Forest fires | California smoke over Montreal

While the sky should normally have been clear in Montreal on Tuesday, it was cloudy in the metropolis due to the smoke from the California wildfires that hit here. How is it possible ? And is it dangerous? Update with Francesco Pausata, professor in the Department of Earth and Atmospheric Sciences at the University of Quebec in Montreal.

Posted September 16, 2020 at 5:00 AM

Louise Leduc


Francesco Pausata, professor in the Department of Earth and Atmospheric Sciences at the University of Quebec in Montreal

How did smoke from California, a state nearly 3,000 miles away, end up in Montreal?

It could be transported even further, to Europe. The smoke is transported by atmospheric currents (jet streams) to a height of 10 to 12 kilometers. The smoke can spread across the Northern Hemisphere.

Why doesn’t the smoke from bushfires necessarily reach even closer to Montreal?

This is because the air circulation often goes from west to east, so a forest fire in New Brunswick, for example, will rarely affect Quebec.

Why is the smoke from California fires hitting Quebec this year when it hasn’t in recent years?

Because this year’s wildfires are particularly intense in California and the aerosol particles released into the atmosphere are extremely high. That said, we’ve already had repercussions from wildfires in the West, but because the amount of particles emitted was lower, it went unnoticed.

Is the air quality affected?

No, Environment Canada has not issued specific warnings. Air quality is good these days because the particles travel high above our heads again, unlike San Francisco, where people bathe in them, when the fires are very close to their homes. city.

So even people with asthma don’t have to worry about it?

In San Francisco, the particles are very fine, they are very dangerous to the lungs, but there is indeed no danger here.

Does the smoke linger above our heads for a long time?

It all depends on the atmospheric circulation. It will be intermittent. The air currents will soon change direction and they will soon be directing the particles towards North Carolina and Virginia, but it is possible that it will return here next week.

See the NASA model on this topic here:

Is there a risk of a more orange sky here, like in San Francisco?

In fact, the sunset can be a little reddish on some days. Compared to noon, when the sun is high, the rays must pass through a greater thickness of the atmosphere as the sun sets. However, like orange, red has a longer wavelength that interacts less with small aerosol particles, while blue and green in particular have longer wavelengths that interact more. with these particles and therefore have to be dispersed.


A wildfire north of Los Angeles

27 fires in California

According to a census by Agence France-Presse, there are 27 fires still going on in California. Since mid-August, they have killed more than 20 people and are currently mobilizing 16,000 firefighters. Wildfires of unprecedented proportions are also devastating Washington, Oregon and Idaho.

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