What has been called the most significant dust cloud in 50 years it has now engulfed the gulf coast of the usa in a thick and dusty haze. The dust layer, which originated in the Sahara desert and crossed the Atlantic, is forecast to continue to move north and east over the weekend, impacting areas from Texas and Florida north to the Canadian border.
For most people, dust will simply be a nuisance, but for many who have respiratory problems, extra particles in the atmosphere can cause complications. The timing couldn’t be much worse, considering that a recent Harvard study shows that long-term exposure to fine particles of air pollution, such as dust, may be linked to higher rates of hospitalization and death from COVID- 19.
The dust is currently thicker from Texas to Florida.
The dust is responsible for the dense haze that envelops the Houston skyline in the photo below.
David J. Phillip / AP
Most of the dust layer exists well above the surface, mainly between a few thousand feet above the surface and between 15,000 and 20,000 feet in height. However, the vertical mixing of the atmosphere and rain can bring that dust to the ground, and that’s when it can become harmful to people with respiratory problems.
In some places, such as the Southeast, enough dust will accumulate that the chances that people there will see a thin layer of dust in their cars.
The dust column is forecast to break into two pieces due to a split in the direction flow at the middle levels of the atmosphere, which will act as a guide.
A portion of the dust cloud will creep north from Texas through the Plains and Midwest States this weekend, and even to the Canadian border on Monday morning. The dust will diffuse and decrease dramatically when it hits the center of the nation, but cities like Kansas City, Minneapolis and Chicago will see a more dangerous than normal sky. Dust in the atmosphere will also generate some especially vivid sunrises and sunsets.
The other batch of dust will be thicker and more persistent in the south, impacting Texas and areas east and northeast into the Tennessee Valley, the Carolinas, and Florida. Here the powder will be thick enough to present respiratory hazards. It is recommended that people in these areas wear a mask when outdoors.
This NASA animation below shows the progression of the dust through Sunday. White areas are where the dust will be densest; the blues and purples show where it will be most diffuse.
Dust now has both positive and negative impacts.
On the plus side, for millions of years the dust has been carried by trade winds from east to west from Africa through the Caribbean to Florida, supplying much of the soil and nutrients in the soil for vegetation growth. Scientists believe the nutrient load in the environment around Florida and the Bahamas is so poor that without African dust, coral reefs would have had a hard time growing and flourishing. The dust columns also supply a large part of the nutrients to maintain life in the Amazon jungle.
Naturally, due to the gravity of this dust cloud, many wonder if it has any connection to climate change. The evidence is mixed. As for whether this dramatic dust cloud was made worse by climate change, there is still no clear answer. But the dust cloud formation process may give some clues.
Dust forms in the Sahara desert and on the lush edge of the Sahel, a narrow transition zone between the desert in the north and the savannah in the south, in North Africa. There is evidence that these areas have generally dried up and the desert has expanded lately due in part to natural cycles and in part to human-caused climate change.
As the Earth warms, evaporation from surface waters increases, further drying up the Sahara and the northern fringe of the Sahel. A 2019 study found that dust transport increased in the past century compared to the past 2,000 years.
In the future, climate models project mixed results in terms of decreasing rainfall and increasing events of heavy rainfall in the area due to climate change. However, it seems practically certain that even if it rains more, it will not be enough to counteract the increased evaporation. Therefore, the Sahara and Sahel are likely to dry up even more. This theoretically would create more dust.
But, on the other hand, a 2016 study found that the biggest control factor for dust clouds may be possible changes in wind flow. In this case, the study finds in the future that tropical circulation may weaken due to global warming. Weaker winds would lift less dust from Africa and thus dust clouds in the Atlantic would decrease.
Decreasing dust in the tropical Atlantic can mean a warmer ocean, because less dust blocks the sun. And less dry, dusty air could mean a better chance for hurricanes to form and intensify. But the jury is still on it.
What is clear is that atmospheric dust plays an important role in our lives, affecting everything from respiratory health to beautiful sunsets, and from fertilizing coral reefs and forests to lessening hurricanes. Positive or negative, what this dust cloud episode teaches us once again is that everything on Earth is interconnected.
.
