台风“美莎克”(2020)的变性过程中降水的微物理机制研究  

Analysis of Microphysical Mechanisms of Torrential Rainfall during the Transitional Process of Typhoon Maysak(2020)

作　　者：杜涵 平凡[2] 谭桂容[1] 周冠博 黄伟 沈新勇[1] DU Han;PING Fan;TAN Guirong;ZHOU Guanbo;HUANG Wei;SHEN Xinyong(Key Laboratory of Meteorological Disaster,Ministry Education/Joint International Research Laboratory of Climate and Environment Change/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters,Nanjing University of Information Science and Technology,Nanjing 210044;Key Laboratory of Cloud−Precipitation Physics and Severe Storms,Institute of Atmospheric Physics(LACS),Chinese Academy of Sciences,Beijing 100029;National Meteorological Center,Beijing 100081;Daishan Meteorological Bureau,Daishan,Zhejiang 316200)

机构地区：[1]南京信息工程大学气象灾害教育部重点实验室/气候与环境变化国际合作联合实验室/气象灾害预报预警与评估协同创新中心,南京210044 [2]中国科学院大气物理研究所云降水物理与强风暴院重点实验室(LACS),北京100029 [3]国家气象中心,北京100081 [4]岱山县气象局,浙江岱山316200

出　　处：《大气科学》2024年第6期2353-2373,共21页Chinese Journal of Atmospheric Sciences

基　　金：东北冷涡致灾机理及预报关键技术项目2023YFC3007700;国家自然科学基金项目41930967。

摘　　要：本文采用数值模式WRF4.2对2020年09号变性台风“美莎克”进行了数值模拟,再现了“美莎克”北上过程中逐渐与高纬度冷槽结合变性并产生暴雨的过程。通过将台风划分为中心低压区及外围云区,并分别分析其热力学、动力学及云微物理特征,得到了冷槽对降水强度空间分布及时间变化特征的影响及机制。研究结果表明:(1)干冷空气由中层入侵台风中心低压区,使对流高度降低,其造成的上干下湿不稳定结构维持了中低层的对流强度。在外围云区,冷空气从低层入侵从而抬升暖空气以及垂直涡度输送作用使得高层的上升运动更强。系统逐渐演变为向前倾斜的对流结构。(2)本次降水的主要云微物理过程为:由水蒸气凝华的雪在下落过程中收集了云水,并融化为雨水,雨水又收集了大量云水导致增长。还有部分雨水源自霰粒子融化和雨水收集霰粒子,霰粒子主要来自雪收集云水的过程。(3)雪融化以及雨水收集云水是雨水的两个最大来源,冷槽通过影响台风的热动力结构,影响到了云水和雪的空间分布,最终影响到降水的空间分布:在中心低压区云水更聚集于台风中心,在外围云区沿出流的方向上雪更超前于云水。而雨水主要分布在雪和云水大值相重合的区域。在量值特征方面,低层干冷空气入侵使得外围云区雪凝华和雨水蒸发效率更高,云水凝结效率低,导致了外围云区水凝物中的雪的占比更大,云水及雨水的占比更少。(4)冷槽主要是通过影响到台风的垂直速度变化,直接影响到雪的凝华和云水凝结效率,继而影响到雪收集云水、雪收集云水增加至霰、雪融化为雨水、雨水收集云水、霰融化为雨水等过程的效率,最终导致了降水量的变化。In September 2020,typhoon Maysak experienced an extratropical transition.The numerical model WRF4.2 was used to simulate this event.The simulation results showed that as the typhoon interacted with a high-latitude cold trough,it resulted in heavy rainfall during its northward journey.This study investigated the thermodynamical,dynamical,and cloud microphysical characteristics of the typhoon’s low-pressure center and outer cloud area.Furthermore,it explored the effects and mechanisms of the cold trough on the spatial distribution and temporal variation of rainfall intensity.Results showed the following.(1)In the typhoon’s low-pressure center,the invasion of dry and cold air from the middle layer decreased the convection height.This created an unstable structure that was dry at the top and wet at the bottom,but the convection intensity was maintained in the middle and lower layers.Conversely,in the typhoon’s outer cloud area,the convection height remained stable owing to vertical vorticity transfer.Cold air invading from lower layers lifted warm air,enhancing the upward motion of the middle and upper layers.As a result,Maysak gradually evolved into a forward-leaning convective structure.(2)The cloud microphysical processes of this precipitation primarily involved the transformation of water vapor into snow through desublimation at the upper levels.As the snow fell,it collected cloud water and grew,eventually melting into rainwater within the melting layer and continuing to absorb additional cloud water.Simultaneously,a portion of the rainwater originated from the melting and rainwater collection of graupel.Graupel was produced as snow particles collected moisture from cloud water.(3)The two major sources of rainwater were the melting of snow and the collection of cloud water by rainwater.The cold trough affected the typhoon’s thermodynamic structure,affecting the spatial distribution of cloud water and snow and the spatial distribution of precipitation.In the lowpressure center,cloud water concentrated towa

关 键 词：台风变性 冷槽 暴雨 云微物理过程 

分 类 号：P447[天文地球—大气科学及气象学]