Study On The Statistic Feature Of The Low Level South-Westerly Strong Wind And The South-westerly LLJ In China And Analysis Of The Role Of The Inertial Stability

The low level south-westerly strong wind (LLSW) includes the low level jet (LLJ) that has the independent axis and the no-axis low level strong wind (NALLSW). By introducing the idea of studying the climatology of the LLJ in Northerly America and considering the feature of the weather in China, new definitions of LLSW,LLJ and NALLSW in China are given, on which the graphs of number of occurrence of them are drawn for the analysis. The results show that there are two centers of occurrence of LLSW respectively in DONG BEI and JIANG NAN; The regional torrential rain over the Yangtze River Basin is closely associated with LLSW during the major periods of heavy rainfall; The diurnal variation of the number of occurrence in the middle and low reaches of the Yangtze River is the strongest in China There are some significant differences between LLJ and NALLSW in positive season, spatial variation, diurnal variation and field of pressure.By the way, the important effect of inertial stability on heavy rainfall with both low level south-westerly jet and high level northerly strong flow is analyzed theoretically. The results show that the existence of the maximum of inertial stability in the left font of the low level jet is favor of the accumulation of the moist thermal energy, and conditional symmetric instability or convective instability can be expected in this region. The maintenance of the high level strong flow provides an advantage to the generation of the dry symmetric instability in its right back region. Furthermore, the inertial stability can make the slantwise convection at low level more vertical and therefore support the convection, meanwhile can make the slantwise convection more horizontal and benefit the divergence in high level.