Simulations of the effects of soil temperature and humidity disturbances on regional climate of China

Summary ?This simulation study was applied by a regional climate model (RegCM2) and forced by reasonable soil temperature and humidity disturbances, in order to examine the disastrous weather and climate-produced such disturbances that were performed in a series of experiments of different climatic zones, seasons and space/time scales, to recognize the persistence and to understand the mechanisms of their respective climatic responses under the current climatic background of China. The simulation results showed that, in regions of East Asian monsoon climate, the soil humidity disturbance (SHD) has greater impact on posterior climate responses than the temperature disturbance has. The SHD forcing exerts noticeable influence on rainfall generally. Although the centers of changed precipitation generally do not coincide with those of the disturbances, the centers are located mostly in downwind areas of the SHD core and in areas of prevailing updraft, even some places far away; with neighboring dry/moist SHD zones, a bigger rainfall increase tends to show up in the dry region instead of in the wet one. The simulation suggested that the SHD lasts for a rather long time, whose length is controlled by the presence of a positive feedback between the precipitation, the synchronous circulation patterns, the latitude and season, and the intensity of the SHD forcing. This study has found that the humidity disturbance (especially from rainfall) is in good correspondence to posterior temperature that the previous SHD enhancement leads to the subsequent temperature drop in the surface and near-surface layer, while the centers of lowered temperature can remain more than three months. Received April 3, 2001; Revised December 19, 2001