Resumen
The barotropic and the mixed barotropic-baroclinic stability problems are treated using a series expansion in trigonometric functions of the mean zonal velocity and the perturbation stream function. A two-level quasi-nondivergent model is used to handle the mixed stability problem, containing both horizontal and vertical wind shears in the basic state. In the present investigation the number of components in the series expansion is limited to four, because the most interesting meridional wind profiles may be simulated within this restriction. The models are formulated on the beta-plane.