NONLINEAR, BAROTROPIC RESPONSE TO A LOCALIZED TOPOGRAPHIC FORCING - FORMATION OF A TROPICAL SURF ZONE AND ITS EFFECT ON INTERHEMISPHERIC PROPAGATION

The nonlinear response of a barotropic, nondivergent, spherical flow r epresentative of the upper troposphere (but without a tropical Hadley cell) to localized, extratropical topographic forcing is examined usin g high-resolution contour surgery calculations. The response is shown to vary greatly with forcing amplitude and can be significantly differ ent from the linear response. At large amplitude, Rossby wave breaking occurs in the tropics irrespective of the direction of the equatorial winds, and leads to small-scale stirring and the formation of a ''tro pical surf zone,'' which inhibits the meridional propagation of the di sturbance.