make a major contribution in establishing the performance characteristics of variety of instruments looking into ozone concentratIons in the 30-4Skm layer.

In response to the growing need for knowledge on the behaviour of ozone concentrations in the troposphere. which are obviously increasing, WMO arranged for a six months long comparison of three different physical methods (using wet and dry chemical or optical sensors) carried out by the Hohenpeissenberg Observatory. The results published in Berichte des Deutschen Wetterdienstes #161 by Dr.W. Attmannspacher and R. Hartmannsgruber indicate interference by both water vapor and NOa in some sensors. However, such interference is usually negligible away from industrial centers and traditionally foggy areas. Furthermore, to encourage the studies of tropospheric ozone changes and their possible effect on climate, WMO has arranged for a meeting of experts on this matter to be held in October 1984 in Shanghai.

WMO together with FAA and NASA organised two meetings to evaluate the data from over 60 rocket flights made in October 1979 to determine the performance characteristics of rocket-borne ozonesondes. The report, expected soon should serve as a record of the state of affairs in this field at that time.

S. Ozone trend detection The WMO Executive Committee (May 1980) gave high priority to

studies aimed at clarifying physical processes, if any, which influence ozone trends and the assesment of such trends. Consequently, a meeting of experts was held in Toronto in April 1982 and its report appeared as #12 in the Ozone Project series. It represents a unique account of possible instrumental errors. the combined effect of various natural processes and possible

-13-

anthropogenic influences which makes ozone trend analysis difficult. A methodology, based on local and international calibrations aimed at thoroughly revising the past records of stations with long years of observations was outlined, and some stations such as Belsk have already submitted to the W0 3DC their completely revised data set (N20 years).

6. Climate impact of ozone changes Another major task of the WMO Ozone Project is to encourage

and assist studies which will clarify the possible climatic impact of future changes in the concentrations of ozone and other minor constituents of the atmosphere related to its chemistry. A meeting on this subject was organized at NCAR (September 1982) which reviewed and assessed the current understanding of the trace gas-climate problem and identified areas where there is considerable uncertainty (WMO Ozone Project Report #14). One of the conclusions of the meeting was that the potential cumulative effect of future alterations of minor trace gases (including ozone) could be as large as those estimated as a result of the C02 increase projected for early in the next century. The meeting noted that possible significant effects on the climate sensitivity could occur as a result of changes and/or redistribution of the trace gas concentration with altitude,as is already probably happening with ozone. To clarify the role of ozone and other trace gases in the climate system further studies of tropospheric chemistry-climate interaction and of stratosphere/troposphere radiative-dynamical interactions were recommended. WMO, jointly with the Radiation Commission of IAMAP initiated comparisons of radiative codes used in climate models as an absolutely necessary first step.

7. New ozone absorption coefficients In recent years, a number of studies have hinted at some

ozone measurement inconsistencies which have been attributed to inadequate accuracy in the presently used values of the ozone absorption coefficients. Assessments suggested that the current WMO scale used for Dobson total ozone calculations yield data which are approximately 3% ~oo high. For indirect ozone profile calculations using solar UV wavelengths the change of the absorption coefficients will produce both a change in scale and a change in the shape of the derived profile. Re-determination of absorption coefficients recommended in Ozone Report #9 was initiated by NBS and sponsored by NASA. WMO has supported three meetings to evaluate the preliminary results. and the adoption of the new coefficients is expected shortly after this Symposium. Rather demanding work re-evaluating most of the indirect vertical ozone distribution data will then be necessary.

8. Stratospheric aerosol effect It is well known from theoretical studies that stratospheric

aerosols, introduced usually by major volcanic eruptions. produce serious errors in the evaluation of vertical ozone profiles from Umkehr. and in some cases satellite measurements. In addition. the volcanic SO~ accompanying the aerosols leads to spurious effects in total ozone data which may mask a possible downward trend. ~hen EI-Chichon errupted in 1982, introducing an estimated 30 to 50 Mt of dust and gases into the atmosphere, WMO immediately encouraged the taking of special measurements, and

-14-

provided partial support to scientists from A.E.S.-Environment Canada and NOAA to participate with their instruments in NASA initiated studies. Additionally, WMO contacted a dozen station& with stratospheric aerosol LIDAR programmes asking their collaboration in providing data for 1982/83. The W03DC and NOAA-Boulder will explore a method for correction of the ozone profiles with these data and, if feasible, it would be implemented internationally.

9. Measurements of rare gases Further to the basic review of measurements of rare

atmospheric gases of importance to ozone chemistry (Seattle, WMO Ozone Project Report *5), in 1983 WMO co-sponsored with NASA two informal planning discussions with the emphasis placed on planning simultaneous multi-species measurements.

10. Draft-Convention for Protection of the Ozone Layer Finally, considering that the possible adoption of a

Convention for the protection of the ozone layer (proposed by UNEP and a number of interested States) would be beneficial for the environment as a whole, and inter alia, would have a pronounced positive impact on ozone observations and research, it should be mentioned that WMO provided the briefing on the atmospheric aspects for the first session on the draft-Convention (Stockholm, January 1982) and has participated in all subsequent sessions. Furthermore, the WMO Executive Council in June 1984, noted with considerable interest the efforts of UNEP and stated that it would be prepared to look into the hosting of a permanent secretariat for the Ozone Convention (if and when it becomes necessary).

11. The future It is hoped that in the coming years the WMO Ozone Project

will continue to be ~mplemented as requested by the WMO Ninth Congress (May 1983). The main emphasis will be on upgrading the total ozone observing network, on maintaining and)or initiating vertical ozone distribution measurements, on improving knowledge of atmospheric photochemistry and on basing prediction of ozone trends on firm scientific grounds.

-~-

C HAP T E R

CHEMICAL-RADIATIVE-DYNAMICAL MODEL CALCULATIONS

- Simulation of 03 distribution using a two-dimensional zonal-mean model in tsentropic coordinate

- A GCM study of the transport of heat, momentum and ozone in the stratosphere

Ozone during sudden stratospheric warming a three­dimensional simulation

- A matrix method for calculating photochemical acceleration

- Photochemical acceleration

- Budgets of stratospheric trace gases from 2-D-Model calculations and satellite observations

- A study of the ozone photochemistry in the upper stratosphere using lims data

A theoretical study of the quasi-biennial oscillation in the tropical stratosphere

- Study of the effect of El Chichon Volcanic Cloud on the stratospheric temperature structure and ozone distribution in a 2-D-Model

Aspects of the comparison of stratospheric trace species measurements with photochemical models

- Derivation of OH concentrations from lims measurements

- Lims data: Inferred stratospheric distribution of NO and HO trace constituents and the calculated odd nitrogeft budget x

- The distribution of ozone and active stratospheric species: results of a two-dimensional atmospheric model

- Multiple scenario ozone change calculations: The substractive perturbation approach

- Trends in ozone and temperature structure: Comparison of theory and measurements

- Ozone in the 21st century: increase or decrease?

SHtULATION OF 03 DISTRIBUTION USING A TWO-DIMENSIONAL ZONAL-MEAN MODEL IN ISENTROPIC COORDINATE

MALCOLM KO,l KA-KIT TUNG,2 DEBRA WEISENSTEIN,l and NIEN DAK SZEl

lAtmospheric and Environmental Research, Inc. Cambridge, Massachusetts

2Department of Mathematics Massachusetts Institute of Technology

Atmospheric and Environmental Research, Inc. 840 Memorial Drive

Cambridge, Massachusetts 02139 U.S.A. (617) 547-6207

ABSTRACT

We present a two-dimensional zonal-mean model formulated in isen­tropic coordinate in which advection of trace gases is driven by the diabatic circulation calculated from the diabatic heating rate. The eddy diffusion portion of the transport arising from the motions of the transient waves is assumed to be restricted in the horizontal direction along the isentropic surfaces. Thus, transport in the model is speci­fied if the diabatic heating rate and one single diffusion coefficient Ky are given. In our previous work, we demonstrated that such a simple moael with essentially two transport parameters can successfully simu­late many of the observed features of N20, HN03, and NOY in the strato­sphere. In this work, we present the result of the simulation of 03 using the full 0x-HOx-NOx-Clx chemistry. Compared to results from con­ventional models using large eddy diffusion coefficients, the calculated column abundance of 03 in the new model shows a stronger equator to pole gradient as well as larger seasonal variations at the high latitudes, features which are in better agreement with observations. Further im­provement of the model can be made pending refinement of the diabatic circulation, addition of seasonal and latitudinal dependence of K_ , and analysis of the possible importance of chemical eddies. yy

1. INTRODUCTION

One difficulty associated with the formulation of a 2-D zonal-mean model of tracer transport is to determine a set of values for the eddy diffusion coefficients which are consistent with the mean meridional circulation. Recent developments in Generalized Lagrangian Mean (Andrew and McIntyre, 1976; Matsuno, 1980), residual mean circulation (Holton, 1981), and isentropic coordinate formulation (Tung, 1982) indicate that the diabatic circulation is responsible for the net zonal-mean advection and that the origin of the eddy term may be traced to zonally asymmetric transient wave motions.

In earlier modeling work using the diabatic circulation (Pyle and Rogers, 1980a; Miller et al., 1981; Garcia and Solomon, 1983; Guthrie et al., 1984), the physical basis of eddy diffusion term remains unspeci­fied. Subsequent works help to clarify the effect of eddies arising from chemical eddies (Pyle and Rogers 1980b, Rogers and Pyle 1984), and transient waves (Tung 1982, 1984). Tung (1984) estimated that the hori­zontal diffusion along the isentropic surfaces should dominate over dif-

Ozone Symposium - Greece 1984 - 19-

fusion in other directions, and that the magnitude of the horizontal diffusion coefficient K should be ~ 3 x 10 9 cm2 s-l, about an order of magnitude smaller than the values adopted in most previous 2-D model calculations. This seems to suggest that the effect of eddy diffusion on tracer transport arising from transient waves might be smaller than that of the diabatic circulation. In a subsequent model study, Ko, Tung, Weisenstein, and Sze (KTWS) (1984) demonstrated that the atmospheric distributions of N20 and HN03, simulated in a model with diabatic circulation and small ~'y' are in good agreement with observations. They also found that certain features, such as the calculated column density of HN03, are sensitive to the adopted value for~, with values in the range of ~ 1-3 x 10 9 cm2 s-l giving results closest to the observation. In this paper, we present some of our preliminary calculations on the simulation of the 03 distribution using the model in isentropic coordinate and full chemistry.

2. HODEL DESCRIPTION

In this model, the distribution of the trace gases are obtained by solving the zonal-mean continuity equation

at - at - at a ( 2 at) - = -v cos<f> - - w -- + - K cos <f> - + P at ay e aPe ay yy ay

(1)

where Pe is the equilibrium pressure coordinate that is used in place of the potential temperature as the vertical coordinate. The detail formu­lation of the model is described in KTWS (1984). Briefly, the model is formulated in isentropic coordinate where the zonal-mean ciruclation is calculated from the d~abatic heating rate which is specified as a func­tion of altitude, latitude, and season based on the values given by Mur­gatroyd and Singleton (1961), Dopplick (1979), and Wei et al. (1982). As indicated in equation (1), the number of eddy diffusion coefficients is reduced to a single horizontal diffusion coefficient representing diffusion along the isentropic surfaces (Tung, 1982, 1984). At the pre­sent stage of development, the value of ~y in the stratosphere is taken to be constant, independent of latitude, altitude, and season. Based on our previou~ result on N20 and HN03, we have selected a value of ~y = 2 x 10 9 cm 2 s 1 in the stratosphere for this experiment. The values tor Kyz and Kzz are taken to be zero. In order to includ= mixing in the troposphe~e, we have included a value of 1 x 105 cm s 1 for Kzz and 5 x 10 9 cm 2 s 1 for ~y in the troposphere. These values, which are chosen on the basis of our analysis of the model calculated surface mixing ratio for CFC-l1 and CFC-12, give the appropriate inter-hemispheric transfer rate as defined by the ALE data (Prinn et al., 1983). Equation (1) is solved in finite difference form using the scheme from Smorlarkiwicz (1983), which assures numerical stability without intro­ducing large numerical diffusion.

The chemical content of the model and the treatment of photochemical production/loss are as described in Ko, Sze, Livshits, McElroy, and Pyle (KSLMP) (1984) with the reaction rates updated to the NASA/JPL (1983) re­commendation. The values of the 02 cross section in the Herzberg contin­uum are taken from the recommendation of Herman and Mentall (1982). The model includes the full range of interactions coupling the oxygen-hydro­gen-nitrogen-chlorine species with appropriate treatment for the diurnal variations of the species. The boundary conditions on the trace gases are as described in KSLMP. The procedure described in KSLMP is used to simulate the trace gas distribution of the present-day atmosphere.

- 20-

The temperature, which is involved in the transformation to the isentropic coordinate as well as in the calculation of temperature dependent reaction rates, is taken from Harwood and Pyle (1977) and is the same as the one used in KSLMP.

3. RESULTS

To focus on the effect of the diabatic circulation, we have per­formed two sets of model calculations using the KTWS transport scheme. (referred to as model I) and the KSLMP transport scheme (referred to as model II). The KSLMP scheme used calculated circulation (Harwood and Pyle, 1977) which corresponds to the zonal-mean circulation in pressure coordinate and eddy diffusion coefficients Kyy , Kyz , and Kzz from Luther (1973) •

It is clear from eq. (1) that the distribution of 03 is affected directly by the effect of transport when the photochemical time scale is longer than the transport time scale. However, transport can also affect 03 by changing the photochemical term through its effects on ~he elY and NOY species and their respective precursors. To isolate the direct ef­fect of transport on 03, we performed an additional experiment in which only hydrogen chemistry is included. Since the concentration of stratospheric water vapor is held fixed at 5 ppmv in the model, the HOX concentrations are not directly affected by transport. The resulting distribution of the column abundance of 03 from model I for the 0x-HOx atmosphere is shown in Figure la. For comparison, the corresponding result calculated using the KSLMP transport scheme (model II) with the exact same chemistry is given in Figure lb. In comparing the results of the two models, we note that the KTWS scheme gives a much larger latitudinal contrast than the KSL~W scheme. The seasonal variation at high latitudes is also somewhat larger. There is very little hemi­spherical asymmetry in the KTWS model. This is to be expected since the diabatic circulation is parameterized to be symmetric with seasonal, and that there is no seasonal or latitudinal dependence in the eddy diffusion coefficients. The small difference between the hemispheres may be attributed to the asymmetry in the adopted temperature distribution which may affect the photochemical rates and the positions of the isentropic surfaces relative to the pressure coordinate.

Figure 1. Model calculated column density of 03 (Dob­son Units) using Ox­HOx chemistry. The result in Figure (a) is calculated using the diabatic circu­lation with small

~'~J~F~M~'~M~J~J~'~S~O~H~D """'".

J , ... A M '" J A $ 0 N 0

"""""

K, (KTWS, 1984). T~~ result in (b)· is obt·ained using the KSLMP (1984) trans­port scheme which

(a)

employed the calculated zonal-mean (Harwood and Pyle 1977) and values (1973) •

(b)

circulation in pressure coordinate of ~y' K~z' and ~z from Luther

- 21-

Figure 2a shows the calculated column abundance of 03 uSing the full chemist~y (model I). Again, the correspondin~ result from model II is given in Figure 2b for comparison. Model I overestimates the 03 abundance by about 10% at the equator and 20% at high latitudes. AL­though model II (Fig. 4) gives a calculated 03 column abundance to with­in a few percent of the observed value at high latitude spring maximum, it overestimates the abundance at the equator by about 20% and shows no seasonal contrast at the high latitudes. The latitudinal and seasonal contrasts produced in model I are more in accord with the observation than the result from model II.

(a) (b)

Figure 2. Same as Figure 1 except the results in figures (a) and (b) are calculated using the full Ox-HOx-NOx-Clx chemistry.

Figure 3 shows the calculated latitude-altitude cross sections of 03 for different seasons for model I. Th~ result is presented in pres­sure coordinate for easier interpretation. Compared to the recent ob­servation reported in' McPeters et al. (1984), the calculated peak den­sity of close to 12 ppmv is slightly too high. However, the general features appear to be in good agreement. Compared to the result from model II (not shown), results from model I show much steeper downward sloping of the mixing ratio surfaces and more severe intrusion of tropo­spheric air in the lower stratosphere. These features account for most of the difference in the calculated column abundance in the two models.

0, ,

CD 1.0

~ w § 10 ., .. w if '00

JANUAFty

--,~; __ 2~j

~=-'~: ~0 1 ~;

APRIL

- '---J:::-'-:;;-.-@~2{ ~ 2 '

~,o.~,

. . . toc!?lO 10 3Q 0 30 eo eo 60 30 0 '0 00 00

LATlTUoE (OEO.) LATinJOE (OEG,)

JULV OCToeER

~'---""'" -'-:.r--' __ __ 2~

~.=--- -----.~

&~ ~C';0 ~: ~' ~~ '2~.~

-eo -30 0 '0 eo .. -60 - 30 0 '0 '0 •• LA T'TlJOE tOEG.! LATiTUDE (OEG.)

Figure 3. Model calculated latitude-altitude behavior of the mixing ratio of 03 (ppmv) for different seasons. The result is calculated using the transport, scheme described in KTWS (1984).

4. CONCLUDING REMARKS

In this paper, we presented some of the preliminary results on the calculated distribution of 03 using a model with diabatic circulation ana small value for the horizontal eddy diffusion coefficient. Compared to the result from the KSLMP scheme which uses the observed zonal-mean circulation in pressure coordinate and large values of eddy diffusion,

- 22-

the present model shows large latitudinal and seasonal contrasts in the calculated column abundances of 03, in better agreement with observa­tion. In this work, we did not include the effect of chemical eddies (Rogers and Pyle, 1984) which may be important. Further refinement of the diabatic heating rate and possible seasonal and latitudinal de pen­~:~c~O~!l~~y should further improve the diagnostic ability of present

5. ACKNOWLEDGEMENT

The work is supported by the Fluorocarbon Program Panel of the Chemical Manufacturers Association.

6. REFERENCES

Andrews, D. G., and M. E. McIntyre (1976) J. Atmos. Sci., 33, 2031-2048. Dopplick, T. G. (1979) J. Atmos. Sci., 36,-1812-1817-.-Garcia, R. R., and S. Solomon (1983) 1..Geophys. Res., ~, 1379-1400. Guthrie, P. D., G. H. Jackman, J. R. Herman, and C. J. Mcquillan (1984)

A Diabatic Circulation Experiment in a Two-Dimensional Photochemical Model. J. Geophys. Res., in press.

Harwood, R. S-:-, and J. A. Pyle (1977) Quart • .:!.. Roy. Meteor. Soc., 103, 319-343.

Herman, J. R. and J. E. Mentall (1982) 1.. Geophys. Res.,~, 8967-8975. Holton, J. R. (1981) 1.. Geophys. Res., ~, 11989-11994. Ko, M. K. W., K. K. Tung, D. Weisenstein, and N. D. Sze, (1984) A zonal­

mean model of stratospheric tracer transport in isentropic coordi­nates: Numerical 'simulations for nitrous oxide and nitric acid,.:!.. Geophys. Res., in press.

Ko, M. K. W., N. D. Sze, M. Livshits, M. McElroy, J. A. Pyle (1984) The seasonal and latitude behavior of trace gases and 03 as simulated by a two-dimensional model of the atmosphere, J. Atmos. Sci., in press.

Luther, F. M.(1973) AIAA paper 73-498, AIAA/AMS: Conference, Denver, CO. Matsuno, T. (1980) Pure and Applied Geophysics, 118, 1899-216. McPeters, R. D., D. F. Heath and P. K. Bhartia (1984) 1.. Geophys. Res.

89, 5199-5214. Mille~ C., D. L. Filkin, A. J. Owens, J. M. Steed, and J. P. Jesson

(1981) 1.. Geophys. Res., ~, 12039-12065. Murgatroyd, R. J., and F. Singleton (1961) Quart. J. Roy. Meteor. Soc.,

87,125-113.' -NASA/JPL (1983) Chemical Kinetics and Photochemical Data for Use in

Stratospheric Modeling Evaluation Number 6. IPL publication 83-62. Prinn, R. G., P. G. Simmonds, R. A. Rasmussen, R. D. Rosen, F. N. Alyea,

C. A. Cardelino, A. J. Crawford, D. M. Cunnold, P. J. Fraser, and J. E. Love lock (1983) 1.. Geophys. Res., ~, 8353-8367.

Pyle, J. A., and C. F. Rogers (1980a) Nature, 287, 711-714. Pyle, J. A., and C. F. Rogers (1980b) Quart • .:!.. Roy, Meteor. Soc., 106,

421-446. Roger, C. F., and J. A. Pyle (1984) Quart • .:!.. Roy, Meteor. Soc., 110,

218-237. Smorlarkiwicz, P. K. (1983) Mon. Wea. Rev., 111, 479-487. Tung, K.-K. (1982) J. Atmos.~i.~9,~30-2356. Tung, K.-K. (1984) ][n nynamicEi()f t~Middle Atmosphere, Terra Scien­

tific Publishing, Japan, 412-444. Wei, M. Y., D. R. Johnson, and R. D. Townsend (1983) Tellus, 35A, 241-255.

- 23-

ABSTRACT

A GCM STUDY OF THE TRANSPORT OF HEAT, MOMENTUM AND OZONE IN THE STRATOSPHERE

D. CARIOLLE and M. DEQUE Centre National de Recherches Meteorologiques, EERM F-31057 Toulouse cedex, France

We have developed an accurate and computationaly efficient parameterization of the ozone photochemistry based on detailed calculations from our two dimensional photochemical model. When this scheme is introduced in our GCM many features of the obser­ved 0 3 behaviour are reproduced . In the winter Northern Hemis­phere the transport of heat, momentum and ozone in the upper stratosphere is mainly due to the standing planetary waves, whereas below 50 mb the role of transient waves of tropospheric origin becomes important. Perhaps the most apparent success of the simulation is the ability of the model to generate medium scale waves often observed in the Southern Hemisphere and to reproduce their characteristic signal on the total ozone distri­bution.

DESCRIPTION OF THE SPECTRAL GCM

The model formulation is closely derived from the operatio­nal spectral model used for weather forecasting at the lIDirec­tion de la Meteorologie ll in France ( Rochas et al,1980) and also used as a global general circulation model GCM at EERM for the study of tropospheric climate (Royer et al, 1983).

It is based on the primitive equations of the atmosphere written in vertical hybrid coordinate: ~*= ~=~; for p)p:=189 mb and (f~= p for p<p (p: pressure ,p : surface pressure, P:r.: in­terfacial pressure) and solved usin~ the spectral method, The

prognostic variables are surface pressure, velocity stream­function ~ and potential ?C,temperature T, water mixing ratio q and the ozone mixing ratio ro.. for each of the 28 vertical levels.

The chosen discre~zation ~llows good resolutions in the troposphere ( 8 levels) and in the stratosphere (16 levels).

Each variable A(A,~) is expanded in Laplace series A(A,,,,,,)=¥F.:'Y;::('X'f-)' where Y:are normalized spherical harmonics with longitudinal wavenumber m and latitudinal index n.Variables expansions are substituted into the primitive set of equations and solved for a truncation of the lItrapezoidal ll type S 10-13 (m <: 10, n ~ 13). Non-linear terms, including physical and chemi­cal parameterizations are computed on the latitude-longitude 11 Gaussian ll grid associated with the chosen truncation. It has 20 latitude circles ( pseudo-equidistant in latitude~4r-8.8-§.7° between 83.3 0 Nand S) with 32 points equidistant in longitude (4)- =11.~5°).

In the troposphere, physical parameterizations include a diurnal radiative cycle and an hydrologic cycle with interactive cloudiness. In the stratosphere the radiative tendency is intro­duced using a simple Newtonian cooling approximation, the ozone production and loss rates are computed using the scheme descri­bed below. A more complete description of the model may be found

Ozone Symposium - Greece 1984 - 24-

in Cariolle and D~que (1984).

DESCRIPTION OF THE OZONE MODEL

In our past study of the stratospheric ozone budget using photochemical models ( Cariolle, 1983) we have found that the various catalytic cycles which control the 0 concentration interplay in a non linear manner, especial19in the lower stra­tosphere. However explicit calculations of the ozone photoche­mical relaxation time ( defined as _(;~-Lr~ if P and L are the photochemical production and loss ratesY~show that the ozone net production and loss varie in a quasi-linear manner for a wide range of 0 1 variations. For instance less than one percent difference was :round between (P-L) (ro, +6ro~ )-(P-L) (ro'!» and Ol~).6 rOJ for ~I~ 20%. We have therefore developed a linearized scheme where r~erence fields and partial derivatives are derived from careful computations and outputs of our 2D photochemical model (Cariolle and Brard,1984). If we consider that the local production and loss rates of 0 depend on three variables: the ozone mixing ratio, the temper~ture because of the temperature dependence of the chemical rates, the optical depth which depends only on the total number of O~ molecules above the local point (~03=r ~ r~dp); we can writ.e:

J) .toJ = ( P _ L) (~ , fA-, P. ) = ( P _ L )2.1> (>' "p ) "J> I:: +(;P,,:Lf(},:p) l-r;(>,·,p)+ro,,(}"f'P)1 "simple relaxation"

+('\",:Lf(A,p) \:-T (X,p)+T (}.,J-L,p)] "temperature effect"

+( ~i~)~(A'f» f!.03(,>"f>~ ~03(A,fL'P)J "mask effect" where the fields marked 2D varie with latitude, pressure and season.

We found less than 10% difference in the ozone con-centration at any level between a long term integration of the 2D model using the above scheme and a full chemistry integration. We think that our parameterization is therefore more accurate than most of the schemes previously introduced in GCM.

RESULTS The model has been integrated from rest for 90 days with

January boundary conditions and solar elevation. The ozone mixing ratio has been initialized at day 30 with a latitude-pressure varying field identical for all longitudes (Figure 1 ). Analysis of the results is carried out for the last 30 days of the inte­gration.

After 45 days of ozone advection, the zonally averaged cross section show a strong photochemical production in the summer Sourthern Hemisphere and significant 03 transport at high lati­tude in the winter lower stratosphere ( Figure 1 ). Figure 2 shows the zonally averaged total ozone content as compared to initial and climatological distributions. In the S H the devia­tion between calculation and observation is less than 10%, where­as in the NH the differences are larger but the model is still far from equilibrium.

In the winter upper stratosphere the transport of momentum, heat and ozone by the quasi-stationary planetary waves dominates but below 50 mb the transient motions play an important role.

- 25-

:J lJi vi 5. 0 LtJ a:

200

soo

5

iJJ

a: 20 :J VI Ui W50

a: (liDO

200

500

SH

---------------------j---------

INITIAL

80 70 60 50 C;O 30 20"-CJ 0 lO 20 30 40 50 60 70 80

LRTITUDE

-

DAY +45

80 70 60 50 40 30 20 lO 0 lO 20 30 40 50 60 70 80

LRTITUDE NH SUMMER WINTER

Figure 1. Initial ozone distribution as a function of pressure and latitude (upper part of the figure). The lower cross section shows the zonally averaged distri­bution after 45 days of model integration.Note the large 03 production in the SH and the increase due to transport at high latitudes in the NH.

- 26-

400 TOTAL OZONE (DOBSONS)

, , '\Initial

, , 200~-"~--~--~--~--~--~--~--~~-'---

N 80 60 40 20 0 20 40 60 80 S LATITUDE

Figure 2. Zonally avera­ged total ozone content for initial distribution, after 45 days of integra­tion and observation.

In particular, substantial transport occurs in a zonal wave number 2 episode during which the main polar vortex breaks into two small vortex. It is important to note that this event occu­red during a blocking sequence of the tropospheric flow. Thus, links between upper tropospheric circulation and 0 1 distribution are very important and a strong correlation is always found between the total 0 1 field andthe 100 mb geopotential field.,in agreement with obsefvation. .

In the summer SH the role of the standing planetary waves is lessened. The ozone variability results from the action of transient waves and especially of medium scale waves. For ins­tance, the model is able to reproduce the pentadiagonal struc­ture ( wave number 5 dominant ) often observed during the summer 1979 in the geopotential fields ( Salby,1982) and also clearly visible in the total ozone SBUV measurements (Schoeberl and Krueger,1983). The model reproduces also episodes with dominant wavenumbers 4 and 6, in agreement with observation.

CONCLUSIONS We have shown that many observed features of the stratos­

pheric dynamics and ozone distribution are reproduced by our spectral GCM with parameterized ozone photochemistry. However we certainly need a simulation of at least one full seasonal cycle to make a more comprehensive model validation.

REFERENCES Cariolle,D. The ozone budget in the stratosphere:Results of a

one dimensional photochemical model.Planet.Space Sci.31, 1033-1052,1983.

Cariolle,D.and D.Brard.The distribution of ozone and active stratospheric species:results of a 2D atmospheric model. This Symposium,1984.

Cariolle,D.and M.Deque.Presentation d'un MCG couple troposphere stratosphere.Note de travail de l'EERM,79,1984.

Rochas,M. et alii.Presentation d'un modele spectral de simulation des mouvements atmospheriques a grandes echelles.Note tech­nique de l'EERM,76,1980.

Royer,J.F.,Deque,M.,and Pestiaux,P.Nature 304,44-46,1983. Salby,M.L.A ubiquitous wavenumber-5 anomaly in the southern

hemisphere during FGGE.Mon.Wea.Rev.110,1712-1720,1982. Schoeberl,M.,r.and A.J.Krueger. Medium scale disturbances in

total ozone during southern hemisphere summer.Bull.Amer. Meteor.Soc.,64,1359-1365,1983.

- 27-

1. INTRODUCTION

OZONE DURING SUDDEN STRATOSPHERIC WARMING

A THREE-DIMENSIONAL SIMULATION

by K. ROSE Institute fur Meteorologie Freie Universitat Berlin - FRG

and G. BRASSEUR Institut d'Aeronomie Spatiale 1180 Brussels - Belgium.

Sudden warmings which are currently observed in the winter strato­sphere are believed to be due to the upward propagation of planetary waves originating in the troposphere. Major warmings are characterized by local increases of the temperature in a deep layer beyond the strato­pause with values of the order of 50 K at 10 mbar appearing over a short period of time (a few days) and leading to significant changes in the rate constant of seyeral chemical reactions. During such events, the dynamical fields in the stratosphere are completely altered, so that dramatic changes in the transport of trace constituents are expected.

The purpose of this short note is to report preliminary results of a 3-D model simulation of the ozone behavior during winter in connection with the appearance of a stratospheric warming. This paper will con­centrate mainly on the middle stratosphere (12 mb or approximately 32 kID) where the chemical lifetime of odd oxygen is quite long and consequently transport plays a major role. Further studies will deal with the response of ozone at higher altitude (where the direct relation between ozone chemistry and temperature becomes more important) and extend into a 3 dimensional frame the previous 2-D studies of Hartmann and Garcia (1979) and Kawahira (1982).

2. BRIEF MODEL DESCRIPTION

The 3-D dynamical model which is used in the present study is described by Rose (1983). It is based on the so-called primitive equations which are solved using a finite difference technique in a space of grid-points with a longitudinal interval of 22°5, a latitudinal interval of 5° and a vertical resolution of 3 kID. The model is hemi­spheric and extends from 10 to 80 kID altitude. Diabatic processes are parameterized using a Newtonian cooling approximation. In order to simulate the propagation of planetary waves, a wavenumber 1 and 2 forcing in the geopotential height is imposed at the lower boundary.

The distribution and evolution of ozone is derived by solving for odd oxygen a continuity equation (see e.g. Brasseur and Solomon, 1984). The chemical source term takes into account the production of odd oxygen by photodissociation of O2 and its destruction by direct reco~bination

Ozo'ne Symposium - Greece 1984 - 28-

of 0 and 03 as well as the loss due to the presence of odd hydrogen and odd nitrogen. In the present stage of development of the model, the water vapor (H20) and odd nitrogen (NO = NO + NO ) content is specified by a given mixing ratio (5 ppmv for H~O and an altitude dependent v3lue for NO ). Photochemical equilibrium conditions are assumed for O( P), O( D), xH, OH and H02 . Moreover, N02 is assumed to be in immediate equilibrium with NO. The model does not yet consider any diurnal variation in the solar illumination and consequently in the photo­dissociation rates, which is a good approximation for the low levels under consideration, where the photochemical lifetime of odd oxygen is much longer than a day. Further development of the model will include longitudinal variations in the source term instead of a zonally averaged value, as in these preliminary calculations.

3. RESULTS

In order to perform an initialisation of._ the odd oxygen distribution, we first run the chemical model for 25 days with the initial temperature field of the dynamical model. After this initia­lisation, a numerical simulation of a sudden stratospheric warming is started and performed as described in detail by Rose (1983).

0

30

OO~ mbar) 0.011

0.046

0.192

0.803

3.350

13.98

58.34

243.4

OON

~ig. 1.- Meridional cross section of the difference in the mean zonal temperature at day 21 relative to the initial state (oK).

- 29-

At day 21 of this simulation, the zonal mean temperature between 30 km and 35 km near the pole has increased by 32°K as compared to the initial state (fig. 1). As in the real atmosphere, a simultaneous cooling in the stratosphere at low latitude and in the mesosphere at high latitude is observed. This change of the mean state corresponds to a southward displacement of the polar vortex (fig. 2), which had its center directly upon the pole in the zonally symmetric initial conditions. The 03 mixing ratio, which, had also a minimum value directly upon the pole in the initial distribution at 12 mbar and which behaves as a perfect tracer in the polar night at the altitude of the 12 mbar level (fig. 3) reveals that the polar vortex might be inter­preted as a material entity, since the air parcels with low 03 mixing ratio remain in the center at the displaced vortex (cf. fig. 2). Air of relatively high 03 mixing ratiQ is advected counterclockwise around the polar vortex lead~ng to higher values in polar latitudes. In the further course of the simulation, the polar vortex is split and air from the region of highest 03 mixing ratio is advected across the pole. At day 21, the region of small gradients in both, geopotential height and 03

Fig. 2.- Geopotential height (gpdam) for the 12 mbar level at day 21.

- 30-

Fig. 3.- Isopleths of 03 mixing ratio at the 12 mbar level at day 21 (10 ppm).

mixing ratio, seems to be the location where mixing of polar air and aLr from the lower latitudes takes place. So, according to ideas of McIntyre (1982), the southward displacement of the polar vortex is not a reversible moving to and fro, but rather the result of nonconservative upward propagating waves.

The meridional cross section of the percentage change of 03 mixing ratio relative to the start of the simulation (fig. 4) displays a nearly overall increase of 0 in the model atmosphere below 60 km. While the large changes north ol 60° N are due to transport the slight increase south of 30 0 N is probably connected with the temperature decrease, which leads to a somewhat lower O~ destruction rate . Thus, a sudden strato­spheric warming, as simulate-d in the present model, leads to an hemi­spheric increase of 03 in the middle atmosphere up to 60 km.

ACKNOWLEDGMENT

We would like to thank E. Falise for his very .efficient help in preparing computer programs.

- 31-

(km) 90 eo 70 50 50 40 30 20 10 Oo~ mbarl

80.0 0 .011

70.0 0.046

60,0 0

0 .192

0.803

3.350

30 13.98

2elO 58.34

lelO 243.4

SK> 80 70 60 50 40 30 20 10 OON

'Fig. 4. - Meridional cross sec tion of the percen tage change of the 03 mixing ratio relative to the first day of simulation (the large increase near 65°N and 40 km is due to a local minimum in the initial state).

REFERENCES

BRASSEUR, G. and S. SOLOMON, Aeronomy of the middle atmosphere, D. Reidel Publ. Cy., Dordrecht, Nederland, 441 pp.

HARTMANN, D.L. and R.R. GARCIA, A mechanistic model of ozone transport by planetary waves in the stratosphere, J. Atm. Sci., 36, 350-364, 1979. --

KAWAHIRA, K., A two-dimensional model for ozone changes by planetary waves in the stratosphere. I. Formulation and the effect of tempe­rature waves on the zonal mean ozone concentration, J. Met. Soc. Japan, 60, 1058-1062, 1982.

McINTYRE, M.~, How well do we understand the dynamics of stratospheric warmings ? J. Met. Soc. Jap., 60, 37-65, 1982.

ROSE, K., On the influence of non linear wave-wave interaction in a 3-D primitive equation model for sudden stratospheric warmings, Beitr. Phys. Atmosph., 56, 14-40, 1983.

Summary

A MATRIX METHOD FOR CALCULATING PHOTOCHEMICAL ACCELERATION

J.D. HAIGH Centre for Remote Sensing

Imperial College of Science and Technology London SW7 2AZ

A fast, accurate method for calculating photochemical acceleration is presented. Using this scheme the deviation of the solar heating rate from its equilibrium profile may be found as a function of the temperature per­turbation at all heights. Thus the method may be used for small vertical scale perturbations. The inclusion of the ozone 9.6~m band into the heating rate calculations is shown to significantly reduce the photochemical relaxation rate above 40km.

Introduc t ion

In the stratosphere the thermal structure and ozone concentration are stro~gly interdependent. As first pointed out by Craig and Ohring (1) the heating due to the absorption of solar radiation by ozone, locally positively correlated with ozone c~ncentration, will be reduced as the ozone itself, locally negatively correlated with temperature, reacts to the changing thermal structure. Because it increases the rate at which a temperature perturbation will relax back to the equilibrium state this effect has become known as 'photochemical acceleration'.

Expanding the solar heating rate Q at height z around an equilibrium temperature Te we have:

Q (T, z) = Q (Te , z) + (~) Te (T(z) - Te(z»

where it is assumed that Q responds only to local temperature perturbations. Numerical models of stratospheric dynamics often do not include photochemi­cal schemes and use fixed ozone profiles to calculate heating rates. Photo­chemical acceleration is represented by an additional term in the thermo­dynamic equation of the form - a(z) (T(z) - Te(z» where the relaxation coefficient a = -(dQ/dT)Te (i). It is the assumption of local response and the form required for a that are discussed in this paper.

2 Theory

The solar heating rate per unit volume at height z is given by: Q(z) = dF(z)/dZ where the solar flux F(z) = F(oo)exp(-:t(O~O~(Zl) + 0303(Zl»dzl) and 03,02 are the cross-sections of 03 a~d O~. (For simplicity here the integration over wavelength and dependence on ignored). The change in heating rate oQ in response to 503 is given by:

oQ(z) = d (OF(z» =

az

] z

zenith angle are a change in ozone

( ii)

The'first term on the right hand side of equation (ii) represents changes

Ozone Symposium - Greece 1984 - 33-

in Q due to local changes in 03. If it is assumed that changes in 03 result only from local changes in temperature this term becomes Q(z) 003(Z) = Q(z) aos oT(z) -Q(z) C(z) oT(z)/T2(Z) where C(z) is the ~ Os(z) aT

03 temperature coefficient (see e.g. Barnett et al (2)) ) cI... has its conven­tional value of QC/T2 and C is often assumed independent of height. The importance of the second term in eq.(ii), which represents changes in Q due to changes in the solar flux at z caused by 03 perturbations at higher altitudes, has been recognised by Strobel (3) and H~ann(4). These authors found a maximum reduction in aof around 25% at 40 km.

3 Matrix Method

The equilibrium ozone concentration may be expressed (see Ref.(2)) as Ose(z) = a(z) k(z) J(z)S where a is a temperature independent coefficient, k represents the temperature dependence of the reaction rates, J represents the ratio of the photodissociation coefficients of 02 and Os and S is a fraction lying between 0.5 and 1.0. This simplified expression for 03e is used here to enable the separation of the perturbations to k and J which is necessary for this analysis. The neglect of the non-linear terms may be justified a posteriori by the accuracy of the results. Hence 003 = 03 (ok/k + SoJ/J). Now k(z) = exp (c(z)/T(z)) so ok/kdT= -c(ZYT(Z)2 = -'(f(z). ~e may take J(z)=J(oo)exp { -1 (0202 + 0 s03)dz 17 so oJ/J = - 0s J.. 003dz1 • 00 z J Thus 003 = 03 (- Y oT - b J 003dz1) (iii) where b S03. Inserting

z this expression into equation (ii):

oQ(z) = Q(z) (":Y(z)oT("z.)- (b+03) 1003 (zl)dz1)

Expression (iii) may be used repeatedly for 003. In finite difference form·

oQi = Qi{-;{icSTi - (b+03) ~',fZjOSj [ - YjOTj - b ~y~Zk03k (- ~\OTk- . • J]? where N is the top level ,1-" k',j ~ •.• indicates additional summation until the lower limit is N ~I indicates that the first term in the series should be halved. Define

~ Xi = ii03i cSTi ; ti = b 03i~z ; si = 0303i~z

oQi =_QjXj + Qi(si+ti) ~i(~ - tj~j(~- tk~k(~- ... ))

03i 03i where x. is a vector with elements Xi and ~i is a row elements are unity, next element is ~ and remainder

cSQi = - QiXi + Qi(si+ti) ei (I - r + r 2 03i 03i

matrix whose first N-i elements zero.

+ (_r)N) X (iv)

where I is the unit matrix and r is a diagonal matrix whose i th row is tiBi. Note that higher powers of r imply higher orders of element optical depth t (presumed «1). Equation (iv) may be written in matrix form Q = -A oT (v) which relates the change in Q at all heights to the change in T-at all-­heights. A is the matrix equivalent of the photochemical relaxation para­meter~: its diagonal elements correspond to the expression for ~ in equation (ii) with 003 = -tOT and 003/03 (Zl F z) = 0, its below diagonal

03 elements contain sums of powers of element optical depths and its above diagonal elements, in the case of no scattering, are zero. It should be possible to calculate A for a given Te , latitude and season and use it to

- 34-

calculate oQ for any temperature structure. It is also anticipated that the matrix canbe made more general by reducing its latitudinal and seasonal dependence.

4 Calculation of the Matrix

Using a detailed photochemical scheme incorporating the major reactions of about twenty-five species of importance in the stratosphere (Pyle, personal communication) and radiation schemes as described by Haigh (5) equilibrium temperature and ozone fields were found using an Adams­Bashforth time stepping scheme. Profiles of Te and diurnally averaged Qe for the equator under solstice conditions are shown in Fig.1. Also shown is the ozone temperature coefficient C.

By perturbing the temperature profile from Te and recalculating Q with and without chemical coupling values for the photochemical acceleration may be obtained. In the case of the inclusion of the ozone feedback the calculation was allowed to proceed until a new equilibrium was reached.

If N calculations of oQ for N profiles oT are available equation (v) may be expressed: OQ = ~AoT where OQ, o~are square matrices. In particular if OT = I, the unit matrix, then A = - oQ. This approach has been adopted in this work with N = 13 levels equally spaced in log (pres­sure) between 105mb and 0.26mb. There is not space to reproduce A here but as expected the diagonal elements are positive and large and the below diagon~l elements negative and of smaller, but significant, magnitude. There are non-zero above diagonal elements due to the diffuse upward beam of solar radiation produced by the inclusion of scattering in the radiation schemes.

5 Inclusion of the Ozone 9.6~m Band

In the upper stratosphere infrared cooling is due mainly to the C02 15~m band but the 9.6~m band of 03 also contributes. As cooling by the latter depends on the ozone concentration it is subject to a similar type of coupling as is the solar heating. In this case, however, there is a positive feedback loop as lower temperatures lead to increased ozone and hence to larger cooling rates. Included in the net heating this will tend to reduce the photochemical acceleration term. For the calculation described in Section 4, in order to compare the results with those of previous authors, the 9.6~m cooling was not recalculated for the perturbed profile. Another matrix has been calculated which includes this coupling. In comparison with the matrix of Section 4 its main features are smaller diagonal elements and more above diagonal elements - reflecting the transfer of thermal radiation between atmospheric levels.

6 Results

Using the matrices with and without the 9.6~m coupling the change in net heating rate due to photochemical acceleration was calculated for a perturbation from the equilibrium profile of (a) a uniform 1K and (b) a wave with amplitude 1K and vertical wavelength 1 pressure scale height (two grid spacings). The results, expressed as an equivalento(= (A oT) / oT(z) are shown in Fig.2. Also shown is 0( calculated using the -- z method of Strobel (6). This method, while fast and fairly accurate for large vertical scale perturbations, is not suitable for waves of smaller vertical scales. The results of Strobel's method and the current method (with no 9.6~m effect) for a uniform perturbation compare well between 40 and 50km. Above 50km Strobel's method produces higher values probably

- 35-

reflecting the simplified chemistry and constant temperature coefficient used. Below 40km Strobel's method is not applicable because of large optical depths. The peak value of for uniform perturbation is about 0.065 d- 1 which is a significant addition to .. he N.~wtonian coc-ling coefficient which, in the upper stratosphere, is of the order of 0.2 d- 1

for uniform perturbation. The effect of including the 9.6~m coupling is to reduce ~ by up to 0.015 d-1 with especially significant effect around 43km.

For the short wavelength perturbations ~ has much higher values corresponding to the no extinction case of Hartman (4).

7 Conclusions

The matrix formulation provides a fast method for calculating the photochemical relaxation of perturbations of any vertical wavelength (longer than 26z). Preliminary results using the matrix on different temperature profiles suggest that the linearisation of equation (ii) does not introduce significant errors.

The inclusion of the 9.6~m coupling reduces the photochemical acceleration coefficient by up to 45%.

Present work is investigating whether by using A Q(z) instead of A q;w

the dependence on latitude and season can be reduced such that one gener­ally applicable A matrix could be defined - or perhaps two or three matrices representative of extreme conditions. It may then be possible to combine A with the matrix that is frequently used to calculate infrared cooling rates (e.g. Fels and Schwarzkopf (7».

REFERENCES

CRAIG, R.A. and OHRING, G. (1958). The temperature dependence of ozone radiational heating rates in the vicinity of the mesopeak. J.Meteor. 15, 59-62.

2 BARNETT, J.J., HOUGHTON, J.T. & PYLE, J.A. (1975). The temperature dependence of the ozone concentration near the stratopause. Quart.J. Roy.Meteor.Soc. 101, 245-257.

3 STROBEL, D.F. (1977). Photochemical - radiative damping and instability in the stratosphere. Geophys.Res.Lett. 4, 424-426.

4 HARTMANN,D.L. (1978). A note concerning the effect of varying extinction on radiative-photochemical relaxation. J.Atmos.Sci.~, 1125-1130.

5 HAIGH, J.D. (1984). Radiative heating in the lower stratosphere and the distribution of ozone in a two-dimensional model. Quart.J.Roy. Meteor.Soc. 110, 167-185.

6 STROBEL, D.F-.-(1979). Parametrization of the thermal relaxation rate in the stratosphere. J.Geophy.Res. 84, 2469-2470.

7 FELS, S.B. & SCHWARZKOPF, M.D. (1981). An efficient accurate algorithm for calculating C02 15~m band cooling rates. J.Geophys.Res. 86, 1205-1232.

Acknowledgement

I am extremely grateful to John Pyle for use of his photochemical ·scheme and advice on chemical matters.

- 36-

1 :0-e: ........ 'U 3 .... ::> <II .., ~ .... ~

Fig.2. Equivalent photochemical relaxation coefficient calculated for: - - -- - Uniform perturbation, no ozone 9.6pm coupling. '" . .... _........ ditto using Strobel's paramo --.--.--.-- Short wavelength perturbation, no ozone 9.6pm coupling. ------ ------ Short wavelength perturbation, including 9.6pm coupling. ----- Uniform perturbation, including ozone 9.6pm coupling.

- 37 -

PHOTOCHEMICAL ACCELERATION

C. Gay* and J.L. Bravo** *Centro de Ciencias de la Atm6sfera and ** Instituto de Geof1sica, V.N.A.M.

Ciudad Vniversitaria, Mexico 04510, D.F. Mexico.

Summary Atmospheric temperature and ozone perturbations are connected through the mechanism of photochemical acceleration. This phenomenon has been studied under different approximations, that have basically involved different ozone photochemical models ranging from the very simple 5 equations Chapman model to very sofisticated ones involving several dozen equations. The radiative part of the problem has been considered in the "Newtonian cooling" approximation which assumes, the radiative relaxation to be a local effect. This study attempts to introduce a more general approach based on the radiative eigenfunctions that consid­ers the influence'of adjacent and remote layers of the atmosphere on the evolution of both, ozone and temperature perturbations profiles at fixed levels. This study shows that the relaxation of ozone and temperature perturbations are not local effects and also, that the relaxation depends on the shape of the perturbations. From the mathematical point of view in this work, a system of integro-differential equations is solved. The approximation reduces the problem to ordinary differential equations which can be easily solved.

1. Int:roduction The coupling of rad~ation and the photochemistry of ozone through the

process of photochemical acceleration has been the subject of several stud­ies (I, 2). In this process radiative relaxation rates of temperature per­turbations are increased significally due to ozone's photochemistry. This occurs due to the temperature dependence of the ozone concentration: if the temperature increases the concentrat~on of ozone decreases and viceversa (3). In the case of a positive temperature perturbation the decrease in ozone with the corresponding decrease in the absortion of solar radiation favors the relaxation of temperature perturbations. The purpose of this paper is to investigate the effect that the structure of the perturbations has on the relaxation rates. This is carried out using the radiative eigen functions as outlined by Gay and Thomas (4). The problem of the photochem~ ical acceleration is mathematically stated as a system of coupled integro­differential equations. The integral term arises due to the non-local character of the radiative processes; this in turn implies that the con­centration of ozone at certain level is also connected with ozone at other levels. This result in different from the coupling that exists between dif ferent levels due to variations in the opacities for the photodissociation­of" ozone and oxigen (5, 6, 7). The results of this work ignore this varia­tions, considering that optical depths associated with the dissociation of ozone do not change.

Ozone Symposium - Greece 1984 - 38-

Previous attempts to study photochemical acceleration have concentrat ed their attention on the photochemical aspects of the problem (1,2,5,6,7)~ However, the radiative aspect of the photochemical acceleration problem has been considered except for one work (4) in a very simplified manner. Namely, using a Newtonian Cooling approach, that considers the radiative relaxation as a local effect, assigning at a certain height the same rate of decay to an optically thick perturbation of to a transparent one.

2. Radiative relaxation The problem of the dissipation of temperature perturbation by ~adia­

tive transfer has been studied by Gay and Thomas (4), and Gay (8). Solu­tions are given in terms of the radiative eigenfunctions. The rate of change of a temperature perturbation is given by the heating equation:

d~\. -:.~\ (T'k.l\t'-~'\d~'-\'\ (1)

where ~ is the transparent rate and the effects of UV absorption have been ignored. Information about the optical properties of the medium is contain ed in the Kernel K ,which can be obtained from absorption and transmis- -sion models. In this work we use the results of Gay (8) appropriate to an atmosphere which transports radiant energy in the 15 ~_ and CO2 ,

T ~ '\len et / fI (2)

where ~l~\is the spatial part of the perturbation and ~ is decay time, from Eq. (1) we obtain~~n integral equation for

Y l'C.) -:: )./~ \0 'VL't')k.,\H'-,,\ ~Z' •

the e-folding 'I' given by

(3)

where A-:''''P/nr-, is the eigenvalue. Equation (3) has been solved for a given by a series of exponentials, viz

, -~.: l(

Kernel

K, l"l. \ -:: 2:. AJ!-The solutions can be written as: _\;.c ~

V C~ \ ~ ~ Co( e " where the index i has been kept to indicate that to certain eigenvalue, Due to the properties of a basic harmonic shape in l: , and are orthogonal

r '!Ie l"t'\\VjC"t\ = XC'I where ~~j is the Kronecker delta.

(4)

) (5)

the solution corresponds ~... and L -< the \jl have in the sense

(6)

Substituting Eq. (5) into Eq. (2), we obtain a solution of Eq.(l). A general solution is obtained combining all possible solutions, that is

T\~.-\:.) ~ L C. 'Il\. C~) e'\/'l.' (7)

where the coefficent c:~ are obtained from the initial condition, and the orthogonality of the \V .

3, Photochemical-Radiative Model. Since our purpose is to illustrate some basic processes in the coup1

ing of radiation and photochemistry, we decided to use Chapman's simple ozone photochemical model, and follow basically the procedure indicated by Lindzen and Goody (1) to stab1ish the relationship to study photochemical acceleration. The strong dependence of the reaction rates with tempera­ture cauSes the coupling with radiation, since this in a sense controls temperature. In the case of coupling of radiation and photochemistry the heating equation, Eq. (1), must be modified to include the effect of the photochemistry of ozone. Lindzen and Goody (1} hav:e shown that the heating produced by ozone perturbations is proportional to the perturbed concentration, and depends on the absorption of solar ultraviolet radia­tion. Therefore we can write the heating equation as:

- 39-

~\'= 1'\\6:" \3\ \L·T-=\l\~""l\\cl4'_11 (8) ~~. )

where ¢~(~, is the perturbation of the mixing ratio of ozone, " the tem­perature perturbation and 1'\ is a coupling coefficent. The rate of change of ozone perturbations is given in (1) by the following equation

~fI5' __ c. "\'_ ~12l' (9) . ~-

Equatlons (8) and (9) show clearly the coupling between temperature and ozone photochemistry. The coefficents l'\,~ and ~ depend upon the equilibri urn atmospheric composition and temperature, and the rates of the reactions­controlling ozone. In this work we have used, as in the paper by Lindzen and Goody, the values given in the classic monography by Craig (8). To solve Eqs (8) and ( 9) we first combine them to obtain

}'T T l1~tIlH! -t Lne -t,B)'f>\~t \\k.ll\I"I\\.Il'.~\i\;:,l\l"l'\~Z'(lO) ~~)~ »'t 1

We assume that the solution'- can be written as T:~C~~L'~)er't (ll)

where ~.~) are solutions of Eq. (3) and the CL are coefficents that must be determined. Substituting Eq. (ll) into Eq. (l2) we obtain

l ~C 'tl.l't\1~t.;. \.'H ... I¥.lI\ \..G"'~ 1 \ f" ... ~<'i \¥~ L't\ll'\.c+ *' 1:. 0 (12)

where we have used Eq. (1 ) and the definition of ).. in terms of '\ To obtain the c. .. we multiply Eq. (12)by 'tl ... ll.\ and integrate over ~ to get

(l3) i\S, .... ~' .. ~i. ... '(".;. ~( ... 1(( -='0

t" t.., .. ", ) \.f.:l't\\.13,~-k:11.\l~\.."l\~~

<> ' (14)

'I.' '2,: ':. \ '\f.l'1)lY\c .. ~ 1 'r(L'l\ ~ ~ ~k 0 ~ ~~

and (15 )

Equation (13)has a solution forC(different from zero when the determinant of the matrix formed with its coefficients is zero. This only happens for certain values of y , the eigenvalues of the problem. Since this approach is rather complicated we opted for an approximated solution consisting in assuming that the spatial part of the perturbation is given only by one of the solutions of Eq, (3). In this case we get (only one term of the series in F..q. (3»

(16)

where we have kept \/n~ to indicate that: solutions can be found for different perturbations. Also Eq. (16) represents the way in which the pure radiative relaxation ( '/~.:) is modified by the coupling with photochemistry. In the case of height-independent coefficents ( ~.~,~.~ ) Eq. (16) is exact having the solutions

and '<', = '/~ \ - l ~ + 'IV\., \ - t l ~ - 'till, \ t _ I.J '\. <: 1 V2 \

<'t.'" \h\-l~" V'l.,"\~l.L~-\I"',\'l.- 4'lc:.1 Y' \

(17)

(18)

This result is similar to the one obtained by Lindzen and Goody, although, it shows that the vertical structure of the temperature perturbation plays an important role in the evaluation of the coupling between radiation and photochemistry.

4. Numerical results and discussion We considered a number of model atmospheres with constant, optical and

photochemical parameters; the values of these corresponding to different heights of the actual (non-homogeneous) atmosphere. We then assume that the behavior of a temperature perturbation in these homogeneous models

-40 -

would be similar to the behavior of a perturbation in the actual atmosphere at the height corresponding to the values of the parameters. Our results are plotted in Figs. (1) and (2) •

. 70

6 0

'Or

' 0-

'0.

__ P" OIO

____ ." MOd' _ _ 2~ M OU

._._. S 10 ... ~.ca,

Fig.2 Radiative Photo chemical decay times (39,40 modes).

Fig. 1. Radiative Photochemical decay times (test modes).

70

.0 I"

__ 110·0

____ l 'ito"" .a C "'Od,u __ $1., .. O'C <l ~

t'O"UIIJ '~ c l

Ing. Fig. (1) we show the times of decay of the first and second eigenfunc­tion (curves (1) and (2» for pure radiative relaxation, and the photo chern ical relaxation time (curve (3» as functions of altitude. These would be­the values for the relaxation of temperature perturbations and ozone pertur bations and ozone perturbations respectively, in the case of no-coupling -radiation-photochemistry. We observe that temperature relaxation times are about 45 and 20 days for the first and second modes respectively. Relaxa­tion times for ozone vary from a small fraction of days for altitudes above 40 km to thousands of days at altitudes below 20km. When coupling is consid ered, for each eigenfunction, we have a fast Eq.(17) and a slow Eq. (18) -mode of relaxation. At altitudes above 30 km, the fast mode (dots) for both perturbations coincides with the photochemical relaxation time. In this case the photochemical acceleration is evident. Below 30 km radiative relaxation times dominate and the different vertical structure of the per­turbations is very important. In this case photochemical relaxations is strongly modified by the coupling with radiation. The slow mode, indicat­ed by open circles, still represents an acceleration of the pure radiative decay at altitudes above 30 km where again the perturbations coincide. Below this height relaxation takes place at the rate of photochemistry with small differences in the times of decay for the first and second mode. Figure (2) shows as in Fig. (1) the decay of the eigenfunctions thirtynine and forty. These correspond to perturbations with a very small vertical scales. Relax in a very different way than modes one and two. The trans­parent limit is also shown, and we observe that the perturbations become

- 41-

transparent above 30 km. Again the photochemical relaxation time is shown. When coupling is considered, above 30 km photochemistry accelerates their relaxation in the fast (dots) and slow (circles)modes. Below 30 km the fast modes are dominated by radiative relaxation, while slow modes decay at the rate of photochemistry. In both figures the heights of oscillatory decay are shown (short arrows). We observe that this r~gions are smaller for the higher order eigenfunctions.

In order to establish some comparisons with Lindzen and Goody's work we showed in both figures their Newtonian colling times eNC). It is simi­lar to the relaxation time of the second eigenfunction but different from those corresponding to the higher order modes. Above 30 km, when coupling is considered the differences (within the fast modes of decay)desapear. This means that the structure of the perturbation is not importat at this levels. Below 30 km the structure of the perturbations in the fast mode of decay becomes very important. Therefore Lindzen and Goody's results coincides with ours for the second eigenfunction.

REFERENCES

1. Lindzen, R. and Goody, R. (1965). Radiative and Photochemical Proces­ses in Mesospheric Dynamics, Part I, Models for Radiative and Photo­chemical Processes. J. Atmos Sci 22, 341-348.

2. Blake, D. and Lindzen, R. (1973).--Effect of Photochemical Models on Calculated Equilibria and Cooling Rates in the Stratosphere. Mon. Wea Rev. 101, 783-802.

3, Craig~.A.and Ohring, G. (1958). The Temperature Dependence of Ozone Radiative Heating Rates in the Vecinity of the Mesopeak. J. of Meteor. 15, 59-62. .

4. Gay, C. and Thomas G.E. (1981). Radiative Temperature Dissipation in a Finite Atmosphere-I. The Homogeneous Case. J. Quant. Specrosc. Radiat. Transfer. 5, 351-380.

5. Hartmann, D.L. (1978). A Note Concerning the Effect of Varying Extinc tion on Radiative-Photochemical Relaxation. J. Atmos.Sc.35, l125-ll30~

6. Hartmann, D.L. (1981). Some Aspects of the Coupling Between Radiation, Chemistry, and Dynamics in the Stratosphere. J. Geophys. Res. 86, 9631-9640. --

7. Strobel, D.R. (1977). Photochemical Radiative Da~ping and Instability in the Stratosphere. Geophys. Res. Lett. 4, 424-426.

8. Gay, C. (1983). Radiative Temperature Dissipation in a Finite Atmos­phere II. The Inhomogeneous Case. J. Quant. Spectrosc. Radiat. Transfer In Press.

9. Craig, R.A. (1950). The Observations and Photochemistry of Atmos­pheric Ozone and their Meteorological Significance. Meteor. Monogr. I, No.2, 50 pp.

- 42-

BUDGETS OF STRATOSPHERIC TRACE GASES FROM 2-D-MODEL

CALCULATIONS AND SATELLITE OBSERVATIONS

U. Schmailzl and P.J. Crutzen Air Chemistry Division, Max-Planck-Institute for Chemistry

P.O. Box 3060, D-6500 M a i n z I F.R. Germany

Summary

We have used satellite data from the SAMS,LIMS and BUV ex­periments to evaluate the stratospheric budgets of the odd nitrogen and odd oxygen families. Total odd nitrogen concen­trations are palculated as a function of 4N aO which is the difference between the mean tropospheric and the local stratospheric NaO mixing ratios. The proportionality factor ~ is a function of global photochemical NaO loss and odd nitrogen production. While this approach seems to work well below 30 kms, there are major discrepancies between calcula­ted and measured odd nitrogen concentrations above 30 km, which cannot be explained with uncertainties in the kinetic an~ photochemical input parameters and the N2 0 observations. This discrepancy in the odd nitrogen concentrations seems to be the reason for a significant overestimation of odd oxygen loss in the range 30 to 40 kms. These results could point toward major uncertainties in the photochemistry of odd nitrogen compounds in the middle stratosphere.

1. Odd ni trogen budgets

The most important source for total odd nitrogen NX ~

N+NO+NO a +N0 3 +2NaOs+HN0 4 +HN0 3 is the reaction of nitrous oxide (NaO) with O('D) in the stratosphere, which forms two molecules of nitric oxide (NO). The magnitude of this source can be estimated using global NaO and 0. distributions from satellite experiments and generally accepted solar fluxes and photo­chemical parameters for the formation of O('D). Since production of NX and total loss of NaO through photodissociation and reaction with O('D) are both centered at subsolar latitudes and at altitudes between 30 and 35 km (3), we can assume that high concentrations of NX correlate with low concentrations of NaO or that NX ~ ~·4NaO. nNaO is the amount of NaO that has been destroyed on its way through the stratosphere. Neglecting chemical loss of NX, this proportionality factor is given by the ratio of global NX production over global NaO loss. With NaO distributions from SAMS (10), 0 3 distributions from LIMS (7) or

Ozone Symposium - Greece 1984 - 43-

BUV (5) respectively and O2 absorption cross sections from Herman and Mentall (9) we calculate values between 13 and 14%. This approach will overestimate the NX concentrations for air parcels that have passed altitudes above 35 km where appreciable loss of NX through reaction NO + N ---> N2 + 0 has occured. This loss process can be taken account of by a correction factor f L, so that ¢ = ~o (l-fL). fL is also a function of LlN20. In figure 1 the function ~ is given for two cases: solar maximum fluxes in the Schumann-Runge band and LIMS ozone (where available); solar minimum fluxes in the Schumann-Runge band and BUV ozone. The contribution of NX loss is less than 20% in the upper strato­sphere, using the NO photodissociation cross sections by Allen and Frederick (1). With the NO photodissociation coefficients from Frederick and Hudson (4) this contribution is below 15%, using the formula by Nicolet (12) in between the two values. The uncertainty in the N20 photodissociation coefficients due to different treatment of the Schumann-Runge band region affects our value for ~ by less than 8 %.

2. Comparison of odd nitrogen distribution

Comparison of the calculated odd nitrogen mixing ratios with results of balloon measurements shows good agreement for HN0 3 , NO and NO, below 30 km. Yet we find a distinct overestima­tion of NO" HN0 3 and possibly NO above 30 km. The columns calculated above 197 mb (~ 11.9 km) seem to be systematically higher than those· of Coffey et a 1 (2), Noxon (13) and Murcray et al (11); only the NO columns of Girard et al (8) are in the same order of magnitude. However, the calculated differences between sunset and sunrise values agree reasonably well with those of Coffey et aI, which points to a good agreement in the N,Os columns.

3. Odd oxygen budgets

The sources and sinks of odd oxygen have been evaluated using N,O and CH, distributions from SAMS (10),° 3 from LIMS (7) or BUV (5) respectively, H,O and T from LIMS (7) and CIX from 1979 distributions calculated with generally accepted chloro­fluorocarbon release scenarios (6). There is an imbalance in the odd oxygen budget P-D, where P is the odd oxygen production through photodissociation of 0, and D is the sum of odd oxygen loss through the Chapman reactions (Do), odd nitrogen catalyzed (DN), odd chlorine catalyzed (DCl) and odd hydrogen catalyzed (DH) reaction cycles. Figure 2 gives P-D for LIMS 0 3 and solar maximum fluxes in the Schumann-Runge region. The hatched area gives the region of overproduction of odd oxygen, which has been discussed in our previous paper (3). This overproduction becomes less severe, when we use an improved approximation for the treatment of the Schumann-Runge band region (1) and the LIMS data. Below 25 km part of the imbalance can be compensated by transport, whereas the region above is only controlled by photochemistry. Figure 3 gives the imbalance of odd oxygen relative to odd oxygen production and shows discrepancies up to

- 44-

100%. Above 30 km we find an extra loss of odd oxygen, which adds up to an average column amount of 4x10'· molec. cm--sec- 1 •

This discrepancy is larger than the uncertainties resulting from inaccuracies of the relevant rate constants, absorption cross sections and solar fluxes. It is however consistent with an overestimation of odd nitrogen concentrations as discussed in the previous chapter. If we assume that reaction N0 2 +O--)NO+O, is the only sink for ozone between 30 and 40 km, N0 2 would have to be corrected by more than 50% in this altitude range to balance the ozone budget.

This result pOints either to substantially higher N2 0 mixing ratios above 30 km than measured by SAMS (10) or to severe deficiencies in the stratospheric odd nitrogen chemistry, e.g. in the photolysis rates of N2 0 or NO. The indicated problems must be resolved in order to improve the predictive capabilities of current models.

<P

[0/0 ]

15 14.3%, solar minimum

r-:-:-::-:-:-=-------:- -L 13.9 % ..........

" solar

10

100 figure 1.

"-

50

"­:\

o

~ = NX/~N20 as function of the average mixing ratio of N20 for different solar fluxes in the Schumann-Runge band region.

- 45-

Imbalance of the odd oxygen budget P-D for LIMS ozone and solar maximum fluxes in the Schumann-Runge band region. Hatched area shows extra production, white area shows extra loss of odd oxygen.

z [km ] ( P- Ol/ P[%J spr ing p(mb] 50~~~~--~~~--~~~--~~~--~~~--~~

40

5

30 10

Q)

"0 :>

<i 20 50

100

< - 100 10

500

o ~-.--.-----.----r-.-.,....,r-r----r-'--r----.----r-"----r---.-......,....J-1000 -80 S

figure 3.

- 60 -40 -20 o Lat itude

20 40 60 80 N

Imbalance of the odd oxygen budget as percent of odd oxygen production.

- 46-

REFERENCES

1. ALLEN, M. and Frederick, J.E. (1982). Effective Photo­dissociation Cross Sections for Molecular Oxygen and Nitric Oxide in the Schumann-Runge Bands. J. Atmos. Sci. 39, 2066-2075.

2. COFFEY, M.T., Mankin, W.G. and Goldman A. (1981) Simultane­ous Spectroscopic Determination of the Latitudinal, Sea­sonal, and Diurnal Variability of Stratospheric N2 0, NO, N0 2

and HN0 3 • J. Geophys. Res. 86, 7331-7341. 3. CRUTZEN, P.J. and Schmailzl, U. (1982). Chemical budgets of

the Stratosphere. Planet. Space Sci. 31, 1009-1032. 4. FREDERICK, J.E. and Hudson, R.D. (1980). Atmospheric opacity

in the Schumann-Runge Bands and the Aeronomic Dissociation of Water Vapor. J. Atmos. Sci. 37, 1099-1106.

5. FREDERICK, J.E., Huang, F.T., Douglass, A.R. and Reber, C.A. (1983). The distribution and annual cycle of ozone in the upper stratosphere. J. Geophys. Res. 88, 3819-3828.

6. GIDEL, L.T., Crutzen, P.J., Fishman, J. (1983). A two­dimensional Photochemical Model of the Atmosphere 1: Chlorocarbon Emissions and their Effect on Stratospheric Ozone. J. Geophys. Res. 88, 6622-6640.

7. GILLE, J.C., Russel III, J.M. (1984). The Limb Infrared Monotor of the Stratosphere (LIMS): Experiment Description, Performance and Results. J. Geophys. Res. 98, 5125-5140. See also references therein.

8. GIRARD, A., Besson, J., Giraudet, R. and Gramont, L. (1978/79)., Correlated Seasonal and Climatic Variation of Trace Constituents in the Stratosphere. Pageoph. 117, 381-394.

9. HERMANN, J.R. and Mentall, J.E. (1982).° 2 absorption cross section (187-225 nm) from stratospheric solar flux measure­ments. J. Geophys. Res. 87, 8967-8975.

10. JONES, R.L. and Pyle, J.A. (1983). Observations of CH 4 and N 2 0 by the Nimbus 7 SAMS. A comparison with in situ data and two dimensionl numerical model calculations. J. Geophys. Res. 89, 5263-5279.

11. MURC.RAY, D.G., Barker, D.B., Brooks, J.N., Goldman, A. and Williams, W.J. (1975). Seasonal and latitudinal variation of the stratospheric concentrations of HN0 3 • Geophys. Res. Lett. 2, 223-225.

12. NICOLET, M. (1979). Photodissociation of Nitric Oxide in the Mesophere and Stratosphere: Simplified Numerical Relations for Atmospheric Model Calculations. Geophys. Res. Lett. 6, 866-868.

13. NOXON, J.F. (1979). Stratospheric N0 2 , Global Behaviour. J. Geophys. Res. 84, 5067-5076.

- 47-

Summary

A STUDY OF THE OZONE PHOTOCHEMISTRY IN THE UPPER STRATOSPHERE USING LIMS DATA

M. NATARAJAN Systems & Applied Sciences Corporation

Hampton, Virginia 23666

L.B. CALLIS, J.M. RUSSELL III, and R.E. BOUGHNER NASA Langley Research Center

Hampton, Virginia 23665

LIMS data at vernal equinox conditions are used to study the photochemistry of the upper stratosphere. The results indicate, and it has been recently reported, that with the use of recommended reaction rates, current models underestimate ozone mixing ratio by 20-40%. We also find that for ozone, good agreement with data is realized with the modification of six key reaction rates within the published limits of uncertainty. These modifications also yield better agreement with data for daytime N0 2• Model results for other parameters such as the ratio HN03/N02 , OH mixing ratio, and the temperature sensi~ivity of 03 are compared with data.

1.1 Introduction

For more than a decade now, the photochemistry of stratospheric ozone has been the subject of much scientific research. The availability of new data, both experimental and observational, has always led to further studies designed to determine whether a consistent picture of the stratosphere emerges. The present work is one such attempt to test our understanding of the stratospheric chemical processes in the light of new data. We have made use of the extensive data set resulting from the LIMS experiment aboard the Nimbus 7 spacecraft. Nearly 7 months of measurements of stratospheric temperature, 03' H20, HN03 , and N02 are available, and we have, for the most part, chosen the radiance averaged data for 300 N during March for this study. Under these conditions, photochemical processes are expected to be dominant in determining the ozone levels in the upper stratosphere.

1.2 Model Description

A contemporary photochemical model that includes Ox' HOx ' NOx ' and C~x chemistry has been used. The zero dimensional model is run in the diurnal mode so that short-term chemistry is properly simulated. An important first step is the inference of the concentrations of those species which are not measured. The procedure used for this purpose is described in (1). Zonal averages of the measured data and the inferred species concentrations form the initial conditions for the diurnal calculation. The temperature and H20 are held fixed at the LIMS value. Zonal averages of CH4 mixing ratios from the SAMS experiment on board Nimbus 7 are used. Transport effects are not treated explicitly, and the calculations at different altitudes are done independently. The reaction rate data are taken from JPL Publication 83-62

Ozone Symposium - Greece 1984 - 48-

(2). The Herzberg continuum cross sections reported by Herman and Mentall (3) have been included in the computation of the photodissociation rate constants. The model calculation is continued through five diurnal cycles in order to remove transient effects. The results from the 5th model day, hereafter referred to as Model J, are described in the following sections.

1.3 Results and Discussion

The ozone mixing ratios from Model J are shown in figure 1 along with the 1IMS measurements. The model, with the use of recommended chemical rates, underestimates ozone mixing ratios by 20-40%. This is in agreement with the results reported in other studies (4, 5). A discrepancy of this magnitude is of concern because the photochemical lifetime of odd oxygen is short in the upper stratosphere and photochemistry should be the dominant mechanism in establishing the ozone levels. These differences between theory and observations could be due to various factors such as erroneous input data in the model studies, measurement inaccuracies, and unknown mechanisms which are not included in the model. 1IMS ozone measurements agree quite well with data from other sources such as SBUV. The reported error in the 1IMS measurements in this pressure range (3 mb - 1 mb) is within 16%.

In the present study, we have attempted to determine conditions under which better agreement is realized between the model and data. Our approach is to study the sensitivity of the model to modifications in certain rate parameters. We have used the current understanding of the odd oxygen photochemistry as a guideline to select the key reaction rates to be modified. Estimates of'uncertainty, recommended in (2), have been used to modify five reaction rates in such a way as to increase the calculated odd oxygen. These modifications are shown in Table I. Catalytic cycles in­volving HOx species form the major path for odd oxygen loss near the stratopause. The changes involving HOx species, shown in Table I, tend to slow down the odd oxygen loss rate and increase the rate of destruction of HOx' The reaction between NO and 03 is not the rate-determining step in the NOx catalytic cycle leading to loss of odd oxygen; however, this reaction has a strong influence on the ratio NO/N02 during the daytime. This ratio is increased by a reduction in the rate constant for this reaction. The reaction cto + ° has been studied by 1eu et al. (6), and their results for the rate constant, shown in Table I, are lower than the recommended value. This reduction has an effect on odd oxygen since CtO + ° is the rate­determining step in the ctx catalytic cycle. Model M refers to the calculations done with modified rate constants. Figure 1 shows the effects of these modifications on the calculated ozone mixing ratio. The agreement between the model result and 1IMS data is much better with the use of this set of modified rates. It should be added that a combination of changes in a group of reaction rates is needed to minimize the discrepancy. The choice of reactions to be considered for modification is, however, not unique. Further studies are needed to examine all the key reactions that influence odd oxygen and also, have large uncertainty in their rates.

It is of paramount interest to study whether such modifications disturb the agreement between theory and data with regard to other photochemical parameters. Figure 2 shows one such comparison, involving the day and night measurements of N02 • Since the initial conditions for the diurnal model made use of the nighttime 1IMS measurements of N02 , the agreement between the model result and data for night is not surprising. The day value of N0 2 calculated in the model is a function of the rate constant data. Around 37

- 49-

km, this value is especially sensitive to the rate of the reaction NO + 03' Figure 2 shows that Model M, with modified rates, gives N0 2 mixing ratios that agree well with the LIMS data for daytime. At 34 km the difference between the two model results is about 10%. This is a consequence of the reduction in the rate constant for the reaction NO + 03' Daytime value of NO/N0 2 is increased by such a modification, and this, while reducing N0 2 during the daytime, also decreases the loss rate of odd oxygen.

A comparison of the daytime ratio HN03/N02 from LIMS data and the model results is shown in figure 3. Below 38 km, both Model J and Model M yield results that compare well with the data. High values of HN03 that the LIMS measurements show above 38 km are not reproduced by either model, and this discrepancy is yet to be explained. Figure 4 compares the noon values of OH from the two models with available data. Even though the time period of measurement is different, this figure shows that the modifications to the rate constants in Model M improve the agreement with the data some­what. This is significant because the modifications shown in Table I involve four reactions of importance to HOx chemistry. It should be recognized that OH mixing ratio is sensitive to variations in H20.

We have studied the alitude distribution of the fractional contribution to odd oxygen loss by the different catalytic cycles in the two models. The effect of the rate modifications we have made is, in general, to in-crease the relative roles of Ox and NOx cycles and decrease roles of HOx and Cix cycles in the destruction of odd oxygen. To examine the effects of such rate changes at a different season and for different latitudes, we have repeated the model calculations using data from December at 37 km and for the latitude range 500 S to the Equator. The results are qualitatively similar, and the modified rates (Model M) yield better agreement with LIMS ozone and daytime N02 •

It has been suggested that the temperature sensitivity of ozone could be used as a parameter to test the consistency of the input data in a photochemical model. We have studied the relation between ozone and temperature around 1 mb using the LIMS data for March. As expected ozone and temperature are found to be negatively correlated. Figure 5 shows the temperature sensitivity parameter B, in the equation in 03 = A + BiT, as a function of latitude. The sensitivity factors for 300 N predicted by the two models, Model J and Model M, are also shown in the figure. The modified rates result in a sensitivity factor closer to the value derived from data. We feel, however, that no conclusive remarks about the photo­chemical data in the two models can be made based on this, since the large latitudinal variation in B cannot be explained by photochemistry alone.

1.4 Conclusions

We have studied the photochemistry of upper stratosphere, making use of the LIMS data. Our study shows that the use of currently recommended photochemical data underestimates the ozone mixing ratio by 20-40%. We find that this discrepancy could be reduced by modifying six of the chemical rate constants to their recommended limits of uncertainty. Such modifi­cations also give better agreement with N02 data. Results also tentative­ly suggest that agreement between observed and calculated temperature sensitivity of 03 improves. We emphasize that this is a sensitivity study which shows that the uncertainties in the present photochemical data may be large enough to resolve discrepancies between theory and observations. One cannot rule out the possibility of an unknown mechanism that is not included in the currently accepted theory.

-50-

REFERENCES

1. CALLIS, L.B., NATARAJAN, M., RUSSELL, J.M. and BOUGHNER, R.E. (1984). LIMS data: Inferred stratospheric distribution of NOx and HOx trace constituents and the calculated odd nitrogen budget. Presented at the IAMAP International Ozone Commission Qudrennial Ozone Symposium, Halkidiki, Greece, Sept. 3-7, 1984.

2. JPL Publication 83-62, (1983). Chemical kinetics and photochemical data for use in stratospheric modeling.

3. HERMAN, J.R. and MENTALL, J.E. (1982). 02 absorption cross sections (187-225 nm) from stratospheric solar flux measurements. J. Geophys. Res., 87, 8967-8975.

4. FROIDEVAUX, L. and YUNG, Y.L. (1982). Radiation and chemistry in the stratosphere: Sensitivity to 02 absorption cross sections in the Herzberg continuum. Geophys. Res. Lett., 9, 854-857.

5. CRUTZEN, P.J. and SCHMAILZL, U. (1983). Chemical budgets of the stratosphere. Planet. Space. Sci., 31, 1009-1032.

6. LEU, M.T. (1983). Kinetics of the reaction ° + C£O+C£ + 02' Submitted to J. Phys. Chern.

TABLE I

REACTION MODEL M

° + OH LOWER LIMIT

° + H0 2 LOWER LIMIT

°3 + H LOWER LIMIT

OH + H02 UPPER LIMIT

NO + °3 LOWER LIMIT

C£O + ° Ref. Leu (1983)

60

50

All (kin) 40

30

20~~~~ __ ~~~ __ ~~~~~~ o 2 4 6 8 10 -40 -20 0 03 PPM .1103 %

o liTIs, 3ON, Ma'ch -- ModeIJ ----ModeIM

Figure 1. Ozone mixing ratio_ LlMS data and model results

- 51 -

All (kin)

60

50

All (kin)

40

30

0 ... ' 0... ...

200=---~4--~8=---1~2~~1~6--~2~0~~24 N02 PP8

• ° Lins. 3 ON , Macl1 --Model J - - - Model M

Figure 2. N02 mixing ratio. lIMS data and model results.

60 • •

50

40

30

2O~.1~1~---L-L~.1~0~~~~~.9~~---L~~~ 10 10 10 10

(OH) Mixilg raIio at nooo • ·4171.0·4/ 77, . ·9/ 77 J. l\oderson (NASA 1049) -- Model J - - - - Model M

Figure 4. OH mixing ratio. MCKlel results and data.

- 52-

45

° °

~ 0-

30 0-< 0 "

25 L-__ -L ____ ~ __ ~--~~~~~~ 0 .5 1.5 2 2.5 3

(HN03 / ~) Day

° Uns. 3ON. Mach: - Model J : - --Moc!ej M

Figure 3. Calculated and observed HNO)INOZ during daytime.

1200

1100

800

AII - 49 kin P=0.913 rTll In (0 3)=A + BIT

o 700L-________ L-________ L-______ ~

24 28 32 La! «(leg N)

Uns, DaIa. Macl1 o Model J II Model M

Figure 5. Temperature sensitivity of 03

36

A THEORETICAL STUDY OF THE OUASI-BIENNIAL OSCILLATION IN THE TROPICAL STRATOSPHERE

XIUDE LING and JULIUS LONDON Department of Astrophysical, Planetary and Atmospheric Sciences

University of Colorado Boulder, Colorado 80309 USA

Introducti on A quasi-biennial oscillation (ORO) of the zonal wind in the tropical

st ratosphere was fi rst reported in the early 1960s by Reed et a 1. (1961) and Ebdon and Veryard (1961). Since that time, the properties of this wind oscillation have been documented by Angell and Korshover (1962); Reed (1965); Tucker (1979); Coy (1979); London et a1. (1983); and others. The observations indicate a number of distinctive features of the oscilla­tion. Easterly and westerly zonal wind systems alternate fairly regularly with an average period of close to 28 months which, however, has varied from about 21 to 34 months (Oui roz, 1981). It has also been observed that the phase of the wi nd OBO changes rather abrupt ly at about 30° 1 atitude where its amplitude is a minimum (see, for instance, Tucker, 1979). The wind oscillation starts in the upper stratosphere and is propogated down­ward at an average rate of slightly more than 1 km per month (see, for instance, Coy, 1979). A stratospheric temperature OBO has also been ob­served near the equator whose amplitude is maxi mum at about 20-22 km and whose phase lag with decreasing height is about the same as that for the wind QBO (London et al., 1983). It is now generally agreed that the mai n features of the tropical wind OBO can be explained on the basis of upward transport of momentum by equatori al Kel vi n waves and mi xed Rossby-gravity waves as discussed by Holton and Lindzen (1972) and Plumb and Bell (1982).

A OBO in total ozone was al so reported by Funk and Garnham (1962). Variations in total ozone are highly correlated with those at levels of maximum concentration and an ozone OBO has been identified in the ozone mixing ratio for the 22-27 km layer in the tropics as calculated from Nimbus-4 BUV observations for the period April 1970 to May 1977 (see, for instance, Ling, 1984). The BUV data show statistically significant coher­ence in the cross-spectral estimate between 50 mb zonal wind OBO at Ralboa (9°N) and that for the ozone mixing ratio at 22 km at about the same lati­tude (Oltmans and London, 1982).

Variations of ozone in the lower and middle stratosphere involve a coup 1 ed atmosphe ri c dynami c and photochemi ca 1 system. The re 1 at i ve i mpor­tance of each of the components of this system in the tropics is largely hei ght dependent such that atmospheri c transport is domi nant in the lower stratosphere (~ 20 km) and temperature dependent photochemistry is dominant in the middle stratosphere (~ 35 km). In the following treatment we dis­cuss the results of a 2-dimensional theoretical/diagnostic study based on the assumption that the ozone OBO in the tropical stratosphere results from oscillations in temperature, meridional, and vertical winds that are all forced by the zonal wind OBO in a radiative/photochemical/dynamic system.

Ozone Symposium - Greece 1984 - 53-

The Basic Equations If we assume hydrostatic balance, neglect molecular friction and ap­

proxi mate infrared statospheri c cool i ng by a Newtoni an cool i ng parameter, we can write the appropri ate system of equat ions in 1 og-pressu re coordi n­ates as (see, for instance, Holton, 1979; Hartmann and Garcia, 1979):

au + (V.V)u - fv = _.!.i (1) at ax

av + (V.V)v + fu a+ (2) at ay

a = a+ (3) liZ

v . (p V) = 0 (A)

aa aa aa we!! + ~a) Sy - p(a - as) + H (5) at +u-+v-+ ax ay az H s

ay + u:~ + v:; + ~ = p (6) at az c

where u, v, ware the east, north and upward directed winds in the norma~ orthogonal coordinate set (z = Hln po/pl. H is the local scale height; v is the 3-dimensional velocity vector; a is a buoyancy acceleration defined as (R/H)T where R is the gas constant for dry ai rand Tis temperature; p is density; K is R/Cp where CD is the specific heat for dry air at constant pressure; S is the rlNting rate per unit mass due to absorption of solar radiation by molcular ozone; as and Hs are the buoyancy acceleration and infrared cooling rate for the U.S. Standard Atmosphere (1976); p is the Newtonian cooling coefficient applied to the temperature. perturbation from the standard atmosphere; y is the ozone volume mixing ratio; and Pc is the net rate of photochemical production and loss of ozone.

We are interested in zonal averages of the various terms appearing in the above equations. These averages consist of mean zonal values plus deviations from the mean for the variables v, w, y and 8. In addition, we separate the zonally averaged fields into two parts: a long-term annual average and a quasi-biennial oscillation. Further, we simplify the system by scali ng the different terms appeari ng in the fu 11 equat i on and keepi ng only the higher order terms in each equation. This results in the follow­ing sets of equations (Ling, 1984).

fUq = - .!.iq ay aq = !!q

az

a +.!~( ) ay Vq p az PWq = 0

:!q + wqN 2 = SYq - paq

(7)

(8)

(9)

(10)

( 11)

where the subscripts a and q refer to the annual and quasi-biennial terms, r and a are photochemical variables describing the photochemical relaxation to equilibrium and the negative feedback effect of temperature on the ozone

-54 -

concentration. N2 in equation (10) is the square of the Brunt-Vaisa11a frequency. The zonal wind OBO is specified as

2 Uq (y,z,t) = UoF(z)e- ay cos (wt+kz)

where Uo is the maximum value for the zonal wind OBO, wand 1 ar frequency and vert i ca 1 wave number of the osci 11 at ion, and the function F(z) were taken to fit the observed data. that the oscillation period is 28 months.

k are the angu­the constant a It was assumed

These equations together with a 2-dimensional mass stream function were used to derive a set of 3 prognostic equations and 1 diagnostic equa­tion from which the dependent variables Vq, Wa , 6q and Yq are solved numer­i ca lly as funct ions of hei ght, 1 at itude, and' time. The 1 atera 1 boundary condit ions assume a vani shi ng meri di ona 1 wi nd at 00 and 30 0 N • All depen­dent variables are set to zero at t=o and the model was run for 3 complete 28 month OBO cycles.

Results The model derived height/latitude distributions of the amplitude and

phase of the ozone OBO along with the values calculated from the Nimbus-7 BUV observations are given in Figures la, b. It can be seen that both the model and observed amplitudes are maximum at about 22-24 km, decrease to a minimum at 28-29 km and then increase. The amplitude also decreases with increasing latitude to a minimum at about 13-14°N (model results) or 10-12°N (observed values) and then increase again to an apparent maximum at

lOON 200 N 30·N

LATITUDE

�BO"L:----~100~N~---:2..J.O·-N---lIO...J·N

LATITUDE

Figure lao Variation with QBO amplitude derived

height and latitude of the ozone mixing ratio from the model (left) and BUV data (right)

(Units: 10-8 ppv)

about 30 0 N. The phase, calibrated to the observed wind maximum at 50 mb at Singapore (ION), shows a retardation with decreasing height that is somewhat larger than that for the wind oscillation, with a pronounced in­creased lag at 28-30 km which coincides with the level of minimum amplitude of the ozone OBOe Above thi s 1 eve 1 the ozone osci 11 at ion is domi nated by the effect of temperatu re dependent photochemi st ry 0 Be low about 25 km vertical ozone transport is chiefly responsible for the ozone variation.

- 55-

!l4

!l2

!l0 E ... ;:28 :r c ;;;:;26 :r

24

22

20

lOON 20'N !lOON LATITUDE

!l4

12 24 22

22L---__ ~L-_L ____ J_ ______ ~

00 lOON 200N !lO'N

LATITUDE

Figure lb. Variation with height and latitude of the ozone QBO phase derived from the model (left) and BUV data (right)

(Units: Honth Where April 1970= 1)

Both model and observed ozone phase variations also show a shift at about 10-12°N such that the phase differences

strong phase between the

variation is equatorial and trogical regions are almost 180°. This particularly noticeable in the model derived values.

The height dependence shown by these results can best be explained by consideration of the characteristic relaxation time for the different radi­ative/photochemical/dynamic processes responsible for the ozone varia­tions. These are shown in Figure 2 for the vertical ozone and enthalpy advective terms and the photochem-ical and radiative relaxation. Above 30 km, vertical ozone trans­ 35

port is relatively unimportant as compared to the other processes in determining the ozone variation, whereas below 30 km photochemical E30 re 1 axat ion is long and the ozone "" variation is increasingly deter- ~ mined largely by vertical advec- ~ tion. w

In the lower 1 ayers, where J: 25 the mixing ratio gradient is posi­tive, upward vertical motion should result in a decrease in the mixing ratio. Thus minimum ozone

~ , \ , ~ , ',t _ __ --':r"

, ..... - \ --·--· ......... f.

- PHOTOCHEMISTRY

-- OZONE TRANSPORT

T";--...... l', "' I" " ,.. .

- - RADIATION • .... THERMAL TRANSPORT

,\ " I. •

'... \ I' • I l \ \: . \ .

at these levels should occur at a 2~O~0'--------I~071~-L----~~----~~'03 phase angl e of 90° after the up- TIME ward vertical wind reaches its maximum value (i.e., a phase lag of 270°). In the upper layers, above 30 km, photochemi ca 1 re 1 axa­tion has a much shorter time scale than that for vertical ozone

Figure 2. Time constants for radia­tive, photochemical and dynamical transport processes in the stratos­phere

- 56-

transport. At these levels upward (positive) vertical motion results in adiabatic cooling which is ameliorated somewhat by rarliative restoration to equilibrium values. However, at these levels there is a strong negative feedback effect of temperature on ozone and the net cooling quickly results in an ozone inc rease through the fast photochemi st ry. Thu s above 30 km there should be a strong tendency for ozone and vertical wind OBOs to be in phase and both to be 1800 out of phase with the temperature OBOe In the i nterum regi on, 28-30 km, where both photochemi cal and transport processes are equally important, the net effects, as discussed above, tend to cancel each other. As a result, the ozone OBO amplitude is a minimum and its phase changes rapidly through the layer.

The model used to derive the results shown in Figures la, b was run for 3 QBO cycles (2520 days) and the evolution of the computed oscillations for ozone, temperature, and vertical wind are shown in Figure 3 for 5°N at 32 km.

(a) (b)

Time (day) .,-

Time (day)

(c) (d) •.• ..

Time (day) .... f-';; ... ;---;;_;---;;_;---;;_~._~ .. ",~._~._::--:.:._=---=_=---= .... =--=:_::J

. ... Time (day)

Figure 3. QBO evolution with time from model for 50 N at 32 km: a) assumed zonal wind b) vertical wind c) ozone mixing ratio d) temperature

The model became quite stable after the second cycle. Also shown in Figure 3 is the assumed periodic variation of the zonal wind at the same latitude and height. At this level the vertical wind and ozone oscillations are in phase and both lag the assumed zonal wind OBO by about 900 (7 months) and, as expected, they are both 180 0 out of phase with the temperature OBOe Model results also indicate that at 32 km near the equator the meridional

- 57-

wind QBO (not shown here) is 1800 out of phase with the assumed zonal wind variation. These results for vq , wq , and Tq are consistent with the pat­tern suggested by Reed (1964).

Conclusions The 2-dimensional theoretical/diagnostic model described can reproduce

the basic features of the observed quasi-biennial oscillation of ozone in the tropical and subtropical stratosphere. The model is based on an assumed (from observations) height and latitude dependent zonal wind oscil­lation to QBOs in temperature, zonal, and meridional winds which through an interacting set of radiative, photochemical, and dynamic processes produce the ozone variation. It was shown that above 30 km photochemical effects, including negative feedback of temperature on ozone, are dominant in pro­ducing the observed oscillation. Below 25 km, vertical advection of ozone is most important. I n the regi on 27-30 km both processes tend to cancel each other.

References Angell, J.K., and J. Korshover (l962). The biennial wind and temperature

oscillations of the equatorial stratosphere and their possible extension to higher latitudes, Mon. Wea. Rev., 90, 127-132.

Coy, L. (l979). An unusually large westerly amplitude of the quasi-biennial oscillation, J. Atmos. Sci., 36, 174-176.

Ebdon, R.A., and R.G. Veryard (1961). Fluctuations in equatorial strato­spheric winds, Nature, 189, 791-793.

Funk, J.P., and G.L. Garnham (1962). Australian ozone observations and a suggested 24-month cycle, Tellus, 14, 378-382.

Hartmann, D.L., and" R.R. Garcia (i'9;9). A mechanistic model of ozone transport by planetary waves in the stratosphere, J. Atmos. Sci.,1§.., 350-364.

Holton, J.R. (l979). An Introduction to Dynamic Meteorology, New York: Academic Press, Inc.

Holton, J.R., and R.S. Lindzen (l972). An updated theory for the quasi-biennial oscillation of the tropical stratosphere, J. Atmos. Sci., ~, 1076-1080.

Ling, X. (1984). A Theoretical Study of the Ozone Quasi-Biennial Oscilla-tion in the Tropical Stratosphere, Ph.D. thesis, Department of Astrophysical, Planetary and Atmospheric Sciences, University of Colorado, Boulder, CO.

London, J., X. Ling, and S.J. Oltmans (l983). Quasi-biennial wind and temperature oscillation in the tropical mid-stratosphere, EOS, 64, 780 (abstract), presented at the AGU 1983 Fall Meeting, San Francisco~A.

Oltmans, S.J., and J. London (19R2). The quasi-biennial oscillation in atmospheric ozone, J. Geophys. Res., 87, 8981-8989.

Plumb, R.A., and R.C. Bell, (1982). A model of the quasi-biennial oscilla­tion on an equatorial beta-plane, Q.J.R. Meteor. Soc., 108, 335-352.

Quiroz, R.S. (1981). Period modulation of the stratospheric quasi-biennial oscillation, Mon. Wea. Rev., 109, 665-674.

Reed, R.J. (1965). The present status of the 26-month oscillation, Bull. Am. Meteor. Soc., 46, 374-387.

Reed, R.J., W.J. Camplbell, L.A. Rasmussen, D.G. Rogers (1961). Evidence of a downward-propagating annual wind reversal in the equatorial strato­sphere, J. Geophys. Res., 66, 813-818.

Tucker, G.B. (1979). The observed zonal wind cycle in the Southern Hemi­sphere stratosphere, Q.J.R. Meteor. Soc., 105, 263-273.

- 58-

Study of the Effect of El Chichon Volcanic Cloud on the Stratospheric Temperature Structure and Ozone Distribution in a 2-D Model

R.K.R. Vupputuri Canadian Climate Centre, Downsview, Ont., Canada

The recent observational data on aerosol optical thickness point out large variations of El Chichon volcanic cloud material with latitude (Dutton and DeLuisi, 1983). This variation in the aerosol optical thickness is ex­pected to produce corresponding significant nifferences in the radiative­photochemical perturbations which in turn will lead to the changes in the latitudinal temperature structure, ozone distribution and mean circulation in the stratosphere. In this paper a 2-D time dependent radiative-photo­chemical dynamical model which takes into account the interaction between ozone photochemistry and volcanic aerosols is used to study the effect of latitudinal spread of the volcanic cloud from the El Chichon eruption on the stratospheric ozone and temperature structure. The 2-D radiative-photochem­ical-dynamical model is described in detail by Vupputuri (1979). For other details regarding the radiative transfer model, the perturbed El Chichon aerosol model and the optical properties of the perturbed stratospheric aerosols the reader is referred to Vupputuri and Blanchet (1983).

Fig. 1 shows the latitude distribution of visible aerosol optical depths measured during December, 1982 roughly eight months after the El Chichon eruption. For the purpose of this study the optical depths shown in Fig. 1 are considered to have reached their peak values by four months after eruption and remaln so for another four months before they begin to de­crease, in an exponential fashion with time. Fig. 2 presents the latitude­height cross-section representing the changes in temperature relative to the ambient stratosphere four months after the El Chichon eruption. The lati­tude height cross-section representing the percentage changes in the ozone mixing ratio and the corresponding percentage change in the total ozone column as a function of latitude eight months after the El Chichon eruption are illustrated in Figs. 3 and 4 respectively. The preliminary results shown in Figs. 2 to 4 indicate that the increased stratospheric aerosol concentrations resulting from the meridional spread of the El Chichon cloud will lead to significant warming which varies with latitude particularly in the lower stratosphere near the cloud center (24 km) (see Fig. 2). The results also indicate that one could expect important latitudinal changes in the ozone mixing ratio following the temperature changes due to temperature­ozone feedback effect and enhanced photodissociation of ozone caused by the multiple scattering effects from the El Chichon aerosol cloud (see Fig. 3). As shown Fig. 4 the total ozone column decreases between 0 and roughly 2% depending upon the latitude and season as a result of the interaction of ozone photochemistry with El Chichon stratospheric aerosol cloud. The changes in ozone and temperature structure produce related changes in the mean circulation. The calculations indicate, that the stratospheric aerosol cloud from the El Chichon eruption has the effect of weakening both the tropical easterlies and mid-latitude westerlies in the N.H. following the eruption.

References Dutton, E., and J. DeLuisi, 1983: Geo. Physical Res. Lett., Vol. 10, No. 11, 1013-1016. Vupputuri, R.K.R., 1979: Pure Appl. Geophys., 117, 448-485. Vupputuri, R.K.R. and J.P. Blanchet, 1983: The paper is in print in the special issue of Geofisica International.

Ozone Symposium - Greece 1984 - 59-

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ASPECTS OF THE COMPARISON OF STRATOSPHERIC TRACE SPECIES MEASUREMENTS WITH PHOTOCHEMICAL MODELS

Summary

P.S. CONNELL and D.J. WUEBBLES University of California

Lawrence Livermore National Laboratory Livermore, California

Observation and measurement of 'reservoir' species, including H202, CeON02, HN04, HOCe, N20S and others, can potentially t~st some portions of photochemical models of the stratosphere, leading to improvements and increased confidence in model predictions. But abundance measurements of a single reservoir species without accompanying values for other species do not serve, in most cases, to constrain the related model mechanism and parameters within the recognized uncertainties. This follows from the sensitivity of abundance of a species to fluctuations in its long-lived pretursors from transport processes. A better test of theory would be provided by correlation studies in which precursor con­centrations and photolytic fluxes are measured simultaneously and in the same air volume as the reservoir species. Three recent reported differ­ing observations or upper limits for H202 give an example of the diffi­culties. All three reported values could be nearly consistent with the current LLNL one-dimensional stratospheric photochemical model, depen­ding on the values of 03, NOx and H20 appropriate to each measurement. The important precursors in each case can be identified by consideration of the appropriate kinetics and observed precursor variability.

1. Introduction Species such as HN04, CeON02 and N20S are poorly characterized or

completely unobserved in the stratosphere, but current models of stratos­pheric photochemistry are sensitive to the rate constants of their reac­tions, which are included based on laboratory results. These atmospheric constituents, collectively termed 'reservoir' species, are closely con­nected to the active radicals in the ozone-controlling catalytic cycles. Understanding model sensitivity to their inclusion is particularly impor­tant in studies of the response of stratospheric ozone to postulated fu­ture increases of nitrogen oxides or chlorine radical species.

Historically, predicted depletions of the ozone column for given per­turbation have varied widely with certain model changes. At the same time calculated ambient distributions of many important species have varied only moderately given mechanisms that predict widely different impacts on ozone (1). Determining the implications of stratospheric observations in terms of alternate theoretical models can then be problematic. The calculated changes in reservoir species concentrations among alternative models are, however, often more pronounced (1). Reservoir molecules are thus of in­trinsic interest for their direct involvement in ozone-controlling photo-

Ozone Symposium - Greece 1984 - 61 -

chemistry as well as for their potential for guiding development of the theoretical chemical models.

The discussion below outlines the photochemistry of several reservoir species and attempts to address the question of their value in constrain­ing theoretical models. The group, H202, HN04, C~ON02, HOC~, N20S and HONO, that might be considered reservoir species is somewhat disparate. Distinctions can be made on the basis of diurnal variability, chemical time constants, and participation in production or loss processes for the rela­ted radical species, HOx, NOx and C~Ox.

2. Behavior of the reservoir species In a mid-latitude one-dimensional model, concentrations of N20S, HONO

HOC~ and to a smaller extent C~ON02 are calculated to vary diurnally, while H202 and HN04 do not deviate significantly from their diurnally averaged value. The calculated diurnal dependences at 30 km are shown in Fig. 1. The diurnal profiles of NOx and C~Ox in the stratosphere are the result of exchange with the temporary reservoirs N200 and C~ON02 for NOx and C~ON02 :for C~O .

Ch~mical time constants above the lower stratosphere for the reser­voir species are shorter than about a day, so that transport is of lesser importance to their abundance than photochemistry. HOC~ and HONO have chemical time constants shorter than an hour in the mid stratosphere. HN03 and HC~ might also be considered reservoir species, with time constants generally longer than a day and thus little diurnal variability. HONO and HOC~ sequester fractions of the C~Ox and NOx families during the day, while HN04, HN03, C~ON02 and HC~ sequester NOx and C~Ox on a longer term and participate in radrcal loss process. H202 participates largely as a tracer for average HOx levels.

3. Kinetics of the reservoir species The reactions controlling reservoir species concentrations are:

H202 : 1 HOO+HOO 2 HO+H202 3 H202 +hv

HN04 : 4 HOO+N02 5 HO+HN04 6 HN04+hv

N2 Os : 7 (N02 +03 8 N02 +N03 9 N205+hv

C~ON02 : 10 C~0+N02 11 C~ON02+hv

HOC~: 12 HOO+C~O 13 HOC~+hv

HONO: 14 HO+NO 15 HONO+hv

H2 02 +02 H20+HOO 2 HO HN04 H2 0+N02 +02 HO+N03 N03 +02) N20S N02 +N03 C~ON02 C~+N03 HOC~+02 HO+C~

HONO HO+NO

prod. loss loss prod. loss loss

7 10 ~

prod. loss prod. loss prod. loss bO­

o prod. r-i

loss.

HN04 • "'-'" I

/ /

I

8e- H2 O2 [ i

fHOC~~ I 7 ~LL~L~L~

o 3 6 9 12 15 18 21 24

Local Time, hr

Fig. 1. Diurnal variation at 30km. Information on the temporary reservoir molecules N20S and C~ON02 can be derived from the diurnal dependence of the associated radicals. While C~ON02 has been only tentatively identified in the stratosphere, the diur­nal·behavior of C~O has been used to infer the validity of the calculated photolytic constant for reaction 11 (2). When good diurnal data for N20S and C~ON02 become available, mass balance and the time dependence of the concentrations can be used to verify rate constants of the reactions listed above and the absence of any important unconsidered reactions.

- 62-

For the reservoir species without significant calculated diurnal var­iability, H202, HN04 and, to a certain extent, C~ON02, abundances reflect the small set of rate parameters shown above and the diurnally averaged concentrations of the source radicals, HOO, N02 and C~O. Neglecting trans­port of these species with lifetimes less than about a day, steady state concentration expressions can be written:

[H2 02] kl [HOO] [HOO] / (j3 + k2 [HO])

[HN04] k4 [HOO] [N02] / (j6 + k5 [HO])

[C~ON02] kl 0 [C~O] [N02] / jll .

The expressions for HONO and HOC~ are similar, using the instantaneous values for radical concentrations and photolytic constants:

[HONO]

[HOCt]

kI4 HO] [NO] / jIb

k12 [HOO] [C~O] / j13·

4. Implications of stratospheric observation of reservoir compounds Taking H202 as an example, measurement of its stratospheric abundance

contains information on kl , k2 ,j3 and concentrations of HO and HOO. To investigate how an observation of H202 could constrain a model by compari­son to a theoretical profile, the uncertainties introduced by each term can be evaluated. The current uncertainty quoted by the NASA panel for data evaluation in JPL Publication 83-62 for the rate constants of reactions 1 and 2 at 220 K are, respectively, factors of about 2.5 and 1.6. The room temperature uv spectrum of H202 has been measured by several groups with good agreement and is probably good to 15%, although the temperature depen­dence below room temperature has not been investigated. The overall uncer­tainty associated with the kinetic parameters at stratospheric temperatures is about a factor of 3.

For model comparison to a profile of H202 taken by itself, concentra­tion values for HO and HOO are those generated by the model for the appro­priate solar zenith angle in a one-dimensional or season and latitude in a two-dimensional model. In the stratosphere, these values, averaged over the chemical lifetime of H202, are characterized by temporal and spatial variability. This results from transport-induced fluctuations in long­lived species' such as 03, NOy, CH4, CO and H20, that are involved in the production and loss of HOx. The spread expected for [HO] and [HOO] can not presently be taken from direct observations, but can be estimated from the photochemical mechanism for HOx and estimates of variability in long-lived species concentrations in available data.

The response of HO can be approximated by a power law expression,

d{ln[HO]}/d{ln[precursor]} = f(rate constants, mechanism).

These logarithmic derivatives can be evaluated for HO and HOO with re­spect to the important precursor species and the results included in the expressions given above for H202 in terms of HO a~d HOO. Using data of Attmannspacher (3) and Pittock (4) for 03, Noxon (5) for N02, and Kley (6) for H20, variabilities in the 20-30 km region can be crudely estimated at 20%, 20% and 15%, respectively. Variations in CO and CH4 are assigned at 15%. This geophysically based uncertainty translates to an expected factor of 2.5 for H202 around 25 km, comparable to the current kinetically based uncertainties. An immediate consequence is that the current theory can not

- 63-

provide guidance in interpreting the three reported observations or upper limits for H202 in the mid stratosphere (7,8,9), since they range over the spread expected. The Waters et al. tentative observation (7) does, how­ever, somewhat exceed the upper limit of the calculated range (see Fig. 2). Results of similar treatments for other reservoir species at 30 km are summarized in Table I.

Harries (10) has shown that propagation of errors for the number of variables in an expression like that for H202 precludes a direct test with any precision. However in situ correlation experiments similar to those proposed for HO could be valuable for several reasons. First, in corre­lating changes in H202 to fluctuations in the precursors, the relationship of H202 with HOx can be tested without precise values of the rate con­stants 1-3. Second, the logarithmic derivatives for H202 are larger than for the HOx radicals themselves. Third, the longer chemical lifetime of H202 relaxes the restraints on temporal and spatial resolution needed for the HO experiment, although the measurement techniques for H202 also suffer from poorer resolution compared to those available for HO. Since H202 is a tag for HOx, H202 correlation experiments would be valuable independent sources of data for verification of the portions of the theoretical photo­chemical mechanism controlling HOx in the stratosphere.

35

30

~

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20

15

Chance and Traub

55

6 7 8 9 40

log10 Concentration, mol cm-3 ~ 35

~H~~~::I Fig. 2. '"dicted r~ge for [", ",] 1: !

TABLE 1 ;:: Logarithmic Derivatives at 30 km ~ 20

HO HOD H202 HN04 HN03 HONO Ce..ON02 HOCe..

03 -0.2 1.1 2.4 1.3

-0.2 -1.2 1.8 2.9

Long-lived Species NOy H20 CH4 0.05 0.4 0.01 0.6 0.45 0.02 1. 1 0.95 0.05 0.2 0.2 0.02 1. 1 0.45 0.01 1.1 0.4 0.01 0.05 0.4 -1.0

-0.35 0.9 -1.0

CO 0.0 0.01 0.01 0.01 0.0 0.0

HCe..

1.0 1.0

-64 -

15 I 10

5

o ~~~~~~w-~~~~~~ o 2 3 5

[Ce..ON02] [H2 O2] / ([HN04 ] lHOCe..])

Fig. 3. Reservoir species ratio.

5. Projections More fancifully in view of the current level of ability in observing

the reservoir species, measurement of reservoir species abundances should be useful as consistency checks on the important direct measurements of radicals. The expressions given above, except for HONO, depend directly only on HO, HOO, ceo and N02 . These radical abundances can be derived in various ways from combinations of the reservoir species abundances. If the chemistry is well understood, these derived values should correspond well to the directly measured data. As an intriguing example, the ratio

can be seen to be independent of geophysical fluctuations at a given lati­tude, since the photolysis terms generally dominate the denominators. It is also roughly constant with altitude in the mid stratosphere (Fig. 3). For column methods like ground-based IR absorption this relationship could be used to infer a species abundance, or, if lines of each molecule could be identified and concentrations quantified, to test the observational method or the corresponding theoretical mechanism.

ACKNOWLEDGMENTS

This work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48 and supported in part by the Department of Energy C02 Research Divi­sion.

REFERENCES

1. DERWENT, R.G. and A.E.J. EGGLETON, "On the validation of one-dimen­sional CFC-ozone depletion models," Nature, 293, 387-389, 1981.

2. SOLOMON, P.M., R. DE ZAFRA, A. PARRISH and J.W. BARRETT, "Diurnal Variation of Stratospheric Chlorine Monoxide: A Critical Test of Chlorine Chemistry in .. the Ozone Layer," Science, 224, 1210-1214, 1984.

3. ATTMANNSPACHER, W., HUber Messungen des vertikalen Ozongehaltes der freien Atmosphare oberhalb 20 km Hohe uber dem Hohenpeipenberg, " BPT -Ber. 2/81 77-84, 1981.

4. PITTOCK, A.B., "Climatology of the vertical distribution of ozone over Aspendale(38S,145E)," Quart. J. R. Met. Soc., 103, 575-584, 1977.

5. NOXON, J.F., E.C. WHIPPLE, JR. and R.S. HYDE, "Stratospheric N02, 1. Observational method and behavior at mid-latitude," J. Geophys. Res., 84, 5047-5065, 1979.

6. KLEY, D., J.W. DRUMMOND and A.L. SCHMELTEKOPF, "On the structure and microstructure of stratospheric water vapor," Atmospheric Water Vapor, A. Deepak, T.D. Wilkerson and L.H. Ruhnke, eds., Academic Press, 315-327, 1980.

7. WATERS, J.W., J.C. HARDY, R.F. JARNOT and H.M. PICKETT," Chlorine monoxide radical, ozone, and hydrogen peroxide: stratospheric measure­ments by microwave limb sounding," Science, 214, 61-64, 1981.

'8. CHANCE, K.V. and W.A. TRAUB, "An upper limit for stratospheric hydro­gen peroxide," J. Geophys. Res., Preprint Series No. 2041, 1984.

9. DE ZAFRA et al., cited in Ref. 8. 10. HARRIES, J.E., "Stratospheric composition measurements as tests of

photochemical theory," J. Atm. Terr. Phys., ~ 591-597, 1982.

-65-

DERIVATION OF OH CONCENTRATIONS FROM LIMS MEASUREMENTS

J A PYLE, A M ZAVODY, J E HARRIES, P H MOFFAT Rutherford Appl eton Laboratory, Chi lton, Di dcot,

Oxfordshire, OXll OQX

Stratospheric concentrations of OH have been derived from LIMS measurements of mi nor consti tuents. Two methods have been used. Assumi ng that HN03 and N02 are in photochemi cal steady state, LIMS measurements of these species, with knowledge of appropriate rate constants and a calculation of the HN03 photolysis rate, allow nearly global fields of OH to be deri ved. The deri ved profi les show sati sfactory agreement with model calculations and the limited number of in situ observations. As a check on our method, OH has also been derived by calculations of its sources and sinks using the LIMS measurements of H20. The two methods agree extremely well in low latitudes. At higher latitudes the agreement is less satisfactory. This is discussed in terms of the diurnal behaviour of the species and the time constant of the HN03/N02 equilibrium.

Introducti on

OH is a very important radi cal in the stratosphere. For example it plays important roles in the destruction of odd oxygen both in the lower stratosphere and upper stratosphere. OH also plays a significant indirect role in ozone destruction. It can remove reactive radicals by reacting with them and forming more stable molecules (eg HN03, HOC1), thus preventing these radicals from taking further part in the catalytic cycles /1/.

There are very few stratospheric measurew~nts of OH, confined to the northern hemi sphere and mi d latitudes /2,3/. Thi s paper presents results on OH concentrations which were derived from measurements made by the limb infrared monitor of the stratosphere (LIMS). Two methods were used. In the fi rst OH was obtai ned by consi deri ng its sources and si nks; in the second use was made of the fact that it determines the ratio of HN03 and N02. Preliminary results using the ratio method have already been published /4/.

Methods of Deriving The OH Concentration

a) From sources and sinks. The principal source of H, OH and H02 in the stratosphere is the

reaction of water with OeD), with a small contribution from the oxidation of methane. The main sink between 20 and 40km is the recombination reaction with H02; reactions of OH with HN0 3 and HNO,+ are important sinks in the lower stratosphere.

Ozone Symposium - Greece 1984 - 66-

We have consi dered a detai led photochemi cal scheme in whi ch the rate of change of odd hydrogen is given by

dHOx = 2kl H20 0(10) + k2 CH4 (010) ~

- 2k4 H0 2 OH - 2ks HN04 OH

- 2k7 HN0 3 OH - ksCH40H - 2ksH202 OH (1 )

Here it was assumed that HN04 is ina photochemi cal steady state, and further production of odd hydrogen from the oxidation of methane has been neglected. The ti me constants for the odd hydrogen fami ly are short throughout the stratosphere, and so the time derivative in equation (1) can be equated to zero.

H20, HN0 3, N02 and 03 concentrations were measured by the LIMS /5/ experi ment. Monthly mean cross - secti ons of methane from the stratospheri c and mesospheric sounder (SAMS}l flown on the same satellite, were provided by Dr R L Jones at Oxford. O( D), HN04, H02, and H202 can be computed from satellite data either explicitly or as a function of OH by using the steady state expressions presented below.

0(10) = Jl0 03

KllM

H k27CO + k280 QH

k13D2M + k30 D3

H02=k1203 + k13 (H/OH) 02M OH k14D + k1S03 + k16 NO

HN04 = k21N02H02M k26DA + J22 HN0 4

H202 = k1S H02 klSDA + J20

(2 )

(3 )

(4 )

(5)

(6 )

The concentrati ons and rate photolysi s coeffi ci ents can be substituted into equation (1) which can be solved iteratively for OH. The rate constants were taken from recent compilations /6,/7/, and photolysis rates were found by using zenith angles appropriate to the latitude, month and time of day of observations.

b) From the ratio of HN0 3 and N0 2• The rate of change in HN0 3is given by:

dHN03

dt

- 67-

(7)

In steady state the time derivative is zero and OH can be expressed expli citly:

(8) OH=

All the parameters involved, except J 3 , are known from measurements and, compared to the 'sources and sinks' method, solution of the equation for OH appears much simpler. Equation (9), however, is inherently less suitable than equation (1) due to the longer time constant for equilibrium between N0 2 and HN0 3 •

Results

Zonal and monthly means of OH were computed, using the above methods, for each month when LIMS operated. The gross features of the dri ved OH are common to all months and ngure 1 show? the cross-section for May 1979. Maximum values of greater than 107 cm- j are found in the upper stratosphere (above about 40km) at low and mi ddl e 1 ati tude. In the regi on of the maximum, the gradients of the OH concentration are very weak and there is no evi dence for any si gni fi cant st ruct ure i nit. The concent rat i on decreases monotoni cally with pressure to a val ue of around 2 x 10 6 cm- 3 at about 20km. The variation which latitude is most pronounced where the smallest concentrations are found.

Although the agreement between the OH values derived in two different ways is good, there are also obvious differences.

(i )

(i) The ratio method yields higher concentrations then the sources and si nks methods at all altitudes>about 38km.

(i i) The hi gh 1 ati tude behavi ours are di fferent. Below about 38km the ratio method gives concentrations that are consistently lower than those given by the sources and sinks method.

The Upper Stratosphere

The larger values derived by the ratio method in the upper stratosphere could be explained in terms of a bias in retrieved LIMS HN0 3 in this region. The HN03 densi ty and hence emi ssi on decreases here rapi dly, and uncorrected stray radi ati on may become a si gni fi cant fracti on of the total power received /8/. This would lead to an over estimation of HN0 3, and hence to a derivation of OH by the ratio method which is too large.

(i i )

Hi gh Lati tudes

The orbit of Ni mbus 7 is such that LIMS makes measurements in low 1 at it udes near to 1 oca 1 noon or mi dni ght.

- 68-

In higher latitudes, however, measurements can be made at local times whi ch are much nearer to sunset. Thi s has important i mpli cati ons for the derivation of OH by the ratio method.

Retai ni ng the ti me dependence from equati on (7), equati on (8) becomes

OH = dHN03/dt + J3 HN03

kzNOzM - k7 HN0 3

(9)

Equation (9) is exact and should give precisely the same derived OH as found usi ng equati on (1). The dHN03/dt term wi 11 be rrost si gni fi cant when J3HN03 is small. This will be just the situation discussed above i.e. at low solar elevations corresponding, for LIMS, to the measurements made at high latitudes in the late afternoon.

To exemplify this point figure 2 shows calculations using a diurnal photochemi ca 1 rrode 1 in whi ch OH was cal cul ated di rect ly from it sources and sinks and also derived, by the ratio method, uSing rrodelled NOz and HN03. At low zenith angles the two methods agree well. For large zenith angles, when J3 becomes small, the discrepancy becomes rrore than an order of magnitude. Notice that in the model dHN03/dt is positive around dusk; ignoring this term leads to a lower OH deri vati on in the rati 0 method.-

Cl early it is evi dent that deri vati ons of OH usi ng LIMS data should show a di screpancy at large zenith angles. Esti mates of dHN03/dt from LIMS data are, as in the rrodel, positi ve in the late afternoon so that the observed di screpancy is in the predi cted sense with the sources and si nks methods predi cti ng larger OH. In fact by usi ng these esti mates of dHN03/dt in equation (9) we have been able to reduce significantly the difference in OH between the two methods'.

May

Ratio 50 S.S

E \ .><

~~171 ~ ..-.c 40 0> ·ill .0 .c 1'-- - ~ 5 E Q)

c \ - _1(7L_~ Q) ~

E 10 ~ ·x 30 \ r"-... II) 0 Q) '- '- 5(6) 5(6) 3(6)_ '-a. a.. a. « \ - i/ 3(~\. /3~-----

20 50 90S 60 30 0 30 60 90N

Latitude

j

Figure I: Derived OH concentration (cm- ) by the two methods.

- 69-

Accuracy of Derived OH

We have considered the errors in the derived OH resulting from errors in both the LIMS data and the kinetic data. To summarise, errors in the LIMS data lead to uncertai nty in deri ved OH by the rati 0 method of -40% in the ~d stratosphere. The errors in the sources and sink method are less, being typically -20%. (Note that this method is quadratic in OH and smaller errors are to be expected).

Errors due to uncertai nti es in ki neti c data are of a si ~ 1 ar order. We believe that given the scarcity of OH measurements, the derivations, despite relati vely large uncertai nty, represent an important advance in knowledge of stratospheric composition.

Conclusions

Global fields of OH have been derived by two independent methods using LIMS and SAMS data for the period from November 1978 to May 1979. The two meth·ods used produce results whi ch are generally in good agreement. It is encouraging that areas of discrepancy can be explained in terms of present theory. Thus we believe that these calculations have shown the consistency of the satellite data sets. Considered as a test of photoche~cal theory, the agreement between the two methods does not suggest inadequacies in our present understandi ng. We do not cl ai m however, that thi s necessari ly represents a confi rmati on of present theory.

"'-107 "-

-32°N, 36 km, May "-Model Sand S - \ Madel ratio ---- \ Run 8

\ \ \ \

106 \ \ \ I I I I

5 1012.00 14·00 16·00

Time

Figure 2: Model calculations of OH by the two methods.

-70 -

References 1. W.M.O. The Stratosphere 1981: Theory and Measurements Rep No 11 (WMO

Global Ozone Research and Monitoring Project, Geneva, 1982)

2. ANDERSON, J.G. et al. (1980). Free radicals in the Earth's stratosphere. A review of recent results. Proc NATO Advanced Study Institute on Atmospheric Ozone (eds M Nicolet and A C Aikin). 223-251.

3. HEAPS, W.S., McGEE T.J., HUDSON, R.D. and CAUDILL, L.O. (1982). Stratospheric ozone and hydroxyl radical measurements by ballon~borne Lidar, Appl Opt 21, 2265-2274.

4. PYLE, J.A., ZAVODY, A.M., HARRIES, J. E. and P H MOFFAT. (1983). Deri vati on of OH concentrati on from satellite infrared measurements of N0 2 and HN0 3 ,Nature 305,690-692.

5. GILLE, J.C. and RUSSELL, J.M. III. (1984). The Li mb Infrared Monitor of the St ratosphere (LIMS) ex peri ment: Experi ment descri pti on, performance and results, J Geophys Res. 89, 5125-5140.

6. J.P.L. Publi cati on 83-62. (1983). Chemi cal Ki netits and Photo-chemi cal Data for use in Stratospheri c Modeli ng, Evaluati on Number 6.

7. CODATA, Eval uated Ki neti c and Photo-chemi cal Data for Atmospheri c Chemi stry: Supplement I J Phys Chem Ref Data 11, 327-496 (1982).

8. GORDLEY, L.L. (1984·). Private Communication.

- 71 -

LIMS DATA: INFERRED STRATOSPHERIC DISTRIBUTION OF NOx AND HOx TRACE CoNsTITUENTs AND TAE CALCULATED ODD NITROGEN BUDGET

L.B. CALLISl, M. NATARAJAN2, J.M~ RUSSELLl, and R.E. BOUGHNER 1 INASA Langley Research Center

Summary

Atmospheric Sciences Division Hampton, Virginia 23665

USA 2Systems and Applied Science Corporation

Hampton, Virginia 23666 USA

LIMS, SAMS, SBUV, and in-situ data have been used to infer species not measured but which are of photochemical interest, e.g. O(3P), 0(10), NO, N205, OH, H02, C10 and HC1. Production and loss of odd nitrogen have been calculated and estimates have been made of the odd nitrogen transport due to a diabatically driven circulation derived from LIMS data. Data used from LIMS inc 1 ude 03, N02, HN03, H20 and T. CH4 and N20 were taken .from SAMS and the UV sola r f1 ux from the SBUV instrument. Species were inferred for periods in October, December, March, and May. The present discussion is for December. Results indicate: (1) maximum stratospheric odd nitrogen levels of 25 ppbv; (2) evidence of odd nitrogen transport from the mesosphere appearing at 25 km in the winter-time polar latitudes; (3) the polar night build-up of high levels of N205 beginning after the Autumnal equinox; and, (4) the possibility of large downward fluxes of odd nitrogen into the troposphere during the winter at latitudes poleward of 60°.

1.1 Introduction

There is an unprecedented volume of data applicable to the study of stratospheric processes. Two parallel efforts have been undertaken at the NASA Lang1 ey Research Center to use LIMS and SAMS data in the study of st ratospheri c photochemi stry. One was to determi ne whether the observat ions were cons i stent with cu rrent ly accepted photochemi stry (1). The present effort is directed towards the inference of species of photochemical interest but not measured by the above instruments. These species include O(3P), 0(10), NO, N03, N205, HN04, OH, H02, H202, C10, C1, HCL, CLN03, HOC1, odd nit rogen and odd hydrogen. These speci es were inferred from 60S to 80N (limited by the LIMS coverage) in 10° latitude bands, from 20.5 to 53.5 km with a grid spacing of 1.5 km, and for periods of time in October, December, March, and May. Only the December results are discussed.

A second aspect of this study involves the calculation of efements of the odd nitrogen budget. The stratospheri c product i on and loss of odd nitrogen, and the photodissociative loss of N20 have been calculated. LIMS measurements of 03, H20, and T have been used with ambient C02 levels and with the Langley radiative code to derive a diabatically driven residual circulation which has been used to estimate odd nitrogen transport.

Ozone Symposium - Greece 1984 -72 -

1.2 Assumptions, Approach, and Photochemical Data Used

The photochemical code used includes 25 species and 61 reactions in the Ox, C1 x, HOx, and NOx family. The radiative code used is a wi de band model. Photochemi ca 1 data used are those recommended by JPL Publication 83-62 with six exceptions. The lower limits described in that reference for 0+H02, O+OH, NO+03 and 03+H were used. The upper limit for OH+H02 and the slow rate for C10+0 were also used. As discussed in (l), use of these six modified rates yield better agreement between observations and model calculated parameters than do the recommended rates. The most recent descriptions of the cross-sections for the Herzberg continuum, NO photodissociation, and treatment of the Schumann Runge band are used.

To permit the derivation of an extended species set from the LIMS and SAMS data the following assumptions are made. (a) All inferred species are assumed to be in equilibrium except N205, and C1N03, (b) Levels of N205 are estab1 ished at a latitude-altitude point with an iJ:erative diurnal calculation used in conjunction with measured values of 03, T, H20, and N02. This is the same procedure used in (2). A diurnal correction is applied to equilibrium C1N03. Levels of H202, calculated according to equilibrium relations, will be in error (30 percent or less) near 20 mb with little effect on other derived species. (c) The mixing ratio of H2 is assumed constant at 0.5 ppmv. (d) Vertical profiles with no latitudinal variation, are assumed for CO and C1 x based upon data and I-D model results and in situ data. The maximum mixing ratio of CO is 0.15 ppm v and occurs at 50 km. The maximum mixing ratio of C1 x occurs at 50 km and is 2.55 ppbv. (e) The net radiative heating is taken to be the net diabatic heating in the calculation of the residual circulation. (f) The residual circulation is calculated assuming that transients may be neglected and that the divergence of the Eliassen-Palm flux vector, FEP, is small. Under ci rcumstances for whi ch these assumpt ions are va 1 i d, the resu ltant residual circulation is a close approximation to Lagrangian transport. For monthly mean averages, they represent at worst, a reasonable estimation of the net transport.

2.1 Results

Results for December are summarized in figures 1 through 12. Figures for specie levels are for daytime conditions at the time of measurement, usually between 12 pm and 4 pm local time. Figure 1 shows contours of OH concentrations as a function of altitude and latitude with a maximum of approximately 2x(107) mo1./cm3 occuring at 45 km and near the sub-solar poi nt. Compa ri sons of OH profil es inferred nea r the Verna 1 equi nox show good agreement with previous measurements [see (1)]. Figure 2 shows the related H02 mixing ratios.

Mixing ratios of NO, the principal daytime component of total odd nitrogen (= NO+N02+N03+2xN205+HN04+C1N03), are shown on figure 3 and the odd nitrogen distribution is given on figure 4. The maximum NO level is approxi mate 1y 18 ppbv and the correspondi ng odd nitrogen 1 eve 1 is 21 ppbv. Intersting1y enough, the maximum odd nitrogen mixing ratio is not found in the middle stratosphere odd nitrogen net production region shown in figure 5. It is found near 25 km poleward of 60N. The maximum levels determined are in excess of 25 ppbv. This suggests that these levels of odd nitrogen, Which are higher than those in the vicinity of its stratospheric source, are a manifestation of the transport of odd nitrogen downward from the mesosphere into the stratosphere during the polar night. Observational evidence of this effect at upper levels of the polar winter stratosphere is

- 73-

described in (3) but this is believed to be the first observationally derived indication at lower levels. Data not shown indicate the appearance of the odd nitrogen "bulge" in late October and persisting through December. By March it has disappeared in the northern hemisphere and is begi nni ng to appear in the southern hemi sphere becomi ng well developed by May.

Figures 6 through 9 present the mixing ratio of N205 for the time periods October, December, March, and May, respecti vely. Illustrated is the build-up of N205 as a major component of odd nitrogen at the higher latitudes in the fall and winter, and its decline in the spring and toward the summer. At 60N and 20 km, N205 compri ses 20-25 percent of the tot a 1 odd nitrogen. Within the polar winter night this percentage will grow with most of the N02 bei ng removed by the react ions N02+03 N03+02 and N03+N02 N205. In December in the lower stratosphere at 60N, there is already more N205 than NO and N02 combined. The two dominant contributors to the odd nitrogen levels are HN03 at 10 ppbv and N205 at 5.6 ppbv. The remaining 4-5 ppbv of odd nitrogen is primarily divided between NO and N02·

The interesting distribution of odd nitrogen with latitude at lower levels of the stratosphere suggests an equally interesting distribution of odd nitrogen transport downward through the 20.5 km level. Figure 10 illustrates the nature of this transport for the four time periods. The transport is based upon the calculated residual circulation field under the assumptions stated earl ier. The results suggest that 1 ittle or no odd nitrogen is transported downward by the residual circulation between the latitudes of 30S and 30N at any time, that the downward transport occurs poleward of these latitudes and then in the fall, winter, and early spring. In comparison with 1-0 model transport across the same level there are substantive differences. The calculated downward flux at the higher 1 at itudes may be hi gher by as much as a factor of 30 or more than the average downward flux calculated in a 1-0 model. Further the composition of the downward fluxes are different with levels of NO+N02 reduced to 15 percent (of the total odd nitrogen) from 30 percent for the 1-0 model, and N205 increased to 34 percent from 17 percent. The HN03 in both cases is 46-50 percent. Such results may have significant ramifications with regard to regional tropospheric photochemistry. especially in the winter.

Figures 11 and 12 illustrate the distributions of HCl and C10. Though Cl x was an assumed input with no latitudinal variation, the equilibrium code partitions the Cl x yielding latitudinal distributions of the family components consistent with the observations and the model.

REFERENCES

1. NATARAJAN. M.; CALLIS. L. B.; RUSSELL. J. M.; and BOUGHNER. R. E. (1984). A study of the ozone photochemistry in the upper stratosphere using LIMS data. Quadrennial Ozone Symposium, Halkidiki. Greece.

2. CALLIS. L. B.; RUSSELL, J. M •• III; NATARAJAN. M.; and HAGGARD. K. V. (1983). Examination of wintertime latitudinal gradients in stratospheric N02 using theory and LIMS observations. Geophys. Res. Lett •• 10, 945-948.

3. RUSSELL. J. M.; SOLOMON. S.; GORDLEY, L. L.; REMSBERG. E.E.; and CALLIS. L. B. (1984). The variabiltiy of stratospheric and mesospheric N02 in the polar winter night observed by LIMS. J. Geophys. Res. (Accepted for publication).

-74 -

OH (mol C",·- . ,0-4) DI:r:EJlBEII 10 DEGIlEE LAT rru DE CIIlD IIEGIONS: 50S-BON

&0 .0

III 121

~~~ 50 50

~~ ~ ~ c.; c.;

?~ ~40 §40 I::: I::: t; I-.

o..l ... ... 3() 30

20 20 - &0 80 - 60 80

ODD N (ppbv) DI:r:EMBEII 10 DEGIlEE LATrrUDE CIIlD IIEGIONS: 50S-BON

60 &0

131 141

50 ~.~~ 50

~ ;:Ii

~( lw!

c.; c.; §40 §40 I::: I::: I-. I-. .., .., ... ...

30 30

20 - 60 0 80

LATrrUDE

PN (mol C"' ..... C··). DI:r:EMBEII 10 IJEGIlEE I.ATrrUDE CIIlD IlECI0NS: 50S-BON

80

(51 161

50 J ~L 50

~ ~ c.; .~ • ••• ~ •••••• ••• _ •• r ••••• ~: c.; §4b ~:.-~.O §4b I::: I::: I-.

~ t; .., ... ...,

30 30

20 ZO -60 80 -80

- 75-

NP. (Pfbv ) DECEJlBER to DECREE LATfrUDE GRID

.orRECT,J_OrN~S~' r5TDS~-~6rOTN~""T<_rTOrr'_rT'_~~~

I7l

~.~O~~~LL~~~~O-L~~IJ~~~~~-LLJ. LATrrUDE

191

..; '" <0

~ ~ ...,

so

~'~0~~~~~~:L~0~~~~~~~~~~~LLj80 LATrrUDE DEC.

1111

-2. 1° _________ 2. 40• ___ -

.j

~-IO Ne - I~

~ .20 tzs S C;: .JO

o LATrrUDE

o March o May Q OctclJe r o Decemller

181

<0 60

1101

·~.OO~~~~~0-L~-~-L-~0~-~L-J--4LO-L~OO-L-J~ South latitUIJ, North

CLC (Pfbv) DECEJlBER to DECREE LATfrUDE GRID

80

60 rRTEC;~rOrN~S~:r5TO;S-~6rO~N~T<_rTOrr,_rT,_rT~~_~

so

~ ..; "'.00 ~ ... .... ...,

so

1121

-76 -

Summary

THE DISTRIBUTION OF OZONE AND ACTIVE STRATOSPHERIC SPECIES: RESULTS OF A THO-DIMENSIONAL ATMOSPHERIC MODEL

D. Cariolle* and D. Brard** *Centre National de la Recherche Meteorologique

31057 TOULOUSE CEDEX, FRANCE **Office National d'Etudes et de Recherches Aerospatiales

92322 CHATILLON CEDEX, FRANCE

He have developed a zonally averaged model which calculates the atmos­pheric composition from ground level to 1 mbar. The model solves the continuity equations of 28 trace species inclu­ding 03 as a function of season and latitude. Results are compared to the in situ measurements of trace gases but also to the zonally averaged monthly mean cross sections derived from LIMS data. The model reproduces the main features of the observations for 03 and N02 but for' HN03 the calculated profiles are too high above 10 mb and at high latitudes in the summer hemisphere.

Model description

The model solves the continuity equations for 12 long-lived species or group of species (Table 1):

ar + div rV + div Fr = P - L at

where r is the mixing ratio, V the wind vector associated to the mean cir­culation, P and L the photochemical production and loss rates, and Fr the flux due to eddy mixing.

In its basic formulation the mean circulation is prescribed for each season according to the calculation of Murgatroyd and Singleton (1961), and the climatology of Louis et al. (1974) is used for the temperature field. Following Miller et al. (1981) this circulation was chosen to approximate the residual mean circulation. The eddy fluxes are calculated by using the diffusion coefficients of Luther (1974).

The chemical scheme is as complete as the one used in our lD model (Cariolle, 1983) except for the products of the methane oxidation chain where CH20 and CO are the only species explicitely calculated. The con­centrations of the short-lived species are updated every model day and used to reevaluate the 24 hours averages of the production and loss rates of the long-lived species • Although the diurnal variations of the species are not explicitely calculated, the detailed averaging procedure takes account of the buildup of N205 and Cl0N02 during the night.

Ozone Symposium - Greece 1984 -77-

The rates of the reactions are taken from the last JPL 82 compilation. The equations are solved on a regular grid with 18 equally spaced latitudes from pole to pole and 25 vertical layers with constant intervals in Log p from 1000 to 1 mb.

Further details of the model formulation may be found in Cariolle (1982).

Description of the LIMS' experiment

The LIMS experiment of infrared radiometry was launched on the Nimbus 7 satellite. It had to sound the vertical structure of temperature and concentrations of four species (03, H20, HN03, N02)'

The satellite was placed in a sun-synchronous, nearly circular orbit, and period of about 104 mn at 955 km altitude. This geometry infers that the compounds are measured at about 13.00 and 23.00 local time of tangent point. The collected data cover a period of about 7 months, for the lati­tudes between 64°S and 84°N, the altitudes between 15 and 65 km (l00-0.1 mb). There are about 20 000 profiles a month for each constituent.

The estimated accuracies for the LIMS measurements taking account of all known error sources (Russell and Gille, 1978) are 15-20% for 03, not more than 3% for T, 25% and 30% for HN03 and N02 respectively in the mid-stratosphere, and 25% for H20.

Calculations of mean cross sections

In order to calculate the zonally averaged monthly mean cross sections derived from the LIMS data, and to compare them with the results of the model, we have interpolated the measured profiles on the nearest layer and latitude of the model.

Comparison measurements/model

We calculate for January, the zonally averaged mean cross sections for 03, H20, HN03 and daytime N02 in the stratosphere.

In figure 1, the model reproduces the observations at low and middle latitudes, but overestimates the 03 amounts near the northern pole below 30 mb. The two modelled and measured H20 fiels (Fig. 2) show an increase from about 3 ppmv in the lower stratosphere to 6 ppmv at the stratopause level which is in good agreement with expected increase due to the methane oxidation.

The measured cross section of HN03 shows a minimum of the mixing ratio in the equatorial region and maximum amounts at the poles (Fig. 3) which is qualitatively reproduced in the calculation. Nevertheless, the model overestimates the concentrations at the summer pole and also above 30 mb at all latitudes.

This latter result is confirmed by the in situ measurements at mid­latitudes (Fig. 5).,

In figure 4, modelled and measured N02 concentrations show a maximum concentration at the summer pole and lower amounts at the winter pole. In the model calculation the dissymmetry is due to the conversion of N02 to N205'

Der.ivation of OH concentration

In the upper stratosphere assuming that N02 and HN03 are in photochemical equilibrium, the daytime OH concentration can be derived from the formula:

-78 -

where the rates kl and k2 were taken from the last JPL 82 report, and the instantaneous value of J3 was calculated with zenith angle, T and 03 data from LIMS. Scattering was included in the calculations.

Results

The figure 6 shows calculated OH profile at 3SoN, along with the in situ measurements of Anderson (1980) for January. Below 3 to 4 mb, the OH profile obtained from the measured HN03 and N02 concentrations, and the in situ measurements agree well with model calculations. Above this level the accuracy of the LIMS measurements are not good enough and the calculation of OH seems meaningless.

.0

.00

TABLE I

Long-lived species or group of species:

Oy = 03 + O(ID) + 0(3p ), NOy = N + NO + N02 + N03 + 2.N20S + HN04 + ClON02 , HN03, N2 0 , Cly = Cl + elO + ClON02 + HOCI + HCl, CH4' H20, CO, CH3Cl, CC14, CFC13, CF2C12·

Short-lived species

O(ID), 0(3p ), H, OH, H02, H202, Cl, ClO, ClON02, HOCl, CH20, N, NO, N02 , N03 , N20 S ' HN04.

------, =====---==:::::: '~:~

20 MOOE ..

.000 E..L...L':':-'~-':-'-~~':-'-''-'-:'~~''''''''~~'':':''-:':'' ~mM~~mmmowm~d~M.M

N L \ "1 ft..Ct. S

Fig. 1 - January zonally averaged mean cross section for the 0 3 concentration.

-79 -

LIMO

~ 10

~ f 100

I~ ~~~~~~~~~~~~LL~~~~~L> 80 10 60 50 i.0 J 20 10 0 10 ZO 3J /,,1 "0 I) 1 €I

N f1 'i,,()l S e(

s

Fig. 2 - Same as figure 1 for the H 2 0 mixing ratio.

2I)MQDEl. -----------. ------------~ 10

l' }O ~e~o~'~0~."~~O~<~~~3~u~2~O~IO~O~,~O~2~O~J~0~<~0~~.~0~,~O~~~ N l..!\rrTlJOt:. •

Fif!. 3 - Same as figure 1 for the HN03 mixing ratio.

LIMO

~ 10 ~~ ~~ 1000 ~.Lo~,J.0~.~o....J.o~<LO~J':-O~2L, ~~~~':'-":"--'--',J.-<-!-''-!-~eL3"

N 1.. " qrUDl S

10 eo T. 6l 5 lor J GI..o 11

N L,I,r I ru[t.

Fig. 4 - Same as figure 1 for the daytime N0 2 •

LIZ. ModeI'II/'9'I 45- N

40 UIo4S 4S-N

30

'"

o Arnold et.1 t980 o E •• ,,, ., •• 191$

• Font.,ull •• t .. 101~ • fl.the. 1980 • H •• tI,. e'tl una _ La"",. MId G,.ndlld ,0'4 D .fI1h.,~r.y , •• 1 l,eO • lo",I,,...rd ., .. 11iI83

, BO'lIIhl ., • t 19B"

o. PPBV

HN0 3

.0

_ Fig. 5 - January mean profile of HN0 3 derived from LlMS data at 45° N compared to in situ

measurements and model range.

- 80-

r i r r II

-- , .... --- Mod.1

"ncI.'.~n 111180

: ' c.~'.~£.'II~q " TIO'\! MO!...(.'-J,

REFERENCES

10 •

- Fig. 6 - Calculated OH profile from LlMS data (see text) and from the model along with the in

situ measurements of Anderson.

Anderson, J .G. (1980). Proc. NATO Advanced Study Institute on Atmospheric Ozone, Edited by Nicolet, a., and Aikin, A.C., 233-251.

Arnold, F., Fabian, R., Henschen, G., and Joos, W. (1980). Stratospheric Trace Gas Analysis from Ions: H20 and HN03. Planet. Space Sci. 28, 58l.

Borghi, R., Cariolle, D., Girard, A., Laurent, J., et Louisnard, N. (1983). Comparaison entre les resultats d I un modele unidimensionnel et des resultats de mesures stratospheriques de CH4, H20 et des oxydes d'azote. Rev. Phys. Appl. 18, 229-237.

Cariolle, D (J. 982). Presentation d' un modele bidimensionnel photochimique de I'ozone stratospherique. Note de Travail de l'EERM, nO 27.

Cariolle, D. (1983). The Ozone Budget in the Stratosphere: Results of a One-dimensional Photochemical )lode!. Planet. Space Sci. 31, 1033-1052.

Evans, W.F.J., Fast, H., Kerr, J.B., Me Elroy, C.T., O'Brien, R.S., Wardle, D.r., Mc Connell, J.C., and Ridley, B.A. (1978). Stratospheric Constituent Measurements from Project Stratoprobe. Proc. WHO Symp. on the Geophysi~al Aspects and Consequences of Change in the Composition of the Stratosphere, WHO Publ. 511, World Meteorological Organization, Geneva, 55-60.

Fontanella, J.C., Girard, A., Gramont, L., and Louisnard, N. (1975). Vertical Distribution of NO, N02 and HN03 as Derived from Stratospheric Absorption Infrared Spectra. Appl. Opt. 14, 825-839.

Harries, J.E., Moss, D.G., Swann, N.R.W., Neill, G.F., Gildward, P. (1976). Simultaneous Measurements of H20, N02 and HN03 in the Daytime Stratosphere from 15 to 35 km. Nature 259, 300-301.

Harwood, R.S., and Pyle, J .A., (1975). A two-dimensional Mean Circulation Model for the Atmosphere below 80 km. Q.J. Roy. Meteorol. Soc. 101, 723-747.

Lazrus, A.L. t Grandrud, B.W., Greenberg, J., Bonelli, J., Mroz, E., and Sedlacek, W.A. (1977). Hidlatitude Seasonal Measurements of Stratospheric Acidic Chlorine Vapor. Geophys. Res. Lett. 4, 587-589.

Louis, J.F., London, J., and Danielsen, E.F., (1974). The Interaction of Radiation and the Meridional Circulation on the Stratosphere. Proc. IAMAP/IAPSO combined First Special Assemblies, Melbourne (Australia), II, 1205-1214.

Louisnard, N. t Fergant, G.) Girard, A., Gramont, L., Lado-Bordowsky, 0., Laurent, J., Le Boiteux, S., and Lemaitre, M.P. (1983). Infrared Absorption Spectroscopy Applied to Stratospheric Profiles of Minor Constituents. J. Geophys. Res. 88, 5365-5376.

Luther, F.M., (1974). Large Scale Eddy Transport. In Lawrence Livermore Laboratory, Second Annual Report DOT-ClAP Program, UCRL-51336-74, Mac Cracken, M.C., 66-73.

Miller, C" Filkin, D.L., Owens, A.J., Steed, J.M., and Jesson, J.P. (1981). A Two-dimensional Model of Stratospheric Chemistry and Transport. J. Geophys. Res. 86, 12039-12065.

)lurgatroyd, R.J., and Singleton, F. (1961). Possible Meridional Circulations in the Stratosphere and Mesosphere, Q. J. Roy, Meteoro1. Soc. 87, 125.

Russell, J.M., and Gille, J.C. (1978). The Limb Infrared Monitor of the Stratosphere (LIMS) Experiment. Edited by Madrid, C., Goddard Space Flight Center, Greenbelt (MO), 71.

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~M6T!~6; ~Q;~bB!Q Q~Q~; gBb~§; gb6Q~6bT!Q~~l TB; ~M~TBbQT!Y; ~;BTMB~bT!Q~ b~~BQbQB

A. J. OWENS, C. H. HALES, D. L. FILKIN, C. KILLER, and K. KC FARLAND

Experi.ental Station, E304 E. I. du Pont de Ne.ours & Co., Inc.

Wil.ington, DE, 19898, U.S.A

Using a coupled one-di.ensional at.ospheric .odel -- consisting of a narrow-band radiative-convective calculation of the vertical te.pera­ture profile plus a co.plete photoche.ical code to deter.ine trace gas concentrations -- we esti.ate the potential effects on at.o­spheric ozone of a continuation through the .iddle of the next century of presently observed trace gas concentration changes. A "Base Case·· scenario proJecting presently observed trends forward in ti.e gives a calculated ozone increase of about +3% by the year 2050. The effect of the individual species is est hated by a new "subtrac­tive perturbation" approach.

During the last decade, it has been recognized that hu.an activities .ay be changing the concentrations of several trace gases that influence stratospheric ozone. Early assess.ents concentrated on the effects of NOx inJected by supersonic transports (SSTs) and conventional aircraft as well as those due to the release of chlorofluorocarbons (CFCs). However, in recent years, the iaportance of increases in carbon dioxide, aethane, and nitrous oxide due to burning of fossil fuel and to changing agricultural practices has been recognized.

Although the influence of these trace gases has usually been calcu­lated by considering concentration changes of each gas separately in an ataosphere that is otherwise ··unperturbed", a aore coaprehensive approach has recently been eaphasized: the ti.e-dependent changes in all these iaportant trace gases are considered si.ultaneously (Wuebbles et al., 1983). Taking this approach one step further, in this paper we adopt as our reference ataosphere a "Base Case" corresponding to a best-guess scenario for all the trace gases, rather than an unperturbed initial ataosphere. Since the interactions between the various trace gases are co.plex and non­linear, this approach gives a aore realistic estiaate of the prOJected effect of a particular species than a single perturbation calculation that is coapared with an otherwise unchanging at.osphere.

We give results froa our one-diaensional ataospheric aodel for the changes in the vertical profiles of the ozone concentration and the local at.ospheric teaperature for a center-line, best-guess scenario prOJecting presently observed trace gas trends through the .iddle of the next cen­tury. We then apply the subtractive perturbation aethod to esti.ate the contribution of the individual species to the coaplete Base Case scenario

Ozone Symposium - Greece 1984 - 82-

calculations. Calculations for several excursions froa the Base Case are given to assess the sensitivity of the results to the adopted scenarios.

The coupled one-diaensional aodel is described in detail in Owens et al. (1984). It consists of a detailed narrow-band radiative-convective aodel coupled with a coaplete cheaistry-transport aodel. The cheaical kinetic data base used is that given in JPL 82-57.

The Base Case scenario used in the calculations reported here is a continuation of the trace gas trends discussed in WKO (1982) and HAS (1984). It is outlined in Table 1. The ground-level concentrations of carbon dioxide and nitrous oxide as well as the aircraft HOx eaission scenario [including the vertical release profile] are identical to those of Wuebbles et al. (1983). In addition, we assuae a ground-level aethane increase of 1.5~/year (Ehhalt et al., 1983). The aaJor chlorofluorocarbons (CFC-11 and CFC-12) are assuaed to be released at a constant rate equal to that reported by the CKA for the year 1981 (CKA, 1982). The effects of other CFCs (CFC-113, CFC-114. CFC-115. and CFC-22) are included but are lllinor. Other aaJor long-lived sour;e species (eg •• CO. H2. CC14, CH3CC13, and CH3Cl) are released froa the ~"rface with a constant flux sufficient to aaintain their presently observed concentrations.

Species

CFC-ll CFC-12 CFC-1l3

Trends in Trace Gns Concentrations Adopted Fro~ 1980 Through 2050 A.D.

·Scenario Adopted

+0.55~/year (surface concentration) +1.5%/year (surface concentration) +0.2~/year (surface concentration) +14~/year to 1990 (release flux);

constant after 1990 620 aillion lbs./year (release flux) 794 aillion lbs./year (release flux)

91 aillion lbs./year (release flux)

The unperturbed background ataosphere for the Base Case is referred to as 1940, a year prior to significant changes in any of the source gases considered (except perhaps carbon dioxide and aethane). The Base Case scenario for the years 1940 through 1980 uses estiaated historical con­centrations or release rates for the species given in Table 1 (HAS, 1984).

We have adopted the year 1985 as the breakpoint for changes in the Base Case scenario for calculations of subtractive perturbations. Table 2 gives the calculated coluan ozone and surface teaperature changes in this scenario for several tiae periods. The calculated total ozone change for the 110-year period froa 1940 through 2050 is +3.8%, with a corresponding surface tea perature change of +2.53 K. For coaparison. the surface teapera­ture change due to doubled carbon dioxide (300 to 600 ppav) calculated with the coupled aodel is +2.0 K.

Figures 1a and 1b give the calculated vertical ozone and teaperature changes froa 1940 to 1985 and froa 1985 to 2050 for the Base Case. The large tropospheric ozone increase is due priaarily to aethane. with a contribution near the tropopause due to aircraft HOx. A calculated tropo-

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I~~6g~: Calculated Total Ozone and Surface TeMperature Changes: The Base Case

Tiae Period

1940 to 1985 1985 to 2050 1940 to 2050

Calculated Changes Ozone ColuMn Surface TeMperature

+0.77" +3.1" +3.8"

+0.65 K +1.88 K +2.53 K

Contribution of Source Species for 1985 to 2050

+1. 2" +4.2" -0.7" -1.2"

+0.98 K +0.57 K +0.06 K +0.18 K

spheric hydroxyl radical (OH) concentration decrease of 30" is associated with the ozone,increase. In the Model. this increases the atMospheric lifetiMe of species like CH3CC13 that are destroyed by OH.

Increases in the local ozone concentration froM 15 to 30 kM due to carbon dioxide. Methane. and CFCs are larger than the calculated decrease due to nitrous oxide. In the upper stratosphere. the Modeled local ozone decrease is due priMarily to CFCs and Methane.

The Modeled teMperature change is characterized by a tropospheric increase. due priMarily to an enhanced greenhouse effect arlslng froM carbon dioxide and Methane. with a large decrease near the stratopause. due to local ozone decreases froM cheMical reactions of CFCs and Methane.

As discussed above. the Most appropriate way to calculate the effect of each trace gas on ozone. in a Model which includes siMultaneous changes in other source gases. ia to use the Baae Case as the reference atMosphere. An individual specie is then left out of the scenario. and its effect is estiMated froM the difference between that run and the Base Case. We refer to such calculations as "subtractive perturbation" studies. The results for the individual contributions of the species shown in Table 2 above were obtained using the subtractive perturbation Method.

Table 3 (first coluMn) lists the subtractive perturbation studies that we have conducted with the coupled one-diMensional Model. The breakpoint in for changes froa the Base Case in each case is the year 1985. Given the Base Case scenario shown in Table 1. the species with the largest calcu­lated effect on the total ozone coluan froa the present through the aiddle of the next century is Methane (+4.2"). The calculated negative iMpact of CFCs (-1.2") and H20 (-0.7") on the ozone coluMn' is dOMinated by the Modeled increase due to Methane and carbon dioxide (+1.2"). The aodeled surface teMperature change COMes priMarily froa carbon dioxide and aethane. The direct radiative effect of aethane in the troposphere is enhanced by the aodeled increase in ozone there.

The Modeled interaction between the species listed in Table 1 on ozone is nonlinear when "steady-state" calculations (on tiaes scales of several hundred years) are considered. For exaMple. increased Methane significantly decreases the aodeled effect of CFCs and nitrous oxide on ozone (Owens et al.. 1982). On these relatively shorter tiMe scales. however. the source gases do not change enough to introduce significant

- 84-

I~~b~~: Subtractive Perturbation Calculations

Colu.n Ozone Change Surface Te.perature Change Perturbation 1985 to 2050 1985 to 2050 ------------ ------------------- ---------------------------Base Case +3.1~ +1.88 K

+ Fixed CO2 +1.9% +0.91 K + Fixed CH4 -1.2~ +1.31 K + Fixed N20 +3.7% +1.82 K + 0.5 x CFC +3.7% +1.79 K + 2.0 x CFC +1.7% +2.06 K

Base Case + 0.5 x CFC &

Fixed CH4 -0.5% +1.21 K + 2.0 x CFC &

Fixed CH4 -2.6% +1.51 K

nonlinearities in the Model calculations of the total ozone coluan change. Figure 2 gives the calculated total ozone change as a function of

tiMe for a nu.ber of the perturbations listed in Table 3. Perhaps the Most striking feature illustrated by these calculations is that the Modeled effect of aethane (increasing at 1.5%/year) is large enough to aake the calculated ozone coluan change positive even for rather large changes in the scenarios for other perturbations (e.g., fixed C02 or doubled CFC release). Even in the absence of a future aethane increase and with a doubled CFC release flux, the aodeled total ozone change froa 1940 through 2050 is less than 2%. It is also apparent froa the results displayed in Tables 2 and 3 that the tropospheric teMperature change is doainated by C02 and CH4 and is relatively insensitive to variations in the scenarios for CFCs and N20.

1. CHEMICAL MANUFACTURERS ASSOCIATION (1982). World production and release of chlorofluorocarbons 11 and 12 through 1980: An update. Washington, DC.

2. EHHALT, D. H., ZANDER, R. J., AND LAMONTAGNE, R. A. (1983). On the teaporal increase in tropospheric CH4. J. Geophys. Res., 88, 8442.

3. JET PROPULSION LABORATORY (1982). Cheaical kinetics and photocheMical data for use in stratospheric aodeling: Evaluation No.5, JPL 82-57. Pasadena, CA.

4. NATIONAL ACADEMY OF SCIENCES (1984). Causes and effects of changes in stratospheric ozone: Update 1983. Washington, DC.

5. OWENS, A. J., HALES, C. H., FILKIN, D. L., MILLER, C., STEED, J. M., AND JESSON, J. P. (1984). A coupled one-diaensional radiative­convective, cheaistry-transport Model of the ataosphere, 1, Model structure and steady-state perturbation calculations. J. Geophys. Res., in press.

6. OWENS, A. J., STEED, J. M., FILKIN, D. L., MILLER, C., AND JESSON, J. P. (1982). The potential effects of increased Methane on atMospheric ozone. Geophys. Res. Lett., 9, 1105.

7. WORLD METEOROLOGICAL ORGANIZATION (1982). The Stratosphere 1981:

8. Theory and Measureaents. Geneva, Switzerland. WUEBBLES, D. J., LUTHER, F. M., AND PENNER, J. E. (1983). coupled anthropogenic perturbations on stratospheric ozone. phys. Res., 88, 1444.

-85-

Effects of J. Geo-

-~8_0~ __ ~O ______ +~8_0 __ ~ __ 1_6_0 ____ ~240 ___ -~1_2 ______ -~8 ______ -_4 ____ ~O~~

(A) (B)

1985 to 2050

CALCULATED 03 CHANGE

(10 9 Mo1ec./cm3 )

CALCULATED TEMPERATURE CHANGE (K )

~!~~Bg!~ Calculated changes in the (a) local ozone concentration, and (b) at.ospheric te.perature, versus altitude. 1-0 coupled .odel.

till . 0 ,955 '910 1985 2000 20'S 2010 20 . 5 0 ~r---~--~--~--~--~~~~--~

Base Case

Fixed CH and 2 i CFCs

o ~

~~~~' 0~~1~9C.55~--'~9~10~--~19~8~5 --~20~O~0----2~O'~S----2~01-0----2~0~.S-1~ YEAR

- 86-

nY~Bg ~. Calculated changes in the total ozone colu.n versus ti.e for several of the scenario. given in Table 3.

TRENDS IN OZONE AND TEMPERATURE STRUCTURE: COMPARISON OF THEORY AND MEASUREMENTS

Donald J. Wuebbles Lawrence Livermore National Laboratory, University of California

Livermore, California 94550

Summary

Comparison of model calculated trends in ozone and temperature due to inferred variations in trace gas concentrations and solar flux, are made with available analyses of observations. In general, the calcu­lated trends in total ozone and the vertical ozone distribution agree well with the measured trends. However, there are too many remaining theoretical and sampling uncertainties to establish causality. Although qualitatively in agreement, the observed temperature decrease in the upper stratosphere is significantly larger than that calcu­lated. Theoretical results suggest a significant influence on strato­spheric ozone from solar flux variations, but observational evidence is at best inconclusive. Overall, the trend comparisons tend to be consistent with the hypothesis that several different anthropogenic influences are affecting the present global atmosphere.

1. Introduction The detectability of changes in ozone and temperature, and the under­

lying causes of observed changes, are of particular interest because of potential anthropogenic influences. In this study, trends in ozone and temperature calculated in the LLNL one-dimensional model of the troposphere and stratosphere are compared with available analyses of observed trends. The purpose is to examine whether substantial discrepancies exist between current theoretical results and observed trends. Because of the limited availability of data, primary emphasis is on the comparison of measurements with model-calculated trends in ozone and temperatures during the decades of the 1960s and 1970s, and the beginning of the 1980s.

Theoretical calculations suggest that changing concentrations of a number of anthropogenically influenced trace gases may presently be alter­ing the global atmospheric ozone distribution and temperature structure. Concentrations and/or emissions of gases such as CO2 , CH , N 0, several chlorocarbons (C~Cs), and NO from aircraft and nuclear ttsts2 are varied historically based on consi~eration of recent emissions evaluations and atmospheric measured trends (1). A variety of natural processes and phe­nomena are also known to affect the stratosphere. Variations in the solar ultraviolet flux over the II-year sunspot cycle are included in this study (case a) based on the solar emissions model of Lean et al. (2). Because of uncertainties, a second case considered only half the solar flux variation at wavelengths greater than 180 nm (case b).

Ozone Symposium - Greece 1984 - 87-

2. Trends in Total Ozone Table 1 shows calculated changes in total ozone over recent decades

for several of the scenarios examined. Cases I and II suggest that total ozone should have increased at a slow but steady rate throughout the 1960s· and 1970s due to the influence of trace gas emissions. This increase in ozone is primarily due to increasing concentrations of CO and CH4 , with a significant influence from aircraft emissions when inclutled. A small de­crease is derived in the total ozone trend when only chlorocarbons are considered.

TABLE 1. Calculated trends in total ozone (%jtime period) for periods 1960-1970, 1970-1980, and 1980-1983.

Case 1960-70 1970-80 1980-83

I (Ce..C + CO +NO+CH) +0.30 +0.30 +0.09 II (I + NO ) 2 2 4 +0.42 +0.60 +0.20 VI Ce..C onl~ -0.03 -0.12 -0.07

VIII I + solar variability (a) +1.29 +0.71 -2.69 IX I + solar variability (b) +0.74 +0.49 -1.19

In evaluating the trend in total ozone during the 1960s, it is neces­sary to consider the NO produced by nuclear tests of the late 1950s and early 1960s. Several dlita analyses suggest that a decrease in total ozone may have occurred at the time of the nuclear test series. Figure 1 shows that the calculated effect of the nuclear tests is a maximum total ozone decrease of 2.5%. These results are consistent with the upper limits « 4%) estimated by the analyses of total ozone data. However, as seen from Fig. 1, a minimum in total ozone is also calculated for the early 1960s when considering the influence of solar cycle variations.

-3 ",-

/"'''-,,~ 1+ solar variability (a) /

I )\ 1+ solar variability (b) I I \ I

I \ I ••••• I \ I 00 0

-2

~ Q) c: o N o

I •••• •••••• \ I •• - II -1, •. - e •• \ 1 •• -

O~··~··~:::::::::··:·\~::=====:~:·==::::~ ] o .... c:

~ -1 c: ell .c U -2

Relative to 1950

11+ Nuclear tests

Year

Figure 1. Calculated change in total ozone for the 1960s.

- 88-

The cases which consider the possible effects of solar cycle varia­tions calculate a change in total ozone of approximately 2.1% (case b) to 4.4% (case a) from solar minimum to solar maximum. Solar cycle variations could make detection of trends in total ozone due to anthropogenic influ­ences more difficult. Observational evidence of a relationship between total ozone and solar activity is at best inconclusive. Larger than normal total ozone amounts were observed in the years of the solar maximums (3). However, a minimum in total ozone calculated to occur in 1975 is not ob­viously evident in the observations.

Assuming Cases I and II correspond approximately to the conditions for the Southern and Northern Hemispheres, respectively, then the results shown in Table 2 suggest a global trend of +0.45% from 1970-1980 due to the ef­fects of trace gases. Reinsel (4), using time series statistical analysis derived the global ozone change from 1970-1980 based on Dobson total ozone column measurements to be 0.49(±1.35)%. The measured trends from this and other similar analyses are in excellent agreement with the calculated glob­al change when all anthropogenic emissions are considered. Unfortunately, no definitive analysis is available of the measured difference in the trends of total ozone between hemispheres.

TABLE 2. Summary of comparison between calculated and observed trends during the 1970s.

Calculated Observed Reference

Total ozone +0.45% +0.49±1.35% (4) Ozone distribution

2-8 km +6% +7% (3) 8-16 km +3% some + (3) 16-31 km +1% little change (3)

Umkehr level 5 +0.9% -0.40±1.39% (9) 6 -0.04% -0.01±1.07% (9) 7 -2.2% -2.23±1.69% (9) 8 -4.1% -3.03±1.64% (9) 9 -2.4% -2.87±3.94% (9)

Stratospheric temperatures 26-35 km -0.2 to -0.6K -1.5 to -3K (7) 38-45 km -1.2 to -1.7K -2.5 to -3.5K (7) 48-55 km -1.4 to -1.5K -3.5 to -5K (7)

3. Trends in the Ozone Vertical Distribution The change in ozone with pressure level is shown in Fig. 2 for Case II

at selected times relative to 1950. Tropospheric and stratospheric ozone are calculated to have changed significantly during the 1970s and 1980s (to 1983). The growing calculated decrease in upper stratospheric ozone re­sults primarily from chlorocarbon emissions. The increase in the middle stratosphere results from increasing CO and CH concentrations as well as the ozone recovery mechanism. The in~rease i~ the troposphere and lower stratosphere results from the assumed aircraft NO emissions and increasing OH concentrations. A maximum decrease over t~e 1970s of 4.4% is calcu­lated in the upper stratosphere (at 3.5 mb). A maximum ozone increase of 6.7% is calculated in Case II in the upper troposphere. A much smaller increase (-2% at the surface and <1% in upper troposphere) is determined for the Southern Hemisphere (Case I) troposphere, which does not include aircraft emissions.

-89-

E 60 ~

oj 50 0.8 '0

--- 1980 :0 ::I ... 40 3.5 E .;:

-'-1970 <a Ql

Ql 30 - .. -1960 14.2 :; ...

'" '" E Relative to 1950 '" Ql 'x 20 58.7 ci: 0

C. ~ 10 243.3 ~ • 0 1013.0 N

-15 -10 -5 0 5 10

Change in local ozone (%)

Figure 2 . Calculated percentage change in ozone for Case II at selected times relative to 1950 .

By comparison, ozonesonde measurements in the tropospheric layer from 2-8 km in northern temperate latitudes suggest nearly a 7% ozone increase during the last decade (3,5) . Little change was found in Southern Hemi­sphere data. The limited amount of data makes interpretation of these analyses highly uncertain. Some ozone increase in Northern Hemisphere data is also indicated for the 8-16 km layer with little change in ozone from 16 to 32 km (3). Umkehr data for upper stratospheric ozone have recently been reanalyzed to correot for potential errors, such as those due to atmo­spheric aerosols and changes in instrumentation (6). Calculated trends are within the observati on confidence limits at all levels (see Table 2).

4 . Trends in Upper Air Temperatures Figure 3 shows the calculated change in stratospheric temperatures at

selected times from January 1950 to January 1983 . The stratosphere is calculated to cool throughout this period, primarily due to the increasing CO2 concentrations, but also due to decreasing ozone amounts in the upper stratosphere . The largest cooling occurs at approximately 2.4 mb (- 42.5 km) . Radiosonde data (7) at 16- 24 km suggest a small decrease in tempera­ture of approximately 0 . 2- 0.4 K during the 1960s, in good general agreement with the calculated results. Measured trends at higher altitudes during the 1960s were not available for comparison . From January 1970 to January 1980, the maximum calculated temperature change of -1.7 K occurred in both Cases I and II at 2.4 mb . Similar upper air temperature changes are calcu­lated for both the Northern and Southern Hemispheres. The calculations agree qualitatively with the analysis of rocketsonde data (7) of a surface and tropospheric warming and stratospheric cooling during the past decade . However, the data suggest larger changes in stratospheric temperatures dur i ng the 1970s than are calculated (see Table 2). Such a large change in temperature , if real and not due to sampling errors, requires additional theoretical analysis as to its cause. It is difficult to develop a mecha­nism for explaining the large observed decrease in temperature. A larger cooling than that calculated would add to the calculated increase in total ozone over the decade and reduce the magnitude of the calculated decreases in upper stratosphere ozone.

5. Discussion Table 2 summarizes the comparisons

trends in ozone and temperature for the lated trends in ozone and temperature for

- 90 -

of calcul ated and observed global 1970s. Although the model calcu­the 1960s and 1970s are generally

60

Case II E 50 0 .8 .::t LLL 1 Kl OJ-"t)

E 40 3.5 :0 .~ E (ij

~ '"

30 1983-- 14.2 ~ ::J

E 1980---- ~ OJ x

20 ci: 0 1970 --- 58.7 C. a. 1960 _._-~ 10 243.3 * relative to 1950 N

0 1013.0 - 5 -4 -3 - 2 - 1 0 2

Change in temperature (K)

Figure 3. Calculated changes in stratospheric temperatures for Case II at selected times relative to January 1950.

in agreement with the measured trends, there are too many remaining theo­retical and sampling uncertainties for causality to be established_ Over­all, the trend comparisons tend to be consistent with the hypothesis that several different anthropogenic influences are affecting the present global atmosphere .

This work was performed under the auspices of the U.S . Department of Energy by the Lawrence Livermore National Laboratory under Contract W-7405-Eng-48 and supported in part by the Environmental Protection Agency.

REFERENCES

1. WUEBBLES, D. J., M. C. MACCRACKEN, and F. M. LUTHER (1984). A proposed reference set of scenarios for raditively active atmospheric constitu­ents. U. S. Department of Energy Carbon Dioxide Research Division Technical Report, in press.

2. LEAN, J . L., O. R. WHITE, W. C. LIVINGSTON, D. F. HEATH, R. F. DONNELLY and A. SKUMANICH (1982). A three component model of the variability of the solar ultraviolet flux: 145-200 nm. J. of Geophys.Res., 87, 10307-10317.

3. ANGELL, J. K., and J. KORSHOVER (1983a). Global Variation in total ozone and layer~mean ozone: an update through 1981. J.of Climate and Appl.Met., 22, 1611-1627.

4. REINSEL, G.IC. (1981) . Analysis of total ozone data for the detection of recent trends and the effects of nuclear testing during the 1960's . Geophys. Res. Lett., ~, 1227-1230.

5. WORLD METEOROLOGICAL ORGANIZATION (1981). The stratosphere 1981: theory and measurements. WMO global ozone research and monitoring project report No. 11.

6. REINSEL, G. C., TIAO, G. C., DELUISI, J. J., MATEER, C. L., MILLER, A. J., and FREDERICK, J. E. (1984). Analysis of upper stratospheric Umkehr ozone profile data for trends and the effect of stratospheric aerosols. J. Geophys. Res., 89, 4833-4840.

7. ANGELL, J. K. and KORSHOVER, J. (1983b). Global temperature variations in the troposphere and stratosphere, 1958-1982. Monthly Weather Review, 111, 901-921.

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OZONE IN THE 21ST CENTURY : INCREASE OR DECREASE?

by

A. DE RUDDER and G. BRASSEUR Institut d'Aeronomie Spatia Ie de Belgique

3, avenue Circulaire, B-1180 Brussels, Belgium.

1. INTRODUCTION

In order to assess the global atmospheric and climatic response to the release of various chemical pollutants, numerical models are commonly used as prognostic tools. The purpose of this paper is to use a fully coupled I-D radiative/chemical model to simulate the future of the ozone layer and the temperature, assuming a realistic scenario of the emission of several gases such as CO2 , CH4 , N20, NO and the chloro­carbons. Another objective is to study the effect or an hypothetical high chlorine perturbation. With the present and projected emissions of CFCs, such a high Clx load is not expected. Nevertheless, this problem will be considered here since it reveals the non-linear behavior of the chemical system in t~e middle atmosphere (Cicerone et aI, 1983).

2. RESPONSE OF OZONE AND TEMPERATURE TO A GIVEN MAN-MADE PERTURBATION

The present study considers a perturbation scenario which is described in detail by Brasseur et al (1984). The chlorocarbons CC1 4 , CFC1 3 , CF 2Cl 2 and CH,CCl3 are increased according to historical data un5iI present time ana a cgnstant emission is assume~ for the future : 10 T/yr for CC1 4 , 3.2 x 10 T/yr for CFC1 3 and 4 x 10 T/yr for CF2C1 2 . Only the release rate Off CH3CC1 3 is assumed to increase, reach~ng a maximum value of 4 x 10 T/yr in year 2070. This scenario therefore accounts for the possibility of an unexpected enhancement in the release of chlorine atoms and therefore leads probably to an overestimated stratospheric response. The corresponding odd chlorine mixing ratio at 50 km altitude is 2.8 ppbv in year 1984, 4.4 ppbv in 2000, 8.2 ppbv in 2050 and 9.5 ppbv in 2080. Carbon dioxide, whose mixing ratio is assumed to be equal to 270 ppmv in year 1850 and 335 ppmv in year 1979, increases in the model by 0.56 percent per year to reach about 575 ppmv in year 2080.

Methane whose actual mixing ratio is close to 1.5 ppmv is assumed to increase by 1.5 percent/year from the present day, reaching consequently a relative concentration of 7.5 ppmv in year 2080. A value of 1 ppmv is assumed between year 1850 and 1950. Nitrous oxide shows a systematic increase of about 0.25 percent per year. A mixing ratio of 285 ppbv is adopted as preindustrial value. The present amount is close to 330 ppmv and the value reached in year 2080 is 425 ppbv. Aircraft emissions of nitrogen oxides are introduced after year 1950 according to the scenario suggested by Wuebbles et al (1983). After year 2000, the NO release, whose maximum is located between 10 and 12 km, is assumed toXremain constant.

Ozone Symposium - Greece 1984 - 92-

The response of several atmospheric and climatic parameters to the scenario described above, is predicted using a I-D chemical model which takes into account the key reactions related to the oxygen, hydrogen, nitrogen, chlorine and carbon chemistry in the range 0 to 100 km. The vertical transport of the long-lived trace species is simulated by an "eddy diffusion" approach. The model is coupled with a radiative routine which considers the attenuation of the solar radiation as well as the emission and absorption of terrestrial infrared radiation. For the latter computation in the troposphere and strato­sphere, a wide-band model similar to that in Morcrette (1983) is used. Figure 1 shows the predicted changes in the ozone column as well as the expected variations in the temperature at the Earth's surface and at the stratopause. Prior to 1980 or so, ozone increases slightly due to the gradual positive trend in the COZ amount and the related temperature decrease in the upper stratosphere. This enhancement in the ozone content is not a direct chemical effect but results from the high dependence of the ozone destruction rate to the temperature leading to the well-known anticorrelation between temperature and 03 above 30 km. After year 1980, the predicted decrease has to be attributed to the chlorocarbons and the chlorine atoms which are produced by photo­dissociation. After year ZOOO, the effect of the rapid growth in the methane concentration plays a key role: it leads to an enhanced production of tropospheric 03 and to a transfer of active chlorine (Cl, CIO ... ) to inactive chlorine (HCI) by reaction Cl + CH4 -7 HCl + CH3 . This second process reduces the efficiency of chlorine for depleting

c­">

5

~ ·5 z o ~ ii' -10 g. w cr: 2 -IS <t cr: W c.. ~ -20 ....

-25

1900 1950 2000 TIME (y<'ar)

2050 2080

2 ~ v Q; 2-z o

I~ <l iX g. w z

0 0 !:J

-I

...J

~ o >-

Fig. 1.- Changes in the ozone column (~03-in percent) and in the temperature (Kelvin) at the Earth's surface (~Ts) and at the stratopause (~T SOkm) , for the adopted perturbation scenario.

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40

E 30 ~

w 0 20 :J .... .... -1 <t

10

-20 o

OZONE

PERTU R BATIONS

Northern Hemisphere

20 40 RELATIVE VAR IAT ION (percent)

80

Fig. 2.- Relative variation in the ozone concentration relative to the preindustrial atmosphere, predicted from 0 to 50 km altitude for years 1983 to 2080, adopting the perturbation scenarios as described in the text.

60

140 w o :::J .... .... ;t 20 TEMPERATURE

OL-__ -L ____ L-__ -L ____ L-__ -L ____ ~W_~

-30 -25 -20 -15 -10 -5 o 5 TEMPERATURE CHANGE IN

Fig. 3.- Same as figure 2 but for the vertical temperature distribution.

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ozone. Finally the slow growth in N ° leads to a weak ozone depletion while the injection of NO by aircra!t engines contributes to the ozone increase in the tropospher~. Figure 1 also shows that the temperature is expected to be reduced by about 25 K at the stratopause in year 2080, which should generate significant changes in the general circulation; at the Earth's surface a temperature increase of about 2.3 K is expected. This value, however, is a lower limit since the direct greenhouse effect due to N 0, CH and the CFCs is not yet considered in the radiative scheme. itigure ~ and 3 shows the corresponding ozone and temperature changes as a function of altitude. It should be noted that, although variations in the ozone column are expected to be small, local changes can be quite large.

3. HIGH CHLORINE PERTURBATIONS

The behavior of the chemical system in the atmosphere for high chlorine increases has been recently discussed by Prather et al (1983). Figure 4 shows that the response of the ozone column becomes highly non linear for Cl mixing ratio becoming of the order of the NO mixing ratio. The e\planation of this effect involves complex Ycoupling mechanisms between odd nitrogen and odd chlorine species (ClON02), non linear response of the OH radical in the middle and lower stratosphere, where it is destroyed essentially by HN03 and H02N02' and the self­healing effect of ozone, especially when large amounts are destroyed at high altitude. The calculation of the ozone response due to high chlorine perturbations requires therefore an accurate knowledge of the total odd nitrogen amount which is present at a specified altitude and latitude. The temperature response at 45 km for large ozone depletion is also shown in figure 4.

-5

_ -10

1:: 5 -15

g ~ -20 a z ~ -25 <5 u

~ -30 o N o

-35

-40

TOTAL OZONE AND

TEMPERATURE AT

45 km

265

250

- 45'-'-_-'----' ___ -'-___ -'-___ -'-___ .l.---"'==---.J-J 245 o 10 15 20 30

CI, VOLUME MIXING RATIO AT SOKM ALTITUDE(ppbv)

Fig. 4.- Change in the ozone column for high chlorine injections (Clx mixing ratio up to 30 ppbv) and for 2 values of the ambient NO y mixing ratio (13 and 19 ppbv). The temperature variation at 45 km (NO y = 19 ppbv) is indicated.

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ACKNOWLEDGMENTS

This work was supported by the Chemical Manufacturers Association under contract 83-468.

REFERENCES

BRASSEUR, G., A. DE RUDDER and Chr. TRICOT, Stratospheric response to chemical perturbations, to be submitted to the Journal of Atmo­spheric Chemistry (1984).

CICERONE, R.J., S. WALTERS and S.C. LIU, Non linear response of strato­spheric ozone column to chlorine injections, J. Geophys. Res., 88, 3647, 1983. -

PRATHER, M.J., M.B. McELROY and S.C. WOFSY, Reductions in ozone at high concentrations of stratospheric halogens, Paper presented at the WHO/NASA workshop, Starnberger See, FRG, June 11-16, 1984.

WUEBBLES, D.J., F.M. LUTHER and J.E. PENNER, Effect of coupled anthro­pogenic perturbations on stratospheric ozone, J. Geophys. Res., 88, 1449, 1983. -

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CHAPTER II

OlONE-CLIMATE INTERACTION

- Climatological effects of atmospheric ozone: a review

- The climatic effects of ozone and trace gases

- The effect of ozone photochemistry on atmospheric and surface temperature changes due to increased CO2, N20, CH 4 and volcanic aerosols in the atmosphere

CLIMATOLOGICAL EFFECTS OF ATMOSPHERIC OZONE: A REVIEW

WEI-CHYUNG WANG Atmospheric and Environmental Research, Inc.

Cambridge, MA

1. Introduction

Concerns have been raised in recent years about the possibilities that the atmospheric 03 concentration might be perturbed as a result of anthropogenic activities, such as the uses of CFCs, application of nitrogen fertilizers, fossil fuel consumptions, aircraft emissions, etc. The 03 perturbation could have serious consequences for mankind. Reducing the 03 amount, for example, could increase the amount of solar UV radiation reaching the earth surface with possible damaging effect to the biological system. Further, change in the amount of 03 could change the distribution of solar heating and thermal cooling in the atmosphere and result in a change of temperature and thus, the climate.

Detailed discussions of 03 formation and destruction processes can be found in many publications (see NRC, 1984, for an update); Figure 1 taken from NRC (1982) illustrates these processes. Briefly, 03 is formed by the photolysis of 02 at wavelengths < 240 nm and is removed by reactions catalyzed by trace species such as odd hydrogen (HOx )' odd nitrogen (NOx ', and. odd chlorine (CVe). The concentrations of these species in the atmosphere depend, to a large extent, on the abundances of precursor gases such as H20, CH4 , N20, CFMs (CCi3F, CCi2F2), chloro­carbons (CH3Ci, CH3CCi3 ) in the troposphere, which may be increasing due to the above-mentioned anthropogenic activities.

Fig. 1. Representation of the processes that determine the concentra­tion of ozone in the stratosphere (after NRC, 1982).

Past model studies of 03 climatological effects have been concen­trated on calculating temperature changes to specified 03 changes, i.e., the coupling effects of temperature, trace gas concentrations and radia­tion are ignored (cf. Ramanathan, 1980; Wang, 1982a). It is only recently that consistent treatments between chemistry and radiation are included in the model estimates of 03 climatological effects. Here we show some of the results, discuss the specific issues involved in 03 climate study and its future research needs.

Ozone Symposium - Greece 1984 - 98-

2. 03 Direct Radiative Effect

03 is of major importance in maintaining the thermal structure in the stratosphere through its absorption of solar radiation in the UV and in the visual. It is believed that the stratospheric 03 is largely responsi ble for the existence of the tropopause, a nearly isothermal region separating the radiatively equilibrated stratosphere from the more dynamically controlled troposphere. In the infrared, 03 has a number of vibration-rotation absorption bands, in particular the 9.6 11m band, which cool the middle and upper stratosphere and provide a green­house warming effect for the lower stratosphere and the troposphere. Therefore, tropospheric 03' although amounts to only about 10% of total atmospheric column, plays an important role in tropospheric climate.

Since 03 greenhouse effect plays the major role in the study of 03 climatic effect, Table 1 shows the thermal flux perturbations due to specified changes of 03 and, for comparison, changes due to increases of CO 2 , CFCs, N20, CH4 and stratospheric H20 are also shown.

A 25% uniform 03 decrease in the stratosphere increases the thermal cooling throughout the atmosphere and results in a 0.82 Wm-2 cooling of the earth-atmosphere system. On the other hand, 25% increase in tropospheric 03 is to warm the troposphere and the surface, but to cool the stratosphere because of the blocking of upwelling warmer thermal emission.

For COL doubling, the troposphere and the ground are warmed by 3.78 and 1.68 Wm 2, respectively, while the stratosphere is cooled by 2.53 Wm- 2 • These lead to a 2.93 Wm-2 warming of the earth-atmosphere sys­tem. N20 doubling yields a 1.19 Wm -2 warming of the earth-atmosphere system while for CH4 doubling, it is warmed by 0.89 Wm-2

When CFC concentrations are increased to 2 ppbv, the stratosphere is warmed by 0.27 Wm-2 , because CFC absorptions are in the optical thin region and therefore are more effective in absorbing the warmer upwel­ling troposphere-ground emissions. Similar to CO2 , N20, and CH4 , CFCs provide greenhouse effect to the troposphere and the ground and _~ ppbv concentrations may heat up the earth-atmosphere system by 1.75 Wm •

Since H20 is an effective absorber and emitter across the whole thermal spectrum, a factor of 2 increase in its stratospheric conentration could lead to large increases of thermal radiation cooling of 3.09 Wm-2 in the stratosphere and of warming of 4 Wm-2 in the troposphere, while the ground is not affected by such stratospheric change.

3. Climatic Effect of 0) Redistribution

Study has suggested that 03 climatological effect depends strongly on 03 altitude distribution (cf. Wang and Sze, 1980). A redistribution of 03 associated with anthropogenic activities could introduce climatic effect of its own. This effect has been examined by Wang et al. (1980), Wang (1982b), Callis et al. (1983), Wuebbles et al. (1983) and others. In the model calculations, the chemistry, trace gas concentrations,

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Table 1

Change of clear sky thermal radiation cooling (Wm- 2) in stratosphere (S), troposphere (T), and ground (G) as well as the earth-atmosphere system due to indicated changes of trace species concentrations.

=~~=~=-=~-=

Earth-Atmosphere Species Concen. Change S T G System

°3 -25% in (S) -0.15 -0.55 -0.12 -0.82 +25% in (T) -0.18 0.04 0.27 0.13

CO2 300 -I- 600 ppmv -2.53 3.78 1.68 2.93 N20 0.28 -I- 0.56 ppmv -0.10 0.65 0.64 1.19 CH4 1.75 -I- 3.5 ppmv -0.07 0.54 0.42 0.89 CF2CR.2 o -I- 2 ppbv } 0.27 0.26 1.22 1.75 CF3CR. o -I- 2 ppbv H2O +100% in (S) -3.09 4.00 0 0.91

temperature and radiation are consistently treated. Here the results of Wang (l982b) is discussed and the calculations are based on the estimated 2010 and

SO

50

.0 ~ 30

~ 20

10

0

a

Fig. 2.

increases of NOx ' CFCs, N2O, CO2 , and CH4 between 1980 and the results are summarized in Figs. 2(a,b).

0.5

4T(K)

-6 -4 -2 0 2 4 6 8 4T 0.39 ("c)

0.'

1980-2010

0.3

0.'

0.1

-15 -10 -5 0 5 10 15 20 co, ClI. "20 CFel l +CF 2'1 2 03

4°3 (,,) b (335. {1.6S.... (0.30.... CFel) (o.m) 389ppmv ) 2.4pp!lv) O.J2ppnv) (0.17 ..

O.46ppbv) CFZClz (0.30.

O.alppbv)

(a) 1-D model calculated changes of atmospheric 03 (ll03) and temperature (llT) between 1980 and 2010 due to combined anthro­pogenic emissions of CFCs, NOx ' CO2 , CH4 , and N20; (b) model calculated surface warming effect due to individual gases between 1980 and 2010.

The results indicate that, for the period 1980-2010, these anthro­pogenic emissions could lead to a few tenths of one percent increase in the global mean column 03' but with a much larger change in the 03 ver-

- 100-

tical distribution. The stratospheric 03 could be decreased, due pri­marily to CFCs, with maximum depletion of 15% around 42 km while NOx and CH4 emissions contribute to the increase of tropospheric 03 with maximum increase of 16% at 7 km. During the same period, these anthropogenic gases and the associated 03 perturbation could warm the surface by 0.8 K. Proj ected increase of 15% of the present CO2 level, 335 ppmv, con­tributes 0.4 K of the total surface warming while the rest (0.4 K) can be attributed equally to the direct radiative effect of NOx ' CFCs, CH4 and N20 and to the indirect radiative effect associated with 03 pertur­bations. In the stratosphere, the combined effect is to cool the middle and upper stratosphere with maximum temperature decrease of ~4 K around 48 km and to slightly warm the lower stratosphere.

4. Tropospheric 03

Recent 03 trend analysis (Angell and Korshover, 1983) has indicated that tropospheric 03 may be increasing. Such increases might have important climate implications (see AMBIO, 1984; Bojkov, 1984). To estimate the effect of tropospheric 03 change on climate, we have used the 1-D radiative-convective model to calculate the temperature changes using the observed changes of June/July 03 vertical distribution measured at Hohenpeissenberg and Resolute. These measurements were kindly provided by Dr. Ruman Bojkov. The changes of 03 and temperatures are shown in Fig. 3. For Hohenpeissenberg the surface temperature could be increased by 0.2 K while a maximum 0.8 K cooling was found around 24 km. The magnitude of the tropospheric warming is quite substantial if we compare the value with those shown in Fig. 2(b). For Resolute, the effect is smaller.

ATCK)

Fig. 3. Observed changes of mean June/July 03 profiles between 1967/68 and 1980/81 at Resolute and Hohenpeissenberg and the associated 1-D model calculated temperature change.

5. Discussion

We have discussed some of the important issues related to 03 cli­mate study. The most important one is probably the change of 03 distri­bution (especially around tropopause region) associated with the anthropogenic activities. The 03 distribution, however, is influenced by chemistry and transport processes and perhaps introduces the largest uncertainties in the model calculated 03 climatological effect.

-101 -

As has been summarized in WMO (1982), the following research is needed: Continued global monitoring of radiatively active minor trace gases; monitor trends in vertical 03 distribution and total ozone within troposphere and stratosphere separately; development of coupled 1- and 2-D models with interactive chemistry and climate to examine and iden­tify various climate-chemistry interactions; GCMs to be used to examine specific climate sensitivity questions, e.g., sensitivity to 03 pertur­bations; development of GCMs capable of simulating stratospheric H20 including dynamical and chemical sources/sinks.

This work was supported by NSF ATM 8400587 and DOE DE-AC02-81ER60023.

References

AMBIO (1984) Ozone pollution. ~,No. 2.

Angell, J. K. and J. Korchoven (1983) Global variation and layer mean ozone: An update through 1981. Appl. Meteorol., ~, 1611-1627.

in total ozone J. Climate and

Bojkov, R. D. (1984) Tropospheric Ozone, its changes and possible radia­tive effects. In Observation and Measurement of Atmospheric Con­taminents. Special Environmental Report No. 16.

Callis, L. B., M. Natarajan and R. E. Boughner (1983) On the relationship between the greenhouse effect, atmospheric photochemistry and species distribution. J. Geophys. Res., ~, 1401-1426.

-National Research Council (1982) ozone reduction: An update. ington, DC.

Causes and effects of stratospheric National Academy of Sciences, Wash-

National Research Council (1984) Causes of effects of changes in strato­spheric ozone: Update 1983. National Academy of Sciences, Wash­ington, DC.

Ramanathan, V. (1980) Ozone effects on climate: A review. Proceedings of the Quadrennial International Ozone Symposium, Boulder, CO.

Wang, W .-C. (1982a) Ozone change: Climatological effects. In Strato­spheric Ozone and Man, F. A. Bower and R. B. Ward (Eds.), Vol. II, CRC Press, Boca Raton, FL.

Wang, W.-C. (1982b) Potential changes in 03 and climate due to anthropo­genic emissions of NOx ' CFCs, N20 , CO 2 and CH4 • AER Technical Report.

Wang, W.-C. and N. D. Sze (1980) Coupled effects of atmospheric N20 and 03 on the earth's climate. Nature, 286, 589-590.

Wang, W.-C., J. P. Pinto, and Y. L. Yung (1980) Climatic effects due to halogenated compounds in the Earth's atmosphere. J. Atmos. Sci., }2., 333-338.

WMO (1982) Potential Climatic Effects of Ozone and Other Minor Trace Gases. Report No. 14, Geneva.

Wuebbles, D. J., F. M. Luther and J. E. Penner (1983) Effect of coupled anthropogenic perturbations on stratospheric ozone. J. Geophys. Res., ~, 1444-1456.

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Summary

THE CLIMATIC EFFECTS OF OZONE AND TRACE GASES

J.T. Kiehl National Center for Atmospheric Research

Boulder, CO 80307

The climatic effects of a large number (>20) of trace gases, many of which have not been considered in previous investigations, are investigated. Usi~g a one-dimensional radiative convective model the climatic impact of these gases is studied for three cases. First, using present day gas concentrations and growth rates, the effect of these gases on the equilibrium thermal structure 50 years from now is estimated. Secondly, pre-industrial gas concentrations are used to estimate climatic effects which should already have taken place. Finally, the relative importance for individual gases is calculated for a uniform ° to 1 ppbv increase in gas concentration. The results of these calculations are: i) Increases in COz from pre-industrial times (1850) to the present cause an increase in equilibrium surface temperature of 0.5 K. This effect due to COz alone is amplified by a factor of 1.5 due to trace gases. ii) Increases in COz from present concentrations to their expected levels 50 years from now result in an increase in equilibrium surface temperature of 0.7 K. The inclusion of all other trace gases enhances this increase by a factor of 2.0. The uncertainties in this factor due to uncertainties in gas concentrations is a change in enhancement from 1.5 to 3.0. iii) A number of trace gases have been identified which are of potential climatic importance based on a per ppbv increase in concentration; among these are CFC-13, 22, 116, CHF 3 and CHzFz • The surface temperature effects, on a per ppbv basis, of these gases are of similar magnitude to those due to CFC11 and 12. Comparison of the present results with previous studies is also made; and sources of differences are discussed. The results of this study are discussed in much greater detail in Ramanathan et al.(1984).

REFERENCES

1. RAMANATHAN, V., H.B. SINGH, R.J. CICERONE and J.T. KIEHL, 1984. Trace gas trends and their potential role in climate change, submitted to J. Geophys. Res.

Ozone Symposium - Greece 1984 - 103-

THE EFFECT OF OZONE PHOTOCHEMISTRY ON ATMOSPHERIC AND SURFACE TEMPERATURE CHANGES DUE TO INCREASED C02~~ AND

VOLCANIC AEROSOLS IN THE ATMOSPHERE

R.K.R. VUPPUTURI Canadian Climate Centre, Downsview, Ontario, Canada

Abstract

Increased atmospheric C02, N20, CH4 and volcanic aerosols can af-fect indirectly the stratospheric ozone by altering the temperature structure and through photochemical coupling. The radiative effects which result from the local ozone perturbations would in turn modify the initial temperature changes due to increased C02, N20, CH4 and volcanic aerosols. In this paper a coupled l-D radiative-convective and photochemical diffusion model is used to study the influence of ozone photochemistry on changes in the vertical temperature structure and surface climate resulting from the doubling of atmospheric C02, N20, CH4 and increased stratospheric aerosols due to El Chichon volcanic eruption. It is found when C02 alone is doubled, the total ozone column has increased by nearly 6% and the resulting growth in the solar heating has contributed to the smaller temperature decrease in the stra­tosphere (up to 40K temperature recovery near the stratopause level). But when the concentrations of C02, N20 and CH4 are doubled, the total ozone column amount has increased only by 2.5%, resulting in a reduced temperature recovery in the stratosphere. Also discussed is the interaction of ozone photochemistry with the stratospheric aerosol cloud produced from the El Chichon eruption.

1.1 Introduction

Radiatively and chemically active gases and aerosols are being injected into the atmosphere at an increasing rate by human activities and by natural means and it is known that these gases and aerosols, which possess strong absorption and scattering properties in solar and terrestrial radiation, can alter the radiative-photochemical balance of the earth-atmosphere system, which in turn leads to changes in the thermal structure of the atmosphere and surface climate. For example, the release of C02, N20, CH4, CFC's and aerosols into the atmosphere can directly change the atmospheric and surface temperature due to their absorption and scattering properties in the solar and terrestrial radiation. In addition, these gases and aerosols and other anthropogenic injections of CO and NOx can affect the atmospheric and'surface temperature indirectly, either by enhancing or decreasing the atmospheric ozone concentration.

Ozone Symposium - Greece 1984 - 104-

During the past several years, various climate models have been used to determine the influence of increased C02 on the thermal structure of the lower atmosphere and surface climate, assuming fixed atmospheric ozone con­centration (Manabe and Wetherald, 1967, 1975; Ramanathan, 1975; Augustsson and Ramanathan, 1977; Hunt and Wells, 1979). However, in the stratosphere, because of the thermal coupling between ozone and temperature, increased atmospheric C02 can also influence the ozone concentration by altering the temperature structure of the stratosphere. In addition, ozone in the stra­tosphere is also influenced by the increases in atmospheric N20, CH4, CFC's and aerosols through photochemical and thermal coupling. Changes in stratospheric ozone resulting from the enhanced levels of atmospheric C02, N20, CH4, CFC's and aerosols may in turn influence the tropospheric climate through radiative and dynamical interactions between the troposphere and stratosphere (Ramanathan, 1980).

Attempts to determine the atmospheric and surface temperature changes due to increased atmospheric C02, N20, CH4 and aerosols with interac-tion of ozone photochemistry have been few. Only recently the effects of radiative-photochemical interactions due to enhanced C02 and other gases have been considered in the 1-D model studies (Boughner, 1978; Groves et aI, 1978; Ramanathan, 1980; Wang et aI, 1980). In this paper, a coupled one­dimensional radiative-convective and photochemical diffusion model is used to investigate the possible effects of the interaction of ozone photochemis­tryon atmospheric and surface temperature changes due to increased atmo­spheric C02, N20, CH4 and aerosols from the EI Chichon eruption.

1.2 The Climate Model The model used for .this study is a coupled one-dimensional radiative­

convective and photochemical diffusion model which takes into account the interaction of atmospheric chemistry on vertical temperature structure and surface climate (Wang et al 1976). Starting from the assumed chemical compo­sition and vertical temperature distribution, the basic procedure is to compute the local radiative heating or cooling and photochemical sources and sinks at each altitude to determine the new vertical temperature and chemi­cal trace constituent structure with time marching method. The upward heat transfer by atmospheric motions is taken into account implicitly by a simple numerical procedure called convective adjustment, which was first introduced in a computer code by Manabe and Strickler (1964). Using this procedure, the model lapse rate is adjusted to the critical observed lapse rate (6.5~ per km) whenever the model lapse rate becomes larger during the time evolu­tion of numerical iterative calculations.

1.3 The Radiative Transfer Model The model used to compute the solar radiative heating within the atmo­

sphere is based on delta-Eddington method which is computationally efficient and fairly accurate. Absorption and scattering by atmospheric gases (H20, C02 and 03), aerosols and clouds are considered. The relevant solar spectral data (solar fluxes, volume absorption coefficients for ozone and Rayleigh volume scattering coefficients) and the computational details of delta-Eddington method are given in Blanchet (1979). To compute the in­frared cooling or heating due to H20, 03, C02 and aerosols, the analy-tical formulae for the mean transmissivities of finite frequency intervals derived by Kuo (1979) have been used. The mean transmission functions de­rived for various spectral intervals, take into account the overlapping absorption between gases and the computed transmissivities have been shown to be in good agreement with the line by line calculations. For cooling

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rate calculations due to NZO and CH4, the empirical expressions for the mean band absorptivities based on laboratory data (Burch et al 196Z) were adopted.

1.4 The Photochemical Model Because of the strong coupling between radiation and photochemistry, the

latter plays an important role in determining the vertical temperature pro­file of the atmosphere and surface climate. The photochemical system consi­dered in this study includes the odd oxygen (0, ° (lD), 03), odd hydro-gen (HO, HOZ), NZO and the odd nitrogen (NO, NOZ and HN03) chemical species. The concentrations of HZ, HZO and CH4, which are required for photochemical calculations, are specified based on observations. The reactions and the reaction rate coefficient used to compute the chemical S0urces and sinks are based on NASA Panel recommendation (JPL publication 83-6Z, 1983). The detailed description of the photochemical model, which includes the discussion on the primary photochemical data and evaluation of photo-dissociation rates for various chemical species, is given by Vupputuri (1975).

1.5 The Perturbed EI Chichon Aerosol Model To determine the interaction of ozone photochemistry on atmospheric and

surface temperature changes due to increased stratospheric aerosols from EI Chichon eruption, it is assumed that the added stratospheric aerosols have a peak optical thic~ness of about 0.1 on a globally-averaged basis and the aerosols also possess optical properties which do not vary in time. The EI Chichon aerosol optical properties chosen for this study are those reported in NASA Technical Memorandum 84959 (Bandeen and Fraser, 198Z). The optical parameters (extinction coefficients, single scattering albedo, asymmetry factors) are derived as a function of wavelength assuming the aerosol parti­cles are composed of 75% HZS04 and Z5% HZO.

1.6 Vertical Grid and Computational Details The vertical grid used for numerical computations extends from the sur­

face to 60.5 km. It consists of 43 discrete layers separated by constant 6Z = 0.Z136 (where Z = -In p/Po' p is the pressure and Po = 1000mb) which corresponds to roughly 1.5 km in the u.S. standard atmosphere. For time integration the model uses Adams-Bashford Scheme with 6-hour time step. The thermal lapse rate within the troposhere is assumed 6.5°K per km. The COZ is assumed to be uniformly mixed in the atmosphere with a constant mixing ratio of 330 ppmv, while specifying the vertical profile values of CH4 based on observations. In the case of HZO, the relative humidity is held fixed and the mixing ratio of water vapour is computed as a function of temperature.

The clouds in the troposphere have significant effect on the radiative energy balance of the atmosphere. In the present model calculations, the clouds are located between 5 and 6.5 km. The clouds are considered to be black in the infrared and the fractional cloud cover is held fixed at 0.446 (Remanathan, 1976). In the solar spectrum an optical thickness of 10 is selected to produce a cloud albedo of 50%. The solar constant is taken to be 1365 w/mZ and the cosine of the mean zenith angle of sun and the day fraction are set at 0.5. These values provide the conditions for the annual average insolation. The surface albedo is highly variable depending upon the surface characteristics. It is generally believed that the global mean surface albedo is between 0.1 and O.Z. After initial experimentation with different values the global mean surface albedo of 0.1 is adopted as the final value. The solar radiation heating calculations are executed separ-

-106-

at ely for clear and cloudy skies and the effective heating is obtained by adding the two calculations linearly using the fractional cloud cover as a weighting factor.

1.7. Discussion of Model Results Fig. 1 shows the computed vertical temperature structure with and with­

out ozone interaction for the ambient atmosphere with background strato­spheric aerosols. Also shown in Fig. 1 for comparison is the temperature distribution for the U.S. standard atmosphere (1962). As can be seen, the agreement between the model calculation with ozone interaction and U.S. standard atmosphere is good, except between 12 and 2Z km. The discrepancy between 1Z and ZZ km may be attributed to the neglect in the 1-D model of horizontal and vertical heat transports and other dynamical processes which become important in this region. In Fig. 2, the calculated vertical ozone distribution with interaction between chemical constituents and temperature taken into account is compared with U.S. standard atmosphere ozone. It can be seen that the two curves are very similar in shape although the computed ozone mixing ratio values are underestimated both below and above the level of ozone maximum. The difference in the lower stratosphere can be attri­buted to neglect of horizontal transports, and above the level of ozone maximum, horizontal transports do not playa significant role (this region is nearly in radiative-photochemical equilibrium) and it is possible that some of the differences in the upper stratosphere may be related to the uncertainties in the U.S. standard atmosphere ozone distribution.

b) Perturbation Experiments with Fixed Ozone

Before the discussion of the results with interactive ozone, it would be instructive to show the results of the perturbation experiments with fixed ozone and compare them with similar calculations in previous studies. Fig. 3 shows the calculated temperature difference as a function of height due to doubling of atmospheric COZ, NZO, CH4 and COZ + NZO + CH4 with fixed ozone distribution. It is seen from Fig. 3 that the doubling of atmo­spheric COZ, NZO and CH4 from their ambient levels would lead to the warming of the troposphere and the surface by 1.71, 0.40 and 0.37°C respec­tively. In the stratosphere, the increased loss of radiational energy to space results in cooling which increases with altitude, particularly in the case of COZ and CH4. Due to the rapid decrease in the NZO mixing ratio in the stratosphere (photodissociation) the temperature change due to double NZO in that region is negligibly small. Note that the individual effects do not quite add linearly to the combined changes due to double C02 + NZO + CH4, particularly in the stratosphere because of the ozone-temperature feedback and radiative-photochemical coupling between gases.

In Table I, the calculated temperature changes due to double COZ, NZO and CH4 are compared with similar calculations by Wang et al (1976) and those reported by the WMO expert committee on potential climatic effects of ozone and other minor trace gases (198Z). The comparison shows that there is a fair agreement among them, although the results for the double COZ are slightly underestimated in the present model.

c) Perturbation Experiments with Ozone Photochemistry Interaction

The dashed curves in Figs. 4 and 5 show the computed temperature changes as a function of altitude due to ZC02 and 2(C02 + NZO + CH4) respec-tively, when the ozone is allowed to adjust to the altered temperature and

-107-

Table I: ComparIson of the Surface Temperature Changes due to Trace Gas Increase

Trace gas Reference Perturbed Change In Change In Change In MIxIng RatIo MIxIng RatIo Surface Temp. Surface Temp. Surface Temp. PPMV PPMV WO Report Present Wang et al.

( 19A2) CalculatIons (1976)

CO2 330 660 2.0 1.71 1.96

N20 0.300 0.600 0.3 - 0.4 0.40 0.44

Ql* • 1.600 3.200 0.30 0.37 0.40

*WMO report uses 1.5 ppMV for Ql4 reference mIxing ratio

chemical structure (the solid lines shown in Figs. 4 and 5 are for the fixed ozone case). The corresponding changes produced in th~ ozone mixing ratio due to temperature feedback and radiative-photochemical coupling effects are illustrated in Fig. 6. In the stratosphere, when temperature decreases due to doubling of atmospheric C02, the ozone concentration increases because of the inverse temperature relationship between ozone and temperature through temperature dependent reaction rate coefficients for chemical reac­tions affecting the ozone concentration. This behaviour of ozone is seen clearly in Fig. 6. In addition, when C02 + N20 + CH4 is doubled, the increases in NOx and HOx concentrations resulting from the doubling of N20 and CH4 have the effect of decreasing the ozone enhancement (see the dashed curve in Fig. 6). The increase in the ozone mixing ratio shown in Fig. 6 leads to the additional heating (particularly in the middle and the upper stratosphere due to enhanced absorption of solar radiation) which compensates partially for the increased IR cooling due to the doubling of C02 and C02 + N20 + CH4. This effect is shown in Figs. 4 and 5, where the temperature changes due to double C02 and C02 + N20 + CH4 are compared with and without ozone photochemistry interaction. It is interesting to note that the temperature cooling is reduced by more than 4°C near the stratopause region when C02 alone is doubled with temperature­ozone feedback included (see Fig. 4). But when C02 + N20 + CH4 is doubled the additional radiative-photochemical coupling due to the increase of N20 and CH4 has the effect of reducing the temperature recovery from 4°C to less than 3°C in the same region. The effect of stratospheric ozone changes resulting from the doubling of C02 ,and C02 + N20 + CH4 on ' tropospheric and surface temperature is negligibly small (cause slight additional heating). This is attributed to the fact that the reduced solar radiation reaching troposphere is nearly compensated by the increase in the downward long wave radiation through 9.6 V band when stratospheric ozone is increased due to doubling of C02 and C02 + N20 + CH4.

d) The Effect of Ozone Photochemistry Interaction on Temperature Changes due to EI Chichon Aerosol Cloud

Fig. 7 shows the changes in the vertical ozone distribution resulting from the interaction of the stratospheric ~l Chichon aerosol cloud with ozone photochemistry for two different assumed aerosol optical properties of the aerosol cloud while the feedback effect of ozone changes on the thermal structure is illustrated in Fig. 8. It can be seen from Fig. 7 that the

- 108-

aerosol cloud from El Chichon eruption has the effect of decreasing the ozone concentration in the stratosphere. This can be attributed to the increased photodissociation rates of 03 and N20 (caused by the multiple scattering of the aerosol cloud) and temperature-ozone feedback effects in the stratosphere. As illustrated in Fig. 8, the feedback effect of ozone changes on the vertical temperature structure is not considered to be signi­ficant. However, it has the effect of cooling the upper stratosphere (re­duced solar heating due to 03 depletion) slight warming the lower strato­sphere (self healing effect of ozone reduction) and increased cooling at the surface (reduced greenhouse effect through 9.6 ~ ozone band).

1.8 Conclusions

The results based on 1-D radiative-convective and photochemical diffu­sion model show that the doubling of atmospheric C02, N20 and CH4 with fixed ozone distribution will lead to warming of the surface and troposphere by 1.71, 0.4 and 0.37°C respectively while C02, causing substantial cool­ing in the stratosphere. The effect of the interaction of ozone photochem­istry on temperature changes due to double C02 and C02 + N20 + CH4 is to reduce the temperature cooling up to several degrees in the strato­sphere (less recovery in the case of double C02 + N20 + CH4) with little change in the heating at the surface and in troposphere. The inter­action of the stratospheric El Chichon aerosol cloud with ozone photochemis­try leads to the ozone reduction in the stratosphere which in turn has the effect of increasing the cooling at the surface and above the cloud center while causing slight warming below in the lower stratosphere.

Acknowledgements The author acknowledges Drs. J.P. Blanchet and J.J. Morcrette for help

with preliminary r~diative code. The author also would like to thank Drs. P.E. Merilees and G.J. Boer for encouragement and support, Mr. F. Szekely for programming support and Lynda Smith for typing the manuscript.

