Rossby Wave Propagation an Beta-Planes

Abstract

The numerical modeling of stratospheric, quasi-geostrophic Rossby wave propagation on a beta-plane channel is examined to determine how wave propagation is affected by the use of low horizontal (spectral) resolution. This study considers time dependent, quasi-linear, wave-mean flow interaction for typical wintertime conditions. Time dependent, wave-mean flow interaction modeling can show nonlinear behavior equivalent to quasi-horizontal planetary wavebreaking. Wave-mean flow interaction modeling requires relatively higher meridional resolution than is needed for the linear wave case because meridionally localized wave-mean flow interaction generally occurs. The interaction is viewed in terms of quasi-geostrophic potential vorticity on isobaric surfaces. The degree to which quasi-geostrophic potential vorticity is conserved locally as it is mixed quasi-horizontally by planetary waves under adiabatic conditions can be estimated by examining the evolution of the isobaric quasi-geostrophic potential vorticity, and this mixing is related to wave propagation by means of the Eliassen-Palm flux. It is shown that at lowest meridional resolution, where a single spectral mode is used to represent all meridional profiles, it is best to consider the channel model to be two dimensional in (x, z).