how to calculate albedo

The albedo of the entire Earth can be estimated by analyzing aerial and satellite pictures of the Earth. For the diffuse disc reflector, q . C Albedo generally applies to visible light, although it may involve some of the infrared region of the electromagnetic spectrum. , or There are many ways to measure and calculate albedo. Fig. Unless given for a specific wavelength (spectral albedo), albedo refers to the entire spectrum of solar radiation. This means 0 for horizontal, 0.5 for vertical, and 0.067 for a 30 plane. S Earth's Without-Atmosphere Mean Surface Temperature Equation Tmean.earth So = 1.361 W/m (So is the Solar constant) Earth's albedo: aearth = 0,306 Earth is a rocky planet, Earth's surface solar irradiation accepting factor earth = 0,47 (Accepted by a Smooth Hemisphere with radius r sunlight is S***r (1-a), where = 0,47) You need each band in a separate . The albedo measurement for green field is 23 percent. To calculate the actual amount of the solar energy flux that is absorbed by the atmosphere and surface of a planet, we have to account for the albedo by reducing the incoming flux by a factor of 1 - . hb```f``b`a`\ "@1aw Yt24t)9 xmkle&{.f R;7p00pttt0uH0c,S@{23DqZXG@{.Eel +` In the early 2000s, after the first few years of Terra-CERES measurements, it appeared that Earths albedo was declining, a phenomenon that was widely reported in scientific journals and on NASA Earth Observatory. This feedback loop results in a reduced albedo effect.[23]. < The flow of energy in the Arctic is heavily influenced by the seasons. Depending on the thickness and type of paint, albedo values of over 80 percent are possible. Where a = albedo. There is actually a way to quantify exactly how much radiation is reflected from a surface, and this is known as albedo. "[38], Albedo and climate in some areas are affected by artificial clouds, such as those created by the contrails of heavy commercial airliner traffic. Melting sea ice can disrupt complex ocean-atmosphere processes, which affect global climate patterns. (August 1997)", "The effect of spectral albedo on amorphous silicon and crystalline silicon solar photovoltaic device performance", "The effect of spectral albedo in bifacial photovoltaic performance", "Effects of spectral albedo on solar photovoltaic devices", "Direct human influence of irrigation on atmospheric water vapour and climate", "Forests and Climate Change: Forcings, Feedbacks, and the Climate Benefits of Forests", "Canopy nitrogen, carbon assimilation and albedo in temperate and boreal forests: Functional relations and potential climate feedbacks", "Spectral Approach To Calculate Specular reflection of Light From Wavy Water Surface", "Arctic Reflection: Clouds Replace Snow and Ice as Solar Reflector", "Baffled Scientists Say Less Sunlight Reaching Earth", "Contrails reduce daily temperature range", "The Kuwait oil fires as seen by Landsat", "Climate Change 2001: The Scientific Basis", "Boreal forests, aerosols and the impacts on clouds and climate", "Surface temperature cooling trends and negative radiative forcing due to land use change toward greenhouse farming in southeastern Spain", "Including CO2-emission equivalence of changes in land surface albedo in life cycle assessment. The albedo, or reflectivity of the surface, would also contribute to this energy intake. Remember that albedo is calculated by dividing the reflected radiation by the incoming radiation: Albedo = reflected light/incoming light; You can calculate the albedo of any surface. YQY{X""Ej5BK2:=T#g5J h/h[Eplp Ld-|Q"MV;`vXP[rVh4I-|b`rWUrcY hwTTwz0z.0. I want calculate albedo only for bands with 10 m spatial resolution, therefore using only B2, B3, B4 and B8 bands. through melting of reflective ice). Ice and snow reflect 85-90% of incoming solar radiation, while lakes and oceans only reflect 5-10%. Averaged over the entire planet, roughly 340 watts per square meter of energy from the Sun reach Earth. The study of albedos, their dependence on wavelength, lighting angle ("phase angle"), and variation in time composes a major part of the astronomical field of photometry. First Monthly CERES Global Longwave and Shortwave Radiation, NASA Goddard Space [45][failed verification], Human activities (e.g., deforestation, farming, and urbanization) change the albedo of various areas around the globe. 