Can simple particle shapes be used to model scalar optical properties of an ensemble of wavelength-sized particles with complex shapes?

We compute the scalar optical properties of size-shape distributions of wavelength-sized randomly oriented homogeneous particles with different nonaxially symmetric geometries and investigate how well they can be modeled with a simple spherical, spheroidal, or cylindrical particle model. We find that a spherical particle model can be used to determine the extinction and scattering cross sections, the single-scattering albedo, and the asymmetry parameter with an error of less than 2%, whereas the extinction-to-backscatter ratio R_eb is reproduced only with an error of 9%. The cylindrical and spheroidal particle models yield slightly improved results for R _eb that deviate from those obtained for the complex particle ensemble by 7% and 5%, respectively. Large discrepancies between results of the different models are observed for the linear depolarization ratio, thus indicating limitations of models based on simple particle shapes.