WorldWideScience

Sample records for surface albedo variations

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

    Science.gov (United States)

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

    2015-01-01

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

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

    OpenAIRE

    A. A. Marks; M. D. King

    2013-01-01

    Black carbon in sea ice will decrease sea ice surface albedo through increased absorption of incident solar radiation, exacerbating sea ice melting. Previous literature has reported different albedo responses to additions of black carbon in sea ice and has not considered how a snow cover may mitigate the effect of black carbon in sea ice. Sea ice is predominately snow covered. Visible light absorption and light scattering coefficients are calculated for a typical first year and multi-y...

  3. SURFACE ALBEDO AND SPECTRAL VARIABILITY OF CERES

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-02-01

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

  4. Albedo matters: Understanding runaway albedo variations on Pluto

    Science.gov (United States)

    Earle, Alissa M.; Binzel, Richard P.; Young, Leslie A.; Stern, S. A.; Ennico, K.; Grundy, W.; Olkin, C. B.; Weaver, H. A.; New Horizons Surface Composition Theme

    2018-03-01

    The data returned from NASA's New Horizons reconnaissance of the Pluto system show striking albedo variations from polar to equatorial latitudes as well as sharp longitudinal boundaries. Pluto has a high obliquity (currently 119°) that varies by 23° over a period of less than 3 million years. This variation, combined with its regressing longitude of perihelion (360° over 3.7 million years), creates epochs of "Super Seasons" where one pole is pointed at the Sun at perihelion, thereby experiencing a short, relatively warm summer followed by its longest possible period of winter darkness. In contrast, the other pole experiences a much longer, less intense summer and a short winter season. We use a simple volatile sublimation and deposition model to explore the relationship between albedo variations, latitude, and volatile sublimation and deposition for the current epoch as well as historical epochs during which Pluto experienced these "Super Seasons." Our investigation quantitatively shows that Pluto's geometry creates the potential for runaway albedo and volatile variations, particularly in the equatorial region, which can sustain stark longitudinal contrasts like the ones we see between Tombaugh Regio and the informally named Cthulhu Regio.

  5. Inclusion of Solar Elevation Angle in Land Surface Albedo Parameterization Over Bare Soil Surface.

    Science.gov (United States)

    Zheng, Zhiyuan; Wei, Zhigang; Wen, Zhiping; Dong, Wenjie; Li, Zhenchao; Wen, Xiaohang; Zhu, Xian; Ji, Dong; Chen, Chen; Yan, Dongdong

    2017-12-01

    Land surface albedo is a significant parameter for maintaining a balance in surface energy. It is also an important parameter of bare soil surface albedo for developing land surface process models that accurately reflect diurnal variation characteristics and the mechanism behind the solar spectral radiation albedo on bare soil surfaces and for understanding the relationships between climate factors and spectral radiation albedo. Using a data set of field observations, we conducted experiments to analyze the variation characteristics of land surface solar spectral radiation and the corresponding albedo over a typical Gobi bare soil underlying surface and to investigate the relationships between the land surface solar spectral radiation albedo, solar elevation angle, and soil moisture. Based on both solar elevation angle and soil moisture measurements simultaneously, we propose a new two-factor parameterization scheme for spectral radiation albedo over bare soil underlying surfaces. The results of numerical simulation experiments show that the new parameterization scheme can more accurately depict the diurnal variation characteristics of bare soil surface albedo than the previous schemes. Solar elevation angle is one of the most important factors for parameterizing bare soil surface albedo and must be considered in the parameterization scheme, especially in arid and semiarid areas with low soil moisture content. This study reveals the characteristics and mechanism of the diurnal variation of bare soil surface solar spectral radiation albedo and is helpful in developing land surface process models, weather models, and climate models.

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

    OpenAIRE

    Y. Liu; W. Wu; M. P. Jensen; 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...

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

    NARCIS (Netherlands)

    Andry, Olivier; Bintanja, Richard; Hazeleger, Wilco

    2017-01-01

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

  8. Assessment of interannual variations in the surface mass balance of 18 Svalbard glaciers from the Moderate Resolution Imaging Spectroradiometer/Terra albedo product

    NARCIS (Netherlands)

    Greuell, W.; Kohler, J.; Obleitner, F.; Glowacki, P.; Melvold, K.; Bernsen, E.; Oerlemans, J.

    2007-01-01

    We estimate annual anomalies of the surface mass balance of glaciers on Svalbard for the period 2000–2005 (six years), by calculating the so-called ‘‘satellite-derived mass balance’’ (Bsat) from time series of satellite-derived surface albedos. The method needs no other input variables. Surface

  9. Surface albedo following biochar application in durum wheat

    International Nuclear Information System (INIS)

    Genesio, L; Miglietta, F; Lugato, E; Baronti, S; Pieri, M; Vaccari, F P

    2012-01-01

    The agronomic use of charcoal from biomass pyrolysis (biochar) represents an interesting option for increasing soil fertility and sequestering atmospheric CO 2 . 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)

  10. Spectral and diurnal variations in clear sky planetary albedo

    Science.gov (United States)

    Briegleb, B.; Ramanathan, V.

    1982-01-01

    Spectral and diurnal variations in the clear sky planetary albedo of the earth are calculated using a radiative transfer model to obtain January and July values for a 5 deg x 5 deg global grid. The model employs observed climatological values of temperatures, humidities, snow and sea-ice cover. The diurnal cycle of clear sky albedo is calculated in the following intervals: 0.2-0.5, 0.5-0.7, and 0.7-4 microns. Observed ozone distribution is specified as a function of latitude and season. The 0.2-0.5 micron spectral albedo is 10-20% higher than the total albedo for all latitudes because of Rayleigh scattering; the 0.5-0.7 micron albedo differs from the total albedo by 1-2% for most latitudes, while the 0.7-4 micron albedo is 5-10% lower than the total because of strong atmospheric absorption. Planetary albedo decreases from morning to local noon, with diurnal variations being particularly strong over water.

  11. Estimation of daily albedo on Tottori sand surface

    International Nuclear Information System (INIS)

    Gu, S.; Otsuki, K.; Kamichika, M.

    2001-01-01

    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)

  12. 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.

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

    Directory of Open Access Journals (Sweden)

    Ying Qu

    2015-01-01

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

  14. PROVE Surface albedo of Jornada Experimental Range, New Mexico, 1997

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of this study was to determine the spatial variations in field measurements of broadband albedo as related to the ground cover and under a range of...

  15. Surface albedo in different land-use and cover types in Amazon forest region

    Directory of Open Access Journals (Sweden)

    Thiago de Oliveira Faria

    2018-05-01

    Full Text Available Albedo is the portion of energy from the Sun that is reflected by the earth's surface, thus being an important variable that controls climate and energy processes on Earth. Surface albedo is directly related to the characteristics of the Earth’s surface materials, making it a useful parameter to evaluate the effects of original soil cover replacement due to human occupation. This study evaluated the changes in the surface albedo values due to the conversion of vegetation to other land uses and to analyze the applicability of the use of albedo in the spatial delimitation of land-use classes in the transitional region between the Cerrado and Amazon biomes. Surface albedo measurements were obtained from processing of Landsat Thematic Mapper data in the Geographic Information System (GIS, and land-use information were collected using Google Earth high-resolution images. The results show that human activities such as the cultivation of crops and burning have contributed substantially to variations in the surface albedo, and that albedo estimates from Landsat imagery have the potential to help in the recognition and delimitation of features of land use and cover.

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

    Science.gov (United States)

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

    2015-12-01

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

  17. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Levinson, Ronnen 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 Multisensor Approach to Global Retrievals of Land Surface Albedo

    Directory of Open Access Journals (Sweden)

    Aku Riihelä

    2018-05-01

    Full Text Available Satellite-based retrievals offer the most cost-effective way to comprehensively map the surface albedo of the Earth, a key variable for understanding the dynamics of radiative energy interactions in the atmosphere-surface system. Surface albedo retrievals have commonly been designed separately for each different spaceborne optical imager. Here, we introduce a novel type of processing framework that combines the data from two polar-orbiting optical imager families, the Advanced Very High-Resolution Radiometer (AVHRR and Moderate Resolution Imaging Spectroradiometer (MODIS. The goal of the paper is to demonstrate that multisensor albedo retrievals can provide a significant reduction in the sampling time required for a robust and comprehensive surface albedo retrieval, without a major degradation in retrieval accuracy, as compared to state-of-the-art single-sensor retrievals. We evaluated the multisensor retrievals against reference in situ albedo measurements and compare them with existing datasets. The results show that global land surface albedo retrievals with a sampling period of 10 days can offer near-complete spatial coverage, with a retrieval bias mostly comparable to existing single sensor datasets, except for bright surfaces (deserts and snow where the retrieval framework shows degraded performance because of atmospheric correction design compromises. A level difference is found between the single sensor datasets and the demonstrator developed here, pointing towards a need for further work in the atmospheric correction, particularly over bright surfaces, and inter-sensor radiance homogenization. The introduced framework is expandable to include other sensors in the future.

  20. 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

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

    Science.gov (United States)

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

    2004-01-01

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

  2. 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

  3. Field measurement of albedo for limited extent test surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Sailor, David J. [Portland State University, Department of Mechanical and Materials Engineering, P.O. Box 751-ME, Portland, OR 97207 (United States); Resh, Kyle; Segura, Del [Tulane University, Department of Mechanical Engineering, 400 Lindy Boggs Center, New Orleans, LA 70118 (United States)

    2006-05-15

    A new method is introduced for field measurement of surface albedo. This method consists of the use of a cylindrical shade ring made of opaque fabric with a known (low) albedo placed over a test surface. The albedo measurement is accomplished using two small pyranometers situated so that the downward-facing pyranometer receives radiation only from the test surface and the shade ring. The upward-facing pyranometer simultaneously records the incoming solar radiation. The radiation received by the downward-facing pyramometer is a combination of reflected radiation from shaded and unshaded portions of these two surfaces, requiring detailed accounting of the resulting view factor geometries. The method presented here improves upon past approaches by allowing for smaller sample sizes, minimizing errors associated with reflective properties of the surroundings, and allowing for accurate measurements even under partially cloudy skies. In addition to these methodological improvements we introduce an approach for estimating the uncertainty in the resulting albedo measurements. Results from field measurements are presented to validate the measurement protocol, and to compare its accuracy with the accuracy of a published standard. (author)

  4. The effect of surface albedo and grain size distribution on ...

    African Journals Online (AJOL)

    Sand dams are very useful in arid and semi arid lands (ASALs) as facilities for water storage and conservation. Soils in ASALs are mainly sandy and major water loss is by evaporation and infiltration. This study investigated the effect of sand media characteristics, specifically surface albedo, grain size and stratification on ...

  5. Evaluation of coarse scale land surface remote sensing albedo product over rugged terrain

    Science.gov (United States)

    Wen, J.; Xinwen, L.; You, D.; Dou, B.

    2017-12-01

    Satellite derived Land surface albedo is an essential climate variable which controls the earth energy budget and it can be used in applications such as climate change, hydrology, and numerical weather prediction. The accuracy and uncertainty of surface albedo products should be evaluated with a reliable reference truth data prior to applications. And more literatures investigated the validation methods about the albedo validation in a flat or homogenous surface. However, the albedo performance over rugged terrain is still unknow due to the validation method limited. A multi-validation strategy is implemented to give a comprehensive albedo validation, which will involve the high resolution albedo processing, high resolution albedo validation based on in situ albedo, and the method to upscale the high resolution albedo to a coarse scale albedo. Among them, the high resolution albedo generation and the upscale method is the core step for the coarse scale albedo validation. In this paper, the high resolution albedo is generated by Angular Bin algorithm. And a albedo upscale method over rugged terrain is developed to obtain the coarse scale albedo truth. The in situ albedo located 40 sites in mountain area are selected globally to validate the high resolution albedo, and then upscaled to the coarse scale albedo by the upscale method. This paper takes MODIS and GLASS albedo product as a example, and the prelimarily results show the RMSE of MODIS and GLASS albedo product over rugged terrain are 0.047 and 0.057, respectively under the RMSE with 0.036 of high resolution albedo.

  6. Monitoring land surface albedo and vegetation dynamics using high spatial and temporal resolution synthetic time series from Landsat and the MODIS BRDF/NBAR/albedo product

    Science.gov (United States)

    Wang, Zhuosen; Schaaf, Crystal B.; Sun, Qingsong; Kim, JiHyun; Erb, Angela M.; Gao, Feng; Román, Miguel O.; Yang, Yun; Petroy, Shelley; Taylor, Jeffrey R.; Masek, Jeffrey G.; Morisette, Jeffrey T.; Zhang, Xiaoyang; Papuga, Shirley A.

    2017-07-01

    bias within the range of ±0.006. These synthetic time series provide much greater spatial detail than the 500 m gridded MODIS data, especially over more heterogeneous surfaces, which improves the efforts to characterize and monitor the spatial variation across species and communities. The mean of the difference between maximum and minimum synthetic time series of albedo within the MODIS pixels over a subset of satellite data of Harvard Forest (16 km by 14 km) was as high as 0.2 during the snow-covered period and reduced to around 0.1 during the snow-free period. Similarly, we have used STARFM to also couple MODIS Nadir BRDF Adjusted Reflectances (NBAR) values with Landsat 5 reflectances to generate daily synthetic times series of NBAR and thus Enhanced Vegetation Index (NBAR-EVI) at a 30 m resolution. While normally STARFM is used with directional reflectances, the use of the view angle corrected daily MODIS NBAR values will provide more consistent time series. These synthetic times series of EVI are shown to capture seasonal vegetation dynamics with finer spatial and temporal details, especially over heterogeneous land surfaces.

  7. Multidecadal Variability in Surface Albedo Feedback Across CMIP5 Models

    Science.gov (United States)

    Schneider, Adam; Flanner, Mark; Perket, Justin

    2018-02-01

    Previous studies quantify surface albedo feedback (SAF) in climate change, but few assess its variability on decadal time scales. Using the Coupled Model Intercomparison Project Version 5 (CMIP5) multimodel ensemble data set, we calculate time evolving SAF in multiple decades from surface albedo and temperature linear regressions. Results are meaningful when temperature change exceeds 0.5 K. Decadal-scale SAF is strongly correlated with century-scale SAF during the 21st century. Throughout the 21st century, multimodel ensemble mean SAF increases from 0.37 to 0.42 W m-2 K-1. These results suggest that models' mean decadal-scale SAFs are good estimates of their century-scale SAFs if there is at least 0.5 K temperature change. Persistent SAF into the late 21st century indicates ongoing capacity for Arctic albedo decline despite there being less sea ice. If the CMIP5 multimodel ensemble results are representative of the Earth, we cannot expect decreasing Arctic sea ice extent to suppress SAF in the 21st century.

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

    Energy Technology Data Exchange (ETDEWEB)

    Levinson, Ronnen Michael [Univ. of California, Berkeley, CA (United States)

    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 frequentlyproposed 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 0.25 perturbs the object’s surface temperature by -1 to +2 K. Comparing a tree’s canopy-to-air convection to the reduction in ground-to-air convection induced by tree shading of the ground indicates that the presence of a tree can either increase or decrease solar heating of ground-level air. The tree’s net effect depends on the extent to which solar heating of the canopy is dissipated by evaporation, and on the fraction of air heated by the canopy that flows downward and mixes with the ground-level air. A two-month lysimeter (plant-weighing) experiment was conducted to measure instantaneous rates of water loss from a tree under various conditions of weather and soil-moisture. Calculations of canopy-to-air convection and the reduction of ground-to-air convection based on this data indicate that canopy-induced heating would negate shadowinduced cooling if approximately 45% of the canopy-heated air mixed with ground level air. This critical fraction is comparable to typical downward mixing

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

    International Nuclear Information System (INIS)

    Shao, Zhu-De; Ke, Chang-Qing

    2015-01-01

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

  10. The seasonal cycle of snow cover, sea ice and surface albedo

    Science.gov (United States)

    Robock, A.

    1980-01-01

    The paper examines satellite data used to construct mean snow cover caps for the Northern Hemisphere. The zonally averaged snow cover from these maps is used to calculate the seasonal cycle of zonally averaged surface albedo. The effects of meltwater on the surface, solar zenith angle, and cloudiness are parameterized and included in the calculations of snow and ice albedo. The data allows a calculation of surface albedo for any land or ocean 10 deg latitude band as a function of surface temperature ice and snow cover; the correct determination of the ice boundary is more important than the snow boundary for accurately simulating the ice and snow albedo feedback.

  11. Seasonal variation of the single scattering albedo of the Jungfraujoch aerosol

    Energy Technology Data Exchange (ETDEWEB)

    Collaud Coen, M.; Weingartner, E.; Corrigan, C.; Baltensperger, U.

    2003-03-01

    The single scattering albedo ({omega}{sub 0}) represents the fraction of the light extinction due to scattering. It is there-fore a key parameter to estimate the aerosol direct radiative forcing. The seasonal and diurnal variation of the single scattering albedo was calculated for the Jungfraujoch dry aerosol, which is representative for clean remote continental conditions. The values of {omega}{sub 0} vary between 0.7 and 0.9 depending on the season and on the wavelength. (author)

  12. Impact of soil moisture and winter wheat height from the Loess Plateau in Northwest China on surface spectral albedo

    Science.gov (United States)

    Li, Zhenchao; Yang, Jiaxi; Gao, Xiaoqing; Zheng, Zhiyuan; Yu, Ye; Hou, Xuhong; Wei, Zhigang

    2018-02-01

    The understanding of surface spectral radiation and reflected radiation characteristics of different surfaces in different climate zones aids in the interpretation of regional surface energy transfers and the development of land surface models. This study analysed surface spectral radiation variations and corresponding surface albedo characteristics at different wavelengths as well as the relationship between 5-cm soil moisture and surface albedo on typical sunny days during the winter wheat growth period. The analysis was conducted using observational Loess Plateau winter wheat data from 2015. The results show that the ratio of atmospheric downward radiation to global radiation on typical sunny days is highest for near-infrared wavelengths, followed by visible wavelengths and ultraviolet wavelengths, with values of 57.3, 38.7 and 4.0%, respectively. The ratio of reflected spectral radiation to global radiation varies based on land surface type. The visible radiation reflected by vegetated surfaces is far less than that reflected by bare ground, with surface albedos of 0.045 and 0.27, respectively. Thus, vegetated surfaces absorb more visible radiation than bare ground. The atmospheric downward spectral radiation to global radiation diurnal variation ratios vary for near-infrared wavelengths versus visible and ultraviolet wavelengths on typical sunny days. The near-infrared wavelengths ratio is higher in the morning and evening and lower at noon. The visible and ultraviolet wavelengths ratios are lower in the morning and evening and higher at noon. Visible and ultraviolet wavelength surface albedo is affected by 5-cm soil moisture, demonstrating a significant negative correlation. Excluding near-infrared wavelengths, correlations between surface albedo and 5-cm soil moisture pass the 99% confidence test at each wavelength. The correlation with 5-cm soil moisture is more significant at shorter wavelengths. However, this study obtained surface spectral radiation

  13. Landsat and Sentinel-2A Surface Albedo Estimation and Evaluation Against In Situ Measurements Across the US SURFRAD Network

    Science.gov (United States)

    Franch, B.; Skakun, S.; Vermote, E.; Roger, J. C.

    2017-12-01

    Surface albedo is an essential parameter not only for developing climate models, but also for most energy balance studies. While climate models are usually applied at coarse resolution, the energy balance studies, which are mainly focused on agricultural applications, require a high spatial resolution. The albedo, estimated through the angular integration of the BRDF, requires an appropriate angular sampling of the surface. However, Sentinel-2A sampling characteristics, with nearly constant observation geometry and low illumination variation, prevent from deriving a surface albedo product. In this work, we apply an algorithm developed to derive a Landsat surface albedo to Sentinel-2A. It is based on the BRDF parameters estimated from the MODerate Resolution Imaging Spectroradiometer (MODIS) CMG surface reflectance product (M{O,Y}D09) using the VJB method (Vermote et al., 2009). Sentinel-2A unsupervised classification images are used to disaggregate the BRDF parameters to the Sentinel-2 spatial resolution. We test the results over five different sites of the US SURFRAD network and plot the results versus albedo field measurements. Additionally, we also test this methodology using Landsat-8 images.

  14. Spatiotemporal variability of Canadian High Arctic glacier surface albedo from MODIS data, 2001-2016

    Science.gov (United States)

    Mortimer, Colleen A.; Sharp, Martin

    2018-02-01

    Inter-annual variations and longer-term trends in the annual mass balance of glaciers in Canada's Queen Elizabeth Islands (QEI) are largely attributable to changes in summer melt. The largest source of melt energy in the QEI in summer is net shortwave radiation, which is modulated by changes in glacier surface albedo. We used measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors to investigate large-scale spatial patterns, temporal trends, and variability in the summer surface albedo of QEI glaciers from 2001 to 2016. Mean summer black-sky shortwave broadband albedo (BSA) decreased at a rate of 0.029±0.025 decade-1 over that period. Larger reductions in BSA occurred in July (-0.050±0.031 decade-1). No change in BSA was observed in either June or August. Most of the decrease in BSA, which was greatest at lower elevations around the margins of the ice masses, occurred between 2007 and 2012, when mean summer BSA was anomalously low. The first principal component of the 16-year record of mean summer BSA was well correlated with the mean summer North Atlantic Oscillation index, except in 2006, 2010, and 2016, when the mean summer BSA appears to have been dominated by the August BSA. During the period 2001-2016, the mean summer land surface temperature (LST) over the QEI glaciers and ice caps increased by 0.049±0.038 °C yr-1, and the BSA record was negatively correlated (r: -0.86) with the LST record, indicative of a positive ice-albedo feedback that would increase rates of mass loss from the QEI glaciers.

  15. Assessing modeled Greenland surface mass balance in the GISS Model E2 and its sensitivity to surface albedo

    Science.gov (United States)

    Alexander, Patrick; LeGrande, Allegra N.; Koenig, Lora S.; Tedesco, Marco; Moustafa, Samiah E.; Ivanoff, Alvaro; Fischer, Robert P.; Fettweis, Xavier

    2016-04-01

    The surface mass balance (SMB) of the Greenland Ice Sheet (GrIS) plays an important role in global sea level change. Regional Climate Models (RCMs) such as the Modèle Atmosphérique Régionale (MAR) have been employed at high spatial resolution with relatively complex physics to simulate ice sheet SMB. Global climate models (GCMs) incorporate less sophisticated physical schemes and provide outputs at a lower spatial resolution, but have the advantage of modeling the interaction between different components of the earth's oceans, climate, and land surface at a global scale. Improving the ability of GCMs to represent ice sheet SMB is important for making predictions of future changes in global sea level. With the ultimate goal of improving SMB simulated by the Goddard Institute for Space Studies (GISS) Model E2 GCM, we compare simulated GrIS SMB against the outputs of the MAR model and radar-derived estimates of snow accumulation. In order to reproduce present-day climate variability in the Model E2 simulation, winds are constrained to match the reanalysis datasets used to force MAR at the lateral boundaries. We conduct a preliminary assessment of the sensitivity of the simulated Model E2 SMB to surface albedo, a parameter that is known to strongly influence SMB. Model E2 albedo is set to a fixed value of 0.8 over the entire ice sheet in the initial configuration of the model (control case). We adjust this fixed value in an ensemble of simulations over a range of 0.4 to 0.8 (roughly the range of observed summer GrIS albedo values) to examine the sensitivity of ice-sheet-wide SMB to albedo. We prescribe albedo from the Moderate Resolution Imaging Spectroradiometer (MODIS) MCD43A3 v6 to examine the impact of a more realistic spatial and temporal variations in albedo. An age-dependent snow albedo parameterization is applied, and its impact on SMB relative to observations and the RCM is assessed.

  16. Simulation and Analysis of Topographic Effect on Land Surface Albedo over Mountainous Areas

    Science.gov (United States)

    Hao, D.; Wen, J.; Xiao, Q.

    2017-12-01

    Land surface albedo is one of the significant geophysical variables affecting the Earth's climate and controlling the surface radiation budget. Topography leads to the formation of shadows and the redistribution of incident radiation, which complicates the modeling and estimation of the land surface albedo. Some studies show that neglecting the topography effect may lead to significant bias in estimating the land surface albedo for the sloping terrain. However, for the composite sloping terrain, the topographic effects on the albedo remain unclear. Accurately estimating the sub-topographic effect on the land surface albedo over the composite sloping terrain presents a challenge for remote sensing modeling and applications. In our study, we focus on the development of a simplified estimation method for land surface albedo including black-sky albedo (BSA) and white-sky albedo (WSA) of the composite sloping terrain at a kilometer scale based on the fine scale DEM (30m) and quantitatively investigate and understand the topographic effects on the albedo. The albedo is affected by various factors such as solar zenith angle (SZA), solar azimuth angle (SAA), shadows, terrain occlusion, and slope and aspect distribution of the micro-slopes. When SZA is 30°, the absolute and relative deviations between the BSA of flat terrain and that of rugged terrain reaches 0.12 and 50%, respectively. When the mean slope of the terrain is 30.63° and SZA=30°, the absolute deviation of BSA caused by SAA can reach 0.04. The maximal relative and relative deviation between the WSA of flat terrain and that of rugged terrain reaches 0.08 and 50%. These results demonstrate that the topographic effect has to be taken into account in the albedo estimation.

  17. Variation in Surficial Hydrated Minerals on Large Low-Albedo Asteroids

    Science.gov (United States)

    Rivkin, Andrew S.; Emery, Joshua P.; Howell, Ellen S.

    2017-10-01

    Observations of asteroids in the 3-µm spectral region, where absorptions diagnostic for hydrated minerals are found, show low-albedo asteroid spectra can be classified into at least 3 groups (Takir et al. 2013, Rivkin et al. 2015). While definitions of these groups vary between authors, they hold in common a group with spectra like what we see for CM/CI meteorites, one group with spectra like that of Ceres, and a group with spectra that have been interpreted as ice frost. The relationship between these groups is not yet clear. One possibility is that the spectrum reflects (no pun intended) the formation location for the asteroids and that a given object is undifferentiated and homogeneous in the composition of its hydrated minerals. However, models of the thermal and chemical evolution of large, low-albedo asteroids suggests that differentiation may be more common than we had thought, and impacts could exhume once-deep layers or expose complicated mixes of salts and silicates (for instance, Castillo-Rogez et al. LPSC 2017 model of Ceres). In this case, we might expect variation in the 3-µm spectral region to be seen on the surfaces of some objects as they rotate. We will present evidence for such variation in the spectrum of two large asteroids, 704 Interamnia (306 km diameter) and 324 Bamberga (220 km diameter). In the first case, Interamnia’s spectrum seems to have a combination of Ceres- and CM/CI-like features and has aspects where one or another component is dominant, while Bamberga’s spectrum is not easily placed in previously-defined groups.

  18. 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.

  19. 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.

  20. Improvement of Mars surface snow albedo modeling in LMD Mars GCM with SNICAR

    Science.gov (United States)

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

    2017-12-01

    The current version of Laboratoire de Météorologie Dynamique (LMD) Mars GCM (original-MGCM) uses annually repeating (prescribed) albedo values from the Thermal Emission Spectrometer observations. We integrate the Snow, Ice, and Aerosol Radiation (SNICAR) model with MGCM (SNICAR-MGCM) to prognostically determine H2O and CO2 ice cap albedos interactively in the model. Over snow-covered regions mean SNICAR-MGCM albedo is higher by about 0.034 than original-MGCM. Changes in albedo and surface dust content also impact the shortwave energy flux at the surface. SNICAR-MGCM model simulates a change of -1.26 W/m2 shortwave flux on a global scale. Globally, net CO2 ice deposition increases by about 4% over one Martian annual cycle as compared to original-MGCM simulations. SNICAR integration reduces the net mean global surface temperature, and the global surface pressure of Mars by about 0.87% and 2.5% respectively. Changes in albedo also show a similar distribution as dust deposition over the globe. The SNICAR-MGCM model generates albedos with higher sensitivity to surface dust content as compared to original-MGCM. For snow-covered regions, we improve the correlation between albedo and optical depth of dust from -0.91 to -0.97 with SNICAR-MGCM as compared to original-MGCM. Using new diagnostic capabilities with this model, we find that cryospheric surfaces (with dust) increase the global surface albedo of Mars by 0.022. The cryospheric effect is severely muted by dust in snow, however, which acts to decrease the planet-mean surface albedo by 0.06.

  1. 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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-09-01

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

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

    Science.gov (United States)

    McFarlane, S. A.; Gaustad, K. L.; Mlawer, E. J.; Long, C. N.; Delamere, J.

    2011-09-01

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

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

    Directory of Open Access Journals (Sweden)

    T. Manninen

    2012-11-01

    Full Text Available 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 aerosol optical depth and the solar zenith angle values, the effect can be as large as 20%. For the cases we tested using data from the Cabauw atmospheric test site in the Netherlands, the atmosphere caused typically up to 5% overestimation of surface albedo with respect to corresponding black-sky surface albedo values.

  5. Long-Term Variability of Surface Albedo and Its Correlation with Climatic Variables over Antarctica

    Directory of Open Access Journals (Sweden)

    Minji Seo

    2016-11-01

    Full Text Available The cryosphere is an essential part of the earth system for understanding climate change. Components of the cryosphere, such as ice sheets and sea ice, are generally decreasing over time. However, previous studies have indicated differing trends between the Antarctic and the Arctic. The South Pole also shows internal differences in trends. These phenomena indicate the importance of continuous observation of the Polar Regions. Albedo is a main indicator for analyzing Antarctic climate change and is an important variable with regard to the radiation budget because it can provide positive feedback on polar warming and is related to net radiation and atmospheric heating in the mainly snow- and ice-covered Antarctic. Therefore, in this study, we analyzed long-term temporal and spatial variability of albedo and investigated the interrelationships between albedo and climatic variables over Antarctica. We used broadband surface albedo data from the Satellite Application Facility on Climate Monitoring and data for several climatic variables such as temperature and Antarctic oscillation index (AAO during the period of 1983 to 2009. Time series analysis and correlation analysis were performed through linear regression using albedo and climatic variables. The results of this research indicated that albedo shows two trends, west trend and an east trend, over Antarctica. Most of the western side of Antarctica showed a negative trend of albedo (about −0.0007 to −0.0015 year−1, but the other side showed a positive trend (about 0.0006 year−1. In addition, albedo and surface temperature had a negative correlation, but this relationship was weaker in west Antarctica than in east Antarctica. The correlation between albedo and AAO revealed different relationships in the two regions; west Antarctica had a negative correlation and east Antarctica showed a positive correlation. In addition, the correlation between albedo and AAO was weaker in the west. This

  6. CLARA-SAL: a global 28 yr timeseries of Earth's black-sky surface albedo

    Directory of Open Access Journals (Sweden)

    A. Riihelä

    2013-04-01

    Full Text Available We present a novel 28 yr dataset of Earth's black-sky surface albedo, derived from AVHRR instruments. The dataset is created using algorithms to separately derive the surface albedo for different land use areas globally. Snow, sea ice, open water and vegetation are all treated independently. The product features corrections for the atmospheric effect in satellite-observed surface radiances, a BRDF correction for the anisotropic reflectance properties of natural surfaces, and a novel topography correction of geolocation and radiometric accuracy of surface reflectance observations over mountainous areas. The dataset is based on a homogenized AVHRR radiance timeseries. The product is validated against quality-controlled in situ observations of clear-sky surface albedo at various BSRN sites around the world. Snow and ice albedo retrieval validation is given particular attention using BSRN sites over Antarctica, Greenland Climate Network stations on the Greenland Ice Sheet (GrIS, as well as sea ice albedo data from the SHEBA and Tara expeditions. The product quality is found to be comparable to other previous long-term surface albedo datasets from AVHRR.

  7. Observations of climate, albedo, and surface radiation over cleared and undisturbed Amazonian forest

    International Nuclear Information System (INIS)

    Bastable, H.G.; Shuttleworth, W.J.; Dallarosa, R.L.G.; Fisch, G.; Nobre, C.A.

    1993-01-01

    Measurements from the first comparative study of climate over Amazonian tropical forest and an embedded deforested clearing are presented. Observations comprise a continuous 60-day run of data from mid-October to mid-December 1990, covering the end of the dry season and the beginning of the wet season. Mean hourly observations are calculated for the whole period; and for two 10-day periods, one in the dry season and one at the start of the wet season. Much greater variation in weather variables was observed at the clearing compared with over the forest. While the mean values of temperature and specific humidity deficit differed by less than 1°C and 1 g kg −1 respectively, their daily ranges at the clearing were twice those at the forest. Mean daily albedo of the forest was 13.1 per cent, agreeing well with other tropical forest measurements, and of the clearing was 16.3 per cent, somewhat lower than the values currently being used in GCMs. The surface energy balance was investigated and mean available energy calculated for each site. The significant difference in the daily pattern of net radiation between the sites was found to be at least as much due to differences in the longwave radiation balance as to differences in albedo. The diurnal pattern of net radiation therefore changed between dry and wet periods as the higher plant water stress experienced by clearing vegetation altered the daily temperature cycle

  8. Spatial and temporal variations of albedo and absorbed solar radiation during 2009 - 2016 from IKOR-M satellite program

    Science.gov (United States)

    Cherviakov, Maksim; Bogdanov, Mikhail; Spiryakhina, Anastasia; Shishkina, Elena; Surkova, Yana; Kulkova, Eugenia

    2017-04-01

    -M. This radiometer worked on board of the "Meteor-M" No 1 satellite for five years. Parameters of linear trends are estimated for the Earth's surface area albedo with approximately constant values of this characteristic and the estimate of sensitivity change over time for the radiometer is obtained. The seasonal and interannual variations of OSR, albedo and ASR were discussed. The variations between SW radiation budget components seem to be within observational uncertainty and natural variability governed by cloudiness, water vapor and aerosol variations. It should be noted that cloudiness makes a significant contribution to the planetary albedo of the Earth, largely determines its spatial-temporal distribution. In particular, it is important to know what contribution cloudiness makes to albedo and what the relationship between them. Therefore, comparisons between albedo and cloudiness were conducted separately for land and oceans. The comparison of the distributions of cloudiness and albedo had identified the existence of significant correlation to the World Ocean, lower values for the World Ocean and land together and small correlation for land. It was assessed spatial and temporal variations of albedo and the absorbed solar radiation over different regions. Latitudinal distributions of albedo and ASR were estimated in more detail. Meridional cross sections over oceans and land were used separately for this estimation. It was shown that the albedo and ASR data received from the radiometer IKOR-M can be used to detect El Nino in the Pacific Ocean and monitoring of the East Asian Summer Monsoon. The report will be presented more detailed results. The reported study was funded by Russian Geographical Society according financial support in the framework of a research project No 40/2016-R. Latitudinal distributions of albedo and ASR study was funded by RFBR according to the research project No.16-35-00284 mol_a. References 1. Sklyarov Yu.A., Vorob'ev V.A., Kotuma A

  9. 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.

  10. Quality assurance of in-situ measurements of land surface albedo: A model-based approach

    Science.gov (United States)

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

    2016-04-01

    This paper presents the development of a model-based framework for assessing the quality of in-situ measurements of albedo used to validate land surface albedo products. Using a 3D Monte Carlo Ray Tracing (MCRT) radiative transfer model, a quality assurance framework is built based on simulated field measurements of albedo within complex 3D canopies and under various illumination scenarios. This method provides an unbiased approach in assessing the quality of field measurements, and is also able to trace the contributions of two main sources of uncertainty in field-measurements of albedo; those resulting from 1) the field measurement protocol, such as height or placement of field measurement within the canopy, and 2) intrinsic factors of the 3D canopy under specific illumination characteristics considered, such as the canopy structure and landscape heterogeneity, tree heights, ecosystem type and season.

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

    International Nuclear Information System (INIS)

    Betts, R.A.

    2000-01-01

    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

  12. Mapping Global Ocean Surface Albedo from Satellite Observations: Models, Algorithms, and Datasets

    Science.gov (United States)

    Li, X.; Fan, X.; Yan, H.; Li, A.; Wang, M.; Qu, Y.

    2018-04-01

    Ocean surface albedo (OSA) is one of the important parameters in surface radiation budget (SRB). It is usually considered as a controlling factor of the heat exchange among the atmosphere and ocean. The temporal and spatial dynamics of OSA determine the energy absorption of upper level ocean water, and have influences on the oceanic currents, atmospheric circulations, and transportation of material and energy of hydrosphere. Therefore, various parameterizations and models have been developed for describing the dynamics of OSA. However, it has been demonstrated that the currently available OSA datasets cannot full fill the requirement of global climate change studies. In this study, we present a literature review on mapping global OSA from satellite observations. The models (parameterizations, the coupled ocean-atmosphere radiative transfer (COART), and the three component ocean water albedo (TCOWA)), algorithms (the estimation method based on reanalysis data, and the direct-estimation algorithm), and datasets (the cloud, albedo and radiation (CLARA) surface albedo product, dataset derived by the TCOWA model, and the global land surface satellite (GLASS) phase-2 surface broadband albedo product) of OSA have been discussed, separately.

  13. The Effect of Bond Albedo on Venus' Atmospheric and Surface Temperatures

    Science.gov (United States)

    Bullock, M. A.; Limaye, S. S.; Grinspoon, D. H.; Way, M.

    2017-12-01

    In spite of Venus' high planetary albedo, sufficient solar energy reaches the surface to drive a powerful greenhouse effect. The surface temperature is three times higher than it would be without an atmosphere. However, the details of the energy balance within Venus' atmosphere are poorly understood. Half of the solar energy absorbed within the clouds, where most of the solar energy is absorbed, is due to an unknown agent. One of the challenges of modeling Venus' atmosphere has been to account for all the sources of opacity sufficient to generate a globally averaged surface temperature of 735 K, when only 2% of the incoming solar energy is deposited at the surface. The wavelength and spherically integrated albedo, or Bond albedo, has typically been cited as between 0.7 and 0.82 (Colin 1983). Yet, recent photometry of Venus at extended phase angles between 2 and 179° indicate a Bond albedo of 0.90 (Mallama et al., 2006). The authors note an increase in cloud top brightness at phase angles fixed. Figure 1b (right). Venus surface temperature as Bond Albedo changes. Radiative-convective equilibrium models predict the correct globally averaged surface temperature at a=0.81. Calculations here show that a Bond albedo of a=0.9 would yield a surface temperature of 666.4 K, about 70 K too low, unless there is additional thermal absorption within the atmosphere that is not understood. Colin, L.,, Venus, University of Arizona Press, Tucson, 1983, pp 10-26. Mallama, A., et al., 2006. Icarus. 182, 10-22.

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

    Directory of Open Access Journals (Sweden)

    J. Delamere

    2011-09-01

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

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

    Directory of Open Access Journals (Sweden)

    A. A. Marks

    2013-07-01

    Full Text Available The response of the albedo of bare sea ice and snow-covered sea ice to the addition of black carbon is calculated. Visible light absorption and light-scattering cross-sections are derived for a typical first-year and multi-year sea ice with both "dry" and "wet" snow types. The cross-sections are derived using data from a 1970s field study that recorded both reflectivity and light penetration in Arctic sea ice and snow overlying sea ice. The variation of absorption cross-section over the visible wavelengths suggests black carbon is the dominating light-absorbing impurity. The response of first-year and multi-year sea ice albedo to increasing black carbon, from 1 to 1024 ng g−1, in a top 5 cm layer of a 155 cm-thick sea ice was calculated using a radiative-transfer model. The albedo of the first-year sea ice is more sensitive to additional loadings of black carbon than the multi-year sea ice. An addition of 8 ng g−1 of black carbon causes a decrease to 98.7% of the original albedo for first-year sea ice compared to a decrease to 99.7% for the albedo of multi-year sea ice, at a wavelength of 500 nm. The albedo of sea ice is surprisingly unresponsive to additional black carbon up to 100 ng g−1 . Snow layers on sea ice may mitigate the effects of black carbon in sea ice. Wet and dry snow layers of 0.5, 1, 2, 5 and 10 cm depth were added onto the sea ice surface. The albedo of the snow surface was calculated whilst the black carbon in the underlying sea ice was increased. A layer of snow 0.5 cm thick greatly diminishes the effect of black carbon in sea ice on the surface albedo. The albedo of a 2–5 cm snow layer (less than the e-folding depth of snow is still influenced by the underlying sea ice, but the effect of additional black carbon in the sea ice is masked.

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

    OpenAIRE

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

    2012-01-01

    We present a sensitivity study of the surface mass balance (SMB) of the Greenland Ice Sheet, as modeled using a regional atmospheric climate model, to various parameter settings in the albedo scheme. The snow albedo scheme uses grain size as a prognostic variable and further depends on cloud cover, solar zenith angle and black carbon concentration. For the control experiment the overestimation of absorbed shortwave radiation (+6%) at the K-transect (west Greenland) for the period 2004–2009 is...

  17. Global Climate Forcing from Albedo Change Caused by Large-scale Deforestation and Reforestation: Quantification and Attribution of Geographic Variation

    Science.gov (United States)

    Jiao, Tong; Williams, Christopher A.; Ghimire, Bardan; Masek, Jeffrey; Gao, Feng; Schaaf, Crystal

    2017-01-01

    Large-scale deforestation and reforestation have contributed substantially to historical and contemporary global climate change in part through albedo-induced radiative forcing, with meaningful implications for forest management aiming to mitigate climate change. Associated warming or cooling varies widely across the globe due to a range of factors including forest type, snow cover, and insolation, but resulting geographic variation remain spoorly described and has been largely based on model assessments. This study provides an observation-based approach to quantify local and global radiative forcings from large-scale deforestation and reforestation and further examines mechanisms that result in the spatial heterogeneity of radiative forcing. We incorporate a new spatially and temporally explicit land cover-specific albedo product derived from Moderate Resolution Imaging Spectroradiometer with a historical land use data set (Land Use Harmonization product). Spatial variation in radiative forcing was attributed to four mechanisms, including the change in snow-covered albedo, change in snow-free albedo, snow cover fraction, and incoming solar radiation. We find an albedo-only radiative forcing (RF) of -0.819 W m(exp -2) if year 2000 forests were completely deforested and converted to croplands. Albedo RF from global reforestation of present-day croplands to recover year 1700 forests is estimated to be 0.161 W m)exp -2). Snow-cover fraction is identified as the primary factor in determining the spatial variation of radiative forcing in winter, while the magnitude of the change in snow-free albedo is the primary factor determining variations in summertime RF. Findings reinforce the notion that, for conifers at the snowier high latitudes, albedo RF diminishes the warming from forest loss and the cooling from forest gain more so than for other forest types, latitudes, and climate settings.

  18. Iapetus Surface Temperatures, and the Influence of Sublimation on the Albedo Dichotomy: Cassini CIRS Constraints

    Science.gov (United States)

    Spencer, J. R.; Pearl, J. C.; Segura, M.; Cassini CIRS Team

    2005-08-01

    The Composite Infrared Spectrometer (CIRS) on the Cassini orbiter obtained extensive observations of Iapetus' thermal emission during the New Year 2005 flyby, with best 8 - 16 μ m spatial resolution of 35 km per pixel. Observed subsolar temperatures on the dark terrain reach nearly 130 K, much warmer than any other satellite surface in the Saturn system, due to the combination of low albedo and slow rotation. These high temperatures mean that, uniquely in the Saturn system, water ice sublimation rates are significant at low latitudes on Iapetus' dark side, and surface water ice is probably not stable there on geological timescales. This result is consistent with the lack of water ice at low latitudes on the dark terrain inferred from Cassini UVIS UV spectra (Hendrix et al., 2005 LPSC). Thermally-controlled migration of water ice may thus contribute to the curious shape of the light/dark boundary on Iapetus, with bright poles and dark terrain extending round the equator onto the trailing side. Impacts of Saturn-centric or prograde heliocentric material cannot alone explain this shape, as their impact flux depends only on distance from the apex of motion (though the impact distribution of Oort cloud comet dust may be consistent with the observed albedo pattern (Cook and Franklin 1970)). We model the ballistic migration of water ice across the surface of Iapetus, determining temperatures and sublimation rates assuming CIRS-constrained thermal inertia and a simple dependence of albedo on distance from the apex of motion. Water ice is lost rapidly from low latitudes on the dark leading side and accumulates near the poles, and is also lost, though more slowly, in equatorial regions near the sub-Saturn and anti-Saturn points. The resulting water ice distribution pattern matches the distribution of Iapetus' bright terrain remarkably well. Albedo modification by thermal migration can thus help to reconcile Iapetus' albedo patterns with albedo control by Saturn-centric or

  19. An Improved Method For Retrieving Land Surface Albedo Over Rugged Terrain

    NARCIS (Netherlands)

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

    2014-01-01

    Land surface albedo is a very important parameter, which can be derived from a bidirectional reflectance distribution function (BRDF) model with angular integration of BRDF in a particular distribution of downward solar irradiance. The Algorithm for MODIS Bidirectional Reflectance Anisotropic of

  20. Validation of AVHRR- and MODIS-derived albedos of snow and ice surfaces by means of helicopter measurements

    NARCIS (Netherlands)

    Greuell, W.; Oerlemans, J.

    2005-01-01

    We describe the validation of surface albedos of snow and glacier ice as derived from Advanced Very High Resolution Radiometer (AVHRR) and MOderate Resolution Imaging Spectrometer (MODIS) satellite data. For this purpose we measured surface albedos from a helicopter over Vatnajökull, Iceland, and

  1. Factors affecting projected Arctic surface shortwave heating and albedo change in coupled climate models.

    Science.gov (United States)

    Holland, Marika M; Landrum, Laura

    2015-07-13

    We use a large ensemble of simulations from the Community Earth System Model to quantify simulated changes in the twentieth and twenty-first century Arctic surface shortwave heating associated with changing incoming solar radiation and changing ice conditions. For increases in shortwave absorption associated with albedo reductions, the relative influence of changing sea ice surface properties and changing sea ice areal coverage is assessed. Changes in the surface sea ice properties are associated with an earlier melt season onset, a longer snow-free season and enhanced surface ponding. Because many of these changes occur during peak solar insolation, they have a considerable influence on Arctic surface shortwave heating that is comparable to the influence of ice area loss in the early twenty-first century. As ice area loss continues through the twenty-first century, it overwhelms the influence of changes in the sea ice surface state, and is responsible for a majority of the net shortwave increases by the mid-twenty-first century. A comparison with the Arctic surface albedo and shortwave heating in CMIP5 models indicates a large spread in projected twenty-first century change. This is in part related to different ice loss rates among the models and different representations of the late twentieth century ice albedo and associated sea ice surface state. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  2. Variability of soil moisture and its relationship with surface albedo

    Indian Academy of Sciences (India)

    Continuous observation data collected over the year 2008 at Astronomical Observatory, Thiruvananthapuram in south Kerala (76° 59′E longitude and 8° 30′N latitude) are used to study the diurnal, monthly and seasonal soil moisture variations. The effect of rainfall on diurnal and seasonal soil moisture is discussed.

