WorldWideScience

Sample records for albedo

  1. Neutron Albedo

    CERN Document Server

    Ignatovich, V K

    2005-01-01

    A new, algebraic, method is applied to calculation of neutron albedo from substance to check the claim that use of ultradispersive fuel and moderator of an active core can help to gain in size and mass of the reactor. In a model of isotropic distribution of incident and reflected neutrons it is shown that coherent scattering on separate grains in the case of thermal neutrons increases transport cross section negligibly, however it decreases albedo from a wall of finite thickness because of decrease of substance density. A visible increase of albedo takes place only for neutrons with wave length of the order of the size of a single grain.

  2. Mars surface albedo and changes

    CERN Document Server

    Vincendon, Mathieu; Altieri, Francesca; Ody, Anouck

    2014-01-01

    The pervasive Mars dust is continually transported between surface and atmosphere. When on the surface, dust increases the albedo of darker underlying rocks and regolith, which modifies climate energy balance and must be quantified. Remote observation of surface albedo absolute value and albedo change is however complicated by dust itself when lifted in the atmosphere. Here we present a method to calculate and map the bolometric solar hemispherical albedo of the Martian surface using the 2004 - 2010 OMEGA imaging spectrometer dataset. This method takes into account aerosols radiative transfer, surface photometry, and instrumental issues such as registration differences between visible and near-IR detectors. Resulting albedos are on average 17% higher than previous estimates for bright surfaces while similar for dark surfaces. We observed that surface albedo changes occur mostly during the storm season due to isolated events. The main variations are observed during the 2007 global dust storm and during the fol...

  3. The temporal scale research of MODIS albedo product authenticity verification

    Science.gov (United States)

    Cao, Yongxing; Xue, Zhihang; Cheng, Hui; Xiong, Yajv; Chen, Yunping; Tong, Ling

    2016-06-01

    This study introduces a method that normalizes the inversed ETM+ albedo to the local solar noon albedo for the temporal scale of the MODIS albedo validation. Firstly, the statistical relation model between the surface albedo and the solar elevation angle was set up, and then deducing relationship between ETM+ albedo and the solar elevation angle, so the ETM+ albedo at local solar noon could be got. Secondly, the ground measurement albedo at the local solar noon was used to assess the inversed ETM+ albedo and the normalized albedo. The experiment results show that the method can effectively improve the accuracy of product certification.

  4. Albedo evolution of seasonal Arctic sea ice

    Science.gov (United States)

    Perovich, Donald K.; Polashenski, Christopher

    2012-04-01

    There is an ongoing shift in the Arctic sea ice cover from multiyear ice to seasonal ice. Here we examine the impact of this shift on sea ice albedo. Our analysis of observations from four years of field experiments indicates that seasonal ice undergoes an albedo evolution with seven phases; cold snow, melting snow, pond formation, pond drainage, pond evolution, open water, and freezeup. Once surface ice melt begins, seasonal ice albedos are consistently less than albedos for multiyear ice resulting in more solar heat absorbed in the ice and transmitted to the ocean. The shift from a multiyear to seasonal ice cover has significant implications for the heat and mass budget of the ice and for primary productivity in the upper ocean. There will be enhanced melting of the ice cover and an increase in the amount of sunlight available in the upper ocean.

  5. SURFACE ALBEDO AND SPECTRAL VARIABILITY OF CERES

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jian-Yang; Reddy, Vishnu; Corre, Lucille Le; Sykes, Mark V.; Prettyman, Thomas H. [Planetary Science Institute, 1700 E. Ft. Lowell Road, Suite 106, Tucson, AZ 85719 (United States); Nathues, Andreas; Hoffmann, Martin; Schaefer, Michael [Max Planck Institute for Solar System Research, Göttingen (Germany); Izawa, Matthew R. M.; Cloutis, Edward A. [University of Winnipeg, Winnipeg, Manitoba (Canada); Carsenty, Uri; Jaumann, Ralf; Krohn, Katrin; Mottola, Stefano; Schröder, Stefan E. [German Aerospace Center (DLR), Institute of Planetary Research, Berlin (Germany); Castillo-Rogez, Julie C. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Schenk, Paul [Lunar and Planetary Institute, Houston, TX 77058 (United States); Williams, David A. [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Smith, David E. [Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Zuber, Maria T. [Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); and others

    2016-02-01

    Previous observations suggested that Ceres has active, but possibly sporadic, water outgassing as well as possibly varying spectral characteristics over a timescale of months. We used all available data of Ceres collected in the past three decades from the ground and the Hubble Space Telescope, as well as the newly acquired images by the Dawn  Framing Camera, to search for spectral and albedo variability on Ceres, on both a global scale and in local regions, particularly the bright spots inside the Occator crater, over timescales of a few months to decades. Our analysis has placed an upper limit on the possible temporal albedo variation on Ceres. Sporadic water vapor venting, or any possibly ongoing activity on Ceres, is not significant enough to change the albedo or the area of the bright features in the Occator crater by >15%, or the global albedo by >3% over the various timescales that we searched. Recently reported spectral slope variations can be explained by changing Sun–Ceres–Earth geometry. The active area on Ceres is less than 1 km{sup 2}, too small to cause global albedo and spectral variations detectable in our data. Impact ejecta due to impacting projectiles of tens of meters in size like those known to cause observable changes to the surface albedo on Asteroid Scheila cannot cause detectable albedo change on Ceres due to its relatively large size and strong gravity. The water vapor activity on Ceres is independent of Ceres’ heliocentric distance, ruling out the possibility of the comet-like sublimation process as a possible mechanism driving the activity.

  6. UV albedo of arctic snow in spring

    Directory of Open Access Journals (Sweden)

    O. Meinander

    2008-02-01

    Full Text Available The relevance of snow for climate studies is based on its physical properties, such as high surface reflectivity. Surface ultraviolet (UV albedo is an essential parameter for various applications based on radiative transfer modeling. Here, new continuous measurements of the local UV albedo of natural Arctic snow were made at Sodankylä (67.37° N, 26.63° E, 179 m a.s.l. during the spring of 2007. The data were logged at 1-min intervals. The accumulation of snow was up to 68 cm. The surface layer thickness varied from 0.5 to 35 cm with the snow grain size between 0.2 and 2.5 mm. The midday erythemally weighted UV albedo ranged from 0.6 to 0.8 in the accumulation period and 0.5–0.7 during melting. During the snow melt period, under cases of an almost clear sky and variable cloudiness, an unexpected diurnal decrease of 0.05 in albedo soon after midday, and recovery thereafter, was detected. This diurnal decrease in albedo was found to be asymmetric with respect to solar midday, thus indicating a change in the properties of the snow. Independent UV albedo results with two different types of instruments confirm these findings. The measured temperature of the snow surface was below 0°C on the following mornings. Hence, the reversible diurnal change, evident for ~1–2 h, could be explained by the daily metamorphosis of the surface of the snowpack, in which the temperature of the surface increases, melting some of the snow to liquid water, after which the surface freezes again.

  7. The low energy atmospheric antiproton albedo

    Science.gov (United States)

    Cole, J. B.; Ormes, J. F.

    1989-01-01

    The flux of albedo antiprotons in the 100-1000 MeV kinetic energy range produced by the cosmic ray primaries in the atmosphere is calculated. It is shown that this is not a significant background to measurements of the low energy anti-proton cosmic ray flux.

  8. Surface Albedo and Spectral Variability of Ceres

    CERN Document Server

    Li, Jian-Yang; Nathues, Andreas; Corre, Lucille Le; Izawa, Matthew R M; Clouts, Edward A; Sykes, Mark V; Carsenty, Uri; Castillo-Rogez, Julie C; Hoffmann, Martin; Jaumann, Ralf; Krohn, Katrin; Mottola, Stefano; Prettyman, Thomas H; Schaefer, Michael; Schenk, Paul; Schröder, Stefan E; Williams, David A; Smith, David E; Zuber, Maria T; Konopliv, Alexander S; Park, Ryan S; Raymond, Carol A; Russell, Christopher T

    2016-01-01

    Previous observations suggested that Ceres has active but possibly sporadic water outgassing, and possibly varying spectral characteristics in a time scale of months. We used all available data of Ceres collected in the past three decades from the ground and the Hubble Space Telescope, and the newly acquired images by Dawn Framing Camera to search for spectral and albedo variability on Ceres, in both a global scale and local regions, particularly the bright spots inside Occator crater, over time scales of a few months to decades. Our analysis has placed an upper limit on the possible temporal albedo variation on Ceres. Sporadic water vapor venting, or any possibly ongoing activity on Ceres, is not significant enough to change the albedo or the area of the bright features in Occator crater by >15%, or the global albedo by >3% over various time scales that we searched. Recently reported spectral slope variations can be explained by changing Sun-Ceres-Earth geometry. The active area on Ceres is less than 1 km$^2...

  9. Albedo decline on Greenland's Mittivakkat Gletscher in a warming climate

    DEFF Research Database (Denmark)

    Mernild, Sebastian H.; Malmros, Jeppe K.; Yde, Jacob C.

    2015-01-01

    Albedo is one of the parameters that govern energy availability for snow and ice surface ablation, and subsequently the surface mass balance conditions of temperate glaciers and ice caps (GIC). Here, we document snow and ice albedo changes for Mittivakkat Gletscher (MG) in Southeast Greenland (20.......10. The greatest decline in albedo, of 0.25, occurred near the equilibrium line altitude (ELA), an important surface cover and albedo transitional zone. The EBY albedo correlates significantly with ELA and net winter and summer glacier mass balance records....

  10. Lunar Regolith Albedos Using Monte Carlos

    Science.gov (United States)

    Wilson, T. L.; Andersen, V.; Pinsky, L. S.

    2003-01-01

    The analysis of planetary regoliths for their backscatter albedos produced by cosmic rays (CRs) is important for space exploration and its potential contributions to science investigations in fundamental physics and astrophysics. Albedos affect all such experiments and the personnel that operate them. Groups have analyzed the production rates of various particles and elemental species by planetary surfaces when bombarded with Galactic CR fluxes, both theoretically and by means of various transport codes, some of which have emphasized neutrons. Here we report on the preliminary results of our current Monte Carlo investigation into the production of charged particles, neutrons, and neutrinos by the lunar surface using FLUKA. In contrast to previous work, the effects of charm are now included.

  11. Modeling Earth Albedo for Satellites in Earth Orbit

    DEFF Research Database (Denmark)

    Bhanderi, Dan; Bak, Thomas

    2005-01-01

    Many satellite are influences by the Earthøs albedo, though very few model schemes exist.in order to predict this phenomenon. Earth albedo is often treated as noise, or ignored completely. When applying solar cells in the attitude hardware, Earth albedo can cause the attitude estimate to deviate...... with as much as 20 deg. Digital Sun sensors with Earth albedo correction in hardware exist, but are expensive. In addition, albedo estimates are necessary in thermal calculations and power budgets. We present a modeling scheme base4d on Eartht reflectance, measured by NASA's Total Ozone Mapping Spectrometer......, in which the Earth Probe Satellite has recorded reflectivity data daily since mid 1996. The mean of these data can be used to calculate the Earth albedo given the positions of the satellite and the Sun. Our results show that the albedo varies highly with the solar angle to the satellite's field of view...

  12. The Spherical Bolometric Albedo of Planet Mercury

    OpenAIRE

    Mallama, Anthony

    2017-01-01

    Published reflectance data covering several different wavelength intervals has been combined and analyzed in order to determine the spherical bolometric albedo of Mercury. The resulting value of 0.088 +/- 0.003 spans wavelengths from 0 to 4 {\\mu}m which includes over 99% of the solar flux. This bolometric result is greater than the value determined between 0.43 and 1.01 {\\mu}m by Domingue et al. (2011, Planet. Space Sci., 59, 1853-1872). The difference is due to higher reflectivity at wavelen...

  13. Albedo and transmittance of inhomogeneous stratus clouds

    Energy Technology Data Exchange (ETDEWEB)

    Zuev, V.E.; Kasyanov, E.I.; Titov, G.A. [Institute of Atmospheric Optics, Tomsk (Russian Federation)] [and others

    1996-04-01

    A highly important topic is the study of the relationship between the statistical parameters of optical and radiative charactertistics of inhomogeneous stratus clouds. This is important because the radiation codes of general circulation models need improvement, and it is important for geophysical information. A cascade model has been developed at the Goddard Space Flight Center to treat stratocumulus clouds with the simplest geometry and horizontal fluctuations of the liquid water path (optical thickness). The model evaluates the strength with which the stochastic geometry of clouds influences the statistical characteristics of albedo and the trnasmittance of solar radiation.

  14. LUNAR TERRAIN AND ALBEDO RECONSTRUCTION FROM APOLLO IMAGERY

    Data.gov (United States)

    National Aeronautics and Space Administration — LUNAR TERRAIN AND ALBEDO RECONSTRUCTION FROM APOLLO IMAGERY ARA V NEFIAN*, TAEMIN KIM, MICHAEL BROXTON, AND ZACH MORATTO Abstract. Generating accurate three...

  15. Surface Albedo Variations Across Opportunity's Traverse in Meridiani Planum

    Science.gov (United States)

    Studer-Ellis, G. L.; Rice, M. S.; Johnson, J. R.; Bell, J. F., III

    2015-12-01

    Surface albedo measurements from the Mars Exploration Rover (MER) Opportunity mission can be used to help understand surface-atmosphere interactions at Meridiani Planum. Opportunity has acquired 117 albedo panoramas with the Pancam instrument as of sol 3870, across the first 40 km of its traverse. To date, only the first 32 panoramas have been reported upon in previous studies [1]. Here we present an analysis of the full set of PDS-released albedo observations from Opportunity and correlate our measurements with terrain type and known atmospheric events. To acquire a 360-degree albedo observation, Pancam's L1 ("clear") filter is used to take 27 broad-spectrum images, which are stitched into a mosaic. Pancam images are calibrated to reflectance factor (R*), which is taken as an approximation of the Lambertian albedo. Areas of interest are selected and average albedo calculations are applied to all of the selections. Results include the average albedo of each scene, as well as equal-area corrections where applicable, in addition to measurements of specific classes of surface features (e.g., outcrops, dusty terrain, and rover tracks). Average scene albedo measurements range from 0.11 ± 0.04 to 0.30 ± 0.04, with the highest value observed on sol 1290 (immediately after the planet-encircling dust storm of 2007). We compare these results to distance traveled, surface morphologies, local wind driven events, and dust opacity measurements. Future work will focus on correlating Pancam albedo values with orbital data from cameras such as HiRISE, CTX, MOC, THEMIS-VIS, and MARCI, and completion of the same analysis for the full Pancam albedo dataset from Spirit. References: [1] Bell, J. F., III, M. S. Rice, J. R. Johnson, and T. M. Hare (2008), Surface albedo observations at Gusev Crater and Meridiani Planum, Mars, J. Geophys. Res., 113, E06S18, doi:10.1029/2007JE002976.

  16. Cloud albedo increase from carbonaceous aerosol

    Directory of Open Access Journals (Sweden)

    W. R. Leaitch

    2010-08-01

    Full Text Available Airborne measurements from two consecutive days, analysed with the aid of an aerosol-adiabatic cloud parcel model, are used to study the effect of carbonaceous aerosol particles on the reflectivity of sunlight by water clouds. The measurements, including aerosol chemistry, aerosol microphysics, cloud microphysics, cloud gust velocities and cloud light extinction, were made below, in and above stratocumulus over the northwest Atlantic Ocean. On the first day, the history of the below-cloud fine particle aerosol was marine and the fine particle sulphate and organic carbon mass concentrations measured at cloud base were 2.4 μg m−3 and 0.9 μg m−3 respectively. On the second day, the below-cloud aerosol was continentally influenced and the fine particle sulphate and organic carbon mass concentrations were 2.3 μg m−3 and 2.6 μg m−3 respectively. Over the range 0.06–0.8 μm diameter, the shapes of the below-cloud size distributions were similar on both days and the number concentrations were approximately a factor of two higher on the second day. The cloud droplet number concentrations (CDNC on the second day were approximately three times higher than the CDNC measured on the first day. Using the parcel model to separate the influence of the differences in gust velocities, we estimate from the vertically integrated cloud light scattering measurements a 6% increase in the cloud albedo principally due to the increase in the carbonaceous components on the second day. Assuming no additional absorption by this aerosol, a 6% albedo increase translates to a local daytime radiative cooling of ∼12 W m−2. This result provides observational evidence that the role of anthropogenic carbonaceous components in the cloud albedo effect can be much larger than that of anthropogenic sulphate, as some global simulations have indicated.

  17. The Albedo of Pervious Cement Concrete Linearly Decreases with Porosity

    Directory of Open Access Journals (Sweden)

    Rui Zhang

    2015-01-01

    Full Text Available Pervious pavements have been advocated as a potential countermeasure to the urban heat island effect. To understand if pervious pavements stay cooler than conventional pavements, the albedo of the pervious concrete must be understood. This study measured the albedo of pervious concrete with different porosity. Four Portland cement concrete mixes were casted, using designed amounts of sand to vary the porosity of the pervious concrete samples. The samples were sliced and the spectral reflectance and albedo of the sliced samples were measured and analyzed. It is found that the albedo of pervious concrete decreases linearly with the increase of the porosity. The albedo of a pervious Portland concrete varies from 0.25 to 0.35, which is 0.05~0.15 lower than the albedo of conventional cement concrete. Due to this lower albedo, it should be cautious to develop pervious concrete to battle with urban heat island unless the evaporation of pervious concrete is promoted to compensate the additional solar absorption caused by the low albedo.

  18. The high albedo of the hot Jupiter Kepler-7b

    DEFF Research Database (Denmark)

    Demory, B.-O.; Seager, S.; Madhusudhan, N.;

    2011-01-01

    of 44 ± 5 ppm. If directly related to the albedo, this translates to a Kepler geometric albedo of 0.32 ± 0.03, the most precise value measured so far for an exoplanet. We also characterize the planetary orbital phase light curve with an amplitude of 42 ± 4 ppm. Using atmospheric models, we find...

  19. Measurements of spectral snow albedo at Neumayer, Antarctica

    Directory of Open Access Journals (Sweden)

    S. Wuttke

    2006-03-01

    Full Text Available Spectral albedo in high resolution, from 290 to 1050 nm, has been measured at Neumayer, Antarctica, (70°39' S, 8°15' W during the austral summer 2003/2004. At 500 nm, the spectral albedo nearly reaches unity, with slightly lower values below and above 500 nm. Above 600 nm, the spectral albedo decreases to values between 0.45 and 0.75 at 1000 nm. For one cloudless case an albedo up to 1.01 at 500 nm could be determined. This can be explained by the larger directional component of the snow reflectivity for direct incidence, combined with a slightly mislevelled sensor and the snow surface not being perfectly horizontal. A possible explanation for an observed decline in albedo is an increase in snow grain size. The theoretically predicted increase in albedo with increasing solar zenith angle (SZA could not be observed. This is explained by the small range of SZA during albedo measurements, combined with the effect of changing snow conditions outweighing the effect of changing SZA. The measured spectral albedo serves as input for radiative transfer models, describing radiation conditions in Antarctica.

  20. The effect of pulverization on the albedo of lunar rocks

    NARCIS (Netherlands)

    Minnaert, Marcel Gilles Jozef

    1969-01-01

    Measures of the albedo under full-moon conditions have been made on two samples of very dark rocks, pulverized and sieved so as to obtain powders of different grain size. Below a size of 0.05 mm the albedo suddenly increases, obviously because the individual grains become transparent. By a rough cal

  1. Greenland surface albedo changes 1981-2012 from satellite observations

    Science.gov (United States)

    Significant melt over Greenland has been observed during the last several decades associated with extreme warming events over the northern Atlantic Ocean. An analysis of surface albedo change over Greenland is presented, using a 32-year consistent satellite albedo product from the Global Land Surfac...

  2. Narrowband to broadband conversion of Landsat TM glacier albedos

    NARCIS (Netherlands)

    Oerlemans, J.; Knap, W.H.; Reijmer, C.

    1999-01-01

    In this paper we present an empirical relationship between the broadband glacier albedo (alpha) and the narrowband glacier albedos in Landsat TM bands 2 and 4 (alpha2 and alpha4, respectively). The relationship was established on the basis of multiple linear regression analysis of 112 ground-based s

  3. Anthropogenic desertification by high-albedo pollution Observations and modeling

    Science.gov (United States)

    Otterman, J.; Rosenberg, N. W.; Rosenberg, E.

    1974-01-01

    ERTS-1 MSS albedo data of Western Negev, Sinai and the Gaza strip are presented. A sharp contrast in albedo exists across the Negev-Sinai and Negev-Gaza strip borders. Anthropogenic desertification has occurred on the Arab side due to overgrazing and Bedouin agriculture, whereas natural vegetation grows much more abundantly on the Israeli side.

  4. NEOWISE Reactivation Mission Year Two: Asteroid Diameters and Albedos

    CERN Document Server

    Nugent, C R; Bauer, J; Cutri, R M; Kramer, E A; Grav, T; Masiero, J; Sonnett, S; Wright, E L

    2016-01-01

    The Near-Earth Object Wide-Field Infrared Survey Explorer (NEOWISE) mission continues to detect, track, and characterize minor planets. We present diameters and albedos calculated from observations taken during the second year since the spacecraft was reactivated in late 2013. These include 207 near-Earth asteroids and 8,885 other asteroids. $84\\%$ of the near-Earth asteroids did not have previously measured diameters and albedos by the NEOWISE mission. Comparison of sizes and albedos calculated from NEOWISE measurements with those measured by occultations, spacecraft, and radar-derived shapes shows accuracy consistent with previous NEOWISE publications. Diameters and albedos fall within $ \\pm \\sim20\\%$ and $\\pm\\sim40\\%$, 1-sigma, respectively, of those measured by these alternate techniques. NEOWISE continues to preferentially discover near-Earth objects which are large ($>100$ m), and have low albedos.

  5. The solar zenith angle dependence of desert albedo

    Science.gov (United States)

    Wang, Zhuo; Barlage, Michael; Zeng, Xubin; Dickinson, Robert E.; Schaaf, Crystal B.

    2005-03-01

    Most land models assume that the bare soil albedo is a function of soil color and moisture but independent of solar zenith angle (SZA). However, analyses of the Moderate Resolution Imaging Spectroradiometer (MODIS) Bidirectional Reflectance Distribution Function (BRDF) and albedo data over thirty desert locations indicate that bare soil albedo does vary with SZA. This is further confirmed using the in situ data. In particular, bare soil albedo normalized by its value at 60° SZA can be adequately represented by a one-parameter formulation (1 + C)/(1 + 2C * cos(SZA)) or a two-parameter formulation (1 + B1 * f1(SZA) + B2 * f2(SZA)). Using the MODIS and in situ data, the empirical parameters C, B1, and B2 are taken as 0.15, 0.346 and 0.063. The SZA dependence of soil albedo is also found to significantly affect the modeling of land surface energy balance over a desert site.

  6. Soil Albedo in Relation to Soil Color, Moisture and Roughness

    Science.gov (United States)

    Fontes, Adan Fimbres

    Land surface albedo is the ratio of reflected to incident solar radiation. It is a function of several surface parameters including soil color, moisture, roughness and vegetation cover. A better understanding of albedo and how it changes in relation to variations in these parameters is important in order to help improve our ability to model the effects of land surface modifications on climate. The objectives of this study were (1) To determine empirical relationships between smooth bare soil albedo and soil color, (2) To develop statistical relationships between albedo and ground-based thematic mapper (TM) measurements of spectral reflectances, (3) To determine how increased surface roughness caused by tillage reduces bare soil albedo and (4) To empirically relate albedo with TM data and other physical characteristics of mixed grass/shrubland sites at Walnut Gulch Watershed. Albedos, colors and spectral reflectances were measured by Eppley pyranometer, Chroma Meter CR-200 and a Spectron SE-590, respectively. Measurements were made on two field soils (Gila and Pima) at the Campus Agricultural Center (CAC), Tucson, AZ. Soil surface roughness was measured by a profile meter developed by the USDA/ARS. Additional measurements were made at the Maricopa Agricultural Center (MAC) for statistical model testing. Albedos of the 15 smooth, bare soils (plus silica sand) were determined by linear regression to be highly correlated (r^2 = 0.93, p > 0.01) with color values for both wet and dry soil conditions. Albedos of the same smooth bare soils were also highly correlated (r^2>=q 0.86, p > 0.01) with spectral reflectances. Testing of the linear regression equations relating albedo to soil color and spectral reflectances using the data from MAC showed a high correlation. A general nonlinear relationship given by y = 8.366ln(x) + 37.802 r^2 = 0.71 was determined between percent reduction in albedo (y) and surface roughness index (x) for wet and dry Pima and Gila field soils

  7. CHARACTERISTICS OF VEGETATION COVER, ROUGHNESS AND ALBEDO DISTRIBUTION OVER CHINA

    Institute of Scientific and Technical Information of China (English)

    张正秋; 周秀骥; 李维亮; 徐兴奎

    2001-01-01

    To build land surface dataset for climate model, with application of remote sensing technique as well as the Geographic Information System (GIS), the data of surface type, roughness and albedo over China in 1997 were retrieved, resolutions being 10 km× 10 km. Based on these data,an analysis is conducted on the geographic distributions and seasonal variations of surface vegetation cover and roughness as well as albedo over China. Results show that surface vegetation cover is mainly located to the south of Yangtze River, in Southwest and Northeast China and sparse vegetation cover is in the Northwest. The variation of land surface cover affects the variations of land surface roughness and albedo. High albedo occurred in the north of Xinjiang Autonomous Region, the north of Northeast China and the Qinghai-Xizang Plateau in winter, in correspondence with the location of snow cover.For most part of China, surface roughness decreases and albedo increases in winter, while the roughness increases and the albedo decreases in summer, which could mainly result from land surface cover (snow cover and vegetation cover) and soil moisture changes. This shows that the geographic distribution and seasonal variation of the albedo are alnost opposite to those of the roughness, in agreement with theoretical results. Temporally, the amplitude of surface roughness change is quite small in comparison with the roughness itself.

  8. Surface albedo measurements in Mexico City metropolitan area

    Energy Technology Data Exchange (ETDEWEB)

    Castro, T; Mar, B; Longoria, R; Ruiz Suarez, L. G [Centro de Ciencias de la Atmosfera, UNAM, Mexico, D.F. (Mexico); Morales, L [Instituto de Geografia, UNAM, Mexico, D.F. (Mexico)

    2001-04-01

    Optical and thermal properties of soils are important input data for the meteorological and photochemical modules of air quality models. As development of these models increase on spatial resolution good albedo data become more important. In this paper measurements of surface albedo of UV (295-385 nm) and visible (450-550 nm) radiation are reported for different urban and rural surfaces in the vicinity of Mexico City. It was found for the downtown zone and average albedo value of 0.05 which is in very good agreement with reported values for urban surfaces. Our albedo values measured in UV region for grey cement and green grass are of 0.10 and 0.009, respectively, and quite similar to those found at the literature of 0.11 and 0.008 for those type of surfaces. [Spanish] Las propiedades opticas y termicas de suelos son datos importantes para los modulos meteorologicos y fotoquimicos de los modelos de calidad del aire. Conforme aumenta la resolucion espacial del modelo se vuelve mas importante contar con buenos datos de albedo. En este articulo se presentan mediciones de albedo superficial de radiacion Ultravioleta (295-385 nm) y visible (450-550 nm) para diferentes superficies urbanas. Los valores medidos de albedo en la region UV para cemento gris y pasto verde son de 0.10 y 0.009, respectivamente, y son muy similares a los reportados en la literatura, 0.11 y 0.008 para este tipo de superficies.

  9. The Gamma-ray Albedo of the Moon

    Energy Technology Data Exchange (ETDEWEB)

    Moskalenko, Igor V.; /Stanford U., HEPL; Porter, Troy A.; /UC, Santa Cruz

    2007-09-28

    We use the GEANT4 Monte Carlo framework to calculate the {gamma}-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of {gamma}-rays from the Moon is very steep with an effective cutoff around 3-4 GeV (600 MeV for the inner part of the Moon disk) and exhibits a narrow pion-decay line at 67.5 MeV, perhaps unique in astrophysics. Apart from other astrophysical sources, the albedo spectrum of the Moon is well understood, including its absolute normalization; this makes it a useful 'standard candle' for {gamma}-ray telescopes. The steep albedo spectrum also provides a unique opportunity for energy calibration of {gamma}-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST). Since the albedo flux depends on the incident CR spectrum which changes over the solar cycle, it is possible to monitor the CR spectrum using the albedo {gamma}-ray flux. Simultaneous measurements of CR proton and helium spectra by the Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics (PAMELA), and observations of the albedo {gamma}-rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the LAT to monitor the CR spectrum near the Earth beyond the lifetime of the PAMELA.

  10. Greenland ice sheet albedo feedback: thermodynamics and atmospheric drivers

    Directory of Open Access Journals (Sweden)

    J. E. Box

    2012-08-01

    Full Text Available Greenland ice sheet mass loss has accelerated in the past decade responding to combined glacier discharge and surface melt water runoff increases. During summer, absorbed solar energy, modulated at the surface primarily by albedo, is the dominant factor governing surface melt variability in the ablation area. Using satellite-derived surface albedo with calibrated regional climate modeled surface air temperature and surface downward solar irradiance, we determine the spatial dependence and quantitative impact of the ice sheet albedo feedback over 12 summer periods beginning in 2000. We find that, while albedo feedback defined by the change in net solar shortwave flux and temperature over time is positive over 97% of the ice sheet, when defined using paired annual anomalies, a second-order negative feedback is evident over 63% of the accumulation area. This negative feedback damps the accumulation area response to warming due to a positive correlation between snowfall and surface air temperature anomalies. Positive anomaly-gauged feedback concentrated in the ablation area accounts for more than half of the overall increase in melting when satellite-derived melt duration is used to define the timing when net shortwave flux is sunk into melting. Abnormally strong anticyclonic circulation, associated with a persistent summer North Atlantic Oscillation extreme since 2007, enabled three amplifying mechanisms to maximize the albedo feedback: (1 increased warm (south air advection along the western ice sheet increased surface sensible heating that in turn enhanced snow grain metamorphic rates, further reducing albedo; (2 increased surface downward shortwave flux, leading to more surface heating and further albedo reduction; and (3 reduced snowfall rates sustained low albedo, maximizing surface solar heating, progressively lowering albedo over multiple years. The summer net infrared and solar radiation for the high elevation accumulation area approached

  11. The Albedo Distribution of Near Earth Asteroids

    CERN Document Server

    Wright, Edward L; Masiero, Joseph; Grav, Tommy; Bauer, James

    2016-01-01

    The cryogenic WISE mission in 2010 was extremely sensitive to asteroids and not biased against detecting dark objects. The albedos of 428 Near Earth Asteroids (NEAs) observed by WISE during its fully cryogenic mission can be fit quite well by a 3 parameter function that is the sum of two Rayleigh distributions. The Rayleigh distribution is zero for negative values, and follows $f(x) = x \\exp[-x^2/(2\\sigma^2)]/\\sigma^2$ for positive x. The peak value is at x=\\sigma, so the position and width are tied together. The three parameters are the fraction of the objects in the dark population, the position of the dark peak, and the position of the brighter peak. We find that 25.3% of the NEAs observed by WISE are in a very dark population peaking at $p_V = 0.03$, while the other 74.7% of the NEAs seen by WISE are in a moderately dark population peaking at $p_V = 0.168$. A consequence of this bimodal distribution is that the Congressional mandate to find 90% of all NEAs larger than 140 m diameter cannot be satisfied by...

  12. An algorithm to determine backscattering ratio and single scattering albedo

    Digital Repository Service at National Institute of Oceanography (India)

    Suresh, T.; Desa, E.; Matondkar, S.G.P.; Mascarenhas, A.A.M.Q.; Nayak, S.R.; Naik, P.

    Algorithms to determine the inherent optical properties of water, backscattering probability and single scattering albedo at 490 and 676 nm from the apparent optical property, remote sensing reflectance are presented here. The measured scattering...

  13. MCNP simulation of the incident and Albedo neutron response of the IRD Albedo Neutron Dosemeter for {sup 241}Am-Be moderated sources

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, Bruno M.; Martins, Marcelo M.; Mauricio, Claudia L.P.; Mauricio, Claudia L.P. da, E-mail: claudia@ird.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Silva, Ademir X. [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear

    2015-07-01

    The IRD TLD Albedo dosemeter measures both incident and albedo neutron component. The incident to Albedo ratio is used to take into account the energy dependence of its response. In this paper, the behavior of the IRD Albedo dosemeter response as a function of the incident to Albedo ratio for {sup 241}Am-Be sources was simulated to improve its algorithm. The simulation was performed in MCNPX transport code and presents a good agreement with experimental measurements. The results obtained in this work are very useful to improve the accuracy of the IRD Albedo dosemeter at real neutron workplace. (author)

  14. Global albedo particles: a new approach from loss cone distributions

    CERN Document Server

    Wang, K; Huang, Ming-Huey A.; Wang, Kaiti

    2006-01-01

    Global distributions of albedo particles measured by Alpha Magnetic Spectrometer (AMS) are investigated by modeling loss cones derived from adiabatic invariants. Particles can be immediately determined as being loss to the atmosphere in a bounce period, or a drift period, or being trapped, without any computing-time consumption on particle trajectories. The results suggest this new approach is a faster tool to categorize the observed albedo particles and it can be applied to particles with energies up to GeV.

  15. IAU nomenclature for albedo features on the planet Mercury

    Science.gov (United States)

    Dollfus, A.; Chapman, C. R.; Davies, M. E.; Gingerich, O.; Goldstein, R.; Guest, J.; Morrison, D.; Smith, B. A.

    1978-01-01

    The International Astronomical Union has endorsed a nomenclature for the albedo features on Mercury. Designations are based upon the mythological names related to the god Hermes; they are expressed in Latin form. The dark-hued albedo features are associated with the generic term Solitudo. The light-hued areas are designated by a single name without generic term. The 32 names adopted are allocated on the Mercury map.

  16. Decadal to seasonal variability of Arctic sea ice albedo

    Science.gov (United States)

    Agarwal, S.; Moon, W.; Wettlaufer, J. S.

    2011-10-01

    A controlling factor in the seasonal and climatological evolution of the sea ice cover is its albedo α. Here we analyze Arctic data from the Advanced Very High Resolution Radiometer (AVHRR) Polar Pathfinder and assess the seasonality and variability of broadband albedo from a 23 year daily record. We produce a histogram of daily albedo over ice covered regions in which the principal albedo transitions are seen; high albedo in late winter and spring, the onset of snowmelt and melt pond formation in the summer, and fall freezeup. The bimodal late summer distribution demonstrates the combination of the poleward progression of the onset of melt with the coexistence of perennial bare ice with melt ponds and open water, which then merge to a broad peak at α $\\gtrsim$ 0.5. We find the interannual variability to be dominated by the low end of the α distribution, highlighting the controlling influence of the ice thickness distribution and large-scale ice edge dynamics. The statistics obtained provide a simple framework for model studies of albedo parameterizations and sensitivities.

  17. High-albedo materials for reducing building cooling energy use

    Energy Technology Data Exchange (ETDEWEB)

    Taha, H.; Sailor, D.; Akbari, H.

    1992-01-01

    One simple and effective way to mitigate urban heat islands, i.e., the higher temperatures in cities compared to those of the surrounds, and their negative impacts on cooling energy consumption is to use high-albedo materials on major urban surfaces such as rooftops, streets, sidewalks, school yards, and the exposed surfaces of parking lots. High-albedo materials can save cooling energy use by directly reducing the heat gain through a building`s envelope (direct effect) and also by lowering the urban air temperature in the neighborhood of the building (indirect effect). This project is an attempt to address high-albedo materials for buildings and to perform measurements of roof coatings. We search for existing methods and materials to implement fighter colors on major building and urban surfaces. Their cost effectiveness are examined and the possible related technical, maintenance, and environmental problems are identified. We develop a method for measuring albedo in the field by studying the instrumentation aspects of such measurements. The surface temperature impacts of various albedo/materials in the actual outdoor environment are studied by measuring the surface temperatures of a variety of materials tested on an actual roof. We also generate an albedo database for several urban surfaces to serve as a reference for future use. The results indicate that high-albedo materials can have a large impact on the surface temperature regime. On clear sunny days, when the solar noon surface temperatures of conventional roofing materials were about 40{degrees}C (72{degrees}F) warmer than air, the surface temperature of high-albedo coatings were only about 5{degrees}C warmer than air. In the morning and in the late afternoon, the high-albedo materials were as cool as the air itself. While conventional roofing materials warm up by an average 0.055{degrees}C/(W m{sup {minus}2}), the high-albedo surfaces warm up by an average 0.015{degrees}C/(W m{sup {minus}2}).

  18. High-albedo materials for reducing building cooling energy use

    Energy Technology Data Exchange (ETDEWEB)

    Taha, H.; Sailor, D.; Akbari, H.

    1992-01-01

    One simple and effective way to mitigate urban heat islands, i.e., the higher temperatures in cities compared to those of the surrounds, and their negative impacts on cooling energy consumption is to use high-albedo materials on major urban surfaces such as rooftops, streets, sidewalks, school yards, and the exposed surfaces of parking lots. High-albedo materials can save cooling energy use by directly reducing the heat gain through a building's envelope (direct effect) and also by lowering the urban air temperature in the neighborhood of the building (indirect effect). This project is an attempt to address high-albedo materials for buildings and to perform measurements of roof coatings. We search for existing methods and materials to implement fighter colors on major building and urban surfaces. Their cost effectiveness are examined and the possible related technical, maintenance, and environmental problems are identified. We develop a method for measuring albedo in the field by studying the instrumentation aspects of such measurements. The surface temperature impacts of various albedo/materials in the actual outdoor environment are studied by measuring the surface temperatures of a variety of materials tested on an actual roof. We also generate an albedo database for several urban surfaces to serve as a reference for future use. The results indicate that high-albedo materials can have a large impact on the surface temperature regime. On clear sunny days, when the solar noon surface temperatures of conventional roofing materials were about 40{degrees}C (72{degrees}F) warmer than air, the surface temperature of high-albedo coatings were only about 5{degrees}C warmer than air. In the morning and in the late afternoon, the high-albedo materials were as cool as the air itself. While conventional roofing materials warm up by an average 0.055{degrees}C/(W m{sup {minus}2}), the high-albedo surfaces warm up by an average 0.015{degrees}C/(W m{sup {minus}2}).

  19. Global Cooling: Effect of Urban Albedo on Global Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Akbari, Hashem; Menon, Surabi; Rosenfeld, Arthur

    2007-05-22

    In many urban areas, pavements and roofs constitute over 60% of urban surfaces (roof 20-25%, pavements about 40%). The roof and the pavement albedo can be increased by about 0.25 and 0.10, respectively, resulting in a net albedo increase for urban areas of about 0.1. Many studies have demonstrated building cooling-energy savings in excess of 20% upon raising roof reflectivity from an existing 10-20% to about 60%. We estimate U.S. potential savings in excess of $1 billion (B) per year in net annual energy bills. Increasing albedo of urban surfaces can reduce the summertime urban temperature and improve the urban air quality. Increasing the urban albedo has the added benefit of reflecting more of the incoming global solar radiation and countering the effect of global warming. We estimate that increasing albedo of urban areas by 0.1 results in an increase of 3 x 10{sup -4} in Earth albedo. Using a simple global model, the change in air temperature in lowest 1.8 km of the atmosphere is estimated at 0.01K. Modelers predict a warming of about 3K in the next 60 years (0.05K/year). Change of 0.1 in urban albedo will result in 0.01K global cooling, a delay of {approx}0.2 years in global warming. This 0.2 years delay in global warming is equivalent to 10 Gt reduction in CO2 emissions.

  20. A Continental United States High Resolution NLCD Land Cover – MODIS Albedo Database to Examine Albedo and Land Cover Change Relationships

    Science.gov (United States)

    Surface albedo influences climate by affecting the amount of solar radiation that is reflected at the Earth’s surface, and surface albedo is, in turn, affected by land cover. General Circulation Models typically use modeled or prescribed albedo to assess the influence of land co...

  1. Improvement of Surface Albedo Simulations over Arid Regions

    Institute of Scientific and Technical Information of China (English)

    BAO Yan; L(U) Shihua; ZHANG Yu; MENG Xianhong; YANG Shengpeng

    2008-01-01

    To improve the simulation of the surface radiation budget and related thermal processes in arid regions, three sophisticated surface albedo schemes designed for such regions were incorporated into the Biosphere-Atmosphere Transfer Scheme (BATS). Two of these schemes are functions of the solar zenith angle (SZA), where the first one has one adjustable parameter defined as SZA1 scheme, and the second one has two empir-ical parameters defined as SZA2 scheme. The third albedo scheme is a function of solar angle and soil water that were developed based on arid-region observations from the Dunhuang field experiment (DHEX) (defined as DH scheme). We evaluated the performance of the original and newly-incorporated albedo schemes within BATS using the in-situ data from the Oasis System Energy and Water Cycle Field Experiment that was carried out in JinTa, Gansu arid area (JTEX). The results indicate that a control run by the original version of the BATS generates a constant albedo, while the SZA1 and SZA2 schemes basically can reproduce the observed diurnal cycle of surface albedo, although these two schemes still underestimate the albedo when SZA is high in the early morning and late afternoon, and overestimate it when SZA is low during noontime. The SZA2 scheme has a better overall performance than the SZA1 scheme. In addition, BATS with the DH scheme slightly improves the albedo simulation in magnitude as compared to that from the control run, but a diurnal cycle of albedo is not produced by this scheme. The SZAl and SZA2 schemes significantly increase the surface absorbed solar radiation by nearly 70 W m~2, which further raises the ground temperature by 6 K and the sensible heat flux by 35 W m~2. The increased solar radiation, heat flux, and temperature are more consistent with the observations that those from the control run. However, a significant improvement in these three variables is not found in BATS with the DH scheme due to the neglect of the diurnal cycle of

  2. Potential effects of forest management on surface albedo

    Science.gov (United States)

    Otto, J.; Bréon, F.-M.; Schelhaas, M.-J.; Pinty, B.; Luyssaert, S.

    2012-04-01

    Currently 70% of the world's forests are managed and this figure is likely to rise due to population growth and increasing demand for wood based products. Forest management has been put forward by the Kyoto-Protocol as one of the key instruments in mitigating climate change. For temperate and boreal forests, the effects of forest management on the stand-level carbon balance are reasonably well understood, but the biophysical effects, for example through changes in the albedo, remain elusive. Following a modeling approach, we aim to quantify the variability in albedo that can be attributed to forest management through changes in canopy structure and density. The modelling approach chains three separate models: (1) a forest gap model to describe stand dynamics, (2) a Monte-Carlo model to estimate the probability density function of the optical path length of photons through the canopy and (3) a physically-based canopy transfer model to estimate the interaction between photons and leaves. The forest gap model provides, on a monthly time step the position, height, diameter, crown size and leaf area index of individual trees. The Monte-Carlo model computes from this the probability density function of the distance a photon travels through crown volumes to determine the direct light reaching the forest floor. This information is needed by the canopy transfer model to calculate the effective leaf area index - a quantity that allows it to correctly represent a 3D process with a 1D model. Outgoing radiation is calculated as the result of multiple processes involving the scattering due to the canopy layer and the forest floor. Finally, surface albedo is computed as the ratio between incident solar radiation and calculated outgoing radiation. The study used two time series representing thinning from below of a beech and a Scots pine forest. The results show a strong temporal evolution in albedo during stand establishment followed by a relatively stable albedo once the canopy

  3. Occurrence of lower cloud albedo in ship tracks

    Directory of Open Access Journals (Sweden)

    Y.-C. Chen

    2012-05-01

    Full Text Available The concept of geoengineering by marine cloud brightening is based on seeding marine stratocumulus clouds with sub-micrometer sea-salt particles to enhance the cloud droplet number concentration and cloud albedo, thereby producing a climate cooling effect. The efficacy of this as a strategy for global cooling rests on the extent to which aerosol-perturbed marine clouds will respond with increased albedo. Ship tracks, cloud regions impacted by ship exhaust, are a well-known manifestation of the effect of aerosol injection on marine clouds. We present here an analysis of the albedo responses in ship tracks, based on in situ aircraft measurements and three years of satellite observations of 589 individual ship tracks. It is found that the sign (increase or decrease and magnitude of the albedo response in ship tracks depends on the mesoscale cloud structure, the free tropospheric humidity, and cloud top height. In a closed cell structure (cloud cells ringed by a perimeter of clear air, nearly 30% of ship tracks exhibited a decreased albedo. Detailed cloud responses must be accounted for in global studies of the potential efficacy of sea-spray geoengineering as a means to counteract global warming.

  4. Occurrence of lower cloud albedo in ship tracks

    Directory of Open Access Journals (Sweden)

    Y.-C. Chen

    2012-09-01

    Full Text Available The concept of geoengineering by marine cloud brightening is based on seeding marine stratocumulus clouds with sub-micrometer sea-salt particles to enhance the cloud droplet number concentration and cloud albedo, thereby producing a climate cooling effect. The efficacy of this as a strategy for global cooling rests on the extent to which aerosol-perturbed marine clouds will respond with increased albedo. Ship tracks, quasi-linear cloud features prevalent in oceanic regions impacted by ship exhaust, are a well-known manifestation of the effect of aerosol injection on marine clouds. We present here an analysis of the albedo responses in ship tracks, based on in situ aircraft measurements and three years of satellite observations of 589 individual ship tracks. It is found that the sign (increase or decrease and magnitude of the albedo response in ship tracks depends on the mesoscale cloud structure, the free tropospheric humidity, and cloud top height. In a closed cell structure (cloud cells ringed by a perimeter of clear air, nearly 30% of ship tracks exhibited a decreased albedo. Detailed cloud responses must be accounted for in global studies of the potential efficacy of sea-spray geoengineering as a means to counteract global warming.

  5. Decadal to seasonal variability of Arctic sea ice albedo

    CERN Document Server

    Agarwal, S; Wettlaufer, J S

    2011-01-01

    A controlling factor in the seasonal and climatological evolution of the sea ice cover is its albedo $\\alpha$. Here we analyze Arctic data from the Advanced Very High Resolution Radiometer (AVHRR) Polar Pathfinder and assess the seasonality and variability of broadband albedo from a 23 year daily record. We produce a histogram of daily albedo over ice covered regions in which the principal albedo transitions are seen; high albedo in late winter and spring, the onset of snow melt and melt pond formation in the summer, and fall freeze up. The bimodal late summer distribution demonstrates the combination of the poleward progression of the onset of melt with the coexistence of perennial bare ice with melt ponds and open water, which then merge to a broad peak at $\\alpha \\gtrsim $ 0.5. We find the interannual variability to be dominated by the low end of the $\\alpha$ distribution, highlighting the controlling influence of the ice thickness distribution and large-scale ice edge dynamics. The statistics obtained pro...

  6. Influência da irrigação sobre o albedo Influence of irrigation on albedo

    Directory of Open Access Journals (Sweden)

    Mário de Miranda V.B.R. Leitão

    2000-01-01

    Full Text Available Uma análise dos efeitos e da influência da irrigação sobre o albedo de uma cultura de amendoim, ao longo do ciclo de desenvolvimento e, em particular, durante um dia em que houve irrigação, é realizada neste estudo, cuja pesquisa de campo foi desenvolvida no perímetro irrigado da Estação Experimental da CODEVASF, no município de Rodelas, BA, no período de setembro a dezembro de 1996. Os resultados mostraram que o albedo variou significativamente nos dias em que foram efetuadas irrigações e nos dias imediatamente posteriores. Sob condições normais, o albedo variou de um máximo de 29,8% na fase inicial do experimento, com o solo ainda descoberto, a um mínimo de 18,6% no final da fase de desenvolvimento de vagem; contudo, nos dias de irrigação, dependendo da hora em que esta foi efetuada, houve influência diferenciada no valor do albedo médio diário, que chegou a reduzi-lo em até 6,4%, quando as irrigações ocorreram nas primeiras horas da manhã.The influence of irrigation on the albedo of a peanut crop during its development cycle, and in particular on the day when irrigation took place, is analyzed in this study. The field research was conducted in the irrigated perimeter of the Experimental Station of CODEVASF, in the municipal district of Rodelas, BA, during the period of September to December of 1996. The results showed that the albedo suffered significant variations on the days of irrigation as well as on the day after irrigation. Under normal conditions, the albedo varied from a maximum of 29.8% in the initial phase of the experiment with the soil still uncovered, to a minimum of 18.6% at the end of the kernel development phase. However, on the days of irrigation, the albedo varied with the time of irrigation. The daily mean value of the albedo reduced by 6.4% when the irrigations took place in the early hours of the morning.

  7. Direct determination of surface albedos from satellite imagery

    Science.gov (United States)

    Mekler, Y.; Joseph, J. H.

    1983-01-01

    An empirical method to measure the spectral surface albedo of surfaces from Landsat imagery is presented and analyzed. The empiricism in the method is due only to the fact that three parameters of the solution must be determined for each spectral photograph of an image on the basis of independently known albedos at three points. The approach is otherwise based on exact solutions of the radiative transfer equation for upwelling intensity. Application of the method allows the routine construction of spectral albedo maps from satelite imagery, without requiring detailed knowledge of the atmospheric aerosol content, as long as the optical depth is less than 0.75, and of the calibration of the satellite sensor.

  8. Detailed spatiotemporal albedo observations at Greenland's Mittivakkat Gletscher

    Science.gov (United States)

    Mernild, Sebastian H.; Knudsen, Niels T.; Yde, Jacob C.; Malmros, Jeppe K.

    2015-04-01

    Surface albedo is defined as the reflected fraction of incoming solar shortwave radiation at the surface. On Greenland's Mittivakkat Gletscher the mean glacier-wide MODIS-estimated albedo dropped by 0.10 (2000-2013) from 0.43 to 0.33 by the end of the mass balance year (EBY). Hand-held albedo measurements as low as 0.10 were observed over debris-covered ice at the glacier margin at the EBY: these values were slightly below observed values for proglacial bedrock (~0.2). The albedo is highly variable in space - a significant variability occurred within few meters at the glacier margin area ranging from 0.10 to 0.39 due to variability in debris-cover thickness and composition, microbial activity (including algae and cyanobacteria), snow grain crystal metamorphism, bare ice exposure, and meltwater ponding. Huge dark-red-brown-colored ice algae colonies were observed. Albedo measurements on snow patches and bare glacier ice changed significant with increasing elevations (180-600 m a.s.l.) by lapse rates of 0.04 and 0.03 per 100 m, respectively, indicating values as high as 0.82 and 0.40 on the upper part of the glacier. Over a period of two weeks from early August to late August 2014 the hand-held observed mean glacier-wide albedo changed from 0.40 to 0.30 indicating that on average 10% more incoming solar shortwave radiation became available for surface ablation at the end of the melt season.

  9. Diurnal variations in the UV albedo of arctic snow

    Directory of Open Access Journals (Sweden)

    O. Meinander

    2008-11-01

    Full Text Available The relevance of snow for climate studies is based on its physical properties, such as high surface reflectivity. Surface ultraviolet (UV albedo is an essential parameter for various applications based on radiative transfer modeling. Here, new continuous measurements of the local UV albedo of natural Arctic snow were made at Sodankylä (67°22'N, 26°39'E, 179 m a.s.l. during the spring of 2007. The data were logged at 1-min intervals. The accumulation of snow was up to 68 cm. The surface layer thickness varied from 0.5 to 35 cm with the snow grain size between 0.2 and 2.5 mm. The midday erythemally weighted UV albedo ranged from 0.6 to 0.8 in the accumulation period, and from 0.5 to 0.7 during melting. During the snow melt period, under cases of an almost clear sky and variable cloudiness, an unexpected diurnal decrease of 0.05 in albedo soon after midday, and recovery thereafter, was detected. This diurnal decrease in albedo was found to be asymmetric with respect to solar midday, thus indicating a change in the properties of the snow. Independent UV albedo results with two different types of instruments confirm these findings. The measured temperature of the snow surface was below 0°C on the following mornings. Hence, the reversible diurnal change, evident for ~1–2 h, could be explained by the daily metamorphosis of the surface of the snowpack, in which the temperature of the surface increases, melting some of the snow to liquid water, after which the surface freezes again.

  10. Albedo control of seasonal South Polar cap recession on Mars

    Science.gov (United States)

    Schmidt, Frédéric; Douté, Sylvain; Schmitt, Bernard; Vincendon, Mathieu; Bibring, Jean-Pierre; Langevin, Yves; Omega Team

    2009-04-01

    Over the last few decades, General Circulation Models (GCM) have been used to simulate the current martian climate. The calibration of these GCMs with the current seasonal cycle is a crucial step in understanding the climate history of Mars. One of the main climatic signals currently used to validate GCMs is the annual atmospheric pressure cycle. It is difficult to use changes in seasonal deposits on the surface of Mars to calibrate the GCMs given the spectral ambiguities between CO 2 and H 2O ice in the visible range. With the OMEGA imaging spectrometer covering the near infra-red range, it is now possible to monitor both types of ice at a spatial resolution of about 1 km. At global scale, we determine the change with time of the Seasonal South Polar Cap (SSPC) crocus line, defining the edge of CO 2 deposits. This crocus line is not symmetric around the geographic South Pole. At local scale, we introduce the snowdrop distance, describing the local structure of the SSPC edge. Crocus line and snowdrop distance changes can now be used to calibrate GCMs. The albedo of the seasonal deposits is usually assumed to be a uniform and constant parameter of the GCMs. In this study, albedo is found to be the main parameter controlling the SSPC recession at both global and local scale. Using a defrost mass balance model (referred to as D-frost) that incorporates the effect of shadowing induced by topography, we show that the global SSPC asymmetry in the crocus line is controlled by albedo variations. At local scale, we show that the snowdrop distance is correlated with the albedo variability. Further GCM improvements should take into account these two results. We propose several possibilities for the origin of the asymmetric albedo control. The next step will be to identify and model the physical processes that create the albedo differences.

  11. NEOWISE REACTIVATION MISSION YEAR ONE: PRELIMINARY ASTEROID DIAMETERS AND ALBEDOS

    Energy Technology Data Exchange (ETDEWEB)

    Nugent, C. R.; Cutri, R. M. [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Mainzer, A.; Masiero, J.; Bauer, J.; Kramer, E.; Sonnett, S.; Stevenson, R. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Grav, T. [Planetary Science Institute, Tucson, AZ (United States); Wright, E. L., E-mail: cnugent@ipac.caltech.edu [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)

    2015-12-01

    We present preliminary diameters and albedos for 7956 asteroids detected in the first year of the NEOWISE Reactivation mission. Of those, 201 are near-Earth asteroids and 7755 are Main Belt or Mars-crossing asteroids. 17% of these objects have not been previously characterized using the Near-Earth Object Wide-field Infrared Survey Explorer, or “NEOWISE” thermal measurements. Diameters are determined to an accuracy of ∼20% or better. If good-quality H magnitudes are available, albedos can be determined to within ∼40% or better.

  12. The retrieval of land surface albedo in rugged terrain

    NARCIS (Netherlands)

    Gao, B.; Jia, L.; Menenti, M.

    2012-01-01

    Land surface albedo may be derived from the satellite data through the estimation of a bidirectional reflectance distribution function (BRDF) model and angular integration. However many BRDF models do not consider explicitly the topography. In rugged terrain, the topography influences the observed s

  13. Forests, nitrogen and albedo, a very interesting trio indeed

    Directory of Open Access Journals (Sweden)

    Borghetti M

    2009-01-01

    Full Text Available A short comment is made on a recent paper (Ollinger et al. 2008 which shows that forest ecosystem carbon uptake in temperate and boreal forests is directly related to canopy nitrogen concentration and that both carbon uptake capacity and canopy nitrogen concentration are positively correlated with shortwave surface albedo measured with broad-band satellite sensors.

  14. Asteroid magnitudes, UBV colors, and IRAS albedos and diameters

    Science.gov (United States)

    Tedesco, Edward F.

    1989-01-01

    This paper lists absolute magnitudes and slope parameters for known asteroids numbered through 3318. The values presented are those used in reducing asteroid IR flux data obtained with the IRAS. U-B colors are given for 938 asteroids, and B-V colors are given for 945 asteroids. The IRAS albedos and diameters are tabulated for 1790 asteroids.

  15. The UV-Optical Albedo of Broad Emission Line Clouds

    CERN Document Server

    Korista, K T; Korista, Kirk; Ferland, Gary

    1997-01-01

    We explore the effective UV-optical albedos of a variety of types of broad emission line clouds, as well as their possible effects on the observed spectra of AGN. An important albedo source in moderately ionized ionization-bounded clouds is that due to neutral hydrogen: Rayleigh scattering of continuum photons off the extreme damping wings of Lya. The photons resulting from this scattering mechanism may contribute significantly to the Lya emission line, especially in the very broad wings. In addition, line photons emitted near 1200 Angstroms (e.g., N V 1240) that stream toward the neutral portion of the cloud may be reflected off this Rayleigh scattering mirror, so that they preferentially escape from the illuminated face. Inclusion of this effect can alter predicted emission line strengths and profiles. In more highly-ionized ionization-bounded clouds, Thompson scattering dominates the UV-optical albedo, but this albedo is lessened by the hydrogen gas opacity. These clouds are most reflective on the long wav...

  16. Albedo changes of the Arctic sea ice cover

    Science.gov (United States)

    Perovich, D. K.; Light, B.; Jones, K. F.; Eicken, H.; Runciman, K.; Nghiem, S. V.; Stroeve, J.; Markus, T.

    2008-12-01

    The summer extent of the Arctic sea ice cover has decreased in recent decades and there have been alterations in the timing and duration of the summer melt season. This has resulted in changes in the evolution of albedo of the Arctic sea ice cover, and consequently in the partitioning of solar energy. These changes are examined on a pan-Arctic scale on a 25 x 25 km Equal Area Scalable Earth Grid for the years 1979 - 2007. Daily values of incident solar irradiance are obtained from ERA-40 reanalysis products and ice concentrations are determined from passive microwave satellite data. The albedo of the ice is modeled by a five-phase process that includes dry snow, melting snow, melt pond formation, melt pond evolution, and freezeup. The timing of these phases is governed by the onset dates of summer melt and fall freezeup, which are determined from satellite observations. Results indicate a general trend of increasing solar heat input to the Arctic ice-ocean system due to reductions in ice concentration and longer melt seasons. This trend may accelerate the loss of sea ice through the ice-albedo feedback. The evolution of albedo, and hence the total solar heating of the ocean, is more sensitive to the date of melt onset than the date of fall freezeup.

  17. Albedo and color maps of the Saturnian satellites

    Science.gov (United States)

    Buratti, Bonnie J.; Mosher, Joel A.; Johnson, Torrence V.

    1990-01-01

    The paper discusses the production of maps of the albedos and colors of Mimas, Enceladus, Tethys, Dione, and Rhea over the full range of their imaged surfaces. Voyager images were used to prepare maps of the normal reflectances and color ratios (0.58/0.41 micron) of these satelites.

  18. Albedo and color maps of the Saturnian satellites

    Energy Technology Data Exchange (ETDEWEB)

    Buratti, B.J.; Mosher, J.A.; Johnson, T.V. (JPL, Pasadena, CA (USA))

    1990-10-01

    The paper discusses the production of maps of the albedos and colors of Mimas, Enceladus, Tethys, Dione, and Rhea over the full range of their imaged surfaces. Voyager images were used to prepare maps of the normal reflectances and color ratios (0.58/0.41 micron) of these satelites. 67 refs.

  19. Spacecraft Attitude Determination with Earth Albedo Corrected Sun Sensor Measurements

    DEFF Research Database (Denmark)

    Bhanderi, Dan

    -Method, Extended Kalman Filter, and Unscented Kalman Filter algorithms are presented and the results are compared. Combining the Unscented Kalman Filter with Earth albedo and enhanced Sun sensor modeling allows for three-axis attitude determination from Sun sensor only, which previously has been perceived...

  20. Size and Albedo of Irregular Saturnian Satellites from Spitzer Observations

    NARCIS (Netherlands)

    Mueller, Michael; Grav, T.; Trilling, D.; Stansberry, J.; Sykes, M.

    2008-01-01

    Using MIPS onboard the Spitzer Space Telescope, we observed the thermal emission (24 and, for some targets, 70 um) of eight irregular satellites of Saturn: Albiorix, Siarnaq, Paaliaq, Kiviuq, Ijiraq, Tarvos, Erriapus, and Ymir. We determined the size and albedo of all targets. An analysis of archive

  1. NLCD - MODIS land cover- albedo dataset for the continental United States

    Data.gov (United States)

    U.S. Environmental Protection Agency — The NLCD-MODIS land cover-albedo database integrates high-quality MODIS albedo observations with areas of homogeneous land cover from NLCD. The spatial resolution...

  2. MISR Level 2 FIRSTLOOK TOA/Cloud Albedo parameters V001

    Data.gov (United States)

    National Aeronautics and Space Administration — This is the Level 2 FIRSTLOOK TOA/Cloud Albedo Product. It contains local,restrictive, and expansive albedo, with associated data, produced using ancillary inputs...

  3. Effect of land cover change on snow free surface albedo across the continental United States

    Science.gov (United States)

    Land cover changes (e.g., forest to grassland) affect albedo, and changes in albedo can influence radiative forcing (warming, cooling). We empirically tested albedo response to land cover change for 130 locations across the continental United States using high resolution (30 m-&t...

  4. Albedo decreasing trend. White cars proposal and new urban scenarios

    Directory of Open Access Journals (Sweden)

    Niccolò Casiddu

    2014-05-01

    Full Text Available Global warming caused the decrease of the albedo. Emission reduction is the most widely proposed response to this problem. However simple ideas such as cool roofs and cool pavements seem successful remedies to counter the threat. However in Italy another strategy appears more effective. By changing from dark to pastel bright automotive colours a considerable increase of the albedo can be hypothesized: the effect should be from 32% to 50% of the results obtained with an extensive application of the “cool roofs” strategy. Such a proposal involves the creation of new, unexpected cityscapes. The city is a place where the perception of space changes. The car, by definition is an object in motion, but still present, sometimes redundant in the urban landscape. What will be the perceived relationship with buildings, streets, squares where the cars are all white or pastel colour?

  5. PAMELA's measurements of geomagnetically trapped and albedo protons

    CERN Document Server

    Bruno, A; Barbarino, G C; Bazilevskaya, G A; Bellotti, R; Boezio, M; Bogomolov, E A; Bongi, M; Bonvicini, V; Bottai, S; Bravar, U; Cafagna, F; Campana, D; Carbone, R; Carlson, P; Casolino, M; Castellini, G; Christian, E C; De Donato, C; de Nolfo, G A; De Santis, C; De Simone, N; Di Felice, V; Formato, V; Galper, A M; Karelin, A V; Koldashov, S V; Koldobskiy, S; Krutkov, S Y; Kvashnin, A N; Lee, M; Leonov, A; Malakhov, V; Marcelli, L; Martucci, M; Mayorov, A G; Menn, W; Mergè, M; Mikhailov, V V; Mocchiutti, E; Monaco, A; Mori, N; Munini, R; Osteria, G; Palma, F; Panico, B; Papini, P; Pearce, M; Picozza, P; Ricci, M; Ricciarini, S B; Ryan, J M; Sarkar, R; Scotti, V; Simon, M; Sparvoli, R; Spillantini, P; Stochaj, S; Stozhkov, Y I; Vacchi, A; Vannuccini, E; Vasilyev, G I; Voronov, S A; Yurkin, Y T; Zampa, G; Zampa, N; Zverev, V G

    2015-01-01

    Data from the PAMELA satellite experiment were used to perform a detailed measurement of under-cutoff protons at low Earth orbits. On the basis of a trajectory tracing approach using a realistic description of the magnetosphere, protons were classified into geomagnetically trapped and re-entrant albedo. The former include stably-trapped protons in the South Atlantic Anomaly, which were analyzed in the framework of the adiabatic theory, investigating energy spectra, spatial and angular distributions; results were compared with the predictions of the AP8 and the PSB97 empirical trapped models. The albedo protons were classified into quasi-trapped, concentrating in the magnetic equatorial region, and un-trapped, spreading over all latitudes and including both short-lived (precipitating) and long-lived (pseudo-trapped) components. Features of the penumbra region around the geomagnetic cutoff were investigated as well. PAMELA observations significantly improve the characterization of the high energy proton populat...

  6. NEOWISE diameters and albedos: now available on PDS!

    Science.gov (United States)

    Masiero, Joseph R.; Mainzer, Amy K.; Bauer, James M.; Cutri, Roc M.; Grav, Tommy; Kramer, Emily A.; Nugent, Carolyn; Sonnett, Sarah M.; Stevenson, Rachel; Wright, Edward L.

    2016-10-01

    We present the recent PDS release of minor planet physical property data from the WISE/NEOWISE fully cryogenic, 3-band cryo, and post-cryo surveys as well as the first year of the NEOWISE-Reactivation survey. This release includes 165,865 diameters, visible albedos, near-infrared albedos, and/or beaming parameters for 140,493 unique minor planets. The published data include near-Earth asteroids, Main Belt asteroids, Hildas, Jupiter Trojans, Centaurs, active Main Belt objects and irregular satellites of Jupiter and Saturn. We provide an overview of the available data and discuss the key features of the PDS data set. The data are available online at: http://sbn.psi.edu/pds/resource/neowisediam.html.

  7. Measuring the influence of aerosols and albedo on sky polarization.

    Science.gov (United States)

    Kreuter, A; Emde, C; Blumthaler, M

    2010-11-01

    All-sky distributions of the polarized radiance are measured using an automated fish-eye camera system with a rotating polarizer. For a large range of aerosol and surface albedo situations, the influence on the degree of polarization and sky radiance is investigated. The range of aerosol optical depth and albedo is 0.05-0.5 and 0.1-0.75, respectively. For this range of parameters, a reduction of the degree of polarization from about 0.7 to 0.4 was observed. The analysis is done for 90° scattering angle in the principal plane under clear sky conditions for a broadband channel of 450 ± 25 nm and solar zenith angles between 55° and 60°. Radiative transfer calculations considering three different aerosol mixtures are performed and and agree with the measurements within the statistical error.

  8. Durability of high-albedo roof coatings and implications for cooling energy savings. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Bretz, S.E.; Akbari, H.

    1994-06-01

    Twenty-six spot albedo measurements of roofs were made using a calibrated pyranometer. The roofs were surfaced with either an acrylic elastomeric coating, a polymer coating with an acrylic base, or a cementitious coating. Some of the roofs` albedos were measured before and after washing to determine whether the albedo decrease was permanent. Data indicated that most of the albedo degradation occurred within the first year, and even within the first two months. On one roof, 70% of one year`s albedo degradation occurred in the first two months. After the first year, the degradation slowed, with data indicating small losses in albedo after the second year. Measurements of seasonal cooling energy savings by Akbari et al. (1993) included the effects of over two months of albedo degradation. We estimated {approximately}20% loss in cooling-energy savings after the first year because of dirt accumulation. For most of the roofs we cleaned, the albedo was restored to within 90% of its initial value. Although washing is effective at restoring albedo, the increase in energy savings is temporary and labor costs are significant in comparison to savings. By our calculations, it is not cost-effective to hire someone to clean a high-albedo roof only to achieve energy savings. Thus, it would be useful to develop and identify dirt-resistant high-albedo coatings.

  9. Effect of land cover change on snow free surface albedo across the continental United States

    Science.gov (United States)

    Wickham, J.; Nash, M. S.; Barnes, C. A.

    2016-11-01

    Land cover changes (e.g., forest to grassland) affect albedo, and changes in albedo can influence radiative forcing (warming, cooling). We empirically tested albedo response to land cover change for 130 locations across the continental United States using high resolution (30 m-×-30 m) land cover change data and moderate resolution (~ 500 m-×-500 m) albedo data. The land cover change data spanned 10 years (2001 - 2011) and the albedo data included observations every eight days for 13 years (2001 - 2013). Empirical testing was based on autoregressive time series analysis of snow free albedo for verified locations of land cover change. Approximately one-third of the autoregressive analyses for woody to herbaceous or forest to shrub change classes were not significant, indicating that albedo did not change significantly as a result of land cover change at these locations. In addition, ~ 80% of mean differences in albedo arising from land cover change were less than ± 0.02, a nominal benchmark for precision of albedo measurements that is related to significant changes in radiative forcing. Under snow free conditions, we found that land cover change does not guarantee a significant albedo response, and that the differences in mean albedo response for the majority of land cover change locations were small.

  10. MISR Level 2 TOA/Cloud Albedo parameters (MIL2TCAL_V2)

    Science.gov (United States)

    Diner, David J. (Principal Investigator)

    The TOA/Cloud Albedo data contain albedo values, including finely-sampled or local (2.2 km) TOA albedos registered to the RLRA, and two coarsely-sampled (35.2 km resolution) TOA albedos projected to 30-km altitude. The local (2.2 km) albedos do not take the obscuration of cloud features into account, so they should only be treated as traditional albedos when the number of obscured pixels is low. The restrictive and expansive albedos are both available at 35.2 km resolution: the restrictive albedos are only calculated using the radiation upwelling from the pixel under consideration, whereas the expansive albedos use all the radiation emanating from the surrounding area. Therefore, the expansive albedo is closer to the traditional definition of top-of-atmosphere albedos. [Temporal_Coverage: Start_Date=2000-02-24; Stop_Date=] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=180] [Data_Resolution: Latitude_Resolution=1.1 km; Longitude_Resolution=1.1 km; Temporal_Resolution=about 15 orbits/day].

  11. Albedo polarimétrico de asteroides del grupo Hungaria

    Science.gov (United States)

    Gil-Hutton, R.; Benavidez, P.

    La región del cinturón de asteroides en donde se encuentra el grupo de los Hungarias (a= 1.79 a 1.98 UA, i=15 a 40 grados) es la única zona donde es común encontrar objetos de tipo taxonómico E, caracterizados por altos albedos, colores relativamente neutros y espectros sin detalles. Este tipo de asteroides está relacionado espectralmente con ciertos meteoritos (aubritas) que indican la existencia de episodios de gran calentamiento que ocurrieron durante la formación del Sistema Solar. Como el espectro de los asteroides de tipo E es idéntico a los de tipo M y P, la única forma de clasificar un asteroide en alguno de estos tres tipos taxonómicos es mediante el albedo. En este trabajo se presentan resultados preliminares sobre la determinación polarimétrica de albedos para objetos de este grupo utilizando el polarímetro CASPROF de CASLEO.

  12. Albedo and Reflection Spectra of Extrasolar Giant Planets

    CERN Document Server

    Sudarsky, D; Pinto, P A; Sudarsky, David; Burrows, Adam; Pinto, Philip

    1999-01-01

    We generate theoretical albedo and reflection spectra for a full range of extrasolar giant planet (EGP) models, from Jovian to 51-Pegasi class objects. Our albedo modeling utilizes the latest atomic and molecular cross sections, a Mie theory treatment of extinction by condensates, a variety of particle size distributions, and an extension of the Feautrier radiative transfer method which allows for a general treatment of the scattering phase function. We find that due to qualitative similarities in the compositions and spectra of objects within each of four broad effective temperature ranges, it is natural to establish four representative EGP albedo classes: a ``Jovian'' class (T$_{\\rm eff} \\lesssim 150$ K; Class I) with tropospheric ammonia clouds, a ``water cloud'' class (T$_{\\rm eff} \\sim 250$ K; Class II) primarily affected by condensed H$_2$O, a ``clear'' class (T$_{\\rm eff} \\gtrsim 350$ K; Class III) which lacks clouds, and a high-temperature class (T$_{\\rm{eff}}$ $\\gtrsim$ 900 K; Class IV) for which alk...

  13. Signatures of volatiles in the lunar proton albedo

    Science.gov (United States)

    Schwadron, N. A.; Wilson, J. K.; Looper, M. D.; Jordan, A. P.; Spence, H. E.; Blake, J. B.; Case, A. W.; Iwata, Y.; Kasper, J. C.; Farrell, W. M.; Lawrence, D. J.; Livadiotis, G.; Mazur, J.; Petro, N.; Pieters, C.; Robinson, M. S.; Smith, S.; Townsend, L. W.; Zeitlin, C.

    2016-07-01

    We find evidence for hydrated material in the lunar regolith using "albedo protons" measured with the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO). Fluxes of these albedo protons, which are emitted from the regolith due to steady bombardment by high energy radiation (Galactic Cosmic Rays), are observed to peak near the poles, and are inconsistent with the latitude trends of heavy element enrichment (e.g., enhanced Fe abundance). The latitudinal distribution of albedo protons anti-correlates with that of epithermal or high energy neutrons. The high latitude enhancement may be due to the conversion of upward directed secondary neutrons from the lunar regolith into tertiary protons due to neutron-proton collisions in hydrated regolith that is more prevalent near the poles. The CRaTER instrument may thus provide important measurements of volatile distributions within regolith at the Moon and potentially, with similar sensors and observations, at other bodies within the Solar System.

  14. Signatures of Volatiles in the Lunar Proton Albedo

    Science.gov (United States)

    Schwadron, N. A.; Wilson, J. K.; Looper, M. D.; Jordan, A. P.; Spence, H. E.; Blake, J. B.; Case, A. W.; Iwata, Y.; Kasper, J. C.; Farrell, W. M.; Petro, N.

    2015-01-01

    We find evidence for hydrated material in the lunar regolith using "albedo protons" measured with the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO). Fluxes of these albedo protons, which are emitted from the regolith due to steady bombardment by high energy radiation (Galactic Cosmic Rays), are observed to peak near the poles, and are inconsistent with the latitude trends of heavy element enrichment (e.g., enhanced Fe abundance). The latitudinal distribution of albedo protons anti-correlates with that of epithermal or high energy neutrons. The high latitude enhancement may be due to the conversion of upward directed secondary neutrons from the lunar regolith into tertiary protons due to neutron-proton collisions in hydrated regolith that is more prevalent near the poles. The CRaTER instrument may thus provide important measurements of volatile distributions within regolith at the Moon and potentially, with similar sensors and observations, at other bodies within the Solar System.

  15. Gamma-ray Albedo of Small Solar System Bodies

    Energy Technology Data Exchange (ETDEWEB)

    Moskalenko, I.V.

    2008-03-25

    We calculate the {gamma}-ray albedo flux from cosmic-ray (CR) interactions with the solid rock and ice in Main Belt asteroids and Kuiper Belt objects (KBOs) using the Moon as a template. We show that the {gamma}-ray albedo for the Main Belt and KBOs strongly depends on the small-body mass spectrum of each system and may be detectable by the forthcoming Gamma Ray Large Area Space Telescope (GLAST). If detected, it can be used to derive the mass spectrum of small bodies in the Main Belt and Kuiper Belt and to probe the spectrum of CR nuclei at close-to-interstellar conditions. The orbits of the Main Belt asteroids and KBOs are distributed near the ecliptic, which passes through the Galactic center and high Galactic latitudes. Therefore, the {gamma}-ray emission by the Main Belt and Kuiper Belt has to be taken into account when analyzing weak {gamma}-ray sources close to the ecliptic. The asteroid albedo spectrum also exhibits a 511 keV line due to secondary positrons annihilating in the rock. This may be an important and previously unrecognized celestial foreground for the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of the Galactic 511 keV line emission including the direction of the Galactic center. For details of our calculations and references see [1].

  16. Multidecadal analysis of forest growth and albedo in boreal Finland

    Science.gov (United States)

    Lukeš, Petr; Stenberg, Pauline; Mõttus, Matti; Manninen, Terhikki; Rautiainen, Miina

    2016-10-01

    It is well known that forests serve as carbon sinks. However, the balancing effect of afforestation and increased forest density on global warming due to carbon storage may be lost by low albedo (thus high absorption) of the forests. In the last 30 years, there has been a steady increase in the growing stock of Finnish forests by nearly a quarter while the area of the forests has remained virtually unchanged. Such increase in forest density together with the availability of detailed forest inventories provided by the Multi-Source National Forest Inventory (MS-NFI) in high spatial resolution makes Finland an ideal candidate for exploring the effects of increased forest density on satellite derived estimates of bio-geochemical products e.g. albedo (directional-hemispherical reflectance, DHR), fraction of photosynthetically active radiation absorbed by canopies (fAPAR), leaf area index (LAI) and normalized difference vegetation index (NDVI) in both current and long-term perspective. In this study, we first used MODIS-based vegetation satellite products for Finnish forests to study their seasonal patterns and interrelations. Next, the peak growing season observations are linked to the MS-NFI database to yield the generic relationships between forest density and the satellite-derived vegetation indicators. Finally, long-term GIMMS3g datasets between 1982 and 2011 (2008 for DHR) are analyzed and interpreted using forest inventory data. The vegetation peak growing season NIR DHR and VIS DHR showed weak to moderate negative correlation with fAPAR, whereas there was no correlation between NIR DHR and fAPAR. Next, we show that the spectral albedos in the near-infrared region (NIR DHR) showed weak negative correlation with forest biomass, basal area or canopy cover whereas, as expected, the spectral albedo in the visible region (VIS DHR) correlated negatively with these measures of forest density. Interestingly, the increase in forest density (biomass per ha) of Finnish

  17. [Temporal and Spatial Characteristics of Lake Taihu Surface Albedo and Its Impact Factors].

