Testing and Improving OMI Tropospheric NO2 Using Observations From the DANDELIONS and INTEX-B Validation Campaigns

Satellite observations of trace gases and aerosols are increasingly used to understand the effects of pollution on regional air quality and global climate change. Validation of these measurements is crucial for evaluating the quality of these novel data products, establishing their use in air quality monitoring and providing top-down constraints on emissions. We present a validation of tropospheric NO2 columns from the Ozone Monitoring Instrument (OMI) using measurements from the DANDELIONS and INTEX-B campaigns in 2006. These campaigns were unique because they covered a wide range of pollution scenarios and provided detailed information on the vertical distribution of NO2 (an important source of error in the OMI retrieval). During the Dutch Aerosol and Nitrogen Dioxide Experiments for vaLIdation of OMI and SCIAMACHY (DANDELIONS), tropospheric NO2 profiles were measured with a lidar over the highly polluted region of the Netherlands. During the Intercontinental Transport Experiment (INTEX-B), NO2 profiles were measured using laser induced fluorescence onboard an aircraft in a range of scenarios over the Gulf of Mexico. We examine how the observed profile shapes differ from the simulated profile shapes (from the 3-D chemistry transport model TM4) used in the OMI retrieval. From these comparisons, we determine an empirical error in the retrieval with respect to profile shape assumptions. We also present case studies related to planetary boundary layer growth in the Netherlands, pollution outflow in the Gulf of Mexico and the effects of using improved Mexico city terrain heights on the OMI NO2 product.