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

    NARCIS (Netherlands)

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

    2014-01-01

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

  4. Observed diurnal variations in Mars Science Laboratory Dynamic Albedo of Neutrons passive mode data

    Science.gov (United States)

    Tate, C. G.; Moersch, J.; Jun, I.; Mitrofanov, I.; Litvak, M.; Boynton, W. V.; Drake, D.; Fedosov, F.; Golovin, D.; Hardgrove, C.; Harshman, K.; Kozyrev, A. S.; Kuzmin, R.; Lisov, D.; Maclennan, E.; Malakhov, A.; Mischna, M.; Mokrousov, M.; Nikiforov, S.; Sanin, A. B.; Starr, R.; Vostrukhin, A.

    2018-06-01

    The Mars Science Laboratory Dynamic Albedo of Neutrons (DAN) experiment measures the martian neutron leakage flux in order to estimate the amount of water equivalent hydrogen present in the shallow regolith. When DAN is operating in passive mode, it is sensitive to neutrons produced through the interactions of galactic cosmic rays (GCR) with the regolith and atmosphere and neutrons produced by the rover's Multi-Mission Radioisotope Thermoelectric Generator (MMRTG). During the mission, DAN passive mode data were collected over the full diurnal cycle at the locations known as Rocknest (sols 60-100) and John Klein (sols 166-272). A weak, but unexpected, diurnal variation was observed in the neutron count rates reported at these locations. We investigate different hypotheses that could be causing these observed variations. These hypotheses are variations in subsurface temperature, atmospheric pressure, the exchange of water vapor between the atmosphere and regolith, and instrumental effects on the neutron count rates. Our investigation suggests the most likely factors contributing to the observed diurnal variations in DAN passive data are instrumental effects and time-variable preferential shielding of alpha particles, with other environmental effects only having small contributions.

  5. Surface photometric properties and albedo changes in the central equatorial region of Mars

    Science.gov (United States)

    Strickland, Edwin L., III

    1992-12-01

    Comparison of the Viking Orbiter 2 Approach mosaic taken 11 Mars months later provides qualitative information on the photometric properties of the martian albedo features, and the distribution of dust and sand deposits responsible for the atmosphere near the northern summer solstice. The approach mosaic was taken at L s 106 degrees (early N. summer), phase angle 106 degrees; and airmasses varying from 4.6 at 30 degrees N to 3.3 near 10 degrees S. The apoapsis mosaic was taken in four sequences between L s 72 degrees and 76 degrees (late N. spring), near phase angles of 47 degrees, and at airmasses near 2.5. Systematic differences in the photometric decalibrations used to generate these mosaics may induce multiplicative errors of 5-10 percent of the observed albedos in comparisons of the mosaics, but they are probably nearer 3 percent of the albedos. In the study area (30 degrees N to 20 degrees S, 57 degrees E to 75 degrees W), scene-average approach Minnaert albedos were about 10 percent greater than apoapsis albedos and slightly less 'red'. The preferred explanation for the observed approach-apoapsis albedo difference is that both Arabia and Meridiani materials are smoother on millimeter and larger scales than other units in the study area. This is in good agreement with preliminary conclusions of Thorpe and (for dark intracrater Meridiani splotches) Regner et al. This is also consistent with reasonable models of these surfaces. 'Dark Blue' Meridiani surfaces are interpreted as consisting of sand dunes and sand sheets, which would be expected to have macroscopically smooth, nonshadowing surfaces. Viking Lander images of the surfaces at both landing sites show that smooth drift area's brightnesses are close to those of adjacent rough soil areas at low phase angles, but drifts become much brighter than rough soils when looking up-sun at high phase angles. Smooth patches of duricrust at both landing sites, interpreted by Strickland as eolian deposits (regardless of

  6. Surface photometric properties and albedo changes in the central equatorial region of Mars

    Science.gov (United States)

    Strickland, Edwin L., III

    1992-01-01

    Comparison of the Viking Orbiter 2 Approach mosaic taken 11 Mars months later provides qualitative information on the photometric properties of the martian albedo features, and the distribution of dust and sand deposits responsible for the atmosphere near the northern summer solstice. The approach mosaic was taken at L (sub s) 106 degrees (early N. summer), phase angle 106 degrees; and airmasses varying from 4.6 at 30 degrees N to 3.3 near 10 degrees S. The apoapsis mosaic was taken in four sequences between L (sub s) 72 degrees and 76 degrees (late N. spring), near phase angles of 47 degrees, and at airmasses near 2.5. Systematic differences in the photometric decalibrations used to generate these mosaics may induce multiplicative errors of 5-10 percent of the observed albedos in comparisons of the mosaics, but they are probably nearer 3 percent of the albedos. In the study area (30 degrees N to 20 degrees S, 57 degrees E to 75 degrees W), scene-average approach Minnaert albedos were about 10 percent greater than apoapsis albedos and slightly less 'red'. The preferred explanation for the observed approach-apoapsis albedo difference is that both Arabia and Meridiani materials are smoother on millimeter and larger scales than other units in the study area. This is in good agreement with preliminary conclusions of Thorpe and (for dark intracrater Meridiani splotches) Regner et al. This is also consistent with reasonable models of these surfaces. 'Dark Blue' Meridiani surfaces are interpreted as consisting of sand dunes and sand sheets, which would be expected to have macroscopically smooth, nonshadowing surfaces. Viking Lander images of the surfaces at both landing sites show that smooth drift area's brightnesses are close to those of adjacent rough soil areas at low phase angles, but drifts become much brighter than rough soils when looking up-sun at high phase angles. Smooth patches of duricrust at both landing sites, interpreted by Strickland as eolian deposits

  7. Surface albedo in relation to disturbance and early stand dynamics in the boreal forest: Implications for climate models

    Science.gov (United States)

    Halim, M. A.; Thomas, S. C.

    2017-12-01

    Surface albedo is the most important biophysical radiative forcing in the boreal forest. General Circulation Model studies have suggested that harvesting of boreal forest has a net cooling effect, in contrast to other terrestrial biomes, by increasing surface albedo. However, albedo estimation in these models has been achieved by simplifying processes governing albedo at a coarse scale (both spatial and temporal). Biophysical processes that determine albedo likely operate on small spatial and temporal scales, requiring more direct estimates of effects of landcover change on net radiation. We established a chronosequence study in post-fire and post-clearcut sites (2013, 2006, 1998), logging data from July 2013 to July 2017 in boreal forest sites in northwestern Ontario, Canada. Each age-class X disturbance had 3 three replicates, matched to 18 permanent circular plots (10-m radius) each with an instrumented tower measuring surface albedo, air and soil temperature, and soil moisture. We also measured leaf area index, species composition and soil organic matter content at each site. BRDF-corrected surface albedo was calculated from daily 30m x 30m reflectance data fused from the MODIS MOD09GA product and Landsat 7 reflectance data. Calculated albedo was verified using ground-based measurements. Results show that fire sites generally had lower (15-25%) albedo than clearcut sites in all seasons. Because of rapid forest regrowth, large perturbations of clearcut harvests on forest albedo started to fade out within a year. Albedo differences between fire and clearcut sites also declined sharply with stand age. Younger stands generally had higher albedo than older stands mainly due to the presence of broadleaf species (for example, Populus tremuloides). In spring, snow melted 10-12 days earlier in recent (2013) clearcut sites compared to closed-canopy sites, causing a sharp reduction in surface albedo in comparison to old clearcut/fire sites (2006 and 1998). Snow melted

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

    KAUST Repository

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

    2017-01-01

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

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

    KAUST Repository

    Evans, Jason P.

    2017-01-24

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

  10. Monitoring glacier albedo as a proxy to derive summer and annual surface mass balances from optical remote-sensing data

    Science.gov (United States)

    Davaze, Lucas; Rabatel, Antoine; Arnaud, Yves; Sirguey, Pascal; Six, Delphine; Letreguilly, Anne; Dumont, Marie

    2018-01-01

    Less than 0.25 % of the 250 000 glaciers inventoried in the Randolph Glacier Inventory (RGI V.5) are currently monitored with in situ measurements of surface mass balance. Increasing this archive is very challenging, especially using time-consuming methods based on in situ measurements, and complementary methods are required to quantify the surface mass balance of unmonitored glaciers. The current study relies on the so-called albedo method, based on the analysis of albedo maps retrieved from optical satellite imagery acquired since 2000 by the MODIS sensor, on board the TERRA satellite. Recent studies revealed substantial relationships between summer minimum glacier-wide surface albedo and annual surface mass balance, because this minimum surface albedo is directly related to the accumulation-area ratio and the equilibrium-line altitude. On the basis of 30 glaciers located in the French Alps where annual surface mass balance data are available, our study conducted on the period 2000-2015 confirms the robustness and reliability of the relationship between the summer minimum surface albedo and the annual surface mass balance. For the ablation season, the integrated summer surface albedo is significantly correlated with the summer surface mass balance of the six glaciers seasonally monitored. These results are promising to monitor both annual and summer glacier-wide surface mass balances of individual glaciers at a regional scale using optical satellite images. A sensitivity study on the computed cloud masks revealed a high confidence in the retrieved albedo maps, restricting the number of omission errors. Albedo retrieval artifacts have been detected for topographically incised glaciers, highlighting limitations in the shadow correction algorithm, although inter-annual comparisons are not affected by systematic errors.

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

    Science.gov (United States)

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

    2012-01-01

    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...

  12. Landcover Change, Land Surface Temperature, Surface Albedo and Topography in the Plateau Region of North-Central Nigeria

    Directory of Open Access Journals (Sweden)

    Shakirudeen Odunuga

    2015-04-01

    Full Text Available This study assessed the change in some environmental parameters in the Plateau region of North-Central Nigeria (Barakinladi, Jos, and Kafachan environs using the nexus of landcover change, land surface temperature, surface albedo, and topography. The study employed both remote sensing and statistical techniques for the period between 1986 and 2014 to analyze the dynamics between and within these environmental variables. In Barakinladi, the built up landcover change is highest (increasing from 39.53% to 47.59% between 1986 and 2014; LST ranges from 19.09 °C to 38.59 °C in 1986 and from 22.68 °C and 41.68 °C in 2014; and the albedo ranges between 0.014 and 0.154 in 1986 and 0.017 and 0.248 in 2014. In Jos, the built-up landcover occupied 34.26% in 1986 and 36.67% in 2014; LST values range between 20.83 °C and 41.33 °C in 1986 and between 21.61 °C and 42.64 °C in 2014; and the albedo ranges between 0.003 and 0.211 in 1986 and 0.15 and 0.237 in 2014. In Kafachan area, the built up landcover occupied 32.95% in 1986 and 39.01% in 2014. Urbanization and agricultural activities, including animal grazing, were responsible for the gradual loss in vegetation and increasing average LST and albedo. The results also revealed that changing landcover and topography have a relationship with surface albedo and land surface temperature, thereby impacting significantly on ecosystem services delivered by the natural system.

  13. The response of Arctic vegetation to the summer climate: relation between shrub cover, NDVI, surface albedo and temperature

    Energy Technology Data Exchange (ETDEWEB)

    Blok, Daan; Heijmans, Monique M P D; Berendse, Frank [Nature Conservation and Plant Ecology Group, Wageningen University, PO Box 47, 6700 AA, Wageningen (Netherlands); Schaepman-Strub, Gabriela [Institute of Evolutionary Biology and Environmental Studies, University of Zuerich, Winterthurerstrasse 190, 8057 Zuerich (Switzerland); Bartholomeus, Harm [Centre for Geo-Information, Wageningen University, PO Box 47, 6700 AA, Wageningen (Netherlands); Maximov, Trofim C, E-mail: daan.blok@wur.nl [Biological Problems of the Cryolithozone, Russian Academy of Sciences, Siberian Division, 41, Lenin Prospekt, Yakutsk, The Republic of Sakha, Yakutia 677980 (Russian Federation)

    2011-07-15

    Recently observed Arctic greening trends from normalized difference vegetation index (NDVI) data suggest that shrub growth is increasing in response to increasing summer temperature. An increase in shrub cover is expected to decrease summer albedo and thus positively feed back to climate warming. However, it is unknown how albedo and NDVI are affected by shrub cover and inter-annual variations in the summer climate. Here, we examine the relationship between deciduous shrub fractional cover, NDVI and albedo using field data collected at a tundra site in NE Siberia. Field data showed that NDVI increased and albedo decreased with increasing deciduous shrub cover. We then selected four Arctic tundra study areas and compiled annual growing season maximum NDVI and minimum albedo maps from MODIS satellite data (2000-10) and related these satellite products to tundra vegetation types (shrub, graminoid, barren and wetland tundra) and regional summer temperature. We observed that maximum NDVI was greatest in shrub tundra and that inter-annual variation was negatively related to summer minimum albedo but showed no consistent relationship with summer temperature. Shrub tundra showed higher albedo than wetland and barren tundra in all four study areas. These results suggest that a northwards shift of shrub tundra might not lead to a decrease in summer minimum albedo during the snow-free season when replacing wetland tundra. A fully integrative study is however needed to link results from satellite data with in situ observations across the Arctic to test the effect of increasing shrub cover on summer albedo in different tundra vegetation types.

  14. The response of Arctic vegetation to the summer climate: relation between shrub cover, NDVI, surface albedo and temperature

    International Nuclear Information System (INIS)

    Blok, Daan; Heijmans, Monique M P D; Berendse, Frank; Schaepman-Strub, Gabriela; Bartholomeus, Harm; Maximov, Trofim C

    2011-01-01

    Recently observed Arctic greening trends from normalized difference vegetation index (NDVI) data suggest that shrub growth is increasing in response to increasing summer temperature. An increase in shrub cover is expected to decrease summer albedo and thus positively feed back to climate warming. However, it is unknown how albedo and NDVI are affected by shrub cover and inter-annual variations in the summer climate. Here, we examine the relationship between deciduous shrub fractional cover, NDVI and albedo using field data collected at a tundra site in NE Siberia. Field data showed that NDVI increased and albedo decreased with increasing deciduous shrub cover. We then selected four Arctic tundra study areas and compiled annual growing season maximum NDVI and minimum albedo maps from MODIS satellite data (2000-10) and related these satellite products to tundra vegetation types (shrub, graminoid, barren and wetland tundra) and regional summer temperature. We observed that maximum NDVI was greatest in shrub tundra and that inter-annual variation was negatively related to summer minimum albedo but showed no consistent relationship with summer temperature. Shrub tundra showed higher albedo than wetland and barren tundra in all four study areas. These results suggest that a northwards shift of shrub tundra might not lead to a decrease in summer minimum albedo during the snow-free season when replacing wetland tundra. A fully integrative study is however needed to link results from satellite data with in situ observations across the Arctic to test the effect of increasing shrub cover on summer albedo in different tundra vegetation types.

  15. A framework for consistent estimation of leaf area index, fraction of absorbed photosynthetically active radiation, and surface albedo from MODIS time-series data

    DEFF Research Database (Denmark)

    Xiao, Zhiqiang; Liang, Shunlin; Wang, Jindi

    2015-01-01

    -series MODerate Resolution Imaging Spectroradiometer (MODIS) surface reflectance data. If the reflectance data showed snow-free areas, an ensemble Kalman filter (EnKF) technique was used to estimate leaf area index (LAI) for a two-layer canopy reflectance model (ACRM) by combining predictions from a phenology...... model and the MODIS surface reflectance data. The estimated LAI values were then input into the ACRM to calculate the surface albedo and the fraction of absorbed photosynthetically active radiation (FAPAR). For snow-covered areas, the surface albedo was calculated as the underlying vegetation canopy...... albedo plus the weighted distance between the underlying vegetation canopy albedo and the albedo over deep snow. The LAI/FAPAR and surface albedo values estimated using this framework were compared with MODIS collection 5 eight-day 1-km LAI/FAPAR products (MOD15A2) and 500-m surface albedo product (MCD43...

  16. PHOTOMETRIC STEREO SHAPE-AND-ALBEDO-FROM-SHADING FOR PIXEL-LEVEL RESOLUTION LUNAR SURFACE RECONSTRUCTION

    Directory of Open Access Journals (Sweden)

    W. C. Liu

    2017-07-01

    Full Text Available Shape and Albedo from Shading (SAfS techniques recover pixel-wise surface details based on the relationship between terrain slopes, illumination and imaging geometry, and the energy response (i.e., image intensity captured by the sensing system. Multiple images with different illumination geometries (i.e., photometric stereo can provide better SAfS surface reconstruction due to the increase in observations. Photometric stereo SAfS is suitable for detailed surface reconstruction of the Moon and other extra-terrestrial bodies due to the availability of photometric stereo and the less complex surface reflecting properties (i.e., albedo of the target bodies as compared to the Earth. Considering only one photometric stereo pair (i.e., two images, pixel-variant albedo is still a major obstacle to satisfactory reconstruction and it needs to be regulated by the SAfS algorithm. The illumination directional difference between the two images also becomes an important factor affecting the reconstruction quality. This paper presents a photometric stereo SAfS algorithm for pixel-level resolution lunar surface reconstruction. The algorithm includes a hierarchical optimization architecture for handling pixel-variant albedo and improving performance. With the use of Lunar Reconnaissance Orbiter Camera - Narrow Angle Camera (LROC NAC photometric stereo images, the reconstructed topography (i.e., the DEM is compared with the DEM produced independently by photogrammetric methods. This paper also addresses the effect of illumination directional difference in between one photometric stereo pair on the reconstruction quality of the proposed algorithm by both mathematical and experimental analysis. In this case, LROC NAC images under multiple illumination directions are utilized by the proposed algorithm for experimental comparison. The mathematical derivation suggests an illumination azimuthal difference of 90 degrees between two images is recommended to achieve

  17. Short-wave albedo of a pine forest

    Energy Technology Data Exchange (ETDEWEB)

    Kessler, A.

    1985-06-01

    In this paper nine years of continuous records of the short-wave albedo above a Scotch pine forest in middle Europe were analysed. Special emphasis was given to the dependencies of the albedo on its diurnal variation, its annual variation, the solar altitude, the structure of the stand, the cloud cover, the soil moisture and the spectral reflectance. A long-termed trend of the albedo could not be found, e.g. caused by the stand growth. Finally the annual variation of the albedo of the Scotch pine forest was compared with measurements above different surface types in middle Europe.

  18. The Influence of a Sandy Substrate, Seagrass, or Highly Turbid Water on Albedo and Surface Heat Flux

    Science.gov (United States)

    Fogarty, M. C.; Fewings, M. R.; Paget, A. C.; Dierssen, H. M.

    2018-01-01

    Sea-surface albedo is a combination of surface-reflected and water-leaving irradiance, but water-leaving irradiance typically contributes less than 15% of the total albedo in open-ocean conditions. In coastal systems, however, the bottom substrate or suspended particulate matter can increase the amount of backscattered light, thereby increasing albedo and decreasing net shortwave surface heat flux. Here a sensitivity analysis using observations and models predicts the effect of light scattering on albedo and the net shortwave heat flux for three test cases: a bright sand bottom, a seagrass canopy, and turbid water. After scaling to the full solar shortwave spectrum, daytime average albedo for the test cases is up to 0.20 and exceeds the value of 0.05 predicted using a commonly applied parameterization. Daytime net shortwave heat flux into the water is significantly reduced, particularly for waters with bright sediments, dense horizontal seagrass canopies waters with suspended particulate matter concentration ≥ 50 g m-3. Observations of a more vertical seagrass canopy within 0.2 and 1 m of the surface indicate the increase in albedo compared to the common parameterization is negligible. Therefore, we suggest that the commonly applied albedo lookup table can be used in coastal heat flux estimates in water as shallow as 1 m unless the bottom substrate is highly reflective or the water is highly turbid. Our model results provide guidance to researchers who need to determine albedo in highly reflective or highly turbid conditions but have no direct observations.

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

    Science.gov (United States)

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

    2011-01-01

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

  20. Exploiting Surface Albedos Products to Bridge the Gap Between Remote Sensing Information and Climate Models

    Science.gov (United States)

    Pinty, Bernard; Andredakis, Ioannis; Clerici, Marco; Kaminski, Thomas; Taberner, Malcolm; Stephen, Plummer

    2011-01-01

    We present results from the application of an inversion method conducted using MODIS derived broadband visible and near-infrared surface albedo products. This contribution is an extension of earlier efforts to optimally retrieve land surface fluxes and associated two- stream model parameters based on the Joint Research Centre Two-stream Inversion Package (JRC-TIP). The discussion focuses on products (based on the mean and one-sigma values of the Probability Distribution Functions (PDFs)) obtained during the summer and winter and highlight specific issues related to snowy conditions. This paper discusses the retrieved model parameters including the effective Leaf Area Index (LAI), the background brightness and the scattering efficiency of the vegetation elements. The spatial and seasonal changes exhibited by these parameters agree with common knowledge and underscore the richness of the high quality surface albedo data sets. At the same time, the opportunity to generate global maps of new products, such as the background albedo, underscores the advantages of using state of the art algorithmic approaches capable of fully exploiting accurate satellite remote sensing datasets. The detailed analyses of the retrieval uncertainties highlight the central role and contribution of the LAI, the main process parameter to interpret radiation transfer observations over vegetated surfaces. The posterior covariance matrix of the uncertainties is further exploited to quantify the knowledge gain from the ingestion of MODIS surface albedo products. The estimation of the radiation fluxes that are absorbed, transmitted and scattered by the vegetation layer and its background is achieved on the basis of the retrieved PDFs of the model parameters. The propagation of uncertainties from the observations to the model parameters is achieved via the Hessian of the cost function and yields a covariance matrix of posterior parameter uncertainties. This matrix is propagated to the radiation

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

    OpenAIRE

    Gao, Bo; Jia, Li; Wang, Tianxing

    2014-01-01

    Land surface albedo is an essential parameter for monitoring global/regional climate and land surface energy balance. Although many studies have been conducted on global or regional land surface albedo using various remote sensing data over the past few decades, land surface albedo product with a high spatio-temporal resolution is currently very scarce. This paper proposes a method for deriving land surface albedo with a high spatio-temporal resolution (space: 30 m and time: 2-4 days). The pr...

  2. Assimilation of MODIS Ice Surface Temperature and Albedo into the Snow and Ice Model CROCUS Over the Greenland Ice Sheet Along the K-transect Stations

    Science.gov (United States)

    Navari, M.; Margulis, S. A.; Bateni, S. M.; Alexander, P. M.; Tedesco, M.

    2016-12-01

    Estimating the Greenland Ice Sheet (GrIS) surface mass balance (SMB) is an important component of current and future projections of sea level rise. In situ measurement provides direct estimates of the SMB, but are inherently limited by their spatial extent and representativeness. Given this limitation, physically based regional climate models (RCMs) are critical for understanding GrIS physical processes and estimating of the GrIS SMB. However, the uncertainty in estimates of SMB from RCMs is still high. Surface remote sensing (RS) has been used as a complimentary tool to characterize various aspects related to the SMB. The difficulty of using these data streams is that the links between them and the SMB terms are most often indirect and implicit. Given the lack of in situ information, imperfect models, and under-utilized RS data it is critical to merge the available data in a systematic way to better characterize the spatial and temporal variation of the GrIS SMB. This work proposes a data assimilation (DA) framework that yields temporally-continuous and physically consistent SMB estimates that benefit from state-of-the-art models and relevant remote sensing data streams. Ice surface temperature (IST) is the most important factor that regulates partitioning of the net radiation into the subsurface snow/ice, sensible and latent heat fluxes and plays a key role in runoff generation. Therefore it can be expected that a better estimate of surface temperature from a data assimilation system would contribute to a better estimate of surface mass fluxes. Albedo plays an important role in the surface energy balance of the GrIS. However, even advanced albedo modules are not adequate to simulate albedo over the GrIS. Therefore, merging remotely sensed albedo product into a physically based model has a potential to improve the estimates of the GrIS SMB. In this work a MODIS-derived IST and a 16-day albedo product are independently assimilated into the snow and ice model CROCUS

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

    Science.gov (United States)

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

    2014-02-01

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

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  5. Retrieval of Surface Lambert Albedos and Aerosols Optical Depths Using OMEGA Near-IR EPF Observations of Mars

    Science.gov (United States)

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

    2007-03-01

    We have analyzed five EPF sequences acquired by OMEGA/Mars Express in the near-IR over ice-free and ice-covered surfaces to retrieve simultaneously the Lambert albedo of the surface and the optical depth of aerosols.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-12-01

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

  7. A transitioning Arctic surface energy budget: the impacts of solar zenith angle, surface albedo and cloud radiative forcing

    Energy Technology Data Exchange (ETDEWEB)

    Sedlar, Joseph; Tjernstroem, Michael; Leck, Caroline [Stockholm University, Department of Meteorology, Stockholm (Sweden); Mauritsen, Thorsten [Max-Planck-Institute for Meteorology, Hamburg (Germany); Shupe, Matthew D.; Persson, P.O.G. [University of Colorado, NOAA-ESRL-PSD, Boulder, CO (United States); Brooks, Ian M.; Birch, Cathryn E. [University of Leeds, School of Earth and Environment, Leeds (United Kingdom); Sirevaag, Anders [University of Bergen, Bjerknes Center for Climate Research, Bergen (Norway); Nicolaus, Marcel [Norwegian Polar Institute, Tromsoe (Norway); Alfred Wegener Institute for Polar and Marine Research, Bremerhaven (Germany)

    2011-10-15

    Snow surface and sea-ice energy budgets were measured near 87.5 N during the Arctic Summer Cloud Ocean Study (ASCOS), from August to early September 2008. Surface temperature indicated four distinct temperature regimes, characterized by varying cloud, thermodynamic and solar properties. An initial warm, melt-season regime was interrupted by a 3-day cold regime where temperatures dropped from near zero to -7 C. Subsequently mean energy budget residuals remained small and near zero for 1 week until once again temperatures dropped rapidly and the energy budget residuals became negative. Energy budget transitions were dominated by the net radiative fluxes, largely controlled by the cloudiness. Variable heat, moisture and cloud distributions were associated with changing air-masses. Surface cloud radiative forcing, the net radiative effect of clouds on the surface relative to clear skies, is estimated. Shortwave cloud forcing ranged between -50 W m{sup -2} and zero and varied significantly with surface albedo, solar zenith angle and cloud liquid water. Longwave cloud forcing was larger and generally ranged between 65 and 85 W m{sup -2}, except when the cloud fraction was tenuous or contained little liquid water; thus the net effect of the clouds was to warm the surface. Both cold periods occurred under tenuous, or altogether absent, low-level clouds containing little liquid water, effectively reducing the cloud greenhouse effect. Freeze-up progression was enhanced by a combination of increasing solar zenith angles and surface albedo, while inhibited by a large, positive surface cloud forcing until a new air-mass with considerably less cloudiness advected over the experiment area. (orig.)

  8. Reductions in soil surface albedo as a function of biochar application rate: implications for global radiative forcing

    International Nuclear Information System (INIS)

    Verheijen, Frank G A; Bastos, Ana Catarina; Keizer, Jan Jacob; Jeffery, Simon; Van der Velde, Marijn; Penížek, Vít; Beland, Martin

    2013-01-01

    Biochar can be defined as pyrolysed (charred) biomass produced for application to soils with the aim of mitigating global climate change while improving soil functions. Sustainable biochar application to soils has been estimated to reduce global greenhouse gas emissions by 71–130 Pg CO 2 -C e over 100 years, indicating an important potential to mitigate climate change. However, these estimates ignored changes in soil surface reflection by the application of dark-coloured biochar. Through a laboratory experiment we show a strong tendency for soil surface albedo to decrease as a power decay function with increasing biochar application rate, depending on soil moisture content, biochar application method and land use. Surface application of biochar resulted in strong reductions in soil surface albedo even at relatively low application rates. As a first assessment of the implications for climate change mitigation of these biochar–albedo relationships, we applied a first order global energy balance model to compare negative radiative forcings (from avoided CO 2 emissions) with positive radiative forcings (from reduced soil surface albedos). For a global-scale biochar application equivalent to 120 t ha −1 , we obtained reductions in negative radiative forcings of 5 and 11% for croplands and 11 and 23% for grasslands, when incorporating biochar into the topsoil or applying it to the soil surface, respectively. For a lower global biochar application rate (equivalent to 10 t ha −1 ), these reductions amounted to 13 and 44% for croplands and 28 and 94% for grasslands. Thus, our findings revealed the importance of including changes in soil surface albedo in studies assessing the net climate change mitigation potential of biochar, and we discuss the urgent need for field studies and more detailed spatiotemporal modelling. (letter)

  9. Potential Long-Term Records of Surface Albedo at Fine Spatiotemporal Resolution from Landsat/Sentinle-2A Surface Reflectance and MODIS/VIIRS BRDF

    Science.gov (United States)

    Li, Z.; Schaaf, C.; Shuai, Y.; Liu, Y.; Sun, Q.; Erb, A.; Wang, Z.

    2016-12-01

    The land surface albedo products at fine spatial resolutions are generated by coupling surface reflectance (SR) from Landsat (30 m) or Sentinel-2A (20 m) with concurrent surface anisotropy information (the Bidirectional Reflectance Distribution Function - BRDF) at coarser spatial resolutions from sequential multi-angular observations by the Moderate Resolution Imaging Spectroradiometer (MODIS) or its successor, the Visible Infrared Imaging Radiometer Suite (VIIRS). We assess the comparability of four types of fine-resolution albedo products (black-sky and white-sky albedos over the shortwave broad band) generated by coupling, (1) Landsat-8 Optical Land Imager (OLI) SR with MODIS BRDF; (2) OLI SR with VIIRS BRDF; (3) Sentinel-2A MultiSpectral Instrument (MSI) SR with MODIS BRDF; and (4) MSI SR with VIIRS BRDF. We evaluate the accuracy of these four types of fine-resolution albedo products using ground tower measurements of surface albedo over six SURFace RADiation Network (SURFRAD) sites in the United States. For comparison with the ground measurements, we estimate the actual (blue-sky) albedo values at the six sites by using the satellite-based retrievals of black-sky and white-sky albedos and taking into account the proportion of direct and diffuse solar radiation from the ground measurements at the sites. The coupling of the OLI and MSI SR with MODIS BRDF has already been shown to provide accurate fine-resolution albedo values. With demonstration of a high agreement in BRDF products from MODIS and VIIRS, we expect to see consistency between all four types of fine-resolution albedo products. This assurance of consistency between the couplings of both OLI and MSI with both MODIS and VIIRS guarantees the production of long-term records of surface albedo at fine spatial resolutions and an increased temporal resolution. Such products will be critical in studying land surface changes and associated surface energy balance over the dynamic and heterogeneous landscapes

  10. Decreased surface albedo driven by denser vegetation on the Tibetan Plateau

    International Nuclear Information System (INIS)

    Tian, Li; Zhang, Yangjian; Zhu, Juntao

    2014-01-01

    The Tibetan Plateau (TP) has fundamental ecological and environmental significance to China and Asia through its influence on regional and continental climates. In recent years, climate warming has caused unprecedented changes to land surface processes on the TP, which would unavoidably undermine the ecological and environmental functions of the TP. Among the numerous land surface processes potentially impacted by climate warming, the effect of vegetation greenness on surface energy balance is one of the most critical, but has been long ignored. In this study, we investigated the spatial and temporal patterns of land surface albedo (LSA) on the TP and evaluated the vegetation greenness in relation to patterns of LSA. We found that LSA has been decreasing in most of the vegetated grasslands on the TP from 2000 to 2013, as compared to a flat trend for desert area. The regions where LSA has been decreasing were spatially correlated to areas of increased vegetation greenness. Along rising altitude, LSA decreasing rate exhibited an overall decreasing trend. Across the TP, elevated vegetation greenness in grasslands acted as a primary factor pulling down LSA. The driving effects of vegetation greenness on LSA vary with grassland types, as revealed by a more significant relationship between vegetation greenness and LSA for the sparsely vegetated zone (i.e. steppe) than the more densely vegetated zone (i.e. meadow). Furthermore, the driving effect of vegetation greenness on LSA exhibited an obvious dependence on altitude as effects with rising altitude were relatively strong up to 3000 m, then weakened from 3500 m to 5000 m, and then the effects again increased from 5000 to 6000 m. The growing season LSA trend revealed in this study emphasizes the need to give greater attention to the growing season LSA flux in future surface energy balance studies. (letter)

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

    Directory of Open Access Journals (Sweden)

    Bo Gao

    2014-09-01

    Full Text Available Land surface albedo is an essential parameter for monitoring global/regional climate and land surface energy balance. Although many studies have been conducted on global or regional land surface albedo using various remote sensing data over the past few decades, land surface albedo product with a high spatio–temporal resolution is currently very scarce. This paper proposes a method for deriving land surface albedo with a high spatio–temporal resolution (space: 30 m and time: 2–4 days. The proposed method works by combining the land surface reflectance data at 30 m spatial resolution obtained from the charge-coupled devices in the Huanjing-1A and -1B (HJ-1A/B satellites with the Moderate Resolution Imaging Spectroradiometer (MODIS land surface bidirectional reflectance distribution function (BRDF parameters product (MCD43A1, which is at a spatial resolution of 500 m. First, the land surface BRDF parameters for HJ-1A/B land surface reflectance with a spatial–temporal resolutions of 30 m and 2–4 day are calculated on the basis of the prior knowledge from the MODIS BRDF product; then, the calculated high resolution BRDF parameters are integrated over the illuminating/viewing hemisphere to produce the white- and black-sky albedos at 30 m resolution. These results form the basis for the final land surface albedo derivation by accounting for the proportion of direct and diffuse solar radiation arriving at the ground. The albedo retrieved by this novel method is compared with MODIS land surface albedo products, as well as with ground measurements. The results show that the derived land surface albedo during the growing season of 2012 generally achieved a mean absolute accuracy of ±0.044, and a root mean square error of 0.039, confirming the effectiveness of the newly proposed method.

  12. The Effect of Increasing Surface Albedo on Urban Climate and Air Quality: A Detailed Study for Sacramento, Houston, and Chicago

    Directory of Open Access Journals (Sweden)

    Zahra Jandaghian

    2018-03-01

    Full Text Available Increasing surface reflectivity in urban areas can decrease ambient temperature, resulting in reducing photochemical reaction rates, reducing cooling energy demands and thus improving air quality and human health. The weather research and forecasting model with chemistry (WRF-Chem is coupled with the multi-layer of the urban canopy model (ML-UCM to investigate the effects of surface modification on urban climate in a two-way nested approach over North America focusing on Sacramento, Houston, and Chicago during the 2011 heat wave period. This approach decreases the uncertainties associated with scale separation and grid resolution and equip us with an integrated simulation setup to capture the full impacts of meteorological and photochemical reactions. WRF-ChemV3.6.1 simulated the diurnal variation of air temperature reasonably well, overpredicted wind speed and dew point temperature, underpredicted relative humidity, overpredicted ozone and nitrogen dioxide concentrations, and underpredicted fine particular matters (PM2.5. The performance of PM2.5 is a combination of overprediction of particulate sulfate and underprediction of particulate nitrate and organic carbon. Increasing the surface albedo of roofs, walls, and pavements from 0.2 to 0.65, 0.60, and 0.45, respectively, resulted in a decrease in air temperature by 2.3 °C in urban areas and 0.7 °C in suburban areas; a slight increase in wind speed; an increase in relative humidity (3% and dew point temperature (0.3 °C; a decrease of PM2.5 and O3 concentrations by 2.7 µg/m3 and 6.3 ppb in urban areas and 1.4 µg/m3 and 2.5 ppb in suburban areas, respectively; minimal changes in PM2.5 subspecies; and a decrease of nitrogen dioxide (1 ppb in urban areas.

  13. Increasing surface albedo in the dry subtropical forests of South America: the role of agriculture expansion and management

    Science.gov (United States)

    Houspanossian, J.; Kuppel, S.; Gimenez, R.; Jobbagy, E. G.; Nosetto, M. D.

    2014-12-01

    The increase in surface albedo inherent to land clearing and cultivation (land-cover change, LCC) in the subtropical dry forests of the South American Chaco offsets part of the radiative forcing (RF) of the related carbon emissions. The magnitude of these albedo changes, however, is also dependent on shifts in agricultural practices (land-management change, LMC) and will influence the net effect on Earth's radiation balance as well as other potential feedbacks on climate. We quantified the surface albedo changes between 2001 and 2013 and the consequent shifts in the radiation balance resulting from LCC and LMC, using MODIS imagery a columnar radiation model parameterized with satellite data. Agricultural systems replacing dry forests presented a large variety of managements, ranging from pasture systems with remnant trees to different grain crops, displaying a wide range of phenologies. Cultivated lands showed higher and more variable albedo values (mean = 0.162, Standard Deviation = 0.013, n = 10,000 pixels) than the dry forests they replace (mean = 0.113, SD = 0.010, n = 10,000). These albedo contrasts resulted in a cooling RF of deforestation of -10.1 W m-2 on average, but both livestock and grain crop production systems showed large differences among the different land management options. For instance, livestock systems based on open pasture lands showed higher albedo change and RF (0.06 and -16.3 W m-2, respectively) than silvopastoral systems (0.02 and -4.4 W m-2). Similarly in cropping systems, the replacement of double-cropping by single summer crops, a widespread process in the region lately, resulted in higher albedo change (0.06 vs. 0.08) and RF (-16.3 vs. -22.3 W m-2). Although the effects of LCC on climate are widely acknowledged, those of LMC are still scarcely understood. In the Chaco region, the latter could play an important role and offer a yet-overlooked pathway to influence the radiative balance of our planet.

  14. Evaluation of the global MODIS 30 arc-second spatially and temporally complete snow-free land surface albedo and reflectance anisotropy dataset

    Science.gov (United States)

    Sun, Qingsong; Wang, Zhuosen; Li, Zhan; Erb, Angela; Schaaf, Crystal B.

    2017-06-01

    Land surface albedo is an essential variable for surface energy and climate modeling as it describes the proportion of incident solar radiant flux that is reflected from the Earth's surface. To capture the temporal variability and spatial heterogeneity of the land surface, satellite remote sensing must be used to monitor albedo accurately at a global scale. However, large data gaps caused by cloud or ephemeral snow have slowed the adoption of satellite albedo products by the climate modeling community. To address the needs of this community, we used a number of temporal and spatial gap-filling strategies to improve the spatial and temporal coverage of the global land surface MODIS BRDF, albedo and NBAR products. A rigorous evaluation of the gap-filled values shows good agreement with original high quality data (RMSE = 0.027 for the NIR band albedo, 0.020 for the red band albedo). This global snow-free and cloud-free MODIS BRDF and albedo dataset (established from 2001 to 2015) offers unique opportunities to monitor and assess the impact of the changes on the Earth's land surface.

  15. An energy balance model exploration of the impacts of interactions between surface albedo, cloud cover and water vapor on polar amplification

    Science.gov (United States)

    Södergren, A. Helena; McDonald, Adrian J.; Bodeker, Gregory E.

    2017-11-01

    We examine the effects of non-linear interactions between surface albedo, water vapor and cloud cover (referred to as climate variables) on amplified warming of the polar regions, using a new energy balance model. Our simulations show that the sum of the contributions to surface temperature changes due to any variable considered in isolation is smaller than the temperature changes from coupled feedback simulations. This non-linearity is strongest when all three climate variables are allowed to interact. Surface albedo appears to be the strongest driver of this non-linear behavior, followed by water vapor and clouds. This is because increases in longwave radiation absorbed by the surface, related to increases in water vapor and clouds, and increases in surface absorbed shortwave radiation caused by a decrease in surface albedo, amplify each other. Furthermore, our results corroborate previous findings that while increases in cloud cover and water vapor, along with the greenhouse effect itself, warm the polar regions, water vapor also significantly warms equatorial regions, which reduces polar amplification. Changes in surface albedo drive large changes in absorption of incoming shortwave radiation, thereby enhancing surface warming. Unlike high latitudes, surface albedo change at low latitudes are more constrained. Interactions between surface albedo, water vapor and clouds drive larger increases in temperatures in the polar regions compared to low latitudes. This is in spite of the fact that, due to a forcing, cloud cover increases at high latitudes and decreases in low latitudes, and that water vapor significantly enhances warming at low latitudes.

  16. Urbanization Process and Variation of Energy Budget of Land Surfaces

    Directory of Open Access Journals (Sweden)

    Ciro Gardi

    2007-06-01

    Full Text Available Urban areas are increasing at a rate much higher than human population growth in many part of the world; actually more than 73 towns in the world are larger than 1000 km2. The European Environmental Agency indicates an urban area average growth rate, over the last 20 years, of 20%. The urbanization process, and the consequent soil sealing, determines not only the losses of the ecological functions of the soil, but also a variation of the energy budget of land surfaces, that affect the microclimatic conditions (heat islands. The alteration of the energy budget are determined by the variations of albedo and roughness of surfaces, but especially by the net losses of evapotranspirating areas. In the present research we have assessed the variation of Parma territory energy budget, induced by the change in land use over the last 122 years. The urban area increase between 1881 and 2003 was 535%.

  17. Variations in water clarity and bottom albedo in Florida Bay from 1985 to 1997

    Science.gov (United States)

    Stumpf, R.P.; Frayer, M.L.; Durako, M.J.; Brock, J.C.

    1999-01-01

    toward Big Pine Key, indicating changes in the bottom cover from before the die-off. The southern and eastern sections of the Bay have not shown significant changes in water clarity or bottom albedo throughout the entire time period.

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

    Science.gov (United States)

    Lei, Ruibo; Tian-Kunze, Xiangshan; Leppäranta, Matti; Wang, Jia; Kaleschke, Lars; Zhang, Zhanhai

    2016-08-01

    SSM/I sea ice concentration and CLARA black-sky composite albedo were used to estimate sea ice albedo in the region 70°N-82°N, 130°W-180°W. The long-term trends and seasonal evolutions of ice concentration, composite albedo, and ice albedo were then obtained. In July-August 1982-2009, the linear trend of the composite albedo and the ice albedo was -0.069 and -0.046 units per decade, respectively. During 1 June to 19 August, melting of sea ice resulted in an increase of solar heat input to the ice-ocean system by 282 MJ·m-2 from 1982 to 2009. However, because of the counter-balancing effects of the loss of sea ice area and the enhanced ice surface melting, the trend of solar heat input to the ice was insignificant. The summer evolution of ice albedo matched the ice surface melting and ponding well at basin scale. The ice albedo showed a large difference between the multiyear and first-year ice because the latter melted completely by the end of a melt season. At the SHEBA geolocations, a distinct change in the ice albedo has occurred since 2007, because most of the multiyear ice has been replaced by first-year ice. A positive polarity in the Arctic Dipole Anomaly could be partly responsible for the rapid loss of summer ice within the study region in the recent years by bringing warmer air masses from the south and advecting more ice toward the north. Both these effects would enhance ice-albedo feedback.

  19. Albedo à superfície a partir de imagens Landsat 5 em áreas de cana-de-açúcar e cerrado Surface albedo from Landsat 5 images in areas of sugar cane and cerrado

    Directory of Open Access Journals (Sweden)

    Pedro R. Giongo

    2010-03-01

    Full Text Available Propôs-se, neste trabalho, estimar dados de albedo à superfície terrestre usando-se o sensor Thematic Mapper (TM do satélite LANDSAT 5 e compará-lo com dados de duas estações agrometeorológicas localizadas em região de Cerrado e a outra em cultivo da cana-de-açúcar. A região de estudo está localizada no município de Santa Rita do Passa Quatro, SP, Brasil. Para a realização do estudo obtiveram-se seis imagens orbitais do satélite Landsat 5 sensores TM, na órbita 220 e ponto 75, nas datas de 22/02, 11/04, 29/05, 01/08, 17/08 e 21/11, todas do ano de 2005, a que correspondem os dias juliano de 53, 101, 149, 213, 229 e 325, respectivamente. As correções geométricas para as imagens foram realizadas e geradas as cartas de albedo. O algoritmo SEBAL estimou satisfatoriamente os valores de albedo de superfícies sobre áreas de cerrado e de cana-de-açúcar, na região de Santa Rita do Passa Quatro, SP, consistentes com observações realizadas do albedo à superfície.This study aimed to estimate albedo data from the land surface sensor using the images of Thematic Mapper (TM satellite LANDSAT 5 and to compare it with data from two agrometeorological stations located in the region of Cerrado, and another in sugar cane cultivation. The study area is located in the municipality of Santa Rita do Passa Quatro - SP, Brazil. To carry out the study six orbital images were obtained from the satellite Landsat 5 TM sensors in the orbit 220 and in the section 75, for the dates of 22/02, 11/04, 29/05, 01/08, 17/08 and 21/11 (all in the year of 2005 which correspond to the days 53, 101, 149, 213, 229 and 325, respectively. The geometric correction for images was performed and the letters of albedo were generated. The algorithm SEBAL estimated, satisfactorily, the values of albedo on the surface areas of Cerrado and sugar cane in the region of Santa Rita do Passa Quatro - SP, consistent with observations made of the surface albedo.

  20. The influence of rolled erosion control systems on soil temperature and surface albedo: part I. A greenhouse experiment

    International Nuclear Information System (INIS)

    Sutherland, R.A.; Menard, T.; Perry, J.L.; Penn, D.C.

    1998-01-01

    A greenhouse study examined the influences of various surface covers (a bare control soil and seven rolled erosion control systems—RECS) on surface radiative properties, and soil temperature. In our companion paper we examine relationships with soil moisture, biomass production, and nutrient assimilation. Randomization and replication were key components to our study of microclimate under tropical radiation conditions. The bare Oxisol control soil exhibited the most extreme microclimatic conditions with the lowest albedo (not significantly different from that of P300© North American Green, a dark green polypropylene system), and the highest mean and maximum hourly temperatures recorded at depths of 5 and 8 cm. This hostile climatic environment was not conducive to biomass production or moisture storage and it is likely that the observed soil surface crusts impeded plant emergence. Rolled erosion control systems, on the other hand, generally moderated soil temperatures by reflecting more shortwave radiation, implying less heat energy at the surface for conduction to the soil. The result was that RECS exhibited lower mean soil temperatures, higher minimum temperatures and lower maximum soil temperatures. An aspen excelsior system (Curlex I© Excelsior) had the highest albedo and the soil beneath this system exhibited the greatest temperature modulation. Open-weave systems composed of jute (Geojute© Price & Pictures) and coconut fibers (BioD-Mat 70© RoLanka) were the RECS most similar in temperature response to the bare control soil. Other systems examined were intermediate in their temperature response and surface albedo (i.e., SC150BN© North American Green, C125© North American Green and Futerra© Conwed Fibers). (author)

  1. Observations of Surfzone Albedo

    Science.gov (United States)

    Sinnett, G.; Feddersen, F.

