What's New
Atmospheric rivers—narrow bands of concentrated water vapor transported polewards from the tropics—don't just deliver a deluge of rainfall, but play a key role in driving extreme heat events and warming winters across the United States, new research suggests.
This winter has already kicked off with atmospheric rivers on both the East and West Coasts, causing widespread flooding, but also relieving drought conditions in some regions.
However, the new study also suggests these weather systems bring heat to the lower atmosphere, creating temperature anomalies 9–18 F above average.
These impacts are especially pronounced in regions like the Pacific Northwest, Midwest and eastern U.S., where atmospheric rivers are linked to warm winters and extreme heatwaves.
Why It Matters
The findings underscore an overlooked consequence of atmospheric rivers in the U.S. and more broadly across the globe: their ability to amplify extreme temperatures, worsening heatwaves and creating unseasonably warm winters.
With atmospheric rivers expected to become more intense and frequent due to climate change, their impact on temperature extremes could pose new challenges for infrastructure, agriculture and public health.
Improved forecasting of AR-driven heat events could help communities prepare for these risks.
Newsweek has contacted the study's authors via email for comment.
What to Know
The study found several significant regional impacts for the U.S.
In the Pacific Northwest, an atmospheric river contributed to the record-breaking 2021 heatwaves, intensifying heat in the region. The researchers found a significant correlation between the frequency of atmospheric rivers and seasonal average temperatures.
The impacts may not be limited to where an atmospheric river makes landfall, either. The 2021 heatwave showed lingering effects far from where it slammed into southeastern Alaska.
Atmospheric rivers penetrate further inland in the Midwest, likely due to the absence of mountain barriers. Here, they can warm the region by approximated 1 F on average during winter.
The North Atlantic, North Pacific, and the Southern Ocean are hotspots for AR-driven warming. Wintertime ARs contribute to significant warming in northern Europe and eastern North America.
All in all, over 70 percent of hourly extreme temperature anomalies in mid-latitudes occur during ARs. In polar regions, extreme heat events are up to 10 times more likely to coincide with ARs than if the events were independent.
What People Are Saying
The study's authors wrote: "Atmospheric rivers have significant impacts on near-surface air temperatures on multiple timescales, from seasonal averages to hourly extreme temperature events.
"Atmospheric rivers cause warm near-surface air temperature anomalies across the mid-latitudes and polar regions, and the majority of extreme hourly temperature anomalies across mid-latitude storm tracks occur within atmospheric river features.
"It is possible that temperature effects associated with atmospheric rivers are even larger than those estimated here.
"The case study of the 2021 Pacific Northwest heatwave showed that lingering effects from an AR impacting southeast Alaska worsened the ongoing heatwave in the Pacific Northwest, far from the initial landfall location. It is therefore likely that areas surrounding the identified ARs could also be impacted by them, and that the effects might remain for some time after the ARs have dissipated."
What's Next
The study underscores the critical need to enhance atmospheric river forecasting capabilities to improve predictions of their heat-related impacts.
As atmospheric rivers intensify and become more frequent due to climate change, researchers are increasingly focused on their role in exacerbating heatwaves, as evidenced by the 2021 Pacific Northwest event.
The researchers highlighted the importance of further investigation into the connection between heatwaves and atmospheric rivers. Specifically, moist heatwaves pose a significant threat to public health, as high humidity levels make it more difficult to maintain body temperature and stay cool.
Do you have a tip on a science story that Newsweek should be covering? Do you have a question about atmospheric rivers? Let us know via science@newsweek.com.
Reference
Scholz, S. R., Lora, J. M. (2024). Atmospheric rivers cause warm winters and extreme heat events. Nature. https://doi.org/10.1038/s41586-024-08238-7
English (US) ·