    Science.gov (United States)

    Cao, Chang; Li, Xu-hui; Zhang, Mi; Liu, Shou-dong; Xiao, Wei; Xiao, Qi-tao; Xu, Jia-ping

    2015-10-01

    Lake surface albedo determines energy balance of water-atmospheric interface and water physical environment. Solar elevation angle, cloudiness, wind speed, water quality and other factors can affect lake surface albedo. Using solar radiation, wind speed, and water quality data (turbidity and chlorophyll-a concentration) which were observed in four eddy covariance sites (Meiliangwan, Dapukou, Bifenggang and Xiaoleishan i. e. MLW, DPK, BFG and XLS) in Lake Taihu and clearness index (k(t)), the influence of these factors on Lake Taihu surface albedo and the reasons that led to its spatial difference were investigated. The results showed that solar elevation angle played a leading role in the diurnal and seasonal change of lake surface albedo; lake surface albedo reached two peaks in 0 BFG > DPK > MLW. XLS and BFG belonged to the higher albedo group, while DPK and MLW belonged to the lower albedo group. The different biological environments caused by aquatic macrophytes and algae resulting in the spatial variation of Lake Taihu surface albedo. The relationship between albedo and chlorophyll-a concentration was not a very sensitive factor for indicating the outbreak of algae. This study can provide theoretical reference for lake albedo parameterization.

  18. Robust estimation of albedo for illumination-invariant matching and shape recovery.

    Science.gov (United States)

    Biswas, Soma; Aggarwal, Gaurav; Chellappa, Rama

    2009-05-01

    We present a nonstationary stochastic filtering framework for the task of albedo estimation from a single image. There are several approaches in the literature for albedo estimation, but few include the errors in estimates of surface normals and light source direction to improve the albedo estimate. The proposed approach effectively utilizes the error statistics of surface normals and illumination direction for robust estimation of albedo, for images illuminated by single and multiple light sources. The albedo estimate obtained is subsequently used to generate albedo-free normalized images for recovering the shape of an object. Traditional Shape-from-Shading (SFS) approaches often assume constant/piecewise constant albedo and known light source direction to recover the underlying shape. Using the estimated albedo, the general problem of estimating the shape of an object with varying albedo map and unknown illumination source is reduced to one that can be handled by traditional SFS approaches. Experimental results are provided to show the effectiveness of the approach and its application to illumination-invariant matching and shape recovery. The estimated albedo maps are compared with the ground truth. The maps are used as illumination-invariant signatures for the task of face recognition across illumination variations. The recognition results obtained compare well with the current state-of-the-art approaches. Impressive shape recovery results are obtained using images downloaded from the Web with little control over imaging conditions. The recovered shapes are also used to synthesize novel views under novel illumination conditions.

  19. Climatic Benefit of Swiss Forest Cover Change: Including Albedo Change into Net Carbon Balance

    Science.gov (United States)

    Schwaab, J.; Lehning, M.; Bebi, P.

    2012-12-01

    Forests influence climate through physical, chemical and biological processes. It has been shown that warming caused by the comparatively low albedo of forests (albedo-effect), can reduce or even exceed cooling caused by carbon storage in forests (CO2-effect). Although warming caused by albedo and the amount of carbon storage depend on local characteristics, studies are lacking that investigate the combined local patterns of albedo and CO2-effect. Our study area, Switzerland, provides a variety of geographical features and thus the possibility to show how different geographical variables influence the two effects. We used the concept of radiative forcing to compare the effect of a changing albedo and a change in atmospheric CO2 concentration due to land cover change in the past. The change of forest cover was analysed over a period of 12 years based on aerial photographs. We estimate the albedo-effect by combining albedo data derived from the satellite sensor MODIS and data on snow cover derived from the satellite sensor AVHRR. Changes in carbon storage were calculated as differences in biomass and soil stocks of specific land cover classes. We found carbon storage induced cooling to be higher than albedo induced warming everywhere in Switzerland. However, especially in altitudes over 1200 m the albedo-effect reduced the benefits of carbon storage by more than 50%. In lower altitudes the albedo change was less important. The albedo-effect in altitudes above 1200 m was more relevant because of a more persistent snow-cover, a slightly higher global radiation and less additional carbon storage. The relevance of warming caused by an albedo change did not only depend on altitude, but also on the characteristics of forest cover change. While transitions from open land to open forest were accompanied by high albedo changes, the albedo change was only marginal if open forest turned into closed forest. Since snow cover has a large influence on the albedo effect, we included

  20. Can increasing albedo of existing ship wakes reduce climate change?

    Science.gov (United States)

    Crook, Julia A.; Jackson, Lawrence S.; Forster, Piers M.

    2016-02-01

    Solar radiation management schemes could potentially alleviate the impacts of global warming. One such scheme could be to brighten the surface of the ocean by increasing the albedo and areal extent of bubbles in the wakes of existing shipping. Here we show that ship wake bubble lifetimes would need to be extended from minutes to days, requiring the addition of surfactant, for ship wake area to be increased enough to have a significant forcing. We use a global climate model to simulate brightening the wakes of existing shipping by increasing wake albedo by 0.2 and increasing wake lifetime by ×1440. This yields a global mean radiative forcing of -0.9 ± 0.6 Wm-2 (-1.8 ± 0.9 Wm-2 in the Northern Hemisphere) and a 0.5°C reduction of global mean surface temperature with greater cooling over land and in the Northern Hemisphere, partially offsetting greenhouse gas warming. Tropical precipitation shifts southward but remains within current variability. The hemispheric forcing asymmetry of this scheme is due to the asymmetry in the distribution of existing shipping. If wake lifetime could reach ~3 months, the global mean radiative forcing could potentially reach -3 Wm-2. Increasing wake area through increasing bubble lifetime could result in a greater temperature reduction, but regional precipitation would likely deviate further from current climatology as suggested by results from our uniform ocean albedo simulation. Alternatively, additional ships specifically for the purpose of geoengineering could be used to produce a larger and more hemispherically symmetrical forcing.

  1. Using albedo to reform wind erosion modelling, mapping and monitoring

    Science.gov (United States)

    Chappell, Adrian; Webb, Nicholas P.

    2016-12-01

    Wind erosion and dust emission models are used to assess the impacts of dust on radiative forcing in the atmosphere, cloud formation, nutrient fertilisation and human health. The models are underpinned by a two-dimensional geometric property (lateral cover; L) used to characterise the three-dimensional aerodynamic roughness (sheltered area or wakes) of the Earth's surface and calibrate the momentum it extracts from the wind. We reveal a fundamental weakness in L and demonstrate that values are an order of magnitude too small and significant aerodynamic interactions between roughness elements and their sheltered areas have been omitted, particularly under sparse surface roughness. We describe a solution which develops published work to establish a relation between sheltered area and the proportion of shadow over a given area; the inverse of direct beam directional hemispherical reflectance (black sky albedo; BSA). We show direct relations between shadow and wind tunnel measurements and thereby provide direct calibrations of key aerodynamic properties. Estimation of the aerodynamic parameters from albedo enables wind erosion assessments over areas, across platforms from the field to airborne and readily available satellite data. Our new approach demonstrated redundancy in existing wind erosion models and thereby reduced model complexity and improved fidelity. We found that the use of albedo enabled an adequate description of aerodynamic sheltering to characterise fluid dynamics and predict sediment transport without the use of a drag partition scheme (Rt) or threshold friction velocity (u∗t). We applied the calibrations to produce global maps of aerodynamic properties which showed very similar spatial patterns to each other and confirmed the redundancy in the traditional parameters of wind erosion modelling. We evaluated temporal patterns of predicted horizontal mass flux at locations across Australia which revealed variation between land cover types that would not

  2. Albedo parametrization and reversibility of sea ice decay

    OpenAIRE

    M. Müller-Stoffels; R. Wackerbauer

    2012-01-01

    The Arctic's sea ice cover has been receding rapidly in recent years, and global climate models typically predict a further decline over the next century. It is an open question whether a possible loss of Arctic sea ice is reversible. We study the stability of Arctic model sea ice in a conceptual, two-dimensional energy-based regular network model of the ice-ocean layer that considers ARM's longwave radiative budget data and SHEBA albedo measurements. Seasonal ice cover, perennial ice and per...

  3. Albedo and laser threshold of a diffusive Raman gain medium

    CERN Document Server

    Selden, Adrian C

    2010-01-01

    The diffuse reflectance (albedo) and transmittance of a Raman random gain medium are calculated via semi-analytic two-stream equations with power-dependent coefficients. The results show good qualitative agreement with the experimental data for barium nitrate powder. A divergence in reflectance at a critical gain is interpreted as the threshold for diffusive Raman laser generation. The dependence of the generation threshold on the scattering parameters is analysed and the feedback effect of Fresnel reflection at the gain boundaries evaluated. The addition of external mirrors, particularly at the pumped surface, significantly reduces the threshold gain.

  4. Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate

    Science.gov (United States)

    Charlson, Robert J.; Warren, Stephen G.; Lovelock, James E.; Andreae, Meinrat O.

    1987-04-01

    The major source of cloud-condensation nuclei (CCN) over the oceans appears to be dimethylsulphide, which is produced by planktonic algae in sea water and oxidizes in the atmosphere to form a sulphate aerosol. Because the reflectance (albedo) of clouds (and thus the earth's radiation budget) is sensitive to CCN density, biological regulation of the climate is possible through the effects of temperature and sunlight on phytoplankton population and dimethylsulphide production. To counteract the warming due to doubling of atmospheric CO2, an approximate doubling of CCN would be needed.

  5. Land Surface Albedos Computed from BRF Measurements with a Study of Conversion Formulae

    Directory of Open Access Journals (Sweden)

    Aku Riihelä

    2010-08-01

    Full Text Available Land surface hemispherical albedos of several targets have been resolved using the bidirectional reflectance factor (BRF library of the Finnish Geodetic Institute (FGI. The library contains BRF data measured by FGI during the years 2003–2009. Surface albedos are calculated using selected BRF datasets from the library. Polynomial interpolation and extrapolation have been used in computations. Several broadband conversion formulae generally used for satellite based surface albedo retrieval have been tested. The albedos were typically found to monotonically increase with increasing zenith angle of the Sun. The surface albedo variance was significant even within each target category / surface type. In general, the albedo estimates derived using diverse broadband conversion formulas and estimates obtained by direct integration of the measured spectra were in line.

  6. Earth's albedo variations 1998-2014 as measured from ground-based earthshine observations

    Science.gov (United States)

    Palle, E.; Goode, P. R.; Montañés-Rodríguez, P.; Shumko, A.; Gonzalez-Merino, B.; Lombilla, C. Martinez; Jimenez-Ibarra, F.; Shumko, S.; Sanroma, E.; Hulist, A.; Miles-Paez, P.; Murgas, F.; Nowak, G.; Koonin, S. E.

    2016-05-01

    The Earth's albedo is a fundamental climate parameter for understanding the radiation budget of the atmosphere. It has been traditionally measured not only from space platforms but also from the ground for 16 years from Big Bear Solar Observatory by observing the Moon. The photometric ratio of the dark (earthshine) to the bright (moonshine) sides of the Moon is used to determine nightly anomalies in the terrestrial albedo, with the aim of quantifying sustained monthly, annual, and/or decadal changes. We find two modest decadal scale cycles in the albedo, but with no significant net change over the 16 years of accumulated data. Within the evolution of the two cycles, we find periods of sustained annual increases, followed by comparable sustained decreases in albedo. The evolution of the earthshine albedo is in remarkable agreement with that from the Clouds and the Earth's Radiant Energy System instruments, although each method measures different slices of the Earth's Bond albedo.

  7. Earth's albedo variations 1998-2014 as measured from ground-based earthshine observations

    CERN Document Server

    Palle, E; Montanes-Rodriguez, P Pilar; Shumko, A; Gonzalez-Merino, B; Lombilla, C Martinez; Jimenez-Ibarra, F; Shumko, S; Sanroma, E; Hulist, A; Miles-Paez, P; Murgas, F; Nowak, G; Koonin, SE

    2016-01-01

    The Earth's albedo is a fundamental climate parameter for understanding the radiation budget of the atmosphere. It has been traditionally measured from space platforms, but also from the ground for sixteen years from Big Bear Solar Observatory by observing the Moon. The photometric ratio of the dark (earthshine) to the bright (moonshine) sides of the Moon is used to determine nightly anomalies in the terrestrial albedo, with the aim is of quantifying sustained monthly, annual and/or decadal changes. We find two modest decadal scale cycles in the albedo, but with no significant net change over the sixteen years of accumulated data. Within the evolution of the two cycles, we find periods of sustained annual increases, followed by comparable sustained decreases in albedo. The evolution of the earthshine albedo is in remarkable agreement with that from the CERES instruments, although each method measures different slices of the Earth's Bond albedo.

  8. Detecting Low-Contrast Features in the Cosmic Ray Albedo Proton Map of the Moon

    Science.gov (United States)

    Wilson, J. K.; Schwadron, N.; Spence, H. E.; Golightly, M. J.; Case, A. W.; Smith, S.; Blake, J. B.; Kasper, J.; Looper, M. D.; Mazur, J. E.; Townsend, L. W.; Zeitlin, C.; Stubbs, T. J.

    2014-01-01

    High energy cosmic rays constantly bombard the lunar regolith, producing (via nuclear evaporation) secondary 'albedo' or 'splash' particles like protons and neutrons, some of which escape back to space. Lunar Prospector and the Lunar Reconnaissance Orbiter (LRO), have shown that the energy distribution of albedo neutrons is modulated by the elemental composition of the lunar regolith, and by ice deposits in permanently shadowed polar craters. Here we investigate an analogous phenomenon with high energy ((is) approximately 100 MeV) lunar albedo protons.

  9. Investigating the spread in surface albedo for snow-covered forests in CMIP5 models

    Science.gov (United States)

    Wang, Libo; Cole, Jason N. S.; Bartlett, Paul; Verseghy, Diana; Derksen, Chris; Brown, Ross; Salzen, Knut

    2016-02-01

    This study investigates the role of leaf/plant area index (LAI/PAI) specification on the large spread of winter albedo simulated by climate models. To examine the sensitivity of winter albedo to LAI, we perform a sensitivity analysis using two methods commonly used to compute albedo in snow-covered forests as well as diagnostic calculations within version 4.2 of the Canadian Atmospheric Model for which PAI is systematically varied. The results show that the simulated albedo is very sensitive to negative PAI biases, especially for smaller PAI values. The LAI and surface albedo of boreal forests in the presence of snow simulated by the Coupled Model Intercomparison Project Phase 5 (CMIP5) models are evaluated using satellite observations. The evaluation of CMIP5 models suggest that inaccurate tree cover fraction due to improper plant functional type specification or erroneous LAI parameterization in some models explains, in part, an observed positive bias in winter albedo over boreal forest regions of the Northern Hemisphere. This contributes to a large intermodel spread in simulated surface albedo in the presence of snow over these regions and is largely responsible for uncertainties in simulated snow-albedo feedback strength. Errors are largest (+20-40%) in models with large underestimation of LAI but are typically within ±15% when simulated LAI is within the observed range. This study underscores the importance of accurate representation of vegetation distribution and parameters in realistic simulation of surface albedo.

  10. Investigating the spread of surface albedo in snow covered forests in CMIP5 models

    Science.gov (United States)

    Wang, Libo; Cole, Jason; Bartlett, Paul; Verseghy, Diana; Derksen, Chris; Brown, Ross; von Salzen, Knut

    2016-04-01

    This study investigates the role of leaf/plant area index (LAI/PAI) specification on the large spread of winter albedo simulated by climate models. To examine the sensitivity of winter albedo to LAI, we perform a sensitivity analysis using two methods commonly used to compute albedo in snow-covered forests as well as diagnostic calculations within version 4.2 of the Canadian Atmospheric Model for which PAI is systematically varied. The results show that the simulated albedo is very sensitive to negative PAI biases, especially for smaller PAI values. The LAI and surface albedo of boreal forests in the presence of snow simulated by the Coupled Model Intercomparison Project Phase 5 (CMIP5) models are evaluated using satellite observations. The evaluation of CMIP5 models suggest that inaccurate tree cover fraction due to improper plant functional type specification or erroneous LAI parameterization in some models explains, in part, an observed positive bias in winter albedo over boreal forest regions of the Northern Hemisphere. This contributes to a large intermodel spread in simulated surface albedo in the presence of snow over these regions and is largely responsible for uncertainties in simulated snow-albedo feedback strength. Errors are largest (+20-40 %) in models with large underestimation of LAI but are typically within ±15% when simulated LAI is within the observed range. This study underscores the importance of accurate representation of vegetation distribution and parameters in realistic simulation of surface albedo.

  11. A Tailorable Structural Composite for GCR and Albedo Neutron Protection on the Lunar Surface Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A tailorable structural composite that will provide protection from the lunar radiation environment, including GCR and albedo neutrons will be developed. This...

  12. Albedo parametrization and reversibility of sea ice decay

    Science.gov (United States)

    Müller-Stoffels, M.; Wackerbauer, R.

    2012-02-01

    The Arctic's sea ice cover has been receding rapidly in recent years, and global climate models typically predict a further decline over the next century. It is an open question whether a possible loss of Arctic sea ice is reversible. We study the stability of Arctic model sea ice in a conceptual, two-dimensional energy-based regular network model of the ice-ocean layer that considers ARM's longwave radiative budget data and SHEBA albedo measurements. Seasonal ice cover, perennial ice and perennial open water are asymptotic states accessible by the model. We show that the shape of albedo parameterization near the melting temperature differentiates between reversible continuous sea ice decrease under atmospheric forcing and hysteresis behavior. Fixed points induced solely by the surface energy budget are essential for understanding the interaction of surface energy with the radiative forcing and the underlying body of ice/water, particularly close to a bifurcation point. Future studies will explore ice edge stability and reversibility in this lattice model, generalized to a latitudinal transect with spatiotemporal lateral atmospheric heat transfer and high spatial resolution.

  13. Albedo parametrization and reversibility of sea ice decay

    Directory of Open Access Journals (Sweden)

    M. Müller-Stoffels

    2012-02-01

    Full Text Available The Arctic's sea ice cover has been receding rapidly in recent years, and global climate models typically predict a further decline over the next century. It is an open question whether a possible loss of Arctic sea ice is reversible. We study the stability of Arctic model sea ice in a conceptual, two-dimensional energy-based regular network model of the ice-ocean layer that considers ARM's longwave radiative budget data and SHEBA albedo measurements. Seasonal ice cover, perennial ice and perennial open water are asymptotic states accessible by the model. We show that the shape of albedo parameterization near the melting temperature differentiates between reversible continuous sea ice decrease under atmospheric forcing and hysteresis behavior. Fixed points induced solely by the surface energy budget are essential for understanding the interaction of surface energy with the radiative forcing and the underlying body of ice/water, particularly close to a bifurcation point. Future studies will explore ice edge stability and reversibility in this lattice model, generalized to a latitudinal transect with spatiotemporal lateral atmospheric heat transfer and high spatial resolution.

  14. Tackling regional climate change by leaf albedo bio-geoengineering.

    Science.gov (United States)

    Ridgwell, Andy; Singarayer, Joy S; Hetherington, Alistair M; Valdes, Paul J

    2009-01-27

    The likelihood that continuing greenhouse-gas emissions will lead to an unmanageable degree of climate change has stimulated the search for planetary-scale technological solutions for reducing global warming ("geoengineering"), typically characterized by the necessity for costly new infrastructures and industries. We suggest that the existing global infrastructure associated with arable agriculture can help, given that crop plants exert an important influence over the climatic energy budget because of differences in their albedo (solar reflectivity) compared to soils and to natural vegetation. Specifically, we propose a "bio-geoengineering" approach to mitigate surface warming, in which crop varieties having specific leaf glossiness and/or canopy morphological traits are specifically chosen to maximize solar reflectivity. We quantify this by modifying the canopy albedo of vegetation in prescribed cropland areas in a global-climate model, and thereby estimate the near-term potential for bio-geoengineering to be a summertime cooling of more than 1 degrees C throughout much of central North America and midlatitude Eurasia, equivalent to seasonally offsetting approximately one-fifth of regional warming due to doubling of atmospheric CO(2). Ultimately, genetic modification of plant leaf waxes or canopy structure could achieve greater temperature reductions, although better characterization of existing intraspecies variability is needed first.

  15. Impacts of Satellite-Based Snow Albedo Assimilation on Offline and Coupled Land Surface Model Simulations.

    Directory of Open Access Journals (Sweden)

    Tao Wang

    Full Text Available Seasonal snow cover in the Northern Hemisphere is the largest component of the terrestrial cryosphere and plays a major role in the climate system through strong positive feedbacks related to albedo. The snow-albedo feedback is invoked as an important cause for the polar amplification of ongoing and projected climate change, and its parameterization across models is an important source of uncertainty in climate simulations. Here, instead of developing a physical snow albedo scheme, we use a direct insertion approach to assimilate satellite-based surface albedo during the snow season (hereafter as snow albedo assimilation into the land surface model ORCHIDEE (ORganizing Carbon and Hydrology In Dynamic EcosystEms and assess the influences of such assimilation on offline and coupled simulations. Our results have shown that snow albedo assimilation in both ORCHIDEE and ORCHIDEE-LMDZ (a general circulation model of Laboratoire de Météorologie Dynamique improve the simulation accuracy of mean seasonal (October throughout May snow water equivalent over the region north of 40 degrees. The sensitivity of snow water equivalent to snow albedo assimilation is more pronounced in the coupled simulation than the offline simulation since the feedback of albedo on air temperature is allowed in ORCHIDEE-LMDZ. We have also shown that simulations of air temperature at 2 meters in ORCHIDEE-LMDZ due to snow albedo assimilation are significantly improved during the spring in particular over the eastern Siberia region. This is a result of the fact that high amounts of shortwave radiation during the spring can maximize its snow albedo feedback, which is also supported by the finding that the spatial sensitivity of temperature change to albedo change is much larger during the spring than during the autumn and winter. In addition, the radiative forcing at the top of the atmosphere induced by snow albedo assimilation during the spring is estimated to be -2.50 W m-2, the

  16. Impacts of Satellite-Based Snow Albedo Assimilation on Offline and Coupled Land Surface Model Simulations.

    Science.gov (United States)

    Wang, Tao; Peng, Shushi; Krinner, Gerhard; Ryder, James; Li, Yue; Dantec-Nédélec, Sarah; Ottlé, Catherine

    2015-01-01

    Seasonal snow cover in the Northern Hemisphere is the largest component of the terrestrial cryosphere and plays a major role in the climate system through strong positive feedbacks related to albedo. The snow-albedo feedback is invoked as an important cause for the polar amplification of ongoing and projected climate change, and its parameterization across models is an important source of uncertainty in climate simulations. Here, instead of developing a physical snow albedo scheme, we use a direct insertion approach to assimilate satellite-based surface albedo during the snow season (hereafter as snow albedo assimilation) into the land surface model ORCHIDEE (ORganizing Carbon and Hydrology In Dynamic EcosystEms) and assess the influences of such assimilation on offline and coupled simulations. Our results have shown that snow albedo assimilation in both ORCHIDEE and ORCHIDEE-LMDZ (a general circulation model of Laboratoire de Météorologie Dynamique) improve the simulation accuracy of mean seasonal (October throughout May) snow water equivalent over the region north of 40 degrees. The sensitivity of snow water equivalent to snow albedo assimilation is more pronounced in the coupled simulation than the offline simulation since the feedback of albedo on air temperature is allowed in ORCHIDEE-LMDZ. We have also shown that simulations of air temperature at 2 meters in ORCHIDEE-LMDZ due to snow albedo assimilation are significantly improved during the spring in particular over the eastern Siberia region. This is a result of the fact that high amounts of shortwave radiation during the spring can maximize its snow albedo feedback, which is also supported by the finding that the spatial sensitivity of temperature change to albedo change is much larger during the spring than during the autumn and winter. In addition, the radiative forcing at the top of the atmosphere induced by snow albedo assimilation during the spring is estimated to be -2.50 W m-2, the magnitude of

  17. Linking glacier annual mass balance and glacier albedo retrieved from MODIS data

    Directory of Open Access Journals (Sweden)

    M. Dumont

    2012-12-01

    Full Text Available Albedo is one of the variables controlling the mass balance of temperate glaciers. Multispectral imagers, such as MODerate Imaging Spectroradiometer (MODIS on board the TERRA and AQUA satellites, provide a means to monitor glacier surface albedo. In this study, different methods to retrieve broadband glacier surface albedo from MODIS data are compared. The effect of multiple reflections due to the rugged topography and of the anisotropic reflection of snow and ice are particularly investigated. The methods are tested on the Saint Sorlin Glacier (Grandes Rousses area, French Alps. The accuracy of the retrieved albedo is estimated using both field measurements, at two automatic weather stations located on the glacier, and albedo values derived from terrestrial photographs. For summers 2008 and 2009, the root mean square deviation (RMSD between field measurements and the broadband albedo retrieved from MODIS data at 250 m spatial resolution was found to be 0.052 or about 10% relative error. The RMSD estimated for the MOD10 daily albedo product is about three times higher. One decade (2000–2009 of MODIS data were then processed to create a time series of albedo maps of Saint Sorlin Glacier during the ablation season. The annual mass balance of Saint Sorlin Glacier was compared with the minimum albedo value (average over the whole glacier surface observed with MODIS during the ablation season. A strong linear correlation exists between the two variables. Furthermore, the date when the average albedo of the whole glacier reaches a minimum closely corresponds to the period when the snow line is located at its highest elevation, thus when the snow line is a good indicator of the glacier equilibrium line. This indicates that this strong correlation results from the fact that the minimal average albedo values of the glacier contains considerable information regarding the relative share of areal surfaces between the ablation zone (i.e. ice with generally

  18. Linking glacier annual mass balance and glacier albedo retrieved from MODIS data

    Science.gov (United States)

    Dumont, M.; Gardelle, J.; Sirguey, P.; Guillot, A.; Six, D.; Rabatel, A.; Arnaud, Y.

    2012-12-01

    Albedo is one of the variables controlling the mass balance of temperate glaciers. Multispectral imagers, such as MODerate Imaging Spectroradiometer (MODIS) on board the TERRA and AQUA satellites, provide a means to monitor glacier surface albedo. In this study, different methods to retrieve broadband glacier surface albedo from MODIS data are compared. The effect of multiple reflections due to the rugged topography and of the anisotropic reflection of snow and ice are particularly investigated. The methods are tested on the Saint Sorlin Glacier (Grandes Rousses area, French Alps). The accuracy of the retrieved albedo is estimated using both field measurements, at two automatic weather stations located on the glacier, and albedo values derived from terrestrial photographs. For summers 2008 and 2009, the root mean square deviation (RMSD) between field measurements and the broadband albedo retrieved from MODIS data at 250 m spatial resolution was found to be 0.052 or about 10% relative error. The RMSD estimated for the MOD10 daily albedo product is about three times higher. One decade (2000-2009) of MODIS data were then processed to create a time series of albedo maps of Saint Sorlin Glacier during the ablation season. The annual mass balance of Saint Sorlin Glacier was compared with the minimum albedo value (average over the whole glacier surface) observed with MODIS during the ablation season. A strong linear correlation exists between the two variables. Furthermore, the date when the average albedo of the whole glacier reaches a minimum closely corresponds to the period when the snow line is located at its highest elevation, thus when the snow line is a good indicator of the glacier equilibrium line. This indicates that this strong correlation results from the fact that the minimal average albedo values of the glacier contains considerable information regarding the relative share of areal surfaces between the ablation zone (i.e. ice with generally low albedo

  19. Linking glacier annual mass balance and glacier albedo retrieved from MODIS data

    Directory of Open Access Journals (Sweden)

    M. Dumont

    2012-07-01

    Full Text Available Albedo is one of the variables controlling the mass balance of temperate glaciers. Multispectral imagers, such as MODerate Imaging Spectroradiometer (MODIS on board the TERRA and AQUA satellites, provide a means to monitor glacier surface albedo. In this study, different methods to retrieve broadband glacier surface albedo from MODIS data are compared. The effect of multiple reflections due to the rugged topography and of the anisotropic reflection of snow and ice are particularly investigated. The methods are tested on the Saint Sorlin Glacier (Grandes Rousses area, French Alps. The accuracy of the retrieved albedo is estimated using both field measurements, at two automatic weather stations located on the glacier, and albedo values derived from terrestrial photographs. For summers 2008 and 2009, the Root Mean Square Deviation (RMSD between field measurements and the broadband albedo retrieved from MODIS data at 250 m spatial resolution was found to be 0.052 or about 10% relative error. The RMSD estimated for the MOD10 daily albedo product is about three times higher. One decade (2000–2009 of MODIS data were then processed to create a time series of albedo maps of Saint Sorlin Glacier during the ablation season. The annual mass balance of Saint Sorlin Glacier was compared with the minimum albedo value (average over the whole glacier surface observed with MODIS during the ablation season. A strong linear correlation exists between the two variables. Furthermore, the date when the average albedo of the whole glacier reaches a minimum closely corresponds to the period when the snowline is located at its highest elevation, thus when the snowline is a good indicator of the glacier equilibrium line. This indicates that this strong correlation results from the fact that the minimal average albedo values of the glacier contains a considerable information regarding the relative share of areal surfaces between the ablation zone (i.e. ice with generally

  20. Implications of albedo changes following afforestation on the benefits of forests as carbon sinks

    Science.gov (United States)

    Kirschbaum, M. U. F.; Whitehead, D.; Dean, S. M.; Beets, P. N.; Shepherd, J. D.; Ausseil, A.-G. E.

    2011-12-01

    Increased carbon storage with afforestation leads to a decrease in atmospheric carbon dioxide concentration and thus decreases radiative forcing and cools the Earth. However, afforestation also changes the reflective properties of the surface vegetation from more reflective pasture to relatively less reflective forest cover. This increase in radiation absorption by the forest constitutes an increase in radiative forcing, with a warming effect. The net effect of decreased albedo and carbon storage on radiative forcing depends on the relative magnitude of these two opposing processes. We used data from an intensively studied site in New Zealand's Central North Island that has long-term, ground-based measurements of albedo over the full short-wave spectrum from a developing Pinus radiata forest. Data from this site were supplemented with satellite-derived albedo estimates from New Zealand pastures. The albedo of a well-established forest was measured as 13 % and pasture albedo as 20 %. We used these data to calculate the direct radiative forcing effect of changing albedo as the forest grew. We calculated the radiative forcing resulting from the removal of carbon from the atmosphere as a decrease in radiative forcing of -104 GJ tC-1 yr-1. We also showed that the observed change in albedo constituted a direct radiative forcing of 2759 GJ ha-1 yr-1. Thus, following afforestation, 26.5 tC ha-1 needs to be stored in a growing forest to balance the increase in radiative forcing resulting from the observed albedo change. Measurements of tree biomass and albedo were used to estimate the net change in radiative forcing as the newly planted forest grew. Albedo and carbon-storage effects were of similar magnitude for the first four to five years after tree planting, but as the stand grew older, the carbon storage effect increasingly dominated. Averaged over the whole length of the rotation, the changes in albedo negated the benefits from increased carbon storage by 17-24 %.

  1. Quantifying the missing link between forest albedo and productivity in the boreal zone

    Science.gov (United States)

    Hovi, Aarne; Liang, Jingjing; Korhonen, Lauri; Kobayashi, Hideki; Rautiainen, Miina

    2016-11-01

    Albedo and fraction of absorbed photosynthetically active radiation (FAPAR) determine the shortwave radiation balance and productivity of forests. Currently, the physical link between forest albedo and productivity is poorly understood, yet it is crucial for designing optimal forest management strategies for mitigating climate change. We investigated the relationships between boreal forest structure, albedo and FAPAR using a radiative transfer model called Forest Reflectance and Transmittance model FRT and extensive forest inventory data sets ranging from southern boreal forests to the northern tree line in Finland and Alaska (N = 1086 plots). The forests in the study areas vary widely in structure, species composition, and human interference, from intensively managed in Finland to natural growth in Alaska. We show that FAPAR of tree canopies (FAPARCAN) and albedo are tightly linked in boreal coniferous forests, but the relationship is weaker if the forest has broadleaved admixture, or if canopies have low leaf area and the composition of forest floor varies. Furthermore, the functional shape of the relationship between albedo and FAPARCAN depends on the angular distribution of incoming solar irradiance. We also show that forest floor can contribute to over 50 % of albedo or total ecosystem FAPAR. Based on our simulations, forest albedos can vary notably across the biome. Because of larger proportions of broadleaved trees, the studied plots in Alaska had higher albedo (0.141-0.184) than those in Finland (0.136-0.171) even though the albedo of pure coniferous forests was lower in Alaska. Our results reveal that variation in solar angle will need to be accounted for when evaluating climate effects of forest management in different latitudes. Furthermore, increasing the proportion of broadleaved trees in coniferous forests is the most important means of maximizing albedo without compromising productivity: based on our findings the potential of controlling forest

  2. Time-variable Earth's albedo model characteristics and applications to satellite sampling errors

    Science.gov (United States)

    Bartman, F. L.

    1981-01-01

    Characteristics of the time variable Earth albedo model are described. With the cloud cover multiplying factor adjusted to produce a global annual average albedo of 30.3, the global annual average cloud cover is 45.5 percent. Global annual average sunlit cloud cover is 48.5 percent; nighttime cloud cover is 42.7 percent. Month-to-month global average albedo is almost sinusoidal with maxima in June and December and minima in April and October. Month-to-month variation of sunlit cloud cover is similar, but not in all details. The diurnal variation of global albedo is greatest from November to March; the corresponding variation of sunlit cloud cover is greatest from May to October. Annual average zonal albedos and monthly average zonal albedos are in good agreement with satellite-measured values, with notable differences in the polar regions in some months and at 15 S. The albedo of some 10 deg by 10 deg. areas of the Earth versus zenith angle are described. Satellite albedo measurement sampling effects are described in local time and in Greenwich mean time.

  3. Assimilation of satellite observed snow albedo in a land surface model

    NARCIS (Netherlands)

    Malik, M.J.; Velde, van der R.; Vekerdy, Z.; Su, Z.

    2012-01-01

    This study assesses the impact of assimilating satellite-observed snow albedo on the Noah land surface model (LSM)-simulated fluxes and snow properties. A direct insertion technique is developed to assimilate snow albedo into Noah and is applied to three intensive study areas in North Park (Colorado

  4. ExploreNEOs: Average albedo by taxonomic complex in the near-Earth asteroid population

    NARCIS (Netherlands)

    Thomas, C. A.; Trilling, D. E.; Emery, J. P.; Mueller, M.; Hora, J. L.; Benner, L. A. M.; Bhattacharya, B.; Bottke, W. F.; Chesley, S.; Delbo, M.; Fazio, G.; Harris, A. W.; Mainzer, A.; Mommert, M.; Morbidelli, A.; Penprase, B.; Smith, H. A.; Spahr, T. B.; Stansberry, J. A.

    2011-01-01

    Understanding the albedo distribution of the Near- Earth Object (NEO) population allows for a better understanding of the relationship between absolute magnitude and size, which impacts calculations of size frequency distribution and impact hazards. Examining NEO albedos also sheds light on the diff

  5. Radiative Albedo from a Linearly Fibered Half Space

    CERN Document Server

    Grzesik, J A

    2016-01-01

    A growing acceptance of fiber reinforced composite materials imparts some relevance to exploring the effects which a predominantly linear scattering lattice may have upon interior radiant transport. Indeed, a central feature of electromagnetic wave propagation within such a lattice, if sufficiently dilute, is ray confinement to cones whose half-angles are set by that between lattice and the incident ray. When such propagation is subordinated to a viewpoint of photon transport, one arrives at a somewhat simplified variant of the Boltzmann equation with spherical scattering demoted to its cylindrical counterpart. With a view to initiating a hopefully wider discussion of such phenomena, we follow through in detail the half-space albedo problem. This is done first along canonical lines that harness the Wiener-Hopf technique, and then once more in a discrete ordinates setting via flux decomposition along the eigenbasis of the underlying attenuation/scattering matrix. Good agreement is seen to prevail. We further s...

  6. Global Monitoring of Martian Surface Albedo Changes from Orbital Observations

    Science.gov (United States)

    Geissler, P.; Enga, M.; Mukherjee, P.

    2013-12-01

    Martian surface changes were first observed from orbit during the Mariner 9 and Viking Orbiter missions. They were found to be caused by eolian processes, produced by deposition of dust during regional and global dust storms and subsequent darkening of the surface through erosion and transportation of dust and sand. The albedo changes accumulated in the 20 years between Viking and Mars Global Surveyor were sufficient to alter the global circulation of winds and the climate of Mars according to model calculations (Fenton et al., Nature 2007), but little was known about the timing or frequency of the changes. Since 1999, we have had the benefit of continuous monitoring by a series of orbiting spacecraft that continues today with Mars Reconnaissance Orbiter, Mars Odyssey, and Mars Express. Daily synoptic observations enable us to determine whether the surface albedo changes are gradual or episodic in nature and to record the seasons that the changes take place. High resolution images of surface morphology and atmospheric phenomena help identify the physical mechanisms responsible for the changes. From these data, we hope to learn the combinations of atmospheric conditions and sediment properties that produce surface changes on Mars and possibly predict when they will take place in the future. Martian surface changes are particularly conspicuous in low albedo terrain, where even a thin layer of bright dust brightens the surface drastically. Equatorial dark areas are repeatedly coated and recoated by dust, which is later shed from the surface by a variety of mechanisms. An example is Syrtis Major, suddenly buried in bright dust by the global dust storm of 2001. Persistent easterly winds blew much of the dust cover away over the course of the next Martian year, but episodic changes continue today, particularly during southern summer when regional dust storms are rife. Another such region is Solis Planum, south of the Valles Marineris, where changes take place

  7. The influence of inter-annually varying albedo on regional climate and drought

    KAUST Repository

    Meng, Xianhong

    2013-05-05

    Albedo plays an important role in land-atmosphere interactions and local climate. This study presents the impact on simulating regional climate, and the evolution of a drought, when using the default climatological albedo as is usually done in regional climate modelling, or using the actual observed albedo which is rarely done. Here, time-varying satellite derived albedo data is used to update the lower boundary condition of the Weather Research and Forecasting regional climate model in order to investigate the influence of observed albedo on regional climate simulations and also potential changes to land-atmosphere feedback over south-east Australia. During the study period from 2000 to 2008, observations show that albedo increased with an increasingly negative precipitation anomaly, though it lagged precipitation by several months. Compared to in-situ observations, using satellite observed albedo instead of the default climatological albedo provided an improvement in the simulated seasonal mean air temperature. In terms of precipitation, both simulations reproduced the drought that occurred from 2002 through 2006. Using the observed albedo produced a drier simulation overall. During the onset of the 2002 drought, albedo changes enhanced the precipitation reduction by 20 % on average, over locations where it was active. The area experiencing drought increased 6.3 % due to the albedo changes. Two mechanisms for albedo changes to impact land-atmosphere drought feedback are investigated. One accounts for the increased albedo, leading to reduced turbulent heat flux and an associated decrease of moist static energy density in the planetary boundary layer; the other considers that enhanced local radiative heating, due to the drought, favours a deeper planetary boundary layer, subsequently decreasing the moist static energy density through entrainment of the free atmosphere. Analysis shows that drought related large-scale changes in the regional climate favour a

  8. The influence of inter-annually varying albedo on regional climate and drought

    Science.gov (United States)

    Meng, X. H.; Evans, J. P.; McCabe, M. F.

    2014-02-01

    Albedo plays an important role in land-atmosphere interactions and local climate. This study presents the impact on simulating regional climate, and the evolution of a drought, when using the default climatological albedo as is usually done in regional climate modelling, or using the actual observed albedo which is rarely done. Here, time-varying satellite derived albedo data is used to update the lower boundary condition of the Weather Research and Forecasting regional climate model in order to investigate the influence of observed albedo on regional climate simulations and also potential changes to land-atmosphere feedback over south-east Australia. During the study period from 2000 to 2008, observations show that albedo increased with an increasingly negative precipitation anomaly, though it lagged precipitation by several months. Compared to in-situ observations, using satellite observed albedo instead of the default climatological albedo provided an improvement in the simulated seasonal mean air temperature. In terms of precipitation, both simulations reproduced the drought that occurred from 2002 through 2006. Using the observed albedo produced a drier simulation overall. During the onset of the 2002 drought, albedo changes enhanced the precipitation reduction by 20 % on average, over locations where it was active. The area experiencing drought increased 6.3 % due to the albedo changes. Two mechanisms for albedo changes to impact land-atmosphere drought feedback are investigated. One accounts for the increased albedo, leading to reduced turbulent heat flux and an associated decrease of moist static energy density in the planetary boundary layer; the other considers that enhanced local radiative heating, due to the drought, favours a deeper planetary boundary layer, subsequently decreasing the moist static energy density through entrainment of the free atmosphere. Analysis shows that drought related large-scale changes in the regional climate favour a

  9. Linking glacier annual mass balance and glacier albedo from MODIS data

    Science.gov (United States)

    Dumont, M.; Gardelle, J.; Arnaud, Y.; Guillot, A.; Sirguey, P.; Six, D.

    2012-04-01

    The albedo is one of the variables controlling the mass balance of temperate glaciers. Multispectral imagers, such as MODIS on board TERRA and AQUA, provide a means to monitor glacier albedo. In this study, different methods to retrieve broadband glacier albedo from MODIS data are compared. In particular, the effect of the multiple reflections due to the rugged topography and that of the anisotropic reflection of snow and ice are investigated. The methods are tested on the Saint Sorlin glacier (Grandes Rousses area, French Alps). The accuracy of the retrieved albedo is estimated using both field measurements and albedo derived from terrestrial photographs. The root mean square deviation between field measurements and the broadband albedo retrieved from MODIS pixels at 250m spatial resolution was found to be less than 0.06. One decade (2000-2010) of MODIS data were then processed to create a time series of albedo maps of Saint Sorlin glacier during the ablation season. It appears that the albedo in the ablation area of the glacier does not exhibit any marked decreasing trend during the decade under study. This contrasts with the situation observed on other glaciers in the Alps. In addition, the annual mass balance of Saint Sorlin Glacier was compared with the minimum albedo value (spatial averaged over the whole glacier) observed with MODIS during the ablation season. A high linear correlation exists between the two variables. Furthermore, the day on which the albedo reaches a minimum over the glacier closely corresponds to the day on which the snowline is found to be at its highest elevation, thus close to the glacier's equilibrium line. This indicates that the high correlation can be explained by the fact that this minimal albedo contains a high degree of information regarding the relative share of areal surfaces between the ablation zone (i.e., ice with a generally lower albedo) and the accumulation zone (i.e., snow with a relatively high albedo). This implies

  10. Multi-modal albedo distributions in the ablation area of the southwestern Greenland Ice Sheet

    Science.gov (United States)

    Moustafa, S. E.; Rennermalm, A. K.; Smith, L. C.; Miller, M. A.; Mioduszewski, J. R.; Koenig, L. S.; Hom, M. G.; Shuman, C. A.

    2015-05-01

    Surface albedo is a key variable controlling solar radiation absorbed at the Greenland Ice Sheet (GrIS) surface and, thus, meltwater production. Recent decline in surface albedo over the GrIS has been linked to enhanced snow grain metamorphic rates, earlier snowmelt, and amplified melt-albedo feedback from atmospheric warming. However, the importance of distinct surface types on ablation area albedo and meltwater production is still relatively unknown. In this study, we analyze albedo and ablation rates using in situ and remotely sensed data. Observations include (1) a new high-quality in situ spectral albedo data set collected with an Analytical Spectral Devices Inc. spectroradiometer measuring at 325-1075 nm along a 1.25 km transect during 3 days in June 2013; (2) broadband albedo at two automatic weather stations; and (3) daily MODerate Resolution Imaging Spectroradiometer (MODIS) albedo (MOD10A1) between 31 May and 30 August 2012 and 2013. We find that seasonal ablation area albedos in 2013 have a bimodal distribution, with snow and ice facies characterizing the two peaks. Our results show that a shift from a distribution dominated by high to low albedos corresponds to an observed melt rate increase of 51.5% (between 10-14 July and 20-24 July 2013). In contrast, melt rate variability caused by albedo changes before and after this shift was much lower and varied between ~10 and 30% in the melting season. Ablation area albedos in 2012 exhibited a more complex multimodal distribution, reflecting a transition from light to dark-dominated surface, as well as sensitivity to the so called "dark-band" region in southwest Greenland. In addition to a darkening surface from ice crystal growth, our findings demonstrate that seasonal changes in GrIS ablation area albedos are controlled by changes in the fractional coverage of snow, bare ice, and impurity-rich surface types. Thus, seasonal variability in ablation area albedos appears to be regulated primarily as a function

  11. ARM Climate Research Facility Spectral Surface Albedo Value-Added Product (VAP) Report

    Energy Technology Data Exchange (ETDEWEB)

    McFarlane, S; Gaustad, K; Long, C; Mlawer, E

    2011-07-15

    This document describes the input requirements, output data products, and methodology for the Spectral Surface Albedo (SURFSPECALB) value-added product (VAP). The SURFSPECALB VAP produces a best-estimate near-continuous high spectral resolution albedo data product using measurements from multifilter radiometers (MFRs). The VAP first identifies best estimates for the MFR downwelling and upwelling shortwave irradiance values, and then calculates narrowband spectral albedo from these best-estimate irradiance values. The methodology for finding the best-estimate values is based on a simple process of screening suspect data and backfilling screened and missing data with estimated values when possible. The resulting best-estimate MFR narrowband spectral albedos are used to determine a daily surface type (snow, 100% vegetation, partial vegetation, or 0% vegetation). For non-snow surfaces, a piecewise continuous function is used to estimate a high spectral resolution albedo at 1 min temporal and 10 cm-1 spectral resolution.

  12. Surface Albedo in Cities: Case Study in Sapporo and Tokyo, Japan

    Science.gov (United States)

    Sugawara, Hirofumi; Takamura, Tamio

    2014-12-01

    The surface albedo of two large cities in Japan was measured using a pyranometer mounted on a helicopter to avoid the bidirectional reflectance distribution. The daytime albedo was 0.12 in the cities, which was less than that of a nearby forest (0.16). The albedo was dependent on building structure in the cities; the albedo was lower in areas with more buildings, and decreased as the aspect ratio of street canyons increased. There are two reasons for this dependency: the multiple reflection of radiation in the building canopy, as has been shown in many previous studies, and the sparse vegetation in urban areas. These two factors concurrently determine the albedo in a real city, where the vegetation amount decreases as the plan roof ratio increases.

  13. Examining Trends in Foliar N and Albedo in Response to Disturbance in Canadian Forests

    Science.gov (United States)

    Plourde, L. C.; Ollinger, S. V.; Martin, M. E.

    2009-12-01

    Disturbance in forest ecosystems bears relevance to the climate system through changes in CO2, water and energy exchange. Recent work revealed a strong link among canopy albedo, nitrogen concentrations and carbon assimilation, suggesting a potential feedback in the climate system involving foliar N as it relates to vegetation reflectance and shortwave surface energy exchange. Nevertheless, how disturbance affects canopy chemistry and albedo over space and time has not been widely studied, and general patterns have yet to emerge. Many questions remain, including: What is the effect of disturbance on albedo over time—how does albedo change over time after fire? Do canopy N and albedo decline over time from harvesting to stand recovery? What effect do altered N inputs have on albedo? Examining the N-albedo relationship in the context of gradients in disturbance and recovery may provide a better understanding of how disturbance impacts the climate system. Here, we examine the degree to which canopy albedo and N concentrations are affected by fire and harvest events, as well as elevated inputs of nitrogen. Our investigation makes use of data from remote sensing, field measurements and eddy flux towers at sites that are part of the Canadian Carbon Program. Specifically, we explore variability in canopy N and albedo along disturbance-recovery chronosequences in Quebec and Saskatchewan, as well as in response to N fertilization at a forested site in British Columbia. Results are discussed with respect to local variation at these sites as a means of understanding disturbance-linked changes in albedo and foliar N.

  14. Mars: Correcting surface albedo observations for effects of atmospheric dust loading

    Science.gov (United States)

    Lee, S. W.; Clancy, R. T.

    1992-01-01

    We have developed a radiative transfer model which allows the effects of atmospheric dust loading on surface albedo to be investigated. This model incorporates atmospheric dust opacity, the single scattering albedo and particle phase function of atmospheric dust, the bidirectional reflectance of the surface, and variable lighting and viewing geometry. The most recent dust particle properties are utilized. The spatial and temporal variability of atmospheric opacity (Tan) strongly influences the radiative transfer modelling results. We are currently using the approach described to determine Tan for IRTM mapping sequences of selected regions. This approach allows Tan to be determined at the highest spatial and temporal resolution supported by the IRTM data. Applying the radiative transfer modelling and determination of Tan described, IRTM visual brightness observations can be corrected for the effects of atmospheric dust loading a variety of locations and times. This approach allows maps of 'dust-corrected surface albedo' to be constructed for selected regions. Information on the variability of surface albedo and the amount of dust deposition/erosion related to such variability results. To date, this study indicates that atmospheric dust loading has a significant effect on observations of surface albedo, amounting to albedo corrections of as much as several tens of percent. This correction is not constant or linear, but depends upon surface albedo, viewing and lighting geometry, the dust and surface phase functions, and the atmospheric opacity. It is clear that the quantitative study of surface albedo, especially where small variations in observed albedo are important (such as photometric analyses), needs to account for the effects of the atmospheric dust loading. Maps of 'dust-corrected surface albedo' will be presented for a number of regions.

  15. Using Remote Sensing to Quantify Roof Albedo in Seven California Cities

    Science.gov (United States)

    Ban-Weiss, G. A.; Woods, J.; Millstein, D.; Levinson, R.

    2013-12-01

    Cool roofs reflect sunlight and therefore can reduce cooling energy use in buildings. Further, since roofs cover about 20-25% of cities, wide spread deployment of cool roofs could mitigate the urban heat island effect and partially counter urban temperature increases associated with global climate change. Accurately predicting the potential for increasing urban albedo using reflective roofs and its associated energy use and climate benefits requires detailed knowledge of the current stock of roofs at the city scale. Until now this knowledge has been limited due to a lack of availability of albedo data with sufficient spatial coverage, spatial resolution, and spectral information. In this work we use a novel source of multiband aerial imagery to derive the albedos of individual roofs in seven California cities: Los Angeles, Long Beach, San Diego, Bakersfield, Sacramento, San Francisco, and San Jose. The radiometrically calibrated, remotely sensed imagery has high spatial resolution (1 m) and four narrow (less than 0.1 μm wide) band reflectances: blue, green, red, and near-infrared. To derive the albedo of roofs in each city, we first locate roof pixels within GIS building outlines. Next we use laboratory measurements of the solar spectral reflectances of 190 roofing products to empirically relate solar reflectance (albedo) to reflectances in the four narrow bands; the root-mean-square of the residuals for the albedo prediction is 0.016. Albedos computed from remotely sensed reflectances are calibrated to ground measurements of roof albedo in each city. The error (both precision and accuracy) of albedo values is presented for each city. The area-weighted mean roof albedo (× standard deviation) for each city ranges from 0.17 × 0.08 (Los Angeles) to 0.29 × 0.15 (San Diego). In each city most roofs have low albedo in the range of 0.1 to 0.3. Roofs with albedo greater than 0.4 comprise less than 3% of total roofs and 7% of total roof area in each city. The California

  16. Variation in foliar nitrogen and albedo in response to nitrogen fertilization and elevated CO2.

    Science.gov (United States)

    Wicklein, Haley F; Ollinger, Scott V; Martin, Mary E; Hollinger, David Y; Lepine, Lucie C; Day, Michelle C; Bartlett, Megan K; Richardson, Andrew D; Norby, Richard J

    2012-08-01

    Foliar nitrogen has been shown to be positively correlated with midsummer canopy albedo and canopy near infrared (NIR) reflectance over a broad range of plant functional types (e.g., forests, grasslands, and agricultural lands). To date, the mechanism(s) driving the nitrogen–albedo relationship have not been established, and it is unknown whether factors affecting nitrogen availability will also influence albedo. To address these questions, we examined variation in foliar nitrogen in relation to leaf spectral properties, leaf mass per unit area, and leaf water content for three deciduous species subjected to either nitrogen (Harvard Forest, MA, and Oak Ridge, TN) or CO(2) fertilization (Oak Ridge, TN). At Oak Ridge, we also obtained canopy reflectance data from the airborne visible/infrared imaging spectrometer (AVIRIS) to examine whether canopy-level spectral responses were consistent with leaf-level results. At the leaf level, results showed no differences in reflectance or transmittance between CO(2) or nitrogen treatments, despite significant changes in foliar nitrogen. Contrary to our expectations, there was a significant, but negative, relationship between foliar nitrogen and leaf albedo, a relationship that held for both full spectrum leaf albedo as well as leaf albedo in the NIR region alone. In contrast, remote sensing data indicated an increase in canopy NIR reflectance with nitrogen fertilization. Collectively, these results suggest that altered nitrogen availability can affect canopy albedo, albeit by mechanisms that involve canopy-level processes rather than changes in leaf-level reflectance.

  17. Near-ground cooling efficacies of trees and high-albedo surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Levinson, R M [Univ. of California, Berkeley, CA (United States). Dept. of Mechanical Engineering

    1997-05-01

    Daytime summer urban heat islands arise when the prevalence of dark-colored surfaces and lack of vegetation make a city warmer than neighboring countryside. Two frequently-proposed summer heat island mitigation measures are to plant trees and to increase the albedo (solar reflectivity) of ground surfaces. This dissertation examines the effects of these measures on the surface temperature of an object near the ground, and on solar heating of air near the ground. Near-ground objects include people, vehicles, and buildings. The variation of the surface temperature of a near-ground object with ground albedo indicates that a rise in ground albedo will cool a near-ground object only if the object`s albedo exceeds a critical value. This critical value of object albedo depends on wind speed, object geometry, and the height of the atmospheric thermal boundary layer. It ranges from 0.15 to 0.37 for a person. If an object has typical albedo of 0.3, increasing the ground albedo by.

  18. Albedo Properties of Small (0.5 to 20 km) Main Belt Asteroids

    Science.gov (United States)

    Ryan, Erin L.; Woodward, C. E.

    2010-01-01

    Serendipitous observations of main belt asteroids by the Spitzer Space Telescope have enabled determination of main belt asteroid albedos and diameters for targets as small as 0.5 km (eg., Ryan et al. 2009, AJ, 137, 5134). We have used multi-epoch data at 5.8, 8.0 and 24 microns from the MIPSGAL and Taurus Legacy Surveys to obtain diameters and albedos for a sample of approximately 2000 main belt asteroids. Using STM and NEATM, we have obtained diameters ranging from 0.5 to 30 km and albedos ranging from 0.02 to 0.5. Results of this program reveal an albedo distribution that is more diverse in range than the albedo distribution seen in the IRAS and MSX surveys. This diversity may reflect effects of space weathering reddening which is selectively reddening larger asteroids. This reddening effect may reinforce the findings from accretion models that indicate that asteroids in the early solar system were 100 km and larger (Morbidelli et al., 2009, Icarus, in press), by suggesting that the larger asteroids are indeed the oldest members of the main belt. We will present results on the albedo distribution as a function of semi-major axis and new analysis of the mean albedo of dynamical families within the main belt. Support for this work provided in part by a National Science Foundation grant AST-0706980 to the University of Minnesota.

  19. Estimation of Instantaneous TOA Albedo at 670 nm over Ice Clouds from POLDER Multidirectional Measurements

    Science.gov (United States)

    Sun, W.; Loeb, N. G.; Kato, S.

    2003-01-01

    An algorithm that determines the 670-nm top-of-atmosphere (TOA) albedo of ice clouds over ocean using Polarization and Directionality of the Earth's Reflectance ( POLDER) multidirectional measurements is developed. A plane-parallel layer of ice cloud with various optical thicknesses and light scattering phase functions is assumed. For simplicity, we use a double Henyey-Greenstein phase function to approximate the volume-averaged phase function of the ice clouds. A multidirectional reflectance best-fit match between theoretical and POLDER reflectances is used to infer effective cloud optical thickness, phase function and TOA albedo. Sensitivity tests show that while the method does not provide accurate independent retrievals of effective cloud optical depth and phase function, TOA albedo retrievals are accurate to within similar to 3% for both a single layer of ice clouds or a multilayer system of ice clouds and water clouds. When the method is applied to POLDER measurements and retrieved albedos are compared with albedos based on empirical angular distribution models (ADMs), zonal albedo differences are generally smaller than similar to 3%. When albedos are compared with those on the POLDER-I ERB and Cloud product, the differences can reach similar to 15% at small solar zenith angles.

  20. Mapping Surface Broadband Albedo from Satellite Observations: A Review of Literatures on Algorithms and Products

    Directory of Open Access Journals (Sweden)

    Ying Qu

    2015-01-01

    Full Text Available Surface albedo is one of the key controlling geophysical parameters in the surface energy budget studies, and its temporal and spatial variation is closely related to the global climate change and regional weather system due to the albedo feedback mechanism. As an efficient tool for monitoring the surfaces of the Earth, remote sensing is widely used for deriving long-term surface broadband albedo with various geostationary and polar-orbit satellite platforms in recent decades. Moreover, the algorithms for estimating surface broadband albedo from satellite observations, including narrow-to-broadband conversions, bidirectional reflectance distribution function (BRDF angular modeling, direct-estimation algorithm and the algorithms for estimating albedo from geostationary satellite data, are developed and improved. In this paper, we present a comprehensive literature review on algorithms and products for mapping surface broadband albedo with satellite observations and provide a discussion of different algorithms and products in a historical perspective based on citation analysis of the published literature. This paper shows that the observation technologies and accuracy requirement of applications are important, and long-term, global fully-covered (including land, ocean, and sea-ice surfaces, gap-free, surface broadband albedo products with higher spatial and temporal resolution are required for climate change, surface energy budget, and hydrological studies.

  1. Deriving albedo maps for HAPEX-Sahel from ASAS data using kernel-driven BRDF models

    Directory of Open Access Journals (Sweden)

    P. Lewis

    1999-01-01

    Full Text Available This paper describes the application and testing of a method for deriving spatial estimates of albedo from multi-angle remote sensing data. Linear kernel-driven models of surface bi-directional reflectance have been inverted against high spatial resolution multi-angular, multi- spectral airborne data of the principal cover types within the HAPEX-Sahel study site in Niger, West Africa. The airborne data are obtained from the NASA Airborne Solid-state Imaging Spectrometer (ASAS instrument, flown in Niger in September and October 1992. The maps of model parameters produced are used to estimate integrated reflectance properties related to spectral albedo. Broadband albedo has been estimated from this by weighting the spectral albedo for each pixel within the map as a function of the appropriate spectral solar irradiance and proportion of direct and diffuse illumination. Partial validation of the results was performed by comparing ASAS reflectance and derived directional-hemispherical reflectance with simulations of a millet canopy made with a complex geometric canopy reflectance model, the Botanical Plant Modelling System (BPMS. Both were found to agree well in magnitude. Broadband albedo values derived from the ASAS data were compared with ground-based (point sample albedo measurements and found to agree extremely well. These results indicate that the linear kernel-driven modelling approach, which is to be used operationally to produce global 16 day, 1 km albedo maps from forthcoming NASA Earth Observing System spaceborne data, is both sound and practical for the estimation of angle-integrated spectral reflectance quantities related to albedo. Results for broadband albedo are dependent on spectral sampling and on obtaining the correct spectral weigthings.

  2. Albedo enhancement over land to counteract global warming: impacts on hydrological cycle

    Energy Technology Data Exchange (ETDEWEB)

    Bala, Govindasamy; Nag, Bappaditya [Indian Institute of Science, Divecha Center for Climate Change and Center for Atmospheric and Oceanic Sciences, Bangalore (India)

    2012-09-15

    A recent modelling study has shown that precipitation and runoff over land would increase when the reflectivity of marine clouds is increased to counter global warming. This implies that large scale albedo enhancement over land could lead to a decrease in runoff over land. In this study, we perform simulations using NCAR CAM3.1 that have implications for Solar Radiation Management geoengineering schemes that increase the albedo over land. We find that an increase in reflectivity over land that mitigates the global mean warming from a doubling of CO{sub 2} leads to a large residual warming in the southern hemisphere and cooling in the northern hemisphere since most of the land is located in northern hemisphere. Precipitation and runoff over land decrease by 13.4 and 22.3%, respectively, because of a large residual sinking motion over land triggered by albedo enhancement over land. Soil water content also declines when albedo over land is enhanced. The simulated magnitude of hydrological changes over land are much larger when compared to changes over oceans in the recent marine cloud albedo enhancement study since the radiative forcing over land needed (-8.2 W m{sup -2}) to counter global mean radiative forcing from a doubling of CO{sub 2} (3.3 W m{sup -2}) is approximately twice the forcing needed over the oceans (-4.2 W m{sup -2}). Our results imply that albedo enhancement over oceans produce climates closer to the unperturbed climate state than do albedo changes on land when the consequences on land hydrology are considered. Our study also has important implications for any intentional or unintentional large scale changes in land surface albedo such as deforestation/afforestation/reforestation, air pollution, and desert and urban albedo modification. (orig.)

  3. Nitrogen Availability and Forest Canopy Albedo from Leaf to Regional Scales

    Science.gov (United States)

    Ollinger, S. V.; Plourde, L. C.; Martin, M.; Wicklein, H. F.; Haddad, D. M.; Richardson, A. D.; Hollinger, D.

    2009-12-01

    CO2 uptake capacity in temperate and boreal forests has been shown to scale directly with whole-canopy nitrogen concentrations, mirroring a leaf-level trend that has been observed for woody plants worldwide. Recent work has also demonstrated that both CO2 uptake capacity and canopy %N are strongly and positively correlated with shortwave surface albedo. This suggests that variation in nitrogen availability may play an additional, and previously overlooked, role in the climate system via its influence on surface energy exchange as well as via its better-known influence on carbon assimilation. Thus far, the carbon-nitrogen-albedo relationship has been demonstrated at relatively coarse spatial scales that cover broad gradients in climate and forest type. It is unclear whether similar trends occur within local landscapes and within ecosystems other than forests. It is also unclear whether N deposition and N fertilization can cause a shift in albedo stemming from changes in foliar %N. Examining finer-scale patterns in the N-albedo relationship is necessary before we can establish the generality of the observed trends and understand their implications for carbon-nutrient-climate interactions. Here, we expand on the C-N-albedo relationship in several important ways: (1) using fine-scale remote sensing data from the U.S. and Canada, we examined albedo in relation to foliar N and canopy structure at local scales for several well characterized landscapes; (2) we examined changes in both foliar N and albedo along a regional-scale nitrogen deposition gradient; (3) we examined leaf-level changes in %N and albedo in response to experimental N additions, and (4) we conducted a global synthesis of data from FLUXNET to examine the C-N-albedo relationship over a broader range of ecosystems. Results are discussed in the context of improving our understanding of interactions between terrestrial biogeochemistry and climate.

  4. Migration of Frosts from High-Albedo Regions of Pluto: what New Horizons Reveals

    Science.gov (United States)

    Buratti, Bonnie J.; Stern, S. A.; Weaver, Hal A.; Young, Leslie A.; Olkin, Cathy B.; Ennico, Kimberly; Binzel, Richard P.; Zangari, Amanda; Earle, Alissa M.

    2015-11-01

    With its high eccentricity and obliquity, Pluto should exhibit seasonal volatile transport on its surface. Several lines of evidence support this transport: doubling of Pluto’s atmospheric pressure over the past two decades (Young et al., 2013, Ap. J. 766, L22; Olkin et al., 2015, Icarus 246, 230); changes in its historical rotational light curve, once all variations due to viewing geometry have been modelled (Buratti et al., 2015; Ap. J. 804, L6); and changes in HST albedo maps (Buie et al., 2010, Astron. J. 139, 1128). New Horizons LORRI images reveal that the region of greatest albedo change is not the polar cap(s) of Pluto, but the feature informally named Tombaugh Regio (TR). This feature has a normal reflectance as high as ~0.8 in some places, and it is superposed on older, lower-albedo pre-existing terrain with an albedo of only ~0.10. This contrast is larger than any other body in the Solar System, except for Iapetus. This albedo dichotomy leads to a complicated system of cold-trapping and thermal segregation, beyond the simple picture of seasonal volatile transport. Whatever the origin of TR, it initially acted as a cold trap, as the temperature differential between the high and low albedo regions could be enormous, possibly approaching 20K, based on their albedo differences and assuming their normalized phase curves are similar. This latter assumption will be refined as the full New Horizons data set is returned.Over six decades of ground-based photometry suggest that TR has been decreasing in albedo over the last 25 years. Possible causes include changing insolation angles, or sublimation from the edges where the high-albedo material impinges on a much warmer substrate.Funding by the NASA New Horizons Project acknowledged.

  5. Measurement of the Absolute Hohlraum Wall Albedo Under Ignition Foot Drive Condition

    Energy Technology Data Exchange (ETDEWEB)

    Jones, O S; Glenzer, S H; Suter, L J; Turner, R E; Campbell, K M; Dewald, E L; Hammel, B A; Kauffman, R L; Landen, O L; Rosen, M D; Wallace, R J; Weber, F A

    2003-08-26

    We present the first measurements of the absolute albedos of hohlraums made from gold or from high-Z mixtures. The measurements are performed over the range of radiation temperatures (70-100 eV) expected during the foot of an indirect-drive temporally-shaped ignition laser pulse, where accurate knowledge of the wall albedo (i.e. soft x-ray wall re-emission) is most critical for determining capsule radiation symmetry. We find that the gold albedo agrees well with calculations using the super transition array opacity model, potentially providing additional margin for ICF ignition.

  6. Measurement of the absolute hohlraum wall albedo under ignition foot drive conditions

    Energy Technology Data Exchange (ETDEWEB)

    Suter, L J; Wallace, R J; Hammel, B A; Weber, F A; Landen, O L; Campbell, K M; DeWald, E L; Glenzer, S H; Rosen, M D; Jones, O S; Turner, R E; Kauffmann, R L; Hammer, J H

    2003-11-25

    We present the first measurements of the absolute albedos of hohlraums made from gold or from high-Z mixtures. The measurements are performed over the range of radiation temperatures (70-100 eV) expected during the foot of an indirect-drive temporally-shaped ignition laser pulse, where accurate knowledge of the wall albedo (i.e. soft x-ray wall re-emission) is most critical for determining capsule radiation symmetry. We find that the gold albedo agrees well with calculations using the super transition array opacity model, potentially providing additional margin for ICF ignition.

  7. Quantifying the missing link between albedo and productivity of boreal forests

    Science.gov (United States)

    Hovi, Aarne; Liang, Jingjing; Korhonen, Lauri; Kobayashi, Hideki; Rautiainen, Miina

    2016-04-01

    Albedo and fraction of absorbed photosynthetically active radiation (FAPAR) determine the shortwave radiation balance and productivity of forests. Several studies have examined the relation between forest structure and albedo in the boreal zone. Studies regarding FAPAR are fewer and the relations between albedo and FAPAR are still poorly understood. To study these relations we simulated shortwave black sky albedo and canopy FAPAR, using the FRT forest reflectance model. We used two sets of field plots as input data. The plots were located in Alaska, USA (N = 584) and in Finland (N = 506) between Northern latitudes of 60° and 68° , and they represent naturally grown and more intensively managed (regularly thinned) forests, respectively. The simulations were carried out with sun zenith angles (SZA) typical to the biome, ranging from 40° to 80° . The simulated albedos in coniferous plots decreased with increasing tree height, whereas canopy FAPAR showed an opposite trend. The albedo of broadleaved plots was notably higher than that of coniferous plots. No species differences in canopy FAPAR were seen, except for pine forests in Finland that showed lowest FAPAR among species. Albedo and canopy FAPAR were negatively correlated (r ranged from -0.93 to -0.69) in coniferous plots. The correlations were notably weaker (r ranged from -0.64 to 0.05) if plots with broadleaved trees were included. To show the influence of forest management, we further examined the response of albedo and FAPAR to forest density (basal area) and fraction of broadleaved trees. Plots with low basal area showed high albedos but also low canopy FAPAR. When comparing the sparse plots to dense ones, the relative decrease in canopy FAPAR was larger than the relative increase in albedo. However, at large SZAs the basal area could be lowered to approx. 20 m2 ha-1 before FAPAR was notably reduced. Increasing the proportion of broadleaved trees from 0% to 100% increased the albedos to approximately

  8. Albedo protons and electrons at ISS - an important contribution to astronaut dose?

    Science.gov (United States)

    Norman, R. B.; Slaba, T. C.; Badavi, F. F.; Mertens, C. J.; Blattnig, S.

    2015-12-01

    Albedo particles, which are created by cosmic ray interactions in the atmosphere and are moving upwards away from the surface of the earth, are often considered a negligible contribution to astronaut radiation exposure on the International Space Station (ISS). Models of astronaut exposure, however, consistently underestimate measurements onboard ISS when these albedo particles are neglected. Recent measurements by instruments on ISS (AMS, PAMELA, and SEDA-AP) hint that there are high energy protons and electrons which are not being modeled and that may contribute to radiation exposure on ISS. Estimates of the contribution of radiation exposure on ISS due to albedo particles, along with open questions, will be discussed.

  9. Angular response performance study of a new Harshaw neutron albedo TLD

    Energy Technology Data Exchange (ETDEWEB)

    Liu, J.C.; Sims, C.S. (Oak Ridge National Lab., TN (USA)); West, L.; Welty, T. (Arkansas Univ., Fayetteville, AK (USA). Southwest Radiation Calibration Center)

    1990-01-01

    The angular response of a new Harshaw albedo neutron TLD was studied with two sources: a bare {sup 252}Cf source and a {sup 252}Cf source moderated by a 15 cm D{sub 2}O sphere covered with a cadmium shell. The effect of photon angular dependence on the neutron response of the albedo TLD was examined with {sup 137}Cs and X rays. The angular response performance of the albedo TLD was also evaluated in terms of the directional dose equivalent quantity. The results of these studies are presented and discussed. (author).

  10. Lightcurves of Stars & Exoplanets: Estimating Inclination, Obliquity, and Albedo

    CERN Document Server

    Cowan, Nicolas B; Haggard, Hal M

    2013-01-01

    [Abridged] It is possible to determine a star or planet's brightness markings by analyzing its disk-integrated brightness variations, in either thermal or reflected light. We compute the "harmonic lightcurves" resulting from spherical harmonic maps of intensity or albedo. These convolutions often contain a nullspace: a class of non-zero maps that have no lightcurve signature. We derive harmonic thermal lightcurves for both equatorial and inclined observers. The nullspace for these two viewing geometries is significantly different, with odd modes being present in the latter case, but not the former. We therefore suggest that the Fourier spectrum of a thermal lightcurve is sufficient to determine the orbital inclination of non-transiting short-period planets, the rotational inclination of stars and brown dwarfs, and the obliquity of directly imaged planets. In the best-case scenario of a nearly edge-on rotator, factor-of-two measurements of the amplitudes of odd modes in the thermal lightcurve provide an inclin...

  11. An evaluation of high-resolution regional climate model simulations of snow cover and albedo over the Rocky Mountains, with implications for the simulated snow-albedo feedback

    Science.gov (United States)

    Minder, Justin R.; Letcher, Theodore W.; Skiles, S. McKenzie

    2016-08-01

    The snow-albedo feedback (SAF) strongly influences climate over midlatitude mountainous regions. However, over these regions the skill of regional climate models (RCMs) at simulating properties such as snow cover and surface albedo is poorly characterized. These properties are evaluated in a pair of 7 year long high-resolution RCM simulations with the Weather Research and Forecasting model over the central Rocky Mountains. Key differences between the simulations include the computational domain (regional versus continental) and land surface model used (Noah versus Noah-MP). Simulations are evaluated against high-resolution satellite estimates of snow cover and albedo from the Moderate Resolution Imaging Spectroradiometer. Both simulations generally reproduce the observed seasonal and spatial variability of snow cover and also exhibit important biases. One simulation substantially overpredicts subpixel fractional snow cover over snowy pixels (by up to 0.4) causing large positive biases in surface albedo, likely due in part to inadequate representation of canopy effects. The other simulation exhibits a negative bias in areal snow extent (as much as 19% of the analysis domain). Surface measurements reveal large positive biases in snow albedo (exceeding 0.2) during late spring caused by neglecting radiative effects of impurities deposited onto snow. Semi-idealized climate change experiments show substantially different magnitudes of SAF-enhanced warming in the two simulations that can be tied to the differences in snow cover in their control climates. More confident projections of regional climate change over mountains will require further work to evaluate and improve representation of snow cover and albedo in RCMs.

  12. Comparison between Snow Albedo Obtained from Landsat TM, ETM+ Imagery and the SPOT VEGETATION Albedo Product in a Mediterranean Mountainous Site

    Directory of Open Access Journals (Sweden)

    Rafael Pimentel

    2016-02-01

    Full Text Available Albedo plays an important role in snow evolution modeling quantifying the amount of solar radiation absorbed and reflected by the snowpack, especially in mid-latitude regions with semiarid conditions. Satellite remote sensing is the most extensive technique to determine the variability of snow albedo over medium to large areas; however, scale effects from the pixel size of the sensor source may affect the results of snow models, with different impacts depending on the spatial resolution. This work presents the evaluation of snow albedo values retrieved from (1 Landsat images, L (16-day frequency with 30 × 30 m pixel size and (2 SPOT VEGETATION albedo products, SV (10-day frequency with 1 × 1 km pixel size in the Sierra Nevada mountain range in South Spain, a Mediterranean site representative of highly heterogeneous conditions. Daily snow albedo map series were derived from both sources, and used as input for the snow module in the WiMMed (Watershed Integrated Management in Mediterranean Environment hydrological model, which was operational at the study area for snow monitoring for two hydrological years, 2011–2012 and 2012–2013, in the Guadalfeo river basin in Sierra Nevada. The results showed similar albedo trends in both data sources, but with different values, the shift between both sources being distributed in space according to the altitude. This difference resulted in lower snow cover fraction values in the SV-simulations that affected the rest of snow variables included in the simulation. This underestimation, mainly due to the effects of mixed pixels composed by both snow and snow-free areas, produced higher divergences from both sources during the melting periods when the evapo-sublimation and melting fluxes are more relevant. Therefore, the selection of the albedo data source in these areas, where snow evapo-sublimation plays a very important role and the presence of snow-free patches is very frequent, can condition the final

  13. Spatially Complete Surface Albedo Data Sets: Value-Added Products Derived from Terra MODIS Land Products

    Science.gov (United States)

    Moody, Eric G.; King, Michael D.; Platnick, Steven; Schaaf, Crystal B.; Gao, Feng

    2004-01-01

    Spectral land surface albedo is an important parameter for describing the radiative properties of the Earth. Accordingly it reflects the consequences of natural and human interactions, such as anthropogenic, meteorological, and phenological effects, on global and local climatological trends. Consequently, albedos are integral parts in a variety of research areas, such as general circulation models (GCMs), energy balance studies, modeling of land use and land use change, and biophysical, oceanographic, and meteorological studies. Recent observations of diffuse bihemispherical (white-sky) and direct beam directional hemispherical (black-sky ) land surface albedo included in the MOD43B3 product from MODIS instruments aboard NASA's Terra and Aqua satellite platforms have provided researchers with unprecedented spatial, spectral, and temporal characteristics. Cloud and seasonal snow cover, however, curtail retrievals to approximately half the global land surfaces on an annual equal-angle basis, precluding MOD43B3 albedo products from direct inclusion in some research projects and production environments.

  14. On the calibration of the relation between geometric albedo and polarimetric properties for the asteroids

    CERN Document Server

    Cellino, A; Gil-Hutton, R; Tanga, P; Canada-Assandri, M; Tedesco, E F

    2015-01-01

    We present a new extensive analysis of the old problem of finding a satisfactory calibration of the relation between the geometric albedo and some measurable polarization properties of the asteroids. To achieve our goals, we use all polarimetric data at our disposal. For the purposes of calibration, we use a limited sample of objects for which we can be confident to know the albedo with good accuracy, according to previous investigations of other authors. We find a new set of updated calibration coefficients for the classical slope - albedo relation, but we generalize our analysis and we consider also alternative possibilities, including the use of other polarimetric parameters, one being proposed here for the first time, and the possibility to exclude from best-fit analyzes the asteroids having low albedos. We also consider a possible parabolic fit of the whole set of data.

