Cloud-Induced Infrared Radiative Heating and Its Implications for Large-Scale Tropical Circulations

Abstract

Three-dimensional global distributions of longwave radiative cooling for the summer of 1988 and the winter of 1989 are generated from radiative transfer calculations using European Centre for Medium-Range Weather Forecasts temperature and humidity profiles and International Satellite Cloud Climatology Project cloudiness as inputs. By adding the cooling of the clear atmosphere to the total radiative heating, cloud-induced atmospheric radiative heating has been obtained. Emphasis is placed on the impact of horizontal gradients of the cloud-generated radiative heating on the global atmospheric circulation. Cloud-induced heating, whose general pattern is well in agreement with total diabatic heating suggested by other studies, exhibits its maximum heating areas within the Indian Ocean and the western Pacific. By contrast, maximum cooling areas are found in the northern and southern flanks of the Indian Ocean, and over the eastern Pacific off the west coasts of both North and South America. The fact that these heating and cooling distributions reinforce the climatologically favored heating gradients both in the meridional and zonal directions indicates that cloud-radiative feedback can enhance the strength of both the north?south Hadley circulation and the east?west Walker circulation.