广西西江流域致洪暴雨过程中尺度特征及机制分析

利用广西逐站逐小时降水量、1°×1°逐小时FY-2C的TBB资料和1°×1°逐6 h NCEP/NCAR再分析资料,应用空间25点平滑滤波方法,分析了2005年6月18~22日西江流域致洪暴雨过程的中尺度特征及其发生、发展的机制。结果表明:这次致洪暴雨过程的降水时空分布不均,具有明显的中尺度特征。雨团集中出现在TBB值的低值中心、低值中心北侧等值线密集的地方以及等值线曲率大的地方。镶嵌于大尺度西南气流中的中尺度涡旋系统在西江流域反复生成,导致对流云团不断生成和加强,是此次暴雨产生的直接原因。暴雨区上空中尺度经向垂直环流圈的存在对中尺度涡旋和对流云团的发生和发展具有促进作用。中低层弱的对流不稳定与强的水平风垂直切变和湿斜压性共存是此次暴雨产生和持续发展的重要机制。

Mesoscale Characteristic and Mechanism Analysis of a Heavy Flooding Rainstorm Process in Xijiang River Basin, Guangxi

Based on the Black-Body Temperature(TBB)data of FY-2C Stationary Meteorological Satellite from China Meteorological Agency(CMA) and the reanalysis dataset from the NCEP/NCAR reanalysis project,combining the data of hourly precipitation at 90 stations in Guangxi,the mesoscale characteristic and the mechanism of a heavy flooding rainstorm process happened in Xijiang River basin is analyzed by the 25-point smooth filter methods.Results show that the spatial and temporal characteristics of the mesoscale convective system that associated with the mesoscale rain mass has significant day variation,and the mesoscale rain mass often appear in the area of the center of low TBB and the lower TBB band,the sharp and dense TBB on the north of the low center and the area where the TBB curve is the larger;the evolution of the mesoscale vortex filtered from large scale SW stream has great impact on the maintaining and development of the mesoscale convective cloud mass over Xijiang River in South China,which is the direct causes for the heavy flooding rainstorm process;the low-level-jet give the rich moisture to the heavy rainfall and the convective instability and the strong vertical shear of horizontal wind are the important condition of the explosive and persistent heavy flooding rainstorm process.