低空急流在重庆2010年“6.7”低能暴雨中的作用

Function of low-level jet in a heavy rainfall event in Chongqing on 7 June 2010

利用常规观测、地面逐时降水、NCEP再分析资料和卫星雷达资料,从影响系统,低空急流强度和位置演变,低空急流对暴雨区动力、水汽和热量输送等方面,对2010年6月7日重庆地区低能暴雨天气过程进行分析。结果表明,西南低空急流加强北抬,引起局地涡度增加,使西南低涡得以生成发展及维持,暴雨产生在西南涡闭合环流形成阶段,同时也是西南低空急流推动θse锋区经过重庆上空的时段,使暴雨区获得充沛的热力和水汽供给,其低层辐合、高层辐散形势明显;强降水在低空急流到达后产生,与急流带上风速加大且向下扩展相对应,降水量随急流上西南风增大而增加。

Based on the data of conventional observation,surface hourly precipitation,reanalysis data from NCEP,as well as the satellite and radar date,the heavy rainfall event occurring in northeast Chongqing region on 7 June 2010 was analyzed focusing on the circulation background,the intensity and location of the evolution of low-level jet and the water vapor and the heat transports by low-level jet.The result show that southwest low-level jet strengthening and moving to north caused the formation of southwest vortex,and heavy rain occurred when the closed circulation of southwest vortex was formed and frontal zoneθse was promoted by the southwest low-level jet over Chongqing,so that rainstorm area got plenty of heat and moisture supply.It had obvious convergence at low level and the divergence at high level in the heavy rainfall areas;Heavy rainfall occurred after the arrival of strong low-level jet corresponding to the wind speed increase and downward extension brought by jet stream,and the precipitation was increased as the increase of speed of southwest wind.