1.8 References

Augustsson, T., and V. Ramanathan, 1977: J. Atmos. Sci., 24, 448-451. Bundeen, W.R. and R.S. Fraser, (Editors), 1983: NASA Technical Memorandum, Goddard Space Flight Centre, Greenbelt, Md. 20771. Burch, D.E., et aI, 1992: AFCRL-62-688, Ohio State Uni. contract AF19(604)-2633. Blanchet, J.-P., 1979: M.Sc thesis, Dept. of Meteorology, McGill University, Montreal, Que. Boughner, R.E., 1978: J. Geophysical Research, 83, pp. 1326-1332. Groves, K.S., et aI, 1978: A paper presented at WHO Ozone Symposium, Toron­to, 26-30 June 1978. Hunt, G.B., and N.C. Wells, 1979: J. Geoph. Res., 84, pp. 787-791. Kuo, H.L., 1979: Contribution to Atmospheric Physics, Vol. 52, No.2. Manabe, S., and R.T. Wetherald, 1967: J. Atmos. Sci., 24, 241-259. Manabe, S., and R.T. Wetherald, 1975: J. Atmos. Sci., 32, 3-15. NASA Panel for Data Evaluation, 1983: JPL publication 83-62. Ramanathan, V., 1975: Science, 190, 50-52. Ramanathan, V., 1980: Proceedings of the Quadrennial International Ozone Symposium, Vol. 11, Boulder, Colorado. Vupputuri, R.K.R., 1975: Atmosphere, 14, 214-236. Wang, W.C., et aI, 1976: Science, Vol. 194, pp. 685-690. WHO, Expert Committee Meeting, 1982: WHO, Report No. 14, 13-17 Sept. 1982, Boulder, Colorado.

-109-

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OBSERVATIONS OF RELEVANT TRJI.CE CONSTI1UENTS AND THEIR BUDGETS

- Map-Globus in 1983

- Vertical profiles of chlorinated source gases in the midlatitude stratosphere

- A laboratory test of cryogenic sampling of longlived trace gases under simulated stratospheric conditions

- The vertical distribution of halocarbons in the stratosphere

- Structures in the vertical profile of nitrous oxide measured ewer a mid latitude station

- Global lower meso spheric water vapor revealed by lims observations

- Intercomparison of stratospheric water vapor profiles obtained during the balloon intercomparison campaign

- Intercomparison of stratospheric measurements of NO and N02

- Intercomparative Measurements of Stratospheric Nitric Acid

- Spatial and temporal variability of the N02 total content based on annual observation data

- Southern hemisphere nitrogen dioxide

- The climatology of upper atmosphere nitrogen dioxide revealed by lims observations

- Comparisons of measured and predicted diurnal changes in stratospheric NO and N02

- Nitric oxide profile from 7 to 32 KM

- Measurement of oxides of nitrogen in the free troposphere over Japan

- Measurements of atmospheric nitric oxide from nimbus 7 SBUV ultraviolet spectral scan data

- Evidence for a thermospheric source of stratospheric NOX

- Measurements of nighttime N01 and N02 in the stratosphere by matrix isolation and ESR spectroscopy

- Variabilite temporelle du N03 stratospherigue

- Quantitative observations of stratospheric chlorine monoxide as a function of latitude and season during the period 1980 - 1983

- Trace species in the stratosphere precision and variability

- Trace constituents measurements deduced from spectrometric observations onboard spacelab

- Simultaneous measurements of stratospheric trace gases as deduoed from air-borne infra-red spectrometry

- The determination of stratospheric nitrogen dioxide concentrations from limb brightness measurements

Summary

MAP-GLOBUS IN 1983

W.A. Matthews* Service d'Aeronomie du CNRS

B.P. 3 91370 Verrieres Ie Buisson

FRANCE

The broad aims of MAP-Globus, where Globus is an acronym for Global Budget of Stratospheric Trace Constituents are to both improve the measurement accuracy of stratospheric trace gas measurements by compara­tive measurements and to enable broader scientific objectives that are beyond the capability of any single group to be met. An initial campaign was organised and held in S.W. Europe in September - October 1983. This paper reviews the experiments that were performed and some of the initial findings.

1.1 Introduction

It was decided that in the first MAP-Globus campaign a series of com­parative measurements, particularly of stratospheric 03 and NOx be made and that complementary measurements of other relevant species be performed. It was also decided that measurements of the solar flux in the region of the spectrum relevant to the photochemistry of these trace gases be measured. Comparative measurements require the establishment of the relative precision of a number of different measurements using differing measuring techniques. To this end instruments were placed either on the same large gondola, or flown in the closest possible succession during stable atmospheric conditions. The mid-latitude autumn equinox provides the opportunity to make atmospheric measurements where, at least to first order, large day to day variations are not expected.

Since, as the name of the campaign suggests, one of the ultimate aims is to understand the composition of the stratosphere on a global scale, measurement campaigns at a number of latitudes and in different seasons are envisaged. This first campaign was therefore important in establishing the comparability of measurement techniques and their inherent precision, so that when instruments are taken to different latitudes, valid conclusions can be drawn from data comparisons.

* Permanent affiliation: PEL Atmospheric Station DSIR

Ozone Symposium - Greece 1984

Lauder, Central Otago NEW ZEALAND

- 115-

The 1983 MAP-Globus campaign was based around a series of large balloon flights from the CNES Balloon Centre in Aire sur l'Adour, S.W. France. Detail of most of these experiments is given in Offermann (1). However, several of those experiments listed, particularly those relating to NOx , did not fly for a variety of reasons. Two cryogenic sampling experiments were however added to the campaign at short notice and both \oJ-ere flown on September 10, 1983. Both experimental systems worked well and consequently data for a good intercomparison has been obtained.

In all, thirteen large balloon payloads were launched during the campaign with an incredible 100% success rate. The good weather throughout September meant that good data was also obtained from the sixteen ground based experiments and some 130 ozone sondes were also flown as part of the campaign. The data from these together with that from the standard meteo­rological temperature soundings will provide information on the stability of the atmosphere over southern Europe during the campaign and i.rill be used to place some temporal and spatial limits on intercomparison validity.

The data obtained during the MAP-Globus 1983 campaign is being discussed in detail at several working group meetings being held in conjunction with the Quadrennial Ozone Symposium and these data will provide the basis for a number of publications in the near future.

1.2 Acknowledgements

We wish to acknowledge the tremendous support and co-operation given to the Globus scientific team at Aire sur l'Adour by Monsieur Prigent and his staff at the Balloon Centre of CNES, Aire sur l'Adour, France and congratulate them on their 100% success rate with the large balloon pay­loads in this first phase of MAP-Globus. We also wish to acknowledge the untiring efforts of Professor D. Offermann who co-ordinated this campaign, and the personal support and interest of Monsieur Auger of CNES. The financial support given to this campaign by the B.M.F.T. of the Federal Republic of Germany is gratefully acknowledged. I also wish to acknowledge the support given to me at the Service d'Aeronomie by CNRS and C.I.E.S.

1.3 Reference

OFFERMAN, D. (1983). Map/Globus Campaign 1983. Handbook for Map ~, 17-43

-116 -

VERTICAL PROFILES OF CHLORINATED SOURCE GASES IN THE

MID LA TITUDE STRATOSPHERE

D. KNAPSKA, U. SCHMIDT, C. JEBSEN, G. KULESSA, and J. RUDOLPH Institut fUr Chemie 3: Atmospharische Chemie der

Kernforschungsanlage Julich GmbH, P.O. Box 1913, D-5170 JLi!ich, FRG

S.A. PENKETT Environmental and Medical Sciences Division AERE Harwell, Oxon, England

Summary

Vertical profiles of the stratospheric CCl", CH 3CI, CH 3CCI, C;F zCl 3 mlxmg ratios derived from two balloon flights over Southern France (44 0 N) in 1982 and 1983 are presented. A total of 26 air samples were collected in situ by a newly developed balloon-borne cryogenic sampler. The samples were analysed in the laboratory within four weeks after the flight employing two different analytical techniques: gas chromatography and a gas chromatograph/ mass spectrometer combination. The observed mixing ratios are well in the range of previous determinations of these species in the stratosphere. Above about 30 km CCI" and CH 3CC13 mixing ratios are below the analytical detec­tion limits of both techniques. A comparison with I-D model calculations shows that for all species the observations are lower than the theoretical profiles.

1. Introduction

The assessment of the impact of anthropogenic chlorine on stratospheric ozone is mainly based on the distribution of CFCl3 (F 11) and CF zClz (F 12) in the atmo­sphere. However, a number of other man-made source gases, such as CCI", CH 3CCI 3, CzF 3Cl3 (F 113), CF 3CI (F 13), CzF "Clz (F 114), CzF sCI (F 115), and CHF zCI (F 22) has been observed and the global mixing ratio distributions and trends for some of them have been measured. CCI" and CH 3CCI3 are the most abundant of these source gases (1), but only limited data are available for the stratosphere (2). First obser­vations of CzF 3C13, CzF "CI" C 2 F sCI, and CHF zCI were reported by Fabian et al (3). The contribution of these chlorinated species equals that of CFCI3 and CF zCl z resulting in a total source strength for stratospheric chlorine that exceeds the pro­duction from the only known natural chlorine source gas, CH 3CI, by about a factor of four.

In 1982 we began a new programme to investigate the stratospheric distribut­ion of several important halocarbons. This paper reports on new observations of CCI", CH 3CCIH CzF 3CI3 and CH 3CI that were obtained during two balloon flights over Southern France (44 ON).

2. Experimental

We collected large stratospheric air samples (8 to 20 I STP) employing a newly developed neon cooled cryogenic sampler (4). This instrument differs from that used by Fabian et al (2, 3) in two essential points. The 15 cryopumps have rather short (15 cm) separate inlet lines in order to reduce the area of the surface exposed to

Ozone Symposium - Greece 1984 - 117-

the sample. Furthermore the inlet lines do not include any catalyst to destroy the ozon amount of the sampled stratospheric air. We know from a laboratory simulation test that this sampling technique compounds the risk of sample alteration due to the high 0 3 amounts in the mid stratosphere. However ozone affects only some of the species that we can measure, and a significant change of the sample composition was only observed at relatively low concentrations (5), whereas the use of an ozone catalyst gives rise to sonsiderable contamination problems for several trace species.

Two sucessful flights were launched from Aire s/l'Adour, Southern France (44 oN). A total of 26 samples was collected on the 21 October 1982 (11 samples) and 10 September 1983 (15 samples) during descent of the balloons between 34 km and 15 km altitude. They were analysed within four weeks after the respective flight employing two different analytical techniques. A first run of analysis was made in JUlich using a gas chromatograph equipped with an electron capture detector (GC/ECD). 2 I-aliquots were preconcentrated at 170 K on glass beads. Separation occured on a spherosil/n-octane column (10 m x 1/16"), temperature programmed between 170 K and 360 K. All samples were measured against two laboratory stand­ards. The contents of the species of interest in these standard corresponded to their mixing ratio in the lower and middle stratosphere. The precision of the GC/ ECD varied for the different species. It is indicated in the figures by horizontal bars at the bottom. Since no absolute calibration was available these standards were compared to the AERE standards at Harwell on ocassion of a second run of analyses applying the gaschromatograph/mass spectrometer combination (GC/MS). The accur­acy of the Harwell standard is about + 5 % and the precision of the individual ana­lyses was about 10 %. Typically, the detection limit was of the order of 0.2 pptv.

3. Results and Discussion

The vertical distributions of the CCl~, CH 3CC13, CH 3Cl and C 2F 3Cl3 mIxIng ratios as derived from both flights are plotted in Fig. 1 trough 4. Different symbols indicate the results obtained with both techniques. Both CCI ~ and CH 3CCI 3 decre­ase very rapidly above 20 km altitude, the observed gradients correspond to a

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- 118-

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Volume MIXing Ratio -

Figure 2: Vertical distribution of CH)CCI) in the stratosphere. See Figure I for details.

scale height of about I km. At about 30 km altitude the mlxmg ratio of these species falls below the lower limit of detection. The sensitivity of the GC-MS was much better than that achieved with the GC-ECD technique. Therefore the results obtained with both methods show large discrepancies for those samples that have mixing ratios in the range of few pptv, i.e. above 25 km altitude. The only other data on CCI 4 and CH)CCI) published to date are also shown in Figure 1 and 2, re­spectively. It should be noted again, that both sets of measurements rely on the

. same absolute calibration "method. Due to the strong gradients both profiles seem to agree reasonably well, however, after closer inspection measurements at Borchers et al (2) appear to be generally lower than those reported here, at least for CCI4. Moreover the CH)CCI) data show more scatter than the CCI4 measure­ments. This behaviour may be explained by the results of a laboratory simulation test (5) that we had performed to study the effects of ozon on the stability of cryogenically collected samples. The test showed, that CH)CCI) was destroyed by about 40 % in some cryopumps whereas the CCI mixing ratio of the samples gener­ally decreased. with time. We finished analyses within four weeks after sampling. The resonable agreement between both data sets indicates that it is possible to obtain reliable profiles even if no ozone catalysts are used.

The vertical profile~ of CH)CI (Fig. 3), display a much weeker gradient in the stratosphere. The mixing ratio decreases between 20 and 30 km altitude by about a factor of five corresponding to a scale height of about 7 km. The new data report­ed here generally agree with the average distribution derived from previous obser­vations (6). however, the profiles display more structure due to the large number of samples. Between 20 and 28 km altitude the mixing ratios observed on the 21. Oc­tober 1982 are much higher than on the 10. September 1983. The data obtained with both analytical techniques agree remarkably well, therefore the observed differen­ces (about a factor of four at 25 km) indicate differences in the CH)CI abundance within this layer. A similar behaviour has been observed for other long lived trace gases (7). It would be explained by large scale horizontal transport processes. During October 1982 the EI Chichon eruption cloud had extended into mid latitudes and was located at about 25 km. CH)c! of volcanic origin (8) might, therefore, also contrib­ute to the enhanced CH)CI level.

The halocarbon C 2 F )CI) (Fig. 4) was first observed in the stratosphere by Fabian et al. (3). The mixing ratios as derived from five samples collected in 1980 are about three times smaller than the new observations. Such a large difference cannot be explained by the long term increase due to anthropogenic release, it must

- 119-

Volume Mlxmg Ratio -

be due to a systematic error in absolute calibration.

Figure 3: Vertical distribution of CH 3CI in the stratosphere. See Figure I for details.

The gradient of the C 2F 3CI3 mixing ratio is comparable to that of CF 2C12' It corresponds to a scale height of about If km. The profiles presented in Fig. If show similar structures as observed for CH 3CI and other long lived source gases. Strato­spheric measurements of C 2F 3CI3 therefore not only provide information about an­other important source gas for reactive chlorine but also a means to study large scale transport processes (7).

The Fig. 1 through .If also show theoretical profiles as predicted by the Law­rence Livermore Laboratory 1 D model (LLL 1 D) (9). For each of the species the observations are generally below the modeled profiles. Possible causes of these des­crepancies may be underestimates of the photochemical destruction rates in the stratosphere and/or an inaccuracy in the vertical transport parametrization though the K -profile used in the LLL I-D model also consideres recent revisions of the absorp'tion cross section for molecular oxygen and photon-flux data in the upper stratosphere (1).

10

-Volume M,x,ng Rat io -

- 120-

-Figure If: Vertical distribution of C 2F-3C13 in the strato­sphere. See Figure I for details.

4-. Conclusions

The new measurements reported for the source gases CH 3CI, CCI 4, CH 3CCl3 and C 2 F 3Cl3 increase the available data base on their stratospheric distribution by at least a factor of two. Available data are still limited to midlatitudes. The com­parison of our measurements with data published previously by Fabian et al. (2) and Borchers et al. (3) shows that representative profiles may be obtained even if no ozone catalyst is used to remove 0 3 during sampling. However it appears to be im­portant, that analyses are finished within a short period of time. Due to the inherent problem of sample alteration at mixing ratios in the pptv-range the time period bet­ween sampling and analyses should always be reported. From experience of the first balloon flights and the laboratory simulation test we know, that representative meas­urements of further halocarbons may be obtained in the future. Such data will con­tribute to a better assessment of the anthropogenic impact on the stratospheric chlorine burden and, in the case of some relatively stable compounds, help to inves­tigate dynamical processes in the stratosphere.

Acknow ledgement

This work was partially funded by the German Ministry of Science and Techno­logy (BMFT) through grant No KBF 66.

REFERENCES

1. WMO (1981). The Stratosphere 1981, Theory and Measurements. Report No 11, WMO, Geneva, Switzerland

2. BORCHERS, R. et al (1983). First measurements of the vertical distribution of CCl 4 and CH 3CCi3 in the stratosphere. Naturwissenschaften ~ 514--516

3. FABIAN, P. et al (1981). Halocarbons in the stratosphere. Nature 294-, 733-735

4-. SCHMIDT, U. et al (1983). Sampling of long-lived trace gases in the middle and upper stratosphere. Proceedings cf the "Sixth ESA Symposium on European Rocket and Balloon Programmes" (ESA, SP-183) 14-1-14-5

5. KNAPSKA; D. et al ,A laboratory test of cryogenic sampling of long­lived trace gases under simulated stratospheric conditions. This volume

6. SCHMIDT, U. et al (1980). The vertical distribution of CH 3Cl, CFCI3, and CF 2 Cl 2

in the midlatitude stratosphere. Proceedings of the Quadrennial International Ozone Symposium, Boulder, Colorado, Vol II, 816-823

7. SCHMIDT, U. et al (1984-). Stratospheric trace gas distributions observed in different seasons. Adv. Space Res., in press

8. RASMUSSEN, R.A. et al (1982). Carbonyl sulfide and carbon disulfide from the eruption of Mount St Helens. Science 215, 665-667

9. WUEBBELS, D.J. (1984-). Personal communication

- 121 -

A LABORATORY TEST OF CRYOGENIC SAMPLING OF LONG LIVED TRACE

GASES UNDER SIMULATED STRATOSPHERIC CONDITIONS

D. KNAPSKA, U. SCHMIDT, C. JEBSEN, F.J. JOHNEN, A. KHEDIM, and G. KULESSA Institut fUr Chemie 3: Atmospharische Chemie

Kernforschungsanlage JUlich GmbH, P.O. Box 1913, D-5170 JUlich, FRG

Summary

During cryogenic collection of stratospheric air samples the presence of large amounts of ozone may initiate contaminating or sample altering processes, either directly in the gas phase or on surfaces. To investigate the possibility of sample alteration, a laboratory experiment was performed under simulated stratospheric conditions. After thorough preflight preparation the sampler was filled with test gas aliquots, containing compounds of interest in the range of several pptv. Amounts of ozone were added to ten out of fifteen samples. After warming, the samples were analysed for CH4, NzO, CO, COz; C zH6, C 3He, CzHzo and for CFCI 3, CFzClzo C zF3 CI 3 • CCI4, CH 3CI, CHCI 3 , CH 3CCl 3 and their long­term stability studied over a period of four weeks. CH 4, NzO, COzo CFCI 3 , and CFzClz measurements do not depend on ozone con­centration while amounts of CzH6, CzH z, C 3He, and CHCl 3 varying from 50 % to 100 % may be affected in the presence of ozone. Affects on the other chlo-; rinated hydrocarbons are less than 50 % with the exception of CCI 4, which slowly decomposes even in the absence of ozone. If analysed within four weeks after sampling, the profiles derived for these compounds will represent their actual stratospheric distribution to better than a factor of two.

1. Introduction

Cryogenic sampling has been proven a very suitable technique for collection of air samples in the stratosphere. To date most of the available data base on the stratospheric distribution of longlived trace gases has been obtained employing this technique. It allows collection of large air samples (20 I STP or more) into small sample containers. The high sample pressures that builds up after warming of the samples considerably reduces the surface to volume ratio in the container. Conse­quently the various potential effects of contamination or alteration (outgassing, surface reactions etc.) of the samples are reduced (1, 2).

Furthermore, with large sample volumes availablE', it is possible to perform mul­tiple analyses of a larger number of trace gases, even those having mixing ratios below the pptv-range, because pre-enrichment techniques may be employed prior to the analyses (GC-ECD, GC-MS). On the other hand there are two features that re­quire special attention during whole air sampling: firstly, the mixing ratios of various trace gases that are rapidly photolyzed decrease strongly to values in the ppt-range at altitudes where, secondly, the ozone mixing reaches its maximum. Thus the risk of contamination increases along with the risk of sample alteration in the presence of large ozone amounts. The first compound for which such effects had been iden­tified was CO (3). Recently we have reported that some chlorinated hydrocarbons

Ozone Symposium - Greece 1984 - 122-

(CH 3CI, CHCIl> CH 3CCI 3 ) and light alkanes (C2H6, C 3 H8 ) may also be affected by similar processes (It). However, no information is available yet for mixing ratio levels below 10 pptv. Such information is needed if cryogenic sampling is to be used for investigations of species that are less stable than those which have been proven to remain unaffected, such as CH 4 , N20,. CO" CFCIl> CF 2CI2•

It has been suggested to remove ozone from the collected air samples by in­cluding an activated copper sieve or a similar catalytic destroying agent into the inlet line (3). However, the insertion of a large active surface may compound the risk of other alteration causes. We observed non-acceptable contamination for some of the aforementioned species, when similar ozone catalysts were used (It).

In the light of these constraints we have recently developed a new neon cooled cryogenic sampler, that .allows collection of 15 distinct samples having a total volume of about 200 I STP (It). When designing and assembling this new instrument we payed special attention to reduce the potential effects of contamination or sample alter­ation during sampling. During test experiments we have tried to investigate these effects both qualitatively and quantitatively. This paper reports on the results of a laboratory test, that simulated the conditions encountered in the middle strato -sphere (25 - 30 km).

2. Experimental

The simulation test consisted of three basic steps: sampler preparation, aliquot­ting of test gas samples, and multiple sample analyses within a period of four weeks. For routine preflight preparation our cryosampler is evacuated to a pressure of about 10- 8 mb and heated at 120°C for about 3 weeks. During this time the residual gas in the cryopumps is 'repeatedly analysed with a mass spectrometer to check for impurities in the system. .

For the test a common inlet manifold was attached to the fifteen distinct in­lets (Fig. 1). In principle this manifold consists of a series of stainless steel capillary tubes with equal lengths that connect the test gas source with the glass caps of the inlet tubes. We chose this arrangement to enable fusing of the glass caps after the

- 123-

Figure 1: Detailed view of the test manifold, illustrating the modified in­let lines of the cryopumps. F indicates the separation point, where the glass caps were fused after the test.

test without exposing any part of the inlet line to laboratory air. Therefore, after the tests, the sampler would be prepared for the next flight and its real conditions would have been documented by the results of the test analyses.

In order to check for any impurities in the system the conditioning process was interrupted and the sampler and manifold flushed with ultrapure helium. Aliquots of this pure gas were then analysed for the species of interest. Since we did not ob­serve any contamination the system could be considered to be clean. After this check the bake-out process was continued under vacuum for several weeks.

We used a dry tropospheric air sample (mH ° < 1 ppm) as a test gas, which was diluted with dry synthetic air to adjust its comp~sition to stratospheric conditions. Several samples of this test gas were prepared for the different series of the simu­lation test. Table I compares the typical test gas composition with the corresponding mixing ratio at 25 km for the species of ~nterest.

Table I: Test gas composition, based on the main laboratory standards (5,9)

volume mixing ratio gas test gas detectable change at 25 km

CO 5 ppb :. 2 ppb 10 ppb

CH 4 35 ppb :. 5 ppb 0.9 ppm

N20 g ppb :. 1 ppb 130 ppb

CFCI3 5 ppt :. 1 ppb 5 ppt

CF2CI2 7 ppt :. 2 ppt gO ppt

C2F3CI3 1 ppt :. 0.1 ppt 5 ppt

CHCI3 2 ppt :. 0.5 ppt 1 ppt

CH 3CJ 20 ppt :. 5 ppt 100 ppt

CCI4 g ppt :. 2 ppt 1 ppt

CH 3CCI3 2 ppt :. 0.5 ppt 2 ppt

C2H6 50 ppt :. 5 ppt 20 ppt

C3Hg 30 ppt :. 5 ppt

C2H2 20 ppt :. 5 ppt 30 ppt

This test gas was fed into a flow system, where various amounts of ozone (pro­duced from pure oxygen by electrodeless discharge) could be added. After this prepa­ration the sampler was cooled to 30 K and connected with the flow system. Five samples each were filled with test gas aliquots and different amounts of ozone added. The pressure at the inlets of the cryopumps could be varied by changing the flow rate and pressure within the test flow system. The actual parameters maintained during the three test series are compiled in Table II.

Table II: Conditions during sampling simulation

Test No. 03 [ppmv] inlet pressure [mb] corresponding altitude [km]

0.0 50.0 20.5

II 6.0 + 1.0 30.0 24.0

III 10.0 + 1.0 20.0 26.5

- 124-

During the test runs the 0 3 mlxmg ratio was monitored and reference samples of the test gas were taken at the manifold inlet. Each cryopump was filled with about 8 I (STP) of the test gas.

After warm up a rather high pressure builds up in the cryopumps. Since ozone was found to decompose in these samples only after five days analyses were begun after about one week. Various groups of trace gases were measured using different gas chromatographic techniques (5, 6). After the first run of analyses, aliquots of the distinct samples were transferred from the cryopumps into 2 I stainless steel con­tainers in order to investigate possible effects that might alterate the sample com­position during this process at very low mixing ratio levels. If the samples would re­main unchanged, aliquotting would have the advantage that logistic problems are considerably reduced if several balloon flights were performed within relatively short time periods. Both the original and the aliquotted samples were repeatedly analysed over a period of five weeks.

3. Results

It is impossible to present the complete set of results in this report. To illu­strate the various effects that were observed, a selection of the results is plotted in Figure 2 and 3. There is one group of trace gases, namely CH." N,O, CO" CFCI 3 and CF ,CI, that are not affected during cryogenic sampling. No significant change of their mixing ratios could be detected for any test conditions. The results of a pre­vious simulation test (4) are hereby confirmed for considerably lower mixing ratio levels. The halocarbon C,F 3CI3 (F 113), which was only analysed during the recent test series may also be included into this group.

0

~ 10 L

Ol c: 'x 'E ~ ~

" Qj 1.0 L

0.5 1

CFCI3

Spptv ~ 2Skm

/'opptv.20krn 0

20pptv I ~km • 0

CF2 CI2 ozone de<omposition 7pptv 9 3Skm

warmup

10 days after sampling tests-

100

Figure 2: Results of the testana­lyses for CFCI 3 and CF ,CI,. (For details see Figure 3).

The results on CO were of special interest, since this was the first trace gas for which alteration processes had been reported (3). The samples that contained no 0 3 showed very good reproducibility. An increase by a factor of about 2 was observed in 2 (out of 7) cryopumps that were analysed 7 days after the test. This is much less a change than that observed by Fabian et al. (3). Since CO mixing ratios were also increased in the aliquotted samples (i.e. in the absence of 03) we suppose that the increase is caused by contamination.

- 125-

The results for the other trace species show effects of contamination and/or decomposition. Figure 3 displays the detailed results for CCI4, CHCl lJ CH)CCI) and CH)CI. However we would like to point out a few of the important features: 1. It appears that CCI4 is generally decaying in the cryopumps, there is no specific

effect due to the presence of 0 3, and the aliquotted samples did not change over a period of three weeks.

2. The mixing ratio of CHCI 3 is strongly affected in the presence of 0 3, we ob­served a decrease to almost 50 % of the original value in the cryopumps, where­as the aliquotted samples were remarkably stable (with one exception). This indi­cates that the decay occurs in the presence of 0 3 and only during sampling and warm up.

3. In the case of CH)CCI) we observed a significant decrease of about itO % in only 2 (out of 7) cryopumps. Both samples had rather high 0) contents (10 ppmv).

it. CH 3CI shows a rather complex behaviour in the cryopumps. The mixing ratio of individual samples either increased or decreased by up to 50 %, if 0 3 was added during sampling. With a few exceptions CH 3CI increased with time after warm up in the cryopumps and the aliquotted samples, too. This large variability of the effects in distinct cryopumps causes strong experimental difficulties in the mea­surement of CH 3CI in the upper stratosphere (7).

15

1 0~~~~ .. --~--~~~~~

~:~~:~~~--,----~. , 2 OS

E 0' ~ x E

CH3 CI 20 pptv • 30 km 05

---',

CHCI3

2pptv: 20km

"

~ O~==========================~ -g lO""!' • 20km CC4 o~==================~ ~ 8pptya 25km

10~~~~~~-~----------7>--~ ~~~ __ ~~_SF-*_~~

.............. --- .... _.... Y'<--6.....-:A.

.... ..... ' .... ,:~ .... --..,- ....... -.JII!-.

" 05

CH3CCb 2 pptv ~ 25km

04---------------r-------------~ 10 100 1 10

days after sampling tesl'; - days after sampling tests-

Figure 3: Results of the test analyses for CH 3CI, CCI4, CH)CCJ lJ and CHCI) in the different samples from the three testseries (see table II): I ;., II ;., III ; •. The respective large open symbols refer to aliquotted samples, while small open symbols indicate the results for the reference samples. The measured values are plotted relatively to the mixing ratio of the distinct species in the original test­gas. The short and the long horizontal bars represent the results of a previous test without 0 3 and with 20 ppmv 0) added, respectively (it). The shaded area shows the range of experimental uncertainty (:,. 1 0).

- 126-

100

The test results for the light hydrocarbons C,H6, C 3 He, and C,H, indicated that these species are strongest effected. In most of the cryopumps these gases al­most completely decayed, if 0 3 was added to the test gas. Only 2 (out of 7) cryo­pumps did not show a significant change, in fact, one sample that had the highest 0 3 content (10 ppmv) remained unchanged. In view of the strong decay processes we did not investigate the long-term stability for these species.

4. Discussion

The quality and stability of samples that were collected by croygenic sampling is rather variable even if the sampler is prepared and conditioned with greatest care. The multiple effects of sample alteration differ between the individual cryo­pumps, and during the period of cryosampling and warm up a combination of chemi­cal and physical processes might cause a change of the original sample composition.

During this simulation test we used a test gas with much lower mixing ratios of the various species than during the previous test (4). Both tests showed similar results for the light hydrocarbons and CHCI 3 , however, as shown in Fig. 3, we ob­served different effects for several chlorinated species. At higher concentration levels CCL, and CH 3CCl 3 were not affected by OJ> whereas CH 3Cl also decayed by about 50 %. We must not expect that both tests show identical results, because the test procedure was not the very same in both cases. Furthermore the sampler had been reconditioned twice between both test experiments. However, there is one remarkable feature; sample alterating effects are more pronounced at low mixing ratio levels. Therefore, results obtained from cryogenic samples collected at higher altitudes ('" 25 km) may not be representative for the actual natural distribution of those species that are affected by ozone.

Nevertheless, we prefer to use our cryosampler without any ozone destroying agents in the inlet line. Stratospheric profiles of CCI". and CH 3CCl 3 derived from cryogenic samples that were collected without removing ozone (6) and those obser­vations obtained using ozone catalysts (8) agree reasonably well. It may well be that some of the observed effects decrease with time, once the sampler has been recon­ditioned several times. We will check for such a "healing process" on the occasion of future flights.

It appears that the new design of our cryosampler and the approved procedure for its preflight conditioning are a good basis for the sucessful measurement of various trace species, even of CO.

1.0

..... ... 30

E -"C:

QJ -0 20 J ...... ...... « T.--- Qa-

10

0 50 Mixing

0 0

CO

100 Ratio

44· N o L FlightS 1977

I FotMon .. 01 19611

: 1009.83

150 (ppbv)

200

- 127-

Figure 4: Comparison of CO mixing ratios as measured in stratospheric samples that were collected by different groups without using an ozon catalyst. Small full dots indi­cate the observed CO increase in the respective cryopumps as measured 4 w.eeks after the first run of analyses. The shaded vertical bar represents the range of spectroscopic observations (10).

5. Conclusion

The results obtained from laboratory simulations of cryogenic sampling confirm that several trace gases such as CH4, N20, CO"CFCI 3 , CF 2Cl" C 2 F 3Cl 3 can easily be measured without removing ozone prior to cryocondensing the sampled air. Other chlorinated species such as CHCI 3 , CCI4, CH 3Cl and CH 3CCl 3 are affected by 0 3

if their mixing ratio is in the range of a few pptv, however observations will repre­sent natural conditions within a factor of two, if samples are analysed within about four weeks. The observation of light hydrocarbons appears to be impossible if 0 3 is not readily removed from the sample. New techniques for 0 3 removal are to be de­veloped if these species are to be investigated since ozone catalysts used to date compound the risk of strong contamination of the samples.

Acknow ledgement

This work was partially funded by the German Ministry of Science and Techno­logy (BMFT) through grant No. KBF 66.

REFERENCES

1. EHHAL T, D.H. (1980). In situ observations. Phil. Trans. Roy. Soc. London, A 196, 175-189

2. FABIAN, P. (1981). Atmospheric sampling. Adv. Space Research, 1 17-27

3. FABIAN, P., BORCHERS, R., FLENTJE, G., MATTEWS, W.A., SEILER, W., GIEHL, H., BUN~E, K., MULLER, F., SCHMIDT, U., VOLZ, A., KHEDIM, A., and JOHNEN, F.J. (1981). The vertical distribution of stable trace gases at mid-latitudes. J. Geophys. Res., ~ 5179-5184

4. SCHMIDT, U., KULESSA, G., KHEDIM, A., KNAPSKA, D., and RUDOLPH, J. (1983). Sampling of long lived trace gases in the middle and upper stratosphere. Proceedings of the "Sixth ESA Symposium on European Rocket &. Balloon Programmes", (ESA SP-183), 141-145

5. VOLZ, A., SCHMIDT, U., RUDOLPH, J., EHHALT, D.H., JOHNEN, F.J., and KHEDIM, A. (1981). Vertical profiles of trace gases at mid latitudes. JUI-Re­port 1742, Kernforschungsanlage JUlich GmbH, D-5170 JUlich, FRG

6. KNAPSKA, D., SCHMIDT, U., JEBSEN, C., KULESSA, G., and RUDOLPH, J. (1984). Vertical Profiles of chlorinated source gases in the mid-latitude stratosphere. This volume

7. SCHMIDT, U., KNAPSKA, D., and PENKETT, S.A. (1984). Vertical profiles of methylchloride (CH 3CJ) in the mid-latitude stratosphere. To be submitted to J. Atm. Chern.

8. BORCHERS, R., FABIAN, P., and PENKETT, S.A. (1983). First measurement of the vertical distribution of CCI4 and CH 3CCI 3 in the stratosphere, Naturwissenschaften ZQ., 514-516

9. RUDOLPH, J. (1983). Personal communication

10. WMO (1981). The Stratosphere 1981, Theory and Measurements. Report No 11, WMO, Geneva, Switzerland

- 128 -

THE VERTICAL DISTRIBUTION OF HALOCARBONS IN THE STRATOSPHERE

P. Fabian, R. Borchers, D. Gomer, B.C. Kruger and S. Lal

Max-Planck-Institut fur Aeronomie (MPAE), D-3411 Katlenburg-Lindau, Germany

S.A. Penkett Environmental & Med.Sci.Div. AERE Harwell, U.K.

Summary

By means of cryogenic sampling and subsequent gaschromatographic ana­lysis vertical profiles of CC1 4, CFC13, CF2C12, CF3Cl, CF 4, C2F3C13, C2F4C12, C2FsCl, C2F6 , CH 3Cl, CH 3CC1 3 and CHF 2Cl were derived up to 35 km. Halocarbon profiles computed with one-dimensional and two-dimen­sional models falloff less rapidly with height than the measured pro­files, this systematic discrepancy being due to deficiencies in the radiation and transport schemes of present models. It is shown that measured profiles of fully halogenated hydrocarbons provide a tool for studying these deficiences and thus improving the models. First stra­tospheric profiles of CHF2Cl show that for the high stratosphere this hydrohalocarbon is an important source of odd chlorine.

1.1 Introduction

Fully halogenated hydrocarbons are almost inert gases in the tropo­sphere. They accumulate and gradually diffuse into the stratosphere, where they decompose by UV photolysis and reactions with O('D). Their overall atmospheric life times are extremely long ranging between 55 to 93 years calculated for CFC13 (F-ll) and 10000 years estimated for CF4 (F-14), (1,2). Partly halogenated hydrocarbons (hydrohalocarbons) such as methyl­chloride (CH3Cl), methyl chloroform (CH3CC13) or CHC1F2 (F-22), react with hydroxyl and are thus largely removed in the troposphere. Their overall atmospheric life times range between 2-3 years, 5.7-10 years, and 12-20 years, respectively (3). The global release rates of CH3Cl, CH 3CC1 3 and F-22 are so large, however, that despite tropospheric removal they contri­bute to the stratospheric chlorine budget.

1.2 Instrumental From stratospheric samples collected with balloon-borne neon-cooled

cryogenic air samplers, stratospheric profiles up to 35 km height, of all major source gases could be measured. The first MPAE cryosampler was des­cribed by Fabian et al. (4). It consists of 8 evacuated stainless steel tubes of 500 ml volume immersed in liquified neon. It had been baked at 380°C, which resulted in partial disappearance of some constituents, in particular F-22, CC14, and CH3CC13. Our new sampler, which, under otherwise identical design, consists of 15 sample tubes, was baked at 150°C. Further­more,interferences caused by stratospheric ozone are eliminated by destroy­ing ozone with a copper-wool filter (5). From samples collected with this

Ozone Symposium - Greece 1984 - 129-

new sampler, the following source gases can be analysed thus allowing to simultaneously determine their vertical profiles with a height resolution of 1-2 km: H2, CH4, CO, N20, CC14, CC13F, CC1 2F2, CC1F3, CF 4, C2C13F3, C2C12F4, C2C1Fs, C2F6, CH3Cl, CH3CC13, CHC1F2, CBrF3, CBrC1F 2, CH 3Br, CO 2, C2H6, and C2Ha. This report focuses on the halocarbons only.

1.3 Model computations Vertlcal proflles of CC1 4, F-11, F-12, CH3Cl, and CH3CC13 were compu­

ted with a one-dimensional model (6), which extends to 80 km, with height resolution of 0.5 loge (p/Po), p and Po denoting the pressure and surface pressure, respectively. The photochemical system comprises 78 collision reactions and 24 photodissociation processes, and continuity equations were integrated for 22 constituents or groups of constituents. Daily averages of photolysis rates were computed as a function of height. Vertical transport was approximated by a diffusion term. Sensitivity stu­dies were performed with reduced absorption cross-sections of O2 suggested on the ground of stratospheric UV measurements (7-9).

1.4 Results and discussion Compared to the measured halocarbon profiles, the computed ones show a

systematically slower falloff in the stratosphere. As an example the verti­cal distributions of CC14 and CH3CC13 are presented in figures 1 and 2.

.... o

30

~ 10 1-...J <{

10

6:; (I 1911. ., b 1974 . ,' 1915

d ,97S I, • 1916

. ' f 1976 0' 9 1976

m' h 1976 , , i 19JJ178

..

. ' j 1979 0 , k 1980 0 " 1981 'S) . ' m 1982 .. :; n 1982

VOLUME MIXING RATIO [pp tV)

Fig. 1 The vertical distri­bution of CC14 in the atmo­sphere. Each symbol repre­sents data from a different group. The time of measure­ment is also given. Unless marked by (S), all data ori­ginate from nothern midlati­tudes. a(lO); b(ll); c(12); d(13); e(14); f(15); g(16); h(17); i(12); j(14); k(18); 1(19); m(20); n(21). The solid line was computed for 4~N (6).

Data published by other groups which are limited to altitudes below 20 km, are also displayed. The systematic discrepancy reflects a general modelling problem. As 2-D computations (24) show almost the same discrepancies, these problems are not confined to 1-0 models. Froidevaux and Yung (9) showed that a substantial part of the discrepancy is removed, when 02 absorption cross-sections in the 200 to 220 nm spectral window are reduced. We have applied this reduction and found that a considerable discrepancy remains, which must be due to other effects.

Figure 3 shows a summary of vertical distributions of fully halogena­ted methanes (a) and ethanes (b) in relative units, with respect to the tropospheric mixing ratios. Average profiles, derived from our complete set of measurements, are shown. As Chou et al. (1) pointed out, UV-absorption cross-sections depend on the number of chlorine atoms attached to a par-

- 130-

ticular carbon atom. The photon absorption by molecules containing only one Cl-atom per molecule is so weak that it is less important as a removal pro-

40 Fig. 2 The vertical

ICH l CClll distribution of CH 3CC13 in the atmo-

30 sphere. a(22); b(18); c(Mount St.Helens

E Plume 18); d(23); e(19); f (20) ; g(21) . =. "" The solid 1 ine was

w..J computed for 45°N 0 20 ::::l o ' 0 1976 (6) . See Fig. 1 for t:::: x ,b 1980 >-- • 'c 1980 further information. -' <{ o , d 1980

Q ' e 1981 IS)

10 • ,f 1982 " : 9 1982

'" n 0

.. . a_. 0.1 10 100 1000

VOLUME MIXING RATIO (pptV)

cess than reactions with O( '0). Thus, F-14 and F-116 are the most stable of these substances, whereas CC14 with 4 chlorine atoms is entirely photolyzed below 26 km. Since halocarbon decomposion occurs in different UV wavelength ranges, chlorine release is accordingly heigh-dependent. For example, ch 1 ori ne format i on from' F -11 is 1 argest be 1 ow 30 km, whereas that from F-115 has a maximum at 40 km (25). Thus the whole set of halocarbon pro­files provides a tool for testing UV-radiation flux schemes to resolve pre­sently existing discrepancies. The fully halogenated hydrocarbons are par­ticularly convenient because they do not react with OH. UV photolysis and 0('0) attack can both be treated in a straightforward scheme. Furthermore, the transport schemes of models need to be improved too. Hunten (26) sug­gested that quasi-horizontal transport is superimposed by wave-like mo­tion. Since photolysis has a non-linear height dependence, this oscillation results in increased photolysis rates. This second-order effect of motion is not taken care of in present models.

40 Fig. 3 Aver-( a ) Ib) aged measured

C2F6 profi 1 es of fully haloge-nated metha-

30 nes (a) and

E ethanes (b)

'" in relative units with

UJ respect to 0 20 ::l the tropo-..... ..... spheric abun-...J dance. «

10

g.O~O:7I-'-""""'o....L..L..L.Io:U. o:7I---'---'-"""""..I...I..LO~. I'---'--'---'--'--'-'~I.OO L .-O I--'--'-'-'-'-""O""'.I--'--'---'--'-J.JL.UJI.O

- 131-

Measurements of CHC1F 2 (F-22) have so far been limited to altitudes below 20km. With our new sampler, which was flown on Sept. 20, 1982 and on Sept. 10, 1983, at 44°N, two complete stratospheric profiles were obtained for the first time. The samples were analyzed at MPAE Lindau using a cryotrap preconcentrator in combination with GC-MS. 6 of the 1982 samples were also analyzed at AERE Harwell using the same procedure. The analytical precision was ±10% and ±5%, or ±3% pptV, whi chever is greater, for the 1982 and 1983 data, respectively. Absolute calibration was achieved to better than ±10%. The solid line (fig. 4) was computed with the 1-0 model using recommended

'0

JO

10

10

o , 00

. : -. .

b .o19 S0 eP6

C ~ b 191!11 o ; c 191!11 lSI '0 = d 198'1

• MPA[ } S.pt. 1982 }

II. AU!£ Ihls vorl! • $lI!!pt. 1981 !.J

L,---~~----:2':-0 ---7J~O --:-'':-0 ----::::--".!!..-~70 10C 0 10

Volume flllx ing ratIo IpplV1

60

50

40

! JO

20

10

0 10" 10" 10' 10'

Fig. 4 Vertical distri­bution of F-22 in the atmosphere. Measurements from different groups of investigators are shown. The time of the measure­ment is also given. All data except those marked by (S) behind the year originate from nothern midlatitudes. a(18); b(27); c(19); d(29).

10'

Fig. 5 Formation rates of odd chlorine species (Cl+C10) from various common halocarbons as a function of altitude calculated by means of a 1-0 model using steady-state condi­tions.

photochemical data (28). The model confirms the slow measured falloff of F-22 in the stratosphere. Despite tropospheric decomposition a large percentage of F-22 is carried high into the stratophere; the mixing ratios

- 132-

only decrease by a factor of 3, whereas those of F-ll and F-12 drop by 3 and 2 orders of magnitude, respectively, over the height region discussed here. Chlorine formation rates for all major halocarbons as computed with our 1-0 model are shown in fig. 5. This suggests that above 40 km F-22 do­minates alone all others except F-12 and CH3Cl. If the present increase of the atmospheric abundance of F-22 of 12%/year (19,20,.29) due to an average growth of the global emission of 16%/year (30) remains unabated, F-22 will soon become the dominating source of odd chlorine above 40 km.

Acknowledgements This work has been sponsored by the German Federal Ministry of Rese­

arch and Technology through grant KBF-MT 0450-0704563 2. Financial support given by Deutsche Forschungsgemeinschaft through grant FA 62/8-3 is grate­fully acknowledged, too.

REFERENCES

1. CHOU, C.C., et al., J. Phys. Chern. 82, 1 (1979) 2. CICERONE, R.J., Science 206,59 (1979) 3. MAKIDE, Y., ROWLAND, F.S~Proc.Nat.Acad.Sci. USA 78,5933 (1981) 4. FABIAN, P., et al., J. Geophys. Res. 84, 3149 (197g-5. FABIAN, P., et al., J. Geophys. Res. 80, 5179 (1981) 6. GOMER, D.: Simulation von Spurenstoffverteilungen in der Atmosphare mit

Hilfe von ein- und zweidimensionalen Modellrechnungen. Ph.D. Dissertation, Gottingen 1983

7. FREDERICK, J.E., MENTALL, J.E., Geophys. Res. Lett. 9, 461 (1982) 8. HERMAN, J.R., MENTALL, J.E., J. Geopyhs. Res. 87, 89b7 (1982) 9. FROIDEVAUX, L., YUNG, Y.L., Geophys. Res. Lett:-9, 854 (1982) 10. LOVELOCK, J.E., Nature 252, 292 (1974) -11. COX,R.A.,DERWENT,R.G.,EGGLETON,A.E.J.,Atmos.Environ.l0,305 (1976) 12. ROBINSON, E., et al., Atmos.Environ. 11, 215 (1977) --13. KREY,P.W.,LAGOMARSINO,R.J.,TOONKEL,L.~,J.Geophys.Res.82,1753 (1977) 14. LEIFER, R., LARSEN, R., TOONKEL, L., Stratospheric Distributions and

Inventories of Trace Gases in the Northern Hemisphere for 1975, in: Report EML-349, 1-2111, U.S. Dept. of Energy (1973)

15. VEDDER, J.F., et al., Geophys. Res. Lett. 5, 33 (1978) 16. SEILER,W., MULLER,F., OESER,H., Pure Appl.Geophys. 116, 556 (1978) 17. TYSON,B.J.,ARVESEN,J.C.,O'HARA,D., Geophys.Res.Lett~ 535 (1978) 18. LEIFER,R.,SOMMERS,K.,GUGGENHEIM,S.F.,Geophs.Res.Lett~8,1079 (1981) 19. RASMUSSEN, R.A., et al., Geophys. Res. Lett. 9, 704 (T982) 20. RASMUSSEN, R.A., KHALIL, M.A.K., Natural and Anthropogenic Trace Gases

in the Lower Troposphere of the Arctic, Dept. ·of Environmental Science, Oregon Graduate Center, Beaverton, manuscript (1983)

21. BORCHERS, R., FABIAN, P., PENKETT. S.A., Naturwiss. 70, 514 (1983) 22. SINGH, H.B., et al., Atmos.Environ. 11, 819 (1977) --23. FABIAN,P., et al. Nature 294, 733 (1~1) 24. GIDEL,L.T.,CRUTZEN,P.J.,FISHMAN,J., J.Geophys.Res.88, 6622 (1983) 25. WUEBBLES, D.H., CHANG, J.S., J. Geophys. Res. 86, ~69 (1981) 26. HUNTEN, D.M., Geophs. Res. Lett. 10, 333 (1983, 27. GOLDMAN, A., et al., Geophys. Res:-Lett. 8, 1012 (1981) 28. NASA, Chemical Kinetics and Photochemical-Data for use in Stratospheric

Modeling, JPL 83-62, Pasadena, California (1983) 29. KHALIL, M.A.K., & RASMUSSEN, R.A., Nature 292, 823 (1981) 30. JESSON, J.P.: Release of industrial halocarbons and tropospheric

budget, in NATO Adv.Study Inst. Atm.Ozone (M.Nicolet, A.C.Aikin, Eds.), FAA-EE-80-20, U.S. Dept. of Transp., 373 (1980)

STRUCTURES IN THE VERTICAL PROFILE OF NITROUS OXIDE MEASURED OVER A MID LATITUDE STATION.

Summary

S. Lal, R. Borchers, P. Fabian

Max-Planck-Institut fUr Aeronomie (MPAE), D-3411 Katlenburg-Lindau, Germany

The results of Nil analysis from stratospheric air samples collected during a balloon flight over Southern France are presented. The air samples were collected by means of two cryogenic samplers flown together for the first time on a single balloon flight to test contamination of the sampling tubes and to collect a larger number of samples. N20 mixing ratios obtained using two different gas chromatographic techniques showed very good agreement, within 3% for most of the samples. They did not show any contamination effect in any of the sample tubes. The Nil mixing ratio profile obtained from this flight reveals steplike features around 16, 22 and 27 km height. These structures are likely to be due to dynamical processes at these height regions.

1.1 Introduction

Nitrous oxide (N20) plays an important role in the chemistry of atmospheric ozone. It is released into the atmosphere by the bacterial denitrification of fixed nitrogen on land and in the ocean (1,2,3). A fraction of this planetary source penetrates to the stratosphere where N20 decomposes by the chemical reaction with the excited form of atomic oxygen producing nitric oxide which in turn acts as a catalyst for the loss of ozone (4;5). This property of Nil and the fact that man-made sources are increasing, have accentuated the importance of its study.

Since there is no presently known source of N20 in the stratosphere, it is the transport which plays a key role in the vertical distribution of Nil in the stratosphere. In fact, observed vertical mixing ratio profiles of N20 have been used to estimate vertical eddy diffusion coefficients (6, 7). Several vertical profiles of N20 have been measured, mostly in the mid latitude region (7,8,9), however, a detailed study of the height profile has been constrained due to the limited number of samples collected during a single flight. We present here the results of an analysis of N20 from 23 samples collected between 10 and 34 km, during a balloon flight from Aire­Sur-l'Adour (44°N, I°E) on September 20, 1982.

1.2 Sample collection and analysis technigues Air samples were collected using two cryogenic samplers, one having

eight sample tubes (cryosampler ~) baked at 350°C and the second one having fifteen tubes (cryosampler ~) baked at 150°C. The cryosampler ~ is a newly designed system which offers greater height resolution compared to that of cryosampler ~ with the same payload weight. The basic design of the sampler is described in (10). While the first 6 samples were collected during the ascent part of the balloon flight between 10.2 km and 16.8 km

Ozone Symposium - Greece 1984 -134 -

altitude, the rest of the 17 samples were taken during the slow valve­controlled descent of the helium-filled balloon, between 32.05 km and 17.0 km altitude.

The analyses of the air samples were carried out for various source gases using gas chromatographic techniques. We report here mainly the analysis technique and results for N20. Most of the air samples were analysed for N20 using two different gas chromatographic techniques employing helium and electron capture detectors.

During the analysis of N20 using a helium detector, C02 was removed using a NaOH trap, while N2 and 02 were removed by freezing the air sample (2-5 ml in volume) in a sample loop immersed in liquid nitrogen. The concentrated sample was then passed through a combination of two columns packed with Porasil C and Porapak QS for trapping the water vapour and seperating N20 from the other constituents. Most of the samples were also analysed using an electron capture detector operated at 350°C. The carrier gas used was a mixture of argon and 10% methane, and the seperating system was the same as used with the helium detector. However, in this case C02 was not removed, since it could be well separated from N20. Every sample was analysed 2-3 times to minimize the analysis error. Peak areas in both types of analyses were obtained using microprocessor based integrators. All samples were analyzed against a reference tropospheric air sample which in turn was calibrated using a static dilution technique. The precision of both sets of analyses was better than ±2%, and the accuracy which mostly arises from the absolute calibration was around ± 5%.

1.3 Results and discussion The results are pr.esented in Fig. 1. Open circles and triangles

~ ... 0 2 ;:: <1

40 r---------~----------,-----------._--------_,

30

,0

AIRE - SUR - I'AOOUR 10 Sf? 1981

o . (ryo Sampler '* 2 • • (ryo Sampler '* 1

.. .

10 0L----------,.LOO,-----------, ...... 0-0 --------::-)0.,,0---*--"--------'400

N,O MIXING RATIO Ipp bv l

Fig. 1 The measured height profile of NzO mixing ratio. The results of the analyses using a helium detector are shown by of~ points while the results obtained using an electron capture detector are represented by .f! points.

- 135 -

represent results of the analyses using the helium detector while the closed circles and triangles represent results using the electron capture detector. Circles and triangles refer to air samples of cryosampler ~ and cryosampler #3, respectively. The results of N20 analyses obtained using two technqiues show very good agreement, within 3% for most of the samples. There is also a good agreement in the N20 mixing ratios obtained from the two samplers' tubes. At two heights, 32.85 km and 16.95 km where tubes from both the samplers were filled almost simultaneously show excellent agreement. At other heights also N20 mixing ratios obtained from both samplers match fairly well. These results suggest that there is no contamination of N20 samples in any of the samplers' tubes.

Fig. 2 shows the mean NzO mixing ratio profile obtained from the two techniques. The dotted line is a free hand drawn curve through the observed points. This profile shows distinct steplike features around 16, 22 and 27 km altitude. These steps are also seen in the mixing ratio profiles of F-12 and F-11 but less clearly as shown in Fig. 3. Similar steplike features have been observed in few individual mixing ratio profiles of N20 as well as that of F-12 measured over Laramie, Wyoming (41°N) (11) and al'ound 22 km altitude in the mean mixing ratio profiles of N20 and CH q measured over Gap Tallard (44°N) and Aire-Sur-l'Adour by Fabian et al. (9). However, the present results show these steps more clearly and at three height regions.

E ~

40

30

g 20 0-;: :;i

10

-60 - 1.0 ,

100

TE MPERATURE 1'( I -10 0 20

I I !

WIND VE LOCITY I knoll 10 I

200

15 !

WIND DIRE( TlON

o

270 90

300

/'

/

H,O MIXING RATIO Ippbvl

40 ,

10 I

, eYRO.] ·(YRO.3

/'

<.00

2S ,

Fig. 2 Mean N20 mlxlng ratio profile obtained from two different gas chromatographic techniques is given by dotted line. The arrows show the wind direction and the wind velocity is given by the points on the arrows (upper scale). The temperature profile is shown by ~ with upper most scale.

- 136.-

The temperatures and wind velocities measured from a nearby radiosonde station (Bordeaux - 44.5°N. 0.42°N) around local noon are also plotted in fig. 2. The wind and temperature data are available upto about 25 km altitude only. The temperature profile does not show any abnormal feature. The meteorological tropopause was at the height of 11.3 km. The wind direction did not change appreciably from ground level to 25 km altitude.

The wind profile shows negative gradients around 16 and 22 km heights where steplike features are found in the N20 profile. These steplike features which are characterized by constant mixing ratio in a narrow height region of about 1 km appears to be due to efficient mixing in these height regions. The step around 27-28 km is different in type as there is a sharp increase in the N20 mixing ratio. These steps are observed at a height interval of about 6 km suggesting that the turbulance may be caused by the wind shears generated by the propagation of an atmospheric wave of about 12 km wavelength. It is important to note here that though the meteorological tropopause was at an altitude of 11.3 km. the temperature continues to decrease up to about 20 km. A further study of the effects of dynamics on N20 profile is being completed; these results will be presented elsewhere.

., 1

"

10

'0 ~fP ';12 . , 111(.f,Cljl 00'111('(1,1

HI It

'.

10 .. lD '· VOUI I'1E 1'1 1)1 1" (; R",r lC

, . ,

,,'

Fig. 3 Vertical distribution of F-l1 and F-12 mixing ratios obtained from the same balloon flight samples.

1.4 Conclusion The results of N20 analyses collected using two cryogenic samplers

show that there is no contamination in the sampling tubes for N20 irrespective of baking temperature. The N20 mixing ratio profile shows steplike features around 6. 22 and 27 km altitude. and the steps around 16 and 22 km altitudes appear to be related to wind perturbations. No wind data were available above 25 km. These steps are also noticed in the mixing ratio profiles of F-12 (CF2C12) and F-ll (CFC13) obtained from the same samples.

- 137-

Acknowledgements ThlS work was carried out when S.L. was working at the MPAE Lindau

under the ISRO (India)-DFVLR (FRG) exchange program. We thank Prof. B.H. Subbaraya of PRL Ahmedabad, India and the members of ISRO and DFVLR organizations for arranging and supporting this program. The MPAE source gas program has been sponsored in part, by the German Federal Ministry of Research and Technology, through grants FKW-03 and KBF-MT 0450-07045632. Additional financial support given by Deutsche Forschungsgemeinschaft, through grant Fa 62-8/3, is gratefully acknowledged.

References

1. JUNGE, C.E. and J. HAHN (1971). N20 measurements in the North Atlantic. J. Geophys. Res. 76, 8143-8146

2. McELROY M.B., J.W. ELKINS, ~C. WOFSY and Y.L. YUNG (1976). Sources and Sinks for Atmospheric N20. Rev. Geophys. Space Phys. 14, 143-150

3. HAHN J. (1974) The North Atlantic Oceane as a Source of atmospheric N20. Tellus 26, 160-168

4. CRUTlEN P.J.-r1974). Estimates of possible variations in total ozone due to natural causes and human activities. Ambio 3, 201-210

5. McELROY M., S. WOFSY, J. PENNER and J. McCONNEL (1~4). Atmospheric ozone: Possible impact of Stratospheric aviation. J. Atmos.Sci. 31, 287-300 -

6. MASSIE S.T., and D.M. HUNTEN (1981). Stratospheric eddy diffusion coefficients from tracer data. J. Geophys. Res. 86, 9859-9868

7. SCHMELTEKOPF A.L., D.L. ALBRITTON, P.J. CRUTlEN,-V.D. GOLDAN, W.J. HARROP, W.R. HENDERSON, J.R. McAFEE, M. McFARLAND, H.I. SCHIFF, T.L. THOMPSON, D.J. HOFMANN and N.T. KJOME (1977). Stratospheric nitrous oxide altitude profiles at various latitudes. J. Atmos. Sci. 34, 729-736 -

8. EHHAL T D.H. (1978). In situ measurements of stratospheric trace constituents. Rev. Geophys. Space Phys. 16, 217-224

9. FABIAN P., R. BORCHERS, G. FLENTJE, W.A.~ATTHEWS, W. SEILER, H. GIEHL, K. BUNSE, F. MULLER, U. SCHMIDT, A. VOLl, A. KHEDIM and F.J. JOHN EN (1981). The vertical distribution of stable trace gases at mid-latitudes. J. Geophys. Res. 86, 5179-5184

10. FABIAN P. (1981). Atmospheric sampling. Adv. Space Res. 1, 17-27 11. GOLDAN P.D., W.C. KUSTER, D.L. ALBRITTON and A.L. SCHMELTEKOPF (1980).

Stratospheric CFC13, CF2C12 and N20 height profile measurement at several latitudes. J. Geophys. Res. 85, 413-423

- 138-

Summary

GLOBAL LOWER MESOSPHERIC WATER VAPOR REVEALED BY LIMS OBSERVATIONS

L. L. GORDLEY Systems and Applied Sciences Corporation

17 Research Drive Hampton, Virginia 23666 USA

J. M. RUSSELL III and E. E. REMSBERG National Aeronautics and Space Administration

Langley Research Center Hampton, Virginia 23665 USA

The Limb Infrared Monitor of the Stratosphere (LIMS) water vapor chan­nel data analysis has been extended from the 1. mb level (- 48 km) to the .3 mb level (- 60 km) through a radiance averaging procedure and better understanding of systematic errors. The data show H20 mixing ratio peaks near the .5 mb level varying from 4 to 7 ppmv with latitude and season. Above this level the mixing ratio drops off quickly with altitude but, due ~o experimental uncertainties, at an uncertain rate. The stratospheric results are virtually the same as determined from the archived LIMS results with a tropical hygropause and enhanced H20 con­centration in the lower levels at high winter latitudes.

1.1 Introduction

The Limb Infrared Monitor of the Stratosphere Experiment was launched on the Nimbus 7 spacecraft to sound the composition and structure of the middle atmosphere using the technique of limb scanning (Figure 1) radiome­try (Gille and Russell)1. The instrument operated flawlessly over the planned lifetime of October 25, 1978 through May 28, 1979 returning 7000 profiles of radiance per channel per day. The channels were selected for the inferral of pressure, temperature, ozone, water vapor, nitric acid and nitrogen dioxide. This paper concentrates on recently improved results of water vapor retrievals obtained by using averages of individual radiance profiles.

1.2 Retrieval Improvements and Difficulties

The archived LIMS results were obtained by retrievals on individual radiance profiles. Due to problems with the water retrievals at high alti­tudes (low signal to noise, poorly understood systematic errors and large diurnal differences), the archived retrievals were confined to pressure altitudes between 100 and 1 mb. The results presented here were obtained by averaging radiance profiles in latitude bands over 600 in longitude and then retrieving temperature and water vapor profiles from the average radiance profiles. Figure 2 shows typical average radiance profiles.

Care must be taken to obtain true averages and not to spatially average over severe variations in profile shapes. Averages must be weighted equally by each included profile at all altitudes. Where this does not

Ozone Symposium - Greece 1984 -139 -

occur, as in upper levels in figure 2, the data is discarded before retrieval.

Small errors in radiance at upper levels have unusually large effects on retrieved mixing ratio that continue for several kilometers into the "onion peel" retrieval procedure. The severity of these error mechanisms is not experienced in other channels. The reason for the severity is par­tially explained by Figures 3 and 4. In Figure 3 we see that even though the band averaged transmission is 99.4%, the weighting function is extreme­ly non-linear, i.e., it extends many kilometers above the tangent level at significantly high relative values. Figure 4 shows that this non-linear effect is greatest at 45 kilometers, improving to a nearly linear character in the lower stratosphere, uncharacteristic of most bands. This behavior is due to the line strength distribution in the 6 micrometer water band which contains a few lines that saturate for high altitude limb paths with little contribution from other transitions occurring above the middle stratosphere. These resulting weighting functions, in combination with high altitude non-1TE effects, also appear to explain the diurnal retrieval results (John Gille, NCAR, Private Communication 1984), although more work is needed to quantify the effect. Therefore, evidence suggests that the night data are more accurate than the average of day and night as previous­ly reported (Russell et al.)2. The results presented here use only data from the night side of the orbits (Nimbus 7 is in a sun-synchronous polar orbi t) •

1.3 Results

Figure 5 shows the 7 month 1IMS mission-average H20 profiles for 3 different latitudes. "Note that all three show peaks occurring between .7 and .3 mb and concentrations at lower stratospheric levels increasing pole­ward. Figure 6 shows the 44°N mission average compared to other measure­ments. It should be remembered that the mission is weighted toward the winter season. Also, although the error bars at the top of the profile, in Figure 6, are large (2 - 3 ppmv) the mechanisms causing the error do not change the qualitative character, specifically a peaked profile.

Figure 7 shows a zonal mean cross section contour for water vapor in January, 1979. The estimated accuracy at all latitudes is similar to that indicated in Figure 6, except for the low stratosphere tropics where cloud emission contaminates the 4 km wide field-of-view. Mesospheric features in the data that should be noted are:

1. The double maximum at .5 mb and ± 280 latitude. This feature is

2.

4.

5.

persistent even for large seasonal temperature changes, lending retrieval credibility. Seasonal symmetry between the northern and southern hemisphere mesosphere, except that the southern hemisphere tends to be about 1 ppmv lower than northern hemisphere. Suggestion of transport of low concentrations from low altitude tropics to high altitude latitudes. This appears to correla!e with methane results from SAMS as reported by Jones and Pyle. Sharp drop-off in concentration above the mesospheric peak. This feature, although observed at the upper limit of the measurements, is persistent and independent of major error mechanisms. Mixing ratio peak concentrations in the lower mesosphere are in general agreement with Solomon et al. (1983)4 and Aikin et al. (1984)5 in their model studies of 03 in the mesosphere.

- 140-

1.4 Conclusions

The LIMS data have been used to infer the first global picture of stratospheric and, now, lower mesospheric water vapor concentration.

High altitude systematic error sources are now better understood leading to increased reliability of mesospheric results obtained using radiance averaging techniques.

REFERENCES

1. GILLE and RUSSELL, (1984). The limb infrared monitor of the stratosphere: Experiment description, performance, and results. Journal of Geo hysical Research, Vol. 84.

2. RUSSELL et al., 1984. Validation of water vapor results measured by the LIMS experiment on Nimbus 7. Journal of Geophysical Research, Vol. 89.

3. JONES and PYLE, (1984). Observations of CH4 and N20 by the Nimbus 7 SAMS: A comparison of in situ data and two dimensional numerical model calculations. Journal of Geo hysical Research, Vol. 89.

4. SOLOMON, FAHEY and CRUTZEN, 1982. On the chemistry of H20, H2 and meteritic ions in the mesosphere and lower thermosphere. Planetary Space Science, Vol. 30.

5. AIKIN et al., (1984). Equatorial ozone profiles from the solar maximum mission - a comparison with theory. Planetary Space Science, Vol. 32.

6. BREWER, A. W., (1949). Evidence for a world circulation provided by the measurements of helium and water vapor distribution in the stratosphere. Quarterly Journal of the Royal Meteorological Society, Vol. 75, 351-363.

- 141 -

FIGURE 1 lUIS GEMTRY

,. n ..

1---===---4'1" *"""~

~' 1"7

!=C:;:, ~.~.!5=~. ::I:?IO:tO'"> .... ....-

6.Tlll'1. C~"~.o"- )

FIGURE 3 lI~S H20 C~ANNEL WEIGHTING FUNCTI~S FOR THREE TANG~NT PATHS. FUNCTI~S ARE NORIIAlIZED TO PEAK VAUlES. ASSUIf:S C~ST ANT 4 P~ OF WATER AND PERFECT RESOlllTIOfi.

- 142-

AVERAGING PR08LEMS

10-,2

HIGH LAT ITUDE

103~--~~--~~--~--~~-~ 10"4 IOZ 1 0~ 10° 10 I

RADIANCE WOltsl M2sr

FIGURE 2 TYPICAL RADIANCE PROFILES AT HIGH. ~lD AND lOW LATITUDE. DASHED LINE IS DIG lTlZATlIJi LEVEL.

/ ""-- - - .... ~ ~ IDEA OIPJ1:A.llY I , , --- -..: .- C><AHffl.

I '\ ... ",- llMS HzO " ...... ...... Oi.W€ l " ............. '-'

°O~~IO~~~,-'~~-.~~-i~,-'oo~~ro TAHGEHT ALTI1l.C€

FIGURE 4 PERCENT (F H20 WEIGHTING FUNCTl~ AREA DUE TO 1.5 ~ THICK TANGENT LAYER.

10'

I

I /1

I LOW LATITI.OE -1 I

- I I I

/

!

I i I

;

I • I I ,

/ I

I I I

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WATER VAPOR MIXING RATIO (ppmvJ 10·0.'-----!~-~.---76---:-------7.

"I' MIX'NG RATIO (...,.1

FIGURE 5 r.ISSION AVERAGE H20 PROFILES AT 760, 440 AND 120 LATITUDE.

W 0:: :> III III w 0::

FIGURE 6 LlIlS 440tl MISSION AVERAGE WATER VAPOR PROFtLE CCl'IPARED TO OTHER MEASUREIIENTS. (FIGURE TAKEN FRO/': BEVILACWA ET AL., JGR, VOL. 88, NO. en, OCT. 1983.

0... 101

, • 10' _~!-:--~~~

FIGURES i JANUARY 1979 ZatAL IlEAH CROSS SECTlat OF H20 (DAYS INCLUDED -JM. 5, 6, 7, 8, 9, 13, 14, 15, U,U,",W,n,n,~,~, 26, 27, 28, 29).

-143 -

INTERCOMPARISON OF STRATOSPHERIC WATER VAPOR PROFILES OBTAINED DURING THE

SUlIIJJary

BALLOON INTERCOMPAIUS5N CAMPAIGN -- -

D.G. Murcray,1 A. Goldman I andJ. Kostersl (DU) R. Zander 2 (ULG) W. Evans 3 (AES) N. Louisnard 4 and C. Alanichel s (ONERA) M. Banghan 6 and S Pollitt 6 (NPL) B. Carli, 7 B. Dinelli, 7 S. Piccioli 7 and A. Volboni 7 (IROE) W. Traub 8 and K. Chance 8 (SAO)

The Balloon Intercomparison Campaign (BIC) was set up to intercompare remote sensing measurements of a number of compounds other than water vapor; however, water vapor has strong absorption features throughout the infrared and mm wave regions of the spectrum. Therefore many of the inves­tigators involved in BIC have absorption or emission features due to water vapor in the data they obtained during the balloon flights made under the campaign. These features have been used by the investigators to determine the stratospheric water vapor profiles which are compared in this paper. The profiles allow comparison of a wide range of remote sensing techniques involving both emission and absorption in the mid-infrared and emission techniques in the far infrared.

Introduction The Balloon Intercomparison Campaign (BIC) was undertaken in an effort

to establish to what extent the variations in atmospheric profile data for a number of constituents observed by various remote sensing techniques are due to measurement techniques and what are due to atmospheric variability. The objective of the measurement program was to remove the question of atmospheric variability by having all instruments observe at the same time in the same air mass. A discussion of how it was planned to accomplish this objective and the various difficulties in achieving it are given in a separate paper presented at this meeting by Dr. Watson. The major emphasis of the Campaign was placed on several trace species (HC1, HN03, etc). Two campaigns were performed, the first (BIC 1) in the fall of' '82 and the second (BIC II) in June of 1983. The instruments used in the intercompari­son were all remote sensing instruments (wi th the exception of a Dasibi ozone system). These instruments use spectral data obtained in various spectral regions from the visible through the microwave to determine con­stituent profiles. Many include regions where H20 has strong absorption

1. Physics Department, University of Denver, USA 2. Institut d'Astrophysique, University of Liege, Belgium 3. Atmospheric Environment Service, Canada 4. Office National d'Etudes et de Recherches Aerospatiales, France 5. Laboratorie de Photophysique Molecularie, CNRS, France 6. National Physical Laboratory, United Kingdom 7. Instituto di Ricerca sulle Onde Elettromagnetiche del CRN, Italy 8. Smithsonian Astrophysical Observatory, USA

Ozone Symposium - Greece 1984 -144-

features and hence the data obtained with the units can also be used to determine the stratospheric water vapor profile. In view of this it was agreed that a secondary objective of many of the groups participating in BIC would be to obtain water vapor mixing ratio profiles. In this paper we present the preliminary water vapor resul ts obtained during the Balloon Intercomparison Campaigns. Since water vapor profiles were a secondary objective of the program, the analysis is not complete and these resul ts are preliminary.

Stratospheric water vapor profiles have been obtained for many years using a number of techniques. Summarie1s and discussi2'ns of the early measurements have been given by Harries and Penndorf • The spread in measured mixing ratios has decreased as instrumentation has improved and as the effects of contamination have been reduced. Although water vapor was not chosen as one of the prime species to be intercom pared during BIC, the need for such an intercomparison has long been recognized. In fact two such intercomparisons have been recently performed. These intercomparisons were made with primary emphasis placed on in situ techniques, whereas this intercomparison is of remote sensing techniques:--

Flight Details ---The first series of flights of the Balloon Intercomparison Campaign (BIC 1) were performed in the fall of 1982. All four balloons were launched on September 22, 1982. The balloon carrying the NPL gondola developed a leak shortly after launch and the flight had to be terminated. The payload was renovated and flown on October 5. Thus the water vapor measurements presented for this intercomparison were obtained on the after­noon of September 22, .the morning of September 23, or the afternoon of October 5. The spread in time between the measurements is greater than had been sought but felt to be close enough to warrant comparing the results.

The second Balloon Intercomparison Campaign (BIC II) flights were performed in June, 1983. Two balloons were launched June 17. The surface winds then came up and forced cancellation of the second series. The third and fourth balloons were launched almost simultaneously on June 20. Water vapor profiles were obtained on the afternoon of June 17 and the afternoon of June 20. Again the spread in dates is greater than hoped for but close enough to warrant initial intercomparison of the results.

Analysis and Results Although the measurement techniques used to obtain the profile infor­

mation vary widely in the wavelength regions used they all employ either solar absorption or atmospheric emission techniques. Since water vapor is a strong absorber, it is possible to obtain data on its distribution with­out gOing to the long path lengths obtained by limb viewing or solar occultation. Profile data can be obtained during ascent or descent of the balloon. Several of the experiments were set up to obtain data only by solar occultation or by limb scanning from float altitude. Their profiles are based on some retrieval algorithm applied to the limb scanning data. Thus in the following discussion the techniques will be characterized as either solar absorption or atmospheric emission and further as ascent or descent data or solar occultation or limb viewing. Discussion of the pro­file retrieval algorithm lies outside the realm of this paper. Detailed descriptions of the instrumentation used by the various groups are also outside the scope of this paper. Readers interested in these details should refer to the other papers by the various groups. Table I contains a description of the techniques used by the various groups presenting H20 results for BIC 1. Table II is a similar table for BIC II.

-145 -

Experimental Group

ULG, Belgiun NPL, UK AES, Canada IROE, Italy

Experimental Group

ULG, Belgiun AES, Canada SAO, USA ONERA, France DU, USA

TABLE I (BIC I) ------~ of Measurement

Solar Absorption (Descent) Atmospheric Emission (Limb Scan) Atmospheric Emission (Ascent) Atmospheric Emission (Limb Scan)

~ of Measurement

Solar Absorption (Total Colunn Only) Atmospheric Emission (Ascent) Atmospheric Emission (Limb Scan) Solar Absorption (Occultation) Atmospheric Emission (Ascent)

Wavelength Region or Spectral Feature Used

3.0 ~m 1339-1350 cm-1

6.~ ~m 41 cm-1 , 62.3 cm-1

Wavelength Region ~ Spectral Feature Used

3.0 ~m 6.3 ~

111 cm-1, 188 cm-1 1600-1608 cm-1

25 ~m, 26 ~m

The profiles obtained during the fall 1982 campaign (BIC I) are shown in Figure 1. Those obtained during the spring 1983 campaign (BIC II) are shown in Figure 2.

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-146 -

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Figure 2. H20 profiles obtained during BIC II. The AES, SAO and ONERA data were obtained on 20 June. The DU and ULG data were obtained on 17 June 1983.

Discussion Several points should be made concerning the data presented in Figures

1 and 2. Since all instruments are remote sensing instruments the mixing ratios represent average values over some altitude range. This presents some problems when it comes to plotting the results for intercomparison. In most cases uniform mixing is assumed within the layers used in the retrieval. In some cases where the altitude between points at which data were taken is large, the layer is split into sublayers which are then included in the plotted profile. This should be kept in mind when com­paring the resul ts. In most cases error bars are included with the mea­sured values. In some cases these are the result of a detailed error analysis. In other cases they represent an estimate by the group based on initial analysis of their results. As mentioned, these results are pre­liminary and furt~er analysis will be made which will include more accurate assessments of the error bars. The results as presented show a wider range of uncertainty than one would like to see in such an intercomparison. The results are preliminary and some changes are expected in the final results which may improve the agreement. In general the values lie within the estimated error bars, however in some cases the error bars are rather large. Hopefully the additional analysis will reduce some of these.

- 147-

Acknowledgements Integrating a large number of individual instruments into four gon­

dolas and launching the gondolas as close together in time as possible has required the dedicated effort of a large number of individuals. Acknowl­edgement of this effort for all of the individuals involved in the various experimental groups is not possible. The assistance of the following individuals who contributed to the overall success of the effort is grate­fully acknowledged: P. Woods, NPL: J. Riccio and R. Killian, JPL, R. Kubara and the NSBF staff. Special mention must be made of the contribution of R. Watson to the success of the program. He not only provided the financial support necessary to accomplish the program, but also provided the moral support required to complete the spring series when everything went wrong on the first attempt.

References Harries, J. E., The Distribution of Water Vapor in the Stratosphere, Rev.

Geophys. Space Phys., 14, 565, 1976. Penndor!', R., Analysis of Ozone and Water Vapor Field Measurement Data,

U.S. Dept. of Transportation, Final Report No. FAA-EE-78-29, Nov. 1978.

- 148-

INTERCOMPARISON OF STRATOSPHERIC MEASUREMENTS OF NO AND N02

H.K.Roscoe, B.J. Kerridge, Dept. of Atmospheric Physics, Oxford Univ. U.K. S. Pollitt, M. Bangham, National Physical Laboratory, U.K. N. Louisnard, ONERA, C. Alamichel, CNRS, France. J.-P. Pommereau, CNRS, France. T. Ogawa, N. Iwagami, Geophys.Research Lab., Univ. of Tokyo. M.T.Coffey, W. Mankin, NCAR, Boulder, U.S.A. J.M. Flaud, C. Camay-peret, CNRS, France. F.J. Murcray, A. Goldman, Dept. of Physics, Univ. of Denver, U.S.A. W.F.J. Evans, T. McElroy, A.E.S., Toronto, Canada.

Major intercomparisons of balloon-borne stratospheric sensors took place in fall 1982 and spring 1983. In each campaign, 4 gondolas were launched close together from Palestine, Texas. Profiles of many constit­uents were determined by a variety of instruments, both radiometric and spectrometric, some observing the sun and some sensing atmospheric emiss­ion. Column amounts of some constituents were determined by supporting spectroscopic measurements from the ground and from aircraft.

Due to problems with some instruments, the first flight yielded no NO intercomparison and only a limited one for N02 sensors. But it was clear that the Oxford radiometer (which uses pressure modulators) measured significantly less N02 below 35km than other sensors.

Figure 1 shows how the second flight highlighted this discrepancy, which reached a factor 5 at 27 km. The good agreement between all the other techniques must cast doubt on the Oxford result.

An examination of the historic data from each technique shows that this discrepancy has always existed. The variability of each technique for all seasons at mid-latitude is usually less than a factor 2, which is borne out by column measurements from the ground and from aircraft. Column meas­urements during the second flight support the higher values of N02 •

This discrepancy cannot be explained by incorrect heights, temperat­ures, or calibrations in the Oxford radiometer. Indeed, figure 2 shows the excellent agreement between its measurement of NO and that of the ONERA spectrometer. Rather, the source of the discrepancy must lie in some as yet undiscovered details of N02 spectroscopy at 1600 em-l • This conclusion is reinforced by the similar profiles deduced from four earlier flights by the Oxford radiometer, each of which used different modulator conditions and in some cases different retrieval schemes.

The resolution of the discrepancy must await fresh laboratory. meas­urements of cooled N02 with a pressure modulator, planned for 1985.

Ozone Symposium - Greece 1984 -149-

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Intercomparative Measurements of Stratospheric Nitric Acid

* + £ - -S. Pollitt, M. Coffey, W. F. J. Evans, A. Goldman, J. J. Kosters, N. Louisnard~ W. G. Mankin~ D. G. Murcray- and W. J. Williams:

* National Physical Laboratory, Teddington, U.K. + National Center for Atmospheric Research,Boulder, Co., USA. £ Atmospheric Environment Service, Downsview, Ontario, Canada. - University of Denver, Denver, Co., USA. o Office National d'Etudes et de Recherches Aerospatiales, Chatillon, France.

Summary

Stratospheric HNO~ concentrations have been measured simultaneously by a number of remote sensing instruments during the Balloon Intercomparison Campaigns. The results are compared and discussed.

Introduction

HNO is an important reservoir and sink for the stratospheric NOx specie~; its equilibrium value being determined by the reactions;

It is closely coupled to the hydroxyl radical which is extremely important in many chemical cycles. Since HN0 3 is a relatively long lived species, dynamics playa significant role in its distribution both with latitude and altitude.

Profiles of HNO published in the literature(l) over the last decade show a large amoune of variation. Since these measurements were not made simultaneously it is impossible to determine whether the scatter is due to natural variability or is due to errors associated with the measurement. The Balloon Intercomparison Campaign (BIC) was conceived to address this problem not only for HN0 3 but for the NO and C10 families of gases. x x

During the campaign groups of remote sensing instruments (based on emission and absorption spectroscopy) have been flown from stratospheric balloons to make simultaneous measurements of stratospheric HNO~ and other gases. As part of the campaign the atmospheric variability around the measurement region has been studied by coincident aircraft and meteorological measurements.

Experimental details

Five balloon-borne instruments and one aircraft-borne instrument have measured stratospheric HNO • The instrumental details, notes on the measurement techniques and ~eferences to the spectroscopic data u~ed in the analysis are given in Table I.

Ozone Symposium - Greece 1984 - 151 -

The balloon flights took place from the National Scientific Balloon Facility, Palestine, Texas, (320 N, 96oW) during autumn 1982 and spring 1983. During BIC I the DU spectrometer was flown simultaneously with the

Table I

Group Instrument Technique Spectral ~~gion Spectroscopic cm data

al(2) NPL Cooled grating Ihlbscanning 876 - 900 Goldman et spectrometer emission

DU Cooled grating ascent Q-branch Goldman et al(2) spectrometer emission 878.73

DU F.T. Inter- limbscanning 1720 - 1730 Rothman et al(3) ferometer absorption

ONERA Grille limbscanning 1325.7 Girard et al(8) spectrometer absorption

AES Cooled CVF ascent 870 - 900 Goldman et al(2) Radiometer emission

NCAR F.T Inter- aircraft 1720 - 1725 Rothman et al(3) ferometer absorption

AES radiometer; the NPL spectrometer was flown 10 days later on the 5 October. Aircraft measurements of the HNO column were made on N-S trajectories west of Palestine on three ocdasions during this period. During BIC II the DU spectrometer was flown on 17 June 1983. The AES radiometer, NPL spectrometer, ONERA spectrometer and DU interferometer were flown on 20 June; aircraft measurements were made on 17 June.

Results

The HN0 3 concentration profiles measured in BIC I and II are shown in figures 1 and 2 respectively. The HNO column amounts are shown in figure 3; the columns measured by NCAR f~om the aircraft are averages of several measurements between latitudes of 27 0 to 350 N. The tropopause was at 16km during both campaigns.

Discussion

The aircraft measurements show no significant variation of the HNO column density during the BIC I period and meteorological measurement~ throughout the BIC periods show that the atmosphere was very stable. We therefore feel that we can, with caution, compare profiles measured a few days apart.

- 152-

BIC I

Comparison of the three profiles measured during BIC I (figure 1) reveals good agreement except in the 18 - 21km range where the AES profile is significantly different. At these altitudes the atmospheric emission spectrum of RNO, in the region of 11.3 microns is contaminated by emission from Freorts 11 and 12, and also ~ing BIC I was contaminated by emission from a layer of aerosol caused by the eruption of EI Chichon, Mexico, in April 1982.

The small discrepancies around 25 and 31km, particularly apparent between the NPL and DU profiles, are not reproduced in the BIC II profiles (figure 2).

Comparison of the column amounts (figure 3) shows a significantly lower value measured _ ~y NCAR. The NCAR columns are obtained from analysis of the 1722cm spectral region of 5.9 micron band whereas the other results are derived from the 11.3 micron band. To investigate whether differences ~~ spectral parameters are the cause of this discrepancy, the 879cm Q-branch, also present in the NC~~ spectra, has been analysed; the results are compared with the 1722cm analysis in Table II. The two methods of analysis agree to wi thin the estimated precision of 10% and show no significant bias.

22 September 1982 23 September 1982

1 October 1982

BIC II

Table II

Column amouni- x 879cm-

7.97 6.92 5.64

10 15 mOleclues/c~~ 1722cm

7.26 6.46 6.74

The DU, AES and NPL BIC II profiles are in good agreement (figure 2). The ONERA profile, although in fair agreement in the upper stratosphere, diverges significantly from the others below 27km. At present the cause of this discrepancy cannot be explained; however the laboratory calibration spectra, used by ONERA in their analysis, is being studied and compared with other available data in an attempt to resolve this discrepancy.

The column amount of RNO (figure 3) measured by both NCAR and the DU interferometer agree, withiJ the error limits, with the amounts obtained by integrating the profiles, however the NCAR value still remains on the low side of the other measurements.

Conclusion

The three RNO profiles obtained by emission spectroscopy in the 11.3 micron band ar~ in good agreement, however the ONERA profile is significantly greater than these in the lower stratosphere. The column amounts measured from the aircraft by NCAR tend to be lower than the rest.

- 153-

There is no significant variation in column amounts between September/October 1982 and June 1983; this is consistent with the conclusion of WMO that there is no strong evidence to support a large seasonal variation of HNO~ amount below 40oN. However the altitude at which the peak concentrati~n occurs has moved from 18km to 23km.

The average profile measured by the emission instruments during ~~S

II is compared in figure 4 with the range of values measured by LIMS at the same latitude. The profiles are consistent except at high altitudes where the LIMS value&) are considerably great(lf). Comparison with the models of Mille~5lt al and Solomon and Garcia (taken from the paper by Gille et al ) shows the models to predict too much HN03 in the upper stratosphere.

The results presented here, in conjunction with those of other stratospheric species measured simultaneously during BIC, provide a valuable data base to test photochemical models of the stratosphere.

References

(1) World Meteorological Organization, The stratosphere 1981: Theory and Measurement, WMO. Global Ozone Res. Monitoring Proj. Rep. 11, Geneva, 1982.

(2) Goldman, A., F.S. Bonomo, F.P.J. Valero, D. Goorvitch and R.W. Boese, App. Opt., 20, 172-174, 1981.

(3) Rothman, L.S., A. Goldman, J.R. Gillis, R.R. Gamache, H.M. Pickett, R.L. Poynter, N. Husson and A. Chedin, App. Opt.,22, 11, 1616-1627, 1983. -

(4) McCormick, M.P. and T.J. Swissler, Geophys. Res. Letts., ..!Q., 9, 877-880 1983

(5) Gille, J.C., J.M. Russell, P.L. Bailey, E.E. Remsberg, L.L. Gordley, W.F.J. Evans, H. Fischer, B.W. Gandrud, A. Girard, J.E. Harries and S.A. Beck, J. Geophys. Res., 89, D4, 5179 - 5190, 1984.

(6) Miller, C., D.L. Filkin, A.J.lDwens, J.M. Steedman and J.P. Jesson, J. Geophys. Res., 86, 12039-12065, 1981.

(7) Solomon, S. and R.~ Garcia, J. Geophys. Res., 88, 5229-5239, 1983. (8) Girard, A., G. Fergant, L. Gramont, O. Lado-Bordowsky, J. Laurent,

S. Le Boiteux, M.P. Lemaitre and N. Louisnard, J. Geophys. Res., 88, C9, 5377, 1983. -

- 154-

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- 156-

SPATIAL AND TEMPORAL VARIABILITY OF THE N02 TOTAL CONTENT BASED ON ANNUAL OBSERVATION DATA

Summary

N.F. ELANSKY, A.Ya. ARABOV, A.S. ELOKHOV and I.A. SENIK

Institute of Atmospheric Physics Academy of Sciences of the USSR

Beginning from 1979 N02 total content measurements have been taking place on a research station of the Institute of Atmospheric Physics of the USSR Academie of Sciences in North Caucasus (43.70 N, 42,7°E; 2070 m above the sea level). Similar observations were carried out in several 1983-84 aircraft flights. Results of these observations are compared to the measurement data of stratospheric N02• The analysis of the NO total content suggests that the Lover stratosphere con~ributes greately, often critically, to the N02 total content variability. This suggestion is confirmed by a characteristic relationship of NO and ozone total content variations. Some examples ar~ given to illustrate the strong influence of dynamic processes in the stratolpheric region below 20 km on N02 total content variations.

1. Introduction

In recent years systematic studies of the NO total con­tent were initiated and undertaken over the Nort~ America, New Zealand and other regions of the globe (1-4). Owing to these observations some important features in the NO dis­tribution, specifically, latitudinal and seasonal vafiations became khown in general terms. However, many details of N02 behaviour remain unknown or uncertain due to scarce data available, thefr nonuniform distribution allover the world and shortcomings in the method of definition of stratospheric NO, which is extremely sensitive to changes in the optical pr~perties of the atmosphere and to changes in the N02 ver­tical profile.

This paper concerns the observation results of the NO total content over North Caucasus and in spring 1983-198~ aircraft flights over the USSR. 2. RESULTS

Ozone Symposium - Greece 1984 - 157-

N02 total content ground and airborne measurements were made from the spectra of direct solar radiation registered at great solar zenith angles (8 =70 0 - 87°). Measurements were made at five wavelengths Ai = 4349 t 4378, 43909, 4413, and 4420 i by a method described in (2) as method I. The spectra were recorded with a resolution of 4 R. We used the following N02 absorption coefficients values: 7.3; 4.0; 6.35; 4.0; and 3.65, respectively, for the above mentioned wavelengths~W~~.

In N02 calculations the ozone absorption is usually ta­ken into account by selecting a specific wavelength combina­tion which would remove its influence, or by introducing in computing formulas the ozone content value obtained for a given spectrum region. The both approaches have certain short­comings. Much more effective is the employment of total ozone content obtained from independent observations in the UV spec­trum region. On the research station of the IAP total ozone measurements have been regularly made since ·1979 in the spec­tral region 3055-3200 R.

A ~andom N02 measurement error does uot exceed 0.3.10 15 mol·cm- for morning and 0.4.1015 mol·cm- 2 for evening. A sy­stematic error in N02 measurements is caused primarly by in­accurate knowledge of N02 absorption coefficients, and possib­ly it equals the random error.

Fig. 1 presents monthly mean morning values of the 1979-84 N02 total content (the data for the months with less than five observational days are omitted). The N02 content in the atmosphere has a.very pronounced seasonal variation. Minimal N02 values are seen i~ November-December and equal approxim~­teIy 3.2'1015 mol·cm- ; maximal N02 values 6.5'10 15 mol·cm­are ma,ked in June-July (evening values, respectively, are 4.1·10 5 and 7.9.10 15 mol·cm-2). A comparison of the obtained values with the observation results by other authors for the latitude region 400 -500 of the northern and southern hemisphe­res reveals that the N02 total content is greater than its amount in the stratosphere by 20% in summer and 35% in winter. Respectively, the factpr of N02 total content variability from winter to summer equals 1.9, wliile, for stratospheric N02 it varies from 2.1 to 2.5 according to various authors.

N02 total content daily variation also differs substanti­ally from stratospheric N02 daily variatiQn. On the average, over the whole observation period N02morn~ng/N02 even~ng = 0.75+0.5. According to (1-5) data this ratio for stratospheric N02 equals 05. to 0.67.

These differences cannot be explained by the N02 presence in the troposphere, and the discrepancies in N02 absorption coefficient values. We believe that a great systematic error intrinsic to the method of stratospheric N02 definition from the scattered in zenith radiation affects the process. The existence of such an error is, first of all; due to the assum­ption of a small N02 amount below 15 km in all seasons in all latitudes; secondly, owing to transition from the night regime of stratospheric state to the daily one during the observa­tion period; and, finally, due to a high model sensitivity to a given aerosol vertical profile. It should be noted here that, since March 1982 the aerosol distribution in the stratosphere has sharply changed owing to the El Chichon vulcano eruption.

- 158-

The N02 and ozone total content temporal series covering warm and cold seasons have a different character. Initially these variations occur in phase, later on in antiphase. On the average, as seen from the analysis of observation data, the transition from the positive 03 and N02 correlation to the negative one is marked in late OctOber, and the reverse tran­sition in the middle of April. This relation of the both con­stituents variation is explained by the coincidence of their latitudinal gradients in summer and their opposite directions in winter. It is worth noticing that the change in the ozone total content takes place at the expence of the change in the ozone concentration in the stratospheric layer below 20 km (6). The high ozone and N02 total content correlation makes one therefore, suppose that N02 changes occur also in the lo­wer stratosphere below its main maximum.

This assumption is confirmed for many specific cases by a simple meteorological analysis. Fig. 2 presents, for ins­tance, the N02 and ozone total content values for January 1979 and January 1982g Ozone variations in the both cases are explained by a change of the deep upper-level pressure trough over the station with a system of intensive downward motions of the upper-level ridge with characteristic upward motions in the lower stratosphere (Fig.3). In the first case N02 be­haviour may be explained by the air mass arrival in the la­yer 20-30 km from the polar vortex region and its subsequent replacement with the mid-latitude air. In January 1982, how­ever, a considerabl€ decrease and subsequent increase of N02 took place within the same air mass, but, at a time when in the lower stratosphere the replacement of the trough by a ridge and than again by a trough. This behaviour of N02 in the planetary wave activity zone is also marked in other win­ter months what makes one suggest either the vertical moti­ons impact on the N02 total content or the influence of hori­zontal transfer of tfiis constituent in the stratospheric re­gion below 18-20 km.

In summer the connection of N02 variations with the sub­tropical upper frontal zone passing over the station is dis­tinctively seen. The N02 total content over the station when it is in the cyclonic s~de of the frontal zone, is, as a ru­le, greater than when the station is in the anticyclonic si­de. Thus, a conclusion may be drawn that the latitUdinal gra­dient of the N02 total content in the upper frontal zone mar­kedly exceeds its average (zonal) value over the hemisphere, i.e., the N02 latitudinal distribution is similar to the ozo­ne zonal structure (6).

It is confirmed by airborne N02 total content observa­tions. Fig.3 gives examples of latitudinal profiles of the NO~_and ozone total content obtained approximately along 60 0 E inlMarch 1983 and April 1984. In the mid-latitudinal air mass at great distances the N02 total content, as well as the ozo­ne one, changes a little. However, they change considerably in the zone of upper frontal interfaces. Such a behaviour of N02 and ozone had also been observed earlier from aircraft (7). As far as the cliff in N02 near 50 ON is concerned, the flights have not revealed its aistinctive appearance.

- 159-

The N02 total content in high latitudes is not much less than its value for middle and moderate latitudes in this time of year.

In order to study the transfer processes from the day­time stratospberic state to the nighttime N0 2 and 03 observa­tions were also made using the moon. In a un2form dynamic si­tuation tbe 03 total content variations from day to night are not so bigh, whereas tbe N02 total content systematically in­creases during tbe nigbt almost two times comparing to day­time values. This nighttime increase of the N02 total content does not contradict the results of chemical modelling of the minor constituents in the stratosphere (6).

3. Conclusion

A more detailed studying of tbe processes forming the ~02 distribution in the atmosphere requires more N02 observ-2ng stations and its measurement methods comparisons. Measu­rement results of nitrogen dioxide which differs from ozone in the life time and vertical distribution, would, together with ozone data, be employed to study dynamic processes in the atmosphere.

REFERENCES

1. NOXON, J.F. (1919). Stratospheric N02' 2. Global behavio­ur, J. Geop~s. Res., 84, 5061-5016.

2. SYED, M.Q. and HARRISON, A.W. (1980). Ground-based obser­vations of stratospheric nitrogen dioxide. Can. J. Pbys., 58, 188-195.

3. McKENZIE, R.L. and JONSTON, P.V. (1982) Seasonal variati­ons in stratospheric N02 at 45°S. Geophys. Res. Lett., 9, 1255-1259.

4. COFFEY, M.T., MANKIN, W.G. and GOLDMAN, A. (1981) Simulta­neous spectroscopic determination of the latitudional, seasonal and diurnal variability of stratospheric N20,NO, N02 and EN03. J. Geophys. Res., 86, 1331-1341.

5. KERR, J.B., McELROY, C.T. and EVANS, W.F.Y. (1982). Mid­latitude summertime measurements of stratospheric N02• Can. J. Phys., 60, 196.

6. KHRGIAN, A.Kh. and KOUZNETZOV, G.I. (1981) The problem of atmospheric ozone. Moscow., Moscow University Press.

1. ELANSKY, N.F. and TRUTZE, Yu.L. (1919). The aircraft ob­servations of some features of the total 01 and N02 dis­tribution in the atmosphere. Izv. Acad. ScI., USSR. At­mosph. Oceanic Phys. 15, 119-121.

- 160-

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SOUTHERN HEMISPHERE NITROGEN DIOXIDE

R.L McKENZIE* and P.V. JOHNSTON PEL Atmospheric Station, DSIR, Omakau, Central Otago, New Zealand

*Present address: Department of Atmospheric Physics, University of Oxford, Clarendon Laboratory, Oxford OXI 3PU, U.K.

Summary

Results from ground based observations of stratospheric nitrogen dioxide from two Southern Hemisphere sites are compared. The measurement method used is long path absorption spectroscopy of scattered sunlight in the wavelength range 435-450nm. At a midlatitude site in New Zealand (45°S) column amounts of N02 are dominated by photochemistry whereas in a high latitude site in Antarctica (78°S) transport effects are more important. Aspects of the simul"taneous measurement of ozone from the same data set and the interpretation of any correlations are discussed.

1. Introduction

Since December 1980 ground based measurements of stratospheric nitro­gen dioxide and ozone have been made routinely at sunrise and sunset from our observation site at 45°S in New Zealand (I, 2). The measurement me­thod is long path absorption spectroscopy of scattered light from the zenith sky in the wavelength region 435 to 450nm. Tropospheric measure­ments which have also been made at this site, show that tropospheric N02 and water vapour have only small effects on the twilight measured strato­spheric column amounts (3). Sixteen months of data from August 1982 have been obtained from Scott Base Antarctica (78°S) using similar instrumenta­tion (4). In the present paper we compare some of the data from these two sites, and present the results from a time series analysis of two year's data (1981 and 1982) from the midlatitude site where the column amounts of nitrogen dioxide are more clearly dominated by photochemistry.

2. Comparison of Data Sets

(a) Midlatitude Data. (Figure 1). There are two striking features of the 45°S N02 data. Firstly there

is a strong seasonal cycle in phase with the day-length so that at the summer solstice evening vertical column amounts are 6.4 x 101Smolecule. cm- 2 , a factor of two greater than at winter. The second feature is the consistent overnight decay giving morning column amounts typically 65% of the value at the previous evening. Similar behaviour has been observed in

Ozone Symposium - Greece 1984 - 163-

the Northern Hemisphere (5, 6). Other short term variabilities are pres­ent, though not a d~minant feature. The estimated random uncertainty in the measurements is ~S%. The midlatitude ozone amounts have estimated uncertainties 10-20%, and show reasonable agreement with readings from a nearby Dobson spectrophotometer. With the observation method used, amounts are weighted to altitudes greater than ls-20km and this can account for the underestimations and absence the expected spring maximum.

(b) Antarctic data. (Figure 2). The midlatitude data described above were obtained at twilight when

the solar zenith angle is 90 0 • This condition is realized only near the equinoxes at Scott Base, and to date only springtime results have been analysed to produce vertical column amounts of nitrogen dioxide. The behaviour contrasts sharply with the midlatitude results. In the early spring column amounts are less than l015molecule.cm-z; but during a short period near the equinox there is a rapid build up to ~s x 1015molecule. cm-z . The overnight decay is small, only becoming comparable with midlat­itude results when the number of daylight-hours at 20km exceeds 12 per day. This asymmetry in the overnight decay implies that the N02 has been stored in a form with a long photolysis time constant. HN03 is one possible candidate for this long-lived species. Solomon and Garcia (7~ have recen­tly shown that using new temperature-dependent photodissociation rates (8), the time constant for N20s photodissociation may be several days at these latitudes, particularly in the lower stratosphere. Thus they argue N20s cannot be discounted as the major reservoir species. Our results also indicate that the layer height of N02 may be near 20km, somewhat lower than at midlatitudes.

The major difference between the midlatitude results and the Antarc­tic results is the greater short term variabilities in the latter. These variabilities are thought to be transport effects and trajectory studies are planned to investigate this further. Solomon and Garcia (9), and Mount et al. (10) have shown that large gradients in northern hemisphere N02 concentrations (eg. Noxon "cliff") can be explained by the history of the air parcel, implying that the N02 retains a 'memory' of its history up to 1 week.

3. Time Series Analysis of Midlatitude results.

At midlatitudes the peak ozone concentration occurs at an altitude of 20-30km (50-20mb, (11», which is significantly higher than in polar regions. Near 30km the photochemical lifetime of ozone is about an hour during the day and increases rapidly below 30km (12). Below 20km trans­port plays a dominant part in determining ozone distribution and secondary maxima observed below 20km (13) are thought to result from large scale motions. With the scattering geometry used, our measurements are relativ­ely insensitive to these low altitude variations. In the case of N02' the peak concentrations are near 30km (7). At these levels the photochemical lifetime is expected to be short. Although no measurements have yet been made in the stratosphere, the tropospheric measurements of Madronich et al. (14) would imply that the photochemical lifetime of stratospheric N02 is less than a minute, significantly shorter than for the case of ozone at these levels. Our midlatitude data set constitutes a long time series of simultaneous observations of nitrogen dioxide and ozone (figure 1). In each case the sampled volumes are the same, though the vertical distribu­tionof the gases within that volume may differ. Since observations are at fixed solar zenith angles (90 0 ), photochemical reaction rates should be

-164-

constant. The overall success rate for observations was better than 80%. Time series analyses of seasonally adjusted data were made. Seasonal

trends were removed by fitting a sinusoid of period one year, and days of missing data were given zero weighting. Correlations were calculated for each year's data for lags up to ±30 days. In all cases the correlation functions implied that the behaviour of these residuals was auto regress­ive, so that the correlograms can be characterized by the following para­meters:

r, the maximum correlation L, the lag in days at which the maximum correlation occurs

Tc ' a coherence time in days for the correlation to decay to lie of its maximum value.

For our data set the minimum significant correlation at the 95% confidence level is 0.12, and the significant results of all analyses are shown in table l.

The diagonal elements of the table are the autocorrelation results. From these it can be seen that N02 amounts are significantly correlated to their values up to 2 days previously whereas 03 has a coherence time of only 1 day. In both cases there are no significant peaks at higher lags. Thus there is no evidence for these measurements being influenced by regu­lar wavelike motions such as the "4-Day Wave" (15).

The cross correlations between morning and evening results show that for both N02 and 03 the maximum correlation occurs at lag -1. This implies that morning measurements are more strongly correlated with measurements the previous evening than they are with measurements later in the same day. This in turn implies that the nighttime is a more stable period in the stratosphere. The crOS$ correlations between nitrogen dioxide and ozone are potentially the most interesting, and also the most speculative and susceptible to error. At these altitudes, current photochemical models (17) predict a decrease in ozone resulting from an increase in NOx(may arise for example from solar proton events (18)). On the other hand, an increase in ozone affects the partitioning between NOx species according to (14)

[N02]

[NO]

which would produce a positive correlation between N02 and 03' In any case the chemistry of the stratosphere is complicated, and transport effects may also be important. It is ther'efore not surprizing that no consistent cross correlations between nitrogen dioxide and ozone have been observed. A significant correlation was found in one case for the 1982 data, but this is probably due to an instrumental effect which gave a discontinuity in the data during that year. When'the analysis was repeated over shorter inter­vals to avoid that discontinuity, there was no significant correlation. Thus we conclude that to our accuracy there is no statistically signifi­cant correlation between measured N02 and 03' If our error bars are taken into account this may be restated: naturally occuring variabilities in measured N02 column amounts produce effects on ozone which are statisti­cally indistinguishable above the 10-20% noise level. This conclusion is hardly surprizing. Clearly to pursue this line of research further, grea­ter accuracy particularly in ozone measurements is required. This could De achieved by optimizing observation parameters for ozone observations rather than N02 as at present. Simultaneous measurement of other species such as NO would also greatly aid the interpretation.

Finally some mention should be made of the possibility of false

-165 -

correlations. Features not allowed for in the data analysis can lead to false correlations if they are correlated with either the N02 or 03 absor­ption spectra. Leakage of solar Fraunhofer structure for example can correlate significantly if care is not taken in selecting the wavelength regions for analysis (2). A particular problem that we have observed with our instrument is a polarization dependence in the instrumental function. This is thought to be due to a grating (Wood's) anomaly, and an inspect­ion of the residual errors for observations over the same period as the reported data shows a strong seasonal dependence, as would be expected from polarization effect with our setup. Steps are being taken to correct for this effect and so improve the accuracy of the ozone estimations.

REFERENCES

1. McKENZIE, R.L. and JOHNSTON, P.V. (1982). Seasonal variations in stratospheric N02 at 45°S. Geophys. Res. Lett., 9, 11, 1255-1258.

2. McKENZIE, R.L. and JOHNSTON, P.V. (1983). stratospheric ozone obser­vations simultaneous with N02 at 45°S. Geophys. Res. Lett., 10, 4, 337-340.

3. JOHNSTON, P.V. and McKENZIE R.L. (1984). Long-path absorption measur­ements of tropospheric N02 in rural New Zealand. Geophys. Res. Lett. 11, 1, 69-72 .

4. McKENZIE, R.L. and JOHNSTON, P.V. (1984). Springtime stratospheric N02 in Antarctica. Geophys. Res. Lett., 11, 1, 73-75.

5. NOXON, J.F. (1979). Stratospheric N02 2. Global behaviour. Journal Geophys. Res., 84, C8, 5067-5076.

6. NOXON, J.F. (1980). Correction [to Papers on Tropospheric and Strato­spheric N02l. Journal Geophys. Res., 85, C8, Aug. 20, 4560-4561.

7. SOLOMON, S. and GARCIA, R.R. (1983). On the distribution of nitrogen dioxide in the high-latitude stratosphere. Journal Geophys. Res., 88, C9, 5229-5239.

8. YAO, F., WILSON, I. and JOHNSON, H.S. (1982). Temperature-dependent ultraviolet absorption spectrum for N205 . J. Phys. Chern., 86, 3611-3615.

9. SOLOMON, S. and GARCIA, R.R. (1983). Simulation of NOx partitioning along isobaric parcel trajectories. J. Geophys. Res., 88, C9, 5497-5501.

10. MOUNT, G. H., RUSCH, D.W., NOXON, J.F., ZAWODNY, J.M. and BARTH, C.A. (1984). Measurements of stratospheric N02 from the solar mesosphere explorer satellite. 1. An overview of the results. J. Geophys. Res., 89, Dl, 1327-1340.

11. DUTSCH, H.U. (1978). Vertical ozone distribution on a global scale. Pageoph., 116, 511-529.

12. NICOLET, M., MEIER, R.R. and ANDERSON, D.E. (1980). Effect of temper­ature and of anisotropic scattering on the O(lD) production in the troposphere and stratosphere. Proc. Quad. Ozone Symposium, Vol. II, 892-901.

13. DOBSON, G.M.B. (1973). The laminated structure of ozone in the atmos­phere. Q. J. Roy. Met. Soc., 99, 422, 599-607.

14. MADRONICH, S., HASTIE, D.R., RIDLEY, B.A., and SCHIFF, H.I. (1983). Measurement of the photodissociation coefficient of NOzin the atmos­phere: I. Method and surface measurements. J. Atmos. Chern. 1, 3-25.

15. PRATA, A.J. (1984). The 4-Day wave. J. Atmos. Sci., 41, 1, 150-155. 16. WMO. (1982). The stratosphere 1981. Theory and measurements. WMO

Global ozone research and monitoring project. Report No.ll, 3-29 to 3-56.

- 166-

17. NASA, (1984). Present state of knowledge of the upper atmosphere. An assessment report. NASA 1984, U.S. Govt. Printing Office.

18. McPETERS, R.D., JACKMAN, C.H. and STASSINOPOULOS, E.G. (1981).

-8 N

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Observations of ozone depletion associated with solar proton events. J. Geophys. Res., 86, C12, 12071-12081.

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N02 VERTICAL COLUMN AMOUNT

1981 1982

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- 167-

THE CLIMATOLOGY OF UPPER ATMOSPHERE NITROGEN DIOXIDE REVEALED BY LIMS OBSERVATIONS

J. M. RUSSELL1, E. E. REMSBERG1, L. L. GORDLEy2, and J. C. GILLE3 1NASA Langley Research Center

Summary

Atmospheric Sciences Division Hampton, Virginia 23665

USA 2Sys tems and Applied Science Corporation

Hampton, Virginia 23666 USA

3National Center for Atmospheric Research Boulder, CO 80307

USA

The LIMS experiment was launched on the Nimbus 7 satell ite on October 24, 1978, for the purpose of sounding the middle atmosphere composition and structu re. One of the LIMS channels was centered spectra lly in the 6,um region to measure vertical profiles and the global distribution of nitrogen dioxide (N02) mixing ratio. The data reveal that N02 is highly variable with altitude, latitude, longitude, and time. Steep latitudi­nal gradients are observed in high latitude winter (lithe N02 Cliff") when a wave number one pattern exists in the geopotential height field. The daytime gradient under these conditions is less than that for the night. The summer hemisphere column amount is considerably greater (by a factor of - 2) than in the winter hemisphere. The largest mixing ratios occur at 4 mb at night (- 20 ppbv) and 9 mb in the day (- 7 ppbv) and the latitude region of the peak mixing ratio is skewed toward the southern hemisphere. The mixing ratio variability is greater at night (by a factor of-2 to 3) than in the day and there are significant long term changes revealed by mixing ratio time series analyses on a pressure versus time grid.

1.0 Introduction

The Limb Infrared Monitor of the Stratosphere (LIMS) experiment operated on the Nimbus 7 spacecraft essentially without flaw for its design lifetime of approximately 7-1/2 months at which time the solid cryogen used for detector cooling was depleted. The experiment returned more than 7000 vertical radiance profiles a day, a portion of which were inverted in ground processing to yield vertical profiles of temperature, 03, H20, HN03, and N02. Since thermal emission was the observed parameter, measurements were obtained both night and day allowing diurnal change studies to be conducted and permitt i ng observat ions to be made of the northern pol a r night region of the globe.

We describe in this paper, the global distribution and variability of N02 mi xi ng rat i o. N02 is an important speci e in the NOx-ozone photochem­istry since it acts as a catalyst in the chain of photochemical reactions that destroy ozone. Here the term NOx refers to the group of gases NO, N02, HN03, N03, N205, and H02N02. Ozone destruction occurs mainly through the pair of reactions [e.g. (1)]:

Ozone Symposium - Greece 1984 - 168-

NO + 03 - N02 + °2 (1) N02 + ° - NO + °2 (2)

At night, this sequence of reactions is believed to be altered by the reactions

N02 + 03 - N03 + 02 (3) N03 + N02 + M - N205 + M (4 )

where M is a third body needed to complete the reaction. In this case N205 becomes a tempora ry reservoi r for NOx• Measu rement of N02 along with HN03 by LIMS, especially in the polar night, and subsequent examina­tion of latitudinal gradients should shed light on NOx storage mecha­nisms. The LIMS observations of diurnal change with altitude, latitude, and time also provide data for a stringent in-situ test of photochemical theory.

The va 1 i dat i on of LIMS N02 data has been di scussed extens i ve ly ina recent paper by Russell et al. (2) and it will not be repeated here. That paper di scusses a 11 of the known error mechani sms, data 1 i mitat ions, and expected accuracy at various altitudes. By way of summary, we note that the largest systematic errors (- 80% estimated from simulations) occur at the lowest altitudes near the tropopause due mainly to uncertainties in accounting for unwanted emission by molecular oxygen; but throughout most of the stratosphere (from 20 mb to 1 mb) errors are in the range from 20 to 30 percent. Precision estimates (i.e. the random component of error) are much smaller and have been verified from orbital data to be in the range of 0.25 ppbv to 0.5 ppbv. or - 5 percent. Comparisons of LIMS N02 with correlative balloon underflight measurements gave mean differences of -15 percent in the 5 mb to 30 mb pressure range.

The LIMS observat ions were spaced app roxi mate ly 25° in longitude and data were reduced every 4° in latitude, over the range from 64°S to 84°N. This latitude range was defined by the orbital geometry and LIMS view direction. The duty cycle was 11 days on and 1 day off, thereby providing measurements nearly continuously in time. All of the data have been reduced, mapped, and archived at the National Space Sciences Data Center in the United States. Zona 1 mean pressure versus 1 at itude cross sect ions, polar stereographic projections, mixing ratio time series on pressure versus time and latitude versus time grids, diurnal change cross sections, and standard deviation-pressure versus latitude cross sections have been prepa red and ana lyses are underway. The next section of thi s paper wi 11 describe some of these results.

2.0 Results

Day and ni ght month ly zonal mean N02 cross sections for Janua ry and May are shown in Fig. 1 and 2. Note the contrast between the day and night results. The night data show considerably more vertical structure, steeper vertical gradients, steeper latitudinal gradients, and they extend to a higher altitude. In each case, except for the May daytime results, the region of peak mixing ratio occurs south of the equator. The daytime May measurements show a peak mixing ratio region which is nearly symmetric about the equator. The very sharp latitudinal gradients in the highest latitudes of each hemisphere occur when the measurement crosses the termi nator either from day to ni ght or vi ce versa. These cross -sect ions

- 169-

are typical of the N02 results obtained throughout the mission. Note that the mid to high northern latitude mixing ratio gradient at -6 mb in January is much sharper than in May. This is a manifestation of the N02 "Cliff" phenomenon first reported in the literature from ground-based measurements by Noxon (3). Th is appea rs to be cau sed by con ve rs i on of N02 to N205 in the polar night coupled with transport processes associated with a wave number one condition in the temperature and height fields (4, 5).

The latitude-time cross section in Fig. 3 shows some characteristic features of the nighttime N02 behavior at the 10-mb level. In the southern hemisphere and tropics, there is generally very 1 ittle variabil ity. The regions of sharp latitudinal gradients extending through day 140 of the mi ss ion in the hi ghest 1 at itudes of the southern hemi sphere and begi nni ng at - day 160 in the northern hemisphere are due to the measurement point crossing the day/night terminator. There is considerably more variation in mixing ratio northward of 30° than in the southern hemisphere until about day 140 when this behavior subsides to some degree. Although detail study is needed to draw conclusions, it appears that planetary wave activity which is present in winter, coupled with the likelihood that nighttime N02 is more under dynamical control than chemical control are the probable reasons for the observed variations. Changes with time in the high latitudes decrease noticeably after day 140 when more quiescent atmospheric conditions prevail.

One of the important questions suggested by theory but before LIMS, had not been verified experimentally, is whether the polar night thermosphere/mesosphere could act as a source for stratosphere N02. Special processing ~sing radiance averaging was performed on the LIMS data allowing the polar night region to be sounded from the middle mesosphere (-70 km) down to the tropopause (-10 km) so that this question could be examined. When this was done, it was discovered that deep in the polar night, the N02 level reached 170 ppbv at 70 km as compared to only 20 ppbv in the stratosphere. Furthermore. the N02 was found to have 1 ongitudi na 1 vari abil ity at 70 km of about a factor of 8 and the regi ons of maxi rna and minima were highly correlated with highs and lows in geopotential. This suggests that downward transport of N02 is occurring and is quite localized. The notion of downward transport is given additional credence by the N02 time series at four pressure levels shown in Fi g. 4. The pressure levels of 0.5 mb, 0.9 mb. 1.7 mb, and 2.3 mb were chosen to cover from the lower mesosphere into the upper st ratosphere. Careful study of the figure shows that at the highest altitude (0.5 mb pressure) the N02 level begins to increase in mid November, followed by an increase at the next highest altitude (0.9 mb) in early December and so on. The increases all occur for the most part during polar night when, in the absence of sunlight. N02 is formed high up and is transported undisturbed down to the stratosphere. Once sunlight returns around mid January. the increases cease and N02 levels decline or remain nearly constant depending on photochemical time constants at the various altitudes. These results represent the fi rst experimental evi dence that the mesosphere is an N02 source for the stratosphere and they provide a key data base for tests of theory. establishment of vertical velocities. and determination of photochemical time constants. This information coupled with other Nimbus 7 data will allow important studies to be conducted of the nitrogen budget in the stratosphere.

These examples represent only a small portion of LIMS N02 results. Detailed analyses of the data are currently underway and results will be discussed in a forthcoming journal paper on the N02 climatology.

- 170-

REFERENCES

1. CRUTZEN, P. J., I. S. A. ISAKSEN, and J. R. MCAFEE, The impact of the chlorocarbon industry on the ozone layer, J. Geophys. Res., 83, 345-363, 1978.

2. RUSSELL, J. M., J. C. GILLE, E. E. REMSBERG, L. L. GORDLEY, P. L. BAILEY, S. R. DRAYSON, H. FISCHER, A. GIRARD, J. E. HARRIES, and W. F. J. EVANS, Validation of Nitrogen Dioxide measured by the Limb Infrared Monitor of the Stratosphere (LIMS) experiment on NIMBUS 7, J. Geophys. Res., 89, 5099-5107, 1984.

3. NOXON, J. F., Stratospheric N02, 2, Global behavior, J. Geophys. Res., 84, 5067-5076, 1979.

4. SOLOMON, S., and R. R. GARCIA, Simulation of NOx partioning along isobaric trajectories, J. Geophys Res., 88, 5497-5501, 1983.

5. CALLIS, L. B., J. M. RUSSELL, M. NATARAJAN, and K. U., HAGGARD, Examination of wintertime latitudinal gradients in stratospheric N02 using theory and LIMS observations, Geophys. Res. Lett., 10, 945-948, 1983.

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-171 -

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(4)

COMPARISONS OF MEASURED AND PREDICTED DIURNAL CHANGES IN STRATOSPHERIC NO AND N02

H.K. Roscoe, B.J. Kerridge,L.J,. Gray, R.J. Wells, Department oJ Atmospheric Physics ,. Clarendon ·Lp.boratory, Oxford University, U. K.

J.A. Pyle, Rutherford Appleton Laboratory, U.K.

For the first time, results are available from the last four balloon flights of the Oxford radiometer, which uses pressure modulators to meas­ure NO and N02 in the stratosphere. Since the radiometer senses thermal emission from the atmospheric limb, vertical profiles can be deduced at any time of day or night. These flights all took place from Texas from 1980 to 1983. Each lasted about 12 hours except the 1982 flight, which lasted over 20 hours.

Careful comparison of the N02 results with predictions from the Oxford ID model show excellent agreement with the measured increase at sunset. Unfortunately all flights except that of 1982 ended too early to see if the predicted night-time fall (due to N205 production) was observed. Figure 1 shows that N02 results from the 1982 fl~ght are consistent with this night-time fall, Dut do not definitively support it.

The Oxford diurnal model was changed in three important ways to allow these very specific comparisons:

(1) model outputs wer~ averaged for the integration time of the measurement:

(2) the albedo could be specified and could be varied during a flight;

(3) temperature and ozone profiles could be specified to the profiles measured during a flight. Figure 2 demonstrates the importance of this,

The NO and N02 profiles for all.the flights are shown in figure 3. It is clear that in 1982 both were substantially lower at 33kID. This was 140 days after the El Chichon eruption, by which time the dust cloud was centred at 25 kID, though earlier it had been above 30 kID. One C9n speculate about possible causes of low NO and, N02 :

(a) total odd nitrogen was scavenged on the higher particles soon after the eruption, 140 days being insufficient at this altitude for decom­position of N20 to restore reactive nitrogen to normal levels;

(b) (NO+N02) was converted to HN03 by high levels of OH due to high water vapour.

Model studies show that at least 20 ppm water vapour would be needed for the latter to be true, and then only if ozone were to change to the new chemical equilibrium. This is not unreasonable since ozone was meas­ured during balloon ascent or looking north of west, whereas the dust cloud was entirely to the south at this time. Similarly, water vapour measure­ments during the flight were by other sensors also looking north of west. However, radiances measured by'the wide-band water vapour channel of SAMS were doubled after the eruption and were still abnormally high in September 1982. Unfortunately this is not unambiguous since the spectral filter on this channel passes some radiance from throughout the mid infrared.

Ozone Symposium - Greece 1984 - 173-

109 43-4km

t J.!.\.t.+4o 108 +0. t 0 o ••

39-6 km

109 .to i. t.+. .t.-t. t + .t. + . . . . • • ... t ••

108

36-0 km

109 ...........

••• 0 ~. t t t t + t \. l 0 to • f +

6 0 Model t Measured 101'::-2 ---'--1;'-;6--'--='20::--'- u':--'---!-4 --'---=-a--'---J

Solar time Figure 1: measured and modelled N0 2 from the 1982 flight.

]40 -..... ..c en OJ

:::r:

35

30

1--

N02 daytime

-- JUNE 83 --- OCT 82 ... .. . MAY 81

ocr 80

----..1 1

NO

lOB -

12 16 20 24 4

,,' ..... .;-. /

,"- //

: I : I : /

I I I

6 Solar time

Figure 2: model predict­ions with climatological temperature ( ... ) and with the observed temper-ature (--).

NO

..... -- ---1

" , \

! I I I , I I,-

1\ I '

I \ I .

/ \. t-.J---<

\ \ \ \ \ \ \ \ \ -

t----~F_7 -,.=;/ ___ _ •

1010

Figure 3: Concentrations of NO and N02 measured by the Oxford radiometer.

-174 -

Summary

NITRIC OXIDE PROFILE FROM 7 TO 32 KM

W.A. Matthews PEL Atmospheric Station, DSIR

Lauder, Central Otago, New Zealand

Y. Kondo, M. Takagi and A. Iwata Research Institute of Atmospherics

Nagoya University Toyokawa, Aichi 442, Japan

Within the framework of the MAP-Globus campaign, a chemiluminescent NO detector was la~~ched, together with a similar experiment from the Max Planck Institut fur Aeronomie, Lindau, West Germany on September 20, 1983 from Aire sur l'Adour, France, (44°N, OOW). The balloon was piloted to perform an excursion from 32 km to 22 km during the flight and returned to float at 32 km one hour before sunset to enable a sunset study to be made. The first ascent profile showed a rapid increase in NO mixing ratio from 50 ppt at 7 km to 250 ppt at the tro­popause indicating a downward transport of NO into the troposphere. The nitric oxide mixing ratio continued to increase to be about 1 ppb at 25 km, and increased even more rapidly above 25 km to reach a value of approximately 10 ppb at 32 km. The first ascent and descent profiles, obtained with a SZA of less than 57° coincided even in detail to within 5% between 22 and 32 km assuring instrumental precision. The unchanging NO mixing ratio during the day is indicative of a very low mixing ratio of NzOS compared to NOx , at least at mid-latitudes. The NO concen­tration at 32 km gradually decreased from when the SZA was 70° to sunset at which time it rapidly decreased by more than an order of magnitude in 10 minutes.

1.1 Introduction

The concentration of the various oxides of nitrogen in the atmosphere are determined by the interplay of complex chemistry and dynamics. It is imperative to obtain, and compare in detail, measured profiles of atmos­pheric trace gases with those obtained from model calculations to check the validity of the models since these reflect our current understanding of the dynamical-chemical processes prevailing in the atmosphere.

A technique to measure stratospheric NO in situ was develope~ by Ridley and Howlett (1) utilising the chemiluminescence emanating from the reaction between ozone carried by their instrument and ambient NO. Since that time several NO profiles (2-9) have been presented in the literature. However in their 1981 paper (8), Ridley and Schiff pointed out that serious errors in deriving NO mixing ratios can arise through losses on the intake tubes and they cast doubts on previous measurements. We have developed an NO detector (10) using Ridley and Howlett's chemiluminescent technique but have the system to a stage where we believe we can make reliable measure­ments in the troposphere as well as the stratosphere.

Ozone Symposium - Greece 1984 -175 -

1.2 Measurements

As part of the MAP-Globus campaign held in Aire sur l'Adour, France in 1983, our instrument together with the chemiluminescent NO-N02 instrument from the Max-Planck-Institut fur Aeronomie, Lindau, West Germany was flown as a combined package on September 20. The balloon reached its ceiling altitude of 32 km mid-morning and after a short time at this float altitude, was piloted through a controlled release of gas and ballast to perform an excursion to 23 km before returning to 32 km before sunset. The flight profile is given as Figure 1. The purpose of this paper is to discuss the data obtained from our sonde and the comparison of this data with that from the Max-Planck-Institut fur Aeronomie sonde will be the subject of a subsequent paper.

With such a flight profile, a unique data set was obtained since it allowed three vertical profiles between 23 and 32 km to be measured with the same instrument on the same day. This allowed the instrumental pre­cision to be checked and it was found to be 5 to 10% between 7 and 32 km and the detection limit at 25 km was between 10 and 20 ppt. This flight profile also allowed a study of diurnal variations in stratospheric NO to be made. The NO mixing ratio as a function of height from data obtained during the first ascent is shown in Figure 2. The gaps in the data are due to in-flight calibration routines being performed in the sonde where the duty cycle was set to be 10 minutes. The NO mixing ratio is seen to increase rapidly from 50 ppt at 7 km to 250 ppt at 12 km, the position of

30

..... 20 E ~

GI "C :I .. ..

Ci 10

Sep. 20,1983

SZA =90deg

separation

Time (UT)

Figure 1 Flight profile for gondola 2a in the MAP-Globus campaign launched at 08.35 UT on September 20, 1983 from Aire sur l'Adour in France. With a controlled release of gas and then ballast an excursion from the float altitude of 32 km down to 23 km and back up to 32 km was performed.

- 176 -

the tropopause. Above the tropopause the increase is less rapid, reaching 0.5 ppb at 20 km. The NO mixing ratio is then seen to increase rapidly again at 25 km and reaches a value of 10 ppb at 32 km. In general these data fit very well with the autumn data of Ridley and Schiff (8) measured at 32°N and within the error bars listed by Loewenstein and Starr (11) for 44°N. One of the most interesting features of this data set is that we were able to measure NO from a height of 7 km on through the tropopause and into the stratosphere. Also, the small feature at 24 km was present in all three profiles for this day and only shifted in height by 500 m. Further, we found that the first descent data measured between 10.40 and 14.40 UT agree within 5%, even in detail, with the profile measured over the same height interval on the first ascent between 9.53 and 10.30 UT. During this whole period the sub-balloon point solar zenith angle (SZA) had ranged between

30 r- )' -

f' , " ...

f-...... .... " E .1

.%.

GI ' .. "1:1 ,t' :::I 20f- .1 -....

.... ~ ~ .,'

-.}

- Tropopause

" • I

10 .' 1 -.'

.... ,I ,I

0.01 0.1 1 10 NO mixing ratio(ppb)

Figure 2 The volume NO mixing ratio in parts per billion is shown as a function of altitude for the first ascent. The gaps in the data are when on-board calibrations were made. The NO mixing ratio increases rapidly from 50 ppt at 7 km to reach 250 ppt at the tropopause measured to be at a height of 12 km on this day. The NO mixing ratio then increases more slowly to be 0.5 ppb at 20 km and then more rapidly again between 25 and 32 km where it reaches a value of 10 ppb.

- 177-

50° to 42° to 57°. Indeed it was not until midway through the second ascent when SZA was 70° that our NO mixing ratios started to significantly depart from those measured on the first ascent and second descent. This departure from the "midday" profile continued smoothly so that by 17.50 UT when the balloon was again at 32 km, at the SZA = 90°, the NO mixing ratios measured were 70% of the corresponding midday values. After this time, the NO mixing ratio was measured to fall very rapidly and reached our lower detection limit of 0 ± 10 ppt in only some 15 minutes with a SZA of 94°.

We feel that the unchanging NO mixing ratio during the day is indica­tive of a low N20S mixing ratio compared with that of NOx and the decrease in the NO concentration for solar zenith angles greater than 70° can be accounted for, at least in part, by increased Rayleigh scattering decreas­ing the effective rate of photodissociation of N02.

1.3 Acknowledgements

A more detailed discussion of the results presented here is submitted for pUblication to J. Geophys. Res. (Kondo et al., 1984). The two figures presented here are reproduced under the copyright of the American Geo­physical Union. This MAP-Globus experiment was supported financially in part by the Federal Republic of Germany's Ministry for Research and Technology through the Max-Planck-Institut fur Aeronomie for which we are indebted. We are also extremely grateful for the support received from the Alexander von Humboldt Foundation. Part of this work was performed while one of us (W.A.M.) was supported at the Service d'Aeronomie du CNRS, Verrieres-le-Buisson, France, by CNRS and C.I.E.S. whose support we also wish to acknowledge. We also wish to take this opportunity to thank Monsieur Prigent-and.his staff at the Balloon Centre of CNES, Aire sur l'Adour for piloting our experiment with such precision.

1.4 References

1. RIDLEY, B.A. and HOWLETT L.C. (1974). An instrument for nitric oxide measurements in the stratosphere. Rev. Sci. Instrum. 45, 742-746

2. RIDLEY, B.A., SCHIFF, H.I., SHAW, A. and MEGILL, L.R. (1975). In situ measurement of stratospheric nitric oxide using a balloon-borne chemiluminescent instrument. J. Geophys. Res. 80, 1925-1929

3. BURKHARDT, E.G., LAMBERT, C.A. and PATEL, C.R.N:-(1975). Stratospheric nitric oxide: Measurements during daytime and sunset. Science 188, 1111-1113 -

4. RIDLEY, B.A., McFARLAND, M., BRUIN, J.T., SCHIFF, H.I. and McCONNEL, J.C. (1977). Sunrise measurements of stratospheric nitric oxide. Can. J. Phys. 55, 212-221

5. SCHIFF, H.I., PEPPER, D. and RIDLEY, B.A. (1979). Tropospheric NO measurements up to 7 km. J. Geophys. Res. 84, 7895-7897

6. ROY, C.R., GALBALLY, I.E. and RIDLEY, B.A. (1980). Measurements of nitric oxide in the stratosphere of the southern hemisphere. Quart. J. Roy. Meteorol. Soc. 106, 887-894

7. WEILER, K.H., FABIAN, P~FLENTJE, G. and MATTHEWS, W.A. (1980). Stratospheric NO measurements: A new balloon-borne chemiluminescent instrument. J. Geophys. Res. 85, 7445-7452

8. RIDLEY, B.A. and SCHIFF, H.I. (1981). Stratospheric odd nitrogen: Nitric oxide measurements at 32°N in autumn. J. Geophys. Res. 86, 3167-3172 -

- 178-

9. RIDLEY, B.A. and HASTIE, D.R. (1981). Stratospheric odd nitrogen: NO measurements at 51°N in summer. J. Geophys. Res. 86, 3162-3166

10. KONDO., Y., IWATA, A., MATTHEWS, W.A. and TAKAGI, M." (1984). A balloon­borne chemiluminescent sonde for the measurement of tropospheric and stratospheric nitric oxide. Rev. Sci. Instrum. (in press).

11. LOEWENSTEIN, M. and STARR, W.L. (1978). Stratospheric NO and HN03 observations in the northern hemisphere for three seasons. Geophys. Res. Lett. 2, 531-534

- 179-

MEASUREMENT OF OXIDES OF NITROGEN IN THE FREE TROPOSPHERE ----- ------OVER JAPAN -----

* Y.KONDO, A.IWATA, W.A.MATTHEWS, Y.MORITA AND M.TAKAGI

Research Institute of Atmospherics, Nagoya University,

Toyokawa, Aichi, Japan

*PEL ~tmospheric Station, DSIR, Lauder, central otago, New Zealand

Summary

Aircraft observations of NOx(NO and N0 2 ) over the sea surrounding

the Japanese islands(30-43 0 N,131-141 oE) were carried out in the winter

of 1983 and 1984 at ~ltitudes between 3 and 8 km. The main NOx features

observed are as follows:

1)Over the Pacific ocean between the latitudes of 30-3SoN, the observed

NOx mixing ratio at 3-8 km is fairly constant at 0.2 ppb. The NO mixing

ratio increases with altitude from 20 ppt at 3 km reaching 40 ppt at 7

km.

2 )The NO x mixing ratio measured in the air mass transported from the

stratosphere was also about 0.2 ppb.

3)over the sea of Japan, the tropospheric NOx mixing ratio starts

increasing with latitude North of 3SoN and reaches about 1 ppb at 40 oN.

1. Introduction

Oxides of nitrogen are now recognized as one of the key species in

the budget of the tropospheric ozone. However, background NOx measure-

ments are still rather sparse, certainly when considered on a global

scale, and there is an urgent need to measure the mixing ratio in a

variety of locations. In response to this need, we began aircraft measu­

rements of background NOx along the eastern rim of the Asian continent

in 1983. The instrument used to measure NOx is a chemiluminescent detec­

tor with a ferrous sulfate converter to reduce N0 2 to NO( 1). The detec­

tion limit has now been improved to be 5 ppt.

Ozone Symposium - Greece 1984 - 180-

2.Results

We present here the re­

sults obtained in the winter of

1983 and 1984. The routes flown

by our aircraft are shown in

Figure 1. The observed mixing

ratios of NO x and NO for alti­

tudes between 3 and 8 km, ob­

tained over the sea and at lati­

tudes between 29.5-34 o N, are

depicted in Figure 2. From this

figure it can be seen immediate-

ly that NO x is quite uniformly

mixed with height and ranges

between 0.2tO.05 ppb, at least

on these three days of measure-

ment. In contrast, NO increases

on the average from 20 ppt at 3

km to be 40 ppt at 7 km. The

flight North, covering latitudes

from 35 to 43 0 N was performed on

Feb. 14, 1984(Figure 1). Latitude­

altitude flight profiles, together

with the position of the tropo~

pause estimated from radiosonde

soundings made by the Japanese

Meteorological Agency radiosonde

network at 0900 hours J.S.T., are

shown in Figure 3. On this day,

stratospheric air intruded down

into the troposphere from about

40 o N. The air~raft entered the

stratosphere and passed through

this intruded air mass. The mixinq

ratios of NOx and NO observed

during the return leg in the tro­

posphere from sapporo to Yao are

..i-__ -r-- .0

... ..2 Figure 1. Flight routes used for

the aircraft observations

in winter.

o . Feb. 18, 11183 o . Jen. 12, 11184

8 • • Feb. 18, 11184

0 0 0

o a",""

" E 8 o,.I>jg /"1. .. e ••• \ .. :'!f& ... " .,.t: := := .. 0 . c 4 ."

0 0

I 0

o '?t.., -00

2 NO NO.

0.01 0.1

IIlxlng r.tlo(ppb)

Figure 2. vertical profiles of NO

and NOx measured in January and

February 1983 and 1984 between the

latitudes of 29.5 0 N and 34oN.

- 181 -

shown in Figure 4 to­

gether with the ozone

mixing ratios that

were measured sirnulta-

neously. The aircraft

maintained a constant

flight level of 4.6 km

for this observation

as is shown in Figure

3. The increase in

ozone corresponds

quite well to the cro-

ssing of the tropo-

pause as shown in Fi­

gure 3 and thus can be

used as an indicator

of air masses of stra-

tospheric origin. In

Figure 4 it can be

seen that the NO x

mixing ratios

fall from the

surrounding higher

tropospheric va­

lues to about 0.2

ppb in the strato~

spheric air mass.

These results are

similar to those

obtained in the

Z a. a.

200 Fob. 1., 198.

10

i Tr

"' 8

~ 400 · · 8 • .t eoo • 800 ::::-

1000 .S Sp .0 At 35 Yeo 30

Lotl1...s.fN1

Figure 3. Altitude profiles of aircraft

observation versus latitude on February

14, 1984. The thick lines denote the

position of the tropopause as determined

by radiosonde temperature measurements

released from meteorological stations

at 0900 JST.

43.1 1.2

41.9

Latltude( 0 NI

40.6 39.2 37. 7 36.2 34.8

Feb. 14, 1984 Sapporo - Yao

~ 0.8

~ !II c .. E 0 .4 .. o z

o 16

NO 0.. _ .. - -0- - - -0- ___ -o- - --~ .....

17 18

Japanese Standard Tlme(JSTI

o 19

stratosphere on

the flight North

Figure 4. Variation of NO, NOx and ozone

mixing ratios with latitude at 4.6 km.

from Yao to sapporo.

This result suggests that the NO x mixing ratio. in the clean air,f"rom the

lower troposphere up to the lower stratosphere, is fairly constant at the

latitudes South of 3S o N. It is also noted that the tropospheric NO x

- 182-

mixing ratios at the lati-

tudes North of

generally higher than those

recorded on the Pacific side

of Japan and reach a maximum

at 40 o N. The 500 mb chart at

2100 JST is given in Figure

5. The observation area was

dominated by the strong wes­

terly flow. The position and

magnitude of the observed

NOx values are superimposed

on this figure for complete-

ness. The relationship of

the observed higher NO x mi­

xing ratio at higher lati­

tudes to the meteorological

situation needs to be inves­

tigated in more detail' and

augmented with further ob-

servations.

Acknowledgements

---:----t"" ..

Figure 5. 500 mb contours at 2100

JST on Feb.14,1984.The observed

NOx mixing ratios{X) ,except

for those observed around 1800

JST, are superimposed on this

figure and are designated as

follows.

Black; X>0.8 ppb, shaded area;

0.3 ppb<X<0.8 ppb, and white;

X<0.3 ppb.

The meteorological analysis and the ozone data have been provided

through the courtesy of H.Muramatsu, M.Hirota and T.Sasaki at the Meteo­

rological Institute, JMA to whom the authors express their thanks.

REFERENCE

1.KONDO,Y, IWATA,A. AND TAKAGI,M.{ 1983). A chemiluminescent NOx-detector

for the aircraft measurement.J.Met.soc.Japan,~, 756-762.

-183 -

Summary

MEASUREMENTS OF ATMOSPHERIC NITRIC OXIDE FROM NIMBUS 7 SBUV ULTRAVIOLET SPECTRAL SCAN DATA

R.D. MCPETERS Laboratory for Atmospheres

NASA, Goddard Space Flight Center Greenbelt, MD 20771 USA

The Solar Backscattered Ultraviolet Instrument (SBUV) on Nimbus 7 is operated one day per month in a spectral scan mode in which it scans from 160nm to 400nm in 0.2nm steps. By measuring the intensity of a series of nitric oxide gamma band fluorescence features in this wavelength range we can estimate the amount of nitric oxide in the upper stratosphere and mesosphere.

The background of atmospherically scattered sunlight normally masks the much weaker nitric oxide gamma band emission, but we discriminate these emission features by subtracting a synthetic spectrum calculated for a model atmosphere that includes only Rayleigh scattering and absorption by ozone and oxygen. The resulting difference plot clearly reveals features resulting from processes not included in the simple model, such as NO gamma band emission. Emission features are seen at wavelengths corresponding to the vibrational transitions v'v" - (10), (22), (00), (01), (02), (14), (03), and (15). Nitric oxide is inferred by measuring the absolute intensity of various bands relative to the adjacent background and relating this intensity to total NO above an altitude determined by the backscattering contribution function for that band. Near the solstice we observe a relatively constant NO distribution of about 4. OE14 molecules per square centimeter cumulative NO above 1.0 mb (approximately 48 km) throughout the summer hemisphere. But NO begins increasing rapidly with latitude beginning at about 40 latitude in the winter hemisphere, reaching a density of 1.0E1s molecules per square centimeter near the winter terminator.

1. Introduction It has been clear that nitric oxide is an important factor in the

atmospheric photochemical balance since Crutzen (2) pointed out that odd nitrogen can destroy ozone in a catalytic cycle. Barth (1) first detected nitric oxide in the lower thermosphere in 1964 by observing emission in the (10) NO gamma band. Recently Frederick and Abrams (3) studied the

Ozone Symposium - Greece 1984 - 184-

feasibility of measuring NO by measuring the intensities of various bands in the Earth IS backscattered spectrum. Here we report results of an analysis of two years of spectral scan data from the solar backscattered ultraviolet instrument (SBUV) on Nimbus 7. We are able to discriminate the nitric oxide emission features from the background of scattered light and estimate the cumulative amount of NO present.

2. Data Analysis Nimbus 7 is in a sun synchronous polar orbit that covers the entire

Earth between 80 5 and 80 N each day with orbits spaced at 26 longitude intervals. SBUV normally measures ozone by operating in a step scan mode, but approximately one day per month it operates in a spectral scan mode in which backscattered sunlight is measured between 160 nm and 400 nm at 0.2 nm intervals with 1 nm resolution. SBUV is designed to measure the atmospheric albedo, the ratio of the atmospherically scattered radiance to the extraterrestrial solar irradiance. In Figure 1 we show the solar irradiance measured by SBUV on February 14, 1979, and the albedo for a scan at 79.3 S the following day.

50~AR ~~UX ~NO A~ecoo

.l ll~

"'.'5

Figure 1

., "

-,

~ESE~.CO-C~~C ALELDD ~ ., '"9

-:'"'1.' , ..... "'" ~'C(1'['!.

~ l"''' ~~

·'-iee i!fIIi 2"11 ~" :M l~ l)t ~~ l-oe I";; ol';4I * ~ ~ 70' ll"li ne nIi ~ 1S/I..C'L( .... 11<1fl

Figure 2

Taking a ratio removes the structure of the solar spectrum from the albedo; the shape of the albedo spectrum is mostly that of the Hartley ozone absorption band. Careful examination reveals small peaks in the albedo at wavelengths coincident with the wavelengths of major NO gamma bands. This structure is much more apparent if we subtract a synthetic spectrum calculated for a model atmosphere that includes Rayleigh scattering, ozone absorption, and Herzberg continuum oxygen absorption. The calculation uses an ozone vertical profile retrieved for each scan using the BUV algorithm and uses a spherical atmosphere at large zenith angles. The percent difference between the observed spectrum and the synthetic spectrum is shown in Figure 2. The wavelengths of the five largest NO gamma bands are marked.

The precision of the spectral scan data is considerably lower than that of the step mode data because the integration time for each data point is twenty-five times less. Moreover, the solar flux itself is much lower below 250 nm. Consequently, we average our data by zones in order

- 185-

to achieve a better signal-to-noise ratio. The relative contribution of an NO emission feature is very sensitive to solar zenith angle, so we bin by solar zenith angle, separating northern and southern hemisphere. We convert the difference between the observed spectrum and the synthetic spectrum to Rayleighs and integrate over each NO band relative to the adjacent background to get the average band intensity for each zone for each day. The (10), (01), and (02) bands have proven to be most useful for NO determination; the (14) band intensity becomes comparable to the noise level at small solar zenith angles.

An NO overburden is inferred by interpolating from a table of NO band intensity versus NO amount for each zone. Calculation of theoretical band intensities requires that the detailed rotational structure within each vibrational transition be accounted for (5), and that self absorption within each rotational line be included. We use an NO profile shape based on the measurements of Horvath et al. (4) at 50 km and below and based on the measurements of Meira (6) above 80 km. The NO overburden at the altitude at which the contribution function for a given band peaks should be relatively insensitive to the assumed NO profile shape.

CUr1L'L~'TI\wE rnT~IC O'ICC 1'1 II""?

~~~.~ 4~.4.~H.~.M ... UHllWI:

Figure 3 3. Results

C UMU~A~I V E NITQJC Oxl0~ .0«(:) . 0« • • K ( 11 OK( n .......

~~4_4~_._'~H.~~ .• ". l-1I1l11.a:

Figure 4

We have determined cumulative NO amounts for 24 days of spectral scan data from the first two years of SBUV operation for each of 20 solar zenith angle zones. For a given band the contribution function peaks at higher altitudes at larger solar zenith angles. We show cumulative NO above 1.0 mb for June and July for years 1979 and 1980 in Figure 3, and for December and January for the same years in Figure 4. 1.0 mb was chosen as a constant altitude because either the (10) or (02) band contribution function peaks near 1.0 mb over most of the globe. The results are somewhat variable but relatively constant in the summer hemisphere. But beginning at approximately 40 latitude in the winter hemisphere in each case we see a consistent pattern of NO increase toward the winter terminator. This may be the result of the downward transport of NO from the thermosphere and mesosphere in the winter.

- 186-

REFERENCES

1. Barth, C. A., "Rocket measurement of the nitric oxide dayglow," J. Geophys. Res., 22,3301,1964.

2. Crutzen, P.J., "Ozone production rates in an oxygen­hydrogen-nitrogen oxide atmosphere," J. Geophys Res.,1§" 7311, 1971.

3. Frederick, J.E. and R.B. Abrams, "Model studies of nitric oxide fluorescence· in the Earth IS backscattered spectrum," Planet. Space Sci., lQ., 137, 1982.

4. Horvath, J.J., J. Frederick, N. Orsini, andA. Douglas, "Nitric oxide in the upper stratosphere: measurements and geophysical interpretation," J. Geophys. Res., M, 10809, 1983.

5. Kovacs, I. "Rotational structure in the spectra of diatomic molecules," American Elsevier Publishing Co., New York, 1969.

6. Meira, L.G. Jr., "Rocket measurements of upper atmospheric nitric oxide and their consequences to the lower ionosphere," J. Geophys. Res., li. 202, 1971.

- 187-

EVIDENCE FOR A THERMOSPHERIC SOURCE OF STRATOSPHERIC NOX

Summary

by

ARLIN J. KRUEGER Planetary Atmospheres Branch Goddard Space Flight Center

Greenbelt, MD Z0771

Analysis of a three year time series of rocket ozone measurements at Wallops Island, Va., a set of rocket ozone soundings across the southern hemisphere, and rocket soundings at Fort Churchill, Manitoba has "produced evidence that the NOx budget is not simply explained by oxidation of biospheric nitrous oxide. A 1-D time-dependent photochemical model is used to compute the amount of NOx required to maintain odd oxygen in a steady state after accounting for Chapman, odd hydrogen, and odd chlorine reactions. The ozone and air densities and the air temperature are measured quantities which are fixed during the calculations. At Wallops Island, a mid-latitude station, the inferred seasonal variation of NOx is small with the fall and winter mixing ratios about ZO% greater than the spring and summer values. The soundings at Fort Churchill require about the same NOx amount as at Wallops Island in the spring and summer months but more than double this amount in late fall and winter. The latitude dependence of NOx, derived from the fall season southern hemisphere ozone data, requires a decrease from the equator to midlatitudes, followed by an increase at higher latitudes. These combined results indicate that the nitrous oxide source of NOx is supplemented by a polar source during the fall and winter months. This is consistent with the descent of thermo­spheric air with its high nitric oxide content during the period of strong cooling in the polar night.

1. Introduction

The photochemistry of ozone in the middle stratosphere is dominated by cyclic reactions with odd nitrogen (NOx) species. Crutzen 1,Z noted that nitrous oxide could be a source of odd nitrogen through the reactions:

1 03 + hv -+- 0z + O( D)

1 O( D) + NZO -+- Z NO.

A second source of odd nitrogen is the large reservoir of nitric oxide in the thermosphere produced by energetic particle dissociation of NZ and ion reactions. The thermospheric nitric oxide, however, cannot diffuse downward across the mesosphere because it self destructs rapidly by photolysis during daytime:

NO + hv -+- N + 0,

Ozone Symposium - Greece 1984 - 188-

followed by:

N + NO + NZ + O.

If this were a significant source of stratospheric NOx it could only be through vertical transport in the polar night. This odd nitrogen then adds to the pool of odd nitrogen from the oxidation of nitrous oxide and, because of its long lifetime in the stratosphere, increases the total amount available for destruc­tion of odd oxygen.

Because the NOx cycle accounts for 60 to 70 % of the odd oxygen destruc­tion between 4 and ZO mb at midlatitudes, the ozone concentration will be strongly influenced by the amount of NOx present. For example, if the NOx were removed and all other factors fixed, the ozone mixing ratio would increase by a factor of Z.5 to 3.0. Thus, one should be able to use the observed variations of ozone as a very sensitive indicator for variations in NOx. In the present study a set of rocket soundings of ozone and air temperature have been analysed to infer the variability and sources of NOx.

Z. Model Characteristics

The photochemical model is one-dimensional and structured on steady-state families of short-lived species of the NOx, HOx, and ~IOx families. Radiation and CIOx codes are adapted from the Crutzen I-D model and tested with several specifications of solar flux and constituent cross s~ctions. The present results are derived using the 1981 NASA-WMO Workshop solar flux distribution and rate coefficients, oxygen Herzgerg cross sections from Shardinand and Ra0 5 , ozone cross sections from Ackerman , and oxygen ~chumann-Runge effective absorption coefficients from Allen and Frederick •

The vertical distributions of ozone, air temperature, and air pressure are specified from rocket measurements. The vertical distributions of HZO, CH4 , and HZ are prescribed and the timg-varying Clx constituents are specified from the model results of Gidel et al.. The time-dependent calculations begin at sunrise and proceed in 15 minute steps to sunset, when the amount of NOx required to remove the residual odd oxygen is computed. Since the partitioning of radicals in other families (eg HOx) depends on the NOx mixing ratios, the final NOx distribution is computed iteratively using the prior day's results as the initial distribution.

3. Ozone and Temperature Data

A twenty-eight month set of regular monthly rocket ozone and temperature soundings provided a baseline data set for evaluating the principal sources of variance in the ozone distribution at Wallops Island, Va. The ozone soundings were initiated in March 1976 and continued ~n a regular basis until the fall of 1978. Rgcoz optical ozone sonde instruments adapted for the Super Loki-Dart vehicle 1 , were used'in this campaign. The data were generally of high quality as illustrated by the initial proof of performance l1 ; the repeatability between two soundings obtained 15 minutes apart on November 17,1976, as shown in Figure 1. (Beginning in the summer of 1978 new interference filters were unstable, causing inconsistent performance and unsatisfactory results).

The sounding series was analysed for the amplitude and phase of the annual and semiannual cycles as a function of pressure level. Most of the variance was contained in the annual cycle in two regions centered near 10 and Z mb which differ in phase by 1800 • This behavior results from the cycling of the mixing ratio peak between the two regions in phase with the solar declina­tion. The data years were composited and the four equinox- or solstice-

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centered seasonal average ozone distributions are illustrated in Figure 2. The individual soundings were used to compute the odd nitrogen seasonal variations with the photochemical model.

Two other sets of rocket ozone and temperature soundings were used to evaluate the latitudinal variations and the seasonal dependence of the odd oxygen residual and the associated odd nitrogen distributions. These are:

1) a series of shipboard rocket ozone soundings 12 taken between 40 Nand '580 S in 1965 (when industrial CFM abundances were much reduced), and,

2) six rocket ozone soundings from Fort Churchill, Canada (590 N) representing different seasons during 1977 and 1978.

The ozone soundings were all made with ROCOZ instruments; the shipboard series using the Arcas rocket version, the Fort Churchill series using the Super Loki version.

4. Odd Oxygen Residuals and Odd Nitrogen Variations

The partitioning of odd oxygen destruction between the four families of radicals for summer and winter at Wallops Island is shown in Figure 3. The Chapman (Ox) reactions account a maximum of 25% in the upper stratosphere and lower mesosphere and are weakly dependent on season above 2 mb. The seasonal variation increases at the lower altitudes and becomes a factor of two at 10 mb. The odd oxygen losses due to the CIOx cycle have an altitude dependence which is similar to the Chapman cycle and account for an additional 10% at upper stratospheric levels. The odd oxygen balance becomes dominated by HOx reactions in the mesosphere, accounting for over 90% of the losses above 0.4 mb and more than 50% of the losses above 1 mb in both summer and winter. The seasonal variations of water vapor required to maintain steady state odd oxygen are small.

The odd oxygen residual after the above processes are accounted for is then attributed to the NOx cycle. From Figure 3 it is apparent that this cycle dominates below the 3 mb level and accounts for 60 to 70% of the losses in the 5 to 10 mb region. Thus, errors in estimating the CIOx and HOx terms will not seriously degrade the NOx results. Each of the Wallops Island soundings was analysed separately and the resulting seasonal average NOx distributions are shown in Figure 4. Th~ distributions are clustered around 20 ppbv and exhibit very little altitude dependence between 10 and 1.5 mb, the highest level where the computations are justified. The fall and winter mixing ratios are higher than the spring and summer values below 3 mb. The standard errors, plotted for selected levels on summer and winter curves, indicate that the 5 ppmv winter excess is significant at the one-sigma level.

When the only source of stratospheric NOx in 2-D stratospheric models is the oxidatio~ of nitrous oxide virtually no seasonal variation is expected at midlatitudes. As thermospheric NOx is included the average NOx concentrations increase and seasonal variationt near the stratopause of almost a factor of two are expected at high latitudes. 3 The winter excess of computed NOx at Wallops Island in consistent with the model results but the amplitude at this latitude is small. The model results, however, indicate that the NOx should vary little with latitude in the summer months but increase toward the pole in winter if the thermospheric NO is being transported to the stratosphere. Thus, to test for the presence of thermospheric NOx it is necessary to examine higher latitude data for which the seasonal change should be larger.

The five ozone distributions from the shipboard latitudinal survey13 in 1965 are shown in Figure 5 for the range from 10 to 0.4 mb. Two equatorial

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soundings were obtained in early March and three high latitude flights in the polar vortex took place in mid-April, 1965 (mid-fall in the Southern Hemi­sphere). The striking change from the simple equatorial distribution at 30 S and 40 N to the polar peaked distributions is evident. The associated air temperature distributions decrease monotonically with latitude. The NOx distri­butions required to balance the odd oxygen production are shown in Figure 6. At 10 mb the mixing ratio increases only slightly from the equator to high latitudes. At higher altitudes a strong latitudinal variation is evident with a peak at the equator of 25 ppmv near 3 mb, a decrease to a relative minimum of 10 - 12 ppbv at 470 S, followed by an increase to more than 50 ppbv at 580 S near 2 mb. This behavior is clearly consistent with the presence of a polar source of NOx, presumably from the thermosphere.

The final analysis makes use of six rocket soundings at Fort Churchill during 1977 and 1978. The ozone distributions are shown in Figure 7 where the upper panel contains fall and winter data, while the lower panel shows spring and summer flights. The winter distributions have the appearance of the high latitude distributions from the Southern Hemisphere while the summer distribu­tions are like the Wallops Island summer average. The average NOx mixing ratios derived from these data are listed in Table 1.

TABLE 1. AVERAGE NOx AMOUNTS REQUIRED AT FORT CHURCHILL

Date 4/20/77 5/18/77 7/20/77 10/12/77 2/22/78 6/14/78 9/20/78

Average NOx mixing ratio, ppbv 25 20 16 40 55 18 14

All of the soundings except for the October and February flights require from 14 to 25 ppmv of NOx for a balance and are consistent with a small latitudinal gradient during the summer months. The other two soundings are in late fall and winter and require at least a factor of two greater NOx.

Although the number of rocket flights is quite small, the calculations presented here provide strong evidence for a significant source of thermo­spheric NOx for the stratosphere. The absolute amounts of NOx depend on the absolute solar fluxes as well as on absorption cross sections and therefore will likely change as better data are obtained. In particular, oxygen Herzberg cross sections may be lower than the laboratory measurements presently used. This will decrease the NOx requirements but are not likely to change the conclusion regarding the sources of NOx.

References

1. Crutzen, P. J., (1970), The influence of nitrogen oxides,on the atmospheric ozone content, Q. J. Roy. Met •. Soc., ~, 320-327.

2. Crutzen, P. J., (1971), Ozone production rates in oxygen-hydrogen-nitrogen oxide atmosphere, J. Geophys. Res., ~, 7311-7327.

3. Crutzen, P. J., (1979), The role of NO and N02 in the chemistry of the troposphere and stratosphere, Ann. Rev. Earth Planet Sci., 2., 443-472.

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4. World Meteorological Organization, (1982), The stratosphere 1981, Theory and Measurements. WMO Global Ozone Research and Monitoring Project, Report No. 11.

5. Shardanand and A. D. Prasad Rao, (1977), Collision-induced absorption of O2 in the Herzberg continuum, J. Quant. Spectrosc. Radiat. Transfer., ~, 433-439.

6. Ackerman, M., (1971), Ultraviolet solar radiation related to mesospheric processes. in Mesospheric Models and Related Experiments, G. Fiocco, Ed., D. Reidel, 149-159.

7. Allen, M. and J. E. Frederick, (1982), Effective photodissociation cross sections for molecular oxygen and nitric oxide in the Schumann-Runge bands, J. Atmos. Sci., 39, 2066-2075.

8. Gidel, L. T., P. J. Crutzen and J. Fishman, (1983), A two-dimensional photochemical model of the atmosphere, 1, Chlorocarbon emissions and their effect on stratospheric ozone, J. Geophys. Res., 88, 6622-6640.

9. Krueger, A. J. and W. R. McBride, (1968), Rocket cn:onesonde (ROCOZ) -Design and development, NWC TP4512, Naval Weapons Center, China Lake, California.

10. Krueger, A. J., (1984), Inference of photochemical trace gas variations from direct measurements of ozone in the middle atmosphere, PhD Dissertation, Colorado State University.

11. Krueger, A. J., D. U. Wright, and G. M. Foster, (1977), Rocket ozone (ROCOZ) sounding network data, Unpublished report, Wallops Flight Center, Wallops Island, Va., August 1977.

12. Krueger, A. J., (1973), The mean ozone distribution from several series of rocket soundings to 52 km at latitudes from 58S to 64N, Pure Appl. Geophys., 81, 1272-1280.

13. Solomon, S~ P. J. Crutzen, and R. G. Roble, (1982a), Photochemical coupling between the thermosphere and the lower atmosphere. 1. Odd nitrogen from 50 to 120 km, J. Geophys. Res., ~, 7206-7220.

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MEASUREMENTS OF NIGHTTIME N0 3 AND N0 2 IN THE STRATOSPHERE

BY MATRIXISOLATION AND ESR SPECTROSCOPY

M. HELTEN, W.PATZ Institut fUr Chemie 2: Chemie der belasteten Atmosphare

D.H. EHHALT Institut fUr Chemie 3: Atmospharische Chemie der

Kernforschungsanlage JUlich GmbH, P.O. Box 1913, D-5170 JUlich, FRG

Summary

E.P. ROTH Gesamthochschule Essen, FRG

N0 3 and N0 2 mixing ratios at 33-29 km altitude were determined during night­time and early morning. The measurements were made ESR spec"troscopy on samples collected in situ by matrix isolation. The species N0 3 and N0 2 were identified and quantitated by comparison with standard samples collected in the laboratory under typical stratospheric conditions. Results of two balloon flights are presented. The flights were carried out over Southern France (4-4-°N) in September 1983 during the MAP Globus Campaign. The data obtained agree with time dependent model calculations and measurements of other groups.

1. Introduction

N02 and N0 3 in particular, are rapidly photolyzed by solar radiation. Both are exspected to show pronounced diurnal variations in concentration at stratospheric altitudes. Model calculations predict a steep decrease in concentration at sunrise and a steep increase at sunset for both (compare Figures 2 and 3). Therefore, the in situ measurement of N0 2 and N0 3 at sunrise or sunset should provide a sensitive test of the ability of a model to describe the radiation flux at large solar zenith angles. We have attempted to perform such measurements. The first results are re­ported below.

2. Experimental

Our measurement of stratospheric radicals proceeds in two steps. First, the radicals are extracted from ambient an with a cryosampler at liquid nitrogen temper­ature, 70 K, employing a matrix isolation technique. In the second step the para­magnetic radicals in the samples are measured by Electron Spin Resonance Spectros­copy (ESR) in the laboratory. The technique as well as the measurement of N0 2 and H0 2 has been described in some detail by Helten et al (1). Here we briefly discuss the measurement of N0 3 which had not been published before.

As in the case of the other radicals the N0 3 radical is identified and its con­centration calculated by comparison with standard samples. The calibration

samples for N0 3 where prepared by adding 0 3 to a calibrated flow of N0 2

N02 + 0 3 + N03 + O 2,

The resulting N0 3 concentration was calculated with a time dependent chemical mo­del assuming plug flow. The resulting ESR spectrum of N0 3 is shown in Figure 1. For comparison we also show the ESR spectrum of NO" the dominant radical in the lower stratosphere and therefore in our samples. The ESR spectrum of nighttime

Ozone Symposium - Greece 1984 - 196-

stratospheric samples is essentially a composite of these two as shown by the ex­ample given in Figure 1. The NO) signal can be clearly discriminated against the N0 2 signal. For the data presented in the following the total uncertainty for NO) is estimated to be + 40 %, and + 25 % for N0 2 including the uncertainties in sam­pling, measurement -and calibration. The final data are expected to show lower uncer­tainties, especially for NO).

25G H I ,

1ge

-~---N0 3 -SPECTRUM

3. Results

Figure 1: ESR-Spectrum of sample II from flight 9-20-83 and two calibration spectra of N0 2 and NO). Each spectrum is presented as the first derivative of the absorption spec­trum with respect to the magnetic field. The sample was measured at a temperature of 5.4 K with a 1 Gauss modulation amplitude and 5 mW microwave power at 8.839 GHz. D2 0 was used as the matrix.

In September 1983 two balloon flights for cryogenic radical sampling were carried out as part of the European MAp· Globus campaign. The balloons were launched by the CNES from Aire sur l'Adour (430 42' N; 00 15' W) in Southern France. Both balloons reached 33 km altitude. Balloon and gondola were allowed to outgas for 30 minutes before sampling was begun. Samples were collected between 33 km and 15 km altitude during both flights. Here we present the data obtained around sunrise, which was observed between the median sampling altitudes of 33 km and 28 km. Altitude range and day time of each measurement are listed in Table 1.

The measured" N,O) mixing ratios are summarized in Figure 2. They are plotted as a function of the solar zenith angle rather than versus the day time, because on-

'ly the former is an invariant measure of the solar radiation flux. The zenith angle of the geometrical sunrise lies between 960 and 95.20 in the altitude range of our measurements. The measured NO) shows the exspected sudden decrease in mixing ratio. It is not perfectly resolved - for two reasons. Firstly, during dawn and early mOrning the NO) concentration drops below the lower limit of detection so that on­ly upper limits of about 20 ppt can be given. Secondly, the time resolution is limit­ed. The sampling time is one hour, and although the samples were collected in an over lapping manner, the time resolution is not better than 30 minutes corresponding to a change of 50 in zenith angle. Nevertheless the measurements clearly plac~ the

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Table 1: Daytime and altitude range of the samples collected during the flights from 9-9-83 (a) and 9-20-83. The mixing ratios of 0 3 , N0 2 and N0 3 are also given.

Time Altitude [UTJ [kmJ

8.10-9.05(a) 32.1-33.0(a)

3.30-4.30 32.5-32.9 4.08-5.10 32.6-32.9 4.31-5.26 32.6 5.11-6.16 30.8-32.6 6.00-6.52 28.9-31.7 6.33-730 26.1-29.7

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SOLAR ZENITH ANGLE

N0 2 N0 3 0 3

[ppbJ [pptJ [ppm]

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12

30

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Figure 2: The mixing ratio of N0 3 as a func­tion of the solar zenith angle. Ver­tical bars give the 1 a error of the measurement; vertical arrows indi­cate the lower limit of detection. The horizontal bars represent the sampling time, roughly one hour. The indicated daytime scale refers to the flight date 9-20-83. The data were obtained over Southern France.

zenith angle, at which the decrease begins, at around 100°, i.e. before the geometric sunrise at 96°.

For comparison Figure 2 also displays the variation of N0 3 around sunrise pre­dicted by a I-D time dependent model. The calculations were carried out for the actual season, latitude and 0 3 mixing ratio which was around 6.6 ppm (see Table 1).

The N0 2 measurements are summarized in Figure 3. They also show the ex­pected decrease in concentration. However, the decrease in N0 2 appears to begin later than that for N0 3 at a zenith angle of 90°. The amplitude of the measured decrease could be somewhat· exaggerated because the day light samples were taken at lower altitudes, i.e. slightly lower average N0 2 mixing ratios.

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TIME (UT) o 3 5 9 12

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4. Discussion

Figure 3: The mixing ratio of NO z as a func­tion of the solar zenith angle. Ver­tical bars give the I a error of the measurement; horizontal bars repre­sent the sampling time. The indicat­ed daytime refers to the flight date 9-20-83. The data were obtained over Southern France.

Our nighttime measurements of NO z and NO) can be compared with earlier spectroscopic measurements of NO z and NO) profiles in the stratosphere by Naudet et al and Rigaud et al (2), (3), (4), (5), (6). Their results for 30 km to 35 km altitude are also shown in Figure 2 and 3. They agree well with our nighttime data.

The NO z measurements also agree reasonably well with the current model pre­dictions shown in Figure 3. This is not quite true for NO). In this case the model predicts nighttime NO) mixing ratios of about a factor of 3 lower than the meas­ured values, despite the fact that the model NO z mixing ratios are slightly higher than the measured nighttime concentrations. Naudet et al (2) argued from a similar finding in the lower stratosphere that the rate constant for the formation of NzO 5

from NO z and NO) may be lower than generally assumed. In addition the model places the zenith angle of the beginning NO) decrease

at 96° or less as compared to the 100° observed. Other, published model calculations of the diurnal cycle of stratospheric NO) are even worse in this respect (7), (8). They predicted the NO) decrease to occur at the same time, and thus the same zenith angle, as the NO z decrease. Clearly, the experimental results contradict this. They indicate that the photolysis of NO) begins to be Significant about an hour earlier than the photolysis of NO z' This is quite plausible, since NO) photolysis pro­ceeds in the visible at a high crossection whereas NO z photolysis takes place at wavelength below 410 nm at lower crossections. Both lower crossection and the delayed onset of solar UV radiation due to stronger absorption and scattering in the lower layers of the atmosphere combine to keep the early NO z photolysis low. The apparent presunrise NO) photolysis is more difficult to accept. More measurements with higher resolution are planned to test this point.

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Acknowledgement

We would like to thank the balloon launch facility of the CNES for their out­standing support. This work was supported by a grant, FKW 25, of the Bundesmini­sterium fUr Forschung und Technologie.

REFERENCES

1. HEL TEN, M., PATZ, W., TRAINER, M., FARK, H., KLEIN, E., and EHHALT, D.H. (J984). Measurements of Stratospheric H0 2 and N0 2 by Matrix Isolation and ESR Spectroscopy. J. of Atm. Chern., in press

2. NAUDET, J.P., HUGUENIN, D., RIGAUD, P., and CARIOLLE, D. (J981). Stratospheric Observations of NO) and its Experimental and Theoretical Distri­bution between 20 and 40 km. Planet. Space Sci. ~ 707-712

3. RIGAUD, P., NAUDET, J.P., and HUGUENIN, D. (J983). Simultaneous Measure­ments of Vertical Distributions of Stratospheric NO) and 0) at Different Periods of the Night. J. Geophys. Res. ~ 1463-1467

4. RIGAUD, P., NAUDET, J.P., and HUGUENIN, D. (1977). Etude de la repartition verticale de N0 2 stratospherique durant la nuit. C.R. Acad. Sci., 284, Serie B, 331-334

5. NAUDET, J.P., RIGAUD, P., and HUGUENIN, D. (1980). Stratospheric N0 2 at Night from Stellar Spectra in the 440 nm Region. Geophys. Res. Letters 0 701-703

6. NAUDET, J.P., RIGAUD, P., and HUGUENIN, D. (1984). Stratospheric N0 2 at Night from Balloons. J. Geophys. Res ~ 2583-2587

7. FABIAN, P., PYLE, J.A., and WELLS, R.J. (J 982). Diurnal Variations of Minor Constituents in the Stratosphere Modeled as a Function of Latitude and Season. J. Geophys. Res. Eo 4981-5000

8. LOGAN, J.A., PRATHER, M.J., WOFSY, S.C., and McELROY, M.B. (1978). Atmospheric chemistry: response to human influence. Phil. Trans. Roy. Soc., 290, 187-234

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v ARIABll.lTE TEMPORELLE DO NO]. S'lRATOSPHERIQUE

J . P. NAUDET, P. RIGAUD et D. HUGUENIN* Laboratoire de Physique et Chimie de l'Environnement

3A Avenue de la Recherche Scientifique, 45045 ORLEANS Cedex, France -::- Observatoire de Geneve, CH - 1290 SAUVERNY, Switzerland

Quatre mesures de la repartition verticale du NO, stratospherique ont ete effectuees par spectrometrie d'absorption ~isible a partir de ballons stratospheriques entre septembre 1980 et septembre 1983. La comparaison des resultats mont rent que les concentrations observees au printemps sont superieures a celles de l'automne.

1. Introduction

Le trioxyde d' azote N03 est produit dans la stratosphere par la reaction de I' ozone avec N02 . II se combine avec N02 pour former N205 considere conme etant I' une aes especes "reservoir" des oxydes d' azote. Ces reactions font de NO un constituant clef de la chimie des oxydes d'azote dans la stratosphe+e. Photodissocle des Ie lever du Soleil, il n'a pu etre observe que pendant la nuit.

La premiere detection de NO a ete faite a partir du sol par Noxon et ses collaborateurs (1) qui ont3 observe la forte bande d' absorption a 662 nm de longueur d'onde sur des spectres de la lune. II en ont deduit Ie nombre de molecules contenues dans une colonne verticale d' atmosphere. L'interpretation de cette observation a ete debattue dans plusieurs articles (2,3,4,5).

La repartition verticale de la concentration du NOl stratospherique a ete deduite d'observations d'une etoile ou d'une planete proche de 1 'horizon effectuees a l'aide d'un spectrophotometre embarque sous ballon stratospherique dans un domaine spectral incluant la bande a 662 nm. Quatre vols de ballon ont ete effectues. Les resultats des deux premiers ont deja ete presentes (6,7). Les vols suivants effectues respectivement en mai 1982 et septembre 1983 sont rapporte lCl. La comparaison de I' ensemble des resul tats permet d' ebaucher une variation sai sonniere du N03 stratospherique.

2. Methode exp§rimentale et analyse des donnees

L'instrument et la procedure d'analyse des donnees de fayon detaillee (7).

Rappelons brievement l'intervalle spectral 647 finale de 1 nm. II est

Ozone Symposium - Greece 1984

que l'instrument est un spectrometre balayant - 672 nm par pas de 2 A avec une resolution embarque sur une nacelle stabilisee qui Ie

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maintient pointe vers la source de lumiere (etoile ou planete) au gre de la trajectoire du ballon. En cours de vol, des spectres sont enregistres pour des distances zenithales de l'astre symetriques de 90°.

Chacun des spectres doit etre rapporte a un spectre de reference hors atmosphere pour obtenir Ie spectre de la transmission atmospherique Ie long du parcours optique correspondant. En pratique, cette reference est donnee par Ie spectre Ie moins attenue mesure depuis la nacelle. Dans Ie domaine spectral etudie, I ' attenuation de la lumiere est due a I 'absorption par I' ozone et par NO , a la diffusion moleculaire et a la diffusion par les aerosols. Un spe2tre synthetique prenant en compte ces attenuations est compare a chaque spectre experimental. La contribution de la diffusion moleculaire est calculee ; les quantites d' ozone et de NO '< integrees Ie long du parcours optique ainsi que I' epaisseur optique du~ aux aerosols sont adaptees au sens des moindres carres de fayon a minimiser I' ecart entre spectre synthetique et spectre experimental. On obtient une courbe de la quantite integree de NO en fonction de la distance zenithale. Cette courbe est inversee par Dhe methode iterative pour obtenir la distribution verticale de la concentration de N03 en fonction de l'altitude.

L ' attenuation par diffusion moleculaire a ete calculee d' apres les masses d'air des tables de Link et Neuzil (8) et les coefficients donnes par Frohlich et Shaw ( 9 ). Recemment, Nicolet ( 10) a rapporte que ces coefficients etaient sous-estimes d' environ 4 %. Nous avons verifie que cette erreur avait un influence negligeable sur la determination des quantites de N01 . Pa~mi les differentes valeurs des sections efficaces de l'ozone disponibles dans la litterature, celles recommandees par Ackerman (11) se sont revelees les plus aptes a rendre compte de nos observations. Pour NO, ' nous aviorts choisi Ie sections efficaces publiees par Graham et Johnstoti (12) corrigees d'un facteur 0,7 pour tenir compte de la determination de Mitchell et al (13). Mais des etudes plus recentes (14,15) ont conclu a des valeurs superieures d'environ 30 % a celles utilisees dans Ie present travail. Cet ecart conduirait a une diminution du meme ordre de grandeur des concentrations de NO. Pour conserver I 'homogeneite de nos resultats cette derniere incertitude n' a pas ete introduite.

3. ResuJtats

Date Source Heure T. U.;' Altitude (km)

12709780 Venus 1h 50 38.7

18709781 Arcturus 21h 42 38.7

03705782 Venus 3h 20 39.5

14709783 Venus 3h 29 38.7

-::- Passage de la source a la distance zenithale z 90°

TABLEAU I : Description des vols de ballon

- 202-

Les caracteristiques des vols de ballon effectues sont resumees dans Ie tableau I. L'altitude de vol etait comprise entre 38 et 40 km. La source de lumiere observee etait soit la planete Venus, soit l'etoile Arcturus. Sur quatre vols, trois ont ete effectues pendant la saison d'automne et un seul au printemps. Les heuresd'observation etaient suffisament eloignees du coucher et du lever du Soleil pour que la concentration de NO, puissent etre consideree a l'etat stationnaire en accord avec l~ theorie photochimique.

40 ,..---.-- ---7 \ ' I I I I ,\: ... J. .... , I

I ~ . , /'. ..., I'·' :.'i. 1\ • I I : I \ I

: I Y.. 1 I '

I I

E .:::i.

Q)

"U 30 FALL ::J

/ ---12-9-80

0 I ········18-9-8t . I ----14 -9-83 . I

I I

I

I I SPRING . I -3-5-82 I

I I

I , I

, I .

I . I .

20 I .... ___ 1

o FIGURE 1 Profils verticaux de N03

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La figure donnent, pour chaque vol de baIlon, Ie profil de la concentration de NO_" en fonction de 11 altitude. La largeur de chaque enveloppe traduit XI incertitude sur la determination des quantites integrees de NO et sur Ie processus d I inversion. L I incertitude sur les sections effica~es nlest pas prise en compte. De par son caractere systematique, cette derniere incertitude deplacerait les courbes de la figure 1 suivant l'axe des concentrations d'une quantite que lIon peut estimer a 30 % en se basant sur la dispersion des mesures des sections efficaces de NO en laboratoire.

En dessous dJ 30 km d'altitude, les profils semblent indiscernables les uns des autres compte tenu de leur incertitude. Au dessus, les profils automnaux restent comparables entre eux tandis que Ie profil printanier indique une croissance rapide de la concentration de NO" avec 1 I altitude. Au dessus de 35 km, les concentrations mesurees e~ Mai deviennent sensiblement superieures a celles de septembre.

En integrant les profils mesures en Septembre 1980, mai 1982 et Septembre 1983, on obtient Ie nombre de molecules de NO_l contenues dans une colonne verticale d'atmosphere comprise entre 22 et J9 km d'altitude. Le result at (fig. 2) est a comparer avec celui de Noxon (16)1~ui a estime qU~2le contenu total d'une colonne vertica1J atteignait 1~2 molecules. cm au printemps et ne depassait pas 4 x 10 molecules. cm en ete. Les valeurs minimums sont en accord tandis que notre valeur printaniere est sensiblement inferieure a celIe de Noxon. II faut cependant noter que notre estimation s I arrete a 39 km d I altitude alors que profil mesure en mai 1982 indique de toute evidence que Ie maximun de concentration se trouve au dessus de la nacelle. En conclusion, on retiendra que Ie present travail parait corroborer, au moins qualitativement, Ie resultat de Noxon sur 1 I existence d'une variation saisonniere de N03 .

10

1 FIGURE 2

column 22-39 km • 12-9-80 • 14-9-83 A 3 -5-82

5 10 MONTH Colonne verlica1e de NO. entre 22 et 39 Ian d'altitude_

Tendance sai~nniere_

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REFERENCES

1. NOXON J.F., NORTON R.B. et HENDERSON W.R (1978). Observation of atmospheric N03 . Geophys. Res. Lett. 2' 675-678

2. HERMAN J.R. (1979). The problem of nighttime stratospheric NO 3. J. Geophys. Res. 84, 6336-6338

3. NOXON J.F., NORTON R.B. et HENDERSON W.R. (1980). Conment on "The problem of nighttime stratospheric NO" par J .R. Herman. J. Geophys. Res. 85, 4556-4557, 1980 3

4. HERMAN J .R. (1980) -Reply.J.Geophys. Res. 85, 4558-4559

5. GELINAS R.J. et VAJK J~. (1981). Diurnal analysis of local variabilities in atmospheric N03 , J. Geophys. Res. 86, 7369-7377

6. NAUDET J.P., HUGUENIN D., RIGAUD P. et CARIOLLE D. (1981) Stratospheric observations of N?, and its experimental and theoretical distribution between 20 and 40 kffi. Planet Space Sci. 29, 707-712

7. RIGAUD P., NAUDET J.P. et HUGUENIN D. (1983) -Simultaneous measurements of vertical distributions of stratospheric NO, and 03 at different periods of the night. J. Geophys. Res. 88, 14b3-1467

8. LINK F. et NEUZIL L. (1969). Tables des trajectoires lumineuses dans I' atmosphere terrestre. Herman, Paris

9. FROHLICH C. et SHAW G.E. (1980) New determinatiol1 of Rayleigh scattering in the terrestrial atmosphere. Appl. Opt. 19, 1773-1775

10. NICOLET M. (1984) -On the molecular scattering in the terrestrial atmosphere an empirical formula for its calculation in the homosphere. A paraitre dans Planet. Space. Sc 32

11. ACKERMAN M. (1971) -Ultraviolet solar radiation related to mesospheric processes, in Mesospheric models and Related Experiments, Ed. G. Fiocco, Reidel Pub. Cy, Dordrecht - Holland, 149-159

12. GRAHAM R.A. et JOHNSTON H.S. (1978) The photochemistry of N03 and the kinetics of the N205-03 system. J. Phys. chern. 82, 254-268

13. MITCHELL D.~ WAYNE R.P., ALLEN P.J., HARRISON R.P. et TWIN R.J. (1980 ) Kinetics and photochemistry of NO J. Chern. Soc. Faraday Trans. 2, 7$, 785-793

14. MARINELLI W.J., SWANSON D.M. et JOHNSTON H.S. (1982) Absorption cross sections and line shape for the N03 (0 - 0) band J. Chern. Phys. 76, 2864-2870

15. RAVISHANKARA A.~ et WINE P.H. (1983) Absorption cross sections for N03 between 565 et 673 nm. Chern. Phys. Lett. 101, 73-78

16. World Meteorological Organisation. The stratosphere 1981 : theory and measurements. Rep. 11 (1981), Geneva, Switzerland

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QUANTITATIVE OBSERVATIONS OF STRATOSPHERIC CHLORINE MONOXIDE AS A

FUNCTION OF LATITUDE AND SEASON DURING THE PERIOD 1980 - 1983

R.L. de Zafra, A. Parrish, P.M. Solomon, and J.W. Barrett State University of New York, Stony Brook, N.Y. 11794, USA

Summary: Results are presented for the CiO column density between -30-35 km, and the mixing ratio at 38 km, from data taken during the period January 1980 to Dec. 1983. These data were taken from three different lo­cations, at 420 , 320 and 200 N. We contrast the limited variation observed in this data set with the substantially large variations observed by the in-situ resonance fluorescence observations of Anderson, et a1.

Chlorine monoxide (CtO) is directly implicated in the catalytic des­truction of ozone by atomic chlorine via the reactions

Ct + 03 + CtO + O2 C~O + 0 + C~ + O2

Thus measurement of the quantitative presence and vertical distribution of C~O furnishes a good indicator of the degree of 03 conversion by free chlo­rine arising from both natural and anthropogenic sources.

Since 1980, we have been making ground-based measurements of chlorine monoxide by observations of rotational emission lines at 204 and 278 GHz, arising from the J=11/2 + 9/2 and J=15/2 + 13/2 transitions, respectively (1,2). A mm-wave heterodyne receiver is employed for this work, along with a 256 channel fi1terbank spectromoeter, with a uniform resolution of 1 MHz/ channel. With this instrumentation, pressure broadened emission line shapes, as well as total intensities, may be measured with a high degree of resolution. -3

The extreme weakness of stratospheric trace-gas emission lines (~10

the intensity of medium to stron~ 03 emission lines) yields raw signa1/ noise ratios on the order of 10- :1, requiring rather long integration times to extract a good signal from background noise. During the course of the measurements described here, we have made substantial and continuous improvements in system performance, so that data of good quality have be­come available covering shorter and shorter averaged time-spans. These im­provements consist of changing from our original room-temperature receiver to one which is cryogenically cooled, moving observations upward in fre­quency to the 278 GHz transition, which is nearly three times stronger than that at 204 GHz, and moving our observational site to the peak of Mauna Kea, Hawaii, at an altitude of 14,000 ft. (4300 m). This location has excep­tionally low water vapor overhead on an essentially year-round basis. Since water vapor is responsible for the predominant atmospheric opacity to mm-wave radiation, this location has freed us from previous seasonal re­strictions on observations, and also improved the quality of data output.

Aside from the observations to be described here, the only other sub­s';:antia1 body of measurements on C~O is the series of in-situ resonance­fluorescence measurements made by J. Anderson and co-workers. The current­ly published data cover 11 flights made between 1976 and 1979, with measure­ments generally available over the altitude range 25-40 km. These data are marked by a wide degree of variability, both in vertical profile in total column density over the range of observations (3). All data were taken over brief intervals near solar noon, from a latitude of -320 N, and

Ozone Symposium - Greece 1984 - 206-

calibration error is thougttto be ~ 20%. Two observations, in July 1976 and July 1977, stand out as anomalies - both being an order of magnitude or more higher in C~O content at nearly all altitudes than the average of all the other ~easurements. No satisfactory explanation has been offered for the discrepant data, although the 1977 measurement in particular would re­quire more C~ present in C~O than is thought to be present in all strato­spheric forms, and is thus aloost certainly incorrect. Setting aside the July 1976 and '77 measurements, the remainder still show a variation of ~500 % in C~O between extremes over the entire altitude range 25-40 km, with no particular seasonal pattern being evident. The time scale of the apparent variability is not defined by the existent measurements, except that it must be less than one month, the shortest time span between obser­vations.

Our own data is in marked contrast to these widely varying results. Observation of the pressure-broadened line shape gives a measure of the vertical distribution (with accuracy depending on SiN ratio of the data) and the total area under the observed signal gives a measure of the inte­grated column density above ~32 km. Our measurements indicate relatively little variation in column density with latitude, for observations taken at 420 , 320 , and 200 N, and a similarly small change in column density measured at various times of year at 200 N. Moderate variations in vertical profile are more difficult to measure given the average SIN ratio of our data; the data is, however, consistent with the average profile of in-situ balloon measurements and that of current models, e.g. by Sze and Ko (4) and Froidevaux (5) after multiplication by a relatively small fixed scaling

140

120

100

80

60

40

20

0 278500 278600 278700 278600 278700

Fig. 1 Left: Data from Anderson and co-workers (see Ref. 3) converted from vertical profiles into equivalent pressure-broadened spectral emission lines. Abscissa = frequency in MHz, ordinate - intensity in milliKelvin. Data covers balloon flights from 1976 through 1979. The line of greatest intensity is for the data of July 14, 1977 and the next highest is for July 28, 1976. All intensities shown here are somewhat lower than true in­tensities would be, because no allowance has been made for C~O above 40 km, where the balloon data cuts off.

Right: Data from ground-based C~O measurements reported here, covering ob­servations from Massachusetts (Winter, 1980. '81), Arizona (May 1981), and Hawaii (October, Dec. 1982, June 1983,. Dec. 1983). Intensities shown in­clude contribution from all C~O above - 30 km.

-207-

factor to the mixing ratios at all altitudes. In Figure 1, we contrast the range of line intensity measured by us

with that which we would expect to obtain from the results of Anderson, et al. For the latter, we have converted the vertical concentration profiles into equivalent pressure-broadened emission line intensities.

We have studied the calibration accuracy of our observed line inten­sities in some detail (6) and believe it to be ~12% under most observing conditions. This conclusion has been independently checked by observing various 03 emission line intensities which are typically within +10% of that expected (7). Table I presents a summary of this data, alo~g with comparable values obtained by averaging the data of Anderson, et al. and from a recent theoretical model by Sze and Ko.

Our own results can be encompassed by a mean column density of (0.9 + 0.2) x 1014 cm-2 , ie. by variations of ~ 20% about the mean. Although the values listed encompass time durations ranging from over a month to less than a week, depending on equipment sensitivity and observing conditions, under virtually all of our observing conditions (particularly at 200 N) a factor of 5 variation, as seen by Anderson, et al., would have been evident within one to two days of observation.

TABLE I

AVERAGE CiO COLUMN DENSITIES AND MIXING RATIOSt

SITE PERIOD OBSERVED

LINE FREQ. (GHz)

Mass. Jan-Feb 1980 204

Mass. Feb 1981 278

Arizona May 1981 (day) 278 (night)

Hawaii Oct (12m-4pm)'82 278

Texas

Oct (night) '82 278 Dec (12m-4pm) '82 278 Dec (night) '82 278 June (12m-4pm) '83 278 Dec (12m-4pm) '83 278

Anderson et. al. (noon) 7 flight average excluding 7/28/76 and 7/14/77

Sze & Ko Model using JPL 82-57 "fast" chemistry for CiON02, 200 N latitude, 2.1 ppb total Ci

COLUMN DENS.

(xl014 cm-2 (30 to 51 Ian)

0.7 ± .2

1.1 + .15 .2

0.7 + .2 .15 ± .04

0.70 + .15 0.1 "+ .02 0.80 "+ .15 0.14 "+ .02 0.96 ± .2 0.7 ± .2

** 1.13

.92

MIXING RATIO

AT 38 KM (xlO-9)

0.43 ± .12

0.66 + .08 .12

0.43 ± .12

0.41 ± .1

0.47 ± .1

0.58 + .1 0.42 ± .1

.73

.55

tAll data have been evaluated by least square fitting of spectral line shape derived from Sze and Ko, Geophys. Res. Letters 10, 341 (1983) using JPL 82-57 "fast" CtON02 chemistry, to obtain values quoted. Mixing ratio at 38 km is not very model sensitive however.

xx 14 -2 Column density from 30-40 Ian is 0.8 x 10 cm We have extrapolated above 40 lan, following Sze and Ko vertical fuixing ratio profile, scaled to fi' Anderson over 36-40 Ian region.

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We have not attempted to correct for the predicted steady increase in C£O concentration as a function of time, either in our own data, or in com­paring with the earlier data of Anderson, et al. The predicted annual increase in C£O concentration is ~5-7%, linearly proportional to the in­crease in total chlorine as previously released CFMs diffuse upward into the stratosphere. The 15-20% increase over the time spans encompassed by either our data or that of Anderson, et al., or in the mean interval be­tween data sets, should be detectable and should be borne in mind when com­paring data sets, but is largely overshadowed by the variations between individual obsp.rvations and by calibration uncertainties etc. in the current data.

References

1. A. Parrish, R.L. de Zafra, P.M. Solomon, J.W. Barrett and E.R. Carlson, Science, 211, 1158 (1981).

2. P.M. Solomon, R.L. de Zafra, A. Parrish, and J.W. Barrett, Science 224, 1210 (1984).

3. E.M. Weinstock, M.J. Phillips, and J.G. Anderson, J. Geophys. Res. 86, 7273 (1981); see also, "Causes and Effects of Stratospheric Ozone Reduction: an Update", National Academy of Sciences, Nat. Acad. Press, Washington D.C. 1982. In the latter, this data is presented on pp 212-214 in terms of con­centration profiles, in which vertical variation is particularly evident.

4. N.D. Sze and M. Ko, Rersonal communication. The basic model and chemis­try used is described in Geophys. Res. Lett. 10, 341 (1983).

5. L. Froidevaux, thesis, California Institute of Technology (1983).

6. A. Parrish, R.L. de Zafra, J.W. Barrett, and P.M. Solomon, to be publish­ed.

7. Expected line intensities for 03 are determined from the known transi­tion strengths and the expected vertical distribution from the U.S. Stan­dard Atmosphere or other appropriate profiles. Our measurements are pro­gressively insensitive to 03 below ~ 28 km, where most observed short-term fluctuations occur for ozone.

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TRACE SPECIES IN THE STRATOSPHERE PRECISION AND VARIABILITY

C. Alamichel o and N. Louisnard oo

o Laboratoire de Photophysique moleculaire, Bat. 213, Universite Paris-Sud, 91405 Orsay, FRANCE.

00 Office National d' Etudes et de Recherches Aerospatiales BP 72, 92322 Chatillon CEDEX, FRANCE.

Infrared absorption spectroscopy by solar occultation from a balloon platform is used to measure the concentration profiles of minor constituents in the stratosphere. The instru­ment is a grating and grille spectrometer scanning narrow spec­tral intervals, in different orders of the grating in a selected sequence for sunset or sunrise periods. The dispersion of the results obtained by various techniques underlines the crucial question of the precision. The comparison with previous results, obtained with the same instrument, points out a natural variabi­lity, while the comparison with other experiments is made confu­sed by the difference in the techniques as well a~ in the analy­sis method. Intercomparison campaigns help to analyse these dif­ferences eliminating the natural variability, and also help to improve the preci~ion of each instrument by a better choice of the parameters.

After the participation to the BIC campaign (Palestine, Texas, june 83) a comparison is now made between different NO, N02, and 03 profiles obtained with the grille spectrometer at sunset (sept 83, june 83) and sunrise (may 82).

The data analysis has been automated through a spectral program, fitting observed and calculated spectra. A multilayered atmosphere model is used with an initial arbitrary profile for each species. To avoid the noise propagating downwards like in the onion peeling method, the procedure uses the Mill's method (1), starting from the lowest to the highest level, and so, gi­ving preference to the data corresponding to the strongest ab­sorptions. An iterative process allows quick convergence between observed and calculated spectra. Implemented at ONERA by G. Ei­chen and J. Laurent (2) the method has been recently tested on atmospheric spectra in order to evaluate the sensitivity to dif­ferent parameters: choice of initial profiles, atmospheric splitting into layers, instrumental function.

Some examples will be shown. Results ------The figures 1,2,3 give the final results for three typical species in the stratosphere NO, N02 and 03 closely photochemi­cally coupled.

The NO 1982 profile has been reevaluated using the spectral feature located at 1846.57 cm-t, analysed for BIC, which appeared a better choice than the one previously analysed (uncontaminated by 03). The sunset and sunrise profiles exhibit exactly the same variation with a strong decrease below 22 km due to decreasing sun intensity and a ratio of about two increasing to three near 38 km.

Ozone Symposium - Greece 1984 - 210-

The N02 and 03 profiles have not been reevaluated. A large varia­bility is observed in the lower part of the profiles but the same tendancy appears at high altitude where the photochemistry is the most important: At 38 km,

convergence of the sunset profiles, - clearly lower values for the sunrise than for the sunset profiles.

REFERENCES

[1] Rept nO 013624 Rael Univ. of Michigan, Ann Arbor, 1977.

[2] Communication to the COSPAR Meeting Innsbrlick, 1978.

Altitude (km) 38

30

~~~.'~' ____________ ~l~O~,. ____________ M_i,_m~;o~~~~'_iO

Ai litudo I~ml 38

~··- .. 44·N Surv'lse Mav 1982 _i.- 44"N Sun!fH Sepl. 19BO - •• : 3'·N -.., ..b18 1983

30

IN021

MiJling rsllo 2~O~·~ .. ----------L-~1~0~_·---------------'0L_--.

Altltud. (kml 38

30

. -· .. ~44& N &.nrtse Mav 19a2

- 44· N Suuel Sept. 1980 .......... 31· N Sooset ..\.ne 1983

2~O~·~'------------~1~OL._.~~~L-------~~

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TRACE CONSTITUENTS HEASUREHENT~ DEDUCED FRON SPECTROMETRIC OBSERVATIONS ONBOARD SPACELAB

by J. Laurent*, M.P. Lemaitre*, J. Besson*, A. Girard*. C. Lippens**, C. Muller**, J. Vercheval**, H. Ackerman**, *Office National d'Etudes et de Recherches Aerospatiales,

BP 72, 92322 Chatillon Cedex, FRANCE. *Belgium Institute for Space Aeronomy,

B1l80 Brussels, BELGIUH.

Introduction

The main goal of the grille spectrometer experiment [1] operated during the Spacelab One Mission was to measure trace constituents in the low thermosphere and mesophere [2]. The use of the sun as a source during sunset or sunrise leads to a large signal to noise ratio and allows the detection of very low concentrations of absorbing molecules due to the limb scanning geometry.

These first re~ults use the orbit parameters available just after the flight and have to be confirmed later. About 6000 spectra have been re­corded, concerning ten species C02, CO, 03, H20, CH4, NO, N02, N20, HF and HC!.

Water vapor

The results presented here below are deduced from spectra recorded on the December 2th, 1983, during sunset, near 33°N and 90 0 E. The spectral range, from 3815 to 3825 cm- l includes several H20 lines with dif­ferent strengths and energy levels. The retrieval process is still running in order to achieve the agreement between observed and computed spectra for the set of observed H20 lines along the whole altitude range.

Figure 1 shows three examples of comparison between experimental and calculated spectra using the H20 vertical profile, figure 2, which gives the best agreement between observed and computed spectra for the strongest line at 3816,09 cm-1 •

The following features can be assessed on the water vapor mixing ratio versus the altitude: a tendancy to increase from 30 to 50 Km and an abrupt decrease from 70 to 80 km.

Carbon monoxide

It is known that carbon dioxide must be strongly photodissociated in the upper mesophere and thermosphere by solar UV radiation [3]. Few ground based mesospheric CO measurements have been published [4,5], they all show a large mixing ratio increase from the stratopause to the mesopause.

Several absorption runs provided data on CO during the Spacelab One Mission. The results presented here are issued from spectra recorded on the November 29th, 1983, at a latitude of 44° North and a longitude of 112° West during sunset.

Ozone Symposium - Greece 1984 - 212-

175 spectra decreasing from 2124 cm- 1 .

were 250

recorded during kIn to 20 kIn

this sunset for in the spectral

tangent heights range 2118 to

The vertical profile of CO was adjusted so that the calculated spectra fit at best the recorded spectra for each tangent height. The simulation of the solar CO lines was achieved in agreement with Rinsland et al [6] using the Hinnaert formula [7] instead of the Beer's law, the value of the saturation constant Rc was chosen at 13% of saturation. The line strengths of the solar lines are those calculated by Seals [8] at 4500 K. The line shape is very similar to the one calculated by Muller and Sauval [ 9] •

The figure 3 shows the results of the comparison between calculated and experimental spectra for three tangent heights. The figure 4 shows the CO vertical profile deduced from the whole set of spectra.

Conclusion

The examples of data given in this paper demonstrate that the record of spectral absorption features from Space lab leads to a set of new data concerning the behavior of trace constituents through the stratosphere, the mesosphere and the low thermosphere.

However, the retrieval process in such a large range of al ti tude requires a complete investigation of the atmospheric absorption processes and may need, as previous observations from rockets and satellites have indicated, to depart from the standard convolution of a Doppler and Lorentz profile. The coherence in the results deduced from several spectral lines is sensitive to the temperature profile and, possibly, to a partial break­down of the thermodynamical equilibrium.

References

[1] BESSON, J., ACKERl'lAN, M., GIRARD, A., and FRIHOUT, D., Spectrometre pour la premiere mission Spacelab, Communication au 28th Congres In­ternational d'Astronautique, Dubrovnik, Oct, 1-8, 1978.

[2] }IDLLER, C., and LAURENT, J., Scientific program for the Spacelab ES013 grille spectrometer. Bull. Acad. Sciences, 5e serie. Tome 68, 1982-6, Bruxelles.

[3] NICOLET, H., Aeronomical aspects of the mesopheric photodissociation: processes resulting from the H lyman alpha line, Planet. Space Sci., in press, 1984.

[4] WATERS, J.W., WILSON, W.J., and SHU1ABUKURS, F.r., Nicrowave measure­ments of mesopheric carbon monoxide, Science, 191, 1174-1175, 1976.

[5] GOLDSHITH, P.F., LITVAK, H.M., PLAHBECK, R.L., and WILLIAHS, D.R.H., Carbon monoxide mixing ratio in the mesophere derived from ground based microwave measurements, J. Geophys. Res., 84, 416-418, 1979.

[6] RINSLAND, C.P., GOLDHAN, A., MURCRAY, F.J., MURCRAY, D.G., SMITH, M.A.H., SEALS Jr, R.K., LARSEN, J.C., and RINSLAND, P'.L., Stra­tospheric N20 mixing ratio profile from high resolution balloon­borne solar absorption spectra and laboratory spectra near 1880 cm-1 , Appl. Opt., vol. 21, nO 23, 4351-4355, 1982.

[7] MINNAERT, M., z. Astrophys., 10, 40, 1935. [8] SEALS, R.K., Private communication. [9] HULLER, C. and SAUVAL, A.J., The CO fundamental bands in the solar

spectrum, Astron. Astrophys., 39, 445-451, 1975.

- 213-

Tranamlaalon ( .. ) Tangenl height

(km)

AII~ude (km)

90

80

70

60

100 .f 71 __ ~~ ~~~" _____ .... a _________ _ .. __ ... ~ .. , _ _ . ~ • • ,'. _____ _____ ____ _

40

20

Experlment.1 epec1,um Calcul'ted apectrum

(ohifted)

0 ~3~8~1~1--~38~1~8~~3~8-2~0--~3-8-2-2----38-2-4~ Wavenumber (em-')

Figure 1

Comparison between experimental and calculated water absorption spectra for three tangent heights: 75.51 and 33 km.

.......... • . • . 3816.092

~ ····3819.906

~ _.- 3824.281 . ~ .~

-- 3818.341

"" .........

~ ~ ~~ """....:.. . -............

'-........ ........ "-..,

~" ~

-.............. ~~ 60

40

~ . .

30

~ .

20 10' 10' 10'· 10" 10"

Number density (em - ')

Figure 2

Water vapor number densities versus altitude retrieved using three lines (3819.905, 3824.281, 3818.340) in We regions where their curves of growth are quasi linear and the line 3816.092 from 80 to 30 km.

- 214-

Transmiaslon ( .. ) 100

100

80

80

40

20

-- E. _ _ tlt opect,um ---- Calculated ~trc.wn

(shilled)

:1~1=9--~2~1~2~0~-2~12~1~~2~1~22~~2-1-2-3---2-J124 Wavenumber (cnr-')

Figure 3

Comparison between experimental and calculated spectra in the CO spectral region for three tangent heights: 116.92 and 62 km. Arrows indicate the location of the main telluric

CO absorption lines.

Altitude ,..------~rT------"'T"""------r--------,

(km)

130~~------_4~~r_----_+----------~--------~

120 ~----~~--~~~~~--+_----------+_--------~

110 r-~~------r_~~_.~--~~~------+_--------__1

100 ~--------~~--------~~--~----~~~------~

90 r-------~~--~----~~--~~~~~------~~

80 r----------r----~~--+_~--~~_+----~~~

70 ~----------~----------+_~~~----+_~~----~

80~--------~~--------~~----~~~~------~ 10' 10' 10' 10'0

Number density (em"')

Figure 4

Carbon monoxide number density versus altitude. The nearly parallel lines represent constant volume mixing ratio from 10-10 to 10 -4

- 215-

SIMULTANEOUS MEASUREMENTS OF STRATOSPHERIC TRACE GASES

AS DEDUCED FROM AIR-BORNE INFRA-RED SPECTROMETRY

M. AMODEI, B. DUFOUR, G. FROMENT, F. KARCHER, J.P. MEYER Centre National de Recherches Meteorologiques (CNRM)

31057 TOuLOUSE CEDEX - FRANCE

J. MARCAULT Office National d'Etudes et de Recherches Aerospatiales (ONERA)

92320 CHATILLON - FRANCE

Spectrometric measuremen~of stratospheric trace gases were made over Western Europe and Greenland in 1983 and during the large "STRATOZ 3" campaign in June 84. The paper describes briefly the retrieval pro­cess of the vertical column density (VCD) from the recorded spectra. Preliminary results for 1983 flights are presented and discussed.

1. Introduction

This paper presents ~esults of spectrometric measurements made on board a caravelle aircraft flying at 11,5 km altitude. The occultation of the sun during sunrise or sunset transitions provides infra-red absorption spectra of the atmosphere.

The measurements are made with a grille spectrometer of A. Girard (1,2,3). The group of Dr Girard (ONERA) made measurements till 1982 with the instrument and we have been carrying on this work since.

At present time, we have few new measurements to show, especially as we were involved in a large measurement campaign, Stratoz 3, in June 1984. The main goal of Stratoz campaigns was to observe latitudinal and season­nal variations of stratospheric trace gases.

The spectra recorded during Stratoz 3 are not yet analysed, so the paper is limited to measurements made last year during

i) a flight over Western France : contribution to the CCSS Globus campaign, Aire sur l'Adour, September 1983

ii) two flights over Greenland in June 83 which served as test flights for Stratoz 3.

The paper is composed of two short sections - review of the analysis of the spectra and recent progress - results of 1983 flights.

2. Analysis of the spectra

The basic principle of the retrieval process can be described in a simple manner :

If one assumes that the shape p(z) of the vertical profile of concen­tration is known, a single superposition of an observed absorption line with a computed line at the same sun elevation and with the same profile shape P(z) allows the calculation of the vertical column density (VCD) by multiplying the VCD of p(z) by an adequate constant k.

Ozone Symposium - Greece 1984 - 216-

Absorption varies both with viewing geometry and w~th the shape of the adopted profile. In the particular case of our experiments, for a set of lines observed at various sun elevations during the same sunrise or sunset, neither profile, nor VCD should change.

So the guess profile P(z) has to be rejected if the VCD'S calculated at various sun elevations show a dependance with the elevation angles.

As ONERA provided in 1982 the spectrometer with a digital output, our group of CNRM started for one year to automatize the retrieval process(cali­brations, fits, statistical testing) in order to analyse rapidly a large quantity of spectra.

At present time, we are able to - select a s~thed profile shape for which a minimal dependance between

VCD and elevation angles can be observed - calculate the vertical column density above 11,5 km with an estimation

of the uncertainity. These quantities are shown in Table I. The sun occultation technique allows also calculations of concentrations

at altitude of flight, which have not been performed for the 1983 flights.

3. Results of 1983 flights

Table I shows 7 values of vertical column densities obtained at present time for 3 flights (June and September 1983). More data are expected in near future from these flights.

3.1. N02

Analysis is made near 1604,6 cm-1 where N02 is the only absorber. The uncertainties are higher than usually observed especially for the

sunrise flight. Nevertheless, some features are in good agreement with the model outputs of D. Cariolle (4,5).

- At summer solstice 60 N, the N02 values are high :

0,72 1016 molecules cm-2 at sunset

0,49 1016 molecules cm-2 at sunrise Such high values have yet been observed by Mankin and Coffey at same

season and latitude (6). Besides, the ratio between morning and evening values is consistent

with 1D model calculation at 60 N (Figure 1). 16 - In automn 45 N the measured N02 value 0,43 10

smaller than the 2 values at 60 N and slightly higher of the 2D model.

3.2. RN03

_2 molecules cm is than the diurnal mean

Evaluation of the VCD is made at 1325,7 cm-1 using an experimental gro­wing curve obtained in the laboratory with an RN0 3 cell in the optical path of the spectrometer.

The principle of the retrieval process is unchanged but the uncertainty of the result may be reduced by more appropriate transmission calibrations. The choice of the most likely profile may in turn also be improved.

17 _2 The values of 0,14 + 0,03 10 molecules cm found at 48 N is consis-

tent with previous work and model outputs which show a large increase with latitude on both hemispheres (see for instance data from different s.ources compared in reference 7).

- 217-

Analysis is made near 1083,9 cm-1 where 03 is practically the only ab­sorber. Three guess profiles were checked :

- The 2D model profiles for 60 N, summer solstice and 45 N, autumn equinox.

- The Brewer-Mast sounding profile (SMS Biscarrosse-9/9j83 06 32 UT). After individual adjustment by adequate correction factors k, all

three profiles give nearly the same ozone contents in the layer 12 km (flight level) - 30 km (balloon burst). These contents (viz.222, 222, 224 DU respectively) are significantly higher than the corresponding value (197 DU) derived from the Brewer-Hast profile. Surprisingly, the best agreement (independence of the VCD'S with Solar elevation e) is obtained for the 60 N guess profile, which exhibits higher ozone contents in the lower stratosphere.

The discrepancies between the in-situ and spectrometric profiles may be explained by the following remarks :

i) the time difference between sounding and flight, some 12 hours apart. ii) the features of total ozone field as retrieved from the TOVS data,

which shows a great time and space variability and a progressive increase in total ozone, especially in the region spectrom.etrically sampled at low sun.

iii) the lowering of the tropopause level as observed during the flight along the plane trajectory, and confirmed by meteorological analysis.

3.4. CH4

Four groups of iines were taken into account near 1323,5-1323,9-1324,0 and 1324,2 cm-1 where CH is the major absorber, with a moderate con­tribution of N20 and H20. The V~D obtained is slightly lower (k factor = .86) than the corresponding 2D model value for the same latitude and season.

This result should be compared with similar ones provided by another spectral region, not yet analysed.

3.5. HCI

The analysis is made at 2944,9 cm-1 and gives a value of 0,40+0,06 1J6 molecules cm-2 which is consistent with earlier measurements with the same instrument and the same spectroscopic parameters (7).

Unfortunately, a good fit between equivalent widths calculated with a model profile and observations could not be obtained at elevations below ° degree. A most likely interpretation is the presence of a strong advection of artie air in the northern part of the measurement area where low eleva­tion observations were made. This situation may contradict our hypothesis of horizontal homogeneity of VCD and profile. A second interpretation is the great variability of tropospheric HCI which cannot be represented in model outputs.

