Between August 21 and September 3, 2017, unusual twilight phenomena could be observed in widespread parts of Germany. In most cases, the sky turned into a bright yellow short after sunset. Some observers reported an increase of brightness when this yellow glow appeared. During the following 20 minutes, the colour changed into orange and later into red with the coloured part of the sky shrinking towards the western horizon. At the end, only a narrow red stripe directly above the horizon remained. Additionally, there was a very intense purple light even during the “orange phase”. Many observers reported that the landscape also appeared in a bright yellow or orange coloured light.
At daytime, the sky appeared in a pale blue as if there was a layer of thin cirrostratus clouds. At low sun elevations, stripes and ripples appeared in this layer. Some observers felt reminded of noctilucent clouds by these structures.
In the mornings, these phenomena also appeared in reversed order.
Similar phenomena were also reported from observers in Austria, Hungary, the United Kingdom, Danmark and Iceland and showed up in several pictures by webcams in the Czech Republic.
These strange twilight phenomena were caused by the smoke of huge wildfires in Canada. The plumes of these fires ascended up to the stratosphere reaching altitudes of about 15 kilometres. Then they were transported over the Atlantic Ocean by the wind.
When travelling through the northeastern parts of the USA to observe the total solar eclipse which ocurred on August 21, Andreas Möller could take photographs of these plumes of smoke.
Author: Peter Krämer, Bochum, Germany
From August 2 to August 16, I was on holiday on the Greek island of Karpathos. Already on the first evening there, on August 2, I was astonished about an intense purple light with crepuscular rays. These purple twilights appeared every evening at about 10 minutes after sunset an were visible for about 10 minutes. This continued over the whole two weeks, except on August 4, when the purple light was only a bit brighter than normal.
The most intense purple twilights occurred on August 9 and 11, when even the water of the Mediterranean Sea turned purple during these twilights.
Between August 9 and August 14, the purple twilight was followed by an intense, dark red glow above the cloudless western horizon, which was visible until about 35 minutes after sunset. Just before sunset, the sunlight illuminated the Kali Limni, the highest mountain of Karpathos island (1215m) in a rose and violet shade, causing a kind of alpenglow which was visible from the beach.
As I learned after my return at home, these unusual twilight effects were caused by volcanic clouds emitted by Mt. Nabro in Eritrea in June and July.
Author: Peter Krämer, Bochum, Germany
In August 2011 I noticed colourful twilights with purple light and venus belt in France and Germany during some days. These intense sunsets resulted from volcanic aerosols in the atmosphere.
On August 12, 2011 I could take some photos of the sunset with the purple light near the Gorges du Verdon (Provence/France). Additionally, there were beautiful crepuscular rays in the sky (photo on top).
Back in Germany I could photograph also such fantastic sunsets with crepuscular rays and anticrepuscular rays.
Author: Daniel Eggert, Augsburg, Germany
In the morning of November 11, 2010, Anke Morbitzer from Gladbeck, Germany could enjoy the alpenglow from above during a flight from Milan over the Bern and Pennine Alps. Especially impressive were the shadows of the mountains being projected upward into the haze. Just before, also the upcoming twilight with its impressive colours had been very exciting.
After the twilights had been getting normal through the past three weeks, where hardly any volcanic aerosoles from Sarychev volcano had been measured, I was very astonished when I saw an intense purple light with crepuscular rays about half an hour before sunrise (sun elevation at -6°) in the morning of November 17. The crepuscular rays crossed the whole sky near the horizon, converging at the antisolar point (1 – 2 – 3).
Of course I immediately asked my colleagues from the Hohenpeissenberg observatory about the phenomenon. And I got a very surprising answer:
At that moment there were two different layers of dust from the Sahara desert above us, a lower one at an altitude of about 8.5 kms with dust from the western parts of the Sahara, and a higher one at about 11 kms, which contained dust from the eastern part of the Sahara. There were two different currents of air at higher levels which overlapped each other above the Alps.
It is new for me to learn that such twilights are also possible in desert dust, just as this dust up to now only caused a kind of certain dimness in the air. But at that moment there was no desert dust directly above us; I only looked into the layers of dust.
However, there was an extra bonus on the next morning. Unfortunately could only watch it from the valley:
Author: Claudia Hinz, Brannenburg, Germany
On June 12, 2009,one of the most active volcanoes of the Kuril islands near Kamtschatka, which is situated near the northwestern end of the island of Matua, Sarychev Peak, erupted.
A NASA picture taken from the ISS gives an impressive sight of the eruption. Ashes have been ejected up to 20 kms into the atmosphere. Only a few hours after the eruption, the sulfur dioxide cloud of the volcano covered an area of2.407 kms in width and 926 kms in length above the island. During the following weeks, the aerosoles spread over the whole northern hemisphere.
Since the end of June, also in Central Europe unusual twilights are observed. The up-to-date Lidar measurement from the Hohenpeissenberg observatory in Bavaria shows three aerosol layers in altitudes of 15, 18 and 22 kms in comparison to the eruption of Mt. Pinatubo. It is very interesting that the layers in 15 and 18 kms have come here with westerly winds passing over Alaska, Canada and the Atlantic Ocean, while the layer in 22 kms has been transported to us by stratospheric easterly winds passing over Asia (Russia/China). So the volcanic aerosoles havetravelled around half of the planet in two different directions (the lower layers eastward and the upper one westward), meeting again here over Europe. I think this is worth to be mentioned.
