LABORATORY OBSERVATIONS OF CLOUD-CLEAR AIR MIXING AT SMALL SCALES

Cloud-clear air mixing at scales from 1 mm to 1 m is observed in a lab oratory chamber. Cross sections through the volume in which the mixing takes place are obtained by illuminating a planar sheet of cloud with laser light (lambda = 0.488 mu m, 1.2-mm thickness); the light is sca ttered by cloud droplets and photographed. Images indicate that compli cated filament-like structures are created during mixing. Due to the p roperties of Mie scattering, this technique is in principle more sensi tive to the larger cloud drops, and volumes with the small droplets ma y be underrepresented in the images. After digitization of the images, an interface between cloudy and Clear-air filaments is investigated. Preliminary results indicate that at the scale of 2 cm the nature of t he interface changes: at larger scales it exhibits self-similar proper ties, whereas at smaller scales it has a simple geometrical structure.