Analysis of Long Time Series of Polar Motion
Speaker: Wei-Yung Chung
Department of Earth Sciences, National Central University, Taiwan
Abstract
The earth's rotational axis does not remain fixed relative to the body of the earth. Instead, the intersection of the axis with the surface of the earth traces out a quasi-periodic path about some mean position. The most prominent signals in the polar motion include the annual wobble (AW), the 14-month Chandler wobble (CW), a "Markowitz wobble" with a period of about 30 years, and a linear secular drift (or the polar wander). These components all arise from various dynamical change of the angular momentum of the Earth's interior, surface, atmosphere, and ocean. The annual wobble is a forced motion of the rotation pole and is commonly believed to be caused by meteorological variations. The Chandler wobble (predicted by Euler but named after its discoverer) can be studied in order to gain an understanding of its geophysical cause as well as its period P and Q-value, two fundamental functional of the Earth's physical properties. P depends sensitively on the mantle elasticity and anelasticity structure, the extent to which the fluid core is decoupled from the mantle, and how close the pole tide is to equilibrium, whereas Q contains information about the budget and processes of kinetic energy dissipation by the oceans, mantle anelasticity, and core-mantle coupling. We synthesized three papers for different kind of mathematically methods in evaluation the parameters of AW and CW.
References
Chao, B. F., 1983. Autoregressive harmonic analysis of the Earth's polar motion using homogeneous international latitude service data. J. Geophys. Res., 88(B12), 299-307.
Schuh, H., S. Nagel, and T. Seitz, 2001. Linear drift and periodic variations observed in long time series in polar motion., J. Geodesy, 74, 701.
M. Furuya and B. F. Chao., 1996. Estimation of period and Q of the Chandler wobble. Geophys. J. lnt. 127, 693-702.