The tropopause is a thin layer of the Earth’s atmosphere, only 2-3 km thick, which is located between 12 and 14 km altitude. It is the part of the atmosphere where the temperature is stable and the coldest. It is the intermediate zone between the troposphere below and the stratosphere above.
The temperature profile shows that the tropopause – between 12 and 14 km above the ground – is the coldest part of the atmosphere.
Most cirrus clouds (clouds formed of ice crystals) form and evolve in the tropopause.