The spectral diffuse reflectance of various types of desert terrain was measured at 500 A intervals in the spectral range 4000 A to 6500 A. For all types investigated except basaltic lava, the diffuse reflectance increased with increasing wavelength of the incident radiation. In general, the diffuse reflectance at 6500 A was approximately twice that at 4000 A. The various types of surfaces showed large differences in diffuse reflectance; the values ranging from 0.03 to 0.74. Measurements made of radiance from a surface of brush and wind-blown sand showed that the reflection does not follow Lambert’s law.
EDWARD V. ASHBURN and RODNEY G. WELDON, "Spectral Diffuse Reflectance of Desert Surfaces," J. Opt. Soc. Am. 46, 583-586 (1956)