Clouds of the Day - Cirrus - Tuesday, October 17, 2023

Looking south we see the solar disk being filtered by thin Cirrus fibratus with Cirrostratus in the low center of the photo.

Cirrus fibratus (top half) and Cirrostratus lower center. The light artifact is caused by sunlight interacting with the camera lens.

The next photo is more interesting than it may look. The thin cloud bands were not immediately visible to the naked eye. After taking the photo I could see the bands in the camera display. The thinnest streaks appear to radiate from a central point in the distance behind the tree in the lower right. They are classified as Cirrus fibratus radiatus because they radiate from a central point. There are at least five bands radiating from that point.

However, the bands do not radiate from the same point. It is an optical illusion. If you are riding in a car down a long straight road look down the road toward the horizon. The road seems to narrow to a point in the distance. This illusion occurs fairly often in the sky and is especially impressive when the bands go from one horizon to overhead then to the opposite horizon. The bands appear to come out of one point on one horizon, spread to their widest size overhead, then converge to a point on the opposite horizon. The real width of the bands is the width you see overhead. As you look toward the horizon the bands gradually narrow as the optical illusion stakes over.

The bands in the top photo do not appear to radiate from a point because I was not standing under the bands when the photo was taken and they did not appear to reach either horizon. If they are long enough you may see the convergence effect anyway.

Cirrus fibratus radiatus center behind the tree on the lower right. The thicker Cirrus (lower center and upper left) are cirrostatus because they turn into a small sheet layer cloud.

It is hard to know the altitude of these clouds. It would have been nice to have a commercial airliner fly through, in front, or behind the clouds for a reference.