ON THE SEASONAL CYCLE OF THE EQUATORIAL ATLANTIC-OCEAN

Although the seasonal cycle of the equatorial Atlantic and Pacific Oce ans have many similarities, for example, an annual signal is dominant at the equator even though the sun ''crosses'' the equator twice a yea r, different processes determine the seasonal cycles of the two oceans and in the Atlantic different processes are important in the east and west. In the Gulf of Guinea in the eastern equatorial Atlantic, the s easonal cycle of surface winds is primarily in response to seasonal va riations in land temperatures so that annual changes in sea surface te mperatures are, to a first approximation, the passive response of the ocean to the winds. The seasonal cycle of the western equatorial Atlan tic has similarities with that of the equatorial Pacific-both are stro ngly influenced by ocean-atmosphere interactions in which the surface winds and sea surface temperature patterns depend on each other-but on ly in the western equatorial Atlantic are the seasonal variations in s ea surface temperature influenced by vertical excursions of the thermo cline. These results are obtained by means of a general circulation mo del of the atmosphere and a relatively simple coupled ocean-atmosphere model.