Wildfire smoke is a regular part of N.W.T.’s summers, but how does it work?

Where there’s fire, there’s smoke.

That’s something that’s keeping Roland Schigas and his team at the Blue Sky Canada project busy. He’s the program manager and the system administrator for the Weather Forecast Research Team at the University of British Columbia. They’re the researchers behind firesmoke.ca, an interactive map tool that shows where wildfire smoke will affect air quality. 

“We model how the fires grow, whether there’s precipitation, the emissions the fires produce, and then the dispersion of the particles that make up the smoke through the atmosphere,” he said.  

When things burn, their complex structures break down, releasing a mix of gases, chemicals and tiny particles known as PM 2.5: particles in the air that are less than 2.5 micrometres in diameter, or the equivalent of about two and a half grains of salt. The World Health Organization estimates that up to 90 per cent of the total mass emitted from wildfires is made up of these super fine particles.

They’re what Schigas and his team use to forecast smoke. The website is updated four times per day, with animated hourly projections of what smoke is doing.

But understanding what makes up wildfire smoke is just part of the equation.

Smoke doesn’t always mean fire

“There are a few different things at play,” said N.W.T. fire information officer Mike Westwick. “Smoke can travel from thousands of kilometres away … Just because you see smoke doesn’t mean that there’s fire necessarily nearby.”

Smoky conditions are generally governed by three factors: fuel, wind and atmospheric conditions. 

For wildfires, fuel is anything that can burn, from the tops of the trees to deep underground. Different fuels can create different quantities, and qualities of smoke.

Ground fuels under the soil can overwinter, while surface fuels can kick up smoke even while just smoldering. And once fire reaches the trees, that can impact smoke too — deciduous trees, like poplar, willow, aspen and birch, produce less smoke than coniferous trees like spruce and pine.

Next, winds can increase fire activity, just like when you blow on a camp fire. But, it can also disperse that smoke, spreading it out. Westwick says slower wind speeds can keep the smoke concentrated in the immediate area of the fire. So high winds may mean you’re breathing smoke from further afield, but it can also mean the smoke is less intense.

Finally, the atmosphere itself plays a part. The troposphere, the layer closest to the surface, holds in the majority of earth’s weather, plus the air. It expands and contracts with heat, shifting with the seasons and even the time of day.

“Smoke is often worse overnight and in the early morning,” said Westwick. “During the day the atmosphere sort of opens up, and that smoke mixes up through the layers and disperses up into the atmosphere.”

Sometimes, fires get so hot they can even reach the next atmospheric layer, the stratosphere, as observed by the U.S. National Oceanic and Atmospheric Administration.

“That’s a specific condition called a pyro cumulonimbus cloud where the fire is so intense that it generates its own cloud system and sort of a micro weather system,” said Schigas. “And that in turn can cause more lightning strikes and updrafts which feed the the fire.”

That’s a phenomenon that’s becoming more and more common. Westwick says it happened this summer, outside Fort Simpson, as well as around Marion Lake in 2022. And Westwick said in 2023 it happened repeatedly, including one that rained ash on Yellowknife from Behchokǫ̀.

So, how can you figure out what to expect? Westwick recommends several tools, including FireSmoke and windy.com, reliable sources used by emergency responders and public health officials.

But, as a reminder, Westwick noted even though these tools are updated multiple times a day, the forecast may change. That doesn’t mean you can’t trust the tools, it’s just the nature of wildfires.