Intensification of subhourly heavy rainfall

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.

Automated summary

There is a significant increase in subhourly extreme rainfall near Sydney over the past 20 years, with a trend of at least 20% per decade. This trend is consistently observed in storms tracked using ground radars, supported by rain-gauge data, and does not appear to be associated with known natural variations. Subhourly rainfall extremes may be increasing substantially faster than those on longer time scales.