Track Model

The circumpolar midlatitude region is modeled as a reentrant channel on a beta-plane between two rigid lateral boundaries (— y < x < y and — \ < V < y)- ^he domain is 30,000km long and 8,000 km wide. A steady external forcing is introduced to support a reference flow, which has a zonally nonuniform velocity field (uref, wref) with corresponding stream function ^ref and vorticity Zref, viz.

J(^ref, Cref + f)+ aZref = Forcing, where a is a friction coefficient, f = fo + f3y and J (A, B) = Ax By — Ay Bx is the Jacobian. We particularly prescribe a reference flow with two localized jets, which plays the role of a proxy forcing.

A localized westerly jet has cyclonic vorticity in its northern flank and anticyclonic vorticity in its southern flank. We therefore introduce a reference flow that has the following idealized distribution of vorticity:

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