Equatorially Trapped Waves of a Coupled Ocean–Atmosphere System

Equatorially trapped waves of a simplified coupled ocean-atmosphere system are described by applying the formalism for conventional equatorially trapped waves with the assumption that the zonal wind stress and sea surface temperature perturbations are proportional. In this system, inertial-gravity and Rossby-gravity waves are unaffected by coupling whereas Rossby and Kelvin waves are affected, and in the low-frequency limit, these Rossby and Kelvin waves transform to slow westward and eastward propagating wave modes, respectively. The primary modifications by air-sea coupling are a decrease in phase speed and an increase in meridional scale. The properties of these coupled waves are useful in discussing several features, observed and modeled, relative to the evolution of the El Niño-Southern Oscillation.