Rotating dipolar gyres on a γ -plane

Nonlinear dipolar vortices/gyres on a γ -plane are investigated both experimentally and theoretically. The solutions describe a fundamental dipolar mode of large scale barotropic motion of the polar ocean or atmosphere on the rotating planet. The entire dipolar gyre is predicted to rotate anticyclonically with a specific angular velocity. The existence and stability of the theoretically predicted flow are confirmed in a laboratory experiment on a rotating platform. The laboratory flows are induced by an electromagnetic method and are observed using the nonintrusive optical method of altimetric imaging velocimetry. The rotation rate of the experimental flow is in good agreement with that predicted theoretically. Detailed measurements of the velocity field and surface elevation demonstrate that an assumption of linearity of the relation between the relative vorticity and the stream function is valid.