  15. The extreme ultraviolet albedos of the planet Mercury and of the moon

    Science.gov (United States)

    Wu, H. H.; Broadfoot, A. L.

    1977-01-01

    The albedo of the moon in the far UV was measured by Mariner 10 at a solar phase angle of 74 deg, and the geometric albedo of Mercury was measured in same wavelength range (584-1657 A) at solar phase angles ranging from 50 to 120 deg. For both the moon and Mercury there is a general increase in albedo for wavelengths decreasing from 1657 to 584 A. The ratio of the albedos of Mercury and the moon increases from about 0.6 to 0.8 in the range 600-1600 A. This merely points to a difference in the surfaces of the moon and Mercury, there being insufficient data to make any conclusions regarding the nature of the difference.

  16. On the calibration of the polarimetric slope - albedo relation for asteroids: Work in progress

    Directory of Open Access Journals (Sweden)

    A. Cellino

    2011-09-01

    Full Text Available Asteroid polarimetry is known to be an excellent tool to derive information on the geometric albedo of these objects. This is made possible by the existence of a relation between the albedo and the morphology of the curve which describes the variation of the degree of linear polarization of asteroid light as a function of the illumination conditions. A major problem is that the calibration of the commonly accepted form of the polarization - albedo relation includes numerical coefficients which are affected by fairly high uncertainties. Following some recommendations issued by IAU Commission 15, we are trying to improve the albedo - polarization relation by taking advantage of new polarimetric data obtained in dedicated observation campaigns. We present here some very preliminary results.

  17. MODIS/COMBINED MCD43B3 Albedo 16-Day L3 Global 1km

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The MODerate-resolution Imaging Spectroradiometer (MODIS) BRDF/Albedo Model Parameters product (MCD43A1) contains three-dimensional (3D) data sets providing users...

  18. MISR Level 3 FIRSTLOOK Component Global Albedo product covering a day V002

    Data.gov (United States)

    National Aeronautics and Space Administration — MISR Level 3 FIRSTLOOK Component Global Albedo publicly available product covering a day to be used starting with MISR Release V4.2. (Suggested Usage: This file...

  19. MODIS/COMBINED MCD43A3 Albedo 16-Day L3 Global 500m

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The MODerate-resolution Imaging Spectroradiometer (MODIS) BRDF/Albedo Model Parameters product (MCD43A1) contains three-dimensional (3D) data sets providing users...

  20. Implications of albedo changes following afforestation on the benefits of forests as carbon sinks

    Directory of Open Access Journals (Sweden)

    M. U. F. Kirschbaum

    2011-08-01

    Full Text Available Increased carbon storage with afforestation leads to a decrease in atmospheric carbon dioxide concentration and thus decreases radiative forcing and cools the Earth. However, land-use change also changes the reflective properties of the surface vegetation from more reflective pasture to relatively less reflective forest cover. This increase in radiation absorption by the forest constitutes an increase in radiative forcing, with a warming effect. The net effect of decreased albedo and carbon storage on radiative forcing depends on the relative magnitude of these two opposing processes.

    We used data from an intensively studied site in New Zealand's Central North Island that has long-term, ground-based measurements of albedo over the full short-wave spectrum from a developing Pinus radiata forest. Data from this site were supplemented with satellite-derived albedo estimates from New Zealand pastures. The albedo of a well-established forest was measured as 13 % and pasture albedo as 20 %. We used these data to calculate the direct radiative forcing effect of changing albedo as the forest grew.

    We calculated the radiative forcing resulting from the removal of carbon from the atmosphere as a decrease in radiative forcing of −104 GJ tC−1 yr−1. We also showed that the observed change in albedo constituted a direct radiative forcing of 2759 GJ ha−1 yr−1. Thus, following afforestation, 26.5 tC ha−1 needs to be stored in a growing forest to balance the increase in radiative forcing resulting from the observed albedo change. Measurements of tree biomass and albedo were used to estimate the net change in radiative forcing as the newly planted forest grew. Albedo and carbon-storage effects were of similar magnitude for the first four to five years after tree planting, but as the stand grew older, the carbon storage effect increasingly dominated. Averaged over the whole

  1. Implications of albedo changes following afforestation on the benefits of forests as carbon sinks

    Directory of Open Access Journals (Sweden)

    M. U. F. Kirschbaum

    2011-12-01

    Full Text Available Increased carbon storage with afforestation leads to a decrease in atmospheric carbon dioxide concentration and thus decreases radiative forcing and cools the Earth. However, afforestation also changes the reflective properties of the surface vegetation from more reflective pasture to relatively less reflective forest cover. This increase in radiation absorption by the forest constitutes an increase in radiative forcing, with a warming effect. The net effect of decreased albedo and carbon storage on radiative forcing depends on the relative magnitude of these two opposing processes.

    We used data from an intensively studied site in New Zealand's Central North Island that has long-term, ground-based measurements of albedo over the full short-wave spectrum from a developing Pinus radiata forest. Data from this site were supplemented with satellite-derived albedo estimates from New Zealand pastures. The albedo of a well-established forest was measured as 13 % and pasture albedo as 20 %. We used these data to calculate the direct radiative forcing effect of changing albedo as the forest grew.

    We calculated the radiative forcing resulting from the removal of carbon from the atmosphere as a decrease in radiative forcing of −104 GJ tC−1 yr−1. We also showed that the observed change in albedo constituted a direct radiative forcing of 2759 GJ ha−1 yr−1. Thus, following afforestation, 26.5 tC ha−1 needs to be stored in a growing forest to balance the increase in radiative forcing resulting from the observed albedo change. Measurements of tree biomass and albedo were used to estimate the net change in radiative forcing as the newly planted forest grew. Albedo and carbon-storage effects were of similar magnitude for the first four to five years after tree planting, but as the stand grew older, the carbon storage effect increasingly dominated. Averaged over the whole

  2. Surface Albedo Darkening from wildfires in Northern Sub-Saharan Africa

    Science.gov (United States)

    Gatebe, C. K.; Ichoku, C. M.; Poudal, R.; Roman, M. O.; Wilcox, E.

    2014-01-01

    Wildfires are recognized as a key physical disturbance of terrestrial ecosystems and a major source of atmospheric trace gases and aerosols. They are known to produce changes in landscape patterns and lead to changes in surface albedo that can persist for long periods. Here, we estimate the darkening of surface albedo due to wildfires in different land cover ecosystems in the Northern Sub-Saharan Africa using data from the Moderate Resolution Imaging Spectroradiometer (MODIS). We determined a decrease in albedo after fires over most land cover types (e.g. woody savannas: (-0.00352 0.00003) and savannas: (- 0.003910.00003), which together accounted for >86% of the total MODIS fire count between 2003 and 2011). Grasslands had a higher value (-0.00454 0.00003) than the savannas, but accounted for only about 5% of the total fire count. A few other land cover types (e.g. Deciduous broad leaf: (0.00062 0.00015), and barren: 0.00027 0.00019), showed an increase in albedo after fires, but accounted for less than 1% of the total fires. Albedo change due to wildfires is more important during the fire season (October-February). The albedo recovery progresses rapidly during the first year after fires, where savannas show the greatest recovery (>77%) within one year, while deciduous broadleaf, permanent wetlands and barren lands show the least one-year recovery (56%). The persistence of surface albedo darkening in most land cover types is limited to about six to seven years, after which at least 98% of the burnt pixels recover to their pre-fire albedo.

  3. The GAC-SAL: A new 27-year surface albedo data record from AVHRR

    Science.gov (United States)

    Riihelä, A.; Manninen, T.; Andersson, K.; Laine, V.

    2012-04-01

    Studies on the Earth's climate require knowledge on the interactions between solar radiation and the Earth's atmosphere-surface system. One of the key variables that govern those interactions is the surface albedo, the ratio of reflected to incoming solar radiation at Earth's surface. Recent studies (Holland et al, 2010, Fletcher et al., 2009) point to surface albedo and its variations being especially important for the climate of the Arctic. Against this background, there is a clear and growing need for robust long-term timeseries of surface albedo on a global scale. The Satellite Application Facility on Climate Monitoring (CM SAF), a project of EUMETSAT, answers this need by releasing the first edition of the GAC-SAL surface albedo data record. The GAC-SAL describes the directional-hemispherical reflectance (or black-sky albedo) of the Earth's surface. The data record covers 27 years (1982-2009), is fully global with 0.25 degree spatial resolution, and implements published algorithms for the calculation of surface albedo over land, snow, sea ice and water. The product also incorporates a correction for topography-induced effects on image geolocation and radiometric accuracy. The data is available for all interested users, free of charge. Of special interest is the Arctic sea ice area, for which this is the first long time series reaching present day. We present an overall description of the albedo retrieval scheme and present some results from an extensive validation effort, where GAC-SAL data was compared against in situ observations of surface albedo at 10 different Baseline Surface Radiation Network (BSRN) and Greenland Climate Network (GC-Net) sites, each validation period spanning ~15 years. We have also performed comparisons between GAC-SAL, CERES FSW, and MODIS 43C3 products. Some results of these comparisons are presented. The achieved mean accuracy over all validation results was ~10% (in relative terms). Stability of the data record will also be

  4. Sunlight, Sea Ice, and the Ice Albedo Feedback in a Changing Arctic Sea Ice Cover

    Science.gov (United States)

    2013-09-30

    ice age, and iv) onset dates of melt and freezeup . 4. Assess the magnitude of the contribution from ice-albedo feedback to the observed decrease of...the impact on albedo evolution of ice concentration and melt and freezeup onset dates. This effort will expand on previous work by i) examining...radiation, ice concentration, ice type, and melt and freezeup onset dates on a 25 x 25 km equal area scalable grid. We have daily values of these parameters

  5. The Extraordinary Albedo Variations on Pluto Detected by New Horizons and Implications for Dwarf Planet Eris

    Science.gov (United States)

    Buratti, Bonnie J.; Hofgartner, Jason D.; Stern, S. Alan; Weaver, Harold A.; Verbiscer, Anne J.; Ennico, Kimberly; Olkin, Catherine B.; Young, Leslie; New Horizons Geology and Geophysics Team

    2016-10-01

    The New Horizons mission returned stunning observations of active geology on the surface of Pluto (Stern et al., 2015, Science 350, 292). One of the markers for activity on planets or moons is normal albedos approaching 1.0, as is the case for Enceladus (Buratti et al., 1984, Icarus 58, 254; Verbiscer et al., 2005, Icarus 173, 66). When all corrections for viewing geometry are made for Pluto, it has normal albedos that approach unity in the regions that show evidence for activity by a lack of craters, notably the region informally named Sputnik Planum. On the other hand, Pluto also has a very dark (normal albedo ~0.10) equatorial belt.The geometric albedo of Eris, another large dwarf planet in the Kuiper Belt, is 0.96 (Sicardy et al., 2011, Nature 478, 493), close to that of Enceladus. Coupled with a high density of 2.5 gm/cc (Sicardy et al., ibid.), implying an even larger amount of radiogenic heating than that for Pluto (with a density near 1.9 gm/cc), we find it highly likely that Eris is also active with some type of solid state convection or cryovolcanism on its surface. Alternate explanations such as complete condensation of methane frost onto its surface in the colder environment at nearly 100 AUs would not lead to the high albedo observed.Another implication of the extreme albedo variations on Pluto is that the temperature varies by at least 20K on its surface, spawning possible aeolian processes and associated features such as wind streaks and dunes, which are currently being sought on New Horizons images. Finally, low albedo regions on Pluto, with normal reflectances less than 0.10, provide possible evidence for dust in the Kuiper Belt that is accreting onto the surface of Pluto. Another - or additional - explanation for this low-albedo dust is native material created in Pluto's hazy atmosphere.New Horizons funding by NASA is gratefully acknowledged.

  6. Global analysis of radiative forcing from fire-induced shortwave albedo change

    Directory of Open Access Journals (Sweden)

    G. López-Saldaña

    2014-05-01

    Full Text Available Land surface albedo, a key parameter to derive Earth's surface energy balance, is used in the parameterization of numerical weather prediction, climate monitoring and climate change impact assessments. Changes in albedo due to fire have not been fully investigated at continental and global scale. The main goal of this study therefore, is to quantify the changes in albedo produced by biomass burning activities and their associated shortwave radiative forcing. The study relies on the Moderate Resolution Imaging Spectroradiometer (MODIS MCD64A1 burned area product to create an annual composite of areas affected by fire and the MCD43C2 BRDF-Albedo snow-free product to compute a bihemispherical reflectance time series. The approximate day of burn is used to calculate the instantaneous change in shortwave Albedo. Using the corresponding National Centers for Environmental Prediction (NCEP monthly mean downward solar radiation flux at the surface, the global radiative forcing associated to fire was computed. The analysis reveals a mean decrease in shortwave albedo of −0.023 (1σ = 0.018 causing a mean positive radiative forcing of 6.31 W m–2 (1σ = 5.04 over the 2002–2012 time period in areas affected by fire. The greatest drop in mean shortwave albedo change occurs in 2002, which corresponds to the highest total area burnt (3.66 Mha observed in the same year and produces the highest mean radiative forcing (6.75 W m–2. Africa is the main contributor in terms of burned area but forests globally are giving the highest radiative forcing per unit area, thus give detectable changes in shortwave albedo. The global mean radiative forcing for the whole studied period ~ 0.04 W m–2 shows that the contribution of fires into the Earth system is not insignificant.

  7. Experimental and Theoretical Studies of Ice-Albedo Feedback Processes in the Arctic Basin

    Science.gov (United States)

    2016-06-07

    collectively make up the ice-albedo feedback mechanism. OBJECTIVES To achieve this goal, we must first determine how shortwave radiation is distributed...information if it does not display a currently valid OMB control number. 1. REPORT DATE 30 SEP 1999 2. REPORT TYPE 3. DATES COVERED 00-00-1999...surface temperature, and surface reflectivity (Figure 1). Significant findings to date include: 1. Changes in albedo are a combination of a gradual

  8. Experimental evidence that microbial activity lowers the albedo of glacier surfaces: the cryoconite casserole experiment.

    Science.gov (United States)

    Musilova, M.; Tranter, M.; Takeuchi, N.; Anesio, A. M.

    2014-12-01

    Darkened glacier and ice sheet surfaces have lower albedos, absorb more solar radiation and consequently melt more rapidly. The increase in glacier surface darkening is an important positive feedback to warming global temperatures, leading to ever growing world-wide ice mass loss. Most studies focus primarily on glacial albedo darkening caused by the physical properties of snow and ice surfaces, and the deposition of dark impurities on glaciers. To date, however, the important effects of biological activity have not been included in most albedo reduction models. This study provides the first experimental evidence that microbial activity can significantly decrease the albedo of glacier surfaces. An original laboratory experiment, the cryoconite casserole, was designed to test the microbial darkening of glacier surface debris (cryoconite) under simulated Greenlandic summer conditions. It was found that minor fertilisation of the cryoconite (at nutrient concentrations typical of glacial ice melt) stimulated extensive microbial activity. Microbes intensified their organic carbon fixation and even mined phosphorous out of the glacier surface sediment. Furthermore, the microbial organic carbon production, accumulation and transformation caused the glacial debris to darken further by 17.3% reflectivity (albedo analogue). These experiments are consistent with the hypothesis that enhanced fertilisation by anthropogenic inputs results in substantial amounts of organic carbon fixation, debris darkening and ultimately to a considerable decrease in the ice albedo of glacier surfaces on global scales. The sizeable amounts of microbially produced glacier surface organic matter and nutrients can thus be a vital source of bioavailable nutrients for subglacial and downstream environments.

  9. Retrieval of snow albedo and grain size using reflectance measurements in Himalayan basin

    Directory of Open Access Journals (Sweden)

    H. S. Negi

    2011-03-01

    Full Text Available In the present paper, spectral reflectance measurements of Himalayan seasonal snow were carried out and analysed to retrieve the snow albedo and effective grain size. The asymptotic radiative transfer (ART theory was applied to retrieve the plane and spherical albedo. The retrieved plane albedo was compared with the measured spectral albedo and a good agreement was observed with ±10% differences. Retrieved integrated albedo was found within ±6% difference with ground observed broadband albedo. The retrieved snow grain sizes using different models based on the ART theory were compared for various snow types and it was observed that the grain size model using two channel method (one in visible and another in NIR region can work well for the Himalayan seasonal snow and it was found consistent with temporal changes in grain size. This method can work very well for clean, dry snow as in the upper Himalaya, but sometimes, due to the low reflectances (<20% using wavelength 1.24 μm, the ART theory cannot be applied, which is common in lower and middle Himalayan old snow. This study is important for monitoring the Himalayan cryosphere using air-borne or space-borne sensors.

  10. Albedo impact on the suitability of biochar systems to mitigate global warming.

    Science.gov (United States)

    Meyer, Sebastian; Bright, Ryan M; Fischer, Daniel; Schulz, Hardy; Glaser, Bruno

    2012-11-20

    Biochar application to agricultural soils can change the surface albedo which could counteract the climate mitigation benefit of biochar systems. However, the size of this impact has not yet been quantified. Based on empirical albedo measurements and literature data of arable soils mixed with biochar, a model for annual vegetation cover development based on satellite data and an assessment of the annual development of surface humidity, an average mean annual albedo reduction of 0.05 has been calculated for applying 30-32 Mg ha(-1) biochar on a test field near Bayreuth, Germany. The impact of biochar production and application on the carbon cycle and on the soil albedo was integrated into the greenhouse gas (GHG) balance of a modeled pyrolysis based biochar system via the computation of global warming potential (GWP) characterization factors. The analysis resulted in a reduction of the overall climate mitigation benefit of biochar systems by 13-22% due to the albedo change as compared to an analysis which disregards the albedo effect. Comparing the use of the same quantity of biomass in a biochar system to a bioenergy district heating system which replaces natural gas combustion, bioenergy heating systems achieve 99-119% of the climate benefit of biochar systems according to the model calculation.

  11. Global Albedos of Pluto and Charon from LORRI New Horizons Observations

    CERN Document Server

    Buratti, B J; Hicks, M D; Weaver, H A; Stern, S A; Momary, T; Mosher, J A; Beyer, R A; Young, L A; Ennico, K; Olkin, C B

    2016-01-01

    The exploration of the Pluto-Charon system by the New Horizons spacecraft represent the first opportunity to understand the distribution of albedo and other photometric properties of the surfaces of objects in the Solar System's "Third Zone" within the context of a geologic world. Images of the entire illuminated surface of Pluto and Charon obtained by the Long Range Reconnaissance Imager (LORRI) camera provide a global map of Pluto that revealed surface albedo variegations larger than any other world except for Saturn's moon Iapetus. Normal reflectances on Pluto range from 0.08-1.0. Charon exhibits a much blander surface with normal reflectances ranging from 0.20-0.73. Pluto's albedo features are well-correlated with geologic features, although some exogenous low-albedo dust may be responsible for features seen to the west of the area informally named Tombaugh Regio. The albedo patterns of both Pluto and Charon are latitudinally organized, with the exception of Tombaugh Regio. The low-albedo areas of Pluto a...

  12. Impact of Dust on Mars Surface Albedo and Energy Flux with LMD General Circulation Model

    Science.gov (United States)

    Singh, D.; Flanner, M.; Millour, E.; Martinez, G.

    2015-12-01

    Mars, just like Earth experience different seasons because of its axial tilt (about 25°). This causes growth and retreat of snow cover (primarily CO2) in Martian Polar regions. The perennial caps are the only place on the planet where condensed H2O is available at surface. On Mars, as much as 30% atmospheric CO2 deposits in each hemisphere depending upon the season. This leads to a significant variation on planet's surface albedo and hence effecting the amount of solar flux absorbed or reflected at the surface. General Circulation Model (GCM) of Laboratoire de Météorologie Dynamique (LMD) currently uses observationally derived surface albedo from Thermal Emission Spectrometer (TES) instrument for the polar caps. These TES albedo values do not have any inter-annual variability, and are independent of presence of any dust/impurity on surface. Presence of dust or other surface impurities can significantly reduce the surface albedo especially during and right after a dust storm. This change will also be evident in the surface energy flux interactions. Our work focuses on combining earth based Snow, Ice, and Aerosol Radiation (SNICAR) model with current state of GCM to incorporate the impact of dust on Martian surface albedo, and hence the energy flux. Inter-annual variability of surface albedo and planet's top of atmosphere (TOA) energy budget along with their correlation with currently available mission data will be presented.

  13. The dependence of the ice-albedo feedback on atmospheric properties

    CERN Document Server

    von Paris, P; Kitzmann, D; Rauer, H

    2013-01-01

    The ice-albedo feedback is a potentially important de-stabilizing effect for the climate of terrestrial planets. It is based on the positive feedback between decreasing surface temperatures, an increase of snow and ice cover and an associated increase in planetary albedo, which then further decreases surface temperature. A recent study shows that for M stars, the strength of the ice-albedo feedback is reduced This study investigates the influence of the atmosphere (in terms of surface pressure and atmospheric composition) for this feedback. A plane-parallel radiative transfer model is used for the calculation of planetary albedos. We varied CO2 partial pressures as well as the H2O, CH4, and O3 content in the atmosphere for planets orbiting Sun-like and M-type stars. Results suggest that for planets around M stars, the ice-albedo effect is significantly reduced, compared to planets around Sun-like stars. Including the effects of an atmosphere further suppresses the sensitivity to the ice-albedo effect. Atmosph...

  14. Estimate the influence of snow grain size and black carbon on albedo

    Institute of Scientific and Technical Information of China (English)

    ZhongMing Guo; NingLian Wang; XiaoBo Wu; HongBo Wu; YuWei Wu

    2015-01-01

    Estimation of the influence of snow grain size and black carbon on albedo is essential in obtaining the accurate albedo. In this paper, field measurement data, including snow grain size, snow depth and density was obtained. Black carbon samples were collected from the snow surface. A simultaneous observation using Analytical Spectral Devices was employed in the Qiyi Glacier located in the Qilian Mountain. Analytical Spectral Devices spectrum data were used to analyze spectral re-flectance of snow for different grain size and black carbon content. The measurements were compared with the results obtained from the Snow, Ice, and Aerosol Radiation model, and the simulation was found to correlate well with the ob-served data. However, the simulated albedo was near to 0.98 times of the measured albedo, so the other factors were as-sumed to be constant using the corrected Snow, Ice, and Aerosol Radiation model to estimate the influence of measured snow grain size and black carbon on albedo. Field measurements were controlled to fit the relationship between the snow grain size and black carbon in order to estimate the influence of these factors on the snow albedo.

  15. Retrieval of snow albedo and grain size using reflectance measurements in Himalayan basin

    Directory of Open Access Journals (Sweden)

    H. S. Negi

    2010-11-01

    Full Text Available In the present paper spectral reflectance measurements of Himalayan seasonal snow were carried out and analysed to retrieve the snow albedo and effective grain size. The asymptotic radiative transfer (ART theory was applied to retrieve the plane and spherical albedo. The retrieved plane albedo was compared with the measured spectral albedo and a good agreement was observed with ±10% measured error accuracy. Retrieved integrated albedo was found within ±6% difference with ground observed broadband albedo. The snow grain sizes retrieved using different models based on ART theory are compared for different snow types and it was observed that presently grain size model using two channel method (one in visible and another in NIR region can work well for Himalayan seasonal snow and it was found consistence with temporal increased grain size. This method can work very well for clean dry snow like in upper Himalaya but sometime due to low reflectances (<0.2 using wavelength 1.24 μm ART theory can not be applied, which is common in lower and middle Himalayan old snow. This study is of importance for monitoring the Himalayan cryosphere using air-borne or space-borne sensors.

  16. Near-infrared spectra of high-albedo outer main-belt asteroids

    Energy Technology Data Exchange (ETDEWEB)

    Kasuga, Toshihiro; Shirahata, Mai [National Institutes of Natural Science, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588 (Japan); Usui, Fumihiko [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Kuroda, Daisuke [Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, 3037-5 Honjo, Kamogata-cho, Asakuchi, Okayama 719-0232 (Japan); Ootsubo, Takafumi [Department of Earth Science and Astronomy, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902 (Japan); Okamura, Natsuko [Department of Complexity Science and Engineering, The University of Tokyo Kiban Bldg. 408, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Hasegawa, Sunao, E-mail: toshi.kasuga@nao.ac.jp [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 252-5210 (Japan)

    2015-02-01

    Most outer main-belt asteroids have low albedos because of their carbonaceouslike bodies. However, infrared satellite surveys have revealed that some asteroids have high albedos, which may suggest the presence of unusual surface minerals for those primitive objects. We present new near-infrared (1.1–2.5 μm) spectra of four outer main-belt asteroids with albedos ≥ 0.1. The C-complex asteroids (555) Norma and (2542) Calpurnia are featureless and have (50%–60%) amorphous Mg pyroxenes that might explain the high albedos. Asteroids (701) Oriola (which is a C-complex asteroid) and (2670) Chuvashia (a D/T-type or M-type asteroid) show possible broad absorption bands (1.5–2.1 μm). The feature can be reproduced by either Mg-rich amorphous pyroxene (with 50%–60% and 80%–95% Mg, respectively) or orthopyroxene (crystalline silicate), which might be responsible for the high albedos. No absorption features of water ice (near 1.5 and 2.0 μm) are detected in the objects. We discuss the origin of high albedo components in the outer main-belt asteroids and their physical relations to comets.

  17. The Alpine snow-albedo feedback in regional climate models

    Science.gov (United States)

    Winter, Kevin J.-P. M.; Kotlarski, Sven; Scherrer, Simon C.; Schär, Christoph

    2017-02-01

    The effect of the snow-albedo feedback (SAF) on 2m temperatures and their future changes in the European Alps is investigated in the ENSEMBLES regional climate models (RCMs) with a focus on the spring season. A total of 14 re-analysis-driven RCM experiments covering the period 1961-2000 and 10 GCM-driven transient climate change projections for 1950-2099 are analysed. A positive springtime SAF is found in all RCMs, but the range of the diagnosed SAF is large. Results are compared against an observation-based SAF estimate. For some RCMs, values very close to this estimate are found; other models show a considerable overestimation of the SAF. Net shortwave radiation has the largest influence of all components of the energy balance on the diagnosed SAF and can partly explain its spatial variability. Model deficiencies in reproducing 2m temperatures above snow and ice and associated cold temperature biases at high elevations seem to contribute to a SAF overestimation in several RCMs. The diagnosed SAF in the observational period strongly influences the estimated SAF contribution to twenty first century temperature changes in the European Alps. This contribution is subject to a clear elevation dependency that is governed by the elevation-dependent change in the number of snow days. Elevations of maximum SAF contribution range from 1500 to 2000 m in spring and are found above 2000 m in summer. Here, a SAF contribution to the total simulated temperature change between 0 and 0.5 °C until 2099 (multi-model mean in spring: 0.26 °C) or 0 and 14 % (multi-model mean in spring: 8 %) is obtained for models showing a realistic SAF. These numbers represent a well-funded but only approximate estimate of the SAF contribution to future warming, and a remaining contribution of model-specific SAF misrepresentations cannot be ruled out.

  18. Characterization of the high-albedo NEA 3691 Bede

    Science.gov (United States)

    Wooden, Diane H.; Lederer, Susan M.; Jehin, Emmanuel; Rozitis, Benjamin; Jefferson, Jeffrey D.; Nelson, Tyler W.; Dotson, Jessie L.; Ryan, Erin L.; Howell, Ellen S.; Fernandez, Yanga R.; Lovell, Amy J.; Woodward, Charles E.; Harker, David Emerson

    2016-10-01

    Characterization of NEAs provides important inputs to models for atmospheric entry, risk assessment and mitigation. Diameter is a key parameter because diameter translates to kinetic energy in atmospheric entry. Diameters can be derived from the absolute magnitude, H(PA=0deg), and from thermal modeling of observed IR fluxes. For both methods, the albedo (pv) is important – high pv surfaces have cooler temperatures, larger diameters for a given Hmag, and shallower phase curves (larger slope parameter G). Thermal model parameters are coupled, however, so that a higher thermal inertia also results in a cooler surface temperature. Multiple parameters contribute to constraining the diameter.Observations made at multiple observing geometries can contribute to understanding the relationships between and potentially breaking some of the degeneracies between parameters. We present data and analyses on NEA 3691 Bede with the aim of best constraining the diameter and pv from a combination of thermal modeling and light curve analyses. We employ our UKIRT+Michelle mid-IR photometric observations of 3691 Bede's thermal emission at 2 phase angles (27&43 deg 2015-03-19 & 04-13), in addition to WISE data (33deg 2010-05-27, Mainzer+2011).Observing geometries differ by solar phase angles and by moderate changes in heliocentric distance (e.g., further distances produce somewhat cooler surface temperatures). With the NEATM model and for a constant IR beaming parameter (eta=constant), there is a family of solutions for (diameter, pv, G, eta) where G is the slope parameter from the H-G Relation. NEATM models employing Pravec+2012's choice of G=0.43, produce D=1.8 km and pv≈0.4, given that G=0.43 is assumed from studies of main belt asteroids (Warner+2009). We present an analysis of the light curve of 3691 Bede to constrain G from observations. We also investigate fitting thermophysical models (TPM, Rozitis+11) to constrain the coupled parameters of thermal inertia (Gamma) and surface

  19. Radiative forcing and temperature response to changes in urban albedos and associated CO2 offsets

    Energy Technology Data Exchange (ETDEWEB)

    Menon, Surabi; Akbari, Hashem; Mahanama, Sarith; Sednev, Igor; Levinson, Ronnen

    2010-02-12

    The two main forcings that can counteract to some extent the positive forcings from greenhouse gases from pre-industrial times to present-day are the aerosol and related aerosol-cloud forcings, and the radiative response to changes in surface albedo. Here, we quantify the change in radiative forcing and land surface temperature that may be obtained by increasing the albedos of roofs and pavements in urban areas in temperate and tropical regions of the globe by 0.1. Using the catchment land surface model (the land model coupled to the GEOS-5 Atmospheric General Circulation Model), we quantify the change in the total outgoing (outgoing shortwave+longwave) radiation and land surface temperature to a 0.1 increase in urban albedos for all global land areas. The global average increase in the total outgoing radiation was 0.5 Wm{sup -2}, and temperature decreased by {approx}0.008 K for an average 0.003 increase in surface albedo. These averages represent all global land areas where data were available from the land surface model used and are for the boreal summer (June-July-August). For the continental U.S. the total outgoing radiation increased by 2.3 Wm{sup -2}, and land surface temperature decreased by {approx}0.03 K for an average 0.01 increase in surface albedo. Based on these forcings, the expected emitted CO{sub 2} offset for a plausible 0.25 and 0.15 increase in albedos of roofs and pavements, respectively, for all global urban areas, was found to be {approx} 57 Gt CO{sub 2}. A more meaningful evaluation of the impacts of urban albedo increases on global climate and the expected CO{sub 2} offsets would require simulations which better characterizes urban surfaces and represents the full annual cycle.

  20. Global warming and climate forcing by recent albedo changes on Mars

    Science.gov (United States)

    Fenton, L.K.; Geissler, P.E.; Haberle, R.M.

    2007-01-01

    For hundreds of years, scientists have tracked the changing appearance of Mars, first by hand drawings and later by photographs. Because of this historical record, many classical albedo patterns have long been known to shift in appearance over time. Decadal variations of the martian surface albedo are generally attributed to removal and deposition of small amounts of relatively bright dust on the surface. Large swaths of the surface (up to 56 million km2) have been observed to darken or brighten by 10 per cent or more. It is unknown, however, how these albedo changes affect wind circulation, dust transport and the feedback between these processes and the martian climate. Here we present predictions from a Mars general circulation model, indicating that the observed interannual albedo alterations strongly influence the martian environment. Results indicate enhanced wind stress in recently darkened areas and decreased wind stress in brightened areas, producing a positive feedback system in which the albedo changes strengthen the winds that generate the changes. The simulations also predict a net annual global warming of surface air temperatures by ???0.65 K, enhancing dust lifting by increasing the likelihood of dust devil generation. The increase in global dust lifting by both wind stress and dust devils may affect the mechanisms that trigger large dust storm initiation, a poorly understood phenomenon, unique to Mars. In addition, predicted increases in summertime air temperatures at high southern latitudes would contribute to the rapid and steady scarp retreat that has been observed in the south polar residual ice for the past four Mars years. Our results suggest that documented albedo changes affect recent climate change and large-scale weather patterns on Mars, and thus albedo variations are a necessary component of future atmospheric and climate studies. ??2007 Nature Publishing Group.

  1. Spatiotemporal variation of surface shortwave forcing from fire-induced albedo change in interior Alaska

    Science.gov (United States)

    Huang, Shengli; Dahal, Devendra; Liu, Heping; Jin, Suming; Young, Claudia J.; Liu, Shuang; Liu, Shu-Guang

    2015-01-01

    The albedo change caused by both fires and subsequent succession is spatially heterogeneous, leading to the need to assess the spatiotemporal variation of surface shortwave forcing (SSF) as a component to quantify the climate impacts of high-latitude fires. We used an image reconstruction approach to compare postfire albedo with the albedo assuming fires had not occurred. Combining the fire-caused albedo change from the 2001-2010 fires in interior Alaska and the monthly surface incoming solar radiation, we examined the spatiotemporal variation of SSF in the early successional stage of around 10 years. Our results showed that while postfire albedo generally increased in fall, winter, and spring, some burned areas could show an albedo decrease during these seasons. In summer, the albedo increased for several years and then declined again. The spring SSF distribution did not show a latitudinal decrease from south to north as previously reported. The results also indicated that although the SSF is usually largely negative in the early successional years, it may not be significant during the first postfire year. The annual 2005-2010 SSF for the 2004 fire scars was -1.30, -4.40, -3.31, -4.00, -3.42, and -2.47 Wm-2. The integrated annual SSF map showed significant spatial variation with a mean of -3.15 Wm-2 and a standard deviation of 3.26 Wm-2, 16% of burned areas having positive SSF. Our results suggest that boreal deciduous fires would be less positive for climate change than boreal evergreen fires. Future research is needed to comprehensively investigate the spatiotemporal radiative and non-radiative forcings to determine the effect of boreal fires on climate.

  2. Global warming and climate forcing by recent albedo changes on Mars.

    Science.gov (United States)

    Fenton, Lori K; Geissler, Paul E; Haberle, Robert M

    2007-04-05

    For hundreds of years, scientists have tracked the changing appearance of Mars, first by hand drawings and later by photographs. Because of this historical record, many classical albedo patterns have long been known to shift in appearance over time. Decadal variations of the martian surface albedo are generally attributed to removal and deposition of small amounts of relatively bright dust on the surface. Large swaths of the surface (up to 56 million km2) have been observed to darken or brighten by 10 per cent or more. It is unknown, however, how these albedo changes affect wind circulation, dust transport and the feedback between these processes and the martian climate. Here we present predictions from a Mars general circulation model, indicating that the observed interannual albedo alterations strongly influence the martian environment. Results indicate enhanced wind stress in recently darkened areas and decreased wind stress in brightened areas, producing a positive feedback system in which the albedo changes strengthen the winds that generate the changes. The simulations also predict a net annual global warming of surface air temperatures by approximately 0.65 K, enhancing dust lifting by increasing the likelihood of dust devil generation. The increase in global dust lifting by both wind stress and dust devils may affect the mechanisms that trigger large dust storm initiation, a poorly understood phenomenon, unique to Mars. In addition, predicted increases in summertime air temperatures at high southern latitudes would contribute to the rapid and steady scarp retreat that has been observed in the south polar residual ice for the past four Mars years. Our results suggest that documented albedo changes affect recent climate change and large-scale weather patterns on Mars, and thus albedo variations are a necessary component of future atmospheric and climate studies.

  3. Photon albedo for water, concrete, and iron at normal incidence, and dependence on the thickness of reflecting material

    Directory of Open Access Journals (Sweden)

    Marković Vladimir M.

    2013-01-01

    Full Text Available Total number and angular albedo were calculated for commonly used shielding materials, water, concrete, and iron, for photons with initial energies from 10 keV up to 10 MeV and normal incident angle. Influence of material thickness on total number albedo was also investigated. Double differential albedo was determined from simulation of photon transport through materials by using PENELOPE and MCNP software. Backscattered photons were scored and grouped in equal intervals of energy and angle. Analytical expressions for angular and total number albedo as a function of initial energy were obtained. It was shown that angular albedo can be determined with the same formula for three examined materials. Corresponding analytical expressions for number albedo as a function of material thickness were presented in this paper. [Projekat Ministarstva nauke Republike Srbije, br. 171021

  4. Change in Urban Albedo in London: A Multi-scale Perspective

    Science.gov (United States)

    Susca, T.; Kotthaus, S.; Grimmond, S.

    2013-12-01

    Urbanization-induced change in land use has considerable implications for climate, air quality, resources and ecosystems. Urban-induced warming is one of the most well-known impacts. This directly and indirectly can extend beyond the city. One way to reduce the size of this is to modify the surface atmosphere exchanges through changing the urban albedo. As increased rugosity caused by the morphology of a city results in lower albedo with constant material characteristics, the impacts of changing the albedo has impacts across a range of scales. Here a multi-scale assessment of the potential effects of the increase in albedo in London is presented. This includes modeling at the global and meso-scale informed by local and micro-scale measurements. In this study the first order calculations are conducted for the impact of changing the albedo (e.g. a 0.01 increase) on the radiative exchange. For example, when incoming solar radiation and cloud cover are considered, based on data retrieved from NASA (http://power.larc.nasa.gov/) for ~1600 km2 area of London, would produce a mean decrease in the instantaneous solar radiative forcing on the same surface of 0.40 W m-2. The nature of the surface is critical in terms of considering the impact of changes in albedo. For example, in the Central Activity Zone in London pavement and building can vary from 10 to 100% of the plan area. From observations the albedo is seen to change dramatically with changes in building materials. For example, glass surfaces which are being used increasingly in the central business district results in dramatic changes in albedo. Using the documented albedo variations determined across different scales the impacts are considered. For example, the effect of the increase in urban albedo is translated into the corresponding amount of avoided emission of carbon dioxide that produces the same effect on climate. At local scale, the effect that the increase in urban albedo can potentially have on local

  5. Bipolar high temporal resolution measurements of snow UV albedo in Sodankylä and Marambio

    Science.gov (United States)

    Meinander, Outi; Kontu, Anna; Asmi, Eija; Sanchez, Ricardo; Mei, Miguel; de Leeuw, Gerrit

    2015-04-01

    In this presentation we will give an overview of our high temporal resolution polar snow UV albedo data from Arctic Sodankylä, and from Marambio, Antarctica. These both are WMO GAW stations with many measurement parameters relevant to the albedo data usage. We will also describe our campaign based polar albedo data (SNORTEX and SOS campaigns), and an important data set of light absorbing impurities (BC) in the Arctic snow. The black carbon (BC) has been estimated to be the second most important human emission after carbon dioxide, in terms of its climate forcing in the present-day atmosphere. The reflectance effect of BC deposited on snow surface is the bigger the smaller the wavelength, i.e. the albedo effect of BC is the biggest at UV. This is also shown in SNICAR-model simulated albedo values. In Sodankylä, our bipolar snow ultraviolet (UV) albedo research started within the International Polar Year (IPY) 2007-2008. In 2007, the continuous Sodankylä snow UV albedo measurements were installed in Sodankylä, in the operational albedo field of the Finnish Meteorological Institute Arctic Research Center (FMI-ARC). These Sodankylä 1-min data during snow time were soon compared with the German Antarctic Neumayer Station UV albedo data, also with the same sensor type. In both data we found an up to 10 % decrease in albedo as a function of time within a day, ranging from 0.77 to 0.67 in Sodankylä and from 0.96 to 0.86 in Neumeyer. Physical explanations to asymmetry were found for cases with high relative humidity and low surface temperature during the previous night, favorable to frost and higher albedo on the next morning; new snow on the previous night; snow melting during day time and refreezing during night. In Marambio, in the beginning of 2013, our new continuous Finnish-Argentinian co-operation snow UV albedo measurements were installed and started as part of a larger continuous meteorological and environmental instrumentation. These new UV radiation data

  6. Changes in blast zone albedo patterns around new martian impact craters

    Science.gov (United States)

    Daubar, I. J.; Dundas, C. M.; Byrne, S.; Geissler, P.; Bart, G. D.; McEwen, A. S.; Russell, P. S.; Chojnacki, M.; Golombek, M. P.

    2016-03-01

    "Blast zones" (BZs) around new martian craters comprise various albedo features caused by the initial impact, including diffuse halos, extended linear and arcuate rays, secondary craters, ejecta patterns, and dust avalanches. We examined these features for changes in repeat images separated by up to four Mars years. Here we present the first comprehensive survey of the qualitative and quantitative changes observed in impact blast zones over time. Such changes are most likely due to airfall of high-albedo dust restoring darkened areas to their original albedo, the albedo of adjacent non-impacted surfaces. Although some sites show drastic changes over short timescales, nearly half of the sites show no obvious changes over several Mars years. Albedo changes are more likely to occur at higher-latitude sites, lower-elevation sites, and at sites with smaller central craters. No correlation was seen between amount of change and Dust Cover Index, relative halo size, or historical regional albedo changes. Quantitative albedo measurements of the diffuse dark halos relative to their surroundings yielded estimates of fading lifetimes for these features. The average lifetime among sites with measurable fading is ∼15 Mars years; the median is ∼8 Mars years for a linear brightening. However, at approximately half of sites with three or more repeat images, a nonlinear function with rapid initial fading followed by a slow increase in albedo provides a better fit to the fading behavior; this would predict even longer lifetimes. The predicted lifetimes of BZs are comparable to those of slope streaks, and considered representative of fading by global atmospheric dust deposition; they last significantly longer than dust devil or rover tracks, albedo features that are erased by different processes. These relatively long lifetimes indicate that the measurement of the current impact rate by Daubar et al. (Daubar, I.J. et al. [2013]. Icarus 225, 506-516. http://dx.doi.org/10.1016/j

  7. A minimal, statistical model for the surface albedo of Vestfonna ice cap, Svalbard

    Directory of Open Access Journals (Sweden)

    M. Möller

    2012-09-01

    Full Text Available The ice cap Vestfonna is located in northeastern Svalbard and forms one of the largest ice bodies of the Eurasian Arctic. Its surface albedo plays a key role in the understanding and modelling of its energy and mass balance. The principle governing factors for albedo evolution, i.e. precipitation and air temperature and therewith snow depth and melt duration, were found to vary almost exclusively with terrain elevation throughout the ice cap. Hence, surface albedo can be expected to develop a comparable pattern. A new statistical model is presented that estimates this mean altitudinal albedo profile of the ice cap on the basis of a minimal set of meteorological variables on a monthly resolution. Model calculations are based on a sigmoid function of the artificial quantity rain-snow ratio and a linear function of cumulative snowfall and cumulative positive degree days. Surface albedo fields of the MODIS snow product MOD10A1 from the period March to October in the years 2001–2008 serve as a basis for both calibration and cross-validation of the model. The meteorological model input covers the period September 2000 until October 2008 and is based on ERA-Interim data of a grid point located close to the ice cap. The albedo model shows a good performance. The root mean square error between observed and modelled albedo values along the altitudinal profile is 0.057±0.028 (mean ± one standard deviation. The area weighted mean even reduces to a value of 0.054. Distinctly higher deviations (0.07–0.09 are only present throughout the very lowest and uppermost parts of the ice cap that are either small in area or hardly affected by surface melt. Thus, the new, minimal, statistical albedo model presented in this study is found to reproduce the albedo evolution on Vestfonna ice cap on a high level of accuracy and is thus suggested to be fully suitable for further application in broader energy or mass-balance studies of the ice cap.

  8. A minimal, statistical model for the surface albedo of Vestfonna ice cap, Svalbard

    Directory of Open Access Journals (Sweden)

    M. Möller

    2012-03-01

    Full Text Available The ice cap Vestfonna is located in Northeastern Svalbard and forms one of the largest ice bodies of the Eurasian Arctic. Its surface albedo plays a key role in understanding and modelling of its energy and mass balance. The principle governing factors for albedo evolution, i.e. precipitation and air temperature and therewith snowdepth and melt duration, were found to vary almost exclusively with terrain elevation throughout the ice cap. Hence, surface albedo can be expected to develop a comparable pattern. A new statistical model is presented that estimates this mean altitudinal albedo profile of the ice cap on the basis of a minimal set of meteorological variables on a monthly resolution. Model calculations are based on a logistic function of the artificial quantity rain-snow ratio and a linear function of cumulative snowfall and cumulative positive degree days. Surface albedo fields of the MODIS snow product MOD10A1 of the period March to October of the years 2001–2008 serve as a basis for both calibration and cross-validation of the model. The meteorological model input covers the period September 2000 until October 2008 and is based on ERA-Interim data of a grid point located close to the ice cap. The albedo model shows a good performance. The root mean square error between observed and modelled albedo values along the altitudinal profile is 0.057 ± 0.028 (mean ± one standard deviation. The area weighted mean even reduces to a value of 0.053. Distinctly higher deviations (0.07–0.09 are only present throughout the very lowest and uppermost parts of the ice cap that are either small in area or hardly affected by surface melt. Thus, the new, minimal, statistical albedo model presented in this study is found to reproduce the albedo evolution on Vestfonna ice cap on a high level of accuracy and is thus suggested to be fully suitable for further application in broader energy or mass-balance studies of the ice cap.

  9. Development of a high spectral resolution surface albedo product for the ARM Southern Great Plains central facility

    Directory of Open Access Journals (Sweden)

    J. Delamere

    2011-09-01

    Full Text Available We present a method for identifying dominant surface type and estimating high spectral resolution surface albedo at the Atmospheric Radiation Measurement (ARM facility at the Southern Great Plains (SGP site in Oklahoma for use in radiative transfer calculations. Given a set of 6-channel narrowband visible and near-infrared irradiance measurements from upward and downward looking multi-filter radiometers (MFRs, four different surface types (snow-covered, green vegetation, partial vegetation, non-vegetated can be identified. A normalized difference vegetation index (NDVI is used to distinguish between vegetated and non-vegetated surfaces, and a scaled NDVI index is used to estimate the percentage of green vegetation in partially vegetated surfaces. Based on libraries of spectral albedo measurements, a piecewise continuous function is developed to estimate the high spectral resolution surface albedo for each surface type given the MFR albedo values as input. For partially vegetated surfaces, the albedo is estimated as a linear combination of the green vegetation and non-vegetated surface albedo values. The estimated albedo values are evaluated through comparison to high spectral resolution albedo measurements taken during several Intensive Observational Periods (IOPs and through comparison of the integrated spectral albedo values to observed broadband albedo measurements. The estimated spectral albedo values agree well with observations for the visible wavelengths constrained by the MFR measurements, but have larger biases and variability at longer wavelengths. Additional MFR channels at 1100 nm and/or 1600 nm would help constrain the high resolution spectral albedo in the near infrared region.

  10. Observational determination of albedo decrease caused by vanishing Arctic sea ice.

    Science.gov (United States)

    Pistone, Kristina; Eisenman, Ian; Ramanathan, V

    2014-03-04

    The decline of Arctic sea ice has been documented in over 30 y of satellite passive microwave observations. The resulting darkening of the Arctic and its amplification of global warming was hypothesized almost 50 y ago but has yet to be verified with direct observations. This study uses satellite radiation budget measurements along with satellite microwave sea ice data to document the Arctic-wide decrease in planetary albedo and its amplifying effect on the warming. The analysis reveals a striking relationship between planetary albedo and sea ice cover, quantities inferred from two independent satellite instruments. We find that the Arctic planetary albedo has decreased from 0.52 to 0.48 between 1979 and 2011, corresponding to an additional 6.4 ± 0.9 W/m(2) of solar energy input into the Arctic Ocean region since 1979. Averaged over the globe, this albedo decrease corresponds to a forcing that is 25% as large as that due to the change in CO2 during this period, considerably larger than expectations from models and other less direct recent estimates. Changes in cloudiness appear to play a negligible role in observed Arctic darkening, thus reducing the possibility of Arctic cloud albedo feedbacks mitigating future Arctic warming.

  11. NASA Airborne Snow Observatory: Measuring Spatial Distribution of Snow Water Equivalent and Snow Albedo

    Science.gov (United States)

    Joyce, M.; Painter, T. H.; Mattmann, C. A.; Ramirez, P.; Laidlaw, R.; Bormann, K. J.; Skiles, M.; Richardson, M.; Berisford, D. F.

    2015-12-01

    The two most critical properties for understanding snowmelt runoff and timing are the spatial and temporal distributions of snow water equivalent (SWE) and snow albedo. Despite their importance in controlling volume and timing of runoff, snowpack albedo and SWE are still largely unquantified in the US and not at all in most of the globe, leaving runoff models poorly constrained. NASA Jet Propulsion Laboratory, in partnership with the California Department of Water Resources, has developed the Airborne Snow Observatory (ASO), an imaging spectrometer and scanning LiDAR system, to quantify SWE and snow albedo, generate unprecedented knowledge of snow properties for cutting edge cryospheric science, and provide complete, robust inputs to water management models and systems of the future. This poster will describe the NASA Airborne Snow Observatory, its outputs and their uses and applications, along with recent advancements to the system and plans for the project's future. Specifically, we will look at how ASO uses its imaging spectrometer to quantify spectral albedo, broadband albedo, and radiative forcing by dust and black carbon in snow. Additionally, we'll see how the scanning LiDAR is used to determine snow depth against snow-free acquisitions and to quantify snow water equivalent when combined with in-situ constrained modeling of snow density.

  12. Spatially Complete Global Spectral Surface Albedos: Value-Added Datasets Derived from Terra MODIS Land Products

    Science.gov (United States)

    Moody, Eric G.; King, Michael D.; Platnick, Steven; Schaaf, Crystal B.; Gao, Feng

    2004-01-01

    Land surface albedo is an important parameter in describing the radiative properties of the earth s surface as it represents the amount of incoming solar radiation that is reflected from the surface. The amount and type of vegetation of the surface dramatically alters the amount of radiation that is reflected; for example, croplands that contain leafy vegetation will reflect radiation very differently than blacktop associated with urban areas. In addition, since vegetation goes through a growth, or phenological, cycle, the amount of radiation that is reflected changes over the course of a year. As a result, albedo is both temporally and spatially dependant upon global location as there is a distribution of vegetated surface types and growing conditions. Land surface albedo is critical for a wide variety of earth system research projects including but not restricted to remote sensing of atmospheric aerosol and cloud properties from space, ground-based analysis of aerosol optical properties from surface-based sun/sky radiometers, biophysically-based land surface modeling of the exchange of energy, water, momentum, and carbon for various land use categories, and surface energy balance studies. These projects require proper representation of the surface albedo s spatial, spectral, and temporal variations, however, these representations are often lacking in datasets prior to the latest generation of land surface albedo products.

  13. Albedo Neutron Dosimetry in a Deep Geological Disposal Repository for High-Level Nuclear Waste.

    Science.gov (United States)

    Pang, Bo; Becker, Frank

    2016-06-24

    Albedo neutron dosemeter is the German official personal neutron dosemeter in mixed radiation fields where neutrons contribute to personal dose. In deep geological repositories for high-level nuclear waste, where neutrons can dominate the radiation field, it is of interest to investigate the performance of albedo neutron dosemeter in such facilities. In this study, the deep geological repository is represented by a shielding cask loaded with spent nuclear fuel placed inside a rock salt emplacement drift. Due to the backscattering of neutrons in the drift, issues concerning calibration of the dosemeter arise. Field-specific calibration of the albedo neutron dosemeter was hence performed with Monte Carlo simulations. In order to assess the applicability of the albedo neutron dosemeter in a deep geological repository over a long time scale, spent nuclear fuel with different ages of 50, 100 and 500 years were investigated. It was found out, that the neutron radiation field in a deep geological repository can be assigned to the application area 'N1' of the albedo neutron dosemeter, which is typical in reactors and accelerators with heavy shielding.

  14. Modeling Earth Albedo Currents on Sun Sensors for Improved Vector Observations

    DEFF Research Database (Denmark)

    Bhanderi, Dan

    2006-01-01

    Earth albedo influences vector measurements of the solar line of sight vector, due to the induced current on in the photo voltaics of Sun sensors. Although advanced digital Sun sensors exist, these are typically expensive and may not be suited for satellites in the nano or pico-class. Previously...... for modeling Sun sensor output by incorporating the Earth albedo model is presented. This model utilizes the directional information of in the Earth albedo model, which is achieved by Earth surface partitioning. This allows accurate simulation of the Sun sensor output and the results are consistent with Ørsted...... and useful for space environment simulations, and may be utilized to improve attitude estimation algorithms applying Sun sensor vector observations....

  15. Characteristics of albedo particles generated in interactions of cosmic-ray hadrons

    Energy Technology Data Exchange (ETDEWEB)

    Avakyan, V.V.; Azaryan, M.O.; Grigoryan, S.A.; Kazaryan, S.S.; Mamidzhanyan, E.A.; Oganyan, G.Z.; Ter-Antonyan, S.V.

    1986-11-01

    The Pion installation, which combines a multimodule detector of x-ray transition radiation with an ionization calorimeter, has been used to investigate the characteristics of particles traveling backward in the lab: albedo particles, generated by cosmic-ray hadrons with energy 0.5--5.0 TeV in interactions with nuclei of lead and iron. The principal features of the albedo effect are as follows: the angular distribution of the backward-traveling particles has a tendency to rise at angles near 180/sup 0/; albedo particles from great depths in matter (>100 g/cm/sup 2/) have a hadronic nature; the intensity of the particles depends on the sign of the charge of the primary hadron; the average multiplicity of the particles increases with increase of the energy of the primary hadron.

  16. Active Amplification of the Terrestrial Albedo to Mitigate Climate Change: An Exploratory Study

    CERN Document Server

    Hamwey, R M

    2005-01-01

    This study explores the potential to enhance the reflectance of solar insolation by the human settlement and grassland components of the Earth's terrestrial surface as a climate change mitigation measure. Preliminary estimates derived using a static radiative transfer model indicate that such efforts could amplify the planetary albedo enough to offset the current global annual average level of radiative forcing caused by anthropogenic greenhouse gases by as much as 30 percent or 0.76 W/m2. Terrestrial albedo amplification may thus extend, by about 25 years, the time available to advance the development and use of low-emission energy conversion technologies which ultimately remain essential to mitigate long-term climate change. However, additional study is needed to confirm the estimates reported here and to assess the economic and environmental impacts of active land-surface albedo amplification as a climate change mitigation measure.

  17. Quality assessment and improvement of the EUMETSAT Meteosat Surface Albedo Climate Data Record

    Science.gov (United States)

    Lattanzio, A.; Fell, F.; Bennartz, R.; Trigo, I. F.; Schulz, J.

    2015-10-01

    Surface albedo has been identified as an important parameter for understanding and quantifying the Earth's radiation budget. EUMETSAT generated the Meteosat Surface Albedo (MSA) Climate Data Record (CDR) currently comprising up to 24 years (1982-2006) of continuous surface albedo coverage for large areas of the Earth. This CDR has been created within the Sustained, Coordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM) framework. The long-term consistency of the MSA CDR is high and meets the Global Climate Observing System (GCOS) stability requirements for desert reference sites. The limitation in quality due to non-removed clouds by the embedded cloud screening procedure is the most relevant weakness in the retrieval process. A twofold strategy is applied to efficiently improve the cloud detection and removal. The first step consists of the application of a robust and reliable cloud mask, taking advantage of the information contained in the measurements of the infrared and visible bands. Due to the limited information available from old radiometers, some clouds can still remain undetected. A second step relies on a post-processing analysis of the albedo seasonal variation together with the usage of a background albedo map in order to detect and screen out such outliers. The usage of a reliable cloud mask has a double effect. It enhances the number of high-quality retrievals for tropical forest areas sensed under low view angles and removes the most frequently unrealistic retrievals on similar surfaces sensed under high view angles. As expected, the usage of a cloud mask has a negligible impact on desert areas where clear conditions dominate. The exploitation of the albedo seasonal variation for cloud removal has good potentialities but it needs to be carefully addressed. Nevertheless it is shown that the inclusion of cloud masking and removal strategy is a key point for the generation of the next MSA CDR release.

  18. Persistent spread in seasonal albedo change radiative forcings linked to forest cover changes at northern latitudes

    Science.gov (United States)

    Bright, R. M.; Myhre, G.; Astrup, R. A.; Antón-Fernández, C.; Strømman, A. H.

    2014-12-01

    Large-scale land use and land cover change (LULCC) can significantly affect regional climates from changes in surface biogeophysics, and a substantial part of historical LULCC from forest to crop or pasture occurred in the mid- and high-latitudes of North America and Eurasia where the snow-masking effect of forests often leads to a negative radiative forcing from albedo changes linked to deforestation. Results from several recent historical LULCC modeling studies, however, reveal an order of magnitude spread in climate forcing from the snow-masking effect by forests. This is likely because, in months with snow cover, the interactions between vegetation and snow significantly complicate the relationship between the change in forest cover fraction and albedo, thus accurate characterizations of land surface-albedo dynamics are essential given the importance of albedo feedbacks when ground or canopy surfaces are covered in snow Here, we evaluate snow masking parameterization schemes of seven prominent climate models in greater detail in order to pinpoint major sources of the persistent variability in albedo predictions across models. Using a comprehensive dataset of forest structure, meteorology, and daily MODIS albedo observations spanning three winter-spring seasons in three regions of boreal Norway, we estimate radiative forcings connected to canopy snow masking and compare it to the observed forcings. We develop a physically-based regression model and compare its performance to existing modeling schemes, concluding with a discussion on the utility of purely empirical parameterizations relative to those rooted in radiative transfer theory and/or process-based modeling.

  19. Global Cooling: Increasing World-Wide Urban Albedos to Offset CO2

    Energy Technology Data Exchange (ETDEWEB)

    Akbari, Hashem; Menon, Surabi; Rosenfeld, Arthur

    2008-01-14

    Modification of urban albedos reduces summertime urban temperatures, resulting in a better urban air quality and building air-conditioning savings. Furthermore, increasing urban albedos has the added benefit of reflecting some of the incoming global solar radiation and countering to some extent the effects of global warming. In many urban areas, pavements and roofs constitute over 60% of urban surfaces (roof 20-25%, pavements about 40%). Using reflective materials, both roof and the pavement albedos can be increased by about 0.25 and 0.10, respectively, resulting in a net albedo increase for urban areas of about 0.1. Many studies have demonstrated building cooling-energy savings in excess of 20% upon raising roof reflectivity from an existing 10-20% to about 60% (a U.S. potential savings in excess of $1 billion (B) per year in net annual energy bills). On a global basis, our preliminary estimate is that increasing the world-wide albedos of urban roofs and paved surfaces will induce a negative radiative forcing on the earth equivalent to removing {approx} 22-40 Gt of CO{sub 2} from the atmosphere. Since, 55% of the emitted CO{sub 2} remains in the atmosphere, removal of 22-40 Gt of CO{sub 2} from the atmosphere is equivalent to reducing global CO{sub 2} emissions by 40-73 Gt. At {approx} $25/tonne of CO{sub 2}, a 40-73 Gt CO{sub 2} emission reduction from changing the albedo of roofs and paved surfaces is worth about $1,000B to 1800B. These estimated savings are dependent on assumptions used in this study, but nevertheless demonstrate considerable benefits that may be obtained from cooler roofs and pavements.

  20. The Far-UV Albedo of the Moon Determined from Dayside LAMP Observations

    Science.gov (United States)

    Bullock, Mark A.; Retherford, K. D.; Gladstone, R.; Greathouse, T. K.; Mandt, K. E.; Hendrix, A. R.; Feldman, P. D.; Miles, P. F.; Egan, A. F.

    2013-10-01

    The Lyman Alpha Mapping Project (LAMP) onboard the Lunar Reconnaissance Orbiter (LRO) has been recording far-UV photons reflected from the lunar surface almost continuously since December 2009 (Gladstone et al., 2010). One photon at a time, LAMP builds up spectra from 575 to 1965 Å with a resolution of 26 Å. We will present 3 years of accumulated LAMP lunar dayside spectral maps and derive the lunar geometric albedo spectrum for a range of phase angles. These LAMP observations can thus be used to reconstruct the lunar far-UV photometric function and refine photometric models of the lunar surface (Hapke, 1963; Lucke et al., 1976). We will also compare LAMP lunar dayside albedo with the albedo from 820-1840 Å obtained by the Hopkins Ultraviolet Telescope (HUT) on the March 1995 Astro-2 Space Shuttle mission (Henry et al., 1995). The improved lunar photometric functions from our analysis of LAMP albedo spectra will enable a better quantitative assessment of how phase angle and composition affect the Moon’s reflectance in the far-UV. Gladstone, G. R., Stern, S. A., Retherford, K. D., Black, R. K., Slater, D. C., Davis, M. W., Versteeg, M. H., Persson, K. B., Parker, J. W., Kaufmann, D. E., Egan, A. F., Greathouse, T. K., Feldman, P. D., Hurley, D., Pryor, W. R., Hendrix, A. R., 2010. LAMP: The lyman alpha mapping project on NASA's lunar reconnaissance orbiter mission. Space Science Reviews. 150, 161-181. Hapke, B. W., 1963. A theoretical photometric function for the lunar surface. Journal of Geophysical Research. 68, 4571-4586. Henry, R. C., Feldman, P. D., Kruk, J. W., Davidsen, A. F., Durrance, S. T., 1995. Ultraviolet Albedo of the Moon with the Hopkins Ultraviolet Telescope. The Astrophysical Journal Letters. 454, L69. Lucke, R. L., Henry, R. C., Fastie, W. G., 1976. Far-ultraviolet albedo of the moon. The Astronomical Journal. 81, 1162-1169.

  1. Relationships between MODIS black-sky shortwave albedo and airborne lidar based forest canopy structure

    Science.gov (United States)

    Korhonen, Lauri; Rautiainen, Miina; Arumäe, Tauri; Lang, Mait; Flewelling, James; Tokola, Timo; Stenberg, Pauline

    2016-04-01

    Albedo is one of the essential climate variables affecting the Earth's radiation balance. It is however not well understood how changes in forest canopy structure influence the albedo. Canopy structure can be mapped consistently for fairly large areas using airborne lidar sensors. Our objective was to study the relationships between MODIS shortwave black sky albedo product and lidar-based estimates of canopy structure in different biomes ranging from arctic to tropical. Our study is based on six structurally different forest sites located in Finland, Estonia, USA and Laos. Lidar-based mean height of the canopy, canopy cover and their transformations were used as predictor variables to describe the canopy structure. Tree species composition was also included for the three sites where it was available. We noticed that the variables predicting albedo best were different in open and closed canopy forests. In closed canopy forests, the species information was more important than canopy structure variables (R2=0.31-0.32) and using only structural variables resulted in poor R2 (0.13-0.15). If the 500 m MODIS pixel contained a mixture of forests and other land cover types, the albedo was strongly related to the forest area percent. In open canopy forests, structural variables such as canopy cover or height explained albedo well, but species information still improved the models (R2=0.27-0.52). We obtained the highest R2=0.52 using only structural variables in Laos on a partially degraded tropical forest with large variation in canopy cover. The different canopy structure variables were often correlated and the one that provided the best model changed from site to site.

  2. Quality assessment and improvement of the EUMETSAT Meteosat Surface Albedo Climate Data Record

    Directory of Open Access Journals (Sweden)

    A. Lattanzio

    2015-07-01

    Full Text Available Surface albedo has been identified as an important parameter for understanding and quantifying the Earth's radiation budget. EUMETSAT generated the Meteosat Surface Albedo (MSA Climate Data Record (CDR currently comprising up to 24 years (1982–2006 of continuous surface albedo coverage for large areas of the Earth. This CDR has been created within the Sustained and Coordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM framework. The long-term consistency of the MSA CDR is high and meets the Global Climate Observing System (GCOS stability requirements for desert reference sites. The limitation in quality due to non removed clouds by the embedded cloud screening procedure is the most relevant weakness in the retrieval process. A twofold strategy is applied to efficiently improve the cloud detection and removal. A first step consists on the application of a robust and reliable cloud mask taking advantage of the information contained in the measurements of the infrared and visible bands. Due to the limited information available from old radiometers some clouds can still remain undetected. A second step relies on a post processing analysis of the albedo seasonal variation together with the usage of a background albedo map in order to detect and screen out such outliers. The usage of a reliable cloud mask has a double effect. It enhances the number of high quality retrievals for tropical forest areas sensed under low view angles and removes the most frequently unrealistic retrievals on similar surfaces sensed under high view angles. As expected, the usage of a cloud mask has a negligible impact on desert areas where clear conditions dominate. The exploitation of the albedo seasonal variation for cloud removal has good potentialities but it needs to be carefully addressed. Nevertheless it is shown that the inclusion of cloud masking and removal strategy is a key point for the generation of the next MSA CDR Release.

  3. Quality assessment and improvement of the EUMETSAT Meteosat Surface Albedo Climate Data Record

    Directory of Open Access Journals (Sweden)

    A. Lattanzio

    2015-10-01

    Full Text Available Surface albedo has been identified as an important parameter for understanding and quantifying the Earth's radiation budget. EUMETSAT generated the Meteosat Surface Albedo (MSA Climate Data Record (CDR currently comprising up to 24 years (1982–2006 of continuous surface albedo coverage for large areas of the Earth. This CDR has been created within the Sustained, Coordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM framework. The long-term consistency of the MSA CDR is high and meets the Global Climate Observing System (GCOS stability requirements for desert reference sites. The limitation in quality due to non-removed clouds by the embedded cloud screening procedure is the most relevant weakness in the retrieval process. A twofold strategy is applied to efficiently improve the cloud detection and removal. The first step consists of the application of a robust and reliable cloud mask, taking advantage of the information contained in the measurements of the infrared and visible bands. Due to the limited information available from old radiometers, some clouds can still remain undetected. A second step relies on a post-processing analysis of the albedo seasonal variation together with the usage of a background albedo map in order to detect and screen out such outliers. The usage of a reliable cloud mask has a double effect. It enhances the number of high-quality retrievals for tropical forest areas sensed under low view angles and removes the most frequently unrealistic retrievals on similar surfaces sensed under high view angles. As expected, the usage of a cloud mask has a negligible impact on desert areas where clear conditions dominate. The exploitation of the albedo seasonal variation for cloud removal has good potentialities but it needs to be carefully addressed. Nevertheless it is shown that the inclusion of cloud masking and removal strategy is a key point for the generation of the next MSA CDR release.

  4. Opposition polarimetry and photometry of the low albedo asteroid 419 Aurelia

    Science.gov (United States)

    Belskaya, I. N.; Shevchenko, V. G.; Efimov, Yu. S.; Shakhovskoj, N. M.; Shkuratov, Yu. G.; Gaftonyuk, N. M.; Gil-Hutton, R.; Krugly, Yu. N.; Chiorny, V. G.

    2002-11-01

    Simultaneous photometric and polarimetric observations at small phase angles were carried out for the low albedo asteroid 419 Aurelia. Two interesting observational features were found: (1) a noticeable very narrow opposition surge in the asteroid magnitude phase curve at phase angles less than 0.6 deg; and (2) a decrease of both the depth and width of the negative polarization branch as compared to other dark asteroids with higher albedo. The significance of these results and their correspondence to available laboratory and theoretical studies are discussed.

  5. Impact of dust deposition on the albedo of Vatnajökull ice cap, Iceland

    Science.gov (United States)

    Wittmann, Monika; Dorothea Groot Zwaaftink, Christine; Steffensen Schmidt, Louise; Guðmundsson, Sverrir; Pálsson, Finnur; Arnalds, Olafur; Björnsson, Helgi; Thorsteinsson, Throstur; Stohl, Andreas

    2017-03-01

    Deposition of small amounts of airborne dust on glaciers causes positive radiative forcing and enhanced melting due to the reduction of surface albedo. To study the effects of dust deposition on the mass balance of Brúarjökull, an outlet glacier of the largest ice cap in Iceland, Vatnajökull, a study of dust deposition events in the year 2012 was carried out. The dust-mobilisation module FLEXDUST was used to calculate spatio-temporally resolved dust emissions from Iceland and the dispersion model FLEXPART was used to simulate atmospheric dust dispersion and deposition. We used albedo measurements at two automatic weather stations on Brúarjökull to evaluate the dust impacts. Both stations are situated in the accumulation area of the glacier, but the lower station is close to the equilibrium line. For this site ( ˜ 1210 m a.s.l.), the dispersion model produced 10 major dust deposition events and a total annual deposition of 20.5 g m-2. At the station located higher on the glacier ( ˜ 1525 m a.s.l.), the model produced nine dust events, with one single event causing ˜ 5 g m-2 of dust deposition and a total deposition of ˜ 10 g m-2 yr-1. The main dust source was found to be the Dyngjusandur floodplain north of Vatnajökull; northerly winds prevailed 80 % of the time at the lower station when dust events occurred. In all of the simulated dust events, a corresponding albedo drop was observed at the weather stations. The influence of the dust on the albedo was estimated using the regional climate model HIRHAM5 to simulate the albedo of a clean glacier surface without dust. By comparing the measured albedo to the modelled albedo, we determine the influence of dust events on the snow albedo and the surface energy balance. We estimate that the dust deposition caused an additional 1.1 m w.e. (water equivalent) of snowmelt (or 42 % of the 2.8 m w.e. total melt) compared to a hypothetical clean glacier surface at the lower station, and 0.6 m w.e. more melt (or 38 % of

  6. Absolute magnitudes of asteroids and a revision of asteroid albedo estimates from WISE thermal observations

    Science.gov (United States)

    Pravec, Petr; Harris, Alan W.; Kušnirák, Peter; Galád, Adrián; Hornoch, Kamil

    2012-09-01

    We obtained estimates of the Johnson V absolute magnitudes (H) and slope parameters (G) for 583 main-belt and near-Earth asteroids observed at Ondřejov and Table Mountain Observatory from 1978 to 2011. Uncertainties of the absolute magnitudes in our sample are estimates reported by asteroid surveys. With our photometric H and G data, we revised the preliminary WISE albedo estimates made by Masiero et al. (Masired, J.R. et al. [2011]. Astrophys. J. 741, 68-89) and Mainzer et al. (Mainzer, A. et al. [2011b]. Astrophys. J. 743, 156-172) for asteroids in our sample. We found that the mean geometric albedo of Tholen/Bus/DeMeo C/G/B/F/P/D types with sizes of 25-300 km is pV = 0.057 with the standard deviation (dispersion) of the sample of 0.013 and the mean albedo of S/A/L types with sizes 0.6-200 km is 0.197 with the standard deviation of the sample of 0.051. The standard errors of the mean albedos are 0.002 and 0.006, respectively; systematic observational or modeling errors can predominate over the quoted formal errors. There is apparent only a small, marginally significant difference of 0.031 ± 0.011 between the mean albedos of sub-samples of large and small (divided at diameter 25 km) S/A/L asteroids, with the smaller ones having a higher albedo. The difference will have to be confirmed and explained; we speculate that it may be either a real size dependence of surface properties of S type asteroids or a small size-dependent bias in the data (e.g., a bias towards higher albedos in the optically-selected sample of asteroids). A trend of the mean of the preliminary WISE albedo estimates increasing with asteroid size decreasing from D ∼ 30 down to ∼5 km (for S types) showed in Mainzer et al. (Mainzer, A. et al. [2011a]. Astrophys. J. 741, 90-114) appears to be mainly due to the systematic bias in the MPCORB absolute magnitudes that progressively increases with H in the corresponding range H = 10-14.

  7. Observation of iron-rich coating on lunar grains and a relation to low albedo

    Science.gov (United States)

    Gold, T.; Bilson, E.; Baron, R. L.

    1974-01-01

    The outermost few atomic layers of lunar soil samples were studied by Auger spectroscopy and were found to contain in each case two to three times more iron than the mean bulk composition of the sample. The amount of excess iron is found to be closely correlated with the optical albedo in the manner that would be theoretically expected if the iron provided absorption centers. Crushed lunar rocks of similar mean composition, but lacking the extra iron coating of the soil grains, have a much higher albedo than most lunar soils sampled or observed on the lunar surface.

  8. Variability in Albedo Associated with Fire-Mediated Controls on Stand Density in Siberian Larch Forests

    Science.gov (United States)

    Loranty, M. M.; Fullmer, J.; Nguyen, C. L.; Alexander, H. D.; Natali, S.; Bunn, A. G.; Davydov, S. P.; Goetz, S. J.; Mack, M. C.

    2015-12-01

    Fire is an integral component of boreal forests, and exerts strong control over ecosystem structure and function. The frequency and spatial extent of fire controls the age-class distribution of forests on the landscape. In addition, recent evidence from North American boreal forests has show that fire severity influences post-fire succession via impacts on seedling recruitment that manifest in mature ecosystems dominated by either deciduous or coniferous tree species. The effects of fire on ecosystem structure have important climate feedback implications; changes in forest density or leaf habit can influence surface net radiation by altering the snow-masking effects of vegetation. Although Siberian larch forests occupy a more than 2.8 million km2 of the boreal biome, and are the most prevalent forests in Russia, the influence of fire severity on succession and associated surface energy dynamics are less well understood in comparison to North American boreal forests. There is evidence suggesting that increased fire severity may lead to higher density of post-fire regrowth, but the influence of stand density on surface energy dynamics remains poorly quantified. Here, we quantify the effects of stand density on albedo across the Kolyma River basin using satellite-derived albedo and fire history in conjunction with maps and field observations of ecosystem structure. During snow-free periods albedo varies little with stand density. During periods of snow cover we find consistent negative correlations between multiple metrics of canopy cover and albedo. Albedo decreased with fire recovery over the forty-year fire record for the study area. However, the range of albedo observed within individual fire scars was similar to the magnitude of albedo recovery during the study period. This result indicates the importance of variability in post-fire regrowth within individual fire scars, potentially associated with fire severity, for understanding fire effects on surface energy

  9. Re-Entrant Albedo Proton Fluxes Measured by the PAMELA Experiment

    CERN Document Server

    Adriani, O; Bazilevskaya, G A; Bellotti, R; Boezio, M; Bogomolov, E A; Bongi, M; Bonvicini, V; Bottai, S; Bruno, A; Cafagna, F; Campana, D; Carlson, P; Casolino, M; Castellini, G; De Donato, C; De Santis, C; De Simone, N; Di Felice, V; Formato, V; Galper, A M; Karelin, A V; Koldashov, S V; Koldobskiy, S; Krutkov, S Y; Kvashnin, A N; Leonov, A; Malakhov, V; Marcelli, L; Martucci, M; Mayorov, A G; Menn, W; Mergé, M; Mikhailov, V V; Mocchiutti, E; Monaco, A; Mori, N; Munini, R; Osteria, G; Palma, F; Panico, B; Papini, P; Pearce, M; Picozza, P; Ricci, M; Ricciarini, S B; Sarkar, R; Scotti, V; Simon, M; Sparvoli, R; Spillantini, P; Stozhkov, Y I; Vacchi, A; Vannuccini, E; Vasilyev, G I; Voronov, S A; Yurkin, Y T; Zampa, G; Zampa, N

    2015-01-01

    We present a precise measurement of downward-going albedo proton fluxes for kinetic energy above $\\sim$ 70 MeV performed by the PAMELA experiment at an altitude between 350 and 610 km. On the basis of a trajectory tracing simulation, the analyzed protons were classified into quasi-trapped, concentrating in the magnetic equatorial region, and un-trapped spreading over all latitudes, including both short-lived (precipitating) and long-lived (pseudo-trapped) components. In addition, features of the penumbra region around the geomagnetic cutoff were investigated in detail. PAMELA results significantly improve the characterization of the high energy albedo proton populations at low Earth orbits.

