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Regional Signals in Atmospheric and Oceanic Excitation of Polar Motion

Published online by Cambridge University Press:  12 April 2016

Jolanta Nastula ,
Rui M. Ponte  and
David A. Salstein
Jolanta Nastula
Affiliation:
Space Research Center of the PAS, Warsaw 00-716, Poland
Rui M. Ponte
Affiliation:
Atmospheric and Environmental Research, Inc., Cambridge, MA 02139, USA
David A. Salstein
Affiliation:
Atmospheric and Environmental Research, Inc., Cambridge, MA 02139, USA

Abstract

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Atmospheric and oceanic variability have been shown to play a role in the excitation of polar motion. Regional patterns of atmospheric and oceanic excitation are analysed and compared. The equatorial excitation functions, χ1 an χ2, for the ocean are computed using velocity and mass fields from a near-global ocean model, driven by observed surface winds stresses, surface heat and freshwater fluxes, for the period from January 1985 to June 1997. To understand the relative role of the ocean versus the atmosphere, we used atmospheric excitation functions computed from the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalyses. We consider regional mass terms [bottom pressure and atmospheric surface pressure with the inverted barometer (IB) correction] and regional motion terms as well (currents and winds). Results here confirm recent findings that oceans supplement the atmosphere as an important source for polar motion excitation. Regional signals in the oceanic bottom pressure terms have comparable amplitudes to those in the atmospheric pressure-IB terms. The regional wind term amplitudes, however, are several times larger than the values for both regional oceanic currents term and atmospheric pressure-IB term. Power in regional oceanic excitation is distributed between seasonal and subseasonal timescales while in the case of atmospheric excitation it is concentrated rather at seasonal timescales.

Type
Part 5. Chandler and Annual Polar Motion: Observations and Excitation
Information
International Astronomical Union Colloquium , Volume 178: Polar Motion: Historical and Scientific Problems , 2000 , pp. 463 - 472
Copyright
Copyright © Astronomical Society of the Pacific 2000

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