Unusual "broken" halo produced by two different ice crystal populations.
Taken by Alan Clark on May 17, 2014 @
Calgary, AB Canada
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Camera Used: Canon Canon PowerShot SX40 HS
Exposure Time: 1/1600
Aperture: f/8.0
ISO: 100
Date Taken: 2014:06:03 14:28:03
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Details:
Unusual “Broken” halo display.
This unusual halo occurred during a day-long display that exhibited various halo forms from a relatively uniform but thin cloud cover. At the time of this rare double-character halo, it appears that a sharp transition between clouds of significantly different ice crystal types crossed in front of the Sun.
The simulation, generated by the HaloSim program written by Les Cowley and Michael Shroeder, used different crystal types in the upper and lower parts of this halo. The upper halo simulation used 30% of horizontal hexagonal columnar crystals and 70% of hexagonal flat-plate crystals with a wide dispersion of angles of their faces to the horizontal. The lower simulation used hexagonal columnar crystals with their axes distributed randomly.
The first image is a combination of the full halo image and an equivalent simulation. The second image is of a small section of the halo around one of the sharp transitions in the halo, along with an unsharp-masked and an embossed image that enhance the features of this unusual transition in the halo.
Photographer's website:
No URL provided.
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