"The only way to know exactly what’s in a wildfire’s smoke is to sample straight from the haze. So during the Rim Fire in Yosemite—which emitted so much smoke it formed its own clouds—a NASA DC-8 passenger plane and an Alpha fighter jet each crisscrossed through the plume. On both planes, scientists had created an in-flight lab to measure exactly what the fire was producing.
The answer seems obvious: Fire makes smoke. But smoke isn’t a uniform entity. It’s a variable portfolio of gases, invisible but for the particles they ferry along. “That’s what you’re actually seeing when you see a smoke plume, you know the big white smoke plume. That’s sunlight bouncing off the little particles,” says Bob Yokelson, an atmospheric chemist at the University of Montana. The composition of that smoke matters for human lungs and the climate—which is why Yokelson’s team and NASA’s Alpha jet crew are busy planning their next flights for late summer.
There are a lot of ways to study those pollutants—from the ozone that makes it hard for humans and crops to breathe to the light-absorbing particulate matter that raises atmospheric temperatures. The US Forest Service runs a Fire Sciences Lab in Missoula, where Yokelson has compared burning manzanita to ponderosa pine to see how fires in different ecosystems might burn. But it’s incredibly difficult to capture every component of a burning forest—with variable light, temperature, and fuel conditions—in a lab. So the truest measurements come straight from the airspace above a burning forest."