What is Albedo: Definition and 23 Discussions

Albedo (pronounced ; Latin: albedo, meaning 'whiteness') is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that reflects all incident radiation.
Surface albedo is defined as the ratio of radiosity Je to the irradiance 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 position of the Sun). 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.
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 visible light (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).
Albedo 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 30–35% because of cloud cover, but widely varies locally across the surface because of different geological and environmental features.The term albedo was introduced into optics by Johann Heinrich Lambert in his 1760 work Photometria.

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  1. Amaterasu21

    I Why are Saturn's moons so bright?

    Hi all, In the Jovian system, Callisto is extremely dark (albedo 0.22) because its ancient surface is covered with meteoritic dust. Ganymede is brighter (albedo 0.43) as its surface has been resurfaced more recently and hasn't had as much time to accumulate dust; that's confirmed by the younger...
  2. M

    I Can ground albedo near a highway refract noise upward?

    I live near some highways that are roughly "a couple of miles" away. On some blessed days they are inaudible, and on other days they roar with a low frequency sound that penetrates into every corner of the basement. (If frequency matters, it would be most preferable to refract sound at 20Hz...
  3. AppleiPad556

    Correlating albedo with temperature?

    As mentioned above, I wanted to devise an equation that can relate the colour of a surface to the temperature on the surface. I tried using the general definition of albedo and combining it with the Stefan-Boltzmann equation (see above, Relevant Equations). However this means that the higher the...
  4. Nik_2213

    I Is a Robust Estimate of Tau Ceti 'f' Albedo Possible?

    tau Ceti 'f' is an *interesting* planet, on habitable zone's outer border-line around a mostly placid, mid-K star, its Sine(i) mass highly sensitive to orbital plane alignment. IIRC, current estimates are based on the big asteroid belt's ~35º inclination to line-of-sight. With necessary...
  5. xpell

    B How hard is it to detect extinct comets?

    Hi! I have read that cometary nuclei have a very low albedo, even lower than coal or asphalt. Because of this, they absorb lots of light and heat rather than reflecting them. So I was wondering how hard is it to detect extinct comets. Could the solar system be full of dead nuclei buzzing around...
  6. E

    Relationship between Reflectance and Albedo

    I have a question regarding the relationship between the reflectance and albedo of a material. What I Know: Both quantities are the ratio between the incoming and outgoing radiation from a material. Correct me if I am wrong, the reflectance of a material depends on the material while the albedo...
  7. quasarLie

    Calculate Average Temperature of Planet in 0.4 AU Orbit: Albedo 30%

    Homework Statement We consider a planet in a circular orbit around a star. I have to calculate the average temperature knowing that the radius of the orbit is 0.4 AU and that the planet reflects 30% of the incident light Homework EquationsThe Attempt at a Solution I used this equation F = L/4...
  8. Battlemage!

    B Albedo, atmosphere, and predicted temperature of Venus

    The reason I am making this thread is because I have a question regarding predicted temperatures of planets based on their area, distance from the sun, and albedo. Going by the planetary equilibrium temperature, T4 = [L(1-a)]/(16σπD2), I have seen numerous websites state that Venus would...
  9. NatFex

    B Difference between albedo and emissivity?

    This has been asked already, but it was either answered incorrectly or I'm just not understanding it right. I was under the impression that albedo is the ratio of radiation reflected off a body compared to the total incident on that body. Hence black bodies have an albedo of 0 and more...
  10. C

    Calculating albedo and eccentricity

    I have a three part question: Background: For a planet on an orbit with semi-major axis a and eccentricity e, the distance of closest approach to the Sun is r = a(1 − e) and the farthest approach is r = a(1 + e). (1) Assuming an albedo A = 0.2, estimate the temperature on Earth in equilibrium...
  11. shmijda

    Does the Presence of Ice Sheets Affect Earth's Energy Balance?

    Homework Statement The presence of a huge ice sheet helps support itself by changing the amount of energy the Earth receives.Question 13 options: True False Homework Equations none The Attempt at a Solution Ice sheets have high albedo, therefore Earth gets less solar energy?
  12. S

    Calculating Orbital Radius from Albedo and Temperature?

    Homework Statement Assume that a planet can have an atmosphere if the escape speed of the planet is 6 times larger than the thermal speed of the molecules in the atmosphere (also known as the root-mean-square molecular velocity). Suppose a hypothetical object having the same mass and radius...
  13. N

    Solar eclipse - magnitude and albedo

    Hello, everyone. On physics Olympiad in our country I get a interesting example... But, I didn't know how to solve it. Can you tell me how? It is known that the Moon when it is full has the apparent magnitude of approximately -12 mag and the Sun during the day has the apparent magnitude of...
  14. D

    Albedo shouldn't change the temperature

    I've never understood why changing the albedo of an object will change the temperature of the object. As I understand it the albedo is a factor that determines the amount of light reflected off the surface. This means that a low albedo will mean that more light-energy is absorbed. Thermal...
  15. M

    Connection between emissivity and albedo

    Hi, I am studying thermal radiation. Does anyone know what is a connection between emissivity and albedo. Regards, Mike
  16. N

    Questions about geometric albedo and phase angle

    If our sun is the source of illumination, how can an object be observed from the Earth at full phase? Wouldn't the Earth eclipse the object? So then why can we see a full moon during full phase? Is it because the moon's orbit is inclined wrt to the Earth-Sun orbit? If so then wouldn't this by...
  17. S

    Albedo equations giving different results

    1. This question isn't so much a homework question per se, however I am having difficulty using certain equations to find the albedo of the Earth. In attempting to find the albedo, I am using two equations, shown below, however each equation gives a different answer. I am given the following...
  18. F

    Albedo and surface temperature of the Earth

    Homework Statement If the Earth's average cloud cover increased, what effect would it have on the albedo temperature? If the Earths albedo increased to 0.32, what would be the average temperature? Ok I thought that if the albedo was higher, it would reflect more light, thus coolign would...
  19. M

    How do I calculate the phase integral for the Bond albedo in astrophysics?

    Hi, Im doing an IB Extended essay on astrophysics, on the planning stage. My aim is to calculate the surface temperature of an extrasolar planet. I have most of the caculations done, but I am stuck on just one part - calculating the Bond albedo of the planet. I know what the geometric albedo...
  20. D

    Albedo Change as the Basis for Recent Northern Planetary Warming-1

    https://www.physicsforums.com/showthread.php?t=245558 The attached table shows polar satellite (MSU) atmospheric temperature patterns posted on UAH covering 29.5 years. Note the LT contrast between the north polar and south polar regions, a 1.3 oC rise vs. a 0.2 oC loss. While the northern...
  21. H

    Earths albedo controlled by cosmic rays

    The Danish scientist Henrik Svensmark has been scorn for several years now because of his alternative explanation of how Earth's temperature varies. His theory states this: High solar activity is a sign of a strong magnetic field from the sun -> Strong magnetic field from the sun will decrease...
  22. B

    Albedo and reflected light from the moon

    Hi all, I'm looking for a way to calculate how much light is reflected from the surface, on the moon, and whether that light would be strong enough to be classed as a bright light source. I have no idea where to start with this, but basically I'm trying to prove a Lunar Hoax Conspiracy...
  23. Andre

    Can Earth's Albedo and Surface Temperatures Increase Together?

    Suppose I was to publish this study. **** Andre et al, 2006, Earth Albedo variations dwarf greenhouse effect EOS, Vol. 87, No. 4, 24 January 2006 Abstract We compute Earth albedo (reflectivity) in the period 1984-2004, using cloud data and coverage, confirmed by measuring reflectivity of...