The sky is orange Why and how do sandstorms occur?

Dust storms form when strong winds blow over soil made up of 'corrosive and packable' materials.

A cloud of dust from the desert may cover Europe, giving the sky a yellow-orange hue; At the time, they appear to be signs of a possible sandstorm.

And writer Juan Costa, in a report published by the French newspaper Le Point, says that it is common during the spring and summer in the French capital to find your car covered with a thin layer of white or yellowish dust, whose origin is precisely due to a dust storm that occurred In the desert.

The author shows that dust storms are formed when strong winds blow over the soil, which consists of “corrosive and packable” materials, that is, materials sensitive to wind erosion, and this is a very common phenomenon in the vast desert areas; Where storms extend from hundreds to thousands of kilometers.

Important effects

And the writer mentioned - in his report - that in the deserts, the wind does not carry sand grains for long distances, because the grains are relatively heavy and fall to the ground near the place of lifting; The wind raises grains of sand from a few centimeters to a few meters above sea level and then makes them fall to the ground.

This creates an effect with the grains on Earth, which breaks them down into smaller particles. This process - called sand jumping - produces grains much lighter than desert dust, which fall very slowly under the influence of gravity. Where dust can remain suspended in the air for several days, and thus travel with the wind over several thousand kilometers, until it reaches the north and south poles.

The writer adds that the very large quantities of dust that erupt in the desert have a major role in the climate and the Earth system; It strongly modifies the Earth's energy balances by reflecting and absorbing sunlight and infrared rays, and thus the absorption of light greatly heats the air where dust is present, thus modulating the circulation of the wind.

When dust settles on land, it is also an essential contribution of minerals to marine and terrestrial ecosystems. In addition, desert dust storms significantly deteriorate air quality and visibility in North Africa, which may significantly affect the health of the population in these areas against the background of exacerbation of respiratory diseases.

How are storms born and develop?

The writer points out that in the middle of the desert, the dust flying in the atmosphere in the summer is more abundant; Atmospheric conditions during this period are strongly influenced by the flow of moisture from the Gulf of Guinea by the winds associated with the African monsoon. Then these moist air masses rise high when they encounter obstacles, such as mountains, or when they pass over highly reflective ground and produce rising air currents, which leads To the formation of very large storms, where rainfall suddenly cools the air by evaporation on contact with the extremely hot desert air.

According to the author, there are pockets of cold air in the extremely hot environment, as they result from the sudden difference in air density between warm and cold regions that generate very strong winds, which in turn raise dust that can collect on the ground and form giant walls of dust.

In short, the writer says that tropical storms in the desert are the source of these dust storms, which are called "haboob", which means "strong winds".

The writer asserts that very little is known about the origin of these storms; On the one hand, they are sporadic in nature and result from complex dynamic mechanisms. On the other hand, atmospheric conditions make observations difficult and often very limited means of investigation in desert regions, where satellite observation plays a major role, making it possible to observe the amounts of dust rising into the atmosphere and its path to other regions.

But so far, conventional satellite observations only distinguish the two-dimensional distribution of desert dust via horizontal mapping performed using passive sensors, which work in a similar way to high-performance cameras.

The importance of 3D phenomena in the evolution of storms

The author points out that dust storms reach very different areas, depending on their height, because the intensity and direction of the winds differ significantly vertically, adding that the effects of dust on the environment also depend strongly on its vertical range, but only dust near the surface directly affects the living conditions to the population by deteriorating air quality and visibility.

The writer explains that dust can settle on the surface, either due to gravity upon contact with the ground, or by raindrops; The effects on the Earth's energy balance and on the circulation of the atmosphere are mainly found at altitudes, where there is dust that absorbs sunlight, thus warming the air around it.

The author cautions that recent scientific research has made it possible to measure the three-dimensional distribution of dust during storms in the heart of the desert, for the first time from space, especially the vast desert dust storm that occurred in June 2020, which reached the Caribbean, then the United States .

It's common during spring and summer to find your car covered in a thin layer of white or yellowish dust (Getty Images)

The author explains that, saying that this work is based on an innovative method developed at the Joint Laboratory of Atmospheric Systems using the Atmospheric Probe Infrared Interferometer (IASI), which measures the intensity of light in thermal infrared very precisely and in detail, according to its wavelength. , that is, the color of light, and the great advantage of this scale is that its measurements cover the entire surface of the Earth twice a day, while the laser monitors the atmosphere only under tracks separated by about two thousand kilometers in longitude.

The author shows that these measurements are sensitive to the vertical distribution of dust, while being very detailed on the horizontal plane, which provides a three-dimensional display of the extent of dust, and thus gives a better understanding of the dynamic mechanisms of dust storms in the desert during the summer, as it gives tremendous potential to study the mechanisms of vertical mixing. of desert dust, as well as an original way to improve the accuracy of digital models of the 3D distribution of dust.