The dependence of topographically forced flows in a quasigeostrophic 2-layer model on the form of dissipation is investigated. In particular, the following 2 cases are examined. (1) The dissipation is proportional to the potential vorticity, and (2) the dissipation is proportional to the Laplacian of the streamfunction,
i.e., Ekman dampings on the upper and lower boundaries.
In the case (1), the bifurcation diagram is qualitatively the same as Pedlosky (1981)'s in which the dissipation is a sum of Ekman dampings on the upper and lower boundaries and an interfacial friction between the upper and lower layers. That is, there exist 2 steady solution bifurcation points, between which 2 stable solutions and 1 unstable one coexist for the same parameter values of the basic zonal flow.
On the other hand, in the case (2), a wave-wave interaction occurs. As a result, although the steady solution diagram is not altered qualitatively, Hopf bifurcation points may emerge on the stable steady solution curve, and the steady solutions between them may lose their stability.
So far as the considerations in this note are concerned, the stability of steady solutions is dependent on the form of dissipation although the steady solution diagram itself is not altered qualitatively.
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