A Model Intercomparison for Homogeneous Flow over Large-Scale Orography

Abstract

The major mountain massifs on earth act as huge barriers to the air flow. Correspondingly there have been intensive research efforts to understand and simulate the flow over and around such obstacles. For example, a bibliography of papers on orographic effects published in 1980 (GARP) contains the titles of more than two hundred theoretical papers on flow over mountains in rotating systems. The approaches chosen differ widely. For example, there is a large group of papers wherein the linear theory of mountain induced planetary waves is developed and extended. Within this group we find papers which rely on the barotropic vorticity equation (e.g. Charney and Eliassen, 1949), on the quasigeostrophic potential vorticity equation (Staff members, 1958) or on the primitive equations (e.g. Webster, 1972). There are papers on the solution of the nonlinear barotropic voricity equation (e.g. Stewart, 1948) and of the shallow water equations (e.g. Kasahara, 1966). The geostrophic momentum approximation has been invoked (Mer-kine and Kalnay-Rivas, 1976) and the full set of the primitive equations has been integrated as well (e.g. Huppert and Bryan, 1976). Moreover general circulation models have been used to study the impact of the large-scale mountain massifs on the atmosphere (e.g. Manabe and Terpstra, 1974).