The Saharan Dust Layer is normal and it’s not a bad thing.
I don’t know if it’s just the whole 2020 thing, but it seems when people see something this year, they assume the worst. Starting last week, I started talking about a massive surge of Saharan Dust coming off the African Coast that would move across the Atlantic and be here next week. Over the past few days, more and more national and local media outlets have been talking about and some times with zero context and making it seem like a massive dust storm or something. So let me explain what it is.
So what is the Saharan Air Layer(SAL)?
NOAA describes it like this
The Saharan Air Layer is a mass of very dry, dusty air that forms over the Sahara Desert during the late spring, summer, and early fall, and moves over the tropical North Atlantic every three to five days. Saharan Air Layer outbreaks usually occupy a 2 to 2.5-miles-thick layer of the atmosphere with the base starting about 1 mile above the surface. The warmth, dryness, and strong winds associated with the Saharan Air Layer have been shown to suppress tropical cyclone formation and intensification.
NOAA
So this dusty dry layer of air is 5,000-15,000′ up in the atmosphere. So you won’t smell it and it won’t affect your breathing or allergies or air quality. It’s just too high off the surface for that.
What it does:
Again this is the good part, it deters tropical activity and hurricanes. Now that is a good thing mostly but because it deters thunderstorm activity as well it can cause very dry and hot conditions in parts of the Caribbean.
The Saharan Air Layer has unique properties of warmth, dry air, and strong winds that can have significant moderating impacts on tropical cyclone formation and intensification. There are three characteristics of these Saharan dust outbreaks that can affect tropical cyclones, tropical disturbances, and the general climatology of the Atlantic tropical atmosphere:
NOAA
First, The Saharan: Air Layer’s dry, dusty air has about 50% less moisture than the typical tropical atmosphere. This extremely dry air can weaken a tropical cyclone or tropical disturbance by promoting downdrafts around the storm.
African Easterly Jet: Second, Strong winds in the Saharan Air Layer (25-55 mph or 10-25 meters per second) can substantially increase the vertical wind shear in and around the storm environment. This “mid-level jet” of enhanced winds, typically found at a height of 6,500-14,500 feet (2000-4500 meters), can cause tilting of the tropical cyclone vortex with height and can disrupt the storm’s internal heat engine.
Warm Temperatures: Third, The Saharan Air Layer’s warmth acts to stabilize the atmosphere, which can suppress the formation of clouds. This stabilizing effect is produced when the Saharan Air Layer’s warm, buoyant air rides above relatively cooler, denser air. The Saharan Air Layer’s suspended mineral dust also absorbs sunlight, which helps maintain its warmth as it crosses the Atlantic Ocean.
NOAA
Great sunsets ahead!
It also causes amazing orange and red sunsets and sunrises once it gets here. It also helps add nutrients to the Amazon rain forest in South America. It’s also very normal and happens every summer, it just varies on the amount and intensity depending on the pattern and year.
So yes it 2020 but this is also about as normal as things get for the tropical Atlantic and for once it’s great news!
