Chunsong Lu — Nanjing University of Information Science and Technology
Yangang Liu — Brookhaven National Laboratory
Shengjie Niu — Nanjing University of Information Science and Technology
Andrew M. Vogelmann — Brookhaven National Laboratory
Category
Cloud Properties
Description
Cloud droplet size distributions as a function of entrainment rate (λ) in 186 growing cumulus clouds during RACORO.
The relationships between fractional entrainment rate and key microphysical quantities (e.g., liquid water content, droplet number concentration, volume-mean radius, standard deviation of cloud droplet size distributions) in shallow cumuli are empirically examined using in situ aircraft observations from the RACORO field campaign over the ARM SGP site. The result shows that the microphysical quantities examined generally exhibit strong relationships with entrainment rate, and that the relationships collectively suggest the dominance of homogeneous entrainment mixing, which is unfavorable to the formation of large droplets and the initiation of warm rain in these clouds. The dominance of the homogeneous mixing mechanism is further substantiated by the dependency on entrainment rate of relationships among various microphysical variables and of cloud droplet size distributions (Figure 1). The dominance of homogeneous mixing mechanism is also quantitatively confirmed by examining the degree of homogeneous mixing in these clouds. The dominance of homogeneous mixing may be an important reason why none of these cumulus clouds were drizzling.