    2014-12-01

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

  2. Fire-induced albedo change and surface radiative forcing in sub-Saharan Africa savanna ecosystems: Implications for the energy balance

    Science.gov (United States)

    Dintwe, Kebonye; Okin, Gregory S.; Xue, Yongkang

    2017-06-01

    Surface albedo is a critical parameter that controls surface energy balance. In dryland ecosystems, fires play a significant role in decreasing surface albedo, resulting in positive radiative forcing. Here we investigate the long-term effect of fire on surface albedo. We devised a method to calculate short-, medium-, and long-term effect of fire-induced radiative forcing and their relative effects on energy balance. We used Moderate Resolution Imaging Spectroradiometer (MODIS) data in our analysis, covering different vegetation classes in sub-Saharan Africa (SSA). Our analysis indicated that mean short-term fire-induced albedo change in SSA was -0.022, -0.035, and -0.041 for savannas, shrubland, and grasslands, respectively. At regional scale, mean fire-induced albedo change in savannas was -0.018 and -0.024 for northern sub-Saharan of Africa and the southern hemisphere Africa, respectively. The short-term mean fire-induced radiative forcing in burned areas in sub-Saharan Africa (SSA) was 5.41 W m-2, which contributed continental and global radiative forcings of 0.25 and 0.058 W m-2, respectively. The impact of fire in surface albedo has long-lasting effects that varies with vegetation type. The long-term energetic effects of fire-induced albedo change and associated radiative forcing were, on average, more than 19 times greater across SSA than the short-term effects, suggesting that fires exerted far more radiative forcing than previously thought. Taking into account the actual duration of fire's effect on surface albedo, we conclude that the contribution of SSA fires, globally and throughout the year, is 0.12 W m-2. These findings provide crucial information on possible impact of fire on regional climate variability.

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

    Directory of Open Access Journals (Sweden)

    Silvia N.M. Yanagi

    Full Text Available 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 radiation transfer code to incorporate the effects of canopy wetness on the vegetation reflectance. In this study, simulations were run using three versions of the land surface/ecosystem model IBIS: the standard version, the same version recalibrated to fit the data of albedo on tropical rainforests and a modified version that incorporates the effects of canopy wetness on surface albedo, for three sites in the Amazon forest at hourly and monthly scales. The results demonstrated that, at the hourly time scale, the incorporation of canopy wetness on the calculations of radiative transfer substantially improves the simulations results, whereas at the monthly scale these changes do not substantially modify the simulated albedo.

  4. Neutron Albedo

    CERN Document Server

    Ignatovich, V K

    2005-01-01

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

  5. Correction of sub-pixel topographical effects on land surface albedo retrieved from geostationary satellite (FengYun-2D) observations

    International Nuclear Information System (INIS)

    Roupioz, L; Nerry, F; Jia, L; Menenti, M

    2014-01-01

    The Qinghai-Tibetan Plateau is characterised by a very strong relief which affects albedo retrieval from satellite data. The objective of this study is to highlight the effects of sub-pixel topography and to account for those effects when retrieving land surface albedo from geostationary satellite FengYun-2D (FY-2D) data with 1.25km spatial resolution using the high spatial resolution (30 m) data of the Digital Elevation Model (DEM) from ASTER. The methodology integrates the effects of sub-pixel topography on the estimation of the total irradiance received at the surface, allowing the computation of the topographically corrected surface reflectance. Furthermore, surface albedo is estimated by applying the parametric BRDF (Bidirectional Reflectance Distribution Function) model called RPV (Rahman-Pinty-Verstraete) to the terrain corrected surface reflectance. The results, evaluated against ground measurements collected over several experimental sites on the Qinghai-Tibetan Plateau, document the advantage of integrating the sub-pixel topography effects in the land surface reflectance at 1km resolution to estimate the land surface albedo. The results obtained after using sub-pixel topographic correction are compared with the ones obtained after using pixel level topographic correction. The preliminary results imply that, in highly rugged terrain, the sub-pixel topography correction method gives more accurate results. The pixel level correction tends to overestimate surface albedo

  6. Comparing MODIS-Terra and GOES surface albedo for New York City NY, Baltimore MD and Washington DC for 2005

    Science.gov (United States)

    Mubenga, K.; Hoff, R.; McCann, K.; Chu, A.; Prados, A.

    2006-05-01

    The NOAA GOES Aerosol and Smoke Product (GASP) is a product displaying the Aerosol Optical Depth (AOD) over the United States. The GASP retrieval involves discriminating the upwelling radiance from the atmosphere from that of the variable underlying surface. Unlike other sensors with more visible and near- infrared spectral channels such as MODIS, the sensors on GOES 8 through 12 only have one visible and a several far infrared channels. The GASP algorithm uses the detection of the second-darkest pixel from the visible channel over a 28-day period as the reference from which a radiance look-up table gives the corresponding AOD. GASP is reliable in capturing the AOD during large events. As an example, GASP was able to precisely show the Alaska and British Columbia smoke plume advecting from Alaska to the northeastern U.S. during the summer of 2004. Knapp et al. (2005) has shown that the AOD retrieval for GOES- 8 is within +/-0.13 of AERONET ground data with a coefficient of correlation of 0.72. Prados (this meeting) will update that study. However, GASP may not be as reliable when it comes to observing smaller AOD events in the northeast where the surface brightness is relatively high. The presence of large cities, such as New York, increases the surface albedo and produces a bright background against which it may be difficult to deduce the AOD. The Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the Earth Observing System Terra and Aqua platforms provides an independent measurement of the surface albedo at a resolution greater than available on GOES. In this research, the MODIS and GOES surface albedo product for New York, Washington and Baltimore are compared in order to see how we can improve the AOD retrieval in urban areas for air quality applications. Ref: K. Knapp et al. 2005. Toward aerosol optical depth retrievals over land from GOES visible radiances: determining surface reflectance. Int.Journal of Remote Sensing 26, 4097-4116

  7. Variation of Arctic's Sea-ice Albedo between 2000 and 2016 by fusion of MISR and MODIS data

    Science.gov (United States)

    Muller, Jan-Peter; Kharbouche, Said

    2017-04-01

    Many research studies have demonstrated that sea-ice plays a key role in climate change and global warming. Most of these studies are based either on ground in-situ data or on remotely sensed data. The latter data are provided mainly by active (SAR and LiDAR) sensors such as Cryosat2, ERS1/2, ENVISAT, Radarsat1/2, ICESat as well as passive sensors such as SSM/I. Nevertheless, the contribution of such active optical sensors data is limited to parameters such as thickness and sea-ice concentration from which albedo may be inferred. The creation of high quality albedo for sea-ice using optical satellites is confronted with two main obstacles: 1) the Arctic is a very cloudy region and, high quality albedo requires multi-angle observations over a relatively short period; 2) cloud masking over sea-ice is a very difficult task, especially for sensor with low spectral resolution. To overcome the above two obstacles, we discuss in a separate report the generation of this fused daily, weekly, fortnightly and monthly product at 1km and 5km resolution on a polar stereographic grid [1]. The limited swath (380km) of MISR means that not all of the Arctic is covered on a daily basis so composites on different time-steps were produced. The results show that sea-ice albedo has been in continuous decline since 2000 with thinner sea-ice and greater leads and open water as well as more ponding at earlier times in the year. The implications of these results are discussed in terms of the sea-ice climate feedback. Animated visualisations of the albedo patterns each year, the decline in average and the increase in standard deviation in albedo for every single day for all 17 years will be shown to demonstrate the effects of climate change over sea-ice albedo. References [1] Kharbouche & Muller, Production of Arctic sea-ice albedo by fusion of MISR and MODIS data. This conference. Acknowledgements This work was supported by www.QA4ECV.eu, a project of European Union's Seventh Framework

  8. Deriving a global land surface albedo product from Landsat MSS, TM, ETM+, and OLI data based on the unified direct estimation approach

    Science.gov (United States)

    Surface albedo is widely used in climate and environment applications as an important parameter for controlling the surface energy budget. There is an increasing need for fine resolution (data for use in small scale applications and for validating coarse-resolution datasets; however,...

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

    OpenAIRE

    A. A. Marks; M. D. King

    2013-01-01

    The response of the albedo of bare sea ice and snow-covered sea ice to the addition of black carbon is calculated. Visible light absorption and light-scattering cross-sections are derived for a typical first-year and multi-year sea ice with both "dry" and "wet" snow types. The cross-sections are derived using data from a 1970s field study that recorded both reflectivity and light penetration in Arctic sea ice and snow overlying sea ice. The variation of absorption cross-section ov...

  10. Effect of surface albedo, water vapour, and atmospheric aerosols on the cloud-free shortwave radiative budget in the Arctic

    Energy Technology Data Exchange (ETDEWEB)

    Di Biagio, C. [ENEA, Laboratory for Earth Observations and Analyses, Rome (Italy); University of Siena, Department of Earth Science, Siena (Italy); Di Sarra, A. [ENEA, Laboratory for Earth Observations and Analyses, Rome (Italy); Eriksen, P. [Danish Climate Centre, DMI, Danish Meteorological Institute, Copenhagen (Denmark); Ascanius, S.E. [DMI, Danish Meteorological Institute, Qaanaaq (Greenland); Muscari, G. [INGV, Istituto Nazionale di Geofisica e Vulcanologia, Rome (Italy); Holben, B. [NASA Goddard Space Flight Center, Greenbelt, MD (United States)

    2012-08-15

    This study is based on ground-based measurements of downward surface shortwave irradiance (SW), columnar water vapour (wv), and aerosol optical depth ({tau}) obtained at Thule Air Base (Greenland) in 2007-2010, together with MODIS observations of the surface shortwave albedo (A). Radiative transfer model calculations are used in combination with measurements to separate the radiative effect of A ({Delta}SW{sub A}), wv ({Delta}SW{sub wv}), and aerosols ({Delta}SW{sub {tau}}) in modulating SW in cloud-free conditions. The shortwave radiation at the surface is mainly affected by water vapour absorption, which produces a reduction of SW as low as -100 Wm{sup -2} (-18%). The seasonal change of A produces an increase of SW by up to +25 Wm{sup -2} (+4.5%). The annual mean radiative effect is estimated to be -(21-22) Wm{sup -2} for wv, and +(2-3) Wm{sup -2} for A. An increase by +0.065 cm in the annual mean wv, to which corresponds an absolute increase in {Delta}SW{sub wv} by 0.93 Wm{sup -2} (4.3%), has been observed to occur between 2007 and 2010. In the same period, the annual mean A has decreased by -0.027, with a corresponding decrease in {Delta}SW{sub A} by 0.41 Wm{sup -2} (-14.9%). Atmospheric aerosols produce a reduction of SW as low as -32 Wm{sup -2} (-6.7%). The instantaneous aerosol radiative forcing (RF{sub {tau}}) reaches values of -28 Wm{sup -2} and shows a strong dependency on surface albedo. The derived radiative forcing efficiency (FE{sub {tau}}) for solar zenith angles between 55 and 70 is estimated to be (-120.6 {+-} 4.3) for 0.1 < A < 0.2, and (-41.2 {+-} 1.6) Wm{sup -2} for 0.5 < A < 0.6. (orig.)

  11. Development of a Novel Multispectral Instrument for Handheld and UAS Measurements of Surface Albedo; First Applications for Glaciers in the Peruvian Andes and for Nevada's Black Rock Desert

    Science.gov (United States)

    Boehmler, J. M.; Stevens, C.; Arnott, W. P.; Watts, A.; All, J.; Schmitt, C. G.

    2017-12-01

    Accurate atmospheric aerosol characteristics derived from satellite measurements are needed over a variety of land surfaces. Nonhomogeneous and bright surface reflectance across California and Nevada may be a contributing factor in the discrepancies observed between ground based and satellite-retrieved atmospheric aerosol optical depth (AOD). We developed and deployed a compact and portable instrument to measure albedo to evaluate a major factor that influences the accuracy of AOD retrievals. The instrument will be operated on an unmanned aircraft system (UAS) to control areal averaging for comparison with satellite derived albedo from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS). A handheld version of the instrument was mounted on a trekking pole and used for obtaining in situ glacier albedo measurements in the Cordillera Blanca of Peru during the summer of 2017. The instrument weighs approximately 433 g and consists of two parts, a mountable, payload portion (300 g) which houses the sensors, and a handheld screen (133 g) to display real-time data from the payload portion. Both parts are powered by a 9V battery and run on a Teensy 3.6/3.2 microcontroller. To retrieve albedo, two micro-spectrometers manufactured by Hamamatsu Photonics, each with a spectral range of 340 -780 nm, are utilized; one for obtaining the downwelling solar radiation and the other for measuring the solar radiation reflected from the surface. Additional components on the instrument include temperature, pressure and humidity sensors with a one second time response; a GPS for position and altitude; an infrared sensor to measure ground temperature; a digital level and compass for orienting the instrument; a camera for taking photos of the sky and surface; a radio for two-way communication between the screen display and sensor payload; and a micro SD card for recording data. We will present the instrument design along with surface albedo measurements for glaciers of the Peruvian

  12. Unexpected and Unexplained Surface Temperature Variations on Mimas

    Science.gov (United States)

    Howett, C.; Spencer, J. R.; Pearl, J. C.; Hurford, T. A.; Segura, M.; Cassini Cirs Team

    2010-12-01

    Until recently it was thought one of the most interesting things about Mimas, Saturn’s innermost classical icy moon, was its resemblance to Star Wars’ Death Star. However, a bizarre pattern of daytime surface temperatures was observed on Mimas using data obtained by Cassini’s Composite Infrared Spectrometer (CIRS) in February 2010. The observations were taken during Cassini’s closest ever encounter with Mimas (<10,000 km) and cover the daytime anti-Saturn hemisphere centered on longitude ~145° W. Instead of surface temperatures smoothly increasing throughout the morning and early afternoon, then cooling in the evening, as expected, a sharp V-shaped boundary is observed separating cooler midday and afternoon temperatures (~77 K) on the leading side from warmer morning temperatures (~92 K) on the trailing side. The boundary’s apex is centered at equatorial latitudes near the anti-Saturn point and extends to low north and south latitudes on the trailing side. Subtle differences in the surface colors have been observed that are roughly spatially correlated with the observed extent of the temperature anomaly, with the cooler regions tending to be bluer (Schenk et al., Submitted). However, visible-wavelength albedo is similar in the two regions, so albedo variations are probably not directly responsible for the thermal anomaly. It is more likely that thermal inertia variations produce the anomaly, with thermal inertia being unusually high in the region with anomalously low daytime temperatures. Comparison of the February 2010 CIRS data to previous lower spatial resolution data taken at different local times tentatively confirm that the cooler regions do indeed display higher thermal inertias. Bombardment of the surface by high energy electrons from Saturn’s radiation belts has been proposed to explain the observed color variations (Schenk et al., Submitted). Electrons above ~1 MeV preferentially impact Mimas’ leading hemisphere at low latitudes where they

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

    Directory of Open Access Journals (Sweden)

    L. Zhu

    2012-12-01

    Full Text Available This study develops an algorithm for representing detailed spectral features of vegetation albedo based on Moderate Resolution Imaging Spectrometer (MODIS observations at 7 discrete channels, referred to as the MODIS Enhanced Vegetation Albedo (MEVA algorithm. The MEVA algorithm empirically fills spectral gaps around the vegetation red edge near 0.7 μm and vegetation water absorption features at 1.48 and 1.92 μm which cannot be adequately captured by the MODIS 7 channels. We then assess the effects of applying MEVA in comparison to four other traditional approaches to calculate solar fluxes and aerosol direct radiative forcing (DRF at the top of atmosphere (TOA based on the MODIS discrete reflectance bands. By comparing the DRF results obtained through the MEVA method with the results obtained through the other four traditional approaches, we show that filling the spectral gap of the MODIS measurements around 0.7 μm based on the general spectral behavior of healthy green vegetation leads to significant improvement in the instantaneous aerosol DRF at TOA (up to 3.02 W m−2 difference or 48% fraction of the aerosol DRF, −6.28 W m−2, calculated for high spectral resolution surface reflectance from 0.3 to 2.5 μm for deciduous vegetation surface. The corrections of the spectral gaps in the vegetation spectrum in the near infrared, again missed by the MODIS reflectances, also contributes to improving TOA DRF calculations but to a much lower extent (less than 0.27 W m−2, or about 4% of the instantaneous DRF.

    Compared to traditional approaches, MEVA also improves the accuracy of the outgoing solar flux between 0.3 to 2.5 μm at TOA by over 60 W m−2 (for aspen 3 surface and aerosol DRF by over 10 W m−2 (for dry grass. Specifically, for Amazon vegetation types, MEVA can improve the accuracy of daily averaged aerosol radiative forcing in the spectral range of 0.3 to 2.5 μm at

  14. Observing at-surface irradiance and albedo from space : The Tibet experiment

    NARCIS (Netherlands)

    Roupioz, L.

    2015-01-01

    Monitoring the solar radiation budget on a daily basis is a prerequisite to study land surface processes, especially in climatology and hydrology, and in derived applications like drought early warning. Current space-born radiometers can provide daily observations to derive surface radiative fluxes

  15. Quantification of seasonal to annual mass balances from glacier surface albedo derived from optical satellite images, application on 30 glaciers in the French Alps for the period 2000-2015.

    Science.gov (United States)

    Davaze, Lucas; Rabatel, Antoine; Arnaud, Yves; Sirguey, Pascal; Six, Delphine; Letreguilly, Anne; Dumont, Marie

    2017-04-01

    Increasing the number of glaciers monitored for surface mass balance is very challenging, especially using laborious methods based on in situ data. Complementary methods are therefore required to quantify the surface mass balance of unmonitored glaciers. The current study relies on the so-called albedo method, based on the analysis of albedo maps retrieved from optical satellite imagery acquired since 2000 by the MODIS sensor, onboard of TERRA satellite. Recent studies performed on single glaciers in the French Alps, the Himalayas or the Southern Alps of New Zealand revealed substantial relationships between summer minimum glacier-wide surface albedo and annual mass balance, because this minimum surface albedo is directly related to accumulation-area ratio and the equilibrium-line altitude. On the basis of 30 glaciers located in the French Alps where annual surface mass balance are available, our study conducted on the period 2000-2015 confirms the robustness and reliability of the relationship between the summer minimum surface albedo and the annual surface mass balance. At the seasonal scale, the integrated summer surface albedo is significantly correlated with the summer mass balance of the six glaciers seasonally surveyed. For the winter season, four of the six glaciers showed a significant correlation when linking the winter surface mass balance and the integrated winter surface albedo, using glacier-dependent thresholds to filter the albedo signal. Sensitivity study on the computed cloud detection algorithm revealed high confidence in retrieved albedo maps. These results are promising to monitor both annual and seasonal glacier-wide surface mass balances of individual glaciers at a regional scale using optical satellite images.

  16. Effects of illumination differences on photometric stereo shape-and-albedo-from-shading for precision lunar surface reconstruction

    Science.gov (United States)

    Chung Liu, Wai; Wu, Bo; Wöhler, Christian

    2018-02-01

    Photoclinometric surface reconstruction techniques such as Shape-from-Shading (SfS) and Shape-and-Albedo-from-Shading (SAfS) retrieve topographic information of a surface on the basis of the reflectance information embedded in the image intensity of each pixel. SfS or SAfS techniques have been utilized to generate pixel-resolution digital elevation models (DEMs) of the Moon and other planetary bodies. Photometric stereo SAfS analyzes images under multiple illumination conditions to improve the robustness of reconstruction. In this case, the directional difference in illumination between the images is likely to affect the quality of the reconstruction result. In this study, we quantitatively investigate the effects of illumination differences on photometric stereo SAfS. Firstly, an algorithm for photometric stereo SAfS is developed, and then, an error model is derived to analyze the relationships between the azimuthal and zenith angles of illumination of the images and the reconstruction qualities. The developed algorithm and error model were verified with high-resolution images collected by the Narrow Angle Camera (NAC) of the Lunar Reconnaissance Orbiter Camera (LROC). Experimental analyses reveal that (1) the resulting error in photometric stereo SAfS depends on both the azimuthal and the zenith angles of illumination as well as the general intensity of the images and (2) the predictions from the proposed error model are consistent with the actual slope errors obtained by photometric stereo SAfS using the LROC NAC images. The proposed error model enriches the theory of photometric stereo SAfS and is of significance for optimized lunar surface reconstruction based on SAfS techniques.

  17. Atmospheric sensitivity to land surface changes: comparing the impact of albedo, roughness, and evaporative resistance on near-surface air temperature using an idealized land model.

    Science.gov (United States)

    Lague, M. M.; Swann, A. L. S.; Bonan, G. B.

    2017-12-01

    Past studies have demonstrated how changes in vegetation can impact the atmosphere; however, it is often difficult to identify the exact physical pathway through which vegetation changes drive an atmospheric response. Surface properties (such as vegetation color, or height) control surface energy fluxes, which feed back on the atmosphere on both local and global scales by modifying temperatures, cloud cover, and energy gradients. Understanding how land surface properties influence energy fluxes is crucial for improving our understanding of how vegetation change - past, present, and future - impacts the atmosphere, global climate, and people. We explore the sensitivity of the atmosphere to perturbations of three land surface properties - albedo, roughness, and evaporative resistance - using an idealized land model coupled to an Earth System Model. We derive a relationship telling us how large a change in each surface property is required to drive a local 0.1 K change in 2m air temperature. Using this idealized framework, we are able to separate the influence on the atmosphere of each individual surface property. We demonstrate that the impact of each surface property on the atmosphere is spatially variable - that is, a similar change in vegetation can have different climate impacts if made in different locations. This analysis not only improves our understanding of how the land system can influence climate, but also provides us with a set of theoretical limits on the potential climate impact of arbitrary vegetation change (natural or anthropogenic).

  18. Early Spring Post-Fire Snow Albedo Dynamics in High Latitude Boreal Forests Using Landsat-8 OLI Data

    Science.gov (United States)

    Wang, Zhuosen; Erb, Angela M.; Schaaf, Crystal B.; Sun, Qingsong; Liu, Yan; Yang, Yun; Shuai, Yanmin; Casey, Kimberly A.; Roman, Miguel O.

    2016-01-01

    Taking advantage of the improved radiometric resolution of Landsat-8 OLI which, unlike previous Landsat sensors, does not saturate over snow, the progress of fire recovery progress at the landscape scale (less than 100 m) is examined. High quality Landsat-8 albedo retrievals can now capture the true reflective and layered character of snow cover over a full range of land surface conditions and vegetation densities. This new capability particularly improves the assessment of post-fire vegetation dynamics across low- to high-burn severity gradients in Arctic and boreal regions in the early spring, when the albedos during recovery show the greatest variation. We use 30 m resolution Landsat-8 surface reflectances with concurrent coarser resolution (500 m) MODIS high quality full inversion surface Bidirectional Reflectance Distribution Functions (BRDF) products to produce higher resolution values of surface albedo. The high resolution full expression shortwave blue sky albedo product performs well with an overall RMSE of 0.0267 between tower and satellite measures under both snow-free and snow-covered conditions. While the importance of post-fire albedo recovery can be discerned from the MODIS albedo product at regional and global scales, our study addresses the particular importance of early spring post-fire albedo recovery at the landscape scale by considering the significant spatial heterogeneity of burn severity, and the impact of snow on the early spring albedo of various vegetation recovery types. We found that variations in early spring albedo within a single MODIS gridded pixel can be larger than 0.6. Since the frequency and severity of wildfires in Arctic and boreal systems is expected to increase in the coming decades, the dynamics of albedo in response to these rapid surface changes will increasingly impact the energy balance and contribute to other climate processes and physical feedback mechanisms. Surface radiation products derived from Landsat-8 data will

  19. Overlapping constraint for variational surface reconstruction

    DEFF Research Database (Denmark)

    Aanæs, Henrik; Solem, J.E.

    2005-01-01

    In this paper a counter example, illustrating a shortcoming in most variational formulations for 3D surface estimation, is presented. The nature of this shortcoming is a lack of an overlapping constraint. A remedy for this shortcoming is presented in the form of a penalty function with an analysi...... of the effects of this function on surface motion. For practical purposes, this will only have minor influence on current methods. However, the insight provided in the analysis is likely to influence future developments in the field of variational surface reconstruction....

  20. Improving snow albedo processes in WRF/SSiB regional climate model to assess impact of dust and black carbon in snow on surface energy balance and hydrology over western U.S.

    OpenAIRE

    Oaida, CM; Xue, Y; Flanner, MG; Skiles, SMK; De Sales, F; Painter, TH

    2015-01-01

    © 2015. American Geophysical Union. All Rights Reserved. Two important factors that control snow albedo are snow grain growth and presence of light-absorbing impurities (aerosols) in snow. However, current regional climate models do not include such processes in a physically based manner in their land surface models. We improve snow albedo calculations in the Simplified Simple Biosphere (SSiB) land surface model coupled with the Weather Research and Forecasting (WRF) regional climate model (R...

  1. The Effects of Surface Properties and Albedo on Methane Retrievals with the Airborne Visible/Infrared Imaging Spectrometer Next Generation (AVIRIS-NG)

    Science.gov (United States)

    Ayasse, A.; Thorpe, A. K.; Roberts, D. A.

    2017-12-01

    Atmospheric methane has increased by a factor of 2.5 since the beginning of the industrial era in response to anthropogenic emissions (Ciais et al., 2013). Although it is less abundant than carbon dioxide it is 86 time more potent on a 20 year time scale (Myhre et al., 2013) and is therefore responsible for about 20% of the total global warming induced by anthropogenic greenhouse gasses (Kirschke et al., 2013). Given the importance of methane to global climate change, monitoring and measuring methane emissions using techniques such as remote sensing is of increasing interest. Recently the Airborne Visible-Infrared Imaging Spectrometer - Next Generation (AVIRIS-NG) has proven to be a valuable instrument for quantitative mapping of methane plumes (Frankenberg et al., 2016; Thorpe et al., 2016; Thompson et al., 2015). In this study, we applied the Iterative Maximum a Posterior Differential Optical Spectroscopy (IMAP-DOAS) methane retrieval algorithm to a synthetic image with variable methane concentrations, albedo, and land cover. This allowed for characterizing retrieval performance, including potential sensitivity to variable land cover, low albedo surfaces, and surfaces known to cause spurious signals. We conclude that albedo had little influence on the IMAP-DOAS results except at very low radiance levels. Water (without sun glint) was found to be the most challenging surface for methane retrievals while hydrocarbons and some green vegetation also caused error. Understanding the effect of surface properties on methane retrievals is important given the increased use of AVIRIS-NG to map gas plumes over diverse locations and methane sources. This analysis could be expanded to include additional gas species like carbon dioxide and to further investigate gas sensitivity of proposed instruments for dedicated gas mapping from airborne and spaceborne platforms.

  2. Long-term archives of land surface albedo products through the EUMETSAT/LSA-SAF and ECMWF/C3S projects: status and project development plan

    Science.gov (United States)

    Carrer, D.; Pinault, F.; Ceamanos, X.; Meurey, C.; Moparthy, S.; Swinnen, E.; Trigo, I.

    2017-12-01

    The two space programs of EUMETSAT (project CDOP3, LSA-SAF) and ECMWF (the Copernicus Climate Change Service; C3S_312a Lot9) provide (or will provide) added-value satellite products for the meteorological and environmental science communities, especially in the fields of climate modeling, environmental management, natural hazards management, and climate change detection. The EUMETSAT/LSA-SAF project started in 1999 with research and development activities. The Third Continuous Development and Operations Phase (CDOP-3) starts in March 2017 and will end in 2022. This project uses instruments on board European satellites that were, or will be, launched between 2004 and 2022. Unlike the LSA-SAF, the COPERNICUS/C3S_312a project has no NRT constraint. Its first phase started in november 2016. One of the major objective of the COPERNICUS/C3S_312a project is to harmonize datasets from various sensors in order to provide consistent and continuous ECV products from the 80's until now.Presently, the delivered operational products comprise several surface albedo products using data from various space missions (METEOSAT, NOAA, METOP, …). We present here the portfolio of the surface albedo products that are disseminated with an operational status. Their characteristics and accuracy are detailed here after. Also we will present the development plan to produce long-term re-analysis and to prepare the arrival of the next generation of satellite (MTG, EPS-SG, ...). This work will lead in 2018 to 40 years of products characterizing the albedo properties of the surface. These programs provide a great opportunity to monitor and identify human-induced climate change since consistent production of data sets is guaranteed until at least 2022.

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

    OpenAIRE

    Lei, Ruibo; Tian-Kunze, Xiangshan; Leppäranta, Matti; Wang, Jia; Kaleschke, Lars; Zhang, Zhanhai

    2016-01-01

    SSM/I sea ice concentration and CLARA black-sky composite albedo were used to estimate sea ice albedo in the region 70 degrees N-82 degrees N, 130 degrees W-180 degrees W. The long-term trends and seasonal evolutions of ice concentration, composite albedo, and ice albedo were then obtained. In July-August 1982-2009, the linear trend of the composite albedo and the ice albedo was -0.069 and -0.046 units per decade, respectively. During 1 June to 19 August, melting of sea ice resulted in an inc...

  4. The importance of accurate glacier albedo for estimates of surface mass balance on Vatnajökull: evaluating the surface energy budget in a regional climate model with automatic weather station observations

    Science.gov (United States)

    Steffensen Schmidt, Louise; Aðalgeirsdóttir, Guðfinna; Guðmundsson, Sverrir; Langen, Peter L.; Pálsson, Finnur; Mottram, Ruth; Gascoin, Simon; Björnsson, Helgi

    2017-07-01

    A simulation of the surface climate of Vatnajökull ice cap, Iceland, carried out with the regional climate model HIRHAM5 for the period 1980-2014, is used to estimate the evolution of the glacier surface mass balance (SMB). This simulation uses a new snow albedo parameterization that allows albedo to exponentially decay with time and is surface temperature dependent. The albedo scheme utilizes a new background map of the ice albedo created from observed MODIS data. The simulation is evaluated against observed daily values of weather parameters from five automatic weather stations (AWSs) from the period 2001-2014, as well as in situ SMB measurements from the period 1995-2014. The model agrees well with observations at the AWS sites, albeit with a general underestimation of the net radiation. This is due to an underestimation of the incoming radiation and a general overestimation of the albedo. The average modelled albedo is overestimated in the ablation zone, which we attribute to an overestimation of the thickness of the snow layer and not taking the surface darkening from dirt and volcanic ash deposition during dust storms and volcanic eruptions into account. A comparison with the specific summer, winter, and net mass balance for the whole of Vatnajökull (1995-2014) shows a good overall fit during the summer, with a small mass balance underestimation of 0.04 m w.e. on average, whereas the winter mass balance is overestimated by on average 0.5 m w.e. due to too large precipitation at the highest areas of the ice cap. A simple correction of the accumulation at the highest points of the glacier reduces this to 0.15 m w.e. Here, we use HIRHAM5 to simulate the evolution of the SMB of Vatnajökull for the period 1981-2014 and show that the model provides a reasonable representation of the SMB for this period. However, a major source of uncertainty in the representation of the SMB is the representation of the albedo, and processes currently not accounted for in RCMs

  5. The importance of accurate glacier albedo for estimates of surface mass balance on Vatnajökull: evaluating the surface energy budget in a regional climate model with automatic weather station observations

    Directory of Open Access Journals (Sweden)

    L. S. Schmidt

    2017-07-01

    Full Text Available A simulation of the surface climate of Vatnajökull ice cap, Iceland, carried out with the regional climate model HIRHAM5 for the period 1980–2014, is used to estimate the evolution of the glacier surface mass balance (SMB. This simulation uses a new snow albedo parameterization that allows albedo to exponentially decay with time and is surface temperature dependent. The albedo scheme utilizes a new background map of the ice albedo created from observed MODIS data. The simulation is evaluated against observed daily values of weather parameters from five automatic weather stations (AWSs from the period 2001–2014, as well as in situ SMB measurements from the period 1995–2014. The model agrees well with observations at the AWS sites, albeit with a general underestimation of the net radiation. This is due to an underestimation of the incoming radiation and a general overestimation of the albedo. The average modelled albedo is overestimated in the ablation zone, which we attribute to an overestimation of the thickness of the snow layer and not taking the surface darkening from dirt and volcanic ash deposition during dust storms and volcanic eruptions into account. A comparison with the specific summer, winter, and net mass balance for the whole of Vatnajökull (1995–2014 shows a good overall fit during the summer, with a small mass balance underestimation of 0.04 m w.e. on average, whereas the winter mass balance is overestimated by on average 0.5 m w.e. due to too large precipitation at the highest areas of the ice cap. A simple correction of the accumulation at the highest points of the glacier reduces this to 0.15 m w.e. Here, we use HIRHAM5 to simulate the evolution of the SMB of Vatnajökull for the period 1981–2014 and show that the model provides a reasonable representation of the SMB for this period. However, a major source of uncertainty in the representation of the SMB is the representation of the albedo, and processes

  6. Evaluation of MODIS albedo product (MCD43A) over grassland, agriculture and forest surface types during dormant and snow-covered periods

    Science.gov (United States)

    Zhuosen Wang; Crystal B. Schaaf; Alan H. Strahler; Mark J. Chopping; Miguel O. Román; Yanmin Shuai; Curtis E. Woodcock; David Y. Hollinger; David R. Fitzjarrald

    2014-01-01

    This study assesses the Moderate-resolution Imaging Spectroradiometer (MODIS) BRDF/albedo 8 day standard product and products from the daily Direct Broadcast BRDF/albedo algorithm, and shows that these products agree well with ground-based albedo measurements during the more difficult periods of vegetation dormancy and snow cover. Cropland, grassland, deciduous and...

  7. Variational mesh segmentation via quadric surface fitting

    KAUST Repository

    Yan, Dongming

    2012-11-01

    We present a new variational method for mesh segmentation by fitting quadric surfaces. Each component of the resulting segmentation is represented by a general quadric surface (including plane as a special case). A novel energy function is defined to evaluate the quality of the segmentation, which combines both L2 and L2 ,1 metrics from a triangle to a quadric surface. The Lloyd iteration is used to minimize the energy function, which repeatedly interleaves between mesh partition and quadric surface fitting. We also integrate feature-based and simplification-based techniques in the segmentation framework, which greatly improve the performance. The advantages of our algorithm are demonstrated by comparing with the state-of-the-art methods. © 2012 Elsevier Ltd. All rights reserved.

  8. Variational mesh segmentation via quadric surface fitting

    KAUST Repository

    Yan, Dongming; Wang, Wen Ping; Liu, Yang; Yang, Zhouwang

    2012-01-01

    We present a new variational method for mesh segmentation by fitting quadric surfaces. Each component of the resulting segmentation is represented by a general quadric surface (including plane as a special case). A novel energy function is defined to evaluate the quality of the segmentation, which combines both L2 and L2 ,1 metrics from a triangle to a quadric surface. The Lloyd iteration is used to minimize the energy function, which repeatedly interleaves between mesh partition and quadric surface fitting. We also integrate feature-based and simplification-based techniques in the segmentation framework, which greatly improve the performance. The advantages of our algorithm are demonstrated by comparing with the state-of-the-art methods. © 2012 Elsevier Ltd. All rights reserved.

  9. Seasonal albedo of an urban/rural landscape from satellite observations

    Science.gov (United States)

    Brest, Christopher L.

    1987-01-01

    Using data from 27 calibrated Landsat observations of the Hartford, Connecticut area, the spatial distribution and seasonal variation of surface reflectance and albedo were examined. Mean values of visible reflectance, near-IR reflectance, and albedo are presented (for both snow-free and snow-cover observations) according to 14 land use/land cover categories. A diversity of albedo values was found to exist in this type of environment, associated with land cover. Many land-cover categories display a seasonal dependence, with intracategory seasonal differences being of comparable magnitude to intercategory differences. Key factors in determining albedo (and its seasonal dynamics) are the presence or absence of vegetation and the canopy structure. Snow-cover/snow-free differences range from a few percent (for urban land covers) to over 40 percent (for low-canopy vegetation).

  10. Estimation of snow albedo reduction by light absorbing impurities using Monte Carlo radiative transfer model

    Science.gov (United States)

    Sengupta, D.; Gao, L.; Wilcox, E. M.; Beres, N. D.; Moosmüller, H.; Khlystov, A.

    2017-12-01

    Radiative forcing and climate change greatly depends on earth's surface albedo and its temporal and spatial variation. The surface albedo varies greatly depending on the surface characteristics ranging from 5-10% for calm ocean waters to 80% for some snow-covered areas. Clean and fresh snow surfaces have the highest albedo and are most sensitive to contamination with light absorbing impurities that can greatly reduce surface albedo and change overall radiative forcing estimates. Accurate estimation of snow albedo as well as understanding of feedbacks on climate from changes in snow-covered areas is important for radiative forcing, snow energy balance, predicting seasonal snowmelt, and run off rates. Such information is essential to inform timely decision making of stakeholders and policy makers. Light absorbing particles deposited onto the snow surface can greatly alter snow albedo and have been identified as a major contributor to regional climate forcing if seasonal snow cover is involved. However, uncertainty associated with quantification of albedo reduction by these light absorbing particles is high. Here, we use Mie theory (under the assumption of spherical snow grains) to reconstruct the single scattering parameters of snow (i.e., single scattering albedo ῶ and asymmetry parameter g) from observation-based size distribution information and retrieved refractive index values. The single scattering parameters of impurities are extracted with the same approach from datasets obtained during laboratory combustion of biomass samples. Instead of using plane-parallel approximation methods to account for multiple scattering, we have used the simple "Monte Carlo ray/photon tracing approach" to calculate the snow albedo. This simple approach considers multiple scattering to be the "collection" of single scattering events. Using this approach, we vary the effective snow grain size and impurity concentrations to explore the evolution of snow albedo over a wide

  11. 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.

  12. 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.

  13. Albedo of the ice-covered Weddell and Bellingshausen Sea

    OpenAIRE

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

    2011-01-01

    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 Sea 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 albed...

  14. Albedo distribution in Lutzow-Holm Bay and its neighborhood

    Directory of Open Access Journals (Sweden)

    Kiyotaka Nakagawa

    1997-03-01

    Full Text Available 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 with the daily means of ground-observed, unfiltered broad band albedo, despite systematic errors of about -4%. It is also clear that there is a characteristic pattern of surface albedo distribution in this area; the open sea has very low albedo of less than 5%, whereas most of the compact pack ice and fast ice has a high albedo of more than 60%. The albedo is lower in the eastern part of Lutzow-Holm Bay than in the western part; especially off the Soya Coast it is less than 40%. The ice sheet of Antarctica has a remarkably high albedo of more than 80%.

  15. Rock discontinuity surface roughness variation with scale

    Science.gov (United States)

    Bitenc, Maja; Kieffer, D. Scott; Khoshelham, Kourosh

    2017-04-01

    hypothesize that roughness can increase or decrease with the joint size, depending on the large scale roughness (or waviness), which is entering the roughness calculation once the discontinuity size increases. Therefore, our objective is to characterize roughness at various spatial scales, rather than at changing surface size. Firstly, the rock surface is interpolated into a grid on which a Discrete Wavelet Transform (DWT) is applied. The resulting surface components have different frequencies, or in other words, they have a certain physical scale depending on the decomposition level and input grid resolution. Secondly, the Grasselli Parameter is computed for the original and each decomposed surface. Finally, the relative roughness change is analyzed with respect to increasing roughness wavelength for four different rock samples. The scale variation depends on the sample itself and thus indicates its potential mechanical behavior. References: - Barton, N. and V. Choubey (1977). "The shear strength of rock joints in theory and practice." Rock Mechanics and Rock Engineering 10(1): 1-54. - Grasselli, G. (2001). Shear strength of rock joints based on quantified surface description. École Polytechnique Fédérale de Lausanne. Lausanne, EPFL. - Tatone, B. S. A. and G. Grasselli (2009). "A method to evaluate the three-dimensional roughness of fracture surfaces in brittle geomaterials." Review of Scientific Instruments 80(12) - Tatone, B. and G. Grasselli (2012). "An Investigation of Discontinuity Roughness Scale Dependency Using High-Resolution Surface Measurements." Rock Mechanics and Rock Engineering: 1-25.

  16. Albedo of the ice covered Weddell and Bellingshausen Seas

    OpenAIRE

    A. I. Weiss; J. C. King; T. A. Lachlan-Cope; 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...

  17. 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...

  18. An interactive ocean surface albedo scheme (OSAv1.0): formulation and evaluation in ARPEGE-Climat (V6.1) and LMDZ (V5A)

    Science.gov (United States)

    Séférian, Roland; Baek, Sunghye; Boucher, Olivier; Dufresne, Jean-Louis; Decharme, Bertrand; Saint-Martin, David; Roehrig, Romain

    2018-01-01

    Ocean surface represents roughly 70 % of the Earth's surface, playing a large role in the partitioning of the energy flow within the climate system. The ocean surface albedo (OSA) is an important parameter in this partitioning because it governs the amount of energy penetrating into the ocean or reflected towards space. The old OSA schemes in the ARPEGE-Climat and LMDZ models only resolve the latitudinal dependence in an ad hoc way without an accurate representation of the solar zenith angle dependence. Here, we propose a new interactive OSA scheme suited for Earth system models, which enables coupling between Earth system model components like surface ocean waves and marine biogeochemistry. This scheme resolves spectrally the various contributions of the surface for direct and diffuse solar radiation. The implementation of this scheme in two Earth system models leads to substantial improvements in simulated OSA. At the local scale, models using the interactive OSA scheme better replicate the day-to-day distribution of OSA derived from ground-based observations in contrast to old schemes. At global scale, the improved representation of OSA for diffuse radiation reduces model biases by up to 80 % over the tropical oceans, reducing annual-mean model-data error in surface upwelling shortwave radiation by up to 7 W m-2 over this domain. The spatial correlation coefficient between modeled and observed OSA at monthly resolution has been increased from 0.1 to 0.8. Despite its complexity, this interactive OSA scheme is computationally efficient for enabling precise OSA calculation without penalizing the elapsed model time.

  19. UV/visible albedos from airborne measurements

    Science.gov (United States)

    Webb, A.; Kylling, A.; Stromberg, I.

    2003-04-01

    During the INSPECTRO campaign effective surface albedo was measured at UV and visible wavelengths from two airborne platforms, a Cessna light aircraft and a hot air balloon. On board the Cessna was a scanning spectroradiometer measuring from 300 - 500nm at 10nm intervals. The NILU cube, with 6 faces and two UV channels at 312 and 340nm, was suspended beneath the hot air balloon. Flights took place over East Anglia during September, 2002. Balloon flights were made below cloud layers, while the Cessna flew both above and below cloud. The Cessna also flew over Barton Bendish, where surface albedos have been measured for ground truthing of satellite data, and measured the effective albedo at four visible wave- lengths in the centres of the satellite bandpass functions. Results of measurements from the different platforms are compared, and model simulations used to deduce the surface albedo from the effective albedo at altitude, giving, for example, an albedo of 0.02 ± 0.01 at 340nm.

  20. Summer Arctic sea ice albedo in CMIP5 models

    OpenAIRE

    Koenigk, T.; Devasthale, A.; Karlsson, K.-G.

    2014-01-01

    Spatial and temporal variations of summer sea ice albedo over the Arctic are analyzed using an ensemble of historical CMIP5 model simulations. The results are compared to the CLARA-SAL product that is based on long-term satellite observations. The summer sea ice albedo varies substantially among CMIP5 models, and many models show large biases compared to the CLARA-SAL product. Single summer months show an extreme spread of ice albedo among models; July values vary between 0....

  1. Widespread albedo decreasing and induced melting of Himalayan snow and ice in the early 21st century.

    Science.gov (United States)

    Ming, Jing; Wang, Yaqiang; Du, Zhencai; Zhang, Tong; Guo, Wanqin; Xiao, Cunde; Xu, Xiaobin; Ding, Minghu; Zhang, Dongqi; Yang, Wen

    2015-01-01

    The widely distributed glaciers in the greater Himalayan region have generally experienced rapid shrinkage since the 1850s. As invaluable sources of water and because of their scarcity, these glaciers are extremely important. Beginning in the twenty-first century, new methods have been applied to measure the mass budget of these glaciers. Investigations have shown that the albedo is an important parameter that affects the melting of Himalayan glaciers. The surface albedo based on the Moderate Resolution Imaging Spectroradiometer (MODIS) data over the Hindu Kush, Karakoram and Himalaya (HKH) glaciers is surveyed in this study for the period 2000-2011. The general albedo trend shows that the glaciers have been darkening since 2000. The most rapid decrease in the surface albedo has occurred in the glacial area above 6000 m, which implies that melting will likely extend to snow accumulation areas. The mass-loss equivalent (MLE) of the HKH glacial area caused by surface shortwave radiation absorption is estimated to be 10.4 Gt yr-1, which may contribute to 1.2% of the global sea level rise on annual average (2003-2009). This work probably presents a first scene depicting the albedo variations over the whole HKH glacial area during the period 2000-2011. Most rapidly decreasing in albedo has been detected in the highest area, which deserves to be especially concerned.

  2. Widespread albedo decreasing and induced melting of Himalayan snow and ice in the early 21st century.

    Directory of Open Access Journals (Sweden)

    Jing Ming

    Full Text Available The widely distributed glaciers in the greater Himalayan region have generally experienced rapid shrinkage since the 1850s. As invaluable sources of water and because of their scarcity, these glaciers are extremely important. Beginning in the twenty-first century, new methods have been applied to measure the mass budget of these glaciers. Investigations have shown that the albedo is an important parameter that affects the melting of Himalayan glaciers.The surface albedo based on the Moderate Resolution Imaging Spectroradiometer (MODIS data over the Hindu Kush, Karakoram and Himalaya (HKH glaciers is surveyed in this study for the period 2000-2011. The general albedo trend shows that the glaciers have been darkening since 2000. The most rapid decrease in the surface albedo has occurred in the glacial area above 6000 m, which implies that melting will likely extend to snow accumulation areas. The mass-loss equivalent (MLE of the HKH glacial area caused by surface shortwave radiation absorption is estimated to be 10.4 Gt yr-1, which may contribute to 1.2% of the global sea level rise on annual average (2003-2009.This work probably presents a first scene depicting the albedo variations over the whole HKH glacial area during the period 2000-2011. Most rapidly decreasing in albedo has been detected in the highest area, which deserves to be especially concerned.

  3. 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...

