The Reduction in Near-Global Cloud Cover After Correcting for Biases Caused by Finite Resolution Measurements

A solution to the common problem that sensors have in overestimating cloud fraction (CF) due to their finite resolution is implemented by the Multi-angle Imaging SpectroRadiometer (MISR) to produce a resolution-corrected CF product. Here we evaluate the efficacy of this product toward the development of an improved global cloud climatology. We found a large reduction in CF across various regions of the globe due to the correction, with reductions >0.4 in regions dominated by shallow cumulus clouds. The MISR resolution-corrected CF lies within ±0.05–0.08 of 180 randomly selected scenes of 15-m resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data, where MISR uncorrected CF and Moderate Resolution Imaging Spectroradiometer (MODIS) CF overestimated this benchmark by 0.40–0.50. We conclude that the CF between 50°N and 50°S is much lower than that reported by the original MISR and MODIS and that the new MISR cloud product indeed provides improved estimates of CF.