The interaction between curvature and lateral shear vorticities in a mean and an instantaneous Florida Current, a comparison

Abstract

The question of how much of the dynamics of an instantaneous current is retained in the dynamics of a model derived from its mean structure is considered in terms of a comparison between two case studies of the Florida Current. In the mean model, fluid elements are restrained from crossing the speed axis. But in an observation of an instantaneous current there was an interaction between curvature and lateral shear vorticities accompanied by a systematic movement of fluid elements across the speed axis. This difference is considered from two points of view. The first is that of the equations governing the interaction process, particularly the banking mechanism that converts curvature vorticity to lateral shear vorticity and vice versa. The second is that of the dynamics of the geostrophic potential vorticity. It is concluded that, because of the imposed geostrophic constraint, the mean model does not retain the interaction process.