Time variable atmospheric and oceanic signals in excitation functions of polar motion

The atmosphere and ocean both play an important role in the excitation of polar motion variations on a broad range of time scales. This interaction between atmosphere, ocean and polar motion is expressed in terms of relationship of atmospheric, oceanic and geodetic excitation functions. These functions contain common signals which can include subdaily, daily, weekly, subseasonal, semiannual, annual signals and longer terms. The common signals and the correlation between atmospheric, oceanic and geodetic excitation functions are time-dependent. Below we consider three topics: the influence of addition of the ocean to the atmosphere on the spectral characteristics and agreement with polar motion excitation functions in time from 10 to 500 days, influence of El Niño on atmospheric excitation function variability in submonthly time scales, comparison of spectral variability of atmospheric and GPS (CODE) geodetic excitation functions for sub-daily time scale.