Smoke Gets In Your Eyes - Wildfires Across the West: Is Wenatchee the Smokiest?

 NCW Life Channel photo 

When Cheryl and I moved from Seattle to eastern Washington near the end of the last century, we had to adapt to our new environment. One big feature of eastern Washington that we did not anticipate was the smoky skies of wildfire season. We have now come to expect that summertime in Wenatchee will probably include multiple days when wildfire smoke will darken our skies, obscure our views, make the air smell of charred forests and scrublands, make the sun red, give the light on the ground a wan yellow cast, and cause our throats and mucous membranes to register the pollution in the air. Even before we get out of bed or turn on the news in the morning, we can tell if the sky is smoky by the color and quality of the light from the east, which comes in through one of our bedroom windows.

When the wildfire smoke is at high pollution levels, the newspapers run articles telling us to avoid exerting ourselves outside. Health authorities advise us to wear N-95-class dust masks if we have to be out, though even the best dust masks only filter out the larger particles of smoke, and don't filter any of the gases. (See below for more on wildfire smoke as air pollution and its effects on human health.)

This year, the smoke from wildfires has reached into western Washington, including Seattle, getting the attention of people over there.

Seattle Times photo

Wildfire season in the Northwest overlaps with summer but can start in spring and extend into fall. Some years fires have burned close enough to where we live for us to see flames tearing across nearby hillsides from our front yard. Once we were put on notice to be prepared to evacuate from our house, which is about a mile inside the city limits of Wenatchee. Fortunately for us, the fire that year stopped short of our neighborhood by half a mile, so we did not have to evacuate. Unfortunately, some people we know were not so lucky and lost their homes. That was the Sleepy Hollow fire, which hit Wenatchee in 2015. 

Wenatchee World photo

Wildfire smoke is generally worst during "ridge weather," when a system of high atmospheric pressure is causing the upper air in the atmosphere to subside. An atmospheric ridge really is a piled-up ridge of air (or else a dome, in which case it's called an anticyclone). The troposphere, the bottom-most layer of the atmosphere, which contains most of earth's air, is extra thick beneath a ridge. All that extra air piled up beneath a ridge makes the atmospheric pressure at ground level extra high. In the summer, the mass of air trapped beneath a ridge in the Pacific Northwest is hot, dry air from the continental interior. 

Beneath a ridge, the sinking air from higher up in the troposphere pushes down on the lower layer of air near the ground, forming an atmospheric inversion that stops the lower air from rising and keeps it from circulating, mixing, and diffusing. The stagnant, ground-level air, trapped beneath the inversion and unable to mix with the rest of the troposphere, accumulates pollutants. 

The weather map from the National Weather Service today (above) shows a ridge in the atmosphere across eastern Montana, spread across the northwest. (Note that if you click on the weather map link, it will have updated to the current weather.) Although cool, moist air off the Pacific  Ocean may penetrate the western flank of the ridge in some places, the broad pattern is hot, dry air over most of the Pacific Northwest. As long as it holds, the ridge traps the surface air and keeps it from mixing and diffusing with the rest of the atmosphere. 

Over the course of the coming week, the high fire activity and continued presence of high atmospheric pressure over much of the Northwest is forecast to keep it mostly smoky around the region. 

A change in wind direction tonight may clear up some of the smoke in Wenatchee, but may blow more smoke and ash into Seattle from the fires in the Cascade Mountains between here and there, which have grown much larger the last couple of days. See the Seattle Times article, "Ash falls like snow in Seattle as wildfires rage in Pacific Northwest." 

Seattle Times photo

The satellite photo below, from this morning, shows white, high clouds and gray, low, wildfire smoke. The wildfire smoke blankets much of the Pacific Northwest, following rapid fire growth yesterday in Washington, Oregon, Idaho, western Montana, and British Columbia.

http://wasmoke.blogspot.com/

A combination of climate and topography makes Wenatchee particularly prone to getting its skies clogged with wildfire smoke during the summer. That's because Wenatchee is tucked away in the rain shadow on the east side of the Cascade Mountain. This puts the city between the dry forests of the eastern side of the Cascades and the hot, sagebrush-covered hills of central Washington, both of which tend to burn more than do the wetter, cooler forests in western Washington.

Another factor that adds to Wenatchee's tendency to be a gathering place for wildfire smoke is that it's in a basin  where the Wenatchee and Columbia River valleys join together. Because topography influences the way air moves, the Wenatchee basin can collect and concentrate air from as far away as parts of Oregon, Idaho, Montana, and British Columbia.

The Wenatchee basin is commonly subjected to atmospheric ridges in its summertime weather, trapping the air for days at a time and making pollutants, or wildfire smoke, accumulate. (Wenatchee is commonly beneath a zone of high-pressure air in the winter, too, causing a layer of "inversion clouds" that blocks the winter sun for days at a time, but that's another story.)

So Wenatchee seems to be set up to get more days of thick wildfire smoke each year than other places in Washington state tend to experience. Or is that just me feeling picked upon? Other population centers in eastern Washington are also in valleys or basins, and the people there know what it's like to live in a zone of highly concentrated wildfire smoke. And, as it stands today, the ongoing combination of wildfire and weather is causing smoke to blanket cities west of the Cascades as well, including Seattle. Which cities in Washington have been smokiest these last few years, and what the causes are, is a topic that could use some more research.

What is wildfire smoke, anyway? It is a combination of particles and gases. Let's start with the particles, which is usually the main concern.

