Ageostrophic Effects on Baroclinic Instability

Abstract

Ageostrophic effects on the stability properties of a frictionless adiabatic atmosphere are investigated. The neutral stability boundary is found to consist of the range of variation in the basic state zonal speed. It is found that fast moving waves are not marginal to the neutral boundary. A numerical study shows that the introduction of lateral dependence results in a selective ageostrophic influence on the growth rates of unstable modes. This result is in contrast to the purely distortive modification in the three-dimensional quasi-geostrophic corresponding case.