TELECONNECTIONS OF THE SOUTHERN OSCILLATION IN THE TROPICAL ATLANTIC SECTOR IN THE OSU COUPLED UPPER OCEAN ATMOSPHERE GCM

The Oregon State University coupled upper ocean-atmosphere GCM has bee n shown to qualitatively simulate the Southern Oscillation. A composit e analysis of the warm and cold events simulated in this 23-year integ ration has been performed. During the low phase of the Southern Oscill ation, when warm anomalies occur in the eastern Pacific, the model sim ulates for the Atlantic region during March-May 1) a deficit of precip itation over the tropical South American continent, 2) Caribbean and G ulf of Mexico sea level pressure and sea surface temperature are in ph ase with the eastern Pacific anomalies, while those east of the Nordes te region are out of phase, and 3) northeast trade winds are anomalous ly weak and southwest trade winds are anomalously strong (as infer-red from surface current anomalies). The anomalies in the oceanic process es are induced by perturbations in the atmospheric circulation over th e Atlantic and are coupled to changes in the Walker circulation. Durin g the high phase of the simulated Southern Oscillation, conditions in the atmosphere and ocean are essentially the reverse of the low phase. The model produces a response in the South American region during the opposing phases of the Southern Oscillation that is in general agreem ent with observations. The interannual variation of Nordeste rainfall is shown to be dominated by a few band-limited frequencies. These freq uencies are found in the SST series of those regions of the Atlantic a nd Pacific oceans where strong correlations with Nordeste precipitatio n exist.