1. Evaluating Lower Tropospheric Ozone Simulations Using GOME/SCIAMACHY/OMI Observations of NO2 and HCHO
Randall Martin Aaron Van Donkelaar
Chris Sioris Kelly Chance
Arlene Fiore

2. SCIAMACHY Tropospheric NO2 Columns
May-July 2004

3. Tropospheric NO2 Columns Evaluate NOx Emissions
SCIAMACHY NO2 (1015 molec cm-2)
May-July 2004
GEOS-CHEM NO2 (1015 molec cm-2)

4. Significant Model/Measurement Differences Exist
SCIAMACHY NO2 (1015 molec cm-2)
May-July 2004
SCIA – GEOS-CHEM (1015 molec cm-2)

5. Errors in the NO2 and HCHO Retrievals from Aerosols, Clouds, Surface Reflectivity Largely Cancel in their Ratio
Solar Io
Backscattered
intensity IB
Scattering by
Earth surface
and by atmosphere

6. HCHO/NO2 Column Ratio Consistent with Model Overestimate of NOx Emissions from Biomass Burning
GOME
GEOS-CHEM
JULY 1997
Tropospheric HCHO/NO2 Column Ratio

7. HCHO/NO2 Ratio is Also An Interesting Indicator
HCHO/NOy Ratio Used as Indicator
Would like to Observe from Space…
(ppbv)
NOx-Saturated
NOx-Sensitive
Sillman and He, 2002

8. Conduct Three Simulations With GEOS-CHEM CTM to Diagnose Quality of HCHO/NO2 Column Indicator
Base Case
Reduce Anthropogenic NOx Emissions by 50%
Reduce Anthropogenic VOC Emissions by 50%

9. Tropospheric HCHO/NO2 Column Ratio Is an Indicator of the Sensitivity of Afternoon Surface Ozone to NOx and VOC Emissions GEOS-CHEM Model Calculation For Polluted Regions, Mar-Nov
NOx Saturated
NOx Sensitive

10. NOx-Sensitive Conditions Over Most Polluted Regions During August Major Industrial Areas are Clear Exceptions
GOME
GEOS-CHEM

11. Seasonal Progression from NOx-Sensitive to NOx-Saturated Conditions
GEOS-CHEM
GOME
More Frequent Ozone Episodes in Fall