基于Copula函数的黄河流域干旱特征研究

Study on drought characteristics in Yellow River basin based on Copula function

干旱是黄河流域的典型自然灾害之一,长期以来对该地区的社会生产和人民生活带来巨大影响。文中以黄河流域作为研究对象,通过收集和整理流域内及其周边102个观测站点1973-2020年的逐日降水和气温观测资料,建立月度标准化降水蒸散指数,提取干旱历时和干旱烈度,使用三种单参数Copula模型和两种双参数Copula模型对全流域的干旱特征开展研究。结果表明:时间维度上,黄河流域干旱灾害发生的频次减少但剧烈程度增加;空间维度上,黄河上游部分地区及渭河流域部分地区干旱重现期较长,"几"字湾内的广大地区和黄河下游地区干旱重现期较短或接近于平均水平。此外,在逐站点干旱特征的Copula密度函数分析中,超过半数的站点具有上尾相关性,说明长的干旱历时和强的干旱烈度同时出现的概率较高。研究结果可为黄河流域不同区域的干旱风险评估与治理提供量化支撑。

Drought is one of the typical natural disasters in the Yellow River basin, which has a great impact on social production and people′s life in this area for a long time. In this paper, by collecting and sorting the daily precipitation and temperature observation data of 102 observation stations in and around the Yellow River basin from 1973 to 2020, the monthly standardized precipitation evapotranspiration index was established, and the drought duration and strength were extracted, three single-parameter Copula models and two two-parameter Copula models were used to study the drought characteristics of the whole basin. Results show that: in the time dimension, the frequency of drought disasters in the Yellow River basin decreased but the strength increased;In spatial dimension, the drought recurrence period was longer in some areas in the upper Yellow River and the Weihe River basin, while the drought recurrence period was shorter or close to the average level in the vast areas of the "Jizi" River bay and the lower reaches of the Yellow River basin. In addition, according to Copula function density analysis of drought characteristics of each station, more than half of the stations have upper-tail dependence, which indicates that the probability of long drought duration and strong drought strength appearing at the same time is higher. The results can provide quantitative support for drought risk assessment and control in different areas of the Yellow River basin.