Fig. 1 Example of the contribution of photon tunneling to absorption efficiency, for a size distribution of hexagonal columns, mean crystal length being 50µm. Tunneling effects essentially vanish at wavelengths (l) > 200µm in the Rayleight regime, and for l < 3µm due to crystal size being > > l.

Fig. 2 Example of the contribution of photon tunneling to extinction efficiency, for a size distribution of hexagonal columns, mean crystal length being 50µm. Tunneling whereby the photon enters the crystal is shown by the short-dashed curve near the bottom, while tunneling due to edge effects is shown by the dot-dashed curve.

Fig. 3
Absorptivities (l < 3 µm) and emissivities with and without photon tunneling from the above size distribution, assuming a cirrus cloud ice water path of 15 g m^-2. Absorptivities are not effected by tunneling due to the large crystal size-to-l ratios.