由台风“海高斯”引起的一次暴雨过程分析

Diagnostic Analysis of a Rainstorm Process Caused by Typhoon “Higos”

摘要: 本文采用台风路径及强度资料(RSMC)、逐小时降水资料、卫星云图资料、ECMWF逐6小时ERA-5再分析资料，对台山市2020年8月19日由台风“海高斯”引起的一次暴雨过程进行天气学诊断分析，结果表明：在本次天气过程中，广东台风受灾地区主要受西太平洋副热带高压控制。850 hPa高度场中印度半岛受低涡控制，有孟加拉湾的水汽和不稳定能量随着气旋向东传输，为“海高斯”的增强以及暴雨的形成提供有利条件。“海高斯”在登陆前的发展过程中由于广东的地形因素有过结构减弱，其对台风“海高斯”重新增强有着重要作用。在台风登陆后两小时内台山市有着低空辐合高空辐散的趋势，垂直速度负值中心出现在400~600 hPa高度层，有明显的上升气流，台山市迎来特大暴雨。台风中心过境后，由于高空气流有辐合趋势低层气流有辐散趋势，致使对流减弱，台山市降水逐渐减少。来自西太平洋以及孟加拉湾地区的水汽供应为此次暴雨过程提供了良好的水汽条件，较强的水汽通量遇上低层辐合气流和垂直方向上升气流形成高湿度气柱为本次降水的关键。该次降水过程中的动力条件以及水汽条件特征可为以后的台风天气预报提供参考和经验。

Abstract: In this paper, typhoon path and intensity data (RSMC), hourly precipitation data, satellite cloud map data, and ECMWF 6-hourly ERA-5 reanalysis data are used to make a weather diagnosis of a heavy rainstorm caused by typhoon “Higos” in Taishan City on 19 August 2020. The results show that during this weather process, the typhoon-affected area of Guangdong was mainly controlled by the western Pacific subtropical high pressure. 850 hPa height field in the Indian peninsula was controlled by a low vortex, with moisture and unstable energy from the Bay of Bengal transferred eastward with the cyclone, which provided the basis for the intensification of Higos and the heavy rainfall. This provides favorable conditions for the intensification of Higos and the formation of heavy rainfall. The development of Higos prior to landfall had a structural weakening due to topographical factors in Guangdong, which played an important role in the re-enhancement of Typhoon Higos. Within two hours of landfall, there was a tendency for low-level convergence and high-altitude dispersion in Taishan, with negative vertical velocity centers in the 400 hPa to 600 hPa altitude layer and significant updrafts, resulting in very heavy rainfall in Taishan. After the transit of the typhoon center, the convection weakened due to the convergence trend of the high-level airflow and the divergence trend of the low-level airflow, resulting in a gradual decrease of precipitation in Taishan. The water vapor supply from the western Pacific Ocean and the Bay of Bengal region provided good water vapor conditions for the rainstorm process. The strong water vapor flux met the low-level converging airflow and the vertical updraft to form a high humidity column as the key to this precipitation. The dynamical conditions and the characteristics of the water vapor conditions during this precipitation process can provide reference and experience for future typhoon weather forecasting.