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Date:  02:15 GMT, 5th July, 2010

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Sun rules Earth's mysterious 'night shining' clouds

Noctilucent clouds appear about 80 kilometres above the Earth in each hemisphere's summer. Their extent and brightness varies over days, weeks and years, but no one knows why.
Now Charles Robert of the University of Bremen, Germany, and colleagues think they have an answer. By measuring changes in the light reflected from the clouds, they found that the clouds appear to wax and wane in prevalence over a 27-day cycle. As the sun takes 27 days to rotate around its axis, the team suggest a link.

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"Night shining" clouds getting brighter worldwide

According to a report in National Geographic News, once seen mostly in the Arctic, night-shining clouds are now appearing more frequently at lower latitudes.
Scientists suspect that the increase in night-shining clouds may be due to climate change.

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NASA's AIM Satellite and Models are Unlocking the Secrets of Mysterious "Night-Shining" Clouds

NASA's Aeronomy of Ice in the Mesosphere (AIM) satellite has captured five complete polar seasons of noctilucent (NLC) or "night-shining" clouds with an unprecedented horizontal resolution of 3 miles by 3 miles. Results show that the cloud season turns on and off like a "geophysical light bulb" and they reveal evidence that high altitude mesospheric "weather" may follow similar patterns as our ever-changing weather near the Earth's surface. These findings were unveiled today at the Fall Meeting of the American Geophysical Union today in San Francisco.
The AIM measurements have provided the first comprehensive global-scale view of the complex life cycle of these clouds, also called Polar Mesospheric Clouds (PMCs), over three entire Northern Hemisphere and two Southern Hemisphere seasons revealing more about their formation, frequency and brightness and why they appear to be occurring at lower latitudes than ever before.

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"Ghost" clouds invade the northern skies
They appear well after sunset with an unmistakable after glow that is sure to catch your eye.
Wispy, thin "ghost"-like clouds may appear like neon smoke in the direction of where the sun recently set.  This is where this type of cloud earns its name "noctilucent" for something that shines during night time.

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