Asperatus Clouds Over New Zealand
What kind of clouds are these?Although their cause is presently unknown, such unusual atmospheric structures, as menacing as they might seem, do not appear to be harbingers of meteorological doom.Known informally as Undulatus asperatus clouds, they can be stunning in appearance, unusual in occurrence, are relatively unstudied, and have even been suggested as a new type of cloud.Whereas most low cloud decks are flat bottomed, asperatus clouds appear to have significant vertical structure underneath.Speculation therefore holds that asperatus clouds might be related to lenticular clouds that form near mountains, or mammatus clouds associated with thunderstorms, or perhaps a foehn wind -- a type of dry downward wind that flows off mountains.Such a wind called the Canterbury arch streams toward the east coast of New Zealand's South Island.The above image[url=], taken above[/url]Hanmer Springs in Canterbury, New Zealand, in 2005, shows great detail partly because sunlight illuminates the undulating clouds from the side.
Sometimes the sky above can become quite a show.Last week, for example, the Moon and Venus converged, creating quite a sight by itself for sky enthusiasts around the globe. From some locations, though, the sky was even more picturesque.In the above image taken last week from Spain, a crescent Moon and the planet Venus, on the far right, were captured during sunset posing against a deep blue sky. In the foreground, dark storm clouds loom across the image bottom, while a white anvil cloud shape appears above.Black specks dot the frame, caused by a flock of birds taking flight.Very soon after this picture was taken, however, the birds passed by, the storm ended, and Venus and the Moon set. The Moon and Venus have now separated, although Venus will remain visible at sunset for the rest of this month.
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Post time 6-12-2011 05:31 PM
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