Baroclinic developments in jet entrances and exits. II: Nonlinear development

This study examines the effect of the ageostrophic circulations associated with jet entrance and exit regions on the nonlinear development of normal m odes. The nonlinear growth and decay phases of the baroclinic life cycle an d, in particular. the vertical propagation and subsequent meridional advect ion of Rossby waves are very sensitive to the exact form of the zonally sym metric basic state. This leads to changes in the associated energetics and eddy fluxes. In order to represent tl;e passage of a disturbance though a j et, a time-varying zonally symmetric meridional circulation was implemented . Many of the factors identified in the time invariant work, such as the no rmal-mode latitudinal and meridional advection, were again found to be impo rtant. Ageostrophic meridional circulations may play an important role in d etermining the magnitude and length of mid-latitude storm tracks.