from the text:
" Of course, when ρ? is small, the in- ternal coupling, i.e., the internal multiple scattering, is negligible, so the internal field is equal to the incident field screened by the Lorentz-Lorenz factor and the RDG limit holds for both aggregates and spheres. As ρ? increases, the internal field is initially enhanced beyond the incident field so the scattered intensity is larger. This enhancement should be larger for larger refractive index real part and smaller with larger internal absorption which is dependent on the imaginary part of the refractive index. These dependencies are, in fact, seen. Ultimately, as ρ?
grows past three, the internal
coupling becomes so strong that the phase relationships between waves from different parts of the scatterer become complex so that destructive interference ensues to cause the drastic decrease in the forward scattering intensity. A similar behavior has been observed for scattering by a wide variety of ice crystal shapes [25] ."
!! This suggest that increasing size parameter should decrese intensity at theta = 0 after a threshold constraint by internal coupling parameter. This is worht to investigate and implmented in the model.