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Multi-windowed spectrum estimates of the ILS polar motion

Published online by Cambridge University Press:  03 August 2017

L. A. Hinnov  and
J. Park
L. A. Hinnov
Affiliation:
U. S. Naval Observatory, Washington, D.C., USA
J. Park
Affiliation:
Yale University, New Haven, Connecticut, USA

Abstract

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We present a set of spectrum analysis techniques described by Thomson (1982) in which the discrete Fourier transform (DFT) is windowed by an expanding set of prolate spheroidal wave functions. The homogeneous ILS polar motion series was chosen for the presentation because of its interesting spectrum. It contains lines at the annual and semi-annual frequencies, a band of uncertain width and structure around Chandler's frequency, and evidence for a 30-year periodicity. None has been measured with great certainty by traditional single-taper DFT spectrum analysis. Here, a multi-taper algorithm significantly improves the bias control and consistency of high-resolution DFT spectrum estimates. An analysis of variance is performed to locate significant harmonic lines, and jackknifed statistics are used as additional cross-checks on the stability of the results. In addition, multi-tapered coherence estimates confirm a previously noted correlation between a meteorological forcing function and a polar motion excitation derived from the ILS series.

Type
III. Determination of Earth Rotation Parameters
Information
Symposium - International Astronomical Union , Volume 128: Earth's Rotation and Reference Frames for Geodesy and Geodynamics , 1988 , pp. 221 - 226
Copyright
Copyright © Reidel 1988 

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