Our second retrieval using a guess profile with zero concentration below 13 km :

is valid for determination of VCD in the southern part of the flight as lower level concentrations have minor importance for positive elevation observations,

- allows to fit the equivalent widths at low elevation too, but the determination of VCD for northern part is doubtfull.

- 218-

4. Conclusion

The purpose of this paper was : i) To show a tool we have now developped, capable of measuring vertical

column densities at various latitudes with a good accuracy for seve­ral stratospheric trace gase~ :

NO, N02 , N2 0, HN0 3 , HCI, HF, H2 0, CO, CH4, 03

ii) To show some of our first results. In addition, we hope to obtain after evaluation of data of Stratoz 3

a consistent set of data (see Table II) with respect to time and latitudes in order to contribute to the knowledge of latitudinal and seasonnal varia­tions especially for N02 , HN03 , HCI and HF.

REFERENCES

1. GIRARD A. (1960). Nouveaux dispositifs de spectroscopie a grande lumi­nosite. Optica Acti, 7, N°1, 81-97

2. GIRARD A. (1963). Spectrometre a grilles. Applied optics,2, N°1,79-87 3. GIRARD A. et al. (1977). Spectrometre automatique aeroporte pour la

surveillance des gaz a l'etat de trace dans la haute atmosphere. La Meteorologie. 6eme serie, N° 10, 3-14.

4. CARIOLLE D.(1983). The ozone budget in the stratosphere: results of a one dimensional photochemical model. Planet. Space Sci., 31,1033-1052.

5. CARIOLLE D. and D. BRARD (1984). The distribution of ozone and active stratospheric species : results of a two-dimensional atmospheric model. These proceedings

6: COFFEY M.T. et al. (1981). Simultaneous spectroscopic determination of the latitudinal, seasonal, and diurnal variability of stratospheric N2 0, NO, N02 , and RN03 • J. Geophys. Res. 86, N° C8, 7331-7341

7. GIRARD A. et al. (1983). Latitudinal distribution of tEn stratospheric species deduced from simultaneous spectroscopic measurements. J. Geo­phys. Res. 88, N° C9, 5377-5392.

- 219-

I N

N o

Tab

le

I R

esu

lts

of

1983

fl

igh

ts

---,---_

.-----

VC

D(m

ol.c

m-2

)

rela

tiv

e

red

uce

d

on

stit

uen

t d

ate

o

f su

nri

se

inte

gra

tio

n

mos

t li

kely

x

k u

ncert

ain

ity

re

lati

ve

flig

ht

/su

nse

t la

titu

de

fro

m

7 to

40

km

p

rofi

le

%

un

cert

ain

ity

%

N0 2

Ju

ne

15

60

N

16

60N

su

mm

e:

x 1

07

SS

0,7

2:,

0,1

2.1

0

17

15

solst~ce

'

Jun

e 17

60

N

16

60

N

sum

me:

x °

73 N

0 2

SR

0,49~. 0

,14

.10

29

29

solst~ce

'

Sep

tem

ber

9 48

N

16

I'O

N ,m

om,;

,0 6

' N

0 2

SS

0,4

3:,

0,0

8.1

0

solst~ce

' 19

19

45

N aut~n

x 1

07

21

21

equ~nox

'

Sep

tem

ber

9

SS

48

N

17

45N

au

tum

n x

1 26

22

19

RN

O]

0, 1

4 :.

0,0

3.

1O

equ~nox

' m

oved

6k

m

dow

n

0]

Sep

tem

ber

9

SS

48

N

19

60N

su

mm

e:

x °

76 7

7 0

,70

:.

0,0

5.1

0

solst~ce

'

Sep

tem

ber

9

SS

48

N

20

45N

aut~n

x °

85 23

23

CR

4 0

, 11

:. 0

,03

. 1O

equ~nox

'

Sep

tem

ber

9

SS

48

N

16

45N

eq

uin

ox

~

RC

l 0

,40

:.

0,0

6

10

autu

mn

x 1

,8

15

15

bel

ow

13

krnx

O.O

-

---

----

rela

tiv

e u

ncerta~n~ty

is

the

stan

dard

d

ev

iati

on

of

the

VCD

mea

sure

men

ts.

Red

uced

un

cert

ain

ity

is

st

and

ard

d

ev

ia­

tio

n o

f VC

D ab

ou

t a

reg

ress

ion

li

ne

of

the

VC

D'S

v

ersu

s v

iew

ing

an

gle

. If

th

e as

sum

ed p

rofi

le is

th

e co

rrect

on

e,

the

reg

ress

ion

co

eff

icie

nt

is

near °

and

the

glo

bal

un

cert

ain

ity

is

du

e o

nly

to

th

e in

stru

men

tal

no

ise

of

the

spectr

osc

op

ic d

ete

rmin

ati

on

s.

The

re

du

ced

uncerta~n~ty

can

th

us

be

con

sid

ered

as

a

min

imal

u

ncert

ain

ity

wh

ich

ca

nn

ot

be

furt

her

red

uce

d b

y tr

yin

g o

ther

pro

file

s.

atitude

75 N

60 N

45 N

30 N

15 N E

15 S

30 S

45 S

60 S

measurement campaigns

Latitude Survey Stratoz 1 Stratoz 2 Greenland CCSS Stratoz3 November 76 Pacific ocean

C C

SS SR

SS

SR+SS

SS

SR

SS

Table II

October/ April/' June 83 Globus November 78 May 80 Aire/A June

Sept 83

SR SR

SS+SS+SR SR

SR SS+SS SS SS+SS

SS SS SR SR SR

SR SR SR SS

SS SS SS SR SR SR

SR SS SS

Data set obtained on aircraft platform by ONERA grille spectrometer SR sunrise measurement SS sunset measurement C constant sun elevation

o

84

--

winter -10 summer - autumn equinox

-o

v To

v V -5 v

0 v 0 v v v 0 v

0 0 II 1\ V 0

0 0

II II II 0

II II II II

:r~ v v v

0 v v 0 0

x - vT 0 II -V o /I 1 SR /I

V 0 v <1ss II V 0 /I

0 II V Z; 0 /I

II 0 /I

/I 1\ /I A , I I I I I I I I

3G 60 30 60 3G 60

Figure 1 : N02 vertical column densities (X 10 15 molecules. cm-2)/latitude Comparison of spectroscopic measureme.nts from this work ( I( >lith error bars) with outputs of 2D model of D. Cariolle ( 0 daytime mean, v sunset value, 1\ sunrise value).

- 221-

1. Summary

THE DETERMINATION OF STRATOSPHERIC NITROGEN DIOXIDE CONCENTRATIONS FROM

LIMB BRIGHTNESS MEASUREMENTS

C.T. MCElroy Atmospheric Environment Service

4905 Dufferin Street Downsview, Ontario

A multiwavelength spectrometer with limb scanning optics was developed to make N02 measurements in the stratosphere. The instrument uses light scattered by molecules of air as a light source, and measures the differential attenuation of light at different wavelengths by N02 . A single scattering model is used to interpret the observations obtained in terms of a vertical profile of stratospheric N02 . The instrument was flown from Palestine, Texas and observed the stratosphere from an altitude of 33 km at 32 0 N 9B oW for a period of several hours on the afternoon of June 17, 19B3. The mixing ratio of NOZ was observed to be (4.0 ± O.B) ppbv at 30 km, in reasonable agreement w~th solar occultation measurements.

2. Introduction

Since the first successful measurements of atmospheric nitrogen dioxide through the use of visible light spectroscopy [2J a number of researchers have measured the stratospheric total column or vertical distribution of this important stratospheric constituent. Measurements have been made using the Umkehr technique, wherein the light scattered from the zenith sky is observed by a ground based instrument [2,7, BJ. Indeed the measurements of Noxon et al are the basis of the currently accepted nitrogen dioxide global distribution (when properly corrected according to Noxon [B J).

In addition to the Umkehr data, a number of measurements of nitrogen dioxide have been made using the method of solar occultation from high altitude platforms. This method is related to the Umkehr method in that the long path enhancements of rays travelling tangent in the spherical atmosphere is used to provide a measureable signal from the nitrogen dioxide in the stratosphere. Solar occultation measurements have been reported by a number of authors [4,5, 6J.

Unfortunately the measurements made using both the occultation method and the Umkehr method yield vertical distributions of N02 at the instant of sunrise or sunset in the layer measured. Because the amount of N02 in the stratosphere is changing during the transition period [3J there are uncertainties introduced in the inversion process which converts the observed optical absorptions into vertical mixing ratio profiles. The amounts measured are not directly comparable to measurements of other ipecies which are made during the daylight period.

In addition to the problem of temporal change in the N02 column abundance during the transition period, there is also a slow change in N02 amount throughout the sunlit period of the day due to the photolysis of N205 in the stratosphere. It is therefore useful to make observations of

Ozone Symposium - Greece 1984 - 222-

the daytime distribution of nitrogen dioxide directly. Measurements of nitrogen dioxide during the day have been reported by Roscoe [10], which were made through the use of infrared limb scanning.

LIMa BRIGHTNESS VIS ELEVATION ANGLE 3+-+-+-+-+-~~-r-r-r-+-t-+-+-+

The measurements reported here ~

were made by observing the brightness ~ of the earth I s limb from a balloon at \£ an altitude of 33 krn. The

~ measurement technique employed is ~ similar in principle to that reported by Mount [7] which was used on the ~ University of Colorado SME (Solar 8 Mesosphere Explorer) satellite. i

A balloon platform for making limb scan measurements is a ! considerable asset since the lower altitude of the observation points results in a higher altitude resolution in the vertical profile

....I

I. e

J\J£ 17, 11113

M.EST1tE, mAS

for a given angular optical resolution in the observing instrument. For example, for an observation at an altitude of 30 krn from a balloon platform with an instrument with optical .resolution of 0.1 0 , the altitude resolution will be approximately 0.3 km. For the same instrument observing the 30 krn altitude region from a 300 krn orbit,

l+-~-r-+~--r-+-~-r-+~--r-+-~-+ ~. -5.. -I.. -3.' . "'1.' -1.1 ... u

ElEVATION ANGLE (DEGREES) Figure 1: The mean observed limb brightness curves for both the up and down scans are plotted. The single scattering model calculations are also shown. The two curves are normalized at approximately _3 0 where the effect of aerosol is at a

the corresponding resolution would be minimum. more than 3 krn. Both the required optical resolution, and the pointing stability altitude observations are much higher than for observations.

3. Method of NOZ Observation

requirements for the higher the balloon based

Nitrogen dioxide measurements are made by the use of differential spectroscopy. The method has been described in the literature [4, 5, 6] and will not be discussed here in detail. The method has several desirable properties which will be listed, but not discussed. The spectrometer is a modified Ebert design [1] with five exit slits which are sequentially opened to allow light to fallon a high sensitivity photomultiplier operated in the photon counting mode. The counts are individually summed by the instrument control computer to generate a measure of the light intensity at significant points in the NOZ spectrum (437.7 nm, 439.Z nm, 44Z.0 nm, 444.8 nrn, 450.1 nm). A linear combination of the logarithms of the observed intensities is formed which is [6] insensitive to 1) Rayleigh scattering of the light from the incident path Z) ozone absorption 3) the absolute sensitivity of the instrument or brightness of the sky 4) small variations of the spectrometer calibration about its precise wavelength calibration. At the same time the absorption function obtained in this way has sensitivity to nitrogen dioxide in the path of the measured light ray.

- 223-

4. Data Collection

The N02 spectrometer was flown on board the Liege high altitude infrared spectrometer [11] payload during the NASA Balloon Intercomparison Campaign (BIC) of June 1983. The data analysed in this paper are the average of 17 limb scans obtained in the afternoon of June 17, 1983. The solar zenith angle was approximately 42.5 degrees and the azimuth angle of view relative to the sun was 60 degrees. A constant azimuth angle relative to the sun was maintained since the Liege payload on which the instrument was mounted, was itself pointed at the sun by a solar tracking system.

The intensity of light at each measured wavelength was telemetered to the ground via an RS232 link from the instrument control computer, and recorded on a digital cassette. The cassette data were subsequently reduced to limb scan records, in terms of both abs~lu~e intensity and the N02 absorption function. The data obtained by averaging 17 successive scans is plotted in Figures 1 and 2.

5. Interpretation

In order to convert the observed radiance and absorption function values to vertical profile information, it is necessary to use a model of the atmospheric scattering process. Since the vertical distribution of N02 in the stratosphere is to be measured, it is sufficient to consider only single scattering in the model. The effects of air, aerosol, nitrogen dioxide, and ozone are included in the calculation.

The vertical profile of aerosol was determined from lidar backscatter measurements privately communicated by P. McCormack. The phase function for aerosol scattering and the scattering coefficients were calculated by C.L. Mateer for an aerosol distribution appropriate to that of the stratosphere at the

e ... E ~ ~ .. 115 ....

~ -< N .. m !i!

.. 115

... -«,I

N02 ABSORPTION VIS ELEVATION ANGLE

-5..

I I I I I I

..... -3,1

JU£ 17, 1983

PAl.ESTItE., IDCAS

~. -1.1 ... ElEV ATION AN~£ CDEGR€Es)

I.'

Figure 2: The mean absorption function values are plotted for both the up and down scans. Each curve is the average of 17 scans.

LIMB BRIGHTNESS VIS ELEVATION ANGLE

• -~ • IOEI. CoILCW.TlIIIS

I • stt.\R A2lIII!H III tmIEES -

i -~ ..,

I. I

~ • l!! ~ • !II

i • •

Hi 21 AEIIOSIl. IlI11IEJ 1M toIlER

! aJM IF EAI:II PAlR ....J

8 ..... -5.. ..... -9.1 ~. -1.1 ... 1.1

ElEVATION ANIli (I£GRE£S)

Figure 3: The effect of the addition of aerosol (0.05 optical depth) to the model atmosphere is shown.

- 224-

time the measurements were made. The nitrogen dioxide and ozone absorption coefficients are those of Johnson [private communicationl. The model concentrations were relaxed by a linear, constrained inversion algorithm to determine a vertical profile of N02 which gave good agreement between the model, and the observed limb absorption function values.

6. Results

It can be seen that agreement between the single scattering model and the observed absolute intensity curves is good; indicating that there will be no significant error in the calculated path taken by the light rays arriving at the instrument, for light originating more than three km below the float altitude.

The vertical profile in Figure S was determined using the inversion scheme and is appropriate to a solar zenith angle of 42.S degrees. This plot also has vertical profiles of N02 measured at Mildura, Australia (340 5, 142 0 E) at the time of sunrise and sunset by the method of visible light solar occultation indicated on it. It can be seen that the agreement with these curves is good, and indicates that there is no substantial problem with the photochemical model calculations which predict a slow increase in NO and N02 throughout the day due to the photolysis of N20S '

Vi III f5 ~ w ...J <-> :z: < :z 8 I--< > w til

N02 EFFECT VIS ELEVATION ANGLE I.' 1.5

1.1 AER!lSIJt. .00 RIIYLEIGl SCAl1ER11I:

... 5

-1.1

-I.S

OZI

OZS

-:1.1

-15

-4.1

~5

-5.1

-5.5 )(12 ADJ\.ISTEIl A 1 !£l [JffS II()I t111£D 000

~'+--1--~--t--t--;-~~-r--+-~---t I.. 1.1 1.2 1.3 1.4 I.S 1.8 1.7 1.8 log LI

NORMrlLlZEO RESPONSE TO N02

Figure S: This figure illustrates the limb scan method's loss of sensitivity to an absorber when aerosol is added to the atmosphere. (O.OS optical depth of aerosol; see text)

N02 MIXING RATIO VIS ALTITUDE .+--1---1---+--+-+-- +------11--;

!I

21

15

JlI£ 17, 1l1li3 PAI..£STll£, TIXAS

THIS I0Il( -

- SIIiUSE

~ ...-------

stKUSE 00 SI.IISE1 IlJMS AlE FIOI

IllSERYATUJIS !WE AT MlUU!A AlISIRALlA

C34S 142El lH 0CTlIER 111711

d+_-~--~--+_-+_·~~-+---+___t . , NITROGEN DIOXIDE MIXING RATIO <PP8V)

Figure 4: The mean of the curves in figure 2 was inverted to yield the distribution in this figure. The comparison data are from reference [S J.

- 225-

It can be seen from Figure 5 that the sensitivity of the limb scanning method to N02 is strongly affected by the presence of aerosol. Significant amounts of aerosol in the atmosphere cause the light source function in a tangent layer to move toward the observer. The incident ray will therefore see a significant reduction in the amount of apparent N02 in the path.

7. Conclusions

The method of balloon-borne limb scanning is a useful tool for the daytime measurement of nitrogen dioxide. The amounts measured during the June 17, 1983 flight were somewhat lower than that which would have been expected based on the solar occultation measurements which have been previously reported [4, 5, 6). It would therefore be valuable to make a balloon flight during which both methods were used, so that their respective results might be better intercompared.

The balloon data analysed in this paper were gathered during the 1983 NASA BIC campaign. The author would like to acknowledge the cooperation of Dr. R. Zander and his group in adapting the N02 instrument to fly on the Liege payload. Mr. W.J. Clark constructed much of the instrument and helped to support it during the balloon campaign. Drs. W_.F.J. Evans, D.l. Wardle, and J.B. Kerr provided valuable advice and assistance. Dr. C.L. Mateer provided information on the scattering properties of stratospheric aerosol, and Dr. P. McCormack provided the lidar backscatter data.

8. References

(1) Brewer, A.W., A Replacement for the Dobson Spectrophotometer?, Pure Appl. Geophys., 106-f08, 919-927, 1973. (2) Brewer, A.W., C.T. MCElroy, J.B. Kerr, Nitrogen Dioxide Concentrations in the Atmosphere, Nature, 246, 129-133, 1973. (3) Kerr, J.B., C.T. McElroY:-Measurement of Stratospheric Nitrogen Dioxide from the AES Stratoprobe Balloon Program, Atmosphere, 14, n.3, 166-171, 1976. --(4) Evans, W.F.J., C.T. McElroy, J.B. Kerr, J.C. McConnell, Simulation of Nitrogen Constituent Measurements from the August 28, 1976, Stratoprobe III Flight, J. Geophys. Res., 86, 12066-12070, 1981. (5) Galbally, I.E., C.R. Roy, R.S. O'Brien, B.A. Ridley, D.R. Hastie, W.F.J. Evans, C.T. McElroy, J.B. Kerr, P. Hyson, W. Knight, J.E. Laby, Measurements of the Trace Composition of the Austral Stratosphere: Chemical and Meteorological Data, CSIRO (Australia), Div. Atmos. Res. Tech. Paper n.l, 1983. (6) Mount, G.A., D.W. Rusch, J.M. Zawodny, J.F. Noxon, C.A. Barth, G.J. Rotman, R.J. Thomas, G.E. Thomas, R.W. Sanders, G.M. Lawrence, Measurements of N02 in the Earth's Stratosphere using a Limb Scanning Visible Light Spectrometer, Geophys. Res. Lett., 10, n.4, 265-268, 1983. (7) Noxon, J.F., Stratospheric N02 ,2, Global Behavior, J. Geophys. Res., 84, 5067-5076, 1979. 1GB) Noxon, J.F., Correction, J. Geophys. Res., 85,4560-4561, 1980. (9) Roscoe, H.K., J.R. Drummond, R.F. Jarnot, Infrared Measurements of Stratospheric Composition. III. The Daytime Changes of NO and N02 , proc. Roy. Soc. Lond. A, 375, 507-528, 1981. (10) Zander, R.,-Moisture Contamination at Altitude by Balloon and Associated Equipment, J. Geophys. Res., 11,3775-3778, 1966.

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C HAP T E R IV

ANALYSIS OF OZONE OBSERVATIONS

- Backscattered ultravtolet measurements of ozone 1970-2000 an overview

- Global total ozone from TIROS measurements : 1979-1983

- The observation of atmospheric structure with Toms and some potential advancements

- Standard profiles of ozone from ground to 60 km obtained by combining satellite and ground based measurements

- Annual and semiannual oscillations of stratospheric ozone

- An evaluation of the performance of umkehr stations by solar backscattered ultraviolet (SBUV) experiment

- Intercomparison of satellite ozone profile measurements

- Total ozone trend in the light of ozone soundings, the impact of El Chichon

- Variability of the vertical ozone distribution

- An ozone soundings program at the eastern equator: preliminary results

- An ozone soundings program at the eastern equator: preliminary results

- Mean vertical distribution ot atmospheric ozone over Cagliari-Elmas (39015'N - 09 03'E)

- A special ozone observation at Syowa station, Antarctica from February 1982 to January 1983

- A comparison of ozone profiles derived from standard umkehr and short umkehr measurements from fifteen stations

- Rocket measurements of the vertical structure of the ozone field in the tropics

Time-periodic variations in ozone and temperature

- Results of umkehr, ozonesonde, total ozone, and sulfur dioxide observations in Hawaii following the eruption of El Chichon volcano in 1982

- On the correspondence between standard umkehr, short umkehr and SBUV vertical ozone profiles

- Effects of the El Chichon stratospheric aerosol cloud on umkehr measurements at Mauna Loa, Hawaii

- Ozone-temperature relationships in the stratosphere

- Lidar ozone measurements in the troposphere and stratosphere at the oQservatoire de Haute Provence

- Vertical ozone distribution over Uccle (Belgium) after correction for systematic distortion of the ozone profiles

- On the relative quality and performance of G.030.S. - total ozone measurements

- Atmospheric ozone in map-globus

- One year European total ozone daily maps from Nimbus 7 and Dobson data

- Une appellation commune du nom des grandeurs utilisees pour designer les quantites d'ozone dans l'air : l'ozonite

- Decreases in the ozone and the SO columns following the appearance of the El Chichon aero~ol cloud at midlatitude

- eorrelative studies of total ozone content with tropospheric properties - results from Indian stations

- A global climatology of total ozone from the Nimbus-7 total ozone mapping spectrometer

BACKSCATTERED ULTRAVIOLET MEASUREMENTS OF OZONE 1970-2000 AN OVERVIEW

Summary

A. J. Fleig Laboratory for Atmospheric Science

Goddard Space Flight Center Greenbelt, Maryland, U.S.A., 20770

w. G. Planet National Environment Satellite, Data and Information Service

NOAA/NESS, Suitland, MD 20233

and

P. K. Bhartia Systems and Applied Sciences Corporation

Hyattsville, MD 20784

Satellite measurement of backscattered ultraviolet radiation will be the major source of long term global information about total ozone and ozone profiles for the rest of this century. These measurements started with the Backscattered Ultraviolet (BUV) experiment flown on Nimbus 4 from 1970 to 1977 and are presently being continued with the Solar and Backscattered Ultraviolet/Total Ozone Mapping Spectrometer (SBUV/TOMS) launched on Nimbus 7 in 1978. NOAA will fly an improved version (SBUV /2) operationally from 1984 until sometime in the 1990's and NASA plans to fly an SBUV /2 on the Upper Atmosphere Research Satellite in 1989. Differences between these instruments and in the algorithms used for deriving ozone amounts from these data sets are discussed.

1.0 History of the BUV Experiment Backscattered Ultraviolet Experiment (BUV) was launched aboara NASA's

Nimbus-4 satellite in April 1970 (1). Designed for a lifetime of only one year, the instrument actually lasted seven years taking some 900,000 earth radiance measurements at 12 separate wavelengths in 255-340 nm range. In 1976, NASA organized Ozone Processing Team (OPT) to develop a data base of total ozone and vertical profiles based on algorithms proposed by Dave and Mateer (2) and by Mateer (3). The team examined the pre and post flight instrument performance, made improvements to the algorithm (4 &: 5), validated the ozone products (6), and archived the ozone data sets at National Space Science Data Center (NSSDC), Goddard Space Flight Center, Greenbelt, MD 20770.

Validation studies showed that the quality of BUV ozone data exceeded all pre-launch expectations. Satellite total ozone values proved good enough to catch errors and drifts in individual ground based Dobson measurements. Vertical profile results from BUV confirm the validity of Umkehr technique of measuring ozone profile from ground (6).

Success of the Nimbus-4 BUV experiment led to the development of SBUV (for solar BUV) and a companion scanning instrument, the Total Ozone Mapping Spectrometer (TOMS), (7) designed to provide daily global ma~ of total ozone at spatial resolutions of up to 50 km. OPT has developed new retrieval algorithms to

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account for the scanning feature of TOMS and to incorporate algorithm improvements proposed by Mateer (8), described by Bhartia et. aL (9) and Klenk et. al. (10). Ozone data sets produced by SBUY /TOMS are unprecedented in quality, coverage, and scope. Over 200 million measurements of total ozone have been made by the TOMS instrument since it started operation. The quality of these measurement is matched by only the best of the eighty or so ground-based Dobson and M83 stations (11). Ozone profiles produced by SBUY have been shown (12) to be valid from tropopa~e to stratopa~e. Primary limitation of the BUY technique for profile retrievals is the lack of vertical resolution which is limited to 8-10 km. Four years of SBUY /TOMS ozone data sets have been archived at NSSDC.

Nimbus-7 is the last in this series of environmental research satellites launched by NASA. A program of long-term monitoring of atmospheric ozone will be initiated by U.S. National Oceanic and Atmospheric Administration (NOAA) which has selected an improved version of SBUY, to be called SBUY /2, for its operational TIROS-N satellites. A series of these instruments will be launched every two years to continue the monitoring program at least into the next decade.

In the next two sections we discuss the differences between these instruments and in the algorithms ~ed in deriving ozone amounts from their radiance measurements.

2.0 Instrument Differences Design of BUY instruments has evolved slowly over the last fifteen years.

Three major differences between the original Nimbus-4 BUY instrument and the most recent TIROS-N SBUY /2 instrument, (scheduled to be flown in Nove.~lber, 1984) are described.

2.1 Diff~er Calibration BUY instruments have been designed to measure the radiation backscattered

by the earth's atmosphere, as well as the extra-terrestrial solar flux. Since ozone is derived from the ratio of these measurements, (often referred to as bi­directional albedo) many instrumental errors common to both types of measurements cancel. However, a diffuse reflector, ~ed for diverting the incoming solar radiation to the instrument's entrance slit, is not ~ed in earth radiance measurements; therefore, a change in the reflecting properties of the diffuser has a direct adverse effect on the computation of albedos from the BUY instrument.

The diffuser used in Nimbus-4 BUY was continuously exposed to space and degraded rapidly after launch, which made it impossible to correct the BUY albedos for instrument drift and for possible variations in the sun's output. The diffuser ~ed in Nimbus-7 SBUY /TOMS is protected from space exposure most of the time except during brief periods of about 10 minutes/day when it is deployed for solar flux measurements. This controlled exposure to space has not only kept the overall degradation small (10-30% over five years) but, more importantly, it has made it possible to do three controlled experiments during which the exposure of the diffuser to the sun was increased ten-fold to 2 hours/day for a couple of months and the resulting change in instrument output monitored to determine the rate of diffuser degradation. Statistical uncertainty in determining the total diff~er degradation over the life time of SBUY /TOMS instrument is expected to be less than 2% at the ozone measuring wavelengths (270 - 340 nm).

GiveR that the degradation of optical surfaces in space environment is inevitable, TIROS-N SBUY /2 instruments will be equipped with a mercury lamp to do on-board diff~er degradation monitoring.

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2.2 Dark Current Correction BUY instruments use sensitive photo-multiplier tubes (PMT) that are

affected by strong ionizing radiation present in the near-earth space environment. Over an area centered over South Atlantic, called South Atlantic Anomaly,

the dark current count in the Nimbus-4 BUY PMT often exceeded the counts generated by the radiance signal from earth. Outside the boundaries of this well defined region, however, the dark current dropped to below 1 % of the radiance signal which made it possible to do ozone retrieval over about 70% of the earth's surface area.

Recent instruments, including those flown on Nimbus-7, have contained an optical chopper and a synchronized up-down counter to automatically eliminate the dark current contamination from the output counts. This feature has worked well leaving no residual dark current anomalies in the radiance data from anywhere on earth.

2.3 Wavelength Change The original BUY instrument had twelve, 1 nm wide, fixed wavelength bands

centered at 256, 274, 283, 288, 292, 298, 302, 306, 313,318,331 and 340 nm. The Nimbus-7 SBUY instrument has, in addition to these bands, a scanning feature that allows it to sweep through 160-400 nm wavelength range at 0.2 nm intervals. This feature has proved extremely useful in measuring short term variations of the solar output at wavelengths important in ozone photochemistry and has also allowed identification of several NO emission and S02 absoprtion features in the earth radiance spectrum. This new information has revealed that the shortest of the twelve fixed BUY/SBUY wavelength bands, centered at 256 nm, is contaminated by atmospheric air glow in the NO - 'Y band. Since this contamination is highly variable, BUY /SBUY ozone retrieval algorithms have not used the measurements taken at 256 nm. For TIROS-N SBUY /2, the center of the shortest wavelength band has been moved to 252 nm, which will allow all twelve bands to be used in ozone retrivals, providing better profile results near the stratopause.

3.0 Algorithm Differences Retrieval of ozone parameters from ultraviolet radiances measured by

satellites requires several types of external information not contained in the radiance data themselves. Types of external information most important in ozone retrievals are: accurate omne absorption spectrum and its temperature dependence in the Hartley-Huggins band, a priori ozone profiles and information about their spatial and temporal variability, cloud height, and snow/ice information. As the quality of these information has improved, the retrieval algorithms have gone through several phases of development to make the best we of them. Seven years of Nimbus-4 BUY data currently in archives were processed using version 3 of the retrieval algorithm (wers in possession of BUY data processed before June, 1979 using earlier versions of the algorithms would be well-advised to discard them). Five years of SBUY /TOMS data currently in archives were processed using a substantially different (version 4) algorithm. Results from these two algorithms are not necessarily compatible. It is anticipated that the entire twelve years of BUY and SBUY /TOMS data will be reprocessed using a new retrieval algorithm - to be called version 5. This internally consistent ozone data set should be available by summer, 1985. For its TIROS-N SBUV /2 instruments NOAA plans to eventually use version 5 algorithm developed by NASA, though minor differences due to changes in instrument design and satellite are likely. A brief overview of the differences between these algorithms are given below.

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3.1 Version 3/Version 4 Differences Version 3 profile retrieval is based on Twomey's minimum departure scheme

(13) using the Pressure Increment (PI) formulation developed by Yarger (14) and Mateer (3). A priori ozone profiles used in this scheme are obtained using a simple analytical technique proposed by Twomey (15) and used by McPeters and Bass (16). Main deficiencies of this retrieval scheme are that it does not make full use of the available ozone climatological information and the PI formulation becomes inadequate for ozone retrievals below 30 km.

Version 4 algorithm is based on "Optimum Statistical Inversion Technique" reviewed by Rodgers (17) and described by Klenk et. al. (10). Detailed ozone climatological information was developed to make full use of the power of this technique (18). Differences between the version 3 and version 4 total ozone algorithm are related to cloud and snow cover information that are described by Bhartia et. al. (9).

3.2 Version 4/Version 5 Differences High resolution, multi-temperature measurements of ozone absorption cross­

sections in the Hartley-Huggins band have recently been completed by several groups around the world. Through the efforts of WMO and NASA, these data sets have been carefully intercom pared with each other and with previous laboratory measurements. Absorption coefficients based on these new laboratory data are significantly different i.e. (2% - 8%) from the coefficients based on early laboratory measurements (19). Removal of absorption coefficient errors from both ground based and satellite ozone mesurements will significantly reduce the existing biases (20). Version 5 algori thm will use the ozone spectrum approved by WMO.

Other differences between version 4 and version 5 are related to improvements in ozone 'climatological information (21) that is being developed in close collaboration with Dr. C.L. Mateer, (AES, Canada) who is in process of implementing a major revision of the Umkehr ozone retrieval algorithm. It is anticipated that the version 5 satellite algorithm will be conceptually similar to the new Umkehr algorithm, so that their intercomparison would reveal differences between the two measuring techniques, rather tllan in their processing techniques.

4.0 Validation of SB UV /2 Data Products A program has been established by NOAA for providing independent data for

validating SBUV /2 ozone data products. Using ground-based Umkehr observations supported by lidar systems and balloon ozonesondes, it is expected that data will be obtained up to 40 km for validating ozone profiles. Total ozone data will be obtained in at least 16 Dobson sites; seven of the sites will be equipped with automated instruments. Three sites will launch weekly balloonsondes to 40 km.

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REFERENCES

1. Heath, D.F., A.J. Krueger and C.L. Mateer, 1970: "Nimbus" User's Guide", R.R. Sabatini, Ed. Goddard Space Flight Center, GreenbelL

2. Dave, J.Y., and Mateer C.L., 1967: "A PrelimiMry Study on the Possibility oC Estimating Total Atmospheric Ozone From Satelllte Measurements", J. Almas. Sci. 24, 414-427.

3. Mateer C.L., 1972: "A review of :".lome aspects of tnferring the ozone profile by inVersion oC ultraviolet radiance measurements", Mathematics of Profile Inversion, p. 1-2 to 1-25, edited by L. Colin NASA Technical Memorandum. TM X-52-150.

4. Klenk K.F., P.K. Bhar"tia, A.J. Fleig, V.G. Kaveeshwaf, R.D. McPeters and P.M. Smith, 1982: "Total Ozone Determination from the Backscattered Ultraviolet (BUY) Experiment", J. Appl. Meteor., 21, 1672 -1684.

5. Bhaftia P.K., K.F. Klenk, V.G. Kaveeshwar, S. Ahmad, A.J. Fleig, R.D. McPeters, and C.L. Mateer, 1981: "Algorithm For Vertical Ozone Profile Determination for the Nlmbus-4 BUV Data Set", Proceedings of the 4th Conference on Atmospheric Radiation, American Meteorological Society, Boston, MA, pp. 27-32.

6. Fleig A.J., K.F. Klenk, P.K. Bhartia, C.G. Wellemeyer and K.D. Lee, 1981: "Vertical Ozone Profiles Results from the Ntmbus-4 BUV Data", Proceedings of the 4th ConCerence on Atmospheric Radiation, American Meteorological Society, Boston, MA, pp. 20-26.

7. Heath D.F., A.J. Krueger, n.R. Roeder, and B.D. Henderson, 1975: "The Solar Backscatter Ultraviolet and Total Ozone Mapping Spectrometer (SBUV!TOMS) Cor Nimbus G", Opt. Eng •• 14. 323-331.

8. Mateer C.L., 1977: "Experience with the Inversion of Nimbus-4 SUV Measurements to Retrieve the Ozone Profile", In Inversion MethociJ In Atmospheric Remote Sounding, edited by A. Deepsk, pp. 577-597. Academic, New York.

9. Shartia P.K., K.F. Klenk, D. Gordon, and A.J. Fleig, 1983: uNimbus-7 Total Ozone Algorithm", Proceedings of the 5th Conference on Atmospheric Radiation, American Meteorological Society, Boston, MA.

10. Klenk K.F., P.K. Shartia, A.J. Fleig, and C.L. Mateer, 1983: "Vertical Ozone ProCile Determination from Nlmbus-7 sauv Measurements", Proceedings of the 5th Conference on Atmospheric Radiation, American Meteorological Society, Boston, MA.

11. Shartla P.K.; K.F. Klenk, C.K. Wong, and D. Gordon, 1984: "Intercom prison of the Nimbus-7 SBUV/TOMS Total Ozone Data Sets with Doooon 6: M83 Network". Vol.!J!., 5239-5247.

12. Bhartla P.K., K.F. Klenk, A.J. Fleig, C.G. Wellemeyer and D. Gordon, 1984: "Intercomparlson of N'lmbus-7 Solar Backs:cattered Ultraviolet (SSUV) Ozone Profiles with Rocket, Balloon and Umkehr Profiles," Journal of Geophysical Research, Vol • .!!.t 5227-5238.

13. Twomey S., 1977: '1fntroduction to the Mathematics of Inversion in Remote Sensing and Indirect Measurements', New York, Elsevier Scientific Publishing, pp. 154-155.

14. Twomey, S., 1970: "An Evaluation of Some Methods of Estimating the Vertical Atmospheric Ozone Distribution From the Inversion of Spectral Ultraviolet Radiation", J. Appl. Meteor •• ~ 921-928.

15. Twomey S., 1961: "On the Deduction of the Vertical Distribution of Ozone by Ultraviolet Spectral Measurements From a Satellite", J. Oeophys. Res.,!!, 2153-2162.

16~ McPeters, R.D. 1980: ''The Behavior of Ozone Near the StratospBuse from Two Years of BUV Oooervatlons'·. J. Geophys. Res..~ 4545-4550.

17. Rodgers C.D., 1976: "Retrieval of Atmospheric Temperature and Composition from Remote Measurements of Thermal Radiadon", Rev. GeophY3. Space Phys.!.!t 609.

lB. Klenk K.F •• P.K. Bha"la. E. HU.enr.th, and A.J. Fleig. 1983: "Standard Ozone ProCil .. From Balloon and Satellite Data Set .. •• J. CUm.te AppL MeteoroL. U. 2012-2022.

19. Klenk K.F., 1980: "Absorption Coefficients of Ozone for the Backscatter UV Experiment", appL Optlcs.!t 236-239.

20. Klenk, K.F., B. Mooosmith and P.K. Shartlst 1984: "Absorption Coefficients of Ozone For the Backscattered UV Instruments - SBUV, TOMS and BUV and For the Dobson Instrument", th1s1ssue.

21. Bharti •• P.K •• D. SUbersteln, and B. Monosmlth, 1984: "Standard profiles or Ozone From Ground to 60 km Obtained by Combining Sat elUte and Ground Based Measurements", this Issue.

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GLOBAL TOTAL OZONE FROM TIROS MEASUREMENTS: 1979-1983 W.G. Planet, J.R. Lienesch and M.L. Rill

National Environmental Satellite, Data, and Information Service National Oceanic and Atmospheric Administration

Washington, D.C. 20233

Summary Infrared radiance measurements by the TIROS Operational Vertical

Sounders (TOVS) aboard the NOAA environmental satellites have been used since early 1979 to deduce global distributions of total ozone amount. Measurements have been made with instruments on four satellites: TIROS-N and NOAA-7 operating near 3 p.m. local time and NOAA-6 and -8 operating near sunrise and sunset.

The method of retrieval is one of linear regression using TOVS mea­surements and total ozone values from a subset of the global Dobson net­work as the dependent data set. Verification of the satellite-derived total ozone values is accomplished by comparisons with a different subset of Dobson determinations as the independent data set.

The satellite data is discussed in terms of its comparison w~th inde­pendent Dobson data. Similar comparisons with Nimbus-7 SBUV and TOMS total ozone determinations are also presented.

Of particular interest is the long-term use of the ozone data acquired by different instruments flown on a series of satellites. An overlap period during which two satellites simultaneously acquired data is discussed in order to understand the applicability of the total time series derived from data from several sate11ities to long-term trend studies.

1.0 Introduction Total ozone amounts are obtained from atmospheric infrared radiances

measured by the TOVS on the NOAA meteorological satellites. The retrieval method is a multivariate regression procedure. Coefficients are obtained by regressing satellite measurements of radiances converted to brightness temperatures in three infrared spectral regions against total ozone amount determined from a selected subset of ground-based Dobson observations. Coincidence criteria of the paired observations are occurrence on the same day and within a 300 km circle. A description of the measurements is given by Planet et a1. (1).

The satellite ozone determinations are traceable to Dobson determina­tions of the same quantity through the regression procedure. Therefore, the satellite system can be considered to be an extension of the ground­based Dobson network.

The coverage of the measurements is shown in Table I. The TIROS-N, NOAA-6 and NOAA-8 instruments are no longer operating. Ozone determina­tions from NOAA-8 and from NOAA-7 beyond July 1983 are not available at this time due to the current lack of the Dobson data necessary too derive the regression coefficients.

2.0 Evaluation of the Satellite Data The quality of the satellite data has been evaluated by comparisons

with data from an independent subset of Dobson stations. Approximately 26 Dobson stations are used to generate this independent data set. Again, comparisons of satellite and Dobson determinations are through paired ob­servations on the same day and within 300 km.

It was concluded from the comparisons that, overall, the satellite

Ozone Symposium - Greece 1984 - 234-

determinations are in good agreement with the Dobson data. Different biases were found for different stations. These differences are, to some extent, due to the procedure for the satellite-Dobson matchups but surely contain some measure of the different performances of the individual Dobson spectrophotometers. The coefficients of variation are generally below 8% for all conditions while correlation coefficients are nearly all positive, generally greater than about 0.75. These results offer confi­dence that the satellite results are comparable to results derived solely from Dobson measurements.

An independent satellite source of total ozone amount is the Solar Backscatter Ultraviolet (SBUV) spectroradiometer on Nimbus-7. Launched in November 1979, the SBUV instrument is still operating. We have obtained SBUV data from NASA for comparisons with the TOVS data. Our SBUV data ex­tend only to March 1983. Specific comparisons of SBUV with TOVS will be discussed below.

3.0 Total Ozone Time Series The time series of the global (60N-60S) total ozone data is shown in

Fig. 1 which presents monthly average total ozone amounts from TOVS and SBUV. An interesting aspect of these data are noted in the region of overlapping measurements from the NOAA-6 and -7 instruments. The differ­ence in the time of observations has been noted previously; 7 a.m. local time for NOAA-6 and 3 p.m. local time for NOAA-7. The greatest difference (about 3%) occurs in January 1983; at other times, the agreement is generally better than 1%. No explanation is readily available for the large January 1983 difference. The differences between TOVS and SBUV is attributed to the known different ozone absorption cross-sections used in data reduction.

To evaluate the TOVS data further, we compute monthly average total ozone amounts globally and in three climate zones, i.e., north temperate (25N-55N), tropics (25N-25S) and south temperate (25S-55S). Furthermore, we combine the data from the three satellites into one continuous set as follows: TIROS-N from May-December 1979; NOAA-6 from January 1980-Septem­ber 1981;' NOAA-7 from October 1981-July 1983. The overlap period of the NOAA-6 and -7 data is shown in Fig. 2 which presents the month-by-month ratios of the data from the two satellites in the specific zones of interest. The combined TIROS-N, NOAA-6 and NOAA-7 data set is shown in Fig. 3 as the deviations from the mean monthly values for each of the four zones.

4.0 Analysis of the Data We have looked at the time series in several aspects, viz., determi­

nation of a long-term (4-year) trend, comparisons with independent analyses of Dobson measurements and comparisons with other satellite data.

4.1 Long-term Trend We have imalyz,ed the time series of total ozone amount in the four

regions mentioned above with an available SAS statistical routine. Linear trends for the s~ries of TIROS-N, NOAA-6 and NOAA-7 data were observed as follows: global, -0.63% per annum; north temperate zone, 0.06% per an.; tropics, -0.59% per an.; south temperate zone, -1.31% per an. In addition, ~ relatively strong periodicity of about two years was noted for all zones. If instead we look at the series comprised only of TIROS-N and NOAA-6 data aver almost the same time period, the global trend is -0.76% which is in goad agreement with that from the three-satellite series. It should be noted that this trend analysis was for only a short period, slightly more

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than four years, and is surely affected by short-term variations.

4.2 Comparisons with Dobson Data The data presented in Fig. 3 show clear variations from the mean

values. These data were compared with Dobson data in an analysis of Dobson and satellite measurements by Angell et al. (2). As the satellite data are traceable to Dobson measurements through the regression proce­dure, the satellite systems in effect provide for a global expansi0n of the current sparse Dobson ground network.

Fig. 4 shows the time variation of total ozone amount from Dobson and TIROS measurements from (2). The data in Fig. 4 are presented and discussed in detail in (2) in a slightly different manner than generally herein. (Downward-pointing arrows indicate times of quasi-biennial west wind maxima at 50 mb in the tropics; upward-pointing arrows, the eruption of El Chichon.) There, analysis of both data sets in combination indi­cates record low (since 1958) total ozone values in the north temperate zone in early 1983 with an apparent later recovery. It was further con­cluded from analysis of Umkehr-derived ozone profiles that the decrease was more likely due to anomalies in atmospheric circu'lation than to anomalies in upper stratosphere photochemistry.

4.3 Comparisons with other Satellite Data The Solar Backscatter Ultraviolet (SBUV) instrument and the Total

Ozone Mapping Spectrometer (TOMS) on Nimbus-7 have been making measure­ments of total ozone amount since 1978. Fig. 5 shows the ratios of TOVS­and SBUV-derived total ozone amounts in the several climate zones. The difference in the ozone absorption coefficients used in the reduction of SBUV and Dobson measurements is clearly noted in the ratio of TOVS/SBUV total ozone. The relatively good agreement in these satellite data sets is important when we consider that both instruments will be flown on future NOAA operational satellites and, hence, will provide complementary data well into the future.

The TOVS data have also been compared with TOMS data over a shorter time span but in a different sense. Regression coefficients were derived from a subset of TOVS/TOMS matched data using TOMS ozone values in the dependent data set in the same manner as is done normally with Dobson data. These coefficients were used to generate total ozone values from NOAA-6 TOVS measurements which were then compared with an independent set of TOMS ozone values. Also available was a set of ozone values derived from re­gression coefficients using the Dobson dependent set in the normal manner. These were compared with an independent set of Dobson ozone values. Stan­dard deviations of the differences between the TOMS-based satellite ozone and the TOMS observations and between Dobson-based satellite ozone and Dobson observations in the northern hemisphere are shown in Table II. The similarity offers evidence that the regression coefficients derived from the sparse Dobson observations are adequate for computing ozone from the TOVS observations on the zonal scales that are considered here.

A complementary comparison was performed for TIROS-N measurements in the tropics using the two sets of regression coefficients (i.e., derived from (a) TOVS/Dobson matches and (b) TOVS/TOMS matches) with an independent set of Dobson determinations. The results are shown in Table III. As in the previous comparison, the seasonal pattern is nearly identical as shown by the similar standard deviations of the differences, demonstrating that the larger data sample from which the TOMS regression coefficients were derived does not yield more accurate results over the standard Dobson-based method.

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5.0 Discussion and Conclusions The atmospheric sounders, TOVS, on the NOAA operational environmental

satellites have demonstrated the capability of providing determinations of total ozone amount on a global scale. Comparisons with Dobson-derived total ozone show a precision generally better than 8%, approaching 3% in the tropics on a station-by-station basis. Instruments on separate satellites providing overlapping coverage reproduce to better than 1% except for isolated cases, giving confidence in the use of an overall long-term data set for ozone trend studies. Comparisons with the indepen­dent SBUV-derived ozone data set clearly show that both techniques yield similar historical results. It is noted that a bias currently exists due to different values of ozone cross-section being used in the reduction of SBUV and Dobson measurements.

Determinations of total ozone will continue on the NOAA satellites into the foreseeable future. Starting in late 1984, two instruments, TOVS and SBUV, will be standard satellite components. It is expected that a useable set of ozone determinations will be generated over a period of time sufficient to recognize natural variations in atmospheric ozone.

Acknowledgment The cooperation of the Canadian Atmospheric Environment Service and

of many of the stations in the Dobson network in supplying ozone data is acknowledged.

References 1. Planet, W.G., D.S. Crosby, J.R. Lienesch and M.L. Rill (1984). "Deter­

mination of total ozone amount from TIROS radiance measurements," J. Climate and Appl. Meteor., 23, 308-316.

2. Angell, J.K., J. Korshover and W.G. Planet (1984). "Ground-based and satellite evidence for a pronounced total-ozone minimum in early 1983 and responsible atmospheric layers," submitted to Mon. Wea. Rev.

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- 237-

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- 238-

THE OBSERVATION OF ATMOSPHERIC STRUCTURE WITH TOMS AND SOME POTENTIAL ADVANCEMENTS

Summary

ARLIN J. KRUEGER Planetary Atmospheres Branch Goddard Space Flight Center

Greenbelt, Md, 20771

The Total Ozone Mapping Spectrometer (TOMS) was designed to observe the spatial characteristics of total ozone which were not resolved by the nadir-viewing Nimbus BUV and SBUV instruments. At the wavelengths suitable for total ozone measurements the radiance is large enough that the entire daytime atmosphere could be surveyed with about 50 km resolu­tion from a polar orbiting satellite. The resulting high spatial resolution TOMS ozone images are found to reflect the internal dynamic structure of the lower atmosphere. Features which can be identified and tracked in the TOMS maps are illustrated. They include planetary wave scale troughs and ridges, mesoscale cutoff lows and rapidly moving troughs, jet stream confluence and difluence areas, hurricanes, and polar night lows. These features control the ozone above any given location and account for nearly all the variance in the total ozone. The TOMS instrument has also been employed to track the volcanic eruption clouds from EI Chi chon , Mount St. Helens, Alaid, and smaller eruptions, such as Galunggung. The volcanic clouds are detected by the absorption of sulfur dioxide at the TOMS wavelengths. Volcanic clouds and meteorological features that are resolved by TOMS change rapidly between the once per day mapping afforded with the Nimbus 7 satellite. A radiometric design analysis indicates that half-hourly maps are feasible using a similar instrument on a geostationary platform. A second application of the TOMS instrument design would permit a determination of the vertical ozone distribution in the lower stratosphere using Radon transform principles. This technique has importance in measurement of jet stream folds and the related troposphere-stratosphere exchange.

1. Introduction

The total ozone maps produced with the Nimbus 7 Total Ozone Mapping Spectrometer represent a logical extension of the total ozone sounding capability first demonstrated with uv albedo data from the Nimbus 4 Backscatter UltraViolet (BUV) instrument 1• The precision of total ozone measurements with TOMS is comparable to that of Dobson Spectrophotometer stations2 and the accuracy is unmatched by any other satellite remote sensing instrument. Although an association between total ozone and pressure systems has been known for 50 years, no means for measuring total ozone on a dense spatial scale were available until the TOMS was flown. The clarity of the meteorological association was surprising3 since rarely

Ozone Symposium - Greece 1984 - 239-

are atmospheric phenomena revealed as well as this. However, a major difficulty in analysing the relationship is in obtaining conventional data that is simultaneous with and in similar spatial resolution as TOMS.

A major new development has been the identification of volcanic clouds which are discernable in the TOMS maps due to volcanic sulfur dioxide which absorbs at the same spectral region as ozone. Since most volcanic clouds are much smaller than the distance between satellite orbits the spatial scanning of TOMS is essential to the observing of these clouds. All significant eruptions that have been reported (and several unreported eruptions) are detected in the two years of data that have been surveyed at present. The current research activity deals with improvement of the ozone-sulfur dioxide discrimination algorithm.

Finally, the full capability of this technique has yet to be realized. The next generation of TOMS instruments could be placed on geostationary satellites where the motions of weather systems can be followed, similar to the visible light cloud imagery provided from GOES-type scanning radio­meters. The same type of TOMS instrument could also be used on low earth orbit satellites to determine the vertical ozone distribution in the lower stratosphere, where present remote sounding techniques have had limited success.

2. Total Ozone and Meterorology

The close relationships between the total ozone and the dynamics of the troposphere are immediately obvious when upper air charts are compared with TOMS ozone maps. The ridges coincide with ozone minima and the troughs are ozone maxima. All of the dynamic features can be located, incl~ding jet streams which coincide with regions of large ozone gradi­ents. These can be traced equally well over the oceans as over the land where the radiosonde stations are primarily located. Thus, an unbiased presentation of jet stream location is available from TOMS. Similarly the full extent of planetary waves into the tropics can be delineated. A theoretical stugy of vertical and horizontal advection for medium scale planetary waves has closely simulated a Southern Hemisphere total ozone pattern.

Of equal interest are the smaller scale features which are only crudely resolved in upper air charts. These include structure within troughs and ridges, amplifying and decaying perturbations on waves, and subtle modulations in the tropical ozone. The physical processes forming the detailed ozone structure are qualitatively understood through the relationship between total ozone, potential vorticity, and tropopause height so that the utility as a dynamic tracer can even now be exploited. Studies of the traveling disturbances along the subtropical jet stream south of the Himalaya mountains and the development of the South Asign anticyclone, a major component of the Indian monsoon synoptic system , and of the development of severe storms in North America7 have already used TOMS data to infer atmospheric structure both in the horizontal and the vertical.

3. Volcanic cloud mapping with TOMS

When EI Chichon erupted in April 1982, the absorption in the cloud was equivalent to more than 700 Dobson units of ozone. A study of the spectral signature of this absorp§ion at the TOMS wavelengths suggested that sulfur dioxide was the absorber. At the suggestion of Dr. James Kerr of the Atmospheric Environment Service, Canada, an algorithm used with the Brewer

- 240-

Spectrometer was tried on the TOMS radiances and found to be very effective in discriminating between ozone and sulfur dioxide. This technique now is employed in the flagging of contaminated ozone data and in the detection of volcanic eruptions. The sensitivity is very impressive, with a detection limit one-thousand times smaller than the El Chichon cloud. An inventory of eruptions during the TOMS data years is presently being prepared.

These observations also permit a quantitative assessment of the area and mass of each eruption cloud. With this information the accuracy of the volcanic sulfur budgets for the troposphere and stratosphere can be greatly improved. Similarly, the rate of loss of sulfur dioxide can now be measured from a sequence of daily S02 amounts. The rate of change of El Chichon S02 has alre§dy ruled out the possible chemical process which would consume odd hydrogen •

4. New developments

Since the discovery of the potential meteorological applications of TOMS it has been clear that the temporal resolution of a polar orbiting satellite is inadequate for many uses of the data. The time scale for severe storms is tens of minutes, while that of jet streams is hours. Volcanic eruptions have similar time scales and it is obvious that an eruption taking place immediately after passage of the satellite will not be detected for almost 24 hours. Therefore an initial study has been made of the feasibility of total ozone mapping from a geostationary orbit where continuous observations would be possible throughout the daylight hours. The same spatial resolution (50 km) has been retained and the sampling time is set at 30 minutes. Such measurements were found to be practical for a spectrometer similar to" TOMS if multiple detectors are used. One satellite covers one-third of the earth; three are required for complete coverage of the tropics and latitudes to about 60 degrees north and south. Polar coverage continues to require a polar orbiter.

A further application of the TOMS instrument design is in the resolu­tion of vertical and horizontal structure of ozone in the lower strato­sphere. By scanning from low earth orbit along the path of the satellite rather than cross track as presently done, it is possible to apply a Radon transform to the series of radiances to infer internal structure, as in tomography. Of particular interest is the tropopause height and structure across the jet stream where the ozone is a useful tracer of troposphere­stratosphere exchange processes.

REFERENCES

1. MATEER, C. L., D. F. HEATH and A. J. KRUEGER, (1971), Estimation of total ozone from satellite measurements of backscattered ultraviolet earth radiances, J. Atmos. Sci., 28, 1307-1311.

2. BHARTIA, P. K., K. F. KLENK, C. K. WONG, D. GORDON, and A. J. FLEIG, (1984), Intercomparison of the NIMBUS 7 SBUV/TOMS total ozone data sets with Dobson and M83 results, J. Geophys. Res., 89, 5239-5248.

3. KRUEGER, A. J., A. J. FLEIG, J. A. GATLIN, D. F. HEATH, P. K. BHARTIA, V. G. KAVEESHWAR, K. F. KLENK, and P. M. SMITH, First results from the Nimbus 7 Total Ozone Mapping Spectrometer, Proc. Quad. IntI. Ozone Symp., Boulder, Colo., Vol. 1, 322-327.

4. SHAPIRO, M. A., A. J. KRUEGER, and P. J. KENNEDY, (1982), Nowcasting the position and intensity of jet streams using a satellite-borne Total Ozone Mapping Spectrometer, in Nowcasting, ed by K. A. Browning, Academic Press, London.

-241-

5. SCHOEBERG, M. R. and A. J. KRUEGER, (1983), Medium scale disturbances in total ozone during southern hemisphere summer, Bull. Am. Meteorol. Soc., 64, 1358-1365.

6. REITER, E. R. and D. GAO, (1982), Heating of the Tibet Plateau and movements of the South Asian high during spring, Mon. Wea. Rev., 110, 1694-1711.

7. UCCELLINI, L. W., D. KEYSER, C. H. WASH, and K. F. BRILL, (1984), The Presidents' Day cyclone of 18-19 February 1979: Influence of a tropopause fold on rapid cyclogenesis, Submitted to Mon. Wea. Rev.

8. KRUEGER, A. J., (1983), Sighting of El Chichon Sulfur Dioxide clouds with the Nimbus 7 Total Ozone Mapping Spectrometer, Science, 220, 1377-1379.

9. MCKEEN S. A., S. C. LIU, and C. S. CHANG, (1984), On the chemistry of stratospheric S02 from volcanic eruptions, J. Geophys. Res., 89, 4873-4883.

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Summary

STANDARD PROFILES OF OZONE FROM GROUND TO 60 KM OBTAINED BY COMBINING SATELLITE AND

GROUND BASED MEASUREMENTS

P.K. Bhartia, D. Silberstein, and B. Monosmith Systems and Applied Sciences Corporation

5809 Annapolis Road, Hyattsville, MD 20784

and

Albert J. Fleig Laboratory for Atmospheric Sciences

NASA, Goddard Space Flight Center, Greenbelt, MD

Recent satellite experiments have produced a large multi-year data base of stratospheric ozone profiles covering the entire globe. Among these, the Solar Backscatter Ultraviolet Experiment (SBUV) has been operating continuously since November 1978 providing some 1000 profiles per day._ Based on detailed comparisons with ozonesondes and other satellite based instruments, SBUV data have been determined to be of excellent quality from about 50 km down to the tropopause.

Combining the satellite derived information with those obtained from o zonesondes, we have developed a data base of standard ozone profiles and of variance/ covariance matrices that define the observed variation of the atmospheric ozone around the mean profiles. Highlights of this data base will be presented. In addition, parameters of an analytical fit that describes the essential features of the data set will also be presented.

Although this data base has been created specifically for use as a priori profiles for SBUV and Umkehr retrievals, it should be l1'5eful in other remote sensing applications, and in modeling the U.V. radiation fields in the stratosphere. Another suggested application of this data set is in estimating ozone above the peak altitude of the ozone balloons. Current estimation procedure can produce up to 10% errors in determining ozonesonde normalization factors.

1.0 Introduction The data baSE: for this study consists of four years of SBUV data and five

years of published ozonesonde data. The SBUV dataset is binned according to total ozone (50 m-atm-cm), latitude (100 ) and time of year (monthly). The final dataset contains approximately 900 composite profiles per year. A description of SBUV data and presentation of profiles from the first year of operation are given in a paper by McPeters et a1 (3). The supplementary balloon data consist of approximately 4000 flights. While balloon data lack the spatial coverage of SBUV, they are still the best source of information from the surface to 10 mb. Balloon measurements have provided low-level data for prior studies, one of which presented a combined BUV/ozonesonde climatology (1).

Ozone Symposium - Greece 1984 - 243-

2.0 Evaluation by Total Ozone The first goal of this analysis was to examine total ozone as a predictor of

layer ozone, primarily in the lower layers of the atmosphere. Thirteen Umkehr layers were investigated, where the pressure at layer (1) base (in units of millibars) is

1013 -;1- 1 = 0,12.

Balloon data were the major source for layers 0 to 6, with Natal (5.50S), Hohenpeissenberg (47.80N), Churchill (58.80 N) and Resolute (74.7°N) providing-the majority of the data while the remaining stations were used to verify the results. For layers 7 to 12, information was provided by SBUV. Yearly average layer ozone values were regressed against total ozone amounts for each of three latitudes, 10w-15°, middle-45° and high-75° through the equation:

Xl = Xlo + al (fl- 300) + bl(fl- 300)2

where Xl represents layer ozone, Xlo represents a predicted layer ozone value for a 300 m-atm-cm profile, al and ~ are the predicted regression coefficients and n is the actual total ozone value tor a given profile. Layer ozone amounts were then generated using the predicted coefficients for specific total ozone amounts at 50 m-atm-cm intervals, with a minimum total ozone value of 225 m-atm-cm for all latitude groups, maxima of 325 m-atm-cm at low latitudes and 525 m-atm­cm at middle and high latitudes.

A spline fitting routine used these layer ozone amounts to interpolate the partial pressure in nanobars at 22 pressure levels from 1 mb to 1000 mb, and the resul ting partial pressure profiles are illustrated in Figures 1-3. These curves display similar characteristics to those presented by Mateer (2), although the high lati tude profiles presented here peak at somewhat higher altitudes.

3.0 Evaluation by Season Another aspect of this analysis is the effect of seasonal variations upon

layer ozone, primarily in the upper layers of the atmosphere. Layer ozone vales, normalized with respect to total ozone, were regressed against season only through use of the equation

where Xlo repr'Miilf the yearly average layer ozone value, Al is the annual amplitude and dl is the day of the peak yearly value. These values were then used to solve for layer ozone amounts for March, June, September and December. The balloon stations used for this evaluation are Natal, Hohenpeissenberg and Resolute, representing low, middle and high latitudes respecti vely. A spline routine produced mixing ratio values (in parts per million by volume) for specified pressure levels and the middle and high latitude results of this evaluation for both balloon and SBUV are plotted in Figure 4. There is strong agreement between SBUV values (solid line) and balloon values (dashed line) for both the June (J) and December (D) months at middle latitudes (45 NORTH). However, this is not the case for the high latitude analysis (75 NORTH). The balloon data show a rather different structure than SBUY data, lacking the secondary mixing ratio peak around 35 mb for both June and March (M). December was not plotted at high latitudes due to the absence of winter season ozonesonde flights at Resolute.

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4.0 Variance - Covariance Matrix In addition to the total ozone and seasonal studies, residual layer ozone

values (measured minus seasonal fit predicted) were investigated for the balloon station at Hohenpeissenberg in order to produce a variance-covariance matrix. Table I displays ,the standard deviation value for each layer (m-atm-cm) and as a percentage of the mean layer ozone amount. Also, included are the correlation values, where the c~rrelation is:

CT j, k

(CT. ) (CT ) ],j k,k

for neighboring U mkehr layer (j,k) evaluations, depth from 1013 mb to 253.25mb.

Table I

1,5 2,6

with layer 1 here representing a

Standard Deviations for Layer Ozone Amounts at Hohenpeissenberg and Correlations Between Neighboring Layers

Layer CT % of Ly:r. Oz. Correlation

6 4.9 12 .50

5 6.1 9 .38

4 9.2 12 .47

3 14.6 27 .53

2 12.8 41 .26

1 6.2 21

5.0 Conclusion Using global SBUV data in conjunction with balloon data, standard ozone

profiles from the ground to 60 kilometers have been developed. There is good agreem~nt between SBUV and balloon at middle latitudes. At high latitudes, there is some discrepancy between balloon and SBUV data in the region from 10 to 50 mb, a dissimilarity which merits further investigation. SBUV data are of great value at all latitudes in providing information on the vertical distribution of ozone above the peak altitude of ozonesondes and the combined SBUV-balloon multi-year data base provides a strong foundation in the effort to construct vertical ozone profiles over the entire depth of the atmosphere.

REFERENCES

1. Klenk, K.F., P.K. Bhartia, E. Hilsenrath and A.J. Fleig, 1983: "Standard Ozone Profiles from Balloon and Satellite Data Sets," Journal of Climate and Applied Meteorology, 22, 2012-2022.

2. Mateer, C.L., J.J. Deluisi and C.C. Porco, 1980: ''The Short Umkehr MethOd, Part I: Standard Ozone Profiles for use in the Estimation of Ozone Profiles by the Inversion of Short Umkehr Observations," NOAA Tech. Memo. ERL ARL-86, 20pp.

3. McPeters, R.D., D.F. Heath and P.K. Bhartia, 1984: "Average Ozone profiles for 1979 From the NIMBUS 7 SBUV Instrument," Journal of Geophysical Research, ~ 5199-5214.

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Figure 1:

'" :>

Figure 2:

LOW LATITUDE OZONE. PROFILES

PARTIAL PRESSURE ( NO )

Low Latitude Ozone Profiles for 225 - 325 m-atm-cm Total Ozone Values

MIO LATITOOE OZONE PROFILES

280

PARl1AL MESSURE ( NB )

Middle Latitude Ozone Profiles for 225 - 525 m-atm-cm Total O:mne Values

- 246-

Figure 3.

Figure 4:

HtGH l. ATITUDE OZONe PROFL ES

25

PARTIAL PRESSURE ( NB )

High Latitude Ozone Profiles Cor 225 - 525 m-atm-cm Total Ozone Values

o 45 NORTH 15 NORTH

10

MIXING RATIO ( PPMV I

Middle and High Latitude Seasonal Ozone Mixing Ratio Promes Cor SBUV (solid) and Balloon (dashed). June and December are Displayed Cor Middle Latitude, with June and March Plotted in the High Latitude Analysis.

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ANNUAL AND SEMIANNUAL OSCILLATIONS OF STRATOSPHERIC OZONE

Summary

K. MAEDA Laboratory for Planetary Atmospheres

NASA/Goddard Space Flight Center Greenbelt, Maryland 20771

The global structures of annual- (AOs) and semiannual-oscillations (SAOs) of stratospheric ozone are examined by spherical harmonic analysis of the data obtained from the Nimbus-7 solar backscattered UV­radiation (SBUV) measurements for the period from November 1978 to October 1980. The results indicate: (i) the vertical distribution of the equatorial ozone SAO has a broad maximum of the order of 0.5 (mixing ratio in ~g/g); and the maximum appears earlier at high altitude (shifting from May [and November] at 0.3 mb to November [and May] at 40 mb); (ii) amplitudes of the polar ozone SAOs are maximum at 2 mb, which is 2 ~g/g at 750 Nand 0.8 ~g/g at 750 S, respectively; (iii) vertical distributions of ~he polar ozone AOs and SAOs show two peaks in amplitude with a minimum (nodal layer) where the phase changes rapidly with altitude.

1.0 Introduction

The cause of the tropical stratospheric SAO in the zonal wind has been ascribed to the wave-flow interaction processes for the wind shifts from easterly to westerly and advection of zonal mean momentum from the summer hemisphere for the westerly-to-easterly shift. Corresponding SAOs in the temperature field are understood in terms of the thermal wind relation. The source of the polar stratospheric SAO is, however, not well estab­lished, although the occurrence of sudden stratospheric warming (SSW) in the northern midwinter can be regarded as one of the possible causes.

The purpose of this paper is to present new aspects of the global structure of the stratospheric SAOs and AOs based on the spherical harmonic analysis of the Nimbus-7 ozone data, extending the previously reported preliminary results (1).

2.0 Data

The stratospheric ozone data used in the present analysis are the ozone mixing ratio (in ~g/g) at the 16 pressure levels between 0.3 and 40 mb (60 ~ 20 km). The mixing ratio as a function of the pressure level is derived from the Nimbus-7 solar backscattered ultraviolet (SBUV) radiation measurement for the period from November 1978 to October 1980.

3.0 Results

The formulation for analysis is described previously (1,2).

Ozone Symposium - Greece 1984 - 248-

3.1 Semiannual Oscillation of Stratospheric Ozone

Figure 1 shows the amplitudes (leftside) and the phases (rightside) of

.. . ,

.. ..

"'. ~.

$fI,.tI.ANNUAI..OSClllATlOH'tolOHE.NIMBUS.7 SIHM the semiannual component is shown em 111')10110' IU., 06 .... n ""'''oIUNJUl.wdlY''aetNO¥MC: as a function of altitude, which

-, , , , , , ",'.. indicates: (i) A broad maximum of '<>'.~~''- C approximately 0.5 Ilg/g exists in

',,- II the equatorial SAO in the latitude ,,·s ..... , ~, between 30 and 42 km with a small

"''y,,})' (I « , "·N_1 .1 c dip at 37 km 5 mb). ii) The l \r ~ ~ polar SAOs have a major peak above

,,·N ~ ws\ ~ the minimum, and the northern r maximum at 2 mb (1.84 JJg/g at 750 I'" t N) is more than twice the southern

EQUATOR

MONTH OF MAXIMUM

'-:::;:'::t":':-.:';,-:'.,:O.:-'. t; .. to .. 'to •• ---;',., w!..o!c ~! .. ':'100~ .~ ... !. ... ~ ...

i maximum at 1.5 mb (0.82 JJg/g at 750 S). (iii) Below the minimum, the amplitude of the southern SAO (0.55 JJg/g at 10 mb) exceeds that of the northern SAO (0.48 JJg/g at 7 mb). (iii) The phase of the equatorial SAO shifts downward,

AMPlIT\.lDE PHASE

Figure 1.

beginning May (and November) at 0.3 mb (~60 km) to November (and May) at 40 mb (~20 km). (iv) The phase of the polar SAO shifts upward above the 10-mb level in the Northern Hemisphere and above the 7-mb level in the Southern Hemisphere, respectively, but is nearly constant below these levels.

The vertical distributions of the ozone SAO amplitudes are replotted with 100 intervals from 850 N to 850 S in Figure 2, which presents: (i) The

height of the ~ncAl OISTRIBU110NS OF OZONE SAO (AMPllruoe IN JIIWol f~

.~ • • 011 , ••• ,. II .~' . .l1li. ' .1 .,

~r:>~~~Z\5 ~ t ?«<~~?~" , ... ~ ~"""""-;'a -'--'--I.~.~. ~.~.~.

VERnCAL. OISmlBllTlONS or: ozo~e SAO IAMPUTUOE IN ,..QlQl lea

Figure 2.

3.2 Annual Oscillation of Stratospheric Ozone

major maximum is higher in higher latitudes and decreases in lower latitudes. (ii) The maximum amplitude decreases with decreasing latitudes.

The vertical distributions of ozone SAO shown in Figure 2 are replotted as a function of latitude in Figure 3.

In Figure 4, the amplitudes (in JJg/g) and the phase (the month of maximum) of the ozone AOs are shown as a function of altitude, which shows: (i) The amplitude of the equatorial AO, whose maximum is 0.6 JJg/g at the 5 mb level, is nearly one order of magnitude smaller than that of the polar AO. (ii) Both polar and equatorial AOs have two maxima in the vertical

- 249-

distribution. (iii) In the northern polar AO, the upper maximum is 1.5 ~g/g at 1 mb, which is lower than the southern polar AO of 2.2 ~g/g at 1.5

mb. (iv) The lower layer maximum, 2.2 ~g/g, of the northern polar AO at 4 mb is larger than that of the southern polar AO maximum of 1.7 ~g/g at 5 mb. (v) The dip is located at about 2 mb in both polar AOs, whereas it is located at 10 mb in the equatorial AO.

The amplitude of the upper ozone SAO is larger in the northern polar stratosphere than in the southern polar stratosphere (Figure I), whereas the amplitude of the upper ozone AO is smaller in the northern polar stratosphere than in the southern polar stratosphere (Figure 4). In the lower stratosphere, however, these ratios are reversed. The causes of these hemispheric asymmetries are well understood. The vertical distributions of the ozone AO amplitudes are replotted in Figures 5 and 6, corresponding to Figs. 2 and 3 of SAO.

.,b .. .. F i: 11 .. .. .

.. .. .,. , . . . ..... II" -. .... _; .......... ..

I , Iii i

IIIIQIlon.Of' "', ""..."..

'1" ......... 1 ., ., .... . ... I.' .... !oJ,cHe; .!. J:.:"'" NoI,,-,lUOf

Figure 4 •

Figure 5.

- 250-

LATITUDE DEPENDENCE OF OZONE SAO (AMPlITUDE IN pg/O)

Figure 3.

3.3 Vertical Phase Shifts of Ozone AOs and SAOs in the Stratosphere

To visualize the variations of amplitudes and phases of the ozone AOs and SAOs in the atmosphere, the AO and SAO components of the harmonics are plotted with respect to time (the month of year 1978), together with the original data in Figure 7. The full lines and dashed lines correspond to SAOs and AOs, respectively. Short vertical bars are the standard devia­tions of each data point obtained by the monthly averaged zonal mean values of the ozone mixing ratio (in Ug/g). Arrows between full lines indicate the direction of phase shifts of the SAOs in the vertical direction.

lATITUOE OEPENDENCE OF IJZIJNE AO (AMPLITUDE IN "gig)

Figure 6.

-.---- --... ::J ..-

Figure 7.

4.0 A Theory of Stratospheric Ozone SAO

4.1 Polar

In contrast to the equatorial atmosphere, there is no obvious cause for the occurrence of the SAO in the polar stratosphere. Furthermore, as can be seen from Figure 1, the phase of the ozone SAO in the polar upper stratosphere shifts upward while that of the equatorial SAO moves downward whi~h has been interpreted in terms of two atmospheric processes (1,2). There can be some contributions to the polar ozone SAO from the polar stratospheric temperature SAO. An estimate based on the well-known relation between the atmospheric temperature and the ozone density in the photochemical equilibrium gives a maximum ozone SAO amplitude of 1.5 Ug/g at 2mb, 750 N (3). According to the Nimbus-5 SCR data, the tempera­ture SAO maximum of 9 K at 750 N occurs in June at 3 mb (4), corresponding to the ozone minimum in June at 750 N. The similar estimate of the ozone

SAO in the Southern Hemisphere presents a maximum amplitude of 0.6 Ug/g at 1 rob, 750 S, in December, corresponding to the thermal SAO maximum of 4 K at 1 mb, 750 S, in agreement with Figure 1. Since the temperature maxima in June at 750 N and in December at 750 S produce only AOs in the polar upper stratosphere, another heating is necessary to generate the thermal SAO in the polar upper stratosphere. The SSW as a source of the polar

- 251-

stratospheric SAO presents, however, several difficulties (2). The apparent upward phase shift of the polar ozone SAO shown on the

right side of Figure 1 can be caused by the combination of the following three factors: (i) the timelag of the ozone maximum appearance from the vernal equinox in the transient layer (~37 km) to the summer solstice in the photochemically controlled upper layer (above 45 km); (ii) upward shift of the maximum ozone production from the summer soltice to the autumnal equinox, corresponding to the increases of the solar zenith angle; and (iii) the upward diffusion of ozone from the SAO maximum (2).

4.2 Equatorial

The cause of the equatorial ozone SAO is different from that of the polar SAO. As shown in Figure 3 of (4), the temperature maximum of the equatorial stratosphere takes place in about the 4-mb (~40 km) level just after the equinoxes, where the ozone variation is close to the photo­chemical equilibrium. Namely, the equatorial upper stratospheric ozone undergoes twice a year minima at the equinoxes.

In summary, the equatorial ozone SAO is generated by the negative temperature effect of ozone photochemistry associated with the semiannual modulation of the temperature field, whereas the polar ozone SAOs are generated by two processes: photochemical production of ozone and dynamical transport from equatorial ozone production maximum. The UV heating in summer and dynamical heating in winter are plausible additional sources for the polar stratospheric temperature SAO but are not a major source for the polar ozone SAO.

5.0 Comments on Stratospheric Ozone AO

Contrary to the SAO, there are no obvious mechanisms for the genera­tion of the AO in the equatorial stratosphere. The following two types of asymmetries are, however, attributable to the cause of AO production in the equatorial stratosphere: (a) North-South Hemispheric Asymmetry--Because of the orographic and topographic differences between the Northern and the Southern hemispheres, large-scale wave activities prevail in the Northern Hemisphere over the Southern Hemisphere (3). (b) Seasonal Asymmetries Due to the Earth's Orbital Eccentricity--The southern hemispheric summer and winter take place near the perihelion and the aphelion of the earth's orbit, respectively. Consequently, the seasonal temperature variation is larger in the southern upper stratosphere, and the ozone content above the 2-mb level is higher in the southern hemispheric winter than in the northern hemispheric winter (Figure 4) (3).

REFERENCES

1. MAEDA, K. (1984). Semiannual oscillation of stratospheric ozone, Geophys. Res. Lett., 11, 583-586.

2. MAEDA, K. (1984). Annual and Semiannual oscillations of stratospheric ozone, NASA/Goddard Space Flight Center, X-961-84-13, July.

3. MAEDA, K. and D. F. HEATH (1983). Asymmetries of the upper stratospheric ozone distribution between two hemispheres, J. Atmos. Sci., 40, 1353-1359.

4. MCGREGOR, J. and W. A. CHAPMAN (1978). Observations of the annual and semi-annual wave in the stratosphere' using Nimbus-5 SCR data, J. Atmos. Terr. Phys., ~, 677-684.

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AN EVALUATION OF THE PERFORMANCE OF UMKEHR STATIONS BY SOLAR BACKSCATTERED ULTRAVIOLET (SBUV)

EXPERIMENT

Summary

P.K. Bhartia, C.K. Wong 5809 Annapolis Rd, Hyattsville, MD 20784 Systems and Applied Sciences Corporation

and

Albert J. Fleig Laboratory for Atmospheric Sciences NASA, Goddard Space Flight Center

Until recently, Umkehr data taken by 20 Do~on stations around the world have been the principal source of information about the behavior of upper stratospheric ozone. U mkehr results are used also for detecting drifts in satellite instruments and for determining intersatellite biases. However, a systematic evaluation of the quality of U mkehr data taken by the various stations has been lacking.

Five years of ozone profile data from the Solar Backscattered Ultraviolet (SBUV) have been used to examine and intercom pare the quality of Umkehr stations, and to assess the degradation of their performance after the El Chichon volcano eruption in southern Mexico. In contrast to Umkehr, the SBUV ozone measurements in layers 7 through 9 (I-8mb) were unaffected by the massive amounts of dust and gases ejected by El Chichon.

1. 0 Introduction The SBUV experiment was launched in October, 1978, on NASA's Nimbus-7

satellite. Five years of total ozone and ozone vertical profile data have been archived at the National Space Science Data Center (NSSDC), Goddard Space Flight Center, Greenbelt, Maryland.

Presented in Section 2.0 is an assessment of biases and drifts between the stations of the Umkehr network using the SBUV as the interstation transfer standard. Among the 20 Umkehr stations analyzed, nine provide three-fourths of all intercomparison results. Results of layers 7, 8 and 9 from these nine stations are presented. In Section 3, a comparison of the SBUV with an Umkehr station in Tateno, Japan, is analyzed to demonstrate the impact of El Chichon on Umkehr data.

2.0 Multiple Regression Analysis of SBUV /UMKEHR Differences For each Umkehr measurement, SBUV data were collected the same day at

no more than 10 in latitude and 100 in longitude away from the station location. A match was found for about 60% of all Umkehr data. Previous studies (1) have shown systematic, seasonally varying differences between Umkehr and SBUV measurements. To determine these and other systematic differences, a multiple­linear regression model was fit to the difference between SBUV and station

Ozone Symposium - Greece 1984 - 253-

measurements in each layer. (For northern hemisphere stations, data taken after the eruption of El Chichon in April, 1982 have been excluded in this part of the study.)

Model: tJ. = b + dt + a1 cos 211"(t + 4>1) + a 2 cos 4 (t + 4>2)

where, A is the percent of difference between SBUV and Umkehr measurements, d is the relative drift; and the last two terms model the difference in the annual and semi-annual cycles between the two types of measurements. Since t is measured from satellite launch time, b gives the bias between an Umkehr station and a freshly calibrated satellite instrument.

2.1 Interstation Variability of SBUV /Umkehr Bias Table I shows the interstation variability of bias (b) for layers 7 through 9,

for nine Umkehr stations. It also gives the (variance weighted) bias for the entire network consisting of 20 stations. Ninety-fi ve percent confidence intervals are shown in parentheses. A positive bias indicates that Umkehr values are larger than the SBUV values.

Results show that large biases exist between the stations in layer 9: Poona is 25% lower than Varanasi; and Lisbon is 10% higher than the three most consistent Umkehr stations - Arosa, Boulder and Tateno. Interstation biases vary from layer to layer: in the case of Varanasi, a positive bias of 10% in layer 9 against the entire network changes to -5% in layer 7; for Lisbon, the bias reduces from 10% in layer 9 to only 2% in layer 7.

2.2 Interstation Variability of U mkehr SB UV Drift The results presented in Table II show that Tateno and Boulder stations are

the most consistent with SBUV over a long term, showing no significant drift in any of the three layers. Other stations, however, have drifted to lower values with Varanasi showing -14% per year drift in layer 9 and - 2% per year drift in layer 7. (No data contaminated by EI Chichon were used in these comparisons.)

3.0 Assessment of the Impact of EI Chichon Volcano on Umkehr Data by SBUV Effects of stratospheric aerosols on Umkehr ozone retrievals are long known

(2). Recently, Reinsel et al. (3) made empirical estimates of the effect of aerosols on Umkehr data and used these estimates to show evidence of a real, long-term decrease in atmospheric ozone in layer 8. These calculations, however, are necessarily based on certain assumptions about the global distribution of aerosols and can be affected by other factors such as change in atmospheric temperature and calibration drifts in U mkehr stations. More direct evidence of the effects of aerosol on U m kehr retrievals is provided by SB UV. Three and one­half years of SBUV data prior to the El Chichon eruption and 1 1/2 years of data after the eruption are now available. Since SBUV results are unaffected by the volcano in layers 7-9 where Umkehr errors are largest, their intercomparison gives a direct estimate of the magnitude of errors in Umkehr.

Figures 1 through 3 show how one can make these estimates for the Tateno Umkehr station. Three and one-half years of intercomparison data before the eruption provide adequate information to conclude that the Umkehr ozone values dropped soon after the eruption by 30% in layer 9, 20% in layer 8 and 10% in layer 7. About a year after the eruption the U mkehr ozone values again returned to normal

To obtain more precise estimates, the systematic seasonal cycles oooerved in the Umkehr/SBUV ratios referred to should be corrected. The cause of these cycles has not been established, but errors in the ozone cross-section at U mkehr

- 254-

NO OF

TABLE I

SBUV/UMKEHR STATION BIAS

BIAS (UMKEHR - SBUV IN %)

STATION MATCHES LAYER 9 LAYER 8 LAYER 7

Arosa 241 2(2) -7(1) -5(1)

Tateno 226 0(1) -8(1) -1(1)

Boulder 138 2(2) -7(1) -7(1)

Lisbon 112 11(3) -4(1) -2(1)

N. Delhi 112 -3(3) -5(1) -3(1)

Poona 95 -15(4) -10(2) -11(2)

Belsk 86 -6(4) -11(2) -1(2)

Varanasi 69 10(4) -7(2) -9(2)

Aspendale 60 -3(4) -7(2) 1(2)

Network Average:

20 stations 1470 0(3) -7(2) -4(2)

TABLE II

SBUV/UMKEHR STATION DRIFTS

DRIFT (UMKEHR - SBUV IN %/YEAR)

STATION LAYER 9 LAYER 8 LAYER 7

Arosa -3(2) -2(1) -2(1)

Tateno 0(1) 0(1) 1(1)

Boulder 1(2) 0(1) 1(1)

Lisbon -5(3) -3(2) -2(1)

N. Delhi -5(3) -3(1) -3(1)

Poona -2(3) 0(2) 2(1)

Belsk -2(4) 0(2) -1(2)

Varanasi -14(4) -7(2) -2(2)

Aspendale -3(4) -2(2) -2(2)

Network Average: -1.6(1.5) -1.2(0.8) -0.6(0.7)

- 255-

wavelengths due to varying atmospheric temperatures are suspected to be the source of error. For SBUV, much shorter ultraviolet wavelengths are used for profile determination and at these wavelengths there is no temperature dependence of the ozone cross-section.

4.0 Conclusion The study presented here shows that the stations in the Umkehr network

provide inconsistent global ozone data sets with large interstation biases and drifts. Long-term trends of ozone derived from Umkehr data are unlikely to be meaningful unless the stations are carefully selected, and are corrected for variations in atmospheric temperature as well as the aerosol effects. SBUV provides an excellent source of data for station selection and for estimating the relevant atmospheric corrections.

REFERENCES

1. Bhartia, P.K., K.F. Klenk, A.J. Fleig, C.G. Wellemeyer, and D. Gordon, 1984: ''Intercomparison of Nimbus-7 Solar Backscattered Ultraviolet Ozone Profile with Rocket, Balloon and Umkehr Profiles," J. Geophys. Res. 89, 5227-5238. -

2. Deluisi, J.J., 1979: "Umkehr Ozone Profile Errors Caused by the Presence of Stratospheric Aerosols," J. Geophys. Res.,ll> 1766-1770.

3. Reinsel, G.C., G.C. Tiao, J.J DeLuisi, C.L. Mateer, A.J. Miller, and J.E. Frederick, 1984: "Analysis of Upper Atmospheric Umkehr Ozone Profile Data for Trends and the Effects of Stratospheric Aerosols," J. Geophys. Res., 89, 4833-4840.

"_0,---------____ ...., TAT£NO LAYER 7

.. , I "~ ?; i ;~~mn ___ n o. ,L_.L..l....LL..L.L.J-L..L..l....LL..L.L.J-L..L..l.---LJ

12 3 6 9 11 J IS 9 12 J Ei 9 12 J 6 9 12 1 6 9 1979 I" 1981 1& 1500

Figure 1: Monthly Average Ozone AmoWlt in La6er 9 measured by the Tateno (36.1 N, 140.1oE) Umkehr station are compared with colocated SBUV measurements. Ratio graphs show the effect of El Chichon eruption on Umkehr data taken after April 1982.

- 256-

oj c w Z 0 N 0

ffi ,. ~

oj C

~ f:l 0

~

10_0

,.0

' .0 Ll-L..LLJL.J.-L..LLJ-L...L.LLl-L..LLJ-!

1.'~ 1.2

;~~ O. 1~

1~ l , 9 Il l , 9 12' J IS 9 .2 1 15 9 12 1 Ii 9 1979 I!B) 1981 I. 199)

Figure 2: Similar to Figure 1 for Layer 80

•. 0,-----------------, tATENO lAVER 9

, .0

00 0-

:j~~==~- --- umd 12 ] 6 9 12 3 6 9 12 ] Ei 9 12 ] Ei 9 12 l , 9

19'9 I" lsal 1ft I!!IJ]

Figure 3: Similar to Figure 1 for Layer 70

- 257-

INTERCOMPARISON OF SATELLITE OZONE PROFILE MEASUREMENTS

Summary

A. J. Fleig Laboratory for Atmospheric Science NASA Goddard Space Flight Center

J. C. Gille National Center for Atmospheric Research

M. P. McCormick NASA Langley Research Center

D. W. Rusch University of Colorado

J. M. Russell III NASA Langley Research Center

and

J. M. Lindsay Systems and Applied Sciences Corporation

Ozone profile data are available from the Limb Infrared Monitor of the Stratosphere (LIMS) and the Solar and Backscattered Ultraviolet Spectrometer (SBUV) flown on Nimbus 7, the Stratospheric Aerosol and Gas Experiment (SAGE) flown on Atmospheric Explorer Mission 2, and the Ultraviolet and Infrared Spectrometers flown on the Solar Mesosphere Explorer (SME). The initial measurements were obtained with a number of fundamentally different measurement techniques. Ozone data were derived from the measurements with independently derived processing algorithms. The data cover different time periods and have different spatial and temporal resolutions. Investigators wishing to make the best use of this multitude of data need to know how these data sets are interrelated. Unfortunately, there is no independent set of ozone profile "truth" measurements which can be used to determine this. An intercomparison of data from each of these sensors is being conducted jointly by the four teams that produced the data to determine the similarities and differences between the individual data sets. This effort will primarily be focused on directly comparing the spacecraft data sets in the form of individual profiles, zonal mean profiles and global analyses. Comparisons with ground data from balloons and Umkehr stations will also be done. Some results of the intercomparison are presented.

1.0 Introduction There is a widely acknowledged need to understand the global habitat and

the effect of our actions on it. Although true in general, we at this meeting are primarily concerned with the Earth's ozonesphere. The range of interests includes atmospheric chemistries, modeling, and development of measuring techniques. Until relatively recently the effort has taken place with a limited set of observational data.

Ozone Symposium - Greece 1984 - 258-

Local ozone measurements have been made for almost sixty years and have been used for many studies. However, it is not clear that studies of long term global phenomena can be based on data of limited temporal or geographic extent. The first set of nearly global multi-year ozone observations came from the Backscattered Ultraviolet (BUY) instrument flown on Nimbus 4. Limitations of spacecraft power and problems with contamination of the diffuser plate reduced the utility of this data for many purposes. BUY presaged a dramatic change in the availability of data for research that has occurred in the last few years.

In the last seven years, ozone data sets based on satellite measurements from a variety of instruments have become available. These data sets provide coverage of large geographic areas and often consist of enormous numbers of individual oooervations. Along with this wealth of data have come new problems. Each of these new data sets has individual features which make them desirable for particular research tasks, but no single data set provides information required by all the aeronomy subdisciplines.

Therefore, researchers will want to use combinations of the indi vidual data sets. This would be relatively easy if all of the data sets were aooolutely accurate or even if the aooolute accuracy of each of the data sets was well known. Unfortunately this is not the case; in fact, standards are not even well established for point measurements of many of the features of these data sets. The 1980 "Report Of The Meeting of Experts On Assessment Of Performance Characteristics Of Yarious Ozone Measuring Systems" recognized this issue and stated that "Full profit of an integrated ozone oooerving system can only be obtained if observations taken by different methods are easily comparable and can easily be combined." (see page 52 of WMO Global Research and Monitoring Project, Report Number 9).

2.0 Description This paper describes our efforts to intercom pare four satellite deri ved ozone

data sets. The goal$ of the intercomparison, which is still underway, are to learn about the similarities and differences between the various sets of measurements, to see if there are improvements that can be made in any of the data sets, and to provide information to potential users of the data which will improve their understanding of the accuracies and interrelationships of the various data sets. The first goal was to see if all four instruments were in fact measuring the same phenomena. This is not a facile question. The measurement techniques are quite different, with measurements made in the ultraviolet, visible, and infrared. The instruments operate in nadir looking, limb scanning and solar occultation modes. The inversion algorithms were independently developed in four separate locations using conceptually different techniques., Despite these differences, the results of the initial comparisons clearly showed suootantial agreement between each of the data sets.

Each of the four oooervation techniques has some unique features which will be of primary interest for individual research tasks. The Limb Infrared Monitor of the Stratosphere (LIMS) experiment provides temperature, water vapor, nitrogen dioxide, and nitric acid measurements as well as the ozone profiles discussed herein. The data pasically run from cloud top height to above 1 mb. The Stratospheric Aerosol Gas Experiment (SAGE) is based on measurements of solar occultation and provides measures of aerosol scattering, nitrogen dioxide, and ozone with very fine vertical resolution from cloud top height to above 1mb. The Solar Backscattered Ultraviolet (SBUY) experiment is a nadir looking instrument which provides medium resolution ozone measurements from the cloud tops to a-pproximately 1mb. The Solar Mesosphere Explorer (SME) satellite measures solar UY, nitrogen dioxide, water vapor, temperature, solar proton events, and ozone in the 5~-90 km region of the atmosphere. The time period covered by the various experlments ranges from seven months for the cryogenically cooled LIMS, three

- 259-

years for the SAGE, three years for the SME, and six years for SB UV. The last two instruments are still operating.

The differences between the basic nature of the measurements introduced the first problem in the intercomparison. The various sensors measure at different times of day in different locations and with different vertical and horizontal resolutions. In order to find common products from each of the sensors which we could compare it was agreed that all instrument data would be reformatted to provide zonal mean values over five latitude ranges (4 degree bands at -56, -40, 0, 40, 72 degrees) and at sixteen pressure levels (0.3, .4, .5; .7, 1., 1.5, 2, 3, 5, 7, 10, 16, 30, 50, 70, 100mb). Data in the above format were assembled at a single facility and the following speCific products were generated and plotted: daily zonal means (at selected pressure levels) versus time, daily zonal means versus latitude, and zonal mean profiles.

These choices required a minim um of data manipulation although they did not fully meet the World Meteorological Organization Experts' recommendation that "All measurements of the vertical ozone distribution be published or stored on tape as mean values over "Umkehr" layers ••• " (ibid pg. 52). There are obvious limitations in this approach in that it does not show the differences in vertical resolution of the various instruments and it only allows for comparison of aggregated data. A major benefit is that the technique tends to average out small scale instrument and atmospheric noise.

A quick review of the various plots (order of a hundred) confirmed that all systems were measuring the same phenomena and that the results in general agreed to well within the error bars associated with the individual experiments. Comparisons at various latitudes and times generally showed agreement to within 10%. Indeed, to accent the agreement, we have selected to show one plot (against normal cultural choice) where the data are at the limits of the measuring regimes of the instruments, and where the values might begin to be considered suspect. The agreement is still quite good. See Figure 1.

In the absence of a comprehensive truth comparison data set it is extremely difficult to known when the algorithm development and validation effort for an individual sensor should end. One of the goals for this initial comparison was to examine the differences between data sets in order to determine whether there were any remaining improvements that should be made.

All of the involved teams were pleased with the intercomparison results, but small changes have already been identified for the LIMS, SAGE, and SBUV data sets. In reviewing the LIMS/SBUV data, an abrupt discontinuity was noted in the LIMS data, which is now being checked. In discussing the comparison between SAGE and the LIMS/SBUV results it was discovered that the National Oceanic and Atmospheric Administration temperature values, which the SAGE team used to transfer from their normal altitude based density presentation to a pressure based mixing ratio presentation, had been revised after they had been obtained by the SAGE team. The corrected values are used in Figure 2. In reviewing the differences between the high latitude mean vertical profiles from LIMS and SBUY it became apparent that there was an error in the a priori profiles used in the SBUY inversion for high latitudes. Corrections for each of these effects are currently being made by the involved teams. Several other action items were developed and work is continuing to resolve the questions that were raised.

In summary, we have conducted the first intercomparison of satellite ozone data sets with very satisfying results. The comparison of LIMS, SAGE, SBUY, and SME shows results generally agreeing to within 10%. There were limited areas of disagreement and some specific corrections have been determined for several of the data sets. The effort is continuing and, after a second meeting, we will present a report describing the similarities and differences between the various data sets.

- 260-

...

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Figure 1: Shows five years of SBUV compared with all the other instruments. Umkehr layer 9 has been corrected to 1 mb mixing ratio assuming that

(°3 scale height)/(atmosphere scale height) ratio is equal to .6 in agreement with rocket results. At 30 mb 500 SBUV curve has been included for better comparison with the balloon data.

- 261-

11"'

M

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SBUV. SAGE & LlMS COMPARISON MARCH 42 · N

.. '111111 .... SBUV --- --- LlMS - - - - SAGE SUNRISE

0.5 ~--------------'---------r------r----r---~--r--r--r-'-------------~

10

10

OZONE MIXING RATIO IN PPMV

Figure 2: Shows zonal mean profiles demonstrating the overall agreement of the three primary instrument in the comparison.

- 262-

08103184 SAsel OPT

TOTAL OZONE TREND IN THE LIGHT OF OZONE SOUNDINGS, THE IMPACT OF EL CHICHON

H. u. Dlitsch

Atmospher ic Phys'ics ETH, Honggerberg, 8093 Zlir ich, Switzerland

Summary

The downward trend of total ozone from Arosa, Switzerland since 1970"is discussed in terms of the changes in the vertical distribution observed simultaneously over payerne. The impact of the El Chichon eruption on the ozone content over Switzerland is specifically considered.

360

o 350

340

330

320

1930 1940 1950 1960 1970 1980 1990

360

o 350

340

330

320

310 L---'---__ -'---__ -'---__ -'---__ --'----__ --'----_-----' 310

Fig. 1

1930 1940 1950 1960 1970 1980 1990

Arosa total ozone series; annual mean values (C-wavelength pair) : full line; 5 year overlapping means: short dashed line; ten year overlapping means: dashed line; regression line : fine dashed.

1. Introduction

The Arosa (Switzerland) total ozone series (since 1926, Fig. 1) shows after predominantly high ozone values between 1940 and 1960 a continuous decrease, especially since about 1970, which led to an all time low in 1983, the latter obviously in connection with the El Chichon eruption. The downward

Ozone Symposium - Greece 1984 - 263-

trend for the whole series is not very steep and amounts to little over 2 % or about 3 ~. per decade - obviously as a consequence of rather low values occuring also at the beginning of the series.

Three out of the four minima deviating more than 2.5 % from the mean were preceeded by volcanic eruptions polluting the stratosphere (Mt. Agung, Fuego and notably El Chichon). The fourth, the 1928 event was following vol­canic activity in the Tonga Islands; it is, however, not known whether the stratosphere was then considerably polluted.

2. The Thalwil/Payerne sounding series

This ozone sounding series (3 times per week) gives the possibility to study the height distribution of the observed ozone decrease. In Fig. 2 the series is presented after elimination of the seasonal variation - three month overlapping means of the deviation of monthly averages from their 18 year means are shown. It is seen that the negative trend since 1967 is al­most uniformly distributed between the tropopause and about the 30 mb level (see also table 1).

-10 + 10

0

-10

-10

Fig. 2

79 81 83

11 mb

20

30

45

65

100

175

1968 70 72 74 76 78 80 82 84

Ozone variation at different levels over Payerne (3 month over­lapping means). Regression lines dashed.

- 264-

Table 1 : Ozone trends at different levels (1967 - 1983) 1956 - 81

Soundinss Payerne (jmkehr Arosa

mb 800 400 175 100 65 45 30 20 11 1.4

nb/decade +1.8 +1.8 -4.0 -5.4 -5,9 -6.5 -2.3 0 +1.0 -0.28

%/ decade +5.8 +9.0 -7.4 -6.7 -4.9 -4,4 -1.6 0 +1.4 -4.0

Fig. 3 shows that mainly the late winter values have become smaller while the late summer-early fall concentrations appear hardly altered. This points to a change in the magnitude of the winter-time poleward ozone trans­port; an other possible explanation, a change in photochemical productivity in the tropical source region (around the 10 mb level) seems less probable. The given explanation is also supported by the fact that the ozone decrease is confined to the layers where for the larger part of the year the ozone content is dominated by transport, while in the middle stratosphere whe~e photochemical processes dominate, except in winter, no loss is observed.

mb

10

20

30

50

100 -

200

300

500

km

30

25

20

15

5

1000 L-_l-_...L-_-'-_--'-_---'

o nb 50 100 150 200 Jon"Morch 50 100 150 nb

Fig, 3

Aug.-Oct.: 0

Comparison between mean verti­cal ozone distribution for January-March (left) and August­October between the periods 1967-1972 and 1980-1984.

- 265-

5 mb

10 ++ I I 20 I

30

50 <y:.:-

100 March 83 ~ __ =r

200 1---1-

500-

I I I ----l I I

1000L--L--L--~-~-~-~~

-50 -40 -30 -20 -10 o 10 nb 20

Fig, 5 vertical distribution of the deviations from normal for December 1982, January, February and March 1983 in nb.

The trends in the troposphere are positive as also reported by other stations, however, not as strongly as at Hohenpeissenberg near Munich; whether this is due to the fact that Eastern Bavaria is more often covered by air with strong industrial influence than Payerne which is in a high percentage of cases reached by Atlantic air arriving via the rural parts of France. This explanation is, however, not quite in line with the fact that Hohenpeissenberg reports a strong positive trend also for winter, when no photosmog activity is expected.

While the behaviour with respect to long term trends is rather uniform from the tropopause to about the 30 mb level this is not true for the medium term fluctuations as shown by Fig. 2. Between the two lower stratospheric levels (175 and 100 mb) the correlation is reasonably high, although not one to one; strong deviations of either sign appear predominantly in late winter at the time of the ozone accumulation by the general circulation at a period which also exhibits the highest variance of single observations.

At 45 mb the picture appears much simpler with a clear cut biennial variation which changes phase twice within this series as to be expected because of the 26 months periodicity of the QBO. Due to the superimposed trend the maxima are more prominent in the first part, the minima in the second part of the series. Again the extrema occur in late winter at the end of the period of annual poleward ozone transport. The 65 mb level shows a similar picture, however, with considerable superimposed noise from the smaller scale processes dominating the lower stratosphere.

There is also considerable but by no means perfect correlation between the fluctuations at the two mid-stratospheric levels (11 and 20 mb). How­ever, the course of the concentrations at these heights has little resem­blance with that at the level of the ozone maximum (45 mb). Although there can be no doubt that during winter the ozone content is also in the middle stratosphere enhanced by advection from low latitudes (2) the overall trans­port influence at that level which is in summer dominated by local photo­chemistry is much less evident than below. The intermediate 30 mb level is not too well correlated with either 45 or 20 mb, whereby the resemblance with the course at the lower height is better.

3. Record low values in 1983 after El Chichon

The most striking feature in the whole series is the all time record of low ozone concentrations in 1983, in the year after El Chichon. Fig. 4 shows its development by a time cross section from 1982 through mid 1984 and Fig. 5. presents the deviation of the monthly mean vertical distribu­tions from their long term average for the central period of ozone defici­ency, for winter 1982/83. The deficit is rather steady at 25-30 nb from December through April between the 40 and 60 mb levels, i.e. at the height of the ozone maximum and just below. It is thus obviously connected to the winter time large scale transport of ozone from low latitudes. The strongest negative ozone deviations (30 - 40 nb and more) are observed at a somewhat lower altitude (18 - 19 km) at times when the smaller scale circulation of the lower stratosphere was such as to yield low ozone values. Below 100 mb the negative anomaly was much smaller, yielding even to positive deviations in February, the middle stratosphere is not strongly affected.

At the top of Fig. 4 the percentage deviation from normal of ozone in layer 9 as computed from the Arosa Umkehr dam is shown. This deviation is

- 266-

Fig. 4

mb

20 r, I 1 1+10

50 \ • .1

3 5 7 9 1983

11 3 5 1984

50

200

Time-height cross section of the deviation of monthly means from their long time average for the period 1982 - June 1984. At the top percentage deviation of ozone concentration in Umkehr layer 9 as a measure of top: stratospheric turbidity.

largely ficticious and is simulated by the Mie-scattering by the El Chichon aerosol veil which disturbed the Umkehr ~curves; it is a good measure for the total stratospheric aerosol load above the station as is seen by compari­son with Lidar data from Garmisch- Partenkirchen (6).

The level of maximum relative scattering of the Lidar system at Garmisch (4) is slightly sloping downward with time ~rom 1982 into 1983 practically in parallel to the slope shown by the ozone anomaly plot (Fig. 4) - the height difference between the two is consistently less than one km.

It may be mentioned that the Canadian stations also observed their low­est ozone values on record (with greatest anomalies in January 1983), al­though the deficit was somewhat smaller than in Switzerland (3).

There can be no doubt that the observed negative ozone anomalies in late 1982 andin 1983 are a consequence of the El Chichon eruption. There are, how­ever, a number of possible links between the two events. As in the Mt. Agung case the El Chichon eruption produced a strong warming through aerosol ab­sorption in the tropical/subtropical stratosphere (1), (5) between 20 and 25 km. This may have caused a weakening of the stratospheric branch of the Hadley cell which transports ozone into the winter hemisphere resulting in a reduced ozone flux towards high latitudes. As the strongest ozone anomaly is found in the layer which is according to the long term obser~ vations (see bienial oscillation) most directly filled by the trans~

- 267-

port process this would be in line with the observations. The close coincidence of the height of the ozone anomaly and of the

volcanic veil indicates. but does not prove, that increased ozone destruc­tion is occurring in the air loaded with the volcanic output possibly al­ready in the low latitude source region and is continuing on its way towards higher latitudes. Two different mechanisms have been proposed: 1. Chlorine output by the volcano which would in the stratosphere be partly converted to active chlorine (3), thus leading to enhanced ozone destruc­tion. To our knowledge,however, there was no direct observation of such chlorine input. 2. It has recently been proposed (7) that aerosols may catalize the conver­sion of inactive to active chlorine and other processes pertinent to the photochemical system heterogeneously. This indicates the possibility of an indirect increase of ozone destruction through aerosols.

In addition the aerosol warming of the tropical ozone source region will by itself lead to a decrease in ozone production in that region, and thus re­duce the transport to higher latitudes. The observed event may have been a superposition of several of the mentioned effects.

4. Conclusions

There is good indication from the sounding series at Payerne, Switzer­land, that the decrease of total ozone observed at Arosa after 1970 is main­ly due to reduced poleward transport of ozone during winter.

The impressive effect of the El Chichon eruption on the ozone content over mid-latitudes seems to be produced by a superposition of several pro­cesses;its in comparison to Agung much stronger intensity is presumably connected with the bigger height reached by the El Chichon injection.

References

1. Angell, J.K. and Korshover, J. (1983). Comparison of stratospheric warming following Agung and Chichon. Month.Weath.Rev. Ill, 2129-2335.

2. Braun, W. and Dlitsch, H.U. (1984). The orlgln of ozone-rich air in the middle stratosphere observed over Europe at the end of January 1979. J.Atmosph.Chem. (in press) .

3. Evans, W.F.J. Personal communication. 4. Jaeger, W., Reiter, R., Carnuth, W. and Sun Jian (1984). Stratospheric

aerosol layers during 1982 and 1983 as observed by Lidar at Garmisch­Partenkirchen,Int. Laser-Radar Conf., Aix en Provence, August 1984.

5. Labitzke, K., Na:ujokat, B. and Mc Cormick, M.P. (1983). Temperature effects on the stratosphere of the April 4, 1982 eruption of El Chichon, Mexico. Geophys.Res.Lett. 10, 24-26.

6. Reiter, R., Jaeger, H., Carnuth, W. and Funk, W. (1983). The El Chichon cloud over Central Europe by Lidar over Garmisch-~artenkirchen, 1982.

7. Rowland, F.S. (private communication).

- 268-

Sumrary

VARIABILITY OF THE VERI'ICAL OZONE DISTRlb(JITON

C.S. ZEREFOS, J.C. ZIOMAS, A.F. BArS Physics Dept., Lab. of Atnospheric Physics,

Box 14 9 University of 'Ihessaloniki Thessaloniki, Greece

A horrogeneous sample of ozonesonde observations covering the past 15 year was tested for the evidence of trends. 'Ihe results show statistically sig­nificant trends in tropospheric ozone over middle and high latitudes throughout the records studied. No significant trends were found at stra­tospheric levels and in the ozone column above the 15 rob isobaric surface.

1 • 1 Introduction

Theoretical calculations on the expected trends in the ozone layer cau­sed by man's activities predict (at the most) a one percent increase of free tropospheric ozone per year and a similar decrease of ozone in a region of the upper stratosphere centered at 40 kIn (Wuebbles et al., 1983, Gidel et al., 1983, Crutzen and Gidel, 1983 and related papers at this meeting).

The above predictions were confirmed with observations from both ground­based, ozonesonde and satellite measurements (Angell and Korshover, 1983, Reinsel et al., 1983 and BojkOv- and Reinsel in this volume). Because of the irop::>rtan:::e-6f these trends to mankind we have decided to provide a new look at these trends by studying a homogeneous data sample from ozone sonde records. This data sample had to satisfy all of the following objective criteria:

1. Measurements at all stations to be used in the analysis should have been obtained with the same instrtmEnt.

2. A station is not included in the analysis if measurements for any given month were systematically missing.

3. A station should have ozonesonde data at least for five consecutive years.

4. The correction factors for the above ozonesondes should be free of trends and within ± a from the mean of their individual values.

5. '!he mean number of observations per month satisfying the above cri­teria should be at least 3 obs/month.

Stations with data satisfying the above criteria and which are included in this analysis are listed in Table 1.

It should be noted that except for Goose, the remaining three Canadian stations have changed instrunEnts from the Brewer-Mast to the :EO:: ozonesonde at the end of the year 1979. However a close look at the trends in the Cana­dian stations (with and without data from 1980) show no effect on the calcu­lated trends except at Resolute in which the positive tropospheric trend be­comes larger when including data from 1980 taken with the :EO:: sonde.

Ozone Symposium - Greece 1984 - 269-

1.2 Results

STATlOO

RFSOLUI'E F. CHURCHILL EI:MONroN GOOSE IDHENPEISSENBERG PAYERNE ASPENDALE

TABLE

lAT.

74°N 58°N 53°N 53°N 4rN 46°N 32°S

PERIOD OF REXXlRD

1967-1980 1974-1980 1973-1980 1969-1980 1968-1980 1966-1980 1965-1979

Figure 1 shows isopleths of trends in percent change of ozone per year over middle and high latitudes. Arrows in the latitude axis indicate the po­sition of stations.

Figure 1 (a) includes the results from the analysis of the CXJrnrron period of reCXJrd which is from October 1973 through October 1989. Significant trends at the 95% level, estimated with Mann-Kendall rank test, are shaded.

Figure 1 (b) shows the sane analysis as in 1 (a) but for the rronth of June during the camon period of record October 73-Clctober 80. Significance of the­se trends CXJuld not be calculated because of the few data points used in this calculation. The analysis for s\.lI!lOOr is justified by the coupled photochemi­cal theory and transport of ozone and related trace gases. From Figures 1 (a) and 1 (b) it is CXJnfil::ned that tropospheric ozone is increasing significantly by an average rate of about 2 to 3% per year over middle and high latitudes, the trends being a little larger when studying a sunmer rronth. On the CXJntra­ry there is no evidence of any significant trends in the stratosphere below 10 nbs. Similar results were found at Aspendale (32°S).

Figure 1 (c) shows the sane trend analysis using all available data at each station (see Table 1). The significant increase in tropospheric ozone is again seen to be rrore or less independent of the period chosen for the analysis. 'Ihis of CXJurse strengthens the reality of the reported trends in tropospheric ozone and the importance of photochemistry as can be inferred from the larger trends of the sunmer rronths (Figs. 1b and 1d).

We next study the trends in ozone above the ceiling of ozonesondes rnea­surerrents. 'Ihe 15 rob level marks the height at which about 80% of the balla:ms burst. Ozone was integrated for each sounding up to the 15 rob level and the result was subtracted from the total ozone observation from the ground. This difference obviously gives the ozone column above. 15 robs. Figure 2 shows the tine series and linear regression lines for the ozone CXJlumn above 15 robs in all station under study. Again significance of trends is tested through Mann­Kendall rank statistics. As it appears from Figure 2 the ozone column above 15 robs is small and insignificant as surrmarized in Table 2 which also shows the CXJrresponding to the ozonesondes trends in total ozone.

- 270-

b

10 U "'--O';;!/

20

\ o

'" 10

o

20 '\

30 30 0

~ P 50 j o

1mb) 70

90 70 1 60 50 R J (~ 11 HP

_sm~

10 0

lJ 20 ~. 0

30

0

P 50 P 50 1

(mb) 70

100

mb) 70

100 0 ·ll 150 U : :;~ ~~e\ ;B 0

500 ~ 0 700 222

1000~ 90 70 ~60 ---t---5~ -,

I Ii '0 R C ffi U

90 70 60 ill 50 40 R C (G 1 HP

Figure 1

- 271-

--, :::J ci

'" -" E ...,

:> 0 CD « w 2 0 N 0 2 :2 :::J ...J 0 u

'1 80 60 AO

'001 60

'001 60

wot 60

'001 60

~Ol 60

" , /,' .

'" ;-, =.: -

..... . . -;,' ' . . , ..... : :.:.

. , - "

',. ",

"." ..... "

,'~ ...... ... ..

',' ", ': ~;-: . ',,:.-

. . ,', :", .. ~ . .. ' _'. ,-:., -::~ I.' ':: ..... :. _~':- ,,' .. "" ,:;.'J',; ;';. ':

'm·'·' ' .. ". " :. ': .. :":::' .: :': ,'"; ,. ":,,,,, :-c:' .... ,: ... I ., I • I ,

66 68 70 72 7A 76 78 80 82

YEAR

Figure 2

- 272-

RESOLUTE

f CHURCHILL

EDMONTON

GOOSE

HOHENPEISSENBERG

PAYERNE

ASPENDALE

STATION

RESOLUI'E F. QIURCHILL EIMOmrn a::xJSE HOHENPEISSENBERG PAYERNE ASPENDALE

REFERENCES

TABLE 2

TREND OF OZONE ABOVE 15 MBS (% PER YEAR)

-0.21 -0.86 0.00 1.01 0.30 0.16 0.24

TREND OF 'IOTAL OZONE (% PER YEAR)

-0.33 0.93 0.41

-0.40 -0.51 -0.26 -0.14

1. ANGELL, J. and KORSHOVER, J. (1980). Update of ozone variations through 1979. Proc. Ozone Syrrposium, Bolder, 393-396 (Ed. J. LONOON)

2. BC\JKOV, R.D. and REINSEL, G.C. (1984). Trends in troPJspheric ozone con­centration. To appear in Proc. Ozone Syrrposium, Halkidiki (Eds. C.ZERE­FOS and A.GHAZI)

3. CRUTZEN, P.J. and GIDEL, L.T. (1983). J.Geophys. Res, 88, 6641-6661 4. GIDEL, L.T., CRUTZEN, P.J. and FISHMAN, J. (1983). J.Geophys. Res., 88,

6622-6640 5. REINSEL, G.C., TIAO, G.C., LEVIS, R. and BOBKOSKI, M. (1983). J.Geophys.

Res., 88, 5393-5402 6. WUEBBLES, D.J., LUTHER, F.M. and PENNER, J.E. (1983). J.GeOphys. Res.,

88, 1444-1456

- 273-

AN OZONE SOUNDINGS PROGRAM AT THE EASTERN EQUATOR: PRELIMINARY RESULTS

M. ILYAS

School of Physics University of Science of Malaysia, Penang, Malaysia

Summary

A balloon-borne project for ozone layer measurements was undertaken using the Mast ozone sondes and Astro radiosondes. The launctlings were conducted from the Malaysian capital Kuala Lumpur (3N 102E). Results show that at the tropospheric and lower stratospheric levels, the ozone concen­trations are much lower than the mid-latitude concentrations. The layer of peak concentration is found to be shifted upward compared to the mid­latitude profile above which the two profiles get closer. The paper dis­cusses seasonal vari~ility and specific problems which make it difficult to obtain data at levels above 20 mb.

1.1 Introduction

Stratospheric ozone has assumed an enhanced importance since the realization that several human activities could lead to adverse biological and climatic effects including the increased erythemal ultraviolet (UV-B) dosage [lJ. Observational data on tropospheric-stratospheric ozone is severely limited at the lower latitudes [2J and is almost non-existant near the equator. This region is however of very much interest because here the ozone production is maximum yet the ozone column depth is minimum; erythe­mal ultraviolet dosage reaching the surface is maximum and the effect of any reduction in ozone column on surface UV-B dosage increase would be maximum. Owing to these considerations, a comprehensive observational program was organized at the University of Science at Penan~. This included measurements of erythemal ultraviolet dosage UV-B L3J, solar ultraviolet (UV-A) flux, surface-level ozone [4J and a pilot study of balloon-borne ozone soundings besides a series of supportive meteorological data. The purpose of this paper is to discuss the results from the ozone soundings program.

1.2 Experimental

The instrumentation consists of a standard Mast ozone sonde and Astor radiosonde with a coupling and time-sharing unit. The equipment is carried by a balloon (Totex) and in situ data are transmitted to a ground based meteorological receiver. The soundings were conducted from the Malaysian Meteorological Station at Kuala Lumpur [3N 102E]. Flight details are summarized in Table I.

Ozone Symposium - Greece 1984 - 274-

Date & Time (LC)

31. 3.81 1435 10.6.81 1335 29.6.81 1210 15.7.81 1250 12.8.81 1135 16.9.81 1223

21.10.81 1145 23.11.81 1215 23.12.81 1215

16 .. 6.82 1250

5 mb

50

Table I: Ozone Sonde Flight Details

Balloon TyEe

CR-600 CR-66-2ooo CR-66-1200 CR-66-2000 CR-66-1200 CR-1200 CR-1200 CR-1200 CR-1200 CR-1200

,/

Flying Time

/

(min)

75 71 68.5 70 87 75 95 80.5 92.9 84.3

, \ I a I

I ,

Max. Altitude mb

25 25 33 33 28 16 11 24 16 17

(km)

(24.9) (24.9) (23.4) (23.4) (23.9) (27.9) (29.8) (25.25) (27.68) (27.57)

30 Km

25

20

1':/,,'/' I KUALA LUMPUR , I - - - PAYERNE

15

I I I

500

1000 Ozone (umb) 0 100 Fig. 1 -80" -600 -400 -200 00

- 275-

10

5

200 250 40°C

The payload is not recoverable due to the presence of strong easterly winds at the upper level which carry the payload over the ocean waters. Just for safety, a simple plastic parachute is attached to the payload. The second flight developed some electronic malfunction during the flight and no useful ozone data could be obtained. The flights were limited to below 10 mb level either due to burst or signal fading. The performance of a new model of balloon (CR-1200) is however promising and the latter flights altitude performance was relatively much better.

1.3 Results

The results from the present series are summarized in Fig. 1, 2 and 3. In Fig. 1 a typical profile at Kuala Lumpur is compared with the one from a mid latitude station. We notice that the upward shift of tropopause from around 200 mb at mid latitudes to about 100 mb at the equator corres­ponds to a shift in the ozone profile as well. The concentrations at the equator are considerably lower upto the peak layer after which both profiles tend to be close.

The profile in Fig. 1 also exhibits the general tropospheric charac­teristics - ozone flux increasing over first 100-200 mb from the surface and then steadily decreasing with altitude to a minimum near the tropo­pause but with slightly varying slopes (with an approximate order of AUg, July, June, March & Sept, Nov, Oct, Dec). Over the tropospheric region, the profiles break-up into the following groups:

IUr-----+------r----~--~---r_----;_----_+----_;

30

km 20~--~----_+----_r.~._~~--+_----~--~

25

50 20

100 15

200

10

500 Fig . 2 5

OOOOzone(WTb) 50 100 150 200 250

- 276-

-~ N o

July, Aug & (end) June profiles showing very little variability among them and indicate lowest flux conditions [late summer to early autumn]

, Sept, Oct, Nov profiles are close to each other and reflect medium ozone flux conditions [autumn to early winter} March profile is very close to Nov profile reflecting medium flux condition [early spring & autumn]

, Dec and Mid June profiles are identical and reflect highest flux condi tion [winter & summer]

110 30mb

50mb

.... '"

'" ",

Fig. :5

- 277-

However, over the stratospheric region, the profiles fall into two groups - a narrow band of summer-profiles lying within a broader band of winter/ spring/autumn profiles (Fig. 2). The narrower band of summer-profiles begins to separate away around 50 rob but the upper level is rather restric­ted for this group of profiles. A more detailed seasonal analysis of the data at six different levels is presented in Fig. 3 which shows summer/ winter maximum and spring/autumn minimum at the lower levels. The seasonal variability is very much less at the upper levels. The trend may be compared with similar analysis for mid latitudes [5].

1.4 Discussion

This pilot study has revealed a number of instrumental problems experienced in trying to cover the stratosphere. First, the upward shift in the tropopause and ozone layer means that the balloon needs to reach a correspondingly higher level to cover the entire layer. Secondly, at our station, there are strong easterlies almost upto 30 km, most of the time. The balloon goes up slanting and by the time it reaches about 20-25 km, it is a long way out diagonally from the receiver which may result in signal fading. A low elevation angle perhaps also results in a non-perfect balloon performance resulting in an early burst. During the course of this project, we were able to experiment with several balloon models and the new model seems to suit the conditions at our station. Also, more favourable periods for launch can be identified to overcome these problems in a future program.

Acknowledgements

The project was supported by grants from the University of Science of Malaysia and technical facilities from the Malaysian Meteorological Services. Special thanks are due to Mr. F. deSilve (CSIRO, Australia) and Dr. W. Attmanspacher (W. Germany) for invaluable technical help. The presentation of this paper was made possible with financial Grants from International Ozone Commission (IAMAP/IUGG) and University of Science of Malaysia.

REFERENCES

1. Ilyas, M. (1979). Adverse biological and climatic effects of ozone layer depleting activities (SST, Aerosol sprays, .... ): an overview in Malaysia context. Sains Malaysiana, 8, 13-37.

2. Dutsch, H.U. (1978). vertical ozone distribution on a global scale. Pure & Appl. Geophys., 116, 512-529.

3. Ilyas, M. and Barton, I.J. (1983). Surface dosage of erythemal solar ultraviolet radiation near the equator. Atmosph. Env., ~, 2069-73.

4. Ilyas, M. (1984). Surface ozone near the equator. Proc. Int'l Ozone Symp. 1984 (this volume) .

5. Dutsch, H.U. (1974). Regular ozone soundings at the aero logical station of the Swiss meteorological office at Payerne, Switzerland 1968-1972. LAPETH 10, Laboratory for Atmospheric Physics, ETH, Zurich, Switzerland. pp. 338.

- 278-

MEAN VERTICAL DISTRIBUTION OF ATMOSPHERIC OZONE OVER CAGLIARI-ELMAS (39°15'N - 09°03'E)

G.PIBIRI, P.RANDACCIO,A.SERRA,A.SOLLAI Istituto Fisica Medica

ITALY Universit~ Cagliari

1. Ozone climatology on Cagliari-Elmas.

Cagliari-Elmas station (39°15'N-09°0B'E, alt.l m asl) is the only European station which carries out ozonosound­ings in the latitudinal belt of 40°. For this reason this station, run by the Italian Air Force Meteorological Ser­vice, has a basic importance for the climatology in this area. For our climatological research, nr. 291 ozonosoundings have been analysed from 196B to 1976: 7B% reached the lev­el of 15 mbar, 55% the level of 10 mbar. Figure 1 shows the vertical section of the mean annual cycle of ozone present in the atmosphere above the west­ern Mediterranean sea. The 03 partial pressure at the var­ious baric levels is expressed in nanobar (nbar). This analysis points out a main spring maximum (beyond 170 nbar) at a stratospheric level of about 30-40 mbar and a secon­dary spring maximum (90 nbar) at a level of about IBO-200 mbar. Minimum values can be found in the low troposphere; here, the process of destruction of ozone molecules (phys­ical and chemical quenching) is more emphasized. In order to perform a more detailed study on 03 climatol­ogy in the atmospheric layers where this gaseous element shows a particular behavior (concentration maxima and minima, photochemistry and circulation process) annual mean cycles have been worked out at different levels. The mean annual cycle at 15 mbar level, above the primary stratospheric maximum shows a maximum during summer months and a minimum in winter. At such level the annual cycle is closely governed by photochemical seasonal processes of ozone production. The mean situation at 30 mbar level shows maximum absolute values of concentration of the whole at­mosphere. There, on a smaller amplitude, the annual cycle shows a maximum in winter and a minimum in autumn. At such a level ozone distribution is mainly governed by circula­tion processes. These processes, connected with the winter stratospheric polar vortex., transfer ozone from equatori-

Ozone Symposium - Greece 1984 - 279-

al regions to high latitudes. The cycle at the tropospheric level of 200 mbar is remarkably wide, particularly during springtime, with presence of the maximum. Minimum is found in autumn. At this level too, the dynamic mechanism connect-ed to the general atmospheric circulation prevails. In fact, the variation between winter and spring months shows that, during the last ones, ozone concentration at such levels probably originates from the processes of turbulent energet-ic exchange. Such processes take ~lace between the low strato­sphere and the troposphere as a consequence of tropopause interruption (phenomenon originated by the winter polar front). The ozone annual distribution at the tropospheric level of 850 mbar and 1000 mbar (planetary boundery layer) shows cy­cles with a nearly similar configuration, with maxima during summer and minima during winter months. The ozone partial pressure is higher at 1000 mbar than at 850 mbar. Cf course, it is hard to explain such configurations according to the photochemical theory, as it can be done for the stratospheric levels which show a nearly similar pattern. The increased ozone availability during the hottest period of the year in the low layers above Cagliari-Elmas could be a consequence of the local summer atmospheric circulation converging air masses comi~g fro~ the sea onto the land. Such air masses, as well known, contain more ozone than those standing on ~he

land: here 03 is destroyed by chemical reactions with all kinds of contaminating materials, by being absorbed by soil, vegetation and organic/inorganic components of atmospheric aerosol, etc.

2. Mean ozone distribution and its variability on Cagliari­Elmas vertical.

In fig.2 the full line shows the mean vertical distribu­tion of 03 partial pressure obtained by the Cagliari-Elmas ozonosoundings. The stratospheric maximum (40 mbar level) and the tropospheric one (200 mbar level) are well emphasized. The dashed line shows the ozone percentage variability obtain­ed as a percentage ratio of the standard deviation of the mean to the same mean value concerning 03 content at differ­ent baric levels. This curve shows maxima at these three le­vels: 1000 mbar (PBL), 500 mbar, and 200 mbar (tropopause area). On the countrary, secondary and primary minima can be found at 800, 400 and 200 mbar levels. Alternation of minima and maxima in the tropospheric region is, without any doubt, correlated to synoptic and mesoscale circulations. Such timescale situations, in determining move­ments of air masses downwards and upwards, originate mixing up, diffusion and accumulation of the atmospheric aerosol

- 280-

components (and ozone is one of them) at the different levels. The maximum variability found at the level of 200 mbar seems to confirm the particular mechanism of excange existing be­tween stratospheric masses rich in ozone and the tropospheric ones, at the same level where tropopause breaks. As well known, the last phenomenon is connected to the winter and spring meteorological course, which is remarkably variable in the latitudinal belt included between 30° and 50°. In fact, the relative maximum ozone concentrationat the level of 200 mbar apeearsis some other statistic elaborations con­cerning the mean vertical distribution obtained by ozono­soundings taken in differentplaces situated in the above mentioned latitudinal belt (such as Aspendale, Australia; Fort Collins, U.S.A.; New Delhi, India).

3. Tropospheric ozone and general atmospheric circulation observed during a short timescale.

Through a series of ozonosoundings taken at intervals shorter than 5 days we looked for a relationship between the temporal evolution of ozone concentration on the Cagliari Elmas vertical and the general atmospheric circulation aloft. Some observations arise from the analysis of the ozonosound­ing taken during sp~ing months when tropospheric ozone vari­ability is at its maximum. Fig.5 shows the isoplethes or ozone partial pressure (nbar), wind (direction and intensity), and tropopause position ob­served between the baric levels of 500 and 100 mbar. The depicted situations are merely indicative and intend to iden­tify linear relationships among the above atmospheric elements as it is obviously impossible to apply statistical methods, even if elementary, as observations are not sufficient to this purpose. The Figure, relative to April 1972, clearly shows the vari­ability of ozone concentration between the low stratosphere and the high troposphere. It seems even possible, for this period, to find an alternation of maxima and minima every 7 days (this appens for each baric level from 300 mbar up). On the contrary, no relationship appears to be possible with windiness. But, other scientists ~ound an increased quantity of tropospheric ozone in connection with an increased wind­iness at a level of 200 mbar. With reference to tropopause, it is possible to observe that, particularly in the second part of the above mentioned period, its course is almost synchronous with ozone isoplethes and repeats theri maxima and minima ~ositions. This result too, as the already abserved concentration variability in the

-281-

low stratosphere, can be very well situated in the theory of transportation and mixing up of stratospheric and tropospheric masses. And finally, the same relationship between ozone concentration and tropopause can be found in the second group of ozonosound­ings taken in March 1976.-

rn be ...

10 70 ____

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50 -C7 -0 __ 170 ~----

-- G-m..!~-- ;50J 20

100 15

~/~ 50

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~,\o ",,\ ~ 1000~ ____ ~ __ ~~ ____ ~ ____ ~ ____ ~ ____ ~ ____________ ~ __ ~ ____ ~~~ ____ ~ ____ ~ ____ ~ __

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FIGURE 1

- 282-

,bD

3 IL

L.

IL. 900i i

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FIGURE Z

FIGURE. 3

- 283-

,.. . ... uo _ - - 1 ~,,- 'II.71 _ t1111 1t ..

/

REFERENCES

1. MATTANA,N., SANNA, S., SERRA A. (1961) Atmospheric ozone at Cagliari during the period 1955-1961. Symp.Atm.Ozone, UGGI Inst.Geog.National - Paris.

2. PORRA',GP, SANNA,S., SERRA,A., SOLLAI,A. Note preliminari sulla concentrazione dell'ozono. Rivista Meteorologia.Aer. vol.XXXVIII, n04? Roma 1977.

3. FABIAN, P. Tropospheric ozone: injection from the strato­sphere versus photochemistry. Nationalkomitee fur geodasie und geophysik bei der. Akademie der Wissenschaften der DDR. Proc.Symp.on Atm.Ozone, vol III, Dresden 1976.

4. PITTOGK, A.B. Climatology of the vertical distribution of ozone over Aspendale. Quart.J.R.Met.Soc., 103, 1977.

- 284-

A SPECIAL OZONE OBSERVATION AT SYOWA STATION, ANTARCTICA FROM FEBRUARY 1982 TO JANUARY 1983

1. Introduction

S. CHUBACHI METEOROLOGICAL RESEARCH INSTITUTE

1-1 NAGAMINE, YATABE, TUKUBA-GUN 305 IBARAKI, JAPAN

The Atmospheric ozone plays a significant role in heat balance of the stratosphere. Its behavior at high latitude is of special interest, since the stratospheric ozone at high latitude is thought to be transported from lower latitude through dynamical processes. However limited information is so far obtained, because the ozone observation at high latitude is sparse. There are only two ozone stations operating in Antarctica; Syowa Station (69°S) and Amundsen-Scott (90 0 S), where the total ozone has been observed in sunlit months only. To make up this deficiency extensive observations were carried out at Syowa Station trom February 1982 to January 19S3 as a part of the international project of Middle Atmosphere Program (MAP). This paper gives some preliminary results of this observation.

2. Instrumentation and Observation 1) Total ozone

Total ozone was observed with the Dobson spectrophotometer No. 122. The observation in summer was made with sunlight by the meteorological team of the 23rd Japanese Antarctic Research Expedition (JARE 23rd). Observations were made on 179 days (730 observations) from February 1 to April 4, 1982 and from September 4, 1982 to January 31, 1983. We also carried out the observation with the moonlight in winter as made by Ishida et al. (1971), when moonlight was brighter than that of a half moon. The A and D pairs of wavelengths were used in the moonlight observation. 220 observations were made at 41 nights from April 13 to October 4. 25 data obtained at 9 nights from September 4 to October 4 were compared with those obtained with sunlight. No systematic difference in total ozone was found between the sunlight and moonlight observations. Combining the data from two types of observations can depict an annual variation of total ozone at Syowa Station.

2) Ozonesonde The vertical distribution of ozone was observed with two types of

ozone sondes KC-79 and KC-79D, which are modified version of KC-65 (Kobayashi and Toyama, 1966). The ozonesonde soundings were carried out two or three times in a month before September. After September, these operations were increased to observe the change of the vertical ozone profile with the sudden increase of total ozone. The number of flights was 35 with the KC-79 sonde and 14 with the KC-79D sonde. 22 ozone profiles obtained with the KC-79 sonde are used in our present analysis;

Ozone Symposium - Greece 1984 - 285-

because other 13 profiles could not be corrected with the total ozone because of no similtaneous Dobson observation or needed a larger correction factor than 1.5. 20 of these 22 observations were carried out above 20 mb level, and 10 were carried out above 10mb.

3. Results The values shown in figure 1 are those representative ot the day

derived from several measurements on the same day. It should be noted that those from moonlight ob~3rvation is preliminary and the probable error may be about + IS xl0 atm-cm because of using the provisional constant in calculation of total ozone. The total ozone decreased in February and March in 19S2, but increased slowly in April, May, and June and again decreased in August through October. A sudden increase ot

Fig.l The total ozone measured at

Syowa Station. Open circles; direct sun measurement, squares; cloudy zenith measurement, and filled circles:· moon measurement.

Fig.2 The time-height cross

section of the partial pressure of ozone at Syowa Station constructed 22 times of ozonesondes.

~ ~oo E ;;

~ 3~0 UJ Z o "tF!" ~ 300 ~-

--' ... ... o ... 2~0

Q by rjl •• cl luI'!

o by cloudy unl'~

• by moon

"

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..

.' I

the total ozone ~3curred on October 28. The total ozone increased from 240 to 380 x 10 atm-cm. Atter this sudden increase, it decreased slowly. The characteristic features of figure 1 are June/July maximum as well the November maximum and extremely low total ozone amount from September to October.

Figure 2 illustrates that the enhancements in total ozone as shown in figure 1 is mainly due to the enhancement in the peak portion of the ozone profile. The enhancement occurred at about 90 mb level in June and July, and in the 60-40 mb region in November.

4. Discussions It is interesting to see the change of the total ozone in winter

as seen in figure 1. There is a maximum of the total ozone in winter

Fig.3 The time-height cross

section of the air temperature at Syowa Station constructed from 33 soundings with ozonesondes.

Fig.4 The comparison of the

total ozone at Amundsen-Scott with those at Syowa Station observed from February 1982 to January 1983.

20

JO J " E 50 w 70 a: ::J

~ 100 w a: a.

200

JOO

500

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1982. However, such an increase was not found in winter 1969 (Ishida et aI, 1971, Sakai 1979). It is not clear whether such an increase in winter is peculiar to 1982 or common.

Figure 2 shows that the sudden increase of total ozone on October 28 is owing to the rapid increase of ozone partial pressure in 100-20 mb. Moreover the phenomenon that the partial pressure of ozone decreased and then increased was observed at 10 mb level on early October preceding the sudden increase of total ozone on October.

Compared Fig.2 with the result in 1966 presented by Shimizu (1969), both shows that the level of the maximum ozone partial pressure is higher in summer than in winter.

Figure 3 shows that the sudden increase of total ozone was accompanied with the warming in 100-30 mb level. At 10 mb level on early October rapid increase of air temperature was observed preceding the sudden increase of total ozone on October 28. Figure 4 indicates that the increase of total ozone occurred at Amundsen- Scott about one month later than at Syowa Station (Atmospheric Environment Service of Canada,

2

~ 5

• 10

w 0<: ~ 20 U1 U1 w 0<: 50 a...

100

Fig.5

100 200 PARTIAL PRESSURE

( •• h )

- 75 -5 0 -25 0 TE MPERA TURE

( . C)

2

5

10

20

SO

100

100 200 PART [AL PRESSURE

( ~ m b)

LEFT: The vertical profilew of the partial pressure of ozone and air temperature with ozone sonde sounding on the day (October

28: heavy curve) and one day before (October 27: thin curve) of the sudden increase of total ozone. RIGHT: With shifting the vertical profile of ozone partial pressure on October 27 in left figure downwardly, we can see

that this profile is corresponding to the protile on October 28.

1982, 1983). Figure 5 compares the profiles of ozone and air temperature observed before and after the sudden increase of total ozone. This figure shows that the both ozone partial pressure and air temperature are increased in the stratosphere. The ozone profiles are very similar to each other, if vertical ozone profile of one is vertically shifted by about 2 km downward.

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6. Sunnnary The preliminary result of the ozone observation from February 1982

to January 1983 at Syowa Station has been reported. The major features of the total ozone amount are as follows:

1) The annual cycle of the total ozone has two maxima. One is in July, and the other is in early November.

2) On October 28, the sudden increase of the total ozone was observed at Syowa Station. About one month later, it appeared at Amundsen- Scott.

3) Just after the sudden increase of total ozone on October 28, 1982 the ozone maximum appeared at 60 mb level, and then ascended to 40 mb level.

Now we are carrying out the data refining, so better results will be presented later.

7. Acknowledgements The author wishes to express his thanks to the members of the

meteorological team of JARE-23, for their support to the observation, to the members of Upper Air Section of Japan Meteorological Agency for the checking ozonesondes in Japan and giving a helpful advice for the data reduction, and to the members of Office of Antarctic Observations for their supplying the meteorological data in Antarctica. Special thanks are due to to the members of the Third Observation Section of Tateno Aerological Observatory for helpful advices.

REFERRECES 1. Atmospheric Environment Service of Canada(1982): Ozone Data for the

World, 23 2. Atmospheric Environment Service of Canada(1982): Ozone Data for the

World, 24 3. Ishida,~,Suzuki,T. and Sakai,S. (1971): Total ozone observation at

Syowa Station, Antarctica in 1969, Nankyoku Shiryo (Antarct.Rec.), 39, 32-38.

4. Kobayashi,J.and Toyama,Y.(1966): On various Methods of measuring the vertical Distribution of atmospheric Ozone(3) (Carbon Iodine Type chemical Ozonesonde) ,Papers in Meteorol.and Geophysics, 17, 113- . 120. --

5. Sakai,S.(1979): Total ozone observations at Syowa Station. Nankyoku Shiryo(Antarct.Rec.), No.67, 115-123.

6. Shimizu,M.(1969): Vertical Ozone distribution at Syowa Station,Antiarctica in 1966.JARE Sci. Rep., 1, 38p.

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A COMPARISON OF OZONE PROFILES DERIVED FROM STANDARD UMKEHR AND SHORT UMKEHR MEASUREMENTS FROM FIFTEEN STATIONS

Summary

C. L. MATEER Atmospheric Environment Service

Downsview, Ontario Canada M3H 5T4

J. J. DELUISI Geophysical Monitoring for Climatic Change

NOAA/ERL, Air Resources Laboratory Boulder, CO 80303

During the past two decades certain Dobson stations made series of simultaneous A-, C-, and D- wavelength pair Umkehr observations, but not in a concertea fashion and usually not as a routine part of the C­wavelength pair Umkehr observational program. These A-C-D- wavelength pair measurements were archived by the World Ozone Data Center at Toronto for future use. Subsequent to the recent development of the Short Umkehr method, the A-C-D- wavelength pair data have been ana­lyzed for ozone profile so that a comparison between the two methods could be done. Analysis criteria are bias, fractional root-mean­square of the difference between profiles, correlation and standard deviation. The analysis was applied to 15 Umkehr stations that range in latitude from 25.8°S to 74.7°N. The results indicate a marked dependence on latitude, and this is believed to be connected with the statistical behavior of the vertical distribution at different lati­tudes. However, other factors, one being the temperature dependence of ozone absorption, might also be responsible for part of the obser­ved differences.

1.1 Introduction

The short Umkehr evaluation system has been described by Mateer and DeLuisi (1) and the standard C-wavelength Umkehr evaluation system by Mateer and Dutsch (2). In reviewing the observations of the Umkehr effect available at the World Ozone Data Center, we found 15 stations with 25 or more observations of both standard C-wavelength Umkehrs and short A-C-D wavelength Umkehrs. In this paper, we report the results of comparing the standard and the short Umkehr ozone profiles derived from these observations. The stations, their latitudes and the number of observations used in the comparisons at each station are listed in Table 1.

Ozone Symposium - Greece 1984 - 290-

Latit4de

25.8S 18.5N 23.0N 24.6N 25.4N 28.6N 34.1N 40.0N 42.5N 43.8N 51. 3N 53.3N 53.6N 58.8N 74.7N

1.2 Results

Table I. Umkehr stations, their latitudes, and number of observations

Station No. of Observations

Pretoria 322 Poona 81 Ahmedabad 378 Mount Abu 376 Varanasi 152 New Delhi 217 Srinagar 25 Boulder 116 Mont Louis 237 Toronto 101 Moosonee 27 Goose 112 Edmonton 145 Churchill 56 Resolute- 36

In Figure 1, we show the ratio of the standard Umkehr average profile to the short Umkehr average profile for each of the nine Umkehr layers. Through middle and high latitudes, the ratio is less than unity for layers 3 and 4 and greater than unity for layers 5 and 6. This should not be surpr~s~ng. The first guess profiles used in deriving the short Umkehr profiles are based on several thousand balloon soundings and the short Umkehr profiles tend to follow this basic shape. When the standard Umkehr evaluation was developed, relatively few balloon soundings were available, but this basic deficiency was noted a few years later, viz., that the standard Umkehr profiles were too low in layers 3 and 4 and too high in layers 5 'and 6. In other words, the new first guess profiles used with the short Umkehr method have corrected this basic deficiency.

FRACTIONAL DiFFERENCE

Standard /Short

Fig. 1. Fractional difference between standard Umkehr and short Umkehr ~xpressed as the ratio standard/short (abscissa), and layer number (ordinate).

At lower latitudes, the comparison picture for layers 3 to 6 is not so consistent. New Delhi, Poona, and Varanasi follow the mid-latitude picture, but Ahmedabad, Mount Abu and Pretoria display some differences. These

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differences may, in part, be attributable to instrument calibration pro­grams. In addition, the first guess profiles for the tropics, even for the short Umkehr, were still based on very few balloon soundings ( ca. 1978) and this may be another contributing factor.

In layers 1 and 2, the comparison picture is not consistent, although in layer 1 the ratio for seven stations exceeds unity and for 4 stations the ratio is less than unity. In layer 2, the ratio for two stations exceeds unity and for 9 stations, the ratio is less than unity. For layer 1, where concentrations are low and variability may be large, differences in the ratio from station-to-station are not surprising. In the tropics, ozone concentrations in layers 2 and even 3 are also low.

In the upper layers, 7-9, the comparisons are not consistent from station-to-station. For the six Canadian stations and Pretoria, in layer 9 the ratio is either close to unity or exceeds it . However, for Boulder, Mont Louis and the Indian stations, the ratio is less than unity . In layer 8 only Pretoria has a ratio exceeding unity. -For these uppermost layers, especially layer 9, the Umkehr profile r e trievals are rather sensitive to small wedge calibration errors, as well as to both tropospheric and stratospheric haze.

CORRELATION

Fig. 2. Correlations between standard and short Umkehr ozone (abscissa), and layer number (ordinate).

Figure 2 shows tile correlation between standard and short Umkehr profiles in the various layers. From 40 0 N to polar latitudes, the correla­tions in layers 2-4 are high. Higher latitudes experience large vari­ability in total ozone and this variability manifests itself in these layers. Consequently, these high correlations should be expected. Layer I has moderate to high correlations, probably indicating that layer I ozone concentration is moderately-correlated with total ozone. Layer 2 shows a relative minimum of correlation at some stations, especially Boulder, probably because it is a layer of minimum relative variability at mid­latitudes. On the other hand, high correlations for layer 5 are present at Ahmedabad, Poona and Mount Abu. At low latitude stations total ozone variability normally manifests itself in this layer.

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STANDARD DEVIATION =~:':Qrd 9~lS~4~S~I&~S~~~~~~~~.~1~(~6.~~~~4;I-r~21~6~~~3~(~I I~~~~~;I-r;4l~5~.~4~36~1~~5~13;.~~5343~.~~~6.~~~~.rrl~4+1;,.

I

.s I E ~ 6

55 -t 4 f 3 ::>

4010 IT Portiol "'-ure (j4Ilb)

Fig. 3. Standard deviations of ozone amounts (abscissa) for each layer (ordinate).

Figure 3 illustrates the standard deviations of the ozone amounts in each layer for both standard and short Umkehr profiles. For both profiles, there is the expected large variability in layers 2 and 3. At Resolute, the variability is artificially reduced because Umkehr observations are possible there only in April, May and June and so the full annual vari­ability range does not impact on the curves.

ROOT MEAN SQUARE

S 251 S lUI 23,0. 2tSi ~4M 2&6. 3411 ~D. IlS. 43U 513. 513. ~6I ~A. 14 I.

I' r 4

I

6

5

:\ ! \ \ \ 1 \ \ \ i\ 1\ I~ \ 1\ \, I lOIO WIO lOIO WIO WlO ~ ~ ~ M ~ lOIO ~ M ~ 1.0

RMS Fig. 4. Fractional root-mean-square difference (abscissa) for each layer (ordinate).

The fractional root-mean-square (RMS) differences between the two profiles are shown in Fig. 4. These are largest in the troposphere (layer 1) where ozone concentrations are low and differences between standard and short profiles are small in absolute value, but large as a percentage of the actual values. At low latitudes the small value applies for layer 2 and to some extent layer 3. At middle and high latitudes, layer 2 con­centration is highly variable and thef~actional differences are also large, even though the correlations are quite high. In the uppermost layers, the increase in the ffractional RMS differences is simply a reflection 'of the noise in the retrieval profiles for these layers.

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REFERENCES

1. MATEER, C. L. and DELUISI, J. J. (1981). The estimation of the vertical distribution of ozone by the short Umkehr method. Proced. Quad. Intern'l. Ozone Sym., !, 4-9 August 1980, Boulder, Colo., 665 pp.

2. MATEER, C. L., and DVTSCH, H. u. (1964). Uniform evaluation of Umkehr observations from the World Umkehr Observation Network. Part 1, NCAR, Boulder, Colo., 105 pp.

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ROCKET M~.ill~ENl'S or THE VERTICAL STRUcrURE OF THE OZONE FIELD IN THE TR OPICS

summary

8 .H. SU88l\RAyA, A. JAYAA!\MAN and SHyAM LAL, Physical Research Laboratory,

Ahmedabad-380009, India.

A rocket ozone programme was initiated at the Physical Research Laboratory to study the height distribution of ozone in the tropical atmosphere. A solar MUV photometer for day­t~e measurements of ozone in the stratosphere and lower mesosphere and a lunar MUV photometer for night time measure­ments have been developed. A series of e~periments to study the day to night changes of ozone at different levels in the tropical stratosphere and lower mesosphere were conducted during 1980-81. The experiments show that while at alti­tUdes below 30 km night t~e concentrations are lower than the daytime values, at altitudes above about 40 km the night t~e values are larger than the daytime values by a factor which increases with increasing altitUde and reaches a value of 1.5 - 1.6 at 55 km. In the intermediate region of 30-40 km the observed changes are small.

1. Introduction

Development of a rocket ozonesonde was initiated at the Physical Research Laboratory, Ahmedabad in 1976. A solar MW photometer to measure the attenuation profile of solar W radi­ation in three wavelength bands centered around 250 om, 280 nm and 310 nm and thereby enable est~ation of ozone concentrat­ions at stratospheric and mesospheric altitudes was developed and a few exploratory measurements were made during the years 1977-79. The instrument, data analysis. calibration and meas­urement accuracies are described by Subbaraya and Lal (1). During daytime, measurements are possible typically in the alti­tUde region of 15 to 60 km but under very favourable experi­mental conditions ozone concentrations can be estimated upto altitudes exceeding 70 km. For night time measurements a lunar ultra violet photometer was developed during 1979-80. The night time instrument works on the same principle as the daytime one but is based on measurement of the lunar W flUxes. Since the lunar flUxes are smaller than the solar flUxes by four to five orders of magnitude, the instrument has to be much more

Ozone Symposium - Greece 1984 - 295-

sensitive. Further the night time instrument is best used during a period three to four days on either side of the full­moon. Beyond this period the geometry of the moon as well as scattering effects make data analysis more difficult. cali­bration and data analysis procedures as well as error estimates for the night time instrument are similar to those of the day time instrument.

2. The Thumba rocket ozonesonde experiments

A number of rocket experiments have been conducted at Thumba during the period 1977-82 using the above instruments. The first set of experiments conducted during 1977-79 were exploratory and during this period the instrumentation was steadily being improved. The instrument was standardised around 1979 and the first set of data with this standard instrument was obtained during the solar eclipse of 10 February 1980. The results from this experiment are reported in literature (2). During 1980-81 a series of experiments were conducted to study the day-night and day-to-day variability of ozone at different levels in the atmosphere. The experimental programme is shown in Table-I below. However due to rocket/instrument failure the day-to-day variability could not be studied. We present here the data from the day-night series and discuss these results.

Table-!,.: Thumba Rocket Ozonesonde - Day Night Series 1980-8l..

Level of Maximum s1. Rocket Date Time Performance ozone ozone No. hrs. maximum concent-

ration --- --I M-08.554 24. 9.80 1500 GoOd data from 27 km 3.2xl012cm-3

15 km to 70 kID 3.3)(1012cm-3 2 M-08.5$ 25. 9.80 0300 Good data from 27 kID

24 km to 68 kID 3 M-08.557 25. 9.80 1500 Failure 4 M-08.619 11.11.81 1515 Failure

3.4x1;12cm-3 5 M-08.621 12.11.81 0305 Good data from 26 kIn 17 kID to 35 kIn

3.2xl012cm-3 6 M-08.622 12.11.81 1500 GoOd data from 27 kID 10 kID to 70 kID

3. ~erimental Results The ozone number densities obtained from the day-night

series conducted on 24-25 Sept. 1980 and 11-12 NOV. 1981 are shown in fig.l. The maximum values as well as the level of the ozone maximum are given in Table-I. From fig.1 it is seen that at all altitUdes above 40 km the night time ozone concentrations are in general larger than the daytime values. The difference lies in the 15-2~1o range in the 30-35 km altitude region and decreases to 5-10% in the 35-40 km region. Above 40 kID the difference increases with increasing altitude and reaches values of 50~0% around 55 km altitude. While the observed differences

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00

•••• -oe-"4 24 SEPT'SO I~OO t«S 1ST

'0 0_ tI-OIJ-SS6 25 SEPT'eo O3OOHRS 1ST

'0

O·~~·~~~,~~~~,~~,~~J,O~"~~~

OZONE DENSITY ai'

60

'0

40

'0

'0

10

..... 11-011-622 1211OY.I~HftSIST

000 11-08-62' 12 NOV" ~.-s_IST

... ...... , .. ~) ..

\..

OI7.~~~~~~--~~d" ~~-~~~~

OZONE DENSITY ai'

Fig.1. Ozone number densities obtained from the 'Day-Night Series' experiments conducted at Thumba during Sept. 1980 and Nov. 1981.

at altitudes below 40 km are comparable to the uncertainties of measurement, at higher altitudes the differences are well above the measurement inaccuracies and are considered genuine. At altitudes below 40 km the night time values tend to be lower than the daytime values. At altitudes above Q 0 kIn measurement inaccuracies are large.

60

'0

~ 40

~ "' :z: '0

20

10

. 10

- t ..... 8 ... ROCKET MEAN.

0-0-0 K a.. 1966 ( ,., LAT.)

" 10 " 10'

OZONE DENSITY em' .

10 ..

10

Fig.2.Mean ozone number densities from the Thumba 'Day-Night Series' rocket experimEfl ts compared with the K&M mid-latitude mOdel values.

Fig.2 shows the mean of the four rocket measurement~~ The mean profile has a maximum ozone concentration of 3.2xlO molecules per cm3 at 27 km. Also shown in figure is the Krueger and Minzner mid-latitUde model for comp~rison. It is seen that in the troposphere and lower stratosphere the ozone concentration over Thumba are smaller than the mid-latitUde model valUes. Maximum deviation of the Thumba profile from the mid-latitude profile is in the 15-25 km region where the Thumba profile shows a well defined minimum around lQ km altitude (the low latitUde tropopause region) and low values all along the profile upto the region of the peak. In this region relative difference in ozone concentration by a factor of 2 or more is possible. This

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constitutes the bulk of the difference between the low latitude and mid-latitude total ozone overburden. The trough in the low latitude tropopause which is also seen on most of the balloon ozonesonde flights made at Trivandrum is believed to be genuine eventhough at these altitudes the errors in the rocket data are large. Above the maximum level, the Thumba profile begins to agree with the mid-latitude profile the differences being with­in measurement errors in the 30-35 km region. The differences become significant only above 35 km and at altitudes above 40km the Thumba profile shows consistantly larger ozone concentrat­ions than the mid-latitude profile and the difference increases with altitUde. At 50 km the Thumba ozone concentrations are larger than the mid-latitude model values by a factor of 1.3. The difference reaches a factor of 2 in the altitude region of E) 0 km. Fig.3 shows the ozone data in terms of mixing ratios.

00

40

'0

- THUMaA ROCKET OZONUOfU.

o A(.-E SATELLITE BUV DATA 1Ol.1TICI.

+ AE-[ SATELLITE BUY DATA tQUMQK.

•• 0

+ 0 + • +0

+0

Fig. 3.

Mean ozone mixing ratio from the Thumba 'Day-Night Series' rocket experiments compared with the BUV

~0~~~.--~.--7.--7~~I~I~M~~.~~. data of Frederick et al (3) from OZONE MIXING AATIO.ppmV the AE-E satellite.

The ozone mixing ratio OVer Thumba reaches a maximum in the 30-35 km region with values of 8-10 ppmv and falls off to values of 2-3 ppmv at altitUdes of 50 km and above. -Mlove 50 km the ozone mixing ratio remains relatively constant. There is an indication of an increase at higher altitUdes, but this feature is not established beyond measurement uncertainties.

4. Discussion The vertical distribution of ozone over the tropics has

been studied by Frederick et al (3) from the AE-E spectrometer data for the 1975-~ period and more recently by Aiken et al (4) from the UV spectrometer polarimeter data on S.MM satellite for the 1980 period. In an attempt to compare the Thumba rocket data with the satellite data the data of Frederick et al is also shown in fig.I. The BUV spectrometer data shows larger ozone mixing ratios in the 30-40 km region, maximum difference being

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in the 34-30 km region where the BW data gives larger values by a factor of 1.5 to 1.6. The two profiles cross over around 41 km and at higher altitudes the rocket data shows larger values. In the 50-55 km region the rocket valUes are 1.5 times larger than the satellite values. Aiken et al (4) have presen­ted tropical ozone data for the 50-70 km altitude for Sept-Oct. 1980 period from different equatorial crossings of the SMM satellite. Their data for 2 Oct. 1980 for a latitude s~ilar to that of Thumba but in a different longitude region also shows smaller ozone concentrations, smaller by a factor of 1.5 to 2. Similar difference is seen for the 9 Sept. 1980 data Which is presented for 1-20 S latitude.

Photo-chemistry of ozone at altitudes above about 50 km is controlled by the Chapman reactions and the HOx chemistry. Lal et al (5) have studied the relative importance of changes in water vapour and changes in temperature at these altitudes and find water vapour changes to be more dominant. At lower alti­tUdes nitrogen chemistry also becomes important and the ozone time constants also become large necessitating the inclusion of transport terms in the continuity equation. A model stUdy to explain the observed distributions has been initiated.

Acknowledgements

Authors would like to record the contributions of Messrs Y.B. Acharya, S.K. Banerjee, K.S. Modh and J.T. vinchhiin varioUS aspects of instrument fabrication, testin;;r and in the rocket launchings. The co-operation of the staff of the Thumba Rocket Range with special mention of Messrs A.C. Bahl and N.P.R. Rao in making the experiments successful is gratefully acknow­ledged.

REFERENCES

1. SUBBARAYA B.H. and LAL S. (1981', Earth and Planetary 5 ciences, 90, 173.

2. LAL S. and SUBBARAyA B.H. (1983), Advances in Space Research 2 (5), 205.

3. mEDERICK J.E., GUENrHER B.W., HAYS P.B. and HEATH D.F. (1978), Journal of Geophysical Research 83, 953.

4. AIKEN A.C., WOODGATE R. and SMITH H.J .P. (1984), Planetary and Space Sciences, 32, 903.

5. !ALS. andSUBBARAYA B.H. (1983), Paper presented at the National Space Science Symposium, Poona, Dec.7-10, 1983.

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nl>1E-PERIODIC VARIATIOIJS IN OZONE AND TEMPERATURE

A.D. Belmont Control Data, P.O. Box 1249, Minneapolis, MN 55440

Summary

The variations in zonal mean ozone and temperature from 30-60 km are compared, with emphasis on annual and semi-annual periods. Seven years of data from Ilimbus 4 and 5 BUV and SCR inStruments are used to prepare altitude-latitude diagrams of amplitude and phase. There are two high-l atitude equinoctial semi-annual waves at 40 km, whose cause is apparently the overlap of two annual waves. Temperature and ozone are in phase near 5 mO or below, and out-of-phase near 2 mb and above. The thick"ness and altitude of the transition zone between them varies greatly with latitude and time, as shown by daily correlation patterns.

1. I ntroducti on

This paper compares the periodic variations of ozone and temperature from 20 to 50 km on time scales ranging from annual to daily. As the quasi-biennial oscillation is virtually in the noise level, it is not included here. The daily data used are the BUV ozone profiles from Nimbus 4 and the SCR temperatures on Nimbus 4 and 5. A multiple regression curve-fitting process was employed rather than a normal harmonic analysis, because it can better treat gaps in the data and does not require an integral number of cycles of data.

2. Results

Figure 1 shows the double maximum in the amplitude of the annual wave. The two centers at high latitudes of each hemisphere are separated by a narrow regiol1 of minimum near 3 or 4 mb. That thei r causes are physically different is apparent in their different phases. Figure 2 shows the northern hemisphere center at 1 mb has a late December maximum, but that at 5 mb is late June. The counterparts in the southern hemisphere have phase dates of mid-June and mid-January respectively.

Given the opposite seasons of the two northern hemisphere centers, One might expect a semi-annual center in the region of overlap in the vertical, near 3 mb, and a semi-annual equinoctial phase date. This would also occur in the Southeru Hemisphere. The semi-annual wave in temperature, in contrast (Figure 3), shows only a single amplitude maximum in the entire altitude range.

Ozone Symposium - Greece 1984 - 300-

The semi-annual a~plitude and phase patterns (Figures 4, 5), indeed show semi-annual maxima near 3 mb in each hemisphere, with equinoctial phase dates. In addition, there is a weak maximum with about half the high-latitude maximum amplitude, centered at the equator and at the same 40 km level as the others. The phase of this center varies from January 1 at 1.5 mb, to April 1 at 10 mb. The phase progresses downward frolll 50 km in Deceliloer at the equator, to 30 km in April and dlso progresses poleward in each hemisphere to April at 40 km.

As with the semi-annual variation at high latitudes in the wind and thermal fields, the question of the physical reality of harmonic components always a ri ses. A common assumpti on is that the second harmonic is caused only by the non-sinusoidal, or squarish first hannonic, which in turn is caused by the lack of insolation (and observations) in the region of, and during, the polar night. A simple explanation of the semi-annual wave in ozone is that mentioned above: the vertical overlap of annual pulses which are out of phase and which could produce an equinoctial maximum between them, near 3 mb, precisely in the level of minimum between the annual waves. Figure 6 is a schematic summary showing the location and phase of the centers of the maximum amplitude of the annual wave and the semi-annual wave.

To explain the tropical semi-annual variation in ozone at 40 km, it seems reasonable that it be related to the semi-annual change in insolation which produces an observed semi-annual change in temperature of 3°C at 40 km at the equator, with equinoctial phase dates. The corresponding changes in intensity of the solar irradiance at frequencies absorbed by ozone may affect the net production of ozone.

There is also a s~mi-annual oscillation in temperature (Figure 7) at high latitudes which has an amplitude of about 6°C near 35 km decreasing upward to 3°C at 60 km. The locations of all three of these semi-annual variations in temperature are similar to those of the semi-annual variations in ozone.

Northern dnd southern hemispheric maps of the periodic and quasi-periodic variations of total ozone have also been prepared which show stationary asymmetries with longitude, reminding the users that zonal means show only a special aspect of the distribution.

Ozone-temperature correlation, Figure 8, shows a two yedr sample of the inter-level correlations of ozone (upper frame) and temperature (lower frame) and with each other. Ozone at 10 and 5 mb, is generally out of phase with ozone at 1 and 2 mb. As can be seen from Figure 2, there is a 180° phase shift near 3 mb which is caused by the inverse relationship of ozone to temperature in the upper stratosphere. Below about 5 mb, ozone and temperature are approximately in phase. Notice in Figure 8 that during the sudden warming of January 1971, the ozone at 1 and 2 mb decreased sharply and then returned to its normal annual maximum in the winter while the temperature at those levels returned to their winter minimum. The temperature field has no phase reversal with altitude so all levels respond in the same way to seasonal vari~tions in insolation. The ozone values at 5 and 10 mb respond directly to the tempe ra tu re •

Figure 9 shows the relationship between ozone and temperature on the scale of.a single month. It illustrates both the daily and monthly correlatlon, before and after subtracting the effect of the monthly trend In January, 1971 the trends were positively correlated and served to decrease the anti-correlation of the daily values.

Figure 10 gives the daily ozone temperature correlation by 10 degree

- 301 -

latitude bands for altitudes above 10 mb after removal of trends for June 1971. This is to demonstrate that the transition zone between the in­and out-of-phase relationship of ozone and temperature is not a fixed altitude, but may vary considerable from day to day depending upon dynami cs and photochemi stry of the atmosphere. I n July 1971, the i n­phase region extended briefly to 1 mb. The seasonal variability of the transition zone is currently under study.

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- 302-

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RESULTS OF UMKEHR, OZONESONDE, TOTAL OZONE, AND SULFUR DIOXIDE OBSERVATIONS IN HAWAII FOLLOWING THE ERUPTION OF EL CHICHON VOLCANO IN 1982

W. D. KOMHYR and S. J. OLTMANS NOAA Air Resources Laboratory, Boulder, Colorado 80303

.~

A. N. CHOPRA" and R. K. LEONARD Cooperative Institute for Research in Environmental Sciences

University of Colorado, Boulder, Colorado 80303

T. E. GARCIA and C. McFEE NOAA, Mauna Loa Observatory, Hilo, Hawaii 96720

Summary

Stratospheric aerosols caused large errors in Umkehr ozone measurements at MLO following the eruption in late March to early April 1982 of El Chichon volcano. Ozonesonde observations at MLO suggest that by early 1983 these errors decreased to ±10%. Mean monthly ozone amounts at selected pressure levels are presented for the ozonesonde observations. Less than 2 milli-atm-cm S02 has been measured at MLO since 17 May 1982, indicating that S02 interference has not adversely affected total ozone measurements. An apparent total ozone depletion at MLO following the eruption of El Chichon volcano is shown unlikely to be real, but the result of a minimum that occurred in the quasibiennial oscillation in ozone in early 1983. Ozonesonde data suggest that the minimum was caused by a reduction in ozone above the ozone maximum, probably due to changes in stratospheric circulation and ozone transport that accompany the quasibiennial oscil12tion phenomenon. A long-term trend in MLO total ozone data exhibits a rate of change in ozone since 1970 of -3% per decade. Whether this trend is due to depletion by chlorofluorocar­bons, or to ozone transport variations caused by changes in the strength of stratospheric circulation between equatorial and polar regions, is unknown.

1. Introduction

A classic set of Umkehr data obtained at Mauna Loa Observatory (MLO) since 17 May 1982, following the eruption of El Chichon volcano in late March to early April 1982, has illustrated dramatically the adverse effects of stratospheric aerosols on Umkehr observations. To aid in interpretation and processing of the Umkehr data, and to obtain ozone profile data for com­parison with satellite ozone measurements, a program of weekly balloon ozone soundings was begun in Hilo, Hawaii, in September 1982 and continued through­out 1983. Some initial results of the Umkehr and ozone sonde measurement programs are presented and examined in light of variations in total ozone observed at MLO. Results are also presented oC S02 measurements made at the observatory.

2. Umkehr and Total Ozone Observations

The Umkehr observations were made with specially calibrated Dobson in­strument 65. On the average 10 observations were made per month during May-

*Now at Meteorological Office, Pune, India.

Ozone Symposium - Greece 1984 - 305-

December 1982; 11 per month during 1983; and 7 per month during January­March 1984. Measured apparent changes in ozone per year, in standard and short Umkehr layers 1 to 9, are plotted month-by-month in Figure 1. The ozone changes are expressed in percent, relative to the ozone amounts present during the months indicated on the plots. CFor example, the May 1982 ozone value minus the May 1983 value, expressed in percent, is plotted for May 1983.) This method of data presentation not only eliminates annual cycle ozone variations, but it focuses on errors in the ozone measurements due to aerosols,

Fig. 1 Ozone changes per year at MLO in standard C-----) and short C-----) Umkehr layers 1 to 9, plotted month-by-month, and ex­pressed in percent relative to the ozone amount present during the month indicated. The dotted curves C·····) are similar data for total ozone.

assuming that the aerosol error effect became markedly diminished 1 year after the eruption of Mt. El Chichon. Evidence for substantial clearing of the stratosphere from May 1982 to early 1983 is available from optical photometry at MLO, indicating that the stratospehric aerosol optical depth decreased during this time period from about 0.27 to 0.05 (1).

The plots of Figure 1 show that the stratospheric aerosols caused ozone amounts initially to be highly overestimated by the standard and short Umkehr methods in layers 1-3. Maximum overestimates in layer 2, for example, were 230% and 166% for the standard and short Umkehr methods, respectively. Both methods underestimate ozone amounts by up to 30% to 40% in Umkehr layers 5 to 8. In layer 9, the standard method underestimates ozone amounts by 115% in May 1982, causing fictitious negative ozone values to be recorded. By December 1982, however, the ~zone underestimates in layers 5 to 9 are reduced to between 5% and 15%, and remain essentially unchanged through March 1983, suggesting that the results are not wholly fictitious, but

- 306-

reflect real differences in ozone, with the early 1983 values being lower than the early 1984 values.

That a real change in ozone occurred at MLO is indicated by the total ozone difference plot of Figure 1. THe plot shows that August 1982 through March 1983 total ozone values at MLO were lower than values in August 1983 through March 1984. The February 1983 value, in particular, was lower than the February 1984 value by 15%.

3. Ozonesonde and Umkehr Observations

Balloon ozone observations were made at Hilo with electrochemical concentration cell (ECC) sondes (2). Monthly mean ozone partial pressures measured during September 1982 through December 1983 are listed in Table I. Because the sondes yield ozone amounts too low above 10 mb (3), the measured values were increased by 2.5% at 10 mb, 5.0% at 7 mb, and 8.0% at 5.0 mb, and are believed to be in error by not more than 10% at 5 mb.

Mean ECC sonde and Umkehr ozone profiles are plotted in Figure 2. The plots for September 1982, when the stratospheric aerosol optical thickness was still relatively high (0.15), clearly demonstrate the adverse effect of aerosols on the Umkehr measurements. Relative to the 'sonde data, Umkehr ozone amounts are particularly low in layers 5 and 6, but much too high in layers 2 and 3. The ozone maximum is erroneously indicated by the short Umkehr method to be in layer 4 instead of layer 5. By December 1982, how­ever, when the stratosphere had substantially cleared (aerosol optical thickness -0.06), representation of the correct mean ozone profile by the Umkehr observations is considerably improved, the main discrepancy being ozone values still too high in Umkehr layers 2 and 3. In 1983, the mean

. seasonal Umkehr data agree well with corresponding ECC sonde data, except for short Umkehr ozone values in layer 5 that are too high. This and other

Table I. Mean Monthly Ozone Partial Pressures at Select Atmospheric Pressure Levels Derived from ECC Ozone sonde Soundings at Hilo, Hawaii

Ozone Partial Pressure Month/ No. 1013 700 500 300 200 150 100 70 50 30 20 Year Flts. 10 5

mb mb mb mb mb mb mb mb mb mb mb mb mb mb

09-82 3 11 26 16 12 5 6 18 46 75 116 137 94 55 29 10-82 19 29 29 13 13 14 30 74 90 137 147 72 30 11-82 12-82 3 6 29 27 12 6 6 13 42 80 123 134 77 48 30 01-83 3 20 30 20 11 8 6 6 23 74 113 125 75 56 35 02-83 4 5 35 28 13 8 4 9 26 53 132 122 84 55 35 03-83 4 28 36 27 18 10 9 12 28 68 97 124 94 63 38 04-83 2 36 33 34 15 13 10 14 29 83 129 138 105 63 33 05-83 16 40 34 24 22 17 52 39 60 112 142 94 54 30 06-83 2 29 46 31 15 18 27 28 47 81 131 142 88 57 36 07-83 2 8 33 14 7 5 11 18 46 88 122 144 96 63 36 08-83 2 11 27 20 12 7 8 29 51 85 118 141 91 62 41 09-83 3 7 23 15 9 10 13 21 45 78 131 142 92 60 40 10-83 1 17 28 21 8 7 4 20 48 80 127 141 86 58 32 11-83 3 10 23 17 11 9 7 9 35 72 118 134 95 59 36 12-83 2 13 24 33 13 10 10 9 35 86 112 134 95 58 38

- 307-

Fig. 2

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Ozone Parlial Pressure in ",mb

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Mean monthly ozone profiles for September and December 1982, and 1983 seasonal profiles, derived from Umkehr and ozonesonde obser­vations in Hawaii. Mean monthly values for September and December 1983 are shown by crosses (+). Numbers in brackets denote the number of observations per month.

differences among the 1983 Umkehr and sonde ozone profiles are not necessarily due to aerosols, but may stem from deficiencies in the algorithms used in processing the Umkehr data. From comparison of the Umkehr and sonde data, it is estimated that the aerosol-effect errors in the 1983 Umkehr ozone profiles probably do not exceed ±10%.

4. Sulfur Dioxide and Total Ozone Observations

S02 in the atmosphere interferes with Dobson spectrophotometer total ozone observations (4); hence, concern has been expressed about the accuracy of ozone observations made at MLO following the eruption of El Chichon vol­cano. Both total ozone and S02 can be deduced from observations with the Dobson instrument on AD and AB wavelengths (4). Such observations were be­gun at MLO on 17 May 1982. Results plotted in Figure 3 indicate that by about 1.5 months after the eruption, total S02 values at MLO had decreased to less than 2 milli-atm-cm, with the uncertainty being about ±1 milli-atm­cm. Thus, errors in ozone measurements after 17 May 1982 due to S02 inter­ference probably do not exceed about 1%.

- 308-

Fig. 3

Fig. 4

.:: ". ., .. :' ':I:S. : . r .... ,. ... . . r .:

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Plot of 12-month running mean total ozone data for MLO.

5. Apparent Ozone Depletion at MLO During 1982-1983

The low ozone values at MLO during August 1982 through March 1983 (Figure 1), compared with August 1983 through March 1984 values, suggest possible ozone depletion by the stratospheric aerosols. This apparent de­pletion is evident also in the September 1982 and 1983 mean ECC sonde pro­files of Figure 2, which show 1982 values to be lower than 1983 values (depicted by crosses (+)) at and below the ozone maximum. Care should be taken in interpreting these data as indicative of a real ozone depletion, however, since if a reducing species (e.g., H2S) was present in the low stratosphere during September 1982, it would have caused the ECC sondes to yield measured ozone amounts too low. Note, also, that ozone values above 10 mb were lower in September 1982 than in September 1983. It is not likely that aerosols caused ozone depletion at these heights.

Markedly lower ozone amounts were present above the ozone maximum in December 1982 compared with December 1983" (Figure 2). Figure 4 is a plot of the 12-month running mean total ozone data for MLO since 1958. The 12-month filter removes the annual cycle from the data and reveals the prominent quasi-

- 309-

biennial oscillations as well as longer period variations in ozone shown in Figure 4. Note that a minimum occurred in early 1983 in the quasibiennial ozone oscillation. The apparent ozone depletion of 1982-1983 is therefore, most likely a natural ozone fluctuation associated with the quasibiennial oscillation phenomenon, and not a consequence of the El Chichon volcano eruption. The reduced ozone values observed above the ozone maximum in December 1982 compared with December 1983 (Figure 2) most likely resulted from stratospheric circulation changes and associated changes in ozone transport of which the quasibiennial oscillation in ozone is a manifestation.

A longer period variation in ozone is clearly evident in Figure 4, with the decrease rate in ozone at MLO since 1970 being about 3% per decade. Whether this decrease in ozone is due to ozone depletion by chlorofluoro­carbons, or is the result of a long-term variation in the strength of the stratospheric circulation between equatorial and polar regions (associated, for example, with solar intensity variations), is unknown.

REFERENCES

1. DELUISI, J. J., MATEER, C. L., and KOMHYR, W. D. (1984). Effects of the El Chichon stratospheric aerosol cloud on Umkehr measurements at Mauna Loa, Hawaii. To be published in Proceedings of the Quadrennial International Ozone Symposium, Thessaloniki, Greece, 3-7 September, 1984.

2. KOMHYR, W. D. (1969). Electrochemical concentration cells [or gas analysis. Annals de Geophysique, t. 25, fasc. 1, 203-210.

3. KOMHYR, W. D., OLTMANS, S. J., CHOPRA, A. N., and FRANCHOIS, P. R. (1984). Performance characteristics of high-altitude ECC ozonesondes. To be published in Proceedings of the Quadrennial International Ozone Symposium, Thessaloniki, Greece, 3-7 September 1984.

4. KOMHYR, W. D. (1980). Dobson spectrophotometer total ozone measurement errors caused by interfering absorbing species in polluted air such as S02' N0 2 , and photochemically produced 03' Geophys. Res. Letters, 7, No.2, 157-160. -

- 310-

ON THE CORRESPONDENCE BETWEEN STANDARD UMKEHR, SHORT UMKEHR AND SBUV VERTICAL OZONE PROFILES

J. J. DELUISI Geophysical Monitoring for Climatic Change

Boulder, Colorado 80303

C. L. MATEER Atmospheric Environment Service

Downsview, Ontario Canada M3H 5T4

P. K. BHARTIA Systems & Applied Sciences Corporation

5809 Annapolis Road, Suite 600 Hyattsville, Maryland 20784

Summary

A series of concurrent surface-based Standard Umkehr, Short Umkehr, and satellite SBUV observations of vertical ozone profile over Boulder, Colorado is used to evaluate their mutual performance as a co-observing system. An understanding of the evaluation results is facilitated with use of theoretically predicted performance characteristics derived in a previous study of the Umkehr methods.

1. Introduction

In the present investigation we are concerned with a comparison be­tween vertical ozone profiles observed by the surface-based Standard Umkehr, Short Umkehr, and the satellite SBUV remote sensor. The SBUV and Umkehr measurements of uv radiance are a measure of essentially the same physical phenomenon, viz, ozone absorption and molecular scattering by the atmo­sphere; the main difference being a measurement from the bottom or top of the atmosphere. The methods of mathematically inverting these remote sensing measurements were developed at different times, and although they are based upon the same physical principals, they are not strictly equiva­lent. In this paper, the comparisons are done using ozone profiles from the Standard Umkehr inversion method, Mateer and Dutsch (1); the Short Umkehr method, Mateer and DeLuisi (2), and the SBUV method, Bhartia et al., (7) .

2. The Data Series and Comparison Criteria

The data series consists of 50 sets of concurrent Short Umkehr and Standard Umkehr observations made at Boulder, Colorado between November 1978 and November 1980, and same-day SBUV overflights within a 15° longi­tude and latitude distance of Boulder. The SBUV travels in noon orbit and Umkehr measurements are taken near sunrise and sunset, so a time difference of several hours exists between the two types of observations. The space and time differences are likely to produce some minor noise in the compari­sons.

Ozone Symposium - Greece 1984 - 311-

The accepted format for reporting Umkehr data is the 9-layer system (see World Ozone Data Center publication Toronto, Canada). The SBUV data are also reported in Umkehr layers.

Criteria for comparison are: 1. Percent difference (%) between the averages of two types of ozone

observations. 2. The standard deviation (SD) of the difference between individual

observations. 3. The correlation r between concurrently observed ozone profiles. 4. The standard deviation (a) of each type of observation. Although all 9 layers are used in the comparison, our primary interest

is with layers 4-9, because the Umkehr effect is most sensitive to ozone changes in these layers, and maximum fluorocarbon photochemical depletion of ozone is expected in layers 7 to 9 (3).

3. Results and Discussion

Figure 1 shows a plot of the percentwise difference between one type of measurement and a reference, i.e. Standard/Short implies the Short as the reference. A variety of factors are probably responsible in varying degrees of importance for the differences seen here. Among these factors are:

l.

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4.

5.

Different a priori ozone profile statistical information used in the measurement inversion algorithms; Wavelength dependent inconsistencies in the ozone absorption coef­ficients used with each measurement technique; Non-random yariations in ozone and temperature profiles i.e., diurnal and seasonal cycles; Imperfections in physical representation of radiation transfer, and, Instrumental errot's.

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- 312-

Figure 2 depicts observed SD's (see criteria for comparison #2) for the three methods if no bias existed among the observations. Theoretically predicted SD's for Standard Umkehr / Short Umkehr are shown as filled circles for 1 % measurement error. These SD's were estimated using the same procedures and Boulder ozone data that DeLuisi (4) used for a perfor­mance evaluation of the Short Umkehr and Standard Umkehr methods. The observed SD patterns appear to follow the theoretical pattern quite nicely with the exception being in layers 1 and 2. We can offer no clear explana­tion for the features seen in layers 1 and 2 other than to note that the a priori statistics used for the Short Umkehr and SBUV inversion algorithms are more closely related.

0,60.----------------------,

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Fig. 2 - Standard deviation of differences SD between different measurement types, normalized to the mean value of the reference measurement vs. layer number. These results exclude the biases shown in Fig. 1. Theoretically predicted SD's for the Short Umkehr method are shown as filled circles for 1% measurement error.

The present results appear to provide a quantitative measure of the systematic and random noise. Judging from the theoretically predicted per­formance patterns plotted as filled circles in Figure 2, the results in layers 3-7, inclusive, behave as if the observational error were about 1% while results for other layers behave as if the observational error were about 8%. This pattern seems to be consistent with the errors we would expect to be caused by the temperature dependence of ozone absorption not being accounted for in the present inversion algorithms, as shown ,by DeLuisi (5), and Mateer and DeLuisi (2).

Figure 3 shows correlations for the same comparison combinations as the previous figures. In layers 2-7 inclusive, the correlations are very good. In layers 1 and 8-9, the correlations are much lower and in layer 5, and to some extent in layer 8, a curious minimum appears in the correlation pattern for all comparisons. Ozone concentration variance in layers 5 and 8 are a minimum; therefore, the precision of the inversion is lessened.

- 313-

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Fig. 3 - Correlations between the different measurement types vs. layer number. Theoretically predicted correlations for the Standard Umkehr to Short Umkehr are shown as plain circles for 1% measurement error and filled circles for 10% measurement error.

14 r-----------------------------------------~

12

10

Stalrstlcs 01 Boulder orone ObsetvatlOllS

I-------i Short I- - - --1 Slandard ~--i SBUV ~ Boulder Oronesooles

Data above ~~ 6 Irom rockets

Laye! number

Fig. 4 - Normalized standard deviations of ozone profiles vs. layer number for Boulder, CO. Measurement types are SBUV, Standard Umkehr, Short Umkehr, and Ozonesonde. The ozone sonde measurements were not concur­rently made with the other measurement types . Filled circles are theore­tically predicted standard deviations for 10% measurement error .

- 314-

Figure 4 shows the calculated standard deviation pattern for each mea­surement type, using the same data set as for the previous figures. Also included in this figure is a plot of an analysis of 354 Boulder ozonesonde vertical profile measurements from the surface up to layers 5 or 6. Above these levels the rocket ozone standard profile and statistics of Krueger and Minzner (6) is used. We show only the Short Umkehr theoretically pre­dicted values for a 10% error because the results for a 1% error are little different (slightly larger than for 10%) with the exception of layer 1 which.is 0.31 and layer 9 which is 0.16.

Conclusion

The biases in ozone profile determinations from the three methods at Boulder show considerable variation, especially in layers 1-3 where the Umkehr uncertainty is large. The standard deviation of the difference be­tween ozone profiles observed with the different methods are 4% to 8% in layers 4-8 inclusively, about 15% in layers 3 and 9, and much larger in layers 1 and 2 for the Umkehr/SBUV comparisons. Over .the entire vertical profile, the pattern of Standard Umkehr/Short Umkehr standard deviations appears to follow the pattern of theoretically predicted standard de­viations when assumed measurement errors range between 1 and 10%. Corre­lations of ozone profiles observed by the three different methods also agree reasonably well with predicted correlations between the Standard Umkehr and Short Umkehr for 1% and 10% measurement error, with the excep­tion of layers ~, 8, and 9, where correlations are much smaller than expected.

In assessing the performance of the measurement methods overall, the correspondence between the measurements is not unexpected, in view of the present deficiencies in ozone absorption coefficients, inversion algorithms and a priori ozone statistics.

References

1. Mateer, C. L. and H. U. Dutsch, Uniform evaluation of Umkehr observations from the World Observation Network, Part 1, NCAR, Boulder, Colorado, 105 pp, 1964.

2. Mateer, C. L., and J. J. DeLuisi, The estimation of the vertical distribution of ozone by the short Umkehr method, Proced. Quad. Intern'1. Ozone~, .1, held 4-9 August 1980, Boulder, Colo. , 665 pp., 1981.

3. Weubbles, D. J., F. M. Luther, and J. E. Penner, Effect of anthropogenic perturbations on stratospheric ozone, ~ Geophys. Res., 1444-1456, 1983.

4. DeLuisi, J. J., Shortened version of the Umkehr method for observing the vertical distribution of ozone, ~ Optics, 18, 3170-3197, 1979.

5. DeLuisi, J. J., Effect of the temperature dependence of ozone absorption on vertical ozone distributions deduced from Umkehr observation, ~ Geophys. Res., ~, 2131-2137, 1971.

6. Krueger, A. J., and R. A. Minzner, A midlatitude ozone model for the 1976 U.S. Standard Atmosphere, ~ Geophys. Res.,.8l, 4477-4481, 1976.

7. Bhartia, K. F. Klenk, A. J. Fleig, C. A. Wellemeyer, and D. Gordon, Intercomparison of NIMBUS 7 solar backscattered ultraviolet ozone profiles with rocket, balloon, and Umkehr profiles, ~ Geophys., Res., ~, 5227-5238, 1984.

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Suraraary

EFFECTS OF THE EL CHICHON STRATOSPHERIC AEROSOL CLOUD ON UHKEHR MEASURE1IENTS AT MUNA LOA, HA~JAII---

J. J. DELUISI Geophysical l~nitoring for Climatic Change

NOAA, ERL, Air Resources Laboratory Boulder, CO 8030]

C. L. HATEER Atmospheric Environment Service

Downsview, Ontario CM1ADA M3H 5T4

W. D. KOHl-IYR Geophysical tlonitoring for Climatic Change

NOAA, ERL, Air Resources Laboratory Boulder, CO HO]O]

Umkehr observations, lidar observations of stratospheric aerosols, and aerosol optical depth observations were obtained concurrently at Mauna Loa observatory shortly after the March-April 1982 erup­tion of EI Chichon. The tremendous increase in stratospheric aero­sol from El Chicl10n produced a profound effect on ozone profiles deduced froD the Umkehr measurements, i.e. >10010 in layer Y. Time series of ozone in Umkehr layers 5-9 are shown for both standard and short Umkehr methods. Also given are stratospheric aerosol optical thickness and vertical profile data. Results of a prelira­inary analysis of error factors are described.

1. Introduction

The Umkehr effect is produced by optical scattering and absorption of solar UV radiation incident on the earth's atmosphere. The inversion algorithm for deducing ozone profile from the Umkehr measurements was developed for a raolecular atmosphere only. Aerosol scattering and absorption will produce an additional significant effect if concentra­tions are relatively in excess (1), and this effect introduces an error in Umkehr ozone profiles. For equivalent amounts of material, aerosol in the stratosphere produces a much greater ozone profile error than if it were located in the troposphere. This occurs because of the relative changes in the physical processes of absorption and scattering at dif­ferent altitudes as the sun's zenith angle changes during a measurement episode (2).

Concurrent standard and short Umkehr raeasurements, stratospheric aerosol optical thickness and profile Deasurements made concurrently at Hauna Loa, provide a unique experimental data set for invesd.gating the Umkehr ozone profile error relatable to stratospheric aerosols. This paper describes the results of a prelirainary analysis of the data set.

Z. Observations

Figure 1 shows standard UDkehr (3) ozone partial pressure in layers 5-Y observed during the time period May 1YHZ to Deceraber lYHJ, plotted

Ozone Symposium - Greece 1984 - 316 -

as a function of cumulative Julian days starting January 1, 1982. The observations were started approximately one month after the eruption of EI Chichon. Figure 2 shows a similar plot, but for the short method (4). The gross features of both figures are in reasonable agreement. During the early stages of the EI Chichon event the partial pressures in all layers are low. Accordingly, as the volcanic cloud diminishes in magnitude, the partial pressures increase toward the levels of clear stratospheric conditions; however, the stratospheric aerosol optical thickness is still significant (0.04 at >-=330 nm) at the end of the plot.

~ . '''''',11-''-:'. '10 -...".\ . . . . .,. ~ .... ..".,.--v;4 ,... • LAYER 6

~ ~ m B _ m ~ ~ _ _ ~

MTS 511(:( .1lII I, 1982

LAYER 9

Fig. 1. Standard Umkehr method ozone partial pressure (]lmb) vs time (Julian day) in Umkehr layers 5-9, for atmospheric pressure intervals 31.3-15.6 mb, 15.6-7.8 mb, 7.8-3.9 mb, 3.9-1.95 mb, 1.95-.98 mb, respectively.

Fig. 2. Same as Fig. 1, but for the short method.

- 317 -

r'igure 3 shows a plot of stratospheric aerosol optical thickness determined from sun photometry at Mauna Loa Observatory. A background tropospheric optical thickness was subtracted from the optical de,pth measurements to give the stratospheric value. Background tropospheric optical thickness varies from year to year. We have estimated the aver­age maximum tropospheric variability (which occurs during April) to be approximately ±0.004 at 330 nm. The annual mean optical depth at 330 nm is 0.018 for combined stratosphere and troposphere. Obviously, as the stratospheric optical thickness decreases, the error in estimating its magnitude will increase.

.;

II .,;

..

.;

II .;

" "

o 0,p " o

a a 0 a

a'b o

" o

a o

a

D

D a o D

lid

'_0 It'l>':. aD Ii 1\ d ca6'DO 0 a 0 ~o .... *i~~ 0 DDDO tI ... ~ '-, .. --aDD .. - q, ,II .." •

o D~"" a

Fig. 3. Stratospheric aerosol optical thickness at 330 nm wavelength originating from the March-April, 1982 eruptions of El Chichon, and observed at Mauna Loa. The background tropospheric optical thickness was removed from the original measurements.

Figure 4 shows monthly mean aerosol profiles over Mauna Loa for selected months in 1982-83. These data nicely show the initially great magnitude of the El Chichon cloud, the changes in magnitude, and changes in altitude of the maximum with increasing time. This information is invaluable for the correct models to theoretically calculate the error to Umkehr ozone profiles.

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Hg.

3.

35

30

E 25

"" N

20

15

10 ~ __________________ ~ ____________________ ~ __________________ -J

10- ' 10-> 10- ' o(km-')

4. Monthly mean stratospheric aerosol profiles over Mauna Loa. Observations weFe made by the Gl-ICC lidar. Plots are in terms of extinction per kilometer. Month and year (month/year) is given on each plot. Optical thickness at 694 rum associated with each profile are: 1, 0.24; 2, 0.20; 3, 0.16; 4, 0.062; and 5, 0.044.

Discussion

Our preliminary examination of tre Hauna Loa ozone and ancillary stratospheric aerosol data shows the expected relationship between aero­sol optical thickness and the negative error to the ozone profile in layers 5-9.

For large aerosol optical thickness, the pattern that seems to be emerging is that errors for layers 7-9 are lower than expected, and for layers 5-6, higher than expected, where the expected behavior is based upon results of previous studies. The previous-study aerosol optical thicknesses were approximately one order of magnitude less than the present. Because the El Chichon stratospheric aerosol layer co-existed with the ozone layer (maximum for both between 25 and 28 km) up to 35 km we cannot rule out the possibility of a real volcanically-induced ozone depletion in layers 5-7. Indeed, the larger-than-expected errors do suggest a possible depletion in these layers.

Since there is no Umkehr ozone profile climatology at Mauna Loa, it is not possible to examine the current data set in the context of an unperturbed ozone profile record. For example, the annual cycle in ozone profile is embedded in the present data set, and it must be removed before an absolute error can be determined. However, because of its completeness, the Mauna Loa combined data set will allow for correct

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inputs into theoretical radiative transfer calculations; thus avoiding a soraetimes crucial dependence on assuraptions. We plan to conduct an empirical-theoretical analysis of the data set in the near future.

References

1. DeLuisi, J. J., Umkehr ozone profile errors caused by the presence of stratospheric aerosols, ~. Geophys. Res., ~, 1766-1770, 1979.

2. Dave, J.V., J.J. DeLuisi, and C.L. Mateer, Results of a comprehen­sive theoretical examination of the optical effects of aerosols on the Umkehr measurements, Papers Presented at the WMO Technical Conference on Regional and Global Observation~f A"t;;oS"Pheric Pollu­tion RelatiVe to Cliraa~ special Environmental Report No.~ Boulder, 20-24 August 1979, 398 pp., 1980. --- - -

3. Mateer, C.L., and H.U. Dutsch, Uniform evaluations of Umkehr obser­vations from the World Observation Network, Part 1, NCAR, Boulder, Colorado, 105 pp., 1964.

4. l1ateer, C.L., and J.J. DeLuisi, The estiraation of the vertical dis­tribution of ozone by the short Umkehr method, Proceed. Quad. Intern'l. Ozone Syrap., 1, 4-9 August 1980, Boulder, Colorado~5 ~981.--- ---

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Ozone-Temperature Relationships in the Stratosphere

Summary

A. J. Miller, R. M. Nagatani NOAA/NMC/Climate Analysis Center

and

J. E. Frederick NASA/Goddard Space Flight Center

Utilizing independent estimates of ozone and temperature fields from the SBUV (Nimbus 7) and NOAA operational satellites, respectively, for the period 1978-1981, we have determined the coefficient of variation between the two parameters. This coefficient is defined as A== A03• (T] !A.,... CO, 1 where Do is an incremental change in either temperature or ozone and the bracket is a mean state. In practice, A is determined on a daily basis by regression of ozone mixing ratio versus temperature around a latitude circle during the winter season and the bracket value is the daily zonal average. This has the advantage of keeping the solar zenith angle fixed for a daily value while allowing it to change during the season. This is done at 30, 10,5,2, and 1 mb from 200 to 600 latitude in both hemispheres. The results are summarized and compared with those determined from a one-dimensional photochemical model applied to different latitudes.

1.1 Introduction

It has long been realized (e.g. Barnett et aI, 1975; Frederick, 1980) that in the upper stratosphere, the ozone mixing ratio is essentially under photochemical control whereas in the lower stratosphere it is under dynamic influence. The implication of this is that at the higher levels the ozone mixing ratio should be negatively correlated with atmospheric temperature while at the lower levels it should be positively correlated. More specifically, within the photochemical regime the ozone-temperature relationship is essentially dictated by the temperature dependence of the reaction rates, with ozone proportional to exp k, where k is on order of 1400 for a pure oxygen

T atmosphere and about 500 for OH chemistry.

Utilizing these fundamental relationships, a one-dimensional photo­chemistry-eddy transport model has been constructed (Rundel et aI, 1978; Horvath et aI, 1983) that allows us to determine the percent change in ozone for a 10 K change in temperature. Our purpose is to compare the re­sults of this model with independent observations of ozone and temperature.

The data utilized for this study are daily, global analyses of ozone mlxlng ratio and temperature from the Solar Backscatter Ultraviolet Ozone Sensor (Nimbus 7) and NOAA operational data series at 30-, 10-, 5-, 2-,

Ozone Symposium - Greece 1984 - 321 -

and 1 mb extending from November '78 to October '81. In practice we calcu­late the coefficient of variation defined as A = 060,3 , (TJ! DoT, 1:03-J by linear regression of ozone versus temperature on a daily basis at a specific latitude. The daily values are then averaged over the 3 month winter period, December-February for the Northern Hemisphere, June-August for the Southern Hemisphere and compared against the model calculations for that latitude.

In Figure 1a we present the results for 3 Northern Hemisphere winters at 350 and 550 latitude. We have included the standard error about the mean for 78-79 to indicate the general variance of the data within the winter. We see that the model results, which include a fixed, parameterized treatment of vertical transport, indicate a negative ozone-temperature relationship throughout the region. The maximum value is about -1.7%/oK at 1.5 mb for 35N moving upward with latitude to about -1. 75~/oK at 1 mb for 55N. At 1 and 2 mb our independent computations are, generally, less negative than the model results although the values for 78-79 at 35N are actually greater than the model at 1 mb. For both latitudes the computations show an increase from 2 to 1 mb and the shift to positive values at lower levels. Also, the zero impact level moves upward with latitude.

For the Southern Hemisphere, Figure 1b, we see that the results are very similar to those of the Northern Hemisphere, but with lower year-to­year variation at the upper levels. With this lower variability we also see that at 2- and 1-mb the coefficient of variation decreases with latitude from a value of about -1.0 to a value of about -0.6, a feature not evident in the model calculations.

Finally, we note that the calculation of the coefficient of variation is susceptible to systematic errors in the data. In the photochemical region where the analyses are entirely derived from satellite data it has long been recognized that the retrievals/analyses tend to be conservative, that is, they do not quite catch the maximum and minimum values. This results in a systematic bias in the estimate of A. Using the results of Gelman et al (1980).for temperature and recent SBUV­LIMS comparisons, we find that this bias can be as high as about 30~ with the coefficient underestimated. This helps somewhat in the consideration of the results at 35, but is not nearly sufficient at 55 degrees.

In an attempt to reconcile these differences, we note that the temperature dependent chemical loss of ozone arises from reactions with (1) odd nitrogen (NO, N02 ), (2) odd chlorine (Cl, CIO), (3) odd hydrogen (H, OH, H02), and (4) the direct reaction of 0 and 03• The reactions involving odd hydrogen and odd chlorine are only weaRly temperature dependent while the 0+03 and odd nitrogen reactions are very temperature sensitive. The temperature sensitivity of ozone at any given pressure depends on the relative contributions of each of these four mechanisms to the total loss rate. In the -35-45 km region the odd nitrogen (very temperature sensitive) reactions dominate ozone loss. If the true atmospheric odd nitrogen abundances are less than in the model, the computed curves would be shifted in the direction of the ones deduced fro~ data. In addition, if the horizontal advection of odd oxygen is significant relative to the chemical loss, especially at 55 degrees, the model would overestimate the ozone-temperature relationship at 2 and 1 mb. This has been suggested by Rood (personal communication) and we are currently examining the data to study this possibility.

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Acknowledgments: This work is supported in part by the National Aeronautics and Space Administration.

References

Barnett, J.J., J.T. Houghton, J.A. Pyle, 1975: The temperature dependence of the ozone concentration near the stratosphere. Quart. J. Roy. Met. Soc., 101,245-257.

Frederick, J.E., 1980: Seasonal variations in high-latitude ozone and metastable molecular oxygen emissions: a theoretical inter­pretation. J. Geoph. Res., 85, 1611-1617.

Gelman, M.E., R.M. Nagatani, A.J. Miller, J.D. Laver, and F.G. Finger, 1980: An evaluation of stratospheric meteorological analyses using satellite sounder and rocketsonde data. Proceedings of International Symposium on Middle Atmosphere Dynamics and Transport, Urbana, IL.

Horvath, J.J., J.E. Frederick, N. Orsini, A.R. Douglas, 1983: Nitric oxide in the upper stratosphere: measurements and geophysical interpretation. J. Geoph. Res., 88, 10809-10817.

Rundel, R.D., D.M. Butler, R.S. Stolarski, 1978: Uncertainty prop­agation in a stratospheric model, 1, Development of a concise stratospheric model. J. Geoph. Res., 83, 3063-3073.

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mb

2

5

10

30

50

% CHANGE IN 0 FOR A I oK CHANGE NORTHERN HEMISPHERE

-79 --- 80 .- 81

SOUTHERN HEMISPHERE

-79 -- 80 -'-81

-2 -I o

Figure 1. Comparison cf 1-D model results versus observations of percent change in ozone for a positive 10 K change in temperature. Top is for Northern Hemisphere, bottom is for Southern Hemisphere.

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LIDAR OZONE MEASUREMENTS IN mE TROPOSPHERE

AND STRATOSPHERE AT mE OBSERVATOlRE DE HAUTE PROVENCE

Summary

J. PELON and G. MEGIE Service d'Aeronomie du C.N.R.S.

As a consequence of research efforts performed to observe any anthro­pogenic influence on atmospheric ozone, new systems have been developped to monitor the ozone profile and total content from the ground. As part of it an ultra-violet lidar system was implemented in 1980 at the Observa­toire de Haute Provence (OHP), and was involved in different international comparison campaigns.

Some results of these campaigns will be presented, with other specific comparisons as they have allowed to validate the lidar measurements performed at the OHP throughout the altitude range from the ground up to 45-50 km. 'Such high altitudes have been reached by means of a new generation of laser systems, the implication of which on the ozone survey in the upper stratosphere will be emphasized.

Lidar systems are also potential instruments for ozone survey in the troposphere and especially their ability to perform high spatial and temporal resolution measurements, below 15 km, allows to describe some aspects of stratosphere-troposphere exchanges as will be presented.

1. Introduction

Possible modification of ozone content and distribution due to human activities has been a major topic in atmospheric physics for about a decade now. Important efforts have been made to develop accurate models of the ozone behaviour in the stratosphere and troposphere under the influence of increased amounts of chlorofluorocarbons and other gases

(C0 2, CH 4, NfJ···)· Simultaneously field testing of instrumentation and developments of

new systems have been pushed forward to allow by confrontation with model predictions the better representation of dynamical and photochemical processes.

Concerning the development of ozone measurement systems, UV lidars should be now considered as reliable candidates for ozone monitoring up to 45 km, proving to reach the upper altitudes where ozone decrease under anthopogenic influence may become very important (20 to 50 km) (1), (2).

However their ability to perform ozone measurements in the lower atmosphere with high time and space resolution can be of great interest not only for ozone survey in this region where its increase could affect

Ozone Symposium - Greece 1984 - 325-

the earth radiative equilibrium (3), but also for describing small scale processes such as those encountered in troposphere-stratosphere exchanges.

2. Validation of the measurements

In 1979-1980 we developped a new ultra-violet lidar system for ozone monitoring in the atmosphere by means of differential absorption technique. It was implemented at the OHP in 1980 (44N, 6E). We will not describe here the system and methodology, which have previously been detailed (4). This system has been involved in two international ozone campaigns in June 1981 and September 1983. Only results of the first campaign have been fully analysed (5), (6). On the Figure 1 we have represented a comparison performed during this campaign between lidar and ECC soundings.

Z km

25

20

15

10

5

OHP JUNE 20/21 • 1981 Lidar--ECC sonde -------

.2

\,

Figure 1 Comparison between lidar and ECC sonde measurements of the vertical ozone distribution.

Z km

35

25

15

5

--- Brewer 30.11 ------- ILidar 1.12 ................ ·,Lidar 2.12

.5 2 5 Figure 2 Comparison between lidar (OHP) and Brewer-Mast sonde (Bis­carrosse) measurements of the ver-tical ozone distribution.

The same short scale variations were recorded by the two instruments, small differences may be attributed to horizontal inhomogeneities of ozone concentration averaged by lidar.

The agreement between the two measurements lies within 5 % above 20 km where homogeneity is greater, which is well within their respective absolute error bars.

These features can also be seen on the Figure 2 where we report comparisons performed in December 1981 with the same lidar system but operated at two wavelength pairs to probe the upper stratosphere (289-295 nm and 306-311 nm) (7).

The Brewer sonde data used for this comparison were obtained by the Meteorologie Nationale at Biscarrosse (44N, 1W). The agreement is very good in the upper stratosphere, and a bias of only 2 % was detected between the measurements in the altitude region from 20 to 32 km.

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During the Globus campaign in September 1983, we experimented a new XeC1 laser, emitting at 308 nm, 10 times more powerful than our dye laser system. In order to perform with this system upper stratosphere measure­ments by differential absorption technique we used for reference wave­length, the third harmonic of a Nd-YAG laser (355 nm). This configuration allows to obtain simultaneously the atmospheric density after normali­sation to radiosounding values between 28 and 32 km e.g. above the aerosol layer.

We are thus able to derive the ozone concentration as previously, but also the ozone mixing ratio and even the temperature following the method deve10pped by previous authors (8). On the figure 3 we have represented the mean ozone mixing ratio observed with this new laser configuration, on a five days period [16-17-18-22-23/09] for a total acquisition time of less than four hours, as compared to the mean profile obtained at 45°N, by Krueger and Minzner (9).

46

KM

35.5

25

US std 1976 L1dar

2 4

.:r' -' ,'/)/ /lj

6

, , , , , , /

[03] ppmv

8 10 Figure 3 : Ozone mixing ratio measured in the upper stratosphere, at the OHP, compared with the mean profile of Krueger and Minzner for 45N.

Around 30 km the relative uncertainty (± 1 0) is about 2 % and decreases to about 7 % at 40 km for a spatial resolution of 1.2 km to 4.8 km. Absolute error due to density normalization and determination of ozone cross sections values is thought to be of the order of 3 to 5 %. This combined with the previous relative errors is promising for the determination of absolute ozone quantity above 25 km, which seemed up to now very difficult to obtain with other 1idar systems, all the more as accuracy can be still improved by increasing acquisition time and emitted energy.

Equivalent 1idar systems could thus be used in near future to monitor simultaneously ozone and temperature in the upper stratosphere which could be of interest to validate photochemical models in this region.

If this lidar configuration is promising for high altitude measure­ments, the first system, which has been operated since 1980, is very well adapted for lower atmospheric measurements due to its wavelength tuning

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ability allowing high space-time resolution. Ozone can be thus used as a passive tracer of dynamical motions in the troposphere and lower strato­sphere.

3. Ozone measurements in the vicinity of polar jet stream deformations

Such measurements have been frequently performed by in situ instru­ments on board aircrafts passing through the jet stream associated fronts (10). But as lidar systems allow to monitor ozone on a quasi continuous basis, it is possible with such systems to observe the evolution of ozone concentration within a cold front from the ground. Several campaigns were conducted at the OHP with collaboration of J. VERNIN from the University of Nice for. turbulence detection in the lower atmosphere by star scintil­lation (11). His experiment was settled at the OHP and measurements of the

C 2 vertical profile could be made simultaneously with lidar ozone soUndings.

All the data have not been yet analysed, and we will give only the main features observed during the most interesting campaign.

Analysis of turbulence and ozone measurements is carried on to caracterise small scale processes.

On the Figure 4 we have reported ozone concentration measured between 19 hand 22 h TU from 5 to 12 km with a 3 mn time resolution in December 1981. Lines of stars represent zones where turbulence was detected.

These data show an important ozone increase in the mid-troposphere correlated with the existence of a front above the OHP. The position of the front can be seen on Figure 5, representing the synoptic map of the isothermal contours at the 500 mb level and the front location at the ground, deduced from" the european meteorological soundings performed this night at 0 h liT.

OHP 7.12 . 1981 0=3E11 7=1 .7E12 03 11

kin

8

1239 1341 TIME (MN ) 1443 Figure 4 : Evolut10n of the ozone concentration in the troposphere during the passage of a cold front.Stars denote turbulent layers (see text). Dots represent concentrations greater than 1.3E12 molecules per cubic centimetre.

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500 rrtJ

Figure 5 : Synoptic chart of isothermal contours at 500 mb and location of ~he front at the ground.

We can see that below the high ozone concentration layer centered around 6.5 km an important turbulent layer was observed the intensity of which was larger when higher ozone concentrations were measured just above. A weaker turbulent layer was detected above the ozone layer near 8.5 km especially by the end of the measurements. The vertical profile of the Richardson number calculated from the radiosounding performed at Nimes (44N, 5E) at 0 h UT shows a well correlated minimum lower than .25 at 5.3 km.

The turbulent and ozone layers observed present the same altitude variation of about 1 km between 19 and 22 h TU. This is due to the passage of the front going from W.N.W. to E.S.E., perpendicularly to the jet axis. Our observations correspond thus to a sectional elevation of the frontal zone at different altitudes producing the idea that ozone descended which was not the case.

The data analysis concerning the day before show a rapid variation of tropospause height as defined by ozone gradient, from 8.5 km to 10 km in less than one hour, correlated with a two fold ozone concentration increase between 5 and 7 km. This was attributed to the observation of a secondary front and associated wavelike patterns were clearly observed which are the purpose of further analysis.

Conclusion

The geophysical station of the OHP is now part of the ozone interna­tional monitoring network, as Dobson measurements, aerosol lidar and ozone Brewer Mast soundings are routinely performed. Ozone lidar measurements should be fully automatized by the end of 1985 to ensure regular observa­tions for ozone trend determination in the troposphere and stratosphere.

This includes the use of a new exciplex lidar system to perform upper stra tospheric measurements with improved performances as compared to the system tested in September 1983.

The grouping of all this measurements on the same site should thus favour a better checking of model predictions by the sake of complemen­tarity of all instruments. But it can be noticed also that lidar system present advantages (teledetection over long distances, high spatial and temporal resolution, non-perturbation of the studied medium) that make them attractive for use from plane, which is a first objective of smaller systems developped in the perspective of space borne application (12).

References 1. WUEBBLES D.J., F.M. LUTHER, J.E. PENNER. J. Geophys. Res., 88, 1444-

1456, 1983 2. PRATHER M.J., M.B. McELROY, S.C. WOFSY. Presented at NASA, FAA, WMO,

BMFT Meeting, Feldafing, Germany, 11-16 June 1984 3. BOJKOV R.D •• Presented at WMO Conference TECOMAL, Vienna, Austria, 17-

21 October 1983 4. PELON J., G. MEGIE. J. Geophys. Res., 87, 4947-4955, 1982 5. MEGIE G., J. PELON. Planet. Space Sci., 31, 7, 791-799, 1983 6. PELON J., G. MEGIE. Planet. Space Sci., 31, 7, 717-721, 1983 7. PELON J., G. MEGIE. Nature, 299, 137-139, 1982 8. HAUCHECORNE A., M.L. CHANIN. Geophys. Res. Let., 7, 565-568, 1980 9. KRUEGER A.J., R.A. MINZNER. J. Geophys. Res., 81, 4477, 1976 10. SHAPIRO M.A •• J. of Atmos. Sci., 37, 994-1004, 1980 11. AZOUIT M., VERNIN J •• J. of Atmos. Sci., 37, 1550-1557,1980 12. MEGIE G., J. PELON, P. FLAMANT. Proceedings of the ESA Workshop on

Space laser applications and technology, les Diablerets, 1984

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VERTICAL OZONE DISTRIBUTION OVER UCCLE (BELGIUM) AFTER CORRECTION FOR SYSTEMATIC DISTORTION OF THE OZONE PROFILES

Sununary

D. DE MUER Meteorological Institute of Belgium

Vertical ozone profiles as determined by means of electrochemical ozone sondes show a large-scale distortion. Three distinct systematic biases on the ozone profiles are discussed : the frequency response of the combined sensor and air-sampling system, the variation of the tempera­ture of the sampled air and the change of the sensitivity of the ozone sensor during a sounding. After correction of the ozone profiles for these effects, the resulting mean ozone amount in the troposphere and the lower stratosphere is considerably higher, while above the ozone peak there is a lowering of the ozone concentration. It is pointed out that a change in the pre-flight conditioning of the ozone sondes may induce a false ozone change at certain levels. Statistics of the ratio of descent to ascent ozone values offer a possibility to verify whether alleged tropospheric ozone trends are real or not.

