Organic Functional Group Contributions to Cloud Condensation Nuclei in the Arctic During ICEALOT 2008

Cloud condensation nuclei (CCN) affect cloud droplet formation processes as well as number concentration. An increase in cloud droplet number concentration influences the Earth’s radiative balance by increasing the reflected incoming solar radiation. Chemical composition influences the properties of the aerosol particles, which impact their ability to act as CCN. Organic functional groups in particles, such as alkanes, which are hydrophobic, and alcohol groups, that are hydrophilic, contribute differently to the CCN potential than completely soluble inorganic functional groups. Measurements of inorganic and organic aerosol were made during the ICEALOT research cruise in the North Atlantic and Arctic in March and April of 2008. Fourier Transform Infrared (FTIR) spectroscopy was used to identify and quantify the organic functional group fractions of submicron particles. The contribution of the organic fraction of internally mixed particles to the formation of CCN has not yet been well established. Here it is shown that defining the organic fraction as soluble increases the average number of percent predicted CCN by 7.92% for an initial diameter of 100nm over a base case in which the organic fraction was considered entirely insoluble. Increasing the organic fraction increases the influence of the solubility of the organic fraction on the predicted percent CCN. Determining the soluble portion of the organic fraction is important for accurate calculations of CCN.