Online measurement of size-resolved CCN activity of polluted marine aerosols using BS2-CCNC in Yellow Sea, Korea

By serving as cloud condensation nuclei (CCN), atmospheric aerosol particle affects Earths climate indirectly. In particular, marine aerosols play an important role in aerosol-cloud-climate interaction on global scale as ocean cover around 70 % of the Earths surface. The CCN activity, the ability of aerosol particles that act as cloud droplet, can be determined by particle size and chemical composition. Understanding physicochemical properties of marine aerosols and its link to the CCN activity is crucial for better understanding of aerosol-cloud-climate interactions in marine environments. The broad supersaturation scanning (BS2)-CCN counter, a CCN counter with a newly designed inlet system measures the activation of size-resolved CCN with a high-time resolution. With low sheath-to-aerosol flow ratio by wider inlet, a monotonic relation between activation fraction and activation supersaturation of aerosol particles can be obtained. The BS2-CCNC reduces the time required for scanning S and thereby obtain , hygroscopicity parameter, with a high temporal and size resolution. Also, our system can be used as a complementary approach for fast detection/estimation of aerosol chemical composition as hygroscopicity is closely related to inorganic/organic fraction. Here, we applied the newly developed system to ship measurement for the first time during the Yellow Sea Air Quality (YES-AQ) 2021 campaign. Gisang 1, a research vessel, cruised over the Yellow Sea, in springtime (March to May 2021). Aerosol properties are affected not only by local marine sources but also continental sources. Campaign averaged values ranged from 0.24 to 0.46 for particle diameters between 70 nm and 280 nm. Clear size dependency is shown in particle diameter between 70 and 120 nm with lower for smaller particle. However, opposite trend was observed when air mass was influenced by the transportation of Asian Dust. These size-dependent values are inferred to be influenced by the size-resolved aerosol chemical composition. For validating the BS2-CCNC results, we conducted short inter-comparison experiment with DMA-CCN measurement during the campaign. Good agreement between two measurements implies that a broad range of CCN activity distribution with a high-time resolution obtained from BS2-CCN system are reliable.