Wetter-than-normal weather expected for the Shire, as Bureau of Meteorology announces negative Indian Ocean Dipole

Dr Sarah Perkins-Kirkpatrick explains the science behind the Indian Ocean Dipole. Plus, what could it mean for the Shire's rainfall in the months ahead?

THE Bureau of Meteorology (BoM) has announced that a negative Indian Ocean Dipole (IOD) is underway, which could impact the Shire's rainfall in the coming months.

In recent decades, parts of southern and eastern Australia have become significantly drier.

Some regions have experienced as much as 20 per cent less rainfall during their cooler months between April and October.

But despite these long-term drying trends, rainfall is highly variable and can fluctuate from year to year.

Data from the BoM suggests the Shire's 2021 winter and spring could be wetter than normal.

This is due to something called a 'negative Indian Ocean Dipole', or negative IOD for short.

What is a negative IOD?

The IOD refers to yearly changes in the temperature across the Indian Ocean.

This year, waters in the Indian Ocean off Indonesia - not too far from the northern coast of Western Australia - are warmer than normal.

Meanwhile, waters in the western part of the Indian Ocean near East Africa are cooler than normal.

Scientists refer to this particular see-saw of ocean temperatures as a negative IOD.

During such an event, the amount of evaporation near Indonesia increases.

So when conditions are right, this moist air moves over Australia, bringing rain to the south and southeast of the country.

This year's negative IOD event means large parts of Australia are likely to experience above average rainfall over the next three months, including the Shire.

How is climate change affecting these patterns?

Recent research from the Australian National University suggests negative IOD phases could become less frequent if global temperatures continue to rise.

In contrast, positive IOD phases - which create dry conditions - are likely to become more common.

This could tamper with the natural cycle of wet and dry years, adding to Australia's drought risk.

The last positive IOD occured in 2019 and was linked to the dry conditions that preceded Australia's catastrophic black summer bushfires.

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Want more information on how your climate is changing? Check out the last article in this series.

Dr Sarah Perkins-Kirkpatrick is a climate scientist at the University of New South Wales.

This column is part of a collaboration between Monash University and News Corp to deliver hyperlocal weather and climate information.