Particles in the air, in terms of air pollution, are called particulate matter, abbreviated PM. Particulate matter consists of particles that are small enough to be suspended - held up in the air - by all the air molecules bouncing off of them. PM_2.5 refers to particles smaller than 2.5 microns in diameter. PM₁₀ refers to particles suspended in the air that are bigger than 2.5 microns, up to 10 microns in size. (A micron is a common name for a millionth of a meter. The metric system calls this the micrometer and abbreviates it as μm. )

Basically, PM_2.5 particles are really small. As the EPA says, "How small is 2.5 micrometers? Think about a single hair from your head. The average human hair is about 70 micrometers in diameter – making it 30 times larger than the largest fine particle."

Below is the map I commonly check for air quality at sites around Washington state. The map shows how many micrograms of fine particulate matter (PM_2.5) there are in each cubic meter of air. The darkest-colored dots, a deep purple color, are monitoring stations registering over 300 micrograms per cubic meter. Such high concentrations of tiny particles in the air are associated with greatly limited visibility and put the health risk at the "hazardous" level, the next step above "very unhealthy." Wenatchee's air quality, measured at a station three blocks away from our house, has one of the highest readings in the state today, as it often does. 

https://fortress.wa.gov/ecy/enviwa/

What are the effects of wildfire smoke on human health? That question goes well beyond my expertise. From what I have read, it is a matter of ongoing research, which includes studying the effects of smoke exposure on firefighters who are breathing the most polluted air at its source, and studying the effects on people and populations breathing wildfire smoke in towns many miles away from the fires. 

Health warnings about wildfire smoke focus mainly on the amount of fine particulate matter in the air, PM_2.5. Those particles are so small they can penetrate the lungs' defenses.  

As for the gases in wildfire smoke, they are not measured by the instruments that monitor particulate matter. The most abundant gas produced by burning plants is water vapor (H₂O_(g)), which is not considered a pollutant. Other gases in wildfire smoke include carbon dioxide (CO₂), carbon monoxide (CO), nitrogen oxide (NO), ozone (O₃), and other gases, including lots of different types of organic molecules, which are molecules built around carbon atoms. Benzene and formaldehyde, two of the organic molecules, are known to be harmful to human health. However, in air far away from the fires, the levels of wildfire-generated gases are generally diluted to much lower levels than in the burn zone itself. 

Not much is known about the long-term, cumulative effects of wildfire smoke on people over the course of many years, because there is little in the way of longitudinal (long-term) studies that have focused on answering that question. It is also hard to get a handle on the short-term health effects of breathing wildfire smoke. The effect on us of wildfire smoke is a sub-category of research on air pollution and its effects on humans that has not received as much attention as other types of air pollution. The unpredictable and ephemeral nature of wildfires makes it difficult to plan and conduct scientific research on the smoke, its contents, and its health effects.

The consensus for now is that breathing wildfire smoke is mainly a concern for young people, old people, and people with certain health risk factors. According to my local Chelan-Douglas Health District:

• "Inhaling smoke is not good for anyone, even healthy people. People most likely to have health problems from breathing smoke include: 
• People with lung diseases such as asthma or chronic obstructive pulmonary disease (COPD), including bronchitis and emphysema. 
• People with respiratory infections, such as cold or flu. 
• People with existing heart or circulatory problems, such as congestive heart failure, coronary artery disease, and angina. 
• People with a prior history of heart attack or stroke. 
• Infants and children because their lungs and airways are still developing and they breathe more air per pound of body weight than adults. 
• Older adults over age 65. Adults age 65 and older may have unrecognized heart or lung disease. 
• Smokers already have lower lung function or lung disease, and breathing smoke can make their conditions worse. 
• Diabetics."

"Air Quality and Your Health", PDF document, Chelan-Douglas Health District

One last note, on how climate change has increased wildfires. Climate change contributes to wildfires by increasing the length of fire season, increasing air temperatures, lowering the relative humidity of the air, drying out the vegetation, and drying soil moisture out of the ground. These are all well-documented changes that have been occurring in recent decades. 

Climate warming is also one of the factors that has led to increased insect infestations of forests, creating wide swaths of dead or partly dead trees, which adds octane (easily burned fuel, I mean) to wildfires. 

Climate change may also increase the occurrence of strong weather events such as thunderstorms and high winds, which can ignite and spread wildfires. For example, the Carlton complex fire of 2014, which decimated large areas of Okanogan County in north central Washington state, was set off by lightning and fanned by incredibly strong, gusting winds, all of it occurring in an air mass that was very hot, and very dry, due to the effect of an atmospheric ridge. 

Photo from PBS Breaking News

People who witnessed the Carlton complex described the fire moving across the landscape under powerful wind gusts as if from a giant blowtorch. Due to the wind, glowing ash and burning twigs from the fires kept jumping large distances, up to miles, ahead of the flames, igniting new fires ahead of the main fire zone.

There are also non-climate factors behind the increasing occurrence of wildfires, such as the forest management practice of fighting virtually all fires. This practice resulted in dense growth of easily burnt shrubs and understory trees, and high tree density in general, making it easy for fires to flare and spread, and making fires burn more intensely than the natural fires forests were adapted to recovering from. This practice of fighting wildfires, combined with how forest cutting and replanting has been managed, has, according to most experts, increased the risk and intensity of fires in many of our forests. 

In recent years, lots of people have been moving into the borderlands between cities and forests, or between cities and shrublands, exposing more people, with their buildings and infrastructure, to wildfires.

Several studies that removed the non-climate factors from the analysis, such as by including areas of forests where fires were never fought, have found that climate change is a major driver behind the increasing occurrence of wildfires in western North America over the last three decades.

Wildfires are a complicated phenomenon, which I have only brushed on here. The main news is that the effects of wildfires are more apparent to people living in the Pacific Northwest than they used to be, as wildfires in recent years have been burning more widely and intensively than in the past, and as the smoke has spread, on some days, to just about every neighborhood in the Pacific Northwest, so that now everybody in the region has gotten smoke in their eyes.