A Comparative Study of Tibetan Plateau Vortex and Southwest Vortex Causing Heavy Rainfall Based on TRMM Data

Abstract:

A comparative study has been made on the three dimensional structure, distribution of the rain top and precipitation profiles of two precipitation system caused by Southwest vortex（SWV） which happened in Sichuan and Chongqing on 17 July, 2007 and Tibetan Plateau vortex （TPV） which happened in the west part of Sichuan on 21 July, 2008 respectively based on TRMM data, combined with the NCEP reanalysis data. Results indicate that: (1) The two precipitation processes were occurred in the southwest-northeast direction of the moisture convergence zone, clouds located in the southeast of SWV. (2) In horizontal, the two precipitations processes are all consisted of a main precipitation rain band and several scattered precipitation clouds, and the rainfall intensity and scope of TPV are much large than those of SWV. The common feature of the two mesoscale precipitation systems detected by precipitation radar (PR) is that most of precipitation are stratiform precipitation which is characterized by large scope and weak intensity in precipitation, but the contribution of convective rains to the total rainfall is much large, the ratio and the contribution to the total rainfall of convective precipitation in SWV is larger than it in TPV. (3) In vertical, the rain top of the two heavy precipitation systems is increased with the increase of surface precipitation rate, and the maximum rain top is close to 16km, but rain top of SWV is higher than TPV, which indicate that the convective than that of TPV. (4) The progress of collision and growth of rain drop and the latent heat release were mainly occurred blow the height of 8km. But the change of precipitation of SWV is greater than that of TPV, and the former is greater than the later for the contribution of rainfall at 8-12km height to total precipitation.

Key words Southwest vortex, Tibetan Plateau vortex, TRMM satellite, precipitation structure