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

The separation of the subtropical and eddy-driven jets are of climatic interest due to their association with the phases of the annular mode. Here we describe the wavelength-dependent role of planetary waves on jet separation in an idealized, primitive equations atmospheric model. The model includes prescribed forcing for off-equatorial heating and the strength of the stratospheric polar vortex. These forcing parameters have been shown to influence the position of the subtropical jet and eddy-driven jet, respectively, and allow us to find a statistically steady state with two well-separated jets. We find that waves longer than the deformation radius have a tendency to merge these two jets while short waves preferentially strengthen the eddy-driven jet. We additionally find that these long waves may be associated with barotropic instability and the onset of low frequency variability.