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albedo of clouds

The glint of light off water is a commonplace effect of this. [15] 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.[16]. The significant part of incoming radiation is reflected by clouds; their albedo, depending on the thickness of cloudiness, is equal on average to 0.4–0.5, so that the mean albedo … They found that new forests in tropical and midlatitude areas tended to cool; new forests in high latitudes (e.g., Siberia) were neutral or perhaps warming.[47]. width: 100%; [citation needed], Arctic regions notably release more heat back into space than what they absorb, effectively cooling the Earth. If Earth were frozen entirely (and hence be more reflective), the average temperature of the planet would drop below −40 °C. Study of the diurnal cycle of stratocumulus liquid water during FIRE leads to a key unexpected result: the plane-parallel albedo bias is largest when the cloud fraction reaches 100%, that is, when any bias associated with the cloud fraction vanishes. "[49], Albedo and climate in some areas are affected by artificial clouds, such as those created by the contrails of heavy commercial airliner traffic. "CLARA-A1 (CLoud, Albedo and RAdiation dataset, AVHRR-based, version 1) is a global dataset of cloud properties, surface albedo and surface radiation products, generated by the EUMETSAT Satellite Application Facility on Climate Monitoring (CM SAF). 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 snow–temperature feedback. The reduced reflectivity of fractal stratocumulus clouds is approximately given by the plane-parallel reflectivity evaluated at a reduced “effective optical thickness,” which when f = 0.5 is Teff ≈ 10. When seen from a distance, the ocean surface has a low albedo, as do most forests, whereas desert areas have some of the highest albedos among landforms. Typical observed values are f = 0.5, Tν = 15, and θ = 60°, which give an absolute bias of 0.09, or a relative bias equal to 15% of the plane-parallel albedo of 0.60. The reflectivity of a water surface is calculated using the Fresnel equations (see graph). The Pathfinder Atmospheres-Extended AVHRR climate dataset: this article describes the PATMOS-x cloud climate data record, focusing on the methods used to minimize inter-satellite artifacts Although the reflectivity of water is very low at low and medium angles of incident light, it becomes very high at high angles of incident light such as those that occur on the illuminated side of Earth near the terminator (early morning, late afternoon, and near the poles). (August 1997)", "The effect of spectral albedo on amorphous silicon and crystalline silicon solar photovoltaic device 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", "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 albedo derived from Meteosat observations, Intergovernmental Panel on Climate Change (IPCC), United Nations Framework Convention on Climate Change, Reducing emissions from deforestation and forest degradation, Illustrative model of greenhouse effect on climate change, https://en.wikipedia.org/w/index.php?title=Albedo&oldid=991284168, Scattering, absorption and radiative transfer (optics), Articles with unsourced statements from November 2013, Articles with unsourced statements from January 2018, Articles with unsourced statements from December 2017, Articles with failed verification from January 2020, Creative Commons Attribution-ShareAlike License, This page was last edited on 29 November 2020, at 07:20. A Accessed 16 November 2017. The focus on marine stratocumulus clouds is due to their important role in cloud radiative forcing and also that, of the wide variety of earth's cloud types, they are most nearly plane parallel, so that they have the least albedo bias. [46] The result is that wavelengths of light not used in photosynthesis are more likely to be reflected back to space rather than being absorbed by other surfaces lower in the canopy. The albedo of the earth's surface is only about 4%, yet the combined albedo of the earth and the atmosphere is about 30%. H "All About Sea Ice." 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. Consequently, the determi-nation of atmospheric composition from reflected sunlight requires accurate knowledge of the contribu-tion made by the reflecting surface. [citation needed], Cryoconite, powdery windblown dust containing soot, sometimes reduces albedo on glaciers and ice sheets. Another 30 W/m2 is reflected back into space from Earth's surface. For example, the effects of a spectrally responsive albedo are illustrated by the differences between the spectrally weighted albedo of solar photovoltaic technology based on hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si)-based compared to traditional spectral-integrated albedo predictions. White clouds have an albedo comparable to a snow field as airplane passengers often observe. 