Abstract
A number of studies revealed the possible eastward movement of the Tibetan Plateau low-pressure system in summer and indicated the enhancement effect of this process on the southwest vortex in the Sichuan Basin, which can induce strong convective precipitation and flood events in China. In this study, a numerical simulation of a southwest vortex rainstorm process was performed. The results show that the low-pressure system originated from the Tibetan Plateau affects the southwest vortex mainly at the middle level, causing the strength increase of southwest vortex (SWV), and acts as a connection between the positive vorticity centers at the upper and lower layers. For the microscopic cloud structure, the vertical updraft of the cloud cluster embedded in the SWV increases as the low-pressure system from the plateau arrives at the Sichuan Basin. Vapor and liquid cloud water at the lower level are transported upward, based on which the ice cloud at the upper level and the warm cloud at the lower level are joined to create favorable conditions for the growth of ice crystals. As the ice crystals grow up, snow and graupel particles form, which substantially elevates the precipitation. This effect leads to the rapid development of SWV rainstorm clouds and the occurrence of precipitation. In addition to the effect of the plateau vortex, the subsequent merging of the convective clouds is another important factor for heavy rainfall because it also leads to development of convective clouds, causing heavy rainfall.
Highlights
Research ArticleReceived 4 November 2017; Revised 27 March 2018; Accepted 2 April 2018; Published 3 May 2018
A number of studies revealed the possible eastward movement of the Tibetan Plateau low-pressure system in summer and indicated the enhancement effect of this process on the southwest vortex in the Sichuan Basin, which can induce strong convective precipitation and flood events in China
(1) To the area and case we studied, the vortex system of the Qinghai-Tibet Plateau shows eastward movement, which is most prominent for the vortex at the middle level above the plateau
Summary
Received 4 November 2017; Revised 27 March 2018; Accepted 2 April 2018; Published 3 May 2018. E influence of the eastward movement of the low-pressure plateau system on the convective clouds embedded in the SWV and the accompanied release of latent heat associated with cloud physics is important for the development and eastward shift of the SWV [22,23,24,25], which is true for the development of positive vorticity in low-mid layers during the occurrence of heavy precipitation [26,27,28]. Based on existing research results, the eastward movement of the low-pressure plateau system might couple with the SWV and lead to the occurrence of heavy rainfall During this process, microphysical processes influence the development and evolution of the dynamic and thermodynamic structures
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