On February 20 there were a lot of cirrus shreds in the foehn area of a strong northern low pressure area. Already in the morning there appeared unusually bright sundogs and a circumzenithal arc of the same brightness in these cirrus shreds. Later also a Parry arc appeared together with parts of the parhelic circle and very bright 120°-parhelia which had an accentuated reddish rim. At 11.50 CET, another arc seemed to form above the left 120°-sundog which stayed at its position for about 10 minutes while the cirrus clouds kept moving on. As the simulation for a sun elevation of 24° shows, the position of that arc fragment is identical to the subheliac arc.
By Claudia Hinz