Jonathan Brown with Centre researchers.

A rapid rain burst is a short period of extreme rain occurring over a duration of about 10 minutes.

During rapid rain bursts, a huge amount of water falls rapidly over a small region, increasing the likelihood and severity of flash flooding, especially in urban and steep mountainous regions.

Extreme rain is defined by the area experiencing it. What’s considered extreme rain in one location might not be considered so in another. Rapid rain bursts are the most extreme 5% of rainfall in a location.

Prior to 2022, it was difficult for climate scientists to identify changes in rapid rain bursts due to limitations on rain gauges, satellite data and climate models in identifying/detecting these small-scale storms.

A new technique, developed by researchers at the ARC Centre of Excellence for Climate Extremes, identified thousands of rapid rain bursts over Sydney Australia using weather radar data over two decades.

Using this technique, they found that the most severe rapid rain bursts are intensifying at least 20% per decade over Sydney, Australia – a phenomenon not explained by regular climate processes.

Researchers also refer to rapid rain bursts as “sub-hourly heavy rainfall”.