Southern Annular Mode (SAM)
Meat & Livestock Australia October 20, 2023
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.
The following videos explain the impact of SAM and how it behaves.
Key points
- There are 3 SAM phases: positive, neutral, and negative.
- During a positive SAM phase, there is higher chance of southern Australia experiencing dry conditions in winter, and a possibility for increased rainfall along the east coast in winter and summer.
- During a negative SAM phase, there is a higher chance of a wetter southern Australia in winter and a drier southeast in summer.
- The SAM is active all year round, but its impacts on southern Australia vary across the different seasons.
- The impact of SAM is influenced by the phases of other climate drivers, including ENSO and the IOD.