| Cloud condensation nuclei (CCN) are aerosols upon which cloud droplets nucleate. Given the importance of cloud formation to levels of incoming solar radiation and climate in general, it is essential that the aerosol-to-droplet activation process be well understood. In this study, our current understanding of cloud droplet formation is tested by comparing measured and calculated concentrations of CCN. Ambient concentrations were measured using a continuous flow thermal gradient diffusion chamber that was built and tested as a part of this work. Within uncertainties, measured concentrations are comparable to concentrations calculated using a two-component Kohler model that accounts for a varying soluble inorganic component and an insoluble organic component. Sensitivity analyses show that assumptions concerning water soluble organic compounds are not crucial but that those regarding surface tension are. |
