Interannual variability in a tropical atmosphere-ocean model: influence of the basic state, ocean geometry and nonlinearity

Abstract

The behavior of a tropical coupled atmosphere/ocean model is analyzed for a range of different background states and ocean geometries. The model is essentially that of Cane and Zebiak for the tropical Pacific, except only temporally constant background states are considered here. For realistic background states and ocean geometry, the model solutions feature oscillations of period of 3-5 yr. By comparing the full model solution with a linearized version of the model, it is shown that the basic mechanism of the oscillation is contained within linear theory. A simple linear analog model is derived that describes the nature of the interannual variability in the coupled tropical atmosphere-ocean system. The numerical and analog models help to explain why organized, large amplitude, interannual variability is prominent in the tropical Pacific basin, and not in Atlantic and Indian basins. -from Authors