Saharan Surprise

A cloud of sand originating in the Saharan region of Africa is heading to the North American Continent. The cloud itself is actually a yearly occurrence however the one this year appears to be larger and more cohesive than in past years. These dust clouds are referred to as “Saharan Air Layers” (SALs). They are generated when massive wind storms blow across the Sahara Desert creating giant plumes of sand and dust somewhat akin to the dust bowl storms that were characteristic of the “dust bowl” years in the U.S. These airborne clouds of sand and dust enter the Atlantic Ocean at the Intertropical Convergence Zone and are then transported by the trade winds that run east-west along the equator. Many times the cloud disperses before completing the roughly 5,000 mile trip to the North American Continent. This year’s cloud is grand in scale, clearly visible from space and still largely intact as it reaches the southern U.S. The dust itself can serve as a respiratory irritant and be especially bothersome for those individuals with asthma or other lung and allergy problems. During the COVID-19 pandemic health authorities were encouraging individuals to spend more time outdoors where the virus was less contagious. With this latest downturn in air quality individuals will most likely be advised to remain indoors for the next week to ten days until air quality improves. During that time period masks should be worn outdoors as well as indoors. The dust cloud could also transport other airborne pathogens such as fungi and bacterial spores that might survive the long journey. Susceptible individuals would be wise to wear masks to reduce the risk of transmission.

The Saharan Air Layers are not all bad. The National Weather Service and the National Oceanic and Atmospheric Administration (NOAA) were both predicting an active hurricane season. However the plumes of sand in the atmosphere suppress the formation of hurricanes and tropical storms. It does this by the presence of a dry layer of hot air that in turn prevents the accumulation of warm moist air. It is this warm, moist air that generates the necessary summer vortexes that become hurricanes. Once the dust has settled from the atmosphere, storms can form in the usual manner. The sands are helping to produce some dazzlingly colorful sunrises and sunsets in the Caribbean. Thick dust clouds tend to create yellow-brown skies while thin clouds generate spectacular red hues due to the scattering of light waves. Scientists believe these Saharan dust storms helped create the thriving ecosystem of the Bahamas by depositing nutrients that support their diverse marine life and coral reefs. Unfortunately it has also brought with it some toxic agricultural contaminants mixed with the dust.

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