Sunday, July 11, 2010
Some time ago, Yvetta sent me an email of photos of lenticular clouds over Mt. Ranier. That was the first I had ever heard of such clouds. But last month when my son, his family, and I were in the Sierras for a vacation, we were lucky to see these clouds from our condo. They were very strange and very beautiful. They seemed almost stationary and I took several photos as the evening progressed and the sun set.
Lenticular clouds are usually formed at high altitudes over mountains. The name lenticular comes from the lens shape these clouds sometimes take. In fact, many have been mistaken for UFOs. But they also frequently form layers such as these due to some very complicated wind patterns.
These clouds are named "lenticular" because they are lens shaped. Strong wind passing over a high mountain produces standing waves in the air above and somewhat downwind of the mountain. If the air is moist, changing pressure (compression followed by decompression) in these waves results in condensation making the shape of these standing waves visible. Their formal name is: "altocumulus standing lenticularis" meaning a high heap of lens shaped clouds formed by a standing wave. Pilots of powered planes and pilots of sail planes (gliders) are particularly interested in "lennies" as they are not only associated with high wind but also vertical wind. They are usually avoided by power plane pilots because of the turbulence but are sought by glider pilots for the rapid vertical lift they give. Some physicists, including the author, think that standing waves are the basic building block of matter and thus the universe. Hence my fascination with lenticular clouds as they give me a visual demonstration of how matter is formed.
D. Mayo, at Lake Ohau, NZ.
I've always been intrigued by standing waves because violin strings vibrate in standing waves. If you Google "lenticular clouds," you can find some strikingly beautiful photos such as those here, here, and here.