Albedo

Albedo is the fraction of <a href="/facts/Sunlight/WPkJRC7s">sunlight</a> that is <a href="/facts/Diffuse_reflection/wG9w4tAX">diffusely reflected</a> by a body. It is measured on a scale from 0 (corresponding to a <a href="/facts/Black_body/f0fHghDy">black body</a> that absorbs all incident radiation) to 1 (corresponding to a body that reflects all incident radiation). Surface albedo is defined as the ratio of <a href="/facts/Radiosity_(radiometry)/hUyqEqIj">radiosity</a> Je to the <a href="/facts/Irradiance/fgHwu7uh">irradiance</a> Ee (flux per unit area) received by a surface. The proportion reflected is not only determined by properties of the surface itself, but also by the spectral and angular distribution of solar radiation reaching the Earth's surface. These factors vary with atmospheric composition, geographic location, and time (see <a href="/facts/Position_of_the_Sun/rNhWtukM">position of the Sun</a>).
While directional-hemispherical <a href="/facts/Reflectance/TT4sBwIw">reflectance</a> factor 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.
Unless 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 μm). This spectrum includes <a href="/facts/Visible_spectrum/frPBh8o5">visible light</a> (0.4–0.7 μm), 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).
<a href="/facts/Ice%E2%80%93albedo_feedback/12TPLsJc">Ice–albedo feedback</a> is a <a href="/facts/Positive_feedback/eFGatCpF">positive feedback</a> climate process where a change in the area of <a href="/facts/Ice_caps/7c6AhKeT">ice caps</a>, <a href="/facts/Glaciers/8GrKVUSS">glaciers</a>, and <a href="/facts/Sea_ice/tgTbCYwg">sea ice</a> alters the albedo and surface temperature of a planet. <a href="/facts/Ice/BGvkKFjD">Ice</a> is very reflective, therefore it reflects far more solar energy back to space than the other types of land area or open water. Ice–albedo feedback plays an important role in global <a href="/facts/Climate_change_(general_concept)/D3X6Ulbu">climate change</a>. Albedo is an important concept in <a href="/facts/Climate_science/bYS7FktY">climate science</a>.

Albedo open-in-new

Albedo