Role of the beta-effect in the decay of the alongshore baroclinic jet associated with transient coastal upwelling and downwelling: Numerical experiments

A numerical study of the decay of an alongshore baroclinic jet (ABJ) formed by transient wind stress favorable for upwelling and downwelling is carried out. The study is based on the Princeton Ocean Model (POM) applied to a circular stratified basin with a constant depth. In the case of a fully developed upwelling (downwelling), the alongshore jet is subjected to baroclinic instability, and its decay is predominantly accompanied by selective formation of cyclonic (anticyclonic) mesoscale eddies. If the upwelling or downwelling is not fully developed, the necessary condition for the baroclinic instability of the ABJ in a basin with a constant depth is the presence of the β-effect. The β-effect causes separation of the ABJ from the shoreline in the eastern part of the basin and thereby stimulates baroclinic instability. As a result, mesoscale meanders and eddies can be generated in the eastern part of the basin only if the diameter of the basin D is large enough to satisfy the inequality D > $\sqrt {{{R_I f} \mathord{\left/ {\vphantom {{R_I f} \beta }} \right. \kern-0em} \beta }} $ , where R _I is the baroclinic Rossby radius, f is the Coriolis parameter, and β = df/dy.