APOD: Asperatus Clouds Over New Zealand (2016 Apr 17)

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APOD Robot
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APOD: Asperatus Clouds Over New Zealand (2016 Apr 17)

Post by APOD Robot » Sun Apr 17, 2016 4:07 am

Image Asperatus Clouds Over New Zealand

Explanation: 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 featured image, taken above Hanmer Springs in Canterbury, New Zealand, in 2005, shows great detail partly because sunlight illuminates the undulating clouds from the side.

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Boomer12k
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Re: APOD: Asperatus Clouds Over New Zealand (2016 Apr 17)

Post by Boomer12k » Sun Apr 17, 2016 8:35 am

Wow... Bizarre... and suggestive if you look at the right places....

I wonder if land structure helps...

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Letoibz
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Re: APOD: Asperatus Clouds Over New Zealand (2016 Apr 17)

Post by Letoibz » Sun Apr 17, 2016 9:00 am

This APOD is repeated, go failure. It is the same on 27 February 2013. :(

http://apod.nasa.gov/apod/ap130227.html

Although the picture is lovely and I do not see her again

NCTom

Re: APOD: Asperatus Clouds Over New Zealand (2016 Apr 17)

Post by NCTom » Sun Apr 17, 2016 11:55 am

Thanks for the repeat. I missed the February, 2013 showing.

heehaw

Re: APOD: Asperatus Clouds Over New Zealand (2016 Apr 17)

Post by heehaw » Sun Apr 17, 2016 2:31 pm

Let's face it, astronomers: sometimes it just gets cloudy. This is one of those days!

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RJN
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Re: APOD: Asperatus Clouds Over New Zealand (2016 Apr 17)

Post by RJN » Sun Apr 17, 2016 3:52 pm

Letoibz wrote:This APOD is repeated, go failure. It is the same on 27 February 2013. :(

http://apod.nasa.gov/apod/ap130227.html

Although the picture is lovely and I do not see her again
Please see question 4 of APOD"s FAQ list: http://apod.nasa.gov/apod/ap_faq.html .

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Chris Peterson
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Re: APOD: Asperatus Clouds Over New Zealand (2016 Apr 17)

Post by Chris Peterson » Sun Apr 17, 2016 4:59 pm

RJN wrote:
Letoibz wrote:This APOD is repeated, go failure. It is the same on 27 February 2013. :(
http://apod.nasa.gov/apod/ap130227.html
Although the picture is lovely and I do not see her again
Please see question 4 of APOD"s FAQ list: http://apod.nasa.gov/apod/ap_faq.html .
This comes up so often, perhaps you should consider a subtitle on Sunday pages, like "Revisited Favorites" or something similar.
Chris

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eyesoars

Re: APOD: Asperatus Clouds Over New Zealand (2016 Apr 17)

Post by eyesoars » Mon Apr 18, 2016 4:13 pm

The clouds are likely related to 'wave' phenomena, which are common and quite spectacular around the Southern Alps of New Zealand.

Particularly when there is a significant windspeed gradient with altitude, air masses show considerable elasticity, and downwind of
large mountains will often create periodic up and downdrafts (think growing sinusoid, though usually the second is the biggest/strongest).
Clouds are sometimes associated with these, though most often "rotor clouds" under the highest points of the sinusoid, which are
typically very ragged, dynamic, horizontal clcouds (and strongly associated with flight turbulence in the Western U.S.). Less frequently,
the up- and down-drafts may generate clouds rather like lenticulars. This is relatively rare over the Rockies, perhaps because the prevailing
westerlies (which blow west-to-east) tend to dry out the airmasses as they pass over mountains west of the rockies.