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Southern Annular Mode (SAM)

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

When the SAM is in its positive phase, the westerly winds are generally stronger and positioned further south, which can lead to reduced rainfall and drought conditions across southern Australia in winter, but increased rainfall across the southeast in summer. During the negative phase of the SAM, the westerly winds are positioned further north, which can lead to increased winter rainfall and flooding across southern Australia. In contrast, a positive SAM phase in summer is typically associated with increased rainfall across the southeast

SAM (Credit: Bureau of Meteorology)

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

Key points