https://www.nasa.gov/press/2013/november/study-finds-climate-link-to-atmospheric-river-storms/
RELEASE 13-329
Study Finds Climate Link to 'Atmospheric River' Storms
A new NASA-led study of “atmospheric river” storms from the Pacific Ocean may help scientists better predict major winter snowfalls that hit West Coast mountains and lead to heavy spring runoff and sometimes flooding.
Atmospheric rivers — short-lived wind tunnels that carry water vapor from tropical oceans to mid-latitude land areas — are prolific producers of rain and snow on California's Sierra Nevada mountains. The finding, published in the journal Water Resources Research, has major implications for water management in the West, where Sierra runoff is used for drinking water, agriculture and hydropower.
The research team studied how two of the most common atmospheric circulation patterns in the Northern Hemisphere interact with atmospheric rivers. They found when those patterns line up in a certain way, they create a virtual freeway that leads the moisture-laden winds straight to the Sierras.
Bin Guan of the Joint Institute for Regional Earth System Science and Engineering, a collaboration between NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif., and the University of California Los Angeles (UCLA), led a team of scientists from NASA, UCLA , and the National Oceanic and Atmospheric Administration (NOAA) on this research.
An atmospheric river is a narrow stream of wind, about a mile high and sometimes of hurricane strength. Crossing the warm tropical Pacific in a few days, it becomes laden with water vapor. A moderate-sized atmospheric river carries as much water as the Mississippi River dumps into the Gulf of Mexico in an average week. When the river comes ashore and stalls over higher terrain, the water falls as snow or rain.