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Sample records for albedo neutron sensing

  1. Ground Albedo Neutron Sensing (GANS) method for measurements of soil moisture in cropped fields

    NASA Astrophysics Data System (ADS)

    Andres Rivera Villarreyes, Carlos; Baroni, Gabriele; Oswald, Sascha E.

    2013-04-01

    Measurement of soil moisture at the plot or hill-slope scale is an important link between local vadose zone hydrology and catchment hydrology. However, so far only few methods are on the way to close this gap between point measurements and remote sensing. This study evaluates the applicability of the Ground Albedo Neutron Sensing (GANS) for integral quantification of seasonal soil moisture in the root zone at the scale of a field or small watershed, making use of the crucial role of hydrogen as neutron moderator relative to other landscape materials. GANS measurements were performed at two locations in Germany under different vegetative situations and seasonal conditions. Ground albedo neutrons were measured at (i) a lowland Bornim farmland (Brandenburg) cropped with sunflower in 2011 and winter rye in 2012, and (ii) a mountainous farmland catchment (Schaefertal, Harz Mountains) since middle 2011. At both sites depth profiles of soil moisture were measured at several locations in parallel by frequency domain reflectometry (FDR) for comparison and calibration. Initially, calibration parameters derived from a previous study with corn cover were tested under sunflower and winter rye periods at the same farmland. GANS soil moisture based on these parameters showed a large discrepancy compared to classical soil moisture measurements. Therefore, two new calibration approaches and four different ways of integration the soil moisture profile to an integral value for GANS were evaluated in this study. This included different sets of calibration parameters based on different growing periods of sunflower. New calibration parameters showed a good agreement with FDR network during sunflower period (RMSE = 0.023 m3 m-3), but they underestimated soil moisture in the winter rye period. The GANS approach resulted to be highly affected by temporal changes of biomass and crop types which suggest the need of neutron corrections for long-term observations with crop rotation. Finally

  2. Measuring planetary neutron albedo fluxes by remote gamma-ray sensing

    NASA Technical Reports Server (NTRS)

    Haines, E. L.; Metzger, A. E.

    1984-01-01

    In order to measure the planetary neutron albedo fluxes, a neutron-absorbing shield which emits gamma rays of characteristic energy and serves as a neutron detector, is added to a gamma-ray spectrometer (GRS). The gamma rays representing the neutron flux are observed against interference consisting of cosmic gamma rays, planetary continuum and line emission, and gamma rays arising from the interaction of cosmic rays with the GRS and the spacecraft. The uncertainty and minimum detection limits in neutron albedo fluxes are calculated for two missions, a lunar orbiter and a comet nucleus rendezvous. A GRS on a lunar orbiter at 100 km altitude detects a thermal neutron albedo flux as low as 0.002/sq cm/s and an expected flux of about 0.6/sq cm/s is measured with an uncertainty of 0.001/sq cm/s, for a 100 h observation period. For the comet nucleus, again in a 100 h observing period, a thermal neutron albedo flux is detected at a level of 0.006/sq cm/s and an expected flux of about 0.4/sq cm/s is measured with an uncertainty of 0.004/sq cm/s. The expanded geological capabilities made possible by this technique include improvements in H sensitivity, spatial resolution, and measurement depth; and an improved model of induced gamma-ray emission.

  3. Integral Quantification of Soil Water Content at the Intermediate Catchment Scale by Ground Albedo Neutron Sensing (GANS)

    NASA Astrophysics Data System (ADS)

    Rivera Villarreyes, C. A.; Baroni, G.; Oswald, S. E.

    2012-04-01

    Soil water content at the plot or hill-slope scale is an important link between local vadose zone hydrology and catchment hydrology. However, so far only few methods are on the way to close this gap between point measurements and remote sensing. One new measurement methodology for integral quantifications of mean areal soil water content at the intermediate catchment scale is the aboveground sensing of cosmic-ray neutrons, more precisely ground albedo neutron sensing (GANS). Ground albedo natural neutrons, are generated by collisions of secondary cosmic rays with land surface materials (soil, water, biomass, snow, etc). Neutrons measured at the air/ground interface correlate with soil moisture contained in a footprint of ca. 600 m diameter and a depth ranging down to a few decimeters. This correlation is based on the crucial role of hydrogen as neutron moderator compared to others landscape materials. The present study performed ground albedo neutron sensing in different locations in Germany under different vegetative situations (cropped and bare field) and different seasonal conditions (summer, autumn and winter). Ground albedo neutrons were measured at (i) a farmland close to Potsdam (Brandenburg, Germany) cropped with corn in 2010 and sunflowers in 2011, and (ii) a mountainous farmland catchment (Schaefertal, Harz Mountains, Germany) in 2011. In order to test this method, classical soil moisture devices and meteorological data were used for comparison. Moreover, calibration approach, and transferability of calibration parameters to different times and locations are also evaluated. Our observations suggest that GANS can overcome the lack of data for hydrological processes at the intermediate scale. Soil water content from GANS compared quantitatively with mean water content values derived from a network of classical devices (RMSE = 0.02 m3/m3 and r2 = 0.98) in three calibration periods with cropped-field conditions. Then, same calibration parameters corresponded

  4. Ground Albedo Neutron Sensing (GANS) for Measurement of Integral Soil Water Content at the Small Catchment Scale

    NASA Astrophysics Data System (ADS)

    Rivera Villarreyes, C.; Baroni, G.; Oswald, S. E.

    2012-12-01

    Soil water content at the plot or hill-slope scale is an important link between local vadose zone hydrology and catchment hydrology. One largest initiative to cover the measuring gap of soil moisture between point scale and remote sensing observations is the COSMOS network (Zreda et al., 2012). Here, cosmic-ray neutron sensing, which may be more precisely named ground albedo neutron sensing (GANS), is applied. The measuring principle is based on the crucial role of hydrogen as neutron moderator compared to others landscape materials. Soil water content contained in a footprint of ca. 600 m diameter and a depth ranging down to a few decimeters is inversely correlated to the neutron flux at the air-ground interface. This approach is now implemented, e.g. in USA (Zreda et al., 2012) and Germany (Rivera Villarreyes et al., 2011), based on its simple installation and integral measurement of soil moisture at the small catchment scale. The present study performed Ground Albedo Neutron Sensing on farmland at two locations in Germany under different vegetative situations (cropped and bare field) and different seasonal conditions (summer, autumn and winter). Ground albedo neutrons were measured at (i) a farmland close to Potsdam and Berlin cropped with corn in 2010, sunflower in 2011 and winter rye in 2012, and (ii) a mountainous farmland catchment (Schaefertal, Harz Mountains) since middle 2011. In order to test this methodology, classical soil moisture devices and meteorological data were used for comparison. Moreover, several calibration approaches, role of vegetation cover and transferability of calibration parameters to different times and locations were also evaluated. Observations suggest that GANS can overcome the lack of data for hydrological processes at the intermediate scale. Soil moisture from GANS compared quantitatively with mean values derived from a network of classical devices under vegetated and non- vegetated conditions. The GANS approach responded well

  5. Calibration of neutron albedo dosemeters.

    PubMed

    Schwartz, R B; Eisenhauer, C M

    2002-01-01

    It is shown that by calibrating neutron albedo dosemeters under the proper conditions, two complicating effects will essentially cancel out, allowing accurate calibrations with no need for explicit corrections. The 'proper conditions' are: a large room (> or = 8 m on a side). use of a D2O moderated 252Cf source, and a source-to-phantom calibration distance of approximately 70 cm. PMID:12212898

  6. Radiation Dose from Lunar Neutron Albedo

    NASA Technical Reports Server (NTRS)

    Adams, J. H., Jr.; Bhattacharya, M.; Lin, Zi-Wei; Pendleton, G.

    2006-01-01

    The lunar neutron albedo from thermal energies to 8 MeV was measured on the Lunar Prospector Mission in 1998-1999. Using GEANT4 we have calculated the neutron albedo due to cosmic ray bombardment of the moon and found a good-agreement with the measured fast neutron spectra. We then calculated the total effective dose from neutron albedo of all energies, and made comparisons with the effective dose contributions from both galactic cosmic rays and solar particle events to be expected on the lunar surface.

  7. Variable control of neutron albedo in toroidal fusion devices

    DOEpatents

    Jassby, Daniel L.; Micklich, Bradley J.

    1986-01-01

    An arrangement is provided for controlling neutron albedo in toroidal fusion devices having inboard and outboard vacuum vessel walls for containment of the neutrons of a fusion plasma. Neutron albedo material is disposed immediately adjacent the inboard wall, and is movable, preferably in vertical directions, so as to be brought into and out of neutron modifying communication with the fusion neutrons. Neutron albedo material preferably comprises a liquid form, but may also take pebble, stringer and curtain-like forms. A neutron flux valve, rotatable about a vertical axis is also disclosed.

  8. The albedo effect on neutron transmission probability.

    PubMed

    Khanouchi, A; Sabir, A; Boulkheir, M; Ichaoui, R; Ghassoun, J; Jehouani, A

    1997-01-01

    The aim of this study is to evaluate the albedo effect on the neutron transmission probability through slab shields. For this reason we have considered an infinite homogeneous slab having a fixed thickness equal to 20 lambda (lambda is the mean free path of the neutron in the slab). This slab is characterized by the factor Ps (scattering probability) and contains a vacuum channel which is formed by two horizontal parts and an inclined one (David, M. C. (1962) Duc and Voids in shields. In Reactor Handbook, Vol. III, Part B, p. 166). The thickness of the vacuum channel is taken equal to 2 lambda. An infinite plane source of neutrons is placed on the first of the slab (left face) and detectors, having windows equal to 2 lambda, are placed on the second face of the slab (right face). Neutron histories are sampled by the Monte Carlo method (Booth, T. E. and Hendricks, J. S. (1994) Nuclear Technology 5) using exponential biasing in order to increase the Monte Carlo calculation efficiency (Levitt, L. B. (1968) Nuclear Science and Engineering 31, 500-504; Jehouani, A., Ghassoun, J. and Abouker, A. (1994) In Proceedings of the 6th International Symposium on Radiation Physics, Rabat, Morocco) and we have applied the statistical weight method which supposes that the neutron is born at the source with a unit statistical weight and after each collision this weight is corrected. For different values of the scattering probability and for different slopes of the inclined part of the channel we have calculated the neutron transmission probability for different positions of the detectors versus the albedo at the vacuum channel-medium interface. Some analytical representations are also presented for these transmission probabilities. PMID:9463883

  9. Earth albedo neutrons from 10 to 100 MeV.

    NASA Technical Reports Server (NTRS)

    Preszler, A. M.; Simnett, G. M.; White, R. S.

    1972-01-01

    We report the measurement of the energy and angular distributions of earth albedo neutrons from 10 to 100 MeV at 40 deg N geomagnetic latitude from a balloon at 120,000 ft, below 4.65 g/sq cm. The albedo-neutron omnidirectional energy distribution is flat to 50 MeV, then decreases with energy. The absolute neutron energy distribution is of the correct strength and shape for the albedo neutrons to be the source of the protons trapped in earth's inner radiation belt.

  10. Neutron dosimetry with TL albedo dosemeters at high energy accelerators.

    PubMed

    Haninger, T; Fehrenbacher, G

    2007-01-01

    The GSF-Personal Monitoring Service uses the TLD albedo dosemeter as standard neutron personal dosemeter. Due to its low sensitivity for fast neutrons however, it is generally not recommended for workplaces at high-energy accelerators. Test measurements with the albedo dosemeter were performed at the accelerator laboratories of GSI in Darmstadt and DESY in Hamburg to reconsider this hypothesis. It revealed that the albedo dosemeter can also be used as personal dosemeter at these workplaces, because at all measurement locations a significant part of neutrons with lower energies could be found, which were produced by scattering at walls or the ground. PMID:17766258

  11. Albedo neutron dosimetry in Germany: regulations and performance.

    PubMed

    Luszik-Bhadra, M; Zimbal, A; Busch, F; Eichelberger, A; Engelhardt, J; Figel, M; Frasch, G; Günther, K; Jordan, M; Martini, E; Haninger, T; Rimpler, A; Seifert, R

    2014-12-01

    Personal neutron dosimetry has been performed in Germany using albedo dosemeters for >20 y. This paper describes the main principles, the national standards, regulations and recommendations, the quality management and the overall performance, giving some examples. PMID:24639589

  12. Variable control of neutron albedo in toroidal fusion devices

    DOEpatents

    Jassby, D.L.; Micklich, B.J.

    1983-06-01

    This invention pertains to methods of controlling in the steady state, neutron albedo in toroidal fusion devices, and in particular, to methods of controlling the flux and energy distribution of collided neutrons which are incident on an outboard wall of a toroidal fusion device.

  13. Analytical modeling of thermoluminescent albedo detectors for neutron dosimetry.

    PubMed

    Glickstein, S S

    1983-02-01

    In order to gain an in-depth understanding of the neutron physics of a 6LiF TLD when used as an albedo neutron dosimeter, an analytical model was developed to simulate the response of a 6LiF chip. The analytical model was used to examine the sensitivity of the albedo TLD response to incident monoenergetic neutrons and to evaluate a multiple chip TLD neutron dosimeter. Contrary to initial experimental studies, which were hampered by statistical uncertainties, the analytical evaluation revealed that a three-energy-group detector could not reliably measure the dose equivalent to personnel exposed to multiple neutron spectra. The analysis clearly illustrates that there may be order of magnitude errors in the measured neutron dose if the dosimeter has not been calibrated for the same flux spectrum to which it is exposed. As a result of this analysis, it was concluded that, for personnel neutron monitoring, a present TLD badge must be calibrated for the neutron spectrum into which the badge is to be introduced. The analytical model used in this study can readily be adopted for evaluating other possible detectors and shield material that might be proposed in the future as suitable for use in neutron dosimetry applications. PMID:6826377

  14. Use of a spherical albedo system for correcting the readings of albedo dosimeters in JINR phasotron neutron radiation fields

    NASA Astrophysics Data System (ADS)

    Mokrov, Yu. V.; Morozova, S. V.

    2014-03-01

    Results of calibrating a spherical albedo system in the radiation fields of a Pu-Be radionuclide neutron source are presented. It is shown that it can be used for correcting the readings of the DVGN-01 albedo dosimeter. The results of measurements with the system in JINR phasotron neutron fields for the purpose of correcting the DVGN-01 readings in these fields are given. The values of the correction factors for DVGN-01 albedo dosimeters when used in personnel neutron dosimetry (PD) on the JINR phasotron are determined.

  15. Standards for the validation of remotely sensed albedo products

    NASA Astrophysics Data System (ADS)

    Adams, Jennifer

    2015-04-01

    Land surface albedo is important component of the Earth's energy balance, defined as the fraction of shortwave radiation absorbed by a surface, and is one many Essential Climate Variables (ECVS) that can be retrieved from space through remote sensing. To quantify the accuracy of these products, they must be validated with respect to in-situ measurements of albedo using an albedometer. Whilst accepted standards exist for the calibration of albedometers, standards for the use of in-situ measurement schemes, and their use in validation procedures have yet to be developed. It is essential that we can assess the quality of remotely sensed albedo data, and to identify traceable sources of uncertainty during process of providing these data. As a result of the current lack of accepted standards for in-situ albedo retrieval and validation procedures, we are not yet able to identify and quantify traceable sources of uncertainty. Establishing standard protocols for in-situ retrievals for the validation of global albedo products would allow inter-product use and comparison, in addition to product standardization. Accordingly, this study aims to assess the quality of in-situ albedo retrieval schemes and identify sources of uncertainty, specifically in vegetation environments. A 3D Monte Carlo Ray Tracing Model will be used to simulate albedometer instruments in complex 3D vegetation canopies. To determine sources of uncertainty, factors that influence albedo measurement uncertainty were identified and will subsequently be examined: 1. Time of day (Solar Zenith Angle) 2. Ecosytem type 3. Placement of albedometer within the ecosystem 4. Height of albedometer above the canopy 5. Clustering within the ecosystem A variety of 3D vegetation canopies have been generated to cover the main ecosystems found globally, different seasons, and different plant distributions. Canopies generated include birchstand and pinestand forests for summer and winter, savanna, shrubland, cropland and

  16. DOSIMETRIC PROPERTIES OF THE NEW TLD ALBEDO NEUTRON DOSEMETER AWST-TL-GD 04.

    PubMed

    Haninger, T; Henniger, J

    2016-09-01

    A new official albedo dosemeter based on thermoluminescent detectors has been introduced in 2015 by the individual monitoring service of the Helmholtz Zentrum München for monitoring persons who are exposed occupationally against photon and neutron radiation. To enhance the sensitivity for fast neutrons, a new badge with an enlarged albedo window has been developed at TU Dresden. The properties of the new albedo dosemeter are discussed, and the results of official intercomparisons and field calibrations are shown.

  17. DOSIMETRIC PROPERTIES OF THE NEW TLD ALBEDO NEUTRON DOSEMETER AWST-TL-GD 04.

    PubMed

    Haninger, T; Henniger, J

    2016-09-01

    A new official albedo dosemeter based on thermoluminescent detectors has been introduced in 2015 by the individual monitoring service of the Helmholtz Zentrum München for monitoring persons who are exposed occupationally against photon and neutron radiation. To enhance the sensitivity for fast neutrons, a new badge with an enlarged albedo window has been developed at TU Dresden. The properties of the new albedo dosemeter are discussed, and the results of official intercomparisons and field calibrations are shown. PMID:26405220

  18. System albedo as sensed by satellites - Its definition and variability

    NASA Technical Reports Server (NTRS)

    Hughes, N. A.; Henderson-Sellers, A.

    1982-01-01

    System albedo, an important climatological and environmental parameter, is considered. Some of the problems and assumptions involved in evaluating albedo from satellite data are discussed. Clear-sky and cloud albedos over the United Kingdom and parts of northwest Europe are treated. Consideration is given to the spectral, temporal, and spatial variations and the effect of averaging. The implications of these results for those using and archiving albedo values and for future monitoring of system albedo are discussed. Normalization is of especial importance since this correction alters many albedo values. The pronounced difference in spectral albedo of the two visible channels reemphasizes the problem of attempting to calculate integrated albedo values from meteorological satellite data. The assumption of isotropic reflection is seen to be invalid, hindering the computation of accurate albedo values.

  19. Effects of geochemical composition on neutron die-away measurements: Implications for Mars Science Laboratory's Dynamic Albedo of Neutrons experiment

    NASA Astrophysics Data System (ADS)

    Hardgrove, C.; Moersch, J.; Drake, D.

    2011-12-01

    The Dynamic Albedo of Neutrons (DAN) experiment, part of the scientific payload of the Mars Science Laboratory (MSL) rover mission, will have the ability to assess both the abundance and the burial depth of subsurface hydrogen as the rover traverses the Martian surface. DAN will employ a method of measuring neutron fluxes called “neutron die-away” that has not been used in previous planetary exploration missions. This method requires the use of a pulsed neutron generator that supplements neutrons produced via spallation in the subsurface by the cosmic ray background. It is well established in neutron remote sensing that low-energy (thermal) neutrons are sensitive not only to hydrogen content, but also to the macroscopic absorption cross-section of near-surface materials. To better understand the results that will be forthcoming from DAN, we model the effects of varying abundances of high absorption cross-section elements that are likely to be found on the Martian surface (Cl, Fe) on neutron die-away measurements made from a rover platform. Previously, the Mars Exploration Rovers (MER) Spirit and Opportunity found that elevated abundances of these two elements are commonly associated with locales that have experienced some form of aqueous activity in the past, even though hydrogen-rich materials are not necessarily still present. By modeling a suite of H and Cl compositions, we demonstrate that (for abundance ranges reasonable for Mars) both the elements will significantly affect DAN thermal neutron count rates. Additionally, we show that the timing of thermal neutron arrivals at the detector can be used together with the thermal neutron count rates to independently determine the abundances of hydrogen and high neutron absorption cross-section elements (the most important being Cl). Epithermal neutron die-away curves may also be used to separate these two components. We model neutron scattering in actual Martian compositions that were determined by the MER Alpha

  20. The Dynamic Albedo of Neutrons (DAN) experiment for NASA's 2009 Mars Science Laboratory.

    PubMed

    Litvak, M L; Mitrofanov, I G; Barmakov, Yu N; Behar, A; Bitulev, A; Bobrovnitsky, Yu; Bogolubov, E P; Boynton, W V; Bragin, S I; Churin, S; Grebennikov, A S; Konovalov, A; Kozyrev, A S; Kurdumov, I G; Krylov, A; Kuznetsov, Yu P; Malakhov, A V; Mokrousov, M I; Ryzhkov, V I; Sanin, A B; Shvetsov, V N; Smirnov, G A; Sholeninov, S; Timoshenko, G N; Tomilina, T M; Tuvakin, D V; Tretyakov, V I; Troshin, V S; Uvarov, V N; Varenikov, A; Vostrukhin, A

    2008-06-01

    We present a summary of the physical principles and design of the Dynamic Albedo of Neutrons (DAN) instrument onboard NASA's 2009 Mars Science Laboratory (MSL) mission. The DAN instrument will use the method of neutron-neutron activation analysis in a space application to study the abundance and depth distribution of water in the martian subsurface along the path of the MSL rover.

  1. Cosmic-ray neutron albedo dose in low-earth orbits

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Townsend, L. W.; Farhat, H.

    1989-01-01

    An earth albedo neutron environmental model is proposed which provides a way to estimate neutron exposure in low-earth orbit. It is shown that, in the predominantly low inclination orbits (i=28.5 deg) used in the U.S. space program, the neutron exposures are relatively low (0.7 cSv/y). The neutron exposures are more significant for polar orbital missions and even high inclination missions, such as Skylab (i=57 deg).

  2. The Dynamic Albedo of Neutrons (DAN) experiment for NASA's 2009 Mars Science Laboratory.

    PubMed

    Litvak, M L; Mitrofanov, I G; Barmakov, Yu N; Behar, A; Bitulev, A; Bobrovnitsky, Yu; Bogolubov, E P; Boynton, W V; Bragin, S I; Churin, S; Grebennikov, A S; Konovalov, A; Kozyrev, A S; Kurdumov, I G; Krylov, A; Kuznetsov, Yu P; Malakhov, A V; Mokrousov, M I; Ryzhkov, V I; Sanin, A B; Shvetsov, V N; Smirnov, G A; Sholeninov, S; Timoshenko, G N; Tomilina, T M; Tuvakin, D V; Tretyakov, V I; Troshin, V S; Uvarov, V N; Varenikov, A; Vostrukhin, A

    2008-06-01

    We present a summary of the physical principles and design of the Dynamic Albedo of Neutrons (DAN) instrument onboard NASA's 2009 Mars Science Laboratory (MSL) mission. The DAN instrument will use the method of neutron-neutron activation analysis in a space application to study the abundance and depth distribution of water in the martian subsurface along the path of the MSL rover. PMID:18598140

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Radiation damage in silicon due to albedo neutrons emitted from hadronic beam dumps (Fe and U)

    SciTech Connect

    Gabriel, T.A.; Bishop, B.L.

    1987-01-01

    Calculations have been carried out to determine the level of radiation damage that can be expected from albedo neutrons when 1- and 5-GeV negative pions are incident on iron and uranium beam dumps. The calculated damage data are presented in several ways including neutron fluence above 0.111 MeV, 1 MeV equivalent neutron fluence, damage energy deposition, and DPA or displacements per atom. Details are presented as to the method of calculation. 14 refs., 1 fig., 1 tab.

  5. Observation of lunar neutron albedo along the 24th Solar cycle

    NASA Astrophysics Data System (ADS)

    Sanin, Anton; Mitrofanov, Igor; Litvak, Maxim; Bodnarik, Julia; Boynton, William; Chin, Gordon; Evans, Larry; Golovin, Dmitry; Harshman, Karl; Livengood, Timothy; Malakhov, Alexey; Mokrousov, Maxim; McClanahan, Timothy; Sagdeev, Roald; Starr, Richard; Vostrukhin, Andrey

    2015-04-01

    It is well known that the Sun is not a steady source of radiation and demonstrates quasi-periodic variations of its activity with an average period of 11 years. The variation in solar activity yields a number of important physical effects that impact the entire heliosphere. Some of these effects are important for human life, since variations of the solar wind and the interplanetary magnetic field in the Solar System may produce variations of geomagnetic field and Van Allen radiation belts. Moreover, after strong Solar Coronal Mass Ejection events global geomagnetic storms are possible. Solar variability generates a strong modulation of the Galactic Cosmic Ray (GCR) flux inside the heliosphere and results in a modulation of the neutron albedo of the Moon and other celestial bodies that lack a strong global magnetic field. Observations of the lunar neutron albedo and its variability are quite important for future human missions on the Moon since they provide an understanding of that radiation environment on the surface and in the subsurface. We have used the data of collimated and omnidirectional epithermal neutron detectors of the Lunar Exploration Neutron Detector (LEND) gathered from September 2009 up to present. This period covers the first half of the 24th Solar cycle from period of minimum solar activity with maximum lunar neutron albedo up to high solar activity and less neutron albedo. It was found that for the observed time period, the amplitude of neutron flux drops down by a factor of ~1.7 after a maximal values observed at December 2009. We have compared LEND measurements with ongoing observations of GCR variability by neutron detectors on-board other spacecraft orbiting around Earth (BTN/ISS) and Mars (HEND/Odyssey). All neutron instruments show similar global trends and local variations. It was found that HEND on Martian orbit has detected highest amplitude of neutron flux variations (~1.8 times) and the peak of neutron flux occurred by a couple of

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

    NASA Astrophysics Data System (ADS)

    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

  7. Fast Neutron Albedo Calculations for a Concrete Shield with Different Curvatures

    NASA Astrophysics Data System (ADS)

    Sayed Ahmed, F. M.; Salama, M.

    The O5R Monte Carlo neutron transport Code had been used to calculate the neutron albedo for neutrons reflected from plane and curved concrete shields. The present calculations were performed to investigate the fast-neutron albedo in case of ordinary concrete shield, in order to perform comparative studies with the case of neutron reflection against a flat wall. The calculations were performed for three different neutron source energies of 1 MeV, 5 MeV and 15 MeV and at neutron incident angles of 5°, 30°, 45°, 60° and 90° and for surfaces with different curvatures (flat, 100, 50, 20 and 5 cm).The results obtained reveal that there will be an appreciable error on using the flat wall albedo value in the case of duct penetration calculations. The error was assumed to be due to the neglection of the curvature effect as well as to the improper choice of the neutron incident angle.Translated AbstractAlbedoberechnungen für schnelle Neutronen an einem Betonschild unterschiedlicher KrümmungDas O5R Monte Carlo Neutronentransport-Programm wurde benutzt, um die Albedo für Neutronen, reflektiert von ebenen oder gekrümmten Betonschilden, zu berechnen. Diese Berechnungen für die Albedo schneller Neutronen an gewöhnlichen Betonschilden wurden zum Vergleich mit ähnlichen Untersuchungen der Neutronenreflektion an flachen Wänden angestellt. Es wird bei drei verschiedenen Neutronenquellenenergien, 1 MeV, 5 MeV, und 15 MeV, Einfallswinkeln von 5°, 30°, 45°, 60° und 90° sowie für verschieden gekrümmte Oberflächen (flach, 100, 50, 20 und 5 cm) gerechnet.Diese Ergebnisse zeigen, daß die Verwendung von Albedowerten an flachen Wänden für den Fall von Durchlaßkanälen zu beträchtlichen Fehlern führt. Sie können sowohl der Vernachlässigung der Krümmung als auch der Wahl falscher Einfallswinkel zugeschrieben werden.

  8. Dynamic Albedo of Neutrons (DAN) Experiment Onboard NASA's Mars Science Laboratory

    NASA Astrophysics Data System (ADS)

    Mitrofanov, I. G.; Litvak, M. L.; Varenikov, A. B.; Barmakov, Y. N.; Behar, A.; Bobrovnitsky, Y. I.; Bogolubov, E. P.; Boynton, W. V.; Harshman, K.; Kan, E.; Kozyrev, A. S.; Kuzmin, R. O.; Malakhov, A. V.; Mokrousov, M. I.; Ponomareva, S. N.; Ryzhkov, V. I.; Sanin, A. B.; Smirnov, G. A.; Shvetsov, V. N.; Timoshenko, G. N.; Tomilina, T. M.; Tret'yakov, V. I.; Vostrukhin, A. A.

    2012-09-01

    The description of Dynamic Albedo of Neutrons (DAN) experiment is presented, as a part of the NASA's Mars Science Laboratory mission onboard the mars rover Curiosity. The instrument DAN includes Pulsing Neutron Generator (PNG) producing pulses of 14.1 MeV neutrons for irradiation of subsurface material below the rover, and Detectors and Electronics (DE) unit, which operates the instrument itself and measures the die-away time profiles of epithermal and thermal neutrons following each neutron pulse. It is shown that the DAN investigation will measure a content of hydrogen along the path of the MSL rover, and it will also provide information about a depth distribution of hydrogen at 10-20 regions selected for the detailed studies and sampling analysis.

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

    PubMed

    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. PMID:21493603

  10. Analyzing of the Die Away Curve of the Msl Dynamic Albedo of Neutrons (dan) Instrument

    NASA Astrophysics Data System (ADS)

    Varenikov, A.; Jun, I.; Litvak, M. L.

    2012-12-01

    The Dynamic Albedo of Neutrons (DAN) is flown on board Mars Science Laboratory (MSL) to provide measurements of the dynamic albedo of thermal and epithermal neutrons induced by a pulse 14 MeV neutron generator. The DAN instrument consists of pulse neutron generator (DAN/PNG) electrically and logically combined with neutron detection system (DAN/DE). The major science objective of DAN instrument is to detect and provide quantitative estimates of the hydrogen content in the sub-surface layer of Mars. The amplitude and shape of the die-away time profile strongly depends on the content, depth and geometry distribution of water ice/bound layer. Die-away curves of thermal neutrons are simulated using a Monte Carlo transport code (MCNPX) for a homogeneous model of regolith with different contents of water. Tw different cases were considered in the initial simulations: single layered model and double layered model. In the first case, the sub-surface is modelled as a homogeneous single layer with different water contents. The preliminary results show that DAN could measure the water content as low as 0.1-0.2 weight %. The second case includes the sub-surface described by two layers. It is used to evaluate the DAN sensitivity to detect water depth (where the bottom layer is richer in water content than the upper layer).

  11. Neutron-Gamma-ray-coupled albedo Monte Carlo method streaming analysis

    SciTech Connect

    Yamauchi, M.; Kawai, M.; Seki, Y.

    1986-11-01

    The neutron-gamma-ray-coupled albedo Monte Carlo (AMC) method has been developed and implemented in MORSE-I. The energy- and angle-dependent differential albedo data, which include secondary gamma rays, are calculated for a slab layer with one dimensional transport theory. Fundamental formulas for this method are described. The applicability to shielding design of fusion reactors is confirmed by analyzing the radiation streaming experiment conducted at the Fusion Neutronics Source facility, Japan Atomic Energy Research Institute. The AMC method has reproduced well the experimental data of radiation dose rates and spectra with an accuracy of approximately 10%. It is shown that the AMC method is several times more efficient than the ordinary Monte Carlo calculation in obtaining data necessary for the design with expected accuracy.

  12. N-SAP and G-SAP neutron and gamma ray albedo model scatter shield analysis program

    NASA Technical Reports Server (NTRS)

    Sapovchak, B. J.; Stephenson, L. D.

    1967-01-01

    Computer program calculates neutron or gamma ray first order scattering from a plane or cylindrical surface to a detector point. The SAP Codes, G-SAP and N-SAP, constitute a multiple scatter albedo model shield analysis.

  13. Use of computer memory chips as the basis for a digital albedo neutron dosimeter.

    PubMed

    Davis, J L

    1985-08-01

    We have measured the sensitivity of commercially available dynamic random access memories (D-RAMs) to alpha particles. Using a beam of 14-meV neutrons and a 6LiF crystal as a converter we have measured sensitivities to neutron radiation as high as 9.25 memory errors per millirem. We estimate that an optimized converter would produce even higher sensitivities as an albedo dosimeter in realistic radiation fields. Such a device would have a number of operational advantages. PMID:4019197

  14. Neutron background environment measured by the Mars Science Laboratory's Dynamic Albedo of Neutrons instrument during the first 100 sols

    NASA Astrophysics Data System (ADS)

    Jun, I.; Mitrofanov, I.; Litvak, M. L.; Sanin, A. B.; Kim, W.; Behar, A.; Boynton, W. V.; DeFlores, L.; Fedosov, F.; Golovin, D.; Hardgrove, C.; Harshman, K.; Kozyrev, A. S.; Kuzmin, R. O.; Malakhov, A.; Mischna, M.; Moersch, J.; Mokrousov, M.; Nikiforov, S.; Shvetsov, V. N.; Tate, C.; Tret'yakov, V. I.; Vostrukhin, A.

    2013-11-01

    Dynamic Albedo of Neutrons (DAN) instrument on board Mars Science Laboratory has been operating successfully since the landing and has been making measurements regularly along Curiosity's traverse at the surface. DAN measures thermal (E < 0.4 eV) and epithermal neutrons (0.4 eV < E < ~1 keV) while operating in two different modes: active and passive. The active mode uses a pulsed neutron generator (PNG) to study the geological characteristics of the subsurface. In the passive mode, DAN measures the background neutron environment. This paper presents results of measurements in the passive mode from landing through to sol 100 and provides an interpretation of the data based on extensive Monte Carlo simulations. The main observations are summarized as follows: (1) the thermal neutron counts vary strongly along the rover traverse while the epithermal counts do not show much variation; (2) the neutrons from the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) are a larger contributor to the DAN passive data than the Galactic Cosmic Ray (GCR)-induced neutrons; (3) for the MMRTG neutrons, both the thermal and the epithermal counts increase as a function of the subsurface water content; (4) on the other hand, for the GCR-induced neutrons, the thermal counts increase but the epithermal counts decrease as a function of the subsurface water content; and (5) relative contributions by the MMRTG and GCR to the DAN thermal neutron counts at the Rocknest site, where the rover was stationed from sol 59 to sol 100, are estimated to be ~60% and ~40%, respectively.

  15. Personal neutron dosimetry in nuclear power plants using etched track and albedo thermoluminescence dosemeters.

    PubMed

    Fernández, F; Bakali, M; Amgarou, K; Nourreddine, A; Mouhssine, D

    2004-01-01

    Measurement of the personal dose equivalent rates for neutrons is a difficult task because available dosemeters do not provide the required energy response and sensitivity. Furthermore, the available wide calibration spectra recommended by the International Standard Organisation does not reproduce adequately the spectra encountered in practical situations of the nuclear industry. There is a real necessity to characterise the radiation field, in which workers can be exposed, and to calibrate personal dosemeters in order to determine the dose equivalent in these installations. For this reason, we measure the neutron spectrum with our Bonner sphere system and we fold this spectrum with energy-dependent fluence-to-dose conversion coefficients to obtain the reference dose equivalent rate. This reference value is then compared with the personal dosemeter reading to determine a field-specific correction factor. In this paper, we present the values of this field-specific correction factor for etched track and albedo thermoluminescence dosemeters at three measurement locations inside the containment building of the Vandellòs II nuclear power plant. We have found that assigning to each personal dosemeter the mean value of the field-specific correction factors of the three measurement locations, allows the evaluation of neutron personal dose equivalent rate with a relative uncertainty of approximately 25 and 15% for the PADC and albedo dosemeters, respectively. PMID:15353734

  16. Solar cosmic ray, solar wind, solar flare, and neutron albedo measurements, part C

    NASA Technical Reports Server (NTRS)

    Burnett, D.; Hohenberg, C.; Maurette, M.; Monnin, M.; Walker, R.; Wollum, D.

    1972-01-01

    All mineral detectors exposed on Apollo 16 had high surface track densities probably produced by a solar flare that occurred during the mission. The heavy ions followed a power law spectrum with exponent approximately 3 down to approximately 200 KeV/nucleon. The abundance of low-energy particle tracks observed in this flare may explain the high track densities observed in lunar dust grains. Pristine heavy-particle tracks in feldspar give long tracks. Shallow pits similar to those expected from extremely heavy solar wind ions were observed in about the expected number. Initial results give a low apparent value of neutron albedo relative to theory.

  17. Remote sensing albedo product validation over heterogenicity surface based on WSN: preliminary results and its uncertainty

    NASA Astrophysics Data System (ADS)

    Wu, Xiaodan; Wen, Jianguang; Xiao, Qing; Peng, Jingjing; Liu, Qiang; Dou, Baocheng; Tang, Yong; Li, Xiuhong

    2014-11-01

    The evaluation of uncertainty in satellite-derived albedo products is critical to ensure their accuracy, stability and consistency for studying climate change. In this study, we assess the Moderate-resolution Imaging Spectroradiometer(MODIS) albedo 8 day standard product MOD43B3 using the ground-based albedometer measurement based on the wireless sensor network (WSN) technology. The experiment have been performed in Huailai, Hubei province. A 1.5 km*2 km area are selected as study region, which locates between 115.78° E-115.80° E and 40.35° N-40.37° N. This area is characterized by its distinct landscapes: bare ground between January and April, corn from May to Octorber. That is, this area is relatively homegeneous from January to Octorber, but in Novermber and December, the surface is very heterogeneous because of straw burning, as well as snow fall and snow melting. It is a big challenge to validate the MODIS albedo products because of the vast difference in spatial resolution between ground measurement and satellite measurement. Here, we use the HJ albedo products as the bridge that link the ground measurement with satellite data. Firstly, we analyses the spatial representativeness of the WSN site under green-up, dormant and snow covered situations to decide whether direct comparison between ground-based measurement and MODIS albedo can be made. The semivariogram is used here to describe the ground hetergeneity around the WSN site. In addition, the bias between the average albedo of the certain neighborhood centered at the WSN site and the center pixel albedo is also calculated.Then we compare the MOD43B3 value with the ground-based value. Result shows that MOD43B3 agree with in situ well during the growing season, however, there are relatively large difference between ground albedos and MCD43B3 albedos during dormant and snow-coverd periods.

  18. Ten years of personal neutron dosimetry with albedo dosemeters in The Netherlands.

    PubMed

    Draaisma, F S; Verhagen, H W

    2002-01-01

    Since 1987, the dosimetry service of the Netherlands Energy Research Foundation (ECN) has been certified by the Dutch government to perform personal dosimetry, using thermoluminescence dosemeters (TLDs). Performing neutron personal dosimetry requires a rather large investment in readers, TLDs and personnel to operate the service. About 800 persons are subjected to routine neutron monitoring in The Netherlands and their annual neutron doses are a relatively small fraction (less than 10%) of the annual Hp(10). In general, the measured neutron dose values are low (on average 93% of the users receive an annual neutron dose <0.2 mSv). The collective annual (neutron) dose has tended to decrease since 1992, but incidentally high doses have been observed. Leaving these incidents out, the average collective annual neutron doses for the different users of neutron sources are about the same. PMID:12382755

  19. Predicting fissile content of spent nuclear fuel assemblies with the passive neutron Albedo reactivity technique and Monte Carlo code emulation

    SciTech Connect

    Conlin, Jeremy Lloyd; Tobin, Stephen J

    2010-10-13

    There is a great need in the safeguards community to be able to nondestructively quantify the mass of plutonium of a spent nuclear fuel assembly. As part of the Next Generation of Safeguards Initiative, we are investigating several techniques, or detector systems, which, when integrated, will be capable of quantifying the plutonium mass of a spent fuel assembly without dismantling the assembly. This paper reports on the simulation of one of these techniques, the Passive Neutron Albedo Reactivity with Fission Chambers (PNAR-FC) system. The response of this system over a wide range of spent fuel assemblies with different burnup, initial enrichment, and cooling time characteristics is shown. A Monte Carlo method of using these modeled results to estimate the fissile content of a spent fuel assembly has been developed. A few numerical simulations of using this method are shown. Finally, additional developments still needed and being worked on are discussed.

  20. Numerical Simulation of the MSL Dynamic Albedo of Neutrons (DAN) Instrument

    NASA Astrophysics Data System (ADS)

    Jun, I.; Mitrofanov, I.; Litvak, M.; Varenikov, A.

    2012-12-01

    The DAN instrument on the Mars Science Laboratory (MSL) has been tasked with detecting enhanced level of hydrogen content in the Martian subsurface. DAN accomplishes this goal by irradiating pulses of 14 MeV neutrons to the subsurface below the rover and by measuring the die-away time profiles of epi-thermal and thermal neutrons from the subsurface. Increased levels of thermal neutron are highly indicative of the presence of hydrogen (and thus water) in the soil. However, there are many factors that influence the thermalization process as well. To better understand the significance of these factors, we used the Monte Carlo N-Particle Extended (MCNPX) code to investigate numerous difference cases simulating conditions on the Martian surface that may affect the characteristics of die away curves. The results provide an insight into the varying impacts of factors such as water content in the soil, soil depth, soil density, temperature, soil elemental composition, and rover internal structure on the level of thermal neutrons, and ultimately better equip us to interpret real data from MSL. We will present some of the numerical simulation results performed on these factors, especially the effect of the mass distribution within the rover on the time profiles of thermal and epi-thermal neutron die-away curves. We also plan to show initial DAN measurement data obtained from a few months' of operation on the mars surface at the time of the conference.

  1. Simulated Performance of the Integrated Passive Neutron Albedo Reactivity and Self-Interrogation Neutron Resonance Densitometry Detector Designed for Spent Fuel Measurement at the Fugen Reactor in Japan

    SciTech Connect

    Ulrich, Timothy J. II; Lafleur, Adrienne M.; Menlove, Howard O.; Swinhoe, Martyn T.; Tobin, Stephen J.; Seya, Michio; Bolind, Alan M.

    2012-07-16

    An integrated nondestructive assay instrument, which combined the Passive Neutron Albedo Reactivity (PNAR) and the Self-Interrogation Neutron Resonance Densitometry (SINRD) techniques, is the research focus for a collaborative effort between Los Alamos National Laboratory (LANL) and the Japanese Atomic Energy Agency as part of the Next Generation Safeguard Initiative. We will quantify the anticipated performance of this experimental system in two physical environments: (1) At LANL we will measure fresh Low Enriched Uranium (LEU) assemblies for which the average enrichment can be varied from 0.2% to 3.2% and for which Gd laced rods will be included. (2) At Fugen we will measure spent Mixed Oxide (MOX-B) and LEU spent fuel assemblies from the heavy water moderated Fugen reactor. The MOX-B assemblies will vary in burnup from {approx}3 GWd/tHM to {approx}20 GWd/tHM while the LEU assemblies ({approx}1.9% initial enrichment) will vary from {approx}2 GWd/tHM to {approx}7 GWd/tHM. The estimated count rates will be calculated using MCNPX. These preliminary results will help the finalization of the hardware design and also serve a guide for the experiment. The hardware of the detector is expected to be fabricated in 2012 with measurements expected to take place in 2012 and 2013. This work is supported by the Next Generation Safeguards Initiative, Office of Nuclear Safeguards and Security, National Nuclear Security Administration.

  2. Cadmium Subtraction Method for the Active Albedo Neutron Interrogation of Uranium

    SciTech Connect

    Worrall, Louise G.; Croft, Stephen

    2015-02-01

    This report describes work performed under the Next Generation Safeguards Initiative (NGSI) Cadmium Subtraction Project. The project objective was to explore the difference between the traditional cadmium (Cd) ratio signature and a proposed alternative Cd subtraction (or Cd difference) approach. The thinking behind the project was that a Cd subtraction method would provide a more direct measure of multiplication than the existing Cd ratio method. At the same time, it would be relatively insensitive to changes in neutron detection efficiency when properly calibrated. This is the first published experimental comparison and evaluation of the Cd ratio and Cd subtraction methods.

  3. MCNP SIMULATION OF THE HP(10) ENERGY RESPONSE OF A BRAZILIAN TLD ALBEDO NEUTRON INDIVIDUAL DOSEMETER, FROM THERMAL TO 20 MeV.

    PubMed

    Freitas, B M; Martins, M M; Pereira, W W; da Silva, A X; Mauricio, C L P

    2016-09-01

    The Brazilian Instituto de Radioproteção e Dosimetria (IRD) runs a neutron individual monitoring system with a home-made TLD albedo dosemeter. It has already been characterised and calibrated in some reference fields. However, the complete energy response of this dosemeter is not known, and the calibration factors for all monitored workplace neutron fields are difficult to be obtained experimentally. Therefore, to overcome such difficulties, Monte Carlo simulations have been used. This paper describes the simulation of the HP(10) neutron response of the IRD TLD albedo dosemeter using the MCNPX transport code, for energies from thermal to 20 MeV. The validation of the MCNPX modelling is done comparing the simulated results with the experimental measurements for ISO standard neutron fields of (241)Am-Be, (252)Cf, (241)Am-B and (252)Cf(D2O) and also for (241)Am-Be source moderated with paraffin and silicone. Bare (252)Cf are used for normalisation. PMID:26276807

  4. Satellite Remote Sensing of Snow/Ice Albedo over the Himalayas

    NASA Technical Reports Server (NTRS)

    Hsu, N. Christina; Gautam, Ritesh

    2012-01-01

    The Himalayan glaciers and snowpacks play an important role in the hydrological cycle over Asia. The seasonal snow melt from the Himalayan glaciers and snowpacks is one of the key elements to the livelihood of the downstream densely populated regions of South Asia. During the pre-monsoon season (April-May-June), South Asia not only experiences the reversal of the regional meridional tropospheric temperature gradient (i.e., the onset of the summer monsoon), but also is being bombarded by dry westerly airmass that transports mineral dust from various Southwest Asian desert and arid regions into the Indo-Gangetic Plains in northern India. Mixed with heavy anthropogenic pollution, mineral dust constitutes the bulk of regional aerosol loading and forms an extensive and vertically extended brown haze lapping against the southern slopes of the Himalayas. Episodic dust plumes are advected over the Himalayas, and are discernible in satellite imagery, resulting in dust-capped snow surface. Motivated by the potential implications of accelerated snowmelt, we examine the changes in radiative energetics induced by aerosol transport over the Himalayan snow cover by utilizing space borne observations. Our objective lies in the investigation of potential impacts of aerosol solar absorption on the Top-of-Atmosphere (TOA) spectral reflectivity and the broadband albedo, and hence the accelerated snowmelt, particularly in the western Himalayas. Lambertian Equivalent Reflectivity (LER) in the visible and near-infrared wavelengths, derived from Moderate Resolution Imaging Spectroradiometer radiances, is used to generate statistics for determining perturbation caused due to dust layer over snow surface in over ten years of continuous observations. Case studies indicate significant reduction of LER ranging from 5 to 8% in the 412-860nm spectra. Broadband flux observations, from the Clouds and the Earth's Radiant Energy System, are also used to investigate changes in shortwave TOA flux over

  5. Determining fissile content in PWR spent fuel assemblies using a passive neutron Albedo reactivity with fission chambers technique

    SciTech Connect

    Conlin, Jeremy Lloyd; Tobin, Stephen J

    2010-01-01

    State regulatory bodies and organizations such as the IAEA that are concerned with preventing the proliferation of nuclear weapons are interested in a means of quantifying the amount of plutonium in a given spent fuel assembly. The complexity of spent nuclear fuel makes the measurement of plutonium content challenging. There are a variety of techniques that can measure various properties of spent nuclear fuel including burnup, and mass of fissile content. No single technique can provide all desired information, necessitating an approach using multiple detector systems and types. This paper presents our analysis of the Passive Neutron Albedo Reactivity Fission Chamber (PNAR-FC) detector system. PNAR-FC is a simplified version of the PNAR technique originally developed in 1997. This earlier research was performed with a high efficiency, {sup 3}He-based system (PNAR-3He) with which multiplicty analysis was performed. With the PNAR technique a portion of the spent fuel assembly is wrapped in a 1 mm thick cadmium liner. Neutron count rates are measured both with and without the cadmium liner present. The ratio of the count rate with the cadmium liner to the count rate without the cadmium liner is calculated and called the cadmium ratio. In the PNAR-3He technique, multiplicity measurements were made and the cadmium ratio was shown to scale with the fissile content of the material being measured. PNAR-FC simplifies the PNAR technique by using only a few fission chambers instead of many {sup 3}He tubes. Using a simplified PNAR-FC technique provides for a cheaper, lighter, and thus more portable detector system than was possible with the PNAR-3He system. The challenge with the PNAR-FC system are two-fold: (1) the change in the cadmium ratio is weaker as a afunction of the changing fissile content relative to multiplicity count rates, and (2) the efficiency for the fission chamber based system are poorer than for the {sup 3}He based detectors. In this paper, we present our

  6. Development of a Neutron Spectroscopic System Utilizing Compressed Sensing Measurements

    NASA Astrophysics Data System (ADS)

    Vargas, Danilo; Cable Kurwitz, R.; Carron, Igor; DePriest, K. Russell

    2016-02-01

    A new approach to neutron detection capable of gathering spectroscopic information has been demonstrated. The approach relies on an asymmetrical arrangement of materials, geometry, and an ability to change the orientation of the detector with respect to the neutron field. Measurements are used to unfold the energy characteristics of the neutron field using a new theoretical framework of compressed sensing. Recent theoretical results show that the number of multiplexed samples can be lower than the full number of traditional samples while providing the ability to have some super-resolution. Furthermore, the solution approach does not require a priori information or inclusion of physics models. Utilizing the MCNP code, a number of candidate detector geometries and materials were modeled. Simulations were carried out for a number of neutron energies and distributions with preselected orientations for the detector. The resulting matrix (A) consists of n rows associated with orientation and m columns associated with energy and distribution where n < m. The library of known responses is used for new measurements Y (n × 1) and the solver is able to determine the system, Y = Ax where x is a sparse vector. Therefore, energy spectrum measurements are a combination of the energy distribution information of the identified elements of A. This approach allows for determination of neutron spectroscopic information using a single detector system with analog multiplexing. The analog multiplexing allows the use of a compressed sensing solution similar to approaches used in other areas of imaging. A single detector assembly provides improved flexibility and is expected to reduce uncertainty associated with current neutron spectroscopy measurement.

  7. Analysis of neutron and photon response of a TLD-ALBEDO personal dosemeter on an ISO slab phantom using TRIPOLI-4.3 Monte Carlo code.

    PubMed

    Lee, Y K

    2005-01-01

    TRIPOLI-4.3 Monte Carlo transport code has been used to evaluate the QUADOS (Quality Assurance of Computational Tools for Dosimetry) problem P4, neutron and photon response of an albedo-type thermoluminescence personal dosemeter (TLD) located on an ISO slab phantom. Two enriched 6LiF and two 7LiF TLD chips were used and they were protected, in front or behind, with a boron-loaded dosemeter-holder. Neutron response of the four chips was determined by counting 6Li(n,t)4He events using ENDF/B-VI.4 library and photon response by estimating absorbed dose (MeV g(-1)). Ten neutron energies from thermal to 20 MeV and six photon energies from 33 keV to 1.25 MeV were used to study the energy dependence. The fraction of the neutron and photon response owing to phantom backscatter has also been investigated. Detailed TRIPOLI-4.3 solutions are presented and compared with MCNP-4C calculations. PMID:16381740

  8. Comparative sensitivity study and reading correction of various albedo dosimeters in neutron fields on the U-400M accelerator

    NASA Astrophysics Data System (ADS)

    Mokrov, Yu. V.; Morozov, S. V.; Shchegolev, V. Yu.

    2013-03-01

    The sensitivities of three types of albedo dosimeters are experimentally studied in U-400M accelerator radiation fields in the experimental hall (one point) and behind its shielding (three points). It is shown that the ratios of the sensitivity of the albedo dosimeter (AD) and the combined personal dosimeter (CPD) used earlier at the Joint Institute for Nuclear Research (JINR) to the sensitivity of the DVGN-01 dosimeter are constant within 25%. This allows the AD and CPD sensitivities obtained earlier at the JINR facilities to be used for correcting readings of the DVGN-01 now used at JINR for personal radiation monitoring. Correction coefficients are found for DVGN-01 readings behind the U-400M shielding. This has allowed a more reliable correction coefficient to be established for the Flerov Laboratory of Nuclear Reactions (FLNR).

  9. Determination of the ground albedo and the index of absorption of atmospheric particulates by remote sensing. II - Application

    NASA Technical Reports Server (NTRS)

    King, M. D.

    1979-01-01

    A hemispherical radiometer has been used to obtain spectrally narrow-band measurements of the downward hemispheric diffuse and total (global) flux densities at varying solar zenith angles on 14 days over Tucson. Data are presented which illustrate the effects of temporally varying atmospheric conditions as well as clear stable conditions on the ratio of the diffuse to direct solar radiation at the earth's surface. The ground albedo and the effective imaginary term of the complex refractive index of atmospheric particulates are derived from the diffuse-direct ratio measurements on seven clear stable days at two wavelengths using the statistical procedure described by King and Herman (1979). Results indicate that the downwelling diffuse radiation field in the midvisible region in Tucson can be adequately described by Mie scattering theory if the ground albedo is 0.279 + or - 0.100 and the index of absorption is 0.0306 + or - 0.0082.

  10. Determination of the ground albedo and the index of absorption of atmospheric particulates by remote sensing. I - Theory

    NASA Technical Reports Server (NTRS)

    King, M. D.; Herman, B. M.

    1979-01-01

    A statistical technique is developed for inferring the optimum values of the ground albedo and the effective imaginary term of the complex refractive index of atmospheric particulates. The procedure compares measurements of the ratio of the hemispheric diffuse to directly transmitted solar flux density at the earth's surface with radiative transfer computations of the same as suggested by Herman et al. (1975). A detailed study is presented which shows the extent to which the ratio of diffuse to direct solar radiation is sensitive to many of the radiative transfer parameters. Results indicate that the optical depth and size distribution of atmospheric aerosol particles are the two parameters which uniquely specify the radiation field to the point where ground albedo and index of absorption can be inferred. Varying the real part of the complex refractive index of atmospheric particulates as well as their vertical distribution is found to have a negligible effect on the diffuse-direct ratio. The statistical procedure utilizes a semi-analytic gradient search method from least-squares theory and includes a detailed error analysis.

  11. Water equivalent hydrogen estimates from the first 200 sols of Curiosity's traverse (Bradbury Landing to Yellowknife Bay): Results from the Dynamic Albedo of Neutrons (DAN) passive mode experiment

    NASA Astrophysics Data System (ADS)

    Tate, C. G.; Moersch, J.; Jun, I.; Ming, D. W.; Mitrofanov, I.; Litvak, M.; Behar, A.; Boynton, W. V.; Deflores, L.; Drake, D.; Ehresmann, B.; Fedosov, F.; Golovin, D.; Hardgrove, C.; Harshman, K.; Hassler, D. M.; Kozyrev, A. S.; Kuzmin, R.; Lisov, D.; Malakhov, A.; Milliken, R.; Mischna, M.; Mokrousov, M.; Nikiforov, S.; Sanin, A. B.; Starr, R.; Varenikov, A.; Vostrukhin, A.; Zeitlin, C.

    2015-12-01

    The Dynamic Albedo of Neutrons (DAN) experiment on the Mars Science Laboratory (MSL) rover Curiosity is designed to detect neutrons to determine hydrogen abundance within the subsurface of Mars (Mitrofanov, I.G. et al. [2012]. Space Sci. Rev. 170, 559-582. http://dx.doi.org/10.1007/s11214-012-9924-y; Litvak, M.L. et al. [2008]. Astrobiology 8, 605-613. http://dx.doi.org/10.1089/ast.2007.0157). While DAN has a pulsed neutron generator for active measurements, in passive mode it only measures the leakage spectrum of neutrons produced by the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) and Galactic Cosmic Rays (GCR). DAN passive measurements provide better spatial coverage than the active measurements because they can be acquired while the rover is moving. Here we compare DAN passive-mode data to models of the instrument's response to compositional differences in a homogeneous regolith in order to estimate the water equivalent hydrogen (WEH) content along the first 200 sols of Curiosity's traverse in Gale Crater, Mars. WEH content is shown to vary greatly along the traverse. These estimates range from 0.5 ± 0.1 wt.% to 3.9 ± 0.2 wt.% for fixed locations (usually overnight stops) investigated by the rover and 0.6 ± 0.2 wt.% to 7.6 ± 1.3 wt.% for areas that the rover has traversed while continuously acquiring DAN passive data between fixed locations. Estimates of WEH abundances at fixed locations based on passive mode data are in broad agreement with those estimated at the same locations using active mode data. Localized (meter-scale) anomalies in estimated WEH values from traverse measurements have no particular surface expression observable in co-located images. However at a much larger scale, the hummocky plains and bedded fractured units are shown to be distinct compositional units based on the hydrogen content derived from DAN passive measurements. DAN passive WEH estimates are also shown to be consistent with geologic models inferred from other

  12. Nuclear cascades in Saturn's rings - Cosmic ray albedo neutron decay and origins of trapped protons in the inner magnetosphere

    NASA Technical Reports Server (NTRS)

    Cooper, J. F.

    1983-01-01

    The nearly equatorial trajectory of the Pioneer 11 spacecraft through Saturn's high energy proton radiation belts and under the main A-B-C rings provided a unique opportunity to study the radial dependence of the greater than 30 MeV proton intensities in the belts in terms of models for secondary nucleon production by cosmic ray interactions in the rings, in situ proton injection in the radiation belts by neutron beta decay, magnetospheric diffusion, and absorption by planetary rings and satellites. Maximum trapped proton intensities measured by Pioneer 11 in the radiation belts are compared with calculated intensities and found consistent with trapping times of roughly 40 years and a radial diffusion coefficient of about 10 to the -15th L to the 9th R sub s squared/s. Differential energy spectra proportional to E to the -2 estimated from integral measurements of trapped photons with E greater than 100 MeV are consistent with the beta decay model, but an inferred turndown of the spectra toward lower energies and reported integral proton anisotropies of a specified form both indicate the need for more realistic calculations of the neutron source from the rings and the radiation belt loss processes.

  13. Neutron Background Measurements by the the MSL Dynamic Albedo of Neutrons (DAN) Instrument during the First 360 sols of the Surface Operation at Mars

    NASA Astrophysics Data System (ADS)

    Jun, I.; Mitrofanov, I. G.; litvak, M. L.; Sanin, A.; Behar, A.; Boynton, W. V.; DeFlores, L.; Golovin, D.; Hardgrove, C. J.; Harshman, K.; Kozyrev, A.; Kuzmin, R.; Malakhov, A.; Mischna, M. A.; Moersch, J.; Mokrousov, M.; Nikiforov, S.; Shvetsov, V.; Tate, C.; Vostrukhin, A.; Team, M.

