Can anyone tell me what is the difference between Albedo and surface reflectance? I know for sure that they are not the same. Any links / comments are most welcome.
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3"Albedo is defined as the fraction of incident radiation that is reflected by a surface. While reflectance is defined as this same fraction for a single incidence angle, albedo is the directional integration of reflectance over all sun-view geometries." -- Retrieval of surface albedo from space.– whuberCommented Oct 15, 2012 at 15:27
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1@whuber, that actually sounds a lot like diffuse (multiple/all angles of reflection) vs. specular (1 angle of reflection).– blah238Commented Oct 15, 2012 at 18:11
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@GBh, what does "Surface Reflectance" mean to you in this context (providing such context will help potential answerers provide better answers).– blah238Commented Oct 15, 2012 at 18:12
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Everyone thanks for the reply. @blah238 -I think surface reflectance and reflectance are probably the same Albedo is different from reflectance , I somewhat agree with whuber. Please let me know If we can further clarify between reflectance and albedo Regards, GBh– user11997Commented Oct 15, 2012 at 21:14
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2There is a good link from OSU here: curry.eas.gatech.edu/Courses/6140/ency/Chapter9/Ency_Atmos/…– Aaron ♦Commented Oct 15, 2012 at 22:16
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4 Answers
Albedo is a measure of the diffuse reflectivity of a surface, as opposed to specular reflectivity such as that of glass or water.
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2I cannot find any reference that equates specular reflection with "surface reflectance." Could you quote an authoritative source for your answer?– whuberCommented Oct 15, 2012 at 15:27
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1I avoided making that equation because I don't know what "surface reflectance" is. AFAIK the statement is factual based on the Wikipedia links given, but a better answer would probably say something specifically about "surface reflectance" and what it means to the OP.– blah238Commented Oct 15, 2012 at 16:17
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1Please, then, consider posting a comment to the question asking for what the meaning of "surface reflectance" is in this context. That preliminary back-and-forth helps assure that the answers that get posted are actually relevant to the questions. :-)– whuberCommented Oct 15, 2012 at 16:19
Albedo is the percentage of solar energy striking a surface that is reflected away from the earth.
Surface Reflectance is ratio of the amount light not absorbed by a surface to the amount of light striking the surface.
Albedo is a measure of energy and Surface Reflectance is a property of a material.
Solar radiation times the percentage that gets through the atmosphere and strikes the surface times the Surface Reflectance ratio equals Albedo.
A perfect mirror at night produces zero Albedo.
I agree with @blah238 here is more information Albedo is the percentage of solar radiation reflected by an object. Reflectivity is the capacity of an object to reflect solar radiation. It is described as a function of radiation wavelength and is determined by the physical composition of the object.
Relation of reflectivity to albedo Albedo is the integrated product of incident solar radiation spectral composition and the spectral reflectivity of the object. Outside the atmosphere, solar radiation spectral composition is relatively constant, peaking at about 0.5µm, decreasing rapidly at shorter wavelengths to small amounts at 0.2µm, and decreasing less rapidly at longer wavelengths to small amounts at about 4.0µm. The atmosphere selectively absorbs and scatters solar radiation. As a result, at the Earth’s surface the spectral composition of solar radiation varies significantly as a function of atmospheric conditions (e.g. clouds, water vapor, and dust) and solar elevation (Robinson, 1966; Dickinson, 1983). The majority of albedo measurements have been carried out under clear-sky, high-sun elevation conditions (Table A15). Under cloudy conditions radiation is predominantly in the visible spectrum. This decreases the albedos of soils and vegetation but increases snow albedo (Miller, 1981). When atmospheric turbidity is high, or the sun is low in the sky, the spectral distribution of solar radiation shifts to the red and infrared portion of the spectrum. Soil and vegetation albedos increase and snow albedo decreases (Kondrotyev, 1973). This variability points out the need to know both the spectral reflectivity of objects and the spectral composition of incident radiation in order to evaluate earth albedos.
Some related quotes:
Computer Vision: A Modern Approach (2012)
• The albedo is the fraction of incoming power that the surface radiates.
• The wavelength-dependent diffuse albedo is sometimes referred to as the spectral reflectance (sometimes abbreviated to reflectance or, less commonly, spectral albedo).
• Most surfaces reflect only some of the incoming light in a specular component, and we can represent the percentage of light that is specularly reflected with a specular albedo. Although the diffuse albedo is an important material property that we will try to estimate from images, the specular albedo is largely seen as a nuisance and usually is not estimated.
Real-Time Rendering (2018):
• Local reflectance is quantified by the bidirectional reflectance distribution function (BRDF).
• Despite its somewhat daunting name, the directional-hemispherical reflectance is a simple concept. It measures the amount of light coming from a given direction that is reflected at all, into any outgoing direction in the hemisphere around the surface normal.
