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That haziness in the Austin sky? It's dust all the way from Africa.

A hazy day with the Austin skyline
Michael Minasi
/
KUT News
A Saharan dust plume settles on the city Monday.

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When you think of summer in Austin, heat is probably the first thing that comes to mind, followed, maybe, by drought. But longtime Austinites will also recognize hazy, sepia-toned skies as a sign of the season.

We will see them again starting this week, and we have the Saharan desert to thank.

Each year massive wind storms in North Africa kick the fine desert dust into the atmosphere, where it rises about 1 to 3 miles high.

The dust stays aloft, as a layer of hazy air about 2 miles thick, but it does not stay still.

Instead, these dust clouds, or plumes, are blown across the Atlantic on powerful trade winds. Once they reach the Western Hemisphere the winds die down and the dust settles back to earth, sometimes over Austin.

According to the Texas Commission on Environmental Quality, the latest plume of Saharan dust moves into Central Texas on Monday.

The dust can create beautiful sunsets, but it also causes problems for people with respiratory conditions.

"It can exacerbate things like asthma [and increase] hospitalization rates," said Anton Cox, air quality program manager with the Capital Area Council of Governments. "It can cause issues with irritated throats."

Cox advises "making sure that you are reducing your exposure so that you're not impacted by those particles."

Keeping AC filters fresh in your home and wearing an N95 face mask while outdoors may help filter out some of the particles, he said.

The Texas Commission on Environmental Quality also expects the dust to reduce moisture levels in the air.

The long, strange trip

You may have heard of the butterfly effect — the notion that the universe is so interconnected that a small thing happening in a distant place (a butterfly flapping its wings, for example) can influence events far away and deep into the future.

This is certainly the case with Saharan dust, though it is ancient lake creatures, not butterflies, that begin the tale. These microscopic diatoms thrived in massive inland lakes in North Africa about 6,000 years ago.

When natural changes in climate brought an end to the African “humid period,” the lakes dried up. But the tiny skeletons of those diatoms remained. They formed a fine, powdery sand that now covers the region.

It is this dust that is picked up annually and distributed across the world, bringing beautiful sunsets and asthma attacks.

Fertilizing the world and more!

Texas is not the only place to receive Saharan dust. It blows across Europe and South America as well.

Thanks to those dead diatoms, the dust is rich in phosphorus, making it a useful fertilizer. It helps plants grow wherever it lands. In fact, researchers believe the Amazon rainforests of South America rely on annual injections of Saharan dust to stay healthy and green.

It’s a butterfly effect we can all get behind.

“Great Mother Africa still sort of feeds its former child South America with nutrients from the African desert," Charlie Zender, an atmospheric physicist UC Irvine, told KUT back in 2018.

Saharan dust also impacts the environment by inhibiting tropical storm and hurricane formation over the Atlantic and reflecting sunlight back into space, slightly cooling the earth as it passes over the ocean.

The dust can also contain radioactive particles, thanks, in part, to French nuclear trials in Algeria in the 1970s.

But, according to the Copernicus Atmosphere Monitoring Service, the radioactivity exists "in concentration levels not considered harmful for health or the environment."

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Mose Buchele focuses on energy and environmental reporting at KUT. Got a tip? Email him at mbuchele@kut.org. Follow him on Twitter @mosebuchele.
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