Meridional Rossby Wave Generation and Propagation in the Maintenance of the Wintertime Tropospheric Double Jet

Abstract

The eddy-driven and subtropical jet are two dynamically distinct features of the midlatitude upper troposphere circulation that are often merged into a single zonal wind maxima. Nonetheless, the potential for a distinct double jet state in the atmosphere exists, particularly in the winter hemi-sphere, and presents a unique zonal mean flow with two waveguides and an interjet region with a weakened potential vorticity gradient upon which Rossby waves may be generated, propagate,reflect, and break. We investigate the interaction of two groups of atmospheric waves, those longer or shorter than the deformation radius, with a double jet mean flow in an idealized atmospheric model. Patterns of eddy momentum flux convergence for long and short waves differ greatly. Short waves behave following classic baroclinic instability theory such that their eddy momentum flux convergence is centered at the eddy-driven jet core. Long waves, on the other hand, reveal strong eddy momentum flux convergence along the poleward flank of the eddy-driven jet and within the interjet region. This pattern is enhanced when two jets are present in the zonal mean zonal wind.