近37年来湖南暴雨时空变化特征分析

Climate Characteristics of Rainstorm in Hunan in the Last 37 Years

利用湖南97个气象站1981—2017年逐日降水资料,采用线性趋势分析、集合经验模态分解(EEMD)等方法,分析了湖南近37年来年暴雨和大暴雨日数、强度、贡献率等气候特征。结果表明,近37年来,湖南年平均暴雨日数在地理上总体呈北多南少的分布。最大值出现在湘中一带,有两个中心,分别位于南岳高山站(暴雨为6.95 d;大暴雨为1.19 d)和安化(暴雨为6.10 d;大暴雨为1.16 d);最小值出现在湘西南的怀化城步(暴雨为2.40 d;大暴雨为0.11 d)。湖南年暴雨与大暴雨日数、强度及对降水的贡献率自1981—2017年均呈显著上升趋势,暴雨与大暴雨日数的2~3年、4~8年周期变化性质明显,且近些年来,有变化频率加快的趋势。

Based on daily precipitation of 97 meteorological observation stations in Hunan Province, statistical diagnostic analyses on annual rainstorm days and heavy rainstorm days over past 37 years(1981-2017) were performed by using several methods, such as linear trend analysis, EEMD(Ensemble Empirical Mode Decomposition). Results show that, generally, the spatial distribution of the annual-averaged rainstorm days had a decreasing trend from north to south, with two distinct high-value centers, one being in Nanyue Station(6.95 days of rainstorm and 1.19 days of heavy rainstorm), the other in Anhua and its surrounding areas(6.1 days of rainstorm and 1.16 days of heavy rainstorm). The lower values appeared in southwest part of Hunan, with the minimum center in Chengbu county(2.4 days of rainstorm and 0.11 days of heavy rainstorm). The rainstorm and heavy rainstorm days, intensities and their contributions to yearly rainfall had a increasing trend. Finally, the days of both rainstorm and heavy rainstorm had obvious 2-3 year and 4-8 year periodic variations, respectively, which tended to have an accelerating frequency in recent years.