Fig. 8

The homogeneous-sphere model can only reproduce the shape of the volume scattering function (VSF) of a complex particle by using multiple homogeneous spheres. Only the forward scattering (angles < 90°) of a coated sphere (black line) can be reproduced by a homogeneous sphere (blue line) with the same size and volume-averaged refractive index. To reproduce the backscattering (angles > 90°) of the coated sphere, twelve homogeneous spheres with diameter equal to 0.2 µm purple line and the same volume-averaged refractive index of the coated sphere must be added to the largest homogeneous sphere (red line). The refractive index of the coat of the coated sphere was set equal to 1.13, the coat thickness was 13% of the radius and the volume-averaged refractive index of the whole particle was set equal to 1.06. The backscattering ratios are equal to 0.88% and 0.85% for coated and combined homogeneous spheres, respectively. VSFs are normalised to the total scattering, and are shown for the wavelength 532 nm