Contents I. Introduction
The scattering characteristics that are typical for pristine ice crystals with smooth surface and basic hexagonal structures either in a form of single particles or aggregates are the halo peaks in the angular distribution of scattered radiation. As articulated by Mishchenko et al. [1] on the basis of the observations reported in the literature, halos are not often seen in the atmosphere, and the phase functions associated with ice clouds might be featureless with no pronounced halo peaks. One of the mechanisms responsible for the featureless phase function might be the surface distortion or roughness of ice crystals [1]–[3]. Ice crystals may have rough surfaces due to evaporation/sublimation [4], [5] or riming process [6]. Rolland et al. [7] studied the sensitivity of retrieved optical thickness and effective particle size of ice particles to surface roughness conditions through its impact on the single-scattering properties. However, in their study, limited reflectance measurements [7], Fig. 7 and Table 5 were used, and the degree of surface roughness condition was not quantitatively stated. Thus, there is a need to further investigate the effect of the surface roughness on the retrieval of the optical and microphysical properties of ice clouds.
