Atmospheric river storms are like punches in a boxing match. It’s okay to have a bunch of weaklings. But it’s best to avoid taking a big hit.
That’s exactly what happened in California this winter. Scientists say the state actually received more atmospheric rivers, known as wet weather events critical to water supplies, from Oct. 1 to April 1 than last year — 44 this winter, compared with There were 31 last winter.
But intensity makes all the difference. This winter, California has only two strong atmospheric rivers across the state, compared with seven last year.
many of the largest this winter Attack Washington and Oregon instead. The result is that, for the most part, California’s rainy season goes very smoothly.
“California is typically either extremely wet or extremely dry,” said Chad Hecht, a meteorologist with the Western Weather and Water Extremes Center at the University of California, San Diego, which compiles the data. “This year has been unusually normal. I’m going to buy it. It’s better than not having any storms at all — or the storms we had last year, one severe storm after another.
The Hecht Center developed a scale in 2019 that measures atmospheric river storms from Category 1 to Category 5, from weakest to strongest, based on the amount of moisture they carry and how long they are expected to stay on land.
Last winter, 11 of the state’s atmospheric river storms were weak, 13 were moderate, and seven were strong. This year, 26 companies are weak, 16 are medium, and 2 are strong.
Result: The reservoir is full. The snowpack in the Sierra Nevada is currently 110% of normal levels, neither too big nor too light.
This time last year, snowpack reached 247% of the historical average, the highest level in 40 years, sparking widespread concerns that a warm late spring storm could melt across the state if it melted too quickly. Causing catastrophic floods.
The March 2023 winter storm destroyed levees on the Pajaro River near Watsonville, tore up the Capitola Pier, created a massive temporary lake in the San Joaquin Valley, caused widespread power outages in the Bay Area, and From Santa Cruz to Pacifica prompted President Biden to travel to survey the damage. This year in Northern California, that chaos has been largely avoided.
“Atmospheric rivers help replenish reservoirs,” said Julie Kalansky, deputy director of the center, which is part of the Scripps Institution of Oceanography. “They increase soil moisture. They pack up snow. They’re not usually dangerous. When they are, we hear more about them. But they tend to be beneficial.
Scientists still aren’t sure why many of this year’s strongest storms moved to the Pacific Northwest. They said this could be caused by differences in sea temperatures, changes in the jet stream or other factors.
But this winter has once again highlighted the importance of these types of storms to the West Coast.
Atmospheric rivers, sometimes called “Pineapple Express” storms, are giant conveyor belts of water in the sky. They are 250 miles wide, 2 miles thick, more than 1,000 miles long, and the largest can carry 25 times the water of the Mississippi River.
When ridges of high pressure repeatedly block such storms, as they did between 2012 and 2016, California can slip into a severe drought. When the storm makes landfall, heavy rainfall is possible.
“A lot of the precipitation in California, in some years even the vast majority of the precipitation, is Gained through them. “Even two or three of them can make or break a water year. Their importance really cannot be overstated.
The strongest atmospheric river storm this year occurred on February 4. Between February 4 and 6, 8.51 inches of rain fell in downtown Los Angeles, making it the second wettest three days since meteorological records began in 1877.
Meanwhile, snowpack in the Sierra Nevada, which entered winter well below normal, jumped from 54% on February 1 to 78% a week later.
Scientists can’t predict exactly how many atmospheric river storms California will experience each year. Since 2012, the average has been 37, with six strong, Hecht said.
Atmospheric river science is still emerging. For years, none of them have been examined in the same detail as hurricanes on the East Coast.
Recent research suggests that as the Earth’s climate continues to warm, California could face the kind of “weather snap” the state has experienced over the past 15 years — a hotter, drier drought followed by a wetter, more wet climate. Soaking winter.
Hecht noted that when temperatures rise, storms absorb more moisture, leading to wetter winters when droughts are eventually broken.
State water planners are increasingly working to adjust California’s water system, which was developed largely from the 1940s to the 1970s, to reflect the new reality.
Gov. Gavin Newsom is pushing for a massive new off-river reservoir, a $4.5 billion project called Sites Reservoir that would be built on a remote ranch in Colusa County 70 miles north of Sacramento. , to capture more water during wet years for use in dry seasons. The project, currently 90% funded by state bonds, the Biden administration and other sources, is scheduled to break ground in 2026.
Newsom said the next severe drought is not a matter of if, but when.
“These extreme conditions are becoming the new reality, and the new reality requires new conditions,” Newsom said on April 2 while working with crews conducting manual snow surveys near the Sierra-at-Tahoe ski resort in El Dorado County. approach. “California’s water system was designed for a world that no longer exists. “
#kind #atmospheric #river #storm #save #California #drought #winter
Image Source : www.mercurynews.com