  10. MCNP - transport calculations in ducts using multigroup albedo coefficients; Calculos de transporte em dutos utilizando coeficientes de albedo multigrupo no codigo MCNP

    Energy Technology Data Exchange (ETDEWEB)

    Ono, Shizuca; Vieira, Wilson J.; Garcia, Roberto D.M. [Centro Tecnico Aeroespacial (CTA-IEAv), Sao Jose dos Campos, SP (Brazil). Inst. de Estudos Avancados

    2000-07-01

    In this work, the use of multigroup albedo coefficients in Monte Carlo calculations of particle reflection and transmission by ducts is investigated. The procedure consists in modifying the MCNP code so that an albedo matrix computed previously by deterministic methods or Monte Carlo is introduced into the program to describe particle reflection by a surface. This way it becomes possible to avoid the need of considering particle transport in the duct wall explicitly, changing the problem to a problem of transport in the duct interior only and reducing significantly the difficulty of the real problem. The probability of particle reflection at the duct wall is given, for each group, as the sum of the albedo coefficients over the final groups. The calculation is started by sampling a source particle and simulating its reflection on the duct wall by sampling a group for the emerging particle. The particle weight is then reduced by the reflection probability. Next, a new direction and trajectory for the particle is selected. Numerical results obtained for the model are compared with results from a discrete ordinates code and results from Monte Carlo simulations that take particle transport in the wall into account. (author)

  11. Areal-Averaged Spectral Surface Albedo from Ground-Based Transmission Data Alone: Toward an Operational Retrieval

    Directory of Open Access Journals (Sweden)

    Evgueni Kassianov

    2014-08-01

    Full Text Available We present here a simple retrieval of the areal-averaged spectral surface albedo using only ground-based measurements of atmospheric transmission under fully overcast conditions. Our retrieval is based on a one-line equation. The feasibility of our retrieval for routine determinations of albedo is demonstrated for different landscapes with various degrees of heterogeneity using three sets of measurements: (1 spectral atmospheric transmission from the Multi-Filter Rotating Shadowband Radiometer (MFRSR at five wavelengths (415, 500, 615, 673, and 870 nm; (2 tower-based measurements of local surface albedo at the same wavelengths; and (3 areal-averaged surface albedo at four wavelengths (470, 560, 670 and 860 nm from collocated and coincident Moderate Resolution Imaging Spectroradiometer (MODIS observations. These integrated datasets cover both temporally long (2008–2013 and short (April–May 2010 periods at the Atmospheric Radiation Measurement (ARM Southern Great Plains site and the National Oceanic and Atmospheric Administration (NOAA Table Mountain site, respectively. The calculated root mean square error (RMSE, defined here as the root mean squared difference between the MODIS-derived surface albedo and the retrieved areal-averaged albedo, is quite small (RMSE ≤ 0.015 and comparable with that obtained previously by other investigators for the shortwave broadband albedo. Good agreement between tower-based measurements of daily-averaged surface albedo for completely overcast and non-overcast conditions is also demonstrated.

  12. Sensitivity of Greenland Ice Sheet surface mass balance to surface albedo parameterization: a study with a regional climate model

    NARCIS (Netherlands)

    van Angelen, J.H.; Lenaerts, J.T.M.; Lhermitte, S.; Fettweis, X.; Kuipers Munneke, P.; van den Broeke, M.R.; van Meijgaard, E.; Smeets, C.J.P.P.

    2012-01-01

    We present a sensitivity study of the surface mass balance (SMB) of the Greenland Ice Sheet, as modeled using a regional atmospheric climate model, to various parameter settings in the albedo scheme. The snow albedo scheme uses grain size as a prognostic variable and further depends on cloud cover,

  13. Comparison of Snow Albedo from MISR, MODIS and AVHRR with ground-based observations on the Greenland Ice Sheet

    Science.gov (United States)

    Stroeve, J. C.; Nolin, A.

    2001-12-01

    The surface albedo is an important climate parameter, as it controls the amount of solar radiation absorbed by the surface. For snow-covered surfaces, the albedo may be greater than 0.80, thereby allowing very little solar energy to be absorbed by the snowpack. As the snow ages and/or begins to melt, the albedo is reduced considerably, leading to enhanced absorption of solar radiation. Consequently, snow melt, comprises an unstable, positive feedback component of the climate system, which amplifies small pertubations to that system. Satellite remote sensing offers a means for measuring and monitoring the surface albedo of snow-covered areas. This study evaluates snow surface albedo retrievals from MISR, MODIS and AVHRR through comparisons with surface albedo measurements obtained in Greenland. Data from automatic weather stations, in addition to other in situ data collected during 2000 provide the ground-based measurements with which to compare coincident clear-sky satellite albedo retrievals. In general, agreements are good with the satellite data. However, satellite calibration and difficulties accurately representing the angular signature of the snow surface make it difficult to reach an albedo accuracy within 0.05.

  14. Procedures for calculation of the albedo with OLI-Landsat 8 images: Application to the Brazilian semi-arid

    Directory of Open Access Journals (Sweden)

    Bernardo B. da Silva

    2016-01-01

    Full Text Available ABSTRACT The surface albedo plays an important role in the exchanges of energy and mass in the planetary boundary layer. Therefore, changes in albedo affect the balance of radiation and energy at the surface, which can be detected with its monitoring. Albedo determination has been performed through various sensors, but there is not yet any publication dealing with albedo calculation procedures using OLI (Operational Land Imager - Landsat 8 images. The objective of the study is to present the procedures for computing the albedo with OLI images and map it in irrigated areas of the São Gonçalo Irrigated District, PB, Brazil. Images of the year 2013, path 215 and row 65, were selected. The data necessary for calculating the albedo were extracted from each image metadata: additive and multiplicative terms of radiance and reflectance, and sun elevation angle. There were large differences between the albedo values of irrigated plots, water bodies and native vegetation. The albedo obtained with OLI images provides a higher degree of differentiation of the various types of land use, due to the substantial increase in the radiometric resolution of this new sensor.

  15. Measurement of daily spectral soil albedo over France from MODIS and MSG: comparison with soil moisture derived from ASCAT observations

    Science.gov (United States)

    Liu, S.; Roujean, J. L.; Kaptue, A.; Carrer, D.; Lafont, S.; Parrens, M.; Szczypta, C.; Calvet, J. C.

    2012-04-01

    Surface albedo determines the partition of energy between land surface and atmosphere, which is a crucial parameter for climate studies. In particular, consistency of coarse scale soil background albedo data set is required to improve the radiative scheme in land surface modeling. As an important component of land surface, soil albedo depends on soil moisture, soil roughness, mineral content, tillage, etc. It can change rapidly at hourly or daily basis, revealing the variation of the state variables, particularly soil moisture. Over dense vegetation areas, radiation interactions exist between the soil background and the bottom of canopy, which adds to the difficulty to yield a clear separation between the respective soil and vegetation attributes. With the advent of a new-generation of Earth observing sensor systems, consistent sets of surface albedo products are regularly distributed at global and regional scales within expected accuracy, particularly MODIS and SEVIRI, which provides the potential of generating soil albedo from satellite observations. The objective of this study is to derive soil background albedo from MODIS and SEVIRI data sets over France. A procedure was developed to derive a MODIS albedo on a daily basis in combining TERRA and AQUA observations and in considering the MODIS BRDF model at the appropriate dates. A novel 1D radiative transfer approach is applied to disentangle soil background albedo and vegetation albedo by using the albedo and LAI data sets of MODIS and SEVIRI. This background albedo from satellite observations is made evolving with the use of a Kalman filter approach. In order to generate a predictive model, temporal trajectories of soil background albedo are extracted for each soil mapping unit and further clustered into several clusters by using k-mean method. The temporal coherence of the resulting soil background albedos was assessed with satellite and in-situ rainfall and soil moisture observations. It comes out that the

  16. Three-year changes of surface albedo of degraded grassland and cropland surfaces in a semiarid area

    Institute of Scientific and Technical Information of China (English)

    LIU HuiZhi; TU Gang; DONG WenJie

    2008-01-01

    Diurnal, seasonal and interannual variations of surface albedo of degraded grassland and cropland surfaces at a semiarid area of Tognyu have been investigated based on the continuous three years observational data from 2003 to 2005. The changes of surface albedo with solar elevation angle and soil moisture have been discussed also. It has been found that surface albedo has almost the same diurnal and seasonal variations on degraded grassland and cropland surfaces in the semiarid area, while sur-face albedo is large in winter and small in summer. The diurnal variation of the surface albedo has re-lationship with the weather condition. The diurnal cycle of the surface albedo likes the "U" shape curve in sunny day, while it is low-high after the rain, and high-low after the snow. The surface albedo has large variation in cloudy day, while it has no any variation in overcast day. The large difference of the surface albedo can be 0.04 in winter between two land surfaces, because the snow has large effects on the surface albedo in winter. The rainfall is an important factor in summer on the surface albedo, while the difference of the surface albedo is 0.01 only between two land surfaces. The differences of the surface aibedo can also be 0.04 in autumn due to vegetation growing. The seasonal-average surface albeo from 2003-2005 is 0.25, 0.22, 0.24, 0.32 respectively in spring, summer, autumn and winter on the degraded grassland surface, while it is 0.25, 0.21,0.22, 0.33 respectively in spring, summer, autumn and winter on the cropland surface. The surface albedo becomes smaller with the increase of solar elevation angle. When the solar elevation angle is greater than 40°, the surface albedo changes very little and tends to be a constant. The surface albedo has negative exponent functions with soil moisture in the growing season.

  17. First albedo determination of 2867 Steins, target of the Rosetta mission

    CERN Document Server

    Fornasier, S; Fulchignoni, M; Barucci, M A; Barbieri, C

    2006-01-01

    We present the first albedo determination of 2867 Steins, the asteroid target o f the Rosetta space mission together with 21 Lutetia. The data were obtained in polarimetric mode at the ESO-VLT telescope with the FORS1 instrument in the V and R filters. Observations were carried out from Jun e to August 2005 covering the phase angle range from 10.3 deg. to 28.3 deg., allowing the determination of the asteroid albedo by the well known experimenta l relationship between the albedo and the slope of the polarimetric curve at th e inversion angle. The measured polarization values of Steins are small, confirming an E-type cla ssification for this asteroid, as already suggested from its spectral propertie s. The inversion angle of the polarization curve in the V and R filters is resp ectively of 17.3 +/-1.5deg. and 18.4+/-1.0 deg., and the corresponding sl ope parameter is of 0.037+/-0.003 %/deg and 0.032+/-0.003 %/deg. On the basis of its polarimetric slope value, we have derived an albedo of 0.45 +/-0.1, that gives...

  18. Sensitivity of cloud albedo to aerosol concentration and spectral dispersion of cloud droplet size distribution

    Energy Technology Data Exchange (ETDEWEB)

    Iorga, G. [Faculty of Chemistry, University of Bucharest, Bucharest (Romania)]. E-mail: giorga@gw-chimie.math.unibuc.ro; Stefan, S. [Faculty of Physics, University of Bucharest, Bucharest (Romania)

    2007-07-15

    Both the enhancement of the aerosol number concentration and the relative dispersion of the cloud droplet size distribution (spectral dispersion) on a regional scale can modify the cloud reflectivity. This work is focused on the role that pre-cloud aerosol plays in cloud reflectivity. Log-normal aerosol size distributions were used to describe two aerosol types: marine and rural. The number of aerosols that activate to droplets was obtained based on Abdul-Razzak and Ghan's (2000) activation parameterization. The cloud albedo taking into account the spectral dispersion effect in the parameterization of cloud effective radius and in the scattering asymmetry factor has been estimated. Two different scaling factors to account for dispersion were used. The sensitivity of cloud albedo to spectral dispersion-cloud droplet number concentration relationship in connection to the changes in liquid water content (LWC), and the cloud droplet effective radius has been also investigated. We obtained higher values of effective radius when dispersion is taken into account, with respect to the base case (without considering dispersion). The inferred absolute differences in effective radius values between calculations with each of the scaling factors are below 0.8 {mu}m as LWC ranges between 0.1 and 1.0 g m-3. The optical depth decreased by up to 14% (marine), and up to 29% (continental) when dispersion is considered in both effective radius and asymmetry factor ({beta}LDR scaling factor). Correspondingly, the relative change in cloud albedo is up to 6% (marine) and up to 11% (continental) clouds. For continental clouds, the calculated effective radius when dispersion is considered fits well within the measured range of effective radius in SCAR-B project. The calculated cloud albedo when dispersion is considered shows better agreement with the estimated cloud albedo from measured effective radius in SCAR-B project than the cloud albedo calculated without dispersion. In cleaner

  19. Temporal and spatial mapping of surface albedo and atmospheric dust opacity on Mars

    Science.gov (United States)

    Lee, S. W.; Clancy, R. T.; Gladstone, G. R.

    1993-01-01

    The Mariner 9 and Viking provided abundant evidence that eolian processes are active over much of the surface of Mars. Past studies have demonstrated that variations in regional albedo and wind-streak patterns are indicative of sediment transport through a region, while thermal inertia data (derived from the Viking Infrared Thermal Mapper (IRTM) dataset) are indicative of the degree of surface mantling by dust deposits. The visual and thermal data are therefore diagnostic of whether net erosion or deposition of dust-storm fallout is taking place currently and whether such processes have been active in a region over the long term. These previous investigations, however, have not attempted to correct for the effects of atmospheric dust loading on observations of the martian surface, so quantitative studies of current sediment transport rates have included large errors due to uncertainty in the magnitude of this 'atmospheric component' of the observations. We have developed a radiative transfer model that allows the atmospheric dust opacity to be determined from IRTM thermal observations. Corrections for the effects of atmospheric dust loading on observations of surface albedo can also be modeled. This approach to determining 'dust-corrected surface albedo' incorporates the atmospheric dust opacity, the single-scattering albedo and particle phase function of atmospheric dust, and the bidirectional reflectance of the surface, and it accounts for variable lighting and viewing geometry.

  20. Land Surface Albedo From EPS/AVHRR : Method For Retrieval and Validation

    Science.gov (United States)

    Jacob, G.

    2015-12-01

    The scope of Land Surface Analysis Satellite Applications Facility (LSA-SAF) is to increase benefit from EUMETSAT Satellites (MSG and EPS) data by providing added value products for the meteorological and environmental science communities with main applications in the fields of climate modelling, environmental management, natural hazards management, and climate change detection. The MSG/SEVIRI daily albedo product is disseminated operationally by the LSA-SAF processing centre based in Portugal since 2009. This product so-called MDAL covers Europe and Africa includes in the visible, near infrared and shortwave bands at a resolution of 3km at the equator. Recently, an albedo product at 1km so-called ETAL has been built from EPS/AVHRR observations in order to primarily MDAL product outside the MSG disk, while ensuring a global coverage. The methodology is common to MSG and EPS data and relies on the inversion of the BRDF (Bidirectional Reflectance Distribution Function) model of Roujean et al. On a given target, ETAL products exploits the variability of viewing angles whereas MDAL looks at the variations of solar illumination. The comparison of ETAL albedo product against MODIS and MSG/SEVIRI products over the year 2015 is instructive in many ways and shows in general a good agreement between them. The dispersion may be accounted by different factors that will be explained The additional information provided by EPS appears to be particularly beneficial for high latitudes during winter and for snow albedo.

  1. Space platform albedo measurements as indicators of change in arid lands

    Science.gov (United States)

    Robinove, C.J.

    1982-01-01

    The change in albedo of arid lands is an indicator of changes in their condition and quality, including density of vegetative cover, erosion, deposition, surficial soil moisture, and man-made change. In general, darkening of an arid land surface indicates an increase in land quality while brightening indicates a decrease in quality, primarily owing to changes in vegetation. Landsat multiband images taken on different dates can be converted to black-and-white albedo images. Subtraction of one image from another, pixel by pixel, results in an albedo change map that can be density sliced to show areas that have brightened or darkened by selected percentages. These maps are then checked in the field to determine the reasons for the changes and to evaluate the changes in land condition and quality. The albedo change mapping technique has been successfully used in the arid lands of western Utah and northern Arizona and has recently been used for detection of coal strip mining activities in northern Alabama. ?? 1983.

  2. Modelled climate sensitivity of the mass balance of Morteratschgletscher and its dependence on albedo parameterization

    NARCIS (Netherlands)

    Klok, E.J.; Oerlemans, J.

    2004-01-01

    This paper presents a study of the climate sensitivity of the mass balance of Morteratschgletscher in Switzerland, estimated from a two-dimensional mass balance model. Since the albedo scheme chosen is often the largest error source in mass balance models, we investigated the impact of using differe

  3. Albedo feedbacks to future climate via climate change impacts on dryland biocrusts

    Science.gov (United States)

    Rutherford, William A.; Painter, Thomas H.; Ferrenberg, Scott; Belnap, Jayne; Okin, Gregory S.; Flagg, Cody; Reed, Sasha C.

    2017-01-01

    Drylands represent the planet’s largest terrestrial biome and evidence suggests these landscapes have large potential for creating feedbacks to future climate. Recent studies also indicate that dryland ecosystems are responding markedly to climate change. Biological soil crusts (biocrusts) ‒ soil surface communities of lichens, mosses, and/or cyanobacteria ‒ comprise up to 70% of dryland cover and help govern fundamental ecosystem functions, including soil stabilization and carbon uptake. Drylands are expected to experience significant changes in temperature and precipitation regimes, and such alterations may impact biocrust communities by promoting rapid mortality of foundational species. In turn, biocrust community shifts affect land surface cover and roughness—changes that can dramatically alter albedo. We tested this hypothesis in a full-factorial warming (+4 °C above ambient) and altered precipitation (increased frequency of 1.2 mm monsoon-type watering events) experiment on the Colorado Plateau, USA. We quantified changes in shortwave albedo via multi-angle, solar-reflectance measurements. Warming and watering treatments each led to large increases in albedo (>30%). This increase was driven by biophysical factors related to treatment effects on cyanobacteria cover and soil surface roughness following treatment-induced moss and lichen mortality. A rise in dryland surface albedo may represent a previously unidentified feedback to future climate. PMID:28281687

  4. Albedo Variations and Surface Energy Balance in Different Snow-Ice Media in Antarctica

    Directory of Open Access Journals (Sweden)

    V.D. Mishra

    1999-12-01

    Full Text Available The present study is aimed at investigating the radiation budget in different snow-ice media (shelf ice,continental ice and natural snow at three different elevated sites in the general area of Prince Astrid Coast of EastAntarctica. Measurements of the dependence of albedo in different snow and ice media on solar elevation angle,cloud cover, liquid water content, grain size, etc. can be interpreted in terms of single and multiple scatteringradiative transfer theory. Detailed albedo measurements were carried out during summer and winter in differentsnow and ice media in 1997-98 at different selected sites at Antarctica. The average albedo values were found to behigh (90 per cent in snow medium, moderate (83 per cent in shelf ice and very low (50 per cent in continentalice medium. The albedo was found to be a function of cloud amount, increasing with the amount and thickness. Inwhite-out condition during blizzards, high albedo (average 83 per cent was found as compared to clear sky day(76 per cent and after blizzard (average 78 per cent. It showed dependence on the type and age of snow also. Newsnowfall over old snow displayed higher values (90 per cent than older snow (70 per cent and decreased with theageof snow from 13- 16 per cent. Naturalmelt-water in snowpack increases from 1- 10 per cent, resulting in albedodecay from 7-10 per cent. As the minimum solar elevation angle in Antarctica goes to 3O, strong qualitativeanalyses have been ma e of the dependenceof albedo on the solar elevation angle. Albedo values showed diurnalhysteresis and m in values were found to be higher than evening values at the same angle of elevation. Thedependence was 4 sligh or solar elevations during day time when 0 % 12-IS0, but became larger with low angleswhen 8 = 3-12'. Solar insolations were also calculated for different months in order to calculate short waveradiation absorbed by snow and ice media. Insolations in different months at different selected sites lie

  5. Impacto do desmatamento de uma área de mangue no albedo superficial

    Directory of Open Access Journals (Sweden)

    Carlos Alexandre Santos Querino

    2013-12-01

    Full Text Available Manguezais são ecossistemas peculiares encontrados nas regiões tropicais. A degradação dos manguezais altera o balanço superficial de radiação, e por consequência o albedo. Para avaliar e comparar o albedo, nesse ambiente foram instaladas duas plataformas de coletas de dados micrometeorológicos no município de Marechal Deodoro, Alagoas, Brasil, no período de outubro de 2004 a outubro de 2005. No mangue nativo (9º42' 18"S; 35º 48' 32" W foram instalados dois piranômetros acima da copa das árvores, e em outubro de 2005, um terceiro dentro do mangue. Na área degradada (9º 36' 38" S; 35º 46' 03" W, os sensores foram posicionados a uma altura de dois metros em relação ao solo. Observou-se que o albedo sobre a floresta de mangue, em geral, é maior em média, 5 pontos percentuais superior em relação à outras florestas tropicais, como por exemplo, a Amazônia. Internamente notou-se que o mesmo não ultrapassou os 13% e seu valor máximo ocorre no horário de menor albedo da copa ≈ 20%, evidenciando a influência da maré. Já na área degradada, o albedo médio foi de 35%, o que implica em uma elevação aproximada de 49% quando substituída a cobertura de floresta natural.

  6. Spatial distribution of mineral dust single scattering albedo based on DREAM model

    Science.gov (United States)

    Kuzmanoski, Maja; Ničković, Slobodan; Ilić, Luka

    2016-04-01

    Mineral dust comprises a significant part of global aerosol burden. There is a large uncertainty in estimating role of dust in Earth's climate system, partly due to poor characterization of its optical properties. Single scattering albedo is one of key optical properties determining radiative effects of dust particles. While it depends on dust particle sizes, it is also strongly influenced by dust mineral composition, particularly the content of light-absorbing iron oxides and the mixing state (external or internal). However, an assumption of uniform dust composition is typically used in models. To better represent single scattering albedo in dust atmospheric models, required to increase accuracy of dust radiative effect estimates, it is necessary to include information on particle mineral content. In this study, we present the spatial distribution of dust single scattering albedo based on the Dust Regional Atmospheric Model (DREAM) with incorporated particle mineral composition. The domain of the model covers Northern Africa, Middle East and the European continent, with horizontal resolution set to 1/5°. It uses eight particle size bins within the 0.1-10 μm radius range. Focusing on dust episode of June 2010, we analyze dust single scattering albedo spatial distribution over the model domain, based on particle sizes and mineral composition from model output; we discuss changes in this optical property after long-range transport. Furthermore, we examine how the AERONET-derived aerosol properties respond to dust mineralogy. Finally we use AERONET data to evaluate model-based single scattering albedo. Acknowledgement We would like to thank the AERONET network and the principal investigators, as well as their staff, for establishing and maintaining the AERONET sites used in this work.

  7. Global biogeophysical interactions between historical deforestation and climate through land surface albedo and interactive ocean

    Science.gov (United States)

    Wang, Ye

    2017-02-01

    Deforestation is expanding and accelerating into the remaining areas of undisturbed forest, and the quality of the remaining forests is declining today. Assessing the climatic impacts of deforestation can help to rectify this alarming situation. In this paper, how historical deforestation may affect global climate through interactive ocean and surface albedo is examined using an Earth system model of intermediate complexity (EMIC). Control and anomaly integrations are performed for 1000 years. In the anomaly case, cropland is significantly expanded since AD 1700. The response of climate in deforested areas is not uniform between the regions. In the background of a global cooling of 0.08 °C occurring with cooler surface air above 0.4 °C across 30° N to 75° N from March to September, the surface albedo increase has a global cooling effect in response to global-scale replacement of forests by cropland, especially over northern mid-high latitudes. The northern mid-latitude (30° N-60° N) suffers a prominent cooling in June, suggesting that this area is most sensitive to cropland expansion through surface albedo. Most regions show a consistent trend between the overall cooling in response to historical deforestation and its resulting cooling due to surface albedo anomaly. Furthermore, the effect of the interactive ocean on shaping the climate response to deforestation is greater than that of prescribed SSTs in most years with a maximum spread of 0.05 °C. This difference is more prominent after year 1800 than that before due to the more marked deforestation. These findings show the importance of the land cover change and the land surface albedo, stressing the necessity to analyze other biogeophysical processes of deforestation using interactive ocean.

  8. Evidence for the Nature of Space Weathering Spectral Signatures on Low Albedo Asteroids

    Science.gov (United States)

    Lantz, Cateline; Clark, B. E.; Barucci, M. A.

    2012-10-01

    We address an existing problem in understanding the reflected light spectral signatures of carbonaceous (low-albedo) asteroids. We know from observations of the moon and high-albedo asteroids that interplanetary surface processes (solar wind and micrometeorite bombardment) can alter the spectral properties of silicates. The problem is that we don’t understand how carbonaceous surfaces respond to surface processes. The question is, what are the spectral signatures of surface processes on low albedo asteroids? To answer this question, we need to study reflected light spectra of asteroid subsurface materials, and compare them with asteroid surface materials. In this work, we assume that primitive asteroids are the parent bodies of carbonaceous chondrites. We begin with a fairly well-established meteorite-asteroid link: several studies have found evidence that links the CM meteorites with the Ch/Cgh asteroids [Hiroi et ao. 1996; Fornasier et al. 1999]. Assuming this link, we reason that differences between spectra of particulate samples of the CM meteorites and spectra of the regolith of the asteroids can be due to either differences in textural properties, or differences caused by surface processes on the asteroid. Previous work has resulted in contradictory predictions. Asteroid color survey data analyzed by Lazzarin et al. (2006) predicted spectral reddening for low albedo asteroids. Laser irradiation experiments by Moroz et al. (1996; 2004; 2004b) indicated both reddening and blueing of various degrees. Our initial results indicate spectral blueing of up to 50%, with little to no concurrent albedo change. We used telescopic observations of 43 Ch and Cgh-type asteroids (0.4 to 2.5 microns) from Binzel, DeMeo, et al. (MIT) and Fornasier et al. (Obs. Paris). We compare them statistically with 106 CM meteorite spectra from RELAB. The goal of this work is to predict what the OSIRIS-REx mission will see at B-type asteroid (101955) 1999RQ36.

  9. Derivation of Land Surface Albedo at High Resolution by Combining HJ-1A/B Reflectance Observations with MODIS BRDF Products

    NARCIS (Netherlands)

    Gao, B.; Jia, L.; Wang, T.X.

    2014-01-01

    Land surface albedo is an essential parameter for monitoring global/regional climate and land surface energy balance. Although many studies have been conducted on global or regional land surface albedo using various remote sensing data over the past few decades, land surface albedo product with a hi

  10. Application of Laplace transform for determination of albedo type boundary conditions for neutronic calculations; Aplicacao da transformada de Laplace para determinacao de condicoes de contorno tipo albedo para calculos neutronicos

    Energy Technology Data Exchange (ETDEWEB)

    Petersen, Claudio Zen

    2008-07-01

    In this dissertation we use the Laplace transform to derive expressions for nonstandard albedo boundary conditions for one and two non-multiplying regions at the ends of one dimensional domains. In practice, the fuel regions of reactor cores are surrounded by reflector regions that reduce neutron leakage. In order to exclude the reflector regions from the calculations, we introduce a reflection coefficient or albedo. We use the present albedo boundary conditions to solve numerically slab-geometry monoenergetic and multigroup diffusion equations using the conventional finite difference method. Numerical results are generated for fixed source and eigenvalue diffusion problems in slab geometry(author)

  11. Sensitivity of Greenland Ice Sheet surface mass balance to surface albedo parameterization: a study with a regional climate model

    Directory of Open Access Journals (Sweden)

    J. H. van Angelen

    2012-10-01

    Full Text Available We present a sensitivity study of the surface mass balance (SMB of the Greenland Ice Sheet, as modeled using a regional atmospheric climate model, to various parameter settings in the albedo scheme. The snow albedo scheme uses grain size as a prognostic variable and further depends on cloud cover, solar zenith angle and black carbon concentration. For the control experiment the overestimation of absorbed shortwave radiation (+6% at the K-transect (west Greenland for the period 2004–2009 is considerably reduced compared to the previous density-dependent albedo scheme (+22%. To simulate realistic snow albedo values, a small concentration of black carbon is needed, which has strongest impact on melt in the accumulation area. A background ice albedo field derived from MODIS imagery improves the agreement between the modeled and observed SMB gradient along the K-transect. The effect of enhanced meltwater retention and refreezing is a decrease of the albedo due to an increase in snow grain size. As a secondary effect of refreezing the snowpack is heated, enhancing melt and further lowering the albedo. Especially in a warmer climate this process is important, since it reduces the refreezing potential of the firn layer that covers the Greenland Ice Sheet.

  12. Sensitivity of Greenland Ice Sheet surface mass balance to surface albedo parameterization: a study with a regional climate model

    Directory of Open Access Journals (Sweden)

    J. H. van Angelen

    2012-04-01

    Full Text Available We present a sensitivity study of the surface mass balance (SMB of the Greenland Ice Sheet, as modeled using a regional atmospheric climate model, to various parameter settings in the albedo parameterization. The snow albedo parameterization uses grain size as a prognostic variable and further depends on cloud cover, solar zenith angle and black carbon concentration. For the control experiment the overestimation of absorbed shortwave radiation (+6 % at the K-transect (West Greenland for the period 2004–2009 is considerably reduced compared to the previous density-dependent albedo parameterization (+22 %. To simulate realistic snow albedo values, a small concentration of black carbon is needed. A background ice albedo field derived from MODIS imagery improves the agreement between the modeled and observed SMB gradient along the K-transect. The effect of enhanced retention and refreezing is a decrease of the albedo due to an increase in snow grain size. As a secondary effect of refreezing the snowpack is heated, enhancing melt and further lowering the albedo. Especially in a warmer climate this process is important, since it reduces the refreezing potential of the firn layer covering the Greenland Ice Sheet.

  13. Satellite observations of changes in snow-covered land surface albedo during spring in the Northern Hemisphere

    Directory of Open Access Journals (Sweden)

    K. Atlaskina

    2015-05-01

    Full Text Available Thirteen years of MODIS surface albedo data for the Northern Hemisphere during the spring months (March–May were analysed to determine temporal and spatial changes over snow-covered land surfaces. Tendencies in land surface albedo change north of 50° N were analysed using data on snow cover fraction, air temperature, vegetation index and precipitation. To this end, the study domain was divided into six smaller areas, based on their geographical position and climate similarity. Strong differences were observed between these areas. As expected, snow cover fraction (SCF has a strong influence on the albedo in the study area and can explain 56% of variation of albedo in March, 76% in April and 92% in May. Therefore the effects of other parameters were investigated only for areas with 100% SCF. The second largest driver for snow-covered land surface albedo changes is the air temperature when it exceeds −15 °C. At monthly mean air temperatures below this value no albedo changes are observed. Enhanced vegetation index (EVI and precipitation amount and frequency were independently examined as possible candidates to explain observed changes in albedo for areas with 100% SCF. Amount and frequency of precipitation were identified to influence the albedo over some areas in Eurasia and North America, but no clear effects were observed in other areas. EVI is positively correlated with albedo in Chukotka Peninsula and negatively in Eastern Siberia. For other regions the spatial variability of the correlation fields is too high to reach any conclusions.

  14. Spectral albedo of seasonal snow during intensive melt period at Sodankylä, beyond the Arctic Circle

    Directory of Open Access Journals (Sweden)

    O. Meinander

    2013-04-01

    Full Text Available We have measured spectral albedo, as well as ancillary parameters, of seasonal European Arctic snow at Sodankylä, Finland (67°22' N, 26°39' E. The springtime intensive melt period was observed during the Snow Reflectance Transition Experiment (SNORTEX in April 2009. The upwelling and downwelling spectral irradiance, measured at 290–550 nm with a double monochromator spectroradiometer, revealed albedo values of ~0.5–0.7 for the ultraviolet and visible range, both under clear sky and variable cloudiness. During the most intensive snowmelt period of four days, albedo decreased from 0.65 to 0.45 at 330 nm, and from 0.72 to 0.53 at 450 nm. In the literature, the UV and VIS albedo for clean snow are ~0.97–0.99, consistent with the extremely small absorption coefficient of ice in this spectral region. Our low albedo values were supported by two independent simultaneous broadband albedo measurements, and simulated albedo data. We explain the low albedo values to be due to (i large snow grain sizes up to ~3 mm in diameter; (ii meltwater surrounding the grains and increasing the effective grain size; (iii absorption caused by impurities in the snow, with concentration of elemental carbon (black carbon in snow of 87 ppb, and organic carbon 2894 ppb, at the time of albedo measurements. The high concentrations of carbon, detected by the thermal–optical method, were due to air masses originating from the Kola Peninsula, Russia, where mining and refining industries are located.

  15. Effect of satellite formations and imaging modes on global albedo estimation

    Science.gov (United States)

    Nag, Sreeja; Gatebe, Charles K.; Miller, David W.; de Weck, Olivier L.

    2016-05-01

    We confirm the applicability of using small satellite formation flight for multi-angular earth observation to retrieve global, narrow band, narrow field-of-view albedo. The value of formation flight is assessed using a coupled systems engineering and science evaluation model, driven by Model Based Systems Engineering and Observing System Simulation Experiments. Albedo errors are calculated against bi-directional reflectance data obtained from NASA airborne campaigns made by the Cloud Absorption Radiometer for the seven major surface types, binned using MODIS' land cover map - water, forest, cropland, grassland, snow, desert and cities. A full tradespace of architectures with three to eight satellites, maintainable orbits and imaging modes (collective payload pointing strategies) are assessed. For an arbitrary 4-sat formation, changing the reference, nadir-pointing satellite dynamically reduces the average albedo error to 0.003, from 0.006 found in the static referencecase. Tracking pre-selected waypoints with all the satellites reduces the average error further to 0.001, allows better polar imaging and continued operations even with a broken formation. An albedo error of 0.001 translates to 1.36 W/m2 or 0.4% in Earth's outgoing radiation error. Estimation errors are found to be independent of the satellites' altitude and inclination, if the nadir-looking is changed dynamically. The formation satellites are restricted to differ in only right ascension of planes and mean anomalies within slotted bounds. Three satellites in some specific formations show average albedo errors of less than 2% with respect to airborne, ground data and seven satellites in any slotted formation outperform the monolithic error of 3.6%. In fact, the maximum possible albedo error, purely based on angular sampling, of 12% for monoliths is outperformed by a five-satellite formation in any slotted arrangement and an eight satellite formation can bring that error down four fold to 3%. More than

  16. Changes in Snow Albedo Resulting from Snow Darkening Caused by Black Carbon

    Science.gov (United States)

    Engels, J.; Kloster, S.; Bourgeois, Q.

    2014-12-01

    We investigate the potential impact of snow darkening caused by pre-industrial and present-day black carbon (BC) emissions on snow albedo and subsequently climate. To assess this impact, we implemented the effect of snow darkening caused by BC emitted from natural as well as anthropogenic sources into the Max Planck Institute for Meteorology Earth System Model (MPI-M ESM). Considerable amounts of BC are emitted e.g. from fires and are transported through the atmosphere for several days before being removed by rain or snow precipitation in snow covered regions. Already very small quantities of BC reduce the snow reflectance significantly, with consequences for snow melting and snow spatial coverage. We implemented the snow albedo reduction caused by BC contamination and snow aging in the one layer land surface component (JSBACH) of the atmospheric general circulation model ECHAM6, developed at MPI-M. For this we used the single-layer simulator of the SNow, Ice, and Aerosol Radiation (SNICAR-Online (Flanner et al., 2007); http://snow.engin.umich.edu) model to derive snow albedo values for BC in snow concentrations ranging between 0 and 1500 ng(BC)/g(snow) for different snow grain sizes for the visible (0.3 - 0.7 μm) and near infrared range (0.7 - 1.5 μm). As snow grains grow over time, we assign different snow ages to different snow grain sizes (50, 150, 500, and 1000 μm). Here, a radius of 50 μm corresponds to new snow, whereas a radius of 1000 μm corresponds to old snow. The deposition rates of BC on snow are prescribed from previous ECHAM6-HAM simulations for two time periods, pre-industrial (1880-1889) and present-day (2000-2009), respectively. We perform a sensitivity study regarding the scavenging of BC by snow melt. To evaluate the newly implemented albedo scheme we will compare the modeled black carbon in snow concentrations to observed ones. Moreover, we will show the impact of the BC contamination and snow aging on the simulated snow albedo. The

  17. A Model for the Spectral Albedo of Snow. II: Snow Containing Atmospheric Aerosols.

    Science.gov (United States)

    Warren, Stephen G.; Wiscombe, Warren J.

    1980-12-01

    Small highly absorbing particles, present in concentrations of only 1 part per million by weight (ppmw) or less, can lower snow albedo in the visible by 5-15% from the high values (96-99%) predicted for pure snow in Part I. These particles have, however, no effect on snow albedo beyond 0.9 m wavelength where ice itself becomes a strong absorber. Thus we have an attractive explanation for the discrepancy between theory and observation described in Part I, a discrepancy which seemingly cannot be resolved on the basis of near-field scattering and nonsphericity effects.Desert dust and carbon soot are the most likely contaminants. But careful measurements of spectral snow albedo in the Arctic and Antarctic paint to a `grey' absorber, one whose imaginary refractive index is nearly constant across the visible spectrum. Thus carbon soot, rather than the red iron oxide normally present in desert dust, is strongly indicated at these sites. Soot particles of radius 0.1 m, in concentrations of only 0.3 ppmw, can explain the albedo measurements of Grenfell and Maykut on Arctic Ice Island T-3. This amount is consistent with some observations of soot in Arctic air masses. 1.5 ppmw of soot is required to explain the Antarctic observations of Kuhn and Siogas, which seemed an unrealistically large amount for the earth's most unpolluted continent until we learned that burning of camp heating fuel and aircraft exhaust indeed had contaminated the measurement site with soot.Midlatitude snowfields are likely to contain larger absolute amounts of soot and dust than their polar counterparts, but the snowfall is also much larger, so that the ppmw contamination does not differ drastically until melting begins. Nevertheless, the variations in absorbing particle concentration which will exist can help to explain the wide range of visible snow albedos reported in the literature.Longwave emissivity of snow is unaltered by its soot and dust content. Thus the depression of snow albedo in the

  18. Global land surface albedo maps from MODIS using the Google Earth Engine

    Science.gov (United States)

    Mitraka, Zina; Benas, Nikolaos; Gorelick, Noel; Chrysoulakis, Nektarios

    2016-04-01

    The land surface albedo (LSA) is a critical physical variable, which influences the Earth's climate by affecting the energy budget and distribution in the Earth-atmosphere system. Its role is highly significant in both global and local scales; hence, LSA measurements provide a quantitative means for better constraining global and regional scale climate modelling efforts. The Moderate Resolution Imaging Spectroradiometer (MODIS) sensor, on board NASA's Terra and Aqua platforms, provides the parameters needed for the computation of LSA on an 8-day temporal scale and a variety of spatial scales (ranging between 0.5 - 5 km). This dataset was used here for the LSA estimation and its changes over the study area at 0.5 km spatial resolution. More specifically, the MODIS albedo product was used, which includes both the directional-hemispherical surface reflectance (black-sky albedo) and the bi-hemispherical surface reflectance (white-sky albedo). The LSA was estimated for the whole globe on an 8-day basis for the whole time period covered by MODIS acquisitions (i.e. 2000 until today). To estimate LSA from black-sky and white-sky albedos, the fraction of the diffused radiation is needed, a function of the Aerosol Optical Thickness (AOT). Required AOT information was acquired from the MODIS AOT product at 1̊ × 1̊ spatial resolution. Since LSA also depends on solar zenith angle (SZA), 8-day mean LSA values were computed as averages of corresponding LSA values for representative SZAs covering the 24-hour day. The estimated LSA was analysed in terms of both spatial and seasonal characteristics, while LSA changes during the period examined were assessed. All computation were performed using the Google Earth Engine (GEE). The GEE provided access to all the MODIS products needed for the analysis without the need of searching or downloading. Moreover, the combination of MODIS products in both temporal and spatial terms was fast and effecting using the GEE API (Application

  19. Analytic expressions for the black-sky and white-sky albedos of the cosine lobe model.

    Science.gov (United States)

    Goodin, Christopher

    2013-05-01

    The cosine lobe model is a bidirectional reflectance distribution function (BRDF) that is commonly used in computer graphics to model specular reflections. The model is both simple and physically plausible, but physical quantities such as albedo have not been related to the parameterization of the model. In this paper, analytic expressions for calculating the black-sky and white-sky albedos from the cosine lobe BRDF model with integer exponents will be derived, to the author's knowledge for the first time. These expressions for albedo can be used to place constraints on physics-based simulations of radiative transfer such as high-fidelity ray-tracing simulations.

  20. Self-similarity Based Editing of 3D Surface Textures Using Height and Albedo Maps

    Institute of Scientific and Technical Information of China (English)

    DONG Junyu; REN Jing; CHEN Guojiang

    2007-01-01

    This paper presents an inexpensive method for self-similarity based editing of real-world 3D surface textures by using height and albedo maps. Unlike self-similarity based 2D texture editing approaches which only make changes to pixel color or intensity values, this technique also allows surface geometry and reflectance of the captured 3D surface textures to be edited and relit using illumination conditions and viewing angles that differ from those of the original. A single editing operation at a given location affects all similar areas and produces changes on all images of the sample rendered under different conditions. Since surface height and albedo maps can be used to describe seabed topography and geologic features, which play important roles in many oceanic processes, the proposed method can be effectively employed in applications regarding visualization and simulation of oceanic phenomena.

  1. Analysis of an Arctic sea ice loss model in the limit of a discontinuous albedo

    CERN Document Server

    Hill, Kaitlin; Silber, Mary

    2015-01-01

    As Arctic sea ice extent decreases with increasing greenhouse gases, there is a growing interest in whether there could be a bifurcation associated with its loss, and whether there is significant hysteresis associated with that bifurcation. A challenge in answering this question is that the bifurcation behavior of certain Arctic energy balance models have been shown to be sensitive to how ice-albedo feedback is parameterized. We analyze an Arctic energy balance model in the limit as a smoothing parameter associated with ice-albedo feedback tends to zero, which makes the system piecewise-smooth. Our analysis provides a case study where we use the piecewise-smooth system to explore bifurcation behavior of the smooth system. In this case study, we demonstrate that certain qualitative bifurcation behaviors of the smooth system can have nonsmooth counterparts. We use this perspective to systematically search parameter space. For example, we uncover parameter sets for which the largest transition, with increasing g...

  2. Biogenic CO2 emissions, changes in surface albedo, and biodiversity impacts from establishment of miscanthus plantation

    DEFF Research Database (Denmark)

    Jørgensen, Susanne Vedel; Cherubini, F.; Michelsen, O.

    as feedstock. Miscanthus has been chosen as feedstock in this study, as current studies suggest that it has a promising potential, being advantageous in several environmental impact categories. However many current studies do not include assessment in impacts such as soil organic carbon change, biodiversity...... and the effect of albedo change on global warming impacts, when miscanthus production takes over from a former land use. The aim of this study is to assess those impacts of miscanthus production, when changing from a former land use of either forest or fallow land in Wisconsin, US. Results from this study show...... that there are large differences between impacts in the two land use change scenarios, using former forest land or former fallow land for miscanthus production. It is shown how the albedo impact has greater impact on global warming potential over time than the change in carbon balance below and above ground in those...

  3. Survey of TES high albedo events in Mars' northern polar craters

    Science.gov (United States)

    Armstrong, J.C.; Nielson, S.K.; Titus, T.N.

    2007-01-01

    Following the work exploring Korolev Crater (Armstrong et al., 2005) for evidence of crater interior ice deposits, we have conducted a survey of Thermal Emission Spectroscopy (TES) temperature and albedo measurements for Mars' northern polar craters larger than 10 km. Specifically, we identify a class of craters that exhibits brightening in their interiors during a solar longitude, Ls, of 60 to 120 degrees, roughly depending on latitude. These craters vary in size, latitude, and morphology, but appear to have a specific regional association on the surface that correlates with the distribution of subsurface hydrogen (interpreted as water ice) previously observed on Mars. We suggest that these craters, like Korolev, exhibit seasonal high albedo frost events that indicate subsurface water ice within the craters. A detailed study of these craters may provide insight in the geographical distribution of the ice and context for future polar missions. Copyright 2007 by the American Geophysical Union.

  4. The Sun among stars. IV - Albedos of Uranus and Neptune and the solar color

    Science.gov (United States)

    Hardorp, J.

    1981-01-01

    Geometric albedos in 48 adjacent 50 A bands from 3250 to 5600 A have been derived from observations of Uranus and Neptune. The solar analog found in earlier papers (Hardorp 1978, 1980) was chosen for these reductions, so these albedos are more reliable systematically than earlier ones and allow a choice among the scattering models of Savage et al. (1980). Green methane bands are stronger on Neptune. Strong solar absorption lines are found to be partially filled in by Raman-scattering. Neglect of this effect caused Croft et al. (1972) to find a solar color that is too blue. It probably also affected the classification of G-type stars in the Michigan Spectral Catalogue as well as Garrison's (1979) interpretation of IUE observations.

  5. SAS 2 observations of the earth albedo gamma radiation above 35 MeV

    Science.gov (United States)

    Thompson, D. J.; Simpson, G. A.; Ozel, M. E.

    1981-01-01

    The earth albedo gamma radiation above 35 MeV in the equatorial region is investigated using observations from the second Small Astronomy Satellite. The zenith angle distribution of the gamma radiation has a peak toward the horizon which is about an order of magnitude more intense than the radiation coming from the nadir, and nearly two orders of magnitude more intense than the gamma radiation from most parts of the sky. The gamma radiation originating from the western horizon is a factor of four more intense than the radiation from the eastern horizon and a factor of three more intense than that from the northern and southern directions. This reflects the geomagnetic effects on the incident cosmic rays whose interactions produce the albedo gamma rays. The variation of the upcoming gamma ray intensity with vertical cutoff rigidity is consistent with the empirical relationship found by Gur'yan et al. (1979).

  6. Incorporating changes in albedo in estimating the climate mitigation benefits of land use change projects

    OpenAIRE

    Bird, D. N.; Kunda, M.; Mayer, A.; Schlamadinger, B.; Canella, L.; Johnston, M.

    2008-01-01

    Some climate scientists are questioning whether the practice of converting of non-forest lands to forest land (afforestation or reforestation) is an effective climate change mitigation option. The discussion focuses particularly on areas where the new forest is primarily coniferous and there is significant amount of snow since the increased climate forcing due to the change in albedo may counteract the decreased climate forcing due to carbon dioxide removal.

    In this pape...

  7. Variation in Foliar Nitrogen and Albedo in Response to Elevated Nitrogen and Carbon Dioxide

    Science.gov (United States)

    Wicklein, H. F.; Ollinger, S. V.; Martin, M. M.; Hollinger, D. Y.; Bartlett, M. K.; Richardson, A. D.

    2010-12-01

    It has recently been demonstrated that foliar nitrogen (N) is positively correlated with midsummer canopy albedo over a broad range of plant functional types. However, the mechanism(s) driving the N- albedo relationship remain elusive, and it is unknown whether factors affecting N availability will also influence albedo. To address these questions, we investigated leaf spectral properties from three deciduous broadleaf species subjected to either N (Harvard Forest, MA and Oak Ridge, TN) or CO2 fertilization (Oak Ridge, TN), and compared results to measured chemical and structural properties. We measured reflectance and transmittance along with foliar N, leaf mass per unit area, and water content for stacks of 1, 2, 4, and 8 leaves. For the Oak Ridge, TN site, we also obtained canopy reflectance data from the airborne visible / infrared imaging spectrometer (AVIRIS) to examine whether canopy level spectral responses were consistent with leaf-level results. At the leaf level, results showed no significant differences in reflectance or transmittance between CO2 or N treatments, despite changes in N concentration caused by N fertilization. Although foliar N was significantly correlated with leaf shortwave and near infrared reflectance across species, the slope of both relationships was negative, which ran counter to our expectations. These results do not support the hypothesis that the canopy-level pattern is driven by leaf-level relationships. In contrast to leaf-level observations, remote sensing data from Oak Ridge did indicate an increase in NIR reflectance with N fertilization. Collectively, these results suggest that altered N availability may have an effect on canopy albedo, albeit by mechanisms that involve stem or canopy level processes rather than changes in leaf structure.

  8. Generation of albedo neutrons in hadron-nucleus interactions at TeV energies

    Energy Technology Data Exchange (ETDEWEB)

    Avakyan, V.V.; Babayan, V.K.; Mamidzhanyan, E.A.; Mirzoyan, T.G.; Muradyan, M.M.; Oganyan, G.Z. (Erevan Physics Institute (SU))

    1989-09-01

    The generation in {ital hA} interactions of neutrons emitted at an angle {theta}{gt}90{degree} relative to the direction of the primary hadron has been confirmed experimentally. The experiment was carried out in the Pion apparatus supplemented by a neutron detector above a target of lead and iron. Measurements of the multiplicity and energy spectrum of albedo neutrons at TeV energies of the primary hadron are reported.

  9. A model-based framework for the quality assessment of surface albedo in situ measurement protocols

    Science.gov (United States)

    Adams, Jennifer; Gobron, Nadine; Widlowski, Jean-Luc; Mio, Corrado

    2016-09-01

    Satellite-based retrievals of land surface albedo are essential for climate and environmental modelling communities. To be of use, satellite-retrievals are required to comply to given accuracy requirements, mainly achieved through comparison with in situ measurements. Differences between in situ and satellite-based retrievals depend on their actual difference and their associated uncertainties. It is essential that these uncertainties can be computed to properly understand the differences between satellite-based and in situ measurements of albedo, however quantifying the individual contributions of uncertainty is difficult. This study introduces a model-based framework for assessing the quality of in situ albedo measurements. A 3D Monte Carlo Ray Tracing (MCRT) radiative transfer model is used to simulate field measurements of surface albedo, and is able to identify and quantify potential sources of error in the field measurement. Compliance with the World Meteorological Organisation (WMO) requirement for 3% accuracy is tested. 8 scenarios were investigated, covering a range of ecosystem types and canopy structures, seasons, illumination angles and tree heights. Results indicate that height of measurement above the canopy is the controlling factor in accuracy, with each canopy scenario reaching the WMO requirement at different heights. Increasing canopy heterogeneity and tree height noticeably reduces the accuracy, whereas changing seasonality from summer to winter in a deciduous forest increases accuracy. For canopies with a row structure, illumination angle can significantly impact accuracy as a result of shadowing effects. Tests were made on the potential use of multiple in situ measurements, indicating considerably increased accuracy if two or more in situ measurements can be made.

  10. Accounting for radiative forcing from albedo change in future global land-use scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Andrew D. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Calvin, Katherine V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Collins, William D. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Edmonds, James A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-08-01

    We demonstrate the effectiveness of a new method for quantifying radiative forcing from land use and land cover change (LULCC) within an integrated assessment model, the Global Change Assessment Model (GCAM). The method relies on geographically differentiated estimates of radiative forcing from albedo change associated with major land cover transitions derived from the Community Earth System Model. We find that conversion of 1 km² of woody vegetation (forest and shrublands) to non-woody vegetation (crops and grassland) yields between 0 and –0.71 nW/m² of globally averaged radiative forcing determined by the vegetation characteristics, snow dynamics, and atmospheric radiation environment characteristic within each of 151 regions we consider globally. Across a set of scenarios designed to span a range of potential future LULCC, we find LULCC forcing ranging from –0.06 to –0.29 W/m² by 2070 depending on assumptions regarding future crop yield growth and whether climate policy favors afforestation or bioenergy crops. Inclusion of this previously uncounted forcing in the policy targets driving future climate mitigation efforts leads to changes in fossil fuel emissions on the order of 1.5 PgC/yr by 2070 for a climate forcing limit of 4.5 Wm–2, corresponding to a 12–67 % change in fossil fuel emissions depending on the scenario. Scenarios with significant afforestation must compensate for albedo-induced warming through additional emissions reductions, and scenarios with significant deforestation need not mitigate as aggressively due to albedo-induced cooling. In all scenarios considered, inclusion of albedo forcing in policy targets increases forest and shrub cover globally.

  11. Climate warming feedback from mountain birch forest expansion: reduced albedo dominates carbon uptake.

    Science.gov (United States)

    de Wit, Heleen A; Bryn, Anders; Hofgaard, Annika; Karstensen, Jonas; Kvalevåg, Maria M; Peters, Glen P

    2014-07-01

    Expanding high-elevation and high-latitude forest has contrasting climate feedbacks through carbon sequestration (cooling) and reduced surface reflectance (warming), which are yet poorly quantified. Here, we present an empirically based projection of mountain birch forest expansion in south-central Norway under climate change and absence of land use. Climate effects of carbon sequestration and albedo change are compared using four emission metrics. Forest expansion was modeled for a projected 2.6 °C increase in summer temperature in 2100, with associated reduced snow cover. We find that the current (year 2000) forest line of the region is circa 100 m lower than its climatic potential due to land-use history. In the future scenarios, forest cover increased from 12% to 27% between 2000 and 2100, resulting in a 59% increase in biomass carbon storage and an albedo change from 0.46 to 0.30. Forest expansion in 2100 was behind its climatic potential, forest migration rates being the primary limiting factor. In 2100, the warming caused by lower albedo from expanding forest was 10 to 17 times stronger than the cooling effect from carbon sequestration for all emission metrics considered. Reduced snow cover further exacerbated the net warming feedback. The warming effect is considerably stronger than previously reported for boreal forest cover, because of the typically low biomass density in mountain forests and the large changes in albedo of snow-covered tundra areas. The positive climate feedback of high-latitude and high-elevation expanding forests with seasonal snow cover exceeds those of afforestation at lower elevation, and calls for further attention of both modelers and empiricists. The inclusion and upscaling of these climate feedbacks from mountain forests into global models is warranted to assess the potential global impacts.

  12. Clear-Sky Narrowband Albedo Variations Derived from VIRS and MODIS Data

    Science.gov (United States)

    Sun-Mack, Sunny; Chen, Yan; Arduini, Robert F.; Minnis, Patrick

    2004-01-01

    A critical parameter for detecting clouds and aerosols and for retrieving their microphysical properties is the clear-sky radiance. The Clouds and the Earth's Radiant Energy System (CERES) Project uses the visible (VIS; 0.63 m) and near-infrared (NIR; 1.6 or 2.13 m) channels available on same satellites as the CERES scanners. Another channel often used for cloud and aerosol, and vegetation cover retrievals is the vegetation (VEG; 0.86- m) channel that has been available on the Advanced Very High Resolution Radiometer (AVHRR) for many years. Generally, clear-sky albedo for a given surface type is determined for conditions when the vegetation is either thriving or dormant and free of snow. Snow albedo is typically estimated without considering the underlying surface type. The albedo for a surface blanketed by snow, however, should vary with surface type because the vegetation often emerges from the snow to varying degrees depending on the vertical dimensions of the vegetation. For example, a snowcovered prairie will probably be brighter than a snowcovered forest because the snow typically falls off the trees exposing the darker surfaces while the snow on a grassland at the same temperatures will likely be continuous and, therefore, more reflective. Accounting for the vegetation-induced differences should improve the capabilities for distinguishing snow and clouds over different surface types and facilitate improvements in the accuracy of radiative transfer calculations between the snow-covered surface and the atmosphere, eventually leading to improvements in models of the energy budgets over land. This paper presents a more complete analysis of the CERES spectral clear-sky reflectances to determine the variations in clear-sky top-of-atmosphere (TOA) albedos for both snow-free and snow-covered surfaces for four spectral channels using data from Terra and Aqua.. The results should be valuable for improved cloud retrievals and for modeling radiation fields.

  13. Possibility for albedo estimation of exomoons: Why should we care about M dwarfs?

    Science.gov (United States)

    Dobos, Vera; Kereszturi, Ákos; Pál, András; Kiss, László L.

    2016-08-01

    Occultation light curves of exomoons may give information on the exomoons' albedo and hence indicate the presence of ice cover on the surface. Icy moons might have subsurface oceans, and thus may potentially be habitable. The objective of our paper is to determine whether next generation telescopes will be capable of albedo estimations for icy exomoons using their occultation light curves. The success of the measurements depends on the depth of the moon's occultation in the light curve and on the sensitivity of the used instruments. We applied simple calculations for different stellar masses in the V and J photometric bands, and compared the flux drop caused by the moon's occultation and the estimated photon noise of next generation missions with 5σ confidence. We found that albedo estimation by this method is not feasible for moons of solar-like stars, but small M dwarfs are better candidates for such measurements. Our calculations in the J photometric band show that E-ELT MICADO's photon noise is just about 4 ppm greater than the flux difference caused by an icy satellite twice the Earth's radius in a circular orbit at the snowline of an 0.1 stellar mass star. However, considering only photon noise underestimates the real expected noise, because other noise sources, such as CCD read-out and dark signal become significant in the near-infrared measurements. Hence we conclude that occultation measurements with next generation missions are far too challenging, even in the case of large, icy moons at the snowline of small M dwarfs. We also discuss the role of the parameters that were neglected in the calculations, for example inclination, eccentricity, orbiting direction of the moon. We predict that the first albedo estimations of exomoons will probably be made for large icy moons around the snowline of M4 - M9 type main sequence stars.

  14. Light curves, Spherical and Bond albedos of Jupiter, Saturn, and exoplanets.

    Science.gov (United States)

    Dyudina, U.

    2015-12-01

    We estimate how the light curve and stellar light reflection of a planet depends on forward and backward scattering, which was observed on Jupiter and Saturn. We fit analytical scattering phase function to Pioneer 10 and 11 spacecraft observations of Jupiter at 0.64 μm and Saturn at 0.64 and 0.44 μm and to Cassini spacecraft observations of Jupiter at 0.938 μm atmospheric window, 0.889 μm CH4 absorption band, and 0.258 μm UV filter. Using scattering ray-tracing model of a planet by Dyudina et al. (2005)*, the images of the planets with different scattering properties are simulated to calculate the reflected luminosity as it varies with scattering phase to produce full-orbit light curves. We compare the light curve shapes and total reflection integrated in all directions (spherical albedos) for Jupiter and Saturn with the ones for planets with Lambertian and semi-infinite Rayleigh-scattering atmosphere. Saturn-like and especially Jupiter-like atmosphere produces light curves that are several times fainter at half-phase than does a Lambertian planet, given the same brightness at transit. The spherical albedo (and hence the wavelengh-integrated Bond albedo) is lower than for a Lambertian planet. Corresponding absorption of the stellar light and planet's heating rate would be higher than estimated for Lambertian planets, especially for bright planets. In extreme case of Jupiter-like scattering at 0.64 μm Lambertian assumption can overestimate spherical albedo by a factor of ˜1.5. We will discuss how the light curves and absorption for planets covered by atmospheres would differ from the light curves of rocky planet without atmosphere. * Dyudina, U. A., et al., Phase Light Curves for Extrasolar Jupiters and Saturns. ApJ, 618, 973-986, 2005

  15. Rectified Asteroid Albedos and Diameters from IRAS and MSX Photometry Catalogs

    Science.gov (United States)

    Ryan, Erin Lee; Woodward, Charles E.

    2010-10-01

    Rectified diameters and albedo estimates of 1517 main-belt asteroids selected from IRAS and the Mid-Course Space Experiment asteroid photometry catalogs are derived from updated infrared thermal models, the Standard Thermal Model and the Near-Earth Asteroid Thermal Model (NEATM), and Monte Carlo simulations, using new Minor Planet Center compilations of absolute magnitudes (H values) constrained by occultation- and radar-derived parameters. The NEATM approach produces a more robust estimate of albedos and diameters, yielding albedos of pv (NEATM mean) =0.081 ± 0.064. The asteroid beaming parameter (η) for the selected asteroids has a mean value of 1.07 ± 0.27, and the smooth distribution of η suggests that this parameter is independent of asteroid properties such as composition. No trends in η due to size-dependent rotation rates are evident. Comparison of derived values of η as a function of taxonomic type indicates that the beaming parameter values for S- and C-type asteroids are identical within the standard deviation of the population of beaming parameters.

  16. Cellulose nanocrystal from pomelo (C. Grandis osbeck) albedo: Chemical, morphology and crystallinity evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Zain, Nor Fazelin Mat; Yusop, Salma Mohamad [Food Science Program, School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Selangor (Malaysia); Ahmad, Ishak [Polymer Research Centre (PORCE), School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Selangor (Malaysia)

    2013-11-27

    Citrus peel is one of the under-utilized waste materials that have potential in producing a valuable fibre, which are cellulose and cellulose nanocrystal. Cellulose was first isolated from pomelo (C. Grandis Osbeck) albedo by combination of alkali treatment and bleaching process, followed by acid hydrolysis (65% H{sub 2}SO{sub 4}, 45 °C, 45min) to produce cellulose nanocrystal. The crystalline, structural, morphological and chemical properties of both materials were studied. Result reveals the crystallinity index obtained from X-ray diffraction for cellulose nanocrystal was found higher than extracted cellulose with the value of 60.27% and 57.47%, respectively. Fourier transform infrared showed that the chemical treatments removed most of the hemicellulose and lignin from the pomelo albedo fibre. This has been confirmed further by SEM and TEM for their morphological studies. These results showed that cellulose and cellulose nanocrystal were successfully obtained from pomelo albedo and might be potentially used in producing functional fibres for food application.

  17. Modulation of ice ages via precession and dust-albedo feedbacks

    Institute of Scientific and Technical Information of China (English)

    Ralph Ellis; Michael Palmer

    2016-01-01

    We present here a simple and novel proposal for the modulation and rhythm of ice-ages and interglacials during the late Pleistocene. While the standard Milankovitch-precession theory fails to explain the long intervals between interglacials, these can be accounted for by a novel forcing and feedback system involving CO2, dust and albedo. During the glacial period, the high albedo of the northern ice sheets drives down global temperatures and CO2 concentrations, despite subsequent precessional forcing maxima. Over the following millennia more CO2 is sequestered in the oceans and atmospheric con-centrations eventually reach a critical minima of about 200 ppm, which combined with arid conditions, causes a die-back of temperate and boreal forests and grasslands, especially at high altitude. The ensuing soil erosion generates dust storms, resulting in increased dust deposition and lower albedo on the northern ice sheets. As northern hemisphere insolation increases during the next Milankovitch cycle, the dust-laden ice-sheets absorb considerably more insolation and undergo rapid melting, which forces the climate into an interglacial period. The proposed mechanism is simple, robust, and comprehensive in its scope, and its key elements are well supported by empirical evidence.

  18. Contributing factors to an enhanced ice albedo feedback in Arctic sea ice

    Science.gov (United States)

    Perovich, D. K.; Jones, K. F.; Light, B.; Holland, M. M.

    2012-12-01

    The Arctic sea ice cover is in decline. In recent years there has been a decrease in summer ice area; a thinning of the ice cover; an increase in the amount of seasonal ice; an earlier onset of summer melt; and a later start of fall freeze up. Decreases in ice concentration substantially increase solar heat input to the ocean. Earlier dates of melt onset reduce ice albedo during a period when incident solar irradiance is large increasing solar heat input to the ice. Seasonal sea ice typically has a smaller albedo than perennial ice throughout the melt season. Thus, the observed shift to a seasonal ice cover causes greater solar heat input to the ice and more melting thereby accelerating ice decay. Thinner ice results in greater transmission of solar heat to the upper ocean, where it contributes to bottom melting, lateral melting, and warming of the water. All of these changes enhance the amount of solar energy deposited in the ice ocean system, and increasing ice melt. We will examine the relative magnitude of each of these changes individually as well as their collective contribution to the ice albedo feedback.

  19. Possibility for albedo estimation of exomoons: Why should we care about M dwarfs?

    CERN Document Server

    Dobos, Vera; Pál, András; Kiss, László L

    2016-01-01

    Occultation light curves of exomoons may give information on their albedo and hence indicate the presence of ice cover on the surface. Icy moons might have subsurface oceans thus these may potentially be habitable. The objective of our paper is to determine whether next generation telescopes will be capable of albedo estimations for icy exomoons using their occultation light curves. The success of the measurements depends on the depth of the moon's occultation in the light curve and on the sensitivity of the used instruments. We applied simple calculations for different stellar masses in the V and J photometric bands, and compared the flux drop caused by the moon's occultation and the estimated photon noise of next generation missions with 5 $\\sigma$ confidence. We found that albedo estimation by this method is not feasible for moons of solar-like stars, but small M dwarfs are better candidates for such measurements. Our calculations in the J photometric band show that E-ELT MICADO's photon noise is just abou...

  20. Land surface albedo and vegetation feedbacks enhanced the millennium drought in south-east Australia

    Science.gov (United States)

    Evans, Jason P.; Meng, Xianhong; McCabe, Matthew F.

    2017-01-01

    In this study, we have examined the ability of a regional climate model (RCM) to simulate the extended drought that occurred throughout the period of 2002 through 2007 in south-east Australia. In particular, the ability to reproduce the two drought peaks in 2002 and 2006 was investigated. Overall, the RCM was found to reproduce both the temporal and the spatial structure of the drought-related precipitation anomalies quite well, despite using climatological seasonal surface characteristics such as vegetation fraction and albedo. This result concurs with previous studies that found that about two-thirds of the precipitation decline can be attributed to the El Niño-Southern Oscillation (ENSO). Simulation experiments that allowed the vegetation fraction and albedo to vary as observed illustrated that the intensity of the drought was underestimated by about 10 % when using climatological surface characteristics. These results suggest that in terms of drought development, capturing the feedbacks related to vegetation and albedo changes may be as important as capturing the soil moisture-precipitation feedback. In order to improve our modelling of multi-year droughts, the challenge is to capture all these related surface changes simultaneously, and provide a comprehensive description of land surface-precipitation feedback during the droughts development.

  1. Solar sail equilibria with albedo radiation pressure in the circular restricted three-body problem

    Science.gov (United States)

    Grøtte, Mariusz E.; Holzinger, Marcus J.

    2017-02-01

    Solar Radiation Pressure (SRP) and albedo effects are investigated in the circular restricted three-body problem for a system consisting of the Sun, a reflective minor body and a solar sail. As an approximation of albedo radiation pressure (ARP), the minor body is treated as Lambertian with reflected flux scattered by the bidirectional reflectance distribution function. Incorporating ARP, which is a function of SRP, into the solar sail equations of motion renders additional artificial equilibrium points in a volume between the L1 and L2 points which is defined as the region of influence. Based on the model, characterization of the findings are provided that are theoretically applicable to any body with discernible albedo such as for instance Earth, Mars or an asteroid. Example results are presented for a Sun-Vesta system which show that the inclusion of ARP generates artificial equilibrium points requiring solar sail designs with very low mass-to-area ratio. The equilibrium points are found to be unstable in general but asymptotic stability may be enforced with sail attitude feedback control.

  2. Spatiotemporal NDVI, LAI, albedo, and surface temperature dynamics in the southwest of the Brazilian Amazon forest

    Science.gov (United States)

    Querino, Carlos Alexandre Santos; Beneditti, Cristina Aparecida; Machado, Nadja Gomes; da Silva, Marcelo José Gama; da Silva Querino, Juliane Kayse Albuquerque; dos Santos Neto, Luiz Alves; Biudes, Marcelo Sacardi

    2016-04-01

    During the last decades, the Amazon rainforest underwent uncontrolled exploitation that modified its environmental variables. The current paper analyzes the spatiotemporal dynamics of the normalized difference vegetation index (NDVI), leaf area index (LAI), and surface albedo, and temperature in two different vegetation covers, preserved and deforested areas. We calculated the remote-sensing products using Landsat 5 TM images obtained during the dry season 1984, 1991, 2000, and 2011 of the central region of the State of Rondônia, Brazil. The results showed a reduction of vegetation indexes NDVI (˜0.70 in 1984 to ˜0.27 in 2011) and LAI (˜1.8 in 1984 to ˜0.3 in 2011), with an increase of surface albedo (0.12 in 1984 to 0.20 in 2011) and temperature (˜24°C in 1984 to 30°C in 2011) as the effect of the rainforest converted in grassland during the study period. No changes in any variables were observed in the protected area. Forest conversion into grassland resulted in a decrease of 69% in NDVI and 110% in LAI and a rise of 59% and 24% in albedo and surface temperature, respectively.

  3. Land surface albedo and vegetation feedbacks enhanced the millennium drought in south-east Australia

    KAUST Repository

    Evans, Jason P.

    2017-01-24

    In this study, we have examined the ability of a regional climate model (RCM) to simulate the extended drought that occurred throughout the period of 2002 through 2007 in south-east Australia. In particular, the ability to reproduce the two drought peaks in 2002 and 2006 was investigated. Overall, the RCM was found to reproduce both the temporal and the spatial structure of the drought-related precipitation anomalies quite well, despite using climatological seasonal surface characteristics such as vegetation fraction and albedo. This result concurs with previous studies that found that about two-thirds of the precipitation decline can be attributed to the El Ninõ–Southern Oscillation (ENSO). Simulation experiments that allowed the vegetation fraction and albedo to vary as observed illustrated that the intensity of the drought was underestimated by about 10ĝ% when using climatological surface characteristics. These results suggest that in terms of drought development, capturing the feedbacks related to vegetation and albedo changes may be as important as capturing the soil moisture–precipitation feedback. In order to improve our modelling of multi-year droughts, the challenge is to capture all these related surface changes simultaneously, and provide a comprehensive description of land surface–precipitation feedback during the droughts development.

  4. Process-model simulations of cloud albedo enhancement by aerosols in the Arctic

    Science.gov (United States)

    Kravitz, Ben; Wang, Hailong; Rasch, Philip J.; Morrison, Hugh; Solomon, Amy B.

    2014-01-01

    A cloud-resolving model is used to simulate the effectiveness of Arctic marine cloud brightening via injection of cloud condensation nuclei (CCN), either through geoengineering or other increased sources of Arctic aerosols. An updated cloud microphysical scheme is employed, with prognostic CCN and cloud particle numbers in both liquid and mixed-phase marine low clouds. Injection of CCN into the marine boundary layer can delay the collapse of the boundary layer and increase low-cloud albedo. Albedo increases are stronger for pure liquid clouds than mixed-phase clouds. Liquid precipitation can be suppressed by CCN injection, whereas ice precipitation (snow) is affected less; thus, the effectiveness of brightening mixed-phase clouds is lower than for liquid-only clouds. CCN injection into a clean regime results in a greater albedo increase than injection into a polluted regime, consistent with current knowledge about aerosol–cloud interactions. Unlike previous studies investigating warm clouds, dynamical changes in circulation owing to precipitation changes are small. According to these results, which are dependent upon the representation of ice nucleation processes in the employed microphysical scheme, Arctic geoengineering is unlikely to be effective as the sole means of altering the global radiation budget but could have substantial local radiative effects. PMID:25404677

  5. A False Positive For Ocean Glint on Exoplanets: the Latitude-Albedo Effect

    CERN Document Server

    Cowan, Nicolas B; Voigt, Aiko

    2012-01-01

    Identifying liquid water on the surface of planets is a high priority, as this traditionally defines habitability. One proposed signature of oceans is specular reflection ("glint"), which increases the apparent albedo of a planet at crescent phases. We post-process a global climate model of an Earth-like planet to simulate reflected lightcurves. Significantly, we obtain glint-like phase variations even though we do not include specular reflection in our model. This false positive is the product of two generic properties: 1) for modest obliquities, a planet's poles receive less orbit-averaged stellar flux than its equator, so the poles are more likely to be covered in highly reflective snow and ice, and 2) we show that reflected light from a modest-obliquity planet at crescent phases probes higher latitudes than at gibbous phases, therefore a planet's apparent albedo will naturally increase at crescent phase. We suggest that this "latitude-albedo effect" will operate even for large obliquities: in that case th...

  6. Iron alteration minerals in the visible and near-infrared spectra of low-albedo asteroids

    Science.gov (United States)

    Vilas, Faith; Jarvis, Kandy S.; Gaffey, Michael J.

    1994-01-01

    Absorption features centered near 0.60-0.65 and 0.80-0.90 micrometers have been identified in the spectra of five low-albedo main-belt and outer-belt asteroids. These absorption features are attributed respectively to the (6)A(sub 1) goes to (4)T(sub 2)(G) and (6)A(sub 1) goes to (4)T(sub 1)(G) charge transfer transitions in minerals such as goethite, hematite, and jarosite that are products of the aqueous alteration of anhydrous silicates. A shoulder near 0.63 micrometers has also been identified in the absorption feature centered near 0.7 micrometers attributed to oxidized iron in phyllosilicates found predominantly in C- and G-class asteroids reflectance spectra. The coexistence of iron oxides with phyllosilicates in asteroids believed to have undergone aqueous alteration would be expected based upon analogy with terrestrial aqueous alteration and the observed mineralogy of carbonaceous chondrites. The number of low-albedo asteroids having only iron alteration absorption features compared to the number of low-albedo asteroids having spectral characteristics indicative of phyllosilicates is small. Either the conditions under which these asteroids formed are rare, or the iron alteration minerals could be formed in the interiors of objects where phyllosilicates dominate the surface mineralogy.

  7. Albedo changes, Milankovitch forcing, and late quaternary climate changes in the central Andes

    Energy Technology Data Exchange (ETDEWEB)

    Kull, C.; Grosjean, M. [Swiss Federal Inst. of Tech., Zurich (Switzerland). Dept. of Geography

    1998-11-01

    Late quaternary humidity changes resulted in substantial modifications of the land surface characteristics in the Altiplano of the Atacama desert, central Andes. Reconstructions of surface albedo, top-of-atmosphere (TOA) albedo, and shortwave net radiation in the Andes of northern Chile for 20,14,10,7 and 0 ka suggest that surface and TOA albedo increased substantially during periods of relatively humid environmental conditions (i.e., with large palaeolakes, glaciers and dense vegetation). The decrease of summer shortwave net radiation and seasonality during the late-glacial/early Holocene humid phase (14 to 10 ka) due to Earth`s surface and atmospheric characteristics added to the effect of orbitally driven negative deviations of southern Hemisphere austral summer insolation and minimum seasonality at 20 S. Therefore, in situ radiative forcing is, in contrast to the Northern Hemisphere tropics, not a suitable explanation for enhanced convective precipitation and, ultimately, humid climatic conditions. Our results suggest that late Quaternary humidity changes on the Altiplano reflect a collective response to (1) environmental changes in the source area of the moisture (e.g., reexpansion of the rain forest and increased release of latent heat over Amazonia and the Chaco, warm sea surface temperatures in the E Pacific) and, (2) large-scale circulation patterns and wave structures in the upper troposphere (strength and position of the Bolivian high, divergent flow stimulating convection over the Altiplano), or that they even reflect a response to (3) interhemispherical teleconnections. (orig.) With 5 figs., 2 tabs., 45 refs.

  8. Modulation of ice ages via precession and dust-albedo feedbacks

    Directory of Open Access Journals (Sweden)

    Ralph Ellis

    2016-11-01

    Full Text Available We present here a simple and novel proposal for the modulation and rhythm of ice-ages and interglacials during the late Pleistocene. While the standard Milankovitch-precession theory fails to explain the long intervals between interglacials, these can be accounted for by a novel forcing and feedback system involving CO2, dust and albedo. During the glacial period, the high albedo of the northern ice sheets drives down global temperatures and CO2 concentrations, despite subsequent precessional forcing maxima. Over the following millennia more CO2 is sequestered in the oceans and atmospheric concentrations eventually reach a critical minima of about 200 ppm, which combined with arid conditions, causes a die-back of temperate and boreal forests and grasslands, especially at high altitude. The ensuing soil erosion generates dust storms, resulting in increased dust deposition and lower albedo on the northern ice sheets. As northern hemisphere insolation increases during the next Milankovitch cycle, the dust-laden ice-sheets absorb considerably more insolation and undergo rapid melting, which forces the climate into an interglacial period. The proposed mechanism is simple, robust, and comprehensive in its scope, and its key elements are well supported by empirical evidence.

  9. An investigation into the sensitivity of various albedo neutron dosimeters aimed at correcting the readings

    Science.gov (United States)

    Alekseev, A. G.; Mokrov, Yu. V.; Morozova, S. V.

    2012-03-01

    The results of an experimental determination of the sensitivity of three types of individual neutron albedo dosimeters in neutron reference fields on the basis of radionuclide sources and at the top concrete shielding of the U-70 accelerator are presented. The results show that the ratios between the responses of the albedo dosimeters designed earlier at the Joint Institute for Nuclear Research (the albedo dosimeter (AD) and the multicomponent dosimeter (MD)) and the currently used DVGN-01 dosimeter are constant within 25% in a wide range of neutron energy. This fact makes it possible to use the results of measuring the AD and MD responses obtained earlier in neutron fields of nuclear-physical installations at the Joint Institute for Nuclear Research (JINR) for the correction of DVGN-01 dosimeter measurement results to apply it to personal radiation monitoring (PRM) at these installations. The correction factors for DVGN-01 measurement results are found and recommended to be used in PRM for most JINR installations.

  10. The Very Low Albedo of an Extrasolar Planet: MOST Spacebased Photometry of HD 209458

    CERN Document Server

    Rowe, Jason F; Seager, Sara; Miller-Ricci, Eliza; Sasselov, Dimitar; Kuschnig, Rainer; Guenther, David B; Moffat, Anthony F J; Rucinski, Slavek M; Walker, Gordon A H; Weiss, Werner W

    2007-01-01

    Measuring the albedo of an extrasolar planet provides insights into its atmospheric composition and its global thermal properties, including heat dissipation and weather patterns. Such a measurement requires very precise photometry of a transiting system sampling fully many phases of the secondary eclipse. Spacebased optical photometry of the transiting system HD 209458 from the MOST (Microvariablity and Oscillations of STars) satellite, spanning 14 and 44 days in 2004 and 2005 respectively, allows us to set a sensitive limit on the optical eclipse of the hot exosolar giant planet in this system. Our best fit to the observations yields a flux ratio of the planet and star of 7 $\\pm$ 9 ppm (parts per million), which corresponds to a geometric albedo through the MOST bandpass (400-700 nm) of $A_g$ = 0.038 $\\pm$ 0.045. This gives a 1$\\sigma$ upper limit of 0.08 for the geometric albedo and a 3$\\sigma$ upper limit of 0.17. HD 209458b is significantly less reflective than Jupiter (for which $A_g$ would be about 0.5...

