How wildfire smoke travels — and how to prepare when it hits

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The wildfire smoke casting an orange glow over Calgary isn’t expected to blot out the skies in Vancouver this week, but experts advise preparing for poor air quality as B.C.’s wildfire season is off to an early start.

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The smoke forecast shows smoke beginning to drift toward the B.C. coast from several large fires in Northern B.C. and Alberta, although the air quality index for Metro Vancouver and the Fraser Valley should remain in the low to moderate range over the next few days. Parts of the Interior, as well as Prince George, Williams Lake, Fort St. John and Quesnel, which are closer to active fires, will be harder hit.

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Doctors are warning people to prepare — but not to panic.

“Wildfire smoke is a form of air pollution, and like other forms of pollution, it’s not good for human health,” said Sarah Henderson, the B.C. Centre for Disease Control’s scientific director for environmental health services.

Research shows the more prepared we are for extreme events, the “better off we’ll be,” with more positive outcomes for people who feel prepared and protected when faced with events outside their control.

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The key is finding cleaner air, said Henderson.

That could mean closing a home’s doors and windows if that doesn’t make it too hot, or setting up an air filter in one room to create a refuge. Going to a place with clean, cool air — like a library or shopping mall — could also help.

Henderson advises people to listen to their body’s own alarm system, taking it easy if they feel the effects of the smoke on their eyes, throat or lungs. Hospitals in smoky regions will likely see a small increase in patients who suffer from lung conditions and are particularly vulnerable to poor air quality.

The smoke may be less detrimental right now because temperatures are a little cooler than they are in mid-summer, said Christopher Carlsten, a medical professor at the University of B.C.

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Much of what we know about the effects of wildfire smoke on the human body is based on pollution research, he said. There is some indication smoke may be more harmful to the lungs than the heart. But a shortage of research makes it difficult to understand the long-term effects of several summers in a row of breathing wildfire smoke.

Vancouver Coastal Health medical health officer Michael Schwandt said issues around wildfire smoke are likely to “be with us for some time.”

“As a matter of climate resiliency, we need to move to a place where our housing is more protective,” he said.

Keeping an eye on smoke forecasts is also important to understand when air quality is worst.

Chris Rodell, a fire weather expert with UBC’s earth, ocean and atmospheric science department, said many factors influence the regional spread of smoke, making forecasting complex.

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Smoke spreads as it is driven by wind, which is created by pressure gradients, he said. There are also “mixing processes” at work in the atmosphere, which move smoke up and down.

Interior smoke sometimes travels to Vancouver through the Fraser Valley.

“As evening cools the Fraser Valley, it is at a higher elevation than Vancouver and therefore the air cools more and becomes denser and wants to drain downhill,” said Rodell. “Subsequently, this follows the drainage paths in the Fraser Valley, which ends up draining out into Vancouver’s area.”

Ocean breezes can move smoke around and may blow smoke east during the day, but the process is reversed at night, when wind tends to blow back toward the ocean.

Rodell said heat also plays a role in the spread of smoke, driving smoke plumes higher, where they may get caught in faster winds that disperse the smoke farther from the source. Smoke plumes that don’t rise as much also don’t spread as far.

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The weather forecasting tool BlueSky was developed at UBC in 2007. After determining the location and size of a fire using satellite and ground reports, smoke forecasters look at several variables to make predictions, including temperature, humidity and pressure gradients, before using a computer model to continue the trajectory of moving air in the atmosphere and predict how smoke will travel.

gluymes@postmedia.com

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