HEMISPHERIC-SCALE CHEMICAL ANDMICROPHYSICAL AEROSOL MODEL

Stephen E. Schwartz, Carmen M. Benkovitz,

Robert McGraw and Douglas L. Wright, Jr.

Upton, New York

DOE Atmospheric Chemistry ProgramAnnual Science Meeting

Alexandria VA

30 Nov. - 2 Dec. 1999

OUTLINERecap on GChM-O (Global Chemical Model driven by Observation-

derived meteorological data)

Application of GChM sulfur chemistry in CCM3 (Collaboration withNCAR)

Disproportionate influence of volcanic sulfur on sulfate burden

Recent model advances

Recap on using the Method of Moments to represent aerosol microphysics

Obtaining aerosol integral properties from moments

Application of Method of Moments to hemispheric scale calculations inGChM-O

Representing cloud microphysics by the Method of Moments

Theory: Examination of ternary NH3 - H2SO4 - H2O nucleation

Ongoing and future work and Collaborations

CHEMICAL AND MICROPHYSICAL AEROSOL MODEL

DRIVEN BYOBSERVATION-DERIVED METEOROLOGICAL DATA

OBJECTIVESDevelop, evaluate, and apply models describing the chemicaland microphysical properties of atmospheric aerosolsresulting from energy related and other activities on ahemispheric geographical scale.

METEOROLOGY

Winds

Clouds

Precipitation

ECMWF

TRANSPORT

Bott/Easter

EMISSIONS

NAPAP

EMEP

Dignon

Bates/Lamb

DRY DEPOSITION

Wesely

WET DEPOSITION

Berkowitz/Hales

CHEMISTRY

Gas

Aqueous

SO2 + OH [OH] Spivakovsky/LoganDMS + OH DMS chem Yin/Seinfeld

SO2 + H2O2 [H2O2] SeasonalSO2 + O3 [O3] Seasonal

COMPONENTS OF THE TRANSPORT - TRANSFORMATION - REMOVAL MODEL

DMSSO2

MSASO4

2-

Anthropogenic

Anthropogenic

Anthropogenic

Anthropogenic

by Production Mechanism

Gas phase

Aqueous

Phase

Primary

October 15, 1986 at 6 UT

Sulfate Column Burden

COMPARISON OF MODEL AND OBSERVATIONSTypical comparisons for 24-hr Sulfate mixing ratio at surface

[SO

42- ],

pp

b

453015

Date Oct/Nov 1986

model

obs'd

14

5

10

0

[SO

42- ],

pp

b

453015

Date Oct/Nov 1986

model

obs'd

14

5

10

0

[SO

42- ],

pp

b

453015

Date Oct/Nov 1986

model

obs'd

14

5

10

0

[SO

42- ],

pp

b

453015

Date Oct/Nov 1986

model

obs'd

14

5

10

0

MANITOBA, CANADA DEUSELBACH, GERMANY

JARCZEW, POLANDJUNGFRAUJOCH, SWITZERLAND

Statistics of Comparisons

NMedianSpread

Obs-Obs 503 1.5Model-Obs

Same locations503 1.9

Model-ObsAll locations

7907 2.3

Benkovitz and Schwartz, JGR, 1997

Rasch, Barth, Kiehl, Schwartz, Benkovitz, JGR, in press, 1999

ANTHROPOGENIC SULFATE COLUMN BURDENBNL Sulfate Model in NCAR CCM3

Zonal Seasonal Cycle

J F M A M J J A S O N D

Kiehl et al., JGR, in press

ANTHROPOGENIC SULFATE DIRECTSHORTWAVE FORCING, ANNUAL AVERAGE

BNL Sulfate Model in NCAR CCM3

Global Mean, -0.56 W m-2

Kiehl et al., JGR, in press

SHORTWAVE FORCING, ANNUAL AVERAGEBNL Sulfate Model in NCAR CCM3

GHG's + O3 + Sulfate (Direct and Indirect)

Two Formulations of Cloud Droplet Concentration

Kiehl et al., JGR, in press

Average Emissions Flux, June 1 to July 25, 1997

Location and Magnitude during ACE-2 Time FrameVOLCANIC SULFUR EMISSIONS

Expressed as Average over ¥ 1˚ Grid Cell1˚

6%

66%

28%

Contribution to

Emissions Sulfate Burden

12%

84%

4%

Volcanos Contribute Disproportionately to Sulfate Burden

Aerosol Chemical Transport Model GChM-O

MomentsMicrophysical PropertiesOptical Properties

METEOROLOGY

Winds

Clouds

Precipitation

ECMWF

1°× 1°, 27 levels

TRANSPORT

Bott/Easter

EMISSIONS

Sulfur species

Primary Sulfate

DMS Daily

Seasalt aerosol

Smith, O'Dowd

DRY DEPOSITION

Time, Locationdependent

Size Resolved

Wesely

WET DEPOSITION

Berkowitz/Hales

CHEMISTRY Gas Phase

Aqueous Phase

SO2

AEROSOL MICROPHYSICSNucleationCoagulationGrowth (clear air, cloud)

