If you are in Florida at the moment, you may have noticed how hazy it’s been the last couple days. That’s because there’s a layer of Saharan dust over Florida that travelled through the atmosphere all the way from the Sahara Desert. That’s an amazing 5,000-mile-long journey!
Known as the Saharan Air Layer (SAL), this dry dust plume commonly forms from late spring through early fall, moving out into the tropical Atlantic Ocean about every three to five days, according to NOAA’s Hurricane Research Division (HRD). The HRD says the SAL is typically located between 5,000 and 20,000 feet above the Earth’s surface. It is transported westward by bursts of strong winds and tropical waves located in the central and western Atlantic Ocean at altitudes between 6,500 and 14,500 feet.
Saharan dust is nothing new. According to the National Oceanic and Atmospheric Administration, strong winds can transport dust several thousand miles across the Atlantic Ocean, tracking as far west as Texas.
So is it a good thing? We’ve broken it down for you.
Day-time skies may appear a little hazy. You may even notice a little orange dust on your car.
In high doses, Saharan dust can be dangerous. The extremely fine particulates can pose a hazard to those with sensitive lungs, frequently prompting the National Weather Service to issue air-quality alerts. This time around, the aerosol’s concentration is low enough to stay below any threshold for concern.
Iron in the dust can act as a fertilizer, helping trigger a localized red tide bloom. A study by NOAA & NASA showed that dust from the plains of Africa contains high levels of iron. When this dust settles in the Gulf, a bacteria called Trichodesium converts the iron into nitrogen. Then nitrogen acts as a fertilizer for karenia brevis, the dinoflagellate responsible for red tide. During the study, the large amount of Saharan Dust arrived on July 1st and by October, red tide had developed in the area with biologically-accessible nitrogen.
This Saharan Dust may end up having no impact on red tide in the Gulf this summer and fall, but it should be one of the variables to watch. Furthermore, it takes time for this entire process to occur. Even if this current increase in Saharan Dust does have an impact, it could take months to see red tide develop in the impacted area.
The arrival of Saharan dust might be good news for Gulf Coast residents & visitors alike, particularly those beleaguered by a destructive 2018 hurricane season. The reason? Saharan dust tends to quell Atlantic hurricane activity. It’s not the dust that does it per se but, rather, that the dust is a tracer embedded in a layer of desert air. Having air that dry in the middle atmosphere puts a damper on any attempts for a tropical cyclone to form.
Saharan Dust makes for beautiful, vivid sunsets.
You can track the Saharan Air Layer here.
*Image via WINK News