A Case Study on the Rainstorm‐Producing Mesoscale Vortices in Central‐Eastern China

Abstract

AbstractDuring 26–27 June 2022, mainly influenced by three mesoscale vortices, central‐eastern China (particularly for Henan and Shandong) experiences the first widespread torrential rainfall event of the 2022 flood season (maximum 24‐hr accumulated precipitation is ∼380.9 mm), resulting in severe social impacts. The three mesoscale vortices form and sustain under favorable background conditions, mainly including a strong upper‐level divergence, an intense middle‐level warm advection, and a powerful lower‐level convergence associated with a low‐level jet. Among the vortices, the vortex which forms over Shandong, lasts for ∼9 hr, and makes a much larger contribution than the other vortices to the accumulated precipitation, is defined as the primary vortex. More than a half of the hourly precipitation peaks in this event appear in the life span of the primary vortex, which is closely related to the variations of the vortex in its cyclonic‐vorticity and vertical extent. Backward trajectory analysis indicates that air particles originating from the lower troposphere southwest of the primary vortex contribute the most to its formation (∼82.7%). These air particles mainly experience a notable increase in their cyclonic‐vorticity due to convergence‐related vertical stretching, which directly renders the formation of primary vortex. During the whole life span of the primary vortex, convergence‐related vertical stretching is the most favorable factor for its development/sustainment, and the convection‐related vertical transport of cyclonic vorticity ranks second; whereas, the horizontal transport is the most detrimental factor. Moisture budget shows that Southeast China is the most important moisture source for this event (accounting for ∼48.9%).