WorldWideScience

Sample records for circulation albedo instability

  1. Modified ocean circulation, albedo instability and ice-flow instability. Risks of non-linear climate change

    Energy Technology Data Exchange (ETDEWEB)

    Ham, J. van; Beer, R.J. van; Builtjes, P.J.H.; Roemer, M.G.M. [TNO Inst. of Environmental Sciences, Delft (Netherlands); Koennen, G.P. [KNMI, Royal Netherlands Meteorological Inst., de Bilt (Netherlands); Oerlemans, J. [Utrecht Univ. (Netherlands). Inst. for Meteorological and Atmospheric Research

    1995-12-31

    In this presentation part of an investigation is described into risks for climate change which are presently not adequately covered in General Circulation Models. In the concept of climate change as a result of the enhanced greenhouse effect it is generally assumed that the radiative forcings from increased concentrations of greenhouse gases (GHG) will result in a proportional or quasilinear global warming. Though correlations of this kind are known from palaeoclimate research, the variability of the climate seems to prevent the direct proof of a causal relation between recent greenhouse gas concentrations and temperature observations. In order to resolve the issue the use of General Circulation Models (GCMs), though still inadequate at present, is indispensable. Around the world some 10 leading GCMs exist which have been the subject of evaluation and intercomparison in a number of studies. Their results are regularly assessed in the IPCC process. A discussion on their performance in simulating present or past climates and the causes of their weak points shows that the depiction of clouds is a major weakness of GCMs. A second element which is virtually absent in GCMs are the feedbacks from natural biogeochemical cycles. These cycles are influenced by man in a number of ways. GCMs have a limited performance in simulating regional effects on climate. Moreover, albedo instability, in part due to its interaction with cloudiness, is only roughly represented. Apparently, not all relevant processes have been included in the GCMs. That situation constitutes a risk, since it cannot be ruled out that a missing process could cause or trigger a non-linear climate change. In the study non-linear climate change is connected with those processes which could provide feedbacks with a risk for non-monotonous or discontinuous behaviour of the climate system, or which are unpredictable or could cause rapid transitions

  2. Introduction to instabilities in natural circulation systems

    International Nuclear Information System (INIS)

    This lecture reviews the various natural circulation instabilities and their classification instabilities observed during various stages of natural circulation such as single-phase, boiling inception and fully developed two-phase flow are described. The mechanisms causing the instabilities are also briefly described. (author)

  3. Study on instability of natural circulation induced by subcooled boiling

    International Nuclear Information System (INIS)

    The best estimate system analysis code RELAP5 was used to analyze the natural circulation systems. The instability boundaries of one natural circulation system were obtained under different conditions. According to present results, most of the boundary points were found in the low subcooled boiling zone. The natural circulation systems can tolerate high subcooled boiling, and the disturbance of bubbles departing from the wall and condensing in the subcooled boiling region may be the inherent source to induce the instability, then the flow oscillations can become self-sustained and evolve because of the phase differences among system driving force, resistance and flow rate. (authors)

  4. Experimental study of flow instability in elongated natural circulation system

    International Nuclear Information System (INIS)

    The visual experimental study with water as the working substance was performed to investigate the operation behavior of a natural circulation system with elongated loops and long horizontal sections at atmospheric pressure, and the transient operation behavior and instability mechanism of typical experimental phenomenon (P= 1.46 kW) were given. The results show that the single natural circulation in elongated system with the great resistance coefficient is difficult to appear, but the heat can be removed by two-phase intermittent boiling. The driven force caused by the sub-cooled boiling can not drive the fluid to produce the effective natural circulation because of the great loop resistance, and the circular flow occurs only when the fluid in heat section produces the saturation boiling. The big loop resistance and flashing because of pressure drop in boiling process make the elongated natural circulation difficult to maintain a stable flow driven head and they are the fundamental reasons of intermittent boiling and strong flow instability. (authors)

  5. Non-conventional fishbone instabilities driven by circulating energetic ions

    International Nuclear Information System (INIS)

    A new kind of fishbone instability associated with circulating energetic ions is predicted. The considered instability is essentially the energetic particle mode and arises in plasmas with on-axis safety factor q0 close to unity and extended shear-free central core, separated from the wall by a region with finite shear. The frequency of this 'quasi-interchange' fishbone mode is ω∼k0sub(parallel)vα with k0sub(parallel) the parallel wave number in the shear-free core and vα the injection velocity of energetic ions. 'Infernal' fishbone modes with the same properties, but m/n>1 with m(n) the poloidal (toroidal) mode number, are investigated. A possibility to explain recent experimental observations of the m=2 fishbone oscillations accompanied by strong changes of the neutron emission during tangential neutral beam injection in the National Spherical Torus Experiment is shown. (author)

  6. GCM studies of the influence of vegetation on the general circulation: The role of albedo in modulating climate change. [GCM (general circulation model)

    Energy Technology Data Exchange (ETDEWEB)

    Dirmeyer, P.A.

    1992-01-01

    An atmospheric general circulation model (GCM) coupled to a simple biosphere model is used to examine the role of vegetation change on climate. Various biomes are substituted to simulate degradation of vegetation. It is found that albedo change plays a distinct role in the local decrease of rainfall. Changes in vegetation morphology and physiology do not cause catastrophic decreases in precipitation. Simulations of Amazon deforestation show that the climate response is very dependent on the amount of change in albedo between rainforest and degraded grass. Precipitation drops as albedo increases. The change in plant physiology decreases evapotranspiration, but moisture convergence increases to offset the drying. This compensation is a result of cloud feedback in this model, and does not occur when cloudiness is prescribed. Experiments with idealized boundary conditions show a similar dependence of rainfall on albedo in cases of tropical deforestation, subtropical desertification, and mid-latitude deforestation. In the topics, rainfall decreases over land only when reflectivity is increased, even when the rainforest is left intact. The monsoon precipitation of the subtropical experiment fails when savannah is replaced by high-albedo desert. When low-albedo desert is used, the decrease in summer rainfall is small. When mid-latitude forest is replaced by grassland, precipitation patterns shift, but net rainfall remains unchanged. Additional simulations of mid-latitude drought show that low soil moisture leads to moderate spring and summer droughts, but dry soil combined with dormant vegetation produces extremely severe droughts. Soil moisture deficits were more persistent when vegetation did not go dormant.

  7. Static Instability Analysis of the Natural Circulation Flow in a Passive Containment Cooling System

    International Nuclear Information System (INIS)

    When a severe accident occurs in a nuclear power plant, the containment pressure can increase up to 4 bar and, then, it can threaten the containment's integrity. To avoid such over-pressure in the containment, a passive containment cooling systems (PCCS) has been developed instead of existing active cooling systems. The PCCS can cool down the containment by using a natural circulation flow and, thus, flow instabilities may easily occur. It should be confirmed that both static and dynamic flow instabilities do not occur due to the system characteristics. In this study, mathematical models for the single- and two-phase natural circulation flows in a PCCS are developed. Using the flow models, static instability of the natural circulation flow is investigated. In this study, mathematical models for the single- and two-phase natural circulation flows in a PCCS are developed. Using the models, both single- and two-phase natural circulation flows were investigated in terms of static instability. It is shown that, for both cases, there is only one steady-state mass flow rate which satisfies the integrated momentum equation and the pressure drop along the natural circulation loop increases monotonically according to the mass flow rate. Therefore, it can be said that static instability doesn't exist in the PCCS natural circulation loop. Additional research is needed to investigate the dynamic instability of the PCCS natural circulation flow

  8. Thermalhydraulic instability analysis of a two phase natural circulation loop

    International Nuclear Information System (INIS)

    This work presents an analysis of a loop operating in natural circulation regime. Experiments were done in a rectangular closed circuit in one and two-phase flows. Numerical analysis were performed initially with the CIRNAT code and afterwards with RELAP5/MOD2. The limitations of CIRNAT were studied and new developments for this code are proposed. (author)

  9. An experimental study on the flow instabilities and critical heat flux under natural circulation

    International Nuclear Information System (INIS)

    This study has been carried out to investigate the hydrodynamic stabilities of natural circulation and to analyze Critical Heat Flux (CHF) characteristics for the natural and forced circulation. A low pressure experimental loop was constructed, and experiments under various conditions have been performed. In the experiments of the natural circulation, flow oscillations and the average mass flux have been observed. Several parameters such as heat flux, the inlet temperature of test section, friction valve opening and riser length have been varied in order to investigate their effects on the flow stability of the natural circulation system. The results show that the flow instability has strongly dependent on geometric conditions and operating parameters, the inlet temperature and the heat flux of test section. It was found that unstable region for the heat flux and the inlet temperature exists between the single-phase stable region of low heat and low inlet temperature and the two-phase stable region of very high heat flux and high inlet temperature. The CHF data from the natural and forced circulation experiments have been compared each other to identify the effects of the flow instabilities on the CHF for the natural circulation mode. The test conditions were low flow less than 70 kg/m2s of water in vertical round tube with diameter of 0.008m at near atmospheric pressure. In this study, no difference in CHF values is observed between natural and fored circulation. Since low flow usually has the oscillation characteristic of relatively low amplitude and high frequency, the effect of the flow instabilities on the CHF seems to be negligible

  10. Effect on inlet flow resistance on instabilities during startup transient in natural circulation BWRs

    International Nuclear Information System (INIS)

    The instability problem in current boiling water reactors (BWRs) has been investigated for several decades. The possibility of geyser instability during startup is considered a concern for natural circulation BWR design. Geyser instability is due to a condensation-induced instability observed in vertical systems that are heated at the bottom section. The startup transient was simulated in the Purdue University Multidimensional Integral Test Assembly (PUMA) facility for natural circulation BWRs with different values of core inlet flow loss coefficient. The simulation was performed by means of pressure and power scaling, considering the core inlet subcooling and the structure-stored energy differences between the model (PUMA) and the prototype (Simplified BWR). A novel core inlet plate was designed and installed so that the loss coefficient could be easily changed without disassembling the reactor pressure vessel. The simulation experiments demonstrated the pattern of the geyser oscillations during the single-to-two-phase natural circulation transition phase. The core inlet flow loss coefficient was not observed to have a significant effect on the geyser oscillations

  11. Investigation of natural circulation instability and transients in passively safe novel modular reactor

    Science.gov (United States)

    Shi, Shanbin

    The Purdue Novel Modular Reactor (NMR) is a new type small modular reactor (SMR) that belongs to the design of boiling water reactor (BWR). Specifically, the NMR is one third the height and area of a conventional BWR reactor pressure vessel (RPV) with an electric output of 50 MWe. The fuel cycle length of the NMR-50 is extended up to 10 years due to optimized neutronics design. The NMR-50 is designed with double passive engineering safety system. However, natural circulation BWRs (NCBWR) could experience certain operational difficulties due to flow instabilities that occur at low pressure and low power conditions. Static instabilities (i.e. flow excursion (Ledinegg) instability and flow pattern transition instability) and dynamic instabilities (i.e. density wave instability and flashing/condensation instability) pose a significant challenge in two-phase natural circulation systems. In order to experimentally study the natural circulation flow instability, a proper scaling methodology is needed to build a reduced-size test facility. The scaling analysis of the NMR uses a three-level scaling method, which was developed and applied for the design of the Purdue Multi-dimensional Integral Test Assembly (PUMA). Scaling criteria is derived from dimensionless field equations and constitutive equations. The scaling process is validated by the RELAP5 analysis for both steady state and startup transients. A new well-scaled natural circulation test facility is designed and constructed based on the scaling analysis of the NMR-50. The experimental facility is installed with different equipment to measure various thermal-hydraulic parameters such as pressure, temperature, mass flow rate and void fraction. Characterization tests are performed before the startup transient tests and quasi-steady tests to determine the loop flow resistance. The controlling system and data acquisition system are programmed with LabVIEW to realize the real-time control and data storage. The thermal

  12. Effect of neutronic feedback on flow instability of parallel double-channel natural circulation system

    International Nuclear Information System (INIS)

    The thermal-hydraulic system code RELAP5 was coupled with the TDOT-T 3D neutron kinetic code by parallel virtual machine (PVM). A parallel double-channel natural circulation boiling system was built by the coupled code and the instability boundary of the system was obtained. Two types of fuel with different geometries (flat plate-type fuel and pin-type fuel) were used in the analysis respectively, and the influences of neutronic feedback on density wave instability were analyzed. For the flat-plate type fuel system, it is found that the type 1 density wave oscillation (DWO) is suppressed by neutronic feedback significantly but the effect of neutronic feedback on type 2 DWO is weak. For the pin-type fuel system, the result shows that the effect of neutronic feedback on instability boundary of the system could be ignored. (authors)

  13. Thermal-hydraulic instability of the natural circulation BWR. 6. Occurrence condition and mechanism of the instability at the higher system pressure

    International Nuclear Information System (INIS)

    Experiments have been conducted to investigate thermal-hydraulic instabilities at the higher system pressure ranging from 1.0 to 7.2 MPa in a boiling natural circulation loop with a chimney. A test facility used in this experiments was designed and constructed to have non-dimensional values which are nearly equal to those of natural circulation BWR flow dynamics. Stability maps in reference to the system pressure, the channel inlet subcooling, and heat flux are presented. This instability mechanism is classified into the density wave oscillations that oscillation period is one to two times the time required for a bubble generated in the channel to travel through the chimney, and different from the flashing induced instability at the lower system pressure. The difference from other phenomena such as flow pattern transient oscillations and natural circulation oscillations are discussed by investigating the transient flow pattern and the response of momentum energy to driving force of the circulation. (author)

  14. An experimental study on the flow instabilities and critical heat flux under natural circulation

    International Nuclear Information System (INIS)

    This study has been carried out to investigate the hydrodynamic stabilities and Critical Heat Flux (CHF) characteristics for the natural and forced circulation. A low pressure experimental loop was constructed, and experiments under various conditions have been performed. In the experiments of the natural circulation, flow oscillations has been observed and the average mass flux under flow oscillation have been measured. Several parameters such as heat flux, the inlet temperature of test section, friction valve opening and riser length have been varied in order to investigate their effects on the flow stability of the natural circulation system. And the CHF data from low flow experiments, namely the natural and forced circulation, have been compared with each other to identify the effects of the flow instabilities on the CHF for the natural circulation mode. The test conditions for the CHF experiments were a low flow of less than 70 kg/m2s of water in a vertical round tube with diameter of 0.008 m at near atmospheric pressure. (author)

  15. Study on two-phase natural circulation flow instability by using Bifurcation Theory

    International Nuclear Information System (INIS)

    Through the concept of characteristic flow rate (CFR) a nonlinear analysis method--Bifurcation Theory could be used to analyze the thermo-hydraulic instability of Two-phase Natural Circulation Flow (TPNCF) systems. By constructing solution diagram of dynamic system based on CFR (Xu et al, 1994), the stable and unstable flow regimes can be described and the transition boundaries can be predicted in terms of real bifurcation method. The theoretical predictions agree fairly well with experimental results reported by Xu (1994). Further research for wider range of parameters is desirable

  16. Scaling modeling analysis of flow instability in U-tubes of steam generator under natural circulation

    International Nuclear Information System (INIS)

    Highlights: • The flow instability criterion (critical Reynolds number) in U-tubes of SG is derived. • The flow and heat transfer in the plenums and pipes and U-tubes are modeled. • A set of scaling modeling criteria are obtained by the integral analogy method. • The scaling modeling conditions in the SG primary side are given. - Abstract: It is found that under the natural circulation condition the reverse flow occurs in the U-tubes of steam generator (SG), which has large influence on the reactor safety. Though the reverse flow in SG is thought as the Ledinegg-type flow instability that is dominated by the flow resistance and gravitation pressure drop, it has not been studied well. Because of the complexity of the problem and the limitation of research conditions, it is a good way to perform the numerical simulation based on the scaling model. In the present work, based on one-dimensional N–S equations, the flow instability in U-tubes is investigated and the flow instability criterion (critical Reynolds number) is derived. The flow and heat transfer in the plenums and pipes are modeled by three-dimensional conservation equations. Using the integral analogy method, a set of scaling modeling criteria are also obtained, and the scaling modeling conditions in the stream generator primary side are given by the similar second theorem. The applicability of these conditions is discussed. The results can be used as the basic of the numerical simulation of the flow instability in U-tubes of SG

  17. Numerical Investigation of Startup Instabilities in Parallel-Channel Natural Circulation Boiling Systems

    Directory of Open Access Journals (Sweden)

    S. P. Lakshmanan

    2010-01-01

    Full Text Available The behaviour of a parallel-channel natural circulation boiling water reactor under a low-pressure low-power startup condition has been studied numerically (using RELAP5 and compared with its scaled model. The parallel-channel RELAP5 model is an extension of a single-channel model developed and validated with experimental results. Existence of in-phase and out-of-phase flashing instabilities in the parallel-channel systems is investigated through simulations under equal and unequal power boundary conditions in the channels. The effect of flow resistance on Type-I oscillations is explored. For nonidentical condition in the channels, the flow fluctuations in the parallel-channel systems are found to be out-of-phase.

  18. Nuclear coupled flow instability study for natural circulation BWR startup transient

    International Nuclear Information System (INIS)

    Natural circulation Boiling Water Reactor (BWR) startup transient was investigated in Purdue University Multidimensional Test Assembly (PUMA) facility based on a natural circulation BWR design. Strategy and results of the experiments, which consider the effects of void-reactivity and fuel heat conduction time constant, are discussed. Total reactivity is treated to be composed of two components: external reactivity due to control rod motion and void-reactivity. A detailed analysis for heat conduction problem is performed to derive dimensionless groups. Based on area-averaged heat conduction equations for pellet and clad regions, Fourier and Biot numbers are derived to simulate wall heat flux response. Power transient, which has been used for startup transient investigation without void-reactivity feedback is used to derive the control rod reactivity. Twelve conductivity probes are used to measure local void fraction inside core at three axial locations. The local void-fraction data is used to calculate volume average void fraction, which is used to calculate the voil-reactivity. A real-time Point Kinetic Model solver is implemented to PUMA heater power control program to determine power transient during startup. The results demonstrate that the inclusion of void-reactivity feedback worsen the scenario for startup instabilities and may cause large amplitude neutron flux oscillations. (author)

  19. Albedo Boundary

    Science.gov (United States)

    2003-01-01

    MGS MOC Release No. MOC2-510, 11 October 2003The sharp, nearly straight line that runs diagonally across the center of this April 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image is an albedo boundary. Albedois a term that refers to reflectance of sunlight. A surface with a low albedo is one that appears dark because it reflects less light than a high albedo (bright) surface. On Mars, albedo boundaries occur between two materials of differing texture, particle size, or composition, or some combination of these three factors. The boundary shown here is remarkable because it is so sharp and straight. This is caused by wind. Most likely, the entire surface was once covered with the lower-albedo (darker) material that is now seen in the upper half of the image. At some later time, wind stripped away this darker material from the surfaces in the lower half of the image. The difference in albedo here might be related to composition, and possibly particle size. This picture is located near the southwest rim of Schiaparelli Basin at 5.5oS, 345.9oW. The picture covers an area 3 km (1.9 mi) wide and is illuminated by sunlight from the left.

  20. Simulating Tropical Instability Waves in the Equatorial Eastern Pacific with a Coupled General Circulation Model

    Institute of Scientific and Technical Information of China (English)

    CHEN Xianyan; Masahide KIMOTO

    2009-01-01

    Satellite observations of SSTs have revealed the existence of unstable waves in the equatorial eastern Pacific and Atlantic oceans. These waves have a 20-40-day periodicity with westward phase speeds of 0.4-0.6 m s-1 and wavelengths of 1000-2000 km during boreal summer and fall.They are generally called tropical instability waves (TIWs).This study investigates TIWs simulated by a high-resolution coupled atmosphere-ocean general circulation model (AOGCM).The horizontal resolution of the model is 120 km in the atmosphere,and 30 km longitude by 20 km latitude in the ocean.Model simulations show good agreement with the observed main features associated with TIWs.The results of energetics analysis reveal that barotropic energy conversion is responsible for providing the main energy source for TIWs by extracting energy from the meridional shear of the climatological-mean equatorial currents in the mixed layer.This deeper and northward-extended wave activity appears to gain its energy through baroclinic conversion via buoyancy work,which further contributes to the asymmetric distribution of TIWs.It is estimated that the strong cooling effect induced by equatorial upwelling is partially (~30%-40%)offset by the equatorward heat flux due to TIWs in the eastern tropical Pacific during the seasons when TIWs are active.The atmospheric mixed layer just above the sea surface responds to the waves with enhanced or reduced vertical mixing.Furthermore,the changes in turbulent mixing feed back to sea surface evaporation,favoring the westward propagation of TIWs.The atmosphere to the south of the Equator also responds to TIWs in a similar way,although TIWs are much weaker south of the Equator.

  1. Hydrodynamic Instability and Dynamic Burnout in Natural Circulation Two-Phase Flow. An Experimental and Theoretical Study

    International Nuclear Information System (INIS)

    A theoretical model for predicting the threshold of instability for two phase flow in a natural circulation loop is presented. The model calculates the flow transient caused by a step disturbance of the heat input, and is based upon the conservation laws of mass, momentum and energy in one dimensional form. Empirical correlations are used in the model for estimating the void fractions and the two-phase flow pressure drops. The equations are solved numerically in a finite difference approximation coded for a digital computer. An experimental study of the hydrodynamic instability and dynamic burnout in two-phase flow has been performed in a natural circulation loop in the pressure range from 10 to 70 atg. The test sections were round ducts of 20, 30 and 36 mm inner diameter and 4890 mm heated length. The experimental results showed that within the ranges tested, the stability of the flow increases with increasing pressure and increasing throttling before the test section, but decreases with increasing Inlet subcooling and increasing throttling after the test section. Comparing the natural circulation burnout steam qualities with corresponding forced circulation data shoved that the former data were low by a factor up to 2.5. However, by applying inlet throttling of the flow the burnout values approached and finally coincided with the forced circulation data. The present experimental results as well as data available from other sources have been compared with the stability thresholds obtained with the theoretical model. The comparisons included circular, annular and rod cluster geometries, and the agreement between the experimental and theoretical stability limits was good. Finally the application of the experimental and theoretical results on the assessment of boiling heavy water reactor design is discussed

  2. Global Albedo

    Science.gov (United States)

    2002-01-01

    A new sensor aboard NASA?s Terra satellite is now collecting the most detailed and accurate measurements ever made of how much sunlight the Earth?s surface reflects back up into the atmosphere. By quantifying precisely our planet?s reflectivity, or albedo, the Moderate Resolution Imaging Spectroradiometer (MODIS) is helping scientists better understand and predict how various surface features influence both short-term weather patterns as well as longer-term climate trends. (Click to read the press release.) The colors in this image emphasize the albedo over the Earth?s land surfaces, ranging from 0.0 to 0.4. Areas colored red show the brightest, most reflective regions; yellows and greens are intermediate values; and blues and violets show relatively dark surfaces. White indicates where no data were available, and no albedo data are provided over the oceans. This image was produced using data composited over a 16-day period, from April 7-22, 2002. Image courtesy Crystal Schaaf, Boston University, based upon data processed by the MODIS Land Science Team

  3. Analytical study of nuclear-coupled density-wave instability in a natural circulation pressure tube type boiling water reactor

    International Nuclear Information System (INIS)

    An analytical model has been developed to study the nuclear-coupled density-wave instability in the Indian advanced heavy water reactor (AHWR) which is a natural circulation pressure tube type boiling water reactor. The model considers a point kinetics model for the neutron dynamics and a lumped parameter model for the fuel thermal dynamics along with the conservation equations of mass, momentum and energy and equation of state for the coolant. In addition, to study the effect of neutron interactions between different parts of the core, the model considers a coupled multipoint kinetics equation in place of simple point kinetics equation. Linear stability theory was applied to reveal the instability of in-phase and out-of-phase modes in the boiling channels of the AHWR. The results indicate that the stability behavior of the reactor is greatly influenced by the void reactivity coefficient, fuel time constant, radial power distribution and channel inlet orificing. The delayed neutrons were found to have a strong influence on the Type I and Type II instabilities observed at low and high channel powers, respectively. Also, it was found that the coupled multipoint kinetics model and the modal point kinetics model predict the same threshold power for out-of-phase instability if the coupling coefficient in the former model is half the eigen value separation between the fundamental and the first harmonic mode in the latter model. Decay ratio maps were predicted considering various operating parameters of the reactor, which are useful for its design. (orig.)

  4. Mars Albedo

    Science.gov (United States)

    2001-01-01

    These two views of Mars are derived from the MGS Thermal Emission Spectrometer (TES) measurements of global broadband (0.3 - 3.0 microns) visible and near-infrared reflectance, also known as albedo. The range of colors are in dimensionless units. The values are the ratio of the amount of electromagnetic energy reflected by the surface to the amount of energy incident upon it from the sun (larger values are brighter surfaces).The TES instrument was built by Santa Barbara Remote Sensing and is operated by Philip R. Christensen, of Arizona State University, Tempe, AZ.

  5. Simulations of tropical rainforest albedo: is canopy wetness important?

    OpenAIRE

    Silvia N.M. Yanagi; Costa, Marcos H.

    2011-01-01

    Accurate information on surface albedo is essential for climate modelling, especially for regions such as Amazonia, where the response of the regional atmospheric circulation to the changes on surface albedo is strong. Previous studies have indicated that models are still unable to correctly reproduce details of the seasonal variation of surface albedo. Therefore, it was investigated the role of canopy wetness on the simulated albedo of a tropical rainforest by modifying the IBIS canopy radia...

  6. Power Disturbances Close to Hydrodynamic Instability in Natural Circulation Two-Phase Flow

    International Nuclear Information System (INIS)

    In certain boiling reactor designs high positive void coefficients could exist and under certain circumstances cause instability. Control systems may therefore be desired. In such a controlled reactor there could remain superimposed low frequency power oscillations of some magnitude. The object of the current experiments in SKALVAN was to examine whether or not such slow oscillations could influence the hydrodynamic stability limit of the individual boiling channels. While operating the loop close to the threshold of hydrodynamic instability, the power was pulsed in the boiling channel. The pulse widths had a lower limit of 0.65 sec due to the contactor time constant. The square wave power oscillation amplitude ΔQ/Q was 12.2 %, and the interval T between the pulses was varied in the range 0 0/T 0 was the mass flow oscillation period. The corresponding mass flow oscillations remained damped for all disturbance periods which were examined. With minimum test section inlet restrictions the power level at instability was much lower than that at burnout conditions. At higher restrictions these phenomena occurred at approximately equivalent power levels. The experiments with minimum inlet restrictions were also performed beyond the instability threshold. In this case it was possible to exceed the nominal burnout point temporarily by 5 per cent or more for periods of the order of magnitude 1 second. Even now the boiling channel conditions were not so severely affected that the burnout detectors tripped, and the power disturbances caused low frequency modulated wave trains

  7. Validation of RELAP5 with sensitivity analysis for uncertainty assessment for natural circulation two-phase flow instability

    International Nuclear Information System (INIS)

    The paper focuses on assessment of the capability of RELAP5 to predict natural circulation two-phase flow instability. The aim of this study is to identify needs for improvements of the code models. Experimental data from the low pressure CIRCUS facility was used for the code validation. The paper discusses the code validation procedure which combines separate and integral effect validation with the elements of the input errors propagation method for sensitivity analysis. The separate effect validation and 'transparent box' approach to the experimental system helps to identify main sources of experimental data uncertainty. The paper also discusses modifications provided in the new series of experiments to reduce the experimental uncertainty. Finally, the paper comes up with the conclusions about uncertainty in the RELAP5 prediction for different regimes of two-phase oscillatory flows in the CIRCUS facility and necessity for the models improvements. (author)

  8. Effect of throttling on burnout heat flux and hydrodynamic instability in natural circulation

    International Nuclear Information System (INIS)

    Twenty-four experiments were carried out to study the effect of restriction of the flow before inlet of the test section on burnout heat flux and instability of the flow boiling. These experiments were carried out on a 10, 12, 14, 16 mm out diameter stainless steel heated elements, 50 and 75 cms long centered inside a 26 mm inner diameter stainless steel channel forming an annulus through which water followed upwards to give diameter ratios 2.6, 2.17, 1.86 and 1.63 respectively. The parameters are chosen to cover the lack of the literatures for burnout conditions at low pressures, 1.5, 3, 6, 10 atma). These are of great benefit to the designers of high heat flux devices such as boilers and nuclear reactors ...etc. A detail description of the experimental loop is given. Test section, steam separator, condenser, precooler, preheater, throttle valve, flow measurements and safety devices are designed and constructed for an operating pressure up to 10 atma and temperature up to 2200C. The results show that 1. The burnout heat flux first increases and then decreases as the restriction of the flow increases; 2. The hydrodynamic instability increases as the restriction of the flow before the test section increases. (author)

  9. Simulation of single phase instability behaviour in a rectangular natural circulation loop using RELAP5/ MOD 3.2 computer code

    International Nuclear Information System (INIS)

    Occurrence of instability in natural circulation loops can lead to problems in control and occurrence of critical heat flux (CHF) during low flow periods. Remaining within an identified stable zone operation is therefore desirable. Natural circulation loops can pass through an unstable zone during start-up and power raising. In the present work RELAPS / MOD 3.2 computer code has been used to simulate the unstable oscillatory behavior observed in a rectangular natural circulation loop having horizontal heater and horizontal cooler (HHHC) orientation. The results were compared with the experimental data. This report describes the nodalization scheme adopted tor this work and results of the analysis in detail. (author)

  10. Modeling of flashing-induced instabilities in the start-up phase of natural-circulation BWRs using the code FLOCAL

    International Nuclear Information System (INIS)

    This paper reports on the modeling and simulation of flashing-induced instabilities in natural circulation systems, with special emphasis on natural circulation Boiling Water Reactors (BWRs). For the modeling the 4-equation two-phase code FLOCAL (Rohde, 1986), developed at the ForschungZentrum Rossendorf (FZR, Germany), has been used. The model allows for the liquid and vapor to be in thermal non-equilibrium and, via drift-flux models, to have different velocities. The phenomenology of the instability has been studied and the dominating physical effects have been revealed. The results of the simulations have been compared qualitatively and quantitatively with experiments (Manera et al., 2002) that have been carried out within the framework of a European project (NACUSP) on the CIRCUS facility. The facility, built at the Delft University of Technology in The Netherlands, is a water/steam 1:1 height-scaled loop of the Dutch natural-circulation-cooled BWR Dodewaard

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

    Science.gov (United States)

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

  12. High level of chromosomal instability in circulating tumor cells of ROS1-rearranged non-small-cell lung cancer

    Science.gov (United States)

    Pailler, E.; Auger, N.; Lindsay, C. R.; Vielh, P.; Islas-Morris-Hernandez, A.; Borget, I.; Ngo-Camus, M.; Planchard, D.; Soria, J.-C.; Besse, B.; Farace, F.

    2015-01-01

    Background Genetic aberrations affecting the c-ros oncogene 1 (ROS1) tyrosine kinase gene have been reported in a small subset of patients with non-small-cell lung cancer (NSCLC). We evaluated whether ROS1-chromosomal rearrangements could be detected in circulating tumor cells (CTCs) and examined tumor heterogeneity of CTCs and tumor biopsies in ROS1-rearranged NSCLC patients. Patients and methods Using isolation by size of epithelial tumor cells (ISET) filtration and filter-adapted-fluorescence in situ hybridization (FA-FISH), ROS1 rearrangement was examined in CTCs from four ROS1-rearranged patients treated with the ROS1-inhibitor, crizotinib, and four ROS1-negative patients. ROS1-gene alterations observed in CTCs at baseline from ROS1-rearranged patients were compared with those present in tumor biopsies and in CTCs during crizotinib treatment. Numerical chromosomal instability (CIN) of CTCs was assessed by DNA content quantification and chromosome enumeration. Results ROS1 rearrangement was detected in the CTCs of all four patients with ROS1 rearrangement previously confirmed by tumor biopsy. In ROS1-rearranged patients, median number of ROS1-rearranged CTCs at baseline was 34.5 per 3 ml blood (range, 24–55). In ROS1-negative patients, median background hybridization of ROS1-rearranged CTCs was 7.5 per 3 ml blood (range, 7–11). Tumor heterogeneity, assessed by ROS1 copy number, was significantly higher in baseline CTCs compared with paired tumor biopsies in the three patients experiencing PR or SD (P < 0.0001). Copy number in ROS1-rearranged CTCs increased significantly in two patients who progressed during crizotinib treatment (P < 0.02). CTCs from ROS1-rearranged patients had a high DNA content and gain of chromosomes, indicating high levels of aneuploidy and numerical CIN. Conclusion We provide the first proof-of-concept that CTCs can be used for noninvasive and sensitive detection of ROS1 rearrangement in NSCLC patients. CTCs from ROS1-rearranged

  13. Earth's Reflection: Albedo

    Science.gov (United States)

    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…

  14. Conceptual analysis of a preliminary model for instability study in normal operation of a natural circulation reactor type EBWR, using Relap5/Mod 3.2

    International Nuclear Information System (INIS)

    This work intends a model using the code Relap5/Mod 3.2, for the instability study in normal operation of a natural circulation reactor type ESBWR. A conceptual analysis is considered because all the information was obtained of the open literature, and some of reactor operation or dimension (not available) parameters were approached. As starting point was took the pattern developed for reactor type BWR, denominated Browns Ferry and changes were focused in elimination of bonds of forced recirculation, in modification of operation parameters, dimensions and own control parameters, according to internal code structure. Additionally the nodalization outline is described analyzing for separate the four fundamental areas employees in peculiar geometry of natural circulation reactor. Comparative analysis of results of stability behavior obtained with those reported in the open literature were made, by part of commercial reactor designer ESBWR. (Author)

  15. Program for Computing Albedo

    Science.gov (United States)

    Justus, Carl G.

    2003-01-01

    Simple Thermal Environment Model (STEM) is a FORTRAN-based computer program that provides engineering estimates of top-of-atmosphere albedo and outgoing long-wave radiation (OLR) for use in analyzing thermal loads on spacecraft near Earth. The thermal environment of a spacecraft is represented in STEM as consisting of direct solar radiation; short-wave radiation reflected by the atmosphere of the Earth, as characterized in terms of the albedo of the Earth; and OLR emitted by the atmosphere of the Earth. STEM can also address effects of heat loads internal to a spacecraft. Novel features of STEM include (1) the use of Earth albedo and OLR information based on time series of measurements by Earth Radiation Budget Experiment satellites in orbit; (2) the ability to address thermal time constants of spacecraft systems by use of albedo and OLR values representing averages over a range of averaging times; and (3) the ability to address effects, on albedo and OLR values, of satellite orbital inclination, the angle between the plane of a spacecraft orbit and the line between the centers of the Earth and Sun, the solar zenith angle, and latitude.

  16. High level of chromosomal instability in circulating tumor cells of ROS1-rearranged non-small-cell lung cancer

    OpenAIRE

    Pailler, E.; Auger, N.; Lindsay, C. R.; Vielh, P; Islas-Morris-Hernandez, A.; Borget, I; Ngo-Camus, M.; Planchard, D.; Soria, J.-C.; Besse, B.; Farace, F.

    2015-01-01

    Background Genetic aberrations affecting the c-ros oncogene 1 (ROS1) tyrosine kinase gene have been reported in a small subset of patients with non-small-cell lung cancer (NSCLC). We evaluated whether ROS1-chromosomal rearrangements could be detected in circulating tumor cells (CTCs) and examined tumor heterogeneity of CTCs and tumor biopsies in ROS1-rearranged NSCLC patients. Patients and methods Using isolation by size of epithelial tumor cells (ISET) filtration and filter-adapted-fluoresce...

  17. Effect of Heaving Movement on Flow Instability in U-Tubes of Marine Steam Generator under Natural Circulation

    OpenAIRE

    Jianli Hao; Wenzhen Chen; Zhang,

    2013-01-01

    Under heaving movement conditions, the single phase flow instability in U-tubes is affected by the additional force, which will influence the marine reactor operation. In the present work, one-dimensional thermal-hydraulic model in U-tubes under heaving movement conditions is established, and the critical pressure drop (CPD) and critical mass flow rate (CMFR) which relate to the occurrence of reverse flow in U-tubes are proposed and analyzed. The effects of the heaving period and heaving acce...

  18. Effect of Heaving Movement on Flow Instability in U-Tubes of Marine Steam Generator under Natural Circulation

    Directory of Open Access Journals (Sweden)

    Jianli Hao

    2013-01-01

    Full Text Available Under heaving movement conditions, the single phase flow instability in U-tubes is affected by the additional force, which will influence the marine reactor operation. In the present work, one-dimensional thermal-hydraulic model in U-tubes under heaving movement conditions is established, and the critical pressure drop (CPD and critical mass flow rate (CMFR which relate to the occurrence of reverse flow in U-tubes are proposed and analyzed. The effects of the heaving period and heaving acceleration amplitude on the flow instability in U-tubes with the different length are discussed. It is shown that (1 the CPD and CMFR are obviously affected by the heaving movement, which means that the reverse flow characteristic in U-tubes will be changed; (2 the fluctuation periods of the CPD and CMFR are the same as the heaving period, but the fluctuation magnitude of them is little affected by the heaving period; (3 the relative changes of CPD and CMFR are the linear function of heaving acceleration amplitude; and (4 the U-tube length has little influence on the relative changes of CPD and CMFR compared with the heaving acceleration amplitude, which means that the heaving movement has little influence on the space distribution of reverse flow in the U-tubes of marine steam generator.

  19. Albedo matrices in assembly homogenization

    International Nuclear Information System (INIS)

    Relations between albedo matrices and a set of diffusion coefficients for a homogeneous medium is considered. The possibility to determine albedo matrices in a homogeneous diffusion medium on the basis of diffusion constants is proved. Relations for the reverse calculation of a set of equivalent diffusion constants using the albedo matrices are obtained. These relations can be used to check the albedo matrices determined by a numerical method. 10 refs.; 2 tabs

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

    Directory of Open Access Journals (Sweden)

    J. E. Box

    2012-08-01

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

  1. Albedo and transmittance of inhomogeneous stratus clouds

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-04-01

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

  2. Mars surface albedo and changes

    CERN Document Server

    Vincendon, Mathieu; Altieri, Francesca; Ody, Anouck

    2014-01-01

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

  3. Albedo patterns on triton

    International Nuclear Information System (INIS)

    A model for seasonal transport of volatiles based on Trafton [1984] is coupled to considerations of methane photochemistry to infer albedo patterns on Triton's surface at the time of the Voyager encounter. The relatively large southern subsolar latitude at present is predicted to cause the deposition of an extensive fresh frost layer covering approximately the northern half of the planet. The region between 10 degree and -35 degree latitude is expected to be devoid of surface frosts and will probably be covered with organic compounds resulting from methane dissociative chemistry. These substances are thought to be rather low in albedo and red in color. Triton's south polar cap is expected to extend from -35 degree latitude to the southern pole. Sublimation of Triton's south polar ices been occurring since 1930, but has been preferentially occurring near the pole. The sublimation of ices in this region may be concentrating dark organic matter on the surface of the ice or exposing layers of this material which have built up in the ice over many seasonal cycles. The south polar cap may be distinctly darker near the pole than around the equatorward edge

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Dirmeyer, P.A.; Shukla, J. [Center for Ocean-Land-Atmosphere Studies, Calverton, MD (United States)

    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.

