Volcanic Twilights

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 of 2.407 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 have travelled 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.