The Antarctic oscillation (AAO, to distinguish it from the Arctic oscillation or AO), also known as the Southern Annular Mode (SAM), is a low-frequency mode of atmospheric variability of the Southern Hemisphere that is defined as a belt of strong westerly winds or low pressure surrounding Antarctica which moves north or south as its mode of variability.
It is a climate driver for Australia, influencing the country's weather conditions – It is associated with storms and cold fronts that move from west to east that bring precipitation to southern Australia.