The Observational Analysis of Shear Line and Low Vortex over the Tibetan Plateau in Summer from 2000 to 2007

Using the radiosonde data on500 hPa level at 08:00 and 20:00 in2000—2007,the ground station observed rainfall data and TRMM satellite data,the shear line and low vortex over the Tibetan Plateau are investigated and analyzed.Some new understandings of the shear line and Plateau vortex activities were obtained.(1) The shear line is more active than the Plateau vortex over the Tibetan Plateau.(2) The most often appearance month of shear line and Plateau vortex are in June;the least,in September in the 8 years.And 2002 years is the more active year;2006 years,less active year with two low weather systems only.Furthermore,the persistent high temperature and drought in Sichuan-Chongqing in 2006 maybe has something with the less active low weather systems over the Plateau.(3) The shear line and Plateau vortex generation region indicates they are mainly appeared in high altitude and steep areas,which means the steep topography and Plateau heating are possibly one of the causes of the generation of the shear line and Plateau vortex.(4) The shear line and Plateau vortex are not easily moved out of the Plateau.When the Plateau vortex moved out of the Plateau,it is often moving eastward along the shear line.(5) The Plateau vortex and the Plateau shear line often appears concurrently or one after another,they have largely weather influence on the Plateau and on the east of the Plateau.