Evolution of Hydrodynamic Parameters of an Ellipsoidal Vortex in a Baroclinic Background Flow

This study examines the behavior of a circular ellipsoidal ocean vortex in an external baroclinic flow with vertical shear. It is established that the vortex lifetime under fixed initial parameter conditions strongly depends on the external shear parameter. Depending on the vortex lifetime, the representative point in the parameter space may reside in one of three zones: (1) the survival zone, where the vortex lifetime tends to infinity, (2) the finite lifetime zone, and (3) the stretching zone, where the vortex lifetime approaches zero. At a certain shear velocity value, the infinite vortex lifetime becomes finite. This shear value, corresponding to the boundary between zones (1) and (2), is characterized as critical. The critical shear, in turn, depends on the initial geometric parameters of the vortex core. The work also investigates the vortex energy evolution. It is shown that during vortex stretching by the baroclinic flow, the total mechanical energy decreases both for the core and the entire vortex. Furthermore, the quasi-geostrophic balance remains valid for all three behavioral regimes.