1989.07.21大暴雨的诊断分析与数值试验

Diagnosis and Simulation of Heavy Rainstorm 21,July 1989

对1989年7月20—21日内蒙古中西部的大暴雨,进行了诊断分析和数值试验。分析表明,南亚高压东北移在该地区对流层上部形成强辐散流场;西来短波槽诱发切变线北抬,使暖湿空气与干冷空气在该区上空交绥,扰动不稳定发展;暴雨落区与辐合线关系密切。数值试验表明,地形的动力作用和热力作用,是产生地面辐合的主要原因之一。

Diagnostic analysis and numerical simulation have been performed for a heavy rainstorm in July,20-21,1989 in the middle western part of the Inner Monglia. The results show that South Asia high causes a strong divergence field in the upper layer of troposphere in this re-gion,the short wave trough from west makes a shear line move northword,warm moisture air and cold dry air suddenly meet each other which produces the unstable wave, and the relationship between the rainfall position and the convergence line is close, the model experiment indicates that dynamic and thermal forcing of topography is one of main reasons for the convergence of the surface wind field to form. The difference caused by the orographic effect and the intensity of the convergence line is significant.