Satellite Remote Sensing of Ozone-NOx-VOC Sensitivity Randall Martin Aaron Van Donkelaar Arlene Fiore

Ozone Control Strategies Require Independent Information on Effectiveness of Reducing NOx or VOCs HCHO/NOy Ratio Used as Indicator Would like to Observe from Space… (ppbv) NOx-Saturated NOx-Sensitive Sillman and He, 2002

Conduct Three Simulations With GEOS-CHEM Model Base Case Reduce Anthropogenic NOx Emissions by 50% Reduce Anthropogenic VOC Emissions by 50%

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

Tropospheric NO2 and HCHO Columns Largely Confined Near the Surface Also Closely Related to NOx and VOC Emissions Tropospheric NO2 column ~ ENOx Tropospheric HCHO column ~ EVOC Boundary Layer CO NO2 NO/NO2   W ALTITUDE NO hours HCHO OH HO2 hours VOC hours HNO3 Emission Emission Nitrogen Oxides (NOx) Volatile Organic Compounds (VOC)

Retrieve Tropospheric NO2 and HCHO Columns from GOME Largest Errors (from AMF) Cancel in the Ratio Solar Io Backscattered intensity IB Spectral Fit (UV/Vis) Total HCHO & NO2 Slant Column Remove Stratosphere Tropospheric NO2 Slant Column Scattering by Earth surface and by atmosphere Calculate AMF Tropospheric NO2 & HCHO Column

GOME Observations Show NOx-Sensitive Conditions Over Most Polluted Regions During August Major Industrial Areas are Clear Exceptions White areas indicate clouds or data below the GOME detection limit August

Biomass Burning Emissions are Clearly NOx-Sensitive, In Contrast with NOx-Saturated Conditions Over the Industrial Highveld Also observe plume evolution August

Seasonal Evolution from NOx-Sensitive to NOx-Saturated Conditions in Fall

GOME Observations Provide Confidence in a Recent Model Prediction NOx-Sensitive in the South and NOx-Saturated in the North in Fall Seasonal Maximum in Surface Ozone in Urban China Occurs in Fall (More High-Pressure Systems) GOME Model Luo et al., JGR, 2000

Conclusions Satellite Observations of the Tropospheric HCHO/NO2 Column Indicate Ozone-NOx-VOC Sensitivity Errors in Ratio Less Than for Individual Species Sensitive Tool for Ozone Model Evaluation OMI Will Be Launched in June 40 Times Higher Spatial Resolution Less sub-grid scale variation Afternoon observation time