STRUCTURAL AND EVOLUTION CHARACTERISTICS OF THE EASTERLY VORTEX OVER THE TROPICAL REGION
YAO Xiu-ping 1, 2, 3, WU Guo-xiong 3, LIU Huan-zhu 4 (1. Jiang State Key Laboratory of Severe Weather (LaSW) Chinese Academy of Meteorological Sciences, 100081 China;2. China Meteorological Administration Training Center, Beijing 100081 China;3. National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029 China;4. China Meteorological Administration National Meteorological Center, 100081 China)
By employing the NCEP/NCAR reanalysis data sets (1000-10hPa, 2.5° × 2.5°), the characteristics have been analyzed of the structure and evolution of an easterly vortex over the tropical upper troposphere relating to the east-west direction shift of the subtropical anticyclone over the Western Pacific Ocean. It is shown that there exists a westward shift simultaneously between the anticyclone and the vortex locating south of it. The anticyclone retreats eastward abnormally while the easterly encounters with the westerly around the same longitudes as they move from the opposite directions. The former is an upper weather system, extending from mid-troposphere to the height of 50 hPa with the center locating on 200 hPa. The vertical thermal distribution illustrates the characteristics of being"warm in the upper layer but cold in the lower layer". The divergence effect and the vertical motion change largely within the east and west sides of the easterly vortex and ascending branch transforms to descending branch near its center.