AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Surface Tension in the Formation of Cloud Droplets
JAMES F. DAVIES, Kevin Wilson, Lawrence Berkeley National Laboratory
Abstract Number: 696 Working Group: Aerosols, Clouds, and Climate
Abstract Organic species in atmospheric aerosol show a propensity for partitioning to the surface of liquid droplets, lowering surface tension and impacting the ability of the aerosol to act as a source of cloud condensation nuclei (CCN). A constant reduction in the surface tension is associated with an increase in the CCN efficiency of an aerosol. However, surface tension must vary as a function of solute concentration and, as water condenses onto CCN and the system is diluted, changes in partitioning increase the surface tension. These effects have been directly observed using a thermal gradient chamber that measures the size of droplets as a function of water vapor saturation. However, typical CCN instrumentation are limited in their ability to resolve surface tension effects. Here, I will discuss measurements made using a commercial Cloud Condensation Nucleus Counter (Droplet Measurement Technologies) to identify signatures of surface tension effects in a series of mixed organic/inorganic aerosol. The effect of organic/inorganic ratio and the role of the inorganic salt will be explored, with initial measurements revealing that surface effects on CCN activity are highly system dependent and non-intuitive. A generalized description capable of capturing both size and composition effects will be explored and discussed.