Method of Moments - McGraw

SO2 + OHDMS + OH DMS chem Yin/Seinfeld

→ H2SO4

HO2 +HO2 → H2O2

SO2 + H 2O2SO2 + O 3

→ H2SO4→ H2SO4

O3, OH, HO2, Daily MOZART (Brasseur et al.)

(Rate Constants NASA, 1997)

Global Chemistry Model Driven by Observation-Derived Meteorological Data

Version 1Version 2Version 3

DMSSO2

MSASO4

2-

AEROSOL DYNAMICS BY THEMETHOD OF MOMENTS

The method of moments is an approach todescribing aerosol properties and dynamics in terms ofthe moments µk of the radial number size distributionf r( ).

µkk

r f r dr= ∞∫0 ( )

Aerosol properties (e.g., light scattering coefficient)can be accurately represented as simple functions oflow order moments.

Aerosol dynamics can be represented by growth laws(differential equations) in the moments.

The moments advect and mix just like chemicalspecies--they are conserved and additive.

Hence representing aerosol properties and dynamics in3-D transport models is equivalent to representing asmall number of additional chemical species.

METHOD OF MOMENTSHeuristic Description

Consider accretion of monomer by existing aerosol.

This can be considered a reaction between monomer(m) and aerosol surface area (A)

m A slightly larger distribution

Rate =

+ →kmA

Aerosol surface area density is

A r f r dr= ∫ =∞π πµ20 2( )

So accretion of monomer by existing aerosol is areaction between monomer and second moment.

LIMITATION TO THEMETHOD OF MOMENTS

GROWTH LAW RESTRICTION

For exact closure of the moment evolution equationsthe growth law must be of the form:

φ( )rdr

dta br≡ = +

where a and b are independent of r. Then integral isevaluated as:

r r f r dr a r f r dr b r f r dr

a b k

k k k

k

− −

−

∫ ∫ ∫= +

= +

1 1

1

φ

µ µ

( ) ( ) ( ) ( )

•This includes the important case of free-moleculargrowth, for which b = 0.

•For other growth laws the Quadrature Methodof Moments replaces exact closure with anapproximate but much less restrictive closurecondition.

QUADRATURE METHOD OF MOMENTS

INTEGRAL APPROXIMATION VIA n-POINT GAUSSIAN QUADRATURE

• The moments are evaluated as

µkk

ik

i

n

ir f r dr r w≡ ≅∞

=∫ ∑0

1( )

The abcissas (ri) and weights (wi) are specified in termsof the low-order moments of f(r).

• Quadrature-based closure is obtained by theapproximation

r r f r dr r r wkik

i ii

n− −

=∫ ∑≅1 1

1φ φ( ) ( ) ( ) ,

k ≥ 1

.

MOMENT INVERSION

Low order moments µk can be efficiently converted toquadrature abcissas ri and weights wi. For 3-point quadrature,6 moments are required.

• Once the abcissas and weights have been determined,the unknown distribution function integrals are obtainedby the summation.

McGraw, Aerosol Sci. Technol. 27, 255 (1997)

CALCULATIONS FOR DIFFUSIONCONTROLLED GROWTH

• For diffusional growthdr / dt = k / r

the moment evolution equations are not in closed form. One approachhas been to use assumed distributions parameterized in terms ofmoments (e.g. Laguerre).

Diffusion controlled growth of water drops for 20 s at T = 278 K andfixed saturation of 101%.

0.4

0 .3

0 .2

0 .1

0 .0NO

RM

ALIZ

ED

DE

NS

ITY

2 01 51 050PARTICLE RADIUS (µm )

Dotted curve: Initial normalized Khrgian-Mazin distribution with meanparticle radius of 5 µm.

Solid curve: Exact evolved distribution obtained by numericalcalculation.

Dashed-dotted curve: Laguerre distribution parameterized by themoments 0 through 2 obtained by the Laguerre closure method.

McGraw, Aerosol Sci. Technol. 27, 255 (1997)

QMOM CALCULATIONS FORDIFFUSION CONTROLLED GROWTH

• Quadrature MOM permits calculation of the evolution of the momentsdirectly, without a priori assumptions about the form of the evolvingdistribution.

