The currents are now carrying this particle cloud to the gates of Europe, where it has already flown over Portugal and is about to cross the Atlantic coast of France. He should arrive in Switzerland overnight from Thursday to Friday. With what effects? The weather takes stock with Christophe Salamin, meteorologist at Météosuisse.

Le Temps: What will we be able to observe when the smoke cloud arrives?

Christopher Salamin: To speak of a “puff of smoke” is a misnomer… The particles are so diluted that they are hardly noticeable. We will not observe much, firstly because cloud passage is expected overnight from Thursday to Friday. Before arriving in Europe, it crossed the Atlantic, covering between 5,000 and 6,000 kilometers, giving it time to shed heavy particles like ash. Only the lighter ones stay in the air. If it were to arrive during the day, a blue sky with no clouds would be required to observe slight haze. It has nothing to do with the Montreal pictures. If the cloud is already there on Thursday evening, we could see a colorful sunset: the dust lengthens the spread of light and enhances the colors.

So there is no impact on air quality?

There is no risk. The smoke particles are very light, diluted and fly very high in the troposphere, between 7000 and 10,000 meters above sea level. Even if it rains and they fall, they’ll be absorbed by the ground, not nose-level. And even if they were, their concentration would be very low.

How do these particles get to us?

Events in the west are coming to us. Fires, volcanic ash, sand from the Sahara… There is an almost permanent flow from west to east, created by the rotation of the earth and the pressure difference between the polar air in the north and the tropical air. The sand dust from the Sahara, for example in 2019, had come up from the south, moved west and first touched Portugal to reach us. According to satellite images, the current cloud is 3,000 kilometers long and 1,000 kilometers wide. It will continue to be fueled as the fires continue to burn in the west.

The cantons of Vaud and Geneva are not concerned

The canton of Vaud points this out Time Please note the opinion of MeteoSwiss. “So there are currently no recommendations from the Environment Directorate-General. However, we continue to monitor air quality and would issue a pollution alert if the situation worsens. The Air, Noise and Non-Ionizing Radiation Service (SABRA) of the Canton of Geneva operates in Geneva. mention, that postthat “the impact on the health of Genevans should be minimal, if not non-existent”.