1. Introduction

The ozone profiles deduced from balloon soundings form the bulk of our knowledge of the vertical ozone distribution in the free troposphere and the low and middle stratosphere. The climatology of these profiles up to about the 6 mb level has proved to be very useful as a priori information for various remote sounding techniques or as input in numerical models.

However, there are indications that the ozone profiles deduced from balloon soundings with the usual evaluation procedures, show a systematic distortion. This dtstortion is not only important for the a priori profi­les but also because of its effect on the discrepancy between average bal­loon profiles and profiles based on U.V. absorption data (see e.g. (1),(7». In the third place, an instrumentally induced bias on the ozone profiles may also have an effect on long term ozone trends calculated from balloon soundings.

The present paper deals with the correction of three distinct sytema­tic biases on ozone profiles. In order to demonstrate the consequence of this correction on the climatology of the vertical distribution we used a series of ten years of regular ozone soundings at Uccle (Belgium) from 1973 to 1982, comprising more than 1200 soundings.

Ozone Symposium - Greece 1984 - 330-

2. Deconvolution of the ozone profiles The different components of the frequency response of an electrochemi­

cal ozone sonde and the analytical form of the corresponding transfer func­tion were studied in detail by De Muer and Malcorps (5). It was pointed out that the deconvolution of the ozone soundings gives a significant im­provement of the correspondence between the ascent and descent profiles, especially as to the position of the ozone peaks. So it is obvious that the deconvolution process results in a better approximation of the real ozone profile.

In ·order to establish the effect of this correction on the mean verti­cal distribution of ozone, the deconvolution procedure described in (5) was applied to all the individual ozone soundings at Uccle for the period 1973-1982.

The main effect of this process on the mean vertical ozone distribu­tion is a shifting of the corrected profile to lower levels, resulting in lower ozone values above the ozone maximum and in the free troposohere, and higher values in the lower stratosphere.

The profile of the relative difference between the uncorrected and corrected mean ozone profiles (curve 1 in Figure 1) shows two sharp maxima, respectively in the mixing layer and at the mean tropopause level. This can be explained by the fact that the ozone concentration shows a steep in­crease at these two levels, causing a large correction for the response time of the ozone sensor.

Fig. 1.- Vertical distribution of the relative change of the calculated ozone concentration caused by deconvolution (curve 1), by the tem­perature change of the sampled air (curve 2), and by the sensiti­vity change of the ozone sensor (curve 3). The values were all obtained after correction of the ozone profiles for the mean total -ozone amount. Max. : mean . level of the maximum ozone partial pres­sure; Trop.:mean tropopause level.

- 331-

3. Correction for the change of air temperature inside the sampling pump The relationship between the ozone concentration and the output cur­

rent of the sensor of an electrochemical ozone sonde is as follows : -3

P3=4.308xl0 itT (1)

where P3 is the ozone partial pressure (nb), i is the output current (f"A), t is the time (s) to pump 100 ml air at a temperature T (K). There appears to be some confusion about the value of T. (For instance Kobayashi and To­yama (6) consider the temperature in the reaction cell for the evaluation of their ozone sonde data). It should be clearly. stated, however, that the only correct value for T is the temperature of the air being sampled : that is the air temperature inside the pump. In the evaluation of ozone soun­dings with the Brewer-Mast sonde, it is usually assumed that T in relation (1) has a constant value of 300 K. But Brewer and Milford (3) already re­cognized that this can easily be lS oC in error.

The actual values of T during an ozone sounding were measured at Uccle by means of a very small pearl thermistor in the air stream of the pump. In order to prevent any radiation effect and any direct contact with the walls of the pump, the thermistor was positioned in the centre of a small alumi­nium cavity that was fixed between the air pump body and the teflon outlet tube. The course of the values of T appeared te be dependent to some ex­tent on the profile of the ambient air temperature, particularly at the tropopause level where the profile of T shows a clear-cut gradient change.

During the ascent, the temperature of the sampled air continuously de­creases from room temperature near the ground to about SoC at burst level. During the descent there is a further decrease to values near OoC. It could be argued that this temperature change has only a minor effect on the mean vertical ozone distribution. However, curve 2 in Figure 1 shows that in the stratosphere the temperature correction acts in the same sense as the de­convolution, so that the ozone decrease above the ozone peak is amplified.

4. Correction for the change of sensitivity of the sensor Soundings with the Brewer-Mast electrochemical ozone sondes show most­

ly systematic differences between ascent and descent data in the tropospHe­re and the lower stratosphere, the descent values being the highest. There are several reasons (De Muer (4)) to assume that the descent data in the lower part of the soundings give a better approximation of the real ozone values than the ascent data.

The pre-flight preparation procedure of the ozone sondes at Uccle was changed from October 1981 on ; an electrostatic discharge ozoniser, in­stead of a u.v. lamp, was used to condition the ozone sensors. From Figure 2 it may be seen that this change had a considerable influence on the raw ozone data. Before October 1981, the descent data were systematically hi­gher than the ascent data, while from that date on, the ratio descent/ascent is not significantly different from one. (The ratios descent/ascent in cur­ve 1 are slightly lower than the values mentioned by De Muer (4), because the latter values were not corrected for the change of air temperature). It appeared that this change in the mean ratio descent/ascent was almost entirely due to higher ascent values in the troposphere and the lower stra­tosphere while the descent values were hardly affected.

For the correction of the ozone soundings during the period Jan. 1973-Sept. 1981, the ratios on the smooth line in Figure 2 were used. From cur­ve 3 in Figure 1 it may be seen that this results in a high relative ozone increase in the troposphere ; as for the other two corrections there is again an ozone decrease above the ozone peak.

- 332-

10 .' mb \ ( 20 ~ 30 (i

... SO

100

'. : 200 \

300 . " • !,oP ...

. 500

'.

1000 0.8 0.9 1.0 1.1 1.2 13 1.4

Fig. 2.

mb

10

20

30

\0

100

100

\00

15 1.6 1.7

1000

./'

--~ ::-- --::::-;= "8= ~ ", ------- ----~ ", ~ =-----======= ,~

~-~~ ~- , ~ ---- .. ~ S5J~-- -- ~ (' ~ ---;-- ~ "

~~~::;.~ ~ ~- - ~ " , ---- --- -----C ~"" '---~-...

12

Fig. 3.

to 11 11 month

Fig. 2.- Vertical distribution of the ratio of the mean ozone partial pres­sure during the descent and the ascent of the ozone soundings at Uccle, after upplication of the corrections explained in sections 2 and 3. Stars: for the period Jan. 1973 - Sept. 1981 ; solid circles: for the period Oct. 1981 - Dec. 1982. Max. and Trop. : as in Figure 1.

Fig. 3.- Time cross-section of the mean vertical distribution of the ozone partial pressure (nb) over Uccle for the period 1973-1982 after all corrections explained in the text.

i'°r-~·er-~-6r-_-'r-~-2r-~~r-~~r-~~1~0~1~2~n~b~-r __ r--r __ ~-r __ r--r-'

mb

10

20

10

100

200

100

soo

I ,

,/ , ,

-Trop.

Fig. 4.- Vertical distribution of t~e relative (curve 1, lower scale) and the absolute (curve 2, upper scale) difference between the ozone profile obtained after the three corrections explained in the text, and the uncorrected ozone profile. Max. and Trop. : as in Figure 1.

- 333-

5. Conclusions Figure 4 shows the total difference between the uncorrected vertical

ozone distribution and the vertical ozone distribution obtained with the three corrections explained in sections 2, 3 and 4.

In the troposphere and the lower stratosphere the resulting ozone con­centration is considerably higher, while above the ozone peak there is a lowering of the calculated ozone concentration that amounts to about -12% at the 10 mb level. This means that by these corrections the discrepancy between average ozone sonde profiles and profiles derived from U.V. radio­meters in the middle stratosphere is enlarged. Unless a major source of systematic errors in the profiles derived from ozone sonde data has been overlooked hitherto, the cause for this discreparcyhas to be searched amrng the parameters used in the evaluation of U.V. absorption data. In Figure 3 the mean time cross-section of the corrected ozone soundings is shown.

The break in the level of the raw tropospheric ozone data at Uccle in October 1981 as explained in section 4, was only caused by one single chan­ge in the preparation procedure of the ozone sondes. This proves that one should be very cautious in inferring ozone trends from ozone sonde data. For such a trend analysis it is necessary to take into account any, even a minor, change in the pre-flight conditioning of the sondes for every ozone station individually.

In section 4 it was pointed out that descent ozone values are much less affected by such changes than ascent ozone values. Therefore, statistics of the ratio descent/ascent ozone values can be very useful in verifying whether the alleged ozone increase in the troposphere during recent years (see e.g. Angell and Korshover (2» is real or not.

REFERENCES

1. AlMEDIEU, P., KRUEGER, A.J., ROBBINS, D.E. and SIMON, P.C. (1983) Ozone profile intercomparisons based on simultaneous observations between 20 and 40 km. Planet. Space Sci., 31, 801-807.

2. ANGELL,J.K. and KORSHOVER, J. (1983). Global variation in total ozone and layer-mean ozone: An update through 1981. J. Climate Appl. Meteor. 22, 1611-1627.

3. BREWER, A.W. and MILFORD, J.R. (1960). The Oxford-Kew ozone sonde.Proc. R. Soc. London, 256, 470-495.

4. DE MUER, D. (1981). A correction procedure for electrochemical ozone soundings and its implication for the tropospheric ozone budget. Pro­ceedings of the Quadrennial Ozone Symposium, Boulder, Colorado, 4-9 Aug. 1980, Vol. 1, pp. 88-95.

5. DE MUER, D. and MALCORPS, H. (1984). The frequency response of an electrochemical ozone sonde and its application to the deconvolution of ozone profiles. J. Geophys. Res., 89, 1361-1372.

6. KOBAYASHI, J. and TOYAMA, Y.(1966). On various methods of measuring the vertical distribution of atmospheric ozone (III). Pap. Met.Geoph., 17, 65-75.

7. MATEER, C.L. (1981). A review of some unresolved problems in the mea­surement/estimation of total ozone and the vertical ozone profile. Proceedings of the Quadrennial Ozone Symposium, Boulder, Colorado, 4-9 Aug. 1980, Vol. I, pp. 1-8.

- 334-

ON THE RELATIVE QUALITY AND PERFORMANCE OF G.03 0.S. - TOTAL OZONE MEASUREMENTS

Rumen D. Bojkov and Carlton L. Mateer

Atmospheric Environment Service of Environment Canada

Summary During the past few years the Global Ozone Observing

System (G030S) benefitted from TOMS satellite data as well as from an innovative exercise - travelling standard lamps, providing new data on the level of performance of ozone stations. In this paper, we summarize the information available from these two sources in order to assist data users in their analyses and to stimulate common action for improving the performance of G03 OS.

1. Introduction The large natural variability of total ozone, particularly

at middle and high latitudes, add to the sometimes uncertain quality of the measurements causing great difficulty in detection of small long-term ozone trends. The determination of these trends is important for the verification of both the model predictions and th~ impact of human activities on atmospheric ozone. The quality of the available ozone data varies because they are obtained by a variety of measurement techniques with nonuniform geographical and altitude coverage, and with variable historical continuities. The uninformed user may be unaware of the uncertainties and limitations of the reported numbers.

In this paper we discuss some of the shortcomings in station performance and the quality of the total ozone observations identified by comparison with TOMS satellite data and travelling standard lamp t~sts.

2.Measurement errors Dobson ozone spectrophotometers serve as standard

instruments for measurement of total ozone. About 70 (out of 105 built) are providing data on a regular basis. In addition, about 20 filter instruments (M-83) are reporting total ozone data. The uneven geographical distribution is a source of spatial sampling error when attempting to determine global ozone amounts and trends. Weather conditions and operational factors which cause losses of data collection may cause biases in some months' mean ozone of u.p to 5-6% especially since total ozone amounts are strongly correlated with synoptic weather conditions.

The accuracy of total ozone measuring instruments is strongly dependent on the quality of their calibration and operation. The quality may vary during an instrument's history, and the past record of the quality for many stations is virtually impossible to establish. The quality of Dobson total ozone measurements depends on a number of factors which are described in WMO, (1980,1981,1982). There the potential long-term total ozone measurement precision, at the 95% confidence level, has been estimated to be 1%. The broad-band filter ozonometer exposes

Ozone Symposium - Greece 1984 - 335-

TABLE I

DOBSON TOTAL OZONE NETWORK PERFORMANCE FOf: 1979-19B2 .UtI.nnunIUIUluuuluuunuluuuu.uuuuunUIUUUiUUlununnUUIUUuiUiUUlliUluunnunnnu STATION LATITUDE COMPARISON WHH TONS SAT[LLITE

1979 1981' 1<'81 ,'82 1982

MEAN!SDEV,NUMI MEAN (SDEV, NUH I MEAN (SDE'), NUH 1 MEAfIISDEV,NUM'

AHUNDSEN-SCOTT -90.0 4.321 0.23, 501 4.75( 0.32, 691 3.30( 0.51, 411 1.7B( 0.33, 861 7.03( 0.B4, 511

3.66( 0.12, S4i 6.93( 0.36, 391

-0.76( 1.24, 151 O.SO( 0.21, 911 4.691 0.55, 681

.. tlU(tlUI, 01 c.02! 0.32. 46} SYOWA -69.0 6.21( 0.21, 87) lO.SS( 0.82, 32) HACGUARIE ISLAND -54.5 -3.S0( 1.33, m iUiU!It~U. 0) INVERCAR61LL -46.4 2.34( 0.29, 70) 1.0S( 0.26, 66) HOBART -42.9 4.S4( 0.3701151 3.6S! 0.1801641 ASPENDALE -38.0 -0.45( 0.16,156)

1.29( 0.3601141 O.21( 0.12,209)

-0.41I 0.210166) O.BO( 0.2001361 LOO( 0.13,221)

G.8l( 0.150184) 0.94( 0.180150) BUENOS AIRES -34.6 2.IS< 0.221175) 2,lS{ 0.30, 90) PERTH -31.9 0.65( 0.13,2461 0.28( 'l.14,2831 BRISBANE -27.5 O.B4( 0.23d20) 2.77{ 0.191165) CACHOEIRA PAULISTA -22.7 u.nt(ntn, 0) tUIU(nni. 01

7.73( 0.251160) 8.46( 0.271173) 0.5S1 0.12,2791 l.m 0.17,2661

CAIRNS -16.9 -lol71 0.3001511 -o.m 0.22,20U -o.n( 0.23,210) -O.2S( 0.24,233) S1. HELENA -15.9 0.37( 0.22, B31 1.201 0.27. 901 -2.M( 0.74, 37) O.5S( 0.5a, 661 TUITUILA ISLAND HUANCAYO NATAL

-14.3 tlnU(in .. , 01 -O.14( 0.15,160) -12.1 -3.53( 0.11,2361 -4.161 0.15,2801

-5.4 nuulItnt, 01 IUUt(lnU, 01

0.071 0.1201751 0.3l( 0.13,2121 -5.02( 0.0903231 -5.0l( 0.13,3131 -1.36( 0.09,2491 -1.09( 0.10,341)

HAHE SEYCHELLES IS -4.7 -3.181 0.1201681 -1.BO( 0.l101B71 -1.87( 0.14,221) -1.91( 0.231192) SINGAPORE 1.3 -2.ll( 0.14,192) -1.55( 0.23, 621 -O.::9( 0.1(;,3C'9) 2.57( 0.14,323) KODAIKANAL BANGKOK HANILA POONA HEXICO CITY HAUNA LOA OBS HOUNT ABU KUNHING VARANASI NAHA/KAGAHIZU NEW DELHI CAIRO DUETTA TALLAHASSEE KAGOSHlHA WHITE SANDS CASABLANCA SRINAGAR TATENO NASHVILLE EL ARENOSILLO WALLOF'S ISLAND LISBON CAGLIAR I -ELHAS SHIANGHER BOULDER BRINDISI VIGNA DI VALLE

HONT-LOUIS SAPPORO TORONTO SESTOLA BISCARROSSE BUCHAREST BISMARCK AROSA CARIBOU BUDAPEST -LORINC HOHENPE I SSENBERG HAGNY-LES-HAHEAUX HRA[IEC KRALOVE UCCLE

10.2 -1.94( 0.22, 361 -0.65( 0.26, 29) 0.09( 0.21, 601 -lo03( 0.1301791 13.7 ittiU( .. tit, 01 -~.82( 0.13,2561 -1.99( 0.16.28BI -1.70! 0.15,2571 14.6 -0.73( 0.25,1441 1.40( 0.18,1841 4.42( 0.31d51) l.07! 0.44, 25) 18.5 2.24( 0.12,15S) O.22( 0.151144) -1.64( 0.111194) -0.89( 0.11,266) 19.3 -4.18( 0.17,/521 -4.39! 0.20,161\ -3.77( 0.191126) -4.52( O.21d50) 19.5 1.0l( 0.140163) 1.7l( 0.13,2141 2.831 0.16,2291 l.Ol( 0.1801701 24.6 0.90( 0.14,1571 1.27( 0.1301681 -L92( 0.19,219) -lo92( 0.13,142) 25.0 ttiut ( .. tit , 01 0.11( 0.1501821 -0.321 0.12,2SII -0.60( 0.16,234) 25.4 0.69(0.28, 53) -0.63! 0.12. 661 -0.4B( 0.15, 811 26.2 0.60( 0.18, 95) 0.35! 0.1601321 0.89( 0.160133) 28.6 0.7S( 0.120175) 1.12! 0.16,1581 1.16( 0.1501241 30.1 -0.99( 0.1601341 -2.29( 0.1501351 -1.55( 0.16017)) 30.2 O.l4( 0.27,252) -1.87{ 0.24,265) -0.93< 0.26,274) 30.4 -1.67( 0.280102) UUU(tUtl, 01 u .... (tnn, 01 31.6 3.SB( 0.31, 741 2.19( 0.30, 74) 1.56( 0.27, 841 32.4 -1.6l( 0.16,2171 -1.85( 0.17,2451 -1.14( 0.15,2101 33.6 utut(tttti, 0) 12.0BI 1.98, 531 7.20( 1.2501031 34.1 -1.77( 0.28, 96) -2.49( 0.23, 921 -1.82( 0.1601301 36.1 0.59( 0.2001301 0.75! 0.190132) 0.52( 0.1701571 35.3 -2.86( 0.26,1231 -3.m 0.2101851 -3.92( 0.180185) 37.1 iUitl(ttiU, 01 uuu(ntu, 01 -3.33! 0.20·1131

O.S7( 0.211 94) 1.29( 0.170124) 2.0S( 0.20d04)

-0.94( 0.1701511 -0.34( 0.13,297) -0.28( 0.14,m) O.Ob! 0.17,1151

-0.35 1 0.62, 42) 8.78( 0. 0 2, 95)

-lo47( 0.1901501 -0.8ll 0.16,/811 -1.11( 0.17,2281 -Z.9B( O.20d5e)

37.9 1.00{ 0.181195) -O.40( 0.11,247) O.ll( 0.16,252) O.04( 0.12,224,0 38.S 2.46( 0.99, 84) G.bS( 0.32,161) O,68( O.2Q,tS9) O.97( O.23!l69i 39.1 2.59( 0.19,242) 3.11( 0.26.2441 tttnt(tiUt, 01 -1.19( 0.14,2341 39.8 0.361 0.240133) 0.131 0.20,2481 0.3ll 0.15,2481 0.04( 0.14,2651 40.0 -1.02( 0.2201361 -0.75( 0.25,1791 -1.77I 0.130177) -O.65( 0.1501861 40.4 tUUt(utu, 01 ntttt(tttn, 01 tutn(tuti, 01 -5.8ll 1.14, 281 42.1 -0.64( 0.17,240 -0.241 0.17,2621 -1.0B( 0.3501431 -1.191 0.15,3211

42.S -2.30( 0.2101931 -0.S3( 0.56, 391 ItfUI(tnn, 0) nUllmnl. 0) 43.1 2.20( 0.21010B) 43.8 -0.8S( 0.30, 891 44.2 -O.92( 0.22,160) 44.4 o.m 0.12,2411 44.5 nnU(liitt, 'li 46.8 'l.57( 0.290124) 46.8 2.25i 0.18,221) 46.9 0.3)( 0.21,1451 47.4 Uliit(ttttt, 01 47.8 2.St( 0.14,209) 48.7 tltitt(Uttl, 01 50.2 1.2S( 0.30,1241 50.8 -2.35( 'l.30, 841

2.9ll 0.23,1151 3.S0( 'l.240143) -0.03( 0.2301021 -o.m 0.1601061 -1.631 0.4001081 uuu(tnu, 0) 2.ll( 0.12,298)

-2.94{ 0.29, 91) 0.04( 0.3201171 3.30{ 0.16,245) 0.09( 0.2501581 2.47( 0.301129) 2.6S( 0.18,2231

-0.7S( 0.35. 451 -O.6S! 0.16d61) -0.28( 0.45, 541

2.16( 0.13,3131 -3.2S( 0.2'11141)

O.51( Q,20J145i 3.32( 0.14,256)

-O.66( 0.24,156) O.S?( 0.20,152) 2.S1( 0.16,234) Z.72( 1.00, 45)

-0.S2( 0.1801611 -1.58( 'l.19, 891

- 336-

0.45( 0.2401641 O.OB( 0.15,1701

-i.S9( O.26r159) 1.9B( 0.13,300)

-3.29( 0.240121) a.63( 0.26d37) 3.191 ·~.13,2641

-O.6S1 0.22,173) O.97( 0.20113S) 2.32( 0.18,2391 2.67( O.3{h 59i

-Ido( O.14r1B2i -l.3S( 0.210129)

STII LflMF' 5T[1 LAHP- TOIi CORRECTION [1[SCREPANCl

-1.32 -3.37

0.29 -0.15

8.8e -0.15

O.OB 8.95 4.11 3.67

-6.60 Utiti

-0.81 4.84

-0.73 tiltU tU1t1 -2.57

-10.7? -2.32 -0.44 -1.32

1.25

2.'l5 1.62 3.5~

0.44 .. nit -1.91 -0.88 -4.55

0.62 ntltl

-1. 76 -3.08 -1.18 -0.66

0.96 0.0; 1.25

-1).15 -0.30 -3.30 -0.44

tUtu 0.44 0.15 0.08 :2.42

-3.30 -0,88 0.88

3.52 6.54

-1.98 3.30

-1.25

·J.3' -14.22 unit -1.20 5.12

-1.09 -c.l0 8.67

-4.35 2.54

-6.32 tllitl

-1.12 9.85 0.36

nu .. UUit -1.54 -9.09 -3.39 0.45 3.20

-0.76 -0.35

0.75 2.23

-1.64 nllit -1.57 -0.60 -5.51 0.,'7

tUtU -0.29 -2.27 -0.07 2.32 0.92

-0.90 2.44

-0.19 0.35 2.51 0.75

tuut -0.01 0.07 1.97 0.44

-0.01 -1.51 -2.31

1.90 2.55 4.2~

-4.65 4.46 0,)3

BRACKNELL 51.4 -1.20\ 0.41, 52) -O.b2( 0.4BI 6,) -1.09! 0.40, 41) :.Ol! 0.38. 66) 0.59 -1.4B BELSK 51.B -2.241 O.lin 9:?) -!J.52e 0.42, 631 -1.59! 0.23, IS) -(i.97{ 1).29, 91) -1.32 -0.35 POTSDAM 52.4 -0.01( 0.211113_1 1.27( O.30d09i 3.5B< 0.35, 77: ('.54( O.24dl~·) -(\ , 5tr' -1.13

GOOSE 53.3 -1.66{ 0,78, 22) -O.38( 0.54, ,3) -o.m 0.37. m -O."! 0.38, 33; 0.00 1).29

EDMONTON STONY PL 53.6 -1.17( 0.17. 71) -0.53! 0.23, 641 -C. 7~{ Co,23, cO) -O.IO! 0.24, 75) -0,08 0.0, CHURCHILL 5S.S 0.O4! 0.38, 391 -1.39! o .2Q, 66) -LID! 0.34, 67) -1.86! 0.31, 65) -1.62 0.24 OSLO 59.9 -l.81( 0.33, 20) -3.2S( 0.00, 2) tUtU(UUt, 0) .uUU{fUU. 01 0.96 IIIIIl LENINGRAD 60.0 "'1.31< 0.45, j7) IInn!UUi, 0) -2.25( 1.36, 141 tutu(ttnt, O! -').,9 nnn LERWICK 60.1 -1.31! 0.38, 4BI 0.93! 0.36, 71 ~ 1.03! 0.44, 361 1.34( 0.54, 51', -:.13 -3.'P REYKJAVIK 64. ( -O.O)! 0.26, B8) 1.'J9( 0.23, B(I l.m 0.28, 54 1 1.82( ('.34, :.2) -0.44 -2.26 BARROW 71.2 1.51( 0.34, 52) O.IS( 0.81, 9) 2.26i 0.35. 56) ;;ilumUi, 01 -1.62 uun RESOLUTE 74.7 1.2l( 0.411 461 1.37( 0.40, 4~) 1.8l( 0).77, 33) -O.3S( 0.35, 39) 0.74 ! .09 iuuunnUiUUUUiUUiUUUUUUUUlluuuunuUIUiHitUUUUittitUiitl1iiiiiiiUiiltItUlllllittUU"U,iltt,

DEVI~TION OF TOMS FROM AVERAGE DOBSON 1979 -6.51 t,.- (. 'S DEVIATION OF TOMS FROM AVERAGE DOBSON 19BO -6.27 1/- 1.91

DEVIATION OF TOMS FROM ~VER~GE I'OBSON ('Bl -S.42 1/- 2.0S DEVIATION OF TOMS Ff:OM AVERAGE I<OBSON (982 -~,.J4 ,/- (.n AVER~GE STANDARI< LAMP COf:RECTION -0.05 f/- 3.00 AVERAGE (STD LAMP-TOMS) DISCRE"ANCI -0.20 1/- 3.55

NO. OF STATIONS 57 t/O. OF S~ATION: 62 NO. OF STATIONS 60 tiD. OF STATIONS 62 NO. OF STATIONS 65 NO. OF STATIONS 61

shortcomings specific for this type of optical instrument and although improvements were noted after 1972 the M-83 instruments are producing data with an average bias in monthly means of up to 5% and with much gr~ater day to day variability than the Dobsons.

3.Travelling standard lamps In 1981 W~lO bought seven standard lamps for· circulation

among the Dobson stations in seven geographical areas covering the globe. The first cycle of control measurements was completed during 1982 and early 1983 (for details see Grass ~ Komhyr, 1984). A summary of these data is given in the second last column of Table I as average percentage correction required to total ozone observations at the station. However, this correction should not be applied to total ozone data automaticaly. It is applicable only if the instrument in question is properly aligned and has a correct wedge calibration. Therefore, a large ()3%) standard lamp correction should be considered as a warning flag that this instrument requires expert attention.

From the frequency distribution of the corrections it is encuraging to see that 45% of the stations would require less than +/-1% adgustment; and only 12% apparently have errors )4%.

4. Nimbus-7 TOMS satellite data. The information summarized here is based on comparisons of

daily total ozone measurements at each of the regularly operating ground stations with the values deduced from TOMS overpasses. The plottings of the deviations at each station for the first year of TOMS operation (Nov.1978-0ct.1979) were published in the World Ozone Data Center annual book-1982 (Fleig et al.,1982) and a description of the comparison procedures is given ther·e.

- 337-

In Table I and Table II the annual averages of the differences (TOMS-Dobson) and (TOMS-M-83) respectively are given as percentage with the Dobson global network average bias subtracted. Therefore, the effect of TOMS has been largely removed from the comparison numbers in the main body of the tables. These numbers represent a percentage deviation from the Dobson network average. The standard deviation of the mean bias and the number of compared pairs are given in parentheses. Only direct-sun data were used in preparing Table I. At the bottom, summaries of the deviations of TOMS from average Dobson are calculated ~~here the biases exceeding 26 deviation from the mean were excluded. The small year-to-year changes in the average bias arise partly because of changes in the TOMS data evaluation system (especially between 1980 and 19811 and partly because of small shifts in the Dobson network average. At present, it is not possible to separate the two effects.

The analyses of the information provided in the Tables should be done in pbrallel with consideration of the scattering diagram for the corresponding station. If the scattering is widely spread arround the zero line the annually averaged descrepancy in Table I could be misleading (see Casablanca). Here are provided only a few examples which are expected to provoke further individual station studies and the same time will flash a warning to all potential users who may be taking the numbers at face value. On Fig.l are shown the scattering diagrams of Aarhus (56 N) and Casablanca (34 N). The unusually large scattering

exceeding (+1-25~) is ~er~ disturbing.

M-83 TOTAL OZONE NETWORK PERFORMANCE FOR 1979 AND 1981

*************************************************************** STATION LATITUDE COMPARISON WITH TOMS SATELLITE

1979 1981 MEAN\SDEV,NUM) MEAN(SDEV,NUM)

*************************************************************** DUSHANABE 39 -1.27(0.18,260) -5.52(0.20,259) ALMA ATA 43 -3.97(0.28,295) -3.70(0.28,291) VLADIVOSTOK 43 6.75(0.38,292) 1.38(0.26,291) ODESSA 46 -2.38(0.26,237) 0.91(0.32,280) BOLSHAYA ELAN 47 -2.93(0.31,250) -0.63(0.23,260) KIEV 50 -4.69(0.33,224) -2.86(0.31,282) IRKUTSK 52 -4.72(0.26,268) -3.08(0.27,258) KUIBISHEV 53 -5.32(0.37,211) -6.90(0.43,230) OMSK 55 -1.65(0.28,267) -1.10(0.24,283) MOSCOW 56 -3.67(0.36,162) -4.18(0.24.232) SVERDLOVSK 57 -4.10(0.27,230) -1.21(0.28,275) RIGA 57 -3.42(0.33,221) -2.67(0.40.270) NAGAEVO 60 -3.21(0.55,159) -1.63(0.46.234) YAKUTSK 62 0.88(0.68,214) 2.34(0.29.242) MURl'1ANSK 69 -4.47(0.29.191> -0.52(0.41,199)

DEVIAT. TOMS FROM AVER.M-83 -3.21+/-1.73(14) -1.61+/-2.18(14)

TABLe II

- 338-

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In Table I, it can be seen that there are a number of stations for which the discrepancy is changing by more than 1.5% from year to year. Since the small year-to-year changes in TOMS have been essentially removed, these large year-to-year differences at a station indicate shortcomings in the state of the instrument and/or improper observing practices, when sufHcient number of data exist.

From the scattering diagrams, which will be widely available (WO,3DC publications 1982,1984), one can easily see that some of the discrepancies are due to the use of improper charts for calculation of the zenith-sky observations. Fot' example Tor-onto and Goose Bay are reporting nearly perfect direct-sun observations while their zenith sky data are more than ten percent off.

Complete sets of data from the M-83 filter instruments were available only for 1979 and 1981 at the time of calculating the discrepancies and therefore Table II incorporates only these results. The standard deviations of the data on the M-83 diagrams are more than twice greater than those of the Dobson stations. However,since the scattering is spread on both sides of the zero line, the overall average of the deviations is erroneously small. On the diagrams of some stations (e.g. Yakutsk-1981, Nagaevo-1979~1981) may be seen the pronounced dependance of the filter readings on the solar zenith angle with an annual amplitude of more than 20% (see also Bojkov, 1969).

5.Final remar-ks It is clear that systematic studies of the compatability of

satellite derived" data with well kept Dobsons may reveal sudden or gradual change due to degradation of the given satellite instrument. The benefit of satellite data for G0,30S is also obvious: facilitating the intercalibration of the ground based total ozone network would be enhanced; revealing the interstation discrepancies; and providing the transfer mechanism for improving the conversion of ground-taken blue and cloudy zenith-sky observations. In keeping proper maintenance of the Dobson stations results from the travelling standard lamp would be of good use.

REFERENCES BOjkov, Rumen D.,(1969): Differences in Dobson and filter

ozonometer measurments of total ozone, J.Appl.Met.,8,362-368. Fleig, A.J., P.K.Bhartia, K.F.Klenk, C.K.Wang and C.L.Mateer

(1982): Comparison of Nimbus-7 TOMS and ground station total ozone measurements,Ozone Data for the World, Index #17, pp XV-XVIII and 1-40, Environment Canada, A.E.S. in co-operation with WMO, WO DC, Toronto.

Grass, R.D., and W.D. Komhyr (1984): Travelling standard lamp calibration checks on Dobson ozone spectrophotometers, Proc. Ozone Sympos. Thessaloniki.

WMO (1980): Assessment of performance characteristics of various ozone observing systems, WMO Ozone Project Report #9, 67pp.

WMO (1981): The stratosphere 1981 WMO Ozone Project Report #11, 502pp.

- theory and measurements,

WMO (19aZ): Sources of errors in detection of ozone trends, WMO Ozone Project Report #12, 48pp.

W03DC (1984): Catalogue of Ozone Data for the World, #18, Environment Canada, A.E.S. in co-operation with WMO, Toronto. - 340-

Summary

ATMOSPHERIC OZONE IN MAP-GLOBUS

W.A. MATTHEWS* Service d'Aeronomie du CNRS

B.P. 3 91370 Verrieres le Buisson

FRANCE

One of the aims of the first MAP-Globus campaign. held in September -October 1983,was to make comparative measurements of stratospheric trace gases with a view to improving their measurement accuracy. To this end, nine ozone measuring instruments using six different measuring techniques were flown on the same gondola twice during the campaign. In addition, co-ordinated releases of some 130 ozone sondes were made from seven stations in S.W. Europe to establish the 3D ozone field during the Globus campaign. Tfiese sondes were also included in the payload of ten of the thirteen large balloon gondola experiments launched from Aire sur l'Adour, France during the campaign. The pre-flight preparation and calibration for each of these sondes followed a common procedure. These seven stations also made remote column content measurements of total ozone. Umkehr and lidar 03 profiles were also measured during the campaign. A large detailed data base of mid-latitude equinoctial atmos­pheric ozone has therefore been established.

1.1 Introduction

The broad aims of MAP-Globus, an acronym for Global Budget of Strato­pheric Trace Constituents are to improve the measurement ~curacy of stratospheric trace gases by comparative measurement and to enable broader scientific objectives in this field, which are beyond the capability of any single group, to be met. An attempt has been made to make the most effect­ive use of resources and provide a forum for an exchange of ideas and expertise. The MAP-Globus community includes groups who are working in the laboratory, groups who are performing modelling experiments as well as those making measurements in the field. An initial campaign particularly empha­sising comparative and complementary measurements was held in September -October 1983. Atmospheric ozone played an important part in this first campaign and the particular scientific objectives relating to atmospheric ozone are listed below.

* Permanent affiliation: PEL Atmospheric Station, DSIR Lauder, Central Otago NEW ZEALAND

Ozone Symposium - Greece 1984 - 341-

1.2 Objectives

Determine the accuracy and precision of a number of 03 measuring techniques.

Improve measurement accuracy and reliability through intercalibration and common methods of preparation.

• Determine 3D ozone field during campaign.

Make a time series study of the height and absolute value of maximum in ozone density.

Study small scale structure in 03 profiles and relate these to atmospheric dynamics.

Study diurnal variations in 03 at heights above 40 km.

Compare comprehensive ground based and in situ 03 measurements with satellite data.

• Refer other trace gas measurements made during Globus to the measured ozone field.

1.3 Status

It is too early to define in detail the results of this first campaign. The data will however provide the basis for discussion at several working group meetings held in conjunction with the Quadrennial Ozone Symposium. One can however summarise the data base that will be available for discussion.

Over 130 free flying ozone sondes were flown during the campaign and these, together with the detailed ground based lidar and microwave prOfiles, Dobson spectrometer Umkehr profiles and Dobson spectrometer, filter photo­meter and infra-red absorption total ozone values,provide a detailed data set of mid-latitude equinoctial atmospheric ozone.

Thirteen large balloon payloads were sucessfully launched in the MAP­Globus 1983 campaign and ten of these payloads included a common ozone sensor as part of their complement. One of the large balloon payloads consisted exclusively of ozone measuring devices. The ozone measuring techniques on this gondola included in-situ chemiluminescence, u.v. absorp­tion, decolouration tubes, potassium iodide sondes plus a remote u.v. absorption experiment. This gondola was flown twice during the campaign, once to 33 km and its second flight to a f.loat altitude of 41.5 km. The float altitude was maintained for l~ and 2 hours respectively to enable adequate time to assemble a statistically sound data base for comparative measurements and to assess instrumental stability. This long float time was also used to make a good measure of the atmospheric ozone overburden. After these periods at float, a slow valved descent followed. This slow descent to 15 km took 6 hours for the first flight and 4 hours for the second flight. This slow descent allowed good intercomparison measurements to be made despite the differing response times of the instruments used and also enabled a detailed analysis of small scale structures in the ozone profile to be measured.

-342-

In all some 23 groups were actively involved in making ozone measure­ments in a co-ordinated way during Globus 1983 and these data will provide the basis for a number of publications in the near future.

1.4 Acknowledgements

We wish to acknowledge the tremendous support and co-operation given to the Globus scientific team at Aire sur l'Adour by Monsieur Prigent and his staff at the Balloon Centre of CNES, Aire sur l'Adour, France and congratulate them on their 100% success rate with the large balloon pay­loads in this first phase of MAP-Globus. We also wish to acknowledge the personal support and interest of Monsieur Auger of CNES. The financial support given to this campaign by the B.M.F.T. of the Federal Republic of Germany is gratefully acknowledged. I also wish to acknowledge the support given to me at the Service d'Aeronomie by CNRS and C.I.E.S.

- 343-

Summary

ONE YEAR EUROPEAN TOTAL OZONE DAILY MAPS FROM NIMBUS 7 AND DOBSON DATA

J. I. CACHO M. GIL M.J. SAINZ DE AJA

Comisi6n Nacional de Investiqaci6n del Espacio. Grupos Cientificos. P.O. Box 8346, Madrid, Spain.

Twenty one stations of total ozone over Europe have been used for daily mapping for the time span Nov. 1, 79/0ct. 31,80 in order to study short term evolution over a data high density area (mostly Dobson spectrophoto meters). The total ozone evolution as well as the maps have been compa -red with those obtained from TO~S/NIMBUS 7 instrument. -Difficulties arosed in map drawing, significant discrepances between maps obtained by the two instruments for a same day, and a comment of ozone evolution are presented in the paper. Data for the work has been collected from World Ozone Data Center (ground-based stations) and National Space Science Data Center (satelli tel on magnetic tape. -Due to unexpected difficulties, at present, only maps for six month p~ riod running from Nov. 1, 79 to April 30, 80 has been drawn.

1.1 Comments on manual maps drawing

Difficulties on maps drawing when using ground-based instruments arosed due to number of reasons such as: a) irregular distribution of the sta­tions over the selected area. b) Weather conditions limit available data to 60% of total possible, with the highest density in spring. c) Measure ments in close observatories for a day, present, in several cases, sUbstan tial differences. d) Extremely high or low data compared with those of its surroundings, difficult and even makes impracticable maps drawing. e) In days scarce data, the field is highly dependent on individual station in such a way that one missing data may modify significantly map pattern.

On the other side, TOMS maps are easily drawable. Data are uniformly distributed with a 77 points network over the studied area, while missing data do not exceed the 4%. The absence of "strange" data (exceptionally high or low compared with those of it environment) enable the drawings.

1.2 Maps and single points comparison

Dobson measurements and TOMS data show important differences. Moreover, for a given day, such differences are quite variable from station to sta tion. This fact makes both maps to have dissimilar patterns. In Fig. 1 two

Ozone Symposium - Greece 1984 - 344-

days (Nov. 29, Feb. 5) representatives of map collection are chosen as an example. In a) low values over central Europe of 240 d.u. contrast with TOMS 80 d.u. higher in same area. In b) ozone high density areas are in differents positions.

Fig. 2 shows daily average evolution of measured ozone from both instru ments for time span Nov. 79/ April 80. A same trend in several days lapse -of time, and total ozone increasing toward the spring maximun are clearly discernible features, in spite of day to day fluctuatibns.

Fig. 3 shows daily averages of the differences between TOMS and DOBSON over the stations. Dobson data are, with the exception of some shorts inter vals, higher than TOMS. A detail led analysis of these differences reveals:­a) For~each station, Fig. 3 pattern is reproduced, that is, periods with positives or negatives values always appear at the same time for all sta tions, or a least for stations located in a common area. b) Constants, or constant trend differences implying wrong calibration or instrument shift do not appear. c) Satellite scanning mode may playa part in the differen ces encountered since data averaged in a 5°x5° grid are not, obviously, -measured at same time (1). d) The origin of the disagreement should be seeked mainly outside the instruments (though a good inter calibration between Dobsons may not exist having, probably,any influe~ce). e) An analy sis of synoptic situation during the studied period, has ~videnced that days with TOMS data higher than Dobson have good correlation with high pressure pattern over the continent surface.

Quite air could contribute to a polution increase in low levels resul ting and error in ground-based and satellite instruments of different maq nitude. As Komhyr & Evans (2) have pointed out, significant measured errors in Dobson occur when observation are made in polluted air containing trace gases that absorb UV radiation, mainly S02 with strong absorption lines in the range 260-320 nm. and N02. Higher values of TOMS total ozone associated to anticiclonic situation may be due to higher instrument sensitivity in shorts wavelength (312.5 and 317.5 nm) to variations in tropospheric S02.

1.3 Maps evolution

An analysis of daily maps evolution shows that day-to-day changes in TOMS single grid-points are larger than in Dobson stations. Nevertheless, daily variations from one station to another of differences are stronger in the later, causing maps to have sudden changing pattern, difficulting the study of the day-to-day evolution.

In Fig. 4 maps for three consecutive days Feb. 26, 27 and 28 are presen ted. TOMS maps at the top, Dobson maps at the bottom. As previously indica­ted, pattern of both instruments have no similarities. TOMS maps daily eva lution is easly observable enabling studies of changing ozone and compari-son with meteorological parameters and synoptic charts. -

Dobson maps, on the other side, are not useful but to get a rough idea of what the total ozone distribution over the continuent is, but hardly to follow the evolution. In fact it is even doubtful that the drawn corifigura tion is the right one since the number of stations, being large comparinq­with other planet areas, is indeed scarce for a realistic daily mapping.

Conclusions

From observation of six month daily maps comes out that lack of discon tinuites in TOMS grid-points allows the mapping for total ozone evolution-

- 345-

study in small areas, and the comparison with meteorological parameteres and charts, while Dobson maps pattern are doubtful due tb the irregular station distribution missing data and "strange" data, that even makes the drawing impracticable.

From ground-based and satellite system comparison at individual loca tions is evidenced that TOMS measurements are lower than Dobson except for anticiclonic situation over the area, presumfbly associated to a different response of both instruments to external agents as S02 or N02 pollution. A continuous observations of pollutant diffusion in a variability of meteroro logical situations would be useful in order to confirm this assumption. -

References

1.- W.M.O. (1981). The Stratospheric 1981-Theory and Measurements. Report n° 11. W.M.O. Global Ozone Research and Monitoring Proyect.

2.- The NIMBUS-7 Users's guide. NASA Goddard Space Flight Center.

' . .. ,

Fig. 1

- 346-

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- 347-

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- 348-

UNE APPELLATION COMMUNE DU NOM DES GRANDEURS

UTILISEES POUR DESIGNER LES QUANTITES D'OZONE DANS L'AIR

L'OZONITE

P. AIMEDIEU Service d'Aeronomie du CNRS

BP 3 - 91370 Verrieres Ie Buisson - France

RESUME

L' experience montre que pour rediger les ouvrages ou articles traitant de questions relatives a l'ozone de l'atmosphere, on utilise un grand nombre d'appellations differentes pour exprimer les quantites d'ozone dans l'air.

Apres avoir passe en revue les noms des grandeurs en usage, nous montrons l'inter@t d' une simplification de la terminologie tout en conservant l'appellation des unites habituelles.

Nous proposons d'unifier Ie nom des grandeurs et d'utiliser dorenavant Ie terme d'ozonite en fran~ais qui trouve aisement sa correspondance en anglais en "ozoni ty" ; I' uni te etant precisee entre parentheses.

Exemple : ozonite (ppmv).

DE NOMBREUSES APPELLATIONS

Quand on consulte un ouvrage ou Ie rapport d'un congres ou d'un symposium s'occupant de physico-chimie de la stratosphere, on est souvent assez surpris pour Ie nombre important d'appellation que les auteurs utilisent pour designer les quanti tes d' ozone qu' ils mesurent dans I' air ou celles auxquelles Us se referent pour faire leur demonstration. Selon qu'ils sont experimentateurs ou theoriciens, physiciens ou chimistes, ils choississent des unites commodes dans leurs displines, issues Ie plus souvent de considerations dont la logique n' est pas toujours evidente. Ainsi certains s' appuiront-ils sur des sections efficaces exprimees dans Ie systeme CGS alors que Ie systeme MKSA doit @tre de rigueur ; d'autres affectionneront-ils les pressions partielles presentees avec un profil vertical de temperature ; d' autres encore compteront-ils les molecules (avec quelle incertitude ?) etc ••• Dans Ie tableau n° I nous avons passe en revue les principales unites rencontrees en fran~ais et en anglais. Nous avons tente un groupement par genre. Dans ce tableau ne figurent pas certaines unites photometriques satellitaires ou celIe relatives a des etats qui n'interessent pas les atmospheristes (miscibilite par exemple). On trouve de la sorte une quinzaine d'appellations dont certaines necessitent trois mots. Au sens des normes certaines sont impropres comme ozone qui exprime l'espece chimique et non sa quantite et a fortiori,

Ozone Symposium - Greece 1984 - 349-

fortiori, .. 03 .. ou encore .. n03 .. ou bien encore mass mixing ratio qui en toute rigueur doit s'ecrire ozone mass mixing ratio" 0 Par ailleurs, il faut noter que 1 'on utilise des unites non conventionnelles qui ne font partie d' aucun des systemes d' uni te classiques. Le":>4 pr~2sions partielles d'ozone s'ecrivent en micromillibar qui vaut 10 Nom ,Ie rapport de melange massique s'exprime en microgramme par gramme (~/g) alors que Ie rapport de melange volumique est donne en partie par million volumique (ppmv)o

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TABLEAU I

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rapport de melange massique

concentration d'ozone

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densite d'ozone

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pression partielle d'ozone

Principales appellations des unites de

mesure de l'ozone dans l'air

UN CLASSEMENT RATIONNEL DES UNITES

Ces unites et leurs appellations sont difficiles a classer par genre. Nous avons adopte, pour degager leur point commun, un classement selon la complexi te de l' equation au dimension les exprimant 0 Nous distinguons ainsi quatre classes :.les nombres purs, les puissances de

- 350-

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longueurs (L), les produits de puissance de longueur (M,L) , enfin les unites ou interviennent en (M, L, T). Le tableau II presente ce classement avec les unites primaires, la formule de 1 'unite, les noms les l'unite usuelle.

UNE NOUVELLE APPELLATION: L'OZONITE (ozonitiO

masse et de plus Ie temps exposants des plus communs,

Cette variete residuelle, pour exprimer en fait la m@me chose (m@me apres cette analyse dimensionnelle), nous conduit naturellement a forger une neologysme synthetique qui exprime a la fois la quantite et l'objet auxquels elle est relative. Par analogie avec d' autres designations utilisees en geologie, en oceanographie ou en meteorologie, nous proposons d' utiliser Ie terme d' ozonite pour remplir cet office. Dans les langes ou les termes scientifiques sont fondes sur les racines grecques, il trouve naturellement son equivalent (Ex anglais, "ozoni ty" ; espagnol, "ozoni tad" etc ... ). Pour lever l' ambiguite sur l'unite utilisee, nous proposons de faire suivre ce mot par deux parentheses isol~nt la notation ,abregee de l'unit~. On _~crira par exemple : ozonite (ppmv), ozonite (Dobson), ozonite (cm ) etc ••• Cette ecriture sera particulierement utile pour la presentation des figures.

Enfin pour des raisons de simplifications supplementaires et compte tenu de l'analyse dimensionnelle du tableau II, nous suggerons de n' utiliser que _fes un_ifes homogenes a u~ nombre ou une puissance d' une longueur ([L] ,[L.1 ) et sauf cas tres exceptionnel de ne pas faire intervenir la masse [M]. Rappelons que seul Ie systeme MKS est admis pour presenter les atmospheres standard. De la sorte, l' ozoni te pourra s' exprimer en partie par million, qui eS;:2 admis et d' un usage commode, en nombre de m~~ecule par metre carre (m ), en nombre de molecule par metre cube (m ) •

REMERCIEMENTS

Je remercie mon collegue, Pierre RIGAUD (LPCE/CNRS, Orleans, France) des discussions que j' ai eu avec lui sur cette question de lexicologie et pour ses encouragements a proposer cette appellation.

- 352-

DECREASES IN THE OZONE AND THE S02 COLUMNS FOLLOWING THE APPEARENCE OF THE EL CHICHON AEROSOL CLOUD AT MIDLATITUDE

A.F. BAIS, C.S. ZEREFOS, I.C. ZIOMAS, N. ZOUMAKIS (1), H.T. MANTIS (2), D.J. HOFMANN (3), and G. FIOCCO (4)

1) Physics Dept., Lab. of Atmospheric Physics, Univ. of Thessaloniki,Greece 2) School of Physics and Astronomy, University of Minnesota, U.S.A.

3) Department of Physics and Astronomy, Univ. of Wyoming, U.S.A. 4) Istituto di Fisica-Universita di Roma, Italy

Summary

Measurements of S02 column at Thessaloniki (41°N) show a mlnlmum in the late spring of 1983, approximately three months after the occurence of the maximum of the El Chichon aerosol in the stratosphere at these la­titudes. It is suggested that the injection of the aerosol into the upper troposphere provides a scavenging mechanism for S02 and other trace gases.

Continuous measurements of ozone and S02 column with the Brewer spec­trophotometer have been made at the Atmospheric Physics laboratory of the University of Thessaloniki since March 1982. Reports of the ozone decrease assosiated with the El Chichon cloud at low latitudes (Heath 1984) have stimulated this comparison of the Thessaloniki record (41°N) with the stra­tospheric aerosol observations at midlatitude. Fig. 1 shows the development of the aerosol cloud at Garmisch (47°N) and at Rome (41°N) as measured by lidar backscattering and the aerosol mass at Laramie WY (41°N) measured by balloon born optical particle counter (dustsonde). The general agreement in the aerosol records shows the global nature of the cloud which reaches a peak concentration at these latitudes early in 1983 eight to nine months after the eruption. The peak is relatively sharp with halfwidth of from 60-110 days. The rapid increase and then decrease from peak concentration is difficult to explain solely on the basis of chemical reaction rates and mole­cular and particle kinetics (Hofmann and Rosen 1984).

The Thessaloniki ozone record for the same period is shown in Fig. 2. The marked seasonal variation of ozone and the large day to day synoptic scale fluctuations in ozone led to the original conclusion that no ozone­aerosol relation could be detected.

The Thessaloniki S02 column observations for the same period are also shown in Fig. 2. The S02 column has no annual trend but there is an interval of generaly low column amounts several months after the aerosol peak. The histogram in this figure represents an estimate of the mean monthly mixing layer contribution to the S02 column calculated from the product of mean monthly surface S02 concentration and mean monthly mixing layer depth as determined from the radiosonde observations. It appears that the fluctuations seen in the S02 column must reflect changes in concentration in the upper troposphere and stratosphere.

Ozone Symposium - Greece 1984 - 353-

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The relation between S02 column amounts and aerosol concentration is made more explicit by a calculation of the lag correlation of S02 departures with the departures of aerosol scattering measured at Garmisch. Lag corre­lations were computed from daily values with 40 to 50 individual observations which were then averaged at ten day intervals with the result shown in Fig. 3. The S02 column minimum has a halfwidth much like that of the aerosol peak and the extrapolated zero crossing of lag correlation of 110 days is a measure of the phase displacement.

The discovery of a S02 minimum 3 months after the aerosol peak led to a reexamination of the ozone record and as may be seen in Fig. 2 there is a suggestion that ozone concentrations in the spring of 1983 are lower than in 1982 and 1984. We have therefore examined monthly departures of ozone at some of the European stations with long records. Monthly departures of ozone at Arosa (46°N), Vigna di Valle (42°N) and Cagliari (39°N) are shown in Fig. 4 along with monthly departures of the S02 column at Thessaloniki (41°N). All three stations show a negative ozone departure in the late spring months of 1983 corresponding to the S02 minimum in May. Since large ozone fluctuations in early spring are common and frequently can be indentified with major circulation anomalies it is not possible without further investi­gation to determine whether the observed relation is fortuitous or even if the ozone departure has the global dimensions of the dust cloud.

Column S02 measurements are more rare than ozone measurements and to suggest a causal relation between S02 and aerosol is most speculative. However, the rapid decrease in aerosol load from April to June 1983 repre­sents an injection of as much as 5x106 tons of aerosol into the troposphere. This large aerosol surface area seems capable of scavenging S02 and other trace gases in the up~er troposphere.

REFERENCES

1. JAGER, H. et al (1984). Stratospheric aerosol layers during 1982 and 1983 as observed by lidar at Garmisch, Presented at the 12th Inter­national Laser Radar Conference, Aix en Provence, Aug. 1984.

2. HOFMANN, D.J. and Rosen, J.M. (1984). On the temporal val"iation of stratospheric aerosol size and mass during the first 18 months following the 1982 eruption of El Chichon, J. Geophys. Res. 89, 4883-4890.

3. HEATH, D.F. and SCHLESINGER, B.M. (1985). Evidence for a decrease in tropical stratospheric ozone following the eruption of El Chichon. (Proceedings of the Quadrennial Ozone Symposium - this volume).

- 356-

C(RRElATIVE STUDIES OF TOTAL OZONE CONTENT WITH 'lROPCSPHESIC mOPEBTIF§- RESUllrS FROM

INDIAN STATIOR;i

D .K. CHAmABJ>.RTY, P.CHAJ<RABARTY and G .BEla Physical Research Laboratory Ahmedabad - 380 009, India

Surnm!!:I

Long term variation of total ozone content over the Indian SUbcontinent has been studied using the data obtained by Dobson spectrophotometer operating for the last 15 to 25 ye.-s at various places in India. varying increasing trendS in total ozone content are observed at different stations. These can not be due to direct solar effect. Tropospheric properties like tropopause height. tropopause temperature, potential temperature at the tropopause and lower stratos­pheric temperature which are indicatiVe of circulation pre­vailing in the lower atmosphere have been correlated with total ozone content in an attempt to identify the cause of the increasing trend of total ozone content. A goOd corre­lation has been found to exist between the total ozone con­tent and the tropopause potent ial temPerature.

1. ~duction

To study the long term trend of ozone. a large nUmber of observations taken over a long period of time are required. The Dobson spectrophotometer is the oldest instrument which has provided continuous observation of ozone at many places of the globe for a considerably long periOd of time. In Indi., there are six stations spreading OVer a latitudinal span of about loON to about 340 N which have been operating for a Period of 15 to 25 years. These are Kodaikanal. Dumdum, Mt. AbU/Ahmedabad, varanasi. New Delhi and Srinagar. The monthly averaged values of total ozone content obtained at these places are available from India Meteorological Department. Pune.

Many studies h.ve been made by various authors to assess the long term variation of ozone. M;)st common .along them is the variation with solar activity of total ozone as well u ozone at different altitude levels [1,2, 3J. The strongest indi­cation for a direct correlation is found in the upper stratos­phere where life time of ozone is short and its distribution is probably controlled mainly by photochemistry. However. indi­cations of other correlations with total ozone exist. which, i£ real, can only be understood ill terms of the circulation mthe

Ozone Symposium - Greece 1984 - 357-

stratosphere and troposphere( 1 ]. Tropopause plays a major role in the distribution of ozone

at a particular place. The Indian atmosphere is mainly domi­nated by the tropical tropopause. It has been found that t.he tropopause is lower in the monsoon months than in winter in the Indian peninSula (4# 5 J. It has also been s hewn that t he tro­popause is higher in winter than in summer at stations south of 200N and reverse is the case at higher latitudes t 6]. Gage and Reid (7] and Reid and Gage [8J have examined the annual varia­tion of tropical tropopaUSe and also the solar variability of the tropical tropopause and have found positive correlation between average annual tropospheric heights and the sunspot number. These authors have proposed a mechanism relating solar activity to tropical tropopaUSe height. The mechanism explains the variation in tropopause height due to the variation in sur­face insolation and hence in the intensity of tropical cumulus convection and the ascending branch of the Hadley cell.

This paper presents the total ozone variations within the Indian subcontinent based upon about 15 to 25 years of measu­rements from the existing network of five stations operating the DObson Spectrophotometer. Radiosonde data of tropopause height, tropopause temperature, and temperature at 100mb level are available since 196 5. Correlative studies between the total ozone content with tropopause height. tropopause tempe­rature. potential temperature at the tropopause and lower stra­tospher ic temperatures have been conducted in an attempt to obtain an indicat.ion of the effect of cirCUlation on total ozone content.

2. Results In Fig.l are shown the yearly averaged values of total

ozone content for all the five Indian stations. The dashed curves are drawn from visual inspection. It is to be noticed from this figure that the trends of variations of total ozone content with years at these stations are not identical. At three western stations, for example. Srinagar. New oelhi and Mount Abu, the trend appears to be similar, the similarity being lese apparent as we go southward. A comparison of the results of two stations situated at north and south of India like New Delhi and KOdaikanal (almost at the same longitUde) shows that the total ozone content variation at the equator and at the tropics are apparently in OPPOS ite phase.

The var iation Of total ozone as seen above could be dUe to solar effects. To examine the extent of solar control on total ozone. in Fig.l is also plotted the solar fluy. at lO.7cm wavelength (FlO. 7) for all the years. A comparison Of this profile with the ozone profiles of all the stations shows no systematic correlation of total ozone with solar activity. Lyman-alpha flux variations are sometimes used to represent t.he variations of UV activity of the sun. In Fig.l is also plott.ed the yearly average of the Lyman-alpha flUxes available to date [9]. The yearly averages of the rocket data are shown by dots and the satellite data from CSO-5 spacecraft are shown by con­tinuous lines. An exaaination of Fig.l shows that while Lyman­alpha correlates very well with FlO.7' it does not show any

- 358-

definite correlation or anticorrelation with total ozone con­tent. Hence from the above no clear evidence about the direct control of the sun on total ozone content is found.

The variation of ozone of the type mentioned above could be due to local effects by dynamical process. As pointed out by Kulkarni [lOJ , the dynamical process which is responsible for the prodUction and maintenance of the tropopause and also of the temperature variation in the lower stratosphere" .1e. also mainly responsible for most of the ozone changes which occur in the lower stratosphere. Hence a close link may exist between total ozone and lower stratospheric parameters. To exa­mine such a link, in Fig.2 we have plotted monthly averaged values of total ozone, tropopause height, tropopause tempera­ture and 100 lib temper ature from 196 5 to 1980. Except ozone, all these parameters have been obtained from the India Meteoro­logical Department, Pune. Calculations show that correlations between ozone and other parameters in this figure are not goOd.

In Fig.3 we have shown a mass plot of monthly averaged values of total ozone against the corresponding values of tro­popause potential temperature. Although scatter in the data is noticed, yet a.."l increasing trend of ozone content with an increase of potential temperature is discernable. When all the data points are taken into consideration and correlation coe­fficient is calculated, its value comes a little over 0.5. HOWever, when a smoothing is done by taking the block average (which is shown by cross marks), and then correlation coeffi­cient is calculated,- its value comes to 0.9.

While doing the above studies an interesting result bas emerged on the variation of total ozone with the time of the day. Since NOvember 1983 many observations are taken in a day from 0900 brs to 1600 hra local time. In Fig.4 a plot of total ozone content against the time of the day has been sho~ for the month of January 1984. It is to be seen from this figure that total ozone content first increases as the zenith angle decreases, attains a maximum value around noon and then dec­reaseS. Such trend has been seen in all the months upto May 1984.

ACKNOWLEDGEME NT We thank the Director General, India Meteorological Depa­

rtment, New Delhi for making available to us the required data. OUr respectful thanks are also due to Professors K.R .Ramanathan, P.R. Pisharoty and P.V. KUlkarni.

REFiRER::ES

1. DUTsCH, H.U. (1979~. J. Atmos. Terr. Phys., ..!!, 771. 2. LONDON, J. and REBER. C.A. (1979). Geophys. Res. Letts.,

0, 8&9. 3. CHAJ<RABARTY, D. K. and CHAI<RABARTY, P. (1982). Geophys. Res.

Letts. 9, 76. 4. I<RlSHNARAO, .P.R. and GANESHA.N, V. (1953). Indian J. Meteoro!.

Geophys. j, 193. 5. ANI'oNl'HAI<R lS HNA.N, R. and RAWARAJAN, S. (196 3). Indian J.

Meteorol. Geophys. M. 173.

- 359-

6. SASTRY, P.S.N. and NARASIMHAN. A.L. (1906). Indian J. Meteorol. Geophys. 17. 9&7.

7. GAGE. K.S. and REID-;-G.e. (1981). Geophys. Res. Letts. 8, 187.

8. REID .. G.e and GAGE, K.S. (1981). J. Atmos. Sci. 38.1928. 9. BCSSY.. L. and NICOLEI'. M. (1981). Planet. space.Sci • .£2.

907. 10. Ia1LI<'ARNI, R.N. (1980'. Pure and App. Geophys. lli .. 387.

- 360-

Fig.2

AHMEDABAD I M ABU

variation of 10.7 cm solar flux (bottom), Lyman-alpha flux (top) and total ozone content at different sta­tions over the years (middle).

::i o

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Variation of total ozone content, tropopause height, tropopause temperature and 100 iii;) teMperature over the years for Ahmedabad. Smoothed curves represent 12 point running averages.

- 361-

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Variation of total ozone content; wit;h time Of the day at Ahmedabad for January 1984.

- 362-

Summary

A GLOBAL CLIMATOLOGY OF TOTAL OZONE FROM THE NIMBUS-7 TOTAL OZONE MAPPING SPECTROMETER

K. P. BOWMAN Laboratory for Atmospheres, Code 613,

Goddard Space Flight Center, Greenbelt, MD 20771, USA

A global climatology of total column ozone was computed from four years of daily observations by the Total Ozone Mapping Spectrometer (TOMS) aboard the NIMBUS-7 satellite. The precision of the TOMS retrievals with respect to well-maintained Dobson instruments is ~2% (1). The TOMS retrievals average 6% lower than the Dobson measurements. The bias is largely explained by differences in the ozone absorption coefficients used with the different instruments (1). Global maps of the time-mean total ozone and the amp 1 itude " phase, and fract i on of the vari ance exp 1 ai ned by the annual and semiannual harmonics were prepared. Similar analyses of the zonal-mean total ozone were carried out.

Methods and results

The high-resolution TOMS data were area-averaged onto a regular 5° by 5° latitude-longitude grid. The global coverage is more than 90% complete during the last three observing years (October 1979 to September 1982) and approximately 70% complete during the first year (October 1978 to September 1979). No observations are available in polar regions during the polar night. .

The time variation of the total ozone was assumed to have the form 2

n(t n) = nO + L nl COS(wlt - <1>1) + En • (1) 1 =1

The time mean nO and the amplitude and phase of the annual and semiannual harmonics were computed by minimizing the squared residual error L (En)2 •

n A selection of the available results is shown in Figures 1 through 6.

This climatology should be useful both for validating numerical models and for inspiring theoretical analyses.

A. Krueger provi ded the TOMS data, whi ch were .processed by the NIMBUS Ozone Processing Team, in a very convenient gridded form.

REFERENCES

1. BHARTIA, P. K., KLENK, K. F., WONG, C. K., and GORDON.D. (1984). Intercomparison of the NIMBUS-7 SBUV/TOMS Total Ozone Data Set With Dobson and M83 Results •. 02..:.. Geophys. Res., 89:5239-5247.

Ozone Symposium - Greece 1984 - 363-

60 60

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o 0.25 0.50 0.75 1.00

TIME (YEARS)

Figure 2. Climatological time-latitude section of the zonal-mean total ozone (Dobson units) for the four year observing period. The field has

been smoothed by computing In-day means.

- 364-

60 60

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90N 90N

60 60

30 30

0 0

30 30

60 60

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1 BOW 150 120 90 60 30 0 30 60 90 120 150 1BOE

Figure 3h. Fraction of the total variance explained hy the annual harmonic (%).

- 365-

60

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60 60

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Figure 4b. Fraction of-the total variance explained by the semiannual harmonic (%).

- 366-

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, V S[!oIIiANNUAl

g ., \ , , , 20 ,/,,/-

.... __ .... ------------- - - - - ..... -----

PHASE JAN1 -,--.-----------------~

OCT 1 ANNUAL

JUL 1

APR 1

JAN1+--~_r--~--~._--_r_--_r--_+

FAACT'ON OF" THE VARIANCE EXPLAINEO

'00

..

.. .. z ... <> 0: .. ... ..

20

lOS .. , . ,. .0 IO.

LATTTUDE

Figure 6. Amplitude and phase of the annual and semiannual harmonics of the zonal means and fraction of the total variance explained by the annual harmonic and the sum of the annual and semiannual harmonics.

- 367-

C HAP T E R V

RECENT DEVELOPMENTS IN OBSERVATIONAL TECHNIQUES

- Umkehr observations with automated Dobson spectrophotometers

- Traveling standard lamp calibration checks on Dobson ozone spectrophotometers during 1981-1983

- Recalibration of Dobson Field Spectra photometers with a travelling Brewer spectrophotometer standard

- Review of the Dobson ~pectrophotometer and its accuracy

- A study of scattered light from zenith at low sun in the near UV region where the ozone absorption changes rapidly

- The automated Brewer spectrophotometer

- Experiences with a Brewer spectrophotometer and intercomparison measurements with a Dobson spectrophotometer

- Ozone profiles derived from umkehr observations obtained with the Brewer ozone spectrophotometer

- Nimbus 7 SBUV/TOMS calibration for the ozone measurement

- Ground-based microwave observations of mesospheric ozone at the Bordeaux observatory

Ozone and water vapor in the middle atmosphere measured with an airborne microwave radiometer

- Vertical profiles and column density measurements of ozone from ground-based MM-wave spectroscopy at Mauna Kea, Hawaii a demonstration of capabilities

- Validation of a fast line-by-line transmittance/radiance algorithm against TIROS-N series channel 9 (ozone)

- Information contained in satellite meteor spectra on the vertical ozone distribution

- High resolution infrared spectroscopic studies of atmospheric ozone and related trace constituents

- Measurements of the ozone profile up to 50 km altitude by differential absorption laser radar

- lntercomparison of ozone profiles obtained by Brewer/Mast sondes and differential absorption laser radar

Results from the balloon ozone intercomparison campaign (BOlC)

- Balloon in-situ measurements of ozone with the NASA-JSC UV photometers

- Ozone intercomparisons from the balloon intercomparison campaign

Ozone measurement from a balloon payload using a new fast-response UV-absorption photometer

- An in-situ multipass UV-absorption ozone sensor designed for stratospheric applications

- Measurement of the vertical profile of ozone from the ascent of a balloon borne ultraviolet spectrophotometer

- Spectrum measurement tEchniques for rocket, balloon and satellite experiments

- Precise ozone measurements using a mass spectrometer beam system

- Performance characteristics of high-altitude ECC ozonesondes

- Error performance of electrochemical ozone sondes OSR

- Mesure de la repartition verticale de l'ozone atmospherique par spectrophotometre d'absorption dans le visible

- Un catalogue de precautions instrumentales a prendre pour faire l'etude in situ de la variation crepusculaire ou diurne d'une espece stratospherique, presentation d'un cas particulier, 1 'ozone

- Measurements of the stratospheric ozone by indigo decoloration

- Satellite measurement of mesospheric ozone form the 1.27 m Airglow emission

- A rocket gas-gas chemiluminescent technique for measurement of atomic oxygen and ozone concentrations in the 15-95 km region

- Constructing emperical zenith ozone charts and tables using the multiple linear regression technique

- Total-ozone measuring instruments used at the USSR station network

Summary

UMKEHR OBSERVATIONS WITH AUTOMATED DOBSON SPECTROPHOTOMETERS

W. D. KOMHYR and R. D. GRASS, NOAA, Air Resources Laboratory, Boulder, Colorado 80303

R. D. EVANS and R. K. LEONARD, Cooperative Institute for Research in Environmental Sciences,

University of Colorado, Boulder, Colorado 80303

and

G. M. SEMENIUK U.S. Environmental Protection Agency, Washington, DC 20460

A seven-station network of Umkehr observatories is being established for the purpose of long-term detection of possible ozone depletion in the stratosphere at 40 km due to anthropogenic pollutants. Stations already in operation are Boulder, Colorado; Haute Provence, France; Mauna Loa, Hawaii; Poker Flat, Alaska; and Perth, Australia. Observa­tions at Huancayo, Peru, and Pretoria, South Africa, are expected to be implemented by early 1985. Umkehr observations at the sites are made with automated Dobson spectrophotometers. Total ozone observa­tions are made semiautomatically. Automation of the Dobson instru­ments is briefly described. Results of comparison Umkehr observations made in Boulder are presented indicating that well-calibrated automated Dobson instruments yield stratospheric Umkehr ozone amounts that agree on the average to within ±5% of mean ozone amounts measured simultaneously with World Standard Dobson Instrument No. 83.

1. Introduction

Considerable concern has been expressed in recent years about possible partial destruction of atmospheric ozone by anthropogenic pollutants. The region near 40 km altitude has been shown to be particularly vulnerable to ozone depletion by chlorofluorocarbons (1). A potentially favorable method of monitoring long-term changes in ozone near 40 km is by means of Dobson ozone spectrophotometer Umkehr observations (2).

Manual Umkehr observations are difficult and tedious to make. With automation of Dobsorl spectrophotometer No. 61 in 1981 at the NOAA Air Resources Laboratory in Boulder, Colorado, new impetus was given to the possibility of using Umkehr observations for monitoring long-term changes in ozone. The automated observations are not subject to operator bias; an increased frequency of observations is likely; and a potential exists for obtaining high-quality data over extended time periods if all instruments in a network are subjected to uniform calibration procedures.

Funding was obtained in 1982 from the U.S. Environmental Protection Agency, the Chemical Manufacturers Association, the World Meteorological Organization (Voluntary Cooperation Program), and The National Oceanic and Atmospheric Administration, for automating six additional Dobson

Ozone Symposium - Greece 1984 - 371-

instruments and establishing them at a global station network for long-term stratospheric ozone observations, and for providing comparison data for satellite ozone measurements. This paper briefly describes the automated Dobson station network, and the methods of instrument automation and operation. Results are presented of intercalibrations in Boulder of the automated instruments with manually operated World Standard Dobson Spectr.ophotometer No. 83.

2. Automated Dobson Instrument Station Network

The seven automated Dobson instrument Umkehr observatories are Boulder, Colorado (40 0 N, 105°W); Haute Provence Observatory, France (44°N, 6°E); Huancayo Observatory, Peru (12°S, 76°W); Mauna Loa Observatory, Hawaii (20 0 N, 156°E); Perth, Australia (32°S, 116°E); Poker Flat, Alaska (65°N, 148°W); and Pretoria, South Africa (26°S, 28°E). The sites were selected for wide latitudinal coverage, favorable observing conditions, logistics ease, and station proximity to an existing or future lidar aerosol observing facility. (Stratospheric aerosols have been shown to affect Umkehr observations adversely; hence the need to monitor the aerosols.) Currently, five of the seven stations are operational. Establishment of the Huancayo and Pretoria stations is expected to be com­pleted by early in 1985.

3. Dobson Instrument Automation and Operation

In automating the Dobson instruments the principle and method of mea­surement are left unchanged, except that a computer rather than a human observer controls instrument functions. Modification of the Dobson in­strument entails the following alterations: To attain long-term optical wedge stability, the glue normally used to bind the wedge sections together is removed. Metal tracks of the optical wedge are replaced with tracks made of Rulon plastic bearing material to prevent possible binding of the wedges during operation. A stepper motor is added to the wedge mechanism for control. For smooth operation, Rulon bearings are also built into the instrument Q (wavelength setting) lever mechanisms, to which stepper motors are also added. Temperature is monitored with transducers built into the instrument. The normal~y used photomultiplier high-voltage power supply is replaced with a progammable high-voltage supply. Finally, a signal-pro­cessing card is added to the output of the Dobson instrument for inter­facing with the computer instrumentation.

A block diagram of the automated instrument system is shown in Figure 1. A Hewlett-Packard 9915A computer controls the Dobson instrument func­tions via an HP2240A Measurement and Control Processor and an electronics drawer. Each day at midnight, the computer calculates the times of Umkehr observations for that day and readies itself for the observations. At the appropriate time in the morning, the instrument shelter hatch opens, pro­vided that precipitation is not occurring, and Umkehr observations commence. As observations progress, the instrument slowly rotates on its pedestal mount so that the axis of the instrument points at all times in the direction of the sun to minimize variations in zenith ·skylight polarization effects. Observational data are recorded on cassette tape, plotted on a video monitor, and output by a printer. A calendar-clock times all operations. Commands and data are input into the computer with an external keyboard or a keyboard built into the 9915A computer.

At prescribed times during the day, the Umkehr observations may be interrupted for total ozone observations. Total ozone measurements are

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SHELTER HATCH AND OUTDOOR PRECIPITATION

DETECTOR

INDOOR BACKUP PRECIPITATION

DETECTOR

I AC POWER AND UNINTERRUPTABLE POWER SUPPLY I

Fig. 1. Schematic diagram of the automated Dobson instrument system.

made semiautomatically. The observer inputs data into the computer, specifying what type of observation to make and, for observations on direct sunlight, places a sun director with ground quartz plate over the in­strument's light inlet window. After aligning the instrument and sun director correctly with respect to the sun, the observer presses a button switch. The observation is then made automatically. Observational data and computed total 0zone values (for direct sun observations) are recorded on the cassette tape and output by the printer. During total ozone or Umkehr observations the instrument continually monitors its own temperature and makes appropriate adjustments to its wavelength selector lever posi­tions so that observations are always made on correct wavelengths.

Up to 17 days of observations can be recorded on one cassette tape. The tapes are mailed to NOAA/Geophysical Monitoring for Climatic Change in Boulder for processing and data selection. Selected observational Umkehr data with applicable total ozone values are mailed to the World Ozone Data Center in Canada for reduction to Umkehr ozone profiles by the standard (3) and short (4) Umkehr data processing techniques.

4. Instrument Calibrations and Comparisons

All of the automated Dobson instruments were calibrated on an absolute scale relative to World Standard Dobson Instrument No. 83. In the future, the calibrations of these instruments will be checked at 3-year intervals. During routine operations, mercury lamp tests are conducted at bi-weekly intervals to ensure that observations are always made on correct wave­lengths. Also, standard lamp tests are performed at monthly intervals to monitor variations in the instruments' spectral response characteristics.

- 373-

Comparison Umkehr observations were made in Boulder with the automated Dobson instruments relative to Instrument No. 83. The comparisons yielded ozone profile data (Figure 2) that agreed on the average to within ±5% in standard Umkehr layers 4 to 9 and in short Umkehr layers 1 to 12. Note that Instrument 83 exhibits a bias in Umkehr layer 1. The cause of the bias is unknown.

The standard Umkehr ozone profiles were averaged for all of the automated Dobson instruments and compared with corresponding data for Instrument 83. Differences in deduced ozone amounts in the stratospheric Umkehr layers were found not to exceed 3%. Similar results were obtained for averaged short Umkehr data comparisons. Here, the ozone amount differences were smaller than 4% throughout the troposphere and the stratosphere.

Averaged standard and short Umkehr ozone profiles, obtained with the automated Dobson instruments, were compared. The differences in ozone measured by the two methods were found to approach 15% in Umkehr layers 1 and 9, and 10% in layers 4 to 6. Standard Umkehr observations in Boulder exhibit, furthermore, maximum ozone amounts in layer 5, whereas short Umkehr observations yield maximum values in layer 4. The discrepancies stem in part from deficiencies in the algorithms used in processing the data, and partly from the observational data which are not identical for standard and short Umkehrs. Standard Umkehr observations are made on the Dobson instrument C wavelength pair only, at solar zenith angles of 60° to 90°. Short Umkehr observations are made on A, C, and D wavelength pairs, at solar zenith angles of 80° to 90°.

Total ozone observations made with the automated Dobson instruments at the time of the Umkehr observation comparisons indicated agreement to better than 1% on the ~verage with ozone amounts measured by Instrument 83, except for instrument 81, where two sets of comparison data exhibited a mean difference of 1.6%.

REFERENCES

1. National Research Council (1984). Causes and effects of changes in stratospheric ozone: Update 1983. The National Academy Press, Washington, D.C. (Library of Congress Catalogue No. 84-60100), 254 pp.

2. REINSEL, G. C., TIAO, G. C., DELUISI, J. J., MATEER, C. L., MILLER, A. J. and FREDERICK, J. E. (1984). Analysis of upper stratospheric Umkehr ozone profile data for trends and effects of stratospheric aerosols. Jour. Geophys. Res., 89, No. D3, 4833-4840.

3. MATEER, C. L. and DUTSCH, H. U. (1964). Uniform evaluation of Umkehr observations from the World Ozone Network, Part 1 - Proposed standard evaluation technique, NCAR, Boulder, Colorado, 105 pp.

4. MATEER, C. L. and DELUISI, J. J. (1981). The estimation of the vertical distribution of ozone by the short Umkehr method. Proc. Quad. Int. Ozone Symp. l, held 4-9 August 1980, Boulder, Colo., (J. London, Editor), 64-73.

- 374-

D E E "" ,S oS

~ ., :l '0

'" :E '" ~ Q. <{

Mean 03 Differences in %

9 40

10 6 30 5 4 20

100 3

D 2 10 E

E "'" c: c: -; 1000 0 ., " 1

'0

'" ~ '" 40 ~ <{ Q.

10 6 30

4

100 3

2 10

1000 0

Mean 03 Differences in %

Fig. 2. Standard and short Umkehr comparison ozone data for instruments 61-87 vs. Instrument 83. Numbers in brackets are the number of comparison observations made. Columnar values on the left of each figure are Umkehr layer numbers; those on the right are percent standard deviations. Instrument 82 is not automated.

- 375-

Summary

TRAVELING STANDARD LAMP CALIBRATION CHECKS ON DOBSON OZONE SPECTROPHOTOMETERS DURING 1981-83

R.D. GRASS and W.D. KOMHYR

National Oceanic and Atmospheric Administration Air Resources Laboratory

Boulder, Colorado 80303

Calibrated standard lamps were sent to 87 Dobson spectrophotometer observatories during 1981-83 to check on the calibration level of Dobson instruments in the global total ozone station network. Data received from 78 stations indicated that 21 instruments required recalibration. Since completion of the tests, instruments in Peru and Thailand have been recalibrated. Arrangements are under way to conduct international comparisons of Dobson instruments in Melbourne, Australia, in late 1984. Participating countries will be Australia, India, Japan, and the United States.

1. Introduction

Dobson ozone spectrophotometers serve as a standard for measurements of atmospheric total ozone. World Standard Dobson Instrument No. 83 is maintained by the U.S. National Oceanic and Atmospheric Administration, Geophysical Monitoring for Climatic Change (GMCC) program, in Boulder, Colorado, at the World Dobson Spectrophotometer Central Laboratory. While international Dobson instrument comparisons in the past have revealed large calibration errors for many of the instruments (1,2), the accuracy of the ozone measurements within the global Dobson station network im­proved markedly following international Dobson spectrophotometer inter­comparisons (3) held in Boulder in 1977. At that time, eight spectropho­tometers, designated by the World Meteorological Organization (WMO) as regional secondary standards, were calibrated relative to instrument No. 83 with the intent that they be used to calibrate field instuments within their respective regions. Currently, calibration of the majority of in­struments in use throughout the world is traceable to either direct or indirect intercalibration with instrument No. 83.

At the 1977 Dobson instrument comparisons in Boulder, a standard lamp method was devised (3) for identifying Dobson instruments that have gross absolute calibration errors. In an ongoing program by the World Dobson Spectrophotometer Central Laboratory to upgrade the calibrations of Dobson instruments throughout the world, seven standard lamp units, each con­sisting of two calibrated lamps and a stable power supply, were fabricated in 1981. The global Dobson instrument network was then divided into seven areas, each containing from 5 to 17 instruments, and a lamp unit was shipped to each area for use in checking the calibrations of the Dobson instruments in each area. Results of the calibration checks are presented herein.

Ozone Symposium - Greece 1984 - 376-

2. Dobson Instrument Calibration Methodology

The standard lamp technique of checking Dobson spectrophotometers for gross calibration errors is based on experimental observations (3) that instruments accurately calibrated on relative and absolute scales yield standard lamp readings

N = log (1/1') + K [1 ]

at the A, B, C, and D Dobson instrument wavelength pairs that are essen­tially constant provided, also, that the internal light-scattering charac­teristics of the instruments are similar. (In the above equation, 1/1' is the lamp light intensity ratio for, say, the A wavelength pair, while K is an associated instrumental constant.) Mean absolute calibration error for such instruments, calibrated with standard lamps, is estimated to be ±1.5% at the 95% confidence interval. This error is about twice as large as that which occurs when spectrophotometers are calibrated by direct compar­ison of instruments. Thus, use of standard lamps for calibrating spectro­photometers on an absolute scale is not generally recommended.

Accurate relative calibration of Dobson spectrophotometers implies accurate optical wedge and wavelength setting calibrations for the instru­ments. An instrument with an improperly calibrated optical wedge will, for example, yield wrong N values in most instances for a standard lamp whose N values have been correctly determined. Because only a limited port~on of the optical wedge is used when a standard lamp test is per­formed, the calibration error determined from correct and observed N-value differences is not, in general, representative of the instrument as a whole. Thus, it is important that spectrophotometer calibration errors determined from tests with standard lamps not be used for correcting ozone data obtained in the past with the improperly calibrated instruments. At most, the lamp tests indicate that an instrument calibration problem exists, and that remedial action is required.

3. Dobson Instrument Calibration-Check Results and Conclusions

Standard lamps sent to the Dobson instrument stations were calibrated using World Standard Dobson Spectrophotometer No. 83. Recalibration of the lamps with instrument No. 83 following return of the lamps to Boulder indicated insignificant changes in originally assigned lamp N values. The time taken to circulate the lamp units among all stations was approximately 2 years. Data were received from 78 of 87 stations. Two stations provided insufficient data, while data from several stations were withheld pending recalibration of the instruments at the sites.

Results of the Dobson instrument calibration checks are given in Table I. Instrument calibration errors shown in the last column of the table are averages derived from

% Error = 100 (~AD) 1.388 ~x [2]

for a total ozone amount x of 300 milli-atm-cm and equivalent ozone path lengths ~ of 1, 2, and 3. The ~AD values were computed from the assigned and measured lamp N values.

Deduced instrument calibration errors of absolute magnitude >2% were taken to signify that an instrument calibration problem exists. According to this criterion, 21 instruments were identified as needing recalibration. Locations of the instruments are the following: two in South America;

- 377-

TABLE I. Results of Calibration Checks on Dobson Spectrophotometers Using Traveling Standard Lamps

Station

Area 1 - North America Toronto, Canada Resolute, Canada Churchill, Canada Goose Bay, Canada Edmonton, Canada Reykjavic, Iceland South Pole, Antarctica Bismark, U.S.A. Caribou, U.S.A. Wallops Is., U.S.A. Tallahassee, U.S.A. Nashville, U.S.A. Mauna Loa, U.S.A. American Samoa, South Pacific Point Barrow, U.S.A. Boulder, U.S.A. Boulder, U.S.A. Area 2 - South America Mexico City, Mexico Huancayo, Peru Cachoeira Paulista, Brazil Natal, Brazil Buenos Aires, Argentina Buenos Aires, Argentina Area 3 - Western Europe (1) Bracknell, U.K. Bracknell, U. K. Halley Bay, U.K. Argentine Is., U.K. Seychelles, Seychelles St. Helena, U.K. King Edward Point, U.K. Lerwick, U.K. Arosa, Switzerland Arosa, Switzerland Hohenpeissenberg, F.R.G. Cologne, G.F.R. Oslo, Norway Oslo, Norway Tromso, Norway Area 4 - Western Europe (2) AArhus, Denmark Uccle, Belgium Biscarrosse, France Magny-Les-Hameaux, France

Inst. No.

77 59 60 62

102 50 80 33 34 38 58 79 63 42 76 61 82

98 87

114 93 97 99

41 2

31 73 57 35

103 32 15

101 104 44

8 56 14

92 40 11 85

Date of Calib. Check

811015 811211 820101 810511 811130 820323 820125 820715 820602 820617 821001 820927 820602 820828 820429 820602 820709

811030 820418 821021 820909 830120 830314

820622 820622

820707 821108 821108 821130

830408 830411 830408

810610 811027 82----820502

Inst. Cali~. Error (%)

- 0.15 - 0.74 + 1.62 + 0.00 + 0.08 + 0.44 + 1.32 + 0.88 - 1.25 - 0.96 + 0.88 + 1.18 - 1.25 + 0.81 + 1.62 - 0.37 + 0.30

+ 1.32 - 4.84 - 3.67 + 0.73 - 0.15 - 0.07

- 0.15 + 0.59

+ 2.13 - 0.88 - 0.08 - 6.10

- 0.96 - 0.29 - 1.17

+ 0.74 + 1.25 - 2.42 + 1.98

* See text for significance of calibration errors. Positive error means that instrument yields ozone values that are too large.

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TABLE I. Continued.

Station

Lisbon, Portugal EI Arenosillo, Spain Vigna Di Valle, Italy Brindisi, Italy Sestola, Italy Cagliari/Elmas, Italy Casablanca, Morocco Cairo, Eqypt Cairo, Egypt Area 5 - East Europe, U.S.S.R. Leningrad, U.S.S.R. Belsk, Poland Hradec Kralove, Czechoslovakia Budapest-Lorinc, Hungary Bucharest, Romania Potsdam, G.D.R. Potsdam, G.D.R. Area 6 - India New Delhi, India New Delhi, India Srinagar,India Varanasi; India Mt. Abu, India Poona, India Kodaikanal, India Quetta, Pakistan Quetta, Pakistan Bangkok, Thailand Singapore, Singapore (U.K) Manila, Philippines Area 7 Australia, Japan Sapporo, Japan Kagoshima, Japan Tateno, Japan Naha/Kagamizu, Japan Tateno, Japan Sapporo, Japan Tateno, Japan Shiangher, China K'un-ming, China Aspendale, Australia Aspendale, Australia Perth, Australia Cairns, Australia Brisbane, Australia Hobart, Australia McQuarie Island, Australia Invercargill, New Zealand

* See text for significance of means that instrument yields

Inst. Date oJ Ins t. Cali £ • No. Calib. Check Error (%)

13 820422 - 0.07 120 82---- + 0.66

47 821213 + 0.44 46 821227 + 3.30 48 830110 - 0.08

113 821221 - 1.25 106 830602 69 840309 - 1.47 96 840310 + 0.52

108 811022 + 0.29 84 820107 + 1.32 74 820204 - 3.30

110 820103 - 3.52 121 820420 + 3.30

71 8205-- + 0.59 64 8205-- - 0.44

36 82---- - 0.44 112 82---- - 1.47

10 82---- + 1.76 55 82---- - 1.62 54 82---- + 2.27 39 82---- + 0.44 45 82---- + 2.57 43

100 830408 + 1.91 90 830610 +10.79

7 52 831101 - 1.25

5702 820105 - 0.44 5704 811210 + 4.55

116 811120 + 3.08 5705 811221 - 3.52

12.2 811120 + 3.37 5703 820106 - 0.44 5706 811124 + 1.32

75 820330 + 0.15 3 820413 - 2.05

105 820906 + 0.59 115 820618 + 0.15 III 820817 - 8.95

81 820713 + 6.60 6 820715 - 4.11

12 820705 - 8.80 78 821028 - 0.29 17 830303 + 0.15

calibration errors. Positive error ozone values that are too large.

-379 -

four in Western Europe; three in Eastern Europe; three in the India­Thailand region; and nine in Australia and Japan. As indicated earlier, care must be taken not to misinterpret the error data of Table I as actual instrument calibration error data, rather than as data indicative of in­struments requiring recalibration. For example, lamp tests indicated a calibration error of 10.8% for Bangkok instrument No. 90. Subsequent direct calibration of instrument No. 90 in Boulder relative to instrument No. 83 indicated a mean calibration error for this instrument of 4.4%.

Since performance of the Dobson instrument calibration checks,' Bangkok instrument No. 90 and Huancayo instrument No. 87 have been recali­brated. Plans are currently under way, under auspices of the WMO, to conduct an international comparison of Dobson instruments in Melbourne, Australia late in 1984, with the participants being Australia, India, Japan, and the United States.

REFERENCES

1. GUSHCHIN, G.P. (1972). Comparison of ozonometric instruments. In Actinometry, Atmospheric Optics, Ozonometry (G.P. Gushchin, editor). Glavnaya Geofizicheskaya Observatoriya 1m. A.I. Voeikova, Trudy No. 279, Gidrometeorizdat, Leningrad, 118-126.

2. DZIEWULSKA-LOSIOWA, A. and WALSHAW, C.D. (1975). The international comparison of ozone spectrophotometers, Belsk, 24 June to 6 July 1974. Publications of the Institute of Geophysics, Polish Academy of Sciences. Vol. 89, 2-59.

3. KOMHYR, W.D., GRASS, R.D. and LEONARD, R.K. (1981). WMO 1977 inter­national comparison of Dobson ozone spectrophotometers. Proceedings of the Quadrennial International Ozone Symposium, Boulder, Colorado, 4-9 August 1980 (J. London, editor). Vol. I, 25-32.

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1. Summary

Recalibration of Dobson Field Spectrophotometers with a Travelling Brewer Spectrophotometer Standard

J.B. Kerr, W.F.J. Evans and I.A. Asbridge Atmospheric Environment Service

4905 Dufferin Street Downsview, Ontario, M3H 5T4

CANADA

The Brewer ozone spectrophotometer has been used to verify the calibration of Dobson spectrophotometers in the field on a trial basis. The test intercomparisons have demonstrated that the Brewer instrument verifies the double pair wavelength AD Dobson measurements of the type Direct Sun Ground Quartz Plate (AD DSGOP). The initial results from comparisons against a well maintained Dobson instrument (the Canadian standard #77) show agreement within 0.5% total ozone over an airmass ranqe of 1 to 3. The method sugqests that the recalibration of a Dobson containing ma.tor calibration errors can be achieved with respect to the double pair wavelength AD measurements and possibly identify the siqnificant instrumental problems within the Dobson. Because the Brewer instrument is portable and can be easily transported without losing its calibration, it is ideal for carrying out field calibrations of instruments in the ozone network.

The Brewer reference is stationed at Toronto and consists of three well maintained instruments whose extraterrestrial constants have been independently determined by the airmass extrapolation technique at Mauna Loa, Hawaii. The travelling Brewer is calibrated against the standard "triad" prior to departure and the calibration is verified upon return. Instrument stability is monitored by an internal standard lamp and wavelength calibration mercury lamp during the field intercomparison.

The calibration procedure is discussed and results of some trial calibrations are presented.

2. Introduction

Results of international comparisons of Dobson ozone spectrophotometers at Belsk in 1974 and in Boulder in 1977 (1) have indicated that the "as is" calibration state of a field instrument yields ozone values which may be in error by as much as 10% when compared to a reference. Most of the instruments participating at the comparison campaigns were designated as reqional secondary standards by the WMO in 1977. Rased on the assumption that the secondary standards are maintained to a higher level than an arbitrary "working" Dobson, the disagreement among the secondary standards at the comparisons is undoubtedly a lower limit of typical errors which would be expected for an arbitrary sample of field instruments.

Comparison of TOMS satellite total ozone measurements and around'based Dobson total ozone measurements at about 60 stations in the world ozone network (2) has indicated that the TOMS values have a bias of between 5% and 6% (Dobson values larger than TOMS). When the bias is removed the station to station variability of Dobson-TOMS comparative values is typically +2% with some deviations as large as 10%.

Ozone Symposium - Greece 1984 - 381 -

It is desirable to determine whether the station to station variability of the si.multaneous sat~llite qrounn based comparisons is due to the TOMS data reduction algorithm errors or the calibration of the individual ground based instruments. The qround based instruments can be checked by carrying out calibrations at ~ach station with a common travellinq instrument as a reference. Because the Brewer ozone spectrophotomet~r is a portable instrument and can reliably hold its calibration while travelling from station to station, it is an ideal instrument to use as a travelling reference to calibrate a ground based ozone network.

3. The Brewer Reference

The Brewer reference is located at the Atmospheric Environment Service (AES) in Downsview, Canada. This reference consists of three Brewer instruments which have been independently calibrated to determine their instrumental extraterrestrial constants usinq the airmass extrapolation technique (Langley plots) at Mauna Loa, Hawaii. This triad of Brewer instrument ensures the presence of a reference which has an accuracy of 0.5% for total ozone meaurements on the direct sun. All three instruments acquire ozone data on a routine basis and the data is monitoren for mutual consistency. Should one member of the triad deviate from the other two, steps are taken to correct the discrepancv in the suspect instrument.

The triad consists of Brewer fm08 which has been in operation since February, 1983 and was calibrated in Hawaii in May and June, 1983, Brewer fm15 which was calibrated in Hawaii in January, 1984 and Brewer #014 which was ca:librated in Hawaii in Auqust 1984. 80th Brewer #014 ann #015 are fully automaten and record measurements in unattended operation on a continuous basis.

The Dobson #77 is operated at the AES alongside the Brewer reference. This Dobson is the Canadian secondary standard. Intercomparative measurements between the 8rewer reference and the Dobson have indicated a bias of 3.9% when Dobson total ozone values are compared to those of the Brewer using the Bass (3) ozone absorption coefficients at -45 DC appHed to the Brewer slit functions. When the bias is removed the aareement between the Dobson and Brewer is within +.5% over long periods of time. This comparison has ensured the continuity of a Dobson/Brewer ozone monitoring network.

A Brewer instrument which is destined for a field station is operated alongside the Brewer reference for at least one full day during which favourable weather persists in order to allow the acquisition of good quality direct sun data. From the intercomparison data, the instrumental extraterrestrial constants as well as the effective ozone absorption coefficients are determined.

The calibration of a field instrument is done by one of two methods: either the field instrument is brought to the Brewer reference or a travellina Brewer whose calibration is well defined by comparative measurements against the reference, is brought to the fieln.

4. Calibration Procedure

The method by which ozone is measured by the Brewer instrument is described by Kerr et aI, (4). This measurement method is similar in pr~nciple to the Dobson measurement method and will not be restated here. Equation 3 in (4) is aiven as follows:

(1)

- 382-

where F M3

m Fo flo.

03 Il

is a linear combination of the loa of measured liqht intensities is the same linear comhination of Rayleiqh scatterinq coefficients at the Rrewer wavelenqths. is Remporad's airmass function. is the instrumental extraterrestrial constant. is the linear combination of the ozone absorotion coefficients at the Brewer wavelengths (em- l ). is the total amount of ozone in the atmosphere (em). is the effective pathlenqth through ozone.

A Brewer instrument is calihrated by takinq many simultaneous direct sun measurements alonqside a reference. The reference measures total ozone to within .5% and the F value in equation 1 is determined from measurements made with the instrument beinq calibrated. The value of (F + flBm) is reqressed aqainst -(03*1l) and Fo (intercept) and flo. (slope) are determined. These two values are the calibration constants on the ozone wavelenqth for the newly calibrated instrument. A similar procedure is used to calibrate the S02 wavelength ratio.

The above calibration procedure differs from that commonly used for calibratinq the f1obson intruments hecause two calihration constants are determined. The Dobson calibration procedure assumes that the effective ozone absorotion coefficients for the A, S, C and n wavelenqth pairs are fixed and the extraterrestrial constants (Lo's) are the only calibration parameters. This assumntion yields satisfactory results provided the spectrometer aliqnment and focussinq is accurate enough to result in absorotion. coefficients which are within one or two oercent of the nominal values. There is typically a one or two percent variahility of the effective ozone absorption coefficients from one f1obson to another. These differences are due to sliqht differences in the slit function of the individual instruments.

By forcinq the intercomparison data to "fit" a nominal absorption coefficient, a comoensatinq offset of the extraterrestrial constant results. This results in noticeable airmass dependence if the absorption coefficient differs more than 2% from the nominal value. For example, the ozone measurement could be 1% too small at small airmass values and 1% too large at large airmass values with a crossover somewhere in between. In some instances it is possible that the effective absorption coefficients differ by UP to 5% from the nominal values (e.g. Dobson #108 at the Relsk intercomparison in 1974).

Perhaps a more serious consequence of assuming a nominal absorption coefficient is when an instrument is independently calibrated by the airmass extrapolation technique. In this situation the extraterrestrial constants are measured and the absorption coefficients are assumerl. There is no compensatinq shift of the extraterrestrial constant to make up for differences in the absorption coefficient. An instrument whose effective absorption coefficient differs bv 2% from the nominal value will always measure ozone with a 2% bias once the extraterrestrial constant has been determined.

The approach used for calibratinq Brewer instruments recoqnizes the fact that all instruments are not made identically and that each instrument has its own unique set of absorption coefficients. For those instruments which are calibrated by the airmass extrapolation technique the synthetic ozone absorption coefficients of Bass, 1982 (at _45°C) are applied to careful Iv measured Rrewer slit functions. For those instruments calibrated by . intercomparison aqainst a reference, absorption coefficients and .

- 383-

extraterrestrial constants are determined by the linear rearession of many data points applierl to the expression aiven in eauation 1.

5. Results

In September and October, 1981, Rrewer #1 travelled to Dobson stations Arosa, Belsk, Bracknell anrl Uccle. In 1981 these stations had biases when comoared to TOMS satell i te data (after an average bias of about 6% is removed) as outlined in Table 1. When the Dobson data is comparerl to the travellinq Brewer data the resllitina hiases are also shown in table 1. (Note that the Bass coefficients applied to the Brewer instrument results in a bias of -3.9% when compared to the Dobson #77 measurements)' The results of this travellina Rrewer intercomoarison were reported in (5).

More recently, Brewer #17 was used as a travellina reference to check the calibration of Oohson instruments #105 and #115 in ~elbourne, -Australia. The results of this calihration trip are shown in Table 2. The "as is" calibration state of Dobsons #105 and #115 yields AD total ozone values whose respective means are 2.7 DU and 1.6 DU smaller than the Brewer reference the rms differences of +3.8 DU and +2.4 DlJ respectively.

If the Dobson AD absorption coefficients are forced to 1.388 cm _1 then the Lo values for Dobson #105 and #115 need to be adjusted by -.58 and -.37 N units respectively. Using these new N values yields an rms difference of +2.3 DU between Brewer #17 and Dobson #105 and an rms difference of +1.6 DU between Brewer #17 and Dobson #115.

If the Dobson AD absorption coefficients are determined by the best fit against the Brewer reference, the resultinq coefficients are 1.416 cm- 1 for Dobson "#105 and 1.402 for Dobson 11115 and the necessary ad.tustment of the Lo values are -2.15 and -1.17 N units for the respective Dobsons. The rms Brewer/Dohson differences are now +1.6 OU for Dobson #105 and +1.4 DU for Dobson 11115, a noticeable improvement over the case when the AD absorption coefficients are forced to 1.388 em- 1 •

The record of Brewer 1117 travel from its initial calibration in July 1983 to September 1984 is given in Tahle 3.

Brewer #13 was in operation in Toronto alonaside the Brewer reference from Auqust 1983 to January 1984. Measurements over this time provided a very accurate calibration for Brewer 1113. In February 1984 Rrewer #13 was installerl in the field at Edmonton and has operated with Dobson #102 since then. A review of the simultaneous Brewer/Dobson measurements marle in Erlmonton between February and May 1984 indicates that the Dobson measures ozone by about .5 DU lower than the Brewer with a standard deviation of +2.4 DlJ (.6%).

6. Conclusions

(1) The Brewer reference has been established at AES in Toronto. The reference provides measurements of atmospheric ozone whose accuracy is within +.5%.

(2) Agreement between calibrated Brewers is qenerally +.5% over long time periods ( 1 year).

(3) Brewers can be used to calibrate Oobson instruments. (4) It has been demonstrated that a travelling Brewer can successfully

calibrate field instruments hased on results of calibration trips to Europe, Australia and within Canada.

-384 -

Acknowlerlqements

Mr. K. Lamb of Sci-Tee Instruments Inc. played a major role in the intercomparison measurements at Melbourne, Australia. Dr. R.A. Olafson made the travellinq Brewer measurements in September, October, 1981. Dr. Olafson also installerl Brewer #13 at Edmonton.

References

(1) W.O. Komhyr, R.n. Grass anrl R.K. Lp.onard, WMO 1977, International comparison of Dobson ozone spectrophotometers, Preceedinqs of the International Ozone Symposium, Boulder, 1980.

(2) R. BO.tkov anrl C.L. Mateer, On the relative quality and performance of G.O.O.S., presented at this Symposium.

(3) A. Bass, Private communication, 1982.

(a) J.B. Kerr, C.T. ~cElroy and R.A. Olafson, Measurements of ozone with the Brewer ozone spectrophotometer, Proceedinqs of the International Ozone Symposium, Aoulder, 1980.

(5) WMO Global Ozone Research and ~onitorinq Project, Report of the Meeting of Experts on Sources of Errors in Detection of Ozone Trends, WMO Report 1112, 1982.

STATION DOBSON # 100* (Brewer-Dobson) 100*(TOMS-Dobson) Dobson Dobson

AROSA 15 4.0 2.1 BELSK 84 -2.8 -2.4 BRACKNELL 41 -1.4 -1.3 UCCLE 40 -1.2 -2.5

Table I: Results of Brewer/Dobson and TOMS/Dobson comparison in September and October, 1981. Brewer data has a -3.9% bias removed and TOMS data has a -6.4% bias removed.

NO ADJUSTMENTS FIT Lo ONLY FIT Lo and ("as is" values) AD 0 3 coeffs

#105 #115 #105 #115 #105 #115

AD Ozone Absorption Coefficient (cm- 1 ) 1.388 1.388 1.388 1.388 1.416 1.402

Lo Adjustment (N units) 0 0 -.58 -.37 -2.15 -1.17

Mean Difference (DU) (Brewer - Dobson) +2.7 +1.6 -.2 0 0 0

RMS Difference (DU) !3.8 !2.4 !2.3 !1.6 !1.6 !1.4

Table II: Results of Brewer #17 comparison with Dobsons #105 and #115 at Melbourne, Australia in March, 1984.

- 385-

DATE PLACE COMMENTS

July 1-8/83 AES, Toronto Calibration against Brewer #8 and Dobson #77. Mean #17-#8 difference -.1 DU. RMS difference +/- 2.1 DU.

July 9-10/83 Palestine, Texas Intercomparison with Brewer #12 and Dobson #82 in support of BOIC.

July/83-Jan/84 Saskatoon, Canada Ozone measurements. SCI-TEC reference.

Feb 21,22/84 AES,Toronto Calibration verification against Brewers #8, #15, and Dobson #77. Mean #17-#8 difference -1.0 DU. RMS difference +/- 1.6 DU.

March 8-12/84 Melbourne, Intercomparison with Dobson #105 Australia. and #115.

March 15-Aug 5/84 Wellington, N.Z. Ozone measurements. August 17-22/84 Saskatoon, Canada Intercomparison with Brewers #11,

#19, #20, and #21. August 22-26/84 AES, Toronto Calibration verification against

Brewers #8, #15, and Dobson #77. Mean #17-#8 difference -.2 DU. RMS difference +/- 2.1 DU.

Aug 27-Sept 1/84 Hohenpeissenberg, Calibration of Brewer #10. West Germany_.

Sept 1-15/84 Thessaloniki, Ozone Symposium. Greece. Intercomparison with Brewer #5.

S02 measurements.

TABLE III: Record of travel for Brewer #17 since its initial calibration against the Brewer Reference at AES in July, 1984.

- 386-

REVIEW OF THE DOBSON SPECTROPHOTOMETER

AND ITS ACCURACY

REI DE. BASHER

New Zealand Meteorological Service

Summary

A detailed analysis of the Dobson spectrophotometer and its accuracy has been made. The spectrophotometer is the princi pa 1 instrument used for measuri ng the atmosphere's ozone overburden. Emphasis has been put on the physics of the measurement method. Summarising the effects of the various error sources is difficult owing to the great variety of error sources, their large variation from instrument to instrument in some cases, and their dependence on external parameters whi ch are often unknown. Three broad general i sat ions can be made; firstly, that instrument-related errors form the greatest aggregate source of error; secondly, that the largest instrument-related errors arise from faulty extraterrestrial constants, stray light and defective optical adjustment; and thirdly, that atmosphere-related errors are small except at sites affected by severe air pollution. It seems that perhaps two thirds of recent years' standard AD direct sun method ozone estimations are accurate to 3% or better, relative to the current absolute scale, and that this absolute scale is itself accurate to about 3%. Some error sources which change with time can cause erroneous trends in ozone data of several percent per decade.

1. Introduction This study aims to provide a thorough review of the error sources

in the Dobson instrument's measurement of column ozone amount (l). It approaches the problem from the point of view of the physics of the measurement method rather than from the point of view of the statistics of co 11 ected data. There is a great vari ety of error sources, there are large variations in the effect of the error sources from instrument to instrument, and the many factors upon which errors are dependent are often not well known. The combining of the error estimates into a single "representative" value is difficult for present day measurements, and is very difficult for measurements made in the past. For most of the errors, especially the larger ones, there is no a priori basis for their representation as variances. Thus there are significant difficulties in assessing the reduction of the errors in data from a time series or from an ensemble of instruments. All of the numerical estimates given here mu~t be used with caution.

2. Errors in individual direct sun AD ozone observations A grand summary of errors, for just the AD direct sun ozone

estimation, is given in Table 1 below. In the table, estimates are made for two loosely defi ned categori es, "typi ca 1 good i ristrument or

Ozone Symposium - Greece 1984 - 387-

w

00

0

0

TABL

E 1

Sunm

ary

of e

rror

sou

rces

for

ind

ivild

ual

dail

y st

anda

rd A

D di

rect

sun

ozo

ne e

stim

atio

ns

Err

or s

ourc

e E

rror

est

imat

es

Typ

ical

go

od

inst

rum

ent

or

situ

atio

n In

stru

men

t so

urce

s:

Tem

pera

ture

de

pend

ence

'(1

%

Mec

hani

cal

defo

rmat

ion

<1%

Stra

y 1 i

ght

<1

%?

Wav

elen

gth

adju

stm

ent

1%

Oth

er o

ptic

al p

robl

ems

<1%

Wed

ge

cali

brat

ion

0.5%

Ba

ndw

i dth

eff

ect

<0.5

%

ETC

dete

rmin

atio

n 1%

ETC

stab

il it

y

1. 5%

E

lect

roni

cs

<0.5

%

Ope

ratio

nal

prec

isio

n <1

% RM

S

Atm

osph

eric

sou

rces

: O

zone

abs

orpt

ion

(i)

abso

lute

co

effi

cien

t 3%

? (i

i)

rela

tive

coe

ffic

ient

1.5

%

Aer

osol

ex

tinc

tion

<0

.2%

In

terf

erin

g ab

sorp

tion

<0

.5%

Oth

er s

ourc

es:

Airm

ass

calc

ulat

ion

Sol

ar v

aria

bili

ty

Sam

plin

g bi

ases

<0.2

%

.,<1%

? <0

.5%

Typ

ical

ba

d ca

se 2%

? 5%

?

2%

1O%

?

2%

<0.15

%

5%

4%

1%?

<2%

Rf

,lS

3%?

1. 5%

3%

5%

<5%

< 1%

? 3%

Com

men

ts

Dep

end'S

on

cl

imat

e an

d op

erat

or c

are.

In

adeq

uate

inf

orm

atio

n.

Inad

equa

te i

nfor

mat

ion.

V

ery

vari

able

. R

apid

inc

reas

e fo

r ai

rmas

ses

>3.

Bet

ter

resu

lts

in

rece

nt y

ears

gen

eral

ly.

Inad

equa

te i

nfor

mat

ion.

So

me

may

be

acco

unte

d fo

r in

ot

her

erro

r so

urce

ent

ries

. M

oder

n eq

uipm

ent

need

ed f

or b

est

resu

lts.

L

arge

r va

lues

fo

r ot

her

band

com

bina

tions

. B

est

resu

lts

from

dir

ect

inte

rcom

pari

son.

La

ngle

y m

etho

d er

ror

ofte

n ab

out

5%.

Dri

ft o

ver

2 to

5 y

ears

bet

wee

n in

terc

ompa

riso

ns.

Inhe

rent

ly s

mal

l. D

epen

ds

on

skil

l, a

tmos

pher

ic s

tab

ilit

y,

airm

ass.

Good

pro

spec

ts f

or 1

to

2%

in n

ear

futu

re.

Due

to s

trat

osph

eric

tem

pera

ture

var

iati

on.

Wor

st ca

se

requ

ires

ext

rem

ely

turb

id s

ky.

Onl

y ba

d ne

ar c

itie

s, v

olca

noes

et

c.,

on o

ccas

ion.

Onl

y ba

d at

hig

h la

titu

des

with

"2

2 km

" as

suni

ptio

n.

Inad

equa

te i

nfor

mat

ion.

Is

ze

ro w

hen

ETC

is s

et.

Prop

orti

onal

to

tem

pora

l an

d sp

atia

l va

riab

ilit

y.

situation", and "typical bad case". The first category describes the errors expected when proper procedures Of maintenance and operation are faithfully carried out and when adverse factors, such as stray light, heavy haze, high pollution or high airmass, are not significantly affecting the measurements. The second category describes the typical errors expected on occasion, or at some sites, or with some instruments, ins ituat ions when the error concerned is -1 arge. The proport ions of instruments falling in and between these categories depend on the particular errror source. A very rough overall estimate is that at present half the network's instruments will meet most of the "typical good" category estimates all or most of the time and that perhaps ten to twenty percent of the network wi 11 be affected by some of the 1 arger "typical bad case" category estimates all or most of the time. In the past, the proportion meeting most of the "typical good" estimates undoubtedly was less.

Three broad general isations can be made on the basis of Table 1. Firstly, the aggregate of the instrument-related error sources is greater than the aggregate of all the other error sources. Secondly, the largest of the instrument-related error sources concern the extra-terrestrial constants, stray light and optical adjustment. Thirdly, atmosphere­related error sources (excluding the absolute accuracy of the ozone absorption coefficient scale) are small except for a few sites affected by severe air pollution. These generalisations have been largely understood and accepted, if not expl icitly demonstrated, by instrument specialists for some time.

The 'error estimates in each column of Table 1 cannot be simply added or RMS added, but some form of aggregation is called for. It seems as if suitable measures of accuracy for present-day daily AD direct sun ozone estimations, relative to the current ozone absorption coefficient absolute scale, are about 3% for instruments mostly meeting the "typical good" category requirements, and about 5% to 10% for instruments which suffer from the larger errors listed in the "typical bad" category. Overall, the author risks the guess that two thirds of recent years' AD direct sun ozone estimations have an accuracy of 3% or better relative to the current absolute scale. This is reasonably consistent with the 1979 comparison of Dobson stations with the BUV-TOMS satellite instrument (2).

3. Errors in other observation types All observation types suffer from the error sources listed for the

AD direct sun observation in Table 1, and usually so to a greater extent. Approximate accuracies relative to the standard AD estimation are as follows. The first figure represents a typical good instrument or situation, while the second figure, in parentheses, represents a typical bad case. AD zen ith blue, 2%RMS (5%RMS? ) ; AD zen ith cloud, 3% RMS (lO%RMS?}; CD direct sun, 2% (5%?); C direct sun, 3% (lO%?); Focussed image, 4%? (20%?). The usefulness of the non-standard observations depends on their information contribution relative to the otherwise available data and to the expected natural variation. In some instances, e.g., at polar latitudes, an observation of 10% accuracy may be very useful.

4. Errors affecting trend estimates The question of the detectabil i ty of trend in ozone data is of

great topical interest. Table 2 1 ists those error sources which could conceivably contribute trend-like error to archived data, and shows that erroneous trends of up to about 10% per decade can be expected for some

- 389-

instruments. This sets a significant limitation to the trend detection capability of the data. It is particularly ironic that the considerable efforts which have been made over the past decade to upgrade the adjustment and calibration of instruments are themselves sources of some of the largest potential erroneous trends.

Table 2: Summary of error sources which could exhibit trend-like behaviour, with estimates of potential erroneous trend for an individual instrument's AD direct sun observations.

Error source

Optical adjustments and

Likely maximuVl trend percent per decade

1973-1983

their historical improvement 5% } ETC determinations 5%

Instrument drift 2%

Ozone 1 ayer tempera ture 0.5%1

Aeroso 1 exti nction 1%

Interfering absorption 2%

Airmass calculation 1%

So 1 ar vari abi 1 ity <1%1

Due to changes to ins truments and periodic cajibrations. especially upgradingsover last ten years.

Effect ;s reduced by frequent calibrations.

No subs tanti a 1 evi dence for thi s.

Requires heavy and changing haze.

Only significant near sources.

Due to change from fi xed 22 km 1 ayer to c 1 imato 1 ogi ca 1 mean heights.

Inadequate i nformat; on.

It is not clear to what extent the nett erroneous trends of instruments in a group will be correlated. In one statistical study (3), the trends at individual stations for the one to two decades before 1979 were found to range from about -4% per decade to about +8% per decade. These values are consistent with the estimated magnitudes of possible erroneous trends gi ven in Tab 1 e 2. Although the detected trends may reflect some real ozone changes, their scatter within a region, especially the -2 to +8% per decade scatter found for Europe, indicates that other factors, probably instrument-related errors, are the main cause.

5. Errors in statistical means In the daily mean for a large number of instruments, or for a large

region, many of the errors will reduce as if part of a random distribution. Systematic error components will be present though, the largest being those due to the determination and stabil ity of extraterrestrial constants, to stray light effects and to other optical adjustments or problems, and altogether these might amount to an error of up to say 3%. The combined effect of aerosol extinction and interfering absorption may amount to a bias of 1 to 2% under extensive urban haze and pollution, or following large volcanic events, but otherwise it should be less than about 0.5%. The combination of biases due to the bandwidth effect, the airmass calculation, solar irradiance variability and sampling biases is likely to be negligible.

At an individual station the errors in time averages, viz, monthly, seasonal and yearly means, will also reduce, to the extent that they are random over time. However, there will remain some significant relative

- 390-

biases, in particular, those from errors of adjustment and calibration, which may cause seasonally dependent errors of up to 10% and which may show step changes due to periodic re-adjustment or re-calibration. Interfering absorption can also cause biases at some sites which might amount to say 2% for some monthly data. The total relative bias in yearly mean data, at a guess, might lie at 3% or less for most individual instruments at present, but would have been greater in the past. This is also moderately consistent with the results of the Dobson-BUV TOMS comparison results (2). The ultimate and more hazardous guess is that the yearly mean global ozone column data might have relative accuracies of about 1 to 2%.

6. Conclusion In the full report on this study (1), a number of specific

recommendations were made, with the aim of improving the accuracy of the Dobson instrument and the observat i ona 1 network. Many of the recommendations have been made before by others, but have yet to be implemented satisfactorily. Ozone absorption coefficients, S02 interference, instrument stray light and other optical problems all requi re further attenti on. There is a need to improve the accuracy of the 1 ess standard observation methods, e. g., zen ith cloud method. The present efforts to upgrade instrument operati on, maintenance and calibration, including international intercomparisons, must be continued. Instrument automation deserves encouragement, and there remains a need to better define the ratios of scientific benefit to financial-cost for present and alternative networks.

Error analyses and error reduction efforts are usually very worthwh 11 e, but thei r success i nevitab ly advances the poi nt of diminishing returns, where only small improvements in accuracy are gained for large efforts. At present there remain several large potential error sources, of the order of 5%, which definitely require further attention. However, once these are generally under control, efforts shoul d increasingly concentrate on ensuring the successful routine operation of the network at this sustainable minimum error level, which for individual instruments in the Dobson network might eventually be, overall, about 2% relative uncertainty, plus the 1 to 2% absolute uncertainty due to the uncertainty in any new standard ozone absorption coefficients.

References

1. Basher, R.E., 1982. Review of the Dobson spectrophotometer and its accuracy. WMO Gl oba 1 Ozone Research and Mon i tori ng Project, Rep. 13, World Meteorological Organisation, 94p.

2. WMO, 1982. Report on the meeting of experts on sources of error in detection of ozone trends. WMO Global Ozone Research and Monitoring Project, Rep. 12, World Meteorological Organisation, 48p.

3. Reinsel, G.C., 1981. Analysis of total ozone data for the detection of recent trends and the effects of nuclear testing during the 1960's. Geophys. Res. Lett., 8, 1227-1230. -

- 391-

A STUDY OF SCATTERED LIGHT FROM ZENITH AT LOW SUN IN THE NEAR UV REGION WHERE THE OZONE ABSORPTION CHANGES RAPIDLY

S.H.H. LARSEN Institute of Physics, University of Oslo

Summary

A Dobson Spectrophotometer is used in Oslo for observation of atmospheric ozone. The instrument measures an intensity ratio of direct sunlight or scattered light from zenith sky in the near UV region, light of wavelength 311.4 nm and 332.4 nm, named the C-wavelength-pair. Theoretical calcula­tions of the scattered sunlight received by the instrument with direction of observation towards zenith has been carried out. A simple model with mass scattering points has been used in the calculations. The earth's curvature has been taken into account, ozone absorption layers are put in and both primary and secondary scattered light are calculated. The first and second "umkehrpoints" in the zenith sky curves are reproduced at same positions as observed and the effect of secondary scattering changes in an unexpected way at low sun. The position of the calculated second "umkehrpoint" changes when the sudden change in ozone amount at sunset in 70 km's height is taken into account. This is hard to observe with a Dobson Spectrophotometer.

1.1 The Atmospheric Model

A study of molecular scattering of sunlight may give information about condition in the upper atmosphere by comparing observed and calculated scattered light intensities. The sunrays will on their way through a clear atmosphere loose energy by absorption and molecular scattering. The energy taken from the radiation in the scattering process is reradiated as radia­tion with same frequency. This scattered radiation is anisotropic and the intens~ty I of the scattered radiation is given as I = I s em(3!16TI) • (l+cos z) where z is the angle between the directions o~ in- and outgoing radiation, s is mass scattering number for the atmosphere depending on wave­length, and em is scattering airmass. In our model we let ~ be a mass scattering element representing part of a vertical aircolumn. The contri­bution of scattered sunlight from all ~ along the vertical column will be the scattered light from zenith which our instrument at ground level re­ceives.

The sunlight, before reaching ~, looses energy by absorption and scattering, and the downward scattered light will also loose energy in the same way. Between the mass scattering elements we put ozone layers which take care of the absorption before and after the scattering process in the vertical column. The curvature of the earth is incorporated in the geome­try of the model. This is necessary for calculating intensities of scat-

Ozone Symposium - Greece 1984 - 392-

tered zenith light for sun below the horizon, and will also be important for low sun.

The mass scattering elements are also iluminated by scattered light from the whole atmosphere, not only by direct sunlight. By this we get second and higher order of scattering in the downward radiation. In our calculations we have taken into account primary and secondary scattering. We don't calculate any absolute intensity, but a log intensity ratio of light of wavelengths 311.4 nm and 332.4 nm, the same log intensity ratio as the Dobson instrument measures. In figure 1 the principle of the scat-

I

Fig. 1. Model of scattering atmosphere

tering processes is illustrated.

I primary scattered light II secondary scattered light S sunrays ~M scattering element X ozone layer K direction of incomming

primary scattering

In our model we have used a distance of one km between the mass scat­tering elements for calculating the primary scattered light, and five km's between the mass scattering elements for calculating the secondary scatter­ed light. The top of the model is at 84 km.

The calibration tables for a Dobson spectrophotometer actually gives the N-values which are defined as follows:

N = 10g(I'I) - 10g(I' /1 ) o 0

Here 10g(I'/I) is the measured log intensity ratio of lights of wavelengths 332.4 and 311.4 nanometers, and 10g(I' /1 ) is the log intensity ratio as it would be measured outside the atmos~he~e with the same instrument. Mea­sured and calculated N-values are then compared.

-393-

1.2 Results

Ozonevalues may be evaluated from zenith sky observations by using a curve chart where each curve gives the change of measured N-values for zenith light versus the sun's zenith distance. The individual curves are labeled with an ozonevalue since the ozone in the atmosphere, by its ab­sorption, contribute to the value of the measured N. The construction of such a curve chart is based on simultaneous direct sun observations and zenith sky observations where the direct sun-observations give us the ozone­amounts. There exist a large amount of zenith sky observations which one may compare with calculated values. However, the shape of the N,z-curves depend on the vertical distribution of the ozone in the atmosphere. Of particular interest for us are the observed N,z-curves from Arosa ·(1) ob­tained o~ days when the vertical distribution of ozone was determined from balloon ascents. We have used the vertical distribution from the balloon ascents in our model, as far up as the balloon goes, and calculated N-val­ues for zenith light with an estimated ozone distribution in the top layers mainly based on rocket measurements. The figure 2A shows an observed N,z­curve from Arosa and the corresponding calculated curve. The calculated N-values are based on primary and secondary scattering. Fig. 2B shows the effect of secondary scattering on the N-values. The effect is surprising, we get a steeper N,z-curve. The discrepancy between calcuLated and obser­ved N-values is also an instrumental effect. The Dobson instrument is a double monocromator so we hope that the internal scattering is negligible

N

150

130

110

90

Prinary + second

N /, sc.,ttering

Arosa curve 130 1-,£

440 Dul hf\~~

'l ~ 70

Fig. 2A. Fig. 2B.

" .... /,/ .... ~ 1'/ Calculated

110 'l;,l ~; I curve /, (Primary + '/ secondary) 90

Primary scattering

A B

70

Z 80 90 70 80 90

Comparison between observed and calculated N-values Effect of secondary scattering.

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100 Z

and assume that the instrumental effect is not varying with the zenith dis-tance of sun.

We have continued the calculation of N-values for z > 900 , it is for sun below the horizon, and the second "umkehr-point" is reproduced. When the sun is so low (z is about 940 ), the shape of the curve is very sensi­tive to the ozone amount in the regions above 50 km. If we increase the ozone amount by the value which the photochemical theory gives (2), a change in the shape of the calculated curve, around the second umkehrpoint, will appear. This effect is difficult to register. Attempts have been made in Oslo with a Dobson spectrophotometer (3) and the result is shown in figure 3. A comparison between observed and calculated N,z-curves at the second umkehrpoint may indicate that an increase in ozone at high le­vels exists.

N

120

115

~ Ob,me// ~" curve

Calculated curves, ~ ~ ~ 1 both with primary " + secondary scattering :::::: ---. /

........... /'

92 93 94 95

1.4 DU

o

z

Fig. 3. Calculated effect on the umkehrcurve from the ozone increase above 50 km at sunset.

References

1. DUTSCH, H.U. (1977). Unkehr measurements from Arosa and the vertical distributions measured by ozone sonde ascents from Payerne. Private conununication.

2. LOGAN, J.A., PRATER, M.J., WOFSY, S.C., McELROY, M.B. (1978). Atmos­pheric Chemistry: response to human influence. Phil. Trans. of the Royal Society of London.

3. DAHLBACK, A. (1982). Cand.Real Thesis, Institute of Physics, Univer­sity of Oslo.

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THE AUTOMATED BREWER SPECTROPHOTOMETER

J.B. Kerr, C.T. McElroy, D.I. Wardle, R.A. Olafson and W.F.J. Evans

Atmospheric Environment Service 4905 Dufferin Street

Downsview, Ontario, M3H 5T4 CANADA.

SUMMARY

The Atmospheric Environment Service and Canadian industry have jointly developed a fully automated version of the Brewer instrument which is now commercially available to the international scientific community. The instrument is gradually being introduced in the World Ozone Network and measurements are currently being made at several sites around the world including Canada, Greece, Germany, Sweden and Belgium. -

In the automated mode, the instrument is capable of taking direct sun, zenith sky, UVB and Umkehr measurments in unattended operation for several days. The instrument may be programmed to perform some special routines such as wavelength scanning and sky scanning.

The Brewer spectrophotometer is described and the methods of measuring ozone, S02 and UVB radiation are outlined. The operation of the fully automa~ed instrument is discussed. Results of routine measurements, i-ntercomparative measurements and special experimental programs are presented.

1. Introduction. Development of a grating spectrophotometer to replace the Dobson

spectrophotometer was initiated at the University of Toronto in the late sixties. An early version of the grating instrument is described in reference (1).

A new prototype was built by AES in 1978. It was designed so that various motor d~iven mechanisms could be added to make it capable of fully automatic operation. Sixteen of these instruments have been manufactured to date and all of the additions required for automatic operation are now available commercially. Several of the instruments have now been automated. The configuration of the fully automatic version and recent experience in operating the three units owned by AES comprise the subject of this paper.

2. The Instrument. The spectrometer is a modification of the Ebert type with focal

length 16 cm, width 11 cm and aperture ratio F/6. A coma correcting lens is located between the entrance slit and the collimating mirror. The dispersive element is a 1800 lines/mm holographic grating used in the second order and the detector is a UV sensitive photomultiplier used in the pulse counting mode.

There are six exit slits. One is used for wavelength calibration against the 302nm group of mercury lines. The other five are for intensity measurements and are normally set at 306.3nm, 310.1nm, 313.5nm, 316.8nm and

Ozone Symposium - Greece 1984 - 396-

320.0nm. The bandpass of each is 0.6nm. A Fabry lens is located beyond the exit slits. Its purpose is to make radiation passing through any of the slits fallon the same area of the photomultiplier.

The passage of light through the exit slits is controlled by a moveable wavelength selecting mask, which is driven by a stepper motor. For each of the six slits there is a mask position at which all other slits are blocked. The mask can also be positioned .so as to block all the slits, or so as to leave open two slits (310.1nm and 316.8nm) while blocking the

remaining four. In normal operation, the mask position is cycled so that the

intensities at the five wavelengths are measured sequentially in ascending order of wavelength and then in descending order. A measurement of the dark count, which is the signal when all slits are blocked, is made both at the start and end of the cycle. The dwell time on each slit is 0.13sec and the total duration of the cycle is about 1.6sec. During each dwell time the photon counts are routed to one of five different registers and, while the mask is in transit from one position to the next, the photon counting circuit is inhibited. Thus the photon count accumulated in each register is proportional to the intensity of the radiation passing through the corresponding wavelength slit.

The central path of radiation passing through the entrance slit is horizontal and defines the axis of the fore-optics. The first element in the fore-optics is a reflecting prism which can be rotated about this horizontal axis by a stepper motor. The orientation of the prism determines the zenith angle of observation. The view of the sky is through a slopin~ flat quartz window at the side of the instrument. It is uninterrupted from just below the horizontal up to the zenith.

The fore-optics include a fixed polarizing prism which passes radiation with the electric vector perpendicular to the entrance slit. Neutral density filters and a diffusing ground quartz plate can be independently inserted into the optical path by stepper motors. As well there is an iris diaphram which controls the field of view when the ground quartz plate is in use.

The azimuth of the measured radiation is determined by the orientation of the whole instrument about the vertical axis. Azimuth control has been achieved by mounting the spectrometer and fore-optics on a "single axis suntracker" whose stepper motor is driven by the same electronics package as the other motors in the system. The resolution of this azimuth drive is 0.02 0 and the accuracy is better than 0.2 0 •

For observations on the zenith sky, the azimuth setting affects only the polarization of the measurement. The direct sun azimuth setting combined with the zenith setting of the reflecting prism causes the parallel polarization component of zenith radiation to be measured (i.e. with the electric vector in the solar azimuth plane).

A mercury vapour lamp and a quartz halogen lamp are located immediately below the reflecting prism. They are in the spectrom~ter field of view when the reflecting prism is rotated as if for a zenith angle of 180 0 • Measurements on these lamps permit wavelength calibration and monitoring of the sensitivity of the spectrometer at different wavelengths.

For the measurement of UVB irradiance a thin disc of teflon is used as a transmitting diffuser. The disc is mounted on the top of the instrument under a 5 em diameter quartz dome, and is thus exposed to the horizontal UV irradiance. Under the disc there is a fixed reflecting prism which is located so that the disc is in the spectrometer field of view when the rotating prism is set for a zenith angle of 270 0 •

When irradiance measurements and other wavelength scans are made, the

- 397-

wavelength mask is usually held stationary with only one slit open. The wavelength is scanned by the motor which controls the grating rotation.

3. The Control System. An RCA CDP18S01 microcomputer is located within the instrument. It

coordinates the movement of the wavelength mask motor with the accumulation of photon counts in different registers and drives the five other stepper motors in the instrument. It also controls the reference lamps and, through an AID interface, monitors various supply voltages and the temperature of the instrument. The microcomputer has an internal battery powered precision Quartz clock.

Communication to an external computer or to an manually operated terminal is by an RS-232 link. The microcomputer accepts ASCII commands, executes each commanded task and signals the task completion back to the external computer (or operator). Some of the commands cause measured data to be transfered back to the external computer. Multiple commands are stored by the microcomputer and executed in sequence.

Any particular observation type or instrument test is performed by the external computer issuing a series of commands and then receiving and analysing the measured data. In fully automatic operation the computer follows a predetermined schedule of observations and tests which may continue indefinitely. Analysed data are recorded on floppy discs and data summaries are printed.

The external computers used to date have been the CBM 8032 and the 4032. Recently the control program has been modified for the Commodore 64.

4. Automated spectral scans. Investigation of direct solar spectra was undertaken in order to

verify current S02 and 03 measurement methods. It has proved quite easy to program automatic wavelength scans and to aQuire and manage the data. Figure 1 shows a calculated extra-terrestial spectrum. It was derived from twelve scans taken in clear atmospheric conditions.

Laboratory absorption spectra for S02 and 03 are plotted in Figure 2 which also indicates the normal wavelength setting of the five slits. Figure 3 shows the ratio of two scans taken during clear and polluted conditions. The pattern of S02 absorption is very clear and the estimated amount in the path is about 20 m.at.cm, which is quite large for Toronto. There is no apparent evidence of other molecular absorption in these spectra though N02 absorption may be present.

~2 and Dobson AD measurements. S02 interference with the Dobson AD measurement is the subject of a

previous paper (2). Figure 4 shows a recent very clear example of the effect. The difference between the Dobson 03 measurement and those from the two Brewer instruments is extremely well correlated with the two Brewer measurements of S02.

6. Automatic Operation. Instrument #013 has been run in Edmonton since March 84 with a program

requiring very limited operator intervention. Instrument #015 has been in continuous automatic operation at Toronto since April 84 using a simple measurement schedule. In each daylight hour four five minute periods are devoted to direct sun measurement and four similar periods to zenith sky measurements. Values for 03 and S02 are computed as described in reference (3). Once each hour the wavelength setting is checked and adjusted if necessary and a reference measurement is taken on the quartz halogen lamp.

- 398-

!

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/ I

/

I

I I

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Figure" 2 Absorption Spectr1a

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Figure 1 Extraterrestrial Spectrum

- 399-

Figure 4 Instrument Comparison Data

~ ~ ;;

~ :; ~

i ~ ~ 3 ~ e ~

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Figure 3 Atmospheric S02 Spectrum

!

TABLE I. SUMMARY OF BREWER DIRECT SUN MEASUREMENTS FOR AUG 26/84

MEASURMENTS MADE AT AES HQ (43.8 oN 79.5 0 W) \olITH INSTRUMENT 1'115

TYPE TIME(GMT) TEMP AIRMASS OZONE ERROR S02 ERROR

DS 0 11:22:11 12 6.46 293.2 ±, 19.3 -10.9 ± 16.8 DS 0 11 :32: 11 13 5.506 295.7 ± 8.3 -7.0 ± 4.9 DS 0 11:52:17 14 4.198 308.5 ± 2.0 -2.6 ± 0.7 DS 0 12:02:22 14 3.743 308.5 ± 1.3 -0.6 ± 0.6 DS 0 12:22:39 16 3.07 309.3 ± 0.9 1.2 ± 0.7 DS 0 12:32:48 17 2.819 309.8 :!: 0.8 1.4 :!: 0.3 DS 0 12:53:08 18 2.427 310.2 ± 1.0 l.9 ± 0.4 DS 0 13:03:23 19 2.272 310.8 ± 0.6 l.9 ± 0.3 DS 1 13:23:55 21 2.02 311.6 :!: 0.7 l.7 :!: 0.0 DS 1 13: 34: 15 22 1.917 310.5 :!: 1.7 l.6 :!: 0.5 DS 1 13:54:51 23 l. 747 307.0 ± 1.4 1.8 ± 0.4 DS 1 14:05:17 24 1.676 308.2 :!: 1.1 l.1 :!: 0.1 DS 1 14:25:58 25 1.557 311.2 ± 1.5 l.6 ± 0.4 DS 1 14:36:29 26 1.507 310.1 ± 2.4 l.4 ± 0.6 DS 1 14:57:22 27 1.422 309.8 ± 1.8 0.8 ± 0.5 DS 2 15:08:03 27 1.386 310.5 ± 1.8 0.4 ± 0.4 DS 2 15:28:58 28 1.326 311. 7 ± 1.5 1.0 ± 0.3 DS 2 15:39:39 29 1.301 311.8 :!: 1.4 0.6 :!: 0.4 DS 2 16:00:51 30 1.261 311.4 ± 1.3 l.3 ± 0.5 OS 2 16: 11 :40 30 1.244 310.5 ± 2.1 l.8 ± 0.6 DS 2 16:32:46 31 l.22 311. 9 ± 1.4 l.6 ± 0.4 DS 2 16:43:39 31 1.211 314.0 ± 2.3 l.2 ± 0.4 DS 2 17:05:04 32 1.2 310.2 ± 0.7 1.6 ± 0.5 DS 2 17:16:02 32 1.199 311.5 ± 0.8 l.7 ± 0.4 DS 2 17:37:20 32 1.202 313.5 ± 1.6 l.8 ± 0.5 DS 2 17:48:25 32 1.207 313.2 ± 2.4 2.4 ± 0.7 DS 2 18:10:09 32 1.224 313.8 ± 1.9 2.4 ± 0.4 DS 2 18:21:21 32 1.237 314.3 ± 2.9 2.8 ± 0.7 DS 2 18:40:28 33 1.265 315.5 ± 2.6 1.9 ± 0.7 DS 2 18:51:46 33 1.286 314.0 :!: 1.5 2.5 :!: 0.4 DS 1 19:13:52 32 1.336 311.9 ± 1.4 2.8 ± 0.4 DS 1 19:25:17 32 1.369 312.1 ± 0.6 2.5 ± 0.3 DS 1 19:44:35 33 1.434 315.8 ± 1.3 1.9 ± 0.2 DS 1 19:56:06 33 1.48 315.2 ± 2.3 2.4 ± 0.5 DS 1 20:18:21 32 1.587 312.2 ± 2.4 2.9 ± 0.7 DS 1 20:29:58 32 1.655 313 .8 :!: 0.5 3.1 :!: 0.2 DS 1 20:49:27 32 1.79 315.9 :!: 1.0 2.8 ± 0.4 DS 0 21:01:15 32 1.888 315.3 :!: 1.7 3.1 ± 0.5 DS 0 21:23:43 31 2.122 313.4 :!: 1.3 3.0 :!: 0.3 DS 0 21:35:33 31 2.276 312.8 :!: 1.7 2.6 ± 0.5 DS 0 21:55:12 30 2.6 311.6 :!: 1.4 2.6 ± 0.6 DS 0 22:07:08 30 2.851 312.6 :!: 1.4 2.2 :!: 0.2 DS 0 22:29:52 29 3.505 308.0 :!: 2.9 1.9 ± 0.9 DS 0 22:41:55 29 3.993 306.1 ± 5.8 -1.2 ± 1.4 DS 0 23:04:11 28 5.34 -421.9 ±219.4 134.7 ± 66.8

DAILY MEANS 312 1.9 STANDARD DEVIATION :!:2 :!:0.7

-400 -

Data summaries for each of these four routines are printed at the end of the day. Table I is a summary of direct sun measurements. The daily means of 03 and S02 are computed only from the observations with standard errors less than 2.5 and 1.0 m.at.cm respectively.

Figure 5 is the result of a search for a mean diurnal effect in S02' It demonstrates operational monitoring of S02 but does not show any persistent daily variation.

7. Conclusions. Fully automated Brewer spectrophotometers have operated reliably at

Toronto and Edmonton for several months. The measurement precision compares favourably with the precision from manual operation. The instrument is adaptable. Spectral scans of the direct solar irradiance and other special measurements can be programmed as required. Sophisticated measuring schedules can be developed.

8. References. (1) Brewer, A.W., A replacement for the Dobson Spectrophotometer?, Pure Appl. Geophys., 106-108, 919-927, 1973. (2) Evans, W.F.J., I.A. Asbridge, J.B. Kerr, C.L. Mateer, R.A. Olafson, The Effects of 502 on Dobson and Brewer Total Ozone Measurements, Proc. Inter Ozone Symposium, Boulder, 48-57, 1980. (3) Kerr, J.B., C.T. McElroy, R.A. Olafson, Measurements of Ozone with the Brewer Ozone Spectrophotometer, Proc. Inter. Ozone Symposium, Boulder, 74-79, 1980a.

10

9

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S02 MEASUREMENT S

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AES. TORO NT O APRIL/64 - AUGUST/ B4

BREWER * 15

. - . - _ ... .. , , ,

.. ;:; ,j; '~i~6§ .FH ~L;} ·<j ·:~:r,:.s--~};:,;· · L;2' r'; ... - 1 12: 00 13: 00 14: 00 15: 00 16: 00 17: 00 18: 00 19: 00 20: 00 21: 00 22: 00 23: 00 24: 00

TIME (GMT)

Figure 5 Daily S02 Variation.

- 401-

EXPERIENCES WITH A BREWER SPECTROPHOTOMETER AND INTERCOMPARI­

SON MEASUREMENTS WITH A DOBSON SPECTROPHOTOMETER

U.KOHLER, R.HARTMANNSGRUBER and W.ATTMANNSPACHER DWD Meteorologisches Observatorium Hohenpeissenberg

D-8126 Hohenpeissenberg, FRG

Summary

Since January 1983 the total ozone amount at the Meteorolo­gical Observatory Hohenpeissenberg (MOHP) is measured by two spectrophotometers: The Dobson 104 (since July 1967) and the Brewer 010. The agreement between both instruments was very good in the first three months of 1983 (Ax 1<1%). Since April the standardlamp test of the Brewer hfnted at a gro­win& drift of the spectral sensitiveness. The difference to the Dobson simultaneously increased. After the repair and calibration of the Brewer during September/October 1983 the intercomparison was continued. Anew the standardlamptest showed the instability of the Brewer. The initial discrepan­cy in the measurements of both instruments rose again and additionally showed a dependence on the relative optical depth p of the ozone layer. Since October 1983 the Brewer is automated (Sun-Tracker etc.); the first experience with this auftomation are mainly positive.

1. Introduction

The standard instrument of the total ozone network is the Dobson spectrophotometer, designed more than 50 years ago (1). The Dobson has generally proved itself as a reliable instrument, if is carefully maintained. The disadvantages of its design, due to its age, (2,3) however, let it appear necessary to de­velop modern instruments, like the Brewer.

A few intercomparisons between Dobson and these instru­ments indicated the qualification of the Brewer as a new stan­dard instrument (4,5,6), but also showed the deficiencies of these instruments. In this paper the results of the Brewer-Dob­son intercomparison and the Brewer long time test at the MOHP from January 1983 until March 1984 are represented.

2. Data Collection

Brewer and Dobson are working on the 30 m high tower of the MOHP (latitude: 47.8040 ; longitude:-11.018°; altitude: 975 m a.s.l.). For the measurements they are placed on the southwest orientated balcony of the 7th floor of the tower.

Ozone Symposium - Greece 1984 - 402-

The intercomparison measurements were continuously performed since January 1, 1983 with only two interrupts: during Septem­ber/October 1983 the Brewer was repaired and automated and during two weeks mid June 1983 the mirrors of the Dobson were changed.

The measurements of both instruments are calculated by computer, printed on hard copy and recorded on discs, the Brewer's even on-line. Each month the data of the Dobson are sent to AES in Toronto to be published in the "Ozone Data For The World". Semi-annually they are published by the German Weather Service in the "Sonderbeobachtungen des Meteorologi­schen Observatoriums Hohenpeissenberg". For this intercompa­rison only Dobson AD- and Brewer DS-measurements were used, which did not lie more than 15 minutes apart, because changes of the total ozone of more than 10 DU are possible within half an hour. If the standard deviation of the Brewer measurement was greater than 2.5 DU, it was not used. After all 159 simul­taneous measurements on 96 days were utilized. As the Brewer measures 03 and S02 separately, both values are added to enable a comparison with the Dobson value, which includes S02.

3. Results

3.1. Intercomparison Brewer-Dobson

During the first comparison period from January to August 1983 the Brewer was calibrated with the Brewer 001, the second calibration after repair in October 1983 was done with Brewer 008, but it was corrected with +4% to get coincidence with the second-standard Dobson 77, because of the principle difference between both instruments.

In the first three month the agreement between both instruments was very good, the monthly averages of the relative differences were always smaller' than +1%, daily averages were not larger than +2% (Figure 1). The absolute difference can be seen in Figure 2. The monthly mean values are between -0.7 DU (March 1983) with a maximum standard deviation of 3.29 DU in February, a very good result compared with other Brewer-Dobson intercomparisons (6). From mid May until end of May 1983 the mean differences increased up to -7 DU (~ -2%). This further growing discrepancy reached -16 DU (~-5%) in August 1983.

Standardlamp tests (Figure 3) showed, that the Brewer caused this drift. The instrument had to be repaired and reca­librated; on this occasion it was automated.

Since end of October the intercomparison was continued with the new calibration, which yields 4% higher ozone values than the first calibration. This is perceptible in the monthly averages of the absolute and relative difference, respectively. In November 1983 the mean difference was +6.9 DU (~ +2.45%), the standard deviation 1.64 DU. Until the end of the year the discrepancy decreased, but then rose again, which might be an effect of ap-dependence of the difference between Brewer and Dobson. At the end of March 1984 the mean deviation of the Brewer from the Dobson was 12.2 DU (~ 2.99%). The standardlamp tests gave a hint (Figure 3), that the Brewer was not stable anew. Thus it is obvious, beside the }.l-dependence, that also

-403 -

a Brewer drift caused the increasing difference. Almost continuous measurements on a single day should

confirm the assumption, that at least one instrument shows a diurnal course of ozone, which is not natural based. On March 22, 1984, many measurements could be made with both instru­ments. Brewer and Dobson mainly represent a diurnal course (Figure 4), but instrumental influences can be seen too. It is not possible to decide clearly, which instrument is responsible for the }I-dependence of partly different running curves. More days with simultaneous measurements and without large natural ozone variations are necessary.

3.2. Long Time Test Brewer

The intercomparison with the Dobson has already shown, that the Brewer was not very stable. The initial values of the standardlamp tests did not remain constant during both presen­ted periods (Figure 3). This hinted to a change of the spectral sensitiveness of the Brewer. During the first period this chan­ge was caused by a defective mountin~ of the Ebert grating. Du­ring the second period the change was not yet as large as du­ring the first, but this was also a hint, that something is wrong with the Brewer.

Another source of mistakes during the first period was the "Deadtime" of the Brewer. The required time, which is used in the calculation, was 3.8*10-8 s, whereas the measured time oscillated between 2.5 - 3.5*10-8 s. The effect was a decrea­sing total ozone value with increasing irradiation intensity. In the second period the deadtime has been rather constant at values between 3.5 - 3.8*10-8 s.

If the Brewer is calibrated in the best way, the }I-range, in which it yields reliable measurements reaches from 1 to 5. This was the case after the first calibration. The second cali­bration, performed in Toronto in October 1983, was possible only between 1.5 (because of the season) and 2.5 (because of Brewer 008). The r~sult is a diminishing accuracy at}I>2.5.

4. Conclusion

The results of the 15-month intercomparison Brewer-Dobson and the long time test of the Brewer are:

- A well calibrated Brewer excellently agrees with the Dobson.

- Short measurement duration and automated operation distin-guish the Brewer.

- The Brewer has optical and electronical deficiencies, which are restricting its working.

An improved Brewer shall be an appropriate standard ozone spect~ophotometer.

References

1. DOBSON, G.M.Bo (1931). A photoelectric spectrophotometer for measuring atmospheric ozone. Proc. Physo Soc. 43, 324-328.

-404 -

2. KOMHYR, W.D. (1980). Dobson spectrophotometer systematic total ozone measurement error. Geophysical Research Letter Vo!.7, No. 2,161-163.

3. KOMHYR, W.D., EVANS, R.D. (1980). Dobson spectrophotometer total ozone measurement errors caused by interfering absor­bing species such as S02' N02 anq photochemically produced 0 3 in polluted air. Geophysical Research Letter Vol.7. No.2, 157-160

4. MATTHEWS, VV.A. (1982). Agreement between Dobson spectro­photometer and Filter Ozonometer measurements of total ozone. Journal of Applied Meteorology Vol.ll, 239-241.

5. MVLLER, H., REITER, R. (1980). Intercomparison of New Zealand Filter Ozonometer and Dobson Spectrophotometer total ozone measurements. Pageoph Vol.118, 847-857.

6. PARSONS, C.L. et al (1982). An intercomparison of ground­based total ozone instrumets. Journal of Applied Meteoro­logy Vol 21, 708-724.

Figures

Fig. 1: Daily averages of the relative diffe­rence of total ozone between'Brewer and Dobson. Bars show the monthly mean value.

Fig. 2: Daily averages of the absolute diffe­rence of total ozone between Brewer and Dobson. Bars show the monthly mean value.

.. z:

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- 405-

Fig. 3: Daily averages of the standardlamp test values R5 (re­presenting the S02-measurement) and R6 (representing the 03-measurement).

Fig. 4: Single measurements of total ozone on March 22, 1984.

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-406 -

Summary

OZONE PROFILES DERIVED FROM U~KEHR 0ASERVATIONS OBTAINED WITH THE RREWER OZONE SPECTROPHOTOMETER

C.L. MATEER, J.R. KERR and W.F.J. EVANS Atmospheric Environment Service

Downsview, Canada

A prototvoe inversion system has been developed for use in evaluatinq Umkehr observations taken with the Arewer Otone Spectroohotometer. The evaluation system is based on the optimum statistical method as used with the Dobson short Umkehr method. Ozone profiles obtained from the Rrewer system are presented and compared with concurrent Dobson standard (C wavelength) and short (A, C, D wavelenqths) Umkehr orofiles and with balloon soundinq profiles obtained during the Aalloon Ozonesonde Intercomparison (ROIC) campaign at Palestine, Texas, in June-July 1983 and at Edmonton, Canada, in Aoril, 1984. The performance of the Brewer Umkehr system is quite comparible to that of the Dobson systems. Considering the limited resolution and smoothing inherent in the Umkehr method, the Umkehr profiles agree satisfactorily with the ozonesonde profiles.

1. Introduction

The Arewer Ozone Soectroohotometer (1) was desiqned as a possiblereolacement for the Dobson Ozone Spectrophotometer. One of the requirements for such a replacement is that it be capable of makinq Umkehr observations. Furthermore, a mathematical inversion alqorithm is needed to evaluate these observations and the resultinq ozone profiles should be of a quality equal to or hetter than those obtained with the widely used Dobson instrument.

The desiqn of the Umkehr observation system and the evaluation algorithm should qo toqether in order to optimize the information content of the observations and, therehy, of the deduced ozone profile. This desiqn problem will be described elsewhere in greater detail. In this paper, a brief outline will be qiven.

2. tlmkehr System Design

The Brewer instrument was desiqned primarily for total ozone observations. In order to minimize cloud effects for zenith cloud observations of total ozone (2) the instrument contains a fixed polarizer so that the measurements are made on the parallel component of the incominq zenith scattered radiation. At very larqe solar zenith anqles, this component consists mostly of multiply scattered radiation. To improve the information content about high level ozone, the instrument is oriented at right anqles to the solar plane so that the perpendicular component of the incoming zenith scattered radiation is measured during Umkehr observations.

Ozone Symposium - Greece 1984 -407 -

In addition, in the total ozone measurement mode, the observations are taken in five wavelength bands, viz., 306.3, 310.1, 313.5, 316.8 and 320.1 nm. Two linear combinations of these measurements are made, one for determination of 03, the other for detection of atmospheric S02 (1). It was found that the information content of measurements in these wavelengths was rather poor compared to that attainable with the standard and short Dobson Umkehrs. To improve the situation, the wavelength mask, with its five slits, is shifted during Umkehr observations so that additional measurements at longer wavelengths are also obtained. In making this shift, the second to shortest wavelength slit is set at 320.1 nm, in order to obtain a reference check on measurements at the two mask oositions. In effect, then, measurements are ohtained at three longer wavelengths, viz., 323.2, 326.4 and 329.5 nm.

The Rrewer I~kehr svstem uses the S02 wavelength combination plus three pairs, viz., (306.3,323.2), (3B.5, 32(';.4), and (320.1, 329.5). Although measurements may he taken over the full zenith anqle range from 60° to 90°, as with the standard Dobson Umkehr, it has heen found that the derived profiles change systematically for different zenith angle combinations. Therefore, to eliminate such svstelTlatic differences, the 8rewer system uses the fixed combination from 80° to 89° as in the Dobson short Umkehr (3). These systematic differences are not understood at the present time but are believed to be related either to polarization effects in the instrument or to deficiencies in the radiative transfer code. This will require further investiaation.

In.all other respects, the Brewer system is virtually identical to the Dobson short Umkehr evaluation system. For comparison purposes, the "variance reduction", a measure of the information content of the observations, is given in Figure 1 for the Brewer system, for the Dobson short Umkehr and for a Dobson standard Umkehr evaluation system also identical to the short Umkehr system. It is evident from these curves that the Brewer, Dobson short and Dobson standard systems should perform quite comparably from the troposphere through layer 9.

3. Comparison of Results

Simultaneous comparison data for ECC ozonesondes, Dobson Umkehrs and Brewer Umkehrs are available from the Balloon Ozone Intercomparison Campaign (BOIC) held in Palestine, Texas in June-JUly 1983 and from the Canadian network operational ozone program at Edmonton in April, 1984.

Figure 2 shows the average of 6 ozonesonde profiles and the average of 7 Brewer Umkehr profiles for the period 20 June through 18 July 1983 at Palestine. Figures 3 and 4 show ozone profiles for 2 and 27 April 1984 at Edmonton for ozonesondes and nobson and Rrewer IImkehrs. In the case of Palestine, the sharD ozonesonde peak in layer 5 is not present in the first guess profile and the retrieval system cannot recover a feature with this vertical resolution unless it is present in the first guess. In order to improve Umkehr profile retrievals at the latitude of Palestine, an ozone profile climatology would have to be developed which incorporates this feature. The Edmonton cases indicate profile structure not generally retrievable from Umkehr observations, whether Brewer or Dobson. There is a secondary ozone maximum in the lower stratosphere in the balloon profiles. In both cases, the Umkehr profile smooths out the structure. In principle, it would he possible

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to develop an elaborate statistical basis for the retrieval system which would recover structure of this type. However, it would also recover the structure in many cases where it was not actually present.

Figures 5 and h show the averaqe ratio for each layer of the ozonesonde and Umkehr profiles to the orofile retrieval by the present standard Umkehr evaluation system (4) in use at the World Ozone nata Centre (WODC). Fiqure 5 is for the Palestine comoarisons, Fiqure 6 is for 27 April 1984 at Edmonton. These fiqures illustrate profile differences not discernihle in Fiqures 2-4. For example, althouqh the 3 statistically similar IImkehr systems aive fairlv similar results from the troposphere (layer 1) through layer 7, the Rrewer retrieves lower ozone at hoth Palestine and Edmonton for lavers 8 and 9. Rearing in mind that different Brewer and Dobson instruments are involved at the two stations, it appears that this may he a systematic difference. At present, we are inclined to suspect the treatment of polarization in the Brewer analysis system as the cause of the difference.

Figures 5 and 6 also illustrate the qenerally systematic differences between the statistically similar retrieval systems and the "IODC retrieval system. A more complete discussion of the differences between the Dobson short Umkehr system and the wonc system is oiven by Mateer and DeLuisi (5).

4. Conclusions and Future Developments

A Brewer Umkehr ohservation and evaluation system has been developed'which provides ozone profiles comparable to those obtained with Dobson Umkehr evaluation systems. The systematic differences in layers 8 and 9 require further study. When new ozone absorption coeffficients are recommended by the Ozone Commission and approved by WMO, the present Brewer system, which is a prototype only, will be finalized in a manner to keep it consistent with both Dobson Umkehr systems and BUV-type satellite systems.

Acknowledgements:

The Brewer, Dohson and ozonesonde measurements were carried out as part of the BOIC campaiqn, conducted hy E. Hilsenrath of NASA Goddard. 3. Rellefleur made most of the AES measurements at Palestine.

REFERENCES

1. KERR, J.B., MCELROY, C.T. and OLAFSON, R.A. (1980). Measurements of Ozone with the Brewer Ozone Soectrophotometer. Proc. Ouad. Ozone Symp., Int. Ozone Comm., pp 74-79.

2. BREWER, A. W. and KERR, 3. B., (1973). Total Ozone Measurements in Cloudy Weather. PAGEOPH, Vol. 106-108, PP. 928-937.

3. MATEER, C.L. and OCLUISI, 3.3. (1980). The Estimation of the Vertical Distribution of Ozone by the Short Umkehr Method. Proc. Quad. Ozone Svmp., Int. Ozone Comm., pp 64-73.

4. MATEER, C.L. and DUTSCH, H.IJ. (1964). Uniform Evaluation of IJmkehr Observations from the World Ozone Network, Part I - Proposed Standard Umkehr Evaluation Technioue. National Centre for Atmospheric Research, Boulder, 105 Pp.

5. MATEER, C.L. and DELUISI, 3.3. (1985). A Comparison of Ozone Profiles Derived from Standard Umkehr and Short Umkehr Measurements from Fifteen Stations. In this volume.

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13 10

12 EDMONTON UMKEHRS 27 APR IL 84 PROFILE COMPARISON 80IC/NS8F

9 II JUNE-JULY 1983

10 8

9 7 S-

a: 8 w DO 6 m ill ::E 7 Y ::::> ::E Z :::I

DO Z

S '" 6 DO >- uJ < >--' <

S -' 4

4

v-:~ 3

3 2

OE

2 8 - 8REWER

0 a 0 . 2 .4 • B .8 0 50 100 150 200 FRACTIONAL ~ARIANCE REDUCT ION OZONE PART! AL PRESSURE CNB)

Fig.1 Fig.2

10

PROFlL E5 2 APR 84 EDMONTON OZONE PROF I LES 27 APR 84 8 9

8 DOBSON STD 8 OOBSON SHORT

7 BREWER 7

DO 6 DO 6 w ill m

:>: :I[

::::> ::> z

S z

5 DO DO W ~ >-<

4 t <

-' -'

3 3

2 2

1 1 ! t 0 ----- --1 0

0 50 100 150 200 0 50 100 150 200

OZONE PART1A~ PRESSURE ( B) OZONE PART! A~ PRESSURE CNB)

Fig.3 Fig.4

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11

10

9

a

7

! 6

~ 5 :5

~

3

2

0

PROFILE COMPARISON

aOIC/NSaF

. 6 .a 1.2 I.. 1.6

RhTIO- PROFILE/VOce STANDARD UMKEHR PROFILE

Fig.5

IX .., m

~ '" .., >-< ..J

-411-

10~·----~-----r----

9 EDMONTON 27 hPR a.

a t 7 j - OZONE SONDE

X - DoaSON STD

6 0 - DoaSOr< SHORT

t B - BREWER

5

3

2

o ~-----+~----~-----+----~--. .6 .a 1 1.2 1.4 1.6

RhTID- PROFILE/WODe STANDARO UMKEHR PROFILE

Fig.6

NIMBUS 7 SBUV/TOMS CALIBRATION FOR THE OZONE MEASUREMENT

H. PARK Systems and Applied Sciences Corporation

5809 Annapolis Road, Hyattsville, MD 20784, U.S.A. (Present Address: OAO Corporation

7500 Greenway Center Drive, Greenbelt, MD 20770, U.S.A.)

Summarv

and

D.F. HEATH Laboratory for Planetary Atomsphere

NASA/Goddard Space Flight Center Greenbelt, MD 20771, U.S.A.

SBUV/TOMS onboard the Nimbus 7 satellite is an atmospheric ozone measuring experiment from solar backscattered ultraviolet radiation off the earth atmosphere. The excellent spatial coverage and long lifetime of SUBV/TOMS make this experiment viable for the long term monitoring of the global ozone. This paper presents a technique used in the in-orbit calibration of SUBV/TOMS for the ozone data processing. This technique employs a model to explain ann correct the observed instrument output due to negradation. From the analyses with the corrected data to verify the model, it is concluded that the in-orbit instrument calibration for the ozone measurement is accurate within 2% for the first four years of the instrument operation.

1. Introduction The backscattered ultraviolet (BUV) technique from a satellite has

emerged as a powerful means to measure the global burden of atmospheric ozone. The Solar Backscatter Ultraviolet and Total Ozone Mapping Spectrometer (SBUV/TOMS) Experiment (1) on Nimbus 7 is an updated version of the BUV experiment (2) on Nimbus 4. SBUV/TOMS measures the total amount of the ozone in the atmospheric column and its altitune profile, and maps the field of the total ozone. The ozone amount is determined from the measurement of the ratio of the backscattered radiance to the incident solar irradiance at the ultraviolet wavelengths where the ozone absorption affect.s the ~ackscattered radiance (this ratio may be loosely called albedo and is intermixed with albedo in this paper). The excellent spatial coverage ann the long lifetime of SBUV/TOMS make this experiment viable for long term monitoring of the global ozone. However, the goal of long term monitoring can only be achieved by maintaining a proper calibration of the instrument in orbit. This paper presents a technique used in the in-orbit calibration of SBUV/TOMS for the four years of ozone data retrieval (3). Specifically, the observed evidence of the instrument de@:radation, the instrument correction model, and the assessment of the accuracy of the instrument correction are discussed.

2. Experiment and Observation The SBUV subsystem, composed of a double Ebert-Fastie ~ono­

chromator, monitors 12 selected wavelength bands in the spectral range

Ozone Symposium - Greece 1984 - 4l.t-

from 255.5 nm to 339.8 nm with 1 nm bandpass. The TOMS subsystem, a fixed grating monochromater with 1 nm bandpass, measures the back­scattered radiation at six wavelengths from 312.5 nm to 380.0 nm by selecting different exit slits. The cross-course scanning enables TOMS to map the ozone field. Both SBUV and TOMS normally view the nadir directin to measure the backscattered radiance and deploy a diffuser to intercept and measure the solar radiation at the northern terminator.

The fact that the ozone measurement utilizes the ratio of the back­scattered radiance to the solar irradiance simplifies problems which may arise in the instrument calibration and from the instrument drift during the prolonged operation in orbit. The accuracy of the prelaunch ratio calibration is about 1%. This has been achieved from current state-of­the-art techniques with the radiometric standards calibrated at the National Bureau of Standards (NBS).

Satellite instruments are subject to degradation during operation in space. Accurate assessment of the degration is critical to the success of the experiment. However, this is not an easy task, especially in UV experiments where the current technology does not allow an onboard calibration source. Fortunately, the ozone measurement by SBUV/TOMS requires only a relative mesurement of the backscattered radiance to the incident solar irradiance. Therefore, most of the instrument effects and even the effect of the solar output variation cancel out in the ratio of the two measurements. But because of the different physical nature between radiance and irradiance, the irradi­ance measurement employs an additional instrument component, a diffuser. Thus the calibration correction in the ozone measurement due to the instrument change is reduced to a correction for the diffuser char­acteristic change if the ratio of the radiance to the irradiance is obtained from simultaneous measurement.

The estimation of the diffuser degradation for SBUV/TOMS has been made using the following procedures. SBUV has regularly measured the solar flux once a day and TOMS once a wee~. In two time periods, SBUV measured the solar flux once an orbit, approximately fourteen times a day. This accelerated the degradation of the diffuser and accordingly the instrument output decreased in the SBUV solar flux measurement. Figure 1 shows relative SBUV instrument output at 273.5 nm in the solar flux measurement and the accumulated exposure time of the diffuser to the sun, which indicates a strong anti-correlation between the two variables.

3. Model for the Instrument Output Based on the above fact, a model has been developed to explain the

instrument output in the solar flux measurement and to estimate the diffuser degradation. The model may be expressed in the following equation:

F(t) = F(t = 0) • -d·E(t) • e-s . t e

where F(t) is the instrument solar flux output at time t, F(t = 0) the instrument solar flux output at t = 0, i.e., at the first measurement after launch, E(t) the accumulated diffuser exposure to the sun at time t, d and s are proportional constants related to the degradation of the diffuser and the instrument (excluding the diffuser), respec­tively.

- 413-

This model assumes that the instrument output change due to the diffuser deRradation has a functional form of e-d·E(t'. This assumption is not unreasonable based on the fact that the instrument output change clue to the degradation often shows an exponentiallY necaying shape. The model also assumes that the instrument output due to the instrument degradation other than the diffuser decreases exponentially as a func­tion of time, Le., e- s • t • The model further assumes that the solar spectral jrradiance at the SBUV/TOMS ozone measuring is constant. At present, no definite evidence of measurement exists for the solar output change in the midclle ultraviolet except for some Fraunhofer lines. For the convenience of fitting the data to the model, the logarithmic form of the equation has been used as shown below:

log F(t) = log F(t = 0) -d·E(t) - s·t

A multiple linear regression in terms of E(t) and t is made for the measured solar flux data to obtain d and s values. This regression is possible because E(t) has a unique functional shape as shown in Fip;ure 1. The regression result from four years of SBUV data for the ozone measuring wavelengths shows that:

1) 99.R% of the variance is explained by the model. 2) The standard deviation of the residue is of the order of 0.5%. 3) Standard errors of d and s are less than 1% and 2%, respec­

tivelv.

This indicates that the model explains the measured data extremely well. The d value obtainecl as described above has heen used to correct the ratio of the backscattered radiance to the incident solar irradiance for both SBUV and TOMS.

4. Discussion The total instrument output chanp;e due to the diffuser degradation

is less than 30% for four years of SBUV data. Conseauentlv, the uncer­tainty of the instrument correction for the ratio of the radiance to the irradiance is onlv on the order of 0.3% from the standard error of d for a period of four years if the model reflects the physical reality. Since there is no direct way to verify the model and its result, a few indirect ways have been used to confirm the accuracy of the instrument correction for the ratio (radiance/irradiance) measurement. A check is made with the zonal 25 0 S to 25 0 N averaged albedo at 339.8 nm. At this wavelength, the ozone absorption i.s very weal(. If the average annual cloudiness over the equatorial zone is constant, the measured albedo by SBUV for the period of four vears will show no trend despite the seasonal variation of the albedo. No significant trend of albedo chanp;e at 3:19.8 nm has been identified even thoup;h the amount of the correction for the diffuser degradation is about 10% at this wavelength. Another check has been made by examining the trend of the minimum reflectivity of a desert area. It is not unreasonable to assume that the reflec­tivitv of the desert remains constant from one year to another. No s~nificant change of the reflectivity has been detected. The third check is made based on the fact that the ozone absorption spectrum is more or less symmetric about 250 nm. We can choose two wavelengths, one above 250 nm and the other below 250 nm, which have the same ozone absorption cross section. Since the optical degradation has a strong

-414-

wavelength dependency, the required instrument corrections for the diffuser degradation are Quite different at the two wavelengths. The observation shows that the albedos at two wavelegths vary in the same wav. It has to be emphasized that the ahove checks can be done only within limitations hecause of insufficient data or the uncertainty of the assumption that the ohysical variables are constant. Considering all the facts examined we conclude that the instrument correction for SBUV/TOMS for the albedo measurement is prohably accurate within 2% for the first four years of the instrument operation.

5. Concluding Remarks Since SBUV/TOMS measures the atmosphere ozone from the ratio of the

backscattered radiance to the incident solar irradjance, the drift of the instrument characteristic and the solar output variation do not contribute to the uncertai.ntv of the ratio, but the diffuser degradation does. Therefore, the accuracy of the SBUV/TOMS radiance/irradiance ratio measurp.ment depends on the accuracv of the correction for the diffuser degradation. A model has been developed to explain the inst.rument output in the sola ... flux measurement and to estimate the instrument change due to t.he diffuser degradation. The model is based on the fact that the instrument output change due to the degradation has an exponentially decaying shape. The model assumes that the instrument output decreases exponentially to the accumulated diffuser exposure to the sun. The model further assumes that the instrument output decreases exponentially as a function of time due to the rest of the instrument. The "'egression of the model with the measured data shows an excellent fit. The' regression result implies that the uncertainty of the diffuser correction is less than 0.3% for the first four years of SBUV/TOMS data. Since there is no direct way to confirm the model and the accuracy of the result, indirect techniques have been used to verify the model. The measured alhedo with the diffuser correction has been examined assum5ng that the equatorial albedo and the minimum reflectivity of the desert at 3~9.R nm is constant. The measured albedos with the diffuser correction at the two wavelengths above and below 250 nm which have the same ozone ahsorption cross section show the same variation within the uncertainty of the techniques even though different diffuser corrections are required. From this examination, we conclude that the model can be used for instrument correction of the albedo measurement with an accuracy within 2% for the first four years of the instrument operation.

Acknowledgement It is a great pleasure to acknowledge the NASA Ozone ProceSSing

Team (OPT) for the support of this work. Without the contrihut.ion from each team member, this work could not have been achieved. One of the authors (H.P.) than1{s OAO Corporation for typing the photo-reany manu­script. The work by one of the authors (H.P.) was performed under the NASA contract NAS5-27393.

References 1. Heath, D.F., Krueger, A.J., Roeder, H.R., and Henderson, B.D.

(1975), Optical Engineering, 1!, 323~331. 2. Heath, D.F., Mateer, C.L., and Krueger, A.J. (1973), Pure Appl.

Geophys., ~~, 1238_1253. 3. The four years of processed ozone data from the SBUV/TOMS

experiment are available from the National Space Sciences Data Center at the NASA/Goddard Space Flight Center in Greenbelt, Maryland.

-415 -

0.850

0.800

0.750

0.700

0.050

J M 5 J M 5 J M 5 J M 5 J N 5

700.00

600.00 01 FF EXPOStR:

If()(J1S)

500.00

J M 5 J M 5 J M 5 J M 5 J M 5

1979 19aJ 1981 1982 1983

Figure 1: the top figure shows the relative instrument output at 273.5 rum in the SBUV solar flux measurement and the bottom figure the accumulated exposure of the diffuser to the sun.

-416 -

Summary

GROUND-BASED MICROWAVE OBSERVATIONS OF MESOSPHERIC OZONE AT THE BORDEAUX OBSERVATORY

1 1 J. de LA NOE, C. TURATI, A. BAUDRY

N. MONNANTEUIL,2 J .M. COLMONT 2 and P. DIERICH 3

1 Observatoire de Bordeaux, France 2 Laboratoire d'Optique Ultra-Hertzienne, Universite

de Lille, France 3 Observatoire de Paris-Meudon, France.

Since 1980, a millimeter-wave radiotelescope located at the Bordeaux Observatory has been used to monitor mesospheric ozone at 110.836 GHz and carbon monoxide at 115.271 GHz. The used equipment is briefly described. Observations of ozone carried out during the four past years will be pre­sented, including results concerning the ozone intercomparison campaign of June 1981 and the european MAP/GLOBUS campaign of September 1983.

From the observed spectra we derive : i) integrated ozone content above an altitude of about 40 km ; ii) vertical concewtration profiles above 40 km deduced from model-fitting computations by using temperature profiles obtained by LIDAR measurements at the Observatoire de Haute­Provence and collisional broadening coefficients measured at the labora­tory; iii) diurnal variationsfrom different altitude ranges.

1.1. Introduction During the last ten years, spectroscopic observations of molecules

in the interstellar medium havebeen considerably developed by means of he­terodyne techniques in the radio millimeter-wavelenght range. These techni­ques can also be applied to the remote sensing of some minor constituents present in the terrestrial atmosphere such as ozone and carbon monoxide at different frequencies, such as 110.836021 and 115.271202 GHz, respectively.

The microwave equipment was set up at the Bordeaux Observatory in 1979 for the measurement of interstellar molecules lines, thanks to the col­laboration of the radioastronomy groups of the Bordeaux and Paris-Meudon observatories. Astrophysical observations were carried out regularly since May 1980. The terrestrial atmosphere molecule lines were first detected in November 1980. Then, they have been observed sporadically with an average observing time of 10 % per year. We participate in two ozone intercompari­son campaigns: the french campaign in june 1981 (1) and the european MAP/ GLOBUS campaign in September 1983.

1.2. Equipment Extensive description of the complete microwave equipment is repor­

ted in (2). Since, numerous improvements and modifications were brought to the system; however, the given description still remains valid. The equip­ment is contituted by a 2.5 m dish which is altitude-azimuth mounted. It includes a 20 K liquid-helium cooled receiver whose total frequency cover-

Ozone Symposium - Greece 1984 - 417-

age is 80-120 GHz. At 110 GHz the beam width is 4.4'. The receiver tempe­rature reaches 300-400 K double side band around 110 GHz. The high fre­quency receiver is followed by a 256 channel spectrometer, whose indivi­dual bandwidth is 100 KHz. The total analyzed bandwidth is 25.6 MHz. A DEC 11/34 computer controls the system and the data acquisition.

1.3 Observations Many sequences of observations of the ozone molecule line were car­

ried out since November 1980 until now but sporadically distributed in time. The up-to-date list is available. Some of the observing sequences were held including sunrise and/or sunset local times, so that it is pos­sible to study the diurnal variation of ozone content from several alti­tude ranges. The data are interpreted by means of three ways : i) inte­grated ozone content above 40 km ; ii) vertical concentration profiles iii) diurnal variations.

The total bandwidth of the spectrometer, i.e. 25.6 MHz, restricts the analysis of the data to the altitude range : 40 km < h < 85 km. These limits are deduced from figure 4 of (3) which shows variations of Doppler and collisional broadenings versus altitude. The collisional broadening curve is computed by using coefficients measured in the laboratory (4). Two spectra are shown, as examples, in figure 1 : one corresponds to day time measurements and the other to night time observations;' The original spectra are integrated over 10 minutes and then stored. Then it is possi­b le to sum up any number of these to get average spectra for day-or night­time, with a better signal to noise ratio.

T. K .12 85 Dog S Sept. 1983 03-110 240 H{n

S.O

0.0

-10.0 -5.0 0.0 5·0 10.0 11Hz

T. K.11 85 Dog 5 Sept. 1983 03-110 340 H{n S.O

0.0

-10.0 -5.0 0.0 5.0 10.0 HHz

- 418-

Figure 1 : average spectra for a daytime sequence on September 5, 1983 and for a nighttime se­quence on September 6, 1983. One notes the clear difference of intensities due to increased con­centration of ozone during the night at high altitudes.

1.4 Results 1.4.1. !~~~BE~!~~_~~~~~_~~~!~~! Assuming that the atmosphere is stratified and th~t the ozone layer

is optically thin, the antenna temperature corrected for the atmosphere is given by T* = TO TO secz, in which T03 is the ozone temperature com­puted from a remper~tur~ profile in the corresponding altitude range,T03 is the ozone opacity which can be deduced from this equation, z being the zenithal distance of the observations. The density column is given by

NO =~~n dZ in which nO =lOOTo dv. Some values of NO are given in Table 3 ! mU13 3 00 3 1 7 3

I ; their order of magnitude is a few 10 molecule/cm2 for altitudes hi­gher than 40 km.

Table I

Integrated ozone content above 40 km for the european MAP/GLOBUS campaign

Date Day/Night N03 17 _2

10 cm Date

1.09.83 D 3,6 + 0,4 15 .. 09.83 1.09.83 N 4,0 +" 0,4 16.09.83 2.09.83 D 3,2 +" 0,3 17.09.83 4.09.83 D 3,8 +" 0,4 19.09.83 5.09.83 D 3,8 +" 0,4 19.09.83 5.09.8~ N 4,3 +" 0,4 20.09.83 6.09.83 D 4,2 +" 0,4 20.09.83 7.09.83 D 4,0 +" 0,4 21.09.83 8.09.83 D 4,2 +" 0,4 22.09.83 9.09.83 D 3,6 +" 0,4 22.09.83 9.09.83 N 3,8 +" 0,4 23.09.83

10.09.83 D 4,3 +" 0,4 24.09.83 10.09.83 N 4,7 +" 0,5 24.09.83 11.09.83 D 4,3 +" 0,4 25.09.83 12.09.83 D 4,0 +" 0,4 26.09.83 13.09.83 D 3,3 +" 0,3 27.09.83 13.09.83 N 5,1 +" 0,5 28.09.83 14.09.83 D 4,3 +" 0,4 28.09.83 14.09.83 N 4,8 ~ 0,5 29.09.83

30.09.83 17 _2

Average daytime NO = 3.85 ~ 0,05 10cm 17 2

Average nighttime' N03 = 4,85 ~ 0,05 10 tm-

1.4.2 Y~E!i~~1_S~~£~~E!~Ei2~_E!2f!1~

Day/Night N03 i7 _2

10 cm

D 3,7 + 0,4 D 4,0 +" 0,4 D 4,0 +" 0,4 D 4,0 +" 0,4 N 4,9 +" 0,5 D 4,4 +" 0,4 N 4,9 +" 0,5 D 4,3 +" 0,4 D 3,3 +" 0,3 N 4,2 +" 0,4 D 3,4 +" 0,3 D 3,5 +" 0,3 N 3,8 +" 0,4 D 3,7 +" 0,4 D 3,9 +" 0,4 D 4,0 +" 0,4 D 3,9 +" 0,4 N 4,3 +" 0,4 D 3,8 +" 0,4 D 3,7 +" 0,4

Neglecting diffusion, the radiative transfer equation may be simply written if one considers that the atmosphere is stratified. We consider 45 layers 2 km - thick in which temperature and density are assumed to be constant. Computations have been done assuming that only remains the 3K cosmological radiation. We use temperature and pressure profiles given by the LIDAR technique at the Observatoire de Haute-Provence (5). The exact calculation of vertical distribution implies the inversion of the transfer radiation. The solution may be obtained more simply if one assumes the altitude dependence of the concentration. We chose the model proposed in (6). It is based on six parameters: density, form factor and altitudes of the two maxima of the profile :D l , Zl' r 1 and DZ' Z2' r 2 •

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The profiles computed for 19 and 26 june 1981 are shown in figure 2 of (1). Figure 2 of this paper show profiles deduced from the spectra dis­played in Fig. 1.

1.4.3. Diurnal variations The cu~~-~f-th~-c~llI~I~nal broadening versus the altitude (Fig. 40f

(3» allowsto determine the number of the spectrometer channels corres­ponding to a given altitude. From these we can compute the ozone content in a given altitude range and then study the variation versus time. We selected the following ranges : Z > 80 km, 70 < Z < 80 km, 60 < Z < 70 km, 50 < Z < 60 km and 40 < Z < 50 km. Examples for these four cases are given in figure 3 on which are reported the local sunrise and sunset times. In spite of the important noise fluctuations, the correlation with these events is clearly seen.

1.5. Conclusion Some results derived from spectroscopic measurements of the ozone

line at 110.836 GHz are given: integrated ozone contents over 40 km, ver­tical concentration profiles, and diurnal variations. Most of our data obtained the four past years are being processed. In next future, we plan to increase the average annual observing time to insure a better coverage of the longer-term variations of the ozone concentration. An other impor­tant improvement is planned which will be an abs.olute calibration system: this should help to increase the accuracy (10-15 %) obtained at the pre­sent time.

REFERENCES

1. DE LA NOE, J., BAUDRY, A., PERAULT, M., DIERICH, P., HONNANTEUIL, N. and COLMONT, J.M. (1983). Measurements of the vertical distribution of ozone by ground-based microwave techniques at the Bordeaux Observatory du­ring the June 1981 intercomparison campaign. Planetary Space Science. 1..!., 737-741.

2. BAUDRY, A., BRILLET, J., DESBATS, J.M., LACROIX, J., MONTIGNAC, G., ENCRENAZ, P., LUCAS, R., BEAUDIN, G., DIERICH, P., GERHONT, A., LANDRY, P. and RERAT, G. (1980). A.new spectroscopic facility at millimeter wave­lenght. Journal Astrophysics. Astronomy 1, 193-196.

3. DE LA NOE, J., BAUDRY, A., MONNANTEUIL, N., COLMONT, J.M. and DIERICH, P. (1983). Observation par detection heterodyne en ondes millimetriques au sol de deuxmnstituants minoritaires de l'atmosphere. C.R. Acad.Scienc. Paris 11-296, 1243-1248.

4. COLMONT, J.M. and MONNANTEUIL, N. (1984). Measurements of N2-,02-,and air-broadered linewidths of ozone in the millimeter region : temperature dependence of the linewidths. Journal Mol. Spectrosc. 104, 122-128.

5. HAUCHECORNE, A. and CHANIN, M.L. (1980). Empirical fits to the Voigt line width: brief review. Geophys. Res. Lett. l, 564.

6. SHIMABUKURO, S.I., SMITH, P.K. and WILSON, W.J. (1977). Estimation of the daytime and nightime distribution of atmosphere ozone from ground­based millimeter wavelenght measurements. J. Appl. Met. ~, 929.

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OZONE AND WATER VAPOR IN THE MIDDLE ATMOSPHERE

MEASURED WITH AN AIRBORNE MICROWAVE RADIOMETER

R.GYGER K.F.KUNZI Institute of Applied Physics, University of Berne, SWitzerland

G.K.HARTMANN Max-Planck-Institute for Aeronomy, Lindau (Harz), Germany(FRG)

Abstract:

Airborne passive micr~Nave sensors are well suited to measure the composition of the strato- and mesosphere. During the MAP-\HNE-Campaign (Winter in Northern Europe) simultaneous airborne microwave measurements (Ozone and Water Vapor) and rocket expe­riments were performed. Here we report on our Ozone and Water Vapor profiles obtained during two flights over a latitude range of 68° - 75° north at a longitude of 10 0 and 25° east in January 1984.

1. Introduction

The middle atmosphere consisting of the stratosphere and mesosphere (10 - 100 km) is one of the less well known regions of the atmosphere. The goal of the MAP-WINE project is to improve our knowledge on composition and dynamics of these layers, during the winter season in northern Europe. More than forty scientific groups are worldwide involved in this program, performing measurements using sensors in satellites, rockets, balloons, airplanes and on the ground. Special questions to be addressed are the study of sudden stratospheric warmings and effects of dynamics and temperature structure on the distribution of minor constituents and to intercompare in-situ measurements with new remote sensing techniques. Our contribution to the latter part was the measurement of Ozone and Water Vapor concentration with an airborne rom-wave radiometer simultaneously with a german rocket experiment making similar measurements with a cooled infrared photometer.

Ozone Symposium - Greece 1984 -423 -

2.Theory

The intensity and spectral distribution of the thermal radiation emitted by rotational transitions of atmospheric molecules contains information on density and altitude distribution of the considered constituent. At microwave frequencies the radiative transfer equation takes a particular simple form since scattering is unimportant at these wavelength and the source function can be replaced by the Rayleigh-Jeans approximation. In the microwave band resonances are usually well separated, therefore we can assume only the constituent under investigation to contribute to the emission and attenuation.

H h

I (-;»=I s exp( -()+cJ T (h)' V(h) . f( a,p) . exp(-J V(h) f( a, p) dh I ) • dh 1) Ho Ho

wi th C = 2k"'V ').. I c '2. H

It =SV(h)'f(a,p)'dh Ho

H total al ti tude of the atmosphere ~ 100 km

Ho = al ti tude of observer ~ 10 km

The first term in equation 1 is the background radiation Is attenuated by the atmosphere with the total opacity IL, this term is very small for an uplooking sensor. The integral in equation 1 describes the atmospheric emission and self absorption, this term depends on temperature T(h), concentration-profiles V(h) of the molecule, and the molecular spectroscopic parameters such as absorption-coefficient a and pressure-line-broadening p. It is this latter parameter which allows to retrieve altitude information from a measurement of I(~) over a sufficiently large bandwidth, because the width of the resonance line is proportional to pressure up to ~ 80 km altitude and therefore narrow lines have to originate at high altitudes and broad lines at low altitudes.

The mathematical technique to retrieve the altitude distribution V(h) of the investigated molecule from a measured set of intensities I (-V) has been described in detail by Randegger [1] and Kunzi [2]. The altitude range accessible by this method is approximately 20 - 80 km with an altitude reso­lution of 10 km. The accuracy of this technique is about 1 to 2 ppm.

3. Techniques

Fig. 1 shows the block schematic of the experiment, which is installed in the meteorological research aircraft (Falcon­Jet) operated by the German Air- and Space Research Organisa­tion (DFVLR). The measurements are typically taken at altitudes of ~10 km in order to avoid the attenuation of the tropospheric Water Vapor.

-424 -

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The system accommodates two MW-frontends (Ozone at 142 GHz and Water Vapor at 183 GHz). The spectrum analyzers, consisting of two acousto-optical "Filterbanks" have resolu­tions of 1 MHz over the total bandwidth of 500 MHz and 0.1 MHz resolution over the center 50 MHz. The instrument is controled by a mini computer which also preprocesses the data, displays "the measured resonance lines, and stores the data on magnetic tape.

The measurements were performed during the MAP-WINE campaign on January 24 and 25, 1984. Starting from the base at Kiruna (Sweden), latitudes from 68 to 75 degrees were covered. Fig. 2 shows a map of the measuring areas the MW-sensor and rockets launched Andoya, Norway.

for the in

4. Measurements

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10° 200

Fig. 2 Location of test sites

-425 -

Fig.3 displays a typical measured Ozone line. For comparison the calcu­lated lineshape from the corresponding retrieved profile (see Fig. 4) is also given.

Fig. 3 03-line 142 GHz

xx measured retrieved

OFF CENTW FREOUENCY IMI IZI (ENTER ll.111S GIIZ

In Fig. 4 and 5 our measured 03 and H~O profiles are compared with other experimental and theoretical data. During one of the Ozone measurements (profile A in Fi9. 4) and for both Water Vapor measurements (Fig. 5) the reference oscillator did malfunction (increased frequency jitter), this results in a lower maximum altitude for the retrieved profi~es .

III 80

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-426 -

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Our Ozone profiles are in good agreement with the US stan­dard profile for arctic winter and other measurements taken over the same latitude range. The Water Vapor data fits into the middle of a very wide range of measured profiles. However it has to be considered that for Water Vapor the data is extremly sparse and Fig. 5 contains data from all latitudes and all saisons. At present no rocket data is available for comparison.

5.Acknowledgement

The authors are greatful to the Deutsche Forschungsgemein­schaft (DFG), the Max-Planck-Gesellschaft and the Swiss Natio­nal Science Foundation for their financial contributions, and would also like to thank the DFVLR Oberpfaffenhofen for the good support while conducting the aircraft experiment. The research reported here was partly financed by DFG under project MIWI Az Ha 1141/4-1.

[lJ A. Randegger

[2J K.F.Kunzi E.R.Carlson

[3J M.Allen et al.

[4J H.U.Dutsch

[5J J.M.Russell et al.

[6J R.M.Bevilacqua et al.

[7J R.S.O'Brien W.F.J.Evans

[8J J.W.Waters et al.

[9J J.W.Rogers et al.

[10J H.E.Radford et al.

[11J K.U.Grossmann et al.

[12J K.F.Kunzi et al.

6.References

Pure Appl. Geophysics Vol. 118, p. 1052-1065, 1980 J. of Geophys. Research Vol. 87, No C9, p. 7235-7241, 1982 J. of Geophys. Research Vol. 89, No D3, p. 4841-4872, 1984 Pure Appl. Geophysics Vol. 116, p. 511-529, 1978 NASA Upper Atm. Res. Summaries p. 293-298, 1984 J. of Geophys. Research Vol. 88, No C13, p. 8523-8534, 1983 J. of Geophys. Research Vol. 86, No 12, p. 101-107, 1981 in 'Atmospheric Water Vapor' p. 229-240, Academic, New York, 1980 Geophys. Research Letters 4 p. 366-368, 1977 J. of Geophys. Research Vol. 82, No 4, p. 472-478, 1977 ESA Symposium SP-183 p. 83-87, 1983 ESA Symposium SP-183 p. 173-174, 1983

-427 -

VERTICAL PROFILES AND COLUMN DENSITY MEASUREMENTS

OF OZONE FROM GROUND-BASED MM-WAVE SPECTROSCOPY AT MAUNA KEA, HAWAII

A DEMONSTRATION OF CAPABILITIES

J.Barrett, A. Parrish, R.L.de Zafra, and P.Solomon State University of New York, Stony Brook, New York,U.S.A

Using ground-based microwave techniques, we have observed the pres­sure broadened emission line of stratospheric ozone at 273.0509 GHz, due to the 18+ 17+180 18 transition in the ground vibrational state of 1603 . Ob­servat~&ns were made at approximately 23h local time on 8, 9, 10 and 11 June 1983 from the Mauna Kea Observatory, on the island of Hawaii, at lati­tude 1998 N, and an altitude of 4.2 km. The integration time for each ob­servation was 20 minutes, which under good conditions at "this high, dry site gives a signal/noise (ratio of peak intensity of line to rms of noise). of 500 or better, at our maximum frequency resolution of 1 MHz/channel, and even higher if the data is smoothed over a few channels.

Since the line is pressure broadened, the line intensity at different frequency offsets from the line center is most strongly contributed to by ozone at different altitudes. This fact, together with the high signal/ noise qf our data, enables us to deconvolve our data to recover a reasonably ac~urate distribution of ozone in altitude. The altitude range over which this can be done (approximately 20 to 55 km.) is limited on the low end by our total bandwidth of 256 MHz, and on the high end by our resolution of 1 MHz. We have used two different methods to deconvolve our data. Both involve comparing the observed line shape with one calculated from an init­ital arbitrary distribution, and adjusting this distribution to give the best match to the observed lineshape. Both methods also adjust a linear baseline to be subtracted from the data, to allow for any linear slope or DC offset it may contain. The first method (LSQ method) uses a non-linear least-squares fitting routine, and the second (CTR method) an iterative technique due to Chahine et al. (1) and combining modification suggested by both Twomey (2) and Randegger (3), and further modified to handle lines as strong as the one observed, where the radiative transfer through the strato­sphere can not be linearized. We are currently running this second method on a DEC VAX computer, where it is very fast, producing usable results in 10 or 20 iterations, taking only a few seconds.

In the figures we show our deconvolutions of the 8 June data com­pared to ozone distributions derived from Umkehr and ECC sonde balloon measurements made earlier the same day from other locations on the island of Hawaii. See paper 5.29 in these proceedings for an analysis of the latter.

The deconvolutions yield column densities of ozone above 20 km. of 5.4 x 1018cm-2 for 8 June, and 5.1 x 1018 cm-2 for 11 June. Above 30 km. the values are 1.8 x 1018 cm-2 for the 8th, and 1.7 x 1018 cm-2 for the 11th. The practical vertical resolution for the CTR deconvolution method appears to be "'7 to 8 km. The LSQ method seems capable of yielding "'5 km resolu­tion, in that computer iterations converge reasonably well on a result similar to those obtained from the other methods when the stratosphere is layered into 5 km thick slices for application of the LSQ technique.

In Fig. 5 we have illustrated the ability of the CTR technique to re­cover a vertical profile. In this sequence, we have used a model profile to compute its equivalent pressure-broadened emission line shape, then fed

Ozone Symposium - Greece 1984 - 428-

this lineshape to the computer as "data" to be deconvolved. Starting from an initial deliberately bad guess, the CTR routine recovers a good approxi­mation in 5 iterations and a much better one in 20. The presence of more than ~l% random noise in the signal line shape causes a rapidly increasing degredation of the results however.

References 1. Chahine, M.T., J. Opt. Soc. Amer. ~, 1634 (1968). 2. Twomey, S. et al., J. Atmos.Sci. 3q; 1085 (1977). 3. Randegger, A.K., Pageoph.118, 10SZ-(1980).

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273 . 1 Figure 1: Data from 8, 9, 10 and 11 June 1983, individually calibrated. Since different days' data may contain different slopes and DC offsets, a linear baseline has been subtracted from each spectra, forcing it to zero near each end of the bandpass. This permits the spectra to be compared with a minimum of processing, and it is seen that the 11 June data differs substantially from the other days.

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Figure 2: Data from 8, 9, 10 and 11 June 1983, normalized to the same peak intensity, showing that the 11 June data differs from that of the other days in line shape as well as intensity.

-429-

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-430-

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VALIDATION OF A FAST LINE-BY-LINE TRANSMITI'ANCE/RADIANCE ALGORITHM AGAINST TIROS-N SERIES CHANNEL 9 (OZONE)

Surmary

N .A. SCOTT, A. CliEDIN and N. HUSSON Lalx:>ratoire de Meteorologie Dynamique du CNRS

Ecole Polytechnique, 91128 Palaiseau Cedex, France

The validation of the "4A" (Autanatized Atnospheric Absorption Atlas) M:ldel (Channel 9 at 9.6 J.IIlI) has been attempted through two different approaches : - "Experimental" approach using in situ measurements of Ozone profiles

made during the June 1981 Ozone Intercomparaison campaign held at Observatoire de Haute-Provence.

- "Theoretical" approach. This approach is based upon comparisons between NOM-7 channel 9 observations and "4A" ccmputed brightness temperatures obtained fran : collocated radiosoundings, total ozone content retrievals given by NESDIS (DSDV files), scaling rrean or standard Ozone profiles developed for different latitudes.

Deviations between "4A" s:i.mulated and observed brightness temperatu­res are discussed.

1.1 Introduction

The fast line-by-line type transmittance and radiant energy algoritbm the "Autanatized Atnospheric Absorption Atlas - 4A" has been developed a few years ago by N.A. Scott and A. Chedin (1981) and is described in Ref. (1). The so-called "4A" nodel is used to ccmpute brightness tempera­tures in the infrared and the microwave channels of the TIROS-N OperatiO­nal Vertical Sounder (rovS) of the series of operational polar-orbiting rreteorological satellites : TIROS-N (launched in 1978), NOM-6 (1979), NQAA-7 (1981), NOM-8 (1983) i arrong the 19 infrared sounding channels of HIRS-2 (High Resolution Infrared Radiation Sounder), channel 9 centered at 9.6 J.IIlI is used for measuring Ozone. The ccmputed brightness temperatures correspond to atnospheric situations described by radiosonde reports col­located with satellite observations, either over sea or over land and dis­tributed over all latitude zones i they are divided into classes represen­tative of one latitude zone (polar, mid or tropical). In connection with the validation of "4A" channel 9 through two different approaches, the one "experimental" and the other "theoretical", comparisons between satellite observations and "4A" canputations are presented and discussed.

1 .2 "Experimental" approach : the Ozone Intercomparison campaign, held at Observatoire de Haute-Provence, France (June 1981) (2)

During the Ozone Intercomparison carrpaign perfonred in the South of France fran 9 to 26 June 1981, a variety of instruments and instrumental

Ozone Symposium - Greece 1984 -432 -

methods were used (3) to probe the atrrosphere Ozone content; satellite data observed above the sites fran existing Ozone experiments have also been used and reliable temperature and Ozone profiles have been obtained. NOAA-7 channel 9 has been "validated" against a set of six collocations obtained fran 17 to 22 June 1981. The agreerrent obtained (see Table I) was alnost perfect provided the intensity of the V3 band of Ozone archived at that time on line parameters catalogs (4) (5) be multiplied by a factor of about 1.10. This has been experimentally confinred (6) and the new inten­sity values are now available.

The results of intercanparison of TIROS-N rreasurerrents in Ozone chan­nel and "4A" m::xlel c:cxrputations using lidar and balloon borne Ozone mea­surements are presented in Table I and Figure 1, which recall principally the results of Ref. (7). lITBl and lITB2 are differences between "4A" c:cxrpu­ted (TB.calc.) and'DJVS observed (TB.obs.) brightness temperatures values (lITB = TB.cal. - TB.obs.), respectively before and after the correction (SV3 x 1.113) of the intensity SV3 of the V3 Ozone band (6). ffi and cr re­present respectively the rreans and standard deviations of those differen­ces and are satisfactorily small, especially for cr which determine the physical coherence of the m::xlel.

1.~ "Theoretical" approach: CX?1!1parisons between satellite observations and "4A" computations using 'DJVS radio sonde matched data.

344 'DJVS radio sonde matched data (see Table II) have been used for NOAA-6, NOAA-7 (Jan.-Feb. 1982) and NOAA-8 (sl.lItlla' 1983 and Jan.-Feb. 1984). These selected matchups were extracted fran files regularly archived by NESDIS, the so-called DSDV files (all the channels being corrected for the viewing angle and surface emissivity, corrputations are made for nadir ob­servation with an emissitivy equal to 1). Since Ozone absorption interfe­res with 15 j..IIIl channels, standard profiles like those obtained by McClat­chey (8) or Hilsenrath (9) have been used in the "4A" m::xlel ; these profi­les are scaled to total Ozone contents retrieved by NESDIS. The corrected intensities values (6) of the Ozone absorbing bands in the 9.6 j..IIIl region have been used.

Tables II to IV present the results of canparisons between "4A" m:x1el computed values and satellite observations ; the collocations selected correspond to night-time observations and apparently cloud free, oceanic or land areas, and are distributed as indicated in Table II.

Three facts may be pointed out fran the results of Table II : a) the rrean deviations are systematically negative, what may be due to an

overestimated value of the total Ozone content (especially for NOAA-6 and NOAA-7) ;

b) there is an obvious difference of behaviour between north and south hemispheres of the mid latitude zone ; what may be explained by asym­metries of the Ozone distribution between the two hemispheres (10) ;

c) NOAA-8 rreans of the differences, Iii, are appreciably better than those of NOAA-6 and NOAA-7, what may be due to an irrproved determination of the retrieved total Ozone content in the NESDIS-DSDV files.

On the other hand, the influence of the quality of the used Ozone profiles may be discussed.

Table III presents the irrpact of the total Ozone content on the dif­ferences between c:cxrputations and calculations. One can remark that in the mid south and tropical latitude zones, a multiplicative factor of 0.85 applied to the initial total Ozone content, gives satisfactorily good agreerrent between computations and calculations. That factor corresponds

- 433-

to the value of the corrective factor applied to the \13 Ozone band inten­sity.

Table IV presents the illlpact of the shape of the Ozone profiles for a constant total Ozone content : a) NOAA-8 very good results obtained for the mid north latitude zone with

Hilsenrath corresponding profiles are degradated if the real profiles are processed as tropical or high latitude zone ones;

b) the results of NOAA-7 mid south latitude are much !TOre better, if the real latitude zone corresponding Hilsenrath profiles are processed as

tropical ones. Figure 2 presents, for one particular situation of NQAA-7 mid lati­

tude south zone (nO 1542 of NESDIS-DSDV files), the vertical distributions of the M::Clatchey (8) and Hilsenrath (9) Ozone profiles, scaled to the initial total Ozone content (313 DU) ; the Hilsenrath profile correspon­ding to the initial content multiplied by 0.85 is also shown.

REFERENCES

1. srorr, N.A. and CHEDIN, A. (1981). A fast line-by-line rrethod for atIrospheric absorption aJrnputations : the Autanatized AtIrospheric Absorption Atlas. Journal of Applied Meteorology 20, 802-812.

2. CHANIN, M.L. (1983). The Intercanparison Ozone CanpaigI) held in France in June 1981 : description of the carrpaign. Journal of Applied Meteorology 31, nO 7, 707-715.

3. MEGIE, G. arrlPEWN, J. (1983). Measurerrents of the Ozone vertical distribution (0-25 kIn) : a:xnparison of various inst:ruIrents. GAP, Observatoire de Haute-Provence. Planetary & Space Sciences 31, nO 7, 791-799. --

4. IDI'HMAN, L.S. (1981). AFGL atIrospheric absorption line pararreters oampilation : 1980 version. Applied Optics 20, 791-795.

5. HUSSON, N., CHEDIN, A., srorr, N.A., CDHEN-HALIALEH, I. and BERIDIR, A. (1982). La banque de donnees GEISA. Mise a jour nO 3. Internal Note LMD n° 116, 1-82.

6. SEX::IDUN, C., BI\RBE, A., JOUVE, P., ARCAS, P. andARIE, E. (1981). In­tensity of the \13 band of Ozone fran a study of its anJIl1alous disper­sion at 10 ~. Journal of M:Jlecular Spectroscopy 85, 8-15.

7. GHOSH, A.B., srorr, N.A., CHEDIN, A., PEWN, J., MEGIE, G., CHANIN, M.L., OCCHARD, G. and MlJLLER, S. (1982). Intera:xnparaison of TIIDS-N rreasurarents in Ozone channel and 4A rrodel oamputations using lidar and balloon borne Ozone rreasurarents. European Geophysical Society and European Seismological Commission .. Leeds, G.B.

8. M::CLI\'ICHEY, PENN, R.W., SELBY, J.E.A. and GARING, S. (1970). Opti­cal properties of the atIrosphere. AFCRL 70-0527.

9. HILSENRATH, E. (1979). Standard Ozone profiles fran balloon and rocket data. Unp.lblished manuscript, 1979. \'M) Global Ozone research and !TO­nitoring project, Report nO 11 (1981).

10. WNIX)N, J. and ANGELL, J.K. (1982). Stratospheric Ozone and man. Bower, F.A. and Ward, R.D. Eds., c:oc:: Press.

Note added in Proof :

A tentative explanation of, some of the discrepancies mentioned in this paper, particularly those concerning the difference in behaviour in the two hemispheres, could be due to the restricted number of Dobson stations used in the NESDIS procedure for deriving the total Ozone content from TOVS as explained in : W.G. Planet, D.S. Crosby, J.H. Lienesch and M.L. Hill, JCAM, ~, nO 2, Feb. 1984. NOAA-6 and NOAA-7 TOVS total Ozone content retrieved by NESDIS were con­taminated by an error in the viewing angle processing (W.G. Planet, Pri­vate Communication, 1984).

- 434-

26

26

2S

TOVS CHANNEL 9 AT 9.6 p.

DATE TOVS TB ( OK) HBI (OK) 6T82 ( OK)

JUNE 1981 OBSERVED (CALC.-OBS.) (CALC.-OBS.)

17 258.12 1.7 - 1.38

18 253.8 1.5 0.3

19 257.5 0.6 - 0.8

20 256.4 0.9 - 0.5

21 255.6 1.2 - 0.6

22 259.4 0.8 - 0.5

m· 1.12 (OK) m • -0.58 (OK)

TABLE I o .0.43 (OK) o • 0.54 (OK)

INTERCOMPARISON OZONE CAMPAIGN - OHP - FRANCE - 81

COMPARISON BETWEEN TO V S OBSERVED BRIGHTNESS TEMPERATURES AND "4A MODEL" COMPUTED VALUES.

TOVS Chinnel 9 Brightness temperature (·10

Comparisons between observations from the "Intercomparison OZONE C ... MP ... IGN FR ... NCE 8'" and "4.6." model computed values FIGURE 1

• Obstrnrions frolll the intercomparison Ozone cilllpiign-OHP-FRANCE 81

o .. 4 ..... calculated "old" "1 bind of Ozone intensity S" 1 value

2S0L-~ __ ~ __ ~~ __ ~ __ -+ ____ ~ ________________ ~O~"'~TE~ 17 18 19 20 21 22 June 1981

-435 -

MID TROPICAL COLLOCATED ~ --------------------------r-------------------------- --------------------------

OBSERVATIONS NORTH SOUTH CHARACTE-

RISTICS SITUA- iii (OK) a (oK) SITUA- in (OK) a (OK) SITUA- in (OK) a (OK) SATELLITE TlONS Nb. TlONS Nb TlONS Nb.

WINTER NOAA 6 20 -0.63 1.14 10 -2.90 0.61

CLOUD-FREE

NIGHT NOAA 7 9 -1.35 1 30 -3.96 0.79 30 -1.98 0.89

OCEAN I C AREA I NOAA 8 15 -0.16 I 0.68 15 -1.64 0.80 30 -0.42 1.47

i WINTER I NOAA 7 30 -2.85 0.92 15 -4.64 0.80 30 -2.36 0.78

CLOUD- FREE

NIGHT I

LAND AREA NOAA 8 20 -0.40 1.14 15 -1.84 0.45 I I

SUMMER - NIGHT

! CLOUD-FREE NOAA 8 30 -0.68 0.63 15 -1.17 0.83 30 0.61 1.17

OCEAN I C AREA

TABLE I I COMPARI SONS BETWEEN "4A" MODEL COMPUTED VALUES AND NOAA-6, tmAA-7, NOAA-8

OBSERVATIONS (BRIGHTNESS TEMPERATURES, OK) FROM THE NESDIS-DSDV FILES.

K""' ".rr" ~""U~"" ""~ I.!.:.Q.. 0.97 0.95 0.90 0.85 0.80

I LATITUDE

ZONE

MID NORTH

MID

SOUTH

TROPICAL

. -iii a iii a m a iii a iii a

-1.35 1 -0.79 0.97 0.6 1.09 -- -

-3.96 0.79 -1.02 I 0.80 -- -- 1 0.96 I -0.79 I 0.96

! -1.98 0.89 I -1.46 -0.081 0.95 I -- --

i i i I i

TABLE I II IMPACT OF THE TOTAL OZONE CONTENT ON THE DIFFERENCES BETWEEN

COMPUTATIONS ("4A" MODEL) AND NOAA-7 NIGHT-WINTER OBSERVATIONS

OVER SEA CLOUD-FREE AREAS (NESDIS-DSDV FILES).

(-) ORIGINAL NESDIS-DSDV FILE OZONE CONTENT.

-436 -

-m a

0.64 0.96

HILSENRATH <1981> OZONE PROFILES

~ MID

LATI :~~: I-~_H~I " Gr_H~_~~-~--~-_-_-N_-~..,~_~H_--~-~-~--_--+l~--_-_-~--~~_~~~T_-~_-_-_--_-_-.j-~T~R~O_P 'f"1 C_A_L~---I in iii

SATELLl TE iii

NOAA-8

NOAA-7

TABLE IV

-2.94 0.65 -0.16 0.68 3.41 l 0.70 ~- -- ----- ---------- ---------- ---------- ---------

SIMULATED LAT. ZONE REAL LA T. ZONE SIMULATED LAT. ZONE

-3.96 I 0.79 --------- ---------- ----------r---------- l ---------

i REAL LAT. ZONE

_~_~~~~ __ L_~~~~ __ _ S IMULATEO LAT. ZONE

IMPACT OF THE OZONE PROFILE ON THE DIFFERENCES BETWEEN

COMPUTATIONS ("4A" MODEL) AND NOAA-7 . NOAA-8 NIGHT WINTER

OBSERVATIONS OVER SEA CLOUD-FREE AREAS (NESDIS-DSDV FILES).

NOAA7 MID. LATIT.SOUTH OZONE PROFILE G/G*1.0E+07

-I

-2

-6

o

+ Mc CLATCHEY PROF I LE

~ } HILSENRATH (1931) PROFILES

". ".

~ '~~~." ' " . ~ .. / ,;

.x' ... ,s:'

: ... :::~: ~: ::: .. ' ..

+I I NITIAL DATA

flJ FROM NESDIS-DSDV FILES.

)( TOTAL INITIAL OZONE

CONTENT X 0.85

) 0 20 '0 .0 SO 60 70 eo 90

ARAILMD 4A MODEL 1984

FIGURE 2

-437 -

INFORMATION CONTAINED IN SATELLITE METEOR SPECTRA ON THE VERTICAL OZONE DISTRIBUTION

U. FEISTER

Summary

Meteorological Service of the GDR Main Meteorological Observatory Telegrafenberg DDR-1500 Potsdam German Democratic Republic

Vertical ozone profiles have been inferred from radian­ces in the 9.6/um ozone band. The radiances have been ob­tained from Fourier spectrometers on board METEOR satellites. Using the satellite-derived ozone profiles and ozone profiles obtained from collocated balloon soundings the real accuracy and the information content of the remote sensing technique have been estimated. Two different approaches have been applied to infer the vertical ozone distribution. Both of them provide a gain of information in the lower stratosphere. Therefore, they can be recommended as a supplement to other remote sensing teohniques that yield information on the ozone concentration in the upper stratosphere.

1. Introduction The vertical ozone distribution has been inferred from

measurem,nts of the upward directed infrared radiance (400 -1600 cm- ) of the earth/atmosphere system. Measurements were taken by Fourier speotrometers flown on board of the satelli­tes METEOR 28 in 19771and METEOR 29 in 1979. The spectra have a resolution of 5 cm~ with a distance between oentral waVe­numbsrs o~ 2.086 cm- • Both instruments have a viewing angle of 2 x 2 corresponding to a field of view on the earth's surface of 23 x 23 km.

2. Methods Two methods were used to derive the ozone distribution.

The first of them is an iteration method originally proposed by Prabbakara et al. (1970). It differs from the original approaoh in that it uses more than one eigenvector of the ozone covariance matrix and an exponential distribution of line intensities instead of an equal distribution in the transmittance model. Both Lorentz and Voigt line shape of the absorption lines have been applied, but the simpler Lorentz line shape has been found to be sufficient for our purposes. Further details on the method used were given by Feister (1983).

Ozone Symposium - Greece 1984 - 438-

, • • Po

'00

III 15 ., II! Po

"

10

Fig. 1 Ozone profile inferred from a METEOR-29 spectrum on 5 February 1979 (1 ---) and sonde ozone profile of Payerne/Switzerland (2 ---); distance between subsatellite­point and sounding station: 260 km and 12 h; Dobson ozone: 350 matm-cm

Radiances in the 9.6 um band (980 - 1080 cm- 1 ) as well as the vertical temperatufe distribution that was inferred from radiances in the_15/um CO2 _yand and in the atmospheric window region (899 cm , 961 cm ) were used as input para­meters to determine the vertical ozone distribution. As an example Fig. 1 shows an ozone profile determined from a ra­diance spectrum of METEOR 29 (curve 1). The comparison with the corresponding sonde ozone profile of Payerne/Switzerland (curve 2) indicates that the satellite-deriTed ozone profile is a smoothed curve, but that the secondary ozone maximum at a height of about 13 km is rather well reproduced.

3. Information content The efficiency of a retrieval method can be estimated

using a quality ind~

G=1-!.. s G > 0 means a gain of information attainable from the satel­lite spectra on the Tertical ozone distribution, and G< 0 means a loss of information. Equality ~ = s (G = 0) corre_ sponds to applying the average ozone profile for the actual ozone profiles. The RMS differences ~ between inferred ozone values and true ozone values as well as the standard deTia­tions s of true ozone values bave been obtained from 12 ozone profiles, whioh were determined from METEOR spectra, and 001-

located balloon ozone soundings with an assumed sonde error being eliminated (Feister, 1983). The values of G in Fig. 2

-439 -

10 P 30

hPa z

20 km

25

50 20

100 15

200 /0

500 5

o

Fig. 2 Quality index determined for the iteration method 1 using radisonde temperatures 2 --- using temperatures in_

ferred from radianoes of METEOR satellites

show that measured radiances in the infrared ozone band with medium resolution do provide a gain of information on the ozone ooncentration, but only in the lower stratosphere, A maximum gain of information in the lower stratosphere has also been found by simulated experiments (Borisenkov et aI" 1977),

As a second approach to determine the vertioal ozone distribution a regression method was applied (Feister and Spankuch, 1977) that uses as predictors the vertical tempera­ture distribution and the total ozone content both of which can be inferred from satellite spectra, Fig, J shows the G values determined for the same 12 cases as before either using the radiosonde temperatures and Dobson ozone or the temperatures and total ozone values inferred from radiances of the satellites METEOR 28 and METEOR 29 (Guldner, 1979; Feister, 1980, 1982). It can be recognized that a gain of in­formation of similar amount as was obtained by the iteration method also occurs in the lower stratosphere, Compared to the iteration method the regression method consumes much less computer time. Its efficiency could be improved by including further predictors (Higgins et aI" 1981). Due to these ad­vantages particularly the prediotor method can be recommended as a supplement to other remote sensing techniques such as

-440-

limb, BUV and heterodyne methods that provide a gain of in­formation in the upper stratosphere (Borisenkov et a1., 1977; Timofeev et a1., 1980).

10

P hPa

20

50

100

200

500 r------_~

-2.0 -1.0 G o 1.0

30

z km

25

20

IS

10

5

o

Fig. 3 Quality index det~rmined for the predictor method 1 using radiosonde temperatures and Dobson ozone 2 --- using temperatures and total ozone both in­

ferred from radiances of METEOR satellites

References

1. BORISENKOV, E.P. et a1. (1977), Meteor. i Gidro1., 5, 11 - 22

2. FEISTER, U. ~1980~, Zeitschr. Meteor., 30, 279 - 295 3. FEISTER, U. 1982, Zeitschr. Meteor., 32, 360 - 368 4. FEISTER, u. 1983, Zeitschr. Meteor., 33, 197 - 217 5. FEISTER, U. and D. SPANKUCH (1977), Proc. Joint Sympos.

Atmosph. Ozone, Dresden 1976, 331 - 360 6. GVLDNER, J. (1979), in Distancionnoe zondirovanie atmosfe­

ry so sputnika METEOR. Leningrad, Gidromateoizdat, 59 - 65

7. HIGGINS, G.J. at a1. (1981), Proc. Quadr. Intern. Ozone Sympos., Boulder 1980, 511 - 518

8, PRABHAKARA, C. et a1. (1970), J. atmospb. Sci., 27, 689 697

9. TIMOFEEV, Ju.M. et al. (1980), Meteor. i Gidrol., 3, 51 -58

- 441-

Summary

High Resolution Infrared Spectroscopic Studies of Atmospheric Ozone and Related Trace Constituents

A. Goldman, D.G. Murcray and F.J. Murcray Department of Physics, University of Denver

Denver, CO 80208

A. Barbe and C. Secroun Laboratoire de Physique Moleculaire

Equipe de Recherche Associee au CNRS Faculte des Sciences, REIMS 51062, FRANCE

Long path high resolution (0.02 cm- l ) atmospheric infrared solar spectra show numerous new absorption features of atmospheric ozone and other trace constituents. Spectroscopic analysis of several ozone bands from these spectra, coupled with laboratory intensity measurements, generated new line parameters compilation for the vi> "'3, "'2, 2~ -\I 2, and \I 1 +'" 2 +\1 3 bands. These provide improved quantification of atmospheric ozone as well as other trace constituents with spectral features overlapping the ozone. Laboratory spectra at 0.02 cm-l resolution assist in the identification and quantification of these trace constituents. Higher resolution (0.004 cm- l ) laboratory and solar spectra measurements are in progress.

University of Denver, Recent Results (1980 - 1984)

* * *

*

* *

1. Atlases

A tlas of Stratospheric ir Solar Absorption Spectra A tlas of South Pole ir Solar Absorption Spectra Handbook of High Resolution Infrared Laboratory Spectra

of Atmospheric Interest (1981) A tlas of High Resolution Infrared Laboratory Spectra (1984)

11. Line Parameters

Line Parameters for 03, "'3fv 1, "'2, 2'2 -"'2, "'I + "'2 + "3 Bands Line Parameters for Solar CO, OH and Atmospheric OH, o,O,HCN,

C2H2, C2N2, C4H2, HC3N, HOC~ H2S, HCOOH, PH3, NH3, HN03

Ozone Symposium - Greece 1984 -442 -

Recent Results (19&0 - 1984) (Continued)

* * *

*

* * * *

*

*

*

* *

III. Identification and Quantification

Identification of 02 and N2 electric quadrupole lines Identification of 02 collision-induced continuum Identifica tion of new ir solar emission and OH pure rotation absorption

lines Identification and measurement of acetylene (C2H2) and ethane (C2H6) in

the troposhere and lower stratosphere Identification and measurement of CHOF2 (F-22) in the lower stratosphere Identification of formic acid (HCOOH) in the upper troposphere Identification and measurement of C~ON02 in the stratosphere Line by line quantification of atmospheric HN03 in the "2 and \J5/2v9

regions Simultaneous stratospheric profiles of NO, N02, HN03, 03, H20, HDO, CH4, and N20 from spectral least squares analysis of flight data Spectral least squares quantification of C02, H20, N20, CH4, and 03 from

the south pole spectra Spectral least squares quantification of HCN and HC~ from ground based

spectra Atmospheric 03, N02 profiles from uv-visible balloon-borne spectra Inversion of stratospheric temperature profile from IO.411m C02 absorption

lines

23 MAR \98\ 33 KM 92.\· 93.3· 95.3·

I I I II II • ~ I f l' I I II I I I 11111 II I III 11 I II 11111 1111'1 1 I J I II '0 20 )IJ .. so

1.0 -rnrrrrn 1.0

l~~~fn:~':~ • I !I I ~ I! I I ~ Ii': ! . ~ ! Ii ' Ii', I I I I I I

, ' , ' I' " I I ' ,

o.

820 822 824 826 828 830

WAVENUMBER (e"'-)

FIG. 1. a typical frame from the stratospheric atlas.

-443 -

Selected References

Goldman, A., D. G. Murcray, F. J. Murcray and E. Niple, "Analysis of High Resolution Balloon-Borne Solar Spectra and Laboratory Spectra in the HN03 1720 cm- l Region," Appl. Opt.,.!2., 3721-3721t, 1980.

lJarbe, A., C. Secroun, P. Jouve, A. Goldman, and D. G. Murcray, "High­Resolution Infrared Atmospheric Spectra of Ozone in the 10 "iJm Region: Analysis of vI and''''3 Bands - Assignment of the (VI + V2) -v2 Band," J. Mol. Spectrosc., 86, 286 -297, 1981.

Goldman, A., F. J. Murcray, R.D. Blatherwick, J.R. Gillis, F.S. Bonomo, F.H. Murcray and D.G. Murcray, "Identification of Acetylene (C2H2) Infrared Atmospheric Spectra," J. Geophys., Res., 86. 12,11t3-12,11t6,1981.

Goldman, A., R.D. Blatherwick, F.J. Murcray, J.W. Van Allen, F.J. Murcrayand D.G. Murcray, "New Atlas of Stratospheric ir Absorption Spectra-Volume I and II," Department of Physics, University of Denver, February 1982.

Goldman, A., J.R. Gillis, D.G. Murcray, A. Barbe and C. Secroun, "Analysis of the v2 and 2vz - v2 Ozone Bands from High Resolution Infrared Atmospheric Spectra," J. Mol. Spectrosc., 96, 279-287, 1982.

Rothman', L.S., R.R. Gamache, A. Barbe, A. Goldman, J.R. Gillis, L.R. Brown, R.A. Toth, J.M. Flaud and C. Camy-Peyret, "AFGL Atmospheric Absorption Line Parameters Compilation: 1982 Version," Appl. Opt., 22, 2247-2256, 1983.

Barbe, A., C, Secroun, A. Goldman and J.R. Gillis, "Analysis of theVI + v2 + '3 Band of the 03," J. Mol. Spectrosc.,.!.QQ, 377-381, 1983.

Goldman, A., F.J. Murcray, D.G. Murcray and C.P. Rinsland, "A Search for Formic Acid in the Upper Troposphere: A Tentative Identification of the 1l05-cm-1 v6 Band Q Branch in High Resolution Balloon-Borne Solar Absorption Spectra," Geophys. Res. Lett.,.!.!., 307-310, 1984.

Goldman, A., C.P. Rinsland, F.J. Murcray, D.G. Murcray, M.T. Coffey and W.G. Mankin, "Balloon-Borne and Aircraft Infrared Measurements of Ethane (C2H6) in the Upper Troposphere and Lower Stratosphere," J. Atmos. Chern., In Press, 1984.

Goldman., J .R. Gillis, C.P. Rinsland, F.J. Murcray and D.G. Murcray, "Stratospheric HN03 Quantification from Line-by-Line, Non-Linear Least Squares Analysis of High Resolution Balloon-Borne Solar Absorption Spectra in the 870-cm-1 Region," Appl. Opt., In Press, June 1981t.

Murcray, D.G., A. Goldman, F.J. Murcray, F.S. Bonomo and R;D. Blatherwick, "High Resolution Infrared Laboratory Spectra," Department of Physics, Universi ty of Denver, Denver, CO 80208, April 1981t.

-444-

Acknowledgments

This research has been supported in part by the National Science Foundation, The National Aeronautics and Space Administration, The Federal Aviation Agency, and The Chemical Manufacturers Association.

Important contributions to these studies were made by J. W. Van Allen I. F.H. Murcrayl, J.J. Kosters\ J.R. Gillisl, R.D. Blatherwick l , F.G. Fernald l , F.S. Bonomo., C.P. Rinsland ,R.K. Seals2, E. Niple3, M.T. Coffey~, W.G. Mankin~, A. Barbe5 and C. Secroun5•

Department of Physics, University of Denver, Denver, CO 80208

2 NASA Langley Research Center, Hampton, VA 23665

3 Perkin-Elmer Corporation, Danbury, CT 06810

~ National Center for Atmospheric Research, Boulder, CO 80307

5 Laboratoire de Physique Moleculaire, CNRS, Reims 51062, FRANCE

-445 -

MEASUREMENTS OF THE OZONE PROFILE UP TO 50 KM ALTITUDE BY DIFFERENTIAL ABSORPTION LASER RADAR

J. Werner l , K.W. Rothe l , H. Walther l ,2

Summary

Sektion Physik der Universitat Munchen Garching, FRG

2 Max-Planck-Institut fur Quantenoptik Garching, FRG

Using laser radar (lidar) and the method of differential absorption the ozone content in the atmosphere was measured up to altitudes of 50 km. The set-up was based on a XeC1 excimer laser operating at repeti­tion rates of up to 100 Hz. The laser radiation at a wavelength of 308 nm is strongly absorbed by ozone. By stimulated Raman scattering light at 353 nm was generated, which is not absorbed by ozone and can there­fore be used as reference.

Ozone profiles below 30 km are obtained in an averaging time of less than one hour with an accuracy of about one per cent and a resolution in height of about one kilometre. Above 40 km, the signals have to be averaged for a whole night to obtain the same precision.

1. Introduction

The ozone distribution around 40 km is of special interest because theoretical models predict that it is particularly influenced by anthropo­genic pollution (1): free chlorine released by photodissociation of chlo­rofluorocarbons is expected to cause final ozone reduction up to 20 % at that height.

According to recent computer models, the increase of other species such as nitrogen oxides and carbon dioxide, however, will stimulate ozone production in the troposphere and lower stratosphere by about the same amount as is the depletion in the upper stratosphere (1).

Consequently a shift of the ozone layer to lower altitudes will take place which changes the temperature distribution in the atmosphere. As a result, influences on the weather, which at present cannot be predicted in detail, are expected.

Since the total ozone content remains nearly unchanged, this effect is not reflected in measurements obtained by techniques which only deter­mine the total ozone concentration as e.g. the well-established Dobson method.

Conventional methods for measuring the height resolved ozone profile are ~ost often balloon based and do normally not work at altitudes higher than 35 km. Hence, there are no reliable continuously recorded data avai­lable around 40 km, where the reduction in ozone should be most pronoun­ced. It will be shown that the set-up described in this paper is suitable to improve this situation.

Ozone Symposium - Gxeece 1984 -446 -

2. Methodology

The differential absorption lidar is based on the use of two wave­lengths ~l and ~2 with different absorption cross-sections (o(~l) * o(~2) for the gas under study: one line is strongly absorbed, the other one - being not absorbed - is used as a reference (2).

As pulsed lasers are used, the time-resolved recording of the back­scattered photons gives information on the altitude. The relative compar­ison of the backscatter intensity at both wavelengths from two adjacent altitudes gives the absolute concentration of the gas under study. The only further information required concerns the absorption cross-sections. With respect to ozone, high resolution data (3) are available which also include the temperature dependence.

In many practical applications, a tunable dye laser system is advan­tageous, which allows the two wavelengths to be very close together (4,5). In this case the wavelength-dependence of the Rayleigh and Mie scattering mechanisms has not to be considered. In our case, however, where a Raman­shifted line is used as reference, the two wavelengths are further apart. Therefore the different wavelength dependence of the two scatter mecha­nisms has to be taken into account.

3. Experimental set-up

A commercial XeCl excimer laser (Lambda Physik EMG 102 E) with a pulse energy of 150 mJ and repetition rates of up to 100 Hz serves as transmitter. The emitted wavelength (308 nm) lies in the wing of a strong uv-absorption band of ozone. The beam divergence is reduced to less than 1 mrad by means of an unstable resonator.

The reference line (353 nm) is generated by stimulated Raman scatte­ring in a high-pressure hydrogen cell. This scheme proved to be very ad­vantageous since it allows the two wavelengths to be emitted simultaneous­ly into the same field of view. This reduces the error of the measurement in comparison with conventional dye laser techniques (5), where the laser is always tuned from one wavelength to the other. Furthermore, the Raman method also simplifies the set-up and the adjustment procedure, and en­sures high pulse energy.

Fig. 1 shows the arrangement schematically. The laser beam is focused into the Raman cell, generating the collinear reference beam of similar divergence. The divergence at both wavelengths is further reduced by a beam expander with a spatial filter.

The backscattered light is collected by a mirror having a diameter of 60 cm and a focal length of 2.4 m. Its field of view is twice the final laser divergence. A dichroic filter separates the backscattered intensity at the two wavelengths with minimum losses. Narrow-band interference fil­ters (6 nm FWHM) reduce the background. The signals are detected by two photomultipliers (EMI 9893) used in the photoncounting mode.

The saturation of· the photomultiplier tubes by the signal backscat­tered from low altitudes has to be avoided. Therefore a mechanical chopper is inserted in the optical path of the receiving system. The chopper is synchronized with the laser pulses and blocks the light which is backscat­tered from altitudes less than 15 km.

The whole equipment is installed in a small container (3 m x 2 m) and was transported by helicopter to the summit of Zugspitze (2964 m) in order to reduce the attenuation by aerosols in lower atmospheric layers.

-~-

y I

Xe CI

lOSer

Fig. 1: Scheme of the experimental set-up. The transmitter is shown on the right and the receiver on the left hand of the figure. (IF: inter­ference filter, PM: photomultiplier tube)

~

~

on M

~

::E:

'" ~~ J:

IS>

'"

~

~

o 100 200 300 q00 03 [UG/H3J

Fig. 2: Ozone density profiles ob­tained in September 1983. Each pro­file represents the mean ozone con­centration measured during one night.

- 448-

Altitude Ikml

Fig. 3: Perspective representation of the temporal evolution of the ozone content during September, 1983 (for further details see text).

4. Ozone profiles

The lidar station has been in operation since October 1982 (6). The inherent height resolution is 200 m, resulting from the sampling time of the storage electronics. In the evaluation procedure the data are smoothed by averaging so that the final resolution is about one kilometre. It ta­kes less than one hour measuring time to obtain profiles up to 30 km with about one percent statistical error. At an altitude above 40 km, however, a whole night of laser operation at a pulse repetition rate of 50 Hz is needed to get an precision of the same order.

Fig. 2 shows the measured ozone profiles of September 1983. Each single profile represents one night of observation. The changes in the distribution are only due to real variations; the error of the measure­ments is much smaller at all altitudes than the natural changes.

The variability of the ozone concentration above 30 km is relatively small because photochemical reactions dominate the ozone concentration in the upper stratosphere. The ozone content in the lower stratosphere, how­ever, is highly variable. This is due to transport phenomena, occurring mainly at these altitudes.

The temporal variation due to transport mechanisms can more clearly be seen in Fig. 3. The time development of the ozone concentration is shown in perspective representation, beginning with the night of September 7/8 (first line) and ending with the night of September 29/30 (last line). The gaps between groups of measurements symbolize interruptions due to bad weather. The abscissa is the altitude, increasing from right to left, the ordinate represents the ozone concentration.

Because of the short period of observation so far it is obviously not yet possible to draw conclusions concerning the possible destruction of the ozone layer or the shift of the ozone layer from high altitudes down­wards. Such effects are masked by the large natural changes of the ozone concentration. A much longer observation time is therefore required before a conclusive comparison with the theoretical models can be performed.

5. Conclusion

The lidar set-up on Zugspitze has been successfully working since October 1982. Its main features are high precision and the ability to per­form measurements up to altitudes of 50 km continuously. The lidar tech­nique is therefore very suitable for detecting long-term trends in the ozone profile at the percent level.

Acknowledgement

The authors gratefully acknowledge financial support from Deutsche Forschungsgemeinschaft.

REFERENCES:

(1) D.J. Wuebbles et al., J. Geophys. Res. 88, 1444 (1983) (2) E.D. Hinkley (Ed.), Laser Monitoring of the Atmosphere, Springer

Verlag, Berlin 1972 (3) R.D. McPeters, A.M. Bass, Geoph. Res. Lett. 9, 227 (1982) (4) K.W. Rothe, u. Brinkmann, H. Walther, Appl. Phys. 3, 115 (1974) and

4, 181 (1974) (5) J. Pelon, G. Megie, J. Geophys. Res. 87, 4947 (1982) (6) J. Werner, K.W. Rothe, H. Walther, Appl. Phys. B 32, 113 (1983)

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INTERCOMPARISON OF OZONE PROFILES OBTAINED BY BREWER/MAST SONDES AND DIFFERENTIAL ABSORPTION LASER RADAR

Summary

W. ATTMANNSPACHERl, R. HARTMANNSGRUBERl, J. WERNER2, K.W. ROTHE2, H. WALTHER2,3

Meteorologisches Observatorium Hohenpeissen­berg des Deutschen Wetterdienstes Hohenpeissenberg, FRG

2 Sektion Physik der Universitat MUnchen Garching, FRG

3 Max-Planck-Institut fUr Quantenoptik Garching, FRG

Ozone profiles are compared which were obtained by two entirelY dif­ferent techniques during the MAP/Globus campaign in September 1983. At Hohenpeissenberg (480 N, 110 0) seventeen Brewer/Mast sondes were launched. These chemical sondes can reach altitudes up to 35 km. About 40 km apart, on top of Zugspitze (47.50 N, 110 0) a laser radar sys­tem was measuring the ozone concentration up to altitudes of 50 km. The weather situation in September 1983 allowed the laser radar to be in operation for sixteen nights, so that a detailed comparison between both methods could be performed.

Despite the basic differences between the two techniques a rather good agreement is obtained already for comparisons on a daily basis. Nearly identical profiles are found up to 30 km altitude by comparing the monthly averages obtained by the two techniques.

1. Experimental set-up

At Hohenpeissenberg Brewer/Mast electrochemical sondes are launched on a routine basis two or three times a week since about fifteen years. For details of the experimental set-up see (1). The sondes are prepared very carefully, a fact which is reflected in the low correction factors. They reach maximum heights of up to 35 km. The accuracy is about five per­cent, decreasing with altitude in the stratosphere. Several comparisons with other ozone sondes were performed in the past (2), confirming the reliability of the Hohenpeissenberg data.

At Zugspitze, a laser radar (lidar) system was installed in autumn 1982. It is based on a commercial powerful XeCl excimer laser, emitting in the uv-band of ozone at 308 nm. Since the differential absorption lidar technique is based on measurements with two lines (3), the XeCl laser ra­diation is also partially converted to a longer wavelength by stimulated Raman scattering. This longer wavelength is not absorbed by ozo~e and serves as a reference line. Details of this equipment are published else­where (4).

The ozone profile measured in one night is typically the average of more than 106 laser shots, providing an over all accuracy of about one percent with the height resolution being in the order of one kilometre.

Ozone Symposium - Greece 1984 -450 -

2. Inherent differences between the two systems

The comparison of the results obtained by the two techniques is far from being trivial. Considering the two locations of measurement which are some 40 km apart, one must not forget that the 1idar is directed vertical­ly into the atmosphere whereas the balloon sondes do not. Strong winds can bring the balloons some hundred kilometres away during their ascent. With respect to the time of measurement one has to keep in mind that the balloons were most often launched in the morning, only some of them later on during the day. TWo launches were performed at night. The 1idar, how­ever, was operated exclusively during the night.

As the 1idar was in operation for about eight hours each night, the data were averaged so that short-term fluctuations of the ozone profile cannot be seen. Therefore the 1idar profiles are rather smooth. They only show features remaining during a major part of a night. On the other hand, the Brewer/Mast sondes give profiles based on successive measurements of the ozone concentration during the ascent. Such a snapshot of the ozone concentration, of course, offers many instantaneous details.

3. Data discussion

The 1idar profiles of each night were compared with the balloon laun­ches performed closest to them in time. The most frequent situation was a launch the next morning, but some balloons were also launched later during the day.

Thete were even two balloon launches at midnight. In those cases of close coincidence in time, exceptionally good agreement of the profiles was found. This is demonstrated by Fig. 1, which shows an obviously stable secondary maximum at about 15 km altitude for the night of September 20/21.

Summarizing the situation for the individual days, it can be stated that in general a shorter time difference between the two measurements lead to a better agreement.

It was only for a few measurements that the discrepancy was signifi­cant. One possible explanation is the difference with respect to time of observation between the ozone sonde and the 1idar. To clarify this beha­vior, further comparison is needed. An example is shown in Fig. 2.

Obviously, a comparison of the monthly averages is by far more infor­mative because the short-term fluctuations are averaged out to a certain extent so that possible systematic differences between the two distinct techniques can be recognized. Indeed, the two monthly averaged profiles show an exceptionally good agreement in the height range between about 18 and 30 km (Fig. 3). At that time, the 1idar was not yet measuring below 18 km whereas the electrochemical sondes principally cannot work at heights above 35 km, The only noticeable discrepancy can be stated for the region between 30 and 35 km, where the sondes tend to find lower ozone concentration values than the 1idar. The reason for this behavior is still subject to speculations.

4. Conclusion

The intercomparison of ozone profiles obtained by two different me­thods (Brewer/Mast sondes and 1idar) obviously demonstrates the high re­liability as well as the distinct features of both methods. In the height range between 18 and 30 km nearly identical monthly averages are found.

-451-

~

'" .,.

l(l

:II ::t: 2: lG :r

'" '" ~ .-~

"

... "

10~ 200 300 q0~

03 (UG/M31

Fig. 1: ~ood agreement is found bet­ween the lidar (straight line) and the Brewer/Mast sonde (dotted line) when the measurements were performed nearly at the same time.

'fi

.. .,.

on

'" '" ..

'" :>:

"" ~~ :r

re .... '

... , .. ~ --,

" , '. !!

"

'"

'" 0 100 :200 03

100 :2110 3~0 q00 03 (UG/M31

Fig. 2: Rather poor agreement is possible when the balloon sonde is launched with a rather large time delay.

--'

a: ""' ro rn Gl

300 q00 (UG/M3J

Fig. 3: The two monthly averages show exceptionally good agreement up to altitudes of 30 km.

-452 -

REFERENCES:

(1) A.W. Brewer, J.R. Milford, Proc. Roy. Soc. London A 256 Nr.1278, 470 (1960)

(2) W. Attmannspacher, H.U. Dutsch, International Ozone Sonde Comparison at the Observatory Hohenpeissenberg, Ber. Dt. Wetterd. Nr. 120 (1970) resp. Nr. 157 (1978), Offenbach am Main, Verlag des Deutschen Wetter­dienstes

(3) E.D. Hinkley (Ed.), Laser Monitoring of the Atmosphere, Springer Verlag, Berlin 1972

(4) J. Werner, K.W. Rothe, H. Walther, Appl. Phys. B 32, 113 (1983)

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E. HILSENRATH

J. AINSWORTH A. HOLLAND J. MENTALL A. TORRES W. ATTMANSPACHER A. BASS W. EVANS W. KOMHYR K. MAUERSBERGER A. J. MILLER M. PROFFITT D. ROBBINS S. TAYLOR E. WEINSTOCK

Summarl

RESULTS FROM THE BALLOON OZONE INTERCOMPARISON CAMPAIGN (BOlC)

NASA/Goddard Space Flight Center Greenbelt, Maryland 20771 USA NASA/Goddard Space Flight Center NASA/Goddard Space Flight Center NASA/Goddard Space Flight Center NASA/Goddard Space Flight Center Germany/Hohenpeissenberg Observatory National Bureau of Standards Canada/Atmospheric Environment Service NOAA/Geophysical Monitoring for Climatic Change University of Minnesota NOAA/National Meteorological Center NOAA/Aeronomy Laboratory NASA/Johnson Space Center Systems and Applied Sciences Corporation Harvard University

The purpose of the Balloon Ozone Intercomparison Campaign (BOlC) is to assess the accuracy and precision of various ozone measurement systems under development and those flown operationally. Several in situ UV absorption photometers, two solar UV absorption photometers, electro­chemical sondes, and a mass spectrometer were intercompared in three flight missions. Concurrent data from Umkehr and satellite observations are also intercomparei. Ozone calibration procedures are also being reviewed as a part of BOIC and the National Bureau of Standards (NBS) provided a "standard" ozone source for intercomparing the in situ instru­ments at ground pressure. The following are some preliminary results. The standard deviation of the sensitivities among 17 instruments against the NBS reference was about 11%. These differences appear in flight at the lower levels, however changed at higher altitudes indicating height dependent errors. The difference among 5 in-situ UV photometers flown together ranged by ±8% during ascent to about 41 km. During float at 42 km the difference nearly doubled. During descent the difference decreased to about 4% which is much closer to the expected accuracy of these instru­ments. A complement of electrochemical sondes flown with the UV photo­meters agreed with them in range of 0-20% depending on the sonde and alti­tude. Some electrochemical sondes gave lower ozone values at pressures lower than 10 mbar (31 km). Balloon sondes also showed systematically lower values than concurrent Umkehr and SBUV satellite observations at altitudes above 10 mb. Intercomparisons among the instruments in the troposphere showed 30% differences.

1.1 Introduction

Balloon ozone sounding data provide the basis for the ozone climatol­ogy in the lower stratosphere and troposphere as we know it today. They have more recently been used as comparison data for satellite ozone sounders. Uncertainty in the quality of the regular soundings continues to be a problem, however. There appear to be station to station

Ozone Symposium - Greece 1984 -454 -

differences due to the use of different instruments, and at high altitudes (near 10 mb) errors are as large as 25% because of uncertainties in pump correction. The international intercomparison of balloon ozone sondes at Hohenpeissenberg in 1978 indicated a systematic difference of 12% in the troposphere between instrument types. An effort to improve the operation­al instruments is now underway. Both NASA and NOAA are performing labora­tory studies to understand better the chemistry of the measurement and performance at low pressure. Improvements in the data processing and quality control are also being initiated. These improvements have resulted in increased precision of the measurement in the last few years.

New techniques have been developed for ozone measurements in the stratosphere. These systems show promise for high precision and accuracy to as high as 45 km. However, none are considered operational for routine soundings, nor are they low cost. One of these techniques might become a standard method and then used with the low cost instrument as a reference. The objective of the Balloon Ozone Intercomparison Compaign (BOIC) is to assess our ability to perform ozone measurements from a balloon. Compari­sons of flight data are used to help evaluate the accuracy and precision of the "operational" instruments and techniques under development. This paper describes the initial results from a series of balloon flights which began in July 1983 and completed in March 1984.

1.2 The Campaign Description

The balloon flights were conducted from National Scientific Balloon Facility '(NSBF) in Palestine Texas (31.8oN, 95.8oW) and included the following three missions:

1. Multiple instrument gondola: This gondola carried six in-situ UV photometers from Harvard University, NOAA Aeronomy Laboratory (AL), NASA's Johnson Space Center (JSC) and Goddard Space Flight Center (GSFC). There were two UV remote sensors (l ROCOZ type) from NASA/GSFC and 12 electro­chemical sondes from NOAA/Geophysical Monitoring for Climatic Change (GMCC), NASA/GSFC, the Canadian Atmospheric Environment Service (AES), and the Hohenpeissenberg Observatory of the German Federal Republic.

2. The University of Minnesota Gondola: This gondola carried the University of Minnesota mass spectrometer, a second NASA/JSC in-situ photometer and a second remote sensor (ROCOZ) from NASA/GSFC.

3. Triplets: A series of 16 balloons each carrying three electro­chemical sondes from Germany, Canada, NASA/GSFC and NOAA/GMCC.

During the balloon flights total and Umkehr ozone profiles were taken by the Dobson and Brewer spectrometers located at Palestine, Texas. In addition Nimbus 7 SBUV satellite ozone data were also extracted over this site.

Ozone standards and calibration procedures were also reviewed as part of BOIC to help interpret the intercomparison results. The National Bureau of Standards provided an ozone source and a standard photometer detector to perform a pre-flight intercomparison of the in-situ instruments at ground pressure.

The in-situ photometers, the mass spectrometer and the UV remote sensors have been reported elsewhere by the authors. The electrochemical ozone sondes were the standard ECC and Mast Brewer types flown in the United States, Canada, and Europe. Each agency sent their teams to prepare, launch and process the data from their flights. The team from the Hohenpeissenberg Observatory could not reproduce the laboratory pre­paration conditions in Palestine that they were accustomed to at their observatory, therefore felt their data quality may have been compromised.

-455 -

2.1 Ground Comparison with NBS Reference Standard

All but the Harvard in-situ instrument sensitives were compared with the National Bureau of Standards ultraviolet photometer by exposing the instruments to a range ozone amounts expected in the stratosphere at ground pressure. The standard deviation of the sensitivities among 17 instruments against the NBS reference was about 11%. The largest contri­butor to the variances were the electrochemical sondes from NASA and Hohenpeissenberg. For example, the NASA ECC sonde compared about 10% high, the NOAA ECC about 3% high and the Mast Brewer about 20% low in one case and 4% low in another against the NBS reference. The in-situ UV photometers read within 5% of the NBS reference. These differences appeared in flight at the lower levels, however changed at higher altitudes indicating height dependent errors. There was some correlation between the normalization factor employed by the elecrochemical sondes and the comparison against the NBS reference.

2.2 Intercomparison of the Electrochemical Sondes

The electrochemical sondes were intercompared on the Triplet flights, which was a series of 16 balloons, flown between June 19 and July 7, 1983, each carrying three instruments from the four participating groups. The four instruments were rotated on the flights so that each instrument had six to eight comparisons with the other instruments. In this analysis the measured ozone data were converted to Umkehr layer values. To eliminate differences from errors in the measured atmospheric pressure only one sonde pressure was used to define the layer divisions during flight, and the data were then correlated through time.

The average ozone profiles taken over the eighteen day period are compared in figures la and Ib which illustrate the average departure of each sonde type from a mean profile (from all soundings) before and after each profile was normalized to total ozone. Before and after normaliza­tion differences between the Mast-Brewer and ECC type sondes are large in the troposphere. This is consistent with results from the Hohenpeissen­berg 1978 intercomparison. Before normalization the Hohenpeissenberg data, during BOIC, are systematically lower with an absolute bias at all levels. After normalization those data become higher than the others near the ozone maximum. This results from the percentage correction (normali­zation) to data that has a bias. The standard deviation of the 18 day data set for each sonde type ranged from 5-10% where the AES data was the highest. From this comparison one concludes that after normalization the sondes most likely agree to within their errors except in the troposphere.

Intercomparison of sondes from the same group (3 sondes together by NOAA/GMCC and by NASA/GSFC) showed excellent agreement after pressure measurement errors were removed. Differences were of the order of 5% in the troposphere and stratosphere even before normalization. This implies that given an established procedure the electrochemical sondes can give high precision. However, when comparing instrument pairs (NOAA-NASA, NOAA-Germany, etc.) with each other, biases exist which may be explained by differences in solution concentration and/or pump efficiency corrections.

In addition to these biases a single sounding can result in erroneous data. Figure 2 illustrates how one sounding may differ markedly from the other two on the same balloon. These exceptions can be characterized as 1) ozone concentration dependent errors, 2) absolute errors, 3) altitude errors, and 4) random errors. In some cases normalization reduces errors

-456 -

of the outliers. These exceptions are highly correlated to the normaliza­tion factors. Differences in the comparisons were significantly reduced when the exceptions were disregarded.

2.3 Comparison of Balloon Sondes, Umkehr, and Satellite Observations

During the BOIC measurement period SBUV data were extracted over Palestine, Texas. Figure 3 summarizes this comparison in Umkehr layers to yield data of comparable altitude resolution. The data consisted of 7 Umkehr, 12 satellite and about 40 balloon soundings. In general the measurements agree to within their standard derivations (~10% in the stratosphere) except in layer 7 (centered near 6 mbar) where the balloon sondes appear to be 20% lower.

2.4 Comparison of the In-Situ UV Photometers

Data were taken from S UV photometers on ascent and descent on the multiple instrument gondola which reached an altitude of about 42 km (2.2 mbar). The data were averaged over two minute intervals resulting in about a 1/2 km altitude resolution. A composite of the measured ozone profiles is shown in figure 4. In general each instrument shows the same structure, however, there are differences ranging up to 16%. The differ­ences are illusrated in more detail in figures Sa and Sb which show relative differences on ascent and descent respectively from the mean profile. As the ascent rate decreased and the balloon reached float altitude the differences among the instruments nearly doubled. It should be noted that ozone concentrations and pressures are very low at these levels and gondola contamination may be significant. Ozone concentrations are also low in the troposphere and small absolute errors show as large percentage errors.

On descent the measurements agreed significantly better except for the Harvard instrument which yielded lower values than the remaining four which agreed with each other to about 3% at pressures higher than S mbar. This improved agreement occurred even though the descent rate was about 1/2 the ascent rate.

2.S Comparison of Electrochemical Sondes with UV Photometers

The Multiple Instrument gondola carried 12 chemical sondes from NOAA/GMCC and NASA/GSFC. The Canadian AES also flew ECC sondes on separate balloons before and after the gondola flight on the same day. The NOAA ECC sondes are compared with the UV average in figure 6. In the troposphere, differences among the sondes ranged more than 30%. In the stratosphere (SO to 10 mbar) the NOAA sondes agree to better than S% among themselves and with the UV photometers. At pressures lower than 10 mb the ECC sondes fall off rapidly relative to the UV photometers. If the UV photometer average is considered to be correct, this falloff is consis­tent with the comparison of balloons, Umkehr and satellite data.

Comparison of the 4 NASA/GSFC sondes on the Gondola and 2 AES ECC sondes with the UV photometer showed considerably more scatter than the NOAA/GMCC sondes. The average difference and scatter was about 8% for the AES data, while the NASA/GSFC was about lS%. For some of the soundings there was also a tendency for the ozone values to drop off relative to the UV photometer at pressures less than 10mb.

-457 -

3.1 Final Remarks

There is evidence that contamination from the balloon and/or platform can effect the quality of the ozone measurements. Laboratory comparisons simulating stratospheric conditions are being planned as a follow on to BOlC. Comparisons on a smaller scale than BOlC should be continued. Missing in this initial report are the comparisons of the UV in-situ photometers and the UV .remote sensors because their data have not been processed in final form at this time.

'"

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FIGURE 1

BOIC I TRIPLET FLIGHTS

RATIO OF INSTRUMENT AVERAGE WITH AVERAGE OF ALL INSTRUMENTS DURING TRIPLET FLIGHT PERIOD

• H W I

H • """" N • t.lOAA • " w w . WAl lOPS \ ~)

W • WALLOPS

l~i . CANAD" A • C,ANAJ)" F • GH~MAHY \\ F _ GIAMAHV

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I A\ i H • W

/ 'l \ /' . , ~'i ~w ,/ "f>'Zw

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RATIO (INSTRUM ENT AVEA:AGEI PER IOO AvERAGE)

(AJ EXPERIMENTER'S DATA IBI WMO NORMALIZED DATA

FIGURE 3

AVERAGE AND STANDARD DEVIATION FOR UMKEHR LAYER VALUES OVER THREE WEEKS

FIGURE 2

SAMPLE OF ERRORS TO GENERAL COMPARABILITY OF ELECTROCHEMICAL SONDES

(NOT NORMALIZEDJ

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-458 -

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NOlI: l,A'ttlt lIS FIIOM 2!D~ .- tOCO III 41 111 . I) 11) lI) :Ill <Ill 51] tID ;II] I!IO iJO 100 '11) 120 1;10 1<10 16\:1

PARTIAL. PRESSURE

FIGURE 4

OZONE DISTRIBUTION MEASURED BY 5 IN·SITU UV PHOTOMETERS - ASCENT

,'" PARTIAl. PRESSUfHi Illbarst

FIGURE 5

'50

RATIO OF EACH IN·SITU UV PHOTOMETER TO AVERAGE UV PHOTOMETER

(AI ASCENT

• - • .NASA. / JSC

- -NOAA I A~ " A ••• NL)AA/ "'~ I'Z •••• KfoAvARO U . -- N"SA IG$FC

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RATIO OF NOAA ECC SONDES TO AVERAGE UV PHOTOMETER

RATIO

- 459-

181 DESCENT

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Surrrnary

BALLOON IN-SITU MEASURENENTS OF OZONE WITH THE NASA-JSC UV PHOTOMETER

D. E. ROBBINS ~la il Code SN 3

NASA-Johnson Space Center Houston, Texas USA

Details of the design and performance of a UV absorption photometer used to measure ozone in the stratosphere from large balloons are given. Mechanisms which might cause a loss of ozone in the intrument are shown to be negligible. An analysis of errors obtains an instrumental precision that is better than 3 % and an accuracy less than 5 %. Improvements are being made that will increase the precision to about 1 % and the accuracy to 3 %. The NASA-JSC photometer has been intercompared with other techni­ques during several balloon campaigns. Agreement with other in-situ techniques was usually within 1 to 5 %, while agreement with remote tec­hniques was typically in the range 10 to 15 %.

1.1 Measurement Technique

The NASA-JSC ozone instrument uses the ultraviolet absorption photo­metry technique to measure ozone in the stratosphere from large scientific balloons. It employs a technology deleloped by the Dasibi Environmental Corp. for laboratory ozone moni tors. Ambient air is continuously drawn through an absorption cell by a pump. UV light at 254 nm from a mercury vapor lamp is passed through the cell. The optical thickness of ozone in the cell is obtained from

x = In (Io/I)

where 10 and I are respectively the unattenuated and attenuated light intensities. The mixing ratio of ozone in the cell is given by

f [Oz]/[M] (x/al)/(p/kT)

where 1 is the cell length, p, [M], and T are the pressure, density, and temperature of the air in the cell, [Oz] is the ozone density in the cell, a is the total absorption cross section of ozone at 254 nm, and k is

Ozone Symposium - Greece 1984 -460 -

Boltzmann's constant. Because ozone losses are believed to be negligible as the air passes through the instrl1.rnent, the mixing ratio in the cell is taken to be the same as that of ambient air. A discussion of possible ozone losses in the instrument is given in Section 1.4.

1.2 Instrument Description

The operating procedure mlnlmlzes effects of variations in the light intensity by using two detectors. One measures the intensity of light passing through the sample of air, and the other monitors the lamp inten­sity under controlled conditions. The measurement cycle of 15 seconds is divided into four periods of approximately 3.5 seconds each. The unatte­nuated light intensity is measured during one of the periods, and the attenuated intensity is measured during another. These periods are sepa­rated by two other periods that are used to flush the absorption cell with air. In one of these periods the air flow is diverted through a chemical scrubber that employs manganese dioxide to remove ozone from the air. In the other, the cell is flushed with ambient air from which the ozone has not been removed.

The two detectors are operated simul taneously. The length of the period in which the unattenuated intensi ty is measured is determined by the time required for the sample detector to accumulate a preset integ­rated intensity. During this period the control detector measures an integrated intensity Ic. The length of the period in which the attenuated intensity is measured is determined by the time required for the control counter to measure an amount of light equivalent to Ic. During this period the sample counter measures the amount of light I. The use of the control detector thereby assures that the same amount of light enters the cell during both periods, i.e. when the unattenuated and attenuated inten­sities are measured.

The detectors, electrometers, lamp, and absorption cell are purchased from Dasibi. The absorption cell is a folded path made of aluminum tubes coated inside with Kynar, an inert fluorocarbon material. All surfaces of the flow system are either coataed with Kynar or made of Teflon. The detectors operate in the current mode by charging a 100 picofarad capaci­tor to a preset vol tage of 0.1 volts. Then the capaci tor is discharged and the process is repeated. The value of 10 is 169,680 counts, where a count corresponds to one charge-discharge cycle, and is equivalent to 0.5 microamps. The detector is a model R404 (or equivalent) phototube made by Hamamatsu. It has a sensitive area of 0.5 sq cm and a radiant sensitivity of about 15 mamps/watt, making the incident flux equal to about BE13 photons/sq em sec.

Ambient air pressure is measured using transducers made by MKS In­struments, Inc. and/or Rosemount Inc. At the highest altitudes pressures are measured using an MKS Model 220B Baratron that is temperature con­troled for maximum accuracy. A MKS Model 223B Baratron measures the pressure differential between air in the cell and ambient air.

The instrument is packaged in a vacuum sealed metal container that is 0.33 m wide, 0.43 m high, and 0.57 m long. A support package, 0.26 m high, 0.48 m wide, and 0.51 m long contains, the pressure transducers and encoder for data telemetry. The total weight of both packages is 35 kg. Eight commands are provided to control the power, pump, and solenoid valve during the flight. The experiment operates on an average current of 2.5 amps at 23 - 32 volts OC.

- 461-

1.3 Precision, Accuracy and Performance

Table I gives the range and uncertainty of parameters used to compute the ozone mixing ratio. Instrumental precision is obtained as the root mean square of uncertainties in the first four parameters. It ranges between 1.1 % and 2.9 %. The aceuracy is obtained by adding the uncertai­nty in the cross section to the precision, and is thus less than 5 %. Instrument sensitivity depends on the cell length and the resolution in measuring the optical thickness; it is about 7E9 molecules/ceo Compari­sons in the laboratory between the NASA-JSC UV photometer and a National Bureau of Standards UV photometer designed and built by Arnold Bass agree wi thin about 1 %.

TABLE 1. RANGE AND UNCERTAINTY OF PARAMETERS.

PARAl-lETER RANGE UNCERTAmTY

T 290 - 315 K O.B % P 2 - 300 mb 0.6 - 2 % x (0.3 - 3)E-3 0.2 - 2 % 1 71.0 an 0.4 % a 1.147E-l ~ an 2 %

Certain improvements wi 11 be made during the next year that wi 11 reduce uncertainties in the precision to a maximum of 1.1 %. Thus, the worse case accuracy will be improved to about 3.1 %. By averaging measu­rements 'over two minutes an accuracy better than 1 % can be obtained.

1.4 Ozone Loss in the Instrument

One possible mechanism for ozone loss in the absorption cell is photolysis by UV light from the mercury vapor lamp. The rate of loss by this mechanism can be obtained from

d[Oz]/dt = - J [Oz]

where J, the photodissociation rate is computed from J = Ia where I is the light intensity and a is the photoabsorption cross section of ozone at 254 nm. In Section 1.3 it is shown that the incident intensity is about BE13 photons/em sq sec. Thus, a value of about lE-3/sec is obtained for J. The diameter of the absorption cell is 1 em, and its length is 71 em, giving a volume of 0.56 liters. At a pumping speed of 5 liters/min the residence time of air in the absorption cell is 0.7 seconds, and the loss rate by this mechanism is therefore less than 0.1 %.

Another possible loss mechanism is chemisorption of ozone on the walls of the flow system. The residence time within the total flow system is about 2 seconds. (The total length of the flow system is 200 an.) The coefficient for interdiffusion of a molecule through another gas depends apon its molecular mass. From reference (1) the coefficient for a mole­cule with the mass of ozone is about 0.14 em sq/sec at 1 atmosphere. Correcting for the reduced pressure at high altitude the distance an ozone molecule will diffuse during 2 seconds is 10 an at 40 km. Thus, each ozone molecule collides with the wall on the order of ten times while passing through the instrument. Laboratory experiments reported in refe-

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rence (2) show that an ozone molecule must undergo over one million wall collisions before being lost by chemisorption. Those experiments were done at stratospheric pressures in a container whose walls were coated with Teflon. It is therefore concluded that losses by this mechanism are also neglig ible.

2.1 Results of Intercomparisons with other Techniques

Interccxnparison of results from the NASA-JSC UV photometer and in­struments employing other techniques have been conducted during several balloon campaigns over the past few years. The results are discussed in detail in references (3)-(6) and are suromarized in Table II.

TABLE II. COMPARISON WITH OTHER TECHNIQUES.

TECHNIQUE ALTITUDES TYPICAL DIFFERENCE

UV photometry 15-41 km 1-5 % Electrochemical 15-30 km 5 %

30-42 km 15 % or more ~lass Spectrcxnetry 19-42 km 3 % (see text) Chemiluminescent 15-40 km 10-15 % UV Solar radiometry 15-42 km 15-20 % Infrared emission 15-40 km 15 % Infrared absorption 15-30 km 15 %

30-40 km 10-15 % Microwave emission 20-35 km 10-15 %

35-40 km u!2 to 45 % @ 40 km

As a rule ccxnparisons with electrochemical (ECC and Brewer) sondes were quite variable above 25 km because of their unreliable performance. However, on severa 1 occasions when extra care was taken by researchers intercomparisons within a few percent were obtained even to an altitude of 40 km. The most consistent and best ccxnparisons have been obtained with other UV photometers [see reference (6»), particularly the NOAA photometer described in reference (7).

Five comparisons have been made with the University of Minnesota Mass Spectrometer Beam System (MSBS). Excellent agreement was obtained (within about 3 %) on four flights. However, on a flight made in July 1983 the agreement began to di verge near 32 km and at 42 km a di fference of about 29 % was observed. Resu 1 ts from the NASA-JSC photometer were less than those from the MSBS. Both experiments appeared to be operating well. An EeC ozonesonde flown by W. Kohmyr of NOAA was also flown on the gondola near the UV photometer. It agreed with the UV photcxneter within about 10 % from 35 km to 42 km. The MSBS was suspended on a load line 400 feet below the photcxneter, and it is possible that some kind of contamination from either the gondola or balloon was being observed by the UV photometer which would result in an ozone decrease in the ambient air prior to its entering the instrument.

Results from UV solar radiometers have been systematically higher than those from UV photometers by 15 to 20 %. This is a very important disagreement that needs to be resolved.

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REFERENCES

1. Dushman, S. (1962). Scientific Foundations of Vacuum Techniques, 2nd ed., John Wi ley & Sons, Inc., New York.

2. Anderson, S. (August 1983). "The study of a mass spectrometer beam system for measuring ozone and other minor constituents of the strato­sphere", Ph. D. Thesis in Physics, University of Minnesota.

3. Mauersberger, K., R. Finstad, S. Anderson, and D. Robbins (1981). "A comparison of ozone measurements", Geophys. Res. Lett., Vol. 8, p 36l.

4. Aimedieu, P., A. Krueger, D. Robbins, and P. Simon (1983). "Ozone profile intercomparison based on simultaneous observations between 20 and 40 km", Planet. Space Sci., Vol. 31, p 80l.

5. Robbins, D., et al. (1984). "Ozone intercomparisons from the Balloon Intercomparison Campaign", Paper given at Quadrennial Ozone Symposium, Greece and published in proceedings.

6. Hi lsenrath, E., et al. (1984). "Resul ts from the Balloon Ozone Inter­comparison Canpaign (BOIC)", Paper given at Quadrennial Ozone Sympo­sium, Greece and published in proceedings.

7. Proffitt, M. (1984). "Fast-response dual-beam UV-absorption ozone photometer suitable for use on stratospheric balloons", Rev. Sci. Instrum. , Vol. 54, P 1719.

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OZONE INTERCOMPARISONS FROM THE BALLOON INTERCOMPARISON CAMPAIGN

Sumnary

D. Robbins, Mail Code SN3, NASA-Johnson Space Center, Houston, Texas 77058 USA

W. Evans, Atmospheric Environmental Services, Canada N. Louisnard, OHERA, France S. Pollitt, National Physical Laboratory, UK W. Traub, Smithsonian Astrophysical Observatory, USA J. Waters, Jet Propulsion Laboratory, USA

Intercomparisons of remote and in-situ techniques used to measure stratospheric ozone are made using results obtained on the Balloon Inter­comparison Campaign of 1982 and 1983. Two in-situ and four remote instru­ments participated. These included ECC ozonesondes, a UV absorption photometer, and microwave emission, IR emission and absorption spectrome­ters. Differences are generally less than 15 %, and are within the quoted error bars. Flights which involved different sets of instruments were made on four separate days, and resul ts are intercompared in plots of ozone density versus altitude. A careful assessment of errors was made for each instrument, and a plot of absolute errors versus altitude is given.

1.1 Introduction

Six techniques for measuring ozone are intercompared using obser­vations obtained during the BIC. Two in-situ and four remote techniques are included. Table I lists the participants, and Figure 1 shows the accuracies for the various instruments as a function of altitude. The accuracies shown for the JPL microwave spectrometer are different for BICI and BIC2 because of modificaions which were made between the two flights. A detailed discussion of the various instruments can be found elsewhere.

TABLE 1. BIC OZONE PARTICIPANTS, TECHNIQUES AND INSTITUTIONS.

TECHNIQUE INSTITUTION

In-situ: Electrochemical Sondes AES UV Absorption Photometry NASA-JSC

Remote: Infrared Solar Absorption (4.7 micron) ONERA Limb Scanning IR Emission (9.6 micron) NPL Limb Scanning IR Emission (88-89 micron) SAO Limb Scanning Microwave Emission (1500 micron) JPL

Ozone Symposium - Greece 1984 - 465-

Four gondolas were used during the BIC, each with its own set of instruments to measure various stratospheric species. The ozone in­struments were divided between the four gondolas, with the AES ozonesondes being flown as free flyers on small balloons. Averages were taken of data from the four ozonesonde flights made within about an hour of the times when the large balloons were launched. The plans called for launching all four of the large balloon gondolas together to obtain simultaneous measu­rements by all instruments. However, weather conditions allowed only the launching of two at a time. Table II gi ves the dates on which flights of the large balloon gondolas were made and lists the ozone instruments that were onboard.

TABLE II. BIC FLIGHT DATES FOR THE VARIOUS OZONE EXPERIMENTS.

BICI BIC2

22 Seet • '82 5 Oct. '82 17 June '83 20 June '83

AES AES AES AES JPL NPL JPL NPL

NASA-JSC NASA-JSC SAO ONERA

Data from the various instruments were reduced using a common set of meteorological parameters which were provided by E. Danielsen of the NAsA­ARC. These included temperature and geometric altitude versus pressure.

2.1 Results

Results from the AES ozonesondes flown during BICI were examined to determine whether condi tions in the stratosphere were stable enough to allow more general intercomparisons. Substantial differences were obser­ved below 20 km, indicating changes in stratospheric conditions between the dates the large balloons were launched. Above 20 km the AES sonde results agree within 10 %. A similar condition was observed for BIC2 except that above 35 km there were differences as large as 20 %. These were probably due more to the unreliability of the sondes than ozone variability. Thus, it was concluded that intercomparisons can reasonably be made of all techniques in the altitude region above 20 km. No canpari­sons are made be 1 ow 20 km. Figures 2 and 3 show resu 1 ts obta i ned dur i ng BICI on 22 September 1982 and 5 October 1982, respectively. Figures 4 and 5, respectively, show results obtained during BIC2 on 17 and 20 June 1983.

Ozone densities obtained by the in-situ techniques, AFS ozonesondes and the NASA-JSC UV photometer, agree within 5 to 10 %. This is much better than was obtained in earlier intercomparisons because ECC sondes became unreliable above 25 km.

JPL microwave emission results for ozone are generally larger than those obtained by the two in-situ techniques. On BICI differences of about 15 % are observed up to 35 km. However, these increase to about 45 % at 40 km. This difference is outside error bars and represents the only exception to the otherwise good agreement. On BIC2 measurements were obtained only to 35 km. Agreement between the microwave and' in-situ results on BIC2 was better than 10 % at all altitudes.

The ozone densities from the NPL IR emission spectrometer agree within 10 % of in-situ values above the peak during BICI. Similar agree-

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ment is observed from BIC2 above 33 km. However, below that NPL ozone densities are less. At 25 kID the NPL values are about 25 % smaller.

SAO IR emission results for ozone are derived from six groups of spectral lines near 88 microns wavelengths. During BIC2 typical diffe­rences between SAO and in-situ values are 10 %, except near 20 km where emission from nearby water vapor bands make retrieval from the IR emission spectra difficult. At 20 km the SAO ozone densities are about 16 % smaller than in-situ values.

Ozone densities obtained by the ONERA IR absorption technique during BIC2 agree with in-situ results within 6 % above 30 km. At the ozone density peak, however, their values are about 15 % less than those ob­tained by the AES ozonesondes.

3.1 Conclusions

"Results obtained during the Balloon Intercomparison Campaign show that remote and in-situ techniques for measuring stratospheric ozone can be intercompared. In general, the agreement between in-situ techniques is 10 % or better over the altiude range 20 to 35 km. Agreement between remote and in-situ techniques is generally wi thin about 15 %. In most cases the agreement between all techniques is within the quoted error bars. The only significant exception is the disagreement between the JPL microwave emission results and in-situ values on BICI above 35 kID.

Analysis of ozone data obtained during BIC will continue during the next year. Comparisons with one-dimensional models will be made using measured densities of other species involved in stratospheric ozone chemi­stry. Most important species were measured by other instruments flown on the BIC gondolas. Results of these comparisons will be reported in suse­quent meetings and publications.

BALLOON INTERCOMPARISON CAMPAIGN ozone Accuracies

45

l

40 \ / I

/ ' . j " I .. . ,-

3!'5 i / 1 . E . " i'! I / " '"

II, : 0 30 I I ' , -

:;) .... i :" .... i ~

! ... -"-" NASA -.J5C ..

J ... 2!'5 ... "'5

i. .JPL (BICI) .JPL !BlC2) '. \ : NPL SAO l \ 20 ONERA

\. "-

1!'5 I 2 6 B 10 20 .0 60 BO 100

ABSOLUT E ERROR ( ~)

FIGURE 1. Accuracies of BIC ozone instruments.

- 467-

45

40

3 5

E ~

III

" 30 :J .... .... .... J ...

25

2 0

15 . I

BALLOON INTERCOMPARISON CAMPAIGN

NASA- .J5C AES -JPL

. 2

22 SeP t e mb e r 19 B2

. 4

OZONE OENSITY ( I Et2 molecules/eel

4 6 a to

FIGURE 2.· Ozone densities measured during SIC on 22 September 1982.

45

40

35 E ~

"' " 30 :J .... ;:: J ...

25

20

- 5 . I

BALLOON INTERCOMPARISON CAMPAIGN

AES NPL

. 2

BIC I: 5 October 1962

. 4 4

OZONE DENS ITY ( IEI 2 mohcules/ccl

6 6 10

FIGURE 3. Ozone densities measured during SIC on 5 October 1982.

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45

40

35 e 2!

w 0 30 :> t-H t-J

'" 25

20

15 . I

FIGURE 4.- Ozone

45

40

35 e 2! w 0 30 :> ... H ... J ..

25

20

15

BALLOON INTERCOMPAR I SON CAMPA I GN 81C2: 17 ..June 1983

~ ." -'\ j NASA- ,JSC

AES d ,JPL

. 2 . 4 . 6 . 8 I 2 6 8 10

OZON OENSITY ( I E 12 mo lec:u les / ec)

densities measured during SIC on 17 June 1983.

BA LL OON INTER COMPAR ISON CAMPA I GN

4ES NPL SAO ONERA

2

20 ,Juno 1983

. 4 . 6 4

OZONE DENSITY ( I EI2 molecu les / cel

6 8 10

FIGURE 5. Ozone densities measured during SIC on 20 June 1983.

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OZONE MEASUREMENT FROM A BALLOON PAYLOAD USING A NEW FAST-RESPONSE UV-ABSORPTION PHOTOMETER

Michael H. Proffitt Aeronomy Laboratory, National Oceanic and Atmospheric Administration

325 Broadway, M/S:R/E/AL6, Boulder, Colorado 80303, USA and

Cooperative Inst~tute for Research in Environmental Sciences (CIRES) University of Colorado, Boulder, Colorado 80309, USA

Summary

A fast-response dual-beam UV-absorption photometer for balloon-borne measurements of atmospheric ozone is described. Fundamentally, the instrument consists of a mercury lamp, two sample chambers that can be periodically scrubbed of ozone, and two detectors that measure the 254 nm radiation transmitted through the chamber. The ozone absorption cross section at this wavelength is accurately known, hence the ozone numbe~ density can be easily calculated. Since the two absorption cham­bers are identical, virtually continuous measurements of ozone are made by alternating the air sample and the scrubbed sample between the two chambers. At a one second data rate, the minimum detectable concentra­tion of ozone (one standard deviation) is 1.5 x 1010 mol/cm3 (0.6 ppbv at STP). When highly accurate ozone measurements are needed, the effects of the balloon and its payload and the losses of ozone within the instrument itsel f must be carefully considered. The dual-beam instrument has provided detailed ozone profiles up to 40 km on balloon ascent and on parachute descent.

1. Introduction The need for accurate in-situ ozone altitude profiles up to at least

40 km for use in atmospheric chemistry stUdies and for comparison with satellite measurements is well established. For this altitude range, the vehicle of choice is a balloon. Although absolute accuracies of 5% to 10% in the troposphere and 3% to 5% in the stratosphere are badly needed for current research, this capability has not been demonstrated. Questions concerning possible losses of ozone within the measuring instrument espe­cially above 30 km (so-called wall losses), accuracy of the accompanying pressure measurement, other instrumental uncertainties (such as zero offsets), and balloon and gondola effects for the larger balloon payloads have made the accuracy of the measurements difficult to assess, if not impossible.

In recent years, modified Dasibi ozone monitors have been used for stratospheric measurements and have been considered one of the most accurate methods available. A new application of the same fundamental method is the dual-beam UV-absorption photometer, which not only has the

Ozone Symposium - Greece 1984 -470 -

accuracy inherent in the single-chamber Dasibi type instruments, but also has a faster time response. Therefore, detailed ozone structure, even on parachute descent, can be observed. Since every component of the dual-beam instrument has been designed particularly for balloon applications, many improvements have been made over the original Dasibi design.

2. Description of Instrument In its simplest form, the dual-beam instrument consists of two photo­

meters sharing the same UV source (see Figure 1). The source is a low pressure mercury lamp with a Vicor shield to eliminate the radiation that produces ozone, without appreciably attenuating the dominant 254 nm line used for the measurement. The two straight 40 cm long chambers are con­structed of Teflon, as are all of the parts in the sample flow path. The detectors and associated electronics have been carefully designed to give very low noise. In front of each detector is a narrow band filter centered at 254 nm which eliminates virtually all light that might leak into the chambers and reduces the weak mercury lines. There are two flow paths through the instrument. The sample, after entering the inlet tube, enters a tee and then either goes directly to a 4-port valve (sample path) or flows through an ozone scrubber before arriving at a different port of the 4-port valve (scrubbed path). The valve then directs the flows into the two chambers, so that one of the chambers contains an air sample and the other contains ozone-free air. Every 10 seconds the valve is rotated 90 degrees to interchange the roles of the two chambers. The flow rate (4 liters/minute) is sufficient to flush the chambers in 1 second, so that only 1 second of data is lost out of each 10 seconds, because of the valve change. .

Laboratory measurements have been made that show an ozone concentra­tion change of 1.5 x 1010 molecule/cm3 can be detected at a 1 second data rate. A more detailed description of the instrument and methods of data reduction is available(l).

3. Uncertainties in the Measurement The primary contributors to the absolute accuracy of the ozone meas­

urement are the uncertainties in 1) the molecular absorption cross section of ozone cr, 2) the path length L, 3) the pressure and temperature measure­ments, and 4) the effects of the instrument, gondola and balloon on the ambient ozone. The uncertainty in cr is generally considered to be ± 1.5%. L is easily measured to ± 0.2% accuracy. Pressure and temperature measure­ments are needed to calculate ozone mixing ratios, partial pressures, and number densities. Each of these measurements should contribute no more than ± 1% uncertainty if done carefully, but it should be emphasized that a 1% accurate ambient temperature and pressure measurement from the ground to 40 km requires great care and is seldom achieved in routine measurements. Since these measurements are required to calculate the altitude, it becomes doubly important to be certain of their accuracy. These altitude calcula­tions are not considered part of the absolute accuracy of the ozone meas­urements.

The most difficult contributors to assess are due to the presence of the balloon, gondola, and instrument. We have found that during balloon ascent, vertical ozone structures can be lost or "washed out" when the balloon is almost fully inflated (near maximum altitude), but the ver­tically averaged value of the ozone measurement does not seem to be altered significantly. In Figure 2, the data were taken in about 30 minutes, with a normal ascent to 40 km and an immediate cut for a parachute descent. The descent data clearly show some large structures that are not apparent on ascent.

-471-

Absorption Cells

~------------------'O cm------------------~

E.:hausl .-

----.. gioS Ilow

---............ l ight be,(llm

N"ffow·8and Filter

Figure 1. Schematk: diagram of the dual-beam UV-absorbtlon ozone photometer .

• O,r-----~----,_----_.----_.----_.-----

39

38

37

34

33

Palestl.no. Te:xu ()(:tober , 0, 1983

3'4~----~----~6----~~--~~--~~--~'O

Ol.one mixing ratiO (pl)my)

40

30

'0

...

"'"

.. , .

PressuflzeO Detector HQUSlng

ToCounlftr$

PaJestlno, Texas Mareh 21, 19&4

6 Ascen1

+ Oi:!$cl!'nt

-"" .10'" +'S~

Figure 2. Ozone vertical profile showing structural washout on ascent. Figure 3. Percent difference between measurements from two

dual-beam instruments to test for ozone wall losses.

- 472-

We have observed gondola effects during balloon float conditions from as low as 21 km up to 42 km. On one such float, a decrease of more than 5% in measured ozone mixing ratio is correlated with a 30 degree increase in ambient temperature and an easterly directed inlet (as measured with a magnetometer) during a long float at 30 km. It seems that a westerly wind gradient between the balloon and the gondola was transporting air warmed by the gondola to the inlet of the instrument, with a corresponding decrease in ozone due to contact with the gondola.

Losses of ozone within the instrument, especially above 30 km, can vary from instrument to instrument and perhaps from day to day within the same instrument. A laboratory calibration of such losses would not likely be of great value. We have found during the balloon ozone intercomparison campaign (BOIC) that ozone losses within an instrument can be at least 10% at 42 km unless it is designed for low losses. During that campaign we flew two dual-beam instruments on the same gondola. One was designed for operation at 40 km, with our best effort at minimizing losses of ozone. The other, although operational at 40 km, had a more restrictive and longer sample flow path. We felt that if losses of ozone were a problem on the Teflon surfaces within the instrument, it would show up as an increasing percentage difference between the instruments from 30 and 40 km. The results of this comparison can be seen in Figure 3. The instrument with the higher measurement is the one optimized for low losses, as we expected.

Another test was made on that same flight with the low loss instru­ment. A command was sent to the instrument to double the flow rate through the instrument while it was floating at 42 km. If there had been large losses in this instrument, we expected to see an increase in measured ozone with the corresponding decrease in residence time within the instrument. With a 5% resolution, we could see no such increase. Unfortunately, the other instrument did not have that same command capability.

As part of the BOIC campaign, we made three comparisons with the National Bureau of Standards' standard ozone photometer. After correcting for an instrument bias, which varies from day to day, the agreement was within about 0.5% over the wide range of concentration used. This instru­ment bias is well known and described by the Dasibi manufacturer as a zero offset. The offset is easily corrected in a laboratory instrument, but this option is not available on balloon instruments. However, in further laboratory bell jar tests, we found that the zero offsets decrease with decreasing ambient pressure and were not present at about 400 mbar and less. Therefore, this effect is usually present only below about 7 km.

4. Conclusions The potential for absolute accuracy with the UV method is clearly in

the 5% to 10% region from the ground up to 40 km, but still has not been fully demonstrated. Included in this estimate are all the uncertainties mentioned in the previous section. For the troposphere, where the ozone losses appear to be negligible, a 5% to 10% accuracy should be achievable above 7 km and, if the zero offset problem were eliminated, this accuracy would be appropriate from the ground. However, the stratospheric measure­ment accuracy is not easy to estimate, due to the difficulty in assigning a firm number to the ozone losses. However, if one restricts the measure­ments to descent, achieves a 1% pressure measurement up to 40 km, and tem­porarily ignores the instrument ozone loss question, a 5% accuracy measure­ment is likely being made. The data presented here suggest that ozone losses within the high-altitude version of the dual-beam instrument are no more than 5%; therefore, a 5% to 10% accurate measurement seems likely, including wall losses.

-473 -

Further tests are underway in our laboratory to understand and hope­fully eliminate the zero offset problem. We also have described a 3-tube photometer that could be used to measure ozone losses within the instrument during flight(l) , thereby being able to correct for such losses and decrease this uncertainty to about 1%. We plan to have such a 3-tube in­strument ready to test within a year. With this instrument, an absolute accuracy of about 6% seems likely.

We feel that further intercomparisons between different ozone instru­ments should be continued, first in the laboratory, simulating strato­spher ic condi tions, and followed by modest balloon intercomparisons to verify the laboratory tests. Although the emphasis has been on strato­spheric measurement accuracy, further effort on estimating and verifying tropospheric accuracies should also be a high priority.

Reference 1. PROFFITT, Michael H. and McLAUGHLIN, Richard J. (1983). Fast-response

dual-beam UV-absorption ozone photometer suitable for use on strato­spheric balloons. Rev. Sci. Instrum., 54, 1719-1728.

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AN IN-SITU MULTIPASS UV-ABSORPTION OZONE SENSOR DESIGNED FOR STRATOSPHERIC APPLICATIONS

E.M. WEINSTOCK, C.M. SCHILLER and J.G. ANDERSON Center for Earth and Planetary Physics

and Department of Chemistry Harvard University, Cambridge, Massachusetts

Summary

A balloon-borne, in situ ozone sensor designed for stratospheric use has participated in a balloon ozone intercomparison campaign. (BOle). Instrumental performance, judged according to pre- and post-flight laboratory calibrations and in-flight diagnostics, was excellent. Systematic differences with other ~ situ instruments were small, but nevertheless well beyond that expected, based on signal-to-noise considerations alone. Gondola effects are considered and the advisability of laboratory intercalibrations is discussed, as a means of further understanding the flight performance of all the in situ UV absorption instruments.

1.1 Introduction

An in situ UV-absorption ozone sensor, utilizing a multipass "White Cell" arrangement combined with a normal ized counting system has been developed in our laboratory (1) and in use since 1981. Designed for stratospheric measurements the instrument combines a large volume (500 cc) teflon coated absorption cell, a 2 liter/sec displacement pump to el iminate "wall loss" of ozone,and in-fl ight diagnostics to verify that fact.

The instrument has operated according to specifications during hundreds of hours of laboratory calibration cross checks as well as in stratospheric balloon flights beginning in 1981. It is informative to delve into the requirements of acceptable laboratory performance as a means of evaluating flight performance. Accordingly, by comparing laboratory data and data taken during BOIC III, The most recent ozone i ntercompari son fl ight, assessment of our ins trument' s performance is readily attained. In addition, we hope to shed some light on the overall success of the BOIC fl ights and the interpretation of instrumen­tal performance.

1.2 The Calibration Facility

Figure 1 pictures the 1 abora tory ozone cali bra ti.on fac i 1 i ty as it is used in conjunction with our flight instrument. Ozone, with better than 3% stability is produced in the fast flow reactor at concentrations of lU12 to 5 x 101 3 mol/cc, at pressures ranging from 3 to .50 torr, and

Ozone Symposium - Greece 1984 -475 -

at flow reactor velocities of 3-10 m/sec. The ozone concentration is measured simultaneously by the flight instrument and by absorption along a 200 cm pa th down the center of the fl ow tube. The two measurements, after corrections for pressure and temperature differences, typically agree to within 3% over the full range of pressures and velocities. Figure 2 depicts an example of the instrument measuring two differe~t ozoneconcentra ti ons for whi ch the uti 1 ity of the 1 abora tory facil ity becomes evident. Figure 2a illustrates the negligible backround or offset of the instrument, the inherent lack of noise at stratospheric pressures, and consequently its excellent signal-to-noise potential. This signal corresponds to an {031 = 2.2] x lOll mol/cc, with approx­imately 8% variability = 1.7 x 10 0 mol/cc. In figure 2b, the {03} is measured to be 7.82 :- 0.21 x lOll mol/cc. By comparing the two values, it can be deduced that this variability is i.nherent in the {03} in the reactor and not caused by noise inherent in the flight instrument. By comparing the structure in the unscrubbed and scrubbed portions of the instrument operating cycle, one easily draws the same conclusion. Figure 3. gives an example of a comparable measurement made in flight during BOle III, taken during float. The data is averaged over 1/4 sec. intervals and must be multiplied by 4 to represent the real count rate since the 2 most significant bits of the digital ward were dropped. Nevertheless, a signal-to-noise comparable to that exhibited in figure 3a is observed.

1.3 BOle III Flight Data

The Harvard instrument performed excellently during BOle III based on the fo 11 owi ng cri teria:

1. Pre- and post-flight laboratory calibration checks. 2. Agreement between ascent & descent profiles. 3. Successful in-flight diagnostics; especially for wall-loss.

Fi gure 4 ill us tra tes agreement between ascent and descent profil es. The ascent profile is plotted from the very first cycle of operation to ill ustrate how rapidly the ozone sensor begins making val id measurements. The profiles, where they overlap, agree to better than 5% and the magnitude and sign of the difference appears to be consistent with other instruments, suggesting that the origin is not instrumental.

In-flight diagnostics, consisting of motor speed and flushing time changes (each by a factor of two), were carried out during ascent with no discernible effect on the measurement. However, we choose to focus on measurements taken dUring float, at 2.5 mhar, where wall-loss in in-situ ozone instruments has been a major concern (2). A return look at figure 3 details an upper 1 imit of wall-loss measured by our instru­ment. The data shows the rate at which the ozone concentration decreases within thE) absorption cell after the motor is stopped on command. The calculation takes into account the gradual decrease in light intensity, overestimates by almost a factor of two the counts lost per second, and yields a maximum ozone loss of 3%/sec. Since the typical residence time in the cellisl/2tO 3/4 of a second, wall loss is definitely not a factori n our instrument.

Figure 5 shows the variation of ozone mixing-ratio with time taken at float. These large fluctuations, which show no correlation with motor speed and fl ush time changes, do corre 1 ate with the temperatures indicated by two probes in the vicinity of our inlet tube. It is noteworthy that based on tbe signature of our measured ozone profile as

-476 -

it approaches float the peaks do not represent ozone production but rather a more realistic measurement of ambient oZone. Moreover, the correlation with temperature, especially during rotation of the gondola, definitively links our measurement to a gondola perturbation which is especially pervasive at float. The obvious question which must be answered is what, if any, is the perturbation during ascent and/or descent. Figure 6 illustrates the temperature profile for the fli~ht as measured by the 2 thermistors located near our inlet tube and indicates the problems associated with a "slow" valve down descent. The correlation which exists between our descent data and the thermal perturbations on descent reaffirm the conclusion that the gondola is affecting our ozone measure­ment. While ascent does not show the similar thermal characteristics, the thermistor location much nearer the top edge of the gondola might in fact be the reason for that lack of correlation.

1.4 Conclusions

Based on all the diagnostics at our disposal, the instrument performed excellently during BOIC III. Comparisons with other in-situ sensors i ndi ca te small but neverthel ess sys tema ti c differences in reported ozone profiles. Available information is insufficient to help determine how much of the difference is instrumental and to what extent perturbations by the gondola and/or balloon are important. This is expeci ally critical because of the apparent sys temati c difference between in-situ and remote ozone measurements in the 30-40 km region that has developed in the past two decades. It is therefore critical that a laboratory intercomparison be organized to follow up the flight effort and help elucidate the questions that remain unanswered. In addition, during future flights, more attention should be paid to gondola effects and efforts be made to map temperature profiles around the gondola and correlate the contours with the measured ozone concen tra t ions.

References

1. Anderson, J.G. (1982) in Causes and Effects of Stratospheric Ozone Reduction: An Update, (National Academy Press, Washington D.C.) p. 240.

2. Ainsworth, J.E., Hagemeyer, J.R. and Reed, E.r. (1981) Geophys. Res. Lett. 8, 1071.

-477 -

ELECTRONICS

SAMPUNG PORT

HOUSING FOR ROOTS BLDWER

~~----------200cm------------~

TO PUMP

0. SOURCE

FIGURE 1 OZONE CALIBRATION FACILITY

FIGURE 2 "White Cell" Ozone Measurements in the Slow Reactor

U 65600 ~ \a) !!! u

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- 478-

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MIXING RATIO (ppmv)

-479 -

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TIME (sec -GMT) It 104

-480-

MEASUREMENT OF THE VERTICAL PROFILE OF OZONE FROM THE ASCENT OF A BALLOON HORNE ULTRAVIOLET SPECTROPHOTOMETER

1. Summary

J.B. Kerr and H.F.J. Evans Atmospheric Environment Service

4905 Dufferin Street Downsview, Ontario, MJR 5T4

An ul traviolet spectrophotometer, similar to the Brelver ozone spec trophotome ter, was flown on the STRATOPROB-O: balloon payload during the Balloon Intercomparison Campaign (BIC) at Palestine, Texas on September 22, 1982. Solar intensity was measured at five wavelengths in the UV absorption spectrum of ozone Inth a resolution of .2 nm. The gondola pointing system directed the instrument at the sun duri~~ the ascent through the atmosphere between 5 km and 40 km. The column amount of ozone above the instrument was determined as a function of balloon height and the vertical ozone profile derived from the height differential of the ozone overburden curve.

The instrument and method of measurement are described and the ozone absorption and vertical profile curves are presented. The derived ozone profile compares favourably with the average of three ozonesonde profiles measured shortly before and after the ascent of the main payload.

2. Introduction

As part of the BIC1(Balloon Intercomparison Campaign) a STRATOPROBE mission was conducted on September 22, 1982 from the NSBF at Palestine, Texas. The STRATOPROBE payload carried a complement of seven instruments; one of them was the spectrophotometer used to make the ozone measurements described in this paper. In the measurement of ozone by direct solar absorption, the spectrophotometer is pointed at the sun during the ascent of a large balloon. The payload was launched at 20:29 GMT and the measurements were made with the solar elevation angle between 40 and 20 degrees during the 3 hour ascent of the balloon. The instrument used to make the measurements was a prototype version of the Brewer spectrophotometer which is described elsewhere in this symposium(2).

The wavelengths employed are shorter than used in the Brewer, as illustrated in Table 1. The spectrophotometer was mounted on the solar pointing table of the STRATOPROBE payload. Since the pointing system of the STRATOPROBE payload is very powerful and sophisticated; solar lock was acquired early in flight enabling measurements to be obtained from 3 km up to the float altitude of 42 km. The solar intensity at 5 wavelengths is measured with the spectrophotometer during the ascent. The measured intensity variations of the sun with time are then converted to absorption as a function of altitude using the balloon altitude variation with time. The differential absorption is then used to calculate the overburden of ozone at any altitude during the ascent. The column ozone overburden curve is then differentiated with respect to altitude to obtain the ozone concentration profile.

Ozone Symposium - Greece 1984 - 481-

3. The Balloon Inversion Technique

A simple explanation of the measurement method was given in the introduction; a more detailed description of the analysis follows.

Absolute measurements were made at 5 wavelengths 303.15, 303.85, 305.59, 308.29 and 309.85 nm with 0.13 nm resolution during the balloon ascent and sunset. Logarithms were then taken of the corrected (dead time) counts on all five wavelengths. When the balloon had reached float altitude and stabilized, Langley plots were made on all 5 wavelength settings to determine the extraterrestrial intensity values:

i.e. log Ii = log IOi + AilJ for i = 1 to 5 log Ii's (i = 1 to 5) are the 5 measured values. lJ is the air mass as determined from balloon position and time. log Ii's were regressed against lJ to determine the log IOi's and Ai. The log IOi's are extraterrestrial values. The Ai's are the effective atmospheric absorptions above the instrument. (i.e. combinations of 03 and Rayleigh scattering).

The Langley data were obtained at 42 km for lJ values between 5 and 15. The determination of the log 10 i' s are quite precise.

The wavelengths, the ozone absorption coefficients used (after Bass and Paur(1) at-45°C), the Rayleigh scattering coefficients and ""the extraterrestrial log10 IOi's are shown in following table.

Table Absorption Parameters

i A Ct03 6 loglOIo nm Base 10 Base 10

1 303.15 2.698 .5075 6.1454

2 303.85 2.529 .5025 6.0641

3 305.59 1.883 ~906 6.0712

4 308.29 1.329 .4727 5.9898

5 309.85 1.014 .4628 5.8816

The following values were then determined for the 5 wavelengths for the intensity measurements during the balloon ascent.

F i = log 10 i-log Ii + Bi m

where m is Bemporad's airmass function.

-482 -

Assuming that ozone and aerosols are the only absorbers, the Fi's are given by:

Fi = A + eliX\l where A is the aerosol contribution to the absorption assumed to be equal for all A,s. eli are ozone absorption coefficients. X is the column ozone amount above balloon.

[Note: Because of strong forward scattering by aerosols and because of the wide field of view, most aerosol scattered light is measured.]

Using the five Fi's at each measurement and the five eli'S, the values of A and X were determined for each measurement by least squares fitting. A is also a constant offset and is equivalent to taking ratios to reduce absolute instrument drift.

The ozone column, X, was then plotted as a function of balloon height.

The running slope of X vs balloon height was calculated at each data point during the ascent to determine

f:.X cm/Ian f:.H

as a function of height, which is the resulting ozone concentration as a function of height (Figure 2).

4. Results

The absorption by ozone at the five wavelengths was measured as a functibn of altitude. Using the inversion method described in section 3, this was converted to the column amount of ozone above the balloon at each altitude. The column ozone as a function of altitude is shown in Figure 1. The total ozone amount at 3 km of 280 DU (Dobson units or matmcm) should be compared with the ground based Brewer measurement of 295 DU at 0.5 Ian. The amount of ozone above the balloon float altitude of 42 km is 9 DU.

The total ozone above the balloon has been differentiated to obtain the ozone concentration profile in Fig'ure 2. The resulting profile has a peak concentration of 4.6 x 1012 molecules/cm3 at 25 km. Overall, the profile is very smooth with the exception of a vertical structure with a wavelength of 5 Ian Which we believe to be an effect due to the presence of gravity waves.

The validity of this new technique for the measurement of ozone can be tested by a comparison with other measurements of ozone by other techniques. In Figure 3 a comparison of the absorption profile with a profile measure by conventional ozone sondes is shown. The ozone sonde profile is the mean of three ozonesonde flights made at 7:00 GMT, 13:00 Q1T, and 20:00 GMT on September 22, 1983. These flights were made with Model 3A ECC ozonesondes; they were flown as part of the STRATOPROBE background meteorological data set which AES conducts as part of each STRATOPROBE campaign. These flights were part of the BIC 1 campaign described by Watson et al (4) in this symposium.

The comparison of the absorption ozone profile with the ozone sonde

- 483-

profile shows excellent overall agreement. There is a small but significant difference in the 10 to 15 km region. There is also a discrepancy in the region from 36 to 41 km, but this is where the ozonesonde data are suspected to be too small. The major difference is the apparent wave in the absorption profile which has peaks at 5 km intervals over the entire profile. This is attributed to the effect of gravity waves on the ozone inversion analysis. We hope to be able to remove this effect when w~ understand it in more detail.

5. Conclusions

An ultraviolet spectrophotometer of the Brewer type has been successfully flown on a STRATOPROBE balloon flight to measure the ozone profile from 3 to 42 km using solar absorption. The column amount of ozone was obtained as a function of balloon altitude and agrees well with groundbased Brewer measurements. A vertical ozone profile was derived from the altitude derivative of the ozone overburden curve •. The ozone profile appears to be of excellent quality. It agrees well with the mean ECC ozonesonde profile measurements from three flights made on the same day. An effect due to the presence of gravity waves appears to be present in the absorption profile. Overall, the absorption technique has promise as an accurate technique for the measurement of vertical ozone profiles from 5 km to altitudes in excess of 45 km.

Acknowledgements

We ~sh to thank Dr. R. Watson for organLzLng and supporting our participation in the Balloon Intercomparison Campaign. We would like to express our appreciation to W. Clark for providing excellent technical support of the instrument, to T. McElroy and Dr. D. Wardle for providing techical assistance and invaluable scientific advice, and to K. Casselman for analysing the data.

References

(1) Bass, A.M., and R.J. Paur, Ultra-violet Absorption Cross-sections of Ozone: the Temperature Dependence, Proceedings of the 1984 Quadrennial Ozone Symposium, this volume.

(2) Kerr, J.B., C.T. McElroy, D.I. Wardle, R.A. Olafson, and W.F.J. Evans, The Automated Brewer Spectrophotometer, this volume.

(3) McElroy, C.T., The Determination of Stratospheric Nitrogen Dioxide Concentrations from Limb Brightness Measurements, this volume.

(4) Watson, R.T., W.F.J. Evans, C.B. Farmer, P.T. Woods, R.J. Zander, and R.K. Seals, Jr., The Balloon Intercomparison Campaign: Measurements of Key Stratospheric Minor Species, this volume.

-484-

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Summary

SPECTRUM MEASUREMENT TECHNIQUES FOR ROCKET, BALLOON AND SATELLITE EXPERIMENTS

A. MATSUZAKI, Y. NAKAMURA, and T. ITOH The Institute of Space and Astronautical Science

4-6-1, Komaba, Meguro-ku, Tokyo 153, JAPAN

This article reports on new techniques for measuring whole spectra in rocket, balloon, and satellite experiments. The rocket-borne spectro­meter was developed for the simultaneous measurement of HZO and 0z con­centrations and temperature in the upper atmosphere. Another spectro­meter for the rocket experiment measured the rotational profile of the atmospheric absorption band of 0z molecules in the middle atmosphere. In the balloon experiment, the stratospheric aerosol extinction was investigated by the measurement of the near-infrared spectra of the solar radiation. The balloon-borne infrared spectrometer is developed for the measurement of HZO, COZ' and CH4 in the stratospheric atmosphere. The limb sounding infrared spectrometer mounted on the satellite "OHZORA" (EXOS-C) measured the infrared absorption spectra of HZO, COZ' CH4 ,01' and NZO in the middle atmosphere. All these spectrometers are basea on multichannel spectroscopy by the aid of image devices such as a photo­diode array, a CCD, an image intensifier, a vidicon, a pyroelectric array sensor, and so on. The experimental results indicate the ad­vantage to the measurement of the whole spectrum in aeronomic optical experiments.

1.1 Introduction

There are many advantages to measurements of whole spectra, i.e., more informative data can be obtained. For example, least-squares curve fitting techniques can be used to obtain more accurate interpretations, rotational and vibrational temperatures can be calculated and dynamic molecular pro­cesses can be studied. However it is not easy to measure spectra in rocket, balloon, and satellite experiments, because of their rapid motions and tem­poral changes in aeronomic phenomena. Another important problem that had to be solved, for example, is the development of a mechanical support for the spectrometer to counteract the violent vibrations and acceleration of the rocket. The present study reports on new instrumentation for measuring spectra in rocket, balloon, ans satellite experiments. Table I shows the spectrometers recently developed by the authors. This article describes predominantly on spectrometers Z and 5, i.e., the rocket-borne spectrometer tor measuring the rotational profile of the atmospheric band of 0z molecule and the satellite-borne infrared spectrometer for the remote senslng of HZO, COZ' CH4 , °3 , NZO, and aerosol in the middle atmosphere.

Ozone Symposium - Greece 1984 - 486-

Table 1.

List of the spectrometers developed by the authors for rocket, balloon, and satellite experiments.

No. on board wavelength Detectors purpose of experiment range

1 rocket near IR photodiode simultaneous measurement of (680-900nm) array H20 and 02 concentrations

and temperature

2 rocket near IR image intensi- rot~t~onal temperature of (755-770nm) fied photodiode 02( Lg) molecule

3 balloon near IR charge coupled stratospheric aerosol extinc-(670-870nm) device (CCD) tion

4 balloon IR pyroelectric H2O, CO2 , CH4 concentrations (2-5jJm) vidicon

5 satellite IR solid-state H20, CO2, CH4 , 03' NtO con-. (1.6-2.4jJm) pyroelectric centratlons and stra ospherlc (2.8-4.8jJm) array sensor aerosol extinction (8.8-1O.2]Jm)

2.1. Measurement of the Rotational Profile of the A-band of 02 Molecule by Rocket Experiment

Measurements of the rotational temperature of atmospheric molecules pro­vide direct information on the molecular processes in the upper atmosphere. The rotational temperature is obtained from high resolution rotational spec­tral profile. Spectrometer 2 was used to measure the rotational profile of the A-band absorption spectrum of oxygen molecules. The measurement of the absorption spectrum was based on a solar occultation method.

Figure 1 shows the schematic diagram of spectrometer 2. The solar light was introduced into a polychromator (f=400mm, 2000 lines/pair) by the optical system, consisting of lenses, a diffusor, and an iris, with a field­of view of 50°; the same intensity of the solar light was introduced within this field-of-view angle. The spectum dispersion of the polychromator was detected with an image intensified (proximity type, ITT F-4769) photodiode array (Reticon RLI024SF). Video signals from the photodiode array were con­verted to the digital signals (8-bit) and stored in the memory (RAM). The spectral data stored in the memory were transmitted by a PCM telemetry sys­tem. FM analog transmission was also used for monitoring the signals of the instrumental conditions.

To start the measurement at lOs after the launch, i.e. before the nose­cone opened, two windows (for the polychromator and the trigger optical sys­tem) were opened on the wall of the rocket. The directions and angles of field-of-view were the same between these windows. Since the rocket spun at the rate I-3Hz, the solar light enters the spectrometer through this win­dow during 139ms for 1Hz and 64ms for 3 Hz. This time is long compared with the scan time of a spectrum, IOms, but is shorter than the time for the trans-

-487 -

755 760 765

A/nm

0.9

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c o e 0.3 o \/I D < I

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- 488-

Fig.l Schematic diagram of spectrometer 2. II: image intensifier, IS: photodiode array, GC: clock generator, CC: clock controller, PD: photodiode.

Fig.2 The spectra measured by the S-310-11 rocket experiment. Spectrum 1: 24.8km, Spectrum 2: 190km in the altitude of the rocket.

Fig.3 The absorption intensity obtained from the plot in Fig.2.

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Fig.5 Standard deviations, obtained for various temperatures, T.

mission of one-spectrum data, approx. 400ms. Therefore, the measure-mode, in which the spectra were scanned and the good spectral data were stored in the memory, were started by the trigger signal from the trigger optical sys­tem, and then, in the data-transmission mode, two good spectra stored in the memory were transmitted by the PCM telemetry at the bit-rate of 25.6 kbit/s. After the data transmission, the measure-mode was started again by the trig­ger signal, and therefore the data were transmitted, and so on. Thus two spectra were measured and transmitted every second in this way; this corre­sponds to the altitude resolution of 2km.

Spectrometer 2 mounted on the S-310-11 rocket was launched fromKagoshima Space Center (KSC) at 1838JST on September 7, 1981. Figure 2 shows the spectra measured. The rotational profile of 02 molecules is observed in spectrum 1 which was measured at 24.8km. In spectrum 2 measured at 190km, the 02 absorption band disappears almost completely and the Fraunhofer lines of the solar radiation are clearly observed. The absorption intensities were calculated by the aid of the Beer-Lambert law; Fig.3 shows the result obtained by using spectra 1 and 2. On the other hand, we can calculated

- 489-

the theoretical spectra for various rotational temperatures; Fig.4 gives the theoretical spectra at 218K. By the comparison of the spectrum observed with the calculated one, we can calculated the standard deviations for vari­ous temperatures, as shown in Fig.5. The rotational temperature of 02 can be obtained 218±1.5K at 24.8km from the minimum standard deviation. This result indicates the thermal equilibrium at this altitude.

2.2. Satellite-platform Remote Sensing of Atmospheric Constituents

The Institute of Space and Astronautical Science (ISAS) launched the 9th scientific satellite "OHZORA" (EXOS-C) on Feburuary 14, 1984 for the in­vestigations of the atmospheric and electromagnetic circumstances of the earth. The satellite bears spectrometer 5, i.e. the infrared spectrometer, for the remote sensing of the atmospheric constituents. This spectrometer measures the infrared spectra of the solar radiation passing the limbatmos­phere by the solar occultation method.

The schematic diagram of this spectrometer is shown in Fig.6. The solar irradiation entering the window is correctly introduced into the poly­chroma tor by the two-axes controlled mirror. The spectral images given by the polychromator are detected by the pyroelectric linear array sensors. Since the pyroelectric sensor detects only the thermal difference, the solar radiation is modulated with the optical chopper. For getting the spectrum with the better spectral resolution and the wider dynamic range, the spectra are measured in the three wavelength ranges, i.e. 1.6-2.4wm for H20, 2.8-4.8 wm for CO2 , H20, CHu' N20, and 8.8-10.2wm for 03' The averaged spectral resolution for each range is 0.025wm, 0.031wm, 0.0875wm, respectively.

Ffgures 7 and 8 show the solar-radiation spectra measured in the 1.6-2. 4wm and 2.8-4.8wm ranges, respectively. The absorption band of H20 is ob­served in the spectrum of the 1.6-2.4wm range. In the spectrum of the 2.8-4.8wm range, we could observe the absorption bands of H20, CHu' CO2 , and N20. Furthermore, the 03 absorption band could be observed in the 8.8-10.2wm range. By the analysis of these data, the distributions of these molecules can be obtained. On the other hand, these spectra become red because of the ex­tinctions from the atmospheric molecules and aerosols. Therefore we can calculate the aerosol extinction from the red effect of the spectrum.

All the spectra measured in Rev.780 are shown in Fig.9. The spectra in the 1.6-2.4wm, 2.8-4.8wm, 8.8-10.2wm ranges are indicated by Sl, S2, and S3, respectively. The signal intensity is represented by the lightness, i.e., the most intense signal is given by white and the weakest one black. The maximum intensity of each spectrum is normalized to be represented by white. Since these spectra were measured near the sunset for the satellite, the absorption intensity increases with the time lapse. At the moment of the sunrise, the two-axes controlled mirror system immediately tracks the sun, we could similarly measure the spectra near the sunrise.

The analysis of these data are being performed with the aid of the de­convolution technique.

-490-

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- 491-

Fig.6 Schematic di­agram of the satellite-borne spectrometer, spectrometer 5.

Fig.7 The spectrum measured in the 1.6-2.4 m range.

Fig.8 The spectrum measured in the 2.8-4.8 m range.

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PRECISE OZONE MEASUREMENTS USING A MASS SPECTROMETER BEAM SYSTEM

K. MAUERSBERGER, S. ANDERSON, D. MURPHY and J, MORTON School of Physics and Astronomy, University of Minnesota

Minneapolis, Minn., 55455

Summary

During the last few years a gas expansion system combined with a mass spectrometer has been developed to measure neutral constituents in the stratosphere. Ambient gas particles are formed into a molecular beam by a sequence of orifices and high speed liquid helium pumps. The beam traverses the ion source of the mass spectrometer without wall inter­actions. The experiment is especially capable of measuring ozone mixing ratios in the upper stratosphere. The highest altitude is limited by the performance of balloons.

Before each flight the experiment is calibrated in the laboratory at stratospheric pressures and temperatures. Studies have shown that an absolute accuracy for ozone calibrations of ±2% or less can be obtained. During the flight many mass ratios of stable, well mixed atmospheric

30 33 38 . gases (e.g., N2 , O2 , Ar) are measured and compared w1th laboratory

calibrat10ns. The isotopes and various ratios serve as in-flight cali­brations to maintain the calibration accuracy throughout the flight.

Results from recent balloon flights show ozone mixing ratios having an absolute accuracy of about 3% and a precision of 3% at 42 km and less than 2% at 35 km.

1. Introduction

Many of the experimental techniques applied for ozone measurements are based on absorption of UV light. The derivation of ozone number den­sities or mixing ratios requires the knowledge of absorption cross sec­tions, as well as of pressures and temperatures. Because in-situ experi­ments flush air through an absorption cell, loss of ozone may occur during this process. On the other hand, the experiments are generally small and light weight, and may easily be carried on balloons and rockets.

During the last five years a new technique for precise ozone measure­ments has been developed which is independent of absorption processes (1,2). In this experiment stratospheric air is formed into a molecular beam which is directed through the ion source of a mass spectrometer where ionization and subsequent mass analysis occurs. This technique is par­ticularly applicable to measure ozone and its isotopes since the mass

Ozone Symposium - Greece 1984 -493 -

MASS SPECTROMETER BEAM SYSTEM Fig. 1: Mass spectrometer beam system (MSBS) attached to the ozone calibration system. 01: gas entrance orifice; B10 and B100: Baratron pressure sensors; RPG: rotating piston gauge; G: ozone generator.

range 48 thrcugh 50 is free of other atmospheric gases. This for ex­ample, is not the case for the detection of NZO which has the same molecu-

lar mass 44 as the much more abundant COZ' As shown in this paper the

mass spectrometer beam system (MSBS) has the sensitivity to measure ozone well above 40 km without a reduction in accuracy or precision.

Z. The Experiment Figure 1 shows the major parts of the MSBS when it is attached to the

laboratory calibration system. Detailed descriptions have been published elsewhere (1,Z,3), thus only a brief summary is given below: Air enters the MSBS through a small orifice 01. This orifice is either attached to a calibration chamber or in flight directly exposed to the stratosphere when the balloon has reached maximum altitude. Most of the gases expanding behind 01 are adsorbed on liquid He pump 1. Only particles which ,travel directly through orifice OZ are formed into a molecular beam which enters the ion source without wall collisions, being intercepted only by the ion­izing electron beam. Neutral particles scattered at the bottom of the ion source are removed by liquid He pump Z. The mass spectrometer is a mag­netic instrument with a multiplier detector operating in ion counting mode.

A small movable flag in front of the ion source is used to lower the detection limit for stratospheric gases into the range of parts per billi9n. Actually all measurements are made twice: when the flag is re­tracted (flag-out) the mass spectrometer measures beam and background

-494 -

gases o The later ones may still be present within the ion source despite the second liquid helium pump. When the flag is blocking the beam (flag-in), the mass spectrometer measures background only. Subtract­ing the flag-in signals from the signals when the flag is retracted will result in a measurement due to ambient particles onlyo During past flights the limit of detection has been below 10 ppbv.

The liquid helium pumps are filled just before a balleon flight. They last for about lZ hours. The experiment is contained in a sealed, all-metal aluminum gondola which is suspended by a lZO m load line below the balloon. The outgassing of balloon and gondola has never influenced the ozone measurements.

3. Ozone Calibrations Before each balloon flight the MSBS is calibrated in the laboratory.

Fig. 1 also shows the major parts of the calibration system. The pressure in the chamber is monitored with Baratron capacitance manometers (BIO and BIOO). Initially outdoor air is admitted at stratospheric pressures through a leak valve into the calibration chamber. Many isotopes of major

atmospheric gases are measured, particularly 30NZ ' 330z , 38Ar and 84Kr •

Various mass ratios are formed such as 30/38 or 33/38. Since the major atmospheric gases are well mixed throughout the stratosphere, all isotopes will have the same mixing ratios during the flight as they have during calibrations. Those isotopes and many mass ratios serve as inflight

calibration standards. Whenever an 38Ar peak is measured by the mass spectrometer, the gas in front of orifice 01 contains the argon isotope at 5.9 ppm. In addition, the mass ratios are compared with flight ratios to check for mass discrimination. Generally an agreement between calibra­tions and flight of ±l% has been found, indicating a very stable experi­ment.

The calibrations for ozone are based on a similar procedure discussed 38

above. In an air-ozone mixture, masses 38 and 48 ( Ar, 03) are

repeatedly sampled to determine the ratio 38Ar/ 03 in units of [ppm/ppm].

Any small change in the experiment sensitivity will not influence the ac­curacy of the ozone mixing ratios measured in flight. Mass discrimination is checked by comparing mass ratios. In summary, the experiment will provide direct ozone mixing ratios based on the well-known mixing ratio of 38Ar •

The formation of the air-ozone mixture has been described in detail by Anderson and Mauersberger (3). Ozone is produced in a discharge process (G) of pure 0Z' and is collected in solid form in a liquid NZ cooled glass trap. When sufficient ozone is accumulated, the flow is stopped and pumping on the trap is maintained to remove primarily OZ.

Ozone is released into the calibration volume by warming the trap. The MSBS provides an analysis of the purity of ozone present in VI, measuring in particular CO, COZ' and HZO. The major impurity, 0Z' is difficult to

measure since ozone produces mass peaks at 48, 3Z and 16 mass units. In a number of separate tests, the actual 48/3Z-ozone fragmentation ratio is determined: Ozone is released into the calibration volume, masses 48 and 3Z are measured and thereafter the glass trap is cooled again with liquid NZ to re-freeze the major portion of 03. 0Z' on the other hand, will

-495 -

remain in the gas phase and will be measured by sampling again 48 and 32.

Past calibrations have shown that the purity of ozone ranges between 97 and 99% when careful calibration procedures are applied. After deter­mining the impurities a correction to the ozone pressure is applied. In the final step, air is expanded from volume V2 into the calibration chamber to produce stratospheric pressures with ozone becoming a minor constituent. Masses 38, 48 and others are repeatedly measured. As shown in (3), the decay time constant of ozone in the teflon-coated calibration volume is approximately 10 hours, long enough to perform precise calibrations within minutes. Recently a small glass volume has been added between trap and calibration volume. It is used to store ozone for a brief period and expand it into Vl to produce low ozone mixing ratios.

The accuracy of the calibrations performed is determined by the ozone purity, by the accuracy of the pressure measurements and by the

. 38 48 statistical accuracy obtained in detect1ng Ar and 03' The purity is

measured to better than ±l%, the pressure to better than ±.5%. The high accuracy of the pressure measurements is accomplished through the use of a rotating piston gauge (RPG) as a pressure standard for the absolute cali­brations of the Baratrons.

4. Flight Results The MSBS has been flown nine times successfully on board a balloon

gondola. Measurements have been made above 42 km. As mentioned earlier, the experiment has the capability to obtain ozone mixing ratios of high

42 - I I \ .. ' ~

Ct. " ,. .. , .. . " \ : 40 ~. ~ \ ~ . .. \

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" .... . 0

. ... .. '.

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. 36Ar {km 3 :.. Ar •

2 1 .

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" " • .. ~ ..

32 . .. . . \ , 't ' . .. ..

30 18,1983 • .. July 41 .:-. \ ..

30 3 I 1 1 1 1 Iii'

10 104 (counts 14 sec) 105

Fig. 2: Net count rates obtained during descent of balloon gondola,

-496 -

44

42

40

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Ozone mixing ratios.

accuracy and preclslon well above 40 km. For high altitude flights a larger experiment entrance orifice 01 is selected, permitting more gas to enter the beam system. This in turn will result in larger signals measured by the mass spec­trometer.

When the balloon has reached float altitude the cap over the entrance orifice is cut and air enters the MSBS. After an ex­tended period at float a valve on top of the balloon is opened and a slow descent is initiated • Generally, measurements are made over an altitude range of about 20 km. The data obtained during float are of particular importance. They are used to evaluate the per­formance of the experiment by checking measured signals for stability, comparing mass ratios with those obtained during cali­brations and by evaluating mass spectra for contamination related to the balloon or gondola. In the past flights water vapor and

hydrocarbons were the major outgassing products. Water vapor outgassing decreased rapidly during float, reaching a constant atmospheric level after about 2 hours. Hydrocarbons decreased slower and remained at a level of a few ppb during day flights and less during the night.

Fig. 2 shows the results from a recent balloon flight. Profiles of 36 38 46 . 44 net signals of Ar, Ar, CO2 (the lsotope of CO2) as well as ozone

are plotted versus altitude. The argon isotopes show the expected ratio 36 38 . of natural abundance of Ar/ Ar = 5.35. The slgnal measured at mass 46

parallels those of 36 and 38, indicating a well mixed CO2 profile. Addi-

tional data for CO2 were obtained by measuring masses 44 and 45. On the

other hand the ozone profile shows more structure and a clear departure

from perfect mixing. Using the 38Ar-profile and the calibration constant determined in the laboratory, ozone mixing ratios were calculated. Fig. 3 shows the results from the entire altitude range of descent.

In a number of balloon flights a UV absorption experiment from JSC, Houston, TX. was part of the balloon payload. In those flights (4) excellent agreement was found in ozone mixing ratios between the MSBS and the UV absorption experiment data. In a more recent balloon ozone inter­comparison a large discrepancy at high altitude was found. Results from this flight will be presented in another paper.

In the near future, further improvements in laboratory calibrations will be made. A system is under construction which will permit a simul­taneous calibration of various experiments. Stratospheric pressures and ozone mixing ratios will be simulated.

-497 -

REFERENCES

1. MAUERSBERGER, K. (1977). Mass spectrometer beam system for applica­tions in the stratosphere. Rev. Sci. Instrum., Vol 48, 1169-1173

2. MAUERSBERGER, K. and FINSTAD, R. (1979). Further laboratory studies and stratospheric flight of a mass spectrometer beam system. Rev. Sci. Instrum., Vol. 50, 1612-1617

3. ANDERSON, S. and MAUERSBERGER, K. (1981). Calibration of a mass spec­trometer experiment for ozone. Rev. Sci. Instrum., Vol. 52, 1025-1028

4. MAUERSBERGER, K. et a1. (1981). A comparison of ozone measurements. Geophys. Res. Lett., Vol. 8, 361-364

-498-

Swnmary

PERFORMANCE CHARACTERISTICS OF HIGH-ALTITUDE ECC OZONESONDES

W. D. KOMHYR, S. J. OLTMANS NOAA Air Resources Laboratory, Boulder, Colorado 80303

and

A. N. CHOPR/, P. R. FRANCHOIS Cooperative Institute for Research in Environmental Sciences

University of Colorado, Boulder, Colorado 80303

Tests and instrument modifications were made to extend the operating range of ECC (electrochemical concentration cell) ozonesondes to 40-km (3-mb) altitudes where photochemical theory predicts significant ozone depletion by chlorofluorocarbons. Heights of 40 km can be routinely attained by new, lightweight, plastic balloons. Six ECC sondes flown simultaneously to 40 km at Palestine, Texas, 21 March 1984 during a NASA-sponsored Balloon Ozone Intercomparison Campaign exhibited a high degree of precision in the measurement of ozone. Compa.rison of the data with results of simultaneous soundings made with UV ozone photometers indicated good agreement to 30 km; the ECC sondes yielded progressively lower values at higher altitudes.

1. Introduction

Balloon-borne ECC ozone sondes (1,2) have been used in recent years for atmospheric ozone measurements to stratospheric heights of about 30 km. Because photochemical theory indicates significant ozone depletion in the future near 40-km altitude by chlorofluorocarbons (3), attempts have been made to extend the operating range of the ECC sondes to these heights. The feasibility of attaining near-40-km balloon-burst altitudes reliably has been made possible by the recent development of tough new plastic materials for balloon fabrication. Whereas in the past plastic balloons capable of carrying ozonesondes to 40 km were heavy and required considerable helium for inflation, balloons fabricated from thin (- 0.0006 cm) new materials weigh only 8 kg and require only 50 m3 of gas at standard temperature and pressure.

2. ECC Sonde Modification for High-Altitude Use

A factor contributing to inaccuracies in stratospheric ozone measure­ments in the past has been use with the ECC sondes of standard radiosondes equipped with mechanical baroswitches for the measurement of pressure. Pressures measured with such radiosondes can be ±50% in error at 3 mb. For high-altitude ozone sonde flights, we use hypsometer radiosondes whose pres­sure measurement uncertainty at 3 mb is about ±6% (M. Friedman, VIZ Corp., Philadelphia, Penn., 1984). Hypsometers operate on the principle that the boiling point of the hypsometer fluid (fluorocarbon) varies with atmos­pheric pressure.

*Now at Meterological Office, Pune, India

Ozone Symposium - Greece 1984 -499 -

Pump efficiency differences among type 3A ECC sondes have also contri­buted to inaccuracies in ozone measurements above 20 mb. The 3A pumps are difficult to manufacture uniformly because their piston-cylinder assemblies have rectangular cross sections. To improve pump performance, a new (type 4A) pump has been designed (4). The pump is fabricated from Teflon TFE reinforced with 15% glass fibers, and has a piston-cylinder of circular cross section. Grooves cut externally in the cylinder wall are fitted with rubber O-rings that press against thin, flexible portions of the cylinder wall within the grooves to maintain an airtight seal between the piston and cylinder.

Pump efficiencies depend on ambient air pressure, pump dead volume, and pump head (the back pressure exerted on the pump by the sensor cathode electrolyte). Efficiencies for type 4A pumps were determined in an en­vironmental chamber using an apparatus similar to that described by Torres (5). Results are shown in Figure 1. Indicated error bars are standard deviations. The tests were performed simulating ECC soundings with 3.0 and 3.5 m3 of cathode electrolyte in the sensor.

50 (b) n=9

100~~L-~L-__ L-L-~~L-~L-~ 1.0 0.9 0.8 0.7 1.0 0.9 0.8 0.7

Pump Efficiency Factor

Figure 1. Pump efficiency factors for type 4A pumps with (a) 3.0 cm 3

and (b) 3.5 cm 3 of cathode sensing solution, respectively.

Because an aqueous sensor solution is used, concern has been expressed about the operability of the instruments above 6 mb (-35 km) in the atmos­phere, since the triple point of water is 0° C and 6.1 mb. The ECC sensor electrolyte consists of 10 g KI, 25 g KBr, plus a small amount of other chemicals dissolved in 1000 ml of water. Molality of the solution is such that its freezing point is lowered to -1° C. As a sounding progresses in the atmosphere to 3 mb, the concentration of salts in the electrolyte in­creases by a factor of two due to evaporation, further lowering the freezing point to -2°'C. Environmental chamber tests have indicated also that abrupt freezing of the solution occurs at 2.9 mb. Thus, the triple point for the ECC sensor cathode electrolyte is -2° C and 2.9 mb (- 40 km), to which the sensor should, in principle, be operable.

High-altitude ozone soundings with 4A sondes take 45 minutes longer to complete than do soundings to 30 km with 3A sondes. To compensate for the increase in evaporation of the cathode electrolyte, the amount of electro­lyte has been increased by 0.5 cm 3 to 3.0 cm 3 . While this causes a small

- 500-

increase in sensor response time to changes in ozone, a sufficient amount of solution is maintained in the sensor throughout the flight to insure against loss of unreacted ozone through the sensor.

3.0 ECC Sonde Performance

Figure 2 shows ozone partial pressure data from six ECC sondes flown 21 March 1984 at Palestine, Texas, during a NASA-sponsored Balloon Ozone Intercomparison Campaign. Only one of the instruments (4A1043) was new. All others had previously participated in one or more ozone instrument com­parisons held at Palestine in June and October 1983, and in France in September 1983. All of the sondes were equipped with type 4A pumps. Sen­sors 4A1013, 4A1043, and 4A1045 were charged with 3.0 cm3 of sensing solu­tion. Sensors 4A1031 and 4A1042 contained 3.5 cm 3 of solution. Sensor 000037 was of special design, having 4 cathode chambers each containing 3.0 cm 3 of solution. Prior to the flight, the sondes had been subjected to numerous laboratory tests, charging and recharging of sensors, contamina­tion in some instances, and considerable cleaning, re-cleaning, and con­ditioning with ozone. (Two other instruments, type 3A, participated in the comparisons: 3A1435, which malfunctioned due to pump contamination; and 3A1440, which worked well to 30 mb, but then lost motor speed regulation.)

A noteworthy feature of the data (Figure 2) is the high degree of cor­respondence in ozone profile details for all instruments. The plots are ±10-s averages centered at 0.5-min intervals. Ozone partial pressures, P3 in nanobars were computed from

P 4.307 x 10-3 1Tbt 3

where I is the sensor output current due to ozone; Tb is the instrument box temperature in kelvins; and t is the time in seconds taken by the pump to force 100 ml of air through the sensor. Pump efficiency corrections were applied to the data, but pump temperature coefficient corrections of <1% were not. The data are not normalized to total ozone, which was 0.334 atm-cm, measured on the day of the flight with a Dobson spectrophotometer. However, normalization factors were computed assuming that 0.007 atm-cm 0 3

was present between ground level and 806 mb, and that the ozone mixing ratio remained constant at the 6-mb value above 6 mb for each sounding. The mean normalization factor was 1.021 with a standard deviation of ±0.025.

Ozone measurement precision is highly satisfactory as indicated by the 95% confidence interval standard errors in Table 1, which range from a low of ±2% at the stratospheric ozone maximum to a high of ±14% at the tropo­spheric ozone minumum. For sonde data normalized to Dobson instrument total ozone, the precision improves by 50%.

The mean ECC sonde data are compared in Table I with mean results ob­tained simultaneously with UV ozone photometers by M. H. Proffitt (instrument 2) of the NOAA Aeronomy Laboratory, Boulder, Colorado, and D. E. Robbins of the L. B. Johnson Space Center, Houston, Texas. The two kinds of data agree well to about 15 mb. Above this height, ECC sonde values are lower by 7% at 10 mb, 15% at 5 mb, and 25% at 3 mb. These results differ from those obtained in Palestine, Texas, in July 1983 with ECCinstrument 4A1042 and the Robbins UV photometer during a University of Minnesota balloon flight. Differences in ozone values obtained then were +5% at 10 mb, -3% at 5 mb, and -12% at 3 mb, with the ECC sonde values lower above 10 mb altitude in the atmosphere.

-501-

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Table 1. Eee Ozonesonde and Mean UV Photometer Ozone Data of Proffitt and Robbins (P/R) Compared +

Atm. Pressure Altitude Hean 0] % O,ff. 0, ECC Sonde 0, Interval (mb) (-km)

4AI045 4AI031 4AI013 4AI042 4AI043 000037 Hean S.d. S.e. ('I.) (P/R) (ECC-P/R)

* (20.8) 703. I - 750.2 2.7 37.0 33.7 36.5 34.4 34.8 34.7 35.2 1.3 3.9 29.2

429.4 - 465.6 6.6 20.6 17 .2 20.3 18.4 18.6 19.1 19.0 1.3 7.2 18.6 2.2

190.5 - 211.3 12.0 12.3 8.6 11.9 10.0 10.3 10.5 10.6 1.4 13.9 10.2 3.6

100.0 - 106.5 11.8 40.3 35.7 39.0 37.6 38.1 37.6 38.1 1.5 4.2 40.4 -5.7

48.8 - 52.3 20.5 141.3 132.3 135.6 135.6 130.6 138.9 135.7 4.0 3.1 137.8 -1.5

29.0 - 31.4 23.9 153.5 147.4 147.5 147.6 149.4 152.5 149.7 2.7 1.9 150.3 -0.4

19. I - 20.6 26.5 134.6 129.6 131.6 128.9 131. 7 136.3 132.1 2.8 2.2 134.0 -1.4

9.7 - 10.4 31.0 89.4 85.8 87.2 82.5 84.4 85.3 85.9 2.4 2.9 92.6 -7.3

6.7 - 7.3 33.4 62.2 60.4 62.4 56.3 59.1 59.3 59.9 2.3 4.0 66.8 -10.2

4.7 - 5.2 35.6 39.6 36.5 40.1 33.9 37.2 36.9 37.4 2.3 6.4 44.5 -15.9

4.2 - 4.5 36.6 29.5 25.4 28.6 23.3 27.1 26.8 2.5 9.8 33.8 -20.7

3.2 - 3.3 38.8 17.5 15.4 16.5 1.5 9.8 22.2 -25.7

+Ozone values in table are partial pressures in j..IIIIb. Indicated standard errors are 95',(, confidence interval e[rors.

Proffitt U.V. photometer value only. Another U. V. photometer by Proffitt yielded the value 34.7 IJmb.

The air intake tubes of ECC sondes flown 21 March 1984 were located within 0.3 m of the large balloon gondola to which the instruments were attached. Partial destruction of ozone by the gondola, or dilution of ozone by exhaust from other instruments aboard the gondola, may have con­tributed to the low ozone amounts measured by the ECC sondes at the higher altitudes. Uncertainty remains, also, about the validity of the pump efficiency corrections applied to the sonde data. A bias in laboratory measurements of the pump efficiencies has not been ruled out.

REFERENCES

1. KOMHYR, W. D. (1979). Electrochemical concentration cells for gas analysis. Annals de Geophysique, t. 25, fasc. 1, 203-210.

2. KOMHYR, W. D., and T. B. HARRIS (1971). Development of an ECC ozonesonde. NOAA Technical Report ERL 200-APCL 18, Boulder, Colorado, 54 pp.

3. National Research Council (1984). Causes and effects of changes in stratospheric ozone: Update 1983. The National Academy Press, Washington, D.C. (Library of Congress Catalogue No. 84-60100), 254 pp.

4. KOMHYR, W. D. (1981). Pump piston cylinder assembly with exterior ring seals. Patent No. 4285642, Commissioner of Patents and Trademarks, U.S. Patent Office, Washington, D.C., 6 pp.

5. TORRES, A. L. (1981). ECC ozonesonde performance at high altitudes: Pump efficiency. NASA Technical Memorandum 73290, NASA Wallops Flight Center, Wallops Island, Virginia, 8 pp.

- 503-

ERROR PERFORMANCE OF ELECTROCHEMICAL OZONE SONDES OSR

U. FEISTER Meteorological SerVice of the GDR Main Meteorological Observatory

p. PLESSING Telegrafenberg DDR-1500 Potsdam

K.-H. GRASNICK German Democratic Republic

G. PETERS

Summary

Meteorological Service of the GDR Aerological Observatory DDR-12J1 Lindenberg German Democratic Republic

Systematic and random errors of the ozone sonde OSR were de­termined using the results of tandem balloon-soundings over Lindenberg in 1982. The information contained in the measure­me~ on the ozone concentration is analyzed.

1. Introduction Electrochemical ozone sondes of the type OSM-2 or OSE-2

(OSR since 1980) have been regularly launched, i.e. once to thrice per week, at Lindenberg (52.22 0 N, 14. 120 E, 98 m above m.s.l.) since the end of 1974. The ozone sondes manu­factured at the Academy of Sciences of the GDR took part in the two Ozone Sonde Intercomparisons at Hohenpeissenberg in 1970 and in 1978 (Attmannspacher and DUtsch, 1970, 1981).

2. Flight programme To assess the reliability and real accuracy of the ozone

sonde a special flight programme consisting of 20 balloons each of which carrying 2 ozone sondes of the same type and one radio sonde RKS-5 was carried out at Lindenberg between May and November 1982. Due to the high correotion factors being outside the range reoommended by WMO (1982) 5 out of the 20 soundings had to be omitted in the further analysis. The remaining 15 soundings have been divided into two groups. Those ozone profiles with smaller oorrection factors have been olassified as belonging to group 1. The average correction faotors are 1.058 ~ 0.128 (group 1) and 1.290 ~ 0.210 (group 2). The standard deviation of differences C2 - C1 is 0.158.

J. Ozone sonde errors ) Fig. 1 shows the relative systematic differenoes a+

between ozone values y. of group 1 and ozone values x of group 2 with Dobson oz~ne correction (curve 1) and without

+) Systematic differences can be regarded as bias if one as­sumes that sondes of group 1 have no systematic error.

Ozone Symposium - Greece 1984 -504 -

correction (curve 2)

a = (i - Y)/Y.

Fig. 1 Percentage systematic differences

( 1 )

1 n = 15 OSR against OSR, Lindenberg 1982 (with Dobson ozone correction) 2 n = 15 OSR against OSR, Lindenberg 1982 (without Dobson ozone correction) 3 n = 6 OSR against other types, Hohenpeissenberg 1978

It oan be seen that above 28 km systematic differenoes arising from too small a sensitivity of those sondes with high cor­rection faotors are not fully eliminated but only reduced by the Dobson ozone correction. The ozone concentration is under­estimated by about 10% above 28 km and overestimated by about 2 to 3% between 19 and 28 km. The negative deviation in the troposphere that was observed at the Hohenpeissenberg inter­comparison (curve 3) and that was probably due to pollution of the GDR sondes just before launch is not discernible in the results of the Lindenberg tandem flights.

Fig. 2 shows an estimate of the relative random error of ozone sondes (Feister et al., 1984)

I) '" [I.: f (d, (2 ) i", ...

with

Random errors are at their maximum of about 12% in the tropo­sphere and reach a minimum of 2 to 5% between 20 and 28 km. The average random error in the stratosphere beneath the height of the ozone maximum (22 km) is 7% and above that height 5.6%. Omitting one sounding that showed unusually great differences provides a better accuracy in the middle strato­sphere (dashed curve in Fig. 2). Both the systematic diffe­rences and the random errors shown do not include the error of Dobson ozone.

- 505-

p

OPo

10

10

so -",IS --nll",.6

100+'-rrT~-rrT~'-~~~rT+ o 10 IS 20

d %

4. Information content

10

Om

2S

10

IS

10

o

Fig. 2 Percentage random errors, Lindenberg 1982

1 n = 15 soundings 2 ----- n = 14 soundings

Several parameters were used to estimate the information contained in the measurements on the atmospherio ozone oonoen­tration (Feister et al., 1984). One of them is Shannon's in­formation parameter

19 (4)

with s as the standard deviation of the true ozone partial pressu~e and s as the RMS differenoe between true ozone and ozone values m~gsured by the sondes of group 2. I > 0 means a gain and I < 0 a loss of information. The info~mation expressed byxI refers to sondes with a higher oorrection factors, i.e. fioth systematic deviations and random errors are taken into account. Fig. 3 shows that the maximum gain of in­formation occurs between 10 and 16 km well below the level of maximum accuracy of the sonde. Negative amounts of I above 31 km are caused by measurement errors increasing wifh height. Taking account of Dobson ozone errors and errors due to non­collocation in space and time between total ozone observation and ozone sounding would change the absolute amounts of I , but not its general shape. x

-506 -

-QJ -Q.J -0.' OJo.zD.JO.4Q.S I.

"

10

Fig. 3 Shannon's information parameter, Lindenberg 1982

--- n = 15 soundings 2 ----- n = 14 soundings

Finally, Table 1 summarizes some of the results averaged for Umkehr layers. Except above 28 km balloon-borne ozone sondes provide better results than the Umkehr method, even if the total ozone measurement errors were included. The bias shown by part of the ozone sondes in the uppermost layers is not wel~ understood. To explain this effect checks of the sonde's performance in the laboratory with low pressure and temperature conditions as well as comparisons of the ozone sonde OSR with other techniques of measurement using big stra­tospheric balloons could be helpful.

ozone sonde OSR ~mkehr measure

layer ments systematic random informatioll random error difr~)enoes e{~)r oontent I (WM?%) 1982) x

11000 - 250 hPa 1.8 11. b 0.186 31

(0 - 10.3 km) 250 - 12.'5 hPa -2.5 8.7 0.383 29

10.3 - 14.8 km) ,. 125 - 62.5 hPa 0.5 7.6 0.285 22 14.8 - 19.2 km) 22• 5 - 31.2 hPa 2.8 5.1 0.121 10 19.2 - 23.6 km) 31.2 - 15.6 hPa 2.1 4.3 0.129 10 23.6 - 28.1 kIn) (1.2) (3.4) (0.193) 15.6 - 7.8 hPa -10.2 8.8 0.027 5 28.1 - 32.7 km) (-10.2) (7.0) ( o. 114)

Table 1 Results of 15 tandem soundings using the ozone sonde OSR (the numbers in brackets refer to 14 soundings)

- 507-

Referenoes

1. ATTMANNSPACHER, W. and H,U, DUYSCH (1970), Ber, Dt, Wetterd., 120

2. ATTMANNSPACHER, W. and H,U. Diltsoh (1981), Ber. Dt. Wetterd., 157

J. FEISTER, U. et al. (1984), Error characteristics of the electrochemical ozone sonde OSR (submitted to Pure and appl. Geophys.)

4. WHO (1981), The stratosphere 1981. Report No. 11 5. WMO (1982), Report of the meeting of experts on souroes

of errors in deteotion of ozone trends. Toronto, Report No. 12

-508-

MFSURE DE LA REPARTITION VERTICALE DE L 'OZONE A1MOSPHERIQUE PAR SPECTROPHO'I'a>IETRIE D I ABSORPTION DANS LE VISIBLE

P. RIGAUD, J.P. NAUDET et D. HUGUENIN* Laboratoire de Physique et Chimie de l'Environnement

3A, Avenue de la Recherche Scientifique F-45045 ORLEANS Cedex France

-::-Observatoire de Geneve CH-1290 SAUVERNY Suisse

After a brief survey of atmospheric ozone measurements-by absorption in the Chappuis bands, we present results of observations of Venus occultations by Earth from a stratospheric gondola. Ozone absorption was simultaneously measured with NO between 647 and 672 nm. Because ozone is the principal absorb ant at these wavelengths, determination of its concentration is very accurate.

1 .. Aperyu historique

Depuis Cabannes ( 1 ) plusieurs auteurs, dont recemment Shaw (2) ont mesure a partir du sol I' epaisseur reduite de I' ozone atmospherique en utilisant sa faible absorption du rayonnement solaire dans les bandes de Chappuis autour de 600 nm. Plus seduisante, car mettant en jeu une epaisseur optique d'ozone plus facilement detectable, apparait l'etude de l'ozone par absorption Ie long d'un parcours optique tangentiel aux couches atmospheriques. L' observation visuelle des bandes de Chappuis a ainsi pu etre effectuee en regardant avec un spectroscope la lumiere du ciel a I' horizon lorsque Ie Soleil est a quelques degres au-dessous de l'horizon (3, 4, 5) ; Gauzit (5) indique qu'il suffit de regarder 1 'horizon, s' il est assez' clair, au moment ou Ie Soleil est a 5° ou 6° au-dessous de lui. La region de la bande de la pluie (nombreuses bandes de la vapeur d'eau comprises entre 585 et 605 nm) parait alors plus lumineuse que les portions voisines du spectre ou se manifeste l'absorption des deux larges bandes principales de l'ozone ; Gauzit en conclut que Ie renforcement des bandes de I' ozone, par rapport aux bandes de la vapeur d' eau, est du au trajet des rayons solaires a travers I' atmosphere dans les couches superieures riches en ozone et pauvres en vapeur d'eau. Toujours dans Ie meme domaine de longueurs d'onde les eclipses de Lune ont permis des mesures quantitati ves (6, 7) avant la spectrophotometrie des eclipses de satellites artificiels du type Echo (8, 9). Ajoutons que recemment Ie satellite SAGE I a pu fournir de tres bonnes mesures (10) grace a sa bande passante dans les bandes de Chappuis, lors des occultations du Solei 1 par 1 'atmosphere terrestre.

Ozone Symposium - Greece 1984 - 509-

2. Methode employee et ses avantages

Nous utilisons la technique de I' occultation d' un astre (planete ou etoile) par l'atmosphere terrestre observee a partir d'une nacelle stratospherique. Comme dans les cas rappeles plus haut, les parcours optiques considerables peuvent alors compenser la faiblesse des coefficients d'absorption de l'ozone dans les bandes de Chappuis.

La technique de mesure, I' appareillage (spectrophotometre construi t autour d'un monochromateur a deux reseaux) et la -methbde de depouillement ont ete decrits par ailleurs (11) et sont rappeles dans ce volume (12).

L'ozone est donc mesure en absorption, en meme temps que N01 , entre 647 et 672 nm, dans Ie flanc des bandes de Chappuis. Dans les c<Ynditions de l'experience , l'ozone est de loin Ie principal absorbant atmospherique et sa mesure presente plusieurs avantages qui semblent importants.

a) II s' agit d' une mesure integree sur quelques centaines de kilometres. Les effets locaux dus a la structure fine de la distribution verticale de l'ozone mise en evidence par les sondes in situ sont moyennes.

b) La me sure se deroule pendant la nuit. L'atmosphere est en equilibre photochimique. La stabilite de la concentration de l'ozone que nous avons constatee au-dessus de 30 km d' altitude para it exclure I' existence de variations sporadiques d'origine dynamique ou autre qui compliquerait l'analyse d'une tendance a long terme.

c) La me sure est relati ve , I' etalonnage absolu de I' instrument n' intervient pas. La comparaison des resul tats s ' en trouve notablement simplifiee.

d) L' observation d' une source lumineuse quasi-ponctuelle etoile) permet d'ameliorer la resolution en altitude par l'observation d'une source plus etendue comme Ie Soleil.

(planete rapport

ou a

e) Dans Ie domaine des bandes de Chappuis, et c' est la un avant age decisif, les sections efficaces d'absorption de l'ozone sont independantes de la temperature et de la pression (13) contrairement aux autres domaines spectraux. De plus les valeurs publiees (14, 15, 16) des sections efficaces d'absorption dans Ie flanc droit des bandes de Chappuis ou nous operons sont tres coherentes entre elles (5 % de dispersion). Nous avons finalement adopte les valeurs moyennes compilees par Ackerman (17).

3. Resultats presentes

Nous presentons les resultats de 4 vols effectues depuis Aire sur I' Adour en utilisant Venus comme source (Figure 1). Les 2 premiers vols (12 septembre 1980 et 18 septembre 1981) ont eu lieu a la meme altitude et indiquent aux barres d'erreurs pres la meme quantite integree d'ozone sur Ie parcours optique tangentiel ( 12) ; ils ont donc ete moyennes et constituent notre reference. Le troisieme vol a eu lieu au printemps (3 mai 1982) et presente au-dessous de 30 km des valeurs plus fortes de la concentration d'ozone, ce qui est en bon accord avec la variation saisonniere bien connue de ce constituant. Quant au dernier vol effectue Ie 14 septembre 1983 lors de la campagne d'intercomparaison MAP-GLOBUS il indique des valeurs relativement fortes d'ozonite pour l'automne.

- 510-

74°1

~

o 2 ':; 35 «

30

25

20

--

Aulomn .. 1980 .1 1981

" P,;nlemp,1982

. ' Aulom •• 1983 (Globu,)

"---151 __________ ~1----------+-~1--""-" "-""·-·-"""-·--~1--------~1

o 2 4 6 12 8 CONCENTRATION OZONE (10 cm- 3 )

FIGURE 1

4. Discussion de la precision

La Figure 2 permet de comparer un spectre mesure de la transmission atmospherique (pointille) pendant l'occultation de Venus Ie 12 septembre 1980 a 93° de distance zenithale et deux spectres calcules (trait plein) avec une quantite d'ozone qui differe respectivement de ± 2 % de la valeur optimale ; on voit nettement que l'erreur sur la quantite integree d'ozone est inferieure a + 2 %. Finalement, par suite de 1 'inversion, la cause principale d'erreur est la determination de l'altitude de vol de la nacelle, deduite actuellement de la pression mesuree par un barometre compensateur Crouzet. De la sorte, l'erreur moyenne sur la concentration peut etre evaluee a 10 %. Ceci rend notre methode de mesure de I' ozone tout a fait competitive avec les methodes utilisees par les aut res auteurs, que ce soit par des mesures a distance en satellites, dans l'ultraviole t (18), Ie visible (10) ou l'infra-rouge (19), en ballons dans l'ultra-violet (20) ou a partir du sol par Lidar (21) ou que ce soit in situ par chimiluminescence (22), par spectrometrie de masse (23) ou par absorption ultra-violette (24, 25).

- 511 -

_~ +10 Vl

ro E '--0 c:

c: 0%

0

VI Vl

E VI c: ro ~ -10

REFERENCES

VENUS 1980

[0 3 J :!:2%

650 660

N0 3

I

A (n m)

FIGURE 2

670

- CABANNES J. (1924). Sur la transparence de 1 'atmosphere. C.R. Acad. Sci. Paris, 179, 191-193.

2 - SHAW G. ( 1979). Atmospheric ozone : Determination by Chappuis-band absorption. J. Appl. Meteor., 18, 1335-1339.

3 - SCHOENE E. (1884). Spectrum of ozone, and the presence of ozone in the atmosphere. Jour. Russ. Chern. Soc., 2, 250-252.

4 - WULF 0., MOORE A. et MELVIN E. (1934). The atmospheric ozone absorption in the visible spectrum. Astrophysical Journal, 79, 270-272.

5 - GAUZIT J. ( 1935). Etude de I' ozone atmospherique par spectroscopie visuelle. Ann. Phys. 4, 450-532.

6 - LINK F. (1946). Le role de l'ozone atmospherique dans les eclipses de Lune. Ann. Astrophysique, 9, 227-231.

7 - VIGROUX E. (1954). Spectrophotometrie de l'eclipse de Lune du 29-30 Janvier 1953. Ann. Astrophysique, 17, 399-415.

8 - LINK F., NEUZIL L. et ZACHAROV I.( 1968). Recherches photometriques des satellites ballons. Space Research VIII, 86-89.

- 512-

9 - VENKATESWARAN S., MOORE J. et KRUEGER A. (1961). Determination of the vertical distribution of ozone by satellite photometry. J. Geophys. Research, 66, 1751-1771.

10 - REITER R.- et Mc CORMICK M. (1982), SAGE-European Ozonesonde comparison. Nature, 300, 337-339.

11 - RIGAUD P. , NAUDET J. P. et HUGUENIN D. (1983) . Simultaneous measurements of vertical distributions of stratospheric N03 and 03 at different periods of the night. J. Geophys. Res., 88, 1463-1467.

12 - NAUDET J.P., RIGAUD P. et HUGUENIN D. (1984). Variabilite du N03 stratospherique. Ce volume.

13 - HUMPHREY G. et BADGER R. (1947). The absorption spectrum of ozone in the visible, J. Chern. Phys., 15, 794-798.

14 - VIGROUX E. (1953). Contribution a 1 'etude experimentale de l'absorption par l'ozone, Ann. Phys., 8, 709-762.

15 - INN E. et TANAKA Y. (1953). Absorption coefficient of ozone in the ultraviolet and visible regions, J. Opt. Soc. Am., 43, 870-873.

16 - GRIGGS M. (1968). Absorption coefficients of ozone in the ultraviolet and visible regions, J. Chern. Phys., 49, 857-859.

17 - ACKERMAN M. (1971) . Ultraviolet solar radiation related to mesospheric processes, in Mesospheric Models and Related Experiments, Ed. G. Fiocco, Reidel publ. Cy., Dordrecht-Holland, 149-159.

18 - KLENK K., BHARTIA P., FLEIG A. et MATEER C. (1983). Vertical ozone profile determination from Nimbus-7 SBUV measurements, Proceedings of fifth Conference on Atmospheric Radiation, Maryland, 103.

19 - GILLE J., BAILEY T., GRAIG R., HOUSE F. et ANDERSON G. (1980). Sounding the stratosphere and mesosphere by Infrared limb scanning from space, Science, 208, 397-399.

20 - GILLIS J., GOLDMAN A.:-wILLIAMS W. et MURCRAY D. (1982). Atmospheric ozone profiles from high resolution UV spectra obtained with a balloon-borne spectrometer, App. Optics, 21, 413-420.

21 - PELON J. et MEGIE G. (1982), Ozone vertical distribution and total content as monitored using a ground based active remote sensing system, Nature, 299, 137-139.

22 - AIMEDIEU P. (198~ Measurement of the vertical ozone distribution by means of an in situ gaz phase chemiluminescence ozonometer during the International Ozone Campaign, Gap, France, June 1981, Planet. Space Sci., 31, 743-748.

23 - MAUERSBERGER K., FINSTAD R., ANDERSON S. et ROBBINS D., (1981). A comparison of ozone measurements, Geophys. Res. Lett., 8, 361-364.

24 - ROBBINS D. (1980). NASA-JSC Ozone observations for validation of Nimbus 7-LIMS Data, Nasa Technical Memorandum 58227.

25 - PROFFITT M. et Mc LAUGHLIN R. (1983). Fast-response dual-beam UV-absorption ozone photometer suitable for use on stratospheric balloons, Rev. Sci. Instrum., 54, 1719-1728.

- 513-

UN CATALOGUE DE PRECAUTIONS INSTRUMENTALES

A PRENDRE POUR FAIRE L' ETUDE IN SITU DE LA VARIATION

CREPUSCULAIRE OU DIURNE D'UNE ESPECE STRATOSPHERIQUE,

PRESENTATION D'UN CAS PARTICULIER, L'OZONE

P. Aimedieu (I), P. Rigaud (2), A. Matthews (3)

(1) Service d'Aeronomie du CNRS BP 3, 91370 - Verrieres Ie Buisson, France

(2) Laboratoire de Physique et Chimie de l'Environnement F-45045 - Orleans Cedex

(3) Department of Scientific and Industrial Research P.E.L. Atmospheric Station Omakau, Central Otago, Nouvelle Zelande

RESUME

L'experience acquise depuis une dizaine d'annees dans la mesure in situ ou a distance de l'ozone stratospherique en vue de l'etude de sa variation crepusculaire, permet aujourd'hui de dresser un inventaire des facteurs contribuant a l'erreur commise sur la mesure dans ce type de situation.

Nous presentons un catalogue de ces facteurs et des precautions experimentales a prendre pour s'en affranchir au mieux. Une estimation chiffree de leur participation aI' erreur est proposee en vue de definir les erreurs partielles acceptables compte tenu de la precision totale desiree. Ces elements sont ensuite generalises a la mesure de la variation diurne d' autres especes du milieu (NO , etc ••• ).

y

GENERALITES

Au cours d'une mesure crepusculaire ou diurne (Aimedieu et al (1981» a niveau de vol constant, de la concentration d'un compose minoritaire de l' atmosphere, de nombreux facteurs peuvent intervenir pour perturber celle-ci et ainsi fausser l'interpretation ulterieure que l'on fera des resultats obtenus. Ces facteurs peuvent ~tre classes en quatre categories. Tout d' abord on distinguera l' ensemble des effets resultant du deplacement de l' instrument dans Ie milieu (Ex : orientation de 1 'instrument , stabilisation de son niveau de vol, effet de sillage sur la prise d'air). Ensuite nous devons envisager tous les types de pollution chimique qui peuvent fausser l' instrument de mesure ou degrader l' echantillon analyse. Puis nous devons prendre en compte tous les aspects thermodynamiques de l'instrumentation. Enfin il faudra chercher tous les facteurs intervenant seulement in-situ, propres a la sensiblite de l'instrument et dont l'experi-

Ozone Symposium - Greece 1984 - 514-

mentation au sol est delicate. Nous allons dans ce catalogue envisager tous ceux que nous

avons rencontre au cours de nos experiences qui couvrent la technique des mesures a distance (Rigaud, 1984) et des mesures par prelevements (Aimedieu, 1983 ; Aimedieu et aI, 1983). Nous allons aussi presente quelques effets dont nous ont parle nos collegues sur Ie terrain. Cette note voulant ~tre un outil de travail, nous avons presente les informations sous forme de tableau avec de brefs commentaires.

1. MOUVEMENT DE L'INSTRUMENT (Tableau I)

On distinguera en general deux degres de liberte par rapport au milieu un mouvement vertical (excursion en altitude) et une rotation de l' instrument autour d' un axe vertical. Dans certains cas viendra s'ajouter un mouvement plus complexe, pendulaire par rapport a la fixation sous Ie ballon. II en resulte par rapport au milieu des effets de sillage dus au ballon et a la nacelle ou est integre l'instrument. L'oscillation verticale est l'effet Ie plus difficile a eviter. Dans certains cas il pourra etre utilise avec profit pour faire une succession de profil verticaux. Un voile eliminera l'effet de sillage de la nacelle. Un systeme de pointage associe a un joint tournant permettra de decoupler Ie mouvement d'orientation de la nacelle - des mouvements de rotation complexes du ballon et de son c~ble de suspension.

Perturbation

Sillage du balloo

Sillage de la nacelle

Oscillations verticales au plafond

Oscillations pendulaires

Mauvais pointage

Incertitude sur la position de 1 'instrument

Affranchissement

Plus Brande distance possible entre la oace lle e t Ie balloo

mesures a la descente

Orientation de la nacelle dans Ie lit du vent

Difficile de s'en affranchir

Difficile de s' en affranchir

2 systemes de pointage - grassier (magnetique) - fin (etoile) pas de vent, amortissement optimum des oscillations pendulaires

- localisation OMEGA - bon Radar de poursui te - bon barometre (eROUZET) - bon thermometre (VIZ)

TMLEAU I HDuvement~ de 1 'instrument

- 515-

Donnees numeriques utiles

Distances nacelle balloo superieure a 200 m

Voile de plusieurs fl" depend du moment d'inertie,'" 10 m2

Excursion de 1 'ordre de la centaine de metre. peri ode d'environ 5 minutes

Amplitude faible, pendule simple

pendule simple ou compose

'V degre ..... 10"

..... 500 m dans Ie plan 'V 1 m trois directions ..... 10- 2 rob absolu ..... IO- lo K

2. POLLUTION CHIMIQUE (Tableau II)

In situ, elles sont tres nombreuses. On pourra distinguer l'agression du milieu sur l'instrument (oxydation de l'instrument par I' ozone), la perturbation du milieu par I' instrument (effluents de l'instrument), enfin des reactions chimiques parasites intervenant dans Ie cas de sondage par prelevement. De maniere generale on cherchera pour s' en affranchir as' eloigner du baIlon, a realiser l'instrument en materiaux inertes. On eloignera les prises d' air de l'instrument et on reduira au mieux les temps de transit dans les canalisations.

Perturbation

Hydrogene du balloo

Vapeur d' eau du balloo

Vapeur J'eau de l'instrument

Reactidns chimiques dans les prises d'air

Perte dans les turbulures

Oxydation de 1 'instrument

Af franchissement

Mesure a 1.1 descente Grande distance ballon- instrument pour la montee

Tres difficile de s'en affranchir

Faible temps de residence dans les turbulures

Hateriaux inertes : verre, teflon. Vi ton, Tygon passivation des tubes

Protection des surfaces optiques. metaux ou all iages ou traitement metallique de surface insensible a I' oxyda. t ion

TABLEAU II : Facteurs chi'lliques

- 516-

Donnees numeriques

Distance > 200 m

Res idu de degazage peut donner plusieurs centaines de ppfTlV dans un instrument

temps res idence <: 1 5

pertes de 1 'ordre du -,; mats variable : verifier ~haque cas

3. EQUILIBRE THERMODYMANIQUE (Tableau III)

On sait la sensibilite d'un instrument de mesure a la temperature. lei l'equilibre thermique sera difficile a realiser. Une grande part d'empirisme preludera a son obtention. Pour cela, nous avons toujours calorifuge nos instruments de telle sorte que les pertes par conduction soient faibles. La peinture optique blanc mat a ete utilisee pour reduire l'echauffement au soleil. Les debits doivent, au mieux, l!tre mesures en vol. Au cours de vol diurne, de longues durees, l'instrument chauffe au soleiI. La nuit il chauffe par ses propres sources d' energie. Le compromis est trouve empiriquement et il semble qu' il est tres difficile de stabiliser thermiquement une nacelle complete. On thermos tate done toujours les points sensibles et on prend Ie parti de mesurer la temperature du plus grand nombre de point sur et dans l' instrument. Force est de cons tater que les problemes que souleverons l' equilibre thermique de l'instrument et les mesures de temperature du milieu au moment de la transition nuit-jour et pendant Ie jour ne sont pas encore resolus.

I

Perturbation Affranchissement I

Ordres de grandeur numerique I I I

I I

Temperature du capteur et Isoler thermiquement I Difficile a ajuster empirisme I I I

inhomogeneites 2 Thermoreguler

I I I

I I

Temperature du milieu La me surer pour en tenir dans I

Le probleme important a resoudre compte I I 1a photochimie I actuellement I I I

TABLEAU III Facteurs thermiques

- 517-

4. AUTRES PERTURBATIONS

Extremement variees, elles dependent de la technique de mesure et de ses conditions d' utilisation. Nous avons releve personnellement les effets suivants :

lumiere parasite sur Ie detecteur - action du rayonnement cosmique sur Ie detecteur - linearite du detecteur optique - chute de lest sur l'instrument

baisse de la force electromotrice des batteries - defaut de linearite de l'electronique

interactions electromagnetiques diverses (brouillages, etc ••• ) dont on doit s'affranchir par des blindages.

CONCLUSION

Cette breve analyse met en evidence que de tous les facteurs qui peuvent perturber une mesure in situ d'un compose stratospherique minoritaire, la chaleur est Ie plus mal connu. Nous recommendons de la sorte de poursuivre les efforts deja entrepris dans la recherche des facteurs determinant Ie bilan thermique d'un instrument embarque et dans la mesure de la temperature des parties de celui-ci, en vol, ainsi que de la temperature vraie du milieu.

REFERENCES

AIMED lEU , P. , P. RIGAUD et J. BARAT, The sunrise ozone depletion problem of the upper stratosphere, Geophys. Res. Lett., 8, 787-789, 1981

AlMEDIEU, P., Measurements of the vertical ozone distribution by means of an in situ gas phase chemiluminescence ozonometer during the intercomparison Ozone Campaign, Gap, France, June 1981, Plan. et Space Sci. 31, n07, 743-748, 1983

AlMEDIEU, P., A.J. KRUEGER, D.E. ROBBINS and P.C. SIMON, Ozone profile intercomparison based on simultaneous observations between 20 and 40 km., Planet Space Sci., 31, n07, 801-807, 1983

- 518-

MEASUREMENTS OF THE STRATOSPHERIC OZONE BY INDIGO DECOLORATION

J.M. CISNEPOS CONIE. po Pintor Rosales 34. Madrid 28008. SPAIN

Summary

A simple system for ozone stratospheric measurements was designed specially to be used with big balloons. The first fliqhts were performed in the Transmediterranean Balloons Program, during the summers 1980, 1981 and 1982. The primitive instrument, nominated EOlO, has been modificated in some aspects. (1). In GLOBUS proyect of MAP, in September 1983, two flights were prepared with EOlO instrument. These flights, performed in Aire-sur-l 'Adour, France, were realizated together with a number of different experiments in the same qondolas in order to compare the measurements. Good measurements of 03 were obtained during the first flight. These results and a brief description of the EOlO instrument and used sensors are presented.

1. Brief description of the instrument

It is composed of two parts clearly differentiated: a) small sensor tubes. b) titration pump.

The small sensor tubes are disponed in a revolver system, with a cadence previou~y programmated, that put in due place each small tube to effectuate the ozone measurement.

The titration pump is a suction and force pump and is connected with the small sensor tubes by a electrovalve, which recurrence rate of aperture and lock is programmated in such a way that the air is suctioned from outside and forced to go through each tube (fig. 1).

Both the revolver system, where small sensor tubes are located, and titra tion pump are moved by electric 12v-motors, supplied by recharqeable nickel-=­cadmium batteries.

All the course of the analized air is internally covered with a teflon film. All used joints in the valuesand other parts in contact with the air of the analysis samples have been made with ozono resistina materials.

The cleaning of the instrument is carried on by a ozonized air flux with high concentration. In this way all the reducer particle are eliminated.

2. The sensors

Ozone Symposium - Greece 1984 - 519-

The sensor tubes used has been of standard type (2) in all the fli~hts (fig. 2), with the following characteristics:

a) size: 1) lenqh: 11 cm 2) diameter: n.7 cm b) rna te ria 1 : g 1 ass c) composition: white sand with indiqo tinture d) measure range: 0.5 - 14.0 ppmv e) relative standard deviation: 10 -15%

All molecule of 03, circulation across the tube, reach with indigo tinture,

which i, deC010;;:d:':oO:;~ O~O ~(b~ NH NH . NH

Indigo (blue) Isatine (white)

The sand contained in the small tube is impregnated with the indigo tinture. The colour turns to white in a lengh depending of the ozone concentration of a prefixed volume of the air passing across. The tube is graduated in ppmv of ozone scale.

As we will see later, main error source of the EOLO instrument arised from the high dispersion of the standard tubes used.

3. Other characteristics of the instrument

The EOLO instruments, used in September 1983 GLOBUS Campaing, has capacity for 40 small sensor tubes, and it had been programmed for the pass of 17 litres of air across each small tube. The lapse of time between two correlative tubes was twenty minutes. The shorter duration of the first fliqht than initiallly expected caused that only were carried out sixteen measurements of 03'

4. Obtained data and errors

The following ozone values were obtained during the first flight in Septe~ ber 1983 GLOBUS Campain0:

Tube (number) Pressure (mb) 03 (pemv ) 1 35.4 3.6 2 9.3 9.4 3 8.4 5.0 4 8.2 4.5 5 9.3 9.3 6 12.0 3.8 7 16.3 4.1 8 20.8 4.1 9 27.5 3.2

10 38.4 2.2 11 49.0 2.5 12 59.0 2.2 13 68.0 1.8 14 77 .3 1.6 15 90.0 1.3 16 104.0 0.4

-520-

The motor of the timer remained in stop position during the second fliqht. Consequently no data were obtained.

The maximun relative error expected is 20%, the best part of which corres pond to the dispersion in the measurements by standard tubes. We expect to -reduce these errors by means a special preparation of the small sensor tubes.

REFERENCES

(1) CACHO, J., CISNEROS, J.M. and SAINZ DE AJA, M.J., (1980) Measurements of Upper Stratosphere Ozono Evolution Symposium on Perspectives for Scientific Ballooning durinq the 1980'S Budapest, Hungary 2-14 June, 1980

(2) DR~GERWERK AG LUBECK. (1979) Manual de los Tubitos de Control, p. 128

e xppU log QI r twilhCloLt OlorteJ

... (

revolver sys em

I II'IDIGO TlJOE S

,/,

SWITCH

titration Rump-

batteries

Fiq. 1.- EOLO Experiment

FiC1. 2.- Small Sensor Tube

- 521-

i'l OTOR

SWITCHES

SUITmary

SATELLITE MEASUREMENT OF MFSOSPHERIC OZOOE

FRa.1 THE 1.27)JIll AIRGLOW EMISSION

H.YAMAIDID, T.MAKINO, H.SEKIGUCHI AND I.NAITO Dep:rrtment of Physics, Rikkyo University

Toshima-ku, Tokyo 171, JAPAN

One of the scientific objectives of a EXOS-C (OHZORA) satellite launched from KSC in Japan on Feb. 14, 1984 is to study ozone in the upper atmo­sphere. An infrared atmospheric-band airglow radiometer (IRA) is loaded on the satellite to measure a limb radiance of the 02 1.27]..lm airglow emission for the purpose of obtaining altitude profiles of mesospheric ozone. It has two 2-dimensional array detectors: a PbS array detector of 4 x 5 elements for the 1.27]..lm emission,and a thermistor bolometer array detector of 2 x 2 elements for the CD2 15]..l m emission. It has been work­ing well since the launching. A descr~ption of IRA instrument is present­ed together with an example of raw data obtained in March.

1. Introduction

Mesospheric ozone plays an important role in the terrestrial atmo­sphere. The thermal structure of the atmosphere is controlled by the absorption of solar uv radition by the mesospheric ozone and the thermal emissions of CD2 15]..lm and 01 9.6 ]..lm. Furthermore, chemical and dynamical processes occur~ng in the atmosphere are originally caused by the ozone photolysis.

One of the scientific objectives of a EXOS-C (OHZORA) satellite is to study ozone in the upper atmosphere. To accanplish this purpose, four sci­entific instruments including an infrared atmospheric-band airglow radio­meter (IRA) are loaded on it. The IRA is designed to measure the 1.27 ]..lm airglow radiation to obtain the atmospheric ozone concentration in 50 - 90 km altitude region, and to detect CD2 15]..lm radiation to get altitude information.

In the daytime,the mesospheric ozone is dissociated by the absorption of the solar uv radiation ( mainly of Hartly continuum) to produce an ex­cited molecular oxygen 02(1 "'g) •. Though the 02 (1 "'g) emits both 1 .27 ]..lm and 1. 58]..lm radiations,the ~ntensity at the 1.27 ]..lm ~s much stronger than one at 1.58 ]..lm. The other processes in which the 1.27 ]..lm radiation can be emitted are solar resonance fluorescence, and Rayleigh scattering of the solar radiation in the lower atmosphere. Since the radiances from the latter two processes are much weaker than that from the ozone photolysis, it is safe for us to obtain the mesospheric ozone by measuring the 1.27 ]..lm radiation in the daytime.

Ozone Symposium - Greece 1984 - 522-

'TIle EXOS-C ( OHZORA ) satellite was launched at 1700 JST on Feb. 14, 1984 from Kagoshima Space Center (31°N,131°E) in Japan. 'TIle initial orbit was determined as follows. Apogee was 865 kin, perigee 354 kin, inclination 74.6° and period 96.9 minutes. The spin axis of the satellite was always controlled to point toward the sun with no spinning motion. This attitude control system gave us a unique scanning method of the atmosphere using a satellite orbital motion.

'TIle satellite SME already launched in autumn of 1981 (1) has the same scientific purpose of measuring the mesospheric ozone. It is observed the ozone profiles always at 3 PM in local time on it. On the other hand, the IRA can obtain them in the solar zenith angle region 70 - 100°. Because 02(1~ ) has a long lifetime ( about 1 hour ), it is possible to deduce the ozonegprofile from the 1.27 ]Jm radiance after the sunset.

In this paper, a description of the IRA instrument and the scanning technique is presented together with an example of raw data at two wave­lengths obtained in March.

2. Instrument and Observation

IRA instrument consists of two filter radiometets for detecting 02 1 .27 ]J m and ffi2 1 5 ]J m airglow emissions. 'TIle 1.27]J m radiometer gives us information of the mesospheric ozone concentration. 'TIle 15 ]J m one is used to determine a tangential height of line-of -sight for each . sensor during measurements.

An optical configuration of IRA is shown in Fig.1. A movable mirror M1 is controlled to rotate 2° wi th a reference signal from the 1.27]J m or 15 ]J m radiation. 'TIle 1.27]J m radiation is focused by an optical lens L 1 ( 5 em¢, f=5 em, transmittance at 1.27]J m T1 27= 95 %) after passing through an interference filter F1 (A = 1.268]J m, ~A· = 20 nm, T = 50 %). To measure the 1.27]J m radiation, a twoodimzntional 4 x 5 PbS ar!fay detector (size of each PbS sensor is 0.1 x 0.1 rom ) is mounted on the focal plane of the lens L1. A wide bandpass filter F2 is used for blocking the thermal radi­ation mainly from a tunning fork chopper. To detect the 15]J m radiation with the same spatial resolution as that of the 1.27]J m one, an array deztor of 2 x 2 thermistor bolometers (size of each bolometer is 0.1 x 0.1 rom ) is used with a Ge lens L2 ( 2 em¢, f= 5 em, T =80 %) and an inter­ference filter F3( ~=14.9]J m, ~A=2.02]J m, T =75 %). ~e incoming radiations are modulated by the tunning fork chopper SO at rates of 140 Hz for 1.27]J m radiation and of 21 Hz for 15]J m one. A noise equivalent radiance for each PbS sensor is about 30 MR on the average at an operational temperature 6°C with an electronical time constant 150 msec. We obtain the output data from all sensors every 0.5 sec under a high bit rate data processing con­dition and every 2 sec under a low bit rate one. Function of the baffling system is the same as that in our previous rocket experiment (2). Since the baffling system could attenuate the off-axis radiation as weak as pos­sible, the limb radiance profile of the 1.27]J m emission could be revealed.

IRA instrument is mounted on the satellite side which is always faced to the anti-solar direction. An observational concept is shown in Fig.2i the satellite moves on its orbit from position 1 to 4 passing position 2 and 3. When tangential height of line-of-sight for each· PbS sensor reaches ¥.ound 100 kin, the sensors begin to detect the incoming radiation from 0/( ~g) produced through the ozone photolysis. As the satellite moves from file position 1 to 2, the tangential heights get close to the earth surface. Below 20 kin, an intensity of the 1.27]J m radiation is governed by the solar radiation scattered on the surface of earth or clouds. If almost all output signals from the PbS sensors show their saturated levels

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due to the scattered radiation, a signal to control the mirror M1 is de­livered to rotate 2°. As a result, the tangential heights go up to more than 1 50 kIn (see two lines separated 4 ° from position 2 in Fig. 2) • In the same way, a limb scanning at each stage of the mirror M1 gives us a limb profile of the 1.27 jJ m radiance. On the other hand, in the case of the observation from the position 3 to 4, a signal to control the mirror M1 is delivered when almost all the output signals go dawn to their zero levels. We can get the limb radiance profiles of the 1.27 jJ m radiaion at various local times and at various places in this way.

View directions of both detector arrays are shown in Fig. 3. Squares represent the directions of the line-of-sight for PbS sensors, and filled circles represent those for thermistor ones. Altitude resolution is limited by a detector size. At the same time, it varies with a height of the satellite; it is 3.5 kIn at the satellite height 300 kIn, 4.7 kIn at 500 kIn, and 6.5 kIn at 800 kIn. When the limb measurement is done at the height 500 kIn, the PbS elements can cover an altitude region of about 50 kIn simultaneously.

3. Observational Data

Since the launching of the EXOS-C ( OHZORA ) satellite, IRA has been working well. We could get the limb radiance profiles of the 1.27 jJ m and the 15 jJ m emissions in March when the satellite had no spinning motion. Since then, such no-spinning mode has been provided for about two days a week because of other scientific mission program. In this paper, we only show an example of raw data obtained in March.

Fig. 4 shows time profiles of output signals from the thermistor sen­sors and those of four examples from the PbS ones. In this case, the ther­mistor output signals show the upper levels representing CO2 emission from the lower atmosphere at first,and then they begin to decrease to the lower levels. When the gradient of time profile of the output signal becomes maximum, the tangential height of thermistor sensor is about 40 kIn. With differences of the times when each thermistor output signal shows the max­imum gradient, we can determine a limb scanning speed of IRA and an angle between the horizon and the line connecting PbS 1 with PbS 17. In this example,the speed was 3.2 kIn/sec and the angle was 26°. By using the speed and angle with the relative view directions shown in Fig. 3, we can trans­form the scale of time shown in Fig. 4 to an altitude for each PbS sensor.

All data obtained in March were .in the latitude region of 60 - 70 0 S at the solar zenith angle 70 - 100° except one data at 70 0 N. Though it is very interesting to know mesospheric ozone profiles near antarctic region, we, in this paper, can show only an example of raw data because of a delay of our data analysis.

We would like to thank Prof. T.Ito, Prof. H.Oya, and Dr. T.Ogawa for working as managers of the EXOS-C satellite. We also thank the ISAS satellite group for the successful operation.

REFERENCES

1. Thomas,R.J., et al., (1983) Geophys.Res.Lett. 10,245-248. 2. Makino,T., et al.,(1984) Bull.lnst.Space Astronaut.Sci.,9,63-71.

(in Japanese)

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1 1 12

1 0 ---t-.,.-~7\ 9 -----l..--~~

14--+--..:.. l---t-.,-~~~

Fig. 1 IRA Instrument Configuration

6

