by Daniel Brouse
December 10, 2023
As the Earth warms, the air will hold more moisture (water vapor). When more moisture-laden air moves over land it can create atmospheric rivers. In the Northwestern USA, the atmospheric rivers are commonly called the Pineapple Express. The Journal EOS in the article Atmospheric Rivers Spur High-Tide Floods on U.S. West Coast said, “Atmospheric rivers are narrow bands of moisture that travel across the lower troposphere, generally at the leading edges of massive low-pressure systems. At their peak, they can carry as much water through the sky as the Amazon River does on land. They unleash intense winds and heavy rain as they surge across the Pacific Ocean, eventually making landfall on the U.S. West Coast, contributing to many high-tide flooding events.”
Historically in the United States, atmospheric rivers (AR) have been associated with the West Coast. Now, AR activity is getting more attention on the East Coast. “Actually their frequency is not really increasing. Meteorologists have used the term for decades. It has simply become popular by the media. Just like polar vortex,” said Jeff Boyne National Weather Service meteorologist and climatologist. Indeed, “atmospheric rivers are more frequent on the East Coast than they are on the West Coast,” said Jason Cordeira, associate professor of meteorology at Plymouth State University. “They’re just not as impactful and don’t usually produce as much rainfall.”
What is changing is the research into the types and increasing intensity of East Coast AR events. “Between 1958 and 2012, the Northeast saw more than a 70% increase in the amount of rainfall measured during heavy precipitation events, more than in any other region in the United States. Projections indicate continuing increases in precipitation, especially in winter and spring and in northern parts of the region,” as reported in The US Fourth National Climate Assessment.
Most types of East Coast ARs are increasing in intensity likely due to climate change. The study Identifying Eastern US Atmospheric River Types and Evaluating Historical Trends reports, “The impact of increasing moisture transport could be significant across the northeast corridor from Washington D.C. to Coastal Maine, as it increases the risk of extreme precipitation from landfalling ARs. The results indicate most ARs in the study domain are forced by extratropical cyclones, with lee side low pressure systems and coastal lows along the Atlantic Coast (e.g. nor’easters) responsible for producing the strongest ARs.”
How Fast Are Atmospheric Rivers Gaining Intensity?
Some areas of the world are now warming so fast, it is becoming more difficult to measure the change from “normal” or average. Jeff Boyne of the NWS said, “There are climate normals that are updated every 10 to 15 years, because the planet is warming so fast. The ENSO (El Nino-Southern Oscillation) regions are warming so fast that those normals are being updated every 5 years.” Overall, how fast is climate change accelerating? Rapidly. “It’s so far outside anything we’ve seen, it’s almost mind-blowing,” says Walter Meier, who monitors sea-ice with the National Snow and Ice Data Center. “September was, in my professional opinion as a climate scientist, absolutely gobsmackingly bananas,” said Zeke Hausfather, at the Berkeley Earth climate data project.”
ALSO SEE:
The Reign of Violent Rain Brouse and Mukherjee (2023)
The Age of Loss and Damage Brouse (2023)
Climate Change Impacts on Flood Risks and Real Estate Values Sidd Mukherjee and Daniel Brouse (2023)