The Walker Circulation – what is it?

ONE of the most reliable indicators for predicting long-term drought is at a historic extreme, and global warming appears to be partially to blame.
The measure – known as the Walker circulation – is a weather phenomenon that describes one of the largest and most important wind systems in the world.
It includes the trade winds that carry moist air across the Pacific from South America to Australia. When those winds are weak – and they are now at historic lows – rain that would otherwise drench the eastern states instead falls into the ocean.
Researchers at the Bureau of Meteorology and the CSIRO checked the strength of the Walker circulation by comparing 30-year averages, and found the measurements were at their weakest since records were first kept in 1876, coinciding with the dry-weather pattern El Nino that has gripped NSW for years. Check the rest of this article ‘New kid on the block complicates forecasting’ by Conrad Walters in today’s online edition of the SMH.
Additional information about El Nino and the Walker circulation (including an animation) is available on the Bureau of Metereology website here.