Stability of zonal flows on Jupiter

Gierasch et al. (1979) have shown that the question of the stability of zonal flows on Jupiter is influenced strongly by the lower boundary condition. In the case of Jupiter, the troposphere rests above a deep layer of fluid which is probably extremely close to adiabatic. The present study extends the earlier investigations to a wider range of conditions, taking into account the nongeostrophic limit and the presence of horizontal shear. The major difference between the behavior of the model derived in the study and the behavior of a model with a rigid lower boundary, corresponding to the terrestrial conditions, is that baroclinic instability by the Eady mechanism is suppressed. The influence of beta (Charney-type instability) operates only at the top of the troposphere, not at its base. The suppression of the Eady modes seems to apply all the way down to the nongeostrophic limit where the Rossby number is order unity.