Structural Analysis of Heavy Precipitation Caused by Southwest Vortex Based on TRMM Data

The horizontal and vertical structure of a heavy rain system caused by southwest vortex happened in the eastern part of Sichuan and the western part of Chongqing on 17 July 2007 has been studied by using tropical measure mission data. The results indicate that: The heavy rain system was consisted of a main precipitation cloud and several scattered precipitation clouds,which was convective precipitation and characterized by high precipitation intensity and wide precipitation range. Although the number of convective rains is less than the stratiform rains,convective rains contribute much more rainfall to the total than stratiform rains for the stronger rainfall rate of convective rains. The rainfall intensity spectral distributions of convective rains mainly occurred in 1 ~50 mm·h-1,the rain rate of almost 90% of the stratiform rains concentrated 10 mm·h-1below. In vertical,the rain top of heavy precipitation system can reach to 16 km from the surface. The most precipitation rate occurred in the atmospheric 2 ~ 6 km above the ground and the distributions of precipitation rate in both vertical and horizontal was inhomogeneous. The coalescence growth progress of cloud drop play an important role in the lower troposphere to precipitation. Whether for the stratiform or the convective precipitation caused by southwest vortex,the precipitation under height of 6 km contributed most,in different heights,the contribution of total precipitation was inversely proportional to the height.