What are these images?
 Billow Clouds on Mt. Shasta Billow clouds are created from instability associated with air flows having marked vertical shear and weak thermal stratification. The common name for this instability is Kelvin-Helmholtz instability. These instabilities are often visualized as a row of horizontal eddies aligned within this layer of vertical shear. Billow clouds are created in the upward branch of each of the eddies if the air within this branch has a high enough relative humidity that, upon lifting, the air parcel reaches saturation. Individual billow clouds generally have life times of a few minutes. The presence of billow clouds provides a visible signal to aviation interests of potentially dangerous turbulence.
 One can construct maps of systems that display roll switching phenomena in Rayleigh Benard convection experiments. The figure shows an example of rolls whose axes intersect at angle pi/2-epsilon. This figure shows some of the extraordinary dynamics for T_1=7, T_3=5, and epsilon=.08 for randomly chosen initial conditions in the fundamental rhombic cell. A normal form expansion about the elliptic fixed point at the intersection of roll axes, can be used to show that the dynamics in that region are generally simple. As we move away from those regions, the motion becomes increasingly chaotic in a three-dimensional sense. This is demonstrated by the blue, light blue, and red orbits. Created by Paul Mullowney |
