1. 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 UMBC
Andreas Richter: Univ. of Bremen
Greg Huey: Georgia Tech
John S. Holloway: NOAA
May 28, 2009

2. Local AMF Calculation Radiative Transfer Model
Geometric AMF:
Radiative Transfer Model
(LIDORT)
Atmospheric Chemistry Model
(GEOS-Chem)
Shape factor
SO2 mixing ratio, CSO2(η)
eta (η)
dτ(η) Io IB
Earth Surface
Scattering weight
May previous AMFs have assumed a global uniform value.
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

3. SO2 Slant Column

4. Reference Sector Correction

5. 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

6. Shape Factor: GEOS-Chem vs In-situ
Differences would change AMF by <10%
In-situ platform
DC-8 & C-130

7. OMI SO2 AMF for 2006
Calculated at nm; Cloud Radiance Fraction < 0.2; SZA < 70
SCIAMACHY AMF at nm within 25%

8. Local AMF Increases Agreement with Aircraft
▲ INTEX-A
■ INTEX-B

9. SO2 Vertical Columns for 2006
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
Cloud Radiance Fraction < 0.2; SZA < 70

10. Sensitivity of Retrieved SO2 to ΔEmissions
GEOS-Chem SO2
changes by ×2
OMI SO2 AMF
changes < 30%

11. Fraction of Anthropogenic SO2

12. 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