Westward-Propagating Rossby Modes in Idealized GCMs

Abstract This work investigates the characteristics of westward-propagating Rossby modes in idealized global general circulation models. Using a nonlinear smoothing algorithm to estimate background spectrum and an objective method extract spectral peaks, four leading meridional can be identified for each first three zonal wavenumbers, with frequencies close predictions from Hough obtained by linearizing about state rest. Variations peak amplitude different modes, both within simulation across simulations, may understood under assumption that forcing scales spectrum. Surface friction affects width peaks but remain finite as goes zero, which implies some other mechanism, arguably nonlinear, must also contribute damping modes. Although are observed precipitation field moist physics, there is no evidence mode enhancement convective heating. Subject same friction, very similar dry models when normalized spectra.