Baroclinic Instability in a Model with Shear and Static Stability Adjustable in the Meridional Plane

Abstract

Abstract Normal mode solutions are found numerically in a quasi-geostrophic model that includes five or ten vertical levels and either five or nine latitude “levels.” Wind shear and static stability may be adjusted at any of the vertical or latitude levels. Attention is focused on arrangements of static stability and, to a lesser extent, vertical shear that produce large growth rates, while restricting the horizontal gradients of static stability and shear to maintain the validity of the quasi-geostrophic assumption. The association of small static stability and/or large vertical shear in the lower troposphere with large growth rate of short wavelengths found by Staley and Gall is further confirmed. It is also found that rapid amplification of short wavelengths is little diminished even when the small static stability is very localized (in latitude) in the lower troposphere. The perturbations, however, attenuate rapidly away from regions of small static stability. Large static stability above low static s...