1470—2008年中国西北干旱地区旱涝变化特征分析

研究西北干旱地区的旱涝变化规律对于区域抗旱减灾具有重要的现实意义。建立区域综合旱涝指数模型，利用西北4省区19个站点的旱涝等级序列，建立区域综合旱涝指数序列。发现区域在1470—2008年间呈现出干旱频发的态势，且区域内的西部比东部、高海拔地区较低海拔地区更易发生干旱灾害。利用经验模态分解方法处理区域综合旱涝指数序列，发现区域综合旱涝指数变化存在2.5年、7.5年、13.1年、25.7年、77.0年和134.8年等准周期变化。且近539年来，西北干旱地区区域综合旱涝指数呈减小趋势，未来区域干旱综合强度有减轻态势。

Drought-flood variation characteristics and trends in arid Northwestern China during 1470—2008

It is important to study the drought-flood variation in the arid Northwestern China for regional development and disaster prevention. This work reconstructs the Regional Comprehensive Drought-flood Index (RCDI) series in arid Northwestern China and relevant provinces, based on the drought-flood grades series of 19 sites in the arid Northwestern China. The RCDI series shows that the drought is a major hazard during the last 539 years. It is also found that the drought happened more frequently in the western and high altitude areas than the eastern and low altitude areas of arid Northwestern China. The paper analyzes the fluctuation characteristics of the RCDI series by Empirical Mode Decomposition (EMD) method. The results show that the variations of drought-flood in arid Northwestern China have six quasi-periodic fluctuations which are 2.5a, 7.5a, 13.1a, 25.7a, 77.0a, and 134.8a, respectively. The results also show that the trend of the regional drought severity decreased in the last 539 years.