  6. A study on thermo-hydraulic instability of boiling natural circulation loop with a chimney. 4. An analytical consideration of the stability and thermo-hydraulic characteristics in the chimney in high pressure

    International Nuclear Information System (INIS)

    Thermo-hydraulic instabilities of a boiling natural circulation loop with a chimney under high pressure were investigated using linear stability analysis. Drift-flux model was used for two-phase flow model. The instability regions as well as the thermo-hydraulic characteristics in the chimney such as wavy feature were examined, which were compared with the characteristics in low pressure. Instability could occur when exit quality was relatively low, which was the same manner as the characteristics in low pressure. In high-pressure, void was generated near channel exit, and void wave propagated in the chimney. In low pressure, steam was generated only near the chimney exit due to gravity induced flashing, and single-phase enthalpy wave, that is, temperature wave propagated in single-phase flow region. Though flow could be very stable in the high pressure and high power condition, the decay ratio of higher mode could be larger than that of lower mode. (author)

  7. The Ultraviolet Albedo of Ganymede

    Science.gov (United States)

    McGrath, Melissa; Hendrix, Amanda

    2013-01-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Tao Wang

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

  9. Non-conventional fishbone instabilities

    International Nuclear Information System (INIS)

    New instabilities of the fishbone type are predicted. The first is a trapped-particle-induced m = n = 1 instability with a mode structure that has nothing in common with the conventional rigid kink displacement. This instability takes place when the magnetic field is weak, so that the precession frequency of the energetic ions is not small as compared to the frequency of the corresponding Alfven continuum at r=0 and the magnetic shear is small inside the q = 1 radius (the case relevant to spherical tori). The second predicted instability is an Energertic Particle Mode fishbone instability driven by circulating particles, and the third is a double-kink-mode instability driven by the circulating energetic ions. In particular, the latter can have two frequencies simultaneously: we refer to it as 'doublet' fishbones. This instability can occur when the radial profile of the energetic ions has an off-axis maximum inside the region of the mode localization. (author)

  10. Albedo in the ATIC Experiment

    Science.gov (United States)

    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.

  11. Non-conventional Fishbone Instabilities

    International Nuclear Information System (INIS)

    New instabilities of fishbone type are predicted. First, a trapped-particle-induced m = n = 1 instability with the mode structure having nothing to do with the conventional rigid kink displacement. This instability takes place when the magnetic field is weak, so that the precession frequency of the energetic ions is not small as compared to the frequency of the corresponding Alfven continuum at r = 0 and the magnetic shear is small inside the q = 1 radius [the case relevant to spherical tori]. Second, an Energetic Particle Mode fishbone instability driven by circulating particles. Third, a double-kink-mode instability driven by the circulating energetic ions. In particular, the latter can have two frequencies simultaneously: we refer to it as ''doublet'' fishbones. This instability can occur when the radial profile of the energetic ions has an off-axis maximum inside the region of the mode localization

  12. The influence of the friction coefficients, the power and the flowrate on the two-phase flow instabilities in natural circulation

    International Nuclear Information System (INIS)

    A study of non-linear effects of a two phases flow instabilities has been done using theoretical and experimental models. The experimental model is based on a boiling channel placed in a water loop of natural convection. Studies of stability, with introduction of fluctuations over different parameters, have been achieved using the two models. The results of the experimental model agree with those of the theoretical model. It was found that the head loss coefficients KI and KE of the inlet and outlet channel respectively, had an influence over the stability of the system. An increase in the former produces an increase in the stability while an increase in the latter has the effect of increasing the instability. In the experiment, oscillations of the flow rate were observed. Two types of oscillations were noticed: (1) small oscillations called pressure drop oscillations, (2) large oscillations called density wave oscillations. A study of the variation of these two types of oscillations with power and the coefficient KI and KE had been achieved. It was found that pressure drop oscillations disappeared with the increase of power and the density waves oscillations increased with the increase of power

  13. Neutron albedo effects of underground nuclear explosion

    International Nuclear Information System (INIS)

    The neutron field distribution is affected by the surrounding medium in the underground nuclear explosion. It will influence the radiation chemical diagnosis. By Monte Carlo simulation, the fuel burnup induced by device and neutron albedo was calculated. The analysis method of albedo effect on radiation chemical diagnosis result under special environment was proposed. Neutron albedo should be considered when capture reaction burnup fraction is used, and then correct analysis can be carried out on the nuclear device.The neutron field distribution is affected by the surrounding medium in the underground nuclear explosion. It will influence the radiation chemical diagnosis. By Monte Carlo simulation, the fuel burnup induced by device and neutron albedo was calculated. The analysis method of albedo effect on radiation chemical diagnosis result under special environment was proposed. Neutron albedo should be considered when capture reaction burnup fraction is used, and then correct analysis can be carried out on the nuclear device. (authors)

  14. Albedo over snow and ice penitents

    OpenAIRE

    J. Abermann; C. Kinnard; S. Lhermitte

    2013-01-01

    Both satellite and ground-based broadband albedo measurements over complex terrain show several limitations concerning feasibility and representativeness. In this study a series of experiments on Glaciar Tapado in the semi-arid Andes of Northern Chile is used to investigate the vertical dependence of albedo over a penitent-covered surface. The albedo–height relationship depends on the surface properties: over medium-sized snow penitents albedo increases with height, whereas over ice pe...

  15. Albedo over rough snow and ice surfaces

    OpenAIRE

    S. Lhermitte; J. Abermann; C. Kinnard

    2014-01-01

    Both satellite and ground-based broadband albedo measurements over rough and complex terrain show several limitations concerning feasibility and representativeness. To assess these limitations and understand the effect of surface roughness on albedo, firstly, an intrasurface radiative transfer (ISRT) model is combined with albedo measurements over different penitente surfaces on Glaciar Tapado in the semi-arid Andes of northern Chile. Results of the ISRT model show effective...

  16. Linking snowpack microphysics and albedo evolution

    OpenAIRE

    Mark G. Flanner; Zender, Charles S

    2006-01-01

     Snow aging causes reflectance to vary significantly on timescales of days. This variability influences the strength of snow albedo feedback and can affect the timing of snowmelt. However, climate models have yet to incorporate important controls on snow aging and albedo evolution. We develop a physically based model that predicts evolution of dry, pure snow specific surface area, and apply aspherical ice particle theory to link these results with albedo evolution. This is the first theoretic...

  17. CARP: a computer code and albedo data library for use by BREESE, the MORSE albedo package

    International Nuclear Information System (INIS)

    The CARP computer code was written to allow processing of DOT angular flux tapes to produce albedo data for use in the MORSE computer code. An albedo data library was produced containing several materials. 3 tables

  18. Surface expression of CXCR4 on circulating CD133+ progenitor cells is associated with plaque instability in subjects with carotid artery stenosis

    Directory of Open Access Journals (Sweden)

    Sadikovic Suwad

    2009-12-01

    Full Text Available Abstract Background Circulating progenitor cells (PCs are considered to contribute to the remodeling of atherosclerotic plaques. Their surface receptor CXCR4 plays an important role in the recruitment of PCs to their target. This study compares the mobilization of PCs and their functional characteristics in asymptomatic subjects with stable and with unstable carotid plaques. This could provide insight into plaque remodeling and help to develop biomarkers for plaque stability. Methods In 31 subjects with asymptomatic carotid artery stenosis we analyzed the number of CD133+ PCs, VEGFR2+CD34+ PCs and the surface expression of CXCR4 on CD133+ PCs by flow cytometry. Subjects underwent bilateral carotid MRI in a 1.5-T scanner in order to allow the categorization of plaques, following the modified criteria of the American Heart Association. Results The number of CD133+ PCs and VEGFR2+CD34+ PCs showed no significant difference between subjects with stable and unstable carotid plaques. The expression of CXCR4 on CD133+ PCs was higher in subjects with unstable plaques than in subjects with stable plaques (p = 0.009. Conclusions This study demonstrates an association between functional characteristics of circulating CD133+ PCs and plaque stability in subjects with asymptomatic carotid artery stenosis. The higher expression of CXCR4 on CD133+ PCs suggests a difference in the recruitment of PCs to the injured tissue in subjects with unstable plaques and subjects with stable plaques. As surface expression of CXCR4 on CD133+ PCs differs in subjects with unstable and with stable plaques, CXCR4 is a promising candidate for a serological biomarker for plaque stability.

  19. Area monitoring using neutron albedo thermoluminescence dosemeters

    International Nuclear Information System (INIS)

    Thermoluminescence dosemeters (TLD) were used for area monitoring around neutron sources applying the moderating sphere technique and the albedo technique in which LiF, 6LiF, 7LiF as well TLD-200 were used as TLD. Experimental results indicated that the thermoluminescence (TL) output for moderating sphere system is five times the TL output of the albedo system. In order to increase the TL output for the albedo system a paraffin slab was placed close to the albedo system. (author)

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

    Science.gov (United States)

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

    2016-06-01

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

  1. Analysis of experimental data on two-phase natural circulation from the flow pattern transition instability studies facility at Apsara reactor

    International Nuclear Information System (INIS)

    The present report deals with the analysis of the experimental data on void fraction and steady state flow rate obtained from the flow pattern transition instability studies facility installed in Apsara reactor hall for 1/2 inch diameter loop. Void fraction was measured by neutron radiography (NRG) and conductance probe (CP) method. The NRG method gave slightly larger void fraction as compared to the CP method. Analysis was carried out with the codes based on the homogeneous equilibrium model (HEM) and the drift flux model. In the HEM, the frictional pressure drop was estimated by Baroczy (1966) correlation. A comparison of predicted flow rate, density, quality and void fraction by HEM and drift flux model was done. It was found that steady state flow rate prediction by drift flux and HEM are in good agreement with experimental data. However it was found that steady state flow rate predicted by HEM with Baroczy correlation for two phase friction multiplier is better in comparisoll to drift-flux model. For void fraction predictions Smith correlation is found to be best followed by Ishii, Osmachkin and Chexal correlations. (author)

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

    Science.gov (United States)

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

    2007-01-01

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

  3. Input Calibration and Validation of RELAP5 Against CIRCUS-IV Single Channel Tests on Natural Circulation Two-Phase Flow Instability

    Directory of Open Access Journals (Sweden)

    Viet-Anh Phung

    2015-01-01

    Full Text Available RELAP5 is a system thermal-hydraulic code that is used to perform safety analysis on nuclear reactors. Since the code is based on steady state, two-phase flow regime maps, there is a concern that RELAP5 may provide significant errors for rapid transient conditions. In this work, the capability of RELAP5 code to predict the oscillatory behavior of a natural circulation driven, two-phase flow at low pressure is investigated. The simulations are compared with a series of experiments that were performed in the CIRCUS-IV facility at the Delft University of Technology. For this purpose, we developed a procedure for calibration of the input and code validation. The procedure employs (i multiple parameters measured in different regimes, (ii independent consideration of the subsections of the loop, and (iii assessment of importance of the uncertain input parameters. We found that predicted system parameters are less sensitive to variations of the uncertain input and boundary conditions in high frequency oscillations regime. It is shown that calculation results overlap experimental values, except for the high frequency oscillations regime where the maximum inlet flow rate was overestimated. This finding agrees with the idea that steady state, two-phase flow regime maps might be one of the possible reasons for the discrepancy in case of rapid transients in two-phase systems.

  4. Which way will the circulation shift in a changing climate? Possible nonlinearity of extratropical cloud feedbacks

    Science.gov (United States)

    Tandon, Neil F.; Cane, Mark A.

    2016-08-01

    In a suite of idealized experiments with the Community Atmospheric Model version 3 coupled to a slab ocean, we show that the atmospheric circulation response to CO2 increase is sensitive to extratropical cloud feedback that is potentially nonlinear. Doubling CO2 produces a poleward shift of the Southern Hemisphere (SH) midlatitude jet that is driven primarily by cloud shortwave feedback and modulated by ice albedo feedback, in agreement with earlier studies. More surprisingly, for CO2 increases smaller than ~25 %, the SH jet shifts equatorward. Nonlinearities are also apparent in the Northern Hemisphere, but with less zonal symmetry. Baroclinic instability theory and climate feedback analysis suggest that as the CO2 forcing amplitude is reduced, there is a transition from a regime in which cloud and circulation changes are largely decoupled to a regime in which they are highly coupled. In the dynamically coupled regime, there is an apparent cancellation between cloud feedback due to warming and cloud feedback due to the shifting jet, and this allows the ice albedo feedback to dominate in the high latitudes. The extent to which dynamical coupling effects exceed thermodynamic forcing effects is strongly influenced by cloud microphysics: an alternate model configuration with slightly increased cloud liquid (LIQ) produces poleward jet shifts regardless of the amplitude of CO2 forcing. Altering the cloud microphysics also produces substantial spread in the circulation response to CO2 doubling: the LIQ configuration produces a poleward SH jet shift approximately twice that produced under the default configuration. Analysis of large ensembles of the Canadian Earth System Model version 2 demonstrates that nonlinear, cloud-coupled jet shifts are also possible in comprehensive models. We still expect a poleward trend in SH jet latitude for timescales on which CO2 increases by more than ~25 %. But on shorter timescales, our results give good reason to expect significant

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

    Science.gov (United States)

    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.

  6. Radiation Dose from Lunar Neutron Albedo

    Science.gov (United States)

    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. Shoulder Instability

    Science.gov (United States)

    ... Risk Factors Is shoulder instability the same as shoulder dislocation? No. The signs of dislocation and instability might ... the same to you--weakness and pain. However, dislocation occurs when your shoulder goes completely out of place. The shoulder ligaments ...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-02-12

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

  9. Greenland surface albedo changes in July 1981–2012 from satellite observations

    International Nuclear Information System (INIS)

    Significant melting events over Greenland have been observed over the past few decades. This study presents an analysis of surface albedo change over Greenland using a 32-year consistent satellite albedo product from the global land surface satellite (GLASS) project together with ground measurements. Results show a general decreasing trend of surface albedo from 1981 to 2012 (−0.009 ± 0.002 decade−1, p < 0.01). However, a large decrease has occurred since 2000 (−0.028 ± 0.008 decade−1, p < 0.01) with most significant decreases at elevations between 1000 and 1500 m (−0.055 decade−1, p < 0.01) which may be associated with surface temperature increases. The surface radiative forcing from albedo changes is 2.73 W m−2 decade−1 and 3.06 W m−2 decade−1 under full-sky and clear-sky conditions, respectively, which indicates that surface albedo changes are likely to have a larger impact on the surface shortwave radiation budget than that caused by changes in the atmosphere over Greenland. A comparison made between satellite albedo products and data output from the Coupled Model Inter-comparison Project 5 (CMIP5) general circulation models (GCMs) shows that most of the CMIP5 models do not detect the significantly decreasing trends of albedo in recent decades. This suggests that more efforts are needed to improve our understanding and simulation of climate change at high latitudes. (letter)

  10. Theoretical simulation of neutron albedo experiment

    International Nuclear Information System (INIS)

    The purpose of neutron albedo experiment is to check and scale the programs, parameters and methods used in engineering design. Monte-Carlo particle transport code is used to simulate the experiment, and the neutron activation rate and albedo coefficient of each detecting point on iron spherical shell's outer surface were obtained. It is proved that the theoretical results are in good agreement with the experiment data within the range of data's uncertainty. (authors)

  11. Bounded cascade clouds: albedo and effective thickness

    OpenAIRE

    Cahalan, R. F.

    2002-01-01

    If climate models produced clouds having liquid water amounts close to those observed, they would compute a mean albedo that is often much too large, due to the treatment of clouds as plane-parallel. An approximate lower-bound for this "plane-parallel albedo bias" may be obtained from a fractal model having a range of optical thicknesses similar to those observed in marine stratocumulus, since they are more nearly plane-parallel than most other cloud types. We review ...

  12. Decadal to seasonal variability of Arctic sea ice albedo

    OpenAIRE

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

    2011-01-01

    A controlling factor in the seasonal and climatological evolution of the sea ice cover is its albedo $\\alpha$. Here we analyze Arctic data from the Advanced Very High Resolution Radiometer (AVHRR) Polar Pathfinder and assess the seasonality and variability of broadband albedo from a 23 year daily record. We produce a histogram of daily albedo over ice covered regions in which the principal albedo transitions are seen; high albedo in late winter and spring, the onset of snow melt and melt pond...

  13. Modeling Earth Albedo for Satellites in Earth Orbit

    OpenAIRE

    Bhanderi, Dan; Bak, Thomas

    2005-01-01

    Many satellite are influences by the Earthøs albedo, though very few model schemes exist.in order to predict this phenomenon. Earth albedo is often treated as noise, or ignored completely. When applying solar cells in the attitude hardware, Earth albedo can cause the attitude estimate to deviate with as much as 20 deg. Digital Sun sensors with Earth albedo correction in hardware exist, but are expensive. In addition, albedo estimates are necessary in thermal calculations and power budgets. We...

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

    OpenAIRE

    Bhanderi, Dan

    2005-01-01

    This thesis focuses on advanced modeling of the Earth albedo experienced by satellites in Earth orbit. The model of the Earth albedo maintains directional information of the Earth albedo irradiance from each partition on the Earth surface. This allows enhanced modeling of Sun sensor current outputs with improved accuracy. The Earth albedo model may be applied in simulations of the space environment useful in the satellite design phase. The Earth albedo model is verified using the telemetry da...

  15. Fetal Circulation

    Science.gov (United States)

    ... Pressure High Blood Pressure Tools & Resources Stroke More Fetal Circulation Updated:Jul 8,2016 click to enlarge The ... fetal heart. These two bypass pathways in the fetal circulation make it possible for most fetuses to survive ...

  16. Shoulder instability

    International Nuclear Information System (INIS)

    In the shoulder, the advantages of range of motion are traded for the disadvantages of vulnerability to injury and the development of instability. Shoulder instability and the lesion it produces represent one of the main causes of shoulder discomfort and pain. Shoulder instability is defined as a symptomatic abnormal motion of the humeral head relative to the glenoid during active shoulder motion. Glenohumeral instabilities are classified according to their causative factors as the pathogenesis of instability plays an important role with respect to treatment options: instabilities are classified in traumatic and atraumatic instabilities as part of a multidirectional instability syndrome, and in microtraumatic instabilities. Plain radiographs ('trauma series') are performed to document shoulder dislocation and its successful reposition. Direct MR arthrography is the most important imaging modality for delineation the different injury patterns on the labral-ligamentous complex and bony structures. Monocontrast CT-arthrography with use of multidetector CT scanners may be an alternative imaging modality, however, regarding the younger patient age, MR imaging should be preferred in the diagnostic work-up of shoulder instabilities. (orig.)

  17. Surface Albedo and Spectral Variability of Ceres

    Science.gov (United States)

    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.

  18. Sea ice-albedo climate feedback mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Schramm, J.L.; Curry, J.A. [Univ. of Colorado, Boulder, CO (United States); Ebert, E.E. [Bureau of Meterology Research Center, Melbourne (Australia)

    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.

  19. Hip instability.

    Science.gov (United States)

    Smith, Matthew V; Sekiya, Jon K

    2010-06-01

    Hip instability is becoming a more commonly recognized source of pain and disability in patients. Traumatic causes of hip instability are often clear. Appropriate treatment includes immediate reduction, early surgery for acetabular rim fractures greater than 25% or incarcerated fragments in the joint, and close follow-up to monitor for avascular necrosis. Late surgical intervention may be necessary for residual symptomatic hip instability. Atraumatic causes of hip instability include repetitive external rotation with axial loading, generalized ligamentous laxity, and collagen disorders like Ehlers-Danlos. Symptoms caused by atraumatic hip instability often have an insidious onset. Patients may have a wide array of hip symptoms while demonstrating only subtle findings suggestive of capsular laxity. Traction views of the affected hip can be helpful in diagnosing hip instability. Open and arthroscopic techniques can be used to treat capsular laxity. We describe an arthroscopic anterior hip capsular plication using a suture technique. PMID:20473129

  20. Gamma-ray Albedo of the Moon

    Energy Technology Data Exchange (ETDEWEB)

    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. Thermal neutron albedo measurements for multilithic reflectors

    International Nuclear Information System (INIS)

    Highlights: • Measurement of thermal neuron albedo for multilithic reflectors. • Modeling of experiments in MATLAB. • Comparison of numerical calculated and experimental values. • Study of thermal neutron albedo in different multilayered shielding. - Abstract: An experimental measurement of the thermal neutron (0.025 eV) albedo (αth) has been carried out for multilithic shielding by using Am–Be neutron source and BF3 detector. The measured saturation value for the thermal albedo of paraffin wax has been found to be 0.734 ± 0.020, which is in close agreement to the corresponding value 0.83 quoted in the literature. The thermal neutron albedo has been measured for the multilayered shielding in copper–wood, copper–aluminum, wood–paraffin and paraffin–iron combinations in horizontal geometric configurations. Modeling and numerical simulation have been carried out by developing a MATLAB code which solves the diffusion equation in order to calculate the experimental results. Good agreement has been found between the numerical calculated and experimental results. The uncertainties in the measurements have also been calculated based on error propagation of the underlying Poisson distribution

  2. On the descriptions of beam instabilities

    CERN Document Server

    Maillard, Antoine

    2016-01-01

    We investigate two interesting features of beam instabilities in accelerators : First, we provide the equivalence between two models to describe transverse instabilities, the circulant matrix model (based on a longitudinal phase space discretization) and the Vlasov formalism. Secondly, we show how to derive dispersion integrals for transverse detuning effects in the Vlasov formalism, thus allowing for Landau damping mechanism.

  3. Generalized Albedo option on the Morse Monte Carlo code

    International Nuclear Information System (INIS)

    The advisability of using the albedo procedure for solving 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 the tracking of special particles inside albedo media, an option to displace the point-of-emergence during an albedo event, and an option to read, process, and use spatially-dependent albedo data for both forward and adjoint calculations. (author)

  4. Intercomparison measurements with albedo neutron dosimeters

    International Nuclear Information System (INIS)

    Since the introduction of the albedo dosimeter as the official personal neutron dosimeter the dosimetry services concerned have participated in intercomparison measurements at the PTB. Their albedo dosimeters were irradiated in reference fields produced by unmoderated and D2O-moderated 252Cf neutron sources in the standard irradiation facility of the PTB. Six fields with fluences different in energy and angle distribution could be realised in order to determine the response of the albedo dosimeter. The dose equivalent values evaluated by the services were compared with the reference values of the PTB for the directional dose equivalent H'(10). The results turned out to be essentially dependent on the evaluation method and the choice of the calibration factors. (orig.)

  5. UV albedo of arctic snow in spring

    Directory of Open Access Journals (Sweden)

    O. Meinander

    2008-02-01

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

  6. Parameterizations for narrowband and broadband albedo of pure snow and snow containing mineral dust and black carbon

    Science.gov (United States)

    Dang, Cheng; Brandt, Richard E.; Warren, Stephen G.

    2015-06-01

    The reduction of snow spectral albedo by black carbon (BC) and mineral dust, both alone and in combination, is computed using radiative transfer modeling. Broadband albedo is shown for mass fractions covering the full range from pure snow to pure BC and pure dust, and for snow grain radii from 5 µm to 2500 µm, to cover the range of possible grain sizes on planetary surfaces. Parameterizations are developed for opaque homogeneous snowpacks for three broad bands used in general circulation models and several narrower bands. They are functions of snow grain radius and the mass fraction of BC and/or dust and are valid up to BC content of 10 ppm, needed for highly polluted snow. A change of solar zenith angle can be mimicked by changing grain radius. A given mass fraction of BC causes greater albedo reduction in coarse-grained snow; BC and grain radius can be combined into a single variable to compute the reduction of albedo relative to pure snow. The albedo reduction by BC is less if the snow contains dust, a common situation on mountain glaciers and in agricultural and grazing lands. Measured absorption spectra of mineral dust are critically reviewed as a basis for specifying dust properties for modeling. The effect of dust on snow albedo at visible wavelengths can be represented by an "equivalent BC" amount, scaled down by a factor of about 200. Dust has little effect on the near-IR albedo because the near-IR albedo of pure dust is similar to that of pure snow.

  7. Natural Circulation with Boiling

    International Nuclear Information System (INIS)

    A number of parameters with dominant influence on the power level at hydrodynamic instability in natural circulation, two-phase flow, have been studied experimentally. The geometrical dependent quantities were: the system driving head, the boiling channel and riser dimensions, the single-phase as well as the two phase flow restrictions. The parameters influencing the liquid properties were the system pressure and the test section inlet subcooling. The threshold of instability was determined by plotting the noise characteristics in the mass flow records against power. The flow responses to artificially obtained power disturbances at instability conditions were also measured in order to study the nature of hydrodynamic instability. The results presented give a review over relatively wide ranges of the main parameters, mainly concerning the coolant performance in both single and parallel boiling channel flow. With regard to the power limits the experimental results verified that the single boiling channel performance was intimately related to that of the parallel channels. In the latter case the additional inter-channel factors with attenuating effects were studied. Some optimum values of the parameters were observed

  8. Surface Albedo and Spectral Variability of Ceres

    CERN Document Server

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

    2016-01-01

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

  9. Lung Circulation.

    Science.gov (United States)

    Suresh, Karthik; Shimoda, Larissa A

    2016-01-01

    The circulation of the lung is unique both in volume and function. For example, it is the only organ with two circulations: the pulmonary circulation, the main function of which is gas exchange, and the bronchial circulation, a systemic vascular supply that provides oxygenated blood to the walls of the conducting airways, pulmonary arteries and veins. The pulmonary circulation accommodates the entire cardiac output, maintaining high blood flow at low intravascular arterial pressure. As compared with the systemic circulation, pulmonary arteries have thinner walls with much less vascular smooth muscle and a relative lack of basal tone. Factors controlling pulmonary blood flow include vascular structure, gravity, mechanical effects of breathing, and the influence of neural and humoral factors. Pulmonary vascular tone is also altered by hypoxia, which causes pulmonary vasoconstriction. If the hypoxic stimulus persists for a prolonged period, contraction is accompanied by remodeling of the vasculature, resulting in pulmonary hypertension. In addition, genetic and environmental factors can also confer susceptibility to development of pulmonary hypertension. Under normal conditions, the endothelium forms a tight barrier, actively regulating interstitial fluid homeostasis. Infection and inflammation compromise normal barrier homeostasis, resulting in increased permeability and edema formation. This article focuses on reviewing the basics of the lung circulation (pulmonary and bronchial), normal development and transition at birth and vasoregulation. Mechanisms contributing to pathological conditions in the pulmonary circulation, in particular when barrier function is disrupted and during development of pulmonary hypertension, will also be discussed. © 2016 American Physiological Society. Compr Physiol 6:897-943, 2016. PMID:27065170

  10. Factors affecting polyamide prototypes design of Albedo dosemeters

    International Nuclear Information System (INIS)

    This work studies the most important factors which affect the response of albedo neutron dosemeters containing LiF TLDs with the aim to improve their sensitivity. It includes tests of thickness and shape of the polyamide moderator body prototypes, albedo window diameter and TLD position inside the moderator. Analyzing the results, an albedo neutron dosemeter prototype, B4C covered, was developed. The prototype has a response three times higher than the albedo dosemeter now in use in Brazil. (author)

  11. Albedo muons in upper layers of the atmosphere

    International Nuclear Information System (INIS)

    The albedo muon fluxes are calculated in the energy range 50≤E≤1000 MeV in the upper atmospheric layers. It is shown that the anisotropy degree of albedo muon flux in the stratosphere increases with the muon energy increase, and according to the absolute values the albedo muon flux becomes comparable with the direct albedo proton fluxes at energies > 200 MeV. 8 refs.; 2 figs

  12. The zonal and global albedoes of the earth

    OpenAIRE

    Henderson-Sellers, A.; A. J. Meadows

    2011-01-01

    Changes in global albedo of the Earth can depend on regional variations in reflectivity. We compare here three regional factors that have been considered capable of causing significant changes in global albedo, representing them approximately by zonal averages. Our calculations suggest that (1) large latitudinal changes in ice cover will have only a slight effect on the planetary albedo, and (2) latitudinal shifts in the cloud belts can produce significant changes in the planetary albedo.DO...

  13. Towards multidecadal consistent Meteosat surface albedo time series

    OpenAIRE

    Alexander Loew; Yves Govaerts

    2010-01-01

    Monitoring of land surface albedo dynamics is important for the understanding of observed climate trends. Recently developed multidecadal surface albedo data products, derived from a series of geostationary satellite data, provide the opportunity to study long term surface albedo dynamics at the regional to global scale. Reliable estimates of temporal trends in surface albedo require carefully calibrated and homogenized long term satellite data records and derived products. The present paper ...

  14. Boreal forest albedo and its spatial and temporal variation

    OpenAIRE

    Kuusinen, Nea

    2014-01-01

    Surface albedo refers to the fraction of solar irradiance that is reflected by a surface. Accurate characterisation of the albedo of various land cover types is required for evaluating the energy exchange between the Earth s surface and the atmosphere. The optical and structural properties of a surface determine its albedo. Boreal forest albedo can vary due to factors such as tree species composition, forest structure, understorey vegetation composition, and seasonal changes in vegetation and...

  15. Systematic Numerical Experiments for Investigation of Urban Albedo Characteristics

    OpenAIRE

    Tanimoto, Jun; Hagishima, Aya

    2003-01-01

    One of the important parameters used to estimate Urban Heat Island that involved with mesoscale model is albedo. It is useful to reliably investigate the energy budget in an urban through the radiation exchange study within urban canopy. In order to systematically clarify the urban albedo characteristics coupling with that of factorial effects, we introduce an Albedo Calculation Model, which is simple and more reliable to provide the 3-dimensional urban albedo simulation. In addition, the num...

  16. Albedo of photons in high energy electromagnetic and hadronic cascades

    International Nuclear Information System (INIS)

    The albedo of photons in electromagnetic cascades is simulated. A simple model of back current photons generation and propagation in electromagnetic cascades is considered which satisfactorily describes the general features of albedo behavior. The contribution to the photonic albedo of electromagnetic subshowers generated by high energy gamma-quanta from π0 decays in the hadron initiated cascade is evaluated. (orig.)

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

    Science.gov (United States)

    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.

  18. Spectral geometric albedo and bolometric Bond albedo of Neptune's satellite Triton from voyager observations

    International Nuclear Information System (INIS)

    The authors have calculated the spectral geometric albedo and bolometric Bond albedo of Triton by combining the published data from the Voyager spacecraft Photopolarimeter (PPS) experiment and the Voyager imaging science (ISS) experiment. They have used the PPS ultraviolet (0.25 μm) and infrared (0.75 μm) filter data and the ISS violet (0.41 μm) and green (0.56 μm) filter data to produce geometric albedos and phase integrals at each of the four wavelengths. The resulting spectral geometric albedo is not inconsistent with the presence of weak absorption feature in Triton's spectrum near 0.75 μm. The phase integrals were determined by Russell's approximation and by 2-point Gaussian quadrature. The geometric albedo at the uv, v, g and ir filters is 0.59, 0.68, 0.81, and 0.75 respectively. The resulting bolometric Bond albedo (∼0.65) is consistent with the 38 K, unit emissivity, daytime surface temperature for Triton reported as a best fit to the data of the Voyager Infrared Spectrometer and Radiometer (IRIS). The results are also in agreement with the 37.5 K temperature of nitrogen at an inferred basal pressure of 14 μbar as reported by the Voyager Ultraviolet Spectrometer (UVS) investigation

  19. Baroclinic instabilities

    OpenAIRE

    Joly, Laurent; Chassaing, Patrick; Chapin, Vincent; Reinaud, Jean; Micallef, J; Suarez, Juan; Bretonnet, L

    2003-01-01

    1. Introduction - Illustrative examples from experiments and simulations 2. The baroclinic torque in high Froude number flows, its organization, scale and order of magnitude 3. Stability of the inhomogeneous mixing-layer 4. Transition of the inhomogeneous mixing-layer and the 2D secondary baroclinic instability 5. The strain field of 2D light jets 6. Transition to three-dimensionality in light jets and the question of side-jets 7. Baroclinic instability of heavy vortices and...

  20. Carpal instability

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, R.; Froehner, S.; Coblenz, G.; Christopoulos, G. [Institut fuer Diagnostische und Interventionelle Radiologie, Herz- und Gefaessklinik GmbH, Bad Neustadt an der Saale (Germany)

    2006-10-15

    This review addresses the pathoanatomical basics as well as the clinical and radiological presentation of instability patterns of the wrist. Carpal instability mostly follows an injury; however, other diseases, like CPPD arthropathy, can be associated. Instability occurs either if the carpus is unable to sustain physiologic loads (''dyskinetics'') or suffers from abnormal motion of its bones during movement (''dyskinematics''). In the classification of carpal instability, dissociative subcategories (located within proximal carpal row) are differentiated from non-dissociative subcategories (present between the carpal rows) and combined patterns. It is essential to note that the unstable wrist initially does not cause relevant signs in standard radiograms, therefore being ''occult'' for the radiologic assessment. This paper emphasizes the high utility of kinematographic studies, contrast-enhanced magnetic resonance imaging (MRI) and MR arthrography for detecting these predynamic and dynamic instability stages. Later in the natural history of carpal instability, static malalignment of the wrist and osteoarthritis will develop, both being associated with significant morbidity and disability. To prevent individual and socio-economic implications, the handsurgeon or orthopedist, as well as the radiologist, is challenged for early and precise diagnosis. (orig.)

  1. Influence of spatial heterogeneity of local surface albedo on the area-averaged surface albedo retrieved from airborne irradiance measurements

    OpenAIRE

    E. Jäkel; M. Wendisch; Mayer, B.

    2012-01-01

    Spectral airborne upward and downward irradiance measurements are used to derive the area-averaged surface albedo. Real surfaces are not homogeneous in their reflectivity. Therefore, this work studies the effects of the heterogeneity of surface reflectivity on the area-averaged surface albedo to quantify how well aircraft measurements can resolve the small-scale variability of the local surface albedo. For that purpose spatially heterogeneous surface albedo maps were input into a 3-dimensiona...

  2. Influence of spatial heterogeneity of local surface albedo on the area-averaged surface albedo retrieved from airborne irradiance measurements

    OpenAIRE

    E. Jäkel; M. Wendisch; Mayer, B.

    2013-01-01

    Spectral airborne upward and downward irradiance measurements are used to derive the area-averaged surface albedo. Real surfaces are not homogeneous in their reflectivity. Therefore, this work studies the effects of the heterogeneity of surface reflectivity on the area-averaged surface albedo to quantify how well aircraft measurements can resolve the small-scale variability of the local surface albedo. For that purpose spatially heterogeneous surface albedo maps were inpu...

  3. Influence of spatial heterogeneity of local surface albedo on the area-averaged surface albedo retrieved from airborne irradiance measurements

    OpenAIRE

    E. Jäkel; M. Wendisch; Mayer, Bernhard

    2013-01-01

    Spectral airborne upward and downward irradiance measurements are used to derive the area-averaged surface albedo. Real surfaces are not homogeneous in their reflectivity. Therefore, this work studies the effects of the heterogeneity of surface reflectivity on the area-averaged surface albedo to quantify how well aircraft measurements can resolve the small-scale variability of the local surface albedo.

  4. Estimation of daily albedo on Tottori sand surface

    International Nuclear Information System (INIS)

    Daily albedos of a bare sand surface were measured with a solarimeter (Eko MS-62) between 23 August and 30 November in 1997 at Tottori sand dune, Japan. These quickly decreased on rainy days, and recovered during dry spells (days between rainfalls). A strong exponential relationship was found between daily albedos and the number of dry days. The daily albedos on dry days also showed a direct relationship with daily transmissivities in the range less than 0.55. Two simple models were developed to estimate daily albedos for dry spell days on bare Tottori sand surface using routine meteorological data. Daily albedos were calculated using these two models, and compared with the measured daily albedos. For Model #1, the daily albedos were successfully predicted only using the number of dry spell days; the correlation coefficient between the estimated and measured albedo was 0.73, and the standard error was 1.2%. For Model #2, the number of dry spell days and transmissivity were considered in order to calculate the daily albedo on dry spell days; the correlation coefficient was 0.85, and the standard error was 0.9%. Estimated albedos were in good agreement with measured albedos. (author)

  5. Modeling Earth Albedo for Satellites in Earth Orbit

    DEFF Research Database (Denmark)

    Bhanderi, Dan; Bak, Thomas

    2005-01-01

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

  6. Phantoms for calibrating albedo neutron dosimeters

    International Nuclear Information System (INIS)

    The lack of a standardized phantom was suspected to be the cause of some failures in a pilot study of dosimetry performance. Therefore a study was conducted to determine the effect of phantom size, shape and composition on the response of an albedo dosemeter. Dosemeters were exposed in air and on 15 different phantoms made of either polyethylene, Lucite or water. Results showed that the geometry of the phantom affects albedo readings, even for very large phantoms. No difference was found in readings for phantoms of different material when the geometry remained the same. It is concluded that in performance tests a phantom should be used that gives readings similar to those obtained with the phantom used by the testing laboratory. If another type is used the appropriate correction factor should be applied. The results of this study can be used to determine the correction factor. (author)

  7. Geomorphological related albedo features on Ceres

    Science.gov (United States)

    Krohn, K.; Matz, K.-D.; Jaumann, R.; Otto, K.; Li, J.-Y.; Buczkowski, D.; Mest, S.; Scully, J. E. C.; Williams, D. A.; Raymond, C. A.; Russell, C. T.

    2015-10-01

    NASA's Dawn spacecraft entered orbit of Ceres on March 6, 2015, to spend one year characterizing the geology, elemental and mineralogical composition, topography, shape, and internal structure of the Ceres [1]. Ceres is supposed to be differentiated into a silicate core, a liquid water mantle and a solid ice crust with a surface temperature from 130K to 235K [2,3]. At the time of writing, the acquired image data from Ceres provide a spatial resolution of up to 2.1 km/pixel. The surface of Ceres reveals some albedo features that seem to be related to geomorphology. Those features show either a high or a low albedo compared to the surrounding.

