|Eyjafjallajokull Skies ~ Over the last few days (April 17 - later developments 1, 2) an ash cloud from the Icelandic volcano has carried over North Europe.
The top image was taken by Hans Nienhuis in The Netherlands on the evening of April 16. It is remarkable for what is does not show as well as its subtle sun pillar. “The sunset was not really reddish. There was just a faint sun pillar, like those seen so many other times. But more interesting is the clean sky around it - no contrails at all. Due to the volcanic ash in the upper troposphere all the commercial air traffic was shut down in Holland, like that in Great Britain also.
I'm not really old, but I have never seen this in my whole life, and probably will never see it again. A contrail free sunset and thus a faint sun pillar, not caused or disturbed by any anthropogenic aircraft activities. Despite it's "usual" appearance a unique view!” Aircraft over a large part of Europe were grounded.
The ash is in a number of thin layers in the troposphere and of fairly large particle size. Some is already falling out. This contrasts with the very fine ash and sulfate aerosol of larger and more explosive eruptions that circulates the planet higher in the stratosphere. The Icelandic larger particles are Mie rather than Rayleigh scatterers.
Thus – and notwithstanding lurid sunset images appearing in the media – there have not been colourful sunsets or twilights outside the normal range of their appearance. Instead, sunsets have so far been subdued, hazy and perhaps slightly yellowish. Twilights have had a slightly more yellow-white twilight arch with a whitish glow near the horizon later on.
The second image shows a Bishop’s Ring over Deventer, Holland on the morning of April 16 and imaged by Peter Paul Hattinga Verschure. These rings are essentially the aureole of a huge corona produced by diffraction by small particles.
The two lower images show Saturday’s (17th) dawn in Hungary pictured by Monika Landy-Gyebnar. “I was out to look at the sunrise. It was really pale. The effect was very similar to that of African dust when sometimes it reaches our region in late spring, Mr. Mie was doing a great job! Even the shadows had no contrast on the ground. The relative humidity was about 75%, so it could not be vapour or mist.
But besides being pale this was a really impressive sunrise. There were no planes up in the sky! No contrails, no glints of light on the aircraft, no noise, only the stunning beautiful song of some nightingales nearby.”
Images ©as described and shown with permission.