Early morning fog release

October 19, 2010: We conducted a release of artificially created fog using two fog machines at different locations in close proximity to the fiber array. Individual fog pulses were 20 sec long and spaced 3 min apart throughout the experiment. The video information was recorded with two cameras: one located South-East of the array in about 50 m distance on the ground, and one attached to a pulley system on the tall tower located at about 20 m above ground. 

The sped-up video clearly indicate the presence of meandering motions while the general flow is Northerly. A cold air 'lens' builds up in the shallow gulley, in which the base of the fiber array is located, and sloshes back and forth most likely driven by larger-scale pressure perturbations of unknown origin. The air is strongly stably stratified with a vertical gradient of about +1 K/m. Toward the end of the movie, the surface heating breaks up the stable stratification leading to enhanced turbulent mixing as indicated by the shear driven overturning of larger eddies.