Interactions between Turbulence and Cloud Microphysics: Insights from the Lab
Clouds are ubiquitously turbulent. The cauliflower-like appearance of cumuli and the shakes and bumps of a plane as you descend through a cloud layer for landing are testaments to the differential motion of air on a macroscopic scale. But does it matter at the scale of a cloud droplet or ice crystal? Are cloud droplets bigger or smaller as a result of fluctuations in the scalar fields caused by turbulence? Do more or fewer aerosol particles become cloud droplets in a turbulent environment?
Questions like these have motivated much of the research in Michigan Tech’s cloud chamber, called the Pi Chamber because of the 3.14 cubic meter volume. The chamber is a Rayleigh-Bénard convection cell; we can create and hold a steady-state mixing cloud in the chamber for tens of hours at a time.
In this talk, I will address three recent avenues of research from the chamber. I will briefly describe experiments and analysis of mixed phase clouds in the chamber where we show the critical value of ice nucleating particles required to glaciate an initially supercooled, liquid water cloud. I will spend the majority of my time discussing experiments and analysis of the effect of turbulence on the aerosol activation process. Finally, I will show some preliminary results from experiments exploring the feasibility of experiments to study entrainment.
