2012年河套地区一次暴雨的天气过程分析

The cause analysis of a Rainstorm in Hetao region in 2012

利用内蒙古高空、地面观测资料及自动气象站的逐小时降水监测资料,对2012年7月20—21日河套地区区域性暴雨天气过程进行分析,结果表明:本次暴雨天气过程是由贝加尔湖冷涡、低空切变线及副热带高压共同影响形成的;副热带高压的位置异常偏西偏北,其外围偏南气流为河套地区提供了充足的水汽输送;高空急流的加强东移为地面倒槽加强和维持提供了动力条件;副热带高压特征线与500h Pa槽线、低空切变线的位置关系与暴雨开始、结束时间的关系密切,而雨带的分布则与切变线及低空最大风速带之间关系密切。

Using the conventional high and surface observation data in inner mongolian, a rainstorm process which happened in Hetao region during the July 20th to 21rd in 2012. The results showed that： the weather process of this storm is formed by the combined infuence of the cold vortex, low altitude shear line and subtropical high pressure. The property of this rainstorm changed signifcantly and evolved from the warm area precipitation of Ordos Area to the cold vortex precipitation of the Inner Mongolia eastern area. After analyzed the trigger mechanism of this rainstorm and the characters during the strong precipitation period, it found that the location of subtropical anticyclone was anomalous westward and northward and the south-southwest air stream around subtropical high provided suffcient water vapor transportation for the Ordos Area. The enhancement and eastward transfer of the high-level jet provided the dynamic condition for the intensifcation and maintenance of ground inverse trough. Besides, the position relation between the subtropical anticyclone, the trough at 500hPa level and low altitude shear line closely related to the beginning and ending time of rainstorm. While the distribution of rain belt closely related to the shear line and the maximum wind zone at the low altitude.