albedosreflectivitygeometrical albedoreflectivesolar reflectancealbedo effectalbedo effectsAstronomical albedo0.090.1–0.05
Albedo (albedo, meaning 'whiteness') is the measure of the diffuse reflection of solar radiation out of the total solar radiation received by an astronomical body (e.g. a planet like Earth).wikipedia
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asteroidsminor bodyMinor Planet
The albedos of planets, satellites and minor planets such as asteroids can be used to infer much about their properties.
Only one asteroid, 4 Vesta, which has a relatively reflective surface, is normally visible to the naked eye, and this only in very dark skies when it is favorably positioned.
nucleuscomet nucleicometary nucleus
A typical comet nucleus has an albedo of 0.04.
A typical comet nucleus has an albedo of 0.04.
LambertJohann LambertJohann H. Lambert
The term albedo was introduced into optics by Johann Heinrich Lambert in his 1760 work Photometria.
In Photometria Lambert also formulated the law of light absorption—the Beer–Lambert law) and introduced the term albedo.
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.
Fresnel reflection is directional and therefore does not contribute significantly to albedo which primarily diffuses reflection.
Enceladus – potential habitabilityEnceldausfountains of frozen particles erupting from Enceladus
Enceladus, a moon of Saturn, has one of the highest known albedos of any body in the Solar System, with an albedo of 0.99.
Only its orbital characteristics were known, with estimations of its mass, density and albedo.
intensitylight intensityspectral irradiance
Surface albedo is defined as the ratio of radiosity to the irradiance (flux per unit area) received by a surface.
These calculations are based on the bidirectional reflectance distribution function (BRDF), which describes how the reflectance of a given surface depends on the view angle of the observer and the solar angle.
The BRDF/Albedo product can be used to model surface albedo depending on atmospheric scattering.
Solar elevation anglealtitude angleelevation
A weighted daily average zenith angle, used in computing the local albedo of the Earth, is given by
ice-albedo feedbackalbedo changesfeedback loop
This feedback loop results in a reduced albedo effect.
Ice–albedo feedback is a positive feedback climate process where a change in the area of ice caps, glaciers, and sea ice alters the albedo and surface temperature of a planet.
MODISModerate-Resolution Imaging SpectroradiometerModerate-Resolution Imaging Spectroradiometer (MODIS)
Earth's surface albedo is regularly estimated via Earth observation satellite sensors such as NASA's MODIS instruments on board the Terra and Aqua satellites, and the CERES instrument on the Suomi NPP and JPSS.
The overall albedo of the Moon is measured to be around 0.14, but it is strongly directional and non-Lambertian, displaying also a strong opposition effect.
The Moon has an exceptionally low albedo, giving it a reflectance that is slightly brighter than that of worn asphalt.
As the amount of reflected radiation is only measured for a single direction by satellite, not all directions, a mathematical model is used to translate a sample set of satellite reflectance measurements into estimates of directional-hemispherical reflectance and bi-hemispherical reflectance (e.g., ).
It is sometimes called "black-sky albedo".
main-beltMain beltmain-belt asteroid
Many small objects in the outer Solar System and asteroid belt have low albedos down to about 0.05.
They are redder in hue than the other asteroids and have a very low albedo.
water planetwater worldocean-covered
In contrast, if the entire Earth was covered by water – a so-called ocean planet – the average temperature on the planet would rise to almost 27 °C.
Several other surface and interior processes affect the atmospheric composition, including but not limited to the ocean fraction for dissolution of and for atmospheric relative humidity, redox state of the planetary surface and interior, acidity levels of the oceans, planetary albedo, and surface gravity.
climate changeglobal climate changeanthropogenic climate change
Both positive feedback loops have long been recognized as important for global warming.
Changing the type of vegetation in a region impacts the local temperature by changing how much sunlight gets reflected back into space, called albedo, and how much heat is lost by evaporation.
weather conditionsweather systemselements
The uneven heating of Earth from albedo variations between land, ice, or ocean surfaces can drive weather.
On local scales, temperature differences can occur because different surfaces (such as oceans, forests, ice sheets, or man-made objects) have differing physical characteristics such as reflectivity, roughness, or moisture content.
feedback loopfeedback loopsfeedback control
When an area's albedo changes due to snowfall, a snow–temperature feedback results.
A simple example is the ice-albedo positive feedback loop whereby melting snow exposes more dark ground (of lower albedo), which in turn absorbs heat and causes more snow to melt.
space-weathereddarkenslighter, disturbed soil
Such a dark surface is thought to be indicative of a primitive and heavily space weathered surface containing some organic compounds.
On the Moon, the spectral effects of space weathering are threefold: as the lunar surface matures it becomes darker (the albedo is reduced), redder (reflectance increases with increasing wavelength), and the depth of its diagnostic absorption bands are reduced These effects are largely due to the presence of nanophase iron in both the agglutinates and in the accreted rims on individual grains.
Cloud albedo has substantial influence over atmospheric temperatures.
Cloud albedo is a measure of the albedo of a cloud.
This has been a concern since arctic ice and snow has been melting at higher rates due to higher temperatures, creating regions in the arctic that are notably darker (being water or ground which is darker color) and reflects less heat back into space.
Some important aspects of snow cover include its albedo (reflectivity of incident radiation, including light) and insulating qualities, which slow the rate of seasonal melting of sea ice.
cool roofcool roofsreflective surface
Reflective surfaces can deliver high solar reflectance (the ability to reflect the visible, infrared and ultraviolet wavelengths of the sun, reducing heat transfer to the surface) and high thermal emittance (the ability to radiate absorbed, or non-reflected, solar energy).
Hbolometric magnitudeabsolute magnitude (H)
The correlation between astronomical (geometric) albedo, absolute magnitude and diameter is:
Earth's albedo varies by a factor of 6, from 0.12 in the cloud-free case to 0.76 in the case of altostratus cloud.
solar radiationinsolationsolar insolation
Albedo (albedo, meaning 'whiteness') is the measure of the diffuse reflection of solar radiation out of the total solar radiation received by an astronomical body (e.g. a planet like Earth).
The proportion of reflected radiation is the object's reflectivity or albedo.
The study of albedos, their dependence on wavelength, lighting angle ("phase angle"), and variation in time comprises a major part of the astronomical field of photometry.
blackBlack carbon particlesblack smoke
Another albedo-related effect on the climate is from black carbon particles.
Black carbon warms the Earth by absorbing sunlight and heating the atmosphere and by reducing albedo when deposited on snow and ice (direct effects) and indirectly by interaction with clouds, with the total forcing of 1.1 W/m 2.