Fig. 4: Variations of the absorption enhancement parameter B with a varying ice refractive index n.

a Variations for spheres. The number of triangular facets used to generate the surface is gradually increased. The BB 1974 curve is the analytical expression for spheres of B in terms of n (Eq. 9 in⁹). b Variations for natural snow. 9 samples are considered, covering most of the main snow types. Three 3D images of snow samples are shown to illustrate the wide diversity of snow microstructures. The simulations are done with the geometric method, and the ice absorption coefficient γ is kept constant and corresponding to the ice absorption at 900 nm.