Tag Archives: circumhorizon arc

Double Rainbow Cloud

Wispy cirrus clouds/contrails against a blue sky, with a rainbow-colored section.

Two fragments of a circumhorizon arc seen on my way back from lunch today. I took some shots with my phone, because that’s what I had, then remembered that I had the good camera with me (I usually don’t) and grabbed it from the office. The clouds had shifted, but not far enough to destroy the effect completely, and I was able to get some interesting shots of one section, even if the other had mostly dissipated.

Saturation has been enhanced on both photos to bring out the colors.

Looking back over others I’ve seen, just about all of them have been visible while I was on my way to or from lunch. It makes sense. The optics do require the sun to be high in the sky for it to appear, so close to noon is a better time to spot them than, say, mid-morning or mid-afternoon.

Wisply cirrus clouds/contrails above palm trees. Two clouds have rainbow-colored segments at the same visual height.

Oh, funny thing: When I initially posted these on Pixelfed, my phone auto-corrected “cirrus cloud” to “citrus cloud.” Twice. And again when I tried to correct it!

Dreariest Circumhorizon Arc Ever

Smudgy clouds, colors enhanced to bring out a straight rainbow effect.

I could barely see any colors in the cloud at all without my polarized sunglasses, and when I took a photo through them, I still had to bump up the saturation.

Thin clouds and contrails cross the sky. A bright rainbow-like ring circles a spot just out of view above the frame. A fainter rainbow-like line runs across the sky below it.I’ve seen several of these over the years. The brightest one was nine years ago, while the longest was just last year. It’s a solar halo caused by reflections inside ice crystals (near ground level or higher up in the atmosphere) that in theory could circle the entire sky parallel to the horizon. In practice, it’s rare for ice crystals of the right shape and orientation to cover more than a small area from any given viewpoint, so mostly people see fragments of them.

Double Solar Halo

Thin clouds and contrails cross the sky. A bright rainbow-like ring circles a spot just out of view above the frame. A fainter rainbow-like line runs across the sky below it.

Two solar ice halos spotted at lunch today.

The 22° halo around the sun is really bright and clear, and not that uncommon even in Los Angeles. I’ve seen so many that I still take photos, but I often forget to post them unless there’s something unusual about the view.

The circumhorizon arc below it, on the other hand, I’ve only seen a few times, usually fragments. It’s faint, but it’s the longest and least wispy of these arcs that I’ve seen (though the best was probably this one from 2010).

The lower one could be an infralateral arc. It wasn’t quite long enough to tell in person whether it curved upward or was parallel to the horizon, and it’s hard to tell how much of the curve in the photo is due to lens distortion. But according to Atmospheric Optics, they’re a lot rarer than circumhorizon arcs.

It’s cool to be able to get pictures of these with my phone. There was a time I’d run to get a camera and hope it wouldn’t fade first.

Saturation enhanced. It was really hazy!

Rainbow Cloud

A small cloud shows a spectrum, cut by a contrail that also cuts through part of a circular halo.

I noticed the halo around the sun as soon as I walked out the door for lunch on Thursday. The rainbow cloud? That appeared as I walked past a building. I saw it as soon as the southern sky came into view again.

The colors got more intense over the next few minutes, and I kept taking photos until my phone locked up. I stood there watching the colors intensify, then fade, while I pulled out the battery and waited for the phone to reboot.

A man who’d been sitting nearby, buried in his phone, looked up wondering what I was taking pictures of. He’d never seen anything like it before, and wondered what it was, and fortunately I was able to answer.

At the right angle, ice crystals in a cirrus cloud refract sunlight to produce a feathery rainbow effect. The circumhorizon arc runs parallel to the horizon, and while it can be long, it’s usually only seen in fragments like this. I’ve only seen a few of these myself, and it’s been years since I’ve seen one this intense. I took this photo through my polarized sunglasses, but the colors were bright even without them.

When my phone froze, he offered to send me one of his pictures just in case mine hadn’t actually saved. Fortunately they had, and I actually posted to Flickr several hours before his message made it through the cell network.

Within a few minutes, the cloud had drifted out of alignment, and the colors had faded completely.

An hour later, on the way back from lunch, I noticed a longer patch in a smoother cloud layer, but it was faint enough that I could only barely see it with my sunglasses on. Without them, it faded completely into the glare.

If I’d had my better camera with the zoom lens, I would have gotten some better shots of just the bright cloud. Then again, I wouldn’t have been carrying it with me to lunch, and the effect was gone in the time it would have taken to run back in and get it. So it’s probably just as well I stayed and watched instead.

Funny thing: I posted a cropped view on on Instagram featuring just the arc fragment and contrail. When I went back to look at the #rainbowcloud tag last night, I found no less than SIX other photos of what was clearly the same cloud at various points in its five-minute lifetime!

Feathery Not-a-Rainbow Cloud

I saw this amazing circumhorizon arc around 1:30 this afternoon. I had just crossed the street while walking to lunch when I looked up, saw it…and walked back to the office to get my camera!

Lesson learned: always bring the camera!*

It started out as just a couple of small segments, but as the clouds drifted into position it quickly grew, and at its strongest it was just long enough to fill the field of view on my camera. There were also a couple of fragments of a 22° circular halo visible at the time.

The whole thing had vanished by 1:50, as the clouds drifted out of alignment, though I did see a more complete circular halo later on.

It looks like a sort of straightened-out rainbow, but it’s actually caused by ice crystals. If the right type of crystals cover the entire sky, this will actually stretch in a circle all the way around the sky, parallel to the horizon.

They’re a lot less common than the 22-degree halos. I’ve seen and photographed a ton of those over just a few years, but this is maybe the second time I’ve seen something like this. Fourth if you count the two feathery fragments I’ve seen.

At times like this, I really wish I had a DSLR, but the point-and-shoot will do in a pinch.

*On the other hand, when I went back, I pointed it out to a couple of people at the office who are into photography, since it was visible through the windows on one side of the building. One of my co-workers has a digital SLR and carries it with him, so he went outside and got some great shots. If I hadn’t taken a late lunch and chosen to walk anyway and been in the habit of looking for halos and forgotten to bring my camera, chances are no one in the office would have seen it.

Update (May 17): I just discovered that there are people who think these clouds are connected to earthquakes. No, they aren’t. They’re caused by ice crystals refracting sunlight, just like most halos, and have been seen in many places that didn’t have earthquakes.