    2013-12-01

    Since first commissioned on sol 3 after landing in August 2012, DAN has been operating successfully and provided a wealth of surface measurement data both in Active mode and in Passive mode operations. Active mode measurements provide a means to determine the characteristics of subsurface in terms of layering structure, content of water equivalent hydrogen (WEH), and/or content of chlorine. Passive mode measurements provide a general background level of low energy (< ~1 keV) neutrons induced by Galactic Cosmic Ray (GCR) interactions with the Martian atmosphere and the surface material and from Multi Mission Radioisotope Thermonuclear Generator (MMRTG). Passive mode measurements have been done on almost every sols with durations ranging from 1 hour to ~9 hour, covering different times of a day. Extensive numerical simulations have been carried out to aid in interpreting the DAN passive data. Both surface operation and numerical simulations show that the passive data correlate very well with the active data. It was also found that the passive data alone could provide a general trend of WEH content variation along the rover traverse. A methodology to estimate the respective contribution from each source (i.e., MMRTG neutrons and GCR-induced neutrons) for the passive data has been developed and was used to understand the neutron background environment at the Rocknest site, where the rover stayed over an extended period of time (from sol 59 to sol 100). The result shows that the MMRTG contribution to the DAN passive counts was about 60% of the total, and the GCR-induced counts were estimated to be about 40%. Details of all these observations, modeling effort, and analysis and interpretation processes will be presented in the final paper by using the passive data collected through sol 360.

  14. Calibration approaches of cosmic-ray neutron sensing for soil moisture measurement in cropped fields

    NASA Astrophysics Data System (ADS)

    Rivera Villarreyes, C. A.; Baroni, G.; Oswald, S. E.

    2013-04-01

    Measurement of soil moisture at the plot or hill-slope scale is an important link between local vadose-zone hydrology and catchment hydrology. This study evaluates the applicability of the cosmic-ray neutron sensing for soil moisture in cropped fields. Measurements of cosmic-ray neutrons (fast neutrons) were performed at a lowland farmland in Bornim (Brandenburg, Germany) cropped with sunflower and winter rye. Three field calibration approaches and four different ways of integration the soil moisture profile to an integral value for cosmic-ray neutron sensing were evaluated in this study. The cosmic-ray sensing (CRS) probe was calibrated against a network of classical point-scale soil moisture measurements. A large CRS parameter variability was observed by choosing calibration periods within the different growing stages of sunflower and winter rye. Therefore, it was not possible to identify a single set of parameters perfectly estimating soil moisture for both sunflower and winter rye periods. On the other hand, CRS signal and its parameter variability could be understood by some crop characteristics and by predicting the attenuated neutrons by crop presence. This study proves the potentiality of the cosmic-ray neutron sensing at the field scale; however, its calibration needs to be adapted for seasonal vegetation in cropped fields.

  15. In what sense a neutron star-black hole binary is the holy grail for testing gravity?

    SciTech Connect

    Bagchi, Manjari; Torres, Diego F. E-mail: dtorres@ieec.uab.es

    2014-08-01

    Pulsars in binary systems have been very successful to test the validity of general relativity in the strong field regime [1-4]. So far, such binaries include neutron star-white dwarf (NS-WD) and neutron star-neutron star (NS-NS) systems. It is commonly believed that a neutron star-black hole (NS-BH) binary will be much superior for this purpose. But in what sense is this true? Does it apply to all possible deviations?.

  16. Albedo in the ATIC Experiment

    NASA Technical Reports Server (NTRS)

    Sokolskaya, N. V.; Adams, J. H., Jr.; Ahn, H. S.; Bashindzhagyan, G. L.; Batkov, K. E.; Case, G.; Christl, M.; Chang, J.; Fazely, A. R.; Ganel, O.; Six, N. Frank (Technical Monitor)

    2002-01-01

    ATIC(Advanced Thin Ionization Calorimeter) is a balloon borne experiment designed to measure the cosmic ray composition for elements from hydrogen to iron and their energy spectra from approx.50 GeV to near 100 TeV. It consists of a Si-matrix detector to determine the charge of a CR particle, a scintillator hodoscope for tracking, carbon interaction targets and a fully active BGO calorimeter. ATIC had its first 16-day flight from McMurdo, Antarctica from 28/12/2000 to 13/01/2000. The ATIC flight collected approximately 25 million events. To measure charge of primary particle in presence of radiation scattered back from the interaction and subsequent shower development in the calorimeter a charge detector must be a mosaic of small detector pads so that the pad containing the signal from the incident particle has no additional signal from albedo particles. Therefore the silicon matrix was built of 4480 individual silicon pads each 2 cm x 1.5 cm. The matrix consists of four planes of detectors and the active detector area, in these planes are partially overlapped to completely cover the aperture. The lateral and amplitude distributions of albedo signals in Si-matrix are analyzed for different primary nuclei and different energy deposits in BGO calorimeter. The greater part of albedo signals has Q near 1, where Q = square root of Amplitude(MIP). The albedo distribution exponentially decreases up to Q near 8. These high values are produced by slow protons and plans. There are also a small number of signals of Q > 8, mainly for heavy nucleus primaries. These signals are apparently generated by neutrons. The comparison of the experimental data and simulations with GEANT 3-21 code using QGSM generator for nucleus-nucleus interactions is presented.

  17. Earth's Reflection: Albedo

    ERIC Educational Resources Information Center

    Gillette, Brandon; Hamilton, Cheri

    2011-01-01

    When viewing objects of different colors, you might notice that some appear brighter than others. This is because light is reflected differently from various surfaces, depending on their physical properties. The word "albedo" is used to describe how reflective a surface is. The Earth-atmosphere has a combined albedo of about 30%, a number that is…

  18. Albedos. Final report

    SciTech Connect

    Hansen, F.V.

    1993-07-01

    The albedo of the earth's surface varies dramatically from values of about 3 to 4 percent for calm bodies of water up to about 55 percent for gypsum sands. This rather broad range of reflected incoming solar radiation presents difficulties when attempting to define an average albedo for terrain over a large region from locally determined values. The patchwork, or checkerboard, appearance of the earth's surface as viewed from above is the result of various human activities, such as agriculture, the proliferation of urban sprawl, and road building. Each of these variable appearing surfaces will have individual albedos, rendering any attempt to determine an a real albedo almost an impossibility on the mesoscale. However, a vast data base exists for microscale applications for individual acreages, for example. A compilation of these data is presented.... Albedo, Solar radiation, Crops, Urban areas, Land uses.

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

    NASA Technical Reports Server (NTRS)

    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.

  20. Observations of Surfzone Albedo

    NASA Astrophysics Data System (ADS)

    Sinnett, G.; Feddersen, F.

    2014-12-01

    The surfzone environment (where waves break) contains several unique and previously unconsidered processes that affect the heat budget. Entering short-wave radiation is a dominant term in both shelf and surfzone heat budgets. In contrast to the shelf, however, depth limited wave breaking in the surfzone generates spray, whitewater and suspended sediments, elevating the surface albedo (ratio of reflected to incident short-wave radiation). Elevated albedo reduces the level of solar short-wave radiation entering the water, potentially resulting in less heating. Additionally, surfzone water quality is often impacted by fecal bacteria contamination. As bacteria mortality is related to short-wave solar radiation, elevated surfzone albedo could reduce pathogen mortality, impacting human health. Albedo in the open ocean has been frequently studied and parameterizations often consider solar zenith angle, wind speed and ocean chlorophyll concentration, producing albedo values typically near 0.06. However, surfzone albedo observations have been extremely sparse, yet show depth limited wave breaking may increase the albedo by nearly a factor of 10 up to 0.5. Here, we present findings from a field study at the Scripps Institution of Oceanography pier to observe the affect of waves on surfzone albedo. Concurrent measurements were taken with a four-way radiometer (to measure both downwelling and upwelling short-wave and long wave radiation) mounted above the surfzone. A co-located GoPro camera was used to relate visual aspects of the surfzone to measured reflectance, and wave height and period were observed with a bottom mounted pressure sensor in 5 m water depth just outside the surfzone. Wind speed and direction were observed on the pier 10 m above the water surface. Here, we will examine the surfzone albedo dependence on surfzone parameters, such as wave height.

  1. Greenland Glacier Albedo Variability

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The program for Arctic Regional Climate Assessment (PARCA) is a NASA-funded project with the prime goal of addressing the mass balance of the Greenland ice sheet. Since the formal initiation of the program in 1995, there has been a significant improvement in the estimates of the mass balance of the ice sheet. Results from this program reveal that the high-elevation regions of the ice sheet are approximately in balance, but the margins are thinning. Laser surveys reveal significant thinning along 70 percent of the ice sheet periphery below 2000 m elevations, and in at least one outlet glacier, Kangerdlugssuaq in southeast Greenland, thinning has been as much as 10 m/yr. This study examines the albedo variability in four outlet glaciers to help separate out the relative contributions of surface melting versus ice dynamics to the recent mass balance changes. Analysis of AVHRR Polar Pathfinder albedo shows that at the Petermann and Jakobshavn glaciers, there has been a negative trend in albedo at the glacier terminus from 1981 to 2000, whereas the Stor+strommen and Kangerdlugssuaq glaciers show slightly positive trends in albedo. These findings are consistent with recent observations of melt extent from passive microwave data which show more melt on the western side of Greenland and slightly less on the eastern side. Significance of albedo trends will depend on where and when the albedo changes occur. Since the majority of surface melt occurs in the shallow sloping western margin of the ice sheet where the shortwave radiation dominates the energy balance in summer (e.g. Jakobshavn region) this region will be more sensitive to changes in albedo than in regions where this is not the case. Near the Jakobshavn glacier, even larger changes in albedo have been observed, with decreases as much as 20 percent per decade.

  2. Deriving surface albedo measurements from narrow band satellite data

    NASA Technical Reports Server (NTRS)

    Brest, Christopher L.; Goward, Samuel N.

    1987-01-01

    A target calibration procedure for obtaining surface albedo from satellite data is presented. The methodology addresses two key issues, the calibration of remotely-sensed, discrete wavelength, digital data and the derivation of an albedo measurement (defined over the solar short wave spectrum) from spectrally limited observations. Twenty-seven Landsat observations, calibrated with urban targets (building roof-tops and parking lots), are used to derive spatial and seasonal patterns of surface reflectance and albedo for four land cover types: city, suburb, farm and forest.

  3. Charred Forests Increase Snow Albedo Decay: Watershed-Scale Implications of the Postfire Snow Albedo Effect

    NASA Astrophysics Data System (ADS)

    Gleason, K. E.; Nolin, A. W.

    2014-12-01

    Recent work shows that after a high severity forest fire, approximately 60% more solar radiation reaches the snow surface due to the reduction in canopy density. Also, significant amounts of black carbon (BC) particles and larger burned woody debris (BWD) are shed from standing charred trees, which concentrate on the snowpack, darken its surface, and reduce snow albedo by 50% during ablation. The postfire forest environment drives a substantial increase in net shortwave radiation at the snowpack surface, driving earlier and more rapid melt, however hydrologic models do not explicitly incorporate forest fire disturbance effects to snowpack dynamics. In this study we characterized, parameterized, and validated the postfire snow albedo effect: how the deposition and concentration of charred forest debris decreases snow albedo, increases snow albedo decay rates, and drives an earlier date of snow disappearance. For three study sites in the Oregon High Cascade Mountains, a 2-yr old burned forest, a 10-yr burned forest, and a nearby unburned forest, we used a suite of empirical data to characterize the magnitude and duration of the postfire effect to snow albedo decay. For WY 2012, WY2013, and WY2014 we conducted spectral albedo measurements, snow surface sampling, in-situ snow and meteorological monitoring, and snow energy balance modeling. From these data we developed a new parameterization which represents the postfire effect to snow albedo decay as a function of days-since-snowfall. We validated our parameterization using a physically-based, spatially-distributed snow accumulation and melt model, in-situ snow monitoring, net snowpack radiation, and remote sensing data. We modeled snow dynamics across the extent of all burned area in the headwaters of the McKenzie River Basin and validated the watershed-scale implications of the postfire snow albedo effect using in-situ micrometeorological and remote sensing data. This research quantified the watershed scale postfire

  4. Assessment of soil moisture dynamics on an irrigated maize field using cosmic ray neutron sensing

    NASA Astrophysics Data System (ADS)

    Scheiffele, Lena Maria; Baroni, Gabriele; Oswald, Sascha E.

    2015-04-01

    In recent years cosmic ray neutron sensing (CRS) developed as a valuable, indirect and non-invasive method to estimate soil moisture at a scale of tens of hectares, covering the gap between point scale measurements and large scale remote sensing techniques. The method is particularly promising in cropped and irrigated fields where invasive installation of belowground measurement devices could conflict with the agricultural management. However, CRS is affected by all hydrogen pools in the measurement footprint and a fast growing biomass provides some challenges for the interpretation of the signal and application of the method for detecting soil moisture. For this aim, in this study a cosmic ray probe was installed on a field near Braunschweig (Germany) during one maize growing season (2014). The field was irrigated in stripes of 50 m width using sprinkler devices for a total of seven events. Three soil sampling campaigns were conducted throughout the growing season to assess the effect of different hydrogen pools on calibration results. Additionally, leaf area index and biomass measurements were collected to provide the relative contribution of the biomass on the CRS signal. Calibration results obtained with the different soil sampling campaigns showed some discrepancy well correlated with the biomass growth. However, after the calibration function was adjusted to account also for lattice water and soil organic carbon, thus representing an equivalent water content of the soil, the differences decreased. Soil moisture estimated with CRS responded well to precipitation and irrigation events, confirming also the effective footprint of the method (i.e., radius 300 m) and showing occurring water stress for the crop. Thus, the dynamics are in agreement with the soil moisture determined with point scale measurements but they are less affected by the heterogeneous moisture conditions within the field. For this reason, by applying a detailed calibration, CRS proves to be a

  5. Advancements in the development of a directional-position sensing fast neutron detector using acoustically tensioned metastable fluids

    NASA Astrophysics Data System (ADS)

    Archambault, Brian C.; Webster, Jeffrey A.; Grimes, Thomas F.; Fischer, Kevin F.; Hagen, Alex R.; Taleyakhan, Rusi P.

    2015-06-01

    Advancements in the development of a direction and position sensing fast neutron detector which utilizes the directional acoustic tensioned metastable fluid detector (D-ATMFD) are described. The resulting D-ATMFD sensor is capable of determining the direction of neutron radiation with a single compact detector versus use of arrays of detectors in conventional directional systems. Directional neutron detection and source positioning offer enhanced detection speeds in comparison to traditional proximity searching; including enabling determination of the neutron source shape, size, and strength in near real time. This paper discusses advancements that provide the accuracy and precision of ascertaining directionality and source localization information utilizing enhanced signal processing-cum-signal analysis, refined computational algorithms, and on-demand enlargement capability of the detector sensitive volume. These advancements were accomplished utilizing experimentation and theoretical modeling. Benchmarking and qualifications studies were successfully conducted with random and fission based special nuclear material (SNM) neutron sources (239Pu-Be and 252Cf). These results of assessments have indicated that the D-ATMFD compares well in technical performance with banks of competing directional fast neutron detector technologies under development worldwide, but it does so with a single detector unit, an unlimited field of view, and at a significant reduction in both cost and size while remaining completely blind to common background (e.g., beta-gamma) radiation. Rapid and direct SNM neutron source imaging with two D-ATMFD sensors was experimentally demonstrated, and furthermore, validated via multidimensional nuclear particle transport simulations utilizing MCNP-PoliMi. Characterization of a scaled D-ATMFD based radiation portal monitor (RPM) as a cost-effective and efficient 3He sensor replacement was performed utilizing MCNP-PoliMi simulations, the results of which

  6. Variation in lunar neutron dose estimates.

    PubMed

    Slaba, Tony C; Blattnig, Steve R; Clowdsley, Martha S

    2011-12-01

    The radiation environment on the Moon includes albedo neutrons produced by primary particles interacting with the lunar surface. In this work, HZETRN2010 is used to calculate the albedo neutron contribution to effective dose as a function of shielding thickness for four different space radiation environments and to determine to what extent various factors affect such estimates. First, albedo neutron spectra computed with HZETRN2010 are compared to Monte Carlo results in various radiation environments. Next, the impact of lunar regolith composition on the albedo neutron spectrum is examined, and the variation on effective dose caused by neutron fluence-to-effective dose conversion coefficients is studied. A methodology for computing effective dose in detailed human phantoms using HZETRN2010 is also discussed and compared. Finally, the combined variation caused by environmental models, shielding materials, shielding thickness, regolith composition and conversion coefficients on the albedo neutron contribution to effective dose is determined. It is shown that a single percentage number for characterizing the albedo neutron contribution to effective dose can be misleading. In general, the albedo neutron contribution to effective dose is found to vary between 1-32%, with the environmental model, shielding material and shielding thickness being the driving factors that determine the exact contribution. It is also shown that polyethylene or other hydrogen-rich materials may be used to mitigate the albedo neutron exposure. PMID:21859325

  7. 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

    NASA Technical Reports Server (NTRS)

    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.

  8. MISR Level 3 Albedo and Cloud Versioning

    Atmospheric Science Data Center

    2016-09-07

    ... MIL3YALN MISR_AM1_CGAL Stage 2:  CLOUD - Wind Vectors, Height Histogram Stage 1:  ALBEDO - Expansive, ... Stage 2 CLOUD - Height Histogram Stage 1 CLOUD - Wind Vectors Stage 1 ALBEDO - Expansive and Restrictive Albedos ...

  9. Measuring soil moisture content using cosmic-ray fast neutrons emitted from soils: a near-field remote sensing tool

    NASA Astrophysics Data System (ADS)

    Desilets, Darin; Zreda, Marek; Zweck, Chris; Ferre, Ty

    2010-05-01

    Average soil moisture over a footprint of hectometers and a depth of decimeters can be inferred from measurements of cosmic-ray fast neutrons that are generated in air and soil, moderated mainly by hydrogen atoms present in the soil, and emitted back to the atmosphere, where they travel in all directions and form a well-mixed reservoir of neutrons. The intensity of neutrons above the ground surface depends strongly on soil moisture content, and does not depend on soil chemistry and texture. The measurement with a cosmic-ray soil moisture probe placed above the ground takes minutes to hours, permitting high-resolution, long-term monitoring of undisturbed soil moisture. Neutron transport modeling using the MCNPX code shows that the footprint is approximately 600 m at sea level, and the measurement depth from 15 cm for saturated soils to 70 cm for dry soils. The footprint size has been confirmed empirically using field measurements of neutron intensity along water-land transects. The cosmic-ray soil moisture probe is calibrated using a theoretical calibration function in which one parameter is constrained by gravimetric soil moisture determinations on multiple samples collected within the footprint, If local calibration samples are not available, the same theoretical calibration function can be constrained using the knowledge of cosmic-ray variations, providing less accurate but still reasonable soil moisture estimates. The large footprint makes the method ideal for bridging the gap between remote sensing methods (such as SMOS and SMAP) and point or small-scale measurements on the ground.

  10. Albedo Pattern Recognition and Time-Series Analyses in Malaysia

    NASA Astrophysics Data System (ADS)

    Salleh, S. A.; Abd Latif, Z.; Mohd, W. M. N. Wan; Chan, A.

    2012-07-01

    Pattern recognition and time-series analyses will enable one to evaluate and generate predictions of specific phenomena. The albedo pattern and time-series analyses are very much useful especially in relation to climate condition monitoring. This study is conducted to seek for Malaysia albedo pattern changes. The pattern recognition and changes will be useful for variety of environmental and climate monitoring researches such as carbon budgeting and aerosol mapping. The 10 years (2000-2009) MODIS satellite images were used for the analyses and interpretation. These images were being processed using ERDAS Imagine remote sensing software, ArcGIS 9.3, the 6S code for atmospherical calibration and several MODIS tools (MRT, HDF2GIS, Albedo tools). There are several methods for time-series analyses were explored, this paper demonstrates trends and seasonal time-series analyses using converted HDF format MODIS MCD43A3 albedo land product. The results revealed significance changes of albedo percentages over the past 10 years and the pattern with regards to Malaysia's nebulosity index (NI) and aerosol optical depth (AOD). There is noticeable trend can be identified with regards to its maximum and minimum value of the albedo. The rise and fall of the line graph show a similar trend with regards to its daily observation. The different can be identified in term of the value or percentage of rises and falls of albedo. Thus, it can be concludes that the temporal behavior of land surface albedo in Malaysia have a uniform behaviours and effects with regards to the local monsoons. However, although the average albedo shows linear trend with nebulosity index, the pattern changes of albedo with respects to the nebulosity index indicates that there are external factors that implicates the albedo values, as the sky conditions and its diffusion plotted does not have uniform trend over the years, especially when the trend of 5 years interval is examined, 2000 shows high negative linear

  11. Cosmic Ray Albedo Proton Yield Correlated with Lunar Elemental Abundances

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    High energy cosmic rays constantly bombard the lunar regolith, producing secondary "albedo" or "splash" particles like protons and neutrons, some of which escape back to space. Two lunar missions, 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[1-4], with reduced neutron fluxes near the lunar poles being the result of collisions with hydrogen nuclei in ice deposits[5] in permanently shadowed craters. Here we investigate an analogous phenomenon with high energy (~100 MeV) lunar albedo protons. LRO has been observing the surface and environment of the Moon since June of 2009. The CRaTER instrument (Cosmic Ray Telescope for the Effects of Radiation) on LRO is designed to characterize the lunar radiation environment and its effects on simulated human tissue. CRaTER's multiple solid-state detectors can discriminate the different elements in the galactic cosmic ray (GCR) population above ~10 MeV/nucleon, and can also distinguish between primary GCR protons arriving from deep space and albedo particles propagating up from the lunar surface. We use albedo protons with energies greater than 60 MeV to construct a cosmic ray albedo proton map of the Moon. The yield of albedo protons is proportional to the rate of lunar proton detections divided by the rate of incoming GCR detections. The map accounts for time variation in the albedo particles driven by time variations in the primary GCR population, thus revealing any true spatial variation of the albedo proton yield. Our current map is a significant improvement over the proof-of-concept map of Wilson et al.[6]. In addition to including twelve more months of CRaTER data here, we use more numerous minimum ionizing GCR protons for normalization, and we make use of all six of CRaTER's detectors to reduce contamination from spurious non-proton events in the data stream. We find find that the flux

  12. Albedo estimates for land surface models and support for a new paradigm based on foliage nitrogen concentration

    SciTech Connect

    Hollinger, D.; Ollinger, S. V.; Richardson, A. D.; Martin, M. E.; Meyers, T. P.; Dail, D. B.; Scott, N. A.; Arkebauer, T. J.; Baldocchi, D. D.; Clark, K. L.; Curtis, Peter; Davis, K. J.; Desai, Desai Ankur R.; Dragoni, Danilo; Goulden, M. L.; Gu, Lianhong; Katul, G. G.; Pallardy, Stephen G.; Pawu, K. T.; Schmid, H. P.; Stoy, P. C.; Suyker, A. E.; Verma, Shashi

    2009-02-01

    Vegetation albedo is a critical component of the Earth s climate system, yet efforts to evaluate and improve albedo parameterizations in climate models have lagged relative to other aspects of model development. Here, we calculated growing season albedos for deciduous and evergreen forests, crops, and grasslands based on over 40 site-years of data from the AmeriFlux network and compared them with estimates presently used in the land surface formulations of a variety of climate models. Generally, the albedo estimates used in land surface models agreed well with this data compilation. However, a variety of models using fixed seasonal estimates of albedo overestimated the growing season albedo of northerly evergreen trees. In contrast, climatemodels that rely on a common two-stream albedo submodel provided accurate predictions of boreal needle-leaf evergreen albedo but overestimated grassland albedos. Inverse analysis showed that parameters of the two-stream model were highly correlated. Consistent with recent observations based on remotely sensed albedo, the AmeriFlux dataset demonstrated a tight linear relationship between canopy albedo and foliage nitrogen concentration (for forest vegetation: albedo 50.0110.071%N, r250.91; forests, grassland, and maize: albedo50.0210.067%N, r250.80). However, this relationship saturated at the higher nitrogen concentrations displayed by soybean foliage. We developed similar relationships between a foliar parameter used in the two-stream albedo model and foliage nitrogen concentration. These nitrogen-based relationships can serve as the basis for a new approach to land surface albedo modeling that simplifies albedo estimation while providing a link to other important ecosystem processes.

  13. Signatures of volatiles in the lunar proton albedo

    NASA Astrophysics Data System (ADS)

    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. Possible Albedo Proton Signature of Hydrated Lunar Surface Layer

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    We find evidence for a surface layer of hydrated material in the lunar regolith using "albedo protons" measured by 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 cannot be accounted for by either heavy element enrichment (e.g., enhanced Fe abundance), or by deeply buried (> 50 cm) hydrogenous material. The latitudinal distribution of albedo protons does not correlate 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 a thin (~ 1-10 cm) layer of hydrated regolith near the surface that is more prevalent near the poles. The CRaTER instrument thus provides critical measurements of volatile distributions within lunar regolith and potentially, with similar sensors and observations, at other bodies within the Solar System.

  15. Neutron detector

    DOEpatents

    Stephan, Andrew C.; Jardret; Vincent D.

    2011-04-05

    A neutron detector has a volume of neutron moderating material and a plurality of individual neutron sensing elements dispersed at selected locations throughout the moderator, and particularly arranged so that some of the detecting elements are closer to the surface of the moderator assembly and others are more deeply embedded. The arrangement captures some thermalized neutrons that might otherwise be scattered away from a single, centrally located detector element. Different geometrical arrangements may be used while preserving its fundamental characteristics. Different types of neutron sensing elements may be used, which may operate on any of a number of physical principles to perform the function of sensing a neutron, either by a capture or a scattering reaction, and converting that reaction to a detectable signal. High detection efficiency, an ability to acquire spectral information, and directional sensitivity may be obtained.

  16. Neutron detector

    SciTech Connect

    Stephan, Andrew C; Jardret, Vincent D

    2009-04-07

    A neutron detector has a volume of neutron moderating material and a plurality of individual neutron sensing elements dispersed at selected locations throughout the moderator, and particularly arranged so that some of the detecting elements are closer to the surface of the moderator assembly and others are more deeply embedded. The arrangement captures some thermalized neutrons that might otherwise be scattered away from a single, centrally located detector element. Different geometrical arrangements may be used while preserving its fundamental characteristics. Different types of neutron sensing elements may be used, which may operate on any of a number of physical principles to perform the function of sensing a neutron, either by a capture or a scattering reaction, and converting that reaction to a detectable signal. High detection efficiency, an ability to acquire spectral information, and directional sensitivity may be obtained.

  17. Spectral albedos of midlatitude snowpacks

    NASA Technical Reports Server (NTRS)

    Choudhury, B.

    1981-01-01

    Spectral albedos of impure-nonhomogeneous snowpacks, typical of midlatitudes, from 400 to 2200 nm were modeled through a numerical solution of the radiative transfer equation in the two-stream approximation. Discrete depth-dependent values of density, grain size and impurity concentration were used to characterize the snowpacks. The model is for diffuse incident radiation, and the numerical method is based on doubling and invariant imbedding. The effect of soot impurities on snowpack albedos is illustrated when a snowpack is several centimeters deep and soot reduces the albedos at visible wavelengths, however, when a snowpack is only a few centimeters deep, soot may increase the albedos at visible wavelengths. By adjusting soot content and snow grain size, good quantitative agreement with some observations at the Cascade Mountains (Washington) and at Point Barrow (Alaska) are obtained; however, the model grain sizes are found to be fifty to four hundred percent larger than the measured values. For satellite snowcover observations, a model for effective albedo of partially snow-covered areas was developed and compared with some NOAA-2 observations of the southeastern United States.

  18. A scaling approach for the assessment of biomass changes and rainfall interception using cosmic-ray neutron sensing

    NASA Astrophysics Data System (ADS)

    Baroni, G.; Oswald, S. E.

    2015-06-01

    Cosmic-Ray neutron sensing (CRS) is a unique approach to measure soil moisture at field scale filling the gap of current methodologies. However, CRS signal is affected by all the hydrogen pools on the land surface and understanding their relative importance plays an important role for the application of the method e.g., validation of remote sensing products and data assimilation. In this study, a soil moisture scaling approach is proposed to estimate directly the correct CRS soil moisture based on the soil moisture profile measured at least in one position within the field. The approach has the advantage to avoid the need to introduce one correction for each hydrogen contribution and to estimate indirectly all the related time-varying hydrogen pools. Based on the data collected in three crop seasons, the scaling approach shows its ability to identify and to quantify the seasonal biomass water equivalent. Additionally, the analysis conducted at sub-daily time resolution is able to quantify the daily vertical redistribution of the water biomass and the rainfall interception, showing promising applications of the CRS method also for these types of measurements. Overall, the study underlines how not only soil moisture but all the specific hydrological processes in the soil-plant-atmosphere continuum should be considered for a proper evaluation of the CRS signal. For this scope, the scaling approach reveals to be a simple and pragmatic analysis that can be easily extended to other experimental sites.

  19. Impact of remotely sensed albedo and vegetation fraction on simulation of urban climate in WRF-urban canopy model: A case study of the urban heat island in Los Angeles

    NASA Astrophysics Data System (ADS)

    Vahmani, P.; Ban-Weiss, G. A.

    2016-02-01

    Modeling the climate of urban areas is of interest for studying urban heat islands (UHIs). Reliable assessment of the primary causes of UHIs and the efficacy of various heat mitigation strategies requires accurate prediction of urban temperatures and realistic representation of land surface physical characteristics in models. In this study, we expand the capabilities of the Weather Research and Forecasting (WRF) model by implementing high-resolution, real-time satellite observations of green vegetation fraction (GVF) and albedo. Satellite-based GVF and albedo replace constant values that are assumed for urban pixels in the default version of WRF. Simulations of urban meteorology in Los Angeles using the improved model show marked improvements relative to the default model. The largest improvements are for nocturnal air temperatures, with a reduction in root-mean-square deviation between simulations and observations from 3.8 to 1.9°C. Utilizing the improved model, we quantify relationships between surface and 2 m air temperatures versus urban fraction, GVF, albedo, distance from the ocean, and elevation. Distance from the ocean is found to be the main contributor to variations in temperatures around Los Angeles. After conditionally sampling pixels to minimize the influence of distance from the ocean and elevation, we find that variations in GVF and urban fraction are responsible for up to 58 and 27% of the variance in temperatures. The satellite-supported meteorological modeling framework reported here can be used for studying UHIs in other cities and can serve as a foundation for testing the efficacy of various heat mitigation strategies.

  20. Correction of the readings of albedo dosimeters at the MC400 LNR cyclotron with the use of the spherical albedo system and comparison with other correction methods

    NASA Astrophysics Data System (ADS)

    Mokrov, Yu. V.; Morozova, S. V.; Timoshenko, G. N.; Krylov, V. A.

    2014-11-01

    The results of correcting the readings of DVGN-01 albedo dosimeters behind the shielding of the MC400 cyclotron at the Laboratory of Nuclear Reactions (LNR) with the use of the spherical albedo system are presented. The formulas approximating the dependences of correction coefficients used to correct the readings on the hardness parameters of low-energy neutron spectra were obtained based on these results and the results of earlier studies. Neutron spectra were measured at three points behind the MC400 shielding, and the correction coefficients for DVGN-01 were calculated based on these spectra. It was demonstrated that these coefficients agree well with the coefficients obtained with the use of the spherical albedo system. This suggests that the obtained correction coefficient values are accurate. The recommended correction coefficient values to be used in the individual dosimetric control at LNR were specified based on the results of the present study and the data given in other papers.

  1. Characterization of neutron field in a NPP workplace.

    PubMed

    Breznik, B; Pochat, J L; Muller, H; Asselineau, B; Pavlin, M

    2007-01-01

    At the Krsko Nuclear Power Plant (NPP), albedo dosimeters are used for personal neutron dosimetry. Spectrometric measurements allow determination of reference dosimetric values of realistic neutron fields to be used for calibration of albedo dosimeters. The Laboratory for Neutron Metrology and Dosimetry from the Institute for Radiological Protection and Nuclear Safety (IRSN) was in charge of characterising neutron fields in the plant at two representative points with high neutron and gamma dose rate. Calibration of the dosimeters in the workplace used to be performed only by a spherical survey meter. Based on the reference dosimetric values, the Plant Dosimetry Laboratory has verified the response of albedo dosimeters.

  2. Characterization of neutron field in a NPP workplace.

    PubMed

    Breznik, B; Pochat, J L; Muller, H; Asselineau, B; Pavlin, M

    2007-01-01

    At the Krsko Nuclear Power Plant (NPP), albedo dosimeters are used for personal neutron dosimetry. Spectrometric measurements allow determination of reference dosimetric values of realistic neutron fields to be used for calibration of albedo dosimeters. The Laboratory for Neutron Metrology and Dosimetry from the Institute for Radiological Protection and Nuclear Safety (IRSN) was in charge of characterising neutron fields in the plant at two representative points with high neutron and gamma dose rate. Calibration of the dosimeters in the workplace used to be performed only by a spherical survey meter. Based on the reference dosimetric values, the Plant Dosimetry Laboratory has verified the response of albedo dosimeters. PMID:17416593

  3. Assessment of VIIRS daily BRDF/Albedo product using in situ measurement of SURFRAD sites and MODIS V006 daily BRDF/Albedo product

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Wang, Z.; Sun, Q.; Schaaf, C.; Roman, M. O.

    2014-12-01

    Surface albedo is defined as the ratio of upwelling to downwelling radiative flux. It's important for understanding the global energy budget. Remote sensing albedo products provide global time continuous coverage to help capture global energy variability and change. The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi-NPP satellite, launched on October 28, 2011, is aiming to provide continues data record with the MODerate resolution Imaging Spectroradiometer (MODIS), which has been providing Bidirectional Reflectance Distribution Function (BRDF)/Albedo product since 2000. By utilizing the same approach that was used for the most recently V006 daily MODIS BRDF/Albedo product, VIIRS has the ability to keep providing products for research and operational users. Validating albedo product of VIIRS using in situmeasured albedo can assure the quality for land surface climate and biosphere models, and comparing with MODIS product can assure time continues of BRDF/albedo product. The daily BRDF/Albedo product still uses 16-day period multispectral, cloud-cleared, atmospherically-corrected surface reflectances to fit the Ross-Thick/Li-Sparse-Reciprocal semi-empirical BRDF model. But the multiday observations are also weighted based on proximity to the production date in order to emphasis on that individual day. Surface Radiation Budget Network (SURFRAD) was established in 1993 through the support of NOAA's Office of Global Programs. In situ albedo was driven from downwelling and upwelling radiative flux measured from the towers. Fraction of diffuse sky light was calculated using the direct and diffuse solar recorded in the data. It was further used to translate VIIRS, MODIS black sky and white sky albedos into actual albedo at local solar noon. Results show that VIIRS, MODIS and in situ albedo agree well at SURFARD spatially representative sites. While the VIIRS surface reflectance, snow, and cloud algorithms are still undergoing revision, the result shows that

  4. Use of Apollo 17 Epoch Neutron Spectrum as a Benchmark in Testing LEND Collimated Sensor

    NASA Technical Reports Server (NTRS)

    Chin, Gordon; Sagdeev, R.; Milikh, G.

    2011-01-01

    The Apollo 17 neutron experiment LPNE provided a unique set of data on production of neutrons in the Lunar soil bombarded by Galactic Cosmic Rays (GCR). It serves as valuable "ground-truth" in the age of orbital remote sensing. We used the neutron data attributed to Apollo 17 epoch as a benchmark for testing the LEND's collimated sensor, as introduced by the geometry of collimator and efficiency of He3 counters. The latter is defined by the size of gas counter and pressure inside it. The intensity and energy spectrum of neutrons escaping the lunar surface are dependent on incident flux of Galactic Cosmic Rays (GCR) whose variability is associated with Solar Cycle and its peculiarities. We obtain first the share of neutrons entering through the field of view of collimator as a fraction of the total neutron flux by using the angular distribution of neutron exiting the Moon described by our Monte Carlo code. We computed next the count rate of the 3He sensor by using the neutron energy spectrum from McKinney et al. [JGR, 2006] and by consider geometry and gas pressure of the LEND sensor. Finally the neutron count rate obtained for the Apollo 17 epoch characterized by intermediate solar activity was adjusted to the LRO epoch characterized by low solar activity. It has been done by taking into account solar modulation potential, which affects the GCR flux, and in turn changes the neutron albedo flux.

  5. Bimodal albedo distributions in the ablation zone of the southwestern Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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 and amplified ice-albedo feedback from atmospheric warming. However, the importance of distinct surface types on ablation zone albedo and meltwater production is still relatively unknown, and excluded in surface mass balance models. 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 dataset collected with an Analytical Spectral Devices (ASD) spectroradiometer measuring at 325-1075 nm, along a 1.25 km transect during three 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. We find that seasonal ablation zone albedos have a bimodal distribution, with two alternate states. This suggests that an abrupt switch from high to low albedo can be triggered by a modest melt event, resulting in amplified surface ablation rates. Our results show that such a shift corresponds to an observed melt rate percent difference increase of 51.6% during peak melt season (between 10-14 and 20-24 July 2013). Furthermore, our findings demonstrate that seasonal changes in GrIS ablation zone albedo are not exclusively a function of a darkening surface from ice crystal growth, but rather are controlled by changes in the fractional coverage of snow, bare ice, and impurity-rich surface types. As the climate continues to warm, regional climate models should consider the seasonal evolution of ice surface types in Greenland's ablation zone to improve projections of mass loss contributions to sea level rise.

  6. Bimodal Albedo Distributions in the Ablation Zone of the Southwestern Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Moustafa, S.; Rennermalm, A. K.; Smith, L. C.; Miller, M. A.; Mioduszewski, J.; Koenig, L.

    2014-12-01

    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 and amplified ice-albedo feedback from atmospheric warming. However, the importance of distinct surface types on ablation zone albedo and meltwater production is still relatively unknown, and excluded in surface mass balance models. In this study, we analyze albedo and ablation rates (m d-1) using in situ and remotely-sensed data. Observations include: 1) a new high-quality in situ spectral albedo dataset collected with an Analytical Spectral Devices (ASD) spectroradiometer measuring at 325-1075 nm, along a 1.25 km transect during three 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. We find that seasonal ablation zone albedos have a bimodal distribution, with two alternate states. This suggests that an abrupt switch from high to low albedo can be triggered by a modest melt event, resulting in amplified ablation rates. Our results show that such a shift corresponds to an observed melt rate percent difference increase of 51.6% during peak melt season (between 10-14 July and 20-24 July, 2013). Furthermore, our findings demonstrate that seasonal changes in GrIS ablation zone albedo are not exclusively a function of a darkening surface from ice crystal growth, but rather are controlled by changes in the fractional coverage of snow, bare ice, and impurity-rich surface types. As the climate continues to warm, regional climate models should consider the seasonal evolution of ice surface types in Greenland's ablation zone to improve projections of mass loss contributions to sea level rise.

  7. Improving the Operability of the Cosmic-ray Neutron Soil Moisture Method: Remote Sensing of Fresh Biomass in Crops

    NASA Astrophysics Data System (ADS)

    Avery, W. A.; Finkenbiner, C. E.; Franz, T. E.; Nguy-Robertson, A. L.; Suyker, A.

    2014-12-01

    Projected increases in global population will put enormous pressure on fresh water resources in the coming decades. Approximately 70 percent of human water use is allocated to agriculture with 40 percent of global food production originating from irrigated lands. Growing demand for food will only worsen the strain placed on many irrigated agricultural systems resulting in an unsustainable reliance on groundwater. This work represents an effort to improve the operability of the recently developed and promising cosmic-ray neutron method for estimating field-scale soil moisture. The cosmic-ray sensor passively measures above ground low-energy neutrons, which correlate to the amount of water within the measurement area (a circle with radius of ~300 m and a depth of ~30 cm). The sensor sees all forms of water (hydrogen), therefore time-varying water in growing biomass should be accounted for to reduce systematic measurement error and bias. Two vegetation indices were used to estimate fresh biomass within study agricultural fields near York, NE. The wide dynamic range vegetation index (WDRVI) and the green normalized difference vegetation index (GRNDVI) were both calculated from MODIS 500 m resolution satellite reflectance data for the summer of 2014. Additionally, in-situ biomass samples were collected from study fields to compare to biomass estimates obtained from MODIS reflectance data. Preliminary results suggest that remotely sensed fresh biomass estimates collected over the course of a growing season were sufficient and accurate enough (~ within 1 kg/m2) to eliminate the systematic error in the cosmic-ray calibration method for both soybean and maize crops. The incorporation of this novel technique for soil moisture management in producer operations has the potential to increase the efficiency of irrigation water use.

  8. Vertical Profiles of Light Scattering, Light Absorption, and Single Scattering Albedo during the Dry, Biomass Burning Season in Southern Africa and Comparisons of In Situ and Remote Sensing Measurements of Aerosol Optical Depths

    NASA Technical Reports Server (NTRS)

    Magi, Brian I.; Hobbs, Peter V.; Schmid, Beat; Redermann, Jens

    2003-01-01

    Airborne in situ measurements of vertical profiles of aerosol light scattering, light absorption, and single scattering albedo (omega (sub 0)) are presented for a number of locations in southern Africa during the dry, biomass burning season. Features of the profiles include haze layers, clean air slots, and marked decreases in light scattering in passing from the boundary layer into the free troposphere. Frequency distributions of omega (sub 0) reflect the strong influence of smoke from biomass burning. For example, during a period when heavy smoke was advected into the region from the north, the mean value of omega (sub 0) in the boundary layer was 0.81 +/- 0.02 compared to 0.89 +/- 0.03 prior to this intrusion. Comparisons of layer aerosol optical depths derived from the in situ measurements with those measured by a Sun photometer aboard the aircraft show excellent agreement.

  9. Operational comparison of TLD albedo dosemeters and solid state nuclear tracks detectors in fuel fabrication facilities.

    PubMed

    Tsujimura, N; Takada, C; Yoshida, T; Momose, T

    2007-01-01

    The authors carried out an operational study that compared the use of TLD albedo dosemeters and solid state nuclear tracks detector in plutonium environments of Japan Nuclear Cycle Development Institute, Tokai Works. A selected group of workers engaged in the fabrication process of MOX (Plutonium-Uranium mixed oxide) fuel wore both TLD albedo dosemeters and solid state nuclear tracks detectors. The TL readings were generally proportional to the counted etch-pits, and thus the dose equivalent results obtained from TLD albedo dosemeter agreed with those from solid state nuclear tracks detector within a factor of 1.5. This result indicates that, in the workplaces of the MOX fuel plants, the neutron spectrum remained almost constant in terms of time and space, and the appropriate range of field-specific correction with spectrum variations was small in albedo dosimetry. PMID:17337735

  10. Long-term Passive Mode Data Measured by the Dynamic Albedo of Neutrons (DAN) Instrument onboard Mars Science Laboratory (MSL) and Comparison to REMS Surface Pressure and Temperature Measurements

    NASA Astrophysics Data System (ADS)

    Jun, I.; Mitrofanov, I. G.; Litvak, M. L.; Sanin, A. B.; Martín-Torres, J.; Zorzano, M. P.; Boynton, W. V.; Fedosov, F.; Golovin, D.; Hardgrove, C. J.; Harshman, K.; Kozyrev, A.; Kuzmin, R.; Malakhov, A. V.; Mischna, M. A.; Moersch, J.; Mokrousov, M.; Nikiforov, S.; Tate, C. G.

    2014-12-01

    Since the landing in August 2012, DAN has provided a wealth of scientific data from the successful surface operation in both Active mode and Passive mode. While the main DAN science investigation so far has focused in estimating the contents of water-equivalent-hydrogen (WEH) and chlorine-equivalent-neutron-absorption in the surface, here we will provide/discuss low energy (less than about 1 keV) background neutron environment at the Martian surface as measured by DAN Passive mode operation. Passive mode measurements have been done on almost every sols with durations ranging from 1 hour to ~9 hour, covering different times of a day. Neutrons from the onboard power source Multi Mission Radioisotope Thermonuclear Generator (MMRTG) and induced by Galactic Cosmic Ray (GCR)/Solar Energetic Particles (SEP) interactions with the Martian atmosphere and the surface material contribute to the DAN passive data. An approach to separate out the respective contributions from the DAN total count rates was developed previously (Jun et al., 2013) using the data collected at Rocknest (where the rover stayed from sol 60 to sol 100). The main goal of this paper is to extend the same analysis to other locations encountered during the rover traverse especially to understand the long-term (through Sol 800, covering more than 1 Martian year) behavior of the neutron environment at the Martian surface as measured by DAN in response to variation of the free space GCR/SEP environment. Extensive Monte Carlo transport simulations using Monte Carlo N-Particle eXtended (MCNPX) have been performed to support the analysis and to aid interpretation of the DAN passive data. In addition, the DAN passive data are compared to the long-term surface temperature and pressure data (both measured and modeled) from Rover Environmental Monitoring Station (REMS) to investigate possible correlation of the DAN data with ambient environmental conditions.

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

    NASA Astrophysics Data System (ADS)

    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

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

    PubMed

    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. PMID:22294028

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

    PubMed

    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.

  14. The Ultraviolet Albedo of Ganymede

    NASA Astrophysics Data System (ADS)

    McGrath, Melissa; Hendrix, A.

    2013-10-01

    A large set of ultraviolet images of Ganymede have been acquired with the Hubble Space Telescope over the last 15 years. These images have been used almost exclusively to study Ganymede’s stunning auroral emissions (Feldman et al. 2000; Eviatar et al. 2001; McGrath et al. 2004; Saur et al. 2011; McGrath et al. 2013), and even the most basic information about Ganymede’s UV albedo has yet to be gleaned from these data. We will present a first-cut analysis of both disk-averaged and spatially-resolved UV albedos of Ganymede, with focus on the spatially-resolved Lyman-alpha albedo, which has never been considered previously for this satellite. Ganymede's visibly bright regions are known to be rich in water ice, while the visibly dark regions seem to be more carbonaceous (Carlson et al., 1996). At Lyman-alpha, these two species should also have very different albedo values. References Carlson, R. and 39 co-authors, Near-infrared spectroscopy and spectral mapping of Jupiter and the Galilean satellites: Results from Galileo’s initial orbit, Science, 274, 385-388, 1996. Eviatar, A., D. F. Strobel, B. C. Wolven, P. D. Feldman, M. A. McGrath, and D. J. Williams, Excitation of the Ganymede ultraviolet aurora, Astrophys. J, 555, 1013-1019, 2001. Feldman, P. D., M. A. McGrath, D. F. Strobel, H. W. Moos, K. D. Retherford, and B. C. Wolven, HST/STIS imaging of ultraviolet aurora on Ganymede, Astrophys. J, 535, 1085-1090, 2000. McGrath M. A., Lellouch E., Strobel D. F., Feldman P. D., Johnson R. E., Satellite Atmospheres, Chapter 19 in Jupiter: The Planet, Satellites and Magnetosphere, ed. F. Bagenal, T. Dowling, W. McKinnon, Cambridge University Press, 2004. McGrath M. A., Jia, Xianzhe; Retherford, Kurt; Feldman, Paul D.; Strobel, Darrell F.; Saur, Joachim, Aurora on Ganymede, J. Geophys. Res., doi: 10.1002/jgra.50122, 2013. Saur, J., S. Duling, S., L. Roth, P. D. Feldman, D. F. Strobel, K. D. Retherford, M. A. McGrath, A. Wennmacher, American Geophysical Union, Fall Meeting

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

    NASA Astrophysics Data System (ADS)

    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.

  16. Lunar Proton Albedo Anomalies: Soil, Surveyors, and Statistics

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Since the launch of LRO in 2009, the CRaTER instrument has been mapping albedo protons (~100 MeV) from the Moon. These protons are produced by nuclear spallation, a consequence of galactic cosmic ray (GCR) bombardment of the lunar regolith. Just as spalled neutrons and gamma rays reveal elemental abundances in the lunar regolith, albedo protons may be a complimentary method for mapping compositional variations. We presently find that the lunar maria have an average proton yield 0.9% ±0.3% higher than the average yield in the highlands; this is consistent with neutron data that is sensitive to the regolith's average atomic weight. We also see cases where two or more adjacent pixels (15° × 15°) have significantly anomalous yields above or below the mean. These include two high-yielding regions in the maria, and three low-yielding regions in the far-side highlands. Some of the regions could be artifacts of Poisson noise, but for completeness we consider possible effects from compositional anomalies in the lunar regolith, including pyroclastic flows, antipodes of fresh craters, and so-called "red spots". We also consider man-made landers and crash sites that may have brought elements not normally found in the lunar regolith.

  17. Empirical models of monthly and annual surface albedo in managed boreal forests of Norway

    NASA Astrophysics Data System (ADS)

    Bright, Ryan M.; Astrup, Rasmus; Strømman, Anders H.

    2013-04-01

    As forest management activities play an increasingly important role in climate change mitigation strategies of Nordic regions such as Norway, Sweden, and Finland -- the need for a more comprehensive understanding of the types and magnitude of biogeophysical climate effects and their various tradeoffs with the global carbon cycle becomes essential to avoid implementation of sub-optimal policy. Forest harvest in these regions reduces the albedo "masking effect" and impacts Earth's radiation budget in opposing ways to that of concomitant carbon cycle perturbations; thus, policies based solely on biogeochemical considerations in these regions risk being counterproductive. There is therefore a need to better understand how human disturbances (i.e., forest management activities) affect important biophysical factors like surface albedo. An 11-year remotely sensed surface albedo dataset coupled with stand-level forest management data for a variety of stands in Norway's most productive logging region are used to develop regression models describing temporal changes in monthly and annual forest albedo following clear-cut harvest disturbance events. Datasets are grouped by dominant tree species and site indices (productivity), and two alternate multiple regression models are developed and tested following a potential plus modifier approach. This resulted in an annual albedo model with statistically significant parameters that explains a large proportion of the observed variation, requiring as few as two predictor variables: i) average stand age - a canopy modifier predictor of albedo, and ii) stand elevation - a local climate predictor of a forest's potential albedo. The same model structure is used to derive monthly albedo models, with models for winter months generally found superior to summer models, and conifer models generally outperforming deciduous. We demonstrate how these statistical models can be applied to routine forest inventory data to predict the albedo

  18. Winter Albedo Characteristics at St. Paul, Minnesota.

    NASA Astrophysics Data System (ADS)

    Baker, Donald G.; Ruschy, David L.

    1989-03-01

    Mean and median daily albedos of the November-April period are presented for a nonforested station in the North Central region of the United States where frozen soil and persistent snow cover are common winter features. Three distinct albedo periods were found, the occurrence of which can be explained by comparison with associated daily records of air temperature and snow depth. These periods are: I) Introduction to Winter, 9-22 November, a transitional period in which snowfalls begin to occur but with insufficient frequency or duration to greatly alter the mean albedo from growing season values; II) the High Albedo Season, 23 November-17 March, that is characterized by mean and median albedos of 50% or higher and by a negatively skewed distribution of albedo values in contrast to periods I and III; and III) the transition period, Introduction to Spring, 18 March-12 April, where late season snowfalls of brief duration occur, but the mean albedo is lower than in period I because of the more common occurrence of moist surfaces due to snowmelt and rains.

  19. Response of TLD-albedo and nuclear track dosimeters exposed to plutonium sources

    SciTech Connect

    Brackenbush, L.W.; Baumgartner, W.V.; Fix, J.J.

    1991-12-01

    Neutron dosimetry has been extensively studied at Hanford since the mid-1940s. At the present time, Hanford contractors use thermoluminescent dosimeter (TLD)-albedo dosimeters to record the neutron dose equivalent received by workers. The energy dependence of the TLD-albedo dosimeter has been recognized and documented since introduced at Hanford in 1964 and numerous studies have helped assure the accuracy of dosimeters. With the recent change in Hanford's mission, there has been a significant decrease in the handling of plutonium tetrafluoride, and an increase in the handling of plutonium metal and plutonium oxide sources. This study was initiated to document the performance of the current Hanford TLD-albedo dosimeter under the low scatter conditions of the calibration laboratory and under the high scatter conditions in the work place under carefully controlled conditions at the Plutonium Finishing Plant (PFP). The neutron fields at the PFP facility were measured using a variety of instruments, including a multisphere spectrometer, tissue equivalent proportional counters, and specially calibrated rem meters. Various algorithms were used to evaluate the TLD-albedo dosimeters, and the results are given in this report. Using current algorithms, the dose equivalents evaluated for bare sources and sources with less than 2.5 cm (1 in.) of acrylic plastic shielding in high scatter conditions typical of glove box operations are reasonably accurate. Recently developed CR-39 track etch dosimeters (TEDs) were also exposed in the calibration laboratory and at the PFP. The results indicate that the TED dosimeters are quite accurate for both bare and moderated neutron sources. Until personnel dosimeter is available that incorporates a direct measure of the neutron dose to a person, technical uncertainties in the accuracy of the recorded data will continue.

  20. Response of TLD-albedo and nuclear track dosimeters exposed to plutonium sources

    SciTech Connect

    Brackenbush, L.W.; Baumgartner, W.V.; Fix, J.J.

    1991-12-01

    Neutron dosimetry has been extensively studied at Hanford since the mid-1940s. At the present time, Hanford contractors use thermoluminescent dosimeter (TLD)-albedo dosimeters to record the neutron dose equivalent received by workers. The energy dependence of the TLD-albedo dosimeter has been recognized and documented since introduced at Hanford in 1964 and numerous studies have helped assure the accuracy of dosimeters. With the recent change in Hanford`s mission, there has been a significant decrease in the handling of plutonium tetrafluoride, and an increase in the handling of plutonium metal and plutonium oxide sources. This study was initiated to document the performance of the current Hanford TLD-albedo dosimeter under the low scatter conditions of the calibration laboratory and under the high scatter conditions in the work place under carefully controlled conditions at the Plutonium Finishing Plant (PFP). The neutron fields at the PFP facility were measured using a variety of instruments, including a multisphere spectrometer, tissue equivalent proportional counters, and specially calibrated rem meters. Various algorithms were used to evaluate the TLD-albedo dosimeters, and the results are given in this report. Using current algorithms, the dose equivalents evaluated for bare sources and sources with less than 2.5 cm (1 in.) of acrylic plastic shielding in high scatter conditions typical of glove box operations are reasonably accurate. Recently developed CR-39 track etch dosimeters (TEDs) were also exposed in the calibration laboratory and at the PFP. The results indicate that the TED dosimeters are quite accurate for both bare and moderated neutron sources. Until personnel dosimeter is available that incorporates a direct measure of the neutron dose to a person, technical uncertainties in the accuracy of the recorded data will continue.

  1. Variability of albedo and utility of the MODIS albedo product in forested wetlands

    USGS Publications Warehouse

    Sumner, David M.; Wu, Qinglong; Pathak, Chandra S.

    2011-01-01

    Albedo was monitored over a two-year period (beginning April 2008) at three forested wetland sites in Florida, USA using up- and down-ward facing pyranometers. Water level, above and below land surface, is the primary control on the temporal variability of daily albedo. Relatively low reflectivity of water accounts for the observed reductions in albedo with increased inundation of the forest floor. Enhanced canopy shading of the forest floor was responsible for lower sensitivity of albedo to water level at the most dense forest site. At one site, the most dramatic reduction in daily albedo was observed during the inundation of a highly-reflective, calcareous periphyton-covered land surface. Satellite-based Moderate-Resolution Imaging Spectroradiometer (MODIS) estimates of albedo compare favorably with measured albedo. Use of MODIS albedo values in net radiation computations introduced a root mean squared error of less than 4.7 W/m2 and a mean, annual bias of less than 2.3 W/m2 (1.7%). These results suggest that MODIS-estimated albedo values can reliably be used to capture areal and temporal variations in albedo that are important to the surface energy balance.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    High energy cosmic rays constantly bombard the lunar regolith, producing (via nuclear evaporation[1]) 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[2-5], and by ice deposits[6] in permanently shadowed polar craters. Here we investigate an analogous phenomenon with high energy lunar albedo protons. Using the CRaTER instrument (Cosmic Ray Telescope for the Effects of Radiation) on LRO, we measure albedo protons (60 to 150 MeV) to construct a cosmic ray albedo proton map of the Moon. Our current map is a significant improvement over the proof-of-concept map of Wilson et al.[7]. In addition to using more numerous minimum ionizing GCR protons for normalization, we filter out all solar particle enhancement periods and make use of all six of CRaTER's detectors to reduce contamination from spurious non-proton events in the data stream. The average yield of albedo protons from the maria is 0.8% × 0.4% higher than the yield from the highlands. In addition there appear to be localized peaks in the albedo proton yield that are co-located with peaks in trace elemental abundances as measured by the Lunar Prospector Gamma Ray Spectrometer. More data may reveal subtler proton yield variations correlated with latitude, time of day, or the locations of permanently shadowed craters, due to the presence of water frost. Given that the most obvious features in the map have a proton yield only 2σ above average, the search for more subtle regions of enhancement or reduction in proton yield will require precise corrections for small but systematic effects of time and spacecraft altitude on the apparent proton yield. We will show the effects of these trends as well as the latest version of the albedo proton map. References: [1] Bethe (1937) Rev. Mod

  3. Arctic sea ice albedo from AVHRR

    SciTech Connect

    Lindsay, R.W.; Rothrock, D.A.

    1994-11-01

    The seasonal cycle of surface albedo of sea ice in the Arctic is estimated from measurements made with the Advanced Very High Resolution Radiometer (AVHRR) on the polar-orbiting satellites NOAA-10 and NOAA-11. The albedos of 145 200-km-square cells are analyzed. The cells are from March through September 1989 and include only those for which the sun is more than 10 deg above the horizon. Cloud masking is performed manually. Corrections are applied for instrument calibration, nonisotropic reflection, atmospheric interference, narrowband to broadband conversion, and normalization to a common solar zenith angle. The estimated albedos are relative, with the instrument gain set to give an albedo of 0.80 for ice floes in March and April. The mean values for the cloud-free portions of individual cells range from 0.18 to 0.91. Monthly averages of cells in the central Arctic range from 0.76 in April to 0.47 in August. The monthly averages of the within-cell standard deviations in the central Arctic are 0.04 in April and 0.06 in September. The surface albedo and surface temperature are correlated most strongly in March (R = -0.77) with little correlation in the summer. The monthly average lead fraction is determined from the mean potential open water, a scaled representation of the temperature or albedo between 0.0 (for ice) and 1.0 (for water); in the central Arctic it rises from an average 0.025 in the spring to 0.06 in September. Sparse data on aerosols, ozone, and water vapor in the atmospheric column contribute uncertainties to instantaneous, area-average albedos of 0.13, 0.04, and 0.08. Uncertainties in monthly average albedos are not this large. Contemporaneous estimation of these variables could reduce the uncertainty in the estimated albedo considerably.

