A Numerical Study of Somali Current Eddies

Abstract

A three-dimensional numerical ocean model is used to study the transient response of the western boundary region of a tropical ocean to the sudden onset of winds parallel to the boundary. In particular, the behavior of resulting western boundary current eddies is studied as a function of various parameters of the model. Alongshore eddy movement is found to decrease and vanish as the horizontal orientation of the western boundary is changed from northward to northeastward. A similar retarding effect is produced upon increasing the nonlinearity of the flow by using weaker vertical turbulent friction or stronger wind stress. Little sensitivity is found to the magnitude of the horizontal turbulent friction coefficient. A term-by-term evaluation of the vorticity balance in the region of the eddies is used to analyze their behavior. A case is run in which the western boundary configuration and applied wind stress approximate that of the northwestern Indian Ocean. An eddy structure evolves which is similar to that observed, indicating that the vorticity balances found in the model may be similar to those determining eddy behavior in the real ocean.