An average of more than 180 millions tons of Saharan dust are blown each year west from the world’s largest hot desert, over the Atlantic to the Americas.
HOUSTON (CN) — Ahh, the first week of summer — a time for a backyard football or Wiffle ball game. Hold that thought if you live in the Southeast. Saharan sands are swirling in on their yearly sojourn.
Blown west from the Sahara in North Africa, the world’s largest hot desert at 3 million square miles, clouds of Sahara dust typically settle in for summer vacation over the tropical North Atlantic in mid-June and start breaking up in August.
This year’s plume is the worst in decades, scientists say. It turned the skies above Caribbean islands brownish gray this week on its way to the Gulf Coast.
Part of the Saharan Air Layer, the plumes usually sit 1 to 3 miles above the ocean’s surface and are visible in weather satellite photos, according to the National Oceanic and Atmospheric Administration.
“The Saharan Air Layer is a mass of very dry, dusty air that forms over the Sahara Desert during the late spring, summer, and early fall, and moves over the tropical North Atlantic every three to five days,” NOAA says in a primer.
Astronauts spotted the dust this week from the International Space Station. “We flew over this Saharan dust plume today in the west central Atlantic. Amazing how large an area it covers!” Astronaut Doug Hurley tweeted Sunday.
The massive plume bodes well for the flora of the Amazon rainforest.
Based on observations from its CALIPSO satellite, NASA found from 2007 through 2013, an average of 182 million tons of dust per year blew from African of which 27 million tons, nearly 15%, was deposited 3,000 miles away in the Amazon Basin.
Scientists say the dust contains phosphorous, a vital plant nutrient in short supply in the Amazon, and replenishes losses of the element from flooding and surface runoff.
The dust plume is not caused by climate change, said Dan Reilly, a meteorologist at the Houston-Galveston office of the National Weather Service.
But it will tamp down the incidence of phenomena experts say are increasing in frequency due to warming ocean surface temperatures: tropical storms.
“The warmth, dryness, and strong winds associated with the Saharan Air Layer have been shown to suppress tropical cyclone formation and intensification,” according to NOAA.
Though the hurricane season officially starts June 1, this year raised the question if that timetable should be revised, as the first two named tropical storms, Arthur and Bertha, formed in the Atlantic by May 27, only the fourth time that’s happened since recordkeeping began in 1851.
The last year it happened was 2012. The others were 1887, 1908 and 1957, according to Colorado State University tropical scientist Phil Klotzbach.
Another silver lining in the dust cloud is that the particles can create vivid sunrises and sunsets.
But for those who like to bike or jog at dusk or dawn to avoid the summer heat of the day — beware.
“It would be best if you do not exercise outdoors, or just do anything outdoors, to the extent reasonably possible,” said Dr. David Corry, a pulmonologist at Baylor College of Medicine in Houston.
He said that while inhaling the dust won’t cause lung diseases it will enflame existing conditions like asthma, sinusitis, chronic obstructive pulmonary disease and emphysema.
For those who suffer from allergies caused by household dust mites, the Saharan dust can make them worse.
“Every house has them. There are no exceptions,” Corry said. “The proteins that come out of these mites can build up in very high levels in certain households, particularly those that have carpets.”
He said people susceptible to allergies can develop a strong immune response to dust mites: itchy, watery eyes, runny nose and sneezing.
“What’s coming in out of the Sahara is not these mites, it’s just dust. It contains mostly the same kind of silica particles that are found in beach sand. But they can also carry fungi, insects, plant debris and other things that can make allergies worse,” Corry said.
What about the coronavirus? Texas reported a record daily high of more than 6,200 new cases on Wednesday. Could the Sahara dust increase transmission of Covid-19, with people sneezing more frequently, or make it more difficult for those who contract the virus to recover?
“It’s something to be concerned about. But it’s really not known what the effect positive or negative of having that dust is in terms of viral transmission,” Corry said.
But he said the fact people are wearing masks to contain spread of Covid-19 has an added benefit. “It’s going to keep the dust out of you, and that can only be a good thing.”
Corry cautioned that even those with healthy lungs should stay inside if the sky is overcast with dust.
“Exercise where you are breathing heavily, that’s going to make that issue even worse. So it would be best to not exercise on the days when the dust is around, or try to do it indoors; that’s the best advice,” he said.