Interpretation of the Effect of Mountains on Synoptic-Scale Baroclinic Waves

Abstract

Abstract Linear and nonlinear simulations of idealized baroclinic waves interacting with topography are examined in the context of quasigeostrophy. The purpose is to provide a simple conceptual interpretation of the transients resulting from this interaction. A perturbation expansion is employed, with the small parameter being proportional to topographic slope, to isolate fundamentally different topographic effects, and show how they enter systematically at each order. First- and second-order corrections appear to capture the essence of the topographic effect for all cases considered, even for values of the “small” parameter as large as 0.5, and are qualitatively useful for a parameter value of unity. Results indicate the importance of surface Rossby wave dynamics at first order near the mountain and downshear from the mountain a distance inversely proportional to the growth rate of the most unstable mode of the system. The second-order correction projects onto the initial baroclinic wave. Being primarily...