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 degrees N and 50 degrees 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.