I encountered a weird weather phenomenon the other day and I am looking for an explanation of it. Basically, it was a whispy cloud formation where the cloud itself contained two distinct colors - yellow on top and blue on bottom. It was a mostly sunny, clear day. The really weird part is I could only see the colors through my polarized sunglasses. When I took them off, it looked like a regular cloud. The formation drifted around for awhile and dispersed not too long after. This occurred in mid-afternoon on July 1st, in the eastern suburbs of Seattle.
I can think of two possible explanations: this was simply due to refraction and was an odd rainbow-like thing, or it was due to pollution of some kind. Either way, I’m confused why it was only visible with the sunglasses.
Most likely a sundog or similar phenomenon. Browse around that site, there’s lots of fascinating pics of atmospheric optical effects. Polarised sunglasses tend to make these things more visible as they cut out the surrounding glare which otherwise obscures the colours.
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I encountered a weird weather phenomenon the other day and I am looking for an explanation of it. Basically, it was a whispy cloud formation where the cloud itself contained two distinct colors - yellow on top and blue on bottom. It was a mostly sunny, clear day. The really weird part is I could only see the colors through my polarized sunglasses. When I took them off, it looked like a regular cloud. The formation drifted around for awhile and dispersed not too long after. This occurred in mid-afternoon on July 1st, in the eastern suburbs of Seattle.
I can think of two possible explanations: this was simply due to refraction and was an odd rainbow-like thing, or it was due to pollution of some kind. Either way, I’m confused why it was only visible with the sunglasses.
Ideas, anyone?
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My first thought was a sundog, too, but there are things that militate against this:
1.) Sundogs are perfectly visible without polarized sunglasses.
2.) the color variation in a sundog is along the horizontal direction, not the vertical direction. Sundogs are either colorless (if the crystals are small), or else run from red on the edge near the sun to blue on the side away from the sun, not yellow on the top to blue on the bottom.
Where was it in relation to the sun? There are other rainbow-colored ice-crystal arcs that it could possibly be, like the circumzenith arc. I haven’t heard of it (or the others) being noticeably polarized, but at least the color variation in this and the arcs tanent to the tpop and bottom of the 22 degree halo have their color variation along the vertical direction.
Or you might conceivably be misremembering the direction. I’ll have to look into that polarization thing, though. Rainbows are certainly polarized (I used to carrt polaroid sheets in my wallet to observe chance rainbows – how geeky is that?), but I never heard this about any ice crystal arcs.
The OP being from my neck of the NW…probably a sundog (and definitely go through that atmospheric optics page linked to earlier, it is one of the coolest sites on the web).
We’ve had an inordinate number of dazzling sundog displays here recently, being the “did you see that?!?!?” topic among many friends. I have no idea why, but just the last year or two they’ve become very common. I’ve seen more in the past few months than my whole lifetime combined (and I’m a habitual sky-watcher).
One amazing one we had last year also had a significant magnification effect on the sun’s brightness, combined with vivid full-spectrum sundogs at either side. My wife made my call the UW Astronomy dept to confirm we weren’t going nova and about to die, hehe.
I’ll bet you’re just noticing them more. In my experience, sundogs are the most common meteorological display in the sky (aside from things like sunrise/sunset). They’re about an order of magnitude more common than rainbows. Meteorologists I’ve read essentially say the same thing.
The problem is that most people don’t know to look for them, and even need to have them pointed out (Siundogs without color separation are obvious if you know what to look for, but if you don’t you can easily miss them.) I’ve spent a lot of time pointing these out to people who have clearly never seen them or heard of them.
That said, if the OP’s description really is accurate, there’s something else going on there, which is why I asked where they were in relation to the sun. Sundogs are at the same altitude as the sun, and about 22 degrees away from it on either side, and are visible without polarizers. If these are elsewhere – above or below the sun’s altitude – then they’re not sundogs.
Are you sure it wasn’t the glasses? I wear a very strong prescription, and on the sides of my lenses, pretty much any object with light behind it shows blue on one side, yellow on the other. When I turn slightly and look straight on through my glasses, the effect disappears. I figured it was just the curve of my thick glasses bending the light. Right now, the half-opened vertical blinds to my left look like this:
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Well, imagine the black stripes are solid, and the blue and yellow are smack on the edge, where the blind meets the brightness beyond.
Seeing a color shift only with a polarizing lens indicates the clouds were bending the light, after something caused a polarization of the sunlight. A prism effect would show colors without a need for a polarized filter lens.
Experiment:
Send a light beam through a polarizing lens. This is a polarized light source.
Shine polarized light through a glass plate.
Put a second polarizing lens over the glass where the light shines through.
Turn the filter and the light will come through or not depending on the degree of rotation between the polarized light and the polarized filter.
Put different layers of cellophane tape on the glass.
Do step 4 again. Each layer of tape will rotate the polarized light and you will see different colors for different thicknesses.
Thanks everyone for the responses. Regarding CalMeacham’s question about where it was in relation to the sun, I don’t remember which direction the sun was, but the cloud was pretty much due south, and it was about 12:30 - 1:00 when we saw it.
I know memory can be a tricky thing, but my wife who also saw it remembers it as being oriented the same way I do. I took a look at the sundog site Colophon sent a link to, and other than the orientation it looked pretty close to the images from northern England, although I’d have to say ours was rather brighter and more pronounced.
Regarding Savannah’s questions about the sunglasses, I don’t think it was them. The colors did not shift with my head position, and my wife who had on a different pair also saw the colors.
I just remembered I had a nice lighted globe that shows the position of the sun based on the time and date. According to it, the sun must have been pretty much due south as well, although I don’t remember having to shield my eyes at all. It may have been obscured by more clouds, but it was a pretty clear day and the clouds that did exist were all pretty thin.
A couple of other interesting points:
. The formation shifted a bit over the course of about 15 minutes before the color went away. It moved east to west and the cloud shape morphed a bit (it was pretty whispy the whole time, though). The color variation stayed pretty consistent the whole time.
. At one point a jet vapor trail cast a shadow on the cloud. I believe there wasn’t any color variation in the shadow, but I’m taxing my memory and observational skills at this point. I don’t know that it’s relevant to the discussion, but it was a pretty cool effect.
The coolest “multicoloured cloud” effect I have ever seen is nacreous clouds (another pic). Those are extremely high in the atmosphere, though, so wouldn’t have been what you saw if a jet trail could cast a shadow on the cloud.
The only time I have ever seen them was actually the very same display that those photos show, in 1996. (I was in Sheffield at the time.)
