Why poor air quality due to wildfire smoke is so difficult to forecast (2024)

While wildfire smoke has become a regular visitor to Calgary over the last few summers, forecasting it remains a difficult task, weather experts say.

After smoke choked the skies in Calgary and various parts of Alberta on Thursday, dragging air quality to the worst levels in three weeks, forecasters expected the air quality health index to remain at 10 — a high risk — into the weekend.

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However, the forecast changed drastically overnight with much improved air quality and, as of Friday morning, only moderate risk from smoke was expected over the next few days.

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Hazy conditions have persisted for 148 hours in Calgary this year, compared with more than 500 hours throughout 2023 — the worst recorded year for smoke and wildfires — said Christi Climenhaga, a scientist with Environment Canada.

The last time a thick smoky haze blanketed the city was on July 24, when air quality plunged to similar depths. Another advisory was issued two months prior, in May. The smoke was mainly driven by wildfires in the north and west, which wound its way to southern Alberta.

Smoke forecasting can be tricky business

Making long-term smoke predictions is challenging.

“Wildfire smoke is pretty tricky to forecast, as it’s very sensitive to some of the initial conditions in an area,” said Justin Shelley, a meteorologist with Environment Canada.

Meteorologists determine smoke patterns using satellite imagery. If clouds obscure the presence of smoke, they may not capture early patterns that shape the direction and distance it might travel, leading them to make inaccurate predictions. Specialists also measure smoke at the surface by tracking particulate matter. But such forecasts are relatively immediate.

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The larger reason, Shelley said, why we’re seeing more smoke is hotter and drier summers, driven in part by El Niño — a natural swing in the weather system when trade winds blowing warm water from the west lose their strength, in turn, increasing sea and surface temperatures, and affecting weather patterns across the globe.

But U of C environment professor Jed Kaplan believes that’s a partial explanation. El Niño, which occurs every two to seven years, causes drier winters, bringing the summer early and stretching the wildfire season. These fluctuations contributed to wildfires blowing into Fort McMurray in May this year, he said. Then, El Niño waned and temperatures fell. However, cooler and wetter weather in June gave way to heatwaves in July, sparking and emboldening conflagrations across the province.

“The El Niño that we had during last winter, already more or less went back to neutral conditions in May or June,” Kaplan said.

The weather pattern can also be explained partly through the volatility of jet streams — ribbons of air high above the ground travel from east to west, separating cooler air to the north and warmer air to the south — but another important reason, Kaplan said, is human-induced climate change.

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“The natural variability in the jet stream might lead us to have these kinds of heatwave conditions once every five years or every 15 years,” he said. “And now we’re sort of seeing these heat wave conditions happening every year.”

Calgary summers becoming more smoky

Calgary has become increasingly hazy over the summer season in the past 10 years. The second-worst year for smoke was recorded in 2018 followed by 2021, said Climenhaga.

A major factor affecting such pollutants is the direction of winds that carry them across areas. For a while, winds in the Alberta region have been travelling south, which have pulled smoke emanating from the north into Calgary, said Shelley. However, it is hard to point exactly to the source.

“Because when you have such a large swath of active wildfires that emit smoke, sometimes it gets into a large mass of smoke that gets transported from place to place,” Shelley said.

“If the smoke can lift towards the jet stream, then the jet stream can transport it hundreds, or in some cases, thousands of kilometres across the country.”

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Another issue shaping conditions is temperature. For instance, when air is cooler at the ground level and hotter above, smoke coursing through the atmosphere falls and is trapped below — so, skies are hazier early and late in the day. As temperatures and the speed of winds rise, the pollutants are pushed back out of the area.

Extended exposure to smoke presents health risk

Meanwhile, smoky air presents a higher risk to people’s health. The pollutants in the air are so minute that they elude natural defences in the nose and throat, directly entering the lungs, said Dr. Anne Hicks, a physician and environmental professor at the University of Alberta who specializes in the health implications of smoke.

“Wildfires are not just burning forests, they’re also burning infrastructure — so tires, houses, that. So, then you have all of the compounds from man-made structures released into the atmosphere,” Hicks said.

Prolonged inhalation of these pollutants can increase the risk of mortality, unhealthier babies and an earlier onset of neurodegenerative diseases, such as Parkinson’s and Alzheimer’s.

“Worldwide, people are expected to lose several years of life on average due to air pollution in general,” Hicks added.

A few ways to mitigate the risks of inhaling smoke, Hicks said, are to avoid outdoor activities on smoky days and install air purifiers that filter out pollutants, such as those rated for PM 2.5.

“If you close up your house and use some of those air filters, you could make a smoke-free or low-smoke area that’s safer to be in.”

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