Rare Arcs at High Sun
A beautiful ice halo display captured by Peter Stone north of Cahors in the Dordogne, France.
©Peter Stone

The top wide angle image is centered almost overhead. A circumscribed halo made by horizontal column crystals encircles the 57° high sun. Within it, randomly oriented ice generates a very weak 22° halo. A complete parhelic circle rings the zenith and passes through the sun.

The rarities are the two arcs from Parry oriented column crystals. The one above the sun is the brightest and stretches to eventually touch the parhelic circle. There is also a lower Parry arc just visible in the enhanced image at lower right. Parry arcs are infrequent - those at high sun the more so.

An added touch is the rare Wegener arc (lower image) looping both inside and outside the parhelic circle. Its inner loop touches the circumscribed halo above the sun. The outer loop is tangent to the circumscribed arc beneath the sun.

At right - the scene computed by HaloSim


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