  11. Inferring heat recirculation and albedo for exoplanetary atmospheres: Comparing optical phase curves and secondary eclipse data

    CERN Document Server

    von Paris, P; Bordé, P; Selsis, F

    2015-01-01

    Basic atmospheric properties such as albedo and heat redistribution between day and nightside have been inferred for a number of planets using observations of secondary eclipses and thermal phase curves. Optical phase curves have not yet been used to constrain these atmospheric properties consistently. We re-model previously published phase curves of CoRoT-1b, TrES-2b and HAT-P-7b and infer albedos and recirculation efficiencies. These are then compared to previous estimates based on secondary eclipse data. We use a physically consistent model to construct optical phase curves. This model takes Lambertian reflection, thermal emission, ellipsoidal variations and Doppler boosting into account. CoRoT-1b shows a non-negligible scattering albedo (0.11

  12. MODIS/COMBINED MCD43B2 BRDF-Albedo Quality 16-Day L3 Global 1km

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The MODerate-resolution Imaging Spectroradiometer (MODIS) BRDF/Albedo Model Parameters product (MCD43A1) contains three-dimensional (3D) data sets providing users...

  13. MODIS/COMBINED MCD43B1 BRDF-Albedo Model 16-Day L3 Global 1km

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The MODerate-resolution Imaging Spectroradiometer (MODIS) BRDF/Albedo Model Parameters product (MCD43A1) contains three-dimensional (3D) data sets providing users...

  14. MODIS/COMBINED MCD43C3 Albedo 16-Day L3 Global 0.05Deg CMG

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The MODerate-resolution Imaging Spectroradiometer (MODIS) BRDF/Albedo Model Parameters product (MCD43A1) contains three-dimensional (3D) data sets providing users...

  15. MODIS/COMBINED MCD43A2 BRDF-Albedo Quality 16-Day L3 Global 500m

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The MODerate-resolution Imaging Spectroradiometer (MODIS) BRDF/Albedo Model Parameters product (MCD43A1) contains three-dimensional (3D) data sets providing users...

  16. MODIS/COMBINED MCD43A1 BRDF-Albedo Model Parameters 16-Day L3 Global 500m

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The MODerate-resolution Imaging Spectroradiometer (MODIS) BRDF/Albedo Model Parameters product (MCD43A1) contains three-dimensional (3D) data sets providing users...

  17. Areal-averaged and Spectrally-resolved Surface Albedo from Ground-based Transmission Data Alone: Toward an Operational Retrieval

    Energy Technology Data Exchange (ETDEWEB)

    Kassianov, Evgueni I.; Barnard, James C.; Flynn, Connor J.; Riihimaki, Laura D.; Michalsky, Joseph; Hodges, G. B.

    2014-08-22

    We present here a simple retrieval of the areal-averaged and spectrally resolved surface albedo using only ground-based measurements of atmospheric transmission under fully overcast conditions. Our retrieval is based on a one-line equation and widely accepted assumptions regarding the weak spectral dependence of cloud optical properties in the visible and near-infrared spectral range. The feasibility of our approach for the routine determinations of albedo is demonstrated for different landscapes with various degrees of heterogeneity using three sets of measurements:(1) spectrally resolved atmospheric transmission from Multi-Filter Rotating Shadowband Radiometer (MFRSR) at wavelength 415, 500, 615, 673, and 870 nm, (2) tower-based measurements of local surface albedo at the same wavelengths, and (3) areal-averaged surface albedo at four wavelengths (470, 560, 670 and 860 nm) from collocated and coincident Moderate Resolution Imaging Spectroradiometer (MODIS) observations. These integrated datasets cover both long (2008-2013) and short (April-May, 2010) periods at the ARM Southern Great Plains (SGP) site and the NOAA Table Mountain site, respectively. The calculated root mean square error (RMSE), which is defined here as the root mean squared difference between the MODIS-derived surface albedo and the retrieved area-averaged albedo, is quite small (RMSE≤0.01) and comparable with that obtained previously by other investigators for the shortwave broadband albedo. Good agreement between the tower-based daily averages of surface albedo for the completely overcast and non-overcast conditions is also demonstrated. This agreement suggests that our retrieval originally developed for the overcast conditions likely will work for non-overcast conditions as well.

  18. An Algorithm for the Retrieval of 30-m Snow-Free Albedo from Landsat Surface Reflectance and MODIS BRDF

    Science.gov (United States)

    Shuai, Yanmin; Masek, Jeffrey G.; Gao, Feng; Schaaf, Crystal B.

    2011-01-01

    We present a new methodology to generate 30-m resolution land surface albedo using Landsat surface reflectance and anisotropy information from concurrent MODIS 500-m observations. Albedo information at fine spatial resolution is particularly useful for quantifying climate impacts associated with land use change and ecosystem disturbance. The derived white-sky and black-sky spectral albedos maybe used to estimate actual spectral albedos by taking into account the proportion of direct and diffuse solar radiation arriving at the ground. A further spectral-to-broadband conversion based on extensive radiative transfer simulations is applied to produce the broadband albedos at visible, near infrared, and shortwave regimes. The accuracy of this approach has been evaluated using 270 Landsat scenes covering six field stations supported by the SURFace RADiation Budget Network (SURFRAD) and Atmospheric Radiation Measurement Southern Great Plains (ARM/SGP) network. Comparison with field measurements shows that Landsat 30-m snow-free shortwave albedos from all seasons generally achieve an absolute accuracy of +/-0.02 - 0.05 for these validation sites during available clear days in 2003-2005,with a root mean square error less than 0.03 and a bias less than 0.02. This level of accuracy has been regarded as sufficient for driving global and regional climate models. The Landsat-based retrievals have also been compared to the operational 16-day MODIS albedo produced every 8-days from MODIS on Terra and Aqua (MCD43A). The Landsat albedo provides more detailed landscape texture, and achieves better agreement (correlation and dynamic range) with in-situ data at the validation stations, particularly when the stations include a heterogeneous mix of surface covers.

  19. Incorporating changes in albedo in estimating the climate mitigation benefits of land use change projects

    Directory of Open Access Journals (Sweden)

    D. N. Bird

    2008-04-01

    Full Text Available Some climate scientists are questioning whether the practice of converting of non-forest lands to forest land (afforestation or reforestation is an effective climate change mitigation option. The discussion focuses particularly on areas where the new forest is primarily coniferous and there is significant amount of snow since the increased climate forcing due to the change in albedo may counteract the decreased climate forcing due to carbon dioxide removal.

    In this paper, we develop a stand-based model that combines changes in surface albedo, solar radiation, latitude, cloud cover and carbon sequestration. As well, we develop a procedure to convert carbon stock changes to equivalent climatic forcing or climatic forcing to equivalent carbon stock changes. Using the model, we investigate the sensitivity of combined affects of changes in surface albedo and carbon stock changes to model parameters. The model is sensitive to amount of cloud, atmospheric absorption, timing of canopy closure, carbon sequestration rate among other factors. The sensitivity of the model is investigated at one Canadian site, and then the model is tested at numerous sites across Canada.

    In general, we find that the change in albedo reduces the carbon sequestration benefits by approximately 30% over 100 years, but this is not drastic enough to suggest that one should not use afforestation or reforestation as a climate change mitigation option. This occurs because the forests grow in places where there is significant amount of cloud in winter. As well, variations in sequestration rate seem to be counterbalanced by the amount and timing of canopy closure.

    We close by speculating that the effects of albedo may also be significant in locations at lower latitudes, where there are less clouds, and where there are extended dry seasons. These conditions make grasses light coloured and when irrigated crops, dark forests or other vegetation such as

  20. Physical and Chemical Properties of Seasonal Snow and the Impacts on Albedo in New Hampshire, USA

    Science.gov (United States)

    Adolph, A. C.; Albert, M. R.; Amante, J.; Dibb, J. E.

    2014-12-01

    Snow albedo is critical to surface energy budgets and thus to the timing of mid-winter and vernal melt events in seasonal snow packs. Timing of these melt events is important in predicting flooding, understanding plant and animal phenology, and the availability of winter recreational activity. The state of New Hampshire experiences large spatial and temporal variability in snow albedo as a result of differences in meteorological conditions, physical snow structure, and chemical impurities in the snow, particularly highly absorptive black carbon (BC) and dust particles. This work focuses on the winters of 2012-2013 and 2013-2014, comparing three intensive study sites. Data collected at these sites include sub-hourly meteorological data, near daily measurements of snow depth, snow density, surface IR temperature, specific surface area (SSA) from contact spectroscopy, and spectrally resolved snow albedo using an ASD FieldSpec4 throughout the winter season. Additionally, snow samples were analyzed for black carbon content and other chemical impurities including Cl-, NO3-, NH4 , K , Na , Mg2+ , Ca2+ and SO42-. For each storm event at the three intensive sites, moisture sources and paths were determined using HYPLIT back trajectory modeling to determine potential sources of black carbon and other impurities in the snow. Storms with terrestrial-based paths across the US Midwest and Canada resulted in higher BC content than storms with ocean-based paths and sources. In addition to the variable storm path between sites and between years, the second year of study was on average 2.5°C colder than the first year, impacting duration of snow cover at each site and the SSA of surface snow which is sensitive to frequency of snow events and relies on cold temperatures to reduce grain metamorphism. Combining an understanding of storm frequency and path with physical and chemical attributes of the snow allows us to investigate snow albedo sensitivities with implications for

  1. Numerical investigation of the single scattering albedo of radiant energy passing through polydisperse crystalline media

    Science.gov (United States)

    Shefer, O. V.; Shefer, V. A.; Sinyukova, E. A.

    2014-12-01

    Studies of the role of atmospheric formations and cosmic dust clouds in the transmission of radiation is one of the most uncertain and difficult problems in astrophysics and climatology. One of the main tasks of practical astrophysics is the interpretation of the results of observations of space objects. There is a necessity of describing the propagation of electromagnetic waves in the environment. In this paper, applying the numerical methods, we study the optical characteristics of polydisperse media consisting of randomly oriented and preferentially oriented crystals, taking into account the distribution function of particle sizes. Particles of spherical shape and ensembles preferentially oriented plate crystals are considered as models. Mie theory and method of physical optics are used to calculate the scattering characteristics. Numerical study of the effects of extinction, scattering and absorption on the single scattering albedo of radiation allowed us to establish the basic patterns of the passage of radiant energy through a translucent medium. At the visible range of wavelengths, both for small and large particles, the single scattering albedo is almost equal to 1. The spectral course of this optical performance is mainly determined by the refractive index of the particles. Features of wave dependence of single scattering albedo are associated with microphysical parameters of the environment, which are more pronounced when the attenuation of the radiation is determined mainly by the scattering. Higher values of the absorption index and optical thickness of the crystal reduce the value of the single scattering albedo, smoothing the features of its spectral course. Values of the absorption index of substance, as value of the order of 0.1, do not lead to a decrease of the single scattering albedo as it is less than 0.5. This allows us to conclude that we should not neglect the microphysical characteristics of the crystals even by strong absorption of radiant

  2. Estimation of Sub Hourly Glacier Albedo Values Using Artificial Intelligence Techniques

    Science.gov (United States)

    Moya Quiroga, Vladimir; Mano, Akira; Asaoka, Yoshihiro; Udo, Keiko; Kure, Shuichi; Mendoza, Javier

    2013-04-01

    Glaciers are the most important fresh water reservoirs storing about 67% of total fresh water. Unfortunately, they are retreating and some small glaciers have already disappeared. Thus, snow glacier melt (SGM) estimation plays an important role in water resources management. Whether SGM is estimated by complete energy balance or a simplified method, albedo is an important data present in most of the methods. However, this is a variable value depending on the ground surface and local conditions. The present research presents a new approach for estimating sub hourly albedo values using different artificial intelligence techniques such as artificial neural networks and decision trees along with measured and easy to obtain data. . The models were developed using measured data from the Zongo-Ore station located in the Bolivian tropical glacier Zongo (68°10' W, 16°15' S). This station automatically records every 30 minutes several meteorological parameters such as incoming short wave radiation, outgoing short wave radiation, temperature or relative humidity. The ANN model used was the Multi Layer Perceptron, while the decision tree used was the M5 model. Both models were trained using the WEKA software and validated using the cross validation method. After analysing the model performances, it was concluded that the decision tree models have a better performance. The model with the best performance was then validated with measured data from the Equatorian tropical glacier Antizana (78°09'W, 0°28'S). The model predicts the sub hourly albedo with an overall mean absolute error of 0.103. The highest errors occur for albedo measured values higher than 0.9. Considering that this is an extreme value coincident with low measured values of incoming short wave radiation, it is reasonable to assume that such values include errors due to censored data. Assuming a maximum albedo of 0.9 improved the accuracy of the model reducing the MAE to less than 0.1. Considering that the

  3. Variability of soil moisture and its relationship with surface albedo and soil thermal diffusivity at Astronomical Observatory, Thiruvananthapuram, south Kerala

    Indian Academy of Sciences (India)

    M S Roxy; V B Sumithranand; G Renuka

    2010-08-01

    Continuous observation data collected over the year 2008 at Astronomical Observatory, Thiruvananthapuram in south Kerala (76° 59′E longitude and 8° 30′N latitude) are used to study the diurnal, monthly and seasonal soil moisture variations. The effect of rainfall on diurnal and seasonal soil moisture is discussed. We have investigated relationships of soil moisture with surface albedo and soil thermal diffusivity. The diurnal variation of surface albedo appears as a U-shaped curve on sunny days. Surface albedo decreases with the increase of solar elevation angle, and it tends to be a constant when solar elevation angle is greater than 40°. So the daily average surface albedo was calculated using the data when solar elevation angle is greater than 40°. The results indicate that the mean daily surface albedo decreases with increases in soil moisture content, showing a typical exponential relation between the surface albedo and the soil moisture. Soil thermal diffusivity increases firstly and then decreases with the increase of soil moisture.

  4. Albedo changes on Vatnajökull associated with dust events, Iceland

    Science.gov (United States)

    Dragosics, Monika; Thorsteinsson, Throstur; Pálsson, Finnur

    2015-04-01

    Deposition of aerosols on the glacier surface changes the albedo, thus enhances melt rates and affects the glacier mass balance. There are extensive sources for particles in Iceland; volcanic sandy deserts and glacial outwash plains cover more than 22% of the country. (Arnalds et al., 2001) Particles from these sources get airborne and transported on to the ice caps in several dust storms in most years, causing changes in albedo and surface energy balance. Long-term observations of atmospheric dust over the last 60 years show a high frequency of dust events in Iceland, with more than 34 dust days per year (Dagsson-Waldhauserova et al., 2013). Volcanoes are sources of large quantities of particles during an eruption, and for some years (even decades or centuries) after, due to re-suspension. Volcanic eruptions are frequent in Iceland, often with subsequent deposition of volcanic tephra on glaciers. The most recent are the eruptions of Eyjafjallajökull and Grímsvötn in 2010 and 2011. The evolution of surface albedo is measured with in-situ automatic weather stations (AWS), during summer, on a few locations on icelandic ice-caps. To detect dust events on Brúarjökull outlet (NE Vatnajökull ice-cap), drops in albedo are compared with energy balance results from the measured values of the AWSs, temperature, dust storm occurrence (recorded at manned weather stations in the lowlands), and visible changes on satellite observations (MODIS images) as in-situ samples. A dust deposition event is detected by comparing the MODIS images of 20 May and 28 May 2012 and explains a drop in albedo on 21 May, lasting to June 4 from 0.86 to 0.51. The in-situ samples are: snow surface samples from Vatnajökull with impurities collected in October 2013, representing the deposition of one summer over the ice cap; and two firn cores of about 8 meters depth from Brúarjökull, taken in June 2014. The firn cores were analysed to detect dust layers and to measure mass, volume, density of

  5. Variations of albedo and spectral reflectance on Qiyi Glacier in Qilian Mountains during the ablation season

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Based on the data observed at two sites (site H1, 4,473 m a.s.l., and site H2, 4,696 m a.s.l.) on Qiyi Glacier in Qilian Mountains, China, by automatic weather station and spectral pyranometer during the period of June 9 through September 27, 2006, we investigated the temporal and spatial variations in surface albedo and spectral reflectance on the glacier. At site H1, the daily mean surface albedos fluctuated between 0.233 and 0.866, which were significantly affected by the air temperature on the glacier. It was found that the albedos clearly showed a diurnal cycle with the lowest value at noon at the two observation sites over the study period, and the difference of albedos between the upper site H2 and the lower site H1 also showed diurnal cycle but with the highest value at noon. The reflectance on the glacier was higher in the ultraviolet (0.28-0.4 μm) and visible (0.4-0.76 μm) wavelengths, lower in the near infrared wavelength (0.76-3 μm), which is quite contrary to the spectral reflectance on other ground surfaces. At the two observation sites, the spectral reflectance declined in all wavelengths with the ablation of snow generally. However, it declined drastically in ultraviolet (0.28-0.4 μm) and 0.6-0.7 μm wavelength, and declined less in 0.4-0.5 μm wavelength. On fresh snow surface, the spectral reflectance had the high values of 0.983 and 0.815 in the ultraviolet and visible (0.4-0.76 μm) wavelengths, respectively; but it had a relatively lower value of 0.671 in near infrared (0.76-3 μm) wavelengths. However, on dirty and melting ice surfaces, the reflectance had the very low values of 0.305 and 0.256 in the ultraviolet and visible wavelengths, with the lowest value of 0.082 in near infrared wavelengths. The spectral reflectance also showed a diurnal cycle like that of albedo. The diurnal variations of spectral reflectance on snow surface in ultraviolet and visible wavelength changed to a greater degree than that on ice surface. The diurnal

  6. Inferring past land use-induced changes in surface albedo from satellite observations: a useful tool to evaluate model simulations

    Directory of Open Access Journals (Sweden)

    J. P. Boisier

    2013-03-01

    Full Text Available Regional cooling resulting from increases in surface albedo has been identified in several studies as the main biogeophysical effect of past land use-induced land cover changes (LCC on climate. However, the amplitude of this effect remains quite uncertain due to, among other factors, (a uncertainties in the extent of historical LCC and, (b differences in the way various models simulate surface albedo and more specifically its dependency on vegetation type and snow cover. We derived monthly albedo climatologies for croplands and four other land cover types from the Moderate Resolution Imaging Spectroradiometer (MODIS satellite observations. We then reconstructed the changes in surface albedo between preindustrial times and present-day by combining these climatologies with the land cover maps of 1870 and 1992 used by seven land surface models (LSMs in the context of the LUCID ("Land Use and Climate: identification of robust Impacts" intercomparison project. These reconstructions show surface albedo increases larger than 10% (absolute in winter, and larger than 2% in summer between 1870 and 1992 over areas that experienced intense deforestation in the northern temperate regions. The historical surface albedo changes estimated with MODIS data were then compared to those simulated by the various climate models participating in LUCID. The inter-model mean albedo response to LCC shows a similar spatial and seasonal pattern to the one resulting from the MODIS-based reconstructions, that is, larger albedo increases in winter than in summer, driven by the presence of snow. However, individual models show significant differences between the simulated albedo changes and the corresponding reconstructions, despite the fact that land cover change maps are the same. Our analyses suggest that the primary reason for those discrepancies is how LSMs parameterize albedo. Another reason, of secondary importance, results from differences in their simulated snow extent

  7. The decreasing albedo of the Zhadang glacier on western Nyainqentanglha and the role of light-absorbing impurities

    Science.gov (United States)

    Qu, B.; Ming, J.; Kang, S.-C.; Zhang, G.-S.; Li, Y.-W.; Li, C.-D.; Zhao, S.-Y.; Ji, Z.-M.; Cao, J.-J.

    2014-10-01

    A large change in albedo has a significant effect on glacier ablation. Atmospheric aerosols - e.g. black carbon (BC) and dust - can reduce the albedo of glaciers and thus contribute to their melting. In this study, two main themes were explored: (1) the decrease in albedo of the Zhadang glacier on Mt. Nyainqentanglha between 2001 and 2012, as observed by the Moderate Resolution Imaging Spectroradiometer (MODIS) on-board the Terra satellite, and the correlation of this albedo with mass balance; and (2) the concentrations of BC and dust in the glacier measured during 2012, and the associated impacts of these impurities on albedo and radiative forcings (RF). The average albedo of the Zhadang glacier from the MODIS increased with the altitude and fluctuated but had a decreasing trend (-0.003 a-1) during the period 2001-2012, with the highest (0.722) in 2003 and the lowest (0.597) in 2009 and 2010. The mass balance of the glacier has a positively significant correlation with its surface albedo derived from MODIS. Snow samples were collected on the Zhadang glacier to measure the BC and dust in the summer of 2012. The impacts of BC and dust on albedo reduction in different melting conditions were identified with the SNow ICe Aerosol Radiative (SNICAR) model initiated by in situ observation data. The sensitivity analysis showed that BC was a major factor in albedo reduction when the glacier was covered by newly fallen snow. Nevertheless, the contribution of dust to albedo reduction can reach as high as 56%, much exceeding that of BC (28%), when the glacier experiences strong surficial melting and its surface is almost bare ice. The average RF caused by dust could increase from 1.1 to 8.6 W m-2, exceeding the RF caused by BC after snow was deposited and surface melting occurred in the Zhadang glacier. This implies that it may be dust that primarily dominates the melting of some glaciers in the inner Tibetan Plateau during melting seasons, rather than BC.

  8. The effects of additional black carbon on Arctic sea ice surface albedo: variation with sea ice type and snow cover

    Directory of Open Access Journals (Sweden)

    A. A. Marks

    2013-03-01

    Full Text Available Black carbon in sea ice will decrease sea ice surface albedo through increased absorption of incident solar radiation, exacerbating sea ice melting. Previous literature has reported different albedo responses to additions of black carbon in sea ice and has not considered how a snow cover may mitigate the effect of black carbon in sea ice. Sea ice is predominately snow covered. Visible light absorption and light scattering coefficients are calculated for a typical first year and multi-year sea ice and "dry" and "wet" snow types that suggest black carbon is the dominating absorbing impurity. The albedo response of first year and multi-year sea ice to increasing black carbon, from 1–1024 ng g−1, in a top 5 cm layer of a 155 cm thick sea ice was calculated using the radiative transfer model: TUV-snow. Sea ice albedo is surprisingly unresponsive to black carbon additions up to 100 ng g−1 with a decrease in albedo to 98.7% of the original albedo value due to an addition of 8 ng g−1 of black carbon in first year sea ice compared to an albedo decrease to 99.6% for the same black carbon mass ratio increase in multi-year sea ice. The first year sea ice proved more responsive to black carbon additions than the multi-year ice. Comparison with previous modelling of black carbon in sea ice suggests a more scattering sea ice environment will be less responsive to black carbon additions. Snow layers on sea ice may mitigate the effects of black carbon in sea ice. "Wet" and "dry" snow layers of 0.5, 1, 2, 5 and 10 cm were added onto the sea ice surface and the snow surface albedo calculated with the same increase in black carbon in the underlying sea ice. Just a 0.5 cm layer of snow greatly diminishes the effect of black carbon on surface albedo, and a 2–5 cm layer (less than half the e-folding depth of snow is enough to "mask" any change in surface albedo owing to additional black carbon in sea ice, but not thick enough to ignore the underlying sea ice.

  9. The Impact of Albedo Increase to Mitigate the Urban Heat Island in Terni (Italy Using the WRF Model

    Directory of Open Access Journals (Sweden)

    Elena Morini

    2016-10-01

    Full Text Available The impacts of the urban heat island (UHI phenomenon on energy consumption, air quality, and human health have been widely studied and described. Mitigation strategies have been developed to fight the UHI and its detrimental consequences. A potential countermeasure is the increase of urban albedo by using cool materials. Cool materials are highly reflective materials that can maintain lower surface temperatures and thus can present an effective solution to mitigate the UHI. Terni’s proven record of high temperatures along with related environmental and comfort issues in its urban areas have reflected the local consequences of global warming. On the other hand, it promoted integrated actions by the government and research institutes to investigate solutions to mitigate the UHI effects. In this study, the main goal is to investigate the effectiveness of albedo increase as a strategy to tackle the UHI, by using the Weather Research and Forecasting (WRF mesoscale model to simulate the urban climate of Terni (Italy. Three different scenarios through a summer heat wave in the summer of 2015 are analyzed. The Base Scenario, which simulates the actual conditions of the urban area, is the control case. In the Albedo Scenario (ALB Scenario, the albedo of the roof, walls and road of the whole urban area is increased. In the Albedo-Industrial Scenario (ALB-IND Scenario, the albedo of the roof, walls and road of the area occupied by the main industrial site of Terni, located in close proximity to the city center, is increased. The simulation results show that the UHI is decreased up to 2 °C both at daytime and at nighttime in the ALB and in ALB-IND Scenarios. Peak temperatures in the urban area can be decreased by 1 °C at daytime, and by about 2 °C at nighttime. Albedo increase in the area of interest might thus represent an opportunity to decrease the UHI effect and its consequences.

  10. Simultaneous Cartography of Aerosol Opacity and Surface Albedo of Titan by the Massive Inversion of the Cassini/VIMS Dataset

    Science.gov (United States)

    Rodriguez, S.; Maltagliati, L.; Sotin, C.; Rannou, P.; Cornet, T.; Hirtzig, M.; Appéré, T.; Solomonidou, A.; Le Mouelic, S.; Coustenis, A.; Brown, R. H.

    2015-12-01

    Mapping Titan's surface albedo is a necessary step to give reliable constraints on its composition. However, surface albedo maps of Titan, especially over large regions, are still very rare, the surface windows being strongly affected by atmospheric effects (absorption, scattering). A full radiative transfer model is an essential tool to remove these effects, but too time-consuming to treat systematically the ~40000 hyperspectral images VIMS acquired since the beginning of the mission. We developed a massive inversion of VIMS data based on lookup tables computed from a state-of-the-art radiative transfer model (Hirtzig et al. 2013), updated with new aerosol properties coming from our analysis of the Emission Phase Function observation acquired recently by VIMS. Once the physical properties of gases, aerosols and surface are fixed, the lookup tables are built for the remaining free parameters: the incidence, emergence and azimuth angles, given by navigation; and two products (the aerosol opacity and the surface albedo at all wavelengths). The lookup table grid was carefully selected after thorough testing. The data inversion on these pre-computed spectra (opportunely interpolated) is more than 1000 times faster than recalling the full radiative transfer at each minimization step. We present here the results from selected flybys. We invert mosaics composed by couples of flybys observing the same area at two different times. The composite albedo maps do not show significant discontinuities in any of the surface windows, suggesting a robust correction of the effects of the geometry (and thus the aerosols) on the observations. Maps of aerosol and albedo uncertainties are also provided, with the absolute error on the albedo being approximately between 1 and 3% (depending on the surface window considered). We are thus able to provide for the first time ever reliable surface albedo maps at pixel scale for the whole VIMS spectral range.

  11. Accuracy of physically based snow albedo model evaluated with measured data at Sapporo, Japan during five winters from 2006 to 2011

    Science.gov (United States)

    Aoki, T.; Kuchiki, K.; Niwano, M.; Kodama, Y.

    2011-12-01

    Physically based snow albedo model (PBSAM) to calculate broadband albedos and solar heating profile in a general circulation model was developed by Aoki et al. (2011), in which the accuracy for albedos was evaluated with the data of radiation budget and snow pit work performed at Sapporo during two winters from 2007 to 2009. The model calculates the broadband albedos for the visible, near-infrared (NIR), and shortwave bands for any snow layer structure of snow grain size, snow impurity concentrations, and snow water equivalent under any solar illumination condition. The estimated root mean square errors (RMSE) from the measured data were 0.047 for the visible albedo and 0.057 for the NIR albedo. In the paper, it is described that possible error causes for calculated albedos are (1) PBSAM faultiness; (2) inappropriately modeled snow layers structure (e.g., number of layers and depths of layer boundaries); (3) the assumption that the diffuse fractions of the visible and NIR bands are the same as the measured diffuse fraction of the shortwave radiation; (4) errors in the measured snow grain size and snow impurity concentrations; and (5) errors in the albedo measurements. Using the data obtained at Sapporo during five winters from 2006 to 2011, we further investigated the effects of snow grain size, mass concentrations of snow impurities (black carbon and dust), air temperature, snow surface temperature, snow depth, diffuse fraction of solar radiation, continuous snow cover days, wet snow days, new snow days, ice layer days, and albedo values themselves on the accuracy of calculated albedos for each winter. Among them, the best (worst) RMSE value of calculated albedos by PBSAM for each winter during five winters is 2008-2009 (2010-2011) for the visible albedo and 2007-2008 (2006-2007) for the NIR albedos. The estimated RMSE for each winter have a high correlation with continuous snow cover days and wet snow days for each winter, meaning that PBSAM error may increase

  12. Size, Albedo, and Taxonomy of the Don Quijote Space Mission Target

    Science.gov (United States)

    Harris, Alan; Mueller, Michael; Fitzsimmons, Alan

    2006-03-01

    Rendezvous and lander missions are a very effective but very expensive way of investigating Solar-System bodies. The planning, optimization and success of space missions depends crucially on prior remotely-sensed knowledge of target bodies. Near-Earth asteroids (NEAs), which are mainly fragments of main-belt asteroids, are seen as important goals for investigation by space missions, mainly due to the role their forebears played in planet formation and the evolution of the Solar System, but also for the pragmatic reason that these objects can collide with the Earth with potentially devastating consequences. The European Space Agency is currently planning the Don Quijote mission to a NEA, which includes a rendezvous (and perhaps a lander) spacecraft and an impactor vehicle. The aim is to study the physical properties of the target asteroid and the effects of the impact on its dynamical state, as a first step in considering realistic mitigation measures against an eventual hazardous NEA. Two potential targets have been selected for the mission, the preferred one being (10302) 1989 ML, which is energetically easier to reach and is possibly a scientifically interesting primitive asteroid. However, due to the ambiguity of available spectral data, it is currently not possible to confidently determine the taxonomic type and mineralogy of this object. Crucially, the albedo is uncertain by a factor of 10, which leads to large uncertainties in the size and mass and hence the planned near-surface operations of Don Quijote. Thermal-infrared observations are urgently required for accurate size and albedo determination. These observations, which can only be carried out by Spitzer and would require only a modest amount of observing time, would enable an accurate diameter to be derived for the first time and the resulting albedo would remove the taxonomic ambiguity. The proposed Spitzer observations are critical for effective mission planning and would greatly increase our

  13. Effect of spectrally varying albedo of vegetation surfaces on shortwave radiation fluxes and direct aerosol forcing

    Directory of Open Access Journals (Sweden)

    L. Zhu

    2012-06-01

    Full Text Available This study develops an algorithm for the representation of large spectral variations of albedo over vegetation surfaces based on Moderate Resolution Imaging Spectrometer (MODIS observations at 7 discrete channels centered at 0.47, 0.55, 0.67, 0.86, 1.24, 1.63, and 2.11 μm. The MODIS 7-channel observations miss several major features of vegetation albedo including the vegetation red edge near 0.7 μm and vegetation absorption features at 1.48 and 1.92 μm. We characterize these features by investigating aerosol forcing in different spectral ranges. We show that the correction at 0.7 μm is the most sensitive and important due to the presence of the red edge and strong solar radiation; the other two corrections are less sensitive due to the weaker solar radiation and strong atmospheric water absorption. Four traditional approaches for estimating the reflectance spectrum and the MODIS enhanced vegetation albedo (MEVA are tested against various vegetation types: dry grass, green grass, conifer, and deciduous from the John Hopkins University (JHU spectral library; aspens from the US Geological Survey (USGS digital spectral library; and Amazon vegetation types. Compared to traditional approaches, MEVA improves the accuracy of the outgoing flux at the top of the atmosphere by over 60 W m−2 and aerosol forcing by over 10 W m−2. Specifically, for Amazon vegetation types, MEVA can improve the accuracy of daily averaged aerosol forcing at equator at equinox by 3.7 W m−2 (about 70% of the aerosol forcing calculated with high spectral resolution surface reflectance. These improvements indicate that MEVA can contribute to vegetation covered regional climate studies, and help to improve understanding of climate processes and climate change.

  14. Reflected Light Curves, Spherical and Bond Albedos of Jupiter- and Saturn-like Exoplanets

    Science.gov (United States)

    Dyudina, Ulyana A.; Zhang, Xi; Li, Liming; Kopparla, Pushkar; Ingersoll, Andrew P.; Dones, Henry C. Luke; Verbiscer, Anne J.; Yung, Yuk

    2016-10-01

    Reflected light curves observed for exoplanets indicate that a few of them host bright clouds. We estimate how the light curve and total stellar heating of a planet depends on forward and backward scattering in the clouds based on Pioneer and Cassini spacecraft images of Jupiter and Saturn. We fit analytical functions to the local reflected brightnesses of Jupiter and Saturn depending on the planet's phase. These observations cover broad bands at 0.59-0.72 and 0.39-0.5 μm, and narrow bands at 0.938 (atmospheric window), 0.889 (CH4 absorption band), and 0.24-0.28 μm. We simulate the images of the planets with a ray-tracing model, and disk-integrate them to produce the full-orbit light curves. For Jupiter, we also fit the modeled light curves to the observed full-disk brightness. We derive spherical albedos for Jupiter and Saturn, and for planets with Lambertian and Rayleigh-scattering atmospheres. Jupiter-like atmospheres can produce light curves that are a factor of two fainter at half-phase than the Lambertian planet, given the same geometric albedo at transit. The spherical albedo is typically lower than for a Lambertian planet by up to a factor of ˜1.5. The Lambertian assumption will underestimate the absorption of the stellar light and the equilibrium temperature of the planetary atmosphere. We also compare our light curves with the light curves of solid bodies: the moons Enceladus and Callisto. Their strong backscattering peak within a few degrees of opposition (secondary eclipse) can lead to an even stronger underestimate of the stellar heating. This work is published: Dyudina, U.,et al., 2016: ApJ, 822, 76, http://arxiv.org/abs/1511.04415.

  15. The slab albedo problem for pure-triplet anisotropic scattering by singular eigenfunction method

    Science.gov (United States)

    Türeci, D.; Türeci, R. G.

    2017-02-01

    One-speed, time independent and homogenous medium neutron transport equation can be solved by using pure-triplet anisotropic scattering. This solution bases on finding the Case's eigenfunctions and the orthogonality relations of these eigenfunctions. The infinite medium Green function can be written by using the jump condition after finding Case's eigenfunctions. The slab albedo problem can be investigated as numerical by using suggested solutions over surfaces with the singular eigenfunction method which bases on the infinite medium Green function. The selected numerical results can be tabulated.

  16. The Slab Albedo Problem Using Singular Eigenfunctions and the Third Form of the Transport Equation

    Science.gov (United States)

    Kaskas, Ayþe; Tezcan, Cevdet

    1997-01-01

    The albedo and the transmission factor for slabs are obtained using the infinite medium Green's function in terms of the singular eigenfunctions in the third form of the transport equation. Our analytical results are simple as in FN-method and the convergence of the numerical results is as faster as in the CN-method. Calculations are also carried out by various incoming angular fluxes and uncollided neutrons are taken into account. Our numerical results are in very good agreement with the results of the CN method.

  17. Testing the Prediction of Iron Alteration Minerals on Low Albedo Asteroids

    Science.gov (United States)

    Jarvis, K. S.; Vilas, Faith; Howell, E.; Kelley, M.; Cochran, A.

    1999-01-01

    Absorption features centered near 0.60 - 0.65 and 0.80 - 0.90 micron were identified in the spectra of three low-albedo main-belt (165, 368, 877) and two low-albedo outer-belt (225, 334) asteroids (Vilas et al., Icarus, v. 109,274,1994). The absorption features were attributed to charge transfer transitions in iron alteration minerals such as goethite, hematite, and jarosite, all products of aqueous alteration. Concurrently, Jarvis et al. (LPSC XXIV, 715, 1993) presented additional spectra of low-albedo asteroids that had absorption features centered near 0.60 - 0.65 micron without the longer wavelength feature. Since these two features in iron oxides originate from the same ground state, and the longer wavelength feature requires less energy to exist, the single shorter wavelength feature cannot be caused by the iron alteration minerals. In addition, spectra of minerals such as hematite and goethite show a rapid increase in reflectance beginning near 0.5 micron absent in the low-albedo asteroid spectra. The absence of this rise has been attributed to its suppresion from opaques in the surface material. Spectra on more than one night were available for only one of these five asteroids, 225 Henrietta, and showed good repeatability of the 0.65-micron feature. We have acquired additional spectra of all five asteroids in order to test the repeatability of the 0.65-micron feature, and the presence and repeatability of the features centered near 0.8 - 0.9 micron. We specifically will test the possibility that longer wavelength features could be caused by incomplete removal of telluric water. Asteroid 877 Walkure is a member of the Nysa-Hertha family, and will be compared to spectra of other members of that family. Data were acquired in 1996 and 1999 on the 2.1-m telescope with a facility cassegrain spectrograph, McDonald Observatory, Univ. Of Texas, and the 1.5-m telescope with facility cassegrain spectrograph at CTIO. This research is supported by the NASA Planetary

  18. The Latitudinal Gradient of Rainfall, Mineralogy, Albedo and Magnetic Susceptibility in West Africa

    Science.gov (United States)

    Williams, E. R.; Balsam, W.; Schaaf, C.; Yang, X.; Zhang, Q.; Ji, J.; Rossman, G.; Garimella, S.; Oldfield, F.; Lyons, J. R.; Ellwood, B.; Hartman, H.; Hicks, E.; Mansot, J. L.; Cesaire, T.; Thomas, P.

    2008-12-01

    In order to investigate the effect of climate on soil and surface sediment properties we examined four transects around the Sahara Desert. The transects were located in Mali, Niger, Benin, Togo, Egypt and Morocco and, with the exception of Egypt, each crossed a significant climatological rainfall gradient. The Egyptian transect was designed to characterize one of the driest portions of the Sahara Desert. Our study included laboratory measurements of mineralogy (XRD), elemental composition (XRF), grain size, optical reflectance (lab), magnetic susceptibility (MS)and remanences. In addition, albedo was determined from the MODIS satellite imagery from space. Many of our laboratory measurements exhibited variations with the rainfall gradient. Iron oxides (hematite and goethite), kaolinite, Al2O3, and TiO2 increased with increasing rainfall whereas SiO2, illite, and grain size decreased with increasing rainfall. Both laboratory-determined reflectivity and satellite-determine albedo decreased as rainfall increased. In part, this decrease in reflectivity/albedo with increasing rainfall appears to be the result of hematite, the dominant coloring agent for the soil in this region and the origin of the 'red' Sahel. The physical interpretation of these results centers on rainfall as a long-term leaching agent of surface material, and the control of physical properties by specific mineralogy. SiO2 is highly reflective and iron oxides are strongly absorptive in the visible range. The solubility of SiO2 in rainwater is orders of magnitude larger than all the iron oxides, with hematite the least soluble. It has long been recognized that leaching by rainfall produces dark red laterite in the near-surface oxidizing environment, a prominent geological feature throughout the high rainfall belt of West Africa. Laterite beds represent simultaneous enrichments of all iron oxides and a reduction in SiO2 by leaching. In the Sahara desert where rainfall is minimal (<10 mm/yr), SiO2 is

  19. CVF spectrophotometry of Pluto - Correlation of composition with albedo. [circularly variable filter

    Science.gov (United States)

    Marcialis, Robert L.; Lebofsky, Larry A.

    1991-01-01

    The present time-resolved, 0.96-2.65-micron spectrophotometry for the Pluto-Charon system indicates night-to-night variations in the depths of the methane absorptions such that the bands' equivalent width is near minimum light. The interpretation of these data in terms of a depletion of methane in dark regions of the planet, relative to bright ones, is consistent with the Buie and Fink (1987) observations. The near-IR spectrum of Pluto seems to be dominated by surface frost. It is suggested that the dark equatorial regions of Pluto are redder than those of moderate albedo.

  20. Improving winter leaf area index estimation in coniferous forests and its significance in estimating the land surface albedo

    Science.gov (United States)

    Wang, Rong; Chen, Jing M.; Pavlic, Goran; Arain, Altaf

    2016-09-01

    Winter leaf area index (LAI) of evergreen coniferous forests exerts strong control on the interception of snow, snowmelt and energy balance. Simulation of winter LAI and associated winter processes in land surface models is challenging. Retrieving winter LAI from remote sensing data is difficult due to cloud contamination, poor illumination, lower solar elevation and higher radiation reflection by snow background. Underestimated winter LAI in evergreen coniferous forests is one of the major issues limiting the application of current remote sensing LAI products. It has not been fully addressed in past studies in the literature. In this study, we used needle lifespan to correct winter LAI in a remote sensing product developed by the University of Toronto. For the validation purpose, the corrected winter LAI was then used to calculate land surface albedo at five FLUXNET coniferous forests in Canada. The RMSE and bias values for estimated albedo were 0.05 and 0.011, respectively, for all sites. The albedo map over coniferous forests across Canada produced with corrected winter LAI showed much better agreement with the GLASS (Global LAnd Surface Satellites) albedo product than the one produced with uncorrected winter LAI. The results revealed that the corrected winter LAI yielded much greater accuracy in simulating land surface albedo, making the new LAI product an improvement over the original one. Our study will help to increase the usability of remote sensing LAI products in land surface energy budget modeling.

  1. Albedo and land surface temperature shift in hydrocarbon seepage potential area, case study in Miri Sarawak Malaysia

    Science.gov (United States)

    Suherman, A.; Rahman, M. Z. A.; Busu, I.

    2014-02-01

    The presence of hydrocarbon seepage is generally associated with rock or mineral alteration product exposures, and changes of soil properties which manifest with bare development and stress vegetation. This alters the surface thermodynamic properties, changes the energy balance related to the surface reflection, absorption and emission, and leads to shift in albedo and LST. Those phenomena may provide a guide for seepage detection which can be recognized inexpensively by remote sensing method. District of Miri is used for study area. Available topographic maps of Miri and LANDSAT ETM+ were used for boundary construction and determination albedo and LST. Three land use classification methods, namely fixed, supervised and NDVI base classifications were employed for this study. By the intensive land use classification and corresponding statistical comparison was found a clearly shift on albedo and land surface temperature between internal and external seepage potential area. The shift shows a regular pattern related to vegetation density or NDVI value. In the low vegetation density or low NDVI value, albedo of internal area turned to lower value than external area. Conversely in the high vegetation density or high NDVI value, albedo of internal area turned to higher value than external area. Land surface temperature of internal seepage potential was generally shifted to higher value than external area in all of land use classes. In dense vegetation area tend to shift the temperature more than poor vegetation area.

  2. Assessing surface albedo change and its induced radiation budget under rapid urbanization with Landsat and GLASS data

    Science.gov (United States)

    Hu, Yonghong; Jia, Gensuo; Pohl, Christine; Zhang, Xiaoxuan; van Genderen, John

    2016-02-01

    Radiative forcing (RF) induced by land use (mainly surface albedo) change is still not well understood in climate change science, especially the effects of changes in urban albedo due to rapid urbanization on the urban radiation budget. In this study, a modified RF derivation approach based on Landsat images was used to quantify changes in the solar radiation budget induced by variations in surface albedo in Beijing from 2001 to 2009. Field radiation records from a Beijing meteorological station were used to identify changes in RF at the local level. There has been rapid urban expansion over the last decade, with the urban land area increasing at about 3.3 % annually from 2001 to 2009. This has modified three-dimensional urban surface properties, resulting in lower albedo due to complex building configurations of urban centers and higher albedo on flat surfaces of suburban areas and cropland. There was greater solar radiation (6.93 × 108 W) in the urban center in 2009 than in 2001. However, large cropland and urban fringe areas caused less solar radiation absorption. RF increased with distance from the urban center (less than 14 km) and with greater urbanization, with the greatest value being 0.41 W/m2. The solar radiation budget in urban areas was believed to be mainly influenced by urban structural changes in the horizontal and vertical directions. Overall, the results presented herein indicate that cumulative urbanization impacts on the natural radiation budget could evolve into an important driver of local climate change.

  3. Effects of boundary layer particle formation on cloud droplet number and changes in cloud albedo from 1850 to 2000

    Directory of Open Access Journals (Sweden)

    J. Merikanto

    2010-01-01

    Full Text Available We use a global aerosol microphysics model to estimate the effect of particle formation through activation nucleation in the boundary layer (BL on cloud droplet number concentration (CDNC on global and regional scales. The calculations are carried out for years 1850 and 2000 using historical emissions inventories for primary particles and aerosol precursor gases. Predicted CDNC in 2000 are in good agreement with in-situ observations when activation nucleation is included. We find that BL particle formation increases global annual mean CDNC by approximately the same relative amount in both years (16.0% in 1850 and 13.5% in 2000. As a result, global mean changes in cloud albedo are similar with and without BL particle formation. However, there are substantial regional effects of up to 50% enhancement or suppression of the 1850–2000 albedo change. Over most modern-day polluted northern hemisphere regions, including BL particle formation scheme suppresses the 1850–2000 increase in CDNC and cloud albedo because BL particle formation is already large in 1850. Over the Arctic the albedo change is suppressed by 23% in the annual mean and by 43% in summer when BL particle formation is taken into account. The albedo change of the persistent stratocumulus cloud deck west of Chile is enhanced by 49%.

  4. Effects of boundary layer particle formation on cloud droplet number and changes in cloud albedo from 1850 to 2000

    Directory of Open Access Journals (Sweden)

    J. Merikanto

    2009-02-01

    Full Text Available We use a global aerosol microphysics model to estimate the effect of boundary layer particle formation on cloud droplet number concentration (CDNC on global and regional scales. The calculations are carried out for years 1850 and 2000 using historical emissions inventories for primary particles and aerosol precursor gases. Predicted CDNC in 2000 are in good agreement with in-situ observations when particle formation is included. We find that particle formation increases global annual mean CDNC by approximately the same amount in both years (16.0% in 1850 and 13.5% in 2000. Thus, global mean changes in cloud albedo are similar with and without particle formation. However, there are substantial regional effects of up to 50% enhancement or suppression of the 1850–2000 albedo change. Over most modern-day polluted Northern Hemisphere regions particle formation suppresses the 1850–2000 increase in CDNC and cloud albedo. Over the Arctic the albedo change is suppressed by 23% in the annual mean and by 43% in summer when particle formation is taken into account. The albedo change of the persistent stratocumulus cloud deck west of Chile is enhanced by 49%.

  5. On Spectral Invariance of Single Scattering Albedo for Water Droplets and Ice Crystals at Weakly Absorbing Wavelengths

    Science.gov (United States)

    Marshak, Alexander; Knyazikhin, Yuri; Chiu, J. Christine; Wiscombe, Warren J.

    2012-01-01

    The single scattering albedo omega(sub O lambda) in atmospheric radiative transfer is the ratio of the scattering coefficient to the extinction coefficient. For cloud water droplets both the scattering and absorption coefficients, thus the single scattering albedo, are functions of wavelength lambda and droplet size r. This note shows that for water droplets at weakly absorbing wavelengths, the ratio omega(sub O lambda)(r)/omega(sub O lambda)(r (sub O)) of two single scattering albedo spectra is a linear function of omega(sub O lambda)(r). The slope and intercept of the linear function are wavelength independent and sum to unity. This relationship allows for a representation of any single scattering albedo spectrum omega(sub O lambda)(r) via one known spectrum omega(sub O lambda)(r (sub O)). We provide a simple physical explanation of the discovered relationship. Similar linear relationships were found for the single scattering albedo spectra of non-spherical ice crystals.

  6. Exoplanet albedo spectra and colors as a function of planet phase, separation, and metallicity

    CERN Document Server

    Cahoy, Kerri L; Fortney, Jonathan J

    2010-01-01

    First generation optical coronagraphic telescopes will obtain images of cool gas and ice giant exoplanets around nearby stars. The albedo spectra of exoplanets at planet-star separations larger than about 1 AU are dominated by reflected light to beyond 1 {\\mu}m and are punctuated by molecular absorption features. We consider how exoplanet albedo spectra and colors vary as a function of planet-star separation, metallicity, mass, and observed phase for Jupiter and Neptune analogs from 0.35 to 1 {\\mu}m. We model Jupiter analogs with 1x and 3x the solar abundance of heavy elements, and Neptune analogs with 10x and 30x. Our model planets orbit a solar analog parent star at separations of 0.8 AU, 2 AU, 5 AU, and 10 AU. We use a radiative-convective model to compute temperature-pressure profiles. The giant exoplanets are cloud-free at 0.8 AU, have H2O clouds at 2 AU, and have both NH3 and H2O clouds at 5 AU and 10 AU. For each model planet we compute moderate resolution spectra as a function of phase. The presence a...

  7. Measurements and modelling of aerosol single-scattering albedo: progress, problems and prospects

    Energy Technology Data Exchange (ETDEWEB)

    Heintzenberg, J. [Institut fuer Troposphaerenforschung e.V. (IfT), Leipzig (Germany); Charlson, R.J.; Clarke, A.D.; Liousse, C.; Ramaswamy, V.; Shine, K.P.; Wendisch, M.; Helas, G.

    1997-11-01

    The net effect of atmospheric aerosols in the radiation balance is determined by both their scattering and absorption of solar radiation. The combined optical effect is expressed in the single scatter albedo, {omega}, of the particles. Currently available data on {omega} are insufficient for definitive use in climate models because most of them are not corrected for the method-dependent effect of the scattering portion of the aerosol on the measured absorption, most refer to the dry state of the aerosol, and the coverage of the globe is far from being complete. Standardisation and calibration of the measurements is needed. Modelling exercises using currently available data on {omega} should clearly state that corrections are required. The purpose of this review is not to suggest a particular range of values for single scatter albedo. Rather, it is to illustrate that the uncertainties are currently imbedded in various data sets because of the lack of calibration, the possibility that many of the extant methods systematically overestimate light absorption coefficients, and the necessity of including the influence of humidity in models. (orig.) 95 refs.

  8. Influence of soil moisture content on surface albedo and soil thermal parameters at a tropical station

    Science.gov (United States)

    Sugathan, Neena; Biju, V.; Renuka, G.

    2014-06-01

    Half hourly data of soil moisture content, soil temperature, solar irradiance, and reflectance are measured during April 2010 to March 2011 at a tropical station, viz., Astronomical Observatory, Thiruvananthapuram, Kerala, India (76°59'E longitude and 8°29'N latitude). The monthly, seasonal and seasonal mean diurnal variation of soil moisture content is analyzed in detail and is correlated with the rainfall measured at the same site during the period of study. The large variability in the soil moisture content is attributed to the rainfall during all the seasons and also to the evaporation/movement of water to deeper layers. The relationship of surface albedo on soil moisture content on different time scales are studied and the influence of solar elevation angle and cloud cover are also investigated. Surface albedo is found to fall exponentially with increase in soil moisture content. Soil thermal diffusivity and soil thermal conductivity are also estimated from the subsoil temperature profile. Log normal dependence of thermal diffusivity and power law dependence of thermal conductivity on soil moisture content are confirmed.

  9. Influence of soil moisture content on surface albedo and soil thermal parameters at a tropical station

    Indian Academy of Sciences (India)

    Neena Sugathan; V Biju; G Renuka

    2014-07-01

    Half hourly data of soil moisture content, soil temperature, solar irradiance, and reflectance are measured during April 2010 to March 2011 at a tropical station, viz., Astronomical Observatory, Thiruvananthapuram, Kerala, India (76° 59’E longitude and 8°29’N latitude). The monthly, seasonal and seasonal mean diurnal variation of soil moisture content is analyzed in detail and is correlated with the rainfall measured at the same site during the period of study. The large variability in the soil moisture content is attributed to the rainfall during all the seasons and also to the evaporation/movement of water to deeper layers. The relationship of surface albedo on soil moisture content on different time scales are studied and the influence of solar elevation angle and cloud cover are also investigated. Surface albedo is found to fall exponentially with increase in soil moisture content. Soil thermal diffusivity and soil thermal conductivity are also estimated from the subsoil temperature profile. Log normal dependence of thermal diffusivity and power law dependence of thermal conductivity on soil moisture content are confirmed.

  10. Assessing climate impacts and risks of ocean albedo modification in the Arctic

    Science.gov (United States)

    Mengis, N.; Martin, T.; Keller, D. P.; Oschlies, A.

    2016-05-01

    The ice albedo feedback is one of the key factors of accelerated temperature increase in the high northern latitudes under global warming. This study assesses climate impacts and risks of idealized Arctic Ocean albedo modification (AOAM), a proposed climate engineering method, during transient climate change simulations with varying representative concentration pathway (RCP) scenarios. We find no potential for reversing trends in all assessed Arctic climate metrics under increasing atmospheric CO2 concentrations. AOAM only yields an initial offset during the first years after implementation. Nevertheless, sea ice loss can be delayed by 25(60) years in the RCP8.5(RCP4.5) scenario and the delayed thawing of permafrost soils in the AOAM simulations prevents up to 40(32) Pg of carbon from being released by 2100. AOAM initially dampens the decline of the Atlantic Meridional Overturning and delays the onset of open ocean deep convection in the Nordic Seas under the RCP scenarios. Both these processes cause a subsurface warming signal in the AOAM simulations relative to the default RCP simulations with the potential to destabilize Arctic marine gas hydrates. Furthermore, in 2100, the RCP8.5 AOAM simulation diverts more from the 2005-2015 reference state in many climate metrics than the RCP4.5 simulation without AOAM. Considering the demonstrated risks, we conclude that concerning longer time scales, reductions in emissions remain the safest and most effective way to prevent severe changes in the Arctic.

  11. Observation of Albedo Particles By The Detectors Nina and Nina-2

    Science.gov (United States)

    Iannucci, A.; Wizard/NINA Collaboration

    Albedo light nuclei in the Earth orbit are generated in parallel with protons and leptons as secondary product of cosmic ray interactions in the atmosphere. The NINA-2 instrument on board the satellite MITA has been in orbit at an altitude of about 400 km and an inclination of 87,3 degrees since July 15th, 2000. In this presentation we report the results of the isotope composition of hydrogen and helium of albedo origin in the range of 10­50 MeV/n in the regions of middle latitude, out of the South Atlantic Anomaly. There is a weak excess of He over He, and the 3 4 2H/1H ratio reaches the value 0.05 in energy range 10­30 MeV/n. In addition a comparison with NINA measurements, the mission prior to NINA-2 carried out on board the satellite Resurs (800 km orbit), will be presented. The com- parison shows that composition and absolute value of fluxes do not depend on the geographical altidude.

  12. A neutron Albedo system with time rejection for landmine and IED detection

    Science.gov (United States)

    Kovaltchouk, V. D.; Andrews, H. R.; Clifford, E. T. H.; Faust, A. A.; Ing, H.; McFee, J. E.

    2011-10-01

    A neutron Albedo system has been developed for imaging of buried landmines and improvised explosive devices (IEDs). It involves irradiating the ground with fast neutrons and subsequently detecting the thermalized neutrons that return. A scintillating 6Li loaded ZnS(Ag) screen with a sensitive area of 40 cm×40 cm is used as a thermal neutron detector. Scintillation light is captured by orthogonal arrays of wavelength-shifting fibers placed on either side of the scintillator surface and then transferred to X and Y multi-pixel PMTs. A timing circuit, used with pulsed neutron sources, records the time when a neutron detection takes place relative to an external synchronization pulse from the pulsed source. Experimental tests of the Albedo system performance have been done in a sand box with a 252Cf neutron source (no time gating) and with pulsed D-D (2.6 MeV) neutrons from the Defense R&D Ottawa Van de Graaff accelerator (with time gating). Information contained in the time evolution of the thermal neutron field provided improved detection capability and image reconstruction. The detector design is described and experimental results are discussed.

  13. A neutron Albedo system with time rejection for landmine and IED detection

    Energy Technology Data Exchange (ETDEWEB)

    Kovaltchouk, V.D., E-mail: kovaltchoukv@bubbletech.ca [Bubble Technology Industries, Chalk River, Ontario (Canada); Andrews, H.R.; Clifford, E.T.H. [Bubble Technology Industries, Chalk River, Ontario (Canada); Faust, A.A. [Defense R and D Canada-Suffield, Medicine Hat, Alberta (Canada); Ing, H. [Bubble Technology Industries, Chalk River, Ontario (Canada); McFee, J.E. [Defense R and D Canada-Suffield, Medicine Hat, Alberta (Canada)

    2011-10-01

    A neutron Albedo system has been developed for imaging of buried landmines and improvised explosive devices (IEDs). It involves irradiating the ground with fast neutrons and subsequently detecting the thermalized neutrons that return. A scintillating {sup 6}Li loaded ZnS(Ag) screen with a sensitive area of 40 cmx40 cm is used as a thermal neutron detector. Scintillation light is captured by orthogonal arrays of wavelength-shifting fibers placed on either side of the scintillator surface and then transferred to X and Y multi-pixel PMTs. A timing circuit, used with pulsed neutron sources, records the time when a neutron detection takes place relative to an external synchronization pulse from the pulsed source. Experimental tests of the Albedo system performance have been done in a sand box with a {sup 252}Cf neutron source (no time gating) and with pulsed D-D (2.6 MeV) neutrons from the Defense R and D Ottawa Van de Graaff accelerator (with time gating). Information contained in the time evolution of the thermal neutron field provided improved detection capability and image reconstruction. The detector design is described and experimental results are discussed.

  14. Yield of albedo flour and pectin content in the rind of yellow passion fruit

    Directory of Open Access Journals (Sweden)

    Eliana Monteiro Soares de Oliveira

    2012-09-01

    Full Text Available In this study, it was evaluated the influence of different shapes, sizes, and maturation stages on the yield of albedo flour and pectin content of yellow passion fruit rinds. Random samples of 40 fruits were used, and the data were compared using significance intervals at 5%. Weight, skin color, fruit size and shape, pulp yield, mesocarp thickness, amount of epicarp and mesocarp, moisture content, and pectin yield were determined. The maturation stages were defined according to measurements of the yellow color of the skin. The shape and size patterns were defined according to the length/width ratio (equatorial diameter of fruits. It was found that the epicarp thickness was not correlated to fruit shape and size, but it was thicker in ripe fruits. The mesocarp was thiner in small ripe fruits, but it did not change with fruit shape. Pulp yield was higher in ripe fruits, and it was not influenced by shape and size of fruits. It was concluded that the content of albedo flour can account for 3.9% of the weight of processed fruits, whereas the amount of pectin powder can account for up to 0.9% of the fruit weight.

  15. Afforestation to mitigate climate change: impacts on food prices under consideration of albedo effects

    Science.gov (United States)

    Kreidenweis, Ulrich; Humpenöder, Florian; Stevanović, Miodrag; Bodirsky, Benjamin Leon; Kriegler, Elmar; Lotze-Campen, Hermann; Popp, Alexander

    2016-08-01

    Ambitious climate targets, such as the 2 °C target, are likely to require the removal of carbon dioxide from the atmosphere. Afforestation is one such mitigation option but could, through the competition for land, also lead to food prices hikes. In addition, afforestation often decreases land-surface albedo and the amount of short-wave radiation reflected back to space, which results in a warming effect. In particular in the boreal zone, such biophysical warming effects following from afforestation are estimated to offset the cooling effect from carbon sequestration. We assessed the food price response of afforestation, and considered the albedo effect with scenarios in which afforestation was restricted to certain latitudinal zones. In our study, afforestation was incentivized by a globally uniform reward for carbon uptake in the terrestrial biosphere. This resulted in large-scale afforestation (2580 Mha globally) and substantial carbon sequestration (860 GtCO2) up to the end of the century. However, it was also associated with an increase in food prices of about 80% by 2050 and a more than fourfold increase by 2100. When afforestation was restricted to the tropics the food price response was substantially reduced, while still almost 60% cumulative carbon sequestration was achieved. In the medium term, the increase in prices was then lower than the increase in income underlying our scenario projections. Moreover, our results indicate that more liberalised trade in agricultural commodities could buffer the food price increases following from afforestation in tropical regions.

  16. Natural Aerosols Explain Seasonal and Spatial Patterns of Southern Ocean Cloud Albedo

    Energy Technology Data Exchange (ETDEWEB)

    McCoy, Daniel; Burrows, Susannah M.; Wood, R.; Grosvenor, Daniel P.; Elliott, Scott; Ma, Po-Lun; Rasch, Philip J.; Hartmann, Dennis L.

    2015-07-17

    Small particles called aerosols act as nucleation sites for cloud drop formation, affecting clouds and cloud properties – ultimately influencing the cloud dynamics, lifetime, water path and areal extent that determine the reflectivity (albedo) of clouds. The concentration Nd of droplets in clouds that influences planetary albedo is sensitive to the availability of aerosol particles on which the droplets form. Natural aerosol concentrations not only affect cloud properties themselves, but also modulate the sensitivity of clouds to changes in anthropogenic aerosols. Here, it is shown that modeled natural aerosols, principally marine biogenic primary and secondary aerosol sources, explain more than half of the spatiotemporal variability in satellite-observed Nd. Enhanced Nd over regions of high biological activity is found to be driven primarily by high concentrations of sulfate aerosol at lower Southern Ocean latitudes (35-45°S) and by organic matter in sea spray aerosol at higher latitudes (45-55°S). Biogenic sources are estimated to increase the summertime mean reflected solar radiation in excess of 10 W m-2 over parts of the Southern Ocean, which is comparable to the annual mean increases expected from anthropogenic aerosols over heavily polluted regions of the Northern Hemisphere.

  17. MERIS albedo climatology for FRESCO+ O2 A-band cloud retrieval

    Directory of Open Access Journals (Sweden)

    Y. Zhou

    2011-03-01

    Full Text Available A new global albedo climatology for Oxygen A-band cloud retrievals is presented. The climatology is based on MEdium Resolution Imaging Spectrometer (MERIS Albedomap data and its favourable impact on the derivation of cloud fraction is demonstrated for the FRESCO+ (Fast Retrieval Scheme for Clouds from the Oxygen A-band algorithm. To date, a relatively coarse resolution (1° × 1° surface reflectance dataset from GOME (Global Ozone Monitoring Experiment Lambert-equivalent reflectivity (LER is used in FRESCO+. The GOME LER climatology does not account for the usually higher spatial resolution of UV/VIS instruments designed for trace gas remote sensing which introduces several artefacts, e.g. in regions with sharp spectral contrasts like coastlines or over bright surface targets. Therefore, MERIS black-sky albedo (BSA data from the period October 2002 to October 2006 were aggregated to a grid of 0.25° × 0.25° for each month of the year and for different spectral channels. In contrary to other available surface reflectivity datasets, MERIS includes channels at 754 nm and 775 nm which are located close to the spectral windows required for O2 A-band cloud retrievals. The MERIS BSA in the near-infrared compares well to Moderate Resolution Imaging Spectroradiometer (MODIS derived BSA with an average difference lower than 1% and a correlation coefficient of 0.98. However, when relating MERIS BSA to GOME LER a distinctly lower correlation (0.80 and enhanced scatter is found. Effective cloud fractions from two exemplary months (January and July 2006 of Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY data were subsequently derived with FRESCO+ and compared to those from the Heidelberg Iterative Cloud Retrieval Utilities (HICRU algorithm. The MERIS climatology generally improves FRESCO+ effective cloud fractions. In particular small cloud fractions are in better agreement with HICRU. This is of importance for atmospheric

  18. Developing a Model-Based Framework for Quality Assessments of In-Situ Measurement Protocols for Albedo

    Science.gov (United States)

    Adams, Jennifer Susan; Gobron, Nadine; Widlowski, Jean-Luc; Mio, Corrado

    2016-08-01

    Validation of satellite-based retrievals of land surface albedo using in-situ measurements is essential to identify differences between them, to improve retrieval algorithms and to assess conformity to accuracy requirements. Differences between in-situ and satellite-based retrievals depend on the actual difference and their associated uncertainties, where it is crucial that the uncertainties of both can be computed to properly understand potential differences. This study introduces a model-based framework for assessing the quality of in-situ albedo measurements. A 3D Monte Carlo Ray Tracing (MCRT) radiative transfer model is used to simulate field measurements of surface albedo, and is able to identify and quantify potential sources of error in the field measurement. Compliance with the World Meteorological Organisation (WMO) requirement for 3% accuracy is tested.

  19. Carbonization in Titan Tholins: implication for low albedo on surfaces of Centaurs and trans-Neptunian objects

    Science.gov (United States)

    Giri, Chaitanya; McKay, Christopher P.; Goesmann, Fred; Schäfer, Nadine; Li, Xiang; Steininger, Harald; Brinckerhoff, William B.; Gautier, Thomas; Reitner, Joachim; Meierhenrich, Uwe J.

    2016-07-01

    Astronomical observations of Centaurs and trans-Neptunian objects (TNOs) yield two characteristic features - near-infrared (NIR) reflectance and low geometric albedo. The first feature apparently originates due to complex organic material on their surfaces, but the origin of the material contributing to low albedo is not well understood. Titan tholins synthesized to simulate aerosols in the atmosphere of Saturn's moon Titan have also been used for simulating the NIR reflectances of several Centaurs and TNOs. Here, we report novel detections of large polycyclic aromatic hydrocarbons, nanoscopic soot aggregates and cauliflower-like graphite within Titan tholins. We put forth a proof of concept stating the surfaces of Centaurs and TNOs may perhaps comprise of highly `carbonized' complex organic material, analogous to the tholins we investigated. Such material would apparently be capable of contributing to the NIR reflectances and to the low geometric albedos simultaneously.

  20. The Influence of green areas and roof albedos on air temperatures during Extreme Heat Events in Berlin, Germany

    Directory of Open Access Journals (Sweden)

    Sebastian Schubert

    2013-04-01

    Full Text Available The mesoscale atmospheric model COSMO-CLM (CCLM with the Double Canyon Effect Parametrization Scheme (DCEP is applied to investigate possible adaption measures to extreme heat events (EHEs for the city of Berlin, Germany. The emphasis is on the effects of a modified urban vegetation cover and roof albedo on near-surface air temperatures. Five EHEs with a duration of 5 days or more are identified for the period 2000 to 2009. A reference simulation is carried out for each EHE with current vegetation cover, roof albedo and urban canopy parameters (UCPs, and is evaluated with temperature observations from weather stations in Berlin and its surroundings. The derivation of the UCPs from an impervious surface map and a 3-D building data set is detailed. Characteristics of the simulated urban heat island for each EHE are analysed in terms of these UCPs. In addition, six sensitivity runs are examined with a modified vegetation cover of each urban grid cell by -25%, 5% and 15%, with a roof albedo increased to 0.40 and 0.65, and with a combination of the largest vegetation cover and roof albedo, respectively. At the weather stations' grid cells, the results show a maximum of the average diurnal change in air temperature during each EHE of 0.82 K and -0.48 K for the -25% and 15% vegetation covers, -0.50 K for the roof albedos of 0.65, and -0.63 K for the combined vegetation and albedo case. The largest effects on the air temperature are detected during midday.

  1. Comparison of Monte Carlo Critical Spectra from B1 Buckling Search and Albedo Search Methods. Preliminary Results

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Yu Gwon; Yun, Sung Hwan; Cho, Nam Zin [KAIST, Daejeon (Korea, Republic of)

    2011-10-15

    Since the Monte Carlo method overcomes limitations in multi-group approximation and geometry description, it is gaining increasing use in reactor physics problems. Recently, a new leakage-corrected method was suggested by the authors, in which the critical spectrum is obtained by albedo-based leakage correction in the Monte Carlo method. In this paper, the critical spectrum based on the albedo-based leakage-corrected method will be compared with the critical spectrum by conventional B1 method (with condensed cross sections) and reference critical whole-core assembly spectrum. These two methods are implemented in our local MCNP5 (version 1.50)

  2. Development of a MODIS-Derived Surface Albedo Data Set: An Improved Model Input for Processing the NSRDB

    Energy Technology Data Exchange (ETDEWEB)

    Maclaurin, Galen [National Renewable Energy Lab. (NREL), Golden, CO (United States); Sengupta, Manajit [National Renewable Energy Lab. (NREL), Golden, CO (United States); Xie, Yu [National Renewable Energy Lab. (NREL), Golden, CO (United States); Gilroy, Nicholas [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-12-01

    A significant source of bias in the transposition of global horizontal irradiance to plane-of-array (POA) irradiance arises from inaccurate estimations of surface albedo. The current physics-based model used to produce the National Solar Radiation Database (NSRDB) relies on model estimations of surface albedo from a reanalysis climatalogy produced at relatively coarse spatial resolution compared to that of the NSRDB. As an input to spectral decomposition and transposition models, more accurate surface albedo data from remotely sensed imagery at finer spatial resolutions would improve accuracy in the final product. The National Renewable Energy Laboratory (NREL) developed an improved white-sky (bi-hemispherical reflectance) broadband (0.3-5.0 ..mu..m) surface albedo data set for processing the NSRDB from two existing data sets: a gap-filled albedo product and a daily snow cover product. The Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard the Terra and Aqua satellites have provided high-quality measurements of surface albedo at 30 arc-second spatial resolution and 8-day temporal resolution since 2001. The high spatial and temporal resolutions and the temporal coverage of the MODIS sensor will allow for improved modeling of POA irradiance in the NSRDB. However, cloud and snow cover interfere with MODIS observations of ground surface albedo, and thus they require post-processing. The MODIS production team applied a gap-filling methodology to interpolate observations obscured by clouds or ephemeral snow. This approach filled pixels with ephemeral snow cover because the 8-day temporal resolution is too coarse to accurately capture the variability of snow cover and its impact on albedo estimates. However, for this project, accurate representation of daily snow cover change is important in producing the NSRDB. Therefore, NREL also used the Integrated Multisensor Snow and Ice Mapping System data set, which provides daily snow cover observations of the

  3. Optimal Nodes Selectiveness from WSN to Fit Field Scale Albedo Observation and Validation in Long Time Series in the Foci Experiment Areas, Heihe

    Directory of Open Access Journals (Sweden)

    Xiaodan Wu

    2015-11-01

    Full Text Available To evaluate and improve the quality of land surface albedo products, validation with ground measurements of albedo is crucial over the spatially and temporally heterogeneous land surface. One of the essential steps for satellite albedo product validation is coarse scale observation technique development with long time ground-based measurements. In this paper, the optimal nodes were selected from the wireless sensor network (WSN to perform observation at large scale and in longer time series for validation of albedo products. The relative difference is used to analyze the spatiotemporal representativeness of each node. The random combination method is used to assess the number of required sites (NRS and then to identify the most representative combination (MRC. On this basis, an upscaling transform function with different weights for each node in the MRC, which are calculated with the ordinary least squares (OLS linear regression method, is used to upscale WSN node albedo from point scale to the field scale. This method is illustrated by selecting the optimal nodes and upscaling surface albedo from point observation to the field scale in the Heihe River basin, China. Primary findings are: (a The method of reducing the number of observations without significant loss of information about surface albedo at field scale is feasible and effective; (b When only few sensors are available, the most representative locations in time and space should be the first priority; when a number of sensors are available in the heterogeneous land surface, it is preferable to install them in different land surface, rather than the most representative locations; (c The most representative combination (MRC combined with the upscaling weight coefficients can give a robust estimate of the field mean surface albedo. These efforts based on ground albedo observations promote the chance to use point information for validation of coarse scale albedo products. Moreover, a

  4. The Size, Shape, and Albedo of Deep Impact Target 9P/Tempel 1

    Science.gov (United States)

    A'Hearn, Michael; Lisse, Carey; Lisse, C.; Fernandez, Y.; Belton, M.; Groussin, O.; Meech, K.; van Cleve, J.

    2004-02-01

    The Deep Impact mission, the eighth mission in NASA's Discovery Program, will launch on 30 Dec 2004 and will impact the nucleus of comet 9P/Tempel 1 on 4 July 2005. Delivering an impactor to a cometary nucleus and observing the results of the impact is a challenging task. Mission success depends critically on the ability of the DI spacecraft to navigate to the comet. Despite robust targeting algorithms, large uncertainties in size, shape, albedo distribution, and rotational state significantly degrade the probability that the impactor will land in a sunlit portion of the surface that is observable from the flyby. The uncertainties in the size, axial ratio, and rotational state further jeopardize the ability of the flyby spacecraft to point its High Resolution Instrument at the actual impact site with sufficient precision to ensure it is in the field of view. Current estimate of the comet's size using Keck LWS observations are uncertain by 50% and they have provided no information on the distribution of albedo. Although uncertainty in the phasing of the optical lightcurve represents a large part of that error, there is also a significant uncertainty due to the combination of low SNR in the data from Keck and the limited spectral range over which data could be obtained. In order to improve our estimate of the size and shape of the nucleus of Tempel 1, we must obtain data with much higher SNR and with one-hour time resolution over a significant portion of the rotation light curve when the comet is inactive. We must determine whether or not there are large variations in albedo across the surface to order to ensure that the rotational lightcurve from optical data can be used to predict the convex hull of the actual shape. Tempel 1 is available in only one Spitzer viewing widow before it is expected to be close enough to the sun to become active, namely the window from 27 Feb through 29 April 2004, before the first GO observing period, at 3.7 AU from the Sun. The expect

  5. Cassini Imaging of Iapetus and Solution of the Albedo Asymmetry Enigma

    Science.gov (United States)

    Denk, Tilmann; Spencer, John

    2014-05-01

    Cassini imaging of Iapetus during one close and several more distant flybys mainly in the first years of the mission revealed an alien and often unique landscape of this third-largest moon in the Saturnian system [1]. The data show numerous impact craters on the bright and dark terrain, equator-facing dark and pole-facing bright crater walls, huge impact basins, rather minor endogenic geologic features, a non-spherical, but ellipsoidal shape, a giant ridge which spans across half of Iapetus' circumference exactly along the equator, a newly detected global 'color dichotomy' presumably formed by dust from retrograde irregular moons, and of course the famous extreme global albedo asymmetry which has been an enigma for more than three centuries. Revealing the cause of this 'albedo dichotomy' enigma of Iapetus, where the trailing side and poles are more than 10x brighter than the leading side, was one of the major tasks for the Cassini mission. It has now been solved successfully. In the mid-1970es, deposition of exogenic dark material on the leading side, originating from outer retrograde moon Phoebe, was proposed as the cause. But this alone could not explain the global shape, sharpness, and complexity of the transition between Iapetus' bright and dark terrain. Mainly with Cassini spectrometer (CIRS) and imaging (ISS) data, all these characteristics and the asymmetry's large amplitude are now plausibly explained by runaway global thermal migration of water ice, triggered by the deposition of dark material on the leading hemisphere. This mechanism is unique to Iapetus among the Saturnian satellites for many reasons. Most important are Iapetus' slow rotation which produces unusually high daytime temperatures and water ice sublimation rates, and the size (gravity) of Iapetus which is small enough for global migration of water ice but large enough that much of the ice is retained on the surface [2]. References: [1] Denk, T., Neukum, G., Roatsch, Th., Porco, C.C., Burns, J

  6. Top-of-Atmosphere Albedo Estimation from Angular Distribution Models using Scene Identification from Satellite Cloud Property Retrievals

    Science.gov (United States)

    Loeb, N. G.; Parol, F.; Buriez, J.-C.; Vanbauce, C.

    2000-01-01

    The next generation of Earth radiation budget satellite instruments will routinely merge estimates of global top-of-atmosphere radiative fluxes with cloud properties. This information will offer many new opportunities for validating radiative transfer models and cloud parameterizations in climate models. In this study, five months of POLarization and Directionality of the Earth's Reflectances (POLDER) 670 nm radiance measurements are considered in order to examine how satellite cloud property retrievals can be used to define empirical Angular Distribution Models (ADMs) for estimating top-of-atmosphere (TOA) albedo. ADMs are defined for 19 scene types defined by satellite retrievals of cloud fraction and cloud optical depth. Two approaches are used to define the ADM scene types: The first assumes there are no biases in the retrieved cloud properties and defines ADMs for fixed discrete intervals of cloud fraction and cloud optical depth (fixed-tau approach). The second approach involves the same cloud fraction intervals, but uses percentile intervals of cloud optical depth instead (percentile-tau approach). Albedos generated using these methods are compared with albedos inferred directly from the mean observed reflectance field. Albedos based on ADMs that assume cloud properties are unbiased (fixed-tau approach) show a strong systematic dependence on viewing geometry. This dependence becomes more pronounced with increasing solar zenith angle, reaching approximately equals 12% (relative) between near-nadir and oblique viewing zenith angles for solar zenith angles between 60 deg and 70 deg. The cause for this bias is shown to be due to biases in the cloud optical depth retrievals. In contrast, albedos based on ADMs built using percentile intervals of cloud optical depth (percentile-tau approach) show very little viewing zenith angle dependence and are in good agreement with albedos obtained by direct integration of the mean observed reflectance field (less than 1

  7. Spent fuel measurements. passive neutron albedo reactivity (PNAR) and photon signatures

    Energy Technology Data Exchange (ETDEWEB)

    Eigenbrodt, Julia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Menlove, Howard Olsen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-03-29

    The International Atomic Energy Agency’s (IAEA) safeguards technical objective is the timely detection of a diversion of a significant quantity of nuclear material from peaceful activities to the manufacture of nuclear weapons or of other nuclear explosive devices or for purposes unknown, and deterrence of such diversion by the risk of early detection. An important IAEA task towards meeting this objective is the ability to accurately and reliably measure spent nuclear fuel (SNF) to verify reactor operating parameters and verify that the fuel has not been removed from reactors or SNF storage facilities. This dissertation analyzes a method to improve the state-of-the-art of nuclear material safeguards measurements using two combined measurement techniques: passive neutron albedo reactivity (PNAR) and passive spectral photon measurements.

