梅雨锋演变与低涡发展的联系

Relationship between the evolvement of Meiyu front and the vortex along it.

采用MM5高分辨率模式,对1999年6月26日至7月1日出现在江淮流域的两次低涡暴雨过程,进行全程四维同化数值模拟研究.发现梅雨锋与低涡关系密切.锋面在750hPa左右强度最大;锋面最强位置与低涡最强位置在纬向上是接近一致的,即锋面最强位置在低涡发展最强位置的北或东北方;锋生比低涡加强早15h左右;锋生存在自西向东的传播,低涡加强发展时锋生东传明显;低涡移过前,锋面北抬,坡度增大;移过后,锋面南压,坡度减小;移过时,锋面基本不动,近乎垂直.低涡发展最强的地区锋面的南北摆动比低涡发展弱的地区幅度大.

The Meso-scale model MM5 were used to analyse the two vortexes that occurred during June 26 to July 1 in 1999. It was found that there is a close relation between them. 750 hPa was the level that the front was the strongest. The front developed most was just of the north where the low vortex developed most. The frontogengsis was about 15 hours earlier than the development of the low vortex. Frontogenesis propagated from west to east, and it was more apparent when the low vortex was developing. The front moved northward before the low vortex passed, and moved southward after the later passed. Furthermore, the slope of the front became large before the low vortex passed, and became small after it passed, and was almost vertical when the vortex passing along it. The shift rang of the front in the place where the low vortex was developing was wider than that in the other places.