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What is a halo?

So you look up in the sky and there is a rainbow. More like a fraction of a rainbow sitting below some very thin clouds. But it's not raining.


This happened today at the CCAG. I looked up westward to see an incoming cirrus cloud mass. Today happened to be the last day of the stormy weather (the TMAD warmed up to 110ºF 38% humidity today) and the last batch of 'storm' clouds moved in. But then I saw the tiny rainbow reflecting off the cirrus clouds. What could this be? It's a halo. Cirrus clouds and lots of other high clouds are cold enough to contain ice. Sun or moonlight reflects across the crystals, which creates a light illusion, and refracts light, which creates the colors of the rainbow. Kind of like how rain droplets refract the sunlight which makes a rainbow, and how a hose shooting at sunlight does as well. Halos don't always happen when there is a cirrus cloud; they require very specific angles for them to form. In fact, you probably can drive within a mile of a halo and it will disappear. There are a bunch of different types; here are some of them:


  1. Light pillars are exactly what you think they are. Close to sunset, you will see a pillar of light streaking above the sun. It is caused by hexagonal ice plates. Each ice shape makes a different halo

  2. the 22º halo is the one that i saw earlier. The light is 22º from the light source, made up with small crystals 0.0005 mm in length.

the halo spotted on November 19

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