Closure between aerosol particles and cloud condensation nuclei at Kaashidhoo Climate Observatory

Predicting the cloud condensation nuclei (CCN) supersaturation spectrum fro m aerosol properties is a fairly straightforward matter, as long as those p roperties are simple. During the Indian Ocean Experiment we measured CCN sp ectra, size-resolved aerosol chemical composition, and aerosol number distr ibutions and attempted to reconcile them using a modified form of Kohler th eory. We obtained general agreement between our measured and modeled CCN sp ectra. However, the agreement was not as good during a time period when org anic carbon comprised a quarter of the total mass of the aerosol in the sub micron size range. The modeled concentrations overpredict those actually me asured during that time period. This suggests that some component, presumab ly organic material, can inhibit the uptake of water by the electrolytic fr action of the mass.