Top panel: dissipation spectrum in our reference case with periodic boundary conditions and one step (solidblue line), also displaying the eigenfrequencies (red crosses) of the free Poincaré equation for which the magnitude of the imaginary part is represented as a function of their real part. Bottom panel: z-dependence of the vertical velocity, Ŵ(z), of a short-wavelength inertial eigenmode corresponding to ω∕2Ω ~ 0.258, the leftmost resonance (left panel); of a short-wavelength gravito-inertial eigenmode corresponding to ω∕2Ω ~ 2.31 (middle panel); and of the gravity eigenmode of the staircase, corresponding to ω∕2Ω ~ 16.1, the rightmost resonance (right panel). For each panel, the solid blue line represents the real part of Ŵ (z), while the dashed orange line represents its imaginary part.