Using Trmm Satellite Data Analysis Of The Low Vortex Precipitation On The Tibetan Plateau

Plateau vortex is one of the main rainfall system of the Tibet Plateau in summer.Only a few can move out of the plateau,which would produce wide disastrous weather to the neighborhood and the lower reaches.In this paper,combining the TRMM data,ECMWF reanalytic data and the rainfall data of Tibet surface meteorological station with synoptic analysis,we researched the precipitation structures and the dynamic structures of the vortex case"98.7.3-4"not moving out of the Tibet Plateau and the case"01.6.1-5"moving out of. conclusions are obtained as follows:(1) The TRMM satellite detect the rainfall areas accurately.The horizontal distribution of precipitation:when the vortexes are on the plateau,the horizontal distribution of rainfalls are uneven.The average intensitys are 2.72mm/h.The rainfall areas are mainly in the south or east of vortexes.The TRMM satellite detected vortex eye in the precipitation filed of"01.6.1-5",but"98.7.3-4"not.when"01.6.1-5"move out of plateau ,precipitation mainly happend outside the vortex and in the font of trough .in the vortex,precipitation is weak or nothing.(2)The vertical precipitation structure: when the vortexes are on the plateau, precipitation happened in the middle and upper troposphere. for"98.7.3-4",the precipitation thickness is 2.5-10km,the maximum height of the precipitation is 11km,even 17km.When"01.6.1-5"is on the plateau,the precipitation thickness is 1.5-5km,the maximum height of the precipitation is 10km. When"01.6.1-5"move to the Sichuan Basin,the precipitation thickness is 2.5-5km,the maximum height of the precipitation is 7.25km.When move to the sea,the precipitation thickness is 5-13.5km,the maximum height of the precipitation is 7.5-13.5km. When"01.6.1-5"move out of the plateau,the biggest precipitation intensity is about at the height of 3km. With height going up,the intensity has a decline trend.(3)The vertical latent heat structure:when the vortexes are on the plateau,the total atmosphere is latent heat release which is biggest at surface layer.When"01.6.1-5"move to Sichuan Basin,the total atmosphere is also latent heat release which is smaller than on the plateau.When"01.6.1-5"move to the sea,below 5km is latent heat absorption,above 5km is latent heat release which is biggest at the height of 7-9km.(4)The dynamic structure:When the vortexes are on the plateau,are thin.Only 500hpa or 400hpa has closed isoline.Below the 400hpa is convergence,and above is divergence.In the vortexes,the total atmosphere rise,and fastest at 400hpa.For"98.7.3-4",positive vorticity is thin,only showing between400 and 500hpa,and is biggest on the 500hpa.After"01.6.1-5"move out of the plateau, begin to get thicker.When it move to the sea,become a cyclonic column from sea level to upper air.When"01.6.1-5"move out of the plateau,both lower-level convergence and upper-level divergence are weak.Correspondently, rise goes down,even sink. In the vertical direction, the"01.6.1-5"shows almost positive vorticity which is biggest at 200hpa.When it is moving,the positive vorticity is oscillation,but at 500hpa,positive vorticity displays increasing trend. For"98.7.3-4",water vapor change from convergence to weak divergence. For"01.6.1-5",when it is on the plateau,there is always water vapor convergence,but when it move out,water vapor convergence turn weak,even turn to divergence.