Analysis of Causes and Mesoscale Characteristics of Heavy Precipitation in Tibet on 24 August 2023
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Abstract:
The causes and mesoscale characteristics of precipitation on 24-26 August 2023, are analysed using ground automatic station observation data, FY-4A satellite observation data, Doppler weather radar data, and ERA-5 reanalysis data. The results show that the heavy precipitation process had the characteristics of long duration, large cumulative rainfall, and wide coverage. During this process, the South Asian high was distributed in a belt-like manner, and the central position controlled the plateau. The shear line was the key influencing system of the heavy precipitation, which provided the necessary water vapour transport and the maintenance mechanism of the convective uplift movement in the middle and low layers for the heavy precipitation weather. The surface convergence line provided a trigger mechanism for the uplift of low-level convection, resulting in heavy precipitation. The establishment and strengthening of the low-level southwest jet stream were conducive to transporting water vapour over the Bay of Bengal to the plateau, providing abundant water vapour for the maintenance of heavy precipitation. Environmental conditions such as a deep wet layer, low LCL and LFC, and weak vertical wind shear had a good indicative effect on the occurrence of severe convective weather. Heavy precipitation mainly occurred in the area with a large reflectance factor in cumulus echoes. When heavy precipitation occurred, the echo intensity reached 50 dBz, and the echo of 50 dBz was located within 3 km and had the characteristics of a low centroid, and there was an obvious mesoscale convergence zone on the middle and low layer velocity map.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.