COLA Report 11
The Impact of Desertification in the Mongolian and the Inner Mongolian Grassland on the East Asian Monsoon
Yongkang Xue
May 1995
Abstract
This is an investigation of the impact of and mechanisms for biosphere feedback in the
northeast Asian grassland on the East Asian summer monsoon. Desertification in the Inner
Mongolian grassland has dramatically increased during the past forty years. The Center for Ocean-Land-Atmosphere Studies atmospheric general circulation model, which includes a biosphere model,
was used to test the impact of this desertification. In the grassland experiment, areas of Mongolia
and Inner Mongolia were specified as grassland. In the desertification experiment, these areas were
specified as desert. Each experiment consists of six integrations with different atmospheric initial
conditions, and different specifications of the extent of the desertification area. All integrations were
90 days in length, beginning in early June and continuing through August, coincident with the period
of the East Asian summer monsoon.
The desertification had a significant impact on the simulated climate. During the past forty
years, the observed rainfall has decreased in northern and southern China, but increased in central
China, and the Inner Mongolian grassland and northern China have become warmer. The simulated
rainfall and surface temperature differences between the desertification integrations and the grassland
integrations are consistent with these observed changes.
The water balance and surface energy balance were altered by the desertification. The
reduction in evaporation in the desertification experiment dominated the changes in the local surface
energy budget. The reduction in convective latent heating above the surface layer resulted in
enhanced sinking motion (or weakened rising motion) over the desertification area and over the
adjacent area to the south. Coincidentally, the monsoon circulation was weakened and the rainfall
was reduced.
Complete copies of this report are available from:
Center for Ocean-Land-Atmosphere Studies
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last update: 24 May 1995
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