  4. The Relationship Between Arctic Sea Ice Albedo and the Geophysical Parameters of the Ice Cover

    NASA Astrophysics Data System (ADS)

    Riihelä, A.

    2015-12-01

    The Arctic sea ice cover is thinning and retreating. Remote sensing observations have also shown that the mean albedo of the remaining ice cover is decreasing on decadal time scales, albeit with significant annual variability (Riihelä et al., 2013, Pistone et al., 2014). Attribution of the albedo decrease between its different drivers, such as decreasing ice concentration and enhanced surface melt of the ice, remains an important research question for the forecasting of future conditions of the ice cover. A necessary step towards this goal is understanding the relationships between Arctic sea ice albedo and the geophysical parameters of the ice cover. Particularly the question of the relationship between sea ice albedo and ice age is both interesting and not widely studied. The recent changes in the Arctic sea ice zone have led to a substantial decrease of its multi-year sea ice, as old ice melts and is replaced by first-year ice during the next freezing season. It is generally known that younger sea ice tends to have a lower albedo than older ice because of several reasons, such as wetter snow cover and enhanced melt ponding. However, the quantitative correlation between sea ice age and sea ice albedo has not been extensively studied to date, excepting in-situ measurement based studies which are, by necessity, focused on a limited area of the Arctic Ocean (Perovich and Polashenski, 2012).In this study, I analyze the dependencies of Arctic sea ice albedo relative to the geophysical parameters of the ice field. I use remote sensing datasets such as the CM SAF CLARA-A1 (Karlsson et al., 2013) and the NASA MeaSUREs (Anderson et al., 2014) as data sources for the analysis. The studied period is 1982-2009. The datasets are spatiotemporally collocated and analysed. The changes in sea ice albedo as a function of sea ice age are presented for the whole Arctic Ocean and for potentially interesting marginal sea cases. This allows us to see if the the albedo of the older sea

  5. Organic metal neutron detector

    DOEpatents

    Butler, M.A.; Ginley, D.S.

    1984-11-21

    A device for detection of neutrons comprises: as an active neutron sensing element, a conductive organic polymer having an electrical conductivity and a cross-section for said neutrons whereby a detectable change in said conductivity is caused by impingement of said neutrons on the conductive organic polymer which is responsive to a property of said polymer which is altered by impingement of said neutrons on the polymer; and means for associating a change in said alterable property with the presence of neutrons at the location of said device.

  6. The Opposition Phase Curve in Low Albedo Media

    NASA Astrophysics Data System (ADS)

    Nelson, R. M.; Hapke, B. W.; Smythe, W. D.; Hale, A. S.; Piatek, J. L.

    2003-04-01

    Introduction: We report the results of an investigation into the opposition surge of low albedo particulate materials of varying particle size and packing density. These very low albedo materials exhibit nearly constant circular polarization ratio with decreasing phase angle consistent with the elimination of shadows being the overwhelming contributitor to the phase curve. The Experiment: The measurements were made on the long arm goniometer at NASA's Jet Propulsion Laboratory The samples of were presented with linearly and circularly polarized light from a laser of wavelength 0.633 mm. The samples (SiC, B_4C, Fe_3O_4 and Co_2O_3) differed in reflectance from 13% to 1.6%. The reflectance of each sample measured at 5^o phase angle relative to Spectralonä was, 13%, 5%, 2.3% and 1.7% for the SiC and B_4C, Fe_3O_4 and Co_2O_3 respectively. They were presented with light that was polarized in and perpendicular to the scattering plane. A quarter wave plate was inserted into the optical train at appropriate places to permit the samples to be presented with both senses of circular polarization. The scattered beam was analyzed in both senses of linear and circular polarization. We combined the data from all of the polarization configurations and these are shown as integrated phase curves. The Results: The phase curves all exhibit an increase in reflectance as phase angle decreases. From 5 to 0^o.05 SiC exhibits a non-linear increase in circular polarization ratio (CPR) compared to the more absorbing media. The increase in CPR with decreasing phase angle can only be caused by significant multiple scattering in the medium. This is consistent with coherent backscattering. Discussion: We have previously shown that significant multiple scattering is observed in materials of high reflectance (70--90%) We found the result for SiC to be unusual given that is it so much more absorbing. However, if the reflectance of a material decreases still further (below (10%) the contribution

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

    NASA Astrophysics Data System (ADS)

    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.

  8. Arctic sea ice albedo from AVHRR

    NASA Technical Reports Server (NTRS)

    Lindsay, R. W.; Rothrock, D. A.

    1994-01-01

    The seasonal cycle of surface albedo of sea ice in the Arctic is estimated from measurements made with the Advanced Very High Resolution Radiometer (AVHRR) on the polar-orbiting satellites NOAA-10 and NOAA-11. The albedos of 145 200-km-square cells are analyzed. The cells are from March through September 1989 and include only those for which the sun is more than 10 deg above the horizon. Cloud masking is performed manually. Corrections are applied for instrument calibration, nonisotropic reflection, atmospheric interference, narrowband to broadband conversion, and normalization to a common solar zenith angle. The estimated albedos are relative, with the instrument gain set to give an albedo of 0.80 for ice floes in March and April. The mean values for the cloud-free portions of individual cells range from 0.18 to 0.91. Monthly averages of cells in the central Arctic range from 0.76 in April to 0.47 in August. The monthly averages of the within-cell standard deviations in the central Arctic are 0.04 in April and 0.06 in September. The surface albedo and surface temperature are correlated most strongly in March (R = -0.77) with little correlation in the summer. The monthly average lead fraction is determined from the mean potential open water, a scaled representation of the temperature or albedo between 0.0 (for ice) and 1.0 (for water); in the central Arctic it rises from an average 0.025 in the spring to 0.06 in September. Sparse data on aerosols, ozone, and water vapor in the atmospheric column contribute uncertainties to instantaneous, area-average albedos of 0.13, 0.04, and 0.08. Uncertainties in monthly average albedos are not this large. Contemporaneous estimation of these variables could reduce the uncertainty in the estimated albedo considerably. The poor calibration of AVHRR channels 1 and 2 is another large impediment to making accurate albedo estimates.

  9. Neutron detector ADRON-RM for ExoMars 2018

    NASA Astrophysics Data System (ADS)

    Nikiforov, Sergey; Mitrofanov, Igor; Kozyrev, Alexander; Fedosov, Fedor; Litvak, Maxim; Mokrousov, Maxim; Sanin, Anton; Tret'yakov, Vlad; Vostrukhin, Andrey; Konovalov, Alexey

    2013-04-01

    ExoMars is a joint mission of the two agencies ESA and Roscosmos to explore the red planet. The 2018 mission of the ExoMars program will deliver a European rover and a Russian surface platform to the surface of Mars. The ADRON-RM is a neutron detector, once onboard European Rover, will provide investigation of the hydrogen content (present as adsorbed water, water ice, and/or OH and H2O molecules in hydrated minerals) in the upper layer (~1 m) of the Martian subsurface. Full description will be presented. The instrument contains two detectors based on the 3He proportional counters. Parallel measurements of thermal and epithermal neutrons allow to make the assessments of the subsurface structure of the Martian soil at the Rover's vicinity and to monitor the average water content. ADRON-RM will work in synergy with other instruments in the ExoMars experiment. Neutron sensing of the Martian subsurface used for the first time since 2012 by the instrument Dynamic Albedo of Neutrons (DAN) on board the NASA's Mars Science Laboratory (MSL). According to the recent results from the DAN/MSL instrument, there is a significant correlation between active and passive measurements. Measurements by the ADRON-RM will make an important contribution at the comparison between results at the Gale crater and at the ExoMars Rover's landing site.

  10. Spectral albedo/reflectance of littered forest snow during the melt season

    NASA Astrophysics Data System (ADS)

    Melloh, Rae A.; Hardy, Janet P.; Davis, Robert E.; Robinson, Peggy B.

    2001-12-01

    Despite the importance of litter on forest floor albedo and brightness, previous studies have not documented forest floor albedo or litter cover in any detail. Our objective was to describe the seasonal influence of litter on spectral albedos and nadir reflectances of a forest snowpack in a mixed-hardwood stand in the Sleepers River Research Watershed (SRRW) in Danville, Vermont (37°39 N, 119°2 W). Experimental measurements in a nearby open area at the Snow Research Station of the SRRW nearly duplicated the spectral trend observed in the forest. Spectral albedo and nadir reflectance measurements in the visible and near infrared (350-2500 nm) transitioned from a gently curved shape through the visible range (for finer-grained, lightly littered snow) to one having a peak in the red/near-infrared (near 760 nm) as the snowmelt season progressed (for coarser-grained, more heavily littered snow). The snowpack became optically thin as surface litter reached high percentages. A point-in-time digital photographic survey of the late-lying snowpacks of three forest stands and the open showed that median litter cover percentages in the coniferous, deciduous, mixed-forest, and an open area were 17·5, 6·1, 1·2, and 0·04 respectively. A Kruskal-Wallis ANOVA on ranks and pairwise comparisons using Dunn's test indicated that the litter covers of the three forest stands were significantly different with >95% confidence. The snowpack was relatively shallow (<1 m), as is typical for this area of Vermont. From a remote-sensing standpoint, and since shallow snow and increased grain size also lower the visible albedo, we can expect that snowpack litter will cause decreased albedo earlier in the snowmelt season, at deeper snow depths, and will tend to shift the maximum albedo peak to the red/NIR range as the melt season progresses. Published in 2001 by John Wiley & Sons, Ltd.

  11. The MODIS (Collection V005) BRDF/albedo product: Assessment of spatial representativeness over forested landscapes

    SciTech Connect

    Roman, Miguel O.; Schaaf, Crystal; Woodcock, Curtis E.; Strahler, Alan; Yang, Xiaoyuan; Braswell, Rob H.; Curtis, Peter; Davis, Kenneth J.; Dragoni, Danilo; Goulden, Michael L.; Gu, Lianhong; Hollinger, David Y; Meyers, Tilden P.; Wilson, Tim B.; Munger, J. William; Wofsy, Steve; Privette, Jeffrey L.; Richardson, Andrew D.

    2009-11-01

    A new methodology for establishing the spatial representativeness of tower albedo measurements that are routinely used in validation of satellite retrievals from global land surface albedo and reflectance anisotropy products is presented. This method brings together knowledge of the intrinsic biophysical properties of a measurement site, and the surrounding landscape to produce a number of geostatistical attributes that describe the overall variability, spatial extent, strength of the spatial correlation, and spatial structure of surface albedo patterns at separate seasonal periods throughout the year. Variogram functions extracted from Enhanced Thematic Mapper Plus (ETM+) retrievals of surface albedo using multiple spatial and temporal thresholds were used to assess the degree to which a given point (tower) measurement is able to capture the intrinsic variability of the immediate landscape extending to a satellite pixel. A validation scheme was implemented over a wide range of forested landscapes, looking at both deciduous and coniferous sites, from tropical to boreal ecosystems. The experiment focused on comparisons between tower measurements of surface albedo acquired at local solar noon and matching retrievals from the MODerate Resolution Imaging Spectroradiometer (MODIS) (Collection V005) Bidirectional Reflectance Distribution Function (BRDF)/albedo algorithm. Assessments over a select group of field stations with comparable landscape features and daily retrieval scenarios further demonstrate the ability of this technique to identify measurement sites that contain the intrinsic spatial and seasonal features of surface albedo over sufficiently large enough footprints for use in modeling and remote sensing studies. This approach, therefore, improves our understanding of product uncertainty both in terms of the representativeness of the field data and its relationship to the larger satellite pixel.

  12. The LLNL CR-39 personnel neutron dosimeter

    SciTech Connect

    Hankins, D.E.; Homann, S.; Westermark, J.

    1987-09-29

    We developed a personnel neutron dosimetry system based on the electrochemical etching of CR-39 plastic at elevated temperatures. The doses obtained using this dosimeter system are more accurate than those obtained using other dosimetry systems, especially when varied neutron spectra are encountered. This CR-39 dosimetry system does not have the severe energy dependence that exists with albedo neutron dosimeters or the fading and reading problems encountered with NTA film. 3 refs., 4 figs.

  13. Sea ice-albedo climate feedback mechanism

    SciTech Connect

    Schramm, J.L.; Curry, J.A.; Ebert, E.E.

    1995-02-01

    The sea ice-albedo feedback mechanism over the Arctic Ocean multiyear sea ice is investigated by conducting a series of experiments using several one-dimensional models of the coupled sea ice-atmosphere system. In its simplest form, ice-albedo feedback is thought to be associated with a decrease in the areal cover of snow and ice and a corresponding increase in the surface temperature, further decreasing the area cover of snow and ice. It is shown that the sea ice-albedo feedback can operate even in multiyear pack ice, without the disappearance of this ice, associated with internal processes occurring within the multiyear ice pack (e.g., duration of the snow cover, ice thickness, ice distribution, lead fraction, and melt pond characteristics). The strength of the ice-albedo feedback mechanism is compared for several different thermodynamic sea ice models: a new model that includes ice thickness distribution., the Ebert and Curry model, the Mayjut and Untersteiner model, and the Semtner level-3 and level-0 models. The climate forcing is chosen to be a perturbation of the surface heat flux, and cloud and water vapor feedbacks are inoperative so that the effects of the sea ice-albedo feedback mechanism can be isolated. The inclusion of melt ponds significantly strengthens the ice-albedo feedback, while the ice thickness distribution decreases the strength of the modeled sea ice-albedo feedback. It is emphasized that accurately modeling present-day sea ice thickness is not adequate for a sea ice parameterization; the correct physical processes must be included so that the sea ice parameterization yields correct sensitivities to external forcing. 22 refs., 6 figs., 1 tab.

  14. Surface Albedo and Spectral Variability of Ceres

    NASA Astrophysics Data System (ADS)

    Li, Jian-Yang; Reddy, Vishnu; Nathues, Andreas; Le Corre, Lucille; Izawa, Matthew R. M.; Cloutis, 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.

    2016-02-01

    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 km2, 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.

  15. Surface Albedo and Spectral Variability of Ceres

    NASA Astrophysics Data System (ADS)

    Li, Jian-Yang; Reddy, Vishnu; Nathues, Andreas; Le Corre, Lucille; Izawa, Matthew R. M.; Cloutis, 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.

    2016-02-01

    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 km2, 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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 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.

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

    NASA Astrophysics Data System (ADS)

    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. Intercomparison of MODIS Albedo Retrievals and In Situ Measurements Across the Global FLUXNET Network

    NASA Technical Reports Server (NTRS)

    Cescatti, Alessandro; Marcolla, Barbara; Vannan, Suresh K. Santhana; Pan, Jerry Yun; Roman, Miguel O.; Yang, Xiaoyuan; Ciais, Philippe; Cook, Robert B.; Law, Beverly E.; Matteucci, Girogio; Migliavacca, Mirco; Moors, Eddy; Richardson, Andrew D.; Seufert, Guenther; Schaaf, Crystal B.

    2012-01-01

    Surface albedo is a key parameter in the Earth's energy balance since it affects the amount of solar radiation directly absorbed at the planet surface. Its variability in time and space can be globally retrieved through the use of remote sensing products. To evaluate and improve the quality of satellite retrievals, careful intercomparisons with in situ measurements of surface albedo are crucial. For this purpose we compared MODIS albedo retrievals with surface measurements taken at 53 FLUXNET sites that met strict conditions of land cover homogeneity. A good agreement between mean yearly values of satellite retrievals and in situ measurements was found (R(exp 2)= 0.82). The mismatch is correlated to the spatial heterogeneity of surface albedo, stressing the relevance of land cover homogeneity when comparing point to pixel data. When the seasonal patterns of MODIS albedo is considered for different plant functional types, the match with surface observation is extremely good at all forest sites. On the contrary, in non-forest sites satellite retrievals underestimate in situ measurements across the seasonal cycle. The mismatch observed at grasslands and croplands sites is likely due to the extreme fragmentation of these landscapes, as confirmed by geostatistical attributes derived from high resolution scenes.

  19. [New index for soil moisture monitoring based on deltaT(s)-albedo spectral information].

    PubMed

    Yao, Yun-Jun; Qin, Qi-Ming; Zhao, Shao-Hua; Shen, Xin-Yi; Sui, Xin-Xin

    2011-06-01

    Monitoring soil moisture by remote sensing has been an important problem for both agricultural drought monitoring and water resources management. In the present paper, we acquire the land surface temperature difference (deltaT(s)) and broadband albedo using MODIS Terra reflectance and land surface temperature products to construct the deltaT(s)-albedo spectral feature space. According to the soil moisture variation in spectral feature space, we put forward a simple and practical temperature difference albedo drought index (TDADI) and validate it using ground-measured 0-10 cm averaged soil moisture of Ningxia plain The results show that the coefficient of determination (R2) of both them varies from 0.36 to 0.52, and TDADI has higher accuracy than temperature albedo drought index (TADI) for soil moisture retrieval. The good agreement of TDADI, Albedo/LST, LST/ NDVI and TVDI for analyzing the trends of soil moisture change supports the reliability of TDADI. However, TDADI has been designed only at Ningxia plain and still needs further validation in other regions. PMID:21847933

  20. Gamma-ray Albedo of the Moon

    SciTech Connect

    Moskalenko, Igor V.; Porter, Troy A.

    2007-06-14

    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 GeV (600 MeV for the inner part of the Moon disc). Since it is the only (almost) black spot in the gamma-ray sky, it provides a unique opportunity for calibration of gamma-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST). The albedo flux depends on the incident CR spectrum which changes over the solar cycle. Therefore, 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 -rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the GLAST LAT to monitor the CR spectrum near the Earth beyond the lifetime of PAMELA.

  1. A cavity radiometer for Earth albedo measurement, phase 1

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Radiometric measurements of the directional albedo of the Earth requires a detector with a flat response from 0.2 to 50 microns, a response time of about 2 seconds, a sensitivity of the order of 0.02 mw/sq cm, and a measurement uncertainty of less than 5 percent. Absolute cavity radiometers easily meet the spectral response and accuracy requirements for Earth albedo measurements, but the radiometers available today lack the necessary sensitivity and response time. The specific innovations addressed were the development of a very low thermal mass cavity and printed/deposited thermocouple sensing elements which were incorporated into the radiometer design to produce a sensitive, fast response, absolute radiometer. The cavity is applicable to the measurement of the reflected and radiated fluxes from the Earth surface and lower atmosphere from low Earth orbit satellites. The effort consisted of requirements and thermal analysis; design, construction, and test of prototype elements of the black cavity and sensor elements to show proof-of-concept. The results obtained indicate that a black body cavity sensor that has inherently a flat response from 0.2 to 50 microns can be produced which has a sensitivity of at least 0.02 mw/sq cm per micro volt ouput and with a time constant of less than two seconds. Additional work is required to develop the required thermopile.

  2. Improvement and calibration of a SSNT personal dosemeter and study of importance of albedo factor for dose calculation.

    PubMed

    Torkzadeh, F; Taheri, M

    2007-01-01

    The Neutriran albedo neutron dosemeter has been improved and calibrated for neutron personal dosimetry. The Monte Carlo code MCNP4b was used to calculate the thermal neutrons backscattered from the body (albedo factor). Backscattering from the wall, ceiling and floor in calibration room was considered also via simulation by MCNP4C. A semi automated counting system applying a high-resolution scanner was used for counting of tracks. An 241Am source was used to produce similar alpha particles from 10B (n,alpha)7Li reaction for the optimisation of scanner parameters to distinguish and separate the tracks in SSNTD, which lead to a better distinction between etched alpha tracks and, consequently, a higher linear region of dose characteristic. PMID:16980708

  3. The determination of surface albedo from meteorological satellites

    NASA Technical Reports Server (NTRS)

    Johnson, W. T.

    1977-01-01

    A surface albedo was determined from visible data collected by the NOAA-4 polar orbiting meteorological satellite. To filter out the major cause of atmospheric reflectivity, namely clouds, techniques were developed and applied to the data resulting in a map of global surface albedo. Neglecting spurious surface albedos for regions with persistent cloud cover, sun glint effects, insufficient reflected light and, at this time, some unresolved influences, the surface albedos retrieved from satellite data closely matched those of a global surface albedo map produced from surface and aircraft measurements and from characteristic albedos for land type and land use.

  4. Multiscale climatological albedo look-up maps derived from moderate resolution imaging spectroradiometer BRDF/albedo products

    NASA Astrophysics Data System (ADS)

    Gao, Feng; He, Tao; Wang, Zhuosen; Ghimire, Bardan; Shuai, Yanmin; Masek, Jeffrey; Schaaf, Crystal; Williams, Christopher

    2014-01-01

    Surface albedo determines radiative forcing and is a key parameter for driving Earth's climate. Better characterization of surface albedo for individual land cover types can reduce the uncertainty in estimating changes to Earth's radiation balance due to land cover change. This paper presents albedo look-up maps (LUMs) using a multiscale hierarchical approach based on moderate resolution imaging spectroradiometer (MODIS) bidirectional reflectance distribution function (BRDF)/albedo products and Landsat imagery. Ten years (2001 to 2011) of MODIS BRDF/albedo products were used to generate global albedo climatology. Albedo LUMs of land cover classes defined by the International Geosphere-Biosphere Programme (IGBP) at multiple spatial resolutions were generated. The albedo LUMs included monthly statistics of white-sky (diffuse) and black-sky (direct) albedo for each IGBP class for visible, near-infrared, and shortwave broadband under both snow-free and snow-covered conditions. The albedo LUMs were assessed by using the annual MODIS IGBP land cover map and the projected land use scenarios from the Intergovernmental Panel on Climate Change land-use harmonization project. The comparisons between the reconstructed albedo and the MODIS albedo data product show good agreement. The LUMs provide high temporal and spatial resolution global albedo statistics without gaps for investigating albedo variations under different land cover scenarios and could be used for land surface modeling.

  5. Monitoring surface albedo change with Landsat

    NASA Technical Reports Server (NTRS)

    Otterman, J.

    1977-01-01

    A pronounced decrease of the surface albedo (reflectivity) has been observed in an area in the Northern Sinai, fenced-in in the summer of 1974. Analysis of the Landsat Multispectral Scanner System digital data from an April 1977 pass indicates a reduction in the albedo in the exclosure by 13%, as compared to the outside, which continues to be subjected to overgrazing and anthropogenic pressures. The reduction of reflectivity is approximately the same in all the spectral bands, and is therefore attributable to accumulation of dead plants and plant debris, and not directly to live vegetation.

  6. The ultraviolet continuum albedo of Uranus

    NASA Astrophysics Data System (ADS)

    Cochran, W. D.; Wagener, R.; Caldwell, J.; Fricke, K. H.

    1990-01-01

    A radiative transfer code explicitly treating the Raman scattering of solar protons by H2 is presently used to analyze the Uranus geometric albedo in the 2000-5000 A range. The Baines and Bergstralh (1986) baseline model used reproduces the geometric albedo peak produced by Raman scattering filling of solar absorption line cores, but is found to be excessively bright for wavelengths below 2400 A. This discrepancy is resolvable through inclusion of an absorbing stratospheric haze layer, and results are thereby obtained which are consistent with the Pollack et al. (1987) model, in which aerosols are generated stratospherically through photochemical effects on hydrocarbons.

  7. The ultraviolet continuum albedo of Uranus

    SciTech Connect

    Cochran, W.D.; Wagener, R.; Caldwell, J.; Fricke, K.H. New York State Univ., Stony Brook York Univ., Toronto Bonn Universitaet )

    1990-01-01

    A radiative transfer code explicitly treating the Raman scattering of solar protons by H{sub 2} is presently used to analyze the Uranus geometric albedo in the 2000-5000 A range. The Baines and Bergstralh (1986) baseline model used reproduces the geometric albedo peak produced by Raman scattering filling of solar absorption line cores, but is found to be excessively bright for wavelengths below 2400 A. This discrepancy is resolvable through inclusion of an absorbing stratospheric haze layer, and results are thereby obtained which are consistent with the Pollack et al. (1987) model, in which aerosols are generated stratospherically through photochemical effects on hydrocarbons. 20 refs.

  8. The albedo of fractal stratocumulus clouds

    NASA Technical Reports Server (NTRS)

    Cahalan, Robert F.; Ridgway, William; Wiscombe, Warren J.; Bell, Thomas L.; Snider, Jack B.

    1994-01-01

    An increase in the planetary albedo of the earth-atmosphere system by only 10% can decrease the equilibrium surface temperature to that of the last ice age. Nevertheless, albedo biases of 10% or greater would be introduced into large regions of current climate models if clouds were given their observed liquid water amounts, because of the treatment of clouds as plane parallel. The focus on marine stratocumulus clouds is due to their important role in cloud radiative forcing and also that, of the wide variety of earth's cloud types, they are most nearly plane parallel, so that they have the least albedo bias. The fractal model employed here reproduces both the probability distribution and the wavenumber spectrum of the stratocumulus liquid water path, as observed during the First ISCCP Regional Experiment (FIRE). A single new fractal parameter 0 less than or equal to f less than or equal to 1, is introduced and determined empirically by the variance of the logarithm of the vertically integrated liquid water. The reduced reflectivity of fractal stratocumulus clouds is approximately given by the plane-parallel reflectivity evaluated at a reduced 'effective optical thickness,' which when f = 0.5 is tau(sub eff) approximately equal to 10. Study of the diurnal cycle of stratocumulus liquid water during FIRE leads to a key unexpected result: the plane-parallel albedo bias is largest when the cloud fraction reaches 100%, that is, when any bias associated with the cloud fraction vanishes. This is primarily due to the variability increase with cloud fraction. Thus, the within-cloud fractal structure of stratocumulus has a more significant impact on estimates of its mesoscale-average albedo than does the cloud fraction.

  9. Albedo boundaries on Mars in 1972: Results from Mariner 9

    USGS Publications Warehouse

    Batson, R.M.; Inge, J.L.

    1976-01-01

    A map of "albedo" boundaries (light and dark markings) on Mars was prepared from Mariner 9 images. After special digital processing, these pictures provide detailed locations of albedo boundaries, which is significant in interpreting recent eolian activity. Derivation of absolute albedo values from the spacecraft data was not attempted. The map correlates well with telescopic observations of Mars after the 1971 dust storm. ?? 1976.

  10. Spectral albedo and emissivity of CO sub 2 in Martian polar caps: Model results

    SciTech Connect

    Warren, S.G. ); Wiscombe, W.J. ); Firestone, J.F. )

    1990-08-30

    A model originally developed to explain the spectral albedo and emissivity of terrestrial snow is extended to the case of carbon dioxide snow on Mars. The variation of albedo and emissivity with wavelength is caused by the spectral variation of the absorption coefficient of solid CO{sub 2}. The most important variables controlling the radiative properties are grain size and contamination by dust or water. Solar zenith angle and snowpack thickness are of less importance. The observation that red albedo is higher than blue albedo in the Martian south polar cap indicates that the snow is contaminated with red dust. The interband absorption coefficient of CO{sub 2} ice in the thermal infrared is 2-3 orders of magnitude smaller than that of H{sub 2}O ice, due to the absence of hydrogen bonding in CO{sub 2}. This allows CO{sub 2} snow emissivity to be sensitive to grain size, emission angle, and impurities, in contrast to water snow which is nearly a blackbody under all conditions. The emissivity of CO{sub 2} snow varies substantially with wavelength, so energy budget modeling should be done in spectral detail. The addition of a thin layer of water frost over CO{sub 2} snow dramatically raises the thermal emissivity but causes little change to the spectrally averaged albedo unless the underlying CO{sub 2} snow is dirty. Remote sensing of CO{sub 2} grain size, H{sub 2}O content, and dust content may be possible. However, the design of a remote-sensing strategy awaits more accurate laboratory determination of the optical constants of CO{sub 2} ice.

  11. A new parameterization of the post-fire snow albedo effect

    NASA Astrophysics Data System (ADS)

    Gleason, K. E.; Nolin, A. W.

    2013-12-01

    Mountain snowpack serves as an important natural reservoir of water: recharging aquifers, sustaining streams, and providing important ecosystem services. Reduced snowpacks and earlier snowmelt have been shown to affect fire size, frequency, and severity in the western United States. In turn, wildfire disturbance affects patterns of snow accumulation and ablation by reducing canopy interception, increasing turbulent fluxes, and modifying the surface radiation balance. Recent work shows that after a high severity forest fire, approximately 60% more solar radiation reaches the snow surface due to the reduction in canopy density. Also, significant amounts of pyrogenic carbon particles and larger burned woody debris (BWD) are shed from standing charred trees, which concentrate on the snowpack, darken its surface, and reduce snow albedo by 50% during ablation. Although the post-fire forest environment drives a substantial increase in net shortwave radiation at the snowpack surface, driving earlier and more rapid melt, hydrologic models do not explicitly incorporate forest fire disturbance effects to snowpack dynamics. The objective of this study was to parameterize the post-fire snow albedo effect due to BWD deposition on snow to better represent forest fire disturbance in modeling of snow-dominated hydrologic regimes. Based on empirical results from winter experiments, in-situ snow monitoring, and remote sensing data from a recent forest fire in the Oregon High Cascades, we characterized the post-fire snow albedo effect, and developed a simple parameterization of snowpack albedo decay in the post-fire forest environment. We modified the recession coefficient in the algorithm: α = α0 + K exp (-nr) where α = snowpack albedo, α0 = minimum snowpack albedo (≈0.4), K = constant (≈ 0.44), -n = number of days since last major snowfall, r = recession coefficient [Rohrer and Braun, 1994]. Our parameterization quantified BWD deposition and snow albedo decay rates and

  12. Assessing change in the earth's land surface albedo with moderate resolution satellite imagery

    NASA Astrophysics Data System (ADS)

    Sun, Qingsong

    Land surface albedo describes the proportion of incident solar radiant flux that is reflected from the Earth's surface and therefore is a crucial parameter in modeling and monitoring attempts to capture the current climate, hydrological, and biogeochemical cycles and predict future scenarios. Due to the temporal variability and spatial heterogeneity of land surface albedo, remote sensing offers the only realistic method of monitoring albedo on a global scale. While the distribution of bright, highly reflective surfaces (clouds, snow, deserts) govern the vast majority of the fluctuation, variations in the intrinsic surface albedo due to natural and human disturbances such as urban development, fire, pests, harvesting, grazing, flooding, and erosion, as well as the natural seasonal rhythm of vegetation phenology, play a significant role as well. The development of times series of global snow-free and cloud-free albedo from remotely sensed observations over the past decade and a half offers a unique opportunity to monitor and assess the impact of these alterations to the Earth's land surface. By utilizing multiple satellite records from the MODerate-resolution Imaging Spectroradiometer (MODIS), the Multi-angle Imaging Spectroradiometer (MISR) and the Visible Infrared Imaging Radiometer Suite (VIIRS) instruments, and developing innovative spectral conversion coefficients and temporal gap-filling strategies, it has been possible to utilize the strengths of the various sensors to improve the spatial and temporal coverage of global land surface albedo retrievals. The availability of these products is particularly important in tropical regions where cloud cover obscures the forest for significant periods. In the Amazon, field ecologists have noted that some areas of the forest ecosystem respond rapidly with foliage growth at the beginning of the dry season, when sunlight can finally penetrate fully to the surface and have suggested this phenomenon can continue until

  13. 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

    SciTech Connect

    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.

  14. Albedo estimation using near infrared photography at Glaciar Norte of Citlaltepetl Volcano (Mexico).

    NASA Astrophysics Data System (ADS)

    Ontiveros, Guillermo; Delgado-Granados, Hugo

    2015-04-01

    In this work we show preliminary results of the application of the methodology proposed by Corripio (2004) for albedo estimation of a glacial surface using oblique photography. This analysis was performed for the Glaciar Norte of Citlaltepetl volcano (Mexico), using images obtained with a modified digital camera for capturing the portion of the near infrared spectrum starting at 950 nm and a digital elevation model with a grid of 2 m. The main goal was to obtain a picture of the spatial distribution of albedo on the glacier, in order to find out if there was any morphological evidence of the influence of the glacier energy balance. Some of the obtained results show a certain spatial distribution with comparatively higher albedo values at the lower parts of the glacier as compared with higher parts. The higher values may correspond to different metamorphism of snow/ice at different heights due to the effects of lower slope. Corripio, J. G. (2004). Snow surface albedo estimation using terrestrial photography. International journal of remote sensing, 25(24), 5705-5729.

  15. Estimating big bluestem albedo from directional reflectance measurements

    NASA Technical Reports Server (NTRS)

    Irons, J. R.; Ranson, K. J.; Daughtry, C. S. T.

    1988-01-01

    Multidirectional reflectance factor measurements acquired in the summer of 1986 are used to make estimates of big bluestem grass albedo, evaluating the variation of albedo with changes in solar zenith angle and phenology. On any given day, the albedo was observed to increase by at least 19 percent as solar zenith angle increased. Changes in albedo were found to correspond to changes in the green leaf area index of the grass canopy. Estimates of albedo made using reflectance data acquired within only one or two azimuthal planes and at a restricted range of view zenith angle were evaluated and compared to 'true' albedos derived from all available reflectance factor data. It was found that even a limited amount of multiple direction reflectance data was preferable to a single nadir reflectance factor for the estimation of prarie grass albedo.

  16. Earth Albedo and the orbit of LAGEOS

    NASA Technical Reports Server (NTRS)

    Rubincam, D. P.; Weiss, N. R.

    1985-01-01

    The long-period perturbations in the orbit of the Lageos satellite due to the Earth's albedo have been found using a new analytical formalism. The Earth is assumed to be a sphere whose surface diffusely reflects sunlight according to Lambert's law. Specular reflection is not considered. The formalism is based on spherical harmonics; it produces equations which hold regardless of whether the terminator is seen by the satellite or not. Specializing to the case of a realistic zonal albedo shows that Lageos' orbital semimajor axis changes periodically by only the a few millimeters and the eccentricity by one part in 100,000. The longitude of the node increases secularly. The effect considered here can explain neither the secular decay of 1.1 mm/day in the semimajor axis nor the observed along-track variations in acceleration of order 2 x 10 to the minus 12 power/sq ms.

  17. The albedo of particles in reflection nebulae

    NASA Technical Reports Server (NTRS)

    Rush, W. F.

    1974-01-01

    The relation between the apparent angular extent of a reflection nebula and the apparent magnitude of its illuminating star was reconsidered under a less restrictive set of assumptions. A computational technique was developed which permits the use of fits to the observed m-log a values to determine the albedo of particles composing reflection nebulae, providing only that a phase function and average optical thickness are assumed. Multiple scattering, anisotropic phase functions, and illumination by the general star field are considered, and the albedo of reflection nebular particles appears to be the same as that for interstellar particles in general. The possibility of continuous fluorescence contributions to the surface brightness is also considered.

  18. A Cloud Hydrology and Albedo Synthesis Mission (CHASM)

    NASA Technical Reports Server (NTRS)

    Davies, Roger

    2004-01-01

    This slide presentation reviews the Cloud Hydrology and Albedo Synthesis Mission (CHASM). The interaction of clouds with radiation and the hydrological cycle represents a huge uncertainty in our understanding of climate science and the modeling of climate system feedbacks. Despite the recognized need for a unified treatment of cloud processes, the present global average values of remotely sensed cloud liquid water and theoretically accepted values used for cloud physics and precipitation modeling differ by an order of magnitude. This is due in part to sampling and saturation effects, as well as to threedimensional cloud structure effects. In recent work with the Multiangle Imaging SpectroRadiometer (MISR) on Terra, we have gained new insights as to how the remote sensing approach could be significantly improved using a new instrument that combines passive optical (visible and near infrared) and microwave measurements, both as pushbroom scanners with multiple viewing angles, to the degree that measurements of liquid water path over deep convective clouds over land also become possible. This instrument would also have the ability of measuring height-resolved cloud-tracked winds using a hyper stereo retrieval technique. Deployment into a precessing low earth orbit would be optimal for measuring diurnal cloud activity. We have explored an instrument design concept for this that looks promising if we can establish partnerships that provide launch and bus capabilities.

  19. Calculated angular distributions of energetic atmospheric neutrons

    NASA Technical Reports Server (NTRS)

    Merker, M.

    1975-01-01

    Calculated angular distributions of atmospheric leakage neutron fluxes from 19 MeV to 1 GeV are presented. Comparisons with the balloon measurements of Preszler et al. and Kanbach et al. are made and show substantial agreement, strengthening the belief in the importance of the CRAND (cosmic-ray albedo-neutron decay) contribution to the high-energy protons in the earth's inner radiation belt. The calculation is presented as a means for investigating features of atmospheric flux distributions.

  20. Correlation of Neutron Data Taken at Commercial Nuclear Sites

    SciTech Connect

    Rathbun, L. A.; Endres, G. W.R.

    1983-10-01

    In this report, data from neutron measurement and dosimetry studies performed by Pacific Northwest Laboratory, the Environmental Measurements Laboratory, and Rensselaer Polytechnic Institute are examined and compared. The purpose of this data correlation effort is to determine whether useful relationships exist between the actual neutron dose equivalent in a typical commercial nuclear power reactor and various measurement parameters, such as ratios of the response of 9-in. to 3-in. spheres, neutron/gamma ratios, albedo dosimeter response and neutron spectrometer readings. In most neutron radiation fields found in the reactors visited, the response of albedo dosimeters can be brought into reasonable agreement with dose equivalents measured with multispheres, tissue equivalent proportional counters (TEPCs) or remmeters. Because the responses of the remmeters, like the responses of albedo dosimeters, are energy dependent, it is preferable to correct the responses of the albedo dosimeters to agree with dose equivalents measured with either TEPCs or multispheres. If one of these laboratory systems has been used to measure neutron dose equivalents at a specific pressurized water reactor, a calculated average albedo dosimeter correction factor can be used for most locations at that reactor. However, if the measured 9-in. to 3-in. remmeter ratio is greater than 0.20, it is advisable to use a plot of 9-in. to 3-in. remmeter ratios versus albedo dosimeter correction factors to obtain an albedo dosimeter correction factor. Because 9-in. to 3-in. remmeter ratios at boiling water reactors are typically greater than 0.20, the latter approach applies to this type of reactor.

  1. Prediction analysis of dose equivalent responses of neutron dosemeters used at a MOX fuel facility.

    PubMed

    Tsujimura, N; Yoshida, T; Takada, C

    2011-07-01

    To predict how accurately neutron dosemeters can measure the neutron dose equivalent (rate) in MOX fuel fabrication facility work environments, the dose equivalent responses of neutron dosemeters were calculated by the spectral folding method. The dosemeters selected included two types of personal dosemeter, namely a thermoluminescent albedo neutron dosemeter and an electronic neutron dosemeter, three moderator-based neutron survey meters, and one special instrument called an H(p)(10) monitor. The calculations revealed the energy dependences of the responses expected within the entire range of neutron spectral variations observed in neutron fields at workplaces. PMID:21498409

  2. Application of cosmic-ray neutron sensing to monitor soil water content in an alpine meadow ecosystem on the northern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Zhu, Xuchao; Shao, Ming'an; Zeng, Chen; Jia, Xiaoxu; Huang, Laiming; Zhang, Yangjian; Zhu, Juntao

    2016-05-01

    Cosmic-ray neutron sensing (CRNS) is a new method for continuously monitoring mean soil water content (SWC) on a hectometer scale. To evaluate the application and accuracy of the method for SWC observation in an alpine meadow ecosystem (AME), we installed the CRNS in a flat meadow near the Naqu prefecture on the northern Tibetan Plateau. We collecting soil samples and applying the system by the oven-drying method. A weather station was also installed near the CRNS for monitoring basic meteorological variables and the soil temperature and water content at various depths. Three Em-50 instruments for monitoring SWC and soil temperature were buried in three sub-quadrats northwest, northeast and southeast of the CRNS at distances of 460, 370 and 373 m, respectively, to observe the variation of SWC at the various depths. The footprint of the CRNS for SWC observation in the meadow was about 580 m, and the mean measuring depth was about 31 cm according to the general calculation equations. The reference neutron flux for dry soil (N0) had a mean and coefficient of variation of 8686 and 3%, respectively, and remained substantially invariant throughout the measuring period. The five SWCs from the independent field samples almost passed through the SWC trend of the CRNS, the root mean square error (RMSE) was 0.011 m3 m-3 for the CRNS and oven-drying method. The time series of SWC measured by the CRNS agreed well with the mean SWC series to a depth of 20 cm measured by the weather station. The trend of SWC measured by the Em-50s generally agreed with the trend of SWC measured by the CRNS, but some values and variations of SWC differed between the Em-50s and CRNS data. Because of the good agreement between the CRNS and independent field samples, we suspect that this disagreement is due to an insufficient representativeness of point observations and the distances of the points from the CRNS. The diurnal variation of hourly SWC from the CRNS was sinusoidal during a dry period

  3. Half space albedo problem for the nonconservative vector equation of transfer with a combination of Rayleigh and isotropic scattering

    NASA Astrophysics Data System (ADS)

    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.

  4. Calculation of the lunar photon albedo from galactic and solar proton bombardment.

    NASA Technical Reports Server (NTRS)

    Armstrong, T. W.

    1972-01-01

    The lunar photon albedo due to cosmogenic and primordial photon sources has been calculated. The individual photon leakage spectra from prompt photons produced by galactic cosmic ray (GCR) and solar cosmic ray (SCR) induced nuclear interactions, from the decay of GCR- and SCR-induced radionuclides, and from the decay of naturally occurring radionuclides are given. An approximate estimate of the leakage from the photon-electron cascade initiated by the decay of neutral pions is also given. Monte Carlo methods have been used to determine the nucleon-meson cascade, and discrete-ordinates methods were used for the photon and low-energy neutron transport.

  5. Assessment of the soil water balance by the combination of cosmic ray neutron sensing and eddy covariance technique in an irrigated citrus orchard (Marrakesh, Morocco)

    NASA Astrophysics Data System (ADS)

    Mroos, Katja; Baroni, Gabriele; Er-Raki, Salah; Francke, Till; Khabba, Said; Jarlan, Lionel; Hanich, Lahoucine; Oswald, Sascha E.

    2014-05-01

    Irrigation water requirement plays a crucial role in many agricultural areas and especially in arid and semi-arid landscapes. Improvements in the water management and the performance of the irrigation systems require a correct evaluation of the hydrological processes involved. However, some difficulties can arise due to the heterogeneity of the soil-plant system and of the irrigation scheme. To overcome these limitations, in this study, the soil water balance is analyzed by the combination of the Eddy Covariance technique (EC) and Cosmic Ray neutron Sensing (CRS). EC provides the measurement of the actual evapotranspiration over the area as it was presented in many field conditions. Moreover CRS showed to be a valuable approach to measure the root zone soil moisture integrated in a footprint of ~30 ha. In this way, the combination of the two methodologies should provide a better analysis of the soil water balance at field scale, as opposed to point observations, e.g. by TDR, evaporimeter and fluxmeter. Then, this could increase the capability to assess the irrigation efficiency and the agricultural water management. The study is conducted in a citrus orchard situated in a semi-arid region, 30 km southwest of Marrakesh (Morocco). The site is flat and planted with trees of same age growing in parallel rows with drip irrigation lines and application of fertilizer and pesticides. The original soil seems modified on the surface by the agricultural use, creating differences between trees, rows and lines. In addition, the drip irrigation creates also a spatial variability of the water flux distribution in the field, making this site an interesting area to test the methodology. Particular attention is given to the adaptation of the standard soil sampling campaign used for the calibration of the CRS and the introduction of a weighing function. Data were collected from June to December 2013, which corresponds to the high plant transpiration. Despite the intention of the

  6. Effect of Reindeer Grazing on Snowmelt, Albedo and Energy Balance Based on Satellite Data Analysis

    NASA Astrophysics Data System (ADS)

    Cohen, Juval; Pulliainen, Jouni; Ménard, Cécile; Johansen, Bernt; Oksanen, Lauri; Luojus, Kari; Ikonen, Jaakko

    2013-04-01

    Surface albedo has a major influence on the energy balance of the Earth. The albedo difference between snow-covered and snow-free tundra is very significant. Therefore, a delay in the snowmelt will decrease the absorbed solar energy on the ground. Earlier studies have shown that higher and denser vegetation causes earlier snowmelt, and that shrub height and abundance, as well as the total biomass in summer reindeer pastures is lower than in winter pastures. The possibility of using reindeer summer grazing to decrease the vegetation, delay the snowmelt and decrease the ground heating during the snowmelt season is investigated in this study. Satellite data is used to compare between summer and non-summer grazing areas in the northern tundra areas of Fennoscandia. A comparison of vegetation types, NDVI, fractional snow cover and albedo between the Finnish year-round pastures and the Norwegian non-summer pastures is performed. Other factors influencing the snowmelt, such as surface temperature, ground elevation and incoming solar radiation are taken into account. Information about the vegetation on the ground is based on a vegetation map compiled from Landsat TM/ETM+ satellite data and ancillary map information. The NDVI, snowmelt and albedo analyses are performed using multi-temporal remote sensing data such as GlobSnow SE and MODIS based NDVI, snow and albedo products. The results here support previous studies and indicate that vegetation in the summer pastures is shorter and sparser and that the snowmelt there occurs later than in the more densely vegetated, non-summer pastures. More shrubs protruding above the snowpack and earlier snowmelt on the Norwegian side lower the albedo during the snowmelt season. This causes higher solar energy absorption of up to 6 W/m2 in the snowmelt season and yearly contribution of up to 0.5 W/m2 to the yearly energy balance. Therefore this study suggests that summer reindeer herding can be used to delay snowmelt, increase surface

  7. Calibrated Color and Albedo Maps of Mercury

    NASA Astrophysics Data System (ADS)

    Robinson, M. S.; Lucey, P. G.

    1996-03-01

    In order to determine the albedo and color of the mercurian surface, we are completing calibrated mosaics of Mariner 10 image data. A set of clear filter mosaics is being compiled in such a way as to maximize the signal-to-noise-ratio of the data and to allow for a quantitative measure of the precision of the data on a pixel-by-pixel basis. Three major imaging sequences of Mercury were acquired by Mariner 10: incoming first encounter (centered at 20S, 2E), outgoing first encounter (centered at 20N, 175E), and southern hemisphere second encounter (centered at 40S, 100E). For each sequence we are making separate mosaics for each camera (A and B) in order to have independent measurements. For each mosaic, regions of overlap from frame-to-frame are being averaged and the attendant standard deviations are being calculated. Due to the highly redundant nature of the data, each pixel in each mosaic will be an average calculated from 1-10 images. Each mosaic will have a corresponding standard deviation and n (number of measurements) map. A final mosaic will be created by averaging the six independent mosaics. This procedure lessens the effects of random noise and calibration residuals. From these data an albedo map will be produced using an improved photometric function for the Moon. A similar procedure is being followed for the lower resolution color sequences (ultraviolet, blue, orange, ultraviolet polarized). These data will be calibrated to absolute units through comparison of Mariner 10 images acquired of the Moon and Jupiter. Spectral interpretation of these new color and albedo maps will be presented with an emphasis on comparison with the Moon.

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

    NASA Astrophysics Data System (ADS)

    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.

  9. Impact of absorbing aerosol deposition on snow albedo reduction over the southern Tibetan plateau based on satellite observations

    NASA Astrophysics Data System (ADS)

    Lee, Wei-Liang; Liou, K. N.; He, Cenlin; Liang, Hsin-Chien; Wang, Tai-Chi; Li, Qinbin; Liu, Zhenxin; Yue, Qing

    2016-07-01

    We investigate the snow albedo variation in spring over the southern Tibetan Plateau induced by the deposition of light-absorbing aerosols using remote sensing data from moderate resolution imaging spectroradiometer (MODIS) aboard Terra satellite during 2001-2012. We have selected pixels with 100 % snow cover for the entire period in March and April to avoid albedo contamination by other types of land surfaces. A model simulation using GEOS-Chem shows that aerosol optical depth (AOD) is a good indicator for black carbon and dust deposition on snow over the southern Tibetan Plateau. The monthly means of satellite-retrieved land surface temperature (LST) and AOD over 100 % snow-covered pixels during the 12 years are used in multiple linear regression analysis to derive the empirical relationship between snow albedo and these variables. Along with the LST effect, AOD is shown to be an important factor contributing to snow albedo reduction. We illustrate through statistical analysis that a 1-K increase in LST and a 0.1 increase in AOD indicate decreases in snow albedo by 0.75 and 2.1 % in the southern Tibetan Plateau, corresponding to local shortwave radiative forcing of 1.5 and 4.2 W m-2, respectively.

  10. Albedo and transmittance of inhomogeneous stratus clouds

    SciTech Connect

    Zuev, V.E.; Kasyanov, E.I.; Titov, G.A.

    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.

  11. Global color and albedo variations on Io

    NASA Technical Reports Server (NTRS)

    Mcewen, Alfred S.

    1988-01-01

    The present Voyager imaging data multispectral mosaics of Io include global mosaics from each of the Voyager 1 and 2 data sets and a high-resolution mosaic of the region centered on the Ra Patera volcano. The constancy of the disk-integrated color and albedo of Io over recent decades despite volcanic activity may be due to the regular occurrence of large Pele-type plumes with relatively dark, red deposits. Io's intrinsic spectral variability involves continuous variation among three major spectral end members. Attention is given to the mapping of the data into five spectral units for the purposes of comparison with laboratory measurements of Io surface material candidates.

  12. Albedo maps of Pluto and Charon - Initial mutual event results

    NASA Technical Reports Server (NTRS)

    Buie, Marc W.; Tholen, David J.; Horne, Keith

    1992-01-01

    By applying the technique of maximum entropy image reconstruction to invert observed lightcurves, surface maps of single-scattering albedo are obtained for the surfaces of Pluto and Charon from 1954 to 1986. The albedo features of the surface of Pluto are similar to those of the Buie and Tholen (1989) spot model maps; a south polar cap is evident. The map of Charon is somewhat darker, with single-scattering albedos as low as 0.03.

  13. THE ALBEDO-COLOR DIVERSITY OF TRANSNEPTUNIAN OBJECTS

    SciTech Connect

    Lacerda, Pedro; Rengel, Miriam; Fornasier, Sonia; Lellouch, Emmanuel; Delsanti, Audrey; Kiss, Csaba; Vilenius, Esa; Müller, Thomas; Santos-Sanz, Pablo; Duffard, René; Guilbert-Lepoutre, Aurélie

    2014-09-20

    We analyze albedo data obtained using the Herschel Space Observatory that reveal the existence of two distinct types of surface among midsized trans-Neptunian objects. A color-albedo diagram shows two large clusters of objects, one redder and higher albedo and another darker and more neutrally colored. Crucially, all objects in our sample located in dynamically stable orbits within the classical Kuiper Belt region and beyond are confined to the bright red group, implying a compositional link. Those objects are believed to have formed further from the Sun than the dark neutral bodies. This color-albedo separation is evidence for a compositional discontinuity in the young solar system.

  14. Enhancement of the MODIS Daily Snow Albedo Product

    NASA Technical Reports Server (NTRS)

    Hall, Dorothy K.; Schaaf, Crystal B.; Wang, Zhuosen; Riggs, George A.

    2009-01-01

    The MODIS daily snow albedo product is a data layer in the MOD10A1 snow-cover product that includes snow-covered area and fractional snow cover as well as quality information and other metadata. It was developed to augment the MODIS BRDF/Albedo algorithm (MCD43) that provides 16-day maps of albedo globally at 500-m resolution. But many modelers require daily snow albedo, especially during the snowmelt season when the snow albedo is changing rapidly. Many models have an unrealistic snow albedo feedback in both estimated albedo and change in albedo over the seasonal cycle context, Rapid changes in snow cover extent or brightness challenge the MCD43 algorithm; over a 16-day period, MCD43 determines whether the majority of clear observations was snow-covered or snow-free then only calculates albedo for the majority condition. Thus changes in snow albedo and snow cover are not portrayed accurately during times of rapid change, therefore the current MCD43 product is not ideal for snow work. The MODIS daily snow albedo from the MOD10 product provides more frequent, though less robust maps for pixels defined as "snow" by the MODIS snow-cover algorithm. Though useful, the daily snow albedo product can be improved using a daily version of the MCD43 product as described in this paper. There are important limitations to the MOD10A1 daily snow albedo product, some of which can be mitigated. Utilizing the appropriate per-pixel Bidirectional Reflectance Distribution Functions (BRDFs) can be problematic, and correction for anisotropic scattering must be included. The BRDF describes how the reflectance varies with view and illumination geometry. Also, narrow-to-broadband conversion specific for snow on different surfaces must be calculated and this can be difficult. In consideration of these limitations of MOD10A1, we are planning to improve the daily snow albedo algorithm by coupling the periodic per-pixel snow albedo from MCD43, with daily surface ref|outanoom, In this paper, we

  15. Estimation of four land surface essential climate variables (albedo, LAI/FAPAR, and Fcover) from VIIRS data

    NASA Astrophysics Data System (ADS)

    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.

  16. FIELD CORRECTION FACTORS FOR PERSONAL NEUTRON DOSEMETERS.

    PubMed

    Luszik-Bhadra, M

    2016-09-01

    A field-dependent correction factor can be obtained by comparing the readings of two albedo neutron dosemeters fixed in opposite directions on a polyethylene sphere to the H*(10) reading as determined with a thermal neutron detector in the centre of the same sphere. The work shows that the field calibration technique as used for albedo neutron dosemeters can be generalised for all kind of dosemeters, since H*(10) is a conservative estimate of the sum of the personal dose equivalents Hp(10) in two opposite directions. This result is drawn from reference values as determined by spectrometers within the EVIDOS project at workplace of nuclear installations in Europe. More accurate field-dependent correction factors can be achieved by the analysis of several personal dosimeters on a phantom, but reliable angular responses of these dosemeters need to be taken into account. PMID:26493946

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

    NASA Astrophysics Data System (ADS)

    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.

  18. From Regional Cloud-Albedo to a Global Albedo Footprint - Studying Aerosol Effects on the Radiation Budget Using the Relation Between Albedo and Cloud Fraction

    NASA Astrophysics Data System (ADS)

    Bender, F.; Engström, A.; Karlsson, J.; Wood, R.; Charlson, R. J.

    2015-12-01

    Earth's albedo is the primary determinant of the amount of energy absorbed by the Earth-atmosphere system. The main factor controlling albedo is the amount of clouds present, but aerosols can affect and alter both clear-sky and cloudy-sky reflectance. How albedo depends on cloud fraction and how albedo varies at a given cloud fraction and a given cloud water content, reveals information about these aerosol effects on the radiation budget. Hence, the relation between total albedo and cloud fraction can be used for illustration and quantification of aerosol effects, and as a diagnostic tool, to test model performance. Here, we show examples of the utilisation of this relation focusing on satellite observations from CERES and MODIS on Aqua, as well as from Calipso and CloudSat, and performing comparisons with climate models on the way: In low-cloud regions in the subtropics, we find that climate models well represent a near-constant regional cloud albedo, and this representation has improved from CMIP3 to CMIP5. CMIP5 models indicate more reflective clouds in present-day climate than pre-industrial, as a result of increased aerosol burdens. On monthly mean time scale, models are found to over-estimate the regional cloud-brightening due to aerosols. On the global scale we find an increasing cloud albedo with increasing cloud fraction - a relation that is very well defined in observations, and less so in CMIP5 models. Cloud brightening from pre-industrial to present day is also seen on global scale. Further, controlling for both cloud fraction and cloud water content we can trace small variations in albedo, or perturbations of solar reflectivity, that create a near-global coherent geographical pattern that is consistent with aerosol impacts on climate, with albedo enhancement in regions dominant of known aerosol sources and suppression of albedo in regions associated with high rates of aerosol removal (deduced using CloudSat precipitation estimates). This mapping can be

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

    NASA Technical Reports Server (NTRS)

    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.

  20. The albedo of snow for partially cloudy skies

    NASA Technical Reports Server (NTRS)

    Choudhury, B. J.; Chang, A. T. C.

    1980-01-01

    The input parameters of the model are atmospheric precipitable water, ozone content, turbidity, cloud optical thickness, size and shape of ice crystal of snow and surface pressure. The model outputs spectral and integrated solar flux snow reflectance as a function of solar elevation and fractional cloudcover. The model is illustrated using representative parameters for the Antarctic coastal regions. The albedo for a clear sky depends inversely on the solar elevation. At high elevation the albedo depends primarily upon the grain size; at low elevation this dependence is on grain size and shape. The gradient of the albedo-elevation curve increases as the grains get larger and faceted. The albedo for a dense overcast is a few percent higher than the clear sky albedo at high elevations. A simple relation between the grain size and the overcast albedo is obtained. For a set of grain size and shape, the albedo matrices (the albedo as a function of solar elevation and fractional cloudcover) are tabulated.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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. Seasonal evolution of the albedo of multiyear Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Perovich, D. K.; Grenfell, T. C.; Light, B.; Hobbs, P. V.

    2002-10-01

    As part of ice albedo feedback studies during the Surface Heat Budget of the Arctic Ocean (SHEBA) field experiment, we measured spectral and wavelength-integrated albedo on multiyear sea ice. Measurements were made every 2.5 m along a 200-m survey line from April through October. Initially, this line was completely snow covered, but as the melt season progressed, it became a mixture of bare ice and melt ponds. Observed changes in albedo were a combination of a gradual evolution due to seasonal transitions and abrupt shifts resulting from synoptic weather events. There were five distinct phases in the evolution of albedo: dry snow, melting snow, pond formation, pond evolution, and fall freeze-up. In April the surface albedo was high (0.8-0.9) and spatially uniform. By the end of July the average albedo along the line was 0.4, and there was significant spatial variability, with values ranging from 0.1 for deep, dark ponds to 0.65 for bare, white ice. There was good agreement between surface-based albedos and measurements made from the University of Washington's Convair-580 research aircraft. A comparison between net solar irradiance computed using observed albedos and a simplified model of seasonal evolution shows good agreement as long as the timing of the transitions is accurately determined.

