基于双重嵌套网格的"8·24"宁夏暴雨成因OA

This study employs the weather research and forecasting model configured with double-nested grids to simulate an extreme torrential rainfall event over Ningxia from August 24th to 25th,addressing the Ningxia Hui Autonomous Region's lack of real-time monitoring data,which limits research on rainstorm mechanisms.The simulation's accuracy was validated against observations from 25 national meteorological stations.The threat score results are as follows:0.73 for light rain,0.56 for moderate rain,and 0.71 for heavy rain.The study indicates significant regional spatial heterogeneity in precipitation distribution during this short-duration heavy rainfall event.A multi-dimensional analysis that considers atmospheric circulation,moisture transport,and topographic effects was conducted to overcome the limitations of traditional single-factor approaches.The analysis revealed that rainstorm mechanisms involved a coupled system formed between the divergence zone associated with the 200 hPa South Asian high and the ascending branch ahead of the 500 hPa shortwave trough.This system,combined with low-level convergence at 700 hPa,created a distinct"upper-level divergence and low-level convergence"dynamic structure,greatly intensifying vertical ascent.Ningxia was situated in the left-front quadrant of a low-level jet's(LLJ)exit region.The overlap of wind speed and moisture flux convergence supplied abundant moisture transport and enhanced lifting,fueling the rainstorm.Topographic effects on the windward slope of the Helan Mountains triggered intense upward motion and a vertically coherent positive vorticity column extending up to 500 hPa,significantly promoting convection.Conversely,negative vorticity on the leeward slope suppressed precipitation.These findings highlight the crucial influence of topography in regulating the spatial heterogeneity of heavy rainfall.The study concludes that the extreme rainfall event in Ningxia resulted from a complex interaction of atmospheric dynamics,moisture transport,and topographical effects.The coupling of large-scale circulation,localized moisture flux convergence,and orographic lifting played key roles in intensifying convection and precipitation.The results emphasize the need to consider multiple factors when studying extreme weather events,and the findings enhance the understanding of rainfall mechanisms in the region.This research elucidates the multifactor synergy involved in Ningxia rainstorms,aiming to establish a theoretical basis for regional rainstorm forecasting and disaster mitigation.