Cloud mask over snow-/ice-covered areas for the GCOM-C1/SGLI cryosphere mission: Validations over Greenland

Cloud detection is a critically important first step required to derive many satellite data products. A novel cloud detection algorithm designed for the cryosphere mission of Global Climate Observation Mission First Climate satellite/Second Generation Global Imager (GCOM-C1/SGLI) is presented. This reflectance-based cloud detection scheme mainly utilizes only two short wavelength infrared channels with dynamic thresholds that depend on Sun-satellite viewing geometry to perform accurate cloud detection over snow/ice surfaces in high latitude as well as high-elevation regions. Profiles of atmospheric absorbing and scattering molecules as well as surface elevation are considered in the determination of the thresholds for the resulting snow/ice cloud mask (SCM) algorithm. Image-based tests and statistical results have been used to validate the performance of the SCM over the Greenland plateau. Statistics using collocated Cloud-Aerosol Lidar with Orthogonal Polarization and Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua observations over Greenland in 2007 show that over snow/ice surfaces the performance of the SCM is generally better than that of the MODIS cloud mask.