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There are rivers in the sky drenching the US because of climate change

Brian K Sullivan, Bloomberg News on

Published in Weather News

Climate change is spurring a new, deep dive into a complex, little-studied weather system blamed for creating billions of dollars in flood damage across the western U.S.

Atmospheric rivers are narrow ribbons of concentrated moisture that originate in the Pacific and can flow thousands of miles before dropping rain and snow on land. Scientists are ramping up their research into the systems this winter fearful that warmer temperatures tied to climate change will boost the moisture they carry, supercharging them moving forward.

"Hurricane hunter" planes are set to fly at least 12 missions directly into the systems, double last year's number, to gather a wide range of meteorological data. At the same time, 100 new ocean buoys will monitor how the systems form. The goal: Better warning processes to stave off flooding.

"It is 100% completely saturated air," said Rich Henning, a flight director for the National Oceanic and Atmospheric Administration who conducts onboard weather observations. "If you're ever wondering how 6 feet of snow can fall in the Cascades in one day, this is exactly how all that moisture is transported."

The systems flow between 1,000 and 2,000 feet above the surface, with 80 mile-per-hour winds pushing the water vapor through the air, Henning said. Last week, crews from the NOAA and the U.S. Air Force Reserve flew into an atmospheric river that traveled from Hawaii to the Pacific Northwest.

The NOAA flight took off as the system bore down on their airport near Portland, Ore., said Lt. Cmdr. Ron Moyers, the pilot. The plane was wrestling with turbulence and icing almost as soon as the wheels left the runway, he said.

 

Once in the air and over water, the NOAA crew dropped about 30 sensors from a height as high as 45,000 feet, the upper end of the Gulfstream IV's ceiling, Henning said. Slowed in their decent by small parachutes, the sensors -- called dropsondes -- measure temperature, moisture, wind and air pressure, data that will later be assessed by scientists at NOAA and the Scripps Institution of Oceanography in San Diego.

A study released in December by Scripps and the Army Corps of Engineers found that atmospheric rivers caused 84% of the flood damage suffered in 11 western states over 40 years through 2017. The average annual cost: $1.1 billion, according to the report.

"In a warmer climate," the study concluded, atmospheric rivers will be "more intense as they become wetter, longer and wider; there is some indication that this is already happening."

It won't take much of a temperature change to boost their moisture content, according to John Dickson, a flood researcher who is the chief executive officer of Aon Edge, a Montana-based flood insurance provider. A rise of just 1.8 degrees Fahrenheit can boost water vapor in the air by 7%, he said.

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