On Polar Motion Equations Applied for Analysis of the Short Term Atmospheric Excitation
The atmospheric excitation data for earth rotation studies are published recently as the so-called “effective angular momentum” functions introduced by Barnes et al (1983). In applications, however, the corresponding polar motion equation is usually simplified to the form of the classical equation given by Munk and MacDonald (1960). The difference between these two equations is small only for perturbations which are slow compared to the diurnal cycle.
In this paper both forms of the polar motion equation are compared from the point of view of their application for analysis of the short-term excitations. It is also shown how the original equation of Barnes et al (1983) can be reduced to the form required by the Kalman filtering method. The solution includes stochastic models for the angular momentum function and for diurnal oscillations in polar motion data. The analytical expression for the corresponding transition matrix is given and the observability conditions are derived.
KeywordsExcitation Function Observability Condition Polar Motion Diurnal Oscillation Free Core Nutation
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