Comparison of OMI and Pandora Ozone and NO2 Measurements in the Mid-Atlantic Region during the OWLETS 2017 Campaign

Air pollution events in coastal environments are complex phenomena. The Ozone Water-Land Environmental Transition Study (OWLETS) campaign in June-August 2017 was aimed at improving the understanding of coastal pollution episodes through observations of chemical species at the surface and aloft. The campaign was largely centered around two sites: NASA's Langley Research Center (LaRC) and the Chesapeake Bay Bridge Tunnel (CBBT) Third Island site. The NASA Wallops Flight Facility (WFF) site was included for background values. LaRC acted as a land site, and CBBT acted as a water site for the observations of land-water gradients in pollution. Total column (TC) O₃ and NO₂ measurements obtained from the Aura Ozone Measuring Instrument (OMI) and ground-based Pandora spectrometer instruments (PSI) at each site are compared. We find that TC ozone agreement between OMI and PSI is within 15% on all days at both sites, although LaRC shows better agreement than CBBT. For low-cloud TC NO₂ values, the percent differences between OMI and PSI range from 6-59%, with CBBT displaying better agreement overall. WFF displayed agreement comparable to LaRC for TC ozone and to CBBT for TC NO₂. We investigated the effect of clouds and aerosols on these comparisons using OMI cloud fraction (CF) and aerosol index (AI). The percent differences for both TC ozone and NO₂ were generally the highest on days when clouds and/or aerosols were significantly elevated. Other meteorological and chemical influences, such as mixing layer heights, are being investigated to better characterize agreement between satellites and ground-based sensors.