Variability on steep, confined topography

Analytical f-plane wave characteristics forced by abrupt topography are computed and compared to numerical solutions. The topography is assumed to be both confined and steep and relative vorticity is not neglected, points that contrast the present study with some recent analyses. Both baroclinic and barotropic cases are considered. It is argued that such waves possess a number of unusual linear dispersive and nonlinear steepening tendencies. For example, baroclinic waves on finite topography mix barotropic and baroclinic dynamics in a manner distinct from those on weak topography. Their nonlinear behavior also discriminates strongly between on and offshore directions in amplitude and scale. Westward group velocities for weak topography are typical only for varicose waves, which does seem to characterize some observed waves. Finite topography however, routinely supports westward group velocities for sinuous and varicose waves because it is effective at filtering barotropic dynamics. It is thus suggested that the intersection of isopycnals with topography introduces a qualitative change to the dynamics of topographic variability. (C) 2004 Elsevier Ltd. All rights reserved.