High-altitude dust blown thousands of miles across the Pacific from Asian and African can make it rain and snow in the Sierra Nevada Mountains, they said.
Scientist say while two similar Sierra storms in winter 2009 carried the same amount of water vapor, one produced 40 percent more precipitation than the other, and an analysis of ground samples of the rain and snow dropped by the wetter storm found an abundance of Asian dust.
In 2011, another analysis of atmospheric samples compared with ground measurements confirmed that when dust particles from halfway around the globe were detected in the clouds swirling above the Sierra peaks, there was more rain and snow.
"There was this sort of magical switch," study co-author Kim Prather, a University of California, San Diego atmospheric chemist, told the Los Angeles Times. "The days with dust you see one thing, and the days without dust you see a different thing."
Previous research has shown windblown mineral dust transported long distances can be a seed for atmospheric ice that can lead to a significant amount of precipitation.
"The fact that something happening on another continent in terms of dust generation could influence precipitation patterns in the United States -- that's a challenging problem," said co-author Marty Ralph, a research meteorologist with the National Oceanic and Atmospheric Administration.
Ralph said he had initially doubted aerosols -- dust and other atmospheric particles -- could affect whether a cloud gives up water or holds on to it.
But the evidence from the 2009 storms "was a bit of a scientific epiphany," he said. "I came into this very skeptical and have come to where I am now, co-authoring a paper that's saying aerosols can have a significant impact."
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