Regional signals in atmospheric and oceanic excitation of polar motion, In Polar Motion: Historical and scientific problems

Author: J. Nastula, Rui M. Ponte and David Salstein
Date: 
November 6, 2000
Type: 
Journal Article
Venue: 
ASP Conference Series
Citation: 

Nastula, J., R.M. Ponte, and D.A. Salstein, 2000: Regional signals in atmospheric and oceanic excitation of polar motion, In Polar Motion: Historical and scientific problems, ASP Conference Series, International Astronomical Union 463-472.

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 and χ2, for the 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-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.