Abstract Anthropogenic climate change has led to nonstationarity in hydrological data and their statistical characteristics. To consider nonstationarity in regional frequency analysis, several nonstationary index flood (NS-IF) methods comprising a time-dependent site-specific scaling factor or nonstationary regional growth curves have been suggested. However, these methods have limitations related to underestimation from using sample statistics as a site-specific scaling factor or considering nonstationarity only in regional parameters. To overcome these drawbacks, this study developed a nonstationary population index flood (NS-PIF) method that considers nonstationarity in the statistical characteristics at each site in a region based on nonstationary generalized extreme value distributions. Monte Carlo simulations were conducted for synthetic regions under various nonstationary conditions to compare the performance of the NS-PIF method with those of existing NS-IF methods. Then the applicability of the NS-PIF method to real-world data was assessed via Monte Carlo simulations of regions with annual maximum rainfall data in South Korea. The results indicated that the NS-PIF method can solve the underestimation problem inherent in existing NS-IF methods. Moreover, the NS-PIF method yielded the best performance and provided more reliable and reasonable quantile estimates considering site-specific trends. In addition, the heterogeneity measure based on L-skewness and L-kurtosis was identified as a suitable test of homogeneity for application of the proposed method.

中文翻译：

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基于非平稳人口指数洪水法的极端降水区域频率分析

摘要 人为气候变化导致水文资料及其统计特征的非平稳性。为了考虑区域频率分析中的非平稳性，已经提出了几种非平稳指数洪水 (NS-IF) 方法，包括与时间相关的站点特定比例因子或非平稳区域增长曲线。然而，这些方法在使用样本统计数据作为特定地点的比例因子或仅考虑区域参数的非平稳性时存在与低估相关的局限性。为了克服这些缺点，本研究开发了一种非平稳人口指数洪水 (NS-PIF) 方法，该方法基于非平稳广义极值分布来考虑区域中每个站点的统计特征的非平稳性。在各种非平稳条件下对合成区域进行蒙特卡罗模拟，以比较 NS-PIF 方法与现有 NS-IF 方法的性能。然后通过对韩国年度最大降雨量数据区域的蒙特卡罗模拟评估 NS-PIF 方法对现实世界数据的适用性。结果表明NS-PIF方法可以解决现有NS-IF方法固有的低估问题。此外，考虑到特定站点的趋势，NS-PIF 方法产生了最佳性能，并提供了更可靠和合理的分位数估计。此外，基于 L 偏度和 L 峰态的异质性度量被确定为适用于所提出方法的同质性测试。