Analysis of weather in Australia across thirty years shows peak downpours during storms are intensifying, leading to greater flash flood risks in urban areas.
University of NSW experts, studying weather records from 79 locations across Australia, found that the downpours will get worse as the climate changes and temperatures warm.
The civil engineers from the university’s Water Research Centre analysed nearly 40,000 storms across Australia.
Warming temperatures are dramatically disrupting rainfall patterns, even within storm events, according to their findings in the journal Nature Geoscience.
The most intense downpours are getting more extreme at warmer temperatures, dumping larger volumes of water over less time.
The least intense periods of rain are getting weaker.
“These more intense patterns are leading to more destructive storms, which can significantly influence the severity of flood flows,” says Conrad Wasko from the UNSW School of Civil and Environmental Engineering.
“The climate zones we studied in Australia are representative of most global climates, so it’s very likely these same trends will be observed around the world.”
Previous studies have looked at rainfall volumes over the total duration of storms.
This latest study is the first to look at rainfall patterns within storms.
“Our results were consistent across all the climate zones in Australia, regardless of season or storm type, without exception,” said co-author and engineer, Professor Ashish Sharma. “This was an unexpected finding, and it supports our hypothesis that increasing temperatures are changing rainfall patterns.”
A five degree celsius temperature rise could mean flood peaks increasing 5% to 20%, depending on the area.
The increase in flood peaks are estimated to be about 19% for Hobart, 12% for Sydney, 10% for Perth, and 45% in Darwin, which has a tropical climate and a markedly different storm pattern than the other cities.
Wasko says the next step is to incorporate the findings into a model which can predict rainfall in future climates.
“That’s the big caveat,” he says. “Is our present-day climate indicative of potential changes to future climates? Or will we begin to see entirely new weather systems emerging as climates change?”
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