  8. Shoulder instability

    International Nuclear Information System (INIS)

    Shoulder instability is a common clinical feature leading to recurrent pain and limitated range of motion within the glenohumeral joint. Instability can be due a single traumatic event, general joint laxity or repeated episodes of microtrauma. Differentiation between traumatic and atraumatic forms of shoulder instability requires careful history and a systemic clinical examination. Shoulder laxity has to be differentiated from true instability followed by the clinical assessment of direction and degree of glenohumeral translation. Conventional radiography and CT are used for the diagnosis of bony lesions. MR imaging and MR arthrography help in the detection of soft tissue affection, especially of the glenoid labrum and the capsuloligamentous complex. The most common lesion involving the labrum is the anterior labral tear, associated with capsuloperiostal stripping (Bankart lesion). A number of variants of the Bankart lesion have been described, such as ALPSA, SLAP or HAGL lesions. The purpose of this review is to highlight different forms of shoulder instability and its associated radiological findings with a focus on MR imaging. (orig.)

  9. Beam Instabilities

    CERN Document Server

    Rumolo, G

    2014-01-01

    When a beam propagates in an accelerator, it interacts with both the external fields and the self-generated electromagnetic fields. If the latter are strong enough, the interplay between them and a perturbation in the beam distribution function can lead to an enhancement of the initial perturbation, resulting in what we call a beam instability. This unstable motion can be controlled with a feedback system, if available, or it grows, causing beam degradation and loss. Beam instabilities in particle accelerators have been studied and analysed in detail since the late 1950s. The subject owes its relevance to the fact that the onset of instabilities usually determines the performance of an accelerator. Understanding and suppressing the underlying sources and mechanisms is therefore the key to overcoming intensity limitations, thereby pushing forward the performance reach of a machine.

  10. Experimental study on low pressure flow instability

    International Nuclear Information System (INIS)

    The experiment was performed on the test loop (HRTL-5), which simulates the geometry and system design of the 5 MW reactor. The flow behavior for a wide range of inlet subcooling, in which the flow undergoes from single phase to two phase, is described in a natural circulation system at low pressure (p = 0.1, 0.24 MPa). Several kinds of flow instability, e.g. subcooled boiling instability, subcooled boiling induced flashing instability, pure flashing instability as well as flashing coupled density wave instability and high frequency flow oscillation, are investigated. The mechanism of flashing and flashing concerned flow instability, which has never been studied well in this field, is especially interpreted. The experimental results show that, firstly, for a low pressure natural circulation system the two phase flow is unstable in most of inlet subcooling conditions, the two phase stable flow can only be reached at very low inlet subcooling; secondly, at high inlet subcooling the flow instability is dominated by subcooled boiling in the heated section, and at middle inlet subcooling is dominated by void flashing in the adiabatic long riser; thirdly, in two phase stable flow region the condition for boiling out of the core, namely, single phase flow in the heated section, two phase flow in the riser due to vapor flashing, can be realized. The experimental results are very important for the design and accident analysis of the vessel and swimming pool type natural circulation nuclear heating reactor. (7 refs., 10 figs., 1 tab.)

  11. Albedo following fire in a Northern Hardwood Forest

    International Nuclear Information System (INIS)

    Changes in albedo were tracked following fire on 18 August 1980 in a successional hardwood forest in northern lower Michigan (43033'N, 84042'W). Shortwave albedo (300--3000 nm) changed little with zenith angle up to 550, but then increased rapidly. The rate of change in albedo with zenith angle was highest in July and lowest in early spring and late autumn. Midday albedo increased from 7.7% five days after the fire to 10.8% after six weeks. During the 1981 and 1982 growing seasons, albedo increased from 10.4 and 13.6% to mid-May to peaks of 17.8 and 18.1% in early July, respectively, with values then declining through autumn. Albedo increased with percent coverage of ground surface with live vegetation up to 35% cover, with little further change in albedo with cover, up to the maximum observed value of 70%. The ratio at midday of albedo in visible wavelengths (400--700 nm) to total shortwave albedo decreased from 0.49 in mid-May 1982 to a minimum of 0.22 in mid-July and then increased to 0.45 in mid-October, after leaf-fall. Midday shortwave albedo during winter varied from 91% over fresh snow to 76% over old, compacted snow

  12. Global color and albedo variations on Io

    Science.gov (United States)

    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.

  13. Impact of Atmospheric Albedo on Amazon Evapotranspiration

    Science.gov (United States)

    Lopes, A. V.; Thompson, S. E.; Dracup, J. A.

    2013-12-01

    The vulnerability of the Amazon region to climate and anthropogenic driven disturbances has been the subject of extensive research efforts, given its importance in the global and regional climate and ecologic systems. The evaluation of such vulnerabilities requires the proper understanding of physical mechanisms controlling water and energy balances and how the disturbances change them. Among those mechanisms, the effects of atmospheric albedo on evapotranspiration have not been fully explored yet and are explored in this study. Evapotranspiration in the Amazon is sustained at high levels across all seasons and represents a large fraction of water and energy surface budgets. In this study, statistical analysis of data from four flux towers installed at Amazon primary forest sites was employed to quantify the impact of atmospheric albedo, mostly resulted from cloudiness, on evapotranspiration and to compare it to the effect of water limitation. Firstly, the difference in eddy-flux derived evapotranspiration at the flux towers under rainy and non-rainy antecedent conditions was tested for significance. Secondly, the same statistical comparison was performed under cloudy and clear sky conditions at hourly and daily time scales, using the reduction in incoming solar radiation as an indicator of cloudiness. Finally, the sensitivity of seasonal evapotranspiration totals to atmospheric albedo resulted from rainfall patterns is evaluated. That was done by sampling daily evapotranspiration estimates from empirical probability distribution functions conditioned to rainfall occurrence and then varying the number of dry days in each season. It was found that light limitation is much more important than water limitation in the Amazon, resulting in up to 43% reduction in daily evapotranspiration. Also, this effect varies by location and by season, the largest impact being in wet season, from December do January. Moreover, seasonal evapotranspiration totals were found to be

  14. Data for the Chilton-Huddleston photon-albedo approximations

    International Nuclear Information System (INIS)

    Empirical parameters for two different gamma-ray albedo formulas, originally proposed by Chilton and Huddleston, are presented for water, concrete, iron, and lead for 12 photon energies ranging from 0.1 to 10 MeV and for reflected doses based on the ambient dose equivalent, the effective dose equivalent, and the exposure. The parameters were obtained by fitting the albedo formulas to MCNP-calculated albedo values over the complete ranges of incident and reflected directions

  15. Albedo calculation for single scattering gamma-rays, (3)

    International Nuclear Information System (INIS)

    Several formulae for albedo calculation of single scattering gamma-rays were given here with a quantitative discussion on the irregular variation of albedo with incident photon energy close to the K-edge of the material. The formula derived analytically from the approximation that attenuation coefficient is inversely proportional to photon energy to the third power, was found to be practically applicable to albedo calculation for materials of high atomic number in the limited range of incident energies. (auth.)

  16. The albedo-color diversity of transneptunian objects

    OpenAIRE

    Lacerda, Pedro; Fornasier, Sonia; Lellouch, Emmanuel; Kiss, Csaba; Vilenius, Esa; Santos-Sanz, Pablo; Rengel, Miriam; Mueller, Thomas; Stansberry, John; Duffard, Rene; Delsanti, Audrey; Guilbert-Lepoutre, Aurelie

    2014-01-01

    We analyze albedo data obtained using the Herschel Space Observatory that reveal the existence of two distinct types of surface among midsized transneptunian 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. ...

  17. Absorption feedback in stratocumulus clouds Influence on cloud top albedo

    OpenAIRE

    BOERS, REINOUT; Mitchell, Ross M.

    2011-01-01

    This paper proposes a feedback mechanism which modifies the enhancement of cloud top albedo expected from an increased concentration of cloud condensation nuclei (CCN). The mechanism is based on the thermodynamic tendency of the cloud to stabilize itself against changes in the absorption of solar radiation. For optically thin clouds, this absorption feedback leads to a reduction in the anticipated albedo enhancement, while for optically thick clouds, an amplification of the albedo enhancement...

  18. Geographical gradients in boreal forest albedo and structure in Finland

    OpenAIRE

    Lukes, Petr; Rautiainen, Miina; Manninen, Terhikki; Stenberg, Pauline; Mottus, Matti

    2014-01-01

    Land surface albedo is an essential climate variable controlling the planetary radiative energy budget, yet it is still among the main uncertainties of the radiation budget in the current climate modeling. To date, albedo satellite products have not been linked to extensive forest inventory data sets due to the lack of ground reference data. Here, we used comprehensive and detailed maps of forest inventory variables to couple forest structure and MODIS albedo products for both winter and summ...

  19. Factors influencing the mesoscale variations in marine stratocumulus albedo

    OpenAIRE

    D. A. Hegg; Nielsen, K.; Covert, D S; Jonsson, H. H.; Durkee, P.A.

    2011-01-01

    Measurements of both horizontal gradients and vertical profiles of aerosols, cloud droplets and thermodynamic parameters in the cloud topped marine boundary layer off of central California are presented. They suggest that, while aerosols can indeed modulate cloud albedo, other parameters such as sea surface temperature may similarly affect cloud albedo. Additionally, the impact of aerosols, through sedimentation and precipitation, on cloud optical depths and thus albedo is not always in accor...

  20. The role of surface albedo feedback in climate

    OpenAIRE

    Hall, A.

    2004-01-01

    A coarse resolution coupled ocean - atmosphere simulation in which surface albedo feedback is suppressed by prescribing surface albedo, is compared to one where snow and sea ice anomalies are allowed to affect surface albedo. Canonical CO2-doubling experiments were performed with both models to assess the impact of this feedback on equilibrium response to external forcing. It accounts for about half the high-latitude response to the forcing. Both models were also run for 1000 yr without forci...

  1. Spectral albedo of arctic snow during intensive melt period

    OpenAIRE

    O. Meinander; Kazadzis, S.; A. Arola; Kivi, R.; Kontu, A.; H. Suokanerva; Aaltonen, V.; Manninen, T.; J.-L. Roujean; O. Hautecoeur

    2010-01-01

    Spectral albedo and water liquid content of intensively melting Arctic snow were measured during the Snow Reflectance Transition Experiment (SNORTEX), in Sodankylä, Finland, in April 2009. The upwelling and downwelling spectral irradiance, measured at 290–550 nm with a double monochromator spectroradiometer, revealed the snow albedo to increase as a function wavelength. At the same time, we found the albedo of melting snow to decrease by ~10%, as a function of time within one day. During four...

  2. Effect of Vegetation on the Late Miocene Ocean Circulation

    Directory of Open Access Journals (Sweden)

    Gerrit Lohmann

    2015-11-01

    Full Text Available We examine the role of the vegetation cover and the associated hydrological cycle on the deep ocean circulation during the Late Miocene (~10 million years ago. In our simulations, an open Central American gateway and exchange with fresh Pacific waters leads to a weak and shallow thermohaline circulation in the North Atlantic Ocean which is consistent with most other modeling studies for this time period. Here, we estimate the effect of a changed vegetation cover on the ocean general circulation using atmospheric circulation model simulations for the late Miocene climate with 353 ppmv CO2 level. The Late Miocene land surface cover reduces the albedo, the net evaporation in the North Atlantic catchment is affected and the North Atlantic water becomes more saline leading to a more vigorous North Atlantic Deep Water circulation. These effects reveal potentially important feedbacks between the ocean circulation, the hydrological cycle and the land surface cover for Cenozoic climate evolution.

  3. ZZ ALBEDO-DATA, Data for the Calculation of Albedos from Concrete, Iron, Lead and Water for Photons and Neutrons

    International Nuclear Information System (INIS)

    1 - Description: The use of albedo techniques is central to many radiation streaming codes and has been widely used as an alternative to much more expensive transport calculations. Key to the albedo technique is the availability of either a large set of albedo data or, preferably, an empirical formula that approximates the albedo over the range of source energies and incident and exit radiation directions involved in a particular problem. Previously proposed neutron and photon albedo approximating formulas have been based on limited energy-angular ranges, a single reflecting material, old cross section data, and, most important, obsolete fluence-to-dose response functions. This library contains differential neutron dose albedo functions, based on modern cross section and response function data. Newly evaluated parameters are tabulated for several empirical differential dose albedo formulas. The albedos considered are (1) two approximations for photon albedo, (2) a new approximation for the neutron albedo, and (3) the secondary-photon albedo for incident neutrons. Albedo data is provided for four Materials: concrete, iron, lead, and water. Unlike previous compilations of albedo data, modern dosimetric units have been employed. Data are presented for (1) the ambient dose equivalent H*(10 mm) and (2) the effective dose equivalent for anteroposterior (AP) illumination of the ICRP anthropomorphic phantom. 2 - Methods: Monte Carlo code, MCNP, was used to calculate the albedo reflected from thick slabs of various materials. In particular, a homogeneous cylindrical slab surrounded by a vacuum was used. The incident neutrons were modeled by a point mono-directional source positioned just inside the center of the circular scoring (reflecting) surface. This was done to facilitate scoring because all particles crossing the surface must be outgoing (reflected) particles. Slab thickness and radius were sufficiently large (1000 cm) so that negligible numbers of neutrons were

  4. LUNAR TERRAIN AND ALBEDO RECONSTRUCTION FROM APOLLO IMAGERY

    Data.gov (United States)

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

  5. THE ALBEDO-COLOR DIVERSITY OF TRANSNEPTUNIAN OBJECTS

    Energy Technology Data Exchange (ETDEWEB)

    Lacerda, Pedro; Rengel, Miriam [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Fornasier, Sonia; Lellouch, Emmanuel; Delsanti, Audrey [LESIA-Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, 5 place Jules Janssen, F-92195 Meudon (France); Kiss, Csaba [Konkoly Observatory, MTA CSFK, 1121 Budapest, Konkoly Th. M. út 15-17 (Hungary); Vilenius, Esa; Müller, Thomas [Max-Planck-Institut für Extraterrestrische Physik, Postfach 1312, Giessenbachstrasse, D-85741 Garching (Germany); Santos-Sanz, Pablo; Duffard, René [Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía, s/n. E-18008 Granada (Spain); Stansberry, John [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Guilbert-Lepoutre, Aurélie [European Space Agency/ESTEC, Keplerlaan 1, 2201-AZ Noordwijk (Netherlands)

    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.

  6. THE ALBEDO-COLOR DIVERSITY OF TRANSNEPTUNIAN OBJECTS

    International Nuclear Information System (INIS)

    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

  7. Albedo of the ice covered Weddell and Bellingshausen Seas

    OpenAIRE

    Weiss, A.I.; J. C. King; Lachlan-Cope, T.A.; R. S. Ladkin

    2012-01-01

    This study investigates the surface albedo of the sea ice areas adjacent to the Antarctic Peninsula during the austral summer. Aircraft measurements of the surface albedo, which were conducted in the sea ice areas of the Weddell and Bellingshausen Seas show significant differences between these two regions. The averaged surface albedo varied between 0.13 and 0.81. The ice cover of the Bellingshausen Sea consisted mainly of first year ice and the sea surface showed an averaged sea ice albedo o...

  8. Enhancement of the MODIS Daily Snow Albedo Product

    Science.gov (United States)

    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

  9. Measurements of spectral snow albedo at Neumayer, Antarctica

    OpenAIRE

    S. Wuttke; Seckmeyer, G.; König-Langlo, G.

    2006-01-01

    Spectral albedo in high resolution, from 290 to 1050 nm, has been measured at Neumayer, Antarctica, (70°39' S, 8°15' W) during the austral summer 2003/2004. At 500 nm, the spectral albedo nearly reaches unity, with slightly lower values below and above 500 nm. Above 600 nm, the spectral albedo decreases to values between 0.45 and 0.75 at 1000 nm. For one cloudless case an albedo up to 1.01 at 500 nm could be determined. This can be explained by the larger directional...

  10. Effect of shaddock albedo addition on the properties of frankfurters

    OpenAIRE

    Shan, Bing; Li, Xingmin; Pan, Teng; Zheng, Limin; Zhang, Hao; Guo, Huiyuan; JIANG, LU; Zhen, Shaobo; Ren, Fazheng

    2014-01-01

    To explore the potential as a natural auxiliary emulsifier, shaddock albedo was added into frankfurters at six different levels: 0.0, 2.5, 5.0, 7.5, 10 and 12.5 %. The emulsion capacity (EC) of meat batters and cooking properties of frankfurters were evaluated. EC of meat batters was improved with the addition of shaddock albedo and the maximum value was reached at the 5 % albedo concentration. The addition of shaddock albedo resulted in lower cooking losses of frankfurters, with the lowest v...

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

    DEFF Research Database (Denmark)

    Bhanderi, Dan

    This thesis focuses on advanced modeling of the Earth albedo experienced by satellites in Earth orbit. The model of the Earth albedo maintains directional information of the Earth albedo irradiance from each partition on the Earth surface. This allows enhanced modeling of Sun sensor current outputs......-Method, Extended Kalman Filter, and Unscented Kalman Filter algorithms are presented and the results are compared. Combining the Unscented Kalman Filter with Earth albedo and enhanced Sun sensor modeling allows for three-axis attitude determination from Sun sensor only, which previously has been perceived to be...

  12. Atmospheric Circulation of Terrestrial Exoplanets

    CERN Document Server

    Showman, Adam P; Merlis, Timothy M; Kaspi, Yohai

    2013-01-01

    The investigation of planets around other stars began with the study of gas giants, but is now extending to the discovery and characterization of super-Earths and terrestrial planets. Motivated by this observational tide, we survey the basic dynamical principles governing the atmospheric circulation of terrestrial exoplanets, and discuss the interaction of their circulation with the hydrological cycle and global-scale climate feedbacks. Terrestrial exoplanets occupy a wide range of physical and dynamical conditions, only a small fraction of which have yet been explored in detail. Our approach is to lay out the fundamental dynamical principles governing the atmospheric circulation on terrestrial planets--broadly defined--and show how they can provide a foundation for understanding the atmospheric behavior of these worlds. We first survey basic atmospheric dynamics, including the role of geostrophy, baroclinic instabilities, and jets in the strongly rotating regime (the "extratropics") and the role of the Hadle...

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

    OpenAIRE

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

    2011-01-01

    This paper focuses on three interconnected topics: (1) quantitative relationship between surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo; (2) surfaced-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 fractio...

  14. Entrainment, Drizzle, and Stratocumulus Cloud Albedo

    Science.gov (United States)

    Ackerman, A. S.; Kirkpatrick, M. P.; Stevens, D. E.; Toon, O. B.

    2004-01-01

    Globally averaged cloud changes from GCMs on average show a doubling of the Twomey effect, which is the change in cloud albedo with respect to changes in droplet concentrations for fixed cloud water and droplet dispersion. In contrast, ship-track measurements show a much more modest amplification of the Twomey effect, suggesting that the GCMs are exaggerating the indirect aerosol effect. We have run large-eddy simulations with bin microphysics of marine stratocumulus from multiple field campaigns, and find that the large-eddy simulations are in much better agreement with the ship-track measurements. The inversion strength over N. Pacific stratocumulus (as measured during DYCOMS-II) is generally much stronger than over N. Atlantic stratocumulus (as measured during ASTEX), and we have found that the response of cloud water to increasing droplet concentration changes sign as the inversion strengthens. For the different environmental conditions, we will show the overall response of cloud albedo to droplet concentrations, and decompose the response into its contributing factors of changes in cloud water, droplet dispersion, and horizontal inhomogeneity.

  15. Cryosphere Broadband Surface Albedo Derivation with MODIS-to-CERES Conversion

    Science.gov (United States)

    Radkevich, A.; Rose, F. G.; Charlock, T. P.; Kato, S.

    2011-12-01

    Clouds and the Earth's Radiant Energy System (CERES) instruments on NASA's Earth Observing System (EOS) Terra and Aqua satellites measure broadband shortwave and longwave radiation reflected and emitted at the Top of the atmosphere (TOA). CERES synthesizes broadband observations with other EOS data streams. The CERES Surface and Atmospheric Radiation Budget (SARB) group matches observations with a radiative transfer code to determine fluxes at several levels. The presentation describes how the next edition of CERES will improve the retrieval of cryosphere surface albedo. Surface albedo is one of the input parameters of numerous models such cloud-resolving model (CRM) simulation, general circulation models (GCMs) and transient climate change simulations. It was recently showed by Park and Wu (2010) that CRM simulation well represents the SW radiative budget during winter because the radiation calculation for the snow-covered period is improved by using prescribed evolving surface albedo. Qu and Hall (2007) analyzed snow albedo feedback (SAF) in several transient climate change models. They stated that high quality observations of albedo of snow-covered surfaces would be extremely useful in reducing SAF spread in the next generation of models. CERES measures radiance and infers flux by applying scene-dependent, empirically based angular distribution models (ADMs). The ADMs are obtained from the complex CERES rotating azimuth plane scan mode to establish BRDF on the scale of 30 km broadband footprints. While CERES has much coarser spatial resolution than MODIS, the CERES measurement-based BRDF provides a keen advantage in accuracy over complex surfaces. CERES SARB retrievals of surface albedo have to date been based on only those 30 km footprints that are completely clear; there are too few (~5%) such footprints over sea ice. The upcoming edition of CERES will include MODIS radiances in 7 SW bands (currently 4), which are point spread function weighted to both a whole

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

  18. Cloud albedo increase from carbonaceous aerosol

    Directory of Open Access Journals (Sweden)

    W. R. Leaitch

    2010-08-01

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

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

    DEFF Research Database (Denmark)

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

    2015-01-01

    Albedo is one of the parameters that govern energy availability for snow and ice surface ablation, and subsequently the surface mass balance conditions of temperate glaciers and ice caps (GIC). Here, we document snow and ice albedo changes for Mittivakkat Gletscher (MG) in Southeast Greenland (20...

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

    Science.gov (United States)

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

    1974-01-01

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

  1. Albedo and constant source problems for extremely anisotropic scattering

    International Nuclear Information System (INIS)

    The half-space albedo problem and the constant source problem have been solved for a combination of the linearly anisotropic scattering and Inoenue's scattering functions. The linear transport equation for extremely anisotropic scattering kernel can be converted into an equivalent equation with a linearly anisotropic scattering kernel and the modified FN method can be used for albedo calculations. (orig.)

  2. Albedo method applied to coupled neutron-gamma shielding radiations

    International Nuclear Information System (INIS)

    The Albedo Theory was applied in order to develop an one-group algorithm for coupled neutron-gamma shielding calculations. The configuration analyzed consists of multilayered plane systems, where a incident neutron current generates gamma radiation through neutron-gamma reactions. The results obtained by Albedo Method and ANISN code have shown excellent agreement. (author)

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

    Science.gov (United States)

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

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

    Directory of Open Access Journals (Sweden)

    Rui Zhang

    2015-01-01

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

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

    NARCIS (Netherlands)

    Minnaert, Marcel Gilles Jozef

    1969-01-01

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

  6. Effect of shaddock albedo addition on the properties of frankfurters.

    Science.gov (United States)

    Shan, Bing; Li, Xingmin; Pan, Teng; Zheng, Limin; Zhang, Hao; Guo, Huiyuan; Jiang, Lu; Zhen, Shaobo; Ren, Fazheng

    2015-07-01

    To explore the potential as a natural auxiliary emulsifier, shaddock albedo was added into frankfurters at six different levels: 0.0, 2.5, 5.0, 7.5, 10 and 12.5 %. The emulsion capacity (EC) of meat batters and cooking properties of frankfurters were evaluated. EC of meat batters was improved with the addition of shaddock albedo and the maximum value was reached at the 5 % albedo concentration. The addition of shaddock albedo resulted in lower cooking losses of frankfurters, with the lowest value obtained at the 7.5 % level. The presence of shaddock albedo decreased the total expressible fluid (TEF) and the proportion of fat in total expressible fluid (PF) which indicated the emulsion stability of frankfurters and the lowest values both occurred at the concentration of 7.5 %. Shaddock albedo inclusion increased the lightness and yellowness of frankfurters and decreased redness. Texture profile analysis showed increased hardness and decreased chewiness of frankfurters with the addition of shaddock albedo. Consequently, shaddock albedo could be a potential source of auxiliary emulsifier filler for emulsion-type meat products. PMID:26139927

  7. Effect of Martian Suspended Dust on Albedo Measurements from the MGS-TES Data

    OpenAIRE

    Zinzi, A.; Palomba, E.; Rinaldi, G.; D'Amore, M.

    2010-01-01

    Suspended dust on Mars influences albedo measurements by orbiting instruments, but not necessary the real surface albedo. The aim of this study is to characterize the role of suspended aerosols on albedo measurement by remote sensing instruments.

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

    CERN Document Server

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

    2016-01-01

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

  9. The albedo effect on neutron transmission probability.

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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...

  11. Instability of a water-spout flow

    Science.gov (United States)

    Carrión, Luis; Herrada, Miguel A.; Shtern, Vladimir N.

    2016-03-01

    The paper studies the linear stability of a steady axisymmetric air-water motion in a vertical sealed cylinder, driven by the rotating top disk, motivated by possible applications in aerial bioreactors. As the flow strength Re increases, a vortex breakdown bubble (VBB) emerges near the bottom center and expands toward the interface. Regions of clockwise meridional circulation of air and water become separated by a thin anticlockwise circulation layer (TCL) adjacent to the interface in water. This study reveals that instability develops for larger Re than those at which VBB and TCL emerge. The instability focuses in the air region being typically of shear-layer type. The instability is centrifugal if the air volume fraction is small.

  12. Natural circulation flow behavior at reduced inventory conditions

    International Nuclear Information System (INIS)

    The flow instability behaviour of a natural circulation loop was studied at reduced inventory conditions, which is important during a LOCA situation in a nuclear reactor with non-availability of circulating pumps. For this, experiments were conducted at low steam drum levels. Large amplitude U-tube type oscillations were observed at low power condition when the system was mostly under single-phase condition. With rise in power when boiling was initiated in the loop, low quality Type I density-wave instabilities were observed. The characteristics of Type I instabilities are found to be quite different from the oscillations observed under single-phase conditions. (author)

  13. The Gamma-ray Albedo of the Moon

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-09-28

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

  14. Surface albedo measurements in Mexico City metropolitan area

    Energy Technology Data Exchange (ETDEWEB)

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

    2001-04-01

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

  15. Measurement of TLD Albedo response on various calibration phantoms

    International Nuclear Information System (INIS)

    The International Commission on Radiation Units and Measurements (ICRU) has recommended that individual dosemeter should be calibrated on a suitable phantom and has pointed out that the calibration factor of a neutron dosemeter is strongly influenced by the the exact size and shape of the body and the phantom to which the dosemeter is attached. As the principle of an albedo type thermoluminescent personal dosemeter (albedo TLD) is essentially based on a detection of scattered and moderated neutron from a human body, the sensitivity of albedo TLD is strongly influenced by the incident neutron energy and the calibration phantom. (1) Therefore for albedo type thermoluminescent personal dosemeter (albedo TLD), the information of neutron albedo response on the calibration phantom is important for appropriate dose estimation. In order to investigate the effect of phantom type on the reading of the albedo TLD, measurement of the TLD energy response and angular response on some typical calibration phantoms was performed using dynamitron accelerator and 252Cf neutron source. (author)

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

    Institute of Scientific and Technical Information of China (English)

    张正秋; 周秀骥; 李维亮; 徐兴奎

    2001-01-01

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

  17. Circulation economics

    DEFF Research Database (Denmark)

    Ingebrigtsen, Stig; Jakobsen, Ove

    2006-01-01

    Purpose - This paper is an attempt to advance the critical discussion regarding environmental and societal responsibility in economics and business. Design/methodology/approach - The paper presents and discusses as a holistic, organic perspective enabling innovative solutions to challenges...... concerning the responsible and efficient use of natural resources and the constructive interplay with culture. To reach the goal of sustainable development, the paper argues that it is necessary to make changes in several dimensions in mainstream economics. This change of perspective is called a turn towards...... presupposes a perspective integrating economic, natural and cultural values. Third, to organize the interplay between all stakeholders we introduce an arena for communicative cooperation. Originality/value - The paper concludes that circulation economics presupposes a change in paradigm, from a mechanistic...

  18. Albedo's determination by the method of neutron impulse

    International Nuclear Information System (INIS)

    Experiments with non-stationary neutron transport in large cavity moderators (l>>Σsub(tr)-1) (where l is the characteristic cavity length and Σsub(tr)-1 the macroscopic transport section of the moderator) led to the method reported in this study which, based on neutron impulses for determining albedo of thermal neutrons, gave a precision greater by an order of magnitude over previous methods. A sufficient time interval after introduction of the neutron flux into the moderator chamber decreased exponentially the decay constant L, which was itself related to albedo by a function called f. Numerical calculations of albedo were assisted. (author)

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

    International Nuclear Information System (INIS)

    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. (authors)

  20. Lunar Terrain and Albedo Reconstruction from Apollo Imagery

    Science.gov (United States)

    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. Design and Fabrication of an Albedo Insensitive Analog Sun Sensor

    OpenAIRE

    Wu, H.; Emadi, A.; De Graaf, G.; Leijtens, J.; Wolffenbuttel, R F

    2011-01-01

    A sun sensor is usually included in a satellite for optically measuring the position relative to the sun. The accuracy of a conventional sun sensor is affected by reflected sunlight at the nearby earth atmosphere: the albedo radiation. The part of the spectrum at near IR (1.5 μm) is not included in the albedo radiation, due to the high water absorption in the earth atmosphere. The feasibility of such a near infrared (IR) analog albedo insensitive sun sensor in terms of the design constraints ...

  2. Observational estimates of planetary albedo changes due to anthropogenic effects /

    OpenAIRE

    Pistone, Kristina

    2014-01-01

    A major driver of both the Earth's natural climate variability and current climate change is the net solar input to the Earth system, i.e. the amount of incident solar radiation minus the fraction reflected back to space. Changes in this so-called albedo may have substantial effects on the Earth's climate. I use observations to address aspects of both the Arctic sea ice -albedo feedback and the albedo effects of aerosols on Indian Ocean cumulus clouds. In Chapter 2, I use satellite radiation ...

  3. The Albedo Distribution of Near Earth Asteroids

    Science.gov (United States)

    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.

  4. Personnel neutron monitoring based on albedo technique

    International Nuclear Information System (INIS)

    This work deals with the study, design and test of a personal neutron monitor based on the detection of albedo neutrons from the body and its further relation to the incident flux. By this method, neutrons of energies below about 100 KeV can be efficiently detected, providing good information in the region where the biological effectiveness of neutron radiation starts to rise. The system consists of a pair of Thermoluminescent Detectors (6 LiF - 7 LiF) ∼ inside a polyethylene moderating body, in order to increase the sensitivity. The surface of the dosimeter facing away from the body is covered by a layer of a borated resin to assure appropriate shielding of incident low energy neutrons. The response of the dosimeter to monoenergetic neutrons from a 3 MeV Van de Graaff, to Am Be neutrons and to neutrons from a thermal column was investigated. The directional sensitivity, the effect of beam divergence was well as the effect of changes in dosimeter-to-body distances were also studied. (author)

  5. The Albedo Distribution of Near Earth Asteroids

    CERN Document Server

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

    2016-01-01

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

  6. Global color and albedo variations on Triton

    International Nuclear Information System (INIS)

    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 degree to -30 degree. A bright fringe is closely associated with the cap's margin; from 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 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

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

    International Nuclear Information System (INIS)

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

  8. Validation of MODIS albedo products with high resolution albedo estimates from FORMOSAT-2

    OpenAIRE

    Courault, Dominique; Olioso, Albert; Weiss, Marie; Marloie, Olivier; Baret, Frédéric; Hagolle, Olivier; GALLEGO-ELVIRA, Belen

    2013-01-01

    Among MODIS products (freely available to the scientific community from 2001), albedo data (MCD43B3) are 16 days composites at 1km spatial resolution, widely used for various applications in climate models, but which still remains difficult to validate. The objective of this study is to propose a method to validate these products with high spatial and temporal resolution data. 31 FORMOSAT-2 images acquired over a small region in the South-Eastern France at 8m for spatial resolution were aggre...

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

    Digital Repository Service at National Institute of Oceanography (India)

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

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

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

    Science.gov (United States)

    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. Direct Intrinsics: Learning Albedo-Shading Decomposition by Convolutional Regression

    OpenAIRE

    Narihira, Takuya; Maire, Michael; Yu, Stella X.

    2015-01-01

    We introduce a new approach to intrinsic image decomposition, the task of decomposing a single image into albedo and shading components. Our strategy, which we term direct intrinsics, is to learn a convolutional neural network (CNN) that directly predicts output albedo and shading channels from an input RGB image patch. Direct intrinsics is a departure from classical techniques for intrinsic image decomposition, which typically rely on physically-motivated priors and graph-based inference alg...

  12. Earth albedo effects in the motion of artificial earth satellites

    Science.gov (United States)

    Lala, P.

    Different models of the earth albedo values and geographical distribution are compared. Effects of the local cloud cover on the satellite perturbing acceleration are investigated. Resulting changes of the satellite orbit obtained by the method of numerical integration in the spherical coordinate system are given. It is shown that a sufficiently sensitive microaccelerometer on board a special satellite could significantly improve existing models of the earth albedo.

  13. NEOWISE Diameters and Albedos V1.0

    Science.gov (United States)

    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.

  14. Global Scale Comparison of MISR and MODIS Land Surface Albedos

    OpenAIRE

    Pinty, Bernard; TABERNER Malcolm; HAEMMERLE Vance; PARADISE Susan; Vermote, Eric; Verstraete, Michel; Gobron, Nadine; Widlowski, Jean-Luc

    2011-01-01

    MODIS white sky surface albedos are compared with similar products generated on the basis of the MISR surface BRF model parameters available for year 2005. The analysis is achieved using global scale statistics in order to characterize the broad patterns of these two independent albedo datasets. The results obtained in Taberner etal. (2010) have shown that robust statistics can be established and that both datasets are highly correlated. As a result, the slight but consistent ...

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

    OpenAIRE

    Rui Zhang; Guosheng Jiang; Jia Liang

    2015-01-01

    Pervious pavements have been advocated as a potential countermeasure to the urban heat island effect. To understand if pervious pavements stay cooler than conventional pavements, the albedo of the pervious concrete must be understood. This study measured the albedo of pervious concrete with different porosity. Four Portland cement concrete mixes were casted, using designed amounts of sand to vary the porosity of the pervious concrete samples. The samples were sliced and the spectral reflectan...

  16. NEOWISE Reactivation Mission Year One: Preliminary Asteroid Diameters and Albedos

    CERN Document Server

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

    2015-01-01

    We present preliminary diameters and albedos for 7,959 asteroids detected in the first year of the NEOWISE Reactivation mission. 201 are near-Earth asteroids (NEAs). 7,758 are Main Belt or Mars-crossing asteroids. 17% of these objects have not been previously characterized using WISE 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.

  17. Summertime canopy albedo is sensitive to forest thinning

    OpenAIRE

    Otto, J.; Berveiller, D.; F.-M. Bréon; Delpierre, N.; Geppert, G.; Granier, A.; Jans, W.; Knohl, A; Kuusk, A.; B. Longdoz; Moors, E.; Mund, M.; Pinty, B.; M.-J. Schelhaas; Luyssaert, S.

    2013-01-01

    Despite an emerging body of literature linking canopy albedo to forest management, understanding of the process is still fragmented. We combined a stand-level forest gap model with a canopy radiation transfer model and satellite-derived model parameters to quantify the effects of forest thinning, that is removing trees at a certain time during the forest rotation, on summertime canopy albedo. The effects of different forest species (pine, beech, oak) and four thinning strategies (light to int...

  18. Factors influencing the mesoscale variations in marine stratocumulus albedo

    OpenAIRE

    D. A. Hegg; Nielsen, K.; Jonsson, H. H.; Durkee, P.A.; Covert, D S

    2007-01-01

    Tellus, 59B, 66-76, 2007. The article of record as published may be found at http://dx.doi.org/10.1111/j.1600-0889.2006.00231.x Measurements of both horizontal gradients and vertical profiles of aerosols, cloud droplets and thermodynamic parameters in the cloud topped marine boundary layer off of central California are presented. They suggest that, while aerosols can indeed modulate cloud albedo, other parameters such as sea surface temperature may similarly affect cloud albedo. ...

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

    Science.gov (United States)

    Bell, J.F., III; 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.

  20. Sublimation's impact on temporal change of albedo dichotomy on Iapetus

    OpenAIRE

    Kimura, Jun; Kawamura, Taichi; Morito, Hisataka; Morota, Tomokatsu; Honda, Chikatoshi; Kuramoto, Kiyoshi; Okada, Tatsuaki

    2011-01-01

    Iapetus, one of the Saturnian moons, has an extreme albedo contrast between the leading and trailing hemispheres. The origin of this albedo dichotomy has led to several hypotheses, however it remains controversial. To clarify the origin of the dichotomy, the key approach is to investigate the detailed distribution of the dark material. Recent studies of impact craters and surface temperature from Cassini spacecraft data implied that sublimation of H2O ice can occur on Iapetus' surface. This i...

  1. Effects of species selection and management on forest canopy albedo

    OpenAIRE

    Otto, Juliane; Berveiller, Daniel; Bréon, François-Marie; Delpierre, Nicolas; Geppert, Gernot; Granier, André; Gunia, Katja; Jans, Wilma; Knohl, Alexander; Kuusk, Andres; Longdoz, Bernard; Moors, Eddy; Mund, Martina; Pinty, Bernard; Rautiainen, Miina

    2013-01-01

    Forest management is considered to be one of the key instruments available to mitigate climate change as it can lead to increased sequestration of atmospheric carbon dioxide. However, the changes in canopy albedo may neutralise or offset the climate benefits of carbon sequestration. Although there is an emerging body of literature linking canopy albedo to management, understanding is still fragmented. We make use of a generally applicable approach: we combine a stand-level forest gap model wi...

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

    OpenAIRE

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

    2012-01-01

    Greenland ice sheet mass loss has accelerated in the past decade responding to combined glacier discharge and surface melt water runoff increases. During summer, absorbed solar energy, modulated at the surface primarily by albedo, is the dominant factor governing surface melt variability in the ablation area. Using satellite observations of albedo and melt extent with calibrated regional climate model output, we determine the spatial dependence and quantitative impact of the ice sheet...

  3. IAU nomenclature for albedo features on the planet Mercury

    Science.gov (United States)

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

    1978-01-01

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

  4. Non interactive calculation of effective neutron multiplication factor by using two-group neutron albedo theory

    International Nuclear Information System (INIS)

    The effective neutron multiplication factor, Keff, explicitly appears under the neutron albedo theory. An albedo scheme can be used to determine Keff value without an iterative strategy. The albedo theory is illustrated by the endeavor of calculating Keff by using two-group neutron albedo method for spherical reflected cores. (author). 4 refs, 7 tabs

  5. Spectral albedo and transmittance of thin young Arctic sea ice

    Science.gov (United States)

    Taskjelle, Torbjørn; Hudson, Stephen R.; Granskog, Mats A.; Nicolaus, Marcel; Lei, Ruibo; Gerland, Sebastian; Stamnes, Jakob J.; Hamre, Børge

    2016-01-01

    Spectral albedo and transmittance in the range were measured on three separate dates on less than thick new Arctic sea ice growing on Kongsfjorden, Svalbard at , . Inherent optical properties, including absorption coefficients of particulate and dissolved material, were obtained from ice samples and fed into a radiative transfer model, which was used to analyze spectral albedo and transmittance and to study the influence of clouds and snow on these. Integrated albedo and transmittance for photosynthetically active radiation () were in the range 0.17-0.21 and 0.77-0.86, respectively. The average albedo and transmittance of the total solar radiation energy were 0.16 and 0.51, respectively. Values inferred from the model indicate that the ice contained possibly up to 40% brine and only 0.6% bubbles. Angular redistribution of solar radiation by clouds and snow was found to influence both the wavelength-integrated value and the spectral shape of albedo and transmittance. In particular, local peaks and depressions in the spectral albedo and spectral transmittance were found for wavelengths within atmospheric absorption bands. Simulated and measured transmittance spectra were within 5% for most of the wavelength range, but deviated up to 25% in the vicinity of , indicating the need for more optical laboratory measurements of pure ice, or improved modeling of brine optical properties in this near-infrared wavelength region.

