NUMERICAL EXPERIMENTS ON THE EFFECT OF QINGHAIXIZANG PLATEAU SNOW COVER ON SUMMER MONSOON FORMATION

The calculating schemes of underlying surface processes in the model described by Li et al.(1989)are modified with inclusion of simple land surface processes and oceanic mixed layer processes,then a simulation on the zonal wind along 90°E from the Northern to the Southern Hemisphere with moun-tains is performed.Comparisons of the results and the observations show that the modified model not onlyhas an excellent stability in calculation but also can better display the seasonal change of the wind field,theability of the present model is improved as compared with that of the previous one.Based on the simulations,the authors investigate the effects of Qinghai-Xizang Plateau snow cover on theformation of South Asian monsoon by thickcning the snow depth and by increasing the snow albedo.Themain results arc as follows:The summer meridional circulation over the south of the Plateau and its vicinityis weakeued,and the precipitation reduced.However,over the northern tropics,the circulation is enhanced,and the ecipitation is increased,and the land and the air above it become warmer,the tropical easterly jetis weakened.