1714号台风“帕卡”后部强降雨成因分析

Analysis of the Causation of a Heavy Rain at the Rear Portion of Typhoon Pakhar(1714)

利用2017年8月27—28日ECMWF逐6 h再分析资料和Micaps观测资料对1714号台风"帕卡"后部强降雨成因进行分析,结果表明:该次强降雨期间广东处于副高边缘东南气流和台风环流后部偏南气流辐合区,同时地面存在多个中小尺度辐合系统,提供有利的动力条件和触发机制;珠三角附近水汽充足且存在强烈水汽辐合,南边界截面较高水汽收入的时间区间与强降雨发生时间较一致;该次强降雨过程可能有条件性对称不稳定和对流不稳定机制共同参与,强降雨落区位于MPV1负值中心或MPV2正值中心及等值线密集区,其动向与MPV2正值中心的移动方向相近。

With 6-hourly ECMWF reanalysis and Micaps observations for 27 -28 August, 2017, the causation for an intense rainfall at the rear portion of Typhoon Pakhar （1714） is studied. The result is shown as follows. During the heavy rain, Guangdong province was in an area where a southeasterly flow at the edge of a subtropical high converged with a southerly flow at the rear portion of the typhoon and a number of meso- and fine-scale converging systems were at the surface level, providing favorable kinematic conditions and triggering mechanism. Water vapor was abundant over the Pearl River Delta area and converged strongly. The time interval associated with a high gain of water vapor through the cross-section of the southern bounda- 17- agreed well with the timing of the intense rain. The rain process may involve mechanisms of both conditional symmetric instability and convective instability. The area receiving the intense rain was located at the center of negative MPV1 or positive MPV2 as well as in places where isolines were densely distributed. It moved in directions close to the migrating direction of the center of positive MPV2.