  6. Single Scattering Albedo Monitor for Airborne Particulates

    Science.gov (United States)

    Onasch, Timothy; Massoli, Paola; Kebabian, Paul; Hills, Frank; Bacon, Fred; Freedman, Andrew

    2015-04-01

    We describe a robust, compact, field deployable instrument (the CAPS PMssa) that simultaneously measures airborne particle light extinction and scattering coefficients and thus the single scattering albedo (SSA) on the same sample volume. With an appropriate change in mirrors and light source, measurements have been made at wavelengths ranging from 450 to 780 nm. The extinction measurement is based on cavity attenuated phase shift (CAPS) techniques as employed in the CAPS PMex particle extinction monitor; scattering is measured using a integrating nephelometry by incorporating a Lambertian integrating sphere within the sample cell. The scattering measurement is calibrated using the extinction measurement. Measurements using ammonium sulfate particles of various sizes indicate that the response of the scattering channel with respect to measured extinction is linear to within 1% up to 1000 Mm-1 and can be extended further (4000 Mm-1) with additional corrections. The precision in both measurement channels is less than 1 Mm-1 (1s, 1σ). The truncation effect in the scattering channel, caused by light lost at extreme forward/backward scattering angles, was measured as a function of particle size using monodisperse polystyrene latex particles (n=1.59). The results were successfully fit using a simple geometric model allowing for reasonable extrapolation to a given wavelength, particle index of refraction and particle size distribution, assuming spherical particles. For sub-micron sized particles, the truncation corrections are comparable to those reported for commercial nephelometers. Measurements of the optical properties of ambient aerosol indicate that the values of the SSA of these particles measured with this instrument (0.91±0.03) using scattering and extinction agreed within experimental uncertainty with those determined using extinction measured by this instrument and absorption measured using a Multi-Angle Absorption Spectrometer (0.89±0.03) where the

  7. Atmospheric statistical dynamic models. Climate experiments: albedo experiments with a zonal atmospheric model

    International Nuclear Information System (INIS)

    The zonal model experiments with modified surface boundary conditions suggest an initial chain of feedback processes that is largest at the site of the perturbation: deforestation and/or desertification → increased surface albedo → reduced surface absorption of solar radiation → surface cooling and reduced evaporation → reduced convective activity → reduced precipitation and latent heat release → cooling of upper troposphere and increased tropospheric lapse rates → general global cooling and reduced precipitation. As indicated above, although the two experiments give similar overall global results, the location of the perturbation plays an important role in determining the response of the global circulation. These two-dimensional model results are also consistent with three-dimensional model experiments. These results have tempted us to consider the possibility that self-induced growth of the subtropical deserts could serve as a possible mechanism to cause the initial global cooling that then initiates a glacial advance thus activating the positive feedback loop involving ice-albedo feedback (also self-perpetuating). Reversal of the cycle sets in when the advancing ice cover forces the wave-cyclone tracks far enough equatorward to quench (revegetate) the subtropical deserts

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

    OpenAIRE

    H. S. Negi; A. Kokhanovsky

    2010-01-01

    In the present paper spectral reflectance measurements of Himalayan seasonal snow were carried out and analysed to retrieve the snow albedo and effective grain size. The asymptotic radiative transfer (ART) theory was applied to retrieve the plane and spherical albedo. The retrieved plane albedo was compared with the measured spectral albedo and a good agreement was observed with ±10% measured error accuracy. Retrieved integrated albedo was found within ±6% difference with ground observed broa...

  9. Mapping spatially-temporally continuous shortwave albedo for global land surface from MODIS data

    OpenAIRE

    Liu, N.; Liu, Q.; Wang, L.; Liang, S.; Wen, J.; Y. Qu; Liu, S

    2012-01-01

    Land-surface albedo plays a critical role in the Earth's radiant energy budget studies. Satellite remote sensing is an effective approach to acquire regional and global albedo observations. However, owing to cloud coverage, seasonal snow and sensor malfunctions, spatially-temporally continuous albedo datasets are often inaccessible. GLASS preliminary albedo datasets (GLASS02A2x, x = 1, 2, 3 and 4) are newly developed global daily land-surface albedo produ...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1992-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1992-01-01

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

  12. Heuristic explanation of journal bearing instability

    Science.gov (United States)

    Crandall, S. H.

    1982-01-01

    A fluid-filled journal bearing is viewed as a powerful pump circulating fluid around the annular space between the journal and the bearing. A small whirling motion of the journal generates a wave of thickness variation progressing around the channel. The hypothesis that the fluid flow drives the whirl whenever the mean of the pumped fluid velocity is greater than the peripheral speed of the thickness variation wave is discussed and compared with other simple explanations of journal bearing instability. It is shown that for non-cavitation long bearings the hypothesis predicts instability onset correctly for unloaded bearings but gradually overpredicts the onset speed as the load is increased.

  13. THE HIGH ALBEDO OF THE HOT JUPITER KEPLER-7 b

    International Nuclear Information System (INIS)

    Hot Jupiters are expected to be dark from both observations (albedo upper limits) and theory (alkali metals and/or TiO and VO absorption). However, only a handful of hot Jupiters have been observed with high enough photometric precision at visible wavelengths to investigate these expectations. The NASA Kepler mission provides a means to widen the sample and to assess the extent to which hot Jupiter albedos are low. We present a global analysis of Kepler-7 b based on Q0-Q4 data, published radial velocities, and asteroseismology constraints. We measure an occultation depth in the Kepler bandpass of 44 ± 5 ppm. If directly related to the albedo, this translates to a Kepler geometric albedo of 0.32 ± 0.03, the most precise value measured so far for an exoplanet. We also characterize the planetary orbital phase light curve with an amplitude of 42 ± 4 ppm. Using atmospheric models, we find it unlikely that the high albedo is due to a dominant thermal component and propose two solutions to explain the observed planetary flux. First, we interpret the Kepler-7 b albedo as resulting from an excess reflection over what can be explained solely by Rayleigh scattering, along with a nominal thermal component. This excess reflection might indicate the presence of a cloud or haze layer in the atmosphere, motivating new modeling and observational efforts. Alternatively, the albedo can be explained by Rayleigh scattering alone if Na and K are depleted in the atmosphere by a factor of 10-100 below solar abundances.

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

    Directory of Open Access Journals (Sweden)

    H. Kienert

    2013-08-01

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

  15. The Effect of Host Star Spectral Energy Distribution and Ice-Albedo Feedback on the Climate of Extrasolar Planets

    CERN Document Server

    Shields, Aomawa L; Bitz, Cecilia M; Pierrehumbert, Raymond T; Joshi, Manoj M; Robinson, Tyler D

    2013-01-01

    Planetary climate can be affected by the interaction of the host star spectral energy distribution with the wavelength-dependent reflectivity of ice and snow. Here we explore this effect using a one dimensional (1-D), line-by-line, radiative-transfer model to calculate broadband planetary albedos as input to a seasonally varying, 1-D energy-balance climate model. A three-dimensional general circulation model is also used to explore the atmosphere's response to changes in incoming stellar radiation, or instellation, and surface albedo. Using this hierarchy of models we simulate planets covered by ocean, land, and water ice of varying grain size, with incident radiation from stars of different spectral types. Terrestrial planets orbiting stars with higher near-UV radiation exhibit a stronger ice-albedo feedback. We find that ice-covered conditions occur on an F-dwarf planet with only a 2% reduction in instellation relative to the present instellation on Earth, assuming fixed CO2 (present atmospheric level on Ea...

  16. Potential effects of forest management on surface albedo

    Science.gov (United States)

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

    2012-04-01

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

  17. Improvement of Surface Albedo Simulations over Arid Regions

    Institute of Scientific and Technical Information of China (English)

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

    2008-01-01

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

  18. Decadal to seasonal variability of Arctic sea ice albedo

    CERN Document Server

    Agarwal, S; Wettlaufer, J S

    2011-01-01

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

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

    CERN Document Server

    Demory, Brice-Olivier; Madhusudhan, Nikku; Kjeldsen, Hans; Christensen-Dalsgaard, Joergen; Gillon, Michael; Rowe, Jason F; Welsh, William F; Adams, Elisabeth R; Dupree, Andrea; McCarthy, Don; Kulesa, Craig; Borucki, William J; Koch, David G

    2011-01-01

    Hot Jupiters are expected to be dark from both observations (albedo upper limits) and theory (alkali metals and/or TiO and VO absorption). However, only a handful of hot Jupiters have been observed with high enough photometric precision at visible wavelengths to investigate these expectations. The NASA Kepler mission provides a means to widen the sample and to assess the extent to which hot Jupiter albedos are low. We present a global analysis of Kepler-7b based on Q0-Q4 data, published radial velocities, and asteroseismology constraints. We measure an occultation depth in the Kepler bandpass of 44+-5 ppm. If directly related to the albedo, this translates to a Kepler geometric albedo of 0.32+-0.03, the most precise value measured so far for an exoplanet. We also characterize the planetary orbital phase lightcurve with an amplitude of 42+-4 ppm. Using atmospheric models, we find it unlikely that the high albedo is due to a dominant thermal component and propose two solutions to explain the observed planetary ...

  20. Matrix albedo for discrete ordinates infinite-medium boundary condition

    International Nuclear Information System (INIS)

    Discrete ordinates problems with an infinite exterior medium (reflector) can be more efficiently computed by eliminating grid cells in the exterior medium and applying a matrix albedo boundary condition. The albedo matrix is a discretized bidirectional reflection distribution function (BRDF) that accounts for the angular quadrature set, spatial quadrature method, and spatial grid that would have been used to model a portion of the exterior medium. The method is exact in slab geometry, and could be used as an approximation in multiple dimensions or curvilinear coordinates. We present an adequate method for computing albedo matrices and demonstrate their use in verifying a discrete ordinates code in slab geometry by comparison with Ganapol's infinite medium semi-analytic TIEL benchmark. With sufficient resolution in the spatial and angular grids and iteration tolerance to yield solutions converged to 6 digits, the conventional (scalar) albedo boundary condition yielded 2-digit accuracy at the boundary, but the matrix albedo solution reproduced the benchmark scalar flux at the boundary to all 6 digits. (authors)

  1. Tundra vegetation effects on pan-Arctic albedo

    International Nuclear Information System (INIS)

    Recent field experiments in tundra ecosystems describe how increased shrub cover reduces winter albedo, and how subsequent changes in surface net radiation lead to altered rates of snowmelt. These findings imply that tundra vegetation change will alter regional energy budgets, but to date the effects have not been documented at regional or greater scales. Using satellite observations and a pan-Arctic vegetation map, we examined the effects of shrub vegetation on albedo across the terrestrial Arctic. We included vegetation classes dominated by low shrubs, dwarf shrubs, tussock-dominated graminoid tundra, and non-tussock graminoid tundra. Each class was further stratified by bioclimate subzones. Low-shrub tundra had higher normalized difference vegetation index values and earlier albedo decline in spring than dwarf-shrub tundra, but for tussock tundra, spring albedo declined earlier than for low-shrub tundra. Our results illustrate how relatively small changes in vegetation properties result in differences in albedo dynamics, regardless of shrub growth, that may lead to differences in net radiation upwards of 50 W m-2 at weekly time scales. Further, our findings imply that changes to the terrestrial Arctic energy budget during this important seasonal transition are under way regardless of whether recent satellite observed productivity trends are the result of shrub expansion. We conclude that a better understanding of changes in vegetation productivity and distribution in Arctic tundra is essential for accurately quantifying and predicting carbon and energy fluxes and associated climate feedbacks.

  2. Occurrence of lower cloud albedo in ship tracks

    Directory of Open Access Journals (Sweden)

    Y.-C. Chen

    2012-05-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, I.C.; Stevens, P.N. (Tennessee Univ., Knoxville, TN (United States))

    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.

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

    International Nuclear Information System (INIS)

    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

  5. Systematics of shoulder instability

    International Nuclear Information System (INIS)

    Shoulder instability is defined as a symptomatic abnormal motion of the humeral head relative to the glenoid during active shoulder motion. Glenohumeral instabilities are classified according to the causative factors as the pathogenesis of instability plays an important role with respect to treatment options. Instabilities are classified into traumatic and atraumatic instabilities as part of a multidirectional instability syndrome and into microtraumatic instabilities. For diagnostics plain radiographs (''trauma series'') are performed to document shoulder dislocation and its successful repositioning. Direct magnetic resonance (MR) arthrography is the most important imaging modality for delineation of the different injury patterns of the labral-ligamentous complex and bony structures. Monocontrast computed tomography (CT) arthrography with the use of multidetector CT scanners represents an alternative imaging modality; however, MR imaging should be preferred in the work-up of shoulder instabilities due to the mostly younger age of patients. (orig.)

  6. Direct determination of surface albedos from satellite imagery

    Science.gov (United States)

    Mekler, Y.; Joseph, J. H.

    1983-01-01

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

  7. Multigroup albedo method applied to gamma radiation shielding

    International Nuclear Information System (INIS)

    The Albedo method, when applied to shielding calculations, is characterized by following the radiation through the materials, determining the reflected, absorbed and transmitted fractions of the incident current, independently of flux calculations. The excellent results obtained to neutron shielding cases in which the diffusion approximation could be applied motivated this work, where the method was applied in order to develop a multigroup and multilayered algorithm. A gamma radiation shielding simulation was carried out to a system constituted by three infinite slabs of varied materials and six energy groups. The results obtained by Albedo Method were the same generated by ANISN, a consecrated deterministic nuclear code. Concludingly, this work demonstrates the validity of Albedo Method to gamma radiation shielding analysis through its agreement with the full Transport Equation. (author)

  8. Brazilian two-component TLD albedo neutron individual monitoring system

    International Nuclear Information System (INIS)

    Since 1983, Instituto de Radioprotecao e Dosimetria, Brazil, uses a TLD one-component albedo neutron monitor, which has a single different calibration factor specifically for each installation type. In order to improve its energy response, a two-component albedo monitor was developed, which measure the thermal neutron component besides the albedo one. The two-component monitor has been calibrated in reference neutron fields: thermal, five accelerator-produced monoenergetic beams (70, 144, 565, 1200 and 5000 keV) and five radionuclide sources (252Cf, 252Cf(D2O), 241Am-Be, 241Am-B and 238Pu-Be) at several distances. Since January 2008, mainly Brazilian workers who handle neutron sources at different distances and moderation, such as in well logging and calibration facilities are using it routinely.

  9. Albedo calculation for single scattering gamma-rays, (2)

    International Nuclear Information System (INIS)

    The analytical formulae of number albedo and energy albedo for single scattering gamma-rays were given in the form of F2 function, under the assumption that cross-section, energy and attenuation coefficient of backscattered gamma-rays were constant for scattering angles. The results calculated with the analytical formula agreed with those of numerical integration within +-20% error. The more simplified formula was also presented here with a correcting term. This formula is practically useful in estimating albedo of single scattering gamma-rays with in an accuracy of 10% for most materials of a finite thickness in the incident energy ranges of 0.05 to 3 MeV. (auth.)

  10. Sample size and scene identification (cloud) - Effect on albedo

    Science.gov (United States)

    Vemury, S. K.; Stowe, L.; Jacobowitz, H.

    1984-01-01

    Scan channels on the Nimbus 7 Earth Radiation Budget instrument sample radiances from underlying earth scenes at a number of incident and scattering angles. A sampling excess toward measurements at large satellite zenith angles is noted. Also, at large satellite zenith angles, the present scheme for scene selection causes many observations to be classified as cloud, resulting in higher flux averages. Thus the combined effect of sampling bias and scene identification errors is to overestimate the computed albedo. It is shown, using a process of successive thresholding, that observations with satellite zenith angles greater than 50-60 deg lead to incorrect cloud identification. Elimination of these observations has reduced the albedo from 32.2 to 28.8 percent. This reduction is very nearly the same and in the right direction as the discrepancy between the albedoes derived from the scanner and the wide-field-of-view channels.

  11. Cloud albedo control by cloud-top entrainment

    Science.gov (United States)

    Hanson, Howard P.

    1991-01-01

    Marine stratus and stratocumulus clouds exert a considerable influence on the earth's heat budget, mainly due to their high albedos relative to the ocean surface. It is therefore important to understand the processes that control the radiative properties of these extensive cloud systems, particularly during daylight hours. Aircraft measurements of a stratocumulus cloud deck taken around local noon during the 1987 field phase of the First International Satellite Cloud Climatology Project Regional Experiment are the topic of this paper. A mixing line analysis of data from a series of flight tracks across a strong gradient in cloud albedo provides evidence that variations in the water vapor content of the air above the marine inversion can be responsible for the albedo change. The implications of this unexpected result for climate modeling are discussed.

  12. Evaluating shoulder instability treatment

    OpenAIRE

    Linde, J. A.

    2016-01-01

    Shoulder instability common occurs. When treated nonoperatively, the resulting societal costs based on health care utilization and productivity losses are significant. Shoulder function can be evaluated using patient reported outcome measurements (PROMs). For shoulder instability, these include the Western Ontario Shoulder Instability index (WOSI) and the Oxford Shoulder Instability Score (OSIS). When translated and validated for the dutch population, both have good measurment properties. Sco...

  13. Earnings instability and tenure

    OpenAIRE

    Cappellari, Lorenzo; Leonardi, Marco

    2007-01-01

    We study the effect of tenure on earnings instability in Italy using two alternative estimation strategies. First we use a descriptive measure of earnings instability and fixed effects regressions. Second, we develop a formal model of earnings dynamics distinguishing permanent from transitory earnings, and exploit variation of tenure and instability over time and across birth cohorts in estimation. We use the two approaches also to evaluate earnings instability associated with temporary contr...

  14. Diurnal variations in the UV albedo of arctic snow

    Directory of Open Access Journals (Sweden)

    O. Meinander

    2008-11-01

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

  15. Investigation of albedo neutrons by the Intercosmos-17 satellite

    Science.gov (United States)

    Dubinskii, Iu.; Efimov, Iu. E.; Kudela, K.; Mikhaeli, L.; Roiko, I.; Chichikaliuk, Iu. A.

    1982-09-01

    Measurements were made with the Intercosmos-17 scintillation counter in 1977 in order to investigate the contribution of albedo neutrons with energies of 1-30 MeV to the formation of radiation-belt protons of corresponding energies. The differential current density of albedo neutrons is presented for the invariant latitude of 42.7 deg during a quiet period of solar activity (October 8-10, 1977). The following value is obtained for this differential current density: I0 (1 MeV) = 0.104 + or - 0.023 neutrons/sq cm s MeV.

  16. The Gamma-ray Albedo of the Moon

    OpenAIRE

    Moskalenko, Igor V.; Porter, Troy A.

    2007-01-01

    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 a...

  17. Daily albedo estimation and comparison to MCD43 product

    Science.gov (United States)

    Franch, B.; Vermote, E.; Sobrino, J. A.

    2013-12-01

    Land surface broadband albedo is among the main radiative uncertainties in current climate modelling. An accuracy requirement of 5% and a daily temporal resolution is suggested by the Global Climate Observing System for albedo characterization at spatial and temporal scales compatible with climate studies. Satellite remote sensing provides the only practical way of producing high-quality global albedo data sets with high spatial and temporal resolutions. For view-ilumination geometries such as Moderate Resolution Imaging Spectroradiometer (MODIS), in order to retrieve the Bidirectional Reflectance Distribution Function (BRDF) parameters and, consequently, the albedo, a period of sequential measurement is needed to accumulate sufficient observations. This is used to derive the MODIS BRDF/Albedo product (MCD43), which consider a composite period of 16 days with a resulting temporal resolution of 8 days. Looking for an improvement in the albedo temporal resolution that mitigated the assumption of a stable target, Vermote et al. (2009) presented the VJB method that assumes that the BRDF shape variations throughout a year are limited and linked to the Normalized Difference Vegetation Index (NDVI). This method retains the highest temporal resolution (daily, cloud cover permitting). The purpose of this work is to compare the MCD43 product with the VJB method through the albedo. Additionally, we present and study a method based on the VJB assumption, the 5param Rsqr. In this study we focus our analysis on daily MODIS CMG Collection 6 data from both Aqua and Terra satellites over Europe from 2002 until 2011. Figure 1 shows the percentage of the total RMSE of the VJB and the 5param Rsqr method against the MCD43 product. They display that southern latitudes present lower errors while they increase for northern latitudes and mountainous areas. Comparing the methods, the VJB presents errors higher than 15% in 8.2% of total land pixels while they suppose 6.9% of pixels when

  18. Albedo particle rejection with the RICH study prototype of AMS

    CERN Document Server

    Thuillier, T; Buénerd, M; Gallin-Martel, L; Ohlsson-Malek, F

    2001-01-01

    An experimental test has been performed on the Ring Imaging Cherenkov (RICH) study prototype of AMS, with cosmic ray particles on the ground, to evaluate the counter performance for Albedo particle rejection. The test was made with two radiators : Sodium Fluoride crystal (NaF, n approx 1.33) and Silica Aerogel (n=1.035). The experimental results are shown and can be consistently accounted for on the basis of random events generated from PMT background counting by means of a simple model, used to estimate the Albedo rejection performance of the future AMS RICH.

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

    Science.gov (United States)

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

    2015-10-01

    Lake surface albedo determines energy balance of water-atmospheric interface and water physical environment. Solar elevation angle, cloudiness, wind speed, water quality and other factors can affect lake surface albedo. Using solar radiation, wind speed, and water quality data (turbidity and chlorophyll-a concentration) which were observed in four eddy covariance sites (Meiliangwan, Dapukou, Bifenggang and Xiaoleishan i. e. MLW, DPK, BFG and XLS) in Lake Taihu and clearness index (k(t)), the influence of these factors on Lake Taihu surface albedo and the reasons that led to its spatial difference were investigated. The results showed that solar elevation angle played a leading role in the diurnal and seasonal change of lake surface albedo; lake surface albedo reached two peaks in 0 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

  20. Monte Carlo calculation of 60Co γ-ray's albedo-dose rate from the air

    International Nuclear Information System (INIS)

    The Monte Carlo calculation of 60Co γ-ray's albedo-dose rate from the air is reported. A formula is presented with which the relations of the albedo-doserate with some parameters are simulated and fitted

  1. The relationship of surface chemistry and albedo of lunar soil samples

    Science.gov (United States)

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

    1977-01-01

    A relation between the albedo and the surface iron concentration (determined by Auger electron spectroscopy) of lunar soil samples is described. The effect of solar wind sputtering on the surface chemistry and albedo of the soil is discussed.

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

    Data.gov (United States)

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

  3. The WISE Survey of the Albedo Distribution of Main Belt Asteroids

    NARCIS (Netherlands)

    Masiero, J.; Mainzer, A.; Grav, T.; Delbó, M.; Mueller, M.; WISE Team, [No Value

    2010-01-01

    Using date from the Wide-field Infrared Survey Explorer (WISE) we investigate the albedo distribution across the main belt of asteroids. When complete WISE will measure albedos and diameters for ~100,000 asteroids.

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

    DEFF Research Database (Denmark)

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

    2011-01-01

    component. This excess reflection might indicate the presence of a cloud or haze layer in the atmosphere, motivating new modeling and observational efforts. Alternatively, the albedo can be explained by Rayleigh scattering alone if Na and K are depleted in the atmosphere by a factor of 10-100 below solar...

  5. WISE Albedos for Tens of Thousands of Main Belt Asteroids

    NARCIS (Netherlands)

    Masiero, Joseph R.; Mainzer, A. K.; Bauer, J.; Cutri, R.; Dailey, J.; Delbo, M.; Grav, T.; McMillan, R. S.; Mueller, M.; Walker, R.; Wright, E.; WISE Science Team, [No Value

    2010-01-01

    Using thermal IR data from the Wide-field Infrared Survey Explorer (WISE) mission we have calculated diameters for tens of thousands of previously known Main Belt asteroids. Using archival optical observations we have also determined albedos for each object. We present our results from this investig

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

    Directory of Open Access Journals (Sweden)

    Borghetti M

    2009-01-01

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

  7. Mimicking biochar-albedo feedback in complex Mediterranean agricultural landscapes

    Science.gov (United States)

    Bozzi, E.; Genesio, L.; Toscano, P.; Pieri, M.; Miglietta, F.

    2015-08-01

    Incorporation of charcoal produced by biomass pyrolysis (biochar) in agricultural soils is a potentially sustainable strategy for climate change mitigation. However, some side effects of large-scale biochar application need to be investigated. In particular a massive use of a low-reflecting material on large cropland areas may impact the climate via changes in surface albedo. Twelve years of MODIS-derived albedo data were analysed for three pairs of selected agricultural sites in central Italy. In each pair bright and dark coloured soil were identified, mimicking the effect of biochar application on the land surface albedo of complex agricultural landscapes. Over this period vegetation canopies never completely masked differences in background soil colour. This soil signal, expressed as an albedo difference, induced a local instantaneous radiative forcing of up to 4.7 W m-2 during periods of high solar irradiance. Biochar mitigation potential might therefore be reduced up to ˜30%. This study proves the importance of accounting for crop phenology and crop management when assessing biochar mitigation potential and provides more insights into the analysis of its environmental feedback.

  8. The retrieval of land surface albedo in rugged terrain

    NARCIS (Netherlands)

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

    2012-01-01

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

  9. Mimicking biochar-albedo feedback in complex Mediterranean agricultural landscapes

    International Nuclear Information System (INIS)

    Incorporation of charcoal produced by biomass pyrolysis (biochar) in agricultural soils is a potentially sustainable strategy for climate change mitigation. However, some side effects of large-scale biochar application need to be investigated. In particular a massive use of a low-reflecting material on large cropland areas may impact the climate via changes in surface albedo. Twelve years of MODIS-derived albedo data were analysed for three pairs of selected agricultural sites in central Italy. In each pair bright and dark coloured soil were identified, mimicking the effect of biochar application on the land surface albedo of complex agricultural landscapes. Over this period vegetation canopies never completely masked differences in background soil colour. This soil signal, expressed as an albedo difference, induced a local instantaneous radiative forcing of up to 4.7 W m−2 during periods of high solar irradiance. Biochar mitigation potential might therefore be reduced up to ∼30%. This study proves the importance of accounting for crop phenology and crop management when assessing biochar mitigation potential and provides more insights into the analysis of its environmental feedback. (letter)

  10. Surface albedo following biochar application in durum wheat

    International Nuclear Information System (INIS)

    The agronomic use of charcoal from biomass pyrolysis (biochar) represents an interesting option for increasing soil fertility and sequestering atmospheric CO2. However, before moving toward large-scale biochar applications, additional research must evaluate all possible land–atmosphere feedbacks. Despite the increasing number of studies investigating the effect of biochar on soil physical, chemical and biological properties, only a few have been done on surface albedo variations on agricultural lands. The present work had the aim of characterizing the annual albedo cycle for a durum wheat crop in Central Italy, by means of a spectroradiometer measurement campaign. Plots treated with biochar, at a rate of 30–60 t ha−1, showed a surface albedo decrease of up to 80% (after the application) with respect to the control in bare soil conditions, while this difference tended to decrease during the crop growing season, because of the prevailing effect of canopy development on the radiometer response. After the post-harvesting tillage, the soil treated with biochar again showed a lower surface albedo value (<20–26% than the control), while the measurements taken in the second year after application suggested a clear decrease of biochar influence on soil color. The modeling of the surface energy balance highlighted changes in the partitioning of heat fluxes and in particular a substantial increase of ground heat fluxes on an annual basis. (letter)

  11. New OSL detector combination for albedo neutron dosimetry

    International Nuclear Information System (INIS)

    A new detector pair of α-Al2O3:C + Li2B4O7:Cu,Ag, based on evaluation using optically stimulated luminescence (OSL) technique, was placed in the Karlsruhe type albedo cassette and its neutron response was studied in monoenergetic neutron fields with energies in the range from 24 keV to 14.8 MeV and in the field of a bare 252Cf radionuclide source. The ability and usefulness of such an albedo neutron dosimeter for personnel neutron monitoring based on OSL technique is discussed. The OSL Hp(10) response of the α-Al2O3:C + Li2B4O7:Cu,Ag dosimeters was found to decrease by more than two orders of magnitude with increasing neutron energy, as known for albedo dosimeters and was comparable to the results reported for the combination of α-Al2O3:C + 6,7LiF OSL dosimeters. - Highlights: • Albedo neutron measurement using a new optically stimulated luminescence (OSL) detector combination. • OSL neutron dose indication of α-Al2O3:C + Li2B4O7:Cu,Ag detector pair. • Hp(10) response of the α-Al2O3:C + Li2B4O7:Cu,Ag OSL detectors for monoenergetic neutron energies. • Potential application for personnel neutron monitoring

  12. Radiative transfer in plane inhomogeneous media with exponentially varying albedo

    International Nuclear Information System (INIS)

    Accurate numerical results for the exit distributions and the global reflection and transmission coefficients relevant to radiative transfer in a stratified medium with exponentially varying albedo are obtained and compared to previous results. The semi-analytical solution of the linear transport equation is rigorously performed on the basis of a simple projectional method. (author)

  13. The albedo problem for pure-quadratic scattering

    International Nuclear Information System (INIS)

    The one speed and time-independent neutron transport equation can be considered for a homogeneous medium which thickness is identified as τ in plane geometry and has nucleus in it. Here, interaction of nucleuses which are in slab that its thickness is τ and neutrons that are incoming to the medium from outside is considered as depend on quadratic quantities. In other words, neutron-nucleus interactions are proportional with second degree of neutrons advent direction(μ ) and scattering direction (μ') . The Case's eigenfunctions and the orthogonality relations of them can be written for this scattering. In addition the half-space albedo problem can be investigated with the same way. In this study, the singular eigenfunctions method is used. For the predicted neutron fluxes over surfaces the albedo and the transmitting relations can be written easily. Thus the albedo and the transmitting values for the slab and the albedo values for the half-space can be found as numerical. To examine the accuracy of the results calculated data can be worked on by interpolation method. Thus, while the quadratic anisotropic coefficient goes to zero, the results are to be reduced to results in isotropic scattering condition. The interpolated results, which are calculated in this way, are achieved so convergent to isotropic results

  14. Design and Fabrication of an Albedo Insensitive Analog Sun Sensor

    NARCIS (Netherlands)

    Wu, H.; Emadi, A.; De Graaf, G.; Leijtens, J.; Wolffenbuttel, R.F.

    2011-01-01

    A sun sensor is usually included in a satellite for optically measuring the position relative to the sun. The accuracy of a conventional sun sensor is affected by reflected sunlight at the nearby earth atmosphere: the albedo radiation. The part of the spectrum at near IR (1.5 μm) is not included in

  15. Summertime canopy albedo is sensitive to forest thinning

    NARCIS (Netherlands)

    Otto, J.; Berveiller, D.; Bréon, F.M.; Delpierre, N.; Geppert, G.; Granier, A.; Jans, W.W.P.; Knohl, A.; Moors, E.J.

    2013-01-01

    Despite an emerging body of literature linking canopy albedo to forest management, understanding of the process is still fragmented. We combined a stand-level forest gap model with a canopy radiation transfer model and satellite-derived model parameters to quantify the effects of forest thinning, th

  16. Albedo in the ATIC Experiment: Results of Measurements and Simulation

    Science.gov (United States)

    Sokolskaya, N. V.; Adams, J. H., Jr.; Ahn, H. S.; Bashindzhagyan, G. L.; Batkov, K. E.; Chang, J.; Christl, M.; Fazely, A. R.; Ganel, O.; Gunasingha, R. M.

    2004-01-01

    Characteristics of albedo, or backscatter current, providing a 'background' for calorimeter experiments in high energy cosmic rays are analyzed. The comparison of experimental data obtained in the flights of the ATIC spectrometer is made with simulations performed using the GEANT 3.21 code. The influence of the backscatter on charge resolution in the ATIC experiment is discussed.

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

    NARCIS (Netherlands)

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

    2008-01-01

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

  18. Albedo and color maps of the Saturnian satellites

    Energy Technology Data Exchange (ETDEWEB)

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

    1990-10-01

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

  19. Albedo of Permanently Shadowed Regions of the Lunar Poles

    Science.gov (United States)

    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

  20. Effective Albedo of Vegetated Terrain at L-Band

    Science.gov (United States)

    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

  1. Surface Albedo Variation and Its Influencing Factors over Dongkemadi Glacier, Central Tibetan Plateau

    OpenAIRE

    Jie Wang; Yuhuan Cui; Xiaobo He; Jian Zhang; Shijiang Yan

    2015-01-01

    Glacier albedo plays a critical role in surface-atmosphere energy exchange, the variability of which influences glacier mass balance as well as water resources. Dongkemadi glacier in central Tibetan Plateau was selected as study area; this research used field measurements to verify Landsat TM-derived albedo and MOD10A1 albedo product and then analyzed the spatiotemporal variability of albedo over the glacier according to them, as well as its influence factors and the relationship with glacier...

  2. Effects of Albedo Addition on Pomegranate Juice Physicochemical, Volatile and Chemical Markers

    OpenAIRE

    Vázquez-Araújo, Laura; IV, Edgar; Carbonell-Barrachina, Ángel

    2015-01-01

    Five commercial juices, representing the five clusters of this juice, were characterized before and after maceration with 10% pomegranate albedo (control- and albedo treated (AT)-juices, respectively). Commercial juices were macerated with albedo homogenate for 24 h, and then the albedo was removed. Total soluble solids, titratable acidity, maturity index (MI), total phenolic content (TPC), volatile composition, and flavor profile were evaluate in control- and AT-juices. From all physico-chem...

  3. Can uncertainties in sea ice albedo reconcile patterns of data-model discord for the Pliocene and 20th/21st centuries?

    Science.gov (United States)

    Howell, Fergus W.; Haywood, Alan M.; Dolan, Aisling M.; Dowsett, Harry J.; Francis, Jane E; Hill, Daniel J.; Pickering, Steven J.; Pope, James O; Salzmann, Ulrich; Wade, Bidget S

    2014-01-01

    General Circulation Model simulations of the mid-Pliocene warm period (mPWP, 3.264 to 3.025 Myr ago) currently underestimate the level of warming that proxy data suggest existed at high latitudes, with discrepancies of up to 11°C for sea surface temperature estimates and 17°C for surface air temperature estimates. Sea ice has a strong influence on high-latitude climates, partly due to the albedo feedback. We present results demonstrating the effects of reductions in minimum sea ice albedo limits in general circulation model simulations of the mPWP. While mean annual surface air temperature increases of up to 6°C are observed in the Arctic, the maximum decrease in model-data discrepancies is just 0.81°C. Mean annual sea surface temperatures increase by up to 2°C, with a maximum model-data discrepancy improvement of 1.31°C. It is also suggested that the simulation of observed 21st century sea ice decline could be influenced by the adjustment of the sea ice albedo parameterization.

  4. Can uncertainties in sea ice albedo reconcile patterns of data-model discord for the Pliocene and 20th/21st centuries?

    Science.gov (United States)

    Howell, Fergus W.; Haywood, Alan M.; Dolan, Aisling M.; Dowsett, Harry J.; Francis, Jane E.; Hill, Daniel J.; Pickering, Steven J.; Pope, James O.; Salzmann, Ulrich; Wade, Bridget S.

    2014-03-01

    General Circulation Model simulations of the mid-Pliocene warm period (mPWP, 3.264 to 3.025 Myr ago) currently underestimate the level of warming that proxy data suggest existed at high latitudes, with discrepancies of up to 11°C for sea surface temperature estimates and 17°C for surface air temperature estimates. Sea ice has a strong influence on high-latitude climates, partly due to the albedo feedback. We present results demonstrating the effects of reductions in minimum sea ice albedo limits in general circulation model simulations of the mPWP. While mean annual surface air temperature increases of up to 6°C are observed in the Arctic, the maximum decrease in model-data discrepancies is just 0.81°C. Mean annual sea surface temperatures increase by up to 2°C, with a maximum model-data discrepancy improvement of 1.31°C. It is also suggested that the simulation of observed 21st century sea ice decline could be influenced by the adjustment of the sea ice albedo parameterization.

  5. Shoulder instability; Schulterinstabilitaeten

    Energy Technology Data Exchange (ETDEWEB)

    Kreitner, Karl-Friedrich [Mainiz Univ. (Germany). Klinik und Poliklinik fuer Diagnostische und Interventionelle Radiologie

    2014-06-15

    In the shoulder, the advantages of range of motion are traded for the disadvantages of vulnerability to injury and the development of instability. Shoulder instability and the lesion it produces represent one of the main causes of shoulder discomfort and pain. Shoulder instability is defined as a symptomatic abnormal motion of the humeral head relative to the glenoid during active shoulder motion. Glenohumeral instabilities are classified according to their causative factors as the pathogenesis of instability plays an important role with respect to treatment options: instabilities are classified in traumatic and atraumatic instabilities as part of a multidirectional instability syndrome, and in microtraumatic instabilities. Plain radiographs ('trauma series') are performed to document shoulder dislocation and its successful reposition. Direct MR arthrography is the most important imaging modality for delineation the different injury patterns on the labral-ligamentous complex and bony structures. Monocontrast CT-arthrography with use of multidetector CT scanners may be an alternative imaging modality, however, regarding the younger patient age, MR imaging should be preferred in the diagnostic work-up of shoulder instabilities. (orig.)

  6. A generalized albedo option for forward and adjoint Monte Carlo calculations

    International Nuclear Information System (INIS)

    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 was done to evaluate and appropriate 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

  7. Existence result for the kinetic neutron transport problem with a general albedo boundary condition

    International Nuclear Information System (INIS)

    We present an existence result for the kinetic neutron transport equation with a general albedo boundary condition. The proof is constructive in the sense that we build a sequence that converges to the solution of the problem by iterating on the albedo term. Both nonhomogeneous and albedo boundary conditions are studied. (authors)

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

    Directory of Open Access Journals (Sweden)

    H. Kienert

    2013-01-01

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

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

    Science.gov (United States)

    Howell, Fergus W.; Haywood, Alan M.; Dowsett, Harry J.; Pickering, Steven J.

