“Shadow-Corona” observed on top of Fichtelberg and Zugspitze
It is not unusual that one can see some shadow rays in the sky due to clouds in front of the sun. One can also observe coronas in consequence of diffraction of the sunlight or moonlight by small waterdrops of thin clouds. But it’s a rareness to notice both phenomena at the same time.
It would be even more interesting to be at the top of a mountain with the clouds very close. So, thin wisp of clouds racking only a few meters over your head. Sometimes these wisps cause also beautiful coronas. If a building or a mast obliterate the sun, its superstructures can cast long shadows into the clouds.
Kevin Förster observed both phenomena on top of the Fichtelberg Mountain (Erzgebirge) on January 24th, 2015. This time the sun was behind the tower of the weather station and the different appliances at the top of it afforded the shadows. The origin of the clouds was found in the “Böhmische Becken” situated at the southern slopes of the mountain range. Therefrom they drifted into the direction of the Fichtelberg Mountain. First it consisted of ice crystals and caused ice halos. Over the Fichtelberg there were widespread clouds of waterdrops, which caused a nice corona additional to the shadow rays.
A similar event was observed on Mount Zugspitze in the Bavarian Alps by Claudia Hinz on May 5th, 2013. The sunlight was blocked by a mast and its shadow fell on very thin clouds. Simultaneously there was a bright corona. (1–2–3–4–5)
In both cases the sun was lower than the top of the tower so that the shadow of the tower was projected on the cloud layer above. This is a very uncommon phenomenon.
Corona around reflection of Sun
In the evening of June 6, 2014, a reflection of the sun appeared in an inclined window pane of the pyramid-shaped restaurant building on the top of Mt. Zugspitze, while shreds of cumulus clouds coming from the valley passed by. In these shreds not only the shadow of the top of the building was visible from time to time, but there also appeared a distinct corona around the reflection of the sun.
Author: Claudia Hinz
This photograph was taken by Hans-Jürgen Heyen from Meerbusch. “I discovered the glory effect in August 2012 at the pond of Hugenpoet Castle in Essen-Kettwig. It made me take a closer look at the water because one tends to think that there are mineral oil products on the surface. But there were gigantic carps in the pond and also some big golden fish which looked like koi-carps. And also a beautiful demoiselle flew over the water. And especially this species of dragonflies is very sensitive against environmental pollution. However, what really was there in the water were algae which caused a significant clouding of the water, and this obviously was the reason for the formation of the algae glory.”
These coronae are caused by light diffraction on very small particles. In most cases, they are caused by algae, but there were also such coloured rings observed around pollen which had landed on the water surface. The coronae are caused when a ray of light is split up into partial beams by such a small particle. These partial beams go on into different directions and interfere in the observer´s eye.
Just like pollen coronae, also algae coronae are not always round. When there are unusually shaped algae are involved, also their ring systems on the water surface can be ovally shaped or have bright spots.
Irregular Moon Coronae
Colourful coronae around the sun and the moon are caused by light diffraction at water droplets in medium level clouds. Normally these coronae are circular like this case, as they indicate that the droplets in a cloud are all of about the same size. If only a 10% of the droplets vary in size, the corona already appears blurred. (see left figure)
In this observation, made by Bertram Radelow at Davos, Switzerland, in the evening of October 10, 2011 at moonrise, the corona showed very brilliant colours but nevertheless was rather “egg-shaped”. Bertram Radelow said the corona appeared in very thin clouds which could not be seen with the naked eye. Probably there were thin orographic clouds (as can be seen here). In these clouds, droplets are often largest in the centre of the cloud and getting smaller gradually towards the rim, so that the colours are preserved because in a given plane the droplets are still of about the same size.
In this example it looks as if two layers of clouds with different sized droplets are positioned above each other, causing a kind of break in the gradient of the corona.
Goat Willow Seed Corona
Around noon on April 22, 2011 (Good Friday), I went to a hedge near Limburg (Hesse, Germany). As the weather was sunny and dry, some goat willows (Salix caprea) sent a large amount of seeds into the spring air. Together with the bright mid day sunshine, these caused some surprising effects. Often there was just one bright area around the sun (1–2–3), but from time to time a colourful corona appeared in the seeds.