~~~'9t-7

8 13

--+-15

1. Movable mirror M1, 2. Mirror M2, 3. Mirror M3, 4. Narrow band­pass filter F1, 5. Optical lens L1, 6. Tunning fork chopper, 7. Wide bandpass filter F2, 8. PbS array detector, 9. Optical lens L2, 10. TUnning fork chopper, 11. Wide bandpass filter F3, 12. Thermistor bolometer array detector, 13. Pre-amplifiers, 14. Electronics, 15. Motor

Solar Radia1 ion Sa"nit.

Fig. 2 Observational Concept of Limb Scanning

1Il-~ : PbS e : Thermistor

,-0 rn ~ [!§] @JeThm2

.25· eThm4

+-ru IT] [ill l!ID DID .38

~-ru [§] ITQ] ~ ~Ttrn3

.26 .-!. -ill m [[] [j] [ill

I • I I I I r- .24 -r- .231'" .221" .221

eThml

Fig. 3 Relative View Directions of Sensors

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CIJ U C

Thermistor 1

2 o I..A..r-.Il • .A

U o ~ ____ ~~~~~~~ a::

.- 3 o CIJ

a:: ~ __ ~~~~~~~~

4

o 20 40 60 80 100 Time (sec)

PbS I

CIJ U 1---, C

4 o u o ~---------=~~---­a:: CIJ >

"0 "i

17

a:: ~ ________ ~~=-__ _

20

o 20 40 60 80 100 Time (sec)

Fig. 4 Example of Time Profiles of Output Signals

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A R!X:KEI' GAS-GAS CHEMIliJMll'lli TECHNIQUE FOR ME'ASUREMENT OF

A'IQv1IC OXYGEN AND OZONE CDNCENTRATIONS IN THE 15-95 KM REGION

S.P. PEIDV and S.V. TISHIN Central Aerological Observatory, USSR State Camnittee for

Hydrcneteorology and Control of Natural Environrrent, Pavlika Morozova str. 12, 123376 Moscav

Surmary

The instrurrentation part of payload, preflight laboratory calibration and experinental procedure are described. The cherniluminescent rocket instrurrent utilizing NO as a titration gas for rreasurerrents of atomic oxygen and ozone concentrations has been developed. The operation of the instrurrent is based on the registration of radiance anitted by electro­nicall y excited N02 nolecules, which are fonred due to the reaction of NO with atomic oxygen or ( and) ozone in the instrurrent reaction charrber volurre.

1 . 1 Introduction There are various in-situ and renote measurerrents of minor constituents

in the atrrosphere by the rocket technique. We present here an instrurrent for determination of atanic oxygen and ozone mixing ratio profiles. The operation of the instrurreut is based on a registration of cheniluminescence which occures in the reactions of o-atans and ozone with nitric oxide.

The gas-gas cherniluminescent reactions are widely used for determining various gases concentration. But only a f€!N rocket experinents are knCJNn in which these reactions have been used for detennining the atomic oxygen con­tent (1-4) and NO concentration (5). A nitric oxide release from rockets into the upper atrrosphere has been used to detennine arrbient atomic oxygen concentrations (1-4). The experinent is rather simple, but there are cer­tain difficulties in the analysis of the resulting glow for determination of O-nt.nnber densities. Besides this rrethod can It be used in the daytirre. To great extent these difficulties can be eliminated by nounting on board the rocket an instrurrent which has a reaction chamber. The radiance which spectrum is in the nain continuum and its maximum lies near 620 run (6), is measured by photorreter. When the payload descends on the parachute, ozone reacts with nitric oxide in the reaction chamber. This reaction is also acC<nq?anied by luminescence, which maximum lies near 1200 run (7). The sane technique is used for measuring both atanic oxygen and ozone concentrations and therefore a superposition of emissions is very probable. But in the earth I S atrrosphere the layers with a maximum content of atomic oxygen and ozone are separated and this circumstance helps to avoid such a superposi­tion, exept for the 50-60 krn region, INhere it nay exist.

1 .2. Experinental The major canponents of payload are the reaction chamber -3 (gas-gas

OZ\lne Symposium - Greece 1984 - 527-

reactor), the NO-storage-4, the light traps -2,5, the j:hOtoIreter -7 (see Fig. 1), the telerretry system, tran.."'lI1itter and pcMer supply.

Fig.L-Scherre of the rocket chemiluminescent instrurrent. L- Air inlet; 2,5.- Light traps; 3.- Reaction chamber; 4.- NO-storage; 6.- Air exit; 7. - Photorreter.

The phOtoIreter output and photanultiplier r:notocathode temperature are tele­metred via transmitter. At 35 seconds after lift-off the reaction chamber is opened and an atJ.rospheric air flCM begins to pass through it. At the sarre t.i.rre the ID stream enters the reactor through a special orifice, which dia­meter can be altered.

The output signal is directly proportional to the Emission intensity and therefore can be written: U = k LID] [0] , where k is a constant factor, [ID] and (0] are the concentrations ocr. ID and o-atans in the reaction

chamber. Theoconcentration of atomic oxygen in the atnosphere can easily be found fran simple expression: [0]00 (Poo fPo ) [oJ 0'

where Po and Poo are pressures in the reaction chamber and the atJ.rosphere, respectively. Factor k was measured in the laboratory (8).

o-atorns were produced by dissociation of rrolecular oxygen in a high­frequency electrodeless discharge. The partial pressures of atomic oxygen were measured by ID2 titration technique (gAn o-a~ concentration in the reaction chamber was also measured bv ID titration technique. In this case high purity nitrogen was used and N=-atams were produced by passing rrolecular nitrogen through the high-frequency discharge. The values of o-atorns concentrations, obtained using both techniques were in a gcod ag­reerrent with each other. The difference between the results obtained was not rrore than 50%. The partial pressures of all other gases were calcula-ted fran their respective flCM rates assuming conditions of viscous flCM within the reaction chamber.

In the case of ozone concentration measurements, the output signal is di­rectly proportional to the ozone mixing ratio and can be written in the follo­wing fonn: U = k F r , where k is a proportional factor dependent on ternperature, sensi~vity of the r:hotanultiplier tube and reaction chamber gearetry; Fo is the mass flCM of air; r - ozone mixing ratio.

The equation written above is valid if the ID concentration is in a such considerable excess that first-order kinetics prevail. The absolute calibra­tion of the instrurrent with respect to ozone has rot been made.

1.3 Results Three rreteorological M-100B rockets were launched fran s. Volgograd,

USSR. The results are presented in Figs.2-4. Dayt.:ilre atomic oxygen profiles are shCMn in Fig. 2.

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[0] , ABITRARY DiHTS Fig.2. - Daytime atomic oxygen profiles. I---s. Volgograd (48oN), 2 June 1983, ascent; 2-- -s. Volgograd, 2 June 1983, descent; 3-·

-~outh Uist, Scotland, II February 1977 (10).

9A 3 .

92

90

88 ~

~ 88 ~

84 ~og ~O-tO ~O"~ ~O"2.

[oj , (cm- 3 ) Fig.3. Nighttime atomic oxygen profiles. I---s. Volgograd, USSR, 31 ~ 1983, ascent; 2---s. Volgograd, 31 May 1983, descent; 3-·-- South Uis1 Scotland, 8/9 September 1975 (10).

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80

10

60

50

~ 40

..-..-/

..-..-" /

OZONE MIXING RATIO (pt:I!IV) Fig. 4. Ozone mixing ratio profiles. I-.,s. Volgograd, 31 May 1983, night; 2---Krueger A.J. and Minzner R.A. (12); 3---.-s. Vol gograd , 28 April 1982, day; ~. Volgograd, 2 June 1983, day; ~ Wallops Island, Virginia, 20 May 1976, day (II).

'Ihe rocket was launched on 2 June 1983, at 0915 local ti.ne. In this figure the dayti.ne atomic oxygen profile fran (10) for ccmparison is plotted. As we can see all curves are in a good agreement with each other and give nearly constant values of atomic oxygen concentrations belCM 80 kIn. Its increase above 80 kIn. Insufficient sensitivity and absence of absolute calibration of

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the instrurrent for 0-atams <Xlncentrations less than 1010 an-3, didn I t penni t. to obtain absolute values of 0-nmnber densities. The nighttine atanic oxygen profiles are shCM1 in Fig. 3. The flight occurred on 31 May 1983, at 0400 local tine. The characteristic feature of this flight is a. sharp decrease of 0-nmnber density near 87 kIn. The value of atcmic oxygen <Xlncentration is

1012 cm-3 near 92 kIn. The atomic oxygen profile for night tine condi­tions fran (11) is also presented in Fig. 3. The divergence of profiles ob­tained during ascent and descent was caused, IlOSt probably, by different orientation of payload in ambient atrrosphere for ascent and descent.

The ozone mixing ratio was rreasured during the descent of pay load on parachute. The results are given in Fig. 4.

The ozone mixing ratio profiles, obtained in M-1ooB flight on 28 Ap­ril 1982 at 1700 local tine in s. Volgograd and on Wallops Island on 20 May 1976 at 1702 (GMl') (11) are also shCM1 in Fig. 4. As it is seen fran this figure, all of the plotted curves are in a good agreement with each other. The divergence between daytirre and nighttine profiles in the 60-80 kIn re­gion nay be caused by the diurnal variations of ozone concentration. The curves 1-3 were obtained by normalisation to the value of ozone mixing ratio at 23 kIn, taken fran an atrrospheric IOCldel (12), because the preflight abso­lute calibration of the instrurrent with respect to ozone has not been made in the laboratory.

REFERENCES

1. C..QLCMB D. et.al. Oxygen atom detennination in the upper atIrosphere by chemiLuminescence of nitric oxide. J. Geoph. Res., 1965, v.70, N 5, p. 1155-1173.

2. VAN HEMELRIJCK E., VAN RANSBEECK E. A rocket-borne instrurrentation for the measurement of atonic oxygen based on a chemical release in the lo­wer thenrosphere. Aeron. acta, 1981, A, N 231, pp. 30.

3. GOI.£:MB D. and GOOD R.E. Atomic oxygen profiles over Cllurchill and Hawaii fran chemical releases. Spaoe Research, 1972, v. XII, Akademie-Verlag, Berlin, p. 675-683.

4. ARMSTRONG R.J., MASEIDE K. and TROlM J. A nitric oxide release in the high latitude ionosphere. J. Atm::>s. and Terr. Phys., 1975, v. 37, Per­gamon Press, p. 797-813.

5. MASON, C. J. and HORVATH J.J. The direct rreasurement of a nitric oxide <Xlncentration in the upper atm::>sphere by a rocket-borne chemiluminescent detector. Geophys. Res. Lett., 1976, 3, p. 391-394.

6. FCNI'IJN A., MEYER C.B. and SCHIFF H.I. Absolute quantum yield rreasure­ments of the ID-O reaction and its use as standard for chemiluminescent reaction. J. Cllem. Phys., 1964, v. 40, N 1, p. 64-70.

7. CIDUGR P.N. and TRUSH B.A. Mechanism of chemiluminescent reaction bet­ween nitric oxide and ozone. Trans. Faraday Soc., 1967, v. 63, p. 915-925.

8. PEROV S.P., TISH;IN S.V. Laboratomya ustanovka dlya izuchenya khemilumi­nescentr;Ykh gazofazynykh reaktsi pri raketnykh izm=renyakh nalykh sostav­lyauschikh atrrosfery (0, 03, NO,), Trudy TSAO, 1980, issue 144, pp.32-41.

9. KAUFMAN F. The air afterglCM and its use in the study of some reactions of atonic oxygen. 1958, Proc. Roy. Soc., A 247, IDndon, p. 123-139.

10. DICKINSON P.R.G. et. al. The deteJ:m:i.nation of the atomic oxygen concen­tration and associated pararreters in the 1<::Mer ionosphere. Proc. Roy. Soc., 1980, A 369, IDndon, p. 379-408.

11. KRI.JEr:ER A.J., FOSTER G.M. Regular rocket ozone sounding data rep:::>rt, March, April and May, 1976. First Quart. Report, August 1976, - 20 p.

12. KRIJEX;ER A.J. and MINZNER R.A. A Mid-latitude ozone nodel for the 1976 US standard atm::>sphere. Joum. Geophys. Res., 1976, v. 81, N 24, p. 4477-4481.

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CONSTRUGrING EMPERICAL ZENITH OZONE CHARTS AND TABLES

USING THE MULTIPLE LINEAR REGRESSION TECHNIQUE

Abstract

by

G.K.Y. HASSAN

Meteorological Authority Cairo

Multiple linear regression technique has been used for deriving a set of emperical linear e~uations, to estimate the total amount of ozone from the zenith-blue sky observations, for wavelengths "AD", "CD" and "C".

Two multiple linear regression equations were derived by considering the direct, then the zenith-blue log-intensity ratio as the dependent variable. In each case the equation variables were: direct log-inten­si~y ratio (DLIR), the zenith log-intensity ratio (ZLIR), and the mean ozone air-mass.

Two other equations were similarly derived by adding the total ozone amount as an independent variable.

The equations containing the ZLIR as dependent variables were used to construct two families of charts, each containing two versions. On the other hand, those containing the DLIR as dependent variables were used to construct a set of four corresponding tables, for each wavelength, including "A", "D", "AC" wavelengths, whose equations were obtained algebraically.

The emperical relations have been checked against data for a different period, and the result was very satisfactory.

The relationships and, their corresponding charts and tables should be applicable to any station, irrespective of its geographical location.

I. INTRODUGrION

The quality of ozone data obtained from zenith sky measurements is highly dependent on the quality of emperical zenith-blue charts used in processing such measurements.

The standard zenith charts, supplied with the Dabson ozone spectrophoto­meters, cannot be used universally, since the shape of the t£~t curves depends on local besides instrumental factors (Dobson; 1975 , Komhyr; 1980(3). Therefore, the charts originally prepared at Oxford have to be checked at each station, and if necessary redrawn before putting them into operation.

Ozone Symposium - Greece 1984 - 532-

Rindert 1973(5), constructed emperical blue sky ozone charts by using smoo­thed group mean values of 'N' or 'N/ fl' for defined intervals of 'fl " for all pairs and double pairs of wavelengths, using measurements of total ozone amount at Uppsala during the period 1951 - 1966.

As Cairo is the Regional ozone Centre for Africa, it was thought beneficial to construct zenith blue-sky ozone charts which would be applicable to the whole region without local adjustment. The work was started in 1981, on a limited scale concentrating on the 'AD' wavelength, producing only one ver­sion of such a chart.

In 1983 the method was developed radically as will be detailed below.

2. THEORETICAL TREATMENT

A very close relation could be expected to hold between the direct log in­tensity ratios 'DLIR', the zenith log intensity ratios 'ZLIR' of nearly simultaneous observations, and their mean ozone air-mass fl . This rests on the fact that the zenith diffuse radiation is produced principally by Ray~ leigh scattering and aerosol scattering. Also since most of the atmospheric molecules lie below the bulk of the ozone layer, the absorption path for zenith diffuse radiation should be similar to that of the direct radiation.

A large number of DLIR and ZLIR values produced from nearly simultaneous observations, and their mean optical ozone airmasses, have been used in in­vestigating such relationships, for pairs and double pairs of wavelengths by the multiple linear regression technique.

Quality control criteria were applied to the observations before computa­tion of the relationships, for rejecting the unreliable observations, and the observations of the turbid atmosphere.

Also DLIR and Zlir values were corrected before computaion by multiplying each value by the factor " fl m/ fl a", where fl m and fl a are the mean and actu 1 ozone air-masses respectively.

Two multiple linear regression .equations (family A) were derived by consi­dering the DLIR and the ZLIR alternatively as the dependent variable. These have the forms :

N ZB k aok + alk . fl + a2K • NDS (1)

~~ ,-aok I t'

+ a lk ·fl + a2k NZB K (2)

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/ ~here k represents the wavelength, aok ' aok are the intercepts, 81k , aZk ' alk and aZk ' are the regression constants.

Two other equations (family B) were similarly derived by adding the total ozone amount as a third independent variable. This enal'le us to investigate the effect of introducing the total ozone amount on such relationships. These have the forms :

N ZB k °ok + blk ./.1 + °Zk

}TDS 'AD + b3k • ~~ (3)

NDS bOk + blk '" NZB /' . ~~ AD ,U + bZk k + b3k (4)

where bOk and bOk are the intercepts, and blK , bZK ' b3k , ~lk' bZk and b3k are the regression constants.

The computations were made for wavelength, AD, CD, and C. Where the DLIR was an independent variable, the linear relationships for the wavelenths A, D and AC have been algebraically derived from the above mentioned equations (1) and (3).Equations (1) and (3) were used to construct two families of charts, A and B, for Nk or I\/flagainst fl . On the other hand, equations (2) and (4) were used fo construct a set of equivalent tables.

3. METHOD OF CONSTRUCTION

3.1. Charts Construction Technique

A computer program has been designed to construct the zenith blue sky ozone charts, by using a new technique. This technique is based upon int"oducing a tabulated set of values for the total ozone amount and computing the cor­responding DLIR values for the 'AD' wavelength using the standard equation:

1 10 • (x + 9.0) • fl . 1.3R8

For each value of total ozone amount, a set of DLIR values were obtained corresponding to a set of fl values; as shown in table 1 below (X values are in milli- atm- cm).

TABLE 1

Min. value Max. value Step

X ZOO 50n 10

fl 1.00 5.Z0 O.OZ

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The corresponding ZLIR values were obtained from the computed DLIR values by using equations (1) and (3) for each pair and double pair of wavelengths.

The charts were prepared for N against !1 and N/!1 against !1'

3.2. Tables Constructing Technique

A computer programme has been designed to construct the zenith-blue ozone tables as follows:

1 - A suitable of ZLIR values were introduced, for each wavelength.

Wa'J'e-NO.

Section of a ~ a 2 r 12 S.E.E. lenrs"th obs. 0

AD 3250 4.42355 0.95161 0.49466 0.987 2.77

1 CD 700 1-53009 -{).33542 0.30027 0.989 1.28

C 7f:IJ 0.34496 0.70421 0.48409 0.976 2.01

AC 2.89346 -0.15924 0.65134

11 A 2.54850 0.54497 1.13643

D -1.87505 1.03963 0.18382

Table 2

section Wave- NO. , / ,

length of ao a1 a2 l.'12 S.E.E. obs.

AD 3250 -2.85063 9.87614 0.81571 0.990 2.5

1 CD 700 -1.51993 16.68320 2.09576 0.994- 3.4-

C 7f:IJ 0.68620 7.17379 1.66672 0.978 3.1

AC -3.69858 5.5383 1.3355

A -1.74808 6.26584- 0.74-142

D 10.2005 -5.6557 5.4401 J

Table 3

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Section Wave- NO. bo b1 b2 b3 r123 lenght Of S.E.E. obs.

AD 3250 8.35266 -2.83268 1.0034-1 ~.0124 0.987 2.8 I C D 700 -16.13705 7.93688 0.12153 0.54.7 0.991 1.8

C 7fCJ -53.245 18.95714 0.D5855 0.17733 0.980 1.8

AC 24.48471 -le.76958 0.88188 ~.66647

II A -28.75520 8.18758 0.94048 0.11086

D -37.10795 11.02026 '0.06298 0.12326

Table 4

~ rf rf b' Section Wave NO. bo r123 S.E.E. length or 1 2 3

obs.

AD 3250 -6-1.33437 38.04248 0.16381 ~.19176 0.998 1.1 I C D 700 -65.62816 38.93509 0.49839 O.20II 0.997 2.4

C 7fIJ -112.16197 41.23621 0.07807 0.37619 0.993 2.1

A C -59.2320 37.flJ539 0.24401 0.18719 11 A -99.31956 40.39406 0.05015 0.33038

D -120.805 41. 66}5? 0.09257 0.40871

Table 5

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Wave NO.OF x :x: Period DS ZB

length obs. Mean S.D. Mean S.D

AD 365 1981-1982 308 21.5 309 19.8 A 308 21.4 D 312 36.4

CD 161 1983-1984 292 17.6 305 18.5 C 295 19.7 D 291 27 0 8

AC 130 1983-1984 296 20.9 287 20.7 A 297 22.5 C 303 26.5

Table 6

2 - The corresponging N~; values were computed for each NZ~ value, using equations (2) and (4).

d · f h . d NDS 3 - The total ozone amounts were er1ved rom t e est1mate AD values by using the transformed equation

t?S _ 10 • NAD AD - 1.388 11 - 9.0 m. atm. cm.

4 - the computation was done for the same values of 11 as given in table 1 with airmass/step 0.2 instead of 0.02.

5 - In the case of family B, the total ozone amounts on the R.H.S of equa­tion (4), were computed first using equation (2).

4. RESULTS AND DISCUSSION

4.1. For Cairo

Table 2, 3, 4, and 5 shows the constants for equations 1,2,3 and 4 respecti­vely.

In each table, section I is obtained from the actual observations, while section II is algebraically derived from section I.

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The last two columns represent the multiple correlation and the standard error of estimate of the ZLIR or the whichever is the dependent variable.

Table 6 shows a comparison between the mean estimated total ozone from zenith blue sky observations using equation (2) and the corresponding direct-sun values, for Cairo Station. It is clear that a good agreement has been obtained in the case of AD, and A and D wavelengths. The deviation which is in no wayan excessive one - in the case of C, CD and AC wavelength, might be due to high values of NC in R - N tables of intrument 96,. which produced higher total ozone values for the C and CD wavelength than the AD values and lower total ozone values for the AC wavelength.

4.2. For Toronto and New-Dehli :

Two other tests have been undertaken on two other locations.

A. Figure 1 : shows a comparison of the estimated to~al ozone amounts for few observations taken at Toronto, Canada in 1976, using the Toronto 'AD' Chart and the new 'AD' methodo The linear regression analysis of the two values in nearly 45 line (44·7 ). Consequently, the new 'AD' method without adjustement to the locality is highly agree with Toronto 'AD' Chart.

B. Figure 2 represents the deviation of the estimated total ozone amounts, using New-Dehli 'AD' Chart and the new 'AD' method, from corresponding direct sun val.ues. The average deviation for New-Dheli is equal to 3.5. while the average deviation of the new methorl. is equal to 1 this means that the new 'AD' Chart without local adjustment in good agreement with New-Dehli correc­ted 'AD' Chart.

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400

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5. CONCLUSIONS

It is clear from the above discussion that there is a high correlation between the direct log intensity ratio, the Zenith LIR and their associa­ted mean optical ozone air mass. The multiple correlation coefficients between the above three variables when total ozone amount is added exceed 99 % in most cases.

It seems that this new technique in constructing the Zenith blue ozone charts is more successful than the classical technique using mean group values of N or N/ /l for intervals of fl ; for the following reasons:

1. The chart curves can be drawn for any value of fl and i.e. for arbitra­rily high or low total ozone values and ozone air masses, while the chart curves in the classical method cannot be drawn for air masses or ozone values other than those'obtained from the actual observations.

2. The time lag between the DLIR and ZLIR was omitted by multiplying each log intensity ratio by the factor}.tm/ /la, this time lag produces an error in computing the mean group values for defined intervals of flin the clas­sical method.

3. The above linear relationships for those using DLIR as dependant varia­bles can be used directly in computing the total ozone amounts from the zenith observations,'since the ZLIR values for any wavelength can be trans­formed to DLIR (AD) and the computation can be derived using the ADDS equ­ation.

The above relationship have been tested upon a few observation taken by the Author at Toronto,Canada, in February and March, 1976, and the result is highly satisfactory, This test and the good results of the comparison bet­ween the total ozone amounts of New Dehli estimated by the Indian Chart, and corresponding estimated values using the new chart, gives us the im-

-539 -

pression that new charts series can be universally used. However, more observations are needed from different latitudes to verify their applica­bility for world wide use.

ACKNOWLEDGEMENT

The author is greatly indebted to Hr. A.F. El-Sabban, Director General of Research Sector for valuable discussion and guidance during the p.re­parati'on of the manuscript.

Thanks are also due to Dr. A.M. Ibrahim for his valuable comments and revi­sion the manuscript.

Thanks are also for drafting section for transfering the charts on trans­parent papers.

REFERENCES

1. Dobson, G.M.B. 1957 a. Observer's hand book for ozone Spectrophometer. Ann. IGY, 5, 46-89, Ferrgamon.

2. Dobson, G.M.B. 1963 Note on the measurement of ozone in the atmos-phere, Q.J.R. Het. Soc., 89, 409 - 411

3. Komhyr, W.D. 1980 b. Operation hand book - ozone observations with Dobson spectrophotometer, WHO Global ozone research and monitoring Project Report, 6, MMG, 125 P.

4. " " 1960 Measurement of atmospheric ozone at Moosonee Canada. Can. Met. Memoiors. N.6.

5. Rindert, S.B., 1973 Constructing Emperical blue - sky ozone Charts, Department of Heteorology. University of Uppsala Report No. 36.

6. Sanyal. S.K., 1964 Determination of ozone amounts from zenith blue skyobser­vations, Indian J. of Met. 1964.

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THE METEOROLOGICAL AUTHOR ITv 2'2.5

OF EGvn

OZONe SPECTROPHOTOMETER NO. Q6

UNITH SlUE·SKY OZONE CHAAT ~ 250

CHAATNO lAO

[ N'A·NO)~ AGAINST p- 1215

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'IDTAL-0Z00E MFASURIt-B INSTRUMENTS USED Nl' THE USSR STNl'IOO NE'lroRK

G.P. Gushdlin, S.A. Sokolenko, V.A. Kovalyov (Main Geophysical Observatory, Leningrad, USSR)

The USSR ozone network comprises 45 stations. During 25 years the regular measurements of the total ozone (TO) at this network have been made with the help of a filter instrument M-83/1,2,3/. This instrument is equipped with optical light filters which consists of a set of optical pigmented glasses with total spectral band pass of 20 nm, the luminous transmit­tance maxima (after modernization of the instrument in 1971) being at wavelengths of 300 and 326 nm. The M-83 instrument was compared with Dobson spectrophometer at the international comp:lrisons held in Belsk, Poland, in 1972/3/; at the Mauna Loa Observatory, Hawaii, in 1976/4/; and in the USA in 1979-1980/5/. The results of the comp:lrisons show that the discrepancies in the daily mean values of total-ozone measurements at the sun elevation range from 170 to 800 do not exceed 3-5 %. Thus, the M-83 instrument meet the requirements of the instruments which are to be used at the station network. The cost of M-83 is approximately 40 times cheaper than the cost of the Dobson spectrophometer.

In the course of operation of M-83 it was revealed that the instrument needed certain modernization. Since this instrument has two photoelectric sensing elements, namely, a photocell for direct sun observations and a photomultiplier for zenith sky observations, it leads to an additional errors in TO measurements due to the fact that for the direct sun measure­ments an ozone nomogramme is used which is determined by the multiplier spectral sensivity; it is assumed that spectral sensitivity of the photocell is strongly similar to that of the photomultiplier. Besides, it was found that after a long period of service the leak-tightness of the instrument deteriorates, and the transmittance of optical light filters changes unreversible due to influence of dust and moisture. A photoelec­tric scheme was also to be modernized. In these circumstances the neces­sity arose of developing a new total-ozone measuring instrument for the use in the USSR station network. The development of such an instrument, M-124/6, 7/, was completed in the USSR in 1983. Like M-83, the M-124 instrument is intended for measuring total ozone in the atmosphere using both the direct sun observation method and zenith sky observation method. Optical and electric systems employed in M-124 are similar to those used in M-83. A characteristic feature of the optical system of M-124 is the presence of a COmp:lct reflector 1 (Fig.1) which allows for direction of the instrument to the sun, the way it is done in the Dobson spectrophoto­meter. Instead of two photoelectric receivers, the M-124 instrument employs only one sensing element - a photocell F-4. As a result, the weight and size of this device were substantially reduced. Leaktightness of the instrument also has been improved: the optical light filters 6, the photocell 3, and the amplifier 4 are placed into a hermetic passive thermostat 2; rroreover, the optical light filters are placed in the hermetic capsules both ends of which are covered with quarts plates.

Ozone Symposium - Greece 1984 - 543-

Basic parameters of M-83 and H-124 are presented in Table 1.

Table 2 shows the parameters of the USSR total-ozone measuring instru­ments as compared with the parameters of intruments used in other coun­tries.

The direct comparisons of three instruments M-124 with Dobson spectro­photometer No.1 08 held in September 1983 revealed that a total relative error of the ill measurement for direct sun observations and for zenith sky observations did not exceed 3 % and 5 % respectively.

Fig. 1 : Ozonometer M-124

1 - optical reflector 2 - thenrostat 3 - photocell 4 - amplifier 5 - electric 6 - optical light filter 7 - output microammeter

2:0.-_-- 1

direct sunlight

6

:;

-544 -

TABLE

Basic parameters of the instruments M-83 and M-124

1. Wave lengths (maxima of the spectral sensiti­vity), nm

2. Sfectral band pass, nm

3. Photoelectric sensing elements

4. Angle of view, (degree of arc) - for direct sun 00-

servations - for zenith sky ob­

servations

5. N~r of basic parts

6. Weight (Kg)

M-83

300, 326

20

Photocell Photomultiplier

6

1 ,5

3

14

M-124

300, 326

20

Photocell

3,5

5,5

5

, _____________ 1 __ _ -------- ---

TABLE 2

Parameters of the total-ozone measuring instruments

Instrument

Dobson spectrophotometer (Britain)

Ozonemeter Mr83 (USSR)

Canterbury ozonemeter (New Zealand)

Brewer Sfectrophotameter (Canada)

Sentran ozonameter (USA)

Ozonameter M-124 (USSR)

----- -Cost --­Weight (approx. (approx.) thousand

roubles

100 70

14 1,6

60 20

40 20

7 5

5,5 1,2

-545 -

Sfectral band pass, nm

Nurrber of Sfectral channels

1,5 8

20 2

3 6

5

3 6

20 2

REFERENCES

1. GUSHCHIN G.P., Ozonometer. USSR patent No. 160877, 1964, 2. GUSHCHIN G.P., Methodic guide for observations and processing of

observational data on the total ozone in the atlIDsphere. USSR, Leningrad, 1981.

3. GUSHCHIN G. P ., VINOGRAOOVA N. N., Total ozone in the atlIDsphere. USSR, Leningrad, 1983.

4. KOVPJ..,YOV V.A., ROMASHKINA K.I., ELISEEV A.A., Canparisons of the instruments for total ozone measurements at the Mauna-Loa station. Meteorol. and hydrology, USSR, 1978, No 6.

5. PARSCNS C.L., GERLAX J .C., WILLIAMS M.E., KERR J .B., Preliminary results of an intercomparison of total ozone spectrophotometers. Proceedings of the quadrennial international ozone symposium 4-9 August 1980. Boulder, Colorado, USA, 1981, p.80-87.

6. GUSHCHIN G.P., Ozonometer, USSR patent, No 892395, 1981. 7. GUSHCHIN G.P., SOKOLENKO S.A., Test mJdel of the new instrument for

total ozone measurements, MX) Proceedings, Leningrad, USSR, 472, 1984.

- 546-

C HAP T E R VI

INTERACTION OF OZONE AND CIRCULATION

Simultaneous measurements of carbon monoxide and ozone in the NASA global atmospheric sampling program (GASP)

- The interannual variations of the global total ozone as a reflection of the general circulation changes in the stratosphere

- Dependency of ozone transport on the vertical structures of pl anetary waves

- Ozone concentration data applied for studying mesoscale wave processes in the atmosphere

- The effect of temperature waves on the zonal mean ozone content

- Aircraft measurements near jet streams

- Wavenumber spectra of ozone from GASP aircraft measurements

- Measures of stratospheric displacements from satellite data

- Variations of radiative heating/cooling in the stratosphere as revealed by satellite observations

- Observation of strong ozone variations during a prestage of the sudden stratospheric warming in January / February 1979

- Sage stHdi es of the waves and eddy fl uxes of ozone and temperature near 55 during the late February 1979 stratospheric warming

SI~illLTANEOUS MEASUREMENTS OF CARBON MONOXIDE AND OZONE IN THE NASA

GLOBAL ATMOSPHERIC SAMPLING PROGRAM (GASP)

R.E. NEWELL Department of Earth, Atmospheric and Planetary Sciences

Massachusetts Institute of Technology Cambridge, Massachusetts 02139

1. Introduction

and

Mao-Fou Wu Atmospheric Chemistry Branch Goddard Space Flight Center Greenbelt, Maryland 20771

The objective of the NASA Global Atmospheric Sampling Program (GASP) was to establish global baseline values of selected atmospheric constituents that could be used for studies of the dynamics of the sampled region as well as for modeling purposes. Instrument packages were carried on four Boeing 747 aircraft in routine commercial service: two from Pan American, one from United.Airlines and one from Qantas Airways of Australia. Geographical coverage was therefore determined by the routes of these airlines, wih the sampling altitude being in the range of 8-13 km and usually close to 200 mb. Air intakes for the instruments were just below the center line in the nose and were opened automatically on ascent through 6 km and closed on descent through that altitude. Constituent data were recorded on tape, generally every 5 minutes, together with altitude, latitude, longitude, air temperature and wind velocity, the latter obtained from the aircraft's inertial guidance system. At a later date, tropopause heights from the analysis by the National Meteorological Center (NMC) in Washington were added to the data set.

Carbon monoxide and ozone data were collected simultaneously from early 1977 to early 1979 when GASP terminated. CO was measured with a Beckman Instruments infrared absorption analyzer using dual isotope fluorescence; a complete description, with a discussion of the modifications made for this program has been presented by Dudzinski, 1979 (3). Uncertainties in the measurements range from ±3 to ±13% of the reading, plus an error of ±3 to ±lS ppbv due to random fluctuations of the output signal. The response time is about 90 seconds (corresponding to 20 km of distance at normal flight speeds). One major problem is drift of the zero level and this is therefore recorded every 20 minutes; data is rejected if the drift is too large (see Papathakos and Briehl 1981 (7) for the criteria used). Another problem was depression of the CO recorded below the true value by migration of Hopcalite particles within the system; these are used to scrub CO from the incoming air so that a zero level may be set. Yet another problem that plagued the Qantas instrument more than others was that after landing at a high moisture tropical airport, the CO reading was depressed for 1 or 2 hours. This was thought to be due to saturation of the dessicant and was minimized by eliminating the first 1 1/2 hours from each flight record when­ever any statistics were computed. The CO instrument was removed from the aircraft and calibrated at the NASA Lewis Research Center every few months. Ozone is measured via absorption of ultraviolet light, using a Dasibi

Ozone Symposium - Greece 1984 - 548-

Environmental Corporation instrument, again modified as discussed by Tieferman (9). A measurement is made every 20 seconds with photon counts being compared between ambient and ozone-scrubbed air. Again, calibration was performed at NASA Lewis. With both instruments, three values are recorded on tape every 5 minutes (except when zero levels are being recorded): the instantaneous reading, the average over the previous 128 seconds and the standard deviation over that period (the latter is not a significant parameter for CO because of the 90-second response time).

2. Selected Results

The routes followed by the Pan Am 655 aircraft over six days in October 1978 are shown in Fig. 1. There are six crossings of the North Atlantic which allow for intercomparisons to be made. The data for the Seattle to London leg are shown in Fig. 2. The wave nature of the tropopause is apparent with high 03' low CO and high temperature in the subsiding regions and low 03 and high CO in the ascending regions. An expanded version of two similar events is shown in Figs. 3 and 4 when the Pan Am 633 aircraft was crossing the Pacific in level flight. In the first path the aircraft flew at an essentially constant altitude of 11.2 km. Ascent of tropo­spheric air on March 13 is indicated by CO rising to 80 ppbv and ozone decreasing to 280 ppbv at 17:40 GMT. The tropopause height is at 10 km but the NMC map cannot resolve this region of what seems to be mixed air. The low temperatures are additional evidence of adiabatic ascent. The opposite situation occurs on March 6 with high 03, low CO and high temperature, all indicatin& subsiding air. This type of situation is reminiscent of maps drawn by Dobson (2) in the early days of ozone research. Dobson noted a clear association with weather systems which can be at least partly under­stood from these aircraft measurements. The high ozone was just to the west of the low pressure at the surface and in the example Dobson gave amounted to about 50 D.D. above the monthly average. If we convert the observed additional ozone of 600 ppbv to a change in total ozone, assuming this concentration is representative of a 3 km thick layer, then the change amounts to 46 D.D. -- very close to Dobson's observations. These events are not unusual and another is shown in Figure 5. This illustrates well the association between high ozone and flow from the south, which is responsible for the observed poleward flux of ozone. When we first studied this poleward transport question (6), we used the observed correlation between total ozone and ozone in the lower stratosphere (5) to take total ozone as a proxy for lower stratospheric ozone. The aircraft measurements show how this comes about. When the ozone is high not all the subsidence occurs in the poleward-moving air as shown by Martin and Brewer's (4) studies of trajectories. Their positive correlations between ozone and vorticity suggest that horizontal convergence and vertical stretching occur as the air moves into the upper level trough before turning northward. These processes are linked to the mechanisms discussed by Danielsen (1) in his discussion of tropopause folds in which some of the subsidence results in the air slipping to the right, completely out of the stratosphere.

Correlations between the CO and the 03 are shown in Table I. These are clearly negative for both troposphere and stratosphere in middle latitudes, indicating that the transport processes between stratosphere and troposphere, discussed above, dominate. But in the low latitude troposphere the correlations are positive, indicating the possible influence of photochemical effects (8).

- 549-

It became clear during this program that ozone in the tropics was a function of latitude and longitude. The climatology was constructed (Fig. 6) and shows an overall minimum to the west of the dateline. We suggest that this comes from lower level air brought to the upper tropo­sphere by the rising arm of the Walker Circulation. Using accepted values for thZ8velocity field at 500 mb we find a downward flux of ozone of about 4 x 10 molecules/sec or approximately 1/5 of the net surface losses. The Walker Circulation therefore plays a significant part in the tropo­spheric ozone flux. Unfortunately the problems with the Qantas instrument at tropical airports precluded a similar sum for CO.

REFERENCES

1. DANIELSEN, E.F. (1964). Project Springfield Report. DASA 1517. H.Q. Defense Atomic Support Agency, Washington, D.C. 20301. 97 pp.

2. DOBSON, G.M.B. (1929). Atmospheric Ozone. Gerlands Beitrage zur Geophysik, 24, 8-15.

3. DUDZINSKI, T.J. (1979). Carbon monoxide measurement in the Global Atmospheric Sampling Program. NASA TN-1526. NASA. Washington, D.C. 20546. 32 pp.

4. MARTIN, D.W. and A.W. BREWER (1959). A synoptic study of day-to-day changes of ozone over the British Isles. Q.J.R. Meteor. Soc., 85, 393-403.

5. MATEER, C.L. and W.L. GODSON (1960). The vertical distribution of atmospheric ozone over Canadian stations from umkehr, observations, Q.J.R. Heteor. Soc., 86, 512-518.

6. NEWELL, R.E. (1961). The transport of trace substances in the atmo­sphere and their implications for the general circulation of the stratosphere. Geofisica Pura e Applicata, 49, 137-158.

7. PAPATlUU(OS, L.C. and D. BRIEHL (1981). NASA GASP data re?ort for Tapes VL0015-VL0020. NASA TN-81661. NASA Washington, DC 20546. 94 pp.

8. SEILER, W. and J. FISHMAN (1981). The distribution of carbon monoxide and ozone in the free troposphere. J. Geophys. Res. 86, 7255-7265.

9. TIEFERMANN, M.W. (1979). Ozone measurement system for NASA Global Atmospheric Sampling Program. NASA TN-1451. NASA, Washington, D.C. 20546.

ACKNOilLEDGEMENT:

Support for this work was provided by NASA under Grant No. NAS3-22541 and the Department of Energy under Grant No. DEAC0276EV12195.

---------*---------

Figure 1

-550-

0 3 (ppO,1 AIRCRAFT 533 PA IN LEVEL FLIGHT AT 11. 2 KM. 13 MARCH 1978

7

500

400

300

200

TI'OC»$C)henr; [llf m<Mng

up Into strQlospl"l@rf 1

TEMPERATURE

CO (ppOvI

80

70

60

- 10 50 ~m

- 9 40

- 8 30

100 -so- -.---.. 20

10

700

600

500

400

20

o

1600 1630 1700 58N, I53 w

1630

TIME (GMT)

1900 56N, I09W

A.RCRAfT 533 PA IN l£VEL FUGHT AT 11.2 K .... 6 ... ARCH 1978 CO '_1 160 T(°CI

-50-

.200 12JO '300 38.6N. I7'5W

TEMPERATuRE

HEKiJ'iT ."".------ .- .. ......... --.-./

Il30 1400 t430 37N,~W

TI ... E (G"'T)

- 551-

100

90

eo 70

60

~

40

'500 31.6N.IJ!)W

Figure 2

Figure 3

Figure 4

PAN AM 5~~ 2 FEBRUARY .1978

CO (PPb¥) I ~O

120

110 Figure 5 100

90

80

..; "- .- 70

60

50

40

0200 O~OO 0400 0700 0800 0900 1000 "ON. M3E 32N • • 28£

co 03 CORRELATIONS FROH TAPES 10-20

AIRCRAFT TROPOSPHERE STRATOSPHERE & SEASON ~ 20 ' N' )20' > 20 ' N ---- TABLE I PAN AMERICAN 535

DEC-FEB 0.32 36 -0.31 m -0.37 1159 ~lARCH-f1Ay -0.67 532 -0.49 1616 JUNE-AuGUST

SEPT-Nov 0.19 lO6 -0.42 414 -0.30 589

PAN AMERICAN 655

DEC-fEB 0.12 152 -0.18 187 -0.61 164 l-1ARcH-;-\Av 0.35 22 -0.28 89 -0.90 4 JuNE-AuGUST

SEPT-Nov 0.21 22 -0.37 238 -0.40 147

UNITED AIRLINES DEC-FEB -0.43 86 -0.61 32 l-iARcH-r·1AY -0.37 1544 -0.70 450 JUNE-AuGUST -0.30 890 -0.84 75

QANTAS

DEC-FEB 0.0 95 -0.04 95 -0.25 26 SEPT-Hoy 0.36 431 -0.28 443 -0.93 9

"N = NUMBER OF OBSERVATIONS

- 552-

Summary

TI!E INTERANNUAL VARIATIONS OF TI!E GLOBAL TOTAL OZONE AS A REFLECI'ION OF TI!E GENERAL CIRCULATION CHANGES

IN TI!E STRATOSPHERE

FUMIO HASEBE Laboratory for Climatic Change Research Geophysical Institute, Kyoto University

Kitashirakawa, Kyoto 606, Japan

Characteristic features of the quasi-biennial and four-year oscillations in total ozone (QBO and FYO) are discussed in connection with the lower stratospheric temperature field. It is found that the equatorial total ozone QBO is theoretically consistent with the observed temperature QBO if the vertical ozone transport by the Lagrangian-mean circulation is considered. There is a possibility that the cross-equatorial phase propagation and the extratropical seesaw structure of the total ozone QBO could be explained by the modulation of tropospheric dynamical forcing associated with the location of zero zonal wind critical surface. The FYO could be qualitatively reproduced in the northern mid- and high latitude ozone fluctuations which are estimated from the residual mean circulation by the use of the lower stratospheric temperature field. Within the availability of the data at the present, no inconsistency is noticed in considering that the FYO would be induced by the sea surface temperature changes in the equatorial eastern Pacific.

1. Introduction As for the interannual variations of global total ozone, previously

reported are the quasi-biennial oscillation (QBO) , the four-year oscilla­tion (FYO) and those related to the solar cycle (e.g., 2,4,20). Recently, the detailed global structures of the QBO and the FYO have been obtained by using the Nimbus 4 BUY and the ground-based network data (5,6). To under­stand the mechanisms of these oscillations, we try to reconstruct the observed QBO and FYO from other meteorological quantity, temperature, by estimating the modulation of the dynamical ozone transport. The description of the circulation will be based on the Lagrangian-mean point of view (3,7, 11,13,14), although only a rough estimate could be obtained, of course. For the sake of simplicity, the ozone is assumed to be an inert tracer follow­ing the atmospheric motion.

2. Quasi-biennial oscillation in total ozone The characteristic features of the QBO, schematically illustrated in

Fig. 1, can be summarized as follows (5,6): In the tropics (200 N-15°S), the positive deviations in total ozone nearly correspond to the westerly phase of the equatorial quasi-biennial zonal wind oscillation at 50 mb. However, the ozone QBO is asymmetric with respect to the equator in marked contrast with the zonal wind oscillation (e.g., 19). Separated by a major node at 15°S, the QBO propagates northward and southward with the phase being

Ozone Symposium - Greece 1984 - 553-

o 1 (Year')

, I '- I MIN MAX " '\ NH node - - - - - - - - - - - - - - - - • - 20-50"N

MAX MIN

win • .;'r win.';r

/ / MAA/ .. IN....... MA.!\../

EQ 7"'®----7'r<'(D----7'r<'\lV- (50"b U)

node - - - - - - . - '- - - - - - - - . - '- - - -.... Inter; .... lnter

IS"S

\ \ \ .. IN

opposite. The northward propaga­tion crosses the equator and con­tinues to northern midlatitudes; the meridional phase velocity is relatively low in spring-summer and high in autumn-winter. In the northern high latitudes, the phase of the QBO is observed often to be opposite to that in the middle latitudes. The QBO in the southern midlatitudes shows a phase delay of about a half year to that in SH the northern midlatitudes.

\ MA\ H\ The zonal wind QBO would

produce the total ozone fluctua­tions through the following dynamical processes. The vertical wind shear associated with the

Fig. 1. Characteristic features of the quasi-biennial oscillation in total ozone.

downward propagating westerly and easterly wind regimes is accompanied by a horizontal temperature gradient satisfying the thermal wind relation. On the time scale of the quasi-biennial oscillation, these temperature anoma­lies suffer from radiative damping (8). The diabatic heating (cooling) in the cold (warm) region drives upward (downward) motion as described in (15) and (16). If the radiative damping could be modeled by the Newtonian cooling, vertical current can be obtained from the temperature field by combining it with the thermodynamic equation. If we have the vertical gradient of the ozone mass mixing ratio, ozone fluctuations associated with the zonal wind QBO can be estimated (see Ref. 6 for the details).

The total ozone changes thus expected from temperature are shown in Fig. 2 together with the observed ones; the temperature data are those from Nimbus 5 SCR. In the equatorial region, very good agreement between the observed and expected total ozone changes is found. However, the meridional phase propagation crossing over the equator in the observed total ozone is not depicted in Fig. 2(b). This may be attributable to the influence from the extratropics; actually it is observed that planetary waves do penetrate from the northern hemisphere to the southern midlatitudes (5,6).

The influence of the equatorial quasi-biennial oscillation in the stratospheric zonal wind on the extratropical circulations has been studied extensively. The evidence so far found includes the seesaw pattern in the lower stratospheric geopotential height field, high latitude wave activity

(a) (b)

N

s

Fig. 2. The biennial oscillations in low latitude total ozone (matm-cm); (a) observed and (b) expected from temperature field. (Ref. 6).

