How baroclinic vortices intensify resulting from erosion of their cores and/or changing environment

Abstract

The structure of circular baroclinic vortices in rotating stratified fluids is examined in order to rationalize the observed amplification of fluid rotation inside long-lived geophysical vortices during their evolution. New relations between basic vortex parameters at horizontal mid-depth are derived in order to compare vortices with the same potential vorticity extremum at the vortex center. The fluid rotation is shown to be larger for smaller vortices, which can be interpreted as a capability of vortex amplification due to radial redistribution of the angular momentum resulting from erosion of their cores and/or changing environment with the cyclo-geostrophic adjustment. The results are consistent with observational, numerical, and laboratory examples. This mechanism of vortex intensification has important implications for understanding the longevity of coherent geophysical vortices.