Isolation of atmospheric effects on rapid polar motion through Wiener filtering

Details Isolation of atmospheric effects on rapid polar motion through Wiener filtering Isolation of atmospheric effects on rapid polar motion through Wiener filtering

Dec 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004geoji.159..863d&link_type=abstract

Geophysical Journal International, Volume 159, Issue 8, pp. 863-873.

Astronomy and Astrophysics

Astronomy

1

Atmospheric Excitation, Ocean-Atmosphere Interactions, Ocean Tides, Rapid Polar Motion, Rotational Variations, Wiener Filtering

Scientific paper

Rapid polar motions are irregular low amplitude fluctuations of the rotation pole of the Earth that occur over timescales of days to months. They have been attributed primarily to variations in atmospheric angular momentum (AAM), with a contribution from oceanic angular momentum as well. Monte Carlo experiments conducted by Stieglitz & Dickman suggest that, given the observed correlations between AAM and rapid polar motion, only two-thirds of the atmospheric excitation is actually being transferred to the solid earth's rotation. Consequently, the traditional procedure for correcting polar motion for atmospheric effects, by simply subtracting the original AAM time-series, is inefficient.
Following a suggestion by Stieglitz & Dickman, we have attempted to optimally correct polar motion for atmospheric effects using the technique of Wiener filtering. With the atmospheric excitation as input and geodetic excitation (produced by deconvolving polar motion) as desired output, we use the Wiener filter to produce an atmospheric time-series that relates as meaningfully as possible to the geodetic excitation. The filter can also account for cross-component excitation of rapid polar motion by AAM, such as might result from atmospheric forcing of the oceans or groundwater.
We find that the Wiener filter acts to screen non-geodetic power (mostly reddish noise) from AAM across the entire frequency spectrum. The resulting Wiener filtered AAM (WAAM) is reduced in amplitude from the original AAM by at least half and shows higher correlation and coherence with geodetic excitation. Additionally, correcting polar motion data with WAAM reveals the presence of tidal signals not seen in previous studies and allows long-period tide models to be tested.

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