Geostrophic Adjustment: Frontogenesis and Energy Conversion

Abstract

Abstract Nonlinear geostrophic adjustment is examined with a Boussinesq model. The motion is restricted to a two-dimensional channel in the horizontal and vertical (x, z) plane; the fluid is in uniform rotation, is stably stratified, inviscid, and incompressible. The flows considered fall under two classes: zero and uniform potential vorticity flows. Steady geostrophic flow fields are determined from initial man imbalances, represented by both symmetric and antisymmetric density anomalies that vary along the x axis. The distinguishing characteristic of these solutions is the development of a front, defined as a zero-order discontinuity in both density and geostrophic velocity at one or both vertical boundaries. Frontal formation occurs, as previously discovered by Ou for zero potential vorticity flow, when the initial horizontal density gradient is sufficiently large. The critical values are displayed for different cases in terms of the initial amplitude and initial scale of the density anomaly. The conve...