Abstract:Based on the daily precipitation data at 97 national stations in Hunan Province from 1981 to 2018, conventional observation data, ERA-Interim data and typhoon path data, the climatic statistics method, meteorological analysis method and composite synthesis method are used to analyze the climatic characteristics of extreme precipitation in Hunan Province and their weather system types. The results show that during the past 38 years, the average threshold of the daily extreme precipitation in Hunan Province was 71.6 mm, and there were 130 extreme precipitation days per year. Both the values had large interannual variability, and there was a significant change in 1993. Before 1993, the average threshold of the daily extreme precipitation was low (65.7 mm), and there were only 99 extreme precipitation days per year; after 1993, the average threshold was high (74.7 mm), and there were 146 extreme precipitation days per year. The spatial distributions of daily extreme precipitation thresholds and extreme precipitation days were uneven. In central Hunan and areas north to it, the thresholds of extreme precipitation were high, the intensity of extreme precipitation was strong, and the frequency of occurrence was low. But in the south of Hunan, the threshold was low, the intensity of extreme precipitation was weak and the frequency of occurrence was high. The regional extreme precipitation processes of Hunan mainly occur from May to August, especially in June. Five types for weather systems of extreme precipitation processes are summarized: the southwest vortex and warm shear line type, the cold trough and shear line type, the typhoon type, the subtropical high edge type, the consistent southerly wind type. The main influence systems of extreme precipitation in Hunan are upper trough, southwest vortex, shear line and low-level jet. If the southwest vortex does not move out of the southwest region of China or its location is to the south, the extreme precipitation in Hunan will be caused by the southwest vortex and warm shear line, and if the location of southwest vortex is to the north, or there is a new vortex developing and strengthening on the east side of Wuling Mountains, then the extreme precipitation in Hunan will be caused by the cold shear line behind the southwest vortex (new vortex). The topography has a significant effect on the increase of extreme precipitation, especially on the extreme precipitation process of typhoon in southeastern Hunan. In different seasons, the subtropical high has different effects on the area and intensity of extreme precipitation. For the extreme precipitation in the warm zone under the background of weak forcing, the application of high spatio-temporal resolution data should be strengthened to analyze the meso- and small-scale trigger mechanism.