| Summary: | Black carbon (BC) from anthropogenic or natural sources can be transported to the Arctic, where it affects the surface radiation budget by scattering and absorbing solar radiation or by acting as cloud condensation nuclei. The extent to which BC is involved in Arctic cloud formation remains uncertain due to the lack of direct and long-term observations. Here, we present a 4-year study on observations of BC concentrations of aerosols and cloud residuals (i.e. dried cloud particles) using a counterflow virtual impactor inlet at Zeppelin Observatory, Svalbard. We will show that the scavenging of BC follows a clear seasonal cycle with almost complete scavenged fractions of BC in summer and smaller scavenged fractions in late winter and early fall during the Arctic haze period. The scavenged BC fractions were positively correlated with cloud water content and showed a dependence on air temperature most likely due to cloud-microphysical processes. A source analysis showed that clouds at the site are mainly of marine origin, in opposite to non-cloudy air, where anthropogenic BC sources over land are more dominant.
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