基于集合敏感性方法的台风“山竹”暴雨预报分析

本文利用实况观测资料以及ECWMF集合预报资料分析了1822号台风“山竹”对广西造成的降水情况,进一步利用集合敏感性方法分析了“山竹”不同降水阶段的关键系统及对降水预报偏差影响。结果表明：(1)台风“山竹”降水可分为三个不同阶段,对应不同降水区域,主要影响系统分别为台风本体、台风外围环流与冷空气结合以及台风后部偏南气流。(2)集合敏感性分析发现,该次过程第一阶段降水与台风位置本身最为敏感,位置越偏向西北,降水越强；第二阶段降水与台风位置、副高西脊区及地面冷高压均敏感,且与副高西脊最为敏感；第三阶段降水与低压位置、强度及副高西脊区、地面冷高压均敏感,且与地面冷高压最为敏感。(3)最优成员与集合平均对比分析显示,第一阶段的降水差异主要取决于台风强度及位置的差异。第二阶段降水的差异与台风位置、台风北侧地面冷高压强度的差异有关。第三阶段的降水差异则主要由低压、地面冷高脊强度及副高南缘差异造成。

Typhoon Mangkhut (1822): A Forecast Analysis of Rainstorm Based on Ensemble Sensitivity Method

Based on the real-time observation data and the European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble forecast data, this study analyzes the heavy precipitation in Guangxi associated with typhoon Mangkhut (1822) and the key systems of different precipitation stages influence on prediction bias by using the ensemble sensitivity method. Results show that: (1) the precipitation associated with typhoon Mangkhut can be divided into three stages, corresponding to different rain areas, the key system is typhoon noumenon, interaction between typhoon periphery and cold air and the southerly flow of typhoon, respectively. (2) ensemble sensitivity analysis indicates that the most sensitive system to the first precipitation stage of the process is typhoon’s location. The more northwestward typhoon is, the stronger the precipitation. In the second stage, the sensitive system is typhoon’s location, subtropical high ridge area and ground cold high pressure, while the most sensitive system is the subtropical high ridge point. The third stage is sensitive to tropical depression’s location and intensity, subtropical high ridge area and ground cold high pressure, which is most sensitive to ground cold high pressure. (3) Comparing best ensemble members and ensemble average, we can find that the difference in the first precipitation stage mainly depends on the typhoon’s intensity and its location. The difference in the second stage is related to typhoon’s location and intensity of the ground cold high pressure that located in the northern of the typhoon. The difference in the third stage mainly corresponding to the tropical depression and the intensity of ground cold high ridge that located in the southern of subtropical high.