Microphysical Contrasts in Atlantic Stratus

Abstract

Measurements of a mid-Atlantic clean and polluted cloud are presented. The cleaner cloud had lower concentrations of larger droplets with a broader spectrum and more drizzle drops. The first two characteristics are attributed to the lower cloud condensation nuclei (CCN) concentrations that were measured near the clean cloud. The greater droplet spectral broadness may just he a manifestation of the usual observation of broader droplet spectra for larger droplet sizes but it may also be related to the higher slope of the CCN spectra that was observed in the cleaner air mass. The larger droplets and wider droplet spectra in the clean cloud seemed to promote drizzle drop production.