Modelling optical properties of atmospheric black carbon aerosols. (March 2020)

• Record Type: Journal Article
• Authors: Kahnert, Michael; Kanngießer, Franz
• Is Part Of: Journal of quantitative spectroscopy & radiative transfer. Volume 244(2020)
• Publication Date: 2020-03
• Subjects: Atmospheric optics -- Aerosol -- Black carbon -- Brown carbon; Spectrum analysis -- Periodicals; Radiation -- Periodicals; Analyse spectrale -- Périodiques; Rayonnement -- Périodiques; Radiation; Spectrum analysis; Periodicals; 543.0858
• DOI: 10.1016/j.jqsrt.2020.106849
• Languages: English
• ISSNs: 0022-4073

Abstract

Highlights: Review of physical, compositional, dielectric, and morphological properties of soot. Review of numerical light-scattering methods applicable to soot. Review of modelling optical properties of bare and coated atmospheric soot. Discussion of morphological properties that dominate the optical properties. Construction of simple models that focus on the dominant morphological features. Abstract: The optical properties of atmospheric black carbon (BC) aerosols are needed to model the direct radiative forcing of the climate system, as well as for interpreting and assimilating remote sensing observations from satellites. Modelling efforts during the past decade have predominantly been based on using morphologically highly realistic representations of the particle geometry in conjunction with numerically exact methods for solving the light-scattering problem. We review (i) the present state of knowledge about the morphological, dielectric, and compositional properties of BC aerosols, (ii) the state-of-the-art in numerical light-scattering methods frequently applied to black carbon, and (iii) the recent literature on modelling optical properties of BC aggregates, both bare and internally mixed with liquid-phase material. From this review we formulate some key lessons learned regarding those morphological properties that have a dominant impact on the optical properties. These morphological key features can form the basis for devising simplified model particles that can be used in large-scale applications. We illustrate this approach with one example appropriate for climate modelling, and one example relevant to the interpretation of lidar remote sensing data.