A NUMERICAL STUDY OF 2-DIMENSIONAL MOIST BAROCLINIC INSTABILITY

A study of baroclinic instability in the presence of moisture is perfo rmed with a primitive equation nonhydrostatic two-dimensional numerica l model. A new assumption regarding the meridional structure of the pe rturbation mixing ratio is discussed in relation to previous work by t he author. Results compare favorably with previous analytic work in re gard to growth rates and spatial structure of the normal modes in an e nvironment of small positive equivalent potential vorticity when the d ry potential vorticity is near uniform as well. More specifically, gro wth rates are nearly doubled with respect to the dry case but are redu ced about 30 percent compared to the semigeostrophic studies. For more general base states, more complex vertical structures than resolved i n the two-level models are evidenced that are also qualitatively diffe rent from the semigeostrophic results.