Some Aspects of the Effects of Sensible Heating on the Development of Summer Weather Systems over the Tibetan Plateau

摘要

The influence of sensible heating from the earth's surface on the development of summertime vortices over the Tibetan Plateau was investigated using a numerical model. It was found that sensible heating could cause local intensification of vortices over high elevation and sometimes act in combination with topography to block intrusion of cold air. Sensible heating can play an important role, not indicated by its magnitude, when it is combined with topography and the proper synoptic situation. Sensible heating had a greater impact over higher elevations, areas with strong cold advection, and areas under the upper-tropospheric jet stream. Sensible heating tends to destabilize an air column, permitting downward transfer of westerly momentum in the vicinity of the jet stream and causing an increase in cyclonic vorticity in the lower troposphere north of the upper-level jet. During the premonsoon period, when the upper-level jet was located over the southern plateau, sensible heating acted to intensify plateau vortices. After the transition into the summer monsoon period, the jet was north of the plateau and sensible heating had only localized and gradual effects on plateau vortices. (Reprints)