西弗吉尼亚州上空的火焰彩虹
(原标题: A Fire Rainbow over West Virginia)
2021-08-30
浏览次数: 38
这片云发生了什么？远处卷云中的冰晶就像漂浮的小棱镜。由于其类似火焰的外观，人们非正式地称之为火彩虹，一个与地平线平行的环地平线弧。要想看到环绕水平的弧线，太阳必须在天空中至少高出58度，而在天空中，卷云在下面出现——在这种情况下，卷云呈纤维状。组成卷云的无数扁平六边形冰晶必须水平排列，才能以类似的方式适当地折射阳光。因此，环绕水平的弧线有些不寻常。本月早些时候，在美国西弗吉尼亚州的北福克山附近拍摄了这幅特色的火彩虹。
查看原文解释
What's happening to this cloud? Ice crystals in a distant cirrus cloud are acting like little floating prisms. Known informally as a fire rainbow for its flame-like appearance, a circumhorizon arc appears parallel to the horizon. For a circumhorizontal arc to be visible, the Sun must be at least 58 degrees high in a sky where cirrus clouds present below -- in this case cirrus fibrates. The numerous, flat, hexagonal ice-crystals that compose the cirrus cloud must be aligned horizontally to properly refract sunlight in a collectively similar manner. Therefore, circumhorizontal arcs are somewhat unusual to see. The featured fire rainbow was photographed earlier this month near North Fork Mountain in West Virginia, USA.