Backscattering anisotropy near $180^{\circ}$: an indication of particle size and shape

Abstract

By modelling the single scattering of particles in the exact backward direction ($180^{\circ}$) and $5^{\circ}$ around, the field of view of an instrument measuring backscattering is simulated. Calculations of the scattering Mueller matrix $M_{ij}$ using a development of the extended boundary condition method [1] are made for spheroidal particles with sizes ($D$ in $\mu$), shapes (defined by spheroidal aspect ratio $\frac{s}{t}$) and refractive indices similar to ($m = 1.05 + 0.01i$) marine particles found in the natural environment.

Results show that information about size and shape can be gathered from the intensity patterns of the backscattering for particles within the anomalous diffraction region. Comparison between the polarised scattering intensity patterns ($I_{\parallel}$ and $I_{\perp}$) produced by these non-spheres and their volume-equivalent spheres provides insight into the information available from backscattering polarimetry on the effects of size and shape in light scattering by differently shaped particles.