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Figure 21.2 (a) Cloud base precipitation rates, RCB, from observational case studies in subtropical marine stratocumulus, plotted against h3/Nd, where h is the cloud thickness and Nd the droplet concentration. Black circles: Pawlowska and Brenguier (2003), in-situ aircraft; white circles: Comstock et al. (2004), radiometric and radar drizzle; triangles: van Zanten et al. (2005), in-situ aircraft and radar drizzle. The lines represent linear least-distance regressions to the case studies for each field campaign. Comparison of model predictions (small triangles) with scaling laws derived from: (b) ACE-2 (large triangles): precipitation rate <R> averaged over the cloud layer, cloud thickness H

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Figure 21.2 (continued) derived from in-situ measurements and droplet concentration, Nact, derived from samples not affected by mixing or droplet scavenging. (c) EPIC (squares): precipitation rate at cloud base <Rbase>, liquid water path (LWP), and mean droplet concentration Nc, derived from surface remote sensing. (d) DYCOMS-II) (circles): precipitation rate at cloud base <Rbase> and cloud thickness <H> derived from remote sensing and mean droplet concentration, Nc, derived from in-situ measurements.

system is evolving sufficiently slowly. They are not suited, however, for studies of the temporal evolution of the system, which call for a different approach.

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