Abstract
The optical properties of snow and ice surfaces at the visible and near infrared wavelengths are accounted by a radiative transfer theory in the atmosphere-snow/ice system. In those optical parameters, the important factors as albedo and BRDF (Bidirectional Reflectance Distribution Function) can be estimated by the radiative interaction between the atmosphere and snow/ice, in which light scattering and absorption are theoretically calculated. These theoretical studies began with the modelings of spectral snow albedo in 1950's, and progressed to the operational stage in 1980's and to the modeling of BRDF in 1990's. On the other hand, the observational studies have advanced from the spectrally integrated measurements to the spectral measurements of snow/ice surfaces. These observational results have contributed to the modelings of albedo and BRDF. The radiative transfer theory in the atmosphere-snow/ice system is also applied to the remote sensing of snow and ice surfaces such as the retrievals of snow grain size and snow impurities. Since the influence of global warming is expected to appear significantly in the cryosphere, the remote sensing of snow/ice physical parameters is effective to monitor the global warming. For that purpose, it is necessary to develop the accurate BRDF model for various snow/ice conditions and to validate it with the measurements.
