Validation of NO2 product from NOAA-20 OMPS with Pandora and OMI/TROPOMI observations

We present the validation of the NO2 product from the Ozone Mapping and Profiler Suite Nadir Mapper (OMPS-NM) instrument onboard the NOAA-20 satellite. NOAA-20 OMPS was launched in November 2017, with a nadir resolution of 17 × 13 km2 similar to the Ozone Monitoring Instrument (OMI). The retrieval of NOAA-20 NO2 vertical columns were achieved through the Direct Vertical Column Fitting (DVCF) algorithm, which was uniquely designed and successfully used to retrieve NO2 from OMPS aboard Suomi National Polar-orbiting Partnership (SNPP) spacecraft, predecessor to NOAA-20. The NO2 retrievals are validated against ground-based Pandora spectrometer measurements over the New York City area as well as other U.S. Pandora locations. It shows OMPS total columns tend to be lower in polluted urban regions and higher in clean areas/episodes associated with relatively small NO2 total columns, but generally the agreement is within ±2.5 × 1015 molecules/cm2. NOAA-20 OMPS tropospheric NO2 columns are further compared with NO2 columns retrieved from other satellites: OMI, TROPOMI and OMPS-SNPP. Our results demonstrate the high sensitivity of NOAA-20 OMPS to tropospheric NO2 and validate its use for monitoring the spatiotemporal variability of NO2 in urban environments and extending the long-term global NO2 record.