A halo among the fibrous cirrus

Cirrus_fibratus_Halo_HannePernilleRyel_OsloNorway_6Sep2013

Hanne Pernille Ryel
Location: Oslo, Norway
Date: 6 September 2013

Cirrus clouds appeared wispy and fibrous across the late summer sky as strong upper-level winds (more than 6 km or 20000 ft above the ground) carried the ice crystals. These ice crystals, specifically those with a columnar shape, bent the sun’s rays to form part of a 22-degree halo around the sun. The sun’s light enters one side of this columnar crystal, is refracted (bent) as it enters and bent again as it exits another side of the crystals resulting in a total bending of 22 degrees from how it enters, with a separation of the light into the colors of the visible spectrum (ROYGBIV).

Here is a diagram showing this refraction through a column ice crystal from the University of Illinois Urbana-Champaign’s online weather guide (http://ww2010.atmos.uiuc.edu/(Gh)/home.rxml)

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