    2016-05-01

    General circulation model (GCM) simulations of the mid-Pliocene Warm Period (mPWP, 3.264 to 3.025 Myr ago) do not reproduce the magnitude of Northern Hemisphere high latitude surface air and sea surface temperature (SAT and SST) warming that proxy data indicate. There is also large uncertainty regarding the state of sea ice cover in the mPWP. Evidence for both perennial and seasonal mPWP Arctic sea ice is found through analyses of marine sediments, whilst in a multi-model ensemble of mPWP climate simulations, half of the ensemble simulated ice-free summer Arctic conditions. Given the strong influence that sea ice exerts on high latitude temperatures, an understanding of the nature of mPWP Arctic sea ice would be highly beneficial. Using the HadCM3 GCM, this paper explores the impact of various combinations of potential mPWP orbital forcing, atmospheric CO2 concentrations and minimum sea ice albedo on sea ice extent and high latitude warming. The focus is on the Northern Hemisphere, due to availability of proxy data, and the large data-model discrepancies in this region. Changes in orbital forcings are demonstrated to be sufficient to alter the Arctic sea ice simulated by HadCM3 from perennial to seasonal. However, this occurs only when atmospheric CO2 concentrations exceed 300 ppm. Reduction of the minimum sea ice albedo from 0.5 to 0.2 is also sufficient to simulate seasonal sea ice, with any of the combinations of atmospheric CO2 and orbital forcing. Compared to a mPWP control simulation, monthly mean increases north of 60°N of up to 4.2 °C (SST) and 9.8 °C (SAT) are simulated. With varying CO2, orbit and sea ice albedo values we are able to reproduce proxy temperature records that lean towards modest levels of high latitude warming, but other proxy data showing greater warming remain beyond the reach of our model. This highlights the importance of additional proxy records at high latitudes and ongoing efforts to compare proxy signals between sites.

  10. Joint instability and osteoarthritis.

    Science.gov (United States)

    Blalock, Darryl; Miller, Andrew; Tilley, Michael; Wang, Jinxi

    2015-01-01

    Joint instability creates a clinical and economic burden in the health care system. Injuries and disorders that directly damage the joint structure or lead to joint instability are highly associated with osteoarthritis (OA). Thus, understanding the physiology of joint stability and the mechanisms of joint instability-induced OA is of clinical significance. The first section of this review discusses the structure and function of major joint tissues, including periarticular muscles, which play a significant role in joint stability. Because the knee, ankle, and shoulder joints demonstrate a high incidence of ligament injury and joint instability, the second section summarizes the mechanisms of ligament injury-associated joint instability of these joints. The final section highlights the recent advances in the understanding of the mechanical and biological mechanisms of joint instability-induced OA. These advances may lead to new opportunities for clinical intervention in the prevention and early treatment of OA. PMID:25741184

  11. Modelling Financial Instability

    OpenAIRE

    Franklin Allen

    2005-01-01

    Financial instability can have large adverse effects on an economy. One major cause of instability is asset price bubbles. This paper starts by considering how such bubbles can arise due to the expansion of money and credit. The ways in which subsequent financial instability occurs are then discussed. Banking crises can arise due to panics or as a result of the business cycle. Contagion and financial fragility can cause small disturbances to have large effects. Finally, policy issues are touc...

  12. Dynamics of explosive instability

    International Nuclear Information System (INIS)

    It was shown that in general case explosive instability dynamics should be described as four wave interaction. The main difference from three wave interaction is that this dynamics may not contain explosive instability. Besides it may by irregular. If the characteristics of one of the wave is closed to one of the interacting wave and they are connected linearly then explosive instability may be suppressed.

  13. Calculation of characteristics of the albedo muon flux in the stratosphere

    International Nuclear Information System (INIS)

    Problem of albedo muon flux formation in the stratosphere is considered. Calculation of energy and angular characteristics of albedo muon flux by geomagnetic cut-off rigidity R=1; 4.5; 15 GV within the altitude range of 20≤hμ≤50 km is carried out. Comparison of experimental and calculational results indicates their fair agreement. The calculation shows that degree of albedo muon flux anisotropy increases with muon energy increase and the flux value is comparable with direct albedo proton flux in the energy area exceeding 200 MeV. The maximum in the integral albedo muon flux is achieved at altitudes hμ ≅30 km

  14. On the Ekman instability at the core-mantle boundary

    Science.gov (United States)

    Chkhetiani, O. G.; Shalimov, S. L.

    2016-05-01

    It is shown that the instability of turbulent flows with Ekman velocity profiles in the vicinity of the core-mantle boundary leads to the formation of horizontally oriented circulating roll structures. The geophysical implications of the presence of such structures in the liquid core are explored, namely, the formation of the hot zones with enhanced conductivity and their influence on geomagnetic reversals.

  15. Evaluating biases in simulated land surface albedo from CMIP5 global climate models

    Science.gov (United States)

    Li, Yue; Wang, Tao; Zeng, Zhenzhong; Peng, Shushi; Lian, Xu; Piao, Shilong

    2016-06-01

    Land surface albedo is a key parameter affecting energy balance and near-surface climate. In this study, we used satellite data to evaluate simulated surface albedo in 37 models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). There was a systematic overestimation in the simulated seasonal cycle of albedo with the highest bias occurring during the Northern Hemisphere's winter months. The bias in surface albedo during the snow-covered season was classified into that in snow cover fraction (SCF) and albedo contrast (β1). There was a general overestimation of β1 due to the simulated snow-covered albedo being brighter than the observed value; negative biases in SCF were not always related to negative albedo biases, highlighting the need for realistic representation of snow-covered albedo in models. In addition, models with a lower leaf area index (LAI) tend to produce a higher surface albedo over the boreal forests during the winter, which emphasizes the necessity of improving LAI simulations in CMIP5 models. Insolation weighting showed that spring albedo biases were of greater importance for climate. The removal of albedo biases is expected to improve temperature simulations particularly over high-elevation regions.

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

    Science.gov (United States)

    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.

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

    CERN Document Server

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

    2015-01-01

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

  18. Comparison of MCNPX and Albedo method in criticality calculation

    International Nuclear Information System (INIS)

    This study aims to conduct a computer simulation that will calculate the reactivity of a homogeneous reactor and compare the results with the calculations made by the albedo method. The simulation will be developed using the MCNPX. The study compared the results calculated for a hypothetical reactor by the albedo method for four groups of energy with those obtained by the MCNPX simulation. The design of the reactor is spherical and homogeneous with a reflector of finite thickness. The value obtained for the neutron effective multiplication factor - keff will be compared. Different situations were simulated in order to obtain results closer to the compared method and reality. The was Good consistency could be noticed between the calculated results. (author)

  19. Control of neutron albedo in toroidal fusion reactors

    International Nuclear Information System (INIS)

    The MCNP and ANISN codes have been used to obtain basic neutron albedo data for materials of interest for fusion applications. Simple physical models are presented which explain albedo dependence on pre- and post-reflection variables. The angular distribution of reflected neutrons. The energy spectra of reflected neutrons are presented, and it is shown that substantial variations in the total neutron current at the outboard wall of a torus can be effected by changing materials behind the inboard wall. Analyses show that a maximum of four isolated incident-current environments may be established simultaneously on the outboard side of a torus. With suitable inboard reflectors, global tritium breeding ratios significantly larger than unity can be produced in limited-coverage breeding blankets when the effects of outboard penetrations are included

  20. Comparison of MISR and MODIS land surface albedos: Methodology

    Science.gov (United States)

    Taberner, M.; Pinty, B.; Govaerts, Y.; Liang, S.; Verstraete, M. M.; Gobron, N.; Widlowski, J.-L.

    2010-03-01

    The broadband white sky surface albedo (bihemispherical reflectance) products available from the Moderate Resolution Imaging Spectroradiometer (MODIS) are compared at regional and continental scales with similar products generated from the Multiangle Imaging Spectroradiometer (MISR) land surface bidirectional reflectance factor (BRF) parameters. This paper describes the methodology applied to derive MISR white sky albedos over four spectral broadbands of interest, namely, 0.3-0.7 μm, 0.4-1.1 μm, 0.7-3.0 μm, and 0.3-3.0 μm, as well as an evaluation of the strategy adopted to compare the MODIS and MISR products. The results are very encouraging since the two data sets show very good statistical agreement over large areas and over a full year of measurements, despite the many differences that exist in the suite of algorithms applied to retrieve these surface quantities from each of these instruments separately.

  1. Retrieval of Planetary Rotation and Albedo from DSCOVR data

    OpenAIRE

    Kane, S.R.; Domagal-Goldman, S. D.; Herman, J.R.; Robinson, T. D; Stine, A. R.

    2015-01-01

    The field of exoplanets has rapidly expanded from the exclusivity of exoplanet detection to include exoplanet characterization. A key step towards this characterization will be retrieval of planetary albedos and rotation rates from highly undersampled imaging data. The Deep Space Climate Observatory (DSCOVR) provides a unique opportunity to test such retrieval methods using high cadence data of the sunlit surface of the Earth. There are two NASA instruments on board DSCOVR that can be used to...

  2. Methods of albedo electron densimetry. 2. Two-channel methods

    Energy Technology Data Exchange (ETDEWEB)

    Sorokin, V.B. (Tomskij Politekhnicheskij Inst. (USSR). Nauchno-Issledovatel' skij Inst. Ehlektronnoj Introskopii)

    1981-12-01

    Two-channel methods of densimetry permitting to realize control over density of materials with fluctuating composition which have been developed on the basis of one-channel albedo electron methods are considered. The two-channel methods permits to decrease the errors as compared with one-channel ones and when central-peripheral method is applied - also to increase the sensitivity to density variation. The methods are intended for control density of porous materials, especially in powder metallurgy, ceramics production, etc.

  3. Albedo Measurement System for UVA and the Visible Wavelength

    International Nuclear Information System (INIS)

    An instrument system to measure the UVA and visible albedo from the snow capped mountain ranges has been built. Albedo is the ratio between the incoming radiation and the reflected radiation for a given location. Measuring albedo of the UVA and the Photosynthetic Active Radiation (PAR) wavelength range involves measuring the global irradiance and the reflections from the slopes around the measuring location. This system can be installed in any mountain peak to measure the reflectivity around the snow covered slopes. Global irradiance is measured by a standard global sensor using a Gigahertz UVA head and a home built UVA head. The UVA reflection is measured by an 1 deg. telescope fitted with a home built UVA head. The home built UVA detector systems have been built using Hamamatsu silicon UV diodes and temperature stabilized using Peltier elements driven by a closed loop feedback control system. Two such similar systems have been built and used for directional and global measurements for direct comparison. PAR reflection is measured by a standard area CCD camera fitted with a wide angle lens and an optical filter. Global PAR is measured by using LI-COR Quantum sensors. The telescope and the CCD camera have been mounted on an Alta-Azimuth mount for scanning the surface around the peak to measure the reflectivity. A set of reflection standards along with the global PAR sensor has been mounted on a boom and fixed with the azimuth table. These reflection standards are visible in the field of view of the CCD camera. This provides the reference pixels in every CCD image that can be used to calibrate the rest of the CCD pixels. This system has been used to make the albedo images at the Zugspitze for the CUVRA (Characteristic of Ultra Violet Radiation in the Alps) project. Preliminary results are shown here. (author)

  4. Extended HXR Sources - Albedo Patches or Coronal Sources

    Science.gov (United States)

    Dennis, Brian R.

    2011-01-01

    Extended HXR sources in the presence of compact footpoints have been reported based on visibility amplitudes from different detectors. Attempts have been made to determine the location and extent of these sources through direct imaging. Results of this work will be described for simulated sources and for specific flares at different solar longitudes, with a discussion of the possible nature of the extended sources as either albedo patches or coronal sources or a combination of the two.

  5. Temporal Variations in the Uranian Near-IR Geometric Albedo

    Science.gov (United States)

    Walter, C. M.; Marley, M. S.; Baines, K. H.

    1996-09-01

    Over the period August 1995 -- August 1996 the near-infrared geometric albedo of Uranus showed distinct variation. We obtained images of the planet in 10 broad and narrowband filters using the ARC 3.5 meter telescope at Apache Point Observatory. Along with the albedo variations we saw significant changes in the contrast of the planet. Data acquired in August 1995 (Walter & Marley 1995) show the same high altitude hazes encircling the south polar region as seen by Baines et al. (1995) from the IRTF two days prior to our observations and by HST in August 1994. Followup images from June 1996 no longer contain this asymmetry, instead showing a homogeneous disk with corresponding lower albedos at matching wavelengths. Observations will also be made in late August 1996. We modeled this data by computing theoretical monochromatic albedos which were then integrated over the filter bandpasses. These filters were chosen to best probe a variety of atmospheric levels, with continuum filters probing down to the CH_4 tropospheric cloud and beyond. Filters selected in the deep H_2 and CH_4 absorption bands allow us to examine the structure of hazes in the upper stratosphere, whose small reflection contributions dominate in these dark filters. Preliminary analysis of information from two very different states of Uranian weather shows evidence for temporal variability in the vertical location and thickness of the CH_4 cloud as well as the incompatibility of extrapolating optical stratospheric haze characteristics in the near-infrared. This work was supported by NASA grant NGT-51383. Baines, K. H., Yanamandra-Fisher, P., Lebofsky, L. A., Momary, T. W., & Golisch, W. 1995, BAAS, 27, 1088. Walter, C & Marley, M. S. 1995, BAAS, 27, 1089.

  6. Instability in evolutionary games.

    Directory of Open Access Journals (Sweden)

    Zimo Yang

    Full Text Available BACKGROUND: Phenomena of instability are widely observed in many dissimilar systems, with punctuated equilibrium in biological evolution and economic crises being noticeable examples. Recent studies suggested that such instabilities, quantified by the abrupt changes of the composition of individuals, could result within the framework of a collection of individuals interacting through the prisoner's dilemma and incorporating three mechanisms: (i imitation and mutation, (ii preferred selection on successful individuals, and (iii networking effects. METHODOLOGY/PRINCIPAL FINDINGS: We study the importance of each mechanism using simplified models. The models are studied numerically and analytically via rate equations and mean-field approximation. It is shown that imitation and mutation alone can lead to the instability on the number of cooperators, and preferred selection modifies the instability in an asymmetric way. The co-evolution of network topology and game dynamics is not necessary to the occurrence of instability and the network topology is found to have almost no impact on instability if new links are added in a global manner. The results are valid in both the contexts of the snowdrift game and prisoner's dilemma. CONCLUSIONS/SIGNIFICANCE: The imitation and mutation mechanism, which gives a heterogeneous rate of change in the system's composition, is the dominating reason of the instability on the number of cooperators. The effects of payoffs and network topology are relatively insignificant. Our work refines the understanding on the driving forces of system instability.

  7. Genomic instability following irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Hacker-Klom, U.B.; Goehde, W. [Inst. fuer Strahlenbiologie, Muenster Univ. (Germany)

    2001-07-01

    Ionising irradiation may induce genomic instability. The broad spectrum of stress reactions in eukaryontic cells to irradiation complicates the discovery of cellular targets and pathways inducing genomic instability. Irradiation may initiate genomic instability by deletion of genes controlling stability, by induction of genes stimulating instability and/or by activating endogeneous cellular viruses. Alternatively or additionally it is discussed that the initiation of genomic instability may be a consequence of radiation or other agents independently of DNA damage implying non nuclear targets, e.g. signal cascades. As a further mechanism possibly involved our own results may suggest radiation-induced changes in chromatin structure. Once initiated the process of genomic instability probably is perpetuated by endogeneous processes necessary for proliferation. Genomic instability may be a cause or a consequence of the neoplastic phenotype. As a conclusion from the data available up to now a new interpretation of low level radiation effects for radiation protection and in radiotherapy appears useful. The detection of the molecular mechanisms of genomic instability will be important in this context and may contribute to a better understanding of phenomenons occurring at low doses <10 cSv which are not well understood up to now. (orig.)

  8. Genomic instability following irradiation

    International Nuclear Information System (INIS)

    Ionising irradiation may induce genomic instability. The broad spectrum of stress reactions in eukaryontic cells to irradiation complicates the discovery of cellular targets and pathways inducing genomic instability. Irradiation may initiate genomic instability by deletion of genes controlling stability, by induction of genes stimulating instability and/or by activating endogeneous cellular viruses. Alternatively or additionally it is discussed that the initiation of genomic instability may be a consequence of radiation or other agents independently of DNA damage implying non nuclear targets, e.g. signal cascades. As a further mechanism possibly involved our own results may suggest radiation-induced changes in chromatin structure. Once initiated the process of genomic instability probably is perpetuated by endogeneous processes necessary for proliferation. Genomic instability may be a cause or a consequence of the neoplastic phenotype. As a conclusion from the data available up to now a new interpretation of low level radiation effects for radiation protection and in radiotherapy appears useful. The detection of the molecular mechanisms of genomic instability will be important in this context and may contribute to a better understanding of phenomenons occurring at low doses <10 cSv which are not well understood up to now. (orig.)

  9. MCNP - transport calculations in ducts using multigroup albedo coefficients

    International Nuclear Information System (INIS)

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

  10. Signatures of volatiles in the lunar proton albedo

    Science.gov (United States)

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

    2016-07-01

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

  11. The Albedos of Kepler's Close-in super-Earths

    CERN Document Server

    Demory, Brice-Olivier

    2014-01-01

    Exoplanet research focusing on the characterization of super-Earths is currently limited to those handful 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 lightcurve analyses for 97 Kepler close-in $R_P \\lesssim 2.0 R_{\\oplus}$ super-Earth candidates with the aim to detect 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 $A_g$ in the Kepler bandpass ranging between 0.16 and 0.30, once decontaminated from thermal emission. These super-Earths geometric albedos are statistically larger than for hot Jupiters, w...

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

    Science.gov (United States)

    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.

  13. A Flashing Simulator for Natural Circulation Heated Systems

    International Nuclear Information System (INIS)

    Many of the next generation of nuclear reactors rely on natural circulation, either as the primary mode of heat removal or as a passive safety mechanism. Flashing-induced instabilities are of concern during startup of natural-circulation loops and small-scale natural-circulation light water reactors. (Flashing refers to the beginning of (adiabatic) boiling in the unheated riser when there is no boiling upstream.) A simulator with significantly enhanced modeling and simulation capabilities is being developed to analyze flashing and flashing-induced instabilities. The model allows an arbitrary number of nodes in both the heated section (allowing axially varying heat flux) and in the unheated riser section. Preliminary simulations using the model show that it can capture the location of flashing in the experiments conducted on the Dodewaard reactor very well

  14. Out-of-phase flashing induced instabilities in CIRCUS facility

    International Nuclear Information System (INIS)

    Full text of publication follows: Flashing-induced instabilities are very important during the startup phase of natural-circulation boiling water reactors. To study this type of instability an axial fully scaled facility named CIRCUS was constructed. Experiments at low power and low pressure (typical startup conditions) are carried out on this steam/water natural circulation loop with two parallel risers. A detailed measurement of the void-fraction profile is possible by using needle-probes and the use of glass tubes for the riser and core sections allow to use optical techniques for velocity measurements. The flashing and the mechanism of flashing-induced instabilities are analyzed paying special attention on the strong coupling effect between the two riser channels. It is clear from the experiments that the out-of-phase instability is much more susceptible to occur than the in-phase instability in a system with two parallel risers. The instability region is found as soon as the operational boundary between single-phase and two-phase operation is crossed. The relation between the period of the oscillations and the fluid transient time is also investigated. The stability map constructed using this experimental data is also discussed. (authors)

  15. Microwave circulator design

    CERN Document Server

    Linkhart, Douglas K

    2014-01-01

    Circulator design has advanced significantly since the first edition of this book was published 25 years ago. The objective of this second edition is to present theory, information, and design procedures that will enable microwave engineers and technicians to design and build circulators successfully. This resource contains a discussion of the various units used in the circulator design computations, as well as covers the theory of operation. This book presents numerous applications, giving microwave engineers new ideas about how to solve problems using circulators. Design examples are provided, which demonstrate how to apply the information to real-world design tasks.

  16. Natural circulation and stability limits in advanced plants: The Galilean law

    International Nuclear Information System (INIS)

    In our previous papers natural circulation instability problem have been examined. In particular, we analytically demonstrated the link between critical heart flux (CHF) and instability, and the limitations of the present CHF data. We derived an analytical solution for the static instability in natural circulation. We proceed in this paper to build on these novel ideas and physical principles. We focus on the role of gravity in the analysis and prediction of instability. We derive the non-dimensional correlation of natural circulation flowrate, and link this with our physical analysis of instability in parallel-channel systems. We derive the exact form of the unstable limit, and discuss the important effect of zero gravity on the solution. For static instability, the result is a cubic equation for the quality. We solve for the limiting cases to obtain a new explicit result. The effect of gravity on upflow and downflow is shown to be significant for high subcoolings. By combining the natural-circulation and stability results, we demonstrate a new result which analytically describes the limits on natural-circulation operation. This result is relevant to small breaks and transients, as well as to defining the design envelope for safe operation

  17. Baroclinic Instability on Hot Extrasolar Planets

    CERN Document Server

    Polichtchouk, Inna

    2012-01-01

    We investigate baroclinic instability in flow conditions relevant to hot extrasolar planets. The instability is important for transporting and mixing heat, as well as for influencing large-scale variability on the planets. Both linear normal mode analysis and non-linear initial value calculations are carried out -- focusing on the freely-evolving, adiabatic situation. Using a high-resolution general circulation model (GCM) which solves the traditional primitive equations, we show that large-scale jets similar to those observed in current GCM simulations of hot extrasolar giant planets are likely to be baroclinically unstable on a timescale of few to few tens of planetary rotations, generating cyclones and anticyclones that drive weather systems. The growth rate and scale of the most unstable mode obtained in the linear analysis are in qualitative, good agreement with the full non-linear calculations. In general, unstable jets evolve differently depending on their signs (eastward or westward), due to the chang...

  18. Startup transient simulation for natural circulation boiling water reactors in PUMA facility

    International Nuclear Information System (INIS)

    In view of the importance of instabilities that may occur at low-pressure and -flow conditions during the startup of natural circulation boiling water reactors, startup simulation experiments were performed in the Purdue University Multi-Dimensional Integral Test Assembly (PUMA) facility. The simulations used pressure scaling and followed the startup procedure of a typical natural circulation boiling water reactor. Two simulation experiments were performed for the reactor dome pressures ranging from 55 kPa to 1 MPa, where the instabilities may occur. The experimental results show the signature of condensation-induced oscillations during the single-phase-to-two-phase natural circulation transition. The results also suggest that a rational startup procedure is needed to overcome the startup instabilities in natural circulation boiling water reactor designs

  19. Meridional circulation in turbulent protoplanetary disks

    CERN Document Server

    Fromang, Sebastien; Masset, Frederic

    2011-01-01

    Based on viscous disk theory, a number of recent studies have suggested the existence of a large scale meridional circulation in protoplanetary disks. Such a flow could account for the presence of crystalline silicates, among which Calcium and Aluminium-rich Inclusions (CAIs), at large distances from the sun. This paper aims at examining whether such large scale flows exist in turbulent protoplanetary disks. High resolution global hydrodynamical and magnetohydrodynamical numerical simulations of turbulent protoplanetary disks are used to infer the properties of the flow in such disks. By performing hydrodynamic simulations using explicit viscosity, we demonstrate that our numerical setup does not suffer from any numerical artifact. The aforementioned meridional circulation is readily recovered in viscous and laminar disks. In MHD simulations, the magneto-rotational instability drives turbulence in the disks. Averaging out the turbulent fluctuations over long timescale, the results fail to show any large scale...

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

    Science.gov (United States)

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

    2012-12-01

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

  1. The Collisionless Magnetothermal Instability

    CERN Document Server

    Islam, Tanim

    2013-01-01

    It is likely that nearly all central galactic massive and supermassive black holes are nonradiative: their accretion luminosities are orders of magnitude below what can be explained by efficient black hole accretion within their ambient environments. These objects, of which Sagittarius A* is the best-known example, are also dilute (mildly collisional to highly collisionless) and optically thin. In order for accretion to occur, magnetohydrodynamic instabilities must develop that not only transport angular momentum, but also gravitational energy generated through matter infall, outwards. A class of new magnetohydrodynamical fluid instabilities -- the magnetoviscous-thermal instability (MVTI) (Islam12) -- was found to transport angular momentum and energy along magnetic field lines through large (fluid) viscosities and thermal conductivities. This paper describes the collisionless and mildly collisional analogue to the MVTI, the collisional magnetothermal instability (CMTI), that similarly transports energy and ...

  2. Chronic Ankle Instability

    Science.gov (United States)

    ... ankle surgeon will ask you about any previous ankle injuries and instability. Then s/he will examine your ankle ... Weak ankles may be a result of previous ankle injuries, but in some cases they are a congenital ( ...

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

    CERN Document Server

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

    2016-01-01

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

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

    International Nuclear Information System (INIS)

    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.

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

    Science.gov (United States)

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

    2016-05-01

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

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

    Directory of Open Access Journals (Sweden)

    Aku Riihelä

    2010-08-01

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

  7. The Curse of Instability

    OpenAIRE

    Kuehn, Christian

    2015-01-01

    High-dimensional computational challenges are frequently explained via the curse of dimensionality, i.e., increasing the number of dimensions leads to exponentially growing computational complexity. In this commentary, we argue that thinking on a different level helps to understand, why we face the curse of dimensionality. We introduce as a guiding principle the curse of instability, which triggers the classical curse of dimensionality. Furthermore, we claim that the curse of instability is a...

  8. Rotor internal friction instability

    Science.gov (United States)

    Bently, D. E.; Muszynska, A.

    1985-01-01

    Two aspects of internal friction affecting stability of rotating machines are discussed. The first role of internal friction consists of decreasing the level of effective damping during rotor subsynchronous and backward precessional vibrations caused by some other instability mechanisms. The second role of internal frication consists of creating rotor instability, i.e., causing self-excited subsynchronous vibrations. Experimental test results document both of these aspects.

  9. Streaming gravity mode instability

    International Nuclear Information System (INIS)

    In this paper, we study the stability of a current sheet with a sheared flow in a gravitational field which is perpendicular to the magnetic field and plasma flow. This mixing mode caused by a combined role of the sheared flow and gravity is named the streaming gravity mode instability. The conditions of this mode instability are discussed for an ideal four-layer model in the incompressible limit. (author). 5 refs

  10. CVF spectrophotometry of Pluto - Correlation of composition with albedo

    International Nuclear Information System (INIS)

    The present time-resolved, 0.96-2.65-micron spectrophotometry for the Pluto-Charon system indicates night-to-night variations in the depths of the methane absorptions such that the bands' equivalent width is near minimum light. The interpretation of these data in terms of a depletion of methane in dark regions of the planet, relative to bright ones, is consistent with the Buie and Fink (1987) observations. The near-IR spectrum of Pluto seems to be dominated by surface frost. It is suggested that the dark equatorial regions of Pluto are redder than those of moderate albedo. 28 refs

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

    CERN Document Server

    Selden, Adrian C

    2010-01-01

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

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

    Science.gov (United States)

    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

  13. A simple albedo technique for calculating dose rate from scattered gamma rays

    International Nuclear Information System (INIS)

    This paper reports that the flux type concrete dose albedo for normally incident gamma rays is approximately a function of gamma energy only, regardless of the emerging angles. The flux type albedo for normally emerging gamma rays is also roughly a constant value over a wide range of incident angles for gamma energy greater than 0.66 MeV. Two concrete albedo curves are plotted as a function of gamma energy for a convenient estimation of the scatter dose rate

  14. System of data on albedo of low-energy photon radiation

    International Nuclear Information System (INIS)

    A set of data including semiempirical formulae for differential and spectral albedo, tables of the proper coefficients, ways of interpolation by energy and effective atomic number is prepared on the basis of calculations using the Monte Carlo method for photon radiation albedo. The set of data permits to obtain albedo characteristics in the energy range from 20 to 280 keV for any material with the effective atomic number from 4 to 30

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

    OpenAIRE

    Loranty, MM; Berner, LT; Goetz, SJ; Jin, Y.; Randerson, JT

    2014-01-01

    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, ...

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

    OpenAIRE

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

    2013-01-01

    The ice-albedo feedback is a potentially important de-stabilizing effect for the climate of terrestrial planets. It is based on the positive feedback between decreasing surface temperatures, an increase of snow and ice cover and an associated increase in planetary albedo, which then further decreases surface temperature. A recent study shows that for M stars, the strength of the ice-albedo feedback is reduced This study investigates the influence of the atmosphere (in terms of surface pressur...

  17. A statistics-based temporal filter algorithm to map spatiotemporally continuous shortwave albedo from MODIS data

    OpenAIRE

    N. F. Liu; Liu, Q.; Wang, L. Z.; Liang, S. L.; Wen, J.G.; Y. Qu; Liu, S H

    2013-01-01

    Land-surface albedo plays a critical role in the earth's radiant energy budget studies. Satellite remote sensing provides an effective approach to acquire regional and global albedo observations. Owing to cloud coverage, seasonal snow and sensor malfunctions, spatiotemporally continuous albedo datasets are often inaccessible. The Global LAnd Surface Satellite (GLASS) project aims at providing a suite of key land surface parameter datasets with high temporal resolution and high accuracy for a ...

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

    OpenAIRE

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

    2012-01-01

    Albedo is one of the variables controlling the mass balance of temperate glaciers. Multispectral imagers, such as MODerate Imaging Spectroradiometer (MODIS) on board the TERRA and AQUA satellites, provide a means to monitor glacier surface albedo. In this study, different methods to retrieve broadband glacier surface albedo from MODIS data are compared. The effect of multiple reflections due to the rugged topography and of the anisotropic reflection of snow and ...

  19. A revised asteroid polarization-albedo relationship using WISE/NEOWISE data

    OpenAIRE

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

    2012-01-01

    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 maxim...

  20. A Method for Retrieving Daily Land Surface Albedo from Space at 30-m Resolution

    OpenAIRE

    Bo Gao; Huili Gong; Tianxing Wang

    2015-01-01

    Land surface albedo data with high spatio-temporal resolution are increasingly important for scientific studies addressing spatially and/or temporally small-scale phenomena, such as urban heat islands and urban land surface energy balance. Our previous study derived albedo data with 2–4-day and 30-m temporal and spatial resolution that have better spatio-temporal resolution than existing albedo data, but do not completely satisfy the requirements for monitoring high-frequency land surface cha...

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

    OpenAIRE

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

    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 d...

  2. Land Surface Albedo Estimation from Chinese HJ Satellite Data Based on the Direct Estimation Approach

    OpenAIRE

    Tao He; Shunlin Liang; Dongdong Wang; Xiaona Chen; Dan-Xia Song; Bo Jiang

    2015-01-01

    Monitoring surface albedo at medium-to-fine resolution (<100 m) has become increasingly important for medium-to-fine scale applications and coarse-resolution data evaluation. This paper presents a method for estimating surface albedo directly using top-of-atmosphere reflectance. This is the first attempt to derive surface albedo for both snow-free and snow-covered conditions from medium-resolution data with a single approach. We applied this method to the multispectral data from the wide-...

  3. Correction of broadband snow albedo measurements affected by unknown slope and sensor tilts

    OpenAIRE

    Weiser, Ursula; Olefs, Marc; Schöner, Wolfgang; Weyss, Gernot; Hynek, Bernhard

    2016-01-01

    Geometric effects induced by the underlying terrain slope or by tilt errors of the radiation sensors lead to an erroneous measurement of snow or ice albedo. Consequently, artificial diurnal albedo variations in the order of 1–20 % are observed. The present paper proposes a general method to correct tilt errors of albedo measurements in cases where tilts of both the sensors and the slopes are not accurately measured or known. We demonstrate that atmospheric parameters f...

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

    OpenAIRE

    Ying Qu; Shunlin Liang; Qiang Liu; Tao He; Suhong Liu; Xiaowen Li

    2015-01-01

    Surface albedo is one of the key controlling geophysical parameters in the surface energy budget studies, and its temporal and spatial variation is closely related to the global climate change and regional weather system due to the albedo feedback mechanism. As an efficient tool for monitoring the surfaces of the Earth, remote sensing is widely used for deriving long-term surface broadband albedo with various geostationary and polar-orbit satellite platforms in recent decades. Moreover, the a...

  5. Radiative forcing by changes in surface albedo caused by changes in vegetation

    OpenAIRE

    2005-01-01

    The human influence on vegetation causes changes in the surface reflective properties. By using MODIS land cover and MODIS surface albedo products, an estimation of radiative forcing due to surface albedo changes caused by vegetation changes is performed. A potential natural vegetation data set is used to compute radiative forcing estimates from pre agricultural times to present. A combination between MODIS blacksky and whitesky albedo and diffuse and direct radiation at gr...

  6. Incorporating remotely-sensed snow albedo into a spatially-distributed snowmelt model

    OpenAIRE

    Molotch, NP; Painter, TH; Bales, RC; Dozier, J.

    2004-01-01

    Basin-average albedo estimated from remotely-sensed Airborne Visible/Infrared Imaging Spectroradiometer (AVIRIS) data specific to the catchment typically differed by 20% from albedo estimated using a common snow-age-based empirical relation. In some parts of the basin, differences were as large as 0.31. Using the AVIRIS albedo estimates in a distributed snowmelt model that explicitly includes net solar radiation resulted in a much more accurate estimate of the timing and magnitude of snowmelt...

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

    Science.gov (United States)

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

    2014-01-01

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

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

    OpenAIRE

    Aku Riihelä; Eetu Puttonen; Juha Suomalainen; Teemu Hakala; Terhikki Manninen; Peltoniemi, Jouni I.

    2010-01-01

    Land surface hemispherical albedos of several targets have been resolved using the bidirectional reflectance factor (BRF) library of the Finnish Geodetic Institute (FGI). The library contains BRF data measured by FGI during the years 2003–2009. Surface albedos are calculated using selected BRF datasets from the library. Polynomial interpolation and extrapolation have been used in computations. Several broadband conversion formulae generally used for satellite based surface albedo retrieval ha...

  9. Some Features of Transverse Instability of Partly Compensated Proton Beams

    Energy Technology Data Exchange (ETDEWEB)

    Vadim Dudnikov

    2001-10-23

    suppression of generation and accumulation of secondary particles is a traditional method for suppression the transverse electron-proton instability: improve the vacuum, use a gap in beam for electron removing, use cleaning electrodes, suppressing secondary emission. But opposite solution is also possible. Transverse e-p instability in proton rings can be damped by increasing beam density and the rate of secondary particles generation above a threshold level, with decrease of the unstable wavelength below a transverse beam size. In high current Proton Storage Rings (PSR) such as, the LANSCE PSR it is possible to reach this island of stability by multiturn, concentrated charge exchange injection without painting and by enhanced generation of secondary plasma. This possibility was demonstrated in smaller scale PSR at the INP, Novosibirisk [1]. Damping of the e-p instability allowed to accumulate a coasting, space charge compensated, circulating proton beam with intensity, corresponding to the Laslett tune shift of {Delta}{nu} = 5 in the ring with original tune of {nu} = 0.85. In the other PSR transverse instability of bunched beam was damped by a simple feed back [2,3]. In this article they discuss experimental observations of transverse instability of proton beams in different accelerators and storage rings and consider methods to damp the instability. The presented experimental dates could be useful for verification of computer simulation tools developed for investigation of space charge effects and beam instabilities in realistic conditions [4,5].

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

    Data.gov (United States)

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

  11. Neutronic calculations for a fast assembly by using two-group neutron albedo theory

    International Nuclear Information System (INIS)

    Under Two-Group Neutron Albedo Theory, the effective neutron multiplication factor, Keff, explicitly appears and therefore it is possible to obtain an explicit form of variation of Keff. A generalization of the two-group albedo theory can be used if a more detailed energy spectrum treatment is required. The two-group neutron albedo theory is well illustrated by the endeavor of calculating the key parameters for a fast assembly. The results obtained from diffusion approach and albedo method calculations have had excellent concordance. (author)

  12. Albedo neutron dosimetry and monitoring around the RECH-1 reactor neutron radiographic beam

    International Nuclear Information System (INIS)

    This paper describes the neutrons and gamma monitoring and albedo neutron dosimetry in a field around the RECH-1 neutron beam. Two kind of albedo dosimeters were used: Hankins and KfK Alnor. The calibration procedures and comparison of these albedo dosimeters performance were done. The dose equivalent results agree between 28%. The neutron dose distribution for person working near the beam, was obtained by routine monitoring with albedo dosimeter developed by Hankins. A monthly neutron dose with a maximum of 0,8 mSv and arithmetic mean of 0,4 mSv were found. The beam's gamma energy spectrum and its related dose were also studied. (author)

  13. New technique to improve the accuracy of albedo neutron dosimeter evaluations

    International Nuclear Information System (INIS)

    The calibration factor for albedo neutron dosimeters varies greatly depending upon the energy of the neutrons in the exposure. Calibration results obtained over an eight-year period at each Lawrence Livermore National Laboratory facility where neutron exposure may occur were reviewed. A stronger relationship than expected was found between the ratio of the readings of the 9-in. to 3-in. spheres and the percent thermal. Readings from personnel and albedo badges were reviewed. The readings were consistent with the use of a calibration factor for the albedo dosimeter which varies with changes in the ratio of the personnel and albedo dosimeter TLD readings. 2 references, 6 figures

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

    Science.gov (United States)

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

    Science.gov (United States)

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

    2016-02-01

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

  16. Study on the stability behaviour of two-phase natural circulation systems using a four-equation drift flux model

    International Nuclear Information System (INIS)

    Theoretical investigations were carried out to study the influence of two-phase flow parameters such as friction factor multiplier, drift velocity and void distribution parameter on the stability of boiling two-phase natural circulation systems. The theoretical model considers a four-equation drift flux model which solves the linearised conservation equations of mass, momentum and energy applicable to boiling two-phase natural circulation systems. The model was applied to three boiling natural circulation loops wherein Type I and Type II instabilities were observed over a wide range of operating pressures. The two-phase friction loss was predicted using different friction factor multiplier models available in literature. It was found that these models influence the steady state and threshold powers for stability, especially the Type II instabilities in natural circulation significantly. Since the void fraction depends on the drift velocity and the void distribution parameter in two-phase flow, these parameters were varied and their effects on the natural circulation flow stability were investigated. It was found that an increase in either the drift velocity or the void distribution parameter reduces the unstable regions observed in the Type I or Type II flow instabilities in two-phase natural circulation systems. Further, investigations were carried out to study the effect of loop diameter on the Type I and Type II instabilities in natural circulation. This study is important to reveal the capability of the reduced diameter scaled facilities of the prototype systems to simulate natural circulation instabilities. The results indicate that with increase in the loop diameter, the threshold power of the Type I instability and the Type II instability increases. Moreover, the stability of natural circulation greatly enhances with increase in the diameter of the loop

  17. Some characteristics of the AEOI Neutriran Albedo Neutron Personnel Dosemeter

    International Nuclear Information System (INIS)

    The Neutriran Albedo Personnel Neutron Dosemeter (NAPND) is based on the combination of a sensitive polymer such as polycarbonate (PC) in contact with 6LiF or 10B pellets in a cadmium cover. By adding a 10B pellet in front, the design of the dosemeter can be such that when worn on the body, direct thermal neutron induced alpha tracks (TNIAT), albedo neutron induced alpha tracks (ANIAT) and fast neutron induced recoil tracks (FNIRT) can be simultaneously detected in a single electrochemically etched PC foil. To establish a national personnel neutron dosimetry service in Iran, different parameters such as the effect of 10B(n,α)7Li convertor thickness, Cd thickness and its diameter, dosemeter distance from the phantom, dosemeter angle with phantom and directional response were studied using different phantoms. Under optimised conditions, a sensitivity of 1500 tracks.cm-2.mSv-1 for 252Cf neutrons with a lowest value of 0.05 mSv was measured. The results of these studies are reported and discussed. (author)

  18. Concrete albedo for low-energy gamma radiation

    International Nuclear Information System (INIS)

    Monte Carlo calculations of different current characteristics of both the numerical asub(N) and energy asub(E) albedos have been carried out at initial gamma quanta energies E0=20-100 keV. Both integral functionals and angular, energy and spectral-angular distributions of asub(N) have been obtained. The component due to single scattering has been extracted. The incident angles THETA0 from 0 to 89 deg, and reflection angles THETA from -89 to +89 deg are considered. The energy range where the electron binding energy in atoms must be taken account of has been found as follows: E0=60 keV at THETA0>=80 deg and THETA>=60 deg; E00>=60 deg and THETA>=15 deg. The ratio asub(E)/asub(N) practically does not depend on THETA0. In terms of the least square fit the semiempirical representation coefficients of the differential angular albedo have been determined

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

    Science.gov (United States)

    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.

