Evolution of the Earth rotation pole position

The study has been carried out with the use of long-term arrays of X, Y coordinates and the resulting vector M of the position of the North Pole of the Earth's rotation (PNPER) (m) with the resolution of 0.05 years for the period of 1890–2020 [1] and 1 day for the period of 1962–2020 [2]. According to the model [3], consisting of day-to-day (synoptic) (SI), irregular intra-annual (IIA), regular seasonal variation (SeasV), and interannual (IA) components, estimates of the contributions of each type of fluctuations to the total temporal variability have been obtained. It is shown that the maximum contributions to the variance of the time series [1, 2] in the interval of 1962– 2020 for all parameters introduce IIA (54.3–61.4%); the specific contribution of SeasV is significant (19.1–27.3%); the contribution of IA is noticeable (9.9–24.9%); the minimum contribution falls on SI (1.0–1.7%). In this case, the specific contribution of SI with increasing resolution from one day to 18–19 days decreases by 0.5–0.8%, and the relative error when replacing daily time series with 18–19-day data for the SI contribution is 33.6–43.9 %, and cannot be correctly used to assess the SI contribution. Therefore, the intra-annual variation of the specific contribution and the SI range is considered for all parameters only for the array [2]. At the same time, the maximum in the annual variation of the specific contribution of SI for M occurs in December (3.7 %), and the minimum in June (0.7 %). The intra-annual variability of the SI range for M, Y, and X is characterized by a semi-annual wave with maximums in February–March and September (1.3÷ 1.4 m) and minimums in June and December (0.1÷0.2 m) for M and Y or with maximums in June (1.5 m) and December (1.4 m) and minimums in March (0.3 m) and September (0.4 m) – for X.

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