-554 -

(9,10), the occurrence of stratospheric sudden warmings (12) and the seasonal advance/delay of the poleward and downward shift of the strato­spheric westerly jet in the southern hemisphere (18). The basic idea for such couplings is that the vertical and meridional propagation of station­ary planetary waves in the winter hemisphere should depend on the zero wind critical surface associated with the easterly and westerly phase of the equatorial zonal wind (10). The scenario including the ozone changes would be as follows (Fig. 3): TOTAL OIONE TEllPERA11JRE

During the easterly KP v,,,,, .,.". KP .------""""0"'''''-,.---''''::;.''::::''--, NP

phase of the equatorial zonal wind, tropospheric forcing is concentrated at latitudes higher than the zero wind line in midlati­tudes. The stronger forc­ing brings about earlier and larger amplification of planetary waves in the winter that follows; this drives the midwinter sud­den warming. The amplifi­cation of the planetary wave is accompanied by poleward transport of ozone (and also potential temperature) in excess of the equatorward transport by the mean meridional circulation. Occasionally an easterly maximum at 50

1 1 YEAR YEAR

Fig. 3. Schematic diagram of the driving mech­anisms of the quasi-biennial oscilla­tion in total ozone and temperature.

mb level, together with a negative deviation in total ozone, occurs in the northern winter, so that the phase of the QBO shows cross-equatorial northward propagation. Owing to the excessive transport by the waves, total ozone and temperature in high latitudes exhibit positive deviations; the out- of-phase relation between middle and high latitudes (the seesaw pattern) of total ozone and temperature is thus realized. In the southern hemisphere, the node at 15°S might be attributable to the counter current of the equatorial vertical motion. In the middle and high latitudes, owing to the weaker tropospheric forcing and/or the miss-matching between the equatorial zonal wind and the southern hemispheric' seasonal march, the distinct out-of-phase relation in ozone (and probably in temperature) does not take place, although a similar tendency is observed.

3. Four-year oscillation in total ozone The four-year oscillation (FYO) was noticed in the northern hemisphere

among the fluctuation$ of the ground-based network data of fifteen years (4). Recently it is' shown that the FYO has a beautifully organized global structure, which is suggestive of the effect of the equatorial sea surface temperature changes (5,6). That is, it has the out-of-phase relation between tropics and extratropics exhibiting the equatorial symmetry. In addition, there is a tendency for warm sea surface temperatures to be folrowed by tropical low and extratropical high ozone in both hemispheres (Fig. 4). Similar correspondence of the northern midlatitude FYO to the sea surface temperature could be noticed in much longer time series derived from the ground-based observations (6). Then it is natural to consider that the FYO would be thermally driven by sea surface temperature changes.

For extratropical tracer transport, the use of the residual circula-

- 555-

tion introduced by Andrews and McIntyre (1 ) is very convenient . :his circulation agrees qualita­tively well with the Lagrangian­mean circulation (17 ) . although the exact agreement requires some conditions such as steady. non­dissipating etc. Especially in case of the FYO. good agreement is expected from the consideration that the wave transiency plays only a minor role on the FYO. This is because (I ) the FYO seems to be simply originated from thermal forcing and (II ) the four-year component of the sensible heat transport of the waves is almost completely canceled out by that of the mean meridional circulation without exhibiting appreciable temperature changes in the mid­latitude lower stratosphere (Fig. 5 (b ». Then. by using the Newtonian cooling approximation and the thermodynamic equation for the expression of the residual mean v~rtical velocity. the gov­erning equation for the zonal mean ozone concentration Y would be approximated by

QX= a xo JL. f h (1 _ ~ ) + a 1 n e } (1 ) at az N2 eat where Xo is a basic state ozone mass mixing ratio and e* is the

o 2 !Year)

I I NH

MAl MIl

node - - - - -, - - - - - - - - . - - - - -

EQ -®--+--©--"fX--@-. !EO SST)

nede - - - - ( - - - - - - - ( - - - - - 20·S

SH MAX MIN

Fig. 4 . Characteristic features of the four-year oscillation in total ozone.

-5 0.4

;: 0.2

~ 0.01--"'-~---Hr-----",,---+---1

3_0,2

-O,q

1952 65 70 75 (YEAR)

zonal mean equilibrium potential (b) 10,-,--~~~'-'-r-~-----.~----r~-r----'---.---,.., temperature; others obey conven- e SS" N

tional notations (see ~ef . 6 for the details ) .

The total ozone fluctuations estimated from the observed 1 (potential ) temperature by using eq. (1) are shown as the time series of monthly mean values in Fig. 6. Because the NMC data available cover only north of Fig. 5 . 2OoN. the result for gOON and 200 N are shown as a representative of high and low latitudes. respec-tively. It is interesting to see that the periodicity near four

Long-term variations in total ozone (Ref. 4 ) . temperature. and sensible heat flux conver­gence at 100 mb . ( a ) high- and (b ) mid-latitude of the NH.

years is resolved in both of the time series with a tendency for an out-of­phase relation between them. It is readily seen. however. that the ampli­tude obtained is very large and that most of the large amplitude for gOON is contributed by an abrupt change in winter like a step function. It is apparent that a precise expression of the winter time circulation is required in order to obtain quantitatively reliable ozone fluctuations.

-556 -

[matm-cmJ

Fig. 6. 1%5 lWO lW5

Fluctuations of total ozone anomalies (matm-cm) for as expected from observed temperature field by using vertical veloci ties. (Ref. 6).

1979

900 N and 200 N the residual

It is also interesting to see that the total ozone FYO is in phase with the temperature FYO in high latitude (Fig. 5(a». This implies that the principal term in eq. (1) is not the first one which represents the local diabatic heating in high latitudes. Therefore, the ozone and the potential temperature variations are brought about passively by a circula­tion which is driven in some other places, that is, low latitudes. This result not only supports the application of the Newtonian cooling approxi­mation, but also emphasizes the idea that the FYO is a reflection of the general circulation changes induced by the equatorial sea surface tempera­ture anomalies.

Acknowledgements The author would like to thank Profs. R.Yamamoto and I.Hirota, Kyoto

Univ., J.R.Holton, Univ. Washington, T.Matsuno, Univ. Tokyo, Drs. J.C.Gille NCAR, and K.K.Tung, MIT, for their helpful comments and discussions. He is also indebted to Mr. M.Shiotani for the treatment of Nimbus 5 SCR data.

References 1. Andrews, D.G., and M.E.McIntyre, 1976: J. Atmos. Sci., 33, 2031-2048. 2. Angell, J.K., and J.Korshover, 1964: J. Atmos. Sci., 21, 479-492. 3. Dunkerton, T., 1978: J. Atmos. Sci., 35, 2325-2333. 4. Hasebe, F., 1980: J. Meteor. Soc. Japan, 58, 104-117. 5. ----, 1983: J. Geophys. Res., 88, 6819-6834. 6. ----, 1984: in Dynamics of the Middle Atmosphere, J. R. Holton and

T. Matsuno, eds., Terra Sci. Pub. Comp., Tokyo, 445-464. 7. Holton, J.R., 1980: Phil. Trans. Roy. Soc. London, A2.OO, 73-85. 8. and R.S.Lindzen, 1972: J. Atmos. Sci., 29, 1076-1080. 9. ---- and H-C.Tan, 1980: J. Atmos. Sci., 37, 2200-2208.

10. ---. and ----, 1982: J. Meteor. Soc. Japan, 60, 140-148. 11. Kida, H., 1983: J. ~feteor. Soc. Japan, 61, 171-187. 12. Labitzke, K., 1982: J. Meteor. Soc. Japan, 60, 124-139. 13. Matsuno, T., 1980: Pure Appl. Geophys., 118, 189-216. 14. Palmer, T.N., 1981: J. Atmos. Sci., 38, 844-855. 15. Plumb, R.A., and R.C.Bell, 1982: Quart. J. Roy. Meteor. Soc., 108,

335-352. 16. Reed, R.J., 1964: Quart. J. Roy. Meteor. Soc., 90, 441-466. 17. Rood, R.B., and M.R.Schoeberl, 1983: J. Geophys. Res., 88, 5208-5218. 18. Shiotani, M., and I.Hirota, 1984: submitted to

Quart. J. Roy. Meteor. Soc. 19. Wallace, J.M., 1973: Rev. Geophys. Space Phys., 11, 191-222. 20. Wilcox, R.W., G.D.Nastrom, and A.D.Belmont, 1977: J. Appl. Meteor., 16,

290-298.

- 557-

DEPENDENCY OF OZONE TRANSPORT ON THE VERTICAL STRUCTURES OF PLANETARY WAVES

KOHJI KAWAHIRA Geophysical Institute of Kyoto University, Kyoto 606, Japan

Summary

The mechanism of the ozone transport by planetary waves in the winter stratosphere is considered on the basis of a quasi-one-dimensional model, where the meridional distributions of physical quatities are expressed by two modes. We consider in the present paper, wave-mean flow interactions as well as dynamical and photochemical effects on the ozone variations. It is, found that the meridional and vertical transports of ozone by the waves depend Dn the vertical structures in its magnitudes and directions. Our finding regarding the character­istics of ozone transports in wavenumber 1 is different from that shown by (2), in that southward transport dominates in the upper stratosphere above 30 km height. This discrepancy is due to the difference in the vertical structures, because it is found that the upward propagating waves can bring about the equator-ward transport, while the internally trapped waves (nearly no phase change with height), the poleward transport in the upper stratosphere. The transport characteristics in the present paper are well consistent with the observational analysis of ozone transport due to large-scale eddies shown by ( 1 ) and ( 4) •

I. Introduction

A new aspect onthe ozone transport by planetary waves in the stratosphere has been proposed by (2), where a particular phase relation between wave motion and perturbed ozone in the middle and upper stratosphere(so called 'transition region') during both decaying and growing stages of wave forcing. They suggested that this mechanism could play an important role on the enhanced poleward transport at the time of stratospheric sudden warmings ( 4) •

On the other hand, (3) reexamined the ozone transport by planetary waves in a model of wave-mean interactions, more realistic than (2), because (2) assumed no time changes of zonally averaged winds and ozcne. (3) showed that large-scale eddy transport of ozone in its magnitudes and directions could be determined by the vertical wave structures; in the upper

Ozone Symposium - Greece 1984 - 558-

stratosphere, the upward propagating waves (westward tilt of phase wi th al ti tude) could bring about southward transport, while internally trapped waves (nearly no change of the phase with altitude), northward transport.

In the present paper, the differences between the results of (2) and (3) will be presented to investigate the dependency of the ozone transport on the vertical wave structures.

2.Models and meridional eddy transports of ozone Main difference of the models between (2) and (3) is that

zonal winds change in time as a result of wave-zonal interac­tions in the model of (3), but constant in time in the model of (2). The initial zonal wind in (3), as shown in Fig.l, is same as time-independent zonal wind in (2). Maximum zonal wind of about 80 mls is located just below 70 km height.

lie

60

70

60

~ 5~

~ -" 40 ;::

50 ("",)

Fig.l Zonal wind used in (2) and in (3) as the initial zonal wind.

60

": AMP (xIOm) WN~I

::: ~ ~

:i ~

~:

~; ::: ~

-

" u(mIS)

-L-----"~~--~I"--~IS--''''-~'~S--~'O~~'~'--~''~~''

."

~ 50

~ 40 =>

Fig.3 Time changes of wave amplitudes of wavenumber I (upper) and zonal wind(lower) in (3). ~

5 30 <l

20 H.;9hIS (ml

____ -100

10L-__ -L ____ ~ __ ~ ____ ~ ____ ~ __ ~

o 10 20 30 40 50 60 TIME (Oaysl

Fig.2 Time change of wave amplitude of wavenumber I in (2).

- 559-

Other physical quatities such as meridional gradient of mean ozone and time change of lower boundary wave forcings are same. (Details of the formulation, see Ref. (3)).

Time-height section of wave amplitudes of wavenumber 1 in the study of (2) is shown in Fig.2, where maximum amplitudes are seen around30 days just below 60 km height. Fig.3 shows the time change of wave amplitudes and zonal winds in the study of (3), where as a result of wave-mean flow interactions, strong westerly wind changes to westerly or even easterly as waves developed. From the comparison between Fig.2 and Fig.3, it can be seen that maximum wave amplitudes in the case of no time change of zonal wind tend to appear later in time and lower in altitude than that in wave-mean flow interaction model. Then the the amplitudes in the former case tend to be trapped due to strong westerly jet near 60 km height, but those in the latter case tend to be upward propagating through changing the zonal winds.

This difference in the vertical profile of the amplitudes also more clearly seen in that of the phases as shown in Fig.4. The profile in the case of constant zonal wind is nearly no tilt with altitude(internally trapped type), but in the time change model of zonal wind, westward tilt with altitude(upward propagating type). This tilt can control the strength of temperature perturbations, and thus control the height of the photochemically controlled region because of strong negative correlation between ozone and temperature (3) . It is apparent

PHASE WN= 1 DAY, 20

70 I , , , , '-- ---::-,) 60 r -- · , ,

\

'w' I

E 50 !r I /

~ , I ,,"r'

~ 40 I => I V' f- I 530 I <

I

eo , I, ~ I \ ~ I \~

70 " I ~ ;, i '-

60 i ~ \ I

~ 50

E 0'

f 40 20 I

I 30

4 5 6 PHASE (Radians ) 20

Fig.4 (left) The phases of v',T' ,w' and"f' of wavenumber 1 at 35 days 10

(after the study of Ref. (2)). (right) same as left but at 20 days (after the study of Ref. (3)).

that upward propagating waves could result in'"Ii"'V' < 0 in the photochemically controlled region because of T j; I :> 0 and nl'O(;-T'. On the other hand, internally trapped waves can cause lesser T', and thus make the photochemical effects to be smaller as compared to the dynamical effects (see,Ref. (3)) .

These differences between vertical wave structures result in

- 560-

those in the characteristics of meridional eddy transport of ozone as shown in Fig.5. Although ozone perturbations in the results of Ref. (2) is expressed in terms of mixing ratio, the difference of the transport due to vertical wave structures are apparent; around 30 days, northward flux is dominant in nearly whole stratosphere in the case of Ref. (2), while in the case of Ref. (3) northward flux below 35 km but above that level southward flux are dominant. Therefore the internally trapped

70

60

©~ e ---4

20 o~ Mixinq Rolic IO~(~w~m~'~IO~l--L--~---~--__ ~ __ ~

70r-~~~?T~--~~=c~-'r-~ 0.1

-0 60

20

r ( 0,

"­-oo5-_--IOO~---1~0-~2~0----~~0~--~40~--~5~0--~GO

TIME IDoy')

~r-------------------------,

~'~~-~iO'-~"--~~"~~'~'--~'O~~l~'--~'O--~~~ ." .,-------------------------,

.a--~

Fig.5 (left) Time change of ozone amplitude(upper) and meridional flux of ozone by the wave (lower) in the results of Ref. (2). (right) same as the left but in theume change model of zonal wind in the results of Ref. (3).

tend to contribute to larger northward transport of ozone, but upward propagating waves bring about the southward flux in the upper stratosphere. These results are evidences of the depen­dency of ozone transport on the vertical wave structures.

Even in time dependent model, we can see the flux as in Fig.5(left&depending on the vertical structures as shown in Fig.6 where time change of wave-induced meridional flux by wavenumber 2 are shown. We can see that around 20 days, northward flux in nearly whole stratosphere is dominant, likely as in Fig.5(left). This is due to that wavenumber 2 tilts with altitude less steep than wavenumber 1. Therefore wavenumber 2 wave can induce larger northward flux of ozone because of less perturbed temperature as shown in Fig.4(left),

though wavenumber is different.

- 561 -

WN . 2 o

~r---~----------~--~rr-------,

o

~1;----

~ . . , .~ ~

o.LI __ ~~~~-L,, __ ~~~~ __ ~~~.~ ~ \:) r.ao filS

3.Discussion

Fig.6 Same as in Fig.5 (left) but for wavenumber 2 (after Ref. (3)).

Observational analysis of large-scale eddy transport of ozone have been made by (1) and (4). The pattern of meridional flux by wavenumber 1 in the results of (1) are same as Fig.5( left), although only the results at single day: Recent study of (4) show interesting characteristics of ozone transport, where more variable pattern of meridional fluxes are analyzed, possibly due to the vertical structures of planetary waves.

However, the importance of 'transition region' first noted by(2) is that this mechanism tend to enhance northward flux of ozone, even when waves are steady and inert trace gas is under 'non-transport condition' .

References

1. Gille, J. C., P. L. Baily and J . M. Russell III, 1980: Phil. Trans. Roy. Soc. London, A296, 205-218.

2. Hartmann, D. L., and R. R. Garcia, 1979: J. Atmos. Sci., 36, 350-364.

3. Kawahira, K., 1982: J. Meteor. Soc. Japan, 60, 831-848. 4. Wang, P. H., M. P. McCormick and W. P. Chu, 1983: J. Atmos.

Sci., 40, 2419-2431.

- 562-

OZONE CONCENTRATION DATA APPLIED FOR STUDYING MESOSCALE WAVE PROCESSES IN THE ATMOSPHERE

Swnmary

A.N. GRUZDEV and N.F. ELANSKY Institute of Atmospheric Physics Academy of Sciences of the USSR

A problem is considered of ozone applying as a tool to study mesoscale wave processes in the atmosphere, inter­nal gravity waves (IGV) and, especially, lee-waves. A meth­od is suggested which permits obtaining vertical displa­cements of the air particles in waves from ozone content measurements.

1. Introduction

Ozone as a tracer of air flows has been knovlIl for a long time. However, in practice, it has unsufficiently effective use up to now. Never ozone was used as a principale tool to study dynamic processes. The main difficulty of its using lies in the photochemical activity of ozone. Its transfer is fol­lowed by photochemical interaction with other atmospheric con­stituents and appropriate changes should be taken into account. These changes are not yet possible to be accounted for in a general case due to uncertainties of many factors and reaction constants. The only possible way for ozone effective using in purposes of the atmospheric dynamics studying is to select situations and processes where the photochemistry plays a so­mewhat insignificant role and may be rather accurately descri­bed on the basis of photochemical links. These prosesses, as seen from the analysis made, involve the internal gravity wa­ves in the atmosphere and, especially, the lee-waves.

2 • WAVES IN THE LEE OF MOUNTAINS

Lee-waves have a complicated spatial structure. They pro­pagate in several tens of kilometers dawn the flow and often penetrate into the stratosphere. The existing methods of their investigation, namely, airborne observations of meteoparame­ters, photographing of wave clouds and tracking of balanced balloon-zondes have certain shortcoming. On the whole, such a system requires further improvements. However, due to conside-

Ozone Symposium - Greece 1984 - 563-

rable vertical stratification of the atmospheric ozone concen­tration wave disturbances even of small amplitude can give ri­se, at a certain level, to sharp ozone changes. Inasmuch as the ozone content can be measured at high accuracy at any po­int in the troposphere and lower stratosphere, there is good reason to believe that, proceeding from the ozone distribution in the ridge region one can effectively restore the flow-aro­und pattern.

It is known that the amplitude of lee-waves reaches 'seve­ral hundreds of meters. These vertical air displacements in­fluence equilibrium distribution of constituents both at the expense of transfer or temperature changes.

The time of ozone photochemical relaxation in the tropos­phere and stratosphere is much more than the typical time of the wave process (near 10 min.), and ozone may be regarded as a conservative constituent. The equation of constituent trans­fer may yield the relation of the conservative constituent (here ozone) concentration deviation, nt, from its value in the flow running on tbe ridge, no, with the st.ream-line ver­tical displacement (1) '1:

n'= (b~ 'V _ ~no) n f?. To OQ ~c l /1/

where To is the air temperature in the running-on flow"a is the adiabatic temperature gradient, Rand Cv are the ga con­stant and specific heat capacity at an air constant volume. The authors of (1) have also obtained the formula for n' in a case of photochemically active ozone. Using /1/ yields the ~ distribution in the lee zone according to n' distribution data.

In August-September 1982 and 198) ozone concentration mea­surements were made from the Yak-40 airplane over the Gegamski ridge in Armenia and some ridges in the Central Asia. Measure­ments were made using the Atmosphere-2 electrochemical cell. Simultaneously, the average air temperature and its variation, altitude and flight speed oscillations and some other parame­ters were registered aboard. The flights were carried out as follows: firstly, the vertical section of the atmosphere was made and vertical ozone and temperature profiles in an undis­turbed flow were determined, then measurements were made on horizontal routes, i.e., along isobars. Fig. 1 presents an example of ozone and temperature oscillations obtained in fli­ghts over the Gegamski ridge on 9 September 1982. A wave struc­ture of the 0) and T curves in the lee zone is distinctively seen.

Different types of the ridge flow-around were observed: (i) laminar flow: no waves., (ii) flow-around in the presence of standing vortex (usually and convective cell are flown aro­und as an integra~. The waves either decay or are absent. (iii) wave flow.

As an example of the flow-around wave pattern restoration we may present observation results over the Gegamski ridge on 4 August 1982. Six horizontal sections at an altitude of 5.1 km were made. The wind speed amounted to 12 ms- 1 at the ridge level and to 16 ms- 1 at the flight altitudeo At an altitude of 4.5 km a temperature inversion region occured, and above this level the ozone concentration sharply increased. So, there are

-564 -

available conditions favourable for the wave formation (the T inversion is followed, as a rule, by a considerable increase in the above ozone content. That is, a zone, where the wave amplitude reaches its maximum (2), coincides with a region of high n gradients, what makes the recovery method for the ozo­ne field flow-around pattern very effective).

Fig.2. shows the picture of the air vertical displacement in the lee zone recovered from 0) content measurements. The regions of positive and negative1cha~ge each other periodi­cally in directions both perpendicular to the ridge and paral­lel to it, what testifies a three-dimensional pattern of the flow-around. Negative ~ quantities reach their highest valu­es of 80-100 m at a line passing between the ridge peaks. So­me isolated isoline fragements have the appearance of a horse­shoue bent to the ridge peak side as it is observed in a case of the three-dimensional flow-around of the isolated obstacle (). The wavelength is about 10 km. The horizontal scale of the disturbances at a direction parallel to the ridge crest is conditioned, appearently, by the distance between peaks, at least near the ridge.

Flights at various altitudes identify the vertical wave structure. For instance, flights on 10 September 1982 at va­rious altitudes over the same place revealed piriodical chan­ges in upward and downward motions with height over the ridge. The observed vertical wavelength ~ 2.5 to 2.7 km is close to a value.A ; 2.8 obtained after Scorer (8) for appropriate con­ditions.

Overall, it appeared that the application of ozone con­tent data for the description of air flows over orographic obstacles has certain advantages over the routine method us­ing temperature oscillation measurements, namely: (a) the qu­antity of vertical displacement may be determined according to n' for every air flow stratification, whereas using T' at

1 - Y ~ 0 does not yield, in fact, displacement values: (b) the ~low-around pattern in a case of cloudy conditions, which introduce essential disturbances into the temperature field, is restored more accurately; (c) in conditions of con­tinuous and nonuniform cloudiness wave amplitudes after n' are determined much more accurately than after T'.

). OTHER WAVE PROCESSES

In the flights 0 1 concentration variations connected with the internal gravity ~aves of non-oreographic origin were re­corded. These variations were most frequently observed near atmospheric fronts. Two instances have been chosen for illus­tration in Fig.J of OJ and T records obtained on 6 August 1982 in flights over the Karakum desert (the Central Asia),in the region of Kzyl-Orda town (flight at an altitude of 6600 m)and in the region of Bukhara (6000 m), respectively. The average wavelength along the flight trajectories (approximately west­east) equaled, in the first case, 10 km and, in the second case, 26 km. In the both cases there are no mountains higher along the air flow west from the mentioned regions. However, on that day synoptic charts registered a cold front near the low pressure centre north from Kzyl-Orda extending in the di-

-565-

rection of Bukhara and tracked up to an altitude of 850 mb. It is known that fronts can be sources of internal gravity wa­ves (3). It may be possible that in this particular case a subtropical jet stream which had on that day a branching over the Central Asia with axes passing approximately over the in­dicated flight regions appeared to be a sorce of the registe­red waves. Unfortunately, wave characteristics, namely, length, frequency, and phase velocity were not obtained due to the lack of data. Nevertheless, the examples show that ozone con­tent measurements may surve a suitable tool to study internal gravity waves. 4. Conclusion

It should be noted that, for detailed study of internal gravity waves and, in particular, lee-waves it is very impor­tant to carry out complex investigations with a greater number of measured parameters and, of course, not to confine them to aircraft measurements only.

As far as ozone content measurements for these purposes is concerned, it should be noted that lidars would have prac­tically unlimited possibilities here. Airborne lidars for up­and down-sounding make possible to obtain the picture of the disturbed ozone layer distribution throughout the troposphere and lower stratosphere, i.e., make the air current structure to be practically visible. REFERENCES

1. GRUZDEV, A.N. and ELANSKY. N.F. (1984). Estimate of lee­wave influence on the distribution of content of gaseous tropospheric species. Izv. Acad. Sci., USSR. Atmosph. Oceanic Phys., 20, 558-567.

2. SCORER, R.S. (1980). Environmental aerodynamics. Moscow, Mir, 549.

3. GOSSARD, E.E. and HOOKE, W.R. (1978). Waves in the at­mosphere. Moscow, Mir, 539.

, ---_/

3

2

I I

/~\.I

- 566-

Tl'''1~.4 -11.8 -12.2 -13.0

-1.'-4 FIGURE 1 : An example of ozone concentration and temperature oscil­lations obtained in flights over the Gegamski ridge on 9 September 1982.

\ Seva./1 la.ke

o 10 20 30 50 60 70 80 I(Irl

FIGURE 2. The picture ot the air vertical displacement in the lee zone over the Gegamski ridge on 4 September 1982 recovered from 03 concentration measurements at the level 5,1 km

(the areas ot the upward displacement are shade~)

[03J,mcg' m-3

40 j5

T,OC -15

30 +--t_~~I---"--~"--+.::JrIC~r.-----~~t-JIC-++-+-t -16 12.55

25 -17

[03])mc~.m-J

;;I~, 17.,,0 lll{)O.._ ... - .... - / ~..... I I .f .... I

',.,,' ...... -- ...... -'--..,,~-..,.-.-

Mosco"" tLme FIGURE 3. An example of ozone concentration and temperature

oscillations nearatmospher1c tronts.

- 567-

THE EFFECT OF TEMPERATURE WAVES ON THE ZONAL MEAN OZONE CONTENT

KOHJI KAWAHIRA

Geophysical Institute of Kyoto University, Kyoto 606, Japan

Summary

The strong negative correlation between ozone,n3 and temperature, T is a well-known fact in the upper stratosphere. When we take into consideration this correlation in our formulation of the ozone variation, the term T'ns in the photochemical lo~rate of the zonal mean ozone can be derived, being proportional to _n~2 Since this term is ahrays negative, it can be concluded that the zonal mean ozone concentration at photochemical equilibrium is higher with the effect of temperature waves than that without the effect as in previous studies. This effect is evaluated to find that a 20 % enhancement in the zonal mean ozone concentration can be brought about by temperature wave of 15°K amplitude; such an amplitude is often observed in the winter upper stratosphere. Therefore, temperature waves can play an important role on the ozone variations, especially during the period of sudden stratospheric warmings when planetary waves could accompany larger amplitude temperature waves.

1. Introduction

Main concern in the present paper is to show a finding of the temperature wave effect on ozone concentration derived by (1); temperature perturbations could cause an enhancement in zonal mean ozone concentration. This effect, as shown in (1), is due to the fact that the correlation between ozone and temperature variations is negative, as being verified from observational(2) and theoretical studies(3). The effect is an interesting example of nonlinear coupling between dynamical and photochemical effects on ozone.

2. Formulation and effect of temperature waves on ozone concentration

In the following, our formulation for ozone variations are concentrated on those at photochemical steady state, as in the upper stratosphere where transport effects due to air motion can be negligible. The chemical reactions are based on the Chapman scheme as shown in Table 1, temperature dependency of k4 is assumed to be -1300oK, different from -2300 oK in 'dry model', in order to include the effect of ozone removal due to hydrogen and nitrogen species(4).

Table 1 Photochemical reactions .

02+ hv2 02+ 0 + M °3+hv3 0 3 +0

Ozone Symposium - Greece 1984

.... 20

.... °3+M

.... O2 +0

.... 202

J2

k2= L1 X 1O-34exp(510/T) J3 k4 =3.5X 1O-12exp( -1300/n

- 568-

Then ozone concentration is determined by the following relation,

o=P - L

= 2Jznz

where P and L are ozone production and loss rate, respectively and K = k4/kz=3.2xlOZexp(-D/T) and D=1810oK.

To represent the ozone changes by temperature waves, all variables except for the photodissociation rates are assumed to be composed of the zonal mean and the deviation from it defined by the quantities put with a suffix 0 and a prime, respectively.

T = T (y,z,t) + T'(x,y,z,t), o

nq = nqo(y,z,t) + nq(x,y,z,t~

JZ~30= Jz o 30 (y,z,t) /

where T is temperature, nq is the number density of the q-th species and z=H In(po/p); H is scale neight (= 7 km) and Po and p are the pressure at the reference level and the level in consideration, respectively.

Now (1) is rewritten as follows,

o P - L

2Jzo(nzo + n~) - 2J30(Ko + K')(n30 + n~)1

«nzo + n2)(nmo + n~)),

where K'=(dK/dT).T' = Ko(D/To).(T'/To ). From (3), we can easily derive the zonal mean of the photochemical

production and loss rate of ozone as

o Po - Lo

2Jzonzo - Con30Z[1 + n~z In30 z+ (1 + 2D/To ).T,zIToz

(4)

where Co = 2Jz oKo/(nzonmo) and Ko = 3.2xlO zz exp(-D/To ). - denotes the zonal average.

For the deviation from zonal mean, we have

o P' - L'

In deriving eq.(4) we used the relations,

n~/nmo = - T'/To and n2/nzo =-T'/To'

which are valid on the pressure surfaces. Though (5) is the same as so far formulated, (4) is quite different

from these ones, especially the chemical loss term Lo. It is to be noted, that the zonal mean of the ozone loss rate is affected by the amplitudes

- 569-

of temperature wave T' and ozone 'wave' n~. In the following, we evaluate quantitatively the effect of temperature

waves on the zonal mean ozone. By using P'=L', we have the following relationship between perturbations in ozone and temperature, negative correlation;

(6 )

P' = J20n~ is neglected in deriving (6) because it is one order smaller than the other terms in the upper stratosphere.

After some manipulations with the use of (6), Lo is rewritten as,

with

(7) is a main result in the present paper. In the previous formulations, n = 1 at any time, so that the temperature wave does not affect the photochemical loss rate. In the present formulation, on the other hand, n < 1 unless T'=O, so that the present loss rate is always smaller than the previous one as far as the temperature perturbation exists. Note that n should be greater than zero because Po = Lo and Po > 0.

Let nse be the zonal mean ozone concentration for.n = 1, then the ratio nso/nse is expressed as follows;

(8)

On the basis of (8), we can evaluate the effect of the temperature wave on ozone at photochemical stationary state.

Figure 1 shows strong dependency of the zonal mean ozone n30 on the temperature wave. The increment rate depends highly on the amplitude of temperature T', and inversely proportional to zonal mean tempearture To.

~ D::181OoK 300,.-__ ~n3~e~ ______ r--, ____ -,r--,r-T7~'

Fig. 1 Enhancement of the zonal mean ozone concentration induced by the temperature wave with the amplitude of T. To is the zonal mean temper­ature. D= 1810oK ... which determines temperature depenaency of the ozone reaction rates. The shaded area indi­cate a domain without physical mean­ing.

280

(T. 260 K)

240

220

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10 20 30 r'~)

40 so

For T'=15°K and To=240oK, which are representative of the monthly averages in the upper stratosphere in winter, n 30 is larger by about 20 % than n3e' Because D=1810oK is consistent with tempearture dependency of the ozone concentration at 2 mb derived from the satellite data, Fig.l may present a realistic change in the zonal mean ozone concentration due to temperature waves.

3. Discussion

The present paper demonstrates an important effect of temperature waves on zonal mean ozone. This must be significant especially at sudden warmings when an 30 0 K amplitude of the temperature wave may occur in the upper stratosphere(Ref.,5).

Although we treated the effect on the zonally averaged ozone, same .estimation hold for the time mean ozone concentration due to temperature change in time, as seen in eq.(7). Thus when we take ,for example, monthly average of ozone, then the time changed temperature affect the monthly averaged ozone concentration in the upper stratosphere.

Since the effect in the present paper has not been pointed out from the observational analysis, thus it is highly desired to elucidate this effect from the detailed analysis from satellite observations.

References

1. Kawahira, K., 1982: J.Meteor.Soc.Japan, 60, 1058-1062. 2. Barnett, J.J., J.T.Houghton and J.A.Pyle, 1975: Quart.J.R.Met.Soc.,

101,245-257. 3. Lindzen, R.S., and R.M.Goody, 1965: J.Atmos.Sci., 31, 1898-1916. 4. Hartmann, D.L., 1978: J.Atmos.Sci., 35, 1125-1130. 5. Labitzke, K., 1981: J.Geophys.Res., 86,9665-9678.

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AIRCRAFT MEASUREMENTS NEAR JET STREAMS

G. Vaughanl & A. F. TUck Meteorological Office, London Road, Bracknell,

Berkshire, RG12 2SZ, UK.

SUMMARY

Aircraft measurements of 03, T and winds with fast response sensors were made about 18 hours apart in a developing jet stream system in the N.E. Atlantic, 15/16 April 1983. The structure of wind, ozone and potential vorticity data on isentropic surfaces is discussed. The ozone data suggest that significant mixing occurs over the entire region of strong cyclonic shear. A region below the jet core on the second flight in which tropospheric values of ozone were concurrent with high values of potential vorticity is examined. High ozone maxima appear to coincide with both strong cyclonic shear and confluence, whereas the potential vorticity maximum corresponds with diffluent flow.

Introduction and synoptic background The Meteorological Office Hercules C130 research aircraft flew on

two successive days in April 1983 to investigate a jet stream and associated frontal system which developed over the north Atlantic before moving eastward towards Scotland. Fast-response instrumentation permitted the fields of ozone, temperature and wind components to be measured in detail, with a view to delineating the processes governing stratospheric-tropospheric exchange around the jet stream. Following the practice of previous such experiments (Briggs and Roach 1963; Danielsen 1968; Shapiro 1974, 1978, 1980) the aircraft flew reciprocal headings at a number of fixed pressure levels transverse to the jet stream direction, each leg lasting for about 1 hour (a distance of 550 km at 150 ms-1 ). Four legs were flown on the first flight and five on the second. The two flights were separated by about 20 hours in time, the first taking place during the night of 15th-16th April (nearest synoptic hour OOZ on 16th) and the second during the following evening (nearest synoptic hour 18Z on the 16th).

Flight positions relative to the jet stream are shown on isentropic charts of the Montgomery stream function in figs. 1 and 2. These charts were derived from the assimilation data sets used to initialise the Meteorological Office operational forecast model (Lyne et al 1983), and are based solely on conventional meteorological information (radiosondes, satellite data and commercial aircraft reports). In broad terms, the charts agree with the flight measurements, but they disagree substantially in detail, overestimating the width and underestimating the strength of the jet core. Nevertheless, they show that the first flight traversed the entrance region of a southwesterly jet stream whose strongest flow was associated with a developing cyclone east of Iceland. Slight cyclonic curvature of the isopleths is shown for this flight. Eighteen hours

Ipresent affiliation: Dept of PhYSiCS, UCW, Aberystwyth, Wales

Ozone Symposium - Greece 1984 - 572 -

later, the jet stream had progressed eastwards and lengthened under the influence of the strong northwesterly flow of cold air behind the surface cold front. The jet core passed over the Moray Firth in a direction of 210 0 , with the chart showing much less evidence of downstream acceleration of the flow than at midnight. Instrumentation and data analysis

Horizontal wind components were obtained from a combination of aircraft instruments - the gust probe, inertial navigation system and Decca radar beacon receiver. The use of the gUst probe guaranteed the resolution of wind fluctuations at frequencies up to 20 Hz (Nicholls 1978) . The probe also measured the short-period vertical wind components, but since the aircraft was not fitted with a radar al timeter (nor a very accurate pressure sensor) mean vertical winds were not measureable. Temperature fluctuations up to 20 Hz were measured with a hot-wire thermometer.

A Bendix model 8000 chemiluminescent type detector provided the ozone measurement. Ambient air was supplied to the instrument through a metal bellows (MB1.58) pump to ensure sufficient pressure at its inlet. A small loss of ozone is inevitable in such an arrangement, and the absolute calibration of the instrument is therefore subject to some uncertainty. Laboratory experiments show this to be less than 10%, however, and experience in the field has proved that the instrument provides reliable relative ozone measurements with a precision of 0.5 ppbv and a time resolution of 1.5 s (2.4km at 1.50 m s-1. ).

BY measuring the wind, temperature and ozone fields on successive traverses of the jet-stream, a two dimensional cross-section of its structure may be inferred. To relate this to a particular synoptiC hour the system must be assumed to progress with a constant velocity without changing its structure over the period of a flight (5h 30 min). An estimate of this velocity may be derived from the synoptiC charts, but because of the paucity of radiosonde stations in the N.E. AtlantiC this method was not considered sufficiently accurate. Better estimates were derived (independently) from METEOSAT cloud photographs and from charts of total ozone column amounts as measured by the TOMS instrument on NIMBUS-7. These estimates were found to agree to within 0.5 m s-1.. Cross-section results

Cross-section diagrams of potential temperature (K, continuous lines) and wind speed (ms-1., dotted lines) were interpolated by hand from the aircraft data and are shown in figs. 3 and 4. North is to the left of the diagrams; the dashed lines show the ozone traces at the flight levels. Considerable differences are revealed between the two cross-sections. The first resembles fairly closely the classical notion of a jet stream, with a well-defined core at 390 rob, strong cycloniC shear on its poleward side, and a region below the core with high stability and strong wind shear corresponding to an upper tropospheric front (or tropopause fold). Such a region is shown more clearly on the second cross-section, where more data were gathered at lower levels. However, the strongest winds on this flight were encountered at the highest level, and the shape of the isotachs is very different to those of fig. 3. The wind shear, both horizontal (at 390 rob) and vertical (467-508 rob), is significantly greater on this flight. Mathematical models of frontogenesis (Hoskins 1.982)

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suggest that the intensification of wind shear beneath a developing jet stream system continues until limited by clear-air turbulence (CAT) when the Richardson nwnber, Ri, falls to 0.25. It is interesting to note that although such values of Ri may be derived from fig. 4 in the strong vertical wind shear zone between 467 and 508 mb the aircraft did not experience CAT while traversing this region, but encountered moderate turbulence near the small secondary wind maximum at 508 mb (associated with a thundery trough behind the main surface cold front). Ozone and Potential Vorticity

The ozone record from both flights may be summarised briefly as showing constant values of 30-40 ppbv where the isentropic wind shear was anticyclonic and enormous variability where it was cyclonic. A doubling of the ozone concentration in 25 km was a common occurrence on the north side of the jet, and because of the lack of any obvious coherence between measurements at different levels the ozone records are presented as traces on figures 5 and 6, so that the nature of the variability is immediately apparent.

Shapiro (l980) has reported a dominant length scale of about 20 km in the ozone variability on the north side of the jet, and the data from our flights confirm this observation. However, a smaller length scale, of about 10 km, was characteristic of the ozone record at 467 mb on the second flight in the 'tropopause fold' region. It is difficult to see how the ubiquitous nature of the ozone variability, and especially its presence at 300 and 329 mb, can be reconciled with the view that irreversible exchange of air between stratosphere and troposphere is confined to tropopause folds beneath the jet core. Rather, the data suggest that significant mixing may occur in the entire region of strong cyclonic shear.

However, this region is also characterised by very high values of potential vorticity - a quantity which, by Ertel's theorem, should be conserved for air parcels in isentropic flow such as pertains near the tropopause (Danielsen 1968). Indeed, according to Danielsen, both potential vortiCity and ozone are created in the stratosphere and destroyed near the ground, implying that both may be used as tracers of stratospheric air in diagnostic studies such as this. We must therefore attempt to reconcile the great variability in ozone (suggesting a region of mixing) with apparently large values of potential vorticity.

Because of the large difference in typical length scales of the flow along and perpendicular to the jet direction, the potential vorticity may be expressed (Shapiro 1978) as

Q = - (-iNe/an + VeiR + f)a9/8p The absolute vorticity contribution to Q may be estimated fairly accurately, since the aircraft measures aVe/an directly, but 89/ap must be derived from charts such as figs. 3 and 4. Most of the uncertainty in estimating Q is therefore asSOCiated with 89/8p. Because of this, the resolution with Which Q may be estimated is strictly limited, but the gross features of its distribution can be depicted. Potential vorticity traces for the second flight are qompared with the ozone data in fig. 5. Some features are seen to correlate well - the regions of anticyclonic shear, for instance, show low ozone and low Q, implying that transfer of air directly across the jet core from stratosphere to troposphere does not take place.

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However, a number of puzzling anomalies are also present - exemplified by the result at 508 mb. The concentration of potential isotherms just beneath the jet core results in an unmistakeable increase in potential vorticity, but the ozone sensor persistently shows normal tropospheric concentrations of ozone. Elsewhere, also, the correlation appears incomplete - a region of very high stability just above the core on the first flight for instance, contained unremarkable ozone concentrations (fig 6). We must therefore conclude that these data do not support the strict association of 03 and Q. Turbulent mixing has been proposed by Shapiro (l976) as a mechanism which can modify Q independently of ozone, and this mechanism coul.d also, of course, promote the mixing of stratospheric and tropospheric air. It is not clear, however, how the confinement of most of the ozone variability to length scales greater than about lO km is consistent with the conventional notion of turbulence - the ozone sensor was capable of detecting variability at scales as smal.l as 2 km, but very little was observed. Turbulent fluxes

Kennedy and Shapiro (1975, 1980) and Shapiro (1980) describe the evolution of tropopause folds by calculating vertical fluxes of ozone, heat and momentum by the covariance method. Such a method can also be used with our data to calculate horizontal fluxes (because of the unreliability of vertical velocity measurements no vertical fluxes will be presented). The data were divided into 5-minute segments (48 km) and a mean wind direction for each segment chosen so that the average transverse wind velocity component, v1 was zero. Transverse ozone fluxes wererfhen calculated from

Foz = (lIT) jo net) V1(t)dt

where n( t) is the ozone number density and T the 5-minute period. The results revealed fairly small ozone fluxes, even on the

northern side of the jet core, where the ozone variability was greatest. The largest values observed were about 3 x 1017m- 2s-1, corresponding to a 'time scale of about 2 days for significant change to the ozone concentration. Of more interest are the signs of the eddy fluxes. These showed no preferential direction - pointing as often from north to south as from south to north - and, even more significantly, appeared to bear absolutely no relation to the sign or magnitude of the mean ozone gradient in the 5-min period. This remained true even when the flux calcu1ation was restricted to the smallest scales (<15km). These results show that horizontal fluxes near jet streams cannot be parameterised by means of eddy diffusion coefficients such as Kennedy and Shapiro derived for vertical fluxes. They also reinforce the hypothesis that some ordered motion, rather than passive turbulence, is responsible for redistributing the ozone concentrations. Wind Directions

A possible clue to the nature of these motions may be derived from the detailed record of wind direction, wind speed and ozone along a flight leg, as shown in fig. 6 for the 343 rob leg of the first flight. If the same assumption is adopted as for the potential vorticity calculations - that variation transverse to the jet direction greatly exceeds that along it - veering of the wind (increase in angle) towards the south-east implies divergent flow and

-575 -

backing (decrease in angle) implies convergent flow. Such an assumption was shown by Shapiro and Kennedy (1981) to be invalid for a sharp1y curved jet exit region, but the effects of curvature are much 1ess in this case and the synoptic data do suggest - &v/8S ~0.2 avl8n, where s and n are natura1 co-ordinates. The greatest changes in wind direction were seen on the first f1ight, especia11y at the two highest levels, with a distinctive minimum in direction angle being seen on all four legs. These minima were aligned much more closely in the vertical than the wind maxima, and offer an explanation for the differently shaped jet streams shown in figs. 3 and 4.

Neglecting the small curvature of the streamlines, the ageostrophic wind component may be written as

vA = 1/f kXdv/dt = 1/f dV/dt n in natura1 co-Ordlnates. The divergence of the geostrophic wind is negligibly small, so

divergence v.~ = V,VA = (1/f)8/8n(dv/dt) - = (1/f)8/8n(vav/8s)

The variation in wind direction is therefore caused by differential acceleration of the flow, and indeed fig. 6 is entirely conSistent with the position of the flight at the jet entrance (Fig. 1). Furthermore, maximum acceleration corresponds to the minima in direction angle (V. V=O) • Downstream of the entrance region, therefore, the maxtroum wind would be expected to align more closely in the vertical at different levels - as was observed on the second flight. The greater changes in angle at 343 and 300 mb are also consistent with the upward displacement of the jet core on the second flight.

From Fig. 6 it is clear that two wind maxima were observed at 343 mb on the first flight, with a small region of anticycloniC shear between them. The ozone variability, however, extends across this region, and steady tropospheric concentrations are only encountered on the southern side of the smaller jet. It should be noted that the most prominent peaks in the ozone record coincide with both cyclonic shear and confluence of the flow - a phenomenon also observed at other levels. The maximum in potential vorticity seen from 2124 to 2128 on this leg corresponds quite clearly with diffluent flow, but, as mentioned earlier, there is no corresponding ozone peak.

Further study is clearly needed to grasp the imp1ications of the link between confluence and ozone indicated by these data. The effect of multiple jet cores and their development on the redistribution of ozone is but hinted at here, but the distribution of acceleration certainly suggests that flow originally on the cyc10nic side of the core might, through differential acceleration, be transferred to the anticycloniC side. Caution is advised in accepting such a hypotheSiS, however, both because of the apparent need to destroy potential vorticity in such a process and because of the uniform tropospheric ozone concentrations observed on the anticyclonic side of the secondary jet core in fig. 6 (and indeed on all other levels).

References Briggs J. & Roach W.T. (1963) Aircraft observations near jet streams.

Quart J. Roy. Met. Soc. 89, 225-247. Danielsen E. F. (1968) stratospheric-tropospheric exchange based on

radioactivity, ozone and potential vortiCity. J. Atmos. Sci. 25 502-518.

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Hoskins B. J. (1982) The mathematical theory of frontogenesis. Ann. Rev. Fluid Mech. 14 131-151.

Kennedy P.J. and Shapiro M.A. (l.975) The energy budget in a clear air turbulence zone as observed by aircraft. Mon. Wea. Rev. 103 650-654. (1980) Further encounters with clear air turbulence in research aircraft. J. Atmos. Sci. 37 986-993.

Lyne W.H., Little C.T., Dumel.owR.K., and Bell. R.S. (l.983) The operational. data assimilation scheme. Met 0 l.l. technical. note No 168, Meteorological. Office, London Road, Brackne1l., Berkshire, U.K.

Nicholls S. (1978) Measurements of turbulence by an instnnnented aircraft in a convective atmospheric boundary layer over the sea. Quart. J. ROy. Met. Soc. 104 653-676.

Shapiro M.A. (1974) A mul.tipl.e-structured frontal. zone jet stream system as reveal.ed by meteorological.ly instnnnented aircraft. Mon. Wea. Rev. 102 244-253. (1976) The role of turbulent heat flux in the generation of potential vorticity in the vicinity of upper level jet stream systems. Mon. Wea. Rev. 104 892-906. (1978) Further evidence Of the mesoscal.e and turbul.ent structure of upper level. jet stream-frontal zone systems. Mon. Wea. Rev. l.06 l.l.00-1l.l.1.. ( 1980) Turbulent mixing wi thin tropopause folds as a mechanism for the exchange of chemical constituents between the stratosphere and troposphere. J. Atmos. Sci. 37 994-1004.

Shapiro M.A. and Kennedy P.J. (1981) Research aircraft measurements of jet stream geostrophic and ageostrophic winds. J. Atmos. Sci. 38 2642-2652.

Fig. 1 Isopleths of Montgomery stream function on the 310 K potential temperature surface at 00 GMT, 16 April 1983. Values are multiples of 100 m2 s-2 in excess of 3 x 105 m2 s-2. Thick lines mark the track of the first flight.

Fig. 2 As for Fig. 1 but at 18 GMT, 16 April 1983, corresponding to the second flight.

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)0

". , .. , .. ... 10 • lOG .. FIG. 3

htstrta" UUBtcbOl , I. JlS td I. 1100 C.IT , II April "n, u n . .. a ,,'11. "foci.,.f 20 .. ", ", ~ I

--. '\ - -'- I ... "

' - - \/ 1 .Y 1 .: 31~

0, 100

0

] ppbw

m

113 :;; ~

~ : i

<II

SOI ---

FIG. 4

-578 -

319

-<::.

~ 393

C :n .s. .. ~ ~7 ! ....

508

570 140 km

[100 ppbv 03

0---------------------------...

O----~~--_-_--#~~----------~--------------------~ ... ~'~--, "

b a • 1~

o----------------#~,~-~--... -,--#-#~-~-~----------------...

o:--::::::#:-::-:-::"':-::':'::::::::::::==::::::::::="'~:;:;~':'::::

Distance transverse to jet

Fig. 5 Grone (continuous line) and potential vorticity (dashed line) for the second flight. The five horizontal straight lines represent the zero for ozone and potential vorticity at each flight level.

m

228

220

-'.

," . " . .. ' \ ....... ,'~". .. ... .." ...

0 20 40 , , ,

2100

60 ,

POlential votlicity mo)(imum 1<----01

.'. \ .. : ~ .. ,,~

...... _.~ 4- "

.... :. ,,: .. '::, " , .y':

.. :-':",.: ~ ':.:'

80 100 'm , , , .: ; .. , ,

2110 2120 2130 Tim. (GMT)

280

"> 240 60

~ " , a. .s.

'.0200 '~" .... " 50

m . ~ 160 40T' 'e i co C "U

2 120 30 .,

0 ~ ,':, "U

c ..... ~ "'''80 20~

40 10

2140 2150 0

Fig. 6 Simultaneous records of ozone (continuous line!, wind speed (dashed line) and lOs means for wind direction for the 343 mb leg of the first flight.

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WAVENLMBER SPECTRA OF OZONE FRO~1 GASP AIRCRAFT MEASUREMENTS

G.D. Nastroml, K.S. Gage 2 , and W.H. Jasperson l

IControl Data Corporation, Minneapolis, MN 55440 USA

2 Aeronomy Laboratory, NOAA, Boulder, CO 80303 USA

Results from spectral analysis of ozone, wind, and temperature measurements collected during the Global Atmospheric Sampling Program (GASP) are presented. These data were taken with instruments pl aced aboard B747 airliners in routine conmercial service. About 90 percent of these data fall in the altitude range 9-13 km and about 75 percent are from latitudes 30 to 60 degrees North. The variance power spectra span the wavelength range from about 10°-10' km for wind and temperature and 10-2400 ,km for ozone. Va ri ati on with 1 ati tude and season and between the troposphere and stratosphere are presented. Results are interpreted in the framework of geostrophic turbulence theory at long wavelengths, and quasi-two-dimensional turbulence and internal gravity waves at wavelengths below about 300-500 km. Numerical examples are used to ill ustrate that the spectrum of ozone vari ati ons is consi stent with a spec trum of verti ca 1 di spl acements acti ng on a background verti ca 1 gradient of ozone.

1. Introducti on

The connection between time and space variations of ozone and other trace constituents and the atmospheric circulation is well documented. Numerous studies have shown relationships between wind patterns and short peri od fl uctuati ons of" su rface ozone or tota 1 ozone measured from the surface. Historically, most information regarding in situ variations of ozone in the remote atmosphere has come from Umkehr data or ozonesonde flights at a handful of stations over the globe (Dutsch, 19b3). With the advent of satell ite based ozone sounders, thi s situation has greatly improved, but the satellite data are only for broad layers in the hori zonta 1 or verti cal and a need for detai 1 ed in si tu measurements sti 11 exists. In this paper we consider a new aspect of ozone variability by using statistical results from spectral analysis of a large data set of atmospheri c trace consti tuent, wi nd, and temperature measurements collected in the Global Atmospheric Sampling Program (GASP). This paper extends the results given in Nastrom and Gage (1984) by including the analyses of ozone.

2. Data

The observati onal phase of GASP was conducted in 1975-1979. Instruments were placed aboard up to four B747 aircraft in routine

Ozone Symposium - Greece 1984 - 580-

convnercial service to obtain information on trace constituents and meteorol ogi ca 1 vari abl e s. Detail ed de scri pti ons of the GASP systems are given by Papathakos and Briehl (1981) and references therein; all data collected in GASP are available from the National Climatic Center, Asheville. Data were recorded on tape at all times during flight above 6 km (19000 feet). Aircraft location, wind, and temperature data were taken from the onboard computer system. Ozone was measured with commercially available ultraviolet absorption photometers modified to operate in an airborne environment. The instrument's dynamic range is from 3 to 20000 ppbv (parts per billion by wlume), and its random error is the greater of 4 percent of the readi ng or 3 ppb v. All instruments were calibrated in the laboratory initially; thereafter, data integrity was assured by in-flight calibration checks and by periodic maintenance.

Readings of the ozone instrument were updated each 20 seconds, and on a few selected flights they were recorded at this rate. On most flights, however, data were recorded at five-minute intervals with each fourth observation missing because the instrument was in a calibration cycle.

Upon reachi ng cruise altitude, aircraft tend to fly along a constant pressure surface for several hours, then cl imbing about 0.6 km (2000 feet) after sufficient fuel is burned off. Long fl i ghts are thus typically comprised of 2 to 4 constant altitude segments. To awid discontinuities due to vertical gradients of atmospheric variables, we have analyzed the ozone data in segments: if the flight altitude changed more than 0.3 km, or if the tropopause (i nterpol ated in space and time from NMC grids to each GASP data location) was crossed, a new segment was started. 'Data were linearly interpolated to evenly spaced points along the fl i ght track, and a Fa st Fouri er Transform was appl i ed to the interpolated data. The sums of the squares of the Fourier coefficients at each wavelength were averaged over many segments, and the results are plotted in the figures presented below.

3. Results

3.1 Wind and Temperature Spectra

Fi gure 1 shows the a verage spectra of wi nd and temperature 0 ver the wavelength range 2.6 - 10~ km. The results from flight segments of three different lengths have been melded to form this overall picture, and the three different symbols along the spectra illustrate the high degree of continuity among the three sections. As discussed in Nastrom and Gage (1984), there is remarkably little dependence of spectral amplitude upon season or latitude or, for wind, across the tropopause. Spectral ampl itudes of temperature are about a factor of three hi gher in the stra tosphere than in the troposphere, pre sumably because the 1 arger static stability in the stratosphere induces larger temperature changes for similar vertical displacements of air parcels and, because all GASP data are from 1 evel s near the tropopause (80% of all data fall between about 9 and 13km) kinematic displacements are of the same approximate size on both sides of the tropopause.

The shape of the spectra shows very small change with respect to time and place. At wavelengths between about 1000 - 3000 km the slope is near -3, in agreement with past stUdies based on rawinsonde data. Following Charney (1971), the -3 region is considered to arise from a downscale cascade of enstrophy. At wavelengths shorter than 500 km or so the slope very nearly matches the -5/3 line. This region could arise from an upscale cascade of energy in quasi-two-dimensional turbulence, or

- 581 -

it cou1 d ref1 ect a spectrum of internal gra vi ty wa ves, or perhaps a combination of processes. These remain open questions at this time.

3.2 Ozone Spectra

Spectra of ozone o'ler the wa'le1ength range 10-2400 km for flight segments in the troposphere and stratosphere are shown in Figure 2. The number of flight segments used for each section of the spectra is given on the figure. The long wa\e1ength portions of the spectra are shown for all wa \e1 engths from 150-2400 km; howe ver. for wa vel engths 1 ess than 300 km, they shou1 d be regarded with cauti on as the gaps in the data during calibration cycles may lead to reduced spectral fidelity. In Figure 2, the stratospheric spectrum appears to follow a -5/3 slope over most of its range. The tropospheric spectra have a slope near -1 for wa \e1engths less than about 100 km, and then approximately follow a -5/3 slope at longer wa'le1engths. The spectral amplitude at all wa\e1engths is o'ler ten times larger in the stratosphere than in the troposphere, resulting from air parcel displacements against the large vertical gradient of background ozone values, as discussed in detail 1 ater.

The spectra plotted in Figure 2 are mean values over several hundred flight segments. Spectral amplitudes of individual flights at a gi\en wa\e1ength are distributed log-normally as illustrated in Figure 3. Nastrom and Gage (1984) found that wind and temperature spectra also ha'le log-normal distributions. Part of this variability can be attributed to variations with latitude and season as summarized in Table 1. For examp1 e. stratospheri c mean amp1 itudes at 30-60 N are about fi ve times larger during winter than during autumn. Also, tropospheric values are four or five times larger north of 15 N than at tropical latitudes.

4. Di scussi on

The fluctuations of ozone and other passi'le additives sampled by the aircraft are due primarily to vertical displacements acting on the 'lertica1 gradient of the passi'le additive. The vertical displacements can be caused by internal gra vity wa \eS or by quasi -two-dimensional turbu1 enc e.

The spectrum ~xx of a passive additive x such as ozone is related to the spectrum of vertic~l di splacement ~~f,; and the 'lertica1 gradient axlaz by

~ = aY ~ xx az f,;~

where x is a conservative quantity such as mlxlng ratio and f,; is vertical displacement. This relationship can easily be tested if the vertical gradient axlaz is well known as well as ~ and ~xx. Here, we shall concern ourse1 \eS wi th the consi stency of Ue ozone spec tra wi th thi s relationship.

In the atmosphere, the displacement spectrum ~S.-~ is not directly measured but can be inferred from the potential temperature spectrum. Si nce

it follows

~ ee

~ee

- 582-

where N Z =i ~ spectrum

It is con~nient to introduce the potential energy

N2 =~ $ = 2 $;; $ee P.E. 2N2e2 It is shown in Nastrom and Gage (1984) that the potential energy spectrum has the same shape as the horizontal kinetic energy spectrum and is about half its magnitude. The potential energy spectrum is about the same magnitude in the troposphere and stratosphere, so the amplitude of the di2sp1 acemen":.~ ~~ectrum is 1 ess in the stratosphere (where N 'V 4 x 10 s ) than in the troposphere (where N2 'V 1O-~ S-2).

The shape of the ozone spectrum shou1 d be the same as the shape of the di sp1 acement spectrum. Consequently, in what foll ows we shall calculate $xx at only one wa~length (400 km). In order to make the calculation, we must use climatological values for ax/az since we ha~ no ozone gradi ent data at the time of the fli ghts. We take our climatological gradients from Dutsch (1978) and Roe (1981). Since climatological values are smoothed considerably, we anticipate our calculated values will be on the low side of the obserwd spectral amplitude. Consider the stratosphere first. Using the analysis of NastrollA ,\nd Gage (1984), we estimate $n: at 400 km waw1ength is 4 x 10 -llJ Irad. In the lower stratosphere, we take ax/az to be .4x 10 \lg/g/m. This leads to an estimate of 64x 10 6 (PPBV)2 m/ rad. Comparison with Table 1 and Figure 2 shows that this value is about a factor of 2 lower than the obser-.ed values.

In the troposphere, ozone mixing ratios are much lower and ozone gradients· are small and variable. At 400 km wa-.elength, we estimate the di spl acement spectrum has an ampl itude of 2 x 109 mS Irad. A typical ozone gradi e nt in the upper tropo sphere is. 03 x 10- 3 Ilg/g/m. These val ues 1 ead to an estimate of 1. 8 x 10 6 (PPBV) 2 m/rad for $. Thi s value is also about a factor of 210wer than the values gi-.en in Table 1.

Table 1. Mean spectral amplitudes of ozone at 400 Km wa~length as a function of season and latitude. Units: 106 (ppbv)2 m/radian.

TroEosEhere StratosEhere mean N mean N

A. Season (winter = D,J,F)

Spring (at 45-60 N) 2.0 5 172 82 Summer 1 138 65 Autumn 5.2 13 66 72 Winter 9.7 5 368 69

Spri ng (at 30-45 N) 5.1 31 164 43 SUlll11er 5.8 56 110 14 Autumn 3.2 57 29 5 Wi nter 3.6 31 137 43

B. LatitUde

15S to 0 1.4 62 0 0 to 15N 1.2 42 0

15 to 30N 4.0 220 64 13 30 to 45N 4.4 175 139 105 40 to 60N 6.0 24 185 288

- 583-

Wavenumber (radians m I) 10' 10 I 10'

H)· ····

".. .. 10'1 1 i!-

1~~ u; c

" .:. ~ u 8. VJ 10'

10U.-

10'

10' 10' 10' 10' 10'

Wavelength (km)

E I ~ s-<Il a. !!:. >-f-iii z w 0 ...J « a: f-e.> w a. (J)

10 ' 10 '

k -5I'J

~TRATOSPHERE

\ '\

Fig.l. Variance power spectra of wind a~d temp­erature. Meridional wind (temoerature) is shifted one (two) decade(s) to the right.

f/) w (J) « t)

u. 0 a: w aJ ::;: ::> z

WAVELENGTH (KM)

Fig.2. Variance power spectra of ozone . .-----'1----.-1 --'1----.-1 --'1----'

• TROPOSPHERE

\ f'x • STRATOSPHERE

/. I 'x -

/ /~\/ \ /1 /' \

./ I /i'->t->C I \,. I Xi\.

60 -

40 r-

2O f-

0

-

-

5 6 8 9

Fi g. 3. LOG SPECTRAL POWER OF OZONE AT 400 KM WAVELENGTH

References

Charney, J.b •• 19n: Geostrophic turbulence. J. Atmos. SCi., 28, 1087-1095. Dutsch, H.U., 1983: Ozone variability. Planet. Spa. SCi., 31, 1053-1064. Dutsch, H.U .. 1978: Vertical Ozone distribution on a global scale. PAGEOPH, 115, 511-529. Nastrom. G.D., and K.S. Gage, 1984: A climatology of atmospheric waloenumber spectra of wind

and temperature obseryed by commercial aircraft. J. Atmos. Sci., submitted. Papathakos., L.C. and D. Briehl, 1981: NASA Global Atmospheric sampling Program data report

for tape VLOO15-VL0020, NASA 1M 81661, 94 pp. Roe. J.M., 1981: A climatology of a newly-defined tropopause using simultaneous

ozone-temperature profiles. AFGL-lR-81-0190, 104 pp.

- 584-

MEASURES OF STRATOSPHERIC DISPLACEMENTS FROM SATELLITE DATA

S. MULLER, F.R. CAYLA and J.P. JULLIER

Etablissement d'Etudes et de Recherches Meteorologiques Centre National de Recherches Meteorologiques

42, Avenue Gustave Coriolis 31057 TOULOUSE CEDE X - FRANCE

Abstract

Ozone transmittance at 9.6 ~m is retrieved from IR radiances measured by TOVS (Tiros Operational Vertical Sounder) on NOAA satellites, using the radiative transfer equation

Where B

~~ 'Te

R9= B(TS) x TR + (l-TR) x B(Te)

is the Planck Function the radiance measured at 9.6 ~m - ozone absorption band the surface temperature measured at 11 ~m - window is the ozone layer mean temperature deduced by regression procedure using R9 and a few others.

Ozone transmittance is used as a predictor of total ozone, which is considered as a tracer in the lower stratosphere. If we track the irregularities (e.g. ozone max.) from map to map (there are 4 maps a day), we measure the displacements and winds in the stratosphere. Those "satellite stratospheric winds" have been compared to wind analysis from the ECMWF at levels from 250 to 30 mb. For each "satellite wind", a level of best fit has been determined, the histogram of which presents a narrow pick around 100 mb. Conside­r ing analysed winds at 100 mb and "satellite winds", we found a coef­ficient of correlation of .86 ; the RMS of the difference wind is 6.6 ms- l as the mean value of the wind is 12rrs- l , Consequently, it is possible to get from ozone maps a large number of reliable "100 mb satellite winds". It would be interesting to intro­duce them as complementary measurements in 100 mb analysi$, especially above the oceans and the Southern Hemisphere which are lacking in conventionnal measurements.

1. : Introduction

A physical method of total ozone retrieval from I.R. satellite radian­ces has been tested during a former "Ozone Measurements Intercomparison Campaign" (June 1981 - Observatoire de Haute Provence). We have obtained total ozone maps, the comparison of which with ground based measurements has given a standard error less than 5% for the considered data set, see (Muller and Cayla, 1983). The study of the maps has shown general structures and local irregularities of the ozone field, that can be followed from map to map (2 maps a day for each satellite). This paper intends to study these displacements and their correlation with stratospheric winds.

Ozone Symposium - Greece 1984 - 585-

2. Summary of the physical method

Ozone transmittance at 9.6 ~m is used as a predictor of total ozone. It is deduced from radiative transfer equation

where B

~~ Te

R9 = B(TS) TR + (1-TR)B(Te)

is the Planck Function the radiance measured at 9.6 ~m. ozone absorption band the surface temperature measured at 11 ~m. window the ozone layer mean temperature deduced by regression procedure using R9 and a few others.

For full details about the method, see (Muller and Cayla, 1983).

3. Measurements of satellite winds

Satellite date have been collected twice a day for NOAA7 and NOAAB over Europ during September, 1983 (MAP GLOBUS campaign). Data have been processed using the above method to obtain total ozone content of the ver­tical column above each spot (4 maps x 30 days). On these maps, we can follow. 1) large scaled structures (up to 2000 km large) for a few days, but they are few. 2) Small maxima (down to 100 km large) which have a shor­ter life time, but still longer than the 6 hours interval of our measure­ments (as the evolution speed may be+2~u per hour, a maximum of + 40 Du may disappear in one day). 3) Small IDlnima. They have been discarded be­cause they may be due to partial tropospheric cloudiness. We have gathered a set of 488 satellite winds.

4. Comparison with wind analysis from ECMWF

We assume that all satellite winds (Wsat) are related to the dynamics of the same range of altitude. In order to determine this range we first interpolate, at time and location of satellite measurement, the wind pro­file (250 to 30 mb) from analysed fields ; we then interpolate inside this profile to find the level (p) that minimise the difference (W(p) - Wsat) , that is the level of best fit (pbf). The histogramm of levels of best fit shows a pick around 100 mb (Fig. 1) (PDf = mean of pbf ; ~pbf = standard deviation of pbf).

I I ,

I

,'+

.: I

I I

I

t

\ , \ \ ,

\ , t\~

\ \ \

\ \ '\

-t, i '~ ...... ~

pTI . II~ ~b IF' p~F: 5~ '"

o ... 1... a- p~F ( .... 1.)

Fi,. I Kid.~rtl!WI ri lecls .t"!oed fit

- 586-

The root mean square difference between the analysed wind at level of best fit and satellite wind is less than 4ms- l .

Since under operationnal conditions, we cannot find the level of best fit, we have to attribute every satellite wind to the same mean level (100 mb). The correlation and RMS difference between satellite wind and analysed winds at level 150, 100, and 50 mb are listed below.

Number of winds 488 level p (mb) correlation

-1 RMS difference (ms) -1 mean of analysed wind (ms_ l ) mean of satellite wind(ms )

150 .81 9 17 13

100 .81

6.6 12 13

50 .69

8.4 8 13

There is no systematic error in direction. The relation between satellite winds and 100 mb analyses is plotted on Fig.2.

f:~ 2. .

~ ... hdli tc. Wi".,js

.. ~ ... ; ... ~t

a. ..... r.,\r.l wi .. cI~

4U ..... < en I-

35 >

VT100

The RMS difference at 100 mb is nearly half the error reported for high winds (200 mb) obtained from geostationnary satellites (Linwood, 1983).

This good correlation between the displacements of the total ozone fluctuations and 100 mb winds was to be expected, as these fluctuations are associated to modification of the ozone profile around 100 mb (Mateer et aI, 1980).

5. Conclusion

Although the ozone maps retrieved by our physical method are not per­fect, the relative determination of ozone is reliable enough to let us track a few big structures and a lot of (even short lasting) small irregu­larities. The quality of these satellite winds is likely to be sufficient to introduce such a sort of measurements, as complementary data, in the 100 mb analysis, specially above the oceans and the Southern Hemisphere.

- 587-

Acknowledgement

The supply of satellite Data by the "Centre de Meteorologie Spatiale" Lannion - France is hereby gratefully acknowledged.

This work has been partially funded by CNES under "Aide d'Incitation a la Recherche" N°83/CNESj252

REFERENCES

1. LINWOOD, F. and WHITNEY, Jr. (1983). International Comparison of Satel­lite Winds - an update. Adv. Space Res. Vol 2, N°6 pp 73-77

2. MULLER, S. and CAYLA, F.R. (1983). Total Ozone Measurements derived from T.O.V.S. Radiances. Planet. Space Sci. 31, 811.

3. MATEER, C.L., J.J. DELUISI and C.C. PORCO, 1980. The Short Umkehr Method. Part I : Standard Ozone profiles for use in the estimation of ozone profiles by the inversion of short Umkehr observations. NOAA Tech. Mems. ERL ARL.86, 20 pp.

- 588-

VARIATIONS OF RADIATIVE HEATING/COOLING IN THE STRATOSPHERE AS REVEALED BY SATELLITE OBSERVATIONS

P.-H. WANG and A. DEEPAK Institute for Atmospheric Optics and Remote Sensing (IFAORS), Hampton, VA

and

A. GHAZI Commission of the European Communities, Brussels, Belgium

Summary

Ozone observations made by Stratospheric Aerosol and Gas Experiment (SAGE) and meteorological temperature data are used to study the coup­ling of radiation and dynamics in the stratosphere. Both radiative heating and cooling rates are calculated using the observations as a function of altitude, longitude, latitude, and season. Fourier analysis of heating/cooling rates is performed to gain an understanding of the radiauion-planetary wave interactions. High correlation is seen to exist between solar heating and the temperature distribution of the upper stratosphere. Radiative damping coefficients are derived and it is found that the coupling between ozone and temperature can produce significant variations in the damping rate which, in turn, critically depends on the vertical structure of the planetary waves.

1. Introduction The sensitivity of the stratosphere to the coupling of radiation,

photochemistry and dynamics is unique. In particular, the distributions of ozone, temperature, and motions are determined by the strong interaction of these mechanisms in this region of the atmosphere [see e.g., (1)]. Satellite observations of ozone (SAGE) and the temperature data provided by NOAA's National Meteorological Center are used here to investigate stratospheric heating and cooling and their interactive behavior associated with planetary waves in influencing the radiative-dynamical properties of the stratosphere. Ghazi et al. (2) have shown a strong negative correlation between variations in the temperature and ozone heating in the stratosphere by using satellite observations in the southern hemisphere for the period of October 16-20, 1970. This correlation between temperature and ozone was shown to almost double the rate of radiative damping of temperature perturbations in the upper stratosphere from that due to infrared radiation alone. Since such strong damping is important for the structure of vertically propagating planetary waves and the zonal mean circulation in the stratosphere, it is worthwhile to extend the investigations to the northern hemisphere where the planetary wave activity is known to be intense during the winter.

2. Computational Procedure and Data Description The model of radiative transfer described in Ramanathan (3) is adapted

for computing heating/cooling rates. The one-dimensional model accounts for surface and cloud reflections and the Rayleigh scattering effects. In

Ozone Symposium - Greece 1984 - 589-

addition, the exchange of infrared radiation between the level under con­sideration and the layers below is also included. The albedos of Rayleigh scattering and cloud are a function of solar zenith angle. The mean solar zenith angle and fractional length of daytime are determined by the approxi­mation of Cogley and Borucki (4). The model, which extends from the ground to about 55 km in altitude, includes the contribution due to C02' H20 and 03 and accounts for Doppler-broadening effects for CO2 and 03" The model utilizes the SAGE ozone density profiles at 11 pressure levels between 50 -0.5 mb. Below 50 mb, we have used the ozone values from the vertical ozone distribution given in (5). McCormick et al. (6) have described the SAGE observations in detail. The corresponding meteorological information at SAGE sampling locations, including temperature and geopotential height, is provided by NOAA's National Meteorological Center (7). For the calculations, C02 and H20 are assumed to be uniformly distributed with concentrations of 320 ppmv and 3 ppmm, respectively. A cloud top altitude of 6 km and a frac­tional cloud cover of 0.45 are used.

3. Results a. Distributions of radiative heating/cooling. Figs. la, band 2a, b

show the zonally averaged distributions of calculated heating/cooling rates ( K/day) as a function of altitude (50 - 0.5 mb) for the periods of Northern Hemisphere winter and spring seasons, respectively. The ozone data from SAGE and the temperature observations were available for the seven winter (December, January, February) and nine spring months ( March, April, May ), of the years 1979-1981. Thus, Figs. la, band 2a, b represent the

general pattern of radiative heating/cooling based upon more than 3000 individual ozone vertical profiles and the corresponding temperature measure­ments. The significant features of Fig. la are the low values of solar heating during the winter in the Northern Hemisphere and an increase of heating toward the summer Hemisphere reaching a maximum of about 14 K/day at the stratopause above 70 0 S. During the Northern Hemisphere springtime (Fig. 2a), there is a symmetrical increase of heating from the middle to the upper stratosphere in both hemispheres with a maximum of about 12 K/day centered at lOON at 1 mb level.

Fig. Ib depicts the pattern of calculated radiative cooling due to C02' 03 and H20 during the northern winter. Cooling rates of less than 1 K/day persist below about 30 mb from 40 0 S to 60 0 N. In the upper stratosphere, there is an increase in radiative cooling from the winter to summer hemi­sphere with a maximum of 9 K/day at the summer stratopause associated with high temperatures (-270 K) in that region. Radiative energy sink (cooling) of equal magnitude (9 K/day occurs at the equatorial stratopause during the northern spring season (Fig. 2b). An interesting feature of Fig. 2b is a secondary maximum of cooling (-7 K/day) in the upper stratosphere of the sub-polar latitudes of the Northern Hemisphere associated with a temperature maximum (-260 K) in that region. The corresponding ozone and temperature distributions are not shown here for the sake of brevity.

b. Radiative Damping. Figure 3 shows the longitudinal variation of solar heating mainly due to 03 absorption at 2 mb level and 55°N on February 25, 1979, as compared to the temperature variations. This strong negative correlation between 03 heating and the temperature implies that the perturbations in heating would tend to damp the temperature perturbations. following Ghazi et al. (2), the magnitude of this damping is estimated by assuming that the rate of longitudinal temperature change in the strato­sphere is given by:

dT'/dt = Pw + Q~ + Q~R (1)

when T' is the perturbation temperature (departure from zonal mean), Pw is

-590-

the source term for temperature change (planetary wave), Q': perturbation radiative heating (or cooling) with subscripts Sand IR denoting solar and infrared terms. We can write approximately:

-a T'

Q~ -b T'

The factors a and b were calculated by the relations:

a = - Q'T'/T,2 IR

b _Q'T'I T,2 S

(2)

(3)

for different levels of the stratosphere. Equation 3 is obtained by multi­plying both sides of Eq. (2) by T' and then averaging over longitudes (over­bar indicates this average over latitude). In applying Eq. 3, T', Q', and QIR have been Fourier decomposed in order to see the contribution du~ to each of the harmonic components. In this analysis, only the long waves (wavenumber one and two) are considered.

Table 1 shows the values of a and b for wavenumber 1 and 2 obtained by Eq. 3 by inserting the calculated values of QS (e.g., see Fig. 3) and Q'IR and of T' for 3 selected days of large temperature and ozone heating per­turbations in the Northern and Southern Hemispheres at about 55° latitude. There are 15 measured SAGE ozone profile and corresponding temperature observations used for calculations of each of these daily cases.

In general, in the upper stratosphere a comparison of a and b values shows that the rate of radiative damping of temperature perturbations is enhanced by the perturbations in ozone heating assocatied with the waves. This result confirms the earlier study (2). Secondly, the maximum values of a and b are seen to be located at 2 and 1 mb, respectively. In addition, the effective radiative damping is overall reduced below 5 mb level, due to the change of sign of b coefficient.

Table 1 also allows a comparison of the damping rates in the Northern or Southern Hemisphere during the corresponding seasons. As can be seen, the general behavior of a and b are similar in both hemispheres.

c. Vertical structure of 03' T', and QS' Figure 4 shows the calculated amplitude (K/day) of wavenumber 1 and 2 of QS on Feb.25, 1979 (a);Feb. 15, 1981 (b); and sept. 8, 1979 (c); at latitudes 55°N, 53°N, and 54°S, respec­tively. In general, the maximum of QS takes place at 1 mb. Below about 3 mb, the amplitude is approximately one order of magnitude smaller than that at 1 mb. The corresponding ozone and temperature amplitudes are not shown here for the sake of brevity. Figure 5 displays the phase profiles of 03' T' and QS for the above mentioned three daily cases. The distinct features are the approximately out-of-phase relationship between the ozone and temperature waves in the upper stratosphere, and the nearly in-phase relationship in the low stratosphere. The phase relationship between QS and 03 is of particular interest. They show generally an in-phase relation­ship above 1 mb and below 10 mb. The departure from the in-phase relation­ship between approximately 1 and 10 mb can be due to the so-called opacity effect (1), since ozone solar absorption depends on the optical path length in addition to local ozone concentration in a region where the optical depth approaches the value of 1 (1).

REFERENCES

1. HARTMANN, D. L. (1981). J. Geophys. Res., 86, 9631-9640.

- 591-

2. GHAZI, A., RAMANATHAN, V. and DICKINSON, R. E. (1979). Geo. Res. Lett . , 6, 437-440.

3. RAMANATHAN , V. (1976) . J. Atmos. Sci. , 1330-1346. 4. COGLEY, A. and BORUCKI, W. J. (1976) . J. Atmos. Sci. 33, 1347-1356. 5. U. S. Standard Atmosphere (1979) . 6. McCORMICK, M. P. , PEPIN, T. J. , CHU, W. P. , SWISSLER, T. J. and

McMASTER, L. R. (1979) . Bull. Amer. Meteor. Soc. 60, 1038-1046. 7. H.l\MILTON, K. (1982) . J. Atmos. Sci. 39, 2737-2747.

ACKNOWLEDGMENT

Thanks are due M. P. McCormick, NASA/LaRC for providing us with the SAGE data and for many stimulating discussions. This work was supported under NASA Contracts NASl-17032 and NASl-16362.

TABLE 1. Radiative Damping Coefficients a and b (Day-l)

WAVENUMBER 1 WAVENUMBER 2

Feb 25. 1979 Feb 15. 1981 Sop 8. 1979 Feb 25. 1979 Feb 15. 1981 Sep 8. 1979

10

55°N 53°N 54°5 P(mb) 5So N 53°N

• .11

.13

.12

.01

b • b • b • b • b .09 .12 .05 .lij .10 .12 .09 .08 .20

.01 .15 .00 .16 .03 .lij .01 .15 -.03

-.01 .15 .01 .09 .02 .12 .00 .13 -.02

-.01 .03 .00 .06 .02 10 .08 -.01 .06 .02

~

~ 'E---==--~ 10· 'F"---__

-10.0 - -m.0 - 10.0 20.0 " .0 ·1C.O ...w.o -10.0 ZO.III ".0 LRTI lUOE . OEG LAIl fUOE. OEG

Fig. 1. Calculated ozone solar heating rate (a), and infrared cooling rate (bJ for northern winter.

(a I Q( K/OI'lYI • (N-SPR I NGI -60. 0 -Xl.O O. 30.0

----_ ....... ---_ ............ ----.....-.. .... ,0 - lQ.O O. ~LO ".0 .... 0 -!CI.O g, XI.O ".0

LRfI fUOE , OEG LRI ITI.()[ , OEG Fig. 2. The same as Fig. 1, except for northern spring.

-592 -

54°5

• b .13 .19

.16 .06

.12 -.07

.07 -.Oij

I •• II /hi'''" U·,·q

~ !1'

~ aD -

" " '" ,

! ~ . , \

~ i , \ r .. , 1....' , , .. . I 0 I

T!"IP[RA TUIU: ;; ,

.J llO

' 110 ." " ... lOi'l'CllUOE. [DrGI

Fig. 3. Longitudinal distribution of ozone (a), and temperature (b) at 2 mb (-55°N) on February 25, 1979.

5~·Hl

! IT'

l .

-f ! .. ~ I. ..

~ I . ..

~ ~ ..

I. , ..

ID. :' i ~ . ...

, I

" .. ' .J 10.

". ,- ,,- .. . .•. ...

SO. D " I.

SO. • P~A SI.

Idl

• I I I I '. :T'

l .

! i ,.

I. I i I. .. ! I . -..... , ..

~ I I .

'. 'x , ~ II ' . 1/1 ...

,}r' /,

.I lO.

10. t 'D. .'

lit •

, ... ... " • PW A,Sf

I"

i ! ~ , ~ ~

I . ~ ...

... lO • ... ...

O.

~[& 25. Itn

"

.. o.

FU 15. Itll .,.. ..

A,,'PLITl,!O( (a I DA-'O

Fig. 4. Amplitude of the first two harmonic waves of ozone solar heating rates:

U-NI

I I I

T',

(a) February 25, 1979 (55'N), (b) February 15, 1981 (53'N), and (c) September 8, 1979 (54'S).

. 1

; T "

! ---~f,

; ) ,

• :1-/,

i..j ~ ~~ ' ..... ---

.'" ~ 1. ~,,/ ...

10 .

1. " ... , ,.

PHA50( PtoI .... u

WN . J, (1115""'. U 4 HJ III .. . 1

: I

T' ! i

l . "

! I •

I . , I .

~

I. ~

IO.

... " . ... ... ,. • pj,IASIE f'H .... U

Fig. 5. Phase of the first two ozone (03) , temperature (T') , and solar heating (Q' ) waves.

Phase increases westward.

- 593-

OBSERVATION OF STRONG OZONE VARIATIONS DURING A PRESTAGE OF THE

SUDDEN STRATOSPHERIC WARMING IN JANUARY / FEBRUARY 1979

W. Braun and H.U. DUtsch

Atmospheric Physics ETH, Honggerberg, 8093 Zlirich, Switzerland

Summary

Ozone transport is investigated by trajectory computations based on the LIMS (Limb Infrared Monitor of the Stratosphere) geopotential height fields. Displacements and deformations of air parcel chains in 48 hours are used to construct ozone maps, using the distribution of a previous day •. At the 10 mb level the correspondence of such kinematically cOn­stru~ted ozone maps with the actual LIMS maps is striking. This method is thus a strong indication of the self-consistency of the different LIMS products (ozone, temperature, geopotential) besides explaining the unusual ozone observations in January 1979.

1. Introduction

The well known winter accumulation of ozone in the lower stratosphere implies that the ozone transport, although directed against the horizontal ozone mixing ratio gradient (3), is accomplished by the net circulation associated with the polar night vortex. Sudden stratospheric warming situa­tions may be accompanied with large poleward excursions of subtropical air masses and are therefore interesting objects for the study of poleward ozone transport.

2. Ozone observation over Switzerland in winter 1979

Daily ozone soundings over Switzerland during the first two months of 1979 indicated that the stratospheric circulation was driven by strong dynamical processes (4). At the end of January, the first powerful pulse of a sudden stratospheric warming event dominated the circulation (7).

Fig. 1 shows different profiles of ozone mixing ratio, clearly demon­strating two facts: The European middle stratosphere has experienced an impressive increase of the ozone content from an extreme minimum to an equally pronounced maximum (4). Secondly, the figure gives an example of quasi simultaneous profiles measured by sondes and satellite, respectively. The overall agreement is encouraging and provides the framework for the following discussion. Some differences which, however, do exist are among other things a consequence of the very strong horizontal gradients in the ozone distribution in the region under consideration. In addition,

Ozone Symposium - Greece 1984 -594 -

instrumental uncertainties as well as limitations of the inversion procedure can not be neglected (for sondes see: 1, LIMS experiment: 5).

3. Channelling of the flow across Europe

At the end of January 1979 the 10 mb geopotential height field was dominated by a large southward extension of the polar night vortex towards Florida. The geopotential contours formed a funnel over the Atlantic Ocean at 300 N (Fig. 2), leading to a channelling of the flow across Europe. Con­sequently, ozone-rich air was transported in one or two days from southern latitudes near the production region of ozone to middle and high latitudes (2) •

4. Horizontal transport of air masses based on trajectory calculations using LIMS data

The very strong horizontal velocity gradients suggested not only a study of trajectories of single air parcels, but rather of a whole set of trajec­tories (6). Air parcels were connected in chains in the zonal direction. Fig. 3 shows such chains, which started at latitudes of 240 N, 280 N, 320 N and 360 N. Their isobaric geostrophic displacement and deformation is presen­ted in 12 hour time steps. Clearly, the channelling effect acts immediately on the northern chains. The ozone-rich air from 240 N, however, is also drawn in and reaches Central Europe within 48 hours.

5. Kinematic construction of ozone charts

The displacement and deformation (here: isentropic) of air parcel chains can be used to kinematically construct ozone maps, which are at the same time a means to discuss the ozone transport mechanism. In the initial position, the air parcels are tagged with their observed ozone mixing ratios. Then,the air parcel positions 48 hours later are drawn and reassigned their respective ozone mixing ratios. Finally, isopleths are plotted displaying the new ozone distribution. In effect ozone is being used as a conservative tracer.

The result of such a procedure is shown in Fig. 4. Fig. 4 b represents, for comparison, the ozone map according to the observed LIMS values on January 29 at the 850 K level over Europe, the most interesting region of this case. Fig. 4 a shows the kinematically constructed ozone map of the same day, based on 48 hour geostrophic isentropic trajectory computations. The good agreement of the two maps demonstrates two points: Firstly, it is a positive self-consistency test of different LIMS data sets. Secondly, it is a verification of the construction method showing that the observed extreme mixing ratio maximum is a consequence of advection from low latitudes.

6. The efficiency of horizontal ozone transport

The clear cut situation of the horizontal flow at the 10 mb level at the end of January 1979 (Fig. 2) allows a simple parametrization to demonstrate the ~fficiency of the horizontal ozone transport. Fig. 5 shows the geometri­cal and physical simplifications. The principal variable is R(t), the mean ozone mixing ratio in the area north of 400 N, which is a function of time. It is assumed that ozone-rich air with a mixing ratio R± flows with speed vi

-595-

through an input channel of width xi into this area. All these input para­meters, as well as the speed Vo and the width Xo of the output channel, are held constant with time. All parameters were calculated using the observed flow pattern together with the horizontal ozone distribution. The model cal­culations were performed assuming complete as well as partial horizontal mixing within the polar vortex. The linearly defined mixing factor can be determined in the same way as the other parameters.

The results of the calculations for the period January 25 to 30 are presented in Fig. 6. The good agreement between the theoretical and the observe values proves that the channelling of ozone-rich air across Europe into the polar night areas was indeed an important aspect of the northward transport of ozone. It further supports the idea that this inflowing air has been quasi-horizontally mixed with air masses of the polar night region. These large poleward excursions of fluid parcels from low latitudes and the successive large scale mixing deduced in this study from a consideration of ozone are consistent with, and corroborate the similar inference made by (8) based upon potential vorticity considerations.

7. Vertical air parcel displacements

The 30 mb-ozone maps of the last days of January 1979 (Fig. 7) show a maximum region over Central Asia with values greater than 7 ppm, which is notably higher than found anywhere else at this level. We may therefore anti­cipate a downward intrusion of ozone-rich air.

In.the attempt to follow the build-up of the ozone maximum at 30 mb (Fig. 7) very closely it became obvious that in some cases the isentropic approximation could not explain the observed ozone increase. Systematic in­vestigations of meridional cross sections of the ozone mixing ratio lead to the conclusion that the downward excursions of these particular air parcels were larger than indicated by the isentropic calculations. The attempt to determine the rate of diabatic cooling qualitatively did, however, not lead to reasonable results. Most probably, the vertical interpolation for the construction of the isentropic maps is not reliable enough, especially in regions with large temperature perturbations. We may therefore conclude that the trajectory method, as described in this paper, leads to good results in the layer of the ozone mixing ration maximum, whereas, using currently avail­able data for layers with strong vertical and horizontal gradients of both, potential temperature a;d ozone mixing ratio, the method seems to be less recommendable.

Acknowledgements

We are very thankful to Dr. J.C. Gille, National Center for Atmospheric Research (NCAR), Boulder, Colorado, and his team, who made the LIMS data available to us before releasing them to the archive. We would like to thank W. Attmanspacher (Deutscher Wetterdienst, Meteorologisches Observatorium, Hohenpeissenberg, FRG) for sending us his balloon-sounding profiles.

References

1. Attmannspacher, W. and Dtitsch, H.U.,(1970): International ozone sonde intercomparison at the observatory Hohenpeissenberg (FRG, Berichte des Deutschen Wetterdienstes, Nr. 120, Band 16.

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2. Braun, W. and Dutsch, H.U. (1984): The origin of ozone-rich air in the middle stratosphere observed over Europe at the end of January 1979. Journal of Atmospheric Chemistry, (in press).

3. Dutsch, H.U., (1978): Vertical ozone distribution on a global scale.Pure Appl. Geophys. 116, 511-529.

4. Dutsch, H.U. and Braun, W. (1980): Daily ozone soundings during two winter months including a sudden stratospheric warming. Geophys. Res. Let., Vol. 7, No 10, 785-788.

5. Gille, J.C. and Russel, J.M., (1984): The Limb Infrared Monitor of the Stratosphere (LIMS): Experiment description, performance and results. (To appear in J. Geophys. Res.)

6. Hsu, Ch.-P.F., (1980): Air parcel motions during a numerically simulated sudden stratospheric warming. JAS, 12, 2768-2792.

7. Labitzke, K., (1979): The major stratospheric warming during January -February 1979. Beilage zur Berliner wetterkarte 8. Mai 1979.

8. McIntyre, M.E., and Palmer, T.W., (1983): Breaking planetary waves in the stratosphere. Nature,305, 593-600.

Captions

Figure 1: Profiles of ozone mixing ratio in ppm. January-Februay mean 1967-78, Payerne January 18, 1979, Sonde Payerne (46.50 N/ 6.60 E) January 29, 1979, Sonde Payerne (46.50 N/ 6.60 E) January 29, 1979, Sonde Hohenpeissenberg (47.50 N/ 11.00 E) January 29, 1979, LIMS (480 N/ 8.30 E)

Figure 2: Schematic representation of the geopotential height field and the channelling effect in the flow SW of Europe.

height contours 3056 and 3088 darn on January 28,79(quasi stationary) isopleth of 9 ppm ozone mixing ratio at the beginning of the period under consideration (around January 26).

Figure 3: Air parcel chains starting on January 28 at 240 N, 280 N, 320 Nand 360 N respectively. Displacements and deformations of air parcel chains shown in 12 hour time steps.

Figure 4: Ozone map for Europ, 850 K, January 29, 1979: a) kinematically constructed map, b) observed LIMS values.

Figure 5: Parametrization of the horizontal poleward transport of ozone at the 10 mb level at the end of January 1979 (see text).

Figure 6: Increase of mean ozone mixing ratio north of 400 N at the end of January 1979.

observed values, model, total mixing assumed (m = 1) model, measured mixing factor (m = 0.86) .

Figure 7: Ozone mixing ratio, 30 mb, January Areas with values greater than 7 ppm or Hatched field: Main area of polar night

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30, 1979. less than 2 ppm are shaded.

jet at the 30 mb level.

6 mb

10

15

20

~'\ '; ( .....

~,:/tC ... -.. " 30

40 '/ ., .

- "

... " ...... , .

50~-L-LJ-~~~~~ o 2 3

Fig. 1

acrwGCl' 40" 20° 0° 20" 40° 60° 80"£

50 0 N 40° 30°

°CH 28,1.79 o Q : ~

50°

~~ .12h 40° 30°

soo 40° .24h 30° .- .. ~-.... -soo

+ 36h 40" . __ ·-"·Z 30"

50" ~ .. ~ +48h 40° ___ 7

30° ... -:. ocrw GCI' 40° 20° 0" 20" 40° 60°

Fig. 3

R'~ Ri __ .1..-___ _

Fig. 5

800 [

Fig. 2

a)

- 598 -

5.0

Fig. 6

o 1 2 3 4 25 26 27 28 'Xl 5 6 7 8 9 10

. L7. 30. Jan 79

. "

' .

Fig. 7

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SAGE STUDIES OF THE WAVES AND EDDY FLUXES OF OZONE AND TEMPERATURE NEAR 55° DURING THE LATE

FEBRUARY 1979 STRATOSPHERIC WARMING

PI-HUAN WANG Institute for Atmospheric Optics and Remote Sensing (IFAORS)

Hampton, Virginia

Summary

Ozone data from the Stratospheric Aerosol and Gas Experiment (SAGE) have been used in conjunction with meteorological information to study the waves and eddy fluxes of ozone and temperature near 55°N during the late February 1979 stratospheric warming. The results indicate an intense poleward eddy ozone transport in the altitude range between approxi­mately 24 and 38 km, and an equatorward transport above an altitude of -38 ~m. It is found that this equatorward eddy ozone transport in the upper stratosphere was accompanied by a poleward eddy heat transport, as expected on the basis of the ozone photochemistry. The results also indicate that the phase relationship between ozone and temperature waves agrees qualitatively with existing model analyses.

1.1 Introduction Amplifying planetary waves have been considered to play important roles

in producing poleward transport of stratospehric 03 and heat during the late winter and spring, and to be responsible for the spring total 03 buildup and stratospheric warmings at high latitudes. Theoretical analyses indicate that there is no net transport for steady nondissipative waves with nonzero Doppler-shifted frequency. On the other hand, dissipative or transient waves are able to produce net transports. In addition, net transports can be also brought about by pure ocillatory waves in the presence of sources or sinks (3). In the case of stratospehric ozone, its transport is further enhanced due to its temperature dependence (4).

Approximately, the stratosphere can be divided into three different regions according to the main ozone controlling mechanism--the photo­chemically-controlled region in the upper stratosphere, the dynamically­controlled region in the lower stratosphere, and a transition region in between. Due to the fact that 03 production/loss rate changes negatively/ positively with respect to the T changes, it is expected that 03 and T waves will show an out-of-phase relationship in the photochemically-controlled region. In contrast, in the dynamically-controlled region, they would be expected to show an in-phase relationship. This is because 03 is now acting as an inert gas. In addition, the 03 and T show generally a similar merid­ional distribution in the lower stratosphere. As a result, there is a shift of the phase relationship between 03 and T waves from the dynamically­controlled region to the photochemically-controlled region. This shift in the phase relationship may lead to an in-phase relationship between 03 and

Ozone Symposium - Greece 1984 - 600-

meridional velocity (V) waves at certain levels in the transition region and results in a large poleward 03 transport (4).

The objective of this analysis is to examine the ozone and temperature waves and their eddy fluxes near 55°N during the late February 1979 strato­spheric warming by using meteorological information and ozone data derived from the Stratospheric Aerosol and Gas Experiment (SAGE). In this report, only highlights of the analysis will be presented. The detailed aspects of the study can be found elsewhere (7).

1.2 Data and Method of Approach The data set of this analysis consists of the SAGE ozone mixing ratio

and meteorological information from February 23 to March 2, 1979 near 55°N. It covers the period during which the stratosphere shows the third warming pulse of this particular winter (6). The detailed aspects of the SAGE instrument can be found in the article by McCormick et al. (5), and the method, which is used for profile retrieval of the interested species, has been discussed by Chu and McCormick (1). It should be mentioned that associated with each SAGE profile there are temperature and height data at 18 standard pressure levels provided by NOAA's National Meteorological Center (2).

In the analysis, the profiles have been vertically smoothed with a 5 km running-mean triangular filter. For convenience of performing Fourier analysis, each daily data set is further used to obtain the information at the grid points of every 20° in the longitude and every 2 km from altitude 10 to 50 km. In order to suppress high-frequency noise components, a 3-day running-~ean smoothing procedure is applied to the entire data at each of the grid points. Finally, the daily harmonic components of 03' T can be obtained, and the 03 and T eddy fluxes can be determined. In this study, the harmonic analysis is made up to the third component. The horizontal meridional eddy velocity is determined from the height wave components based on the geostrophic wind relationship.

1.3 Results and Discussion Evolution of the planetary waves. The wave amplitudes of the first

two harmonic components of the temperature are given in Figs. la and lb, respectively. In the upper stratosphere, above 35 km, both components exhibit distinct amplifications of the waves from 23 to 27 February, fol-' lowed by a reduction of their strength during the remainder of the third warming pulse. The peak values for both waves take place at 42 km corre­sponding to 28 February, and 26 February for wavenumbers 1 and 2, respec­tively. On these days, the upper stratosphere showed the third reversal of the meridional gradient of zonal mean temperature (6). Below an altitude of about 30 km, the behavior of these waves is more complex.

The analyzed results of V' are shown in Figs. 2a and 2b. The wave component 1 shows an intensification from 26 February to 2 March at alti­tudes between 24 and 42 kID. As to the wavenumber 2, it exhibits a decline at these altitudes over the entire data period of this analysis. Figs. 3a and 3b give the isopleths of the first two 03 harmonic components. Above 34 km, wavenumber 1 exhibits an intensification from 23 to 28 February, and declines afterward. This evolution of 03 wavenumber 1 seems to be asso­ciated with that of T' in the upper stratosphere (Fig. 1a). In the lower stratosphere below about 30 km, 03 wavenumber 1 shows only mild variation. In the case of 03 wavenumber 2, the wave is generally declining over the entire period of the third warming pulse except in the three layers centered at 16, 33, and 43 km. Perhaps the development of 03 wavenumber 2 centered at 43 km is related to that of thermal wavenumber 2 in the upper

- 601 -

stratosphere (Fig. lb). Horizontal ozone and temperature transports by planetary waves. The

behavior of the eddy ozone transport associated with the first two wave components is shown in Fig. 4. The distinct features of the wavenumber 1 component (Fig. 4a) above 35 km are the development of the equatorward eddy ozone transport over the period from 23-28 February, and the poleward trans­port afterward. The variation below 35 km seems to be just the opposite. In the case of wavenumber 2 (Fig. 4b), an intense poleward eddy ozone trans­port appeared in the middle stratosphere approximately between 25 and 36 km throughout the entire data period of this analysis. Above -38 km, ozone was mainly transported to lower latitudes. The net ozone transport as a result of the first three waves is given in Fig. 4c.

It has been recognized that eddy heat transport plays a significant role in stratospheric warmings. Because of a negative correlation between ozone and temperature in the upper stratosphere, equatorward/poleward eddy ozone transports are expected to be associated with poleward/equatorward eddy heat transports. To examine this feature, the calculated results of eddy heat transports due to wavenumbers 1 and 2 are given in Figs. Sa and 5b, respectively. By inspecting the wavenumber 1 of ozone and temperature eddy transports, it is found that the behavior of the eddy ozone and heat transports above -35 km is indeed close to the expected feature just dis·­cussed. A similar feature can also be found, in the case of wavenumber 2, above -38 km. The net eddy heat transports due to the first three waves are displayed in Fig. 5c.

Analysis in terms of phase relationships between the eddy fields. The phases of 03' T, and V for wavenumber I on 25 February 1979 is given in Fig. 6a. 03' and T' indeed show a nearly in-phase relationship in the lower stratosphere between -18 and 30 km. Above -35 km, the 03 and T' are approximately out-of-phase. These results suggest that the 03 in the upper stratosphere (above 35 km) is under photochemical control, and is determined by dynamical processes below -30 km. A transition region seems to exist between -30 and 35 km.

In the upper stratosphere (above 35 km), Fig. 6a also shows a nearly out-of-phase relationship between 03 and V3 and a phase difference of about -TI/3 between -20 and 35 km. This phase relationship explains the poleward eddy ozone transport in the middle stratosphere and the equatorward trans­port in the upper stratosphere on 25 February 1979 (Fig. 4a). As for the wavenumber 1 phase relationship between T' and V', they show approximately an in-phase relationship in the upper stratosphere (above 30 km) and a phase difference of -TI/3 below -30 km. This phase relationship explains the poleward eddy heat transport in the entire altitude region, which occurred on 25 February 1979 (Fig. Sa). A similar phase relationship is also shown between wavenumber 2, O~ , T' and V' (Fig. 6b). It should be pointed out that the approximate in-phase relationship between 0 3 and T' in the upper stratosphere and their nearly out-of-phase relationship in the lower stratosphere are found to be evident throughout the entire data period of this analysis (Fig. 7).

REFERENCES

1. CHU, W. P., and McCORMICK, M. P. (1979). Inversion of stratospheric aerosol and gaseous constituents from spacecraft solar extinction data in the 0.38-1.0 ~ wavelength region. Appl. opt., 18, 1404-1413.

2. HAMILTON, K. (1982). Some features of the climatology of the Northern Hemisphere stratosphere revealed by NMC upper atmosphere analyses. J. Atmos. Sci., 39, 2737-2749.

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3. HARTMANN, D. L. (1981). Some aspects of the coupling between radiation, chemistry, and dynamics in the stratosphere. J. Geophys. Res., 86, 9631-9640.

4. HARTMANN, D. L., and GARCIA, R. R. (1979). A mechanistic model of ozone transport by planetary waves in the stratosphere. J. Atmos. Sci., 36, 350-364.

5. McCORMICK, M. P., PEPIN, T. J., CHU, W. P., SWISSLTER, T. J., and McMASTER, L. R. (1979). Satellite studies of the stratospheric aerosol. Bull. Amer. Meteor. Soc., 60, 1038-1046.

6. QUIROZ, R. S. (1979). Tropospheric-stratospheric iteration in the major warming event of January-February 1979. Geophys. Res. Lett. 6, 645-648.

7. WANG, P.-H., McCORMICK, M. P., and CHU, W. P. (1983). A study on the planetary wave transport of ozone during the later February 1979 stratospheric warming using the SAGE ozone observation and meteorologi­cal information. J. Atmos. Sci., 40, 2419-2431.

ACKNOWLEDGMENT

Support of this work by NASA Contracts NASl-16362 and NASl-17032 is grate­fully acknowledged.

1["". -.. ...... U"

Fig. 1. Evolution of the amplitudes tOe) of the first two temperature waves [(a) and (b), respectively, contour interval 2°e].

IIInIIlIOIW. YlUXlrr,WlWDII.MaLI I

11I'11III • • "

Fig. 2. Evolution of the amplitudes (rn s-~) of V': (a) wavenumber 1, con­tour interval 2 m 5-1; (b) wavenumber 2, contour interval 6 m 5- 1 .

11II1II . -........:. I NIIIII: . ~.' l i n . ,.. '" .1 ... .~ .. ..

. .. ~ , ",

~ ~

..... ..,. tllll( . "",

Fig. 3. Evolution of the ampl itudes (ppmv) of OJ, (a) wavenumber 1,

(b) wavenumber 2, contour interval 0.2 ppmv.

- 603-

. I t ll( ,

,,,

. . U .... . OII'.

Fig. 4. Time variations of eddy ozone flux (ppm m 5-1 ) due to (a) wavenumber I, contour interval 1 ppm m 5-1 ; and (b) wavenumber 2, contour interval 2 ppm m 5-1 , The sum of the first three waves is given in (e), contour interval 3 ppm In 5-1.

fill(.

Fig. 5. Time variation of eddy heat flux (K m 5- 1 ) due to (a) wavenumber I, contour interval IOce m 5- 1 ; and (b) wavenumber 2, contour interval 2 ppm m 5- 1 . The sum of the first three waves, contour interval 30°C m s-1,

PHRS{

., ..

" " .!--..J.....iw...4.L._ ......... ~ ..

PHR~E

Fig. 6, Phase relationship between qzone (solid line), tempera­ture (da shed 1 ine) I and eddy meridional velocity (solid and dashed lines). Phase increases westward: (a) wave­number I, (b) wavenumber 2i 25 February 1979.

Fig. 7. Time variation of the phase relationship between ozone (solid line), temperature (dashed line), and eddy meridional velocity (solid and dashed lines). Phase increases westward: (a) wavenumber 1, 44 km altitude; (b) wavenumber 1, 26 km; (c) wavenumber 2, 44 kIn; (d) wavenumber 2, 26 km.

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C HAP T E R VII

LABORATORY MEASUREMENTS OF ABSORPTION CROSS-SECTIONS AND OF CHEMICAL RATE CONSTANTS

- The ultraviolet cross-sections of ozone: I. The measurements

- The utraviolet cross-sections of ozone: II. Results and temperature dependence

- New values of ozone absolute cross-sections in the ultraviolet spectral range at 298 and 228 K, by a method based upon pressure measurements at constant volume

- Absolute absorption cross section measurements of ozone

- Absorption coefficients of ozone for the backscattered UV instruments - SBUV, TOMS, and BUV - and for the Dobson instrument

- Mesure de l'absorption par la haute atmosphere dans le domaine de longueurs d'onde de la "Fenetre atmospherique" au voisinage de 200 m

- Theoretical N2-, 02-, and Air-broadened halfwidths of ozone calculated by quantum fourier theory with realistic rollision dynami cs

- Altitude resolved measurements of the N20 photolysis frequency in the stratosphere

THE ULTRAVIOLET CROSS-SECTIONS OF OZONE: I. THE MEASUREMENTS

* . A. M. BAS;* ' NBS, WashIngton, DC 20234 R. J. PAUR, EPA , Research Triangle Park, NC 27711

Summary

Absorption cross-sections of ozone have been measured over the range 230 nm to 350 nm, and for temperatures 200K to 300K, with improved photometric accuracy and spectral resolution. These measurements are referred to the cross-section at the 253.65 nm mercury line, 1147 x 10-20cm2 (1), and show an internal consistency of ±1%.

1. Method and experimental

The determination of absorption cross-sections in systems that obey the Beer-Lambert Law is, in principle, a fairly straightforward measurement problem requiring knowledge only of path lengths, light transmittance, and sample concentration. Ozone presents a particular problem in the diffi­culty Of characterizing accurately the sample concentration. In measure­ment applications the absorption of radiation at 253.65 nm is frequently used as a means of assaying the ozone content of a sample. In such applications a best estimate of the cross-section from published results has been used. The published values range from about 1136 x 10-20 to about 1162 x 10-2 cm2 , and the value reported by Hearn (1) (1147 x 10-20 cm2 ) has frequently been selected as the reference value for the cross-section at 253.65 nm.

We refer all measurements to the absorption at 253.65 nm by using the Hearn value of the cross-section.

The absorption cross-sections were determined from the relation

no = kcL = IOge(io)

where: 10, I are the incident and transmitted radiation intensities L is the pathlength (cm); c is the ozone concentration (atm) k is the absorption coefficient (cm-1 atm-1 ) o is the absorption cross-section (cm2 ) n is the column density of the ozone sample (cm-2 ).

The incident continuum radiation was produced by a DC arc in argon at atmospheric pressure (2) operating at a power of 3000 watts. The radiation from the arc was focused on the entrance slit of a 1.8 meter focal length Ebert scanning monochromator. The instrument uses a 1200 grooves/mm grating, and for the mechanical slit widths that were used in these measurements has a spectral resolution less than 0.025 nm. The monochromator is driven, through a precision screw, by a stepping motor

* Work supported in part by NASA Upper Atmosphere Program. **Any policy issues discussed should not be construed to represent EPA

policy.

Ozone Symposium - Greece 1984 - 606-

that is capable of moving the grating through extremely small intervals. Wavelength steps of 0.05 nm were used to insure that the ozone absorption bands would be accurately reproduced. The wavelength scale of the instru­ment was calibrated between 200 and 365 nm by reference to 23 emission lines of mercury, cadmium, and zinc. The uncertainty of the wavelength de­termination is less than 0.025 nm. The emergent radiation from the monochromator passed through a narrow-band filter to remove stray radiation before entering the absorption cells.

The measurement of sample transmittance was made by using a novel photometric technique (Figure 1). Two pyrex absorption cells, each 1 meter long and 12mm diameter, were mounted in a double-walled chamber in which they were submerged in methanol. The exit beam from the monochromator was split by a partially aluminized reflector into two approximately equal beams that were directed through the cells. At the exit end of each cell was a photomultiplier detector. The photocurrent in each tube was con­verted to frequency, and the signals were connected to scalers for display and counting.

A gas handling system provided two streams: air (or oxygen) in one, and ozonized air (or oxygen) in the other. The ozone was produced either by UV photolysis or by electrical discharge in the air (or oxygen) stream. No differences were noted in the results of measurements with respect to the method of ozone production. By operating appropriate valves the flow of the ozonized air was directed alternately to each of the absorption cells. The residence time of a sample in the cells was about two seconds. Figure 2 shows how the transmittance of the ozone sample may be derived from the ~easurements in this system. (Tfreq is the intensity of the beam as detected by the photomultiplier tube for each cell, where the photocurrent is converted to a frequency for digital measurement). It should be noted that the transmittance as determined by this method is equivalent to that of a single cell equal in length to the combined lengths of the two cells. Since the UV radiation source is viewed simultaneously by both photomultiplier detectors, fluctuations in the source intensity do not effect the transmittance measurement. Also, impurities in the air stream will not affect the transmittance measurement unless the impurity can react with ozone.

The uncertainty in the transmittance determination is estimated to be 2 in 105 arising from counting statistics.

The ozone concentration, or number density, in the sample is determined by making absorption measurements at 253.65 nm in two pairs of absorption cells (assay cells). A mercury lamp placed at one end of the assay cells is viewed by solar-blind photodiodes through narrow-band interference filters which isolate the Hg 253.65 nm line. As shown in Figure 1 the assay cells are placed at the entrance and exit of the main absorption cells and serve to indicate the degree of ozone loss in passing through the main cells. The pairs of assay cells are 1 cm and 5 cm long. These lengths allow us to make accurate concentration measurements over an ozone concentration range of 10 to 4000 ppm.

The temperature and pressure of the air/ozone mixture are measured by sensors within the sample stream. The sample temperature is varied by circulating methanol from a refrigerated reservoir into the chamber in which the absorption cells are located. Temperature control to better than 1 K can be maintained over the temperature range 198 K to 300 K. The sample temperature uncertainty is about 0.25 K; the uncertainty of the pressure measurement is about 1 mbar.

-607 -

The entire measurement process and data collection and reduction are controlled by a computer. In the measurement sequence the monochromator is set at the desired wavelength and a flow pattern is established with reference air in one set of absorption cells and ozonized air in the other cell. After a time interval sufficient for the ozone distribution to reach equilibrium (about 30 seconds) the photo-detectors begin to record the signal intensity through each cell. The digitized signals are accumulated in the appropriate scalers and the total counts the transferred to the computer for storage on magnetic tape. A pair of solenoid valves (Fig. 1) is next activated by the computer to interchange the flow pattern in the absorption cells. During all the intervals while waiting for equilibrium to be achieved, pressure and temperature readings are made and updated frequently and transferred to the computer for storage. Then the transmittance signals are recorded and stored and again the flows are interchanged. After another equilibrium interval the signals are recorded and stored as previously. The three sets of measurements provide two determinations of the sample transmittance according to the procedure shown in Figure 2. The computer performs this process and computes the cross-section for the wavelength at which these data have been taken and stores the results on magnetic tape. When this process has been completed the computer signals the stepping motor controller to move the spectrometer drive to the next observation wavelength (in this case the wavelength step used is 0.05 nm) and the entire measurement sequence begins again.

2. Post-measurement data processing.

Following completion of a measurement run the data tapes are read into a larger computer system for more extensive processing.

This processing consists of: checking for outliers; recomputation of the cross sections with appropriate corrections; sorting the data into convenient logical wavelength blocks; averaging spectra of similar tempera­ture; generation of temperature coefficients and a variety of plotting and printing functions.

The transmittances of the various cell pairs were computed according to Fig. 2. When the ozone concentration was sufficient so that the transmittance of the 5 cm assay cells dropped below 1% the processing used concentration data only from the 1 cm cells. Similarly, if the ozone concentration was low enough to cause the transmittance of the 1 cm cells to exceed 99% the processing used ozone concentration data only from the longer cells.

Three types of corrections to the data were included in the data processing. The first of these resulted from the fact that the cross-sections measured early in the measurement program relied on Vycor lamp envelopes and solar blind vacuum photodiodes to isolate the 253.65 Hg line in the assay cells. This combination was not ideally monochro­matic. Later experiments showed that a 1% correction must be made to concentrations derived from early measurements to compensate for the lack of monochromaticity.

nm

A second correction was made to account for the present in the flowing gas system. The pressure is upstream assay cell than in the rest of the system.

pressure distribution slightly greater in the The correction

resulted in a change of 0.2%.

- 608-

The third correction was made to account for window reflections in the instrument. The correction was made by modelling the instrument with the assumptions: 1) each window had a reflectivity of 8%; 2) the windows were parallel; 3) the beam divergence was limited by the aperture of the detector

The resulting correction to the computed absorbance was fitted (2nd or 3rd order polynomial) to the transmittance for each of the 3 pairs of cells.

The above corrections tended to offset each other (lack of monochromaticity caused low estimates of the concentration while window reflections caused high estimates of the concentrations) so that the overall correction was typically less than 1% and in extreme cases reached only about 1.4%.

The data were extensively examined for internal consistency. Cross­sections determined from half-cycles 1 and 2 were compared with cross sections determined from half-cycles 2 and 3. Means and standard deviations of concentrations, transmittances, and other variables were computed for each run to verify the reproducibility of the measurements. Examination of these checks generally supports the conclusion that the system has approximately a 1% random noise in the determination of the cross sections.

One measure of the reliability of the data is the ability to reproduce the same values for the cross sections at the Hg line wavelengths when scanning using a continuum source and when making measurements using a Hg lamp. This tests both the photometric reproducibility of the system and the wavelength calibration since some of the lines (notably, the 334.15 nm line) occur at rapidly changing portions of the spectrum. Table I shows our scan data (continuum source) vs our line data (Hg source), and also gives Hearn's values for compar i son.

Table I Cross Sections at Selected Hg Lines (x 1019cm2)

Hearn Bass-Paur Hg line Hg line Continuum

Hg line T(C) sourcp source source 253.65 25 114.7

-45 289.36 25 14.7 15.01 15.03

-45 14.23 14.37 296.73 25 5.97 6.07 6.11

-45 5.59 (5.66)* 302.15 25 2.86 2.94 2.98

-45 2.64 (2.68)* 334.15 25 0.043 0.047 0.047

-45 0.035 0.032

*Values computed from quadratic coefficients in absence of measured values.

References:

1. A. G. Hearn, Proc. Phys. Soc., 78, 932 (1961)

2. J. M. Bridges and W. R. Ott, Appl. Opt. ~, 367 (1977).

- 609-

.. e

.~--I

I I

~---Lr~~r-----~------------------~~~u

Schemltic dilgrlM of system for ozone cross-section mll.urement.

Figure 1

I 'k--f~ _________ c_e1_1_1 ____________ ~

I

I

~ - -1'-_____ --'c:..:e:..:;l"'l-=-z _______ -' ID2 F

cell 1 cell Z

gas REF 0 3 + REF

J

One

Tfreq fi(nom) fZ(nom) , Tcell Z half

fZ(nom)'TcellZ cycle

ratio f 1 (nom)

gas °3+REF REF r" Tfreq f1 (nom)'Tcell fz(nom) half

Ratio fZ (nom) cycle

f1 (nom) 'Tcell

RATIO- Ratio 1 fZ (nom) 'Tcell f1 (noml x Tcell Jrati"()7 •

f 1 (nom) fZ(nom) - T , T 2 • Transmittance cell 1 cell

Determination of transmittance of ozone sempl. Figure 2

- 610-

Summary

THE ULTRAVIOLET CROSS-SECTIONS OF OZONE: II. RESULTS AND TEMPERATURE DEPENDENCE

R. J. Paur, EPA*, Res~~rch Tr~angle Park, NC 27711 A. M. Bass, NBS , WashIngton, DC 20234

Tables of ozone absorption cross-section in the ultraviolet have been prepared for intervals. of 0.05 nm over the range 245 to 340 nm. At each wavelength entry in the table a set of coefficients has been derived that permits the cross-section to be computed as a function of temperature, between 200 K and 300 K, with an accuracy of 1%.

1. Temperature Dependence of the Cross-Section

As described in the preceding paper, ultraviolet absorption measurements of ozone were made at several temperatures in the range 200 to 300 K: The measurement temperatures were selected to be those most useful in atmospheric applications (-70, -55, -45, -30, 0, +25C). However, in order to extend the utility of these data we attempted to characterize quantitatively the nature of the temperature dependence of the ozone cross-sections. This was done by selecting several fixed wavelengths and by making measurements of the cross-sections at those wavelengths as the sample temperature was changed. We controlled the rate of cooling or warming of the system between 200 and 300 K so that we could measure the slowly changing cross-sections at three-minute intervals over a twelve to eighteen hour period. These temperature scans typically included 200-400 individual determinations, and were made for nine different wavelengths.

A plot of cross-section versus temperature for each of these measurements clearly shows curvature. A quadratic function was found to fit the data very well (Fig. 1). This observation is an agreement with the behavior of the temperature dependence as reported by Barbier and Chalogne (1) and forms the basis for the treatment of the temperature dependence of the entire absorption spectrum.

2. Computation of the Quadratic Coefficients

The cross sections were measured in assorted wavelength blocks as described in the preceding paper. The data were compiled into logical wavelength blocks of 5 nm and the spectra were then submitted to a two-pass filter which rejeoted outliers based on the amplitude of the cross sections and the noise in the data set at each wavelength. Following filtering of the data by the computer the data were plotted on a CRT for visual inspection; the operator was able to reject individual points or entire runs during the inspection procedure. Some of the spectra were

* Any policy issues discussed should not be construed to represent EPA policy.

**Work supported in part by the NASA Upper Atmosphere Program.

Ozone Symposium - Greece 1984 - 611-

quite noisy the filter was designed to reject entire runs if more than 20% of the ndividual points were rejected. The second pass through the filter was dentical to the first except that the tolerance band was reduced by more than a factor of two. Less that 5% of the total data set was rejected.

The average spectrum at each of the six measurement temperatures was obtained by averaging all spectra of the reported temperature plus or minus 2 degrees.

Quadratic coefficients for the following equation were computed at each wavelength:

where T is the temperature in degrees Celsius and X-sec is the cross section in units of 10-20 cm2 •

The quadratic coefficients were computed from all the available spectra. Thus the coefficients are temperature-weighted in proportion to the number of spectra at a given temperature. In some cases only 7 or 8 spectra were available; in other cases up to 30 spectra were available. Typically 14 to 18 spectra were used to determine the quadratic coefficients.

The accuracy of the quadratic model was computed for each 2.5 nm segment of the spectrum at each temperature. With few exceptions, the model agrees to within 1 percent of the measured values in the wavelength range from 245 to 330 nm.

At wavelengths longer than 330 nm the accuracy of the coefficients appears 'to deteriorate. In general this is due to a combination of less data and smaller cross sections. For example, in the range of 335 nm to 337.5 nm an average difference of less than 0.01 (less than 1 part in 105 of the cross section at 254 nm) leads to an error of more than 5 percent.

The average spectra and quadratic coefficients were printed along with data indicating the accuracy with which the synthetic spectra generated from the coefficients matched the measured spectra of various temperatures. A graphic presentation of the synthetic vs measured spectra is presented in Figure 2 for the wavelength range from 320 to 330 nm.

3. Temperature Dependence at 253.65 nm

As we have discussed previously, these measurements are based on the assumption that the ozone cross-section at 253.65 nm is not tempera­ture-dependent. That assumption requires validation because if it is not correct then our low temperature values will have to be modified somewhat. The only published report on the temperature dependence of the ozone cross-section at this wavelength is that of Vigroux (2) which indicated that the cross-sec.tion decreases by 3% with the decrease in temperature between 18C and -75C.

We have made an effort to verify the nature of this relationship by inserting a second photometer in the ozone sample stream before the main photometer. The second photometer is an instrument that was designed to be the NBS laboratory standard for ozone calibrations, and ·is characterized by extremely good stability, sensitivity, and precision of measurement. It was found that when the two photometers were operated with the ozone sample at the same ambient temperature in both, they indicated essentially the same ozone concentration present in both photometers. However, when

- 612-

the temperature of the cross-section photometer was reduced while the reference standard photometer was kept at room temperature, the cross-section photometer indicated an apparent increase in the ozone concentration. Since the same sample flows through both photometer and the concentration in the second photometer cannot increase, we believe this indicates an increase in the cross-section as the temperature is reduced. Our measurements suggest an increase of about 1.3% for a change in temperature from +25C to -70C. Some other recent measurements (3,4) also suggest that the cross-section actually increases with decreasing tempera ture.

Although our method of measurement is somewhat indirect, we believe that this effect is real. An absolute measurement of higher accuracy than previously achievable would be required to verify these observations on the temperature effect and to specify the magnitude of the effect more exactly. Therefore, we have not included any temperature effect for the 253.65 nm wavelength. If later measurements establish the magnitude for the temperature effect, a linear correction can be made to update the entire data set.

4. The Data Tables

Estimation of the overall accuracy of these measurements is not straightforward. The measurements use a value of 1147 x 10-20cm2 for the 254 cm cross section. It has been assumed that the value does not vary with temperature.

From-the photometric precision of the instrument and the quality of agreement of the concentrations from the two pairs of assay cells, it appears likely that the concentration is measured to within 1%. From the photometric precision of the instrument and comparison of the cross section with the standard reference photometer for the assay of ozone it appears likely that the cross sections are measured to within 1%. Examination of the internal consistency of several sets of measurements at each of six temperature shows that for cross sections larger than 0.2 x 10-20 cm2 the data lie within 1% of a model which assumes a (different) quadratic temperature dependence at each wavelength measured. This latter fact leads us to estimate that the relative cross sections are accurate to about 1% for the wavelength range 245 nm to 330 nm.

The results of this measurement program have been collected in a set of tables that provides cross-sections vs wavelength and temperature. The tables consist of two parts. (Figures 3 and 4 are sample pages from the tables.) In Part A the table entry contains the wavelength (in 0.05 nm intervals) and the value of the cross-section for each of the six measure­ment temperatures. In Part B the table entry contains the wavelength and the three coefficients that permit the cross-section to be computed for any temperature between 200 K and 300 K with an estimated accuracy of 1%.

References:

1. D. Barbier and D. Chalogne, Ann de phys. (11) fl, 272 (1942). 2. E. Vigroux, Ann physique 8, 709 (1953). 3. D. E. Freeman, unpublished results. 4. L. Molina, unpublished results.

- 613-

CSI 18 C\J <

CSI 16

* 14 C\J < :E 12 u I 10

Z 0 ..... 8 >--u w 6 U1 I

U1 U1 4 0 Q' U 2

Dots: Measured Cross Sections vs Temperature

Solid: Quadratic Fit to Measured Cross Sections

. , ··,·,-l :~~ . j j(('s nm

.... !l . ..-• . ....,......,..-....-,.,.--:;-:-~--' 317.6 nm

1.8

1 . 6

1 . 4

1.2

1.0

.8

.6

.4

.2 ~ .~

. 339.8 nm

200 220 240 260 280 300 TE MPERRTURE - deg K

200 220 240 260 280 300 TEMPERATURE - deg K

IS! 2.88 (\J

< IS! 2.56

* 2.24 (\J

< 5 1.92

z o H

I­U W Ul I

Ul Ul o a:: u

1.60

1 .28

.96

.64

.32

- 25 deg C

'" deg C - -3 0 de9 C - - 45 de9 C - - 55 deg C --70 deg C

CM-l NM

31241 320

31046 322

Figure l

30855 324

Dots - measured pOInts

Sol i d - synthetic spectra

30666 326

30479 328

30294 330

Figure 2

- 614-

Ozone spectruM' 267.5 to 270.0 nMi Xsecs*10'20 cM'2 July 9,1984 Page 10A

NH (air) CH-1(vac)

267.511 267.561 267.611 267.661 267.711 267.761 267.811 267.861 267.911 267.960 268.010 268.060 268.110 268.160 268.210 268.260 268.310 268.360 268.410 268.460 268.510 268.560 268.610 268.660 268.710 268.760 268.810 268.860 268.910 268.960 269.010 269.060 269.110 269.160 269.210 269.260 269.310 269.360 269.410 269.460 269.510 269.560 269.610 269.660 269.710 269.760 269.810 269.860 269.910 269.960

37370.5 37363.6 37356.6 37349.6 37342.6 37335.6 37328.7 37321.7 37314.7 37307.9 37301.0 37294.0 37287.0 37280.1 37273.1 37266.2 37259.3 37252.3 37245.4 37238.4 37231.5 37224.6 37217.6 37210.7 '37203.8 37196.9 37190.0 37183.0 37176.1 37169.2 37162.3 37155.4 37148.5 37141.6 37134.7 37127.8 37120.9 37114.0 37107.1 37100.2 37093.4 37086.5 37079.6 37072.7 37065.9 37059.0 37052.1 37045.3 37038.4 37031.5

-70 C

887.39 889.35

882.86 881.64 881.30 875.10 870.94 863.01 859.90 857.15 852.65 841.17 841.34 837.64 832.80 830.32 825.82 818.13 810.20 814.92 81'1.44 810.90 808.98 805.62 805.32 801.56 799.55 792.37 790.06 791.17 785.93 785.38

788.55 789.23 790.39 794.86 798.95 806.85 806.63 808.26 813. OS 815.04 816.43 813.40 804.43 799.88 797.24 790.74

-55 C

889.95 889.36 886.93 886.73 884.36 885.69 876.64 870.16 873.17 868.47 864.81 864.02 847.50 844.10 842.17 838.70 829.32 825.07 820.80 822.35 819.38 818.54 821.23 814.18 808.81 813.68 806.72 799.17 796.24 797.21 794.21 786.54 791.63 789.73 796.92 802.20 796.99 803.85 807.90 806.67 810.49 815.99 816.60 822.19 813.39 809.69 806.56 800.81 801.86 792.59

-45 C

880.49 887.29 883.51 881. 90 868.29 872.43 867.41 858.30 857.96

850.35 850.79

846.17

828.51 822.00 819.54 823.11 824.20

813.08 816.89 810.31

809.90 806.58 B05.04 794.55 796 .12 800.50 789.49 789.09 B03.63

800.77 790.52 807.81 802.43 811.86

B15.10 814.21 805.82 B07.06 806.17 793.00 7B5.84

-30 C

B92.73 892.46 B89.29 886.B2 Bn.58 877.79 B79.32 876.21 867.8B 866.75 862.06 856.62 B49.32 849.74 845.6B 840.13 836.97 831.B7 B25.43 823.03 B21.27 B17.8B 819.73 811 . B1 B11.45 80B.55 B04.B4 803.18 799.69 797.35 796.21 795.24 790.03 794.80 795. OS 800.26 798.62 802.58 809.30 815.54 817.50 817.05

813.28

809.28 807.16 792.85 787.43 788.10

o C

883.11 880.90 87B.94 881.48 875.38 871.27 870.70 866.53 865.91 858.32 854.49 851. OS 842.60 843.46 839.83 847.20 839.81 824.94 824.41 820.29 819.83 823.54 809.62 810.17 809.47 806.80 803.58 798.15 797.16 794.32 794.93 795.30 789.99 789.24 794.04 793.47 798.71 803.73 801.57 806.12 804.37 809.17 807.68 806.89 805.55 802.25 804.24 795.32 790.38 788.36

25 C

885.22 886.58 886.07 883.99 881. 37 879.07 876.40 876.25 870.23 865.05 861.94 860.68 855.83 851. SO 846.32 843.56 839.56 834.97 829.70 827.27 826.28 823.90 820.98 818.62 815.13 814.44 812.41 808.20 806.16 802.51 800.90 798.25 797.22 796.18 797.61 797.97 799.21 801.03 804.94 807.11 808.23 811.69 811.54 810.63 810.69 807.53 809.72 802.41 798.50 795.40

Fit of synthetic (quadratic coefs) spectra to Measured average spectra

Aver differemce Std dey of Dif 100*AveDif/AveXS

-1.90 1.47 -.23

2.30 2.89

.28

- 615-

-.21 4.09 -.03

1. 74 2.43

.21

-3.56 2.37 -.43

.54

.36

.07

July 9,1984 Page lOB

Coef's for quadratic T dependence; 25 C Measured and synthetic spectra

NH (air) CM-l(vac)

267.511 267.561 267.611 267.661 267.711 267.761 267.811 267.861 267.911 267.960 268.010 268.060 268.110 268.160 268.210 268.260 268.310 268.360 268.410 268.460 268.51.0 268.560 268.610 268.660 268.710 268.760 268.810 268.860 268.910 268.960 269.010 269.060 269.110 269.160 269.210 269.260 269.310 269.360 269.410 269.460 269.510 269.560 269.610 269.660 269.710 269.760 269.810 269.860 269.910 269.960

37370.5 37363.6 37356.6 37349.6 37342.6 37335.6 37328.7 37321.7 37314.7 37307.9 37301.0 37294.0 37287.0 37280.1 37273.1 37266.2 37259.3 37252.3 37245.4 37238.4 37231.5 17224.6 37217.6 37210.7 37203.8 37196.9 37190.0 37183.0 37176.1 37169.2 37162.3 37155.4 37148.5 37141.6 37134.7 37127.8 37120.9 37114.0 37107.1 37100.2 37093.4 37086.5 37079.6 37072.7 37065.9 37059.0 37052.1 37045.3 37038.4 37031.5

co

887.67 885.00 883.63 884.41 878.38 873.91 874.98 872.01 867.48 863.30 860.21 856.06 850.85 848.58 845.48 844.88 837.91 829.30 826.40 826.02 824.02 822.88 817.34 814.95 812.67 810.60 808.37 804.08 803.03 798.80 798.03 798.54 793.05 792.72 798.63 799.27 800.88 801.90 807.26 808.65 811 . 15 814.05 811.23 810.75 805.12 805.10 807.24 795.46 790.13 790.13

CUT)

-9.3797E-02 1.7341E-02 2.1380E-02

-2.3939E-02 5.1030E-02 1.0693E-Ol 2.2324E-02 1.0777E-Ol 8.0381E-02 3.3096E-02 1.11 59E-02 1.1008E-01 1.3144E-01 8.7885E-02 2.0406E-02 1.1560E-02 9.5611E-02 1.6467E-01 1.1919E-01 5.3421E-02 7.2143E-02 6.8385E-02 8. 1963E-02 9.4233E-02 7.9498E-02 1.0038E-01 1.0840E-Ol 1.0584E-01 9.4533E-02 1. 1128E-0 1 9.0316E-02 2.2289E-02 1.2688E-01 9.6334E-02

-3.0154E-02 -4.3228E-02 -2.7648E-02

8.1097E-03 -7.3357E-02 -3.8297E-02 -1.0019E-01 -7.7321E-02 -2.3295E-02 -5. 1436E-02

1.2026E-01 2.9753E-02 6.5561E-02 1.7941E-01 2.0692E-01 1.3714E-Ol

C2(T"2)

-1. 1454E-03 1.1206E-03 2.0872E-03

-3.8186E-04 1.8869E-03 3.3844E-03 4.9254E-04 1.3586E-03 7.6272E-04 3.3375E-04 2.2728E-04 1.7159E-03 6.7204E-04 1.9581E-05

-8.3983E-04 -2. 1971E-03 -5.9093E-04

1.6158E-03 9.5065E-05

-1.5899E-03 -3.5489E-04 -1.0578E-03

6.9907E-04 7.8357E-04

-2.4921E-05 1.0595E-03 8.11 75E-04 9.2180E-04

-2.6079E-04 3.5850E-04 1.8862E-04

-2.0998E-03 7.5211E-04 9.6562E-04

-1.6785E-03 -1.7735E-03 -2. 1122E-03 -1.2009E-03 -2.0817E-03 -1.1603E-03 -2.0302E-03 -1.7422E-03

5.1692E-04 8.5027E-04 4.0512E-03 2.0982E-03 6.2294E-04 3.7035E-03 4.8780E-03 2.3967E-03

Fi?ure 4

- 616-

25C(syn) 25C(Meas)

884.61 886.13 885.47 883.57 880.83 878.70 875.85 875.55 869.97 864.34 860.63 859.89 854.56 850.79 845.47 843.79 839.93 834.42 829.44 826.36 825.60 823.93 819.83 817.79 814.64 813.77 811.59 807.30 805.23 801.80 800.41 797.78 796.69 795.73 796.82 797.08 798.87 801.35 804.13 806.96 807.38 811. 02 810.97 809.99 810.66 807.16 809.27 802.26 798.35 795.06

885.22 886.58 886.07 883.99 881.37 879.07 876.40 876.25 870.23 865.05 861.94 860.68 855.83 851.50 846.32 843.56 839.56 834.97 829.70 827.27 826.28 823.90 820.98 818.62 815.13 814.44 812.41 808.20 806.16 802.51 800.90 798.25 797.22 796.18 797.61 797.97 799.21 801.03 804.94 807.11 808.23 811.69 811.54 810.63 810.69 807.53 809.72 802.41 798.50 795.40

NEW VALUES OF OZONE ABSOLUTE CROSS-SECTIONS IN THE

ULTRA VIOLET SPECTRAL RANGE AT 298 AND 228 K, BY A METHOD BASED UPON

PRESSURE MEASUREMENTS AT CONSTANT VOLUME.

J. MALICET ; J. BRION; D. DAUMONT

Unite Associee au CNRS 776 Spectrometrie Moleculaire et Atmospherique

U.E.R. Sciences - B.P. 347 51062 REIMS CEDEX - FRANCE

The main problem in the study of the stratosphere is to determine with accuracy the ozone trend, and its absolute total amount. This invol­ves a be tte r knowledge 0 f the cross-section be tween 300 and 350 nm at s tra­tospheric temperature.

Recently, we have determined ozone absolute cross-section in this spectral range at 298 and 228 K. The measurements were done with a Czerny­Turner monochromator (Focal length: 1.5 m - Grating: 2400 g.p.rnrn) cou­pled to a second low dispersion quartz monochromator to avoid the effect of the scattered light. The lines of iron hollow cathode lamp were used to calibrate the spectrum in the wavelengths unit. The standard deviation was found to be less than 0.005 nm.

Ozone was prepared by a ID2thod described by GRIGGS (1) and filled a 692 rnrn quartz absorption cell. The pressure of the gas mixtures (02 + 03 containing about 90 % of ozone) were choosen in the range 5 - 200 torrs. For such experiments the knowledge of the absolute total ozone amount contained in the absorption cell is fundamental. Therefore we have worked out a method using pressure me as ureID2n ts • At constant voluID2 and temperature, the partial pressures for ozone is given by :

P03 = 2 [(P02 )i - PTl (Po ). is the initial pressure filling the absorption cell bet6r~ ozonisation.

PT is the total pressure of the (03 + 02) mixture and was re­corded simultaneously with the absorption spectrum.

The relationship is based upon the reaction ->-

3 02 -<-

The method needs a special care with the experiID2nts and many tests were done for the same measureID2nts in order to minimize the error on the estimation of the final quantities.

The absolute cross-sections measureID2nts were carried out:

- at the five usual reference wavelengths of the ID2rcury lines (253.65 289.36; 296.73 302.15 and 334.15 nm)

Ozone Symposium - Greece 1984 - 617-

- in the continuous spectral range 320-330 nm. Several experiments were done (8) and the mean values were computed step by step (0.02 nm). The randon errors are about 1 to 3 %.

Continuous measurements in the range 220-230 nm

A comparison with the other recent data (BASS and PAUR (BAP)(2), FREEMAN (FRE) (3), MOLINA (MOL) (4) hi'.s been made

1°_ For the wavelengths calibration, it shows

- A very good agreement between BDM'sxand FRE's data.· The different between the two sets of measurements is nearly constant (0.0025 nm) in the spectral range 321.56 - 322.57 nm studied by FRE and is less than our standard deviation ; therefore we can be confident with the wavelengths calibration.

- A discrepency with the data of BAP and MOL (0.03 nm to 0.17 nm respectively.

2°_For the cross-sections, there is a good agreement in relative between the four data, if one takes account of the shift observed in wave­lengths for MOL and BAP. The ratio between the different data is nearly a constant for the whole spectral range (Fig. 1).

crBDiO"FRE = 0.990 O"BDM!O"BASS = 0.947 O"BDM!O"MOL = 0.944

I 0.03 nm

ABDM-AFRE =0.0025 nmjABDM-ABASS = 0.025 nm ABDM-AMOL = to 0.17 nm

Measurements of the mercury lines

In order to remove the problem of the wavelength calibration and in order to allow a better comparison of absolute values, measurements were done at the wavelengths of the mercury lines.

Among, the available data, we have choosen those (HEARN, BDM, FRE, MOL) which were obtained at the same mercury wavelengths and in simi­lar experimental conditions. Thus, BAP's relative data and the absolute val ues ob tained from continuous cross-sections curves (INN and TANAKA (5)) GRIGGS (1) - VIGROUX~(6)) have not been taken into account.

The comparison between the absolute data (Fig. 2) shows that our results are in agreement with those of FRE and H!ARN

- 2.7 % and 0" - 0"

BDM HEARN = _ 1. 4 % 0"

except at A = 253.6 nm. On the other hand, there is a large shift (mean value 5.8 %) with the results of MOL, particularly at 334.15 nm (8.2 %) * BDM = BRION, DAUMONT, MALICET

- 618-

N

E '!:'''

x

'" c o ~3 .. .. , '" '" ~ u

o 320

1.05

0.95

Fig L Companson between BDMand 8APresuils (T=298K)

Curve 1 BOM

Curve 2 BAP shifted O. 025nm

Curve 3 BAPxO.95 shifted O.025nm

322

FIg LComponson 01 the absolule vatues

a l the mercury wavelengths

326 328

._ MOL

Anm

---------./-- +SAP x O. 97 • ( r. lallv. values)

----" - ' -------- -------::,.,.,.---................ .. ......... ..... . ~.~.~~~-~ .......... ~ .......... + ........ ~ ...... ....... .. = .. =.~ --::: t. __ 4::.::::~~--- - - ---------- ..... HEARN .... -

250 260 270 2S0 290 300 310 320 330

- 619-

A (nm) HEARN BDM FREEMAN }1OLlNA }lean

253.65 I 114.7 ( Ill) * (110.3)* 115 114.85 ± 0.21 I

289.36 14.7 14.36 14.88 15.09 14.86 ± 0.31

296.73 5.971 5.83 5.97 6.12 5.97 ± o. 12

302.15 2.860 2.83 2.91 3.01 2.90 ± 0.08

334.15 0.0427 0.0428 0.0437 0.0463 0.0439 ± 0.0017

* Provi sional val ues. Not incl uded in the mean

Therefore, only the data of HEARN, FRE and BDM which are consis­tent- are used for the further comparisons.

A comparison with the relative BAP's measurements, calibrated at 253.65 nm with the HEARN's value (114.7.10- 19 cm2 ) shows a significant discrepancy between BAP and the others specially at 334.15 nm, where the deviation with HEARN is about 10.1%.

However, the results of BAP are consistent with the others if a multiplicative coefficient (0.97) is applied to his data; in this case the standard deviation between the four data sets (HEARN - BDM - FRE -BAP cOrrEcted) is minimum .

• Multiplicative coefficient 1 0.99 0.98 0.97 0.96 0.95 applied to relative BAP 's data

Standard Deviation 0.0246 0.0218 0.01850.0173 0.0176 0.018 e (x 10 19 cm2)

A (nm) 253.65 289.36 293.73 302.15

HEARN 114.7 14.7 5.971 2.860

BDM (Ill) * 14.36 5.83 2.83

BAP x 0.97 111. 27 14.55 5.89 2.85

FRE (110.3)* 14.88 5.97 2.91

Therefore, there is :

- A very good agreement (1.2%) for the four sets at A 296.7 and 302.1 nm.

-620 -

33 lf.15

0.0427

0.0428

0.0456

0.0437

289.3,

- A very good agreement (0.45%) for FRE, BDM and BAP (corrected values) at A = 253.6 nm. The agreement is not so good (1.8%) if the re­sults of HEARN are included.

- A difference between the results at 334.1 nm. It is notewortly, that in the same spectral range the records of BAP show a noise increasing when the wavelengths increase; therefore, this lack of accuracy can dis­turb the resul t at 334.15 nm.

It may be concluded that the data sets of HEARN, FRE, BDM and BAP (multiplied by 0.97) are very consistent if one excepts the value of HEARN at 253.6 nm and that of BAP at 334.1 nm.

This conclusion shows the necessity of a reinvestigation in order to remove

- the discrepancies at the 334.1 nrn wavelength which is the spec­tral range of a Dobson windows.

- the problem arising from the choice of the 253.6 nm wavelength as a reference line.

References

(1) GRIGGS, M.J., Chern. Phys. (1968) 49, p 857

(2) BASS, A.M. and PAUR R.J. (1981) IOC - WO/OACS, Reirns Meeting May 1984

(3) FREEMAN D.E., IOC - WO/OACS, Reirns Meeting May 1984

(4) MOLINA L.T. and MOLINA M.J., IOC - WO/OACS, Reirns Meeting May 1984

(5) INN E.C.Y. and TANNAKA Y., J. Opt. Soc. Amer. (1953) 43, p 870

(6) VIGROUX E. Ann. Phys. Paris (1953) 8, p 709 Ann. Phys. Paris (1967) 2, P 209

- 621-

ABSOLUTE ABSORPTION CROSS SECTION MEASUREMENTS OF OZONE

D.E. FREEMAN, K. YOSHINO, J.R. ESMOND and W.H. PARKINSON Harvard-Smithsonian Center for Astrophysics

Summary

Laboratory measurements of the absolute absorption cross section of ozone at the temperatures 195 K, 228 K and 293 K have been made at several discrete wavelengths in the region 281-335 nm. Our results for ozone at 293 K are in excellent agreement with those of Hearn [Proc. Phys. Soc. Lond. 78, 932 (1961)], who used a different tech­nique. Our absolute cross section measurements of ozone at 195 K have been used to put our recent relative cross section measurements [D:E. Freeman, K. Yoshino, J.R. Esmond and W.H. Parkinson, Planet. Space Sci. 32, 239 (1984)] on a firm absolute basis throughout the region 281-335 nm.

1. Introduction

In the usual method of determining the absolute cross section a(A) of a molecule, the formula In IOCA)/I(A) = NaCA) is used in '.;hich the measured quantities are the ratlo of the incident flux I (A) to that transmitted I(A) through the gas and the column density 9 of absorbing molecules. In the application to ozone the major difficulty has been that the ozone column density is generally not obtainable directly from meas­urements of the total pressure, because ozone is difficult to prepare free from oxygen and because it decomposes, especially under irradiation, into oxygen. However, we have found that, when special precautions are taken to prepare pure ozone and to prevent its subsequent decomposition, the column density can be obtained accurately from measurement of the total pressure, which can be used with measurements of the optical depth to yield accurate absolute absorption cross sections of ozone.

We have recently published cross section measurements of ozone at 195 K throughout the wavelength region 240-350 nm at a resolution of 0.003 nm (1). In that paper we first determine relative or provisional cross sections which are then put on an absolute basis by means of the following assymptions:

(a) The absolute cross section measurements of Hearn for ozone at room temperature at the mercury line wavelengths 253.7, 289.4, 296.8, 302.2 and 334.2 nm are correct.

Ozone Symposium - Greece 1984 - 622-

(b) The difference in cross section at 253.7 nm for ozone at 195 K and 293 K is negligible.

(c) The purity of ozone is unaffected by cooling it from 293 K to 195 K.

The reason for this procedure is that some ozone decomposes during the time required for extensive high resolution cross section scans. Therefore, these provisional cross section measurements must subsequently be adjusted for this effect by renormalization at a number of discrete wavelengths at which absolute ozone cross sections are known. Since the publication of our paper we have performed some absolute cross section measurements, with the result that our cross sections of ozone at 195 K throughout the wavelength region 281.4-334.2 nm are now absolute and inde­pendent of Hearn's determinations. This end was accomplished by develo­ping techniques for the preparation of pure ozone and for the measurement of its absolute cross section at several discrete wavelengths longer than 281 nm, and in some continuous narrow wavelength intervals (in regions where the cross section varies rapidly with wavelength).

2. Experimental Procedure

The general experimental arrangement has already been described, and only the differences required for the present absolute cross section de­terminations will be given. Ozone is prepared from pure oxygen at 77 K in a Tesla discharge, collected as liquid ozone at 77 K, and purified by pumping off residual oxygen from the ozone/oxygen mixture at 77 K. The ozone was, not stored on silica gel because silica gel adsorbs not only ozone but also some oxygen.

The fixed wavelengths used were set up with hollow cathode or mercury lamps and the photoelectric scanning detector was moved along the focal surface of the 6.65 m spectrometer (2) until the signal was maximized. Wavelength errors are estimated to be 0.0006 nm. The optical depth meas­urements were done with predispersed continuum radiation, of bandwidth 1 nm, from a xenon lamp (1).

The pressure of ozone, in the same 50 cm long cell used in our pre­vious work (1), was measured with capacitance manometers (MKS Baratron) which are accurate to ~ 1% in the static system. No pressure change was discernible during the time required for an optical depth measurement.

3. Results and Discussion

The present absolute cross section measurements of ozone at the tem­peratures 195 K, 228 K and 293 K at the mercury line wavlengths in the region 289-335 nm are listed in Table I, together with the room tempera­ture results of Hearn (3). From Table I it is evident that our cross section measurements at room temperature are, at the four mercury line wavelengths, in excellent agreement with Hearn's; the two sets of results are essentially identical, differing at most by 2.3% which is within the range of the mutual experimental errors. This agreement is striking in view of the differences in the experimental techniques used, and it pro­motes confidence in the validity of our results at the lower temperatures and at other wavelengths.

-623-

Another measurement of the cross section of ozone at room temperature at the mercury line wavelength 334.2 nm has recently been published by Daumont et al. (4). Their value is 4.8% lower than ours. We are also alvare of on-going determinations of ozone cross sections by other workers (5-7), but further comparisons are postponed until those results are pub­lished in final form.

REFERENCES

1. FREEMAN, D.E., YOSHINO, K., ESMOND, J.R. and PARKINSON, tv.H. (1984). Planet. Space Sci. 1£, 239.

2. YOSHINO, K., FREEMAN, D.E. and PARKINSON, W.H. (1980). Appl. Opt. ~, 66.

3. HEARN, A.G. (1961). Proc. Phys. Soc. Lond. 78, 932. 4. DAUMONT, D., BRION, J. and MALICET, J. (1983). Planet. Space Sci.

l!., 1229. 5. BRION, J., DAUMONT, D. and MALICET, J. Personal communication. 6. BASS, A.M. and PAUR, R.J. (1981). J. Photochem. 12, 141. 7. MOLINA, L. Personal communication.

TABLE I. ABSOLUTE ABSORPTION CROSS SECTIONS OF OZONE

Wavelength Hearn Present work Unit (vac. nm) (1961 )

292-295K 293K 228K 195K

289.445 1.47 1.49 1.40 1.40 10-18 2 cm

296.815 5.97 5.97 5.61 5.50 10-19 2 cm

302.238 2.86 2.91 2.65 2.58 10-19 2 cm

334.244 4.27 4.37 3.11 2.82 10-2l 2 cm

-624 -

ABSORPTION COEFFICIENTS OF OZONE FOR THE BACKSCATTERED UV INSTRUMENTS - SBUV, TOMS, AND BUV- AND

Summary

FOR THE DOBSON INSTRUMENT

K.F. Klenk, B. Monosmith and P .K. Bhartia Systems and Applied Sciences Corporation

5809 Annapolis Road, Hyattsville, Maryland 20784

Band averaged absorption coefficients are presented for the wavelength bands of the Nimbus-7 Solar Backscattered Ultraviolet (SBUV) and Total Ozone Mapping Spectrometer (TOMS) experiments, and the Nimbus-4 Backscattered Ultraviolet experiment using the recent laboratory ozone cross-section measurements at the U.S. National Bureau of Standards (NBS) by A. Bass and R. Paur being presented at this symposium. Also, coefficients for the Dobson bands are presented. The new coefficients based on the NBS data are compared with coefficients computed using earlier laboratory absorption measurements. For total ozone, we present the biases which will result if these new coefficients are adopted by IOC and used by the Dobson and satellite networks.

1.0 Absorption Coefficients in Current Use The BUV-satellite and Dobson networks are currently using coefficients

based on different laboratory measurements. Dobson: The Dobson network is currently using absorption coefficients

adopted by the International Ozone Commission in 1968 (1) which are based primarily on the 1967 Vigroux work. (2).

Nimbus-4 BUV: The Nimbus-4 Backscattered Ultraviolet (BUV) absorption coefficients are based on the 1953 Vigroux (3) and 1953 Inn and Tanaka (4) spectra. For the wavelengths used to derive total ozone (3125, 3175, 3312 and 3398A) Vigroux cross-sections at -440 C were used. For the shorter wavelengths used for profiling (3019 A and shorter), Inn and Tanaka cross-sections were used. The Inn and Tanaka coefficients were adjusted to -440 C using Vigroux temperature dependency measurements.

Nimbus-7 SBUV /TOMS: For the Nimbus-7 Solar Backscattered Ultraviolet (SBUV) and Total Ozone Mapping Spectrometer (TOMS), Inn and Tanaka adjusted to -440 C using Vigroux temperature correction factors were used in both the total ozone and ozone profile retrievals.

2.0 Comparison of Dobson and BUV Coefficients Obtained from Various Laboratory Spectra Table I compares the band averaged absorption coefficients for the Dobson

and Nimbus-4 BUV wavelengths and pairs for several sets of laboratory measurements of the ozone cross-section. The coefficients are computed for a temperature of -440 C. The Dobson and BUV pairs are defined as follows:

BUV: A: (3125, 3312), DOBSON: A: (3055, 3254),

B: (3175, 3390), B: (3088, 3291),

C: (3312, 3398) C: (3114.5, 3324), D: (3176; 3398),

where the wavelengths are given in Angstroms. Note that the A- and B- pair are defined differently for BUV and Dobson. Also, the wavelengths given above are nominal values. For the satellite experiments BUV, SBUV and TOMS the actual

Ozone Symposium - Greece 1984 - 625-

Tab

le I:

B

UY

and

Dob

son

Abs

oret

ion

Coe

ffic

ien

ts

VIG

RO

UX

· S

IMO

NS

· V

IGR

OU

X·

INN

&.

BA

SS &

**

WA

VE

LE

NG

TH

E

TA

L

TA

NA

KA

P

AU

R

RA

NG

E

NO

MIN

AL

19

53

1975

19

67

1953

19

84

(~S_IRAQTION)

DO

BSO

N

3055

1.

882

2.13

9 1.

863

1.99

9 1.

914

.14

3088

1.

287

1.4

1.27

6 1.

33

1.25

7 .1

1 31

14.5

.9

12

1.01

4 .8

5 .9

22

.867

9 .1

8 31

76

.391

.4

22

.377

.4

.3

810

.11

3254

.1

2 .1

23

.117

.1

23

.115

2 .0

7 32

91

.064

.0

87

.07

.075

.0

629

.34

3324

.0

47

.05

.043

.0

5 .0

385

.25

3398

.0

17

.021

.0

12

.017

.0

0971

.7

4

DO

BSO

N P

AIR

S A

1.

762

2.01

6 1.

746

1.87

6 1.

7988

.1

5 I

B

1.22

3 1.

313

1.20

6 1.

255

1.19

41

.10

a-.

N a-.

C

.865

.9

64

.807

.8

72

0.82

94

.18

I

D

.374

.4

01

.365

.3

83

0.37

13

.10

AD

1.

388

1.61

5 1.

381

1.49

3 1.

4275

.1

6 C

D

.491

.5

63

.442

.4

89

0.45

81

.25

BU

V 31

25

.705

6 .8

315

.664

.7

456

.698

.2

3 31

75

.392

3 .4

108

.378

.3

949

.377

.0

9 33

12

.073

5 .0

756

.07

.072

3 .0

6 .2

2 33

98

.018

7 .0

135

.017

.0

18

.013

.3

6

BU

VP

AIR

S A

.6

321

.755

9 .5

94

.673

3 .6

38

.25

B

.373

6 .3

973

.361

.3

769

.364

.1

0 C

.0

548

.062

1 .0

53

.054

3 .0

47

.28

• • lro

m K

lenk

, 19

80

(5).

B

and

cen

ters

-30

54.8

, 30

87.8

, 31

14.6

, 31

75.8

, 32

51.4

, 32

91.5

, 33

23.9

, 33

98.0

A

ngst

rom

s fr

om D

obso

n (1

2)

wavelengths are within 2 Angstroms of the nominal wavelengths. For D.obson, the actual band center wavelengths are also slightly different.

The ranges of the coefficients are given in the last column of Table I. The range is defined as the maximum value minus the minimum divided by the average. The coefficients at the shorter wavelengths of the BUV /Dobson pairs have a range of up to 23% and the longer wavelengths of up to 74%. The new measurements of Bass and Paur (6) are generally smaller than the previous measurements.

Table IT compares the Bass and Paur (BP) to the other 4 measurement sets from Table I. For the 4 Dobson single pairs and the 2 BUV pairs, the average of the ratio of BP to the other coefficients in Table I is shown in column 1 of Table IT. The range in the value of this ratio is given in the second column of Table IT. The BP coeffficients shows a very remarkably constant bias relative to Inn and Tanaka. The range in the ratio being only 2%.

Table IT: Average Ratio of BP to Others and Range of the Ratio

Vigroux 1953 Simons et al. 1975 Vigroux 1967 Inn and Tanaka 1953

A verage Ratio of BP to Others

For Pair Coefficients .99 .88

1.02 .96

Range in

Ratio --:Ii!

.11

.05

.02

3.0 Comparison of Coefficients Based on Bass and Paur to Coefficients Currently in Use

Table ill compares the coefficients which are currently in use (see Section 1.0) to those obtained with the BP cross-sections.

The BP based coefficients in Table ill are computed for the following conditions:

o Cross-sections for a temperature of -440 C were used o Komhyr's (7) best measurement of the Dobson band center and band­

pass shape were used o Dobson values are extra-terrestrial coefficients o BUV /SBUV /TOMS are effective coefficients as defined in Klenk (5).

The ratio of the BP coefficients to those in current use is shown in the last column.

The coefficient for the primary Dobson observation - AD double pair -increases by 4% which means that the Dobson AD ozone would be adjusted downward by 4% if the BP coefficient were-used operationally.

For the SBUV and TOMS, the BP coefficients are 3-6% smaller, which would increase the derived SBUV /TOMS ozone values if BP were adopted. For BUV the adjustments are different from thsoe for SBUV /TOMS because the coefficients for BUV in current use are based on Vigroux and not Inn and Tanaka as are the SBUV /TOMS coefficients.

4.0 Observational Biases Using BP Cross-Sections Current biases among Dobson and satellite UV measurements are

summarized in the following Table IV. The predicted biases using BP data are given as well.

- 627-

Table Ill: Absorption Coefficients for BUY, SBUY, TOMS and Dobson - Current and BP WAVELENGTH CURRENT BP (1984) RATIO

DOBSON 3055.2 3088.7 3114.6 3175.1 3250.2 3291.2 3324.0 3399.0

A B C D

AD CD

SBUY 3124.75 3174.69 3311.66 3397.95

A B C

BUY 3126.0 3176.3 3312.9 3399.3

A B C

TOMS 3124.24 3174.20 3311.58 3397.64

A B C

1.748 1.14

.8 .36

1.388 .44

.7601

.3999

.0727

.0176

.6874

.3823

.0551

.7056

.3923

.0735

.0187

.6321

.3736

.0548

.7717

.4023

.0728

.0176

.6989

.3847

.0552

1.926 1.246 .8727 .3805 .1149 .0648 .0398 .0109

1.8111 1.1812

.8329

.3696 1.4415

.4633

.7132

.3792

.0612 .011

.6520

.3682

.0502

.7011

.3729

.0581

.0118

.6430

.3611

.0463

.7189

.3805

.0614

.0108

.6575

.3697

.0506

Table IV: Observed Ozone and Projected Biases Using BP

Dobson CD: AD BUY B: Dobson AD BUY A: Dobson AD SBUY B: Dobson AD SBUY A: Dobson AD TOMS B: Dobson AD TOMS A: Dobson AD

Current 1.000 Ref. (8) 0.970 Ref. (11) 1.006 Ref. (11) 0.927 Ref. (13) 0.917 Ref. (10) 0.939 Ref. (13) 0.934 Ref. (10)

-628 -

BP 1984 0.986 1.042 1.027 1.002 1.007 1.016 1.032

1.04 1.04 1.04 1.03 1.04 1.05

.94

.95

.84

.63

.95

.96

.91

.99

.95

.79

.63 1.02

.97

.85

.93

.95

.84

.61

.94

.96

.92

5.0 Coefficients for the Satellite Vertical Profiling: Bands

Table V: Coefficients for BUY and SBUV Profile Wavelenghts

Wavelength BP Ratio to Current Temp BUV SBUV BUV SBUV BUV SBUV °c

2556.5 2555.75 134.4 134.5 1.043 1.042 ---:s 2737.0 2735.27 72.74 73.79 1.044 1.045 -5 2831.0 2830.16 34.45 34.67 1.044 1.044 -7 2877.0 2876.17 20.74 20.97 1.064 1.065 -10 2922.8 2922.04 11.97 12.08 1.056 1.057 -14 2976.4 2974.99 5.796 5.915 1.031 1.033 -22 3020.5 3018.84 3.172 3.239 1.023 1.022 -29 3059.1 3057.83 1.836 1.859 .961 0.961 -42

The BP coefficients in Table V were computed for ozone weighted temperatures given in the last column.

Calculations have been done to determine the change in profile shape which results when Bass and Paur coefficients are used in place of the coefficients currently used for SBUV retrievals. For a mid-latitude profile of 325 Dobson units total ozone, the change in profile shape is shown for a series of solar zenith angles in Figure 1.

Figure 1. Change in the derived SBUV profile due to adoption of the Bass-Paur cross-sections.

..

0 . ' 0 .0

07

'0

.! '-5 ~ i 20

" .. 3 .0

U 4 ,0

! ~o

~ 10 o ~ 100

\ 5 .0

.00

EFFECT OF BASS ABSORPTIOH eOEF'FICIENT8 ON SBUV PROF1lE

30.0

.0.0L.......----'"~--'-...J....:.!.U....-I-_'__.L.-o.......J

REFERENCES - 18 - 12 -e - 4 0 4 a 12 Ie 2Q 2'4

PERCENT CHANGE IN OZONE: " ,A.

1. IOC, IAMAP, Report of Proceedings, Publ. IAMAP 14 (IOC, Toronto, 1968), p. 18. 2. E. Vigroux, Ann. Phys. (Paris) 2, 209 (1967). 3. E. Vigroux, Ann. Phys. (Paris) 8, 709 (1953). 4. E. C. Y. Inn and Y. Tanaka, J. Opt. Soc. Am. 43, 870 (1953). 5. K. F. Klenk, Appl. Op. 19, 236-242 (1980). 6. A. Bass and R. Paur, this conference (1984). 7. W. Komhyr and C. Mateer, private communications. 8. C. L. Mateer, Proc. Quad. Inter. Ozone Sym., Boulder, Col. p. 1-8 (198{)j and

private communication. 9. G. M. B. Dobson, Q. J. R. Meterol. Soc. 89, 409 (1963). 10. P. K. Bhartia et al, J. Geophys. Res 89, 5239-5247 (1984) 11. K. F. Klenk et aI, J. Appl. Meteor, 21, 1672-1684 (1982) 12. G.M.B. Dobson, Ann. Intl. Geophys. Year 5,46 (1957) 13. Ozone Processing Team, NASA, private communication.

- 629-

MESURE DE L I ABSORPTION PAR LA HAUTE A'IMOSPHERE DANS LE ~ DE LONGUEURS D'ONDE DE LA "FENETRE A'IMOSPHERIQUE" AU VOISINAGE DE 200 nm

M. PIRRE*, P. RIGAUD et D. HUGUENIN-~-::­

Laboratoire de Physique et Chimie de l'Environnement 3A, Avenue de la Recherche Scientifique

45045 ORLEANS CEDEX FRANCE

-::- Uni versite d' ORLEANS -:HcObservatoire de GENEVE

The atmospheric absorption in the Herzberg continuum has been measured at stratospheric altitudes over AIRE sur L'ADOUR (FRANCE). The ozone column content was deduced from the measurement of the absorption between 278 and 289 nm and used together with the atmospheric absorption to derive the absorption cross-sections of O2 from 200 to 220 nm. The results do not confirm the lowest values obtained recently in the stratosphere and at the laboratory. However they are consistent with the other measurements but the largest ones. A comparison of the labor.atory measurements with in situ measurements suggests that the laboratory measurements of SHARDANAND and PRASAD RAO (1977) or those of OGAWA (1971) are the most likely.

Introduction

L'aborption atmospherique dans le continuum de Herzberg est d'une importance fondamentale pour la chimie de la moyenne atmosphere. En effet entre 200 et 242 nm l' absorption atmospherique est a l' origine de la creation de l'ozone par l'intermediaire de la reaction 0 + O2 + M~ + M. De plus dans la fenetre atmospherique comprise entre 200 et 210 ~ les faibles sections efficaces d' absorption de l' oxygene moleculaire et de l' ozone permettent au rayonnement solaire U. V . de p6netrer tres profondement dans l'atmosphere et de photodissocier les constituants minoritaires provenant de la pollution anthropogenique tels que les molecules de freons.

Un grand nombre de mesures de la section efficace de O2 ont ete effec­tuees dans cet intervalle de longueurs d'onde, tout d'aboril en laboratoire (DITCHBURN et YOUNG, 1962), (HASSON et NICHOLLS, 1971), (OGAWA 1971) et (SHARDANAND et PRASAD RAO, 1977 ) puis beaucoup plus recemment dans l'atmosphere a partir de nacelles stratospheriques (FREDERICK et MENTALL, 1982) HERMAN et MENTALL (1982) et ANDERSON et HALL (1983). Des mesures dans l' atmosphere avaient ete egalement effectuees a partir cIu sol des 1940 (VASSY, 1941). Toutes les mesures jusqu'en 1977 etaient compatibles a ± 20 % et comprises entre les plus basses obtenues par SHARDANAND et PRASAD RAO (1977 ) et les plus hautes obtenues par HASSON et NICHOLLS (1971) .

Ozone Symposium - Greece 1984 - 630-

Recemment les mesures effectuees a partir de nacelles stratospheriques semhlent montrer que les sections efficaces pourraient etre, suivant les auteurs, beaucoup plus faibles (HERMAN et MENTALL, 1982) ou plus faibles ou egales a celles de SHARDANAND et PRASAD RAO (FREDERICK et MENTALL, 1982), (ANDERSON et HALL, 1983). Il est a noter que ces faibles va leurs semblent confirmees par de tres recentes mesures en laboratoire (CHUENG et al., 1984).

Si celles-ci etaient definitivement confirmees les modeles (BRASSEUR et al., 1983) indiqueraient une augmentation de la photodissociation de composes minoritaires tels que CF C13 , CF 2C12' N20 et HNO, dans la basse stratosphere, ce qui tendrait a reconcllier les mddeles et les observations, mais en revanche indiqueraient une diminution de la concen­tration d' ozone entre 40 et 50 km ce qui augmenterait l'incompatiblite entre ces memes modeles et la majorite des observations.

Nous avons recemment soumis au G.R.L., un papier present ant des resultats de mesures de ces sections efficaces entre 200 et 220 nm effectuees a bord d'un ballon stratospherique muni d'un clapet, de nuit, au cours du plafond et de la descente lente (PIRRE et al., 1984). Les resultats que nous resumons plus loin indiquent des valeurs plus elevees que celles de HERMAN et MENTALL (1982) et de CHUENG et al. ( 1984) mais compatibles avec la plupart des aut res mesures aussi bien celles effectuees en laboratoire que celIe effectuees dans I' atmosphere. Elles sont cependant inferieures aux plus hautes va leurs obtenues en laboratoire par HASSON et NICHOLLS (1971).

Les va leurs mesurees dans la stratosphere sont necessairement fortement imprecises pour des longueurs d'onde superieures a 210 nm car l'absorption par l'ozone devient alors preponderante. Dans ces conditions, de faibles incertitudes dans la determination de la quantite integree d'ozone entrainent de grandes incertitudes sur les sections efficaces d'absorption de 02' Dans Ie but d'utiliser ces sections efficaces dans des modeles nous avons ete amenes en consequence a rechercher l'ensemhle de va leurs Ie plus probable, obtenu en laboratoire.

Description de l'experience et principallX resultats

Le vol a eu lieu dans la nuit du 13 au 14 mai 1983 au dessus de AIRE SUR L' ADOUR (FRANCE). Les mesures utilisees ont ete obtenues entre 2114 : 51 et 2400 : 40 T. U. au cours du plafond a une pression variant entre 3,66 mh et 3,85 mh et d'une descente lente jusqu'a 4,28 mh.

La mesure de I' absorption atmospherique etait effectuee grace a un appareillage Mcrit precedemment (RIGAUD et al., 1983). Il comprend un telescope Cassegrain de 20 cm d'ouverture, un monochromateur Jobin Yvon DH 10 controle par un moteur pas a pas qui permettait de mesurer Ie spectre par pas de 2 A a la vitesse de 1 nm/s entre 187 et 289.4 nm, avec une resolution de 1 nm. Le detecteur est un photomultiplicateur bialcalin avec une fenetre en quartz, utilisee en comptage de photons.

La source de lumiere utilisee etait I' etoile a Lyr dont I' angle zenitale a varie de 63 0 a 34 0 ,6 au cours des mesures que nous presentons ici.

Le spectre entre 278 et 289,2 nm a tout d' abord ete utilise pour determiner la quantite integree d'ozone en fonction de la pression. Pour determiner cette quantite nous avons eu besoin des sections efficaces d' absorption de 0 1 _ qui sont relati vement bien connues dans ce domaine de longueurs d'onde.~ous avons utilise les va leurs donnees par INN et TANAKA ( 1959) corrigees pour tenir compte des variations avec la temperature

- 631 -

comme indiquee par VIGROUX (1953) et celIe de BASS et PAUR (1981) a 243 K. En utilisant les valeurs moyennes nous avons montre que la quantite d'ozone peut s'ecrire :

N(03' P) = N(03' Po) x (p/po )HP/ H0 3

ou 17 2 17 2 = 3,93 10 em ± 0,~5.10 em pour P o =3,77mb

HO = 4,85 ± 0,45 km, Pest la pression et H la hauteur de reference moyedne de la pression entre les niveaux P et POP

Ces va leurs sont tres proches du profil moyen de KRUEGER et MINZNER (1976), elles sont cependant legerement inferieures aces dernieres. Les incertitudes proviennent principalement de l'imprecision sur la derive en longueur d' onde (:+: 2 A).

En utilisant les valeurs de la quantite integree d' ozone nous avons alors pu deduire les sections efficaces d' absorption de 03 entre 220 et 235 nm et celles de 02 entre 200 et 220 nm. Dans Ie dernier cas on a admis que les sections efficaces de ° donnees par INN et TANAKA (1959) etaient excates. Nous avons represente f'intervalle de confiance de nos mesures de la section efficace de ° sur la figure 1 ainsi que des points experimentaux obtenus par d,zautres auteurs. II faut y ajouter la mesure obtenue par BREWER et WILSON ( 1965) qut est 8 % inferieure a celle de SHARDANAND et PRASAD RAO (i977) a 2100 A, celles de FREDERICK et MENTALL (1982) entre 2000 et 2100 A qui sont 7 a 15 % + 10 a 15 % plus faibles que ces dernieres, celles de ANDERSON et HALL (1983) qui sont en m~yenne superietITes de 5 % ± 30 % a celles de HERMAN et MENTALL entre 203 et 207 nm et celles de CHUENG et al. (1984) qui sont identiques aces dernieres a 200 nm mais inferieures de 20 % :+: 18 % a 204 nm.

~18~------__ ~ ________ ~L-________ L-________ ~ __ ,-

.~ 'I 1

~

200

Figure 1.

+ t

_ Vou., A. II04'. ... Oitchbu,." III You " IJ[1~61 )

• Hallon.1 Nh:holhl1911 I • °90wahD711 o Shordal'lo",cI ,,' Aaoh9n) t H ..... mon lit Mentall [1gal)

Intervalle de confiance des sections efficaces d'absorption de 02 mesurees par PIRRE et al. ( 1984) . D' autres mesures sont indiquees par differents symboles.

-632 -

Discussion

Les mesures en laboratoire de SHARDANAl"lD et PRASAD RAO (1977) et celles de OGAWA (1971) sont pratiquement identiques entre 200 et 210 nm. Elles sont de plus, si l' on tient compte des incertitudes indiquees par les auteurs, compatibles dans ce domaine de longueurs d'onde avec les mesures in situ de BREWER et WILSON (1965), FREDERICK et MENTALL (1982), ANDERSON et HALL (1983) et PIRRE et al. (1984). Les mesures de HASSON et NICHOLLS (1971) en revanche sont compatibles avec aucune des mesures in situ tandis que celles de DITCHBURN et YOUNG (1962) ne Ie sont qu I avec celles de VASSY (1941) et PIRRE et al. (1984). Quand aux tres recentes mesures de CHUENG et al. ( 1984) qui ne sont encore que partielles (les sections efficaces n'ont ete calculees que pour des longueurs d'onde inferieures a 204 nm), elles semblent compatibles avec les mesures de HERMAN et MENTALL (1982) et de Al"lDERSON et HALL (1983). II faut remarquer cependant que les sections efficaces de HERMAN et MENTALL (1982) sont quasiment constantes entre 200 et 210 nm alors que celles de CHUENG et al.· (1984), confirmant en cela les autres mesures, decroissent regulierement entre 200 et 204 nm. La compatibilite entre ces deux ensembles de valeurs n'est donc pas encore totalement prouvee. Dans ces conditions nous pensons quia l'heure actuelle les mesures de SHARDANAND et PRASAD RAO (1977) ou de OGAWA (1971) sont les plus probables et devraient etre utilisee dans les modeles. II est clair cependant que d'autres mesures sont necessaires pour confirmer ou infirmer cette hypothese.

Conclusion

Des mesures de l' absorption atmospherique effectuees a partir d 'lU1e nacelle stratospherique nous ont permis de determiner les sections efficaces de O2 entre 200 et 220 nm. Ces valeurs sont plus elevees que les faibles va leurs presentees recenunent par HERMAN et MENTALL (1982) et CHUENG et al. (1984). Elles sont cependant compatibles avec la plupart des autres mesures, exceptees les plus elevees donnees par HASSON et NICHOLLS (1971). En comparant l'ensemble des mesures effectuees en laboratoire avec celles obtenues in situ, nous pensons qu I actuellement les mesures de SHARDANAND et PRASAD RAO (1977) et celles de OGAWA (1971) sont les plus probables.

Bibliographie

ANDERSON, G.R., and L.A. hall, Attenuation of solar irradiance in the stratosphere Spectrometer measurements between 191 and 207 nm ~ Geophys. Res., 88, 6801-6806, 1983. BASS, A.M., and R.J. PAUR, Ultraviolet absorption cross sections of 0 : The temperature dependance, Upper Atmos. Prog. Bull. 81-4, fed Aviat~on Admin., Washington, D.C., 1981. BRASSEUR G., A. DE RUDDER, and P.C. SIMON, Implication for stratospheric composition of a reduced absorption cross section in the Herzberg continuum of molecular oxygen Geophys. Res. Lett, 10, 1, 20-23, 1983 BREWER, A.W., and A.W. WILSON, Measurements of solar ultraviolet radiation in the stratosphere, Quart. J. Roy. Met. Soc., ~, 452-461, 1965.

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CHUENG, A.S.C., K. YOSHINO, W.H. PARKINSON, and D.E. FREEMAN, Herzberg continuum cross section of oxygen in the wavelength region 193.5 - 204.0 nm : New laboratory measurements and stratospheric implications, Geophys. Res. Lett., 11, 6, 580-582, 1984 DITCHBURN, R.W., and P.A. YOUNG, The absorption of molecular oxygen between 1850 and 2500 A, J. Atmos. Terrest. Phys., 24, 127 - 139, 1962. FREDERICK, J.E., and J.E. MENTALL, Solar irradiance~n the stratosphere: implications for the Herzberg continuum absorption of O2, Geophys. Res. Lett., 9, 461 - 464, 1982 HASSON, -V., and R. \1'. NICHOLLS, Absolute spectral absorption measurements on molecular oxygen form 1640 - 1920 A, 2, Continuum measurements 2430 -1920 A, J. Phys. B, 4, 1789 - 1797, 1971. HERMAN, J.R., and J~. MENTALL, O2 Absorption cross-section (187-225 nm) from stratospheric solar flux measurements, J. Geophys. Res., 87, 8967 -8975, 1982. INN, E.C.Y., and Y. TANAKA, Ozone absorption coefficients in the visible and ultraviolet regions, Adv. Chem. Ser., 21, 263 - 268, 1959. KRUEGER, A.J., and R.A. ~rrNZNER, A mid-latitude ozone model for the 1976 U.S. standard atmosphere, J.Geosphys. Res., ~, 4477 - 4481, 1976. OGAWA, M., Absorption cross sections of O2 and CO2 continua in the Schumann and far UV regions, J. Geophys. Res., 88, 1463-1467, 1983. PIRRE M., P. RIGAUD, and D. HUGUENIN, New in situ measurements of the absorption cross section of 02 in Herzberg continuum, soumis a Geophys. Res. Lett. 1984 RIGAUD, P., J . P. NAUDET, and D. HUGUENIN, Simultaneous measurements of vertical distributions of stratospheric N03 and 03 at different periods of the night, J. Geophys. Res., 88, 1463-1467, 1983 SHARDANAND, and A.D. PRASAD RAO, collision-induced absorption of ° in the Herzberg continuum, J. Quant. Spectroc. Radiat. Transfer, .!Z., ~33-439, 1977 VIGROUX, E., Contributions a I' etude experimentale de I' absorption de 1 'ozone, Ann. Phys., ~, 709-762, 1953. ~·.~SSY, A., Sur l'absorption atmospherique dans 1 'ultra-violet, These, 61 pp, iaculte des Sciences de l'Universite de Paris, 26 Mars 1941.

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THEORETICAL N2-. 02-. AND AIR-BROADENED HALFWIDTHS OF OZONE CALCULATED BY QUANTUM FOURIER TRANSFORM THEORY WITH REALISTIC COLLISION DYNAMICS.

Robert R. Gamache. The Center for Atmospheric Research. The University of Lowell. Lowell. MA 01854 USA Richard W. Davies. GTE/Sylvania Laboratories. Waltham. MA 02154 USA Laurence S. Rothman. Air Force Geophysics Laboratory. Hanscom AFB. Bedford. MA USA

Abstract We have evaluated collision broadened halfwidths of ozone with nitrogen. oxygen. and air as the perturbing gases. We show that it is important to consider more realistic collision dynamics in the calculations. By replacing the classical path trajectories by linear trajectories with constant velocities chosen to give the equations of motion exact to first order in time we develop the interruption function in terms of the actual distance of closest approach determined by the intermolecular potential and the velocity at this point. This improvement to the theory results in halfwidths which are in good agreement with experimental measurements. The temperature dependence of the halfwidth has been determined for 126 transitions for N~-broadening and for 10 transitions for O~-broadening. Comparison with experimental measurements is given.

Because of its importance to our planet. the nature of ozone in the atmosphere must be well understood. One of the more powerful methods to study atmospheric ozone and monitor its concentration is infrared remote sensing of total column density and concentration-altitude profiles. To implement remote sensing techniques an accurate knowledge of the wavenumber. intensity. and collision broadened halfwidth of ro-vibrational transitions is necessary. Unfortunately most spectroscopic studies have concentrated on obtaining wavenumbers ..• strengths. and assignments. Relatively few studies have reported collisional broadened halfwidths of ozone (1-5). Together they total some hundred and fifty transitions only. - -

For ozone some theoretical calculations of collision broadened halfwjdths have been performed (~-!). The calculations are difficult owing to the types of inte~actions that must be considered for ozone. In the first two studies (6-7) the molecular quadrupole constants were not well known. producing i~a;curate results. The last study (8) did use improved quadrupole moment components. however only ten transitions were studied. In all of these studies the classical path Anderson-Tsao-Curnutte (ATC) method was used to determine the halfwidths. and the corresponding pressure shifts were not evaluated. We have performed conventional ATC calculations on =135 transitions which have been experimentally studied and find the theoretical values some 20 to 35' too low. In order to better interpret infrared remote sensing results for ozone, collision broadened halfwidths must be determined more accurately and for a broad range of transitions.

Ozone Symposium - Greece 1984 -635 -

In this paper we report halfwidths and shifts for N~- and O~-, and air- broadening of ozone calculated by the ATC method and by the quantum Fourier transform (QFT) method with improved dynamics, ATC-ID and (QFT-ID) respectively. These theories are refined to consider more realistic collision dynamics than those obtained from classical straight path trajectories and yie ld much better agreement with experiment. The application of approximate trajectories in binary collision calculations was first done by Tipping and Herman (9). Their method and extensions of the method have been applied by Bonamy el. al. (10) and by Berard and Lallemand (!!). In all studies, improved results were ob-tained using these methods.

2. THEORY

In Reference 12 a complete description of the QFT-ID theory is given, here we summarize the main features of the theory. As a starting point we take the classical path ATC method or QFT method which considers an anisotropic interaction between the radiating and perturbing molecules which is treated in the usual second order perturbation theor.y. As an improvement in the theory we cons ider approximate traj ector ies which better represent actual trajectories and which are described by an isotropic potential. Here as in other works (9-11) which use approximate trajectories a Lennard-Jones potential is used. The resulting equations of motion can be solved by expanding in a time series (t=O at r=the distance of closest approach) and evaluating the integrals numerically. For ozone-perturbing gas systems this approach is too difficult and time consuming so we must rely on approximations.

The approach adopted here is to use linear trajectories with constant velocities chosen such that the equations of motion are correct to first order in time. This corresponds to replacing b (impact parameter) and v in the interruption function by the distance of closest approach rc and the relative velocity at this point Vc as determined from the potential. This is shown in figure 1 where the classical path at b (straight solid line) is related to the first order in time trajectory at rc (straight dashed line) by the actual trajectory (curved line) determined by a potential.

Figure 1 Comparison of classical path, first order in time and actual trajectories.

Before the interruption function can be evaluated the classical parameters b and v must be related to the distance of closest approach rc and the relative velocity vc' This is accomplished through the equations for conservation of energy and momentum in the collision.

-636 -

3. CALCULATIONS

We have performed calculations via QFT-ID theory on the O,-N~ and 0,­O2 systems. In these calculations we have considered the dipole(O,)­quadrupole(N~ or O~) interaction(d-q) and the quadrupole(O,)-quadrupole(N~ or O~) interaction(q-q). Explicit vibrational dependence was taken into account for the ground. 111 and II, states of ozone using very accurate Hamiltonian constants for these states (12). The molecular constants used in the calculations are given in Ref. 12 a~- are in all cases reproducible and confirmed by several studies. In all calculations. the d-q and q-q interactions arising from Anderson's S~middle term were also included. For the QFT theory. as in ATC theory. the numerical coefficients for the middle term are just twice those given for the outer terms. The asymmetric quadrupole moment of 0, was included using precisely the same formalism as developed by Yamamoto and Aoki (~). and our definition of quadrupole moment components is identical to theirs.

In all calculations the temperature was fixed at 296 K. The QFT scaling parameter. a. was adjusted to give the best fit to the theoretical halfwidth of three transitions computed using the ATC method.--iiiciudiiig velocity averaging. Thus the theories are on the same footing with no experimental bias in the QFT results.

4. DISCUSSION AND CONCLUSION

The assumption of linear trajectories with a constant velocity chosen to give the equations of motion correct to first order in time has produced results for N~- and O~-broadening well within 10% of experiment. For N~ as the perturbing gas we can compare our results with 127 experimental measurements from Refs. 3 and S. The average percent error for the QFT-ID calculations was 8.4% with a standard deviation of the halfwidths of 0.0086 cm- 1 • A better comparison of the two theories can be obtained by using only the data of Meunier. Marche. and Barbe which conta ins error bars for each measurement and is more accurate than that of reference S. In figure 2 we present a comparison of the QFT-ID and velocity averaged ATC-ID N2 -broadened result with the 9 111 +11, lines studied. The average absolute percent difference (AAPD) from the QFT-ID results compared with experiment is 2.3% with a maximum difference of 4.2%. As presented above. the comparison with the complete set of 127-transitions studied does not give as good agreement. however the accuracy of most of this data is ±10% whereas the accuracy of Meunier et. al. for N2-broadening is better than ±4.4%. We note most of the QFT-ID results are within or close to the error bars on the measurements of Meunier et. al •• with the largest discrepancy observed being just under 0.003 cm- 1 /atm.

In addition to the N~-broadening. the work of Meunier et.al. contains results for O~- and air-broadening as well. We present a comparison of our calculations with experiment in Figure 3 for O~ as the perturbing gas. and in Figure 4 for air-broadening. For O~-broadening Meunier et. al.'s results are accurate to 8.8%. Our QFT-ID results have an average absolute percent difference of 7.3% with the largest discrepancy being 15.6%. The QFT-ID results are quite satisfactory considering the nature of the O~-broadening

calculations. Although the air-broadening results of Meunier et. a1. does not list error bars. one can estimate the accuracy to be slightly greater than S%. the QFT-ID results agree very well with the measurements. 2.0% AAPD with a 3.9% maximum difference.

A final parameter derived from this study is the ratio of air broadening to nitrogen broadening. the usefulness of this parameter arises

-637 -

from the method in which air-broadened results are usually generated, i.e . N2-broadened results are calculated and then scaled to air-broadened values. This method saves the time necessary to calculate 02-broadened results and is sometimes necessary since the results for 02 calculations are more questionable. From the calculations for the 127 transitions, we find a very constant air/N2 ratio with an average of 0.95 and a standard deviation of 0.0056. This compares well with Meunier et. al . 's value of 0.94 .

~

Ii

"'":IE U

l:

E i '.';

" l:

007~

T

X

0070

1

O.06~ + +

O~ l

Figure 2

"

Figure 3

• t • •

+ + +

+ +

3 5 8 9 TRANSITION

RESlA.TS FOR NITlIOGf;N - 8R0A0ENI'IG

Comparison of QFT-ID, ATC-ID, and for N2-broadening.

, L~_ , , . . , .

t iUJdl lOl

- MEUNIER ET AL

• -QFT-IO

+ -ATC-IO

I., I -2~1 24 261 2~

2 - 23 8 I~ 24 8 16

3 - 20 1110 21 I I II

1 • - 24 ~ 20 25 ~ 21

:iI- 23 7 16 24 7 11

6-2.42125422

7- 2~ 0 2~ 26 0 26

8 - 243 222~~ 23

9 - 23 6 17 24 6 18

experimental results

.- W(Uroo(JIII[ I ""

'. U" ~ ~ • .to

. - 2"$ lOa,,,,. $ - l ,,,,.. ,, ,

Figure 4

Comparison of QFT-ID, ATC-ID, and experimental results for 02- and air­broadening respectively.

-638 -

We have studied the temperature dependence of 125 transitions of 0 3

broadened by N2 and 10 transitions broadened by O2• The transitions were chosen to consider a wide range of J". Ka"' and to compare with experiment when possible. Nine temperatures were studied for N3 broadening from 200-1000 K and nine for 02 broadening fron 171-500 K. The temperature dependence is given by the exponent n in the formula

(1)

We have calculated n for each transition and find for N3-broadening an average value of ii=0.77(0.04) (We note that one line did not give a value close to the average). For O2 broadening we find an average of ii=I.08(0.04). These values compare well with the value of n reported in Ref 13 for N2 -

broadening (0.71) and with the value of n reported in Ref 14 for O2 -

broadening (1.3). however Ref 13 gives a value of n of 0.30 for O2 -

broadening. Our values also compare well with the theoretical values from ATC calculations reported in reference 8.

REFERENCES 1. M. Lichtenstein. J.J. Gallagher. and S.A. Clough. J. Mol. Spectrosc.

40. 10(1971). 2. J.M. Hoell. C.N. Harward. C.H. Bair. and B.S. Williams. Optical

Engineering. May/June (1982). 3. C. Meunier. P. Marche. and A. Barbe. J. Mol. Spectrosc. 95. 271(1982). 4. S. Lundqvist. J. Margolis. and J. Reid. Appl. Opt. 21. 3109(1982). S. J. Margolis. J. Quant. Spectrosc. Radiat. Transfer 29. 539(1983). 6. G. Yamamoto and T. Aoki. J. Quant. Spectrosc. Radiat. Transfer 12.

227(1972) • 7. G.T.D. Tejwani and E.S. Yeung. J. Chem. Phys. 63. 1513(1975). 8. J.-Y. Mandin. J.-M. Flaud and C. Camy-Peyret. "Calculs de Coefficients

d'Elargissement de la Molecule D'Ozone." Final Report. CNRS.Baitment 221. Campus d'Orsay. (1983).

9. R.H. Tipping and R.M. Herman. J. Quant. Spectrosc. Radiat. Transfer 10. 897(1970). and references therein.

10. J. Bonamy. L. Bonamy. and D. Robert. J. Chem. Phys. 67. 4441(1977). 11. M. Berard and P. Lallemand. J. Quant. Spectros. Radiat. Transfer 19,

387(1978) 12. R.R. Gamache and R.W. Davies."Theoretical N2-. O2-, and Air-Broadened

Halfwidths of Ozone Calculated By Quantum Fourier Transform Theory with realistic Collision Dynamics." submitted to J. Mol. Spectrosc. July(1984) •

13. J.M. Colmont and N. Monnanteuil. J. Mol. Spectrosc. 104. 122(1984). 14. A. Barbe. P. Marche. C. Meunier and P.Jouve. J. Physique 44(1983).

ACKNOWLEDGEMENI'S We would like to acknowledge the following colleagues for stimulating

discussions and for their encouragement; S. A. Clough. and R. H. Tipping. This work was supported by the Air Force Office of Scientific Research

through AFGL task 231061.

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ALTITUDE RESOLVED MEASUREMENTS OF THE N20 PHOTOLYSIS FREQUENCY

IN THE STRATOSPHERE

ABSTRACT

W. Hans, C. Kessler and U. Schurath Institut f. phys. Chemie der Universitat Bonn

Wegelerstr. 12, D-5300 Bonn, FRG

A balloon-borne continuous actinometer is described which measures the photolysis frequency of N20 in the stratosphere with 2 min time re­solution. The instrument was launched as part of the MAP-GLOBUS cam­pagne from Aire sur l'Adour, France. An experimental profile is com­pared with model calculations based upon different absorption cross sections of oxygen in the Herzberg continuum.

INTRODUCTION N20 plays a key role in ozone chemistry since its reaction with ex­

cited atomic oxygen, O(lD), is the dominant source of odd nitrogen in the stratosphere. The N20 source is in the troposphere, where the gas is stable and its mixing ratio is almost constant. N20 is destroyed in the strato­sphere by photolysis below 220 nm, and to a lesser extent «10 %) by reaction with O(lD), which results in the formation of 2 NO molecules with 62 % probability. Accordingly, the vertical profile of N20 is only depen­dent on the upward flux through the tropopause, the photolysis rate, the reaction with O(l D), and on vertical mixing. Vertical eddy diffusion coef­ficients for one-dimensional models have in fact been obtained from experi­mental N20 profiles. This requires the photolysis frequency, and thus the photon flux in the stratospheric window between 190 and 230 nm,to be calculated from the extraterrestrial solar flux and the optical properties of the atmosphere. The solar flux is relatively well known. Its penetration into the stratosphere, above the onset of strong Schuman-Runge absorption at 190 nm, and below the onset of the Hartley band of ozone, is governed by oxygen absorption in the Herzberg continuum which is extremely weak and difficult to measure. Recent laboratory and field investigations strongly suggest that absorption cross sections in the Herzberg continuum are sub­stantially lower than previously assumed (1). The impact of lower cross sections on model calculations, and on photolysis frequencies in particular, has recently been examined by Brasseur et al. (2).

Altitude resolved measurements of the N20 photolysis frequency which are presented below provide a sensitive means of validating actinic flux calculations. N20 is the prototype of several other trace compounds such as the chlorofluoromethanes which are also predominantly destroyed by photo­lysis in the stratospheric window.

EXPERIMENTAL The actinometer had to be flown pick-a-back on gondolas of other

experimenters which imposed a weight limit of not more than 40 kg, includ­ing batteries and cryogens. This restriction required certain technical simplifications. The principle of operation and the essential parts of the actinometer are depicted in figure 1:

Ozone Symposium - Greece 1984 - 640-

e.a.1 TE~y

P .... ct<

/ / / / / / a uARIZ

GAS SUPPLY t

FLOw CO"iTAOl

NO DETECTOR PUMP OZONE 'RAP

Figure 1. Schematics of the balloon-borne actinometer.

A constant flow of 1.6 Nml/min N20 was photolyzed in a thin-walled suprasil tube of 0.4 cm internal diameter and 166 cm length. The circular tube was mounted horizontally on a flexible rod above the gondola. The N20 pressure in the quartz tube was 10 torr, resulting in a transit time of 120 sec at atmospheric temperatures. The photolysis of pure N20 produces NO with a qu~ntum yield of 1.24, and N2 with a quantum yield of 1.38:

(Rl) N20 + hv ~ N2 + O(lD), <l> 1.00

(R2) N20 + O(l D) ~ 2 NO (62 %), or N2 + 02 (38 %)

The branching ratio of reaction R2 is independent of wavelength and temp­erature (3). The photolysis frequency can thus be deduced from the N20 flow, the photolysis time (= the transit time through the quartz tube), and the yield of NO which was measured with a chemiluminescence detector.

The gas supply unit housed two stainless steel vessels of 5 1 volume each, filled with 4 atm N20, and 02' respectively, and a 2 1 glass bulb containing calibration gas (200 ppm NO in 300 torr N20). Encapsuled pres­sure regulators and critical orifices maintained constant pressures and flows. The N20 pressure in the quartz tube and the 02 pressure were meas­ured during the flights with pressure transducers.

The chemiluminescence detector consisted of a thermostatted reaction chamber (20 Oe), a photomultiplier tube (EMI 9659QB) at dry ice tempera­ture, an ozone source, and a molecular sieve sorption pump cooled with liquid nitrogen. Ozone was eluated from silica gel with 1 atm oxygen at dry ice temperature. The trap yielded 5.5 % ozone in oxygen for at least 10 h. The flow into the chemiluminescence detector was 0.8 Nml/min through a critical orifice. The detector cell pressure was 0.14 torr constant. The photomultiplier anode current was fed into a log/lin electrometer. Photo­lysis frequencies of 10-10 sec- 1 could be measured.

The outputs of the electrometer were telemetered to the ground. Every 10 min the log channel was interrupted to transmit temperatures and pres­sures. An automatic zero control and calibration cycle was started every 60 min: The actinometer was zeroed by diverting the N20/NO flow through a pre-reaction cell in the 02/03 duct. Before switching back to normal meas-

- 641-

uring mode, 0.05 Nml/min calibration gas were admitted for 5 min. Figure 2, a section of an original recording strip, shows the various signals as re­ceived at the ground.

TEMPERATURE & :PRESSURE TRANSMISSION

"I " • .:

15:30

CALIBRATION

GAIN OFFSET

15:15

: !

; 1

LOG,. CHANNEL

.. LIN . :. • t-

":'CHANNEL

-- UT

Figure 2. Actinometer output signals (section of flight 4, see below): Linear (bottom) and logarithmic (top) NO channel, the latter periodically interrupted for transmission of pressure and temperature data.

The calibration factor f of the actinometer was checked by time inte­grating actinometers which were exposed throughout the flight. They con­sisted of quartz bulbs filled with 10 torr N20. The N2 yield which was in the order of few mtorr was measured after the flight by mass spectrometry. The calibration factor f must be consistent with the following integration:

J f·S·dt 1.38 . (N2 ) / (N20) for (N2 ) « (N20),

where (N 2) and (N20) are the partial pressures in the sphere, 1.38 is the overall N2 quantum yield, and S is the output of the continuous instru­ment.

- 642-

RESULTS AND DISCUSSION The actinometer performed well on 6 missions between October 1982 and

October 1983. Two flights had to be terminated before sunrise due to un­favourable weather conditions, and thus did not yield photolysis frequen­cies. Some data of the four successful flights are listed in table I, for further information consult (4).

Table I. Balloon flights of the actinometer from Aire sur l'Adour. The pressures at peak altitude are from CNES, and altitudes were calculated using the US Standard Atmosphere. Integrating actinometers were used on flights 3 and 4 only.

no. date start and plateau times pressure peak altitude ( UT ) mb kID

17-0ct-82 8: 13 10:23 - 11: 50 2.6 40.66

2 21-0ct-82 7:51 9:34 - 10:08 7.3 33.6

3 28-Sep-83 5:49 7:38 - 9:52 7.3 33.6

4 5-0ct-83 13:30 16:04 - 17:33 2.5 40.9

For flights 2 and 4, independent pressure data were obtained with a calibrated transducer on the gondola, which were slightly higher at high altitudes. These data (cf. dotted line in figure 3) were used in the model calculations.

1O. 7s · 1

, ~ >-u

12 z w ~ e

10 w a:: .....

V') 08 iii >-..J 06 e l-e I OL n-

o 02 '" z

ZEN ITH A GI E

58' 60' 62' 6L' 66' 66' 70' 72' n' 76'

17 UT

l> r ... ...

30 c Cl ",

Figure 3. Comparison of the N20 photolysis frequency profile observed durin~ flight 4 (dotted line: flight profile), and two calculated profiles A and B (full lines), see text.

The circles in figure 3 are experimental photolysis frequencies from flight 4. The data are plotted versus universal time (UT). The correspond-

-643 -

ing solar zenith angles, corrected for the true position of the balloon, are also given (top of figure 3). Since altitude (dotted line) was constant after 16:00 UT, the change in photolysis frequency became a function of zenith angle only. The full lines in figure 3 represent model calculated photolysis frequencies. The ozone profile used in these calculations was for 450 N, which differs slightly from Aire (430 42'). The calculation ¥ield­ed photolysis frequencies as function of altitude (1 km resolution) and time (30 min resolution). The times were converted to zenith angles, and photolysis frequencies for the flight trajectories were obtained by inter­polation between the grid pOint data. Two calculated profiles are shown in figure 3: profile A was calculated using oxygen absorption cross sections tabulated by Ackerman (5); profile B relates to the lower data proposed by Herman and Mentall (1). Profiles A and B differ significantly, but the com­bined uncertainties of the actinometer and of the pressure measurements -the latter were even less accurate - are larger than this difference. E.g., using pressure data of CNES in the calculations would have yielded approx. 40 % higher photolysis frequencies for flight 4.

Comparable agreement between observed and calculated profiles was ob­tained for flights 2 and 3, vlhereas in flight 1 the observed photolysis frequencies were in the order of 40 % lower than the calculated profile. This discrepancy is most likely due to instrumental inadequacies on this very first mission.

The accuracy of the actinometer - presently in the order of 15 % -will be improved for future flights. The importance of correct pressure data in altitude resolved measurements of photolysis frequencies is appar­ent.

ACKNOWLEDGEMENTS The authors are indebted to U. Schmailzl, MPI Mainz, for performing

the stratospheric model calculations. This work was supported by the Deutsche Forschungsgemeinschaft.

LITERATURE

(1) J.R. Herman and J.E. Mentall, J. Geophys. Res., 87, 8967, 1982

(2) G. Brasseur, A. de Rudder and P.C. Simon, Geophys. Res. Lett., ~, 20, 1983

(3) W.N. Marx, F.C. Bahe and U. Schurath, Ber. Bunsenges. phys. Chern., ~, 225, 1979

(4) CNES, Compte-Rendu de la campagne MAP/GLOBUS 83, note 012/CT/DRT/BA/CL/Pr, 1984

(5) M. Ackerman, in: Mesospheric Models and Related Experiments, Fiocco (ed.), Reidel, 1971

-644 -

C HAP T E R VIII

RADIATION TOPICS RELEVANT TO ATMOSPHERIC OZONE

- Solar irradiance and its spectral distribution through the terrestrial atmosphere

- Solar ultraviolet irradiance 1982 and 1983

- A review of solar irradiance measurements between 270 and 480 nanometers

- The global response of stratospheric ozone to ultraviolet solar flux variations

- Ozone and sunspots: why can we not find a direct correlation?

- Ozone depletion during solar proton events in solar cycle 21

- Ultraviolet imagery of the sky

- Monochromatic UV-magnification factors and total ozone

- Ozone concentration and aurora frequency in relation to solar-terrestrial indices

- Calculations of Lyman Alpha absorption in the mesosphere

- Radiative interactions of stratospheric ozone and aerosols in the solar spectrum

- A sensitivity study of calculations of atmospheric ozone transmittances

SOLAR IRRADIANCE AND ITS SPECTRAL DISTRIBUTION THROUGH THE TERRESTRIAL

ATMOSPHERE

M. NICOLET Space Aeronomy Institute, 3 Avenue Circulaire, 1180 Brussels.

Summary

A review of the general subject of solar UV irradiance of importance to the photochemistry of stratospheric and mesospheric ozone is given. An analysis is made of the spectral solar irradiance and of its atmo­spheric transmissivity in the various regions associated with the absorption of molecular oxygen and of ozone.

1. Introduction

A review of the general subject of solar UV irradiance of importance to the photochemistry of stratospheric and mesospheric ozone requires the simultaneous analysis of the solar spectral irradiance of wavelengths greater than 100 nm and of its atmospheric transmittance which depends essentially on the absorption of molecular oxygen and ozone. It can be assumed that molecular nitrogen plays a role in the atmospheric transmi­ttance only by its scattering cross section which is of the order of 5.6 x 10-24 cm2 at Lyman-alpha (Dalgarno et al., 1967). The total scattering cross section (a RS ) in the homosphere can be determined by a simple formula (Nicolet, 1984), based on a recent theoretical determination by Bates (1984), (A in ~m),

where

2 cm

x = 0.389 + 0.09426/A - 0.3228

(1)

(2)

The formula accounts for the degree of depolarisation which varies with the wavelength and, as an example, leads to the following values for the total cross section

(~m) 0.190 0.195

cr x 10-25 4.63 4.07

a x 10-24(*) 2.22 1.95

0.200

3.60

1.73

0.205

3.19

1. 53

0.210

2.84

1.37

0.220

2.54

1.22

The last line (*) corresponds to the scattering cross section related to the total number of O2 molecules cm-2 in order to lead to an immediate comparison of the role of the molecular scattering with that of the O2

Ozone Symposium - Greece 1984 -646 -

absorption in the determination of the atmospheric optical depth. Thus, the degree of penetration of solar radiation is determined by

the absorption of 02 and 03 (mainly) and by the molecular scattering of the air molecules. In consequence, the way in which ozone chemistry in the mesosphere and stratosphere can be influenced by variations (with wave­length and time) in the solar radiation flux is controlled primarily by 02 and its direct product 03' The solar spectrum must, therefore, be divided in various spectral regions related to the variations of the 02 and 03 absorptions.

2. Spectral regions from 100 nm to the visible

First, 02 is photodissociated in various spectral ranges of wavelengths less than 242 nm. The solar radiation is successively absorbed : (1) in the mesosphere, at the Lyman alpha line (121.57 nm) since the absorption cross section is only of the order of 10-20 cm2 . (2) in the thermosphere, at wavelengths less than 175 nm in the region of the Schumann-Runge continuum with absorption cross sections between 10- 18 and 10-17 cm2 . (3) in the whole mesosphere down to the upper stratosphere, in the region (200 to 175 nm) of the Schumann-Runge bands with a cross section varying from about 10- 19 to 10-22 cm2 . (4) in the stratosphere, at wavelengths less than 242 nm in the region of the Herzberg continuum with low absorption cross sections of the order or less than. 10-23 cm2 .

Second, 03 is important because of its absorption of solar radiation in three spectral regions : (5) in the stratosphere, in the spectral region of the Hartley band at wavelengths less than 315 nm with a cross section varying between 10- 17 cm2 and about 10-19 cm2 . At wavelengths less than 242 nm there is a simultaneous absorption zy 02 and 03' The Hartley band leads to the ozone photodissociation with 02 and 0* in their first excited level. (6) in the lower stratosphere and in the troposphere, in the spectral regions of the Huggins bands where the cross sections vary between 10-19 and 10-22 cm2 and depend strongly on the temperature. These bands corresponds to the limit of the 03 ultraviolet absorption. (7) in the stratosphere from the ozone peak to ground level, in the visible region (450 - 850 nm) with the Chappuis bands with a low absorption cross section from about 5 x 10-21 to 10-22 cm2 . These bands play an important role in the photodissociation of 03 not only in the troposphere, but also in the major part of the stratosphere.

3. The Schumann-Runge continuum at A < 175 nm

All the oxygen atoms that are produced in the thermosphere by absorption of solar radiation at wavelengths less than 175 nm are transported downward by dt'ffusion before recombining by a three-body association a few km above the mesopause. Recent analysis (Nicolet, 1981 and references contained therein) shows that the minimum solar irradiance corresponding to the quiet sun is of the order of 6 x lOll photons cm-2 s-l (Radiation temperature about 4500 K) and that the maximum observed for active sun conditions is about 1.5 x '1012 photons cm-2 s-l (TR = 4750 K).

-647 -

All recent observations by Mount and Rottman (1983a, bj 1984) confirm that the total number of oxygen atoms produced from a minimum to a maximum of a solar activity cycle varies from about (1.25 + 0.25) x 1012 to (3.0 + 0.5) x 1012 oxygen atoms cm-2 sec-I. These thermospheric atoms produced by photodissociation lead to variations with solar activity on the upper boundary conditions near the mesopause.

4. The Lyman-alpha radiation at 121.57 nm

The solar hydrogen Lyman alpha radiation which is of great importance in mesospheric chemistry has been subject of many astrophysical and aero­nomical studies (see Nicolet 1984a, d and references contained therein). The irradiance of the line and its variation with solar activity must be considered in the determination of the photoionization of NO and of the photodissociation of CH4 , of CO2 and particularly of H20 and of 02' Its mesospheric absorption by molecular oxygen, and therefore its atmospheric transmissivity, depend on wavelength and temperature. The solar H Lyman­alpha line is characterized by a 'profile with a central reversal, and wings extending to about + 0.175 nm where the intensity reaches about 1% of that the peak (Figure l)~ The unit effective optical depth for solar Lyman alpha is reached near N ~ 1020 02 molecules cm-2 (near 75 km for an over­head sun, or near 70 km for a solar zenith angle of 60°). Th~I depth rises to about 8 near 60 km for an overhead sun, namely for N ~ 10 With a mean temperature of T ~ 230 K, the solar H Lyman alpha transmittance

TO (Ly a) ~ exp [- 2.115 x 10- 18 No.8855] 2

(3)

This formula can be used as a basis for all calculations when appropriate photodissociation-absorption cross sections are simultaneously adopted. For CH4, CO2 and NO constant photodissociation cross sections must be adopted sincefuere is no detailed analysis (high resolution) of the spectrum at Lyman alpha. As far as H20 is concerned, a mean cross section can be determined (Nicolet, 1984d), with an excellent accuracy,

-17 2 GD(H20)Lya ~ (1.57 ~ 0.05) x 10 cm

if the experimental data of Lewis et al. (1983) are adopted. Since the absorption of Lyman alpha by oxygen depends strongly on both temperature and wavelength, its effective absorption-photodissociation cross section GD(02) is given for T ~ 230 K by the following expression:

(5)

A global analysis, covering more than a solar cycle, of observations made by various satellites for the irradiance of H Lyman-alpha at the top of the earth's atmosphere, leads to the expression (photons cm-2 s-l)

11 FlO . 7 - 65 q (Lya) ~ 2.5 x 10 (1 + 0.2

00 100

if 2.5 x lOll photons cm-2 sec- l is accepted for the irradiance of a quiet sun.

-648-

To conclude, solar H Lyman-alpha plays a leading role in the photo­dissociation of C02 and of H20. At its absorption peak, the life time of water vapor is only of a few days and its concentration must decrease rapidly with height. The observations from Spacelab (Lippens et al. 1984) show that the H20 number density (Figure 2) decreases by about a factor of ten between 70 and 75 km and between 75 km and RO km.

5. The Schumann-Runge band region at A < 200 nm

The study of the absorption of the Schumann-Runge bands poses a difficult problem arising from the rotational structure

TABLE I.- Cross sections (cr cm2) and transmittance T(02) in molecular oxygen (N = cm-2 ) for the (5-0) band of the Schumann-Runge system (mean wavelength 193.3 nm).

Temperature 190 210 230 250 270 300 K

(JMAX Oo- 2l ) 1.00 1.01 1.02 1.04 1.06 1. 12

N 1 21. 00-22 ) 2.35 2.48 2.64 2.83 3.08 3.58 o ,(JA

N 1022 ; (JA OO- 23 ) 6.99 7.55 8.27 9.18 10.30 12.22 21

N 10 ; T(02) o. 79 0.78 0.77 0.75 0.73 0.70 22

0.36 0.30 N 10 ;. T(02) 0.50 0.47 0.44 0.40

related not only to the oscillator strengths and rotational line widths of all bands, but also to the temperature. Figure 3 illustrates differences in the optical thickness that are due to the line width and temperature. The (5-0) band is characterized by a strong sensitivity to the temperature which is greater than that caused by changes of line widths. Another problem in the spectral region of the Schumann-Runge bands is that of the solar irradiance. At the present time it is not yet possible, from the limited number of observations, to deduce, with any certainty, the absolute irradiance and the exact effect of changing solar activity. An increase by a factor of 1.11 + 0.04 in the mesosphere may be accepted for the photodissociation of O2 if the solar activity action is characterized by increases of 20'%, 15%, 10'% and 5'% for the four groups of bands 09-0) to 05-0), 04-0) to (10-0), (9-0) to (6-0) and (5-0) to (2-0), respect­ively (Nicolet 1984b). A limitation to an accurate determination derives also from the fact that in the region of the (v' ,0) bands with v' < 6 which are stratospherically important, the Herzberg continuum plays a role. In their studies of the atmospheric absorption, all authors (1970-1980, see Nicolet 1981) used the theoretical values of Jarmain and Nicholls which are too high. In practice, parameterisations of detailed calculations (Frederick and Hudson 1980a, b; Nicolet and Peetermans, 1980; Nicolet, 1981; Allen and Frederick, 1982) can provide simple expressions for application to atmospheric models. A new attempt to resolve these problems requires new observational data such as those given by Solar Mesosphere Explorer and laboratory studies as obtained by Yoshino et al. 09R2) with high resolution to insure that exact rotational line widths can be determined.

