Retrieval of snow physical parameters using a ground-based spectral radiometer.

A ground-based spectral radiometer system for albedo and flux (GSAF) was developed to retrieve a mass concentration of snow impurities and effective snow grain size automatically. The GSAF measures spectral albedo and diffuse fraction with a single sensor to omit a radiometric calibration. The deviation from an ideal cosine response of the sensor to insolation is precisely corrected. The snow physical parameters can be retrieved with the GSAF even under cloudy conditions, because the effect of illumination conditions on albedo is considered in a retrieval algorithm. Continuous measurements with the GSAF at two snowfields in Hokkaido, Japan, showed the correlations between the retrieved parameters and in situ measurements (R=0.595 to 0.940).