Development mechanisms of the vortex causing a regional rainstorm in Guangxi
Vortex is the key system that causes regional rainstorms in Guangxi,it is important to clarify its development and mainte-nance mechanism for rainstorm forecast.Based on the diagnosis analysis method,the development and maintenance mechanism of the vortex causing a regional rainstorm in Guangxi on June 10-11,2022 is studied by using multi-source observation data and ERA5 re-analysis data of the European Centre for Medium-Range Weather Forecasts.The results show that the vortex generated in northwest Guangxi and stayed stably and moved little,which provided thermal and dynamic conditions for the occurrence and development of the regional rainstorm.Convective cloud clusters and precipitation areas were mainly distributed in the east and south sides of the vortex.The diagnosis of vorticity equation shows that the development and maintenance of the vortex are mainly affected by the vorticity advec-tion and horizontal divergence terms.The geostrophic component consumes the local vorticity continuously in the whole process,while the ageostrophic wind component contributes to the local vorticity.The horizontal divergence term of the ageostrophic wind component is the main reason for the development and maintenance of the vortex.Under the influence of the inertial oscillation mechanism,the ageostrophic wind on the north side of the vortex center shows obvious clockwise rotation with time.The ageostrophic wind rotates to the northerly wind and converges with the southerly ageostrophic wind near the vortex center,which leads to the development and mainte-nance of the vortex.The positive feedback of latent heating near the mid troposphere is also conducive to the development and mainte-nance of the vortex.
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