Fractional activation of accumulation-mode aerosols in continental stratiform clouds

摘要

The concentration, size and composition of cloud droplets are important variables influencing radiative and chemical properties of clouds, as well as the potential for precipitation formation and scavenging. Since cloud droplets form on pre-existing aerosol particles, these variables depend strongly on the microphysical process of activation of such particles into droplets. Of particular interest is the role of anthropogenic aerosols in modifying regional and global climate and atmospheric chemistry. This study investigates the partitioning of in-cloud particles between activated cloud droplets, CD, and unactivated, interstitial accumulation-mode particles, AMP. It is based on aircraft measurements of particle concentrations (N) in stratiform clouds near Syracuse, NY. The magnitude, variation and dependence of the activated fraction F (triple bond) N(sub cd)/N(sub tot), where N(sub tot) = N(sub cd) + N(sub amp), are studied.