On the forcing of planetary‐scale Rossby waves by Antarctica

The propagation of Rossby waves forced at high latitudes into middle and low latitudes is studied using the barotropic vorticity equation on the sphere. Ray tracing theory indicates that fundamental differences exist between the response of an atmosphere initialized with typical northern hemisphere winter flow and typical southern hemisphere winter flow to such a forcing, with a substantial response more likely for the southern hemisphere case. Integrations with a fully nonlinear barotropic model confirm this suggestion and indicate that away from the local forcing region, linear theory provides a good description of the response. The most notable feature in the steady solutions is a split of the mid‐latitude jet close to New Zealand. The location of this split coincides well with a region where blocking is observed to be prevalent in the southern hemisphere.