我国旱涝交替事件识别及演变规律

为了识别我国旱涝交替事件以及探究其时空演变规律,引入降雨距平指数(RAI),并提出了一种在月尺度上识别旱涝交替事件的简便易操作的研究方法。结果表明:我国旱涝交替事件具有明显的年内分布规律,4—8月份旱涝交替事件发生频次明显增加,8月份以后,旱涝交替事件发生次数减少。不同月份,旱涝交替事件高频区的分布也不同,4—6月份主要在华南地区,6—9月份主要在西南、华中、华北和东北地区。总体而言,全国旱涝交替发生的频率呈现东南高西北低的特点。而旱涝交替强度的空间格局与频率完全不同,呈现出西北高东南低的特点。21世纪以来,珠江流域、黄河、海河流域片旱转涝事件发生频率呈上升趋势;全国旱涝交替事件强度无明显变化趋势。研究成果能为我国旱涝灾害管理与防控提供科学参考,具有较强的实用价值。

Dry-Wet Transition Events in China:Identification,Temporal Dynamics,and Spatial Patterns

To identify dry-wet transition events over China and analyze their temporal and spatial distribution characteristics, we present a method to identify dry-wet transition events on monthly scale based on the rainfall anomaly index (RAI). Our findings indicate that the frequency of dry-wet transition events increased from April to August, while declined after August. The spatial patterns of dry-wet transition frequency vary among different months. During April to June, the high-frequency area mainly located in south China, while southwestern, northern, northeastern parts of China experienced more frequent dry-wet transition events during June to September. In general, dry-wet transition events occurred more frequently in southeastern part of China than the northwestern part, while intensity distribution of such events showed an opposite pattern. We further examined the variations of both the frequency and intensity in nine large river basins over different periods. Our results demonstrate that the occurrence of dry to wet events showed an increasing trend in Pearl River Basin, Yellow River Basin, Haihe River Basin, since 2000. However, there was no significant trend in the intensity of transition events. The study would provide a valuable reference for the flood and drought managements in China.