Circumhorizon Arc, Parhelic Circle and Circular Halo over Whiting NJ on July 22, 2007
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Jet Stream
Circumhorizon
Arc, Infralateral Arc, A Parhelic Circle and a
Circular Halo.  Parhelic and Circular Halo  Circumhorizon Arc
Circumhorizon
Arc
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The Jet Stream was moving quickly to the North over New Jersey that day. An Upper High Pressure System brought cold Cirrus Clouds from the North, while warm Cumulus clouds came from the South. The Sun was at 68 degrees elevation when the Circumhorizon Arc was imaged. The Sun was at 62 degrees elevation when the halo and circle were imaged. Hexagonal Column Crystals most likely formed these Arcs, as per the simulation. HaloSim was run to produce this simulation. The odds of a Circumhorizon Arc forming are ~ once every ten years. Parahelic Circles form ~4x per Year Circular Halos form 100 x per Year. http://www.atoptics.co.uk/halo/whyinfr.ht  There was discussion that the Circumhorizon Arc may have been a rare 46 degree Halo. However, when a simulation was run for a 46 degree Halo, no Parhelic Circle would form, just a 22 degree Halo. As a Parhelic Circle was visible, that rules out a 46 degree Halo. When I first saw this I thought it was an iridescent cloud. Only the Ice Crystals in the upper atmosphere. Scattered the sunlight. Even on a hot July day, there is ice in the air. The Cumulus clouds are moving quickly to the east, while the Cirrus are moving to the South. The arc is playing hide and seek. A wide angle view (27 mm focal length) reveals multiple pieces of the arc that are visible. Judging by the wide field of view a Circumhorizon Arc would stretch among the separated Cirrus clouds. The Circumhorizon Arc dissipates, while the Parhelic Circle and Circular Halo become prominent. Please see the above image for the Parhelic Circle and Circular Halo. Earth Science Picture of the Day has a wonderful photo of the Circumhorizon Arc as well, taken from Pilesgrove NJ. A special Thanks to Les Cowley ( Atmospheric Optics) for his work on determining the phenomon in play. |
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