Theoretical and experimental studies of microwave radiation from a natural snow field

The brightness temperature of a natural snow field in northern Europe was studied theortically and experimentally at 5, 12, and 37 GHz for satellite remote sensing applications. A snow model consisting of ice spheres covered by a water shell was used in calculation, taking into account scattering and absorption. The brightness temperature of a natural snow field as a function of view angle was measured from a tower in 1978 and 1979. The measured brightness temperature curves can be fitted with calculated ones by assuming reasonable values for the wetness and the particle size of snow. Experimental results also show that relatively small changes in the snow conditions cause large changes in the brightness temperature. In order to obtain a more controlled situation, experiments were continued in 1980 using a measuring site covered with aluminum sheets and determining the wetness and the particle size in addition to the density and physical temperature.