Search results
We used machine learning to estimate natural flows (expected streamflow in the absence of human modification) for all streams and rivers in California to help water managers identify and manage flows to support native freshwater species.
Feb 1, 2024 · what happens when an atmospheric river reaches land? When the moisture-laden air moves over mountain ranges such as the Sierra Nevada along the California-Nevada line, the water vapor rises and cools, becoming heavy precipitation that falls as rain or snow, according to NOAA.
- Atmospheric rivers transport water vapor from the tropics towards the poles. Animation showing AR plumes over the Pacific during January 2012. The formation of an atmospheric river starts near the equator.
- Atmospheric rivers are the largest “rivers” of fresh water on Earth. While atmospheric rivers are pretty different from rivers of liquid water down on the ground, they transport enough water to deserve their moniker as rivers.
- There’s a rating system for atmospheric rivers like there is for hurricanes. Like the scales for hurricanes and other hazards, the rating scale for atmospheric rivers is based both its physical characteristics (wind speed for hurricanes, quantity of water vapor for atmospheric rivers) and on the level of destruction it causes.
- Though an atmospheric river can help extinguish fall fires, they can increase the hazard of past and future wildfires. When a severe wildfire burns on a hillside, little vegetation remains, and the slope is vulnerable to flash floods and debris flows.
Nov 21, 2024 · A rainy winter season in California tends to surface the phrase, but what exactly is an atmospheric river and what does it mean for the region? NBC 7 Meteorologist Brooke Martell explains.
- Overview
- What is an atmospheric river?
- The damp sponge effect
- Atmospheric rivers and the warming climate
Atmospheric rivers move huge amounts of water through the air above us—and dump rain and snow on land.
In the coming weeks, buckets of rain are likely to batter California. The culprit? Atmospheric rivers.
“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 into the atmosphere, and winds and storms concentrate that water vapor into long, narrow, speedy trains of extra-wet air. Then, big global winds in the lower few miles of the atmosphere accelerate those amped-up, stretched-out, water-rich versions of normal storms.
The sky-borne rivers can stretch for thousands of miles. In 2017, an enormous atmospheric river 5,000 miles long slammed into the Pacific Northwest, dumping over two inches of rain on the region over a few days. Most aren't that massive, though—the average atmospheric river is about 500 miles wide and 1,200 miles long.
They transport huge volumes of water around the world, carrying it along as vapor and cloud droplets. In an average atmospheric river, about 25 times as much water flows through the air high overhead as through the Mississippi River—and on any given day, about three or four are either developing or flowing through the sky in each hemisphere.
“In a way, they're actually the biggest rivers on earth,” says Marty Ralph, a researcher at the Scripps Institution of Oceanography in La Jolla, California, who been studying the phenomena for years. “They're just in the air instead of on the ground.”
All in all, more than 90 percent of the water that gets moved around Earth's midlatitudes—its midsection, where most of the world's population lives—gets transported via these sinuous sky streams. "They play this really key role in bringing moist tropical and subtropical air into the drier mid-latitudes," says Nina Oakley, an atmospheric scientist at the Desert Research Institute in Reno.
The water vapor locked up in an atmospheric river will stay just that—vapor—until something comes along to squeeze it out of the air as rain or snow. Often, that trigger is the edge of a continent: along the west coast of North and South America, for instance, atmospheric rivers crash into mountains, which forces the sodden air masses higher into the atmosphere. As they get forced upward into colder air, the water vapor gets squeezed out—and falls out of the sky as rain or snow. Any cold air can trigger that squeeze-out, though.
“These saturated plumes of air are like a damp sponge,” says Swain, “and a mountain range or a storm system is like a hand wringing that sponge out.”
California gets somewhere between 25 to 50 percent of all its annual precipitation from atmospheric rivers. Often, that's good news—the events have ended droughts, refilled reservoirs, and greened rolling hills. When the precipitation falls as snow in the high mountains, it acts as a kind of long-term water storage system, melting in the spring and summer when the state is parched. But when it comes down as rain, the effects can be devastating, causing floods, mudslides, dam breaches, and more.
The kinds of extreme, destructive rain events that have made news in California over the past few years are not alone: atmospheric rivers are at play in up to half of the most intense, extreme rain storms experienced across the planet.
Air temperatures have ticked upward by about 1 degree Celsius, or about 2 degrees Fahrenheit, over the last century—and they're expected to rise by more than that by the end of the century. With warmer air comes wetter air: toastier temperatures evaporate more water from the ocean. On top of that, air can hold about seven percent more water vapor for each degree warmer it gets. So scientists expect that in a hotter future, atmospheric rivers will get correspondingly wetter and stronger.
This article originally published on March 10, 2023.
Aug 14, 2014 · Federal regulations define the ordinary high water mark (OHWM) as “that line on the shore established by the fluctuations of water and indicated by physical characteristics such as a clear, natural line impressed on the bank, shelving, changes in the character of soil, destruction of terrestrial vegetation, the presence of litter and debris ...
People also ask
Do atmospheric rivers affect California's water supply?
What fueled California's 'atmospheric river' storm?
How can we improve the management of California's rivers and streams?
How does a jet stream transport air to California?
Did atmospheric river storms end California's drought?
How much precipitation does California get from rivers?
In California, water and land management activities have substantially altered river flows and degraded river channels and their floodplains. The result has been a precipitous decline in native fish populations, including the collapse of valued salmon fisheries, and widespread imperilment of freshwater biodiversity.
