By means of a specially constructed portable goniophotometer the directional reflectance of numerous surfaces of snow was measured during the winter of 1951–1952. While some samples reflected more nearly diffusely than others, all showed much specular reflection at high angles of incidence. An approximate theory of the specular reflection is given and its results compared with experiment. The experimental fact that the angle of maximum reflectance is greater than the angle of incidence is explained by the theory.
W. E. KNOWLES MIDDLETON and A. G. MUNGALL, "The Luminous Directional Reflectance of Snow," J. Opt. Soc. Am. 42, 572-579 (1952)