Upper Concave Parry Arc
December 14, 2003
This is one of many photos I took of a remarkable halo display that had at any given time 6 different rare halos. One of them can be seen here, the upper concave parry arc. This peculiar arc was named for Admiral Parry who described then in his voyages trying to discover the Northwest Passage. It's found just above the common 22 degree halo. Parry arcs are formed by columnar, hexagonal (pencil-shaped) crystals having their long axes in a horizontal position so that a pair of opposite side faces are also horizontally oriented. The other arc visible on this photo is the circumscribed halo, which is the arc tangent and above the 22 degree halo.
Other optical treats, not visible here, included the parhelic circle, dazzling parhelia, infralateral arcs, 120 degree parhelia, all three Lowitz arcs, and 46 degree halo. A truly amazing display!