Assessment of Total Ozone Retrieval from DSCOVR EPIC with MERRA-2 and Brewer Measurements

Abstract:

The Earth Polychromatic Imaging Camera (EPIC) on the DSCOVR spacecraft, combining high spatial resolution with high-frequency temporal sampling from the unique vantage point of Lagrange-1, provides unprecedented Earth observations, from sunrise to sunset simultaneously. Total ozone and other geophysical quantities, like sulfur dioxide and aerosol index, are retrieved from the EPIC UV measurements using the direct vertical column fitting (DVCF) algorithm. We compare the synoptic ozone from EPIC with the ozone field from the Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) reanalysis over the five years (June 2015 – June 2020) of EPIC operation. The results show excellent agreements between EPIC and MERRA-2 during this period, illustrating that EPIC captures the ozone spatial and temporal variations realistically, with a mean difference, O3(EPIC) - O3(MERRA2), equal to 0.9±2.0%. We further validate the EPIC ozone with coincident Brewer measurements, showing a high degree of correlation between them with better than 1% agreement and a standard deviation of less than 2.5%.