Atmospheric excitation of the Chandler wobble, 1983-1998

The excitation of the Chandler wobble (CW) by atmospheric wind and pressure variations is studied for the period 1983-1998. The data used here are the atmospheric angular momentum (AAM) functions computed from the operational objective analysis data of the Japan Meteorological Agency, compared with. observed Earth wobble data. In the vicinity of the Chandler frequency (0.847 cycle per year), the AAM function has a broad spectral peak with somewhat excessive power and about 30 degrees phase lead to that inferred from the observed wobble, with a coherence exceeding 95% confidence threshold. In addition, the temporal variation in the CW excitation calculated from the shifted 8-year data of the AAM function is found to have nearly the same pattern as that inferred from observation, in which the wind and inverted barometer (IB) pressure contributions complement each other. They reveal that the atmospheric wind and IB pressure variations by themselves maintain a major part of the observed CW during the analysis period.