THE SCATTERING OF ROSSBY WAVES BY OCEAN RIDGES

摘要

Overview and equation of motion. Rossby waves, or planetary waves, play a crucial role in global oceanic circulation. These waves propagate in regions of non-uniform ambient potential vorticity by conserving the potential vorticity of the flow. Bottom topography and the variation of the Coriolis parameter (a quantity proportional to the normal component of the Earth's angular velocity at the surface; see, for example, Cushman-Roisin [1]) with latitude both give rise to a non-uniform ambient potential vorticity field. Baroclinic Rossby waves typically propagate at low speeds (relative to the inertial Poincare waves or coastally trapped Kelvin waves) and have periods of the order of six months or longer. Further details may be found in Pedlosky. We are interested in the interactions of these waves with the topography of the ocean floor, in particular ridges. Scattering of Rossby waves has been considered previously by a number of authors. The diffraction of a Rossby wave by a semi-infinite, surface piercing barrier in a homogeneous ocean has been considered in [3]. Topographic scattering of Rossby waves by ridges, has been in- vestigated using layered models, first by Huthnance and later by Wang & Koblinsky amongst others. Similar work has been done in a continously stratified context by Schmidt & Johnson.