The impact of resolution on a numerical simulation of barotropic instability

Abstract

The barotropic point jet problem is used to study the impact of resolution on a numerical simulation of barotropic instability. This particular problem is studied because of the close relation of the linearized version of the problem to baroclinic instability. This study finds that the channel-averaged wave enstrophy and the fluxes at the jet in the wave-mean flow equilibrated state are understimated when the resolution of the model is inadequate to resolve the analytic linear growth rates. Moreover, the resolution of the model is found to impact the wave-mean flow equilibrated state even when the analytic linear growth rates are resolved. This is due to potential vorticity gradients and fluxes in the equilibrated state being largely independent of resolution, as long as the linear growth rates are adequately resolved. In a coarse-resolution model this results in momentum fluxes and shear at the vertex of the jet that are dependent upon the resolution of the model. The results of this study suggest that resolution will also impact the numerical simulation of baroclinic instability.