Analysis of Rainstorm Characteristics and Precipitation Distribution Associated with Southwest Vortices in Northeastern Sichuan
Analysis of Rainstorm Characteristics and Precipitation Distribution Associated with Southwest Vortices in Northeastern Sichuan
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Abstract
Based on the conventional meteorological observation data, surface intensive automatic station data and ERA5 reanalysis data, rainstorm events in Northeastern Sichuan induced by Southwest Vortices from 2010 to 2021 were statistically classified according to the movement paths, and the characteristics of different types of circulation background, thermodynamic and dynamic structure and rainstorm distribution were compared and analyzed. The results show that the paths of Southwest Vortices affecting the rainstorm in northeastern Sichuan are mainly divided into three types: northeast type (NE), east type (E) and stagnation type (S). The rainfall area of the NE type covers the entire region, while that of the E type is concentrated in the east, and the S type is in the north. The rainfall centers of all three types show a northeast-southwest orientation. At the 500 hPa level, the NE type is characterized by a typical "east-high, west-low" pattern at mid-low latitudes, which hinders the eastward movement of the 500 hPa trough and the 700 hPa Southwest Vortex. For the E type, the western Pacific subtropical high is situated farther east and south compared to the NE type, which is conducive to the continued eastward movement of the 500 hPa trough and the 700 hPa Southwest Vortex along the Yangtze River Basin. The S type features a stronger high-pressure circulation, which more effectively blocks the Southwest Vortex, thereby inhibiting its development and eastward movement. The convective activity is weak near the center of the low vortex, and the middle and low levels on the east side of the low vortex are the ascending motion area and the positive vorticity area. For the S type, heavy precipitation occurs within 2.0~3.0 degrees longitude east of the 700 hPa vortex center. In contrast, for the E and NE types, heavy rainfall is located within 1.0~2.0 degrees longitude east of the 700 hPa vortex center, and this range is the center of the southerly strong wind core or the maximum wind speed convergence zone.
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