  3. Neutron measurements in near-Earth orbit with COMPTEL

    NASA Technical Reports Server (NTRS)

    Morris, D. J.; Aarts, H.; Bennett, K.; Lockwood, J. A.; Mcconnell, M. L.; Ryan, J. M.; Schoenfelder, V.; Steinle, H.; Peng, X.

    1995-01-01

    The fast neutron flux in near-Earth orbit has been measured with the COMPTEL instrument on the Compton Gamma Ray Observatory (CGRO). For this measurement one of COMPTEL's seven liquid scintillator modules was used as an uncollimated neutron detector with threshold of 12.8 MeV. The measurements cover a range of 4.8 to 15.5 GV in vertical cutoff rigidity and 3 deg to 177 deg in spacecraft geocenter zenith angle. One of the measurements occurred near the minimum of the deepest Forbush decrease ever observed by ground-level neutron monitors. After correction for solar modulation, the total flux is well fitted by separable functions in rigidity and zenith angle. With the spacecraft pointed near the nadir the flux is consistent with balloon measurements of the atmospheric neutron albedo. The flux varies by about a factor of 4 between the extremes of rigidity and a factor of 2 between the extremes of zenith angle. The effect of the spacecraft mass in shielding the detector from the atmospheric neutron albedo is much more important than its role as a source of additional secondary neutrons. The neutron spectral hardness varies little with rigidity or zenith angle and lies in the range spanned by earlier atmospheric neutron albedo measurements.

  4. Satellite Albedo products Validation by Upscaling Multi-nodes in situ Data into a Satellite Pixel Scale over Heterogeneous Land Surface

    NASA Astrophysics Data System (ADS)

    You, D.; Wen, J.; Wu, X.; Liu, Q.; Peng, J.; Xiao, Q.; Qinhuo, L.

    2015-12-01

    Land surface albedo is a key parameter for energy budgets. There are many available products from remote sensing sensors, such as Moderate Resolution Imaging Spectroradiometer (MODIS), Visible Infrared Imaging Radiometer Suite (VIIRS), and Advanced Very High Resolution Radiometer (AVHRR) and so on. Their accuracy should be carefully quantified before being used. Most validations directly use a single-point in situ measurement in the relatively homogeneous land surface. However, it is not valid over heterogeneous cases. A multi-scale validation strategy using a high-resolution albedo imagery as a bridge is alternative, with several uncertainties from high-spatial-resolution albedo imagery, geometric registration, and the upscaling process. It results a relative precision. Hence, for more effective validation, the albedo absolute value based on ground measurements is still required, which can be conceptualized as the "truth" value of pixel scale albedo. In this study, a sampling strategy based on using wireless sensor network (WSN) technology to measure albedo at multiple nodes is proposed to capture the land surface heterogeneity in Huailai remote sensing test station, Hebei province, China, which is one station of a Chinese validation network (fig. 1). The nodes are distributed in an optimal layout determined by a sequential selection method using theirs representativeness. The first six nodes with the highest degree of representativeness are finally selected (fig. 2). Upscaling functions with different weights for each node, calculated by the ordinary least squares (OLS) linear regression, are used to upscale them to a coarse pixel scale. Application is exemplified by the validation of the MODIS albedo product (fig. 3), and VIIRS albedo product (fig.4), from Jul. 18, 2013 to Jul. 31, 2014. The RMSEs are 0.025 and 0.020 for MCD43B3 full inversion and magnitude inversion, respectively. The overall accuracy of VIIRS albedo is 0.021 and 0.014 under clear sky and

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    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 (NEAs) and 8885 other asteroids. Of the NEAs, 84% NEAs 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 ±˜20% and ±˜40%, 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.

  7. Global color and albedo variations on Io

    USGS Publications Warehouse

    McEwen, A.S.

    1988-01-01

    Three multispectral mosaics of Io have been produced from Voyager imaging data: a global mosaic from each of the Voyager 1 and Voyager 2 data sets and a high-resolution mosaic of the region surrounding the volcano Ra Patera. The mosaics are maps of normal albedo and color in accurate geometric map formats. Io's photometric behavior, mapped with a two-image technique, is spatially variable, especially in the bright white areas. The disk-integrated color and albedo of the satellite have been remarkably constant over recent decades, despite the volcanic activity and the many differences between Voyager 1 and 2 images (acquired just 4 months apart). This constancy is most likely due to the consistent occurrence of large Pele-type plumes with relatively dark, red deposits in the region from long 240 to 360??. A transient brightening southeast of Pele during the Voyager 1 encounter was probably due to real changes in surface and/or atmospheric materials, rather than to photometric behavior. The intrinsic spectral variability of Io, as seen in a series of two-dimensional histograms of the multispectral mosaics, consists of continuous variation among three major spectral end members. The data were mapped into five spectral units to compare them with laboratory measurements of candidate surface materials and to show the planimetric distributions. Unit 1 is best fit by the spectral reflectance of ordinary elemental sulfur, and it is closely associated with the Peletype plume deposits. Unit 2 is strongly confined to the polar caps above about latitude ??50??, but its composition is unknown. Unit 5 is probably SO2 with relatively minor contamination; it is concentrated in the equatorial region and near the long-lived Prometheus-type plumes. Units 3 and 4 are gradational between units 1 and 5. In addition to SO2 and elemental sulfur, other plausible components of the surface are polysulfur oxides, FeCl2, Na2S, and NaHS. ?? 1988.

  8. Fire disturbance effects on land surface albedo in Alaskan tundra

    NASA Astrophysics Data System (ADS)

    French, Nancy H. F.; Whitley, Matthew A.; Jenkins, Liza K.

    2016-03-01

    The study uses satellite Moderate Resolution Imaging Spectroradiometer albedo products (MCD43A3) to assess changes in albedo at two sites in the treeless tundra region of Alaska, both within the foothills region of the Brooks Range, the 2007 Anaktuvuk River Fire (ARF) and 2012 Kucher Creek Fire (KCF). Results are compared to each other and other studies to assess the magnitude of albedo change and the longevity of impact of fire on land surface albedo. In both sites there was a marked decrease of albedo in the year following the fire. In the ARF, albedo slowly increased until 4 years after the fire, when it returned to albedo values prior to the fire. For the year immediately after the fire, a threefold difference in the shortwave albedo decrease was found between the two sites. ARF showed a 45.3% decrease, while the KCF showed a 14.1% decrease in shortwave albedo, and albedo is more variable in the KCF site than ARF site 1 year after the fire. These differences are possibly the result of differences in burn severity of the two fires, wherein the ARF burned more completely with more contiguous patches of complete burn than KCF. The impact of fire on average growing season (April-September) surface shortwave forcing in the year following fire is estimated to be 13.24 ± 6.52 W m-2 at the ARF site, a forcing comparable to studies in other treeless ecosystems. Comparison to boreal studies and the implications to energy flux are discussed in the context of future increases in fire occurrence and severity in a warming climate.

  9. Snow-albedo feedback in future climate change

    NASA Astrophysics Data System (ADS)

    Qu, Xin

    We quantify the two factors controlling Northern Hemisphere springtime snow-albedo feedback in transient climate change based on scenario runs of 18 climate models used in the Intergovernmental Panel of Climate Change 4th Assessment. The first factor is the dependence of planetary albedo on surface albedo. We find in all simulations surface albedo anomalies are attenuated by approximately half in Northern Hemisphere land areas as they are transformed into planetary albedo anomalies. The intermodel standard deviation in this factor is surprisingly small. Moreover, when we calculate an observational estimate of this factor using the satellite-based International Satellite Cloud Climatology Project data, we find most simulations agree with ISCCP values to within about 10%. The second factor, related exclusively to surface processes, is the change in surface albedo associated with an anthropogenically-induced temperature change in Northern Hemisphere land areas. It exhibits much more intermodel variability. This large intermodel spread is attributable mostly to a correspondingly large spread in mean effective snow albedo. Models without explicit treatment of the vegetation canopy in their surface albedo calculations typically have high effective snow albedos and strong SAF, often stronger than observed. In models with explicit canopy treatment, completely snow-covered surfaces typically have lower albedos and the simulations have weaker SAF, generally weaker than observed. These large intermodel variations in feedback strength in climate change are nearly perfectly correlated with comparably large intermodel variations in feedback strength in the context of the seasonal cycle. Moreover, the feedback strength in the real seasonal cycle can be measured and compared to simulated values. These mostly fall outside the range of the observed estimate. Because of the tight correlation between simulated feedback strength in the seasonal cycle and climate change, eliminating the

  10. Relationship between cloud radiative forcing, cloud fraction and cloud albedo, and new surface-based approach for determining cloud albedo

    SciTech Connect

    Liu, Y.; Wu, W.; Jensen, M. P.; Toto, T.

    2011-07-21

    This paper focuses on three interconnected topics: (1) quantitative relationship between surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo; (2) surface-based approach for measuring cloud albedo; (3) multiscale (diurnal, annual and inter-annual) variations and covariations of surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo. An analytical expression is first derived to quantify the relationship between cloud radiative forcing, cloud fraction, and cloud albedo. The analytical expression is then used to deduce a new approach for inferring cloud albedo from concurrent surface-based measurements of downwelling surface shortwave radiation and cloud fraction. High-resolution decade-long data on cloud albedos are obtained by use of this surface-based approach over the US Department of Energy's Atmospheric Radiaton Measurement (ARM) Program at the Great Southern Plains (SGP) site. The surface-based cloud albedos are further compared against those derived from the coincident GOES satellite measurements. The three long-term (1997-2009) sets of hourly data on shortwave cloud radiative forcing, cloud fraction and cloud albedo collected over the SGP site are analyzed to explore the multiscale (diurnal, annual and inter-annual) variations and covariations. The analytical formulation is useful for diagnosing deficiencies of cloud-radiation parameterizations in climate models.

  11. Generating multi-scale albedo look-up maps using MODIS BRDF/Albedo products and landsat imagery

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surface albedo determines radiative forcing and is a key parameter for driving Earth’s climate. Better characterization of surface albedo for individual land cover types can reduce the uncertainty in estimating changes to Earth’s radiation balance due to land cover change. This paper presents a mult...

  12. Quality assessment and improvement of the EUMETSAT Meteosat Surface Albedo dataset

    NASA Astrophysics Data System (ADS)

    Lattanzio, Alessio; Fell, Frank; Bennartz, Ralf; Muller, Jan-Peter; Trigo, Isabel; Löw, Alexander; Schulz, Jörg

    2015-04-01

    Surface albedo is an important parameter for quantifying and understanding the nature of the Earth's radiation budget. This study describes a comprehensive validation of the EUMETSAT Meteosat Surface Albedo (MSA) Climate Data Record (CDR) currently comprising up to 24 years (1982-2006) of continuous surface albedo coverage for large areas covering Africa, Europe and western parts of Asia. In addition it is discussing retrieval improvements as a consequence of the validation results. The MSA CDR has been generated within a project of the WMO entitled Sustained and Coordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM) initiative. The MSA CDR went into a two step validation process. Firstly, the satellite product has been compared to available in situ and satellite data assessing systematic and random deviations among the products. This also included an assessment of the temporal stability over desert sites that are assumed to remain stable over time. Furthermore impact on product quality due to anisotropic effects or snow covered surfaces has been analysed. The evaluation has revealed a number of specific strengths and weaknesses. The long-term consistency is very high and meets the Global Climate Observing System (GCOS) stability requirements for desert reference sites. The limitation in quality appears to be due primarily to clouds not removed by the embedded cloud screening procedure as the most significant weakness of the retrieval process. Two alternative strategies are followed to efficiently improve the cloud detection and removal. The first is based on the application of a robust and reliable cloud mask during the retrieval taking advantage of the information contained in the measurements of the infrared and visible bands. The second, in order to screen out outlier values, relies on a post processing analysis of the albedo seasonal variation together with the usage of "a priori" information contained in a background albedo

  13. Pulsed neutron detector

    DOEpatents

    Robertson, deceased, J. Craig; Rowland, Mark S.

    1989-03-21

    A pulsed neutron detector and system for detecting low intensity fast neutron pulses has a body of beryllium adjacent a body of hydrogenous material the latter of which acts as a beta particle detector, scintillator, and moderator. The fast neutrons (defined as having En>1.5 MeV) react in the beryllium and the hydrogenous material to produce larger numbers of slow neutrons than would be generated in the beryllium itself and which in the beryllium generate hellium-6 which decays and yields beta particles. The beta particles reach the hydrogenous material which scintillates to yield light of intensity related to the number of fast neutrons. A photomultiplier adjacent the hydrogenous material (scintillator) senses the light emission from the scintillator. Utilization means, such as a summing device, sums the pulses from the photo-multiplier for monitoring or other purposes.

  14. Differential neutron energy spectra measured on spacecraft low Earth orbit

    NASA Technical Reports Server (NTRS)

    Benton, E. V.; Frank, A. L.; Dudkin, E. V.; Potapov, Yu. V.; Akopova, A. B.; Melkumyan, L. V.

    1995-01-01

    Two methods for measuring neutrons in the range from thermal energies to dozens of MeV were used. In the first method, alpha-particles emitted from the (sup 6) Li(n.x)T reaction are detected with the help of plastic nuclear track detectors, yielding results on thermal and resonance neutrons. Also, fission foils are used to detect fast neutrons. In the second method, fast neutrons are recorded by nuclear photographic emulsions (NPE). The results of measurements on board various satellites are presented. The neutron flux density does not appear to correlate clearly with orbital parameters. Up to 50% of neutrons are due to albedo neutrons from the atmosphere while the fluxes inside the satellites are 15-20% higher than those on the outside. Estimates show that the neutron contribution to the total equivalent radiation dose reaches 20-30%.

  15. The Gamma-ray Albedo of the Moon

    SciTech Connect

    Moskalenko, Igor V.; 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.

  16. ALBEDOS OF SMALL HILDA GROUP ASTEROIDS AS REVEALED BY SPITZER

    SciTech Connect

    Ryan, Erin Lee; Woodward, Charles E. E-mail: chelsea@astro.umn.edu

    2011-06-15

    We present thermal 24 {mu}m observations from the Spitzer Space Telescope of 62 Hilda asteroid group members with diameters ranging from 3 to 12 km. Measurements of the thermal emission, when combined with reported absolute magnitudes, allow us to constrain the albedo and diameter of each object. From our Spitzer sample, we find the mean geometric albedo, p{sub V} = 0.07 {+-} 0.05, for small (D < 10 km) Hilda group asteroids. This Spitzer-derived value of p{sub V} is greater than and spans a larger range in albedo space than the mean albedo of large (D {approx}> 10 km) Hilda group asteroids which is p{sub V} = 0.04 {+-} 0.01. Though this difference may be attributed to space weathering, the small Hilda group population reportedly displays greater taxonomic range from C-, D-, and X-type whose albedo distributions are commensurate with the range of determined albedos. We discuss the derived Hilda size-frequency distribution, color-color space, and geometric albedo for our survey sample in the context of the expected migration induced 'seeding' of the Hilda asteroid group with outer solar system proto-planetesimals as outlined in the 'Nice' formalism.

  17. Arid land monitoring using Landsat albedo difference images

    USGS Publications Warehouse

    Robinove, Charles J.; Chavez, Pat S.; Gehring, Dale G.; Holmgren, Ralph

    1981-01-01

    The Landsat albedo, or percentage of incoming radiation reflected from the ground in the wavelength range of 0.5 [mu]m to 1.1 [mu]m, is calculated from an equation using the Landsat digital brightness values and solar irradiance values, and correcting for atmospheric scattering, multispectral scanner calibration, and sun angle. The albedo calculated for each pixel is used to create an albedo image, whose grey scale is proportional to the albedo. Differencing sequential registered images and mapping selected values of the difference is used to create quantitative maps of increased or decreased albedo values of the terrain. All maps and other output products are in black and white rather than color, thus making the method quite economical. Decreases of albedo in arid regions may indicate improvement of land quality; increases may indicate degradation. Tests of the albedo difference mapping method in the Desert Experimental Range in southwestern Utah (a cold desert with little long-term terrain change) for a four-year period show that mapped changes can be correlated with erosion from flash floods, increased or decreased soil moisture, and increases or decreases in the density of desert vegetation, both perennial shrubs and annual plants. All terrain changes identified in this test were related to variations in precipitation. Although further tests of this method in hot deserts showing severe "desertification" are needed, the method is nevertheless recommended for experimental use in monitoring terrain change in other arid and semiarid regions of the world.

  18. The Gamma-Ray Albedo of the Moon

    SciTech Connect

    Moskalenko, I.V.; Porter, T.A.; /UC, Santa Cruz

    2008-03-25

    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.

  19. Aerial albedos of natural vegetation in South-eastern Australia

    NASA Technical Reports Server (NTRS)

    Howard, J. A.

    1977-01-01

    Black-and-white low-level 70mm photography was used to record the track of the aircraft, which was then plotted on conventional 1:80,000 23 cm photogrammetric photographs and referenced against simultaneous measurements of the beam albedos of vegetation. Using stereoscopic pairs of the 70mm photographs, the vegetation was classified into sub-formations. Marked differences in the 'sub-formation' albedos were observed. A two-way table using stand height and crown cover of the sub-formations clearly showed a very distinctive trend of albedos. This finding may be important in other vegetal studies.

  20. Lunar Terrain and Albedo Reconstruction from Apollo Imagery

    NASA Technical Reports Server (NTRS)

    Nefian, Ara V.; Kim, Taemin; Broxton, Michael; Moratto, Zach

    2010-01-01

    Generating accurate three dimensional planetary models and albedo maps is becoming increasingly more important as NASA plans more robotics missions to the Moon in the coming years. This paper describes a novel approach for separation of topography and albedo maps from orbital Lunar images. Our method uses an optimal Bayesian correlator to refine the stereo disparity map and generate a set of accurate digital elevation models (DEM). The albedo maps are obtained using a multi-image formation model that relies on the derived DEMs and the Lunar- Lambert reflectance model. The method is demonstrated on a set of high resolution scanned images from the Apollo era missions.

  1. Regional Land Surface Hydrology Impacts from Fire-Induced Surface Albedo Darkening in Northern Sub-Saharan Africa

    NASA Astrophysics Data System (ADS)

    Bolten, J. D.; Gupta, M.; Gatebe, C. K.; Ichoku, C. M.

    2015-12-01

    Land surface hydrology models serve as an effective approach to simulate hydrological processes, especially in areas which lack in situ observational datasets. A key component to constraining the water, energy, and carbon dynamics within these models is land surface albedo because it links these cycles by driving evapotranspiration and also helps characterize soil infiltration behavior. However, most hydrological models estimate the land surface albedo based on generalized climatologic information, which can introduce uncertainty into the surface energy balance processes and water storage availability in the root-zone if done improperly. In particular, changes in surface albedo can have significant effects where dynamic and spatially heterogeneous land surface changes occur due to abrupt land cover changes, such as wildfire. Sub-Saharan Africa is one of the most fire-prone regions of the world. Thus, the current study employs the new parameterization approach based on estimated change of surface albedo due to fires over different land cover types using long term MODIS time series in the catchment-based land surface model to investigate the potential for improving soil moisture and evapotranspiration simulations in fire-prone Northern Sub-Saharan Africa. We also compare the estimated soil moisture based on new and pre-existing baseline parameterization scheme to remotely-sensed observations obtained from satellite-based soil moisture observations from the Advanced Microwave Scanning Radiometer (AMSR-E), the Soil Moisture Ocean Salinity (SMOS), and the recently launched satellite, Soil Moisture Active Passive (SMAP) instruments.

  2. The Albedo Distribution of Near Earth Asteroids

    NASA Astrophysics Data System (ADS)

    Wright, Edward L.

    2016-01-01

    The cryogenic WISE mission in 2010 was extremely sensitive to asteroids and not biased against detecting dark objects. Mainzer et al (2011, ApJ, 743, 156) fit the distribution of albedos of the 428 NEAs observed by WISE with a double Gaussian function with 5 parameters.This note describes a 3 parameter function that fits as well as the double Gaussian: a sum of two Rayleigh distributions. The Rayleigh distribution is zero for negative values, and follows f(x) = x exp[-x2/(2σ2)]/σ2 for positive x. The peak value is at x=σ, 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 normal peak. 25.1% of the NEAs observed by WISE are in a very dark population peaking at pV = 0.03, while the other 74.9% of the NEAs seen by WISE are in a moderately dark population peaking at pV = 0.167.A consequence of this bimodal distribution is that the Congressional mandate to find 90% of all NEOs larger than 140 m diameter cannot be satisfied by surveying to H=22 mag, since a 140 m diameter asteroid at the very dark peak has H=23.7 mag, and more than 10% of NEAs are darker than pV = 0.03.

  3. The Albedo Distribution of Near Earth Asteroids

    NASA Astrophysics Data System (ADS)

    Wright, Edward L.; Mainzer, Amy; Masiero, Joseph; Grav, Tommy; Bauer, James

    2016-10-01

    The cryogenic Wide-field Infrared Survey Explorer (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 three 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{σ }2)]/{σ }2 for positive x. The peak value is at x = σ, 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 = 0.030, 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 surveying to H = 22 mag, since a 140 m diameter asteroid at the very dark peak has H = 23.7 mag, and more than 10% of NEAs are darker than p V = 0.03.

  4. Global color and albedo variations on Triton

    NASA Technical Reports Server (NTRS)

    Mcewen, Alfred S.

    1990-01-01

    Global multispectral mosaics of Triton have been produced from Voyager approach images; six spectral units are defined and mapped. The margin of the south polar cap (SPC) is scalloped and ranges in latitude from + 10 deg to -30 deg. A bright fringe is closely associated with the cap's margin; form it, diffuse bright rays extend north-northeast for hundreds of kilometers. Thus, the rays may consist of fringe materials that were redistributed by northward-going Coriolis-deflected winds. From 1977 to 1989, Triton's full-disk spectrum changed from markedly red and UV-dark to nearly neutral white and UV-bright. This spectral change can be explained by new deposition of nitrogen frost over both the northern hemisphere and parts of a formerly redder SPC. Frost deposition in the southern hemisphere during southern summer is possible over relatively high albedo areas of the cap (Stansberry et al., 1990), which helps to explain the apparent stability of the unexpectedly large SPC and the presence of the bright fringe.

  5. A preliminary global oceanic cloud climatology from satellite albedo observations

    NASA Technical Reports Server (NTRS)

    Hughes, N. A.; Henderson-Sellers, A.

    1983-01-01

    A predictive relationship is developed between over-ocean cloud system albedo and the cloud amount present, using as a data base ERB satellite microwave readings at 0.5-0.7 micron and the USAF three-dimensional nephanalysis archive. The ERB data provided global coverage at a resolution of 2.5 x 2.5 deg during the 1974-78 period. Regression analyses were performed on the amounts and albedos for several years of data for one month in order to detect seasonal variations. A logarithmic relationship was found between the cloud system albedo and cloud amount over the oceans, with negligible seasonal variance. The analysis is noted to apply only where low surface albedos are encountered, and further work to extend the study to continental vegetated areas is indicated.

  6. The Changing Albedo of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Human, J. M.; Box, J. E.

    2009-12-01

    The study evaluates Greenland ice sheet surface albedo sensitivity to surface melt intensity, air pollution, and precipitation using data from the MODIS and MOPITT sensors operating on the NASA Terra satellite 2000-2009. Precipitation rates are simulated by the Polar WRF climate model running in data assimilation mode. Statistical regression facilitates ranking the relative importance of each of the albedo forcings in space and time. Further, quantitative estimates of the albedo sensitivity to its forcing factors are made, for the first time and over the observed inter-annual range. The work investigates regional patterns in detail to quantify melt water production associated with absorbed solar radiation variability. In-situ records are used to evaluate the cloud radiative effect as another important factor of absorbed solar radiation and ice melt. Insight into Greenland ice sheet melt-precipitation-pollution-albedo feedback is gained, key in better understanding the mass balance response of the ice sheet to future climate change.

  7. Cloud condensation nucleus-sulfate mass relationship and cloud albedo

    NASA Technical Reports Server (NTRS)

    Hegg, Dean A.

    1994-01-01

    Analysis of previously published, simultaneous measurements of cloud condensation nucleus number concentration and sulfate mass concentration suggest a nonlinear relationship between the two variables. This nonlinearity reduces the sensitivity of cloud albedo to changes in the sulfur cycle.

  8. On the definition of albedo and application to irregular particles

    NASA Technical Reports Server (NTRS)

    Hanner, M. S.; Giese, R. H.; Weiss, K.; Zerull, R.

    1981-01-01

    The various definitions of albedo used in planetary astronomy are reviewed. In particular, the Bond albedo, which refers only to the reflected and refracted components, is not applicable to small particles or highly irregular particles, where diffraction is not restricted to a well-defined lobe at small scattering angles. Measured scattering functions for irregular particles are presented in a normalized form and are applied to the case of zodiacal light.

  9. NEOWISE Diameters and Albedos V1.0

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    This PDS data set represents a compilation of published diameters, optical albedos, near-infrared albedos, and beaming parameters for minor planets detected by NEOWISE during the fully cryogenic, 3-band cryo, post-cryo and NEOWISE-Reactivation Year 1 operations. It contains data covering near-Earth asteroids, Main Belt asteroids, active Main Belt objects, Hildas, Jupiter Trojans, Centaurs, and Jovian and Saturnian irregular satellites. Methodology for physical property determination is described in the referenced articles.

  10. Measurements of Black Carbon Induced Snow-Albedo Reduction

    NASA Astrophysics Data System (ADS)

    Hadley, O. L.; Kirchstetter, T. W.

    2011-12-01

    Several modeling studies have indicated that black carbon (BC) reduces the albedo of snow and ice and appreciably contributes to Northern Hemisphere warming and glacier retreat. Observations of the BC impact on snow albedo are needed to verify model predictions. Whereas field studies dating back to the early 1980s measured BC concentrations in snow and ice in the arctic, the BC effect on snow albedo and melting has been difficult to observe directly because the albedo reduction is small and often masked by other natural variables. This study evaluates both the initial impact of BC on snow albedo, as well as associated feedbacks due to snow age and BC scavenging during snow melting. The first feedback is related to the increasing grain size of snow as it ages. Larger snow grains allow sunlight to penetrate farther, where it is exposed to and may be increasingly absorbed by BC. This enhances the albedo reduction attributable to the mass of BC present in the snow and deposits energy at greater depths in the snowpack, potentially increasing the melt rate and therefore the growth rate of the snow grains. The second potential feedback, associated with BC transport through a melting snowpack, occurs if BC is scavenged from the melt water by the ice grains thus increasing the BC concentration in the remaining snow. Measurement of pristine and sooty snow made in the laboratory verifies that BC reduces snow albedo to a greater extent for larger-grained snow. Experimental observations yield an empirical model of the BC snow albedo reduction. Measurements of BC transport in both laboratory and natural snow were used to develop a model of the evolution of the vertical distribution of BC in melting snow. These measurements provide the first quantification of a BC concentration enhancement in melting snow.

  11. Surface albedo observations at Gusev Crater and Meridiani Planum, Mars

    USGS Publications Warehouse

    Bell, J.F.; Rice, M.S.; Johnson, J. R.; Hare, T.M.

    2008-01-01

    During the Mars Exploration Rover mission, the Pancam instrument has periodically acquired large-scale panoramic images with its broadband (739??338 nm) filter in order to estimate the Lambert bolometric albedo of the surface along each rover's traverse. In this work we present the full suite of such estimated albedo values measured to date by the Spirit and Opportunity rovers along their traverses in Gusev Crater and Meridiani Planum, respectively. We include estimated bolometric albedo values of individual surface features (e.g., outcrops, dusty plains, aeolian bed forms, wheel tracks, light-toned soils, and crater walls) as well as overall surface averages of the 43 total panoramic albedo data sets acquired to date. We also present comparisons to estimated Lambert albedo values taken from the Mars Global Surveyor Mars Orbiter Camera (MOC) along the rovers' traverses, and to the large-scale bolometric albedos of the sites from the Viking Orbiter Infrared Thermal Mapper (IRTM) and Mars Global Surveyor/Thermal Emission Spectrometer (TES). The ranges of Pancam-derived albedos at Gusev Crater (0.14 to 0.25) and in Meridiani Planum. (0.10 to 0.18) are in good agreement with IRTM, TES, and MOC orbital measurements. These data sets will be a useful tool and benchmark for future investigations of albodo variations with time, including measurements from orbital instruments like the Context Camera and High Resolution Imaging Science Experiment on Mars Reconnaissance Orbiter. Long-term, accurate albedo measurements could also be important for future efforts in climate modeling as well as for studies of active surface processes. Copyright 2008 by the American Geophysical Union.

  12. IAU nomenclature for albedo features on the planet Mercury

    NASA Technical Reports Server (NTRS)

    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.

  13. Neutron Spectrometer Prospecting in the Mojave Volatiles Project Analog Field Test

    NASA Technical Reports Server (NTRS)

    Elphic, R. C.; Heldmann, J. L.; Colaprete, A.; Hunt, D. R.; Deans, M. C.; Lim, D. S.; Foil, G.; Fong, T.

    2015-01-01

    We know that volatiles are sequestered at the poles of the Moon. While we have evidence of water ice and a number of other compounds based on remote sensing, the detailed distribution, and physical and chemical form are largely unknown. Additional orbital studies of lunar polar volatiles may yield further insights, but the most important next step is to use landed assets to fully characterize the volatile composition and distribution at scales of tens to hundreds of meters. To achieve this range of scales, mobility is needed. Because of the proximity of the Moon, near real-time operation of the surface assets is possible, with an associated reduction in risk and cost. This concept of operations is very different from that of rovers on Mars, and new operational approaches are required to carry out such real-time robotic exploration. The Mojave Volatiles Project (MVP) was a Moon-Mars Analog Mission Activities (MMAMA) program project aimed at (1) determining effective approaches to operating a real-time but short-duration lunar surface robotic mission, and (2) performing prospecting science in a natural setting, as a test of these approaches. Here we describe some results from the first such test, carried out in the Mojave Desert between 16 and 24 October, 2014. The test site was an alluvial fan just E of the Soda Mountains, SW of Baker, California. This site contains desert pavements, ranging from the late Pleistocene to early-Holocene in age. These pavements are undergoing dissection by the ongoing development of washes. A principal objective was to determine the hydration state of different types of desert pavement and bare ground features. The mobility element of the test was provided by the KREX-2 rover, designed and operated by the Intelligent Robotics Group at NASA Ames Research Center. The rover-borne neutron spectrometer measured the neutron albedo at both thermal and epithermal energies. Assuming uniform geochemistry and material bulk density, hydrogen as

  14. Albedo as a modulator of climate response to tropical deforestation

    NASA Technical Reports Server (NTRS)

    Dirmeyer, Paul A.; Shukla, J.

    1994-01-01

    An atmospheric general circulation model with land surface properties represented by the simplified Simple Biosphere model is used to investigate the effects on local climate due to tropical deforestation for the Amazon basin. One control and three anomaly integrations of 4 years' duration are performed. In the anomaly integrations, rain forest in South America is replaced by degraded grassland. The anomaly integrations differ only in the optical properties of the grassland vegetation, with net surface albedos ranging from the same as to 0.09 lighter than that of rain forest. It is found that the change in climate, particularly rainfall, is strongly dependent on the change in surface albedo that accompanies deforestation. Replacement of forest by grass causes a reduction in transpiration and reduces frictional convergence by decreasing surface roughness. However, precipitation averaged over the deforested area is not necessarily reduced. Average precipitation decreases when the increase in albedo is greater than 0.03. If surface albedo is not increased appreciably as a result of deforestation, moisture flux convergence driven by the increase in surface temperature can offset the other effects, and average precipitation increases. As albedo is increased, surface temperature does not change, but surface latent and sensible heat flux decreases due to reduced radiational energy absorbed at the surface, resulting in a reduction in convection and precipitation. A change in the distribution of precipitation due to deforestation that appears to be independent of the albedo is observed.

  15. Albedo as a modulator of climate response to tropical deforestation

    SciTech Connect

    Dirmeyer, P.A.; Shukla, J.

    1994-10-01

    An atmospheric general circulation model with land surface properties represented by the simplified Simple Biosphere model is used to investigate the effects on local climate due to tropical deforestation for the Amazon basin. One control and three anomaly integrations of 4 years` duration are performed. In the anomaly integrations, rain forest in South America is replaced by degraded grassland. The anomaly integrations differ only in the optical properties of the grassland vegetation, with net surface albedos ranging from the same as to 0.09 lighter than that of rain forest. It is found that the change in climate, particularly rainfall, is strongly dependent on the change in surface albedo that accompanies deforestation. Replacement of forest by grass causes a reduction in transpiration and reduces frictional convergence by decreasing surface roughness. However, precipitation averaged over the deforested area is not necessarily reduced. Average precipitation decreases when the increase in albedo is greater than 0.03. If surface albedo is not increased appreciably as a result of deforestation, moisture flux convergence driven by the increase in surface temperature can offset the other effects, and average precipitation increases. As albedo is increased, surface temperature does not change, but surface latent and sensible heat flux decreases due to reduced radiational energy absorbed at the surface, resulting in a reduction in convection and precipitation. A change in the distribution of precipitation due to deforestation that appears to be independent of the albedo is observed.

  16. Postfire influences of snag attrition on albedo and radiative forcing

    NASA Astrophysics Data System (ADS)

    O'Halloran, Thomas L.; Acker, Steven A.; Joerger, Verena M.; Kertis, Jane; Law, Beverly E.

    2014-12-01

    This paper examines albedo perturbation and radiative forcing after a high-severity fire in a mature forest in the Oregon Cascade Range. Correlations between postfire albedo and seedling, sapling, and snag (standing dead tree) density were investigated across fire severity classes and seasons for years 4-15 after fire. Albedo perturbation was 14 times larger in winter compared to summer and increased with fire severity class for the first several years. Albedo perturbation increased linearly with time over the study period. Correlations between albedo perturbations and the vegetation densities were strongest with snags, and significant in all fire classes in both summer and winter (R < -0.92, p < 0.01). The resulting annual radiative forcing at the top of the atmosphere became more negative linearly at a rate of -0.86 W m-2 yr-1, reaching -15 W m-2 in year 15 after fire. This suggests that snags can be the dominant controller of postfire albedo on decadal time scales.

  17. Precise calculations in simulations of the interaction of low energy neutrons with nano-dispersed media

    NASA Astrophysics Data System (ADS)

    Artem'ev, V. A.; Nezvanov, A. Yu.; Nesvizhevsky, V. V.

    2016-01-01

    We discuss properties of the interaction of slow neutrons with nano-dispersed media and their application for neutron reflectors. In order to increase the accuracy of model simulation of the interaction of neutrons with nanopowders, we perform precise quantum mechanical calculation of potential scattering of neutrons on single nanoparticles using the method of phase functions. We compare results of precise calculations with those performed within first Born approximation for nanodiamonds with the radius of 2-5 nm and for neutron energies 3 × 10-7-10-3 eV. Born approximation overestimates the probability of scattering to large angles, while the accuracy of evaluation of integral characteristics (cross sections, albedo) is acceptable. Using Monte-Carlo method, we calculate albedo of neutrons from different layers of piled up diamond nanopowder.

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

    SciTech Connect

    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. High-albedo materials for reducing building cooling energy use

    SciTech Connect

    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}).

  20. Preferential cooling of hot extremes from cropland albedo management

    PubMed Central

    Davin, Edouard L.; Seneviratne, Sonia I.; Ciais, Philippe; Olioso, Albert; Wang, Tao

    2014-01-01

    Changes in agricultural practices are considered a possible option to mitigate climate change. In particular, reducing or suppressing tillage (no-till) may have the potential to sequester carbon in soils, which could help slow global warming. On the other hand, such practices also have a direct effect on regional climate by altering the physical properties of the land surface. These biogeophysical effects, however, are still poorly known. Here we show that no-till management increases the surface albedo of croplands in summer and that the resulting cooling effect is amplified during hot extremes, thus attenuating peak temperatures reached during heat waves. Using a regional climate model accounting for the observed effects of no-till farming on surface albedo, as well as possible reductions in soil evaporation, we investigate the potential consequences of a full conversion to no-till agriculture in Europe. We find that the summer cooling from cropland albedo increase is strongly amplified during hot summer days, when surface albedo has more impact on the Earth’s radiative balance due to clear-sky conditions. The reduced evaporation associated with the crop residue cover tends to counteract the albedo-induced cooling, but during hot days the albedo effect is the dominating factor. For heatwave summer days the local cooling effect gained from no-till practice is of the order of 2 °C. The identified asymmetric impact of surface albedo change on summer temperature opens new avenues for climate-engineering measures targeting high-impact events rather than mean climate properties. PMID:24958872

  1. Preferential cooling of hot extremes from cropland albedo management.

    PubMed

    Davin, Edouard L; Seneviratne, Sonia I; Ciais, Philippe; Olioso, Albert; Wang, Tao

    2014-07-01

    Changes in agricultural practices are considered a possible option to mitigate climate change. In particular, reducing or suppressing tillage (no-till) may have the potential to sequester carbon in soils, which could help slow global warming. On the other hand, such practices also have a direct effect on regional climate by altering the physical properties of the land surface. These biogeophysical effects, however, are still poorly known. Here we show that no-till management increases the surface albedo of croplands in summer and that the resulting cooling effect is amplified during hot extremes, thus attenuating peak temperatures reached during heat waves. Using a regional climate model accounting for the observed effects of no-till farming on surface albedo, as well as possible reductions in soil evaporation, we investigate the potential consequences of a full conversion to no-till agriculture in Europe. We find that the summer cooling from cropland albedo increase is strongly amplified during hot summer days, when surface albedo has more impact on the Earth's radiative balance due to clear-sky conditions. The reduced evaporation associated with the crop residue cover tends to counteract the albedo-induced cooling, but during hot days the albedo effect is the dominating factor. For heatwave summer days the local cooling effect gained from no-till practice is of the order of 2 °C. The identified asymmetric impact of surface albedo change on summer temperature opens new avenues for climate-engineering measures targeting high-impact events rather than mean climate properties. PMID:24958872

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

    SciTech Connect

    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.

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

    EPA Science Inventory

    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...

  4. The nature of albedo features on Mercury, with maps for the telescopic observer. Part II: The nature of the albedo markings

    NASA Astrophysics Data System (ADS)

    Graham, D. L.

    1995-04-01

    Part One of this paper (J. Brit. Astron. Assoc., 105(1), 1995) reviewed the classical telescopic observations of albedo markings on Mercury and reproduced the definitive albedo map to assist visual observers of the planet. In Part Two, an investigation into the relationship between albedo and physiography is conducted, and the significance of the historical observations is discussed.

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

    NASA Astrophysics Data System (ADS)

    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

  6. Understanding the Factors That Control Snow Albedo Over Central Greenland

    NASA Astrophysics Data System (ADS)

    Wright, P.; Bergin, M. H.; Dibb, J. E.; Domine, F.; Carmagnola, C.; Courville, Z.; Sokolik, I. N.; Lefer, B. L.

    2011-12-01

    Snow albedo plays a critical role in the energy balance of the Greenland Ice Sheet. In particular, the snow albedo influences the extent to which absorbing aerosols over Greenland (i.e. dust and black carbon) force climate. With this in mind the spectral snow albedo, physical snow properties, and snow chemistry were measured during May, June, and July 2011 at Summit, Greenland to investigate the variability in snow spectral albedo and its impact on aerosol direct radiative forcing. Optical and chemical properties of aerosol and aerosol optical depth were also measured as part of this study. Strellis et. al. will present a preliminary assessment of aerosol radiative forcing at Summit in summer 2011, in a separate presentation at this meeting. Spectral albedo was measured from 350-2500 nm with an ASD FieldSpec Pro spectroradiometer daily at four permanent sites and a moving fifth site where snow was sampled for characterization, as well as in more intensive diurnal and spatial surveys. Snow specific surface area (SSA), the ratio of snow crystal surface area to mass, was measured with a Dual Frequency Integrating Sphere (DUFISSS) at 1310 nm and 1550 nm, as well as with dyed and cast samples collected for stereology analysis. Snow stratigraphy, crystal size, and density were also measured on a daily basis, and snow samples will be analyzed for microstructural parameters determined from micro-CT imaging. Snow chemistry measurements include specific elements, major ions, and elemental and organic carbon. The time series of daily albedo measurements ranged from 0.88 to nearly 1.0 in visible wavelengths and from 0.42 to 0.65 in the near infrared. Changes as large as 0.1 were observed between consecutive daily measurements across the spectrum. Preliminary results show a strong correlation between variation in albedo and co-located measurements of snow specific surface area, specifically in the near infrared. By conducting our measurements near solar noon every day, and

  7. Potential effects of forest management on surface albedo

    NASA Astrophysics Data System (ADS)

    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

  8. Occurrence of lower cloud albedo in ship tracks

    NASA Astrophysics Data System (ADS)

    Chen, Y.-C.; Christensen, M. W.; Xue, L.; Sorooshian, A.; Stephens, G. L.; Rasmussen, R. M.; Seinfeld, J. H.

    2012-05-01

    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.

  9. Occurrence of lower cloud albedo in ship tracks

    NASA Astrophysics Data System (ADS)

    Chen, Y.-C.; Christensen, M. W.; Xue, L.; Sorooshian, A.; Stephens, G. L.; Rasmussen, R. M.; Seinfeld, J. H.

    2012-09-01

    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.

  10. Spectral surface albedo derived from GOME-2/Metop measurements

    NASA Astrophysics Data System (ADS)

    Pflug, Bringfried; Loyola, Diego

    2009-09-01

    Spectral surface albedo is an important input for GOME-2 trace gas retrievals. An algorithm was developed for estimation of spectral surface albedo from top-of-atmosphere (TOA)-radiances measured by the Global Ozone Monitoring Experiment GOME-2 flying on-board MetOp-A. The climatologically version of this algorithm estimates Minimum Lambert-Equivalent Reflectivity (MLER) for a fixed time window and can use data of many years in contrast to the Near-real time version. Accuracy of surface albedo estimated by MLER-computation increases with the amount of available data. Unfortunately, most of the large GOME pixels are partly covered by clouds, which enhance the LER-data. A plot of LER-values over cloud fraction is used within this presentation to account for this influence of clouds. This "cloud fraction plot" can be applied over all surface types. Surface albedo obtained using the "cloud fraction plot" is compared with reference surface albedo spectra and with the FRESCO climatology. There is a general good agreement; however there are also large differences for some pixels.

  11. THE ALBEDOS OF KEPLER'S CLOSE-IN SUPER-EARTHS

    SciTech Connect

    Demory, Brice-Olivier

    2014-07-01

    Exoplanet research focusing on the characterization of super-Earths is currently limited to the handful of targets orbiting bright stars that are amenable to detailed study. This Letter proposes to look at alternative avenues to probe the surface and atmospheric properties of this category of planets, known to be ubiquitous in our galaxy. I conduct Markov Chain Monte Carlo light-curves analyses for 97 Kepler close-in R{sub P} ≲ 2.0 R {sub ⊕} super-Earth candidates with the aim of detecting their occultations at visible wavelengths. Brightness temperatures and geometric albedos in the Kepler bandpass are constrained for 27 super-Earth candidates. A hierarchical Bayesian modeling approach is then employed to characterize the population-level reflective properties of these close-in super-Earths. I find median geometric albedos A{sub g} in the Kepler bandpass ranging between 0.16 and 0.30, once decontaminated from thermal emission. These super-Earth geometric albedos are statistically larger than for hot Jupiters, which have medians A{sub g} ranging between 0.06 and 0.11. A subset of objects, including Kepler-10b, exhibit significantly larger albedos (A{sub g} ≳ 0.4). I argue that a better understanding of the incidence of stellar irradation on planetary surface and atmospheric processes is key to explain the diversity in albedos observed for close-in super-Earths.

  12. Spitzer Space Telescope Albedo Survey of Small Jovian Trojans

    NASA Astrophysics Data System (ADS)

    Fernandez, Yanga R.; Jewitt, D. C.; Grisetti, R.; Igyarto, C.

    2006-09-01

    We will present preliminary results from our Spitzer Space Telescope (SST) survey of small Jovian Trojan asteroids. For the first time, we have been able to make thermophysical measurements of objects at the faint end of the known Trojan magnitude distribution. Our scientific goal is to determine the mean albedo of these small Trojans. Our sample contains 35 objects with approximate absolute magnitudes (H) between 13 and 14 (diameter 10 to 15 km for 0.05 albedo). For this survey we obtained 24-micron (mid-IR) photometry with the MIPS instrument aboard SST, and visible-wavelength CCD photometry using the University of Hawaii 88-inch Telescope. This lets us constrain each Trojan's effective radius and geometric albedo. While the two datasets were not simultaneous, this is not detrimental to the achievement of our goal since we only need for the effect of the rotational context to average out. In an earlier survey, we found that the mean V-band geometric albedo for large Trojans (sample median diameter of 110 km) is 0.041±0.002 (Fernandez et al. 2003, AJ 126, 1563). If the small Trojans' mean albedo is significantly higher, this would be evidence for a significant volatile component in the Trojan population having survived since formation, and would have implications for the contribution of Trojan asteroids to the Jupiter-family comet population. This research was made possible through a SIRTF Fellowship to YRF and through a GO data analysis grant from SSC to YRF and DCJ.

  13. Evapotranspiration and remote sensing

    NASA Technical Reports Server (NTRS)

    Schmugge, T. J.; Gurney, R.

    1982-01-01

    There are three things required for evapotranspiration to occur: (1) energy (580 cal/gm) for the change of phase of the water; (2) a source of the water, i.e., adequate soil moisture in the surface layer or in the root zone of the plant; and (3) a sink for the water, i.e., a moisture deficit in the air above the ground. Remote sensing can contribute information to the first two of these conditions by providing estimates of solar insolation, surface albedo, surface temperature, vegetation cover, and soil moisture content. In addition there have been attempts to estimate precipitation and shelter air temperature from remotely sensed data. The problem remains to develop methods for effectively using these sources of information to make large area estimates of evapotranspiration.

  14. MORSE/STORM: A generalized albedo option for Monte Carlo calculations

    SciTech Connect

    Gomes, I.C.; Stevens, P.N. )

    1991-09-01

    The advisability of using the albedo procedure for the Monte Carlo solution of deep penetration shielding problems that have ducts and other penetrations has been investigated. The use of albedo data can dramatically improve the computational efficiency of certain Monte Carlo calculations. However, the accuracy of these results may be unacceptable because of lost information during the albedo event and serious errors in the available differential albedo data. This study was done to evaluate and appropriately modify the MORSE/BREESE package, to develop new methods for generating the required albedo data, and to extend the adjoint capability to the albedo-modified calculations. Major modifications to MORSE/BREESE include an option to save for further use information that would be lost at the albedo event, an option to displace the point of emergence during an albedo event, and an option to use spatially dependent albedo data for both forward and adjoint calculations, which includes the point of emergence as a new random variable to be selected during an albedo event. The theoretical basis for using TORT-generated forward albedo information to produce adjuncton albedos was derived. The MORSE/STORM package was developed to perform both forward and adjoint modes of analysis using spatially dependent albedo data. Results obtained with MORSE/STORM for both forward and adjoint modes were compared with benchmark solutions. Excellent agreement and improved computational efficiency were achieved, demonstrating the full utilization of the albedo option in the MORSE code. 7 refs., 17 figs., 15 tabs.

  15. Portable Neutron Sensors for Emergency Response Operations

    SciTech Connect

    ,

    2012-06-24

    This article presents the experimental work performed in the area of neutron detector development at the Remote Sensing Laboratory–Andrews Operations (RSL-AO) sponsored by the U.S. Department of Energy, National Nuclear Security Administration (NNSA) in the last four years. During the 1950s neutron detectors were developed mostly to characterize nuclear reactors where the neutron flux is high. Due to the indirect nature of neutron detection via interaction with other particles, neutron counting and neutron energy measurements have never been as precise as gamma-ray counting measurements and gamma-ray spectroscopy. This indirect nature is intrinsic to all neutron measurement endeavors (except perhaps for neutron spin-related experiments, viz. neutron spin-echo measurements where one obtains μeV energy resolution). In emergency response situations generally the count rates are low, and neutrons may be scattered around in inhomogeneous intervening materials. It is also true that neutron sensors are most efficient for the lowest energy neutrons, so it is not as easy to detect and count energetic neutrons. Most of the emergency response neutron detectors are offshoots of nuclear device diagnostics tools and special nuclear materials characterization equipment, because that is what is available commercially. These instruments mostly are laboratory equipment, and not field-deployable gear suited for mobile teams. Our goal is to design and prototype field-deployable, ruggedized, lightweight, efficient neutron detectors.

  16. A new parameterization of spectral and broadband ocean surface albedo.

    PubMed

    Jin, Zhonghai; Qiao, Yanli; Wang, Yingjian; Fang, Yonghua; Yi, Weining

    2011-12-19

    A simple yet accurate parameterization of spectral and broadband ocean surface albedo has been developed. To facilitate the parameterization and its applications, the albedo is parameterized for the direct and diffuse incident radiation separately, and then each of them is further divided into two components: the contributions from surface and water, respectively. The four albedo components are independent of each other, hence, altering one will not affect the others. Such a designed parameterization scheme is flexible for any future update. Users can simply replace any of the adopted empirical formulations (e.g., the relationship between foam reflectance and wind speed) as desired without a need to change the parameterization scheme. The parameterization is validated by in situ measurements and can be easily implemented into a climate or radiative transfer model. PMID:22274228

  17. Moon: lunar albedo for soft x-rays

    NASA Astrophysics Data System (ADS)

    Ibadov, Subhon

    2016-07-01

    Albedo of the Moon for soft X-rays (0.1-2 keV photons) is determined on the basis of the X-ray luminosity of the Moon detected and measured for the first time by orbital space telescope ROSAT in 1990. It is found that the lunar albedo for the solar soft X-rays is less than the lunar visual region albedo almost thousand times. The data allow to estimate more correctly X-ray luminosity of dusty comets like Hyakutake C/1996 B2 and Hale-Bopp C/1995 O1 due to scattering of solar soft X-rays and to reveal thus the dominant mechanism for production of X-rays in dusty comets.

  18. Direct determination of surface albedos from satellite imagery

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Mapping global land surface albedo from NOAA AVHRR

    NASA Astrophysics Data System (ADS)

    Csiszar, I.; Gutman, G.

    1999-03-01

    A set of algorithms is combined for a simple derivation of land surface albedo from measurements of reflected visible and near-infrared radiation made by the advanced very high resolution radiometer (AVHRR) onboard the National Oceanic and Atmospheric Administration (NOAA) polar orbiting satellites. The system consists of a narrowband-to-broadband conversion and bidirectional correction at the top of the atmosphere and an atmospheric correction. We demonstrate the results with 1 month worth of data from the NOAA National Environmental Satellite, Data, and Information Service (NESDIS) global vegetation index (GVI) weekly data set and the NOAA/NASA Pathfinder Atmosphere (PATMOS) project daily data. Error analysis of the methodology indicates that the surface albedo can be retrieved with 10-15% relative accuracy. Monthly albedo maps derived from September 1989 GVI and PATMOS data agree well except for small discrepancies attributed mainly to different preprocessing and residual atmospheric effects. A 5-year mean September map derived from the GVI multiannual time series is consistent with that derived from low-resolution Earth Radiation Budget Experiment data as well as with a September map compiled from ground observations and used in many numerical weather and climate models. Instantaneous GVI-derived albedos were found to be consistent with surface albedo measurements over various surface types. The discrepancies found can be attributed to differences in areal coverage and representativeness of the satellite and ground data. The present pilot study is a prototype for a routine real-time production of high-resolution global surface albedo maps from NOAA AVHRR Global Area Coverage (GAC) data.

  2. Bolometric albedos and diurnal temperatures of the brightest regions on Io

    NASA Technical Reports Server (NTRS)

    Simonelli, Damon P.; Veverka, Joseph

    1988-01-01

    Cylindrical maps of the locations and estimated Bond albedos of the brightest regions on the Io surface have been constructed on the basis of Voyager data; the albedos are then rescaled to correct for radiometric calibration uncertainties. The highest surface albedos are found to be only moderately higher than the Bond albedo of Io as a whole. The brightest regions include two bright patches southeast of the Maui and Amirani active vents, as well as a large equatorial field of high-albedo material and a lone bright patch at high northern latitudes. These maps indicate that Io's albedos are strongly latitude-dependent.

  3. Transformation of surface albedo to surface: Atmosphere surface and irradiance, and their spectral and temporal averages

    NASA Technical Reports Server (NTRS)

    Nack, M. L.; Curran, R. J.

    1978-01-01

    The dependence of the albedo at the top of a realistic atmosphere upon the surface albedo, solar zenith angle, and cloud optical thickness is examined for the cases of clear sky, total cloud cover, and fractional cloud cover. The radiative transfer calculations of Dave and Braslau (1975) for particular values of surface albedo and solar zenith angle, and a single value of cloud optical thickness are used as the basis of a parametric albedo model. The question of spectral and temporal averages of albedos and reflected irradiances is addressed, and unique weighting functions for the spectral and temporal albedo averages are developed.

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

    SciTech Connect

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

    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.

  5. Mariner 9 high-resolution albedo mapping of Mars

    NASA Technical Reports Server (NTRS)

    Devaucouleurs, G.

    1974-01-01

    Large and small scale albedo markings obtained from Mariner 9 photographs and ground based telescope observations are shown on quadrangle charts with a scale of 1:5,000,000. Mercator and stereographic projections at the same scale are presented of the various regions of Mars along with explanatory information about their preparation. Changes in the albedo for the Solis Lacus area were observed and are compared with previous data for the same region. Large scale relief maps covering up to 1.7 million sq miles of the Martian surface are included.

  6. Measurements and Modeling of Aerosol Absorption and Single Scattering Albedo at Ambient Relative Hum

    NASA Technical Reports Server (NTRS)

    Redemann, J.; Russell, P. B.; Hamill, P.

    2000-01-01

    Uncertainties in the aerosol single scattering albedo have been identified to be an important source of errors in current large-scale model estimates of the direct aerosol radiative forcing of climate. A number of investigators have obtained estimates of the single scattering albedo from a variety of remote sensing and in situ measurements during aerosol field experiments. During the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX, 1996) for example, estimates of the aerosol single scattering albedo were obtained (1) as a best-fit parameter in comparing radiative flux changes measured by airborne pyranometer to those computed from independently measured aerosol properties; (2) from estimates of the aerosol complex index of refraction derived using a combination of airborne sunphotometer, lidar backscatter and in situ size distribution measurements; and (3) from airborne measurements of aerosol scattering and absorption using nephelometers and absorption photometers. In this paper, we briefly compare the results of the latter two methods for two TARFOX case studies, since those techniques provide height-resolved information about the aerosol single scattering albedo. Estimates of the aerosol single scattering albedo from nephelometer and absorption photometer measurements require knowledge of the scattering and absorption humidification (i.e., the increase in these properties in response to an increase in ambient relative humidity), since both measurements are usually carried out at a relative humidity different from the ambient atmosphere. In principle, the scattering humidification factor can be measured, but there is currently no technique widely available to measure the absorption of an aerosol sample as a function of relative humidity. Frequently, for lack of better knowledge, the absorption humidification is assumed to be unity (meaning that there is no change in aerosol absorption due to an increase in ambient relative humidity). This

  7. Greenland ice sheet albedo feedback: mass balance implications

    NASA Astrophysics Data System (ADS)

    Box, J. E.; Tedesco, M.; Fettweis, X.; Hall, D. K.; Steffen, K.; Stroeve, J. C.

    2012-12-01

    Greenland ice sheet mass loss has accelerated 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. NASA MODIS data spanning 13 summers (2000 - 2012), indicate that mid-summer (July) ice sheet albedo declined by 0.064 from a value of 0.752 in the early 2000s. The ice sheet accordingly absorbed 100 EJ more solar energy for the month of July in 2012 than in the early 2000s. This additional energy flux during summer doubled melt rates in the ice sheet ablation area during the observation period. Abnormally strong anticyclonic circulation, associated with a persistent summer North Atlantic Oscillation extreme 2007-2012, enabled 3 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 reached positive values during this period, contributing to an abrupt melt area increase in 2012. A number of factors make it reasonable to expect more melt episodes covering 100% of the ice sheet area in coming years: 1) the past 13 y of increasing surface air temperatures have eroded snowpack 'cold content', preconditioning the ice sheet for earlier melt onset. Less heat is required to bring the surface to melting; 2) Greenland temperatures, have lagged the N Hemisphere average in the 2000s, need to increase further for Greenland to be in phase with the N Hemisphere average. 3) Arctic amplification

  8. Martian Neutron Energy Spectrometer (MANES)

    NASA Technical Reports Server (NTRS)

    Maurer, R. H.; Roth, D. R.; Kinnison, J. D.; Goldsten, J. O.; Fainchtein, R.; Badhwar, G.

    2000-01-01

    High energy charged particles of extragalactic, galactic, and solar origin collide with spacecraft structures and planetary atmospheres. These primaries create a number of secondary particles inside the structures or on the surfaces of planets to produce a significant radiation environment. This radiation is a threat to long term inhabitants and travelers for interplanetary missions and produces an increased risk of carcinogenesis, central nervous system (CNS) and DNA damage. Charged particles are readily detected; but, neutrons, being electrically neutral, are much more difficult to monitor. These secondary neutrons are reported to contribute 30-60% of the dose equivalent in the Shuttle and MIR station. The Martian atmosphere has an areal density of 37 g/sq cm primarily of carbon dioxide molecules. This shallow atmosphere presents fewer mean free paths to the bombarding cosmic rays and solar particles. The secondary neutrons present at the surface of Mars will have undergone fewer generations of collisions and have higher energies than at sea level on Earth. Albedo neutrons produced by collisions with the Martian surface material will also contribute to the radiation environment. The increased threat of radiation damage to humans on Mars occurs when neutrons of higher mean energy traverse the thin, dry Martian atmosphere and encounter water in the astronaut's body. Water, being hydrogeneous, efficiently moderates the high energy neutrons thereby slowing them as they penetrate deeply into the body. Consequently, greater radiation doses can be deposited in or near critical organs such as the liver or spleen than is the case on Earth. A second significant threat is the possibility of a high energy heavy ion or neutron causing a DNA double strand break in a single strike.

