Astronomy, Photography and Weather

General Category => Weather & Atmospherics => Topic started by: Steveo74 on August 09, 2008, 04:27:42 pm



Title: Iridescent Clouds!
Post by: Steveo74 on August 09, 2008, 04:27:42 pm
Just got home from work and I was setting up the webcam to do a wee bit of time lapse and I noticed the a faint colouring in the sky near the sun. I would be right in saying that these shots are of Iridescent clouds? if so here you go.....

(http://farm4.static.flickr.com/3142/2747018006_10be184d29.jpg)

(http://farm4.static.flickr.com/3283/2747018554_62b5f57ff6.jpg)

(http://farm4.static.flickr.com/3138/2746183519_2e8bcb829b.jpg)

(http://farm4.static.flickr.com/3254/2746183669_e32492ed77.jpg)

(http://farm4.static.flickr.com/3013/2746183891_b838a72a04.jpg)

(http://farm4.static.flickr.com/3058/2747019462_730af3cb70.jpg)

(http://farm4.static.flickr.com/3094/2747019774_f028438309.jpg)

(http://farm3.static.flickr.com/2242/2746184897_d0cf229bdc.jpg)

(http://farm4.static.flickr.com/3278/2747019946_86dae8cffd.jpg)

Anyhow hope you like...  ;D


Title: Re: Iridescent Clouds!
Post by: John9929 on August 09, 2008, 04:39:02 pm
Steve those are beautiful! You also have Lacunosus holes in No 3 and a nice corona in the last one.
Much too much cloud here for that, in fact I was keeping an eye for more funnels ;)


Title: Re: Iridescent Clouds!
Post by: Steveo74 on August 09, 2008, 04:44:46 pm
Thanks John, Never heard of such a cloud.... checked it out, ‘lacunosus’, which is the latin for ‘full of holes’. Thanks for letting me know....  ;D


Title: Re: Iridescent Clouds!
Post by: martinastro on August 09, 2008, 04:47:04 pm
Steven, you sure have Irr clouds and they are great images to as John said. The bottom 7 are beautiful. Keep your web cam running early tonight just incase of a few flashes  :)

Keep watching John, I'm doing the same here at the min. Cumulus clouds only seem to be shooting up now. Instability increases during the evening, so then, and early tonight, look to be the best times for big convection. I noticed that there is a low risk of mesocyclones/supercells over N. Ireland this evening.


Title: Re: Iridescent Clouds!
Post by: Steveo74 on August 09, 2008, 05:04:58 pm
Thanks Martin for your comments...  ;D


Title: Re: Iridescent Clouds!
Post by: brianb on August 09, 2008, 08:53:44 pm
There was some iridescence visible in high level cloud seen from the IAA solar observing event at Carnfunnock this afternoon - I took this image which is a lot more subtle than the ones above but nevertheless shows the effect clearly - round the top of the cloud as well as down the lower right where the hidden Sun is.
(http://www.bbhvig.uklinux.net/IMG_0867.jpg)
13:31 UT 9th Aug 2008. Canon 40D, 70mm, 1/1600 @ f/8, ISO 100

BTW we even got a few gaps in the cloud and the Sun was seen :o


Title: Re: Iridescent Clouds!
Post by: Roman White on August 19, 2008, 10:49:43 am
What type are these clouds (photo #1)? Altocumulus? I have seen something similar on Aug.15 in Feodosiya, Crimea


Title: Re: Iridescent Clouds!
Post by: Steveo74 on August 20, 2008, 08:43:12 am
Hi Roman! I'm still learning myself about cloud formations, I'd say you would be right with Altocumulus...   ;D


Title: Re: Iridescent Clouds!
Post by: Roman White on August 20, 2008, 12:05:16 pm
Yes, Steven. I'm also not very common with cloud formations. Sometimes it could be hard to define what type is a cloud above your head, and when looking on the photo it is even harder.


Title: Re: Iridescent Clouds!
Post by: brianb on August 20, 2008, 01:05:03 pm
Quote
Sometimes it could be hard to define what type is a cloud above your head, and when looking on the photo it is even harder.
Indeed, with a photo the sense of scale is often missing.

But cloud classification is not a precise science anyway. There's a continuous spectrum between e.g. altocumulus and cirrocumulus; sometimes it's really clear as to whether a particular cloud formation is one or the other, sometimes it isn't.

All you need for iridescence is for the cloud particles to be small and of a very uniform size - this is really an indication that the cloud is either forming or dispersing (or sometimes both, on the opposite sides of a lenticular formation) and in these conditions the visible indicators of cloud type (like shadowing in altocumulus) are often missing.

The cloud formation with iridescence which I photographed (above) was quite definitely altocumulus though of an unusually thin and transparent kind.


Title: Re: Iridescent Clouds!
Post by: Roman White on August 20, 2008, 03:54:22 pm
(...) There's a continuous spectrum between e.g. altocumulus and cirrocumulus; sometimes it's really clear as to whether a particular cloud formation is one or the other, sometimes it isn't.
(...)
The cloud formation with iridescence which I photographed (above) was quite definitely altocumulus though of an unusually thin and transparent kind.
Exactly!
Steven's #1 photo is a good example of those "thin Ac", which are hard to define whether they are Ac, Ci or even Cc

Here some photos of similar cloud forms which I found in my latest archives:
July, 03
(http://s60.radikal.ru/i168/0808/f0/2e8cafda06f2.jpg)
July, 26
(http://s40.radikal.ru/i089/0808/a8/c119ca36e570.jpg)
August, 15
(http://s40.radikal.ru/i087/0808/74/222d7d2ebbd3.jpg)
All of them, in my opinion, are Altocumulus