I love this story. Atmospheric scientists flying in C-130 aircraft over the Sierra Nevada discovered that, in at least one instance, more snow fell when the water droplets coalesced around particles of airborne dust that blew across the Pacific Ocean from China. Plain old California dust didn't have the same magic power to induce snow fall, which we all know is the key to California's water supply. The scientists presented at the American Association for the Advancement of Science this week in Vancouver. From the Bay Citizen (in the New York Times:)
In experiments that began in 2009, the scientists discovered that dust that glides on high-altitude jet streams from Asia over the Pacific Ocean plays a substantial role in seeding snowflakes that fall over the Sierras.
Industrial pollution, bacteria, heavy metals, dust and other aerosols flow freely from Asia to California. ... Raindrops and snowflakes cannot fall out of a cloud unless there is a floating seed husk, piece of pollen, speck of dust or other aerosol that they can cling to and grow around.
“In order for water to condense out of the water vapor and into a droplet, it has to have a surface to condense on,” said Doug Collins, a chemist at the University of California who is involved with the Sierra studies. “Aerosols provide that surface.”
The work is part of the CalWater project to study our water supply by the California Energy Commission, the National Oceanic and Atmospheric Administration and Scripps Institution of Oceanography at UC San Diego. Collins is at UCSD.