It has been reported previously that the filtered semiannual oscillation (SAO) of polar motion has a variable amplitude modulated with a period of about 3 years. Assuming, that this quasi 3-year modulation of the amplitude is caused by the beat of two oscillations, namely the SAO and the semi-Chandler oscillation (SCHO), we filtered them using the Fourier Transform Band Pass Filter (FT BPF) with carefully choosen parameters. These two oscillations filtered from the astrometric polar motion set of data and the IERS (90C04) combined polar motion data have slightly variable amplitudes modulated with the period of about 11 to 13 years and reaching maxima of about several mass. Similar oscillations were found in the equatorial components of the atmospheric excitation functions computed by the NMC (National Meteorological Center) and JMA (Japan Meteorological Agency). The epochs of the maxima of the time variable coherence between these oscillations of geodetic and atmospheric excitation functions are correlated with El Ni¿o epochs.¿ 1997 American Geophysical Union