Causes of the Organizational Development for Short Convection in a Warm Sector Convective Event
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Abstract:
A warm sector severe convective event dominated by short-term heavy precipitation occurred in southern Anhui early in the morning of 27 May, 2023. The train effect formed by a number of north-south trend parallel meso-β scale short convections caused more than 100 mm sudden local heavy precipitation in 2 hours. The numerical simulation of this event was carried out by using WRF-EnKF, a rapid update assimilation system for service operation in Anhui Meteorological Observatory. The results show that (1) the interaction between large-scale environmental field and mesoscale convective system results in the increase of horizontal scale and intensification of several short convections. In terms of dynamic action, after the occurrence of convection, a meso-γ scale cyclonic vortex formed between the short convection and the low level jet core, causing the development of eastward convection. Meanwhile, the surface convergence line formed between the outflow of thunderstorm and the environmental wind triggers new convection in the south side of the short convection, making continuously development linearly to the south for the short convection. In terms of environmental conditions, multiple parallel low level jet cores provide favorable dynamic and thermal conditions for the development of convection. Inverse secondary circulation in the middle and upper levels occurred by the strong development of convection leads to the significant enhancement of atmospheric instability on the south side and the development of convection leads to the strengthen of deep vertical wind shear. (2) The interaction between the convections causes the maintenance of the short convection structure. Parallel convection forms parallel thunderstorm high pressure, and the interaction between the outflow of adjacent thunderstorms leads to the formation of multiple parallel positive and negative divergence pairs, thus bringing about multiple parallel zonal-vertical circulations between adjacent convections in the vertical direction. This is conducive to the maintenance and development of the structure of multiple short convections.