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The Forced Annual Wobble in Earth's Polar MotionThe annual wobble in Earth's polar motion is a forced motion, as opposed to an excited natural oscillation which is the Chandler wobble in the case of polar motion. It is forced by the combination of many angular momentum variations in the geophysical fluids that exchange these variations with the solid Earth, hence changing its rotation. Among all forcing sources of the annual wobble the geophysical fluid that has the dominant contribution is the atmosphere, while the oceans and the land hydrology make up the remaining budget together with tidal influences. The latter include that from the solid Earth deformation and that from the ocean tides at the annual period. The combined forcing produces both prograde and retrograde wobbles; the prograde wobble gets magnified substantially by the near-by presence of the natural Chandler wobble resonance. On the other hand, the closeness of the prograde annual forcing power to the Chandler period is an indication that some of the power leakage into the Chandler period band becomes the main excitation source for the Chandler wobble. In this paper we will review our knowledge about annual wobble and show the status in the effort of closing the budget with the annual angular momentum variations from the various geophysical fluids.
Document ID
20040077201
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Chao, Benjamin F.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2004
Subject Category
Geophysics
Meeting Information
Meeting: Forcing of Polar Motion in the Chandler Frequency Band
Location: Luxembourg
Country: Netherlands
Start Date: April 20, 2004
End Date: April 23, 2004
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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