A Numerical Experiment Study for Effects of the Grassland Desertification on Summer Drought in North China

In this paper, the summer climate of 1991 in North China is simulated by using the high- resolution regional climate model (RegCM2) and the effects of the grassland desertification on summer drought in the central and the northern parts of North China as well as Mongolia are studied. It shows that the regional climate model essentially catches the characteristics on distribution and seasonal variation of the precipitation that keep good agreement with the observation. The desertification makes precipitation in the central part of North China during its flood period de-crease obviously in July. The border of the precipitation or the soil moisture reduction in the desertification region extends about one latitude southeastward and beyond the southeast edge of the desertification. Thus, vegetation in the border region approaches desertification further. How-ever, there appears evident difference of variation of precipitation over the whole desertification region. The grassland desertification greatly changes the transfers of fluxes between land and at-mosphere. The secondary circulation or secondary circulation cells in the desertification region are excited and as a result moisture transport is changed. The variation of flux transfers between land and atmosphere as well as the vertical motion of atmosphere is closely related to that of precipita-tion.