Lesson of the Day: Noctilucent Clouds

2013-08-24 16:13:31.000 – Brian Fitzgerald,  Weather Observer/Education Specialist

Noctilucent clouds. Courtesy NASA.

As a lover of science, weather, astronomy and nature I was immediately struck by a recent article posted on My Science Academy’s website. Having failed to view any Aurora Borealis last night I stumbled upon this article about something called ‘Noctilucent Clouds And Aurora Over Scotland.’ For those of you who are not familiar with a noctilucent cloud type, fear not, because they are quite rare to observe.

Noctilucent clouds are a whispy cloud-like phenomena that appear very, very high up in the sky, usually only visible in deep twilight and shimmer and glow white or electric blue. These clouds are essentially ice crystals found on the edge of space some 50 miles above the surface of the Earth within the mesosphere. The mesosphere exists between 31 and 50 miles above the surface of the Earth and is a very cold layer of air (with temperatures dipping as low as -130 degrees F) where space debris begins to burn up, including meteors. The mesosphere is a notoriously dry place as well (remember, very cold air cannot hold much moisture) with the exception of the ice crystals that help to form these noctilucent clouds. Many scientists believe that moisture ejected from meteors, water vapor from upwelling summertime winds, rockets, and even volcanic eruptions (search 1883 eruption of Krakatoa) are responsible for moisture found in the mesosphere.

For more information about noctilucent clouds, visit NASA’s Science News Page– and of course for more information and news from the Mount Washington Observatory, visit our site!

Brian Fitzgerald,  Weather Observer/Education Specialist