Spectral and seasonal dependence of sun glint observations from deep space

Abstract:

From a distance of about one million miles, the Earth Polychromatic Camera (EPIC) onboard the Deep Space Climate Observatory (DSCOVR) spacecraft takes roughly hourly images of the sunlit side of Earth. Several earlier studies showed that these images often feature sun glint from water surfaces and from ice crystals that float inside clouds in a horizontal orientation. This presentation expands on the earlier analyses of observed glints caused by clouds, focusing on the way the appearance of these glints varies with wavelength and season. The statistical analysis of all EPIC images taken in 2017 reveals that the wavelength dependence of glints is shaped predominantly by the Rayleigh scattering and gaseous absorption caused by the atmosphere above the cloud top. The analysis also reveals that the radiative impact of cloud glints displays seasonal variations that are consistent with seasonal changes in the amount of ice clouds that were observed independently by the Moderate resolution imaging spectroradiometer (MODIS).