Comparison of high frequency variations of the atmosphere and the polar motion

The inferred excitation function χm derived from EOP(IERS 97C04) polar motion series and the series χp and χpib of the atmospheric angular momentum (AAM) provided by NCEP/NCAR for 1988–1999 are used to assess the contribution of AAM to the polar motion. Power spectra and complex wavelet analysis show that there are high peaks and similar structures in χm and χp, and their cross correlation coefficient is 0.75 (retrograde) and 0.60 (prograde). The peaks in χpib are lower. The phase of χp is about one day ahead of χm. The indications are that atmosphere variation is the main source of excitation of polar motion in the high-frequency range, and particularly so for the retrograde motion, while there may be other sources.