Analysis of the High Frequency Components of Earth Rotation Demodulated from VLBI Data

In the recent work (Boehm et al., 2011, submitted to J. Geodynamics) we demonstrated the application of the complex demodulation technique to VLBI parameter estimation for determination of the high frequency signals in Earth rotation. The diurnal and semidiurnal components of polar motion and UT1 are expected to contain the harmonic terms due to imperfections of the conventional model of the ocean tide influence, but also less regular signals of atmospheric origin which are not included in the a priori models. In contrast, the terdiurnal and higher order terms are not expected to contain any significant signal of geophysical origin. Here we present results of the analysis of the high frequency components of Earth rotation demodulated from VLBI data - diurnal, semidiurnal, terdiurnal and quarterdiurnal. Results are compared to the geophysical contributions estimated earlier from the high resolution atmospheric and nontidal oceanic excitation data.