A Study of Cloud Holes in Stratocumulus Clouds

Cloud holes, the spaces between clouds that have zero water content, have been used along with the terms downdraughts and entrainment. The study of cloud holes is most tightly connected with stratocumulus clouds as they are found to be the preferred locations of entrainment, which is a significant transportation process regulating stratocumulus clouds. This study uses the in-situ data collected from the research flights that fly through stratocumulus clouds during the Southern Ocean (SO) Cloud, Radiation, Aerosol Transport Experimental Study (SOCRATES) campaign, conducted mainly at 45^oS to 60^oS in the Australia and New Zealand sector. The result of this study rejects the common assumption about the dominant downdraft in cloud holes (Gerber et al., 2004; Haman, 2009; Yamaguchi and Feingold, 2013). The vertical velocities in the cloud holes are found to be mostly updrafts, which is a similar result as the vertical velocity in in-cloud condition. However, a closer comparison using cumulative probability has shown that the wind in cloud holes has a higher likelihood of being updraft than the wind in cloud. A possible reason is hypothesized to be the collision/coalescence of large droplets or the riming or ice particles.