Ocean-atmosphere interaction and the tropical climatology. Part II: why the Pacific cold tongue is in the east

Abstract

The influence of coupled processes on the climatology of the tropical Pacific is studied in a model for the interaction of equatorial SST, the associated component of the Walker circulation, and upper-ocean dynamics. When model parameters give a suitable balance between effects of upwelling and thermocline depth on sea surface temperature and for suitable atmospheric parameters, a good prototype for the observed cold-tongue configuration is produced. Presence of an easterly wind stress component produced by factors external to the Pacific basin can be important in setting up a cooling tendency, but this is magnified and modified by a chain of nonlinear feedbacks between trade winds and coean dynamics affecting the SST gradient within the basin. These feedbacks determine a preferred spatial pattern that does not strongly depend on the form of the external wind stress and that tends to place the cold tongue in the east-central basin. -from Authors