Baroclinic Jets in Confluent Flow*

Abstract

Abstract The nonlinear, three-dimensional behavior of baroclinic fronts in a barotropic deformation field is investigated. A major finding is that baroclinic instability of the frontal zone can play an important role in limiting frontogenesis forced by the large-scale deformation. This results in a statistically equilibrated state in which the front oscillates about a mean vertical shear and frontal width. This equilibration mechanism is effective over a wide range of parameter space and is relevant to a variety of fronts in both the ocean and the atmosphere. Sufficiently strong deformation fields, however, can stabilize the baroclinic jet, yielding the two-dimensional result in which the frontogenesis is ultimately limited by the model subgrid-scale mixing parameterization. The time-dependent three-dimensional equilibrated state is achieved for those cases in which perturbations can grow to sufficient amplitude such that the nonlinearities counteract the frontal steepening induced by the large-scale defo...