World's wettest rainstorms are getting wetter, increasing flood and drought risk

The world’s wettest rainstorms, which account for roughly half of total global annual rainfall, are becoming shorter in duration and fewer in number, according to a new study. Research by Chiyuan Miao and colleagues at Beijing Normal University in China indicates that this compression of rainfall into quicker, more intense events has significant implications for flood and drought risks.

The team analysed daily measurements taken from over 19,000 rain gauges across the globe between 1980 and 2022. They discovered that, on average, about half of the planet’s rain falls during approximately nine multi-day storms, occurring over a total time of about 28 days.

Since 1980, the average duration of these intense storms has decreased by about 86 minutes a decade. This trend has reduced the time required to deliver half of the global annual rainfall by just over 9.5 hours, the study published in Earth’s Future noted.

These changes are occurring on every continent, though regional variations exist. Europe and South America have experienced the most rapid rate of storm compression, with the wettest events shortening by as much as 144 minutes a decade. Such shifts could impact flash flooding, water security, drought risk, wildfire susceptibility, soil erosion and farm productivity.