- 649-

6. The Herzberg continuum at A < 242 nm

Recent values of the solar irradiance at A > 200 nm obtained by satellites and rockets (see Nicolet, 1983, with references contained there­in; Mount and Rottman, 1983a, band 1984; Mentall et al. to be published) lead to mean values for 6A = 1 nm which differ as much as 10~. Such differences are due to difficulties of making accurate measurements and are uncounnected with changes with solar activity. Nevertheless, the solar activity is detected around 240 nm by the 27-day variations observed in the irradiance. Such results show that the photodissociation of 02, i.e. the formation of 03' is related to solar activity when the photodissocia­tion of 03 is practically independent of solar activity. Because the absorption cross section is very small in the Herzberg continuum, the various laboratory measurements are susceptible to large errors (Nicolet 1983, for references contained therein and Fig. 4). According to recent laboratory measurements (Cheung et al., 1984; Johnston et al. 1984; Ackerman and Biaume, (unpublished) at wavelengths greater than 200 nm, measurements made in June 1969), there must be an reestimation of the first experimental cross sections. The cross section near 210 nm may be as low as 5 x 10-24 cm2 . Stratospheric measurements (Frederick and Mentall, 1982; Herman and Mentall 1982; Anderson and Hall, 1983) lead to derived 02 cross sections which are smaller than the Herzberg continuum values generally used before 1982. (It may be added that nighttime stratospheric observations were made by Pirre, Rigaud and Huguenin in May 1983. These authors reject the new results and consider that old laboratory measurements are confirmed by their observations; according to a poster shown at the Symposium).

The existence of discrepancies in the absolute number densities of 03 or of N20, CF2CI2, CFC1 3 , ... in the upper stratosphere between photo­chemical models and observations made at mean latitudes is related to the discrepancies in the absolute absorption cross sections of 02 (and 03) in the region of the Herzberg continuum at 210 + 20 nm.

7. The Hartley band at A < 310 nm

The spectral region from approximately 315 nm to about 200 nm corresponding to the 03 Hartley band is of prime importance for the whole of atmospheric chemistry, and considerable attention has been paid to its photolysis leading to products being formed in the first excited states (02 and 0*, respectively). New measurements are being made (Bass and Paur, Brian et al., Freeman et al., Molina; and report by Hudson at this symposium) and therefore this problem cannot be discussed here. Never­theless, it is important to show that previous measuremerits can be compared with the new measurements. Nicolet (1981) has tabulated, as representative of the best available data, the results of the analysis of Ackerman (1971) made in 1969 and based on the work of Vigroux (1953 and 1969), Inn and Tanaka (1959) and Hearn (1961). Since these values have been available for several years for atmospheric application (6v = 500 cm- l ), a comparison has been made with the laboratory data obtained by Bass at 228 K (private communication). The comparison shown in Table II indicates that no significant difference is observed between 235 and 280 nm. At greater wavelengths the temperature effect leads to increasing differences reaching about 10% at 300 nm. Since there is practically no difference for a

-650-

TABLE II. Ozone absorption cross section (6V 500 cm -1) in the Hartley band.

6v(cm -1 10-2) 6A(nm) ( 2)(*) 2 (**) x cr cm cr(cm ) Ratio

430 - 425 235 - 233 5.79 x 10- 18 5.92 x 10- 18 1.02 425 - 420 238 - 235 6.86 6.98 1. 02 420 - 415 241 - 238 7.97 8.06 1. 01 415 - 410 244 - 241 9.00

x 10- l7 9.12

-17 1.01

410 - 405 247 - 244 1.00 1.00 x 10 1. 00 405 - 400 250 - 247 1.07 1.08 1.01 400 - 395 253 - 250 1.11 1.12 1.01 395 - 390 256 - 253 1. 12 1.14 1. 02 390 - 385 260 - 256 1.11 1. 11 1.00 385 - 380 263 - 260 1.03 -18 1.05

x 10- 18 1.02

380 - 375 267 - 263 9.43 x 10 9.57 1.01 375 - 370 270 - 267 8.23 8.29 1.00 370 - 365 274 - 270 6.81 6.86 1.00 365 - 360 278 - 274 5.31 5.35 1.00 360 - 355 282 - 278 3.99 3.93 0.98 355 - 350 286 - 282 2.84 2.71 0.95 350 - 345 290 - 286 1.92 1.75 0.91 345 - 340 294 - 290 1.14

x 10- 19 1.05

x 10-19 0.92

340 - 335 298 - 294 6.60 6.04 0.92 335 - 330' 303 - 298 3.69 3.34 0.91 330 - 325 308 - 303 1.97 1.73 0.88

spectral region of 50 nrn width (230-280 nm) where the cross section reaches values greater than 10-18 cm2 , the uncertainties involved in atmospheric modelling are not relevant to this spectral region. However, the use in atmospheric calculations of the 03 cross sections at wavelengths greater than 290 nm requires a careful analysis of the temperature effect associated with the quantum yield of the O(l D) production, particularly in the lower stratosphere. At 300 nm, the 03 cross section increases from T = 200 K to 240 K, 270 K and 300 K by 5%, 10% and 15%, respectively. This temperature dependence should be considered carefully for modelling applications. Additional work is needed since, in the ultraviolet region, at wavelengths greater than 300 nm, the Huggins bands (Figure 5) playa role in the absorption and the reported cross section variations with temperature are greater than the errors tolerable in the ozone observations.

8. Note

Various other aspects have not been discussed here. As an example, the atmospheric conditions must be taken into account so that effects due to anisotropic scattering and the albedo in the solar radiation field can be treated.

- 651-

z o ;:: II Z ::J u.. w II a: ::J o (/)

,~,------------------------------~

SO AR H LYMAN ALPHA

MESOS~HERIC PROFILE Figure 1

The variation (and deformation) of the profile of the solar H Lyman­alpha line, i.e. of the source function defined by q. L (6A =

0.1 A)fq"" Lya(.6/, = 3.5'Ar: with increasing number N of 02 absorbing molecules: (q = number of photons cm- 2 s-l). Six curves are shown for N = 0, 10 19 , 1020, 2.5 x 1020, 5 x 1020 and 1021 cm-~ Approximate values of the effective transmittance of the H Lyman-alpha irradiances, i.e. the ratio q(Lya)/~(Lya), are also given for the various profiles.

WAVELENGTH(nm)

i 70 ::.:::

UJ 060 :J I-

~ SO ..;{

0000 3616 .092 •••• 3819 .905 -,- 382~ , 281

- 3818.341

H20 EVT 13 SUNSET

33' N. SO'E

40~B~------~~------~~----~~~--~~~ 2 10 109 1010 1011 101

NUMBER DENSITY (tm ~ 3)

Figure 2

Water vapor nlmber densities versus altitude retrieved using only lines in the regions where their curve of growth is quasi linear. The nearly parallel lines represent constant volume mixing ratios from 10-7 to 10-9 .

- 652-

+I~ SCHUMANN-RUNGE

BAND 190K

15 - 0) d, ' - 22~cm· '

+1 0 - - -

+05 - - - - - - - - - - - - - - - - - - - -

o i= « a:

• :~g: = -= -=- = = = = = = ----_ -_ -=-._ -=- -=:t -= == -= = 10 ... 230K - 10'" - - - - - - - - - - - - - - - A- - -.- - --2M. - - - - - - - - - - - - - - - - - - - 0 - - -

-0.5 + FREDERICK HUDSON (1979)

x GIES E1 AL. (1ge1) - 10

• t\ I' - 1,75 em·' .. - 2.00

A - 250

01

Figure 3

T - 230K

OS. -7. xIQ"

• OPTICAL THICKNESS

300< 210K

Illustration of differences (+ %) in the transmittance of the (5-0) Schumann-Runge band with the temperature and line width if T = 230 K 6.v = 2.25 em-I, and oscillator strength = 7.4 x 10-7 . Curves drawn f~r T = 190, 270, and 300 K show that the sensitivity to temperature is high and is greater than that caused by the variation of line widths .

E .<:1

b .::. 15

z o i= <.) . w CI)

CI) '0 CI)

o a:: <.)

180

Figure 4

O:z HERZBERG - CON"ThlWM o DITCHBURN and YOUNG (11162)

• HASSON and NICHOLLS (1971)

" OGAWA (1971) SRB(4.olf>.o

(3 - 01 ..

(2-01 ..

.eo

• •

x SHl<RDANAI«l and RAO (1I1n)

.. HERMAN end MENTALL (1982)

• • Fl'lEDER1CK end I.EHT ALL (1982)

• o

200 210 220 230

WAVELENGTH (mI)

Experimental and theoretical values of the absorption cross-section in the Herzberg continuum of 02 _ The exceme experimental values differ by a factor of 2_ If absorption due to atmospheric Rayleigh scattering is taken into account, the theoretical value of Jarmain­

Nicholls could be reduced by a factor of 2 to account for the observa­tional cross-sections deduced by Herman-Mentall and Frederick-Mentall_

- 653-

References

,. -. 0 -

W )0 -o :J .... .... .J ,. <

' 0

-. 4 _", . ---.----r-;-<'-0 -

", "'HfL. i: ~ I

, ~ '0 10 Mt 'IXI

0 3 PHOTODISSOC IAT ION FREOUENCY ('11.)

Figure 5

Photodissociation of ozone (,,) as a function of altitude and solar zenith angle (sec X = 1, 2 and 4) for the main spectral regions: Herzberg continuum to 240 nm. Hartley band to 310 nm and Huggins bands beyond 310 nm. The Chappuis bands cover the visible region.

I. ACKERMAN, M. (1971). Ultraviolet solar radiation related to meso­spheric processes, in Mesospheric Models and Related Experiments, Fiocco (Ed) pages 149-159, Reidel Publishing Company.

2. ALLEN, M. and FREDERICK, J.E. (1982). Effective photodissociation cross sections for moleculer oxygen and nitric oxide in the Schumann-Runge bands, J. Atmos. Sci., 39, 2066.

3. ANDERSON, G.P. and HALL, L.A. (1983). Attenuation of solar irradiance in the stratosphere : Spectrometer measurements between 191 and 207 nm, J. Geophys. Res., 88, 6801.

4. BATES, D.R. (1984) .. Rayleigh scattering by air, Planet. Space Sci., 32, 785.

5. CHEUNG, A.S.-C., YOSHINO, K., PARKINSON, W.H. and FREEMAN, D.E. (1984). Herzberg continuum cross section of oxygen in the wave­length region 193.5-204.0 nm and band oscillator strengths of the (0-0) and (1-0) Schumann-Runge bands, Canadian J. Phys. in press.

6. DALGARNO, A., DEGGES, T. and WILLIAMS, D.A. (1967). Dipole properties of molecular nitrogen, Proc. Phys. Soc., 92, 291.

7. FREDERICK, J.E. and HUDSON, R.D. (1980a). Dissociation of molecular oxygen in the Schumann-Runge bands, J. Atmos. Sci., 37, 1099.

8. FREDERICK, J.E. and HUDSON, R.D. (1980b). Atmospheric oppacity in the Schumann-Runge bands and the aeronomic dissociation of water vapor, J. Atmos . Sci., 37, 1088.

- 654-

9. FREDERICK, J.E. and MENTALL, J.E. (1982). Solar irradiance in the stratosphere : Implications for the Herzberg continuum absorption of O2 , Geophys. Res. Lett., 9, 461.

10. HEARN, A.G. (1961). The absorption of ozone in the ultraviolet and visible regions of the spectrum, Proc. Phys. Soc., 78, 932.

II. HERMAN, J.R. and MENTALL, J.E. (1982).02 absorption cross sections (187-225 nm) from stratospheric solar flux measurements, J. Geophys. Res., 87, 8967.

12. INN, E.C.Y. and TANAKA, Y. (1959). Ozone coefficients in the visible and ultraviolet regions, in Ozone Chemistry and Technology, Advances in Chemistry Series, 21, 263, Amerc. Chern. Society, Washington D.C.

13. JOHNSTON, H.S., PAIGE, M. and YAO, F. (1984). Oxygen absorption cross section in the Herzberg continuum and between 206 and 327 K, J. Geophys. Res., 89, ...

14. LEWIS, B.R., VANDAVAS, I.M. and CARVER, J.H. (1983). The aeronomic dissociation of water vapor by solar H Lyman a radiation, J. Geo­phys. Res., 88, 4935.

15. LIPPENS, C. et al (1984). Trace constituents measurements deduced from spectro~~t;Ic observations on board Spacelab, Advances ~n Space Research, to be published, Pergamon Press.

16. MEN TALL , J.E., FREDERICK, J.E. and HERMAN, J.R. (1981). The solar irradiance from 200 to 330 nm, J. Geophys. Res., 86, 9881.

17. MOUNT, G.H. and ROTTMAN, G.J. (1983). The solar absolute spectral irradiance 1150-3173 A May 17 1982, J. Geophys. Res., 88, 5403.

18. MOUNT, G.H. and ROTTMAN, G.J. (1983). The solar absolute spectral irradiance at 1216 A and 1800-3173 A : January 12 1983, J. Geophys. Res., 88, 6807.

19. HOUNT, G.H. and ROTTMAN, G.J. (1984). The solar absolute spectral irradiance 118-300 nm : July 25, 1983, J. Geophys. Res., 89, ....

20. NICOLET, M. (1981). The solar spectral irradiance and its action in the atmospheric photodissociation processes, Planet. Space Sci., 29,951.

21. NICOLET, M. (1983). The influence of solar radiation on atmospheric chemistry, Annales Geophysicae, I, 493.

22. NICOLET, M. (1984a). On the photodissociation of water vapour in the mesosphere, Planet. Space Sci., 32, 871.

23. NICOLET, M. (1984b). Photodissociation of molecular oxygen in the terrestrial atmosphere : Simplified numerical relations for the spectral range of the Schumann-Runge bands, J. Geophys. Res., 89,2573.

24. NICOLET, M. (1984c). On the molecular scattering in the terrestrial atmosphere: an empirical formula for its calculation in the homo­sphere, Planet. Space Sci., 32, ...

25. NICOLET, M. (1984d). Aeronomical aspects of mesospheric photo­dissociation: processes resulting from solar H Lyman alpha line, Planet. Space Sci., 32, ....

26. NICOLET, M. and PEETERMANS, W. (1980). Atmospheric absorption in the 02 Schumann-Runge band spectral range and photodissociation rates in the stratosphere and mesosphere, Planet. Space Sci., 28, 85.

27. VIGROUX, E. (1953). Contribution experimentale de l'absorption de l'ozone, Ann. Phys. Paris 12e Ser., 8, 709.

28. VIGROUX, E. (1969). Coefficients d'absorption de l'ozone dans la bande de Hartley, Ann. Geophys., 25, 169.

29. YOSHINO, K., FREEMAN, D.E., EDMOND, J.R. and PARKINSON, W.H. (1983). High resolution absorption cross' section measurements and band oscillator strengths in the (1-0) - (12-0) Schumann-Runge bands of O2 , Planet. Space Sci., 31, 339.

-655 -

SUMMARY

SOLAR ULTRAVIOLET IRRADIANCE 1982 AND 1983

G. J. Rottman Laboratory for Atmospheric and Space Physics

University of Colorado Boulder, Colorado 80309 USA

The Solar Mesosphere Explorer (SME) has been in operation since October 6th 1981. In addition to making measurements of ozone and other trace const i tuents of the ea rth' s atmosphere the observatory i ncl udes a small spectrometer to make daily measurements of the solar ultraviolet i rradi ance in the spect ra 1 range 115 to 305 nm. The solar spectra are obtained with 0.75 nm spectral resolution. Examination of the data show a strong signature of the 27-day solar rotation displaying a time varing modulation of incoming solar radiation exceeding ±15% near Lyman-a, de­creasing to a few percent at 200 nm, and less than one percent near 300 nm. Long term trends in the data, due both to changes in the instrument response and to true long term solar variations, are removed in order to obtain quantitative measure of the intermediate term variation with time periods of a few days to weeks.

1. INTRODUCTION

The solar ultraviolet radiation below 300 nm is almost completely absorbed in the Earth's upper atmosphere. Absorption of this radiation results in the photodissociation of various atmospheric gases and is thereby a prime component of the complicated upper atmosphere photochem­ical system, including all major ozone production and destruction pro­cesses. It is reasonable to expect that variations in the solar UV pro­duce a di rect and measu rab 1 e response in va ri at ions of upper atmosphere temperature, motions, and concentrations of trace gases. This due to the fact that the solar UV radiation provides the major energy input to the interactive radiative/photochemical/dynamic processes at these levels and because radiation and most photochemical relaxation times are relatively short in the upper stratosphere and mesosphere.

Four limb scanning instruments on the Solar Mesosphere Explorer make measurements of ozone and other minor atmospheric constituents, for ex­ample, H20' and N0 2• A prime objective of the SME is to study the distri­bution and changes in the distribution of mesospheric ozone. To aid in

Ozone Symposium - Greece 1984 -656 -

the interpretation of observed changes in ozone, accurate daily measure­ments of the solar irradiance at Lyman-a and in the spectral interval 175 to 300 nm are required. For this reason a small two channel spectrometer was included in the SME observatory. This scanning spectrometer has 0.75 nm spectral resolution and takes a solar data sample once per rotation of the spacecraft (12 seconds) as the Sun passes through the plane perpendi­cular to a diffusive screen scattering radiation into the spectrometer. To cover the full spectral range the instrument uses two different scat­tering screens, also two separate optical channels each with its own exit slit and photomult i p 1 i er tube detector. The short wavelength channel uses a cesium-iodide photocathode covering the spectral range 115 to 250 nm and the long wavelength channel uses a cesi um-te 11 uri de photocathode for the range 175 to 300 nm. For each calendar day a solar spectrum is pieced together, calibrated and integrated in 1.0 nm intervals using data of the short wavelength channel from 115 to 185 nm and the data from the long wavelength channel above 185 nm. For the discussion that follows these data have been integrated in 5.0 nm intervals in order to improve the signal to noise ratio of the data. Figure 1 is the mean solar irrad­iance in 5.0 nm intervals for all of 1983.

In addition to the pri mary set of scatteri ng screens a separate set of calibration screens are used with a low duty cycle «1% of solar viewing time) and their comparison with the screens used for the dai ly observations provides an estimate of the scattering su rface degradation. The resulting correction to the SME data is moderately small and does not exceed 6% at any wavelength for the en­tire year of 1982 and is considerably less than 1% for 1983. After correcting the SME data for scatteri ng screen degradation there is still a net downward trend at all wavelengths during the 1982 and 1983 period. When the two years of SME

";" u 14 Q)

'" ~ E 13

" Ul

15 12 I-o IE 11

o 6" o 10 ...J

SME IRRADIANCE (5nm)

100 120 140 160 180 200 220 240 260 280 300

WAVELENGTH (nm)

Figure 1. SME mean solar irradiance spectrum for the entire year 1983.

data are compared to data from three calibration rockets flown on May 17th, 1982, January 13th, 1983 and July 25th, 1983 (2,3,4), the agreement is within one to two percent and well within the error bars of the comparison. Therefore no adjustment to the SME calibration has been made.

2. INTERMEDIATE TERM SOLAR VARIATIONS

Ti me seri es of the SME data at each 5.0 nm i nterva 1 show a 27 -day solar variation superposed on a general downward trend. This downward trend represents an upper limit to the long term solar variability during

- 657-

this two year period. The trend is -30% at Lyman-a, -3.7% for 175 to 190 nm, -0.7% for 240 to 260 nm, and -0.2% for 260 to 300 nm. These latter two values are small in comparison with the probable error of the rela­tive measurement (probably one to two percent) and therefore would permit a "constant" or slightly increasing Sun during this two year period.

In order to study the i ntermedi ate term va ri at ions evi dent in the time series, the long term linear trends were first removed from the data. Figure 2 shows three wavelength intervals with the long term trends removed. Throughout most of this two year period the strong 27-day modulation of the irradiance dominates. Near the end of i981 a strong act i vity center on the Sun produced a well defi ned 27 -day vari a­tion and the declining phase of this activity persisted for approximately four rotations into 1982 (5,6). For the following three months activity was more uniformly distributed on the solar disk and no strong 27-day signal is evident. In June 1982 a single solar longitude again became active and a remarkable 27-day signal continued throughout 1982 and into 1983.

The root mean squares (RMS) of the SME solar data with the long term trends removed are given in Figure 3a as a function of wavelength. In general the RMS of these data is somewhat smaller for 1983 than for 1982

· 20

• '0

o and above 210 nm it falls to the noise level of the individual measurements (~0.5%). Although § the RMS provides a quantitative ....

::; " 0 measu re of the magni tude of the a:: 27-day variations, it is not ;;

SOLAR IRRADIANCE , - , L YMAN ·n

B particularly valuable to studies ~ ' 20

of atmospheric phenomenon (un- w less precise solar observations )i +6

can be di rectly compared to ~ 0

corresponding atmospheric obser- ~~~~ vations, for example, the data sets provided by SME). For comparison, Figure 3b gives the percent solar variation for a single large and well defined rotation period. The period chosen was in July 1982 and is designated by the letters 'A' and 'B I in the Lyman-a time series of Figure 1. This single solar rotation produced a modul­ation approximately five times the RMS devi at i on of the ent ire data set (note: the RMS of Figure 3a represents the plus

· 6 0 2 PHOTODISSOC'AT ' ON

• 4 240 ' 260 nm

o I", " .J\ '" III. n .

' 4 0 3 PHOTODISSOCIA liON

J F M A M J J AS 0 N D J F M A MJ J A SON D

1982 1983

Figure 2. Two year time series of SME data for three wavelength intervals with the long term trend removed.

and minus deviation about the mean and the variation of Figure 3b is the tota 1 peak-to-peak change). London et a 1. (1) analyzed the fi rst 20 solar rotations observed by SME including the 18 rotations from January 1982 throug.h May 1983. Thei r work cal cul ated the percent range (maximum

- 658-

to minimum) for each rotation and from these values determined the average percent range as a function of wavelength. The average percent range is also a peak-to-peak value and is closely approximated by three times the RMS variation given in Figure 3a.

Z 0 i= « a: « ::-(j)

~ a:

0.5 0. 1

--1982 ~ 0 .4 .s 0 ,06 _._.- 1983 CD

:5 0 .3 3S 0 .06 z 0 i=

0 ,04 « 0.2 2" a: « ::- 0.1 IS 0.02

O L-~~~ __ ~~~~~UL~~

100 120 140 160 180 200 220 240 260 280300

WAVELENGTH (nm)

O ~~-L~ __ ~~-L~~~-L-U 100 120 140 160 180 200 220 240 260280300

WAVELENGTH (nm)

Figure 3a. RMS of SME solar data time series as a function of wavelength. 3b. Total peak-to-peak variation for a typical large 27-day rotation as designated "A" and "8" in Figure 2.

An autocorrelation analyses of the SME irradiance time series show strong peaks at 27 days, 54 days, and 81 days. The magnitude of the 27 day peak in the autocorrelation is approximately 0.5 and fairly constant for wavelengths between 120 and 220 nm. Longward of 250 nm the magnitude of the 27 day peak is lost in the noise of the autocorrelation techni­que. The magni tude of the 54 day peak follows the 27 day peak but is weaker by approximately a factor of two. The anti-correlation at 13.5 day is weak, but nonetheless present from 120 nm to the Al umi num I ab­sorption edge near 208 nm.

3. CONCLUSIONS

Time series of the SME ultraviolet irradiance data for 1982 and 1983 show a strong intermediate term variation, characterized by the 27-day rotation period of the Sun, superposed on a long term downward trend of the data. This downward trend is considered evidence of a solar cycle variation and ranges from a 30% decrease (over the two year period) at Lyman-a, to 1 to _ 2% decrease near 200 nm, and to 0.2% decrease near 300nm. This latteF value is well below the relative accuracy of the measurements but provides an upper limit to the solar variations. After removing the long term trends from the data the intermediate term varia­tions remain. Although the magnitudes of these shorter term variations differ throughout this two year period, general statistical features have be~ deduced. The root mean square deviation of the data sets decreases with increasing wavelength from ±8% at Lyman-a to a value of less than ±I% above 200 nm. The average percent range in these 27 -day rotations (1), exceeds the RMS value by approximately a factor of three.

-659-

ACKNOWLEDGMENTS

The SME project is managed by the Jet Propuslion Laboratory for the National Aeronautics and Space Administration. C.A. Barth is Principal Investigator for SME. The project is supported by JPL Contract 955357. The sounding rocket experiments are supported by NASA Grants NSG 5178 and NAG 5212.

REFERENCES

1. London, J., G.G. Bjarnason, G.J. Rottman, (1984). 18 Months of UV Irradiance Observations from the Solar Mesosphere Explorer. Geophys. Res. Lett., .!!..' 54.

2. Mount, G.H., G.J. Rottman, (1983). The Solar Absolute Spectral Ir-radiance 1150-3173 A: May 17, 1982. ~. Geophys. Res., 88, C9, 5403.

3. Mount, G.K., G.J. Rottman, (1983). The Solar Absolute Spectral Ir­radiance at 1216 A and 1800-3173 A: January 12, 1983. ~. Geophys. Res., ~, C11, 6807.

4. Mount, G.H., G.J. Rottman, (1984). The Solar Absolute Spectral Ir-radi ance 118-300 nm: July 25, 1983. ~. Geophys. Res., in press.

5~ qottman, G.J., C.A. Barth, R.J. Thomas, G.H. Mount, G.M. Lawrence, ·D.W. Rusch, R.W. Sanders, G.E. Thomas and J. London, (1982). Solar Spectral Irradiance 120 to 190 nm, October 13, 1981 - Janu­ary 3, 1982. Geophys. Res. Lett • .2..0 587.

6. Rottman, G.J., (1983). 27-Day Variations Observed in Solar Ultravio­let (120-300 nm) Irradiance. Planet. Space Sci ., 00, 1.

- 660-

A REVIEW OF SOIAR IRRADIANCE MEASUREMENTS BEIWEEN 270 AND 480 NANCMETERS

Sumnary

KENNETH MOE Department of Geolo:rical Sciences

California State University, FUllerton, CA 92634, USA

Recent measurements which have dramatically reduced the uncertainty in the solar irradiance are reviewed: Whereas discrepancies between 10 and 30 % were ccmron ten years ago, these have been reduced to 5 to 10% to­day. Present methods of calibrating solar measurements often depend on a black body as the primary standard. New instruments which can utilize other primary standards are described: These include the electrical substitution radiometer and the self-calibrating photodiode. A new ca­libration technique using an amplitude-stabilized tunable dye laser is also described. It is shown how these new developments can lead to fu­ture illprovements in accuracy.

1. Introduction

The spectral irradiance of the sun is an important quantity used in measurements of total ozone (1-4). The irradiance field at various levels in the earth's atmosphere also enters into photochemical modeling calcu­lations (5). If there are long-term trends in solar irradiance, the global climate could be affected. A decade ago, discrepancies of 10 to 30% in measurements of the solar irradiance were not unusual (6,7). Recently, an ultraviolet double rnonochrcnator with the latest US National Bureau of Standards calibration (8) agreed within 5 to 10% with the highly-regarded measurements of Labs and Neckel (9,10). We therefore think that this is an opportune time to review the recent measurements and to describe sane of the newer developments which we expect will reduce the uncertainties to 1 or 2 % in the next decade.

2. A Comparison of Recent M2asurements with Those of Labs and Neckel

In 1977, when Oran White edited his book on The Solar Output and Its Variation (6), the three best data sets in the near UV still differered by 10 to 20%, and the actual variability of the solar output in this spectral range had not been accurately measured. Beginning about 1981, the discre­pancies among measurements in this spectral range narrowed considerably, and the possible range of solar variability was also reduced:

M2ntall, et al. ( 11) measured the solar irradiance by means of a dou­ble rnonochranator on a parachute between 63 and 53 krn. They corrected for the small amount of ozone absorption by extrapolating the ozone measure­ments made at lower altitudes.

Ozone Symposium - Greece 1984 - 661-

M:Junt and RotbTan (12) reported the latest in a series of rocket mea­surEments in which the accuracy of calibration has steadily improved. They revised the calibration of their 1980 flight, and concluded that (within the instrumental accuracy of about 10%) there was no detectable change be­tween the 1980 and 1982 flights at wavelengths between 210 and 317 run. This result was confirmed by Hall (13) who, canparing the results of four balloon flights of a solar UV sr;ectraneter between 1977 and 1981, found that the solar irradiance in the range 235 to 287 run was constant within 7% during that period; except that the emission cores deep in the Mq II h and k Fraunhofer lines at 280.3 and 279.6 run (which originate in the so­lar chranosphere) increased with solar activity by about 20%.

Heath, et al. (8) and Heath and Schlesinger (14) studied the 27-day solar variations in great detail, using the Nirnbus-7 Satellite. They found variations smaller than 0.5% between 290 and 400 run. At wavelengths near 255 run, the 27 -day variations were typically 3%. In one strong Fraunhofer line, the variation was 6%. Heath et al. (8) also carefully reduced the absolute solar spectral irradiance measured with a UV double rnonochranator on the first day Nirnbus-7 was in orbit. They believe its absolute accuracy to be 5% in the near UV.

These recent measurements are averaged over 10 run intervals and can-pared in Table 1 with the data taken by Labs and Neckel (9,10,15) at Jung-fraujoch.

TABLE 1

SOLAR SPECl'RAL IRRADIANCE AT 1 A. U.

Central Labs & Heath Mentall Mount revelength Neckel 1983 1981 1983

(nananeters) (microwatts per square centimeter per nananeter)

275 (17.7) 19.1 19.3 20.0 285 (27.3) 27.5 28.0 29.7 295 (50.5) 53.3 52.9 54.8 305 (53.7) 57.2 57.2 53.9 315 (65.8) 68.2 68.2 325 (81.8) 87.2 87.2 335 90.0 97.0 345 89.4 94.6 355 94.9 100. 365 105. 113. 375 104. 115. 385 94.5 102. 395 113. 117. 405 163. 415 170. 425 166. 435 167. 445 193. 455 201. 465 199. 475 199.

Unoertainty < 4% 1"V5% '""8% 12 to 14%

- 662-

labs and Neckel constructed their values below 330 nm by constraining rocket rreasurements of other scientists to fit srroothly into their own data at longer wavelengths. For this reason, their data below 330 nm have been placed in parentheses. Note that as measurements improve in accuracy, they approach those of labs and Neckel. We attribute this to the painstaking attention to detail of these two scientists: Details of calibration and rreasurerrent involving geometry, wavelength, and polarization. For example, labs and Neckel measure the center of the solar disc and the center of the ribbon of a standard lamp through the same pinhole, to avoid using differ­ent geometries for calibration and measurement (10).

The imJX>rtance of geometry was confirmed in recent work by the us Na­tional Bureau of Standards: Measurements with and without a diffuser dif­fered by 5.2% (16). In order to derive the average intensity over the whole solar disc (i.e., the spectral irradiance), Labs and Neckel integrate the center-to-limb variation, which has been measured by several observers. They say that this can be done with an accuracy of 1 % or better. Several rrethods of integrating the limb darkening data have recently been can­pared (17). An illuminating discussion of the problems of solar measure­rrent has been given by Pierce and Allen (15).

3. New Developnents

The discrepancies among measurements in the near UV have been re­duced to .the 5 to 10% level, as was shown in Table 1. It appears possible that more careful attention to detail can bring these discrepancies down to the 3 to 5% level, using the prevailing technology of standard lamps calibrated by reference to black bodies as the primary standard; however, in order to measure the long-term variations in ozone and in solar UV ra­diation, it would be desirable to have an accuracy of 1% or better. Let us oonsider several ways in which this might be approached.

A decade ago, Geist et al. (18) demonstrated that a tunable dye laser oould calibrate to an accuracy of 1% the canbination of a silicon photo­diode and narroW-bandpass filter by canparison with an electrically cali­brated pyroelectric detector. This method has not yet been demonstrated in the UV because a sufficiently stable tunable UV laser has not been found. A more promising develoJXClent for the UV is the electrical substitu­tion radianeter (ESR) (19). The ESR substitutes electrical standards for optical, achieving an accuracy of 0.3% in the visible, and 1% in the UV. This instrument is JX>rtable, and operates at room temperature. A more e­laborate stationary ESR which operates at 2C1< and has an estimated accu­racy of several parts in 104 was developed at the National Physical Labor­atory (England) by Martin and QJinn (20).

An even more amazing develoJXCleTIt is the self-calibrating photodiode (21,22). This little device was calibrated by an ESR, using an amplitude­stabilized He-Ne laser at 632.99 nm, with the renarkable results shown in Table 2. The absolute accuracy of the diodes is believed to be ±. 0.04%, but in this case the two diodes agreed within 0.01%. The absolute accura­cy of this ESR in the visible is ± 0.3%, but its mean difference fran the average of the two diodes was + 0.06%, with a standard deviation of :!: 0.11%.

-663 -

TABLE 2

CCMPARISON OF POWER MEASUREMENTS BY THE ESR AND SELF-CALIBRATING PHOIDDIODES

Run Photodiodes ESR SN 11 Diodes NJ. SN 11 SN 190 SN 190 ESR

(rrw) (rrw) (rrw) 1 1.0117 1.0114 1.0096 1.0003 1.0019 2 1.0131 1.0131 1.0116 1.0000 1.0015 3 1.0132 1.0133 1. 0148 0.9999 0.9985

Table 2 illustrates the unusual situation in which the transfer stan­dard (the photodiode) has higher ac=acy than the primary standard which is reing used to calibrate it. Unfortunately, the new diodes do not func­tion so ~11 at the shorter wavelengths: Between 550 and 380 run the inter­nal quantum efficiency of individual diodes can be reduced by 5 to 20% be­cause of Auger transitions and midgap states associated with defects and impurities; however, the quantum efficiency can be maintained at 99% or a­bove in this interval by a corona discharge to the oxide surface (22). At wavelengths shorter than 380 run, the quantum efficiency increases because some photons are sufficiently energetic to create more than one electron­hole pair. This increase can be seen in Table 3. The efficiency of the photodiode which has been pretreated by a corona discharge is 100% at 400 run with an uncertainty considerably srraller than 1%. The efficiency has risen to 108% at 290 run, with an uncertainty of 1 % (23).

TABLE 3

INTERNAL QUANrUM EFFICIENCY OF PHOIDDIODES AT UV WAVELENGI'HS

W:lvelength (run) Efficiency (%)

400 100

350 101

310 105

290 108

270 106

250 118

Although the internal quantum efficiency is close to unity, the ex­ternal quantum efficiency is not so high, and is strongly dependent on wavelength and polarization because of the reflection of the incident light at the surface of the diode. A device has been built incorporating four photodiodes so that nearly all the incident light is absorbed by mul­tiple reflections. Another device which would also be insensitive to po­larization has been designed (22). This is important because gratings and prisms polarize the light corning from the sun, and therefore can cause er­rors in measurement. The double rnonochranator which was at the National Center for Atmospheric Research contained an optical scrambler which aver­aged all polarizations, but I do not know of any other monochromator which has this feature.

4. Conclusions

Recent measurements of the solar UV irradiance agree within 5 to 10%. Present methods, which depend for their absolute calibration on black bodies, have the potential to measure the solar irradiance with an ac=a­cy of 3 to 5%. If better accuracy is to be achieved, methods of calibra­tion based on other primary standards must be employed. 'TWo promising new devices are the electrical substitution radiometer (ESR) and the self-

-664-

calibrating photodiode. Each of these devices appears capable of calibrat­ing W rreasurements with an accuracy of 1% or better. With more careful attention to details of geometry, polarization, and limb-darkening, it seems reasonable to expect that solar irradiance measurements using these new devices will come to agree within 1 to 2% in the next decade. This, in turn, could lead to improved measurement and monitoring of total ozone.

ACKNCMlLEDGEMENI'S

I would like to thank Jon Geist for many valuable discussions, and Donald Heath for supplying his solar data in tabular form.

REFERENCES

1. Dobson, G. M. B., Annals of IGY, 5, 46 (1957). 2. Paetzold, H.-K., and F. Piscalar,-Beitr. zur Physik der Atm., 34, 1/2

(1961). 3. DeLuisi, J. J., J. Geophys. Res., 80, 345 (1975). 4. Garrison, L. M., D. D. Dada, and A-:-E. S. Green, Appl. Opt., ]&, 850

(1979) • 5. Logan, J. A., M. J. Prather, S. C. Wofsy, and M. B. McElroy, J. Geo­

phys. Res., 86, 7210 (1981). 6. White, O. R.(Ed.), The Solar OJtput and Its Variation, Colorado Assoc.

U. Press, Boulder, CO (1977). 7. Kohl, J. L., W. H. Parkinson, and C. A. Zapata, Astrophys. J., Suppl.

Ser. 44, 295 (1980). 8. Heath-;-D. F., R. F. Donnelly, and R. G. Merrill, Nimbus-7 SBW Observa­

tions ••. NOAA T. R. ERL 424- ARL 7 (Aug., 1983). 9. Labs, D. and H. Neckel, Z. Astrophys., 69, 1 (1968).

10. Labs, D. and H. Neckel, in Proc. Smithsonian Conf. on Radiation, 269, Smi thsonian Inst., Washington (1973).

11. Mentall, J. E., J. E. Frederick, and J. R. Herman, J. Geophys. Res., 86,9881 (1981).

12. Mount, G. H. and G. J. Rottman, J. Geophys. Res., 88, 5403 (1983). 13. Hall, L. A., J. Geophys. Res., 88, 6797 (1983). 14. Heath, D. F. and B. M. Schlesinger, Abstract SA 22-01, EOS - Trans.

Am. Geophys. U., 64 (No. 45), 780 (Nov. 8, 1983). 15. Pierce, A. K. and:R. G. Allen, in REF. 6, 169 - 192. 16. Saunders, R. D., H. J. Kostkowski, A. E. S. Green, J. F. Ward, and

C. H. Popenoe, High Precision Atmospheric Ozone Measurements, J. Geo­phys. Res., in press.

17. Moe, K., Solar Phys., 88, 9 (1983). 18. Geist, J., B. Steiner,:R. Schaefer, E. Zalewski, and A. Corrons, Appl.

Phys. Ltrs., 26, 309 (1975). 19. Geist, J., L. B. Schmidt, and W. E. case, Appl. Opt., 12, 2773 (1973). 20. Quinn, T. J. and J. E. Martin, in Temperature, Its Measurement and

Control ••. , 5, 169 (1982). . 21. Zalewski, E.-F. and J. Geist, Appl. Opt., 12, 1214 (1980). 22. Zalewski, E. F. and C. R. Duda, Appl. Opt, 22, 2867 (1983). 23. Wilkinson, J. F., A. J. D. Fanner, and J. Geist, J. Appl. Phys., 21.,

1172 (1983).

-665 -

THE GLOBAL RESPONSE OF STRATOSPHERIC OZONE TO ULTRAVIOLET SOLAR FLUX VARIATIONS

DONALD F. HEATH NASA/Goddard Space Flight Center, Laboratory for Atmospheres

BARRY M. SCHLESINGER Systems and Applied Sciences Corporation

Summary

The relation between rotational modulation of the ultraviolet solar irradiance and variations in atmospheric ozone has been investigated, using Fourier transform harmonic analysis and cross-correlations. Ozone variations with the same period and phase as 13.5 ~ay or 27-day solar flux variations occur at tropical and subtropical latitudes, over a range of pressure levels centered about 3 mbar. The solar­forced oscillation is stronger in the summer hemisphere; as tempera­ture-related variations would be stronger in winter. Changes in solar irradiance over the II-year cycle can be estimated by scaling rotational modulation. Using this estimate and the ozone-sun rela­tion obtained for rotational modulation yields solar cycle changes of 3.5% in 3 % mixing ratio comparable to that predicted from halo-carbons, and 0.7 mbar in total ozone.

1.0 Introduction

Evidence is accumulating (1) that solar variability influences cli­mate, weather, and other atmospheric properties, in particular as solar radiation drives photochemistry. Ozone profiles derived from the Limb Infrared Monitor of the Stratosphere (LIMS) on Nimbus-7 for a seven month period (2), along with concurrent measurements of the solar flux from the Nimbus-7 Solar Backscatter Ultraviolet (SBUV) experiment show variations in atmospheric ozone in phase with 13.5 day solar variabil­ity. The two years of ozone data available from the SBUV experiment now permit investigation of the relation between variability in ozone and in the solar ultraviolet flux, as a function of altitude, latitude, season, and variation period.

The SBUV instrument is described in (3). Three consecutive contin­uous scan measurements of solar irradiance are made once each day, at the northern terminator. Approximately 100 ozone soundings are recorded each day, near local noon. A detailed deployment schedule appears in (4). Data gaps greater than one day are rare; none is greater than 3. The measurements are thus well suited for time series analysis.

2.0 Variations in Solar Ultraviolet Spectral Irradiance

Solar irradiance near the aluminum absorption edge at 208 nm should influence stratospheric ozone. Variations in the vicinity of the Herz­berg band of O2 (maximum dissociation rate at 220 nm) will change the rate of production of 03, when O2 dissociation at 35 km produces 0 with

Ozone Symposium - Greece 1984 -666 -

subsequent three-body recombination yielding 03. Examination of the solar flux measured by SBUV has shown it to vary in a way consistent with that expected from modulation by the rotation of active regions into and out of the sun-earth line. Figure 1 shows the daily variation

10, 5 ~------------------------------------------------------------------,

205 nm

- 10,0

1 w u z < o ~ go

9,5

!--IVIHAI--j

I----IIX-C'-------+-----IIIX-C'------+------"'X-Cl------i 9 ,0 L_~~ __ ~~~ __ L_-L~L_~~ __ L-__ ~ __ ~~~ __ L__L~ __ L--L~ __ ~_J

11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11

1978 1979 1980

Figure 1. Solar flux variations at 205 nm.

of the sun at 205 nm November 1978-November 1980. The solar flux under­goes quasi-cyclic variations; the period switches between 27 days when there is one active longitude and 13.5 days when there are two. Associ­ated atmospheric changes should switch between 27 and 13.5 day periods with the period of the forcing solar flux variations.

3.0 Changes Associated with Rotational Modulation

Figure 2 shows the variation of ozone mixing ratio as a function of time for the first year, together with'the concurrent variations of ultraviolet solar flux. In addition to the normal seasonal ozone varia­tions, shorter-term variations in ozone coincident with those in solar flux can be seen, especially for April and May 1979 for 2-7 mbar.

Fourier transform harmonic analysis was used to verify the period­icity of the ozone variations and to survey their altitude and latitude dependence. Harmonics were calculated for a lOB-day interval, May 14-August 30, 1980, IV(HA), for which Figure 1 shows especially strong solar flux variations. Figure 3 shows the altitude dependence of the peak-to-peak amplitude of the 27-day wave for 100 latitude zones cen­tered at 300 S (winter), 0°, and 300 N (summer). The solid line shows the amplitude of the 27-day wave itself in percent peak-to-peak. The dashed line. is an estimate of the background noise based on the amplitude at neighboring periods. Harmonic analysis of the solar flux confirmed the dominance of 27-day variability in the solar flux. Ozone varies with the same period as the solar flux over a wide range of altitudes. The maximum amplitude in the southern (winter) hemisphere, about 3%, occurs

-667 -

at 1.5 mbar. In the tropics and northern hemisphere, the maxima occur at 3 mbar, with amplitudes of 2.0% and 1.6% respectively. The derived day of ozone maximum in the 27-day cycle is within a day of that for the solar flux.

The harmonic analysis showed ozone variations to be most pronounced at the 3 mbar level. Cross-correlations between time series of 3 mbar mixing ratio and solar flux were calculated. In order to distinguish

the effects of solar forcing from periodic ozone changes ·in­duced by quasi-periodic temper­ature fluctuations (5), ozone mixing ratios and solar flux were cross-correlated for three

~6 six-month equinox to equinox

-2 ~I II~l m ~arNil. I ~ periods covering a winter sea-son in one hemisphere and sum-mer in the other: periods I, II, and IlIon Figure 1. Cross-correlations were calcu-

10~ • 5 lated for lags' of 0-59 days for 00 , 300 , and 600 north and

~~2m Bar ~.. south and for 800 in the summer ';. hemisphere. Figure 4 plots

9 ~ f 9 cross-correlation as a function of lag; positive lag signifies

:-E "63~\.II~~~:kt\Barr/~~~i 13 that solar flux is being corre-~ r~ r.r~.i' lated with ozone at a later

time. For 300 N, 00 , and 30°5,

~I I 12 with the possible exception of

6 300 5 (winter) for period I, U 15 r l 4m Bar I!. _ . ~ 15 there is a relative maximum at ~._Eo-: ~.', !s4~. AI!~l ~~~:....\l17 0 days lag; other relative 'Y .~.~. ·irY~ IE maxima occur at intervals of 27

14 I I ~ days (Periods II and III) or 13 ~ r: 1 1/2 days Period I). The maxi-~ ',68

~r,t!k:, 5~J.11 B,:a: ~L ~ "~ ..... :'u 16 mum at zero lag shows that ~ -'~l ~I~=~~~~~ ozone and solar flux vary in ~ phase; the maximum in ozone is o 7m Bar" 15 within a day of the maximum in o 17 I~ 17 solar flux. The other relative

maxima represent the correla-Z tion between the ozone and the

00 16u~~~-u--~~~~~~~~-=~~~16 solar flux separated by an in-

N Nov. tegral number of cycles. The 1978 interval between cross-corre-

Figure 2. Solar flux and stratospheric lation maxima is the same as ozone November 1978-0ctober 1979. the period of solar flux var-

iations: 27 days for periods II, III, 13.5 days for period I, additional evidence for an ozone UV link. The strongest maximum to minimum variations in cross-correlation occur in the summer hemisphere, whether it is the southern or northern one. Possible changes in ozone related to temperature variations would be strongest in winter.

-668 -

4.0 Long Term Changes

Heath and Schlesinger (6) estimate long-term and slowly varying changes in UV solar irradiance by comparison with the F(10.7 cm) radio flux. The modulation ratio R between irradiance at a given time and its value at minimum is given by an equation of the form

R = 1 + a[F(lO.7) - 65)/100 (1)

0.' , 0,' " , , 0.' '.

1.0 ,

... ) ~ ' ,0 ~ / d

3,0 , , ' ,0 ,

: - M

•. M -M

305 o 30N

1.0 ' .0 3 ,0 1.0 ' .0 3.0 1.0 ' .0 3.0

WAvE AMf'UTUOt: I'"

Figure 3. Harmonic analysis of ozone variations during 108 days May 14-August 30, 1980.

~[,-----~'~--~------

I I " I • ! ·1----'--'4--.1+-++- /--'1-1"-I .

;g- :: . . ~ ~

~~- ::-.

.t to " ... .. " l'I.

"~ · . · " , - -- . · .. · . " - '"

l~ ~i .. . · .. ~ ~ " . · .. .. . · . · -.~. .. . · . · .

~ . ~ .n • » w ~h

Figure 4. Cross-correlations: 205 nm solar flux vs. 3 mbar ozone.

- 669-

For R(20S nm), a = S.SxlO-2 in equation (1), yielding a change of 8.8% over cycle 21. Harmonic analysis yields an average maximum ozone variation of about 2.0%, while average modulation of the solar flux at 205 nm is 5.0%. Integrating these observed changes in the ozone profile gives changes in column ozone of 0.22% at 300 S, 0.48% at 00 , and 0.41% at 300 N, corresponding to a 0.4% average change in column ozone for a 5% change in solar flux at 205 nm. These relationships can be used to es­timate ozone change given the FlO.7 cm radio flux. For ozone near 3 mbar, the altitude of maximum amplitude ~f ozone variations R(03 3 mbar) is given by equation (1) w!§h a = 2.2xlO 2, while for total column ozone R[n(O )], a = 4.4xlO • These formulas predict a solar cycle variation of about 3.5% for ozone near 3 mbar and about 0.7% variation in total column ozone.

The estimated 3.5% change in ozone at 3 mbar due to the solar cycle variations in solar spectral irradiance is comparable to the predicted ozone depletion due to chlorofluorocarbons (CFC's). During the rising part of the UV flux solar cycle it will counteract the predicted trend to CFC's while during declining phases it will approximately double the rate of ozone decrease.

5.0 REFERENCES

1. NATIONAL ACADEMY OF SCIENCES (1982). Solar variability, weather, and climate. National Academy Press, Hashington, D.C.

2. GILLE, .J. C., SMYTHE, C. M., and HEATH, D. F. (1984). Observed ozone response to variations in solar ultraviolet radiation. Science, 225, 317-320.

3. HEATH, D. F., KRUEGER, A. J., ROEDER, H. A., and HENDERSON, B. D. (1975). The solar backscatter ultraviolet and total ozone mapping spectrometer for Nimbus G. Opt. Eng., 14, 323-331.

4. FLEIG, A. J., HEATH, D. F., KLENK, K. F., OSLIK, N., LEE, K. D., PARK, H., and GORDON, D. (1983). User's guide for the Solar Back­scatter Ultraviolet (SBUV) and the Total Ozone Mapping Spectrometer (TOMS) RUT-S and RUT-T data sets: October 31, 1978 to November 1, 1980. NASA.

5. ELLING, W. and SCHWENTEK, H. (1981). Similar periodicities in the range 12 to 150 days in solar, ionospheric, and atmospheric time series. Solar Physics, 74; 373-384.

6. HEATH, D. F. and SCHLESINGER, B. M. (1984). Temporal variability of UV solar spectral irradiance from 160-400 nm over periods of the evolution and rotation of active regions to maximum and minimum phases of the sunspot cycle. Proceedings International Radiation Symposium, Perugia, Italy.

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OZONE AND SUNSPOTS: WHY CAN WE NOT FIND A DIRECT CORRELATION?

MANFRED SCHMIDT Max-Planck-Institut fUr Aeronomie, D-3411 Katlenburg-Lindau, F.R. Germany

Abstract: A direct relationship between total ozone and sunspot numbers cannot be found, if we also consider the recent solar cycles No. 20 and 21. The dominating factor for the total ozone over stations in middle and higher latitudes is the stratospheric meridional transport. The strength of the zonal and meridional circulation in middle latitudes of the Northern Hemisphere is largely influenced by the solar activity, if, beside the sunspot numbers, the solar faculae areas are also taken into account. Considering that, there exists an indirect relationship between total ozone and the solar activity via the atmospheric circulation.

1. Total ozone, sunspots and atmospheric airculation Total ozone measurements in Arosa ha started ln the late twenties,

this series of data is the longest that exists. In Fig. 1, the smoothed monthly values of Arosa, from which the annual variation was eliminated, are compared with the sunspots. The deviation in time between the maxima of the two series has shortened from 38 and 42 months during the solar cycles 17 and 18, 1934-1954, to 16 and 8 months during cycles 19 and 20, 1954-1975, and 'even to -14 or -37 months in the recent sunspot cycle No 21. That means, the respective ozone maximum shifted from the decreasing part of the sunspot cycle via the maximum part in 1969/70 to the increasing part in the recent cycle. The last ozone maximum around 1977/78 was much smaller than the earlier ones. It can be concluded from Fig. 1 that there exists no direct correlation to the sunspot cycle.

A very good correl ation can be found if the ,Arosa total ozone values are correlated with circulation indices. Stratospheric maps are available since,., 1958 (30 hPa) and N 1962 (100 hPa). We used them to calculate the potential height differences between Gibraltar (36°N) and Bear Island (74°N), i.e. over Western Europe. The monthly values ~~, deviations from 17 year monthly means, are an index for the strength of the zonal circula­tion over Europe in the respective height. These ~~ are anticorrelated with the Arosa total ozone, i.e. we have a good correlation with the strength of the meridional circulation (Fig. 2, reversed scale for ~~).

i \)0 z 0 100 ~ ~ so

OL....::>=::"_

10

o <l 10 . ! o~~~A.~~4r--~~~~~~~~~~~~#-~~~~~~~~

~.1 0

1931 35 19<0 ~5 1950 55 1960 6S 1910 JS 1980

Fig. 1 Sunspot numbers, and total Qzone of Arosa and Hohenpei~enberg. 1lO3 [DU] = deviations from average monthly means, smoothed

Ozone Symposium - Greece 1984 - 671-

The correlation coefficient between ~3 and ~~ 30 hPa is -0.30 at a significance level of > 99%.

There exist no aerological measurements or maps of higher atmospheric levels for a comparison with earlier years of Dobson measurements in Arosa. For this reason, we also used two circulation indices ZI, based on air pressure measurements at the surface. These are defined as ZI = ~ (35°N - 650 N); ZIcp (circumpolar) = summarized around the globe, ZIa (sectorial) = summarized in the European sector between 200W and 40 E. The indices, based on the total air pressure are also an expression for the strength of the zonal circulation in middle northern latitudes. Fig. 3 shows the good correlation of the strength of meridional circulation (re­versed scale of ZI, ~ = deviations from 68 year monthly means) with the Arosa total ozone. Especially the high maxima in the parameters N 1940/41 and 1968 - 70 and the minima ~1948/49, 1974/75 and in recent years are im­pressive, but also nearly all the other maxima and minima have a good tem­poral correlation. These correlations between total ozone and the different circulation parameters also suggest a satisfactory correlation between the different kinds of circulation indices used. Fig. 4 shows that this is the case if generally considered. A detailed discussion, especially of the de­viations in the stratospheric 30 hPa circulation at several times, cannot be given in this brief report. Strongly smoothed and considered in an ex­tended time interval, the circulation shows nearly the same features at all atmospheric levels up to middle stratospheric heights. We conclude, that the ozone over Arosa is generally governed by the strength of meridional circulation, i.e. the meridional transport of ozone from source regions in the tropics dominates.

2. Possible influences of solar radiation and solar activity on the northern hemlsEherlc circulation

The clrculatlon parameters ZI CR are available since 1899. If we treat the values from 1899 to 1931 in the same manner like those of the following years, plotted in Fig. 3 and 4, an interesting fact can be deri­ved, Fig. 5: From 1899 to 1938 the zonal circulation mainly was increased (~ZIcp > 0, with only a few exceptions), from 1939 to 1971 it mainly was decreased (~ZIcp<O). That means, a "secul arlO change in the zonal circul a­tion took place around 1938/39. Changes in the solar radiation could be a possible reason for this basic difference. Baur (1) introduced a radiation index S, which he used for long range weather predictions. This index S combines the presumed contrary influences of sunspots and solar faculae on the solar radiation. The radiation is probably enlarged when the influence of solar faculae exceeds that of the sunspots, related to "middle solar conditions", an vice versa. The faculae are brighter and hotter than the normal photosphere of the sun, the sunspots are colder. We have calculated the index S from 1882 to 1971 (after 1971 no faculae data are available). In Fig. 5, the smoothed values of S are plotted together with ~ZIcp and the values of the spots and faculae. With few exceptions, the same course of the circumpolar zonal index and the radiation index S can be seen, partly even in detail. The correlation coefficient between both indices is +0.35, s.l. > 99%. Obviously, S is mainly < 0 and the zonal circulation is reduced, when within the Glei~berg cycle of the sunspots their numbers are large and the spots exceed the influence of the faculae, and vice versa. The sunspots are governed by the Glei~berg cycle, while the variation in the amplitude of the faculae is much smaller. The course of S, plotted in Fig. 5, is supported by recent papers of Smith and King (2) about relation­ships between sunspots, faculae and the ionosphere, and of Hoyt (3) who calculated a "theoretical solar constant". These three calculated parame­ters about the solar radiation run parallel.

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gpdm "-.-r-r,-,-,-,-"-.-r-r,-,-.-,,,,-.-r-r,-.-,, ;, ·8 ~

i:5

Fig. 2 Total ozone of Arosa and the potential height difference 6H between Gibraltar and Bear Island in the 500, 100 and 30 hPa levels ~ ...... 5.5, 16 and 24 km height. ~6H = deviations from average monthly means, smoothed, reversed scale

