Classification of rainstorms in Hunan Province affected by the Southwest China vortex

By using the Southwest China Vortex Yearbook, ERA-Interim reanalysis data, national meteorological station precipitation data and TRMM (Tropical Rainfall Measuring Mission) gridded precipitation, Southwest China vortex (SWCV) rainstorms occurring in Hunan Province during the 2012-2016 period are investigated. And the multivariate EOF and k-means clustering method were used to objectively classify the weather situation of SWCV rainstorms. The results show that: (1) SWCV rainstorms accounted for one-third of total rainstorms in Hunan, which was mostly caused by eastward basin SWCV and Jiulong SWCV. (2) SWCV rainstorms in Hunan can be classified into three categories: warm convection, reversal flow, and cold front. The intensity of warm convection rainstorms were the strongest and the other two had similar intensity. (3) Warm convection rainstorms were mainly distributed in north of Hunan, located at deep warm and humid air flow in front of SWCV trough. Reversal flow rainstorms were mainly distributed in southeast of Hunan, formed in coupling area of reversal flow behind the high-pressure anticyclone and front of SWCV trough, which were typical weather situation of autumn SWCV rainstorms. Frontal rainstorms were directly affected by cold air, and usually formed along the frontal zone and horizontal wind shear line.