Orographic Flow and the Instability of Neutral Eady Waves

The problem of the interaction of a primary baroclinic wave with localized topography is studied in a quasi geostrophic Eady model with a two-dimensional finite amplitude neutral wave in the base state. The instability of the neutral Eady wave is studied by long time integrations of the model which let the most unstable normal mode appear. The characteristics of the orographic perturbations vary with the amplitude of the primary wave. The results are discussed in terms of the "absolute" or "convective" instability properties of the basic flow.