LAUSR

Short-duration rainfall extremes can cause flash flooding with associated impacts. Previous studies of climate impacts on extreme precipitation have focused mainly on daily rain totals. Subdaily extremes are often generated in small areas that can be missed by gauge networks or satellites and are not resolved by climate models. Here, we show a robust positive trend of at least 20% per decade in subhourly extreme rainfall near Sydney, Australia, over 20 years, despite no evidence of trends at hourly or daily scales. This trend is seen consistently in storms tracked using multiple independent ground radars, is consistent with rain-gauge data, and does not appear to be associated with known natural variations. This finding suggests that subhourly rainfall extremes may be increasing substantially faster than those on more widely reported time scales. Description A hard rain is falling Short-duration, extreme rainfall can cause dangerous flash flooding, threatening life, infrastructure and the landscape. Studies of this type of event have focused mainly on daily rain totals, not considering how precipitation might vary on shorter time scales. Ayat et al. analyzed subhourly rainfall extremes near Sydney, Australia, over 20 years and found that they are increasing much faster than those over longer periods. Better understanding of such extremes is vital for effective climate adaptation and to reduce the vulnerability of populated regions. —HJS Subhourly rainfall extremes are intensifying faster than those on longer time scales.