Below are links for animations of barotropic instability on a Gaussian strip of vorticity. The first loop shows the evolution of the vorticity field in a barotropic model from the linear, exponentially growing phase, through to nonlinear saturation where the strip is broken into a string of vortices. The second loop shows the evolution of the surface potential-temperature field in an sQG model (zero PV above a rigid surface). Notice how the filaments connecting the vortices also become unstable and roll up. Why doesn't this happen in the barotropic case?
Barotropic vortex-strip instability loop.
sQG vortex-strip instability loop.
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