Atmospheric Rivers as Drivers of Precipitation Variability and Flood Extremes

Atmospheric rivers (ARs) are narrow corridors of concentrated moisture that play a key role in global precipitation and extreme hydroclimatic events. Despite their importance, their contribution to precipitation variability, flood risk, and long-term climate change remains poorly quantified. In this study, we combine global hydrological observations, high-resolution precipitation datasets, and multi-model climate simulations to assess the impact of ARs on interannual variability, extreme precipitation, and rare flooding. Our results indicate that ARs account for 70–90% of year-to-year precipitation variability across mid-latitude regions and are linked to more than 70% of the largest precipitation and streamflow events globally. Their presence can increase the likelihood of rare flood events by up to an order of magnitude in parts of North America, Europe, and Australia. Additionally, there have been notable increases in the frequency of ARs and the associated precipitation totals over the past decades. Climate model projections further suggest that AR-induced precipitation is likely to become more frequent and intense in the future, even in areas where mean precipitation may decline, potentially amplifying their role in hydroclimatic extremes. Together, these findings highlight that ARs are not only key drivers of present-day precipitation and flood events but will also increasingly shape future global hydroclimatic conditions. Understanding AR processes is therefore essential for anticipating changes in regional water availability, managing flood hazards, and adapting to a changing climate.