基于多维Copula的中国干旱特征及危险性分析

Drought characteristics and risk hazard in China based on multidimensional Copula model

干旱是中国主要的自然灾害之一。在全国开展干旱的特征分析,评估干旱的发生概率,有利于宏观了解中国整体干旱风险格局,对干旱监测和预警工作具有重要意义。基于1980—2019年国家气象科学数据中心地面气候资料日值数据集计算标准化降水蒸散指数(SPEI),通过游程理论识别历史干旱事件并提取干旱历时、干旱强度和烈度峰值3个特征变量,利用Copula分析了中国不同类型干旱事件的发生概率和重现期。结果表明:从干旱强度看,中国最容易发生“轻旱”和“中旱”;从干旱历时看,中国最容易发生“跨季”干旱,其中北方干旱区较其他农业区最容易发生“半年以上”干旱。“高烈度峰值”干旱的发生概率远小于“低烈度峰值”干旱,其发生概率随干旱历时递增而增加。各类型“高烈度峰值”干旱在黄淮海平原区、长江中下游地区和华南区的联合重现期普遍较短。

Drought is one of the most serious natural disasters that human society is facing,which substantially affects agriculture and animal husbandry.China is a region with high incidents of drought disasters globally.For drought monitoring,early warning and ecological environment protection in China,analyzing the characteristics of drought and assessing its occurrence probability is crucial.The standardized precipitation-evapotranspiration index(SPEI)series at 1-,3-,6-,and 12-month timescales were calculated using the daily surface climate data set of the National Meteorological Data Center from 1980 to 2019.After comparing and analyzing the fluctuations in the SPEI series at different timescales,the 3-month-timescale SPEI(SPEI-3)was selected to identify historical drought events and extract three characteristic variables(drought duration,drought severity,and intensity peak)based on the theory of runs.SPEI-3 can fully reflect the seasonal dryness and humidity and is commonly used in agricultural drought monitoring.Then,using two-and three-dimensional Copula models,the joint distribution between two-and three-dimensional drought characteristic variables was constructed to estimate the occurrence probabilities of drought events under different combinations of drought duration and drought severity and those under different combinations of drought duration,drought severity,and intensity peak,respectively.Finally,the return periods of a single drought characteristic variable and the joint return periods of different types of“high-intensitypeak drought”were calculated.The results show that“mild drought”and“moderate drought”are most likely to occur in China from the perspective of drought severity.In terms of drought duration,“cross-season drought”is most likely to occur in China,and“drought over half a year”is most likely to occur in the northern arid region compared with other agricultural regions.The occurrence probability of“high-intensity-peak drought”is much less than that of“low-intensity-peak drought”,and its probability increases with increasing drought duration.The joint return periods of“high-intensity-peak drought”in the North China Plain,middle and lower Yangtze River Plain,and southern China are generally shorter than those in other regions.Short duration(“monthly drought”,“intra-season drought”,and“cross-season drought”)and low severity(“mild drought”and“moderate drought”)are the dominant factors for the joint return periods of various drought events in China.In this study,multidimensional drought characteristic analysis and hazard assessment were conducted nationwide,which are conducive for macroscopic understanding of the overall drought risk pattern in China and provide reference for drought control and prevention.