Equatorward Propagation of Coupled Air–Sea Disturbances with Application to the Annual Cycle of the Eastern Tropical Pacific

A simple coupled ocean–atmospheric boundary layer model is used to study the annual variability in the eastern tropical Pacific. The air–sea coupling, particularly the feedback of the total wind speed effect on evaporation and wind mixing entrainment, produces a rapid equatorward and westward propagation of annual disturbances. For reasonable parameters, both amplitude and phase of the annual disturbance can be reproduced fairly well over most of the Tropics. It is then suggested that a substantial part of equatorial annual variability may come from the extratropics (say beyond 15°) due to the propagation of coupled waves.