Saturday, 22 October 2011

Helic and Tape arc in Cirrus

In the afternoon of October 14, I observed a large halo display in Bochum, Germany.
It started at 14.25 CET (15.25 CEST) with circumzenithal and supralateral arc. During the following minutes, also the upper tangent arc, a bright Parry arc and the 22°-halo appeared, followed by both sundogs and a faint upper circular Lowitz arc on the left side. ( 1 )

At 14.50 CET, I noticed a conspicuous white arc, forming a circle around the zenith together with the CZA. A closer look showed that this circle was not really circular, but rather had the shape of an American football.

This white arc grew longer and longer, an as ist passed the supralateral arc, it turned out to be the heliac arc, clearly visible in thin cirrus clouds.
At 14.55 CET, also the upper left Tape arc appeared as a bright colourful spot on the supralateral arc. At the same time, the left part of the Parry arc grew very long, almost reaching the supralateral arc, while its upper part faded away. ( 2 )

After 15.00 CET, the halo display slowly vanished, but before it faded away, left Lowitz arc was visible for about 10 minutes, as well as a very bright part of the parhelic circle. The display ended at 15.25 CET, having showed 10 different types of haloes with up to 8 being visible at the same time.

Peter Krämer, Bochum, Germany

1 comment:

  1. That display is like the one I got back in 2006 and it had helic arc in cirrus cloud like this one one difference though is mine did not have tape arc but it did have wegener arcs.