  4. Seasonal Variations of the Surface Urban Heat Island in a Semi-Arid City

    Directory of Open Access Journals (Sweden)

    Sirous Haashemi

    2016-04-01

    Full Text Available The process of the surface urban heat island (SUHI varies with latitude, climate, topography and meteorological conditions. This study investigated the seasonal variability of SUHI in the Tehran metropolitan area, Iran, with respect to selected surface biophysical variables. Terra Moderate Resolution Imaging Spectroradiometer (MODIS Land Surface Temperature (LST was retrieved as nighttime LST data, while daytime LST was retrieved from Landsat 8 Thermal Infrared Sensor (TIRS using the split-window algorithm. Both data covered the time period from September 2013 to September 2015. To assess SUHI intensity, we employed three SUHI indicators, i.e., the LST difference of urban-rural, that of urban-agriculture and that of urban-water. Physical and biophysical surface variables, including land use and land cover (LULC, elevation, impervious surface (IS, fractional vegetation cover (FVC and albedo, were selected to estimate the relationship between LST seasonal variability and the surface properties. Results show that an inversion of the SUHI phenomenon (i.e., surface urban cool island existed at daytime with the maximal value of urban-rural LST difference of −4 K in March; whereas the maximal value of SUHI at nighttime yielded 3.9 K in May. When using the indicators of urban-agriculture and urban-water LST differences, the maximal value of SUHI was found to be 8.2 K and 15.5 K, respectively. Both results were observed at daytime, suggesting the role of bare soils in the inversion of the SUHI phenomenon with the urban-rural indicator. Maximal correlation was observed in the relationship between night LST and elevation in spring (coefficient: −0.76, night LST and IS in spring (0.60, night LST and albedo in winter (−0.53 and day LST with fractional vegetation cover in summer (−0.41. The relationship between all surface properties with LST possessed large seasonal variations, and thus, using these relationships for SUHI modeling may not be

  5. Arctic sea ice albedo from AVHRR

    Science.gov (United States)

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

    1994-01-01

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

  6. 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...

  7. Influence of stratospheric aerosol on albedo

    Energy Technology Data Exchange (ETDEWEB)

    Gormatyuk, Yu K; Kaufman, Yu G; Kolomeev, M P

    1985-06-01

    The influence of stratospheric aerosol (SA) on the transfer of solar radiation in the atmosphere is the principal factor determining the effect of SA on climate. The change in the radiation balance under the influence of SA is computed most precisely in radiative-convective models. However, the complex method used in these models cannot be used for other types of climate models. The objective of the study was to obtain a quantitative evaluation of the influence of SA on albedo without the use of simplifying assumptions. In the approximation of single scattering an expression is derived for change in albedo under the influence of stratospheric aerosol taking into account the dependence of albedo of the atmosphere-earth's surface system on solar zenith distance. The authors give the results of computations of the response of mean annual albedo to sulfuric acid aerosol for 10/sup 0/ latitude zones in the Northern Hemisphere. Specifically, computations of the optical characteristics of aerosol were made using the Mie theory for 10 spectral intervals taking in the range of wavelengths of solar radiation from 0.29 to 4.0 ..mu.. m. The refractive index of aerosol was stipulated in accordance with Palmer and Williams. The angular dependence of albedo for cloudless and cloudy atmospheres given by Harshvardhan was used. The values of undisturbed albedo were assumed to be identical for all wavelengths due to lack of climatological data on the spectral dependence of albedo of the atmosphere-earth's surface system. The angular distribution of the intensity of solar radiation for each of the latitude zones was computed by the method described by I.M. Alekseyev, et al.

  8. 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.

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

    Science.gov (United States)

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

    2013-12-01

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

  10. Influence of cloud fraction and snow cover to the variation of surface UV radiation at King Sejong station, Antarctica

    Science.gov (United States)

    Lee, Yun Gon; Koo, Ja-Ho; Kim, Jhoon

    2015-10-01

    This study investigated how cloud fraction and snow cover affect the variation of surface ultraviolet (UV) radiation by using surface Erythemal UV (EUV) and Near UV (NUV) observed at the King Sejong Station, Antarctica. First the Radiative Amplification Factor (RAF), the relative change of surface EUV according to the total-column ozone amount, is compared for different cloud fractions and solar zenith angles (SZAs). Generally, all cloudy conditions show that the increase of RAF as SZA becomes larger, showing the larger effects of vertical columnar ozone. For given SZA cases, the EUV transmission through mean cloud layer gradually decreases as cloud fraction increases, but sometimes the maximum of surface EUV appears under partly cloudy conditions. The high surface EUV transmittance under broken cloud conditions seems due to the re-radiation of scattered EUV by cloud particles. NUV transmission through mean cloud layer also decreases as cloud amount increases but the sensitivity to the cloud fraction is larger than EUV. Both EUV and NUV radiations at the surface are also enhanced by the snow cover, and their enhancement becomes higher as SZA increases implying the diurnal variation of surface albedo. This effect of snow cover seems large under the overcast sky because of the stronger interaction between snow surface and cloudy sky.

  11. (90377) SEDNA: INVESTIGATION OF SURFACE COMPOSITIONAL VARIATION

    International Nuclear Information System (INIS)

    Barucci, M. A.; De Bergh, C.; Merlin, F.; Morea Dalle Ore, C.; Cruikshank, D.; Alvarez-Candal, A.; Dumas, C.

    2010-01-01

    The dwarf planet (90377) Sedna is one of the most remote solar system objects accessible to investigations. To better constrain its surface composition and to investigate the possible heterogeneity of the surface of Sedna, several observations have been carried out at ESO-VLT with the powerful spectrometer SINFONI observing simultaneously the H and K bands. The analyzed spectra (obtained in 2005, 2007, and 2008) show a non-uniform spectral signature, particularly in the K band. Spectral modeling using the Shkuratov radiative transfer code for surface scattering has been performed using the various sets of data, including previous observations at visible wavelengths and photometry at 3.6 and 4.5 μm by the Spitzer Space Telescope. The visible and near-infrared spectra can be modeled with organic materials (triton and titan tholin), serpentine, and H 2 O ice in fairly significant amounts, and CH 4 , N 2 , and C 2 H 6 in varying trace amounts. One of the spectra obtained in 2005 October shows a different signature in the K band and is best modeled with CH 3 OH in place of CH 4 , with reduced amounts of serpentine and with the addition of olivine. The compositional surface heterogeneity can give input on the past history as well clues to the origin of this peculiar, distant object.

  12. Deterministic prediction of surface wind speed variations

    Directory of Open Access Journals (Sweden)

    G. V. Drisya

    2014-11-01

    Full Text Available Accurate prediction of wind speed is an important aspect of various tasks related to wind energy management such as wind turbine predictive control and wind power scheduling. The most typical characteristic of wind speed data is its persistent temporal variations. Most of the techniques reported in the literature for prediction of wind speed and power are based on statistical methods or probabilistic distribution of wind speed data. In this paper we demonstrate that deterministic forecasting methods can make accurate short-term predictions of wind speed using past data, at locations where the wind dynamics exhibit chaotic behaviour. The predictions are remarkably accurate up to 1 h with a normalised RMSE (root mean square error of less than 0.02 and reasonably accurate up to 3 h with an error of less than 0.06. Repeated application of these methods at 234 different geographical locations for predicting wind speeds at 30-day intervals for 3 years reveals that the accuracy of prediction is more or less the same across all locations and time periods. Comparison of the results with f-ARIMA model predictions shows that the deterministic models with suitable parameters are capable of returning improved prediction accuracy and capturing the dynamical variations of the actual time series more faithfully. These methods are simple and computationally efficient and require only records of past data for making short-term wind speed forecasts within practically tolerable margin of errors.

  13. Radiative forcing over the conterminous United States due to contemporary land cover land use change and sensitivity to snow and interannual albedo variability

    Science.gov (United States)

    Barnes, Christopher A.; Roy, David P.

    2010-01-01

    Satellite-derived land cover land use (LCLU), snow and albedo data, and incoming surface solar radiation reanalysis data were used to study the impact of LCLU change from 1973 to 2000 on surface albedo and radiative forcing for 58 ecoregions covering 69% of the conterminous United States. A net positive surface radiative forcing (i.e., warming) of 0.029 Wm−2 due to LCLU albedo change from 1973 to 2000 was estimated. The forcings for individual ecoregions were similar in magnitude to current global forcing estimates, with the most negative forcing (as low as −0.367 Wm−2) due to the transition to forest and the most positive forcing (up to 0.337 Wm−2) due to the conversion to grass/shrub. Snow exacerbated both negative and positive forcing for LCLU transitions between snow-hiding and snow-revealing LCLU classes. The surface radiative forcing estimates were highly sensitive to snow-free interannual albedo variability that had a percent average monthly variation from 1.6% to 4.3% across the ecoregions. The results described in this paper enhance our understanding of contemporary LCLU change on surface radiative forcing and suggest that future forcing estimates should model snow and interannual albedo variation.

  14. Inversion of the Earth spherical albedo from radiation-pressure

    Science.gov (United States)

    Wilkman, Olli; Herranen, Joonas; Näränen, Jyri; Virtanen, Jenni; Koivula, Hannu; Poutanen, Markku; Penttilä, Antti; Gritsevich, Maria; Muinonen, Karri

    2017-04-01

    We are studying the retrieval of the spherical albedo and net radiation of the Earth from the perturbations caused by the planet's radiation on the dynamics of its satellites. The spherical or Bond albedo gives the ratio of the fluxes incident on and scattered by the planet. The net radiation represents the net heat input into the planet's climate system and drives changes in its atmospheric, surface, and ocean temperatures. The ultimate aim of the study is inverting the problem and estimating the Earth albedo based on observations of satellites, simultaneously improving the space-geodetic positioning accuracy. Here we investigate the effect of the spherical albedo on satellite orbits with the help of a simplified model. We simulate the propagation of satellite orbits using a new simulation software. The simulation contains the main perturbing forces on medium and high Earth orbits, used by, e.g., navigation satellites, including the radiation pressure of reflected sunlight from the Earth. An arbitrary satellite shape model can be used, and the rotation of the satellite is modeled. In this first study, we use a box-wing satellite model with a simple surface BRDF. We also assume a diffusely reflecting Earth with a single global albedo value. We vary the Earth albedo and search for systematic effects on different orbits. Thereafter, we estimate the dependence of the albedo accuracy on the satellite positioning and timing data available. We show that the inversion of the spherical albedo with reasonable accuracy is feasible from the current space-geodetic measurements.

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

    Science.gov (United States)

    Chappell, Adrian; Webb, Nicholas P.

    2016-12-01

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

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

    Science.gov (United States)

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

    2008-04-01

    Some climate scientists are questioning whether the practice of converting of non-forest lands to forest land (afforestation or reforestation) is an effective climate change mitigation option. The discussion focuses particularly on areas where the new forest is primarily coniferous and there is significant amount of snow since the increased climate forcing due to the change in albedo may counteract the decreased climate forcing due to carbon dioxide removal. In this paper, we develop a stand-based model that combines changes in surface albedo, solar radiation, latitude, cloud cover and carbon sequestration. As well, we develop a procedure to convert carbon stock changes to equivalent climatic forcing or climatic forcing to equivalent carbon stock changes. Using the model, we investigate the sensitivity of combined affects of changes in surface albedo and carbon stock changes to model parameters. The model is sensitive to amount of cloud, atmospheric absorption, timing of canopy closure, carbon sequestration rate among other factors. The sensitivity of the model is investigated at one Canadian site, and then the model is tested at numerous sites across Canada. In general, we find that the change in albedo reduces the carbon sequestration benefits by approximately 30% over 100 years, but this is not drastic enough to suggest that one should not use afforestation or reforestation as a climate change mitigation option. This occurs because the forests grow in places where there is significant amount of cloud in winter. As well, variations in sequestration rate seem to be counterbalanced by the amount and timing of canopy closure. We close by speculating that the effects of albedo may also be significant in locations at lower latitudes, where there are less clouds, and where there are extended dry seasons. These conditions make grasses light coloured and when irrigated crops, dark forests or other vegetation such as biofuels replace the grasses, the change in carbon

  17. NASA/GEWEX Surface Radiation Budget: Integrated Data Product With Reprocessed Radiance, Cloud, and Meteorology Inputs, and New Surface Albedo Treatment

    Science.gov (United States)

    Cox, Stephen J.; Stackhouse, Paul W., Jr.; Gupta, Shashi K.; Mikovitz, J. Colleen; Zhang, Taiping

    2016-01-01

    The NASA/GEWEX Surface Radiation Budget (SRB) project produces shortwave and longwave surface and top of atmosphere radiative fluxes for the 1983-near present time period. Spatial resolution is 1 degree. The current release 3.0 (available at gewex-srb.larc.nasa.gov) uses the International Satellite Cloud Climatology Project (ISCCP) DX product for pixel level radiance and cloud information. This product is subsampled to 30 km. ISCCP is currently recalibrating and recomputing their entire data series, to be released as the H product, at 10km resolution. The ninefold increase in pixel number will allow SRB a higher resolution gridded product (e.g. 0.5 degree), as well as the production of pixel-level fluxes. In addition to the input data improvements, several important algorithm improvements have been made. Most notable has been the adaptation of Angular Distribution Models (ADMs) from CERES to improve the initial calculation of shortwave TOA fluxes, from which the surface flux calculations follow. Other key input improvements include a detailed aerosol history using the Max Planck Institut Aerosol Climatology (MAC), temperature and moisture profiles from HIRS, and new topography, surface type, and snow/ice. Here we present results for the improved GEWEX Shortwave and Longwave algorithm (GSW and GLW) with new ISCCP data, the various other improved input data sets and the incorporation of many additional internal SRB model improvements. As of the time of abstract submission, results from 2007 have been produced with ISCCP H availability the limiting factor. More SRB data will be produced as ISCCP reprocessing continues. The SRB data produced will be released as part of the Release 4.0 Integrated Product, recognizing the interdependence of the radiative fluxes with other GEWEX products providing estimates of the Earth's global water and energy cycle (I.e., ISCCP, SeaFlux, LandFlux, NVAP, etc.).

  18. Reactive solid surface morphology variation via ionic diffusion.

    Science.gov (United States)

    Sun, Zhenchao; Zhou, Qiang; Fan, Liang-Shih

    2012-08-14

    In gas-solid reactions, one of the most important factors that determine the overall reaction rate is the solid morphology, which can be characterized by a combination of smooth, convex and concave structures. Generally, the solid surface structure varies in the course of reactions, which is classically noted as being attributed to one or more of the following three mechanisms: mechanical interaction, molar volume change, and sintering. Here we show that if a gas-solid reaction involves the outward ionic diffusion of a solid-phase reactant then this outward ionic diffusion could eventually smooth the surface with an initial concave and/or convex structure. Specifically, the concave surface is filled via a larger outward diffusing surface pointing to the concave valley, whereas the height of the convex surface decreases via a lower outward diffusion flux in the vertical direction. A quantitative 2-D continuum diffusion model is established to analyze these two morphological variation processes, which shows consistent results with the experiments. This surface morphology variation by solid-phase ionic diffusion serves to provide a fourth mechanism that supplements the traditionally acknowledged solid morphology variation or, in general, porosity variation mechanisms in gas-solid reactions.

  19. Variational reconstruction using subdivision surfaces with continuous sharpness control

    Institute of Scientific and Technical Information of China (English)

    Xiaoqun Wu; Jianmin Zheng; Yiyu Cai; Haisheng Li

    2017-01-01

    We present a variational method for subdivision surface reconstruction from a noisy dense mesh.A new set of subdivision rules with continuous sharpness control is introduced into Loop subdivision for better modeling subdivision surface features such as semi-sharp creases,creases,and corners.The key idea is to assign a sharpness value to each edge of the control mesh to continuously control the surface features.Based on the new subdivision rules,a variational model with L1 norm is formulated to find the control mesh and the corresponding sharpness values of the subdivision surface that best fits the input mesh.An iterative solver based on the augmented Lagrangian method and particle swarm optimization is used to solve the resulting non-linear,non-differentiable optimization problem.Our experimental results show that our method can handle meshes well with sharp/semi-sharp features and noise.

  20. A FALSE POSITIVE FOR OCEAN GLINT ON EXOPLANETS: THE LATITUDE-ALBEDO EFFECT

    International Nuclear Information System (INIS)

    Cowan, Nicolas B.; Abbot, Dorian S.; Voigt, Aiko

    2012-01-01

    Identifying liquid water on the surface of planets is a high priority, as this traditionally defines habitability. One proposed signature of oceans is specular reflection ('glint'), which increases the apparent albedo of a planet at crescent phases. We post-process a global climate model of an Earth-like planet to simulate reflected light curves. Significantly, we obtain glint-like phase variations even though we do not include specular reflection in our model. This false positive is the product of two generic properties: (1) for modest obliquities, a planet's poles receive less orbit-averaged stellar flux than its equator, so the poles are more likely to be covered in highly reflective snow and ice; and (2) we show that reflected light from a modest-obliquity planet at crescent phases probes higher latitudes than at gibbous phases, therefore a planet's apparent albedo will naturally increase at crescent phase. We suggest that this 'latitude-albedo effect' will operate even for large obliquities: in that case the equator receives less orbit-averaged flux than the poles, and the equator is preferentially sampled at crescent phase. Using rotational and orbital color variations to map the surfaces of directly imaged planets and estimate their obliquity will therefore be a necessary pre-condition for properly interpreting their reflected phase variations. The latitude-albedo effect is a particularly convincing glint false positive for zero-obliquity planets, and such worlds are not amenable to latitudinal mapping. This effect severely limits the utility of specular reflection for detecting oceans on exoplanets.

  1. Albedos of Jovian Trojans, Hildas and Centaurs

    Science.gov (United States)

    Romanishin, William; Tegler, Stephen C.

    2017-10-01

    We present distributions of optical V band albedos for samples of outer solar system minor bodies including Centaurs, Jovian Trojans and Hildas. Diameters come almost entirely from the NEOWISE catalog (Mainzer etal 2016- Planetary Data System). Optical photometry (H values) for about 2/3 of the approximately 2700 objects studied are from PanStarrrs (Veres et al 2015 Icarus 261, 34). The PanStarrs optical photometry is supplemented by H values from JPL Horizons (corrected to be on the same photometric system as the PanStarrs data) for the objects in the NEOWISE catalog that are not in the PanStarrs catalog. We compare the albedo distributions of various pairs of subsamples using the nonparametric Wilcoxon rank sum test. Examples of potentially interesting comparisons include: (1) The Hildas are 15-25% darker than the Trojans at a very high level of statistical significance. If the Hildas and Trojans started out with similar surfaces, the Hildas may have darkened due to the effects of gardening as they pass through zone III of the asteroid belt. (2) The median albedo of the gray Centaurs lies between that of the L4 and L5 Trojan groups (3) The median L5 Trojan cloud albedo is about 10% darker than that of the L4 cloud at a high level of significance. However, the modes of the L4 and L5 albedo distributions are very similar, perhaps indicating the presence of a distinct brighter component in the L4 cloud that is not found in the L5 cloud.

  2. Quantifying the ice-albedo feedback through decoupling

    Science.gov (United States)

    Kravitz, B.; Rasch, P. J.

    2017-12-01

    The ice-albedo feedback involves numerous individual components, whereby warming induces sea ice melt, inducing reduced surface albedo, inducing increased surface shortwave absorption, causing further warming. Here we attempt to quantify the sea ice albedo feedback using an analogue of the "partial radiative perturbation" method, but where the governing mechanisms are directly decoupled in a climate model. As an example, we can isolate the insulating effects of sea ice on surface energy and moisture fluxes by allowing sea ice thickness to change but fixing Arctic surface albedo, or vice versa. Here we present results from such idealized simulations using the Community Earth System Model in which individual components are successively fixed, effectively decoupling the ice-albedo feedback loop. We isolate the different components of this feedback, including temperature change, sea ice extent/thickness, and air-sea exchange of heat and moisture. We explore the interactions between these different components, as well as the strengths of the total feedback in the decoupled feedback loop, to quantify contributions from individual pieces. We also quantify the non-additivity of the effects of the components as a means of investigating the dominant sources of nonlinearity in the ice-albedo feedback.

  3. The opposition effect in Saturn's main rings as seen by Cassini ISS: 4. Correlations of the surge morphology with surface albedos and VIMS spectral properties

    Science.gov (United States)

    Déau, Estelle; Dones, Luke; Mishchenko, Michael I.; West, Robert A.; Helfenstein, Paul; Hedman, Matt M.; Porco, Carolyn C.

    2018-05-01

    In this paper, we continue our analysis of the saturnian ring opposition effect seen by Cassini ISS. The ring opposition effect is a peak in the rings' reflectivity caused as the directions from a spot on the rings to the observer and to the light source, respectively, converge toward zero degrees. So far, the exact origin of the ring's opposition effect is still a matter of debate. In our previous work (Déau, et al., 2013, Icarus, 226, 591-603), we compared the opposition effect morphology with the rings' optical depth and found that only the slope of the linear part of the rings' phase curves was strongly correlated with the optical depth. We interpreted this as an indication of the predominant role of interparticle shadowing at moderate phase angles (α ∼ 10-40o). More recently (Déau, 2015, Icarus, 253, 311-345), we showed that interparticle shadowing cannot explain the behavior at low phase angles (α Journal Letters, 711, L71-L74). We find that the opposition surge morphology is strongly correlated with the water ice band depth and the regolith albedo. We interpret this finding as an indication that coherent backscattering plays a role in affecting both the water ice band depths and the opposition surge at low phase angles (α < 1o). As the regolith albedo and spectral properties are related to the grain size, porosity, roughness, and composition, we try to assess which of these regolith properties are preponderant in coherent backscattering. Our study is able to narrow down the parameter space of these properties, whose values allow a good match between the angular width predicted by models of coherent backscattering and the width of the observed peak.

  4. Suppression of the water ice and snow albedo feedback on planets orbiting red dwarf stars and the subsequent widening of the habitable zone.

    Science.gov (United States)

    Joshi, Manoj M; Haberle, Robert M

    2012-01-01

    M stars comprise 80% of main sequence stars, so their planetary systems provide the best chance for finding habitable planets, that is, those with surface liquid water. We have modeled the broadband albedo or reflectivity of water ice and snow for simulated planetary surfaces orbiting two observed red dwarf stars (or M stars), using spectrally resolved data of Earth's cryosphere. The gradual reduction of the albedos of snow and ice at wavelengths greater than 1 μm, combined with M stars emitting a significant fraction of their radiation at these same longer wavelengths, means that the albedos of ice and snow on planets orbiting M stars are much lower than their values on Earth. Our results imply that the ice/snow albedo climate feedback is significantly weaker for planets orbiting M stars than for planets orbiting G-type stars such as the Sun. In addition, planets with significant ice and snow cover will have significantly higher surface temperatures for a given stellar flux if the spectral variation of cryospheric albedo is considered, which in turn implies that the outer edge of the habitable zone around M stars may be 10-30% farther away from the parent star than previously thought.

  5. Long-term record of top-of-atmosphere albedo generated from AVHRR data

    Science.gov (United States)

    Song, Z.

    2017-12-01

    Top-of-Atmosphere (TOA) albedo is a fundamental component of Earth's energy budget. Previously, long-term accurate TOA albedo products did not exist due to the lack of stable broadband observations. With a new albedo estimation methodology based on multispectral observations, TOA albedo since 1981 has been retrieved using data from the Advanced Very High Resolution Radiometer (AVHRR), which provides the longest record of satellite observations across the globe. To develop the long-term TOA albedo record, the instantaneous TOA albedo was calculated by the direct estimation method, which was built on training data pairs from coincident AVHRR TOA reflectance and Moderate Resolution Imaging Spectroradiometer (MODIS) TOA albedo. The instantaneous TOA albedo was then converted to daily mean and monthly mean albedo based on the diurnal curves from geostationary satellites. The TOA albedo results (AVHRR-TAL) were compared with Clouds and the Earth's Radiant Energy System (CERES) flux products for 2007. The monthly mean AVHRR-TAL agreed well with the CERES products, with a root mean square difference (RMSD) of 0.032 and a bias of 0.013. In addition, AVHRR-TAL showed similar seasonal variations to those seen in the CERES products. Further analysis on long-term time series showed good consistency between the two datasets (R2 > 0.95 and relative RMSD < 4%) from 2000 to 2015. Although some calibration issues remain to be solved, our datasets show the potential ability to observe the global TOA albedo from 1981 to the present.

  6. Thermoluminescence albedo-neutron dosimetry

    International Nuclear Information System (INIS)

    Strand, T.; Storruste, A.

    1986-10-01

    The report discusses neutron detection with respect to dosimetry and compares different thermoluminescent dosimetry materials for neutron dosimetry. Construction and calibration of a thermoluminescence albedo neutron dosemeter, developed by the authors, is described

  7. Variations of surface ozone concentration across the Klang Valley, Malaysia

    Science.gov (United States)

    Latif, Mohd Talib; Huey, Lim Shun; Juneng, Liew

    2012-12-01

    Hourly air quality data covering the period 2004-2008 was obtained from the Air Quality Division, the Department of Environment (DOE) through long-term monitoring by Alam Sekitar Sdn. Bhd. (ASMA) were analysed to investigate the variations of surface ozone (O3) in the Klang Valley, Malaysia. A total of nine monitoring stations were selected for analysis in this study and the results show that there are distinct seasonal patterns in the surface O3 across the Klang Valley. A high surface O3 concentration is usually observed between January and April, while a low surface O3 concentration is found between June and August. Analysis of daily variations in surface O3 and the precursors - NO, NO2, CO, NMHC and UVb, indicate that the surface O3 photochemistry in this study area exhibits a positive response to the intensity and wavelength in UVb while being influenced by the concentration of NOx, particularly through tritration processes. Although results from our study suggested that NMHCs may influence the maximum O3 concentration, further investigation is required. Wind direction during different monsoons was found to influence the concentration of O3 around the Klang Valley. HYSPLIT back trajectories (-72 h) were used to indicate the air-mass transport patterns on days with high concentrations of surface O3 in the study area. Results show that 47% of the high O3 days was associated with the localized circulation. The remaining 32% and 22% were associated with mid-range and long-range transport across the South China Sea from the northeast.

  8. Ceres Photometry and Albedo from Dawn Framing Camera Images

    Science.gov (United States)

    Schröder, S. E.; Mottola, S.; Keller, H. U.; Li, J.-Y.; Matz, K.-D.; Otto, K.; Roatsch, T.; Stephan, K.; Raymond, C. A.; Russell, C. T.

    2015-10-01

    The Dawn spacecraft is in orbit around dwarf planet Ceres. The onboard Framing Camera (FC) [1] is mapping the surface through a clear filter and 7 narrow-band filters at various observational geometries. Generally, Ceres' appearance in these images is affected by shadows and shading, effects which become stronger for larger solar phase angles, obscuring the intrinsic reflective properties of the surface. By means of photometric modeling we attempt to remove these effects and reconstruct the surface albedo over the full visible wavelength range. Knowledge of the albedo distribution will contribute to our understanding of the physical nature and composition of the surface.

  9. Sea Ice, Clouds, Sunlight, and Albedo: The Umbrella Versus the Blanket

    Science.gov (United States)

    Perovich, D. K.

    2017-12-01

    The Arctic sea ice cover has undergone a major decline in recent years, with reductions in ice extent, ice thickness, and ice age. Understanding the feedbacks and forcing driving these changes is critical in improving predictions. The surface radiation budget plays a central role in summer ice melt and is governed by clouds and surface albedo. Clouds act as an umbrella reducing the downwelling shortwave, but also serve as a blanket increasing the downwelling longwave, with the surface albedo also determining the net balance. Using field observations from the SHEBA program, pairs of clear and cloudy days were selected for each month from May through September and the net radiation flux was calculated for different surface conditions and albedos. To explore the impact of albedo we calculated a break even albedo, where the net radiation for cloudy skies is the same as clear skies. For albedos larger than the break-even value the net radiation flux is smaller under clear skies compared to cloudy skies. Break-even albedos ranged from 0.30 in September to 0.58 in July. For snow covered or bare ice, clear skies always resulted in less radiative heat input. In contrast, leads always had, and ponds usually had, more radiative heat input under clear skies than cloudy skies. Snow covered ice had a net radiation flux that was negative or near zero under clear skies resulting in radiative cooling. We combined the albedo of individual ice types with the area of those ice types to calculate albedos averaged over a 50 km x 50 km area. The July case had the smallest areally averaged albedo of 0.50. This was less than the breakeven albedo, so cloudy skies had a smaller net radiation flux than clear skies. For the cases from the other four months, the areally averaged albedo was greater than the break-even albedo. The areally averaged net radiation flux was negative under clear skies for the May and September cases.

  10. A Multi-Scale Validation Strategy for Albedo Products over Rugged Terrain and Preliminary Application in Heihe River Basin, China

    Directory of Open Access Journals (Sweden)

    Xingwen Lin

    2018-01-01

    Full Text Available The issue for the validation of land surface remote sensing albedo products over rugged terrain is the scale effects between the reference albedo measurements and coarse scale albedo products, which is caused by the complex topography. This paper illustrates a multi-scale validation strategy specified for coarse scale albedo validation over rugged terrain. A Mountain-Radiation-Transfer-based (MRT-based albedo upscaling model was proposed in the process of multi-scale validation strategy for aggregating fine scale albedo to coarse scale. The simulated data of both the reference coarse scale albedo and fine scale albedo were used to assess the performance and uncertainties of the MRT-based albedo upscaling model. The results showed that the MRT-based model could reflect the albedo scale effects over rugged terrain and provided a robust solution for albedo upscaling from fine scale to coarse scale with different mean slopes and different solar zenith angles. The upscaled coarse scale albedos had the great agreements with the simulated coarse scale albedo with a Root-Mean-Square-Error (RMSE of 0.0029 and 0.0017 for black sky albedo (BSA and white sky albedo (WSA, respectively. Then the MRT-based model was preliminarily applied for the assessment of daily MODerate Resolution Imaging Spectroradiometer (MODIS Albedo Collection V006 products (MCD43A3 C6 over rugged terrain. Results showed that the MRT-based model was effective and suitable for conducting the validation of MODIS albedo products over rugged terrain. In this research area, it was shown that the MCD43A3 C6 products with full inversion algorithm, were generally in agreement with the aggregated coarse scale reference albedos over rugged terrain in the Heihe River Basin, with the BSA RMSE of 0.0305 and WSA RMSE of 0.0321, respectively, which were slightly higher than those over flat terrain.

  11. Genetic variation and significance of hepatitis B surface antigen

    Directory of Open Access Journals (Sweden)

    ZHANG Zhenhua

    2013-11-01

    Full Text Available Hepatitis B virus (HBV is prone to genetic variation because there is reverse transcription in the process of HBV replication. The gene mutation of hepatitis B surface antigen may affect clinical diagnosis of HBV infection, viral replication, and vaccine effect. The current research and existing problems are discussed from the following aspects: the mechanism and biological and clinical significance of S gene mutation. Most previous studies focused on S gene alone, so S gene should be considered as part of HBV DNA in the future research on S gene mutation.

  12. Clear-sky narrowband albedos derived from VIRS and MODIS

    Science.gov (United States)

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

    2004-02-01

    The Clouds and Earth"s Radiant Energy System (CERES) project is using multispectral imagers, the Visible Infrared Scanner (VIRS) on the tropical Rainfall Measuring Mission (TRMM) satellite and the Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra, operating since spring 2000, and Aqua, operating since summer 2002, to provide cloud and clear-sky properties at various wavelengths. This paper presents the preliminary results of an analysis of the CERES clear-sky reflectances to derive a set top-of-atmosphere clear sky albedo for 0.65, 0.86, 1.6, 2.13 μm, for all major surface types using the combined MODIS and VIRS datasets. The variability of snow albedo with surface type is examined using MODIS data. Snow albedo was found to depend on the vertical structure of the vegetation. At visible wavelengths, it is least for forested areas and greatest for smooth desert and tundra surfaces. At 1.6 and 2.1-μm, the snow albedos are relatively insensitive to the underlying surface because snow decreases the reflectance. Additional analyses using all of the MODIS results will provide albedo models that should be valuable for many remote sensing, simulation and radiation budget studies.

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

    Science.gov (United States)

    Marcialis, Robert L.; Lebofsky, Larry A.

    1991-01-01

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

  14. A MATHEMATICAL APPROACH TO ECONOMY OF EXPERIMENT IN DETERMINATIONS OF THE DIFFERENTIAL DOSE ALBEDO OF GAMMA RAYS

    Energy Technology Data Exchange (ETDEWEB)

    Shoemaker, N. F.; Huddleston, C. M.

    1962-12-10

    Treatments of the differential dose albedo of gamma rays on concrete have supposed that the albedo value is a function of: the energy of the incident gamma radiation, the polar angle of incidence, the polar angle of reflection (or scatter), and the azimuthal angle of reflection. It is demonstrated that, if certain reasonable assumptions are made regarding the mechanism of reflection, it is not necessary to investigate variations in albedo with azimuthal angle of refiection. Once differential dose albedo has been determined for a complete set of incident and reflected polar angles with zero azimuth, albedo at any azimuth can be derived by a suitable transformation. (auth)

  15. ALBEDO PATTERN RECOGNITION AND TIME-SERIES ANALYSES IN MALAYSIA

    Directory of Open Access Journals (Sweden)

    S. A. Salleh

    2012-07-01

    Full Text Available 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

  16. ANALYSIS OF THE INTRA-CITY VARIATION OF URBAN HEAT ISLAND AND ITS RELATION TO LAND SURFACE/COVER PARAMETERS

    Directory of Open Access Journals (Sweden)

    D. Gerçek

    2016-06-01

    Full Text Available Along with urbanization, sealing of vegetated land and evaporation surfaces by impermeable materials, lead to changes in urban climate. This phenomenon is observed as temperatures several degrees higher in densely urbanized areas compared to the rural land at the urban fringe particularly at nights, so-called Urban Heat Island. Urban Heat Island (UHI effect is related with urban form, pattern and building materials so far as it is associated with meteorological conditions, air pollution, excess heat from cooling. UHI effect has negative influences on human health, as well as other environmental problems such as higher energy demand, air pollution, and water shortage. Urban Heat Island (UHI effect has long been studied by observations of air temperature from thermometers. However, with the advent and proliferation of remote sensing technology, synoptic coverage and better representations of spatial variation of surface temperature became possible. This has opened new avenues for the observation capabilities and research of UHIs. In this study, "UHI effect and its relation to factors that cause it" is explored for İzmit city which has been subject to excess urbanization and industrialization during the past decades. Spatial distribution and variation of UHI effect in İzmit is analysed using Landsat 8 and ASTER day & night images of 2015 summer. Surface temperature data derived from thermal bands of the images were analysed for UHI effect. Higher temperatures were classified into 4 grades of UHIs and mapped both for day and night. Inadequate urban form, pattern, density, high buildings and paved surfaces at the expanse of soil ground and vegetation cover are the main factors that cause microclimates giving rise to spatial variations in temperatures across cities. These factors quantified as land surface/cover parameters for the study include vegetation index (NDVI, imperviousness (NDISI, albedo, solar insolation, Sky View Factor (SVF, building

  17. Analysis of the Intra-City Variation of Urban Heat Island and its Relation to Land Surface/cover Parameters

    Science.gov (United States)

    Gerçek, D.; Güven, İ. T.; Oktay, İ. Ç.

    2016-06-01

    Along with urbanization, sealing of vegetated land and evaporation surfaces by impermeable materials, lead to changes in urban climate. This phenomenon is observed as temperatures several degrees higher in densely urbanized areas compared to the rural land at the urban fringe particularly at nights, so-called Urban Heat Island. Urban Heat Island (UHI) effect is related with urban form, pattern and building materials so far as it is associated with meteorological conditions, air pollution, excess heat from cooling. UHI effect has negative influences on human health, as well as other environmental problems such as higher energy demand, air pollution, and water shortage. Urban Heat Island (UHI) effect has long been studied by observations of air temperature from thermometers. However, with the advent and proliferation of remote sensing technology, synoptic coverage and better representations of spatial variation of surface temperature became possible. This has opened new avenues for the observation capabilities and research of UHIs. In this study, "UHI effect and its relation to factors that cause it" is explored for İzmit city which has been subject to excess urbanization and industrialization during the past decades. Spatial distribution and variation of UHI effect in İzmit is analysed using Landsat 8 and ASTER day & night images of 2015 summer. Surface temperature data derived from thermal bands of the images were analysed for UHI effect. Higher temperatures were classified into 4 grades of UHIs and mapped both for day and night. Inadequate urban form, pattern, density, high buildings and paved surfaces at the expanse of soil ground and vegetation cover are the main factors that cause microclimates giving rise to spatial variations in temperatures across cities. These factors quantified as land surface/cover parameters for the study include vegetation index (NDVI), imperviousness (NDISI), albedo, solar insolation, Sky View Factor (SVF), building envelope

  18. The importance of snow albedo for ice sheet evolution over the last glacial cycle

    Directory of Open Access Journals (Sweden)

    M. Willeit

    2018-05-01

    Full Text Available The surface energy and mass balance of ice sheets strongly depends on the amount of solar radiation absorbed at the surface, which is mainly controlled by the albedo of snow and ice. Here, using an Earth system model of intermediate complexity, we explore the role played by surface albedo for the simulation of glacial cycles. We show that the evolution of the Northern Hemisphere ice sheets over the last glacial cycle is very sensitive to the representation of snow albedo in the model. It is well known that the albedo of snow depends strongly on snow grain size and the content of light-absorbing impurities. Excluding either the snow aging effect or the dust darkening effect on snow albedo leads to an excessive ice build-up during glacial times and consequently to a failure in simulating deglaciation. While the effect of snow grain growth on snow albedo is well constrained, the albedo reduction due to the presence of dust in snow is much more uncertain because the light-absorbing properties of dust vary widely as a function of dust mineral composition. We also show that assuming slightly different optical properties of dust leads to very different ice sheet and climate evolutions in the model. Conversely, ice sheet evolution is less sensitive to the choice of ice albedo in the model. We conclude that a proper representation of snow albedo is a fundamental prerequisite for a successful simulation of glacial cycles.

  19. The global albedo of the Moon at 1064 nm from LOLA

    Science.gov (United States)

    Lucey, P. G.; Neumann, G. A.; Riner, M. A.; Mazarico, E.; Smith, D. E.; Zuber, M. T.; Paige, D. A.; Bussey, D. B.; Cahill, J. T.; McGovern, A.; Isaacson, P.; Corley, L. M.; Torrence, M. H.; Melosh, H. J.; Head, J. W.; Song, E.

    2014-07-01

    The Lunar Orbiter Laser Altimeter (LOLA) measures the backscattered energy of the returning altimetric laser pulse at its wavelength of 1064 nm, and these data are used to map the reflectivity of the Moon at zero-phase angle with a photometrically uniform data set. Global maps have been produced at 4 pixels per degree (about 8 km at the equator) and 2 km resolution within 20° latitude of each pole. The zero-phase geometry is insensitive to lunar topography, so these data enable characterization of subtle variations in lunar albedo, even at high latitudes where such measurements are not possible with the Sun as the illumination source. The geometric albedo of the Moon at 1064 nm was estimated from these data with absolute calibration derived from the Kaguya Multiband Imager and extrapolated to visual wavelengths. The LOLA estimates are within 2σ of historical measurements of geometric albedo. No consistent latitude-dependent variations in reflectance are observed, suggesting that solar wind does not dominate space weathering processes that modify lunar reflectance. The average normal albedo of the Moon is found to be much higher than that of Mercury consistent with prior measurements, but the normal albedo of the lunar maria is similar to that of Mercury suggesting a similar abundance of space weathering products. Regions within permanent shadow in the polar regions are found to be more reflective than polar surfaces that are sometimes illuminated. Limiting analysis to data with slopes less than 10° eliminates variations in reflectance due to mass wasting and shows a similar increased reflectivity within permanent polar shadow. Steep slopes within permanent shadow are also more reflective than similar slopes that experience at least some illumination. Water frost and a reduction in effectiveness of space weathering are offered as possible explanations for the increased reflectivity of permanent shadow; porosity is largely ruled out as the sole explanation. The

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

    Energy Technology Data Exchange (ETDEWEB)

    Akbari, Hashem; Menon, Surabi; Rosenfeld, Arthur

    2007-05-22

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

  1. The New Global Gapless GLASS Albedo Product from 1981 to 2014

    Science.gov (United States)

    Dou, B.; Liu, Q.; Qu, Y.; Wang, L.; Feng, Y.; Nie, A.; Li, X.; Zhang, J.; Niu, H.; Cai, E.; Zhao, L.

    2016-12-01

    Long-time series and various spatial resolution albedo products are needed for climate change and environmental studies at both global and regional scale. To meet these requirements, GLASS (Global LAnd Surface Satellites) gapless albedo product from 1981 to 2010 was firstly released in 2012 and widely used in long-term earth change researches. However, only shortwave albedo product in spatial resolution of 0.05 degree and 1 km were provided, which limits extensive applications for visible and near-infrared bands. Thus, new GLASS albedo product are produced and comprehensively enhanced in time series, algorithm and product content. Five major updates are conducted: 1) Time region is expanded from 1981-2010 to 1981-2014; 2) Physically ART (radiative transfer theory) and TCOWA (Three-Component Ocean Water Albedo) models rather than previous RTLSR (Rose-Thick Li-Sparse Reciprocal kernel combination) model are adopted for snow and inland water albedo estimation, respectively; 3) global shortwave, visible, and near-infrared albedos in spatial resolution of 0.05 degree and 1 km are released; 4) Clear-sky albedo is provided beyond the traditional black-sky albedo and white sky-albedo for amateurish user; 5) 250 m albedo product is provided in part of global for regional application. In this study, we firstly detail the updates of this inspiring product. Then the product is compared with the previous GLASS albedo product and preliminary assessed against field measurements under various land covers. Significant improvements are reported for snow and water albedo. The results demonstrate that the new GLASS albedo product is a gapless, long-term continuous, and self-consistent data-set. Comparing to previous GLASS albedo product, lower black-sky albedo and higher white-sky albedo are proved for permanent snow-cover region. Moreover, higher albedo of inland water and seasonal snow-cover mountain are captured. This product brings new chance and view to understanding long

  2. Diurnal Variations of Titan's Surface Temperatures From Cassini -CIRS Observations

    Science.gov (United States)

    Cottini, Valeria; Nixon, Conor; Jennings, Don; Anderson, Carrie; Samuelson, Robert; Irwin, Patrick; Flasar, F. Michael

    The Cassini Composite Infrared Spectrometer (CIRS) observations of Saturn's largest moon, Titan, are providing us with the ability to detect the surface temperature of the planet by studying its outgoing radiance through a spectral window in the thermal infrared at 19 m (530 cm-1) characterized by low opacity. Since the first acquisitions of CIRS Titan data the in-strument has gathered a large amount of spectra covering a wide range of latitudes, longitudes and local times. We retrieve the surface temperature and the atmospheric temperature pro-file by modeling proper zonally averaged spectra of nadir observations with radiative transfer computations. Our forward model uses the correlated-k approximation for spectral opacity to calculate the emitted radiance, including contributions from collision induced pairs of CH4, N2 and H2, haze, and gaseous emission lines (Irwin et al. 2008). The retrieval method uses a non-linear least-squares optimal estimation technique to iteratively adjust the model parameters to achieve a spectral fit (Rodgers 2000). We show an accurate selection of the wide amount of data available in terms of footprint diameter on the planet and observational conditions, together with the retrieved results. Our results represent formal retrievals of surface brightness temperatures from the Cassini CIRS dataset using a full radiative transfer treatment, and we compare to the earlier findings of Jennings et al. (2009). The application of our methodology over wide areas has increased the planet coverage and accuracy of our knowledge of Titan's surface brightness temperature. In particular we had the chance to look for diurnal variations in surface temperature around the equator: a trend with slowly increasing temperature toward the late afternoon reveals that diurnal temperature changes are present on Titan surface. References: Irwin, P.G.J., et al.: "The NEMESIS planetary atmosphere radiative transfer and retrieval tool" (2008). JQSRT, Vol. 109, pp

  3. Changes in the Albedo of the Pegasus and Phoenix Runways, 2000-2017

    Science.gov (United States)

    2017-07-18

    by the net heat transfer into the runway surface during the brief but intense peak of austral summer. The flux of downwelling shortwave solar energy...snow; and as ERDC/CRREL TR-17-10 2 mentioned above, the presence of melt water in the snow further reduces albedo and increases heating of the snow...interpolating over all possible angles, end member albedo cases (“white sky” and “black sky”) can be modeled . The actual albedo or “blue sky” albedo falls

  4. Modeling seasonal surface temperature variations in secondary tropical dry forests

    Science.gov (United States)

    Cao, Sen; Sanchez-Azofeifa, Arturo

    2017-10-01

    Secondary tropical dry forests (TDFs) provide important ecosystem services such as carbon sequestration, biodiversity conservation, and nutrient cycle regulation. However, their biogeophysical processes at the canopy-atmosphere interface remain unknown, limiting our understanding of how this endangered ecosystem influences, and responds to the ongoing global warming. To facilitate future development of conservation policies, this study characterized the seasonal land surface temperature (LST) behavior of three successional stages (early, intermediate, and late) of a TDF, at the Santa Rosa National Park (SRNP), Costa Rica. A total of 38 Landsat-8 Thermal Infrared Sensor (TIRS) data and the Surface Reflectance (SR) product were utilized to model LST time series from July 2013 to July 2016 using a radiative transfer equation (RTE) algorithm. We further related the LST time series to seven vegetation indices which reflect different properties of TDFs, and soil moisture data obtained from a Wireless Sensor Network (WSN). Results showed that the LST in the dry season was 15-20 K higher than in the wet season at SRNP. We found that the early successional stages were about 6-8 K warmer than the intermediate successional stages and were 9-10 K warmer than the late successional stages in the middle of the dry season; meanwhile, a minimum LST difference (0-1 K) was observed at the end of the wet season. Leaf phenology and canopy architecture explained most LST variations in both dry and wet seasons. However, our analysis revealed that it is precipitation that ultimately determines the LST variations through both biogeochemical (leaf phenology) and biogeophysical processes (evapotranspiration) of the plants. Results of this study could help physiological modeling studies in secondary TDFs.

  5. MODIS-Derived 1.64 micron white-sky albedo on a global, 1-minute equal angle grid (Collection 004 and 005)

    Data.gov (United States)

    National Aeronautics and Space Administration — The Filled Land Surface Albedo Product is a global data set of spatially complete albedo maps. It was derived from the MODIS MOD43B3 Land product and includes both...

  6. SAI/EPRI Albedo Information Library

    International Nuclear Information System (INIS)

    Simmons, G.L.

