World’s wettest rainstorms are getting wetter, affecting flood and drought risk

The world's wettest rainstorms produce about half of the global annual rainfall. Now a study shows that these intense downpours have become shorter in duration and fewer in number, compressing the same amount of rain into quicker and more extreme events, with implications for flood and drought risk.

Chiyuan Miao and colleagues from Beijing Normal University in China analysed daily measurements between 1980 and 2022 from more than 19,000 rain gauges around the world. They found that an average of about half of the world's rainfall fell during about nine multi-day storms, delivered over a cumulative time of about 28 days.

Storm Compression

But they also found that since 1980 the average length of an intense storm has reduced by about 86 minutes a decade, cutting the overall time to deliver half of the world's annual rainfall by just over 9.5 hours.

The findings, published in Earth's Future, show these changes are happening across all continents but with regional differences. Europe and South America have recorded the strongest rate of compression of storms, with the wettest shortening by as much as 144 minutes a decade.

Regional Impacts

Implications will also vary between regions and include changes to drought risk, flash flooding, water security, farm productivity, soil erosion and wildfire susceptibility.