What is hidden in the sands of the Sahara

It certainly did not escape you, yesterday they were everywhere: bicycles, cars, windows, soil, covered with sand coming directly from the Sahara, pictures of orange sky flooded the internet, hashtags #Sahara and #SaharaDust is among the most present on Twitter and Instagram.

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Also with lots of pictures and videos of the ski slopes where the snow has turned orange:

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Beatrice Josse atmospheric chemistry modeling specialist at Météo France:

“Getting sand from the Sahara back to the French mainland is really common. There is a very strong, very intense wind at the level of the desert, which tears desert dust off so fine that it does not fall immediately and can stay high in thousands of miles. “

But do not imagine tornadoes, Benoit Laurentworking precisely on these sandstorms at the Interuniversity Laboratory for Atmospheric Systems, specifies:

“The phenomenon is divided into two phases: first, strong winds near the ground, which sweep the surface and tear off the particles, which are then suspended in the atmosphere, then these particles find themselves trapped in large air masses that travel long distances such as Sirocco e.g.”

A southern current, which also brings up some mildness, and which is blocked by an anticyclone on the side of Greece. This is why the phenomenon, which particularly affects Spain and France, lasts a little longer than usual and with rather high concentrations:

We are about a gram per square meter, it seems a little, but it’s huge! (Beatrice Josse)

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This represents in total hundreds of thousands of tons are moving over our heads given the scale of the phenomenon. With consequences for air quality in Spain and in France in the southwest. Hautes-Pyrénées, for example, is on red alert on the monitoring laboratory’s map. Particles that are terrible for our bronchi, but which on the other hand can have positive effects in other areas. Explanation by the researcher in chemistry and environment Benoit Laurent:

“This desert dust is composed of various minerals, sometimes rich in nutrients such as nitrogen or phosphorus, and when it falls, it can become a contribution to certain ecosystems, which would be limited by it.”

The teams are in the process of taking this dust directly from the atmosphere and on the ground to better study it. While at Meteo France we take the opportunity to check and, if necessary, improve the already very effective models that make it possible to predict these phenomena.

Also read:
Why has the sky been ocher in part of the country since Saturday morning?

ERRATUM: it’s Béatrice Josse and not Brigitte Josse

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