MODELING THE VARIABILITY OF THE SOMALI CURRENT

The dynamics of the Somali Current system during the southwest Monsoon are investigated using a 16 level general circulation model. Solutions are found for a number of model geometries and wind-forcing patterns. The first integrations reported use a model domain exactly equivalent to that of the layer model of McCreary and Kundu allowing a direct comparison between the level and layer models. In the second set of integrations a more realistic Indian Ocean geometry is used, but still with an idealized wind forcing, while in the third, the Hellerman and Rosenstein wind stresses are used to simulate the seasonal cycle. The main results are that the GCM does not easily produce the cold wedge observed in SST at approximately 4N, although a current separation does develop there. A cold wedge can be produced but only if there is cold water quite close to the surface, the SST being sensitive to the vertical temperature profile. The cold wedge at approximately 10N forms easily in all integrations. As the water flows offshore it slides beneath the surface giving rise to the impression that it corkscrews its way around the Great Whirl gyre. To the east, northeast, of the Great Whirl, a series of jet filaments develop, associated with strong vertical circulations. In broad outline the GCM and layer model of MK are similar, but the details of the eddy fields and coastal response are quite different. In no cases are there vacillations or gyre interactions comparable to those in the layer model.