    1979-03-01

    The SAI/EPRI Albedo Information Library (SAIL) is described. This description included the techniques used to develop the data and comparisons with albedo data. Albedo data are presented for Type 04 Concrete and Low Carbon Steel, the most common materials encountered in radiation streaming analysis. Applications of the SAIL data are presented and compared with experimental results

  7. A new albedo parameterization for use in climate models over the Antarctic ice sheet

    NARCIS (Netherlands)

    Kuipers Munneke, P.|info:eu-repo/dai/nl/304831891; van den Broeke, M.R.|info:eu-repo/dai/nl/073765643; Lenaerts, J.T.M.|info:eu-repo/dai/nl/314850163; Flanner, M.G.; Gardner, A.S.; van de Berg, W.J.|info:eu-repo/dai/nl/304831611

    2011-01-01

    A parameterization for broadband snow surface albedo, based on snow grain size evolution, cloud optical thickness, and solar zenith angle, is implemented into a regional climate model for Antarctica and validated against field observations of albedo for the period 1995–2004. Over the Antarctic

  8. A variational approach to closed bosonic strings on bordered Riemann surfaces

    International Nuclear Information System (INIS)

    Ohrndorf, T.

    1987-01-01

    Polyakov's path integral for bosonic closed strings defined on a bordered Riemann surface is investigated by variational methods. It is demonstrated that boundary variations are generated by the Virasoro operators. The investigation is performed for both, simply connected Riemann surfaces as well as ringlike domains. It is shown that the form of the variational operator is the same on both kinds of surfaces. The Virasoro algebra arises as a consistency condition for the variation. (orig.)

  9. Tundra vegetation effects on pan-Arctic albedo

    International Nuclear Information System (INIS)

    Loranty, Michael M; Goetz, Scott J; Beck, Pieter S A

    2011-01-01

    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.

  10. 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.

  11. Albedo and color maps of the Saturnian satellites

    International Nuclear Information System (INIS)

    Buratti, B.J.; Mosher, J.A.; Johnson, T.V.

    1990-01-01

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

  12. Relating black carbon content to reduction of snow albedo

    Science.gov (United States)

    Brandt, R. E.; Warren, S. G.; Clarke, A. D.

    2011-12-01

    In remote snow of the Northern Hemisphere, the levels of soot pollution are in the parts-per-billion (ppb) range, where the effect on albedo is at the level of a few percent. A reduction of albedo by 1-2% is significant for climate but is difficult to detect experimentally, because snow albedo depends on several other variables. In our work to quantify the climatic effect of black carbon (BC) in snow, we therefore do not directly measure the albedo reduction. Instead, we use a two-step procedure: (1) We collect snow samples, melt and filter them, and analyze the filters spectrophotometrically for BC concentration. (2) We use the BC amount from the filter measurement, together with snow grain size, in a radiative transfer model to compute the albedo reduction. Our radiative transfer model uses the discrete ordinates algorithm DISORT 2.0. We have chosen a representative BC size distribution and optical constants, and have incorporated those of mineral dust as well. While a given mass of BC causes over an order of magnitude more snow albedo reduction compared to dust, a snowpack containing dust mutes the albedo-reducing effect of BC. Because the computed reduction of snow albedo is model-based, it requires experimental verification. We doubt that direct measurement of albedo-reduction will be feasible in nature, because of the vertical variation of both snow grain size and soot content, and because the natural soot content is small. We conclude that what is needed is an artificial snowpack, with uniform grain size and large uniform soot content (ppm not ppb), to produce a large signal on albedo. We have chosen to pursue this experiment outdoors rather than in the laboratory, for the following reasons: (1) The snowpack in the field of view is uniformly illuminated if the source of radiation is the Sun. (2) Visible radiation penetrates into the snow, so photons emerge horizontally distant from where they entered. In the limited width of a laboratory snowpack, radiation

  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. Evaluation of Operational Albedo Algorithms For AVHRR, MODIS and VIIRS: Case Studies in Southern Africa

    Science.gov (United States)

    Privette, J. L.; Schaaf, C. B.; Saleous, N.; Liang, S.

    2004-12-01

    Shortwave broadband albedo is the fundamental surface variable that partitions solar irradiance into energy available to the land biophysical system and energy reflected back into the atmosphere. Albedo varies with land cover, vegetation phenological stage, surface wetness, solar angle, and atmospheric condition, among other variables. For these reasons, a consistent and normalized albedo time series is needed to accurately model weather, climate and ecological trends. Although an empirically-derived coarse-scale albedo from the 20-year NOAA AVHRR record (Sellers et al., 1996) is available, an operational moderate resolution global product first became available from NASA's MODIS sensor. The validated MODIS product now provides the benchmark upon which to compare albedo generated through 1) reprocessing of the historic AVHRR record and 2) operational processing of data from the future National Polar-Orbiting Environmental Satellite System's (NPOESS) Visible/Infrared Imager Radiometer Suite (VIIRS). Unfortunately, different instrument characteristics (e.g., spectral bands, spatial resolution), processing approaches (e.g., latency requirements, ancillary data availability) and even product definitions (black sky albedo, white sky albedo, actual or blue sky albedo) complicate the development of the desired multi-mission (AVHRR to MODIS to VIIRS) albedo time series -- a so-called Climate Data Record. This presentation will describe the different albedo algorithms used with AVHRR, MODIS and VIIRS, and compare their results against field measurements collected over two semi-arid sites in southern Africa. We also describe the MODIS-derived VIIRS proxy data we developed to predict NPOESS albedo characteristics. We conclude with a strategy to develop a seamless Climate Data Record from 1982- to 2020.

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

    Science.gov (United States)

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

    2016-11-01

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

  16. Evolution of Mars’ Northern Polar Seasonal CO2 deposits: variations in surface brightness and bulk density

    Science.gov (United States)

    Mount, Christopher P.; Titus, Timothy N.

    2015-01-01

    Small scale variations of seasonal ice are explored at different geomorphic units on the Northern Polar Seasonal Cap (NPSC). We use seasonal rock shadow measurements, combined with visible and thermal observations, to calculate density over time. The coupling of volume density and albedo allows us to determine the microphysical state of the seasonal CO2 ice. We find two distinct endmembers across the NPSC: 1) Snow deposits may anneal to form an overlying slab layer that fractures. These low density deposits maintain relatively constant densities over springtime. 2) Porous slab deposits likely anneal rapidly in early spring and fracture in late spring. These high density deposits dramatically increase in density over time. The endmembers appear to be correlated with latitude.

  17. Understanding the Effect of Atmospheric Density on the Cosmic Ray Flux Variations at the Earth Surface

    OpenAIRE

    Dayananda, Mathes; Zhang, Xiaohang; Butler, Carola; He, Xiaochun

    2013-01-01

    We report in this letter for the first time the numerical simulations of muon and neutron flux variations at the surface of the earth with varying air densities in the troposphere and stratosphere. The simulated neutron and muon flux variations are in very good agreement with the measured neutron flux variation in Oulu and the muon flux variation in Atlanta. We conclude from this study that the stratosphere air density variation dominates the effects on the muon flux changes while the density...

  18. Spatio-temporal Variability of Albedo and its Impact on Glacier Melt Modelling

    Science.gov (United States)

    Kinnard, C.; Mendoza, C.; Abermann, J.; Petlicki, M.; MacDonell, S.; Urrutia, R.

    2017-12-01

    Albedo is an important variable for the surface energy balance of glaciers, yet its representation within distributed glacier mass-balance models is often greatly simplified. Here we study the spatio-temporal evolution of albedo on Glacier Universidad, central Chile (34°S, 70°W), using time-lapse terrestrial photography, and investigate its effect on the shortwave radiation balance and modelled melt rates. A 12 megapixel digital single-lens reflex camera was setup overlooking the glacier and programmed to take three daily images of the glacier during a two-year period (2012-2014). One image was chosen for each day with no cloud shading on the glacier. The RAW images were projected onto a 10m resolution digital elevation model (DEM), using the IMGRAFT software (Messerli and Grinsted, 2015). A six-parameter camera model was calibrated using a single image and a set of 17 ground control points (GCPs), yielding a georeferencing accuracy of accounting for possible camera movement over time. The reflectance values from the projected image were corrected for topographic and atmospheric influences using a parametric solar irradiation model, following a modified algorithm based on Corripio (2004), and then converted to albedo using reference albedo measurements from an on-glacier automatic weather station (AWS). The image-based albedo was found to compare well with independent albedo observations from a second AWS in the glacier accumulation area. Analysis of the albedo maps showed that the albedo is more spatially-variable than the incoming solar radiation, making albedo a more important factor of energy balance spatial variability. The incorporation of albedo maps within an enhanced temperature index melt model revealed that the spatio-temporal variability of albedo is an important factor for the calculation of glacier-wide meltwater fluxes.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    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. (letter)

  20. Clear-Sky Narrowband Albedo Datasets Derived from Modis Data

    Science.gov (United States)

    Chen, Y.; Minnis, P.; Sun-Mack, S.; Arduini, R. F.; Hong, G.

    2013-12-01

    Satellite remote sensing of clouds requires an accurate estimate of the clear-sky radiances for a given scene to detect clouds and aerosols and to retrieve their microphysical properties. Knowing the spatial and angular variability of clear-sky albedo is essential for predicting the clear-sky radiance at solar wavelengths. The Clouds and the Earth's Radiant Energy System (CERES) Project uses the near-infrared (NIR; 1.24, 1.6 or 2.13 μm) and visible (VIS; 0.63 μm) channels available on the Terra and Aqua Moderate Resolution Imaging Spectroradiometers (MODIS) to help identify clouds and retrieve their properties. Generally, clear-sky albedo for a given surface type is determined for conditions when the vegetation is either thriving or dormant and free of snow. The clear-sky albedos are derived using a radiative transfer parameterization of the impact of the atmosphere, including aerosols, on the observed reflectances. This paper presents the method of generating monthly clear-sky overhead albedo maps for both snow-free and snow-covered surfaces of these channels using one year of MODIS (Moderate Resolution Imaging Spectroradiometer) CERES products. Maps of 1.24 and 1.6 μm are being used as the background to help retrieve cloud properties (e.g., effective particle size, optical depth) in CERES cloud retrievals in both snow-free and snow-covered conditions.

  1. Using BRDFs for accurate albedo calculations and adjacency effect corrections

    Energy Technology Data Exchange (ETDEWEB)

    Borel, C.C.; Gerstl, S.A.W.

    1996-09-01

    In this paper the authors discuss two uses of BRDFs in remote sensing: (1) in determining the clear sky top of the atmosphere (TOA) albedo, (2) in quantifying the effect of the BRDF on the adjacency point-spread function and on atmospheric corrections. The TOA spectral albedo is an important parameter retrieved by the Multi-angle Imaging Spectro-Radiometer (MISR). Its accuracy depends mainly on how well one can model the surface BRDF for many different situations. The authors present results from an algorithm which matches several semi-empirical functions to the nine MISR measured BRFs that are then numerically integrated to yield the clear sky TOA spectral albedo in four spectral channels. They show that absolute accuracies in the albedo of better than 1% are possible for the visible and better than 2% in the near infrared channels. Using a simplified extensive radiosity model, the authors show that the shape of the adjacency point-spread function (PSF) depends on the underlying surface BRDFs. The adjacency point-spread function at a given offset (x,y) from the center pixel is given by the integral of transmission-weighted products of BRDF and scattering phase function along the line of sight.

  2. Neutron albedo effects of underground nuclear explosion

    International Nuclear Information System (INIS)

    Yang Bo; Ying Yangjun; Li Jinhong; Bai Yun

    2013-01-01

    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)

  3. The Ultraviolet Albedo of Ganymede

    Science.gov (United States)

    McGrath, Melissa; Hendrix, A.

    2013-10-01

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

  4. Growing season carries stronger contributions to albedo dynamics on the Tibetan plateau.

    Science.gov (United States)

    Tian, Li; Chen, Jiquan; Zhang, Yangjian

    2017-01-01

    The Tibetan Plateau has experienced higher-than-global-average climate warming in recent decades, resulting in many significant changes in ecosystem structure and function. Among them is albedo, which bridges the causes and consequences of land surface processes and climate. The plateau is covered by snow/ice and vegetation in the non-growing season (nGS) and growing season (GS), respectively. Based on the MODIS products, we investigated snow/ice cover and vegetation greenness in relation to the spatiotemporal changes of albedo on the Tibetan Plateau from 2000 through 2013. A synchronous relationship was found between the change in GSNDVI and GSalbedo over time and across the Tibetan landscapes. We found that the annual average albedo had a decreasing trend, but that the albedo had slightly increased during the nGS and decreased during the GS. Across the landscapes, the nGSalbedo fluctuated in a synchronous pattern with snow/ice cover. Temporally, monthly snow/ice coverage also had a high correspondence with albedo, except in April and October. We detected clear dependencies of albedo on elevation. With the rise in altitude, the nGSalbedo decreased below 4000 m, but increased for elevations of 4500-5500 m. Above 5500 m, the nGSalbedo decreased, which was in accordance with the decreased amount of snow/ice coverage and the increased soil moisture on the plateau. More importantly, the decreasing albedo in the most recent decade appeared to be caused primarily by lowered growing season albedo.

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

    International Nuclear Information System (INIS)

    Emmett, M.B.; Rhoades, W.A.

    1978-10-01

    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

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

    KAUST Repository

    Meng, Xianhong

    2013-05-05

    strengthening of the second mechanism. That is, the second mechanism is stronger in a drought year compared to a normal year and this difference is larger than for the first mechanism. When both mechanisms are active, the second mechanism tends to dominate across the model domain, particularly during the 2002 drought period. The introduction of observed inter-annual variations in albedo produces an enhancement of the first mechanism and a weakening of the second mechanism during the onset of the drought. © 2013 Springer-Verlag Berlin Heidelberg.

  7. Albedo of a hybrid poplar plantation in central Alberta, Canada

    Science.gov (United States)

    Price, D. T.; Bernier, P. Y.; Orchansky, A.; Thomas, B.

    2012-04-01

    Canada's boreal forest resources are coming under increasing pressure from competing land-uses, including establishment of protected areas, and losses of harvestable forest to mining and oil and gas exploration. In the prairie region, concerns about lack of wood supply for pulpmills and potential opportunities for bioenergy production and carbon sequestration for climate change mitigation, have spurred interest in afforestation of marginal agricultural land, notably with fast-growing hybrid poplars (HP). However, global modelling studies suggest that a shift from grassland or crops to forest cover in temperate and boreal regions could result in reduced surface albedo, particularly in winter, causing an increase in radiative forcing and reducing any climate mitigation benefits due to net GHG removal. We report on seven growing seasons of measurements of short-wave canopy albedo using tower-mounted instruments, along with eddy covariance measurements of carbon, water and energy balance, at a site in central Alberta planted with HP cuttings in spring 2005. The data show little systematic change in average albedo as vegetation has changed from bare ground to a plantation of 6 m trees. Reasons for this include very wide (3 m) spacing between the trees, and snow cover which often persists for 4-5 months and is highly visible below the bare canopies during winter. While measurements should continue as the trees grow larger, we postulate that extensive afforestation with HP is unlikely to have major effects on regional-scale surface albedo compared to the agricultural systems they replace. Normal rotation lengths are 15-20 years, hence even if older plantations have significantly lower winter albedo, their contribution to the regional average would be relatively small because they will cover only a small fraction of the landscape (e.g., compared to forests of boreal conifers or temperate broadleaved species).

  8. Surface texture generation during cylindrical milling in the aspect of cutting force variations

    International Nuclear Information System (INIS)

    Wojciechowski, S; Twardowski, P; Pelic, M

    2014-01-01

    The work presented here concentrates on surface texture analysis, after cylindrical milling of hardened steel. Cutting force variations occurring in the machining process have direct influence on the cutter displacements and thus on the generated surface texture. Therefore, in these experiments, the influence of active number of teeth (z c ) on the cutting force variations was investigated. Cutting forces and cutter displacements were measured during machining process (online) using, namely piezoelectric force dynamometer and 3D laser vibrometer. Surface roughness parameters were measured using stylus surface profiler. The surface roughness model including cutting parameters (f z , D) and cutting force variations was also developed. The research revealed that in cylindrical milling process, cutting force variations have immediate influence on surface texture generation

  9. Accurate top of the atmosphere albedo determination from multiple views of the Multi-angle Imaging Spectro-Radiometer (MISR) instrument

    Energy Technology Data Exchange (ETDEWEB)

    Borel, C.C.; Gerstl, S.A.W. [Los Alamos National Lab., NM (United States); Tornow, C. [German Aerospace Research Establishment, Berlin (Germany)

    1996-05-01

    Changes in the Earth`s surface albedo impact the atmospheric and global energy budget and contribute to the global climate change. It is now recognized that multispectral and multiangular views of the Earth`s top of the atmosphere (TOA) albedo are necessary to provide information on albedo changes. In this paper we describe four semi- empirical bidirectional reflectance factor (BRF) models which are inverted for two and three unknowns. The retrieved BRF parameters are then used to compute the TOA spectral albedo for clear sky conditions. Using this approach we find that the albedo can be computed with better than one percent error in the visible and one and a half percent in the near infrared (NIR) for most surface types. Global monitoring of the earth radiation budget is one of the main goals in global change research programs. Thus global measurements of the TOA albedo are important. Our goals is to compute the TOA spectral albedo for clear sky conditions.

  10. EVALUATION OF THE MAIN CEOS PSEUDO CALIBRATION SITES USING MODIS BRDF/ALBEDO PRODUCTS

    Directory of Open Access Journals (Sweden)

    S. Kharbouche

    2016-06-01

    Full Text Available This work describes our findings about an evaluation of the stability and the consistency of twenty primary PICSs (Pseudo-Invariant Calibration Sites. We present an analysis of 13 years of 8-daily MODIS products of BRDF parameters and white-sky-albedos (WSA over the shortwave band. This time series of WSA and BRDFs shows the variation of the “stability” varies significantly from site to site. Using a 10x10 km window size over all the sites, the change in of WSA stability is around 4% but the isotropicity, which is an important element in inter-satellite calibration, can vary from 75% to 98%. Moreover, some PICS, especially, Libya-4 which is one of the PICS which is most employed, has significant and relatively fast changes in wintertime. PICS observations of BRDF/albedo shows that the Libya-4 PICS has the best performance but it is not too far from some sites such as Libya-1 and Mali. This study also reveals that Niger-3 PICS has the longest continuous period of high stability per year, and Sudan has the most isotropic surface. These observations have important implications for the use of these sites.

  11. Mars Surface Heterogeneity From Variations in Apparent Thermal Inertia

    Science.gov (United States)

    Putzig, N. E.; Mellon, M. T.

    2005-12-01

    Current techniques used in the calculation of thermal inertia from observed brightness temperatures typically assume that planetary surface properties are uniform on the scale of the instrument's observational footprint. Mixed or layered surfaces may yield different apparent thermal inertia values at different seasons or times of day due to the nonlinear relationship between temperature and thermal inertia. To obtain sufficient data coverage for investigating temporal changes, we processed three Mars years of observations from the Mars Global Surveyor Thermal Emission Spectrometer and produced seasonal nightside and dayside maps of apparent thermal inertia. These maps show broad regions with seasonal and diurnal differences as large as 200 J m-2 K-1 s-½ at mid-latitudes (60°S to 60°N) and ranging up to 600 J m-2 K-1 s-½ or greater in the polar regions. Comparison of the maps with preliminary results from forward-modeling of heterogeneous surfaces indicates that much of the martian surface may be dominated by (1) horizontally mixed surfaces, such as those containing differing proportions of rocks, sand, dust, duricrust, and localized frosts; (2) higher thermal inertia layers over lower thermal inertia substrates, such as duricrust or desert pavements; and (3) lower thermal inertia layers over higher thermal inertia substrates, such as dust over sand or rocks and soils with an ice table at depth.

  12. Colour, albedo and nucleus size of Halley's comet

    Science.gov (United States)

    Cruikshank, D. P.; Tholen, D. J.; Hartmann, W. K.

    1985-01-01

    Photometry of Halley's comet in the B, J, V, and K broadband filters during a time when the coma was very weak and presumed to contribute negligibly to the broadband photometry is reported. The V-J and J-K colors suggest that the color of the nucleus of Halley's comet is similar to that of the D-type asteroids, which in turn suggests that the surface of the nucleus has an albedo less than 0.1.

  13. Variation on wettability of anodic zirconium oxide nanotube surface

    International Nuclear Information System (INIS)

    Wang, Lu-Ning; Shen, Chen; Shinbine, Alyssa; Luo, Jing-Li

    2013-01-01

    The present study reports the effect of fabrication conditions and environmental conditions, such as anodization voltage and aging period, on the wetting of zirconium dioxide nanotube (ZrNT) surfaces. Comparing with intact zirconium foil, which was inherently less hydrophilic, possessing an approximate contact angle of 60–70°, the as-formed ZrNT surfaces were much hydrophilic with an approximate contact angle of 18°. However, the hydrophilicity of the surfaces exhibited a decrease when the nanotubular opening diameters decreased while maintaining the nanotubular layer thickness. This phenomenon was attributed to the balance of capillary force and force generated by compressed air in the ZrNTs. The annealing treatment further increased the hydrophilic property of the ZrNTs. In addition, it was found that the wettability of ZrNTs, when aged in air over a period of 105 days, demonstrated a decrease in hydrophilic characteristics and exhibited, to some extent, an increase in hydrophobic characteristics. It was believed that the surface wettability was able to be changed due to the decreasing content of hydroxyl groups in ambient atmosphere. This work can provide guidelines for improving the structural and environmental conditions responsible for changing surface wettability of ZrNT surfaces for biomedical application. - Highlights: ► Wettability of zirconium oxide nanotubes (ZrNTs) was observed and characterized. ► Increasing of nanotubular diameter decreased the hydrophilicity of ZrNTs. ► Annealing processes enhanced the hydrophilicity of ZrNTs. ► Long term aging resulted in the hydrophobicity of ZrNTs

  14. PENGAMBILAN PEKTIN DARI ALBEDO SEMANGKA DENGAN PROSES EKSTRAKSI ASAM

    Directory of Open Access Journals (Sweden)

    Melisa Triandini Maulani

    2014-04-01

    Full Text Available Watermelon is a plant that is resistant to dry climate so it can be grown in tropical and semi-desert. Watermelon albedo is a potential source of pectin because it contains pectin compounds. To decompose the pectin in the watermelon albedo can be done by acid extraction process because it will lesser the possibility of damage pectin, whereas alcohol is use to precipitate pectin. In this research watermelon albedo as basic ingredients would be extracted to produce pectin to identified the differences in the influence of temperature variation and the type of solvent extraction of the pectin content of the albedo watermelon and determined variations in maximum temperature and type of solvent extraction to produce pectin. The study was conducted with a 90-minute extraction time and extraction temperature 60, 70, and 80 °C and 500 mL the solvent HCl and CH3COOH with 2.6 pH. The results were obtained taking the maximum conditions of pectin using solvent extraction HCl at a temperature of 80 °C and obtained pectin levels of 11.2635%. Solvent which is a strong acid HCl is easier to untie protopektin pectin so pectin levels has generated a high level. The higher the operating temperature, the bigger pectin levels that are obtained until the temperature limit of 80 °C. This caused by the movement of the H+ ions more reactive, the more contact between the substances dissolved in the sample with solvent and obtained more pectin.

  15. Variation in skin surface lipid composition among the Equidae.

    Science.gov (United States)

    Colton, S W; Downing, D T

    1983-01-01

    Skin surface lipids from Equus caballus, E. przewalskii, E. asinus, E. grevyi, E. hemionus onager and a mule (E. asinus/E. caballus) were analyzed in detail. In all species the surface lipid mixtures consisted of giant-ring lactones, cholesterol, cholesteryl esters and minor amounts of wax diesters. In E. caballus, the lactone hydroxyacids were entirely branched chained, while in E. asinus and E. grevyi they were almost exclusively straight chained. In E. przewalskii, the onager and the mule there were both straight and branched chain hydroxyacid lactones. These results are in harmony with published interpretations of the evolutionary relationships among Equus species.

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

    International Nuclear Information System (INIS)

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

    2010-01-01

    The two main forcings that can counteract to some extent the positive forcings from greenhouse gases from pre-industrial times to present day are the aerosol and related aerosol-cloud forcings, and the radiative response to changes in surface albedo. Here, we quantify the change in radiative forcing and 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 W m -2 , and temperature decreased by ∼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 US the total outgoing radiation increased by 2.3 W m -2 , and land surface temperature decreased by ∼0.03 K for an average 0.01 increase in surface albedo. Based on these forcings, the expected emitted CO 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 ∼57 Gt CO 2 . A more meaningful evaluation of the impacts of urban albedo increases on global climate and the expected CO 2 offsets would require simulations which better characterize urban surfaces and represent the full annual cycle.

  17. Arctic sea ice albedo - A comparison of two satellite-derived data sets

    Science.gov (United States)

    Schweiger, Axel J.; Serreze, Mark C.; Key, Jeffrey R.

    1993-01-01

    Spatial patterns of mean monthly surface albedo for May, June, and July, derived from DMSP Operational Line Scan (OLS) satellite imagery are compared with surface albedos derived from the International Satellite Cloud Climatology Program (ISCCP) monthly data set. Spatial patterns obtained by the two techniques are in general agreement, especially for June and July. Nevertheless, systematic differences in albedo of 0.05 - 0.10 are noted which are most likely related to uncertainties in the simple parameterizations used in the DMSP analyses, problems in the ISCCP cloud-clearing algorithm and other modeling simplifications. However, with respect to the eventual goal of developing a reliable automated retrieval algorithm for compiling a long-term albedo data base, these initial comparisons are very encouraging.

  18. 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

    Building Energy Efficiency Standard (Title-24, Part 6) includes the use of high-albedo surfaces on low-sloped roofs on non-residential buildings. Analyzing a subset of large presumably commercial buildings, we find high albedo roofs represent 0.5% and 10% of total roofs and roof surface area, respectively. The potential for high albedo roofs to reduce urban temperatures was investigated for a California city (Bakersfield) with warm summers using a state-of-the-art meteorological model (Weather Research and Forecasting, WRF). Base case and cool roof scenarios were simulated with the only difference being that the surface albedo was increased under the cool roof scenario. Roof albedos derived from the aerial imagery were used as an input to the climate model in the base case scenario. Simulation results indicate that seasonal average afternoon (1500 h) temperatures could be reduced by up to 0.2 °C across Bakersfield during both the summer and winter. While temperature changes are similar during winter and summer, only summer shows statistically significant temperature changes downwind (southeast) from Bakersfield. This indicates that reduced summertime temperatures may be felt over a distance that is 2 or 3 times the length scale of the region with high albedo roofs.

  19. On the importance of the albedo parameterization for the mass balance of the Greenland ice sheet in EC-Earth

    NARCIS (Netherlands)

    Helsen, Michiel M.; van de Wal, Roderik S. W.; Reerink, Thomas J.; Bintanja, Richard; Madsen, Marianne S.; Yang, Shuting; Li, Qiang; Zhang, Qiong

    2017-01-01

    The albedo of the surface of ice sheets changes as a function of time due to the effects of deposition of new snow, ageing of dry snow, bare ice exposure, melting and run-off. Currently, the calculation of the albedo of ice sheets is highly parameterized within the earth system model EC-Earth by

  20. On the importance of the albedo parameterization for the mass balance of the Greenland ice sheet in EC-Earth

    NARCIS (Netherlands)

    Helsen, Michiel M.; Van De Wal, Roderik S.W.; Reerink, Thomas J.; Bintanja, Richard; Madsen, Marianne S.; Yang, Shuting; Li, Qiang; Zhang, Qiong

    2017-01-01

    The albedo of the surface of ice sheets changes as a function of time due to the effects of deposition of new snow, ageing of dry snow, bare ice exposure, melting and run-off. Currently, the calculation of the albedo of ice sheets is highly parameterized within the earth system model ECEarth by

  1. Analysis of earth albedo effect on sun sensor measurements based on theoretical model and mission experience

    Science.gov (United States)

    Brasoveanu, Dan; Sedlak, Joseph

    1998-01-01

    Analysis of flight data from previous missions indicates that anomalous Sun sensor readings could be caused by Earth albedo interference. A previous Sun sensor study presented a detailed mathematical model of this effect. The model can be used to study the effect of both diffusive and specular reflections and to improve Sun angle determination based on perturbed Sun sensor measurements, satellite position, and an approximate knowledge of attitude. The model predicts that diffuse reflected light can cause errors of up to 10 degrees in Coarse Sun Sensor (CSS) measurements and 5 to 10 arc sec in Fine Sun Sensor (FSS) measurements, depending on spacecraft orbit and attitude. The accuracy of these sensors is affected as long as part of the illuminated Earth surface is present in the sensor field of view. Digital Sun Sensors (DSS) respond in a different manner to the Earth albedo interference. Most of the time DSS measurements are not affected, but for brief periods of time the Earth albedo can cause errors which are a multiple of the sensor least significant bit and may exceed one degree. This paper compares model predictions with Tropical Rainfall Measuring Mission (TRMM) CSS measurements in order to validate and refine the model. Methods of reducing and mitigating the impact of Earth albedo are discussed. ne CSS sensor errors are roughly proportional to the Earth albedo coefficient. Photocells that are sensitive only to ultraviolet emissions would reduce the effective Earth albedo by up to a thousand times, virtually eliminating all errors caused by Earth albedo interference.

  2. Performance verification of focus variation and confocal microscopes measuring tilted ultra-fine surfaces

    DEFF Research Database (Denmark)

    Quagliotti, Danilo; Baruffi, Federico; Tosello, Guido

    2016-01-01

    The behaviour of two optical instruments, scilicet a laser scanning confocal microscope and a focus-variation microscope, was investigated considering measurements of tilted surfaces. The measured samples were twelve steel artefacts for mould surface finish reference, covering Sa roughness...... parameter in the range (101—103) nm. The 3D surface texture parameters considered were Sa, Sq and Sdq. The small working distance of the confocal microscope objectives influenced the measurement setup, preventing from selecting a high tilting angle. The investigation was carried out comparing measurements...... of flat surfaces (0° tilt) with measurements of 12.5° tilted surfaces. The confocal microscope results showed a high sensitivity to tilting due to the laser beam reflection on the metal surfaces. The focus variation microscope results were more robust with respect to the considered angular variation...

  3. Stochastic dynamics of melt ponds and sea ice-albedo climate feedback

    Science.gov (United States)

    Sudakov, Ivan

    Evolution of melt ponds on the Arctic sea surface is a complicated stochastic process. We suggest a low-order model with ice-albedo feedback which describes stochastic dynamics of melt ponds geometrical characteristics. The model is a stochastic dynamical system model of energy balance in the climate system. We describe the equilibria in this model. We conclude the transition in fractal dimension of melt ponds affects the shape of the sea ice albedo curve.

  4. Simulation and Analysis of the Topographic Effects on Snow-Free Albedo over Rugged Terrain

    Directory of Open Access Journals (Sweden)

    Dalei Hao

    2018-02-01

    Full Text Available Topography complicates the modeling and retrieval of land surface albedo due to shadow effects and the redistribution of incident radiation. Neglecting topographic effects may lead to a significant bias when estimating land surface albedo over a single slope. However, for rugged terrain, a comprehensive and systematic investigation of topographic effects on land surface albedo is currently ongoing. Accurately estimating topographic effects on land surface albedo over a rugged terrain presents a challenge in remote sensing modeling and applications. In this paper, we focused on the development of a simplified estimation method for snow-free albedo over a rugged terrain at a 1-km scale based on a 30-m fine-scale digital elevation model (DEM. The proposed method was compared with the radiosity approach based on simulated and real DEMs. The results of the comparison showed that the proposed method provided adequate computational efficiency and satisfactory accuracy simultaneously. Then, the topographic effects on snow-free albedo were quantitatively investigated and interpreted by considering the mean slope, subpixel aspect distribution, solar zenith angle, and solar azimuth angle. The results showed that the more rugged the terrain and the larger the solar illumination angle, the more intense the topographic effects were on black-sky albedo (BSA. The maximum absolute deviation (MAD and the maximum relative deviation (MRD of the BSA over a rugged terrain reached 0.28 and 85%, respectively, when the SZA was 60° for different terrains. Topographic effects varied with the mean slope, subpixel aspect distribution, SZA and SAA, which should not be neglected when modeling albedo.

  5. A Variational Model for Two-Phase Immiscible Electroosmotic Flow at Solid Surfaces

    KAUST Repository

    Shao, Sihong; Qian, Tiezheng

    2012-01-01

    We develop a continuum hydrodynamic model for two-phase immiscible flows that involve electroosmotic effect in an electrolyte and moving contact line at solid surfaces. The model is derived through a variational approach based on the Onsager

  6. Combining NLCD and MODIS to create a land cover-albedo database for the continental United States

    Science.gov (United States)

    Wickham, J.; Barnes, Christopher A.; Nash, M.S.; Wade, T.G.

    2015-01-01

    Land surface albedo is an essential climate variable that is tightly linked to land cover, such that specific land cover classes (e.g., deciduous broadleaf forest, cropland) have characteristic albedos. Despite the normative of land-cover class specific albedos, there is considerable variability in albedo within a land cover class. The National Land Cover Database (NLCD) and the Moderate Resolution Imaging Spectroradiometer (MODIS) albedo product were combined to produce a long-term (14 years) integrated land cover-albedo database for the continental United States that can be used to examine the temporal behavior of albedo as a function of land cover. The integration identifies areas of homogeneous land cover at the nominal spatial resolution of the MODIS (MCD43A) albedo product (500 m × 500 m) from the NLCD product (30 m × 30 m), and provides an albedo data record per 500 m × 500 m pixel for 14 of the 16 NLCD land cover classes. Individual homogeneous land cover pixels have up to 605 albedo observations, and 75% of the pixels have at least 319 MODIS albedo observations (≥ 50% of the maximum possible number of observations) for the study period (2000–2013). We demonstrated the utility of the database by conducting a multivariate analysis of variance of albedo for each NLCD land cover class, showing that locational (pixel-to-pixel) and inter-annual variability were significant factors in addition to expected seasonal (intra-annual) and geographic (latitudinal) effects.

  7. Calculation of double energy angle differential neutron albedos for radiation shielding applications

    International Nuclear Information System (INIS)

    Litaize, O.; Diop, C.M.; Nimal, J.C.

    2000-01-01

    Void radiation shielding problems can be dealt with albedo concept which is an alternative to the complex bringing into operation of the 'exact' transport method calculations (SN, Monte Carlo). Up to here, differential albedos are used for single reflections from walls in the NARCISSE-3 propagation albedo code developed at CEA and used for project calculations. For taking into account the neutron multiple reflections on lacunar medium walls, double energy-angle differential albedos are needed. TRIPOLI-4 neutral particle transport Monte Carlo code in three dimensional geometries, has been chosen to implement a double differential albedo calculus routine and therefore to generate albedo data for different kinds of medium. The surfacic estimator, which could be used, is not enough efficient because all neutrons do not contribute to the result. A new estimator is carried out. At each collision site, during the neutron history simulation, it allows to compute the probability of the neutron to go through the medium and to come through the reflection surface in the direction and at the energy considered. This estimator is about hundred times more efficient than the surfacic estimator. (author)

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

    Science.gov (United States)

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

    2015-12-01

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

  9. 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.)

  10. 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.

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

    Science.gov (United States)

    Kreuter, A; Emde, C; Blumthaler, M

    2010-11-01

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

  12. Modelling Mean Albedo of Individual Roofs in Complex Urban Areas Using Satellite Images and Airborne Laser Scanning Point Clouds

    Science.gov (United States)

    Kalantar, B.; Mansor, S.; Khuzaimah, Z.; Sameen, M. Ibrahim; Pradhan, B.

    2017-09-01

    Knowledge of surface albedo at individual roof scale is important for mitigating urban heat islands and understanding urban climate change. This study presents a method for quantifying surface albedo of individual roofs in a complex urban area using the integration of Landsat 8 and airborne LiDAR data. First, individual roofs were extracted from airborne LiDAR data and orthophotos using optimized segmentation and supervised object based image analysis (OBIA). Support vector machine (SVM) was used as a classifier in OBIA process for extracting individual roofs. The user-defined parameters required in SVM classifier were selected using v-fold cross validation method. After that, surface albedo was calculated for each individual roof from Landsat images. Finally, thematic maps of mean surface albedo of individual roofs were generated in GIS and the results were discussed. Results showed that the study area is covered by 35% of buildings varying in roofing material types and conditions. The calculated surface albedo of buildings ranged from 0.16 to 0.65 in the study area. More importantly, the results indicated that the types and conditions of roofing materials significantly effect on the mean value of surface albedo. Mean albedo of new concrete, old concrete, new steel, and old steel were found to be equal to 0.38, 0.26, 0.51, and 0.44 respectively. Replacing old roofing materials with new ones should highly prioritized.

  13. MODELLING MEAN ALBEDO OF INDIVIDUAL ROOFS IN COMPLEX URBAN AREAS USING SATELLITE IMAGES AND AIRBORNE LASER SCANNING POINT CLOUDS

    Directory of Open Access Journals (Sweden)

    B. Kalantar

    2017-09-01

    Full Text Available Knowledge of surface albedo at individual roof scale is important for mitigating urban heat islands and understanding urban climate change. This study presents a method for quantifying surface albedo of individual roofs in a complex urban area using the integration of Landsat 8 and airborne LiDAR data. First, individual roofs were extracted from airborne LiDAR data and orthophotos using optimized segmentation and supervised object based image analysis (OBIA. Support vector machine (SVM was used as a classifier in OBIA process for extracting individual roofs. The user-defined parameters required in SVM classifier were selected using v-fold cross validation method. After that, surface albedo was calculated for each individual roof from Landsat images. Finally, thematic maps of mean surface albedo of individual roofs were generated in GIS and the results were discussed. Results showed that the study area is covered by 35% of buildings varying in roofing material types and conditions. The calculated surface albedo of buildings ranged from 0.16 to 0.65 in the study area. More importantly, the results indicated that the types and conditions of roofing materials significantly effect on the mean value of surface albedo. Mean albedo of new concrete, old concrete, new steel, and old steel were found to be equal to 0.38, 0.26, 0.51, and 0.44 respectively. Replacing old roofing materials with new ones should highly prioritized.

  14. Core surface flow modelling from high-resolution secular variation

    DEFF Research Database (Denmark)

    Holme, R.; Olsen, Nils

    2006-01-01

    -flux hypothesis, but the spectrum of the SV implies that a conclusive test of frozen-flux is not possible. We parametrize the effects of diffusion as an expected misfit in the flow prediction due to departure from the frozen-flux hypothesis; at low spherical harmonic degrees, this contribution dominates...... the expected departure of the SV predictions from flow to the observed SV, while at high degrees the SV model uncertainty is dominant. We construct fine-scale core surface flows to model the SV. Flow non-uniqueness is a serious problem because the flows are sufficiently small scale to allow flow around non......-series of magnetic data and better parametrization of the external magnetic field....

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

    Science.gov (United States)

    Cescatti, Alessandro; Marcolla, Barbara; Vannan, Suresh K. Santhana; Pan, Jerry Yun; Roman, Miguel O.; Yang, Xiaoyuan; Ciais, Philippe; Cook, Robert B.; Law, Beverly E.; Matteucci, Girogio; hide

    2012-01-01

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

  16. 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.

  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. Global warming related transient albedo feedback in the Arctic and its relation to the seasonality of sea ice

    Science.gov (United States)

    Andry, Olivier; Bintanja, Richard; Hazeleger, Wilco

    2015-04-01

    The Arctic is warming two to three times faster than the global average. Arctic sea ice cover is very sensitive to this warming and has reached historic minima in late summer in recent years (i.e. 2007, 2012). Considering that the Arctic Ocean is mainly ice-covered and that the albedo of sea ice is very high compared to that of open water, the change in sea ice cover is very likely to have a strong impact on the local surface albedo feedback. Here we quantify the temporal changes in surface albedo feedback in response to global warming. Usually feedbacks are evaluated as being representative and constant for long time periods, but we show here that the strength of climate feedbacks in fact varies strongly with time. For instance, time series of the amplitude of the surface albedo feedback, derived from future climate simulations (CIMP5, RCP8.5 up to year 2300) using a kernel method, peaks around the year 2100. This maximum is likely caused by an increased seasonality in sea-ice cover that is inherently associated with sea ice retreat. We demonstrate that the Arctic average surface albedo has a strong seasonal signature with a maximum in spring and a minimum in late summer/autumn. In winter when incoming solar radiation is minimal the surface albedo doesn't have an important effect on the energy balance of the climate system. The annual mean surface albedo is thus determined by the seasonality of both downwelling shortwave radiation and sea ice cover. As sea ice cover reduces the seasonal signature is modified, the transient part from maximum sea ice cover to its minimum is shortened and sharpened. The sea ice cover is reduced when downwelling shortwave radiation is maximum and thus the annual surface albedo is drastically smaller. Consequently the change in annual surface albedo with time will become larger and so will the surface albedo feedback. We conclude that a stronger seasonality in sea ice leads to a stronger surface albedo feedback, which accelerates

  19. 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.

  20. Use of AMSR-E microwave satellite data for land surface characteristics and snow cover variation

    Directory of Open Access Journals (Sweden)

    Mukesh Singh Boori

    2016-12-01

    Full Text Available This data article contains data related to the research article entitled “Global land cover classification based on microwave polarization and gradient ratio (MPGR” [1] and “Microwave polarization and gradient ratio (MPGR for global land surface phenology” [2]. This data article presents land surface characteristics and snow cover variation information from sensors like EOS Advanced Microwave Scanning Radiometer (AMSR-E. This data article use the HDF Explorer, Matlab, and ArcGIS software to process the pixel latitude, longitude, snow water equivalent (SWE, digital elevation model (DEM and Brightness Temperature (BT information from AMSR-E satellite data to provide land surface characteristics and snow cover variation data in all-weather condition at any time. This data information is useful to discriminate different land surface cover types and snow cover variation, which is turn, will help to improve monitoring of weather, climate and natural disasters.

  1. 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

  2. Surface adhesion and confinement variation of Staphylococcus aurius on SAM surfaces

    Science.gov (United States)

    Amroski, Alicia; Olsen, Morgan; Calabrese, Joseph; Senevirathne, Reshani; Senevirathne, Indrajith

    2012-02-01

    Controlled surface adhesion of non - pathogenic gram positive strain, Staphylococcus aureus is interesting as a model system due to possible development of respective biosensors for prevention and detection of the pathogenic strain methicillin resistant Staphylococcus aureus (MRSA) and further as a study for bio-machine interfacing. Self Assembled Monolayers (SAM) with engineered surfaces of linear thiols on Au(111) were used as the substrate. Sub cultured S. aureus were used for the analysis. The SAM layered surfaces were dipped in 2 -- 4 Log/ml S. aureus solution. Subsequent surface adhesion at different bacterial dilutions on surfaces will be discussed, and correlated with quantitative and qualitative adhesion properties of bacteria on the engineered SAM surfaces. The bacteria adhered SAM surfaces were investigated using intermittent contact, noncontact, lateral force and contact modes of Atomic Force Microscopy (AFM).

  3. The AMMA-CATCH Gourma observatory site in Mali: Relating climatic variations to changes in vegetation, surface hydrology, fluxes and natural resources

    Science.gov (United States)

    Mougin, E.; Hiernaux, P.; Kergoat, L.; Grippa, M.; de Rosnay, P.; Timouk, F.; Le Dantec, V.; Demarez, V.; Lavenu, F.; Arjounin, M.; Lebel, T.; Soumaguel, N.; Ceschia, E.; Mougenot, B.; Baup, F.; Frappart, F.; Frison, P. L.; Gardelle, J.; Gruhier, C.; Jarlan, L.; Mangiarotti, S.; Sanou, B.; Tracol, Y.; Guichard, F.; Trichon, V.; Diarra, L.; Soumaré, A.; Koité, M.; Dembélé, F.; Lloyd, C.; Hanan, N. P.; Damesin, C.; Delon, C.; Serça, D.; Galy-Lacaux, C.; Seghieri, J.; Becerra, S.; Dia, H.; Gangneron, F.; Mazzega, P.

    2009-08-01

    SummaryThe Gourma site in Mali is one of the three instrumented meso-scale sites deployed in West-Africa as part of the African Monsoon Multi-disciplinary Analysis (AMMA) project. Located both in the Sahelian zone sensu stricto, and in the Saharo-Sahelian transition zone, the Gourma meso-scale window is the northernmost site of the AMMA-CATCH observatory reached by the West African Monsoon. The experimental strategy includes deployment of a variety of instruments, from local to meso-scale, dedicated to monitoring and documentation of the major variables characterizing the climate forcing, and the spatio-temporal variability of surface processes and state variables such as vegetation mass, leaf area index (LAI), soil moisture and surface fluxes. This paper describes the Gourma site, its associated instrumental network and the research activities that have been carried out since 1984. In the AMMA project, emphasis is put on the relations between climate, vegetation and surface fluxes. However, the Gourma site is also important for development and validation of satellite products, mainly due to the existence of large and relatively homogeneous surfaces. The social dimension of the water resource uses and governance is also briefly analyzed, relying on field enquiry and interviews. The climate of the Gourma region is semi-arid, daytime air temperatures are always high and annual rainfall amounts exhibit strong inter-annual and seasonal variations. Measurements sites organized along a north-south transect reveal sharp gradients in surface albedo, net radiation, vegetation production, and distribution of plant functional types. However, at any point along the gradient, surface energy budget, soil moisture and vegetation growth contrast between two main types of soil surfaces and hydrologic systems. On the one hand, sandy soils with high water infiltration rates and limited run-off support almost continuous herbaceous vegetation with scattered woody plants. On the other

  4. Distinguishing the albedo of exoplanets from stellar activity

    Science.gov (United States)

    Serrano, L. M.; Barros, S. C. C.; Oshagh, M.; Santos, N. C.; Faria, J. P.; Demangeon, O.; Sousa, S. G.; Lendl, M.

    2018-03-01

    Context. Light curves show the flux variation from the target star and its orbiting planets as a function of time. In addition to the transit features created by the planets, the flux also includes the reflected light component of each planet, which depends on the planetary albedo. This signal is typically referred to as phase curve and could be easily identified if there were no additional noise. As well as instrumental noise, stellar activity, such as spots, can create a modulation in the data, which may be very difficult to distinguish from the planetary signal. Aims: We analyze the limitations imposed by the stellar activity on the detection of the planetary albedo, considering the limitations imposed by the predicted level of instrumental noise and the short duration of the obervations planned in the context of the CHEOPS mission. Methods: As initial condition, we have assumed that each star is characterized by just one orbiting planet. We built mock light curves that included a realistic stellar activity pattern, the reflected light component of the planet and an instrumental noise level, which we have chosen to be at the same level as predicted for CHEOPS. We then fit these light curves to try to recover the reflected light component, assuming the activity patterns can be modeled with a Gaussian process. Results: We estimate that at least one full stellar rotation is necessary to obtain a reliable detection of the planetary albedo. This result is independent of the level of noise, but it depends on the limitation of the Gaussian process to describe the stellar activity when the light curve time-span is shorter than the stellar rotation. As an additional result, we found that with a 6.5 magnitude star and the noise level of CHEOPS, it is possible to detect the planetary albedo up to a lower limit of Rp = 0.03 R*. Finally, in presence of typical CHEOPS gaps in the simulations, we confirm that it is still possible to obtain a reliable albedo.

