Recent Intensification of Moderate-to-Extreme Atmospheric Rivers and Associated Hydroclimate Extremes

Atmospheric Rivers (ARs) play a fundamental role in global and regional hydroclimate, accounting for up to 35% of annual mean precipitation, approximately 50% of extreme precipitation, and around 85% of flood events in the midlatitudes.  Using multiple observational and reanalysis datasets spanning 1979-2025 and applying several AR detection techniques, including the SCAlable Feature Extracting and Tracking (SCAFET) method, we systematically examine recent changes in AR characteristics and their associated hydroclimate extremes. Our analysis shows no significant trend in the total annual frequency of all AR events, despite a pronounced long-term increase in integrated vapor transport over the last several decades. In contrast, the frequency and maximum intensity of moderate-to-extreme ARs have increased significantly, accompanied by a robust intensification of AR-related extreme precipitation.  We further find pronounced seasonal dependence in these changes, characterized by a robust poleward shift of ARs, associated with storm-track displacement and moisture-transport pathway migration during boreal winter, and by a notable increase in AR activity over East Asia and the western North Pacific during boreal summer. These findings are consistent across different reanalysis products and detection algorithms, underscoring the robustness of the detected signals. The recent increase in moderate-to-extreme AR events highlights an emerging amplification of hydroclimate extremes, with important implications for water resources management, flood risk assessment, and climate adaptation strategies in midlatitude regions.