Initial Development of Eddies in High-Speed Zonal Flow: One Interpretation for NTB Activity of Jupiter

Abstract

The initial development of an anticyclonic eddy in a high-speed jet flow has been examined using a two-layer rigid-lid model for incompressible fluid governed by the shallow water equations. In the case of large Rossby deformation radius an inertia-gravity wave can propagate in all directions, but in the small deformation radius case the gravity wave propagates only in the upstream direction. In the latter case, the phase speed of the internal gravity wave is less than the zonal flow speed, and latitudinal propagation of the wave seems to be prevented by the strong shear region both north and south of the eddy.This behavior of the internal wave seems to have some common features with the dark spots of the North Temperate Belt of Jupiter, which is the latitude of the fastest eastward zonal flow in Jupiter. These spots appear only west (upstream side) of the white spot, and move westward relative to the spot.If our hypothesis that the dark spots are due to an inertia-gravity wave is valid, it suggests small values of the Rossby deformation radius.