NASA's Atmospheric Science Data Center (ASDC) has released the DSCOVR EPIC Level 4 Tropospheric Ozone High Resolution Version 01 dataset. The DSCOVR_EPIC_L4_TrO3_highres_01 data product reports gridded synoptic maps of tropospheric ozone columns (TCO) measured over the sunlit portion of Earth on a 1 to 2 hour basis.
Sampling times for these hourly TCO data files are the same as for the DSCOVR EPIC L2 total ozone product. Version 1 of the TCO product is based on Version 3 of the EPIC L1B product and the DSCOVR EPIC L2 Total Ozone Column Version 3 product. The stratospheric columns were derived from the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) ozone fields (Gelaro et al., 2017). In contrast to the EPIC total ozone maps that are reported at high spatial resolution of 18 × 18 km2 near the center of the image, the TCO maps are spatially averaged over several EPIC pixels and reported on a regular spatial grid (0.25° latitude × 0.25° longitude).
The Earth Polychromatic Imaging Camera (EPIC) measures Earth-reflected radiances from the entire sunlit portion of the Earth. The measurements from four EPIC UV channels are used to reconstruct global distributions of total ozone. The tropospheric ozone columns are then derived by subtracting independently measured stratospheric ozone columns from the EPIC total ozone.
EPIC is a 10-channel spectroradiometer (317–780 nm) operating onboard the National Oceanic and Atmospheric Administration's Deep Space Climate Observatory (DSCOVR). The spacecraft provides a unique angular perspective of Earth from the Earth-Sun Lagrange-1 (L-1) point, enabling continuous full-disk imaging of the entire sunlit face of the Earth.
EPIC's position at L-1—combined with its 0.62-degree field of view and 2048 × 2048 pixel CCD detector coupled to a 30-cm aperture Cassegrain telescope—supports a broad range of Earth science applications. Due to DSCOVR's tilted (Lissajous) orbit about the L-1 point, the apparent angular size of Earth varies from 0.45 to 0.53 degrees within its 6-month orbital period, with a complete set of per-band images captured every 60 to 100 minutes depending on the season.
Kramarova et al. (2021) provides a detailed description of the EPIC TCO product and its evaluation against independent ozonesondes and satellite measurements. Table 1 in Kramarova et al. (2021) lists all variables included in the TCO product files. Ozone arrays in the product files are integrated vertical columns in Dobson Units.
References
Gelaro, R., W. McCarty, M.J. Suárez, et al., (2017) The Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2), J. Climate, 30, 5419–5454. doi:10.1175/JCLI-D-16-0758.1
Kramarova NA, Ziemke JR, Huang L-K, Herman JR, Wargan K, Seftor CJ, Labow GJ and Oman LD (2021) Evaluation of Version 3 Total and Tropospheric Ozone Columns From Earth Polychromatic Imaging Camera on Deep Space Climate Observatory for Studying Regional Scale Ozone Variations. Front. Remote Sens. 2:734071. doi:10.3389/frsen.2021.734071