Retrieving Diurnal and Semidiurnal Signals in Polar Motion and UT1 from Analysis of the Routine VLBI Observations

Details Retrieving Diurnal and Semidiurnal Signals in Polar Motion and UT1 from Analysis of the Routine VLBI Observations Retrieving Diurnal and Semidiurnal Signals in Polar Motion and UT1 from Analysis of the Routine VLBI Observations

Aug 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006iaujd..16e..29b&link_type=abstract

Nomenclature, Precession and New Models in Fundamental Astronomy, 26th meeting of the IAU, Joint Discussion 16, 22-23 August 200

Astronomy and Astrophysics

Astronomy

Scientific paper

Polar motion and UT1 contain physical signals within the diurnal and semidiurnal frequency bands. The dominant part (< 1 milliarcsecond - mas) is due to the gravitationally forced ocean tides. There is also a small variation (< 0.1 mas) due to the direct influence of the tidal gravitation on the triaxial structure of the Earth. The remaining part (of the order of 0.1 mas) comprises the atmospheric and nontidal oceanic influences driven by the daily cycle in the solar heating. The observational evidence of diurnal and semidiurnal signals in polar motion and UT1 concerns mostly the purely harmonic ocean tide signals which are expressed by conventional models (IERS Conventions 2003). The intensive observation campaigns, like CONT94, CONT02, CONT05, have been also organized to estimate a less regular high frequency geophysical signals in Earth rotation and compare them with models. But even from the routine VLBI observations with one session in 3 to 5 days, it is possible to determine a quasi periodical high frequency geophysical signals. The method, proposed originally by (Herring and Dong, 1994) and further developed by (Mathews and Herring, 2000; Brzezinski, 2000), relies upon the so-called complex demodulation technique. In the recent investigation (Bolotin and Brzezinski, Geophys. Res. Abstracts, Vol.8, 2006, abstr. EGU06-A-01665) we applied the software SteelBreeze to process all the available VLBI observations which are suitable for simultaneous determinations of the celestial and terrestrial reference frames and the Earth orientation parameters, in order to extract the diurnal and semidiurnal signals in polar motion and UT1. Spectral analysis of the demodulated time series reveals corrections to the conventional model of the ocean tide variations as well as the broad band variability with excess of power near the frequencies of the tidal lines S1 and S2. These time series are suitable for the time domain comparisons with the available subdiurnal estimates of the atmospheric and oceanic excitation.

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