Global assessment of the effect of cloud properties on surface longwave radiative fluxes estimates in the NASA/GEWEX Surface Radiation Budget and Calipso-CloudSat-CERES-MODIS data sets

Clouds cover spatial and temporally most of the Earth surface and therefore have a strong modulating influence on the radiative exchange between the TOA and surface. From this radiative exchange, the surface Longwave Radiative Fluxes (LRFs) are an important component in the Earth's energy budget and, also are strongly related with the greenhouse effect and therefore with the climate change. This study shows a global assessment of the cloud properties and their radiative effects on the surface longwave fluxes by the NASA/GEWEX Surface Radiation Budget, in its release 3.1, and the CALIPSO-CloudSat-CERES-MODIS, thereafter C3M, this one in its release B1. The period of time used in this study correspond during the whole overlapping year of 2007. First, the different spatial and temporal resolutions in both projects were considered. Then, it was necessary to develop a tool to combine all the collocated footprints from the different instruments abroad the three satellites in the A-train (CloudSat, CALIPSO and Aqua) with each SRB cloud properties (from ISCCP) and fluxes on a grid box (1°X1°) global grid. The results of this study quantify the agreement between both projects on different spatial and temporal scales showing mean monthly differences. The study also looks for the origin of these differences between SRB and C3M longwave fluxes. The different cloud properties (cloud fraction, cloud top and bottom pressure and cloud optical depth) are shown to determine the differences on the longwave radiative fluxes.