  5. Growing season carries stronger contributions to albedo dynamics on the Tibetan plateau.

    Directory of Open Access Journals (Sweden)

    Li Tian

    Full Text Available The Tibetan Plateau has experienced higher-than-global-average climate warming in recent decades, resulting in many significant changes in ecosystem structure and function. Among them is albedo, which bridges the causes and consequences of land surface processes and climate. The plateau is covered by snow/ice and vegetation in the non-growing season (nGS and growing season (GS, respectively. Based on the MODIS products, we investigated snow/ice cover and vegetation greenness in relation to the spatiotemporal changes of albedo on the Tibetan Plateau from 2000 through 2013. A synchronous relationship was found between the change in GSNDVI and GSalbedo over time and across the Tibetan landscapes. We found that the annual average albedo had a decreasing trend, but that the albedo had slightly increased during the nGS and decreased during the GS. Across the landscapes, the nGSalbedo fluctuated in a synchronous pattern with snow/ice cover. Temporally, monthly snow/ice coverage also had a high correspondence with albedo, except in April and October. We detected clear dependencies of albedo on elevation. With the rise in altitude, the nGSalbedo decreased below 4000 m, but increased for elevations of 4500-5500 m. Above 5500 m, the nGSalbedo decreased, which was in accordance with the decreased amount of snow/ice coverage and the increased soil moisture on the plateau. More importantly, the decreasing albedo in the most recent decade appeared to be caused primarily by lowered growing season albedo.

  6. Simulated cold bias being improved by using MODIS time-varying albedo in the Tibetan Plateau in WRF model

    Science.gov (United States)

    Meng, X.; Lyu, S.; Zhang, T.; Zhao, L.; Li, Z.; Han, B.; Li, S.; Ma, D.; Chen, H.; Ao, Y.; Luo, S.; Shen, Y.; Guo, J.; Wen, L.

    2018-04-01

    Systematic cold biases exist in the simulation for 2 m air temperature in the Tibetan Plateau (TP) when using regional climate models and global atmospheric general circulation models. We updated the albedo in the Weather Research and Forecasting (WRF) Model lower boundary condition using the Global LAnd Surface Satellite Moderate-Resolution Imaging Spectroradiometer albedo products and demonstrated evident improvement for cold temperature biases in the TP. It is the large overestimation of albedo in winter and spring in the WRF model that resulted in the large cold temperature biases. The overestimated albedo was caused by the simulated precipitation biases and over-parameterization of snow albedo. Furthermore, light-absorbing aerosols can result in a large reduction of albedo in snow and ice cover. The results suggest the necessity of developing snow albedo parameterization using observations in the TP, where snow cover and melting are very different from other low-elevation regions, and the influence of aerosols should be considered as well. In addition to defining snow albedo, our results show an urgent call for improving precipitation simulation in the TP.

  7. Thermal neutron albedo measurements for multilithic reflectors

    International Nuclear Information System (INIS)

    Mehboob, Khurram; Ahmed, Raheel; Ali, Majid; Tabassam, Uzma

    2013-01-01

    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 BF 3 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

  8. 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

  9. Sea ice roughness: the key for predicting Arctic summer ice albedo

    Science.gov (United States)

    Landy, J.; Ehn, J. K.; Tsamados, M.; Stroeve, J.; Barber, D. G.

    2017-12-01

    Although melt ponds on Arctic sea ice evolve in stages, ice with smoother surface topography typically allows the pond water to spread over a wider area, reducing the ice-albedo and accelerating further melt. Building on this theory, we simulated the distribution of meltwater on a range of statistically-derived topographies to develop a quantitative relationship between premelt sea ice surface roughness and summer ice albedo. Our method, previously applied to ICESat observations of the end-of-winter sea ice roughness, could account for 85% of the variance in AVHRR observations of the summer ice-albedo [Landy et al., 2015]. Consequently, an Arctic-wide reduction in sea ice roughness over the ICESat operational period (from 2003 to 2008) explained a drop in ice-albedo that resulted in a 16% increase in solar heat input to the sea ice cover. Here we will review this work and present new research linking pre-melt sea ice surface roughness observations from Cryosat-2 to summer sea ice albedo over the past six years, examining the potential of winter roughness as a significant new source of sea ice predictability. We will further evaluate the possibility for high-resolution (kilometre-scale) forecasts of summer sea ice albedo from waveform-level Cryosat-2 roughness data in the landfast sea ice zone of the Canadian Arctic. Landy, J. C., J. K. Ehn, and D. G. Barber (2015), Albedo feedback enhanced by smoother Arctic sea ice, Geophys. Res. Lett., 42, 10,714-10,720, doi:10.1002/2015GL066712.

  10. Surface Tension of Multi-phase Flow with Multiple Junctions Governed by the Variational Principle

    International Nuclear Information System (INIS)

    Matsutani, Shigeki; Nakano, Kota; Shinjo, Katsuhiko

    2011-01-01

    We explore a computational model of an incompressible fluid with a multi-phase field in three-dimensional Euclidean space. By investigating an incompressible fluid with a two-phase field geometrically, we reformulate the expression of the surface tension for the two-phase field found by Lafaurie et al. (J Comput Phys 113:134–147, 1994) as a variational problem related to an infinite dimensional Lie group, the volume-preserving diffeomorphism. The variational principle to the action integral with the surface energy reproduces their Euler equation of the two-phase field with the surface tension. Since the surface energy of multiple interfaces even with singularities is not difficult to be evaluated in general and the variational formulation works for every action integral, the new formulation enables us to extend their expression to that of a multi-phase (N-phase, N ≥ 2) flow and to obtain a novel Euler equation with the surface tension of the multi-phase field. The obtained Euler equation governs the equation for motion of the multi-phase field with different surface tension coefficients without any difficulties for the singularities at multiple junctions. In other words, we unify the theory of multi-phase fields which express low dimensional interface geometry and the theory of the incompressible fluid dynamics on the infinite dimensional geometry as a variational problem. We apply the equation to the contact angle problems at triple junctions. We computed the fluid dynamics for a two-phase field with a wall numerically and show the numerical computational results that for given surface tension coefficients, the contact angles are generated by the surface tension as results of balances of the kinematic energy and the surface energy.

  11. Variations in sea surface roughness induced by the 2004 Sumatra-Andaman tsunami

    Directory of Open Access Journals (Sweden)

    O. A. Godin

    2009-07-01

    Full Text Available Observations of tsunamis away from shore are critically important for improving early warning systems and understanding of tsunami generation and propagation. Tsunamis are difficult to detect and measure in the open ocean because the wave amplitude there is much smaller than it is close to shore. Currently, tsunami observations in deep water rely on measurements of variations in the sea surface height or bottom pressure. Here we demonstrate that there exists a different observable, specifically, ocean surface roughness, which can be used to reveal tsunamis away from shore. The first detailed measurements of the tsunami effect on sea surface height and radar backscattering strength in the open ocean were obtained from satellite altimeters during passage of the 2004 Sumatra-Andaman tsunami. Through statistical analyses of satellite altimeter observations, we show that the Sumatra-Andaman tsunami effected distinct, detectable changes in sea surface roughness. The magnitude and spatial structure of the observed variations in radar backscattering strength are consistent with hydrodynamic models predicting variations in the near-surface wind across the tsunami wave front. Tsunami-induced changes in sea surface roughness can be potentially used for early tsunami detection by orbiting microwave radars and radiometers, which have broad surface coverage across the satellite ground track.

  12. Surface Freshwater Storage Variations in the Orinoco Floodplains Using Multi-Satellite Observations

    Directory of Open Access Journals (Sweden)

    Frédéric Frappart

    2014-12-01

    Full Text Available Variations in surface water extent and storage are poorly characterized from regional to global scales. In this study, a multi-satellite approach is proposed to estimate the water stored in the floodplains of the Orinoco Basin at a monthly time-scale using remotely-sensed observations of surface water from the Global Inundation Extent Multi-Satellite (GIEMS and stages from Envisat radar altimetry. Surface water storage variations over 2003–2007 exhibit large interannual variability and a strong seasonal signal, peaking during summer, and associated with the flood pulse. The volume of surface water storage in the Orinoco Basin was highly correlated with the river discharge at Ciudad Bolivar (R = 0.95, the closest station to the mouth where discharge was estimated, although discharge lagged one month behind storage. The correlation remained high (R = 0.73 after removing seasonal effects. Mean annual variations in surface water volume represented ~170 km3, contributing to ~45% of the Gravity Recovery and Climate Experiment (GRACE-derived total water storage variations and representing ~13% of the total volume of water that flowed out of the Orinoco Basin to the Atlantic Ocean.

  13. Intercomparison measurements with albedo neutron dosimeters

    International Nuclear Information System (INIS)

    Alberts, W.G.; Kluge, H.

    1994-01-01

    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 D 2 O-moderated 252 Cf 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.) [de

  14. Photometric evidence on long-term stability of albedo and colour markings on Io

    International Nuclear Information System (INIS)

    Morrison, D.; Pieri, D.; Veverka, J.; Johnson, T.V.

    1979-01-01

    This article re-examines the historical measurements of the albedo and colour of Io to determine whether there is evidence of variations, or if not, to set a limit on major resurfacing events resulting in hemispheric brightness changes during the past half century. (author)

  15. Albedo estimation for scene segmentation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, C H; Rosenfeld, A

    1983-03-01

    Standard methods of image segmentation do not take into account the three-dimensional nature of the underlying scene. For example, histogram-based segmentation tacitly assumes that the image intensity is piecewise constant, and this is not true when the scene contains curved surfaces. This paper introduces a method of taking 3d information into account in the segmentation process. The image intensities are adjusted to compensate for the effects of estimated surface orientation; the adjusted intensities can be regarded as reflectivity estimates. When histogram-based segmentation is applied to these new values, the image is segmented into parts corresponding to surfaces of constant reflectivity in the scene. 7 references.

  16. Microgeometry capture and RGB albedo estimation by photometric stereo without demosaicing

    Science.gov (United States)

    Quéau, Yvain; Pizenberg, Mathieu; Durou, Jean-Denis; Cremers, Daniel

    2017-03-01

    We present a photometric stereo-based system for retrieving the RGB albedo and the fine-scale details of an opaque surface. In order to limit specularities, the system uses a controllable diffuse illumination, which is calibrated using a dedicated procedure. In addition, we rather handle RAW, non-demosaiced RGB images, which both avoids uncontrolled operations on the sensor data and simplifies the estimation of the albedo in each color channel and of the normals. We finally show on real-world examples the potential of photometric stereo for the 3D-reconstruction of very thin structures from a wide variety of surfaces.

  17. Estimates of the Spectral Aerosol Single Sea Scattering Albedo and Aerosol Radiative Effects during SAFARI 2000

    Science.gov (United States)

    Bergstrom, Robert W.; Pilewskie, Peter; Schmid, Beat; Russell, Philip B.

    2003-01-01

    Using measurements of the spectral solar radiative flux and optical depth for 2 days (24 August and 6 September 2000) during the SAFARI 2000 intensive field experiment and a detailed radiative transfer model, we estimate the spectral single scattering albedo of the aerosol layer. The single scattering albedo is similar on the 2 days even though the optical depth for the aerosol layer was quite different. The aerosol single scattering albedo was between 0.85 and 0.90 at 350 nm, decreasing to 0.6 in the near infrared. The magnitude and decrease with wavelength of the single scattering albedo are consistent with the absorption properties of small black carbon particles. We estimate the uncertainty in the single scattering albedo due to the uncertainty in the measured fractional absorption and optical depths. The uncertainty in the single scattering albedo is significantly less on the high-optical-depth day (6 September) than on the low-optical-depth day (24 August). On the high-optical-depth day, the uncertainty in the single scattering albedo is 0.02 in the midvisible whereas on the low-optical-depth day the uncertainty is 0.08 in the midvisible. On both days, the uncertainty becomes larger in the near infrared. We compute the radiative effect of the aerosol by comparing calculations with and without the aerosol. The effect at the top of the atmosphere (TOA) is to cool the atmosphere by 13 W/sq m on 24 August and 17 W/sq m on 6 September. The effect on the downward flux at the surface is a reduction of 57 W/sq m on 24 August and 200 W/sq m on 6 September. The aerosol effect on the downward flux at the surface is in good agreement with the results reported from the Indian Ocean Experiment (INDOEX).

  18. Variational analysis of topological stationary barotropic MHD in the case of single-valued magnetic surfaces

    International Nuclear Information System (INIS)

    Yahalom, A

    2014-01-01

    Variational principles for magnetohydrodynamics have been introduced by previous authors both in Lagrangian and Eulerian form. Yahalom and Lynden-Bell (2008) have previously introduced simpler Eulerian variational principles from which all the relevant equations of barotropic magnetohydrodynamics can be derived. These variational principles were given in terms of six independent functions for non-stationary barotropic flows with given topologies and three independent functions for stationary barotropic flows. This is less then the seven variables which appear in the standard equations of barotropic magnetohydrodynamics which are the magnetic field B-vector the velocity field v-vector and the density ρ. Later, Yahalom (2010) introduced a simpler variational principle in terms of four functions for non-stationary barotropic magnetohydrodynamics. It was shown that the above variational principles are also relevant for flows of non-trivial topologies and in fact using those variational variables one arrives at additional topological conservation laws in terms of cuts of variables which have close resemblance to the Aharonov- Bohm phase (Yahalom (2013)). In previous examples (Yahalom and Lynden-Bell (2008); Yahalom (2013)) the magnetic field lines with non-trivial topology were at the intersection of two surface one of which was always multivalued; in this paper an example is introduced in which the magnetic helicity is not zero yet both surfaces are single-valued

  19. Criticality analysis of thermal reactors for two energy groups applying Monte Carlo and neutron Albedo method

    International Nuclear Information System (INIS)

    Terra, Andre Miguel Barge Pontes Torres

    2005-01-01

    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)

  20. Albedo control as an effective strategy to tackle Global Warming: A case study

    International Nuclear Information System (INIS)

    Cotana, Franco; Rossi, Federico; Filipponi, Mirko; Coccia, Valentina; Pisello, Anna Laura; Bonamente, Emanuele; Petrozzi, Alessandro; Cavalaglio, Gianluca

    2014-01-01

    Highlights: • We modeled the energy exchanges for the system Earth–Atmosphere–Outer space. • We proposed a method quantifying the CO 2eq offset potential of high-albedo surfaces. • We presented the application of the method to a case study in Tunis. • The CO 2eq offsetting potential depends on the geometry-orientation of the surfaces. • An economic value was attributed to the Albedo control compensation mechanism. - Abstract: Recent research developments focused on Climate Change issue aimed at achieving Kyoto targets. In this context, an innovative methodology (officially recognized by WEC in 2009) is proposed to mitigate Global Warming by artificially enhancing earth’s Albedo. Such a methodology allows to quantify the maximum environmental benefit achievable through the installation of Albedo control technologies, as a function of the geographical features of the installation site, local meteorological conditions, radiative properties, tilt angle, and orientation of the surfaces. This benefit is directly quantified in terms of CO 2eq offset. Albedo control can be an effective mitigation strategy by means of three synergistic effects: a direct contribution towards Global Warming mitigation produced by an enhanced reflection to the space of the shortwave incident radiation; the indirect contribution from energy saving in buildings with high Albedo envelopes; the indirect contribution from the mitigation of Urban Heat Island phenomenon. Since the effectiveness of Albedo control is mostly relevant in Mediterranean area, for both climate conditions and historical-architectural heritage, this work presents procedures and findings of the ABCD project (Albedo, Building green, Control of Global Warming and Desertification) concluded in 2012, funded by the Italian Ministry for the Environment. A description of the analytic model is also presented. The paper focuses on the application of the methodology to a Tunisian factory site, showing that approximately

  1. Super-quasi-conformal transformation and Schiffer variation on super-Riemann surface

    International Nuclear Information System (INIS)

    Takahasi, Wataru

    1990-01-01

    A set of equations which characterizes the super-Teichmueller deformations is proposed. It is a supersymmetric extension of the Beltrami equation. Relations between the set of equations and the Schiffer variations with the KN bases are discussed. This application of the KN bases shows the powerfulness of the KN theory in the study of super-Riemann surfaces. (author)

  2. Spatial and temporal variation of surface waves in shallow waters along the eastern Arabian Sea.

    Digital Repository Service at National Institute of Oceanography (India)

    Anoop, T.R.; SanilKumar, V.; Shanas, P.R.

    We studied the spatial and temporal variation of surface waves along the eastern Arabian Sea during 2011 and 2012. Measured directional wave data at two shallow water locations and re-analysis datasets (ERA-Interim) at 0.751 intervals at four...

  3. Variations of surface temparature with solar activity at two stations in ...

    African Journals Online (AJOL)

    Nigeria Journal of Pure and Applied Physics ... A consistent and persistent diurnal variation in surface air temperature exists which shows an almost constant level in the early morning hours (0000 0600 hours LT.); a rise at sunrise till about 1500 hr LT., a subsequent fall to the constant level by about 1900 hr LT. at sunset.

  4. Factors affecting polyamide prototypes design of Albedo dosemeters

    International Nuclear Information System (INIS)

    Martins, M.M.; Mauricio, C.L.P.; Fonseca, E.S.

    1996-01-01

    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, B 4 C covered, was developed. The prototype has a response three times higher than the albedo dosemeter now in use in Brazil. (author)

  5. On the importance of the albedo parameterization for the mass balance of the Greenland ice sheet in EC-Earth

    Directory of Open Access Journals (Sweden)

    M. M. Helsen

    2017-08-01

    Full Text Available The albedo of the surface of ice sheets changes as a function of time due to the effects of deposition of new snow, ageing of dry snow, bare ice exposure, melting and run-off. Currently, the calculation of the albedo of ice sheets is highly parameterized within the earth system model EC-Earth by taking a constant value for areas with thick perennial snow cover. This is an important reason why the surface mass balance (SMB of the Greenland ice sheet (GrIS is poorly resolved in the model. The purpose of this study is to improve the SMB forcing of the GrIS by evaluating different parameter settings within a snow albedo scheme. By allowing ice-sheet albedo to vary as a function of wet and dry conditions, the spatial distribution of albedo and melt rate improves. Nevertheless, the spatial distribution of SMB in EC-Earth is not significantly improved. As a reason for this, we identify omissions in the current snow albedo scheme, such as separate treatment of snow and ice and the effect of refreezing. The resulting SMB is downscaled from the lower-resolution global climate model topography to the higher-resolution ice-sheet topography of the GrIS, such that the influence of these different SMB climatologies on the long-term evolution of the GrIS is tested by ice-sheet model simulations. From these ice-sheet simulations we conclude that an albedo scheme with a short response time of decaying albedo during wet conditions performs best with respect to long-term simulated ice-sheet volume. This results in an optimized albedo parameterization that can be used in future EC-Earth simulations with an interactive ice-sheet component.

  6. Kinetic and isotherm studies of bisphenol A adsorption onto orange albedo(Citrus sinensis): Sorption mechanisms based on the main albedo components vitamin C, flavones glycosides and carotenoids.

    Science.gov (United States)

    Kamgaing, Theophile; Doungmo, Giscard; Melataguia Tchieno, Francis Merlin; Gouoko Kouonang, Jimmy Julio; Mbadcam, Ketcha Joseph

    2017-07-03

    Orange albedo and its adsorption capacity towards bisphenol A (BPA) were studied. Adsorption experiments were conducted in batch mode at 25-55°C. Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and Fourier transform infrared (FTIR) spectroscopy were used to characterise the biosorbent. The effects of various parameters including adsorption time, equilibrium pH, adsorbent dosage and initial adsorbate concentration were investigated. The optimum contact time and pH for the removal of BPA were 60 min and 2, respectively. It was found that the adsorption isotherms best matched the Freundlich model, the adsorption of BPA being multilayer and that of the albedo surface heterogeneous. From the kinetic studies, it was found that the removal of BPA best matched the pseudo-second order kinetic model. An adsorption mechanism based on the albedo surface molecules is proposed and gives a good account of π-π interactions and hydrogen bonding. Orange albedo, with a maximum BPA loading capacity of 82.36 mg g -1 (significantly higher than that of most agricultural residues), is a good candidate for BPA adsorption in aqueous media.

  7. A variational model of disjoining pressure: Liquid film on a nonplanar surface

    Energy Technology Data Exchange (ETDEWEB)

    Silin, D.; Virnovsky, G.

    2009-06-01

    Variational methods have been successfully used in modelling thin liquid films in numerous theoretical studies of wettability. In this paper, the variational model of the disjoining pressure is extended to the general case of a two-dimensional solid surface. The Helmgoltz free energy functional depends both on the disjoining pressure isotherm and the shape of the solid surface. The augmented Young-Laplace equation (AYLE) is a nonlinear second-order partial differential equation. A number of solutions describing wetting films on spherical grains have been obtained. In the case of cylindrical films, the phase portrait technique describes the entire variety of mathematically feasible solutions. It turns out that a periodic solution, which would describe wave-like wetting films, does not satisfy the Jacobi's condition of the classical calculus of variations. Therefore, such a solution is nonphysical. The roughness of the solid surface significantly affects liquid film stability. AYLE solutions suggest that film rupture is more likely at a location where the pore-wall surface is most exposed into the pore space and the curvature is positive.

  8. Algorithm to retrieve the melt pond fraction and the spectral albedo of Arctic summer ice from satellite optical data

    OpenAIRE

    Zege, E.; Malinka, A.; Katsev, I.; Prikhach, A.; Heygster, Georg; Istomina, L.; Birnbaum, Gerit; Schwarz, Pascal

    2015-01-01

    A new algorithmto retrieve characteristics (albedo and melt pond fraction) of summer ice in the Arctic fromoptical satellite data is described. In contrast to other algorithms this algorithm does not use a priori values of the spectral albedo of the sea-ice constituents (such asmelt ponds,white ice etc.). Instead, it is based on an analytical solution for the reflection from sea ice surface. The algorithm includes the correction of the sought-for ice and ponds characteristics with...

  9. Snow driven Radiative Forcing in High Latitude Areas of Disturbance Using Higher Resolution Albedo Products from Landsat and Sentinel-2

    Science.gov (United States)

    Erb, A.; Li, Z.; Schaaf, C.; Wang, Z.; Rogers, B. M.

    2017-12-01

    Land surface albedo plays an important role in the surface energy budget and radiative forcing by determining the proportion of absorbed incoming solar radiation available to drive photosynthesis and surface heating. In Arctic regions, albedo is particularly sensitive to land cover and land use change (LCLUC) and modeling efforts have shown it to be the primary driver of effective radiative forcing from the biogeophysical effects of LCLUC. In boreal forests, the effects of these changes are complicated during snow covered periods when newly exposed, highly reflective snow can serve as the primary driver of radiative forcing. In Arctic biomes disturbance scars from fire, pest and harvest can remain in the landscape for long periods of time. As such, understanding the magnitude and persistence of these disturbances, especially in the shoulder seasons, is critical. The Landsat and Sentinel-2 Albedo Products couple 30m and 20m surface reflectances with concurrent 500m BRDF Products from the MODerate resolution Imaging Spectroradiometer (MODIS). The 12 bit radiometric fidelity of Sentinel-2 and Landsat-8 allow for the inclusion of high-quality, unsaturated albedo calculations over snow covered surfaces at scales more compatible with fragmented landscapes. Recent work on the early spring albedo of fire scars has illustrated significant post-fire spatial heterogeneity of burn severity at the landscape scale and highlights the need for a finer spatial resolution albedo record. The increased temporal resolution provided by multiple satellite instruments also allows for a better understanding of albedo dynamics during the dynamic shoulder seasons and in historically difficult high latitude locations where persistent cloud cover limits high quality retrievals. Here we present how changes in the early spring albedo of recent boreal forest disturbance in Alaska and central Canada affects landscape-scale radiative forcing. We take advantage of the long historical Landsat record

  10. Cloud albedo changes in response to anthropogenic sulfate and non-sulfate aerosol forcings in CMIP5 models

    Directory of Open Access Journals (Sweden)

    L. Frey

    2017-07-01

    Full Text Available The effects of different aerosol types on cloud albedo are analysed using the linear relation between total albedo and cloud fraction found on a monthly mean scale in regions of subtropical marine stratocumulus clouds and the influence of simulated aerosol variations on this relation. Model experiments from the Coupled Model Intercomparison Project phase 5 (CMIP5 are used to separately study the responses to increases in sulfate, non-sulfate and all anthropogenic aerosols. A cloud brightening on the month-to-month scale due to variability in the background aerosol is found to dominate even in the cases where anthropogenic aerosols are added. The aerosol composition is of importance for this cloud brightening, that is thereby region dependent. There is indication that absorbing aerosols to some extent counteract the cloud brightening but scene darkening with increasing aerosol burden is generally not supported, even in regions where absorbing aerosols dominate. Month-to-month cloud albedo variability also confirms the importance of liquid water content for cloud albedo. Regional, monthly mean cloud albedo is found to increase with the addition of anthropogenic aerosols and more so with sulfate than non-sulfate. Changes in cloud albedo between experiments are related to changes in cloud water content as well as droplet size distribution changes, so that models with large increases in liquid water path and/or cloud droplet number show large cloud albedo increases with increasing aerosol. However, no clear relation between model sensitivities to aerosol variations on the month-to-month scale and changes in cloud albedo due to changed aerosol burden is found.

  11. Interannual Variation of Surface Circulation in the Japan/East Sea due to External Forcings and Intrinsic Variability

    Science.gov (United States)

    Choi, Byoung-Ju; Cho, Seong Hun; Jung, Hee Seok; Lee, Sang-Ho; Byun, Do-Seong; Kwon, Kyungman

    2018-03-01

    The interannual variation of surface ocean currents can be as large as seasonal variation in the Japan/East Sea (JES). To identify the major factors that cause such interannual variability of surface ocean circulation in the JES, surface circulation was simulated from 1998 to 2009 using a three-dimensional model. Contributions of atmospheric forcing (ATM), open boundary data (OBC), and intrinsic variability (ITV) of the surface flow in the JES on the interannual variability of surface ocean circulation were separately examined using numerical simulations. Variability in surface circulation was quantified in terms of variance in sea surface height, 100-m depth water temperature, and surface currents. ITV was found to be the dominant factor that induced interannual variabilities of surface circulation, the main path of the East Korea Warm Current (EKWC), and surface kinetic energy on a time scale of 2-4 years. OBC and ATM were secondary factors contributing to the interannual variation of surface circulation. Interannual variation of ATM changed the separation latitude of EKWC and increased the variability of surface circulation in the Ulleung Basin. Interannual variation of OBC enhanced low-frequency changes in surface circulation and eddies in the Yamato Basin. It also modulated basin-wide uniform oscillations of sea level. This study suggests that precise estimation of initial conditions using data assimilation is essential for long-term prediction of surface circulation in the JES.

  12. Variations and asymmetries in regional brain surface in the genus Homo.

    Science.gov (United States)

    Balzeau, Antoine; Holloway, Ralph L; Grimaud-Hervé, Dominique

    2012-06-01

    Paleoneurology is an important field of research within human evolution studies. Variations in size and shape of an endocast help to differentiate among fossil hominin species whereas endocranial asymmetries are related to behavior and cognitive function. Here we analyse variations of the surface of the frontal, parieto-temporal and occipital lobes among different species of Homo, including 39 fossil hominins, ten fossil anatomically modern Homo sapiens and 100 endocasts of extant modern humans. We also test for the possible asymmetries of these features in a large sample of modern humans and observe individual particularities in the fossil specimens. This study contributes important new information about the brain evolution in the genus Homo. Our results show that the general pattern of surface asymmetry for the different regional brain surfaces in fossil species of Homo does not seem to be different from the pattern described in a large sample of anatomically modern H. sapiens, i.e., the right hemisphere has a larger surface than the left, as do the right frontal, the right parieto-temporal and the left occipital lobes compared with the contra-lateral side. It also appears that Asian Homo erectus specimens are discriminated from all other samples of Homo, including African and Georgian specimens that are also sometimes included in that taxon. The Asian fossils show a significantly smaller relative size of the parietal and temporal lobes. Neandertals and anatomically modern H. sapiens, who share the largest endocranial volume of all hominins, show differences when considering the relative contribution of the frontal, parieto-temporal and occipital lobes. These results illustrate an original variation in the pattern of brain organization in hominins independent of variations in total size. The globularization of the brain and the enlargement of the parietal lobes could be considered derived features observed uniquely in anatomically modern H. sapiens. Copyright

  13. Variation of air--water gas transfer with wind stress and surface viscoelasticity

    OpenAIRE

    Frew, Nelson M.; Bock, Erik J.; McGillis, Wade R.; Karachintsev, Andrey V.; Hara, Tetsu; Münsterer, Thomas; Jähne, Bernd

    1995-01-01

    Previous parameterizations of gas transfer velocity have attempted to cast this quantity as a function of wind speed or wind-stress. This study demonstrates that the presence of a surface film is effective at reducing the gas transfer velocity at constant wind-stress. Gas exchange experiments were performed at WHOI and UH using annular wind-wave tanks of different scales. Systematic variations of wind-stress and surfactant concentration (Triton-X-100) were explored to determ...

  14. Retrieving Single Scattering Albedos and Temperatures from CRISM Hyperspectral Data Using Neural Networks

    Science.gov (United States)

    He, L.; Arvidson, R. E.; O'Sullivan, J. A.

    2018-04-01

    We use a neural network (NN) approach to simultaneously retrieve surface single scattering albedos and temperature maps for CRISM data from 1.40 to 3.85 µm. It approximates the inverse of DISORT which simulates solar and emission radiative streams.

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

    Science.gov (United States)

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

    2017-01-01

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

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

    Science.gov (United States)

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

    2017-03-01

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

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

    Science.gov (United States)

    2015-09-30

    fraction product and the remotely sensed albedo product in the context of understanding the surface radiation budget. Particular attention is paid to...Stamnes, Chapter 2 The Polar Environment: Sun, Clouds, and Ice, in Ocean Colour Remote Sensing in Polar Seas, p 5-25, in press. Istomina, L, G

  18. Sunlight, Sea Ice, and the Ice Albedo Feedback in a Changing Artic Sea Ice Cover

    Science.gov (United States)

    2015-11-30

    the remotely sensed albedo product in the context of understanding the surface radiation budget. Particular attention is paid to the infrequent...Chapter 2 The Polar Environment: Sun, Clouds, and Ice, in Ocean Colour Remote Sensing in Polar Seas, p 5-25, in press. Istomina, L, G. Heygster, M

  19. Impurities and Electronic Property Variations of Natural MoS 2 Crystal Surfaces

    KAUST Repository

    Addou, Rafik; McDonnell, Stephen; Barrera, Diego; Guo, Zaibing; Azcatl, Angelica; Wang, Jian; Zhu, Hui; Hinkle, Christopher L.; Quevedo-Lopez, Manuel; Alshareef, Husam N.; Colombo, Luigi; Hsu, Julia W P; Wallace, Robert M.

    2015-01-01

    Room temperature X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICPMS), high resolution Rutherford backscattering spectrometry (HR-RBS), Kelvin probe method, and scanning tunneling microscopy (STM) are employed to study the properties of a freshly exfoliated surface of geological MoS2 crystals. Our findings reveal that the semiconductor 2H-MoS2 exhibits both n- and p-type behavior, and the work function as measured by the Kelvin probe is found to vary from 4.4 to 5.3 eV. The presence of impurities in parts-per-million (ppm) and a surface defect density of up to 8% of the total area could explain the variation of the Fermi level position. High resolution RBS data also show a large variation in the MoSx composition (1.8 < x < 2.05) at the surface. Thus, the variation in the conductivity, the work function, and stoichiometry across small areas of MoS2 will have to be controlled during crystal growth in order to provide high quality uniform materials for future device fabrication. © 2015 American Chemical Society.

  20. Impurities and Electronic Property Variations of Natural MoS 2 Crystal Surfaces

    KAUST Repository

    Addou, Rafik

    2015-09-22

    Room temperature X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICPMS), high resolution Rutherford backscattering spectrometry (HR-RBS), Kelvin probe method, and scanning tunneling microscopy (STM) are employed to study the properties of a freshly exfoliated surface of geological MoS2 crystals. Our findings reveal that the semiconductor 2H-MoS2 exhibits both n- and p-type behavior, and the work function as measured by the Kelvin probe is found to vary from 4.4 to 5.3 eV. The presence of impurities in parts-per-million (ppm) and a surface defect density of up to 8% of the total area could explain the variation of the Fermi level position. High resolution RBS data also show a large variation in the MoSx composition (1.8 < x < 2.05) at the surface. Thus, the variation in the conductivity, the work function, and stoichiometry across small areas of MoS2 will have to be controlled during crystal growth in order to provide high quality uniform materials for future device fabrication. © 2015 American Chemical Society.

  1. Modeling Earth Albedo for Satellites in Earth Orbit

    DEFF Research Database (Denmark)

    Bhanderi, Dan; Bak, Thomas

    2005-01-01

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

  2. Assessment of broiler surface temperature variation when exposed to different air temperatures

    Directory of Open Access Journals (Sweden)

    GR Nascimento

    2011-12-01

    Full Text Available This study was conducted to determine the effect of the air temperature variation on the mean surface temperature (MST of 7- to 35-day-old broiler chickens using infrared thermometry to estimate MST, and to study surface temperature variation of the wings, head, legs, back and comb as affected by air temperature and broiler age. One hundred Cobb® broilers were used in the experiment. Starting on day 7, 10 birds were weekly selected at random, housed in an environmental chamber and reared under three distinct temperatures (18, 25 and 32 ºC to record their thermal profile using an infrared thermal camera. The recorded images were processed to estimate MST by selecting the whole area of the bird within the picture and comparing it with the values obtained using selected equations in literature, and to record the surface temperatures of the body parts. The MST estimated by infrared images were not statistically different (p > 0.05 from the values obtained by the equations. MST values significantly increased (p < 0.05 when the air temperature increased, but were not affected by bird age. However, age influenced the difference between MST and air temperature, which was highest on day 14. The technique of infrared thermal image analysis was useful to estimate the mean surface temperature of broiler chickens.

  3. Impact of Water Withdrawals from Groundwater and Surface Water on Continental Water Storage Variations

    Science.gov (United States)

    Doell, Petra; Hoffmann-Dobrev, Heike; Portmann, Felix T.; Siebert, Stefan; Eicker, Annette; Rodell, Matthew; Strassberg, Gil

    2011-01-01

    Humans have strongly impacted the global water cycle, not only water flows but also water storage. We have performed a first global-scale analysis of the impact of water withdrawals on water storage variations, using the global water resources and use model WaterGAP. This required estimation of fractions of total water withdrawals from groundwater, considering five water use sectors. According to our assessment, the source of 35% of the water withdrawn worldwide (4300 cubic km/yr during 1998-2002) is groundwater. Groundwater contributes 42%, 36% and 27% of water used for irrigation, households and manufacturing, respectively, while we assume that only surface water is used for livestock and for cooling of thermal power plants. Consumptive water use was 1400 cubic km/yr during 1998-2002. It is the sum of the net abstraction of 250 cubic km/yr of groundwater (taking into account evapotranspiration and return flows of withdrawn surface water and groundwater) and the net abstraction of 1150 km3/yr of surface water. Computed net abstractions indicate, for the first time at the global scale, where and when human water withdrawals decrease or increase groundwater or surface water storage. In regions with extensive surface water irrigation, such as Southern China, net abstractions from groundwater are negative, i.e. groundwater is recharged by irrigation. The opposite is true for areas dominated by groundwater irrigation, such as in the High Plains aquifer of the central USA, where net abstraction of surface water is negative because return flow of withdrawn groundwater recharges the surface water compartments. In intensively irrigated areas, the amplitude of seasonal total water storage variations is generally increased due to human water use; however, in some areas, it is decreased. For the High Plains aquifer and the whole Mississippi basin, modeled groundwater and total water storage variations were compared with estimates of groundwater storage variations based on

  4. Diurnal and seasonal variations in surface methane at a tropical coastal station: Role of mesoscale meteorology.

    Science.gov (United States)

    Kavitha, M; Nair, Prabha R; Girach, I A; Aneesh, S; Sijikumar, S; Renju, R

    2018-08-01

    In view of the large uncertainties in the methane (CH 4 ) emission estimates and the large spatial gaps in its measurements, studies on near-surface CH 4 on regional basis become highly relevant. This paper presents the first time observational results of a study on the impacts of mesoscale meteorology on the temporal variations of near-surface CH 4 at a tropical coastal station, in India. It is based on the in-situ measurements conducted during January 2014 to August 2016, using an on-line CH 4 analyzer working on the principle of gas chromatography. The diurnal variation shows a daytime low (1898-1925ppbv) and nighttime high (1936-2022ppbv) extending till early morning hours. These changes are closely associated with the mesoscale circulations, namely Sea Breeze (SB) and Land Breeze (LB), as obtained through the meteorological observations, WRF simulations of the circulations and the diurnal variation of boundary layer height as observed by the Microwave Radiometer Profiler. The diurnal enhancement always coincides with the onset of LB. Several cases of different onset timings of LB were examined and results presented. The CH 4 mixing ratio also exhibits significant seasonal patterns being maximum in winter and minimum in pre-monsoon/monsoon with significant inter-annual variations, which is also reflected in diurnal patterns, and are associated with changing synoptic meteorology. This paper also presents an analysis of in-situ measured near-surface CH 4 , column averaged and upper tropospheric CH 4 retrieved by Atmospheric Infrared Sounder (AIRS) onboard Earth Observing System (EOS)/Aqua which gives insight into the vertical distribution of the CH 4 over the location. An attempt is also made to estimate the instantaneous radiative forcing for the measured CH 4 mixing ratio. Copyright © 2018 Elsevier B.V. All rights reserved.

  5. Attitude estimation from magnetometer and earth-albedo-corrected coarse sun sensor measurements

    Science.gov (United States)

    Appel, Pontus

    2005-01-01

    For full 3-axes attitude determination the magnetic field vector and the Sun vector can be used. A Coarse Sun Sensor consisting of six solar cells placed on each of the six outer surfaces of the satellite is used for Sun vector determination. This robust and low cost setup is sensitive to surrounding light sources as it sees the whole sky. To compensate for the largest error source, the Earth, an albedo model is developed. The total albedo light vector has contributions from the Earth surface which is illuminated by the Sun and visible from the satellite. Depending on the reflectivity of the Earth surface, the satellite's position and the Sun's position the albedo light changes. This cannot be calculated analytically and hence a numerical model is developed. For on-board computer use the Earth albedo model consisting of data tables is transferred into polynomial functions in order to save memory space. For an absolute worst case the attitude determination error can be held below 2∘. In a nominal case it is better than 1∘.

  6. Spatial variation in spoil and vegetative characteristics of pastures on reclaimed surface mined land

    International Nuclear Information System (INIS)

    Teutsch, C.D.; Collins, M.; Ditsch, D.C.

    1999-01-01

    Kentucky has large areas of reclaimed surface mined land that could provide grazing for livestock. Research is needed to determine optimal stocking densities and to evaluate the sustainability of such grazing systems for this region. A long-term grazing study was initiated in 1997 on 151 ha of reclaimed land near Chavies, KY to determine spatial and temporal variation with stocking densities of 0, 0.28, 0.42, or 0.83 beef cow-calf units/ha. Global Positioning System and GIS technologies were used to establish pasture boundaries, locate permanent sampling markers at a density of 1 per 0.4 ha, and interpolate maps of physical, spoil, and vegetable pasture characteristics. Herbage and spoil samples were collected around the permanent markers in May of 1997. Stepwise regression was used to determine factors affecting the vegetative characteristics of the sites. Biomass density ranged from 0 to 2500 kg/ha with a mean of 570 kg/ha. Factors affecting biomass included legume and weed proportions in the sward, grazing activity, soil potassium, elevation, and potential acidity, cumulatively accounting for 32% of the variation. Ground cover ranged from 10 to 100% with an average of 74%. Soil pH, potassium, and grass in the sward accounted for 14% of the variation in ground cover. Legumes made up 0 to 61% of the sward with a mean of 13% over the pasture area. Variables affecting the amount of legume in the sward included biomass density, slope, elevation, pH, and stocking density, together accounting for 21% of the variation. Spatial variation in the physical, spoil, and vegetative characteristics of the pastures was large. Overall, regression accounted for a limited amount of the variation in the vegetative characteristics of the site indicating that other important variables exist

  7. Temporal variation of 228Ra in the near-surface Gulf of Mexico

    International Nuclear Information System (INIS)

    Reid, F.D.; Moore, W.S.; Sackett, W.M.

    1979-01-01

    The Mn-fiber technique for extracting radium from seawater has proved useful for studying the marine geochemistry of 228 Ra. In the Gulf of Mexico, this technique was used to measure the surface and near-surface distribution of 226 Ra and 228 Ra. The observed surface distribution of 228 Ra, and particularly the radium activity ratio (228/226) can be explained by known circulation patterns, or, when local surface currents are not well understood, may provide insight into their general characteristics. The radium activity ratio has increased from 0.5 in 1968 to 0.7 in 1973 in the surface Gulf of Mexico. This observed increase cannot be attributed to known anthropogenic or natural source perturbations within the Caribbean Sea-Gulf of Mexico system. Possible causes include a change in the residence time for near-surface water, or variations in the relative dominance of the two eastern Caribbean; the North Equatorial Current and the Guiana Current. The temporal distribution of 228 Ra is unstable and naturally variable over a time period less than or equal to five years in the Gulf of Mexico and by extrapolation, the Caribbean Sea. Therefore, its usefulness in calculations of eddy diffusion coefficients for these regions is greatly diminished. (Auth.)

  8. Lateral variation in crustal and mantle structure in Bay of Bengal based on surface wave data

    Science.gov (United States)

    Kumar, Amit; Mukhopadhyay, Sagarika; Kumar, Naresh; Baidya, P. R.

    2018-01-01

    Surface waves generated by earthquakes that occurred near Sumatra, Andaman-Nicobar Island chain and Sunda arc are used to estimate crustal and upper mantle S wave velocity structure of Bay of Bengal. Records of these seismic events at various stations located along the eastern coast of India and a few stations in the north eastern part of India are selected for such analysis. These stations lie within regional distance of the selected earthquakes. The selected events are shallow focused with magnitude greater than 5.5. Data of 65, 37, 36, 53 and 36 events recorded at Shillong, Bokaro, Visakhapatnam, Chennai and Trivandrum stations respectively are used for this purpose. The ray paths from the earthquake source to the recording stations cover different parts of the Bay of Bengal. Multiple Filtering Technique (MFT) is applied to compute the group velocities of surface waves from the available data. The dispersion curves thus obtained for this data set are within the period range of 15-120 s. Joint inversion of Rayleigh and Love wave group velocity is carried out to obtain the subsurface information in terms of variation of S wave velocity with depth. The estimated S wave velocity at a given depth and layer thickness can be considered to be an average value for the entire path covered by the corresponding ray paths. However, we observe variation in the value of S wave velocity and layer thickness from data recorded at different stations, indicating lateral variation in these two parameters. Thick deposition of sediments is observed along the paths followed by surface waves to Shillong and Bokaro stations. Sediment thickness keeps on decreasing as the surface wave paths move further south. Based on velocity variation the sedimentary layer is further divided in to three parts; on top lay unconsolidated sediment, underlain by consolidated sediment. Below this lies a layer which we consider as meta-sediments. The thickness and velocity of these layers decrease from north

  9. Color Variation on the Surfaces of Jupiter’s Greek and Trojan Asteroids

    Science.gov (United States)

    Chatelain, Joseph; Trilling, David E.; Emery, Joshua P.

    2017-10-01

    The L4 and L5 Lagrange points of Jupiter are populated with thousands of known, and possibly hundreds of thousands of unknown, Greek and Trojan Asteroids. Understanding the environmental and weathering conditions experienced by these objects over their lifetimes could constrain formation models for the Solar System. In an effort to shine some light on this issue, we have collected partial, simultaneous, lightcurves in both Johnson-Cousins V and I filters for a dozen large Jupiter Trojans. We found significant signs of color variation over the surfaces of four of these objects, and more subtle signs on an additional four. The most convincing examples of variation occur on (4709) Ennomos and (4833) Meges. Such a variation in color with rotation likely implies a large surface feature such as a recent crater. That such a high fraction of observed Trojans display these signatures could imply a more active collisional history for Jupiter Trojans than previously thought. It is therefore likely that one or more of the targets for the Lucy mission will have experienced a large, relatively recent, cratering event. This may help us obtain a much more in-depth understanding of the evolutionary processes ongoing for the Jupiter Trojan populations.

  10. The effect of a dynamic background albedo scheme on Sahel/Sahara precipitation during the mid-Holocene

    Directory of Open Access Journals (Sweden)

    F. S. E. Vamborg

    2011-02-01

    Full Text Available We have implemented a new albedo scheme that takes the dynamic behaviour of the surface below the canopy into account, into the land-surface scheme of the MPI-ESM. The standard (static scheme calculates the seasonal canopy albedo as a function of leaf area index, whereas the background albedo is a gridbox constant derived from satellite measurements. The new (dynamic scheme additionally models the background albedo as a slowly changing function of organic matter in the ground and of litter and standing dead biomass covering the ground. We use the two schemes to investigate the interactions between vegetation, albedo and precipitation in the Sahel/Sahara for two time-slices: pre-industrial and mid-Holocene. The dynamic scheme represents the seasonal cycle of albedo and the correspondence between annual mean albedo and vegetation cover in a more consistent way than the static scheme. It thus gives a better estimate of albedo change between the two time periods. With the introduction of the dynamic scheme, precipitation is increased by 30 mm yr−1 for the pre-industrial simulation and by about 80 mm yr−1 for the mid-Holocene simulation. The present-day dry bias in the Sahel of standard ECHAM5 is thus reduced and the sensitivity of precipitation to mid-Holocene external forcing is increased by around one third. The locations of mid-Holocene lakes, as estimated from reconstructions, lie south of the modelled desert border in both mid-Holocene simulations. The magnitude of simulated rainfall in this area is too low to fully sustain lakes, however it is captured better with the dynamic scheme. The dynamic scheme leads to increased vegetation variability in the remaining desert region, indicating a higher frequency of green spells, thus reaching a better agreement with the vegetation distribution as derived from pollen records.

  11. Generalized Calibration of the Polarimetric Albedo Scale of Asteroids

    Science.gov (United States)

    Lupishko, D. F.

