This post is a guest post from my colleague Caroline (Carrie) Womack. Carrie studies how aerosol interact with light at NOAA ESRL. She got her PhD in chemistry at the University of Chicago, and is one of my ski/adventure buddies here in Colorado!
A certain type of news headline is becoming depressingly familiar these days: Climate change is altering weather patterns, increasing the frequency of extreme weather events, and making both droughts and floods worse . Wildfires have also become increasingly common and intense in the western United States, as well as many other places. Apart from the devastating effect that wildfires can have on those in the path of the blaze, wildfires release pollutants and smog into the air, which can contribute to climate change, which then in turn makes wildfires even more likely – a positive feedback loop. Unfortunately, wildfires are also really complicated to study!
To better understand the effect that wildfires have on atmospheric chemistry and air quality, we are currently in the midst of a six-week field campaign at the Fire Sciences Lab in Missoula, MT – the first major initiative of NOAA’s FIREX campaign . The US Forest Service fire scientists here normally study the physics of fire behavior, and how best to fight fires (see this very cool video from the Atlantic), but they have lent us their facility this fall so that we can set some controlled indoor fires to study smoke chemistry. The hope is that if we better understand what pollutants are emitted by different types of fires, climate models can incorporate wildfires with great accuracy. Additionally, since wildfires are a necessary part of maintaining a healthy forest ecosystem, these models can also help experts know which kinds of fires to allow to burn.
The Fire Sciences Lab’s main experimental space is an enormous room with a giant central smoke stack rising toward the ceiling – basically a huge indoor chimney. Some instruments are installed on a catwalk about 50 feet above the ground, with small tubes from each instrument inserted into the top of the smoke stack. When the fire is ignited, those instruments see the chemical species that form in the initial few seconds, and can differentiate between chemical species formed in the flaming vs smoldering stage, which is important for including wildfires in climate models, as they represent two different types of fuel combustion.
We can also study how the atmospheric chemistry of fire emissions continues to evolve long after being emitted by allowing smoke to fill the entire room while the instruments sample the air through tubes in the wall for several hours at a time.
There are over 60 instruments here from NOAA and other institutions, measuring a wide range of chemical species. I am part of a group of scientists studying the aerosol particles that form in fires. Regular readers of this blog will know that aerosol particles (small droplets suspended in air) are both very important to climate change research, but also very difficult to study, due to their complexity. Our instruments monitor different aspects of particles, including: chemical composition, size, shape, and the way they evolve when exposed to UV light and chemical oxidants. My instrument measures how aerosol particles interact with UV and visible light by using an extremely sensitive light detector to measure the difference in light intensity with and without aerosol particles in the path of the light beam. This can be directly correlated to the effect that aerosol have on climate change, which is one of the most uncertain components in climate models.
We’re in the last week of the campaign, so at this point we’ve mostly settled into a routine. We’re currently doing the experiments where we let smoke fill the entire room, so we arrive at the lab first thing in the morning to warm up the instruments for an hour or two. At 9am two Fire Lab scientists build a fire of that day’s fuel type (to get representative data, we measure all kinds of fire – flaming, smoldering, different nitrogen and moisture contents etc.), and leave the room. Within five to ten minutes, the room is full of smoke and particles. The instruments sample for about 3 hours, and then the smoke is flushed out of the room over lunch, and the whole process repeats at 1:30pm. At the end of the day, we shut down the instruments in time for the daily 5pm meeting, then we set up for the next day’s experiments, fix any minor problems with the instruments, then it’s back to the hotel for a quick look at the data.
In a few days, we will be packing everything up into a semi-truck for the trip back to Boulder. Then we will begin the process of analyzing the data, which could take a year or two, in preparation for the final major FIREX initiative – a large scale field campaign aboard the NOAA P3 aircraft, sampling real wildfires in western North America during the summer of 2018. It’s an amazing project, and I’m very excited to see how it will all turn out.
For more, check out this video of the first few days here at the Fire Lab.