星载雷达在台风暴雨宏微观特征分析中的应用

Application of Space-Borne Radar in the Analysis of Macro and Micro Characteristics of Typhoon Rainstorm

摘要: “烟花”台风是有气象记录以来首个在浙江省内两次登陆的台风，其引导气流弱，移速缓慢，影响时间长。为探究“烟花”台风减弱阶段在浙北地区造成的强降水的分布特征及其云微物理垂直特征，本文利用星载雷达GPM资料，研究了2021年7月27日夜间“烟花”台风的降水率分布、雨顶高度、降水宏微观垂直结构及云顶亮温的分布特征，并与地基雷达观测进行了对比。结果表明：在“烟花”减弱阶段，台风雨带中20~40 mm/hr的雨强落区基本对应6~10 km的雨顶高度，位于台风眼壁处。微观方面，强雨区三维空间内均对应50以上的粒子数密度，相较而言，台风眼壁处水凝物粒子直径更大，在1.5~1.9 mm；台风外围处水凝物粒子直径在1.5 mm以内，但其粒子数浓度最大可达到55以上，这种高浓度的环境条件有利于降水粒子碰并聚合和直径增长，使得降水有加强潜势。位于台风眼壁的降水多数由对流性降水所组成，少部分层云性降水；西南象限外围螺旋雨带中对流性降水比重减小，但仍带来15 mm/hr以上的雨强。台风影响区域均有丰富冰水混合物存留，降水云滴的有效碰并增长活跃，对地面强降水的形成有正向贡献。同时，GPM与地基双偏振雷达探测结果十分相近，这证实了星载雷达反演产品在探测反演台风降水中的可靠性。

Abstract: “In-Fa” typhoon is the first typhoon to land twice in Zhejiang Province since meteorological rec-ords. Its guiding air is weak, moving slowly and affecting time is long. To explore the distribu-tion characteristics of heavy precipitation and its vertical characteristics of cloud microphysics caused by “In-Fa” typhoon in Northern Zhejiang during the weakening stage, this paper studied the distribution characteristics of precipitation rate, rain top height, macro- and micro-vertical structure, and cloud top brightness temperature of “In-Fa” typhoon in the night of July 27, 2021 using space-borne radar GPM data, and compared them with ground-based radar observation. The results show that during the weakening stage of “In-Fa” typhoon, the 20~40 mm/hr rain in-tensity area in the typhoon rain band corresponds to the rain top height of 6~10 km, which is located at the eye wall of the typhoon. In the microcosmic aspect, the particle number density in the three-dimensional space of the strong rain belt corresponds to more than 50. In comparison, the diameter of hydrocondensate particles at typhoon eye wall is larger, ranging from 1.5 to 1.9 mm. The diameter of hydrocondensate particles outside the typhoon is less than 1.5 mm, but the maximum particle concentration can reach 55 or more. The high concentration ambient condi-tion is beneficial to precipitation particle collision and aggregation and the growth of diameter, which makes precipitation have an enhanced potential. Most of the precipitation at typhoon eye is composed of convective precipitation, with less stratiform precipitation. In the outer spiral rain belt of the southwest quadrant, the proportion of convective precipitation decreased, but still brought more than 15 mm/hr of rain intensity. The typhoon-affected areas are rich in aqueoglacial mixture, and the effective collision and growth of cloud droplets are active, which makes a positive contribution to the formation of heavy rainfall. At the same time, the detection results of GPM and ground-based dual-polarization radar are very similar, confirming the relia-bility of space-borne radar inversion products in detecting and retrieving typhoon precipitation.