The effectiveness of atmospheric and oceanic processes in exciting the Earth's wobbles
Reporter : Wei-Yung Chung
Abstract
The wobbling motion of the Earth was first detected more than a century ago and the observable timescales are from subdaily to decadal in response to a variety of forcing mechanisms. As If absence of the excitation, these natural wobbles of the Earth would freely decay due to the action of dissipation processes. Although atmospheric wind and pressure fluctuations have an important influence on the Earth's wobbles, as the issue that I had mention last talk , they are not the sole source of excitation. Ocean tides have been shown to be the dominant cause of the Earth's wobbles on subdaily timescales and their effect on the Earth's wobbles at termensual, fortnightly, and monthly periods. In this time, I'll talk about the conception of the ocean model which have been used to investigate the contribution of nontidal oceanic effects to exciting the forced wobbles of the Earth. And we will emphasize that the errors in the oceanic circulation induced by Boussinesq approximations vary greatly, depending on the spatial and temporal scales of perturbations. Furthermore, the main discussion are the source of polar motion is diagnosed by decomposing its excitation into those caused by changes in winds, currents, and pressure loading by the atmosphere and oceans, which are separately evaluated.
References
Gross, R. S. (2003) Atmospheric and oceanic excitation of the Earth's wobbles during 1980–2000, J. Geophys. Res., 108(B8), 2370
Hung, R. X. (2002) Sea Surface Elevation and Bottom Pressure Anomalies due to thermohaline Forcing, J. Phys. Oceanogr., Vol. 32, p2131-2150