Two passengers leaving the airport in Tenerife, Spain, February 22, 2020. -
Andres Gutierrez / AP / SIPA
At the beginning of February, a cloud of sand from the Sahara had touched part of France, giving rise to impressive landscapes, tinged with orange, ocher or pink colors.
A new wave of sand dust has been flying over Europe, and in particular France since this weekend, and should reach its maximum intensity on Monday.
This phenomenon, quite common, occurs under specific weather conditions.
"20 Minutes" explains why.
Will the sky turn an orange color like at the beginning of the month?
A cloud of sand from the Sahara has been flying over Europe since this weekend, and should reach its maximum level on Monday, according to Météo France forecasts.
However, the phenomenon should be less visible than that of early February.
On February 8, a "sepia-colored" sky was observed in part of France, in particular in the south and east.
The "desert dust", as Météo France calls it, crossed the Mediterranean and arrived in France on Sunday, with a maximum level expected on Monday.
Where does this cloud come from?
How is it formed?
20 Minutes
takes stock.
ℹ️⏳As on February 6: the 'dust from the desert' crosses the Mediterranean and gently arrives in France.
First arrivals expected this Sunday, with a maximum level tomorrow Monday.
pic.twitter.com/LyCu6eWx3n
- Météo-France (@meteofrance) February 21, 2021
How does a sand cloud form?
Sand clouds form in the great deserts, and in particular the Sahara, near Europe.
For a sand cloud to form, special conditions are needed, such as the passage of a front or a depression.
“The wind picks up fine dust, sand particles, and lifts them off the ground.
The wind must be strong enough so that the dust does not fall immediately.
They then rise in the atmosphere and are transported in the air, where the flow takes them, ”explains Vincent Guidard, researcher at the National Meteorological Research Center of Météo France.
Are these phenomena frequent?
This is a phenomenon that occurs fairly regularly, but certain seasons are more favorable than others.
“The fact that dust rises in the air, it often happens.
But for them to be transported over a long distance, specific favorable conditions are required, including wind and rain.
This is the reason why this phenomenon occurs most of the time in autumn and winter ”, describes the specialist.
On the other hand, it is quite rare that two strong episodes, "as is the case this month", happen in such a short time, observes Vincent Guidard.
Certain regions are more affected than others: "We often observe deposits of sand in the south of France, especially on cars, or on mountain ranges, such as the Pyrenees or the Alps", specifies the researcher, who adds that the phenomenon is, for example, rarer in the Paris region.
How far can a cloud of sand go?
To where the wind takes him.
Depending on the depressions, the sand can rise to a higher or lower altitude and can be transported over longer distances.
"The distance varies depending on the altitude at which this sand cloud rises and if it encounters rain situations, which would make it fall to the ground", describes the specialist.
Last June, for example, a very strong episode crossed the Atlantic and affected the West Indies, degrading the air quality in Guadeloupe and Martinique and making the atmosphere unbreathable.
Will this new episode be as visible as the one at the beginning of the month?
At the beginning of February, part of France had observed an ocher, yellow or pink cloud - depending on the region - for a few days.
The episode had been particularly visible in the Pyrenees and the Alps.
“At the beginning of February, the phenomenon was very visible, because the cloud had arrived in the early morning, with a very low sun,” explains Vincent Guidard.
Unfortunately, on Monday, the sand cloud should be less visible to the naked eye.
"Its intensity will be stronger than that of early February, but visually, it will not be as noticeable," adds the specialist, who specifies that it is in the Vercors that the sky will be the most tinted.
🔍 Small comparison between the episode of February 6 and the current one.
France should be a little more covered, with plumes going further north (as far as Scandinavia!).
🛰 #MOCAGE (Large Scale Atmospheric Chemistry Model) |
CNRM (@meteofrance / @ CNRS) pic.twitter.com/gN2M3ctp4R
- Météo-France (@meteofrance) February 21, 2021
Is this phenomenon dangerous?
If some Internet users were delighted with the photos they were able to take in early February, the researcher warns: the higher the intensity, the more this desert dust can have an impact on air quality, and therefore on health. .
In the atmosphere, this phenomenon can result in a sharp rise in the levels of PM10 particles suspended in the air.
These fine, very fine and ultrafine particles, called “breathable”, can enter the bronchi.
"Due to an import of dust of desert origin, the levels of fine particles could increase locally," warns Atmo Auvergne-Rhône-Alpes, responsible for monitoring air quality in the region.
To find out about the air quality in your region, you can consult the Atmo France site.
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