Comparison of SW radiances/fluxes from a model with coincident CERES/MODIS measurements

Here we show some examples of comparisons between the measurements from CERES/MODIS and the radiative transfer calculations for some "simple" cases (i.e., ocean and unmelting snow surfaces for clear sky; deep uniform clouds for cloudy sky). We employ the Coupled Ocean Atmosphere Radiative Transfer code. The emphasis is on the TOA radiances from CERES (nadir FOV ~20 km) and MODIS (several channels sampled within each CERES FOV) over ocean and snow, the darkest and brightest surface types respectively. MODIS radiance standard deviation within each CERES FOV is also used to determine the uniformity for CERES data selection. The model-observation discrepancy in radiance is largest for the clear ocean case, likely due to the highly anisotropic reflection of the rough ocean surface; it is smallest over deep uniform clouds, due to the intense multiple scattering within cloud and the isolation of effects from surface and boundary layer aerosols. Aerosol effects on the discrepancy under clear skies are also presented.