Abstract
We examine the stability of a baroclinic layer between two unbounded barotropic layers in a model neglecting β -effect. Without using geostrophic approximation, calculations are made for an extended range of the Rossby number, and for the Richardson number=0.5 and 50. For the large Rossby number the solutions in the barotropic layer may be sinusoidal (gravity wave). Then, we invoke " radiation condition" to choose between the gravity wave propagating upwards and the one propagating downwards. For the comparison, same calculations are made under the condition that horizontal rigid walls exist at both boundaries of the baroclinic layer.
The results of the calculations show that the nature of the disturbances is not drastically modified by the alteration of the boundary condition, although values of growth rate and phase velocity of the disturbances are to some extent changed.
With an increase of the Rossby number, one of two critical points (i.e.a level at which U(z)-cγ =f/k or -f/k) appears in the baroclinic layer. However, for either boundary condition it is found that for more increased value of the Rossby number, steering level of the disturbances approaches to a boundary of the baroclinic layer, so that both critical points can not appear at the same time in the baroclinic layer.
