Motions visualized by fog provide time-space evolution of the turbulent eddies and small-scale motions that can only be tentatively inferred from fixed site measurements. Such visualization has provided us with completely new perspective on the development of turbulent eddies and small-scale motions and dispelling some previous misconceptions.
Principal limitations of the technique include restriction to a two-dimensional picture although three dimensional structure using three cameras is shown below. Natural fog visualizations are limited to situations where thin fog develops although such natural fog has revealed a rich variety of motions at our sites. Machine-generated fog is more labor intensive but allows a wider variety of situations. The impact of the water droplet distribution in machine-generated fog on the motions is not known.
Three dimensional wind vectors
Red arrows indicate wind vectors deduced from the motion of machined-generated fog revealing complex transverse structure constructed by Andrew Geiss. The motions were determined objectively using a method based on pattern recognition applied to three cameras. The black framework represents the 4 fiber optic cross sections of fast response temperature measurements while the yellow markers locate the sonic anemometers. This information provided general verification of the wind vectors derived from the fog motions.
Turbulence and Local Circulations 