Cloud Height Retrieval with Oxygen A and B bands for the Deep Space Climate Observatory (DSCOVR) Mission

At the Earth's L1 Lagrangian point, the Deep Space Climate Observatory (DSCOVR) would see the whole sunlit half of the Earth and would provide simultaneous data on cloud and aerosol properties from its Earth Polychromatic Imaging Camera (EPIC). EPIC images the Earth on a 2Kx2K CCD array, which gives a horizontal resolution of about 10 km at nadir. A filter-wheel provides consecutive images in 10 spectral channels ranging from the UV to the near-IR, including the oxygen A and B bands, which are designed for cloud height retrievals. In this talk, we will present the progress on EPIC cloud height retrieval using Oxygen A and B band. As the first step, a study on the effect of cloud phase, particle size, optical depth, extinction coefficient, cloud fraction, sun-view geometry, and surface type on the cloud height determination is conducted. Second, based on the simple Lambertian cloud reflectance model, two cloud pressure retrieval algorithms are developed: one utilizes the absolute radiances at the Oxygen A and B bands and the other uses the radiance ratios between the absorption and reference channels of the two bands. Third, a cloud height retrieval model that is suitable for operational use is implemented. Test results with the data from the EPIC simulator will be presented.