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'Flash droughts' strike fast and hard, and researchers are still racing to identify them before they happen

Kate Doyle, Friday July 19, 2019 - 19:31 EST
ABC image
Flash droughts saw areas such as Scenic Rim go from okay to critical within weeks. - ABC

It is November 2017 — you just had some good rain, the paddocks have a hint of green about them, there is water in the dam, you are doing okay.

It is December — it has not rained. But it is Christmas, the family has descended, you are not that worried.

It is January — the green is now a crinkled, withered brown. As you walk through the paddocks the crackling beneath your boots echoes across the dying landscape.

You are in a serious drought. What the hell happened?

A flash drought happened.

This story played out from southern Queensland down through New South Wales, spreading all the way down to Victoria over the last few months of 2017 and into the new year.

It is also the sudden burst that has since drawn these areas into one of the worst in living memory, joining large swathes of eastern Australia .

So what are flash droughts? And how do we know they are coming?

What is a flash drought?

David Hoffmann of Monash University has taken up studying flash droughts.

"Well, as the name suggests, it's a flashy event that happens very rapidly," he said.

"It's the decrease of soil moisture from non-drought conditions to an agricultural drought."

According to Mr Hoffmann, when the root zone soil moisture is affected it impacts on crops and other agricultural products.

"For farmers, the problem is that there's almost no time to react to it because it's happened on such a short timescale," he said.

"We are speaking about a couple of weeks or just a month.

"Normal drought policies that are in place are just too long to apply to that."

The term flash drought is only referring to the drought's rapid onset, not about how bad or how long it ends up being.

When and where do they occur?

It is not a huge surprise to hear Australia is in the firing line.

Mr Hoffmann has been using computer modelling to study when and where flash droughts occur.

"There are certain regions that stick out, mostly the ones which have a high variability of rainfall and high evaporative demand," he said.

"Australia would be definitely a place for that.

"So far, flash droughts have [also] been reported in the central or midwestern US, central south-eastern China."

is a good example.

"It seems like the spring and summer seasons are the most prominent, which is quite obvious because in a variable climate when you don't have much rain and a high rate of evapotranspiration in the spring and during the growing season, the soil moisture is even quicker depleted," he said.

Can you predict a flash drought?

Dr Hanh Nguyen has been going through the Bureau of Meteorology data searching for flash droughts.

At the moment, parts of inland northern New South Wales and into Queensland are in a flash drought, as well as patches in the Northern Territory, according to Dr Nguyen.

She and her team are now trying to come up with a way of predicting future flash droughts.

"That's the next step that I'm going to look at. We do have precursors that indicate, so far, up to four weeks in advance that we are leaning toward a flash drought event," Dr Nguyen said.

"So that is good information and useful enough for the farmers if we can tell them a month in advance 'Warning! There's a flash drought that is very likely to occur. Get prepared'.

"That is what the farmers look for. They want warnings even up to two weeks in advance."

The bureau is working with the Northern Australia Climate Program (NACP) and the Climate Mates service on this work.

There are hopes it will be publicly available soon.

And how are flash droughts changing over time? Well, that's future work.


© ABC 2019

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