On July 4, Peter Krämer observed the caracteristic crepuscular rays (picture above). On July 13, Reinhard Nitze photographed the most spectacular volcanic twilight in Barsinghausen near Hanover (Fig. 3). In his picture, the high aerosol clouds can easily be recognized. These clouds still receive sunlight while normal cirrus clouds are already within the shadow of the earth.
During the past few days, there were also noctilucent clouds visible, which passed over to the reddish aerosol clouds in lower layers. There should be unusual twilights visible also during the following weeks.
Posted by Claudia Hinz
On August 7, the Kasatochi Volcano, situated on the Aleutian Islands near Alaska, erupted. Clouds of ashes and sulfur dioxide were ejected up to 15 km into the stratosphere.
During the following 3 weeks, the volcanic clouds spread over the whole northern hemisphere, causing widespread intense twilight colours and often also crepuscular rays. These were first reported from Northern America during mid August, but at the end of the month, these “volcanic twilights” were also observed in Europe.
In the evening of August 29, several observers reported a strange and intense yellow light around sunset, followed by a purple light. Some of them were reminded of the unusual twilights between February 17 and 20, which were caused by PSC.
On August 30, skies were clear over Germany, and so many observers could see a kind of silvery cloud stripes a few minutes before sunset. These stripes were orientated north-south and at first glance looked like cirrus or cirrostratus clouds. But during the day these clouds had not been visible at all, and when looking at them carefully, one could see that they were higher than normal high clouds. The contrails of some airplanes were obviously below these clouds, and as the contrails turned reddish in the light of the setting sun, the clouds still remained bright. So they must have been floating higher up in the air, somewhere in the
After sunset, the clouds got a more brownish-yellow hue, but turned pink only about 20 minutes after sunset. Some observers also reported intense crepuscular rays. The purple light faded about half an hour after sunset.
In the morning of August 31, the colours and cloud stripes could also been observed. In the evening, a cold front with thunderstorms approached the western parts of Germany. While even the tops of the cumulonimbus clouds were already dark, the stratospheric clouds still lay in plain sunlight. That evening, instead of the regular stripes of the day before, they looked more like irregular waves.
During the first days of September, the strange twilight colours could still be observed over southern Germany, while for the rest of the country morning and evening skies looked quite normal again.
But as there are still volcanic ashes in the stratosphere, the colours may return. So keep watching the skies before sunrise and after sunset.
Author: Peter Krämer, Bochum, Germany
On August 13, I could witness another atmospheric phenomenon in Bochum, Germany.
In the evening, about half an hour before sunset, a rainshower approached from the west. Behind the shower, the sky cleared up very rapidly, so that the low evening sun could shine through the veil of rain. This caused very strange light conditions I never experienced before.
First there was a yellow squall line visible, followed by a bright yellow veil of precipitation. As it came nearer, another shelfcloud-like structure passed from south to east. This cloud was also strangely illuminated and showed orange and brownish colours.
The squall line in the western and northwestern part of the sky turned more and more orange, too, while the rain got an intense and bright yellow. The whole landscape was bathing in a strange and intense yellow light with orange-coloured clouds above and in the east.
When it began to rain, a rainbow appeared in the east, visible as a full semi-circle. The blue part of the bow had already gone, only red, yellow and a faint green were visible.
Then the sun sank beneath the horizon, and all colours faded away within a few minutes. So there was no really red rainbow that evening, but nevertheless it had been very impressive to me.
Author: Peter Krämer, Bochum, Germany
Between February 17 and February 20, 2008, large parts of Western Europe witnessed a seriesof unusually bright morning and evening twilights.
A few minutes after a quite normal sunset, the western skies began to burn in a strange yellow light which was bright enought to illuminate the landscape and giving a quite unreal touch to houses and trees.
Some minutes later, the yellow light in the west became surrounded by a brownish rim, turning into purple within some minutes. The yellow part of the sky slowly shrank towards the horizon, turning into orange and later into red and crimson. Some observers also reported of a dark, brownish-red light in the east which surrounded the whole horizon reaching up to 10° high.
The strange lights and colours in the sky were visible for up to about one hour after sunset. A similar “light-show” also appeared in the morning, starting with a crimson light over the eastern horizon and ending with the bright yellow light short before sunrise. The yellow illumination of the landscape could even be perceived through layers of low clouds (stratus) in some areas.
These in some cases weird-looking twilights were probably caused by an outbreak of polar stratospheric clouds (PSC). These form at temperatures below -78°C in the stratosphere, at an altitude of about 20 – 25 km above the ground.
Soundings made at several stations showed that temperatures in the stratosphere really were unusually low over western Europe; up to -87°C (De Bilt) were measured, the lowest since measurements began in the 1980s. This makes the formation of PSC over a large area possible. Some photographs also show faint structures in the light, giving hints that they actually were caused by PSC.
Polar stratospheric clouds have never before been observed so far south. Normally, they can only be seen from Scandinavia, Canada and Alaska. Only in 1999 there was a confirmed observation of PSC from northern Germany.
Authors: Peter Krämer, Bochum & Claudia Hinz, Brannenburg