Dust matters when it comes to rainfall

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Small dust particles emitted from the land surface pack an out-sized punch when it comes to influencing rainfall and the water cycle, according to a presentation this week by Ruby Leung of the Department of Energy’s Pacific Northwest National Laboratory.

Leung was a keynote speaker at a symposium on the chemistry of our planet at the fall meeting of the American Chemical Society in Washington, D.C. The symposium was organized by ACS President and PNNL Associate Laboratory Director Allison Campbell.

Leung spoke about the impacts of dust on precipitation and our climate. She noted that dust travels great distances and has effects far from its source. For instance, dust from Asia and even the Sahara (blowing eastward across Asia and the Pacific) makes up a significant portion of the dust in California during the winter. The dust is responsible for a good proportion of the heavy rains from “atmospheric rivers” that periodically pummel California.

Dust also powers the heavy rains from monsoons, Leung said, noting that monsoons are affected by dust emitted from nearby deserts. Monsoons are strengthened when dust in the sky absorbs the sun’s energy, increasing the temperature in the atmosphere but decreasing the amount of sunlight hitting the planet surface. Leung discussed one instance -the southwestern United States, where more rain is falling in storms due to elevated heating from dust emitted from the southwestern deserts.

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