Intertropical Convergence Zone Studied With an Interacting Atmosphere and Ocean Model¹

A simple, two-layer numerical model of the upper tropical ocean has been added to a pre-existing primitive-equation model of a zonally symmetric tropical atmosphere to predict a north-south profile of sea-surface temperature and its relationship to the atmospheric intertropical convergence zone (ITCZ). With an initially flat temperature profile near the Equator, it is found that a cold equatorial surface progressively develops as a result of upwelling and vertical mixing in the sea. A single ITCZ establishes itself at first over the Equator, but then migrates poleward as the Equator cools; the convergence zone remains single, despite the eventual double surface-temperature maximum. This marked hemispheric asymmetry is in accord with satellite observations.