Solar cycle modulation of the Southern Annular mode

The effect of the 11-year solar cycle modulation on the Southern Annular Mode (SAM) in the Southern Hemisphere is examined through analysis of observational data. It is found that the year-to-year variability of the October-November mean SAM differs significantly according to the solar activity. In high solar activity years, the SAM signal extends to the upper stratosphere during October to December and activity in the troposphere lasts until autumn, whereas in low solar activity years, the SAM signal is confined almost inside the troposphere from October to December and it disappears by January. This situation is very similar to that observed for the modulation of the winter mean North Atlantic Oscillation in the Northern Hemisphere. Observation as well as the model simulation indicates important role of lower stratospheric ozone for the long-lived SAM in high solar activity years.