View from our back yard this morning. I had to tweak the colors a bit to approximate what it looked like to the naked eye. It’s still not quite right — there was a bit more pink in it, and maybe a bit less purple.
Sometimes it’s worth getting up at this hour.
On my way back to work after lunch today, I looked out the window and saw this feathery wisp of cloud with a clear rainbow pattern running from red at the the top to violet in the middle, then turning plain white below.
As I drove south, the colors moved down the cloud, disappearing entirely by the time I got back. By the time I could safely snap a photo, it was already more or less midway down the cloud.
I believe it’s a fragment of a circumhorizon arc, judging by the description:
Look for a circumhorizon arc near to noon near to the summer solstice when the sun is very high in the sky (higher than 58°). It lies well below the sun — twice as far from it (two hand spans) as the 22º halo.
The arc is a very large halo and is close to, and parallel to the horizon. Usually only fragments are visible where there happen to be cirrus clouds.
We’re still 2 months from the summer solstice, but it was 12:38 PM DST (half an hour before true noon), and the sun was apparently near 70.6° high. (The site is aimed at UK visitors, after all.) It also looked too far away from the sun to be part of the 22º halo, plus of course the colors were more well-defined.
This also points out the should-be-obvious fact that ice crystals can still form in the upper atmosphere even when it’s warm — say, 90°F — on the ground, so there’s no need to limit halo-hunting to winter.
I recommend checking out Atmospheric Optics’ additional pictures of circumhorizon arcs, most of which are more complete than this one. Some of them quite spectacular and must have been really impressive to see live.
Update: I spotted and photographed a much larger and more solid arc in May 2010.
Sunset on Tuesday, March 25th, with feathery cirrus clouds and contrails. A faint sundog is visible as a slight brightening at the level of the sun, about 2/3 of the way across the picture.
I had to get up early today, early enough that I could still see a couple of stars (or more likely planets, but I’ve lost track of where most of them are right now). When I got to work, I was treated to the sight of these contrails lit up against the morning sky. The rising sun was still behind the mountains, below the frame.
Look at the cloud directly above the contrail on the right, near the leaves. You’ll see a dark nearly-vertical line, which I initially took for a contrail’s shadow, possibly even the one below it. A minute or so later, though, it looked like it might have actually been another contrail, one not lit up by the sun and therefore darker than the cloud behind it.
Oddly enough, half an hour later the entire area was blanketed in fog.
Spotted this on Thursday, between rain showers. It’s a slightly distorted corona, formed by diffraction of sunlight around cloud droplets, splitting the spectrum and producing rainbow-like colors. According to the Atmospheric Optics site, the distortion indicates that the droplet size varies across different parts of the cloud.
This was shot through a window, and I’m 99% certain that the straight line running down the middle of the darker foreground cloud is a reflection from inside the room.