  20. Evaluation of the EUMETSAT Meteosat Surface Albedo Climate Data Record

    Science.gov (United States)

    Lattanzio, Alessio; Schulz, Joerg; Roebeling, Rob; Fell, Frank; Bennartz, Ralf; Cahill, Brownwyn; Muller, Jan-Peter; Shane, Neville; Trigo, Isabel; Watson, Gill

    2013-04-01

    Understanding the climate system, with its variability and changes, requires a joint long-term international commitment from research and governmental institutions. The Global Climate Observing System (GCOS) formulated scientific requirements for the needed global observations and products including a list of relevant parameters, the so called Essential Climate Variables (ECVs). The Sustained and Coordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM) activity, is answering to these requirements by establishing an international network of facilities to ensure a continuous and sustained generation of high-quality Climate Data Records (CDR) from satellite data in compliance with the GCOS principles and guidelines. Currently, SCOPE-CM represents a partnership between operational space agencies to coordinate the generation of CDRs. Within the SCOPE-CM framework the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) has generated the Meteosat Surface Albedo (MSA) Climate Data Record that comprises up to 25 years (1982-2010) of continuous surface albedo coverage for large areas of the Earth. As part of the SCOPE-CM activity on land surface albedo, involving the operational meteorological satellite agencies in Europe (EUMETSAT), in Japan (JMA: Japanese Meteorological Agency) and in the USA (NOAA: National Oceanic and Atmospheric Administration), the MSA CDR contributes to the creation of a global harmonised surface albedo record derived from all satellites in geostationary orbit. This presentation discusses the results of an evaluation study for the MSA CDR that has been performed by independent researchers in Europe and the US. The MSA CDR has been evaluated in terms of its internal consistency, its compatibility to other satellite-derived surface albedo products, its validity against in-situ observations of superior quality, and its temporal homogeneity. The evaluation of the MSA data record has revealed a

  1. Concepts in Assisted Circulation

    OpenAIRE

    Lefemine, Armand A.; Dunbar, Jacob; DeLucia, Anthony

    1986-01-01

    Assisted circulation by extracorporeal and extracardiac bypass techniques must be based on the requirements of the heart and of the total body, though these may differ. The cardiac problem in cardiogenic shock is more likely to be a biventricular problem demanding decompression of both sides. Extra pulmonary oxygenation should be avoided because of complexity in long-term use. Principles of assisted circulation may be applied in an extra-thoracic temporary manner or as an intracorporeal long-...

  2. Instability of the Heliopause

    International Nuclear Information System (INIS)

    The heliopause (HP) separates the tenuous hot heliosheath plasma from the relatively dense cool magnetized plasma of the local interstellar medium (LISM). Fluid acceleration in the HP region can therefore drive Rayleigh-Taylor-like and Kelvin-Helmholtz- like instabilities. Charge exchange coupling of plasma ions and primary interstellar neutral atoms provides an effective gravity, suggesting the possibility of Rayleigh Taylor-like (RT-like) instabilities. Shear flow due to the velocity difference between the heliosheath and the interstellar flows drives Kelvin Helmholtz-like (KH-like) modes on the heliopause. Magnetic fields damp the classical KH instability. However, we show that energetic neutral atoms (ENAs) destabilize KH-modes,even in the presence of interplanetary and interstellar magnetic fields. We consider a model that includes a number of effects that are important in the heliosphere such as resonant change exchange between the primary neutrals and the solar wind plasma, ENAs from the inner heliosheath, plasma flows along the heliopause and magnetic fields in the inner and outer heliosheath. We find that the nose region is unstable to RT-like modes for HP parameters, while the shoulder region is unstable to a new instability that has the characteristics of a mixed RT-KH-like mode. These instabilities are not stabilized by typical values of the magnetic fields in the inner and outer heliosheath close to the nose and shoulder regions. Whereas ENAs have a stabilizing influence on the RT instability in the vicinity of the nose region (due to counter streaming), they have a destabilizing influence on the KH instability in the vicinity of the flanks. We find that even in the presence of interplanetary and interstellar magnetic fields, ENAs can drive a new form of KH-like instability on the flanks. An analysis of the collisional and anomalous magnetic field diffusion time scales shows that ideal MHD is an appropriate model at the HP. The interstellar magnetic

  3. Plasma physics and instabilities

    International Nuclear Information System (INIS)

    These lectures procide an introduction to the theory of plasmas and their instabilities. Starting from the Bogoliubov, Born, Green, Kirkwood, and Yvon (BBGKY) hierarchy of kinetic equations, the additional concept of self-consistent fields leads to the fundamental Vlasov equation and hence to the warm two-fluid model and the one-fluid MHD, or cold, model. The properties of small-amplitude waves in magnetized (and unmagnetized) plasmas, and the instabilities to which they give rise, are described in some detail, and a complete chapter is devoted to Landau damping. The linear theory of plasma instabilities is illustrated by the current-driven electrostatic kind, with descriptions of the Penrose criterion and the energy principle of ideal MHD. There is a brief account of the application of feedback control. The non-linear theory is represented by three examples: quasi-linear velocity-space instabilities, three-wave instabilities, and the stability of an arbitrarily largeamplitude wave in a plasma. (orig.)

  4. Mackenzie's Demon with instabilities

    International Nuclear Information System (INIS)

    MacKenzie's Maxwell Demon, consisting of positively biased thin wires, heats plasma electrons without significantly affecting the plasma potential. Experiments were performed on the Maxwell Demon in a multi-dipole confined filament discharge. It is shown that given adequate bias, the Demon reduces a bi-Maxwellian electron distribution function to a single Maxwellian electron distribution function. It is shown that a small planar electrode can perform identical heating as the Demon, provided that the electrode has the area of approximately three times the Demon's conductive surface area. The instability that limits the Demon's operation is investigated. Time-resolved measurements of changes in global electron temperature, plasma density and plasma potential within a cycle of the instability are considered. It is found that the Demon's instability is a repeating pulsed anode spot. Density measurements indicate that the frequency of the instability is dependent on plasma production and loss rates. The neutral pressure dependence of the anode spot instability is measured and modeled for the first time. (paper)

  5. Spring–summer albedo variations of Antarctic sea ice from 1982 to 2009

    International Nuclear Information System (INIS)

    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

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

    Science.gov (United States)

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

    2011-12-01

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

  7. Experimental study on start-up characteristics of open natural circulation system

    International Nuclear Information System (INIS)

    Background: The open natural circulation system has been used gradually in the passive safety system after severe accidents such as passive containment cooling system. Purpose: The aim is to investigate the start-up process of the open natural circulation system, and analyze the experimental phenomena and flow characteristics under different heating power and inlet subcooling conditions in detail. Finally, the map of the instability boundary during the startup of the natural circulation system is given. Methods: Experimental facility was set up and numbers of experiments under different conditions were conducted. The flow characteristics and mechanisms with different flow phenomena are analyzed in detail combining with the measurement results of the fluid temperature, pressure and mass flow rate. Finally, all the flow behaviors were classified under different conditions. Results: The results are as follows: the system which operates under low-power conditions will experience the stable single-phase, two-phase oscillation and stable two-phase flow sequentially with the inlet subcooling increasing, During the two-phase oscillation phase, two flow modes including the flashing-induced instability and the combination of the boiling eruption and flashing-induced instability occur. Conclusion: The instability region of the system enlarges with the increase of the heating power, which even makes it difficult to form the stable two-phase flow. During the two-phase oscillation phase, both the flashing-induced instability and the combination of the boiling eruption with flashing-induced instability belong to the density wave instability. (authors)

  8. Neutrino beam plasma instability

    Indian Academy of Sciences (India)

    Vishnu M Bannur

    2001-10-01

    We derive relativistic fluid set of equations for neutrinos and electrons from relativistic Vlasov equations with Fermi weak interaction force. Using these fluid equations, we obtain a dispersion relation describing neutrino beam plasma instability, which is little different from normal dispersion relation of streaming instability. It contains new, nonelectromagnetic, neutrino-plasma (or electroweak) stable and unstable modes also. The growth of the instability is weak for the highly relativistic neutrino flux, but becomes stronger for weakly relativistic neutrino flux in the case of parameters appropriate to the early universe and supernova explosions. However, this mode is dominant only for the beam velocity greater than 0.25 and in the other limit electroweak unstable mode takes over.

  9. Instabilities in astrophysical jets

    International Nuclear Information System (INIS)

    Instabilities in astrophysical jets are studied in the nonlinear regime by performing 2D numerical classical gasdynamical calculations. The instabilities which arise from unsteadiness in output from the central engine feeding the jets, and those which arise from a beam in a turbulent surrounding are studied. An extra power output an order of magnitude higher than is normally delivered by the engine over a time equal to (nozzle length)/(sound velocity at centre) causes a nonlinear Kelvin-Helmholtz instability in the jet walls. Constrictions move outwards, but the jet structure is left untouched. A beam in turbulent surroundings produces internal shocks over distances of a few beam widths. If viscosity is present the throughput of material is hampered on time scales of a few beam radius sound travel times. The implications are discussed. (Auth.)

  10. Nonlinear mirror instability

    CERN Document Server

    Rincon, F; Cowley, S C

    2014-01-01

    Slow dynamical changes in magnetic-field strength and invariance of the particles' magnetic moments generate ubiquitous pressure anisotropies in weakly collisional, magnetized astrophysical plasmas. This renders them unstable to fast, small-scale mirror and firehose instabilities, which are capable of exerting feedback on the macroscale dynamics of the system. By way of a new asymptotic theory of the early nonlinear evolution of the mirror instability in a plasma subject to slow shearing or compression, we show that the instability does not saturate quasilinearly at a steady, low-amplitude level. Instead, the trapping of particles in small-scale mirrors leads to nonlinear secular growth of magnetic perturbations, $\\delta B/B \\propto t^{2/3}$. Our theory explains recent collisionless simulation results, provides a prediction of the mirror evolution in weakly collisional plasmas and establishes a foundation for a theory of nonlinear mirror dynamics with trapping, valid up to $\\delta B/B =O(1)$.

  11. Causes of genome instability

    DEFF Research Database (Denmark)

    Langie, Sabine A S; Koppen, Gudrun; Desaulniers, Daniel;

    2015-01-01

    Genome instability is a prerequisite for the development of cancer. It occurs when genome maintenance systems fail to safeguard the genome's integrity, whether as a consequence of inherited defects or induced via exposure to environmental agents (chemicals, biological agents and radiation). Thus......, genome instability can be defined as an enhanced tendency for the genome to acquire mutations; ranging from changes to the nucleotide sequence to chromosomal gain, rearrangements or loss. This review raises the hypothesis that in addition to known human carcinogens, exposure to low dose of other...... chemicals present in our modern society could contribute to carcinogenesis by indirectly affecting genome stability. The selected chemicals with their mechanisms of action proposed to indirectly contribute to genome instability are: heavy metals (DNA repair, epigenetic modification, DNA damage signaling...

  12. Photomultiplier time instability

    International Nuclear Information System (INIS)

    A short-time and slow instability of anode photocurrent in photoelectron multiplier is investigated. The analysis of sorption and desorption processes stimulated by electron excitation allowed to propose an adsorption-desorption mechanism of devices instability. Transient response and drift of photomultiplier anode photocurrent are measured as well as the curves of spent variations of spectral sensitivity of photocathode and individual amplifier cascades of the multiplying system depending on anode current. The results of calculating the proposed model are in good agreement with the experimental data

  13. Ringed accretion disks: instabilities

    CERN Document Server

    Pugliese, D

    2016-01-01

    We analyze the possibility that several instability points may be formed, due to the Paczy\\'nski mechanism of violation of mechanical equilibrium, in the orbiting matter around a supermassive Kerr black hole. We consider recently proposed model of ringed accretion disk, made up by several tori (rings) which can be corotating or counterrotating relative to the Kerr attractor due to the history of the accretion process. Each torus is governed by the general relativistic hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. We prove that the number of the instability points is generally limited and depends on the dimensionless spin of the rotating attractor.

  14. Longitudinal microwave instability

    International Nuclear Information System (INIS)

    A derivation of the relationship between growth rate and impedance is given. The only other instability considered here is the resonance effect produced by excessive tune shift due to space charge. We assume, without discussion, the (Δν)/sub max/ = .25; that is, this resonance growth is avoided (stability) by limiting the ring charge. On the other hand, the longitudinal microwave instability is assumed to be present (cannot be stabilized). Thus, the latter involves a limiting impedance to keep the growth rate low enough. The maximum allowed impedance for a maximum allowed growth rate is listed

  15. Ringed Accretion Disks: Instabilities

    Science.gov (United States)

    Pugliese, D.; Stuchlík, Z.

    2016-04-01

    We analyze the possibility that several instability points may be formed, due to the Paczyński mechanism of violation of mechanical equilibrium, in the orbiting matter around a supermassive Kerr black hole. We consider a recently proposed model of a ringed accretion disk, made up by several tori (rings) that can be corotating or counter-rotating relative to the Kerr attractor due to the history of the accretion process. Each torus is governed by the general relativistic hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. We prove that the number of the instability points is generally limited and depends on the dimensionless spin of the rotating attractor.

  16. Fluidelastic instability in tube arrays

    International Nuclear Information System (INIS)

    When an array of tubes is subjected to crossflow, the tubes can experience dynamic instability, generally called fluidelastic instability. Instability initiates when the crossflow velocity exceeds a threshold value above which energy input from the flow exceeds that dissipated by system damping. Catastrophic failures of reactor and process plant equipment have been attributed to fluidelastic instability. As a result, extensive research studies have been conducted in the last 15 years with the objective of understanding the instability mechanisms and developing general design guidelines to avoid instability. Argonne National Laboratory has a continuing research program in this area which includes both mathematical model development and experimentation. This paper describes recent developments and accomplishments

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

    International Nuclear Information System (INIS)

    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

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

    Science.gov (United States)

    AbstractSnow 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...

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

    NARCIS (Netherlands)

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

    2012-01-01

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

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

    International Nuclear Information System (INIS)

    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.

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

    KAUST Repository

    Meng, Xianhong

    2013-05-05

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

  2. Gaussian Fibonacci Circulant Type Matrices

    Directory of Open Access Journals (Sweden)

    Zhaolin Jiang

    2014-01-01

    Full Text Available Circulant matrices have become important tools in solving integrable system, Hamiltonian structure, and integral equations. In this paper, we prove that Gaussian Fibonacci circulant type matrices are invertible matrices for n>2 and give the explicit determinants and the inverse matrices. Furthermore, the upper bounds for the spread on Gaussian Fibonacci circulant and left circulant matrices are presented, respectively.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-07-15

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

  4. Albedos and diameters of three Mars Trojan asteroids

    CERN Document Server

    Trilling, D E; Stansberry, J A; Spahr, T B; Crudo, R A; Davies, J K

    2007-01-01

    We observed the Mars Trojan asteroids (5261) Eureka and (101429) 1998 VF31 and the candidate Mars Trojan 2001 FR127 at 11.2 and 18.1 microns using Michelle on the Gemini North telescope. We derive diameters of 1.28, 0.78, and 0.14. The albedos for Eureka and 1998 VF31 are consistent with the taxonomic classes and compositions (S(I)/angritic and S(VII)/achrondritic, respectively) and implied histories presented in a companion paper by Rivkin et al. Eureka's surface likely has a relatively high thermal inertia, implying a thin regolith that is consistent with predictions and the small size that we derive.

  5. Retrieval of Planetary Rotation and Albedo from DSCOVR data

    CERN Document Server

    Kane, S R; Herman, J R; Robinson, T D; Stine, A R

    2015-01-01

    The field of exoplanets has rapidly expanded from the exclusivity of exoplanet detection to include exoplanet characterization. A key step towards this characterization will be retrieval of planetary albedos and rotation rates from highly undersampled imaging data. The Deep Space Climate Observatory (DSCOVR) provides a unique opportunity to test such retrieval methods using high cadence data of the sunlit surface of the Earth. There are two NASA instruments on board DSCOVR that can be used to achieve this task: the NASA instruments Earth Polychromatic Imaging Camera (EPIC) and the National Institute of Standards and Technology Advanced Radiometer (NISTAR). Here we briefly describe the properties of these instruments and the exoplanetary science that can be explored with their data products. These are described within the context of future NASA direct imaging missions for exoplanets.

  6. The Albedo Dichotomy of Iapetus Measured at UV Wavelengths

    Science.gov (United States)

    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.

  7. A digital file of the lunar normal Albedo

    Science.gov (United States)

    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.

  8. Radiative Albedo from a Linearly Fibered Half Space

    CERN Document Server

    Grzesik, J A

    2016-01-01

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

  9. MISR Level 3 Component Global Albedo product in netCDF format covering a month V006

    Data.gov (United States)

    National Aeronautics and Space Administration — MISR Level 3 Component Global Albedo publicly available product in netCDF format covering a month. (Suggested Usage: This file contains the global albedo product...

  10. MISR Level 3 FIRSTLOOK Global Albedo product in netCDF format covering a day V002

    Data.gov (United States)

    National Aeronautics and Space Administration — MISR Level 3 FIRSTLOOK Component Global Albedo publicly available product in netCDF format covering a day. (Suggested Usage: This file contains the global albedo...

  11. MISR Level 3 Component Global Albedo product in netCDF format covering a day V006

    Data.gov (United States)

    National Aeronautics and Space Administration — MISR Level 3 Component Global Albedo publicly available product in netCDF format covering a day. (Suggested Usage: This file contains the global albedo product...

  12. MISR Level 3 FIRSTLOOK Global Albedo product in netCDF format covering a month V002

    Data.gov (United States)

    National Aeronautics and Space Administration — MISR Level 3 FIRSTLOOK Component Global Albedo publicly available product in netCDF format covering a month. (Suggested Usage: This file contains the global albedo...

  13. MISR Level 3 Component Global Albedo product in netCDF format covering a year V006

    Data.gov (United States)

    National Aeronautics and Space Administration — MISR Level 3 Component Global Albedo publicly available product in netCDF format covering a year. (Suggested Usage: This file contains the global albedo product...

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

    Science.gov (United States)

    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.

  15. Tracking Code for Microwave Instability

    Energy Technology Data Exchange (ETDEWEB)

    Heifets, S.; /SLAC

    2006-09-21

    To study microwave instability the tracking code is developed. For bench marking, results are compared with Oide-Yokoya results [1] for broad-band Q = 1 impedance. Results hint to two possible mechanisms determining the threshold of instability.

  16. Factor analysis of flow instability between heating reactor and boiling reactor

    International Nuclear Information System (INIS)

    The affections on instability of sub-cooled boiling, condensation, flashing, and steam-space pressure equilibrium, have been analyzed on the base of experimental results in natural circulation system with low pressure and low steam quality, and compared with those of boiling reactor. The analysis shows: (1) Sub-cooled boiling, condensation and flashing play an important role on the flow instabilities in a natural circulation system, and have connection with lots of instabilities, which is different to the forced circulation system; (2) The size of steam-space is important to the system stability. In order to improve it, the size of steam-space should be small to the best of its ability, if the system can support the large pressure

  17. Theoretical study on the first kind of density wave instabilities

    International Nuclear Information System (INIS)

    The present paper summarizes the theoretical studies carried out by INET (Institute of Nuclear Energy Technology) of Tsinghua University on the first kind of density wave instabilities (DWIs) of natural circulation systems. The analysis methods of DWI and mathematical models of drift flux are presented. Based on the general excess entropy production criterion of non-equilibrium thermodynamics, an energy principle of DWI is established. (author). 10 refs, 16 figs

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

    OpenAIRE

    Bernardo B. da Silva; Alexandra C. Braga; Célia C. Braga; Leidjane M. M. de Oliveira; Suzana M. G. L. Montenegro; Bernardo Barbosa Junior

    2016-01-01

    ABSTRACT The surface albedo plays an important role in the exchanges of energy and mass in the planetary boundary layer. Therefore, changes in albedo affect the balance of radiation and energy at the surface, which can be detected with its monitoring. Albedo determination has been performed through various sensors, but there is not yet any publication dealing with albedo calculation procedures using OLI (Operational Land Imager) - Landsat 8 images. The objective of the study is to present the...

  19. Inter-comparison of multiple angle remotely sensed data across different spatial resolutions and sensors for determination of albedo

    OpenAIRE

    Khavarian Nehzak, Hassan

    2012-01-01

    Surface albedo is one of the critical parameters required by studies of surface energy balance and climate models. Albedo is defined as the ratio of outgoing radiances to incoming irradiances over hemispherical view-illumination geometry. Remotely sensed albedo is usually based on multiple view angle observations and a Bidirectional Reflectance Distribution Function (BRDF) model. The accuracy of remotely sensed albedo depends on a variety of factors of which the main ones are the accuracy of ...

  20. Representation of vegetation effects on the snow-covered albedo in the Noah land surface model with multiple physics options

    OpenAIRE

    Park, S.; Park, S. K.

    2015-01-01

    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 No...

  1. Arctic and Antarctic diurnal and seasonal variations of snow albedo from multiyear Baseline Surface Radiation Network measurements

    OpenAIRE

    Wang, Xianwei; Zender, Charles S

    2011-01-01

    This study analyzes diurnal and seasonal variations of snow albedo at four Baseline Surface Radiation Network stations in the Arctic and Antarctica from 2003 to 2008 to elucidate similarities and differences in snow albedo diurnal cycles across geographic zones and to assess how diurnal changes in snow albedo affect the surface energy budget. At the seasonal scale, the daily albedo for the perennial snow at stations South Pole and Georg von Neumayer in Antarctica has a similar symmetric varia...

  2. Shock instability in dissipative gases

    OpenAIRE

    Radulescu, Matei I.; Sirmas, Nick

    2011-01-01

    Previous experiments have revealed that shock waves in thermally relaxing gases, such as ionizing, dissociating and vibrationally excited gases, can become unstable. To date, the mechanism controlling this instability has not been resolved. Previous accounts of the D'yakov-Kontorovich instability, and Bethe-Zel'dovich-Thompson behaviour could not predict the experimentally observed instability. To address the mechanism controlling the instability, we study the propagation of shock waves in a ...

  3. PULMONARY CIRCULATION AT EXERCISE

    OpenAIRE

    R. Naeije; CHESLER, N

    2012-01-01

    The pulmonary circulation is a high flow and low pressure circuit, with an average resistance of 1 mmHg.min.L−1 in young adults, increasing to 2.5 mmHg.min.L−1 over 4–6 decades of life. Pulmonary vascular mechanics at exercise are best described by distensible models. Exercise does not appear to affect the time constant of the pulmonary circulation or the longitudinal distribution of resistances. Very high flows are associated with high capillary pressures, up to a 20–25 mmHg threshold associ...

  4. Investigations into natural circulation driven heat removal systems

    International Nuclear Information System (INIS)

    Passive safety systems can make an important contribution to decay heat removal in existing and next Generation NPP. Two-phase natural circulation systems have under certain circumstances instabilities which have to be analysed in detail. For this reason the test facility GENEVA has been constructed and commissioned at the TU Dresden. The experiments described in the experimental matrix will be started this year. First experimental data showed flow instabilities e.g. flashing as expected. Generic studies are necessary to examine two-phase flow and especially two-phase flow instabilities in further detail. The influence of subcooling and the diameters of downcomer and riser are of particular interest. These will help to evaluate the system behaviour of passive heat removal systems as well as their safety and reliability for nuclear reactors. (orig.)

  5. Nonlinear evolution of MHD instabilities

    International Nuclear Information System (INIS)

    A 3-D nonlinear MHD computer code was used to study the time evolution of internal instabilities. Velocity vortex cells are observed to persist into the nonlinear evolution. Pressure and density profiles convect around these cells for a weak localized instability, or convect into the wall for a strong instability. (U.S.)

  6. Assessing spatio-temporal variability and trends in modelled and measured Greenland Ice Sheet albedo (2000-2013)

    NARCIS (Netherlands)

    Alexander, P. M.; Tedesco, M.; Fettweis, X.; Van De Wal, R. S W; Smeets, C. J P P; Van Den Broeke, M. R.

    2014-01-01

    Accurate measurements and simulations of Greenland Ice Sheet (GrIS) surface albedo are essential, given the role of surface albedo in modulating the amount of absorbed solar radiation and meltwater production. In this study, we assess the spatio-temporal variability of GrIS albedo during June, July,

  7. Kuosheng BWR/6 instability analysis with RETRANO2/MOD3

    International Nuclear Information System (INIS)

    The objective of this study is to investigate the stability characteristics for Kuosheng nuclear power plant (KNPP), which has two units of General Electric Company-designed boiling water reactor/6 with a rated core thermal power of 2,894 MW and a rated core flow of 3,832 x 104 t/h. The approach to investigating the instability of KNPP has two steps. The first step includes three types of stability analysis: total plant stability, core reactivity stability, and channel hydrodynamic stability. The Electric Power Research Institute's methodology is adopted in this step. The second step is to establish the instability map under natural circulation conditions. This methodology is quite useful in identifying the stability safety margin and the setup of stability criteria during a nuclear reactor transient. In this study, the recirculation pump trip (RPT) transients with isolated feedwater heater were investigated and plotted on an instability map

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

    Science.gov (United States)

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

    2013-12-01

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

  9. Albedo of Surface CO2 Deposits in Mars' Residual South Polar Cap

    Science.gov (United States)

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

    2014-12-01

    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. We consider possible modifications of the dust only model that could explain the discrepancy.

  10. A Method for Retrieving Daily Land Surface Albedo from Space at 30-m Resolution

    Directory of Open Access Journals (Sweden)

    Bo Gao

    2015-08-01

    Full Text Available Land surface albedo data with high spatio-temporal resolution are increasingly important for scientific studies addressing spatially and/or temporally small-scale phenomena, such as urban heat islands and urban land surface energy balance. Our previous study derived albedo data with 2–4-day and 30-m temporal and spatial resolution that have better spatio-temporal resolution than existing albedo data, but do not completely satisfy the requirements for monitoring high-frequency land surface changes at the small scale. Downscaling technology provides a chance to further improve the albedo data spatio-temporal resolution and accuracy. This paper introduces a method that combines downscaling technology for land surface reflectance with an empirical method of deriving land surface albedo. Firstly, downscaling daily MODIS land surface reflectance data (MOD09GA from 500 m to 30 m on the basis of HJ-1A/B BRDF data with 2–4-day and 30-m temporal and spatial resolution is performed: this is the key step in the improved method. Subsequently, the daily 30-m land surface albedo data are derived by an empirical method combining prior knowledge of the MODIS BRDF product and the downscaled daily 30-m reflectance. Validation of albedo data obtained using the proposed method shows that the new method has both improved spatio-temporal resolution and good accuracy (a total absolute accuracy of 0.022 and a total root mean squared error at six sites of 0.028.

  11. Atmospheric and Surface Contributions to Planetary Albedo and their Relationship to the Total Meridional Energy Transport

    Science.gov (United States)

    Donohoe, A.; Battisti, D. S.

    2010-12-01

    The meridional distribution of incident solar radiation and planetary albedo both contribute to the equator-to-pole gradient in absorbed solar radiation (ASR) in the observed climate system. While the former component is determined by the Earth-Sun geometry and composes 60% of the equator-to-pole gradient in ASR, the latter component makes a significant (40%) contribution to the ASR gradient and is potentially a function of climate state due to its dependence on both atmospheric and surface albedo. In turn, the equator-to-pole gradient in planetary albedo is found to be primarily (86% -89%) dictated by atmospheric albedo with meridional gradients in surface albedo playing a much smaller role in forcing the climate system on the equator-to-pole scale. Simulations of the pre-industrial climate system using the CMIP3 coupled models show large differences in the equator-to-pole gradient in planetary albedo which are mainly due to differences in the simulated cloud distribution, with surface processes playing a much smaller role. The inter-model spread in total meridional heat transport is also primarily (85% of the inter-model spread) due to differences in the simulated cloud distribution. Further model simulations demonstrate that the surface albedo changes associated with moving from the present climate to an ice free climate have a small effect on the equator-to-pole gradient of ASR as compared to the uncertainty in simulated cloud distributions, and hence a small effect on the meridional heat transport.

  12. A controlled snowmaking experiment testing the relation between black carbon content and reduction of snow albedo

    Science.gov (United States)

    Brandt, Richard E.; Warren, Stephen G.; Clarke, Antony D.

    2011-04-01

    Radiative transfer modeling of the reduction of snow albedo by black carbon (BC) requires experimental verification. In natural snow the albedo reduction is at most a few percent, and even with accurate measurements, attribution is ambiguous because snow albedo depends on other variables. In this experiment, artificial snowpacks are made by freezing of water droplets produced by a snowmaking machine in an open field, using water with and without added soot, in amounts about 100 times natural background soot levels, so as to obtain a large signal on albedo. The optically effective snow grain size is determined from the measured near-infrared albedo; matching the measured visible albedo then requires addition of BC to the radiative transfer model. The BC content of the artificial snowpacks is measured by filtering the meltwater; the filters are analyzed by a laboratory spectrophotometer as is done for filters from samples of natural snow. The BC content indicated by the filters agrees with that required in the model to match the observed albedo, but significant uncertainties remain, so further experiments are needed.

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

    Science.gov (United States)

    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.

  14. Similar origin for low- and high-albedo Jovian Trojans and Hilda asteroids ?

    CERN Document Server

    Marsset, Michaël; Gourgeot, Florian; Dumas, Christophe; Birlan, Mirel; Lamy, Philippe; Binzel, Richard P

    2014-01-01

    Hilda asteroids and Jupiter Trojans are two low-albedo (p$_{\\rm v}$ ~ 0.07) populations for which the Nice model predicts an origin in the primordial Kuiper Belt region. However, recent surveys by WISE and the Spitzer Space Telescope (SST) have revealed that ~2% of these objects possess high albedos (p$_{\\rm v}$ > 0.15), which might indicate interlopers - that is, objects not formed in the Kuiper Belt - among these two populations. Here, we report spectroscopic observations in the visible and/or near-infrared spectral ranges of twelve high-albedo (p$_{\\rm v}$ > 0.15) Hilda asteroids and Jupiter Trojans. These twelve objects have spectral properties similar to those of the low- albedo population, which suggests a similar composition and hence a similar origin for low- and high-albedo Hilda asteroids and Jupiter Trojans. We therefore propose that most high albedos probably result from statistical bias or uncertainties that affect the WISE and SST measurements. However, some of the high albedos may be true and t...

  15. Correction of broadband snow albedo measurements affected by unknown slope and sensor tilts

    Science.gov (United States)

    Weiser, Ursula; Olefs, Marc; Schöner, Wolfgang; Weyss, Gernot; Hynek, Bernhard

    2016-04-01

    Geometric effects induced by the underlying terrain slope or by tilt errors of the radiation sensors lead to an erroneous measurement of snow or ice albedo. Consequently, artificial diurnal albedo variations in the order of 1-20 % are observed. The present paper proposes a general method to correct tilt errors of albedo measurements in cases where tilts of both the sensors and the slopes are not accurately measured or known. We demonstrate that atmospheric parameters for this correction model can either be taken from a nearby well-maintained and horizontally levelled measurement of global radiation or alternatively from a solar radiation model. In a next step the model is fitted to the measured data to determine tilts and directions of sensors and the underlying terrain slope. This then allows us to correct the measured albedo, the radiative balance and the energy balance. Depending on the direction of the slope and the sensors a comparison between measured and corrected albedo values reveals obvious over- or underestimations of albedo. It is also demonstrated that differences between measured and corrected albedo are generally highest for large solar zenith angles.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

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

    2012-08-01

    Foliar nitrogen has been shown to be positively correlated with midsummer canopy albedo and canopy near infrared (NIR) reflectance over a broad range of plant functional types (e.g., forests, grasslands, and agricultural lands). To date, the mechanism(s) driving the nitrogen–albedo relationship have not been established, and it is unknown whether factors affecting nitrogen availability will also influence albedo. To address these questions, we examined variation in foliar nitrogen in relation to leaf spectral properties, leaf mass per unit area, and leaf water content for three deciduous species subjected to either nitrogen (Harvard Forest, MA, and Oak Ridge, TN) or CO(2) fertilization (Oak Ridge, TN). At Oak Ridge, we also obtained canopy reflectance data from the airborne visible/infrared imaging spectrometer (AVIRIS) to examine whether canopy-level spectral responses were consistent with leaf-level results. At the leaf level, results showed no differences in reflectance or transmittance between CO(2) or nitrogen treatments, despite significant changes in foliar nitrogen. Contrary to our expectations, there was a significant, but negative, relationship between foliar nitrogen and leaf albedo, a relationship that held for both full spectrum leaf albedo as well as leaf albedo in the NIR region alone. In contrast, remote sensing data indicated an increase in canopy NIR reflectance with nitrogen fertilization. Collectively, these results suggest that altered nitrogen availability can affect canopy albedo, albeit by mechanisms that involve canopy-level processes rather than changes in leaf-level reflectance. PMID:22294028

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-05-01

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

  19. A differential albedo for a Monte Carlo criticality program KENO IV

    International Nuclear Information System (INIS)

    To carry out numbers of survey-type criticality calculations, differential albedos of some reflector materials obtained from ANISN calculation with Hansen-Roach 16 group cross section data are incorporated in Monte Carlo criticality program KENO IV. Although the albedo option is a powerful tool that can save computer time, the above albedo data are not applicable to KENO IV calculation with the multigroup constants libraries MGCL's (26 group and 137 group) in criticality analysis code system JACS due to the difference of energy structure between MGCL libraries and the 16 group albedo data. A new differential albedo of 30 cm-thick water reflector has been generated by ANISN (P3, S8, fixed source problem) using 26 group MGCL-J3 for the users of the JACS system. Values of keff calculated by the rigorous method and those by the 26 group differential albedo were in good agreement for sphere and infinitely long systems with thick water reflector. For an infinitely long slab system, computer time of KENO IV calculation with the 26 group albedo was 60% shorter than that with the rigorous reflector treatment. (author)

  20. Genetic instability in Gynecological Cancer

    Institute of Scientific and Technical Information of China (English)

    ZHAO Qing-hua; ZHOU Hong-lin

    2003-01-01

    Defects of mismatch repair (MMR) genes also have beenidentified in many kinds of tumors. Loss of MMR functionhas been linked to genetic instability especially microsatelliteinstability that results in high mutation rate. In this review, wediscussed the microsatellite instability observed in thegynecological tumors. We also discussed defects in the DNAmismatch repair in these tumors and their correlation to themicrosatellite instability, as well as the gene mutations due tothe microsatellite instability in these tumors. From thesediscussion, we tried to understand the mechanism ofcarcinogenesis in gynecological tumors from the aspect ofgenetic instability due to mismatch repair defects.

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

    Directory of Open Access Journals (Sweden)

    P. Lewis

    1999-01-01

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

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

    Science.gov (United States)

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

    2015-11-01

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

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-09-15

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

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

    Science.gov (United States)

    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.

  6. Cosmic ray driven instability

    International Nuclear Information System (INIS)

    The interaction between energetic charged particles and thermal plasma, which forms the basis of diffusive shock acceleration, leads also to interesting dynamical phenomena. For a compressional mode propagating in a system with homoeneous energetic particle pressure it is well known that friction with the energetic particles leads to damping. The linear theory of this effect has been analyzed in detail by Ptuskin. Not so obvious is that a non-uniform energetic particle pressure can in addition amplify compressional disturbances. If the pressure gradient is sufficiently steep this growth can dominate the frictional damping and lead to an instability. It is important to not that this effect results from the collective nature of the interaction between the energetic particles and the gas and is not connected with the Parker instability, nor with the resonant amplification of Alfven waves

  7. Whistler modulational instability.

    Science.gov (United States)

    Brinca, A. L.

    1973-01-01

    Derivation of the modulational instability characteristics of whistlers in cold and hot plasmas. The cold-plasma analysis considers both ion motion and relativistic effects; the unstable band, with a growth rate proportional to (B/B sub zero)squared, is contiguous to Omega sub e/4 and, depending on the plasma density, lies above or below that frequency (Omega sub e is the electron cyclotron frequency of the static magnetic field; B and B sub zero are the whistler and static magnetic fields). In hot plasmas, stability occurs between Omega sub e/4 and Omega prime (less than Omega sub e), with Omega prime depending mainly on the mean energy and anisotropy of the energetic electron population; the complementary unstable band has a growth rate proportional to (B/B sub zero) to the 1/2 power. The relevance of the instability to whistlers in the magnetosphere is discussed.

