Relationship between Critical Supersaturation and Cloud Droplet Size: Implications for Cloud Mixing Processes

Abstract

Cloud condensation nuclei (CCN) measurements within stratus clouds that have involved droplet separation have revealed a clear preference for droplet activation on the nuclei with the lowest critical supersaturations (S_c). When droplets of various sizes were separated from a sample, a consistent relationship between cloud droplet size and nucleus S_c was discovered—large droplets tend to grow on large (low S_c) nuclei and vice versa. Interpretation in terms of various modes of mixing between clouds and the dry environment demonstrates a preference for the homogeneous mixing process.