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Nonlinear Processes in Geophysics An interactive open-access journal of the European Geosciences Union
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Volume 22, issue 4
Nonlin. Processes Geophys., 22, 473–484, 2015
https://doi.org/10.5194/npg-22-473-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Nonlin. Processes Geophys., 22, 473–484, 2015
https://doi.org/10.5194/npg-22-473-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 05 Aug 2015

Research article | 05 Aug 2015

Search for the 531-day-period wobble signal in the polar motion based on EEMD

H. Ding1 and W. Shen1,2 H. Ding and W. Shen
  • 1School of Geodesy and Geomatics, Key Laboratory of Geospace Environment and Geodesy of the Ministry of Education, Wuhan University, Wuhan 430079, China
  • 2State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, China

Abstract. In this study, we use a nonlinear and non-stationary time series analysis method, the ensemble empirical mode decomposition method (EEMD), to analyze the polar motion (PM) time series (EOP C04 series from 1962 to 2013) to find a 531-day-period wobble (531 dW) signal. The 531 dW signal has been found in the early PM series (1962–1977), but cannot be found in the recent PM series (1978–2013) using conventional analysis approaches. By virtue of the demodulation feature of EEMD, the 531 dW can be confirmed to be present in PM based on the differences of the amplitudes and phases between different intrinsic mode functions. Results from three sub-series divided from the EOP C04 series show that the period of the 531 dW is subject to variations, in the range of 530.9–524 days, and its amplitude is also time-dependent (about 2–11 mas). Synthetic tests are carried out to explain why the 531 dW can only be observed in recent 30-year PM time series after using EEMD. The 531 dW is also detected in the two longest available superconducting gravimeter (SG) records, which further confirms the presence of the 531 dW. The confirmation of the 531 dW existence could be significant in establishing a more reasonable Earth rotation model and may effectively contribute to the prediction of the PM and its mechanism interpretation.

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Short summary
A 531-day wobble (531 dW) signal is clearly detected with a mean amplitude of about 7 mas after applying the ensemble empirical mode decomposition (EEMD) to the 1962-2013 polar motion (PM) time series. This signal is also detected in the two longest available superconducting gravimeter (SG) records. Synthetic tests are carried out to explain why the 531 dW signal can only be observed in recent 30-year PM time series after using EEMD.
A 531-day wobble (531 dW) signal is clearly detected with a mean amplitude of about 7 mas after...
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