The Role of Shallow Convection over the Tibetan Plateau

Abstract

umulus (Cu) from shallow convection is one of the dominant cloud types over the Tibetan Plateau (TP) in the summer according to CloudSat-CALIPSO observation. Its thermodynamic effects on the atmospheric environment and impacts on the large scale atmospheric circulation are studied in this paper by using the Community Atmospheric Model CAM5. It is found that the model can reasonably simulate the unique distribution of diabatic heating and Cu over the TP. Shallow convection provides the dominant diabatic heating and drying to the lower and middle atmosphere over the TP. Sensitivity experiment indicates that without Cu over the TP, large-scale condensation and stratiform clouds would increase dramatically, which will induce enhanced low level wind and moisture convergence toward the TP, resulting in significantly enhanced monsoon circulation with remote impact on the areas far beyond the TP. Cu therefore acts as a safety valve to modulate the atmospheric environment that prevents the formation of super-clusters of stratiform clouds and precipitation over the TP.