Supercritical baroclinic disturbances under the influence of topography

• Published in: Journal of the atmospheric sciences 1991-12, Vol.48 (23), p.2461-2475
• Main Authors: Chou, Shih-Hung, Loesch, Arthur Z.
• Format: Article
• Language: English
• Subjects: Convection, turbulence, diffusion. Boundary layer structure and dynamics; Earth, ocean, space; Exact sciences and technology; External geophysics; Meteorology; Meteorology And Climatology
• ISSN: 0022-4928; 1520-0469
• DOI: 10.1175/1520-0469(1991)048<2461:SBDUTI>2.0.CO;2

An Eady model modified to include Ekman dissipation and sloping horizontal boundaries is used to investigate the nonlinear evolution of baroclinic waves in the presence of surface topography. The effectiveness of the topography to phase lock and equilibrate a given mode vs that of baroclinity to propagate and vacillate that mode is found to depend on the topographic height, its zonal structure, and the level of supercriticality. When topography is sinusoidal and of the same wavelength as the baroclinically most unstable mode, it induces a short-period amplitude modulation whose envelope represents the baroclinic evolution. The dynamics of this modulation is explored analytically. When the sinusoidal topography is of a longer zonal wavelength, a 'mixed' wave state persists with amplitude dominance shifting between the topographic mode and the baroclinic mode, depending on the relative strength of form drag and baroclinicity. Model results are also compared, in appropriate parameter limits, with near-resonance asymptotic results and annulus experiments.