A Numerical Study of Two-Dimensional Moist Baroclinic Instability

Abstract

A study of baroclinic instability in the presence of moisture is performed with a primitive equation nonhydrostatic two-dimensional numerical model. A new assumption regarding the meridional structure of the perturbation mixing ratio is discussed in relation to previous work by the author. Results compare favorably with previous analytic work in regard to growth rates and spatial structure of the normal modes in an environment of small positive equivalent potential vorticity when the dry potential vorticity is near uniform as well. More specifically, growth rates are nearly doubled with respect to the dry case but are reduced about 30 percent compared to the semigeostrophic studies. For more general base states, more complex vertical structures than resolved in the two-level models are evidenced that are also qualitatively different from the semigeostrophic results.