Spectral Characteristic of Polar Motion in the 2005-2006 and 1999-2000 Winters Seasons

J Nastula,B Kolaczek

doi:10.2478/v10018-007-0013-5

Abstract

Spectral Characteristic of Polar Motion in the 2005-2006 and 1999-2000 Winters SeasonsThe Earth's pole moves on the Earth's surface along the spiral curve known as "polhody". Polhody computed from the IERS C04 pole coordinates were compared with those computed after removing successively oscillations with periods shorter than 150, 30, 10, 2 days. The comparison of these polhody show that the loops in the winter seasons of 2005-2006 and 1999-2000 are caused by the oscillations of polar motion with periods shorter than 30 days. These short periodical oscillations of geodetic excitation function of polar motion were correlated with those of the atmospheric and oceanic excitation functions. There are high correlations with coefficients equal to 0.8-0.9 during epochs when loops occur.

Highlights

Variations of the Earth's pole motion have a wide spectral range with periods from hours to decades
There are two large oscillations of pole motion, the free Euleurian wobble known as the Chandler wobble with period of about 433 days and variable amplitude ranging to 300 milliarseconds, and the annual oscillation forced by seasonal displacements of air and water masses with amplitude around 100 mas
The spectrum of the polar motion with periods shorter than semiannual contains several oscillations with periods around 120, 60, 50, 30 days and some shorter ones with variable amplitudes of several mas, which are correlated with such oscillations of atmospheric excitation function (Atmospheric Angular Momentum - AAM) and oceanic excitation function (Oceanic Angular Momentum - OAM), [Kolaczek, 1993, 1995; Kosek et al, 1995; Kolaczek et al, 2000] (Figures 2, 3).The Chandler and annual oscillations interfere about every 6.4 years (Figure 4)

Summary

Introduction

Variations of the Earth's pole motion have a wide spectral range with periods from hours to decades. At the turn of years 2005-2006 and 1999-2000, the time of interference of the Chandler and annual oscillations the polhody have similar sizes and the loops and high frequency features are visible on the polhody (Figures 4, 5-7).

Results

Conclusion