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Noctilucent Clouds (6.0 Mb) -
Noctilucent clouds, also known as polar mesospheric clouds are rare bright cloudlike atmospheric phenomena visible in a deep twilight. The name means roughly "night shining" in the Latin language. They are most commonly observed in the summer months at latitudes between 50° and 60° north and south of the equator. They are the highest clouds in the Earth's atmosphere, being located in the mesosphere at altitudes of around 85 kilometers, and are visible only when illuminated by sunlight from below the horizon while the ground and lower layers of the atmosphere are in the Earth's shadow; otherwise they are too faint to be seen. Noctilucent clouds are not fully understood, as under most understood meteorological concepts, clouds generally are not able to reach such high altitudes, especially under such thin air pressures. |
