近60年中国区域干湿转换早期预警信号

Early Warning Signals of Dry-Wet Transition in China in Recent 60 Years

近年来,中国各地干湿转换越来越频繁。干湿转换事关区域性洪涝、干旱等灾害事件的形成。如何有效识别干湿转换过程,寻找其早期预警信号是目前非线性动力学研究的热点科学问题,但目前对此类转换过程的识别及其早期预警信号尚缺乏有效且深入的研究。幸运的是,临界慢化理论在研究复杂非线性动力系统的早期预警信号方面展示了重要潜力。鉴于此,本文基于临界慢化原理,对我国13个干旱分区的代表站的K干旱指数资料进行处理,研究其干湿转换的早期预警信号。首先通过滑动t检验确定K干旱指数序列干湿转换的时间,进而借助于表征临界慢化现象的方差和自相关系数,研究了K干旱指数干湿转换的早期预警信号。结果表明,不同干旱分区代表站的K干旱指数序列均出现了不同程度的干湿转换;各代表站在其干湿转换发生前10年内均出现了方差和自相关系数增大的临界慢化现象,表征了临界慢化现象可能是干湿转换发生前的一个早期预警信号;论证了临界慢化理论作为突变早期预警信号的可靠性,为该方法的广泛应用提供了理论和实验基础。

In recent years, the dry-wet transition has become more and more frequent. The dry-wet transition is related to the formation of regional flood, drought and other disaster events. It is a hot scientific issue in the current nonlinear dynamics research that how to effectively identify the dry-wet transition process and search for its early warning signals. But at present, the identification of such transition process and its early-warning signal are still lack of effective and in-depth research. Fortunately, the critical slowing theory shows great potential in the study of early-warning signals of complex nonlinear dynamical systems. In view of this, based on the theory of critical slowing down and the K drought index data of representative stations in 13 drought regions in China, the early warning signals of dry-wet transition are investigated. Firstly, the time of dry-wet transition of the K drought index series is determined by moving t-test. Then, the early warning signals of dry-wet transition are studied by the variance and auto-correlation coefficient which represent the critical slowing-down phenomenon.The results show that the K drought index series of representative stations in different drought regions have different degrees of dry-wet transition. The critical slowing-down phenomena with the increase of variance and autocorrelation coefficient occur in each representative station within 10 years before the dry-wet transition, indicating that the critical slowing-down phenomenon may be an early warning signal before the dry-wet transition. This study proves the reliability of critical slowing-down theory as an early warning signal of mutation, and can provide a theoretical and experimental basis for the wide application of this theory.