Doyle Rice

USA TODAY

Yes, there are rivers up in the sky, and they're responsible for up to 65% of the western USA's extreme rain and snow events — such as the storm that blasted Northern California on Monday — a new study finds.



Made visible by clouds, these ribbons of water vapor known as atmospheric rivers extend thousands of miles from the tropics to the western USA. They provide the fuel for the massive rainstorms and subsequent floods along the U.S. West Coast.

The study released Monday, which appeared in the peer-reviewed British journal Nature Geoscience, said it's not only the USA that sees these weather troublemakers: Globally, up to 75% of extreme precipitation events come from atmospheric rivers, said study lead author Duane Waliser, an atmospheric scientist at NASA's Jet Propulsion Laboratory.

In western Canada, northern Europe, New Zealand and southern South America, atmospheric rivers occur on 30 to 35 days per year, Waliser said.

Though beneficial for water supplies in the western USA, these events can wreak havoc on travel, bring deadly mudslides and cause catastrophic damage to life and property, the National Oceanic and Atmospheric Administration said.

One well-known nickname for an atmospheric river is the "Pineapple Express," which occurs when the source of the moisture is near Hawaii. A single strong atmospheric river can transport up to 15 times the water vapor compared with the average flow of water at the mouth of the Mississippi River, according to NOAA's Earth System Research Laboratory.

This winter has been especially active for atmospheric rivers in the West, said meteorologist Jeff Zimmerman of the National Weather Service. As many as 10 separate rivers have been identified. On average, Northern California gets five to seven atmospheric rivers per wet season, the weather service said

The onslaught has knocked out the five-year drought in Northern California. Much of the Sierra Nevada saw its rainiest and snowiest October-February period on record, the weather service said.

Though their influence on rain and snow has been studied before, one surprising new finding from the study is that up to 75% of extreme wind events in the western USA are due to atmospheric rivers.

In Europe, of the 19 windstorms that each did at least a billion U.S. dollars in damage from 1979 to 2003, 14 of those storms were due to damage from atmospheric rivers, Waliser said​.

Contributing: KXTV-TV, Sacramento