circumhorizontal arc


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circumhorizontal arc

[¦sər·kəm‚här·ə′zänt·əl ′ärk]
(optics)
A halo phenomenon consisting of a colored arc, red on its upper margin; it extends for about 90° parallel to the horizon and lies about 46° below the sun.
References in periodicals archive ?
An 'upside down rainbow' or circumhorizontal arc, is an optical phenomenon formed by the sun shining on and reflecting off ice crystals in high level cirrus clouds to form a halo.
Scientists say a circumhorizontal arc is an optical phenomenon - an ice-halo formed by plate-shaped ice crystals in high level cirrus clouds.
What I'm describing is an ideal display of the circumhorizontal arc.
But the circumhorizontal arc can occur only when the Sun is at least 58 [degrees] high.