Black carbon aerosol optics in chemical data assimilation and climate forcing studies
M. Kahnert
- Swedish Meteorological and Hydrological Institute, Folkborgsvägen 1, 601 76 Norrköping, Sweden.
Optical properties of freshly emitted black carbon aerosols are computed with a numerically exact method for fractal aggregates. Computations are performed for 14 bands in the wavelength range 0.2–12.195 μm. The results are integrated into the aerosol optical observation operator of the Multiple-scale Atmospheric Transport and CHemistry modelling system MATCH. 3D-fields of ensemble-averaged aerosol optical properties computed with MATCH are coupled to radiative transfer calculations to assess the regional radiative forcing effect of black carbon over Europe. The results indicate that the forcing estimates obtained with the aggregate model can be up to a factor of 2 higher than corresponding estimates obtained with the homogeneous sphere approximation, which is still commonly employed in chemical transport and climate modelling.