Noctilucent cloud

Definition of Noctilucent Clouds

Noctilucent clouds, denominated night-shining clouds, exist as tenuous atmospheric occurrences within the uppermost strata of the Earth's atmosphere. Composed of minuscule ice crystals, these clouds display visibility during deep twilight and are stationed at altitudes extending from 76 to 85 kilometers (47 to 53 miles) - an elevation considerably surpassing that of any other cloud formations within Earth's atmospheric confines.

Formation of Noctilucent Clouds

These clouds encompass minute ice crystals resulting from the condensation of water vapor onto particulate matter within the mesosphere, the atmospheric layer positioned above the stratosphere. The origin of the particulate matter remains uncertain, with hypotheses pointing to micrometeorites, volcanic ash, and terrestrial dust as potential contributors. In light of their composition, the formation of noctilucent clouds necessitates extremely cold temperatures, explaining their frequent observation within polar regions during their respective summer periods.

Appearance of Noctilucent Clouds

The noctilucent clouds manifest a unique, luminous presence in the night sky, appearing radiant during twilight due to their altitude, high enough to reflect sunlight not directly observable from the Earth's surface. Generally displaying a faint, bluish or silvery white coloration, their exact hue can fluctuate based on the elevation of the ice particles and the angle of incident sunlight.

Scientific Importance of Noctilucent Clouds

Noctilucent clouds undergo scientific scrutiny to enhance the understanding of the upper atmosphere, given that their behavior can offer valuable insights into meteorological and climatic processes. They serve as efficient indicators of alterations in the temperature and humidity conditions of the upper atmosphere. Moreover, as their formation hinges on the availability of dust and extremely cold temperatures, investigation into these clouds could offer substantial clues pertaining to climatic shifts.

Viewing Noctilucent Clouds

The observation of noctilucent clouds depends on specific conditions. They are primarily observable during the summer months at latitudes positioned between 50° and 70°, and either post-sunset or pre-sunrise when the sun is marginally below the horizon. Their appearance does not adhere to specific weather patterns and the frequency of noctilucent clouds exhibits considerable yearly variations.
Updated: May 26, 2023
Published by: Weather U.S. | About Us