Wind-Driven Coastal Generation of Annual Mesoscale Eddy Activity in theCalifornia Current

摘要

Two candidate sources for the generation of mesoscale eddy activity in theCalifornia Current are local baroclinic instability and/or the wind stress adjacent to the coast. The latter constitutes remote forcing with eddy activity propagating westward from the coast into California Current via Rossby wave dynamics. In this study, two wind-driven models are utilized to test the relative significance of these two sources. One is an eddy resolving quasigeostrophic (QG) model, with the ability to represent baroclinic instability but not the coastal response to winds. The other is a 1 1/2-layer primitive equation (PE) model with the ability to represent the coastal response to winds but not baroclinic instability. Both models have the same spatial grid (i.e.. approximately 20 km) and are driven by the same coarse-grid wind stress forcing fields over the same one year time period (i.e. January 1987 to December 1987). The PE model is able to simulate qualitatively this distribution of the eddy variance as it appears in altimetric sea level, yielding significant coherence and phrase between model and observed sea-level residuals along longitude/time matrices at 30 deg N and 40 deg N. The QG model on the other hand, is found incapable of simulating the main features of this distribution of eddy variance.