Synergetic roles of dynamic and cloud microphysical processes in extreme short‐term rainfall: A case‐study

Abstract Both dynamic and cloud microphysical processes play significant roles in the intensity of severe rainfall within a convective storm. In this study, a quantitative analysis has been performed to investigate dynamic and cloud microphysical contributions to extreme hourly rainfall (EHR) with the peak value of 201.9 mm in Zhengzhou City, China, on 20 July 2021. It is found that the EHR is generated by the overlay of rainwater provided by both dynamic delivery and cloud microphysical production within a meso‐γ‐scale convective storm over Zhengzhou. Specifically, part of the rainwater is directly produced by cloud microphysical processes over the EHR region. More importantly, considerable rainwater, which is produced in the front of the storm associated with strong updraughts, is delivered into the EHR region. The dynamically delivered rainwater overlays the rainwater produced by cloud microphysical processes, forming a deep layer with a large amount of rainwater over the EHR region. As the massive rainwater pours down within a short time, EHR is formed. It should be highlighted that the dynamic delivery plays a decisive role in EHR formation, although sometimes EHR can be generated mainly through cloud microphysical production in the case of weak dynamic delivery. Concerning the cloud microphysical processes, the collision of cloud droplets by raindrops produces the largest amount of rainwater, followed by graupel melting. Linking the EHR with dynamic and cloud microphysical processes within a convective storm, a new light on further understanding and forecasting of short‐duration extreme rainfall would be shed.