Characteristics of a short-duration extreme heavy rainfall in Zhejiang Province based on S-band and X-band radar

Based on ERA5 reanalysis data,S-band dual-polarization radar and X-band dual-polarization phased array radar observation data,wind retrieval and lightning location data,the characteristics of local short-duration extreme heavy rainfall in Zhejiang on July 22,2023 were analyzed.Our results illustrate that: This event took place under the control of the subtropical high.The unstable stratification caused by the intrusion of cold dry air in the middle layer and the high energy and humidity in the lower layer provided the beneficial environment for the event.The initial linear convection occurred near the surface convergence line.The structure of the mesoscale convective system experienced from the single linear convection to the Connected double linear convection then to the separation.The development of Z_DR and K_DP columns indicate the strengthening of the convective system.When heavy rainfall occurs,the large areas of Z_H,Z_DR and K_DP decrease rapidly,and the variation of rainfall intensity is closely related to K_DP.The frequencies of cloud flash and negative ground flash significantly increase during heavy rainfall periods.The configuration of inclined updrafts and downdrafts is conducive to the development and maintenance of convective systems.The encounter of downdraft and ambient wind is benefit for the backward-propagation of convective system.Extreme heavy rainfall is also associated with the "train effect" and deep warm cloud layer.