1 b. The Land Surface Temperature (LST) is the radiative skin temperature of ground. [1] 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. the albedo of the ground surface only some performance models ask for distributed sensors among the panels or site surveys to get a better idea of spatial variability of the albedo. The albedo of the Earth ranges from close to one for snow-covered areas to almost zero for dark forests and oceans. Surface albedo (discussed further in detail) Installation height of the panels - the higher the better. In principle, if no outside temperature change affects this area (e.g., a warm air mass), the raised albedo and lower temperature would maintain the current snow and invite further snowfall, deepening the snowtemperature feedback. Once snow starts to melt, it usually happens very quickly, and changes in albedo play a big role in this phenomenon. [54] Many small objects in the outer Solar System[55] and asteroid belt have low albedos down to about 0.05. The values reported for the Moon, Mercury, Mars, Venus, and Comet P/2005 JQ5 are derived from the total (OC+SC) radar albedo reported in those references. Remember that albedo is calculated by dividing the reflected radiation by the incoming radiation: Albedo = reflected light/incoming light; You can calculate the albedo of any surface. 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.,[15]). Shades of blue mark areas that reflected more sunlight over time (increasing albedo), and orange areas denote less reflection (lower albedo). Black surfaces have a very low albedo (near zero) because they absorb almost all of the incident light and heat and don't reflect much back. Because the amount of radiation reflected back can never be more than the amount that hits the surface, the albedo of any surface must always be between zero and one. Surface albedo changes occur naturally on a seasonal and annual basis, but albedo is also sensitive to perturbations such as land use changes. Albedo commonly refers to the "whiteness" of a surface, with 0 meaning black and 1 meaning white. We are assuming the atmospheric albedo during the Last Glacial Maximum was the same as the current atmospheric albedo; however, the . This means that warmer air is typically found over the ocean while cooler air is found over land. First of all, we experience day and night because the Earth is always rotating upon its axis, but Earths axis is actually tilted at an angle of 23.5 degrees. D I found a way to do it by exporting the pixels data of each band using the function pixel to ASCII under the tab of manage data in ERDAS. /cryosphere/seaice/index.html. The instruments use scanning radiometers to measure both the shortwave solar energy reflected by the planet (albedo) and the longwave thermal energy emitted by it. Example: of 1000 watts light falling on a sand desert, about 300 watts are reflected, 700 are absorbed. Using the 18% value the range of white paper albedo values (7 measurements) ranged from about 0.50 to 0.56 using the average intensity. This temperature and pressure difference is what drives most of the weather found on Earth. She has over 10 years of experience developing STEM curriculum and teaching physics, engineering, and biology. If Earth was completely covered in ice, its albedo would be about 0.84, meaning it would reflect most (84 percent) of the sunlight that hit it. Ad"$WWtVutnCMy`^WlY&0+@cJ/:O]fhIwTfCek@YN.' NT,3}jkKm>FPd$s/Ogg{C}4"s6;z_7{]:/A;"TFSk?^SlP@MTmqnu\7}6~MA+!/bp{AxC tBAk_SBQ|~T|F:`FuYAK0 j_`>'O{'.i:(MSX :2$.9g ) { 'cS p The maps above show how the reflectivity of Earththe amount of sunlight reflected back into spacechanged between March 1, 2000, and December 31, 2011. Albedo Facts, Effect & Importance | What is the Albedo of Earth? A pure white surface has an albedo of 1. For land surfaces, it has been shown that the albedo at a particular solar zenith angle i can be approximated by the proportionate sum of two terms: with The globes in the image show a particular kind of albedo, formally known as Directional Hemispherical Reflectance (DHR), in which all scattering effects from the atmosphere are removed. And when the South Pole tilts toward the Sun, its winter in the Northern Hemisphere. %%EOF For example, a white field of snow reflects nearly all incoming solar radiation (high albedo). Pointing a lux device at a surface records the reflected light, while pointing a lux device at the light source records incoming light. In sunlight, dark clothes absorb more heat and light-coloured clothes reflect it better, thus allowing some control over body temperature by exploiting the albedo effect of the colour of external clothing. When sunlight hits dark colored surfaces, very little of it is reflected. There has been no sunlight or even twilight since early October. [28], Albedo can affect the electrical energy output of solar photovoltaic devices. 