一次登陆台风倒槽暴雨过程的初步诊断

利用常规探空和地面观测资料、卫星雷达资料以及NCEP再分析数据,应用非地转湿Q矢量和湿位涡理论,诊断分析了2018年第4号台风"艾云尼"登陆后的倒槽暴雨过程。结果表明,台风倒槽东侧偏南气流为暴雨区温湿能量的主要来源,倒槽顶部的暖式切变和倒槽西侧高值湿位涡的下传,使大气斜压性和低层不稳定度增强。倒槽附近温度场与风场的不平衡配置易于激发次级环流,有利于潜热能的释放和暴雨的增幅。暴雨区对流层低层(925 hPa)湿位涡分量总满足MPV10,MPV20。中层非地转湿Q矢量散度与未来6 h降水落区对应较好,对此类台风倒槽类暴雨预报具有一定的指示意义。

Preliminary diagnostic of a torrential rain caused by inverted trough of landing typhoon

Based on the routine sounding and surface observation data, as well as NCEP reanalysis data, the non geostrophic Q vector and the concept of moist potential vorticity theory was used to analyze a process of torrential rain caused by inverted trough of 1804 typhoon Ewiniar. The results showed that southerly airstream at the east side of typhoon provided main source of temperature and humidity energy in rainstorm area. Both the warm shear at the top of inverted trough and the downward transmission of high value MPV at the west side of inverted trough increased baroclinicity and low level instability. Moreover, the uneven distribution of temperature field and wind field nearby inverted trough induced to form sub circulation, which was conducive to the release of latent heat and the enhancement of rainstorms. MPV at 925 hPa across the rainstorm always satisfied MPV1 <0 and MPV2 >0. The non geostrophic Q vector divergence in the middle layer was in good agreement with the location of 6 h rainfall in the future, which was a guidance for the prediction of such rainstorm.