Linear drift and periodic variations observed in long time series of polar motion

Abstract

Two long time series were analysed: the C01 series of the International Earth Rotation Service and the pole series obtained by re-analysis of the classical astronomical observations using the HIPPARCOS reference frame. The linear drift of the pole was determined to be 3.31 - 0.05 milliarcseconds/year towards 76.1 - 0.80° west longitude. For the least-squares fit the a priori correlations between simultaneous pole coordinates xp, yp were taken into account, and the weighting function was calculated by estimating empirical variance components. The decadal variations of the pole path were investigated by Fourier and wavelet analysis. Using sliding windows, the periods and amplitudes of the Chandler wobble and annual wobble were determined. Typical periods in the variable Chandler wobble and annual wobble parameters were obtained from wavelet analyses.