Laboratory model of the Obukhov geostrophic vortex

The results of laboratory modeling of geostrophic adjustment in a shallow-water layer in rotating paraboloid are presented. According to the Rossby-Obukhov theory, this process excites nonstationary wave and stationary vortex (geostrophic) components of motion in a rotating fluid. In our experiments, the wave and vortex components were excited by extracting a preliminarily imbedded hemisphere (which made the initial distribution of the depth of the fluid inhomogeneous) from the central area of a rotating vessel with a parabolic base. Under this excitation technique, a prominent cyclonic eddy is formed in the central portion; the structure of this eddy is satisfactorily described within the linear theory of adjustment. Along with the shallow-water experiments, the published experimental data on modeling geostrophic adjustment in a two-layer medium are analyzed. A simple analytic solution to the corresponding problem of the adjustment theory is obtained, and this solution agrees with the experiment.