An exceptional quantity of dust from the Sahara has shrouded the Swiss sky since Friday, dramatically reducing visibility and giving a yellowish tint to daylight over much of the country.
The south-east of France was also affected on Saturday by this episode of fine particle pollution, announced the prefectures of the Provence-Alpes-Côte-d’Azur (Paca) region and Hérault.
“The arrival of #dust from the #Sahara leads to a very clear decline in sunshine and visibility. There is also an increase in concentrations of fine particles,” underlines MétéoSuisse in a message on X.
As the dust is concentrated below 3000 meters, the air quality has particularly deteriorated, from the shores of Lake Geneva to the rest of the country.
According to AirCHeck, the application launched by the cantons to deliver real-time data on air quality in Switzerland, air pollution is high in a corridor from the southwest to the northeast of the country. .
This dust reached some 180,000 tonnes, according to the calculation models used, meteorologist Roman Brogli of SRF Meteo told public radio.
This is an exceptionally high quantity, according to Brogli, with recent events of this type having brought only half of this volume to Switzerland.
In the south-east of France, “the alert threshold” was exceeded on Saturday throughout the Paca region but also in Hérault and Gard.
“These particles are added to the sea spray, formed by very windy weather conditions on the coast. These natural phenomena lead to a significant increase in PM10 concentrations,” the Hérault prefecture said in a press release.
Already on Friday, a strong southerly wind had transported sand from the Sahara from northern Africa to Switzerland.
The Sahara is the largest source of mineral dust, releasing between 60 and 200 million tonnes per year and while the larger particles fall quickly to the ground, the smaller ones can be transported thousands of kilometers and reach all of Europe .
As it settles, this sand gives an orange tint to the snow.
If this dust cannot scratch skis, as MeteoSwiss has assured, it can, however, have an effect on melting, particularly that of glaciers.
By reducing the reflective power of ice, dust facilitates the absorption of solar energy.
In France, this situation should decline on Sunday due to storms forecast in the south of the country.
The situation should also improve in Switzerland where the phenomenon should have disappeared by Sunday morning.