两次极端暴雨过程对比分析
Comparison Analysis of Two Extreme Rainstorm Cases

本文基于观测资料，欧洲中心第五代大气再分析资料(ERA5)从两者环流背景、物理量场等方面对发生在2021年夏季河南郑州7月20日(简称“7.20”过程)和浙江湖州8月11日(简称“8.11”过程)的两次极端性暴雨过程进行了对比分析，结果表明：1) 两次降水过程均发生在副高边缘，且都有三支气流在本地交汇形成气旋式涡旋，但“7.20”过程中低层切变更强，范围更大，维持时间更长，且低层还存在超低空急流，因此天气剧烈程度、影响范围、极端性也比“8.11”过程更强。2) 两次过程整层湿度条件均较好。在强降水发生时段，都表现为高层水汽辐散，低层水汽辐合，但“7.20”过程低层水汽辐合区持续时间更长，中心辐合区强度更强。3) 两次过程均有高层辐散，中低层辐合区相配合，但“8.11”过程倾斜度小，整层配合更好。在强降水时段，两者与低层强辐合区对应较好，“7.20”过程辐合中心强度更强。4) 两次过程垂直速度分布与强天气发生有一定的对应关系，垂直速度最强时段对应降水效率最高时段。“8.11”过程垂直上升运动高度虽不及“7.20”过程，但是强度较大。而“7.20”过程表现在垂直上升运动维持时间较长，强上升运动中心比“8.11”过程更低。
Based on the national and regional automatic meteorological observation data and the high resolution European central atmospheric reanalysis (ERA5), this paper makes a comparative analysis of the two extreme rainstorm cases that occurred in Zhengzhou, Henan Province on July 20 (referred to as “7.20” process) and Huzhou, Zhejiang Province on August 11 (referred to as “8.11” process) in the summer of 2021 from the aspects of their atmospheric circulations background and physical quantities. As shown by the results: 1) Both processes occurred at the edge of the Subtropical high, and three air streams converged locally to form cyclonic vortices. However, in the “7.20” process, the low-level shear line is more significant and lasts longer. In addition, there are ultra-low level jets at the lower level, so the weather intensity, influence range and extremes are stronger than those in the “8.11” process. 2) The humidity conditions of the whole layer of the two processes are good. In the occurrence period of heavy precipitation, both of them show high-level water vapor divergence and low-level water vapor convergence. However, in the “7.20” process, the duration of the low-level water vapor convergence area is longer, and the intensity of the convergence center area is stronger. 3) Both processes have high-level divergence and low-level convergence, but the inclination of “8.11” process is relatively small, and the whole layer coordination is better. In the period of heavy precipitation, the two correspond well to the low-level strong convergence area, and the intensity of the convergence center in the “7.20” process is stronger. 4) In the two processes, the distribution of vertical velocity has a certain corresponding relationship with the occurrence of strong weather, and the strongest period of vertical velocity corresponds to the highest period of precipitation efficiency. Although the height of the vertical upward movement in the “8.11” process is lower than that in the “7.20” process, the intensity is greater. However, the “7.20” process