Characterization and Origin of Mixed Phase Cloud

Cloud, as a mix of ice particles and supercooled droplets, provides an environment for ice phase precipitation, for charge separation, for secondary ice production and for chemical reactions related to enhanced concentration of evaporating cloud droplets. Measurement of such an environment by aircraft penetration requires high resolution instruments to differentiate between the relative concentrations of water and ice on a variety of scales. The T probe, an instrument having three sensors (total, ice plus water, water, and reference) provides measurements with 1 and 0.1 second resolution. Different size sensors provide different collection efficiencies between larger and smaller particles and high and low density particles. Results from NCAR C-130 flights in winter time mixed-phase clouds around the Great Lakes show discontinuities down to the limit of resolution, consistent with earlier measurements using replication techniques in convective clouds. It is concluded that the detail of the interface regions between all ice and all supercooled water cloud provides informatiion on regions having monotonically varying ice/water content ratios leading to changing physical and chemical processes over distances greater than 100m to well below 10m. Different situations occur for different horizontal shear and for different multifolded horizontal layering at inversions. The turbulent structure of such interfaces, as waves at the inversion or as turbulence resulting from the horizontal shear of the vertical velocity between up and downdraft become critical to the interpretation of the observations.