Global assessment longwave radiative fluxes estimated by NASA/GEWEX Surface Radiation budget (SRB) project and Calipso-CloudSat-CERES-MODIS (C3M)

Longwave radiative fluxes are a key driver of the terrestrial energy budget. These fluxes are strongly related with the greenhouse effect and therefore with the climate change. Significant progress has been made in this field since the ground-base and satellite measurements. A better estimation of these fluxes would provide an understanding of the origin of their variability and trends. And therefore the implications in the current climate change.

This study shows a global assessment for the longwave radiative fluxes estimated for two different projects. These projects are: the NASA/GEWEX Surface Radiation Budget, in its latest and improved 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.

Different aspects are considered in this assessment, which are related with spatial and temporal resolution of both projects. While, SRB achieve its fluxes on a 1°X1° global grid each 3 hours, C3M is the collocated footprints from different instruments abroad three satellites in A-train. So then, it was necessary to develop a tool to combine all the footprints matched per each grid box.

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. Therefore, differences on the downwelling fluxes were assessed relative to differences in cloud properties. Upwelling flux differences were mainly associated with sampling issues in the diurnal cycle on the surface temperature.