Budapest Circumhorizontal Arc
September 12, 2007
A spectacular halo display was visible over central Hungary on June 8, 2007. The circumscribed halo, circumzenithal arc and parhelia were all easily observed from Budapest to Veszprem. Later that morning when the Sun was high enough, a beautiful circumhorizonal arc appeared (over the domed structure above). Rarely viewed in central Europe, our hearts missed a beat when we first caught sight of the "shocking arcus," as it was referred to by Mark Laczko, one of our sky-watching friends. We watched in awe as it changed hue from mostly reddish to green and yellowish -- it was just so beautiful and dream-like.
The Sun must be more than 58 degrees above the horizon in order to see the circumhorizontal arc. Ice crystals in cirrus type clouds are responsible for these stirring arcs. Sunlight enters the vertical side faces of ice crystals and exits through their lower horizontal basal face.