On Moist Quasi-Geostrophic Baroclinic Instability

Abstract

Abstract The analytic theory of quasi-geostrophic baroclinic instability is generalized with the consideration of condensational heating. The heating is parameterized in terms of the vorticity field of the baroclinic wave itself, on the basis of the postulate that the baroclinically induced, low-level convergence sustains the moisture supply to the condensational processes. This heating parameterization is expressed in terms of an integral relationship between the baroclinically induced vertical velocity at a low level, say 900 mb, and the whole vorticity field. This formulation is tested with a model of baroclinic instability in its purest form. An exact characteristic equation is obtained with which all instability properties can be precisely determined. The solution reveals that as the heating intensity parameter is increased, the most unstable wave's growth rate significantly increase, its wavelength significantly decreases and its phase speed increases. The first two trends diminish as the heating in...