A NUMERICAL EXPERIMENT STUDY FOR INFLUENCE OF THE TRANSITION ZONE MIGRATION ON SUMMER DROUGHT IN NORTH CHINA^*

In this paper,the summer climate of 1991 is taken as a case to study the influence of the transition zone migration on summer drought in North China by using the regional climate model (RegCM2).The results show that the transition zone migrates inland,the summer monsoon rainband of 1991 also moves inland.The intensive rainband in the Changjiang River Valley during the Meiyu period moves north.The precipitation in North China increases and the surface air temperature decreases.As a consequence,it results in a good circle between ecosystem and climate.The transition zone migration changes flux transfers between land and atmosphere,and excites secondary circulation or circulation cells around it.All those are closely related with the variation of precipitation.