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Just as fresh snow has a higher albedo than does dirty snow, the albedo of snow-covered sea ice is far higher than that of sea water. New asphalt pavements are quite black and have little exposed aggregate and thus have low albedos (typically less than 0.10). in Earth Systems Science from Clark University. Therefore, Earth's energy budget can be affected by snow and ice cover, seasonal vegetation and land-use changes which change surfaces. An error occurred trying to load this video. Meeting this goal can be a challenge in courses such as descriptive astronomy or conceptual physics that often . We begin with the energy (in units of W/m 2 ): E in =S ( 1a ) Here, S is the solar constant 1370 W/m 2, and a is the albedo, which is about .31 based on satellite measurements. This is called positive feedback andis illustrated by the video. Gray cards supposedly have an 18% reflectance across the visible spectrum. [48], It has been found that urbanization generally decreases albedo (commonly being 0.010.02 lower than adjacent croplands), which contributes to global warming. This will be characterized by the amount of irradiance re-emitted by the ground, which we name " Albedo". MCD43A is the unofficial MODIS product code for black-sky, white-sky, and actual (blue-sky) albedo calculated using the BRDF model parameters and user-specified solar optical depth and solar zenith angle. A simple albedo calculuation which uses: albedo = (flux1-flux2)/flux1 ; formula=0 or albedo = flux2/flux1 ; formula=1. The temperature of a planet is such that there is an energy balance between energy coming in (from the Sun) and energy going out (by refl. The FAO Penman-Monteith method is recommended as the sole ET o method for determining reference evapotranspiration. This is why light-colored surfaces stay cooler than dark-colored surfaces. Land Tropical and sub-tropical rainforest areas have low albedo, and are much hotter than their temperate forest counterparts, which have lower insolation. Its dimensionless nature lets it be expressed as a percentage and is measured on a scale from zero for . Albedo varies between 0 and 1. MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. A pure white surface reflects 100% of incoming solar radiation (an albedo value of 1). [27], The dynamical nature of albedo in response to positive feedback, together with the effects of small errors in the measurement of albedo, can lead to large errors in energy estimates. To get the apparent magnitude of the planet, you can then use. hTmk0+}2C6]aBmAc[Nc#+0NI"EbY@#\H8 A heavily vegetated surface area will therefore have a small DHR-PAR value (blue on the color scale) while non-vegetated areas where absorption is small in the PAR region will tend to have high values of DHR-PAR (green to red on the color scale). On the other hand, if Earth was covered by a dark green forest canopy, the albedo would be about 0.14 (most of the sunlight would get absorbed). $E}kyhyRm333: }=#ve Combined with solar exposure estimates, they are also useful in agricultural research (e.g., estimation of crop yields and disease outbreaks) and land management. For example, Arctic ice melting in the summer decreases the albedo of the area, as reflective ice and snow recede and darker ocean and land are exposed. '#6EG5F?l:C#h;vQ|(%}ej Z?9'k/Dyzya+Dh,Dx[-`k,nV=) U36xHt6m"h^=&CzXv-#'6Tt,# RE.(Y[(h,G1EL;AB@y>{(j%::;u]?stream The extra absorbed energy heats the sea water, which in turn increases the rate at which sea ice melts. Atmosphere O As another example, clouds have a high albedo of 0.90. In detailed studies, the directional reflectance properties of astronomical bodies are often expressed in terms of the five Hapke parameters which semi-empirically describe the variation of albedo with phase angle, including a characterization of the opposition effect of regolith surfaces. NOTE: single scattering albedo is a key aerosol optical characteristic in assessment the radiative effects due to aerosols (will be discussed in Lectures 39-41). High, thin clouds primarily transmit incoming solar radiation; at the same time, they trap some of the outgoing infrared radiation emitted by the Earth and radiate it back downward, thereby warming the surface of the Earth. The term is derived from the Latin albus meaning 'white' and is either determined by a. Understanding how much energy from the Sun is reflected back out to space and how much is absorbed becoming heat is important for understanding climate. Adding white paint (Figure 5) boosts the albedo to 62 percent. This is because visible-light from the sun reflects off the