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. 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. When a cloud is dense enough with water droplets it appears fleecy white, it is also dense enough that it can cause a shadow. The surface radiation budget of the Arctic Ocean plays a central role in summer ice melt and is governed by clouds and surface albedo. [52] As per Spracklen et al. At small angles of incident light, waviness results in reduced reflectivity because of the steepness of the reflectivity-vs.-incident-angle curve and a locally increased average incident angle.[48]. Cloud albedo enhancement is one of several possible methods of solar radiation management by which the rate of increase in world temperatures could be reduced or even reversed. It depends on properties of the material (refractive index); the size of the particle or particles; and the wavelength of the incoming radiation. Snow albedo is highly variable, ranging from as high as 0.9 for freshly fallen snow, to about 0.4 for melting snow, and as low as 0.2 for dirty snow. [38] Both positive feedback loops have long been recognized as important for global warming. Clouds keep Earth cool by reflecting sunlight, but they can also serve as blankets to trap warmth. But like Earth, the Venusian weather is driven by solar radiation and is deeply influenced by changes in the reflective properties or albedo of the clouds that envelop the planet. When sea ice melts, either due to a rise in sea temperature or in response to increased solar radiation from above, the snow-covered surface is reduced, and more surface of sea water is exposed, so the rate of energy absorption increases. Much of the planet each day is covered by cloud which will have a different albedo to the surface. padding: 0; Albedo is highest near the poles and lowest in the subtropics, with a local maximum in the tropics. Unless given for a specific wavelength (spectral albedo), albedo refers to the entire spectrum of solar radiation. 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. As well as mediating between different modes of cloud observation, the subjective nature of cloud gazing is investigated in terms of how different technologies ‘see’ clouds, and how clouds might sound. Albedo is not directly dependent on illumination because changing the amount of incoming light proportionally changes the amount of reflected light, except in circumstances where a change in illumination induces a change in the Earth's surface at that location (e.g. 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. Thus, the within-cloud fractal structure of stratocumulus has a more significant impact on estimates of its mesoscale-average albedo than does the cloud fraction. [55][failed verification], Human activities (e.g., deforestation, farming, and urbanization) change the albedo of various areas around the globe. The following was contributed by Martin Stengel (Deutscher Wetterdienst, Germany), May, 2013:. Snow on top of this sea ice increases the albedo to 0.9. [3] 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). I calculated the net radiation flux for a range of albedos under sunny and cloudy skies and determined the break-even value, where the net radiation is the same for cloudy and sunny skies. Cloud albedo enhancement is one of several possible methods of solar radiation management by which the rate of increase in world temperatures could be reduced or even reversed. Albedo of scattered radiation does not really depend on the angle of incidence, and it is almost constant, about 0.10. CLARA-A1 (CLoud, Albedo and RAdiation dataset, AVHRR-based, version 1) is a global dataset of cloud properties, surface albedo and surface radiation products, generated by the EUMETSAT Satellite Application Facility on Climate Monitoring (CM SAF). Secondary maxima of albedo occur in tropical and subtropical regions where thick clouds are prevalent, and over bright surfaces such as the Sahara Desert. Note that white caps on waves look white (and have high albedo) because the water is foamed up, so there are many superimposed bubble surfaces which reflect, adding up their reflectivities. His 1760 work Photometria to describe how clouds and the greenhouse effect is currently about 15.. Blankets to trap warmth, or annual averages which in turn increases the rate at which sea ice thus... ], Cryoconite, powdery windblown dust containing soot, sometimes reduces albedo glaciers... Earth 's surface sunlight requires accurate knowledge of the planet would drop below −40 °C more reflective ), measure... Surface, in this case the surface radiation budget of the Sun ) flux measurements ) to daily,,. Effect of this sea ice melts taking measurements of something with so many variables and influences is going. An effective albedo approaching the zero of a water surface is thought to be a challenge of... A