  8. Geomagnetically trapped, albedo and solar energetic particles: trajectory analysis and flux reconstruction with PAMELA

    CERN Document Server

    Bruno, A; Barbarino, G C; Bazilevskaya, G A; Bellotti, R; Boezio, M; Bogomolov, E A; Bongi, M; Bonvicini, V; Bottai, S; Cafagna, F; Campana, D; Carlson, P; Casolino, M; Castellini, G; Christian, E C; De Donato, C; de Nolfo, G A; De Santis, C; De Simone, N; Di Felice, V; Galper, A M; Karelin, A V; Koldashov, S V; Koldobskiy, S; Krutkov, S Y; Kvashnin, A N; Leonov, A; Malakhov, V; Marcelli, L; Martucci, M; Mayorov, A G; Menn, W; Mergé, M; Mikhailov, V V; Mocchiutti, E; Monaco, A; Mori, N; Munini, R; Osteria, G; Palma, F; Panico, B; Papini, P; Pearce, M; Picozza, P; Ricci, M; Ricciarini, S B; Ryan, J M; Sarkar, R; Scotti, V; Simon, M; Sparvoli, R; Spillantini, P; Stochaj, S; Stozhkov, Y I; Vacchi, A; Vannuccini, E; Vasilyev, G I; Voronov, S A; Yurkin, Y T; Zampa, G; Zampa, N

    2016-01-01

    The PAMELA satellite experiment is providing comprehensive observations of the interplanetary and magnetospheric radiation in the near-Earth environment. Thanks to its identification capabilities and the semi-polar orbit, PAMELA is able to precisely measure the energetic spectra and the angular distributions of the different cosmic-ray populations over a wide latitude region, including geomagnetically trapped and albedo particles. Its observations comprise the solar energetic particle events between solar cycles 23 and 24, and the geomagnetic cutoff variations during magnetospheric storms. PAMELA's measurements are supported by an accurate analysis of particle trajectories in the Earth's magnetosphere based on a realistic geomagnetic field modeling, which allows the classification of particle populations of different origin and the investigation of the asymptotic directions of arrival.

  9. Sensitivity of Pliocene Arctic climate to orbital forcing, atmospheric CO2 and sea ice albedo parameterisation

    Science.gov (United States)

    Howell, Fergus; Haywood, Alan; Pickering, Steven

    2016-04-01

    General circulation model (GCM) simulations of the mid-Pliocene Warm Period (mPWP, 3.264 to 3.025 Myr ago) do not reproduce the magnitude of Northern Hemisphere high latitude surface air and sea surface temperature (SAT and SST) warming that proxy data indicates. There is also large uncertainty regarding the state of sea ice cover in the mPWP. Evidence for both perennial and seasonal mPWP Arctic sea ice is found in analyses of marine sediments, whilst in a multi-model ensemble of mPWP climate simulations, half of the ensemble simulated ice-free summer Arctic conditions. Given the strong influence that sea ice exerts on high latitude temperatures, a better understanding of the nature of mPWP Arctic sea ice would be highly beneficial in understanding proxy derived estimates of high latitude surface temperature change, and the ability of climate models to reproduce this. In GCM simulations, the mPWP is typically represented with fixed orbital forcing, usually identical to modern, and atmospheric CO2 concentrations of ˜ 400 ppm. However, orbital forcing varied over the ˜ 240,000 years of the mPWP, and it is likely that atmospheric CO2 varied as well. A previous study has suggested that the parameterisation of sea ice albedo in the HadCM3 GCM may not reflect the sea ice albedo for a warmer climate, where seasonal sea ice constitutes a greater proportion of the Arctic sea ice cover. These three factors, in isolation and combined, can greatly influence the simulation of Arctic sea ice cover and the degree of high latitude surface temperature warming. This paper explores the impact of various combinations of potential mPWP orbital forcing, atmospheric CO2 concentrations and minimum sea ice albedo on sea ice extent and high latitude warming. The focus is on the Northern Hemisphere, due to availability of proxy data, and the large data-model discrepancies in this region. Changes in orbital forcings are demonstrated to be sufficient to alter the Arctic sea ice simulated by

  10. Tables of phase functions, opacities, albedos, equilibrium temperatures, and radiative accelerations of dust grains in exoplanets

    CERN Document Server

    Budaj, Jan; Salmeron, Raquel; Hubeny, Ivan

    2015-01-01

    There has been growing observational evidence for the presence of condensates in the atmospheres and/or comet-like tails of extrasolar planets. As a result, systematic and homogeneous tables of dust properties are useful in order to facilitate further observational and theoretical studies. In this paper we present calculations and analysis of non-isotropic phase functions, asymmetry parameter (mean cosine of the scattering angle), absorption and scattering opacities, single scattering albedos, equilibrium temperatures, and radiative accelerations of dust grains relevant for extrasolar planets. Our assumptions include spherical grain shape, Deirmendjian particle size distribution, and Mie theory. We consider several species: corundum/alumina, iron, olivines with 0% and 50% iron content, pyroxenes with 0%, 20% and 60% iron content, carbon at two different temperatures, water ice, liquid water, and ammonia. The presented tables cover the wavelength range of 0.2 to 500 micron and modal particle radii from 0.01 mi...

  11. Carbon nanohorn-based nanofluids: characterization of the spectral scattering albedo

    Science.gov (United States)

    Mercatelli, Luca; Sani, Elisa; Giannini, Annalisa; di Ninni, Paola; Martelli, Fabrizio; Zaccanti, Giovanni

    2012-02-01

    The full characterization of the optical properties of nanofluids consisting of single-wall carbon nanohorns of different morphologies in aqueous suspensions is carried out using a novel spectrophotometric technique. Information on the nanofluid scattering and absorption spectral characteristics is obtained by analyzing the data within the single scattering theory and validating the method by comparison with previous monochromatic measurements performed with a different technique. The high absorption coefficient measured joint to the very low scattering albedo opens promising application perspectives for single-wall carbon nanohorn-based fluid or solid suspensions. The proposed approximate approach can be extended also to other low-scattering turbid media. PACS: 78.35.+c Brillouin and Rayleigh scattering, other light scattering; 78.40.Ri absorption and reflection spectra, fullerenes and related materials; 81.05.U- carbon/carbon-based materials; 78.67.Bf optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures, nanocrystals, nanoparticles, and nanoclusters.

  12. Verification analysis of thermoluminescent albedo neutron dosimetry at MOX fuel facilities.

    Science.gov (United States)

    Nakagawa, Takahiro; Takada, Chie; Tsujimura, Norio

    2011-07-01

    Radiation workers engaging in the fabrication of MOX fuels at the Japan Atomic Energy Agency-Nuclear Fuel Cycle Engineering Laboratories are exposed to neutrons. Accordingly, thermoluminescent albedo dosemeters (TLADs) are used for individual neutron dosimetry. Because dose estimation using TLADs is susceptible to variation of the neutron energy spectrum, the authors have provided TLADs incorporating solid-state nuclear tracks detectors (SSNTDs) to selected workers who are routinely exposed to neutrons and have continued analysis of the relationship between the SSNTD and the TLAD (T/R(f)) over the past 6 y from 2004 to 2009. Consequently, the T/R(f) value in each year was less than the data during 1991-1993, although the neutron spectra had not changed since then. This decrease of the T/R(f) implies that the ratio of operation time nearby gloveboxes and the total work time has decreased.

  13. Global climate impacts of bioenergy from forests: implications from biogenic CO2 fluxes and surface albedo

    Science.gov (United States)

    Cherubini, Francesco; Bright, Ryan; Strømman, Anders

    2013-04-01

    Production of biomass for bioenergy can alter biogeochemical and biogeophysical mechanisms, thus affecting local and global climate. Recent scientific developments mainly embraced impacts from land use changes resulting from area-expanded biomass production, with several extensive insights available. Comparably less attention, however, is given to the assessment of direct land surface-atmosphere climate impacts of bioenergy systems under rotation such as in plantations and forested ecosystems, whereby land use disturbances are only temporary. In this work, we assess bioenergy systems representative of various biomass species (spruce, pine, aspen, etc.) and climatic regions (US, Canada, Norway, etc.), for both stationary and vehicle applications. In addition to conventional greenhouse gas (GHG) emissions through life cycle activities (harvest, transport, processing, etc.), we evaluate the contributions to global warming of temporary effects resulting from the perturbation in atmospheric carbon dioxide (CO2) concentration caused by the timing of biogenic CO2 fluxes and in surface reflectivity (albedo). Biogenic CO2 fluxes on site after harvest are directly measured through Net Ecosystem Productivity (NEP) chronosequences from flux towers established at the interface between the forest canopy and the atmosphere and are inclusive of all CO2 exchanges occurring in the forest (e.g., sequestration of CO2 in growing trees, emissions from soil respiration and decomposition of dead organic materials). These primary data based on empirical measurements provide an accurate representation of the forest carbon sink behavior over time, and they are used in the elaboration of high-resolution IRFs for biogenic CO2 emissions. Chronosequence of albedo values from clear-cut to pre-harvest levels are gathered from satellite data (MODIS black-sky shortwave broadband, Collection 5, MCD43A). Following the cause-effect chain from emissions to damages, through radiative forcing and changes

  14. FLUKA Calculation of the Neutron Albedo Encountered at Low Earth Orbits

    CERN Document Server

    Claret, Arnaud; Combier, Natacha; Ferrari, Alfredo; Laurent, Philippe

    2014-01-01

    This paper presents Monte-Carlo simulations based on the Fluka code aiming to calculate the contribution of the neutron albedo at a given date and altitude above the Earth chosen by the user. The main input parameters of our model are the solar modulation affecting the spectra of cosmic rays, and the date of the Earth’s geomagnetic fi eld. The results consist in a two-parameter distribution, the neutron energy and the angle to the tangent plane of the sphere containing the orbi t of interest, and are provided by geographical position above the E arth at the chosen altitude. This model can be used to predict the te mporal variation of the neutron fl ux encountered along the orbit, and thus constrain the determination of the instrumental backg round noise of space experiments in low earth orbit.

  15. 9969 Braille: Deep Space 1 infrared spectroscopy, geometric albedo, and classification

    Science.gov (United States)

    Buratti, B.J.; Britt, D.T.; Soderblom, L.A.; Hicks, M.D.; Boice, D.C.; Brown, R.H.; Meier, R.; Nelson, R.M.; Oberst, J.; Owen, T.C.; Rivkin, A.S.; Sandel, B.R.; Stern, S.A.; Thomas, N.; Yelle, R.V.

    2004-01-01

    Spectra of Asteroid 9969 Braille in the 1.25-2.6 ??m region returned by the Deep Space 1 (DS1) Mission show a ???10% absorption band centered at 2 ??m, and a reflectance peak at 1.6 ??m. Analysis of these features suggest that the composition of Braille is roughly equal parts pyroxene and olivine. Its spectrum between 0.4 and 2.5 ??m suggests that it is most closely related to the Q taxonomic type of asteroid. The spectrum also closely matches that of the ordinary chondrites, the most common type of terrestrial meteorite. The geometric albedo of Braille is unusually high (pv = 0.34), which is also consistent with its placement within the rarer classes of stony asteroids, and which suggests it has a relatively fresh, unweathered surface, perhaps due to a recent collision. ?? 2003 Elsevier Inc. All rights reserved.

  16. Effect of atmospheric gases, surface albedo and cloud overlap on the absorbed solar radiation

    Directory of Open Access Journals (Sweden)

    Ashok Sinha

    Full Text Available Recent studies have provided new evidence that models may systematically underestimate cloud solar absorption compared to observations. This study extends previous work on this "absorption anomaly'' by using observational data together with solar radiative transfer parameterisations to calculate fs (the ratio of surface and top of the atmosphere net cloud forcings and its latitudinal variation for a range of cloud types. Principally, it is found that (a the zonal mean behaviour of fs varies substantially with cloud type, with the highest values obtained for low clouds; (b gaseous absorption and scattering can radically alter the pattern of the variation of fs with latitude, but gaseous effects cannot in general raise fs to the level of around 1.5 as recently determined; (c the importance of the gaseous contribution to the atmospheric ASR is such that whilst fs rises with surface albedo, the net cloud contribution to the atmospheric ASR falls; (d the assumed form of the degree of cloud overlap in the model can substantially affect the cloud contribution to the atmospheric ASR whilst leaving the parameter fs largely unaffected; (e even large uncertainties in the observed optical depths alone cannot account for discrepancies apparent between modelled and newly observed cloud solar absorption. It is concluded that the main source of the anomaly may derive from the considerable uncertainties regarding impure droplet microphysics rather than, or together with, uncertainties in macroscopic quantities. Further, variable surface albedos and gaseous effects may limit the use of contemporaneous satellite and ground-based measurements to infer the cloud solar absorption from the parameter fs.

  17. Albedo and heat transport in 3-D model simulations of the early Archean climate

    Directory of Open Access Journals (Sweden)

    H. Kienert

    2013-08-01

    Full Text Available At the beginning of the Archean eon (ca. 3.8 billion years ago, the Earth's climate state was significantly different from today due to the lower solar luminosity, smaller continental fraction, higher rotation rate and, presumably, significantly larger greenhouse gas concentrations. All these aspects play a role in solutions to the "faint young Sun paradox" which must explain why the ocean surface was not fully frozen at that time. Here, we present 3-D model simulations of climate states that are consistent with early Archean boundary conditions and have different CO2 concentrations, aiming at an understanding of the fundamental characteristics of the early Archean climate system. In order to do so, we have appropriately modified an intermediate complexity climate model that couples a statistical-dynamical atmosphere model (involving parameterizations of the dynamics to an ocean general circulation model and a thermodynamic-dynamic sea-ice model. We focus on three states: one of them is ice-free, one has the same mean surface air temperature of 288 K as today's Earth and the third one is the coldest stable state in which there is still an area with liquid surface water (i.e. the critical state at the transition to a "snowball Earth". We find a reduction in meridional heat transport compared to today, which leads to a steeper latitudinal temperature profile and has atmospheric as well as oceanic contributions. Ocean surface velocities are largely zonal, and the strength of the atmospheric meridional circulation is significantly reduced in all three states. These aspects contribute to the observed relation between global mean temperature and albedo, which we suggest as a parameterization of the ice-albedo feedback for 1-D model simulations of the early Archean and thus the faint young Sun problem.

  18. Albedo enhancement of marine clouds to counteract global warming: impacts on the hydrological cycle

    Energy Technology Data Exchange (ETDEWEB)

    Bala, G. [Indian Institute of Science, Divecha Center for Climate Change, Bangalore (India); Indian Institute of Science, Center for Atmospheric and Oceanic Sciences, Bangalore (India); Caldeira, Ken; Cao, Long; Ban-Weiss, George; Shin, Ho-Jeong [Carnegie Institution, Department of Global Ecology, Stanford, CA (United States); Nemani, Rama [NASA Ames Research Center, Moffett Field, CA (United States)

    2011-09-15

    Recent studies have shown that changes in solar radiation affect the hydrological cycle more strongly than equivalent CO{sub 2} changes for the same change in global mean surface temperature. Thus, solar radiation management ''geoengineering'' proposals to completely offset global mean temperature increases by reducing the amount of absorbed sunlight might be expected to slow the global water cycle and reduce runoff over land. However, proposed countering of global warming by increasing the albedo of marine clouds would reduce surface solar radiation only over the oceans. Here, for an idealized scenario, we analyze the response of temperature and the hydrological cycle to increased reflection by clouds over the ocean using an atmospheric general circulation model coupled to a mixed layer ocean model. When cloud droplets are reduced in size over all oceans uniformly to offset the temperature increase from a doubling of atmospheric CO{sub 2}, the global-mean precipitation and evaporation decreases by about 1.3% but runoff over land increases by 7.5% primarily due to increases over tropical land. In the model, more reflective marine clouds cool the atmospheric column over ocean. The result is a sinking motion over oceans and upward motion over land. We attribute the increased runoff over land to this increased upward motion over land when marine clouds are made more reflective. Our results suggest that, in contrast to other proposals to increase planetary albedo, offsetting mean global warming by reducing marine cloud droplet size does not necessarily lead to a drying, on average, of the continents. However, we note that the changes in precipitation, evaporation and P-E are dominated by small but significant areas, and given the highly idealized nature of this study, a more thorough and broader assessment would be required for proposals of altering marine cloud properties on a large scale. (orig.)

  19. Albedo and heat transport in 3-dimensional model simulations of the early Archean climate

    Directory of Open Access Journals (Sweden)

    H. Kienert

    2013-01-01

    Full Text Available At the beginning of the Archean eon (ca. 3.8 billion yr ago, the Earth's climate state was significantly different from today due to the lower solar luminosity, smaller continental fraction, higher rotation rate and, presumably, significantly larger greenhouse gas concentrations. All these aspects play a role in solutions to the "faint young Sun problem" which must explain why the ocean surface was not fully frozen at that time. Here, we present 3-dimensional model simulations of climate states that are consistent with early Archean boundary conditions and have different CO2 concentrations, aiming at an understanding of the fundamental characteristics of the early Archean climate system. We focus on three states: one of them is ice-free, one has the same mean surface air temperature of 288 K as today's Earth and the third one is the coldest stable state in which there is still an area with liquid surface water (i.e. the critical state at the transition to a "snowball Earth". We find a reduction in meridional heat transport compared to today which leads to a steeper latitudinal temperature profile and has atmospheric as well as oceanic contributions. Ocean surface velocities are largely zonal, and the strength of the atmospheric meridional circulation is significantly reduced in all three states. These aspects contribute to the observed relation between global mean temperature and albedo, which we suggest as a parameterisation of the ice-albedo feedback for 1-dimensional model simulations of the early Archean and thus the faint young Sun problem.

  20. The melt pond fraction and spectral sea ice albedo retrieval from MERIS data: validation and trends of sea ice albedo and melt pond fraction in the Arctic for years 2002–2011

    Directory of Open Access Journals (Sweden)

    L. Istomina

    2014-10-01

    Full Text Available The presence of melt ponds on the Arctic sea ice strongly affects the energy balance of the Arctic Ocean in summer. It affects albedo as well as transmittance through the sea ice, which has consequences on the heat balance and mass balance of sea ice. An algorithm to retrieve melt pond fraction and sea ice albedo (Zege et al., 2014 from the MEdium Resolution Imaging Spectrometer (MERIS data is validated against aerial, ship borne and in situ campaign data. The result show the best correlation for landfast and multiyear ice of high ice concentrations (albedo: R = 0.92, RMS = 0.068, melt pond fraction: R = 0.6, RMS = 0.065. The correlation for lower ice concentrations, subpixel ice floes, blue ice and wet ice is lower due to complicated surface conditions and ice drift. Combining all aerial observations gives a mean albedo RMS equal to 0.089 and a mean melt pond fraction RMS equal to 0.22. The in situ melt pond fraction correlation is R = 0.72 with an RMS = 0.14. Ship cruise data might be affected by documentation of varying accuracy within the ASPeCT protocol, which is the reason for discrepancy between the satellite value and observed value: mean R = 0.21, mean RMS = 0.16. An additional dynamic spatial cloud filter for MERIS over snow and ice has been developed to assist with the validation on swath data. The case studies and trend analysis for the whole MERIS period (2002–2011 show pronounced and reasonable spatial features of melt pond fractions and sea ice albedo. The most prominent feature is the melt onset shifting towards spring (starting already in weeks 3 and 4 of June within the multiyear ice area, north to the Queen Elizabeth Islands and North Greenland.

  1. 21 Lutetia and other M-types: Their sizes, albedos, and thermal properties from new IRTF measurements

    NARCIS (Netherlands)

    Mueller, M.; Harris, A. W.; Delbo, M.; MIRSI Team, [No Value

    2005-01-01

    The M-type taxonomic group, introduced by Tholen (1989), contains asteroids with generally featureless spectra and IRAS albedos of around 0.2. M-type asteroids were originally believed to have a metallic surface composition. However, it now seems that other types of surface composition may also give

  2. Time-Dependent Variations in the Arctic’s Surface Albedo Feedback and the Link to Seasonality in Sea Ice

    NARCIS (Netherlands)

    Andry, Olivier; Bintanja, Richard; Hazeleger, Wilco

    2017-01-01

    The Arctic is warming 2 to 3 times faster than the global average. Arctic sea ice cover is very sensitive to this warming and has reached historic minima in late summer in recent years (e.g., 2007 and 2012). Considering that the Arctic Ocean is mainly ice covered and that the albedo of sea ice is ve

  3. Thermal-Infrared Surveys of Near-Earth Object Diameters and Albedos with Spitzer and IRTF/MIRSI

    NARCIS (Netherlands)

    Mommert, Michael; Trilling, David; Hora, Joseph L.; Chesley, Steven; Emery, Josh; Fazio, Giovanni; Harris, Alan W.; Moskovitz, Nick; Mueller, Michael; Smith, Howard

    2015-01-01

    More than 12000 Near-Earth Objects (NEOs) have been discovered over the past few decades and current discovery surveys find on average 4 new NEOs every night. In comparison to asteroid discovery, the physical characterization of NEOs lags far behind: measured diameters and albedos exist only for rou

  4. The impact of Saharan dust and black carbon on albedo and long-term glacier mass balance

    Directory of Open Access Journals (Sweden)

    J. Gabbi

    2015-02-01

    Full Text Available Light-absorbing impurities in snow and ice control glacier melt as shortwave radiation represents the main component of the surface energy balance. Here, we investigate the long-term effect of snow impurities, i.e. Saharan dust and black carbon (BC, on albedo and glacier mass balance. The analysis was performed over the period 1914–2014 for two sites on Claridenfirn, Swiss Alps, where an outstanding 100 year record of seasonal mass balance measurements is available. Information on atmospheric deposition of mineral dust and BC over the last century was retrieved from two firn/ice cores of high-alpine sites. A combined mass balance and snow/firn layer model was employed to assess the dust/BC-albedo feedback. Compared to pure snow conditions, the presence of Saharan dust and BC lowered the mean annual albedo by 0.04–0.06 and increased melt by 15–19% on average depending on the location on the glacier. BC clearly dominated absorption which is about three times higher than that of mineral dust. The upper site has experienced mainly positive mass balances and impurity layers were continuously buried whereas at the lower site, surface albedo was more strongly influenced by re-exposure of dust-enriched layers due to frequent years with negative mass balances.

  5. Influence of passion fruit albedo, citric acid, and the pulp/sugar ratio on the quality of banana preserves

    Directory of Open Access Journals (Sweden)

    Igor Galvão Silva

    2012-06-01

    Full Text Available The objective of this research was to evaluate the effect of the citric acid concentration, pulp/sugar ratio, and albedo concentration of the passion fruit peel on physical, physiochemical, and sensorial characteristics of the 'Silver' banana preserves. A 2³ factorial design and 3 repetitions in the central point were used. The albedo concentration between 0 and 3% had significant influence on the reduction of the reducing sugars and on the decrease in titratable acidity. The increase in the pulp/sugar ratio exerted a negative effect on the pH and positive on the titratable acidity; the acid addition reduced the non-reducing sugar level. The sensorial evaluation and purchase intention indicated that the incorporation of a maximum of 1.5% albedo in formulations containing 50% pulp and 0.5% citric acid resulted in products with good acceptability in comparison with the formulation in which 60% pulp and an absence of acid or albedo is utilized.

  6. Cross-Comparison of Albedo Products for Glacier Surfaces Derived from Airborne and Satellite (Sentinel-2 and Landsat 8 Optical Data

    Directory of Open Access Journals (Sweden)

    Kathrin Naegeli

    2017-01-01

    Full Text Available Surface albedo partitions the amount of energy received by glacier surfaces from shortwave fluxes and modulates the energy available for melt processes. The ice-albedo feedback, influenced by the contamination of bare-ice surfaces with light-absorbing impurities, plays a major role in the melting of mountain glaciers in a warming climate. However, little is known about the spatial and temporal distribution and variability of bare-ice glacier surface albedo under changing conditions. In this study, we focus on two mountain glaciers located in the western Swiss Alps and perform a cross-comparison of different albedo products. We take advantage of high spectral and spatial resolution (284 bands, 2 m imaging spectrometer data from the Airborne Prism Experiment (APEX and investigate the applicability and potential of Sentinel-2 and Landsat 8 data to derive broadband albedo products. The performance of shortwave broadband albedo retrievals is tested and we assess the reliability of published narrow-to-broadband conversion algorithms. The resulting albedo products from the three sensors and different algorithms are further cross-compared. Moreover, the impact of the anisotropy correction is analysed depending on different surface types. While degradation of the spectral resolution impacted glacier-wide mean albedo by about 5%, reducing the spatial resolution resulted in changes of less than 1%. However, in any case, coarser spatial resolution was no longer able to represent small-scale variability of albedo on glacier surfaces. We discuss the implications when using Sentinel-2 and Landsat 8 to map dynamic glaciological processes and to monitor glacier surface albedo on larger spatial and more frequent temporal scales.

  7. Changes in summer sea ice, albedo, and portioning of surface solar radiation in the Pacific sector of Arctic Ocean during 1982-2009

    Science.gov (United States)

    Lei, Ruibo; Tian-Kunze, Xiangshan; Leppäranta, Matti; Wang, Jia; Kaleschke, Lars; Zhang, Zhanhai

    2016-08-01

    SSM/I sea ice concentration and CLARA black-sky composite albedo were used to estimate sea ice albedo in the region 70°N-82°N, 130°W-180°W. The long-term trends and seasonal evolutions of ice concentration, composite albedo, and ice albedo were then obtained. In July-August 1982-2009, the linear trend of the composite albedo and the ice albedo was -0.069 and -0.046 units per decade, respectively. During 1 June to 19 August, melting of sea ice resulted in an increase of solar heat input to the ice-ocean system by 282 MJ·m-2 from 1982 to 2009. However, because of the counter-balancing effects of the loss of sea ice area and the enhanced ice surface melting, the trend of solar heat input to the ice was insignificant. The summer evolution of ice albedo matched the ice surface melting and ponding well at basin scale. The ice albedo showed a large difference between the multiyear and first-year ice because the latter melted completely by the end of a melt season. At the SHEBA geolocations, a distinct change in the ice albedo has occurred since 2007, because most of the multiyear ice has been replaced by first-year ice. A positive polarity in the Arctic Dipole Anomaly could be partly responsible for the rapid loss of summer ice within the study region in the recent years by bringing warmer air masses from the south and advecting more ice toward the north. Both these effects would enhance ice-albedo feedback.

  8. A Synthetical Estimation of Northern Hemisphere Sea-ice Albedo Radiative Forcing and Feedback between 1982 and 2009

    Science.gov (United States)

    Cao, Y.

    2014-12-01

    The decreasing surface albedo caused by continously vanishing sea ice over the Arctic plays a very important role in Arctic warming amplification. However, the quantification of the change of radiative forcing at top of atmosphere (TOA) introduced by the decreasing sea ice albedo and its generated feedback to the climate remain uncertain. Two recent representative studies showed a large difference with each other: Flanner et al. (2011) used a method of synthesis of surface albedo and radiative kernels and found that the change of sea ice radiative forcing (ΔSIRF) in Northern Hemisphere (NH) from 1979 to 2008 was 0.22 (0.15 - 0.32) W m-2, and the corresponding sea ice albedo feedback (SIAF) over NH was 0.28 (0.19 - 0.41) W m-2 K-1; while Pistone et al. (2014) directly used the observed planetary albedo to estimate the NH ΔSIRF and SIAF from 1979 to 2011 and draw a NH ΔSIRF of 0.43 ± 0.07 W m-2, which was nearly twice as larger as Flanner's result, and the estimated global SIAF was 0.31 ± 0.04 W m-2 K-1. Motivated by reconciling the difference between these two studies and obtaining a more accurate qualification of the NH ΔSIRF, we used a newly released satellite-retrieved surface albedo product CLARA-A1 and made an attempt in two steps: Firstly, based on synthesising the surface albedo and raditive kernels, we calcualted the ΔSIRF from 1982 to 2009 was 0.20 ± 0.05 W m-2, and the NH SIAF was 0.25 W m-2 K-1; After comparing with TOA observed radiative flux, we found it's quite likely the kernel methods yield an underestimation for the all-sky ΔSIRF. Then, we tried to use TOA observed broadband radiative flux to adjust the estimation with kernels. After an adjustment, the NH all-sky ΔSIRF was 0.34 ± 0.09 W m-2, and the corresponding SIAF was 0.43 W m-2 K-1 over NH and 0.31 W m-2 K-1 over the entire globe.

  9. Assessing modeled Greenland surface mass balance in the GISS Model E2 and its sensitivity to surface albedo

    Science.gov (United States)

    Alexander, Patrick; LeGrande, Allegra N.; Koenig, Lora S.; Tedesco, Marco; Moustafa, Samiah E.; Ivanoff, Alvaro; Fischer, Robert P.; Fettweis, Xavier

    2016-04-01

    The surface mass balance (SMB) of the Greenland Ice Sheet (GrIS) plays an important role in global sea level change. Regional Climate Models (RCMs) such as the Modèle Atmosphérique Régionale (MAR) have been employed at high spatial resolution with relatively complex physics to simulate ice sheet SMB. Global climate models (GCMs) incorporate less sophisticated physical schemes and provide outputs at a lower spatial resolution, but have the advantage of modeling the interaction between different components of the earth's oceans, climate, and land surface at a global scale. Improving the ability of GCMs to represent ice sheet SMB is important for making predictions of future changes in global sea level. With the ultimate goal of improving SMB simulated by the Goddard Institute for Space Studies (GISS) Model E2 GCM, we compare simulated GrIS SMB against the outputs of the MAR model and radar-derived estimates of snow accumulation. In order to reproduce present-day climate variability in the Model E2 simulation, winds are constrained to match the reanalysis datasets used to force MAR at the lateral boundaries. We conduct a preliminary assessment of the sensitivity of the simulated Model E2 SMB to surface albedo, a parameter that is known to strongly influence SMB. Model E2 albedo is set to a fixed value of 0.8 over the entire ice sheet in the initial configuration of the model (control case). We adjust this fixed value in an ensemble of simulations over a range of 0.4 to 0.8 (roughly the range of observed summer GrIS albedo values) to examine the sensitivity of ice-sheet-wide SMB to albedo. We prescribe albedo from the Moderate Resolution Imaging Spectroradiometer (MODIS) MCD43A3 v6 to examine the impact of a more realistic spatial and temporal variations in albedo. An age-dependent snow albedo parameterization is applied, and its impact on SMB relative to observations and the RCM is assessed.

  10. Retrieval of Areal-averaged Spectral Surface Albedo from Transmission Data Alone: Computationally Simple and Fast Approach

    Energy Technology Data Exchange (ETDEWEB)

    Kassianov, Evgueni I.; Barnard, James C.; Flynn, Connor J.; Riihimaki, Laura D.; Michalsky, Joseph; Hodges, G. B.

    2014-10-25

    We introduce and evaluate a simple retrieval of areal-averaged surface albedo using ground-based measurements of atmospheric transmission alone at five wavelengths (415, 500, 615, 673 and 870nm), under fully overcast conditions. Our retrieval is based on a one-line semi-analytical equation and widely accepted assumptions regarding the weak spectral dependence of cloud optical properties, such as cloud optical depth and asymmetry parameter, in the visible and near-infrared spectral range. To illustrate the performance of our retrieval, we use as input measurements of spectral atmospheric transmission from Multi-Filter Rotating Shadowband Radiometer (MFRSR). These MFRSR data are collected at two well-established continental sites in the United States supported by the U.S. Department of Energy’s (DOE’s) Atmospheric Radiation Measurement (ARM) Program and National Oceanic and Atmospheric Administration (NOAA). The areal-averaged albedos obtained from the MFRSR are compared with collocated and coincident Moderate Resolution Imaging Spectroradiometer (MODIS) white-sky albedo. In particular, these comparisons are made at four MFRSR wavelengths (500, 615, 673 and 870nm) and for four seasons (winter, spring, summer and fall) at the ARM site using multi-year (2008-2013) MFRSR and MODIS data. Good agreement, on average, for these wavelengths results in small values (≤0.01) of the corresponding root mean square errors (RMSEs) for these two sites. The obtained RMSEs are comparable with those obtained previously for the shortwave albedos (MODIS-derived versus tower-measured) for these sites during growing seasons. We also demonstrate good agreement between tower-based daily-averaged surface albedos measured for “nearby” overcast and non-overcast days. Thus, our retrieval originally developed for overcast conditions likely can be extended for non-overcast days by interpolating between overcast retrievals.

  11. Estimation of four land surface essential climate variables (albedo, LAI/FAPAR, and Fcover) from VIIRS data

    Science.gov (United States)

    Liang, Shunlin

    2016-07-01

    As the successor of MODIS, the Visible Infrared Imaging Radiometer Suite (VIIRS) from the Suomi National Polar-orbiting Partnership (S-NPP) and future Joint Polar Satellite System (JPSS) brings us into a new era of global daily Earth observations. VIIRS was designed to improve upon the capabilities of the operational AVHRR and provide observation continuity with MODIS. This presentation will describe the progress in estimating four Essential Climate Variables (ECV): shortwave albedo (Wang, et al., 2013; Zhou, et al., 2016), leaf area index (LAI) (Xiao et al., 2016), fraction of absorbed photosynthetically active radiation (FAPAR) (Xiao et al., 2016), and fractional vegetation coverage (Fcover) (Li, et al., 2016) from VIIRS data. The algorithms have been peer reviewed, and shortwave albedo has been operationally produced by NOAA and accessible to the scientific community. Li, Y., K. Jia, S. Liang, Z. Xiao, X. Wang, L. Yang, (2016), An operational algorithm for estimating fractional vegetation cover from VIIRS reflectance data based on general regression neural networks, Remote Sensing, revised Xiao, Z., S. Liang, T. Wang, and B. Jiang, (2016), Retrieval of Leaf Area Index and Fraction of Absorbed Photosynthetically Active Radiation from VIIRS Time Series Data, Remote Sensing, revised. Wang, D., S. Liang, T. He, and Y. Yu, (2013), Direct Estimation of Land Surface Albedo from VIIRS Data: Algorithm Improvement and Preliminary Validation, Journal of Geophysical Research, 118(22):12,577-12,586 Zhou, Y., D. Wang, S. Liang, Y. Yu, and T. He, (2016), Assessment of the Suomi NPP VIIRS Land Surface Albedo Data Using Station Measurements and High-Resolution Albedo Maps, Remote Sensing, in press.

  12. Landcover Change, Land Surface Temperature, Surface Albedo and Topography in the Plateau Region of North-Central Nigeria

    Directory of Open Access Journals (Sweden)

    Shakirudeen Odunuga

    2015-04-01

    Full Text Available This study assessed the change in some environmental parameters in the Plateau region of North-Central Nigeria (Barakinladi, Jos, and Kafachan environs using the nexus of landcover change, land surface temperature, surface albedo, and topography. The study employed both remote sensing and statistical techniques for the period between 1986 and 2014 to analyze the dynamics between and within these environmental variables. In Barakinladi, the built up landcover change is highest (increasing from 39.53% to 47.59% between 1986 and 2014; LST ranges from 19.09 °C to 38.59 °C in 1986 and from 22.68 °C and 41.68 °C in 2014; and the albedo ranges between 0.014 and 0.154 in 1986 and 0.017 and 0.248 in 2014. In Jos, the built-up landcover occupied 34.26% in 1986 and 36.67% in 2014; LST values range between 20.83 °C and 41.33 °C in 1986 and between 21.61 °C and 42.64 °C in 2014; and the albedo ranges between 0.003 and 0.211 in 1986 and 0.15 and 0.237 in 2014. In Kafachan area, the built up landcover occupied 32.95% in 1986 and 39.01% in 2014. Urbanization and agricultural activities, including animal grazing, were responsible for the gradual loss in vegetation and increasing average LST and albedo. The results also revealed that changing landcover and topography have a relationship with surface albedo and land surface temperature, thereby impacting significantly on ecosystem services delivered by the natural system.

  13. Impact of soil moisture and winter wheat height from the Loess Plateau in Northwest China on surface spectral albedo

    Science.gov (United States)

    Li, Zhenchao; Yang, Jiaxi; Gao, Xiaoqing; Zheng, Zhiyuan; Yu, Ye; Hou, Xuhong; Wei, Zhigang

    2016-12-01

    The understanding of surface spectral radiation and reflected radiation characteristics of different surfaces in different climate zones aids in the interpretation of regional surface energy transfers and the development of land surface models. This study analysed surface spectral radiation variations and corresponding surface albedo characteristics at different wavelengths as well as the relationship between 5-cm soil moisture and surface albedo on typical sunny days during the winter wheat growth period. The analysis was conducted using observational Loess Plateau winter wheat data from 2015. The results show that the ratio of atmospheric downward radiation to global radiation on typical sunny days is highest for near-infrared wavelengths, followed by visible wavelengths and ultraviolet wavelengths, with values of 57.3, 38.7 and 4.0%, respectively. The ratio of reflected spectral radiation to global radiation varies based on land surface type. The visible radiation reflected by vegetated surfaces is far less than that reflected by bare ground, with surface albedos of 0.045 and 0.27, respectively. Thus, vegetated surfaces absorb more visible radiation than bare ground. The atmospheric downward spectral radiation to global radiation diurnal variation ratios vary for near-infrared wavelengths versus visible and ultraviolet wavelengths on typical sunny days. The near-infrared wavelengths ratio is higher in the morning and evening and lower at noon. The visible and ultraviolet wavelengths ratios are lower in the morning and evening and higher at noon. Visible and ultraviolet wavelength surface albedo is affected by 5-cm soil moisture, demonstrating a significant negative correlation. Excluding near-infrared wavelengths, correlations between surface albedo and 5-cm soil moisture pass the 99% confidence test at each wavelength. The correlation with 5-cm soil moisture is more significant at shorter wavelengths. However, this study obtained surface spectral radiation

  14. Effect of increasing urban albedo on meteorology and air quality of Montreal (Canada) - Episodic simulation of heat wave in 2005

    Science.gov (United States)

    Touchaei, Ali G.; Akbari, Hashem; Tessum, Christopher W.

    2016-05-01

    Increasing albedo is an effective strategy to mitigate urban air temperature in different climates. Using reflective urban surfaces decreases the air temperature, which potentially reduces the rate of generation of smog. However, for implementing the albedo enhancement, complicated interactions between air, moisture, aerosols, and other gaseous contaminant in the atmosphere should be considered. We used WRF-CHEM to investigate the effect of increasing albedo in Montreal, Canada, during a heat wave period (July 10th through July 12th, 2005) on air quality and urban climate. The reflectivity of roofs, walls, and roads are increased from 0.2 to 0.65, 0.6, and 0.45, respectively. Air temperature at 2-m elevation is decreased during all hours in the simulation period and the maximum reduction is about 1 °C on each day (Tmax is reduced by about 0.7 °C) The concentration of two regulated pollutants -ozone (O3) and fine particulate matters (PM2.5) - is calculated at a height of 5-m above the ground. The maximum decrease in 8-h averaged ozone concentration is about 3% (∼0.2 ppbv). 24-h averaged PM2.5 concentration decreases by 1.8 μg/m3. This relatively small change in concentration of pollutants is related to the decrease in planetary boundary layer height caused by increasing the albedo. Additionally, the combined effect of decreased solar heat gain by building surfaces and decreased air temperature reduces the energy consumption of HVAC systems by 2% (∼0.1 W/m2), which exacerbates the positive effect of the albedo enhancement on the air quality.

  15. The G4Foam Experiment: Global Climate Impacts of Regional Ocean Albedo Modification

    Energy Technology Data Exchange (ETDEWEB)

    Gabriel, Corey; Robock, Alan; Xia, Lili; Zambri, Brian; Kravitz, Benjamin S.

    2017-01-12

    Reducing insolation has been proposed as a geoengineering response to global warming. Here we present the results of climate model simulations of a unique Geoengineering Model Intercomparison Project Testbed experiment to investigate the benefits and risks of a scheme that would brighten certain oceanic regions. The National Center for Atmospheric Research CESM-CAM4-CHEM global climate model was modified to simulate a scheme in which the albedo of the ocean surface is increased over the subtropical ocean gyres in the Southern Hemisphere. In theory, this could be accomplished using a stable, nondispersive foam, comprised of tiny, highly reflective microbubbles. Such a foam has been developed under idealized conditions, although deployment at a large scale is presently infeasible. We conducted three ensemble members of a simulation (G4Foam) from 2020 through 2069 in which the albedo of the ocean surface is set to 0.15 (an increase of 150%) over the three subtropical ocean gyres in the Southern Hemisphere, against a background of the RCP6.0 (representative concentration pathway resulting in +6 W m-2 radiative forcing by 2100) scenario. After 2069, geoengineering is ceased, and the simulation is run for an additional 20 years. Global mean surface temperature in G4Foam is 0.6 K lower than RCP6.0, with statistically significant cooling relative to RCP6.0 south of 30°N. There is an increase in rainfall over land, most pronouncedly in the tropics during the June-July-August season, relative to both G4SSA (specified stratospheric aerosols) and RCP6.0. Heavily populated and highly cultivated regions throughout the tropics, including the Sahel, Southern Asia, the Maritime Continent, Central America and much of the Amazon, experience a statistically significant increase in precipitation minus evaporation. The temperature response to the relatively modest global average forcing of –1.5 W m-2 is amplified through a series of positive cloud feedbacks, in which more shortwave

  16. The G4Foam Experiment: global climate impacts of regional ocean albedo modification

    Science.gov (United States)

    Gabriel, Corey J.; Robock, Alan; Xia, Lili; Zambri, Brian; Kravitz, Ben

    2017-01-01

    Reducing insolation has been proposed as a geoengineering response to global warming. Here we present the results of climate model simulations of a unique Geoengineering Model Intercomparison Project Testbed experiment to investigate the benefits and risks of a scheme that would brighten certain oceanic regions. The National Center for Atmospheric Research CESM CAM4-Chem global climate model was modified to simulate a scheme in which the albedo of the ocean surface is increased over the subtropical ocean gyres in the Southern Hemisphere. In theory, this could be accomplished using a stable, nondispersive foam, comprised of tiny, highly reflective microbubbles. Such a foam has been developed under idealized conditions, although deployment at a large scale is presently infeasible. We conducted three ensemble members of a simulation (G4Foam) from 2020 through to 2069 in which the albedo of the ocean surface is set to 0.15 (an increase of 150 %) over the three subtropical ocean gyres in the Southern Hemisphere, against a background of the RCP6.0 (representative concentration pathway resulting in +6 W m-2 radiative forcing by 2100) scenario. After 2069, geoengineering is ceased, and the simulation is run for an additional 20 years. Global mean surface temperature in G4Foam is 0.6 K lower than RCP6.0, with statistically significant cooling relative to RCP6.0 south of 30° N. There is an increase in rainfall over land, most pronouncedly in the tropics during the June-July-August season, relative to both G4SSA (specified stratospheric aerosols) and RCP6.0. Heavily populated and highly cultivated regions throughout the tropics, including the Sahel, southern Asia, the Maritime Continent, Central America, and much of the Amazon experience a statistically significant increase in precipitation minus evaporation. The temperature response to the relatively modest global average forcing of -1.5 W m-2 is amplified through a series of positive cloud feedbacks, in which more

  17. Variation in forest canopy nitrogen and albedo in response to N fertilization and elevated CO2

    Science.gov (United States)

    Wicklein, H. F.; Ollinger, S. V.; Martin, M.; Hollinger, D. Y.; Collatz, G. J.

    2009-12-01

    It is important to understand how high levels of nitrogen (N) deposition, through changes in N status, could influence a forest’s albedo and photosynthetic rates, and therefore the forest’s overall feedback (positive or negative) to global warming. Foliar N and albedo have recently been shown to covary at the canopy level across temperate and boreal forests. The purpose of this study is to examine the nature of this relationship from leaf to canopy scales and how it might change in response N and CO2 fertilization. Research was conducted at two long-term forest experimental sites. The chronic N amendment site at Harvard Forest in Petersham, MA includes three treatments: high N (fertilized with 150 kg N ha-1 yr-1), low N (50 kg N ha-1 yr-1), and ambient deposition (around 8 kg N ha-1 yr-1). The Oak Ridge National Environmental Research Park in Oak Ridge, TN includes a Free Air CO2 Enrichment (FACE) site where plots receive either ambient and elevated CO2 (540 ppm), and an N amendment site where plots are either fertilized with N (200 kg N ha-1 yr-1) or receive ambient deposition (10-15 kg N ha-1 yr-1). At Harvard Forest we measured seven black oak (Quercus velutina) and five red maple (Acer rubrum) trees in each treatment plot. At Oak Ridge we measured five sweetgum (Liquidambar styraciflua) trees in each FACE treatment plot, and four sweetgum trees in each N amendment treatment plot. Leaves were collected from two to three canopy heights from trees in each treatment plot. For each tree height we measured reflectance and transmittance spectra for stacks of 1, 2, 4, and 8 leaves, both abaxial and adaxial sides. We also measured N concentration, water content, and leaf mass per unit area (LMA) of the leaves. Canopy-level reflectance was modeled using the Scattering by Arbitrarily Inclined Leaves (SAIL-2) radiative transfer model. Preliminary results show significant differences in average leaf-level reflectance in the N fertilized treatments, with higher NIR

  18. MODIS-derived albedo changes of Vatnajökull (Iceland) due to tephra deposition from the 2004 Grímsvötn eruption

    Science.gov (United States)

    Möller, Rebecca; Möller, Marco; Björnsson, Helgi; Guðmundsson, Sverrir; Pálsson, Finnur; Oddsson, Björn; Kukla, Peter A.; Schneider, Christoph

    2014-02-01

    Occasionally, the surface albedo of glaciers may be abruptly altered by deposition of light-absorbing aerosols, which consequently has a sustained impact on their energy- and mass balance. Volcanic eruptions may spread tephra deposits over regional-scale glacierized areas. In November 2004, an explosive, phreatomagmatic eruption of the subglacial Grímsvötn volcano, located in the centre of the Icelandic ice cap Vatnajökull, produced ash fall covering an area of ∼1280 km2 in the northwestern part of the ice cap. This event affected the surface albedo of the glacier over several years after the eruption. We use MODIS surface-albedo data and an ash-dispersal dataset obtained from in situ measurements on the ice cap to develop a novel, empirically based modelling approach to describe the albedo decrease across the glacier surface caused by the deposited tephra. We present analyses of the temporal and spatial variability of the albedo pattern over the post-eruption period from November 2004 to December 2008. The tephra-induced albedo changes were largest and most widely distributed over the glacier surface during the summer season 2005. The observed albedo decrease reached 0.35 when compared to modelled, undisturbed conditions. In the low-lying ablation area, where strong surface melting takes place, the tephra influence on albedo diminished with time and completely faded out within four years after the eruption. In contrast, at the rim of the Grímsvötn caldera surrounding the eruption site the tephra influences on albedo considerably increased with time. Throughout the rest of the high-lying accumulation area, the influences were scattered in both space and time.

  19. Derivation of Land Surface Albedo at High Resolution by Combining HJ-1A/B Reflectance Observations with MODIS BRDF Products

    Directory of Open Access Journals (Sweden)

    Bo Gao

    2014-09-01

    Full Text Available Land surface albedo is an essential parameter for monitoring global/regional climate and land surface energy balance. Although many studies have been conducted on global or regional land surface albedo using various remote sensing data over the past few decades, land surface albedo product with a high spatio–temporal resolution is currently very scarce. This paper proposes a method for deriving land surface albedo with a high spatio–temporal resolution (space: 30 m and time: 2–4 days. The proposed method works by combining the land surface reflectance data at 30 m spatial resolution obtained from the charge-coupled devices in the Huanjing-1A and -1B (HJ-1A/B satellites with the Moderate Resolution Imaging Spectroradiometer (MODIS land surface bidirectional reflectance distribution function (BRDF parameters product (MCD43A1, which is at a spatial resolution of 500 m. First, the land surface BRDF parameters for HJ-1A/B land surface reflectance with a spatial–temporal resolutions of 30 m and 2–4 day are calculated on the basis of the prior knowledge from the MODIS BRDF product; then, the calculated high resolution BRDF parameters are integrated over the illuminating/viewing hemisphere to produce the white- and black-sky albedos at 30 m resolution. These results form the basis for the final land surface albedo derivation by accounting for the proportion of direct and diffuse solar radiation arriving at the ground. The albedo retrieved by this novel method is compared with MODIS land surface albedo products, as well as with ground measurements. The results show that the derived land surface albedo during the growing season of 2012 generally achieved a mean absolute accuracy of ±0.044, and a root mean square error of 0.039, confirming the effectiveness of the newly proposed method.

  20. The effect of host star spectral energy distribution and ice-albedo feedback on the climate of extrasolar planets.

    Science.gov (United States)

    Shields, Aomawa L; Meadows, Victoria S; Bitz, Cecilia M; Pierrehumbert, Raymond T; Joshi, Manoj M; Robinson, Tyler D

    2013-08-01

    Planetary climate can be affected by the interaction of the host star spectral energy distribution with the wavelength-dependent reflectivity of ice and snow. In this study, we explored this effect with a one-dimensional (1-D), line-by-line, radiative transfer model to calculate broadband planetary albedos as input to a seasonally varying, 1-D energy balance climate model. A three-dimensional (3-D) general circulation model was also used to explore the atmosphere's response to changes in incoming stellar radiation, or instellation, and surface albedo. Using this hierarchy of models, we simulated planets covered by ocean, land, and water-ice of varying grain size, with incident radiation from stars of different spectral types. Terrestrial planets orbiting stars with higher near-UV radiation exhibited a stronger ice-albedo feedback. We found that ice extent was much greater on a planet orbiting an F-dwarf star than on a planet orbiting a G-dwarf star at an equivalent flux distance, and that ice-covered conditions occurred on an F-dwarf planet with only a 2% reduction in instellation relative to the present instellation on Earth, assuming fixed CO(2) (present atmospheric level on Earth). A similar planet orbiting the Sun at an equivalent flux distance required an 8% reduction in instellation, while a planet orbiting an M-dwarf star required an additional 19% reduction in instellation to become ice-covered, equivalent to 73% of the modern solar constant. The reduction in instellation must be larger for planets orbiting cooler stars due in large part to the stronger absorption of longer-wavelength radiation by icy surfaces on these planets in addition to stronger absorption by water vapor and CO(2) in their atmospheres, which provides increased downwelling longwave radiation. Lowering the IR and visible-band surface ice and snow albedos for an M-dwarf planet increased the planet's climate stability against changes in instellation and slowed the descent into global ice

  1. Albedo of a cucumber culture in polyethylene greenhouses in the North-South and East-West orientations; Albedo da cultura do pepino (Cucumis sativus) em estufas de polietileno, nas orientacoes norte-sul e leste-oeste

    Energy Technology Data Exchange (ETDEWEB)

    Assis, Simone V. de [Pelotas Univ., RS (Brazil). Dept. de Meteorologia; Escobedo, Joao F. [UNESP, Botucatu, SP (Brazil). Faculdade de Ciencias Agronomicas

    1998-12-31

    The calculation of albedo on a complete cycle of a cucumber culture was obtained in two polyethylene greenhouses with different orientations (north-south and east-west) and outside. The area of the greenhouse was 35 m{sup 2} and outside 80 cm longer than the surface. They were built in the Solar Radiometer Station, in Botucatu, SP. They are formed by central body, two glasses dome and two glasses dome and two sensors (thin film thermopiles). The sensors are positioned on the up and down part of the instrument. Th up sensor is used to measure global solar radiation and the down sensor is used to measure reflected solar radiation. The signs received from albedo meters were sent to a system of the data acquisition Datalogger 21 XL - CAMPBELL. (author) 5 refs., 5 figs., 2 tabs.

  2. Efficiency measure of a neutron dosimeter Albedo and of the room floor calibration; Medida de la eficiencia de un dosimetro de neutrones y del Albedo del suelo de la sala de calibracion

    Energy Technology Data Exchange (ETDEWEB)

    Blazquez, J.

    2010-07-01

    In this work we have applied the method to measure the source image detection efficiency of a dosimeter using Studsvik 2202D neutron source intensity Am-Be known. It has been shown experimentally that the conditions for the correction and albedo estimated the extent of the room. Since the correction is independent of dosimeter, the result is a measure of the efficiency of other types of neutron counters.

  3. Reflected Light Curves, Spherical and Bond Albedos of Jupiter- and Saturn-like Exoplanets

    CERN Document Server

    Dyudina, Ulyana; Li, Liming; Kopparla, Pushkar; Yung, Yuk L; Ingersoll, Andrew P; Dones, Luke

    2015-01-01

    We estimate how the light curve and total stellar heating of a planet depend on forward and backward scattering clouds. To do that, we construct light curves for Jupiter- and Saturn-like planet based on observations. We fit analytical functions to the reflected brightness of Jupiter's and Saturn's surface versus planet's phase. We use Pioneer and Cassini spacecraft images to estimate these functions. These observations cover broad bands at 0.59-0.72 microns and 0.39-0.5 microns, and narrow bands at 0.938 microns (atmospheric window), 0.889 microns (CH4 absorption band), and 0.24-0.28 microns. We simulate the images of the planets at different phases with ray-tracing model of a planet by Dyudina et al. (2005). The full-disk luminosity of these simulated images changes with planet's phase producing the full-orbit light curves. We also derive total planet's reflection integrated in all directions (spherical albedos) for Jupiter, Saturn, and for planets with Lambertian and Rayleigh-scattering atmosphere. For Jupi...

  4. Meltwater produced by wind-albedo interaction stored in an East Antarctic ice shelf

    Science.gov (United States)

    Lenaerts, J. T. M.; Lhermitte, S.; Drews, R.; Ligtenberg, S. R. M.; Berger, S.; Helm, V.; Smeets, C. J. P. P.; Broeke, M. R. Van Den; van de Berg, W. J.; van Meijgaard, E.; Eijkelboom, M.; Eisen, O.; Pattyn, F.

    2017-01-01

    Surface melt and subsequent firn air depletion can ultimately lead to disintegration of Antarctic ice shelves causing grounded glaciers to accelerate and sea level to rise. In the Antarctic Peninsula, foehn winds enhance melting near the grounding line, which in the recent past has led to the disintegration of the most northerly ice shelves. Here, we provide observational and model evidence that this process also occurs over an East Antarctic ice shelf, where meltwater-induced firn air depletion is found in the grounding zone. Unlike the Antarctic Peninsula, where foehn events originate from episodic interaction of the circumpolar westerlies with the topography, in coastal East Antarctica high temperatures are caused by persistent katabatic winds originating from the ice sheet’s interior. Katabatic winds warm and mix the air as it flows downward and cause widespread snow erosion, explaining >3 K higher near-surface temperatures in summer and surface melt doubling in the grounding zone compared with its surroundings. Additionally, these winds expose blue ice and firn with lower surface albedo, further enhancing melt. The in situ observation of supraglacial flow and englacial storage of meltwater suggests that ice-shelf grounding zones in East Antarctica, like their Antarctic Peninsula counterparts, are vulnerable to hydrofracturing.

  5. Planetary Temperatures : Early Estimates, Lowell, and the Albedo of the Earth

    Science.gov (United States)

    Lorenz, Ralph

    2016-10-01

    While it was recognized by Huygens, as soon as the architecture of the solar system was understood, that outer planets would be much cooler than Earth, quantitative estimation of planetary temperatures only became possible with understanding of radiant heat, and specifically the Stefan law relating heat flux to the fourth power of absolute temperature. This relation appears to have been first applied to planetary temperatures by the Danish physicist Christiansen in 1885, and he derived results for Mars and Saturn of -40 and -180C, rather reasonable values. However, the separate values of the solar constant, absolute planetary albedos (including that of the Earth) and the short- and long-wave transparency of planetary atmospheres were not known, although mountaintop measurements by Langley made some first steps to quantifying these effects. Lowell recognized that the Martian atmosphere was thinner than ours, but had more carbon dioxide, and so considered these factors to cancel out. However, he suggested that the Earth had a reflectivity of some 75%, such that darker Mars would absorb a larger fraction of incident sunlight than the Earth, compensating for Mars' greater distance from the sun and thus allowing clement temperatures. It is difficult not to see this as pushing the numbers to obtain a desired result, and indeed a robust refutation of his calculations swiftly followed by Poynting and Alfred Russel Wallace. I present a brief review of these early days of planetary climate modeling.

  6. Contribution of Arctic seabird-colony ammonia to atmospheric particles and cloud-albedo radiative effect

    Science.gov (United States)

    Croft, B.; Wentworth, G. R.; Martin, R. V.; Leaitch, W. R.; Murphy, J. G.; Murphy, B. N.; Kodros, J. K.; Abbatt, J. P. D.; Pierce, J. R.

    2016-11-01

    The Arctic region is vulnerable to climate change and able to affect global climate. The summertime Arctic atmosphere is pristine and strongly influenced by natural regional emissions, which have poorly understood climate impacts related to atmospheric particles and clouds. Here we show that ammonia from seabird-colony guano is a key factor contributing to bursts of newly formed particles, which are observed every summer in the near-surface atmosphere at Alert, Nunavut, Canada. Our chemical-transport model simulations indicate that the pan-Arctic seabird-influenced particles can grow by sulfuric acid and organic vapour condensation to diameters sufficiently large to promote pan-Arctic cloud-droplet formation in the clean Arctic summertime. We calculate that the resultant cooling tendencies could be large (about -0.5 W m-2 pan-Arctic-mean cooling), exceeding -1 W m-2 near the largest seabird colonies due to the effects of seabird-influenced particles on cloud albedo. These coupled ecological-chemical processes may be susceptible to Arctic warming and industrialization.

  7. Cladonia lichens on extensive green roofs: evapotranspiration, substrate temperature, and albedo.

    Science.gov (United States)

    Heim, Amy; Lundholm, Jeremy

    2013-01-01

    Green roofs are constructed ecosystems that provide ecosystem services in urban environments. Shallow substrate green roofs subject the vegetation layer to desiccation and other environmental extremes, so researchers have evaluated a variety of stress-tolerant vegetation types for green roof applications. Lichens can be found in most terrestrial habitats.  They are able to survive extremely harsh conditions, including frequent cycles of desiccation and rehydration, nutrient-poor soil, fluctuating temperatures, and high UV intensities. Extensive green roofs (substrate depth green roofs.  In a modular green roof system, we tested the effect of Cladonia lichens on substrate temperature, water loss, and albedo compared to a substrate-only control. Overall, the Cladonia modules had significantly cooler substrate temperatures during the summer and significantly warmer temperatures during the fall.  Additionally, the Cladonia modules lost significantly less water than the substrate-only control. This implies that they may be able to benefit neighboring vascular plant species by reducing water loss and maintaining favorable substrate temperatures.

  8. Accounting for spectral albedo, solar light penetration and impurity content in detailed snowpack simulations

    Science.gov (United States)

    Dumont, Marie; Lafaysse, Matthieu; Picard, Ghislain; Arnaud, Laurent; Libois, Quentin; Morin, Samuel

    2016-04-01

    The energy balance of the snowpack, driven in particular by its spectral albedo and the penetration depth of solar light, is of primary importance to drive the time evolution of snow on the ground. Here we introduce new developments of the detailed snowpack model SURFEX/ISBA-Crocus (Brun et al., 1992 ; Vionnet et al., 2012) which now includes a spectrally-resolved two-stream calculation of solar light absorption within the snowpack (Libois et al. ,2013) and of the spectral partitioning of the direct and diffuse atmospheric irradiance and a prognostic snow impurity content. The added value of these refined representation of processes is evaluated with respect to field measurements of snow spectral reflectance and snow water equivalent. Simulations were performed at Col de Porte site (Chartreuse, France, 1325 m a.s.l.) using in situ meteorological forcings during winter 2013-2014 and aerosols deposition fluxes from MOCAGE chemistry transport atmospheric model. A major Saharian dust deposition event occurred in February 2014. Using simulations and measurements, we investigate in particular the impact of this event on the physical characteristics of the snowpack with a special focus on metamorphism and on the timing of melt.

  9. Solar Irradiance from GOES Albedo performance in a Hydrologic Model Simulation of Snowmelt Runoff

    Science.gov (United States)

    Sumargo, E.; Cayan, D. R.; McGurk, B. J.

    2015-12-01

    In many hydrologic modeling applications, solar radiation has been parameterized using commonly available measures, such as the daily temperature range, due to scarce in situ solar radiation measurement network. However, these parameterized estimates often produce significant biases. Here we test hourly solar irradiance derived from the Geostationary Operational Environmental Satellite (GOES) visible albedo product, using several established algorithms. Focusing on the Sierra Nevada and White Mountain in California, we compared the GOES irradiance and that from a traditional temperature-based algorithm with incoming irradiance from pyranometers at 19 stations. The GOES based estimates yielded 21-27% reduction in root-mean-squared error (average over 19 sites). The derived irradiance is then prescribed as an input to Precipitation-Runoff Modeling System (PRMS). We constrain our experiment to the Tuolumne River watershed and focus our attention on the winter and spring of 1996-2014. A root-mean-squared error reduction of 2-6% in daily inflow to Hetch Hetchy at the lower end of the Tuolumne catchment was achieved by incorporating the insolation estimates at only 8 out of 280 Hydrologic Response Units (HRUs) within the basin. Our ongoing work endeavors to apply satellite-derived irradiance at each individual HRU.

  10. Retrieval of aerosol single scattering albedo and polarized phase function from polarized sun-photometer measurements for Zanjan atmosphere

    Directory of Open Access Journals (Sweden)

    A. Bayat

    2013-04-01

    Full Text Available Aerosol optical depth, Ångström exponent, single scattering albedo, and polarized phase function have been retrieved from polarized sun-photometer measurements for atmosphere of Zanjan (36.70° N, 48.51° E, and 1800 m a.m.s.l. from January 2010 to December 2012. The results show that the maximum value of aerosol polarized phase function as well as the polarized phase function retrieved for a specific scattering angle (i.e. 60°, are strongly correlated with the Ångström exponent. The latter one has a meaningful variations respect to the changes in the complex refractive index of the atmospheric aerosols. Furthermore the polarized phase function shows a moderate negative correlation respect to atmospheric aerosol optical depth and single scattering albedo. Therefore the polarized phase function can be regarded as a key parameter to characterize the atmospheric particles.

  11. Comprehensive Wide-Band Magnitudes and Albedos for the Planets, With Applications to Exo-Planets and Planet Nine

    CERN Document Server

    Mallama, Anthony; Pavlov, Hristo

    2016-01-01

    Complete sets of reference magnitudes in all 7 Johnson-Cousins bands (U, B, V, R, I, Rc and Ic) and the 5 principal Sloan bands (u', g', r', i', and z') are presented for the 8 planets. These data are accompanied by illumination phase functions and other formulas which characterize the instantaneous brightness of the planets. The main source of Johnson-Cousins magnitudes is a series of individualized photometric studies reported in recent years. Gaps in that dataset were filled with magnitudes synthesized in this study from published spectrophotometry. The planetary Sloan magnitudes, which are established here for the first time, are an average of newly recorded Sloan filter photometry, synthetic magnitudes and values transformed from the Johnson-Cousins system. Geometric albedos derived from these two sets of magnitudes are consistent within each photometric system and between the systems for all planets and in all bands. This consistency validates the albedos themselves as well as the magnitudes from which ...

  12. The effect of earth's atmosphere on contrast reduction for a nonuniform surface albedo and 'two-halves' field

    Science.gov (United States)

    Mekler, Y.; Kaufman, Y. J.

    1980-01-01

    The paper presents a model for contrast reduction by atmospheric haze developed for the 'two-halves' field of the earth's surface and other geometries of the earth's surface albedo. The model is based on a simplified solution of the equation of radiative transfer in two dimensions, resulting in a method for calculation of the upward zenith intensity in the atmosphere as a function of the distance from the border between the two half planes, for an unabsorbing atmosphere. The adjacency effect between two infinitesimal areas of different albedos is calculated; the resultant simplified solution is used to develop expressions for the line-spread function of the atmosphere and the modulation transfer function. The line-spread function is used to calculate the point spread function, which can be used to compute the intensity above any surface with given spatial dependence of the reflectivity.

  13. Half space albedo problem for the nonconservative vector equation of transfer with a combination of Rayleigh and isotropic scattering

    Science.gov (United States)

    Şenyiğit, M.

    2016-09-01

    The half-space albedo problem has been solved for a combination of Rayleigh and isotropic scattering using HN method which is developed for the neutron transport studies. The numerical results are compared with exact values obtained using variational method and Chandrasekhar's equation for the {H}-matrix. The analytical solutions of HN method are easy to handle in comparison with the other methods. The numerical results are in good agreement with previous works in literature.

  14. Century-Long Monitoring of Solar Irradiance and Earth's Albedo Using a Stable Scattering Target in Space

    CERN Document Server

    Judge, Philip G

    2015-01-01

    An inert sphere of a few meters diameter, placed in a special stable geosynchronous orbit in perpetuo, can be used for a variety of scientific experiments. Ground-based observations of such a sphere, "GeoSphere", can resolve very difficult problems in measuring the long-term solar irradiance. GeoSphere measurements will also help us understand the evolution of Earth's albedo and climate over at least the next century.

  15. Characterizing Intimate Mixtures of Materials in Hyperspectral Imagery with Albedo-based and Kernel-based Approaches

    Science.gov (United States)

    2015-09-01

    hyperspectral imagery with albedo-based and kernel-based approaches Robert S. Rand National Geospatial- Intelligence Agency (NGA), Springfield, VA 22150... INTRODUCTION In a broad sense, spectral mixing phenomenology in multispectral and hyperspectral imagery can be treated in two ways, depending on how the...in the plots. Artificial discontinuities are apparent for three of the four bad-band regions that were removed, at horizontal coordinates 35, 55, and

  16. Phase-Angle Dependence of Determinations of Diameter, Albedo, and Taxonomy: A Case Study of NEO 3691 Bede

    Science.gov (United States)

    Wooden, Diane H.; Lederer, Susan M.; Jehin, Emmanuel; Howell, Ellen S.; Fernandez, Yan; Harker, David E.; Ryan, Erin; Lovell, Amy; Woodward, Charles E.; Benner, Lance A.

    2015-01-01

    Parameters important for NEO risk assessment and mitigation include Near-Earth Object diameter and taxonomic classification, which translates to surface composition. Diameters of NEOs are derived from the thermal fluxes measured by WISE, NEOWISE, Spitzer Warm Mission and ground-based telescopes including the IRTF and UKIRT. Diameter and its coupled parameters Albedo and IR beaming parameter (a proxy for thermal inertia and/or surface roughness) are dependent upon the phase angle, which is the Sun-target-observer angle. Orbit geometries of NEOs, however, typically provide for observations at phase angles greater than 20 degrees. At higher phase angles, the observed thermal emission is sampling both the day and night sides of the NEO. We compare thermal models for NEOs that exclude (NEATM) and include (NESTM) night-side emission. We present a case study of NEO 3691 Bede, which is a higher albedo object, X (Ec) or Cgh taxonomy, to highlight the range of H magnitudes for this object (depending on the albedo and phase function slope parameter G), and to examine at different phase angles the taxonomy and thermal model fits for this NEO. Observations of 3691 Bede include our observations with IRTF+SpeX and with the 10 micrometer UKIRT+Michelle instrument, as well as WISE and Spitzer Warm mission data. By examining 3691 Bede as a case study, we highlight the interplay between the derivation of basic physical parameters and observing geometry, and we discuss the uncertainties in H magnitude, taxonomy assignment amongst the X-class (P, M, E), and diameter determinations. Systematic dependencies in the derivation of basic characterization parameters of H-magnitude, diameter, albedo and taxonomy with observing geometry are important to understand. These basic characterization parameters affect the statistical assessments of the NEO population, which in turn, affects the assignment of statistically-assessed basic parameters to discovered but yet-to-be-fully-characterized NEOs.

  17. Extra-tropical origin of equatorial Pacific cold bias in climate models with links to cloud albedo

    Science.gov (United States)

    Burls, Natalie J.; Muir, Leslie; Vincent, Emmanuel M.; Fedorov, Alexey

    2016-11-01

    General circulation models frequently suffer from a substantial cold bias in equatorial Pacific sea surface temperatures (SSTs). For instance, the majority of the climate models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) have this particular problem (17 out of the 26 models evaluated in the present study). Here, we investigate the extent to which these equatorial cold biases are related to mean climate biases generated in the extra-tropics and then communicated to the equator via the oceanic subtropical cells (STCs). With an evident relationship across the CMIP5 models between equatorial SSTs and upper ocean temperatures in the extra-tropical subduction regions, our analysis suggests that cold SST biases within the extra-tropical Pacific indeed translate into a cold equatorial bias via the STCs. An assessment of the relationship between these extra-tropical SST biases and local surface heat flux components indicates a link to biases in the simulated shortwave fluxes. Further sensitivity studies with a climate model (CESM) in which extra-tropical cloud albedo is systematically varied illustrate the influence of cloud albedo perturbations, not only directly above the oceanic subduction regions but across the extra-tropics, on the equatorial bias. The CESM experiments reveal a quadratic relationship between extra-tropical Pacific albedo and the root-mean-square-error in equatorial SSTs—a relationship with which the CMIP5 models generally agree. Thus, our study suggests that one way to improve the equatorial cold bias in the models is to improve the representation of subtropical and mid-latitude cloud albedo.

  18. The impact of Saharan dust and black carbon on albedo and long-term mass balance of an Alpine glacier

    Directory of Open Access Journals (Sweden)

    J. Gabbi

    2015-07-01

    Full Text Available Light-absorbing impurities in snow and ice control glacier melt as shortwave radiation represents the main component of the surface energy balance. Here, we investigate the long-term effect of snow impurities, i.e., mineral dust and black carbon (BC, on albedo and glacier mass balance. The analysis was performed over the period 1914–2014 for two sites on Claridenfirn, Swiss Alps, where an outstanding 100-year record of seasonal mass balance measurements is available. Information on atmospheric deposition of mineral dust and BC over the last century was retrieved from two firn/ice cores of high-alpine sites. A combined mass balance and snow/firn layer model was employed to assess the effects of melt and accumulation processes on the impurity concentration at the surface and thus on albedo and glacier mass balance. Compared to pure snow conditions, the presence of Saharan dust and BC lowered the mean annual albedo by 0.04–0.06 depending on the location on the glacier. Consequently, annual melt was increased by 15–19 %, and the mean annual mass balance was reduced by about 280–490 mm w.e. BC clearly dominated absorption which is about 3 times higher than that of mineral dust. The upper site has experienced mainly positive mass balances and impurity layers were continuously buried whereas at the lower site, surface albedo was more strongly influenced by re-exposure of dust and BC-enriched layers due to frequent years with negative mass balances.

  19. The impact of Saharan dust and black carbon on albedo and long-term mass balance of an Alpine glacier

    Science.gov (United States)

    Gabbi, J.; Huss, M.; Bauder, A.; Cao, F.; Schwikowski, M.

    2015-07-01

    Light-absorbing impurities in snow and ice control glacier melt as shortwave radiation represents the main component of the surface energy balance. Here, we investigate the long-term effect of snow impurities, i.e., mineral dust and black carbon (BC), on albedo and glacier mass balance. The analysis was performed over the period 1914-2014 for two sites on Claridenfirn, Swiss Alps, where an outstanding 100-year record of seasonal mass balance measurements is available. Information on atmospheric deposition of mineral dust and BC over the last century was retrieved from two firn/ice cores of high-alpine sites. A combined mass balance and snow/firn layer model was employed to assess the effects of melt and accumulation processes on the impurity concentration at the surface and thus on albedo and glacier mass balance. Compared to pure snow conditions, the presence of Saharan dust and BC lowered the mean annual albedo by 0.04-0.06 depending on the location on the glacier. Consequently, annual melt was increased by 15-19 %, and the mean annual mass balance was reduced by about 280-490 mm w.e. BC clearly dominated absorption which is about 3 times higher than that of mineral dust. The upper site has experienced mainly positive mass balances and impurity layers were continuously buried whereas at the lower site, surface albedo was more strongly influenced by re-exposure of dust and BC-enriched layers due to frequent years with negative mass balances.

  20. The Response of an Albedo Neutron Dosimeter to Moderated AmBe and 252(Cf) Neutron Sources.

    Science.gov (United States)

    2014-09-26

    neutrons is deter- mined by making multiple integrations on the glow curves from the detectors [41, or by computer analysis of the glow curves [5-61...Falk, "A Personnel Neutron Dosimeter Using Lithium Fluoride Thermoluminescent Dosim- eters," Report No. RFP-1581, Dow Chemical Co., Golden CO (1971...Addison Wesley, Reading, MA, 1953). 18. D.E. Hankins, "Factors Affecting the Design of Albedo Neutron Dosimeters Containing Lithium Fluoride

  1. The Effect of Host Star Spectral Energy Distribution and Ice-Albedo Feedback on the Climate of Extrasolar Planets

    CERN Document Server

    Shields, Aomawa L; Bitz, Cecilia M; Pierrehumbert, Raymond T; Joshi, Manoj M; Robinson, Tyler D

    2013-01-01

    Planetary climate can be affected by the interaction of the host star spectral energy distribution with the wavelength-dependent reflectivity of ice and snow. Here we explore this effect using a one dimensional (1-D), line-by-line, radiative-transfer model to calculate broadband planetary albedos as input to a seasonally varying, 1-D energy-balance climate model. A three-dimensional general circulation model is also used to explore the atmosphere's response to changes in incoming stellar radiation, or instellation, and surface albedo. Using this hierarchy of models we simulate planets covered by ocean, land, and water ice of varying grain size, with incident radiation from stars of different spectral types. Terrestrial planets orbiting stars with higher near-UV radiation exhibit a stronger ice-albedo feedback. We find that ice-covered conditions occur on an F-dwarf planet with only a 2% reduction in instellation relative to the present instellation on Earth, assuming fixed CO2 (present atmospheric level on Ea...

  2. MCD43A2: MODIS/Terra and Aqua BRDF/Albedo Quality Daily L3 Global 500 m SIN Grid Version 6

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The MODerate-resolution Imaging Spectroradiometer (MODIS) BRDF/Albedo Model Parameters product (MCD43A1) contains three-dimensional (3D) data sets providing users...

  3. MODIS/COMBINED MCD43C1 BRDF-Albedo Model Parameters 16-Day L3 0.05Deg CMG

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The MODerate-resolution Imaging Spectroradiometer (MODIS) BRDF/Albedo Model Parameters product (MCD43A1) contains three-dimensional (3D) data sets providing users...

  4. Operational comparison of bubble (super heated drop) dosimetry with routine albedo TLD for a selected group of Pu-238 workers at Los Alamos National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Romero, L.L.; Hoffman, J.M.; Foltyn, E.M.; Buhl, T.E.

    1998-09-01

    Personnel neutron dosimetry continues to be a difficult science due to the lack of availability of robust passive dosimeters that exhibit tissue- or near-tissue- equivalent response. This paper is an operational study that compares the use of albedo thermoluminescent dosimeters with bubble dosimeters to determine whether bubble dosimeters do provide a useful daily ALARA tool that can yield measurements close to the dose-of-record. A group of workers at Los Alamos National Laboratory (LANL) working on the Radioisotopic Thermoelectric Generators (RTG) for the NASA Cassini space mission wore both bubble dosimeters and albedo dosimeters over a period from 1993 through 1996. The personal albedo dosimeter was processed on a monthly basis and used as the dose-of-record. The results of this study indicated that cumulative daily bubble dosimetry results agreed with whole-body albedo dosimetry results within about 37% on average.

