Asian and African Dust Influences North American Weather
Dust from far abroad—with help from skyborne bacteria—helps determine how much rain and snow fall in the western U.S.
In the western United States, winter precipitation is key to providing the water states like Colorado and California need to survive their dry summers. The snow and rain that comes in the cold season runs off into reservoirs, where it is stored for drinking water, agriculture, hydropower and other uses.
Now, researchers have linked airborne dust and other particles from as far away as the Sahara and Asian deserts with the precipitation that falls over California's Sierra Nevada mountains. The paper, published online yesterday in the journal Science, was co-authored by Jessie Creamean, a postdoctoral associate at the National Oceanic and Atmospheric Administration's Earth System Research Laboratory in Boulder, Colo., and Kaitlyn Suski, a graduate student at the University of California, San Diego.
"Basically, we were able to show that dust and biological aerosols that were lofted from deserts all the way across the world in the Sahara and Asia were airlifted all the way across the world to make ice crystals in clouds in the western United States," Creamean said.
Before this study, researchers had no idea that dust from such distant places would show up in clouds in California. "Evidence of Saharan dust in precipitation along the U.S. West Coast is somewhat surprising. It is more than half a world of circumnavigation away," said Ryan Spackman, a NOAA atmospheric scientist familiar with the study.
The aerosols catalyze the formation of ice in the clouds, which could increase precipitation, although more research needs to be done on that linkage, Creamean said.
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