2020年深汕区两次特大暴雨过程成因的诊断对比

DIAGNOSTIC ANALYSIS OF TWO TORRENTIAL RAINFALL EVENTS IN 2020 IN SHENZHEN-SHANWEI SPECIAL COOPERATION ZONE

关键词:  特大暴雨  物理量  诊断分析  对比分析  深汕特别合作区

Key words:  torrential rainfall  physical parameters  diagnostic analysis  comparative analysis  Shenzhen-Shanwei Special Cooperation Zone

摘要:

利用ERA5再分析、地面观测和雷达资料等，对广东省深圳汕尾特别合作区(下称“深汕区”)2020年5月20—22日(简称过程1)和2020年6月6—8日(简称过程2)两次极端性的特大暴雨过程中的降雨实况、环流形势、物理量、雷达回波特征等进行对比分析。结果表明：两次过程均是在有利的大尺度环流背景下发生，低层的西南急流持续带来充沛的水汽，同时低空暖湿气流的输送使暴雨落区低层长时间处于高能高湿区控制，强烈的辐合上升运动也提供了很好的动力条件，并在海上暖湿气流北推与陆上偏冷气流沿汕尾莲花山脉南下共同作用下形成地面辐合线，且特殊地形起到滞留作用。不同点是过程1暴雨落区低层风速更大，加强更明显，中尺度能量锋区强度更强，回波形态为海上北移至深汕区南侧辐合线附近迅速发展加强的强单体回波，稳定少动并伴有中γ尺度涡旋特征。过程2中水汽通量大值区较偏北，暴雨落区大气层结不稳定状态维持更长时间，垂直运动大值区高度范围更宽，回波形态为强降水回波在长时间维持的地面辐合线附近不断触发并形成列车效应的线状强回波带。

Abstract:

Using the ERA5 reanalysis data, observational data from automated weather stations, and local radar data, this paper presents a comparative study to analyze the rainfall, weather patterns, physical parameters, and radar echo characteristics during two extreme torrential rainfall events on May 20—22, 2020 (Process 1) and on June 6—8, 2020 (Process 2) in the Shenzhen-Shanwei Special Cooperation Zone (SSCZ). The results show that both of the two events occurred under the background of favorable large-scale circulation, and low-level jet (LLJ) streams provided sufficient water vapor. Meanwhile, the transport of low-level warm and humid airflow kept the low level of the rainstorm area under the control of high energy and high humidity for a long time, and the strong convergent upward motion provided favorable dynamic conditions. A surface convergence line was formed under the influence of a warm and moist airflow from the ocean and a southward cold airflow along the Lianhua Mountain. The difference was that the low-level wind speed in the rainfall area was stronger and the strengthening was more obvious, and the intensity of the mesoscale kinetic energy front was stronger in Process 1. In Process 2, the large value of water vapor flux was more northerly, and the unstable atmospheric stratification in the rainfall area was maintained for a longer period of time. The height range of the large value area of vertical motion was wider. The radar echo of Process 1 was a strong mono echo moving northward to the surface convergence line of the SSCZ. Subsequently, it developed rapidly and moved less, and was accompanied by a meso-γ-scale vortex. In Process 2, the radar echo was a linear strong echo that was triggered continuously near the long-maintained surface convergence line and thus the “train effect” was developed.