Experimental assessment of visible sunlight radiative transfer process in diffusive media

Light transmission, which is determined by scattering and absorption, is the result of a combination of snow characteristics and illumination conditions as well as to the different optically distinct layers, such as surface hoar and ice lenses. Furthermore, optically active particles such as dust and black carbon in the snowpack can significantly diminish both visible and near-infrared reflectance and transmission, resulting in substantial fluctuations in absorbed radiation and therefore to an acceleration of the melting processes.

Although a few measurements have been attempted in the past decades with several approaches, light penetration through the snowpack is currently almost only modelled numerically, frequently using severe assumptions and several parameters not always easy to be fixed. The lack of experimental data and dedicated studies leave a remarkable scientific gap in the snow research. In our laboratory we have developed a novel probe to assess sunlight flux in three different spectral bands as a function of depth in the upper few centimetres of the ground and sea ice. The instrument, which has been designed to be very compact and lightweight, thus easily transportable on the field, measures the scattered light propagating horizontally with respect to the surface with high spatial resolution (3 mm).