noctilucent clouds


Also found in: Acronyms.

noctilucent clouds

Clouds of unknown composition that occur at great heights, 45 to 55 miles (70–90 km). They resemble thin cirrus clouds but usually with a bluish or silverish color, although sometimes orange to red, standing out against a dark night sky. Also referred to as luminous clouds. These clouds have been observed rarely and then only during twilight in the summer months in both hemispheres and only between latitudes 50° to 75° N and 40° to 60° S.
References in periodicals archive ?
Professor Gary Thomas, from the University of Colorado in Denver, USA, who studies noctilucent clouds, said, 'Extreme cold is required to form ice in a dry environment like the mesosphere.
The commonly held view is that when this vapour reaches the freezing mesopause region, ice crystals form and turn into noctilucent clouds.
Prof Gary Thomas, of the University of Colorado's laboratory for atmospheric and space physics and a world expert on noctilucent clouds, said: "This is a big event.
And while, in the presence of noctilucent clouds, temperatures in the polar mesopause do indeed get down to -260| F--the lowest atmospheric temperature recorded--clouds have also been observed by Soviet cosmonauts over the equator, where mesopause temperatures are too warm for condensation.
The Director spoke about Noctilucent Clouds and assistant Director, Dave Gavine, about the aurora in history.
NOCTILUCENT CLOUDS IN MOTION: Swedish photographer Peter Rosen took this close-up, time-lapse movie of Noctilucent Clouds (NLCs) over Stockholm, Sweden on the evening of July 16, 2012.
The research connects the two events by what followed each about a day later: brilliant, night-visible clouds, or noctilucent clouds, that are made up of ice particles and only form at very high altitudes and in extremely cold temperatures.
John Rowlands is building up a dossier on the spectacular but unexplained summer sailor's sky phenomenon, officially known as noctilucent clouds (NLCs).
Meteor trails, satellites, the International Space Station, noctilucent clouds and the northern lights can all be photographed with long exposure photography.
These included a magnificent white light image of the sunspot group AR1520 by Damian Peach, observations of the transit of Venus, spectacular images of the major planets by the Association's growing band of high-resolution imagers, Tom Boles' 150th supernova discovery in August, and numerous sightings of aurorae and noctilucent clouds, despite the generally poor weather of summer 2012.
STOCKHOLM (CyHAN)- Swedish photographer Peter Rosen took this close-up, time-lapse movie of Noctilucent Clouds (NLCs) over Stockholm, Sweden on the evening of July 16, 2012.
But higher up, above all the usual clouds, at a height of about 50 miles is a layer known as the mesosphere - and it's here that we can observe a phenomena called noctilucent clouds.