1. Definition of albedo

Albedo is a quantitative measure of a surface's reflectivity, indicating the proportion of reflected sunlight to incident sunlight. Albedo varies from 0 (absorbs all light) to 1 (reflects all light). The higher the albedo coefficient, the more reflective the surface. Albedo can be used to quantify the solar energy reflected by the Earth and its atmosphere, or to characterize the texture and color of surfaces, such as snow, clouds, water or urban surfaces.

Depending on the field of application, several definitions of albedo have been proposed. The first use of the term albedo, which means whiteness in Latin, was proposed by the astronomer Jean Henri Lambert in the 18th century. Astronomers generally use a two-way definition of albedo. It defines the luminance in the direction of observation of a planet or natural satellite illuminated by the sun.

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