title: Optical properties of light absorbing carbon aggregates mixed with sulfate: assessment of different model geometries for climate forcing calculations.
abstract: Light scattering by light absorbing carbon (LAC) aggregates encapsulated into sulfate shells is computed by use of the discrete dipole method. Computations are performed for a UV, visible, and IR wavelength, different particle sizes, and volume fractions. Reference computations are compared to three classes of simplified model particles that have been proposed for climate modeling purposes. Neither model matches the reference results sufficiently well. Remarkably, more realistic core-shell geometries fall behind homogeneous mixture models. An extended model based on a core-shell-shell geometry is proposed and tested. Good agreement is found for total optical cross sections and the asymmetry parameter.
authors.affiliation: Swedish Meteorological and Hydrological Institute (SMHI), Research Department, Folkborgsvägen 1, SE-601 76 Norrköping, Sweden. michael.kahnert@smhi.se
authors.forename: Michael
authors.initials: M
authors.lastname: Kahnert
authors.forename: Timo
authors.initials: T
authors.lastname: Nousiainen
authors.forename: Hannakaisa
authors.initials: H
authors.lastname: Lindqvist
authors.forename: Martin
authors.initials: M
authors.lastname: Ebert
mesh_terms: D000042:Absorption; D000336:Aerosols / Q000032:analysis*; D000393:Air Pollutants / Q000032:analysis*; D002244:Carbon / Q000032:analysis*; D003198:Computer Simulation; D004784:Environmental Monitoring / Q000379:methods*; D008956:Models, Chemical; D009391:Nephelometry and Turbidimetry / Q000379:methods*; D013431:Sulfates / Q000737:chemistry*
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D013431:Sulfates; D002244:Carbon