Many past researchers, beginning with Gill (1977), have proposed that coastally trapped disturbances (CTD) are essentially Kelvin waves and that energy is vertically trapped in these disturbances by a marine inversion. Elevated stable layers do not, however, prevent vertical energy propagation in linear internal gravity waves or internal Kelvin waves unless their horizontal wavelengths are an order of magnitude larger than the wavelengths associated with observed CTDs. The central thesis of this paper is that CTDs, and similar atmospheric disturbances propagating along the edges of inland mountain barriers in the extratropics, are vertically trapped by the finite height of the topography.
This vertical trapping is demonstrated by computing linear solutions for disturbances on an f-plane propagating parallel to an infinitely long step mountain of finite height. A semi-analytic solution technique is employed following the the methodology of Chapman (1982) and Samelson (1998), but the approach is generalized to include arbitrary vertical profiles of atmospheric stability. The presence of an elevated inversion "seaward" of the vertical step is shown to play no essential role in the vertical trapping of the disturbance. The "finite-mountain-height" trapping mechanism is easily explicable in terms of elementary wave dynamics.
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12th Conference on Atmospheric and Oceanic Fluid Dynamics