California may be in for more extreme dryness in coming years, thanks to the increasingly common "ridiculously resilient ridge."
This atmospheric pattern — a stubborn ridge of high pressure that periodically forms off the West Coast — has been appearing more frequently, according to a Stanford University study published Friday in the journal Science Advances.
The ridge pushes Pacific storms over California. It's one of the reasons why the state has missed out on precious rain during recent drought years.
According to the new study led by Stanford graduate student Daniel Swain, this ridge has been taking shape more often in recent years.
He said that this persistent pattern has amplified the negative effects of climate change in California.
"California is definitely getting warmer, quickly. And that is increasing the risk of drought," he said. "And at the same time there is some evidence that the kinds of atmospheric patterns that lead to extremely dry years are also increasing."
The state could be in for more extreme dryness in the future if this trend continues, Swain said. But the rise of the ridiculously resilient ridge hasn't necessarily caused a decline in other atmospheric patterns associated with extremely wet years. According to Swain, the result for California could be more dramatic swings between extreme dryness to extreme wetness, with fewer normal years in between.
"It's those really dry years or those really wet years that tend to present issues, in terms of drought or flood risk," Swain said. "The best available evidence right now suggests we're going to have to prepare for more of these extremes on both ends."
Despite a strong El Niño being in effect, California has experienced a fairly average wet season this year. A high-pressure ridge that kept storms at bay throughout February was partly to blame for this season's lack of heavy precipitation.
