Cloud microphysical relationships in California marine stratus

Abstract

Cloud microphysical measurements off the southern California coast are presented and compared with in situ airborne measurements of cloud condensation nuclei (CCN) spectra. Large-scale variations in cloud droplet concentrations were due to CCN variations, some medium-scale variations may be a result of the conversion of droplets to drops by coalescence, while small-scale variations were due to different proportions of the CCN spectra being activated because of variations in updraft velocity at cloud base. This latter internal mixing process produces an inverse relationship between droplet concentration and mean size and an increase in droplet spectral width with mean droplet size. Drizzle drop concentrations are strongly associated with lower droplet concentrations, larger droplets, and greater droplet spectral width. -Authors