Analysis of variability of the LOD from 6-year to 10s-year oscillations

The subject of this study is the 6-, 20- and 60-year fluctuations in the length of the day LOD. A spectral and wavelet analysis of the length of the day was carried out, decadal harmonics were adjusted, and an elementary forecast was made. The influence of variations of the oceanic and atmospheric angular momentum on LODs with periods 6, 20, and 60 years were studied. It was found that the effect of the ocean and the atmosphere on the fluctuations of the LOD at periods of 20 and 60 years does not exceed 0.25 milliseconds. 6-year change of LOD, after the subtraction of the atmospheric influence, is quite stable with an amplitude of about 0.2 ms. Filtering this work was carried out using Panteleev’s bandpass filter in MATLAB. While the significant (up to 6 milliseconds) multi-decadal oscillations of the LOD remain unexplained, they were compared with anomalies of temperature and sea level, the envelope of the Chandler polar motion and its excitation, with the anomalies of the Earth’s magnetic field. The listed processes also contains long-term variations, somewhat similar to LOD variations. The work contains 35 pages, includes 26 figures. In the list of references 11 sources were used.