Meridional wave propagation in baroclinic models

It is well known that the extratropical jet is forced by the momentum transport by baroclinic eddies that propagate away from their generation region in the midlatitudes. One-layer models, in which baroclinic generation is replaced with some form of stirring, provide a useful framework to describe this process and hence to investigate the dynamics of jet variability. The modeled layer is usually thought of as representing the upper troposphere, as it is in this region that the bulk of the momentum transport occurs. However, meridional propagation in the full baroclinic model is not governed by the upper level mean flow alone and Rossby wave group speeds are better characterized using barotropic than upper level potential vorticity gradients. In this presentation we will discuss factors determining the vertical structure of the eddy momentum flux and the meridional dispersion at upper levels.