Microphysical and optical properties of noctilucent clouds

Noctilucent clouds play an important role in the physics of the summer polar mesopause. They consist of tiny ice crystals with characteristic dimensions smaller than 200 nm. However, neither exact shape of particles nor their precise chemical composition or concentration is known with a high accuracy. Also the origin of the particulate layer at such a high level in the terrestrial atmosphere (about 80 km) is a matter of a considerable controversy. aper summarizes recent advances in our understanding of nature of noctilucent clouds (NLCs) with special emphasis on the size and shape of crystals.