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 us ing the high-resolution regional climate model (RegCM2) and the effects of the grassland desertification on summer drought in the central and the nort hern parts of North China as well as Mongolia are studied. It shows that th e regional climate model essentially catches the characteristics on distrib ution and seasonal variation of the precipitation that keep good agreement with the observation. The desertification makes precipitation in the centra l part of North China during its flood period decrease obviously in July. T he border of the precipitation or the soil moisture reduction in the desert ification region extends about one latitude southeastward and beyond the so utheast edge of the desertification. Thus, vegetation in the border region approaches desertification further. However, there appears evident differen ce of variation of precipitation over the whole desertification region. The grassland desertification greatly changes the transfers of Duxes between l and and atmosphere. The secondary circulation or secondary circulation cell s in the desertification region are excited and as a result moisture transp ort 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 precipitation.