Beautiful clouds decorated the sky last week over Thessaloniki, which were the reason of the impressive optical phenomena that appeared not only during daylight, but also at night!
I think it must be those clouds, called nacreous, which appear in winter and may form even higher than Cirrus and their altitude is around 15-25km (stratosphere). However, I have some doubts, if they really were nacreous clouds, because they mainly appear in higher latitudes, such as Scandinavia...
Maybe you can understand, whether it's nacreous or not, by looking at the following photos.
Beautiful colors appeared on the clouds, which were close to the sun. 
Their appearance were combined with the formation of some lenticularis clouds. Unfortunately, those nacreous clouds disappeared before sunset. That was a pity, because they can make a sunset really majestic. Only some lenticularis were still forming, as night was setting in...
The same night a corona was surrounding the moon.
That day (18/2) the min temperature was -4oC and the max +4oC. At the height of 500hPa the temperature was around -40oC and maybe this is the reason, that such clouds appeared.
Three days later, the weather was more like spring, than winter. It was warm and some Cirrus appeared at night. Luckily, I suddenly noticed a huge halo around the moon (full moon). It was really exciting, first time I see this phenomenon at night, so I tried to capture it. 
The halo is not clearly seen, but it isn't that difficult to see it, after editing the photo. 
Next day a corona surrounding the moon appeared again!
Such optical phenomena are always beautiful and if you are interested, you can find some info and beautiful photos I found here!
Nacreous clouds
http://www.atoptics.co.uk/highsky/nacr1.htm
http://en.wikipedia.org/wiki/Polar_stratospheric_cloud
http://www.cloudappreciationsociety.org/gallery/index.php?x=browse&category=23&pagenum=1
Corona
http://en.wikipedia.org/wiki/Corona_(meteorology)
http://www.cloudappreciationsociety.org/gallery/index.php?x=browse&category=33&pagenum=1
Halo
http://en.wikipedia.org/wiki/22%C2%B0_halo
http://www.cloudappreciationsociety.org/gallery/index.php?x=browse&category=32&pagenum=1
UPDATE 1/3/08: After searching for some more info in the Internet, I found out that those clouds on the photos are not nacreous.
4 comments:
Yes I am! I work on an RAF base and send hourly and special reports as my main duty. Nice blog by the way, you're very diligant!
Are you sure they're nacreous clouds? It looks more like irisation in cirrus to me. Still very impressive :)
Yes, you'r probably right...Nacreous appear in higher latitudes...
I hope I will be a meteorologist in the future, too...
Your blog keeps getting better and better! Your older articles are not as good as newer ones you have a lot more creativity and originality now keep it up!
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