基于希尔伯特-黄变换与小波变换的无定河径流变化周期对比分析

Comparative analysis on periodic variations of Wudinghe annual runoffs using Hilbert-Huang transform and wavelet transform

【目的】对基于希尔伯特-黄变换(Hilbert-Huang transform,HHT)与小波变换的径流周期分析方法进行比较,为选择适合研究流域的径流变化周期判定方法提供参考。【方法】采用HHT与小波变换,对无定河流域干流上的代表水文站白家川站1956-2009年天然径流资料进行分析,探讨2种方法在分析无定河流域年径流变化周期上的差异性。【结果】无定河天然径流演化模式由4个本征模态函数和1个零均值趋势项组成,通过分析各个固有模态函数(Intrinsic Mode Function)分量,由希尔伯特谱及经验分解图可以看出,不同尺度径流波动对径流演变的作用为,随尺度增大,径流平均周期由短变长,由年际变化转为代际变化。无定河流域天然径流演化存在3,7,12和21～22年的近似周期。通过小波系数实虚部及模、模方等值线图,判定其径流丰枯变化及主要周期中心为7,25,40和53年。【结论】基于HHT与小波变换的径流周期分析方法的计算结果基本吻合,但小波分析只能分析出近似周期,而HHT分析还可发现年内变化和年际变化在周期变化中占主导作用,表明HHT方法更为优越。

【Objective】 The study was conducted to select appropriate research methods on analysis of watershed runoff change cycle by comparing Hilbert-Huang transform（HHT） and wavelet transform.【Method】 This article applied the Hilbert-Huang transform and wavelet transform in the multiple-time-scale analysis of annual runoff series in the Wudinghe basin with measured annual runoff data from 1956 to 2009 at Baijiachuan hydrologic station in the Wudinghe basin.Differences of the periodic analysis of annual runoff variation were also discussed.【Result】 Wudinghe basin natural runoff evolution model was composed of four Intrinsic Mode Functions and a zero residual value.By analyzing each Intrinsic Mode Function component,it concluded that effects of runoff fluctuationin were in different scales： average cycle of runoff elongated as scale on runoff evolution increased,and the variation time scale changed to generationally instead of interannually.Estimated variation of the rainy periods and drought periods,and the main cycle center were 7,25,40 and 53 years,respectively using wavelet transform.【Conclusion】 The annual runoff periods of Wudinghe Basin included 3,7,12,and 21-22 years,respectively.Results of two methods generally matched.However,wavelet transform can only draw approximate period while HHT transform can also found that the seasonal change and the interannual variability play a leading role in the periodic changes.This study indicates that HHT method is superior.