According to the New Orleans Times-Picayune (nola.com), “A large Saharan dust plume will soon blanket Gulf Coast.” That was the headline on June 6.

The brown haze over the central and western Caribbean is a Saharan dust outbreak that left the African coast on May 21 and was forecast to reach the Gulf Coast and Southeast early the second week of June. Greg Bostwick, chief meteorologist for KFDM in Beaumont, Texas, said that the dust in the Gulf is expected to thin considerably over Florida by Sunday evening. He noted another surge moving westward should enter the eastern Caribbean Sea the second week of June.

Each summer, huge clouds of dust are brought up from the Sahara Desert off the coast of Africa due to strong winds. During peak season, enormous dust outbreaks the size of the continental U.S. are released off Africa’s western coast every three to five days. This year, the season began the last week of May when a large plume of these airborne particles made its way through the Gulf Coast.

While the National Weather Service (NWS) does not track Saharan dust as part of its forecast, meteorologists at NWS said the dust lowered the chances for rain the first weekend of June. They also said that a large plume of Saharan dust would blanket the Gulf Coast after traveling across the Atlantic.

Local meteorologists said that Louisiana should expect to see hazy skies and picturesque sunrises and sunsets over the next few days. Southwest Louisiana meteorologist Payton Malone reported that Gulf Coast residents could expect the skies to look their haziest June 6 and 7. The haze was predicted to be especially noticeable during sunset and sunrise, Malone said.

The hazy sunrise over New Orleans the morning of June 5. Photo by David Mora

The Saharan air layer (SAL), a massive dust cloud originating from the Sahara Desert, carries phosphorus, iron and other nutrients across the Atlantic, impacting ecosystems in the Americas. The dust acts as a natural fertilizer, enriching the soil and waters where it precipitates out, particularly in regions like the Amazon Rainforest and the Atlantic Ocean.

According to the National Oceanic & Atmospheric Agency (NOAA), SAL outbreaks can form when ripples in the lower to middle atmosphere, called tropical waves, track along the southern edge of the Sahara Desert and loft vast amounts of dust upward. As the SAL crosses the Atlantic, it usually occupies a 2- to 2.5-mile-thick layer of the atmosphere with its base starting about one mile above the surface. The warmth, dryness and strong winds associated with the SAL have been shown to suppress tropical cyclone formation and intensification. It’s common for dust from the Sahara to cross the Atlantic on a regular basis.

SAL activity typically ramps up in mid-June and peaks from late June to mid-August, with new outbreaks occurring every three to five days. During this peak period, it’s common for individual SAL outbreaks to reach farther to the west – as far west as Florida, Central America and even Texas – and cover extensive areas of the Atlantic – sometimes as large as the continental U.S. Reaching up to New Jersey isn’t uncommon.

The main source of phosphorus in the Saharan air layer is dust from the Bodélé Depression in Chad, an ancient lakebed. This lakebed contains rock minerals rich in phosphorus, particularly from dead microorganisms. Additionally, African biomass – specifically, smoke from natural savannah fires – also contributes to the phosphorus content of the Saharan air layer, especially during autumn and winter months.

A new paper published Feb. 24 in Geophysical Research Letters, a journal of the American Geophysical Union, provides the first satellite-based estimate of this phosphorus transport over multiple years, said lead author Hongbin Yu, an atmospheric scientist at the University of Maryland who works at NASA’s Goddard Space Flight Center in Greenbelt, MD.

An earlier paper published online by Yu and colleagues on Jan. 8, in Remote Sensing of the Environment, provided the first multi-year satellite estimate of overall dust transport from the Sahara to the Amazon. This trans-continental journey of dust is important because of what is in the dust, Yu said. Phosphorus is an essential nutrient for plant proteins and growth, which the Amazon Rainforest depends on in order to flourish.

But not all dust originating in the SAL travels westward. About three years ago, my son Will, who lives in Switzerland, sent me pictures of light orange snow which had blanketed his part, as well as other parts, of Europe. Saharan dust falls several times a year in Switzerland. The air becomes cloudy and turns yellowish in high concentrations.

According to Meteonews (one of their news networks), 60% of Saharan dust consists of quartz. According to studies, it is less harmful to health than traffic-related particulate matter. Each summer, dust from the dunes of the world’s largest desert pours into the atmosphere over the North Atlantic and Europe to seed the world’s oceans with nutrients that are sorely limited in many marine ecosystems.

While the agricultural contribution from this discoloration may be one thing, I’ve yet to see any Swiss tourist literature bragging it up.