Comparison on Structure Characteristics of Two Tibetan Plateau Vortexes in Summer,1998

Using the historical Micaps weather charts,the Tibetan Plateau Science Experiment(TIPEX) data in 1998 and NCEP/NCAR 1°×1° reanalysis data and analyzing the condition of two Tibetan Plateau vortexes moving out of the Plateau and keeping within the Plateau in 1998,the Plateau vortex intensity,thickness,rainfall characteristic,wind symmetry,vertical movement,baroclinicity,potential vorticity,latitudinal cross-section of temperature and vorticity are compared of Plateau vortex moving out and not moving out of the Plateau.The marked structure difference of the moving out and not moving out of the Plateau vortex are as follows:(1) The vortex circulation is circular shape of the moving out of the Plateau vortex,with altitude about 3000 m and accompanying with circular rainfall area distribution.The vortex circulation is circular elliptical shape of the not moving out of the Plateau vortex,with altitude about 1500 m and accompanying with rainfall distribution in south to southwest region of the vortex.(2) The most of area is ascending movement,is being stronger and with expanding area of the moving out of the Plateau vortex.The ascending movement is being weaker with shrunken area of the not moving out of the Plateau vortex.(3) The baroclinicity of the moving out of the Plateau vortex is stronger in not moving out of the ones,with value about two times than the later one.(4) There is high potential vorticity flow to northeast and upward direction on 500 hPa in moving out of the Plateau vortex area and with flow to southeast and downwards direction in not moving out of the Platea vortex.(5) There are positive vorticity,warm area in under level and negative vorticity,cold area in upper level of the moving out of the Plateau vortex.There are positive vorticity,cold area in under level,negative vorticity,weak cold area in middle level and positive vorticity,cold area of the not moving out of the Plateau vortex.All these enriched understanding of easterly movements of the Plateau vortex characteristics and offers scientific basis to the flood and storm rainfall caused by Plateau vortex moving out of the Plateau.