文章基本信息

标题：Recovery of the 6-year signal in length of day and its long-term decreasing trend
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作者：Pengshuo Duan ; Genyou Liu ; Lintao Liu 等
期刊名称：Earth, Planets and Space
电子版ISSN：1880-5981
出版年度：2015
卷号：67
期号：1
页码：1-11
DOI：10.1186/s40623-015-0328-6
出版社：Springer Verlag
摘要：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.
关键词：Length of day; Long-term decreasing trend; NMWT method; Background trend