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
For a few days since 13 Aug. 2011, observers in Germany have noticed colourful twilight phenomena like intense crepuscular rays, and thus were reminded of the volcanic twilights from the Kasatochi and Sarychev. An aerosol layer is presently verifiable in the entire northern hemisphere, indeed. At the moment, measurements from the Meteorological Observatory Hohenpeissenberg (Germany), Evora (Portugal), Mauna Loa (Hawaii), Ukraine and Russia, all record this layer at heights between 12 and 19 km.
Most probably, these volcanic aerosols can be traced back to the Nabro Volcano in Eritrea. Despite having undergone no historically reported eruptions, the Nabro Volcano erupted shortly after local midnight on 13 June 2011, after a series of earthquakes ranging up to magnitude 5.7 in the Eritrea-Ethiopia border region. Its ash plume was observed on satellite images and drifted to the west-northwest along the said border, spanning a width of about 50 km and extending for several hundred kilometers westward in the immediate hours following the onset of the eruption, while reportedly reaching a ceiling near 15 km of altitude. The ash cloud also disrupted air traffic, as United Arab Emirates based flights were cancelled along with Saudi Arabian Airlines flights. Egypt’s Luxor International Airport was placed in a state of emergency for a while.
This aerosol layer seems to have been present since 15 July 2011 as shown by the Lidar measurements from Hohenpeissenberg.
More pictures and plots of the measurements are summarized here (PDF download):
Link to the NASA-Website with further measurements.
Support for this documentation on behalf of the Meteorological Observatory Hohenpeissenberg is gratefully acknowledged.
Author: Claudia Hinz, Brannenburg, Germany