Friday was a good day for atmospheric optics. I watched a sundog for most of my drive home.
Tag: sun
Halo and Shadow: Cloud Optics Two-Fer
Yesterday morning while driving to work, I looked up from the road and saw two parallel lines in the sky: One white, one dark blue. They were, of course, a contrail and its shadow on a thin cloud layer below. Because it was a thin layer, I started looking (when I had the chance) for fragments of halos.
When I finally stopped the car, I took a picture of the contrail and its shadow (now nearly aligned with the sun), looked up and saw a faint edge of a halo. I moved a bit to the left, putting a tree in front of the sun, and there it was: a clear 22-degree circular halo centered on the sun..
Halo & Sundog
While driving toward the sun a little after 1:00 this afternoon, I noticed a faint reddish, slightly upturned patch in the sky ahead of me, and realized it was probably the bottom edge of a 22° sun halo. I was surprised, since the cloud cover looked too heavy for it, but it was there. At the next intersection, I looked out the side window to see if I could catch anything above the sun, and there was a clear arc running left of the sun, from a little below sun level to as high as I could see.
We stopped the car, found a tree to block the sun, and both looked. There was so much glare it was easier to see with sunglasses on, so I lent mine to Katie so she could catch it. Finally I grabbed the camera and took a few pictures, most of them using a gate post instead of the tree.
We ran some more errands, and I caught up with her at the grocery store. On my way from the car, I looked up and saw a perfect bright sundog to the right of the sun, much brighter than the clouds around it and showing the full red-to-blue spectrum. I should have gone back to the car for the better camera, but I used my phone camera instead, and got this shot.
I got to the edge of the lot just as Katie was leaving, and immediately said something like, “Look! Right above that palm tree!” Then I took off my sunglasses, realized that it was completely washed out without them (though it seems to have come out all right on my cheesy phone camera), and handed them over again. It continued to be visible, though less well-defined (it was a lot sharper than this photo shows) for at least half an hour.
A circle around the sun, and a bright rainbow-colored spot in the sky. I wonder how many people walking around never even noticed.
Halos and Rainbows and Clouds, Oh My!
Whenever there’s a light layer of cirrus clouds in the sky, I keep an eye out for halos. I catch the occasional iridescent cloud, or a faint sundog that’s only visible through sunglasses. Today I spotted a 22° halo as I walked back to my car after lunch, around 2:00pm on March 6.
It’s not as sharp as the one I caught 2 years ago, but there was more color. It was clearly reddish toward the inside and bluish toward the outside. Like last time, I didn’t have the good camera, just my cell phone, but at least this time it was a better phone!
This reminds me, our trip to San Francisco a few weeks ago was through patchy clouds, sun, and rain—perfect for rainbows. We spotted several, including one which was not only extremely bright, but actually showed supernumaries inside the band.
We saw this on Thursday, February 21, somewhere between Paso Robles and San Jose along US Highway 101. Katie remarked that it looked almost double-layered, I looked over, and said, “Grab the camera! It has fringes!”
I’d never seen, or never noticed supernumaries before. I’d never even heard of them until I was reading through Atmospheric Optics a few years ago. If you look on this color-enhanced picture (actually from another photo of the same rainbow), you can see several extra bands inside the violet arc, alternating green and pink.
The really weird thing? Classical optics doesn’t explain them. Refraction and reflection can only explain the red-to-violet band and the secondary bands that sometimes appear outside the main arc. These are actually wave interference patterns that occur if the water droplets are small enough.
On a related note, last Sunday (March 2) I saw what I’m fairly certain was a lenticular cloud, except it didn’t look remotely like a lens. It was just a long, narrow flat cloud floating above the Santa Ana Mountains. I noticed it around 3:00 in the afternoon, and a couple of very thin, also flat clouds above it, and thought it looked like the beginnings of the stack formation. What clinched it was the fact that the cloud was still there, 5 hours later (visible at night by reflected city light), despite the high Santa Ana winds. You know, after spotting two sets last summer, it looks like they form in Orange County a lot more often than I thought.
Corona
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.