from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Luminous at night. Used especially of certain high clouds.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Shining or glowing at night, especially of very high-altitude clouds that reflect sunlight long after sunset.
from The Century Dictionary and Cyclopedia
- Shining by night or in the dark; nuctilucid: as, the noctilucent eyes of a cat.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. shining or glowing by night
Sorry, no etymologies found.
That route saves fuel and avoids high-altitude ice clouds, called noctilucent clouds, that form during the summer between 50 degrees and 70 degrees north and south of the equator.
The clouds are intended to simulate naturally-occurring phenomena called noctilucent clouds, which are the highest clouds in the atmosphere.
Scientists claim these "noctilucent" clouds -- formations that are similar to what was seen after the Tunguska event -- reach the poles because water vapor appears to be quickly traveling in two dimensions, rather than three.
"noctilucent" clouds have become more common in the past 50 years.
Look for the Plough in the NW, the Square of Pegasus in the E, and remain on the alert for noctilucent clouds above the NW to NE horizon, perhaps near Capella in Auriga.
Noguchi sent down other beautiful shots, including “priceless” noctilucent clouds above Antarctica, city lights above Tokyo, and Port-Au-Prince, Haiti with “prayers” from the crew.
The noctilucent or “night-shining” clouds are at an altitude of 47 to 53 miles (76 to 85 km), where meteors and bright aurora lights are not uncommon and the atmosphere gives way to the blackness of space.
As the sun rose in the morning, remnants of the explosion were visible as noctilucent clouds over the region.
The experiment created a man-made noctilucent cloud using the fourth stage of a NASA Black Brant XII suborbital sounding rocket that spewed exhaust particles 173 miles 278 km above Earth.
During that time we observed radar soundings consistent with noctilucent clouds.