While the idea of a massive dust cloud from the deserts of Africa hitting the United States might seem like the plot of a sci-fi movie — it’s actually just an annual weather event that can give way to some spectacular seaside sunsets.
What is an SAL? What Causes It?
Thunderstorms and the jostling position of a weather pattern known as the Bermuda-Azores high have helped lift tons of dust and dirt from the Sahara and sent it swirling across the Atlantic. These Saharan dust clouds, also known as the Saharan Air Layer (SAL) plays out every year, though some years see more dramatic plumes than others.
The weather phenomenon is a normal, annual event that is often present in the region from late June to mid-August with dust eruptions coming as often as every three to five days, according to NOAA. The billowing clouds tend to peak between June and July, and NASA said 100 million tons of dust can be sent around the globe each year, reaching parts of Europe in addition to the US.
What does the Saharan dust cloud look like?
The dust plumes create colorful, picturesque sunrises and sunsets, giving way to deeper oranges and reds when the conditions allow it. Some say the dust cloud makes the sky appear “milkier” or “hazy gray” during the day.
Dry air from the dust cloud can limit the formation of tropical systems, but the moisture over Florida is likely to be stronger than the dust can squash. If storms persist despite the Sahara dust cloud, the dust and rain combination could lend its way to dropping a mud-like consistency over the area.
When will the dust cloud reach the U.S.?
The dust mass, which forms in the Sahara Desert in northern Africa and blows thousands of miles across the Atlantic Ocean, is forecast to arrive in Florida this week. The size of the cloud is approximately 2,000 miles wide from west to east and 750 miles long from north to south, according to Accuweather.
Each year, the atmosphere transfers several hundred million tons of dust, made of minerals such as iron and phosphorus, across the Atlantic to the Caribbean, Central America and South America. The dust mainly affects Puerto Rico but can reach states, including Florida and Texas.
The central Atlantic is particularly susceptible to the impacts of Saharan dust. That stretch of ocean, which meteorologists call the main development region, is where some of history’s worst hurricanes have spun up. Yet it’s typically quiet early in hurricane season, which begins on June 1, thanks in part to the dry air.
Is the SAL Bad for Your Health?
When the dust reaches the surface, as happened in Puerto Rico and other parts of the Caribbean earlier this week, it can be a health hazard for people who inhale it, according to the U.S. Centers for Disease Control and Prevention. Fine particles enter the bloodstream, triggering asthma attacks and “aggravating other respiratory conditions.”
Air quality can become poor as particulate matter increases in the air. Additionally, the particles can be breathed in, entering the lungs and bloodstream and affecting those with asthma and upper respiratory complications. Others have described feeling symptoms often related to allergies, the CDC reports. Large particles from Sahara dust can also cause skin and eye irritation, the CDC said.
While anyone can be affected by Saharan dust, there are some groups at higher risk than others, including babies and children, older adults, people with underlying conditions and those with heart or lung conditions, according to the federal health agency. Some studies suggest that exposure to desert dust events is associated with a higher risk of heart attacks, particularly in older and already vulnerable populations.
To protect one’s health, the CDC recommends checking the local air quality index, reconsider spending time outdoors and, if you go outdoors, perform easy activities like walking as opposed to running.
Pros and Cons for the Environment
There are some upsides to the dust, though. For one, it can help fertilize the Amazon rainforest by transporting minerals such as iron and phosphorus, research shows. Minerals in the dust, often rich in iron and phosphorus, can act like a fertilizer and help forests and other vegetation and soils gain nutrients.
Additionally, the ocean’s phytoplankton and other marine life benefit from the minerals in the dust. This is important because phytoplankton are the beginning of the food chain in the ocean and help sequester significant amounts of carbon. The sunsets can also be spectacular if enough dust stays aloft because it scatters blue light, leaving more dazzling oranges and reds, according to the National Weather Service.
However, there are cons, including that dust can accumulate and cover plants, cutting off their ability to undergo photosynthesis, harming or killing the vegetation. What’s more, the dust could be hiding plant-like bacteria, which — when deposited into the ocean — can lead to harmful algal blooms, which can lead to a “red tide” of toxins in the oceans. The dust can also aid in coral bleaching, along with other factors such as very warm water and ocean acidification.
Bonus – the Dust Tampers Hurricanes
For those living in hurricane-prone areas, the dust also holds another benefit. The plumes — and the dry Saharan air that transports them — make it hard for storms to form. Hurricanes are born from moist air and draw power from the ocean itself. But the arid air cuts off would-be storms’ fuel and shrivels thunderstorms that are the building blocks of tropical systems.
Even so, some storms find gaps in the dust and manage to tap into the warm Atlantic water and burst onto the scene. That happened a year ago when Hurricane Beryl, which killed at least 69 people, formed in late June and became the earliest storm to reach Category 5 strength in the Atlantic. Once the dust starts to die down in mid-August, the main development region becomes much more conducive to spinning up monster storms.
At this time of year, storms in the Atlantic tend to cluster around the shores of North America and the western Caribbean Sea. The US National Hurricane Center is tracking a potential storm that may grow out of a weather front off the coast of South Carolina in the coming week. The odds of it forming into a tropical system remain low, though. For now, the brakes are on across the central Atlantic as the 750-mile-wide plume pulses across the hemisphere.
“It is pretty impressive,” Alex DaSilva, a meteorologist with commercial forecaster AccuWeather, said of the dust. “It is the strongest one of the year so far.”
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