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L'esprit est comme un parapluie = il ne sert que s'il est ouvert ....Faire face à la désinformation

Parhélie en ALabama

Publié par Brujitafr sur 14 Novembre 2012, 05:09am

Catégories : #CIEL et ESPACE

Parhelia20121030HSV (2)


Photographer: David Hathaway
Summary Authors: Andra Langoussis; David Hathaway; Joseph DePasquale; Jim Foster

Yesterday's Earth Science Picture of the Day featured an inconspicuous halo phenomenon; today's features a halo display that was hard to miss. It was observed over Huntsville, Alabama on October 30, 2012 and associated with Superstorm Sandy's exhaust (upper cloud structure). The arcs and halos shown above include the 22 degree halo, parhelia, parhelic circle, Parry arc, upper tangent arc, supralateral arc, circumzenithal arc, and Wegner arc. High clouds composed of ice crystals having various shapes, sizes and orientations, some spinning some still, triggered this dazzling display.

Another halo display was noticed in and around Boston, Massachusetts on October 27, preceding the arrival of Hurricane Sandy. This display lasted 30 minutes or more. During this time, several of the arcs brightened and grew more vivid as others washed out in the clouds. Sandy was a once-in-a-generation storm -- perhaps a once-in-a-lifetime storm. It's likely that a halo display such as the one above, produced in the cirrus circulation of Sandy, may be seen only once in a generation. However, even some of the rarer arcs glimpsed in this display can be detected perhaps every year or so by a sharp-eyed and patient observer. Always make sure to protect your eyes when looking toward the Sun.

Photo details: Camera Model: Canon EOS DIGITAL REBEL XT; Focal Length: 10mm; Aperture: f/10.0; Exposure Time: 0.0031 s (1/320); ISO equiv: 100; Orientation: Normal.

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