- Environment
- Explainer
‘Rivers in the sky’ are why California keeps flooding
Atmospheric rivers move huge amounts of water through the air above us—and dump rain and snow on land.
Buckets of rain and snow are battering California. The culprit? Atmospheric rivers.
The rains were born far away, deep in the tropical Pacific, where water evaporated from the warm ocean surface and fizzed into the atmosphere. The drenched air parcel flow then moved sinuously along, an “atmospheric river” winding its way toward land. When that wet air hit a coast—in this case the West Coast of the United States—it unleashed torrents of water.
“You need two ingredients for an atmospheric river,” says Daniel Swain, a climate scientist at the University of California, Los Angeles. “A plume of really concentrated moisture in the atmosphere and strong, fast winds to move it around.”
The concentrated moisture comes from the ocean. Warm oceans evaporate water