AO, ou

20

060) A~ -62J st!(tOtIGI -AZl (irrurnpDlor_

-4

-2 ~

~~~~~~~~~~~~~~~~~Y-~~~~~~~ oj

,9l2 35 '940 .950 55 65 mo 15

Fig. 3 Total ozone of Arosa compared with a circumpolar and sectorial zonal index ZI. ~ = deviations from average monthly means, smoothed. ~I-scale reversed meridional index

64H - 44H 30 hPo 4ZJ lOhP.

hP. gpdrn - 4Z J sectorial

'I -8 - lI.ZJ (ir(u mpotor_

i -2 ~ -1

~ 0

~ ., ~ ·2 "-

·3 ·8 gpdm e ·4

~ 0 c ~ .t. -.. :c

;f ·8 1960 65 1910 15 1980

Fig. 4 Comparison between the potential height differences ~~ Gibraltar­Bear Island in the 30 and 500 hPa levels and the two zonal indices ~I. Smoothed, all scales reversed

- 673-

Fig. 5 Radiation index S, circumpolar zonal index ~ZI, sunspot numbers f and solar faculae area index F. All series smoothed

In Fig. 6, within the ~ears 1959-1971, the best correlation is noticeable between S and ~~ 30 hPa. This suggests the possibility of a stronger influence of that solar radiation on the upper stratospheric circulation than on lower stratospheric and tropospheric circulation. Fig. 7 demonstrates that the Arosa total ozone values are representative at least for Europe, and these values run parallel also with the North American and the Temperate North ozone series. The main maximum in 1969/70 appears in all series and is the most impressive feature, it is in coincidence with the main maximum of the meridional circulation in 30, 100 and 500 hPa in Fig. 2. For this reason the just discussed presumable influence of solar activity on the general atmospheric circulation and the influence of the latter on the Arosa total ozone could probably also be valid for larger areas of the earth's atmosphere and its ozone content. That means that there probably exists an indirect influence on the ozone content via the atmospheric circulation.

The detailed results of this paper will be published elsewhere.

REFERENCES

1. BAUR, F. (1956). Physikalisch-statistische Regeln als Grundlagen fUr Wetter- und Witterungsvorhersagen. 1. Band, Fankfurt am Main

2. SMITH, P.A. and J.W. KING (1981). Long-Term Relationships between Sunspots, Solar Faculae and the Ionosphere. J. Atm. Terr. Physics 43, 1057-1063

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.... "" .. "...,..~~~r-.-r~~-rr~~~,.--.-~~-r....., "

Fig. 6 Radiation index 5, ~ in the 30, 100 and 500 hPa level and ~ZIs' ~ZIcp, all smoothed

au ''''1 r--r-r-...-.--.-.-"-,----,--,,,--r-,,-,----,--,r-r--r-T"'"'T-r-,-,-,

.,

., · 1

Fig. 7 Seasonal values of total ozone (after Angell and Korshover (4)), smoothed. Values of Arosa added

3. HOYT, D. V. (1979). V ari at ions in the Solar Constant Caused by Changes in the Active Features on the Sun. In: McCormac, B.M. and T.A. Seliga (Eds.): Solar-Terrestrial Influences on Weather and Climate, Reidel Publ. Dordrecht/Holland

4 .. ANGELL, J.K. and J. KORSHOVER (1978). Global Ozone Variations: An Update into 1976. Monthly Weather Review 106, 725-737

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Summary

OZONE DEPLETION DURING SOLAR PROTON EVENTS IN SOLAR CYCLE 21

R.D.MCPETERS AND C.H.JACKMAN Laboratory for Atmospheres

NASA, Goddard Space Flight Center Greenbelt, MD 20771 USA

We have analyzed ozone profile data from the Solar Backscattered Ultraviolet Instrument on Nimbus 7 from 1979 to the present and have found clear cases of ozone destruction associated with five SPEs: on June 7, 1979, August 21, 1979, October 13-14, 1981, July 13, 1982, and December 8, 1982. During the SPE on July 13, 1982, the largest of this solar cycle, we observed no depletion at all at 45 km, but a 15% ozone depletion at 50 km increasing to 27% at 55 km, all at a solar zenith angle of 85°. We find a strong variation of the observed depletion with solar zenith angle, with maximum depletion occurring at the largest zenith angles (near 85°) decreasing to near zero for angles below about 70°. The observed depletion is short lived, disappearing within hours of the end of the SPE.

1. Introduction Near the peak of the solar cycle the sun sporadically emits very large

numbers of high energy protons that enter the Earth's atmosphere in the polar regions (above 60 degrees geomagnetic latitude) producing HOx and NOx which catalytically destroy ozone. While changes in ozone caused by the introduction of chorofluorocarbons would be very gradual and difficult to identify, changes caused by an SPE are produced very rapidly, typically in a matter of hours, and are confined to a limited geographic area, the region above 60° geomagnetic latitude.

Weeks et a1. (4) reported a rocket measurement of decreased ozone between 50 km and 70 km during an SPE on November 2, 1969. Heath et al. (1) observed a large ozone decrease near 45 km in Nimbus-4 BUV data following the large solar proton event (SPE) of August 4-8, 1972. McPeters et al. (2) reanalyzed the BUV data and found evidence of ozone depletion during two additional SPEs, in January and September, 1971-Recently Thomas et al. (3) found a large reduction in mesospheric ozone (50-85 km) during the SPE on July 13, 1982 from both the infrared spectrometer and the ultraviolet spectrometer on the SME satellite.

Ozone Symposium - Greece 1984 - 676-

2. Data Analysis An SPE is a transient event lasting only a matter of hours to a few

days at most. Also, at 50 km and above the effect of the particles on ozone is mainly due to the HOx which is produced, and the time scale of this chemistry is again only a matter of hours. Thus, we find it necessary to analyze the ozone data on an orbit by orbit basis to resolve this rapidly changing behavior. We bin the ozone data into solar zenith angle zones, which is equivalent to binning by latitude but separating the ascending and descending parts of the orbit. Of course this means that we are sampling different geomagnetic latitudes from orbit to orbit, but fortunately, the proton flux appears to be fairly uniform above the geomagnetic cutoff latitude. The time dependence and energy spectrum of the proton flux were measured by instruments on IMP-8 and NOAA 6. An energy deposition code was used to model the penetration and degradation of particles in each SPE as a function of altitude and time. For each SPE we correlate the ozone behavior with a contour plot of the proton ion pair production as a function of time and altitude.

3. Results We examined ozone data during fifteen SPEs from this solar cycle and

found that ozone depletion occurred during at least five SPEs: on June 7, 1979, on August 21 , 1979 , on October 13-14, 1981, on July 13, 1982, and on December 8, 1982. None of the SPEs in this solar cycle were comparable to that of August 1972 ; the ozone depletion in each case was short lived and at 50 km and above.

PROTON DEPOSITION PROTON DEPOSITION

.oN PAIRS • >Jt«JCftI NO;

ION PAIRS

• l!X1O·lOXI • >

I • !IOO-l .,

C 200-~ I a 500-1000

~ 02'00-500

~ ~ cJ

~ .. . -.. 2",.

I' I 2",. 8 1 Q c

i a:

i. '! ~ " lmo , ~ ~ (l

0 051"11)

OAV- JUI.V 1i82 OAV - DECE'-"BER 1982

Figure 1 Figure 2

- 677-

In Figure 1 we show the ozone mixing ratio for one week centered on the SPE plotted for three pressure levels: 0.5 mb, 1.0 mb, and 2.0 mb corresponding approximately to 55 km, SO km, and 45 km altitude. The solid straight line plotted for each pressure level for reference purposes is a linear fit to 18 days of ozone data excluding July 13. A linear fit is made to account for possible long term (seasonal) ozone changes. The bounding dashed lines give the one sigma variance over the averaging period.

It is clear that during and immediately after the SPE, ozone at 0.5 mb and 1 mb decreases much more than would be expected from normal variability, while at 2 mb there is no sign of ozone depletion. During the SPE!we see an average 27% ozone depletion from the long term average ozone at 0.5 mb, a 14% depletion at 1 mb, but an insignificant depletion of 0.7% at 2 mb. Although not shown here, data from the same latitude but for solar zenith angle zone SOOto 55° show no evidence of ozone depletion.

The second largest proton event of this solar cycle occurred on December 8, 1982. In Figure 2 we plot data for the 82.5" to 86" solar zeni th angle zone, but now at 71° S. We find the same pattern of ozone depletion in this SPE as in the July SPE: a clear coincidence of ozone decrease at 0.5 mb with the SPE itself, a smaller, coincident depletion at 1 mb, and no depletion at all at 2 mb. We see a 9.1% depletion at 0.5 mb and a 6.1% depletion at 1 mb.

4. Zenith Angle Dependence vs Theory In Figure 3 we show the explicit solar zenith angle dependence of two

SPEs a.t 0.5 mb (upper set of curves) and at 1.0 mb (lower set of curves) .

..

~

I"~·~~ a .. ~ \1 •

~

Figure 3

. ... I

'.Ol r--"'r.=-'=-;1_:::::t:;:~~.:::---.-............. !~ .M Ii If Pol ~

Ii • ,.VN v ;., I ." ! ... ~

."

.10

.n

·"~~"~"'; .. :,,,,":,,~!O~-';! .. ~ .. !;'-'-'-~ .. u.....:;!"'~":'-'""'=:"'~05~'" *_ l(K1 fll arQ.t

IILHMI I '50.0

Figure 4

The largest SPE, that of July 13, 1982 (solid curve), and a small SPE, tha,t (.f June 7, 1979 (dashed curve), are shown here. We are plotting the ratio of the ozone during the SPE to the long term ozone value for each solar zenith angle zone, so that 1.0 represents no depletion at all. A

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good way to distinguish solar proton related effects from other effects is to compare the behavior of ozone from geomagnetic latitudes greater than and less than 60 geomagnetic, since the proton flux drops abruptly to zero between 55 and 60 geomagnetic. The zenith angle dependence plotted in Figure 3 for 10 to 45 is for geomagnetic latitudes less than 55 , while the zenith angle dependence plotted for 40 to 86 is for geomagnetic latitudes greater than 60. For the July event the fact that the 40-45 zenith angle zone shows depletion when the geomagnetic latitude is 60 or greater while the same zone for geomagnetic latitudes less than 55 shows no depletion clearly est·ablishes that the ozone depletion was related to the proton event. In the June event. on the other hand, the lack of a transition at 42.5 indicates that any depletion at this solar zenith angle was too small to distinguish. Only above 70 solar zenith angle and at 0.5 mb is ozone depletion clear for this event.

In Figure 4 we compare the ozone depletion versus solar zenith angle for the July 13, 1982 SPE as observed by SBUV (N), by the SME ultraviolet spectrometer (X), and by the SME infrared spectrometer(O) with the results of a one-dimensional photochemical equilibrium model (lines). Line A is the model predicted ozone depletion assuming no ozone depletion above 50 km. Line B results when the model includes ozone depletion above 50 km commensurate with observations; the increased penetration of UV to lower altitudes rather than direct particle effects produces the ozone depletion at 50 km. The model estimates less ozone depletion at 50 km than is observed by SBUV but reproduces the zenith angle dependence, including a "self-healing" effect at solar zenith angles greater than 84.

REFERENCES

1. Heath, D.F., A.J. Krueger, and P.J. Crutzen, "Solar proton event: Influence on stratospheric ozone," Science, ill, 886-889, 1977 •

2. McPeters, R.D., C.H. Jackman, and E.G. Stassinopoulos, "Observations of ozone depletion associated with solar proton events," J. Geophys. Res.,,§§, 12071-12081, 1981.

3. Thomas, R.J., C.A. Barth, G.J. Rottman, D.W. Rusch, G.H. Mount, G.M. Lawrence, R.W. Sanders, G.E. Thomas, and L.E. Clemens, "Mesospheric ozone depletion during the solar proton event of July 13, 1982 : Part I Measurement," Geophys. Res. Lett., 1.2., 235-255, 1983.

4. Weeks, C.H., R.S. Cuikay, and J.R. Corbin, "Ozone measurements in the mesosphere during the solar proton event of 2 November, 1969," J. Atmos. Sci., l2, 1138, 1972.

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1. Summary

ULTRAVIOLET IMAGERY OF THE SKY

W.F.J. Evans, J.B. Y~rr and n.I. Wardle Atmospheric Environment Service

4905 Dufferin Street Downsview, Ontario, M3R 5T4, Canada

Sky scans in the ultraviolet spectrum have been obtained with a Brewer ozone spectrophotometer programmed to measure the ultraviolet light intensity at 320 nm from the sky as a function of azimuth and zenith angles. The spatial scanning was achieved by programming the solar tracker unit for a raster scan of the sky. Colour images of the celestial hemisphere are constructed by assigning the UV intensity measurement to a colour scale and mapping them as a picture on a colour display. Sky scans have been taken at 20 minute intervals throughout selected days.

Preliminary results of some of the colour images are presented. In the UVB region, on a clear day, the zenith is brighter than the horizon (in contrast to the situation for visible wavelengths). Future refinement and applications planned for this UV imagery are discussed. One ex~mple of these applications is the detection of S02 plumes from stac ks.

2. Introduction

It is intriguing to speculate on how the worl~ looks in wavelength regions which we cannot see. The ultraviolet region around 300 nm has not been explored in much detail. In this paper we describe an instrumental method to create ultraviolet images of the sky. Since the Brewer spectrophotometer is mounted on a computer pointing azimuth system and the zenith pointing is an integral part of the instrument, it is easy to generate any desired scan of the sky by programming the Commodore PET (CBM 8032) computer in BASIC language. Once the mathematical procedure for the scan is designed it is easy to program the scan into the computer.

3. Methodology

In this project we decided to scan the entire sky in a rectangular grid; an array with 13 by 13 pixels was generated beginning in the north and scanning from west to east in a line by line raster. This generated an array raster of 13 lines with 13 elements in each. In making the measurements, the Brewer was pointed at the midpoint direction of the pixel.

The raster scan was a Celestial Projection linearly proportioned with elevation angle. A 13 x 13 matrix with look angle azimuths and elevations was precalculated to yield uniform coverage of the sky on the all sky projection. The scan starts at 0° azimuth and 0° elevation.

Ozone Symposium - Greece 1984 - 680-

The order of the scan element is determined by increasing azimuth angle and then by increasing zenith angle for 2 or more scan elements at the same azimuth. The sky is scanned for 0 0 azimuth to 360 0 azimuth and then back to zero azimuth.

The equipment used for the data acquisition was an automated Brewer which consists of a Brewer spectrophotometer mounted on an azimuth pointing system. The Brewer has an elevation scanning prism to follow the solar variations in zenith.

The Brewer and the azimuth pointer are controlled by the same Commodore CBMmicrocomputer. Thus an algorithm for scanning the sky could be programmed in RASIC. The scans of the sky were conducted over a 20 minute period.

The data were recorded on the PF.T model 4040 disc drive. The 4040 disc is compatible with the Commodore 64 model 1541 Disc Drive. The data were then displayed on a Commodore 64 \vith a 1702 Colour Monitor. The monitor screen was photographed with a Polaroid camera and a 35mm Pentax camera. An image analysis and display routine was programmed in BASIC on the Commodore 64. The C64 system is capable of 16 colours with a resolution of 25 by 40 pixels. A 25 by 25 area was used to display the sky scan; the remaining 15 by 25 area of the screen was used for the intensity colour scale and the identifying information. This resulted in an oval rather than a round sky image due to the retangular pixel of the C64.

To assist in the interpretation of the Brewer ultraviolet data, some visible images from a MOlHTEQ sky scanner were processed into the same data format as the Brewer data. The visible images could then be viewed on the same format display for comparison.

The field of view of the Brewer is only 2 degrees; however, the central direction was considered to be representative of the 2 degree pixel. The 13 by 13 array was interpolated into a 25 by 25 pixel array to facilitate display on the Commodore 64 computer.

At the horizon, the Brewer measures the horizontally polarized component of the sky radiance; the polarization configuration of the instrument is described by Kerr et al (1). We will not explain the complexities of the polarization on the sky image, but caution the reader of the presence of this effect on the appearance of the sky images.

4. Sky Imagery

The Brewer was used to acquire sky raster scans on several days. In order to interpret the ultraviolet images from the Brewer, some visible imagery taken with an instrument called the Sky Scanner, manufactured by Moniteq for AES, will be considered.

Figure 1 shows an all sky photograph taken with a fisheye lens on a 35mm camera. The image of the horizon is oval rather than round to match the image display system used with the Brewer data. There are buildings on the horizon, clouds in the blue sky and the sun is in the southwest quadrant of the sky.

Figure 2 shows an image on a clear day taken with the sky scanner in the visible spectrum at 550 nm. The intensity to colour scale shown on the right side of the photograph has been chosen to give a uniform blue sky and a bright sun indicated by the yellow pixel in the south­west quadrant. The sky scanner has only a resolution of 30 degrees, but

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the data has been interpolated down to the 25 by 25 pixel format of the Brewer raster so that the same display program could be used.

Figure 3 shows another visible sky scanner image at 550 nm taken on a clear day as well. Here, no attempt has been made to simulate the appearance of the sky to a human eye. ~ather, a spectral intensity to colour scale has been used with blue representing the brightest pixels and red the dimmest (in astronomy, this corresponds to blue stars being hotter and brighter than red stars). Note that the zenith is the darkest (red) while the horizon is bright (yellow) due to the Van Rhijn effect. The sun of course is much brighter as represented by the orange dot within the bright halo (blue pixels).

Figure 4 shows a sky scanner image in the 360 nm region, in the violet end of the spectrum. The same astronomical intensity colour scale has been used as for Figure 3. ,he nature of the image has changed somewhat. The zenith sky is still dark (black), but as the sky (light brown) brightens towards the horizon, it reverses and dims again close to the horizon (black) due to atmospheric absorption. This effect is even more pronounced with the Brewer image.

Figure 5 shows a Brewer image in the ultraviolet at 320 nm. Here the same astronomical intensity scale has been used as for Figures 3 and 4. The sun is apparent as the dark blue dot in the centre of the light blue halo in the southwest quadrant. Now, the zenith sky is brightest (dark green) and the intensity falls rapidly with increasing zenith angle towards the horizon (dark red). This effect of horizon dimming is caused by ozone absorption. The path through the atmosphere is much larger for horizon rays and the strong absorption by ozone dominates the horizon brightening due to the Van Rhijn effect on scattering. The strange "peanut" shape of the zenith sky (green colour) is caused by the effect previously mentioned in the introduction. In any case, this is an image of what the sky looks like in the ultraviolet, a region which we cannot see by eye.

In order to enhance our understanding of the ultraviolet image, we have tried to make it appear natural as we see the sky in the visible, by changing the intensity colour scale. Figure 6 shows a version of the same image which looks similar to a visual sky. The sun has been marked by a solar symbol "9" and the halo is yellow. But we have failed in our attempt because the sky dims towards the horizon (grey).

In order to study this horizon dimming effect, we have reversed the intensity colour scale from Figure 6 to Figure 7. Now, the horizon is brighter (green and yellow), the zenith is dark (grey), but the sun and the halo are also dark (black). This demonstrates both the power and the limitations of colour image analysis.

Figure 8 shows a Brewer image in the ultraviolet on the afternoon of another clear day (January 12, 1984). The sun is still locatable and the polarization "peanut" shape is distinguishable; as well the rest of the picture is similar to Figure 5; although the sky intensity levels are lower.

5. Conclusions

Spatial scans of the entire sky in the ultraviolet region of the spectrum at 320 nm have been measured with the Brewer ozone spectrophotometer. These have been displayed on an inexpensive colour image analysis system. The ultraviolet images have been compared

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with visible sky scans at 550 and 360 nm. In contrast to the horizon brightening apparent in the visible image, the ultraviolet image dims towards the horizon due to ozone absorption. Although the images demonstrated in this paper have only a resolution of 14 degrees, they show excellent potential for applications such as the detection of S02 plumes from stacks. To realize the full potential it will probably be necessary to add some polarization refinements to the Brewer. A zero order quarter wave plate and another polarizing prism would allow a complete polarization description of the sky radiance. The Brewer images give a vision of the sky in the ultraviolet which is considerably different from the visible view to which we are accustomed.

Acknowledgements

The image display system software was developed by Glenn Evans. Dr. B. McArthur made a major contribution by processing the Moniteq sky scanner data to our Brewer data format.

References

(1) Kerr, J.B., C.T. McElroy, R.A. Olafson, D.I. Wardle, and W.F.J. Evans, The Automated Brewer Spectrophotometer, this volume.

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Figure 1 An all sky photograph of a clear day with clouds.

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2118116 8

t i

+"t -, •••••

Figure 3 Sky scanner image on a cle~r day for wavelength of 550 nm.

Figure 2 Sky scanner image at 550 nm on a clear day in a photographic simulation.

Figure 4 Sky scanner image on a clear day for wavelengths below 360 nm.

-684 -

Figure 5 ~ Brewer sky scan on a clear day at 320 nm (23 January 1984).

Figure 7 A reversed intensity scale version of fi0ure 2 (a clear day scan).

- 685-

Figure 6 A random pixel version of the Brewer image in figure 2 (a clear day scan).

"~ : .... ; ; "( lS4e 2' ...... : e

: ... ... ... : ••• ... 1

: ... .: •• 2 ... •• • 3

: .. •• 4 •• •• •• , •• •• .~ •• 1 •

• :H •

::._ .. ::: S\.I .. ~ .. S£

Figure 8 A Brewer sky scan on another clear day (12 February 1984).

MJNOCHRC1vlATIC W-MAGNIFICATION FACI'ORS AND TCYI'AL OZONE

C.S. ZEREFOS, A.F. BAIS, I.C. ZIOMAS Physics Dept., Lab. of Atrrospheric Physics, Box 149, University of Thessa10niki, Greece

Surranary

The BREWER MARK II spectrophotometer is used to obtain simultaneous mea­surements of total ozone and W flux at about 302, 306, 310, 313, 317 and 320 run are used to estinate the ratio of the percent change in to­tal ozone which is the W nagnification factor (W-MF). The dependence of the nonochronatic W-MF on solar zenith angle and initial total ozo­ne under representative envirornenta1 quality conditions is presented.

1 • 1 Introduction

The shortest W wave1enghts penetrating the atrrosphere are the najor cause of skin carcinoma as it has been documented by several investigators (Urbach et al., 1974, Urbach, 1966). The nost effective wavelength in sun­light about skin erythena is within 3nrn of 305 nrn and for carcinogenesis the effective wavelength is in the region 290-320 nrn (Urbach et al., 1974).

Various models and several field measurements provided estimates of the relation between the increase in W-B that is associated with a decre­ase in atnospheric ozone (Urbach et a1., 1975, Machta et a1., 1975, Cutchis 1974, Dave and Halpern, 1976). The ratio of the percent increase in W-B to the associated percent decrease in co1unmar ozone is usually quoted as the W nagnification factor. In the following we shall use the abbreviation W-rn. f. to denote the magnification factor of the direct component of solar W caused by a change in columnar ozone. Quoted values of the W-rn. f. range between 1.2 and 2.5 (Machta et a1., 1975, Urbach and Davies, 1975).

The photochemical, dynamical and diffusion processes lead to large la­titudinal, seasonal and synoptic variations in the total ozone arrount and the biosphere is capable of adjusting to changes in the W-B at ground le­vel caused by the natural ozone variability. In the last 15 years, concern about anthropogenic ozone depletions (SST, CFC) led several investigators to obtain a c1inatol6gy of the W-B and its magnification factors in the uv (eg. Machta et al., 1975).

Although ozone is a strong absorber in the W-B region, sulfur dioxide (S02) is also a competent absorber in parts of the W-B spectrum (Brassin­gton, 1981). Assuming a constant absorption and scattering by particulates and'water drops in an urban troposphere under clear skies, the presence of variable S02 arrounts in industrialized regions must also be taken into account in determinations of the W-B magnification factors. In this report we present experimental and theoretical determination of the direct compo­nent of the W-B (i.e. the W-rn.f.) under representative atrrospheric condi-

Ozone Symposium - Greece 1984 -686 -

tions in the presence of variable columnar S02 arrounts.

1 .2 Instrumentation The instrurrentation used in this vork includes tvo identical and inter­

calibrated Eppley tN rreters which rreasure the total solar radiation in the spectral region 295-385 run. One of these instruments has bef'Jl installed at a distance of about 15 krn from the city of Thessaloniki (41 oN) which is mJderately industrialized (600000 inhabitants) and the other tN rreter was installed at the University canpus near downtown. These instruments were used in the first place in the classification of days with exceptionally clear skies, supplerrented by routine weather observations at the airport and at the University canpus.

The basic instrument used in this report for the rreasurerrent of the tN-m. f. is the Brewer Mark II spectrophotometer which rreasures the inten­sity of direct solar radiation in the tN absorption spectrum of ozone. As mentioned before, because S02 has also variable absorption in the tN-B re­gion the Brewer spectrophotometer has been designed at AES (Canada) to rrea­sure both total ozone and oolumnar S02 at the sarre tirre (Kerr et al., 1980). Routine measurerrents of the direct solar component are carried out near lo­cal noon since March, 1982 at six wavelengths with a resolution of 0.6 run namely :302.2 run, 306.3 nm, 310.1 run, 313.5 run, 316.8 run and 320.1 run.

1.3 Results The results presented in the following refer to exceptionally clear

skies and to the direct corrponent of the solar tN-B radiation. Fig. 1 shows the tN-m,f. at the wavelength 306.3 run versus ].l, for different values of initial total ozone. In all cases the percent change in total ozone was between 10% and 15% and the S02 column was practically unchanged. The con-

400 O.U.

A~JIf.Jnm ~OJ/~"'11 C.lcuklt.d

350D.U. 4S..;;:10U

~ ~

n. ". '" '1" 300 D.U. 0 I-

~ U

'" ... Z , .. 0

~ '" , .. ;! 2 .363 ... , .. Z , .. <!> ·"':3 '" ,I, ::;:

"" '" . ;! . "" ."" I- 3046 • !I/).336

'" ,..

;: 0 ~ , ,so

U 0 z 0 ::;:

0, 1.25 '.5 1,75 2.0 2,25

SECANT OF SOLAR ZENITH ANGLE

Fig. 1. Observed and calculated monochrorratic magnification at 306.3 run versus the secant of solar zenith angle for various values of initial total ozone.

- 687-

3

II:

~ Z o 2

~ u ii: z \!l « ~

u ;:: ~ 1 o II: :I: U o Z o ~

". o

J=ll1.Jnm

• .n' AS .... tDU

370 O.U. 'M

:========O==;=---_~o~,.~. _...:O~'.::.7-======== 340 D.U. 0 332 6 3418 310 D.U.

0331

°0~-----~5----------710~----------~1~5----------~2~0~----------~

PERCENT CHANGE IN TOTAL OZONE

Fig. 2. Observed (open circles) and calculated (solid lines) nagnifica­tion at 306.3 run vs. percent change in total ozone under small changes in col1.lIlU1ar S02 and for 310, 340 and 370 (DU) of initial total ozone.

tinuous lines were calculated for a 12% change in total ozone. In Fig. 2 the open circles show the measured W-m. f. versus the percent change in total ozone for various initial total ozone values. JI.1easurerrents and theoretical calculations refer to solar zenith angle of 21 0 , to the wavelength 306.3 run and to practically unchanged oolUIm1ar S02 .

From figures 1 and 2 it is evident that the W-m.f. increases more strongly with ].J. than with the percent change in total ozone, other factors of the equation (5) renaining oonstant. The difference between the theore­tical and the experirrental data points is partly due to the non-trivial change in the col1.lIlU1ar S02 the effect of which is shown next in figure 3.

Fig. 3 (a) shows the annual course of the solar zenith angle at local noon at the latitude of Thessaloniki (41°N). Fig. 3 (b) and (c) show monthly mean values of oolUIm1ar ozone and. oolUIm1ar S02 measured at Thessaloniki du­ring 1983. Vertical bars are one standard deviation of the daily values in a given month measured near local noon. Figure 3 (d) shows estinates of the direct solar W-m. f. (integrated between 300 run and 317 run) which is calcu­lated from a decrease of monthly mean total ozone by 1 0 of the daily va­l~s without allowance to the S02 variability. Fig. 3 (e) is the same as Fig. 3 (d) except that the col1.lIlU1ar S02 is now increased by 1 0 of the daily values in each month. This example illustrates the expected effect the dai­ly S02 variability has on the integrated direct solar W-m.f. in any month.

Fran the comparison between Figs 3 (e) and (d) it appears that the com­bined effect of both ool1.lIlU1ar 0 3 and S02 daily variability is to change the integrated W-m. f. up to about 20% from the non-S02 case.

-688 -

70 THtSSAlOtiKI c Al"N )

0 60 0

(j 0 w o . 0 50 0 Q)

Cl 40 0 C ttl 0

£; 30 0 'c

Q) 0 N 0 ... 20 0 ~ 0 0

(/) 10 N

t t f 0

:J f f

(/)

f f m E

f c '-7

t E

! :::l E - "0 co f ::::> u E

0 w

f Z 380

t 0

t N 360

t ! 0

...J 340

f <{

f ! I- 320

t 0

t I- 300 , 280 t 260

2 0 0

1 0 0

0 ,. .. ..- 0

E >< , 0 > ,. 0 :::l

8 " 0

0 0 ,. 0 0

"" ,. >' )<

6 ,. i I I

F M A M J J A S 0 N 0

YEAR 1983 Fig 3. (a) Arumal variation of solar zenith angle at 41°N near local

noon (b) rronthly mean columnar S02 over Thessaloniki (41°N) and (c) rronthly mean total ozone during 1983. (d) integrated W-mf between 300 and 317 run for each month with:>ut the effect of the daily change in the S02 column !::S and (e) with the observed !::S included.

-689 -

REFERENCES

1. BRASSINGTON, D.J. (1981). Sulfur dioxide absorption cross section measu­rements from 290 nm to,317 pm. Applied Optics, 20, }b 21, 3774-3779.

2. CUICHIS, P. (1974). Stratospheric ozone depletion and solar ultravio­let variation on Earth. Science, 184, No 4132, 13-19.

3. DAVE, J.V. and HALPERN, P. (1976). Effect of changes in ozone amount on the ultraviolet radiation received at sea level of a rrodel atmosphe­re. Atmospheric Enviroment, 10, 547-555.

4. KERR, J.B. et al. (1980). Measurerrents of ozone with the Brewer ozone spectrophotorreter. IAMAP Proc., Quadrenmial Ozone SynpJsium (Ed. J. IDndon), 74-79.

5. MACHTA, L. et al. (19'/5). Erythemal ultraviolet solar radiation and enviromental factors. U.S. Dept. of Trans, CIAP, 405-411.

6. URBACH, F. et al. (1974). Field measurements of biologically effective UV radiation and its relation to skin cancer in man. U.S. Dept. of Trans., CIAP, 523-535.

7. URBACH, F. and DAVIES, R.E. (1975). Estimate of the effect of ozone re­duction in the stratosphere on the incidence of skin cancer in man. U.S. Dept. of Trans., CIAP, 6678.

8. URBACH, F. (1966). Ultraviolet radiation and skin cancer in man. Advan­ces in Biology of Skin, VII, 195-214, Oxford, Pergarron.

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OZONECONCENTRATION AND AURORA FREQUENCY IN RELATION TO SOLAR-TERRESTRIAL INDICES

* R. PETROPOULOS and Y. LIRITZIS Research Center foy' Astronomy and App 1 i ed Ma themati cs, Academy of Athens, 14 Anagnostopoulou Str., Athens, Greece.

* Research Associ ate, financed by UNESCO proj ect.

Summary

An investigation is carried out to examine the degree of dependence of ozon~03) production in the atmosphere from solar phenomena i.e. sun­spot numbers (Rz), the solar '.'!ine! streamers derived from coronal holes (H), from flares (F) and the geomagnetic index (Ap). As both ozon&andAurora share a common triggering production mechanism a search for a iJossible relationship between them was made. These relationships helped to put foreward possible hypotheses concering total ozonedistri­bution and production in the atmosphere.

1.1 Introduction

Solar wind particles and the geomagnetic field become interconnected which along with the subsequent collisions, excitations and ionizations of atoms and molecul~s in the high latitudes upper atmosphere which, as a weakly ionized gas, respond dynamically and chemically to large and variable aurorally associated phenomena. The aurorally produced particles along with the balance production of Ox NOx and C10x by chemical reactions and the solar U.V radiation maintains the natural 03 content.

Various authors have found relations between solar-terrestrial indices and ozone content, i.e. with the geomagnetic field (1), (3) with sunspot cycle (2) with proton events(4) and studied 03 distribution (5). However the 0, variations over the Earth are not fully understood. In a previous work t19) we found a strong correlation between (A), (A:the frequency of the aurora) and Rz' H, F, Ap for 50-60oN. Here we relate 03 content with these indices as a further generalized elaboration involving all these indices. 1.2 Selection of data

Ozone concentration measured by Dobson spectrophotometers on ground based stations was taken from ozon data of the world (6) (7) and cover the period 1957-1977. We have used ozonedata obtained by the satellite Nimbu~4 for the period 1970-76, employing the scattering U.V method (8). In order to compare ozone data and aurora we chose the latitudinal belt 50-60oN (including lOoN for comparison) where available aurora data were made to us,Livesey (1983, pers. comm.). The stations of total ozone measurements used are given in Table 1.

Ozone Symposium - Greece 1984 - 691-

TABLE I

Station ~ Keda i kanal 10 0 14 N

Kiev 50 0 20 N

Irkutsk 52 0 16 fl

Omsk 54 0 50 N

Sverdlovsk 56 0 48 N

Leningrad 59 0 58 N

Lerwick 60 0 09 N

1. 3 Ozon variations

Longitude

77 28£

30 58£

104 21£

73 24£

60 38£

30 18£

J09 W

~gbNN~~~~S~:e~~eR~~o~~~a!~df~rd~~:NW:~~ taken from !JAG reports and F, H from ref (9).

Early review articles have shown the lack of good statistics concerning solar-cycle and ozone relationship from gt:Qundbased and airborne measure­ments (10). Using satellite measurements global mean ozone concentrations have been determined which smooth out the effects of local dymanics.

For these reasons we compare total ozonecontents in the two extreme of latitudes 500 N and 600 N from Kiev ground station and Nimbl,ls-4 at 500 N (Fig. 1) and Leningrad (Lerwick) and Nimbus-4 at 600 N (Fig. 1).

0, .r-t. JI. ' , . , ,

,\ l'Ir'~ :i -, . , ,.

"1 .. .. ". ~ ' _ • I ';

I. I \ , I j j

Figure 1. :001 .-, '~ .J

. ' f'.'I. ~' I \ • • \ f' - , j 1 / \ ,0.. .' • ,. .. ~ • !~o 0 · ... -'0 ..

,.0 ~ ~o" 4 .'1:

rill i 'h , ... ~ I .

,07.

The lOoN ground station is also included for comparison. In Fig. 1 the variations in ozoneconcentration for Kiev station seems to exhibit a guasi­periodicity of 2-yrs, which is not detected by Nimbus-4. A similar quasi­periodicity of 2 yrs was detected for Leningrad and again Nimbus-4 failed to show this up. A 2 yrs quasi periodicity ozonehas been found by other authors for other stations e.g. in Fukuoka and Akita, in Japan (11). A lO­II yrs periodicity has al?o been found (12). 1.4. Ozon - Rz relationship

Fowle (1929) (13) attempted to link ozon variability to the 11 yrssolar cycle. Subsequent authors have found the 10-11 yrs periodicity in ozon which however, occassionally lags the solar activity, thus the best correlation coefficient (r) between ozon-Rz for 1932-1969 over Arosa station is found for a 3-yrs phase lag. In general 10-11 yrs oscillations in ozone are evident but are not necessarily in phase with solar activity variations. Ithas also been stated that the solar activity cycle occurring at various locations are not necessarily global phenomena but may be local phenomena ~robab ly due to dynami ca 1 effects (14). For thi s reason we made a

correlation study between Ozon-Rz for different latitudes of Table r. In Fig. 1 the Rz variations is shown which is compared to ozonefrom Kiev. The mean trend of their variation is similar. The same applies for Leningrad. The rmax (03, Rz) for different stations is given in Table II. In this table time lags between 03 and Rz are given in narenthesis.

- 692-

~ In order to study more accu-Latitude rmax for 03-index, relationships rately the variation of (r) for

N (03-Rz) °3-F

lcF 0.73(-1)- 0.66(-1)

5f 0.82( -2) 0.70(-2)

54' 0.66(0) 0.74(0)

56' 0.46(-3) 0.25(0)

-6cf' 0:64(-3) 0.06(0)

°3-H °3-Ap

0.33(0) 0.24(0)

0.44(0) 0.12(0)

0.47(-3) 0.47(-1)

0.25(0) 0.40(-2) e· 34(O) 0.60(O}--

0.36(-1) 0.43(-3)

°3-A

0.23(-2)

0.63(-2)

0.54(-2)

0.50(-2)

various time lags of 03-R? in different latitudes, the ~r) between ~03 (=03i - 03) and Rz was examined. We found that for low latitudes the lag is small (or zero) and increases for higher latitudes. This applies to both 03 - Rz and ~03 - Rz· This means that correlates well

with Rz for negligible time gap, albeit the shift of 03 (due to the circu­lation of winds) to northern latitudes takes place after a time period which, perhaps, is the time for 03 transportation from the equator to higher latitudes. We have also found that the magnitute of (r) increases with lcngitude, but there is not any longitude effect.

1.5 03 - F relationship It is known that the solar proton events influence the ozone production

(4)(14). It should be mentioned, here, that the variable production rate of cosmic rays and solar wind particles, in general, has been discussed as causing "ancient catastrophes", observed often on the evolutionang trend of life on earth as well as destruction of the ozone layer (15)(16). We have found tha t the Rz and number of fl a re occurrences f, of i rnnortance > 1, are highl.y correlated at least for the period 1934-1974. As a result we have obtained a linear dependence of Rz and f for Rz > 30 with rmax = 0.93 and the equation that holds is given from the relation:

log f = 1,95 + 0.0086 Rz (1) It was thought, therefore, worth including the flare's index in the corre­lation study with ozone. For the 20th solar cycle the rmax (Rz, f) = 0.95, while the rmax (Rz, F) = 0.91, where F = solar wind streamers derived from flares. Therefore as expected, for the 20th solar cycle there is good correlation between the (f) as well as the (F) with Rz. Otherwise the r ( f, F) = 0.88. For this reason we use (F) in the following statistical study as representing the solar I·tind streamers. Table II shOltIS the rrnax (03, F) for various stations, and the corresp0nding time lags betwee~ 03 and F. 1.6 03 - H relationships

In Fig. 1 the 03 variations for Kiev are compared. With the variation of streamers from coronal holes (H), which themselves exhibit a guasi­periodicity of 2 yrs. A similar quasi-biennial period was found 1n the neutrino flux of solar origin for 1970-1977 (17). The rmax (03, H) are given in Table II. 1.7 03 - Ap relationship

Attention should be paid to the remarkable similarity which exists between the global map of ozone and the intensity of the geomagnetic field and it may be said that the ozon content is controlled in some way by the Earth's magnetic field (1), (18). For this reason the geomagnetic index (Ap) was used for correlation studies with 03 for different time lags. For the time pRriod 1964 - 1976, Figure 1,shows 03 variations for Kiev and Leningrad compared to the (Ap) and the index (H). The rmax(03,Ap) for different stations is given in Table II.

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The variations of H (time lag = -l),Ap (t = - 2) and (G3) follows the same sort of trend. It should be recalled that ~n the ozon's dynamic region t~e reactions of ozon (03) and (0) are faster and their collisions denser so that, they are not obeying to the magnetic field, force (small c1ependen-ce on maqnetic effect (An)) as molecules and atoms in higher altitudes do. ' 1.8 Q.L:- A relationship

We have found elsewhere (19) that (A) exhibits a periodicity of 3-4 yrs with 99% significance. This periodicity has to be compared to the quasi-biennial one mentioned above. The rmax (03' A) is given in Table II. It was found that for higher latitudes the rmax is reduced. It is worth also nothing the two rmax for Omsk station at t ~ ° (r = 0.63) and t = -2 (r = 0.83).

Having studied the correlation between 03 and the other solar-terre­strial indices, l'ie also use Nimbus-4 03 data for similar purposes. It was interested also to investigate the behaviour of the ascending and des­cending time parts of the 20th solar cycle in relation to the indices. Nevertheless, a comparison of the backscattered UV ozone data with ground based measurements from the global ozone network gives evidence of a time and latitude dependent bias (14). The present correlation study was made because it has been shown in other works than the ascending and descending branches of the sunspot cycle behave in different ways for different cycles (20). 1.9 Nimbus-4 VS ground Stations (O~, ojit)

The relationship between 03 from Nimbus-4 and some ground based stations has been examined (14). We here further extent this, including some more ground stations. The differences between these two sets of data at 50oN, 540 N and 600 N were at worst of ± 3%. The r(03N, 03st ) is given in Table III. However the Lerwick and Kiev 03 variation for 1970-76 seem to preceed by 1 yr that of Nimbus-4 03. 1.10 Ascending part 1964/1969 and ground based stations

Table III gives the rmax (ojt, indices) for 1964/69. The ascending part has higher rmax with the indices than the whole cycle. This is pro­bably due to the fact that some of these indices exhibit a 2nd maximum during the descending part. 1.11 Descending part 1970/76 and Nimbus-4 data

It is seen in Fig. 1 that the general trend for Rz, H, (03) from Nimbus-4 follows a slight drop in magnitude from 1970 to 1976 (except that for (H) the data are a few and such a trend is not obvious). However for the 1964/71 the (H) variations seem to follow the Kiev (50N) 03 changes with a time lag = 1 yr prnceeding the (H). The rmax between Nimbus-4 as well as ground station (03) data and the other indices are given in Table III. We see that the rmax (03, indices) for Nimbus-4 03 data is generally higher for Leningrad and lower than Kiev (500 N), while is almost similar to Lerwick. This could be explained as due perhaps to the fact that a)Nimbus-4 measures total zonal latitude 03 contents, whilst the ground based stations measure the local 03 (i.e. that of the station's latitude) and b)the (r) becomes higher with eastern longitude (see 1.4 above). The descending part however has smaller (r) than the ascending part. 1.12 Generalized relationship 03 = f (Rz' F, H, Ap)

The fact that 03 correlates reasonably well with the indices of Rz, F,

-694 -

Hand Ap lead us to find a generalized relationship between 03 and all these indices. We used the residues method (19) and we expressed 03 concentration as a fUnction of all these indices as:03=Ao+A1Rz+A2F+A3H+A4Ap(2). The coeffi­cients of eq.(l) as well as the standard deviations (0) and accuracies (Ac) are given in Table IV. If we study the 03 concentration as a linear function of every index the Ac is smaller that the Ac given by eq.(2). In Table IV we give also analogous coefficients computed for aurora frequency (19).

TABLE I II

r max for (OS3t , i ndi ces) and (Os3t , ON ) 3

(03,Rz) (03,F) (03,H) (03,Ap) (03,A)

Len. 0.89(-3) 0.74(-2) 0.85(-2) 0.70(-2) 0.77(-2) 1964/69 Kiev. 0.83(-2) 0.66(0) o. 94(-t) 0.97(-2) 0.78(0)*

1970/76 Len. : L=60o N 0.43(-1) 0.19(-1) 0.93(-1) 0.49(-1) 0.60(-1)

Lerw. : L=60o N 0.79(0) 0.70(-1) 0.75(-3) 0.98(-3) 0.54(0) Nimbus:L=60o N O. 72( -2) 0.80(0) 0.65(0) 0.93(-1) 0.53(-1)

**Ki ev. : L=50o N 0.97(-1) 0.99(-1) 0.92(-1) 0.86(-1) Nimbus:L=50o N 0.36(-2) 0.31(-2) 0.56(-2) 0.73(0)

Nimbus-Len. rmax (O~ , 0 ~en) = 0.56 (0)

Nimbus-Lerw. rmax (O~, 0 ~erw)= 0.55(-1)

Nimbus-Kiev. r max (ON 0 K ) 3, 3 = 0.50(-1)

* Aurorae for L=530N ** Kiev. data were small and 1971 missing.

TAB L E IV

Generalized relationship between 03 and other indices. Linear regression coefficients of eq.(2) as well as the corresponding accuracy and standard deviation for various latitudes.

Lat. Long Station a Ac % Ao A1{Rz) A2{F) A3{H) A4{Ap)

ION 77E Kodaikanal 8.97 96.7 245 0.26{-1)* 0.12{ -1) 0.1l(0) -3.7(0) 52N 104E Irkutsk 25.9 93.4 340 1.1 (-2) 0.75{-2) 0.067(0) -1.23(0) 54N 73E Omsk 13.7 96.4 396 0.45(0) 0.70(0) -1. 23{ -3) 0.9(0)

(l.66) (57.3) (3.95) (0.0099) (7.737) (0.034) (-0.098) 56N 60E Sverdlovsk 7.8 97.8 320 0.20(-3) 0.75(0) 0.22(0) 1.69( -3)

(0.89)** (91) (4.83) 0.004 (70) (0.077) (-0.0164) 59.6 (-60N) 30E Leningrad 11.05 96.8 304 0.27{-3) -0.27(0) 0.3(0/-1) 1.99(-2)

(4.95) (89.5) (89.8) (0.93) (ll) (-O.0083) (1.32)

* No. in parenthesis is the time lag. ** Coefficient for A = f (indices) in parenthesis under respective latitudes.

-695 -

1.13 Conc 1 us ions Overall we might draw the following conslusions:The Rz coefficients in

Table IV are large for (A) and small for 03 for higher latitudes and are in a reverse order to lower latitudes. The (H) coefficients of Table IV seem to behave in a similar way for both (A),(03) in all latitudes. Flares affect mos tly (A) than 03 because thei r coeffi ci ents in Tab 1 e IV a re much hi gher than those for 03' The Ap' coefficients change in absolute values, with latitude for both (A) ana (03)' In our present model we found that the 03 production (and distribution) is significantly dependent from Rz, F, H, An indices for the 20th solar cycle that implies these indices playa consitle­rable role in the 03 mechanism. Further studies are needed to refine such a relationship and to define energy effects of these indices to the dynamics of (03) production mechanism spatialy and temporaly. REFERENCES 1. KING J.W.(1975) Aeoron. and Astronant. 13, 4. 10-19 2. WILLET H.G., PROMASKA J. (1965). Atmosph. Sci. 22, 493-497. 3. DOBSON G.M .• HARRISON D.N., LAWRENCE J.(1929). Proc.Roy.Soc. 4,122,456-486 4. WEEKS L.H.,CUIKAY R.S.& CORBIN J.R.(1972) J.Atmosph.Sci.29,1138-1142 5. DBTSCH H.U.(1979) J. Atmosph.Terrest.Phys.41,771 6. LONDON J.,BOJKOV R.D.,OLTMANS S., KELLEY J.I. (1976)NCAR/TN/113+STR Nat.

Centr.Atm. Res., Bolder, CO .• USA 7. REPAPIS C.C., ZEREFOS C.S.,JENNE R.L., KOTINI S. (1980) Twenty years of

total ozone observations for the world (1957-77), Academy of Athens, Res. Cent.Atm.Phys.Clim.,Publ. 1)0 2, Athens p. 127.

8. HEATH D.F. etal (1982), NASA Ref.Publ. 1098 9. LINDBLAND B.A., LUNDSTEDT H. (1981) So 1 a r phys i cs 74.197-206.

10. PITTOCK A.B.(1978) Rev.Geophys.Space Phys.- 16,400 11. ANGELL J.K., KORSHOVER J.(1978) Monthly-Weather Rev.106, 325 12. HILL W.J., SHELDON P.N.(1975) Geophys.Res.Letters 2, 541 13. FOWLE F.E.(1929) Smithsonian Miscellaneous Collections 81,11,1 14. KEATING G.M.(1981) Solar Physics, 74, 321-347 15. WDOWCZYK J. , WOLFENDALE A.W. (1977) Nature 268, 510 16. SAKURAI K.(1979) Astr.Space science 63, 369-378 17. SAKURAI K.(1979) Nature. 278, 146 18. LONDON J.,KELLEY J. (1974) Science, 184, 987-989 19. LlRITZIS Y.~ - PETROPOULOS B. (1984) Geophysicae Annales (Subm.) 20. TRITAKIS B.P. (1983) Astrophys.Space Science 93, 141-147

-696 -

CALCULATIONS OF LYMAN ALPHA ABSORPTION IN THE MESOSPHERE

J. L. LEAN Cooperative Institute for Research in Environmental Sciences (CIRES),

University of Colorado/NOAA, Boulder CO. 80309.

Summary Detailed calculations of the absorption of solar Lyman alpha flux in

the earth's mesosphere which include wavelength and temperature dependent 02 and H20 absorption cross sections, are used to investigate the effects on the water vapour photodissociation of a) absorption by atmospheric species other than 02 b) changes in the solar Lyman alpha line profile with solar activity and c) atmospheric temperature and density variations. These calculations indicate that neglecting the absorption by N2, H20, CO2 and CH4, in addition to that by 02' may overestimate the Lyman alpha photo­dissociation of H20 by 8-9% in the altitude region of maximum photodes­truction. 'Changes in the Lyman alpha line profile from the minimum to the maximum of the 11 year solar activity cycle cause only a 2% increase in photodissociation, which can be compared with the approximately factor of two increase associated with the solar cycle variation of the integrated line flux. However, at solar maximum, using the Meier and Prinz line profile underestimates the peak photodestruction by 4%.

1. Introduction Solar Lyman alpha radiation at 121.567 nm is incident on top of the

earfh's atmosphere with an integrated flux that varies from 2.3 to >5 X 10 photons/cm2/sec (1). This radiation is absorbed in the earth's atmo­sphere, at altitudes between 60 and 100 km, primarily by 02. It penetrates into the mesosphere b:.,cause the 02 absorption cross section at 121.567 nm is small, about 1 X 10 20 cm 2 (2). Lyman alpha radiation dissociates atmo­spheric H20, CO2 and CH4, and ionizes NO. It is important to calculate the Lyman alpha photodissociation rate of H20 to a high degree of accuracy because the resultant production of OH is a critical element in the meso­spheric chemistry (3). The integrated Lyman alpha flux available for photo­dissociation at a particular altitude depends on its absorption by the atmosphere at higher altitudes. Detailed calculations of the absorption of Lyman alpha radiation by 02' which have included the wavelength and temp­erature dependence of both the 02 and H20 absorption cross sections, have been reported in the literature (4,5). However, even the most recent detailed calculations of water vapour photodissociation have assumed that 02 is the sole absorber of Lyman alpha radiation (4,5).

It has long been recognised (6,7,8) that, in addition to 02' a number of other atmospheric constituents absorb Lyman alpha radiation, and that these constituents, in particular N2, H20, CO2 and CH4, may contribute to the atmosphere's opacity at 121.57 nm. Qualitative estimates of the eff-

Ozone Symposium - Greece 1984 -697 -

ects of other absorbers (6,8) indicate that they may increase the local optical depth of the mesosphere by a few percent above that due to 02 absorption alone.

It has also been speculated (3) that changes in the Lyman alpha line profile may contribute to differences in calculations of Lyman alpha photo­dissociation rates.

2. Calculations of Lyman Alpha Absorption and the Photodissociation of Water Vapour Atthe top of the earth's atmosphere the photodissociation rate of

water vapour by Lyman alpha radiation is J H20 = f 0--H20 (>-,T) 10 (>-) d>-

L-alpha where 10 (>-) is the unattenuated Lyman alpha flux (Fig 1a) and 0--H20 (>-,T) is the water vapour absorption cross section (Fig 1b) at wavelength A and temperature T. The Lyman alpha flux that reaches height hI is calculated from the flux at a higher altitude hO by

I(h 1,>-)=I(hO,>-)exp[- r(hav )] where

is the optical depth of the atmosphere, with ~h=hO-hl and ha =(h1+hO)/2. ~i is the absorption cross section (Fig 1b), evaluated at the focal atmo­spheric temperature, and ni is the atmospheric concentration (Fig. 2) of the ith absorbing constituent. X is the solar zenith angle. The H20 photo­dissociation rate at height hI is then J H20 (h 1)= f~H20(>-,T)I(hl'>-)dA

L-alpha and is calculated at success­ively lower 1 km height inter­vals, starting from the top of the atmosphere, and including appropriate atmospheric dens­ity and temperature profiles.

3. Absorbers other than .2.2 The concentrations-of

0(9), N (9), H 0(10,11), c6 2(9) ana CH4(10Y, shown in Figure 2, the O2 and H20 ab­sorption cross sections in Figure 1b, with 6{N ) = 6X10-23c 2(6) 6{C52)= 7.3X10-'OC Ill/(l2) and 6{CH4 )= 1.8XlO-17 cm (8), were used to determine the atmo­spheric optical depth. The calculated H20 photodissoc­iation and photodestruction rates are provided in Fig 3. For these calculations, the

--- Meier and Prinz (1970) Solar min .................. lemaire el al. (1981); quiet Sun

Solar max ------- estimated trom plage and quiet sun line protlles

12,---,------r-----,,-----, 11 10

!! 9 'c 8 ;:) 7

c .2 "0 <I) (/)

~ 6 ~ 5 :.0 ~

IJl 1Jlf<" e E o 0 c ~ .2 b o..!:' o IJl .0 « ON O~ ____ -L ______ ~ ____ -L ____ ~

121.467 121.517 121.567 121.617 121.667 Wavelength (nm)

c .S! o <I) (/)

IJl

1Jl" e E 0 0

c" 0 1 :;:0 0."-0-IJl .0 « ON :x:

Figure 1. a) Lyman alpha line profiles b) 02 and H20 absorption

cross sections (5).

-698 -

quiet sun line profile in Fig la, normalized to an inte¥-

;:/~:1/se!,l ~:s U~!d. 3 X 10 1

Figure~. Concentrations of atmospheric species which absorb Lyman alpha radiation.

120

110

100 E -" I .,

90 '0

~ «

E -" I .,

'0

~ «

Densities of Atmospheric Absorbers of Lyman·Alpha Radiation

l~r-Tr--r----.r----'~-.-'r----'-----'

120

110

100

90

60

70

60

50 . 10

Log. (number/m')

--absorpllon by 0" N" H,O, CO" CH. ------ absorption by 0,

-- ...... , __ ---- -::8.7'1.

-""""'"'""""- I-- .... )

... - ... ---_ ... ..-.

-7.5 -7 -6.5 -6 -5.5 -5 50 100 150 200 250 ~ 350 400

PhotodlsSOClation Rate (sec") Photodestruction Rate (em" sec")

Figure 1 Photodissociation ard photodestruction rate of H20, calculated by including all absorbers, and by 02 absorption alone.

The peak H20 photodestruction rate is overestimated by 8.7% if the absor­bers other than 02 ate neglected. This can be compared with a change of 8-9% when the temperature dependence of the 02 absorption is ignored and a change of 14 % when both the wavelength and temperature dependence of the 02 absorption cross section across the Lyman alpha line profile are neglected (5).

The specific contributions to the reduction in the photodissociation at the altitude of peak photodestruction (75 km for X=37°) are 3.5%(N 2), 3.5%(H20), 0.9%(C02) and 0.9%(C~!k ~f, as suggested by (8), the N2 absorption cross section of 6 X 10 cm is too large, and the N2 absorp-

-699-

tion negligible, the photodestruction is only overestimated by 5%. On the other hand, the H20 mixing ratio has been observed to be at least a factor of two larger than that shown in Figure 2 (11), in which case the H20 absorption alone reduces the peak photodestruction rate by 6-7%.

4. Changes in the Lyman alpha Line Profile with Solar Activity Spatially resolved observations of Lyman alpha emission from the solar

disc have shown that the shape of the line profile is different for emi­ssion from the quiet sun, and from magnetically active plage regions. At solar minimum there are no plage regions on the disc and the full disc Lyman alpha line profile is estimated to be that of the quiet sun (Fig la). From the minimum to the maximum of the eleven year solar cycle, the number of plage regions on the disc increases, so the Lyman alpha line profile at solar maximum will be some combination of plage and quiet sun profiles. The Lyman alpha profile estimated for solar maximum conditions in Fig la was determined from plage and quiet sun Lyman alpha line profiles provided by (13). Ratioing these profiles gives the contrast Cp( 1\ ) for plage to quiet sun emission at different wavelengths across the line profile. Then at solar maximum, for a factor of two solar cycle increase in the inte­grated line flux, the irradiance at wavelength 1\ is given by (1)

1m x( 1\) = 1Q( 1\)[1 + 0.264[C p( 1\) - III Note the difference tetween both the quiet sun and solar maximum line profiles, and that used by (14). The effects of different line profiles on the calculated photodissociation rate are summarized in Figure 4. Using the Meier and Prinz (14) profile at solar maximum underestimates the peak photodestruction rate by 4%. There is an increase in the peak photo­destruction rate of only 2% when the line profile at solar maximum is used, -instead of the quiet sun line profile.

5. Atmospheric Temperature and Density Variations The temperature and density profiles of the mesosphere and thermo­

sphere vary seasonally. For example, at 600 N latitude the mesopause is typically colder by as much as 50 K, and lower in height by about 10km, in summer than in winter. Both the temperature and the 02 densities respond to the seasons and to the eleven year solar activity cycle. USSA(1976) oxygen and temperature profiles are typically used in calculations of the water vapour dissociation rates (5). Using appropriate summer/winter and solar max/solar min temperature profiles for 600 N, instead of the USSA, caused differences in ~he peak photodestruction of about 1%. However, in winter time, the absorption occurs above about 80 km, in a region of the atmosphere that is dominated by turbulence rather than solar heating. 02 densities may therefore be quite variable, in a way not properly accounted for when the ideal gas laws are used to convert temperature to density variations in absorption calculations.

6. Discussion Species other than 02 contribute to the atmosphere's opacity at 121.57

nm, and hence effect Lyman alpha photodissociation in the mesosphere. The most important absorber after 02 is H20. The effect of N2 absorption is poorly known because of uncertainty in its absorption cross section at 121.57 nm. Variations in the Lyman alpha line profile with solar activity cause changes of 2% in the calculated H20 photodissociation rate. More important are differences between the Meier and Prinz profile and the higher resolution profiles of Lemaire et al. Results of these calculations are summarized in Figure 4.

-700-

Figure~. Differences in calculated H20 photodissociation rates, due to other absor­bers and different Lyman alpha line profiles.

References

Calculations with solar minimum line profile and absorption by 0" N" H,O, CO, and CH. are compared with

----absorption by 0, only _ ............ _ ........ - solar maximum line profile --------- Meier and Prinz (1972) line profile

100.--.-------------,

95

~ 90 I 85

Q) "0 .3 80

, , : l I : I :. \ :

~ 75 "j 70 ___ :~.,.." 65

0.9 to

x: 37'

.llItude at which photodlssoclatlon rate * 1 x ,o-r sec·'

1.1

Ratio 1.4

1. LEAN, J.L. and SKUMANICH, A. (1983). Variability of the Lyman alpha flux with solar activity. J. Geophys. Res.,88, 5751-5759. 2. CARVER, J.H., GElS, H.P., HOBBS, T.I., LEWIS, B.R. and McCOY, D.G. (1977). Temperature dependence of the molecular oxygen photoabsorption cross section near the H Lyman alpha line. J. Geophys. Res., 1955-1960. 3. NICOLET, M. (1980). The photodissociation of water vapour in the mesosphere. J. Geophys. Res., 86, 5203-5208. 4. FREDERICK, J.E. and HUDSON, R.D. (1980). Atmospheric opacity in the Schumann-Runge bands and the aeronomic dissociation of water vapour. J. Atmospheric Sci., 37, 1088-1098. 5. LEWIS, B.R., VARDAVAS, I.M. and CARVER, J.H. (1983). The aeronomic dissociation of water vapour by solar H Lyman alpha radiation. J. Geophys. Res., 88, 4935-4940. 6. HALL, J.E. (1972). Atmospheric pressure, density and scale height calculated from H Lyman alpha absorption allowing for the variation in cross-section with wavelength. J. Atmos. Terrest. Phys., 34, 1337-1348. 7. WEEKS, L.H. (1975). Determination of O2 density from Lyman alpha ion chambers. J. Geophys. Res., 80, 3655-3660. 8. PRINZ, D.K. and BRUECKNER, G.E. (1977). Observations of the O2 column density between 120 and 70 km and absorption cross section in the vicinity of H Lyman alpha. J. Geophys. Res., 82, 1481-1486. 9. U.S. Standard Atmosphere (1976) 10. GARCIA, R.R. and SOLOMON, S. (1983). A numerical model of the zonally averaged dynamical and chemical structure of the middle atmosphere. J. Geophys. Res., 88, 1379-1400. 11. BEVILACQUA, R.M., OLIVERO, J.J., SCHWARTZ, P.R., GIBBINS, C.J., BOLOGNA, J.M. and THACKER, D.J. (1983). An observational study of water vapour in the mid-latitude mesosphere using ground-based microwave techniques. J. Geophys. Res., 88, 8523-8534. 12. BANKS, P.M. and KOCKARTS, G. (1973). Aeronomy, Academic Press. 13. LEMAIRE, P., GOUTTEBROZE, P., VIAL, J.C. and ARTZNER, G.E. (1981). Physical properties of the solar chromosphere deduced from optically thick lines. Astron. Astrophys. 103, 160 176. 14. MEIER, R.R. and PRINZ, D.K. (1970). Absorption of the solar Lyman alpha line by geocoroni atomic hydrogen. J. Geophys. Res., 75, 6969-6979.

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Suunnary

RADIATIVE INTERACTIONS OF STRATOSPHERIC OZONE AND AEROSOLS IN THE SOLAR SPECTRUM

V. Ramaswamy National Center for Atmospheric Research*

Boulder, Colorado 80307 USA

The presence of aerosol s in the stratosphere following maj or volcanic eruptions alters the disposition of the downward and upward solar ir­radiances as a result of enhancement in scattering. These pertur­bations are significant for the photodissociation of ozone molecules in the UV and the visible bands. The perturbations occur due to increased loading of scatterers as well as due to changes in the size distri­butions of the particulates. In a transition from the quiescent state to the post-volcanic eruption state, there is an increase in the mode radius of the aerosols which results in a decrease in their specific extinction; the decreases are nonuniform across the solar spectrwn, being larger at the shorter wavelengths (a factor of 4). A multiple scattering, one-dimensional radiative transfer model, based on the delta-Eddington technique, is used to derive the vertical profile of the irradiance fields. Two wavelengths--one in the tail of the Huggins band (AO. 331m) and the other in the center of the Chappuis band (AO.6 1JDl) are selected for the perturbation study. With increases in the aerosol mass loadings, there is a decrease in the downward irradi­ance at lower altitudes and an increase in the upward irradiance at the higher altitudes. For a fixed loading, an increase in the surface mode radius of the aerosols results in a greater downward and smaller upward irradiances. High surface albedos amplify the perturbations through larger upward irradiances.

1.1 Introduction The transfer of solar radiation in the stratosphere is influenced by

the extinction due to ozone, trace gases and aerosols. The aerosols are efficient scatterers of UV and visible radiation and thus cause pertur­bations in the radiative energy budgets; this assumes significance due to photodissociation of ozone molecules in these spectral regimes. We con­fine our attention in the paper to t~ specific wavelengths--one in the Huggins and the other in the Chappuis spectral band. We consider the effects of enhanced loadings and changes in the size distribution of sul­fate aerosols in the stratosphere, following major volcanic eruptions.

1.2 Optical Characteristics of Aerosols There are t~ physical mechanisms which affect the interaction of

radiation between stratospheric aerosols and ozone. The radiative fluxes can be altered by changes in stratospheric aerosol loadings and by changes in the sizes of the particulates. The size distributions of sulfate aero-

*The National Center for Atmospheric Research is sponsored by the National Science Foundation.

Ozone Symposium - Greece 1984 -702 -

sols during quiescent periods is well approximated by a log-normal func­tion (Toon and Pollack, 1976), with a surface mode radius (rs ) of 0.15 ~m (Farlow et al., 1981). During and after periods of volcanic erup­tions, there is a continuous evolution of the size distribution, as ob­served for the E1 UJichon aerosols by lbfmann and Rosen (1984) with the particle mode radius varying from 0.26 to 0.65 ~.

To illustrate the effects due to changes in the size distribution of the aerosols, we assume a surface log-normal function, with a standard deviation of 2. The specific extinction (extinction coefficient per unit mass) of sulfate aerosols in the UV and visible spectrtm is shown in Fig. 1. Details on the optical parameters can be found in van de Hulst (1957). The density of the particles is 1.67 g/cm 3 (Pinnick et a1., 1980), while the refractive indices are obtained from Palmer and Williams (1975).

The effects for different mode radius are dissimilar, reflecting the differences in the scattering efficiency of the size distributions. For a fixed column mass loading, the specific extinction and, hence, the optical depth changes by a factor of up to 4.8 for a change in rs from 0.16 to 0.65 ~m at the shorter wavelengths. At these wavelengths, the distribu­tion with the smaller mode radius is more efficient in the extinction of radiation. For small particles, an increase with wavelength results in a lowering of the Mie scattering e ffic iency, yielding a decrease of the specific extinction with wavelength. For the larger sizes, the Mie efficiencies are approximately constant with wavelength so that the speci­fic extinction is independent of wavelength. Note that at the shorter wavelengths (e.g., ),0.25 ~), the variation due to size distribution is approximat~ly twice as much as that at ),0.6 ~.

1.3 Radiative Transfer Model The one-dimensional model used to study the radiative perturbations

is based on the delta-Eddington technique of solving the radiative trans­fer equation for inhomogeneous atmospheres (Joseph et a1., 1976). The wavelength regime between 0.2 and O. 7 ~ is partitioned into 48 spectral intervals. In each spectral interval, the absorption cross-sections fol­low Ackerman (1971). The ozone number density follows that of the U. S. Standard Atmosphere. The irradiance at the top of the model atmosphere (60 km), which has a 1 km resolution, follows Thaekakara (1973). Rayleigh scattering follows Penndorf (1957). Calculations are carried out for a solar zenith angle of 45° under clear sky conditions, with a surface albedo of 0.1.

The vertical concentration profile for the quiescent stratospheric aerosols is adapted from Lazrus and Gandrud (1977). This profile displays a peak in the aerosol concentration at 20 km. Note that the ozone number density also has a peak at -20 km. No aerosols are present below 10 km or above 36 km. During volcanically active periods, enhancements in the stratospheric aerosols loading occurs at altitudes around 20 km (see Hofmann and Rosen, 1984). Accordingly, to simulate perturbed conditions in the present model, the quiescent concentrations are mUltiplied by a constant factor at all altitudes.

1.4 Results Two wavelengths are selected for examining the nature of the pertur­

bations They are (i) O. 33 ~, which is located in the tail of the Huggins band, and (ii) 0.60 ~, which .is at the center of the Chappuis band. Other spectral regimes, where ozone absorption is strong, will be less sensitive to aerosol loadings. The presence of scatterers alters the

-703 -

disposition of the irradiance fields (L W/m 2/]lIJl) in the atmosphere, which directly affects the ozone photodissociation rates (Fiocco et al., 1978). The total irradiance at any altitude is composed of a downward component, L+ (direct + diffuse beams), and an upward component, Lt. The vertical (z) profile of the direct downward diffuse and upward diffuse irradiances in a Rayleigh atmosphere is shown in Fig. 2 for AO.33]lIJl. Below 30 km, the proportion of the direct beam converted into diffuse radiation increases with decreasing al t itude. Near the surface, the downward ir­radiance is composed of equal contributions from both beams. At AD.6 I.I!n (Fig. 3), the proportion of the direct beam converted into diffuse is very small, even in the lower most layers. Because of smaller Rayleigh optical depths at AO.6 1.I!n, the downward irradiance is larger at all altitudes rel­ative to the value at AO.33]lIJl. Similarly, the ratio of the upward irra­d iance to that inc ident at the top is higher at all al tit udes for the shorter wavelength.

Perturbations to the irradiances due to aerosol loadings at AO.6 ]lIJl are shown in Fig. 4. The downward irradiance, as a function of aerosol collUlln mass, is shown in Fig. 4(b~. The loading ranges from 0.002 gm/m 2

(a background value) to 0.05 gm/m (observed during post-El Chichon times by Hofmann and Rosen, 1984). At 20 km, the downward irradiance decreases with increasing aerosol extinction, caused by increasing mass loading. Because the specific extinction at a rs of 0.65 ]lIJl is lower relative to that at 0.16 1.I!n, there resul ts a higher irradiance at that mode rad ius. At a lower altitude (10 km), since there is a larger column mass of aero­sols through which the radiation must traverse, the irradiance is less than for the 20 km case. The differences due to changes in mode radius increase with increasing loading.

The perturbation to the upward irradiance is shown in Fig. 4(a). The upward irradiance arises due to reflection from the surface and backscat­tering by aerosols. The upward irradiances are higher for an rs of 0.1 I.I!n than for an rs of 0.65 ]lIJl since the optical depths are greater at the lower mode radius, which implies greater backscattering. Contribution by the aerosols to the backscattering increases with increasing loading and the effect is greater at 20 km than at 10 km.

Results at AO.33 ~ are qualitatively similar and are not shown here. The effect of variations in the albedo of the underlying surface has a significant influence on the upward irradiances. Table I indicates that the upward irradiance, in varying the surface albedo from 0.1 to 0.5, for an El Chichon type loading (-0.04 gm/m 2), changes by a factor of 3.6 and 1.5 at AO.6 ]lIJl and AD.33 ]Jm, respectively.

Table I. Upward irradiance (20 km) at AO.33 and AO.60 ]Jm for three surface albedos. Aerosol mass loading is 0.04 gm/m 2 •

AD.33

AO.60

1.5 Conclusion

Surface albedo 0.1 0.3 0.5 0.1 0.3 0.5

Lt (20 km) (W/m2/~) 243.2 303.0 373.2 149.2 342.5 539.5

A higher proportion of the direct beam is converted into diffuse at shorter wavelengths due to larger Rayleigh optical depths. Changes in the aerosols' size distribution following volcanic eruptions (such as El

-704-

Chichon) result in a decrease in the extinction for a fixed mass loading; the decrease is higher at the shorter wavelengths (a factor of -4 at A=0.3 ~). With increases in aerosol loadings, there is a decrease in the downward irradiance at lower altitudes and an increase in the upward ir­radiance at the higher altitudes (10% increase in Lt at 20 km in an in­crease from background to El Chichon type loadings of 0.04 gm/m 2). The perturbations in the aerosol size distributions result in larger changes to the irradiances at higher mass loadings (approximately 4% decrease in Lt at 20 km for a loading of 0.04 gm/m2). High surface albedos amplify the upward irradiances. A change from clear to partially cloudy condi­tions results in an increase in the upward irradiance at 20 km by a factor of 3.6. These perturbations to the irradiance fields imply changes in the photodissociation rates of ozone molecules following volcanic eruptions.

REFERENCES

1. ACKERMAN, M., (1971). Mesospheric Models and Related Experiments. (Ed. L. Fiocco), D. Reidel, Dordrecht.

2. FARLOW, N. H., OBERBECK, V. R., COLBURN, D. S., FERRY, G. V., LEN, H. Y. and HAYES, D. M., (1981). Comparison of stratospheric aerosol measurements over Poker Flat, Alaska, July 1979. Geophys. Res. Lett., 8, 15-17.

3. FIOCCO, G., MUGNAI, A. and FORLIZZI, W., (1978). Effects of radi­ation scattered by aerosols on the photodissociation of ozone. J. Atmos. Terr. Phys., 40, 949-961.

4. HOFMANN, D. J. and ROSEN, J. M., (1984). On the temporal variation of stratospheric aerosol size and mass during the first 18 months following the 1982 eruption of El Chichon. J. Geophys. Res., 89, 4883-4890.

5. JOSEPH, J. H., WISCOMBE, W. J. and WEINMAN, J. A., (1976). The delta-Eddington approximation for radiative flux transfer. J. Atmos. Sci., 33, 2452-2459.

6. LAZRUS, A. L. and GANDRUD, B. W., (1977). Stratospheric sulfate at high altitudes. Geophys. Res. Lett., 4, 521-522.

7. PALMER, K. F. and WILLIAMS, D., (1975). Optical constants of sul­furic acid: Application to the clouds of Venus? Appl. Opt., 14, 208-219.

8. PENNDORF, R., (1957). Tables of the refractive index for standard air and the Rayleigh scattering coefficient for the spectral region between 0.2 and 20 ~ and their application to atmospheric optics. J. Opt. Soc. Amer., 47, 176-182.

9. PINNICK, R. L., JENNINGS, S. G. and CHYLEK, P., (1980). Relation­ships between extinction, absorption, backscattering and mass content of sulfuric acid aerosols. J. Geophys. Res., 85, 4059-4066.

10. THAEKAKARA, M. P., (1973). Solar energy outside the Earth's atmo­sphere. Solar Energy, 14, 109-127.

11. TOON, O. B. and POLLACK, J. B., (1976). A global average model of atmospheric aerosols for radiative transfer calculations. J. Appl. Meteor., 15, 225-246.

12. VAN DE HULST, H. C., (1957). Light Scattering by Small Particles, John Wiley Sons, New York.

-705 -

Figure I

Figure 2

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A SENSITIVII'Y STUJJY OF CAI,CUIJATION OF AT::CSPHErUC OZOKE TRAl1SYi1TTANCE§----------

F. ;:ISKOLCZI Ecnd I. LASZLO Department of Physics, University of Calabar, Calabar

Institute for Atmospheric Physics, Budapest

Summary

To improve the understanding of the radiative effect of atmospheric ozone it is necessary to incorporate the most reliable spectroscopic calculations into the radiative models. Remote sensing applications also require atmospheric transmittances of high accuracy. In tqis paper the atmos­pheric transmittances in the 1042 cm- region are calculated by line-by-line integration method and hence the following questions are examined in detail: 1. the dependence of the ·transmittance on the temperature and ozone content, 2. the effect of the water vapor, 3. line shape function, 4. line wing cut off problem, 5. vertical resolution. Calculations are performed for different profiles of temperature and ozone concentration and also for several combinations of parameters listed above and the effects of the variation of the parameters on the transmittances are examined.

1. Introduction

It is estimated that by the middle of the next century the sratospheric column ozone reduction due to the anthropo­genic chemicals is going to be about 5% (1) and similar reason­ing forecasts a 30% increase in the tropospheric ozone by approximately the same time (2). As the resulting change in the total ozone amount would be very small it might be diff­icult to reveal any trend in its natural fluctuation by analys­ing the data of the surface-based ozone monitoring network.

Concerning the vertical distribution of the atmospheric ozone more marked variations are expected. F'urthermore as a result of the direct radiative effect these perturbations are bound to be accompanied by drastic changes in the vertical thermal structure of the atmosphere. .

To predict the possible climatic effect of ozone changes even in the case of a simple 1D radiative-convective model one has to perform detailed calculations of radiative transfer taking into account the flux divergence, short wave solar heating and the convective heat transport.

Ozone Symposium - Greece 1984 -708 -

On the other hand, to monitor the variation of the atmos­pheric ozone by satellite spectral measurements in the IR region (both n~dir and limb method) we have again to be engaged with the question of the accuracy of atmospheric transmittances.

Regarding these problems it is obvious that in the future the accurate transmission functions shall have a more important role in connection with the measurement of the atmospheric ozone and the calculation of the climatic effects of its variation.

2. Description

Here we will not go into the mathematical details of the direct integration method but we can refer to some comprehen­sive work on this field, see for example (3). Our method is essentially similar to that used by Aida (4). To represent the fundamental modifications and differences we give the ultimate expression (Eq. 1) that was used for the calculation of the column transmittances averaged over the wave number interval c.v:

In Eq. 1 Wo. and Wb,i are the quadrature weights with respect to the wave number and pressure integration, g is the gravity acceleration, }J. =cose and e is the zenith angle, Sj,\<. is the intensi ty of the k-th line of the j-th molecular species, Fj is the line shape function, <Xl =cXJ(T(Pb) ,Pb.) and cx:j=CX)(T(Pb)' v.,) are the Lorentz and Doppler half width, T(p) and qj(p) are the temperature and mass mixing ratio profiles, and finally p is the pressure. The quantity Cj =Cj (T(Pb) ,Pb,') is the continuum absorption coefficient. Here we should note that the far wing absorptions of the strong lines (distance frQm the line center greater than 10 cm-1 and Sj,k greater than 10-5. atm-1cm- 2 at STP) were treated as "continuum" absorption in the sense that Fj was independent of the wave number within A~.

In the Eq. 1 the first sum indicates the wave number integration. The length of the interval (AV) over which four­point Gaussian quadrature was applied (wi th abscisses V • .) de­pended on the distances of the line centers from v~, which in our case varied between 0.0005 and 0.05 cm-1 • Concerning the line shape function the Voigt profile was used for pressures lower than 100 mb. For other pressures the Lorentz line shape was used up to the distance of 100~J. At larger distances the exponential die-away was applied.

The second and third sum in Eq. 1 represent the pressure integration along the path. Instead of using the Curtis-Godson approximation we preferred the numerical pressure integration (two-point Gaussian quadrature over the pressure layers with abscisses Pb). 'i'he total number of the layers was L (=29) in logari thmically linear scale. The values of 'r(Pb)' qj (Pb') and Cj (T(Pb) ,Pb) wi thin the i-th layer were determined by para­bolic interpolation.

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The fourth sum refers to the different molecular species. In the present calculation the lines of ozone, carbon dioxide and water vapor were considered. The temperature dependence of ajwas taken into account by a power function. As a power -0.5

was applied for 03 and C02 and (after Deepack (5) -0.62 for HZO. In the last sum N is the number of the individual lines wlthin the interval determined by +10 and -10 cm-'I. Altogether 14000 03, 700 C02 and 250 H20 lines were taken into account. Although relatively good spectroscopic data are available for most of the atmospheric gas components (see for example \6) and \7» there remained some problems. Concerning the 03 one of these is the intensity of the ozone band. It is suspected that the value of 312 atm-1cm- 2 is too small \1). In this work the line parameters were taken from the compila­tion published by McClatchey et al. (6) with the modification that the intensity of the ozone band was increased by 8%.

The transmittance calculations were performed for the model profiles represented in Fig. 1.

1.0

.D E - 10

01 ~ ~ <!I oJ> ... >

0.100

/.0

.!l

E /0 .;

... ::S <II ,f) <II >

0. jOo

1000'~..L--'--_-"-_-r-_-. o 100 200 300 'fDa Ozone po.rt. press, nb

O.

1 OOO'-l--_~'----,--~-,.--=:"..,; o 'I 8 12 i Spec. huml.d.C-/;!j, 9/k9

Fig.1 Atmospheric model £rofiles used for the calcula­tion of transmittances. 03(P) and T(p) are the annual average profiles measured in Potsdam (8). The water vapor profiles were measured in Budapest.

3. Results

The calculated transmittances for 03(P) and T(p) are pre­sented in Fig. 2. (The effect of H20 and C02 is included.) Since no other direct calculations for atmospheric ozone are available we confirmed our results indirectly against satellite spectral measurements (9). This calculation improves the accuracy of the total ozone values derived from the data of the satellite Meteor-25 (st. dev. 11 Du, syst. error +3 Du). In Fig. 3 the total absorption is compared to those calculated by Aida (10). Here effective pressure and temperature values were used for the homogeneous path from the indicated pressure levels. In Fig. 4 the effect of the variation in the tempera­ture and ozone profile is presented. The effect of the H20 is shown separately in Fig. 5. In the last figure (Fig. 6) the effect of the vertical resolution on the accuracy is presented.

-710-

.. v C d .... ..... oj

E oil c d

r=

'" v c

~ , O ... 5 I E

0., u ___ ThLS Coo.l<. -:l 'fo

- 0 -.- Ai. cl.e. l1'3161 0.8 -d (HoMooeneouA ,..."

~ p a.i. h .) "" 0,1 ~ 30 ~, .. r.""'" ~ -0,6 72 -

ProfL.'e~ : -'-« 0.5 03(P), T(p). H .. Q(vl

O.~

M+--__r_-_._--,...--...---''-r---. 9&0

\..Io.IIe number. cm-~

Fig. 2 Atmospheric transmit­tances for the vertical path from the indicated pressure levels.

' - ' - ' - _._. - _.-.-.- .-:....-....:..-- .. _--- -------- ----o.~

0.'2:

'--,

~oo to 0

Pres",u.~e. mb

Fig .3 Integrated absorp­tions vs. vertical path from the different pres­sure levels

," .',~\

I , ; \ , \

I " ; \~

\:\.. \\

Prof i.l e 5 :

\\. \ , , "

'<"-<'O](p), i(p)+30K "[ Ollpl. Tlp)

o,?>lpl, T(pl-30k

O,O"-;-::r:-::--...-_...--..--.---:-:=-= _ _r__--,--~____:_:r:_:-_r__-_._-__r_--=0TS=( p).,2 . • T( p) 4020 40210 10~0 40 5 0

4.0

Wo.ve nl"unber, cm-~ Fig.4 The dependence of the ozone transmittances on the ozone and temperature profiles ~t the centre of the band. (Average values over 2 cm- intervals. )

-1 ~o

.$ o.g -to> 'g .. dO., ~

0.1 Profi. Jes :

A: I-i .. O(pl. e.o.o· O.~ B: H"'O"'Q~(Pl. e- 50·

0.5i--~:_r:-_._-:-:"I:""---.--:_:T"--, 3 0 lO20 4060

Wa.ve number, cm-~

J~ i f" . 5 The water vapor transmittances due to the \·rater vapor absorption lines.

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~5 30 "15 &0 15 9 Number of lh~ IQ~ers, n

Fig. G The effect of the vertical resolution on the integrated absorption.

4. Conclusions

The overall effect of temperature on the ozone transmit­tances (through the line intensities and half width factors) is slightly positive. 30 degree uniform increase of temperature at each pressure level results in about 5% decrease in the integrated absorption. Between 1035-1039 cm-1 and 1055-1060cm-1 intervals two temperature independent region appears which might be useful in remote sensing application. The effect of the water vapor becomes noticable if the total precipitable water in the atmospheric column is more than 5 mm and the zenith angle is over 500 • With the possible availablity of more accurate spectroscopic data ~n future, the overlapping effects of the CH3Cl 950-1110 cm- and the NH7CO 500-1350 cm-1 bands would require further investigations. Tbe vertical reso­lution given by the above described pressure integration method using 30 layers is quite satisfactory. A 50% decrease in the number of the layers increases the relative error in the integrated absorption from 0.01% to 1%. According to our test calculations, the effect of the strong ozone absorption lines (about 1800 lines) should be taken into account through' the whole band, even in the case of exponential line wing being used. Applying the exponential die away the long wave opacity of the tropospheric ozone proved to be 20% less than that of the stratospheric one. As a consequence the climatic effect of the tropospheric ozone must be more moderate.

REFERENCES

1.

2.

3.

4. 5. 6.

7.

8.

9.

10. 11.

WMO Global Ozone Research and rlJonitoring Project (1982). Report No. 14 LOGAN, J., A. et ale (1978). Atmospheric chemistry: res­ponse to human influence. 1Tans. Roy. Soc. 290, 187-243 DRAYSON, S., R. (1964). Atmospheric slant path transmission in the 15 C02 band. Univ. Michigan, Techn.Hep. 05863-T AIDA, M. (1975). J.Q.S.R.T. 15, 389 DEEPACK, A. (1981). The atmospheric water vapor. Acad.Press McCLATCHEY, R., A. et ale (1973). AFCRL atmospheric ab­sorption line parameters compilation. AFCRL-TR-0096 HUSSON, N. et ale (1982). La banque de donnes "GEISA". Lab. de Meteorologie Dyn. du C.N.R.S. Note Int. LMD no.116 SPANKUCH, D. and DOHLER, W. (1975). Geodatische und Geo­phJ.sikalische Veroff. Reihe II. H.19 SPANKUCH, D. and MISKOLCZI, F. (1983). Validation of 9.6 m ozone transmittances by spectral radiance satellite measurements. Advances in Space Research VOl.2,No.6, 89-92 AIDA, riJ. (1976). Private communication. jVIURCRAY, D. and GOLm'IAN, A. (1981). Handbook of high resolution infrared laboratory spectra of atmospheric interest. C~C Press Inc.

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C HAP T E R IX

NON-URBAN TROPOSPHERIC OZONE

- The rol~ of isoprene oxidation in the tropospheric ozone budget in the tropics

- Methane oxidation in aerosol-containing atmosphere

- Hydrox¥~ fgdical concentration in ambient air estimated from C 0 oxidation

- Tropospheric ozone: transport or chemistry?

- Effect of stratospheric intrusions on the tropospheric ozone

- Vertical ozone profiles in the lower atmosphere and their relation to long-range transport

- Cumulus cloud venting of mixed layer ozone

Sources and budget of tropospheric ozone ~ a rural site in north west England

Seasonal behaviour of the tropospheric ozone in Japan

- Photochemical oxidants at Niwot Ridge, Colorado

- Diurnal variation of ozone in fine weather situations over hilly terrain

- Opposite behaviour of the ozone amount in the troposphere and lower stratosphere durinq the last years, based on the ozone measurements at the Hohenpeissenberg observatory from 1967 - 1983

- Trends in tropospheric ozone concentration

- Long-term surface ozone increase at Arkona (54,680 N, 13,430 E)

- A neglected long-term series of ground-level ozone

- Surface ozone near the equator

- Tropospheric ozone at four remote observatories

- Diurnal variations of non-urban ozone concentrations in Israel

- Differences in tropospheric ozone profiles obtained by Mast (Brewer) and EEC (Komhyr) Sondes

Uncertainties in surface ozone measurements in clean air

- L'ozone serait-il l'oxydant principal du sulfure de dimethyle en milieu oceanique

Ozone production and transfer in the FOS-BERRE basin area

THE ROLE OF ISOPRENE OXIDATION IN THE TROPOSPHERIC OZONE BUDGET IN THE TROPICS

Summary

D.A. BREWER Systems and Applied Sciences Corp.

Hampton, Virginia 23666 USA

and

J.S. LEVINE NASA Langley Research Center Hampton, Virginia 23665 USA

A comprehensive chemical mechanism for the oxidation of isoprene by OH and 03 in the troposphere was developed and incorporated into a one­dimensional steady-state photochemical model of the troposphere. Flux boundary conditions for NOx (NO + N02), HN03, OJ' and CO were used to investigate the changes produced in the tropospheric concentrations and integrated column of ozone from including iso8rene chemistry in the model. Two calculations were performed at 15 N latitude for annual conditions using identical flux boundary conditions for NOx ' HN03, 03' and CO; in one calculation, the chemistry describing isoprene oX1dat1on was included while, in the other calculation, it was not included. Both sets of calculations included reactions describing the chemistry of anthropogenic nonmethane hydrocarbons. The calculations showed de­creases in concentrations of ozone throughout the troposphere when isoprene chemistry was included. Concentrations of NOx and HN03 in­creased in the lower troposphere and decreased in the upper troposphere while concentrations of CO and PAN increased throughout the troposphere when isoprene chemistry was included. Implications of this study to the budgets of these species in the tropics will be discussed.

1.1 Introduction

Isoprene (C5HS) and monoterpenes (C 10H16), hydrocarbons emitted pri­marily by vegetation, have larger emission source strengths than the com­bined strengths of all anthropogenic nonmethane hydrocarbon (NMHC) emissions. The anthropogenic ~*C emissions have been estimated to account for about 10% by weight or 10 g/yr (1) of the total hydrocarbon ef!ssions, while natural emissions account for the remaining 90% or 9 X 10 g/yr (2) of the NMHC emissions. Isopre~e, monoterpenes, and a portion of the anthropogenic NMHCs are olefins. Reactions of these ole fins with OH and 03 at the carbon­carbon double bond are sources of alkylperoxy (R02) and peroxyacyl (RC03) radicals. The radicals participate in radical chain reactions to produce partially oxygenated organic species, namely simpler aldehydes (RCHO) and ketone~ (RC(O)R'), alkylperoxides (ROOR), alkylperoxy acids (RC(O)OOH), peroxyacylnitrates (RC(0)02N02 where R=CH3 is denoted as PAN and R)CR3 is denoted as PAN2), and carboxylic acids (RC(O)OH)

Ozone Symposium - Greece 1984 -715 -

RC03 + N0 2 R02 + H02 RC03 + H02

... ROOH + 02

+====""'" RC(O)OOH + 02

RCHO + 02 ... RC(O)OH

They can also react with NO, oxidizing NO to N0 2 RC03 + NO ... R02 + N0 2 + CO2

(R 1)

(R 2)

(R 3)

(R 4)

(R 5)

R02 + NO ... RO + N0 2 (R 6)

Photolysis of N02 (by visible wavelength radiation) produces 0(3p), and the

reaction of 0(3p ) with 02 produces 03

N02 + hv ... NO + 0(3p ) (270 ~ ~ ~410 nm) (R 7)

0(3p ) + 02 + M ... 03 + M (R 8)

If the reactions of the radicals with NO (R5 and R6) are more important than the radical chain reactions (R1-R4), there will be a net production of ozone that may exceed the amount of ozone consumed in the initial oxidation of isoprene by ozone. The change in the calculated amount of ozone in the troposphere from introducing a mechanism for the oxidation of isoprene into model calculations has been examined in this study.

1.2 Mechanism and Model Description

A Dne-dimensional steady-state photochemical model of the troposphere which has been described previously (3) was used for all model simulations. Calculations have been performed for 150 N latitude using an annual temper­ature profile (4) and a specified vertical profile for water vapor (5). The chemical mechanism used in all calculations includes the gas-phase reactions for species in the oxygen, hydrogen, carbon, nitrogen, and anthro­pogenic NMHC chemical families. For each species, 16 concentrations are calculated as a function of altitude--at every kilometer from the surface to 10 km (the tropopause in the model) and at 0.05, 0.10, 0.20, 0.40, and 0.70 km. The values for the eddy diffusion coefficient vary as a function of altitude and are identicaL to those of (6). For some calculations, the chemical mechanism describing the oxidation of isoprene by OH and 03 (7) has also been included. All rates of reactions have been updated to reflect current recommended values (8). The only change in the mechanism for the oxidation of isoprene and anthropogenic NMHCs used in this study from previous studies was the inclusion of carboxylic acid formation.

1.3 Results and Discussion

Two model calculations were performed to assess the effect of including isoprene oxidation on the calculated profiles of tropospheric species. Identical flux boundary conditions for 03' NOx (NO + N02), RNO), and CO were used in both calculations; they were determined by adjust.ing the lower and upper fluxes to provide agreement between measurements (5) and calculated concentrations at the surface and at 10 km using the version of the model which did not include isoprene oxidation. Profiles obtained from these cal­culations are given in Figure 1. Calculated concentrations of NOx and HN03 increased in the lower and decreased in the upper troposphere when isoprene oxidation was included; there was a net increase of 20% in the integrated

-716 -

tropospheric column of NOx and a net decrease of 8% in the integrated column of HN03 when isoprene oxidation was included. Concentrations of CO and PAN, the simplest peroxyacylnitrate, increased throughout the troposphere when isoprene oxidation was included; the integrated columns of CO and PAN increased by 52% and 21%, respectively, and the column of 03 decreased by 8%. At the surfac5, th3 destfuction of ozone by isoprene oxidation accounted for 16% (or 2 X 10 cm- sec-) of the loss of o~one by chemical reaction, and destruction of ozone by isoprene-produced aldehyde oxidation accounted for an additional 3% of the loss. Above 2 kID, the loss of ozone from these reactions was negligible, in large part attributed to the short lifetimes of isoprene and the isoprene-produced aldehydes against oxidation by OH, the primary reaction which destroys these species.

A comparison of the effects of the addition of isoprene oxidation on the magnitudes of the column contents and distribution of reactive nitrogen species is given in Table f. Th~ total integrated reactive nitrogen in­creases by 48% or 1.2 X 10 5 cm- when isoprene oxidation is included, and the increase is attributed to the inclusion of reactions that form longer carbon-chain peroxyacylnitrates (PAN2) and to additional sources for peroxyacetyl radicals (CH3C03), the radical precursors to PAN. When the reactions describing isoprene oxidation are not included, a substantial source of reactive nitrogen, namely the longer carbon-chain peroxyacyl­nitrates (PAN2), is not described. The inclusion of the PAN2 species results in a redistribution of the percentages of reactive nitrogen species­decreases in the percentages of reactive nitrogen present in HN03 and NOx and incref~es i~ both PAN and PAN2. The column content of PAN increaf~s bY2 1.08 X 10. cm- at the expense of HN03 , which decreases by 1.12 X 10 cm­when isoprene 0f~dat~~n is included. The increase in the column content of NOx of 6.7 X 10 cm is attributed to the thermal dissociation of an equal quantity of PAN2 near the surface. The percentage of reactive nitrogen in the form of nitrates (H02N02 and RN04' R~CH3) is small.

The effects of the addition of ~soprene oxidation on the magnitudes of column contents and the distribution of reactive carbon species are given in Table II. All column contents are shown on a pe2-carbon basis; that is, the column content calculated on the basis of mol/cm has been multiplied by the number of carbon atoms in the molecule. As expected, the majority of the reactive carbon, greater than 95%, is in the form of CO in the tropics. The column content of CO increased 52% and the surface concentration increased 48%, from 141 to 209 ppbv, when isoprene oxidation was included. This re­sult implies that about half of the total CO in the tropics is derived from the oxidation of isoprene. Because the remaining reactive carbon species are more reactive than CO and changes in their concentrations are tied to the reactivities of other families of species, it is of interest to examine the changes in the distribution of the organic species (excluding CO) that result from including isoprene oxidation. The percentage of anthropogenically-emitted hydrocarbons (alkanes, C2H4 , olefins, and C2H2) decreased from 46% to 24% of the reactive carbon species (excluding'CO) when isoprene oxidation was included; this result was anticipated because conti­nental anthropogenic NMHC emissions are relatively minor compared to natural emissions in the tropics. The increase in the importance of the oxygenated organic species (alkylperoxy acids, alkyl peroxides , carboxylic acids, and aldehydes and ketones) were somewhat surprising; 67% of the reactive carbon species were oxygenated compounds, and this result has implications for the ozone budget in the tropics.

The alkylperoxy and peroxyacyl radicals that are produced in the oxida­tion of isoprene and aldehydes by OH and ozone react both with NO to

-717 -

eventually produce ozone (R5 and R6) as well as with N0 2 , H0 2 , and 02 (Rl to R4) to produce oxygenated organic species. If the oxidation of NO to N0 2 is more important than the reactions to produce the oxygenated species, there should be a net increase in the calculated concentrations of ozone above 2 km, the altitude at which the oxidation of isoprene and aldehydes by ozone becomes unimportant to ozone destruction in the troposphere when isoprene oxidation is included. The decreased concentrations of ozone calculated above 2 km when isoprene oxidation is included are evidence that the reactions of the peroxyacyl and alkylperoxy radicals with NO (R5 and R6) are relatively unimportant processes in comparison to the reactions to form the oxygenated organic species (Rl to R4). It is evident that the oxygenated hydrocarbons may play a substantial role in tropospheric photochemistry and should be the subject of further study. Experimental difficulties in measuring concentrations and rate constants of oxygenated organic species will complicate further studies.

REFERENCES

1. HANST, P.L., SPENCE, J.W. and EDNEY, E.O. (1980). Carbon monoxide production in photooxidation of organic molecules in air. Atmospheric Environment, Vol. 14, pp. 1077-1088.

2. ZIMMERMAN, P.R., CHATFIELD, R.B., FISHMAN, J., CRUTZEN, P.J. and HANST, P.L. (1978). Estimates on the production of CO and H2 from oxidation of hydrocarbon emissions from vegetation. Geophysical Research Letters, Vol. 5, pp. 679-682.

3. BREWER, D.A., AUGUSTSSON, T.R. and LEVINE, J.S. (1983). The photo­chemistry of anthropogenic nonmethane hydrocarbons in the troposphere. Journal of Geophysical Research, Vol. 83, pp. 6683-6695.

4. u.S. Standard Atmosphere Supplement, U.S. Government Printing Office, Washington, D.C., 1976.

5. LOGAN, J.A., PRATHER, M.J., WOFSY, S.C. and MCELROY, M.B. (1981). Tropospheric chemistry: a global perspective. Journal of Geophysical Research, Vol. 86, pp. 7210-7254.

6. THOMPSON, A.M. and CICERONE, R.J. (1982). Clouds and wet removal as causes of variability in the trace-gas composition of the marine troposphere. Journal of Geophysical Research, Vol. 87, pp. 8811-8826.

7. BREWER, D.A., OGLIARUSO, M.A., AUGUSTSSON, T.R. and LEVINE, J.S. (1984). The oxidation of isoprene in the troposphere: Mechanism and model calculations. Atmospheric Environment, Vol. 18, In Press.

8. DEMORE, W.B., MOLINA, M.J., WATSON, R.T., GOLDEN, D.M., HAMPSON, R.F., KURYLO, M.J., HOWARD, C.J. and RAVISHANKARA, A.R. (1983). Chemical Kinetics and Photochemical Modeling Data for Use in Stratospheric Modeling. Evaluation Number 6. JPL Publ. No. 83-62, Jet Propulsion Laboratory, Pasadena, California.

Acknowledgement

D.A.B. acknowledges support from NASA Contract No. NASl-16456.

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Table 1.- Effect of the addition of isoprene chemistr~y on the column contents of reactive nitrogen species.

Species

lIN03

NOx

H02NOZ + RNO 4

PAN

PAN2

Total

Without Isoprene Chemist!1:

Column Content Percentage (cm-2) of Total

1.57 X 1015 63%

3.35 X 1014 14%

6.94 x 1013 3%

5.04 X 1014 20%

2.48 X,1015

With Isoprene Chem!strx

Column Content Percentage (cm-2 ) ~

1.45 X 1015 39r.

4.02 X 1014 11i.

8.90 X 1013 H

6.12 X 1014 17%

1.20 X 1015 32%

3.68 X 1015

Table 11.- Effect of addition of isoprene chemistry on the column contents (per carbon basis) of reactive carbon species.

Species

co Remainder

Total

Composition of Remainder:

Anthropogenic NMHC

RC(O)OOH

RDOH

RCHO + RC(O)R'

PAN + PAN2

RC(O)OH

Isoprene

Total

" - ItI TIIOIJ'I

~

~ :1,

(a)

Without Isoprene Chemist!!

Column Content Percentage (cm-2) ~

1. 70 X 1018 97i.

5.21 X 1016 37-

1. 75 X 1018

2.44 X 1016 467.

4.02 X 1015 8%

1.64 X 1016 32%

4.69 X 1015 9%

1.01 X 1015 2%

1.54 X 1015 3r. Or.

5.21 X 1016

~ 6

~ :1

With Isoprene Chemistry

Column Content Percentage (cm-2 ) of Total

2.59 X 1018 95%

1.44 X 1017 57-

2.73 X 1018

3.43 X 1016

3.55 x 1016

3.63 X 1016

1.66 X 1016

6.53 X 1015

7.47 X 1015

7.11 X 1015

1.44 X 1017

-_Iflalt Isom:JCJ; ;

- -WITII , I ,

I , I I I

,' ., I I I

I I I I I I I , I I , , I I I

, I I I I I I I I I ". , , , , , , , , ,

I , , I ,

24%

25%

25%

12%

4%

5%

57-

2xW 10· 10" I'Ilxlrlli MTIO

(b)

Figure 1.- Comparison of profiles calculated with and without the inclusion of the chemical mechanism for isoprene oxidation at ISoN latitude. (a) NO (NO + N02) , RN03, and PAN; and (b) 0 3 and CO. x

-719-

METHANE OXIDATION IN AEROSOL-CONTAINING ATMOSPHERE

V.L. TALROSE, A.I. POROIKOVA and E.E. KASIMOVSKAYA Institute of Chemical Physics of the Academy of Sciences of the USSR

Sunmary

S.G. ZVENIGORODSKY and S.P. SMYSHLYAEV Hydrometeorological Institute, Leningrad, USSR

A one-dimensional photochemical model of atmosphere (z=O-50km) has been used to study the effect of methane oxidation on azone content in troposphere at different NOx fluxes from Earth surface SN=I.109-4.10 11 cm-2s-1 and constants kW of washing out the water-soluble sustances. Ozone content in the lower atmosphere increases as SN grows, two diffe­rent reaction mechanisms being obtained for troposphere: at small and moderate NOx fluxes the tropospheric OH content and HN03 fraction in NOy'-family increase as SN increases, at greater SN the reverse depen den­ces are observed, while NO and NO x fraction begin growing. This can be explained by insufficient amount of OH radicals required for removal of NOx in reaction OH+N02+M - HN03+M. Decrease in OH concentration stops the growth of the 03 content in troposphere (Fig. 3).Calculations show that ground-level NO concentrations of the ppb order, often taken as background ones for the air over the continents (1-2) can be obtain­ed only at great NOx fluxes equal to hundreds and thousands of Mt N yr-1 (1) with calculated concentration of the tropospheric ozone becoming higher than experimental values (Fig. 2). The best agreement of the mo­del tropospheric ozone profiles with observed ones has been obtained for NOx fluxes of (1-3).10 10 cm- 2s- 1 (Fig. 2), the contribution of tro­pospheric ozone is 8-10% to the total ozone content.

1.1 Introduction

NO x species are known to be catalysts of ozone production in oxidation of CH4 and CO (3-6). Tropospheric NOx is mainly of Earth surface origin (3). According to (1-2) background surface concentration of NO in the air over continents is high enough to reach ppb-range. An one-dimensional photoche­mical model is used to find out: 1) what NOx fluxes from Earth surface provide the NOx ground-level concentrations of ppb-range; 2) how calculated profiles for 03 fit the experimental ones; 3) how tropospheric ozone con­tent depends on methane concentrations at different NOx fluxes.

The model considers the heterogeneous removal of 03, NOx, HN03, H202, CH302H and CO at the earth's surface and rainout and washout of water-so­luble substances in the troposphere. To estimate methane effect on tropos­pheric ozone calculations were made for methane-free (case A) and methane­c?ntaining atmosphere (8) .. At.a lower bound~ry (CH4)z=0 = 1,60 ppm. Reac­tlons schemes, model descrlptlon and numerlcal data are presented in (6).

Ozone Symposium - Greece 1984 -720 -

Photolysis constants were calculated according to (7), in some cases light scattering on aerosol particles was taken into account. Chlorine cycle was not considered. NO x fluxes ranged from 1.109 to 4.1011 cm-2s- l •

1.2 Results and Discussions

In the layer z=0-50km the calculated NO and HOx altitude profiles at moderate NOx flux are fairly well consistent with oalculations in (8) with the exception of ground-level layer, where different boundary condi­tions are accepted.

Altitude profiles for NOy have minimum at z=6-10km, which reflects an intense tropospheric sinks of these substances. As SN increases the ground­level concentration of NO rises a little, increasing ninefold with the change of SN from 1.109 up t02·10 11 cm- 2s- l • At very high SN=4.I0 11 cm-2s- 1 (1500 Mt N yr- I ) NO fraction in the total tropospheric content of NOy increases greatly and ground-level NO concen­tration reaches the level of ppb. Here a change in the reaction mechanism can be observed: the concentration of HOx radicals is insufficient to re­move NOx species, OH and H02 concentrations decreasing, while NO and NOx concentrations rising. Altitude profiles for OH-radicals are shown in Fig.I. Methane oxidation is a source of HOx, but Fig. 1 shows that it affects OH concentration differently in troposphere and lower stratosphere: it reduces OH content below the tropopause level but enhances it above this level. This effect is primarily accounted for by different water vapour content in these atmospheric regions.

1 t", 50

3ij

20

10

Fi g. 1.

10'

Calculated altitude profiles for OH at different NOx fluxes (SN, cm-2s- I ). Curve 1 - OH prof1le ~t SN=4.I0II (case B);

2 - SN=2.I0 1 (8); 4 - SN=I.109(B); 2'- SN=2.10 11 (A); 4'- SN=I.109(A).

-721-

At low SN the tropospheric OH concentration rises as SN increases, but at high SN the ·OH concentration in the lower troposphere decreases and ty­pical maxima appear at the curves (compare curve 2' with 4' and 1 with 2 in Fi!g. 1).

Active hydrogen is present in the atmosphere as a sum of HOy=HOx+2H202+HN03+HN02+H02N02+CH3+CH302+CH30+HCO+2(CH3OH+ CH302H) where molecules are HO x reservoirs, radicals of methane origin are radical­carriers of HO x. The continuity equation for HOy incorporates solely sour­ces and sinks of HOx (5,6). HOx fraction is not more than 1% of the total content of HOy. Methane enhances the content of tropospheric HOy and HOx, but decreases OH content due to redistribution of HOy species by the fast reactions 02,NO O2

OH+CH4 - CH 3 -- CH 30 - CH20+H02

At high SN the HOx content begins to fall as SN rises reflecting a change in the reaction mechanism mentioned above.

Calculated altitude profiles for ozone are shown in Fig. 2. Here dots stand for an average experimental 03 profile according to the data from (4) for the conditions close to the model ones. The effect of methane on the tropospheric ozone is seen from the comparison of curves 2 and 4 with 2' and 4' respectively. In the methane-free atmosphere the main source of tropospheric ozone is the downward 03 flux from the stratosphere (3,4). The calculated 03 flux is (2,5-3).1010 cm-2s- 1 and it is only weakly dependent on SN'

l' 3D .!. 28 {} 26 ...:! zt ~u <:0:: 20

18 16 I~

/2

fO

6 6

fig. 2.

01 NumOtl Dtflsi 1'1 (em - ~)

Calculated altitude profiles for ozone in lower atmosphere at different HOx fluxes (SN, cm-2s- 1). Curves 1-5 and 1', 2' are calculated at maximal values of kW'

I' - SN=I.109(case A); 1 - SN=I.109 (B); 2' - SN=2.1Q11 (A); 2 - SN=2.lQll (B); 3 - SN=4.1011 (B); 4 - SN=I.1010 (B); 5 - SN=2,8·1Q1O(B).

Curve 6 - SN=2,8·1010 (B) is calculated at minimal kW' Dots - see text.

-722 -

Calculated tropospheric concentrations of 03 at high SN=(2-4). 1011 cm- 2s- 1 appreciably exceed the experimental ones. Agreement of the experi­mental 03 profile (dots) and calculated ones is much better at moderate OOx fluxes S~(l-2,8).1OIOcm-2s-1 (with exception of some differenr" in a ground-level layer that has not yet been explained). At moderate SN NO sur­face concentration is 30-50 ppt. The calculation showed that for obtaining an average background NO concentration of the ppb order NOx fluxes from Earth surface should be equal to hundreds and thousands of Mt N yr- 1 (1), tropospheric concentration of 03 exceeding the experimentally observed one. The most suitable NOx fluxes are SN=38-105 Mt N yr- 1 comparable with the recently published: 21,5 - 78 (8) and 21 Mt N yr-1 (antropogenic com­ponent only) (3). Fig. 3 gives the dependence of tropospheric ozone content upon SN' It follows from comparison of the curves in Fig. 3 that the in­fluence of methane oxidation on the content of tropospheric ozone enhances as the NOx flux grows. In the presence of methane the 03 content in the troposphere increase by approximately 50% at SN=1.109 cm-2s- 1 and more than 150% at SN=2.1011 cm- 2s- 1.

Q 15 J (OJ)dz (lOfTon- t )

!O

.,-,/

./ ,/

,/ ./

..-"-5 ...,..--' ..,., ...............

/ ;I

/ /

,/ ,/

/ /

/ /

/

/ ....... ---/

/

Fig. 3 Tropospheric ozone content as a function of NOx flux from Earth surface. Solid line - case A, dotted line - (B).

-723 -

A weak rise in 03 content in case (A) is due to H2 and CO oxidation in the troposphere. In case (B) tropospheric ozone provides 8% of its total content at the moderate flux SN=1.10 10 cm-2s-1 and 15,5% at the maximal fluxes SN=(2-4}.1Q11 cm-2s- l . Further NOx flux incr:ease does not res.ult in rising the 03 content because of a sharp decrease ln the tropospherlc OH content.

REFERENCES

1. ROBINSON, E.R. and ROBBINS, R.C. (1972). In: Air pollution control. Ed. W. Strauss, N.Y., J. Wiley Intersci., pt. II, 93 p.

2. GRAEDEL, T.T. (1978). Chemical compounds in the atmosphere. New York, San Francisco, London, Acad. Press, 439 p.

3. CRUTZEN, P.J. and GIDEL L.T. (1983). J. Geophys. Res. 88, No. 11, p. 6641-6661. -

4. LOGAN, J.A., PRATHER M.J., WOFSY, S.C. and McELROY, M.B. (1981). J. J. Geophys. Res. 86, No. C 8, p. 7210-7254.

5. JOHNSTON, H.S. and~ODOLSKE J. (1978). Rev. Geophys. Space Phys. 16, No.4, p. 491-519. -

6. TAL ROSE , V.L., POROIKOVA, A.I., ZWENIGORODSKY, S.G., SMYSHLYAEV, S.P. and KASIMOVSKAYA, E.E. (in press). Izvestiya of Academy of Sciences of the USSR, Atmospheric and Ocean Physics.

7. ISAKSEN, J.S.A., MITDBO, K.H., SUNDE, J. and CRUTZEN, P.J. (1977). Geophys. Norvegica, 31, Nos. 4-6, p. 11-26.

8. CODATA Bulletin, No.45, January 1982, p. 9-10.

-724 -

HYDROXYL RADICAL CONCENTRATION IN AMBIENT AIR ESTIMATED FROM C130 16 OXIDATION

J. Hjorth, G. Ottobrini, F. Cappel:l:ani, G. Restel:l:i, H. Stangl:

Summary

Commission of the European Communities Joint Research Centre - Ispra Establ:ishment

21020 Ispra (Va) Ital:y

C. Lohse University of Odense, Chemistry Dept., Odense - Denmark

The average OH radical: concentration on sunny days at the semirural: site of Ispra (~ 45~) was estimated from measurements of c 130 16 oxi­dation. Tefl:on bags fil:l:ed with ambient air with added c 13016 were exposed to sunl:ight and the c130 16 decrease measured by infrared ab­sorption spectroscopy.

From the resul:ts of thirteen experiments (May-Jul:y) an OH radi­cal: concentration averaged over the dail:y irradiation time (~ 8 hours around noon) equal: to 2.106 cm- 3 was estimated with an upper l:imit of 4·106 ·cm- 3 . From these data onl:y a minor rol:e can be attributed to carbon monoxide as ozone precursor in this area.

The use of bags for this type of experiments is discussed on the basis of experimental: observations.

1.1 Introduction

The concept of the OH-radical: as the principal: driving force of atmos­pheric chemistry has created much interest in methods to be used for the measurements of OH radical:s in ambient air; however, there is stil:l: onl:y l:ittl:e and ambiguous knowl:edge about the prevail:ing hydroxyl: radical: dis­tribution in the troposphere /1/.

These measurements of c 13016 oxidation in ambient air sampl:es have been done in the context of previous studies on the infl:uence of carbon monoxide on tropospheric ozone formation in a semirural: site /2/. A detail:ed descrip­tion of the experiments has been presented at the Varese Symposium on "Phy­sico-Chemical: Behaviour of Atmospheric Pol:l:utants" /3/. Here we wil:l: put more emphasis on some resul:ts and anal:ysis nat previousl:y presented.

Method

As original:l:y suggested in Ref./4/ for c 140, daytime averages of OH ra­dical: concentrations are cal:cul:ated from the consumption of c 130!6, added in smal:l: (~ 1 ppmv) amounts to ambient air irradiated in l:arge (~ 2 m3) Teflon bags. c 13016 and c 12016 (in the foll:owing indicated as c130 and C120) con­centrations are determined by long path Fourier transform infrared spectros­copy (FTIR). The consumption of c130 can then be measured even if carbon monoxide is rel:eased from the bag walls, because c 130 constitutes only a smal:l: and known fraction of the C120.

CF2Cl2 is added at < 1 ppmv level:, simuLtaneousl:y measured by FTIR and used as an inert internal standard.

Ozone Symposium - Greece 1984 -725 -

The oxidation of carbon monoxide in ambient air is believed to proceed almost exclusively with the OR radical according to reaction (a), followed by reaction (b):

co + OR ~ C02 + R (a) k = 2.66.10- 13 cm3 molec- 1 s-l

R + 02 + M ~ R02 + M (b)

In the presence of NOx , HO radicals can then be regenerated by reaction (c): l

NO + H02 ~ N02 + OH (c)

which eventually leads to ozone production. Calculations are based on the approximation that c 130 is oxidized by

OH only; the above mentioned rate-constant is used, thus disregarding any isotopic effect. The added CO is assumed to have essentially no influence on the OH concentration in the bag for two reasons: 1) the recycling of OH by NO, 2) in the ambient air considered, CO is not an important reaction partner

for OH radicals.

1.2 Experimentals

~~!~~~_~~2~. Pillow-shaped FEP Teflon (Du Pont Inc.) bags with surface to volume ratio of ~ 5 m- 1 were used. The bags were prepared by heat sealing 2 mil (0.05 rom) thick film followed by an outside mechanical support of the sealing consisting of two Teflon-strips fastened by staplers. The ability of the bags for the experiment is an important problem; for this reason we report here the results of different tests performed to answer this question.

Bags prepared from new Teflon-film release under sunlight irradiation relatively large amounts of carbon monoxide (several ppmv in the 2 m3 bag after one day irradiation). Following 20-40 hours exposure in sunlight, the release is reduced to levels equivalent to the build-up of ~ 100 ppbv of CO for one day irradiation; this was considered to be an acceptable level (conditioned bag) .

The contamination with hydrocarbons of a conditioned bag was investiga­ted by GC in conjunction with cryogenic sampling (C1 -Ch ) and for heavier hydrocarbons by GC-MS with sampling on a column. For the c1 -c6 hydrocarbons no contaminants at the ppb-level were found. For the higher boiling com­pounds further investigations are in progress, but also in this case conta­mination seems negligible.

Ozone formation (5-20 ppbv) was observed in bags filled with purified air and irradiated in sunlight during one day; this, however, might not be a good test for the ability of the bags to generate radicals since the re­sult is affected by the performance of the zero air generator. To test the possibility of OH radical generation by the film material the bags were fil­led with C130 (or propene)-added zero air and irradiated by an artificial UV source (osram UVISTRA HVI) with a wavelength cut-off somewhat below the so­lar spectrum (~ 275 nm). In new unconditioned bags a significant C130 de­crease was observed. This effect was drastically reduced at the next irra­diation and by the following ones no significant decrease was observed either on C130 (~ 1 ppmv) or on propene (15-20 ppmv). The UV-flux as well as the time integrated flux was exceeding that of the experiments where sunlight was used. On the other hand, two new bags were used for irradiating purified air added ~ 1 ppmv of C130 in sunlight. After one day irradiation about 6 ppmv of CO were produced in both bags, but no significant effect on the C130 concentration was seen.

Vacuum-heating of Teflon-film is reported /5/ to be an efficient way of cleaning it up for impurities. A small Teflon bag was then heated at ~ 1650 C in vacuum overnight; however, production of CO reached the normal

-726-

level after subsequent irradiation. Finally zero air was left overnight in a new, unconditioned bag and

then transferred to a well-conditioned bag, which was afterwards irradiated; CO concentration built up at the level typical of a well-conditioned bag.

From the results of these experiments, it could be inferred that for­mation of CO originates on the bag walls by photolysis probably of a high boiling, thermally stable compound. The photochemical wall-reactions do not seem to involve OH radical generation in sunlight irradiation of the bags. Formation of OH radicals was, however, observed when NOx (~ 12 ppb) was added to purified air and irradiated in a conditioned Teflon-bag; when CO (~ 50 ppmv) was added to this mixture, a large increase (~ 200 ppbv) in ozone formation was seen.

For our present experience it seems most likely that OH radical forma­tion in the bags due to photolysis of wall-contaminants is not an important problem. Heterogeneously catalyzed formation at the walls of HN02 (that is photolyzed to OH) from NO and/or N02 could, however, influence our experi­ments. HN02 formation on the walls from N02 has been observed and described in Ref./6/.

Spectroscopic measurements. A Bruker IFS 113 V Fourier Transform Spectrome­ter-in-;onjun;tion-with-a-70 m beampath 25 1 volume White cell was used to record infrared absorption spectra of the air samples on the 3-10 ~m region. Three interferograms were recorded for each sample, each one with 100 scans co-added. Spectra were then obtained at 0.06 cm- 1 instrumental resoihution using Happ-Genzel apodization and zero filling factor 4. The concentrations were det~rmined from peak adsorbances; the use of routines for calculating peak areas did not result in better precision. The c 120 and C130 concentra­tions were calculated using four transitions for each isotopic species, lo­cated in the 2169-2184 cm- 1 and 2130-2145 cm- 1 , respectively. The concen­tration of CF2Cl2 was evaluated from the sharp Q branch of the v6 band at 1160 cm- l . The uncertainties (one standard deviation) were equal to 1.0% for CO and 0.6% for CF2C12' nearly constant over the concentration range used. These limits were most probably set by a combination of instrumental noise, baseline fluctuation and imperfect description of the absorption line shape by the instrument.

1. 3 Results

In the calculation of the percentual change in C130 (6C 130), the C130 (and C120) values were normalized to the CF2C12 values. The 6c 130 for each experiment was generally too small and close to the uncertainty of the de­termination of the c 130 concentration to permit a meaningful calculation; however, using all the data an estimate of the average OH concentration for these summer days could be made. For this purpose it was assumed that the duration of each experiment was 8 hours and that all the experiments were performed during the same hours of the day, so that the results were com­patible. This assumption did not introduce a remarkable error, as all the experiments include the time period 9 a.m. - 3 p.m., where the sun intensity is at its maximum.

The average 6c 130 was -1.75%. This corresponds to an average OH con­centration of 2.3.106 molecules/cm3 for the time period considered. Assu­ming a normal distribution of the data, the upper limit can be derived from 6c13Omean - ts//n = 6c 13Ominimum, where t is the student t value (2.18 at a 95% level of significance), s is the standard deviation (1.68) of the 13 C130-determinations and n is the number o"f measurements. This upper limit (lower limit of the 6C 130) becomes -2.8%, corresponding to an OH concentra­tion of 3.7'106 molecules/cm3 •

-727 -

To avoid making assumptions about the distribution of the values, non­parametric statistics must be used. The values are ranked and the median is found to be -1.3%, corresponding to an OH concentration of 1.7,106 . The upper limit is -3.0% at a 95% level of significance, corresponding to an OH concentration of 4.0'106 molecules/cm3 .The lower limit found by assuming a normal distribution is 1.0'106 molecules/em3 . From the non-parametric statistics a limit of 0.8'106 molecules/cm3 is obtained.

Blank experiments were performed without sunlight irradiation, in or­der to test whether absorption, d~ffusion through the walls or instrumental errors could produce an apparent variation in the C130 concentration. Ase­ries of 13 experiments with conditions similar to those of the irradiation experiments, gave an average c 130 change of 0.02%, when the tracer norma­lization was applied.

1.4 Discussion Photolysis of ozone in the presence of water vapour is an important

source of OH radicals. The validity of the method was then tested using irradiation of purified air added with 03 (400-1500 ppb), H20 and NO; the 03 photolysis rate was calculated "a posteriori" from the results using the model of Ref./7/ and compared to the literature value. An agreement within a factor 2 was found with an apparent overestimate of the OH radical concentration (excess OH radical formation in the bag).

From the analysis of the ambient air experiments, a non-linear correla­tion between the product UV light, 03, H20 concentrations and the observed decrease in c 130 was found as expected in those experiments characterized by a si~ilar initial NOx concentration.

The dark experiments permit to exclude that effects such as wall dif­fusion, absorption or instrumental artifacts seriously affect the results. It is generally observed that smog chambers (in this case the Teflon bag) exhibit radical-initiating effects. The experiments performed seem to indi­cate that OH radical generation in the bags from photolysis of wall conta­minants is not an important problem. On the other hand heterogeneously catalyzed formation of HN02' subsequently photolyzed to OH might be a pro­blem.

It is then reasonable to take the measured OH radical concentration as an upper limit to the real ambient air value.

Bags were filled with ambient air between 7.00 and 8.00 a.m.; previous experiments however /2/ have shown that ozone formation in the Ispra area on typical hazy and sunny days was nearly the same (± 25%) inside the bag and in the free outside air.

The average OH radical concentration estimated from this work is in good agreement with the recent results of direct measurements /8/ concer­ning slightly and moderately polluted air.

The average ambient concentration of carbon monoxide measured in Ispra in the period considered was equal to 330 ppbv. Using for the OH concentra­tion the value of 2.106 molecules.cm- 3 , a build-up of ozone due to carbon monoxide oxidation in the 8 hour period equal to 5 ppbv can be inferred. Since the net ozone production observed by monitoring on days with a ne­gligible influence of transport is 70-80 ppbv, carbon monoxide can be only a minor contributor to tropospheric ozone formation in this area.

References

1. P.J. Crutzen (1982) Atmospheric Chemistry - Dahlem Konferenzen, E.D. Goldberg (Ed.), Springer-Verlag, Berlin, p.313.

2. C. Lohse et al. (1982) Proc. 2nd Eur. Symp. on Physico-Chem~cal Beha­viour of Atmospheric Pollutants, Varese (September 29 - October 1, 1981)

-728 -

B. Versino and H. Ott (Eds.) Reidel Publ. Co., p.212. 3. J. Hjorth et al. (1984) Proc. 3rd Eur. Symp. of Physico-Chemical Beha-

viour of Atmospheric Pollutants, Varese (April 10-13) in press. 4. M.J. Campbell et al. (1979) Geophys. Res. Letters, Vol.6, No.3, p.17S. 5. w. Lonnernan et al. (1981) Env. Sci. Techn., Vol.1S, No.1, p.99. 6. F. Sakamai et al. (1983) Int. J. Chern. Kinetics, Vol.1S, p.l013. 7. L. Demerjian and L. Scheere (1980) Adv. Environ. Sci. Technol., Vol.l0,

p.369. 8. G. Hubbler et al. (1984) J. Geophys. Res. Vol. 89, No.Dl, p.1309.

TABLE I - Data of ambient air teflon bag irradiation experiments. All the values refer to the content of the bags except "ozone-outside air"; 6C 130 was corrected for photochemical C130 production. The NO concentration was too small to be measured « 2 ppbv). The N02 values might be too high due to interference in the measurement (from other NOy species (HN0 3 , PAN).

S Ozone ppb NO, CnO CU 0 M.x Temp. ReI. hum." UV. max. Integr. UV 4Cu O C! Bog Time Ambient Air Bog ppb ppb ppb ·C atT max. arbitr.ry units .. ~ 7.30 15 15 5-6 392 216 it; 832 27 42 3.9 17.5 -1.5

::I; 15.00 35 110 5-8 469 214

;;; 7.20 25 25 6 315 173

I 832 29 31 3.3 - 0.7 16.20 65 76 2-3 432 173

7.55 35 28 9 - 10 400 377 832 33 32 3.1 20.3 -1.5

0> 16.45 90 - 95 2-5 494 373

l 7.55 35 28 8 - 10 391 304 834 33 31 3.1 21.5 - 0.6

17.45 90 - 95 107 3-6 500 303

8.30 43 40 8- 10 295 1110 832 35 <20 3.6 23.3 - 3.0

~ 16.30 60 122 5 361 1077

~ 830 43 43 8- 10 322 2718 B34 35 <20 3.6 26.2 -5.0

18.30 62 135 3-4 388 2583

.~ 8.30 30 35 8 - 10 916

l 834 28 44 3.5 12.1 +0.1 14.45 80 103 6-10 918

8.45 30 20 4-6 285 1043 832 29 42 +0.5

~ 16.00 50 75 6 362 1049

l 8.45 30 20 4-6 292 1097 834 28 51 -1.3

18.00 50 87 5 397 1083

8.45 40 40 4 242 728 832 34 44 2.8 18.5 -4.6

N 17.45 120 98 2-3 342 695 N > ~ 9.45 40 37 4 248 759

834 34 39 2.8 15.9 -2.9 15.45 123 100 3 335 738

8.20 30 30 9 -10 431 1061 832 38 37 3.0 18.3 -1.3

~ 16.25 95 115 8-10 553 1049 ~ .i! 8.20 30 30 8-9 387 1130

834 29 54 3.0 19.6 -0.9 18.30 95 108 8-10 495 1121

-729-

Summary

TROPOSPHERIC OZONE: TRANSPORT OR CHEMISTRY?

H. Levy II Geophysical Fluid Dynamics Laboratory/NOAA

P.O. Box 308, Princeton, New Jersey 08542

This study examines the contributions of large scale atmospheric trans­port to the behavior of tropospheric ozone and identifies potential roles for tropospheric chemistry. The GFDL general circulation/ transport model, with photochemistry in the top (middle stratosphere) level only, is used to simulate the climatology of tropospheric ozone for upper and lower limits of surface removal rates. The transport model's vertical profiles of mixing ratio and variability are in quali­tative agreement with observation, and, south of 40 o N, the same is true for the local seasonal cycles and the latitude gradient. However, the transport simulation needs an additional destruction mechanism at low latitudes over the ocean, has the wrong seasonal cycle at mid- and high­northern latitudes, and produces too much ozone at high latitudes in the north. The lack of tropospheric chemistry plays an important role in the first two disagreements between simulation and observation, but the cause of the excess 03 at high northern latitudes is not clear.

1. Introduction

Ozone is an important oxidant in its own right, a precursor for highly reactive radicals, and a significant absorber of long-wave radiation. It is, therefore, important that we understand the behavior of ozone in the troposphere and are able to predict its response to perturbations, both natural and anthropogenic. The earliest view of tropospheric ozone had it forming photochemically in the stratosphere, being transported downward through the troposphere, and ultimately destroyed at the surface. While most observations of ozone still support this picture, global budget calcu­lations are dominated by chemical production and destruction. Two recent reviews (1,2) explore the past history of the debate over chemical and transport control and summarize the two positions. The reviews conclude that both transport and chemistry are important, but that the chemical and physical processes which control the tropospheric ozone climatology are not completely understood.

We propose to explore the role of atmospheric transport· by comparing available observations with the results of a GFDL general circulation/ transport model (GCTM) simulation which specifically excludes tropospheric chemistry. Rather than debating global budgets which are currently beyond realistic calculation and/or verification by observations, we focus on the ozone climatology with particular emphasis on the "free troposphere" and the maritime boundary layer. The continental boundary layer is greatly compli­cated by small scale transport processes which are poorly simulated by the GCTM and by an active and highly variable pollution chemistry. By combining the global, though far from perfect, ozone fields of the GCTM with the accurate, though greatly limited, observation data, we gain a more complete picture of ozone in the troposphere.

Ozone Symposium - Greece 1984 -730 -

2. General Circulation Transport Model

A detailed description of the GCTM and relevant references are given in a recent paper (3). The model has 11 vertical levels, a horizontal grid size of approximately 265 km and contains 78,540 grid boxes. The continuity equation for the volume mixing ratio of ozone in each grid box is given in schematic form below:

oR at Transport (Flux Convergence or Divergence)

+ Chemical Tendency (Chemical Production - Chemical Destruction)

- Deposition (Surface Loss)

The tr.ansport term is calculated using the 6 hr averaged wind fields gener­ated by the parent GCM. The chemical tendency is calculated only in the top model level (10mb). The mixing ratio of reactive nitrogen species has been set at a constant value of 17.5 ppbv to force the correct equatorial 10mb 03 • This is sufficient to simulate the observed latitude gradient, seasonal cycle, and absolute values of 03 at 10mb. The deposition term, which must balance the photochemical tendency of the top level when both are averaged globally over the year, is expressed in terms of a deposition velocity, Woo While Wo for ozone is highly variable, it is much faster over land than over water, snow, and ice. In this study we take advantage of the approximate factor of 10 difference and construct an upper limit deposition case "Fast Destructi'on" (W = 1.0 cm sec-lover land and 0.1 cm sec-lover ice and ocean) and a 10Zer limit deposition case "Slow Destruction" (W 0.2 cm sec-lover land and 0.02 cm sec-lover ice and ocean). 0

3. Simulation Results

A detailed intercomparison of the transport model simulations and available observations is given in sections 3 and 4 of the paper just men­tioned (3). A brief summary will be provided here: 1) the simulated global­mean cross-tropopause flux of 5xl0 lO molecules cm-2 sec- l is in the range of previous estimates; 2) the simulated and observed latitude gradients are in agreement from the South Pole to 40 0 N; 3) in that same region the upper- and lower-limit simulations bracket the observed values and reproduce the local seasonal cycles; 4) at all latitudes the simulated vertical profiles of 03 and its temporal variability are in qualitative agreement with observa­tion. Up to 40 0 N the upper- and lower-limits bracket the observed profiles.

The three major disagreements between transport simulation and observa­tion are: 1) North of 40 0 N the lower-limit exceeds observation by as much as 50% and the latitude gradient increases until 60 0 N instead of leveling off at 40 0 N as observed; 2) At Samoa (14°s) and Mauna Loa (20 0 N) the observed 03 mixing ratios appr0ach the simulated "Fast Destruction" limit which would require an unrealistically high deposition velocity (0.1 cm sec-I) over the ocean; 3) The transport model clearly fails to simulate the broad summertime maxima and winter minima observed throughout the troposphere at a number of continental stations at northern mid- and high latitudes •

• Disagreement 1) may be related to a lack of tropospheric photoche­mistry, but a number of probable model deficiencies in stratospheric and tropospheric transport, as well as the lack of chemistry in the lower strat­osphere, must be considered. Studies with an improved GCTM will try to identify current model deficiencies in transport.

-731-

Disagreement 2) is similar to the recent observation that low 03 values in the tropical Pacific boundary layer imply chemical destruction, if current measurements of Wo over the ocean are correct (4).

The summer maxima in 3) have been observed at 14 mid- and high-latitude ozonesonde stations (private communication, J. London) at 700, 500, and fre­quently 300mb. They are not just a local phenomenon though no data from ocean sites are available. While a multi-year average shows a rather clear picture, individual years are not that simple as we see in Figure 1.· This data comes from an analysis by Logan (5).

60

SO

:E ~

40

30

120

110

100

90

80

~ 70 0-.e 60

50

40

30

20

10

100

90

80

70

:E 60 0-.e 50

40

30

20

10

-MN Ro

3

R:MN

°3

R:MN

° 3

Figure 1.

300mb

500mb .,..-----

5 6 8 9 10

PAYERNE 500mb 1977.81

PA YERNE 1980

PAY ERNE 1981

II 12

In the top panel we see a great deal of interannual variability though the minima occur in the winter and one or more maxima occur in the spring and summer. Clearly the meteorological impact on seasonal behavior is more complex than a simple spring maximum in cross-tropopause transport. In 1980

-732-

all four tropospheric levels (the dots are surface data) had similar seasonal cycles while they were quite dissimilar in 1981. If these types of behavior are not the direct result of the 03 transport, then they are the result of transport control of the chemical precursors of 03.

It should be noted that during the summer maxima, the monthly mean ozone mixing ratio still increases with height. Even if the daily surface maxima are used, the profiles are, at best, well mixed to 500mb for a number of summer months (private communication, J. Logan). Therefore, an active chemistry at the surface does not imply a net transport of surface ozone to 500mb, since there can be no net vertical transport without a vertical gra­dient.

4. Tropospheric Chemistry

A schematic diagram of the major reaction paths controlling tro­pospheric ozone chemistry is given in Figure 2.

MIDDLE TROPOSPHERE

H0 2 +NO

""-NO~' hv 0

3

HO hv

o x 01'01 H 0 , '\.......L

OH

Figure 2.

BOUNDARY LAYER

HO,+NO

""-RO, +NO

Nt {"Methane Cycle'" NO,

0,

,

01'01 \H,o

OH

(Surface Deposition)

The chemical source of 03 is the peroxy oxidation of NO to N02 • In the boundary layer, the methane oxidation paths provides peroxy radicals but this process essentially shuts off at 500mb temperatures. The reactions of O( ID) with H20 and of H02 with 03 are the principle gas phase loss pro­cesses. In the continental boundary layer, surface loss has a time scale of 1-3 days and becomes dominant. Surface loss, CH4 oxidation, and the sharp decrease in H20 mixing ratio with height are the major differences between boundary layer and 500mb ozone chemistry.

Returning to the ozone continuity equation in section 2., the two key chemical issues are the sign of the chemical tendency and its magnitude. Since the chemical steady state of 03 is mainly a function of t~e NOx level, the same is true for the sign of the chemical tendency. While the strength of the tendency also depends to some extent on the distance of the local 03 mixing ratio from photochemical steady state (i.e., the NO level), the rate of O(ID) formation and the H20 mixing ratio are most imp~rtant. There­fore, while 03 chemical steady state calculations depend weakly on season, the strength of the chemical tendency at 500mb and 45°N ranges from an upper limit of ± .3ppb/day in the winter to ± 5.0ppb/day in the summer. Because of the much greater H20 mixing ratio, the corresponding tendencies are

- 733-

significantly faster at the surface. The chemical tendency calculations are discussed in more detail in section 5. in reference (3).

The chemical tendency in the tropical ocean boundary layer can be nega­tive for very low NO levels and larger than the weak surface deposition (4). Since this ten~ency is controlled by the HZO mixing ratio which decreases rapidly with height, it acts as an addl.tional surface or boundary layer removal process and must be included in tropospheric ozone simulations, particularly where W is very slow. An accurate treatment requires the NO distribution singe the chemical tendency is only negative for very low vafues. While observations do exist that confirm the low values over the tropical and subtropical Pacific, no climatological data set exists.

At 500mb at mid-latitude we have the same situation with NO. For levels greater than 100ppt, a positive chemical tendency exist a~ the nor­mally observed levels of 03' 40-80ppb. To reach a +5.0ppb/day chemical ten­dency the NO level must increase to 300ppt or more. These chemical tendencies m~y be sufficient to extend the 03 maxima through the summer but, again, no climatological NOx data set exists.

5. Conclusion

A pure photochemical model will explain little, if any, of the observed tropospheric ° climatology. While much of the observed climatology can be at least quali€atively explained by a tropospheric transport model with injection from the stratosphere and removal at the surface, there are at least two general observations that appear to require a joint transport/ chemistry model in the troposphere: 1) The low values of 03 observed over the tropical and sub-tropical oceans require a significant net destruction from chemistry; 2) The observed seasonal cycle at northern mid- and high latitudes requires a net chemical production during the summer and fall.

In order to fully resolve the joint role of transport and chemistry in the climatology of tropospheric ozone, multi-year measurements of 03' NOx ' H20 and temperature profiles at representative locations about the globe are needed. Furthermore, improved high resolution GCTM's must be developed which include multiple chemical species (NOx ' 03 and H20 at a minimum).

REFERENCES

1 •

2.

3.

4.

5.

BOJKOV, R. (1984). Tropospheric ozone, its changes and possible radiative effects. WMO special environmental report no. 16. FISHMAN, J. (1984). 03 in the free atmosphere. Ed. Whitten and Prasad, Van Norstrand/Rheinhold, NYC. LEVY, H., MAHLMAN, J.D., MOXIM, W.J., and LIU, S.C. (1984). Tropospheric 03: The role of transport. J. Geophys. Res., to be published. LIU, S.C., MCFARLAND, M., KLEY, D., ZAFIRIOU, 0., and HUEBERT, B. (1983). Tropospheric NO and 03 budgets in the equatorial Pacific. J. Geophys. Res., 88, 13~0-1368. LOGAN, J. (1984). Tropospheric ozone: The influence of chemistry. Submitted to J. Geophys. Res.

-734-

EFFECT OF STRATOSPHERIC INTRUSIONS ON THE TROPOSPHERIC OZONE

K. Munzert, R. Reiter, H.-J. Kanter and K. P6tzl

Fraunhofer Institute for Atmospheric Environmental Research

D-8100 Garmisch-Partenkirchen, FRG

Summary

Using a measuring series of tropospheric ozone obtained since 1977 at three neighboring, vertically graduated mountain stations different sources of tropospheric ozone can be identified. A measuring series of cosmogenic radionuclides, starting 1970, serves as an indicator for stra­tospheric intrusions. In the valley, chemical reactions lead to a daily variation of the ozone concentration, which is missed in the free tro­posphere. Here, in 3.0 km asl a distinct seasonal variation can be ob­servedMith rather quick transitions between a summer and a winter regime, each prevailing over periods of about 5 months. The time series of stra­tospheric intrusions reveals a 2.4 yr period free of seasonal effects. Stratospheric intrusions in the mean occur 2.3 times per month and lead to an averaged stratospheric ozone contribution of 3 - 6 ppb. A correla­tion analysis shows that the annual variation of the C3 concentration, regarding phase and amplitude, is independent of the Be7 concentration. This means, that stratospheric intrusions have no controlling influence on the tropospheric ozone. A trend analysis reveals the successive rise of the tropospheric 03 in the documented 7.5 years. Singularities in the time series can not be explained by the stratospheric/tropospheric ex­change.

1. Introduction

Since 1977, continuous recordings of the local ozone concentration have been taken at 3 mountain stations over an altitude range of more than 2 km and a horizontal distance of at max. 16 km. The stations are situated at the northern edge of the Bavarian alps (47.50 N, 11.loE) in the valley at 0.7 km, at Wank peak in 1.8 km and on Zugspitze peak in 3.0 km asl. At the station in 3.0 km since 1970 the atmospheric concentration of cosmogenic ra­dionuclides such as Be7 and p32 are determined. The present paper discusses the correlation between 03 and Be7 at 3.0 km asl in the period from 1977 to 1981.

2. Ozone regime in the observation area

The annual frequency distributions of the hourly 03 values at the sta­tions are shown by Fig. 1. At the mountain peak stations rather identical normal distributions are found. The distribution in 3.0 km asl is typical for the free troposphere, only 2% of all values fall below 20 ppb and 3% of the values exceed the limit of 60 ppb under the influence of stratospheric

Ozone Symposium - Greece 1984 -735 -

intrusions. In contrast, at the valley station influenced by atmospheric pollutions up to the limit of 20 ppb already 47% of all values are observed. The high values in the valley (3%>60ppb) originate from local photochemical ozone production. The values in 1.8 km asl are influenced by that valley regime especially under good exchange conditions. The lack of the photo­chemical ozone production at the peak stations is documented in the averaged daily variations of the Fig 2. Here the period 1977/1983 is plotted, but the period 1977/1981 gives the same results. A daily variation up to 4 ppb exists at the mountain peaks even in summer only as a weak modification induced by vertical exchange. In contrast, in the valley caused by photochemical 03 production during the daytime and the nocturnal 03 destruction the daily amplitude comes up to 29 ppb in summer and 4 ppb in winter. After this short survey about the strong vertical differences in the 03 regime the further p~rts restrict to the smoother conditions in 3.0 km asl.

3. Annual variation of ozone at 3.0 km asl

The monthly cumulative frequency distributions of the 1735 documented daily means in the period 1977/1981 are plotted in Fig 3. For all 12 months of the year, the cumulative frequency up to the value of a_certain isoline can be read at the ordinate. At the distinct seasonal variation can be distin­guished between a summer and a winter regime prevailing over periods of about 5 months each. Transition from one regime to the other occurs within a very short time. Fig 3 documents the steep increase in the frequency of values >40 ppb in April and the decrease in September. From May to August all daily means exceed the limit of 20 ppb, in June even that of 30 ppb. Whereas-in winter the 03 concentration rarely reaches more than 40 ppb, values of nearly 70 ppb are regularly observed during summer. Most of the high concentrations occur in August, the highest monthly mean often is ob­served already in May. In contrast to the well established seasonal variation of 03' the cosmogenic radionuclides from the stratosphere have no statisti­cally significant annual variation.

4. Time behaviour of the cosmogenic radionuclides

At the station in 3.0 km asl since 1970 filters over a time of 24h each get exposed to seize the atmospheric concentration of the cosmogenic radio­nuclides Be7, p32 and p33. These nuclides are mainly produced in the stra­tosphere and their identification in the troposphere serves for the investi­gation of the stratospheric/tropospheric exchange and the stratospheric re­sidence times. The mean level of the lognormal Be7 distribution in 3.0 km is 92 fCim- 3 . The threshold value of 161 fCim- 3 for a stratospheric intrusion was exceeded in 13.7% of all measurement days. Strong intrusions with Be7 >230 fCim- 3 occurred on 3.2% of all days. The time series of the number of intrusions reveals that no annual variation exists but a quasi biannual oscillation with a period of 2.4 yr can be recognized. The same result is well established by a power spectrum of the Be7 daily values. In times with strong stratospheric/tropospheric exchange 3.5 events per month can be ob­served and during minimum exchange 1.7 events per month occur in the mean. The averaged duration of an event is 1.8 days.

5. Relation between ozone and beryllium 7

The relation between ozone and Be7 comprises two quantities, the first of which is gaseous and chemically instable and fluctuates just slightly around a well defined annual variation,the second one however is bound to aerosol particles and subject to physical depOSition and wet removal and

-736 -

shows irregular fluctuations without a distinct annual variation. The ratio of the values of the two tracer elements is only a poor indicator of stra­tospheric air masses. In order to elucidate the ozone input from the stra­tosphere connected with intrusions mainly after tropopause foldings, linear regressions have been computed for the whole period classified by months. If all days are considered, these correlations lead to high significant re­gressions on the 0.1% error level. The regression coefficients are rather independent of whether the high Be7 values are included or not.

6. Influence of stratospheric intrusions on the tropospheric ozone

The ozone levels for different threshold values of the Be7 concen­tration calculated from the monthly linear regressions are shown in Fig 4. With the annual Be7 median of 79 fCim- 3 emerges quite well the actual annual variation of ozone. The patterns of the 03 curves for Be7=25 fCim- 3 (mode of the annual distribution) and for the hypothetical Be7 value ° continue to reflect the real annual variation of ozone regarding all, phase, amplitude and absolute 03 level. This means, that also without stratospheric influx - at least without stratospheric intrusions - the annual variation of ozone is maintained in the noted manner and therefore a tropospheric origin must be supposed. The same conclusion can be drawn from cable car soundings of the ozone profile between 1.0 and 3.0 km asl. They document, that stratospheric intrusions do not reach layers below 2.5 km and the high ozone values in summer originate from local photochemical production in the valley. At the mountain peak station in 3.0 km asl the tropospherically steered annual ozone variation is merely shifted by 3 - 6 ppb and the stratospheric intru­sions have no controlling influence on the tropospheric ozone. This result is further substantiated by the fact that frequency and intensity of stra­tospheric intrusions do not show a statistically significant annual variation The range between the ozone curves indicated by Be7=161 resp. 300 fCim- 3 re­presents the ozone values during the injection of stratospheric air masses. In late spring (April/May) with maximum ozone concentrations in the lower stratosphere intrusions cause the highest increase in ozone concentration. If the annual variation of ozone in the troposphere would be determined only by the exchange with the stratosphere caused by intrusions, an 03 minimum would result in February with a steep increase to the maximum in May and a uniform. flat decline over 9 months back to the minimum. The shape of the curve 03 (Be7=300 fCim- 3 ) - 03 (Be7=79 fCim- 3 ) plotted at the bottom of Fig 4 is thus in excellent agreement with the annual variation of ozone in the lower stratosphere.

7. Time series of ozone

The monthly means of ozone in Fig 5 with their increase from 36.8 ppb in 1977/1978 up to 47.5 ppb in 1982/1983 point out no parallel to the time series of stratospheric intrusions. In contrast, the episod from summer 1981 to summer 1982, when the 03 concentrations were about 10 ppb higher than usual in the corresponding seasons, fell into a minimum time in the 2.4 yr intrusion cycle. An explanation of this episod is still missed and matter of discussion.

8. Conclusions

Simultaneous recordings at neighboring mountain stations from the valley to 3.0 km asl provide hints that the tropospheric ozone regime is steered by nearground chemical reactions and not by the impulsive exchange between stratosphere and troposphere. The annual variation of 03 originates from the

-737 -

photochemical ozone production during summer. Due to the time lag and the temporal smoothing caused by the vertical exchange, no daily variation can be found in the free troposphere. Stratospheric intrusions raise the tro­pospheric ozone level in the mean by 4 ppb nearly independent of season.

REFERENCES

1. R. Reiter et al. (1970-1983). Measurement of airborne radioactivity and its meteorological application. Balance of the tropospheric ozone and its relation to stratospheric intrusions indicated by cosmogenic radio­nuclides. Annual reports I-X for US Department of Energy

2. R. Reiter et al. (1983). Cosmogenic radionuclides and ozone at a mountain station at 3.0 km asl. Arch. Met. Geoph. Biocl., Ser. B, 32, 131-160

3. R. Reiter and K. Munzert (1983). Cosmogenic radionuclides at a mountain station under fallout background conditions with consideration of the stratospheric residence time. Arch. Met. Geoph. Biocl., Ser. B, 33, 187-197

4. E.R. Reiter (1971/1972/1978). Atmospheric transport processes Parts 2-4, Chemical, hydrodynamic, radioactive tracers. DOE Critical Review Series

For further references see 2 and 4

Acknowledgement: Most of this research has been supported since 1969 by the U.S. Department of Energy

FIGURES

0104 OR I~'~ - I)h .. ---l a ..

£ .. ~ .. ~ ,.!--,-=-=-.,.,------c-=,.,.-----,,=-,;

i .. ,--- ...

III .... .. II 1 • • 1

Fig 1 Annual frequency distribution of local ozone: 1977/1981

Fig 2 Daily variation of ozone in December and June: 1977/1983

.. " I ' IlIa n

-738 -

..; o

~~----------------~---------, .. 50

" ..

Fig 3 Cumulative frequency distribution of local ozone in 3.0 km asl month by month: 1977/1981

Fig 4 Local ozone in 3.0 km asl depending on Be7 value: 1977/1981 Lowest curve: -3 03(Be7=300 fCim , - 03(Be7=79 fCim- 3 ,

Fig 5 Time series of 03 monthly means in 3.0 km asl

-739 -

Summary

VERTICAL OZONE PROFILES IN THE LOWER ATMOSPHERE AND THEIR RELATION TO LONG-RANGE TRANSPORT

F. L. LUDWIG Atmospheric Science Center

SRI International Menlo Park, California 94025 USA

Vertical profiles of ozone collected by several investigators fall into one of 6 categories governed by meteorological conditions and time of day. Some types are associated with long range transport of ozone aloft. The frequency of occurrence of the 6 types for different times of day, and locations relative to the city are presented. Specific cases show the effect of nighttime downward-mixing from an ozone reser­voir aloft, and cross sections well downwind of urban areas.

1. Introduction

Air quality is usually defined by ground level measurements that do not provide an adequate picture of any ozone reservoir aloft that can be trans­ported over long distances, undetected until there is vertical mixing. The fact that ozone is not always a local problem was recognized long ago (1) and has often been measured or inferred since (2-9). This paper presents an ozone profile classification system based on 268 ozone profiles from the following geographical areas--St. Louis (10), Washington/Baltimore (11), Houston (12), Los Angeles (13,14), Indianapolis (15), Toronto (16) and cities in the northeastern United States (17-21).

2. Background

Ozone distribution is determined by precursor sources, chemical forma­tion and destruction proce-sses, transport and mixing. Formation is a slow daytime process, while destruction can occur rapidly anytime through reaction with nitric oxide (NO) or surface contact. Destruction is slower in the free atmosphere, making atmospheric mixing an impor­tant factor in the vertical distri­bution of ozone. Mixing determines the height to which precursors are carried, and the downward flux of ozone to the surface. Ozone pro­files reflect combinations of these processes.

Figure 1 shows 6 common ozone profile types; height and concentra­tion scales are generally typical. In a well mixed air mass, concentra­tions are nearly uniform with height

, 0 t;; 0

i 3

Ozone Symposium - Greece 1984 -740-

I A I I

i I I I I ,

.. eo

.. eo

Figure I

4(1 ao 120

, , : t ___ _

'; ,--- . -UAau L."VIJII

40 ICI 120 leo

, \ ,

.... _--..... , M III:"U) ,.~;"""'f"Yu

40 IICI 120 40 10 120 180

OlONE CONCENTR" TION _ _

Ozone Profile Types

except for the lowest layers that are altered by destruction near the ground [Figure lea) 1. In natural air masses, concentrations tend to be around 40 or 50 ppb (24); the accumulation of anthropogenic precursors often leads to higher background concentrations (25). Figure l(b) shows the profile evolu­tion when a stable layer forms at the surface (from nighttime cooling or passage over cool water), and prevents replacement of destroyed ozone by downward mixing. Figure l(c) shows a profile when precursors have not been mixed completely through the boundary layer. Wi th mixing, the profile evolves to Figure led). A surface stable layer produces strong gradients as in Figure lee). If a new mixed layer forms, but does not extend as high as the earlier mixed layer, a profile like Figure l(f) results, giving a higher concentration layer above the mixed layer.

The 6 categories in Figure 1 were used to classify 268 ozone pro­files. Table I summarizes the joint frequency of occurrence of profile type by time of day and location relative to the city. The observations are con­sistent with the above discussion. Profile types A, D and F represent well mixed conditions and occur in 78 percent of the cases between 0900 and 1500 local time, so that midday surface ozone measurements are representative of conditions aloft. Average ozone concentration through the mixed layer is linearly related to surface values (correlation = 0.91) with a standard error of estimate of 21 ppb (23). At other times of day, or when air tra­vels over a cooler underlying surface, the ozone aloft is effectively isolated from surface destruction processes so that it can be transported for long distances and surface observations have little relation to condi­tions aloft. The next section, discusses some specific cases that illu­strate long range transport.

3. Example

Figure 2 (25) shows two vertical cross sections, (measured above the hatched bars on the map). Vertical lines show the extent of aircraft

Table I

FREQUENCY OF OCCURRENCE PERCENT OF PROFILE TYPE BY TIME OF DAY AND LOCATION

Total Profile Type

Condition Cases A B C D E

Location:

Upwind or to one 49 38 4 7 18 14 side of city

Downwind of city 19 18 8 18 37 8

Above city 25 21 6 2 28 13

Time:

06-09 LST 22 21 10 0 3 17

09-15 LST 56 40 3 9 25 11

15-21 LST 2 13 0 15 54 6

21-06 2 17 50 0 0 33

-741-

F

18

12

}O

48

13

11

0

soundings on which the cross sections are based. Stipled bars show stable layers. Streamlines at 850 mb (1900 EST) are shown. High concentrations at higher altitudes corres­pond to Figure 1 (e) • The eastern cross sec­tion has lower concen­trations in the stable layer over the cool water. Lower surface concentrations to the west may have arisen during passage over the urbanized Connecticut coast, where NO emis­sions could destroy

200

TllM' of p • .,a8e- of ..... r that left New York between it. .\600 EST

At.t1T1Jt)t toJ.m I~~ 1..1T'C~rULD <fc , I'ISL) 16()O UI.O ."lCi t$'t .... '000

, ... 4000

)000

'000

'000

'~ .~

10000

"

Figur e 2 Cross Sections for the afternoon of Aug. 10, 1975

\ "', ...

, ... .... '000 '000

1000

'000

1000

ozone more rapidly than it could be replaced from aloft.

o

... o z o ~ " >-

,~o

'00

o

~ EASTFORD VI) ~ ISO

u '00

FRr:!NGHAM

~o ~ o -SALEM

TIllE (EST)

1$0

,00

o

'00

Figure 3 Ozone Records for July 18-19, 1975

Figure 2 shows that ozone can be trans­ported aloft, isolated from the surface by a stable layer. If that layer is disrupted, higher ozone concentrations can be mixed down­ward, as happens during the day from surface hea ting. Night time cases provide clear examples of how downward mixing of ozone transported over long distances can affect surface concentrations because they are not masked by the daytime production of ozone. Figure 3 shows such an incident in southern New England on 18 July 1975, along with approximate times of passage of air that left the New York area during midafternoon. The locations of the sites are shown in Figure 4. The ozone peaks moved through the region much faster than the air, because they were caused by a rapidly moving line of vertical mixing that affected the widespread high ozone concentrations aloft. The National Weather Service weather map for 1600 EST shows a trough in the surface pressure field in the area of interest. Subsequent maps dropped this feature from the analysis because of sparse observations off the coast. If the trough persisted and moved reasonably, as shown in Figure 4, the trough's instability

-742 -

and enhanced vertical mixing would explain the observed ozone records.

4. Concluding Remarks

The 6 vertical ozone profile types in Figure 1 provide a basis for classifying and interpreting observed ozone data, and guidance as to when surface concentrations pro­vide reliable estimates of concen­trations through the mixed layer. Long range transport of ozone is most often associated with profiles like those in Figures 1(e) and l(f), especially at night or over water. Recent results (9) generally support

Figure 4 July 18, 1975, Trough Positions

this conclusion. The fact that relatively high concentrations of ozone can persist aloft, isolated from the ground until vertical mixing occurs has important implications for the design of ozone control strategies and sug­gests that the measurement of ozone concentrations aloft should be emphasized more.

ACKNOWLEDGMENTS

The. work described here was largely supported by the U.S. Environ­mental Protection Agency (EPA) under contracts 68-02-2662 and 68-02-2352.

REFERENCES

1. Bell, G.B., 1960: "Meteorological Conditions During Oxidant Episodes in Coastal San Diego County in October and November, 1959," California Department of Public Health, Berkeley, California.

2. Lyons, W.A. and H.S. Cole, 1976: "Photochemical Oxidant Transport; Mesoscale Lake Breeze and Synoptic-Scale Aspects," .:!.. Appl. Meteorol., IS, 733-743.

3. White, W.H. et ai., 1976: "Formation and Transport of Secondary Air Pollutants; Ozone and Aerosols in the St. Louis Urban Plume," Science, 194, 187-189.

4. Spicer, C.W., 1977: "Experimental Evidence of Long Distance Pollutant Transport," Paper presented at the 83rd Nat. AIChE Meet., Houston.

5. Wolff, G. T. et al., 1977: "Anatomy of Two Ozone Transport Episodes in the Washington to Boston, Corridor," Env. Sci. Tech., 11, 506-510.

6. Zeller, K.F., R.B. Evans, C.K. Fitzsimmons and G.w. Siple, 1977: "Mesoscale Analysis of Ozone Measurements in the Boston Environs," J. Geophys. Res., 82, 5879-5888. -

7. Dabberdt ,TF. ,-1983: "Ozone Transport in the North Central Coast Air Basin, " Final Report Executive Summary for California Air Resources Board Contract A9-143-31, SRI International, Menlo Park, California.

8. Unger, C.D., 1983: "Transport of Photochemical Smog in the Central Valley and the Sierra Neyada Mountains of California," Air Resources. Board (Draft).

9. Clark, T.L. and J.F. Clarke, 1984: "A Lagrangian Study of the Bound­ary Layer Transport of Pollutants in the Northeastern United States," ~. Environ., .!!!" 287-298.

-743 -

10. Mage, D. T., et al., 1979: "The RAPS Helicopter Air Pollution Mea­surement Program, St. Louis, Missouri--1974-1976," EPA No. 600/4-79-078.

11. Fitzsimmons, C.K., K. Zeller and M.J. Pearson, 1978: "Analysis of Aerometric Data collected by Aircraft During a Stagnation Period in Washington, D.C., August 1976," Air Poll. Cont. Assoc. No. 78-10.7.

12. Westberg,H., K. Allwine and E. Robinson, 1977: "Measurement of Light Hydrocarbons and Studies of Oxidant Transport Beyond Urban Areas," Houston Study, 1977; U.S. EPA Contract 68-02-2298, Washington St. U., Pullman, WA.

13. Blumenthal, D.L. et al., 1974: "Determination of the Feasibility of the Long-Range Transport of Ozone or Ozone Precursors," EPA No. 450/3-74-061.

14. Johnson, W.B. and H.B. Singh, 1977: "Vertical Profiles from Aircraft Soundings Conducted During the Los Angeles Reactive Pollutant Program (LARPP)," Appendix A of Interim Prog Report for Coordinating Research Council, CRC-APRAC CAPA-12/72(1-76), Stanford Research Institute, Menlo Park, Calif.

15. Lovelace, D.E. et al., 1975: "Indianapolis 1974 Summer Ozone Study," Indianapolis Center for Advanced Research, Indianapolis, Indiana.

16. Wiebe, H.A., M. Lusis and K.G. Anlauf, 1975: "The Toronto Oxidants Study: Aircraft Ozone Survey of the Metropolitan Toronto Region," Atmospheric Environment Service Report ARQA 29-75; Downs view, Ontario, Canada.

17. Siple, G.W., K. F. Zeller and T .M. Zeller, 1976: "Air Quality Data for the Northeast Oxidant Transport Study," Environmental Protection Ag~ncy, Environmental Monitoring and Support Lab., Las Vegas, Nevada.

18. Spicer, C.W., D.W. Joseph and G.F. Ward, 1976: "Final Data Report on the Transport of Oxidant Beyond Urban Areas," EPA No. 68-02-2441.

19. Washington State University, 1976: "Measurement of Light Hydrocarbons and Studies of Oxidant Transport Beyond Urban Areas," EPA No. 68-02-2339.

20. Wolff, G.T. et al., 1975: "An Aerial Investigation of Photochemical Oxidants Over New Jersey, Southeastern New York and Long Island, West­ern Connecticut, Northern Delaware, Southeastern Pennsylvania and Northeastern Maryland," Interstate Sanitation Commission, New York.

21. Environmental Monitoring Support Laboratory, 1975: "Meteorological Data for the Northeast Oxidant Study," EPA, Las Vegas, Nevada (draft).

22. Johnson, W.B. and H.B. Singh, 1977: "The Origin and Significance of Ozone Maxima Aloft," Report for Coordinating Research Council Contract CRC-APRAC CAPA-12/72( 1-76), Stanford Research Institute, Menlo Park, Calif.

23. Ludwig, F.L., 1979: "Assessment of Vertical Distributions of Photo-chemical Pollutants and Meteorological Variables in the Vicinity of Urban Areas," EPA No. 450/4-79-017.

24. Singh, H.B., et al., 1980: "The Impact of Stratospheric Ozone on Tropospheric Air Quality," J. Air. Poll. Cont. Assoc., 30, 1009-1017.

25. Ripperton, L.A. et al., 1977: "Research Triangle Institute Studies of High Ozone Concentrations in Non Urban Areas," EPA No. 600/3-77-001a, pp. 413-424.

26. Ludwig, F.L. and E. Shelar, 1977: "Ozone in the Northeastern United States," EPA No. 901/9-76-007.

-744-

Summary

CUMULUS CLOUD VENTING OF MIXED LAYER OZONE

J.K.S. CHING* U. S. Environmental Protection Agency

Research Triangle Park, North Carolina 27711 USA

S.T. SHIPLEY and E. V. BROWELL National Aeronautics and Space Administration

Langley Research Center Hampton, Virginia 23665 USA

and

D.A. BREWER Systems and Applied Sciences Corp.

Hampton, Virginia 23666 USA

Observations are presented which substantiate the hypothesis that signif­icant vertical exchange of ozone and aerosols (and possibly other com­pounds) occurs between the mixed layer and the free troposphere during cumulus cloud convective activity. The experiments conducted in July 1981 utilized the airborne UV-DIAL (Ultra-Violet Differential Absorption Lidar) system developed by NASA. This system provides simultaneous range resolved ozone concentration and aerosol backscatter profiles with high spatial resolution. Data were obtained during the afternoon along 130 km east to west and south to north intersecting transects over North Carolina when non-uniformly distributed cumulus clouds were most active. Evening transects were obtained in the downwind region, where the air mass had been advected. Space-height analyses for the evening flight show the cloud "debris" as patterns of ozone typically in excess of the ambient free tropospheric background. This ozone excess was approxi­mately the value of the concentration difference between the mixed layer and free troposphere determined by DIAL and independent vertical soundings made by another aircraft in the afternoon.

1.1 Introduction

This paper provides evidence that photochemical oxidants (and other pollutants) are transported and deposited above the mixed layer by nonpre­cipitating cumulus convective cloud processes. Conceptually, during periods of strong solar insolation, vigorous rising thermals produce cumulus convective clouds which carry mixed layer air in their updrafts. Some of these clouds can penetrate the inversion at the top of the mixed layer and rise into the free troposphere. These clouds are character­istically short lived, and as they dissipate, mixed layer pollutants are deposited aloft. The net pollutant exchange will depend both on the strength and the areal extent of convective clouds as well as on the

*On assignment from the National Oceanic and Atmospheric Administration, U. S. Department of Commerce.

Ozone Symposium - Greece 1984 -745 -

pollutant concentration differences between the mixed layer and the over­lying free troposphere. The US EPA is currently developing a regional scale photochemical oxidant model (6) which addresses the linkage and exchange that occurs between the mixed layer and the overlying free tropo­sphere by cumulus convective processes. Recent studies (1, 3, 4, and 5) provide supporting evidence that this process of cloud venting occurs, and these studies are useful in developing the parametric framework for models. However, there is as yet insufficient observational data to prove that net vertical transport actually occurs from the mixed layer into the free tropo­sphere by cumulus cloud venting. Since cloud activity is highly variable in time and space, an experimental sampling strategy requires highly de­tailed spatial and temporal resolution of the pollutant fields. Detailed space-height cross sections of ozone (and other pollutants) would provide a suitable analytical base. These measurements are now obtainable from airborne UV-DIAL systems capable of remote and range resolved observations of ozone, aerosols, and other trace gases (2).

The UV-DIAL is a UV differential absorption lidar (DIAL) system consisting of two frequency-doubled Nd:YAG lasers which optically pump two high conversion efficiency tunable dye lasers. The dye lasers are frequency-doubled in to the UV. DIAL measurements of ozone._ are made in the Hartley absorption band with the on-line wavelength nominally set near 286 nm and the off-line wavelength set near 300 nm. The back­scattered return signals at these wavelengths are collected by a telescope, detected by photomultiplier tubes, digitized, and stored on magnetic tape. The logarithmic difference between the two backscattered signals is direc.tly proportional to ozone concentration. The UV-DIAL data acquisition system provides real-time calculations of ozone concentra-tion profiles. A more detailed description of the UV-DIAL system is contained in (2).

NASA has successfully developed, demonstrated and deployed the UV­DIAL system on board an Electra aircraft in a number of field studies (2,8). Data for this cloud study was sampled at the rate of 5 profiles/second with a vertical resolution of 15 m for aerosol and 210 m for ozone. Maximum horizontal resolution at a nominal ground speed of 100 m/sec is 20 meters. Confidence in the measurement of ozone concentration is increased by horizontal averaging. The preliminary analysis presented here uses a 25 shot horizontal average corresponding to a horizontal resolution of 500 m.

1.2 Description of the Experiment

This experiment follows and characterizes the pollutant distribution in an air mass known to have experienced active and penetrative cumulus clouds. Pollutants observed to be imbedded in the layer above the top of the mixed layer can then be assumed to be remnants of the dissipated clouds. Such an experiment was conducted by NASA Langley Research Center using the airborne UV-DIAL on board an Electra. On July 22, 1981, the Electra flew two missions over North Carolina, USA. The first mission pattern consisted of along-wind (east to west) and cross-wind (south to north) transects centered over Raleigh/Durham (35 0 52'N, 780 47'W) between 1500 and 1600 LDT. Each leg was about 130 km long. The evening mission was located over an area near the Carolina coast which was the projected trajec­tory of the air mass sampled during the afternoon. The air mass trajectory was subsequently verified by an isentropic analysis. Concurrently, an instrumented Cessna 402 twin engine aircraft provided correlative vertical profiles of ozone (03), Bscat (6), temperature (T) and dew point (Td)

-746 -

derived from sequential down and up ramp patterns along the same flight co­ordinates. The Electra cruised at 4 km MSL, and provided lidar data from the surface to 3 km MSL. The Cessna profiles varied from near surface to greater than 3 km MSL. Satellite data and routine NWS/NOAA surface and upper air weather observations were archived for subsequent data analyses.

1.3 Results and Discussion

The mixed layer winds over central North Carolina were generally north-northwesterly, becoming more westerly with altitude. Above the mixed layer, the west-northwest flow backed with height to a westerly flow at 3000 m AGL (Above Ground Level). The wind speed shear was 2.5 m/sec/km. Nonprecipitating penetrative cumulus clouds were active over the sampling area from 1400 to 1700 LDT. Cumulus tops varied from 1.5 km to 4 km AGL. The afternoon soundings of T, Td , 03 and 8 obtained by the Cessna aircraft suggest a mixed layer height of 1600 m. The lapse rate in the mixed layer was adiabatic up to the base of the elevated inversion at 1600 m, and the thermal stratification was stable above. Dew point decreased only slightly within the mixed layer but decreased markedly with altitude above 1600 m. Nephelometer readings indicate some variability in Bscat with alti­tude and horizontal position. Highest values appear to be associated with the Raleigh-Durham urban plume. However, the Bscat values also exhibit sharp decreases with altitude above 1600 m. The ozone profiles show mean mixed layer ozone of about 80 ppbv, but significant horizontal variations were observed ranging from 75 to greater than 120 ppbv. The latter value appears t® be associated with the Raleigh-Durham urban plume. Above the mixed layer, a mean but highly variable ozone concentration of about 70 ppbv was observed; ozone concentrations which correspond to mixed layer values of 80 ppbv were observed when the soundings were taken in the vicinity of the active cloud areas. The evening soundings indicate a lower inversion height suggesting subsidence aloft, and are consistent with a downward motion of approximately 1 cm/sec obtained in the isentropic flow calculation and kinematic calculation from the NWS soundings (7).

Figure 1 displays UV-DIAL observations of aerosol and ozone cross sections. In the top panel (Figure 1a), the lidar backscatter cross section is shown for the south to north transect starting at 1538 LDT and crossing over the Raleigh-Durham airport. Active cumulus clouds attenuate the return signals and appear as white vertical columns. The mixed layer is clearly evident where cumulus convection is relatively inactive, as seen in the southern section at 1540 LDT. The haze is concentrated within the mixed layer, while lighter shading at higher altitudes indicates low aero­sol concentrations aloft. On the other hand, the middle and northern seg­ments of the flight contain active cloud convection. The backscatter dis­play suggests a higher mixed layer from 1542 to 1554 LDT in the vicinity of cloud activity. These convective elements literally cloud the issue of defining a mixed layer depth.

The next panel (F~gure Ib) depicts the along-wind cross section of aerosol backscatter on the evening flight mission. With the exception of a few isolated clouds, the field of cumulus convection is replaced by lay­ers and patches of aerosol. These layers tilt upward in the vertical from west to east with an average slope of 16 m/km due to wind speed shear. Stronger winds at higher altitudes advect the upper portion of the cloud remnant a greater downwind distance relative to the lower part. Due to a small but non-negligible shear in wind direction, the flight leg only intersects a portion of the tilted cloud remnant.

-747-

Figure 1c shows the along-wind ozone concentration cross section measured concurrent with the aerosol display of Figure 1b. The ozone data extends vertically from 1300 to 2500 m MSL. Contour intervals are 10 ppb, and much of the fine detail seen in the aerosol gray scale displays has been smoothed by horizontal and vertical averaging. Ozone concentrations in excess of 70 ppbv are observed to be distributed in layers coincident with the aerosol layers of Figure 1b, with identical tilting due to wind shear. These simultaneous ozone and aerosol scattering measurements are highly correlated in space. These positive ozone concentration anomalies are comparable to the average ozone concentrations observed in the after­noon mixed layer.

It should be emphasized that these vented products are not the result of isolated cumulus eve~ts, but represent the integration of many convective intrusions with subsequent injections of aerosol and ozone into the free troposphere throughout the afternoon. From this study it is apparent that intrusive nonprecipitating clouds do deposit mixed layer oxidants and other pollutants above the mixed layer. These injected pollutants exhibit small spatial structure and can now be readily investigated by airborne DIAL systems.

REFERENCES

2.

3.

4.

5.

6.

7.

8.

ALKEWEENY, A. and HALES, J.M. (1981). The impact of nonprecipitating clouds on the transport and formation of acid aerosols. Annual Meeting of the American Chemical Society, New York, New York, USA. BROWELL, E.V., CARTER, A.F., SHIPLEY, S.T., ALLEN, R.J., BUTLER, C.F., SIVITER, J.H.,JR., MAYO, M.N. and HALL, W.M. (1983). NASA multipurpose airborne DIAL system and measurements of ozone and aerosol profiles. Applied Optics, Vol. 22(4), pp. 522-534. CHING, J.K.S. (1982). The role of convective clouds in venting ozone from the mixed layer. Third Joint Conference on Applications of Air Pollution Meteorology, San Antonio, Texas. Preprint, American Meteorological Society, Boston, Massachusetts. CHING, J.K.S., CLARKE, J.F., IRWIN, J.S. and GODOWITCH, J.M. (1983). Relevance of mixed layer scaling for daytime dispersion based on RAPS and other field programs. Atmospheric Environment, Vol. 17(4), pp. 854-871. GREENHUT, G.K., CHING, J.K.S., PEARSON, R., JR. and REPOFF, T. (1984). Transport of ozone by "turbulence and clouds in an urban boundary layer. Journal of GeOPh~Sical Research, Vol. 89 (D3), pp. 4757-4766. LAMB, R.J. (1982. A regional scale (1000 km) model of photochemical air pollution - Part 1: Theoretical formulation. U.S. Environmental Protection Agency Report No. EPA-600/3-83-035, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, 239 pp. RITTER, J.A. (1983). The vertical redistribution of a pollutant tracer due to cumulus convection. Ph.D. Dissertation, University of Michigan, Ann Arbor, Michigan, 156 pp. SHIPLEY,S.T., BROWELL, E.V., MCDOUGAL, D.S., ORNDORFF, B.L. and HAAGENSON, P. (1984). Airborne lidar observations of long-range transport in the free troposphere. Environmental Science and Technology, Vol. 18(9), In Press.

Notes: This is an extended abstract of a presentation and does not necessarily reflect EPA policy. D. A. Brewer acknowledges support for this research from NASA Contract No. NASl-16456.

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o

Figure 1.- Airborne 1idar observations of aerosol backscattering and ozone concentrations in the same air mass on July 22, 1981 over North Carolina. (a) Cross-wind afternoon cross section of aerosol backscatter; (b) a1ong­wind evening cross section of aerosol backscatter; and (c) along-wind evening ozone concentration cross section measured simultaneous with (b).

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SOURCES AND BUDGET OF TROPOSPHERIC OZONE AT A RURAL SITE IN NORTH WEST ENGLAND

I. COLBECK * and R.M. HARRISON Department of Environmental Sciences, University of Lancaster

Lancaster, LAl 4YQ

Summary

Ambient groun~-level concentrations of ozone have been monitored at a rural site in N.W. England since 1977. Background levels of tropospheric ozone range from 20 to 50 ppb and show a seasonal variation. Appreciably elevated levels of ozone (hourly average concentration in excess of 80 ppb) occurred on 4.2% of the days monitored, with a maximum concentration of 156 ppb. Most commonly, these elevated levels of ozone are due to transport of ozone and/or ozone precursors from continental and British sources, the latter contributing up to 50 ppb in urban plumes. Occasion­ally, elevated levels result from an enhanced intrusion of stratospheric air. Measurements of precursor hydrocarbon concentrations indicate that they have the potential to form up to 80 ppb ozone. The dry deposition of ozone has a possible ozone destruction potential of up to 2.6 ppb hr-1•

1. Introduction

It is now well established that under certain meteorological con­ditions, the high emissions of precursor pollutants in urban areas may give rise to formation of photochemical air pollution. Such pollution occurs in many regions of the world with potentially damaging effects on human health, materials and vegetation. Ozone concentrations in Britain have been monitored every summer since 1971 and during particular periods of strong sunshine and high temperatures have been well in excess of the natural background levels (30-40 ppb). This background ozone is the result of transport of ozone rich stratospheric air down to ground level by atmospheric mixing processes. Additional ozone may be of photochemical origin derived from anthropogenic sources, or occasionally may simply result from enhanced intrusions of stratospheric air.

2. Sources of ozone

Ambient concentrations of ozone have been monitored in N.W. England since 1977. Details of the sampling sites, periods of study and apparatus have been described elsewhere (1). Figure 1 shows the variation in ozone from May 1981 to December 1983 (M = May, 0 = October). Curves Band C show the seasonal variation in tropospheric ozone with a spring maximum and winter minimum. The maximum hourly ozone average (curve A) exceeded 80 ppb on 12 of the 32 months with a maximum concentration of 156 ppb. Over the period 1981-1983 the percentage of days when peak hourly ozone concentrations exceeded 60, 80 and 100 ppb were 13.5, 4.8 and 1.5%, re­spectively, while from 1977-1979 the corresponding percentages were 8.6, 3.5 and 1.6%. Possible sources of elevated ozone in remote areas are en­hanced stratospheric intrusions and photochemical formation (advection

* Present address: British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 OET.

Ozone Symposium - Greece 1984 -750 -

from middle and long distance sources as well as formation from local sources). It has been estimated that the ozone on 93% of the days when the peak hourly ozone concentration exceeded 80 ppb was photochemical in origin, while on the remaining 7% the ozone was stratospheric in origin (1).

Figures 2 and 3 show two contrasting ozone records. Figure 2 is an example of a day when the high ozone concentrations were possibly the result of a stratospheric air intrusion, while Figure 3 shows a day when transport of photochemical ozone and/or ozone precursors was important. The synoptic charts for the corresponding days are also very different. On 26 November 1978 a depression was centred to the N.W. of Ireland and a warm front was approaching Britain (Figure 4); temperatures were low, the cloud cover was high and wind speed was moderate. Hence the meteorologi­cal conditions were markedly different from those favouring photochemical production (2). A cross section of the troposphere and lower stratosphere indicates that a stratospheric intrusion in the trailing edge of the jet stream is likely to have occurred. Generally, this ozone-rich strato­spheric air is mixed into the troposphere and only rarely reaches the ground. On 17 September 1982 an anticyclone was centred over Denmark (Figure 5) bringing a southerly airstream to the sampling site. The temperature and insolation were high: typical meteorological conditions for the formation of photochemical ozone. The ozone concentration peaked around 1500 GMT; such peaks in the mid to late afternoon are normally associated with photochemical production of ozone from precursors that are transported to the monitoring site. The air mass trajectory shows the air to be continental in origin, having passed over London, the Midlands and Manchester before arriving at the sampling site. Such an air mass con­tains both long-range transported ozone and ozone formed from the precur­sors injected during the passage of the air mass over middle-distance source areas in England, the latter contributing up to 50 ppb in urban plumes (3).

3. Ozone budget

Atmospheric concentrations of precursor hydrocarbons and NOx were measured during periods of photochemical pollution. These were used, to­gether with ozone dry deposition fluxes, to estimate a crude budget for tropospheric photochemical ozone. To a first approximation, the potential ozone formation from the measured hydrocarbons ranged from 11 to 86 ppb. The destruction potential by the dry deposition of ozone was then calcu­lated assuming a deposition velocity of 0.53 cm/s (4) and a mixing height of 1 km. The destruction potential ranged from 0.74 to 2.58 ppb hr-1 and was in most instances more important than the fast reacting olefins as a sink for ozone.

REFERENCES

1. COLBECK, I. and HARRISON, R.M. (1984) The frequency and causes of elevated concentrations of ozone at ground-level at rural sites in N.W. England, in preparation 2. COLBECK, I. and HARRISON, R.M. (1984) Tropospheric ozone, Environ­mental Chemistry, 3, 1-48 3. HARRISON, R.M~ and HOLMAN, C.D. (1979) The contribution of middle and long range transport of tropospheric photochemical ozone to pollution at a rural site in North-West England, Atmos. Environ., 13, 1535-1545 4. COLBECK, I. and HARRISON, R.M. (1984) Some measurements of the de­position velocity and atmospheric vertical profiles of ozone up to 100 m, in preparation

-751-

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- 752-

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FIG. 5. SYNOPTIC SITUATION AT 1200 GMT ON 17TH SEPTEMBER 1982

-753 -

SEASONAL BEHAVIOR OF THE TROPOSPHERIC OZONE IN JAPAN

Summary

T. OGAWA and A. MIYATA Geophysics Research Laboratory

University of Tokyo Bunkyo-ku, Tokyo 113, Japan

Ozone concentration of the surface air is analyzed by using the data from rural stations of the environmental monitori.ng network in Japan. At four chosen stations, NOx concentration is usually less than a few ppb or below the detection limit. The relative amplitude of the diurnal variation of ozone is 10 - 40 percent of the diurnal average, and does not vary with season significantly. The diurnal average values, as well as the diurnal maximum and minimum values, exhibit a seasonal trend with a maximum in spring, as revealed so far in middle latitudes. A minimum in summer is also found to be a common feature in rural Japan. The ozonesonde data from Tateno and Kagoshima show a similar trend in the altitudes below 600 mb level, whereas those from Sapporo show the spring maximum only. Consequently, the summer minimum is thought to be a usual phenomenon of the tropospheric ozone in the 30 - 400N latitudes over Japan. It may be interpreted in terms of the decrease in ozone transport from the stratosphere to the troposphere, since the air exchange between the stratosphere and the troposphere associated with baroclinic disturbances becomes weak in summer over Japan.

1. Introduction

Two principal sources of tropospheric ozone have been proposed. One is transport from the stratosphere, and the other is photochemical production. The ozone transport from the stratosphere to the troposphere occurs in air exchange processes associated with baroclinic disturbances in mid-latitudes, characterized by polar jet and extratropical cyclones (1). On the other hand, the strength of photochemical production of ozone in the troposphere depends upon the tropospheric densities of nitrogen oxides (NOx), hydrogen oxides and hydrocarbons (2). According to recent observations, tropospher­ic NOx is rare and its density is highly variable (3). Consequently, the strengths of these two sources vary with weather conditions of synoptic scale, and with geophysical and geochemical conditions of the troposphere and its neighboring domains such as oceans, land surfaces and biosphere.

Some characteristics of tropospheric ozone, with respect to diurnal, seasonal and latitudinal variations and temporal variations associated with weather variations of synoptic scale, have been revealed mainly by observations in America and Europe (4). In this study, we are concerned

Ozone Symposium - Greece 1984 -754-

with their similarities and differences between the Far East and American­European sectors.

2. Data of Tropospheric Ozone in Japan

The long-term data of tropospheric ozone in Japan are available from environmental monitoring stations as well as intermittent observations by ozonesondes at the aerological observatories of Sapporo, Tateno and Kagoshima. Almost all the monitoring stations are located in city areas to measure air pollution, but several stations are located in rural sites away from big sources of air pollution. They continuously measure ozone, nitrogen oxides and other pollutant gases by using a standardized method, and provide an hourly averaged value every hour. The ozone measurement is made in terms of chemical detection by potassium iodide solution; therefore,it may suffer contaminations of other pollutant gases. However, we find that some stations usually exhibit NOx concentrations of a few ppb or under the detection limit. They are Rokkasho, Wakuya, Oseto and Kushima, which are located in rural sites.

3. Seasonal Variation of the Ozone Concentration on the Ground Level

Figure 1 illustrates the seasonal variation of the ozone concentration in rural Japan. The characteristic feature appearing on the data from Rokkasho, Wakuya, Oseto and Kushima is a maximum in spring ( March, April and May) and a minimum in summer ( June, July and August). The data from Kushiro a~d Ishikawa is referred to only for checking the latitudinal extent of this seasonal characteristics; the monitoring site of Kushiro is located in the central region of the city with a population of about 200 thousands, and the data quality of Ishikawa, which is located in a small city, is not good. The spring maximum is a common feature in the seasonal variation of tropospheric ozone in middle latitudes, and may be interpreted in terms of enhanced downward transport of ozone from the stratosphere, since the vertical mixing associated with baroclinic disturbances in middle latitudes is most active in spring over Japan. On the other hand, the summer minimum of tropospheric ozone is not evident in the mid-latitude data reported so far. The summer minimum suggests that the photochemical production of ozone in the troposphere is not a major factor.

As seen in Figure 2, the global insolation exhibits an inverse correlation with ozone concentration. Note that its small minimum in June is due to the rainy period "bai-u" which usually begins on around June 10 and lasts for about one month. Since photochemical production of tropospheric ozone is initiated by N02 photolysis in the ultraviolet, the ultraviolet insolation is better to be referred to than the global insolation, but unfortunately it has not been measured at any adjacent stations.

An inverse correlation similar to Figure 2 is also observed at other rural stations. This results may imply that the ozone data from Rokkasho, Wakuya, Oseto and Kushima is not seriously influenced by photochemical air pollution. In the urban atmosphere in Japan, a positive correlation between solar radiation and ozone is common, and the ozone concentration is much higher in daylight hours than at night.

Ihe diurnal behavior of ozone may provide us some information about the effect of solar radiation. Figure 3 represents the diurnal variations in different seasons at Wakuya and Oseto. The relative amplitude of the daytime increase from the nighttime level is much smaller than those observed in the urban atmosphere in Japan, and it shows only a slight

-755 -

enhancement in summer. Wakuya and Rokkasho show a smaller amplitude in the diurnal change than Oseto and Kushima; therefore, the formers are affected by air pollution less than the latters.

The diurnal variation of ozone in the surface air may be interpreted as follows: (a) in case of a high NO concentration, photochemical production in daytime, and loss reaction with NO at night, and (b) destruction on and around the ground surface, and daytime activation of vertical mixing in the boundary layer ( together with the stabilized layer at night y. The solar radiation may affect the diurnal variation in these two ways. Moreover, it may induce wind systems such as land-sea breeze and mountain-valley breeze. These wind systems may also affect the ozone concentration. As a result, it is difficult to draw a conclusion on the causality from limited information related to the ozone variation.

4. Tropospheric Ozone Observed by Ozonesondes

It is interesting to examine whether the seasonal trend shown in Figure 1 is common to the troposphere or is specific to the boundary layer. We use the ozonesonde data from the aerological observatories at Sapporo, Tateno and Kagoshima, where extensive observations were made during 1969 -1971. Figure 4 represents the mixing ratios at 700 mb level. The spring maximum is seen at all three observatories, but the summer minimum is seen only at Kagoshima and Tateno ( despite limited data for July and August at Tateno) •

Figure 5 shows the seasonal variations at various pressure levels constructed from the data obtained in 1969 - 1981. The data for 1000 mb level at Kagoshima are not available, because the launch site of sondes is 282.6 m high from the sea level. The spring maximum and the summer minimum are seen below 600 mb level ( i.e., 4 - 5 km altitude) at Kagoshima and Tateno. At Sapporo, however, only the spring maximum is evident below 600 mb level, as commonly observed in the mid-latitude troposphere.

In the upper troposphere, the ozone mixing ratio exhibits a large day­to-day variation due to intermittent downflows of the stratospheric air. The latitude of the most active downflow is related to the pathway of polar jet and mid-latitude lows, and changes with season. The maximum phase of the seasonal variation of ozone in the upper troposphere may be a consequence of the above process. Since Kagoshima is almost always located south of the active downflQw from the stratosphere, the subsequent diffusion in the troposphere seems to be effective over there.

REFERENCES

1. DANIELSEN, E.F. (1968). J. atm. Sci. 25, 502-518; PIAGET, A. (1969). Ann. Geophys. 25, 183-194; DANIELSEN, E.F. (1980). J. geophys. Res. 85, 401-412.

2. CRUTZEN, P.J. (1973). Pure appl. Geophys. 106/108, 1385-1399; CHAMEIDES, W. and WALKER, J.C.G. (1973). J. geophys. Res. 78, 8751-8760; FISHMAN, J., SOLOMON, S. and CRUTZEN, P.J. (1979). Tellus 31, 432-446.

3. COX, R.A. (1977). Tellus 29, 356-362; McFARLAND, M. et al. (1979). Geophys. Res. Lett. 6, 605-608; HELAS, G. and WARNECK, P. (1981). J. geophys. Res. 86, 7283-7290.

4. JUNGE, C.E. (1962). Tellus 14, 363-377; FABIAN, P. and PRUCHNIEWICZ, P.G. (1977). J. geophys. Res. 82, 2063-2073; CHATFIELD, R. and HARRISON, H. (1977). J. geophys. Res. 82, 5969-5976; SINGH, H.B. et a1. (1978). Atm. Env. 12, 2185-2196; OLTMANS, S.J. (1981). J. geophys. Res. 86,1174-1180; FEHSENFELD, F.C. et al. (1981). J. atm. Chern. 1,87-105.

-756 -

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-757 -

Figure 3 Diurnal variations of the ozone concentration in different seasons at Wakuya and Oseto,

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-758 -

PHOTOCHEMICAL OXIDANTS AT NIWOT RIDGE, COLORADO

M. Trainerl ,3, D.O. Parrish2, D.W. Fahey, J.M. Roberts l ,3, S.C. Liu, D.L. Albritton, and F.C. Fehsenfeld3

Aeronomy Laboratory, NOAA Environmental Research Laboratories 325 Broadway, R/E/AL4

Boulder, Colorado 80303 U.S.A.

Summary

Data collected over a one year period at Niwot Ridge, a rural site located in the Colorado mountains, are presented. The con­centrations of NO, N02 and 03 have been measured as well as solar UV intensity and supporting meteorological parameters. The ratio of the concentration of NO to the concentration of N02 reflects the photolysis of N02 balanced by the conversion of NO to N02 by 03 and other oxidants. The level of the oxidants, OX, in addi­tion to ozone required to explain this balance is found to be directly proportional to solar UV intensity and to depend on NOx (NO + N02) concentration and on season. The maximum OX levels occur for NOx concentrations of about 400 pptv and decrease at higher and lower concentrations. For NOx concentrations below 100 pptv no substantial OX concentration is observed. In the winter the level of OX is about a factor of 4 smaller than the summer levels at each NOx concentration and solar UV intensity. The effect of the oxidants on ozone production at the site allows inferences concerning the identity of OX to be drawn.

1.1 Introduction

Nitric oxide (NO), nitrogen dioxide (N02) and ozone (03) are three of the major participants in atmospheric photochemistry. In the troposphere the concentrations of these compounds are interrelated through one of the primary atmospheric photochemical cycles, reactions (1) - (3)

j N02 N02 + hv -+- NO + 0 A ~ 420 nm

o + 02 + M -+- 03 + M

Also:

1 NRC/NOAA Postdoctoral Research Associate

(1)

(2)

2 Department of Chemistry, Metropolitan State College, Denver, CO 80204, U.S.A.

3 Cooperative Institute for Research in Environmental Sciences, University of Colorado, NOAA, Boulder, CO 80309 U.S.A.

Ozone Symposium - Greece 1984 -759 -

At a typical tropospheric ozone mixing ratio of 40 ppbv the half-life, T, of NO oxidation in reaction (3) is about one minute. Thus under most atmospheric conditions the concentrations of the three species are in a photostationary state. If the NO production by reaction (1) is balanced solely by the loss through reaction (3) the so called pho­tostationary state equation (4) applies

j N02· [ N02] --=---=---=---:- = 1 k3• [NO] • [O~

(4)

Several studies (Le., 11 I -I 4) ) show that, at a variety of non­urban tropospheric sites, the Ie t side of equation (4) is typically larger than unity. Further, measurements like those presented by Fehsenfeld et. a1. I 5 I show that a net production of ozone attribu­table to the NOx - 03 photochemical cycle occurs in non urban areas. Both of these observed effects can be attributed to the presence of one or more additional species, represented symbolically as OX, that can compete with ozone in the oxidation of NO:

k5 OX + NO + X + N02 (5)

In order to more fully understand these processes we have measured the concentrations of NO, N02 and ozone, as well as solar UV flux, at a field site located in the Colorado mountains. These measurements comprise a full year of nearly continuous operation. This paper pre­sents these results as they pertain to the photostationary state described above.

The deviation from the 03 - NO x photostationary state (Eq. (4)) is expressed here in terms of the concentration of OX necessary to account for the observed inbalance. Steady state considerations including reaction (5) give

[Ox] = j N02· [N02] k3· [NO]

- [O~ (6)

Equation (6) gives the concentration of the oxidant in terms of equivalent 03 cOQce~trations. We shall exa~ine]the diurnal and sea­sonal trends in LoxJ and its dependence on LNOx , whiCh represents a good indication of the degree of anthropogenic pollution in the air masses that we sample.

A discussion of the effect of the oxidant on the tropospheric ozone production allows further inferences to be drawn concerning the possible identity of this photochemical oxidant.

1.2 Experimental

The measurements were made at the C-l research site of the Mountain Research Station of the University of Colorado (400 2'N,

-760 -

1050 32'W, 3.05 km elevation) in a forest clearing approximately 150 m below timberline. The site combines several desirable features: (1) depending on the meteorological conditions the site receives air masses with chemical composition that range from very clean continen­tal air to slightly aged urban pollution. (2) Many concurrent measurements of atmospheric parameters that have been carried out at the site place the present measurements in the context of a wider study of tropospheric chemistry. (3) A comprehensive study of jN02 has been carried out at this site, so that much of the uncertainty in the determination of this quantity has been removed.

To obtain a value for the concentration of additional oxidant [Ox] from equation (5), values for all parameters on the right side of the equation must be determined. The concentrations of NO, N02 and 03 were measured directly by well-charaterized instruments. The photo­dissociation rate of N02, jN02' was inferred from measurements of the solar UV flux I 6 I. The reaction rate constant k3 was calculated for the measured ambient temperature.

Ozone was measured by a commercial UV - absorption instrument (OASISI, Inc.). The detection limit was approximately 3 ppbv and the estimated uncertainty in anyone measurement is no more than 10%.

The level of NO in ambient air was measured using chemilumi­nescence. The N02 levels were measured by photodissociating N02 with UV light and detecting the NO thus generated by chemiluminescence. The measurements described herein were obtained from two instruments operated simultaneously. The instruments were calibrated every two to three hours against NO and N02 standards. The detection limits were approximately 2 pptv for NO and 10 pptv for N02' At levels well above the detection limit, the precisions of the measurements are estimated to be 15% for NO and 30% for N02'

Air for all the concentration determinations is sampled through inlets approximately 4 m above the ground atop a van housing the measuring instruments. '

A propagation of error treatment allows afl,uncertat'nt¥ to be assigned to any individual determination of [OXJ. For oXJ ~ 0, the ~nc~rtainty is ±15 ppbv for clear sky conditions. For a typical high LOxJ level (~ 100 ppbv), the uncertainty is ±50% for clear sky conditions.

1.3 Results

As in previous studies ( I 1 I - I 4 I ) many of the present measure­ments show the presence of substantial concentrations of one and more oxidants that in addition to ozone convert NO to N02' During the summer months the measurements indicate the presence of an oxidant at most times during the daylight hours except near sunrise and sunset. The diurnal behavio~ of the oxidant concentration suggests a photoche­mical origin since LOxJ at least qualitatively follows the sunlight intensity.

The concentration of the photochemical oxidant is strongtYJorre­lated with the concentration of the Rxides of nitrogen. The ;~.liS very low in very clean ~ir jhen LNOxJ is below 100 pptv. T~e XJ reaches a maximum near LNOx of 400 pptv and th~ drops as LNOx increases. [M~surements near this maximum ([NO bjtween 250 ano 1000 pptv where OxJ is not a sensitive function of NOx ) show that LoxJ is directly proportional to jN02' Thus the oxidant appears to have a

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photochemical origin and displays a strong linear dependence on UV intensity under cloud free conditions. The average value of the oxi­dant concentration at noon time under clear skies is 80 ppbv in equivalent ozone. (All of the results discussed here are for clear sky conditions, i.e. ultraviolet radiation flux within 10% of that measured under cloud free skies at the same solar zenith angle. Direct correlation with jN02 persists under all sky conditions. The diurnal variations of the oxidant is symmetric about noon, for given NO x values, which indicates that the oxidant lifetime must be short compared to an hour. A strong seasonal variation of the OX levels is observed. For the same intervals of NOx and jN02, the OX values measured in winter are a factor of four lower than those measured in summer.

The effect of the oxidant on photochemical ozone formation will depend on the nature of the oxidant. The characteristics of diurnal ozone variations at the site have been described previously I 5 I· In the winter there is no apparent systematic diurnal variation in the 03 mixing ratio because there is little diurnal change of transport and the photochemistry is slow. In the summ~rJzone is observed to incr~ase] during the day. The increase in Lo correlates with increasing LNO x as well as with the levels of other compounds of anthropogenic origin. This correlation has been interpreted as in­situ or in-transit photochemical production of ozone from these pre­cursors that are transported to the sampling site. The levels of ozone recorded approach 100 ppbv under clear skies at NOx mixing ratios of apPFoximately 3 ppbv.

1.4 Discussion

The identity of the additional oxidant, OX, has not been established. It has been suggested that OX is the hydroxyperoxy radi­cal, H02 and/or organic peroxy radicals, R02 I 1 I ' I 2 I ' I 4 I. The photochemical origin that is indicated by previous studies I 21 ' I 4 I and the present measurements suggests OX is photochemically generated as are H02 and R02' In addition, ascribing the extent of the measured deviation from the 03 - NOx photostationary state to peroxy radicals would also imply a large rate of ozone production, at the site.

Alternatively, the NO oxidation in addition to that by ozone may be due to an oxidant that does not lead to ozone formation. The effect of the reaction sequence (5), (7)

OX + NO + X + N02

X + 03 + OX + 02

(5)

(7)

followed by reactions (1) and (2) leads to an enhancement of the N02 to NO ratio without directly affecting the ozone concentration. In the following we will label an oxidant that does not produce ozone in the NO to N02 conversion a XO - type oxidant compared to the R02 -type that does lead to photochemical ozone production. An example of a XO - type oxidant is iodine monoxide, 10. It has been suggested by Chameides and Davis I 7 1 that 10 may playa role in the maritime tro­posphere.

-762 -

In the following we will compare the observed late afternoon ozone levels with those predicted from models including the two types of oxidant.

A simple photochemical model which considers the CH4, CO, H20, 03 and NOx chemistry (referred to here as the reference model) can quali­tatively simulate the NOx dependence of the ozone increase during the daytime. At low NOx values, NOx ~ 600 ppty, the model predicts only a moderate ozone production. This is in accordance with the obser­vations which show that the ozone remains in the range of 35 to 55 ppbv throughout the mid-day hours at these NOx levels. At NOx levels above 600 pptv the ozone concentrations show daytime increases. The measurements indicate that maximum ozone concentrations of up to 100 ppbv are observed for NOx mixing ratios of 2 - 3 ppbv. The reference model predicts ozone mixing ratios of around 80 ppbv for NOx = 2 ppb corresponding to a daytime ozone increase of about 40 ppbv. Thus, the peak ozone concentration is somewhat underestimated in this model. Oxidants which lead to ozone formation and are included in this model are H02 and CH302. The sum of toeir concentrations expressed in ~qui¥alent ozone in 20 ppbv for LNOxJ less than 1000 pptv and drops as LNOxJ increases to 10 ppbv. Th~se ¥alues are much smaller than the observed OX concentrations for LNOxJ > 100 pptv. Inclusion of hydro­carbons of anthropogenic and natural origin (i.e. alkanes C2 - C4, C2H4, C3H6, a-pinene and isoprene) increases the predicted ozone pro­duction and brings it into better agreement with the measured ozone levels. However, the oxidant level can not be matched either in magnitude or by the shape of the dependence on NOx•

To reproduce the observed N02 - to - NO ratios additional oxidant of the type XO or R02 was superimposed on the reference model. For this comparison average values for the concentrations of the oxidants observed at our site were used. If the oxidant is a R02-type mole­cule, a large increase in ozone productions compared to the reference model is observed at all NOx levels greater than 200 pptv. At NOx = 400 pptv where the oxidant has its maximum (~ 80 ppbv equivalent ozone) daytime ozone production of about 48 ppb would be expected.

Ozone loss processes neglected in the model (eq. dilution and surface deposition) could not prevent the observation of such a large ozone increase. If on the other hand the oxidant is of the XO-type a small reduction in the predicted ozone production results at all NOx level compared to the reference model. This occurs because, as the N02 - to - NO ratio is increased by the additional oxidant, the HOx (OH + H02) losses become more important. Cons~quently a shift of the N02 to NO ratio through a XO-type oxidant leads to a small decrease in HOx radical concentrations which is accompanied by a small decrease in ozone production. Hence it does not seem possible to identify the oxidant as either R02 type or XO type, rather it is more plausible to consider the oxidant to be a combination of the two.

REFERENCES

1. MCFARLAND, M., D. KLEY, and J. DRUMMOND (1978). Simultaneous NO, N02 and 03 vertical profile measurements from ground level to 6 km. Paper presented at the 4th Biennial Rocky Mountain Regional Meeting of the American Chemical Society, Boulder, CO.

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2. RITTER, J.A., D.H. STEDMAN and T.J. KELLY (1979). Ground level measurements of nitric oxide, nitrogen dioxide and ozone in rural air. Nitrogeneous air pollutants: Chem~cal and biological implications, Ed. D. Grosjean, Ann Arbor Science Publishers, Ann Arbor, MI.

3. BUSH, Y.A., D.O. PARRISH, and F.C. FEHSENFELD (1979). Measurements of trace gases in the troposphere, paper presented at the Fourth International Conference of the 'Commission on Atmospheric Chemistry and Global Pollution, Boulder, CO.

4. KELLY, T.J., D.H. STEDMAN, J.A. RITTER, and R.B. HARVEY (1980). Measurements of oxides of nitrogen and nitric acid in clean air. J. Geophy. Res., 85, 7417-7425.

5. FEHSENFELD, F.C., M.J. BOLLINGER, S.C. LIU, D.O. PARRISH, M. MCFARLAND, M. TRAINER, D. KLEY, P.C. MURPHY, D.L. ALBRITTON, and D.H. LENSHAW, (1983). A study of ozone in the Colorado moun­tains. J. Atmos. Chem., 1, 87-105.

6. PARRISH, D.O., P.C. MURPHY, D.L. ALBRITTON, and F.C. FEHSENFELD (1983). The measurement of the photodissociation rate of N02 in the atmosphere, Atmos. Environ., 17, 1365-1379.

7. CHAMEIDES, W.L. and D.O. DAVIS (1980). Iodine: Its possible role in tropospheric photochemistry, J. Geophys. Res., 85, 7383-7398.

-764-

DIURNAL VARIATION OF OZONE IN FINE WEATHER SITUATIONS OVER HILLY TERRAIN

H.A. GYGAX and B. BRODER

Atmospheric Physics ETH, Honggerberg, 8093 Zlirich, Switzerland

Summary

The diurnal cycle of ozone in fine weather situations within the planetary boundary layer above a flat bottomed valley is discussed. Ozone losses in the air below the hill crest level are attributed mainly to dry deposition and to a lesser extent to homogeneous chemistry. The influence of a local thermal wind system on the diurnal cycle of ozone at different sites (i.e. valley bottom, slopes) is clearly demonstrated. For the layers above crest height it is concluded that processes at the ground are contributing strongly to the ozone losses and the increase in humidity observed during nighttime. The coupling of the surface layer effects with those in the upper part of the boundary layer is brought about by transport processes, resulting from the interaction between the wind field and the topography.

1. Introduction

In the last decade a large number of investigations were published on the chemical and dynamical processes and their coupling in the planetary boundary layer (PBL) over homogeneous terrain, whereas for nonhomogeneous topography only few results are known as yet. For an improved understanding of this coupling over hilly terrain a field study on the Swiss plateau \~as conducted 1982. First results of this program are presented.

2. Measurements

The measurements were conducted in the Reuss valley, a flat bottomed valley near Zurich (1). Five ground stations were operated in a section across the valley going through Merenschwand (Fig. 1).

~1000~ .,; ~ 8000 G

i 600 H~ ~ 400

£ 0 5 10 15 20 ~ Horizontal Distance (km)

Ozone Symposium - Greece 1984 -765 -

Fig. 1 : Vertical cross section through the Reuss valley at Merenschwand. Positions of the ground stations are indicated by G: Grod (410 m above valley ground level (AGL», H: Herd­matten (120 m AGL), M: Meren­schwand (O'm AGL), S: Schliren (150 m AGL), A: Aeugst (350 m

AGL) •

They were equipped for continuous measurements of ozone, temperature and wind. At Merenschwand (M) and SchUren (S) (Fig. 1) vertical profiles of ozone, temperature, wind and humidity were determined up to 800 m AGL using tethered balloons. In addition, a grab sampling instrument was used at Meren­schwand for measuring the NOx-content at certain distinct levels within the PBL.

3. Results

3.1 Structure of the lower part of the PBL A statistical analysis of the rate of ozone loss at night for the lower

part of the PBL was undertaken. The results indicate that homogeneous chemis­try accounts on the average for about 20 % of the observed ozone destruction (2). The remaining ozone destruction (4.1011 mol. cm-2s- l ) is attributable to the dry deposition of ozone at the surface. From a comparison with rela­ted studies conducted over flat topography it is concluded that during the nighttime regime this process is much more effective in hilly terrain, the increase in efficiency being linked to the influence of a local cross valley wind system.

This system is most clearly shown by the measurements of winddirection at the ground stations (Fig.2). The ozone destruction occurs mainly in re­gions of nighttime downslope winds, where high destruction rates are expec­ted because the ozone concentration remains rather high (Fig. 3). This re­sults in air with low ozone content reaching the valley ground and hence

BS ~ 03-04 . 6 . I ge2 as G 03-04.6.1982

Fig. 2 : Ground station data from Aeugst (eastern slope) and Grod (western slope) for 3-4 June 1982. Parameters: Ozone and winddirection (+).

the associated upward airflow gives rise to continuous ozone depletion with­in the lower part of the PBL (Fig. 3). After the reversal of the local wind system in the morning a sharp decrease in ozone content can be observed at SchUr en (Fig. 3), since ozone weak air is brought up from the bottom of the valley by the anabatic winds. It is interesting to note that during the same time interval an increase of the ozone content is observed at Meren­schwand, which must be attributed to the downward airflow associated with the reversed local wind system.

3.2 Structure of PBL height interval 400-800 m Under certain circumstances stagnant or so-called blocked air masses

may exist in the part of the PBL below the crest level (3). Applying the criteria given in (3) for the occurrence of blocking phenomena to our data, it can be concluded that the conditions were met during all nights. In con-

-766 -

rB oM IU-0-4 .6 . 6:i1 BZO« IIltfiVI

.. , ".

" " " 12 1~

'" D.

". '"

1:1 1~

12' 15

Fig. 3 : Tethered balloon data for 3-4 June 1982. Parameters: Ozone and water vapour mixing ratio (W) at Merenschwand, ozone at Schliren. Heights are in meters above valley ground level. Symbols:

(!) 100M + 300H ~ 600H

Cl OM 6. 200M X 400H '600H

+ 300M ~ 600H

lIE 150ll 6. 200M X 400M '600H

trast no blocking processes are to be expected in the upper part of the PEL. Consequently, the influence of strictly local effects is less strongly felt in these upper layers.

Since horizontal transport processes are mostly important in the upper part of the PBL, it is striking that the meteorological parameters and trace gas concentrations show very distinct tendencies: In the interval between 6 p.m. LST and 6 a.m. LST next morning, the mean ozone mixing ratio decreases on the average of 14 days by a value of 28 % or 20 ppb (extreme values 44 ppb and 12 ppb), the mean water vapour mixing ratio increases on the average by 12 % or 1 g/kg (extreme values 2.8 g/kg and 0.1 g/kg) (cL Fig. 3).

The results of a statistical analysis of the wind field and the change in ozone and water vapour content within the upper part of the PEL indicate that in addition to horizontal advective transport, which is mainly respon­sible for short time variations, further processes must occur which give rise to the distinct nighttime trends.

3.2.1 Effects of local processes The observations show, that during our measuring periodsNOx m~x~ng

ratios in the order of 5 ppb occured in the layers above the crest height and no significant nighttime change in the NOx-content was observed (2). At t:'hese levels NOx exists mainly in the form of N02 due to the reaction between NO and 03' During night a complete loss of N02 were to be expected, since

-767 -

the reaction between N02 and 03 is fairly fast;

(R 1)

This conclusion follows from the fact that no efficient reaction exists to rebuild NO and N02 from the products of (R 1) and following reactions (4). Therefore in our case with a mean NOx mixing ratio of about 5 ppb, an ozone reduction of about the same amount is to be expected under the influence of nighttime homogeneous chemistry. In turn the N02-content should drop to 0. Both is not observed.

An explanation of this fact by a much lower efficiency of reaction (R 1) as expected seems rather unlikely, since the rate constant is very well known (4). Further the assumption, that as yet unknown reactions exist, which re­build NO and N02 from N03 and N205' must be rejected (2). The most likely ex­planation seems to be an overestimation of the NOx-mixing ratio due to inter­ference of N03 and N205 with our NOx measuring devices. Therefore the maximum possible mean contribution of homogeneous chemistry to the nighttime ozone decrease in the upper part of the PBL can be estimated by approx. 5 ppb,i.e. 25% of the observed ozone loss. It follows that other processes than strictly horizontal adv~on and homogeneous chemistry must be taken into considera­tion for explaining the daily ozone variation in the upper part of the PBL.

The same conclusion applies to the humidity, since water vapour can in no case be produced by local processes at this height interval. As only the earth surface can simultaneously act as a source of water vapour and as a sink fOr ozone, we shall assume the existence of a transport mechanism, which gives rise to a coupling of processes near ground with those in the upper part of the PBL.

3.2.2 Transport processes over nonhomogeneous terrain The daytime PBL in flat as well as hilly terrain is governed by turbu­

lent transport; therefore the vertical gradients of the mixing ratio of ozone and water vapour nearly vanish (cf.Fig. 3). The layers above and be­low the ridge line are strongly coupled (cf. Fig. 4). After sunset drastic changes occur: The ozone production vanishes and the ozone content near ground diminishes due to the combined effects of dry deposition, homogeneous chemistry and local induced transport. The ground is further acting as a source of water vapour, since the transpiration by the plants does not cease fully during nighttime.

If now blocked air masses form, then air having been in close contact with the ground somewhere in the neighbouring regions is transported across our valley at levels above the crest height (Fig. 4, streamlines A). Thus the effect of processes near ground can also be observed at the upper levels.

However, further processes must exist, since the efficiency of the above mentioned coupling decreases with proceeding nighttime cooling, as air masses near ground are increasingly blocked on the windward of the hills.

One of these processes occurs due to the influence of local wind systems in neighbouring valleys. It can be concluded, that considering exclusively the Reuss valley, only a small part of the layer above the crests can be in­fluenced by the air ascending due to the upward flow induced by the local wind system. But if this process occurs also in the neighbouring valleys, the effects cumulate, when the air is transported across the different valleys (Fig. 4, process B).

-768-

Fig. 4 : Schematic repre­sentation of topography­induced transport processes in a regional scale of the Swiss plateau (for ex­planation of processes A, Band C see text).

A further process which gives rise to the observed coupling, was first discussed using results of a numerical model (5): On the windward side of a two-dimensional hill, zones with very efficient turbulent exchange exist due to the interaction between the mean wind field and the downslope winds. This interaction leads to the occurrence of recirculation phenomena, which can be expected to occur in similar manner in our measuring area (Fig. 4, pro­cess C) •

These three processes together can maintain a certain coupling between the lower and the upper part of the PBL during the whole night and in con­sequence relatively ozone weak and water vapour rich air at levels above the crests can be observed.

4. Conclusion

Whereas below the crest height level the diurnal cycle of ozone is strongly influenced by a thermal wind system, in the upper part of the PBL the observations cannot entirely be explained by local effects. Additionally the influence of processes due to the complex topography on a regional scale is felt. This fact leads to large deviations in the daily variation of ozone compared to the results from experiments in flat topography.

Many details of the nonlinear interaction between large scale wind field and terrain induced phenomena are still unknown; further experimental research is needed for a complete understanding of the specific processes occurring in the PBL over nonhomogeneous terrain.

References

1. Broder,B., Dlitsch, H.U. and Graber, W. (1981): Ozone fluxes in the noc­turnal planetary boundary layer over hilly terrain. Atm. Env., 15, 1195-1199

2. Broder, B. (1984): Kopplung zwischen Transportvorgangen und chemischen Prozessen liber komplexer Topographie. Pub1. Atmospheric Physics ETH, LAPETH-21, Zlirich

3. Manins, P.C. and Sawford, B.L. (1982): Mesocale obervations of upstream blocking. Quart. J. R. Met. Soc., 108, 427-434

4. Platt, U., Perner, D., Schroder, S., Kessler, C. and Toennissen, A.(1981): The diurnal variation of N03 • J. Geophys. Res., 86, 11965-11970

5. Yamada, T. (1983): Simulations of nocturnal drainage flows by a q?l tur­bulence closure model. J. Atmos. Sci., 40, 90-106

-769 -

OPPOSITE BEHAVIOUR OF THE OZONE AMOUNT IN THE TROPOSPHERE

~ND LOWER STRATOSPHERE DURING THE LAST YEARS. BASED ON THE

OZONE MEASUREMENTS AT THE HOHENPEISSENBERG OBSERVATORY

FROM 1967 - 1983

R. HARTMANNSGRUBER, W. ATTMANNSPACHER and H. CLAUDE,

DWD Meteorologisches Observatorium Hohenpeissenberg

D-8126 Hohenpeissenberg, FRG

Summary

Some results of continuous atmospheric ozone observations over 16 years, based on regular ozone soundings and Dobson measurements at the Hohenpeissenberg Observatory are re­presented. In the troposphere a steady ozone increase es­pecially since 1980 was found, which also can be seen from the continuous ozone measurements near the ground. In the opposite stratospheric ozone values show a small decrease above 26 km since 1977. 1983 a surprising but well marked ozone decrease °in the lower stratosphere between 14-23 km was measured. Possible reasons for this event are given.

1. Introduction

At the Hohenpeissenberg Obsoervatory (MOHp) since 1967 regular balloon soundings of the vertical ozone distribution were made every Wednesday. For monitoring the model-predicted ozone layer depletion due to fluorocarbon releases since 19~7 the soundings were intensified for 2times a week in summer and 3times in winter. All the time carefully prepared Brewer­Mast ozonesondes were used, which have proven its reliability in two intercomparisons at Hohenpeissenberg (1,2) and with high sophisticated ozone instruments on big balloons. During the period named above total ozone measurements were made with a Dobson spectrophotometer. The experience and intercomparison with a new Brewer spectrophotometer will be discussed in a separate paper.

The difference between the integrated ozone amount from a sounding and the corresponding Dobson value - the so called correction factor - also can be used as an assessment of the a~curacy of each sounding. This mean annual factor and its standard deviation was during the first years 1,15 ± 0,134; since 1976 it is about 1,08 s 0,07. A recommendation of an ozone expert meeting arranged by WMO 1980 at Toronto calls all soundings with factors between 1,00 and 1,35 :t 0,20 as useful.

Ozone Symposium - Greece 1984 -770-

2. Results

2.1 Tropospheric ozone

The origin of tropospheric ozone seems to be a controver­sial subject. Under dynamic controlled conditions ozone is transported from the stratosphere and destroyed at the surface. Corresponding observations could be made at the MOHp (3) es­pecially during the winter season with strong vertical exchan­ges in the vicinity of jet streams. Some authors argue, that gasphase photochemical production and destruction of ozone in the troposphere are more important than injection of ozone from the stratosphere.

Some years ago higher concentration of anthropogenic produced ozone mainly could be observed within and in the vicinity of large cities or industrial areas. But in recent years in non urban and rural regions increasing ozone values are recorded. Continuous measurements at MOHp of ozone near the ground with 3 ozone sensors of different physical methods confirm this tendency.

H (Iml 12

lG 0- <1963 --1962 ··· ······ · 1981 ------ 191. '- '- '- '-1961

,0 2il 30 z.O 03 (nbarl

so

Fig. 1: Tropospheric ozone profiles, MOHp 1967-1983

As it can be seen in figure 1 ozone increases in the entire troposphere. The significant ozone peak at 2 km marks the upper limit of the planetary boundary layer. The increase from 1967-1974, from 1974-1981 and from 1981-1982 is of the same magnitude. 1983 shows slight lower values than 1982.

A few investigators call photo­oxidants as one of the possible reasons for intensifying forest decline during the last years. Ozone is one of these oxidants and a good indicator for photo­chemical reactions.

The strong ozone increase from 1981 to 1982 cannot be declared only by a corresponding increase of solar radiation due to normal good weather conditions in 1982. 1983 the amount of solar radiation was higher than 1982, but the tropospheric ozone was lower. The ozone profile up to 7 km for the first 6 month (January - June) of 1984 and of 1982 are about the same, but between 8-14 km a remarkable increase up to 40 % of the mean values (1970-1980) was measured.

-771-

2.2 Stratospheric ozone

Figure 2 shows the behaviour of the mean annual ozone partial pressure in 2 km steps from 14 to )2 km altitude. Straight lines indicate the long-term mean 1970-80 (11 years).

Since 1969 altogether a light decrease is shown between 14 and 24 km. Above 28 km the ozone decreas~at least since 1977, till 1982 about - ) to -4%, till 198) about -7 to -11%. The general decrease from 1982 to 198) at all levels can also be seen at the total ozone curve below, with 8) as an abso­lute minimum.

- M.an .alun 1970-10

Fig. 2: Annual mean ozone values at 2 km steps, total ozone and relative sunspot numbers, MOHp 1967-198)

_Ihr.) ... .~

II

J]

2.

It

" II

20

11

"

", '" .

- ttN-"

!II' .... _- "'1 ........... ., ~trfWWII

Fig. ): Mean ozone profiles MOHp for 1982, 198) and for 1970-1980

The annual mean ozone profiles (fig.) for 1982, 83 repre­sent an ozone decrease above 25 km in comparison to the long­term mean 1970-80, also remarkable is the ozone increase in the troposphere. The curve 198) demonstrates an enormous ozone de­crease between 14 and 23 km, being outside the bars marking the mean standard deviation (cr) for 11 years. It leads to a total ozone reduction of about 6,4% of the long-term mean. During the first half year (not plotted in fig.) the values in this layer are going back to normal.

Tropospheric ozone as a whole is less than 10% of the to­tal ozone. Thus the outlined tropospheric ozone increase (sec­tion 2.1) is relatively small and cannot compensate ozone losses in the stratosphere. In opposite, if we consider the intrusion from the lower stratosphere into the troposphere, the 198) stra­tospheric ozone depletion seems to be an explanation why the steady ozone increase in the troposphere was stopped since 1982.

-772 -

101 ~[O.Ul

J!IO

I fMAM I l AS 0 I OMo,tO

- ,m-Io 1912

------191) - - - -191'

I rWINI I ASOJONooth

Fig. 4: Mean monthly total ozone values for Arosa and MOHp

1010) [OUI '10

LIII : /\~\ ll) \

600S E

\ .. --UJ .., ..

I r w 101 OJ [OJIJ

uo

OIOM .. 'h

10ROII0 -1161-11 1912

-- -- - Ill)

IrwiNIIASOIONDlllh

Fig. 5: Mean monthly total ozone values for Goose and Toronto

To get a better knowledge of the ozone decrease about 1983 the mean monthly total ozone data for Arosa and Hohen­peissenberg were plotted for the same period as before (fig.4). A stronger ozone decrease started in winter 1982/83 and con­tinued till August 1983; again low values can be seen in October/November 1983. Finally a total ozone reduction of 9,6% for the first half year of 1983 was reached. At the beginning of 1984 the total ozone amounts are more or less normalized.

A similar behaviour of total ozone values in 1983 can also be found at many other Dobson stations. A check of the European data shows more pronounced deviations at the middle and south European stations than at the northern part. The comparison of monthly Dobson data of 2 Canadian stations (fig.5) Goose and Toronto provides a similar picture.

The world's longest Dobson observation at Arosa (fig.6) (1926-1983) reveales 1983 its absolute minimum during the 57 years of total ozone measurements.

A reason for this unexpected event may be found in connection with the volcanic eruption of El Chichon (Mexico) in April 1982 (4), which was claimed by experts as the largest of this century.

-773 -

----------- ' \ '/' ----- ------------------

Fig. 6: Mean annual total ozone at Arosa 1926-198)

Looking for other nzone minima in Arosa's long-period curve low values can be found in connection with volcanic eruptions, e.g. Fuego 1974 and Agung 196).

). Conclusion

For investigation and detection of natural of anthro­pogenic produced ozone variations further representative measurements of the vertical ozone distribution are neces­sary.

REFERENCES

1. ATTMANNSPACHER, W., DUETSCH, H.U.: International Ozone Sonde Intercomparison at the Observatory Hohenpeissen­berg 19. Jan. - 15. Febr. 1970, Ber. Dt. Wetterd. Nr. 120 (1970)

2. ATTMANNSPACHER, W., DUETSCH, H.U.: 2nd International Ozone Sonde Intercomparison at the Observatory Hohenpeissenberg 5. - 20. April 1978, Ber.Dt. Wetterd. Nr. 157 (1981)

). ATTMANNSPACHER, W., HARTMANNSGRUBER, R.: Trend and extreme values of 8 years continu~ measurements of ozone near the surface at the Met. Observatory Hohenpeissenberg, Proc. Quadrennial Int. Ozone Symp. Boulder 1980

4. WCP Newsletter Nr. 6 (July 1984), page 8

-774-

TRENDS IN TROPOSPHERIC OZONE CONCENTRATION

Rumen D. Bojkov Atmospheric Environment Service 0+ Environment Canada

and Gregory C. Reinsel

Dept. 0+ Statistics. University 0+ Wisconsin at Madison

Summary Ozonesonde data (11 stati~ns) and Umkehr pro+iles (13

stations) are analysed +or trend detection in the troposphere. All but one of the stations are located in the northern hemisphere. The weighted average trend estimate for Umkehr layer-l is (0.63:0.69)% per year increase over the period 1970-81. The increase in the free troposphere (850-400mb) detected in the ozonesonde data over the northern hemisphere is (1.12!0.34)% per year during the past 15 years. These are 95% confidence interval estimates. Pronounced seasonal differences are revealed from the ozonesonde data, with the increase being greatest in the summer season.

1 •• I ntroduct i on During the past decade. triggered by concern of possible

ozone destruction caused by human actiVity. considerable attention has been given to stratospheric ozone stUdies. Sporadic spells of high surface ozone concentrations were properly related to city pollution and tropopause folding events. However. an improved understanding of the photochemistry (e.g. the role 0+ OH. N02 • CH4 ' CO)suggested that gas-phase generation and destruction of ozone in clean tropospheric air may be more important in controlling the tropospheric ozone concentration than transport from the stratosphe~e. The issue is still very much disputed, although there is evidence that complicated tropospheric chemistry plays an important role in the tropospheric ozone balance. Determination of ozone trends may assist in clarifying this contrOVersial issue.

A global increase of troposperic ozone. based on analysis performed in WMO by Angell (1979), was first documented in the WMO report to CeOL (Bojkov. 1979) and again reported at the Ozone Symposium in Boulder (Angell ~ Korshover. 1980). The increase at Hohenpei!5senberg was reported by At-tmannspacher (1982). Further details on this ~nd other stations indicated tropospheric ozone increases allowed ~o look closer into its possible causes. and to calculate that its radiative effect could contribute close to 0.30

e warming through the entire troposphere during the last 15 years (Bojkov. 1983).

This paper summarizes results of two detailed statistical .tu4ies utilizing ozonesonde and Umkehr data in search of trends in the tropospheric ozone. The station by station analysis of the ozone changes reveal very interesting features, which will be described elsewhere in great her detail.

2. Data and methodology A thorough review of the quality of tropospheric ozene data

Ozone Symposium - Greece 1984 -775 -

I-0 --I-

l- •

-30

30

'"' ~ 0 ~

l-

I-

-30

DESEASONALIZED MONTHLY AVERAGES OF AP3 FOR Umkehr Layer-l

EDMONTON

--•

• . · .. .. . .. • -.. , , . .' - ~ ~ .. - . . ... - .: . ..: ':1.-: -- • "\; • • . . . . •

65 70 75 80

BELSK

-• - ~ -.' . . "-' . . . . . .. .. .- .... '- , ...... ,. . . - , ~,-. - - .. ~ #. ",-"... I. .... ~. -. • .• - •• • ._ ......... -. - ,. -...... .. . ),: ....... I.-~.... .. · . ........... .. - \ ,~. ... . .

65 70

SAPPORO

7S 80

30~-----------------------------------~------------~ . I"

.. 0--..

10

o~

-10 I-

• • • •

• . -. . •

---.. . . ,'" '6 -. ... •••

-. .. - • 65

• • • •

• • • • I - • .. •

• ...

.. • • • • • • • • . . . ~:-. ---. . .' • • •

70

!ROSA

• •

• <t •• · ... • . . • ••

•

75

, ,-. . . ... .. . • •• ; ..,..1-

•• . . . -• . .

80

. - .. .. · .. .. ... . -.. ~.'. .. ........ -I. . .... _ .. . -:. ~ ••• " _.- _., .'.- '. ••• • ._.. :.e • • Il~ •• " •••••

'\ .. .. ..... .. .. .- ,- ." . ~ ... ' .. ~. .- -, ... . . -. .... ~. -.... -. .: .". ,. . "... .-. .... - .... . -. -,. " . :.,. .. . • ... .

65 70 75 80

Fig.l

-776-

was reported recently (Bojkov, 1983) and will not be repeated. The ozonesonde data from 11 stations listed in Table I refer

only to observations of the same type sonde at each station. The few stations which have changed the type of sonde during the years need a correction to be ap~lied in the statistical model, however some indications of an altitude dependance of the magnitude of the differences between MAST(Brewer) and ECC(Komhyr) sondes suggest the need of further studies before the entire data series c~n be used intelligently. Only profiles which have reached 40mb and for which the total·ozone correction factor was between 0.8 and 1.35 have been considered. Analyses were performed at normally fifteen levels: 850, 700, 600, 500, 400, 300, 250, 200, 175, 150, 125, 100, 70, 50, and 40mb. Only a few stations allowed analyses to be extended to 20mb. Information discussed here refers to levels below 300mb.

Tests were made for the effect of the frequencies of soundings on the final trend value. It appears that the trend d.eter·mination is not affected, for example, by decreasing the soundings used from particular station from 2-3 per week down to 1 per two weeks, providing the series is uninterrupted and long enough. Lower frequency and irregularity of soundings could affect the derived results. Correction, of importance mainly for the concentration in the tropospheric boundary layer, due to changes in the local time of release of the sondes needs to be considered in at least one station(Thalwil-Payerne).

TABLE I OZONE TRENDS ( % per year) IN THE FREE TROPOSPHERE (850-400 mb)

Station all months Npbs summer per'iod

Resolute 1.23 :!: 0.44 504 1.38 :!: 0.57 1968-79 Churchill 2.05 ! 2.39 150 1.26 ! 1. 43 1973-79 Goose Bay 0.47 :!: 0.48 339 0.58 :!: 0.77 1969-80 Edmonton 0.91 :!: 0.99 260 1.58 :!: 1.89 1972-79 Hohenpeissenberg 2.13 :!: 0.29 1288 2.84 ! 0.43 1965-83 Th.-Payerne 0.39 ± 0.33 1824 0.55 :!: 0.63 1966-82 Biscarousse 1.42 ! 1. 10 308 1.30 :!: 2.38 1976-82 Cagliari 1.28 :!: 1.30 260 1.59 :t 1.29 1972-79 Tateno 0.43 ± 0.55 226 N.A. t968-82 Kagoshima 1.84 :!: 0.61 197 2.56 ! 1.97 .968-83 Aspendale 0.13 :!: 0.34 588 N.A. 1965-82

The ozonesonde linear regression was calCUlated for the entire observing period indicated in Table I. The partial pressure at all levels~f each individual sounding were deseasonalized and to the monthly (and separately to'the seasonally) averaged data a linear regression was applied to obtain the trend and the standard error of each individual estimate, both expressed in % per year (see Table I).

Despite the relatively noisy information generated by the Umkehr solutions for the ozone partial pressure in' layer-I, it has been demonstrated that large sets of uniformly evaluated Umkehr measurements could produce a satisfactory vertical ozone distribution c:limatolo9Y. In this study, the time series model for

-777 -

mont~ly averages of Um~~hr data was applied on data from 13 stations, shown in Table II, in th~ same manner as Reinsel et al., 1983. The model u~ed takes the trend function to be zero ~efore 19~O and linear thereafter. The "mean level" indicated as P3[nbJ in Table II is essentially the constant term in the model, with shifts added at some stations based on indications from the instruments' calibration record (not always found recorded). For example if no intervention is made around 1973 to layer-1 data in Felsk, the trend estimate is quite extreme at 6.1% per year.

Station

Edmonton Goose Bay Belsk Arosa Mt.Louis Lisbon Sapporo Tateno Kagoshima New Delhi Varana"Si Mt.Abu Aspendale

TABLE II OZONE TRENDS ( % per year) IN THE UMKEHR LAYER-1

MONTHLY AVERAGES

28.8 33.3 32.6 31.8 29.0 18.2 26.3 34.4 16.4 23.5 21.9 18.4 23.6

trend %

0.98tO.85 -1.02±0.98

2.80.:!;0.90 -0. 63:!;0. 29

1. 52:!;0. 98 2.62±0.82 3.19!0.~8

-0.97;!;0.42 0.93t2.46 0.86!;1.56 1. 13±1.92 1. 56!1. 31 0.76:!;0.72

({ resid. No.obs. (m) period

9.1 10.2 6.8 4.1 5.7 5.4 8.7 5.8 5.8 4.8 4.6 4.1 6.7

153(108) 10/58-10/81 126( 74) 2/63- 7/81

1088(174) 4/63-10/81 2/73 4876(244) 3/61-12/81

661(138) 6/63- 5/78 1/69 889(133) 6/67-12/81 482(148) 11/61-12/81

2786(239) 1/60-12/81 637(165) 2/61-12/81 11/63&70&7 805( 78) 6/74-12/81 847(108) 1/67-12/81 11/75 699(101) 10/69- 6180 10/75 653 (216) 1/62-12/81

*Intervention shifts in mean level included in time series models fa these stations due to indications in the instruments' calibration record.

The model used also includes terms to account for the annual and semi annual variations. The standard deviation of the residuals of the deseasonalized ozone data is given as ~ resid.[nbJ in Table II. Examples of the monthly deviations from the average of the deseasonalized values are shown on Fig.1. Careful analysis of similar scattering diagrams could provide very instructive indications for step or other shifts in the data series. Such shifts .... r·e apparent in the record of Arosa "'1963 and

""1970; of Lisbon "'1977; of Tateno "'1963 and ""1977; in Varanasi "..". 1972 (this is in addition to the correction already applied in November 1975); and in Aspendale-1970.However these are only indications which warrant and require further and more detailed study.

3.Results from the analysis. As already explained, Table II contains a summary of the

trends based on the monthly mean Umkehr layer-l data. They should be considered as tentative until further studies clarify whether more interventions could be justifyed without to jeopardize the confidence in the derived results. Additional precaution on some individual stations is called for by virtue of the large gaps in the data (e.g. Goose Bay 1965/66, 1969/70/71 and 1977/78/79 -eight years with 24 observations!). The weighted average of all stations estimate, obtained as in Reinsel et al., 1983, is (0.65~0.69)% per year for 1970-81.

~ 778-

Table I lists the trends from the ozonesondes, which over the northern hemisphere stations give a weighted average estimate of Cl.12±0.54)% per year, which defines as above the 95% confidence interval. It should be mentioned here that the trend analysis of the total ozone data for the days with soundings show, for most of the eleven stations, a slightly negative, but. not in all cases statistically significant, trend. This supports the view that the tropospheric concentrations increases are not due to a general (or by chance) increase of the total ozone during the days with soundings. Fig.2 shows deseasonalized average values of the ozone partial pressure at 600mb for the three ozone-seasons. Superimposed is a regression line of the trend 11.33+0.47) calculated using all seasonally averaged data based on 504 MASTCBrewer) soundings at Resolute. At this station after December 1979 ECCCKomhyr) sondes started to be used giving, on the average, ~15% more ozone in the troposphere. The step-like upward change starting with the 1980 data is very clearly visible.

nb ~

40

20

OZONE TREND at 600mb

winter-spr1na (1)

summer

autumn

(2)

(3)

------------- - -- -----2

.~ v

)

.L

1965 1970

Fig.2

.1

1975

RESOLUTE

1.33 ± 0.47 (504)

--- --------- .

l! \" )

. ,i \

2 1 ]

~/\/.\/~ • I

1980

The trend estimates based on the summer season (defined May through September as in Bojkov, 1969) data indicate in most stations noticeably higher values, which may be used as an argument in support of the view for anthropogenic reasons for the increase of tropospheric ozone.

As an illustration of the distribution of the trends with altitude, Fig.3 shows the estimates (using monthly averages) over four European stations. At about the height of the tropopause there is a switch in the sign of the trends, which is observed also in all other stations.

-779-

1Ib

.w

30

so I

/ .

HO

HEH

PEIS

SEM

BEIG

OZO

NE

TIEH

DS

mb

OZO

NE

TRE

ND

S

IIIO

Ilthl

y 10

0 I

100 ~ ~

. \

vin

ter-

spr!

na

• •

• W

}

.. j'

....

a_

r

--

-S

I ,.,

H

oh

enp

e1ss

. ..

au

t_

A

/ \

Th.

-P

ayer

ne

I

·200

~ ..

, \

B1

scar

ou

sse

->

,,' 20

0 "

, C

ala

iari

0

0

, ,

0

r'-

'-'-

' 30

0 I

300

I I

A

400

'. I

:

I

500

I-;...

t"~\

50

0 . I

i· .

.... ...

s 60

0 I

. . !

I I

I'

w~ 1

.r

700

. .

, ,

, \

I 85

0 r

'.r

, \

, ,

% p

er y

enr

850

. -3

-2

-1

0

2 3

I %

per

year

-3

-2

-1

0 1

2 3

Fig

.4

Fig

.3

The seasonal differences in the trend estimates are very clearly visible on Fig.4 which uses the Hohenpeissenberg data. The higher values of the trends during the summer and partly in the autumn are well pronounced. From Fig.4 it is also obvious that change of the sign occurs not only around the tropopause but also a second time between 40 and 30mb. That feature could be related to the differences in the circulation regimes in these broad layers as indicated in earlier Umkehr profiles analyses IBojkov, 1968 ~ 1969).

4. Final remarks Although there is still room to further study and verify

both the Umkehr and the ozone sonde data for homogeneity the exact magnitudes of the trends shown above should be considered tentative. This study confirms however that there is strong evidence that the tropospheric ozone has been steadily increasing during the last 15 years.

REFERENCES

Angell, J.K.,(1979): Analysis of ozone data performed in WMO (private communication)

Angell, J.K. and J. Korshover,(1980): Update of ozone variations through 1979, Proc. Ozone Sympos. Boulder. 393-396.

Attmannspacher, Walter, (1982): The behaviour of atmospheric ozone during the last 15 years, based on results of ozone soundings at Hohenpeissenberg, Proc.Workshop on Biolog.Effects of UV-B Radiation, BPT-Berich. 5/82, 12-19.

Bojkov, Rumen D., (1968): Features of the vertical ozone distribution deduced from five years observation at Belsk, Acta Geophys.Polonica, XVI/4, 295-313.

Bojkov, Rumen D., (1969):\ Ozone distribution over the Mediterranean, Central and Southeast Europe during the IQSY(1964-65) , Pure a. Appl.Geophys. 74/3, 165-185.

Bojkov, Rumen D., (1979): Preliminary results of study of trends in ozone concentration, App.to WMO presentation. UNEP/CCOL-III/3 Add.3, PariS, 7pp.

BOjkov, Rumen D., (1983): Tropospheric ozone, its changes and possible radiative effects, Proc. WMO Techn. Conf. on Observ. of Atmosph. Contamin. Vienna, Oct.1983, WMO Sp.Environm.Report *16. 34pp.

Reinsel, Gregory C., G.C. Tiao, R. Levis and M. Bobkoski,(1983): AnalysiS of upper stratospheric ozone profile data from the ground-based Umkehr method and the Nimbus-4 BUV satellite experiment. 3.Geophys.Res. 88/C9. 3393-5402.

-781-

LONG-TERM SURFACE OZONE INCREASE AT ARKONA (54.680 N, 13.430 E)

U. FEISTER

W. WARMBT

Summary

Meteorological Service of the GDR Main Meteorological Observatory Telegrafenberg DDR-1500 Potsdam German Democratic Republic

Meteorological Servioe of the GDR Meteorologioal Observatory Alt-Wahnsdorf 12 DDR-8122 Radebeul 5 German Demooratic Republio

Measurements of the ozone oonoentration near the ground oarried out at Arkona since 1956 are analyzed for short-time variabili!~ ~yd for trends. A long-term ozone increase of 0.68/ug m a has been observed.

1. Introduction Arkona is one of the 9 meteorological stations in the

GDR measuring the ozone ooncentration near the ground. Sur­face ozone measurements were started at Arkona in 1956; there­fore, this record is one of the longest (Dresden since 1952, Kaltennordheim and Fichtelberg since 1954). Arkona is situ­ated at the northernmost tip of the country on the Ruegen island immediately at the Baltic Sea coast 42 m above3m.s.l. The annual average SO conoentration of only 10/ug m- is rather low as compare& to industrial areas. Ozohe measuremen~ were taken 4 times daily up to 1981 using the manual wet­ohemioal iodometrio method developed by Cauer. Since 1982 surface ozone has been continuously recorded using the Ozono­graph II developed by Mrose and Warmbt (1974). At the Inter­comparison of Instruments measuring ozone near the ground at Hohenpeissenberg in 1978/79 (Attmannspacher and Hartmannsgru­ber, 1982) the Ozonograph showed an accuracy of ~2% for 30-min averages and due to the chromiumtrioxide filter no inter­ference of S02' The influence of N02 can be neglected for tYpioal ooncentrations (0.5 to 4 ppfiV).

2. Short-time variability Fig.1 shows the average seasonal ozone variation deter­

mined from daily mean ozone values of the period April 1956 to March 1983 and the standard deviation of individual values from monthly mean values. The di~tinct ozone maximum during spring/summer of {52 ~ 18)/ug m- in May and the winter mini­mum of {26 ± lS)Lug m-3 is assumed to be mainly a result of a higher photolysis rate of N02 caused by the UV radiation (A~ 400 nm) that is about 10 times higher in summer than in winter. Ozone is then photochemically produced from NO in the troposphere and accumulates there particularly in stagnating air masses with high air pressure. An additional ozone pro-

Ozone Symposium - Greece 1984 -782-

80r------------------------.40

pgm-3

60

20

Fig.

ppbv

30

20

10

o

Average seasonal variation 1956 -1983 of surface ozone at Arkonaj bars designate the 26' standard de­viation of the individual values from monthly means

Fig. 2 Autocorrelation function of surface ozone for three time intervals (--- without seasonal variation, --- with seasonal variation)

, 0 2 3 4 5 5

K(-r) \

\-----~ .......... o .......... ~ ...... '"""~

1.1.55-22.1.50 N=1392

K(r) \

\,,------o

-1

15.355 -4.10. 68 N= 1299

1~-r-.--r-'--.----'

K(T)~ \~-----...J

O· '--..... ....----....... _--9.10.74 -8.1.75 N=457

-1 ~~ __ -L __ ~ __ L-~ __ ~

o 2 3 4 5 5 T

duction ooours in anthropogenically polluted air with high concentration of CO and NO •

The total standard de~iation of surface ozone was deter­mined as a sum of three components (Feister et al., 1984)

2 s

with the stochastic2variance s2 including random noi~e, the seasonal variance sB and the i!ter-an~ual va~~ance se' Table 1 shows the amount of the components 1n j ug m and tneir per­centage portion. The smallest portion or 13.5% of the total variance is provided by the inter-annual variability. This amount is reduced to 5.1%, if the trend is eliminated. Short­time variability yields more than half of the variance. Therefore, the use of climatological ozone values instead of actual values is assumed to be insufficient for many purpose~

Table 1 Stan~rd deviation components. n = 8795. Y = 39.2 r g m

'. "s "c 100 8,\,')= 100 -D'Y 100 .C''Y 100 ./i 100 8 ... 2 ,.2 100 8 02/,.2 100 _,;;_

.J"" .-J_7 c.,._~ ::-f._~

1(1 th trend 13.4 11.2 6.9 18.8 J4.1 :!8.5 17.6 47.8 51.0 '5.5 ').5

wi thout I'. '. 11. , 4.0 18.0 '4.2 28.8 10.' 45.' 55.4 '9.5 5.1 t.rend

-783 -

The persistence can be seen in Fig. 2. If the seasonal variation is removed, the autocorrelation function approaches zero for time lags of 1 to 3 days.

3. Trend Linear and quadratic regression equations have been de­

termined from monthly mean ozone values for individual months (n = 27) as well as for the whole series (n = 324) after eli­minating the seasonal variation. Fig. 3 shows linear regres­sion lines and standard deviations of daily averages from the total monthly mean values w. as well as from the total mean s. All quadratic trends ard below the 95% significance level, and all linear trends except that of July are above the significance level of 95% to 99.9% (Ka5ol1 et al., 1976). Table 2 shows the differences ~y injug m- between 1956 and 1983 determined from the regression 2ines. The greatest in­creases occur in May and in August, but the smallest increa-

'0

10

'0

--------------,.0 JAN (Jc5~.

w, .15.0 "l1nr' ($,.,% I

FEB , .. 0.1% ",."_'II,,,,.JIU.'~)

o 0

o

ppbll

.0 •• 10

.0

00

.0

-pph

- 30

JUL /1_'0·" .,.1& 2 Jjgm-j (JS IV.)

° 0 ° l:~~--~~~----~~_IO

qO J

o -L..L--L ! , , " , , , , , , , " 10 ItUSlIOU" If ")10 '"'''''''' eo 12

'O~G .I"O,'~. J:~Il" w,_ /5.3 II''''''' (n .• ".,

.0

.0 10

o 10 10 .0

01tSl 51 50 51 " 51 II 'l) 71 74 " ,. 10 U 60

01SlSl 51 10 fZ " " " 10 11. '4 7. " 10 IJ 0 40 .0 ~40 ppIw _ OCT, .. ,-/. I ppbw -' 60

Af}1f , .. a.1'" .... ' .. ·'11"".. (Jl.'~J JO ..... ,·0 .... '5.'''''"..., .. U~) 30

.0

10 loEr;: ~ .- •

10 40

00 10 10 ___ •• 00

00 0

00

- '0 o 0

.0

~ '0 .0

O~---L-L..L.l.....1...1.LJ..l_ll_.I_I.l..jLIO

~"-'''-'''-'''-'''-'''--=~''-'''''--'''=-='''-''=-"o '0"" 51 eo II .... 10 11 ,. " " 10 U .0

___ o_O_:;-,:1w ~ DEC :~';:'II""" (58.0% J

° 0

20 Ie ,,,­.... " .• .,.,." (.N.''''

10 40 •• .10

> ~ __ ~~~rO~O~~ __ ~~ 10 101.......-... .- 10

°115151 10 11 " If N '" 11. " " " 10.1 0

40

'Or .- ----.- --

•• 10

'0

°m.51 10 U" • II )10 11 :II ,. " 10 IZ 0

-784 -

Fig. 3 Monthly mean values and annual mean value of sur­face ozone (100 - B: signifi­cance level)

ses in Janua~~ and July. On the average, the ozone increase is 18.3/ug m or 60.9% of the ozone value in 1956 or 2.3% per year. The fifth and sixth column of Table 2 show the years with 50% and 100% more ozone than in 1956. The extrapo­lation is based on the assumption that the trend will con­tinue. As compared to 1956 the ozone concentration will poss~ bly have doubled around the turn of the century.

Table 2 Results of the trend analysis, Arkona 1956 - 1983

19~6_198, 4y 4y/n IOO4y/ IOO4y/ ),eur wi th yeaT '''It.h )'(.'<11" 'dtl'

nY'956 5~ lIIore lO~ IIIOr(" :i i b I11f'ic .• ncl.'

/;Jg m-:[] /jIg m-3a-lj Mfl956 02.one than o;r.one tLIi.ln ] c"ol 9".'1;: C/o a-I] n 1956 in 1956

J ..... 11 .. 5 0 .. 425 ~".:J 2.0 I"AI ::00', 1')<'10

FBD 15 .. 6 0 • .576 6' •• ~ 2. I, 1978 1~9B

~L\n 14.6 0.539 '-:) .. 1 1.6 1988 :20: R "):)1

Am 20 .. 5 0.761 }9.1 -. - 197q ~oo-"

'IAY 28. :3 1 .. 048 75.0 ~.8 197" 1991

.n."!< 19.8 O.7J5 "8.R 1.8 1')8) 2010 1"~;

""L 12.G o.4tiB )2.2 I.~ 1997 :!OJi 1:)('1:,

... l-'CO 2".0 0.890 73.:2 2.7 197" 19?~

SET' 19. i 0.7)0 5R.'1 ;!.2: 1979 :':001

OC"r 111.6 0.5'12 5'1.1 :!.o 19 RO ~OOj I"R'i

NO\' 1!t.8 0.)47 70.9 ~. 6 l~i5 1')9)

Dt;C 16.4 0.607 87. I 3.2 1971 1~1::I6 1~1=I'1

YE~ t8.3 0.678 60.9 2. J 197R :':000

The last column of Table 2 shows those years in which the signifioance leve199.9% will be reached. The stronger abso­lute inorease in summer as compared to winter can be regarded as an indication of the photochemical origin of ozone.

Fig. 4 shows the seasonal variation of regression values of surface ozone for the years 1956 and 1983. If the trends co~tiDUe, an increase in ~he seasopal variation from 21.8/ug m- in 1956 to 44.5/ug m- in 2000 could be expected. The ab­normally small inorease in June and July could be explained by the trends of global radiation about 5% of which is con­tributed by wavelengths less than 400 nm. The global radia­tion G has been determined from sunshine duration S

G = GR (0.2 + b ~) max

with the Rayleigh global radiation GR, the maximum sunshine duration S and a coefficient b ranging between 0.60 and 0.63. TablW~ shows a decrease of global radiation G in June and July that could at least be partly responsible for the .maller increase in surface ozone during those months as com­pared to May and August. Therefore, the smoothed curve in Fig. 4 (dashed line) is suggested to be a more likely predic­tion of surface ozone than is shown by the solid ourve. As global radiation cannot continuously further increase due to astronomioal limitations, it remains to be seen whether the seasonal ozone maximum shifts to June in the coming years.

-785 -

Tab1e 3 Month1y means and trends of dai1y sums of g10ba1 radiation at Arkona, 1956 - 1982

May (f (J cm-o.:-) 462.4 :I'REND (%) 6.9

80

60

40

20

o J F ~ A ~ J J A SON D

June 505.8 -9.9

40 ppbv

30

20

10

o

Fig. 4 Seasonal variation of surface ozone determined from re­gression for tbe years 1956, 198) and 2000 (solid lines) and expected ozone concentration for tbe year 2000 {dasbed curve)

Ju1y 451.0 -3.4

· 15 · 10 10

p (hPa)

10

50

100

200

500

'00~'5 .10 . 5

August 384.0

14.6

° Fig. 5 Percentage linear trend rR£NO'"

between 1975 and 1982 as deter-mined from ba11oon-borne ozone sondes over Lindenberg

10

5

15

Long-term inoreases in surfaoe ozone have also been observed at otber stations sucb as Dresden, Kaltennordbeim and Ficbtel­berg (Warmbt, 1979). In Fig. 5 it can be seen tbat tbere is an inorease in ozone in tbe free tropospbere, tbougb not yet signifioant, over Lindenberg. Tbe o~~n~lincrease ~,tween 800 and 400 bPa (2 - 7 ~~ ~f 0.40 j ug ~1 a (0.46% a ) witb a maximum of 0.77jug m a (0.92% a ) at 500 bPa (5.6 km) witbin tbe period 1975 to 1982 is oomparable to tbe o!,~+l ozone inorease near tbe ground a~ Arkona of 0.68 ug m a • It is a1so in 1ine witb tropospberic ozone trends of 0.5 to 1.0% per year observed in otber regions (Angell and Korsbover, Bojkov, 1983) and with results of model calculations tbat si­mulate tbe influence of anthropogenic emissions on the ozone ooncentration (WMO, 1981).

References 1. ANGELL, J.K. and J. KORSHOVER (1983), J. Climate appl. Me­

teor. 22, 1611 - 1627 2. ATTMANNSPACHER, W. and K. HARTMANNSGRUBER (1.982), Ber. Dt.

Wetterd., 161 3. BOJKOV, R.D. (19B), Tropospheric ozone, its changes and

possib1e radiative effects. WHO Special Environmental Report No. 16

4. FEISTER, U. et al. (1984), 7 years of ozone soundings over LingQ~be~~GG1975 - 1961 (submitted to Geod. Geopbys. Verol-l- ..NA der DDR)

-786 -

5. KAROL', I.L. et al. (1976), Pure and appl. Geophys., 114, 965 - 974

6, MROSE, H, ann W, WARMBT (1974), Geod. Geophys. Vero:f:f, NKGG der DDR, II, 18, 58 - 63

7. WARMBT, w. (1979), Zeichtschr. Meteor., 29, 24 - 31 8. WMO (1981), The Stratosphere 1981. Report No. 11

-787 -

A NEGLECTED LONG-TERM SERIES OF GROUND-LEVEL OZONE

E.G. MARIOLOPOULOS, C.C. REPAPIS, C.S. ZEREFOS, C. VAROTSOS, I. ZIOMAS, A. BAIS

1\cademy of Athens and laboratory of Atnospheric Physics, Box 149 , University of 'Ihessaloniki, Greece

Surrmary

Surface ozone concentration based on coloration of De James test-papers corresponding to daytime and nightime exposure was IIDnitored daily at the Athens Cbservatory during the period 1901-1940. This neglected se­ries was converted to ozone levels using hourly relative humidity (R.H.) data and the R.H.- ozone conversion chart of Linvill et al. (1980). '!he climatic fluctuations of the resulting long-term surface ozone series are .presented in this report.

1.1 Introduction

Surface "ozone" was IIDnitored in Athens at a well exposed site in the National Cbservatory using De James test paper from 1901 through 1940. The Athens old surface ozone rreasurements were based on Berigny's (1858) obje­ctive colorimetric scale (0-21) which is IIDre detailed than the arbitrary (0-1 0) Scht5enbein scale (Berigny, 1857, 1 858). Paper ozonometry has been criticized as early as 1857 by A.Houzeau (1857) because of the interference due to various causes such as halogens, nitrogen comp::>unds, H2 0 2 , atIIOsphe­ric electricity and IIDSt important of all the relative humidity.

About 120 years later, Linvill et al. (1980) have experimentally con­structed a conversion chart to relate the Scht5enbein scale at various re­lative humidities to ozone levels rreasured with a Dasibi instrument. 'lb construct their calibration chart, Linvill et al. (193-0) have prepared SchOenbein test paper according to the instructions they found in the old bibliography. Unfortunately \-Je \-Jere unable to find any publication conce­rning the preparation of De James test paper used in the Athens record in order to construct a calibration chart pertinent to these data. However, Berigny (1857) reported that there exists a linear relation bet\oJeen the "ozone" colorimetric readings of SchOenbein and of De James scales. M:lre­over, by comparing the response of SchCienbein test paper with the test paper of De James, Berigny reported a constant bias of 20% to exist be­t\oJeen the tw::> colorimetric ozone estimates, De James paper overestimating th~ "ozone" levels. '!his led us to reduce by 20% the colorimetric ozone readings of the Athens record before entering the Scht5enbein-relative humidity conversion chart by Linvill et al.(1980).

The Athens record consists of daytime (08:00-20:00 L.T.) and nighti­rre (20:00-08:00 L.T.) colorimetric ozone exposure during the period 1901-1940. For the same time intervals (daytime and nightime) we have calcula-

Ozone Symposium - Greece 1984 - 788-

co 0-e. S !ij

~ "

100

80

60

.00

f\,,/\ I V \

/\ I \ / 'I,.) \

) \ \.(8J

20 ,b,

111'0 01+9OO~------------19r'0------------~ln~0------------~'9T~0------------~

YEAR

- .. 0

z +30 Q

< +.10 :5

!!! +10 u

~

e -10 ~

i5 -20 >-

-30 I . ..., II:

Fig. t(a). 12-month running means of ozone levels from day-time exposure of De James test paper during the period 1901-1940. (b) Long-term trend in the frequency of meridional circulation patterns over the northern hemisphe­re adapted from Lamb (1972).

. .",

.30 ~ <

.", :5 !!!

+ 10 U

I -10 ;

Ca) i5 -20

~ 20 w Cb) -30 ::> a

..., ~

0 I 1900 1910 1420 19~O. 19~O

YEAR

Fig. 2. Same as Fig. 1 except for nightime exposure.

-789-

ted average values of relative humidity from hourly observations made at the sane site where the colorirretric ozone was rronitored. After applying the relative humidity oorrection to the ozone readings, the long-term rrean daytirre exposure level was found to be 66 ppb and the nightirre mean 59 ppb. The mean (1901-1940) annual cycle of the converted oolorirnetric ozone le­vels has a maximum in Decerrber (40 ppb). In the following 'We shall be con­centrated in the long-term trends of surface ozone levels during this forty year period, after removing the annual cycle from the data.

1.2 Results Fig.1 (a) shows 12-rronth running means of daytirre exposure (08:00-

20: 00 L. T .) and Fig. 2 (a) the corresponding tirre s;;'!ries of nightirne expo­sure (20:00-08:00 L.T.) during the period 1901-1940. Figures (1(b) and 2 (b) show for canparison the long-term trend in the frequency of meri­dional circulation patterns observed in the northern hemisphere during the same period as reported by Iamb (1972). M=ridional circulation pat­terns are associated in Greece with prolonged transport of ozone-rich air from higher latitudes. From these figures 'We may tentatively propose that the observed long-term trend in surface ozone in Athens can be explained at least partly from the observed trend in transport processes. We should also emphasize that Athens urbanization and rapid industrial development started 'Well after the 40~s and between 1901 and 1940 Athens can be con­sidered as a semi-rural site. Finally the authors plan to extend the pre­liminary results presented here in the near future.

REFERENCES

1. BERIGNY, D. (1857). Annuaire de la Sosiete Meteorologique de France, 5, II, 149-156.

2. BERIGNY, D. (1858). Annuaire de la Societe Meteorologique de France, 6, II, 25-29.

3. HOUZEAU, A. (1857). Annuaire de la Societe Meteorologique de France, 5, II, 43-56.

4. LAMB, H.H. (1972). Climate Present, Past and Future, Vol.I, p.272, Methuen & Co Ltd, G.B.

5. LINVILL, D. et al. (1980). Mon. Weather Rev., p. 1883-1891.

-790 -

SURFACE OZONE NEAR THE EQUATOR

M. ILYAS

School of Physics University of Science of Malaysia, Penang, Malaysia

A wet-chemical type ozone detector has been employed to measure surface level ozone concentration at the equatorial location of Penang (SoN). Results from several years of data indicate the ozone concentra­tions undergoing significant diurnal and seasonal variations. The peak concentrations are observed at around midday (upto 3Snb) but the flux generally drops to zero level in the early evening period maintaining this level until forenoon. Monthly averaged daily hourly average concentra­tions are generally small (4-13nb) with a downward trend towards the end of the year. Frequently varying local weather conditions seem to have a dominant effect on the ozone fluxes. Ozone data are discussed with other radiational and climatic data.

1.1 Introduction

Considerable attention has been paid to the study of surface level ozone in many industrialized countries [1,2J. In many of these situations air is chemically polluted due to industrial operations and the informa­tion is of direct health value. In non-industrial locations free of chemical air pollution the production of pollutants like ozone is of natural origin and such measurements are helpful in studying the natural production mechanism as well as in providing bench-mark data for future comparisons.

Studies on surface level and vertical ozone over the equatorial belt are generally not available. To overcome this paucity, a comprehensive observational program involving balloon-borne ozone soundings [3J, surface level ozone, solar erythemal ultraviolet (UV-B) dosage [4J, solar UV-A and other meteorological data like solar radiation components and climatic parameters etc. was initiated at the University of Science recently. Results from the surface level ozone measurements are the subject of this paper.

1.2 Experimental

The Island of Penang where University of Science S.SoN lOOoE is located is ideal for equatorial measurements. The air is reasonably clean of industrial polluting chemicals and the climate is moderate due to sea to land breezes and the centrally running (N-S) hill passing by the side of the campus. There are frequent cloudy and shower/rainy days even out­side the monsson season. The laboratory is located near the mean sea level.

Ozone Symposium - Greece 1984 - 791-

The instrument used for the surface ozone measurements is a simple wet chemical (KI solution) Brewer type. The intake tube was located at the top of the building (20 meter) where freely flowing air is available. The instrument was activated at the end of 1980 and was operational through 1982. Unfortunately in early 1982, the instrumenta~sensitivity decreased. The instrument was not operational during 1983 but became operational at the beginning of 1984. The results presented here are based on the more reliable data of 1980, 1981 and 1984.

1.3 Results and Discussion

The results based on the data are shown in Fig. 1. The two .curves show seasonal variation using monthly average of daytime hourly average and hourly average maximum concentrations of ozone in the surface air respectively. The ozone concentrations usually drop to zero level in the late evening and maintain this level until late in the forenoon. In obtaining a daytime average, the total of average-hourly fluxes is averaged over 12 hours. In the present situation where for almost 12 hours or more the flux remains zero, this is considered to be a more meaningful quantity for considerations of human health rather than the usual 24 hour average. However, if the daily (rather than the present 12 hour day-time) average is desired, it can be obtained simply by reading the scale to ~ of its indicated value. Although, the daytime average hourly concentrations are relatively low (4-13nb), the average hourly maximum concentrations are significantly higher (lO-20nb) especially in the early part of the year. The instantaneous (and even hourly averaged values) on individual days are found tQ reach as high as 35nb. Both curves (Fig. 1) show a narrow dip

Monthly Average of Daily Hourly

16 Maximum Concentration

/ .D-C

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Hourly Avera<,1e Concentrations

N J M Fig. 1

M Jy s N

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-793 -

"

Fig. :3

-794 -

- r.=.:..r -·1- -.

·1 '- -1i . I -_.

- ' 1' •

.'

... !

around February. To study this and the other factors affecting the seasonal behaviour, the daytime average curve is compared with seasonal plots of several other parameters based on many years of data at Penang. Besides the February dip, the general trend of decreasing ozone concen­trations seem to be well mached with the seasonal variability in sunshine­hours, solar radiation, wind speed and cloud cover & rain fall (reverse direction). However, the data for solar ultraviolet-A (AA295-385nm; FWHM AA312-372nm) and erythemal dosage of solar ultraviolet-B (AA290-330nm) do not seem to show as clear impact on the ozone concentrations as the total solar radiation and wind speeds. The dip in February may be clari­fied only with the help more data.

In a typical diurnal behaviour, the ozone flux increases from zero at around 9 a.m. (solar time), sharply reaching a maximum slightly before noon and maintaining a high level in the early afternoon and slowly decreasing to zero level in the later part of the evening. There are, however, significant variations to this pattern depending upon weather conditions which undergo rapid changes over the period of a day. Occasionally an ozone level of as high as 5-10nb may be maintained right through the night to the next morning. Some peculiar examples of diurnal behaviour are shown in tracings in Fig. 3. Although the nightime concen­trations are usually at zero level, on nights with significant thunderstom activity (early morning) traces of ozone concentrations are recorded on the chart thus indicating ozone production during these activities.

From"the present study, it is also found that despite the cost effectiveness and simplicity of operation, the bubbler type of instrument requires a lot of continuous attention for successful operation. The main difficulty seems to arise with the electrodes needing frequent attention. Use of a standard/reference ozone source for regular calibration should be greatly helpful especially in rapidly varying weather conditions like ours where data comparison on a day to day basis may not be very helpful. Over long periods of operation, the pump also developes problems especially if the air is sampled through a long intake tube.

Acknowledgements

Presentation of this paper was made possible with grants from the Int'l Ozone Commission (IAMAP) and University of Science of Malaysia.

REFERENCES

1. Guicherit, R. and Van Dop, H. (1977). ozone in Western Europe (1971-75) and Atmosph. Env., ~, 145-155.

Photochemical production of its relation to meteorology,

2. Post, K. and Bilger, R.W. (1978). Ozone-precusor relationships in the Sydney airshed, Atmosph. Env., ~, 1857-1865.

3. Ilyas, M. (1984). An ozone soundings program at the eastern equator; Preliminary results. Proc. Int'l Ozone Symposium (this volume).

4. Ilyas, M. and Barton, I.J. (1983). Surface dosage of erythemal solar ultraviolet radiation near the equator. Atmosph. Env., 17, 2069-2073.

-795 -

Summary

TROPOSPHERIC OZONE AT FOUR REMOTE OBSERVATORIES

S. J. Oltmans

Geophysical Monitoring for Climatic Change Air Resources Laboratory, ERL, NOAA

Boulder, Colorado 80303

Continuous observation of ozone near the surface at the four Geophysical Monitoring for Climatic Change (GMCC) observatories over the past ten years reveals important characteristics of the ozone variability of the troposphere. An observational record of this length not only gives information on the diurnal, day-to-day and seasonal variations, but also is long enough to look at long term trends. Ozonesonde observations are used to judge the representativeness of the near surface observations as indicators of tropospheric ozone behavior.

1.1 Introduction

The controlling role of ozone in the chemistry of the troposphere through its involvement with the hydroxol radical emphasizes the importance of understanding the behavior of ozone in the remote troposphere. Verification and further development of models of tropospheric ozone behavior is hampered by the sparseness of observations of ozone in the lower atmosphere. The ability of both the surface and ozone sonde measurements that do exist to represent ozone behavior in the troposphere may also be questioned.

The four stations of the GMCC network located at Barrow, Alaska, Mauna Loa, Hawaii, American Samoa and the South Pole have had programs to continuously monitor ozone near the surface for up to ten years. This data set beginning in 1973 at Barrow and Mauna Loa and two years later at Samoa and South Pole, is used to describe ozone variations over a range of time scales. In addition use is made of ozonesonde observations made at or near the observatories to evaluate the representativeness of the surface measurements in describing overall tropospheric ozone behavior.

The surface ozone measurements since 1976 have been made primarily with th~ Dasibi ozone meter (1) which uses ultraviolet photometry as its principle of operation. Prior to 1976 the measurements were made using the potassium iodide based electrochemical concentration cell (ECC) sensor (2) adapted for continuous observation. Both types of instruments were run concurrently from 1976 to 1980. At South Pole through 1978 and Samoa through 1980, the ECC record is more complete and is used. Beginning in

Ozone Symposium - Greece 1984 -796 -

1978 a network standard Dasibi photometer has been compared to a standard ultraviolet ozone photometer maintained by the U.S. National Bureau of Standards. All the surface ozone data are traceable to this standard.

1.2 Seasonal variations

The dominant feature of the surface ozone record at all of the observatories is the annual variation (Figure 1). Also quite apparent are year-to-year differences in the character of this seasonal cycle. At Barrow (70 0 N) the annual maximum has a double peak in November and February which is very repeatable. The seasonal minimum, on the other hand, shows great variability in both timing and magnitude. Figure 2 depicts the average variability for each month for the 10 years of observations. The thicker portion of the bars attached to the monthly averages represents plus and minus one standard deviation of the year-to-year variability for that month. The total length of the bar represents the variability within the month. At Barrow the months of March, April and May show the largest day-to-day as well as year-to-year variability. This is also the period associated with the strongest episodes of Arctic haze. The secondary maximum in Mayor June also appears every year (Figure 1). The persistence of these features points to forcing mechanisms that appear regularly each year.

At Mauna Loa (19°N) the minimum of the seasonal cycle in the autumn shows less year-to-year variability than does the spring maximum (Figure 2). For Mauna Loa the data are for the downslope wind regime at the observatory (21-04 LST) which is considered to be more representative of the free troposphere (3). Based on a limited series (55) of ozonesonde soundings at Hilo, Hawaii located about 55 km from the Mauna Loa observatory, the maximum of the seasonal cycle in the middle and lower troposphere occurs about one month earlier than the May maximum in stratospheric ozone. Since the mixing ratio of ozone at 200 and 300 mb in April is less than that at 500 mb the suggestion is that horizontal advection from higher latitudes where tropospheric ozone concentrations are higher is responsible for the earlier seasonal maximum in the troposphere at the latitude of Hawaii.

At Samoa (14°S) and South Pole (90 0 S) the surface ozone seasonal cycles are very nearly in phase and in both cases the annual maximum leads that in stratospheric ozone by several months again suggesting loose coupling between tropospheric ozone behavior and stratospheric ozone above the station.

1.3 Long term variations

With a length of record of at least 8 years at each station it is possible to investigate changes over periods of several years. A linear least squares fit to the monthly anomalies (monthly means from which the long term monthly mean has been subtracted) for each station is summarized in Table I. Although none of the trends are statistically significant it appears that at Mauna Loa, in particular, since 1976 there has been a rather marked increase. This seems to result almost entirely from changes in the seasonal maximum. The largest monthly mean recorded at Mauna Loa came in 1983.

-797 -

TABLE I. Linear least squares trend and confidence interval of surface ozone monthly anomalies in nanobars per year.

Station

Barrow (1973-83) Mauna Loa (1973-83) Samoa (1976-83) South Pole (1975-82)

Trend -1 (nb yr )

.34

.44 -.11 -.08

1.4 Comparison of surface and ozonesonde data

95% Confidenc~1Interval (nb yr )

±1.99 ±2.00 ±2.43 ±2.46

From September 1982 to December 1983 ECC ozonesonde flights were made from Hilo, Hawaii providing an opportunity to compare results from the ozone­sonde profiles and surface measurements at Mauna Loa. Tropospheric ozone profiles with surface data plotted at the pressure altitude of the observa­tory for March and April 1983 are shown in Figure 3. The ozonesonde flights were made between 08-09 LST which is during the downslope flow at the observatory. It can be seen that the observatory is at a level above the effects of boundary layer destruction of ozone. Below this level, how­ever, the ozone often diminishes markedly down to sea level. This demon­strates rather clearly why the upslope flow at the observatory is depleted of oZQne relative to the downslope flow. The correspondence between the surface values at Mauna Loa and the Hilo soudings for the 8 cases shown are representative of the entire set. For the entire 36 flights the mean differ­ence was 1.0 nbar (sondes lower) and the standard deviation of the differences was 3.9 nbars. It thus appears that the continuous measure­ments at the surface at the Mauna Loa observatory provide representative measurements of tropospheric ozone behavior for this region of the atmosphere. The small mean difference between the two sets of data is also a confirmation that the ECC ozonesondes give tropospheric measurements on the same absolute scale with the UV photometry based measurements made at the observatory.

Several examples of enhanced ozone amounts in the middle relative to the higher troposphere are demonstrated in the set of 8 profiles at Hilo giving credence to the argument for horizontal advection of ozone at the observatory level.

At the South Pole a series of 125 ECC ozonesonde soundings were made during the period 1966-71. Both at the surface and 500 mb the seasonal pattern is similar to that found in the surface ozone record with a late summer minimum and a rather broad maximum stretching through the winter (Figure 4). By the 300 mb level, however, the phase has reversed with a sharp February maximum and a long winter minimum. This phasing suggests that horizontal transport in the middle troposphere may be an important element in establishing the seasonal cycle. It is also possible that variations in the rate of vertical transfer of air from the upper to lower troposphere are important since the mixing ratio increases with height during all months. It appears that surface ozone behavior at the South Pole is representative of mid-tropospheric ozone. A set of 70 ECC type soundings at Syowa (69°S) on the Antarctic coast shows a very similar seasonal pattern to that at South Pole for the low and middle troposphere suggesting that the South Pole surface measurements are quite represen­tative of south polar latitudes.

-798-

Ozonesonde soundings at Resolute, NWT (75°N) show a seasonal cycle at the surface very similar to the surface ozone measurements at Barrow, Alaska. By 700 mb at Resolute, however, the phase is markedly different suggesting that surface measurements do not well represent the free troposphere.

At Mauna Loa and South Pole it appears that surface ozone measurements should be useful in tracking long term changes in mid-tropospheric ozone.

REFERENCES

1. BOWMAN, L., and R. HORAK (1972). A continuous ultraviolet absorption ozone photometer, Rep. ISA AID 72430, 103-108, lnstrum. Soc. of Am., Pittsburgh, PA.

2. KOMHYR, W. D. (1969). Electrochemical cells for gas analysis, Ann. Geophys., 25, 203-210.

3. OLTMANS, S. J. (1981). Surface ozone measurements in clean air, J. Geophys. Res., 86, 1174-1180.

-799-

10

73 74 75 76 77 78 79 80 61 82 63 84

flji:_ 1 Monthly mean surf~ce ozone partial pressures at the four GMCC obser~alOr'tS

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NI~"'lCNI!Hou,~1118U' 1 19118]

M"". Fig 2 Averaged morJthly surface Olone concentralKlns. Thicker portion of error bars

represents plus and minus one standard deViatIOn for year 10 year varIations Total length of bat IS lor wlthm month variability

Fig. 4. Seasonal cross·sectlOn of ozone mixing ratIO In PPB at South Pole based on ozonesonde profiles from 1966· 71

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-71.

DIURNAL VARIATIONS OF NON-URBAN OZONE CONCENTRATIONS IN ISRAEL

* E.H. STEINBERGER* and R. LEVY**

Department of Atmospheric Sciences, The Hebrew University, Jerusalem, Israel

** Environmental Protection Service, Ministry of the Interior, Ben Gurion City, Jerusalem, Israel

Summary

Ozone concentations were monitored continuously at 7 sites, distributed over an area of about 10x30 km2, along the Mediterranean Coast of northern Israel. The stations were located in rural sites. The general and diurnal ozone variations differed in several respects from urban behavior: (1) Diurnal variations, (if any), were determined by the wind regime (2) Ozone levels were not dependent on insolation (3) Concentrations of above 100 ppb were occasionally measured, although

in situ generation could be ruled out due to lack of precursors. High ozone levels were associated with westerly - and low levels with easterly winds. These findings could be explained by assuming that an ozone reservoir may exist over the Mediterranean Sea, and the ozone is carried inland by the wind. When the wind is easterly an inflow of NOx, (from the main roads), reduced the ozone levels. A simple numerical model incorporating chemistry and diffusion was constructed. The computed results agree fairly well i~ith the observed val ues.

1. Introduction

The diurnal ozone pattern in the urban centers of Israel has been widely studied ((1),(2),(3),(4)) and is reasonably well understood. Diurnal variations are determined by the interaction of urban and meteorological parameters, such as traffic density, large - and mesoscale synoptic patterns, insolation, etc., and their temporal variations.

Very little was known previously about ozone levels in the rural areas of Israel. However, evidence from other countries indicates that ozone inflow to rural areas occur. ( (5), (6), W, (8), (9), (10), (11) ).

With the completion of a new power station in 1982, located on the coast in northern Israel, a network of 12 air pollution monitoring stations was established by the Hadera .Association of Towns, mainly for monitoring S02 and NOx concentrations. Ozone is measured in 7 of these stations.' Most of these stations are located in rural areas or small villages, which experience Itttle vehicular traffic.

Thus it was decided to utilize the available data for studying diurnal ozone variations in non-urban areas.

Ozone Symposium - Greece 1984 - 803-

--Main Roads

N

t

10 , , I

5.

Fig. 1. Location map of the area.

2. Experimental Methods

The instrumentation in the monitoring stations was manufactured by the Phillips Co. S02, NOx, NO, N02, wind speed, velocity, temperature and humidity were measured at all stations, ozone at 7 stations and insolation at one station. The location of these 7 stations is shown in Fig. 1.

The data were processed by the computer center of the Association. Pollutant concentrations were expressed in terms of half-hourly average~. This period is considered long enough to be representative, but short enough to resolve all variations of interest to this study.

3. Results

For this study 20 days were selected, covering a period from late April to early October, in 1981 and 1982. Inspection of the data showed several types of diurnal ozone regimes:

(1) Type A, illustrated in Fig. 2., shows a "normal" pattern, that is, higher values during the day and lower values at night. (2) Type S, illustrated in Fig. 3., covering a period of more than 36 hours (from noon on 9.9.81 to about 6 p.m. on 11.9.81), when ozone concentration is constant. (3) Type C, also shown in Fig. 3., combines features of both A and S, featuring sharp ozone decreases during part of the night only.

When wind directions and ozone concentrations were looked at together, (Figs. 2. and 3.) it was immediately clear that high ozone levels were associated with westerly winds, and low ozone levels with easterly winds. This behavior was consistently reproduced in all stations and for all 3 types of ozone patterns. In fact, a correlation coefficient of r=0.87 was found between ozone concentration and wind velocity. (11)

For a detailed study of type C pattern (Fig. 3.), measured on 9.9.1981, the data from station 1 was chosen, due to its unique location. This station was erected in a nature reserve, is the nearest to the shore, and all vehi cular traffi cis due east, (Fig. 1.)

Comparing ozone and NOx concentrations and considering wind directions also, the time interval between midnight and 8:30 L.S.T. could be divided into 3 periods: (a) 0:00-3:30 (b) 3:30-6:00 (c) 6:00-8: 30

loS.T. loS.T. loS.T.

- 804-

60

o

. - GIVAT ADA 21.6.1981 tf. A-HAMAAPI L tJk,.~~ ~

~-- ~! . : !lI. ~ A

i •

6 18 24 6 L.S.T. t hours

300

200

100

12 18 24

Fig. 2. Diurnal ozone and wind direction variations for Stations 6

and 7. (Type A).

'" ~ 25or-------~-------_.------____, I O _ e;, 9 .9.1 961 10 .9 .196 1 11.9 . 19~61 ' w.~ u

"'0 ~------,... ." ~ ~ J ~ ,'!~ ~ ! ~w 200 j ~W__~,{> ~'~lbA " : ; 5 ttJa..

• ..,.-- Irli" t:1>A ""'k:.V'~ cr: .<>. • :, : t{' tift. " <>"1A &P " J.: " 'h.. (f) o ~I lh :~ ~ ~ i:;, I 0

o ~4. ~ ~Z Z ~ MAAGAN MICHAEl tr r -~ 150 03:

80 .Cl

~ 60 w z 40 o N o 20

o

~ , ,

18 24 6 12 18 24 6 12 18 24 L.S.T. . hours

Fig. 3. Diurnal ozone and wind velocity variations for

Station 1. (types B and C).

- 805-

(f) Q) Q) ..... CJI Q)

"0

CD

Z 0 I-U W n:: 0

0 z 3:

During period (a) wind direction was westerly, ozone concentration was above 50 ppb, and NOx level was zero (Figs. 3. and 4.). Ozone was advected from the Mediterranean and apart from dispersion and ground effects no further destruction took place.

At the beginning of period (b) wind direction changed suddenly to south-easterly, followed by an immedi ate rfse of NOx and consequent drop in ozone levels. Presumably NOx was advected from the highway and probably also from the Tel Aviv metropolitan area. Ozone was then destroyed by the fast reaction NO + 03 N02 + 02, and since the wind was easterly, ozone could not be replenished by advection from the sea. This process continued until about 6:00 L.S.T ..

The commencement of period (q coincided with sunrise. From this time on ozone levels started to rise, NOx levels to drop, but wind direction was still easterly. The changes in ozone and NOx concentrations then must be attributed to the beginning of photochemical reactions. As long as NOx and presumably hydrocarbons were still advected, the reactions would continue, resulting in ozone production and NOx reduction. By about 8:30 L.S.T. the wind veered to westerly, NOx was swept out of the area and ozone concentration quickly returned to its pre-dawn high value. (Fig. 3.)

The conditions prevailing during period (c) can be regarded as approximating a giant smog chamber experiment, with continuous supply of precursors and varying illumination. Therefore it was thought that a relatively uncomplicated photochemical scheme could be used for simulation experiments. Accordingly, a simple dispersion model was constructed, incorporating a reaction scheme proposed by Heicklen (12) (and modified and updated by us). The computation results were compared to the measured 03 and 'NOx values and are shown in Fig. 4.. It can be seen that, in spite of the simple scheme, the agreement is rather good.

Thus it appears that in situ ozone generation occured only for short periods in the early morning, under easterly wind regimes. This assumption is further supported by additional evidence: (1) During westerly wind regimes NOx concentrations were low, ranging between 0-10 ppb, depending on the exact location of the monitoring station. Moreover, when ozone concentrations exhibited type B pattern, it was found that NOx levels were also constant and diurnal variations could not be discerned. (2) The ozone concentrations were independent of insolation. This conclusion was found when daily average ozone levels were correlated with daily total insolation for 100 days between May-August 1981. The correlation coefficient for the entire period was r=O.lO; for the individual months r ranged between -.11 and + 0.21. It should be mentioned, that for Jerusalem, for example, a similar attempt yielded positive correlation coefficients, ranging in value between 0.6-0.8. (13)

4. Cone! us ions

It has been shown that in the rural coastal area of Israel the rather high ozone levels were not due to local production, but to advection from above the Mediterranean. The diurnal ozone variations were determined by the prevailing wind regime. Photochemical ozone production was restricted to the special case of easterly winds during daylight hours. During the summer season this situation occurs only for short periods after sunrise.

- 806-

,I", • c.ompu..ted me.a.sc.l. re.d, Acknow I edgements •• ,... ". f, ..... " ... 000

.-.---o 0 0 '.

50~ /\

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+++

+ +

,",40- ~. ......"'\ "ilL ' /' \ , /w . ......... '. :t' \to -l ,I'. ~ " ;' \ ~30~ ... i \ ~ /~ \:+ 0

oj.> I ... '\ ~2 /' ",+ , Q) 0 - .... § N~!"", /"'\,

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REFERENCES

6 7 (hours)

8

One of the authors (E.H.S.) would like to thank the National Research Council of Israel for partial funding of this project.

Fig. 4. Measured and computed 03 and NOx concentration in Station 1. (9.9.1981)

(1) E.H. Steinberger, (1974); Israel Y. Earth Sci., 23, 19-22 (2) E. Ganor, Y. (R.E.), Beck & A. Donagi (1978); Atmospheric

Environment, 12, 1081-85 (3) E.H. Steinberger & E. Ganor, (1980); Atmospheric Environment, ~,

221-25 (4) E.H. Steinberger, (1980); in Atmospheric Pollution, ed.

M.M. Benarie, pp. 165-172 (5) R. Chatfield & H. Halstead, (1975); J. Geaphys. Res., 82, 6965-68 (6) K.G. Anlauf, M.A. Lusis, H.A. Wiebe & R.D.S. Stevens, 11975);

Atmospheric Environment, 9, 1137-39 (7) R.G. Derwent, A.E.J. Eggleton, M.L. Williams & C.A. Bell, (1978);

Atmospheric Environment, 12, 2173-77 (8) H.B. Singh, F.L. Ludwig &W.B. Johnson, (1978); Atmospheric

Environment, 12, 2186-96 (9) T.R. Karl, (1978); Atmospheric Environment, 12, 1421-31 (10) J.H. Shrefler & R.B. Evans, (1982); Atmospheric Environment, ~,

1311-2t (11) E.H. Steinberger, E. Glaser & R. Levy, (1983); in Developments in

Ecology and Environmental Quality, ed. H. Shuval, 145-154 (12) J. Heicklen, (1976); Atmospheric Chemistry, pp (13) E.H. Steinberger, (1982); Sci. Total Environ., Q, 11-16

- 807-

DIFFERENCES IN TROPOSPHERIC OZONE PROFILES OBTAINED BY Mast (Brewer) and ECC (Komhyr) SONDES

RUMEN D. BOJKOV Atmospheric Environment Service of Environment Canada

(Extended Abstract)

Wet chemical ozone sondes of the MAST (Brewer) and ECC (Komhyr) types are the most commonly used in the Global Ozone Observing System (G030S). Since 1970 WHO sponsored direct comparisons of these sondes in 1970, 1978 and with NASA 1983 during which less than two dozen tandem flights were made. These revealed that the ECC, on the average, gives more than ten percent ldgher tropospheric ozone concentrations than the MAST. These intercomparisons took place over a few days only and after special "personalized" preparation of the sondes. Therefore the information is considered too limited to establish correction coefficients for application to the two types of data sets resulting from year round weekly soundings. On the other hand there is an urgent need to establish more common correction factor because some stations have switched from use of one to the other type of sonde which introduces additional problems when one needs homogenized and nor~alized sets of data, for example for trend analysis.

Taking advantage of the excellent soundings at Hohenpeissenberg Observatory (MAST) and the series of soundings taken for special research purposes (with ECC) at the Fraunhofer Institut fur Atmospharische Umweltforschung at Garmisch (only 33km distance), about 130 nearly simultaneous ozone flights undertaken during the last three years are currently undergoing analysis. The thrust of the study is not to determine which type of oZ'one sonde performs better but to assist the deduction of a transfer coefficient(s) for homogenizing the G030S data, and with some precaution, for normalizing the data at stations which have used both types of sondes. The preliminary results, however indicate the existance of systematic differences. The ECC (Komhyr) sonde gives higher tropospheric ozone concentration on average. However, the ratio of the differences varies with altitude which means that it would not be practical to establish one correction factor but several based on altitude. Unfortunately, the Garmisch flights used in the begining total ozone data from Aroson and not Hohenpeissenberg. Reevaluations of the data are thus necessary before any definitive

conclusions can be drawn.

The study is still in progress and the results will be published in some detail elswhere when completed.

Ozone Symposium - Greece 1984 - 808-

UNCERTAINTIES IN SURFACE OZONE MEASUREMENTS IN CLEAN AIR

C. MALCOLM ELSWORTH, IAN E. GALBALLY & MICHAEL D. DOUGLAS CSIRO Division of Atmospheric Research

Private Bag No.1, Mordialloc. Victoria.

Australia. 3195.

SUMMARY

A critical examination of the ozone monitoring program at Cape Grim, Tasmania, reveals the following sources of imprecision and inaccuracy when the system is operating at an optimum level:

(a) Zero drift ± 0.2 ppb/day; (b) Change in response ± 1% / day. (c) Ozone loss in the inlet system ~3%.

and (d) Corruption of digital data records ~0.2% of monitoring period. In seven months of edited ambient records from two ultraviolet ozone monitors the differences on 99% of occasions do not exceed 4.5ppb for hourly mean concentrations.

We find that the concentrations observed are significantly affected by the height of the sample intake and on the type of surface upwind. Differences between inlets at 3m and 10m above the laboratory roof level at wind speeds of 20km/hr were up to 10% for winds from over land and around 2% for winds from the ocean.

1. Monitoring of Ozone in Surface Air

As part of a global program (1), established to detect long term changes of ozone concentration in the lower atmosphere (2) and to provide data for studies of the chemistry and transport of ozone in the troposphere, surface ozone measurements have been made at the Australian Baseline Air Pollution Station, Cape Grim Tasmania since October 1976.

Cape Grim is a remote location, 50km from a small town, on the western side of the northwestern extremity of Tasmania. Its coordinates are 40°40'56"5, l44°4l'18"E and the laboratory is on the crest of the cape 94m above sea level. Figure 1 indicates the locality.

In all monitoring programs the data must be gathered with sufficient accuracy and precision so that the monit~ring objectives can be attained. To achieve this the following processes must be quantitatively evaluated to ensure that the measurement program is functioning correctly (3). (1) Sample pretreatment; (2) Measurement; (3) Calibration of the measuring instruments; (4) Recording of the measurements; (5) Verification of the results; (6) Validation of the methods; (7) .Documentation of the procedure. Furthermore it is a requirement of the monitoring program that the ozone measurements be representative of the lower atmosphere. To achieve this sampling should be continuous and attention paid to the micrometeorology of the sampling station site and the air inlet elevation.

Ozone Symposium, - Greece 1984 - 809-

2. The Measurement System

The equipment used in the ozone monitoring program at Cape Grim includes the following items: (a) an air inlet system which consists of a 150 mm diameter stainless steel pipe which extends 10 m above and 2 m below the laboratory roof (4). A stainless steel dome covers the air intake to prevent the entry of rainwater into the inlet. The air flow through the inlet and the manifold is laminar thus mi~tmizing air contact with the walls. The volume fl~y rate is 0.7 m min , the air velocity in the vertical inlet 0.67 m s and the air residence time in that section 18s. An all teflon ozone sample line is fitted into the base of the vertical air inlet: (b) an inline "Ozone Monitor Comparison System", OMCS, (5), which includes a particle filter, an ozone destroyer and a ozone generator. This system provides the monitors with filtered ambient air during normal monitoring, but once per day provides a sequence of zero air, air with a reference ozone level, and finally unfiltered ambient air. This checks the operation of the monitors and ozone losses on the inlet filter. The OMCS unit is designed with teflon flow restrictors so that the pressure drop across the system (3 to 4 kPa) is unchanged irrespective of which mode of the sequence is operational; (c) three ozone monitors, a BENDIX model 8002 chemiluminescent ozone monitor serial no. 300146 (purchased 1974), a DASIBI model 1003-AH ultraviolet ozone monitor serial no. 1759 (purchased 1977) and a Thermo Electron (TECO) Model 49 ultraviolet ozone monitor serial no. 11525 (purchased 1981); (d) an air density module is attached to the DASIBI ozone monitor to measure the temperature and pressure of the air emerging from the optical cell within the instrument; (e) a Thermoelectron Model 49PS absolute ozone calibrator, serial number 40C-10687-120 (purchased 1983); and (f) a data recording system including both chart recorders and a microprocessor based digital cassette system.

A schematic diagram of the measurement system is shown in Figure 2.

FIGURE 1

- 810-

,~_ !;lIlt ~all"I4'1' 10"'" Inl,1 .,,,1,.

l~lhP'IGr Pll)w 0 -')11) IJlln

- ' . . '. . ~ .. - ", .. --_.' . ~ ... ---_ ...... -.. "~ - ----- -... -. ~

A-llQlO9Ut "I9M1 I @ :::: 0I.It""'11-::.J ("'arl

rfCOI'IIH

1 ~'1:·'0j»1 ,.,,'

FIGURE 2

3. Calibration and Correction of the Ozone Monitors

The calibration of the ozone monitors at Cape Grim is based on the ultraviolet absorption technique. All comparisons and calibrations are made with ozone concentrations in the range 0-100 ppb. Ambient air (ozone free) is used for these and zero checks. This air is not dried.

The results of one such quarterly calibration in December 1982 are shown in Figure 3. The calibrator (Thermo Electron 49 PS) is not used for ambient measurements and can be regarded as an ozone "standard" (6). Multiple measurements (> 20) are made for each data point so that it is possible to determine mean values of zero's etc. with a standard error of 0.1 ppb.

The response of the TECO monitor initially differed from the "standard" by '\, 4% but after service, including cleaning the optics and resetting the lamp intensities the difference was only 0.1%. Similarly at this time the responses of the DASIBI and TECO instruments differed by '\, 3% upon initial comparison, but after service (of both instruments) the discrepancy decreased to < 1%. (The 1% difference in response of newly serviced instruments represents a difference of only'\, 0.2 ppb for ozone monitoring in background air). The difference in zero signal varied from 0.0 to 0.4 ppb during the calibration.

As well as calibration, corrections must be made to the data because of ozone losses in the inlet and on the filter. Measurements of these and other losses are presented in Table 1. The techniques for determining these losses are described elswhere (5).

TABLE 1

Ozone losses in the Cape Grim ozone measurements. measured at ambient ozone levels).

(All losses are

System Component Ozone loss %

10 m s.s. Inlet

Ozone Monitor Comparison System (including filter)

Inefficiency (Transmission) of Ozone Scrubber DASIBI TECO

Ozone loss within instruments DASIBI

4. Data Storage and Editing

1.5

0.2

0.4-1.0 0.1

0.3-1.6

The data handling system accumulates around 3xl06 measurements per year stored as files on a computer system. This includes 1 minute ozone averages and air density data. Files of these data are edited to remove periods of known data loss due to extended power failures, instrument failures, etc ••

- 811-

~

z 0

~ 10 r=0999

r 60

50

00

l1i ~ }{) :I: FlEO I.STR\JMEN, S{RVI({O

~ 10 If CO '9 ~ 1 0011 mo '9PSl- 0 Jl

~ n: 0 999 10

0 0 10 10 Jo '0 SO 60 70 80

THO .c.9PS CAllBRATOR PPSV OZONE

FIGURE 3

dQlt~ me-Iln 100 O:lfferl~n(es.

March-Sept 63 1117 YOlue, 1

...... mont Ny mean dlffe rene es 0., 62 -Sepl 83

10 121 YOI .. ,)

" 0

" i: ~ 0

'l;

~

0-1

-4 -3 -2 -1 0 1

60) (CASIIll - nCO ) ppb'

FIGURE 5

10 '

10 ' dN

d log II 101

101

10

90 10 0-1

10

01

- 812-

(ape Grim °3 data

N=11.7016 99-8%

IAneptedl

1·0

July. Au~ust . SfI'pttmbtr. 196J

02% I ReJected I

10 100 1000 10000 II ppbv

FIGURE 4

- hourly rn~[ln

IDASJIII - T{COI dlHerentes, MA'R -SEpal ~.z 1..31. values)

__ A howl)' mean ~&NDlX - lECO)

dltferE!nc~s . O£( e1 - JUN 82 1131.1 y.olue-s]

-} -2 -1

FIGURE 6

The edited files still contain some spurious readings which escape the initial editing routines. The data files are filtered in an attempt to remove any remaining erroneous data records which appear as spikes in the record (7).

Differences, n, are taken between sucessive one minute ozone records. If sucessive n's exceed 10 ppb and the simultaneous inter-instrument difference also exceeds 10 ppb then the appropriate ozone record is deleted. Other rules cover special cases.

The effect of this filtering is shown in Figure 4 where the number distribution of values of n per logarithmic size interval vs absolute value of n is presented. The filter has removed all data where n is greater than 10 ppb. Examination of the original records shows that the 0.2% of the records with values of n in the range 10 to 5000 ppb are associated with instrument malfunction and electrical noise. Therefore the filter technique appears very satisfactory.

5. Verification of Ambient Data

The verification of measured ozone concentrations monitored at Cape Grim is achieved by comparison of the values obtained from two or three of the ozone monitors. We see from Figure 5 and 6 that on 99% of occasions the hourly lmean concentrations differ by less than 4.5 ppb, on 99% of occasions daily mean concentrations differ by less than 2.5 ppb and all 21 monthly mean concentrations differ by less than 2 ppb.

An international comparison, of a similar nature involving five types of ozone ~onitors used for measurements in clean air was carried out at the Hohenpeissenberg Observatory between 1 October, 1978 and 30th April, 1979, (8). The deviations of the hourly mean values of each monitor from the collective mean were within the range ±9 ppb with about 60% of the deviations lying in the range ±2 to ±3 ppb depending on the monitor.

More international comparisons of this type are desirable to provide a firm basis for relating measurements made at different stations or in different networks.

6. The Representativeness of These Ambient Measurements

One particular concern with this program is whether the ozone concentration measured is representative of that present in baseline (unpolluted lower tropospheric) air.

When ozone was sampled at 3 m and 10 m height above the roof deck at Cape Grim using the two indistinguishable teflon inlets a systematic difference in ozone concentration was found with lower values occuring at the 3 m level, as illustrated in Figure 8. The extreme cases observed were: (1) when winds were from 180° through 270° to 360°, that is from over the ocean (see figure 7) the ozone difference was 2-3% {(10m - 3m)xlOOjlOm} for the wind speed range 20 to 75 km/hr; whereas (2) with winds from 0° through 90° to l800,_that is from over land, the_ l ozone loss varied from around 8% at 20 km hr to around 2% at 55 km hr

This difference in ozone loss for the land and oceanic sectors probably reflects both the different ozone destruction rates of the underlying surfaces and the greater stability (weaker atmospheric mixing) which occurs over land compared with ocean surfaces (9,10).

Hence data selection based on wind speed and direction is necessary if the ozone data from Cape Grim is to be representative of the lower atmosphere.

- 813-

FIGURE 7

References

...... 000-1110 OiG ~~ 180 - no !lEG _ . 110 - 360 DEG

s w ~ ro ~ ~ ~ ~ ~ ~ ~ ~ ~ ro H WIND SPEED KM IHR

FIGURE 8

1. Department of Science and Technology, "Baseline Air Monitoring Report 1979-1980", Australian Government Publishing Service, Canberra, 35 p. (1983).

2. WMO Global Ozone Research and Monitoring Project Report No. 9 "Assessment of Performance Characteristics of Various Ozone Observing Systems", World Meteorological Organization, Geneva, Switzerland (1980).

3. American Chemical Society, Subcommittee on Environmental Analytical Chemistry, "Guidelines for Data Aquisition and Data Quality Evaluation in Environmental Chemistry". Anal. Chern. 52, 2242-2249 (1980).

4. Komhyr, W.D., "An Aerosol and Gas Sampling Apparatus for Remote Observatory Use", J. Geophys. 88, 3913-3918 (1983).

5. Elsworth, C.M. & I.E. Ga1ba11y, "Accurate Surface Ozone Measurements in Clean Air: Fact or Fiction", Proc. 8th International Clean Air Conf. Melbourne Australia, 1093-1112 (1984).

6. Paur, R.J., and McElroy, F.F., "Technical Assistance Document for the Calibration of Ambient Ozone Monitors", US Environmental Protection Agency. Report EPA-600j4-79-057, 69 P (1979).

7. Fleming, H.E., and Hill, M.L., "An Objective Procedure for Dectecting and Correcting Errors in Geophysical Data: lOne-Dimensional Applications", J. Geophys. Res., 87, 7312-7324 (1982).

8. Attmannspacher, W., and R. Hartmannsgruber, "Intercomparison of Instruments measuring Ozone near the Ground at the Hohenpeissenberg Observatory 1 October, 1978 - 30 April, 1979", Berichte des Deutschen Wetterdienstes, 161, pp 1-14 (1982).

9. Ga1ba11y, I., "Some Measurements of Ozone Variation and Destruction in the Atmospheric Surface Layer", Nature (Lond.)., 218, 456-457 (1968).

10. Galbal1y, I.E. and Roy, C.R., "Destruction of Ozone at the Earth's Surface", Quart. J. Roy. Meteoro1. Soc., 106, 599-620 (1980).

- 814-

L'OZONE SERAIT-IL L'OXYDANT PRINCIPAL DU SULFURE

DE DlMETHYLE EN MILIEU OCEANIQUE ?

P. CARLIER Laboratoire de Physico-Chimie Instrumentale Universite PARIS VII - 2, place Jussieu F - 75251 PARIS CEDEX 05 (France).

Les composes organo-soufres sont la principale source de.dioxyde de soufre en milieu oceanique non pollue. Le probleme du mecanisme deleur photooxydation n'est pas encore completement elucide. Pour mettre en accord certains resultats recemment publies, nous avons ete amene a formuler l'hypothese de l'existence d'un cycle catalytique d'oxydation du DMS par l'ozone impliquant les especes I"et 10·.

Introduction

En milieu oceanique non pollue, les composes organo-soufres d'origine biogenique et particulierement Ie sulfure de dimethyle sont les precurseurs principaux du dioxyde de soufre, et par consequent de la fraction du sulfate de l'aerosol qui ne provient pas directement de la mer par petillement.

Les mecanismes de l'oxydation du sulfure de dimethyle (DMS) dans la troposphere ont fait l'objet de nombreuses etudes, plus particulierement ces cinq dernieres annees, mais comme Ie montrera notre discussion, tous les resultats ne concordent pas et aucun mecanisme pleinement satisfaisant n'a encore ete demontre. Grace a des resultats nouveaux, obtenus a la Pointe de Penmarc'h en Bretagne, ou un tres grand champ d'algues emet loca­lement des quantites extremement importantes de composes organo-soufres dans une atmosphere tres peu polluee, il nous est possible d'emettre certaines hypotheses qu'il faudra verifier minutieusement, mais qui permettent aujour­d'hui de concilier certains resultats apparamment contradictoires.

Donnees Geochimiques

Des 1972, LOVELOCK et al. (1) avan~ait l'hypothese que l'ocean emettait d'importantes quantites de soufre reduit sous forme de DMS. Depuis, plusieurs equipes de geochimistes ont precise Ie flux d'emission global et la reparti­tion geographique de ces emissions (2-20). On peut aujourd'hui estimer que Ie flux total de DMS de l'ocean vers l'atmosphere est compris entre 28 et 360 Mt(S)/an. La repartition des emissions a la surface des mers est tres inegale, et en premiere approximation varie comme la production biogenique primaire. Grace a une etude du profil vertical de la concentration de DMS et de S02, NGUYEN et colI. (15,20) ont pu determiner une premiere estimation de l'ordre de grandeur de la duree de vie du DMS dans la basse troposphere

Ozone Symposium - Greece 1984 - 815-

qui serait d'environ un quart d'heure.

Donnees Cinetiques

On peut trouver dans la litterature des mesures de la vitesse de reaction du DMS avec quatre reactifs classiques de la troposphere : O·(3P), OR· , et NO)

- DMS + O· (3P) (21-25)

Malgre la forte reactivite de 0·(3P) (k ~ Sxl0- ll ), cette reaction n'intervient surement pas car 0·(3P) est beaucoup trop peu abondant.

- DMS + OR· (26-35)

03

si lIon excepte la valeur de WINE et al., on dispose de 4 mesures presque coherentes de la constante de vitesse (k ~ 9xl0-12). Tres recemment BARNES et al. (33) ont trouve que cette constante variait tres legerement avec la pression d'oxygene. Cependant la valeur de k = 9xl0- 12 et une concentration diurne typique de 2.106 radicaux/cm3 (36 7 37) pour OR· condui­sent a une duree de demi-vie de l'ordre de 20 h. pour Ie DMS.

- DMS + 03 (38)

La reaction directe est beaucoup trop lente et sa constante de vitesse n'a pu etre mesuree.

- DMS + NO) (35) NO) est probablement Ie responsable principal des transformations

chimiqtles nocturnes dans la troposphere (37,39-42). La constante de vitesse de la reaction DMS + NO) a ete, tout recemment, mesuree par ATKINSON et al. (35) : k = S,4xl0-13 • Comme la concentration nocturne de NO) peut etre elevee ~ 2 10 8 radicaux/cm3, on obtient alors une duree de demi-vie du DMS de l'oIdre de 3 h.

Donnees de la campagne a Penmarc'h (43-44)

Cette campagne a eu lieu du 12 au 30 Septembre 1983. Sa conception et les premiers resultats ont ete presentes au 3eme Symposium Europeen sur Ie Comportement Physico-Chimique des Polluants. L'ensemble des resultats sera publie par ailleurs. Outre l'analyse des composes organo-soufres en trois points de mesure, nous avons mesure egalement Ie S02,1'ozone, les oxydes d'azote et fait quelques tentatives de mesures des composes carbonyles. Par ailleurs, nous disposons de donnees meteorologiques classiques, tempe­rature, pression, humidite, direction et vitesse de vent, puissance de l' irradiation solaire.

Les conclusions principales sont les suivantes :

- Les concentrations de DMS observees sont, a l'abord du champ d'algues, souvent de plusieurs ordres de grandeurs superieuresau fond oceanique, tel qu'il a ete caracterise par d'autres equipes et tel que nous l'avons me sure a la Pointe du Raz, situe a 60 km dans une zone depourvue d'algues.

- Outre Ie DMS, trois autres composes organo-soufres ont ete identifies sans ambiguite : Ie sulfure de diethyle, Ie disulfure de dimethyle et l' ethanedithiol.

Le disulfure de dimethyle est surement un compose secondaire issu du DMS.

Les teneurs en aldehydes mesures pres du champ d'algues sont tres

- 816-

elevees pour Ie milieu naturel (par ex : 30 ppb CR20, 20 ppb CR3CRO) et sont comparables a celles d'un milieu urbain moyennement pollue. Ces fortes te­neurs ne s'expliquent que par la conversion des emissions du champ d'algues.

- La duree de demi-vie du DMS, estimee a partir des variations de con­centration relative du DMS et du DMDS entre les divers points de mesure, est tres courte (5 - 20 min.) et est en excellent accord avec les resultats de NGUYEN et al., compte-tenu des tres fortes incertitudes entachant neces­sairement ce type d'estimation. De ce fait, on n'observe pas de difference significative entre les valeurs diurnes et nocturnes.

Discussion

II est donc manifeste que ces resultats sont en desaccord avec l'hypo­these que l'etape determinante de la disparition du DMS soit l'attaque des radicaux OR' a la concentration de 2.106 radicaux/cm3. II faut donc envisa­ger l'intervention d'autres phenomenes.

- La concentration de 2.106 OR'/cm3, issue des modeles de LOGAN et al. (31) ou de WEINSTOCK et al. (36) est generalement consideree comme un maximum possible (atmosphere parfaitement calme, irradiation maximum) en l'absence de pollution hydrocarbonee. Comme justement, les teneurs en aldehydes mesu­rees sont assez elevees, on peut soup~onner une plus forte concentration en radicaux OR'. Cependant, atteindre une concentration de 108 OR'/em3 parait bien improbable.

- L~ reaction avec N03 semble effectivement expliquer une bonne partie des transformations chimiques de nuit, mais ne peut en aucun cas etre evo­quee pour les transformations de jour.

- Une explication plausible peut etre trouvee, en tenant compte du role possible d'un autre compose tres facilement photolysable, present dans les atmospheres marines: l'iodure de methyle (45-46).

Par photolyse CR31 donne deux radicaux CR3 et I'. CR3 va essentiel­lement contribuer a enrichir l'atmosphere en formaldehyde. Le role possible de l'atome d'iode dans la troposphere a ete discute par CHAMEIDES & DAVIS (41). Le phenomene qui nous importe Ie plus pour l'oxydation du sulfure de dimethyle est la formation d'espece IO'par la reaction:

IO'est un, oxydant energique de CO et NO

10' + NO -+ l' + N02 (k = 1, 7 10-11 ) 10 + CO -+ I' + CO2 (k = 10- 17)

gomparable a NO) NOj + NO -+ 2 N02 (k = 2xlO-1l )

NOj + CO -+ N02 + CO2 (k = 10-17)

On peut alors emettre l'hypothese que la reaction

CR3-S-CH3 + 10' -+ CR3-SO-CR3 + I' a une constante de vitesse du meme ordre de grandeur que

CH3-S-CR3 + NO~ -+ CH3-SO-CR3 + N02 c'est-a-dire 10-13~]0-12 Ainsi. on voit la possibilite de 1 'existence dation du DMS par l'ozone

d'un cycle catalytique d'oxy-

1" +

10' +

--+ 10' + 02

DMSO + I'

(1)

(2)

- 817-

Pour confirmer ou infirmer cette hypothese de travail, il convient maintenant de mesurer la constante de vitesse de la reaction (2) et d'esti­mer la valeur de la concentration de 10' dans la troposphere.

BIBLIOGRAPHIE

01 J.E. LOVELOCK, R.J. MAGGS & R.A. RASMUSSEN, N~e 231 (1912) 452. 02 B. BONSANG, B.C. NGUYEN & J.Y. PAUGAM, C.R.Aead.Sci:-P~ Se4.V. 283

(1916) 1285. -03 P.J. MAROULIS & A.R. BANDY, Scienee 196 (1911) 641. 04 B.C. NGUYEN, A. GAUDRY, B. BONSANG &~ LAMBERT, N~e 215 (1918) 631. 05 M.R. MOSS, Sources of Sulfur in the Environment :. The global sulfur

cycle. Dans: Sulfur in the Environment - Part. I, p. 23 ~. J.O. NRIAGU Ed., Wiley Int~e. (1918).

06 T.E. GRAEDEL, GeophY6. Re6. Lett. 6 (1919) 329. 01 D.F. ADAMS, S.O. FARWELL, M.R. PACK & W.L. BAMESBERGER, J. ~ Poti.

Co~o! A66oe. 29 (1919) 381. 08 V.P. ANEJA, J.M:-OVERTON Jr., L.T. CUPITT, J.L. DURHAM & W.E. WILSON,

Te!fu6 31 (1919) 114. 09 B. BON SANG , The6e de VoctotuU e6 Scienee6 ~ Univruile de P'£eMdi.e

24 MaJL6 1980. 10 C.F. CULLIS & M.M. HIRSCHLER, Atm. EnviAon. 14 (1980) 1263. 11 B. BON SANG , B.C. NGUYEN, A. GAUDRY & G. LAMBERT, J. Geophy6. Re6. 85

(1980) 1410. --12 D.F. ADAMS, S.O. FARWELL, E. ROBINSON, M.R. PACK & W.L. BAMESBERGER,

Env. Sci. Teeh. 15 (1981) 1493. 13 D.F. ADAMS, S.O.~ARWELL, M.R. PACK & E. ROBINSON, J. AiA Poti. Co~o!

A6Me. 31 (1981) 1083. 14 V.P. ANEJA, J.M. OVERTON & A.P. ANEJA, J. ~ Poti. Co~o! A66oe. 31

(1981) 256. --15 P. NADAUD, The6e de 3e Cye!e ~ Univ~ile PARIS VII (1981). 16 W.R. BARNARD, M.O. ANDREAE, W.E. WATKINS, M. BINGEMER & H.W. GEORGII,

J. GeophY6. Re6. 81 (1982) 8181. 11 B. BONSANG, La Recne4ehe 13 (1982) 1132. 18 M.O. ANDREAE, W.R. BARNARD--& R.J. FEREK, CACGP Sympo6ium on TltOpo6ph~e

Chem-<.6tJty, OX6oJtd 28.8 - 3.9.83, Communieation II~8. 19 H.G. BINGEMER & H.W. GEORGII, CACGP Sympo6ium on Tltopo6ph~e Chem-<.6tJty

Ox6oltd 28.8 - 3.9.83, Communieat-<-on 111-2. 20 B.C. NGUYEN, B. BON SANG & A. GAUDRY, J. GeophY6. Re6. 88 (1983) 10903. 21 I.R. SLAGLE, R.E. GRAHAM & D. GUTMAN, Int. J. Chern. Kinei. 8 (1916) 451. 22 J.H. LEE, R.B. TIMMONS & L.J. STIEFF, J. Chern. Phy4. 64 (19;6) 300. 23 J.H. LEE, I.N. TANG & R.B. KLEMM, J. Chern. PhY6. 12 (1980) 1193. 24 W.S. NIP, D.L. SINGLETON & R.J. CVETANOVIC, J. Ame4. Chern. Soe. 103

(1981) 3526. -25 R.J. CVETANOVIC, D.L. SINGLETON & R.S. IRWIN, J. Ame4. Chern. Soe. 103

(1981) 3530. -26 R. ATKINSON, R.A. PERRY & J.N. PITTS Jr., Chern. Phy~. Lett. 54 (1918) 14. 21 M.J. KURYLO, Chern. PhY6. Lett. 58 (1918) 233. --28 R.A. COX & D. SHEPPARD, N~~ 1r4 (1980) 330. 29 P.M. WINE, N.M. KREUTTER, G.A. GUMP & A.R. RAVISCHANKARA, J. Phy~. Chern.

85 (1981) 2660. 30 J.U. LEE & N. TANG, J. Chern. PhY6. 18 (1983) 6646. 31 H. Mc LEOD, G. POULET & G. LEBRAS, ~ Chim. PhY6. 80 (1983) 281. 32 H. Mc LEOD, J.L. JOURDAIN, G. POULET & G. LEBRAS, ~CGP Sympo4iUm on

TltopMph~e Chem-<.6tJty, OxOO!td 28.8 -·3.9.83, Communic.a.tion VI-2.

- 818-

33 H. Me LEOD, The6e de 3e Cycte, Univ~~e PARIS VII (1983). 34 I. BARNES, K.H. BECKER, E.H. FINCK, CACGP Sympo6ium on T~Op06ph~c

Chemi6~y, Ox6o~d 28.8 - 3.9.83, Communication VI-I. 35 R. ATKINSON, J.N. PITTS Jr., S.M. ASCHMANN, J. PhY6. Chern. !! (1984)

1584. 36 B. WEINSTOCK, H. NIKI & T.Y. CHANG, in Adv. Env. Sc. Techno~. Vo~. 10

p. 221 (J.N. PITTS g R.L. METCALF, Ed.), W~ey Int~c. (1980). --37 J.A. LOGAN, M.J. PRATHER, S.L. WOFSY & M.B. Me ELROY, J. GeophY6. Re6.

86 (1981)- 7210. 38 R.I. MARTINEZ & J.J. HERRON, Int. J. Chem. Kine.t. 10 (1978) 433. 39 R.A. GRAHAM & H.S. JOHNSTON,J. PUY6. Chern. 82 (197!T 254. 40 W.J. MARINELLI, D.W. SWANSON & H.S. JOHNSTON,J. Chern. PhY6. ~ (1982)

2864. 41 R. ATKINSON, C.N. PLUM, W.P.L. CARTER, A.M. WINER & J.N. PITTS Jr.,

J. Chern. PhY6. 88 (1984) 1210. 42 R. ATKINSON, C.~ PLUM, W.P.L. CARTER, A.M. WINER & J.N. PITTS Jr.,

J. Chern. PhY6. 88 (1984) 2362. 43 P. CARLIER, C. LUCE, R. GIRARD, G. MOUVIER, J. MORELLI, L. GIRARD­

REYDET, T. MARCHAL & S. CADENE, 3eme Sympo6ium 6Ult ~e compMiernent phY6ico-chimique dec po~uant6 a.tmo6ph~que6. Vane6e 10~12.4.84.

44 C. LUCE, P. CARLIER, R. GIRARD, H. HANNACHI, P. FRESNET & G. MOUVIER, Al'Uttuei6 (1984) ¢Due p~e66e.

45 J.E. LOVELOCK, R.J. MAGGS & R.J. WADE, N~e 241 (1973) 194. 46 R.A. RASMUSSEN, M.A.K. KHALIL, R. GUNAWARDENA ~.D. HOYT, J. GeophY6.

Re6. 87 (1982) 3086. 47 W.L. CHAMEIDES & D.D. DAVIS, J. GeophY6. Re6. ~ (1980) 7383.

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OZONE PRODUCTION AND TRANSFER IN THE FOS-BERRE BASIN AREA

G.TOUPANCE and P.PERROS Laboratoire de Physico-Chimie de l'Environnement

Universite Paris Val de Marne, Av. Gen. de Gaulle, F 94000 CRETEIL

Summary : During the 1983 European Campaign of Fos-Berre, the local ozone pollution survey network (5 analysers) have been completed by measurements on 3 sites distant of about 30-50 km far from the industrial area. A regional analysis of the set of data is performed with respect to meteorological para­meters. The Fos-Berre area appears to be one of the major source of photooxi­dant pollution in the region (Ozone concentration of 230 ppb have been measu­red). Medium range transport of ozone have been evidenced and local peak concentrations have been tentatively interpreted.

1. INTRODUCTION During the 6th. European Campain of Atmospheric Pollu­tion held in the Fos-Berre harbor agglomeration in June 83, we proposed to evaluate the behaviour of ozone at a regional scale. Our purpose was to understand the process of photooxidant pollution in the Fos -Berre area. We wanted qlso verify in what extend the industrial zones of the basin act as a source of ozone, formed within the plume and transported to downwind areas, as it has been studied in the case of north-eastern U.S (6-7) , or as a sca­venger for preexisting ozone, as it has been shown in certain cases in north­eastern Europe (3-4). A description of the area can be found elsewhere (1-2).

2. SELECTION OF STUDIED AREAS Important meteorological and physico­chemical means were installed within a radius of 10 km around Berre basin during the campaign. In addition, two well equipped air pollution monitoring networks operate continuously in the area. We chose to complete the whole network by carrying out ozone measurements in three rural sites, supposed to be influenced by the emission of pollutants from the industrial areas. This allowed us to follow the evolution of the ozone composition of the plume in two downwind transfert cases: 1). S to SE wind system ( Baux de Provence) and 2). SW wind system (St. Cannat and Sommet du Luberon). The exact locali­sation of the sites is shown in fig. 2.

3. MEASUREMENTS AND METEOROLOGY Ozone was measured by a U.V absorption method using Environnement SA apparatus. The meteorological and other (S02, NoX, HC, Aerosols ... ) data used in this study were provided by the permanent monitoring network and by other teams participating in the campaign. The meteorological caracterisation of the area and the description of the situa­tions encountered during the campaign were provided by AUGUSTIN et al (2).

4. RESULTS AND INTERPRETATION An initial analysis of the results is presented in this paper. The high diurnal ozone profiles during the campaign are shown in fig.l. Sharp and intense morning peaks of ozone in the eastern area of the basin (Vitrolles, Rognac and St. Cannat), as well as in the rural areas of Baux and Luberon can be noticed. These profiles can be interpreted in terms of four major parameters : -Background level. The rural areas clearly presented a background level of

50 ppb. This level is usually encountered, there, at an altitude between 300

Ozone Symposium - Greece 1984 - 820-

and 1200 m, whatever the meteorological conditions are. The situation obser­ved on June 6 tho at 6.00 am (fig 2) is significant of a nocturnal situation: background levels in the three rural areas and low levels in the industrial area. In rural area no diurnal cycle was observed with a few exceptions which will be discussed later on.

- Local sources of ozone scavengers. The analyser installed at Marseille was located in the center of the city. The discharge of NO emitted by traffic appears to be permanently higher than photochemical ozone production. The ozone level remains low, as it has been previously observed in other great urban centers (4-8-9). Rognac is located at sea level in the vicinity of Berre industrial area. The strong nocturnal stability of the atmosphere in this part of the basin confines the industrial emissions in the lower air layer, leading to total consumption of existing ozone during the night: noc­turnal concentrations of ozone, in order of 5 ppb only, are therefore often registred in Rognac. On the contrary, the analyser at Port de Bouc, installed at a height of 60 m above sea level, was placed in an atmospheric section less supplied, during the night, of ozone scavengers. For this reason the nocturnal ozone concentration in Port de Bouc is usually higher than in other industrial areas. The residential area of Vitrolles, situated at a height of 40 m, although at the immediate proximity of Rognac, presented an interme­diate nocturnal situation. All these results show that the intensity of the observed minima throughout the ozone profiles can mainly be attributed to the intensity of local sources of reducing agents that lead to ozone scavenging. - Convection. Ground level ozone concentrations are strongly governed by

convection (3-4-5-9). Low ozone levels, observed during the night in some areas, are due to negligible nocturnal convection associated with local sources of scavengers. During the day, the convection has two opposite effects. The first is that it leads air massee,rich in ozone,to the ground level. The second effect is the dilution of primary pollutants emitted by industrial sources in a mixing layer whose height increases during the day, therefore influencing the rate of photochemical ozone production. This pro­cess will not be discussed in detail here ; we will recall it, however, in order to interprete some episodes in Vitrolles and Rognac.

- Transport. The observations carried out in the three rural sites clearly evidence ozone transports. Fig.2 shows the evolution of the concentration in the area during the daytime at June 6. The wind system is established as SW from 10 h on. The plume, rich in ozone, that was observed in Vitrolles at 10 am is carried down to St Cannat during the day where it is observed at 11 h-12 h , and it reaches Luberon at about 15 h. A this moment, the highest ozone concentration of all sites is observed at the top of Luberon. This si­tuation lasted until about 6 pm. It should be noted that transport observa­tion at the top of Luberon supposes a development of the mixing layer up to 1000 m. In all cases, this phenomenon may delay the hour of maximum observa­tion at the summit with respect to the normal transfer duration. In certain cases it is possible that the plume is blocked in lower altitude.

A sharp ozone peak at Baux at noon was simultaneously observed (fig.1). The sharpness of the peak and the fact that Baux was downwind of the Berre basin since 9-10 am led us to reconstitute the air masses trajectory, using all the available data concerning the velocity and direction of the wind at ground level. Fig.3 shows the trajectories of the air masses reaching Baux respectively at 10 h, 12 h, 14 h. It can be noted that the air mass that was slowly transported above the industrial sites during the night reached Baux at noon. The observed ozone was produced in large part by photochemical

- 821-

process within the plume during the morning. This situation, however, was short-lived, due to the rapid rotation of the winds, after the sea-breeze system has been established : earlier, Baux was supplied with air coming from the east ; later, it is the non polluted sea air that reaches the site.

The situation in Baux at the 7 th was very different (fig. 1). The average wind direction (2) is fixed to SE. the site is downwind of the Fos­Berre basin and concentrations clearly higher than background level are ob­served all day long : the profile is broad and concentrations in the order of 100 ppb or more are observed for many hours. In the same time, no particu­lar accident was detected in Luberon.St Cannat was not downwind of the Fos­Berre basin ; the concentrations observed that day are clearly lower than the other days.

During the study, the only day when the wind blowed from the west was June 9 tho A very high ozone concentration in Vitrolles and Rognac was then observed. It was also the only day when a hight ozone concentration was de­tected in St Baume. The trajectory of the air mass reaching St Baume at 2 am. appears in fig 4. Despite the difficulties in making such a reconstitution (very instable breeze at night,insufficient meteorological data for the zone of nocturnal transit), it appears that the air mass passed for a first time over the Berre basin in daytime of June 8 th., then over the industrial centre of Gardanne during the night, to pass a second time over the Berre basin in the morning of the 9 tho A subsidence in the centre of the basin can probably be associated with a pond breeze observed at 9 am.(10). It can be assumed that the air mass passing around 8 am. over the basin is reintroduced at ground level by this subsidence. The particularly high ozone level obser­ved in Vitrolles-Rognac could have been produced photochemically at high altitude during the first morning hours within the air layer rich in ozone precursors, for a first time on June 8 tho over the basin and for a second time over Gardanne during the night. The briefness of the episode can be con­nected on the one hand to the briefness of the pond breeze phenomenon, and on the other hand to the dilution within the mixing layer, due to an increa­sing convection during the morninq.

5. CONCLUSIONS The observed ozone profiles over the area during the study result from the competition of many factors : background level, sources of ozone scavengers, precursors sources, photochemistry, convection and transport. In the early morning, an intense photochemistry with high produc­tion of oxidants occurs within the high layers rich in 03 precursors, which are typically situated at an altitude of 100 to 300 m. At ground level, the accumulation, during the night, of an important stock of reducing agents slows down the ozone production. Ozone peaks occur when ozone produced in high altitude is injected in the mixing layer because of the increase in the mixing layer height. The disappearance of the peak is due to both homogeni­sation by convection and displacement of the air masses. These effects can be accentuated according to the history of air masses and to specific phenomena, such as the pond breeze. Long distance transports have been observed, indica­ting that high ozone levels can be observed far away from any sources of precursors of photochemical pollutants.

We intend to analyse further the fransfer process as soon as the whole wind data concerning the study zone will be available.

Acknowledgement : This study was supported by the Ministry of the Environne­ment, contract No 83 133.

- 822-

REFERENCES. (1) - PERRIN M.L., MADELAINE G.,FRAMBOURG C., Third European symposium on Physico-Chemical Behaviour of Atmospheric Pollutants, Varese, Italy, April 1984, Preprints Volume, p. 1. (2) - AUGUstIN H. et BESSEMOULIN P. Ibid p. 541. (3) - SCHERER B., STERN R., i~ proceeding of Second Symposium on Behaviour of Atmospheric Pollutants, Varese, Italy, Sept 1981, D. REIDEL Pub. Co Edit., 1982, p. 561. (4) - Van DUREN H., ROMER F.G., Ibid p. 460. (5) - LOPEZ A., PRIEUR 5., FONTAN J., KIM P.S., Ibid p. 362. (6) - CLEVELAND W.S., KLEINER B., Mc RAE J.E., WARNER J.L.(1976) Sciences 91,179 (7) - CLARK T.L., CLARKE J.F. (1984), Atmospheric Environment 18,287 (8) - BENARIE M., BENECH A., CHUONG B.T., MENARD T. (1979), 81, 44. (9) - TOUPANCE G., Rapport de contrat No 78 142, Ministere de l'Environnement France, 1981. (10) - SOL B. Resume des conditions meteorologiques au cours de la Campagne Fos-Berre, Polygraphie, 3p, Juin 1983 .

..... ... IO'

" ... '" .. ... ...

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)\

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,-

Figure

1 ... .. 1 1

;/\ ",'.I\. ~ -...... '.N -f .. ! .. • ~ i-I. ).. -,

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tll 1: 't 1\ Ll L ~ J .\-. ~ ~ . J • /1- Ih Il fr....... f:.....

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-.. •

Ii l

\.. I!'\ ...... J>..... A""..

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rr. ~ n f.I. k ''''\ ~" t':vo. J L J \. J 1. ~ V '.1 \ J;n J , ~ -V

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• '"'" ~~"'" -J' .....f, ...... f--F ., -... • rv I -- f..J .... i"V" I ....... IJ ~ It'"'" V

Diurnal ozone profiles during the campaign.

- 823-

IN

6 .JUIN 6 H (TUl

10 KH : 03,00_ :

13 HIS : ..........

........

~

12 H (TU)

'0 I<H :

........

IN ../

6 .)UIN 10 H (TUl

,0 I<H : 03 100 PP8 ~

t5N/S: """"-

9f 1~ H (TU)

10 KM : O • 100 PP8 :

.. MIS : """'--

Figure 2 Ozone distribution over the studied area on June 6.

Figure 3 : Air mass trajectories reaching Baux at 10 am(- -),12 am(-) and -14am(---1 on June 6.

4_ STE BAUME

Figure 4 : Air mass trajectory reaching Vitrolles at 10 am and St Baume at 14 am on June 9.

xxx x

Industrial areas

- 824-

LIS T 0 F PAR TIC I PAN T S

- 825-

AIMEDIEU, P. Service dlAeronomie du C.N.R.S. BP 3 F - 91370 VERRIERES LE BUISSO~

ALAMICHEL, C. CNRS Laboratoire de Photophysique Mo lec ula ire Batiment 213, Universite Paris-Sud F - 91405 ORSAY

ALEKSANDROV, E. Institute of Experimental Meteorology 82, Lenin St. USSR - 249020 OBNINSK

AMANATIDIS, G. Mitropolitoy Fotioy 13 GR - 61100 KILKIS

ATTMANNSPACHER, W. DWD - Meteqrological Observatory Hohenpeissenberg Albin Schwaiger - Weg D - 8126 HOHENPEISSENBERG

AUSTIN, J. UK MET Offi ce London road GB - BRACKNElL, BERKS, RG12 2SZ

BAIS, A. University of Thessaloniki Physics department Camp.ls Box 149 GR - THESSALONIKI

BARBE, A. Laboratoire de Physique MoLeculaire Faculte des Sciences de Reims B.P. 347 F - 51062 REIMS CEDEX

BASHER, R.E. New Zealand Meteorological Service P.O. BOX 722 NEW ZEALAND - WELLINGTON

BASS, A.M. National Bureau of Standards Chemi stry B-364 USA - WASHINGTON D.C. 20234

BHARTIA, P.K. Systems and Applied Sciences Corpo­ration 5809 Annapolis Road USA - HYATTSVILLE - MARILAND 20784

BELMONT, A. Control Data P.O. Box 1249 USA - MINNEAPOLIS MN 55418

BOJKOV, R.D. Atmospheric Environment Service of Can. 4905 Dufferin Street CAN - DOWNSVIEW, ONTARIO M3H 5T4

BOWMAN, K.P. Laboratory for Atmospheres, NASA, Goddard Space Flight Center - Code 613 USA - GREENBELT, MD 20706

BRARD, D. ONERA F - 92320 CHATILLON/BAGNEUX

BRASSEUR, G. Institut d'Aeronomie SpatiaLe 3, avenue Circulaire B - 1180 BRUSSELS

-826 -

BRAUN, W. Laboratory for Atmospheric Physics, ETH Hoenggerberg CH- 8093 ZUERICH

BREWER, D.A. Systems and Applied Sciences Corporation 17 Research Drive USA - HAMPTON, VIRGINIA 23666

CACHO, J. Comision Nacional De Investiga­cion Del Espacio Pso Pintor Rosales 34 E - MADRID 28008

CALLIS, L.B. NASA - LANGLEY MS 401B USA - HAMPTON, VA 23434

CARIOLLE, D. Direction de la Meteorologie EERM Avenue Eisenhover F - 31057 TOULOUSE

CARLIER, P. Laboratoire de Physique Chimie Instrumentale 2, place Jussieu F - 75251 PARIS CEDEX 05

CHAKRABARTY, D.K. Physical Research Laboratory INDIA - AHMEDABAD 380009

CHANG, J. NationaL Center for Atmos­pheric Research P.O. Box 3000 USA - BOULDER, CO 80307

CHLICHLIA, K. Leoforos MegaLou Alexandra 43 A GR - THESSALONI~I

CHUBACHI, S. Japan Meteorological Research Inst. Nagamine 1-1, Yatabe, Tsukubagun JAPAN - IBARAKI 305

CIATTAGLIA, L. ItaLian MeteoroLogical Service Vigna di VaLLe Observatory I - 00062 BRACCIANO - ROME

CISNEROS, J .M. CONIE Po Pintor RosaLes 34 P.O. Box 8346 E - MADRID 28008

COFFEY, M.T. NationaL Center for Atmospheric Research P.O. Box 3000 USA - BOULDER, COLORADO 80307

COLBECK, I. British Antartic Survey High Cross Madingley Road GB - CAMBRIDGE CB3 OET

CONNELL, P.S. Lawrence Livermore NationaL Laboratory P.O. Box 808 USA - LIVERMORE CALIFORNIA 94550

DAUMONT, D. UA 776 Spectrometrie MoLeculaire et Atmospherique - Univ. de Reims BP 347 F - 51062 REIMS CEDEX

- 827-

DE LA NOE, J. Observatoire de Bordeaux Av. P. Semi rot BP 21 F - 33270 FLOIRAC

DE MUER, D. MeteoroLogicaL Institute of BeLgium RingLaan 3 B - 1180 BRUSSELS

DEQUE, M. Centre NationaL de Recherche MeteoroLogique Avenue CorioLis F - 31057 TOULOUSE

DE RUDDER, A. Institut d'Aeronomie SpatiaLe 3, avenue CircuLaire B- 1000 BRUXELLES

DE ZAFRA, R. Department of Physics State University of New York USA - STONY BROOK, NEW YORK

DIAMOND, G. Atmospheric Environment Service 4905 Dufferin St. CAN - TORONTO, ONTARIO, M3H 5TH

DIERICH, P. Observatoire de Meudon 5 pLace JuLes Janssen F - 92195 MEUDON - PRINCIPAL

DIONYSSIOS, M. University of Ioannina GR - iOANNINA

DUETSCH, H.U. Laboratory for Atmospheric Physics, ETH, HPP Hohggerberg CH - 8093 ZUERICH

FABIAN, P. Max-PLanck-Institut fur Aeronomie Postfach 20 D - 3411 KATLENBURG-LINDAU-3

FARMER, C.B. Jet PropuLsion Laboratory CaLifornia Institute of TechnoLogy 4800 OAK Grove Drive USA - Pasadena, CaLifornia 91103

FEISTER, U. MeteoroLogicaL Service of the GDR, Main MeteoroLogicaL Observatory TeLegrafenberg D - 1500 POTSDAM

FIOCCO, G. Dipartimento di Fisica Citta Universitaria I - 00185 ROMA

FLEIG, A.J. Laboratory for Atmospheric Science Goddard Space FLight Center USA - GREENBELT, MARILAND - 20771

FREEMAN, D.E. Harvard - Smithsonian Center for Astrophysics 60 Ga rden St. USA - CAMBRIDGE, MASSACHUSETTS

FROMENT, G. Centre NationaL de Recherches MeteoroLogiques 42, avenue Gustave CorioLis F - 31057 TOULOUSE CEDEX

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GALBALLY, I. CSIRO Atmospheric Research Private BAG 1 MORDIALLOC AUSTRALIA - VICTORIA

GAMACHE, R. The Center for Atmospheric Research The University of Lowell Research Foun. 450 Aiken Street USA - MASSACHUSETTS 01854

GAY, C. Centro de Ciencias de la Atmosfera UNAM Giudad Universitaria MEXICO - MEXICO 04510 D.F.

GHAZI, A. Commission of the European Communities, DG XII Science; Research and Development 200, rue ~e la loi B - 1049 BRUXELLES

GIL, M. Comision Nacional de Investi­gacion del Espacio Rosales 34, P.O. Box 8346 E - MADRID 28008

GIRARD, A. ONERA F - 92320 CHATILLON

GOLDMAN, A. Department of Physics University of Denver University Park USA - DENVER, COLORADO 80208

GOEMER, D. Technische Hochschule Darmstadt Hochschul str. 1 D - 6100 DARMSTADT

GORDLEY, L. Systems and Applied Sciences Corporation 17 Research Drive USA - HAMPTON, VIRGINIA

GRAY, L. Atmospheric Physics Department, Oxford University Clarendon Laboratory, Oxford Univ. GB - OXFORD

GR EENHUT, G. K. NOAA Environmental Research Laborato­ries 325 Broadway USA - BOULDER COLORADO 80303

GYGAX, H.A. Laboratory for Atmospheric Physics ETH Honggerberg D - 8093 ZUER ICH

GYGER, R. Institute of Applied Physics University of Berna Sidlerstr. 5 CH - 3012 BERN

HAIGH, J. D. Centre for Remote J ensing, Imperial College of Science and Technology Blackett Laboratory GB - LONDON SW7 2BZ

HARTMANNSGRUBER, R. DWD Meteorologisches Observatorium Mohenpeissenberg Albin-Schwaiger-Weg 10 D - 8126 HOHENPEISSENBERG

HASEBE, F. Laboratory for Climatic Change Researct Geophysical Institute, Kyoto Univers. Kitashirakawa, Sakyo-Ku JAPAN - KYOTO, 606

- 829-

HASSAN, G.K.Y. MeteoroLogicaL Authority of Egypt Kobbry EL Qobba P.O. ET - CAIRO

HEATH, D. F. NASA/Goddard Space FLight Center USA- GREENBELT, MARYLAND 2077

HELTEN, M. ICH - 2 KernforschungsanLage J uL i ch GmbH Postfach 1913 D - 5170 JUELICH

HILSENRATH, E. NASA/Goddard Space FLight Center Code 616 USA - GREENBELT MD 20708

HJORTH, J. Commission of the European Communities, Joint Research Centre, ISPRA I - ISPRA 21020

HOFMANN, D.J. Dept. of Physics and Astronomy University of Wyoming USA - LARAMIE, WYOMING 82071

HUDSON, R. NASA/HQ Code EE USA - WASHINGTON, D.C. 20546

HUSSON, N. CNRS Laboratoire de Meteoro­Logie Dynamique - EcoLe PoLy technique Route DepartementaLe 36 F - 91128 PALAISEAU CEDEX

ILYAS, M. SchooL of Physics Universiti Sains MaLaysia MALAYSIA - PENANG

ISAKSEN, I. University of OsLo Blindern OsLo Boks 1022 N - OSLO 3

IWAGAMI, N. Geophysics Research Laborato­ry, University of Tokyo 113 Bunkyo-Ku JAPAN - TOKYO

KAPLAN, L.D. Atmospheric and EnvironmentaL Research, Inc. 840 MemoriaL Drive USA - CAMBRIDGE, MASSACHUSETTS 02139

KAWAHIRA, K. GeophysicaL Institute of Kyoto University Kitashi rakawa Sakyo~u JAPAN - KYOTO 606

KELESSIS, A. University of ThessaLoniki, Laboratory of Atmospheric Physics Physics Dept. Campus Box 149 GR - THESSALONIKI

KERR, J. B. Atmospheric Environment Service 4905 Dufferin Street CAN - DOWNSVIEW ONTARIO M3H5T4

KESSLER, C. Institut F. Phys. Chemie WegeLerstr. 12 D - 5300 BONN

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KIEHL, J. N.C.A.R. P .0. Bo x 3000 USA - BOULDER, CO

KLAIS, O. Hoech st AG Postfach 80 03 20 D - 6230 FRANKFURT

KLENK, K. F. Systems and AppLied Sciences Corpora­tion 5809 AnnapoLis Road USA - HYATTSVILLE, MD 20784

KNAPSKA, D. KernforschungsanLage JuLich GmbH Institut Fur Chemie 3 Postfach 1913 D - 5170 JUELICH

KOEHLER, U. DWD MeteoroLogisches Observato­rium Hohenpeissenberg ALbin-Schwaiger-Weg 10 D- 8126 HOHENPEISSENBERG

KOMHYR, W.D. NOAA/GMCC NOAA-Air Resources Laboratory R /ElAR4 USA - BOULDER, COLORADO 80303

KONDO, Y Research Institute of Atmos­pherics, Nagoya University Honochara 3-13 JAPAN - TOYOKAWA

KOVALEV, V. Main GeophysicaL Observatory Karbysheva, 7 USSR - LENINGRAD

KRUEGER, A.J. NASA/Goddard Space FLight Center Code 614 USA - GREEBELT, MD 20771

KRUEGER, B.C. Max-PLanck-Institut F. Aeronomie KatLenburg-Lindau Postfach 20 D-3411 KATLENBURG-LINDAU

KUNZI, K. Inst. App. Physics University of Bern SidLerstrasse 5 CH - 3012 BERN

LAL, S. Max PLanck Institute Fur Aeronomi e Postfach 20 D - 3411 KATLENBURG-LINDAU

LAMB, K. SCI-TEC Instruments Inc. 1526 FLetcher Road CAN - SASKATOON, SASK S1M5M1

LARSEN, S.H. Institute of Physics University of OsLo 0316 BLindern N - OSLO 3

LAURENT, S. Office NationaL dlEtudes et Recherches AI'! rospa tia Les 29, avo du GeneraL LecLerc F - 92320 CHATILLON

LEAN, J. CIRES, University of CoLorado/NOAA NOAA/ERL/ARL, R/E/ARXZ 325 Broadway USA - BOULDER CO 80303

- 831-

LEROY, B. Laboratoire de Physique et Chimie de l'Environnement 3A, avenue de la Rech. scientifique F - 45045 ORLEANS CEDEX

LEVY II, H. Geophysical Fluid Dynamics Laboratory NOAA P.O. Box 308 USA - PRINCETON, NEW JERSEY 08542

LONDON, J. Department of APAS University of Colorado Box 391 USA - BOULDER-COLORADO

LOSIOWA, A. Institute of Geophysics Polish Academy of Sciences Pasteura 3 , P. O. Box 155 PL - 00973 WARSAW

LOUISNARD, N. ONERA F - 92320 CHATILLON/BAGNEUX

LOVILL, J.E. Lawrence Livermore National Laboratory, University of California USA - LIVERMORE, CALIFORNIA 94550

LUDWIG, F.L. SRI International 333 Ravenswood Ave. USA - MENLO PARK, CALIF 94025

MAEDA, K. NASA/Goddard Space Flight Center Code 696 USA - GREENBELT, MARYLAND 20771

MALICET, J. U.A. Spectrometrie Moleculaire et Atmospherique Univers. de Reims - B.P. 347 F - 51062 REIMS CEDEX

MANTIS, H. University of Minnesota School of Physics and Astronomy, Church St. USA - MINNEAPOLIS MN 55455

MARAGOS, D. SICNG S.A. Diavata Region GR - THESSALONIKI 10183

MARCHE', P. Universite de Reims BP 347 F - 51062 REIMS

MATEER, C. Atmospheric Environment Service 4905 Dufferin St. CAN - DOWNSVIEW-ONTARIO

MATSUZAKI, A. The Institute of Space and Astronautical Science Komaba 4-6-1, Megu ro - Code 153 JAPAN - TOKYO

MATTHEWS, W.A. PEL Atmpspheric Station D.S.I.R. Private BAG NEW ZEALAND - AMAKAU, CENTRAL OTAGO

MAUERSBERGER, K. University of Minnesota, School of Physics and Astronomy 148 Physics Building USA - MINNEAPOLIS, MiNN 55455

- 832-

McELROY, C. Atmospheric Environment Service 4905 Dufferin St. CAN - DOWNSVIEW, ONTARIO M3H5T4

McKENZIE, R .L. Department of Atmospheric Physics, University of Oxford, Clarendon Lab. GB - OXFORD OX1 3PU

McPETERS, R .D. NASA/Goddard Space Flight Center Code 616 USA - GREENBELT, MD 20771

MEGIE, G. Service d'Aeronomie CNRS BP 3 F - 91370 VERRIERES LE BUISSON

MI LLER, A. NOAA/National Weather Service/Climat~ Analysis Center 5200 Auth ROJd, RM 201 USA - WASHINGTON, DC 20233

MISKOLCZI, F. University of Calabar, Department of Physics P.M.B. NIGERIA -1115 CALABAR

MOE, K. Department of Geological Sciences California State University USA - FULLERTON, CA 92634

MULLER, C. Bel~ian Institute for Space Aeronomy Avenue Circulaire, 3 B - 1180 BRUSSELS

MULLER, S. Centre National de Recherches Meteorologiques 42, avenue Gustave Coriolis F - 31057 TOULOUSE CEDEX

MUNZERT, K. Inst. for Atmospheric Environ­mental Research Kreuzeckbahn Str. 19 D - 81 GARMISCH-PARTENKIRCHEN

MURCRAY, D.G. University of Denver Physics Department USA - DENVER, COLORADO 80208

NASTROM, G.D. Control Data Corporation USA - MINNEAPOLIS, MN 55440

NATARAJAN, M. Systems and Applied Sciences Corporation 17 Research Drive USA - HAMPTON VIRGINIA 23666

NAUDET, J.P. Laboratoire de Physique et de Chimie de l'Environnement 3A, avenue de la Recherche scientifique F - 45045 ORLEANS CEDEX

NEWELL, R.E. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology USA - CAMBRIDGE, MA 02139

NOXON, J.F. NOAA Aeronomy Laboratory 325 Broadway,R/E/AL5 USA - BOULDER, CO 80302

- 833-

OELHAF, H. PeteoroLogisches Institut Universitat Munchen Theresienstr. 37 D - 8000 MUENCHEN 2

OLTMANS, S.J. GeophysicaL Monitoring for CLimatic Change/ERL/NOAA 325 Broadway USA - BOULDER CO

OVENDEN, M. Dept. of Atmospheric Physics Oxford University The Queen's CoLLege GB - OXFORD OX1 4AW

OWENS, A. E.A. du Pont de Nemours and CO E 304, Du Pont CO USA - WILMINGTON, DE 19898

PALLISTER, R.C. UK MeteoroLogicaL Office London Road GB - BRACKNELL, BERKS RG12 2SZ

PELON, J. Service d'Aeronomie du CNRS BP 3 F - 91370 VERRIERES-LE-BUISSON

PERROS, P. L.P.C.E. Universite de CreteiL Avenue du GeneraL de GauLLe F - 94010 CREITEL CEDEX

PETROPOULOS, B. Research Center for Astronomy and AppLied Mathematics, Athens Academy 14 AnagnostopouLou GR - ATHENS

PICKETT, H.M. Jet propuLsion Laboratory, CaLifornia Institute of TechnoLogy, USA - CALIFORNIA, PASADENA

PIRRE, M. Laboratoire de Physique et Chimie de L'Environnement/CNRS 3 A, avenue de La Recherche Scientifique F - 45045 ORLEANS CEDEX

PLANET, W. NOAA E/RA21 NOAAiNESDIS USA - WASHINGTON DE 20233

POMMEREAU, J.P. CNRS, Service d'Aeronomie BP 3 F - 91370 VERRIERES-LE-BUISSON

PROFFITT, M.H. Aeronomy Lab. NationaL Oceanic and Atmospheric Administration 325 Broadway MS R/E/AL6 USA - BOULDER, COLORADO 80303

PYLE, H.A. Rutherford AppLeton Laboratory, Atmospheric Sciences Group GB - CHILTON, DIDCOT, OXFORDSHIRE

RAMASWAMY, V. NCAR P.O. Box 3000 USA - BOULDER, CO 80307

REPAPIS, C.-Academy of Athens Research Center For Atmospheric Physics and CLimat. 3rd September Street 131 GR - ATHENS 11251

- 834-

RESTELLI, G. Commission of the European Commu­nities - Joint Research Centre Ispra Establishment I - 21020 ISPRA <VA)

RIGAUD, P. Laboratoire de Physique et Chimie de l 'Envi ronnement 3A, avenue de la Rech. Scientifique F - 45045 ORLEANS

ROBBINS, D. NASA - Johnson Space Center NASA - JSC Mail Code SN3 USA - HOUSTON, TEXAS 77058

ROTTMAN, G. Laboratory for Atmospheric and Space Physics-Univers. of Colorado Space Science Building USA - BOULDER, COLORADO 80309

ROWLAND, F.S. Department of Chemistry - University of Califormia USA - IRVINE, CALIFORNIA 92717

RUSCH, D.W. Laboratory for Atmospheric and Space Physics, University of Colorado Campus Box 392 USA - BOULDER, COLORADO 80309

ROSCOE, H.K. RUSSELL III, J.N. Clarendon Laboratory, Dept. of Atmos-NASA pheric Physics, Oxford University Langley Research Center GB - OXFORD OX1 3PU N.5 401 B

ROSE, K. Institut fur Meteorologie Freie Universitat Dietrich-Schater-Weg 6-10 D - 1000 BERLIN 41

ROSSBY, S. NOAA Office of Aircraft Operations P.O. Box 020197 USA - MIAMI,FLORIDA 33102-0197

ROTHE, K.W. Sektion Physik University of Munich Am Coulombwall 1 D - 8046 GAR CHING

ROTHMAN, L.S. Optical Physics Division Air Force Geophysics Laboratory USA - HANSCOM AFB, MA 01731

USA - HAMPTON VA 23665

SAINZ-DE-AJA, M.J. Comision Nacional de Investigacion del Espacio Pintor Rosales nO 34, P.O. Box 8346 E - MADRID 22008

SCHMAILZL, U. Max-Planck-Institute for Chemistry Air Chemistry Department SAAR St. 23, P.O. Box. 3060 D - 6500. MAINZ

SCHMIDT, M. Max-Planck-Institut Fur Aeronomie Max-Planck-Str 1 D - 3411 KATLENBURE-LI~AU

SCHMIDT, U. Kernforschungsanlage~uelich GmbH Institut fur Chemie 3 Postfach 1913 D - 5170 JUELICH

-835 -

SCHURATH, U. Institut fur PhysikaLische Chemie Universitat Bonn WegeLerstr. 12 D - 53 BONN 1

SIGERU, C. MeteoroLogicaL Research Institute 1-1 Nagami ne JAPAN - YATABE TSUKUBAGUN 305

SIMON, P. Institut d'Aeronomie SpatiaLe de BeLgique 3, avenue CircuLaire B - 1180 BRUXELLES

STEINBERGER, E.H. Dept. Atmospheric Sciences, the Hebrew University ISRAEL - JERUSALEM 91904

STRONGYLIS, G. CCE, DG XI, Environnement, protec­tion des consommateurs et sec. nucLe. 200, rue de La Loi 1049 - BRUXELLES

SUBBARAYA, B. PhysicaL Research Laboratory Nava rangapura INDIA - AHMEDABAD 380009

SUNDARARANAN, N. WorLd MeteoroLogicaL Oraganization CH - 1211 GENEVA 20

SZE, N.D.

THOMAS, G. E . L.A.S.P. University of CoLorado USA - BOULDER, CO 80309

THOMAS, R. University of CoLorado L.A.S.P. USA - BOULDER, COLORADO

TOSHIHIRO, O. Geophysics Research Laboratory, University of Tokyo Bunkyo-Ku JAPAN - TOKYO 113

TOUPANCE, G. Lab. Physicochimie de L'Environnement Universite Paris-VaL-DE-Marne Avenue du GeneraL de GauLLe F - 94000 CRETEIL

TRAINER, M. Aeronomy Laboratory NOAA and Cooperative Inst. F. Research in Envi ron. Sciences 325 Broadway MS : RiEiAL4 USA - BOULDER, COLORADO 80303

TSALKANI, N. Laboratoire de Physicochimie de L'Envi­ronnement, Univ. Paris-VaL-De-Marne Avenue du GeneraL de GauLLe F - 94010 CRETEIL CEDEX

TSIKOYDI, V. Department of Astro-geophysics, University of Ioannina GR - IOANNINA

Atmospheric and EnvironmentaL Incorporation

Research,TUNG, K.K.

840 MemoriaL Drive USA - CAMBRIDGE, MA 02139

Department of Mathematics, M.I.T. RM 2 - 332 USA - CAMBRIDGE, MA

- 836-

USHER, P.E. United Nations Environment Programme UNEP P.O. Box 30552 KENYA - NAIROBI

VAROTSOS, C. Niliforou Ouranou 7 GR - ATHENS

VASSY, A. C.N.R.S. 110, Quai Louis Bleriot F - 75781 PARIS CEDEX 16

VAUGHAN, G. University College of Wales Aberrystwyth Physics Dept. U.C.W. GB - ABERYSTWYTH, DYFED

VERSINO, B. Commission of the European Communities, Joint Research Centre - ISPRA I - 21020 ISPRA <VA)

VUPPUTLRI, R .K.R. Atmospheric Environment Servi ce, Canada 4905 Dufferin St. CAN - DOWNSVIEW, ONT

WALSHAW, C.D. Dept. of Atmospheric Physics Clarendon Laboratory Parks Road GB - OXFORD OX1 3PU

WANG, P.H. Institute for Atmospheric Optics and Remote Sensing P.O. Box P. HAMPTON USA - VIRGINIA 23666

WANG, W.C. Atmospheric and Environ­mental Research, Inc. 840 Memorial Drive USA - CAMBRIDGE, MA 02139

WATSON, R.T. NASA Code EE 600 Independence Ave. USA - WASHINGTON, DE 20546

WEINSTOCK, E. Harvard University, Atmos­pheric Research Project ESL, 40 Oxford St. USA - CAMBRIDGE, MA 02138

WUEBBLES, D.J. Lawrence Livermore National Laboratory P.O. Box 808, L - 262 USA - LIVERMORE, CALIF 94550

YAMAMOTO, H. Department of Physics, Rikkyo Universe 3-34-1, Nish-lkebukuro JAPAN - TOSHIMA-KU, TOKYO, 121

ZEREFOS, C. University of Thessaloniki Physics Department Campus Box 149 GR - THESSALONIKI

ZlOMAS, I. University of Thessaloniki Physics Department Campus Box 149 GR - THESSALONlKI

-837 -

INDEX OF AUTHORS

ACCKERMAN, M. ; (212) AIMEDIEU, P. : (349, 514) AINSIDRI'H, J. ; (454) ALAMICHEL, C. : (144, 149, 210) ALBRITTON, D.L. ; (759) AMODEI, M. ; (216) ANDER300, J.G. ; (475) ANDER300, S. ; (493) ARABOV, A.Ya. ; (157) ASBRIDGE~ LA. ; (381) ATTMANNSPACHER, W. : (402, 450, 454, 770)

BAlS, A.F. : (269, 353, 686, 788) BANGHAM, M. ; .(144, 149) BARBE, A. ; (442) BARRETT, J.W. ; (206, 428) BASHER, R.E. ; (387) Bl\SS, A.M. ; (606, 611) BAUDRY, A. ; (417) BEIG, G. ; (357) BELMONT, A.D. ; (300) BESSON, J. ; (212) BHARTIA, P.K. ; (229, 243, 253, 311, 625) BOJKOV, R.D. ; (11, 335,775, 808) BORCHERS, R. ; (129, 134) BOUGHNER, R.E. ; (48, 72) BOWMAN, K.P. ; (363) BRARD, D. ; (77) BRASSEUR, G. ; (28, 92) BRAUN, W. ; (594) BRAVO, J.L. ; (38) BREWER, D.A. ; (715, 745) BRION, J. ; (617) BRODER, B. ; (765) BROWELL, E.V. ; (745)

CACHO, J.I. ; (344) CALLIS, L.B. ; (48, 72) CAMAY-PERET, C. ; (149) CAPPELLANI, F. ; (725) CARIOLLE, D. ; (24, 77)

- 839-

CARLI, B. : (144) CARLIER, P. ; (815) CAYLA, F.R. ; (585) CHAKRABARTY, D.K. ; (357) CHAKRABARTY, P. ; (357) CHANCE, K. ; (144) CHEDIN, A. ; (432) CHING, J.K.S. ; (745) CHOPRA, A.N. ; (305, 499) CHUBACHI, S. ; (285) CISNEROS, J.M. ; (519) C~UDE, H. ; (770) COFFEY, M.T. ; (149, 151) COLBECK, I. ; (750) COI.M:Nr, J .M. ( 417 ) CONNELL, P.S. ; (61) CRUTZEN, P.J. ; (43)

mUMJNT, D. : (617) mVIES, R.W. ; (635) DE LA NOE, J. : (417) DE MUER, D. : (330) rE RUDDER, A. ; (92) DE ZAFRA, R.L. ; (206, 428) DEEPAK, A. ; (589) DELUISI, J.J. ; (290,311,316) DEX:lUE, M. : (24) DIERICH, P. ; (417) DlNELLI, B. ; (144) DOUGLAS, M.D. ; (809) DOETSCH, H.U. ; (263, 594) IXJFOOR, B. ; (216)

EHHALT, D.H. ; (196) ELANSKY, N.F. ; (157, 563) ELOKHOV, A.S. ; (157) ELSWORTH, C.M. ; (809) ESMOND, J.R. ; (622) EVANS, R.D. ; (371) EVANS, W.F.J. ; (144, 149, 151, 381,396,407, 454 465 481 680)

FABIAN, P. ; (129, 134) FAHEY, D.W. ; (759) FEHSENFELD, C. ; (759 ) FEISTER, U. ; (438, 504, 782) FILKIN, D.L. ; (82) FIOCCO, G. ; (353) FLAUD, J.M. ; (149) FLEIG, A.J. ; (229, 243, 253, 258) FRANCOIS, P.R. ; (499) FREDERICK, J.E. ; (321) FREEMAN, D.E. ; (622) FROMENT, G. ; (216)

GAGE, K.S. ; (580) GALBALLY, I.E. ; (809) Gl\MACHE, R.R. : (635) GARCIA, T.E. ; (305) GAY, C. ; (38) GHAZI, A. ; (589) GILLE, J.C. ; (168, 258) GIL, M. : (344) GIRARD, A. i (212) GOEMER, D. ; (129) GOLDMAN, A. : (144,149,151,442) GORDLEY, L.L. ; (139, 168) GRASNICK, K.-H. ; (504) GRASS, R.D. ; (371, 376) GRAY, L.J. ; (173) GRUZDEV, A.N. ; (563) GUSHCHIN, G.P. ; (543) GYGAX, H.A. ; (765) GYGER, R. ; (423)

HAIGH, J.D. ; (33) HALES, C.H. i (82) HANS, W. i (640) HARRIES, J.E. ; (66) HARRISON, R.M. ; (750) HARTMANN, G.K. ; (423) HARTMANNSGRUBER, R. ; (402, 450, 770) HASEBE, F. ; (553) HASSAN, G.K.Y. ; (532) HEATH, D.F. ; (412, 666) HELTEN, M. ; (196) HILL, M.L. i (234) HILSENRATH, E. ; ( 454 ) HJORTH, J. ; (725) EDFMANN, D.J. ; (353) EDLLAND, A. i (454) HUGUENIN, D. ; (201, 509, 630) HUSSCN, N. ; (432)

ILYAS, M. ; (274, 791) rIDH, T. ; (486) IWAGl\roU, N. ; (149) IWA.TA, A. ; (175, 180)

- 840-

JACKMAN, C.H. ; (676) JASPERSON, W.H. ; (580) JAYARAMAN, A. ; (295) JEBSEN, C. ; (117,122) JOHNEN, F.J. ; (122) JOHNSTON, P.V. : (163) JOLLIER, J.P. (585)

KA-KIT TUNG, : (19) KANTER, H.-J. i (735) KARCHER, F. ; (216) KASlMOVSKAYA, E.E. ; (720) KAWAHlRA, K. ; (558, 568) KERRIDGE, B.J. i (149, 173) KERR, J.B. : (381,396,407, 481, 680) KESSLER, C. ; (640) KHEDIM, A. ; (122) KIEHL, J. T • ; (1 03 ) KLENK, K.F. ; (625) KNAPSKA, D. ; (117, 122) KO, M. ; (19) KOEHLER, U. ; (402) KDMHYR, W.D. ; (305, 316, 371, 376, 454, 499) KClIDO, Y. ; (175, 180) KOSTERS, J.J. ; (144, 151) KOVALYOV, V.A. ; (543) KRUEGER, B.C. ; (129) KRUEGER, A.J. ; (188, 239) KUENZI, K.F. ; (423) KULESSA, G. ; (117, 122)

LAL, S. ; (129, 134, 295) LARSEN, S.H.H. ; (392) LASZIO, I. ; (708) LAURENT, J. ; (212) LEAN, J.L. ; (697) LEMAITRE, M.P. ; (212) LEONARD, R.K. ; (305, 371) LEVINE, J.S. ; (715) LEVY II, H. ; (730) LEVY, R. ; ( 803 ) LIENESCH, J.H. ; (234) LINDSAY, J.M. ; (258) LING, X. ; (53) LIPPENS, C. ; (212) LIRITZIS, Y. ; (691) LIU, S.C. ; (759) IDHSE, C. ; (725) LONDON, J. ; (53) LOUISNARD, N. ; (144, 149, 151, 210, 465) LUDWIG, F.L. ; (740)

MAEDA, K. ; (248) MAKINO, T. ; (522)

MALICET, J. ; (617) MANKIN, W.G. ; (149, 151) MANTIS, H.T. : (353) MAo-rou WU, ; (548) MARCAULT, J. ; (216) MARIOLOPOUIDS, E.G. ; (788) MATEER, C.L. ; (3, 290, 311, 316, 335, 407) MATSUZAKI, A. ; (486) MATTHEWS, W.A. ; (115, 175, 180, 341, 514) MAUERSBERGER, K. ; (454, 493) MEGIE, G. ; (325) MENI'AIL, J. ; (454) MEYER, J.P. ; (216) MILIER, A.J. ; (321, 454) MILLER, C. ; (82) MISKOLCZI, F. ; (708) MIY~A, A. : (754) IDE, K. ; (661) MOFF~, P.H. ; (66) MONNANTEUIL, N. ; (417) MONOSMITH, B. ; (243, 625) MORITA, Y. (180) MORlW, J. ; (493) MULLER, C~ ; (212) MULLER, S. ; (585) MUNZERT, K. ; (735) MURCRAY,D.G. ; (144, 151, 442) MURCRAY, F.J. ; (149, 442) MUmIY, D. ; (493) McCORMICK, M.P. ; (258) McELROY, C.T. ; (149, 222, 396) Mcc~, M. ; (82) McFEE, C. ; (305) McKENZIE, R.L. ; (163) McPETERS, R.D. ; (184, 676)

NA~ANI, R.M. ; (321) NAKAMURA, Y. ; (486) NASTROM, G.D. ; (580) NATAAAJAN, M. ; (48, 72 ) NAUDET, J.P. ; (201,509) NEWELL, R.E. ; (548) NICOLET, M. ; (646) NIEN OAK SZE, ; (19)

OGAWA, T. ; (149, 754) OLAFSON, R.A. ; (396) OLTMANS, S.J. ; (305, 499, 796) Ol"IOBRINI, G. ; (725) OWENS, A.J. ; (82)

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PAETZ, W. ; (196) PARK, H. ; (412) PARKINSCN, W.H. ; (622) PARRISH, A. ; (206, 428) PARRISH, D.O. ; (759) PAUR, R.J. ; (606, 611) PELON, J. ; (325) PENKETT, S.A. ; (117, 129) PEROV, S.P. ; (527) PERRaS, P. : (820) PETERS, G. ; (504) PETROIDULOS, R. ; (691)' PI-HUAN WANG, ; (600) PIBIRI, G. ; (279) PICCIOLI, S. ; (144) PIRRE, M. ; (630) PLANET, W.G. ; (229, 234) PLESSING, P. ; (504) IDETZL, K. ; (735) IDLLITT, S. ; (144, 149, 151,465) PCM1EREAU, J .-P. ,"; (149) POROIKOVA, A. I. : (720) PROFFITT, M.H. ; (454, 470) PYLE, J.A. ; (66, 173)

RAMASWNMY, V. ; (702) RANDACCIO, P. ; (279) REINSEL, G.C. ; (775) REITER, R. ; (735) REMSBERG, E.E. ; (139, 168) REPAPIS, C.C. ; (788) RESI'EILI, G. ; (725 ) RIGAUD, P. ; (201,509,514,630) ROBBINS, D.E. ; (454, 460, 465) ROBERTS, J.M. ; (759) RCETH, E.P. ; (196) ROSCOE, H.K. ; (149, 173) I03E, K. ; (28) IDTHE, K.W. ; (.446, 450) ROTHMAN, L.S. ; (635) ROTTMAN, G.J. ; (656) RUDOLPH, J. ; (117) RUSCH, D.W. ; (258) RUSSELL III, J.M. ; (48, 72, 139, 168, 258)

SAINZ DE AJA, M.J. ; (344) SCHILLER, C.M. ; (475) SCHLESINGER, B.M. ; (666) SCHMAILZL, U. ; (43) SCHMIDT, M. ; (671) SCHMIDT, U. ; (117, 122)

SCHURATH, U. ; ( 640 ) scarr, N.A. ; (432) SECROUN, C. ; (442) SEKIGUCHI, H. ; (522) SEMENIUK, G.M. ; (371) SENIK, I.A. : (157) SERRA, A. ; (279) SHIPLEY, S.T. : (745) SILBERSTEIN, D. : (243) SMYSHLYAEV, S. P • ; ( 720 ) SOKOLENKO, S.A. ; (543) SOUAI, A. ; (279) SOLOMON, P.M. ; (206, 428) STANGL, H. : (725) STEINBERGER, E.H. ; (803) SUBBARAYA, B.H. ; (295)

TAKAGI, M. : (175, 180) ~E, V.L. ; (720) ~YLOR, S. ; (454) TISHIN, S.V. ; (527) TORRES, A. : (454) ~ANCE, C. ; (820) TRAINER, M. ; (759) TRAUB, W. ; (144, 465) TURATI,.C. ; (417)

VAROTSOS, C. ; (788) VAUGHAN, G. : (572) VERCHEVAL, J. ; (212) VOLB:NI, A. ; (144) VOPPUTURI, R.K.R. ; (59, 104)

WALSHAW, C.D. ; (9) WALTHER, H. : (446, 450) WANG, P.-H. : (589) WARDLE, D.I. ; (396, 680) WARMDT, W. ; (782) WATERS, J. ; (465) WEI -CHYUNG WAN;, ; ( 98 ) WEINSTOCK, E.M. ; (454, 475) WEISENSTEIN, D. : (19) ~~LLS, R.J. : (173) WERNER, J. ; (446, 450) WILLIAMS, W.J. ; (151) WONG, C.K. ; (253) WUEBBLES, D.J. ; (61, 87)

YAMAMOTO, H. ; (522) YOSHINO, K. : (622)

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~ER, R. ; (144) ZAVODY, A.M. ; (66) ZEREFOS, C.S. ; (269, 353, 686, 788) ZIOMAS, J.C. ; (269, 353, 686, 788) ZOOMI\KIS, N. ; (353) ZVENlGORODSKY, S.G. : (720)