    2018-03-01

    Six different calibrations of the polarimetric albedo scale of asteroids have been published so far. Each of them contains its particular random and systematic errors and yields its values of geometric albedo. On the one hand, this complicates their analysis and comparison; on the other hand, it becomes more and more difficult to decide which of the proposed calibrations should be used. Moreover, in recent years, new databases on the albedo of asteroids obtained from the radiometric surveys of the sky with the orbital space facilities (the InfraRed Astronomical Satellite (IRAS), the Japanese astronomical satellite AKARI (which means "light"), the Wide-field Infrared Survey Explorer (WISE), and the Near-Earth Object Wide-field Survey Explorer (NEOWISE)) have appeared; and the database on the diameters and albedos of asteroids obtained from their occultations of stars has substantially increased. Here, we critically review the currently available calibrations and propose a new generalized calibration derived from the interrelations between the slope h and the albedo and between P min and the albedo. This calibration is based on all of the available series of the asteroid albedos and the most complete data on the polarization parameters of asteroids. The generalized calibration yields the values of the polarimetric albedo of asteroids in the system unified with the radiometric albedos and the albedos obtained from occultations of stars by asteroids. This, in turn, removes the difficulties in their comparison, joint analysis, etc.

  12. Photometric Modeling and VIS-IR Albedo Maps of Dione From Cassini-VIMS

    Science.gov (United States)

    Filacchione, G.; Ciarniello, M.; D'Aversa, E.; Capaccioni, F.; Cerroni, P.; Buratti, B. J.; Clark, R. N.; Stephan, K.; Plainaki, C.

    2018-03-01

    We report about visible and infrared albedo maps and spectral indicators of Dione's surface derived from the complete Visual and Infrared Mapping Spectrometer (VIMS) data set acquired between 2004 and 2017 during the Cassini tour in Saturn's system. Maps are derived by applying a photometric correction necessary to disentangle the intrinsic albedo of the surface from illumination and viewing geometry occurring at the time of the observation. The photometric correction is based on the Shkuratov et al. (2011, https://doi.org/10.1016/j.pss.2011.06.011) method which yields values of the surface equigonal albedo. Dione's surface albedo maps are rendered at five visible (VIS: 0.35, 0.44, 0.55, 0.7, and 0.95 μm) and five infrared (IR: 1.046, 1.540, 1.822, 2.050, and 2.200 μm) wavelengths in cylindrical projection with a 0.5° × 0.5° angular resolution in latitude and longitude, corresponding to a spatial resolution of 4.5 km/bin. Apart from visible and infrared albedo maps, we report about the distribution of the two visible spectral slopes (0.35-0.55 and 0.55-0.95 μm) and water ice 2.050 μm band depth computed after having applied the photometric correction. The derived spectral indicators are employed to trace Dione's composition variability on both global and local scales allowing to study the dichotomy between the bright‐leading and dark‐trailing hemispheres, the distribution of fresh material on the impact craters and surrounding ejecta, and the resurfacing of the bright material within the chasmata caused by tectonism.

  13. Variation in Pockels constants of silicate glass-ceramics prepared by perfect surface crystallization

    Science.gov (United States)

    Takano, Kazuya; Takahashi, Yoshihiro; Miyazaki, Takamichi; Terakado, Nobuaki; Fujiwara, Takumi

    2018-01-01

    We investigated the Pockels effect in polycrystalline materials consisting of highly oriented polar fresnoite-type Sr2TiSi2O8 fabricated using perfectly surface-crystallized glass-ceramics (PSC-GCs). The chemical composition of the precursor glass was shown to significantly affect the crystallized texture, e.g., the crystal orientation and appearance of amorphous nanoparasites in the domains, resulting in variations in the Pockels constants. Single crystals exhibiting spontaneous polarization possessed large structural anisotropy, leading to a strong dependence of the nonlinear-optical properties on the direction of polarized light. This study suggests that variations in the Pockels constants (r13 and r33) and tuning of the r13/r33 ratio can be realized in PSC-GC materials.

  14. Seasonal Variations in Surface Metabolite Composition of Fucus vesiculosus and Fucus serratus from the Baltic Sea.

    Directory of Open Access Journals (Sweden)

    Esther Rickert

    Full Text Available Perennial macroalgae within the genus Fucus are known to exude metabolites through their outer thallus surface. Some of these metabolites have pro- and/or antifouling properties. Seasonal fluctuations of natural fouling pressure and chemical fouling control strength against micro- and macrofoulers have previously been observed in Fucus, suggesting that control strength varies with threat. To date, a study on the seasonal composition of surface associated metabolites, responsible for much of the fouling control, has not been done. We sampled individuals of the two co-occurring species F. vesiculosus and F. serratus at monthly intervals (six per species and month during a one-year field study. We analysed the chemical composition of surface associated metabolites of both Fucus species by means of gas chromatography-mass spectrometry (GC-MS to describe temporal patterns in chemical surface composition. Additionally, we correlated abiotic and biotic parameters recorded monthly within the sampled habitat with the variation in the chemical surface landscape of Fucus. Our study revealed that the chemical surface composition of both Fucus species exhibits substantial seasonal differences between spring/summer and autumn/winter months. Light and temperature explained most of the seasonal variability in surface metabolite composition of both Fucus species. A strong summerly up-regulation of eighteen saccharides and two hydroxy acids in F. vesiculosus as well as of four fatty acids and two saccharides in F. serratus was observed. We discuss how these up-regulated molecules may have a complex effect on associated microfoulers, both promoting or decreasing fouling depending on metabolite and bacterial identity. These seasonal shifts in the surface metabolome seem to exert a compound control of density and composition of the Fucus associated biofilm.

  15. A Variational Model for Two-Phase Immiscible Electroosmotic Flow at Solid Surfaces

    KAUST Repository

    Shao, Sihong

    2012-01-01

    We develop a continuum hydrodynamic model for two-phase immiscible flows that involve electroosmotic effect in an electrolyte and moving contact line at solid surfaces. The model is derived through a variational approach based on the Onsager principle of minimum energy dissipation. This approach was first presented in the derivation of a continuum hydrodynamic model for moving contact line in neutral two-phase immiscible flows (Qian, Wang, and Sheng, J. Fluid Mech. 564, 333-360 (2006)). Physically, the electroosmotic effect can be formulated by the Onsager principle as well in the linear response regime. Therefore, the same variational approach is applied here to the derivation of the continuum hydrodynamic model for charged two-phase immiscible flows where one fluid component is an electrolyte exhibiting electroosmotic effect on a charged surface. A phase field is employed to model the diffuse interface between two immiscible fluid components, one being the electrolyte and the other a nonconductive fluid, both allowed to slip at solid surfaces. Our model consists of the incompressible Navier-Stokes equation for momentum transport, the Nernst-Planck equation for ion transport, the Cahn-Hilliard phase-field equation for interface motion, and the Poisson equation for electric potential, along with all the necessary boundary conditions. In particular, all the dynamic boundary conditions at solid surfaces, including the generalized Navier boundary condition for slip, are derived together with the equations of motion in the bulk region. Numerical examples in two-dimensional space, which involve overlapped electric double layer fields, have been presented to demonstrate the validity and applicability of the model, and a few salient features of the two-phase immiscible electroosmotic flows at solid surface. The wall slip in the vicinity of moving contact line and the Smoluchowski slip in the electric double layer are both investigated. © 2012 Global-Science Press.

  16. Surface ozone at Nam Co in the inland Tibetan Plateau: variation, synthesis comparison and regional representativeness

    Science.gov (United States)

    Yin, Xiufeng; Kang, Shichang; de Foy, Benjamin; Cong, Zhiyuan; Luo, Jiali; Zhang, Lang; Ma, Yaoming; Zhang, Guoshuai; Rupakheti, Dipesh; Zhang, Qianggong

    2017-09-01

    Ozone is an important pollutant and greenhouse gas, and tropospheric ozone variations are generally associated with both natural and anthropogenic processes. As one of the most pristine and inaccessible regions in the world, the Tibetan Plateau has been considered as an ideal region for studying processes of the background atmosphere. Due to the vast area of the Tibetan Plateau, sites in the southern, northern and central regions exhibit different patterns of variation in surface ozone. Here, we present continuous measurements of surface ozone mixing ratios at Nam Co Station over a period of ˜ 5 years (January 2011 to October 2015), which is a background site in the inland Tibetan Plateau. An average surface ozone mixing ratio of 47.6 ± 11.6 ppb (mean ± standard deviation) was recorded, and a large annual cycle was observed with maximum ozone mixing ratios in the spring and minimum ratios during the winter. The diurnal cycle is characterized by a minimum in the early morning and a maximum in the late afternoon. Nam Co Station represents a background region where surface ozone receives negligible local anthropogenic emissions inputs, and the anthropogenic contribution from South Asia in spring and China in summer may affect Nam Co Station occasionally. Surface ozone at Nam Co Station is mainly dominated by natural processes involving photochemical reactions, vertical mixing and downward transport of stratospheric air mass. Model results indicate that the study site is affected differently by the surrounding areas in different seasons: air masses from the southern Tibetan Plateau contribute to the high ozone levels in the spring, and enhanced ozone levels in the summer are associated with air masses from the northern Tibetan Plateau. By comparing measurements at Nam Co Station with those from other sites on the Tibetan Plateau, we aim to expand the understanding of ozone cycles and transport processes over the Tibetan Plateau. This work may provide a

  17. Mechanisms of Surface Antigenic Variation in the Human Pathogenic Fungus Pneumocystis jirovecii.

    Science.gov (United States)

    Schmid-Siegert, Emanuel; Richard, Sophie; Luraschi, Amanda; Mühlethaler, Konrad; Pagni, Marco; Hauser, Philippe M

    2017-11-07

    Microbial pathogens commonly escape the human immune system by varying surface proteins. We investigated the mechanisms used for that purpose by Pneumocystis jirovecii This uncultivable fungus is an obligate pulmonary pathogen that in immunocompromised individuals causes pneumonia, a major life-threatening infection. Long-read PacBio sequencing was used to assemble a core of subtelomeres of a single P. jirovecii strain from a bronchoalveolar lavage fluid specimen from a single patient. A total of 113 genes encoding surface proteins were identified, including 28 pseudogenes. These genes formed a subtelomeric gene superfamily, which included five families encoding adhesive glycosylphosphatidylinositol (GPI)-anchored glycoproteins and one family encoding excreted glycoproteins. Numerical analyses suggested that diversification of the glycoproteins relies on mosaic genes created by ectopic recombination and occurs only within each family. DNA motifs suggested that all genes are expressed independently, except those of the family encoding the most abundant surface glycoproteins, which are subject to mutually exclusive expression. PCR analyses showed that exchange of the expressed gene of the latter family occurs frequently, possibly favored by the location of the genes proximal to the telomere because this allows concomitant telomere exchange. Our observations suggest that (i) the P. jirovecii cell surface is made of a complex mixture of different surface proteins, with a majority of a single isoform of the most abundant glycoprotein, (ii) genetic mosaicism within each family ensures variation of the glycoproteins, and (iii) the strategy of the fungus consists of the continuous production of new subpopulations composed of cells that are antigenically different. IMPORTANCE Pneumocystis jirovecii is a fungus causing severe pneumonia in immunocompromised individuals. It is the second most frequent life-threatening invasive fungal infection. We have studied the mechanisms

  18. Detection of a surface breaking crack by using the centroid variations of laser ultrasonic spectrums

    International Nuclear Information System (INIS)

    Park, Seung Kyu; Baik, Sung Hoon; Lim, Chang Hwan; Joo, Young Sang; Jung, Hyun Kyu; Cha, Hyung Ki; Kang, Young June

    2006-01-01

    A laser ultrasonic system is a non-contact inspection device with a wide-band spectrum and a high spatial resolution. It provides absolute measurements of the moving distance and it can be applied to hard-to-access locations including curved or rough surfaces like in a nuclear power plant. In this paper, we have investigated the detection methods of the depth of a surface-breaking crack by using the surface wave of a laser ultrasound. The filtering function of a surface-breaking crack is a kind of a low-pass filter. The higher frequency components are more highly decreased in proportion to the crack depth. Also, the center frequency value of each ultrasound spectrum is decreased in proportion to the crack depth. We extracted the depth information of a surface-breaking crack by observing the centroid variation of the frequency spectrum. We describe the experimental results to detect the crack depth information by using the peak-to-valley values in the time domain and the center frequency values in the frequency domain.

  19. Does quality control matter? Surface urban heat island intensity variations estimated by satellite-derived land surface temperature products

    Science.gov (United States)

    Lai, Jiameng; Zhan, Wenfeng; Huang, Fan; Quan, Jinling; Hu, Leiqiu; Gao, Lun; Ju, Weimin

    2018-05-01

    The temporally regular and spatially comprehensive monitoring of surface urban heat islands (SUHIs) have been extremely difficult, until the advent of satellite-based land surface temperature (LST) products. However, these LST products have relatively higher errors compared to in situ measurements. This has resulted in comparatively inaccurate estimations of SUHI indicators and, consequently, may have distorted interpretations of SUHIs. Although reports have shown that LST qualities are important for SUHI interpretations, systematic investigations of the response of SUHI indicators to LST qualities across cities with dissimilar bioclimates are rare. To address this issue, we chose eighty-six major cities across mainland China and analyzed SUHI intensity (SUHII) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) LST data. The LST-based SUHII differences due to inclusion or exclusion of MODIS quality control (QC) flags (i.e., ΔSUHII) were evaluated. Our major findings included, but are not limited to, the following four aspects: (1) SUHIIs can be significantly impacted by MODIS QC flags, and the associated QC-induced ΔSUHIIs generally accounted for 24.3% (29.9%) of the total SUHII value during the day (night); (2) the ΔSUHIIs differed between seasons, with considerable differences between transitional (spring and autumn) and extreme (summer and winter) seasons; (3) significant discrepancies also appeared among cities located in northern and southern regions, with northern cities often possessing higher annual mean ΔSUHIIs. The internal variations of ΔSUHIIs within individual cities also showed high heterogeneity, with ΔSUHII variations that generally exceeded 5.0 K (3.0 K) in northern (southern) cities; (4) ΔSUHIIs were negatively related to SUHIIs and cloud cover percentages (mostly in transitional seasons). No significant relationship was found in the extreme seasons. Our findings highlight the need to be extremely cautious when using LST

  20. Extensive computation of albedo contrast between martian dust devil tracks and their neighboring regions

    Science.gov (United States)

    Statella, Thiago; Pina, Pedro; da Silva, Erivaldo Antônio

    2015-04-01

    We have developed a method to compute the albedo contrast between dust devil tracks and their surrounding regions on Mars. It is mainly based on Mathematical Morphology operators and uses all the points of the edges of the tracks to compute the values of the albedo contrast. It permits the extraction of more accurate and complete information, when compared to traditional point sampling, not only providing better statistics but also permitting the analysis of local variations along the entirety of the tracks. This measure of contrast, based on relative quantities, is much more adequate to establish comparisons at regional scales and in multi-temporal basis using imagery acquired in rather different environmental and operational conditions. Also, the substantial increase in the details extracted may permit quantifying differential depositions of dust by computing local temporal fading of the tracks with consequences on a better estimation of the thickness of the top most layer of dust and the minimum value needed to create dust devils tracks. The developed tool is tested on 110 HiRISE images depicting regions in the Aeolis, Argyre, Eridania, Noachis and Hellas quadrangles. As a complementary evaluation, we also performed a temporal analysis of the albedo in a region of Russell crater, where high seasonal dust devil activity was already observed before, comprising the years 2007-2012. The mean albedo of the Russell crater is in this case indicative of dust devil tracks presence and, therefore, can be used to quantify dust devil activity.

  1. Calculation of neutron albedo from laminated semiinfinite media

    International Nuclear Information System (INIS)

    Dobrynin, Yu.L.; Mikaehlyan, L.A.; Skorokhvatov, M.D.

    1978-01-01

    A version of a laminated neutron detector with increased efficiency for recording external neutron fluxes by gamma-quanta from neutron capture is considered. The detector comprises two zones. The first zone constitutes an absorbent layer (europium oxide) 0.5 cm thick, and the second one is a moderator (water with gadolinium salt at the concentration of 0.8 g/l). Mono-energetic neutrons fall normally onto the detector surface. Neutron energy varied from 0.1 eV to MeV. The results of calculations of the integral numerical current albedo (INCA) of neutrons by the Monte Carlo method are presented. The INCA dependences on neutron energy are obtained for one moderator with different gadolinium contents; for the absorbent with the moderator containing and lacking the gadolinium. The resultant dependences are indicative of preferential capture of neutrons by the gadolinium in the moderator, this being more desirable for recording neutrons in the (n, γ) reaction

  2. 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.

  3. 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.

  4. Bright is the New Black - Multi-Year Performance of Generic High-Albedo Roofs in an Urban Climate

    Science.gov (United States)

    Gaffin, S. R.; Imhoff, M.; Rosenzweig, C.; Khanbilvardi, R.; Pasqualini, A.; Kong, A. Y. Y.; Grillo, D.; Freed, A.; Hillel, D.; Hartung, E.

    2012-01-01

    High-albedo white and cool roofing membranes are recognized as a fundamental strategy that dense urban areas can deploy on a large scale, at low cost, to mitigate the urban heat island effect. We are monitoring three generic white membranes within New York City that represent a cross-section of the dominant white membrane options for U.S. flat roofs: (1) an ethylene propylene diene monomer (EPDM) rubber membrane; (2) a thermoplastic polyolefin (TPO) membrane and; (3) an asphaltic multi-ply built-up membrane coated with white elastomeric acrylic paint. The paint product is being used by New York City s government for the first major urban albedo enhancement program in its history. We report on the temperature and related albedo performance of these three membranes at three different sites over a multi-year period. The results indicate that the professionally installed white membranes are maintaining their temperature control effectively and are meeting the Energy Star Cool Roofing performance standards requiring a three-year aged albedo above 0.50. The EPDM membrane however shows evidence of low emissivity. The painted asphaltic surface shows high emissivity but lost about half of its initial albedo within two years after installation. Given that the acrylic approach is an important "do-it-yourself," low-cost, retrofit technique, and, as such, offers the most rapid technique for increasing urban albedo, further product performance research is recommended to identify conditions that optimize its long-term albedo control. Even so, its current multi-year performance still represents a significant albedo enhancement for urban heat island mitigation.

  5. THE STATISTICS OF ALBEDO AND HEAT RECIRCULATION ON HOT EXOPLANETS

    International Nuclear Information System (INIS)

    Cowan, Nicolas B.; Agol, Eric

    2011-01-01

    If both the day-side and night-side effective temperatures of a planet can be measured, it is possible to estimate its Bond albedo, 0 B 0 , and associated uncertainty. We then use a simple model-independent technique to estimate a planet's effective temperature from planet/star flux ratios. We use thermal secondary eclipse measurements-those obtained at λ>0.8 μm-to estimate day-side effective temperatures, T d , and thermal phase variations-when available-to estimate night-side effective temperature. We strongly rule out the 'null hypothesis' of a single A B and ε for all 24 planets. If we allow each planet to have different parameters, we find that low Bond albedos are favored (A B 0 , the day-side effective temperatures of the 24 planets describe a uni-modal distribution. The two biggest outliers are GJ 436b (abnormally hot) and HD 80606b (abnormally cool), and these are the only eccentric planets in our sample. The dimensionless quantity T d /T 0 exhibits no trend with the presence or absence of stratospheric inversions. There is also no clear trend between T d /T 0 and T 0 . That said, the six planets with the greatest sub-stellar equilibrium temperatures (T > 2400 K) have low ε, as opposed to the 18 cooler planets, which show a variety of recirculation efficiencies. This hints that the very hottest transiting giant planets are qualitatively different from the merely hot Jupiters. We propose an explanation of this trend based on how a planet's radiative and advective times scale with temperature: both timescales are expected to be shorter for hotter planets, but the temperature dependence of the radiative timescale is stronger, leading to decreased heat recirculation efficiency.

  6. Evaluation of preindustrial to present-day black carbon and its albedo forcing from ACCMIP

    Science.gov (United States)

    LEE, Y.; Lamarque, J.; Flanner, M. G.; Jiao, C.; Shindell, D. T.; Berntsen, T.; Bisiaux, M. M.; Cao, J.; Collins, B.; Curran, M. A.; Edwards, R.; Faluvegi, G.; Ghan, S. J.; Horowitz, L. W.; McConnell, J. R.; Myhre, G.; Nagashima, T.; Naik, V.; Rumbold, S.; Skeie, R.; Sudo, K.; Takemura, T.; Thevenon, F.

    2012-12-01

    As part of the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP), we evaluate the historical black carbon (BC) aerosols simulated by 8 ACCMIP models against observations including 12 ice core records, long-term surface mass concentrations and recent Arctic BC snowpack measurements. We also estimate BC albedo forcing by performing additional simulations using offline models with prescribed meteorology from 1996-2000. We evaluated the vertical profile of BC snow concentrations from these offline simulations using the recent BC snowpack measurements. Despite using the same BC emissions, the global BC burden differs by approximately a factor of 3 among models due to differences in aerosol removal parameterizations and simulated meteorology: 34 Gg to 103 Gg in 1850 and 82 Gg to 315 Gg in 2000. However, the global BC burden from preindustrial to present-day increases by 2.5-3 times with little variation among models, roughly matching the 2.5-fold increase in total BC emissions during the same period. We find a large divergence among models at both Northern Hemisphere (NH) and Southern Hemisphere (SH) high latitude regions for BC burden and at SH high latitude regions for deposition fluxes. The ACCMIP simulations match the observed BC surface mass concentrations well in Europe and North America except at Jungfraujoch and Ispra. However, the models fail to predict the Arctic BC seasonality due to severe underestimations during winter and spring. The simulated vertically resolved BC snow concentrations are, on average, within a factor of 2-3 of the BC snowpack measurements except for Greenland and the Arctic Ocean. For the ice core evaluation, models tend to capture both the observed temporal trends and the magnitudes well at Greenland sites. However, models fail to predict the decreasing trend of BC depositions/concentrations from the 1950s to the 1970s in most Tibetan Plateau ice cores and the overall temporal trends in the Alps ice core. The

  7. Understanding the drivers of post-fire albedo and radiative forcing across Alaska and Canada: implications for management.

    Science.gov (United States)

    Potter, S.; Solvik, K.; Erb, A.; Goetz, S. J.; Johnstone, J. F.; Mack, M. C.; Randerson, J. T.; Roman, M. O.; Schaaf, C. L.; Turetsky, M. R.; Veraverbeke, S.; Wang, Z.; Rogers, B. M.

    2017-12-01

    Boreal forest dynamics including succession, composition, carbon cycling, and surface-atmosphere energy exchanges are largely driven by fire. In Alaska and Canada, burned area and fire frequency have increased since the 1970s, and are projected to continue increasing into the 21st century. In contrast to other biomes, alterations to surface albedo from fires in North American boreal forests are one of the primary feedbacks to climate. Understanding how altered fire regimes impact vegetation composition and energy budgets is therefore critical to forecasting regional and global climate change. High-severity fires cause winter and spring albedo to increase due to increased snow exposure and replacement of evergreen conifers by deciduous broadleaf trees. Although summer albedo decreases initially due to the deposition of black carbon and charred surfaces, it typically increases for several decades thereafter when younger and brighter deciduous trees dominate. The net effect of these albedo changes is expected to result in substantive radiative cooling, but there has been little research to examine how albedo trajectories differ spatially and temporally as a result of differences in burn severity, species composition, topography, climate and soil properties, and what the associated implications for future energy balances are. Here we investigate drivers of post-fire monthly albedo trajectories across Canada and Alaska using a new Collection V006 500 m MODIS daily blue-sky albedo product and historical fires from the Canadian and Alaskan National Fire Databases. The impacts of varying fuel type, landscape position, soils, climate, and burn severity on monthly albedo trajectories are explored using a Random Forest model. This information is then used to predict long-term monthly albedo and radiative forcing for fires that occurred during the MODIS era (2001-2012). We find that higher severity burns in denser forests and environmental conditions that promote either

  8. Spatiotemporal Variation in Surface Urban Heat Island Intensity and Associated Determinants across Major Chinese Cities

    Directory of Open Access Journals (Sweden)

    Juan Wang

    2015-03-01

    Full Text Available Urban heat islands (UHIs created through urbanization can have negative impacts on the lives of people living in cities. They may also vary spatially and temporally over a city. There is, thus, a need for greater understanding of these patterns and their causes. While previous UHI studies focused on only a few cities and/or several explanatory variables, this research provides a comprehensive and comparative characterization of the diurnal and seasonal variation in surface UHI intensities (SUHIIs across 67 major Chinese cities. The factors associated with the SUHII were assessed by considering a variety of related social, economic and natural factors using a regression tree model. Obvious seasonal variation was observed for the daytime SUHII, and the diurnal variation in SUHII varied seasonally across China. Interestingly, the SUHII varied significantly in character between northern and southern China. Southern China experienced more intense daytime SUHIIs, while the opposite was true for nighttime SUHIIs. Vegetation had the greatest effect in the day time in northern China. In southern China, annual electricity consumption and the number of public buses were found to be important. These results have important theoretical significance and may be of use to mitigate UHI effects.

  9. [Ciliate diversity and spatiotemporal variation in surface sediments of Yangtze River estuary hypoxic zone].

    Science.gov (United States)

    Feng, Zhao; Kui-Dong, Xu; Zhao-Cui, Meng

    2012-12-01

    By using denaturing gradient gel electrophoresis (DGGE) and sequencing as well as Ludox-QPS method, an investigation was made on the ciliate diversity and its spatiotemporal variation in the surface sediments at three sites of Yangtze River estuary hypoxic zone in April and August 2011. The ANOSIM analysis indicated that the ciliate diversity had significant difference among the sites (R = 0.896, P = 0.0001), but less difference among seasons (R = 0.043, P = 0.207). The sequencing of 18S rDNA DGGE bands revealed that the most predominant groups were planktonic Choreotrichia and Oligotrichia. The detection by Ludox-QPS method showed that the species number and abundance of active ciliates were maintained at a higher level, and increased by 2-5 times in summer, as compared with those in spring. Both the Ludox-QPS method and the DGGE technique detected that the ciliate diversity at the three sites had the similar variation trend, and the Ludox-QPS method detected that there was a significant variation in the ciliate species number and abundance between different seasons. The species number detected by Ludox-QPS method was higher than that detected by DGGE bands. Our study indicated that the ciliates in Yangtze River estuary hypoxic zone had higher diversity and abundance, with the potential to supply food for the polyps of jellyfish.

  10. An assessment of surface emissivity variation effects on plasma uniformity analysis using IR cameras

    Science.gov (United States)

    Greenhalgh, Abigail; Showers, Melissa; Biewer, Theodore

    2017-10-01

    The Prototype-Material Plasma Exposure eXperiment (Proto-MPEX) is a linear plasma device operating at Oak Ridge National Laboratory (ORNL). Its purpose is to test plasma source and heating concepts for the planned Material Plasma Exposure eXperiment (MPEX), which has the mission to test the plasma-material interactions under fusion reactor conditions. In this device material targets will be exposed to high heat fluxes (>10 MW/m2). To characterize the heat fluxes to the target a IR thermography system is used taking up to 432 frames per second videos. The data is analyzed to determine the surface temperature on the target in specific regions of interest. The IR analysis has indicated a low level of plasma uniformity; the plasma often deposits more heat to the edge of the plate than the center. An essential parameter for IR temperature calculation is the surface emissivity of the plate (stainless steel). A study has been performed to characterize the variation in the surface emissivity of the plate as its temperature changes and its surface finish is modified by plasma exposure.

  11. SPATIAL AND TEMPORAL VARIATION OF LAND SURFACE TEMPERATURE IN FUJIAN PROVINCE FROM 2001 TO 2015

    Directory of Open Access Journals (Sweden)

    Y. Li

    2018-04-01

    Full Text Available Land surface temperature (LST is an essential parameter in the physics of land surface processes. The spatiotemporal variations of LST on the Fujian province were studied using AQUA Moderate Resolution Imaging Spectroradiometer LST data. Considering the data gaps in remotely sensed LST products caused by cloud contamination, the Savitzky-Golay (S-G filter method was used to eliminate the influence of cloud cover and to describe the periodical signals of LST. Observed air temperature data from 27 weather stations were employed to evaluate the fitting performance of the S-G filter method. Results indicate that S-G can effectively fit the LST time series and remove the influence of cloud cover. Based on the S-G-derived result, Spatial and temporal Variations of LST in Fujian province from 2001 to 2015 are analysed through slope analysis. The results show that: 1 the spatial distribution of annual mean LST generally exhibits consistency with altitude in the study area and the average of LST was much higher in the east than in the west. 2 The annual mean temperature of LST declines slightly among 15 years in Fujian. 3 Slope analysis reflects the spatial distribution characteristics of LST changing trend in Fujian.Improvement areas of LST are mainly concentrated in the urban areas of Fujian, especially in the eastern urban areas. Apparent descent areas are mainly distributed in the area of Zhangzhou and eastern mountain area.

  12. Spatial and Temporal Variation of Land Surface Temperature in Fujian Province from 2001 TO 2015

    Science.gov (United States)

    Li, Y.; Wang, X.; Ding, Z.

    2018-04-01

    Land surface temperature (LST) is an essential parameter in the physics of land surface processes. The spatiotemporal variations of LST on the Fujian province were studied using AQUA Moderate Resolution Imaging Spectroradiometer LST data. Considering the data gaps in remotely sensed LST products caused by cloud contamination, the Savitzky-Golay (S-G) filter method was used to eliminate the influence of cloud cover and to describe the periodical signals of LST. Observed air temperature data from 27 weather stations were employed to evaluate the fitting performance of the S-G filter method. Results indicate that S-G can effectively fit the LST time series and remove the influence of cloud cover. Based on the S-G-derived result, Spatial and temporal Variations of LST in Fujian province from 2001 to 2015 are analysed through slope analysis. The results show that: 1) the spatial distribution of annual mean LST generally exhibits consistency with altitude in the study area and the average of LST was much higher in the east than in the west. 2) The annual mean temperature of LST declines slightly among 15 years in Fujian. 3) Slope analysis reflects the spatial distribution characteristics of LST changing trend in Fujian.Improvement areas of LST are mainly concentrated in the urban areas of Fujian, especially in the eastern urban areas. Apparent descent areas are mainly distributed in the area of Zhangzhou and eastern mountain area.

  13. Developing a Validated Long-Term Satellite-Based Albedo Record in the Central Alaska Range to Improve Regional Hydroclimate Reconstructions

    Science.gov (United States)

    Kreutz, K. J.; Godaire, T. P.; Burakowski, E. A.; Winski, D.; Campbell, S. W.; Wang, Z.; Sun, Q.; Hamilton, G. S.; Birkel, S. D.; Wake, C. P.; Osterberg, E. C.; Schaaf, C.

    2015-12-01

    Mountain glaciers around the world, particularly in Alaska, are experiencing significant surface mass loss from rapid climatic shifts and constitute a large proportion of the cryosphere's contribution to sea level rise. Surface albedo acts as a primary control on a glacier's mass balance, yet it is difficult to measure and quantify spatially and temporally in steep, mountainous settings. During our 2013 field campaign in Denali National Park to recover two surface to bedrock ice cores, we used an Analytical Spectral Devices (ASD) FieldSpec4 Standard Resolution spectroradiometer to measure incoming solar radiation, outgoing surface reflectance and optical grain size on the Kahiltna Glacier and at the Kahiltna Base Camp. A Campbell Scientific automatic weather station was installed on Mount Hunter (3900m) in June 2013, complementing a longer-term (2008-present) station installed at Kahiltna Base Camp (2100m). Use of our in situ data aids in the validation of surface albedo values derived from Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat satellite imagery. Comparisons are made between ASD FieldSpec4 ground measurements and 500m MODIS imagery to assess the ability of MODIS to capture the variability of surface albedo across the glacier surface. The MODIS MCD43A3 BRDF/Albedo Product performs well at Kahiltna Base Camp (albedo (10-28% relative to ASD data) appear to occur along the Kahiltna Glacier due to the snow-free valley walls being captured in the 500m MODIS footprint. Incorporating Landsat imagery will strengthen our interpretations and has the potential to produce a long-term (1982-present) validated satellite albedo record for steep and mountainous terrain. Once validation is complete, we will compare the satellite-derived albedo record to the Denali ice core accumulation rate, aerosol records (i.e. volcanics and biomass burning), and glacier mass balance data. This research will ultimately contribute to an improved understanding of the

  14. A Stabilizing Feedback Between Cloud Radiative Effects and Greenland Surface Melt: Verification From Multi-year Automatic Weather Station Measurements

    Science.gov (United States)

    Zender, C. S.; Wang, W.; van As, D.

    2017-12-01

    Clouds have strong impacts on Greenland's surface melt through the interaction with the dry atmosphere and reflective surfaces. However, their effects are uncertain due to the lack of in situ observations. To better quantify cloud radiative effects (CRE) in Greenland, we analyze and interpret multi-year radiation measurements from 30 automatic weather stations encompassing a broad range of climatological and topographical conditions. During melt season, clouds warm surface over most of Greenland, meaning the longwave greenhouse effect outweighs the shortwave shading effect; on the other hand, the spatial variability of net (longwave and shortwave) CRE is dominated by shortwave CRE and in turn by surface albedo, which controls the potential absorption of solar radiation when clouds are absent. The net warming effect decreases with shortwave CRE from high to low altitudes and from north to south (Fig. 1). The spatial correlation between albedo and net CRE is strong (r=0.93, palbedo determines the net CRE seasonal trend, which decreases from May to July and increases afterwards. On an hourly timescale, we find two distinct radiative states in Greenland (Fig. 2). The clear state is characterized by clear-sky conditions or thin clouds, when albedo and solar zenith angle (SZA) weakly correlates with CRE. The cloudy state is characterized by opaque clouds, when the combination of albedo and SZA strongly correlates with CRE (r=0.85, palbedo and solar zenith angle, explains the majority of the CRE variation in spatial distribution, seasonal trend in the ablation zone, and in hourly variability in the cloudy radiative state. Clouds warm the brighter and colder surfaces of Greenland, enhance snow melt, and tend to lower the albedo. Clouds cool the darker and warmer surfaces, inhibiting snow melt, which increases albedo, and thus stabilizes surface melt. This stabilizing mechanism may also occur over sea ice, helping to forestall surface melt as the Arctic becomes dimmer.

  15. Potential decadal predictability and its sensitivity to sea ice albedo parameterization in a global coupled model

    Energy Technology Data Exchange (ETDEWEB)

    Koenigk, Torben; Caian, Mihaela; Doescher, Ralf; Wyser, Klaus [Swedish Meteorological and Hydrological Institute, Rossby Centre, Norrkoeping (Sweden); Koenig Beatty, Christof [Universite Catholique de Louvain, Louvain-la-Neuve (Belgium)

    2012-06-15

    Decadal prediction is one focus of the upcoming 5th IPCC Assessment report. To be able to interpret the results and to further improve the decadal predictions it is important to investigate the potential predictability in the participating climate models. This study analyzes the upper limit of climate predictability on decadal time scales and its dependency on sea ice albedo parameterization by performing two perfect ensemble experiments with the global coupled climate model EC-Earth. In the first experiment, the standard albedo formulation of EC-Earth is used, in the second experiment sea ice albedo is reduced. The potential prognostic predictability is analyzed for a set of oceanic and atmospheric parameters. The decadal predictability of the atmospheric circulation is small. The highest potential predictability was found in air temperature at 2 m height over the northern North Atlantic and the southern South Atlantic. Over land, only a few areas are significantly predictable. The predictability for continental size averages of air temperature is relatively good in all northern hemisphere regions. Sea ice thickness is highly predictable along the ice edges in the North Atlantic Arctic Sector. The meridional overturning circulation is highly predictable in both experiments and governs most of the decadal climate predictability in the northern hemisphere. The experiments using reduced sea ice albedo show some important differences like a generally higher predictability of atmospheric variables in the Arctic or higher predictability of air temperature in Europe. Furthermore, decadal variations are substantially smaller in the simulations with reduced ice albedo, which can be explained by reduced sea ice thickness in these simulations. (orig.)

  16. Urban Morphology Influence on Urban Albedo: A Revisit with the S olene Model

    Science.gov (United States)

    Groleau, Dominique; Mestayer, Patrice G.

    2013-05-01

    This heuristic study of the urban morphology influence on urban albedo is based on some 3,500 simulations with the S olene model. The studied configurations include square blocks in regular and staggered rows, rectangular blocks with different street widths, cross-shaped blocks, infinite street canyons and several actual districts in Marseilles, Toulouse and Nantes, France. The scanned variables are plan density, facade density, building height, layout orientation, latitude, date and time of the day. The sky-view factors of the ground and canopy surfaces are also considered. This study demonstrates the significance of the facade density, in addition to the built plan density, as the explanatory geometrical factor to characterize the urban morphology, rather than building height. On the basis of these albedo calculations the puzzling results of Kondo et al. (Boundary-Layer Meteorol 100:225-242, 2001) for the influence of building height are explained, and the plan density influence is quantitatively assessed. It is shown that the albedo relationship with plan and facade densities obtained with the regular square plot configuration may be considered as a reference for all other configurations, with the exception of the infinite street canyon that shows systematic differences for the lower plan densities. The curves representing this empirical relationship may be used as a sort of abacus for all other geometries while an approximate simple mathematical model is proposed, as well as relationships between the albedo and sky-view factors.

  17. Surface ozone at Nam Co in the inland Tibetan Plateau: variation, synthesis comparison and regional representativeness

    Directory of Open Access Journals (Sweden)

    X. Yin

    2017-09-01

    Full Text Available Ozone is an important pollutant and greenhouse gas, and tropospheric ozone variations are generally associated with both natural and anthropogenic processes. As one of the most pristine and inaccessible regions in the world, the Tibetan Plateau has been considered as an ideal region for studying processes of the background atmosphere. Due to the vast area of the Tibetan Plateau, sites in the southern, northern and central regions exhibit different patterns of variation in surface ozone. Here, we present continuous measurements of surface ozone mixing ratios at Nam Co Station over a period of  ∼ 5 years (January 2011 to October 2015, which is a background site in the inland Tibetan Plateau. An average surface ozone mixing ratio of 47.6 ± 11.6 ppb (mean ± standard deviation was recorded, and a large annual cycle was observed with maximum ozone mixing ratios in the spring and minimum ratios during the winter. The diurnal cycle is characterized by a minimum in the early morning and a maximum in the late afternoon. Nam Co Station represents a background region where surface ozone receives negligible local anthropogenic emissions inputs, and the anthropogenic contribution from South Asia in spring and China in summer may affect Nam Co Station occasionally. Surface ozone at Nam Co Station is mainly dominated by natural processes involving photochemical reactions, vertical mixing and downward transport of stratospheric air mass. Model results indicate that the study site is affected differently by the surrounding areas in different seasons: air masses from the southern Tibetan Plateau contribute to the high ozone levels in the spring, and enhanced ozone levels in the summer are associated with air masses from the northern Tibetan Plateau. By comparing measurements at Nam Co Station with those from other sites on the Tibetan Plateau, we aim to expand the understanding of ozone cycles and transport processes over the Tibetan Plateau

  18. Surface Temperature Variation Prediction Model Using Real-Time Weather Forecasts

    Science.gov (United States)

    Karimi, M.; Vant-Hull, B.; Nazari, R.; Khanbilvardi, R.

    2015-12-01

    Combination of climate change and urbanization are heating up cities and putting the lives of millions of people in danger. More than half of the world's total population resides in cities and urban centers. Cities are experiencing urban Heat Island (UHI) effect. Hotter days are associated with serious health impacts, heart attaches and respiratory and cardiovascular diseases. Densely populated cities like Manhattan, New York can be affected by UHI impact much more than less populated cities. Even though many studies have been focused on the impact of UHI and temperature changes between urban and rural air temperature, not many look at the temperature variations within a city. These studies mostly use remote sensing data or typical measurements collected by local meteorological station networks. Local meteorological measurements only have local coverage and cannot be used to study the impact of UHI in a city and remote sensing data such as MODIS, LANDSAT and ASTER have with very low resolution which cannot be used for the purpose of this study. Therefore, predicting surface temperature in urban cities using weather data can be useful.Three months of Field campaign in Manhattan were used to measure spatial and temporal temperature variations within an urban setting by placing 10 fixed sensors deployed to measure temperature, relative humidity and sunlight. Fixed instrument shelters containing relative humidity, temperature and illumination sensors were mounted on lampposts in ten different locations in Manhattan (Vant-Hull et al, 2014). The shelters were fixed 3-4 meters above the ground for the period of three months from June 23 to September 20th of 2013 making measurements with the interval of 3 minutes. These high resolution temperature measurements and three months of weather data were used to predict temperature variability from weather forecasts. This study shows that the amplitude of spatial and temporal variation in temperature for each day can be predicted

  19. 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.

  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. LLL development of a combined etch track: albedo dosimeter

    International Nuclear Information System (INIS)

    Griffith, R.V.; Fisher, J.C.; Harder, C.A.

    1977-01-01

    The addition of polycarbonate sheet to albedo detectors for electrochemical etching provides a simple, inexpensive way to reduce the spectral sensitivity of the personnel dosimeter without losing the albedo features of sensitivity and ease of automation. The ECEP technique also provides the dosimetrist with the potential for identifying conditions of body orientation that might otherwise lead to significant error in dosimeter evaluation

  2. Frost behavior of a fin surface with temperature variation along heat exchanger fins

    International Nuclear Information System (INIS)

    Kim, Jung Soo; Kim, Min Soo; Lee, Kwan Soo; Kim, Ook Joong

    2007-01-01

    This paper presents a mathematical model for predicting the frost behavior formed on heat exchanger fins, considering fin heat conduction under frosting condition. The model is composed of air-side, the frost layer, and fin region, and they are coupled to the frost layer. The frost behavior is more accurately predicted with fin heat conduction considered (Case A) than with a constant fin surface temperature assumed (Case B). The results indicate that the frost thickness and heat transfer rate for Case B are over-predicted in most regions of the fin, as compared to those for Case A. Also, for Case A, the maximum frost thickness varies little with the fin length variations, and the extension of the fin length over 30 mm contributes insignificantly to heat transfer

  3. Regional variations of cell surface carbohydrates in human oral stratified epithelium

    DEFF Research Database (Denmark)

    Vedtofte, P; Dabelsteen, Erik; Hakomori, S

    1984-01-01

    The distribution of blood group carbohydrate chains with antigen A, B, H type 2 chain (A and B precursor), and N-acetyllactosamine (H type 2 precursor) specificity was studied in human oral epithelium from different anatomical regions. These represented various epithelial differentiation patterns...... epithelium from nine blood group A, two blood group B, and nine blood group O individuals. The blood group carbohydrate chains were examined in tissue sections by immunofluorescence microscopy. The A and B blood group antigens were detected by human blood group sera, and antigen H type 2 chains and N...... antigen H type 2 chains in metaplastically keratinized buccal epithelium was found to differ significantly from that seen in normal non-keratinized buccal epithelium. The regional variations demonstrated in cell surface carbohydrates are suggested to reflect differences in tissue differentiation....

  4. Variational analysis for simulating free-surface flows in a porous medium

    Directory of Open Access Journals (Sweden)

    Shabbir Ahmed

    2003-01-01

    is used to obtain a discrete form of equations for a two-dimensional domain. The matrix characteristics and the stability criteria have been investigated to develop a stable numerical algorithm for solving the governing equation. A computer programme has been written to solve a symmetric positive definite system obtained from the variational finite element analysis. The system of equations is solved using the conjugate gradient method. The solution generates time-varying hydraulic heads in the subsurface. The interfacing free surface between the unsaturated and saturated zones in the variably saturated domain is located, based on the computed hydraulic heads. Example problems are investigated. The finite element solutions are compared with the exact solutions for the example problems. The numerical characteristics of the finite element solution method are also investigated using the example problems.

  5. Annual and latitudinal variations of surface fluxes and meteorological variables at Arctic terrestrial sites

    Science.gov (United States)

    Grachev, Andrey; Uttal, Taneil; Persson, Ola; Konopleva-Akish, Elena; Crepinsek, Sara; Cox, Christopher; Fairall, Christopher; Makshtas, Alexander; Repina, Irina

    2016-04-01

    This study analyzes and discusses seasonal and latitudinal variations of surface fluxes (turbulent, radiative, and soil ground heat) and other ancillary surface/snow/permafrost data based on in-situ measurements made at two long-term research observatories near the coast of the Arctic Ocean located in Canada and Russia. The hourly averaged data collected at Eureka (Canadian territory of Nunavut) and Tiksi (East Siberia) located at two quite different latitudes (80.0 N and 71.6 N respectively) are analyzed in details to describe the seasons in the Arctic. Although Eureka and Tiksi are located at the different continents and at the different latitudes, the annual course of the surface meteorology and the surface fluxes are qualitatively very similar. The air and soil temperatures display the familiar strong seasonal trend with maximum of measured temperatures in mid-summer and minimum during winter. According to our data, variation in incoming short-wave solar radiation led the seasonal pattern of the air and soil temperatures, and the turbulent fluxes. During the dark Polar nights, air and ground temperatures are strongly controlled by long-wave radiation associated generally with cloud cover. Due to the fact that in average the higher latitudes receive less solar radiation than lower latitudes, a length of the convective atmospheric boundary layer (warm season) is shorter and middle-summer amplitude of the turbulent fluxes is generally less in Eureka than in Tiksi. However, since solar elevation angle at local midnight in the middle of Arctic summer is higher for Eureka as compared to Tiksi, stable stratification and upward turbulent flux for carbon dioxide is generally did not observed at Eureka site during summer seasons. It was found a high correlation between the turbulent fluxes of sensible and latent heat, carbon dioxide and the net solar radiation. A comprehensive evaluation of energy balance closure problem is performed based on the multi-year data sets

  6. Temporal variation of optimal UV exposure time over Korea: risks and benefits of surface UV radiation

    Science.gov (United States)

    Lee, Y. G.; Koo, J. H.

    2015-12-01

    Solar UV radiation in a wavelength range between 280 to 400 nm has both positive and negative influences on human body. Surface UV radiation is the main natural source of vitamin D, providing the promotion of bone and musculoskeletal health and reducing the risk of a number of cancers and other medical conditions. However, overexposure to surface UV radiation is significantly related with the majority of skin cancer, in addition other negative health effects such as sunburn, skin aging, and some forms of eye cataracts. Therefore, it is important to estimate the optimal UV exposure time, representing a balance between reducing negative health effects and maximizing sufficient vitamin D production. Previous studies calculated erythemal UV and vitamin-D UV from the measured and modelled spectral irradiances, respectively, by weighting CIE Erythema and Vitamin D3 generation functions (Kazantzidis et al., 2009; Fioletov et al., 2010). In particular, McKenzie et al. (2009) suggested the algorithm to estimate vitamin-D production UV from erythemal UV (or UV index) and determined the optimum conditions of UV exposure based on skin type Ⅱ according to the Fitzpatrick (1988). Recently, there are various demands for risks and benefits of surface UV radiation on public health over Korea, thus it is necessary to estimate optimal UV exposure time suitable to skin type of East Asians. This study examined the relationship between erythemally weighted UV (UVEry) and vitamin D weighted UV (UVVitD) over Korea during 2004-2012. The temporal variations of the ratio (UVVitD/UVEry) were also analyzed and the ratio as a function of UV index was applied in estimating the optimal UV exposure time. In summer with high surface UV radiation, short exposure time leaded to sufficient vitamin D and erythema and vice versa in winter. Thus, the balancing time in winter was enough to maximize UV benefits and minimize UV risks.

