长江中下游流域降水分区及其气象干旱时间变化特征

基于1961~2015年逐月降水格点数据，首先通过系统聚类法对长江中下游流域进行降水分区，然后以标准化降水指数为指标，结合小波分析方法，探讨了长江中下游流域各亚区气象干旱的时间演变规律及周期变化特征。结果表明：（1）空间上，可将长江中下游流域分为6个降水亚区，即：大巴山地农业区（Ⅰ）、湘鄂贵渝山地农业区（Ⅱ）、鄂中东平原农业区（Ⅲ）、湘赣平原丘陵农业区（Ⅳ）、鄱阳湖平原农业区（Ⅴ）和长江三角洲平原农业区（Ⅵ）。（2）不同降水亚区干湿事件交替过程存在差异，Ⅵ区与其它亚区差异较大，Ⅱ区、Ⅳ区和Ⅴ区的干湿事件具有相似的时间演变模式；除Ⅵ区外，2000年后其它降水亚区干旱发生频率增加明显。（3）不同降水亚区气象干旱的第一主周期存在差异，北部（Ⅰ区、Ⅲ区、Ⅵ区）和南部（Ⅱ区、Ⅳ区、Ⅴ区）具有明显的区域分化特征，但各气候亚区大都显示出3.5年左右的显著周期。研究结果可为长江中下游流域各亚区气象干旱驱动因素的解释、干旱监测计划的制定、水资源的管理和旱灾的防治提供参考依据。

Precipitation Regionalization in the Middle and Lower Reaches of the Yangtze River and Temporal Evolution of Meteorological Drought in Each Sub-region

Based on the gridded dataset of monthly precipitation from 1961 to 2015, precipitation regionalization is firstly carried out by spatial hierarchical cluster method in the middle and lower reaches of the Yangtze River (MLYR). Then, standardized precipitation index is employed to explore the temporal evolution of drought events, and wavelet method is used to detect the drought periodicity in each sub-region of MLYR. The results show that: (1) Spatially, MLYR can be divided into six sub-regions, namely, Daba Mountain (Region I), Intersection of Hunan-Hubei-Guizhou-Chongqing (Region II), Central and eastern plain of Hubei province (Region III), Hilly plain area of Hunan-Jiangxi (Region IV), Poyang Lake Plain (Region V), Yangtze River Delta Plain (Region VI). (2) There are obvious differences in the alternating processes of dry and wet events in different sub-regions. The dry and wet evolution in Region VI differs greatly from other sub-regions. The wet and dry events in Region II, Region IV and Region V have similar temporal evolution patterns. Except for the Region VI, the frequencies of drought in other sub-regions have increased significantly after 2000. (3) There are differences in the first main cycles of meteorological drought in different sub-regions. Drought periods of the northern (Region I, Region III and Region VI) and southern (Region II, Region IV and Region V) regions have obvious regional differentiation characteristics, but a significant cycle of about 3.5 years exists in the most of the sub-regions. The results of this paper can provide reference for the interpretation of meteorological drought driving factors, the formulation of drought monitoring plan, the management of water resources and the prevention and control of drought in the sub-regions of MLYR.