Never again! Earlier this week, California experienced heavy rain, high winds and heavy snow. The once drought-stricken state has been hit by three months of severe weather, resulting in devastating floods, paralyzing blizzards and dozens of deaths. Data released Thursday showed the snow cover to be the highest on record. Nature We spoke to atmospheric and climate scientists about what’s driving the spike in wet weather and what the state might look like in a warmer future.
Why do so many storms hit California?
California’s recent series of storms are driven by atmospheric rivers, long, narrow plumes of moist air that migrate from the tropics to high latitudes. When these “empty rivers” sweep through mountainous terrain, they condense into clouds, bringing heavy rain and snow, says Alison Michaelis, an atmospheric scientist at Northern Illinois University in DeKalb.
Atmospheric rivers can carry enormous amounts of water vapor.Some rivers discharge more than twice as much water as the Amazon1In the western United States, atmospheric rivers account for up to half of the region’s annual rainfall and snowfall. According to data from the Scripps Institute of Oceanography in La Jolla, California, 31 atmospheric rivers have hit California since last November, more than half of which range from moderate to extreme.
Back-to-back atmospheric rivers aren’t unheard of, but they do have a big impact, says Michaelis. “While it might have been a more beneficial event normally, it could be potentially dangerous if it follows another system.”
how much snow is there?
In eastern California’s Sierra Nevada mountains, it’s the snowiest season since 1952, says Andrew Schwartz, an atmospheric scientist who leads the Central Sierra Snow Lab at the University of California, Berkeley. “It just dumps the snow,” he says. A total of 18 meters of snow fell on the lab this season. This is almost double the annual average. And across the state, snow moisture content—the amount of water that forms when snow melts—is about twice the average, Schwartz says.
According to the National Oceanic and Atmospheric Administration’s U.S. Spring Outlook, after three of the driest years on record in California, conditions have seen a welcome easing, marking the first “exceptional” and “extreme” since 2020. Enabled drought-specified rollbacks. But capturing and storing the water released when thick snowpacks begin to melt can be a race against time, says Scripps research economist Tom Corringham. If the snow melts too quickly, excess water will flow into the ocean instead of being stored and distributed where it’s needed most, he says. “It’s not ideal for water management.”
Is climate change playing a role?
As the atmosphere warms, atmospheric rivers will flow more frequently and hold more water, resulting in heavy rain and snow, Schwartz said. He says California has been going back and forth between wet and dry seasons more extreme than in the past. “This variability has always existed, but it has been amplified by climate change,” he says.
To understand how climate change will affect the jet stream and other systems that influence the direction of rivers in the atmosphere, Kim Reid, a climate scientist at Monash University in Melbourne, Australia, says: He said more research needs to be done. If atmospheric rivers shift a few degrees in latitude, they could become more common in some areas and rarer in others, she says.