  9. Observations of the moon by the global ozone monitoring experiment: radiometric calibration and lunar albedo.

    PubMed

    Dobber, M R; Goede, A P; Burrows, J P

    1998-11-20

    The Global Ozone Monitoring Experiment (GOME) is a new instrument, which was launched aboard the second European Remoting Sensing satellite ESA-ERS2 in 1995. For its long-term radiometric and spectral calibration the GOME observes the sun and less frequently the moon on a regular basis. These measurements of the lunar radiance and solar irradiance have been used in a study to determine, for the first time to the authors' knowledge, the geometric lunar albedo from 240 to 800 nm at high spectral resolution from space. For a waning moon there is good agreement with ground-based measurements in the visible region and with recent space-based measurements in the ultraviolet region. In addition, the use of these measurements for the characterization of in-orbit degradation of instruments operating in this spectral region has been adequately demonstrated.

  10. Modeling radiative transfer in tropical rainforest canopies: sensitivity of simulated albedo to canopy architectural and optical parameters.

    PubMed

    Yanagi, Sílvia N M; Costa, Marcos H

    2011-12-01

    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 (χup) and to the reflectivity in the near-infrared spectral band (ρNIR,up), a smaller sensitivity to the reflectivity in the visible spectral band (ρVIS,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 χup = 0.86, ρVIS,up = 0.062 and ρNIR,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.

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

    NASA Astrophysics Data System (ADS)

    Popp, C.; Wang, P.; Brunner, D.; Stammes, P.; Zhou, Y.; Grzegorski, M.

    2011-03-01

    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 trace gas

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

    NASA Astrophysics Data System (ADS)

    Popp, C.; Wang, P.; Brunner, D.; Stammes, P.; Zhou, Y.; Grzegorski, M.

    2010-10-01

    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 trace gas

  13. NEUTRONIC REACTOR CORE INSTRUMENT

    DOEpatents

    Mims, L.S.

    1961-08-22

    A multi-purpose instrument for measuring neutron flux, coolant flow rate, and coolant temperature in a nuclear reactor is described. The device consists essentially of a hollow thimble containing a heat conducting element protruding from the inner wall, the element containing on its innermost end an amount of fissionsble materinl to function as a heat source when subjected to neutron flux irradiation. Thermocouple type temperature sensing means are placed on the heat conducting element adjacent the fissionable material and at a point spaced therefrom, and at a point on the thimble which is in contact with the coolant fluid. The temperature differentials measured between the thermocouples are determinative of the neutron flux, coolant flow, and temperature being measured. The device may be utilized as a probe or may be incorporated in a reactor core. (AE C)

  14. The Reiner Gamma Albedo Marking on Earth's Moon: Old or Young?

    NASA Astrophysics Data System (ADS)

    Nicholas, J. B.; Purucker, M. E.; Sabaka, T. J.

    2007-03-01

    A minimum magnetization necessary to explain the Reiner Gamma albedo feature was determined, and estimates made of spatial distribution of magnetization, depth of source and magnetization direction. The evidence suggests that the albedo feature arises fro

  15. Albedo Study of the Depositional Fans Associated with Martian Gullies

    NASA Astrophysics Data System (ADS)

    Craig, J.; Sears, D. W. G.

    2005-03-01

    This work is a two-part investigation of the albedo of the depositional aprons or fans associated with Martian gully features. Using Adobe Systems Photoshop 5.0 software we analyzed numerous Mars Global Surveyor MOC and Mars Odyssey THEMIS images.

  16. Albedo and color maps of the Saturnian satellites

    NASA Technical Reports Server (NTRS)

    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.

  17. Detection of light transformations and concomitant changes in surface albedo

    PubMed Central

    Gerhard, Holly E.; Maloney, Laurence T.

    2010-01-01

    We report two experiments demonstrating that (1) observers are sensitive to information about changes in the light field not captured by local scene statistics and that (2) they can use this information to enhance detection of changes in surface albedo. Observers viewed scenes consisting of matte surfaces at many orientations illuminated by a collimated light source. All surfaces were achromatic, all lights neutral. In the first experiment, observers attempted to discriminate small changes in direction of the collimated light source (light transformations) from matched changes in the albedos of all surfaces (non-light transformations). Light changes and non-light changes shared the same local scene statistics and edge ratios, but the latter were not consistent with any change in direction to the collimated source. We found that observers could discriminate light changes as small as 5 degrees with sensitivity d′ > 1 and accurately judge the direction of change. In a second experiment, we measured observers' ability to detect a change in the surface albedo of an isolated surface patch during either a light change or a surface change. Observers were more accurate in detecting isolated albedo changes during light changes. Measures of sensitivity d′ were more than twice as great. PMID:20884599

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

    NASA Technical Reports Server (NTRS)

    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.

  19. Impact of drought on surface albedo in Canadian Prairie observed from Terra- MODIS

    NASA Astrophysics Data System (ADS)

    Luo, Y.; Trishchenko, A. P.; Wang, S.; Khlopenkov, K. V.

    2009-05-01

    A new technology was developed at the Canada Centre for Remote Sensing (CCRS) for generating Canada wide clear-sky surface albedo data based on observations from MODIS sensor onboard TERRA satellite. The data include all seven MODIS land bands (B1-B7) mapped at 250m spatial resolution and 10-day temporal interval from year 2000 through 2008. The new product presents an important spatial enhancement as well as an improved retrieval of water fraction and snow characteristics relative to the standard MODIS archival products. The regional data for the entire Canadian Prairie region are extracted and aggregated for different ecozones, such as north to south, the boreal transition, aspen parkland, moist mixed grassland, and mixed grassland etc. The preliminary results indicate that in comparison to normal summer conditions (2006-2008), the albedo for the drought years (2000-2003) summer increases up to 20 percent in the visible band (B1) and decreases as low as 10 percent in the near infrared band (B2). In the shortwave infrared band (B6) where a large absorption by leaf water occurs, the albedo increases as much as 15 percent for the drought years due to less leaf water content. The derived Normalized Difference Vegetation Index (NDVI), which represents a density of healthy vegetation, drops dramatically (up to 30 percent) for the drought period of 2000-2003. Among the different ecozones, the grassland shows the largest response to droughts while the boreal zone shows the least. Further applications of this product include mapping of snow cover (fraction and grain size), the fraction of absorbed photo-synthetically active radiation (fAPAR), ecosystem productivity, water and energy budget, as well as impact of various disturbances, such as wildfires, and long term climate induced trends. This work was conducted at the Canada Centre for Remote Sensing (CCRS), Earth Sciences Sector of the Department of Natural Resources Canada as part of the Project J35 of the Program on

  20. Atmospheric neutrons

    NASA Technical Reports Server (NTRS)

    Korff, S. A.; Mendell, R. B.; Merker, M.; Light, E. S.; Verschell, H. J.; Sandie, W. S.

    1979-01-01

    Contributions to fast neutron measurements in the atmosphere are outlined. The results of a calculation to determine the production, distribution and final disappearance of atmospheric neutrons over the entire spectrum are presented. An attempt is made to answer questions that relate to processes such as neutron escape from the atmosphere and C-14 production. In addition, since variations of secondary neutrons can be related to variations in the primary radiation, comment on the modulation of both radiation components is made.

  1. Albedo of Permanently Shadowed Regions of the Lunar Poles

    NASA Astrophysics Data System (ADS)

    Riner, M. A.; Lucey, P. G.; Bussey, B.; Cahill, J. T.; McGovern, A.

    2012-12-01

    Due to the slight tilt in the Moon's spin axis, some topographic depressions near the lunar poles experience permanent shadow and may serve as cold traps, harboring water ice and/or other volatile compounds [1]. Permanently shadowed regions (PSRs) provide an opportunity toward understanding the amount, nature and transport of volatiles on the Moon and may also be a potential resource for human exploration. While many different data sets have suggested the presence of water ice in PSRs near the lunar poles many questions remain. For example, ice does not appear to be uniformly distributed across identified PSRs. More work is needed to understand the distribution of ice in PSRs and how delivery and retention mechanisms influence the distribution. The active illumination of the Lunar Orbiter Laser Altimeter (LOLA) provides a unique contribution toward exploration PSR exploration. While LOLA is principally a laser altimeter used for quantitative topography and related cartographic and geodetic applications [2], LOLA also measures the intensity and width of the return laser pulse (1064 nm) from the surface. Here we use a global mosaic (4 pixels per degree) of LOLA albedo data corrected for instrumental drift, irregular variations, and calibrated to normal albedo using local equatorial measurements of normal albedo obtained by the Kaguya Multiband Imager [3]. Recent work using LOLA albedo shows the floor of Shackleton crater, near the lunar south pole, is brighter than the surrounding terrain (and the interior of nearby craters) at 1064 nm [4]. This albedo difference may be due to decreased space weathering due to shadowing from the Sun or to a 1 μm thick layer with 20% water ice a the surface of the crater floor [4]. Here we use LOLA dayside reflectance measurements to examine the albedo of PSRs catalogued by [5] derived from illumination modeling of a hybrid 100 m/pixel LOLA-LROC digital terrain model (DTM) up to 83° north and south latitudes. The upper latitude

  2. Effective Albedo of Vegetated Terrain at L-Band

    NASA Technical Reports Server (NTRS)

    Kurum, Mehmet; O'Neill, Peggy E.; Lang, Roger H.

    2011-01-01

    This paper derives an explicit expression for an effective albedo of vegetated terrain from the zero- and multiple- order radiative transfer (RT) model comparison. The formulation establishes a direct physical link between the effective vegetation parameterization and the theoretical description of absorption and scattering within the canopy. The paper will present an evaluation of the derived albedo for corn canopies with data taken during an experiment at Alabama A&M Winfield A. Thomas Agricultural Research Station near Huntsville, Alabama in June, 1998. The test site consisted of two 50-m x 60-m plots - one with a bare surface and the other with grass cover - and four 30-m x 50-m plots of corn at different planting densities. One corn field was planted at a full density of 9.5 plants/sq m while the others were planted at 1/3, 1/2 and 2/3 of the full density. The fields were observed with a truck-mounted L-band radiometer at incident angle of 15 degree for the period of two weeks. Soil moisture (SM) changed daily due to irrigation and natural rainfall. Variations in gravimetric SM from 18 % to 34 % were seen during this period. Ground truth data, including careful characterization of the corn size and orientation statistics, and its dielectric, was also collected and used to simulate the effective albedo for the vegetation. The single-scattering albedo is defined as the fractional power scattered from individual vegetation constituents with respect to canopy extinction. It represents single-scattering properties of vegetation elements only, and is independent of ground properties. The values of the albedo get higher when there is dense vegetation (i.e. forest, mature corn, etc.) with scatterers, such as branches and trunks (or stalks in the case of corn), which are large with respect to the wavelength. This large albedo leads to a reduction in brightness temperature in the zero-order RT solution (known as tau-omega model). Higher-order multiple-scattering RT

  3. A quantification of errors in surface albedo due to common assumptions

    NASA Technical Reports Server (NTRS)

    Arduini, Robert F.; Suttles, J. T.

    1990-01-01

    A study comparing the performance of three approaches to estimating the spectral albedo of a typical land surface is presented. The most accurate albedo estimates under all atmospheric situations are those for which the scattering properties of the atmosphere can be used. Simply utilizing the direct-to-total ratio as a weight between direct and Lambertian albedos reduced the errors in broadband albedo to less than one percent for almost all simulated atmospheric conditions.

  4. Neutron guide

    DOEpatents

    Greene, Geoffrey L.

    1999-01-01

    A neutron guide in which lengths of cylindrical glass tubing have rectangular glass plates properly dimensioned to allow insertion into the cylindrical glass tubing so that a sealed geometrically precise polygonal cross-section is formed in the cylindrical glass tubing. The neutron guide provides easier alignment between adjacent sections than do the neutron guides of the prior art.

  5. Neutron dosimetry

    DOEpatents

    Quinby, Thomas C.

    1976-07-27

    A method of measuring neutron radiation within a nuclear reactor is provided. A sintered oxide wire is disposed within the reactor and exposed to neutron radiation. The induced radioactivity is measured to provide an indication of the neutron energy and flux within the reactor.

  6. Albedo Response of Native and Artificial Soils to a Wetting Event: Implications for Critical Zone Processes

    NASA Astrophysics Data System (ADS)

    Lovell, L.; Sanchez-Mejia, Z. M.; Papuga, S. A.

    2012-12-01

    The Landscape Evolution Observatory (LEO) at Biosphere 2 is composed of three experimental hill slopes filled to one meter depth of a ground basaltic tephra soil, set up to investigate critical zone processes. Our goal is to understand the energy aspects of this artificial LEO soil; surfaces with a high surface reflectance (albedo) may limit energy available for critical zone processes. The albedo of a surface can change, e.g. by vegetation growth or soil wetting, which can further influence available energy. Here, we examine the soil moisture and albedo response of LEO soil to a 10 mm rainfall event, and compare the results to those found using traditional potting and native desert soils that differ in color and texture. We hypothesized that: 1) increased soil moisture would decrease albedo for all soil types; 2) a smaller wetting front would maximize any decrease in albedo, and 3) albedo will reach a minimum within hours of a rainstorm, returning to a maximum albedo value within the day. We found that albedo was lowest under wet conditions for all soils, regardless of initial color and texture. Additionally, the LEO soil experienced the shallowest wetting front and also showed the most significant decrease in albedo following rainfall. After the rainfall event, all soils showed an initial decrease in albedo, followed by an increase in albedo as the soil dried. While the albedo and soil moisture of each soil reacted similarly, the very dark and fine LEO soil showed the strongest response to wetting.

  7. Differential neutron energy spectra measured on spacecraft in low Earth orbit.

    PubMed

    Dudkin, V E; Potapov YuV; Akopova, A B; Melkumyan, L V; Benton, E V; Frank, A L

    1990-01-01

    Two methods for measuring neutrons in the range from thermal energies to dozens of MeV were used. In the first method, alpha-particles emitted from the 6Li(n,alpha)T reaction are detected with the help of plastic nuclear track detectors, yielding results on thermal and resonance neutrons. Also, fission foils are used to detect fast neutrons. In the second method, fast neutrons are recorded by nuclear photographic emulsions (NPE). The results of measurements on board various satellites are presented. The neutron flux density does not appear to correlate clearly with orbital parameters. Up to 50% of neutrons are due to albedo neutrons from the atmosphere while the fluxes inside the satellites are 15-20% higher than those on the outside. Estimates show that the neutron contribution to the total equivalent radiation dose reaches 20-30%. PMID:11537519

  8. Differential neutron energy spectra measured on spacecraft in low Earth orbit

    NASA Technical Reports Server (NTRS)

    Dudkin, V. E.; Akopova, A. B.; Melkumyan, L. V.; Benton, E. V.; Frank, A. L.

    1990-01-01

    Two methods for measuring neutrons in the range from thermal energies to dozens of MeV were used. In the first method, alpha-particles emitted from the 6Li(n,alpha)T reaction are detected with the help of plastic nuclear track detectors, yielding results on thermal and resonance neutrons. Also, fission foils are used to detect fast neutrons. In the second method, fast neutrons are recorded by nuclear photographic emulsions (NPE). The results of measurements on board various satellites are presented. The neutron flux density does not appear to correlate clearly with orbital parameters. Up to 50% of neutrons are due to albedo neutrons from the atmosphere while the fluxes inside the satellites are 15-20% higher than those on the outside. Estimates show that the neutron contribution to the total equivalent radiation dose reaches 20-30%.

  9. Long term surface albedo datasets generated with Meteosat images

    NASA Astrophysics Data System (ADS)

    Lattanzio, A.; Govaerts, Y. M.; Theodore, B.

    2009-04-01

    The Global Climate Observing System (GCOS) has recognized the importance and the key-role of the surface albedo in the study of the climate change. This and the other climate variables, called Essential Climate Variables (ECVs), must satisfy the following requirements: (i) a global coverage over long-term periods with adequate spatial and temporal resolution, (ii) reliability and accuracy as well as a (iii) quality control. The Coordination Group for Meteorological Satellites (CGMS) assigned to EUMETSAT an action (T18 (TF7)) in order to prototype and test a new algorithm able to retrieve surface albedo using geostationary satellites as described in the "Implementation plan for the global observing system for climate in support of the UNFCCC" document (WMO/TD No. 1219). In this frame EUMETSAT decided to develop a new specific algorithm, named Meteosat Surface Albedo (MSA), based on a method proposed by Pinty et al. The MSA algorithm is currently running in the operational reprocessing facility of EUMETSAT in order to generate reliable albedo data set starting from 1982. These data have been acquired by six different radiometers. As Meteosat first generation satellites have not been designed for climate monitoring, before proceeding with the interpretation of the complete archive (~ 25 years of data), a detailed temporal consistency analysis of the albedo data set generated with the MSA algorithm has been performed in order to check the compliance with points (ii) and (iii). Specific efforts have been put on the estimation of the measurement error accounting for the observation uncertainties and retrieval method assumptions. Currently 100% of the archive for the prime mission at 0 degree has been processed and the albedo data set can be requested from the EUMETSAT archive facility. This paper will present the method elaborated for the evaluation of the temporal consistency of the MSA data set and illustrate typical problems raising from the processing of old data and

  10. Active neutron sensing of the Martian surface with the DAN experiment onboard the NASA "Curiosity" Mars rover: Two types of soil with different water content in the gale crater

    NASA Astrophysics Data System (ADS)

    Mitrofanov, I. G.; Kozyrev, A. S.; Lisov, D. I.; Vostrukhin, A. A.; Golovin, D. V.; Litvak, M. L.; Malakhov, A. V.; Mokrousov, M. I.; Nikiforov, S. Yu.; Sanin, A. B.

    2016-04-01

    This paper presents the water and chlorine content estimates on the bottom of the Martian crater Gale obtained by processing the data of active neutron sensing with the DAN experiment onboard theNASA "Curiosity"Mars rover at 412 spots along the 11-kilometer track. For 78% of the examined spots the water distribution in depth is found to be homogeneous with a mean content of 2.1±0.5% by mass (here and elsewhere variations correspond to the mean square deviations). For 22% of the examined spots the data require a two-layer model of water distribution down to the sensitivity limit of about 60 cm. The mean water content in upper layer of these spots is about 2-3% by mass, which is close to the content for spots with the homogeneous water distribution. In 8% of the examined spots the water content in the bottom layer at a depth of 27 ± 18 cm increases to 5.6 ± 2.7%. In 14% of the examined spots the water content in the bottom layer at a depth of 14 ± 7 cm decreases to 1.2 ± 0.5%. For interpretation of these results we conclude that the Gale crater has areas both with high and low water content, which correspond to distinct sedimentary layers from different past epochs, when sedimentation process took place underwater and in air correspondingly.

  11. Radiative transfer in dusty nebulae. III - The effects of dust albedo

    NASA Technical Reports Server (NTRS)

    Petrosian, V.; Dana, R. A.

    1980-01-01

    The effects of an albedo of internal dust, such as ionization structure and temperature of dust grain, were studied by the quasi-diffusion method with an iterative technique for solving the radiative heat transfer equations. It was found that the generalized on-the-spot approximation solution is adequate for most astrophysical applications for a zero albedo; for a nonzero albedo, the Eddington approximation is more accurate. The albedo increases the average energy of the diffuse photons, increasing the ionization level of hydrogen and heavy elements if the Eddington approximation is applied; the dust thermal gradient is reduced so that the infrared spectrum approaches blackbody spectrum with an increasing albedo.

  12. Measurement result of the neutron monitor onboard the Space Environment Data Acquisition Equipment - Attached Payload (SEDA-AP)

    NASA Astrophysics Data System (ADS)

    Koga, K.; Muraki, Y.; Shibata, S.; Yamamoto, T.; Matsumoto, H.; Okudaira, O.; Kawano, H.; Yumoto, K.

    2013-12-01

    To support future space activities, it is crucial to acquire space environmental data related to the space-radiation degradation of space parts and materials, and spacecraft anomalies. Such data are useful for spacecraft design and manned space activity. SEDA-AP was mounted on 'Kibo' of the ISS (International Space Station) to measure the space environment at a 400-kilometer altitude. Neutrons are very harmful radiation, with electrical neutrality that makes them strongly permeable. SEDA-AP measures the energy of neutrons from thermal to 100 MeV in real time using a Bonner Ball Detector (BBND) and a Scintillation Fiber Detector (FIB). BBND detects neutrons using He-3 counters, which have high sensitivity to thermal neutrons. Neutron energy is derived using the relative response function of polyethylene moderators of 6 different thicknesses. FIB measures the tracks of recoil protons caused by neutrons within a cubic arrayed sensor of 512 scintillation fibers. The charged particles are excluded using an anti-scintillator which surrounds the cube sensor, and the neutron energy is obtained from the track length of a recoil proton. There are three sources of neutrons in space; 1. Albedo Neutrons Produced by reactions of galactic cosmic rays or radiation belt particles with the atmosphere 2. Local Neutrons Produced by the reactions of galactic cosmic rays or radiation belt particles with spacecraft 3. Solar Neutrons Produced by accelerated particles in solar flares An accurate energy spectrum of the solar neutrons includes important information on high-energy particle generation mechanism in a solar flare, because neutrons are unaffected by interplanetary magnetic fields. These data will become useful to forecast solar energetic particles in future. Some candidate events involving solar neutrons were found as a result of analyzing data of the solar flare of M>2 since September 2009. Moreover, it is important to measure albedo neutrons, since protons generated by neutron

  13. Calculations of neutron flux spectra induced in the earth's atmosphere by galactic cosmic rays

    NASA Technical Reports Server (NTRS)

    Armstrong, T. W.; Chandler, K. C.; Barish, J.

    1972-01-01

    Calculations have been carried out to determine the neutron flux induced in the earth's atmosphere by galactic protons and alpha particles at solar minimum for a geomagnetic latitude of 42 N. Neutron flux spectra were calculated using Monte Carlo and discrete ordinates methods, and various comparisons with experimental data are presented. The magnitude and shape of the calculated neutron-leakage spectrum at the particular latitude considered support the theory that the cosmic-ray-albedo-neutron-decay mechanism is the source of the protons and electrons trapped in the Van Allen belts.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    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.

  16. Effect of canopy structure and the presence of snow on the albedo of boreal conifer forests

    NASA Astrophysics Data System (ADS)

    Ni, Wenge; Woodcock, Curtis E.

    2000-05-01

    A Geometric-Optical and Radiative Transfer (GORT) approach for modeling the radiation regime within plant canopies is capable of predicting temporal variation in the albedo of boreal conifer forests. Model predictions of daily surface albedo patterns and reflected solar radiation during the winter and summer seasons were validated using field measurements from two forest stands in the northern study area of BOReal Ecosystem-Atmosphere Study (BOREAS) in 1995. The model is able to predict the "W" shape for the daily albedo over the sparse old jack pine forest stand during the snow season and the "bowl" shape of daily albedo during clear days in the summer. Results immediately following new snow and at the end of the snowmelt season indicate the sensitivity of overall forest albedos to the albedo of snow. Incorporation of time-varying values for snow albedo may improve future efforts to estimate forest albedos in the winter. Forest albedos are a complicated function of the canopy structure, the presence or absence of snow on the ground and the angular distribution of irradiance. These effects differ for the visible, near-infrared and midinfrared portions of the solar spectrum. Forest albedos vary dramatically as a function of canopy cover when snow covers the ground, but very little when snow is not present. It is found that for tree cover over about 70%, the presence of snow has little effect on albedo.

  17. Albedo of coastal landfast sea ice in Prydz Bay, Antarctica: Observations and parameterization

    NASA Astrophysics Data System (ADS)

    Yang, Qinghua; Liu, Jiping; Leppäranta, Matti; Sun, Qizhen; Li, Rongbin; Zhang, Lin; Jung, Thomas; Lei, Ruibo; Zhang, Zhanhai; Li, Ming; Zhao, Jiechen; Cheng, Jingjing

    2016-05-01

    The snow/sea-ice albedo was measured over coastal landfast sea ice in Prydz Bay, East Antarctica (off Zhongshan Station) during the austral spring and summer of 2010 and 2011. The variation of the observed albedo was a combination of a gradual seasonal transition from spring to summer and abrupt changes resulting from synoptic events, including snowfall, blowing snow, and overcast skies. The measured albedo ranged from 0.94 over thick fresh snow to 0.36 over melting sea ice. It was found that snow thickness was the most important factor influencing the albedo variation, while synoptic events and overcast skies could increase the albedo by about 0.18 and 0.06, respectively. The in-situ measured albedo and related physical parameters (e.g., snow thickness, ice thickness, surface temperature, and air temperature) were then used to evaluate four different snow/ice albedo parameterizations used in a variety of climate models. The parameterized albedos showed substantial discrepancies compared to the observed albedo, particularly during the summer melt period, even though more complex parameterizations yielded more realistic variations than simple ones. A modified parameterization was developed, which further considered synoptic events, cloud cover, and the local landfast sea-ice surface characteristics. The resulting parameterized albedo showed very good agreement with the observed albedo.

  18. Albedo maps of Comets P/Giacobini-Zinner and P/Halley

    NASA Technical Reports Server (NTRS)

    Hammel, H. B.; Storrs, A. D.; Cruikshank, D. P.; Telesco, C. M.; Decher, R. M.; Campins, H.

    1986-01-01

    Near-simultaneous infrared and visual maps of P/Giacobini-Zinner (P/G-Z) and P/Halley are combined to create maps of the spatial variation of geometric albedo. Giacobini-Zinner shows a minimum in albedo near 0.07 with an increase of a factor of 2 over 30 arcsec. The lowest albedos are offset from the nucleus in the antisunward direction, coincident with a dust tail observed in the IR. The P/Halley albedos are higher than those for P/G-Z and range from 0.2 to 0.4, but the trend of darker albedo in the antisunward direction (along the tail) is the same. The albedo distribution is attributed to large, dark, fluffy grains confined to the orbital plane close to the nucleus. The high albedo values in P/Halley may be due to enhanced flux in the visual image because of the comet's very small phase angle.

  19. Reentrant albedo proton fluxes measured by the PAMELA experiment

    NASA Astrophysics Data System (ADS)

    Adriani, O.; Barbarino, G. C.; 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.; Donato, C. De; 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.

    2015-05-01

    We present a precise measurement of downward going albedo proton fluxes for kinetic energy above ˜70 MeV performed by the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (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 untrapped spreading over all latitudes, including both short-lived (precipitating) and long-lived (pseudotrapped) 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Exogenic and endogenic albedo and color patterns on Europa

    NASA Technical Reports Server (NTRS)

    Mcewen, A. S.

    1986-01-01

    New global and high-resolution multispectral mosaics of Europa have been produced from the Voyager imaging data. Photometric normalizations are based on multiple-image techniques that explicitly account for intrinsic albedo variations through pixel-by-pixel solutions. The exogenic color and albedo pattern on Europa is described by a second-order function of the cosine of the angular distance from the apex of orbital motion. On the basis of this second-order function and of color trends that are different on the leading and trailing hemispheres, the exogenic pattern is interpreted as being due to equilibrium between two dominant processes: (1) impact gardening and (2) magnetospheric interactions, including sulfur-ion implantation and sputtering redistribution. Removal of the model exogenic pattern in the mosaics reveals the endogenic variations, consisting of only two major units: darker (redder) and bright materials. Therefore Europa's visual spectral reflectivity is simple, having one continuous exogenic pattern and two discrete endogenic units.

  2. Land Surface Albedo from MERIS Reflectances Using MODIS Directional Factors

    NASA Technical Reports Server (NTRS)

    Schaaf, Crystal L. B.; Gao, Feng; Strahler, Alan H.

    2004-01-01

    MERIS Level 2 surface reflectance products are now available to the scientific community. This paper demonstrates the production of MERIS-derived surface albedo and Nadir Bidirectional Reflectance Distribution Function (BRDF) adjusted reflectances by coupling the MERIS data with MODIS BRDF products. Initial efforts rely on the specification of surface anisotropy as provided by the global MODIS BRDF product for a first guess of the shape of the BRDF and then make use all of the coincidently available, partially atmospherically corrected, cloud cleared, MERIS observations to generate MERIS-derived BRDF and surface albedo quantities for each location. Comparisons between MODIS (aerosol-corrected) and MERIS (not-yet aerosol-corrected) surface values from April and May 2003 are also presented for case studies in Spain and California as well as preliminary comparisons with field data from the Devil's Rock Surfrad/BSRN site.

  3. Deriving Albedo from Coupled MERIS and MODIS Surface Products

    NASA Technical Reports Server (NTRS)

    Gao, Feng; Schaaf, Crystal; Jin, Yu-Fang; Lucht, Wolfgang; Strahler, Alan

    2004-01-01

    MERIS Level 2 surface reflectance products are now available to the scientific community. This paper demonstrates the production of MERIS-derived surface albedo and Nadir Bidirectional Reflectance Distribution Function (BRDF) adjusted reflectances by coupling the MERIS data with MODIS BRDF products. Initial efforts rely on the specification of surface anisotropy as provided by the global MODIS BRDF product for a first guess of the shape of the BRDF and then make use all of the coincidently available, partially atmospherically corrected, cloud cleared, MERIS observations to generate MERIS-derived BRDF and surface albedo quantities for each location. Comparisons between MODIS (aerosol-corrected) and MERIS (not-yet aerosol-corrected) surface values from April and May 2003 are also presented for case studies in Spain and California as well as preliminary comparisons with field data from the Devil's Rock Surfrad/BSRN site.

  4. Studies of seasonal variations on Mars based on orbital and surface observations of neutron radiation

    NASA Astrophysics Data System (ADS)

    Litvak, Maxim; Mitrofanov, Igor; Sanin, Anton; Golovin, Dmitry; Nikiforov, Sergey; Lisov, Denis

    2014-05-01

    Starting from February 2002 High Energy Neutron Detector (HEND) onboard Mars Odyssey is performing continuous monitoring of regional and seasonal variations of martian neutron albedo to deconvolve and to map subsurface water distribution at different latitudes and to observe Mars climate cycle processes over a long baseline. In our investigation we have used HEND/Odyssey observations accumulated for seven successive martian years to search for the seasonal and inter annual variations of orbital neutron flux at equatorial latitudes due to seasonal variations of atmospheric thickness and seasonal cycle of subsurface water distribution. The obtained results have been compared with a ground truth measurements of local environment obtained by Dynamic Albedo of Neutrons instrument onboard MSL Curiosity rover during first year of surface operations in vicinity of Gale crater.

  5. PING Gamma Ray and Neutron Measurements of a Meter-Sized Carbonaceous Asteroid Analog

    NASA Technical Reports Server (NTRS)

    Bodnarik, J.; Burger, D.; Evans, L.; Floyd, S.; Lim, L.; McClanahan, T.; Namkung, M.; Nowicki, S.; Parsons, A.; Schweitzer, J.; Starr, R.; Trombka, J.

    2011-01-01

    Determining the elemental composition of carbonaceous (spectral type C) asteroids is still one of the basic problems when studying these objects. The only main source of elemental composition information for asteroids is from their optical, NIR and IR properties, which include their spectral reflectance characteristics, albedo, polarization, and the comparison of optical spectroscopy with meteorite groups corresponding to asteroids of every spectral type. Unfortunately, these sources reflect observations from widely contrasting spatial scales that presently yield a void in the continuum of microscopic and macroscopic evidence, a lack of in situ measurement confirmation, and require deeper sensing techniques to discern the nature of these asteroids. The Probing In situ with Neutrons and Gamma rays (PING) instrument is ideally suited to address this problem because it can be used to determine the bulk elemental composition, H and C content, the average atomic weight and density of the surface and subsurface layers of C-type asteroids, and can provide measurements used to determine the difference between and distinguish between different types of asteroids. We are currently developing the PING instrument that combines gamma ray and neutron detectors with a 14 Me V pulsed neutron generator to determine the in-situ bulk elemental abundances and geochemistry of C-type asteroids with a spatial resolution of 1 m down to depths of tens of cm to 1 m. One aspect of the current work includes experimentally testing and optimizing PING on a known meter-sized Columbia River basalt C-type asteroid analog sample that has a similar composition and the same neutron response as that of a C-type asteroid. An important part of this effort focuses on utilizing timing measurements to isolate gamma rays produced by neutron inelastic scattering, neutron capture and delayed activation processes. Separating the gamma ray spectra by nuclear processes results in higher precision and sensitivity

  6. a Generalized Albedo Option for Forward and Adjoint Monte Carlo Calculations

    NASA Astrophysics Data System (ADS)

    Gomes, Itacil Chiari

    1991-02-01

    The advisability of using the albedo procedure for the Monte Carlo solution of deep penetration shielding problems which have ducts and other penetrations is investigated. It is generally accepted that the use of albedo data can dramatically improve the computational efficiency of certain Monte Carlo calculations--however the accuracy of these results may be unacceptable because of lost information during the albedo event and serious errors in the available differential albedo data. This study has been done to evaluate and appropriately modify the MORSE/BREESE package, to develop new methods for generating the required albedo data, and to extend the adjoint capability to the albedo-modified calculations. The major modifications include an option to save for further use information that would be lost at the albedo event, an option to displace the emergent point during an albedo event, and an option to read spatially -dependent albedo data for both forward and adjoint calculations --which includes the emergent point as a new random variable to be selected during an albedo reflection event. The theoretical basis for using TORT-generated forward albedo information to produce adjuncton-albedos is derived. The MORSE/STORM code was developed to perform both forward and adjoint modes of analysis using spatially-dependent albedo data. The results obtained using the MORSE/STORM code package for both forward and adjoint modes were compared with benchmark solutions--excellent agreements along with improved computational efficiencies were achieved demonstrating the full utilization of the albedo option in the MORSE code.

  7. Gamma-ray Albedo of Small Solar System Bodies

    SciTech Connect

    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].

  8. Albedo polarimétrico de asteroides del grupo Hungaria

    NASA Astrophysics Data System (ADS)

    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.

  9. Supercritical Salt Spray for the Implementation of Cloud Albedo Modification

    NASA Astrophysics Data System (ADS)

    Neukermans, A. P.; Cooper, G.; Foster, J. D.; Galbraith, L.; Ormond, B.; Wang, Q.; Johnston, D.; Cloud Brightening Research

    2011-12-01

    Of all the geo-engineering schemes proposed so far, the Latham-Salter cloud albedo modification scheme is perhaps the most benign and "natural" method. In its full deployment, it proposes to densify and thereby modify the albedo of low-hanging marine boundary clouds by a few percent such that the overall earth albedo might be changed by 1%. The scheme would require the production of vast numbers of salt cloud condensation nuclei (CCN), in one implementation on the order of 10^17 per second from each of some 1500 autonomous sailing vessels. We have investigated a number of possible techniques to create these nuclei. We reported previously the laboratory production of suitable nuclei from saltwater using Taylor cones. This method would require about 10^8 Taylor cones per vessel to get to the required CCN production rate, and hence needs a very extensive scale-up effort. We report here on the use of saltwater sprayed at or near its critical temperature and pressure through small nozzles. Although a number of technical problems remain, results to date suggest that this method might be suitable, at least for research purposes. The mean particle size distributions of nuclei generated (40-100 nm) are acceptable, and the scale-up effort to the estimated number of nozzles required (1000-2000) seems reasonable.

  10. Seasonal changes in surface albedo of Himalayan glaciers from MODIS data and links with the annual mass balance

    NASA Astrophysics Data System (ADS)

    Brun, F.; Dumont, M.; Wagnon, P.; Berthier, E.; Azam, M. F.; Shea, J. M.; Sirguey, P.; Rabatel, A.; Ramanathan, Al.

    2015-02-01

    Few glaciological field data are available on glaciers in the Hindu Kush-Karakoram-Himalayan (HKH) region, and remote sensing data are thus critical for glacier studies in this region. The main objectives of this study are to document, using satellite images, the seasonal changes of surface albedo for two Himalayan glaciers, Chhota Shigri Glacier (Himachal Pradesh, India) and Mera Glacier (Everest region, Nepal), and to reconstruct the annual mass balance of these glaciers based on the albedo data. Albedo is retrieved from Moderate Resolution Imaging Spectroradiometer (MODIS) images, and evaluated using ground based measurements. At both sites, we find high coefficients of determination between annual minimum albedo averaged over the glacier (AMAAG) and glacier-wide annual mass balance (Ba) measured with the glaciological method (R2 = 0.75). At Chhota Shigri Glacier, the relation between AMAAG found at the end of the ablation season and Ba suggests that AMAAG can be used as a proxy for the maximum snow line altitude or equilibrium line altitude (ELA) on winter-accumulation-type glaciers in the Himalayas. However, for the summer-accumulation-type Mera Glacier, our approach relied on the hypothesis that ELA information is preserved during the monsoon. At Mera Glacier, cloud obscuration and snow accumulation limits the detection of albedo during the monsoon, but snow redistribution and sublimation in the post-monsoon period allows for the calculation of AMAAG. Reconstructed Ba at Chhota Shigri Glacier agrees with mass balances previously reconstructed using a positive degree-day method. Reconstructed Ba at Mera Glacier is affected by heavy cloud cover during the monsoon, which systematically limited our ability to observe AMAAG at the end of the melting period. In addition, the relation between AMAAG and Ba is constrained over a shorter time period for Mera Glacier (6 years) than for Chhota Shigri Glacier (11 years). Thus the mass balance reconstruction is less robust

  11. Calculation of single-scattering albedos: Comparison of Mie results with Hapke approximations

    NASA Astrophysics Data System (ADS)

    Hansen, G. B.

    2009-10-01

    The grain size of water ice can be determined from its near-infrared spectrum, which has numerous diagnostic absorption bands of different opacities. Models that have been used to determine water ice grain size from infrared spectra of icy outer Solar System objects have shown discrepancies in modeled grain size of a factor of two or more. Here the single-scattering albedo calculated using the commonly used Hapke model given by Roush [Roush, T.L., 1994. Icarus 108, 243-254] is compared with the exact calculation for spheres from a Mie series. An earlier approximation of single-scattering albedo called the Hapke "slab" model is also used in the comparison. All three models are implemented using the same optical constants for water ice at ˜110 K. Results are displayed for a large range of grain sizes from 1 μm to 1 mm. In general neither Hapke model can mimic the Rayleigh effects from particles sized near the wavelength of light that the Mie model predicts. For 10 μm particles, the slab model matches the Mie calculation quite well, but larger sizes are more discrepant. The Hapke/Roush model grain size needs to be ˜2.5 times larger to mimic the Mie results, and there are additional discrepancies in the continuum levels and band strengths. The Mie calculation for spheres is recommended for analysis of unknown remote sensing measurements, as it can mimic the spectra of oblate, prolate, and hollow particles given by equivalent sphere theories.

  12. Neutron measurements onboard the space shuttle.

    PubMed

    Badhwar, G D; Keith, J E; Cleghorn, T F

    2001-06-01

    The radiation environment inside a shielded volume is highly complex, consisting of both charged and neutral particles. Since the inception of human space flights, the charged particle component has received virtually all of the attention. There is however, a significant production of secondary neutrons, particularly from the aluminum structure in low earth orbiting spacecrafts. The interactions of galactic cosmic rays (GCR), and solar energetic particles with the earth's atmosphere produce a non-isotropic distribution of albedo neutrons. Inside any reasonable habitable module, the average radiation quality factor of neutrons is about 4-5 times larger than the corresponding average quality factor of charged particles. The measurement of neutrons and their energy spectra is a difficult problem due the intense sources of charged particles. This paper reviews the results of Shuttle flight experiments (made during both solar maximum and solar minimum) to measure the contribution of neutrons to the dose equivalent, as well as theoretical calculations to estimate the appropriate range of neutron energies that contribute most to the dose equivalent.

  13. Neutron measurements onboard the space shuttle.

    PubMed

    Badhwar, G D; Keith, J E; Cleghorn, T F

    2001-06-01

    The radiation environment inside a shielded volume is highly complex, consisting of both charged and neutral particles. Since the inception of human space flights, the charged particle component has received virtually all of the attention. There is however, a significant production of secondary neutrons, particularly from the aluminum structure in low earth orbiting spacecrafts. The interactions of galactic cosmic rays (GCR), and solar energetic particles with the earth's atmosphere produce a non-isotropic distribution of albedo neutrons. Inside any reasonable habitable module, the average radiation quality factor of neutrons is about 4-5 times larger than the corresponding average quality factor of charged particles. The measurement of neutrons and their energy spectra is a difficult problem due the intense sources of charged particles. This paper reviews the results of Shuttle flight experiments (made during both solar maximum and solar minimum) to measure the contribution of neutrons to the dose equivalent, as well as theoretical calculations to estimate the appropriate range of neutron energies that contribute most to the dose equivalent. PMID:11852943

  14. Neutron measurements onboard the space shuttle

    NASA Technical Reports Server (NTRS)

    Badhwar, G. D.; Keith, J. E.; Cleghorn, T. F.

    2001-01-01

    The radiation environment inside a shielded volume is highly complex, consisting of both charged and neutral particles. Since the inception of human space flights, the charged particle component has received virtually all of the attention. There is however, a significant production of secondary neutrons, particularly from the aluminum structure in low earth orbiting spacecrafts. The interactions of galactic cosmic rays (GCR), and solar energetic particles with the earth's atmosphere produce a non-isotropic distribution of albedo neutrons. Inside any reasonable habitable module, the average radiation quality factor of neutrons is about 4-5 times larger than the corresponding average quality factor of charged particles. The measurement of neutrons and their energy spectra is a difficult problem due the intense sources of charged particles. This paper reviews the results of Shuttle flight experiments (made during both solar maximum and solar minimum) to measure the contribution of neutrons to the dose equivalent, as well as theoretical calculations to estimate the appropriate range of neutron energies that contribute most to the dose equivalent. Published by Elsevier Science Ltd.

  15. Atmospheric neutrons

    NASA Technical Reports Server (NTRS)

    Preszler, A. M.; Moon, S.; White, R. S.

    1976-01-01

    Additional calibrations of the University of California double-scatter neutron detector and additional analysis corrections lead to slightly changed neutron fluxes. The theoretical angular distributions of Merker (1975) are in general agreement with the reported experimental fluxes but do not give the peaks for vertical upward and downward moving neutrons. The theoretical neutron escape current is in agreement with the experimental values from 10 to 100 MeV. The experimental fluxes obtained agree with those of Kanbach et al. (1974) in the overlap region from 70 to 100 MeV.

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

    NASA Astrophysics Data System (ADS)

    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. Personnel neutron dose assessment upgrade: Volume 1, Personnel neutron dosimetry assessment: (Final report)

    SciTech Connect

    Hadlock, D.E.; Brackenbush, L.W.; Griffith, R.V.; Hankins, D.E.; Parkhurst, M.A.; Stroud, C.M.; Faust, L.G.; Vallario, E.J.

    1988-07-01

    This report provides guidance on the characteristics, use, and calibration criteria for personnel neutron dosimeters. The report is applicable for neutrons with energies ranging from thermal to less than 20 MeV. Background for general neutron dosimetry requirements is provided, as is relevant federal regulations and other standards. The characteristics of personnel neutron dosimeters are discussed, with particular attention paid to passive neutron dosimetry systems. Two of the systems discussed are used at DOE and DOE-contractor facilities (nuclear track emulsion and thermoluminescent-albedo) and another (the combination TLD/TED) was recently developed. Topics discussed in the field applications of these dosimeters include their theory of operation, their processing, readout, and interpretation, and their advantages and disadvantages for field use. The procedures required for occupational neutron dosimetry are discussed, including radiation monitoring and the wearing of dosimeters, their exchange periods, dose equivalent evaluations, and the documenting of neutron exposures. The coverage of dosimeter testing, maintenance, and calibration includes guidance on the selection of calibration sources, the effects of irradiation geometries, lower limits of detectability, fading, frequency of calibration, spectrometry, and quality control. 49 refs., 6 figs., 8 tabs.

  18. Effect of oxide films and structural inhomogeneities on transmission of ultracold neutrons through foils

    NASA Astrophysics Data System (ADS)

    Pokotilovski, Yuri N.

    2016-02-01

    Monte Carlo simulations are performed of the ultracold neutron (UCN) transmission through metal foils relevant to experiments with UCN, and the UCN albedo from an inhomogeneous 6LiF layer. The computations are based on the measured energy dependent cross sections of real materials.

  19. Physical basis for prompt-neutron activation analysis

    SciTech Connect

    Chrien, R.E.

    1982-01-01

    The technique called prompt ..gamma..-ray neutron activation analysis has been applied to rapid materials analysis. The radiation following the neutron radiation capture is prompt in the sense that the nuclear decay time is on the order of 10/sup -15/ second, and thus the technique is not strictly activation, but should be called radiation neutron capture spectroscopy or neutron capture ..gamma..-ray spectroscopy. This paper reviews the following: sources and detectors, theory of radiative capture, nonstatistical capture, giant dipole resonance, fast neutron capture, and thermal neutron capture ..gamma..-ray spectra. 14 figures.

  20. Quantifying the Impacts of Surface Albedo on Climate Using the WRF Model

    NASA Astrophysics Data System (ADS)

    Schlosser, C. A.; Xu, L.; Xu, X.; Gregory, J.; Kirchain, R.

    2015-12-01

    Surface albedo is an important part of the energy budget in shaping local and regional climate. It could also be a potential tool to mitigate the anthropogenic effect on climate change. However, the current level of scientific understanding of surface albedo on global warming potential is medium to low. In order to investigate the anthropogenic impact of surface albedo on climate, different scenarios of urban surface albedo over continental US using the WRF model are simulated. In this study, the change in surface albedo applies to rooftops, pavements, and walls of urban land cover grid cells. The two groups of simulations (low and high albedo) were compared to determine the impacts of elevating urban surface albedo and to account for the uncertainty in the errors or noise introduced by the slightly different initial conditions. The results are represented as the differences in surface temperature and the top of the atmosphere radiation between the two scenarios when urban surface albedos are elevated from 0.15 to 0.40. The ensemble mean of all potential outcomes as a whole, instead of individual initial conditions, shows that the impact of elevating surface albedo has a cooling effect that is robust at both local and regional scales during the summer season. More refined analyses of urban areas will provide insights on surface albedo impacts in specific regions. Future analyses may address changes in CO2 equivalence.

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

    PubMed

    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. PMID:19299862

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

    PubMed

    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 < k(t) < 0.1 and 0.4 < k(t) < 0.6 respectively, when solar elevation angle was below 35 degrees. The surface albedo increased with the increasing wind speed, turbidity and chlorophyll-a concentration. However, wind could indirectly affect surface albedo through leading to the changes in sediment resuspension and chlorophyll-a distribution. The sequence of albedo in the four sites was XLS > 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. PMID:26841592

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

    PubMed

    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 < k(t) < 0.1 and 0.4 < k(t) < 0.6 respectively, when solar elevation angle was below 35 degrees. The surface albedo increased with the increasing wind speed, turbidity and chlorophyll-a concentration. However, wind could indirectly affect surface albedo through leading to the changes in sediment resuspension and chlorophyll-a distribution. The sequence of albedo in the four sites was XLS > 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.

  4. Neutronic reactor

    DOEpatents

    Wende, Charles W. J.

    1976-08-17

    A safety rod for a nuclear reactor has an inner end portion having a gamma absorption coefficient and neutron capture cross section approximately equal to those of the adjacent shield, a central portion containing materials of high neutron capture cross section and an outer end portion having a gamma absorption coefficient at least equal to that of the adjacent shield.

  5. NEUTRONIC REACTOR

    DOEpatents

    Fermi, E.; Zinn, W.H.; Anderson, H.L.

    1958-09-16

    Means are presenied for increasing the reproduction ratio of a gaphite- moderated neutronic reactor by diminishing the neutron loss due to absorption or capture by gaseous impurities within the reactor. This means comprised of a fluid-tight casing or envelope completely enclosing the reactor and provided with a valve through which the casing, and thereby the reactor, may be evacuated of atmospheric air.

  6. Neutron tubes

    DOEpatents

    Leung, Ka-Ngo; Lou, Tak Pui; Reijonen, Jani

    2008-03-11

    A neutron tube or generator is based on a RF driven plasma ion source having a quartz or other chamber surrounded by an external RF antenna. A deuterium or mixed deuterium/tritium (or even just a tritium) plasma is generated in the chamber and D or D/T (or T) ions are extracted from the plasma. A neutron generating target is positioned so that the ion beam is incident thereon and loads the target. Incident ions cause D-D or D-T (or T-T) reactions which generate neutrons. Various embodiments differ primarily in size of the chamber and position and shape of the neutron generating target. Some neutron generators are small enough for implantation in the body. The target may be at the end of a catheter-like drift tube. The target may have a tapered or conical surface to increase target surface area.

  7. Neutron source

    DOEpatents

    Cason, J.L. Jr.; Shaw, C.B.

    1975-10-21

    A neutron source which is particularly useful for neutron radiography consists of a vessel containing a moderating media of relatively low moderating ratio, a flux trap including a moderating media of relatively high moderating ratio at the center of the vessel, a shell of depleted uranium dioxide surrounding the moderating media of relatively high moderating ratio, a plurality of guide tubes each containing a movable source of neutrons surrounding the flux trap, a neutron shield surrounding one part of each guide tube, and at least one collimator extending from the flux trap to the exterior of the neutron source. The shell of depleted uranium dioxide has a window provided with depleted uranium dioxide shutters for each collimator. Reflectors are provided above and below the flux trap and on the guide tubes away from the flux trap.

  8. Energetic neutrons leaking from the top of the atmosphere.

    NASA Technical Reports Server (NTRS)

    Merker, M.

    1972-01-01

    The energy, angular, and latitude distributions of energetic neutrons (up to 2 GeV) leaking from the top of the atmosphere have been calculated. The results agree with the recent measurement of Preszler, Simnett, and White, whose leakage rates were well above the calculation of Lingenfelter. Since the spectrum of Lingenfelter has served for evaluating the cosmic-ray albedo-neutron decay (CRAND) source of energetic protons in Earth's inner radiation belt, it is suggested that the results reported here be used to reevaluate the CRAND contribution.

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

    NASA Astrophysics Data System (ADS)

    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

  10. The fission track detector revisited: application to individual neutron dosimetry.

    PubMed

    Prêtre, S; Aroua, A; Boschung, M; Grecescu, M; Valley, J F; Wernli, C

    1996-08-01

    A system based on fission fragment tracks had previously been developed for individual neutron dosimetry. The dosimeter detects both fast neutrons by means of the 232Th(n,f) reaction, and thermal and albedo neutrons by means of the 235U(n,f) reaction. The fission tracks produced in a plastic foil are chemically etched and counted by spark discharges. The response of the dosimeter has recently been re-investigated in 36 different neutron fields: monoenergetic beams, reference fields near isotopic sources, and radiation fields encountered in a variety of situations inside nuclear power plants. The results obtained have been compared to those computed by convolution of the neutron spectra with the energy response functions of the dosimeters. In practical situations, it is essential to know the shape of the neutron spectrum, approximately at least, in order to perform an acceptably accurate dose evaluation. For that purpose, the neutron fields encountered inside nuclear power plants have been grouped into four categories, for which algorithms for dose evaluation have been developed. Concerning the neutron equivalent dose, the error associated with this approach does not exceed a factor of 2, a performance which is comparable to other detection systems used in the field of individual neutron dosimetry. PMID:8690594

  11. UV signatures of carbonaceous species on low-albedo asteroids

    NASA Astrophysics Data System (ADS)

    Hendrix, A.; Vilas, F.

    2014-07-01

    Asteroids in the low-albedo classes (C, B, G, F) are known to have spectra that are relatively feature-free in the visible/near-infrared (VNIR) spectral region, making them classically difficult to study in terms of surface mineralogy. Many of these bodies exhibit a 3-micron absorption band (e.g., [1]), which can be used to study hydration and organics. The primary other spectrally active region --- less well studied so far --- is the ultraviolet (UV). In this study, we utilize UV spectra of low-albedo asteroids (C, B, G, and F class) to study surface composition. In particular, we investigate implications for the presence of carbonaceous compounds, including tholins and Polycyclic Aromatic Hydrocarbons (PAHs), which have unique spectral features in the UV. Low-albedo asteroids are typically rather bland spectrally at VNIR wavelengths. Many of these objects exhibit an absorption band near 3 microns, indicative of some type of hydration (OH and-or H_2O). A subset of the asteroids with the 3-micron features also exhibit absorption near 0.7 microns, due to a ferrous-ferric charge-transfer transition likely resulting from aqueous alteration (the interaction of material with liquid water formed by melting of water upon a heating event). Some asteroids likely do not exhibit these features due to a history of heating experienced at some point in the asteroid's evolution. Despite having little spectral activity in the VNIR, all low-albedo asteroids absorb at wavelengths shorter than ˜500 nm. This has been generally attributed to a ferric-iron intervalence charge-transfer transition absorption. Carbon-bearing phases have long been assumed to be important on low-albedo asteroids (e.g., [2]) due to the dark, mostly-featureless VNIR spectra of these bodies. However, there are many forms of carbonaceous species and the species are expected to undergo phase modifications (e.g., due to thermal, aqueous, and radiation processes) that affect the spectra [3,7]. Tholins are residues

  12. Mars Polar Thermal Inertia and Albedo Properties Using TES Data

    NASA Astrophysics Data System (ADS)

    Scherbenski, J. M.; Paige, D. A.

    2002-12-01

    We present north and south polar thermal inertia and albedo maps derived from MGS TES observations. The maps were derived using the same robust approach developed to make polar thermal and inertia and albedo maps using IRTM observationsby Paige, Bachman, and Keegan (1994) and Paige and Keegan (1994). The data processing approach involved reading TES reduced data records in PDS format using the Vanilla software tool, and sending the data down a processing pipeline that constrains and bins the data, and compares it to the results of a diurnal and seasonal thermal model to obtain the best fit thermal inertia and apparent albedo. To facilitate comparison, the TES maps were created at the same Ls ranges as the published IRTM maps using TES spectral surface temperature results. The north polar maps used TES nadir observations obtained during a 50-day period from Ls 98.39 to Ls 121.25. The south polar maps used TES nadir observations obtained during a 30-day period from Ls 321.58 to 338.07. The creation of these maps employ a basic thermal model that does not include the effects of the atmosphere, as well as a one-dimensional radiative-convective model that does include the effects of the atmosphere. The spatial resolution of the north polar maps is 0.1 degrees of latitude and 1.0 degrees of longitude. The spatial resolution of the south polar maps is 2 degrees of latitude and 2 degrees of longitude. The TES north polar maps show the residual cap area in significantly greater detail than has been available previously. The IRTM maps showed that the north polar sand sea that surrounds the cap has unusually low thermal inertia. The TES maps confirm this conclusion, but also show that the dark renetrant features in chama boreal and elsewhere on the cap also have low thermal inertias. This strongly supports the proposal that these dark rentrants are the sources of the dune material. The TES maps also show that the darker layered deposits which are found at the periphery of the

  13. Splash and Re-entrant Albedo Fluxes Measured in the PAMELA Experiment

    NASA Astrophysics Data System (ADS)

    Mayorov, A. G.; Moiseeva, A. I.; Adriani, O.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov, E. A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carbone, R.; Carlson, P.; Casolino, M.; Castellini, G.; DeDonato, C.; DeSantis, C.; DeSimone, N.; DiFelice, V.; Formato, V.; Galper, A. M.; Karelin, A. V.; Koldashov, S. V.; Koldobskiy, S.; Kvashnin, A. A.; Kvashnin, A. N.; Leonov, A.; Malakhov, V.; Marcelli, L.; Martucci, M.; Mayorova, M. A.; Menn, W.; Merge', M.; Mikhailov, V. V.; Mocchiutti, E.; Monaco, A.; Mori, N.; Munini, R.; Osteria, G.; Palma, F.; Panico, B.; Papini, P.; Pearce, M.; Picozza, P.; Pizzolotto, C.; Ricci, M.; Ricciarini, S. B.; Sarkar, R.; Scotti, V.; Simon, M.; Sparvoli, R.; Spillantini, P.; Stozhkov, Y. I.; Vacchi, A.; Vannuccini, E.; Voronov, S. A.; Yurkin, Y. T.; Zampa, G.; Zampa, N.; Zverev, V. G.

    This work devoted to the description of the method for splash albedo protons identification in the satellite-born experiment PAMELA. In contrast to the reentrant albedo particles, which enter into the main aperture of the instrument, the direct albedo particles enter from the opposite direction, so they pass a few detectors, including calorimeter, before being register by the magnetic spectrometer. The developed method take into account the influence of these detectors on the selection of events and measurements of their characteristics. To test this method the energy spectrum of reentrant albedo protons in various regions of the near-Earth space reconstructed; it is in a good agreement with the classical measurements in the main aperture. Therefore, this method can be useful to obtain a new physical data about fluxes of splash albedo protons in the PAMELA experiment, which, unlike the reentrant albedo, can be study even at high geomagnetic latitudes.

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

    NASA Astrophysics Data System (ADS)

    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.

  15. A REVISED ASTEROID POLARIZATION-ALBEDO RELATIONSHIP USING WISE/NEOWISE DATA

    SciTech Connect

    Masiero, Joseph R.; Mainzer, A. K.; Bauer, J. M.; Wright, E. L.; McMillan, R. S.; Tholen, D. J.; Blain, A. W.

    2012-04-20

    We present a reanalysis of the relationship between asteroid albedo and polarization properties using the albedos derived from the Wide-field Infrared Survey Explorer. We find that the function that best describes this relation is a three-dimensional linear fit in the space of log (albedo)-log (polarization slope)-log (minimum polarization). When projected to two dimensions, the parameters of the fit are consistent with those found in previous work. We also define p* as the quantity of maximal polarization variation when compared with the albedo and present the best-fitting albedo-p* relation. Some asteroid taxonomic types stand out in this three-dimensional space, notably the E, B, and M Tholen types, while others cluster in clumps coincident with the S- and C-complex bodies. We note that both low albedo and small (D < 30 km) asteroids are underrepresented in the polarimetric sample, and we encourage future polarimetric surveys to focus on these bodies.

  16. Albedo Drop on the Greenland Ice Sheet: Relative Impacts of Wet and Dry Snow Processes

    NASA Astrophysics Data System (ADS)

    Chen, J.; Polashenski, C.

    2014-12-01

    The energy balance of the Greenland Ice Sheet (GIS) is strongly impacted by changes in snow albedo. MODIS (Moderate Resolution Imaging Spectroradiometer) observations indicate that the GIS albedo has dropped since the early part of this century. We analyze data from the MODIS products MOD10A1 for broadband snow albedo and MOD09A1 for surface spectral reflectance since 2001 to better explain the physical mechanisms driving these changes. The MODIS products are filtered, and the data is masked using microwave-derived surface melt maps to isolate albedo changes due to dry snow processes from those driven by melt impacts. Results show that the majority of recent changes in the GIS albedo - even at high elevations - are driven by snow wetting rather than dry snow processes such as grain metamorphosis and aerosol impurity deposition. The spectral signature of the smaller changes occurring within dry snow areas suggests that grain metamorphosis dominates the albedo decline in these regions.

