The stratosphere's the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It's stratified in temperature, with warmer layers higher up and cooler layers farther down. This's in contrast to the troposphere near the Earth's surface, which's cooler higher up and warmer farther down. The border of the troposphere and stratosphere, the tropopause,'s marked by where this inversion begins, which in terms of atmospheric thermodynamics's the equilibrium level… (More on Stratosphere)