Instability of a neutral eady wave and orography

The problem of the interaction of a primary baroclinic wave with localized topography is studied in a quasi geostrophic Eady model in which a basic state constituted of a two-dimensional finite amplitude neutral wave superposed on the zonal wind with uniform shear is made to interact with a linearized mountain. The behavior of the orographic perturbations vary with the amplitude of the primary wave. In order to understand the characteristics of the orographically generated disturbances 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 results are discussed in terms of the "absolute" or "convective" instability properties of the basic flow