Modeling Equatorial Annual Cycle with a Linear Coupled Model

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  • 1 Department of Atmospheric and Oceanic Sciences, University of Wisconsin—Madison, Madison, Wisconsin
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Abstract

A simple linear coupled ocean–atmosphere model is used to study the equatorial annual cycle. The ocean is a stab mixed-layer model and the atmosphere is the Lindzen–Nigam model. The model is shown to capture most features of the observed equatorial annual cycle. A significant part of the tropical annual cycle is found to be generated by the extratropical annual variability that propagates toward the equator through a coupled ocean–atmosphere wave. The back-pressure effect in the atmosphere model can contribute to several important aspects of the variability, especially in the vicinity of the equator. Comparison with other mechanisms for the equatorial annual cycle is also discussed.

Abstract

A simple linear coupled ocean–atmosphere model is used to study the equatorial annual cycle. The ocean is a stab mixed-layer model and the atmosphere is the Lindzen–Nigam model. The model is shown to capture most features of the observed equatorial annual cycle. A significant part of the tropical annual cycle is found to be generated by the extratropical annual variability that propagates toward the equator through a coupled ocean–atmosphere wave. The back-pressure effect in the atmosphere model can contribute to several important aspects of the variability, especially in the vicinity of the equator. Comparison with other mechanisms for the equatorial annual cycle is also discussed.

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