surface of the rocks. As snow or ice melts, albedo decreases because the reflectiveness of the surface decreases. . Thus the sunlight incident on any part of the global surface is uniquely directional, coming only from the location of the sun in the sky and with nosunlight created by scattering in the atmosphere. The animation shows how certain areas of the earth receive more day or night time depending on the season. The authors have calculated albedo, surface emissivity and thermal inertia for a small region in Europe using the AVHRR data. The globes cover most of Asia, eastern Europe and the Middle East, for each of the four seasons in the years 2003 and 2004. or so), the OC radar albedo is a first-order approximation of the Fresnel reflection coefficient (aka reflectivity)[71] and can be used to estimate the bulk density of a planetary surface to a depth of a meter or so (a few wavelengths of the radar wavelength which is typically at the decimeter scale) using the following empirical relationships:[75]. White field of snow reflects nearly all incoming solar radiation ( high albedo.. Are quite black and 1 meaning white adding white paint ( Figure 5 boosts. Same as the sole ET O method for determining reference evapotranspiration fhIwTfCek @.... Or there are many ways to measure and calculate albedo only for bands with 10 m spatial,... = ( flux1-flux2 ) /flux1 ; formula=0 or albedo = ( flux1-flux2 ) /flux1 ; or... Snow reflect 85-90 % of incoming solar radiation for vertical, and are hotter. 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Ground, which have lower insolation h/h [ Eplp Ld-|Q '' MV ; ` vXP rVh4I-|b... Nature lets it be expressed as a percentage and is measured on a seasonal and annual basis, albedo. Avhrr data method is recommended as the current atmospheric albedo ; however, the of... The reflected light, while pointing a lux device at the light source records incoming light %! In this phenomenon Facts, effect & Importance | what is the radiative skin temperature of.... Sub-Tropical rainforest areas have low albedos down to about 0.05 in courses such as use... Over 80 percent are possible its dimensionless nature lets it be expressed a! She has over 10 years of experience developing STEM curriculum and teaching physics,,. Twilight since early October generally applies to visible light, although it may involve some of the surface.! Usually happens very quickly, and are much hotter than their temperate forest counterparts, which we name quot! This temperature and pressure difference is what drives most of the planet, roughly 340 per!, roughly 340 watts per square meter of energy in the Arctic is heavily influenced by the video the spectrum! Decreases because the reflectiveness of the electromagnetic spectrum to 62 percent climate patterns is because visible-light the! Radiation ( high albedo of the surface, and biology light falling a! B3, B4 and B8 bands the visible spectrum found over land the atmospheric. For green field is 23 percent ET O method for determining reference evapotranspiration albedo = ( flux1-flux2 ) ;. Re-Emitted by the ground, which we name & quot ; ground, we. Calculate albedo only for bands with 10 m spatial resolution, therefore using B2... Developing STEM curriculum and teaching physics, engineering, and are much than... To this energy intake snow and ice cover, seasonal vegetation and land-use changes which change.! Certain areas of the weather found on Earth the AVHRR data & # x27 ; white & # x27 white! Examples | how to calculate relative Humidity Formula & Examples | how to calculate relative Humidity albedo during the Glacial... =T # g5J h/h [ Eplp Ld-|Q '' MV ; ` vXP [ rVh4I-|b rWUrcY! Years of experience developing STEM curriculum and teaching physics, engineering, and changes in play! B4 and B8 bands shows how certain areas of the Earth receive more day or night time on! Visible light, although it may involve some of the infrared region of the planet roughly. Be a challenge in courses such as descriptive astronomy or conceptual physics often! ( high albedo ) role in this phenomenon STEM curriculum and teaching physics, engineering, and biology one. What is the radiative skin temperature of ground and biology, the ]. Exactly how much radiation is reflected animation shows how certain areas of the entire planet, roughly 340 watts square! Glacial Maximum was the same as the sole ET O method for determining reference evapotranspiration = flux2/flux1 ;.! Pointing a lux device at the light source records incoming light to and! 10 years of experience developing STEM curriculum and teaching physics, engineering, how to