Sun Sentinel Palm Beach Edition
Saharan plume of dust may bring pollution, suppress hurricanes
A huge plume of dust arriving from the Sahara desert may bring Florida a few days of air pollution, as well as a break from the risk of hurricanes and the chance of brilliant sunsets.
The mixed blessings come from a particularly giant version of the clouds of dusty air that routinely drift across the Atlantic from north Africa’s vast desert. About 2 miles thick and more than 1,500 miles across, the plume appears on satellite images as fine, dull brown whirls.
“This is certainly one of the most intense we’ve ever seen,” said Joe Prospero, a scientist who pioneered the study of Saharan dust, now professor emeritus at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science.
Although the bulk of the plume is expected to pass south of Florida, it could bring a few days of worsened air quality that could affect people with heart or lung problems.
The region’s normally good air quality could fall into the orange “unhealthy for sensitive groups” category or the red “unhealthy” level, said Monica Pognon, who runs Broward County’s air quality program.
“We’ve been watching
it,” she said. “We’re used to seeing Saharan dust this time of year, but this one is a huge plume.”
The dust is expected to worsen air pollution by raising the level of particulate matter, tiny particles that can lodge deep in the lungs. This can cause difficulty breathing and aggravate existing heart or respiratory problems, such as asthma. She said it’s possible it could have an impact on people suffering from COVID-19, since that’s a respiratory illness.
The impacts could begin late Tuesday or early Wednesday and last through Friday, she said.
The dust cloud is forecast to drift through the Gulf of Mexico, veer north across the southern and midwestern United States, and loop back across the Atlantic toward Europe.
Such clouds are common in summer, even if this one is unusually dense and thick.
“This is the time of year we expect them,” said Frank Marks, director of hurricane research at
NOAA’s Atmospheric and Oceanographic Laboratory. “Anyone who lives in South Florida has seen these dust plumes. You get a slate-gray sky and the sun is kind of milky. You wake up in the morning and you might have some orange dust on your car or windows.”
As it passes, he said, it
will suppress the formation of hurricanes. This hurricane season has produced four tropical storms so far, a quick start in what’s predicted to be an unusually active season. The tally reached four Tuesday with the formation of Tropical Storm Dolly off the coast of Nova Scotia.
The hurricane-suppressing action comes not from the dust itself but from the hot, dry air that carries it. Hurricanes feed off moist air. Dry air kills them, either preventing them from forming or choking them off after they get going, shutting down the deep convection pattern at the core of the storm.
Unfortunately, the suppression of hurricane-formation may last only a week or so, as the plume moves through. It will be well gone by the arrival of the peak of the season, which runs from mid-August through October. But Marks said such plumes regularly roll off the African coast, even if they’re generally not this big, so future plumes could suppress hurricanes in future weeks and months.
The plumes, which transport plant nutrients such as iron and phosphorus across the ocean, form a feature of the environment of the Americas that is still being studied, said Cassandra Gaston, assistant professor of atmospheric science at UM’s Rosenstiel school. They could contribute to tree growth in the Amazon rainforest, she said, as well as promote the growth of red tide in the Gulf of Mexico and carry various consequences for the weather.