Inversion! (And a little bit about indoors air quality)

After an incredibly warm (and low-snow) start of winter in 2018, temperatures plunged to proper sub-Arctic winter values. A few days ago, we were worrying about thawing (with temperatures in the 30s °F / around 0 °C), and then down the curve went. Last night we reached -40 (choose your unit: the scales meet at -40) as per our consumer-grade Davis weather station. That’s the official definition of “cold snap”, and it’s the first of the season.

The Fairbanks area is well known for its extreme atmospheric temperature inversion patterns. And on map provided by the commercial service Wunderground it is very apparent today (click on the image for a bigger version with readable temperature labels):

Higher elevations, such as Cleary Summit, a mountain pass on the Steese Highway north of Fairbanks, are currently about 30 °F/17 °C warmer than the valley bottoms. Where we happen to live (and which is why “a house in the hills” is something we keep looking out for).

Life as -40 slows down. You can go out just fine, and you’ll be amazed by how well sled dogs are adapted to this extremely harsh weather, but it’s not really fun to exercise outside, plastic is brittle, batteries go flat … and you don’t have time for recreation because you need to keep an eye on the house systems. Especially to make sure that water stays liquid, be it in drains or incoming pipes.

The house we live in is made from three-sided logs, which retain heat quite well. We mostly heat with a very efficient and Toyo oil stove. But we have a wood stove to fall back on, in case the electricity or the Toyo have an outage. We decided to fire it up today, to make sure it works well and because it creates a nicer warmth in the corners too far from the Toyo. Wood burning is a huge and complicated political hot potato in interior Alaska, and a topic too complicated to go into in this post. The short version is: it’s traditional, economical and doesn’t require electricity; but it also contributes to air pollution in a way to occasionally render the winter air in Fairbanks one of the worst in the planet, so at a minimum eliminating the most polluting types of burners is quite imperative for the health of the population.

Our stove is an EPA-certified Blaze King with a catalytic converter, but even so: however pleasant wood heat is, you’ll get an impact on the air you breathe. Air quality indices only talk about outdoors air (and usually averaged over 24h). Another topic, though, is indoors air. I took the opportunity to pull out a little PM2.5 sensor that I bought online a while ago. (Disclaimer: I haven’t checked the calibration. At least during the summer wildfires it seemed to work reasonably well and deliver believable values.) Today, before starting the wood stove and with a blazing oil stove, it measured around 15 µg/m3, which is an ok value. With the wood stove, it was at 66 µg/m3 after an hour, went up to just above 100 µg/m3 and then settled in the 80s, which you will find labeled as “unhealthy for vulnerable populations”. My setup is here, with the sensor in the left foreground. It talks to the computer via a USB-to-serial interface. (I wrote the app to teach myself Dash for interactive real-time applications.)

This, of course, is measured indoors, not outdoors, and in the 24h average we will quite likely end up in the “moderate” range for the day. We’re fine.

On a related note, no one should retain too rosy a picture of the air pre-historic and pre-industrial populations used to breathe. Notwithstanding, of course, their insights about the relationship to nature: if a culture or people practices indoors wood or coal burning for cooking and warmth, chances are that respiratory illnesses were prevalent.

Addendum: Approximately 5-6 h after we first started the wood stove, the picture has changed a little bit. PM2.5 values came progressively down to 15-25 µg/m3, pretty much to where they were before we started. Clearly, the first fire-up phase is what generates the most pollution, while collected crud from inside and outside the stove burned off. In contrast, low-to-medium hot, steady operation deteriorates the air much less. Also, I believe it takes a few hours for the catalytic converter to reach its operating temperature. Apparently, letting the stove cool down completely and sit cold for extended periods is a recipe for air pollution. The lesson from this is: If you want to heat with firewood, make sure you have a device with a certified catalytic converter, use it continuously and burn dry, well-seasoned wood.

What I do using the ten hundred most common English words

What better way to start a geoscience blog than to jump on a memetic bandwagon, right? Inspired by an XKCD cartoon — what else — a creative person called Theo Sanderson coded the Up-Goer Five text editor to incide people to write about a hard idea using only the most common 1000 (ten hundred, as “thousand” is forbidden) words of the English language. I’m not going to quibble about his selection at the lower edge of the 1000 number: it’s a charming idea and it became a geo-blogger meme. So here’s my attempt:

In the colder parts of the world a lot of the land is covered by trees. Every summer, some of the trees catch on fire. The fires can grow very large and burn a lot of the wood and other ground cover. Many of the fires happen far away from people because not many people live up here, but the smoke from the fires moves with the wind so in the towns and other places where people live they often can smell it. The smoke and little black bits from the fires are bad for people, especially children and sick people.

I work with a group that uses computers to find out where the smoke from the fires will move. We run the computers for hours and then make pictures of the land and put them where people can see them. There are the cities on the pictures and red and green and blue and so on, so people can see if there is going to be smoke where they live. To make the pictures we need to find out very fast when there is a new fire, and how big it is. For this I use other pictures — very large pictures that are taken from space. I get those pictures on my computer and have written something that makes the computer take a very close look at the pictures and tell me where the fires are and how big they are.

Another way to use the computer is to make it figure out where a fire is going. This is very hard for the computer, because it needs to know what grows on the ground, if there is water on the ground or rain falling, where the ground goes up and down, and so on. So I use a computer made from over one hundred smaller computers to make a picture of where the fire will be the next two or three days.

We also know that the cold parts of the world are getting warmer, and it is important to know if there are going to be more fires or maybe larger fires or the same place burns more often. This is a very interesting job to do.

More here.