MMM SEMINAR NCAR
Interactions of Cloud Droplets and Small-scale Turbulence: Laboratory Experiments
Szymon Malinowski
Warsaw University Institute of Geophysics
Results of two experiments performed in the cloud chamber will be presented. In the first experiment preferential concentration of cloud droplets due to small-scale turbulence is investigated. The chamber of size 2*1*1m3 is filled with cloud droplets of diameters in range from 10 to 20 micrometers. A weak decaying turbulence with the TKE dissipation rate of order of 6e-5 m2/s3 results in formation of the patterns in the flow. Investigation of the droplet positions in the planar section through the chamber indicate deviations from random, uncorrelated pattern. These deviations are quantified by the clustering index, the volume averaged correlation function and by the correlational analysis. The last method clearly shows, that a typical droplet has more close neighbors than expected from the average droplet concentration. In the second experiment motion of droplets at the cloud-clear air interface is investigated by means of the particle image velocimetry. Observed small-scale turbulent velocities are anisotropic with the preferred direction in vertical due to ation of buoyancy force generated by evaporative cooling at the interface. Results of laboratory work are in agreement with the recently published numerical results of Falkovich and Pumir (experiment 1) and Andrejczuk et. al. (experiment 2).
Thursday, September 23,
2004, 3:30 PM
NCAR-Foothills Laboratory
3450 Mitchell Lane
Bldg 2, Rm 1022, Auditorium