As I write this, we’ve just moved into Fall, at least here in the Northern Hemisphere. Our friends “down south” are enjoying the first bursts of Spring. In the busy world of email and text messages, rushing off to the airport and ordering a pizza for dinner, who cares about the equinox? Who even remembers that it marks the time of year when day and night are equal in length? Let’s face it, on too many days most of us no longer even seeing the sun, and our view of the stars are obliterated by light pollution or nighttime television. It’s depressing how little attention we sometimes give our surroundings!
A thermographer is, in essence, a sort of “thermal Sherlock Holmes.” We must pay attention to our thermal surroundings if we are to make sense of what we are viewing through out imagers. The concept of “thinking thermally,” is based on not even needing an imager. Look around and if you are observant, you will see countless examples of the temperature of our world. We could simply say the planet is a vast thermal engine.
Two weeks ago, for instance, we had our first frost here in Central Vermont. This typically occurs in the mountains around the September full moon. Why the full moon? Honestly, it could be any night the sky is clear, but if the sky is clear and the full moon is up, it gets your attention! Clear sky that allows the Earth to radiate so much energy to space that we cool to the freezing point. Even with frost at higher elevations, however, we often don’t get a frost down in the valleys because they fill up with cold air, that along with the moisture in the valleys, results in clouds or ground fog forming. That fog acts just like a blanket to reduce nighttime radiational cooling. As the water vapor condenses, it too gives off a tremendous amount of heat. In the end the valleys stay warmer.
For many of us, this time of year—while we are in this seasonal thermal transition—is ripe with examples of Thinking Thermally. I’d encourage you to get out, open up your “sensors” and learn from them. One word of warning, don’t be too quick to jump to conclusions from your observations. Often we can’t even see all the variables and as a result, making a valid conclusion becomes suspect. Just enjoy some patient observing, preferably from several different points of view, until the Thermal Truth, if you are lucky, reveals itself.
Not sure where to even start? Here are a couple of suggestions:
• Why do bees crawl around on a flower early in the morning, but fly from one to another later in the day?
• What difference will a lower sun angle make on how your conduct building inspections over the next six months versus how you did them in the past six months?
• Think about an aluminum electrical conductor in an outdoor substation on a clear, warm day. When you view this through your imager, what “apparent” temperature difference will you see between the top and bottom of the conductor?
• You are up on a low-sloped roof in the evening, preparing to conduct a roof moisture inspection. You notice much of the roof is damp with dew, except for several rectangular-shaped areas that are dry. What do you think a subsurface moisture reading in these dry areas would indicate?
• After a rain storm, can you predict the relative temperature of puddles of various sizes?
• How much energy does a Bicknell Thrush, a small bird that summers on the mountain tops in Vermont, need to store to successfully migrate this month to the Dominican Republic?
By the way, despite the horrendous flood damage much of Vermont suffered from the wrath of Hurricane Irene, the annual color show of Fall Foliage looks like it will be spectacular. We’d love to have you visit and see this amazing sight, as clear a thermal signature as you will ever see! Check out the foliage report here.
Many thanks also to Scott Warga for his comments and discussion last week. He is a superb example of someone who is very thermally inquisitive! Next week I’ll explore some of these issues and any others you’d like to discuss.
John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner