California is once again being deluged by atmospheric rivers. What are they and will climate change make them worse?

California is once again being deluged by atmospheric rivers that have unleashed major flooding across the state, with river number 12 scheduled to dump more precipitation the week of March 19.

Experts from Northeastern explained in a story that originally ran in January what causes these flowing streams of vapor that causing the record rains and deadly floods that have put millions of people under an evacuation order.

They talked with Northeastern Global News about the science behind the weather events–and whether climate change and global warming will increase the intensity of rainfall associated with these rivers in the sky.

Atmospheric rivers are responsible for ferrying fresh water from the warm tropics eastward to the Western United States, where the associated vapors condense into rain and sometimes snow.

The ‘Pineapple Express’

“There are these ribbons of very moisture laden air that extend out of the tropics,” says Samuel Munoz, associate professor of marine and environmental science at Northeastern’s Marine Science Center and Coastal Sustainability Institute.

“When they collide with a coast, that’s the dominant mechanism by which California and much of the Western U.S. and Pacific Northwest in Canada get rain,” he says.

Because the atmospheric rivers originate in Pacific tropic areas such as Hawaii, meteorologists dub them “the Pineapple Express,” says Lindsay Lawrence, a Northeastern Ph.D. student who has bachelor’s and master’s degrees in meteorology.

“Generally speaking, atmospheric rivers are most extreme during winter months, December, January and February,” Lawrence says.

Even in a normal season, atmospheric rivers can wreak havoc.

Capable of being 300 miles wide and thousands of miles long, the moisture-laden streams can carry many times the volume of water of the Mississippi River, says Auroop Ganguly, director of the Sustainability & Data Sciences Laboratory at Northeastern.

“When these massive waterfronts—the largest transporters of freshwater on the planet Earth—hit land, they usually result in massive rain and snow events leading often to devastating floods.”

Read more at Northeastern Global News.

Author: Cynthia McCormick Hibbert