The Role of Density Stratification in Generating Zonal Flow Structures in a Rotating Fluid

Abstract

Local generation of vorticity occurs in rotating density-stratified fluids as fluid parcels move radially, expanding or contracting with respect to the background density stratification. Thermal convection in rotating 2D equatorial simulations demonstrates this mechanism. The convergence of the vorticity into zonal flow structures as a function of radius depends on the shape of the density profile, with the prograde jet forming in the region of the disk where the greatest number of density scale heights occurs. The number of stable jets that form in the fluid increases with decreasing Ekman number and decreases with increasing thermal driving. This local form of vorticity generation via the density stratification is likely to be of great importance in bodies that are quickly rotating, highly turbulent, and have large density changes, such as Jovian planets. However, it is likely to be of lesser importance in the interiors of planets such as the Earth, which have smaller density stratifications and are less turbulent.