Analysis of heavy precipitation caused by the vortices in the lee of the Tibetan Plateau from TRMM (the Tropical Rainfall Measuring Mission) observations

Abstract

By using not only TRMM (the tropical rainfall measuring mission) precipitation radar (TRMM/PR) and microwave imager data, but also NCEP/NCAR reanalysis data, the paper compares and analyzes the two rainstorms caused by the southwest vortex (SWV) and eastward Tibetan Plateau vortex (TPV) in Southwest China, respectively. It shows that the heavy rainfall systems of both two vortex rainstorms are consist of a main rain band and several scattered precipitation clouds, with non-uniform distributed precipitation intensity. The horizontal scale of the main rain band and the intensive precipitation clouds of TPV rainstorm on 21st July, 2008 are larger than those of SWV on 17th July, 2007. The common feature of the two mesoscale precipitation systems detected by precipitation radar (PR) is that most of precipitation are stratiform precipitation which has large scale but weak intensity caused by the two kinds of precipitation. However, the convective precipitation contributes more to the total precipitation, with larger rain rate than the stratiform precipitation. The rainfall intensity spectrum of the convective precipitation is wider than that of the stratiform precipitation, which ranges from 1 to 50 mm/h. It also indicates that the height of the rain top increases along with the surface precipitation intensity in the two rainstorms. The highest height of the rain top reaches 16km. The SWV rainstorm is more intensive than TPV rainstorm, and the microwave brightness temperature varies inversely as the height of the rain top. The release of the precipitation latent heat, the increase of the raindrops and the change of the ice particles mainly occur below 8km. Moreover, mid- and low-level precipitation are the main source of the column precipitation. The convective precipitation and the stratiform precipitation caused by SWV release much more latent heat than those caused by TPV.