Modelling light scattering by mineral dust using spheroids: assessment of applicability 1Climate Change, Finnish Meteorological Institute, P.O. Box 503, 00101 Finland
09 Jun 2011
2Department of Physics, University of Helsinki, P.O. Box 48, 00014 Finland
3Swedish Meteorological and Hydrological Institute, Folkborgsvägen 1, 601 76 Norrköping, Sweden
Received: 17 Dec 2010 – Published in Atmos. Chem. Phys. Discuss.: 03 Feb 2011 Abstract. We study the applicability of spheroidal model particles for simulating the
single-scattering optical properties of mineral dust aerosols. To assess the
range of validity of this model, calculations are compared to laboratory
observations for five different dust samples at two wavelengths. We further
investigate whether the best-fit shape distributions of spheroids for
different mineral dust samples have any similarities that would allow us to
suggest a generic first-guess shape distribution for suspended mineral dust.
We find that best-fit shape distributions vary considerably between samples
and even between wavelengths, making definitive suggestions for a shape
distribution difficult. The best-fit shape distribution also depends strongly
on the refractive index assumed and the cost function adopted. However, a
power-law shape distribution which favours those spheroids that depart most
from the spherical shape is found to work well in most cases. To reproduce
observed asymmetry parameters, best results are obtained with a power-law
shape distribution with an exponent around three.
Revised: 05 May 2011 – Accepted: 16 May 2011 – Published: 09 Jun 2011
Citation: Merikallio, S., Lindqvist, H., Nousiainen, T., and Kahnert, M.: Modelling light scattering by mineral dust using spheroids: assessment of applicability, Atmos. Chem. Phys., 11, 5347-5363, doi:10.5194/acp-11-5347-2011, 2011.