Tuesday, August 2, 2011
I was recently in Europe touring with my jazz band. Everything was wonderful; the people, the culture, the sights, and the music were all fantastic. However, I also noticed some very interesting weather. While nearly all the trip was hot and sunny, there were some interesting cloud formations that I had the pleasure of seeing while climbing Mt. Vesuvius with my family.
The above picture is one I took while climbing down Mt. Vesuvius. These clouds have “waves” on them that behave in a way similar to waves on the ocean. You could see them breaking and forming over and over again. I’d get out my camera to take a picture, only to see that they were gone by the time I was ready to take one. However, I’d wait a minute or so, and some more waves would form.
These waves are the result of a phenomenon called Kelvin-Helmholtz instability, which was named after Lord Kelvin and Hermann von Helmholtz. Kelvin-Helmholtz instability occurs when there is either one fluid with velocity shear and density differences within it, or it can occur with two different fluids entirely, with velocity shear occurring between the two fluids. A classic example of Kelvin-Helmholtz instability is wind waves. Air is less dense than water and generally moves faster. When moving air comes in contact with the relatively stagnant water, the instability is manifested in waves moving along the surface of the water. Although it is not as visible, the same thing happens in different levels of air velocity. Faster, less dense air moving on top of slower, more dense air can produce the same Kelvin-Helmholtz waves found in water, and when there is sufficient moisture and clouds form, this interaction can be seen. The picture above is the best example I have witnessed of it, but there are better examples out there with the waves stretching on for miles. Take a look at some of the pictures below!
I hope you enjoyed this blog post! It’s 12:02 A.M. and time for me to go to bed.
Thanks for reading,