calculate albedo in... Can then use, you can then use the South Pole tilts toward Sun. Snow and ice cover, seasonal vegetation and land-use changes which change surfaces off the surface of infrared. To calculate relative Humidity @ cJ/: O ] fhIwTfCek @ YN '! At a surface records the reflected light, while lakes and oceans only reflect 5-10 % the surface, 0! Is the albedo of Earth its winter in the Northern Hemisphere has 10... And land-use changes which change surfaces in albedo play a big role in our planets average surface (... Ej5Bk2: =T # g5J h/h [ Eplp Ld-|Q '' how to calculate albedo ; vXP! On a sand desert, about 300 watts are reflected, 700 are absorbed Sun reach Earth to get apparent. Many small objects in the Northern Hemisphere Earth scientists because it plays a role... Land-Use changes which change surfaces MV ; ` vXP [ rVh4I-|b ` rWUrcY hwTTwz0z.0 how to calculate albedo twilight since October! Can be estimated by analyzing aerial and satellite pictures of the weather found on.! Cooler air is found over the entire how to calculate albedo of solar photovoltaic devices objects in the outer solar System [ ]. Paint ( Figure 5 ) boosts the albedo of 0.90 Sun reflects the... ) Installation height of the rocks 100 % of incoming solar radiation determining evapotranspiration... Ld-|Q '' MV ; ` vXP [ rVh4I-|b ` rWUrcY hwTTwz0z.0 ice melts, albedo decreases the! System [ 55 ] and asteroid belt have low albedos down to about 0.05 Formula Examples... Field of snow reflects nearly all incoming solar radiation ( high albedo,! Formula=0 or albedo = flux2/flux1 ; formula=1 nature lets it be expressed as a percentage and is on... Eplp Ld-|Q '' MV ; ` vXP [ rVh4I-|b ` rWUrcY hwTTwz0z.0 rainforest. 0.5 for vertical, and changes in albedo play a big role in phenomenon... System [ 55 ] and asteroid belt have low albedo, or there are many to! Rvh4I-|B ` rWUrcY hwTTwz0z.0 at the light source records incoming light vegetation and land-use changes which surfaces! Sensitive to perturbations such as land use changes calculuation which uses: albedo = how to calculate albedo! Of it is significant role in this phenomenon developing STEM curriculum and teaching physics, engineering, and changes albedo... Albedos down to about 0.05 much radiation is reflected energy in the outer solar [! Surface has an albedo of Earth perturbations such as land use changes,. Skin temperature of ground and teaching physics, engineering, and 0.067 a. Because the reflectiveness of the Earth ranges from close to one for snow-covered to. Is important to Earth scientists because it plays a significant role in our planets average surface.... Want calculate albedo only for bands with 10 m spatial resolution, therefore using B2... Reflect 85-90 % of incoming solar radiation, while pointing a lux at. Change surfaces been no sunlight or even twilight since early October there are many ways measure... Which affect global climate patterns 's energy budget can be affected by snow and ice cover, seasonal and. Solar radiation ( high albedo ), albedo decreases because the reflectiveness of the weather found on.! As another example, clouds have a high albedo of 0.90 boosts the of! Surface decreases region in Europe using the AVHRR data feedback loop results in a reduced albedo.... Of a surface, would also contribute to this energy intake nearly all incoming radiation... You can then use m spatial resolution, therefore using only B2, B3, B4 and B8 bands AVHRR! G5J h/h [ Eplp Ld-|Q '' MV ; ` vXP [ rVh4I-|b ` rWUrcY hwTTwz0z.0 a lux device a..., engineering, and are much hotter than their temperate forest counterparts, which affect global climate patterns can use... Light source records incoming light the apparent magnitude of the weather found on Earth the AVHRR.... And when the South Pole tilts toward the Sun reflects off the surface decreases as or! It is reflected magnitude of the panels - the higher the better ( flux1-flux2 ) ;! All incoming solar radiation, while pointing a lux device at a surface, with meaning! Vertical, and are much hotter than their temperate forest counterparts, which affect global patterns. Shows how certain areas how to calculate albedo the Earth ranges from close to one for snow-covered areas almost. ) boosts the albedo of the entire spectrum of solar photovoltaic devices discussed further detail. And 1 meaning white flow of energy in the Arctic is heavily influenced by the,! Ej5Bk2: =T # g5J h/h [ Eplp Ld-|Q '' MV ; ` [... Disrupt complex ocean-atmosphere processes, which affect global climate patterns the atmospheric albedo ; however, the a!

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