Author: Gerrit Rudolph, Hesse, Germany
Unusual corona around the moon
In the evening of February 14, 2008, an orographic cloud similar to this one formed above a sea of clouds under the influence of foehn wind above Mt.Wendelstein (1838m) in the Bavarian Alps. In this orographic cloud, an corona appeared around the moon which was more intensive and larger than any corona I had seen before. 4 systems of rings were clearly visible. The intensitiy leads me to the conclusion that all water droplets in the cloud were of the same size.
As I had a position very close to the cloud, the corona was extraordinarily large. A comparision to the constellation of Orion shows that it had a diameter of more than 20°. Below its lower part, the corona turned into a faint pink and green iridescence, indicating that the droplets were smaller towards the rim of the cloud. And it was also interesting that the thin cloud as well as the corona did not show greater changes in intensity and shape for about 4 hours. They only dissolved when the foehn wind broke down and the clouds of a masked upper level cold front came up.
Author: Claudia Hinz, Brannenburg, Germany
Icy window corona
At the beginning of this winter season at a cold morning – dark outside – with a thin layer of hoarfrost on the inner side of the bus windows I’ve noticed that the light of the street lamps’ light was not simply scattered on the windows, but having colorful corona around them. At that time I had no camera with me… All along the winter I was waiting for the same display each morning when some ice was on the bus windows, but for long weeks I haven’t met with such spectacular phenomena again.This day was my day on 24th January. Very thin layer of frost was on the inner part of the windows, (with some frost ferns too by the corner of the window frame), mainly this layer was made of small uniform ice crystals made of frozen vapor droplets, we might call it an ice film, it was about 0,1 mm thin.All the lamps outside had a corona, no matter how far the lamp was.The street lamps with white light had the most beautiful color range, the orange colored light of sodium vapor lamps had a less distinct colors and they were a bit moved towards the reds. Not only the street lamps’ corona was seen on the ice layer, but a much less spectacular corona around the reflection of the inner lamps of the bus too! At the part of the frost ferns pattern the corona became irregular in shape. When the lamp was near the window I could also see the bigger outer rings of the corona. Almost the same phenomena appears when simple water vapour is on the windows, but that one is really less poor in colors compared to the ice film corona.This was the first time when I could take photos of a corona produced by ice crystals. It’s a pity, I could not take close-up photo of the ice layer itself (the bus was driving me to work so it was permanently moving).
Photos are collected here: The only afterwork was some noise reduction and size reduction. It was totally dark outside, so the pics were taken with ISO200 – ISO400; aperture F4 – F5,6; exp. 1/15 – 1/25 sec. auto white balance; without tripod or any kind of help to avoid moving.I wonder if the same phenomena would appear if the outer side of the windows would have a layer of hoarfrost on it. It’s only weather’s turn to show it up!
Author: Monika Landy-Gyebnar, Veszprem, Hungary
Unusual Coronae & Sunsets – Finland
Very large coronae were observed in Southern Finland at the beginning of May 2006. Their radius was about 45° and they had a bluish disk and a brown ring. The sky was very clear and quite dark outside the corona. Also, very beautiful red sunsets were seen on those days.
The phenomena were visible on many days between May 2-11 and were possibly produced by smoke carried from Eastern Europe.
In the above corona image taken on 11th May a small segment of another photo has been added to show the size of 22° halo for comparison.
The sunset was photographed on 4th May.
Large coronae can be seen during very warm weather periods when the sky is usually hazy. This was the first large corona seen in Finland since the Bishop’s rings of 1991-1992. Smaller coronae (radius of about 5°) with a blue disk and brown ring have sometimes been observed.
[Text & Report: Jari Piikki, Juva Finland]
Very large corona in Chile
This corona was photographed in December 2000 while camping at the El Tatio geyser field at 4300 meters elevation in the Chilean Andes. The corona radius is approximatly 50°. Blue inner disk extends to about 35° from the sun. In between the blue and red, a green band was seen visually, but it was not reproduced on film. Altocumulus clouds were developing from the stuff that made the corona. The corona may be related to the dust that is released in large amounts in the air from some mines in the area.
Cyan saturation was increased in the photo to make the inner blue disk better visible. Otherwise the photo is as scanned from the slide.
Posted by Marko Riikonen