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The Moon (lemmy.world)

submitted 11 months ago by [email protected] to c/[email protected]

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The Moon just now in the UK. No idea what is creating the halo

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[–] [email protected] 19 points 11 months ago (3 children)

Ice crystals. The old-fashioned name for it is a corona, and according to folk wisdom, a corona of that size is usually a harbinger of cold weather coming.

[–] [email protected] 7 points 11 months ago* (last edited 11 months ago)

This is the 22° halo. A Corona is an entirely different phenomenon caused by diffraction and interference of light around tiny water or ice particles, or other such particles of similar size. Halos on the other hand are formed by refraction. Here's another great resource about coronae (and pretty much every other atmospheric optical phenomenon out there).

You're correct about halo phenomena being caused by ice crystals. As such, they are most often observed when there's Cirrostratus in the sky, and that in turn is often the result of an incoming warm front. The Cirrostratus may start to thicken into Altostratus and Nimbostratus, so overcast and rainy would be the safest bet.

[–] [email protected] 6 points 11 months ago (1 children)

colder and wetter weather on the way, is what i was told

[–] [email protected] 2 points 11 months ago

I wonder if it varies regionally?

Where I live, cold almost always comes with some degree of wet, whereas wet doesn't always come with cold because we get the tail end of tropical cyclones.

[–] [email protected] 0 points 11 months ago* (last edited 11 months ago)

Thanks for sharing this. Here's one that I saw a while back