How Does Wildfire Smoke Travel?

In 2022, wildfires are becoming common in many parts of the world. Drought and rising temperatures are causing wildfires to break out, wreaking havoc on many forest ecosystems, their aftermath leaving dense clouds of smoke lingering—sometimes as far as the other side of the world. To get a better idea of how wildfire smoke results in confusing air quality readings, we can look at how it travels and what precautions we can take to protect ourselves following a serious wildfire event.

The Traveling Aftermath of California’s 2020 Wildfires

In September 2020, wildfires raged across North America, traveling along the Cascade Range from Washington down through California and all the way to Mexico. Some of the worst air quality measurements north of 500 were recorded in San Francisco, far exceeding the Environmental Protection Agency’s (EPA) maximum limit of 300. Not even a week later, smoky skies covered several East Coast cities and Europe.

How is this possible?

The Wildfire Smoke’s Journey

The bigger the wildfire, the more likely the smoke will travel farther from the source. Why? The smoke from a wildfire typically gets shot up into the sky vertically, after which it expands outward into a plume. These monstrous clouds of smoke are called pyrocumulonimbus clouds. For this reason, the air quality in the region directly surrounding a wildfire may not be as bad as in the downwind areas. After shooting high up into the atmosphere, sometimes even as far as the stratosphere, the smoke moves outward horizontally, landing on top of cities.

Wildfires and Regional Air Quality

As opposed to large, raging wildfires that shoot smoke high up into the atmosphere, milder forest fires tend to have a bigger impact on the air quality of local communities. This is because the smoke isn't big enough to shoot into the stratosphere, and thus gets trapped, expanding locally. Therefore, the severity of the wildfire greatly impacts how it travels, how fast, and where air quality will be most affected.

Can Wildfire Smoke Harm Me?

The mix of gases and particles that make up wildfire smoke poses several serious risks to human health. Adverse health effects following wildfire smoke inhalation are immediate and mostly target the eyes and respiratory system. Some common reactions immediately following exposure include coughing, difficulty breathing, irritated sinus, chest pain, headaches, asthma attacks, fatigue, and increased heartbeat. High-risk groups, such as children, pregnant women, and anyone with a preexisting respiratory or cardiovascular condition, are urged to take caution and avoid wildfire smoke, as they are most susceptible to these adverse effects.

However, healthy individuals are not immune to wildfire smoke, even in small amounts. We recommend you stay vigilant of wildfires in your region and adjacent areas due to their traveling nature. One of the best ways to do this is to check in with a real-time map that offers air quality data collected from various local sensors.

The real-time PurpleAir Map provides users with air quality information collected by Community Scientists. They provide in-depth values regarding local particulate matter (PM₂.₅) concentrations and other harmful airborne pollutants.

Reading PurpleAir Maps Following a Wildfire

Often, when we check the air quality in the region immediately surrounding the wildfire, the map will show a green reading, which corresponds to a “good” air quality index. However, this may be because of the traveling smoke phenomenon caused by the pyrocumulonimbus clouds. Air quality monitors, therefore, may not be picking up on the smoke that is traveling through the stratosphere until it lands many miles away. The yellow, orange, or even red readings, as a result of the wildfire, may be picked up in surrounding cities instead.

Due to the traveling and often unpredictable nature of wildfire smoke, it is advisable to check a real-time air quality index map, such as the PurpleAir Map, to stay informed whenever a wildfire occurs. As we’ve seen in the case of the 2020 US wildfires, even those on the other side of the country can face the effects of traveling wildfire smoke!

References

https://www.cdc.gov/disasters/wildfires/smoke.html

https://www.popsci.com/story/environment/where-wildfire-smoke-goes/

https://www.nasa.gov/topics/earth/features/pyrocb.html

https://www.airnow.gov/aqi/aqi-basics/

https://fire.airnow.gov/

2 comments

  • Hi Michael, Thomas here from PurpleAir. Thank you for finding the mistake, we’ve corrected it now :)

    Thomas Lee
  • You might want to double-check what part of the Rocky Mountains mountain range runs through California, as mentioned in the first paragraph under “THE TRAVELING AFTERMATH OF CALIFORNIA’S 2020 WILDFIRES”. (Answer: “none”)

    Michael House

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