Research on Variations in the North Pole Offsets to Improve the Forecasts Accuracy of its Coordinates Changes

V. M. Tissen, A. S. Tolstikov, G. V. Shuvalov

Transactions of IAA RAS, issue 70, 3–12 (2024)

DOI: 10.32876/ApplAstron.70.3-12

Keywords: Earth rotation, harmonic model, pole split, analysis, forecasting methods, quasi-periodic variations, Chandler period, trends

Abstract

This paper presents researches concerning the features of the geographical North Pole offset. The main components of this offset have been identified that can be conditionally split into some groups depending on their nature. The first two include aperiodic variations which demonstrate the character of trend changes, and quasi-periodic ones which are the superposition of a certain set of power harmonics with the periods of more than two years. Special attention is paid to regular variations, which are represented by the Chandler period with unstable parameters and the annual wave, whose nature is of a forced character, so its annual period is more stable in comparison other variations. To approximate these variations, harmonic models are proposed, consisting of groups of harmonics selected according to the features and criteria discussed in the paper. At the same time, the parameters of the harmonic components of these variations were evaluated over time intervals of different duration. The necessary graphic material is provided, explaining the nature of the variations listed as well as the essence of the method developed by the authors for predicting the coordinates of the pole over the past 23 years. Among the interesting results of the research carried out on the subject of the paper is the resulting model of the change in the amplitude of the Chandler period for the period analyzed. So, for example, over the period from 2006 to 2017, there is a gradual decrease in the amplitude of the Chandler period up to zero, while from 2020 to the present, there is a similar increase in it. The models parameters of the variations listed were estimated using the method of singular spectral analysis and the least squares method over the known pole coordinates values range from 15 to 50 years, depending on the type of variation under research. The practical implementation of the method proposed was expressed in developing the programs for predicting the coordinates of the pole for any given time. According to independent experts, the accuracy of the forecasts calculated using these programs, exceeds the accuracy of similar forecasts posted on the website of the International Earth Rotation Service.

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