Role of seasonal cycle forcing in simulating the summer monsoon circulation and precipitation

Abstract

Using a General Circulation Model (GCM), the role of seasonal cycle surface boundary conditions in simulating some large scale features of Indian summer monsoon circulation, rainfall and some surface parameters during two contrasting years (1987 and 88) of monsoon have been examined. When the seasonal variations in surface conditions are incorporated in the GCM, some important fields such as the magnitudes of zonal wind over Arabian Sea at 850 hPa, meridional wind over Somalia at 850 hPa, strength of easterly jet at 200 hPa and the rainfall rate over land to the north of Bay of Bengal are reasonably well simulated compared to their respective climatological values. Components of surface wind stress show three distinct branches of monsoon located over the Arabian Sea, Bay of Bengal and South China Sea. The model simulated June,July,August (JJA) mean monsoon winds over India at 200 hPa and 850 hPa are weak and the interannual variations in simulated surface wind, net heat flux and rainfall are very small.