Here's what emergency responders need to know: Atmospheric rivers do not account only for wettest storms but for tremendous winds too, researchers said.
Up to 50 percent of the most severe storm cases in non-tropical countries are due to atmospheric rivers, which can bring more water than the flow of Mississippi River.
"This has been a very active winter, atmospheric river-wise," Jeff Zimmerman of the National Weather Service reported after atmospheric rivers ended a five-year drought in Northern California with more than enough soaking the state has experienced.
More Than 10 Rivers In The Sky
With more than 10 separate rivers in the sky identified this winter, Northern California can have up to seven atmospheric rivers. In Sierra Nevada, the weather service said it had its rainiest and snowiest from October to February.
La Niña and the cooler water in the tropics led to the abundance of the rivers.
Atmospheric river, also known as river in the sky, is a long and narrow region in the atmosphere that transports water vapor outside of the tropics.
The term was first coined in a scientific paper published in 1998 by researchers Yong Zhu and Reginald E. Newell at Massachusetts Institute of Technology. Researchers found out that water vapor is transported in narrow regions of the atmosphere roughly 400 kilometers wide. Atmospheric rivers occur when winds associated with the storm gather moisture in the air into a narrow region just ahead the cold front.
Wettest, Windiest Storms Cost A Billion US Dollars
Atmospheric scientist Duane Waliser, in his study covering two decades of storms in places outside the tropics, found out that "atmospheric rivers are typically associated with 30 and even up to 50 percent" of the most severe storm cases.
Wettest storms, he found out, were due to atmospheric rivers.
The windiness, however, surprised him. Waliser said wind speed is twice of the average storm's speed in an atmospheric river.
The result of the study conducted by Waliser is a no-brainer for emergency responders.
Atmospheric rivers are now being understood that it will not only bring flooding hazards but also come with strong winds that can pose hazards to lives and properties.
In Europe, Waliser said, 14 of the 19 windstorms for the 1979 to 2003 period were due to atmospheric rivers. Each of these windstorms wreaked so much havoc that cost at least a billion dollars.
The link between the atmospheric rivers and climate change has not yet been studied.