Each summer, huge columns of dust traverse the atmosphere over the tropical Atlantic Ocean, traveling 5,000 miles from the Sahara desert in North Africa to the southern United States.
While summer dust feathers are a common occurrence, the one sailing the Caribbean right now is creating quite a stir. That’s because it appears to be one of the most extreme in recent memory and is targeting the southeastern states.
In satellite imagery from space, the dust generally appears somewhat subtle and faint, but this plume can be seen as clearly as day. The photo below was taken on Sunday from the International Space Station. “We flew over this Saharan dust plume today in the Midwest Atlantic. The area it covers is amazing!” astronaut Doug Hurley tweeted.
Doug Hurley (@Astro_Doug) / NASA
These columns of Saharan dust, called by meteorologists as the Saharan air layer (SAL), are hit by strong wind storms that cross the Sahara desert. Dust enters the Atlantic Ocean near the Cape Verde islands, within the Intertropical Convergence Zone, where tropical systems often begin.
NOAA’s GOES satellite captured this series of animated images on Friday when dust entered the deep tropical Atlantic from Africa.
Dust hits a ride along the trade winds, a belt of winds moving from east to west near the equator that are firmly established during the summer. The dust layer can extend from a few thousand feet above the surface to 20,000 feet in height.
While dust masses often remain generally intact for most of the transatlantic voyage, they generally become diffuse and dilute when they reach the Caribbean. So far, however, this particular layer of dust is defying the odds.
Here are a series of before and after photos taken on Sunday in Caribbean islands like Antigua, St. Barts, Puerto Rico, and Trindad and Tobago:
The dust is so thick that the Barbados Meteorological Services issued a “Severe Dust Haze Warning” urging residents to take action due to significantly reduced visibility and possible respiratory problems for people experiencing breathing difficulties.
As you can see, when the dust is thick, it creates very yellowish brownish yellowish skies. But when the dust is weak enough, the refraction and reflection of light can contribute to stunning sunrises and sunsets, which may help explain at least partially the Sunday sunset in Miami.
In the coming days, the thickest layer of dust will remain in southern Florida, over Cuba. Later this week, it will spread throughout Texas and the rest of the Southeast, creating misty skies and colorful sunrises and sunsets.
For most people, dust is simply a nuisance, creating cloudy skies, and often leaving a dirty film on cars as it falls out of the air. But for people with pre-existing respiratory illnesses, it can lead to difficulty breathing.
Dust is best known for being a hurricane killer. Anyone who has lived at Hurricane Alley can tell you that these dry, dusty layers subdue the moisture necessary to power the hurricane engine. Usually, when there are thick layers of dust around, tropical activity remains calm, and that’s what is expected for the next week.
Surprisingly, much of the soil and nutrients in the soil, in places like southern Florida and the Caribbean, are made up of African dust that has settled for millions of years. Studies show that nutrients from African dust in subtropical and tropical soils can be critical to maintaining vegetation.
For the oceans it can be both a blessing and a curse. Scientists theorize that nutrients transported from the Sahara desert have helped build and nurture coral reefs in the Caribbean, Bahamas and Florida for millions of years. Without those minerals, they say, the area around the Bahamas is too nutrient-poor to support the vibrant reefs that exist.
On the other hand, during years of severe dust storms, the coral seems to suffer or even die. One theory is that pollutants mixed with dust from agricultural practices in the Sahel region of Africa may be contributing. Also, too many minerals in the powder can cause hyperfertilization, contributing to the proliferation of algae that are harmful to corals.
Furthermore, dust may also be contributing to the warming of our atmosphere. In a study published this April, researchers found that scientific climate models currently underestimate the amount of coarse dust in our atmosphere four times. This is because models deposit dust from the atmosphere too quickly. Dust, they say, appears to have a net heating influence on our atmosphere.
But in the immediate future, the biggest concern is how pervasive the dust layer will be in the tropical Atlantic this summer. With all the signs pointing to a very active hurricane seasonA more persistent layer of dust could help defend against tropical activity. However, once the dust begins to settle, it looks like there won’t be much of an obstacle in the way of a busy hurricane season.
