湖南持续性区域暴雨气候特征及暴雨落区分型

Climatic Characteristics of Regional Persistent Heavy Rain and Heavy Rainfall Pattern over Hunan

基于1961-2016年湖南88个台站逐日降水及NCEP再分析数据,利用突变分析、聚类分析、合成分析等方法,分析了湖南持续性区域暴雨的气候特征,并对暴雨落区进行了分型。结果表明,近56年湖南持续性区域暴雨过程年平均出现2次,最长持续日数为5天;夏季发生次数最多占73%,冬季未发生,出现较多的月份5,6,7和8月分别占16%,38%,20%和14%;持续性区域暴雨过程次数在1993年发生了均值突变,年平均过程次数从1961-1992年的1.4次增加至1993-2016年的2.8次。持续性区域暴雨过程年均发生0.9次以上的区域主要分布在湘中以北,湘中以北较湘南年均次数偏多。持续性区域暴雨强度全省区域平均值为82.5 mm·d^-1,大于85 mm·d^-1的台站主要分布在湘西北及湘东南。暴雨日强降水落区可分为4类空间分布型即湘西北型、湘中偏北型、湘中偏南型及湘东南型,4类空间分布型的累计暴雨日数占总持续性区域暴雨日数的百分比依次为25.6%,30.1%,21%和18.4%,湘西北型与湘东南型的降水强度较湘中偏北型与湘中偏南型的降水强度大,且强降水落区相对更集中;对应4类暴雨落区分型合成的925 hPa风场切变及水汽辐合大值区的位置、走向与4类暴雨空间分布型的强降水落区基本吻合,对强降水的落区有较好指示性。

The frequency of extreme heavy precipitation events over Hunan is increasing under the background of global warming. Based on the daily precipitation data collected from 88 stations over Hunan and NCEP reanalysis data during 1961-2016, the climate characteristics of regional persistent heavy rain and heavy rainfall pattern over Hunan were analyzed by using the abrupt change analysis, clustering analysis, composite analysis and so on. The results shows that the regional persistent heavy rain during the past 56-year over Hunan has occurred annual average 2 times, and the maximum number of consecutive days is 5. The percent of regional persistent heavy rain is 73% and 0% in summer and winter, and is 16%, 38%, 20% and 14% in May, June, July and August respectively. Annual regional persistent heavy rain process times changed from 1.4 in 1961-1992 to 2.8 in 1993-2016, and 1993 is the mutational year. The regional persistent heavy rain mainly occurred more than 0.9 times a year over the north of central Hunan, and the frequency of regional persistent heavy rain over north of central Hunan was significantly more than that over southern Hunan. The regional persistent heavy rain intensity averaged over Hunan is 82.5 mm·d^-1, which is 7.7 mm·d^-1 bigger than that of non-sustained regional heavy rain, and the stations of regional heavy rain intensity greater than 85 mm·d^-1 are mainly distributed over northwest and southeast Hunan. The heavy rainfall can be divided into four spatial distribution pattern:northwestern, north-central, south-central and southeastern type, and the percent of the four heavy rainfall pattern days to the total heavy rainfall days is 25.6%, 30.1%, 21% and 18.4%, respectively. The precipitation intensity of the northwestern type and southeastern type was higher than that of the north-central type and south-central type, and the heavy rainfall area of the former two types was more concentrated. The location and direction of synthesis wind field shear and large value area of water vapor convergence on 925 hPa are basically consistent with the strong precipitation area of four heavy rainfall pattern over Hunan, which has a good indication for prediction about the heavy rainfall area over Hunan.