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| The Impact of the Eastward Propagation of Convective Systems over the Tibetan Plateau on the Southwest Vortex Formation in Summer |
| FU Shen-Ming,SUN Jian-Hua,ZHAO Si-Xiong,LI Wan-Li |
| Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029; State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100084,Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,Graduate University of Chinese Academy of Sciences, Beijing 100049; Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000 |
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Abstract Based on the temperature of the black body (TBB), station observed and NCEP reanalysis data, the impacts of the eastward propagation of convective cloud systems over the Tibetan Plateau on the southwest vortex (SWV) formation that occurred at 1800 UTC on 29 June 2003 are analyzed by using the Zwack-Okossi (Z-O) equation to diagnose the thermal and dynamic processes. It is found that, in summer, severe convective activities often occur over the Tibetan Plateau due to the abundant supply of moisture. The convective cloud near the east edge of the plateau could move eastward with a short-wave trough in the westerly. The divergent center that is induced by latent heat release, which is associated with severe convective activities, moves out with the convective cloud and contributes to the low level decompression which is favorable for the formation of plateau edge cyclogenesis (PEC). The Z-O equation indicates that, in this case, the latent heat release and convergence are the two most important factors for SWV formation, which amounts to about 42% and 15% of the term TOTAL, respectively. It is implied that the thermal process effect was more important than the dynamic process during SWV formation.
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Received: 29 September 2009
Revised: 22 December 2009
Accepted: 08 January 2010
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