Origin of the 30–60 Day Oscillation in the LOD and Atmospheric Angular Momentum: New Findings from the UCLA General Circulation Model
Significant 30-60 day oscillations have been detected in both length-of-day (LOD) and atmospheric angular momentum (AAM) data sets. This study examines AAM fluctuations arising in a numerical simulation of the global atmosphere, performed with the UCLA General Circulation Model. A strong 30–60 day AAM (zonal wind) oscillation is found in the NH extratropics of the model, associated with periodic blocking over the northeast Pacific and Atlantic oceans. A coupled, zonally-symmetric mass redistribution leads to coherent fluctuations in the atmosphere’s moment of inertia. No intraseasonal oscillations are found in an experiment with surface elevations set to zero, suggesting an orographic origin of the extratropical 30–60 day AAM oscillation.
KeywordsZonal Wind Empirical Orthogonal Function Earth Rotation Intraseasonal Oscillation Global Atmosphere
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- Dickey, J. O., Eubanks, T. M., and Steppe, J. A., 1986, “High Accuracy Earth Rotation and Atmospheric Angular Momentum”, in Earth Rotation: Solved and Unsolved Problems, A. Cazenave (ed.), D. Reidel, Dordrecht, 137–162.Google Scholar
- Eubanks, T. M., Steppe, J. A., and Dickey, J. O., 1986, “The El Niño, the Southern Oscillation, and the Earth Rotation”, in Earth Rotation: Solved and Unsolved Problems, A. Cazenave (ed.), D. Reidel, Dordrecht, 163–186.Google Scholar
- Feissel, M., and Gambis, D.,1980, “La Mise en Evidence de Variations Rapides de la Durée du Jour”, C. R. Acad. Sei. (Paris), Series B, 291, 271–273.Google Scholar
- Ghil, M., 1987, “Dynamics, Statistics, and Predictability of Planetary Flow Regimes”, in Irreversible Phenomena and Dynamical Systems Analysis in Geosciences, C. Nicolis and G. Nicolis (eds.), D. Reidel, Dordrecht, 241–283.Google Scholar
- Ghil, M., 1988, “The 1–2 Month Oscillation in the Global Atmosphere and Nonlinear Atmospheric Dynamics”, Ann. Geophys., special 1988 issue, 105–106.Google Scholar
- Klousky, V. E., 1988, “Zonally Averaged Fluctuations in Tropical Sea Level Pressure”, Tropical Ocean-Atmosphere Newletter, August, 1988, p. 6–9.Google Scholar
- Münk, W. H., and MacDonald, G. I., 1960, The Rotation of the Earth, Cambridge University Press, New York, 323 pp.Google Scholar