基于GAMLSS模型的古黄河宿迁段流域降雨序列非一致性特征研究

Study on the non-stationary characteristics of rainfall series in Suqian reach of ancient Yellow River Basin based on GAMLSS model

【目的】水文时间序列的非一致性分析可有效提高水文频率分析计算结果的合理性与准确性。非一致性序列的研究对象主要集中于洪水和径流,而对降雨的研究相对较少。【方法】运用Mann-Kendall(MK)趋势检验法以及广义可加模型(Generalized Additive Models for Location Scale and Shape,GAMLSS),以古黄河宿迁段流域的10个雨量站1980—2018年逐月降雨数据为例,研究年、汛期以及非汛期降雨序列的非一致性特征并分析非一致性特征对降雨频率设计值的影响。【结果】结果如下:(1)在5%的显著性水平下,MK法检验的结果表明研究区各降雨序列虽存在趋势但不显著;(2)GAMLSS模型可以揭示MK检验无法反映的显著趋势,从而发现研究区年、汛期、非汛期降雨序列的非一致性特征较为明显,且主要表现为方差非一致性;(3)由于降雨序列的非一致性特征,一致性模型存在高估或低估的风险,且不同时期的频率设计值呈现较大的差异,新袁站非汛期降雨、金锁站年降雨某一时期的2 a一遇降雨量级甚至可能超过其他时期的50 a一遇降雨量级。【结论】应综合考虑时间趋势和频率要素来推求降雨频率设计值,可为GAMLSS模型在流域降雨非一致性定量分析的应用中提供参考。

[Objective]The non-stationary analysis of hydrological time series can effectively improve the rationality and accuracy of hydrological frequency analysis results.The research object of non-stationary series mainly focused on flood and runoff,rather than rainfall.[Methods]In this paper,the Mann-Kendall(MK)trend test and the Generalized Additive Models for Location Scale and Shape(GAMLSS)are adopted to study the non-stationary characteristics of annual,flood season and non-flood season rainfall series,and analyze the influence of the non-stationary characteristics on the design value of rainfall frequency,taking the monthly rainfall data of 10 rainfall stations in the Suqian Reach of the Ancient Yellow River Basin from 1980 to 2018 as the case study.[Results]Results are as follows:(1)At the significance level of 5%,MK test results show that although there is a trend for all rainfall series in the study area,it is not significant.(2)GAMLSS model can reveal significant trends which MK test can not reflect,and it is found that the non-stationary of rainfall series are significant in the study area,which are mainly manifested as the variance non-stationary.(3)Due to the non-stationary characteristics of rainfall series,stationary models have the risk of overestimation or underestimation for the rainfall design values,which shows great differences in different periods.The 2-year precipitation level in a certain period of non-flood season rainfall at Xinyuan Station and annual rainfall at Jinsuo Station may even exceed the 50-year precipitation level in other periods.[Conclusion]Therefore,the design value of rainfall should be calculated by considering the time trend and frequency factors comprehensively.The research results are expected to provide reference for the application of GAMLSS model in the quantitative analysis of rainfall non-stationary characteristics.