  17. Effect of reflectance model choice on earthshine-based terrestrial albedo determinations.

    NASA Astrophysics Data System (ADS)

    Thejll, Peter; Gleisner, Hans; Flynn, Chris

    2016-04-01

    Earthshine observations can be used to determine near-hemispheric average terrestrial albedos by careful observation of the relative strength of the earthshine-lit half of the Moon coupled with correct modelling of the reflectances of Earth and Moon, as well as lunar single-scattering albedo maps. Using our own observations of the earthshine, from Mauna Loa Observatory in 2011-12, we investigate the influence of the choice of bidirectional reflectance models for the Moon on derived terrestrial albedos. We find a considerable dependence on albedo results in this choice, and discuss ways to determine what the origin of the dependence is - e.g is it in the joint choices of lunar and terrestrial BRDFs, or is the choice of terrestrial BRDF less important than the lunar one? We report on the results of modelling lunar reflectance and albedo in 6 ways and terrestrial reflectance in two ways, assuming a uniform single-scattering albedo on Earth.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Surface Albedo/BRDF Parameters (Terra/Aqua MODIS)

    DOE Data Explorer

    Trishchenko, Alexander

    2008-01-15

    Spatially and temporally complete surface spectral albedo/BRDF products over the ARM SGP area were generated using data from two Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on Terra and Aqua satellites. A landcover-based fitting (LBF) algorithm is developed to derive the BRDF model parameters and albedo product (Luo et al., 2004a). The approach employs a landcover map and multi-day clearsky composites of directional surface reflectance. The landcover map is derived from the Landsat TM 30-meter data set (Trishchenko et al., 2004a), and the surface reflectances are from MODIS 500m-resolution 8-day composite products (MOD09/MYD09). The MOD09/MYD09 data are re-arranged into 10-day intervals for compatibility with other satellite products, such as those from the NOVA/AVHRR and SPOT/VGT sensors. The LBF method increases the success rate of the BRDF fitting process and enables more accurate monitoring of surface temporal changes during periods of rapid spring vegetation green-up and autumn leaf-fall, as well as changes due to agricultural practices and snowcover variations (Luo et al., 2004b, Trishchenko et al., 2004b). Albedo/BRDF products for MODIS on Terra and MODIS on Aqua, as well as for Terra/Aqua combined dataset, are generated at 500m spatial resolution and every 10-day since March 2000 (Terra) and July 2002 (Aqua and combined), respectively. The purpose for the latter product is to obtain a more comprehensive dataset that takes advantages of multi-sensor observations (Trishchenko et al., 2002). To fill data gaps due to cloud presence, various interpolation procedures are applied based on a multi-year observation database and referring to results from other locations with similar landcover property. Special seasonal smoothing procedure is also applied to further remove outliers and artifacts in data series.

  20. Independent pixel and Monte Carlo estimates of stratocumulus albedo

    NASA Technical Reports Server (NTRS)

    Cahalan, Robert F.; Ridgway, William; Wiscombe, Warren J.; Gollmer, Steven; HARSHVARDHAN

    1994-01-01

    Monte Carlo radiative transfer methods are employed here to estimate the plane-parallel albedo bias for marine stratocumulus clouds. This is the bias in estimates of the mesoscale-average albedo, which arises from the assumption that cloud liquid water is uniformly distributed. The authors compare such estimates with those based on a more realistic distribution generated from a fractal model of marine stratocumulus clouds belonging to the class of 'bounded cascade' models. In this model the cloud top and base are fixed, so that all variations in cloud shape are ignored. The model generates random variations in liquid water along a single horizontal direction, forming fractal cloud streets while conserving the total liquid water in the cloud field. The model reproduces the mean, variance, and skewness of the vertically integrated cloud liquid water, as well as its observed wavenumber spectrum, which is approximately a power law. The Monte Carlo method keeps track of the three-dimensional paths solar photons take through the cloud field, using a vectorized implementation of a direct technique. The simplifications in the cloud field studied here allow the computations to be accelerated. The Monte Carlo results are compared to those of the independent pixel approximation, which neglects net horizontal photon transport. Differences between the Monte Carlo and independent pixel estimates of the mesoscale-average albedo are on the order of 1% for conservative scattering, while the plane-parallel bias itself is an order of magnitude larger. As cloud absorption increases, the independent pixel approximation agrees even more closely with the Monte Carlo estimates. This result holds for a wide range of sun angles and aspect ratios. Thus, horizontal photon transport can be safely neglected in estimates of the area-average flux for such cloud models. This result relies on the rapid falloff of the wavenumber spectrum of stratocumulus, which ensures that the smaller

  1. Albedos and densities of the inner satellites of Saturn

    NASA Technical Reports Server (NTRS)

    Morrison, D.

    1974-01-01

    Broad-band radiometry at 20 microns is presented for Rhea and Dione; the measured flux densities, together with visual photometry, indicate that both satellites have geometric albedos near 0.6 and that their radii are, respectively, 800 plus or minus 125 and 575 plus or minus 100 km. The density of Dione is 1.4 plus or minus 0.6 g per cu cm; for Tethys, Enceladus, and Mimas, whose densities have not been measured, a 'photometric density' is defined from the available data, and it is shown that their densities are probably near unity. These satellites must therefore all be composed primarily of ices.

  2. Albedo, thermal inertia and rotation of ring particles (Invited)

    NASA Astrophysics Data System (ADS)

    Morishima, R.; Spilker, L. J.; Ohtsuki, K.; Cassini Cirs Ring Team

    2010-12-01

    Since the Saturn orbit insertion of the Cassini spacecraft in mid-2004 up to now, the Cassini composite infrared spectrometer (CIRS) has measured temperatures of Saturn's main rings at various observational geometries. We present results of parameter fits using our new thermal model (Morishima et al. 2009). Our model is based on classical radiative transfer and takes into account the heat transport due to particle motion in the azimuthal and vertical directions. The model assumes a bimodal size distribution consisting of small fast rotators and large slow rotators. Important parameters are the Bolometric bond albedo, A_V, the fraction of fast rotators in cross section, f_fast, and the thermal inertia, Γ. Two different data sets are used to estimate these parameters. The first set, which consists of four radial scans obtained at low and high solar phases both on the lit and unlit faces of rings (Spilker et al. 2006), is suitable for accurate estimations of A_V and f_fast with high radial resolution. Another one, which consists of azimuthal scans that include data in Saturn shadow (Leyrat et al. 2008), is suitable for estimations of Γ. The estimated parameters are shown in Fig.1. The albedo is 0.1-0.4, 0.5-0.7, 0.4, 0.5 for the C ring, the B ring, the Cassini division, and the A ring, respectively. The fraction of fast rotators is roughly half for all the rings. The thermal inertia is 7-21 in MKS units. For the mid B ring, values of parameters obtained from two data sets are consistent with each other if ring particles are assumed to bounce at the midplane due to mutual collisions. We also find that fits to azimuthal scans are improved if Γ for fast rotators is larger than that for slow rotators. Albedo, fraction of fast rotators in cross section, and thermal inertia estimated from parameter fits. Two different thermal data sets are used: radial scans at four different geometries (solid curves) and azimuthal scans including data in Saturn shadow (diamonds). Dashed

  3. The asteroid albedo scale. II - Laboratory polarimetry of dark carbon-bearing silicates

    NASA Technical Reports Server (NTRS)

    Zellner, B.; Lebertre, T.; Day, K.

    1977-01-01

    Laboratory reflection polarimetry is presented for eight samples of artificial, poorly crystalline magnesian silicates with varying admixtures of carbon black. The polarimetric slope-albedo law saturates for geometric albedos lower than about 0.05, and good agreement with the telescopic polarization-phase curves of C-type asteroids is found for albedos as low as 0.02. Thus the conclusion from thermal radiometry is confirmed that the C objects are very dark, darker than any known carbonaceous chondrite.

  4. Geophysical aspects of remote sensing

    NASA Technical Reports Server (NTRS)

    Watson, K.

    1971-01-01

    Results obtained through the NASA Earth Resources Aircraft Program at Mill Creek, Oklahoma, provide a case history example of the application of remote sensing to the identification of geologic rock units. Thermal infrared images are interpreted by means of a sequence of models of increasing complexity. The roles of various parameters are examined: rock properties (thermal inertia, albedo, emissivity), site location (latitude), season (sun's declination), atmospheric effects (cloud cover, transmission, air temperature), and topographic orientation (slope, azimuth). The results obtained at this site also illustrate the development of an important application of remote sensing in geologic identification. Relatively pure limestones and dolomites of the Mill Creek test area can be differentiated in nighttime infrared images, and facies changes between them can be detected along and across strike. The predominance on the earth's surface of sedimentary rocks, of which limestone and dolomite are major members, indicates the importance of this discrimination.

  5. An Albedo-Ice Regression Method for Determining Ice Water Content of Polar Mesospheric Clouds from UV Observations

    NASA Astrophysics Data System (ADS)

    Thomas, G. E.; Bardeen, C.; Benze, S.

    2014-12-01

    Simulations of Polar Mesospheric Cloud (PMC) brightness and ice water content (IWC) are used to develop a simple robust method for IWC retrieval from UV satellite observations. We compare model simulations of IWC with retrievals from the UV Cloud Imaging and Particle Size (CIPS) experiment on board the satellite mission Aeronomy for Ice in the Mesosphere (AIM). This instrument remotely senses scattered brightness related to the vertically-integrated ice content. Simulations from the Whole Atmosphere Community Climate Model (WACCM), a chemistry climate model, is combined with a sectional microphysics model based on the Community Aerosol and Radiation Model for Atmospheres (CARMA). The model calculates high-resolution three-dimensional size distributions of ice particles. The internal variability is due to geographic and temporal variation of temperature and dynamics, water vapor, and meteoric dust. We examine all simulations from a single model day (we chose northern summer solstice) which contains several thousand model clouds. Accurate vertical integrations of the albedo and IWC are obtained. The ice size distributions are thus based on physical principles, rather than artificial analytic distributions that are often used in retrieval algorithms from observations. Treating the model clouds as noise-free data, we apply the CIPS algorithm to retrieve cloud particle size and IWC. The inherent "errors" in the retrievals are thus estimated. The linear dependence of IWC on albedo makes possible a method to derive IWC, called the Albedo-Ice regression method, or AIR. This method potentially unifies the variety of data from various UV experiments, with the advantages of (1) removing scattering-angle bias from cloud brightness measurements,(2) providing a physically-useful parameter (IWC),(3) deriving IWC even for faint clouds of small average particle sizes, and (4) estimating the statistical uncertainty as a random error, which bypasses the need to derive particle size.

  6. Improving neutron dosimetry using bubble detector technology

    SciTech Connect

    Buckner, M.A.

    1993-02-01

    Providing accurate neutron dosimetry for a variety of neutron energy spectra is a formidable task for any dosimetry system. Unless something is known about the neutron spectrum prior to processing the dosimeter, the calculated dose may vary greatly from that actually encountered; that is until now. The entrance of bubble detector technology into the field of neutron dosimetry has eliminated the necessity of having an a priori knowledge of the neutron energy spectra. Recently, a new approach in measuring personnel neutron dose equivalent was developed at Oak Ridge National Laboratory. By using bubble detectors in combination with current thermoluminescent dosimeters (TLDs) as a Combination Personnel Neutron Dosimeter (CPND), not only is it possible to provide accurate dose equivalent results, but a simple four-interval neutron energy spectrum is obtained as well. The components of the CPND are a Harshaw albedo TLD and two bubble detectors with theoretical energy thresholds of 100 key and 1500 keV. Presented are (1) a synoptic history surrounding emergence of bubble detector technology, (2) a brief overview of the current theory on mechanisms of interaction, (3) the data and analysis process involved in refining the response functions, (4) performance evaluation of the original CPND and a reevaluation of the same data under the modified method, (5) the procedure used to determine the reference values of component fluence and dose equivalent for field assessment, (6) analysis of the after-modification results, (7) a critique of some currently held assumptions, offering some alternative explanations, and (8) thoughts concerning potential applications and directions for future research.

  7. NEUTRON SOURCE

    DOEpatents

    Bernander, N.K. et al.

    1960-10-18

    An apparatus is described for producing neutrons through target bombardment with deuterons. Deuterium gas is ionized by electron bombardment and the deuteron ions are accelerated through a magnetic field to collimate them into a continuous high intensity beam. The ion beam is directed against a deuteron pervious metal target of substantially the same nnaterial throughout to embed the deuterous therein and react them to produce neutrons. A large quantity of neutrons is produced in this manner due to the increased energy and quantity of ions bombarding the target.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Influence of surface-albedo in subtropical regions on July circulation

    NASA Technical Reports Server (NTRS)

    Sud, Y.; Fennessy, M.

    1981-01-01

    A simulation study to examine the influence of surface-albedo on July circulation in subtropical regions is presented. The results are based on two 47-day integrations. In the first integration, called the control run, surface albedos were normally prescribed, whereas in the second integration, called the anomaly run, the surface albedo was modified in four regions: the Sahel in Africa, the Great Plains in the United States, the Thar Desert border in the Indian subcontinent, and Brazil in South America. Each run was started from observed initial conditions for June 15, 1979 based on NMC analysis. The surface albedo in each of the regions was arbitrarily made 30%.

  11. Surface features on Mars: Ground-based albedo and radar compared with Mariner 9 topography

    NASA Technical Reports Server (NTRS)

    Frey, H.

    1973-01-01

    Earth-based albedo maps of Mars were compared with Mariner 9 television data and ground-based radar profiles to investigate the nature of the bright and dark albedo features. Little correlation was found except at the boundaries of classical albedo features, where some topographic control is indicated. Wind-blown dust models for seasonal and secular albedo variations are supported, but it is not clear whether the fines are derived from bright or dark parent rock. Mars, like the Earth and Moon, has probably generated two distinct types of crustal material.

  12. Natural versus anthropogenic factors affecting low-level cloud albedo over the North Atlantic

    NASA Technical Reports Server (NTRS)

    Falkowski, Paul G.; Kim, Yongseung; Kolber, Zbigniew; Wilson, Cara; Wirick, Creighton; Cess, Robert

    1992-01-01

    Cloud albedo plays a key role in regulating earth's climate. Cloud albedo depends on column-integrated liquid water content and the density of cloud condensation nuclei, which consists primarily of submicrometer-sized aerosol sulfate particles. A comparison of two independent satellite data sets suggests that, although anthropogenic sulfate emissions may enhance cloud albedo immediately adjacent to the east coast of the United States, over the central North Atlantic Ocean the variability in albedo can be largely accounted for by natural marine and atmospheric processes that probably have remained relatively constant since the beginning of the industrial revolution.

  13. Vegetation controls on northern high latitude snow-albedo feedback: observations and CMIP5 model simulations.

    PubMed

    Loranty, Michael M; Berner, Logan T; Goetz, Scott J; Jin, Yufang; Randerson, James T

    2014-02-01

    The snow-masking effect of vegetation exerts strong control on albedo in northern high latitude ecosystems. Large-scale changes in the distribution and stature of vegetation in this region will thus have important feedbacks to climate. The snow-albedo feedback is controlled largely by the contrast between snow-covered and snow-free albedo (Δα), which influences predictions of future warming in coupled climate models, despite being poorly constrained at seasonal and century time scales. Here, we compare satellite observations and coupled climate model representations of albedo and tree cover for the boreal and Arctic region. Our analyses reveal consistent declines in albedo with increasing tree cover, occurring south of latitudinal tree line, that are poorly represented in coupled climate models. Observed relationships between albedo and tree cover differ substantially between snow-covered and snow-free periods, and among plant functional type. Tree cover in models varies widely but surprisingly does not correlate well with model albedo. Furthermore, our results demonstrate a relationship between tree cover and snow-albedo feedback that may be used to accurately constrain high latitude albedo feedbacks in coupled climate models under current and future vegetation distributions.

  14. Changes on albedo after a large forest fire in Mediterranean ecosystems

    NASA Astrophysics Data System (ADS)

    Quintano, Carmen; Fernández-Manso, Alfonso; Fernández-García, Victor; Marcos, Elena; Calvo, Leonor

    2015-09-01

    Fires are one of the main causes of environmental alteration in Mediterranean forest ecosystems. Albedo varies and evolves seasonally based on solar illumination. It is greatly influenced by changes on vegetation: vegetation growth, cutting/planting forests or forest fires. This work analyzes albedo variations due to a large forest fire that occurred on 19- 21 September 2012 in northwestern Spain. From this area, albedo post-fire images (immediately and 1-year after fire) were generated from Landsat 7 Enhanced Thematic Mapper (ETM+) data. Specifically we considered total shortwave albedo, total-, direct-, and diffuse-visible, and near-infrared albedo. Nine to twelve weeks after fire, 111 field plots were measured (27 unburned plots, 84 burned plots). The relationship between albedo values and thematic class (burned/unburned) was evaluated by one-way analysis of variance. Our results demonstrate that albedo changes were related to burned/unburned variable with statistical significance, indicating the importance of forestry areas as regulators of land surface energy fluxes and revealing the potential of post-fire albedo for assessing burned areas. Future research, however, is needed to evaluate the persistence of albedo changes.

  15. Thermal neutron detection system

    DOEpatents

    Peurrung, Anthony J.; Stromswold, David C.

    2000-01-01

    According to the present invention, a system for measuring a thermal neutron emission from a neutron source, has a reflector/moderator proximate the neutron source that reflects and moderates neutrons from the neutron source. The reflector/moderator further directs thermal neutrons toward an unmoderated thermal neutron detector.

  16. NEUTRONIC REACTOR

    DOEpatents

    Wade, E.J.

    1958-09-16

    This patent relates to a reflector means for a neutronic reactor. A reflector comprised of a plurality of vertically movable beryllium control members is provided surrounding the sides of the reactor core. An absorber of fast neutrons comprised of natural uramum surrounds the reflector. An absorber of slow neutrons surrounds the absorber of fast neutrons and is formed of a plurality of beryllium blocks having natural uranium members distributcd therethrough. in addition, a movable body is positioned directly below the core and is comprised of a beryllium reflector and an absorbing member attached to the botiom thereof, the absorbing member containing a substance selected from the goup consisting of natural urantum and Th/sup 232/.

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

    PubMed

    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.

  18. Mars - Experimental study of albedo changes caused by dust fallout

    NASA Technical Reports Server (NTRS)

    Wells, E. N.; Veverka, J.; Thomas, P.

    1984-01-01

    A laboratory apparatus was used to simulate the uniform fallout and deposition of particles 1 to 5 microns in diameter in an experimental study on how the spectral and photometric properties of representative Martian areas are affected by fallout of atmospheric dust (smaller than or equalling 60 microns) suspended during dust storms. In this study, measurements are made in the changes in reflectance at optical and near-infrared wavelengths (0.4 to 1.2 micron) caused by deposition of varying amounts of a Mars-analog dust on bright and dark substrates before and after deposition of 6 x 10 to the -5th to 1.5 x 10 to the -3rd g/sq cm of simulated fallout. It is believed that only small amounts of dust particles (approximately 3 x 10 to the -4th g/sq cm) are needed to make significant albedo changes in dark areas of Mars, and that this would rule out uniform dust deposition on the surface of the planet. Data also indicate that other high albedo features like bright crater-related wind streaks may not be areas of significant sediment deposits. Laboratory simulations have permitted estimates of how much the reflectance of an area on Mars would change given a certain amount of dust fallout (g/sq cm) or reflectance data. These simulations may also be useful in tracking the transport and deposition of the dust.

  19. Soot climate forcing via snow and ice albedos.

    PubMed

    Hansen, James; Nazarenko, Larissa

    2004-01-13

    Plausible estimates for the effect of soot on snow and ice albedos (1.5% in the Arctic and 3% in Northern Hemisphere land areas) yield a climate forcing of +0.3 W/m(2) in the Northern Hemisphere. The "efficacy" of this forcing is approximately 2, i.e., for a given forcing it is twice as effective as CO(2) in altering global surface air temperature. This indirect soot forcing may have contributed to global warming of the past century, including the trend toward early springs in the Northern Hemisphere, thinning Arctic sea ice, and melting land ice and permafrost. If, as we suggest, melting ice and sea level rise define the level of dangerous anthropogenic interference with the climate system, then reducing soot emissions, thus restoring snow albedos to pristine high values, would have the double benefit of reducing global warming and raising the global temperature level at which dangerous anthropogenic interference occurs. However, soot contributions to climate change do not alter the conclusion that anthropogenic greenhouse gases have been the main cause of recent global warming and will be the predominant climate forcing in the future.

  20. Soot climate forcing via snow and ice albedos

    PubMed Central

    Hansen, James; Nazarenko, Larissa

    2004-01-01

    Plausible estimates for the effect of soot on snow and ice albedos (1.5% in the Arctic and 3% in Northern Hemisphere land areas) yield a climate forcing of +0.3 W/m2 in the Northern Hemisphere. The “efficacy” of this forcing is ∼2, i.e., for a given forcing it is twice as effective as CO2 in altering global surface air temperature. This indirect soot forcing may have contributed to global warming of the past century, including the trend toward early springs in the Northern Hemisphere, thinning Arctic sea ice, and melting land ice and permafrost. If, as we suggest, melting ice and sea level rise define the level of dangerous anthropogenic interference with the climate system, then reducing soot emissions, thus restoring snow albedos to pristine high values, would have the double benefit of reducing global warming and raising the global temperature level at which dangerous anthropogenic interference occurs. However, soot contributions to climate change do not alter the conclusion that anthropogenic greenhouse gases have been the main cause of recent global warming and will be the predominant climate forcing in the future. PMID:14699053

  1. Soot climate forcing via snow and ice albedos

    NASA Astrophysics Data System (ADS)

    Hansen, James; Nazarenko, Larissa

    2004-01-01

    Plausible estimates for the effect of soot on snow and ice albedos (1.5% in the Arctic and 3% in Northern Hemisphere land areas) yield a climate forcing of +0.3 W/m2 in the Northern Hemisphere. The "efficacy" of this forcing is 2, i.e., for a given forcing it is twice as effective as CO2 in altering global surface air temperature. This indirect soot forcing may have contributed to global warming of the past century, including the trend toward early springs in the Northern Hemisphere, thinning Arctic sea ice, and melting land ice and permafrost. If, as we suggest, melting ice and sea level rise define the level of dangerous anthropogenic interference with the climate system, then reducing soot emissions, thus restoring snow albedos to pristine high values, would have the double benefit of reducing global warming and raising the global temperature level at which dangerous anthropogenic interference occurs. However, soot contributions to climate change do not alter the conclusion that anthropogenic greenhouse gases have been the main cause of recent global warming and will be the predominant climate forcing in the future. aerosols | air pollution | climate change | sea level

  2. NEUTRONIC REACTOR

    DOEpatents

    Fraas, A.P.; Mills, C.B.

    1961-11-21

    A neutronic reactor in which neutron moderation is achieved primarily in its reflector is described. The reactor structure consists of a cylindrical central "island" of moderator and a spherical moderating reflector spaced therefrom, thereby providing an annular space. An essentially unmoderated liquid fuel is continuously passed through the annular space and undergoes fission while contained therein. The reactor, because of its small size, is particularly adapted for propulsion uses, including the propulsion of aircraft. (AEC)

  3. NEUTRON SOURCES

    DOEpatents

    Richmond, J.L.; Wells, C.E.

    1963-01-15

    A neutron source is obtained without employing any separate beryllia receptacle, as was formerly required. The new method is safer and faster, and affords a source with both improved yield and symmetry of neutron emission. A Be container is used to hold and react with Pu. This container has a thin isolating layer that does not obstruct the desired Pu--Be reaction and obviates procedures previously employed to disassemble and remove a beryllia receptacle. (AEC)

  4. Aerial Neutron Detection: Neutron Signatures for Nonproliferation and Emergency Response Applications

    SciTech Connect

    Maurer, Richard J.; Stampahar, Thomas G.; Smith, Ethan X.; Mukhopadhyay, Sanjoy; Wolff, Ronald S.; Rourke, Timothy J.; LeDonne, Jeffrey P.; Avaro, Emanuele; Butler, D. Andre; Borders, Kevin L.; Stampahar, Jezabel; Schuck, William H.; Selfridge, Thomas L.; McKissack, Thomas M.; Duncan, William W.; Hendricks, Thane J.

    2012-10-17

    From 2007 to the present, the Remote Sensing Laboratory has been conducting a series of studies designed to expand our fundamental understanding of aerial neutron detection with the goal of designing an enhanced sensitivity detection system for long range neutron detection. Over 35 hours of aerial measurements in a helicopter were conducted for a variety of neutron emitters such as neutron point sources, a commercial nuclear power reactor, nuclear reactor spent fuel in dry cask storage, depleted uranium hexafluoride and depleted uranium metal. The goals of the project were to increase the detection sensitivity of our instruments such that a 5.4 × 104 neutron/second source could be detected at 100 feet above ground level at a speed of 70 knots and to enhance the long-range detection sensitivity for larger neutron sources, i.e., detection ranges above 1000 feet. In order to increase the sensitivity of aerial neutron detection instruments, it is important to understand the dynamics of the neutron background as a function of altitude. For aerial neutron detection, studies have shown that the neutron background primarily originates from above the aircraft, being produced in the upper atmosphere by galactic cosmic-ray interactions with air molecules. These interactions produce energetic neutrons and charged particles that cascade to the earth’s surface, producing additional neutrons in secondary collisions. Hence, the neutron background increases as a function of altitude which is an impediment to long-range neutron detection. In order to increase the sensitivity for long range detection, it is necessary to maintain a low neutron background as a function of altitude. Initial investigations show the variation in the neutron background can be decreased with the application of a cosmic-ray shield. The results of the studies along with a representative data set are presented.

  5. NEUTRONIC REACTOR

    DOEpatents

    Wigner, E.P.

    1958-04-22

    A nuclear reactor for isotope production is described. This reactor is designed to provide a maximum thermal neutron flux in a region adjacent to the periphery of the reactor rather than in the center of the reactor. The core of the reactor is generally centrally located with respect tn a surrounding first reflector, constructed of beryllium. The beryllium reflector is surrounded by a second reflector, constructed of graphite, which, in tune, is surrounded by a conventional thermal shield. Water is circulated through the core and the reflector and functions both as a moderator and a coolant. In order to produce a greatsr maximum thermal neutron flux adjacent to the periphery of the reactor rather than in the core, the reactor is designed so tbat the ratio of neutron scattering cross section to neutron absorption cross section averaged over all of the materials in the reflector is approximately twice the ratio of neutron scattering cross section to neutron absorption cross section averaged over all of the material of the core of the reactor.

  6. FOREWORD: Neutron metrology Neutron metrology

    NASA Astrophysics Data System (ADS)

    Thomas, David J.; Nolte, Ralf; Gressier, Vincent

    2011-12-01

    The International Committee for Weights and Measures (CIPM) has consultative committees covering various areas of metrology. The Consultative Committee for Ionizing Radiation (CCRI) differs from the others in having three sections: Section (I) deals with radiation dosimetry, Section (II) with radionuclide metrology and Section (III) with neutron metrology. In 2003 a proposal was made to publish special issues of Metrologia covering the work of the three Sections. Section (II) was the first to complete their task, and their special issue was published in 2007, volume 44(4). This was followed in 2009 by the special issue on radiation dosimetry, volume 46(2). The present issue, volume 48(6), completes the trilogy and attempts to explain neutron metrology, the youngest of the three disciplines, the neutron only having been discovered in 1932, to a wider audience and to highlight the relevance and importance of this field. When originally approached with the idea of this special issue, Section (III) immediately saw the value of a publication specifically on neutron metrology. It is a topic area where papers tend to be scattered throughout the literature in journals covering, for example, nuclear instrumentation, radiation protection or radiation measurements in general. Review articles tend to be few. People new to the field often ask for an introduction to the various topics. There are some excellent older textbooks, but these are now becoming obsolete. More experienced workers in specific areas of neutron metrology can find it difficult to know the latest position in related areas. The papers in this issue attempt, without presenting a purely historical outline, to describe the field in a sufficiently logical way to provide the novice with a clear introduction, while being sufficiently up-to-date to provide the more experienced reader with the latest scientific developments in the different topic areas. Neutron radiation fields obviously occur throughout the nuclear

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

    PubMed Central

    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

  8. Spring-summer albedo variations of Antarctic sea ice from 1982 to 2009

    NASA Astrophysics Data System (ADS)

    Shao, Zhu-De; Ke, Chang-Qing

    2015-06-01

    This study examined the spring-summer (November, December, January and February) albedo averages and trends using a dataset consisting of 28 years of homogenized satellite data for the entire Antarctic sea ice region and for five longitudinal sectors around Antarctica: the Weddell Sea (WS), the Indian Ocean sector (IO), the Pacific Ocean sector (PO), the Ross Sea (RS) and the Bellingshausen-Amundsen Sea (BS). Time series data of the sea ice concentrations and sea surface temperatures were used to analyse their relations to the albedo. The results indicated that the sea ice albedo increased slightly during the study period, at a rate of 0.314% per decade, over the Antarctic sea ice region. The sea ice albedos in the PO, the IO and the WS increased at rates of 2.599% per decade (confidence level 99.86%), 0.824% per decade and 0.413% per decade, respectively, and the steepest increase occurred in the PO. However, the sea ice albedo in the BS decreased at a rate of -1.617% per decade (confidence level 95.05%) and was near zero in the RS. The spring-summer average albedo over the Antarctic sea ice region was 50.24%. The highest albedo values were mainly found on the continental coast and in the WS; in contrast, the lowest albedo values were found on the outer edge of the sea ice, the RS and the Amery Ice Shelf. The average albedo in the western Antarctic sea ice region was distinctly higher than that in the east. The albedo was significantly positively correlated with sea ice concentration (SIC) and was significantly negatively correlated with sea surface temperature (SST); these scenarios held true for all five longitudinal sectors. Spatially, the higher surface albedos follow the higher SICs and lower SST patterns. The increasing albedo means that Antarctic sea ice region reflects more solar radiation and absorbs less, leading to a decrease in temperature and much snowfall on sea ice, and further resulted in an increase in albedo. Conversely, the decreasing albedo

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

    PubMed

    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

  10. FOREWORD: Neutron metrology Neutron metrology

    NASA Astrophysics Data System (ADS)

    Thomas, David J.; Nolte, Ralf; Gressier, Vincent

    2011-12-01

    The International Committee for Weights and Measures (CIPM) has consultative committees covering various areas of metrology. The Consultative Committee for Ionizing Radiation (CCRI) differs from the others in having three sections: Section (I) deals with radiation dosimetry, Section (II) with radionuclide metrology and Section (III) with neutron metrology. In 2003 a proposal was made to publish special issues of Metrologia covering the work of the three Sections. Section (II) was the first to complete their task, and their special issue was published in 2007, volume 44(4). This was followed in 2009 by the special issue on radiation dosimetry, volume 46(2). The present issue, volume 48(6), completes the trilogy and attempts to explain neutron metrology, the youngest of the three disciplines, the neutron only having been discovered in 1932, to a wider audience and to highlight the relevance and importance of this field. When originally approached with the idea of this special issue, Section (III) immediately saw the value of a publication specifically on neutron metrology. It is a topic area where papers tend to be scattered throughout the literature in journals covering, for example, nuclear instrumentation, radiation protection or radiation measurements in general. Review articles tend to be few. People new to the field often ask for an introduction to the various topics. There are some excellent older textbooks, but these are now becoming obsolete. More experienced workers in specific areas of neutron metrology can find it difficult to know the latest position in related areas. The papers in this issue attempt, without presenting a purely historical outline, to describe the field in a sufficiently logical way to provide the novice with a clear introduction, while being sufficiently up-to-date to provide the more experienced reader with the latest scientific developments in the different topic areas. Neutron radiation fields obviously occur throughout the nuclear

  11. Phase-sensitive two-dimensional neutron shearing interferometer and Hartmann sensor

    SciTech Connect

    Baker, Kevin

    2015-12-08

    A neutron imaging system detects both the phase shift and absorption of neutrons passing through an object. The neutron imaging system is based on either of two different neutron wavefront sensor techniques: 2-D shearing interferometry and Hartmann wavefront sensing. Both approaches measure an entire two-dimensional neutron complex field, including its amplitude and phase. Each measures the full-field, two-dimensional phase gradients and, concomitantly, the two-dimensional amplitude mapping, requiring only a single measurement.

  12. Data processing of the active neutron experiment DAN for a Martian regolith investigation

    NASA Astrophysics Data System (ADS)

    Sanin, A. B.; Mitrofanov, I. G.; Litvak, M. L.; Lisov, D. I.; Starr, R.; Boynton, W.; Behar, A.; DeFlores, L.; Fedosov, F.; Golovin, D.; Hardgrove, C.; Harshman, K.; Jun, I.; Kozyrev, A. S.; Kuzmin, R. O.; Malakhov, A.; Milliken, R.; Mischna, M.; Moersch, J.; Mokrousov, M. I.; Nikiforov, S.; Shvetsov, V. N.; Tate, C.; Tret'yakov, V. I.; Vostrukhin, A.

    2015-07-01

    Searching for water in the soil of Gale Crater is one of the primary tasks for the NASA Mars Science Laboratory rover named Curiosity. The primary task of the Dynamic Albedo of Neutrons (DAN) experiment on board the rover is to investigate and qualitatively characterize the presence of water along the rover's traverse across Gale Crater. The water depth distribution may be found from measurements of neutrons generated by the Pulsing Neutron Generator (PNG) included in the DAN instrument, scattered by the regolith and returned back to the detectors. This paper provides a description of the data processing of such measurements and data products of DAN investigation.

  13. Impurities in Snow: Effects on Spectral Albedo of Prairie Snowpacks

    NASA Astrophysics Data System (ADS)

    Morris, J. N.; Klein, A. G.

    2007-12-01

    While extensive research on soot in snow has been done in the Polar Regions, there remains a lack of observations addressing the effect of soot on snow albedo in North American prairie snowpacks which causes uncertainty to the overall global effect that soot in snow has on climate. Measurements of snow impurities in freshly fallen prairie snowpacks in northwestern Iowa and central Texas collected from February 28 - March 5, 2007 and April 6, 2007, respectively. Two significant snowfall events occurred in northwestern Iowa during the study; the second snowfall event produced the most severe blizzard conditions in northwestern Iowa in the last thirty years. An unusual snowfall event in central Texas offered a unique sampling opportunity Several types of sites were sampled during the field campaign; this includes: frozen lakes with minimal human impact, agricultural fields impacted by agricultural dust, and human impacted sample sites. At twelve sites in northwestern Iowa samples were collected on multiple days and for both snow events to examine changes in snow impurities over time. At all site locations snow samples, temperature, density, and grain size were recorded. Snow reflectance and snow radiance was collected at a subset of the sites with an ASD VNIR Spectroradiometer (350 - 1500 nm). Snow impurities of light-absorbing particulate matter were measured by filtering the meltwater through a nuclepore 0.4 micrometer filter. Impurity concentration was determined by comparing the filters against a set of standards. A photometer will provide a more exact determination of snow impurities in the near future. Preliminary soot observations indicate prairie snow pack concentrations ranging from 1 ngC/g to 236 ngC/g with an average of 61.4 ngC/g. These measurements are within range of previously published values in the Arctic and can lower snow albedo. Differences in soot concentrations were observed between the two Iowa snowfall events. Impurity concentrations measured

  14. Analysis of QUADOS problem on TLD-ALBEDO personal dosemeter responses using discrete ordinates and Monte Carlo methods.

    PubMed

    Kodeli, Ivo; Tanner, Rick

    2005-01-01

    In the scope of QUADOS, a Concerted Action of the European Commission, eight calculational problems were prepared in order to evaluate the use of computational codes for dosimetry in radiation protection and medical physics, and to disseminate "good practice" throughout the radiation dosimetry community. This paper focuses on the analysis of the P4 problem on the 'TLD-albedo dosemeter: neutron and/or photon response of a four-element TL-dosemeter mounted on a standard ISO slab phantom'. Altogether 17 solutions were received from the participants, 14 of those transported neutrons and 15 photons. Most participants (16 out of 17) used Monte Carlo methods. These calculations are time-consuming, requiring several days of CPU time to perform the whole set of calculations and achieve good statistical precision. The possibility of using deterministic discrete ordinates codes as an alternative to Monte Carlo was therefore investigated and is presented here. In particular the capacity of the adjoint mode calculations is shown. PMID:16381782

  15. ALBEDO MODELS FOR SNOW AND ICE ON A FRESHWATER LAKE. (R824801)

    EPA Science Inventory

    Abstract

    Snow and ice albedo measurements were taken over a freshwater lake in Minnesota for three months during the winter of 1996¯1997 for use in a winter lake water quality model. The mean albedo of new snow was measured as 0.83±0.028, while the...

  16. Connection between the spherical albedo and the observable characteristics of a planetary atmosphere

    SciTech Connect

    Fomin, N.N.; Yanovitskii, E.G.

    1986-07-01

    Semiempirical dependences of the geometrical albedo and the reflection coefficient at the center of a planetary disk on the spherical albedo are found. The nonsteady analogs of these quantities are studied on the basis of the approximate equations obtained. These analogs can be used in the analysis of radiation transfer in forbidden molecular absorption bands.

  17. Main-belt asteroids with WISE/NEOWISE: Near-infrared albedos

    SciTech Connect

    Masiero, Joseph R.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; Sonnett, S.

    2014-08-20

    We present revised near-infrared albedo fits of 2835 main-belt asteroids observed by WISE/NEOWISE over the course of its fully cryogenic survey in 2010. These fits are derived from reflected-light near-infrared images taken simultaneously with thermal emission measurements, allowing for more accurate measurements of the near-infrared albedos than is possible for visible albedo measurements. Because our sample requires reflected light measurements, it undersamples small, low-albedo asteroids, as well as those with blue spectral slopes across the wavelengths investigated. We find that the main belt separates into three distinct groups of 6%, 16%, and 40% reflectance at 3.4 μm. Conversely, the 4.6 μm albedo distribution spans the full range of possible values with no clear grouping. Asteroid families show a narrow distribution of 3.4 μm albedos within each family that map to one of the three observed groupings, with the (221) Eos family being the sole family associated with the 16% reflectance 3.4 μm albedo group. We show that near-infrared albedos derived from simultaneous thermal emission and reflected light measurements are important indicators of asteroid taxonomy and can identify interesting targets for spectroscopic follow-up.

  18. ANALYTIC MODELS FOR ALBEDOS, PHASE CURVES, AND POLARIZATION OF REFLECTED LIGHT FROM EXOPLANETS

    SciTech Connect

    Madhusudhan, Nikku; Burrows, Adam E-mail: burrows@astro.princeton.edu

    2012-03-01

    New observational facilities are becoming increasingly capable of observing reflected light from transiting and directly imaged extrasolar planets. In this study, we provide an analytic framework to interpret observed phase curves, geometric albedos, and polarization of giant planet atmospheres. We compute the observables for non-conservative Rayleigh scattering in homogeneous semi-infinite atmospheres using both scalar and vector formalisms. In addition, we compute phase curves and albedos for Lambertian, isotropic, and anisotropic scattering phase functions. We provide analytic expressions for geometric albedos and spherical albedos as a function of the scattering albedo for Rayleigh scattering in semi-infinite atmospheres. Given an observed geometric albedo our prescriptions can be used to estimate the underlying scattering albedo of the atmosphere, which in turn is indicative of the scattering and absorptive properties of the atmosphere. We also study the dependence of polarization in Rayleigh scattering atmospheres on the orbital parameters of the planet-star system, particularly on the orbital inclination. We show how the orbital inclination of non-transiting exoplanets can be constrained from their observed polarization parameters. We consolidate the formalism, solution techniques, and results from analytic models available in the literature, often scattered in various sources, and present a systematic procedure to compute albedos, phase curves, and polarization of reflected light.

  19. MAIN BELT ASTEROIDS WITH WISE/NEOWISE. I. PRELIMINARY ALBEDOS AND DIAMETERS

    SciTech Connect

    Masiero, Joseph R.; Mainzer, A. K.; Bauer, J. M.; Eisenhardt, P. R. M.; DeBaun, E.; Elsbury, D.; Gautier, T. IV; Gomillion, S.; Wilkins, A.; Cutri, R. M.; Dailey, J.; McMillan, R. S.; Spahr, T. B.; Skrutskie, M. F.; Tholen, D.; Walker, R. G.; Wright, E. L.

    2011-11-10

    We present initial results from the Wide-field Infrared Survey Explorer (WISE), a four-band all-sky thermal infrared survey that produces data well suited for measuring the physical properties of asteroids, and the NEOWISE enhancement to the WISE mission allowing for detailed study of solar system objects. Using a NEATM thermal model fitting routine, we compute diameters for over 100,000 Main Belt asteroids from their IR thermal flux, with errors better than 10%. We then incorporate literature values of visible measurements (in the form of the H absolute magnitude) to determine albedos. Using these data we investigate the albedo and diameter distributions of the Main Belt. As observed previously, we find a change in the average albedo when comparing the inner, middle, and outer portions of the Main Belt. We also confirm that the albedo distribution of each region is strongly bimodal. We observe groupings of objects with similar albedos in regions of the Main Belt associated with dynamical breakup families. Asteroid families typically show a characteristic albedo for all members, but there are notable exceptions to this. This paper is the first look at the Main Belt asteroids in the WISE data, and only represents the preliminary, observed raw size, and albedo distributions for the populations considered. These distributions are subject to survey biases inherent to the NEOWISE data set and cannot yet be interpreted as describing the true populations; the debiased size and albedo distributions will be the subject of the next paper in this series.

  20. Intercomparison Between in situ and AVHRR Polar Pathfinder-Derived Surface Albedo over Greenland

    NASA Technical Reports Server (NTRS)

    Stroeve, Julienne C.; Box, Jason E.; Fowler, Charles; Haran, Terence; Key, Jeffery

    2001-01-01

    The Advanced Very High Resolution (AVHRR) Polar Pathfinder Data (APP) provides the first long time series of consistent, calibrated surface albedo and surface temperature data for the polar regions. Validations of these products have consisted of individual studies that analyzed algorithm performance for limited regions and or time periods. This paper reports on comparisons made between the APP-derived surface albedo and that measured at fourteen automatic weather stations (AWS) around the Greenland ice sheet from January 1997 to August 1998. Results show that satellite-derived surface albedo values are on average 10% less than those measured by the AWS stations. However, the station measurements tend to be biased high by about 4% and thus the differences in absolute albedo may be less (e.g. 6%). In regions of the ice sheet where the albedo variability is small, such as the dry snow facies, the APP albedo uncertainty exceeds the natural variability. Further work is needed to improve the absolute accuracy of the APP-derived surface albedo. Even so, the data provide temporally and spatially consistent estimates of the Greenland ice sheet albedo.

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

    NASA Technical Reports Server (NTRS)

    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.

  2. Nonadditive Mixed State Phases in Neutron Optics

    SciTech Connect

    Klepp, J.; Sponar, S.; Filipp, S.; Lettner, M.; Badurek, G.; Hasegawa, Y.

    2009-03-10

    In a neutron polarimetry experiment mixed neutron spin phases are determined. We consider evolutions leading to purely geometric, purely dynamical and combined phases. It is experimentally demonstrated that the sum of the geometric and dynamical phases--both obtained in separate measurements--is not equal to the associated total phase as obtained from a third measurement, unless the system is in a pure state. In this sense, mixed state phases are not additive.

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

    SciTech Connect

    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.

  4. Measurements of neutron fluxes with energies from thermal to several MeV in near-Earth space: SINP results.

    PubMed

    Shavrin, P I; Kuzhevskij, B M; Kuznetsov, S N; Nechaev, O Yu; Panasyuk, M I; Ryumin, S P; Yushkov, B Yu; Bratolyubova-Tsulukidze, L S; Lyagushin, V I; Germantsev, Yu L

    2002-10-01

    Neutron measurement results obtained at SINP MSU since 1970 are presented. These measurements were made using techniques based on neutron moderation and subsequent detection in a Li6I(Eu) crystal or a He3 coronal counter. The measurements were mainly carried out in orbits with inclination of 52 degrees and altitudes of 200-450 km. The spatial and angular distributions of the measured neutron fluxes were studied. The albedo neutron flux was estimated according to the count rate difference for opposite detector orientations towards Earth and away from it. This flux is comparable to the local neutron flux outside the Brazil anomaly region, where local neutrons dominate. Neutron fluxes, generated by solar protons, were detected during a solar flare on June 6, 1991 for the first time. Their spectrum was estimated as a power law with alpha>2. PMID:12442751

  5. Measurements of neutron fluxes with energies from thermal to several MeV in near-Earth space: SINP results.

    PubMed

    Shavrin, P I; Kuzhevskij, B M; Kuznetsov, S N; Nechaev, O Yu; Panasyuk, M I; Ryumin, S P; Yushkov, B Yu; Bratolyubova-Tsulukidze, L S; Lyagushin, V I; Germantsev, Yu L

    2002-10-01

    Neutron measurement results obtained at SINP MSU since 1970 are presented. These measurements were made using techniques based on neutron moderation and subsequent detection in a Li6I(Eu) crystal or a He3 coronal counter. The measurements were mainly carried out in orbits with inclination of 52 degrees and altitudes of 200-450 km. The spatial and angular distributions of the measured neutron fluxes were studied. The albedo neutron flux was estimated according to the count rate difference for opposite detector orientations towards Earth and away from it. This flux is comparable to the local neutron flux outside the Brazil anomaly region, where local neutrons dominate. Neutron fluxes, generated by solar protons, were detected during a solar flare on June 6, 1991 for the first time. Their spectrum was estimated as a power law with alpha>2.

  6. A digital file of the lunar normal Albedo

    USGS Publications Warehouse

    Wildey, R.L.

    1977-01-01

    A digital file of the normal albedo of the Moon has been produced at a resolution of about 1/550 of a lunar diameter (about 6.3 km). The file was produced from five photographs taken with the 61-cm reflector of the Northern Arizona University Astrophysical Observatory. No mosaicking was necessary. Spatial control is selenodetic rather than landmark-morphologic. Photometric control is provided through a combination of electrography and regular photoelectric photometry. Pixel photometric function corrections are employed. The file was provided as data base for the Lunar Consortium. Brief discussion of the scientific implications of the frequency histogram is offered, and the negligibility of lunar limb darkening below e{open} = 77?? is affirmed. It is specifically desired not to withhold these data from publication while more significant and detailed scientific interpretation is carried on. ?? 1977 D. Reidel Publishing Company, Dordrecht-Holland.

  7. Joint AOT-Single Scattering Albedo Retrieval in Algorithm MAIAC

    NASA Astrophysics Data System (ADS)

    Lyapustin, A.

    2015-12-01

    Multi-Angle Implementation of Atmospheric Correction (MAIAC) is a new algorithm which uses time series analysis and processing of groups of pixels for advanced cloud detection and retrieval of aerosol and surface bidirectional reflectance properties. MAIAC C6+ re-processing of MODIS data record, scheduled to begin in November 2015, will create a suite of products MCD19. Due to high 1km resolution, MAIAC provides information about fine scale aerosol variability required in different applications such as urban air quality analysis. During the past year, we developed a new MAIAC capability to retrieve Single Scattering Albedo (SSA) from MODIS by adapting OMI heritage approach of O. Torres. We will describe MAIAC retrieval approach, AERONET AOT and SSA validation for different world biomass burning regions, and will compare MAIAC results with other sensors.

  8. The albedos of Pluto and Charon - Wavelength dependence

    NASA Technical Reports Server (NTRS)

    Marcialis, Robert L.; Lebofsky, Larry A.; Disanti, Michael A.; Fink, Uwe; Tedesco, Edward F.; Africano, John

    1992-01-01

    The March 3, 1987 occultation of Charon by Pluto was monitored simultaneously with three telescopes. Each site covered a distinct wavelength interval with the total range spanning 0.44-2.4 microns. Observing the same event ensures an identical sun-Pluto-earth geometry for all three sites, and minimizes the assumptions which must be made to combine results. This spectrophotometry is used to derive the individual geometric albedos of Pluto and Charon over a factor of at least 5 in wavelength. Combining the results with those of Binzel (1988) improved (B - V) color estimates (on the 'Johnson Pluto' system) are obtained for the components of the system at rotational phase 0.75: (Pluto + Charon) = 0.843 +/- 0.006; Pluto alone = 0.866 +/- 0.007; and Charon alone = 0.702 +/- 0.010.

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

    NASA Astrophysics Data System (ADS)

    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

  10. Cassini VIMS Preliminary Exploration of Titan's Surface Hemispheric Albedo Dichotomy

    NASA Technical Reports Server (NTRS)

    Nelson, R. M.; Brown, R. H.; Hapke, B. W.; Smythe, W. D.; Kamp, L.; Boryta, M.; Baines, K. H.; Bellucci, G.; Bibring, J.-P.; Buratti, B. J.

    2005-01-01

    We present preliminary evidence that suggests a hemispheric albedo dichotomy on Titan, the largest planetary satellite in the Solar System. We have also studied the photometric properties of several dark circular features on Titan's surface to test if they might be of impact origin. The evidence is derived from photometric analysis of selected surface regions taken at different Titanian longitudes and solar phase angles using images from the Cassini Saturn Orbiter Visual and Infrared Mapping Spectrometer (VIMS). The VIMS instrument is able to image Titan's surface at spectral windows (e.g. 2.02 microns) in its atmosphere where methane, the principal atmospheric absorber is transparent. Additional information is included in the original extended abstract.

  11. The Albedo Dichotomy of Iapetus Measured at UV Wavelengths

    NASA Technical Reports Server (NTRS)

    Hendrix, Amanda R.; Hansen, Candice J.

    2007-01-01

    The dramatic hemispheric dichotomy in albedo displayed by Saturn's moon Iapetus has intrigued astronomers for centuries. Here we report on far-ultraviolet observations of Iapetus' bright and dark terrains from Cassini. We compare the reflectance spectra of Iapetus's dark terrain, Hyperion and Phoebe and find that both Phoebe and Hyperion are richer in water ice than Iapetus' dark terrain. Spectra of the lowest latitudes of the dark terrain display the diagnostic water ice absorption feature; water ice amounts increase within the dark material away from the apex (at 90 deg W longitude, the center of the dark leading hemisphere), consistent with thermal segregation of water ice. The water ice in the darkest, warmest low latitude regions is not expected to be stable and may be a sign of ongoing or recent emplacement of the dark material from an exogenic source.

  12. Two generations of Canadian active imaging systems: ALBEDOS and ELVISS

    NASA Astrophysics Data System (ADS)

    Larochelle, Vincent; Mathieu, Pierre; Simard, Jean-Robert

    1999-07-01

    Search and rescue and general surveillance mission pose a serious challenge to conventional imaging systems used by actual aircraft crews. These systems must often work in low- light and low-visibility conditions to find the identify targets. A new airborne imaging technology has been developed to overcome several deficiencies encountered with common CCD cameras, image intensified system and thermal imaging sensors. The recent developments in laser diode arrays, laser diode beam collimation and gatable micro- channel plate intensifier have made possible the construction of a compact active imagin system, called the Airborne Laser-Based Enhanced Detection and Observation Systems (ALBEDOS). This system proved particularly efficient at night and in degraded weather conditions. In addition, it was demonstrated that range gating, besides eliminating most of the light backscattered by aerosols, provided to some extent immunity to blooming effects specific to highly sensitive cameras. The system was installed on a helicopter and tested in various scenarios in October 1995 to demonstrate its potential. To enhance the surveillance capability over large areas of coverage, to optimize detection of humans and small objects and to improve the effectiveness of the search aircraft, a second-generation payload is presently developed and combines the benefits of two complementary imaging sensors. The Enhanced Low-Light level Visible and IR Surveillance System (ELVISS) consists of an improved range-gated active imager and a high-quality thermal imager, installed in two separate airborne platforms slaved together and controlled by a single user interface. It is expected that such a sensor systems will have a direct impact on improving the response time in finding those in need of assistance or simply in increasing the performance, reliability and efficiency of crews involved in general surveillance operations. This paper explains the concept of range gating, details a preliminary

  13. Water Ice Albedo Variations on the Martian Northern Polar Cap

    NASA Technical Reports Server (NTRS)

    Hale, A. S.; Bass, D. S.; Tamppari, L. K.

    2003-01-01

    The Viking Orbiters determined that the surface of Mars northern residual cap is water ice. Many researchers have related observed atmospheric water vapor abundances to seasonal exchange between reservoirs such as the polar caps, but the extent to which the exchange between the surface and the atmosphere remains uncertain. Early studies of the ice coverage and albedo of the northern residual Martian polar cap using Mariner 9 and Viking images reported that there were substantial internannual differences in ice deposition on the polar cap, a result which suggested a highly variable Martian climate. However, some of the data used in these studies were obtained at differing values of heliocentric solar longitude (L(sub s)). Reevaluation of this dataset indicated that the residual cap undergoes seasonal brightening throughout the summer, and indicated that this process repeats from year to year. In this study we continue to compare Mariner 9 and Viking Orbiter imaging observations and thermal data of the north residual polar cap to data acquired with Mars Global Surveyor s Mars Orbiter Camera (MOC) instrument. In the current study, our goal is to examine all released data from MGS MOC in the northern summer season, along with applicable TES data in order to better understand the albedo variations in the northern summer and their implications on water transport. To date, work has focused primarily on the MOC dataset. In 1999, data acquisition of the northern polar regions began at L(sub s) = 107, although there was little north polar data acquired from L(sub s)= 107 to L(sub s) = 109. We examined a total of 409 images from L(sub s) = 107 to L(sub s)=148. We have also examined data from 2000 from L(sub s)= 93 to L(sub s)= 110; additional progress is ongoing. Here we present a progress report of our observations, and continue to determine their implications for the Martian water cycle.

  14. Neutron therapy of cancer

    NASA Technical Reports Server (NTRS)

    Frigerio, N. A.; Nellans, H. N.; Shaw, M. J.

    1969-01-01

    Reports relate applications of neutrons to the problem of cancer therapy. The biochemical and biophysical aspects of fast-neutron therapy, neutron-capture and neutron-conversion therapy with intermediate-range neutrons are presented. Also included is a computer program for neutron-gamma radiobiology.

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

    NASA Technical Reports Server (NTRS)

    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.

  16. Surface albedo darkening from wildfires in northern sub-Saharan Africa

    NASA Astrophysics Data System (ADS)

    Gatebe, C. K.; Ichoku, C. M.; Poudyal, R.; Román, M. O.; Wilcox, E.

    2014-05-01

    Northern sub-Saharan Africa (NSSA) has a wide variety of climate zones or biomes, where albedo dynamics are highly coupled with vegetation dynamics and fire disturbances. Quantifying surface albedo variations due to fire disturbances on time scales of several months to several years is complex and is made worse by lack of accurate and spatially consistent surface albedo data. Here, we estimate the surface albedo effect from wildfires in different land cover types in the NSSA region using Moderate Resolution Imaging Spectroradiometer (MODIS) multi-year observational data (2003-11). The average decrease in albedo after fires at the scale of 1 km MODIS footprint is -0.002 02 ± 0.000 03 for woody savanna and -0.002 22 ± 0.000 03 for savanna. These two land cover types together account for >86% of the total MODIS fire count between 2003 and 2011. We found that only a small fraction of the pixels (≦̸10%) burn in two successive years and about 47% had any fire recurrence in 9 years. The study also derived the trajectories of post-fire albedo dynamics from the percentages of pixels that recover to pre-fire albedo values each year. We found that the persistence of surface albedo darkening in most land cover types in the NSSA region is limited to about 6-7 years, after which at least 99% of the burnt pixels recover to their pre-fire albedo. Our results provide critical information for deriving necessary input to various models used in determining the effects of albedo change due to wild fires in the NSSA region.

  17. NEUTRONIC REACTOR

    DOEpatents

    Hurwitz, H. Jr.; Brooks, H.; Mannal, C.; Payne, J.H.; Luebke, E.A.

    1959-03-24

    A reactor of the heterogeneous, liquid cooled type is described. This reactor is comprised of a central region of a plurality of vertically disposed elongated tubes surrounded by a region of moderator material. The central region is comprised of a central core surrounded by a reflector region which is surrounded by a fast neutron absorber region, which in turn is surrounded by a slow neutron absorber region. Liquid sodium is used as the primary coolant and circulates through the core which contains the fuel elements. Control of the reactor is accomplished by varying the ability of the reflector region to reflect neutrons back into the core of the reactor. For this purpose the reflector is comprised of moderator and control elements having varying effects on reactivity, the control elements being arranged and actuated by groups to give regulation, shim, and safety control.

  18. NEUTRONIC REACTOR

    DOEpatents

    Fermi, E.; Szilard, L.

    1957-09-24

    Reactors of the type employing plates of natural uranium in a moderator are discussed wherein the plates are um-formly disposed in parallel relationship to each other thereby separating the moderator material into distinct and individual layers. Each plate has an uninterrupted sunface area substantially equal to the cross-sectional area of the active portion of the reactor, the particular size of the plates and the volume ratio of moderator to uranium required to sustain a chain reaction being determinable from the known purity of these materials and other characteristics such as the predictable neutron losses due to the formation of radioactive elements of extremely high neutron capture cross section.

  19. NEUTRONIC REACTOR

    DOEpatents

    Wigner, E.P.; Weinberg, A.W.; Young, G.J.

    1958-04-15

    A nuclear reactor which uses uranium in the form of elongated tubes as fuel elements and liquid as a coolant is described. Elongated tubular uranium bodies are vertically disposed in an efficient neutron slowing agent, such as graphite, for example, to form a lattice structure which is disposed between upper and lower coolant tanks. Fluid coolant tubes extend through the uranium bodies and communicate with the upper and lower tanks and serve to convey the coolant through the uranium body. The reactor is also provided with means for circulating the cooling fluid through the coolant tanks and coolant tubes, suitable neutron and gnmma ray shields, and control means.

  20. The Dependence of the Ice-Albedo Feedback on Atmospheric Properties

    PubMed Central

    Selsis, F.; Kitzmann, D.; Rauer, H.

