Night Shining Clouds
|NLCs are found a few miles below the mesopause, the coldest layer of the atmosphere.
At that level temperatures start to be a meaningless concept except for characterising molecular velocities and energies because the pressure is a mere 1 bar, 1/1000 of that at sea level. Ordinary conductive and convective heat transfer becomes insignificant to us at those pressures.
The increased occurrence of NLCs implies an increasingly colder and wetter summer mesosphere. Paradoxically, tropospheric global warming leads to lower mesosphere temperatures.