东海台风对四川东部暴雨的影响研究

INFLUENCE OF TYPHOON IN THE EAST CHINA SEA ON THE SOUTHWEST VORTEX RAINSTORM IN SICHUAN PROVINCE

利用NCEP逐6 h的FNL再分析资料、地面气象站逐小时降水资料以及中尺度数值模式WRF对2010年9月5日14时—6日20时发生在四川东部的一次西南涡暴雨天气过程进行诊断分析和数值研究。重点探讨了东海远距离台风对西南涡的移动和维持、水汽输送作用。结果表明:(1)这次川东暴雨是在中纬度30~50°N的两槽一脊的环流背景下,川西高原的东移低值系统(西南涡)受位于东海的北上台风间接阻挡,及源于南海和孟加拉湾的水汽不断输送等有利条件下形成的;(2)台风"玛瑙"并未向西南涡降雨区直接输送水汽;(3)东海台风"玛瑙"对上游东移的西南涡具有阻挡作用:台风的出现,使西风带上游东移的系统(含西南涡)东移的速度减慢,西南涡因此在四川东部地区滞留时间延长,是造成该地区暴雨天气发生的重要原因。

Using NCEP 6-hourly reanalysis data、the hourly rain data and the mesoscale numerical model WRF,the southwest vortex rainstorm(SVR)occurred in the eastern part of Sichuan province from 5th September,2010,14pm(UTC+8)to 6th,20pm is diagnostically analyzed and numerically simulated.Intensive discussions are made about the impact of typhoon in the East China Sea on movement and maintenance of the southwest vortex and the transportation of water vapor.The results show as follows.(1)The SVR in eastern Sichuan province was formed under favorable conditions.Such as the circulation background of"two troughs and one ridge"in the mid-latitude 30~50°N,the eastward moving low system(southwest vortex)of the western plateau of Sichuan province was indirectly blocked by the northward typhoon in the East China Sea,and the water vapor from the South China Sea and the bay of Bengal was continuously transported to the storm area.(2)Typhoon“Malou”did not transport water vapor to the southwest vortex rainstorm area.(3)The typhoon in the East China Sea had a"blocking"effect on the moving eastward southwest vortex:the speed of Eastward system(including southwest vortex)in westerlies upstream slowed down because of the effect of typhoon,and prolonging the"retention"time of southwest vortex in the eastern part of Sichuan province,which played an important role in causing the heavy rainfall in the region.