Noctilucent Clouds Above Scotland

August 10, 2005


Provided and copyright by: David Weir
Summary authors & editors: David Weir

This photograph showing a vivid display of noctilucent clouds was taken at about 0206 British Standard Time on the morning of June 23, 2005 from South Queensferry, Scotland. In the foreground is the Forth Rail Bridge, constructed over a hundred years ago. Unlike normal clouds which form within the first 10 km or so of the Earth's surface, noctilucent clouds form at about 80 km. They're therefore visible at night during the summer months when the Sun can illuminate the clouds while below the viewer's horizon. This occurs within a specific band between about 50 and 60 degrees on either side of the Equator. Too far north and the Sun doesn't go far enough below the horizon; too far south and the Sun is too low to illuminate the clouds.

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