Cathay Pacific 2nd Officer Interview Practice Test

The main idea is the transition between atmospheric layers characterized by a change in how temperature changes with height. In the lowest part of the atmosphere, temperature generally falls as you go up—the troposphere. At the top of this layer, the rate of cooling with height levels off and the temperature remains roughly constant with altitude up to around 11 km (about 36,000 ft). This boundary is the tropopause. Above it, in the stratosphere, temperature again changes with height, but in this region it actually increases with altitude due to ozone heating. So the tropopause is the point where the cooling stops and the temperature stays near the same over that height range. The other layers describe regions where temperature continues to fall (troposphere, mesosphere) or rises with height (stratosphere), not a boundary with a flat temperature profile.