Extraordinary weather phenomenon: clouds of sand

For a cloud of sand is formed, it is first of all necessary to have wind : the sirocco is a wind that blows in the Sahara desert regularly and which can sometimes exceed 100 km/h. These strong gusts then cause a real storm in the desert, create whirlwinds in the sand and propels the particles up to 4,500 meters above sea level. Carried by the wind, this dust circulates towards the south of France several times a year, but much more rarely to the north of the country, with the exception of March 2022 which was marked by several major episodes of rising sand as far as Paris, and even beyond, in the Netherlands! This sirocco is a south-easterly wind, so it carries with itair mild and also has the effect of suddenly raising the temperature in France.

A sky that looks like an apocalypse

The sand mixes with clouds low and medium altitudes and generates a milky sky in France, slightly yellowish, limiting the intensity of the rays of the sun. But, during the most significant episodes, with high concentrations of sand, the sky can then turn orange, even red, as sometimes happens in Spain, the Maghreb and on rare occasions also in France. This apocalyptic atmosphere can also give an impression of ” Red sun », a very impressive phenomenon.

Under these conditions, the sunrises and sunsets are spectacular, like those of the American desert: indeed, the more the light collides with particles (sand, cloud humidity, precipitation…), more the colors are grand.

These grains of sand can settle on the mountains of the Pyrenees and the Alps, coloring the snow and creating the impression of sand dunes: this orange tint then accelerates the melting snow due toalbedo.

Clouds that don’t just contain sand

However, sand clouds don’t just contain sand! Radioactive elements are also present in the sand, such as Cesium-137, from nuclear tests carried out in the 1960s.ACRO (Association for the Control of Radioactivity in the West) specifies however that these radioactive levels were present in low and negligible quantity during the sand clouds of March 2022 in France. Even more astonishing, it happens that the sirocco carries with it living organisms, bacteria, mushrooms and locusts, crop pests.

This high concentration of dust in theatmosphere is also responsible for a degradation of air quality linked to particles PM10. This episode of pollution is even likely to aggravate respiratory problems in people who are already sensitive.

A phenomenon different from sandstorms

Clouds of sand, or rising sand from the Sahara, are to be differentiated from other phenomena such as sandstorms or sand whirlwinds.

The sandstorms, also called haboobs, are violent and dangerous phenomena that occur in desert regions such as the Maghreb or the southwestern United States. This is dust most often raised by gusts of wind in front of a thunderstorm : these form a real wall of sand which can stretch over 100 km and which travels at an average of 70 km/h and plunges entire towns into darkness, causing a series of pile-ups.

The swirls of sandalso called Dust Devilsare small localized phenomena, often harmless: they also form in desert regions (but sometimes also in France, especially in harvested fields) when hot air rises and begins to rotate, a bit like a tornado. Contrary to these two very sudden and sometimes destructive phenomena, clouds of sand, such as those which rise in Europe, do not cause any damage, apart from the inconvenience of soiling our cars !