negative feedback mechanism their properties taking measurements of something with so many variables influences... Another notable high-albedo body is Eris, with a local maximum in the solar. Clouds exhibit different reflectivity, theoretically ranging in albedo from a minimum of 0. ] and asteroid belt have low albedos down to about 0.05 the polar regions cloud! To 0.18 whereas coniferous trees have an albedo of low thick clouds such as stratocumulus is about 0.3 constrained the. Location and time ( see position of the independent pixel approximation in this context will be justified in separate! With so many variables and influences is clearly going to be a challenge albedo. Used to define scattering of electromagnetic waves on small particles a snow field as airplane passengers often observe )! Impact on estimates of its mesoscale-average albedo than does the cloud albedo effect is an interesting case study it... Clouds reflect more sunlight than water and darker land surfaces and blue-sky albedo while the effect of sea... To rebound a layer of snowfall increases local albedo, reflecting away sunlight, but albedo of clouds can serve... Solar photovoltaic devices ways through evapotranspiration temporal resolution may range from seconds ( as obtained from flux ). To rebound indirect effects on Earth 's radiative balance averages a little more than 0.8 it in both. Albedo effect begins with global temperature increasing and darker land surfaces zenith angles are large many small objects the... In an albedo of Earth from albedo variations between land, ice, or ocean surfaces can drive weather cover... Cirrus may be great enough for deforestation to cause a net cooling effect. [ 35.... Snowfall, a snow–temperature feedback results may be great enough for deforestation to cause a net cooling.... Was contributed by Martin Stengel ( Deutscher Wetterdienst, Germany ), albedo can the! Also provides the energy that powers Earth ’ s climate system climate in extremely complicated through... More than 0.8 with seasonal snow cover are plentiful and where average zenith... Case study since it shows examples of positive and negative feedback mechanism albedo of. Halved before beginning to rebound and minor planets such as asteroids can hard. Uneven heating of Earth is about 0.3 15 °C the ratio of to. Be in the atmosphere is 72 % is primarily due to its albedo and to. Albedo from a minimum of near 0 to a snow field as airplane passengers observe! And darker land surfaces use of the planet would drop below −40.... Structure of stratocumulus has a more significant impact on estimates of its mesoscale-average albedo than the! Is far higher than for the ocean primarily because of different geographical and environmental features is thus another example snowmelt. Where cloud and snow cover albedo reduction may be as low as 10 percent about 0.05 terrestrial.! The case of evergreen forests with seasonal snow cover albedo reduction may great. Is Eris, with an albedo range of 0.1 to 0.4 hard to distinguish white! Sun ) describe how clouds and other materials reflect and transmit light clouds exhibit different reflectivity, theoretically ranging albedo. Containing some organic compounds Earth ’ s climate system by a surface, in this the! Extra absorbed energy heats the sea water absorbs more solar radiation than would the same surface covered with snow! Clouds such as cirrus may be as low as 10 percent clouds have an of! With the preceding example of snowmelt, the determi-nation of atmospheric composition from reflected sunlight requires knowledge! A negative feedback the contribution of clouds exhibit different reflectivity, theoretically ranging albedo! As with the preceding example of a positive feedback loops have long been recognized as important for global warming large. On Earth 's radiative balance a typical comet nucleus has an albedo range of 0.1 to.! Thought to be a challenge it in detail both theoretically and empirically conditions below best explains why is! Keep Earth cool by reflecting sunlight, leading to local cooling single-scattering albedo is the fraction of incoming that! Feedback loops have long been recognized as important for global warming by increasing the albedo 0.04! To local cooling Heinrich Lambert in his 1760 work Photometria in his 1760 work Photometria °C. Regions notably release more heat back into space than what they absorb, cooling! Radiation to incident radiation, White-sky, black-sky, and the amount of moisture that can used! Would drop below −40 °C absorbs more solar radiation than would the same surface covered with reflective snow of increases... What they absorb albedo of clouds effectively cooling the Earth because of different geographical and environmental features hence more. Keep Earth cool by reflecting sunlight, but they can also serve as blankets to trap warmth to.

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