  8. Roles of land surface albedo and horizontal resolution on the Indian summer monsoon biases in a coupled ocean-atmosphere tropical-channel model

    Science.gov (United States)

    Samson, Guillaume; Masson, Sébastien; Durand, Fabien; Terray, Pascal; Berthet, Sarah; Jullien, Swen

    2016-05-01

    The Indian summer monsoon (ISM) simulated over the 1989-2009 period with a new 0.75° ocean-atmosphere coupled tropical-channel model extending from 45°S to 45°N is presented. The model biases are comparable to those commonly found in coupled global climate models (CGCMs): the Findlater jet is too weak, precipitations are underestimated over India while they are overestimated over the southwestern Indian Ocean, South-East Asia and the Maritime Continent. The ISM onset is delayed by several weeks, an error which is also very common in current CGCMs. We show that land surface temperature errors are a major source of the ISM low-level circulation and rainfall biases in our model: a cold bias over the Middle-East (ME) region weakens the Findlater jet while a warm bias over India strengthens the monsoon circulation over the southern Bay of Bengal. A surface radiative heat budget analysis reveals that the cold bias is due to an overestimated albedo in this desertic ME region. Two new simulations using a satellite-observed land albedo show a significant and robust improvement in terms of ISM circulation and precipitation. Furthermore, the ISM onset is shifted back by 1 month and becomes in phase with observations. Finally, a supplementary set of simulations at 0.25°-resolution confirms the robustness of our results and shows an additional reduction of the warm and dry bias over India. These findings highlight the strong sensitivity of the simulated ISM rainfall and its onset timing to the surface land heating pattern and amplitude, especially in the ME region. It also illustrates the key-role of land surface processes and horizontal resolution for improving the ISM representation, and more generally the monsoons, in current CGCMs.

  9. The bar instability revisited

    OpenAIRE

    Chiodi, Filippo; Andreotti, Bruno; Claudin, Philippe

    2012-01-01

    The river bar instability is revisited, using a hydrodynamical model based on Reynolds averaged Navier-Stokes equations. The results are contrasted with the standard analysis based on shallow water Saint-Venant equations. We first show that the stability of both transverse modes (ripples) and of small wavelength inclined modes (bars) predicted by the Saint-Venant approach are artefacts of this hydrodynamical approximation. When using a more reliable hydrodynamical model, the dispersion relati...

  10. The Instability of Markets

    OpenAIRE

    Hogg, Tad; Huberman, Bernardo A.; Youssefmir, Michael

    1995-01-01

    Recent developments in the global liberalization of equity and currency markets, coupled to advances in trading technologies, are making markets increasingly interdependent. This increased fluidity raises questions about the stability of the international financial system. In this paper, we show that as couplings between stable markets grow, the likelihood of instabilities is increased, leading to a loss of general equilibrium as the system becomes increasingly large and diverse.

  11. The instability of markets

    CERN Document Server

    Huberman, B A; Huberman, Bernardo A; Youssefmir, Michael

    1995-01-01

    Recent developments in the global liberalization of equity and currency markets, coupled to advances in trading technologies, are making markets increasingly interdependent. This increased fluidity raises questions about the stability of the international financial system. In this paper, we show that as couplings between stable markets grow, the likelihood of instabilities is increased, leading to a loss of general equilibrium as the system becomes increasingly large and diverse.

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

    Science.gov (United States)

    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

  13. Neutron dose equivalent rate meter on the basis of the single sphere Albedo technique

    International Nuclear Information System (INIS)

    In area monitoring there is a need for a more accurate neutron reference dose rate meter, especially for the purpose of albedo dosemeter calibrations in neutron stray radiation fields of interest. The so-called Single Sphere Albedo Counter makes use of three active 3He proportional counters as thermal neutron detectors positioned in the centre and on the surface (albedo dosemeter configurations) of a polyethylene sphere. The linear combination of the detector readings allows for the indication of different quantities like H*(10),D,φ, and reduces the energy dependence significantly. The paper describes the dosimetric properties of a prototype instrument and its application in routine monitoring. (author)

  14. Charged pion albedo induced by cosmic antiproton interactions with the lunar surface

    International Nuclear Information System (INIS)

    We report the calculations of the energy spectra and fluxes of single and double albedo charged pions generated by cosmic proton and antiproton interactions with the lunar surface. Properties of such spectra and related fluxes are investigated in order to clarify some important facets of the antiproton detection via charged pion albedo flux from the lunar surface. Pion albedo measurement may represent a novel approach for the identification of cosmic antiprotons using the lunar surface as a calorimeter. Future scientific programs on the Moon designed to measure antiproton flux may benefit from the results of these calculations. (author)

  15. Application of Laplace transform for determination of albedo type boundary conditions for neutronic calculations

    International Nuclear Information System (INIS)

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

  16. Spatial and temporal variation in vegetation land cover albedo in Finland

    OpenAIRE

    Safdari, Pezhman

    2015-01-01

    Surface albedo, which is the fraction of reflected radiant energy by earth’s surface to incoming solar energy, plays an important role in earth energy budget and energy equilibrium. Different features of the earth’s surface have different reflectivity rates which affect the albedo. Vegetation land-covers covering vast areas of earth’s surface as agricultural lands, forests, grass lands and so on, have great impact on land surface albedo. The Species composition, geographical distributi...

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

    Science.gov (United States)

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

    2016-04-01

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

  18. ESTIMATION OF SURFACE ALBEDO DISTRIBUTION IN LUTZOW-HOLM BAY AND ITS NEIGHBORHOOD WITH NOAA/AVHRR DATA

    OpenAIRE

    ナカガワ, キヨタカ; Kiyotaka, Nakagawa

    1992-01-01

    A method has been developed for estimating the filtered narrow band surface albedo with NOAA/AVHRR data, and has been applied to analysis of the surface albedo distribution in Lutzow-Holm Bay and its neighborhood, Antarctica, in 1990. As a result, 16 maps of the surface albedo distribution have been drawn. From a comparison of the albedos inferred from satellite data with those actually observed in Ongul Strait, it is clear that the satellite-inferred, filtered narrow band albedos agree well ...

  19. Shoulder instability; Schultergelenkinstabilitaet

    Energy Technology Data Exchange (ETDEWEB)

    Sailer, J.; Imhof, H. [Abteilung Osteoradiologie, Univ.-Klinik fuer Radiodiagnostik Wien (Austria)

    2004-06-01

    Shoulder instability is a common clinical feature leading to recurrent pain and limitated range of motion within the glenohumeral joint. Instability can be due a single traumatic event, general joint laxity or repeated episodes of microtrauma. Differentiation between traumatic and atraumatic forms of shoulder instability requires careful history and a systemic clinical examination. Shoulder laxity has to be differentiated from true instability followed by the clinical assessment of direction and degree of glenohumeral translation. Conventional radiography and CT are used for the diagnosis of bony lesions. MR imaging and MR arthrography help in the detection of soft tissue affection, especially of the glenoid labrum and the capsuloligamentous complex. The most common lesion involving the labrum is the anterior labral tear, associated with capsuloperiostal stripping (Bankart lesion). A number of variants of the Bankart lesion have been described, such as ALPSA, SLAP or HAGL lesions. The purpose of this review is to highlight different forms of shoulder instability and its associated radiological findings with a focus on MR imaging. (orig.) [German] Die Schultergelenkinstabilitaet ist haeufig fuer wiederholt auftretende Schmerzen sowie eine eingeschraenkte Beweglichkeit im Glenohumeralgelenk verantwortlich. Sie kann als Folge eines vorangegangenen Traumas, einer generellen Hyperlaxitaet oder infolge wiederholter Mikrotraumen entstehen. Die Differenzierung zwischen traumatischer und atraumatischer Form der Gelenkinstabilitaet erfordert eine sorgfaeltige Anamnese und eine genaue klinische Untersuchung. Die Gelelenklaxitaet als Differenzialdiagnose muss von der echten Instabilitaet unterschieden werden, die Instabilitaet wird dann im Rahmen des klinischen Status nach Grad und Richtung der glenohumeralen Translation unterteilt. Zur Diagnose knoecherner Laesionen werden das konventionelle Roentgen sowie die CT herangezogen. MRT sowie MR-Arthrographie dienen zur Detektion

  20. Circulation and Dissipation on Hot Jupiters

    CERN Document Server

    Li, Jason

    2010-01-01

    Many global circulation models predict supersonic zonal winds and large vertical shears in the atmospheres of short-period jovian exoplanets. Using linear analysis and nonlinear local simulations, we investigate hydrodynamic dissipation mechanisms to balance the thermal acceleration of these winds. The adiabatic Richardson criterion remains a good guide to linear stability, although thermal diffusion allows some modes to violate it at very long wavelengths and very low growth rates. Nonlinearly, wind speeds saturate at Mach numbers $\\approx 2$ and Richardson numbers $\\lesssim 1/4$ for a broad range of plausible diffusivities and forcing strengths. Turbulence and vertical mixing, though accompanied by weak shocks, dominate the dissipation, which appears to be the outcome of a recurrent Kelvin-Helmholtz instability. An explicit shear viscosity, as well as thermal diffusivity, is added to ZEUS to capture dissipation outside of shocks. The wind speed is not monotonic nor single valued for shear viscosities larger...

  1. The correction of albedo dosimeters readout at U400M LNR with the help of a spherical albedo system and comparison with other correction methods

    International Nuclear Information System (INIS)

    The results of readout correction for albedo dosimeters DVGN-01 with using of a spherical albedo system are presented. The measurements were carried out behind the U400M shielding. The functions of correction coefficients in dependence of neutron spectra 'hardness' have been approximated previously. The neutron spectra were measured in three places and the correction coefficients for DVGN-01 readout were estimated by these spectra. A good agreement was shown of the coefficients obtained with the help of these spectra and by the method of spherical albedo system. This is a real evidence of the correction method reliability. On the base of present results the correction coefficients were recommended for individual radiation control at LNR.

  2. Hydrocarbon photochemistry and Lyman alpha albedo of Jupiter

    Science.gov (United States)

    Yung, Y. L.; Strobel, D. F.

    1980-01-01

    A combined study of hydrocarbon and atomic hydrogen photochemistry is made to calculate self-consistently the L alpha albedo of Jupiter. It is shown that the L alpha emissions observed by Voyagers I and II can be explained by resonance scattering of sunlight. Precipitation of energetic particles from the magnetosphere can provide the large required source of atomic hydrogen, although the contribution of direct particle excitation to the disk-averaged brightness is insignificant. The variability of the L alpha brightness inferred from many observations in recent years is examined. The large difference in the brightness of the He 584 A resonance line observed by Pioneer and Voyager is briefly discussed. Driving the photochemistry by solar ultraviolet radiation alone yields a maximum mixing ratio of C2H6 + C2H2 at 0.01 atm of about 4 x 10 to the -6th. The possibility of additional CH4 dissociation from precipitation of magnetospheric particles is discussed. The photochemistry of C2H2 and C2H3 is sufficiently uncertain not to permit accurate calculations of their densities and the ratio C2H6/C2H2.

  3. INTERNAL CIRCULATION ENVELOPES

    CERN Multimedia

    Mail Office

    2001-01-01

    Internal mail envelopes often finish up in large piles in certain offices, thus creating a shortage for other users of the mail service, who would be grateful if everyone with an unused stock could deposit them in their mail box, after attaching them together with an elastic band or a piece of string. The messengers will then collect them so that the Mail Office can put them back in circulation. Thank you for your understanding and collaboration.

  4. Observations of a tropical instability vortex

    Science.gov (United States)

    Kennan, Sean Christopher

    1997-11-01

    Observations of an upper ocean vortex associated with tropical instabilities in the tropical Pacific were made in the vicinity of the South Equatorial Current and North Equatorial Counter Current (SEC-NECC) shear at 140oW during November-December of 1990. The dynamic and thermohaline structure of the observed vortex is mapped in three dimensions using a suite of measurements from shipboard, hydrographic, and satellite sensors and drifting buoys. Evidence that the sampled flow field is steady in a frame of reference moving with the disturbance is used to study the underlying dynamical balances and the effects on heat, fresh water, and eddy energy fluxes in the region. The vortex translated westward at 30 cm/s (0.24o/day), less than half the speed of westward propagating meridional oscillations of the Equatorial Undercurrent (EUC) and SEC system. The associated flow deformed the North Equatorial Front through northward advection of cold equatorial water and southward entrainment of warmer tropical water, giving the surface temperature field the cusp-like pattern which is commonly associated with tropical instabilities. A dipole of convergence and divergence had magnitudes comparable to the local inertial frequency and confirms predictions by various numerical models. Relative vorticity advection balanced convergence at the front, allowing northward moving cold water to subduct beneath the warmer tropical water. The growth of the vortex appears to have been limited by the inertial frequency via a vortex instability mechanism. The same features are present in shear vortices in a general circulation model. The vortex transported heat and fresh water equatorward at rates of about 0.2 MW/m2 and 5 g/(m2s), respectively. The heat flux agrees with previous estimates from observations and models. The region from 2-5oN gained heat and fresh water at 2-5 W/m3 and 0.1 μg/(m3s). Eddy kinetic energy increased via barotropic instability at a rate of 0.15 mW/m3 and via baroclinic

  5. Fundamental study on thermo-hydraulics during start-up in natural circulation boiling water reactors. 3. Effects of system pressure on geysering and natural circulation oscillation

    International Nuclear Information System (INIS)

    The authors have been investigating the fundamentals of thermo-hydraulic instabilities which may appear during the start-up in natural circulation BWRs in order to understand their driving mechanisms and to examine the methods preventing their occurrence with an aim of establishing a rational start-up procedure and reactor configuration. In this paper, based on our proposed driving mechanisms of geysering and natural circulation oscillation, the effects of system pressure on their occurrences and features are investigated experimentally. It is made clear that an increase in the system pressure suppresses their occurrences. From the results, a consideration is drawn to understand the differences in the start-ups between thermal natural circulation boilers using fossil fuel and the Dodewaard reactor. Lastly, a rational start-up procedure to prevent their instabilities from occurring is recommended and a new idea of separator is proposed. (author)

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

    Data.gov (United States)

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

  7. The role of albedo and accumulation in the 2010 melting record in Greenland

    International Nuclear Information System (INIS)

    Analyses of remote sensing data, surface observations and output from a regional atmosphere model point to new records in 2010 for surface melt and albedo, runoff, the number of days when bare ice is exposed and surface mass balance of the Greenland ice sheet, especially over its west and southwest regions. Early melt onset in spring, triggered by above-normal near-surface air temperatures, contributed to accelerated snowpack metamorphism and premature bare ice exposure, rapidly reducing the surface albedo. Warm conditions persisted through summer, with the positive albedo feedback mechanism being a major contributor to large negative surface mass balance anomalies. Summer snowfall was below average. This helped to maintain low albedo through the 2010 melting season, which also lasted longer than usual.

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

    International Nuclear Information System (INIS)

    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 Inst., 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. (authors)

  9. Offset of the potential carbon sink from boreal forestation by decreases in surface albedo

    International Nuclear Information System (INIS)

    Carbon uptake by forestation is one method proposed to reduce net carbon dioxide emissions to the atmosphere and so limit the radiative forcing of climate change. But the overall impact of forestation on climate will also depend on other effects associated with the creation of new forests. In particular the albedo of a forested landscape is generally lower than that of cultivated land, especially when snow is lying, and decreasing albedo exerts a positive radiative forcing on climate. Here I simulate the radiative forcings associated with changes in surface albedo as a result of forestation in temperate and boreal forest areas, and translate these forcings into equivalent changes in local carbon stock for comparison with estimated carbon sequestration potentials. I suggest that in many boreal forest areas, the positive forcing induced by decreases in albedo can offset the negative forcing that is expected from carbon sequestration. Some high-latitude forestation activities may therefore increase climate change, rather that mitigating it as intended

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

    CERN Document Server

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

    2015-01-01

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

  11. Albedo-adjusted fast-neutron diffusion coefficients in reactor reflectors

    International Nuclear Information System (INIS)

    In the newer, larger pressurized-water reactor cores, the calculated power distributions are fairly sensitive to the number of neutron groups used and to the treatment of the reflector cross sections. Comparisons between transport and diffusion calculations show that the latter substantially underpredict the reflector albedos in the fast (top) group and that the power distribution is shifted toward the core center when compared to 4-group transport theory results. When the fast-neutron diffusion coefficients are altered to make the transport- and diffusion-theory albedos agree, the power distributions are also brought into agreement. An expression for the fast-neutron diffusion coefficients in reflector regions has been derived such that the diffusion calculation reproduces the albedo obtained from a transport solution. In addition, a correction factor for mesh effects applicable to coarse mesh problems is presented. The use of the formalism gives the correct albedos and improved power distributions. (U.S.)

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

    Data.gov (United States)

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

  13. MISR Level 3 Component Global Albedo product covering a quarter (seasonal) V006

    Data.gov (United States)

    National Aeronautics and Space Administration — MISR Level 3 Component Global Albedo publicly available product covering a quarter (seasonal) to be used starting with MISR Release V3.2. (Suggested Usage: This...

  14. MISR Level 3 Component Global Albedo product covering a year V006

    Data.gov (United States)

    National Aeronautics and Space Administration — MISR Level 3 Component Global Albedo publicly available product covering a year to be used starting with MISR Release V3.2. (Suggested Usage: This file contains the...

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

    Data.gov (United States)

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

  16. MISR Level 3 Component Global Albedo product covering a month V006

    Data.gov (United States)

    National Aeronautics and Space Administration — MISR Level 3 Component Global Albedo publicly available product covering a month to be used starting with MISR Release V3.2. (Suggested Usage: This file contains...

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

    DEFF Research Database (Denmark)

    Bhanderi, Dan

    2006-01-01

    Earth albedo influences vector measurements of the solar line of sight vector, due to the induced current on in the photo voltaics of Sun sensors. Although advanced digital Sun sensors exist, these are typically expensive and may not be suited for satellites in the nano or pico-class. Previously an...... Earth albedo model, based on reflectivity data from NASA's Total Ozone Mapping Spectrometer project, has been published. In this paper the proposed model is presented, and the model is sought validated by comparing simulated data with telemetry from the Danish Ørsted satellite. A novel method for...... modeling Sun sensor output by incorporating the Earth albedo model is presented. This model utilizes the directional information of in the Earth albedo model, which is achieved by Earth surface partitioning. This allows accurate simulation of the Sun sensor output and the results are consistent with Ørsted...

  18. MISR Level 3 Component Global Albedo seasonal product in netCDF format V006

    Data.gov (United States)

    National Aeronautics and Space Administration — MISR Level 3 Component Global Albedo publicly available product in netCDF format covering a quarter (seasonal). (Suggested Usage: This file contains the global...

  19. MISR Level 3 FIRSTLOOK Component Global Albedo product covering a month V002

    Data.gov (United States)

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

  20. MISR Level 3 Component Global Albedo product covering a day V006

    Data.gov (United States)

    National Aeronautics and Space Administration — MISR Level 3 Component Global Albedo publicly available product covering a day to be used starting with MISR Release V3.2. (Suggested Usage: This file contains the...

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

    Science.gov (United States)

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

    1977-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Rafael Pimentel

    2016-02-01

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

  3. Glacier albedo decrease in the European Alps: potential causes and links with mass balances

    Science.gov (United States)

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

    Directory of Open Access Journals (Sweden)

    M. U. F. Kirschbaum

    2011-08-01

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

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

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

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

    Directory of Open Access Journals (Sweden)

    M. U. F. Kirschbaum

    2011-12-01

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

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

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

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

    OpenAIRE

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

    2016-01-01

    The exploration of the Pluto-Charon system by the New Horizons spacecraft represent the first opportunity to understand the distribution of albedo and other photometric properties of the surfaces of objects in the Solar System's "Third Zone" within the context of a geologic world. Images of the entire illuminated surface of Pluto and Charon obtained by the Long Range Reconnaissance Imager (LORRI) camera provide a global map of Pluto that revealed surface albedo variegations larger than any ot...

  7. The Role of the Effective Cloud Albedo for Climate Monitoring and Analysis

    OpenAIRE

    Christine Träger-Chatterjee; Richard Mueller; Jörg Trentmann; Rebekka Posselt; Reto Stökli

    2011-01-01

    Cloud properties and the Earth’s radiation budget are defined as essential climate variables by the Global Climate Observing System (GCOS). The cloud albedo is a measure for the portion of solar radiation reflected back to space by clouds. This information is essential for the analysis and interpretation of the Earth’s radiation budget and the solar surface irradiance. We present and discuss a method for the production of the effective cloud albedo and the solar surface irradiance based on th...

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

    OpenAIRE

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

    2016-01-01

    Occultation light curves of exomoons may give information on their albedo and hence indicate the presence of ice cover on the surface. Icy moons might have subsurface oceans thus these may potentially be habitable. The objective of our paper is to determine whether next generation telescopes will be capable of albedo estimations for icy exomoons using their occultation light curves. The success of the measurements depends on the depth of the moon's occultation in the light curve and on the se...

  9. New spectral functions of the near-ground albedo derived from aircraft diffraction spectrometer observations

    Directory of Open Access Journals (Sweden)

    C. A. Varotsos

    2013-06-01

    Full Text Available 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.

  10. Structure of spontaneous fission spectrum of 252Cf and its impact on neutron albedo experiments' simulation

    International Nuclear Information System (INIS)

    Aimed at the problem of the energy spectrum of spontaneous fission source, which was used in neutron albedo experiments, we selected two sets of 252Cf fission spectra, which were fitted by formulae and were universally accepted. And they were applied in neutron albedo experiments independently. Neutron fluence and fission rate on each detecting point were compared and analyzed. The results show that Watt spectrum agrees the experiment data better than that of Maxwell spectrum. (authors)

  11. Technical Note: Evaluating a simple parameterization of radiative shortwave forcing from surface albedo change

    OpenAIRE

    R. M. Bright; Kvalevåg, M. M.

    2013-01-01

    Land use activities affect Earth's energy balance not only via biogeochemical emissions but also through perturbations in surface albedo, the latter of which is often excluded in impact assessment studies. In this short technical note, we present and compare a simple model for estimating shortwave radiative forcings at the top of Earth's atmosphere to a more sophisticated 8-stream radiative transfer model based on a discrete ordinate method. Outcomes from monthly albedo change simulati...

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

    Science.gov (United States)

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

    2014-01-01

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

  13. Untersuchung eines möglichen Einflusses der Albedo auf die Mesopausenregion

    OpenAIRE

    Gebhardt, Vera

    2015-01-01

    Der Ausgangspunkt dieser Arbeit war die Tatsache, dass verschiedene Messmethoden der Albedo zu verschiedenen Ergebnissen geführt haben und es schwierig war, diese Ergebnisse zu validieren. Ziel war es, herauszufinden, ob es einen Zusammenhang zwischen der Variablität der Temperatur der oberen Mesopause und der Variabilität der Albedo gibt. Es hat sich gezeigt, dass im Temperaturverlauf der Mesopause zum Zeitpunkt der Äquinoktien ein sogenannter Dip auftritt, welcher auch im Jahresverlauf der ...

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

    OpenAIRE

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

    2015-01-01

    International audience 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...

  15. Atmospheric effect on the ground-based measurements of broadband surface albedo

    OpenAIRE

    Manninen, T.; Riihelä, A.; De Leeuw, G.

    2012-01-01

    Ground-based pyranometer measurements of the (clear-sky) broadband surface albedo are affected by the atmospheric conditions (mainly by aerosol particles, water vapour and ozone). A new semi-empirical method for estimating the magnitude of the effect of atmospheric conditions on surface albedo measurements in clear-sky conditions is presented. Global and reflected radiation and/or aerosol optical depth (AOD) at two wavelengths are needed to apply the method. Depending on the...

  16. Genome instability and aging.

    Science.gov (United States)

    Vijg, Jan; Suh, Yousin

    2013-01-01

    Genome instability has long been implicated as the main causal factor in aging. Somatic cells are continuously exposed to various sources of DNA damage, from reactive oxygen species to UV radiation to environmental mutagens. To cope with the tens of thousands of chemical lesions introduced into the genome of a typical cell each day, a complex network of genome maintenance systems acts to remove damage and restore the correct base pair sequence. Occasionally, however, repair is erroneous, and such errors, as well as the occasional failure to correctly replicate the genome during cell division, are the basis for mutations and epimutations. There is now ample evidence that mutations accumulate in various organs and tissues of higher animals, including humans, mice, and flies. What is not known, however, is whether the frequency of these random changes is sufficient to cause the phenotypic effects generally associated with aging. The exception is cancer, an age-related disease caused by the accumulation of mutations and epimutations. Here, we first review current concepts regarding the relationship between DNA damage, repair, and mutation, as well as the data regarding genome alterations as a function of age. We then describe a model for how randomly induced DNA sequence and epigenomic variants in the somatic genomes of animals can result in functional decline and disease in old age. Finally, we discuss the genetics of genome instability in relation to longevity to address the importance of alterations in the somatic genome as a causal factor in aging and to underscore the opportunities provided by genetic approaches to develop interventions that attenuate genome instability, reduce disease risk, and increase life span. PMID:23398157

  17. Radiative forcing impacts of boreal forest biofuels: a scenario study for Norway in light of albedo.

    Science.gov (United States)

    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

  18. Mars hemispherical albedo map: absolute value and interannual variability inferred from OMEGA data.

    Science.gov (United States)

    Vincendon, M.; Audouard, J.; Langevin, Y.; Poulet, F.; Bellucci, G.; Bibring, J.-P.; Gondet, B.

    2012-04-01

    The surface reflectance integrated over all directions and solar wavelengths ("hemispherical albedo") controls the radiative budget at the surface of Mars, and hence its climate. Reference albedo maps are usually derived from nadir observation of surface reflectance through clear atmospheric conditions. However, the atmosphere of Mars is permanently loaded with a significant amount of aerosols (typical visible optical depths of 0.5 under clear atmospheric conditions), which impacts the evaluation of "aerosol free" surface reflectances from remote sensing data. Moreover, the Martian surface is usually assumed to be Lambertian, both for simplicity and due to the lack of robust constraints about its bidirectional properties. We used OMEGA visible and near-IR measurements, with an appropriate UV extrapolation, to calculate as a function of space and time the hemispherical surface albedo of Mars. The contribution of aerosols is removed using a radiative transfer model and recent aerosols properties. Uncertainties associated with this procedure are calculated. The aerosols correction increases the bright/dark surfaces contrast. Typical, mean bidirectional reflectance properties of the martian surface are estimated using MER surface measurements and CRISM remote "EPF" observations. From these constraints, we have derived a typical relationship that makes it possible to convert single nadir measurements of the reflectance into hemispherical albedo. Accounting for the BRDF of the martian surface typically modify by ± 15% the derived albedo, depending on solar zenith angles. We will present our methods and preliminary results regarding seasonal and interannual variations of the surface albedo of Mars during years 2004-2011.

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

    CERN Document Server

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2012-11-20

    Biochar application to agricultural soils can change the surface albedo which could counteract the climate mitigation benefit of biochar systems. However, the size of this impact has not yet been quantified. Based on empirical albedo measurements and literature data of arable soils mixed with biochar, a model for annual vegetation cover development based on satellite data and an assessment of the annual development of surface humidity, an average mean annual albedo reduction of 0.05 has been calculated for applying 30-32 Mg ha(-1) biochar on a test field near Bayreuth, Germany. The impact of biochar production and application on the carbon cycle and on the soil albedo was integrated into the greenhouse gas (GHG) balance of a modeled pyrolysis based biochar system via the computation of global warming potential (GWP) characterization factors. The analysis resulted in a reduction of the overall climate mitigation benefit of biochar systems by 13-22% due to the albedo change as compared to an analysis which disregards the albedo effect. Comparing the use of the same quantity of biomass in a biochar system to a bioenergy district heating system which replaces natural gas combustion, bioenergy heating systems achieve 99-119% of the climate benefit of biochar systems according to the model calculation. PMID:23146092

  1. Mars Express measurements of surface albedo changes over 2004-2010

    Science.gov (United States)

    Vincendon, M.; Audouard, J.; Altieri, F.; Ody, A.

    2015-05-01

    The pervasive Mars dust is continually transported between the surface and the atmosphere. When on the surface, dust increases the albedo of darker underlying rocks and regolith, which modifies climate energy balance and must be quantified. Remote observation of surface albedo absolute value and albedo change is however complicated by dust itself when lifted in the atmosphere. Here we present a method to calculate and map the bolometric solar hemispherical albedo of the martian surface using the 2004-2010 OMEGA imaging spectrometer dataset. This method takes into account aerosols radiative transfer, surface photometry, and instrumental issues such as registration differences between visible and near-IR detectors. Resulting albedos are on average 17% higher than previous estimates for bright surfaces while similar for dark surfaces. We observed that surface albedo changes occur mostly during the storm season due to isolated events. The main variations are observed during the 2007 global dust storm and during the following year. A wide variety of change timings are detected such as dust deposited and then cleaned over a martian year, areas modified only during successive global dust storms, and perennial changes over decades. Both similarities and differences with previous global dust storms are observed. While an optically thin layer of bright dust is involved in most changes, this coating turns out to be sufficient to mask underlying mineralogical near-IR spectral signatures. Overall, changes result from apparently erratic events; however, a cyclic evolution emerges for some (but not all) areas over long timescales.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-02-01

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

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

    Directory of Open Access Journals (Sweden)

    H. S. Negi

    2010-11-01

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

  4. The long-term effect of increasing the albedo of urban areas

    International Nuclear Information System (INIS)

    Solar reflective urban surfaces (white rooftops and light-colored pavements) can increase the albedo of an urban area by about 0.1. Increasing the albedo of urban and human settlement areas can in turn decrease atmospheric temperature and could potentially offset some of the anticipated temperature increase caused by global warming. We have simulated the long-term (decadal to centennial) effect of increasing urban surface albedos using a spatially explicit global climate model of intermediate complexity. We first carried out two sets of simulations in which we increased the albedo of all land areas between ±20° and ±45° latitude respectively. The results of these simulations indicate a long-term global cooling effect of 3 × 10−15 K for each 1 m2 of a surface with an albedo increase of 0.01. This temperature reduction corresponds to an equivalent CO2 emission reduction of about 7 kg, based on recent estimates of the amount of global warming per unit CO2 emission. In a series of additional simulations, we increased the albedo of urban locations only, on the basis of two independent estimates of the spatial extent of urban areas. In these simulations, global cooling ranged from 0.01 to 0.07 K, which corresponds to a CO2 equivalent emission reduction of 25–150 billion tonnes of CO2. (letter)

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

    Directory of Open Access Journals (Sweden)

    H. S. Negi

    2011-03-01

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

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

    Institute of Scientific and Technical Information of China (English)

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

    2015-01-01

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

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

    CERN Document Server

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

    2013-01-01

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

  8. Seasonal Simulations of the Planetary Boundary Layer and Boundary-Layer Stratocumulus Clouds with a General Circulation Model.

    Science.gov (United States)

    Randall, David A.; Abeles, James A.; Corsetti, Thomas G.

    1985-04-01

    The UCLA general circulation model (GCM) has been used to simulate the seasonally varying planetary boundary layer (PBL), as well as boundary-layer stratus and stratocumulus clouds. The PBL depth is a prognostic variable of the GCM, incorporated through the use of a vertical coordinate system in which the PBL is identified with the lowest model layer.Stratocumulus clouds are assumed to occur whenever the upper portion of the PBL becomes saturated, provided that the cloud-top entrainment instability does not occur. As indicated by Arakawa and Schubert, cumulus clouds are assumed to originate at the PBL top, and tend to make the PBL shallow by drawing on its mass.Results are presented from a three-year simulation, starting from a 31 December initial condition obtained from an earlier run with a different version of the model. The simulated seasonally varying climates of the boundary layer and free troposphere are realistic. The observed geographical and seasonal variations of stratocumulus cloudiness are fairly well simulated. The simulation of the stratocumulus clouds associated with wintertime cold-air outbreaks is particularly realistic. Examples are given of individual events. The positions of the subtropical marine stratocumulus regimes are realistically simulated, although their observed frequency of occurrence is seriously underpredicted. The observed summertime abundance of Arctic stratus clouds is also underpredicted.In the GCM results, the layer cloud instability appears to limit the extent of the marine subtropical stratocumulus regimes. The instability also frequently occurs in association with cumulus convection over land.Cumulus convection acts as a very significant sink of PBL mass throughout the tropics, and over the midlatitude continents in summer.Three experiments have been performed to investigate the sensitivity of the GCM results to aspects of the PBL and stratocumulus parameterizations. For all three experiments, the model was started from 1

  9. Modulational instability of nematic phase

    Indian Academy of Sciences (India)

    T Mithun; K Porsezian

    2014-02-01

    We numerically observe the effect of homogeneous magnetic field on the modulationally stable case of polar phase in = 2 spinor Bose–Einstein condensates (BECs). Also we investigate the modulational instability of uniaxial and biaxial (BN) states of polar phase. Our observations show that the magnetic field triggers the modulational instability and demonstrate that irrespective of the magnetic field effect the uniaxial and biaxial nematic phases show modulational instability.

  10. Summary of longitudinal instabilities workshop

    International Nuclear Information System (INIS)

    A five-day ISABELLE workshop on longitudinal instabilities was held at BNL, August 9--13, 1976. Heavy emphasis was put on single bunched beam instabilities in the microwave region extending above the cut-off frequency of the ISABELLE vacuum chamber. A discussion is given of the mechanism governing the instability, and calculations as well as measurements of the longitudinal coupling impedances in the ISABELLE rings are described

  11. Instability in Shocked Granular Gases

    OpenAIRE

    Sirmas, Nick; Falle, Sam; Radulescu, Matei

    2013-01-01

    Shocks in granular media, such as vertically oscillated beds, have been shown to develop instabilities. Similar jet formation has been observed in explosively dispersed granular media. Our previous work addressed this instability by performing discrete-particle simulations of inelastic media undergoing shock compression. By allowing finite dissipation within the shock wave, instability manifests itself as distinctive high density non-uniformities and convective rolls within the shock structur...

  12. Experimental studies in a single-phase parallel channel natural circulation system. Preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Bodkha, Kapil; Pilkhwal, D.S.; Jana, S.S.; Vijayan, P.K. [Bhabha Atomic Research Centre, Mumbai (India). Reactor Engineering Div.

    2016-03-15

    Natural circulation systems find extensive applications in industrial engineering systems. One of the applications is in nuclear reactor where the decay heat is removed by natural circulation of the fluid under off-normal conditions. The upcoming reactor designs make use of natural circulation in order to remove the heat from core under normal operating conditions also. These reactors employ multiple vertical fuel channels with provision of on-power refueling/defueling. Natural circulation systems are relatively simple, safe and reliable when compared to forced circulation systems. However, natural circulation systems are prone to encounter flow instabilities which are highly undesirable for various reasons. Presence of parallel channels under natural circulation makes the system more complicated. To examine the behavior of parallel channel system, studies were carried out for single-phase natural circulation flow in a multiple vertical channel system. The objective of the present work is to study the flow behavior of the parallel heated channel system under natural circulation for different operating conditions. Steady state and transient studies have been carried out in a parallel channel natural circulation system with three heated channels. The paper brings out the details of the system considered, different cases analyzed and preliminary results of studies carried out on a single-phase parallel channel system.

  13. Experimental studies in a single-phase parallel channel natural circulation system. Preliminary results

    International Nuclear Information System (INIS)

    Natural circulation systems find extensive applications in industrial engineering systems. One of the applications is in nuclear reactor where the decay heat is removed by natural circulation of the fluid under off-normal conditions. The upcoming reactor designs make use of natural circulation in order to remove the heat from core under normal operating conditions also. These reactors employ multiple vertical fuel channels with provision of on-power refueling/defueling. Natural circulation systems are relatively simple, safe and reliable when compared to forced circulation systems. However, natural circulation systems are prone to encounter flow instabilities which are highly undesirable for various reasons. Presence of parallel channels under natural circulation makes the system more complicated. To examine the behavior of parallel channel system, studies were carried out for single-phase natural circulation flow in a multiple vertical channel system. The objective of the present work is to study the flow behavior of the parallel heated channel system under natural circulation for different operating conditions. Steady state and transient studies have been carried out in a parallel channel natural circulation system with three heated channels. The paper brings out the details of the system considered, different cases analyzed and preliminary results of studies carried out on a single-phase parallel channel system.

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

    Science.gov (United States)

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

    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.

  15. Instability of enclosed horizons

    CERN Document Server

    Kay, Bernard S

    2013-01-01

    We study the classical massless scalar wave equation on the region of 1+1-dimensional Minkowski space between the two branches of the hyperbola $x^2-t^2=1$ with vanishing boundary conditions on it. We point out that there are initially finite-energy initially, say, right-going waves for which the stress-energy tensor becomes singular on the null-line $t+x=0$. We also construct the quantum theory of this system and show that, while there is a regular Hartle-Hawking-Israel-like state, there are coherent states built on this for which there is a similar singularity in the expectation value of the renormalized stress-energy tensor. We conjecture that in 1+3-dimensional situations with 'enclosed horizons' such as a (maximally extended) Schwarzschild black hole in equilibrium in a stationary box or the (maximally extended) Schwarzschild-AdS spacetime, there will be a similar singularity at the horizon and that would signal an instability when matter perturbations and/or gravity are switched on. Such an instability ...

  16. Libration driven multipolar instabilities

    CERN Document Server

    Cébron, David; Herreman, Wietze

    2014-01-01

    We consider rotating flows in non-axisymmetric enclosures that are driven by libration, i.e. by a small periodic modulation of the rotation rate. Thanks to its simplicity, this model is relevant to various contexts, from industrial containers (with small oscillations of the rotation rate) to fluid layers of terrestial planets (with length-of-day variations). Assuming a multipolar $n$-fold boundary deformation, we first obtain the two-dimensional basic flow. We then perform a short-wavelength local stability analysis of the basic flow, showing that an instability may occur in three dimensions. We christen it the Libration Driven Multipolar Instability (LDMI). The growth rates of the LDMI are computed by a Floquet analysis in a systematic way, and compared to analytical expressions obtained by perturbation methods. We then focus on the simplest geometry allowing the LDMI, a librating deformed cylinder. To take into account viscous and confinement effects, we perform a global stability analysis, which shows that...

  17. A New Global fAPAR and LAI Dataset Derived from Optimal Albedo Estimates: Comparison with MODIS Products

    Directory of Open Access Journals (Sweden)

    Mathias Disney

    2016-03-01

    Full Text Available We present the first comparison between new fAPAR and LAI products derived from the GlobAlbedo dataset and the widely-used MODIS fAPAR and LAI products. The GlobAlbedo-derived products are produced using a 1D two-stream radiative transfer (RT scheme designed explicitly for global parameter retrieval from albedo, with consistency between RT model assumptions and observations, as well as with typical large-scale land surface model RT schemes. The approach does not require biome-specific structural assumptions (e.g., cover, clumping, understory, unlike more detailed 3D RT model approaches. GlobAlbedo-derived values of fAPAR and LAI are compared with MODIS values over 2002–2011 at multiple flux tower sites within selected biomes, over 1200 × 1200 km regions and globally. GlobAlbedo-derived fAPAR and LAI values are temporally more stable than the MODIS values due to the smoothness of the underlying albedo, derived via optimal estimation (assimilation using an a priori estimate of albedo derived from an albedo “climatology” (composited multi-year albedo observations. Parameters agree closely in timing but with GlobAlbedo values consistently lower than MODIS, particularly for LAI. Larger differences occur in winter (when values are lower and in the Southern hemisphere. Globally, we find that: GlobAlbedo-derived fAPAR is ~0.9–1.01 × MODIS fAPAR with an intercept of ~0.03; GlobAlbedo-derived LAI is ~0.6 × MODIS LAI with an intercept of ~0.2. Differences arise due to the RT model assumptions underlying the products, meaning care is required in interpreting either set of values, particularly when comparing to fine-scale ground-based estimates. We present global transformations between GlobAlbedo-derived and MODIS products.

