Characterization of non-stationary meteorological drought in Huaihe River Basin based on Copula function
[Objective]The temporal and spatial variations of drought in the Huaihe River Basin are significant,with some areas prone to severe drought.Studying the characteristics of drought in this region is crucial for agricultural production,water resource management,and ecological protection.[Methods]Monthly non-stationary standardized precipitation evapotranspiration index(NSPEI)datum from 195 meteorological stations in the Huai River Basin from 1980 to 2019 were analyzed to study meteorologi-cal drought in the region.Historical drought events were identified using run theory,extracting drought duration and drought se-verity.These were then analyzed using univariate functions and multivariate Copula functions.[Results]The result show that drought events in the Huaihe River Basin are mainly characterized by mild and moderate drought,accounting for 39%and 47%of all drought events,respectively.These events are primarily distributed in the northwest and south of the basin,with extreme drought being rare.The Generalized Pareto function is the most suitable for fitting the univariate distribution of drought duration and drought severity,with 87 stations indicating that the t-Copula function is the best fit for the joint distribution.When the return period exceeds 20 years,the spatial distribution characteristics of drought duration and drought severity are found to be approximate-ly the same,with high-value areas concentrated in the southwest of the basin.The spatial distribution of the joint return period and concurrent return period probabilities is observed to remain nearly unchanged as the return period increases,with high-value areas mainly located in the southern and western parts of the basin.[Conclusion]Drought events in the Huaihe River Basin are primarily characterized by moderate droughts within months,mild droughts within seasons,and moderate droughts within seasons,with the occurrence of extreme droughts being found to be very low.As the return period increases,the high-value areas for drought duration and drought severity are mainly distributed in the southwest of the Huaihe River Basin,making this region identified as the highest risk area for drought disasters.The spatial distribution characteristics of the joint return period and concurrent return period are shown to change insignificantly,and a long-duration,high-intensity drought event with a duration of up to 10.8 months and a drought intensity of up to 11.9 occurs in the southwestern part of the basin when the return period is 100 a.
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