5000

4000

3000

µ 4

500

400

300

µ 3

60x103

50

40

30

µ 5

Exact QMOM Laguerre

60

50

40

µ 2

7

6

5

µ 1

20151050

TIME(s)

McGraw, Aerosol Sci. Technol. 27, 255 (1997)

DISTRIBUTIONS USED IN TEST OF RETRIEVALOF OPTICAL PROPERTIES FROM MOMENTS

D. L. Wright, Jr., J. Aerosol Sci., in press, 1999

SYNTHESIS OF OPTICAL PROPERTIESFROM MOMENTS OF SIZE DISTRIBUTION

Multiple Isomomental Distribution Aerosol Synthesis (MIDAS) Method(Six moments, µ0 - µ5)

Extinction Coefficient Asymmetry Parameter Normalized Forcing

Exact, 632.8 nmSynthesized, lognormal, 632.8 nmSynthesized, modified gamma, 632.8 nmSynthesized, modified gamma, solar spectrum

D. L. Wright, Jr., J. Aerosol Sci., in press, 1999

SIZE OF SULFATE PARTICLESDependence on Latitude, Longitude, Altitude

Mediterranean Sea, October 15, 1986, 1200 UTC

Particle mean radius is proportional to radius of disk, 10-250 nm.

D. Wright, unpublished

AEROSOL SULFATE, October 22, 1986Method of Moments in Subhemispheric Model

(32 m)

(32 m)

Number10

5

104

103

102

10

1

µm

µm

cm-3

W m-2

r = µ /µ1 0_

r = µ /µ3e 2

Forcing

0.01

0.1

1

10

0

0.1

0.2

0.3

0.4

0.50

0.1

0.2

0.3

0.4

0.5

conc.

Mean

radius

radius

Effective

0µ

(ambient)

(32 m)(ambient)

TOA

Wright, McGraw, Benkovitz & Schwartz, GRL, submitted, 1999

AEROSOL SULFATE, October 22, 1986Method of Moments in Subhemispheric Model

Columnvolume

Ambient

(dry)

(0-1 km)

Columnvolume

(ambient

r/rdry

NormalizedForcingForcing

W

10

100

1000

g(SO )2-4

-1

2

3

1

0.1

0.01

0.001

0.0001

0.1

0.01

0.001

0.0001

cm m-23

cm m-23

to dryradiusratio

sulfatecolumnburden

Forcing per

RH)

Wright, McGraw, Benkovitz & Schwartz, GRL, submitted, 1999

CLOUD DROPLET ACTIVATION FROM MOMENTS OF AEROSOL SIZE DISTRIBUTION

Multiple Isomomental Distribution Aerosol Synthesis (MIDAS) Method

D. L. Wright and R. L. McGraw, to be submitted

AMMONIA INFLUENCE ON SULFURIC ACID NUCLEATION THRESHOLD

Korhonen P., M. Kulmala, A. Laaksonen, Y. Viisanen, R. McGraw, and J.H. Seinfeld,Ternary nucleation of H2SO4, NH3, and H2O in the atmosphere, JGR, accepted, 1999.

COLLABORATIONS

Helsinki, Kuopio,London, Caltech

Examine nucleation mechanisms and rates

NCAR Incorporate BNL chemistry model in CCM3 toexamine direct and indirect forcing

Purdue Evaluate model by comparison of model outputand satellite data

NOAA PMEL Interpret modeling results during ACE-2 campaignCaltech, Irvine Incorporate moment methods into regional aerosol

models and compare with alternative approachesDuke Incorporate moment method into GFDL GCM to

examine aerosol forcing for various scenariosCompare moment and bin methods in low-dimensional calculationsApply moment methods to evaluation of regionalscale PM 2.5

LLNL Implement aerosol microphysics in LLNLchemical transport model

CURRENT ACTIVITIES/FUTURE PLANS

• GChM-O Version 2 (Sulfate Mass, Enhanced Chem, 360° Long, 0-81° Lat)

ACE-2 (June 1 - July 25, 1997, Northern Hemisphere). Model runsunderway.

ACE-1 (Nov 1 - December 15, 1995, Southern Hemisphere). Shortly.

• Develop enhancements to representation of aerosol microphysicalproperties.

• Incorporate additional species: Seasalt, Dust, Carbonaceous

• GChM-O Version 3 (QMOM for Aerosol Properties)

ACE-2 Sulfate, Seasalt, Dust

ACE-1 Sulfate and Seasalt

• Collaborate with others in applying these methods.

COMPARISON WITH OBSERVATIONS!