    2013-01-01

    Abstract Ice-albedo feedback is a potentially important destabilizing 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 due to the strong spectral dependence of stellar radiation and snow/ice albedos; that is, M stars primarily emit in the near IR, where the snow and ice albedo is low, and less in the visible, where the snow/ice albedo is high. This study investigates the influence of the atmosphere (in terms of surface pressure and atmospheric composition) on this feedback, since an atmosphere was neglected in previous studies. A plane-parallel radiative transfer model was 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. Atmospheric key properties such as surface pressure, but also the abundance of radiative trace gases, can considerably change the strength of the ice-albedo feedback. For dense CO2 atmospheres of the order of a few to tens of bar, atmospheric rather than surface properties begin to dominate the planetary radiation budget. At high CO2 pressures, the ice-albedo feedback is strongly reduced for planets around M stars. The presence of trace amounts of H2O and CH4 in the atmosphere also weakens the ice-albedo effect for both stellar types considered. For planets around Sun-like stars, O3 could also lead to a very strong decrease of the ice-albedo feedback at high CO2 pressures. Key Words

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

    PubMed

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

    2013-10-01

    Ice-albedo feedback is a potentially important destabilizing 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 due to the strong spectral dependence of stellar radiation and snow/ice albedos; that is, M stars primarily emit in the near IR, where the snow and ice albedo is low, and less in the visible, where the snow/ice albedo is high. This study investigates the influence of the atmosphere (in terms of surface pressure and atmospheric composition) on this feedback, since an atmosphere was neglected in previous studies. A plane-parallel radiative transfer model was 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. Atmospheric key properties such as surface pressure, but also the abundance of radiative trace gases, can considerably change the strength of the ice-albedo feedback. For dense CO₂ atmospheres of the order of a few to tens of bar, atmospheric rather than surface properties begin to dominate the planetary radiation budget. At high CO₂ pressures, the ice-albedo feedback is strongly reduced for planets around M stars. The presence of trace amounts of H₂O and CH₄ in the atmosphere also weakens the ice-albedo effect for both stellar types considered. For planets around Sun-like stars, O₃ could also lead to a very strong decrease of the ice-albedo feedback at high CO₂ pressures.

  2. Effects of forest litter and aeolian dust deposition on snow surface albedo

    NASA Astrophysics Data System (ADS)

    Perrot, D.; Pugh, E. T.; Molotch, N. P.; Small, E. E.

    2011-12-01

    Litter from bark beetle-infested trees and aeolian dust deposition are current perturbations to the snowpack surface albedo in subalpine forested environments in the Colorado River Basin. We examine the combined effects of dust and litter on snow surface albedo through field and controlled laboratory modification of snow surface dust and litter concentrations. From field experiments, applications of needles resulted in an albedo decrease of 0.0146 per percent increase in litter cover. Dust application resulted in an albedo decrease of 0.0061 per percent increase in litter cover. Needle application to a dusty snow surface resulted in 0.0043 albedo reduction per percent litter cover, and dust application to a snow surface with needles already present resulted in 0.0036 albedo reduction per percent litter cover. We tested the effects of yellow and red lodgepole needles on albedo reduction both in the field and the laboratory, and though yellow needles are slightly smaller, found that there is no significant difference between the slopes of yellow and red needles. However, there is a significant difference between the laboratory and field experiments resulting from different media (snow in the field and a whiteboard in the lab) that litter was applied to. Generally, we also find that it takes 120.7 lodgepole pine needles to affect the same increase in percent litter cover as 1 g/m2 of dust, and that it takes 53.2 needles to affect the same reduction in albedo as 1 g/m2 of dust. This suggests that per unit surface area, needles are more important than dust for albedo reduction. Experiments performed in the field and in the lab demonstrate the stronger albedo reducing effect of needles. However, dust has a greater capacity to cover more snow surface area than needles, increasing its overall importance. Because dust can cover more snow surface area than needles can, we suspect that dust deposition in forested environments will serve to significantly reduce subcanopy

  3. Development of a high spectral resolution surface albedo product for the ARM Southern Great Plains Central Facility

    SciTech Connect

    McFarlane, Sally A.; Gaustad, Krista L.; Mlawer, Eli J.; Long, Charles N.; Delamere, Jennifer

    2011-09-01

    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.

  4. Neutronic reactor

    DOEpatents

    Carleton, John T.

    1977-01-25

    A graphite-moderated nuclear reactor includes channels between blocks of graphite and also includes spacer blocks between adjacent channeled blocks with an axis of extension normal to that of the axis of elongation of the channeled blocks to minimize changes in the physical properties of the graphite as a result of prolonged neutron bombardment.

  5. NEUTRONIC REACTORS

    DOEpatents

    Anderson, H.L.

    1958-10-01

    The design of control rods for nuclear reactors are described. In this design the control rod consists essentially of an elongated member constructed in part of a neutron absorbing material and having tube means extending therethrough for conducting a liquid to cool the rod when in use.

  6. NEUTRONIC REACTOR

    DOEpatents

    Wigner, E.P.

    1960-09-27

    A unit assembly is described for a neutronic reactor comprising a tube and plurality of spaced parallel sandwiches in the tube extending lengthwise thereof, each sandwich including a middle plate having a central opening for plutonium and other openings for fertile material at opposite ends of the plate.

  7. A global assessment of forest surface albedo and its relationships with climate and atmospheric nitrogen deposition.

    PubMed

    Leonardi, Stefano; Magnani, Federico; Nolè, Angelo; Van Noije, Twan; Borghetti, Marco

    2015-01-01

    We present a global assessment of the relationships between the short-wave surface albedo of forests, derived from the MODIS satellite instrument product at 0.5° spatial resolution, with simulated atmospheric nitrogen deposition rates (Ndep ), and climatic variables (mean annual temperature Tm and total annual precipitation P), compiled at the same spatial resolution. The analysis was performed on the following five forest plant functional types (PFTs): evergreen needle-leaf forests (ENF); evergreen broad-leaf forests (EBF); deciduous needle-leaf forests (DNF); deciduous broad-leaf forests (DBF); and mixed-forests (MF). Generalized additive models (GAMs) were applied in the exploratory analysis to assess the functional nature of short-wave surface albedo relations to environmental variables. The analysis showed evident correlations of albedo with environmental predictors when data were pooled across PFTs: Tm and Ndep displayed a positive relationship with forest albedo, while a negative relationship was detected with P. These correlations are primarily due to surface albedo differences between conifer and broad-leaf species, and different species geographical distributions. However, the analysis performed within individual PFTs, strengthened by attempts to select 'pure' pixels in terms of species composition, showed significant correlations with annual precipitation and nitrogen deposition, pointing toward the potential effect of environmental variables on forest surface albedo at the ecosystem level. Overall, our global assessment emphasizes the importance of elucidating the ecological mechanisms that link environmental conditions and forest canopy properties for an improved parameterization of surface albedo in climate models. PMID:25044609

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

    NASA Astrophysics Data System (ADS)

    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.

  9. Evaluation of Moderate-Resolution Imaging Spectroradiometer (MODIS) Snow Albedo Product (MCD43A) over Tundra

    NASA Technical Reports Server (NTRS)

    Wang, Zhuosen; Schaaf, Crystal B.; Chopping, Mark J.; Strahler, Alan H.; Wang, Jindi; Roman, Miguel O.; Rocha, Adrian V.; Woodcock, Curtis E.; Shuai, Yanmin

    2012-01-01

    This study assesses the MODIS standard Bidirectional Reflectance Distribution Function (BRDF)/Albedo product, and the daily Direct Broadcast BRDF/Albedo algorithm at tundra locations under large solar zenith angles and high anisotropic diffuse illumination and multiple scattering conditions. These products generally agree with ground-based albedo measurements during the snow cover period when the Solar Zenith Angle (SZA) is less than 70deg. An integrated validation strategy, including analysis of the representativeness of the surface heterogeneity, is performed to decide whether direct comparisons between field measurements and 500- m satellite products were appropriate or if the scaling of finer spatial resolution airborne or spaceborne data was necessary. Results indicate that the Root Mean Square Errors (RMSEs) are less than 0.047 during the snow covered periods for all MCD43 albedo products at several Alaskan tundra areas. The MCD43 1- day daily albedo product is particularly well suited to capture the rapidly changing surface conditions during the spring snow melt. Results also show that a full expression of the blue sky albedo is necessary at these large SZA snow covered areas because of the effects of anisotropic diffuse illumination and multiple scattering. In tundra locations with dark residue as a result of fire, the MODIS albedo values are lower than those at the unburned site from the start of snowmelt.

  10. Albedo of Carbon Dioxide Ice in Mars' Residual South Polar Cap

    NASA Astrophysics Data System (ADS)

    James, P. B.; Wolff, M. J.; Bonev, B.

    2015-12-01

    The albedo of surface CO2 deposits in the Residual South Polar Cap (RSPC) of Mars controls their net condensation / sublimation over a martian year and is therefore a crucial parameter in determining RSPC stability. The albedo used in previous analyses is obtained by dividing I/F, determined from radiometrically calibrated imaging data, by the cosine of the incidence angle. Because of atmospheric aerosols, the albedo calculated from I/F above the atmosphere is not the surface albedo that enters into stability considerations. In order to determine the surface albedo, we interpolate optical depths determined from CRISM EPF measurements to provide estimates of the dust and ice opacities over the RSPC (Wolff et al., 2009) and use these to determine the actual surface albedos from MARCI images using the radiative transport program DISORT (Stamnes et al., 1988). Assuming that dust is the only contributor to atmospheric opacity, the retrieved surface albedos for the longer wavelength MARCI filters in MY 28 and 29 are found to be consistent despite very different dust opacities in the two years (James et al., 2014). However, this model fails to reproduce the short wavelength behavior in early summer and suggests either an additional opacity source or modification of the CRISM dust opacity or the dust phase function. The consequences of these changes will be discussed.

  11. Relations between albedos and emissivities from MODIS and ASTER data over North African Desert

    NASA Astrophysics Data System (ADS)

    Zhou, L.; Dickinson, R. E.; Ogawa, K.; Tian, Y.; Jin, M.; Schmugge, T.; Tsvetsinskaya, E.

    2003-10-01

    This paper analyzes relations among MODIS surface albedos, ASTER broadband (3-14 μm) emissivities, and a soil taxonomy map over the arid areas of Algeria, Libya, and Tunisia in North Africa at 30 second (about 1 km) and 2 minute (about 4 km) spatial resolutions. The MODIS albedo data are from 7 spectral bands and 3 broadbands during dust-free seasons and the emissivity data are derived from a linear combination of the waveband emissivities of the ASTER five thermal infrared channels. Both albedo and emissivity data in the study region show similar considerable spatial variability, larger than assumed by most climate models, and such variability is related to the surface types (sands, rock, and soil orders). Emissivity over bare soils exhibits statistically significant correlations with albedos at both broadbands and most of spectral bands and decreases linearly with albedos. Albedo and emissivity are more strongly correlated with each other than either is to the surface types, apparently because of their higher resolution either spatially or in surface mineralogy. This paper provides guidance for the possible inclusion of such correlation to specify albedo and emissivity in climate models.

  12. Relations Between Albedos and Emissivities From MODIS and ASTER Data Over North African Desert

    NASA Astrophysics Data System (ADS)

    Zhou, L.; Dickinson, R.; Ogawa, K.; Tian, Y.; Jin, M.; Schmugge, T.; Tsvetsinskaya, E.

    2003-12-01

    This paper analyzes relations among MODIS surface albedos, ASTER broadband (3-14 μ m) emissivities, and a soil taxonomy map over the arid areas of Algeria, Libya, and Tunisia in North Africa at 30 second (about 1 km) and 2 minute (about 4 km) spatial resolutions. The MODIS albedo data are from 7 spectral bands and 3 broadbands during dust-free seasons and the emissivity data are derived from a linear combination of the waveband emissivities of the ASTER five thermal infrared channels. Both albedo and emissivity data in the study region show similar considerable spatial variability, larger than assumed by most climate models, and such variability is related to the surface types (sands, rock, and soil orders). Emissivity over bare soils exhibits statistically significant correlations with albedos at both broadbands and most of spectral bands and decreases linearly with albedos. Albedo and emissivity are more strongly correlated with each other than either is to the surface types, apparently because of their higher resolution either spatially or in surface mineralogy. This paper provides guidance for the possible inclusion of such correlation to specify albedo and emissivity in climate models.

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

    SciTech Connect

    Levinson, R M

    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.

  14. A global assessment of forest surface albedo and its relationships with climate and atmospheric nitrogen deposition.

    PubMed

    Leonardi, Stefano; Magnani, Federico; Nolè, Angelo; Van Noije, Twan; Borghetti, Marco

    2015-01-01

    We present a global assessment of the relationships between the short-wave surface albedo of forests, derived from the MODIS satellite instrument product at 0.5° spatial resolution, with simulated atmospheric nitrogen deposition rates (Ndep ), and climatic variables (mean annual temperature Tm and total annual precipitation P), compiled at the same spatial resolution. The analysis was performed on the following five forest plant functional types (PFTs): evergreen needle-leaf forests (ENF); evergreen broad-leaf forests (EBF); deciduous needle-leaf forests (DNF); deciduous broad-leaf forests (DBF); and mixed-forests (MF). Generalized additive models (GAMs) were applied in the exploratory analysis to assess the functional nature of short-wave surface albedo relations to environmental variables. The analysis showed evident correlations of albedo with environmental predictors when data were pooled across PFTs: Tm and Ndep displayed a positive relationship with forest albedo, while a negative relationship was detected with P. These correlations are primarily due to surface albedo differences between conifer and broad-leaf species, and different species geographical distributions. However, the analysis performed within individual PFTs, strengthened by attempts to select 'pure' pixels in terms of species composition, showed significant correlations with annual precipitation and nitrogen deposition, pointing toward the potential effect of environmental variables on forest surface albedo at the ecosystem level. Overall, our global assessment emphasizes the importance of elucidating the ecological mechanisms that link environmental conditions and forest canopy properties for an improved parameterization of surface albedo in climate models.

  15. Methods for absorbing neutrons

    DOEpatents

    Guillen, Donna P.; Longhurst, Glen R.; Porter, Douglas L.; Parry, James R.

    2012-07-24

    A conduction cooled neutron absorber may include a metal matrix composite that comprises a metal having a thermal neutron cross-section of at least about 50 barns and a metal having a thermal conductivity of at least about 1 W/cmK. Apparatus for providing a neutron flux having a high fast-to-thermal neutron ratio may include a source of neutrons that produces fast neutrons and thermal neutrons. A neutron absorber positioned adjacent the neutron source absorbs at least some of the thermal neutrons so that a region adjacent the neutron absorber has a fast-to-thermal neutron ratio of at least about 15. A coolant in thermal contact with the neutron absorber removes heat from the neutron absorber.

  16. On Spectral Invariance of Single Scattering Albedo for Weakly Absorbing Wavelengths

    NASA Technical Reports Server (NTRS)

    Marshak, Alexander

    2012-01-01

    The single scattering albedo omega (sub 0 lambda) in atmospheric radiative transfer is the ratio of the scattering coefficient to the total extinction coefficient. For cloud water droplets both the scattering and absorption coefficients, thus the single scattering albedo, are functions of wavelength A and droplet size r. In this presentation we will show that for water droplets at weakly absorbing wavelengths, the ratio omega (sub 0 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 omega (sub 0 lambda) via one known spectrum omega (sub 0 lambda)(r(sub o)). We will provide a simple physical explanation of the discovered relationship. In addition to water droplets, similar linear relationships were found for the single scattering albedo of non-spherical ice crystals. The single scattering albedo $\\omega _ {0\\lambda }$ in atmospheric radiative transfer is the ratio of the scattering coefficient to the total extinction coefficient. For cloud water droplets both the scattering and absorption coefficients, and thus the single scattering albedo, are functions of wavelength $\\lambda $ and droplet size $r$. We show that for water droplets at weakly absorbing wavelengths, the ratio $\\omega _ {0\\lambda } (r)$/$\\omega _ {0\\lambda } (r_{0})$ of two single scattering albedo spectra for two different droplet sizes is a linear function of $\\omega _{0\\lambda }(r)$. 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 $\\omega_{0\\lambda }(r)$ via one known spectrum $\\omega_{0\\lambda }(r_{0})$. We provide a simple physical explanation of the discovered relationship. Similar linear relationships characterize the single scattering albedo of non-spherical ice crystals.

  17. Impacts of Synoptic Weather Patterns on Snow Albedo at Sites in New England

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Winter snow in the northeastern United States has changed over the last several decades, resulting in shallower snow packs, fewer days of snow cover and increasing precipitation falling as rain in the winter. In addition to these changes which cause reductions in surface albedo, increasing winter temperatures also lead to more rapid snow grain growth, resulting in decreased snow reflectivity. We present in-situ measurements and analyses to test the sensitivity of seasonal snow albedo to varying weather conditions at sites in New England. In particular, we investigate the impact of temperature on snow albedo through melt and grain growth, the impact of precipitation event frequency on albedo through snow "freshening," and the impact of storm path on snow structure and snow albedo. Over three winter seasons between 2013 and 2015, in-situ snow characterization measurements were made at three non-forested sites across New Hampshire. These near-daily measurements include spectrally resolved albedo, snow optical grain size determined through contact spectroscopy, snow depth, snow density and local meteorological parameters. Combining this information with storm tracks derived from HYSPLIT modeling, we quantify the current sensitivity of northeastern US snow albedo to temperature as well as precipitation type, frequency and path. Our analysis shows that southerly winter storms result in snow with a significantly lower albedo than storms which come from across the continental US or the Atlantic Ocean. Interannual variability in temperature and statewide spatial variability in snowfall rates at our sites show the relative importance of snowfall amount and temperatures in albedo evolution over the course of the winter.

  18. Recent Advances in Neutron Physics

    ERIC Educational Resources Information Center

    Feshbach, Herman; Sheldon, Eric

    1977-01-01

    Discusses new studies in neutron physics within the last decade, such as ultracold neutrons, neutron bottles, resonance behavior, subthreshold fission, doubly radiative capture, and neutron stars. (MLH)

  19. Neutron reflecting supermirror structure

    DOEpatents

    Wood, J.L.

    1992-12-01

    An improved neutron reflecting supermirror structure comprising a plurality of stacked sets of bilayers of neutron reflecting materials. The improved neutron reflecting supermirror structure is adapted to provide extremely good performance at high incidence angles, i.e. up to four time the critical angle of standard neutron mirror structures. The reflection of neutrons striking the supermirror structure at a high critical angle provides enhanced neutron throughput, and hence more efficient and economical use of neutron sources. 2 figs.

  20. Neutron reflecting supermirror structure

    DOEpatents

    Wood, James L.

    1992-01-01

    An improved neutron reflecting supermirror structure comprising a plurality of stacked sets of bilayers of neutron reflecting materials. The improved neutron reflecting supermirror structure is adapted to provide extremely good performance at high incidence angles, i.e. up to four time the critical angle of standard neutron mirror structures. The reflection of neutrons striking the supermirror structure at a high critical angle provides enhanced neutron throughput, and hence more efficient and economical use of neutron sources.

  1. Climate implications of including albedo effects in terrestrial carbon policy

    NASA Astrophysics Data System (ADS)

    Jones, A. D.; Collins, W.; Torn, M. S.; Calvin, K. V.

    2012-12-01

    Proposed strategies for managing terrestrial carbon in order to mitigate anthropogenic climate change, such as financial incentives for afforestation, soil carbon sequestration, or biofuel production, largely ignore the direct effects of land use change on climate via biophysical processes that alter surface energy and water budgets. Subsequent influences on temperature, hydrology, and atmospheric circulation at regional and global scales could potentially help or hinder climate stabilization efforts. Because these policies often rely on payments or credits expressed in units of CO2-equivalents, accounting for biophysical effects would require a metric for comparing the strength of biophysical climate perturbation from land use change to that of emitting CO2. One such candidate metric that has been suggested in the literature on land use impacts is radiative forcing, which underlies the global warming potential metric used to compare the climate effects of various greenhouse gases with one another. Expressing land use change in units of radiative forcing is possible because albedo change results in a net top-of-atmosphere radiative flux change. However, this approach has also been critiqued on theoretical grounds because not all climatic changes associated with land use change are principally radiative in nature, e.g. changes in hydrology or the vertical distribution of heat within the atmosphere, and because the spatial scale of land use change forcing differs from that of well-mixed greenhouse gases. To explore the potential magnitude of this discrepancy in the context of plausible scenarios of future land use change, we conduct three simulations with the Community Climate System Model 4 (CCSM4) utilizing a slab ocean model. Each simulation examines the effect of a stepwise change in forcing relative to a pre-industrial control simulation: 1) widespread conversion of forest land to crops resulting in approximately 1 W/m2 global-mean radiative forcing from albedo

  2. Effect of anthropogenic sulfate aerosols on low-level cloud albedo over oceans

    NASA Technical Reports Server (NTRS)

    Kim, Youngseung; Cess, Robert D.

    1993-01-01

    By reducing cloud droplet size, anthropogenic sulfate aerosols are capable of increasing cloud albedo and thus possibly changing the climate. To test the detectability of this effect, we examined satellite-measured low-level cloud albedo off the east coasts of North America and Asia at midlatitudes where anthropogenic sulfate sources are large and aerosols are transported eastward over the oceans by prevailing westerlies. The satellite data demonstrate enhanced cloud albedo near the coastal boundaries where sulfate concentrations are large. Similar trends are absent over ocean regions of the Southern Hemisphere that are removed from anthropogenic sulfate sources.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    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.

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

    SciTech Connect

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

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Astrophysics Data System (ADS)

    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. In situ observations of black carbon in snow and the corresponding spectral surface albedo reduction

    NASA Astrophysics Data System (ADS)

    Pedersen, C. A.; Gallet, J.-C.; Ström, J.; Gerland, S.; Hudson, S. R.; Forsström, S.; Isaksson, E.; Berntsen, T. K.

    2015-02-01

    Black carbon (BC) particles emitted from incomplete combustion of fossil fuel and biomass and deposited on snow and ice darken the surface and reduce the surface albedo. Even small initial surface albedo reductions may have larger adjusted effects due to snow morphology changes and changes in the sublimation and snow melt rate. Most of the literature on the effect of BC on snow surface albedo is based on numerical models, and few in situ field measurements exist to confirm this reduction. Here we present an extensive set of concurrent in situ measurements of spectral surface albedo, BC concentrations in the upper 5 cm of the snowpack, snow physical parameters (grain size and depth), and incident solar flux characteristics from the Arctic. From this data set (with median BC concentrations ranging from 5 to 137 ng BC per gram of snow) we are able to separate the BC signature on the snow albedo from the natural snow variability. Our measurements show a significant correlation between BC in snow and spectral surface albedo. Based on these measurements, parameterizations are provided, relating the snow albedo, as a function of wavelength, to the equivalent BC content in the snowpack. The term equivalent BC used here is the elemental carbon concentration inferred from the thermo-optical method adjusted for the fraction of non-BC constituents absorbing sunlight in the snow. The first parameterization is a simple equation which efficiently describes the snow albedo reduction due to the equivalent BC without including details on the snow or BC microphysics. This can be used in models when a simplified description is needed. A second parameterization, including snow grain size information, shows enhanced correspondence with the measurements. The extracted parameterizations are valid for wavelength bands 400-900 nm, constrained for BC concentrations between 1 and 400 ng g-1, and for an optically thick snowpack. The parameterizations are purely empirical, and particular focus

  9. Global Survey of the Relationship Between Cloud Droplet Size and Albedo Using ISCCP

    NASA Technical Reports Server (NTRS)

    Han, Qingyuan; Rossow, William B.; Chou, Joyce; Welch, Ronald M.

    1997-01-01

    The possible indirect aerosol effect on climate is examined. First, the spatial relationship is checked between cloud droplet radii and cloud albedo in different areas where aerosol concentration are known to differ significantly. Second, the temporal relationship between r(sub e) and cloud albedo is explored for each 2.5 deg x 2.5 deg grid box to reveal in which regions of the globe the variations of cloud albedo are correlated with changes in r(sub e) consistent with the indirect aerosol effect hypothesis.

  10. Dose-equivalent response CR-39 track detector for personnel neutron dosimetry

    NASA Astrophysics Data System (ADS)

    Oda, K.; Ito, M.; Yoneda, H.; Miyake, H.; Yamamoto, J.; Tsuruta, T.

    1991-09-01

    A dose-equivalent response detector based on CR-39 has been designed to be applied for personnel neutron dosimetry. The intrinsic detection efficiency of bare CR-39 was first evaluated from irradiation experiments with monoenergetic neutrons and theoretical calculations. In the second step, the radiator effect was investigated for the purpose of sensitization to fast neutrons. A two-layer radiator consisting of deuterized dotriacontane (C 32D 66) and polyethylene (CH 2) was designed. Finally, we made the CR-39 detector sensitive to thermal neutrons by doping with orthocarborane (B 10H 122C 2), and also estimated the contribution of albedo neutrons. It was found that the new detector — boron-doped CR-39 with the two-layer radiator — would have a flat response with an error of about 70% in a wide energy region, ranging from thermal to 15 MeV.

  11. Albedo distribution of main-belt asteroids based on IRAS, AKARI, and WISE

    NASA Astrophysics Data System (ADS)

    Usui, F.; Hasegawa, S.; Ishiguro, M.; Mueller, T.; Ootsubo, T.

    2014-07-01

    Presently, the number of asteroids is known to be more than 630,000, and more than 90 % of asteroids with known orbital elements are classified as main-belt asteroids (MBAs). The spatial distribution of compositions among MBAs is of particular interest, because the main belt is the largest reservoir of asteroids in the solar system. Asteroids are thought to be the remnants of planetesimals formed in the early solar system, and allow us to study the formation and evolution of asteroids, origin of meteoroids and the near-Earth asteroids, as well as the formation of the solar system. Size and albedo are one of the most basic physical quantities of asteroid. Knowledge of size and albedo is essential in many aspects of asteroid research, such as the chemical composition and mineralogy, the size-frequency distribution of dynamical families and populations of asteroids, and the relationship between small bodies in the outer solar system and comets. Several techniques have been developed to determine the size of asteroids; by direct imaging with the Hubble Space Telescope or large ground-based telescopes with adaptive optics, radar observations, speckle interferometry, stellar occultation combined with lightcurve inversion techniques, and spacecraft flyby / rendezvous / sample return. One of the most effective methods for measuring asteroid size and albedo indirectly is through the use of radiometry, which combines information of the thermal emission (infrared flux) and the reflected sunlight (absolute magnitude). This method can provide unique data for asteroid size and albedo. Using radiometric measurements, a large number of objects can be observed in a short period of time, providing coherent data for large populations of asteroids within the asteroid belt. Infrared observations can be made still better under ideal circumstances, from space. The first space-borne infrared telescope is the Infrared Astronomical Satellite (IRAS; [1]), launched in 1983 and performed a

  12. Remote sensing and geologic studies of the planetary crusts

    NASA Technical Reports Server (NTRS)

    Hawke, B. R.

    1983-01-01

    Dark haloed craters and regions of the Moon which were sites of ancient volcanism were remotely sensed as well as KREEP deposits in the Inbrium region. The relationship between geology and geochemistry in the Undarum/Spumans region was also examined. Results are summarized for observations of the Reiner Gamma formation, studies of impact cratering mechanics and processes, spectral variations of asteroidal surfaces, albedo and color variations on Ganymede, and studies of lunar impact structures.

  13. Subpixel variability of MODIS albedo retrievals and its importance for ice sheet surface melting in southwestern Greenland's ablation zone

    NASA Astrophysics Data System (ADS)

    Moustafa, S.; Rennermalm, A. K.; Roman, M. O.; Koenig, L.; Smith, L. C.; Schaaf, C.; Wang, Z.; Mioduszewski, J.

    2013-12-01

    On the Greenland ice sheet, albedo declined across 70% of its surface since 2000, with the greatest reduction in the lower 600 m of the southwestern ablation zone. Because albedo plays a prominent role in the ice sheet surface energy balance, its decline has resulted in near doubling of meltwater production. To characterize ice sheet albedo, Moderate Imaging Spectrometer (MODIS) surface albedo products are typically used. However, it is unclear how the spatial variability of albedo within a MODIS pixel influences surface melting and whether it can be considered a linear function of albedo. In this study, high spatiotemporal resolution measurements of spectral albedo and ice sheet surface ablation were collected along a ~ 1.3 km transect during June 2013 within the Akuliarusiarsuup Kuua (AK) River watershed in southwest Greenland. Spectral measurements were made at 325-1075 nm using a Analytical Spectral Devices (ASD) spectroradiometer, fitted with a Remote Cosine Receptor (RCR). In situ albedo measurements are compared with the daily MODIS albedo product (MCD43A) to analyze how space, time, surface heterogeneity, atmospheric conditions, and solar zenith angle geometry govern albedo at different scales. Finally, analysis of sub-pixel albedo and ablation reveal its importance on meltwater production in the lower parts of the ice sheet margin.

  14. NEUTRONIC REACTORS

    DOEpatents

    Vernon, H.C.

    1959-01-13

    A neutronic reactor of the heterogeneous, fluid cooled tvpe is described. The reactor is comprised of a pressure vessel containing the moderator and a plurality of vertically disposed channels extending in spaced relationship through the moderator. Fissionable fuel material is placed within the channels in spaced relationship thereto to permit circulation of the coolant fluid. Separate means are provided for cooling the moderator and for circulating a fluid coolant thru the channel elements to cool the fuel material.

  15. 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

    NASA Astrophysics Data System (ADS)

    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.

  16. Arctic sea ice albedo - A comparison of two satellite-derived data sets

    NASA Technical Reports Server (NTRS)

    Schweiger, Axel J.; Serreze, Mark C.; Key, Jeffrey R.

    1993-01-01

    Spatial patterns of mean monthly surface albedo for May, June, and July, derived from DMSP Operational Line Scan (OLS) satellite imagery are compared with surface albedos derived from the International Satellite Cloud Climatology Program (ISCCP) monthly data set. Spatial patterns obtained by the two techniques are in general agreement, especially for June and July. Nevertheless, systematic differences in albedo of 0.05 - 0.10 are noted which are most likely related to uncertainties in the simple parameterizations used in the DMSP analyses, problems in the ISCCP cloud-clearing algorithm and other modeling simplifications. However, with respect to the eventual goal of developing a reliable automated retrieval algorithm for compiling a long-term albedo data base, these initial comparisons are very encouraging.

  17. Atmospheric effects on the mapping of Martian thermal inertia and thermally derived albedo

    NASA Technical Reports Server (NTRS)

    Hayashi, J. N.; Jakosky, B. M.; Haberle, R. M.

    1994-01-01

    The most widely used thermal inertia data for Mars assumes the atmospheric contribution is constant and equal to 2 percent of the maximum solar insolation. Haberle and Jakosky investigated the effect of including a dusty CO2 atmosphere and sensible heat exchange with the surface on thermal inertia. We recently utilized Haberle and Jakosky's coupled surface-atmosphere model to investigate the effects of such an atmosphere on the thermally derived albedo. The thermally derived albedo is the albedo which, together with the thermal inertia, provides model surface temperatures which best match the observed temperatures. New maps are presented of thermal inertia and thermally derived albedo which incorporate dust opacities derived from IRTM data.

  18. Atmospheric effects on the mapping of Martian thermal inertia and thermally derived albedo

    NASA Technical Reports Server (NTRS)

    Hayashi, Joan N.; Jakosky, Bruce M.; Haberle, Robert M.

    1995-01-01

    We examine the effects of a dusty CO2 atmosphere on the thermal inertia and thermally derived albedo of Mars and we present a new map of thermal inertias. This new map was produced using a coupled surface atmosphere (CSA) model, dust opacities from Viking infrared thermal mapper (IRTM) data, and CO2 columns based on topography. The CSA model thermal inertias are smaller than the 2% model thermal inertias, with the difference largest at large thermal inertia. Although the difference between the thermal inertias obtained with the two models is moderate for much of the region studied, it is largest in regions of either high dust opacity or of topographic lows, including the Viking Lander 1 site and some geologically interesting regions. The CSA model thermally derived albedos do not acurately predict the IRTM measured albedos and are very similar to the thermally derived albedos obtained with models making the 2% assumption.

  19. Atmospheric effects on the mapping of Martian thermal inertia and thermally derived albedo

    NASA Technical Reports Server (NTRS)

    Hayashi, Joan N.; Jakosky, Bruce M.; Haberle, Robert M.

    1995-01-01

    We examine the effects of a dusty C02 atmosphere on the thermal inertia and thermally derived albedo of Mars and we present a new map of thermal inertias. This new map was produced using a coupled surface atmosphere (CSA) model, dust opacities from Viking infrared thermal mapper (IRTM) data, and C02 columns based on topography. The CSA model thermal inertias are smaller than the 2% model thermal inertias, with the difference largest at large thermal inertia. Although the difference between the thermal inertias obtained with the two models is moderate for much of the region studied, it is largest in regions of either high dust opacity or of topographic lows, including the Viking Lander 1 site and some geologically interesting regions. The CSA model thermally derived albedos do not accurately predict the IRTM measured albedos and are very similar to the thermally derived albedos obtained with models making the 2% assumption.

  20. The albedo, effective temperature, and energy balance of Uranus, as determined from Voyager IRIS data

    SciTech Connect

    Pearl, J.C.; Conrath, B.J.; Hanel, R.A.; Pirraglia, J.A.; Coustenis, A. Paris, Observatoire, Meudon )

    1990-03-01

    The albedo, T(eff), and energy balance of Uranus are presently derived from Voyager IR Spectrometer and Radiometer data. By obtaining the absolute phase curve of Uranus, it has become possible to evaluate the Bond albedo without making separate determinations of the geometric albedo and phase integral. An orbital mean value for the bolometric Bond albedo of 0.3 + or - 0.049 yields an equilibrium temperature of 58.2 + or - 1.0 K. Thermal spectra from pole-to-pole latitude coverage establish a T(eff) of 59.1 + or - 0.3 K, leading to an energy balance of 1.06 + or - 0.08 for Uranus. 39 refs.

  1. TNO and Centaur Diameters, Albedos, and Densities V4.0

    NASA Astrophysics Data System (ADS)

    Johnston, W. R.

    2016-07-01

    This data set is a compilation of published diameters, albedos, and densities for Transneptunian Objects (TNOs) and Centaurs. A total of 190 objects are listed, many with more than one entry. This version covers published values through 31 March 2016.

  2. Comparing MODIS-Terra and GOES surface albedo for New York City NY, Baltimore MD and Washington DC for 2005

    NASA Astrophysics Data System (ADS)

    Mubenga, K.; Hoff, R.; McCann, K.; Chu, A.; Prados, A.

    2006-05-01

    The NOAA GOES Aerosol and Smoke Product (GASP) is a product displaying the Aerosol Optical Depth (AOD) over the United States. The GASP retrieval involves discriminating the upwelling radiance from the atmosphere from that of the variable underlying surface. Unlike other sensors with more visible and near- infrared spectral channels such as MODIS, the sensors on GOES 8 through 12 only have one visible and a several far infrared channels. The GASP algorithm uses the detection of the second-darkest pixel from the visible channel over a 28-day period as the reference from which a radiance look-up table gives the corresponding AOD. GASP is reliable in capturing the AOD during large events. As an example, GASP was able to precisely show the Alaska and British Columbia smoke plume advecting from Alaska to the northeastern U.S. during the summer of 2004. Knapp et al. (2005) has shown that the AOD retrieval for GOES- 8 is within +/-0.13 of AERONET ground data with a coefficient of correlation of 0.72. Prados (this meeting) will update that study. However, GASP may not be as reliable when it comes to observing smaller AOD events in the northeast where the surface brightness is relatively high. The presence of large cities, such as New York, increases the surface albedo and produces a bright background against which it may be difficult to deduce the AOD. The Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the Earth Observing System Terra and Aqua platforms provides an independent measurement of the surface albedo at a resolution greater than available on GOES. In this research, the MODIS and GOES surface albedo product for New York, Washington and Baltimore are compared in order to see how we can improve the AOD retrieval in urban areas for air quality applications. Ref: K. Knapp et al. 2005. Toward aerosol optical depth retrievals over land from GOES visible radiances: determining surface reflectance. Int.Journal of Remote Sensing 26, 4097-4116

  3. Glacier albedo decrease in the European Alps: potential causes and links with mass balances

    NASA Astrophysics Data System (ADS)

    Di Mauro, Biagio; Julitta, Tommaso; Colombo, Roberto

    2016-04-01

    Both mountain glaciers and polar ice sheets are losing mass all over the Earth. They are highly sensitive to climate variation, and the widespread reduction of glaciers has been ascribed to the atmospheric temperature increase. Beside this driver, also ice albedo plays a fundamental role in defining mass balance of glaciers. In fact, dark ice absorbs more energy causing faster glacier melting, and this can drive to more negative balances. Previous studies showed that the albedo of Himalayan glaciers and the Greenland Ice Sheet is decreasing with important rates. In this contribution, we tested the hypothesis that also glaciers in the European Alps are getting darker. We analyzed 16-year time series of MODIS (MODerate resolution Imaging Spectrometer) snow albedo from Terra (MOD13A1, 2000-2015) and Aqua (MYD13A1, 2002-2015) satellites. These data feature a spatial resolution of 500m and a daily temporal resolution. We evaluated the existence of a negative linear and nonlinear trend of the summer albedo values both at pixel and at glacier level. We also calculated the correlation between MODIS summer albedo and glacier mass balances (from the World Glaciological Monitoring Service, WGMS database), for all the glaciers with available mass balance during the considered period. In order to estimate the percentage of the summer albedo that can be explained by atmospheric temperature, we correlated MODIS albedo and monthly air temperature extracted from the ERA-Interim reanalysis dataset. Results show that decreasing trends exist with a strong spatial variability in the whole Alpine chain. In large glaciers, such as the Aletch (Swiss Alps), the trend varies significantly also within the glacier, showing that the trend is higher in the area across the accumulation and ablation zone. Over the 17 glaciers with mass balance available in the WGMS data set, 11 gave significant relationship with the MODIS summer albedo. Moreover, the comparison between ERA-Interim temperature

  4. Features of re-entrant albedo deuteron trajectories in near Earth orbit with PAMELA experiment

    NASA Astrophysics Data System (ADS)

    Koldobskiy, S. A.; Adriani, O.; Barbarino, G. C.; 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.; Krutkov, S. Y.; Kvashnin, A. N.; Leonov, AA; 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.; Sarkar, R.; Scotti, V.; Simon, M.; Sparvoli, R.; Spillantini, P.; Stozhkov, Y. I.; Vacchi, A.; Vannuccini, E.; Vasilyev, GI; Voronov, S. A.; Yurkin, Y. T.; Zampa, G.; Zampa, N.

    2016-02-01

    The results of trajectory reconstruction for re-entrant albedo deuteron fluxes obtained in the PAMELA experiment are presented in this work. PAMELA is an international experiment aimed on measurements of cosmic ray particle fluxes in wide energy range. In particular, analysis of PAMELA data gives possibility to identify deuterons. Classification of re-entrant albedo deuterons with energies from 70 to 400 MeV/nucleon depending on theirs reconstructed lifetimes and generation zones is presented here at first time.

  5. New spectral functions of the near-ground albedo derived from aircraft diffraction spectrometer observations

    NASA Astrophysics Data System (ADS)

    Varotsos, C. A.; Melnikova, I. N.; Cracknell, A. P.; Tzanis, C.; Vasilyev, A. V.

    2013-06-01

    The airborne spectral observations of the upward and downward irradiances are revisited to investigate the dependence of the near-ground albedo as a function of wavelength in the entire solar spectrum for different surfaces (sand, water, snow) and in different conditions (clear or cloudy sky). The radiative upward and downward fluxes were determined by a diffraction spectrometer flown on a research aircraft that was performing multiple flight paths near ground. The results obtained show that the near-ground albedo does not generally increase with increasing wavelengths for all kinds of surfaces as is widely believed today. Particularly, in the case of water surfaces we found that the albedo in the ultraviolet region is more or less independent of the wavelength on a long-term basis. Interestingly, in the visible and near-infrared spectra the water albedo obeys an almost constant power-law relationship with wavelength. In the case of sand surfaces we found that the sand albedo is a quadratic function of wavelength, which becomes more accurate, if the ultraviolet wavelengths are neglected. Finally, we found that the spectral dependence of snow albedo behaves similarly to that of water, i.e. both decrease from the ultraviolet to the near-infrared wavelengths by 20-50%, despite of the fact that their values differ by one order of magnitude (water albedo being lower). In addition, the snow albedo versus ultraviolet wavelength is almost constant, while in the visible-near infrared spectrum the best simulation is achieved by a second-order polynomial, as in the case of sand, but with opposite slopes.

  6. New spectral functions of the near-ground albedo derived from aircraft diffraction spectrometer observations

    NASA Astrophysics Data System (ADS)

    Varotsos, C. A.; Melnikova, I. N.; Cracknell, A. P.; Tzanis, C.; Vasilyev, A. V.

    2014-07-01

    The airborne spectral observations of the upward and downward irradiances are revisited to investigate the dependence of the near-ground albedo as a function of wavelength in the entire solar spectrum for different surfaces (sand, water, snow) and under different conditions (clear or cloudy sky). The radiative upward and downward fluxes were determined by a diffraction spectrometer flown on a research aircraft that was performing multiple flight paths near the ground. The results obtained show that the near-ground albedo does not generally increase with increasing wavelengths for all kinds of surfaces as is widely believed today. Particularly, in the case of water surfaces it was found that the albedo in the ultraviolet region is more or less independent of the wavelength on a long-term basis. Interestingly, in the visible and near-infrared spectra the water albedo obeys an almost constant power-law relationship with wavelength. In the case of sand surfaces it was found that the sand albedo is a quadratic function of wavelength, which becomes more accurate if the ultraviolet wavelengths are neglected. Finally, it was found that the spectral dependence of snow albedo behaves similarly to that of water, i.e. both decrease from the ultraviolet to the near-infrared wavelengths by 20-50%, despite the fact that their values differ by one order of magnitude (water albedo being lower). In addition, the snow albedo vs. ultraviolet wavelength is almost constant, while in the visible near-infrared spectrum the best simulation is achieved by a second-order polynomial, as in the case of sand, but with opposite slopes.

  7. The search for the cause of the low albedo of the moon

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    Experimentation concerning lunar weathering and its effect on the albedo of the surface cover consisted of: (1) determination of the surface chemical composition of lunar soil and ground-up rock samples by Auger electron spectroscopy, (2) measurement of the optical albedo of these samples, and (3) proton or alpha-particle irradiation of terrestrial rock chips and rock powders and of ground-up lunar rock samples in order to determine the optical and surface chemical effect of simulated solar wind.

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Are the circular, dark features on Comet Borrelly's surface albedo variations or pits?

    USGS Publications Warehouse

    Nelson, R.M.; Soderblom, L.A.; Hapke, B.W.

    2004-01-01

    The highest resolution images of Comet 19P/Borrelly show many dark features which, upon casual inspection, appear to be low albedo markings, but which may also be shadows or other photometric variations caused by a depression in the local topography. In order to distinguish between these two possible interpretations we conducted a photometric analysis of three of the most prominent of these features using six of the highest quality images from the September 22, 2001 Deep Space 1 (DS1) flyby. We find that: 1. The radiance in the darkest parts of each feature increases as phase angle decreases, similarly to the radiance behavior of the higher albedo surrounding terrain. The dark features could be either fully illuminated low albedo spots or, alternatively, they could be depressions. No part of any of the three regions was in full shadow. 2. One of the regions has a radiance profile consistent with a rimmed depression, the second, with a simple depression with no rim, and the third with a low albedo spot. 3. The regolith particles are backscattering and carbon black is one of the few candidate regolith materials that might explain this low albedo. We conclude that Borrelly's surface is geologically complex to the limit of resolution of the images with a combination complex topography, pits, troughs, peaks and ridges, and some very dark albedo markings, perhaps a factor of two to three darker than the average 3-4% albedo of the surrounding terrains. Our technique utilizing measured radiance profiles through the dark regions is able to discriminate between rimmed depressions, rimless depressions and simple albedo changes not associated with topography. ?? 2003 Elsevier Inc. All rights reserved.

  11. Albedo changes occurring in stationary forest covers over France during the last decade

    NASA Astrophysics Data System (ADS)

    Planque, C.; Carrer, D.; Roujean, J. L.

    2015-12-01

    Climate warming has caused unprecedented changes in the vegetation cycle of forests. In return, forests play a substantial role on climate by directly modifying the amount of carbon dioxide in the atmosphere. Besides the shifts occurring in forest architecture and diversity, the climate pressure influences the canopy structure and the leaf physiological characteristics. A direct consequence is the modification of reflectivity properties of the whole canopy. This study examines the evolution of the direct radiative forcing due to the evolution of reflectivity properties of the canopy (canopy albedo). We restrict our analysis to the albedo trends occurring in stationary forest covers over France during the last decade (2001-2013). Satellite surface albedo, LAI (leaf area index), and FCOVER (fraction of vegetation cover) from MODIS (on Terra and Aqua satellites) and BioPar (Bio-geophysical Parameter) projects are used in order to 1/ isolate stationary forest covers, and 2/ detect local tendencies in their canopy albedo. First, the statistical tests were applied to LAI, FCOVER, and surface albedo data over the areas that are classified as forest by ESA-CCI land cover database. In case of temporal break in LAI or FCOVER data series, we assume that the forest was managed at least once during the last decade or the vegetation cover has changed. This hypothesis was verified over the Landes forest in southwestern France, where a major storm damaged 300000 hectares in 2009. This work allowed to isolate relative stationary forest covers that were not managed. Secondly, we show that the visible surface albedo has decreased due to the gradual closing and increase in greenness of some of these forest covers. Finally, we quantified the change in direct radiative forcing due to this shift of surface albedo by using ERA-Interim incoming solar radiation data. The next step will be to better characterize the physiological and structural factors that drive these albedo changes.

  12. Estimation of aerosol single scattering albedo from solar direct spectral radiance and total broadband irradiances measured in China

    NASA Astrophysics Data System (ADS)

    Zhao, Fengsheng; Li, Zhanqing

    2007-11-01

    Aerosol single scattering albedo (ωo) is a primary factor dictating aerosol radiative effect. Ground-based remote sensing of ωo has been employed most widely using spectral sky radiance measurements made from a scanning Sun photometer. Reliable results can be achieved for high aerosol loadings and for solar zenith angle >50°. This study presents an alternative method using spectral direct radiance measurements or aerosol optical depths together with total sky irradiance to retrieve ωo. The method does not require sky radiance data that can only be acquired by the expensive scanning Sun photometer. The method is evaluated using extensive measurements by a suite of instruments deployed in northern China under the East Asian Study of Tropospheric Aerosols: An International Regional Experiment (EAST-AIRE) project. The sensitivities of the retrieval to various uncertain factors were first examined by means of radiative transfer simulations. It was found the retrieval is most sensitive to cloud screening, total irradiance and the Angstrom Exponent (AE), but only weakly depends on surface albedo and the fine structure of aerosol size distribution. Using 1 year of rigorously screened clear-sky measurements made at the Xianghe site, the retrieved ωo values were found to agree with those retrieved from the Cimel Sun photometer by the AERONET method to within ˜0.03 (RMS), and ˜0.003 (mean bias). As part of the differences originate from different sky views seen by the Sun photometers and pyranometer under comparison, a further test was conducted by using total sky irradiances simulated with the retrieved aerosol properties from the AERONET. The resulting estimates of ωo agree to within 0.01-0.02 (RMS differences) and 0.002-0.003 (mean bias). These values are better measure of the true retrieval uncertainties, as they are free from any data mismatch. The characteristics of ωo retrievals were discussed.

  13. Response of the Hanford Combination Neutron Dosimeter in plutonium environments

    SciTech Connect

    Endres, A.W.; Brackenbush, L.W.; Baumgartner, W.V.

    1996-02-01

    This report documents response characteristics and the development of dose algorithms for the Hanford Combination Neutron Dosimeter (HCNO) implemented on January 1, 1995. The HCND was accredited under the U.S. Department of Energy (DOE) Laboratory Accreditation Program (DOELAP) during 1994. The HCND employs two neutron dose components consisting of (1) an albedo thermoluminescent dosimeter (TLD), and (2) a track-etch dosimeter (TED). Response characteristics of these two dosimeter components were measured under the low-scatter conditions of the Hanford 318 Building Calibration Laboratory, and under the high-scatter conditions in the workplace at the Plutonium Finishing Plant (PFP). The majority of personnel neutron dose at Hanford (currently and historically) occurs at the PFP. National Institute of Standards and Technology (NIST) traceable sources were used to characterize dosimeter response in the laboratory. At the PFP, neutron spectra and dose-measuring instruments, including a multisphere spectrometer, tissue equivalent proportional counters, and specially calibrated rem meters, were used to determine the neutron dose under several configurations from three different plutonium sources: (1) plutonium tetrafluoride, (2) plutonium metal, and (3) plutonium oxide. In addition, measurements were performed at many selected work locations. The HCNDs were included in all measurements. Comparison of dosimeter- and instrument-measured dose equivalents provided the data necessary to develop HCND dose algorithms and to assess the accuracy of estimated neutron dose under actual work conditions.

  14. Energy spectrum and flux of fast neutrons in the atmosphere

    NASA Technical Reports Server (NTRS)

    Saint Onge, R. N.

    1977-01-01

    The neutron energy spectrum and flux in the atmosphere at the Pfotzer maximum (about 100 g per cm squared) were measured at geomagnetic latitude 42 deg N, using a system capable of detecting a small flux of fast (5 to 20 MeV) neutrons in a much larger background flux of gamma rays and charged particles. The detector consisted of a cylindrical cell of organic liquid scintillator coupled to a high-resolution two-parameter multiparticle pulse shape discriminator with a two-parameter logarithmic pulse-height analyzer. The spectral parameter for the differential neutron energy spectrum was found to decrease from 4.4 plus or minus 0.8 between 3.5 and 6.0 MeV to 1.5 plus or minus 1.0 in the interval 11 to 20 MeV; a value of 0.36 plus or minus 0.10 neutrons per cm squared was calculated for neutron flux between 3.5 and 10 MeV. The importance of these results for evaluating the role of albedo neutron leakage as a source of the energetic proton flux in the radiation belts is also considered.

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

    NASA Astrophysics Data System (ADS)

    Bartlett, P. A.; Wang, L.; Cole, J. N.; Verseghy, D. L.; Arora, V.; Derksen, C.; Brown, R.; von Salzen, K.

    2015-12-01

    A persistent spread in winter albedo has been found in Phase 3 and Phase 5 of the Coupled Model Intercomparison Project (CMIP) simulations, and is particularly pronounced in boreal forest regions. The primary goal of this study is to investigate the role of leaf area index (LAI) specification in the large spread in winter albedo simulated by the CMIP5 models. Simulated LAI and surface albedo from the CMIP5 models are compared with satellite observations. The results show that improper plant functional type specification and erroneous LAI parameterization in some models can explain 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. The errors are largest (+20-40 %) in models with large underestimation of LAI and are typically within ±15% when simulated LAI is within the observed range. This is confirmed by sensitivity tests with the Canadian Atmospheric Global Climate Model coupled with the Canadian Land Surface Scheme version 3.6.

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

    PubMed

    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.

  17. CLARA-SAL: a global 28-yr timeseries of Earth's black-sky surface albedo

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

    We present a novel 28-yr dataset of Earth's black-sky surface albedo, derived from AVHRR instruments. The dataset is created using algorithms to separately derive the surface albedo for different land use areas globally. Snow, sea ice, open water and vegetation are all treated independently. The product features corrections for the atmospheric effect in satellite-observed surface radiances, a BRDF correction for the anisotropic reflectance properties of natural surfaces, and a novel topography correction of geolocation and radiometric accuracy of surface reflectance observations over mountainous areas. The dataset is based on a homogenized AVHRR radiance timeseries. The product is validated against quality-controlled in situ observations of clear-sky surface albedo at various BSRN sites around the world. Snow and ice albedo retrieval validation is given particular attention using BSRN sites over Antarctica, Greenland Climate Network stations on the Greenland Ice Sheet (GrIS), as well as sea ice albedo data from the SHEBA and Tara expeditions. The product quality is found to be comparable to other previous long-term surface albedo datasets from AVHRR.

  18. CLARA-SAL: a global 28 yr timeseries of Earth's black-sky surface albedo

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    We present a novel 28 yr dataset of Earth's black-sky surface albedo, derived from AVHRR instruments. The dataset is created using algorithms to separately derive the surface albedo for different land use areas globally. Snow, sea ice, open water and vegetation are all treated independently. The product features corrections for the atmospheric effect in satellite-observed surface radiances, a BRDF correction for the anisotropic reflectance properties of natural surfaces, and a novel topography correction of geolocation and radiometric accuracy of surface reflectance observations over mountainous areas. The dataset is based on a homogenized AVHRR radiance timeseries. The product is validated against quality-controlled in situ observations of clear-sky surface albedo at various BSRN sites around the world. Snow and ice albedo retrieval validation is given particular attention using BSRN sites over Antarctica, Greenland Climate Network stations on the Greenland Ice Sheet (GrIS), as well as sea ice albedo data from the SHEBA and Tara expeditions. The product quality is found to be comparable to other previous long-term surface albedo datasets from AVHRR.

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

    NASA Astrophysics Data System (ADS)

    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.

  20. High-albedo C-complex outer-belt asteroids: The near-infrared spectra

    NASA Astrophysics Data System (ADS)

    Kasuga, T.; Usui, F.; Ootsubo, T.; Hasegawa, S.; Kuroda, D.; Shirahata, M.; Okamura, N.

    2014-07-01

    Primitive, outer-belt asteroids are generally of low albedo, reflecting carbonaceous compositions like those of CI and CM meteorites. However, a few outer-belt asteroids having high albedos are known, suggesting the presence of unusually reflective surface minerals or, conceivably, even exposed water ice. Here, we present near-infrared (1.1--2.5 micron) spectra of four outer-belt C-complex asteroids with albedos > 0.1. We find no absorption features characteristic of water ice (near 1.5 and 2.0 micron) in the objects. Intimate mixture models set limits to the water ice by weight < 2 %. Asteroids (723) Hammonia and (936) Kunigunde are featureless and have (60--95 %) amorphous Mg pyroxenes that might explain the high albedos. Asteroid (1276) Ucclia also shows a featureless reflection spectrum with (50--60 %) amorphous Mg pyroxenes. Asteroid (1576) Fabiola shows a possible weak, broad absorption band (1.5--2.1 micron). The feature can be reproduced by either (80 %) amorphous Mg pyroxenes or orthopyroxene (crystalline silicate), being likely to cause its high albedo. We discuss the origin of high-albedo components in primitive asteroids. This study is published in The Astronomical Journal, Volume 146, Issue 1, article id. 1, 6 pp. (2013).

  1. Spectral albedo and emissivity of CO2 in Martian polar caps - Model results

    NASA Technical Reports Server (NTRS)

    Warren, Stephen G.; Wiscombe, Warren J.; Firestone, John F.

    1990-01-01

    In this paper, a snow albedo model previously developed for terrestrial snow is extended to the case of CO2 snow on Mars. Pure CO2 snow is calculated to have high albedo at visible wavelengths but not as high as that of water snow. At any given wavelength, the primary variable controlling albedo and emissivity is the snow grain size, with albedo decreasing and emissivity increasing as grain size increases. Observations that red albedo is much higher than blue albedo in the Martian south polar cap indicates that the snow or the atmosphere is contaminated with red dust. The absorption coefficient of CO2 ice in the thermal infrared is two to three orders of magnitude smaller than that measured for H2O ice. CO2 snow emissivity is therefore much lower than H2O snow, varying substantially with wavelength and quite sensitive to grain size and emission angle. Factors tending to increase emissivity are large grain size, small emission angle, and large concentrations of dust or water.

  2. Landsat monitoring of albedo changes in northwestern Arizona, 1977-1980

    USGS Publications Warehouse

    Robinove, Charles Joseph

    1982-01-01

    As part of a cooperative project between the U.S. Geological Survey and the Bureau of Land Management, changes in albedo (percentage of light reflected from the ground) were calculated and mapped from Landsat images for an area in northwestern Arizona for three periods: August 26, 1977, to September 3, 1979; September 3, 1979, to August 28, 1980; and August 26, 1977, to August 28, 1980. The mapped albedo changes were field checked in April 1981. Decreases in albedo were associated with increases in vegetation, primarily the flush of annual vegetation and the regrowth of vegetation in chained areas and sites of past fires. Increases in albedo were due to recent fires. Continuous monitoring of changes in albedo using current, rather than historical, Landsat images can provide the Bureau of Land Management with a means of monitoring vegetation growth, determining areas of high fire potential, and more efficiently deploying of field personnel to sites where severe changes are occuring in the quality of the land and vegetation resources. For example, an albedo change could be an indication of encroachment by an invader species. Similarly, it could indicate where rangeland is being lost to desertification.

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

    SciTech Connect

    Kasuga, Toshihiro; Shirahata, Mai; Usui, Fumihiko; Kuroda, Daisuke; Ootsubo, Takafumi; Okamura, Natsuko; Hasegawa, Sunao

    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.

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

    PubMed

    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. PMID:23146092

  5. Radiative forcing impacts of boreal forest biofuels: a scenario study for Norway in light of albedo.

    PubMed

    Bright, Ryan M; Strømman, Anders Hammer; Peters, Glen P

    2011-09-01

    Radiative forcing impacts due to increased harvesting of boreal forests for use as transportation biofuel in Norway are quantified using simple climate models together with life cycle emission data, MODIS surface albedo data, and a dynamic land use model tracking carbon flux and clear-cut area changes within productive forests over a 100-year management period. We approximate the magnitude of radiative forcing due to albedo changes and compare it to the forcing due to changes in the carbon cycle for purposes of attributing the net result, along with changes in fossil fuel emissions, to the combined anthropogenic land use plus transport fuel system. Depending on albedo uncertainty and uncertainty about the geographic distribution of future logging activity, we report a range of results, thus only general conclusions about the magnitude of the carbon offset potential due to changes in surface albedo can be drawn. Nevertheless, our results have important implications for how forests might be managed for mitigating climate change in light of this additional biophysical criterion, and in particular, on future biofuel policies throughout the region. Future research efforts should be directed at understanding the relationships between the physical properties of managed forests and albedo, and how albedo changes in time as a result of specific management interventions. PMID:21797227

  6. A time variable model of Earth's albedo. [for climatology studies and interpretation of satellite data

    NASA Technical Reports Server (NTRS)

    Bartman, F. L.

