Retrieval of SO2 Vertical Columns from SCIAMACHY and OMI: Air Mass Factor Algorithm

Development and Validation

Chulkyu Lee, Aaron van Dokelaar, Gray O’Byrne: Dalhousie Univ.Randall V. Martin: Dalhousie Univ. and Harvard-Smithsonian

Nickolay Krotkov: NASA Goddard and UMBCAndreas Richter: Univ. of Bremen

Greg Huey: Georgia TechJohn S. Holloway: NOAA

May 28, 2009

Local AMF Calculation

dτ(η)

IoIB

Earth Surface

Radiative Transfer Model(LIDORT)

Scattering weight

Calculate ω(η) as function of:• solar and viewing zenith angle (θs, θv) from OMI, SCIAMACHY

• surface reflectivity (TOMS Climatology) • pressure, aerosol from GEOS-Chem

• Clouds, O3 column from OMI, SCIAMACHY

For individual scenes

1

)()(T

dSAMFAMF G

Shape factor

SO2 mixing ratio, CSO2(η)

eta

(η)

2

)()(SO

airCS

Geometric AMF: )sec()sec( vsGAMF

Atmospheric Chemistry Model(GEOS-Chem)

ColumnsVertical

ColumnsSlantAMF

)(ln1

)( B

G

I

AMF

SO2 Slant Column

Reference Sector Correction

GEOS-Chem Simulation

GEOS-Chem v8-01-04 - GEOS-4, 30 η vertical levels, 2º latitude by 2.5º longitude - Based on EDGAR inventory - Regional inventories: NEI99, BRAVO, CAC, Streets, EMEP

Shape Factor: GEOS-Chem vs In-situDifferences would change AMF by <10%

In-situ platform DC-8 & C-130

0 2 4 6 8 10 12

1000

900

800

700

600

500

400

300

2000.0 0.8 1.6 2.4

0 2 4 6 8 10 12

1000

900

800

700

600

500

400

300

200

0.0 0.2 0.4 0.6

0 2 4 6 8 10 12

1000

900

800

700

600

500

400

300

200

0 2 4 6 8 10 12

1000

900

800

700

600

500

400

300

200

0 1 2 3

0 1 2 3

Pre

ssur

e [h

Pa]

SO2 Shape Factor [unitless]

INTEX-A: Land GEOS-Chem In-situ

12

152

1721268920978113704253617098138224

In-situ Mixing Ratio [ppbv]

SO2 Shape Factor [unitless]

INTEX-A: Ocean GEOS-Chem In-situ

8

3

3

45978117812181615

In-situ Mixing Ratio [ppbv]

3

3

2

4712121811121113182923

Pre

ssur

e [h

Pa]

SO2 Shape Factor [unitless]

INTEX-B: Houston GEOS-Chem In-situ

SO2 Shape Factor [unitless]

INTEX-B: North Pacific GEOS-Chem In-situ

31

316

353254197220161160115111127151106162283112

In-situ Mixing Ratio [ppbv]

In-situ Mixing Ratio [ppbv]

OMI SO2 AMF for 2006

Calculated at 313.2 nm; Cloud Radiance Fraction < 0.2; SZA < 70 SCIAMACHY AMF at 319.7 nm within 25%

Local AMF Increases Agreement with Aircraft

▲ INTEX-A■ INTEX-B

-0.3 0.0 0.3 0.6 0.9 1.2 1.5 1.8-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-0.3 0.0 0.3 0.6 0.9 1.2 1.5 1.8-0.3

0.0

0.3

0.6

0.9

1.2

1.5

1.8

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

OM

I SO

2 [D

U]

In Situ SO2 [DU]

- - - Reduced major-axis linear fit Y = 1.61X + 0.21 (r = 0.71)

Using constant AMF = 0.36

In Situ SO2 [DU]

- - - Reduced major-axis linear fit Y = 0.95X + 0.05 (r = 0.92)

SC

IAM

AC

HY

SO

2 [D

U]

- - - Reduced major-axis linear fit Y = 1.38X + 0.01 (r = 0.78)

With Old AMF

Using constant AMF = 0.88

- - - Reduced major-axis linear fit Y = 1.12X + 0.06 (r = 0.89)

With New AMF

SO2 Vertical Columns for 2006

Cloud Radiance Fraction < 0.2; SZA < 70

Correlation with

GEOS-Chem (GC)

: Globally r ~0.78

: ~0.84 over US

: ~0.83 over China

GC with OMI AMF within 10% GC with SCIAMACHY AMF

Sensitivity of Retrieved SO2 to ΔEmissions

GEOS-Chem SO2

changes by ×2

OMI SO2 AMFchanges < 30%

Fraction of Anthropogenic SO2

Summary

Local AMFs improve agreement of OMI and SCIAMACHY with in-situ

Validation of SO2 vertical columns from SCIAMACHY and OMI with airborne in-situ measurements for INTEX-A and B

: r = 0.9 Validation of GEOS-Chem SO2 shape factors with airborne in-situ measurements for INTEX-A and B : <10% change in AMF Large signal from anthropogenic emissions in retrieved SO2

columns