The Southern Annular Mode (SAM) is a climate driver that occurs in the southern hemisphere affecting the strength and position of westerly winds which influence southern Australia’s weather patterns. 

During a positive SAM event, the westerly winds are stronger and positioned further south, which can lead to reduced rainfall and drought conditions across southern Australia. In contrast, during a negative SAM event, the westerly winds are weaker and positioned further north, which can lead to increased rainfall and flooding across southern Australia. 

SAM (Credit: Bureau of Meteorology)

The following videos explain the impact of SAM and how it behaves. 

Key points