利用经验模态分解提高极移预报精度（英文）

Enhancement of the Prediction Accuracy of Pole Coordinates with Empirical Mode Decomposition

经验模态分解(Empirical Mode Decomposition,EMD)是一种数据驱动的自适应非线性、非平稳信号分解方法。为提高极移预报精度,将经验模态分解应用于极移预报中。首先利用经验模态分解方法对极移序列进行分解,获得极移的高频分量和低频分量;然后采用最小二乘(Least Squares,LS)外推模型对极移低频分量进行拟合,获得最小二乘拟合残差;其次采用自回归(Autoregressive,AR)模型对极移高频分量和最小二乘拟合残差之和进行建模预报;最后将最小二乘模型和自回归模型外推值相加获得极移预报值。将经验模态分解和LS+AR组合模型预报结果与LS+AR模型预报以及地球定向参数预报比较竞赛(Earth Orientation Parameters Prediction Comparison Campaign,EOP PCC)的预报结果进行比较,结果表明,将经验模态分解应用于极移预报中,可以明显改善极移预报精度。

This paper is aimed at separation treatment of low-and high-frequency components in polar motion forecasting and then improving time-series predictions.For the purpose,the empirical mode decomposition(EMD)is employed as a filter to extract low-and high-frequency signals from original pole coordinate data.The decomposition of the pole motion observations between 1986 and 2015 from the International Earth Rotation and Reference Systems Service(IERS)C04 series illustrates that the low-frequency fluctuations including inter-decadal,inter-annual,Chandler and annual wobbles and shorter-period high-frequency oscillations can be separated from the observed time-series by the EMD.On the basis of separation,the least-squares(LS)extrapolation of models for annual and Chandler wobbles and for the linear trend are used for deterministic prediction of the low-frequency fluctuations,while the autoregressive(AR)technology is applied to forecasting the high-frequency oscillations plus LS fitting residuals.Pole coordinate forecasts are calculated as the sum of LS extrapolation and AR predictions(LS+AR).We have evaluated the accuracy of our long-term predictions(up to 1 year in the future)in comparison with the IERS official predictions in terms of year-by-year statistics of 5 years.It is shown that the accuracy of the LS+AR method can be significantly improved using a combination of the EMD and LS+AR(EMD+LS+AR).Also,the proposed prediction strategy overall outperforms the IERS solutions.In addition,the predictions are compared with those from the Earth Orientation Parameters Prediction Comparison Campaign(EOP PCC).The comparison demonstrates that the developed scheme is a very accurate approach to predict polar motion.According to this study,it is concluded that polar motion predictions may be enhanced through separation treatment of different time-scale fluctuations and thus such processing seems to be necessary in pole coordinate prediction.