Localized Storm Tracks in the Absence of Local Instability

Abstract

An idealized, linear barotropic model on an f plane is used to demonstrate the existence of a zonally localized storm track in the absence of any kind of local instability; with a background flow consisting of two jets separated by a local minimum, two distinctly localized eddy streamfunction variance (and eddy kinetic energy) peaks emerge on either side of the local jet minimum. In contrast, the decrease of the eddy vorticity variance at the jet minimum is essentially negligible. As the stretching deformation field of the background flow strengthens, the transient eddy is deformed irreversibly in the deformation region. The resulting enstrophy cascade toward smaller scale plays an important role in terminating the model's storm tracks, and in this case the second storm track downstream of the local jet minimum is substantially weakened.