Dust
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Hi, I'm Bryan Yeaton and this is The Weather Notebook.
If you've ever stopped to think about how far a bird flies during migration or what a long path your New Zealand apple took on its way to your grocery store, here's another one to ponder: where have the particles in your air come from? As Amy Mayer explains, dust that blows in from the world's deserts can tell you a lot.
High winds and the jet stream pick up dust from desert storms blowing thousands of miles across the planet. As that dust travels, particles from car exhaust and industrial plants climb on board for the ride. Atmospheric chemist Cathy Cahill says the dust that eventually lands in her filters at the University of Alaska in Fairbanks acts as a tracer, revealing where it's been.
"We can say, okay we've got dust from the Gobi Desert at our site at this point. How did that air get here, and what else might it have picked up? it's going to pick up a lot of human emissions, which can give us potential contaminants, it can give us potential nutrients for ecosystems".
So Cahill can tell if her samples contain Chinese dust that picked up metal particles over Russia or car emissions over Korea. Knowing how the dust travels can lead to discoveries about how a seemingly pristine environment, such as Denali National Park here, or the Grand Canyon, gets hazy skies or smog.
"The biggest sources of visibility degradation at the Grand Canyon is actually Los Angeles, it's because it's downwind of it. As Los Angeles is getting cleaner, Grand Canyon's air is getting cleaner".
Identifying the particles and where they originated is just the beginning of a separate process - cleaning up the air. I'm Amy Mayer.
Correspondent Amy Mayer ferrets through dust particles in Fairbanks, Alaska. The Weather Notebook is a production of the Mount Washington Observatory. The program is supported by the National Science Foundation. For more on airborne dust and just air, visit our website at weathernotebook.org.
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