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New theories about the origins of noctilucent clouds

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By Chris St. Clair
Weather Broadcaster
@cstclair1
Monday, April 14, 2014, 8:35

For years NASA and the science community have been studying Noctilucent Clouds high above earth. Of late some new theories about the origins these clouds have been emerging.

Our atmosphere is composed of layers. The troposphere extends from the surface upwards to about 12 kilometres, it’s where most of our weather occurs. The next layer rises about 55 kilometres higher, this is the Stratosphere. Above that is the Mesosphere, Thermosphere and finally the Exosphere which reaches space around 700 kilometres above the surface.

Noctilucent clouds form about 85 kilometres above earth, in the upper Mesosphere. They were fist noticed in 1885, two years after the massive eruption of Krakatoa, in Indonesia. It’s likely we noticed the clouds then because of the spectacular sunrises and sunsets the volcanic ash was offering us.


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Study in recent years hints that the clouds are likely comprised of minute bits of ash and ice crystals that have adhered together. The ash is particulate from volcanoes, meteors and comets that litter the upper reaches of our protective atmosphere, but never fall to earth.

These night shining clouds (that’s what noctilucent means) appear at night as the sun drops below the horizon to illuminate the upper reaches of our atmosphere.

Interestingly, some new research from The University Of Colorado Atmospheric and Space Physics Laboratory indicates that these clouds have become more widespread in the past decades leading to suggestions that there is a link to climate change due to increased emissions of methane, carbon and water vapor.


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Fifty years ago the clouds were noticed mostly above a latitude of 60 degrees; in recent years they have been visible below the 45th degree of latitude. Look for them at twilight, shortly after sunset or before sunrise (when the sun is between six and 16 degrees below the horizon). In the northern hemisphere you can see them from May to August when the sky is clear.

It again would seem that the more we know, the more questions we have.

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