A giant plume of dust from the Saharan Desert will drift over South Carolina this weekend after casting a haze and tanking air quality over the Caribbean and Gulf states.
On forecast models, the plume is an extensive river of sand in the upper atmosphere, flowing for thousands of miles from the western coast of Africa to swirl over the Southeastern U.S. (and potentially the mid-Atlantic by later in the weekend).
An early image of the flow, taken on June 18 by a NASA satellite, shows a striking orange smudge over the Atlantic that entirely blocked out the Cape Verde islands.
There's no doubt that the plume, dubbed "Godzilla," is a remarkable one. While some have predicted this is the largest Saharan dust event in half a century, Hongbing Yu, a research scientist at NASA's Goddard Space Center, said it's safe to say this is the biggest event at least since a similar dusting over the Caribbean in the 1980s.
The layer of sediment, which mostly hangs about a mile high in the atmosphere, is only predicted to make sunsets more colorful in the Palmetto State over the weekend, said Steve Rowley, a meteorologist with the National Weather Service in Charleston.
"We really expect little or none of this to get down to the surface," Rowley said, though there was some indication that the plume was creating hazy conditions near a buoy offshore of Savannah on Friday afternoon.
The reduced visibility had not yet reached as far north as another buoy near Edisto Beach.
The Saharan Dust Layer is in full swing across the Deep South into parts of the Southeast U.S. Here are webcams from our 2 buoys offshore of Savannah and Charleston. 41008 (Greys Reef Buoy) is quite hazy while 41004 (Edisto Buoy) is out of the dust. @GraysReefNMS #scwx #savwx pic.twitter.com/INnFkMBjpU— NWS Charleston, SC (@NWSCharlestonSC) June 26, 2020
Dust plumes are a regular, and vital, method of transporting nutrients off the African continent, said Yu, who specializes in the atmospheric movement of tiny airborne particles.
Limited sources of iron and phosphorous put a cap on ocean life in many regions, and the dust events provide fresh sources of those essential minerals, Yu said. It's also a source of nutrients for the Amazon basin, which is usually the destination for dust flows in the winter and spring.
In all, an estimated 180 million tons of dust floats off the Sahara each year; only about 50 million tons actually reaches the shores of the Americas, Yu said.
The hot, dry air that carries the dust also serves to suppress tropical weather like hurricanes, which need a stable, wet atmosphere for formation.
It's uncommon, however, that such a concentrated plume emerges all at once. In some places, the event had given rise to concerns over another possible breathing irritant, particularly in the wake of COVID-19.
On Friday, the Weather Service in Brownsville, Texas, warned of poor air quality and urged people to avoid exercising outside. People with asthma are particularly sensitive and should closely monitor their known triggers, said Kenny Mendez, president of Asthma and Allergy Foundation of America.
"We’re basically like canaries in the coalmine in terms of air quality," Mendez said. "People with asthma are really at risk."
Some past studies have actually linked Saharan dust flows to the incidence of asthma in the Caribbean, Yu said. Air particulates of all kinds can cause respiratory damage, but smaller particles can cause more damage and penetrate deeper.
Relatively little is known about the makeup of the dust that drifts from Africa, but Yu said there's one small upside to the event blanketing the tropics and Southeast right now: researchers in Puerto Rico who started a dust sampling program in June now have plenty of material to analyze.