When you look at the average weather map, you are looking at weather just at the surface. But what about the rest of that fluid we call “air” over our heads, stacked up in layers like a Devil’s Food cake? Hi, I’m Bryan Yeaton, and this is The Weather Notebook.

Let’s take a look at those layers, and what happens in each. Starting at the surface and working upward, we first cruise through the troposphere, the place where pretty much all of our weather happens. Depending on where you are, the troposphere is, say, 8-12 miles thick; it is usually thinner near the poles, since the cold air is denser. Through the troposphere, the temperature drops from the ground temperature to close to minus 70 C.

At the top is a boundary called the tropopause, which leads us into the next layer, the stratosphere. Here the temperature stays fairly constant until about 20 miles up, where it starts to climb again. What blocks this energy from coming down any farther? The Ozone Layer!

By the time we reach the mesosphere, the temperature has climbed again to somewhat above freezing, although with so few air molecules at this altitude, “temperature” doesn’t quite mean the same thing. You probably wouldn’t want to be out in shorts and a t-shirt up here. And by the time you reach the mesopause, about 50 miles up, you’d need a lot more clothing, for the minus 110 degree “air”.

The topmost tiers are the thermosphere and the exosphere, sometimes collectively called the “ignorosphere,” as we know so little about it. But, here, we find the glowing, flashing streaks of the aurorae.

Although traces of the atmosphere reach out to more than 600 miles, 90 percent of its mass is contained in just the bottom ten miles.

The Weather Notebook is funded by Subaru of America.