Tropospheric ozone derived from DSCOVR EPIC satellite measurements

The Earth Polychromatic Imaging Camera (EPIC) on board of the DSCOVR spacecraft provides measurements of earth-reflected radiances from the entire sunlit portion of the Earth. The measurements from EPIC's four UV channels are used to reconstruct global distributions of total ozone from sunrise to sunset with multiple observations over the same location each day. The tropospheric ozone column is derived by subtracting an independently measured stratospheric column from the EPIC total ozone. These synoptic maps of tropospheric ozone column enable a new study of the short-term variability of tropospheric ozone and its connection to atmospheric chemistry and dynamics. Global tropospheric column ozone for August 2015-present is derived by subtracting co-located stratospheric column ozone (SCO) from the EPIC total column ozone. SCO is determined using Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) analyses that assimilates Microwave Limb Sounder (MLS) stratospheric ozone profiles. The EPIC total ozone is derived from a new version 3 algorithm that invokes improved geolocation and a dynamical cloud product derived via the oxygen A-Band from EPIC. EPIC tropospheric ozone is tested against balloon sonde and lidar ozone, and other tropospheric ozone satellite measurements including the Ozone Mapping Profiler Suite (OMPS) and Ozone Monitoring Instrument (OMI). We also test against the Goddard Earth Observing System (GEOS) model with the Global Modeling Initiative (GMI) chemical mechanism (replayed to data-derived reanalysis meteorology). The GMI simulation is used for identifying and correcting problems with EPIC tropospheric ozone including reduced sensitivity to boundary-layer ozone. We present several results of geophysical effects on EPIC tropospheric ozone such intra-seasonal and shorter timescale transport in the tropics and subtropics, and hourly migration of extra-tropical baroclinic weather systems.