  5. Correlation between Increases of the Annual Global Solar Radiation and the Ground Albedo Solar Radiation due to Desertification—A Possible Factor Contributing to Climatic Change

    Directory of Open Access Journals (Sweden)

    Emanuele Calabrò

    2016-12-01

    Full Text Available Background: This study investigates the connection between annual global solar radiation and ground albedo solar radiation due to desertification in line with previous research on the correlation between climatic changes and desertification. Methods: A simulation study was performed using an algorithm formulated by the authors and the typical albedo coefficient values of forested ground, green grass and desert sand. Results: It is shown that changing the albedo coefficients from values corresponding to forested ground or green grass to values corresponding to the desert sand causes a significant increase in the annual global solar radiation acquired at different latitudes, leading one to hypothesize a mechanism of reduction of convective overturning and precipitation decreases due to desertification. Conclusion: In this scenario, modifications of local and global climate can be connected to changes of ground solar albedo induced by desertification.

  6. MODIS/COMBINED MCD43C2 BRDF-Albedo Snow-Free Quality 16-Day L3 Global 0.05Deg CMG

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The MODerate-resolution Imaging Spectroradiometer (MODIS) BRDF/Albedo Model Parameters product (MCD43A1) contains three-dimensional (3D) data sets providing users...

  7. 全球变化下地表反照率研究进展%Research Progress on Surface Albedo under Global Change

    Institute of Scientific and Technical Information of China (English)

    肖登攀; 陶福禄; Moiwo Juana P

    2011-01-01

    Surface albedo is a critical consideration for energy balance at the land-air interface. It determines the allocation of radiant energy between the earth's surface and atmosphere. Changes in surface albedo affect the energy balance of land-air system, which could in turn lead to climate change. Land Use/Cover Change (LUCC) is an important element of global climate change. LUCC affects surface albedo, and thus climate change. Surface albedo is controlled by solar elevation angle, land surface nature, soil moisture, weather condition, etc. This paper presents an in-depth review of the driving factors of surface albedo. Conventional observations of surface albedo are point-based, and therefore have limited spatial representation. On the other hand, surface albedo retrieved by Re- mote Sensing (RS) could have a large spatial representation. However, RS-driven surthce albedo needs validation by ground-truth observations. Hence this paper reviews and epitomizes observational and RS-based analyses surface albedo. It also summarizes research progress in surface albedo in relation to global climate. Moreover, this review highlights the strengths, weaknesses and future directions of sufface-albedo/climate-change research. The points documented herein could profoundly augment current understanding about global climate change and related driving factors.%地表反照率表征地球表面对太阳辐射的反射能力,决定着地表与大气之间辐射能量的分配过程,是影响地球气候系统的关键变量。在全球变化日益突出的今天,地表反照率与全球变化的相互影响机制已经成为地球科学研究领域的热点问题之一。地表反照率的细微变化,会影响到地气系统的能量收支平衡,进而引起区域以至全球气候变化。详细介绍地表反照率影响因素、研究方法等方面的最新研究进展,并从全球变化的角度阐述地表反照率的研究动态及其研究方向。

  8. Assessing the measurement of aerosol single scattering albedo by Cavity Attenuated Phase-Shift Single Scattering Monitor (CAPS PMssa)

    Science.gov (United States)

    Perim de Faria, Julia; Bundke, Ulrich; Onasch, Timothy B.; Freedman, Andrew; Petzold, Andreas

    2016-04-01

    The necessity to quantify the direct impact of aerosol particles on climate forcing is already well known; assessing this impact requires continuous and systematic measurements of the aerosol optical properties. Two of the main parameters that need to be accurately measured are the aerosol optical depth and single scattering albedo (SSA, defined as the ratio of particulate scattering to extinction). The measurement of single scattering albedo commonly involves the measurement of two optical parameters, the scattering and the absorption coefficients. Although there are well established technologies to measure both of these parameters, the use of two separate instruments with different principles and uncertainties represents potential sources of significant errors and biases. Based on the recently developed cavity attenuated phase shift particle extinction monitor (CAPS PM_{ex) instrument, the CAPS PM_{ssa instrument combines the CAPS technology to measure particle extinction with an integrating sphere capable of simultaneously measuring the scattering coefficient of the same sample. The scattering channel is calibrated to the extinction channel, such that the accuracy of the single scattering albedo measurement is only a function of the accuracy of the extinction measurement and the nephelometer truncation losses. This gives the instrument an accurate and direct measurement of the single scattering albedo. In this study, we assess the measurements of both the extinction and scattering channels of the CAPS PM_{ssa through intercomparisons with Mie theory, as a fundamental comparison, and with proven technologies, such as integrating nephelometers and filter-based absorption monitors. For comparison, we use two nephelometers, a TSI 3563 and an Aurora 4000, and two measurements of the absorption coefficient, using a Particulate Soot Absorption Photometer (PSAP) and a Multi Angle Absorption Photometer (MAAP). We also assess the indirect absorption coefficient

  9. MERIS albedo data set with improved spatial resolution for SCIAMACHY NO2 retrieval over the European Alpine region

    Science.gov (United States)

    Popp, Christoph; Brunner, Dominik; Zhou, Yipin; Wang, Ping; Stammes, Piet

    Despite NOx emissions have been reduced in the past two decades in Switzerland, the NO2 concentrations today still occasionally exceed their threshold as in most other European coun-tries. In addition, the neighboring Po Valley in Northern Italy is well known for generally high levels of air pollutants which are often transported to the southern part of Switzerland. Vertical tropospheric column (VTC) densities of NO2 obtained from spaceborne UV/VIS sensors pro-vide spatially homogeneous information complementing local ground-based measurements. For instance, SCIAMACHY (Scanning Imaging Absorption SpectroMeter for Atmospheric Cartog-raphY) derived NO2-VTC are available from 2002 onward potentially enabling trend analysis as well as monitoring of air quality in our region of interest. In general, a large part of the NO2-VTC retrieval uncertainty can be assigned to the air mass factor which, in turn, depends on model parameters such as surface albedo, surface pressure, cloud fraction and cloud pres-sure. Previous studies indicated that improving the spatial resolution of these forward param-eters can lead to more accurate estimates of NO2-VTC. Herein, we concentrate on the surface albedo. In ESA's TEMIS (Tropospheric Emission Monitoring Internet Service) project, the SCIAMACHY NO2-VTC retrieval makes use of combined GOME/TOMS Lambertian equiva-lent reflectance data mapped onto a grid with a spatial resolution of 1x1. However, variations of surface albedo at the scale of individual satellite pixels (30x60km2 for SCIAMACHY) are difficult to be resolved with this grid size, especially in areas like the European Alps and ad-jacent regions characterized by heterogeneous land cover. For these reasons, we compiled a new land surface albedo climatology for each month of the year from MERIS (The Medium Resolution Imaging Spectrometer) Albedomap data covering the period October 2002 to Oc-tober 2006 with a spatial resolution of 0.25x0.25. The wavelength bands considered are

  10. Aerosol single-scattering albedo retrieval over North Africa using critical reflectance

    Science.gov (United States)

    Wells, Kelley C.

    The sign and magnitude of the aerosol radiative forcing over bright surfaces is highly dependent on the absorbing properties of the aerosol. Thus, the determination of aerosol forcing over desert regions requires accurate information about the aerosol single-scattering albedo (SSA). However, the brightness of desert surfaces complicates the retrieval of aerosol optical properties using passive space-based measurements. The aerosol critical reflectance is one parameter that can be used to relate top-of-atmosphere (TOA) reflectance changes over land to the aerosol absorption properties, without knowledge of the underlying surface properties or aerosol loading. Physically, the parameter represents the TOA reflectance at which increased aerosol scattering due to increased aerosol loading is balanced by increased absorption of the surface contribution to the TOA reflectance. It can be derived by comparing two satellite images with different aerosol loading, assuming that the surface reflectance and background aerosol are similar between the two days. In this work, we explore the utility of the critical reflectance method for routine monitoring of spectral aerosol absorption from space over North Africa, a region that is predominantly impacted by absorbing dust and biomass burning aerosol. We derive the critical reflectance from Moderate Resolution Spectroradiometer (MODIS) Level 1B reflectances in the vicinity of two Aerosol Robotic Network (AERONET) stations: Tamanrasset, a site in the Algerian Sahara, and Banizoumbou, a Sahelian site in Niger. We examine the sensitivity of the critical reflectance parameter to aerosol physical and optical properties, as well as solar and viewing geometry, using the Santa Barbara DISORT Radiative Transfer (SBDART) model, and apply our findings to retrieve SSA from the MODIS critical reflectance values. We compare our results to AERONET-retrieved estimates, as well as to measurements of the TOA albedo and surface fluxes from the

  11. Candidate perennial bioenergy grasses have a higher albedo than annual row crops

    Science.gov (United States)

    Miller, J. N.; VanLoocke, A.; Gomez-Casanovas, N.; Bernacchi, C.

    2015-12-01

    The production of perennial cellulosic feedstocks for bioenergy presents the potential to diversify regional economies and the national energy supply, while also serving as climate 'regulators' due to a number of biogeochemical and biogeophysical differences relative to row crops. Numerous observational and model based approaches have investigated biogeochemical tradeoffs, such as increased carbon sequestration and increased water use, associated with growing cellulosic feedstocks. A less understood aspect is the biogeophysical changes associated with the difference in albedo (α), which could alter the local energy balance and cause local to regional cooling several times larger than that associated with offsetting carbon. Here, we established paired fields of Miscanthus × giganteus (miscanthus) and Panicum virgatum (switchgrass), two of the leading perennial cellulosic feedstock candidates, and traditional annual row crops in the highly productive "Corn-belt". Our results show that miscanthus did and switchgrass did not have an overall higher α than current row crops but a strong seasonal pattern existed. Both perennials had consistently higher growing season α than row crops and winter α did not differ. The lack of observed differences in winter α, however, masked an interaction between snow cover and species differences, with the perennial species, compared with the row crops, having a higher α when snow was absent and a much lower α when snow was present. Overall, these changes resulted in an average net reduction in annual absorbed energy of about 5 W/m2 for switchgrass and about 8 W/m2 for miscanthus relative to annual crops. Therefore, the conversion from annual row to perennial crops alters the radiative balance of the surface via changes in α and could lead to regional cooling.

  12. Quantifying organic aerosol single scattering albedo over the tropical biomass burning regions

    Science.gov (United States)

    Chu, Jung-Eun; Ha, Kyung-Ja

    2016-12-01

    Despite growing evidence of light-absorbing organic aerosols (OAs), their contribution to the Earth's radiative budget is still poorly understood. In this study we derived a new empirical relationship that binds OA single scattering albedo (SSA), which is the ratio of light scattering to extinction, with sulfate + nitrate aerosol optical depth (AOD) and applied this method to estimate OA SSA over the tropical biomass burning regions. This method includes division of the attribution of black carbon (BC) and OA absorption aerosol optical depths from the Aerosol Robotic Network (AERONET) observation and determination of the fine-mode ratio of sea-salt and dust AODs from several atmospheric chemistry models. Our best estimate of OA SSA over the tropical biomass burning regions is 0.91 at 550 nm. Uncertainties associated with observations and models permit a value range of 0.82-0.93. Furthermore, by using the estimated OA SSA and comprehensive observations including AERONET, Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging Spectroradiometer (MISR), we examined the first global estimate of sulfate + nitrate AOD through a semi-observational approach. The global mean sulfate + nitrate AOD of 0.017 is in the lower range of the values obtained from 21 models participated in AeroCom phase II. The results imply that most aerosol models as well as climate models, which commonly use OA SSA of 0.96-1.0, have so far ignored light absorption by OAs and have overestimated light scattering by sulfate + nitrate aerosols. This indicates that the actual aerosol direct radiative forcing should be less negative than currently believed.

  13. Simultaneous improvement in water use, productivity and albedo through canopy structural modification

    Science.gov (United States)

    Drewry, Darren; Kumar, Praveen; Long, Stephen

    2015-04-01

    Agricultural lands provide a tremendous opportunity to address challenges at the intersection of food and water security and climate change. Global demand for the major grain and seed crops is beginning to outstrip production, while population growth and the expansion of the global middle class have motivated calls for a doubling of food production by the middle of this century. This is occurring as yield gains for the major food crops have stagnated. At current rates of yield improvement this doubling will not be achieved. Plants have evolved to maximize the capture of radiation in the upper leaves, resulting in sub-optimal monoculture crop fields for maximizing productivity and other biogeophysical services. Using the world's most important protein crop, soybean, as an example, we show that by applying numerical optimization to a micrometeorological crop canopy model that significant, simultaneous gains in water use, productivity and reflectivity are possible with no increased demand on resources. Here we apply the MLCan multi-layer canopy biophysical model, which vertically resolves the radiation and micro-environmental variations that stimulate biochemical and ecophysiological functions that govern canopy-atmosphere exchange processes. At each canopy level photosynthesis, stomatal conductance, and energy balance are solved simultaneously for shaded and sunlit foliage. A multi-layer sub-surface model incorporates water availability as a function of root biomass distribution. MLCan runs at sub-hourly temporal resolution, allowing it to capture variability in CO2, water and energy exchange as a function of environmental variability. By modifying total canopy leaf area, its vertical distribution, leaf angle, and shortwave radiation reflectivity, all traits available in most major crop germplasm collections, we show that increases in either productivity (7%), water use (13%) or albedo (34%) could be achieved with no detriment to the other objectives, under climate

  14. Simultaneous Improvement in Water Use, Productivity and Albedo Through Crop Structural Modification

    Science.gov (United States)

    Drewry, D.; Kumar, P.; Long, S.

    2014-12-01

    Agricultural lands provide a tremendous opportunity to address challenges at the intersection of climate change, food and water security. Global demand for the major grain and seed crops is beginning to outstrip production, while population growth and the expansion of the global middle class have motivated calls for a doubling of food production by the middle of this century. This is occurring as yield gains for the major food crops have stagnated. At current rates of yield improvement this doubling will not be achieved. Plants have evolved to maximize the capture of radiation in the upper leaves, resulting in sub-optimal monoculture crop fields for maximizing productivity and other biogeophysical services. Using the world's most important protein crop, soybean, as an example, we show that by applying numerical optimization to a micrometeorological crop canopy model that significant, simultaneous gains in water use, productivity and reflectivity are possible with no increased demand on resources. Here we apply the MLCan multi-layer canopy biophysical model, which vertically resolves the radiation and micro-environmental variations that stimulate biochemical and ecophysiological functions that govern canopy-atmosphere exchange processes. At each canopy level photosynthesis, stomatal conductance, and energy balance are solved simultaneously for shaded and sunlit foliage. A multi-layer sub-surface model accounts for water availability as a function of root biomass distribution. MLCan runs at sub-hourly temporal resolution, allowing it to capture variability in CO2, water and energy exchange as a function of environmental variability. By modifying total canopy leaf area, its vertical distribution, leaf angle, and shortwave radiation reflectivity, all traits available in most major crop germplasm collections, we show that increases in either productivity (7%), water use (13%) or albedo (34%) could be achieved with no detriment to the other objectives, under United

  15. The Stellar Obliquity, Planet Mass, and Very Low Albedo of Qatar-2 from K2 Photometry

    Science.gov (United States)

    Dai, Fei; Winn, Joshua N.; Yu, Liang; Albrecht, Simon

    2017-01-01

    The Qatar-2 transiting exoplanet system was recently observed in short-cadence mode by Kepler as part of K2 Campaign 6. We identify dozens of starspot-crossing events, when the planet eclipses a relatively dark region of the stellar photosphere. The observed patterns of these events demonstrate that the planet always transits over the same range of stellar latitudes and, therefore, that the stellar obliquity is less than about 10°. We support this conclusion with two different modeling approaches: one based on explicit identification and timing of the events and the other based on fitting the light curves with a spotted-star model. We refine the transit parameters and measure the stellar rotation period (18.5 ± 1.9 days), which corresponds to a “gyrochronological” age of 1.4 ± 0.3 Gyr. Coherent flux variations with the same period as the transits are well modeled as the combined effects of ellipsoidal light variations (15.4 ± 4.8 ppm) and Doppler boosting (14.6 ± 5.1 ppm). The magnitudes of these effects correspond to a planetary mass of 2.6+/- 0.9 {M}{Jup} and 3.9+/- 1.5 {M}{Jup}, respectively. Both of these independent mass estimates agree with the mass determined by the spectroscopic Doppler technique (2.487+/- 0.086 {M}{Jup}). No occultations are detected, giving a 2σ upper limit of 0.06 on the planet’s visual geometric albedo. We find no evidence for orbital decay, although we are only able to place a weak lower bound on the relevant tidal quality factor: {Q}\\star \\prime > 1.5× {10}4 (95% confidence).

  16. The effects of timing and rate of marine cloud brightening aerosol injection on albedo changes during the diurnal cycle of marine stratocumulus clouds

    Directory of Open Access Journals (Sweden)

    A. K. L. Jenkins

    2012-09-01

    Full Text Available The marine-cloud brightening geoengineering technique has been suggested as a~possible means of counteracting the positive radiative forcing associated with anthropogenic atmospheric CO2 increases. The focus of this study is to quantify the albedo response to aerosols injected into marine stratocumulus cloud from a point source at different times of day. We use a cloud-resolving model to investigate both weakly precipitating and non-precipitating regimes. Injection into both regimes induces a first indirect aerosol effect. Additionally, the weakly precipitating regime shows evidence of the second indirect aerosol effect and leads to cloud changes indicative of a regime change to more persistent cloud. This results in a cloud albedo increase up to six times larger than in the non-precipitating case. These indirect effects show considerable variation with injection at different times in the diurnal cycle. For the weakly precipitating case, aerosol injection results in average increases in cloud albedo of 0.28 and 0.17 in the early and mid morning (03:00:00 local time (LT and 08:00:00 LT, respectively and 0.01 in the evening (18:00:00 LT. No cloud develops when injecting into the cloud-free day (13:00:00 LT. However, the all-sky albedo increases (which include both the indirect and direct aerosol effects are highest for early morning injection (0.11. Mid-morning and daytime injections produce increases of 0.06, with the direct aerosol effect compensating for the lack of cloud albedo perturbation during the cloud-free day. Evening injection results in an increase of 0.04. Penetration and accumulation of aerosols above the cloud top may lead to a reduction of all-sky albedo that tempers the cloud albedo increases. The apparent direct aerosol tempering effect increases with injection rate, although not enough to overcome the increase in all-sky planetary albedo resulting from increases in cloud albedo. For the weakly precipitating case

  17. Aerosol Single Scattering Albedo retrieved from ground-based measurements in the UV-visible

    Directory of Open Access Journals (Sweden)

    V. Buchard

    2010-07-01

    Full Text Available Estimates of Aerosol Single Scattering Albedo (SSA from ground-based spectral measurements in the UV-visible are conducted at Villeneuve d'Ascq (VdA in France. In order to estimate this parameter, measurements of global and diffuse UV-visible solar irradiances performed under cloud-free conditions since 2003 with a spectroradiometer operated by the Laboratoire d'Optique Atmosphérique (LOA are used. The technique consists in comparing the measured irradiance values to modelled irradiances computed for various SSA. The retrieval is restricted to the 330–450 nm range to avoid ozone influence.

    For validation purpose, the retrieved values of SSA at 440 nm are compared to the ones obtained from sunphotometer measurements of the AERONET/PHOTONS network available on the LOA site. The results are rather satisfying: in 2003 and 2005–2006 the Root Mean Square (RMS of the differences are about 0.05, these values are within the uncertainty domain of retrieval of both products. Distinction between days characterized by different aerosol content, by means of the aerosol optical thickness (AOT retrieved from ground-based measurements at the same wavelength, shows that the comparisons between both products are better when AOT are higher. Indeed in case AOT are greater than 0.2, the RMS is 0.027 in 2003 and 0.035 in 2005–2006. The SSA estimated at 340 and 380 nm from ground-based spectra are also studied, though no validation can be carried out with sunphotometer data (440 nm is the shortest wavelength at which the SSA is provided by the network. The good comparisons observed at 440 nm can let assume that the SSA retrieved from spectroradiometer measurements at the two other wavelengths are also obtained with a good confidence level. Thus these values in the UV range can be used to complete aerosol data provided by AERONET/PHOTONS at VdA. Moreover they can be used for a best knowledge of the aerosol absorption that is necessary to quantify the

  18. Mutation of albedo and growth response produces oscillations in a spatial Daisyworld

    Science.gov (United States)

    Wood, A. J.; Ackland, G.; Lenton, T.

    2005-12-01

    We present an extension of a 2-dimensional cellular automata (CA) Daisyworld to include mutation of optimum growth temperature as well as mutation of albedo. It is well established for the latter case such models exhibit homeostasis of the environment -- temperature in this case. In our model the organisms (daisies) can adapt to prevailing environmental conditions or evolve to alter their environment. This setup allows us to examine whether or not the former inhibits or even destroys the homeostatic effect. We find the resulting system to be capable of regulation on average but that it oscillates with a period of hundreds of daisy generations. The ability of the daisies to alter their optimal growing temperature leads initially to a planet which is less able to sustain itself, but the planet becomes steadily more stable (on average) for greater rates of genetic drift in this characteristic. Weaker and less regular oscillations have already been predicted in Daisyworlds before but in this model they become stronger and more regular as the mutation rate of the optimum growth temperature is increased. The oscillation itself is non-trivial and is composed by a series of well defined stages: when the population is maximal, a local region of daisies may lower (raise) the local temperature and adapt to it offering them a competitive advantage. The thermal time delay means that their newly adapted offspring are more successful, spiraling the daisies away from the optimal temperature. Once the population fragments, growth occurs primarily at boundaries between daisy patches and the bare earth - so warm (cold) adapted daisies are more successful, the direction of heating changes and the cycle reverses. We have analysed in detail the dependency of the period of oscillation on the various external parameters. It is found to decrease with increasing death rate, and to increase separately with increasing heat diffusion and heat capacity. The dependence of the period is

  19. Snow Metamorphism and Albedo Process (SMAP) model for climate studies: Model validation using meteorological and snow impurity data measured at Sapporo, Japan

    Science.gov (United States)

    Niwano, Masashi; Aoki, Teruo; Kuchiki, Katsuyuki; Hosaka, Masahiro; Kodama, Yuji

    2012-09-01

    We developed a multilayered physical snowpack model named Snow Metamorphism and Albedo Process (SMAP), which is intended to be incorporated into general circulation models for climate simulations. To simulate realistic physical states of snowpack, SMAP incorporates a state-of-the-art physically based snow albedo model, which calculates snow albedo and solar heating profile in snowpack considering effects of snow grain size and snow impurities explicitly. We evaluated the performance of SMAP with meteorological and snow impurities (black carbon and dust) input data measured at Sapporo, Japan during two winters: 2007-2008 and 2008-2009, and found SMAP successfully reproduced all observed variations of physical properties of snowpack for both winters. We have thus confirmed that SMAP is suitable for climate simulations. With SMAP, we also investigated the effects of snow impurities on snowmelt at Sapporo during the two winters. We found that snowpack durations at Sapporo were shortened by 19 days during the 2007-2008 winter and by 16 days during the 2008-2009 winter due to radiative forcings caused by snow impurities. The estimated radiative forcings due to snow impurities during the accumulation periods were 3.7 W/m2 (it corresponds to albedo reduction in 0.05) and 3.2 W/m2 (albedo reduction in 0.05) for the 2007-2008 and 2008-2009 winters, respectively. While during the ablation periods they were 25.9 W/m2 (albedo reduction in 0.18) and 21.0 W/m2 (albedo reduction in 0.17) for each winter, respectively.

  20. Regional albedo of Arctic first-year drift ice in advanced stages of melt from the combination of in situ measurements and aerial imagery

    Directory of Open Access Journals (Sweden)

    D. V. Divine

    2014-07-01

    Full Text Available The paper presents a case study of the regional (≈ 150 km broadband albedo of first year Arctic sea ice in advanced stages of melt, estimated from a combination of in situ albedo measurements and aerial imagery. The data were collected during the eight day ICE12 drift experiment carried out by the Norwegian Polar Institute in the Arctic north of Svalbard at 82.3° N from 26 July to 3 August 2012. The study uses in situ albedo measurements representative of the four main surface types: bare ice, dark melt ponds, bright melt ponds and open water. Images acquired by a helicopter borne camera system during ice survey flights covered about 28 km2. A subset of > 8000 images from the area of homogeneous melt with open water fraction of ≈ 0.11 and melt pond coverage of ≈ 0.25 used in the upscaling yielded a regional albedo estimate of 0.40 (0.38; 0.42. The 95% confidence interval on the estimate was derived using the moving block bootstrap approach applied to sequences of classified sea ice images and albedo of the four surface types treated as random variables. Uncertainty in the mean estimates of surface type albedo from in situ measurements contributed some 95% of the variance of the estimated regional albedo, with the remaining variance resulting from the spatial inhomogeneity of sea ice cover. The results of the study are of relevance for the modeling of sea ice processes in climate simulations. It particularly concerns the period of summer melt, when the optical properties of sea ice undergo substantial changes, which existing sea ice models have significant diffuculty accurately reproducing.

  1. Biogenic CO2 fluxes, changes in surface albedo and biodiversity impacts from establishment of a miscanthus plantation.

    Science.gov (United States)

    Jørgensen, Susanne V; Cherubini, Francesco; Michelsen, Ottar

    2014-12-15

    Depletion in oil resources and environmental concern related to the use of fossil fuels has increased the interest in using second generation biomass as alternative feedstock for fuels and materials. However, the land use and land use change for producing second generation (2G) biomass impacts the environment in various ways, of which not all are usually considered in life cycle assessment. This study assesses the biogenic CO2 fluxes, surface albedo changes and biodiversity impacts for 100 years after changing land use from forest or fallow land to miscanthus plantation in Wisconsin, US. Climate change impacts are addressed in terms of effective forcing, a mid-point indicator which can be used to compare impacts from biogenic CO2 fluxes and albedo changes. Biodiversity impacts are assessed through elaboration on two different existing approaches, to express the change in biodiversity impact from one human influenced state to another. Concerning the impacts from biogenic CO2 fluxes, in the case of conversion from a forest to a miscanthus plantation (case A) there is a contribution to global warming, whereas when a fallow land is converted (case B), there is a climate cooling. When the effects from albedo changes are included, both scenarios show a net cooling impact, which is more pronounced in case B. Both cases reduce biodiversity in the area where the miscanthus plantation is established, though most in case A. The results illustrate the relevance of these issues when considering environmental impacts of land use and land use change. The apparent trade-offs in terms of environmental impacts further highlight the importance of including these aspects in LCA of land use and land use changes, in order to enable informed decision making.

  2. Investigating the Impacts of Surface Temperature Anomalies due to Burned Area Albedo in Northern sub-Saharan Africa

    Science.gov (United States)

    Gabbert, T.; Matsui, T.; Capehart, W. J.; Ichoku, C. M.; Gatebe, C. K.

    2015-12-01

    The northern Sub-Saharan African region (NSSA) is an area of intense focus due to periodic severe droughts that have dire consequences on the growing population, which relies mostly on rain fed agriculture for its food supply. This region's weather and hydrologic cycle are very complex and are dependent on the West African Monsoon. Different regional processes affect the West African Monsoon cycle and variability. One of the areas of current investigation is the water cycle response to the variability of land surface characteristics. Land surface characteristics are often altered in NSSA due to agricultural practices, grazing, and the fires that occur during the dry season. To better understand the effects of biomass burning on the hydrologic cycle of the sub-Saharan environment, an interdisciplinary team sponsored by NASA is analyzing potential feedback mechanisms due to the fires. As part of this research, this study focuses on the effects of land surface changes, particularly albedo and skin temperature, that are influenced by biomass burning. Surface temperature anomalies can influence the initiation of convective rainfall and surface albedo is linked to the absorption of solar radiation. To capture the effects of fire perturbations on the land surface, NASA's Unified Weather and Research Forecasting (NU-WRF) model coupled with NASA's Land Information System (LIS) is being used to simulate burned area surface albedo inducing surface temperature anomalies and other potential effects to environmental processes. Preliminary sensitivity results suggest an altered surface radiation budget, regional warming of the surface temperature, slight increase in average rainfall, and a change in precipitation locations.

  3. On the Non-Monotonic Variation of the Opposition Surge Morphology with Albedo Exhibited by Satellites' Surface

    Science.gov (United States)

    Deau, E. A.; Spilker, L. J.; Flandes, A.

    2011-01-01

    We used well know phase functions of satellites and rings around the giant planets of our Solar System to study the morphology of the opposition effect (at phase angles alpha morphological model to retrieve the morphological parameters of the surge (A and HWHM). These parameters are found to have a non-monotonic variation with the single scattering albedo, similar to that observed in asteroids, which is unexplained so far. The non-monotonic variation is discussed in the framework of the coherent backscattering and shadow hiding mechanisms.

  4. Modelling long-term impacts of mountain pine beetle outbreaks on merchantable biomass, ecosystem carbon, albedo, and radiative forcing

    Science.gov (United States)

    Landry, Jean-Sébastien; Parrott, Lael; Price, David T.; Ramankutty, Navin; Damon Matthews, H.

    2016-09-01

    The ongoing major outbreak of mountain pine beetle (MPB) in forests of western North America has led to considerable research efforts. However, many questions remain unaddressed regarding its long-term impacts, especially when accounting for the range of possible responses from the non-target vegetation (i.e., deciduous trees and lower-canopy shrubs and grasses). We used the Integrated BIosphere Simulator (IBIS) process-based ecosystem model along with the recently incorporated Marauding Insect Module (MIM) to quantify, over 240 years, the impacts of various MPB outbreak regimes on lodgepole pine merchantable biomass, ecosystem carbon, surface albedo, and the net radiative forcing on global climate caused by the changes in ecosystem carbon and albedo. We performed simulations for three locations in British Columbia, Canada, with different climatic conditions, and four scenarios of various coexisting vegetation types with variable growth release responses. The impacts of MPB outbreaks on merchantable biomass (decrease) and surface albedo (increase) were similar across the 12 combinations of locations and vegetation coexistence scenarios. The impacts on ecosystem carbon and radiative forcing, however, varied substantially in magnitude and sign, depending upon the presence and response of the non-target vegetation, particularly for the two locations not subjected to growing-season soil moisture stress; this variability represents the main finding from our study. Despite major uncertainty in the value of the resulting radiative forcing, a simple analysis also suggested that the MPB outbreak in British Columbia will have a smaller impact on global temperature over the coming decades and centuries than a single month of global anthropogenic CO2 emissions from fossil fuel combustion and cement production. Moreover, we found that (1) outbreak severity (i.e., per-event mortality) had a stronger effect than outbreak return interval on the variables studied, (2) MPB

  5. The Effect of Host Star Spectral Energy Distribution and Ice-Albedo Feedback on the Climate of Extrasolar Planets

    Science.gov (United States)

    Shields, Aomawa; Meadows, V.; Bitz, C. M.; Pierrehumbert, R. T.; Joshi, M. M.; Robinson, T. D.

    2013-01-01

    Planetary climate can be affected by the interaction of the host star spectral energy distribution with the wavelength-dependent reflectivity of ice and snow. A one dimensional (1-D), line-by-line, radiative-transfer model is used to calculate broadband planetary albedos as input to a seasonally varying, 1-D energy-balance climate model. We simulated planets covered by ocean, land, and water ice of varying grain size, with incident radiation from stars of different spectral types. Our results show that terrestrial planets orbiting stars with higher near-UV radiation exhibit a stronger ice-albedo feedback. Using a general circulation model we demonstrate that an ocean-covered planet orbiting in the habitable zone of an M-dwarf star has a higher global mean surface temperature than a planet orbiting the Sun (a G-dwarf star) at an equivalent stellar flux distance. The effect is even more pronounced when the albedos of snow and ice are lowered, indicating the importance of the spectral dependence of surface ice and snow on climate for these planets. We find that the sensitivity of climate to changes in stellar insolation for M-dwarf planets is weaker than for planets orbiting stars with greater visible and near-UV radiation. While a planet orbiting the Sun becomes ice-covered with an 8% reduction in stellar insolation, a similar planet orbiting an M dwarf requires a 27% reduction to become ice-covered. A 2% reduction in stellar insolation is all that is required for global ice cover on a planet orbiting an F-dwarf star. Consequently the habitable zone for surface liquid water on planets with Earth-like greenhouse gas concentrations may be ~12% wider for M-dwarf stars than for G-dwarf stars, and ~3% narrower for F-dwarf stars. Higher obliquities expand the outer habitable zone boundary for surface liquid water. Raising atmospheric CO2 can reduce the ice-albedo effect on M-dwarf planets, but ~3-10 bars are required to entirely mask the climatic effect of ice and snow.

  6. The effects of additional black carbon on the albedo of Arctic sea ice: variation with sea ice type and snow cover

    Directory of Open Access Journals (Sweden)

    A. A. Marks

    2013-07-01

    Full Text Available The response of the albedo of bare sea ice and snow-covered sea ice to the addition of black carbon is calculated. Visible light absorption and light-scattering cross-sections are derived for a typical first-year and multi-year sea ice with both "dry" and "wet" snow types. The cross-sections are derived using data from a 1970s field study that recorded both reflectivity and light penetration in Arctic sea ice and snow overlying sea ice. The variation of absorption cross-section over the visible wavelengths suggests black carbon is the dominating light-absorbing impurity. The response of first-year and multi-year sea ice albedo to increasing black carbon, from 1 to 1024 ng g−1, in a top 5 cm layer of a 155 cm-thick sea ice was calculated using a radiative-transfer model. The albedo of the first-year sea ice is more sensitive to additional loadings of black carbon than the multi-year sea ice. An addition of 8 ng g−1 of black carbon causes a decrease to 98.7% of the original albedo for first-year sea ice compared to a decrease to 99.7% for the albedo of multi-year sea ice, at a wavelength of 500 nm. The albedo of sea ice is surprisingly unresponsive to additional black carbon up to 100 ng g−1 . Snow layers on sea ice may mitigate the effects of black carbon in sea ice. Wet and dry snow layers of 0.5, 1, 2, 5 and 10 cm depth were added onto the sea ice surface. The albedo of the snow surface was calculated whilst the black carbon in the underlying sea ice was increased. A layer of snow 0.5 cm thick greatly diminishes the effect of black carbon in sea ice on the surface albedo. The albedo of a 2–5 cm snow layer (less than the e-folding depth of snow is still influenced by the underlying sea ice, but the effect of additional black carbon in the sea ice is masked.

  7. Influence of Dust and Black Carbon on the Snow Albedo in the NASA Goddard Earth Observing System Version 5 Land Surface Model

    Science.gov (United States)

    Yasunari, Teppei J.; Koster, Randal D.; Lau, K. M.; Aoki, Teruo; Sud, Yogesh C.; Yamazaki, Takeshi; Motoyoshi, Hiroki; Kodama, Yuji

    2011-01-01

    Present-day land surface models rarely account for the influence of both black carbon and dust in the snow on the snow albedo. Snow impurities increase the absorption of incoming shortwave radiation (particularly in the visible bands), whereby they have major consequences for the evolution of snowmelt and life cycles of snowpack. A new parameterization of these snow impurities was included in the catchment-based land surface model used in the National Aeronautics and Space Administration Goddard Earth Observing System version 5. Validation tests against in situ observed data were performed for the winter of 2003.2004 in Sapporo, Japan, for both the new snow albedo parameterization (which explicitly accounts for snow impurities) and the preexisting baseline albedo parameterization (which does not). Validation tests reveal that daily variations of snow depth and snow surface albedo are more realistically simulated with the new parameterization. Reasonable perturbations in the assigned snow impurity concentrations, as inferred from the observational data, produce significant changes in snowpack depth and radiative flux interactions. These findings illustrate the importance of parameterizing the influence of snow impurities on the snow surface albedo for proper simulation of the life cycle of snow cover.

  8. Enhancement of life cycle assessment (LCA) methodology to include the effect of surface albedo on climate change: Comparing black and white roofs.

    Science.gov (United States)

    Susca, Tiziana

    2012-04-01

    Traditionally, life cycle assessment (LCA) does not estimate a key property: surface albedo. Here an enhancement of the LCA methodology has been proposed through the development and employment of a time-dependent climatological model for including the effect of surface albedo on climate. The theoretical findings derived by the time-dependent model have been applied to the case study of a black and a white roof evaluated in the time-frames of 50 and 100 years focusing on the impact on global warming potential. The comparative life cycle impact assessment of the two roofs shows that the high surface albedo plays a crucial role in offsetting radiative forcings. In the 50-year time horizon, surface albedo is responsible for a decrease in CO(2)eq of 110-184 kg and 131-217 kg in 100 years. Furthermore, the white roof compared to the black roof, due to the high albedo, decreases the annual energy use of about 3.6-4.5 kWh/m(2).

  9. Evaluation of MODIS Albedo Product (MCD43A) over Grassland, Agriculture and Forest Surface Types During Dormant and Snow-Covered Periods

    Science.gov (United States)

    Wang, Zhousen; Schaaf, Crystal B.; Strahler, Alan H.; Chopping, Mark J.; Roman, Miguel O.; Shuai, Yanmin; Woodcock, Curtis E.; Hollinger, David Y.; Fitzjarrald, David R.

    2013-01-01

    This study assesses the Moderate-resolution Imaging Spectroradiometer (MODIS) BRDF/albedo 8 day standard product and products from the daily Direct Broadcast BRDF/albedo algorithm, and shows that these products agree well with ground-based albedo measurements during the more difficult periods of vegetation dormancy and snow cover. Cropland, grassland, deciduous and coniferous forests are considered. Using an integrated validation strategy, analyses of the representativeness of the surface heterogeneity under both dormant and snow-covered situations are performed to decide whether direct comparisons between ground measurements and 500-m satellite observations can be made or whether finer spatial resolution airborne or spaceborne data are required to scale the results at each location. Landsat Enhanced Thematic Mapper Plus (ETM +) data are used to generate finer scale representations of albedo at each location to fully link ground data with satellite data. In general, results indicate the root mean square errors (RMSEs) are less than 0.030 over spatially representative sites of agriculture/grassland during the dormant periods and less than 0.050 during the snow-covered periods for MCD43A albedo products. For forest, the RMSEs are less than 0.020 during the dormant period and 0.025 during the snow-covered periods. However, a daily retrieval strategy is necessary to capture ephemeral snow events or rapidly changing situations such as the spring snow melt.

  10. Development of a High Resolution BRDF/Albedo Product by Fusing Airborne CASI Reflectance with MODIS Daily Reflectance in the Oasis Area of the Heihe River Basin, China

    Directory of Open Access Journals (Sweden)

    Dongqin You

    2015-05-01

    Full Text Available A land-cover-based linear BRDF (bi-directional reflectance distribution function unmixing (LLBU algorithm based on the kernel-driven model is proposed to combine the compact airborne spectrographic imager (CASI reflectance with the moderate resolution imaging spectroradiometer (MODIS daily reflectance product to derive the BRDF/albedo of the two sensors simultaneously in the foci experimental area (FEA of the Heihe Watershed Allied Telemetry Experimental Research (HiWATER, which was carried out in the Heihe River basin, China. For each land cover type, an archetypal BRDF, which characterizes the shape of its anisotropic reflectance, is extracted by linearly unmixing from the MODIS reflectance with the assistance of a high-resolution classification map. The isotropic coefficients accounting for the differences within a class are derived from the CASI reflectance. The BRDF is finally determined by the archetypal BRDF and the corresponding isotropic coefficients. Direct comparisons of the cropland archetypal BRDF and CASI albedo with in situ measurements show good agreement. An indirect validation which compares retrieved BRDF/albedo with that of the MCD43A1 standard product issued by NASA and aggregated CASI albedo also suggests reasonable reliability. LLBU has potential to retrieve the high spatial resolution BRDF/albedo product for airborne and spaceborne sensors which have inadequate angular samplings. In addition, it can shorten the timescale for coarse spatial resolution product like MODIS.

  11. Suppression of the water ice and snow albedo feedback on planets orbiting red dwarf stars and the subsequent widening of the habitable zone.

    Science.gov (United States)

    Joshi, Manoj M; Haberle, Robert M

    2012-01-01

    M stars comprise 80% of main sequence stars, so their planetary systems provide the best chance for finding habitable planets, that is, those with surface liquid water. We have modeled the broadband albedo or reflectivity of water ice and snow for simulated planetary surfaces orbiting two observed red dwarf stars (or M stars), using spectrally resolved data of Earth's cryosphere. The gradual reduction of the albedos of snow and ice at wavelengths greater than 1 μm, combined with M stars emitting a significant fraction of their radiation at these same longer wavelengths, means that the albedos of ice and snow on planets orbiting M stars are much lower than their values on Earth. Our results imply that the ice/snow albedo climate feedback is significantly weaker for planets orbiting M stars than for planets orbiting G-type stars such as the Sun. In addition, planets with significant ice and snow cover will have significantly higher surface temperatures for a given stellar flux if the spectral variation of cryospheric albedo is considered, which in turn implies that the outer edge of the habitable zone around M stars may be 10-30% farther away from the parent star than previously thought.

  12. ESTIMACIÓN DE LA CONCENTRACIÓN FOLIAR USANDO PARAMETRIZACIÓN DIRECTA ALBEDO/ABSORTANCIA DE HOJAS

    Directory of Open Access Journals (Sweden)

    Fernando Paz Pellat

    2014-06-01

    Full Text Available El establecimiento de relaciones directas entre la información accesible por sensores remotos y las propiedades ópticas y bioquímicas de las hojas requiere primero de convertir medios heterogéneos, a escala de parcela, rodal o píxel, a homogéneos (radiativamente turbios. En este trabajo se plantea un esquema de conversión operacional para estimar las reflectancias en el infinito (medios ópticamente densos y de éstas los albedos foliares. Con los albedos foliares estimados es posible utilizar modelos radiativos de transferencia en hojas para estimar las concentraciones bioquímicas de sus constituyentes. Esto establece bases sólidas para el desarrollo de índices espectrales bioquímicos. Adicionalmente, los medios homogéneos convertidos tienen la propiedad de frontera de suelo negro, permitiendo su relación con la teoría de invariantes espectrales o teoría-p.

  13. Retrieval of aerosol single-scattering albedo and polarized phase function from polarized sun-photometer measurements for Zanjan's atmosphere

    Directory of Open Access Journals (Sweden)

    A. Bayat

    2013-10-01

    Full Text Available The polarized phase function of atmospheric aerosols has been investigated for the atmosphere of Zanjan, a city in northwest Iran. To do this, aerosol optical depth, Ångström exponent, single-scattering albedo, and polarized phase function have been retrieved from the measurements of a Cimel CE 318-2 polarized sun-photometer from February 2010 to December 2012. The results show that the maximum value of aerosol polarized phase function as well as the polarized phase function retrieved for a specific scattering angle (i.e., 60° are strongly correlated (R = 0.95 and 0.95, respectively with the Ångström exponent. The latter has a meaningful variation with respect to the changes in the complex refractive index of the atmospheric aerosols. Furthermore the polarized phase function shows a moderate negative correlation with respect to the atmospheric aerosol optical depth and single-scattering albedo (R = −0.76 and −0.33, respectively. Therefore the polarized phase function can be regarded as a key parameter to characterize the atmospheric particles of the region – a populated city in the semi-arid area and surrounded by some dust sources of the Earth's dust belt.

  14. Modeling of ground albedo neutrons to investigate seasonal cosmic ray-induced neutron variations measured at high-altitude stations

    Science.gov (United States)

    Hubert, G.; Pazianotto, M. T.; Federico, C. A.

    2016-12-01

    This paper investigates seasonal cosmic ray-induced neutron variations measured over a long-term period (from 2011 to 2016) in both the high-altitude stations located in medium geomagnetic latitude and Antarctica (Pic-du-Midi and Concordia, respectively). To reinforce analysis, modeling based on ground albedo neutrons simulations of extensive air showers and the solar modulation potential was performed. Because the local environment is well known and stable over time in Antarctica, data were used to validate the modeling approach. A modeled scene representative to the Pic-du-Midi was simulated with GEANT4 for various hydrogen properties (composition, density, and wet level) and snow thickness. The orders of magnitudes of calculated thermal fluence rates are consistent with measurements obtained during summers and winters. These variations are dominant in the thermal domain (i.e., En 20 MeV) is weakly impacted. The role of hydrogen content on ground albedo neutron generation was investigated with GEANT4 simulations. These investigations focused to mountain environment; nevertheless, they demonstrate the complexity of the local influences on neutron fluence rates.

  15. Mixing of anthropogenic dust and carbonaceous aerosols in seasonal snow on snow albedo reduction in 2014 China survey

    Science.gov (United States)

    Wang, Xin; Huang, Jianping; Pu, Wei

    2016-04-01

    Anthropogenic dusts produced from the affected by human activities derived from the industrial areas and carbonaceous aerosols (black carbon and organic carbon) deposited into snow or ice core via wet and dry deposition play key roles to the regional and global climate. Recently, a China survey was performed to measure the concentrations of insoluble light-absorbing particles (ILAP) in seasonal snow across northern China in January and February of 2014. The results indicate that the higher concentration of NO3- and SO42- and heavy metals of Zn, Pb, Cd, Ni, and Cu are likely to be attributed to enhanced local industrial emissions due to human activities. The emissions from fossil fuel combustion and biomass burning are likely to be important for the chemical elements in the seasonal snow with long-range transport, while medium enrichment factors of Mg, Ca, and Al were predominantly associated with soil dust, which is the most important natural source. There are large ranges of the BC and AD in seasonal snow over northeast China because of the anthropogenic emissions, which are caused by human activities. In addition, although the values of the snow albedo by model simulations are little higher in the visible to near-infrared wavelength than that during the China survey, the surface snow albedo by field campaign measurements have good agreement with the model simulations in the visible wavelength.

  16. The far-ultraviolet dust albedo in the Upper Scorpius subgroup of the Scorpius OB2 association

    Science.gov (United States)

    Gordon, Karl D.; Witt, Adolf N.; Carruthers, George R.; Christensen, Susan A.; Dohne, Brian C.

    1994-01-01

    During NRL's Far Ultraviolet Cameras experiemnt on STS-39, four images of the giant reflection nebula encompassing the Upper Scorpius subgroup of the Sco OB2 association were obtained in two ultraviolet bandpasses with lambda(sub eff) = 1362 A and 1769 A. From these images and IUE and TD-1 stellar spectra, the ratio of nebular to stellar flux was calculated. The ratio ranged from 0.577 to 0.921 at 1362 A and 0.681 to 0.916 at 1769 A with the spread in the ratio arising mainly from uncertainties in the sky background. In order to analyze these images, a model utilizing Monte Carlo techniques to describe radiative transfer in a spherical nebula with asymmetrically distributed stars was developed by elaborating on previous work by Witt. This model was used to determine the range of albedos reproducing the observed nebular-to-stellar flux ratios while allowing the scattering phase function asymmetry to vary between 0.0 and 0.8. The resulting albedos were 0.47-0.70 at 1362 A and 0.55-0.72 at 1769 A.

  17. Seasonal variation of vertical distribution of aerosol single scattering albedo over Indian sub-continent: RAWEX aircraft observations

    Science.gov (United States)

    Suresh Babu, S.; Nair, Vijayakumar S.; Gogoi, Mukunda M.; Krishna Moorthy, K.

    2016-01-01

    To characterize the vertical distribution of aerosols and its seasonality (especially the single scattering albedo, SSA) extensive profiling of aerosol scattering and absorption coefficients have been carried out using an instrumented aircraft from seven base stations spread across the Indian mainland during winter 2012 and spring/pre-monsoon 2013 under the Regional Aerosol Warming Experiment (RAWEX). Spatial variation of the vertical profiles of the asymmetry parameter, the wavelength exponent of the absorption coefficient and the single scattering albedo, derived from the measurements, are used to infer the source characteristics of winter and pre-monsoon aerosols as well as the seasonality of free tropospheric aerosols. The relatively high value of the wavelength exponent of absorption coefficient over most of the regions indicates the contribution from biomass burning and dust aerosols up to lower free tropospheric altitudes. A clear enhancement in aerosol loading and its absorbing nature is seen at lower free troposphere levels (above the planetary boundary layer) over the entire mainland during spring/pre-monsoon season compared to winter, whereas concentration of aerosols within the boundary layer showed a decrease from winter to spring. This could have significant implications on the aerosol heating structure over the Indian region and hence the regional climate.

  18. Contribution to the determination of the double angular and energy differential neutron albedo. Application to the propagation in lacunar medium; Contribution a la determination de l'albedo doublement differentiel en angle et en energie des neutrons. Application a la propagation dans les milieux lacunaires

    Energy Technology Data Exchange (ETDEWEB)

    Litaize, O

    2000-07-01

    The goal of this thesis is to study the neutron propagation by reflection from lacunar medium interfaces. The most efficient method to calculate this type of propagation is to use the concept of albedo. Actual version of NARCISSE code uses a simple formulation of angular differential albedos and so, can only treat single reflections. Multiple reflections treatment needs the knowledge of neutron spectrum after reflection. This energetic information is contained in double angular and energy differential albedos. The first step of this study consists to generate these albedos for various materials. Several methods have been tested and the Monte Carlo method was retained. A new estimator has been developed and validated in the Mote Carlo transport code TRIPOLI-4. It computes, during the simulation of the neutron history, the angular and energy reflection probability at each collision site. The second step consists to generate an interpolation scheme and albedo libraries for various materials. A new version of NARCISSE was developed to use these libraries and the interpolation module. Spectrum and dose rates comparisons were made between codes to validate these albedos. The neutron propagation by multiple reflections can be studied now, by using this new version of Narcisse. (author)

  19. Modeling radiative transfer in tropical rainforest canopies: sensitivity of simulated albedo to canopy architectural and optical parameters

    Directory of Open Access Journals (Sweden)

    Sílvia N. M. Yanagi

    2011-12-01

    Full Text Available This study evaluates the sensitivity of the surface albedo simulated by the Integrated Biosphere Simulator (IBIS to a set of Amazonian tropical rainforest canopy architectural and optical parameters. The parameters tested in this study are the orientation and reflectance of the leaves of upper and lower canopies in the visible (VIS and near-infrared (NIR spectral bands. The results are evaluated against albedo measurements taken above the K34 site at the INPA (Instituto Nacional de Pesquisas da Amazônia Cuieiras Biological Reserve. The sensitivity analysis indicates a strong response to the upper canopy leaves orientation (x up and to the reflectivity in the near-infrared spectral band (rNIR,up, a smaller sensitivity to the reflectivity in the visible spectral band (rVIS,up and no sensitivity at all to the lower canopy parameters, which is consistent with the canopy structure. The combination of parameters that minimized the Root Mean Square Error and mean relative error are Xup = 0.86, rVIS,up = 0.062 and rNIR,up = 0.275. The parameterizations performed resulted in successful simulations of tropical rainforest albedo by IBIS, indicating its potential to simulate the canopy radiative transfer for narrow spectral bands and permitting close comparison with remote sensing products.Este estudo avalia a sensibilidade do albedo da superfície pelo Simulador Integrado da Biosfera (IBIS a um conjunto de parâmetros que representam algumas propriedades arquitetônicas e óticas do dossel da floresta tropical Amazônica. Os parâmetros testados neste estudo são a orientação e refletância das folhas do dossel superior e inferior nas bandas espectrais do visível (VIS e infravermelho próximo (NIR. Os resultados são avaliados contra observações feitas no sítio K34 pertencente ao Instituto Nacional de Pesquisas da Amazônia (INPA na Reserva Biológica de Cuieiras. A análise de sensibilidade indica uma forte resposta aos parâmetros de orienta

  20. The Deep Blue Color of HD189733b: Albedo Measurements with Hubble Space Telescope/Space Telescope Imaging Spectrograph at Visible Wavelengths

    CERN Document Server

    Evans, Thomas M; Sing, David K; Aigrain, Suzanne; Barstow, Joanna K; Désert, Jean-Michel; Gibson, Neale; Heng, Kevin; Knutson, Heather A; Etangs, Alain Lecavelier des

    2013-01-01

    We present a secondary eclipse observation for the hot Jupiter HD189733b across the wavelength range 290-570nm made using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. We measure geometric albedos of Ag = 0.40 \\pm 0.12 across 290-450nm and Ag < 0.12 across 450-570nm at 1-sigma confidence. The albedo decrease toward longer wavelengths is also apparent when using six wavelength bins over the same wavelength range. This can be interpreted as evidence for optically thick reflective clouds on the dayside hemisphere with sodium absorption suppressing the scattered light signal beyond ~450nm. Our best-fit albedo values imply that HD189733b would appear a deep blue color at visible wavelengths.

  1. Case study of spatial and temporal variability of snow cover, grain size, albedo and radiative forcing in the Sierra Nevada and Rocky Mountain snowpack derived from imaging spectroscopy

    Science.gov (United States)

    Seidel, Felix C.; Rittger, Karl; McKenzie Skiles, S.; Molotch, Noah P.; Painter, Thomas H.

    2016-06-01

    Quantifying the spatial distribution and temporal change in mountain snow cover, microphysical and optical properties is important to improve our understanding of the local energy balance and the related snowmelt and hydrological processes. In this paper, we analyze changes of snow cover, optical-equivalent snow grain size (radius), snow albedo and radiative forcing by light-absorbing impurities in snow and ice (LAISI) with respect to terrain elevation and aspect at multiple dates during the snowmelt period. These snow properties are derived from the NASA/JPL Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data from 2009 in California's Sierra Nevada and from 2011 in Colorado's Rocky Mountains, USA. Our results show a linearly decreasing snow cover during the ablation period in May and June in the Rocky Mountains and a snowfall-driven change in snow cover in the Sierra Nevada between February and May. At the same time, the snow grain size is increasing primarily at higher elevations and north-facing slopes from 200 microns to 800 microns on average. We find that intense snowmelt renders the mean grain size almost invariant with respect to elevation and aspect. Our results confirm the inverse relationship between snow albedo and grain size, as well as between snow albedo and radiative forcing by LAISI. At both study sites, the mean snow albedo value decreases from approximately 0.7 to 0.5 during the ablation period. The mean snow grain size increased from approximately 150 to 650 microns. The mean radiative forcing increases from 20 W m-2 up to 200 W m-2 during the ablation period. The variability of snow albedo and grain size decreases in general with the progression of the ablation period. The spatial variability of the snow albedo and grain size decreases through the melt season while the spatial variability of radiative forcing remains constant.

  2. Decadal changes in aerosol optical thickness and single scattering albedo estimated from ground-based broadband radiometers: A case study in Japan

    Science.gov (United States)

    Kudo, Rei; Uchiyama, Akihiro; Yamazaki, Akihiro; Sakami, Tomonori; Ijima, Osamu

    2011-02-01

    A method to estimate aerosol optical thickness and single scattering albedo from broadband direct and diffuse irradiances was developed. Using irradiances simulated with and without errors, the accuracies of estimated optical thickness from 0.7 to 0.8 μm and single scattering albedo in the visible wavelength region were determined to be about 0.02 and 0.05, respectively. Resulting time variations in optical thickness and single scattering albedo by broadband radiometers agreed well with sky radiometer retrievals. Long-term variations in optical thickness and single scattering albedo from 1975 to 2008 at Tsukuba, Japan, were estimated by the method described. Optical thickness increased until the mid-1980s, then decreased until the late 1990s, and was almost constant in the 2000s. The single scattering albedo was about 0.8 until the late 1980s, gradually increased, and has remained at approximately 0.9 since the mid-1990s. The surface global irradiance under clear sky conditions calculated from estimated aerosol optical properties showed an apparent transition from dimming to brightening around the mid-1980s. The magnitude of the brightening was about 12.7 W m-2; of this, 8.3 W m-2 was due to a decrease in optical thickness, and the remaining 4.4 W m-2 was due to an increase of single scattering albedo. On the other hand, the surface global irradiance measured under cloudy conditions increased by 2.6 W m-2. The dimming and brightening by aerosols were weakened by the changes in clouds. The method described could be useful in evaluating aerosol influences on long-term changes in the surface solar radiation at many sites around the world.

  3. Efeito da banana da Terra verde e do albedo do maracujá sobre o perfil lipídico de ratos

    OpenAIRE

    BARBOSA, Eloiza Helena Carrijo

    2011-01-01

    Foram elaboradas farinhas de banana da terra verde (Musa AAB- Terra) e albedo de maracujá (Passiflora edulis f. flavicarpa) para o desenvolvimento do presente trabalho. Após determinação da composição química dessas farinhas realizou-se um ensaio biológico cujo objetivo foi avaliar os efeitos da farinha do albedo de maracujá (rica em fibra solúvel), da farinha de banana da terra verde (rica em amido resistente) sobre os níveis lipídicos de ratos com dieta hipercolesterolêmica. Para o ensai...

  4. Observations and model simulations of snow albedo reduction in seasonal snow due to insoluble light-absorbing particles during 2014 Chinese survey

    Science.gov (United States)

    Wang, Xin; Pu, Wei; Ren, Yong; Zhang, Xuelei; Zhang, Xueying; Shi, Jinsen; Jin, Hongchun; Dai, Mingkai; Chen, Quanliang

    2017-02-01

    A snow survey was carried out to collect 13 surface snow samples (10 for fresh snow, and 3 for aged snow) and 79 subsurface snow samples in seasonal snow at 13 sites across northeastern China in January 2014. A spectrophotometer combined with chemical analysis was used to quantify snow particulate absorption by insoluble light-absorbing particles (ILAPs, e.g., black carbon, BC; mineral dust, MD; and organic carbon, OC) in snow. Snow albedo was measured using a field spectroradiometer. A new radiative transfer model (Spectral Albedo Model for Dirty Snow, or SAMDS) was then developed to simulate the spectral albedo of snow based on the asymptotic radiative transfer theory. A comparison between SAMDS and an existing model - the Snow, Ice, and Aerosol Radiation (SNICAR) - indicates good agreements in the model-simulated spectral albedos of pure snow. However, the SNICAR model values tended to be slightly lower than those of SAMDS when BC and MD were considered. Given the measured BC, MD, and OC mixing ratios of 100-5000, 2000-6000, and 1000-30 000 ng g-1, respectively, in surface snow across northeastern China, the SAMDS model produced a snow albedo in the range of 0.95-0.75 for fresh snow at 550 nm, with a snow grain optical effective radius (Reff) of 100 µm. The snow albedo reduction due to spherical snow grains assumed to be aged snow is larger than fresh snow such as fractal snow grains and hexagonal plate or column snow grains associated with the increased BC in snow. For typical BC mixing ratios of 100 ng g-1 in remote areas and 3000 ng g-1 in heavy industrial areas across northern China, the snow albedo for internal mixing of BC and snow is lower by 0.005 and 0.036 than that of external mixing for hexagonal plate or column snow grains with Reff of 100 µm. These results also show that the simulated snow albedos by both SAMDS and SNICAR agree well with the observed values at low ILAP mixing ratios but tend to be higher than surface observations at high ILAP

  5. Prognostic land surface albedo from a dynamic global vegetation model clumped canopy radiative transfer scheme and satellite-derived geographic forest heights

    Science.gov (United States)

    Kiang, N. Y.; Yang, W.; Ni-Meister, W.; Aleinov, I. D.; Jonas, J.

    2014-12-01

    Vegetation cover was introduced into general circulations models (GCMs) in the 1980's to account for the effect of land surface albedo and water vapor conductance on the Earth's climate. Schemes assigning canopy albedoes by broad biome type have been superceded in 1990's by canopy radiative transfer schemes for homogeneous canopies obeying Beer's Law extinction as a function of leaf area index (LAI). Leaf albedo and often canopy height are prescribed by plant functional type (PFT). It is recognized that this approach does not effectively describe geographic variation in the radiative transfer of vegetated cover, particularly for mixed and sparse canopies. GCM-coupled dynamic global vegetation models (DGVMs) have retained these simple canopy representations, with little further evaluation of their albedos. With the emergence lidar-derived canopy vertical structure data, DGVM modelers are now revisiting albedo simulation. We present preliminary prognostic global land surface albedo produced by the Ent Terrestrial Biosphere Model (TBM), a DGVM coupled to the NASA Goddard Institute for Space Studies (GISS) GCM. The Ent TBM is a next generation DGVM designed to incorporate variation in canopy heights, and mixed and sparse canopies. For such dynamically varying canopy structure, it uses the Analytical Clumped Two-Stream (ACTS) canopy radiative transfer model, which is derived from gap probability theory for canopies of tree cohorts with ellipsoidal crowns, and accounts for soil, snow, and bare stems. We have developed a first-order global vegetation structure data set (GVSD), which gives a year of satellite-derived geographic variation in canopy height, maximum canopy leaf area, and seasonal LAI. Combined with Ent allometric relations, this data set provides population density and foliage clumping within crowns. We compare the Ent prognostic albedoes to those of the previous GISS GCM scheme, and to satellite estimates. The impact of albedo differences on surface

  6. Spaceborne estimated long-term trends (1980s - 2013) of albedo and melting season length over the Greenland ice sheet and linkages to climate drivers

    Science.gov (United States)

    Tedesco, M.; Stroeve, J. C.

    2014-12-01

    The length of the melting season and surface albedo modulate the amount of meltwater produced over the Greenland ice sheet. The two quantities are intimately connected through a suite of non-linear processes: for example, early melting can reduce the surface albedo (through constructive grain size metamorphism), hence affecting the surface energy balance and further increasing melting. Over the past years, several studies have highlighted increased melting concurring, with a decrease of mean surface albedo over Greenland. However, few studies have examined the duration of the melting season, its implication for surface processes and linkages to climate drivers. Moreover, the majority (if not all) of the studies assessing albedo trends from spaceborne data over Greenland have focused on the last decade or so (2000 - 2013) because they use data collected over the same period by the Moderate Resolution Imaging Spectroradiometer (MODIS). Here, we evaluate and synthesize long-term trends in the length of the melting season (1979 - 2013) derived from spaceborne microwave observations together with surface albedo trends for the period 1982 - 2013 using data from the Advanced Very High Resolution Radiometer (AVHRR). To our knowledge, this is the first time that trends in Greenland albedo and melt season length are discussed for the periods considered in this study. Our results point to a lengthening of the melting season as a consequence of earlier melt onset and later refreeze and to a decrease of mean albedo (1982 - 2013) over the Greenland ice sheet, with trends being spatially variable. To account for this spatial variability, the results of an analysis at regional scales over 12 different regions (defined by elevation and drainage systems) are also reported. The robustness of the results is evaluated by means of a comparative analysis of the results obtained from both AVHRR and MODIS when overlapping data are available (2000 - 2013). Lastly, because large

  7. A framework for consistent estimation of leaf area index, fraction of absorbed photosynthetically active radiation, and surface albedo from MODIS time-series data

    DEFF Research Database (Denmark)

    Xiao, Zhiqiang; Liang, Shunlin; Wang, Jindi

    2015-01-01

    Currently available land-surface parameter products are generated using parameter-specific algorithms from various satellite data and contain several inconsistencies. This paper developed a new data assimilation framework for consistent estimation of multiple land-surface parameters from time...... model and the MODIS surface reflectance data. The estimated LAI values were then input into the ACRM to calculate the surface albedo and the fraction of absorbed photosynthetically active radiation (FAPAR). For snow-covered areas, the surface albedo was calculated as the underlying vegetation canopy...

  8. Comprehensive wide-band magnitudes and albedos for the planets, with applications to exo-planets and Planet Nine

    Science.gov (United States)

    Mallama, Anthony; Krobusek, Bruce; Pavlov, Hristo

    2017-01-01

    Complete sets of reference magnitudes in all 7 Johnson-Cousins bands (U, B, V, R, I, RC and IC) and the 5 principal Sloan bands (u', g', r', i', and z') are presented for the 8 planets. These data are accompanied by illumination phase functions and other formulas which characterize the instantaneous brightness of the planets. The main source of Johnson-Cousins magnitudes is a series of individualized photometric studies reported in recent years. Gaps in that dataset were filled with magnitudes synthesized in this study from published spectrophotometry. The planetary Sloan magnitudes, which are established here for the first time, are an average of newly recorded Sloan filter photometry, synthetic magnitudes and values transformed from the Johnson-Cousins system. Geometric albedos derived from these two sets of magnitudes are consistent within each photometric system and between the systems for all planets and in all bands. This consistency validates the albedos themselves as well as the magnitudes from which they were derived. In addition, a quantity termed the delta stellar magnitude is introduced to indicate the difference between the magnitude of a planet and that of its parent star. A table of these delta values for exo-planets possessing a range of physical characteristics is presented. The delta magnitudes are for phase angle 90° where a planet is near the greatest apparent separation from its star. This quantity may be useful in exo-planet detection and observation strategies when an estimate of the signal-to-noise ratio is needed. Likewise, the phase curves presented in this paper can be used for characterizing exo-planets. Finally, magnitudes for the proposed Planet Nine are estimated, and we note that P9 may be especially faint at red and near-IR wavelengths.

  9. A transitioning Arctic surface energy budget: the impacts of solar zenith angle, surface albedo and cloud radiative forcing

    Energy Technology Data Exchange (ETDEWEB)

    Sedlar, Joseph; Tjernstroem, Michael; Leck, Caroline [Stockholm University, Department of Meteorology, Stockholm (Sweden); Mauritsen, Thorsten [Max-Planck-Institute for Meteorology, Hamburg (Germany); Shupe, Matthew D.; Persson, P.O.G. [University of Colorado, NOAA-ESRL-PSD, Boulder, CO (United States); Brooks, Ian M.; Birch, Cathryn E. [University of Leeds, School of Earth and Environment, Leeds (United Kingdom); Sirevaag, Anders [University of Bergen, Bjerknes Center for Climate Research, Bergen (Norway); Nicolaus, Marcel [Norwegian Polar Institute, Tromsoe (Norway); Alfred Wegener Institute for Polar and Marine Research, Bremerhaven (Germany)

    2011-10-15

    Snow surface and sea-ice energy budgets were measured near 87.5 N during the Arctic Summer Cloud Ocean Study (ASCOS), from August to early September 2008. Surface temperature indicated four distinct temperature regimes, characterized by varying cloud, thermodynamic and solar properties. An initial warm, melt-season regime was interrupted by a 3-day cold regime where temperatures dropped from near zero to -7 C. Subsequently mean energy budget residuals remained small and near zero for 1 week until once again temperatures dropped rapidly and the energy budget residuals became negative. Energy budget transitions were dominated by the net radiative fluxes, largely controlled by the cloudiness. Variable heat, moisture and cloud distributions were associated with changing air-masses. Surface cloud radiative forcing, the net radiative effect of clouds on the surface relative to clear skies, is estimated. Shortwave cloud forcing ranged between -50 W m{sup -2} and zero and varied significantly with surface albedo, solar zenith angle and cloud liquid water. Longwave cloud forcing was larger and generally ranged between 65 and 85 W m{sup -2}, except when the cloud fraction was tenuous or contained little liquid water; thus the net effect of the clouds was to warm the surface. Both cold periods occurred under tenuous, or altogether absent, low-level clouds containing little liquid water, effectively reducing the cloud greenhouse effect. Freeze-up progression was enhanced by a combination of increasing solar zenith angles and surface albedo, while inhibited by a large, positive surface cloud forcing until a new air-mass with considerably less cloudiness advected over the experiment area. (orig.)

  10. Changing Climate Sensitivity in Response to Forest-Tundra Snow Albedo Feedback during the mid to late Pliocene Cooling

    Science.gov (United States)

    Paiewonsky, P.

    2015-12-01

    The forest-tundra snow albedo feedback is an important feedback in Earth's climate system, especially due to its potential role in modulating glacial cycles. Until now, little research has been done on how the strength of this feedback might vary with the background climate state. Over the last 4 million years, I hypothesize that the feedback has been generally weaker under warm Northern Hemispheric conditions when tundra has been primarily confined to the high Arctic and forest has extended to most of the Arctic coastline than under cooler Northern Hemispheric conditions in which the forest-tundra boundary has generally lain to the south, extending across the interiors of the large continental land masses. To test the hypothesis of the weakened/strengthened feedback, I used an Earth System Model of Intermediate Complexity that consists of a dynamic terrestrial vegetation model coupled to a climate model. A set of time-slice experiments with different orbital and greenhouse gas concentrations were analyzed. In one set of experiments, the feedback gain with respect to annual average top-of-atmosphere net short wave radiation due to vegetation was 1.42 for modern conditions but only 1.14 for the mid-Pliocene. Additionally, we compared experiments with different shortwave-radiation parameterizations, which differed in the amount of shortwave energy flux reaching the surface (and subsequently affecting vegetative biomass). These techniques allowed us to isolate the mechanisms responsible for the varying strength of the forest-tundra snow albedo feedback. The results also show that many factors affect the strength of feedback. In this presentation I will concentrate on the availability of land for conversion of forest to tundra (and vice versa), cloud cover near the forest-tundra boundary, and the integrated surface insolation contrast between tundra and forest during the snow-covered season.

  11. Operational comparison of bubble (super heated drop) dosimetry results with routine albedo thermoluminescent dosimetry for a selected group of Pu-238 workers at Los Alamos National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Romero, L.L.; Hoffman, J.M.; Foltyn, E.M.; Buhl, T.E.

    1999-03-01

    This paper is an operational study that compares the use of albedo thermoluminescent dosimeters with bubble dosimeters to determine whether bubble dosimeters do provide a useful daily ALARA tool that can yield measurements close to the dose-of-record. A group of workers at the Los Alamos National Laboratory (LANL) working on the Radioactive Thermoelectric Generators (RTG) for the NASA Cassini space mission wore both bubble dosimeters and albedo dosimeters over a period from 1993 through 1996. The bubble dosimeters were issued and read on a daily basis and the data were used as an ALARA tool. The personnel albedo dosimeter was processed on monthly basis and used as the dose-of-record. The results of this study indicated that cumulative bubble dosimetry results agreed with whole-body albedo dosimetry results within about 37% on average. However it was observed that there is a significant variability of the results on an individual basis both month-to-month and from one individual to another.

  12. Narrowband-to-broadband albedo conversion for glacier ice and snow: equations based on modeling and ranges of validity of the equations

    NARCIS (Netherlands)

    Greuell, W.; Oerlemans, J.

    2004-01-01

    In this paper, we propose equations for narrowband-to-broadband (NTB) albedo conversion for glacier ice and snow for four types of satellite sensors: thematic mapper (TM), advanced very high resolution radiometer (AVHRR), moderate resolution imaging spectroradiometer (MODIS), and multi-angle imaging

  13. Suppression of the water ice and snow albedo feedback on planets orbiting red dwarf stars and the subsequent widening of the habitable zone

    CERN Document Server

    Joshi, M

    2012-01-01

    M-stars comprise 80% of main-sequence stars, and so their planetary systems provide the best chance for finding habitable planets, i.e.: those with surface liquid water. We have modelled the broadband albedo or reflectivity of water ice and snow for simulated planetary surfaces orbiting two observed red dwarf stars (or M-stars) using spectrally resolved data of the Earth's cryosphere. The gradual reduction of the albedos of snow and ice at wavelengths greater than 1 ?m, combined with M-stars emitting a significant fraction of their radiation at these same longer wavelengths, mean that the albedos of ice and snow on planets orbiting M-stars are much lower than their values on Earth. Our results imply that the ice/snow albedo climate feedback is significantly weaker for planets orbiting M-stars than for planets orbiting G-type stars such as the Sun. In addition, planets with significant ice and snow cover will have significantly higher surface temperatures for a given stellar flux if the spectral variation of c...

  14. "TNOs are Cool": A Survey of the Transneptunian Region IV. Size/albedo characterization of 15 scattered disk and detached objects observed with Herschel Space Observatory-PACS

    CERN Document Server

    Santos-Sanz, P; Fornasier, S; Kiss, C; Pal, A; Müller, T G; Vilenius, E; Stansberry, J; Mommert, M; Delsanti, A; Mueller, M; Peixinho, N; Henry, F; Ortiz, J L; Thirouin, A; Protopapa, S; Duffard, R; Szalai, N; Lim, T; Ejeta, C; Hartogh, P; Harris, A W; Rengel, M

    2012-01-01

    Physical characterization of Trans-Neptunian objects, a primitive population of the outer solar system, may provide constraints on their formation and evolution. The goal of this work is to characterize a set of 15 scattered disk (SDOs) and detached objects, in terms of their size, albedo, and thermal properties. Thermal flux measurements obtained with the Herschel-PACS instrument at 70, 100 and 160 \\mu m, and whenever applicable, with Spitzer-MIPS at 24 and 70 \\mu m, are modeled with radiometric techniques, in order to derive the objects' individual size, albedo and when possible beaming factor. Error bars are obtained from a Monte-Carlo approach. We look for correlations between these and other physical and orbital parameters. Diameters obtained for our sample range from 100 to 2400 km, and the geometric albedos (in V band) vary from 3.8 % to 84.5 %. The unweighted mean V geometric albedo for the whole sample is 11.2 % (excluding Eris); 6.9 % for the SDOs, and 17.0 % for the detached objects (excluding Eris...

  15. SHAPE AND ALBEDO FROM SHADING (SAfS FOR PIXEL-LEVEL DEM GENERATION FROM MONOCULAR IMAGES CONSTRAINED BY LOW-RESOLUTION DEM

    Directory of Open Access Journals (Sweden)

    B. Wu

    2016-06-01

    Full Text Available Lunar topographic information, e.g., lunar DEM (Digital Elevation Model, is very important for lunar exploration missions and scientific research. Lunar DEMs are typically generated from photogrammetric image processing or laser altimetry, of which photogrammetric methods require multiple stereo images of an area. DEMs generated from these methods are usually achieved by various interpolation techniques, leading to interpolation artifacts in the resulting DEM. On the other hand, photometric shape reconstruction, e.g., SfS (Shape from Shading, extensively studied in the field of Computer Vision has been introduced to pixel-level resolution DEM refinement. SfS methods have the ability to reconstruct pixel-wise terrain details that explain a given image of the terrain. If the terrain and its corresponding pixel-wise albedo were to be estimated simultaneously, this is a SAfS (Shape and Albedo from Shading problem and it will be under-determined without additional information. Previous works show strong statistical regularities in albedo of natural objects, and this is even more logically valid in the case of lunar surface due to its lower surface albedo complexity than the Earth. In this paper we suggest a method that refines a lower-resolution DEM to pixel-level resolution given a monocular image of the coverage with known light source, at the same time we also estimate the corresponding pixel-wise albedo map. We regulate the behaviour of albedo and shape such that the optimized terrain and albedo are the likely solutions that explain the corresponding image. The parameters in the approach are optimized through a kernel-based relaxation framework to gain computational advantages. In this research we experimentally employ the Lunar-Lambertian model for reflectance modelling; the framework of the algorithm is expected to be independent of a specific reflectance model. Experiments are carried out using the monocular images from Lunar Reconnaissance

  16. Shape and Albedo from Shading (SAfS) for Pixel-Level dem Generation from Monocular Images Constrained by Low-Resolution dem

    Science.gov (United States)

    Wu, Bo; Chung Liu, Wai; Grumpe, Arne; Wöhler, Christian

    2016-06-01

    Lunar topographic information, e.g., lunar DEM (Digital Elevation Model), is very important for lunar exploration missions and scientific research. Lunar DEMs are typically generated from photogrammetric image processing or laser altimetry, of which photogrammetric methods require multiple stereo images of an area. DEMs generated from these methods are usually achieved by various interpolation techniques, leading to interpolation artifacts in the resulting DEM. On the other hand, photometric shape reconstruction, e.g., SfS (Shape from Shading), extensively studied in the field of Computer Vision has been introduced to pixel-level resolution DEM refinement. SfS methods have the ability to reconstruct pixel-wise terrain details that explain a given image of the terrain. If the terrain and its corresponding pixel-wise albedo were to be estimated simultaneously, this is a SAfS (Shape and Albedo from Shading) problem and it will be under-determined without additional information. Previous works show strong statistical regularities in albedo of natural objects, and this is even more logically valid in the case of lunar surface due to its lower surface albedo complexity than the Earth. In this paper we suggest a method that refines a lower-resolution DEM to pixel-level resolution given a monocular image of the coverage with known light source, at the same time we also estimate the corresponding pixel-wise albedo map. We regulate the behaviour of albedo and shape such that the optimized terrain and albedo are the likely solutions that explain the corresponding image. The parameters in the approach are optimized through a kernel-based relaxation framework to gain computational advantages. In this research we experimentally employ the Lunar-Lambertian model for reflectance modelling; the framework of the algorithm is expected to be independent of a specific reflectance model. Experiments are carried out using the monocular images from Lunar Reconnaissance Orbiter (LRO

  17. Factors Leading to Variability of Emission Factors, Single Scattering Albedo, and Elemental Carbon Fraction from Biofuel Emissions

    Science.gov (United States)

    Roden, C. A.; Bond, T. C.; Conway, S.; Osorto Pinel, B.; Maccarty, N.

