云南两高辐合背景下低涡强降水过程对比分析

基于气象观测和欧洲中期天气预报中心第五代大气再分析资料（ERA5），选取2018—2020年发生在云南的3次两高压辐合区（以下简称两高辐合）背景下低涡连续性强降水过程进行对比分析，探究其环流形势、动热力因子及水汽辐合的相似性和差异性.结果显示：(1)夏半年西太平洋副热带高压（以下简称西太副高）西伸时，云南常受两高辐合影响，当辐合区中有低涡生成，易发生连续性强降水，且强降水落区并不完全分布在整个狭长的两高辐合区内.(2)两高辐合区低涡降水具有相似的雨带分布和移动特征，但雨带的集中程度、分布范围、小时雨强和总雨量存在差异.强降水开始时，落区偏东，随着西太副高西伸及东北引导气流的引导，低涡向南向西移动，强降水落区也随之向南向西移动.低涡在某一地区徘徊导致降水集中在该区域，且西太副高西伸较强时，两高辐合形势更强，低涡降水大雨及以上量级雨带也更窄.(3)低涡造成的降水主要分布在低涡中心及低涡切变附近，且降水发生在低层暖湿的环境中，低层及中高层有冷空气侵入时，小时雨强的极端性更强，降水落区也相对偏北.两高辐合区低涡降水落区与水汽辐合区对应较好，水汽辐合强度较弱时，对应的总降水量较小.

A comparative analysis of low-vortex heavy precipitation events over Yunnan Province under the convergence area between two highs

Based on meteorological observation and ERA5 reanalysis data, three persistent low-vortex heavy precipitation events that occurred from 2018 to 2020 over Yunnan Province under the atmospheric circulation background of the convergence area between two highs were selected, and a comparative analysis of the three events was conducted to explore the similarities and differences of circulation patterns, dynamic and thermal factors, and the convergence of water vapor associated with the low-vortex heavy precipitation. The results showed: ① With the westward extension of the West Pacific Subtropical High (WPSH) in the warm half year, the atmospheric circulation patterns of the convergence area between two highs tended to occur over Yunnan Province. Meanwhile, the persistent heavy precipitation event was commonly observed over Yunnan Province if a low vortex occursed in the convergence area. Besides, the heavy precipitation over Yunnan Province was not completely distributed in the narrow and long convergence zone. ② There were similar characteristics of precipitation distribution and movement of the rainband among the precipitation events, while the concentration of the rainband, the range of the precipitation distribution, the hourly precipitation intensity, and the total precipitation amount were different. At the beginning of the event, the location of the heavy precipitation was easterly. With the westward extension of the WPSH and the guidance of the northeast guiding airflow, the low vortex moved southward and westward, which also leads to the southward and westward movements of the rainband. The stagnation of the vortex over a region may led the precipitation to be concentrated over the region. In addition, under the circulation background with stronger westward extension of the WPSH, the convergence zone was more concentrated, and the rainband with precipitation amount equal to or more than heavy rain was also narrower. ③ The precipitation caused by the low vortex was mainly distributed over the center of the low vortex and the low-vortex shears, and the precipitation occurred under the situation with high temperature and high humidity over low-level troposphere. However, with the intrusion of low-level and mid-to-high level cold air, the hourly precipitation intensity would be stronger, and the location of the precipitation would be northerly. The location of low-vortex precipitation showed a tight relationship with convergence region of water vapor. During the situation with weaker convergence of water vapor, the total precipitation amount would also be less.