Mesosphere

Temperatures in the mesosphere decrease with height from the stratopause up to the mesopause, at around 85 km. Temperatures at the mesopause vary from as low as -120°C at high latitudes in summer to -50°C in winter. The cold summer temperatures and the warm winter temperatures are therefore a reverse of what happens at the stratopause.

As in the troposphere, the unstable profile means that the vertical motions are not inhibited. During the summer, there is enough lifting to produce clouds in the upper mesosphere at high latitudes - it is then that the stratopause achieves its highest temperature due to the optimum amount of solar radiation being received. These clouds are known as noctilucent, and are very thin. Despite this, they are visible against a night sky when the sun is at a small angle below the horizon, so that they are high enough to be in sunlight. By using triangulation techniques, these clouds have been estimated to form up to around 80 km above the surface.