    2006-12-01

    In a three-year study of field and laboratory emissions of traditional and improved biofuel cookstoves, we found that field measured particulate emissions of actual cooking events average 2.5 times those of reproduced lab emissions. Emission factors are highly dependent on the care and skill of the operator, and the resulting combustion; these do not appear to be accurately reproduced in the lab. The single scatter albedo (SSA) of the emissions is very low in both lab and field measurements, averaging about 0.3 for lab tests and around 0.5 for field tests, indicating that the primary particles are climate warming. In Honduras, improved stoves generally had lower emission factors than traditional stoves. Over the course of 3 summers we have measured field emissions from traditional cookstoves, relatively-new improved cookstoves, and "broken-in" improved cookstoves. For improved stoves, the presence of a chimney generally resulted in lower emission factors but left the SSA unaffected. Traditional cookstoves had an average PM emission factor of 8.5 g/kg significantly larger than previous studies. Particulate emission factors for improved cookstoves without and with chimneys averaged about 5.7 g/kg and 3.5 g/kg respectively. The elemental carbon (EC) fraction of PM varied significantly between individual tests, but averaged about 25% for each of the categories. Wood type affects on the PM emission factor, the SSA of the emissions and EC fraction. During our 2006 field measurements, we performed multiple emission measurements on the same stove while varying the fuel. Pine wood generally produced more PM than oak per kilogram of fuel. Additionally, Ocote, a resinous pitch pine often used in Central America for lighting fires, produces emissions which have a very low SSA and high EC fraction. We present the elemental carbon fraction and mass emission factors for different type of stoves and testing conditions. We summarize the characteristics of the particles emitted

  18. Measurements of Nascent Soot Using a Cavity Attenauted Phase Shift (CAPS)-based Single Scattering Albedo Monitor

    Science.gov (United States)

    Freedman, A.; Onasch, T. B.; Renbaum-Wollf, L.; Lambe, A. T.; Davidovits, P.; Kebabian, P. L.

    2015-12-01

    Accurate, as compared to precise, measurement of aerosol absorption has always posed a significant problem for the particle radiative properties community. Filter-based instruments do not actually measure absorption but rather light transmission through the filter; absorption must be derived from this data using multiple corrections. The potential for matrix-induced effects is also great for organic-laden aerosols. The introduction of true in situ measurement instruments using photoacoustic or photothermal interferometric techniques represents a significant advance in the state-of-the-art. However, measurement artifacts caused by changes in humidity still represent a significant hurdle as does the lack of a good calibration standard at most measurement wavelengths. And, in the absence of any particle-based absorption standard, there is no way to demonstrate any real level of accuracy. We, along with others, have proposed that under the circumstance of low single scattering albedo (SSA), absorption is best determined by difference using measurement of total extinction and scattering. We discuss a robust, compact, field deployable instrument (the CAPS PMssa) that simultaneously measures airborne particle light extinction and scattering coefficients and thus the single scattering albedo (SSA) on the same sample volume. The extinction measurement is based on cavity attenuated phase shift (CAPS) techniques as employed in the CAPS PMex particle extinction monitor; scattering is measured using integrating nephelometry by incorporating a Lambertian integrating sphere within the sample cell. The scattering measurement is calibrated using the extinction measurement of non-absorbing particles. For small particles and low SSA, absorption can be measured with an accuracy of 6-8% at absorption levels as low as a few Mm-1. We present new results of the measurement of the mass absorption coefficient (MAC) of soot generated by an inverted methane diffusion flame at 630 nm. A value

  19. Impacts of global open-fire aerosols on direct radiative, cloud and surface-albedo effects simulated with CAM5

    Science.gov (United States)

    Jiang, Yiquan; Lu, Zheng; Liu, Xiaohong; Qian, Yun; Zhang, Kai; Wang, Yuhang; Yang, Xiu-Qun

    2016-11-01

    Aerosols from open-land fires could significantly perturb the global radiation balance and induce climate change. In this study, Community Atmosphere Model version 5 (CAM5) with prescribed daily fire aerosol emissions is used to investigate the spatial and seasonal characteristics of radiative effects (REs, relative to the case of no fires) of open-fire aerosols including black carbon (BC) and particulate organic matter (POM) from 2003 to 2011. The global annual mean RE from aerosol-radiation interactions (REari) of all fire aerosols is 0.16 ± 0.01 W m-2 (1σ uncertainty), mainly due to the absorption of fire BC (0.25 ± 0.01 W m-2), while fire POM induces a small effect (-0.05 and 0.04 ± 0.01 W m-2 based on two different methods). Strong positive REari is found in the Arctic and in the oceanic regions west of southern Africa and South America as a result of amplified absorption of fire BC above low-level clouds, in general agreement with satellite observations. The global annual mean RE due to aerosol-cloud interactions (REaci) of all fire aerosols is -0.70 ± 0.05 W m-2, resulting mainly from the fire POM effect (-0.59 ± 0.03 W m-2). REari (0.43 ± 0.03 W m-2) and REaci (-1.38 ± 0.23 W m-2) in the Arctic are stronger than in the tropics (0.17 ± 0.02 and -0.82 ± 0.09 W m-2 for REari and REaci), although the fire aerosol burden is higher in the tropics. The large cloud liquid water path over land areas and low solar zenith angle of the Arctic favor the strong fire aerosol REaci (up to -15 W m-2) during the Arctic summer. Significant surface cooling, precipitation reduction and increasing amounts of low-level cloud are also found in the Arctic summer as a result of the fire aerosol REaci based on the atmosphere-only simulations. The global annual mean RE due to surface-albedo changes (REsac) over land areas (0.03 ± 0.10 W m-2) is small and statistically insignificant and is mainly due to the fire BC-in-snow effect (0.02 W m-2) with the maximum albedo effect

  20. Impact of brown and clear carbon on light absorption enhancement, single scatter albedo and absorption wavelength dependence of black carbon

    Directory of Open Access Journals (Sweden)

    D. A. Lack

    2010-01-01

    Full Text Available The presence of clear coatings on atmospheric black carbon (BC particles is known to enhance the magnitude of light absorption by the BC cores. Based on calculations using core/shell Mie theory, we demonstrate the enhancement of light absorption (EAbs by atmospheric black carbon (BC when coated in mildly absorbing material (CBrown is reduced, relative to the enhancement by non-absorbing coatings (CClear. This reduction, sensitive to CBrown shell thickness and imaginary refractive index (RI, can be up to 50% for 400 nm radiation and 25% averaged across the visible radiation spectrum for reasonable core/shell diameters. The enhanced direct radiative forcing possible due to the enhancement effect of CClear is therefore reduced if the coating is absorbing. Additionally, the need to explicitly treat BC as an internal, as opposed to external, mixture with CBrown is shown to be important to the calculated single scatter albedo only whensub models treat BC as large spherical cores (>50 nm. For smaller BC cores (or fractal agglomerates consideration of the BC and CBrown as an external mixture leads to relatively small errors in the particle single scatter albedo of <0.03. It is often assumed that observation of an absorption Angstrom exponent (AAE >1 indicates non-BC absorption. Here, it is shown that BC cores coated in CClearcan reasonably have an AAE of up to 1.6, a result that complicates the attribution of observed light absorption to CBrown within ambient particles. However, an AAE<1.6 does not exclude the possibility of CBrown, rather CBrown cannot be confidently assigned unless AAE>1.6. Comparison of these results to some ambient AAE data shows that large-scale attribution of CBrown is a challenging task using current in-situ measurement methods. We suggest that coincident measurements of particle core and

  1. Effect of surface albedo, water vapour, and atmospheric aerosols on the cloud-free shortwave radiative budget in the Arctic

    Energy Technology Data Exchange (ETDEWEB)

    Di Biagio, C. [ENEA, Laboratory for Earth Observations and Analyses, Rome (Italy); University of Siena, Department of Earth Science, Siena (Italy); Di Sarra, A. [ENEA, Laboratory for Earth Observations and Analyses, Rome (Italy); Eriksen, P. [Danish Climate Centre, DMI, Danish Meteorological Institute, Copenhagen (Denmark); Ascanius, S.E. [DMI, Danish Meteorological Institute, Qaanaaq (Greenland); Muscari, G. [INGV, Istituto Nazionale di Geofisica e Vulcanologia, Rome (Italy); Holben, B. [NASA Goddard Space Flight Center, Greenbelt, MD (United States)

    2012-08-15

    This study is based on ground-based measurements of downward surface shortwave irradiance (SW), columnar water vapour (wv), and aerosol optical depth ({tau}) obtained at Thule Air Base (Greenland) in 2007-2010, together with MODIS observations of the surface shortwave albedo (A). Radiative transfer model calculations are used in combination with measurements to separate the radiative effect of A ({Delta}SW{sub A}), wv ({Delta}SW{sub wv}), and aerosols ({Delta}SW{sub {tau}}) in modulating SW in cloud-free conditions. The shortwave radiation at the surface is mainly affected by water vapour absorption, which produces a reduction of SW as low as -100 Wm{sup -2} (-18%). The seasonal change of A produces an increase of SW by up to +25 Wm{sup -2} (+4.5%). The annual mean radiative effect is estimated to be -(21-22) Wm{sup -2} for wv, and +(2-3) Wm{sup -2} for A. An increase by +0.065 cm in the annual mean wv, to which corresponds an absolute increase in {Delta}SW{sub wv} by 0.93 Wm{sup -2} (4.3%), has been observed to occur between 2007 and 2010. In the same period, the annual mean A has decreased by -0.027, with a corresponding decrease in {Delta}SW{sub A} by 0.41 Wm{sup -2} (-14.9%). Atmospheric aerosols produce a reduction of SW as low as -32 Wm{sup -2} (-6.7%). The instantaneous aerosol radiative forcing (RF{sub {tau}}) reaches values of -28 Wm{sup -2} and shows a strong dependency on surface albedo. The derived radiative forcing efficiency (FE{sub {tau}}) for solar zenith angles between 55 and 70 is estimated to be (-120.6 {+-} 4.3) for 0.1 < A < 0.2, and (-41.2 {+-} 1.6) Wm{sup -2} for 0.5 < A < 0.6. (orig.)

  2. Analysis on long-term variability of sea ice albedo and its relationship with sea ice concentration over Antarctica

    Science.gov (United States)

    Seo, Minji; Kim, Hyun-cheol; Seong, Noh-hun; Kwon, Chaeyoung; Kim, Honghee; Han, Kyung-Soo

    2016-10-01

    Sea ice is an important factor for understanding Antarctic climate change. Especially, annual change of sea ice shows different trend in Antarctica and Arctic. This different variation need to continuously observe the Polar Regions. Sea Ice Albedo (SIA) and Sea Ice Concentration (SIC) are an indicator of variation on sea ice. In addition, albedo is key parameter to understand the energy budget in Antarctica. This being so, it is important to analyze long-term variation of the two factors for observing of change of Antarctic environment. In this study, we analyzed long-term variability of SIC and SIA to understand the changes of sea ice over Antarctic and researched the relationship with two factors. We used the SIA data at The Satellite Application Facility on Climate Monitoring (CM SAF) and the SIC data provided by Ocean and Sea Ice Satellite Application Facility (OSI-SAF) from 1982 to 2009. The study period was selected to Antarctic summer season due to polar nights. We divided study periods into two terms, Nov-Dec(ND) and Jan-Feb(JF) in order to reflect the characteristics of sea ice area, which minimum extend occurred in September and maximum extend occurred in February. We analyzed the correlation between SIA and SIC. As a results, two variables have a strong positive correlation (each correlation coefficients are 0.91 in Nov-Dec and 0.90 in Jan-Feb). We performed time series analysis using linear regression to understand the spatial and temporal tendency of SIA and SIC. As a results, SIA and SIC have a same spatial trend such as Weddle sea and Ross sea sections show the positive trend and Bellingshausen Amundsen sea shows the negative trend of two factors. Moreover, annual SIA change rate is 0.26% 0.04% yr-1 over section where represent positive trend during two study periods. And annual SIA change rate is - 0.14 - 0.25 % yr-1 of in the other part where represent negative trend during two study periods.

  3. Development and characterization of two-component albedo based neutron individual monitoring system using thermoluminescent detectors; Desenvolvimento e caracterizacao de um sistema de monitoracao individual de neutrons tipo albedo de duas componentes usando detectores termoluminescentes

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Marcelo Marques

    2008-07-01

    A TLD-albedo based two-component neutron individual monitoring system was developed and characterized in this work. The monitor consists of a black plastic holder, an incident neutron boron loaded shield, a moderator polyethylene body (to increase its response), two pairs of TLD-600 and TLD-700 (one pair to each component) and an adjustable belt. This monitoring system was calibrated in thermal neutron fields and in 70 keV, 144 keV, 565 keV, 1.2 MeV and 5 MeV monoenergetic neutron fields. In addition, it was calibrated in {sup 252C}f(D{sub 2}O), {sup 252}Cf, {sup 241}Am-B, {sup 241}Am-Be and {sup 238}Pu-Be source fields. For the latter, the lower detection levels are, respectively, 0.009 mSv, 0.06 mSv, 0.12 mSv, 0.09 mSv and 0.08 mSv. The participation in an international intercomparison sponsored by IAEA with simulated workplace fields validated the system. The monitoring system was successfully characterized in the ISO 21909 standard and in an IRD - the Brazilian Institute for Radioprotection and Dosimetry - technical regulation draft. Nowadays, the neutron individual system is in use by IRD for whole body individual monitoring of five institutions, which comprehend several activities. (author)

  4. Understanding changes in the Arctic basin sea ice mass budget as simulated by CCSM4: Implications from melt season characteristics and the surface albedo feedback

    Science.gov (United States)

    Pollak, D. A.; Holland, M. M.; Bailey, D. A.

    2010-12-01

    Observations reveal alarming drops in Arctic sea ice extent, and climate models project that further changes will occur that could have global repercussions. An important aspect of this change is the surface albedo feedback, driven by the contrast between the albedos of snow/ice and the open ocean. In response to warming, this feedback enhances ice melt and amplifies surface warming in the Arctic. The newly released, fully coupled Community Climate System Model Version 4 (CCSM4) is used to assess long-term changes in the Arctic sea ice mass budget. Analysis of monthly-averaged mass budget time series from the 20th and 21st centuries revealed drastic changes from 1980-2050, the focus years of this study. While numerous factors determine the Arctic sea ice mass budget, we focus on the surface melt terms as they are most closely related to the surface albedo feedback. During the study period, annually averaged difference plots of sea ice thickness and area both revealed substantial decreases across the entire Arctic domain. Helping to clarify these long-term changes, new daily output data from this model allowed for the examination of melt season characteristics such as melt onset and cessation dates as well as season duration. One of the most interesting aspects was the shift to earlier melt onset dates throughout the Arctic Basin. This shift, coupled with the seasonal solar cycle has substantial implications. Earlier onset dates imply an earlier decrease of albedo that overlaps with the seasonal maximum of downward shortwave radiation. This leads to increases in shortwave absorption and results in amplified ice melt that directly impacts the strength of the surface albedo feedback. The strong relationship between earlier melt onset dates and increased absorbed radiation therefore is a key factor influencing Arctic amplification. This figure is created from daily model output and displays changes in melt season duration, end date, and onset date from the first and

  5. An Approach for the Long-Term 30-m Land Surface Snow-Free Albedo Retrieval from Historic Landsat Surface Reflectance and MODIS-based A Priori Anisotropy Knowledge

    Science.gov (United States)

    Shuai, Yanmin; Masek, Jeffrey G.; Gao, Feng; Schaaf, Crystal B.; He, Tao

    2014-01-01

    Land surface albedo has been recognized by the Global Terrestrial Observing System (GTOS) as an essential climate variable crucial for accurate modeling and monitoring of the Earth's radiative budget. While global climate studies can leverage albedo datasets from MODIS, VIIRS, and other coarse-resolution sensors, many applications in heterogeneous environments can benefit from higher-resolution albedo products derived from Landsat. We previously developed a "MODIS-concurrent" approach for the 30-meter albedo estimation which relied on combining post-2000 Landsat data with MODIS Bidirectional Reflectance Distribution Function (BRDF) information. Here we present a "pre-MODIS era" approach to extend 30-m surface albedo generation in time back to the 1980s, through an a priori anisotropy Look-Up Table (LUT) built up from the high quality MCD43A BRDF estimates over representative homogenous regions. Each entry in the LUT reflects a unique combination of land cover, seasonality, terrain information, disturbance age and type, and Landsat optical spectral bands. An initial conceptual LUT was created for the Pacific Northwest (PNW) of the United States and provides BRDF shapes estimated from MODIS observations for undisturbed and disturbed surface types (including recovery trajectories of burned areas and non-fire disturbances). By accepting the assumption of a generally invariant BRDF shape for similar land surface structures as a priori information, spectral white-sky and black-sky albedos are derived through albedo-to-nadir reflectance ratios as a bridge between the Landsat and MODIS scale. A further narrow-to-broadband conversion based on radiative transfer simulations is adopted to produce broadband albedos at visible, near infrared, and shortwave regimes.We evaluate the accuracy of resultant Landsat albedo using available field measurements at forested AmeriFlux stations in the PNW region, and examine the consistency of the surface albedo generated by this approach

  6. Bulk Hydrogen Content OF High-Silica Rocks in Gale Crater With the Active Dynamic Albedo of Neutrons Experiment

    Science.gov (United States)

    Gabriel, T. S. J.; Hardgrove, C.; Litvak, M.; Mitrofanov, I.; Boynton, W. V.; Fedosov, F.; Golovin, D.; Jun, I.; Mischna, M.; Tate, C. G.; Moersch, J.; Harshman, K.; Kozyrev, A. S.; Malakhov, A.; Mokrousov, M.; Nikiforov, S.; Sanin, A. B.; Vostrukhin, A.; Archer, P. D., Jr.; Franz, H. B.; Thompson, L.

    2017-01-01

    The Mars Science Laboratory (MSL) Curiosity rover recently traversed over plateaus of mafic aeolian sandstones (the 'Stimson' formation) that overlie mudstones (the 'Murray' formation). Within the Stimson formation we observed many lighter-toned, halo-forming features, that are potentially indicative of fluid alteration (see Fig. 1). These halo features extend for tens of meters laterally and are approx.1 meter wide. The halo features were characterized by Curiosity's geochemical instruments: Alpha Proton X-Ray Spectrometer (APXS), Chemin, Chemcam and Sample Analysis at Mars (SAM). With respect to the host (unaltered) Stimson rocks, fracture halos were significantly enriched in silicon and low in iron [1]. Changes in hydrogen abundance (due to its large neutron scattering cross section) greatly influence the magnitude of the thermal neutron response from the Dynamic Albedo of Neutrons (DAN) instrument [2]. There are also some elemental species, e.g. chlorine, iron, and nickel, that have significant microscopic neutron absorption cross sections. These elements can be abundant and variable results provide a useful estimate of the lower bound for bulk hydrogen content (assuming a homogeneous distribution).

  7. The effect of albedo neutrons on the neutron multiplication of small plutonium oxide samples in a PNCC chamber

    CERN Document Server

    Bourva, L C A; Weaver, D R

    2002-01-01

    This paper describes how to evaluate the effect of neutrons reflected from parts of a passive neutron coincidence chamber on the neutron leakage self-multiplication, M sub L , of a fissile sample. It is shown that albedo neutrons contribute, in the case of small plutonium bearing samples, to a significant part of M sub L , and that their effect has to be taken into account in the relationship between the measured coincidence count rates and the sup 2 sup 4 sup 0 Pu effective mass of the sample. A simple one-interaction model has been used to write the balance of neutron gains and losses in the material when exposed to the re-entrant neutron flux. The energy and intensity profiles of the re-entrant flux have been parameterised using Monte Carlo MCNP sup T sup M calculations. This technique has been implemented for the On Site Laboratory neutron/gamma counter within the existing MEPL 1.0 code for the determination of the neutron leakage self-multiplication. Benchmark tests of the resulting MEPL 2.0 code with MC...

  8. THE SIZE, SHAPE, ALBEDO, DENSITY, AND ATMOSPHERIC LIMIT OF TRANSNEPTUNIAN OBJECT (50000) QUAOAR FROM MULTI-CHORD STELLAR OCCULTATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Braga-Ribas, F.; Vieira-Martins, R.; Camargo, J. I. B. [Observatorio Nacional, Rio de Janeiro (Brazil); Sicardy, B.; Lellouch, E.; Lecacheux, J. [Observatoire de Paris, LESIA, F-92195 Meudon (France); Ortiz, J. L.; Morales, N. [Instituto de Astrofisica de Andalucia-CSIC, E-18080 Granada (Spain); Tancredi, G.; Roland, S.; Bruzzone, S. [Observatorio Astronomico Los Molinos, Montevideo U-12400 (Uruguay); Assafin, M. [Observatorio do Valongo/UFRJ, Rio de Janeiro (Brazil); Behrend, R. [Observatoire de Geneve, Sauverny (Switzerland); Vachier, F.; Colas, F. [Observatoire de Paris, IMCCE, F-75014 Paris (France); Maury, A. [San Pedro de Atacama Celestial Explorations, San Pedro de Atacama (Chile); Emilio, M. [Universidade Estadual de Ponta Grossa, Ponta Grossa (Brazil); Amorim, A. [Universidade Federal de Santa Catarina, Florianopolis (Brazil); Unda-Sanzana, E. [Unidad de Astronomia, Universidad de Antofagasta, Antofagasta (Chile); Almeida, L. A., E-mail: ribas@on.br [Instituto Nacional de Pesquisas Espaciais, DAS, Sao Jose dos Campos (Brazil); and others

    2013-08-10

    We present results derived from the first multi-chord stellar occultations by the transneptunian object (50000) Quaoar, observed on 2011 May 4 and 2012 February 17, and from a single-chord occultation observed on 2012 October 15. If the timing of the five chords obtained in 2011 were correct, then Quaoar would possess topographic features (crater or mountain) that would be too large for a body of this mass. An alternative model consists in applying time shifts to some chords to account for possible timing errors. Satisfactory elliptical fits to the chords are then possible, yielding an equivalent radius R{sub equiv} = 555 {+-} 2.5 km and geometric visual albedo p{sub V} = 0.109 {+-} 0.007. Assuming that Quaoar is a Maclaurin spheroid with an indeterminate polar aspect angle, we derive a true oblateness of {epsilon}= 0.087{sup +0.0268}{sub -0.0175}, an equatorial radius of 569{sup +24}{sub -17} km, and a density of 1.99 {+-} 0.46 g cm{sup -3}. The orientation of our preferred solution in the plane of the sky implies that Quaoar's satellite Weywot cannot have an equatorial orbit. Finally, we detect no global atmosphere around Quaoar, considering a pressure upper limit of about 20 nbar for a pure methane atmosphere.

  9. Aerosol single-scattering albedo and asymmetry parameter from MFRSR observations during the ARM Aerosol IOP 2003

    Directory of Open Access Journals (Sweden)

    E. I. Kassianov

    2006-12-01

    Full Text Available Multi-filter Rotating Shadowband Radiometers (MFRSRs provide routine measurements of the aerosol optical depth (τ at six wavelengths (0.415, 0.5, 0.615, 0.673, 0.870 and 0.94 μm. The single-scattering albedo0 is typically estimated from the MFRSR measurements by assuming the asymmetry parameter (g. In most instances, however, it is not easy to set an appropriate value of g due to its strong temporal and spatial variability. Here, we introduce and validate an updated version of our retrieval technique that allows one to estimate simultaneously ϖ0 and g for different types of aerosol. We use the aerosol and radiative properties obtained during the Atmospheric Radiation Measurement (ARM Aerosol Intensive Operational Period (IOP to validate our retrieval in two ways. First, the MFRSR-retrieved optical properties are compared with those obtained from independent surface, Aerosol Robotic Network (AERONET and aircraft measurements. The MFRSR-retrieved optical properties are in reasonable agreement with these independent measurements. Second, we perform radiative closure experiments using the MFRSR-retrieved optical properties. The calculated broadband values of the direct and diffuse fluxes are comparable (~5 W/m2 to those obtained from measurements.

  10. A database of global reference sites to support validation of satellite surface albedo datasets (SAVS 1.0)

    Science.gov (United States)

    Loew, Alexander; Bennartz, Ralf; Fell, Frank; Lattanzio, Alessio; Doutriaux-Boucher, Marie; Schulz, Jörg

    2016-09-01

    Validating the accuracy and long-term stability of terrestrial satellite data products necessitates a network of reference sites. This paper documents a global database of more than 2000 sites globally which have been characterized in terms of their spatial heterogeneity. The work was motivated by the need for potential validation sites for geostationary surface albedo data products, but the resulting database is useful also for other applications. The database (SAVS 1.0) is publicly available through the EUMETSAT website (http://savs.eumetsat.int/" target="_blank">http://savs.eumetsat.int/, http://dx.doi.org/10.15770/EUM_SEC_CLM_1001" target="_blank">doi:10.15770/EUM_SEC_CLM_1001). Sites can be filtered according to different criteria, providing a flexible way to identify potential validation sites for further studies and a traceable approach to characterize the heterogeneity of these reference sites. The present paper describes the detailed information on the generation of the SAVS 1.0 database and its characteristics.

  11. Dependence of the spectral diffuse-direct irradiance ratio on aerosol spectral distribution and single scattering albedo

    Science.gov (United States)

    Kaskaoutis, D. G.; Kambezidis, H. D.; Dumka, U. C.; Psiloglou, B. E.

    2016-09-01

    This study investigates the modification of the clear-sky spectral diffuse-direct irradiance ratio (DDR) as a function of solar zenith angle (SZA), spectral aerosol optical depth (AOD) and single scattering albedo (SSA). The solar spectrum under various atmospheric conditions is derived with Simple Model of the Atmospheric Radiative Transfer of Sunshine (SMARTS) radiative transfer code, using the urban and continental aerosol models as inputs. The spectral DDR can be simulated with great accuracy by an exponentially decreasing curve, while the aerosol optical properties strongly affect the scattering processes in the atmosphere, thus modifying the DDR especially in the ultraviolet (UV) spectrum. Furthermore, the correlation between spectral DDR and spectral AOD can be represented precisely by an exponential function and can give valuable information about the dominance of specific aerosol types. The influence of aerosols on spectral DDR increases with increasing SZA, while the simulations using the urban aerosol model as input in SMARTS are closer to the measurements taken in the Athens urban environment. The SMARTS simulations are interrelated with spectral measurements and can be used for indirect estimations of SSA. Overall, the current work provides some theoretical approximations and functions that help in understanding the dependence of DDR on astronomical and atmospheric parameters.

  12. A Pluto-like radius and a high albedo for the dwarf planet Eris from an occultation

    Science.gov (United States)

    Sicardy, B.; Ortiz, J. L.; Assafin, M.; Jehin, E.; Maury, A.; Lellouch, E.; Hutton, R. Gil; Braga-Ribas, F.; Colas, F.; Hestroffer, D.; Lecacheux, J.; Roques, F.; Santos-Sanz, P.; Widemann, T.; Morales, N.; Duffard, R.; Thirouin, A.; Castro-Tirado, A. J.; Jelínek, M.; Kubánek, P.; Sota, A.; Sánchez-Ramírez, R.; Andrei, A. H.; Camargo, J. I. B.; da Silva Neto, D. N.; Gomes, A. Ramos; Martins, R. Vieira; Gillon, M.; Manfroid, J.; Tozzi, G. P.; Harlingten, C.; Saravia, S.; Behrend, R.; Mottola, S.; Melendo, E. García; Peris, V.; Fabregat, J.; Madiedo, J. M.; Cuesta, L.; Eibe, M. T.; Ullán, A.; Organero, F.; Pastor, S.; de Los Reyes, J. A.; Pedraz, S.; Castro, A.; de La Cueva, I.; Muler, G.; Steele, I. A.; Cebrián, M.; Montañés-Rodríguez, P.; Oscoz, A.; Weaver, D.; Jacques, C.; Corradi, W. J. B.; Santos, F. P.; Reis, W.; Milone, A.; Emilio, M.; Gutiérrez, L.; Vázquez, R.; Hernández-Toledo, H.

    2011-10-01

    The dwarf planet Eris is a trans-Neptunian object with an orbital eccentricity of 0.44, an inclination of 44 degrees and a surface composition very similar to that of Pluto. It resides at present at 95.7 astronomical units (1AU is the Earth-Sun distance) from Earth, near its aphelion and more than three times farther than Pluto. Owing to this great distance, measuring its size or detecting a putative atmosphere is difficult. Here we report the observation of a multi-chord stellar occultation by Eris on 6 November 2010 UT. The event is consistent with a spherical shape for Eris, with radius 1,163+/-6kilometres, density 2.52+/-0.05 grams per cm3 and a high visible geometric albedo, . No nitrogen, argon or methane atmospheres are detected with surface pressure larger than ~1nanobar, about 10,000 times more tenuous than Pluto's present atmosphere. As Pluto's radius is estimated to be between 1,150 and 1,200 kilometres, Eris appears as a Pluto twin, with a bright surface possibly caused by a collapsed atmosphere, owing to its cold environment. We anticipate that this atmosphere may periodically sublimate as Eris approaches its perihelion, at 37.8 astronomical units from the Sun.

  13. Aerosol single-scattering albedo and asymmetry parameter from MFRSR observations during the ARM Aerosol IOP 2003

    Directory of Open Access Journals (Sweden)

    E. I. Kassianov

    2007-06-01

    Full Text Available Multi-filter Rotating Shadowband Radiometers (MFRSRs provide routine measurements of the aerosol optical depth (τ at six wavelengths (0.415, 0.5, 0.615, 0.673, 0.870 and 0.94 μm. The single-scattering albedo0 is typically estimated from the MFRSR measurements by assuming the asymmetry parameter (g. In most instances, however, it is not easy to set an appropriate value of g due to its strong temporal and spatial variability. Here, we introduce and validate an updated version of our retrieval technique that allows one to estimate simultaneously π0 and g for different types of aerosol. We use the aerosol and radiative properties obtained during the Atmospheric Radiation Measurement (ARM Program's Aerosol Intensive Operational Period (IOP to validate our retrieval in two ways. First, the MFRSR-retrieved optical properties are compared with those obtained from independent surface, Aerosol Robotic Network (AERONET, and aircraft measurements. The MFRSR-retrieved optical properties are in reasonable agreement with these independent measurements. Second, we perform radiative closure experiments using the MFRSR-retrieved optical properties. The calculated broadband values of the direct and diffuse fluxes are comparable (~5 W/m2 to those obtained from measurements.

  14. Approach and procedure of measuring the albedo of urban prototype%城市模型反射率测量方法与运用

    Institute of Scientific and Technical Information of China (English)

    谭康豪; 覃英宏; 苏益声; 梁槚; 庞如月

    2016-01-01

    介绍了一种测试城市模型反射率的试验方法。制作10个条形和十字形的城市模型进行测试,观测路面不同反射率对城市反射率的影响,并将实测模型反射率与ASTM E1918-06规范计算结果进行对比。研究发现:瞬时太阳辐射强度变化值在规范允许范围内,模型计算的反射率与ASTM E1918-06测量值的误差在0~0.1之间。当峡谷纵横比(建筑物高度与路面宽度之比)为1.0时,路面反射率从0.15提高到0.65,城市峡谷反射率增幅在0~0.30之间;提高路面反射率并不能有效提高城市峡谷反射率,尤其是纵横比较大的深峡谷。城市峡谷中的多重反射抑制城市反射率的提高。同时,反射路面将给行人增加额外的辐射通量,可能带来热不适感和眩光刺眼等问题。因此,应谨慎看待反射路面作为一个缓解城市热岛效应策略。%A new method of measuring the albedo of urban prototype is proposed.The method is used to measure ten urban prototypes with different pavement reflectivity and with south-north orientation,west-east orientation and cross-street orientation,respectively.The results are compared with those obtained by the ASTM E1918-06 and the modified ASTM E1918-06.It is found that when the variation of the incident solar intensity is less than 20 W/m2 (a tolerant error stated by ASTM E1918A),the ASTM E1918-06 can either underestimate or overestimate the albedo of the urban canyon prototype up to 0.10.For an urban canyon (UC)with an aspect ratio of 1.0,an change from 0.15 to 0.65 of pavement albedo would cause an increase of the albedo of the UC from about 0.15 to 0.35 if the albedo of the roof and wall is about 0.40. Raising the albedo of the pavement in a UC is not an effective way to increase the albedo of the urban area, especially for UC with great aspect ratio.For low aspect ratio UC,raising the albedo of the pavement or of the parking lot introduces a sizable

  15. Thermal cracking of CO2 slab ice as the main driving force for albedo increase of the martian seasonal polar caps

    Science.gov (United States)

    Philippe, S.; Schmitt, B.; Beck, P.; Brissaud, O.

    2015-10-01

    Understanding the microphysical processes occuring on the Martian seasonal cap is critical since their radiative properties can affect the martian climate. A well documented phenomenom is the albedo increase of the Martian seasonal caps during spring, Fig.1. There are a lot of hypotheses that have been proposed as an explanation for this observation : the decrease of the CO2 grain size [2], a cleaning process of the CO2 slab that would imply either the sinking or the ejection of the dust contained in its volume ([1], [2], [5]), a water-layer accumulation on the top of the slab [5], the role played by aerosols [2] etc ... So far, no experimental simulations have been realized to discriminate between these processes. We designed an experiment to investigate the hypothesis of CO2 ice grain size decrease through thermal cracking as well as that of dust segregation as the possible reasons for albedo increase.

  16. Solution of the radiative heat transfer equation with internal energy sources in a slab by the GFD method for anisotropic albedo

    Energy Technology Data Exchange (ETDEWEB)

    Azevedo, Fabio Souto de, E-mail: fabio.azevedo@ufrgs.b [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Inst. de Matematica; Sauter, Esequia, E-mail: esequia.sauter@canoas.ifrs.edu.b [Instituto Federal do Rio Grande do Sul (IFRS), Canoas, RS (Brazil); Thompson, Mark; Vilhena, Marco Tulio B., E-mail: mark.thompson@mat.ufrgs.b, E-mail: vilhena@mat.ufrgs.b [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Programa de Pos-Graduacao em Matematica Aplicada

    2011-07-01

    In this work we apply the Green Function Decomposition Method the radiative transport equation in a slab. The method consists in converting the radiative transport equation into a integral equation and projecting the integral operators involved into a finite dimensional space. This methodology does not involve an a priori discretization on the angular variable {mu}, requiring only that the kernel is numerically integrated on {mu}. Numerical results are provided for isotropic, linearly anisotropic, and Rayleigh scattering near the unitary albedo. (author)

  17. Parameterization of single-scattering albedo (SSA) and absorption Ångström exponent (AAE) with EC / OC for aerosol emissions from biomass burning

    OpenAIRE

    Pokhrel, R. P.; N. L. Wagner; Langridge, J. M.; D. A. Lack; T. Jayarathne; E. A. Stone; C. E. Stockwell; Yokelson, R. J.; S. M. Murphy

    2016-01-01

    Single-scattering albedo (SSA) and absorption Ångström exponent (AAE) are two critical parameters in determining the impact of absorbing aerosol on the Earth's radiative balance. Aerosol emitted by biomass burning represent a significant fraction of absorbing aerosol globally, but it remains difficult to accurately predict SSA and AAE for biomass burning aerosol. Black carbon (BC), brown carbon (BrC), and non-absorbing coatings all make substantial contributions to the absor...

  18. A celestial gamma-ray foreground due to the albedo of small solar system bodies and a remote probe of the interstellar cosmic ray spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Moskalenko, Igor V.; Porter, Troy A.; Digel, Seth W.; Michelson, Peter F.; Ormes, Jonathan F.

    2007-12-17

    We calculate the {gamma}-ray albedo flux from cosmic-ray (CR) interactions with the solid rock and ice in Main Belt asteroids and Kuiper Belt objects (KBOs) using the Moon as a template. We show that the {gamma}-ray albedo for the Main Belt and Kuiper Belt strongly depends on the small-body mass spectrum of each system and may be detectable by the forthcoming Gamma Ray Large Area Space Telescope (GLAST). The orbits of the Main Belt asteroids and KBOs are distributed near the ecliptic, which passes through the Galactic center and high Galactic latitudes. If detected, the {gamma}-ray emission by the Main Belt and Kuiper Belt has to be taken into account when analyzing weak {gamma}-ray sources close to the ecliptic, especially near the Galactic center and for signals at high Galactic latitudes, such as the extragalactic {gamma}-ray emission. Additionally, it can be used to probe the spectrum of CR nuclei at close-to-interstellar conditions, and the mass spectrum of small bodies in the Main Belt and Kuiper Belt. The asteroid albedo spectrum also exhibits a 511 keV line due to secondary positrons annihilating in the rock. This may be an important and previously unrecognized celestial foreground for the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of the Galactic 511 keV line emission including the direction of the Galactic center.

  19. Atlas of albedo and absorbed solar radiation derived from Nimbus 7 earth radiation budget data set, November 1985 to October 1987

    Science.gov (United States)

    Smith, G. Louis; Rutan, David; Bess, T. Dale

    1992-01-01

    An atlas of monthly mean global contour maps of albedo and absorbed solar radiation is presented for 21 months from Nov. 1985 to Oct. 1987. These data were retrieved from measurements made by the shortwave wide-field-of-view radiometer of the Earth Radiation Budget (ERB) instrument aboard the Nimbus 7 spacecraft. Profiles of zonal mean albedos and absorbed solar radiation were tabulated. These geographical distributions are provided as a resource for researchers studying the radiation budget of the Earth. The El Nino/Southern Oscillation event of 1986-1987 is included in this data set. This atlas of albedo and absorbed solar radiation extends to 12 years the period covered by two similar atlases: NASA RP-1230 (Jul. 1975 - Oct. 1978) and NASA RP-1231 (Nov. 1978 - Oct. 1985). These three compilations complement the atlases of outgoing longwave radiation by Bess and Smith in NASA RP-1185, RP-1186, and RP-1261, which were also based on the Nimbus 6 and 7 ERB data.

  20. Proposal of requirements for performance in Brazil for systems of external individual monitoring for neutrons applying the TLD-albedo technique; Proposta de requisitos de desempenho no Brasil para sistemas de monitoracao individual externa para neutrons empregando a tecnica TLD-albedo

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Marcelo M.; Mauricio, Claudia L.P.; Pereira, Walsan W.; Fonseca, Evaldo S. da, E-mail: marcelo@ird.gov.b, E-mail: claudia@ird.gov.b, E-mail: walsan@ird.gov.b, E-mail: evaldo@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Silva, Ademir X., E-mail: ademir@con.ufrj.b [Coordenacao dos Programas de Pos-Graduacao de Engenharia (COPPE/UFRJ), RJ (Brazil).

    2009-07-01

    This work presents a criteria and conditions proposal for the regulations in Brazil of individual monitoring systems for neutrons applying the albedo technique with thermoluminescent detectors. Tests are proposed for the characterization performance of the system based on the Regulation ISO 21909 and on the experience of the authors

  1. Albedo and estimates of net radiation for green beans under polyethylene cover and field conditions Albedo e estimativas do saldo de radiação em feijão-vagem sob cobertura de plástico e ambiente externo

    Directory of Open Access Journals (Sweden)

    José Leonaldo de Souza

    1999-10-01

    Full Text Available This paper describes the albedo (r and estimates of net radiation and global solar irradiance for green beans crop (Phaseolus vulgaris L., cultivated in greenhouse with cover of polyethylene and field conditions, in Botucatu, SP, Brazil (22º 54' S; 48º 27' W; 850 m. The solar global irradiance (Rg and solar reflected radiation (Rr were used to estimate the albedo through the ratio between Rr and Rg. The diurnal curves of albedo were obtained for days with clear sky and partially cloudy conditions, for different phenological stages of the crop. The albedo ranged with the solar elevation, the environment and the phenological stages. The cloudiness range have almost no influence on the albedo diurnal amount. The estimation of radiation were made by linear regression, using the global solar irradiance (Rg and net short-waves radiation (Rc as independent variables. All estimates of radiation showed better adjustment for specific phenological periods compared to the entire crop growing cycle. The net radiation in the greenhouse has been estimated by the global solar irradiance measured at field conditions.Este trabalho objetivou determinar o albedo (r no espectro solar e estimar o saldo de radiação, em ambientes cultivados com feijão-vagem (Phaseolus vulgaris L., em condições de campo e em casa de vegetação com cobertura de polietileno, em Botucatu, SP, (22º 54' S; 48º 27' W; 850 m. A irradiância solar global (Rg e a radiação solar refletida (Rr foram utilizadas na determinação do albedo através da razão entre Rr e Rg. Curvas diurnas de r foram traçadas para dias com céu parcialmente nublado e claro, em fases fenológicas da cultura. Os valores do albedo diurno, obtidos através dos totais de radiações, foram utilizados para analisar a variação desse índice durante o ciclo da cultura, nos dois ambientes. O albedo variou com a elevação solar, o ambiente e as fases fenológicas da cultura. A variação de nebulosidade

  2. Arctic sea ice albedo in summer: observation and modelling experiments%北极夏季海冰反照率的观测和数值模拟试验

    Institute of Scientific and Technical Information of China (English)

    杨清华; 程斌; 雷瑞波; 王先桥; 杨宇; 张占海

    2011-01-01

    在中国第3次北极科学考察浮冰站开展了积雪/海冰反照率观测.本文对观测结果进行了分析,并结合一维高分辨雪/冰模式(HIGHTSI)对3个常用的反照率参数化方案在天气尺度的表现进行了评估.观测期间测站反照率变化范围0.75~0.85,其天气尺度变化同天气和表面冰、雪状况紧密相关,降雪和吹雪过程可改变表面积雪厚度及水平分布,进而显著影响反照率.考虑雪、冰厚度变化时,模式能很好的再现反照率的变化趋势,但难以准确模拟出反照率的日变化.%The surface albedo was observed at the Ice Camp during the Chinese National Arctic Research Expedition (CHINARE) at the end of melting season in 2008. The in situ data were investigated in this paper. Several albedo parameterizations were incorporated into a one-dimensional high-resolution thermodynamic snow/ice model (HIGHTSI) to simulate local surface albedo. The observed albedo varies between O. 75~0. 85 during the observation period with a slightly decreasing trend, the local change of albedo was strongly linked with snowfall/sleet and snow drift events. The trend of observed surface albedo can be captured by an albedo scheme taken snow and ice thicknesses into account. Albedo schemes with the current complexity, however, are difficult to reconstruct the short-term variability.

  3. Poster 13: Large-scale simultaneous mapping of Titan's aerosol opacity and surface albedo by a new massive inversion method of Cassini/VIMS data

    Science.gov (United States)

    Maltagliati, Luca; Rodriguez, Sebastien; Sotin, Christophe; Rannou, Pascal; Bezard, Bruno; Solomonidou, Anezina; Coustenis, Athena; Appere, Thomas; Cornet, Thomas; Le Mouelic, Stephane%F. Aa(Aim Cea Saclay; Lesia Observatoire de Paris), Ab(Aim Cea Saclay; Universite Paris 7), Ac(Jpl; Lpg Nantes), Ad(Gsma Reims), Ae(Lesia Observatoire De Paris), Af(Jpl), Ag(Lesia Observatoire De Paris), Ah(Aim Cea Saclay), Ai(Esac/Esa), Aj(Lpg Nantes)

    2016-06-01

    We have still limited information on Titan's surface albedo in the near-infrared. Only few spectral windows exist in between the intense methane bands, and even those windows are strongly affected by atmospheric contributions (absorption, scattering). Yet, this part of the spectrum is important to determine the surface composition thanks to the wealth of absorption bands by minerals and ices present there. A radiative transfer model is an effective tool to take the atmospheric effects into consideration in the analysis (e.g. Rannou et al. 2010, Griffith et al 2012, Solomonidou et al. 2016,...), but it is too time-consuming to process the whole VIMS hyperspectral dataset (millions of spectra) and create large-scale maps of the surface albedo. To overcome this problem, we developed an inversion method of VIMS data that employs lookup tables of synthetic spectra produced by a state-of-the-art radiative transfer model (described in its original form in Hirtzig et al. 2013). The heavy computational part (calling the radiative transfer model) is thus done only once for all during the creation of the modeled spectra. We updated the model with new methane spectroscopy and the new aerosol parameters we found in our analysis of the VIMS Emission Phase Function (see the other Maltagliati et al. abstract in this workshop). We analyzed in detail the behavior of the spectra as a function of the free parameters of the model (three inputs, the incidence, emergence and azimuth angles; and two products: the aerosol opacity and the surface albedo) in order to create an optimized grid for the lookup table. The lookup tables were then grafted onto an ad-hoc inversion model. Our method can process a whole 64x64 VIMS datacube in few minutes, with a gain in computational time of a factor of more than one thousand with respect to the standard method. This will consent for the first time a truly massive inversion of VIMS data and large-scale acquisition of Titan's surface albedo, paving the

  4. Impacts of global open-fire aerosols on direct radiative, cloud and surface-albedo effects simulated with CAM5

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yiquan; Lu, Zheng; Liu, Xiaohong; Qian, Yun; Zhang, Kai; Wang, Yuhang; Yang, Xiu-Qun

    2016-11-29

    Aerosols from open-land fires could significantly perturb the global radiation balance and induce climate change. In this study, Community Atmosphere Model version 5 (CAM5) with prescribed daily fire aerosol emissions is used to investigate the spatial and seasonal characteristics of radiative effects (REs, relative to the case of no fires) of open-fire aerosols including black carbon (BC) and particulate organic matter (POM) from 2003 to 2011. The global annual mean RE from aerosol–radiation interactions (REari) of all fire aerosols is 0.16 ± 0.01 W m-2 (1σ uncertainty), mainly due to the absorption of fire BC (0.25 ± 0.01 W m-2), while fire POM induces a small effect (-0.05 and 0.04 ± 0.01 W m-2 based on two different methods). Strong positive REari is found in the Arctic and in the oceanic regions west of southern Africa and South America as a result of amplified absorption of fire BC above low-level clouds, in general agreement with satellite observations. The global annual mean RE due to aerosol–cloud interactions (REaci) of all fire aerosols is -0.70 ± 0.05 W m-2, resulting mainly from the fire POM effect (-0.59 ± 0.03 W m-2). REari (0.43 ± 0.03 W m-2) and REaci (-1.38 ± 0.23 W m-2) in the Arctic are stronger than in the tropics (0.17 ± 0.02 and -0.82 ± 0.09 W m-2 for REari and REaci), although the fire aerosol burden is higher in the tropics. The large cloud liquid water path over land areas and low solar zenith angle of the Arctic favor the strong fire aerosol REaci (up to -15 Wm-2) during the Arctic summer. Significant surface cooling, precipitation reduction and increasing amounts of low-level cloud are also found in the Arctic summer as a result of the fire aerosol REaci based on the atmosphere-only simulations. The global annual mean RE due to surface-albedo changes (REsac) over land areas (0.03 ± 0.10 W m-2) is small

  5. Reemergence of sea ice cover anomalies and the role of the sea ice-albedo feedback in CCSM simulations

    Science.gov (United States)

    Deweaver, E. T.

    2008-12-01

    The dramatic sea ice decline of 2007 and lack of recovery in 2008 raise the question of a "tipping point" for Arctic sea ice, beyond which the transition to a seasonal sea ice state becomes abrupt and irreversible. The tipping point is essentially a "memory catastrophe", in which a dramatic loss of sea ice in one summer is "remembered" in reduced ice thickness over the winter season and leads to a comparably dramatic loss the following summer. The dominant contributor to this memory is presumably the sea ice - albedo feedback (SIAF), in which excess insolation absorbed due to low summer ice cover leads to a shorter ice growth season and hence thinner ice. While these dynamics are clearly important, they are difficult to quantify given the lack of long-term observations in the Arctic and the suddenness of the recent loss. Alternatively, we attempt to quantify the contribution of the SIAF to the year-to-year memory of sea ice cover anomalies in simulations of the NCAR Community Climate System Model (CCSM) under 20th century conditions. Lagged autocorrelation plots of sea ice area anomalies show that anomalies in one year tend to "reemerge" in the following year. Further experiments using a slab ocean model (SOM) are used to assess the contribution of oceanic processes to the year-to-year reemergence. This contribution is substantial, particularly in the winter season, and includes memory due to the standard mixed layer reemergence mechanism and low-frequency ocean heat transport anomalies. The contribution of the SIAF to persistence in the SOM experiment is determined through additional experiments in which the SIAF is disabled by fixing surface albedo to its climatological value regardless of sea ice concentration anomalies. SIAF causes a 50% increase in the magnitude of the anomalies but a relatively small increase in their persistence. Persistence is not dramatically increased because the enhancement of shortwave flux anomalies by SIAF is compensated by stronger

  6. Comparison of Aerosol Single Scattering Albedo Derived from the Ozone Monitoring Instrument with Aerosol Robotic Network Observations

    Institute of Scientific and Technical Information of China (English)

    LIU Qi; HONG Yu-Lan

    2012-01-01

    The single-scattering albedo (SSA), which quantifies radiative absorption capability, is an important optical property of aerosols. Ground-based methods have been extensively exploited to determine aerosol SSA but there were no satellite-based SSA measurements available until the advent of advanced remote sensing techniques, such as the Ozone Monitoring Instrument (OMI). Although the overall accuracy of OMI SSA is estimated to approach 0.1, its regional availability is unclear. Four-year SSA daily measurements from three Aerosol Robotic Network (AERONET) sites in China (Xianghe, Taihu, and Hong Kong) are chosen to determine the accuracy of OMI SSA in specific locations. The results show that on a global scale, the OMI SSA is systematically higher (with a mean relative bias of 3.5% and a RMS difference of ~0.06) and has poor correlation with the AERONET observations. In the Xianghe, Taihu, and Hong Kong sites, the correlation coefficients are 0.16, 0.47, and 0.44, respectively, suggesting that the distinct qualities of OMI SSA depend on geographic locations and/or dominant aerosol environments. The two types of SSA data yield the best agreement in Taihu and the worst in Hong Kong; the differing behavior is likely caused by varying levels of cloud contamination. The good consistency of the aerosol variation between the two SSA datasets on a seasonal scale is promising. These findings suggest that the current-version OMI SSA product can be applied to qualitatively characterize climatological variations of aerosol properties despite its limited accuracy as an instantaneous measurement.

  7. Modified ocean circulation, albedo instability and ice-flow instability. Risks of non-linear climate change

    Energy Technology Data Exchange (ETDEWEB)

    Ham, J. van; Beer, R.J. van; Builtjes, P.J.H.; Roemer, M.G.M. [TNO Inst. of Environmental Sciences, Delft (Netherlands); Koennen, G.P. [KNMI, Royal Netherlands Meteorological Inst., de Bilt (Netherlands); Oerlemans, J. [Utrecht Univ. (Netherlands). Inst. for Meteorological and Atmospheric Research

    1995-12-31

    In this presentation part of an investigation is described into risks for climate change which are presently not adequately covered in General Circulation Models. In the concept of climate change as a result of the enhanced greenhouse effect it is generally assumed that the radiative forcings from increased concentrations of greenhouse gases (GHG) will result in a proportional or quasilinear global warming. Though correlations of this kind are known from palaeoclimate research, the variability of the climate seems to prevent the direct proof of a causal relation between recent greenhouse gas concentrations and temperature observations. In order to resolve the issue the use of General Circulation Models (GCMs), though still inadequate at present, is indispensable. Around the world some 10 leading GCMs exist which have been the subject of evaluation and intercomparison in a number of studies. Their results are regularly assessed in the IPCC process. A discussion on their performance in simulating present or past climates and the causes of their weak points shows that the depiction of clouds is a major weakness of GCMs. A second element which is virtually absent in GCMs are the feedbacks from natural biogeochemical cycles. These cycles are influenced by man in a number of ways. GCMs have a limited performance in simulating regional effects on climate. Moreover, albedo instability, in part due to its interaction with cloudiness, is only roughly represented. Apparently, not all relevant processes have been included in the GCMs. That situation constitutes a risk, since it cannot be ruled out that a missing process could cause or trigger a non-linear climate change. In the study non-linear climate change is connected with those processes which could provide feedbacks with a risk for non-monotonous or discontinuous behaviour of the climate system, or which are unpredictable or could cause rapid transitions

  8. Albedo do Solo abaixo do Dossel em Área de Vochysia divergens Pohl no Norte do Pantanal

    Directory of Open Access Journals (Sweden)

    Jonathan Willian Zangeski Novais

    2016-06-01

    Full Text Available Resumo Este artigo analisou o albedo do solo (αsolo abaixo do dossel considerando duas etapas no ciclo hidrológico, a primeira em que o solo estava inundado e a segunda em que o solo estava coberto por serrapilheira acumulada sobre o solo em área inundável de Vochysia divergens Pohl no Pantanal, Brasil. Os valores de αsolo foram calculados pela relação entre as radiação solar global refletida e a incidente medidas abaixo do dossel por meio de estações meteorológicas. A inundação da área ocorreu durante fevereiro a junho e posteriormente houve um aumento gradativo de serrapilheira acumulada sobre o solo. O αsolo variou sazonalmente com maiores valores durante o período seco em que houve um aumento de aproximadamente 42% do αsolo em relação ao período com inundação. Análises de correlação cruzada entre o αsolo e precipitação, umidade do solo e a serrapilheira acumulada sobre o solo explicam em parte a influência direta e/ou indireta sobre o αsolo. A precipitação não influenciou diretamente sobre o αsolo do mês atual, enquanto que a umidade do solo influenciou diretamente sobre o αsolo no mês atual e nos seguintes meses, e a serrapilheira acumulada do solo correlacionou-se positivamente com o αsolo indicando influência direta no mês atual.

  9. How effective is albedo modification (solar radiation management geoengineering) in preventing sea-level rise from the Greenland Ice Sheet?

    Science.gov (United States)

    Applegate, Patrick J.; Keller, Klaus

    2015-08-01

    Albedo modification (AM) is sometimes characterized as a potential means of avoiding climate threshold responses, including large-scale ice sheet mass loss. Previous work has investigated the effects of AM on total sea-level rise over the present century, as well as AM’s ability to reduce long-term (≫103 yr) contributions to sea-level rise from the Greenland Ice Sheet (GIS). These studies have broken new ground, but neglect important feedbacks in the GIS system, or are silent on AM’s effectiveness over the short time scales that may be most relevant for decision-making (<103 yr). Here, we assess AM’s ability to reduce GIS sea-level contributions over decades to centuries, using a simplified ice sheet model. We drive this model using a business-as-usual base temperature forcing scenario, as well as scenarios that reflect AM-induced temperature stabilization or temperature drawdown. Our model results suggest that (i) AM produces substantial near-term reductions in the rate of GIS-driven sea-level rise. However, (ii) sea-level rise contributions from the GIS continue after AM begins. These continued sea level rise contributions persist for decades to centuries after temperature stabilization and temperature drawdown begin, unless AM begins in the next few decades. Moreover, (iii) any regrowth of the GIS is delayed by decades or centuries after temperature drawdown begins, and is slow compared to pre-AM rates of mass loss. Combined with recent work that suggests AM would not prevent mass loss from the West Antarctic Ice Sheet, our results provide a nuanced picture of AM’s possible effects on future sea-level rise.

  10. An original interpretation of the surface temperature-albedo space to estimate crop evapotranspiration (SEB-1S

    Directory of Open Access Journals (Sweden)

    O. Merlin

    2013-05-01

    Full Text Available The space defined by the pair surface temperature (T and surface albedo (α, and the space defined by the pair T and fractional green vegetation cover (fvg have been extensively used to estimate evaporative fraction (EF from optical remote sensing data. In both space-based approaches, evapotranspiration (ET is estimated as remotely sensed EF times the available energy. For a given data point in the T − α space or in the T − fvg space, EF is derived as the ratio of the distance separating the point from the line identified as the dry edge to the distance separating the dry edge and the line identified as the wet edge. The dry and wet edges are classically defined as the upper and lower limit of the spaces, respectively. When side-by-side investigating the T − α and the T − fvg spaces, one observes that the range covered by T values on the (classically determined wet edge is different for both spaces. In addition, when extending the wet and dry lines of the T − α space, both lines cross at α ≈ 0.4 although the wet and dry edges of the T − fvg space never cross for 0 ≤ fvg T − α space to make its wet edge consistent with that of the T − fvg space. SEB-1S is tested over a 16 km by 10 km irrigated area in northwestern Mexico during the 2007–2008 agricultural season. The classical T − α space-based model is implemented as benchmark to evaluate the performance of SEB-1S. Input data are composed of ASTER (Advanced Spaceborne Thermal Emission and Reflection radiometer thermal infrared, Formosat-2 shortwave, and station-based meteorological data. The fluxes simulated by SEB-1S and the classical T − α space-based model are compared on seven ASTER overpass dates with the in situ measurements collected at six locations within the study domain. The ET simulated by SEB-1S is significantly more accurate and robust than that predicted by the classical T − α space-based model. The correlation coefficient and slope of the linear

  11. Application of AERONET Single Scattering Albedo and Absorption Angstrom Exponent to Classify Dominant Aerosol Types during DRAGON Campaigns

    Science.gov (United States)

    Giles, D. M.; Holben, B. N.; Eck, T. F.; Schafer, J.; Crawford, J. H.; Kim, J.; Sano, I.; Liew, S.; Salinas Cortijo, S. V.; Chew, B. N.; Lim, H.; Smirnov, A.; Sorokin, M.; Kenny, P.; Slutsker, I.

    2013-12-01

    Aerosols can have major implications on human health by inducing respiratory diseases due to inhalation of fine particles from biomass burning smoke or industrial pollution and on radiative forcing whereby the presence of absorbing aerosol particles (e.g., black carbon) increases atmospheric heating. Aerosol classification techniques have utilized aerosol loading and aerosol properties derived from multi-spectral and multi-angle observations by ground-based (e.g., AERONET) and satellite instrumentation (e.g., MISR). Aerosol Robotic Network (AERONET) data have been utilized to determine aerosol types by implementing various combinations of measured aerosol optical depth or retrieved size and absorption aerosol properties (e.g., Gobbi et al., 2007; Russell et al., 2010). Giles et al. [2012] showed single scattering albedo (SSA) relationship with extinction Angstrom exponent (EAE) can provide an estimate of the general classification of dominant aerosol types (i.e., desert dust, urban/industrial pollution, biomass burning smoke, and mixtures) based on data from ~20 AERONET sites located in known aerosol source regions. In addition, the absorption Angstrom exponent relationship with EAE can provide an indication of the dominant absorbing aerosol type such as dust, black carbon, brown carbon, or mixtures of them. These classification techniques are applied to the AERONET Level 2.0 quality assured data sets collected during Distributed Regional Aerosol Gridded Observational Network (DRAGON) campaigns in Maryland (USA), Japan, South Korea, Singapore, Penang (Malaysia), and California (USA). An analysis of aerosol type classification for DRAGON sites is performed as well as an assessment of the spatial variability of the aerosol types for selected DRAGON campaigns. Giles, D. M., B. N. Holben, T. F. Eck, A. Sinyuk, A. Smirnov, I. Slutsker, R. R. Dickerson, A. M. Thompson, and J. S. Schafer (2012), An analysis of AERONET aerosol absorption properties and classifications

  12. Hydrous mineralogy of CM and CI chondrites from infrared spectroscopy and their relationship with low albedo asteroids

    Science.gov (United States)

    Beck, P.; Quirico, E.; Montes-Hernandez, G.; Bonal, L.; Bollard, J.; Orthous-Daunay, F.-R.; Howard, K. T.; Schmitt, B.; Brissaud, O.; Deschamps, F.; Wunder, B.; Guillot, S.

    2010-08-01

    IR spectroscopy is one of the few techniques that can directly probe water molecules in rocks. This method has been used to characterize the mineralogy of hydrated/hydrous carbonaceous chondrites, and to link known meteorite families with spectroscopic observations of low albedo asteroids. In this paper, we present measurements of the infrared transmission spectra of matrix chunks from 3 CI and 9 CM chondrites. Spectra were measured at ambient conditions and then at different temperatures along a dehydration path toward high- T (˜300 °C) under primary vacuum. At ambient conditions, the 3-μm spectral range is always dominated by adsorbed atmospheric water molecules. Upon moderate (˜100 °C) and high (˜300 °C) heating under low pressure ( P < 10 -4 mbar), adsorbed water and then phyllosilicates interlayer water are removed, revealing a residual absorption band around 3 μm. This band is a characteristic IR feature of the phyllosilicate phases which dominate the mineralogical assemblage of hydrated carbonaceous chondrites. Among the CM chondrites, the high- T spectra reveal a strong variability that appears correlated with the alteration classification scheme of Rubin et al. (2007) and Howard et al. (2009a). The 3-μm band continuously evolves from a broad feature peaking at 3550-3600 cm -1 for the weakly altered CMs (Murchison-type) to a sharp asymmetric peak at ˜3675 cm -1 for the more extensively altered samples (Cold Bokkeveld-type). We attribute this spectral evolution to variations in the chemistry of the phyllosilicate phases from Fe-rich to Mg-rich. On the other hand, the 10-μm spectral region shows a single broad peak which does not compare with known terrestrial serpentine spectra, probably due to high structural disorder of the chondrite phyllosilicate phases. The present work clearly shows that previously published reflectance spectra of chondrites are biased by the presence of adsorbed terrestrial water molecules. Laboratory data collected under

  13. Advancing Glaciological Applications of Remote Sensing with EO-1: (1) Mapping Snow Grain Size and Albedo on the Greenland Ice Sheet Using an Imaging Spectrometer, and (2) ALI Evaluation for Subtle Surface Topographic Mapping via Shape-from Shading

    Science.gov (United States)

    2003-01-01

    The Hyperion sensor, onboard NASA's Earth Observing-1 (EO-1) satellite,is an imaging spectroradiometer with 220 spectral bands over the spectral range from 0.4 - 2.5 microns. Over the course of summer 2001, the instrument acquired numerous images over the Greenland ice sheet. Our main motivation is to develop an accurate and robust approach for measuring the broadband albedo of snow from satellites. Satellite-derived estimates of broadband have typically been plagued with three problems: errors resulting from inaccurate atmospheric correction, particularly in the visible wavelengths from the conversion of reflectance to albedo (accounting for snow BRDE); and errors resulting from regression-based approaches used to convert narrowband albedo to broadband albedo. A typerspectral method has been developed that substantially reduces these three main sources of error and produces highly accurate estimates of snow albedo. This technique uses hyperspectral data from 0.98 - 1.06 microns, spanning a spectral absorption feature centered at 1.03 microns. A key aspect of this work is that this spectral range is within an atmospheric transmission window and reflectances are largely unaffected by atmospheric aerosols, water vapor, or ozone. In this investigation, we make broadband albedo measurements at four sites on the Greenland ice sheet: Summit, a high altitude station in central Greenland; the ETH/CU camp, a camp on the equilibrium line in western Greenland; Crawford Point, a site located between Summit and the ETH/CU camp; and Tunu, a site located in northeastern Greenland at 2000 m. altitude. Each of these sites has an automated weather station (AWS) that continually measures broadband albedo thereby providing validation data.

  14. A moment method for radiative transfer in an anisotropically-scattering slab medium with space-dependent albedo omega(x)

    Science.gov (United States)

    Wilson, S. J.; Wan, F. S.

    1987-10-01

    A variation of the moment method of Wilson and Sen (1986) is used to solve the radiative transfer problem in an anisotropic scattering plane-parallel medium with an arbitrary space-dependent albedo, omega (x). Considering the case of both forward and backward scattering, the reflectance and transmission functions for linear and quadratic variation of omega(x) are given for isotropic incidence of unit intensity. The exit distribution of radiation for a linear variation of omega(x) is also given for both isotropic and normal incidence of intensity. Results from the present delta approximation method are in good agreement with those of Cengel and Ozisik (1985).

  15. Assessment of post-fire changes in land surface temperature and surface albedo, and their relation with fire-burn severity using multitemporal MODIS imagery

    OpenAIRE

    Veraverbeke, Sander; Verstraeten, Willem W.; Lhermitte, Stefaan; Van De Kerchove, Ruben; Goossens, Rudi

    2012-01-01

    This study evaluates the effects of the large 2007 Peloponnese (Greece) wildfires on changes in broadband surface albedo (a), daytime land surface temperature (LSTd) and night-time LST (LSTn) using a 2-year post-fire time series of Moderate Resolution Imaging Spectroradiometer satellite data. In addition, it assesses the potential of remotely sensed a and LST as indicators for fire-burn severity. Immediately after the fire event, mean a dropped up to 0.039 (standard deviation = 0.012) (P < 0....

  16. The Marco Polo mission: a sample return from a low-albedo Near Earth Object in the ESA Cosmic Vision Program 2015-2025

    OpenAIRE

    Michel, Patrick; Barucci, Antonella; Yoshikawa, Makoto; Koschny, Detlef; Boenhardt, Hermann; Brucato, John Robert; Coradini, Marcello; Dotto, Elisabetta; Franchi, Ian; Green, Simon F.; Josset, Jean-Luc; Kawaguchi, Junichiro; Muinonen, Karri; Oberst, Jürgen; Yano, Hajime

    2009-01-01

    Marco Polo is a sample return mission to a Near-Earth Object (NEO) which was originally proposed as a joint European-Japanese mission for the scientific program Cosmic Vision 2015-2025 of the European Space Agency (ESA) in June 2007 and selected for an assessment study until fall 2009. The main goal of this mission is to return a sample from a dark taxonomic type (low albedo) NEO for detailed laboratory analysis in order to answer questions related to planetary formation, evolution and the or...

  17. The responses of surface albedo to climatic changes in Xilin Gol grassland%锡林郭勒草原地表反照率对气候变化的响应

    Institute of Scientific and Technical Information of China (English)

    张学珍

    2012-01-01

    This study assessed the reliability of Moderate Resolution Imaging Spectroradiometer(MODIS)-derived land surface albedo products for Xilin Gol grassland,illustrated the seasonal cycles and inter-annual variations of land surface albedo in Xilin Gol grassland,and analyzed correlations between surface albedo variations and climatic changes.The results show MODIS-derived dataset is able to capture seasonal cycle and inter-annual variations of surface albedo,though there is a difference between the MODIS-derived albedo and ground instrumental measurements.The MODIS-derived dataset illustrates that the seasonal cycle patterns of surface albedo vary with spectrum.For the visible band surface albedo,the seasonal cycle presents a "V"-shaped variation with the bottom in the first ten days of August.For the near-infrared band surface albedo,the seasonal cycle is "U"-shaped with the bottom in the period from June to September.However,both visible band surface albedo and near-infrared band surface albedo had consistent inter-annual variations.Moreover,the inter-annual variations of surface albedo were partly attributed to climatic variations.The effects of temperature were significant in the early(April to May) and late(September to November) growth season.The correlation coefficients between temperature and surface albedo were-0.67 and 0.63 in the early and late growth season,respectively.The effects of precipitation were significant through out the growth season.The correlation coefficients between precipitation and surface albedo ranged from-0.54 to-0.76.It is worthy noting that the effects of precipitation were usually lagged by 2-3 months.%在对锡林郭勒草原地区MODIS的地表反照率产品(MCD43C3)的可靠性进行评估的基础上,利用该产品分析了2002~2009年锡林郭勒草原地表反照率的变化及其与温度和降水的关系。结果表明:(1)MODIS的反演结果能够很好地反映地表反照率的季节

  18. Albedo of X-ray through the region of rarefaction wave%X光辐射通过稀疏波区的反照率

    Institute of Scientific and Technical Information of China (English)

    张钧

    2001-01-01

    在激光间接驱动内爆动力学过程中,软X射线烧蚀形成的高温低密度等离子体处于非局部热动平衡状态,X射线的传播需要用输运方法处理。利用简化物理模型给出了X射线烧蚀形成的高温低密度等离子体的流场空间分布,介绍了一种计算X射线反照率的方法,并给出反照率的解析表达式。%In the process of implosion indirectly driven by laser,the high temperature and low density plasma produced by X-ray ablation is in the state of non-local thermodynamic equilibrium. And the propagation of X-ray needs to be treated by transportation method. X-ray energy flow reflected by plasma depends on the density,temperature of radiation and electrons,and their space profiles if the plasma produced by ablation is fully ionized. In addition, the plasma parameters in the region of rarefaction wave is determined by means of a simplified model. The approach to compute X-ray albedo is presented and the analytical formulae of the albedo are given in this paper.

  19. Yearly and seasonal variations of low albedo surfaces on Mars in the OMEGA/MEx dataset: Constraints on aerosols properties and dust deposits

    CERN Document Server

    Vincendon, Mathieu; Poulet, François; Pommerol, Antoine; Wolff, Michael; Bibring, Jean-Pierre; Gondet, Brigitte; Jouglet, Denis; 10.1016/j.icarus.2008.12.012

    2011-01-01

    The time variations of spectral properties of dark martian surface features are investigated using the OMEGA near-IR dataset. The analyzed period covers two Mars years, spanning from early 2004 to early 2008 (includes the 2007 global dust event). Radiative transfer modeling indicates that the apparent albedo variations of low to mid-latitude dark regions are consistent with those produced by the varying optical depth of atmospheric dust as measured simultaneously from the ground by the Mars Exploration Rovers. We observe only a few significant albedo changes that can be attributed to surface phenomena. They are small-scaled and located at the boundaries between bright and dark regions. We then investigate the variations of the mean particle size of aerosols using the evolution of the observed dark region spectra between 1 and 2.5 {\\mu}m. Overall, we find that the observed changes in the spectral slope are consistent with a mean particle size of aerosols varying with time between 1 and 2 {\\mu}m. Observations w...

  20. A semianalytical algorithm for quantitatively estimating sediment and atmospheric deposition flux from MODIS-derived sea ice albedo in the Bohai Sea, China

    Science.gov (United States)

    Xu, Zhantang; Hu, Shuibo; Wang, Guifen; Zhao, Jun; Yang, Yuezhong; Cao, Wenxi; Lu, Peng

    2016-05-01

    Quantitative estimates of particulate matter [PM) concentration in sea ice using remote sensing data is helpful for studies of sediment transport and atmospheric dust deposition flux. In this study, the difference between the measured dirty and estimated clean albedo of sea ice was calculated and a relationship between the albedo difference and PM concentration was found using field and laboratory measurements. A semianalytical algorithm for estimating PM concentration in sea ice was established. The algorithm was then applied to MODIS data over the Bohai Sea, China. Comparisons between MODIS derived and in situ measured PM concentration showed good agreement, with a mean absolute percentage difference of 31.2%. From 2005 to 2010, the MODIS-derived annual average PM concentration was approximately 0.025 g/L at the beginning of January. After a month of atmospheric dust deposition, it increased to 0.038 g/L. Atmospheric dust deposition flux was estimated to be 2.50 t/km2/month, similar to 2.20 t/km2/month reported in a previous study. The result was compared with on-site measurements at a nearby ground station. The ground station was close to industrial and residential areas, where larger dust depositions occurred than in the sea, but although there were discrepancies between the absolute magnitudes of the two data sets, they demonstrated similar trends.

  1. Photometric Observations Constraining the Size, Shape, and Albedo of 2003 El61, a Rapidly Rotating, Pluto-Sized Object in the Kuiper Belt

    CERN Document Server

    Rabinowitz, D L; Brown, M E; Roe, H; Schwartz, M; Tourtellotte, S; Trujillo, C; Rabinowitz, David L.; Barkume, Kristina; Brown, Michael E.; Roe, Henry; Schwartz, Michael; Tourtellotte, Suzanne; Trujillo, Chad

    2006-01-01

    We present measurements at optical wavelengths of the spectral reflectance, the rotational light curve, and the solar phase curve of 2003 EL61,. With apparent visual magnitude 17.5 at 51 AU from the sun, this newly discovered member of the classical Kuiper Belt is now the third brightest KBO after Pluto and 2005 FY9. Our observations reveal an unambiguous, double-peaked rotational light curve with period 3.9154 +/- 0.0002 hours and peak to peak amplitude 0.28 +/- 0.04 mag. This is the fastest rotation period reliably determined for any body in the solar system larger than 100 km. Assuming the body has relaxed over time to the shape taken by a homogenous fluid body, our observations tightly constrain the shape and density. Given the mass we recently determined for 2003 EL61 from the orbit of a small satellite, we also constrain the size and albedo. We find a total length of 1960 to 2500 km, a mean density of 2600 to 3340 kg m-3, and a visual albedo greater than 0.6. We also measure a neutral reflectance at vis...

  2. Influence of Venus topography on the zonal wind and UV albedo at cloud top level: The role of stationary gravity waves

    Science.gov (United States)

    Bertaux, Jean-Loup; Khatuntsev, I. V.; Hauchecorne, A.; Markiewicz, W. J.; Marcq, E.; Lebonnois, S.; Patsaeva, M.; Turin, A.; Fedorova, A.

    2016-06-01

    Based on the analysis of UV images (at 365 nm) of Venus cloud top (altitude 67 ± 2 km) collected with Venus Monitoring Camera on board Venus Express (VEX), it is found that the zonal wind speed south of the equator (from 5°S to 15°S) shows a conspicuous variation (from -101 to -83 m/s) with geographic longitude of Venus, correlated with the underlying relief of Aphrodite Terra. We interpret this pattern as the result of stationary gravity waves produced at ground level by the uplift of air when the horizontal wind encounters a mountain slope. These waves can propagate up to the cloud top level, break there, and transfer their momentum to the zonal flow. Such upward propagation of gravity waves and influence on the wind speed vertical profile was shown to play an important role in the middle atmosphere of the Earth by Lindzen (1981) but is not reproduced in the current GCM of Venus atmosphere from LMD. (Laboratoire de Météorologie Dynamique) In the equatorial regions, the UV albedo at 365 nm varies also with longitude. We argue that this variation may be simply explained by the divergence of the horizontal wind field. In the longitude region (from 60° to -10°) where the horizontal wind speed is increasing in magnitude (stretch), it triggers air upwelling which brings the UV absorber at cloud top level and decreases the albedo and vice versa when the wind is decreasing in magnitude (compression). This picture is fully consistent with the classical view of Venus meridional circulation, with upwelling at equator revealed by horizontal air motions away from equator: the longitude effect is only an additional but important modulation of this effect. This interpretation is comforted by a recent map of cloud top H2O, showing that near the equator the lower UV albedo longitude region is correlated with increased H2O. We argue that H2O enhancement is the sign of upwelling, suggesting that the UV absorber is also brought to cloud top by upwelling.

  3. Elaboração de biscoitos de chocolate com substituição parcial da farinha de trigo por polvilho azedo e farinha de albedo de laranja Chocolate biscuits preparation with partial substitution of wheat flour by fermented cassava starch and orange albedo flour

    Directory of Open Access Journals (Sweden)

    Aline Alves Oliveira Santos

    2011-03-01

    Full Text Available Os consumidores estão cada vez mais exigentes e preocupados com a saúde e, por consequência, exigindo produtos naturais que deverão ser seguros e promover qualidade de vida. O presente trabalho teve o objetivo de desenvolver biscoitos com farinhas mistas de polvilho azedo e farinha de albedo de laranja, utilizando um planejamento fatorial 2³, com variáveis independentes: concentração de polvilho azedo, açúcar e farinha de albedo de laranja, e variáveis respostas: as características sensoriais: aparência, aroma, textura e sabor, além da impressão global, utilizando escala hedônica estruturada de nove pontos. Os biscoitos foram avaliados também quanto às características físico-químicas. As médias obtidas para as características sensoriais estiveram na faixa que vai de cinco (não gostei nem desgostei até sete (gostei moderadamente, não apresentando diferença significativa (P≤0,05 para todas as características sensoriais avaliadas. Dessa maneira, foi possível escolher a formulação ideal obtida de acordo com os parâmetros nutricionais, por não existir diferença sensorial significativa, que foi 35% de polvilho azedo, 100% de açúcar e 7,5% de farinha de albedo de laranja. No teste sensorial comparativo com os biscoitos comercial, padrão e otimizado, as características sensoriais aparência, sabor e textura apresentaram diferença significativa (P≤0,05. As características físico-químicas apresentaram resultados correspondentes aos padrões estabelecidos pela legislação brasileira, e o teor de fibra bruta do biscoito otimizado foi de 3,08%, assim, pode ser classificado como biscoito "fonte de fibras".The consumers are increasingly demanding and worried about health and, consequently, requiring natural products that should be safe and that promote life quality. The present research had the objective to develop biscuits with mixed flour of fermented cassava starch and orange albedo flour, using a 2³ factorial

  4. On the effects of size factor on albedo versus wavelength for light scattered by small particles under Mie and Rayleigh regimes

    CERN Document Server

    Brown, Adrian J

    2013-01-01

    Scattering by particles significantly smaller than the wavelength is an important physical process in the rocky bodies in our solar system and beyond. A number of observations of spectral bluing (referred to in those papers as "Rayleigh scattering") on planetary surfaces have been recently reported, however, the necessary mathematical modeling of this phenomenon has not yet achieved maturity. This paper is a first step to this effect, by examining the effect of grain size and optical index on the albedo of small conservative and absorbing particles as a function of wavelength. The basic conditions necessary for spectral bluing or reddening to be observed in real-world situations are identified. We find that any sufficiently monomodal size distribution of scattering particles will cause spectral bluing in some part of the EM spectrum regardless of its optical index.

  5. Evaluation of preindustrial to present-day black carbon and its albedo forcing from Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP

    Directory of O