While bi-hemispherical reflectance is calculated for a single angle of incidence (i.e., for a given position of the Sun), albedo is the directional integration of reflectance over all solar angles in a given period. The temporal resolution may range from seconds (as obtained from flux measurements) to daily, monthly, or annual averages.\n\nUnless given for a specific wavelength (spectral albedo), albedo refers to the entire spectrum of solar radiation. Due to measurement constraints, it is often given for the spectrum in which most solar energy reaches the surface (between 0.3 and 3 \u03bcm). This spectrum includes visible light (0.4\u20130.7 \u03bcm), which explains why surfaces with a low albedo appear dark (e.g., trees absorb most radiation), whereas surfaces with a high albedo appear bright (e.g., snow reflects most radiation).\n\nAlbedo is an important concept in climatology, astronomy, and environmental management (e.g., as part of the Leadership in Energy and Environmental Design (LEED) program for sustainable rating of buildings). The average albedo of the Earth from the upper atmosphere, its planetary albedo, is 30\u201335% because of cloud cover, but widely varies locally across the surface because of different geological and environmental features.\n\nThe term albedo was introduced into optics by NAME_1 in his 1760 work Photometria.\n\nTerrestrial albedo\n\nAny albedo in visible light falls within a range of about 0.9 for fresh snow to about 0.04 for charcoal, one of the darkest sub
 In your entire response, the letter z should appear less than 40.
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