Numerical Model of Long-Lived Jovian Vortices

Abstract

A nonlinear numerical model of long-lived Jovian vortices has been constructed. We assume that the measured zonal velocity profile ubar(y) extends into the adiabatic interior, but that the eddies and large oval structures are confined to a shallow stably stratified upper layer. Each vortex is stationary with respect to the shear flow ubar(y) at a critical latitude yc, that is close to the latitude of the vortex center, in agreement with observed flows on Jupiter. Our model differs from the solitary wave model of Maxworthy and Redekopp in that the stratification is not large in our model (the radius of deformation is less than the latitudinal scale of the shear flow), and therefore stationary linear wave solutions, neutral or amplified, do not exist. The solutions obtained are strongly nonlinear in contrast to the solitary wave solutions which are the weakly nonlinear extensions of ultralong linear waves. Both stable and unstable vortices are found in the numerical experiments. When two stable vortices collide, they merge after a short transient phase to form a larger stable vortex. This merging, rather than the non-interaction behavior predicted by the solitary wave theory, is more in agreement with observations of Jovian vortices. We suggest that the long-lived Jovian vortices maintain themselves against dissipation by adsorbing smaller vortices which are produced by convection.