strange evening light - Lassen Volcanic Park

5:21 p.m. on June 11, 2008 (EDT)
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Hi All,

I took this shot in the evening (at about 645PM) one day in early May, in Lassen Volcanic National Park. I thought this light on the clouds was unusual.

The shot is taken toward the southwest, so the sun is setting off to the right.

Have you seen this kind of thing before?

6:37 p.m. on June 11, 2008 (EDT)
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It's "sun dog" rainbow; the low light was reflecting off of the water vapor or crystals in the sky. It just was a atmospheric phenomenon. It is not that unusual up here in the northwest.

It can be likened to having vapor in the sky with in coming front and a ring forms around the moon. (a "moon dog")

At least, that is what I grew up calling it :)

9:13 p.m. on June 11, 2008 (EDT)
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It is part of a more general phenomenon called "parhelia". When the solar halo phenomenon is fully developed it is truly spectacular - an inner halo 22-1/2 degrees with an outer halo at 45 degrees radius around the sun, 4 subsidiary halos at the same altitude, directly above, and directly below the sun surrounding the "sundogs". For the sun, it is caused by ice crystals at high altitude. Sometimes you can see the thin cirrus, sometimes not. The lunar halo is a bit different, being caused by water droplets.

The spectral distribution in your photo is very hard to see for the lunar halo, but often spectacular for the solar halo and sundogs (the often disc-shaped object that appears at the same altitude or directly above or below the sun on either the inner or outer halo). The sundogs sometimes can be brighter than the sun, because of the way the light refracts, and sometimes they can have an "ice cream cone" shape, with the red tip resembling the exhaust of a rocket. When I was a grad student and working part time at Griffith Planetarium, we used to regularly get calls about UFOs, which were just a particularly bright sundog (often you only see one or two). They are most common in desert areas and at high altitudes. Then there was the time we got a call from someone who reported a dark disc around the sun. As each of us went out to look, we could not see a dark disc, but we could see a bright halo. Eventually we realized that this was the old "ground and field" perception phenomenon - the "dark disc" was the darker area between the sun and the surrounding halo. We tried to convince the caller this was what he was seeing, but he insisted that it was no halo, but a dark disc.

Atmospheric optics is a really fun and fascinating thing. Take a look at the book "Physics from your airplane window" - very non-technical explanation of solar halos, Brocken's Spectre, rainbows, and all sorts of things seen in the sky, not just from airplane windows, either. (early alpinists used to believe Brocken's Spectre was a ghost following them up mountain ridges).

There are some biblical scholars who think that Ezekiel's wheels within wheels were a fully developed solar halo. Having seen a few of these, I can understand why someone not familiar with the phenomenon could make such an interpretation. These days, with the decline of religion, people see UFOs instead.

Oh, a practical use for things like solar and lunar halos and sundogs - since they are produced by high altitude ice clouds (water droplets for the lunar halos), they often precede an incoming frontal system - blowoff from the tops of thunderclouds. So you are likely to get rain in 24 to 48 hours, particularly if you see the halo in the western part of the sky (for the West Coast).

9:24 p.m. on June 11, 2008 (EDT)
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Wow, thanks for the detailed info! That had been puzzling me since I saw it, and I knew I came to the right place to find out what it was :-).

12:56 a.m. on June 13, 2008 (EDT)
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Will try to dig up some pics I took a few years ago. The rainbow was a perfect 360 degree circle around the sun. extending about 10 sun diameters outwards from the sun. Quite amazing. Got a surprising number of clear shots.

March 27, 2017
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