Development and Evaluation of SO2 Vertical Columns from OMI

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Development and Evaluation of SO2 Vertical
Columns from OMI
Chulkyu Lee, Aaron van Donkelaar, Gray OByrne
Dalhousie University Randall Martin, Dalhousie
and Harvard-Smithsonian Nickolay Krotkov, NASA
Goddard and UMBC Greg Huey, Georgia Tech John
Holloway, NOAA
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Air Mass Factor (AMF) Calculation Needs External
Info on Shape of Vertical Profile
Radiative Transfer Model
Atmospheric Chemistry Model
a-priori Shape factor
sigma (?)
SO2 mixing ratio CSO2(?)
Scattering weight
?(?) is temperature dependent cross-section
INDIVIDUAL OMI SCENES

• Calculate w(?) as function of
• solar and viewing zenith angle
• surface albedo, pressure
• cloud pressure, aerosol
• OMI O3 column

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Significant Agreement of Simulated and Measured
ProfilesDifferences Would Change AMF by lt10
Significant Agreement of Simulated and Measured
ProfilesDifferences Would Change AMF by lt10
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Seasonal Mean SO2 AMFs for OMI
DJF
OMI PBL AMF0.36
Radiative Cloud Fraction (lt0.2)
JJA
AMF (Unitless)
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Local AMF Increases Contrast Between Polluted and
Clean Regions
r 0.32 Decreases mean SO2 Column by 0.04 DU
Reference Sector Applied Radiative Cloud Fraction
(lt0.2)
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Changes Improve Agreement with INTEX-B Aircraft
Measurements
Using BL AMF (slope1.08, r0.66)
Using Local AMF (slope0.95, r0.92)
r20.56
Using lower trop AMF (slope 0.74, r0.67)
Using mid-trop AMF (slope 0.35, r0.73)
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Remaining Differences with GEOS-Chem to Understand
r 0.32 Bias -0.02 DU
Reference Sector Applied Radiative Cloud Fraction
(lt0.2)
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Extra
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Apply Reference Sector Method to Correct
Retrieval Artifacts
OMI PBL Product
After Reference Sector