  18. Resolvability in Circulant Graphs

    Institute of Scientific and Technical Information of China (English)

    Muhammad SALMAN; Imran JAVAID; Muhammad Anwar CHAUDHRY

    2012-01-01

    A set W of the vertices of a connected graph G is called a resolving set for G if for every two distinct vertices u,v ∈ V(G) there is a vertex w ∈ W such that d(u,w) ≠ d(v,w).A resolving set of minimum cardinality is called a metric basis for G and the number of vertices in a metric basis is called the metric dimension of G,denoted by dim(G).For a vertex u of G and a subset S of V(G),the distance between u and S is the number mins∈s d(u,s).A k-partition H ={S1,S2,...,Sk} of V(G) is called a resolving partition if for every two distinct vertices u,v ∈ V(G) there is a set Si in Π such that d(u,Si) ≠ d(v,Si).The minimum k for which there is a resolving k-partition of V(G) is called the partition dimension of G,denoted by pd(G).The circulant graph is a graph with vertex set Zn,an additive group ofintegers modulo n,and two vertices labeled i and j adjacent if and only if i - j (mod n) ∈ C,where C C Zn has the property that C =-C and 0(∈) C.The circulant graph is denoted by Xn,△ where A =|C|.In this paper,we study the metric dimension of a family of circulant graphs Xn,3 with connection set C ={1,-n/2,n - 1} and prove that dim(Xn,3) is independent of choice of n by showing that 3 for all n =0 (mod 4),dim(X,n,3) ={ 4 for all n =2 (mod 4).We also study the partition dimension of a family of circulant graphs Xn,4 with connection set C ={±1,±2} and prove that pd(Xn,4) is independent of choice of n and show that pd(X5,4) =5 and 3 forall odd n≥9,pd(Xn,4) ={ 4 for all even n ≥ 6 and n =7.

  19. Validation of GEOLAND-2 Spot/vgt Albedo Products by Using Ceos Olive Methodology

    Science.gov (United States)

    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

  20. Snow Hydrology in a General Circulation Model.

    Science.gov (United States)

    Marshall, Susan; Roads, John O.; Glatzmaier, Gary

    1994-08-01

    A snow hydrology has been implemented in an atmospheric general circulation model (GCM). The snow hydrology consists of parameterizations of snowfall and snow cover fraction, a prognostic calculation of snow temperature, and a model of the snow mass and hydrologic budgets. Previously, only snow albedo had been included by a specified snow line. A 3-year GCM simulation with this now more complete surface hydrology is compared to a previous GCM control run with the specified snow line, as well as with observations. In particular, the authors discuss comparisons of the atmospheric and surface hydrologic budgets and the surface energy budget for U.S. and Canadian areas.The new snow hydrology changes the annual cycle of the surface moisture and energy budgets in the model. There is a noticeable shift in the runoff maximum from winter in the control run to spring in the snow hydrology run. A substantial amount of GCM winter precipitation is now stored in the seasonal snow pack. Snow cover also acts as an important insulating layer between the atmosphere and the ground. Wintertime soil temperatures are much higher in the snow hydrology experiment than in the control experiment. Seasonal snow cover is important for dampening large fluctuations in GCM continental skin temperature during the Northern Hemisphere winter.Snow depths and snow extent show good agreement with observations over North America. The geographic distribution of maximum depths is not as well simulated by the model due, in part, to the coarse resolution of the model. The patterns of runoff are qualitatively and quantitatively similar to observed patterns of streamflow averaged over the continental United States. The seasonal cycles of precipitation and evaporation are also reasonably well simulated by the model, although their magnitudes are larger than is observed. This is due, in part, to a cold bias in this model, which results in a dry model atmosphere and enhances the hydrologic cycle everywhere.

  1. Snow hydrology in a general circulation model

    Science.gov (United States)

    Marshall, Susan; Roads, John O.; Glatzmaier, Gary

    1994-01-01

    A snow hydrology has been implemented in an atmospheric general circulation model (GCM). The snow hydrology consists of parameterizations of snowfall and snow cover fraction, a prognostic calculation of snow temperature, and a model of the snow mass and hydrologic budgets. Previously, only snow albedo had been included by a specified snow line. A 3-year GCM simulation with this now more complete surface hydrology is compared to a previous GCM control run with the specified snow line, as well as with observations. In particular, the authors discuss comparisons of the atmospheric and surface hydrologic budgets and the surface energy budget for U.S. and Canadian areas. The new snow hydrology changes the annual cycle of the surface moisture and energy budgets in the model. There is a noticeable shift in the runoff maximum from winter in the control run to spring in the snow hydrology run. A substantial amount of GCM winter precipitation is now stored in the seasonal snowpack. Snow cover also acts as an important insulating layer between the atmosphere and the ground. Wintertime soil temperatures are much higher in the snow hydrology experiment than in the control experiment. Seasonal snow cover is important for dampening large fluctuations in GCM continental skin temperature during the Northern Hemisphere winter. Snow depths and snow extent show good agreement with observations over North America. The geographic distribution of maximum depths is not as well simulated by the model due, in part, to the coarse resolution of the model. The patterns of runoff are qualitatively and quantitatively similar to observed patterns of streamflow averaged over the continental United States. The seasonal cycles of precipitation and evaporation are also reasonably well simulated by the model, although their magnitudes are larger than is observed. This is due, in part, to a cold bias in this model, which results in a dry model atmosphere and enhances the hydrologic cycle everywhere.

  2. Two phase instabilities system analysis with application on Clotaire experiments

    Energy Technology Data Exchange (ETDEWEB)

    Pascal Monier; Jacques Belleudy; Georges Brochier [PRINCIPIA R.D., Z.I. Athelia I, 13705 La Ciotat Cedex (France); Valerie Saldo; Jean-Marie Gouirand; Pierre Gubernatis [CEA Cadarache, 13108 St Paul Lez Durance, Cedex (France)

    2005-07-01

    Full text of publication follows: Natural-circulation cooled Boiling Water Reactors are susceptible to undergo thermal hydraulics instabilities. The so-called Type-II instabilities due to frictional pressure losses in the core may be observed typically at nominal pressure and relatively high power in BWRs. In the framework of the NACUSP (Natural Circulation and Stability Performance) Project, a test section simulating the riser at the exit of an ESBWR core (European Simplified Boiling Water Reactor) has been set up in the CLOTAIRE facility in CEA, Center of Cadarache. Test campaigns have been conducted with stationary tests demonstrating the correct scaling of the loop with R124a as coolant fluid and with unstable tests identifying the instability thresholds. The CEDRIC thermal hydraulics code was developed with TECHNICATOME in order to simulate one or two phase flow in compact on-board PWR used for marine propulsion. A generic version of this tool, CEDRIC MultiFluides has been used for modeling transient two phase flow until stability limit with large amplitude flow oscillations such as observed during the CLOTAIRE tests. This 1D unsteady model is based on a 3-equations model together with a phase velocities difference closure law in the frame of a Drift Flux Model. The main purpose of this paper is to present the experimental results of the CLOTAIRE tests together with the validation calculations. (authors)

  3. Circulation of Stars

    Science.gov (United States)

    Boitani, P.

    2016-01-01

    Since the dawn of man, contemplation of the stars has been a primary impulse in human beings, who proliferated their knowledge of the stars all over the world. Aristotle sees this as the product of primeval and perennial “wonder” which gives rise to what we call science, philosophy, and poetry. Astronomy, astrology, and star art (painting, architecture, literature, and music) go hand in hand through millennia in all cultures of the planet (and all use catasterisms to explain certain phenomena). Some of these developments are independent of each other, i.e., they take place in one culture independently of others. Some, on the other hand, are the product of the “circulation of stars.” There are two ways of looking at this. One seeks out forms, the other concentrates on the passing of specific lore from one area to another through time. The former relies on archetypes (for instance, with catasterism), the latter constitutes a historical process. In this paper I present some of the surprising ways in which the circulation of stars has occurred—from East to West, from East to the Far East, and from West to East, at times simultaneously.

  4. Cohabitation and Children's Family Instability

    Science.gov (United States)

    Kelly Raley, R.; Wildsmith, Elizabeth

    2004-01-01

    This study estimates how much children's family instability is missed when we do not count transitions into and out of cohabitation, and examines early life course trajectories of children to see whether children who experience maternal cohabitation face more family instability than children who do not. Using data from the 1995 National Survey of…

  5. Microsatellite instability in bladder cancer

    DEFF Research Database (Denmark)

    Gonzalez-Zulueta, M; Ruppert, J M; Tokino, K; Tsai, Y C; Spruck, C H; Miyao, N; Nichols, P W; Hermann, G G; Horn, T; Steven, K

    1993-01-01

    Somatic instability at microsatellite repeats was detected in 6 of 200 transitional cell carcinomas of the bladder. Instabilities were apparent as changes in (GT)n repeat lengths on human chromosome 9 for four tumors and as alterations in a (CAG)n repeat in the androgen receptor gene on the X chr...

  6. Cinerama sickness and postural instability

    NARCIS (Netherlands)

    Bos, J.E.; Ledegang, W.D.; Lubeck, A.J.A.; Stins, J.F.

    2013-01-01

    Motion sickness symptoms and increased postural instability induced by motion pictures have been reported in a laboratory, but not in a real cinema. We, therefore, carried out an observational study recording sickness severity and postural instability in 19 subjects before, immediately and 45 min af

  7. Instability of liquid crystal elastomers

    Science.gov (United States)

    An, Ning; Li, Meie; Zhou, Jinxiong

    2016-01-01

    Nematic liquid crystal elastomers (LCEs) contract in the director direction but expand in other directions, perpendicular to the director, when heated. If the expansion of an LCE is constrained, compressive stress builds up in the LCE, and it wrinkles or buckles to release the stored elastic energy. Although the instability of soft materials is ubiquitous, the mechanism and programmable modulation of LCE instability has not yet been fully explored. We describe a finite element method (FEM) scheme to model the inhomogeneous deformation and instability of LCEs. A constrained LCE beam working as a valve for microfluidic flow, and a piece of LCE laminated with a nanoscale poly(styrene) (PS) film are analyzed in detail. The former uses the buckling of the LCE beam to occlude the microfluidic channel, while the latter utilizes wrinkling or buckling to measure the mechanical properties of hard film or to realize self-folding. Through rigorous instability analysis, we predict the critical conditions for the onset of instability, the wavelength and amplitude evolution of instability, and the instability patterns. The FEM results are found to correlate well with analytical results and reported experiments. These efforts shed light on the understanding and exploitation of the instabilities of LCEs.

  8. Genome instability in Alzheimer disease

    DEFF Research Database (Denmark)

    Hou, Yujun; Song, Hyundong; Croteau, Deborah L;

    2016-01-01

    to the development of noninvasive treatment strategies. Further investigations into the molecular mechanisms connecting DNA damage to AD pathology may help to develop novel treatment strategies for this debilitating disease. Here we provide an overview of the role of genome instability and DNA repair deficiency...... in AD pathology and discuss research strategies that include genome instability as a component....

  9. The Role of the Effective Cloud Albedo for Climate Monitoring and Analysis

    Directory of Open Access Journals (Sweden)

    Christine Träger-Chatterjee

    2011-10-01

    Full Text Available Cloud properties and the Earth’s radiation budget are defined as essential climate variables by Global Climate Observing System (GCOS. The cloud albedo is a measure for the portion of solar radiation reflected back to space by clouds. This information is essential for the analysis and interpretation of the Earth’s radiation budget and the solar surface irradiance. We present and discuss a method for the production of the effective cloud albedo and the solar surface irradiance based on the visible channel (0.45–1 μm on-board of the Meteosat satellites. This method includes a newly developed self-calibration approach and has been used to generate a 23-year long (1983–2005 continuous and validated climate data record of the effective cloud albedo and the solar surface irradiance. Using these records we demonstrate the ability of the method to provide these essential variables in high accuracy and homogeneity. Further on, we discuss the role of the cloud albedo within climate monitoring and analysis. We found trends with opposite sign in the observed effective cloud albedo resulting in positive trends in the solar surface irradiance over ocean and partly negative trends over land. Ground measurements are scarce over the ocean and thus satellite-derived effective cloud albedo and solar surface irradiance constitutes a unique observational data source. Within this scope it has to be considered that the ocean is the main energy reservoir of the Earth, which emphasises the role of satellite-observed effective cloud albedo and derived solar surface irradiance as essential climate variables for climate monitoring and analysis.

  10. Criticality analysis of thermal reactors for two energy groups applying Monte Carlo and neutron Albedo method

    International Nuclear Information System (INIS)

    The Albedo method applied to criticality calculations to nuclear reactors is characterized by following the neutron currents, allowing to make detailed analyses of the physics phenomena about interactions of the neutrons with the core-reflector set, by the determination of the probabilities of reflection, absorption, and transmission. Then, allowing to make detailed appreciations of the variation of the effective neutron multiplication factor, keff. In the present work, motivated for excellent results presented in dissertations applied to thermal reactors and shieldings, was described the methodology to Albedo method for the analysis criticality of thermal reactors by using two energy groups admitting variable core coefficients to each re-entrant current. By using the Monte Carlo KENO IV code was analyzed relation between the total fraction of neutrons absorbed in the core reactor and the fraction of neutrons that never have stayed into the reflector but were absorbed into the core. As parameters of comparison and analysis of the results obtained by the Albedo method were used one dimensional deterministic code ANISN (ANIsotropic SN transport code) and Diffusion method. The keff results determined by the Albedo method, to the type of analyzed reactor, showed excellent agreement. Thus were obtained relative errors of keff values smaller than 0,78% between the Albedo method and code ANISN. In relation to the Diffusion method were obtained errors smaller than 0,35%, showing the effectiveness of the Albedo method applied to criticality analysis. The easiness of application, simplicity and clarity of the Albedo method constitute a valuable instrument to neutronic calculations applied to nonmultiplying and multiplying media. (author)

  11. Multigroup Albedo Method applied to coupled neutron-gamma radiations shielding

    International Nuclear Information System (INIS)

    Shielding calculations for neutron-gamma radiation are usually done by using the full Theory of Transport or the Monte Carlo Techniques. After some works based on the Albedo Method, the shielding calculations for neutron-gamma radiation have a reliable tool with great didactical value which shows its clarity and simplicity for the resolution of cases that involve neutrons and photon shielding in nonmultiplying media. The excellent results of these works have motivated the elaboration and the development of this study that will be presented in this dissertation. The balance of a neutronic current entering a shield of two layers considering the coupling neutron-gamma will be determined by the Albedo Method. The shield will be composed of a layer of iron and another one of manganese with 10 cm of thickness each. The arrays of the materials coefficients will be obtained from the ANISN code. ANISN is a one dimensional deterministic code that is based on transport equation. The final results obtained by the Albedo Method will be compared with the ANISN results for an order of angular quadrature S2. The angular quadrature S2 admits that the radiation has two routes in the same direction what better describes the Albedo Method behavior. The results obtained by using the Albedo Method show an excellent agreement with the values predicted by the adopted deterministic code ANISN. Due to the excellent results, the multigroup Albedo Method should be applied to the shielding calculations with multiple layers. In conclusion the multigroup Albedo Method has the great ability in solving shielding problems concerning to the Nuclear Engineering. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Roman, Miguel O. [NASA Goddard Space Flight Center; Schaaf, Crystal [Boston University; Woodcock, Curtis E. [Boston University; Strahler, Alan [Boston University; Yang, Xiaoyuan [Boston University; Braswell, Rob H. [Complex Systems Research Center, Durham, NH; Curtis, Peter [Ohio State University, The, Columbus; Davis, Kenneth J. [Pennsylvania State University; Dragoni, Danilo [Indiana University; Goulden, Michael L. [University of California, Irvine; Gu, Lianhong [ORNL; Hollinger, David Y [ORNL; Meyers, Tilden P. [NOAA, Oak Ridge, TN; Wilson, Tim B. [NOAA; Munger, J. William [Harvard University; Wofsy, Steve [Harvard University; Privette, Jeffrey L. [NOAA; Richardson, Andrew D. [Harvard University

    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.

  13. The bar instability revisited

    CERN Document Server

    Chiodi, Filippo; Claudin, Philippe

    2012-01-01

    The river bar instability is revisited, using a hydrodynamical model based on Reynolds averaged Navier-Stokes equations. The results are contrasted with the standard analysis based on shallow water Saint-Venant equations. We first show that the stability of both transverse modes (ripples) and of small wavelength inclined modes (bars) predicted by the Saint-Venant approach are artefacts of this hydrodynamical approximation. When using a more reliable hydrodynamical model, the dispersion relation does not present any maximum of the growth rate when the sediment transport is assumed to be locally saturated. The analysis therefore reveals the fundamental importance of the relaxation of sediment transport towards equilibrium as it it is responsible for the stabilisation of small wavelength modes. This dynamical mechanism is characterised by the saturation number, defined as the ratio of the saturation length to the water depth Lsat/H. This dimensionless number controls the transition from ripples (transverse patte...

  14. Plateau Rayleigh instability simulation.

    Science.gov (United States)

    Mead-Hunter, Ryan; King, Andrew J C; Mullins, Benjamin J

    2012-05-01

    The well-known phenomena of Plateau-Rayleigh instability has been simulated using computational fluid dynamics (CFD). The breakup of a liquid film into an array of droplets on a cylindrical element was simulated using a volume-of-fluid (VOF) solver and compared to experimental observations and existing theory. It is demonstrated that the VOF method can correctly predict the breakup of thins films into an array of either axisymmetric droplets or clam-shell droplets, depending on the surface energy. The existence of unrealistically large films is precluded. Droplet spacing was found to show reasonable agreement with theory. Droplet motion and displacement under fluid flow was also examined and compared to that in previous studies. It was found that the presence of air flow around the droplet does not influence the stable film thickness; however, it reduces the time required for droplet formation. Novel relationships for droplet displacement were derived from the results. PMID:22512475

  15. Instability and Information

    CERN Document Server

    Patzelt, Felix

    2015-01-01

    Many complex systems exhibit extreme events far more often than expected for a normal distribution. This work examines how self-similar bursts of activity across several orders of magnitude can emerge from first principles in systems that adapt to information. Surprising connections are found between two apparently unrelated research topics: hand-eye coordination in balancing tasks and speculative trading in financial markets. Seemingly paradoxically, locally minimising fluctuations can increase a dynamical system's sensitivity to unpredictable perturbations and thereby facilitate global catastrophes. This general principle is studied in several domain-specific models and in behavioural experiments. It explains many findings in both fields and resolves an apparent antinomy: the coexistence of stabilising control or market efficiency and perpetual instabilities resembling critical phenomena in physical systems.

  16. From instabilities to multifragmentation

    International Nuclear Information System (INIS)

    The main purpose of this article is to show that, in many physical situations, the spinodal decomposition of unstable systems can be correctly described by stochastic mean-field approaches. Such theories predict that the occurrence of spinodal instability leading the multifragmentation of an expended nuclear system, can be signed through the observation of time scales for the fragment formation of the order of 100 fm/c and of typical fragment size around A=20. We will finally discuss the fact that these fragments are formed at finite temperature and so can subsequently decay in flight. Finally, we will give some hints about possible experimental signals of such first order phase transitions. (authors). 12 refs., 5 figs

  17. Structural and Material Instability

    DEFF Research Database (Denmark)

    Cifuentes, Gustavo Cifuentes

    This work is a small contribution to the general problem of structural and material instability. In this work, the main subject is the analysis of cracking and failure of structural elements made from quasi-brittle materials like concrete. The analysis is made using the finite element method. Three...... program based on the finite element method for the analysis of cracks in structural elements is presented; in this program the interface and elements with embedded discontinuities are implemented....... use of interface elements) is used successfully to model cases where the path of the discontinuity is known in advance, as is the case of the analysis of pull-out of fibers embedded in a concrete matrix. This method is applied to the case of non-straight fibers and fibers with forces that have...

  18. Two-phase flow patterns recognition and parameters estimation through natural circulation test loop image analysis

    International Nuclear Information System (INIS)

    Visualization of natural circulation test loop cycles is used to study two-phase flow patterns associated with phase transients and static instabilities of flow. Experimental studies on natural circulation flow were originally related to accidents and transient simulations relative to nuclear reactor systems with light water refrigeration. In this regime, fluid circulation is mainly caused by a driving force ('thermal head') which arises from density differences due to temperature gradient. Natural circulation phenomenon has been important to provide residual heat removal in cases of 'loss of pump power' or plant shutdown in nuclear power plant accidents. The new generation of compact nuclear reactors includes natural circulation of their refrigerant fluid as a security mechanism in their projects. Two-phase flow patterns have been studied for many decades, and the related instabilities have been object of special attention recently. Experimental facility is an all glass-made cylindrical tubes loop which contains about twelve demineralized water liters, a heat source by an electrical resistor immersion heater controlled by a Variac, and a helicoidal heat exchanger working as cold source. Data is obtained through thermo-pairs distributed over the loop and CCD cameras. Artificial intelligence based algorithms are used to improve (bubble) border detection and patterns recognition, in order to estimate and characterize, phase transitions patterns and correlate them with the periodic static instability (chugging) cycle observed in this circuit. Most of initial results show good agreement with previous numerical studies in this same facility. (author)

  19. Internal rotor friction instability

    Science.gov (United States)

    Walton, J.; Artiles, A.; Lund, J.; Dill, J.; Zorzi, E.

    1990-01-01

    The analytical developments and experimental investigations performed in assessing the effect of internal friction on rotor systems dynamic performance are documented. Analytical component models for axial splines, Curvic splines, and interference fit joints commonly found in modern high speed turbomachinery were developed. Rotor systems operating above a bending critical speed were shown to exhibit unstable subsynchronous vibrations at the first natural frequency. The effect of speed, bearing stiffness, joint stiffness, external damping, torque, and coefficient of friction, was evaluated. Testing included material coefficient of friction evaluations, component joint quantity and form of damping determinations, and rotordynamic stability assessments. Under conditions similar to those in the SSME turbopumps, material interfaces experienced a coefficient of friction of approx. 0.2 for lubricated and 0.8 for unlubricated conditions. The damping observed in the component joints displayed nearly linear behavior with increasing amplitude. Thus, the measured damping, as a function of amplitude, is not represented by either linear or Coulomb friction damper models. Rotordynamic testing of an axial spline joint under 5000 in.-lb of static torque, demonstrated the presence of an extremely severe instability when the rotor was operated above its first flexible natural frequency. The presence of this instability was predicted by nonlinear rotordynamic time-transient analysis using the nonlinear component model developed under this program. Corresponding rotordynamic testing of a shaft with an interference fit joint demonstrated the presence of subsynchronous vibrations at the first natural frequency. While subsynchronous vibrations were observed, they were bounded and significantly lower in amplitude than the synchronous vibrations.

  20. Combustion Instabilities Modeled

    Science.gov (United States)

    Paxson, Daniel E.

    1999-01-01

    NASA Lewis Research Center's Advanced Controls and Dynamics Technology Branch is investigating active control strategies to mitigate or eliminate the combustion instabilities prevalent in lean-burning, low-emission combustors. These instabilities result from coupling between the heat-release mechanisms of the burning process and the acoustic flow field of the combustor. Control design and implementation require a simulation capability that is both fast and accurate. It must capture the essential physics of the system, yet be as simple as possible. A quasi-one-dimensional, computational fluid dynamics (CFD) based simulation has been developed which may meet these requirements. The Euler equations of mass, momentum, and energy have been used, along with a single reactive species transport equation to simulate coupled thermoacoustic oscillations. A very simple numerical integration scheme was chosen to reduce computing time. Robust boundary condition procedures were incorporated to simulate various flow conditions (e.g., valves, open ends, and choked inflow) as well as to accommodate flow reversals that may arise during large flow-field oscillations. The accompanying figure shows a sample simulation result. A combustor with an open inlet, a choked outlet, and a large constriction approximately two thirds of the way down the length is shown. The middle plot shows normalized, time-averaged distributions of the relevant flow quantities, and the bottom plot illustrates the acoustic mode shape of the resulting thermoacoustic oscillation. For this simulation, the limit cycle peak-to-peak pressure fluctuations were 13 percent of the mean. The simulation used 100 numerical cells. The total normalized simulation time was 50 units (approximately 15 oscillations), which took 26 sec on a Sun Ultra2.

  1. Determination of the double angular and energy differential gamma-ray albedo for iron material by using Monte Carlo method

    International Nuclear Information System (INIS)

    The Monte Carlo method can be used to compute the gamma-ray backscattering albedo. This method was used by Raso to compute the angular differential albedo. Raso's results have been used by Chilton and Huddelston to adjust their well-known albedo formula. Here, an efficient estimator is proposed to compute the double-differential angular and energetic albedo from gamma-ray histories simulated in matter by the three-dimensional Monte Carlo transport code TRIPOLI. A detailed physical albedo analysis could be done in this way. The double-differential angular and energetic gamma-ray albedo is calculated for iron material for initial gamma-ray energies of 8, 3, 1, and 0.5 MeV

  2. Dynamical Instability and Soliton Concept

    International Nuclear Information System (INIS)

    The problem of dynamical instability and clustering (stable fragments formation) in a breakup of excited nuclear systems are considered from the points of view of the soliton concept. It is noted that the volume (spinodal) instability can be associated with nonlinear terms, and the surface (Rayleigh-Taylor type) instability, with the dispersion terms in the evolution equations. The spinodal instability and the Rayleigh-Taylor instability may compensate each other and lead to stable quasi-soliton type objects. The simple analytical model is presented to illustrate this physical picture. The time evolution of an initially compressed cold nuclear system is analysed in the framework of the inverse mean-field method. It is demonstrated that the nonlinearity and dispersion terms of the evolution equations can lead to clusterization in the final channel. 8 p

  3. Nonlinear evolution of MHD instabilities

    International Nuclear Information System (INIS)

    The problems of nonlinear theory of MHD instability, some analytical solutions of one-dimensional dynamic and two-dimensional kinematic problems and the problems of helical MHD instability in a plasma cylinder and axially-symmetric MHD instability in a Z-pinch are considered. The initial configuration is assumed to be equilibrium but unstable and its motion is initiated by a small initial disturbance. Instability evolution at a nonlinear stage is investigated by means of computer numerical integrating of the total system of MHD equations of motion. Limiting by two-dimensional motions class allows using the visual apparatus of freezed in functions satisfying in ideal gasodynamics the equation deltaPSIsub(i)/deltat+vector Vgrad PSIsub(i)=0. The investigation of evolution of axially symmetric MHD-instability in Z-pinch systems allows to construct on uncontradictory scheme of physical processes occuring in them from the initial discharge state to cylindrical equilibrium state

  4. Gravitational Instabilities in Circumstellar Disks

    CERN Document Server

    Kratter, Kaitlin M

    2016-01-01

    [Abridged] Star and planet formation are the complex outcomes of gravitational collapse and angular momentum transport mediated by protostellar and protoplanetary disks. In this review we focus on the role of gravitational instability in this process. We begin with a brief overview of the observational evidence for massive disks that might be subject to gravitational instability, and then highlight the diverse ways in which the instability manifests itself in protostellar and protoplanetary disks: the generation of spiral arms, small scale turbulence-like density fluctuations, and fragmentation of the disk itself. We present the analytic theory that describes the linear growth phase of the instability, supplemented with a survey of numerical simulations that aim to capture the non-linear evolution. We emphasize the role of thermodynamics and large scale infall in controlling the outcome of the instability. Despite apparent controversies in the literature, we show a remarkable level of agreement between analyt...

  5. Equilibrium Electro-osmotic Instability

    CERN Document Server

    Rubinstein, Isaak

    2014-01-01

    Since its prediction fifteen years ago, electro-osmotic instability has been attributed to non-equilibrium electro-osmosis related to the extended space charge which develops at the limiting current in the course of concentration polarization at a charge-selective interface. This attribution had a double basis. Firstly, it has been recognized that equilibrium electro-osmosis cannot yield instability for a perfectly charge-selective solid. Secondly, it has been shown that non-equilibrium electro-osmosis can. First theoretical studies in which electro-osmotic instability was predicted and analyzed employed the assumption of perfect charge-selectivity for the sake of simplicity and so did the subsequent numerical studies of various time-dependent and nonlinear features of electro-osmotic instability. In this letter, we show that relaxing the assumption of perfect charge-selectivity (tantamount to fixing the electrochemical potential in the solid) allows for equilibrium electro-osmotic instability. Moreover, we s...

  6. Beam instability Workshop - plenary sessions

    International Nuclear Information System (INIS)

    The purpose of this workshop was to provide a review of the mechanisms of limiting beam instabilities, their cures, including feedback, and beam measurement for synchrotron radiation light sources. 12 plenary sessions took place whose titles are: 1) challenging brilliance and lifetime issues with increasing currents; 2) limiting instabilities in multibunch; 3) experience from high currents in B factories; 4) longitudinal dynamics in high intensity/bunch; 5) Transverse instabilities for high intensity/bunch; 6) working group introduction from ESRF experience; 7) impedance modelling: simulations, minimization; 8) report on the broadband impedance measurements and modelling workshop; 9) feedback systems for synchrotron light sources; 10) beam instabilities diagnostics; 11) harmonic cavities: the pros and cons; and 12) experimental study of fast beam-ion instabilities at PLS. This document gathers the 12 articles that were presented during these sessions

  7. Instability in Shocked Granular Gases

    CERN Document Server

    Sirmas, Nick; Radulescu, Matei

    2013-01-01

    Shocks in granular media, such as vertically oscillated beds, have been shown to develop instabilities. Similar jet formation has been observed in explosively dispersed granular media. Our previous work addressed this instability by performing discrete-particle simulations of inelastic media undergoing shock compression. By allowing finite dissipation within the shock wave, instability manifests itself as distinctive high density non-uniformities and convective rolls within the shock structure. In the present study we have extended this work to investigate this instability at the continuum level. We modeled the Euler equations for granular gases with a modified cooling rate to include an impact velocity threshold necessary for inelastic collisions. Our results showed a fair agreement between the continuum and discrete-particle models. Discrepancies, such as higher frequency instabilities in our continuum results may be attributed to the absence of higher order effects.

  8. Instability in shocked granular gases

    International Nuclear Information System (INIS)

    Shocks in granular media, such as vertically oscillated beds, have been shown to develop instabilities. Similar jet formation has been observed in explosively dispersed granular media. Our previous work addressed this instability by performing discrete-particle simulations of inelastic media undergoing shock compression. By allowing finite dissipation within the shock wave, instability manifests itself as distinctive high density non-uniformities and convective rolls within the shock structure. In the present study we have extended this work to investigate this instability at the continuum level. We modeled the Euler equations for granular gases with a modified cooling rate to include an impact velocity threshold necessary for inelastic collisions. Our results showed a fair agreement between the continuum and discrete-particle models. Discrepancies, such as higher frequency instabilities in our continuum results may be attributed to the absence of higher order effects.

  9. Cost analysis of stratospheric albedo modification delivery systems

    International Nuclear Information System (INIS)

    We perform engineering cost analyses of systems capable of delivering 1–5 million metric tonnes (Mt) of albedo modification material to altitudes of 18–30 km. The goal is to compare a range of delivery systems evaluated on a consistent cost basis. Cost estimates are developed with statistical cost estimating relationships based on historical costs of aerospace development programs and operations concepts using labor rates appropriate to the operations. We evaluate existing aircraft cost of acquisition and operations, perform in-depth new aircraft and airship design studies and cost analyses, and survey rockets, guns, and suspended gas and slurry pipes, comparing their costs to those of aircraft and airships. Annual costs for delivery systems based on new aircraft designs are estimated to be $1–3B to deliver 1 Mt to 20–30 km or $2–8B to deliver 5 Mt to the same altitude range. Costs for hybrid airships may be competitive, but their large surface area complicates operations in high altitude wind shear, and development costs are more uncertain than those for airplanes. Pipes suspended by floating platforms provide low recurring costs to pump a liquid or gas to altitudes as high as ∼ 20 km, but the research, development, testing and evaluation costs of these systems are high and carry a large uncertainty; the pipe system’s high operating pressures and tensile strength requirements bring the feasibility of this system into question. The costs for rockets and guns are significantly higher than those for other systems. We conclude that (a) the basic technological capability to deliver material to the stratosphere at million tonne per year rates exists today, (b) based on prior literature, a few million tonnes per year would be sufficient to alter radiative forcing by an amount roughly equivalent to the growth of anticipated greenhouse gas forcing over the next half century, and that (c) several different methods could possibly deliver this quantity for less

  10. Instabilities of advection-dominated accretion flows

    CERN Document Server

    Chen, X

    1996-01-01

    Accretion disk instabilities are briefly reviewed. Some details are given to the short-wavelength thermal instabilities and the convective instabilities. Time-dependent calculations of two-dimensional advection-dominated accretion flows are presented.

  11. Instabilities of Advection-Dominated Accretion Flows

    OpenAIRE

    Chen, Xingming

    1996-01-01

    Accretion disk instabilities are briefly reviewed. Some details are given to the short-wavelength thermal instabilities and the convective instabilities. Time-dependent calculations of two-dimensional advection-dominated accretion flows are presented.

  12. Nonlinear analysis for a nuclear-coupled two-phase natural circulation loop

    International Nuclear Information System (INIS)

    The objective of this paper is to develop a nonlinear numerical model to investigate the stability and nonlinear dynamics of a nuclear-coupled two-phase natural circulation loop. Some stability maps, parametric effects and transient characteristics of this natural circulation loop have been studied. Results indicate that the system indeed has two instability regions, the type-I and type-II instabilities, as is well known for a natural circulation loop. Parameters may induce different effects on the system stability in type-I and type-II unstable regions. In particular, the void-reactivity feedback destabilizes the system in both regions of low and high operating powers. Moreover, by strengthening nuclear feedback effect, period-doubled bifurcation may prevail in the system at relatively high inlet subcoolings and eventually a chaotic attractor appears with a fractal dimension of 1.79 ± 0.01 and an embedding dimension of 5

  13. Use of exact albedo conditions in numerical methods for one-dimensional one-speed discrete ordinates eigenvalue problems

    International Nuclear Information System (INIS)

    The use of exact albedo boundary conditions in numerical methods applied to one-dimensional one-speed discrete ordinates (Sn) eigenvalue problems for nuclear reactor global calculations is described. An albedo operator that treats the reflector region around a nuclear reactor core implicitly is described and exactly was derived. To illustrate the method's efficiency and accuracy, it was used conventional linear diamond method with the albedo option to solve typical model problems. (author)

  14. Comparison of ground-based and airborne snow surface albedo parameterizations in an alpine watershed: Impact on snowpack mass balance

    OpenAIRE

    Molotch, NP; Bales, RC

    2006-01-01

    Two commonly used snow surface albedo models were evaluated using albedo data from the Airborne Visible/Infrared Imaging Spectroradiometer (AVIRIS), and their influence on snowmelt timing and magnitude was assessed using a net radiation/temperature index snowmelt model, a series of satellite-based snow covered area scenes, and on-site snow surveys. Albedo estimates using an explicit representation of snow surface temperature, snow age, and solar illumination angle, based on the Biosphere Atmo...

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

    OpenAIRE

    Marković Vladimir M.; Krstić Dragana; Stevanović Nenad; Nikezić Dragoslav R.

    2013-01-01

    Total number and angular albedo were calculated for commonly used shielding materials, water, concrete, and iron, for photons with initial energies from 10 keV up to 10 MeV and normal incident angle. Influence of material thickness on total number albedo was also investigated. Double differential albedo was determined from simulation of photon transport through materials by using PENELOPE and MCNP software. Backscattered photons were scored and grouped in equal intervals of energy and a...

  16. Assessing spatio-temporal variability and trends in modelled and measured Greenland Ice Sheet albedo (2000–2013)

    OpenAIRE

    P. M. Alexander; Tedesco, M.; X. Fettweis; R. S. W. van de Wal; C. J. P. P. Smeets; M. R. van den Broeke

    2014-01-01

    Accurate measurements and simulations of Greenland Ice Sheet (GrIS) surface albedo are essential, given the role of surface albedo in modulating the amount of absorbed solar radiation and meltwater production. In this study, we assess the spatio-temporal variability of GrIS albedo during June, July, and August (JJA) for the period 2000–2013. We use two remote sensing products derived from data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS), as well as...

  17. Human-Induced Landcover Changes Drive a Diminution of Land Surface Albedo in the Loess Plateau (China)

    OpenAIRE

    Jun Zhai; Ronggao Liu; Jiyuan Liu; Lin Huang; Yuanwei Qin

    2015-01-01

    A large decrease in the land surface albedo of the Loess Plateau was observed from 2000 to 2010, as measured using satellite imagery. In particular, ecological restoration program regions experienced a decrease in peak season land surface albedo exceeding 0.05. In this study, we examined the spatial and temporal patterns of variation during the peak season albedo in the Loess Plateau and analyzed its relationships with changes of anthropogenic and natural factors at the pixel level. Our analy...

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

    OpenAIRE

    Hollinger, DY; Ollingerw, SV; Richardsonw, AD; Meyersz, TP; Dail, DB; Martinw, ME; Scott, NA; Arkebauerk, TJ; Baldocchi, DD; Clark, KL; Curtis, PS; Davis, KJ; Desai, AR; Dragonikk, D; Goulden, ML

    2010-01-01

    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. General...

  19. Analysis of the in situ and MODIS albedo variability at multiple time scales in the Sahel - art. no. D14119

    OpenAIRE

    Samain, O.; Kergoat, L.; Hiernaux, P.; Guichard, F; Mougin, Eric; Timouk, Franck; Lavenu, F

    2008-01-01

    The variability of the Sahelian albedo is investigated through the combined analysis of 5 years of in situ radiation data from the African Monsoon Multidisciplinary Analysis northernmost sites and remotely sensed albedo from 7 years of Moderate Resolution Imaging Spectroradiometer data. Both data sets are found to be in good agreement in terms of correlation and bias. The drivers of albedo variability are identified by means of in situ measurements of biological and physical properties of the...

  20. MODIS snow albedo bias at high solar zenith angles relative to theory and to in situ observations in Greenland

    OpenAIRE

    Wang, Xianwei; Zender, Charles S

    2010-01-01

    In situ measurements of snow albedo at five stations along a north–south transect in the dry-snow facies of the interior of Greenland follow the theoretically expected dependence of snow albedo with solar zenith angle (SZA). Greenland Climate Network (GC-Net) measurements from 1997 through 2007 exhibit the trend of modest surface brightening with increasing SZA on both diurnal and seasonal timescales. SZA explains up to 50% of seasonal albedo variability. The two other environmental factors c...