1951-2016年长江荆南三口地区旱涝演变与急转特征分析

根据荆南三口地区22个气象站点1951—2016年月降水资料，采用标准化降水指数（SPI）及夏季长周期旱涝急转指数（LDFAI），辅以EOF分析、小波分析、M-K检验等相关分析方法，分析荆南三口地区66年旱涝的变化特征。结果表明：（1）旱涝年际变化较大，20世纪50年代前涝后旱、60—70年代整体干旱、80年代旱涝交替、90年代洪涝、21世纪前涝后旱，且四季均可发生旱涝事件。（2）空间尺度可分为3个区域类型，东南部（湿润区）、中部（降水均匀区）、西北部（偏干区），且季节空间分布上存在较大差异，西北部的五峰、宜昌、荆州等地四季干旱较多，中部的安乡、南县、华容等地四季洪涝较多。（3）年与四季多以5年、10年周期为主，并具有30~35年的长周期。（4）旱涝急转指数在1981年和2015年发生显著变化，而旱涝强度在1972年和2014年发生显著突变。（5）宜昌、石门、澧县等夏季多为旱转涝；五峰、宁乡、安乡、华容、常德等地夏季多为涝转旱。

An Analysis on Evolution of Drought-flood and Its Abrupt Alternation in Three Outlets Along Jingjiang Reaches of Yangtze River from 1951 to 2016

Based on the monthly precipitation data of 22 meteorological stations in three outlets region along Jingjiang reaches of Yangtze River from 1951 to 2016, the characteristics of drought-flood variation during 66 years were analyzed by using the standardized precipitation index (SPI), long cycle drought-flood abrupt alternation index (LDFAI), EOF (empirical orthogonal function) analysis, Morlet wavelet analysis and M-K (Mann-Kendall) test. Results showed that:(1)There were large inter-annual variations. Specifically, drought after flood in 1950s, entire drought in 1960s and 1970s, alternation of drought and flood in 1980s, entire flood in 1990s, drought after flood in 2000s, and even-distributed drought-flood in any seasons.(2) Spatially, there were three types of drought-flood in the area, i.e. the flood-prone southeastern zone, the central zone with normal precipitation, and the drought-prone northwest zone, which had distinct seasonal distribution patterns of drought-flood. (3) Frequencies of some 5 and 10 years could be conceived, and stable frequencies of 30~35 years were significant. (4) The LDFAI index was changed in 1981 and 2015, while the intensity changed in 1972 and 2014. (5) In summer, the precipitation in Yichang, Shimen and Lixian changed from drought to flood, while the trends were opposite in and that i Wufeng, Ningxiang, Anxiang, Huarong and Changde.