Surface albedo measurements over snow and blue ice in thematic mapper bands 2 and 4 in Dronning Maud Land, Antarctica

Ground-based observations of broadband, narrowband (in Landsat thematic mapper bands 2, 0.52 - 0.60 μm, and 4, 0.76 - 0.90 μm), and bidirectional reflectance are used to study the albedo of blue ice and snow. The measured broadband albedos for blue ice and snow are 0.60 and 0.78, respectively. The narrowband albedos in bands 2 and 4 for snow are 0.97 and 0.86, respectively, and for blue ice are 0.87 and 0.51, respectively. The measurements are point values and used to verify existing weighting functions between the broadband and narrowband albedos. Blue ice data do not comply with the existing functions. Furthermore, a new function for blue ice is derived. A simple two-stream model is used to illustrate the behavior of the snow and ice albedo as a function of reflection and absorption. The bidirectional reflectance measurements are used to derive bidirectional reflectance distribution functions (BRDFs) for snow and blue ice. The BRDF of blue ice exhibits a maximum brightening in the forward limb around a zenith angle close to the solar zenith angle, indicating specular reflectance of blue ice which is not visible for snow and glacier ice surfaces.