Researchers from the University of New South Wales in Australia have found that rainfall extremes at sub-hourly timescales are intensifying as a result of climate change much faster than those on longer hourly or daily timescales.
These intense, short-duration precipitation events are often responsible for damaging environmental hazards, such as flash flooding. Examples in Europe over thee past 3 years include Valencia, Spain in May 2022 and in August 2019; Liguria, Italy in October 2021; Slovenia in October 2021; Andalusia, Spain, September 2021; and France in September 2021 and October 2019.
The study shows that these sub-hourly rainfall extremes are becoming more intense, with rainfall totals increasing by at least 20% per decade. This highlights the need for a better understanding of how climate change is affecting short-duration rainfall to improve climate adaptation and mitigation efforts.
Climate change is expected to alter the intensity and frequency of heavy rainfall worldwide. However, despite advances in understanding the effects of a warming climate on rainfall extremes at daily or longer timescales, less is known about its effect on short-duration or sub-daily rainfall totals.
Heavy precipitation at these scales is often responsible for destructive natural hazards, including flash floods, landslides, and debris flows in urban and rural regions. Because sub-daily rainfall extremes often occur over small areas, they can be missed by rain gauge networks, overlooked by satellite measurements, and are poorly predicted by regional climate models.
To better understand how climate change impacts sub-hourly rainfall totals, Hooman Ayat and colleagues from the University of New South Wales and the Australian Bureau of Meteorology used satellite-calibrated observations from three ground-based weather radars surrounding greater Sydney, Australia to evaluate trends in extreme rainfall down to the 10-minute scale over the last 20 years.
Ayat et al. discovered that these short-duration rainfall extremes are becoming more intense – rainfall totals during these sub-hourly events are increasing – much faster than those over longer periods. According to the findings, despite no evidence of positive trends on the hourly or daily scales, sub-hourly extreme rainfall extremes in the Sydney area has been rising by at least 20% per decade, the study found.
