郑州“7·20”暴雨的精细化特征及主要成因分析

Refined features and main causes of“7·20”rainstorm in Zhengzhou

为研究2021年7月20日郑州地区历史罕见暴雨洪涝灾害的精细化特征及其成因,基于实况观测和再分析资料,采用合成分析、距平分析等统计方法对此次暴雨过程进行了分析。结果表明:郑州“7·20”暴雨过程具有突发性极强、短时雨量极强、降水极端性突出的特征;200 hPa存在异常偏强且稳定的高空槽及高空冷涡,使暴雨区上空高层具备强的辐散条件;偏强偏北的副热带高压、台风“烟花”和“查帕卡”向暴雨区持续输送了大量水汽;郑州上空回波发展旺盛,且有对流性回波不断汇聚,呈现明显的“列车效应”;在地形作用下,郑州具备比周边更强烈的低层辐合及上升运动条件,对降水量的增幅起到了重要作用;高、中、低空极为有利的环流配置、极强的水汽条件,以及地形的增幅作用共同导致了此次致洪暴雨过程。

The torrential rain on July 20,2021 in Zhengzhou was one of the heaviest disasters in history.By using the observation and re-analysis data,the characteristics and main causes of the torrential rain are analyzed via statistical methods,such as the composite analysis and anomaly analysis.The results show that this torrential rain event was characterized by the extremely strong sudden,short-time and heavy rainfall,and prominent extreme.For the atmospheric pressure of 200 hPa,there are abnormally strong and stable high-altitude troughs and high-altitude cold vortices,which make the upper layers above the rainstorm area have a strong divergence condition.Moreover,the western Pacific subtropical high was significantly strong and shifted northward.Under the joint effect of the Typhoon“In-Fa”and“Cempaka”,the moisture transport and its convergence were extremely strong over Zhengzhou.The echoes over Zhengzhou are developing vigorously,and convective echoes are continuously converging,showing an obvious“train effect”.Additionally,the topography of the Fu-niu Mountain and the Tai-hang Mountain also contributed to the low-level convergence and ascending motion over Zhengzhou,and played an important role in the increase of precipitation.Therefore,the general circulation and extremely strong water vapor conditions in high,medium and low airs as well as the amplification of local topography were all beneficial to the development of the heavy rain,leading to the occurrence of extreme flood-causing torrential rain event in Zhengzhou on July 20,2021.