基于Copula函数的干旱特征分析

Abstract

研究干旱事件有利于水资源的规划和管理。本文以标准降水指数SPI作为干旱指标，基于Copula函数，提出了一种新的干旱分析模型。该模型首先生成M年的日降雨数据，首次采用干旱历时、干旱程度、最小SPI值和干旱间隔时间来定义干旱事件，引入四维对称和非对称型Archimedean和椭圆Copula函数构建多维联合分布；最后依据联合重现期和条件重现期的计算公式，分析了干旱事件的重现期，并以汉江上游为例进行了应用研究。结果表明，所提方法考虑了多个变量，与现有方法相比，能够更全面地反映干旱事件的真实特征；本文的分析结果将为南水北调中线工程调度决策提供科学依据和技术支持。 Droughts are of great importance in the planning and management of water resources. This study proposed a new model for analyzing the characteristics of droughts based on copula functions and Standardized Precipitation Index (SPI). First, M years of daily rainfall data were simulated for evaluating drought characteristics. Second, drought characteristics, namely, drought duration, severity, interval time and minimum SPI values, were introduced and determined in this model. Then, several copulas, including symmetric and asymmetric Archimedean and meta-elliptical copulas were applied to construct four-dimensional joint distributions. Drought probabilities and return period were calculated and analyzed based on a four-dimensional copula using the upper Han River basin,China, as a study area. The results show that compared with the current methods, the four-dimensional joint distribution considering more variables can reveal the real characteristics of droughts. The analysis results can provide technique support for the well-known South- to-North Water Diversion Project (SNWDP) inChina.