The Basic Observational Analysis of "7.20" Extreme Rainstorm in Zhengzhou

Affected by the easterly jet around the Huang-Huai vortex, extreme rainstorm occurred in Zhengzhou from 08:00 BT 18 to 08:00 BT 22 July 2021, and caused serious landslides, mudslides, urban waterlogging and casualties. Based on observations from sounding, automatic weather stations and radar composite products, the preliminary analysis of this event was made. The results indicate that the extreme rainstorm has the characteristics of long duration of heavy rainfall, large accumulated rainfall, outstanding extremes, and strong short-term rainfall. The reasons for the extreme heavy rain are complicated. However, based on the preliminary analysis results, the basic causes are stable atmospheric circulation, sufficient water vapor and energy, terrain effect obviously and the convective systems that continuously accumulated, merged and stagnated in Zhengzhou. This study focuses on the analysis of the basic observational phenomena of this extreme rainstorm, sorts out the original data for the subsequent research, and lays the foundation for further in-depth study on the mechanism and predictability of this rare extreme rainstorm.