火彩虹，又称日载、环水平弧或环地平弧，正式名称为日承，是一种发生在大气层中罕见的自然现象。火彩虹并非真正的彩虹，与火也没有任何关系，由于它看起来像是在天空中自燃的彩虹而得名。

要出现这样的自然现象，须满足发生条件：

环地彩虹弧现象是一种发生概率极低的罕见现象，一般发生在太阳位于高空位置，其光线穿过高海拔带有较多冰晶的卷云层形成的情况下。带有冰晶的卷云层折射光线形成不同可视光谱的波段，由于其罕见性，迄今火彩虹现象很少被拍摄到，是极罕见、宛如童话般的胜景奇观。古人常称伟人降生时天空彩云五颜六色有如火烧，即指此现象。

-photo taken by Shayla Doering

A circumhorizontal arc is an optical phenomenon - an ice-halo formed by the refraction of sun- or moonlight in plate-shaped ice crystals suspended in the atmosphere, typically in cirrus or cirrostratus clouds. In its full form, the arc has the appearance of a large, brightly spectrum-coloured band running parallel to the horizon, located below the Sun or Moon. The distance below the Sun or Moon is twice as far as the common 22-degree halo. Red is the uppermost colour. Often, when the halo-forming cloud is small or patchy, only fragments of the arc are seen. As with all halos, it can be caused by the Sun as well as (but much more rarely) by the Moon.