“衡邵娄干旱走廊”干旱时空演变特征分析

Spatio-temporal evolution characteristics of drought in the“Heng-Shao-Lou drought corridor”

近年来,长江流域干旱事件频发,干旱灾害造成的损失越来越大,为进一步提升区域干旱灾害风险管理及防旱抗旱能力,开展典型旱区干旱时空演变规律研究具有重要意义。“衡邵娄干旱走廊”是湖南省干旱最严重区域,利用该区域33个气象站1971—2022年逐月降水量构建标准化降水指数(Standardized Precipitation Index,SPI)序列数据集,以邵阳县为示例,应用游程理论整合干旱事件,基于Gumbel-Copula函数构建干旱历时和强度联合分布函数,计算干旱联合重现期并推广至整个研究区域,在此基础上构建干旱等级划分标准,分析整个研究区域各等级干旱概率空间分布特征。主要结论如下:邵阳县Ⅰ型和Ⅱ型干旱历时和强度理论联合重现期峰值分别约97、27 a,表明长历时且高强度干旱事件发生概率很小,远低于长历时或高强度干旱事件发生概率,这是研究区干旱事件的共性。基于干旱历时和强度联合分布组合可有效避免单一变量在识别干旱等级时对干旱事件整体的分割,能够更准确评估干旱的复杂性及大范围影响。近52 a来,“衡邵娄干旱走廊”西部轻旱最频繁,重旱与特旱发生频率低,特旱主要分布在邵阳县、邵东县及双峰县一带。

Recently,the droughts attack frequently in the Yangtze River basin,resulting in more and more loss.To further improve re⁃gional drought risk management and drought resistance capabilities,it is of great significance to conduct research on the spatiotemporal evolution characteristics of drought in typical drought-prone areas.“Heng-Shao-Lou drought corridor”in Hunan Province is a region with most severe droughts,the standardized precipitation index(SPI)dataset based on monthly precipitation data from 33 meteo⁃rological stations in this area from 1971 to 2022 is constructed.Citing the case of Shaoyang County,run theory is applied to integrate drought events,and Gumbel-Copula is adopted to construct the joint distribution function of drought duration and severity,then the joint return periods of drought are calculated and the method is extended to the whole study area.On the basis of it,the classification standard of drought grades is established,and the spatial distribution characteristics of drought probability for each level in the whole study area are analyzed.The results show that the peaks of theoretical joint return period of drought duration and severity for the typeⅠand typeⅡin Shaoyang County are around 97 a and 27 a,respectively,which indicates that the probability of drought events with long duration and high severity is very small and far lower than that of drought events with long duration or high severity,it is a common feature of drought events in research area.Furthermore,the combination of drought duration and severity joint distribution can effec⁃tively avoid segmentation of the whole drought event when drought grades are identified by a single variable,and can evaluate the com⁃plexity and large-scale impact of drought more accurately.In the past 52 years,the slight drought occurs most frequently in western re⁃gion of the“Heng-Shao-Lou drought corridor”,while the frequency of severe or extreme drought is low.Extreme drought mainly distrib⁃utes in Shaoyang County,Shaodong County and Shuangfeng County.