Recovery of the 6-year signal in length of day and its long-term decreasing trend

Earth, Planets and Space - Tập 67 - Trang 1-11 - 2015
Pengshuo Duan1,2, Genyou Liu1, Lintao Liu1, Xiaogang Hu1, Xiaoguang Hao1, Yong Huang1,2,3, Zhimin Zhang1,2, Binbin Wang1,2
1Institute of Geodesy and Geophysics, Chinese Academy of Sciences, State Key Laboratory of Geodesy and Earth’s Dynamics, Wuhan, China
2University of Chinese Academy of Sciences, Beijing, China
3Department of Physics, School of Science, Wuhan University of Technology, Wuhan, China

Tóm tắt

There is a significant 6-year oscillation signal (called 6-year signal in this paper) existing in the interannual variations of length of day (LOD). It is unclear to understand its nature variation features. This paper extracts quantitatively the 6-year signal, from 1962~2012, using normal Morlet wavelet (NMWT) method combining wavelet packet and Fourier analysis technique, for the first time, and we investigate it in both time and frequency domains. The results indicate that the amplitude of a 6-year signal shows a long-term decreasing trend and the total amplitude reduction is about 0.05 ms during the past 50 years. The ratio of above reduction to the mean amplitude of 0.124 ms reaches 40 %. For interpreting the phenomenon on the above long-term decreasing trend, this paper proposes two alternatives; however, there is still no firm conclusion and it is required to be further explored.

Tài liệu tham khảo

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Earth, Planets and Space

Tập 67

1-11

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