Harmonisation of stratospheric NO2/O3 column data products

NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 1

F. Hendrick and M. Van Roozendael

Belgian Institute for Space Aeronomy (IASB-BIRA), Brussels, Belgium

+ NDACC UV-VIS Working Group

Context• NDACC UV-vis Working Group meeting at British Antarctic

Survey in November 2007:

« There is a need to harmonize stratospheric O3 and NO2 column retrievals »

• Main reasons:

• Lack of consistency between the stations due to the use of different DOAS settings (e.g., NO2 XS at different temperature) and AMFs

• Satellite groups encountered problems in the validation of their data using the NDACC UV-vis database, e.g. Wetzel et al., ACP, 2007 for the validation of MIPAS NO2

NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 2

Harmonisation of O3 column retrieval:

1. DOAS settings

NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 3

Parameter Recommendation

Fitting interval 450-550 nm

Wavelength calibration solar atlas

Cross sections

O3 Bogumil et al. (2003), 223°K

NO2 Vandaele et al. (1998), 220°K

H2O Hitran 2004 (Rothman et al., 2005)

O4 Hermans (http://spectrolab.aeronomie.be/o2.htm)

Ring effect NDACC source for Ring effect correction

Molecular and aerosol scattering

Polynomial of order 3, or equivalent non-polynomial high-pass filtering

AMF calculation BIRA-IASB O3 AMF LUTs

Determination of residual amount in reference spectrum

Langley plot (Vaughan et al., 1997)

SZA range for twilight averaging of vertical columns

86-91°SZA

Harmonisation of O3 column retrieval:

2. O3 AMF look-up tables

NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 4

• TOMS V8 (TV8) ozone and temperature profile climatology (Bhartia, 2004; McPeters et al., 2007) + total O3 column dependence

Parameter Value

O3 profile TV8:-Latitude: 85°S to 85°N step 10°-Month: 1 (Jan) to 12 (Dec) step 1-Ozone column: 125 to 575 DU step 50 DU

Temperature and pressure profiles

TV8

Altitude grid 0 to 120 km step 1 km

Wavelength 440 to 580 nm step 35 nm

Surface albedo 0 and 1

Altitude 0 and 4 km

SZA 30, 50, 70, 80, 82.5, 85, 86, 87, 88, 89, 90, 91, and 92°

• LUTs, AMF extraction routine as well as DOAS settings publicly available at: http://uv-vis.aeronomie.be/groundbased

Validation of new retrieval settings

NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 5

V1

V2 Corr temp

Comparison to: Dobson at OHP (44°N, 5.5°E)

Amplitude of Dobson-SAOZ seasonal variation:

V1 6.9% SAOZ Yearly AMF

V2 3.2% SAOZ LUT AMF

Bias / Std Dev after temperature correction:

-1.2% ± 3.7%

Brewer at Sodankyla (67°N, 27°E)

Amplitude of Brewer-SAOZ seasonal variation:

V1 6.5% SAOZ Yearly AMF

V2 2.4% SAOZ LUT AMF

Bias / Std Dev after temperature correction:

1.9% ± 3.2%

Impact on the difference satellites - SAOZ

NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 6

Station TOMS GOME SCIA OMI-TOMS OMI-DOAS SCO 8.8/4.8 9.8/9.6 9.0/12.0 3.9/2.4 10.7/12.8 ZHI 8.2/4.9 9.3/6.4 9.6/15.3 6.0/8.4 6.7/11.3 SOD 10.8/6.3 11.0/8.3 2.9/6.0 6.3/4.0 3.5/5.6 OHP 8.0/4.7 4.9/1.2 3.0/2.8 7.7/3.4 4.0/2.0 REU 2.1/1.4 4.4/3.4 2.2/1.8 3.1/2.6 1.9/1.8 BAU 1.8/1.5 3.5/3.0 2.5/3.1 3.6/3.0 2.2/2.8 KER 3.9/2.8 1.9/2.0 1.7/3.1 2.2/1.7 2.2/3.7

•Reduced amplitude of seasonal variation

•Reduced bias

V1 Yearly AMF

V2 LUT AMF

More details on the recommendation and comparison studies in Hendrick et al., ACP, 2011

Harmonisation of NO2 column retrieval:

1. DOAS settings

NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 7

Parameter Recommendation

Fitting interval 425-490 nm

Wavelength calibration solar atlas

Cross sections

NO2 Vandaele et al. (1998), 220°K

O3 Bogumil et al. (2003), 223°K

H2O Hitran 2004 (Rothman et al., 2005)

O4 Hermans (http://spectrolab.aeronomie.be/o2.htm)

Ring effect Chance and Spurr (1997)

Molecular and aerosol scattering

Off-set correction

Polynomial of order 3 to 5 maximum, or equivalent non-polynomial high-pass filtering

Slope

AMF calculation BIRA-IASB NO2 AMF LUTs

Determination of residual amount in reference spectrum

Modified Langley plot (Vaughan et al., 1997)

SZA range for twilight averaging of vertical columns

86-91°SZA

Harmonisation of NO2 column retrieval:

2. Stratospheric NO2 AMF LUTs

NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 8

• LUTs, AMF extraction routine as well as DOAS settings publicly available at: http://uv-vis.aeronomie.be/groundbased

Parameter Values

Lambert et al.’s NO2 profile

climatology

-Latitude: 85°S to 85°N step 10°-Month: 1 (Jan) to 12 (Dec) step 1-Sunrise and sunset-Altitude range : 20-60 km

SAOZ balloon NO2 profile

climatology

-Latitude: tropics, mid- and high-latitudes-Resolved in seasons (spring, summer, fall, winter)-Altitude range: 12-20 km

Wavelength 350 to 550 nm step 40 nm

Surface albedo 0 and 1

Altitude of the station

0 and 4 km

SZA 10, 30, 50, 70, 80, 82.5, 85, 86, 87, 88, 89, 90, 91, and 92°

Lambert et al.’s climatology consists of a Fourier harmonic decomposition of UARS HALOE v19 and SPOT-4 POAM-III v2 NO2 profile data records.

NO2 questionnaire (1)

NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 9

NO2 questionnaire (2)

NORS/NDACC UV-VIS meeting, Brussels, 3-4 July 2012 10

Question Recommendation

• Correction for the variation of the stratospheric t° (around 220K) ?

Temperature correction using a simple monthly zonal climatology of temperature profiles. Could be coupled to the AMF climatology.

• Filtering of the data conta-minated by tropospheric NO2

Langley-plot method (data points not lying on 'smooth‘ lines indicate a tropospheric contamination)

• Explicit correction for the impact of the Ring effect on the NO2 SCDs ?

post-processing option, based on simple SZA parameterization

• Should we take into account the NO2 photochemistry and its impact on the AMF ?

Sensitivity tests needed. Explicit correction is rather complex to implement. Could be included in the error budget

• Best estimates of the random and systematic uncertainties ?

Random uncertainty derived from fitting residuals. Systematic uncertainty to be estimated off-line based on sensitivity studies. Should be performed for each station. Note that both errors must be provided separately according to GEOMS.

• AMF correction for the period affected by the Pinatubo aerosols ?

Sensitivity tests needed. Not easy to include in standard recommendations.

Impact of aerosols

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0

-5%

-10%

0

-5%

-10%

Satellites (TEMIS) - SAOZ

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GOME-2 - SAOZ SCIAMACHY-SAOZ

GOME-SAOZ OMI-SAOZ