Southern Hemisphere Stationary Wave Response to Changes of Ozone and Greenhouse Gases

The southern hemisphere (SH) stratospheric stationary wave amplitude shows a significant increase in late spring and early summer during the last two decades of the 20th century. To explore the underlying cause and the separate effects of anthropogenic forcing from ozone depleting substances (ODSs) and greenhouse gases (GHGs) we examine a suite of chemistry climate model simulations. The model simulations produce trends in the wave amplitude similar to observed, although somewhat weaker. In simulations with changing ODSs, this increase in amplitude is reproduced during the ozone depletion period, and is reversed during the ozone recovery period. This response is related to changes in the strength and timing of the breakdown of the SH polar vortex associated with ozone depletion and recovery. Increases in GHG have little impact on the simulated stratospheric stationary wave amplitude, but induce an eastward phase shift of the waves. This phase shift is linked to the strengthening of the subtropical jets driven by GHG forcing via sea surface warming.