引入地基GPS可降水量资料对一次西南涡暴雨水汽场的初步分析

利用成都地区4个地基GPS站遥感的大气可降水量(GPS-PWV)数据,结合自动气象站雨量和NCEP再分析等资料,对2008年7月20～22日一次由高原涡诱生西南涡引发的四川盆地暴雨过程的水汽变化进行了分析。结果表明,降水开始前GPS-PWV有一个急升过程,且与过程1h最大雨量有较好的对应关系,GPS-PWV的增幅和所达到的最大值可以较好地反映西南暖湿气流对四川盆地水汽的影响程度;而GPS-PWV的骤降则预示降水即将结束。西南涡在GPS-PWV急速上升之后形成于盆地;在其发展强盛时段,盆地处于低空水汽通量大值区和水汽辐合中心,随着西南涡的东移,GPS-PWV逐渐减小至最低水平。

Analysis on the Moisture Flux of a Rainstorm by Southwest Vortex Using Precipitable Water Vapor Data of Ground-based GPS

Based on the GPS Precipitable Water Vapor(GPS-PWV) data from the ground-based GPS network in Chengdu plain,the observed precipitation at automatic weather stations(AWS) and NCEP reanalysis data,the changes of water vapor in a heavy rainstorm in Sichuan basin during 20~22 July 2008 are analyzed,which is caused by the plateau vortex and southwest vortex.The results show that there is a good relationship between the variation of GPS-PWV and the precipitation,especially in the heavy rainstorm,the amplitude of GPS-PWV happens before the formation of heavy precipitation while the dramatica decrease of GPS-PWV indicates the end of the precipitation process.As the shown relationship between water vapor flux,water vapor flux divergence and GPS-PWV,the increase of GPS-PWV and its maximum value can better reflect the impact of southwest warm and humid airflow on the changes of water vapor over the Sichuan Basin.The southwest vortex is formed on the basis of the amplitude of GPS-PWV and the following heavy precipitation.During the time of prosperity,there is a center of water vapor convergence in the low level over the Sichuan basin and the GPS-PWV gradually reduced to the lowest level with the eastward shift of the southwest vortex.In summary,the ground-based GPS-PWV can correctly reflect the changes of water vapor for a southwest vortex over the Sichuan basin.