Climate change can supercharge atmospheric rivers that can deliver drought-ending rains.

What Are Atmospheric Rivers?

Atmospheric rivers, jet streams of moisture that can carry about 10 times as much water vapor as the Mississippi River at its mouth, are responsible for most of the horizontal transport of water vapor outside of the tropics.

Atmospheric Rivers Can Bring Drought-Ending Rains And Catastrophic Damages

The atmospheric rivers that brought record-breaking rains to California this winter did some good by ending drought in most parts of the state but the phenomenon does not always bring good news.

Atmospheric rivers with the largest amounts of water vapor and the strongest winds can produce extreme floods and rainfalls, which can affect travel, cause catastrophic damage to life and property and induce mudslide. California may be recovering from a five-year drought but it now has to contend with oppressive storms and floods.

Atmospheric rivers have been associated with historic floods including all seven floods on the Russian River in California that occurred between 1996 and 2007 and all 10 of the largest floods that occurred in Britain since the 1970s.

Researchers have also discovered how atmospheric rivers resulted in the decimation of species. They found that between 97 and 100 percent of wild Olympia oysters in north San Francisco Bay died after the region was hit by rainfall caused by atmospheric rivers dumping vast amounts of rain over a short period of time, which caused floods.

Researchers of a new study published in the journal Nature Geoscience also found that between the years 1997 and 2014, about half of the top 2 percent of the most extreme storms that occurred in the world's coastal regions were tied to atmospheric rivers. Between 40 and 70 percent of extreme winds as well as snowfall and rainfall events across coastlines worldwide were also linked to these so-called "rivers in the sky."

"Atmospheric rivers produce the extreme rainfall because this moisture is lifted above mountain ranges. The lifting of the air initiates some rainfall, but this then feeds off this huge quantity of water in the atmospheric river to lead to much heavier rainfall," explained climate scientist Richard Allan, from the University of Reading in the UK.

Climate Change And Intensity Of Atmospheric Rivers

Allan added that the intensity of atmospheric rivers is anticipated to increase because of climate change. Experts have long associated climate change and more frequent occurrence of atmospheric rivers.

Weather events can likewise become more intense in a warmer world because warmer air can hold more moisture and lead to bigger atmospheric rivers. A warmer world could mean stronger moisture transport and heavier rainfall.

U.S. Geological Survey hydrologist Mike Dettinger explained that climate change could also affect mountain snowfall patterns as it raises the elevation at which it is cold enough for snow to fall, which means that more rain than snow will fall, which could also lead to more flooding.

"That's not good, because more rain means more flood risk," Dettinger said. "California's atmospheric rivers are every bit as big as land-falling hurricanes."

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