POLAR MOTION AT SEASONAL FREQUENCIES

Studying the planetary-dynamic behaviour of the Earth connected with g eophysical processes as sources of excitation is of particular importa nce. 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 Pa rameters and Atmospheric Angular Momentum parameters from 1976 to 1987 were performed. Atmospheric Angular Momentum changes are the dominant cause of polar motion and length-of-day variation at seasonal frequen cies. Since there is another excitation source, the problem is to be c onsidered such that the total excitation portion is composed of atmosp heric and non-atmospheric portions. Particularly in polar motion, the paper deals with the separation of these portions for the seasonal con stituents and presents interesting information about their character. Copyright (C) 1996 Elsevier Science Ltd