Variability in Planetary Wave Activity over the 20th Century

The contrasting geographies of the Southern and Northern hemispheres play a significant role in the observed Rossby wave regimes. In addition to differences in the continental distribution and the location of major north-south mountain chains, the mean equator-to-pole temperature difference is significantly larger in the Southern Hemisphere (around 70 K) than in the Northern Hemisphere (around 40 K). As such, the evolving nature of these wave regimes have been extensively studies in climate models and re-analyses. Planetary wave amplitude is a challenging measurement compared to parameters such as wave propagation speed, jet strength and location, and wavenumber. In this study, the evolution of planetary wave amplitudes over the 20^th Century are analyzed using a novel implementation of the quasi-geostrophic wave activity parameter. The trajectories of change are distinctive between the hemispheres and can be linked to sea ice properties.