June–July 2010

A positive SAM event occurred during June to July 2010. This positive SAM occurred during the initial development of the very strong 2010–12 La Niña. It was characterised by lower than average pressure around Antarctica and higher than average pressure around the southern Indian Ocean and southern Pacific Ocean (see image). This positive SAM phase was strong, with July coming in as the strongest positive SAM for the month of July, and second highest for June since records began in 1979.

Mean sea level pressure anomalies for June–July 2010 for the southern hemisphere
Mean sea level pressure anomaly chart for June–July 2010 for the southern hemisphere. Base period is 1979–2000. Lower than average pressure is evident near Antarctica (as indicated by the blue and purple colours) and higher than average pressure over the southern Indian Ocean and the southern Pacific Ocean (as indicated by the yellow and reds). This pattern is common during a positive SAM event. Data: ERA interim.
Australian rainfall deciles for June–July 2010
Australian rainfall deciles for June–July 2010. Deciles relative to 1900–2018.

The rainfall patterns for June and July 2010 show below average rainfall in southwest Western Australia, southeast South Australia, Victoria and western Tasmania. This shows a clear positive SAM influence, which typically acts to reduce rainfall in these regions during winter.