Moist Eady Waves in a Quasigeostrophic Three-Dimensional Model

Abstract

A three-dimensional quasigeostrophic model in which the base state is neutral to moist symmetric stability, following Emanuel et al., is used to obtain the experimental result that the two-dimensional moist Eady waves are the most unstable ones, as was known a priori only for the dry case, from Squire's theorem. The horizontal structure of moist baroclinic waves of nonzero meridional wavenumber presents deviations from the high-low symmetry that it is usually seen in dry models. The evolution of the normal modes of the moist Eady model is also followed in the nonlinear regime, where they display updraft contraction in the meridional direction and a fast meridional drift.