Saturday, 31 May 2008

Subhelic arc in Finland

A halo display was observed on 28 May 2008 in Oulu, Finland. It was reported even by local newspaper Kaleva and some photos sent by readers were published - see 29.5.2008 photos ( 1 ). According to those photos, the display did have a very strong and colorful supralateral arc with great circumzenith arc in the earlier stage.

First photos were reported an hour earlier than I noticed the display. When I was outside the display was not very bright anymore ( 2 ).

Soon a faint white arc got my attention at atzimut around 100 degrees and high above horizon. It was first faint and hard to see and it also disappeared for a moment. Toward the end of the display, the arc got better intensity and lenght. The halo was a subhelic arc from column oriented ice crystals. An arc located this way could be also be a heliac arc, but no halos related to Parry orientation was seen. Subhelic arc was already visible as a faint and short arc in some photos which I took before I noticed the arc.


  1. Nice catch Jarmo! The sky here is blank with the exception of common halos but nothing rare.

    Did you hear about my two hour long elliptical halo display?

  2. Does another copy of this image exist? The image ref above is broken-404.