THE IMPACT OF DESERTIFICATION IN THE MONGOLIAN AND THE INNER MONGOLIAN GRASSLAND ON THE REGIONAL CLIMATE

This is an investigation of the impact of and mechanisms for biosphere feedback in the northeast Asian grassland on the regional climate. De sertification in the Inner Mongolian grassland has dramatically increa sed during the past 40 years. The Center for Ocean-Land-Atmosphere Stu dies atmospheric general circulation model, which includes a biosphere model, was used to test the impact of this desertification. In the gr assland experiment, areas of Mongolia and Inner Mongolia were specifie d as grassland. In the desertification experiment, these areas were sp ecified as desert. Each experiment consists of six integrations with d ifferent atmospheric initial conditions and different specifications o f the extent of the desertification area. All integrations were 90 day s in length, beginning in early June and continuing through August, co incident with the period of the East Asian summer monsoon. The deserti fication had a significant impact on the simulated climate. During the past 40 years, the observed rainfall has decreased in northern and so uthern China but increased in central China, and the Inner Mongolian g rassland and northern China have become warmer. The simulated rainfall and surface temperature differences between the desertification integ rations and the grassland integrations are consistent with these obser ved changes. The water balance and surface energy balance were altered by the desertification. The reduction in evaporation in the desertifi cation experiment dominated the changes in the local surface energy bu dget. The reduction in convective latent heating above the surface lay er enhanced sinking motion (or weakened rising motion) over the desert ification area and over the adjacent area to the south. Coincidentally , the monsoon circulation was weakened and the rainfall was reduced.