Snowalbedo

Snow albedo refers to the reflectivity of snow surfaces to incoming shortwave solar radiation. It is a key parameter in the surface energy balance and the climate system because snow-covered areas reflect a large portion of sunlight, helping to keep surface temperatures cooler. Fresh, clean snow can have a broadband albedo around 0.85 to 0.95 under bright sun, while older or dirty snow may drop to 0.4–0.7. Albedo also depends on the solar angle and spectral composition, with higher reflectance in the visible and more absorption in the near-infrared.

Several factors influence snow albedo. Snow grain size and metamorphism reduce albedo as grains grow. Liquid water in the snow or crust formation lowers reflectivity. Impurities such as mineral dust, soot, or organic matter darken the snow. Snow depth, temperature, moisture, and the spatial structure of the surface (roughness, plumes, or patches of bare ground) also affect the measured albedo.

Measurement and data sources include ground-based instruments such as spectroradiometers and albedometers that directly measure surface reflectance, and satellite sensors (for example MODIS and other remote sensing instruments) that estimate albedo over large areas by retrieving reflectance in multiple bands and applying radiative transfer corrections.

Climate relevance is strong: snow albedo feedback amplifies seasonal and regional climate responses. In climate models, albedo is parameterized as a function of snow cover, grain size, impurity load, and snow age, influencing energy balance, melt timing, and regional climate projections.