    1980-01-01

    A time variable model of Earth's albedo was prepared for use in climate studies and as an aid to the interpretation of satellite Earth radiation budget data. The features of the model include: a 10 deg latitude 10 deg longitude grid for numerical integration, surface albedo specified at 1 month intervals, calculation of zenith angle effect for surface albedo and of the additional effect of the atmosphere on the albedo. Percent cloud cover is specified for 29 different climatological cloud type regions at 8 times of the day for 12 months of the year. Cloud albedos were specified for each of the cloud climatological types. Diurnal and monthly variations of this model are described and results are compared with a model which is based on satellite measurements. A computer program was also written for use in studying the sampling effects in satellite radiation budget measurements. An example of the results of calculations with this program are compared with a previous study of the sampling effects. This program for satellite orbit characteristics is to be combined with the time-variable albedo model for further study of the sampling problem.

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

    NASA Astrophysics Data System (ADS)

    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.

  8. Investigating the Cause of Moving Albedo Boundaries in the Oxia Palus Region of Mars

    NASA Astrophysics Data System (ADS)

    Mukherjee, P.; Geissler, P. E.

    2010-12-01

    Recent imagery from the MARCI camera on Mars Reconnaissance Orbiter (MRO) in addition to previous analyses of Mars Global Surveyor MOC data reveals a variety of large scale changes in the appearance of the Martian surface (Geissler and Mukherjee, this meeting). The MOC and MARCI data revealed a surprising range of behavior in various regions of Mars. Our area of focus is a region featuring such albedo changes in Oxia Palus in western Arabia Terra. The albedo boundary between dark and bright terrain at western Oxia Palus moved 26 km eastwards between a MOC mosaic from September 2005 and a MARCI mosaic from July 2009. The goal of this project is to understand what is causing this albedo boundary to move. A distinctive feature of the Oxia Palus albedo boundary is a narrow (~25 km wide) fringe of locally high albedo that shifts as the boundary advances from the dark region (Acidalia) towards the bright terrain (Oxia). High resolution images from MRO’s CTX and HiRISE cameras will be used to test the hypothesis that the high albedo fringe is a coating of bright dust that is stripped by the winds from the advancing dark terrain and deposited ahead of the moving boundary.

  9. Neutron Environment Calculations for Low Earth Orbit

    NASA Technical Reports Server (NTRS)

    Clowdsley, M. S.; Wilson, J. W.; Shinn, J. L.; Badavi, F. F.; Heinbockel, J. H.; Atwell, W.

    2001-01-01

    The long term exposure of astronauts on the developing International Space Station (ISS) requires an accurate knowledge of the internal exposure environment for human risk assessment and other onboard processes. The natural environment is moderated by the solar wind, which varies over the solar cycle. The HZETRN high charge and energy transport code developed at NASA Langley Research Center can be used to evaluate the neutron environment on ISS. A time dependent model for the ambient environment in low earth orbit is used. This model includes GCR radiation moderated by the Earth's magnetic field, trapped protons, and a recently completed model of the albedo neutron environment formed through the interaction of galactic cosmic rays with the Earth's atmosphere. Using this code, the neutron environments for space shuttle missions were calculated and comparisons were made to measurements by the Johnson Space Center with onboard detectors. The models discussed herein are being developed to evaluate the natural and induced environment data for the Intelligence Synthesis Environment Project and eventual use in spacecraft optimization.

  10. Remote Sensing.

    ERIC Educational Resources Information Center

    Williams, Richard S., Jr.; Southworth, C. Scott

    1983-01-01

    The Landsat Program became the major event of 1982 in geological remote sensing with the successful launch of Landsat 4. Other 1982 remote sensing accomplishments, research, publications, (including a set of Landsat worldwide reference system index maps), and conferences are highlighted. (JN)

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    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.

  12. NEUTRON COUNTER

    DOEpatents

    Curtis, C.D.; Carlson, R.L.; Tubinis, M.P.

    1958-07-29

    An ionization chamber instrument is described for cylindrical electrodes with an ionizing gag filling the channber. The inner electrode is held in place by a hermetic insulating seal at one end of the outer electrode, the other end of the outer electrode being closed by a gas filling tube. The outer surface of the inner electrode is coated with an active material which is responsive to neutron bombardment, such as uranium235 or boron-10, to produce ionizing radiations in the gas. The transverse cross sectional area of the inner electrode is small in relation to that of the channber whereby substantially all of the radiations are directed toward the outer electrode.

  13. NEUTRON SOURCE

    DOEpatents

    Reardon, W.A.; Lennox, D.H.; Nobles, R.G.

    1959-01-13

    A neutron source of the antimony--beryllium type is presented. The source is comprised of a solid mass of beryllium having a cylindrical recess extending therein and a cylinder containing antimony-124 slidably disposed within the cylindrical recess. The antimony cylinder is encased in aluminum. A berylliunn plug is removably inserted in the open end of the cylindrical recess to completely enclose the antimony cylinder in bsryllium. The plug and antimony cylinder are each provided with a stud on their upper ends to facilitate handling remotely.

  14. Compressive sensing for nuclear security.

    SciTech Connect

    Gestner, Brian Joseph

    2013-12-01

    Special nuclear material (SNM) detection has applications in nuclear material control, treaty verification, and national security. The neutron and gamma-ray radiation signature of SNMs can be indirectly observed in scintillator materials, which fluoresce when exposed to this radiation. A photomultiplier tube (PMT) coupled to the scintillator material is often used to convert this weak fluorescence to an electrical output signal. The fluorescence produced by a neutron interaction event differs from that of a gamma-ray interaction event, leading to a slightly different pulse in the PMT output signal. The ability to distinguish between these pulse types, i.e., pulse shape discrimination (PSD), has enabled applications such as neutron spectroscopy, neutron scatter cameras, and dual-mode neutron/gamma-ray imagers. In this research, we explore the use of compressive sensing to guide the development of novel mixed-signal hardware for PMT output signal acquisition. Effectively, we explore smart digitizers that extract sufficient information for PSD while requiring a considerably lower sample rate than conventional digitizers. Given that we determine the feasibility of realizing these designs in custom low-power analog integrated circuits, this research enables the incorporation of SNM detection into wireless sensor networks.

  15. Validation of GEOLAND-2 Spot/vgt Albedo Products by Using Ceos Olive Methodology

    NASA Astrophysics Data System (ADS)

    Camacho de Coca, F.; Sanchez, J.; Schaaf, C.; Baret, F.; Weiss, M.; Cescatti, A.; Lacaze, R. N.

    2012-12-01

    This study evaluates the scientific merit of the global surface albedo products developed in the framework of the Geoland-2 project based on SPOT/VEGETATION observations. The methodology follows the OLIVE (On-Line Validation Exercise) approach supported by the CEOS Land Product Validation subgroup (calvalportal.ceos.org/cvp/web/olive). First, the spatial and temporal consistency of SPOT/VGT albedo products was assessed by intercomparison with reference global products (MODIS/Terra+Aqua and POLDER-3/PARASOL) for the period 2006-2007. A bulk statistical analysis over a global network of 420 homogeneous sites (BELMANIP-2) was performed and analyzed per biome types. Additional sites were included to study albedo under snow conditions. Second, the accuracy and realism of temporal variations were evaluated using a number of ground measurements from FLUXNET sites suitable for use in direct comparison to the co-located satellite data. Our results show that SPOT/VGT albedo products present reliable spatial and temporal distribution of retrievals. The SPOT/VGT albedo performs admirably with MODIS, with a mean bias and RMSE for the shortwave black-sky albedo over BELMANIP-2 sites lower than 0.006 and 0.03 (13% in relative terms) respectively, and even better for snow free pixels. Similar results were found for the white-sky albedo quantities. Discrepancies are larger when comparing with POLDER-3 products: for the shortwave black-sky albedo a mean bias of -0.014 and RMSE of 0.04 (20%) was found. This overall performance figures are however land-cover dependent and larger uncertainties were found over some biomes (or regions) or specific periods (e.g. winter in the north hemisphere). The comparison of SPOT/VGT blue-sky albedo estimates with ground measurements (mainly over Needle-leaf forest sites) show a RMSE of 0.04 and a bias of 0.003 when only snow-free pixels are considered. Moreover, this work shows that the OLIVE tool is also suitable for validation of global albedo

  16. Apparatus and method for the simultaneous detection of neutrons and ionizing electromagnetic radiation

    DOEpatents

    Bell, Zane W.

    2000-01-01

    A sensor for simultaneously detecting neutrons and ionizing electromagnetic radiation comprising: a sensor for the detection of gamma radiation, the sensor defining a sensing head; the sensor further defining an output end in communication with the sensing head; and an exterior neutron-sensitive material configured to form around the sensing head; wherein the neutron-sensitive material, subsequent to the capture of the neutron, fissions into an alpha-particle and a .sup.7 Li ion that is in a first excited state in a majority of the fissions, the first excited state decaying via the emission of a single gamma ray at 478 keV which can in turn be detected by the sensing head; and wherein the sensing head can also detect the ionizing electromagnetic radiation from an incident radiation field without significant interference from the neutron-sensitive material. A method for simultaneously detecting neutrons and ionizing electromagnetic radiation comprising the steps of: providing a gamma ray sensitive detector comprising a sensing head and an output end; conforming an exterior neutron-sensitive material configured to form around the sensing head of the detector; capturing neutrons by the sensing head causing the neutron-sensitive material to fission into an alpha-particle and a .sup.7 Li ion that is in a first excited state in a majority of the fissions, the state decaying via the emission of a single gamma ray at 478 keV; sensing gamma rays entering the detector through the neutron-sensitive material; and producing an output through a readout device coupled to the output end; wherein the detector provides an output which is proportional to the energy of the absorbed ionizing electromagnetic radiation.

  17. Axial expansion methods for solution of the multi-dimensional neutron diffusion equation

    SciTech Connect

    Beaklini Filho, J.F.

    1984-01-01

    The feasibility and practical implementation of axial expansion methods for the solution of the multi-dimensional multigroup neutron diffusion (MGD) equations is investigated. The theoretical examination which is applicable to the general MGD equations in arbitrary geometry includes the derivation of a new weak (reduced) form of the MGD equations by expanding the axial component of the neutron flux in a series of known trial functions and utilizing the Galerkin weighting. A general two-group albedo boundary condition is included in the weak form as a natural boundary condition. The application of different types of trial functions is presented.

  18. Use of neutron reflection method to assay nuclear materials in solutions.

    PubMed

    Mohapatra, D K; Reddy, C P

    2001-11-01

    Neutron reflection methods are used in the chemical analysis of bulk samples, especially for the determination of contents in hydrogenous solutions. In these techniques albedo is measured by measuring either the activation of a foil, or count rate from a neutron detector. In the present paper Monte Carlo simulations are performed using this method for the possibility of detecting inadvertent criticality in the reprocessing plants and also estimation of 10B in heavy water, which is used as a moderator in PHWRs. PMID:11573803

  19. Linking the fPAR, forest albedo and biomass in the northern biomes of Europe

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    Land surface albedo and the fraction of photosynthetically active radiation (fPAR) absorbed by plant canopies are two of the essential climate variables controlling the planetary radiative energy budget. Albedo is directly related to the energy exchange between land and the atmosphere as it is the reflectivity of the surface - the higher the albedo, the more incoming solar radiation is reflected and the less absorbed by the surface. The fPAR is related to plant productivity, quantifying the amount of absorbed light available for photosynthesis. It is a key parameter in the modelling of net primary production (NPP) of terrestrial ecosystems. Global climate scenarios are very sensitive to albedo and fPAR estimates, and thus, the effect of changes in canopy structure and density (biomass) on these two variables needs to be quantified reliably. Both parameters are routinely retrieved from current Earth Observation sensors using specialized algorithms. To date, these satellite products have not been linked to extensive forest inventory data sets due to the lack of ground reference data. Data availability for Finland has significantly improved in December 2012, when National Forest Inventory (NFI) data became freely available to the public. The dataset covers the geographical area of Finland (26.1 million hectares) at a spatial resolution of 20 meters including several forest structural variables. In this study, we use the NFI data to study the links between forest albedo, fPAR and forest structure and density during the green vegetation season. More specifically, we investigated the seasonal trends in fPAR and albedo of different spectral regions of northern forests. Empirical relationships between forest albedo, fPAR and total aboveground biomass were established for selected days within the vegetation growing period and across a latitudinal transect of Finland.

  20. Radiative Forcing and Temperature Response to Changes in Urban Albedos and Associated CO2 Offsets

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

    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 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. Using the catchment land surface model (the land model coupled to the GEOS-5 Atmospheric General Circulation Model), we quantify the response of the total outgoing (outgoing shortwave+longwave) radiation to urban albedo changes. Globally, the total outgoing radiation increased by 0.5 W/square m and temperature decreased by -0.008 K for an average 0.003 increase in albedo. For the U.S. the total outgoing total radiation increased by 2.3 W/square meter, and temperature decreased by approximately 0.03 K for an average 0.01 increase in albedo. These values are for the boreal summer (Tune-July-August). Based on these forcings, the expected emitted CO2 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 approximately 57 Gt CO2 . A more meaningful evaluation of the impacts of urban albedo increases on climate and the expected CO2 offsets would require simulations which better characterizes urban surfaces and represents the full annual cycle.

  1. Impacts of ocean albedo alteration on Arctic sea ice restoration and Northern Hemisphere climate

    DOE PAGES

    Cvijanovic, Ivana; Caldeira, Ken; MacMartin, Douglas G.

    2015-04-01

    The Arctic Ocean is expected to transition into a seasonally ice-free state by mid-century, enhancing Arctic warming and leading to substantial ecological and socio-economic challenges across the Arctic region. It has been proposed that artificially increasing high latitude ocean albedo could restore sea ice, but the climate impacts of such a strategy have not been previously explored. Motivated by this, we investigate the impacts of idealized high latitude ocean albedo changes on Arctic sea ice restoration and climate. In our simulated 4xCO₂ climate, imposing surface albedo alterations over the Arctic Ocean leads to partial sea ice recovery and a modestmore » reduction in Arctic warming. With the most extreme ocean albedo changes, imposed over the area 70°–90°N, September sea ice cover stabilizes at ~40% of its preindustrial value (compared to ~3% without imposed albedo modifications). This is accompanied by an annual mean Arctic surface temperature decrease of ~2 °C but no substantial global mean temperature decrease. Imposed albedo changes and sea ice recovery alter climate outside the Arctic region too, affecting precipitation distribution over parts of the continental United States and Northeastern Pacific. For example, following sea ice recovery, wetter and milder winter conditions are present in the Southwest United States while the East Coast experiences cooling. We conclude that although ocean albedo alteration could lead to some sea ice recovery, it does not appear to be an effective way of offsetting the overall effects of CO₂ induced global warming.« less

  2. Impacts of ocean albedo alteration on Arctic sea ice restoration and Northern Hemisphere climate

    SciTech Connect

    Cvijanovic, Ivana; Caldeira, Ken; MacMartin, Douglas G.

    2015-04-01

    The Arctic Ocean is expected to transition into a seasonally ice-free state by mid-century, enhancing Arctic warming and leading to substantial ecological and socio-economic challenges across the Arctic region. It has been proposed that artificially increasing high latitude ocean albedo could restore sea ice, but the climate impacts of such a strategy have not been previously explored. Motivated by this, we investigate the impacts of idealized high latitude ocean albedo changes on Arctic sea ice restoration and climate. In our simulated 4xCO₂ climate, imposing surface albedo alterations over the Arctic Ocean leads to partial sea ice recovery and a modest reduction in Arctic warming. With the most extreme ocean albedo changes, imposed over the area 70°–90°N, September sea ice cover stabilizes at ~40% of its preindustrial value (compared to ~3% without imposed albedo modifications). This is accompanied by an annual mean Arctic surface temperature decrease of ~2 °C but no substantial global mean temperature decrease. Imposed albedo changes and sea ice recovery alter climate outside the Arctic region too, affecting precipitation distribution over parts of the continental United States and Northeastern Pacific. For example, following sea ice recovery, wetter and milder winter conditions are present in the Southwest United States while the East Coast experiences cooling. We conclude that although ocean albedo alteration could lead to some sea ice recovery, it does not appear to be an effective way of offsetting the overall effects of CO₂ induced global warming.

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

    USGS Publications Warehouse

    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.

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

    SciTech Connect

    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.

  5. Observations of albedo and radiation balance over postforest land surfaces in the eastern Amazon Basin

    SciTech Connect

    Giambelluca, T.W.; Nullet, M.A.; Ziegler, A.D.

    1997-05-01

    Regional climatic change, including significant reductions in Amazon Basin evaporation and precipitation, has been predicted by numerical simulations of total tropical forest removal. These results have been shown to be very sensitive to the prescription of the albedo shift associated with conversion from forest to a replacement land cover. Modelers have so far chosen to use an {open_quotes}impoverished grassland{close_quotes} scenario to represent the postforest land surface. This choice maximizes the shifts in land surface parameters, especially albedo (fraction of incident shortwave radiation reflected by the surface). Recent surveys show secondary vegetation to be the dominant land cover for some deforested areas of the Amazon. This paper presents the results of field measurements of radiation flux over various deforested surfaces on a small farm in the eastern Amazonian state of Para. The albedo of fields in active use was as high as 0.176, slightly less than the 0.180 recently determined for Amazonian pasture and substantially less than the 0.19 commonly used in GCM simulations of deforestation. For 10-yr-old secondary vegetation, albedo was 0.135, practically indistinguishable from the recently published mean primary forest albedo of 0.134. Measurements of surface temperature and net radiation show that, despite similarity in albedo, secondary vegetation differs from primary forest in energy and mass exchange. The elevation of midday surface temperature above air temperature was found to be greatest for actively and recently farmed land, declining with time since abandonment. Net radiation was correspondingly lower for fields in active or recent use. Using land cover analyses of the region surrounding the study area for 1984, 1988, and 1991, the pace of change in regional-mean albedo is estimated to have declined and appears to be leveling at a value less than 0.03 above that of the original forest cover. 41 refs., 3 figs., 8 tabs.

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

    PubMed

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

    2007-04-01

    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 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.

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

    PubMed

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

    2007-04-01

    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 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. PMID:17410170

  8. ExploreNEOs. V. AVERAGE ALBEDO BY TAXONOMIC COMPLEX IN THE NEAR-EARTH ASTEROID POPULATION

    SciTech Connect

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

    2011-09-15

    Examining the albedo distribution of the near-Earth object (NEO) population allows for a better understanding of the relationship between absolute (H) magnitude and size, which impacts calculations of the size frequency distribution and impact hazards. Examining NEO albedos also sheds light on the differences between the NEO and Main Belt populations. We combine albedo results from the ExploreNEOs Warm Spitzer Exploration Science program with taxonomic classifications from the literature, publicly available data sets, and new observations from our concurrent spectral survey to derive the average albedos for C-, D-, Q-, S-, V-, and X-complex NEOs. Using a sample size of 118 NEOs, we calculate average albedos of 0.29{sup +0.05}{sub -0.04}, 0.26{sup +0.04}{sub -0.03}, and 0.42{sup +0.13}{sub -0.11} for the Q-, S-, and V-complexes, respectively. The averages for the C- and D-complexes are 0.13{sup +0.06}{sub -0.05} and 0.02{sup +0.02}{sub -0.01}, but these averages are based on a small number of objects (five and two, respectively) and will improve with additional observations. We use albedos to assign X-complex asteroids to one of the E-, M-, or P-types. Our results demonstrate that the average albedos for the C-, S-, V-, and X-complexes are higher for NEOs than the corresponding averages observed in the Main Belt.

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

    USGS Publications Warehouse

    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.

  10. COMPTEL measurements of the omnidirectional high-energy neutron flux in near-earth orbit.

    PubMed

    Morris, D J; Aarts, H; Bennett, K; Lockwood, J A; McConnell, M L; Ryan, J M; Schonfelder, V; Steinle, H; Weidenspointner, G

    1998-01-01

    On four occasions, twice in 1991 (near solar maximum) and twice in 1994 (near solar minimum), one COMPTEL D1 detector module was used as an omnidirectional detector to measure the high-energy (> 12.8 MeV) neutron flux near an altitude of 450 km. The D1 modules are cylindrical, with radius 13.8 cm and depth 8 cm, and are filled with liquid scintillator (NE213A). The combined flux measurements can be fit reasonably well by a product of the Mt. Washington neutron monitor rate, a linear function in the spacecraft geocenter zenith angle, and an exponential function of the vertical geomagnetic cutoff rigidity in which the coefficient of the rigidity is a linear function of the neutron monitor rate. When pointed at the nadir, the flux is consistent with that expected from the atmospheric neutron albedo alone. When pointed at the zenith the flux is reduced by a factor of about 0.54. Thus the production of secondary neutrons in the massive (16000 kg) Compton Gamma-Ray Observatory spacecraft is negligible. Rather, the mass of the spacecraft provides shielding from the earth albedo. PMID:11542901

  11. Characterization of the High-Albedo NEA 3691 Bede

    NASA Technical Reports Server (NTRS)

    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 E.

    2016-01-01

    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

  12. Characterization of the high-albedo NEA 3691 Bede

    NASA Astrophysics Data System (ADS)

    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

  13. Neutron matter, symmetry energy and neutron stars

    SciTech Connect

    Stefano, Gandolfi; Steiner, Andrew W

    2016-01-01

    Recent progress in quantum Monte Carlo with modern nucleon-nucleon interactions have enabled the successful description of properties of light nuclei and neutron-rich matter. Of particular interest is the nuclear symmetry energy, the energy cost of creating an isospin asymmetry, and its connection to the structure of neutron stars. Combining these advances with recent observations of neutron star masses and radii gives insight into the equation of state of neutron-rich matter near and above the saturation density. In particular, neutron star radius measurements constrain the derivative of the symmetry energy.

  14. A method for evaluating personal dosemeters in workplace with neutron fields.

    PubMed

    de Freitas Nascimento, Luana; Cauwels, Vanessa; Vanhavere, Filip

    2012-04-01

    Passive detectors, as albedo or track-etch, still dominate the field of neutron personal dosimetry, mainly due to their low-cost, high-reliability and elevated throughput. However, the recent appearance in the market of electronic personal dosemeters for neutrons presents a new option for personal dosimetry. In addition to passive detectors, electronic personal dosemeters necessitate correction factors, concerning their energy and angular response dependencies. This paper reports on the results of a method to evaluate personal dosemeters for workplace where neutrons are present. The approach here uses few instruments and does not necessitate a large mathematical workload. Qualitative information on the neutron energy spectrum is acquired using a simple spectrometer (Nprobe), reference values for H*(10) are derived from measurements with ambient detectors (Studsvik, Berthold and Harwell) and angular information is measured using personal dosemeters (electronic and bubbles dosemeters) disposed in different orientations on a slab phantom. PMID:21565843

  15. Neutron-induced 2.2 MeV background in gamma ray telescopes

    NASA Technical Reports Server (NTRS)

    Zanrosso, E. M.; Long, J. L.; Zych, A. D.; White, R. S.

    1985-01-01

    Neutron-induced gamma ray production is an important source of background in Compton scatter gamma ray telescopes where organic scintillator material is used. Most important is deuteron formation when atmospheric albedo and locally produced neutrons are thermalized and subsequently absorbed in the hydrogenous material. The resulting 2.2 MeV gamma ray line radiation essentially represents a continuous isotropic source within the scintillator itself. Interestingly, using a scintillator material with a high hydrogen-to-carbon ratio to minimize the scintillator material with a high hydrogen-to-carbon ratio to minimize the neutron-induced 4.4 MeV carbon line favors the np reaction. The full problem of neutron-induced background in Compton scatter telescopes has been previously discussed. Results are presented of observations with the University of California balloon-borne Compton scatter telescope where the 2.2 MeV induced line emission is prominently seen.

  16. Calculations of neutron flux spectra induced in the earth's atmosphere by galactic cosmic rays.

    NASA Technical Reports Server (NTRS)

    Armstrong, T. W.; Chandler, K. C.; Barish, J.

    1973-01-01

    Calculations have been carried out to determine the neutron flux induced in the earth's atmosphere by galactic protons and alpha particles at solar minimum for a geomagnetic latitude of 42 N. Neutron flux spectra in the energy range from about 10 to the minus 8th to about 100,000 MeV at various depths in the atmosphere were calculated by using Monte Carlo and discrete ordinates methods, and various comparisons with experimental data are presented. The magnitude and shape of the calculated neutron leakage spectrum at the particular latitude considered support the theory that the cosmic ray albedo neutron decay (Crand) mechanism is the source of the protons trapped in the inner radiation belt.

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

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Astrophysics Data System (ADS)

    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

  20. Neutron reflecting supermirror structure

    DOEpatents

    Wood, James L.

    1992-01-01

    An improved neutron reflecting supermirror structure comprising a plurality of stacked sets of bilayers of neutron reflecting materials. The improved neutron reflecting supermirror structure is adapted to provide extremely good performance at high incidence angles, i.e. up to four time the critical angle of standard neutron mirror structures. The reflection of neutrons striking the supermirror structure at a high critical angle provides enhanced neutron throughput, and hence more efficient and economical use of neutron sources. One layer of each set of bilayers consist of titanium, and the second layer of each set of bilayers consist of an alloy of nickel with carbon interstitially present in the nickel alloy.

  1. NEUTRONIC REACTOR

    DOEpatents

    Stewart, H.B.

    1958-12-23

    A nuclear reactor of the type speclfically designed for the irradiation of materials is discussed. In this design a central cyllndrical core of moderating material ls surrounded by an active portlon comprlsed of an annular tank contalning fissionable material immersed ln a liquid moderator. The active portion ls ln turn surrounded by a reflector, and a well ls provided in the center of the core to accommodate the materlals to be irradiated. The over-all dimensions of the core ln at least one plane are equal to or greater than twice the effective slowing down length and equal to or less than twlce the effective diffuslon length for neutrons in the core materials.

  2. NEUTRONIC REACTORS

    DOEpatents

    Wigner, E.P.; Young, G.J.

    1958-10-14

    A method is presented for loading and unloading rod type fuel elements of a neutronic reactor of the heterogeneous, solld moderator, liquid cooled type. In the embodiment illustrated, the fuel rods are disposed in vertical coolant channels in the reactor core. The fuel rods are loaded and unloaded through the upper openings of the channels which are immersed in the coolant liquid, such as water. Unloading is accomplished by means of a coffer dam assembly having an outer sleeve which is placed in sealing relation around the upper opening. A radiation shield sleeve is disposed in and reciprocable through the coffer dam sleeve. A fuel rod engaging member operates through the axial bore in the radiation shield sleeve to withdraw the fuel rod from its position in the reactor coolant channel into the shield, the shield snd rod then being removed. Loading is accomplished in the reverse procedure.

  3. Direct Measurement of Neutron-Neutron Scattering

    SciTech Connect

    Sharapov, E.I.; Furman, W.I.; Lychagin, W.I.; Muzichka, G.V.; Nekhaev, G.V.; Safronov, Yu.V.; Shvetsov, V.N.; Strelkov, A.V.; Bowman, C.D.; Crawford, B.E.; Stephenson, S.L.; Howell, C.R.; Tornow, W.; Levakov, B.G.; Litvin, V.I.; Lyzhin, A.E.; Magda, E.P.; Mitchell, G.E.

    2003-08-26

    In order to resolve long-standing discrepancies in indirect measurements of the neutron-neutron scattering length ann and contribute to solving the problem of the charge symmetry of the nuclear force, the collaboration DIANNA (Direct Investigation of ann Association) plans to measure the neutron-neutron scattering cross section {sigma}nn. The key issue of our approach is the use of the through-channel in the Russia reactor YAGUAR with a peak neutron flux of 10{sup 18} /cm2/s. The proposed experimental setup is described. Results of calculations are presented to connect {sigma}nn with the nn-collision detector count rate and the neutron flux density in the reactor channel. Measurements of the thermal neutron fields inside polyethylene converters show excellent prospects for the realization of the direct nn-experiment.

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

    NASA Technical Reports Server (NTRS)

    Moody, E. G.; King, M. D.; Platnick, S.; Schaaf, C. B.; Gao, F.

    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. The availability of global albedo data over a large range of spectral channels and at high spatial resolution has dramatically improved with the launch of the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard NASA s Earth Observing System (EOS) Terra spacecraft in December 1999. However, lack of spatial and temporal coverage due to cloud and snow effects can preclude utilization of official products in production and research studies. We report on a technique used to fill incomplete MOD43 albedo data sets with the intention of providing complete value-added maps. The technique is influenced by the phenological concept that within a certain area, a pixel s ecosystem class should exhibit similar growth cycle events over the same time period. The shape of an area s phenological temporal curve can be imposed upon existing pixel-level data to fill missing temporal points. The methodology will be reviewed by showcasing 2001 global and regional results of complete albedo and NDVl data sets.

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

    PubMed

    Pistone, Kristina; Eisenman, Ian; Ramanathan, V

    2014-03-01

    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.

  6. Evaluation of the MODIS Albedo Product over a Heterogeneous Agricultural Area

    NASA Technical Reports Server (NTRS)

    Sobrino, Jose Antonio; Franch, B.; Oltra-Carrio, R.; Vermote, E. F.; Fedele, E.

    2013-01-01

    In this article, the Moderate Resolution Imaging Spectroradiometer (MODIS) Bidirectional Reflectance Distribution Function (BRDF)/Albedo product (MCD43) is evaluated over a heterogeneous agricultural area in the framework of the Earth Observation: Optical Data Calibration and Information Extraction (EODIX) project campaign, which was developed in Barrax (Spain) in June 2011. In this method, two models, the RossThick-LiSparse-Reciprocal (RTLSR) (which corresponds to the MODIS BRDF algorithm) and the RossThick-Maignan-LiSparse-Reciprocal (RTLSR-HS), were tested over airborne data by processing high-resolution images acquired with the Airborne Hyperspectral Scanner (AHS) sensor. During the campaign, airborne images were retrieved with different view zenith angles along the principal and orthogonal planes. Comparing the results of applying the models to the airborne data with ground measurements, we obtained a root mean square error (RMSE) of 0.018 with both RTLSR and RTLSR-HS models. The evaluation of the MODIS BRDF/Albedo product (MCD43) was performed by comparing satellite images with AHS estimations. The results reported an RMSE of 0.04 with both models. Additionally, taking advantage of a homogeneous barley pixel, we compared in situ albedo data to satellite albedo data. In this case, the MODIS albedo estimation was (0.210 +/- 0.003), while the in situ measurement was (0.204 +/- 0.003). This result shows good agreement in regard to a homogeneous pixel.

  7. Diurnal variations of outgoing longwave radiation and albedo from ERBE scanner data

    NASA Technical Reports Server (NTRS)

    Hartmann, Dennis L.; Kowalewsky, Karen J.; Michelsen, Marc L.

    1991-01-01

    The scanning instruments of the Earth Radiation Budget Experiment provide measurements of instantaneous broadband albedo and outgoing longwave radiation (OLR) with a spatial resolution of about 50 km. Data from the Earth Radiation Budget Satellite (ERBS), which is in an orbit that precesses through local time at the rate of one hour every three days, can be used to describe the mean, hourly diurnal variations in the distribution of OLR and albedo on this scale. Much of this variation is caused by cloud type and amount changes. Two-dimensional histograms show the coevolution of OLR and albedo with the diurnal cycle, and the distribution of albedo-OLR pairings associated with the cloud distribution in a particular region and season. The albedo-OLR pairing characterizes a cloud type and determines its net effect on the energy balance at the top of the atmosphere. Diurnal variations in cloud type and amount in many regions are sufficient to cause substantial errors in radiation budget quantities and cloud properties estimated from observations taken from a single sun-synchronous orbit. Errors in estimated net radiation can be as large as 50 W/sq m for oceanic stratus regions and for land regions during summer.

  8. Radiative forcing over the conterminous United States due to contemporary land cover land use albedo change

    USGS Publications Warehouse

    Barnes, Christopher; Roy, David P.

    2008-01-01

    Recently available satellite land cover land use (LCLU) and albedo data are used to study the impact of LCLU change from 1973 to 2000 on surface albedo and radiative forcing for 36 ecoregions covering 43% of the conterminous United States (CONUS). Moderate Resolution Imaging Spectroradiometer (MODIS) snow-free broadband albedo values are derived from Landsat LCLU classification maps located using a stratified random sampling methodology to estimate ecoregion estimates of LCLU induced albedo change and surface radiative forcing. The results illustrate that radiative forcing due to LCLU change may be disguised when spatially and temporally explicit data sets are not used. The radiative forcing due to contemporary LCLU albedo change varies geographically in sign and magnitude, with the most positive forcings (up to 0.284 Wm−2) due to conversion of agriculture to other LCLU types, and the most negative forcings (as low as −0.247 Wm−2) due to forest loss. For the 36 ecoregions considered a small net positive forcing (i.e., warming) of 0.012 Wm−2 is estimated.

  9. The Earth's Albedo - The other side to Tyndall's contributions to climate

    NASA Astrophysics Data System (ADS)

    Stephens, G. L.

    2011-12-01

    Graeme L Stephens Director, Center for Climate Sciences and Juilin Li Jet Propulsion Laboratory California Institute of Technology 4800 Oak Grove Drive Mail Stop: 233-300 Pasadena, CA 91109 John Tyndall's contributions to understanding earth's climate are mostly thought of in terms of the planets absorbing gases and the greenhouse effect. However, there is another aspect of his contributions that lie in the so-called Tyndall effect that relates to scattering of sunlight by large particles. Such scattering is an important contribution to Earth's albedo. In the days of Tyndall's foundational work on Earth's greenhouse effect, the Earth's albedo was thought to be about 50%. Satellite observations in the late 1960s and early 1970s however led to a revision downwards to about 30%. Modern satellite observations suggest that more than half of this amount comes from reflection of sunlight by clouds. What is remarkable though is that the planet's albedo is almost invariant over the time of advanced satellite measurements despite large variability of cloudiness that has occurred. Furthermore, model projections imply that the albedo of Earth is not expected to change over the projected course of global warming. Thus a number of fundamental question emerge - why is the planet's albedo so constant, what factors really control its change and are there natural processes that act to buffer those changes expected from changes to clouds and other factor within the atmosphere? This talk will address these questions.

  10. Post-fire influences of snag attrition on albedo and radiative forcing

    NASA Astrophysics Data System (ADS)

    O'Halloran, T. L.; Acker, S. A.; Joerger, V.; Kertis, J.; Law, B. E.

    2014-12-01

    We examine albedo perturbation and associated radiative forcing after a high-severity fire in a mature forest in the Oregon Cascade Range. Correlations between post-fire albedo and seedling, sapling, and standing dead tree (snag) density were investigated across fire severity classes and seasons for years 4-15 after fire. Albedo perturbation was 14 times larger in winter compared to summer and increased with fire severity class for the first several years after fire. Summer and winter albedo perturbation increased approximately linearly over the study period. Albedo correlations were strongest with snags, and significant in all fire classes in both summer and winter. The resulting annual radiative forcing at the top of the atmosphere decreased (became more negative) linearly for the first 15 years after fire. These results suggest that snags, more than recovering vegetation, can control the shortwave energy balance of the burned land surface. As such, the dynamics of snag attrition may need to be included in coupled land-atmosphere models to properly represent the climate impacts of wildfire.

  11. Quantifying the influence of deep soil moisture on ecosystem albedo: The role of vegetation

    NASA Astrophysics Data System (ADS)

    Sanchez-Mejia, Zulia Mayari; Papuga, Shirley Anne; Swetish, Jessica Blaine; van Leeuwen, Willem Jan Dirk; Szutu, Daphne; Hartfield, Kyle

    2014-05-01

    As changes in precipitation dynamics continue to alter the water availability in dryland ecosystems, understanding the feedbacks between the vegetation and the hydrologic cycle and their influence on the climate system is critically important. We designed a field campaign to examine the influence of two-layer soil moisture control on bare and canopy albedo dynamics in a semiarid shrubland ecosystem. We conducted this campaign during 2011 and 2012 within the tower footprint of the Santa Rita Creosote Ameriflux site. Albedo field measurements fell into one of four Cases within a two-layer soil moisture framework based on permutations of whether the shallow and deep soil layers were wet or dry. Using these Cases, we identified differences in how shallow and deep soil moisture influence canopy and bare albedo. Then, by varying the number of canopy and bare patches within a gridded framework, we explore the influence of vegetation and soil moisture on ecosystem albedo. Our results highlight the importance of deep soil moisture in land surface-atmosphere interactions through its influence on aboveground vegetation characteristics. For instance, we show how green-up of the vegetation is triggered by deep soil moisture, and link deep soil moisture to a decrease in canopy albedo. Understanding relationships between vegetation and deep soil moisture will provide important insights into feedbacks between the hydrologic cycle and the climate system.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Albedos of homogeneous semi-infinite canopies - Comparison of two-stream analytic and numerical solutions

    NASA Technical Reports Server (NTRS)

    Dickinson, Robert E.; Sellers, Piers J.; Kimes, Daniel S.

    1987-01-01

    The albedo of plant canopies is treated as a problem in radiative transfer. Albedos calcualted from an iterative multistream numerical model are compared with those calculated with an analytic two-stream solution. With the assumption of a randomly homogeneous distribution of leaf positions and orientations and isotropic scattering by individual leaves, the single-scattering albedo of the canopy can be found analytically. This single-scattering solution is incorporated into the two-stream solution and used to benchmark the multistream numerical model in the single-scattering limit. Relative errors so established in the multistream model are O(0.3 percent) or less. The two-stream model is also found to be remarkably accurate, with the error in multiply scattered radiation O(5 percent) or less, corresponding to absolute errors in visible albedo of less than 0.001 and near-infrared albedo of less than or equal to 0.01. Thus the two-stream model should be adequate for many purposes, such as climate modeling, provided the assumptions of homogeneous canopy and isotropic scattering are not too unrealistic.

  14. Representation of vegetation effects on the snow-covered albedo in the Noah land surface model with multiple physics options

    NASA Astrophysics Data System (ADS)

    Park, S.; Park, S. K.

    2015-04-01

    Snow albedo plays a critical role in calculating the energy budget, but parameterization of the snow surface albedo is still under great uncertainty. It varies with snow grain size, snow cover thickness, snow age, forest shading factor and other variables. Snow albedo of forest is typically lower than that of short vegetation; thus snow albedo is dependent on the spatial distributions of characteristic land cover and on the canopy density and structure. In the Noah land surface model with multiple physics options (Noah-MP), almost all vegetation types in East Asia during winter have the minimum values of leaf area index (LAI) and stem area index (SAI), which are too low and do not consider the vegetation types. Because LAI and SAI are represented in terms of photosynthetic activeness, the vegetation effect rarely exerts on the surface albedo in winter in East Asia with only these parameters. Thus, we investigated the vegetation effects on the snow-covered albedo from observations and evaluated the model improvement by considering such effect. We found that calculation of albedo without proper reflection of the vegetation effect is mainly responsible for the large positive bias in winter. Therefore, we developed new parameters, called leaf index (LI) and stem index (SI), which properly manage the effect of vegetation structure on the winter albedo. As a result, the Noah-MP's performance in albedo has been significantly improved - RMSE is reduced by approximately 73%.

  15. Passive detectors for neutron personal dosimetry: state of the art.

    PubMed

    d'Errico, Francesco; Bos, Adrie J J

    2004-01-01

    Passive, solid-state detectors still dominate the field of neutron personal dosimetry, mainly thanks to their low cost, high reliability and elevated throughput. However, the recent appearance in the market of several electronic personal dosemeters for neutrons presents a challenge to the exclusive use of passive systems for primary or official dosimetry. This scenario drives research and development activities on passive dosemeters towards systems offering greater accuracy of response and lower detection limits. In addition, further applications and properties of the passive detectors, which are not met by the electronic devices, are also being explored. In particular, extensive investigations are in progress on the use of solid-state detectors for aviation and space dosimetry, where high-energy neutron fields are encountered. The present situation is also stimulating an acceleration in the development of international standards on performance and test requirements for passive dosimetry systems, which can expedite significantly the implementation of techniques in commercial personal dosimetry services. Upcoming standards will cover thermoluminescence albedo dosemeters, etched-track detectors, superheated emulsions and direct ion storage chambers, attesting to the level of maturity reached by these techniques. This work reviews the developments in the field of passive neutron dosimetry emerged since the previous Neutron Dosimetry Symposium, reporting on the current status of the subject and indicating the direction of ongoing research. PMID:15353644

  16. The Use of Data from Two Major Lunar Neutron Campaigns (Apollo 17 and Lunar Prospector) as a Benchmark for the Lunar Exploration Neutron Detector (LEND, on board LRO spacecraft)

    NASA Astrophysics Data System (ADS)

    Nandikotkur, G.; Sagdeev, R.; Usikov, D.; Milikh, G. M.; Chin, G.; McClanahan, T. P.; Starr, R. D.; Evans, L. G.; Boynton, W. V.; Harshman, K.; Droege, G.; Mitrofanov, I.; Litvak, M. L.; Sanin, A.; Golovin, D.

    2011-12-01

    The Apollo 17 Lunar Neutron Probe Experiment (LPNE, 1972) has opened an era of the neutron probing technique in studying the elemental composition and its stratification in lunar soil bombarded by Galactic Cosmic Rays. The unique in situ measurements provided a guideline for the next generation neutron experiments based on remote sensing from the orbit of Lunar Prospector around the Moon (LPNS,1998-1999). Current lunar neutron studies from LEND, on board LRO, constitute the next step in remote sensing by adding higher spatial resolution (for epithermal range of neutron energies) over Lunar surface and allowing us to "look" inside permanently shaded craters in a search of frozen water. This is why it is important to cross calibrate neutron detecting capabilities of these Lunar neutron campaigns and facilitate the creation of unique data set encompassing in situ and remote sensing.

  17. Neutron radiation dosimetry in high altitude flight personnel.

    PubMed

    Baily, P E

    1982-08-01

    In an attempt to determine cosmic radiation exposure in high altitude NASA flight personnel, eight WB-57F flight crewmen were monitored for a period of six months using a combination radiation dosimeter. Each dosimeter consisted of two thermoluminescent chips capable of measuring gamma dose and one Albedo and two Track Etch neutron dosimeters. A total of 78 flights were monitored consisting of 251 flight hours at altitudes above 14 km (45,000 ft). The maximum yearly dose equivalent measured was 104 mrem, a value well below the Maximum Permissible Dose (MPD) of 5.0 rem/y for occupational exposures and 0.5 rem/y for members of the general public. A discussion of the theory and use of several types of neutron dosimeters is included. PMID:7181814

  18. Neutron energy measurements in emergency response applications

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Sanjoy; Guss, Paul; Hornish, Michael; Wilde, Scott; Stampahar, Tom; Reed, Michael

    2009-08-01

    We present significant results in recent advances in the measurement of neutron energy. Neutron energy measurements are a small but significant part of radiological emergency response applications. Mission critical information can be obtained by analyzing the neutron energy given off from radioactive materials. In the case of searching for special nuclear materials, neutron energy information from an unknown source can be of importance. At the Remote Sensing Laboratory (RSL) of National Security Technologies, LLC, a series of materials, viz., liquid organic scintillator (LOS), Lithium Gadolinium Borate (LGB) or Li6Gd(BO3)3 in a plastic matrix, a recently developed crystal of Cesium Lithium Yttrium Chloride, Cs2LiYCl6: Ce (called CLYC)[1], and normal plastic scintillator (BC-408) with 3He tubes have been used to study their effectiveness as a portable neutron energy spectrometer. Comparisons illustrating the strengths of the various materials will be provided. Of these materials, LGB offers the ability to tailor its response to the neutron spectrum by varying the isotopic composition of the key constituents (Lithium, Gadolinium [Yttrium], and Boron). All three of the constituent elements possess large neutron capture cross section isotopes for highly exothermic reactions. These compounds of composition Li6Gd(Y)(BO3)3 can be activated by Cerium ions Ce3+. CLYC, on the other hand, has a remarkable gamma response in addition to superb neutron discrimination, comparable to that of Europium-doped Lithium Iodide (6LiI: Eu). Comparing these two materials, CLYC has higher light output (4500 phe/MeV) than that from 6LiI: Eu and shows better energy resolution for both gamma and neutron pulse heights. Using CLYC, gamma energy pulses can be discriminated from the neutron signals by simple pulse height separation. For the cases of both LGB and LOS, careful pulse shape discrimination is needed to separate the gamma energy signals from neutron pulses. Both analog and digital

  19. Neutron scattering gets short-changed

    NASA Astrophysics Data System (ADS)

    Skipper, Neal

    2009-10-01

    In your excellent coverage of the latest round of funding cuts by the UK's Science and Technology Facilities Council (STFC), you highlight the problems that will be caused by the severely reduced operations of the ISIS neutron source (August p7 and p15). As a frequent neutron scatterer, I can only echo your sentiment that it makes no sense at all for the UK to build a superb new facility like the £148m ISIS second target station if it can be switched on for only 120 days per year.

  20. A semianalytical algorithm for quantitatively estimating sediment and atmospheric deposition flux from MODIS-derived sea ice albedo in the Bohai Sea, China

    NASA Astrophysics Data System (ADS)

    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. Using response characteristics of neutron measurement devices to improve neutron dosimetry

    SciTech Connect

    Casson, W.H.; Hsu, H.H.; Hoffman, J.M.

    1995-12-01

    Recent administrative restrictions on personnel dose equivalent have resulted in increased pressure to more accurately report the neutron component without the traditional conservative added factors which sometimes inflate the reported values. Improvements include a new albedo neutron dosimeter which is capable of some limited energy discrimination. Also, additional emphasis has been placed on improving field measurements using traditional survey instrumentation and specialized spectroscopic techniques such as tissue equivalent proportional counters, Bonner spheres, and a modified 9 inches to 3 inches ratio technique. Improvements in these techniques along with a better understanding of the response of the TLD system have resulted in substantial reduction in the reported dose equivalent by improving the accuracy of the dosimeter system. The response characteristics of the TLD system and other instrumentation are obtained through modeling with the Monte Carlo code MCNP-4A. Neutron fields in work-areas are initially characterized with Bonner spheres. Routine updates are accomplished using a modified 9 inches to 3 inches ratio technique. These measurements are then used to predict the response of the TLD system when worn in that area. Correction curves are derived for the principal spectrum with various fractions of moderated or reflected neutrons. Work assignments are tracked through a database systems which is used to determine the principal spectrum that results in the neutron dose equivalent. The energy discrimination capability of the TLD system is used with the correction curve to derive an average correction appropriate to the readings of the dosimeter thus giving an energy corrected dose equivalent for the individual.

  2. On Spectral Invariance of Single Scattering Albedo for Weakly Absorbing Wavelengths

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    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, omega(sub O lambda(r) and omega(sub O lambda(r (sub O)), 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 omega(sub O lambda(r) via one known spectrum omega(sub O lambda(r(sub O)). The note provides a simple physical explanation of the discovered relationship. In addition to water droplets, similar linear relationships were found for the single scattering albedo of non-spherical ice crystals.

  3. Influence of single scattering albedo on reflected and transmitted light from clouds.

    PubMed

    Plass, G N; Kattawar, G W

    1968-02-01

    The dependence of the reflected and transmitted light from clouds on the single scattering albedo omega(0) is studied. The multiple scattered path of the photon in the cloud is accurately simulated by Monte Carlo techniques. When the cloud is optically thin and the surface albedo A = 0, the reflected and transmitted radiances vary nearly as omega(0) for fixed angles of incidence and observation and they depend strongly on the value of A. As omega(0) becomes small and for optically thick clouds, the reflected radiance approaches more closely the value calculated from the single scattering function. As the absorption increases, the transmitted radiance at the zenith becomes larger relative to the value near the horizon. Also, as the optical thickness increases, the maximum of the transmitted radiance moves from the incident direction toward the zenith. The variations in the flux, cloud albedo, and the mean optical path are also discussed.

  4. Effects of dust and black carbon on albedo of the Greenland ablation zone

    NASA Astrophysics Data System (ADS)

    Boggild, C. E.; Warren, S. G.; Brandt, R. E.; Brown, K. J.

    2006-12-01

    Recent thinning of the perimeter of the Greenland ice sheet has prompted several studies that are focused on identifying possible mechanisms. Surface melting in the ablation zone is known to be highly sensitive to changes in the surface albedo. However, explanations for the variable albedo of the ablation zone in Greenland have not yet been established because ground validation is often difficult due to the inaccessibility of much of the marginal zone. The emergence and melting of old ice in the ablation zone creates a surface layer of dust that was originally deposited with snowfall high on the ice sheet. This debris cover is augmented by locally-derived windblown sediment. Subsequently, the surface dust particles often aggregate together to form millimeter to centimeter scale clumps that melt into the ice, creating cryoconite holes. The debris in the cryoconite holes becomes hidden from sunlight, thus raising the area-averaged albedo. These processes were examined on the readily accessible ice sheet margin of northeast Greenland in Kronprins Christians Land (80 N, 24 W). To assess the effects of dust and black carbon deposition on ice albedo, spectral albedo measurements across the solar spectrum at ultraviolet, visible and near-infrared wavelengths were taken on snow, slush, ice hummocks, debris-covered ice and cryoconite-studded ice. In addition, albedo measurements were likewise taken on the debris in the cryoconite holes. Areal distribution of the aforementioned surface types was estimated as a function of distance from the ice edge (330 m elevation). Ablation rates were measured on a 5-km transect from the ice margin that spanned both Pleistocene and Holocene ice, eventually terminating in the slush zone (550 m). Impurity concentrations (per unit area of surface and per unit volume for snow and subsurface ice) were measured. Snow was also collected for analysis of impurities at distances of 40 and 90 km from the margin, at elevations of 950 and 1440 m

  5. UV irradiance and albedo at Union Glacier Camp (Antarctica): a case study.

    PubMed

    Cordero, Raul R; Damiani, Alessandro; Ferrer, Jorge; Jorquera, Jose; Tobar, Mario; Labbe, Fernando; Carrasco, Jorge; Laroze, David

    2014-01-01

    We report on the first spectral measurements of ultraviolet (UV) irradiance and the albedo at a Camp located in the southern Ellsworth Mountains on the broad expanse of Union Glacier (700 m altitude, 79° 46' S; 82° 52'W); about 1,000 km from the South Pole. The measurements were carried out by using a double monochromator-based spectroradiometer during a campaign (in December 2012) meant to weight up the effect of the local albedo on the UV irradiance. We found that the albedo measured at noon was about 0.95 in the UV and the visible part of the spectrum. This high surface reflectivity led to enhancements in the UV index under cloudless conditions of about 50% in comparison with snow free surfaces. Spectral measurements carried out elsewhere as well as estimates retrieved from the Ozone Monitoring Instrument (OMI) were used for further comparisons. PMID:24598906

  6. UV Irradiance and Albedo at Union Glacier Camp (Antarctica): A Case Study

    PubMed Central

    Cordero, Raul R.; Damiani, Alessandro; Ferrer, Jorge; Jorquera, Jose; Tobar, Mario; Labbe, Fernando; Carrasco, Jorge; Laroze, David

    2014-01-01

    We report on the first spectral measurements of ultraviolet (UV) irradiance and the albedo at a Camp located in the southern Ellsworth Mountains on the broad expanse of Union Glacier (700 m altitude, 79° 46′ S; 82° 52′W); about 1,000 km from the South Pole. The measurements were carried out by using a double monochromator-based spectroradiometer during a campaign (in December 2012) meant to weight up the effect of the local albedo on the UV irradiance. We found that the albedo measured at noon was about 0.95 in the UV and the visible part of the spectrum. This high surface reflectivity led to enhancements in the UV index under cloudless conditions of about 50% in comparison with snow free surfaces. Spectral measurements carried out elsewhere as well as estimates retrieved from the Ozone Monitoring Instrument (OMI) were used for further comparisons. PMID:24598906

  7. UV irradiance and albedo at Union Glacier Camp (Antarctica): a case study.

    PubMed

    Cordero, Raul R; Damiani, Alessandro; Ferrer, Jorge; Jorquera, Jose; Tobar, Mario; Labbe, Fernando; Carrasco, Jorge; Laroze, David

    2014-01-01

    We report on the first spectral measurements of ultraviolet (UV) irradiance and the albedo at a Camp located in the southern Ellsworth Mountains on the broad expanse of Union Glacier (700 m altitude, 79° 46' S; 82° 52'W); about 1,000 km from the South Pole. The measurements were carried out by using a double monochromator-based spectroradiometer during a campaign (in December 2012) meant to weight up the effect of the local albedo on the UV irradiance. We found that the albedo measured at noon was about 0.95 in the UV and the visible part of the spectrum. This high surface reflectivity led to enhancements in the UV index under cloudless conditions of about 50% in comparison with snow free surfaces. Spectral measurements carried out elsewhere as well as estimates retrieved from the Ozone Monitoring Instrument (OMI) were used for further comparisons.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. The price of snow: albedo valuation and a case study for forest management

    NASA Astrophysics Data System (ADS)

    Lutz, David A.; Howarth, Richard B.

    2015-06-01

    Several climate frameworks have included the role of carbon storage in natural landscapes as a potential mechanism for climate change mitigation. This has resulted in an incentive to grow and maintain intact long-lived forest ecosystems. However, recent research has suggested that the influence of albedo-related radiative forcing can impart equal and in some cases greater magnitudes of climate mitigation compared to carbon storage in forests where snowfall is common and biomass is slow-growing. While several methodologies exist for relating albedo-associated radiative forcing to carbon storage for the analysis of the tradeoffs of these ecosystem services, they are varied, and they have yet to be contrasted in a case study with implications for future forest management. Here we utilize four methodologies for calculating a shadow price for albedo radiative forcing and apply the resulting eight prices to an ecological and economic forest model to examine the effects on optimal rotation periods on two different forest stands in the White Mountain National Forest in New Hampshire, USA. These pricing methodologies produce distinctly different shadow prices of albedo, varying from a high of 9.36 × 10-4 and a low of 1.75 × 10-5 w-1yr-1 in the initial year, to a high of 0.019 and a low of 3.55 × 10-4 w-1yr-1 in year 200 of the simulation. When implemented in the forest model, optimal rotation periods also varied considerably, from a low of 2 to a high of 107 years for a spruce-fir stand and from 35 to 80 years for a maple-beech-birch stand. Our results suggest that the choice of climate metrics and pricing methodologies for use with forest albedo alter albedo prices considerably, may substantially adjust optimal rotation period length, and therefore may have consequences with respect to forest land cover change.

  11. Radiative Forcings from Albedo and Carbon Dynamics after Disturbance in Massachusetts Forests

    NASA Astrophysics Data System (ADS)

    MacLean, R. G.; Williams, C. A.

    2014-12-01

    Recent efforts have sought to compare and contrast the radiative forcings excited by forest disturbances due to both biogeochemical and biogeophysical mechanisms (Bonan et al., 2008) using either in situ measurements (e.g. Randerson et al., 2005; Randerson et al., 2006) or modeling (e.g. Brovkin et al., 2004). Study of boreal forest disturbances led to the important finding that the albedo increase from snow exposure after a canopy destroying fire offsets the warming from carbon emissions (Randerson et al. 2005). Similar study is lacking for temperate forests, leading to uncertainty about the net effect of albedo and carbon forcings following their disturbance. This work quantifies the gross and net radiative forcings from albedo and carbon mechanisms at two clear cut sites in Harvard Forest, Massachusetts, one a Norway spruce plantation clear cut in 2008 and the other a red pine plantation cleared in 1990. Carbon fluxes are estimated from detailed biomass inventories at both sites, as well as additional measurement with eddy covariance at the 2008 clearing. Associated radiative forcing is estimated with conventional methods estimating the perturbation to CO2 in the atmosphere and its lifetime considering ocean uptake (pulse response) and vegetation regrowth. Albedo change is assessed with Landsat derived albedo for both sites, as well as in situ measurements at the 2008 clearing. Associated radiative forcing is estimated with the model-derived radiative kernels provided by Shell et al (2008). From these extensive records we offer an in depth characterization of albedo and carbon forcings immediately following disturbance through to canopy closure and stem exclusion stages of forest growth in a mid-latitude temperate forest region.

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

    SciTech Connect

    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.

  13. Titan-Like Exoplanets: Variations in Geometric Albedo and Effective Transit Height with Haze Production Rate

    NASA Technical Reports Server (NTRS)

    Checlair, Jade; McKay, Christopher P.; Imanaka, Hiroshi

    2016-01-01

    Extensive studies characterizing Titan present an opportunity to study the atmospheric properties of Titan-like exoplanets. Using an existing model of Titan's atmospheric haze, we computed geometric albedo spectra and effective transit height spectra for six values of the haze production rate (zero haze to twice present) over a wide range of wavelengths (0.2-2 microns). In the geometric albedo spectra, the slope in the UV-visible changes from blue to red when varying the haze production rate values from zero to twice the current Titan value. This spectral feature is the most effective way to characterize the haze production rates. Methane absorption bands in the visible-NIR compete with the absorbing haze, being more prominent for smaller haze production rates. The effective transit heights probe a region of the atmosphere where the haze and gas are optically thin and that is thus not effectively probed by the geometric albedo. The effective transit height decreases smoothly with increasing wavelength, from 376 km to 123 km at 0.2 and 2 microns, respectively. When decreasing the haze production rate, the methane absorption bands become more prominent, and the effective transit height decreases with a steeper slope with increasing wavelength. The slope of the geometric albedo in the UV-visible increases smoothly with increasing haze production rate, while the slope of the effective transit height spectra is not sensitive to the haze production rate other than showing a sharp rise when the haze production rate increases from zero. We conclude that geometric albedo spectra provide the most sensitive indicator of the haze production rate and the background Rayleigh gas. Our results suggest that important and complementary information can be obtained from the geometric albedo and motivates improvements in the technology for direct imaging of nearby exoplanets.

  14. Surface albedo observations of Hudson Bay (Canada) landfast sea ice during the spring melt

    NASA Astrophysics Data System (ADS)

    Ehn, J. K.; Granskog, M. A.; Papakyriakou, T.; Galley, R.; Barber, D. G.

    The shortwave albedo is a major component in determining the surface energy balance and thus the evolution of the spring melt cycle. As the melt commences, the ice is partitioned into multiple surface types ranging from highly reflective white ice to absorptive blue ice. The reflectance from these surfaces shows significant spatial and temporal variability. Spectral albedo measurements were made at six different sites encompassing these two surface types, from 19 March to 3 May 2005, on 1.5 m thi