Vertical Gradient of Size-Resolved Aerosol Compositions over the Arctic Reveals Cloud Processed Aerosol in-Cloud and above Cloud.

Arctic aerosols play a significant role in aerosol-radiation and aerosol-cloud interactions, but ground-based measurements are insufficient to explain the interaction of aerosols and clouds in a vertically stratified Arctic atmosphere. This study shows the vertical variability of a size resolved aerosol composition via a tethered balloon system at Oliktok Point, Alaska, at different cloud layers for two representative case studies (background aerosol and polluted conditions). Multimodal microspectroscopy analysis during the background case reveals a broadening of chemically specific size distribution above the cloud top with a high abundance of sulfate particles and core-shell morphology, suggesting possible cloud processing of aerosols. The polluted case also indicates broadening of aerosol size distribution at the upper layer within the clouds with the dominance of carbonaceous particles, which suggests that the carbonaceous particles play a potential role in modulating Arctic cloud properties.