On June 14th, 2014, I could observe green flamelets at the upper rim of an altocumulus cloud from Mt. Zugspitze (2963 m above sea level). The cloud was located left from the rising sun, and the phenomenon lasted from two minutes before the visible sunrise until shortly after it. At the moment of the astronomical sunrise the green flamelets at the cloud vanished. Additionally, green and blue rims appeared at the sun’s disk (see pictures 1 – 2).
I already observed a similar phenomenon a few seconds after sunset on September 24th, 2013, from Mt. Zugspitze. However, I could only take a single photograph of it. As there were seemingly no other reports about green cloud rims I decided to let the matter rest at that time. It was only after the second occurrence that I re-visited the case of the older observation.
When doing a new search for similar reports I encountered an observation from by Robert Wagner, January 7th, 2008, who also recorded green cloud rims during sunset on La Palma (2136 m above sea level).
No other documented observations could be found on the internet so far.
We cannot offer a complete explanation yet. It may be that the cloud edge, when illuminated from behind, acts as a separate light source and the green flamelets are then caused by the refractive dispersion of a weak mirage effect. This is consistent with the presence of blue and green rims at the sun, which indeed have been observed in all three cases. Furthermore, all observations were carried out from high mountains, from where the true geographic horizon already lies below zero elevation, and even the ordinary elevation shift due to refraction is already pretty high due to the long light path through the atmosphere.
More ideas and reports of similar observations are welcome in any case.
Author: Claudia Hinz
Edit 21th March, 2017:
I would like to add a video to this article, in which I was record the green rimmed clouds on the Mt. Fichtelberg/Ore Mountains on 20-12-2016.
I am currently working as an astronomy lecturer for a German tour group sailing the Norwegian cost on the Hurtigruten vessel MS Nordnorge. On October 8, around sunset we crossed the Vestfjord a stretch of open sea between the Norwegian mainland and the Lofoten islands. Since I expected to see a green flash, I prepared everything to capture the phenomenon.
I was not disappointed. Through my 600 mm telephoto lens I could clearly see the green an blue flash. Closer inspection of the images afterwards also revealed that I also manage to capture a purple flash in the last fractions of a second before the upper limb of the Sun entirely disappeared.
I am attaching a panel which collects crops from the last 30 images in my picture series which show the development of the phenomen over the last 12.66 seconds (according the time stamps created using GPS time). I have also created a very nice gif animation of the event, which you can find (along with additional pictures) on my homepage.
Author: Benjamin Knispel, Hannover, Germany
On June 06, 2012, the rare constellation of the planet Venus crossing through the solar disk could be observed from the day side of the earth.
When in Germany the sun rose, the Venus transit was already in its final stage. Where the sun passed through differently dense air layers during its rise, the mirage phenomenon was visible, i.e. the sun as well as Venus appeared distorted or as a combination of multiple images. These effects are due to the different bending of the light waves at air layers of varying density. Moreover, an incident ray of light will be reflected at the interface between cool and warm air. When there are more than one of these interfaces, multiple reflection might occur.
Rico Hickmann could even observe the Green Flash during the Venus transit from Dresden: “I was incredible lucky with respect to the weather. Yesterday evening, it was still very cloudy, and after the end of the transit there were again clouds filling the sky. Before sunrise, a light pillar could be seen, that served as a pointer towards the sun. The sunrise over Dresden was spectacular, Green Flashes and disconnected segments… I’m still speechless.” Here are some more incredible pictures from this series: 1–2–3–4–5
Another spectacular image of a triple Venus was obtained by Frank Killich, who observed the Venus transit from the Wolfswarte in the Harz mountains (916 m / 0 °C). The image is a single frame from a HD video file.
Some more and equivalently wonderful observations were reported. Alexander Haussmann made a Video showing a triple Venus, green segments and distorted Venus passing through different air layers that were responsible for the green segments some seconds before. Further examples of impressive green flashes are the pictures of Andreas Möller, taken in Zinnowitz (photo and and animation as gif or MP4 [better quality]) and Hermann Koberger from Fornach, Austria (1–2–3).
Almost every times when on Mt. Wendelstein the sun is setting behind the main chain of the Alps in very clear air, I can watch the green and the blue flash. These phenomena were especially impressive on February 2, 2011, when the sun sat behind 2962 meters high Mt. Zugspitze, and on March 3 at sunset behind the 1801 meters high Benediktinerwand (series 2).
Author: Claudia Hinz, Brannenburg, Germany
After a bleak low stratus day, I decided to escape from the fog in the evening of the 13th of January 2009. I drove to the nearby Witthoh (Hegaualb, western Lake Constance, Southern Germany). There I wanted to record the rise of the moon – at least I hoped for a clinched moonrise, because of a prevailing atmospheric inversion.
Along the 860-metre-high Witthoh there was still a temperature of -10 degree centigrade. Two kilometers further away and 100 m higher the temperature was just 0 degree centigrade. Consequently, a very remarkable temperature layer existed in this region.
On the pre-calculated time, the moon’s upper margin pushed over the horizon.
What happened afterwards exceeded my boldest dreams. A “bubbling” of the rising moon followed as I had never seen it before.
Three times, approximately half of the rising moon completely detached from the lower half with red lightning.
The moon “boiled” on the upper half and it let vanish red and green rays upwards.
Only after circa 15 minutes, the moon calmed down completely.
Posted by Harald Wochner
This sequence of sunset images was taken from the Canadian prairies, looking ovcr the Rocky Mountains from a distance of about 100 km, in mid-December, 2007. The remaining solar limb shows distinct blue colour following green tints, but the sequence ends with a faint red band, which is probably caused by faint clouds on the horizon.
Author: Alan Clark, Canada
On December 26th I climbed the 1000m high Plettenberg to observe and photograph the setting sun with 1m focal length to look for the green flash. The transparent air and an inversion layer were promising, however a few clouds with their top at approximately the same altitude were disturbing. The upper limb of the sun turned out to be quite turbulent showing green rims and flashes, but also some blueish apparitions.
Why a blue flash?
A green rim of the setting or rising sun occurs due to differential refraction in the atmosphere. If conditions are extremely clear, also the blue light has a chance to get through, and there might be even a blueish rim. With a temperature inversion layer in the atmosphere, upper segments of the solar image might get separated from the rest of the solar disc. In the final moments of these elusive segments they do appear green and sometimes even blue (green or blue flash). However, it is not clear to me why in my observations both happens. Most last moments are green, whereas the third frame shows a blue color and at the same time other turbulent segments with a green color. Should not every segment turn from green to blue, at least in the very last visible moment?
Maybe something more than just clear air plays a role for a blue flash visibility!?
It is the first time I see green and blue flashes simultaneously in one image. I strongly encourage other observers to record video data to show these effects in higher time resolution.
Author: Till Credner