The Impact of Subscale Inhomogeneity on Oxygen A Band Cloud-Top Pressure Estimates: Using ESA's MERIS as a Proxy for DSCOVR-EPIC

Medium Spectral Resolution Imaging Spectrometer (MERIS) oxygen A band measurements were used as a proxy for the Earth Polychromatic Imaging Camera (EPIC), to be launched on NASA’s Deep Space Climate Observatory (DSCOVR). The high spatial resolution of MERIS (1 × 1 km) is exploited to study the effects of subscale spatial heterogeneity of clouds on the cloud-top pressure retrieved at the coarser spatial resolution of EPIC (10 × 10 km). In general, for a sub-scale cloud fraction less than 1, a shift of cloud-top pressure toward the middle atmosphere is found, with a low-bias for high clouds and a high-bias for low clouds. In addition, the deviation is found to be a function of surface reflectance. The subscale variability of fully clouded EPIC pixels causes a weak underestimation of cloud-top pressure, when compared to averaged high-resolution retrievals.