Climatic characteristics of regional heavy rain over Hunan during the last 54 years

Basted on the daily precipitation data collected from 88 stations over Hunan during 1960-2013, the temporal and spatial distribution characteristics of heavy rain in Hunan were analyzed using statistical methods. For temporal characteristics, the most heavy rain days are observed in June and the least in January with 208 days and 0 day in June and January, respectively. The percentage of summer, spring, autumn, or winter heavy rain days to annular heavy rain days is 60, 29, 10, or 1, respectively. Mean value jump point of heavy rain days, heavy rain intensity, the beginning dates of heavy rain are in 1994, in 1995, in 1983 and in 1994, respectively, and there is no catastrophe point for heavy rain ending dates. Heavy rain days and heavy rain intensity (the ending dates of rainstorm) show a rising (later) trend. Only heavy rain days during 1994-2013 and heavy rain intensity during 1960-1994 show decreasing trends according to the piecewise linear trend analysis based on mean value jump point. For spatial distribution, the large value region of the difference of heavy rain intensity between the regional heavy rain and the non-regional heavy rain, the difference of regional heavy rain intensity between lasted 2 days or more and lasted 1 day are located in northwestern Hunan and southeast Hunan. At the same time, the small value regions of the above differences are located in belt area from southwestern to northeastern Hunan. Regional heavy rain intensity is greater than non-regional heavy rain intensity at all stations. The percentage of the stations whose regional heavy rain lasted 2 days or more greater than that lasted 1 day to total stations is about 89. The stations’ maximum duration of regional heavy rain and total heavy rain are 1~4 day and 2~4 day, and the percentage of maximum duration of them between 2 day to 3 day are 97.7, and 96.6, respectively.