Polar motion at seasonal frequencies

Studying the planetary-dynamic behaviour of the Earth connected with geophysical processes as sources of excitation is of particular importance. In order to make a contribution concerning seasonal influences of near-surface geophysical processes on polar motion and Earth rotation, numerical investigations based on a time series of Earth Rotation Parameters and Atmospheric Angular Momentum parameters from 1976 to 1987 were performed. Atmospheric Angular Momentum changes are the dominant cause for polar motion and length-of-day variation at seasonal frequencies. Since there is another excitation source, the problem is to be considered in this way that the total excitation portion is composed of an atmospheric and a non-atmospheric portions. Particularly in polar motion, the paper deals with the separation of these portions for the seasonal constituents and presents interesting information about their character. (orig.)Available from TIB Hannover: RR 6134(96/02) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman