How cyclonic eddies become more energetic than anticyclonic ones.

Georgi Sutyrin, Univ Rhode Island, Narragansett, RI, United States
The peripheral erosion of vortices in the rotating shallow water model is analyzed aiming to rationalize observed amplification of fluid rotation during the evolution of long-lived geophysical eddies like Meddies in the ocean or the Jovian Great Red Spot. The stripping of typically elliptical vortex core due to an external strain or weak instability is taken into account for vortices with uniform potential vorticity outside the solid body rotating vortex core. Matching the geostrophycally adjusted velocity at the core boundary allows for evaluating the growth of fluid rotation in the vortex core due to radial redistribution of the angular momentum for a given rate of the core shrinking and the model parameters. Cyclonic vortices with thinner cores are shown to become more energetic than anticyclonic vortices with thicker cores assuming preservation of finite potential vorticity anomaly inside their cores. Stronger vortices resist more efficiently to the straining effects having important implications for understanding physical mechanisms of the longevity of geophysical eddies and the energy transfer in rotating fluids.