Excitation of Earth’s polar motion by atmospheric angular momentum variations, 1980–1990

Abstract

We compute the polar‐motion excitation function due to the atmospheric angular momentum (AAM) for both IB (inverted‐barometer) and non‐IB cases, as well as the excitation function from geodetically observed Earth orientation data for the period 1980–1990. The two are then compared in studying the AAM contribution to the polar motion excitation. The polar drifts with periods longer than ∼2 years have similar characteristics, but the comparison is inconclusive because of data uncertainties. For the seasonal wobble excitation, the agreement is poor except for the prograde annual wobble, indicating the influence of other geophysical excitations than AAM. For the Chandler wobble excitation, a correlation coefficient of 0.53 for non‐IB and 0.58 for IB are found for 1986–1990. Together with a coherence spectral analysis, they clearly demonstrate a strong contribution of AAM to the Chandler wobble excitation.