基于经验模态分解与传统水文分析法的降雨序列研究

Study on rainfall time series based on empirical mode decomposition and traditional hydrological methods

为研究经验模态分解(EMD)法和传统水文分析方法在水文时间序列研究中的特点,以陕西省榆林市1951—2017年降雨时间序列为例,对该数据的趋势性和周期性成分进行了分析对比。结果表明:传统的Mann-Kendall(M-K)检验法与EMD方法都可反映出水文序列的趋势及转折点,且两种方法所得结果相似,反映出榆林市降雨量先增后减的变化趋势,但转折点时间有所差异。EMD方法与M-K方法得到的趋势项结果呈现形式不同,EMD方法所得趋势线可更加直观地表现原始序列的升降情况。周期性成分分析方面,榆林市年降雨量与夏季降雨量具有相同的周期规律。EMD方法所得模态相较于傅里叶分析法所得频谱更为丰富,但各模态所对应周期不明确,也难以对应实际的物理意义。EMD方法可作为传统水文分析方法在趋势分析及周期成分提取时的有效补充。

Abstract:In order to study the characteristics of the empirical mode decomposition(EMD)method and the traditional hydrological analysis method for the analysis of hydrological time series,the1951-2017year rainfall time series in Yulin of Shaanxi Province are taken for instance to analyze and compare the trends and periodic components of the hydrological time series.The results show that the traditional Mann-Kendall(MK)test and the EMD method can reflect the trend of hydrological series and the corresponding turning points,and the analysis results of the two methods are similar,which can both reflect the trend that the rainfall in Yulin City increased first and then decreased with different turning point.The trend results obtained by the EMD method and the M-K method are different in form and the trend curve obtained by the EMD method which shows more directly the ascending and falling of the original time series.In terms of the periodic components analysis,the annual rainfall in Yulin City displays the same periodicity as that in summer.The modalities obtained by the EMD method are more abundant than those by the Fourier analysis.However,the periods corresponding to the modalities are not clear and difficult to find the corresponding actual physical meanings.The EMD method can be used as an complement to the traditional hydrological methods in trend and periodic component analysis.