On the stability of a cold-core eddy in the presence of convection: hydrostatic versus non-hydrostatic modeling

Abstract

Geostrophic eddies in a stratified liquid are susceptable to baroclinic instabilities.In this paper,we consider these instabilities when such an eddy is simultaneously cooled homoge- neously from above.As a linear stability analysis shows,the developing convection modi ?es the background stratification,the stability boundaries and the patterns of the dominant modes.The coupling between the effects of convection and the large scale fiow devel- opment of the eddy is studied through high resolution numerical simulations,using both non-hydrostatic and hydrostatic models.In the latter models,several forms of convective adjustment are used to model convection.Both type of models conform the development of the dominant modes and indicate that their nonlinear interaction leads to localized in- tense convection.By comparing non-hydrostatic and hydrostatic simulations of the flow development carefully,it is shown that convective adjustment may lead to erroneous small scale variability.A simple alternative formulation of convective adjustment is able to give a substantial improvement.