Abstract
The stability of a barotropic, horizontally sheared, zonal current in a stratified atmosphere is investigated. It is found that several unstable internal modes may exist. These unstable disturbances have longer wave-lengths and somewhat smaller growth rates than unstable, two-dimensional, non-divergent disturbances. The energetics of the unstable internal modes are investigated and it is found that the energy source is the zonal kinetic energy while the disturbances convert eddy kinetic energy to eddy available potential energy. Several examples are shown for an atmosphere characterized by a constant lapse rate.
