The Role of Kelvin Waves in Evolution of the Catalina Eddy

Abstract

The response to pressure falls near a coastline is studied with a linear shallow-water representation of the inversion-capped marine layer. The aim is to examine Catalina eddy development in the southern California bight region. Of particular interest is response sensitivity to background flow parallel to the coastline, as quantified by a Froude number (Fr). A conceptual model of eddy evolution is formulated that focuses on a pair of Kelvin waves triggered by the pressure falls. For subcritical Fr,|Fr| < 1, the waves move out of the regions of most favored growth located to the immediate north and south of the pressure fall center. Only a weak residual circulation remains in the bight region and an eddy does not form, For supercritical Fr, the waves tend to be held in place by the background flow. They thus undergo considerable amplification before dissipation eventually halts growth. A vigorous eddy circulation results in the bight region that resembles observed structures.