Środowiskowe Seminarium Fizyki Atmosfery

Turbulent mixing and entrainment in clouds is readily visible feature of atmospheric clouds, especially at cloud edge. Atmospheric clouds have one of highest Reynolds numbers of any terrestrial phenomenon. Cloud particles, cloud droplets and cloud ice crystals, respond to turbulence and entrainment in a three-phase system via evaporation-condensation and other phase changes, collision and coalescence and riming and sedimentation. Cloud scales vary from roughly ~10 km in stratocumulus clouds, down to ~1 mm dissipation scale, and one way how clouds are structured on these scales can be examined is in how the cloud particles appear as ensembles in local sample volumes relative to their position in the whole cloud. While entire cloud volumes are beyond any imaginable human method of measurement, recent developments in digital holography allow local measurements on the cm-scale spaced every 10 to 50 m in a cloud. A significant breakthrough is algorithm improvement to process holograms and sift the real particles from noise and artifacts using among other things supervised machine learning. Sample results are shown of measurements in a variety of clouds, cloud particle sizes, and altitudes or temperatures.