The dust of the Sahara desert en route to the Deep South
MONTGOMERY, Ala. (WSFA) – It’s that time of year again! Dust from Africa’s Sahara Desert looks skyward over the Atlantic, Caribbean, Gulf of Mexico and southeastern United States
This includes Alabama, which has more than 6,000 miles of the Sahara Desert!
It will push into the Gulf of Mexico on Friday evening and eventually reach Texas, Louisiana, Mississippi, Alabama, Georgia and Florida this weekend. For us in Alabama, he’ll be there on the weekend and early next week at varying levels of focus. This plume won’t be too thick for us, but we’ll probably be able to notice it in our skies.
It may seem impossible for dust to travel from Africa to the United States, but it is a normal annual phenomenon. Dust plumes continually push westward off the African coast during June, July and August. This can happen as early as May in some years if the conditions are met.
This occurs when tropical waves and their corresponding stronger winds over central Africa blow large amounts of dust into the atmosphere. the Saharan Air Layer (SAL) then pushes across the Atlantic Ocean thanks to easterly winds.
Each dust plume differs in size, thickness and concentration, but we typically see dust outbreaks sprout off the African coast every 3-5 days between mid-June and mid-August. Dust outbreaks typically occupy a 2 to 2.5 mile thick layer of the atmosphere beginning just over a mile from the surface, according to NOAA.
Heavier and larger dust plumes often travel to the Caribbean, Gulf of Mexico, Florida and other southern states, but the extent of their impacts differ.
We can use forecasting models to look at potential impacts by analyzing the concentrations of dust particles in the atmosphere and where outbreaks of that dust are likely to move over about 10 days. Knowing when and where Saharan dust will go is important because it has multiple impacts – both good and not so good.
If the concentration of dust is thick enough, air quality problems and respiratory/health problems May occur. This is especially true for those who suffer from respiratory problems. If the dust concentration is high enough, some people may need to avoid outdoor exposure.
The dust concentration is rarely high enough in Alabama to cause significant air quality problems. Poor air quality is just one of the effects of these annual invasions of Saharan dust.
It is believed that the dust helps build beaches in the Caribbean and enrich the soil and ocean ecosystems through the minerals and nutrients they contain. These ingredients help fertilization of the Amazon rainforest, especially the limited amounts of phosphorus. Some scientists suggest that iron in dust can fertilize the ocean, feeding microorganisms in the water.
For us here in Alabama, the noticeable impacts of Saharan dust are particularly colorful sunrises and sunsets, milky/hazy skies during the day, and a suppression of tropical cyclone development in the Atlantic Basin (including the Gulf of Mexico).
The hot and dusty SAL creates very dry conditions in the atmosphere. This is why the development of tropical storms and hurricanes is strongly suppressed. Tropical systems need warm, humid air to form, strengthen and sustain themselves. With the hot, dry and dusty air in place, the Atlantic is generally calmer in May, June and July.
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