A new study has linked subtle changes in the wettest weather to the occurrence of drought across Australia.

The study, led by Tess Parker from the Australian Research Council Centre of Excellence for Climate Extremes at Monash University, shows that a few days less of heavy rainfall annually contributed to severe drought.

The authors used 120 years of Australian rainfall data to show that the absence of just three to five heavy rainfall days was typically responsible for well over half of the rainfall decline during past droughts.

“The majority of rainfall comes from these heavy rainfall days (above 20mm/day), which is typically only one to two weeks’ worth of annual rainfall, sometimes less,” Dr Parker said.

“But it’s the slight reduction of this heavy rain, equivalent to around five or fewer days per year on average, that is responsible for most of the rainfall decline during past drought, right across Australia.”

The study also shows that when droughts break, it’s because these days of heavy rain return. However, they often lead to wetter than normal conditions.

“Droughts typically break in spectacular fashion because those heavy rain days return to excess, rather than just returning to normal,” Dr Parker said.

“This shows that drought-breaking rains can also be down to relatively few, but heavy, rainfall events.

“In wetter climates, like on the east coast, it’s days with rainfall above 50mm that make the biggest difference.”

Dr Parker described the significance of the result lies in the links that can be made to rain-bearing weather systems that cause the heavy rainfall that make and break droughts.

“Now ... we can begin to investigate the types of weather systems related to these heavy rainfall days, which will reveal a lot about important meteorological processes that send us into and out of drought,” she said.

According to the Bureau of Meteorology, of all the climate challenges to afflict Australia, drought is one of the most feared and costly.

Apart from crop failure and stock loss, droughts set the scene for bushfires, dust storms and land degradation.

Source - https://www.sheppnews.com.au