Diabatic Heating in the UCLA General Circulation Model

Abstract

Diabatic heating rates calculated in the UCLA general circulation model are analyzed. The heating rates are for the December–January–February season for the mean of four climatological runs and the mean of four runs with observed 1982/83 sea surface temperatures as boundary conditions. Vertically integrated total diabatic heating for the climatological calculations agrees well with observations. Unfortunately, the available observations of zonally averaged vertical structure differ from each other so substantially that comparisons with the model are inconclusive. Nevertheless, the vertical structure of the model seems quite realistic and in general agreement with analyses of tropical cloud clusters or middle latitude cyclones. The model diabatic heating is stratified in a number of ways. Zonal average height-latitude cross sections of the heating due to cumulus and large-scale precipitation and radiation show complex profiles for the rates associated with precipitation and much less structure with those associated with radiation except near the ground. Sample vertical profiles for regions in the tropics and new 45°N suggest that the zonal averages are generally representative of the individual heating profiles except near the surface. Anomalous heating rates associated with the model 1982/83 season, in which a a strong El Niño was observed, show a moderate alteration in diabatic heating over the breadth of the tropical Pacific. In the eastern equatorial Pacific, increases are evident for the heating rates associated with cumulus and large-scale precipitation and radiation. Reductions in cumulus and radiative heating over other parts of the tropics are also apparent.