Widespread Increase in Atmospheric River Frequency and Impacts Over the 20th Century

Atmospheric rivers (ARs) are long, narrow regions of atmospheric moisture transport that provide water resources to many regions, but can also cause hazards such as extreme rainfall and moist heatwaves. Despite their importance, there is uncertainty about how the frequency and impacts of ARs may be changing with time. Our study extends the global record of AR activity back to 1940. We find that the frequency of ARs has increased broadly across the midlatitude regions, rather than shifting polewards as observed in recent decades. This increase in AR frequency leads to more rain and snow associated with these features in both the mid‐ and high‐latitudes. We also find that there is an increase in humid heatwaves associated with ARs over the same period