According to a report in the Los Angeles Times, new research shows that high-altitude dust from Asian and African deserts blown thousands of miles across the Pacific Ocean can make it rain and snow in the Sierra Nevada.

The study, published in the online edition of the journal Science, suggests that tiny particles from afar play a role in California’s water supply.

This study grew out of researchers’ questions about two similar Sierra storms in winter 2009. Even though the storm systems carried the same amount of water vapour, one produced 40% more precipitation than the other.

When scientists analysed ground samples of the rain and snow dropped by the wetter storm, they found an abundance of Asian dust. Two years later, a science team spent days flying through Sierra storm clouds on a government research plane, collecting an array of atmospheric samples and instruments below in the Tahoe National Forest took ground measurements. The results: When dust and tiny biological particles from halfway around the globe were detected in the clouds swirling above the Sierra peaks, there was more rain and snow.

Previous research by one of the paper’s 12 authors had shown that windblown mineral dust transported long distances acts as a seed for atmospheric ice that is key to forming a significant amount of precipitation. But the scientists said the Sierra study is the first direct documentation that dust and biological particles from as far away as the Sahara Desert and the deserts of China and Mongolia can help wring water out of the sky in the western United States.