WASHINGTON — To help solve the problem of California’s long-running drought, NOAA scientist Chris Fairall of Colorado took a trip last month to one of the wettest places he could find: a ferocious winter storm about 800 miles west of San Francisco.
There, for five straight days, Fairall and the rest of the research team aboard the ship Ronald H. Brown were rocked by 18-foot waves, 35-knot winds and the relentless roll that comes with an angry Pacific Ocean.
“You couldn’t stand up without having an arm holding on to something,” said Fairall, who works for the National Oceanic and Atmospheric Administration in Boulder. “On the really rough nights, people had trouble sleeping.”
The voyage was part of a massive, effort by NOAA, NASA, the Department of Energy and other partners to study how the West Coast is affected by “atmospheric rivers,” an unusual weather event that can deliver .
More than 30 staff members at NOAA’s facility in Boulder have played some role in the CalWater 2015 project, a $10 million effort that — if successful — would help improve weather forecasts and enable California to better prepare for harsh conditions.
The key to the campaign is understanding atmospheric rivers — one of which was tied to the storm Fairall endured for five days.
“I was surprised there were very few people who were seasick,” he said.
Common to the Pacific Ocean but found worldwide, atmospheric rivers work as their name implies. They take water vapor from one region and then — like a fire hose or squirt gun — to a new spot hundreds of miles away.
Unlike normal rivers, however, atmospheric rivers aren’t pinned to an exact, continuous route — though, when they do appear, it’s often in similar areas.
The most famous example is the Pineapple Express, which got its name because it carries water from Hawaii to the West Coast at a flow rate faster than the Amazon River.
(Pineapple Express also is the name of a , which Fairall said led to a few jokes at the expense of the Boulder-based team.)
Thirst for atmosphere
Scientists have studied atmospheric rivers for decades, but predicting their behavior is still difficult. Depending on the conditions, they can cause destructive storms or, when weaker, deliver “rain or snow that is crucial to water supply,” .
Atmospheric rivers are “an integral part of Earth’s water budget,” said Allen White, a research meteorologist at NOAA. “Their role is to remove excess heat and moisture from the tropics. But when they interact with the jet stream, they get associated with storms and then are heavy rain producers.”
In the last three years, however, a persistent ridge of high pressure has diverted atmospheric rivers from California and sent the moisture north to places such as British Columbia, he said.
The result has been parched conditions in the Golden State — so much so that California officials have debated whether to force restaurant patrons .
“Array of assets”
Because of the importance of atmospheric rivers to California’s water supply, NOAA has made it a priority to learn more about them. In addition to the ship used by Fairall, the CalWater 2015 project has deployed aircraft from NOAA, NASA and the Department of Energy. These add to ground-based observations at field sites in California.
“We have never had this array of assets tackling the atmospheric river and precipitation problem before,” said Ryan Spackman, who works for NOAA in Boulder. It’s “unprecedented.”
As part of the campaign, Spackman said he rode NOAA’s “hurricane hunter” aircraft and flew through an atmospheric river — an experience he compared to whitewater rafting. “We were skimming the bottom of the cloud,” he said.
His role has been investigating how aerosols affect atmospheric rivers. Aerosols, which range from sea salt to sulfates, are believed to affect levels of rainfall. As part of CalWater 2015, Spackman is examining whether man-made aerosols and natural aerosols have different impacts on the atmospheric rivers.
Because of its mix of the two, the California coast is a “great laboratory” for studying aerosols, he said.
As it stands, aerosol measurements are not included in forecasting models used by the National Weather Service. But Spackman said the research being done as part of CalWater 2015 could change that — and, in turn, make forecasts more accurate.
“We are a long way from that, but this is where you start,” he said.
Going with the flow
So how would this help California?
For one, improved weather forecasts would help water managers better plan for the future, White said.
The U.S. Army Corps of Engineers manages dozens of reservoirs and dams in California and — to reduce the risk of flooding — often is required to “release” thousands of gallons or more of water. With better forecasts, the Corps could be more precise with its water policy, he said.
One way to do that is better understand the mechanics of atmospheric rivers.
While aboard the Ronald H. Brown, Fairall said he observed very little interaction between the atmospheric river and the ocean below — which suggests the moisture running through the river primarily came from the tropics.
“It tells us what’s formed in the tropics is what’s in there,” Fairall said.
The observation is sure to become another data point in the ongoing effort to decode the Pineapple Express and other atmospheric rivers. Indeed, White said there has been talk of a future mission to the tropical “breeding grounds” of atmospheric rivers.
“It would be great to do that,” he said.
Mark K. Matthews: 202-662-8907, mmatthews@ denverpost.com or twitter.com/mkmatthews
