Baroclinic Instability of a Zero-PVE Jet: Enhanced Effects of Moisture on the Life Cycle of Midlatitude Cyclones

Abstract

Numerical experiments that compare the life cycles of baroclinic cyclones in either a dry or a saturated atmosphere in Cartesian geometry are performed starting from a jetlike mean initial state designed to maximize the effects of latent heat release by condensation. Time evolution and spatial structure are discussed. While the final effect of the dry life cycle on the mean state is to destroy baroclinicity and arrest the development, the modified cyclone evolution, due to the presence of moisture, is able to reform an intense baroclinic belt on the northern side of the original one, which is newly unstable to even shorter baroclinic perturbations.