Analysis of a Heavy Rainstorm Process in Zunyi,Guizhou,under the Influence of Meso-small Scale Topography in Daloushan Mountains
Based on the data of automatic weather stations,radiosonde data,Doppler weather radar data and ERA5 reanalysis data,this paper analyzes the precipitation characteristics,circulation situation,physical quantity field and mesoscale convective system evolution of a local heavy precipitation process over the night of May 20,2023 in Zunyi,Guizhou Province.The dynamic and thermodynamic effects of the meso-small scale landforms in Daloushan Mountains during this process are discussed.The results show that:(1)This heavy rainfall process occurred under the influence of the 200 hPa divergence and the convergence of low trough and low vortex shear in the middle and lower atmospheres.The continuous upward movement and high temperature and high humidity in the whole layer are the important reasons for the long-lasting precipitation and large accumulated rainfall in the process.(2)The topography of Daloushan Mountains made the 850 hPa southeast warm and humid air gathere on the windward side,resulting in the θse and relative humidity gradient large-value area in the northeast-southwest distribution along the Daloushan Mountain range.There was a θse and relative humidity large-value area on the east side of the mountain range,that is,the unstable state of the stratification of high energy and high humidity was always maintained in the heavy rain area,providing favorable conditions for the occurrence of heavy precipitation.(3)The continuous upward movement and the transport of warm-humid air made the two mesoscale convective systems merge and move eastward and southward,causing obvious train effect and finally heavy rainfall.(4)The steady flow of low-level southeast air passed over the mountain from the south side of"V"shaped terrain between Xishui and Tongzi in the northern part of Daloushan Mountain range.Due to the blocking of the north end of western Daloushan Mountain range and the Jinfou Mountain,a large-value center of water vapor flux and a downwind water vapor convergence zone were formed,resulting in water vapor accumulation effect.Convection was triggered at the overlapping position between the northern part of the surface convergence line and the large-value area of the divergence gradient of water vapor flux.These analyses show that the meso-small scale topography of Daloushan Mountains has an important influence on the dynamic and thermodynamic conditions in the precipitation process in Zunyi,Guizhou Province,which could provide a reference for revealing the causes of such heavy precipitation weather processes under the influence of Daloushan Mountain terrain.
Dalou Mountainsmeso-small scale topographyterrain effectpseudo-equivalent potential temperaturemesoscale convective system
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