Linear instability of a mixed‐layer front

Abstract

The linear instabilities of a geostrophically balanced frontal jet are computed numerically in an effort to understand the origin of intense small‐scale cold‐core features observed in the North Atlantic subtropical convergence zones during the Frontal Air‐Sea Interaction Experiment (FASINEX). A simple analytic continuously‐stratified basic state is used to represent the observed frontal structure. The most unstable linear modes have e‐folding timescales of 2–3 days, alongfront wavelengths near 70 km, and significant asymmetry across the front. The results provide indirect evidence that baroclinic instability of the frontal jet is a possible source of the cold‐core features observed during FASINEX.