Evidence of Kelvin Waves in California's Marine Layer and Related Eddy Generation

Abstract

Evidence suggests that an internal solitary Kelvin wave exists in the marine layer along California. The marine layer is lifted over the central coast by a weak cyclonic circulation. This ?bump,? initially 850 m high, moves to the north along the coast at 6 m s?1. The undisturbed layer depth is 100?200 m thick. The crest height of the wave decreases to 500 m farther north. Winds under the raised marine layer are southerly. The leading edge of the wave is easily followed by satellite as the thickened marine layer is marked by overcast stratus. A greatly curved offshore leading edge indicates that nonlinear effects are important. Offshore scale in the overcast is about 300 km in the south and 50 km in the north. Surface pressure gradient alongshore is closely related to the marine layer depth. The surface wind shifts when the leading and trailing edge of the wave passes. Northerly wave progression ceases at the sharp bend formed by Cape Mendocino. At this time, a vortex is formed in the marine layer off Point Arena. This cyclonic vortex, on the order of 50 km across, is designated as the Point Arena Eddy.