Model admitting baroclinic instability in which the jets in each layer lie exactly on top of each other (Δ = 0). The plot depicts the variation of the growth rates as a function of the shear q and the so-called “lid” of the atmosphere α (see text). For this atmosphere model the radial boundaries are set to L = 10. Keeping all parameters fixed but rerunning this atmosphere model with L = 15 reveals that all instabilities depicted in this figure vanish.