ANALYSIS OF ATMOSPHERIC CIRCULATION AND STRUCTURE OF YUNNAN-GUIZHOU QUASI-STATIONARY FRONT DURING ITS EVOLUTION

Based on general ground observation data and NCEP data,the atmospheric circulation and the structure of Dian-Qian Quasi-stationary Front (named as DQQSF,same hereafter) during Jan. 2001 are studied. The results show that the DQQSF is a front of humidity and its circulation features are highly related to Tibetan Plateau. The weather of Yunnan-Guizhou Plateau is greatly impacted by the emergence of the Ferrel cell,which is resulted from the lifting effect of Tibetan Plateau and the southward anomaly of the Hadley cell. Corresponding to Pattern I and Ⅱ Quasi-Stationary Front,the north-south distance of Hadley cell is short and its sinking branch is southward,which helps form counter-circulation with its rising branch at the south plateau. It is the counter -circulation that result in the severe weather such as snow,ice rain etc. In contrast,the Ⅲ and IV pattern Quasi-Stationary Front occurs with the north Hadley cell with longer north-south distance,and there is no counter-circulation over the south Tibetan plateau. Because of the indirect influence of the strengthening subtropical anticyclone,the Hadley cell shows a two-layer structure corresponding to the quasi-stationary front in Pattern Ⅱ,Ⅲ and Ⅳ.