Calculation of optical properties of light-absorbing carbon with weakly absorbing coating: A model with tunable transition from film-coating to spherical-shell coating
Journal article, 2018

Optical properties of particles consisting of light-absorbing carbon (or soot) and a weakly absorbing coating material are computed at a wavelength of 355 nm and 532 nm. A morphological particle model is used, in which small amounts of coating are applied as a thin film to the surface of the aggregate, while heavily coated aggregates are enclosed in a spherical shell. As the amount of coating material is increased, a gradual transition from film-coating to spherical-shell coating is accounted for. The speed of this transition can be varied by specifying a single parameter. Two different choices of this parameter, corresponding to a slow and a rapid transition from film-coating to spherical-shell coating, respectively, are investigated. For low soot volume fractions the impact of this transition on the linear depolarisation ratio δlis most pronounced. The model that describes a rapid transition to a spherical coating yields results for δlthat are more consistent with existing lidar field measurements than the slow-transition model. At 532 nm the relative uncertainty in modelled δlfor a rapid transition values due to uncertainties in the aggregate's geometry and chemical composition are estimated to range from 109 to 243%, depending on the soot volume fraction. At 355 nm the relative uncertainties were estimated to range from 90.9 to 200%.

Soot

Scattering

Aerosol

Depolarisation ratio

Author

Franz Kanngiesser

Chalmers, Space, Earth and Environment, Microwave and Optical Remote Sensing

Michael Kahnert

SMHI

Chalmers, Space, Earth and Environment, Microwave and Optical Remote Sensing

Journal of Quantitative Spectroscopy and Radiative Transfer

0022-4073 (ISSN)

Vol. 216 17-36

Subject Categories

Manufacturing, Surface and Joining Technology

Other Chemistry Topics

Other Materials Engineering

DOI

10.1016/j.jqsrt.2018.05.014

More information

Latest update

7/4/2018 1