Are we underestimating the probable maximum rainfall?

Are we underestimating the probable maximum rainfall?

New research has revealed that we don’t take climate change into account when considering current and future extreme rainfall.

Probable Maximum Precipitation (PMP) is theoretically the highest possible precipitation at a given location.

It is essential in the calculation of the probable maximum flood (CMP).

These may be theoretical flood calculations, but they are fundamental to ensuring that our dams and other infrastructure are built to withstand the worst thrown at them.

So if the PMP and therefore the PMF are too low, the worst-case scenario is underestimated.

“While this is an extremely low risk, the consequences of this event are so dire that we need to take it into account,” said Johan Visser, PhD student at the University of New South Wales and lead author. of the article on the impact of climate change. on the operational estimates of the PMP.

Water gushing through the gates of Wivenhoe Dam during a water release.
Dams are spreading across the country as a new study finds extreme rainfall is likely to increase.(ABC News: Marton Dobras)

Despite the high stakes, Visser said guidelines on how to calculate PMP are updated “rarely”.

“Australian guidelines for estimating PMP have not been updated since the late 1990s and early 2000s,” he said.

“That’s why we have a period of about 20 years of unaccounted climate data that hasn’t made it into the guidelines.

“So our question was, are these PMPs and the way they were calculated in the past still relevant if we know that atmospheric humidity has increased?”

Rising dew point

To see if atmospheric humidity has really increased, Visser and his colleagues looked at the dew point record.

The dew point is a measurement of atmospheric humidity, taken regularly at weather stations across the country.

“We are able to track what this dew point measurement has been doing over time and we can see that there are clear upward trends in atmospheric humidity over time,” said he declared.

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