Modifications in the optical properties of black carbon (BC) due to ageing are presented and quantified in this study using a state-of-the-art description scheme of BC fractal aggregates. It is shown that the relative change in BC radiative forcing can be larger than 50 % as a function of changing fractal dimension and organic content. A comprehensive parameterization scheme for coated BC optical properties is developed with applications for modelling, ambient, and laboratory-based BC studies.
Long-term ice-nucleating particle (INP) data are presented from four semi-pristine sites located in the Amazon, the Caribbean, Germany and the Arctic. Average INP concentrations did not differ by orders of magnitude between the sites. For all sites short-term variability dominated the time series, which lacked clear trends and seasonalities. Common drivers to explain the INP levels and their variations could not be identified, illustrating the complex nature of heterogeneous ice nucleation.
Biomass burning smoke from African savanna and grassland is transported across the South Atlantic Ocean in defined layers within the free troposphere. The combination of in situ aircraft and ground-based measurements aided by satellite observations showed that these layers are transported into the Amazon Basin during the early dry season. The influx of aged smoke, enriched in black carbon and cloud condensation nuclei, has important implications for the Amazonian aerosol and cloud cycling.
Varmere og tørrere forhold vil utløse flere branner i Amazonasregnskogen. Det vil frigjøre store mengder karbon til atmosfæren.