The Effect On Weathers Of Guizhou Of Quasi-stationary Front Over Yunnan And Guizhou Privinces

Based on the four sub-categories of classification made on the quasi-stationary front(QSF) over Yunnan and Guizhou, there are three research missions being conduct: (1)The time and space distribution of each category QSF and differences for meterological elements between 2000 and 2003 are analyzed by statistical method. (2)Studies are made on the structure and circulation characteristics of QSF during it evolves. (3)The 16 times heavy freezes during the period from 1964 to 2000 and the heavy storm rainfall on Guizhou resulted from QSF over Yunnan and Guizhou on June 5th in 2006 are analyzed, respectively. The main results are as follows:There are some conclusions based on the statistical results: The QSF appears go down abruptly and up slowly during the spring and summer, autumn and winter have taken turn; It is theâ…¡category of QSFs that make the prominent influence on the weather of Yunnan and Guizhou; There appears storm rainfall on May, June, and Auguest with the occurance ofâ…¡category QSF.The characteristics of the structure and circulation during the QSF evolves are as follows: There are heavy humidity in the QSF zone and high relation between its circulation and Tibetan Plateau. The influence on the weather over Yunnan and Guizhou is enhanced by the appearance of Ferrel cell resulted from the southly position of Hadley cell and the lifting effect of Qi-Zhang Plateau for the air. The counter-circulation that can result catastrophic weathers such as heavy snowfall and freezes are formed by the union actions ofâ… andâ…¡categories QSFs, the upcurrent at the south of Plateau and the more southern position of the downcurrent of Hardley cell for its smaller cross distance from south to north, and Vice versa; The clear double level structure for the Hadley cell during appearance ofâ… ,â…¡, andâ…£category QSF is resulted from the indirect effects of the enhance of subtropical high.The main reasons for the serious congeal weather process are the close to Asia of the polar vortex over north hemisphere, the abnormal southerly position of the east Asian large-scale trough, and the maintainance of the QSF; The inversion layer under 700hPa is advantageous to forming the supercooled raindrop which can froze to the congeal with the 3-level advection model of "cold-warm-cold". Moreover, the cold air mass moving south is lifted by the blocking of Yunnan-Guizhou Plateau, and resulting in the convergence of moist air and strong ascending motion, which produce moist and dynamic condition for the formation of congeal.The mechanism for the formation of this storm rainfall is the union effect of the moving out of the small wave on 500hPa and the frontogenesis of QSF; The reason for the weak convection motion up to 700hPa is the shallow QSF system; The heavy precipitation is located around the QSF zone, and the frontogenesis function is a good indicator for the position and period of heavy rainfall.