Global assessment for the aerosol and cloud interactions and their shortwave radiative effects estimated by NASA/GEWEX Surface Radiation budget (SRB) project and Calipso-CloudSat-CERES-MODIS (CCCM)

Aerosols and clouds are strongly related as drivers of the terrestrial energy budget and therefore with weather and climate. Significant progress has been made in this field due to improved ground-based and satellite measurements that provide a better understanding of the different interactions between aerosols and clouds for various physical processes.

This study shows an assessment of the global shortwave radiative effects of aerosols and clouds derived from two different satellite data products, NASA/GEWEX Surface Radiation Budget (SRB) edition 3.0, and the CALIPSO-CloudSat-CERES-MODIS (hereinafter CCCM) edition B1 for 2007. GEWEX SRB relies on satellite radiances and cloud information from the International Satellite Cloud Climatology project (ISCCP).

In comparing the radiative effects, the difference in spatial and temporal resolutions used in two products is considered. SRB provides irradiance in a 1°X1° global grid every 3 hours, while CCCM provides instantaneous irradiances for every CERES footprints. Irradiances from two products are collocated to within a 1°×1° grid and plus minus 1.5 hour., Comparisons of seasonal mean irradiances from two products are then performed using a 2°x5° grid.

Results show an overestimation of aerosol radiative effect over land in SRB compared to CCCM and an overestimation of he global mean by about 11 Wm-2. In addition, SRB also shows an overestimation of the global mean net radiative effect of clouds at the surface by 1.6 Wm-2.This study discusses the cause of the difference in the seasonal irradiance derived from SRB and CCCM.