  7. Seasonal variation in aragonite saturation in surface waters of Puget Sound – a pilot study

    Directory of Open Access Journals (Sweden)

    Gregory Pelletier

    2018-01-01

    Full Text Available A pilot study of sampling, using monthly marine flights over spatially distributed stations, was conducted with the aim to characterize the carbonate system in Puget Sound over a full year-long period. Surface waters of Puget Sound were found to be under-saturated with respect to aragonite during October–March, and super-saturated during April–September. Highest pCO2 and lowest pH occurred during the corrosive October–March period. Lowest pCO2 and highest pH occurred during the super-saturated April–September period. The monthly variations in pCO2 , pH, and aragonite saturation state closely followed the variations in monthly average chlorophyll a. Super-saturated conditions during April–September are likely strongly influenced by photosynthetic uptake of CO2 during the phytoplankton growing season. The relationship between phytoplankton production, the carbonate system, and aragonite saturation state suggests that long-term trends in eutrophication processes may contribute to trends in ocean acidification in Puget Sound

  8. Distribution and temporal variation of trace metal enrichment in surface sediments of San Jorge Bay, Chile.

    Science.gov (United States)

    Valdés, Jorge; Román, Domingo; Guiñez, Marcos; Rivera, Lidia; Morales, Tatiana; Morales, Tomás; Avila, Juan; Cortés, Pedro

    2010-08-01

    Cu, Pb, and Hg concentrations were determined in surface sediment samples collected at three sites in San Jorge Bay, northern Chile. This study aims to evaluate differences in their spatial distribution and temporal variability. The highest metal concentrations were found at the site "Puerto", where minerals (Cu and Pb) have been loaded for more than 60 years. On the other hand, Hg does not pose a contamination problem in this bay. Cu and Pb concentrations showed significant variations from 1 year to another. These variations seem to be a consequence of the combination of several factors, including changes in the loading and/or storage of minerals in San Jorge Bay, the dredging of bottom sediments (especially at Puerto), and seasonal changes in physical-chemical properties of the water column that modify the exchange of metals at the sediment-water interface. Differences in the contamination factor and geoaccumulation index suggest that pre-industrial concentrations measured in marine sediments of this geographical zone, were better than geological values (average shale, continental crust average) for evaluating the degree of contamination in this coastal system. Based on these last two indexes, San Jorge Bay has a serious problem of Cu and Pb pollution at the three sampling locations. However, only Cu exceeds the national maximum values used to evaluate ecological risk and the health of marine environments. It is suggested that Chilean environmental legislation for marine sediment quality--presently under technical discussion--is not an efficient tool for protecting the marine ecosystem.

  9. Interannual Variation of the Surface Temperature of Tropical Forests from Satellite Observations

    Directory of Open Access Journals (Sweden)

    Huilin Gao

    2016-01-01

    Full Text Available Land surface temperatures (LSTs within tropical forests contribute to climate variations. However, observational data are very limited in such regions. This study used passive microwave remote sensing data from the Special Sensor Microwave/Imager (SSM/I and the Special Sensor Microwave Imager Sounder (SSMIS, providing observations under all weather conditions, to investigate the LST over the Amazon and Congo rainforests. The SSM/I and SSMIS data were collected from 1996 to 2012. The morning and afternoon observations from passive microwave remote sensing facilitate the investigation of the interannual changes of LST anomalies on a diurnal basis. As a result of the variability of cloud cover and the corresponding reduction of solar radiation, the afternoon LST anomalies tend to vary more than the morning LST anomalies. The dominant spatial and temporal patterns for interseasonal variations of the LST anomalies over the tropical rainforest were analyzed. The impacts of droughts and El Niños on this LST were also investigated. Differences between early morning and late afternoon LST anomalies were identified by the remote sensing product, with the morning LST anomalies controlled by humidity (according to comparisons with the National Centers for Environmental Prediction (NCEP reanalysis data.

  10. NEOWISE REACTIVATION MISSION YEAR TWO: ASTEROID DIAMETERS AND ALBEDOS

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-09-01

    The Near-Earth Object Wide-Field Infrared Survey Explorer (NEOWISE) mission continues to detect, track, and characterize minor planets. We present diameters and albedos calculated from observations taken during the second year since the spacecraft was reactivated in late 2013. These include 207 near-Earth asteroids (NEAs) and 8885 other asteroids. Of the NEAs, 84% NEAs did not have previously measured diameters and albedos by the NEOWISE mission. Comparison of sizes and albedos calculated from NEOWISE measurements with those measured by occultations, spacecraft, and radar-derived shapes shows accuracy consistent with previous NEOWISE publications. Diameters and albedos fall within ±∼20% and ±∼40%, 1-sigma, respectively, of those measured by these alternate techniques. NEOWISE continues to preferentially discover near-Earth objects which are large (>100 m), and have low albedos.

  11. Use of wrist albedo neutron dosimeters

    International Nuclear Information System (INIS)

    Hankins, D.E.

    1983-01-01

    We are developing a wrist dosimeter that can be used to measure the exposure at the wrist to x-rays, gamma rays, beta-particles, thermal neutrons and fast neutrons. It consists of a modified Hankins Type albedo neutron dosimeter and also contains three pieces of CR-39 plastic. ABS plastic in the form of an elongated hemisphere provides the beta and low energy x-ray shielding necessary to meet the requirement of depth dose measurements at 1 cm. The dosimeter has a beta window located in the side of the hemisphere oriented towards an object being held in the hands. A TLD 600 is positioned under the 1 cm thick ABS plastic and is used to measure the thermal neutron dose. At present we are using Velcro straps to hold the dosimeter on the inside of the wrist. 9 figures

  12. Seasonal and latitudinal variations of surface fluxes at two Arctic terrestrial sites

    Science.gov (United States)

    Grachev, Andrey A.; Persson, P. Ola G.; Uttal, Taneil; Akish, Elena A.; Cox, Christopher J.; Morris, Sara M.; Fairall, Christopher W.; Stone, Robert S.; Lesins, Glen; Makshtas, Alexander P.; Repina, Irina A.

    2017-11-01

    This observational study compares seasonal variations of surface fluxes (turbulent, radiative, and soil heat) and other ancillary atmospheric/surface/permafrost data based on in-situ measurements made at terrestrial research observatories located near the coast of the Arctic Ocean. Hourly-averaged multiyear data sets collected at Eureka (Nunavut, Canada) and Tiksi (East Siberia, Russia) are analyzed in more detail to elucidate similarities and differences in the seasonal cycles at these two Arctic stations, which are situated at significantly different latitudes (80.0°N and 71.6°N, respectively). While significant gross similarities exist in the annual cycles of various meteorological parameters and fluxes, the differences in latitude, local topography, cloud cover, snowfall, and soil characteristics produce noticeable differences in fluxes and in the structures of the atmospheric boundary layer and upper soil temperature profiles. An important factor is that even though higher latitude sites (in this case Eureka) generally receive less annual incoming solar radiation but more total daily incoming solar radiation throughout the summer months than lower latitude sites (in this case Tiksi). This leads to a counter-intuitive state where the average active layer (or thaw line) is deeper and the topsoil temperature in midsummer are higher in Eureka which is located almost 10° north of Tiksi. The study further highlights the differences in the seasonal and latitudinal variations of the incoming shortwave and net radiation as well as the moderating cloudiness effects that lead to temporal and spatial differences in the structure of the atmospheric boundary layer and the uppermost ground layer. Specifically the warm season (Arctic summer) is shorter and mid-summer amplitude of the surface fluxes near solar noon is generally less in Eureka than in Tiksi. During the dark Polar night and cold seasons (Arctic winter) when the ground is covered with snow and air temperatures

  13. Baring high-albedo soils by overgrazing - A hypothesized desertification mechanism

    Science.gov (United States)

    Otterman, J.

    1974-01-01

    Observations are reported of high-albedo soils denuded by overgrazing which appear bright, in high contrast to regions covered by natural vegetation. Measurements and modeling show that the denuded surfaces are cooler, when compared under sunlit conditions. This observed 'thermal depression' effect should, on theoretical grounds, result in a decreased lifting of air necessary for cloud formation and precipitation, and thus lead to regional climatic desertification.

  14. Quantifying the climate impacts of albedo changes due to biofuel production: a comparison with biogeochemical effects

    International Nuclear Information System (INIS)

    Caiazzo, Fabio; Malina, Robert; Staples, Mark D; Wolfe, Philip J; Yim, Steve H L; Barrett, Steven R H

    2014-01-01

    Lifecycle analysis is a tool widely used to evaluate the climate impact of greenhouse gas emissions attributable to the production and use of biofuels. In this paper we employ an augmented lifecycle framework that includes climate impacts from changes in surface albedo due to land use change. We consider eleven land-use change scenarios for the cultivation of biomass for middle distillate fuel production, and compare our results to previous estimates of lifecycle greenhouse gas emissions for the same set of land-use change scenarios in terms of CO 2 e per unit of fuel energy. We find that two of the land-use change scenarios considered demonstrate a warming effect due to changes in surface albedo, compared to conventional fuel, the largest of which is for replacement of desert land with salicornia cultivation. This corresponds to 222 gCO 2 e/MJ, equivalent to 3890% and 247% of the lifecycle GHG emissions of fuels derived from salicornia and crude oil, respectively. Nine of the land-use change scenarios considered demonstrate a cooling effect, the largest of which is for the replacement of tropical rainforests with soybean cultivation. This corresponds to − 161 gCO 2 e/MJ, or − 28% and − 178% of the lifecycle greenhouse gas emissions of fuels derived from soybean and crude oil, respectively. These results indicate that changes in surface albedo have the potential to dominate the climate impact of biofuels, and we conclude that accounting for changes in surface albedo is necessary for a complete assessment of the aggregate climate impacts of biofuel production and use. (paper)

  15. Quantifying the climate impacts of albedo changes due to biofuel production: a comparison with biogeochemical effects

    Science.gov (United States)

    Caiazzo, Fabio; Malina, Robert; Staples, Mark D.; Wolfe, Philip J.; Yim, Steve H. L.; Barrett, Steven R. H.

    2014-01-01

    Lifecycle analysis is a tool widely used to evaluate the climate impact of greenhouse gas emissions attributable to the production and use of biofuels. In this paper we employ an augmented lifecycle framework that includes climate impacts from changes in surface albedo due to land use change. We consider eleven land-use change scenarios for the cultivation of biomass for middle distillate fuel production, and compare our results to previous estimates of lifecycle greenhouse gas emissions for the same set of land-use change scenarios in terms of CO2e per unit of fuel energy. We find that two of the land-use change scenarios considered demonstrate a warming effect due to changes in surface albedo, compared to conventional fuel, the largest of which is for replacement of desert land with salicornia cultivation. This corresponds to 222 gCO2e/MJ, equivalent to 3890% and 247% of the lifecycle GHG emissions of fuels derived from salicornia and crude oil, respectively. Nine of the land-use change scenarios considered demonstrate a cooling effect, the largest of which is for the replacement of tropical rainforests with soybean cultivation. This corresponds to - 161 gCO2e/MJ, or - 28% and - 178% of the lifecycle greenhouse gas emissions of fuels derived from soybean and crude oil, respectively. These results indicate that changes in surface albedo have the potential to dominate the climate impact of biofuels, and we conclude that accounting for changes in surface albedo is necessary for a complete assessment of the aggregate climate impacts of biofuel production and use.

  16. Temporal aspects of surface water quality variation using robust statistical tools.

    Science.gov (United States)

    Mustapha, Adamu; Aris, Ahmad Zaharin; Ramli, Mohammad Firuz; Juahir, Hafizan

    2012-01-01

    Robust statistical tools were applied on the water quality datasets with the aim of determining the most significance parameters and their contribution towards temporal water quality variation. Surface water samples were collected from four different sampling points during dry and wet seasons and analyzed for their physicochemical constituents. Discriminant analysis (DA) provided better results with great discriminatory ability by using five parameters with (P < 0.05) for dry season affording more than 96% correct assignation and used five and six parameters for forward and backward stepwise in wet season data with P-value (P < 0.05) affording 68.20% and 82%, respectively. Partial correlation results revealed that there are strong (r(p) = 0.829) and moderate (r(p) = 0.614) relationships between five-day biochemical oxygen demand (BOD(5)) and chemical oxygen demand (COD), total solids (TS) and dissolved solids (DS) controlling for the linear effect of nitrogen in the form of ammonia (NH(3)) and conductivity for dry and wet seasons, respectively. Multiple linear regression identified the contribution of each variable with significant values r = 0.988, R(2) = 0.976 and r = 0.970, R(2) = 0.942 (P < 0.05) for dry and wet seasons, respectively. Repeated measure t-test confirmed that the surface water quality varies significantly between the seasons with significant value P < 0.05.

  17. Charging effects and surface potential variations of Cu-based nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Nunes, D., E-mail: daniela.gomes@fct.unl.pt [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Calmeiro, T.R.; Nandy, S.; Pinto, J.V.; Pimentel, A.; Barquinha, P. [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Carvalho, P.A. [SINTEF Materials and Chemistry, PB 124 Blindern, NO-0314, Oslo (Norway); CeFEMA, Instituto Superior Técnico, Universidade de Lisboa, 1049-001, Lisboa (Portugal); Walmsley, J.C. [SINTEF Materials and Chemistry, Materials and Nanotechnology, Høgskoleringen 5, 7034 Trondheim (Norway); Fortunato, E., E-mail: emf@fct.unl.pt [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Martins, R., E-mail: rm@uninova.pt [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal)

    2016-02-29

    The present work reports charging effects and surface potential variations in pure copper, cuprous oxide and cupric oxide nanowires observed by electrostatic force microscopy (EFM) and Kelvin probe force microscopy (KPFM). The copper nanowires were produced by wet synthesis, oxidation into cuprous oxide nanowires was achieved through microwave irradiation and cupric oxide nanowires were obtained via furnace annealing in atmospheric conditions. Structural characterization of the nanowires was carried out by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. During the EFM experiments the electrostatic field of the positive probe charged negatively the Cu-based nanowires, which in turn polarized the SiO{sub 2} dielectric substrate. Both the probe/nanowire capacitance as well as the substrate polarization increased with the applied bias. Cu{sub 2}O and CuO nanowires behaved distinctively during the EFM measurements in accordance with their band gap energies. The work functions (WF) of the Cu-based nanowires, obtained by KPFM measurements, yielded WF{sub CuO} > WF{sub Cu} > WF{sub Cu{sub 2O}}. - Highlights: • Charge distribution study in Cu, Cu{sub 2}O and CuO nanowires through electrostatic force microscopy • Structural/surface defect role on the charge distribution along the Cu nanowires • Determination of the nanowire work functions by Kelvin probe force microscopy • Three types of nanowires give a broad idea of charge behavior on Cu based-nanowires.

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

    Directory of Open Access Journals (Sweden)

    Elena Morini

    2016-10-01

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

  19. Derivation of high spatial resolution albedo from UAV digital imagery: application over the Greenland Ice Sheet

    Science.gov (United States)

    Ryan, Jonathan C.; Hubbard, Alun; Box, Jason E.; Brough, Stephen; Cameron, Karen; Cook, Joseph M.; Cooper, Matthew; Doyle, Samuel H.; Edwards, Arwyn; Holt, Tom; Irvine-Fynn, Tristram; Jones, Christine; Pitcher, Lincoln H.; Rennermalm, Asa K.; Smith, Laurence C.; Stibal, Marek; Snooke, Neal

    2017-05-01

    Measurements of albedo are a prerequisite for modelling surface melt across the Earth's cryosphere, yet available satellite products are limited in spatial and/or temporal resolution. Here, we present a practical methodology to obtain centimetre resolution albedo products with accuracies of 5% using consumer-grade digital camera and unmanned aerial vehicle (UAV) technologies. Our method comprises a workflow for processing, correcting and calibrating raw digital images using a white reference target, and upward and downward shortwave radiation measurements from broadband silicon pyranometers. We demonstrate the method with a set of UAV sorties over the western, K-sector of the Greenland Ice Sheet. The resulting albedo product, UAV10A1, covers 280 km2, at a resolution of 20 cm per pixel and has a root-mean-square difference of 3.7% compared to MOD10A1 and 4.9% compared to ground-based broadband pyranometer measurements. By continuously measuring downward solar irradiance, the technique overcomes previous limitations due to variable illumination conditions during and between surveys over glaciated terrain. The current miniaturization of multispectral sensors and incorporation of upward facing radiation sensors on UAV packages means that this technique will likely become increasingly attractive in field studies and used in a wide range of applications for high temporal and spatial resolution surface mapping of debris, dust, cryoconite and bioalbedo and for directly constraining surface energy balance models.

  20. The role of sea-ice albedo in the climate of slowly rotating aquaplanets

    Science.gov (United States)

    Salameh, Josiane; Popp, Max; Marotzke, Jochem

    2018-04-01

    We investigate the influence of the rotation period (P_{rot}) on the mean climate of an aquaplanet, with a focus on the role of sea-ice albedo. We perform aquaplanet simulations with the atmospheric general circulation model ECHAM6 for various rotation periods from one Earth-day to 365 Earth-days in which case the planet is synchronously rotating. The global-mean surface temperature decreases with increasing P_{rot} and sea ice expands equatorwards. The cooling of the mean climate with increasing P_{rot} is caused partly by the high surface albedo of sea ice on the dayside and partly by the high albedo of the deep convective clouds over the substellar region. The cooling caused by these deep convective clouds is weak for non-synchronous rotations compared to synchronous rotation. Sensitivity simulations with the sea-ice model switched off show that the global-mean surface temperature is up to 27 K higher than in our main simulations with sea ice and thus highlight the large influence of sea ice on the climate. We present the first estimates of the influence of the rotation period on the transition of an Earth-like climate to global glaciation. Our results suggest that global glaciation of planets with synchronous rotation occurs at substantially lower incoming solar irradiation than for planets with slow but non-synchronous rotation.

  1. Measurement of TLD Albedo response on various calibration phantoms

    International Nuclear Information System (INIS)

    Momose, T.; Tsujimura, N.; Shinohara, K.; Ishiguro, H.; Nakamura, T.

    1996-01-01

    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 252 Cf neutron source. (author)

  2. Toward Spectroscopically Detecting the Global Latitudinal Temperature Variation on the Solar Surface

    Science.gov (United States)

    Takeda, Y.; UeNo, S.

    2017-09-01

    A very slight rotation-induced latitudinal temperature variation (presumably on the order of several kelvin) on the solar surface is theoretically expected. While recent high-precision solar brightness observations reported its detection, confirmation by an alternative approach using the strengths of spectral lines is desirable, for which reducing the noise due to random fluctuation caused by atmospheric inhomogeneity is critical. Toward this difficult task, we carried out a pilot study of spectroscopically investigating the relative variation of temperature (T) at a number of points in the solar circumference region near to the limb (where latitude dependence should be detectable, if any exists) based on the equivalent widths (W) of 28 selected lines in the 5367 - 5393 Å and 6075 - 6100 Å regions. We paid special attention to i) clarifying which types of lines should be employed and ii) how much precision is attainable in practice. We found that lines with strong T-sensitivity (|log W/log T|) should be used and that very weak lines should be avoided because they inevitably suffer strong relative fluctuations (Δ W/W). Our analysis revealed that a precision of Δ T/T ≈ 0.003 (corresponding to ≈ 15 K) can be achieved at best by a spectral line with comparatively large |log W/log T|, although this can possibly be further improved When a number of lines are used all together. Accordingly, if many such favorable lines could be measured with subpercent precision of Δ W/W and by averaging the resulting Δ T/T from each line, the random noise would eventually be reduced to ≲ 1 K and detection of a very subtle amount of global T-gradient might be possible.

  3. Measurement of spectral sea ice albedo at Qaanaaq fjord in northwest Greenland

    Science.gov (United States)

    Tanikawa, T.

    2017-12-01

    The spectral albedos of sea ice were measured at Qaanaaq fjord in northwest Greenland. Spectral measurements were conducted for sea ice covered with snow and sea ice without snow where snow was artificially removed around measurement point. Thickness of the sea ice was approximately 1.3 m with 5 cm of snow over the sea ice. The measurements show that the spectral albedos of the sea ice with snow were lower than those of natural pure snow especially in the visible regions though the spectral shapes were similar to each other. This is because the spectral albedos in the visible region have information of not only the snow but also the sea ice under the snow. The spectral albedos of the sea ice without the snow were approximately 0.4 - 0.5 in the visible region, 0.05-0.25 in the near-infrared region and almost constant of approximately 0.05 in the region of 1500 - 2500 nm. In the visible region, it would be due to multiple scattering by an air bubble within the sea ice. In contrast, in the near-infrared and shortwave infrared wavelengths, surface reflection at the sea ice surface would be dominant. Since a light absorption by the ice in these regions is relatively strong comparing to the visible region, the light could not be penetrated deeply within the sea ice, resulting that surface reflection based on Fresnel reflection would be dominant. In this presentation we also show the results of comparison between the radiative transfer calculation and spectral measurement data.

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

    Science.gov (United States)

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

    2014-12-01

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

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

    International Nuclear Information System (INIS)

    Flores Calderon, J.E.

    1982-01-01

    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)

  6. Interannual Variations of Surface Currents and Transports in the Sicily Channel Derived From Coastal Altimetry

    Science.gov (United States)

    Jebri, Fatma; Zakardjian, Bruno; Birol, Florence; Bouffard, Jérôme; Jullion, Loïc.; Sammari, Cherif

    2017-11-01

    A 20 year coastal altimetry data set (X-TRACK) is used, for the first time, to gain insight into the long-term interannual variations of the surface circulation in the Sicily Channel. First, a spectral along with a time/space diagram analysis are applied to the monthly means. They reveal a regionally coherent current patterns from track to track with a marked interannual variability that is unequally shared between the Atlantic Tunisian Current and Atlantic Ionian Stream inflows in the Sicily Channel and the Bifurcation Tyrrhenian Current outflow northeast of Sicily. Second, an empirical altimetry-based transport-like technique is proposed to quantify volume budgets inside the closed boxes formed by the crossing of the altimetry tracks and coastlines over the study area. A set of hydrographic measurements is used to validate the method. The inferred altimetry transports give a well-balanced mean eastward Atlantic Waters baroclinic flow of 0.4 Sv and standard deviations of 0.2 Sv on a yearly basis throughout the Sicily Channel and toward the Ionian Sea, which is fairly coherent with those found in the literature. Furthermore, the analysis allows to quantify the intrusions of Atlantic Waters over the Tunisian Shelf (0.12 ± 0.1 Sv) and highlights two main modes of variability of the main surface waters path over the Sicily Channel through the Bifurcation Atlantic Tunisian Current and Atlantic Ionian Stream systems. Some physical mechanisms are finally discussed with regards to changes in the observed currents and transports.

  7. Energy-balance climate models: stability experiments with a refined albedo and updated coefficients for infrared emission

    NARCIS (Netherlands)

    Oerlemans, J.

    1978-01-01

    A zonally averaged' climate model of the energy-balance type is examined. Recently published satellite measurements were used to improve existing parameterizations of planetary albedo and outgoing radiation in terms of surface and sea level temperature. A realistic constant for the diffusion of

  8. Seasonal variations of seismicity and geodetic strain in the Himalaya induced by surface hydrology

    OpenAIRE

    Bettinelli, Pierre; Avouac, Jean-Philippe; Flouzat, Mireille; Bollinger, Laurent; Ramillien, Guillaume; Rajaure, Sudhir; Sapkota, Som

    2008-01-01

    One way to probe earthquake nucleation processes and the relation between stress buildup and seismicity is to analyze the sensitivity of seismicity to stress perturbations. Here, we report evidence for seasonal strain and stress (~ 2–4 kPa) variations in the Nepal Himalaya, induced by water storage variations which correlate with seasonal variations of seismicity. The seismicity rate is twice as high in the winter as in the summer, and correlates with stress rate variations. We infer ~ 10–20 ...

  9. Comparisons of spectral aerosol single scattering albedo in Seoul, South Korea

    Science.gov (United States)

    Mok, Jungbin; Krotkov, Nickolay A.; Torres, Omar; Jethva, Hiren; Li, Zhanqing; Kim, Jhoon; Koo, Ja-Ho; Go, Sujung; Irie, Hitoshi; Labow, Gordon; Eck, Thomas F.; Holben, Brent N.; Herman, Jay; Loughman, Robert P.; Spinei, Elena; Lee, Seoung Soo; Khatri, Pradeep; Campanelli, Monica

    2018-04-01

    Quantifying aerosol absorption at ultraviolet (UV) wavelengths is important for monitoring air pollution and aerosol amounts using current (e.g., Aura/OMI) and future (e.g., TROPOMI, TEMPO, GEMS, and Sentinel-4) satellite measurements. Measurements of column average atmospheric aerosol single scattering albedo (SSA) are performed on the ground by the NASA AERONET in the visible (VIS) and near-infrared (NIR) wavelengths and in the UV-VIS-NIR by the SKYNET networks. Previous comparison studies have focused on VIS and NIR wavelengths due to the lack of co-incident measurements of aerosol and gaseous absorption properties in the UV. This study compares the SKYNET-retrieved SSA in the UV with the SSA derived from a combination of AERONET, MFRSR, and Pandora (AMP) retrievals in Seoul, South Korea, in spring and summer 2016. The results show that the spectrally invariant surface albedo assumed in the SKYNET SSA retrievals leads to underestimated SSA compared to AMP values at near UV wavelengths. Re-processed SKYNET inversions using spectrally varying surface albedo, consistent with the AERONET retrieval improve agreement with AMP SSA. The combined AMP inversions allow for separating aerosol and gaseous (NO2 and O3) absorption and provide aerosol retrievals from the shortest UVB (305 nm) through VIS to NIR wavelengths (870 nm).

  10. Derivation of High Spatial Resolution Albedo from UAV Digital Imagery: Application over the Greenland Ice Sheet

    Directory of Open Access Journals (Sweden)

    Jonathan C. Ryan

    2017-05-01

    Full Text Available Measurements of albedo are a prerequisite for modeling surface melt across the Earth's cryosphere, yet available satellite products are limited in spatial and/or temporal resolution. Here, we present a practical methodology to obtain centimeter resolution albedo products with accuracies of ±5% using consumer-grade digital camera and unmanned aerial vehicle (UAV technologies. Our method comprises a workflow for processing, correcting and calibrating raw digital images using a white reference target, and upward and downward shortwave radiation measurements from broadband silicon pyranometers. We demonstrate the method with a set of UAV sorties over the western, K-sector of the Greenland Ice Sheet. The resulting albedo product, UAV10A1, covers 280 km2, at a resolution of 20 cm per pixel and has a root-mean-square difference of 3.7% compared to MOD10A1 and 4.9% compared to ground-based broadband pyranometer measurements. By continuously measuring downward solar irradiance, the technique overcomes previous limitations due to variable illumination conditions during and between surveys over glaciated terrain. The current miniaturization of multispectral sensors and incorporation of upward facing radiation sensors on UAV packages means that this technique could become increasingly common in field studies and used for a wide range of applications. These include the mapping of debris, dust, cryoconite and bioalbedo, and directly constraining surface energy balance models.

  11. Diffusion Filters for Variational Data Assimilation of Sea Surface Temperature in an Intermediate Climate Model

    Directory of Open Access Journals (Sweden)

    Xuefeng Zhang

    2015-01-01

    Full Text Available Sequential, adaptive, and gradient diffusion filters are implemented into spatial multiscale three-dimensional variational data assimilation (3DVAR as alternative schemes to model background error covariance matrix for the commonly used correction scale method, recursive filter method, and sequential 3DVAR. The gradient diffusion filter (GDF is verified by a two-dimensional sea surface temperature (SST assimilation experiment. Compared to the existing DF, the new GDF scheme shows a superior performance in the assimilation experiment due to its success in extracting the spatial multiscale information. The GDF can retrieve successfully the longwave information over the whole analysis domain and the shortwave information over data-dense regions. After that, a perfect twin data assimilation experiment framework is designed to study the effect of the GDF on the state estimation based on an intermediate coupled model. In this framework, the assimilation model is subject to “biased” initial fields from the “truth” model. While the GDF reduces the model bias in general, it can enhance the accuracy of the state estimation in the region that the observations are removed, especially in the South Ocean. In addition, the higher forecast skill can be obtained through the better initial state fields produced by the GDF.

  12. Empirical Mode Decomposition on the sphere: application to the spatial scales of surface temperature variations

    Directory of Open Access Journals (Sweden)

    N. Fauchereau

    2008-06-01

    Full Text Available Empirical Mode Decomposition (EMD is applied here in two dimensions over the sphere to demonstrate its potential as a data-adaptive method of separating the different scales of spatial variability in a geophysical (climatological/meteorological field. After a brief description of the basics of the EMD in 1 then 2 dimensions, the principles of its application on the sphere are explained, in particular via the use of a zonal equal area partitioning. EMD is first applied to an artificial dataset, demonstrating its capability in extracting the different (known scales embedded in the field. The decomposition is then applied to a global mean surface temperature dataset, and we show qualitatively that it extracts successively larger scales of temperature variations related, for example, to topographic and large-scale, solar radiation forcing. We propose that EMD can be used as a global data-adaptive filter, which will be useful in analysing geophysical phenomena that arise as the result of forcings at multiple spatial scales.

  13. The influence of green areas and roof albedos on air temperatures during extreme heat events in Berlin, Germany

    Energy Technology Data Exchange (ETDEWEB)

    Schubert, Sebastian; Grossmann-Clarke, Susanne [Potsdam Institute for Climate Impact Research, Potsdam (Germany)

    2013-04-15

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

  14. Effects of meteorological models on the solution of the surface energy balance and soil temperature variations in bare soils

    Science.gov (United States)

    Saito, Hirotaka; Šimůnek, Jiri

    2009-07-01

    significantly improve soil temperature predictions. On the other hand, while models for the albedo and soil emissivity had little impact on soil temperature predictions, the choice of the atmospheric emissivity models had a greater impact. A comparison of all the different models indicates that the error introduced at the soil atmosphere interface propagates to deeper layers. Therefore, attention needs to be paid not only to the precise determination of the soil hydraulic and thermal properties, but also to the selection of proper meteorological models for the components involved in the surface energy balance calculations.

  15. 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...

  16. Albedo neutron dosimetry in Germany: regulations and performance

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  17. Surface BRDF estimation from an aircraft compared to MODIS and ground estimates at the Southern Great Plains site

    Energy Technology Data Exchange (ETDEWEB)

    Knobelspiesse, Kirk D.; Cairns, Brian; Schmid, Beat; Roman, Miguel O.; Schaaf, Crystal B.

    2008-10-21

    Ames Airborne Tracking Sunphotometer (AATS-14), which was operated on the same aircraft as the RSP. The RSP data can therefore be used to validate the MODIS BRDF product and diagnose the reason for the discrepancies with BEFLUX. Our analysis indicates that MODIS and RSP estimates of surface absorption and BEFLUX measurements do agree and that previously noticed differences between MODIS albedo products and BEFLUX were due as much to the analysis techniques used as to any instrumental effects. We conclude that the MODIS BRDF products provide a useful measure of surface albedo that can be used to determine whether the surface radiative heating in climate models has a realistic spatial and seasonal variation.

  18. Variations in pCO2 during summer in the surface water of an unproductive lake in northern Sweden

    International Nuclear Information System (INIS)

    Jonsson, A.; Aaberg, J.; Jansson, M.

    2007-01-01

    Unproductive lakes are generally supersaturated with carbon dioxide (CO 2 ) and emit CO 2 to the atmosphere continuously during ice-free periods. However, temporal variation of the partial pressure of CO 2 (pCO 2 ) and thus of CO 2 evasion to atmosphere is poorly documented. We therefore carried out temporally high-resolution (every 6 h) measurements of the pCO 2 using an automated logger system in the surface water of a subarctic, unproductive, lake in the birch forest belt. The study period was June-September 2004. We found that the pCO 2 showed large seasonal variation, but low daily variation. The seasonal variation was likely mainly caused by variations in input and mineralization of allochthonous organic matter. Stratification depth probably also influenced pCO 2 of the surface water by controlling the volume in which mineralization of dissolved organic carbon (DOC) occurred. In lakes, with large variations in pCO 2 , as in our study lake a high (weekly) sampling intensity is recommended for obtaining accurate estimates of the evasion of CO 2

  19. Variations in pCO{sub 2} during summer in the surface water of an unproductive lake in northern Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Jonsson, A.; Aaberg, J.; Jansson, M. [Dept. of Ecology and Environmental Sci ence, Umeaa Univ., 901 87 Umeaa (Sweden)]. e-mail: anders.jonsson@emg.umu.se

    2007-11-15

    Unproductive lakes are generally supersaturated with carbon dioxide (CO{sub 2}) and emit CO{sub 2} to the atmosphere continuously during ice-free periods. However, temporal variation of the partial pressure of CO{sub 2} (pCO{sub 2}) and thus of CO{sub 2} evasion to atmosphere is poorly documented. We therefore carried out temporally high-resolution (every 6 h) measurements of the pCO{sub 2} using an automated logger system in the surface water of a subarctic, unproductive, lake in the birch forest belt. The study period was June-September 2004. We found that the pCO{sub 2} showed large seasonal variation, but low daily variation. The seasonal variation was likely mainly caused by variations in input and mineralization of allochthonous organic matter. Stratification depth probably also influenced pCO{sub 2} of the surface water by controlling the volume in which mineralization of dissolved organic carbon (DOC) occurred. In lakes, with large variations in pCO{sub 2}, as in our study lake a high (weekly) sampling intensity is recommended for obtaining accurate estimates of the evasion of CO{sub 2}.

  20. Variability of soil moisture and its relationship with surface albedo ...

    Indian Academy of Sciences (India)

    Time (s). A. Amplitude of the soil thermal wave at any depth (. ◦. C). A0. Amplitude of thermal ... system, soil moisture has a long memory (Pielke et al 1999; Wu et al .... measurements of the short wave radiation compo- nents as follows: α = Su.

  1. Atmospheric Polarization Imaging with Variable Aerosols, Clouds, and Surface Albedo

    Science.gov (United States)

    2013-07-01

    values found in this region only during episodes of intense wildfire smoke. Detailed analysis of the aerosols in this smoke plume and their effect...Continuous outdoor operation of an all-sky polarization imager,” Proc. SPIE 7672 (Polarization: Measurement, Analysis , and Remote Sensing IX), 76720A-1-7, 7...Pust, “ Lunar corona in ice wave cloud,” 10th International Meeting on Light and Color in Nature, St. Mary’s College of Maryland, 16-20 June 2010. 2

  2. Simultaneous improvement in water use, productivity and albedo through canopy structural modification

    Science.gov (United States)

    Drewry, Darren; Kumar, Praveen; Long, Stephen

    2015-04-01

    Agricultural lands provide a tremendous opportunity to address challenges at the intersection of food and water security and climate change. Global demand for the major grain and seed crops is beginning to outstrip production, while population growth and the expansion of the global middle class have motivated calls for a doubling of food production by the middle of this century. This is occurring as yield gains for the major food crops have stagnated. At current rates of yield improvement this doubling will not be achieved. Plants have evolved to maximize the capture of radiation in the upper leaves, resulting in sub-optimal monoculture crop fields for maximizing productivity and other biogeophysical services. Using the world's most important protein crop, soybean, as an example, we show that by applying numerical optimization to a micrometeorological crop canopy model that significant, simultaneous gains in water use, productivity and reflectivity are possible with no increased demand on resources. Here we apply the MLCan multi-layer canopy biophysical model, which vertically resolves the radiation and micro-environmental variations that stimulate biochemical and ecophysiological functions that govern canopy-atmosphere exchange processes. At each canopy level photosynthesis, stomatal conductance, and energy balance are solved simultaneously for shaded and sunlit foliage. A multi-layer sub-surface model incorporates water availability as a function of root biomass distribution. MLCan runs at sub-hourly temporal resolution, allowing it to capture variability in CO2, water and energy exchange as a function of environmental variability. By modifying total canopy leaf area, its vertical distribution, leaf angle, and shortwave radiation reflectivity, all traits available in most major crop germplasm collections, we show that increases in either productivity (7%), water use (13%) or albedo (34%) could be achieved with no detriment to the other objectives, under climate

  3. Simultaneous Improvement in Water Use, Productivity and Albedo Through Crop Structural Modification

    Science.gov (United States)

    Drewry, D.; Kumar, P.; Long, S.

    2014-12-01

    Agricultural lands provide a tremendous opportunity to address challenges at the intersection of climate change, food and water security. Global demand for the major grain and seed crops is beginning to outstrip production, while population growth and the expansion of the global middle class have motivated calls for a doubling of food production by the middle of this century. This is occurring as yield gains for the major food crops have stagnated. At current rates of yield improvement this doubling will not be achieved. Plants have evolved to maximize the capture of radiation in the upper leaves, resulting in sub-optimal monoculture crop fields for maximizing productivity and other biogeophysical services. Using the world's most important protein crop, soybean, as an example, we show that by applying numerical optimization to a micrometeorological crop canopy model that significant, simultaneous gains in water use, productivity and reflectivity are possible with no increased demand on resources. Here we apply the MLCan multi-layer canopy biophysical model, which vertically resolves the radiation and micro-environmental variations that stimulate biochemical and ecophysiological functions that govern canopy-atmosphere exchange processes. At each canopy level photosynthesis, stomatal conductance, and energy balance are solved simultaneously for shaded and sunlit foliage. A multi-layer sub-surface model accounts for water availability as a function of root biomass distribution. MLCan runs at sub-hourly temporal resolution, allowing it to capture variability in CO2, water and energy exchange as a function of environmental variability. By modifying total canopy leaf area, its vertical distribution, leaf angle, and shortwave radiation reflectivity, all traits available in most major crop germplasm collections, we show that increases in either productivity (7%), water use (13%) or albedo (34%) could be achieved with no detriment to the other objectives, under United

  4. 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.

  5. Effect of surface roughness variation on the transmission characteristics of D-shaped fibers with ambient index change

    International Nuclear Information System (INIS)

    Kim, Hyun-Joo; Kwon, Oh-Jang; Han, Young-Geun

    2010-01-01

    The influence of surface roughness on the sensitivity of D-shaped fibers to changes in the ambient index was investigated. In order to obtain D-shaped fibers with different surface roughness, we polished one side of the fibers by using different abrasive grits. The topographies of the surfaces of the polished D-shaped fibers were then observed by using atomic force microscopy (AFM). The light scattered from the rough surfaces of the D-shaped fibers was measured by using optical microscopy. The effect of an ambient index change on the transmission characteristics of D-shaped fibers was measured for various values of the surface roughness. The experimental results indicate that variations in the surface roughness have a considerable influence on the sensitivity of the transmission characteristics of D-shaped fibers to changes in the ambient index.

  6. Variation in nutrient characteristics of surface soils from the Luquillo Experimental Forest of Puerto Rico: A multivariate perspective.

    Science.gov (United States)

    S. B. Cox; M. R. Willig; F. N. Scatena

    2002-01-01

    We assessed the effects of landscape features (vegetation type and topography), season, and spatial hierarchy on the nutrient content of surface soils in the Luquillo Experimental Forest (LEF) of Puerto Rico. Considerable spatial variation characterized the soils of the LEF, and differences between replicate sites within each combination of vegetation type (tabonuco vs...

  7. Radiation balance at the surface in the city of São Paulo, Brazil: diurnal and seasonal variations

    NARCIS (Netherlands)

    Ferreira, M.J.; Oliveira, de A.P.; Soares, J.; Codato, G.; Wilde Barbaro, E.; Escobedo, J.F.

    2012-01-01

    The main goal of this work is to describe the diurnal and seasonal variations of the radiation balance components at the surface in the city of São Paulo based on observations carried out during 2004. Monthly average hourly values indicate that the amplitudes of the diurnal cycles of net radiation

  8. Seasonal Variations of the Earth's Gravitational Field: An Analysis of Atmospheric Pressure, Ocean Tidal, and Surface Water Excitation

    Science.gov (United States)

    Dong, D,; Gross, R.S.; Dickey, J.

    1996-01-01

    Monthly mean gravitational field parameters (denoted here as C(sub even)) that represent linear combinations of the primarily even degree zonal spherical harmonic coefficients of the Earth's gravitational field have been recovered using LAGEOS I data and are compared with those derived from gridded global surface pressure data of the National meteorological center (NMC) spanning 1983-1992. The effect of equilibrium ocean tides and surface water variations are also considered. Atmospheric pressure and surface water fluctuations are shown to be the dominant cause of observed annual C(sub even) variations. Closure with observations is seen at the 1sigma level when atmospheric pressure, ocean tide and surface water effects are include. Equilibrium ocean tides are shown to be the main source of excitation at the semiannual period with closure at the 1sigma level seen when both atmospheric pressure and ocean tide effects are included. The inverted barometer (IB) case is shown to give the best agreement with the observation series. The potential of the observed C(sub even) variations for monitoring mass variations in the polar regions of the Earth and the effect of the land-ocean mask in the IB calculation are discussed.

  9. 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

  10. Spatial distribution, temporal variation and risks of parabens and their chlorinated derivatives in urban surface water in Beijing, China

    International Nuclear Information System (INIS)

    Li, Wenhui; Gao, Lihong; Shi, Yali; Wang, Yuan; Liu, Jiemin; Cai, Yaqi

    2016-01-01

    The occurrence and distribution of 13 target compounds, including eight parabens, four chlorinated parabens and p-hydroxybenzoic acid (PHBA), were detected in surface water samples at 35 sampling sites in the Beijing River system, China. The surface water samples were collected from the main rivers and lakes in the urban area monthly from July 2013 to June 2014 (except the frozen period). Laboratory analyses revealed that parabens were ubiquitous in the surface water of Beijing. PHBA was the predominant compound in the surface water samples, with the average concentration of 239 ng L −1 , followed by the total amount of chlorinated parabens (average 50.1 ng/L) and parabens (average 44.3 ng/L). It is noteworthy that octylparaben with longer chain was firstly detected in the surface water. Significant difference was observed for paraben concentrations from different sampling sites, and the highest level of parabens was found in the Xiaotaihou River, which was mainly due to the untreated sewage discharge. Seasonal variation of target compounds in the urban surface water was also studied, and parabens exhibited a different temporal variation from chlorinated derivatives. A combination of factors including high residual chlorine level and water temperature as well as intense ultraviolet radiation might enhance the persistence of chlorinated parabens in chlorinated water during the wet season. Risk assessment showed that parabens and their chlorinated derivatives are not likely to produce biological effects on aquatic ecosystems at current levels in the surface water of Beijing. - Highlights: • Parabens and chlorinated parabens are ubiquitous in surface water in Beijing. • Octylparaben with longer chain was firstly detected in surface water. • Untreated sewage discharge was the main source of parabens in river. • Parabens exhibited a different seasonal variation from chlorinated derivatives. • The risks of target compounds are negligible at environmentally

  11. Spatial distribution, temporal variation and risks of parabens and their chlorinated derivatives in urban surface water in Beijing, China

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wenhui; Gao, Lihong [School of Chemistry and Biological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Shi, Yali; Wang, Yuan [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Science, Chinese Academy of Sciences, Beijing 100085 (China); Liu, Jiemin, E-mail: liujm@ustb.edu.cn [School of Chemistry and Biological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Cai, Yaqi, E-mail: caiyaqi@rcees.ac.cn [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Science, Chinese Academy of Sciences, Beijing 100085 (China)

    2016-01-01

    The occurrence and distribution of 13 target compounds, including eight parabens, four chlorinated parabens and p-hydroxybenzoic acid (PHBA), were detected in surface water samples at 35 sampling sites in the Beijing River system, China. The surface water samples were collected from the main rivers and lakes in the urban area monthly from July 2013 to June 2014 (except the frozen period). Laboratory analyses revealed that parabens were ubiquitous in the surface water of Beijing. PHBA was the predominant compound in the surface water samples, with the average concentration of 239 ng L{sup −1}, followed by the total amount of chlorinated parabens (average 50.1 ng/L) and parabens (average 44.3 ng/L). It is noteworthy that octylparaben with longer chain was firstly detected in the surface water. Significant difference was observed for paraben concentrations from different sampling sites, and the highest level of parabens was found in the Xiaotaihou River, which was mainly due to the untreated sewage discharge. Seasonal variation of target compounds in the urban surface water was also studied, and parabens exhibited a different temporal variation from chlorinated derivatives. A combination of factors including high residual chlorine level and water temperature as well as intense ultraviolet radiation might enhance the persistence of chlorinated parabens in chlorinated water during the wet season. Risk assessment showed that parabens and their chlorinated derivatives are not likely to produce biological effects on aquatic ecosystems at current levels in the surface water of Beijing. - Highlights: • Parabens and chlorinated parabens are ubiquitous in surface water in Beijing. • Octylparaben with longer chain was firstly detected in surface water. • Untreated sewage discharge was the main source of parabens in river. • Parabens exhibited a different seasonal variation from chlorinated derivatives. • The risks of target compounds are negligible at

  12. Leishmania-specific surface antigens show sub-genus sequence variation and immune recognition.

    Directory of Open Access Journals (Sweden)

    Daniel P Depledge

    2010-09-01

    Full Text Available A family of hydrophilic acylated surface (HASP proteins, containing extensive and variant amino acid repeats, is expressed at the plasma membrane in infective extracellular (metacyclic and intracellular (amastigote stages of Old World Leishmania species. While HASPs are antigenic in the host and can induce protective immune responses, the biological functions of these Leishmania-specific proteins remain unresolved. Previous genome analysis has suggested that parasites of the sub-genus Leishmania (Viannia have lost HASP genes from their genomes.We have used molecular and cellular methods to analyse HASP expression in New World Leishmania mexicana complex species and show that, unlike in L. major, these proteins are expressed predominantly following differentiation into amastigotes within macrophages. Further genome analysis has revealed that the L. (Viannia species, L. (V. braziliensis, does express HASP-like proteins of low amino acid similarity but with similar biochemical characteristics, from genes present on a region of chromosome 23 that is syntenic with the HASP/SHERP locus in Old World Leishmania species and the L. (L. mexicana complex. A related gene is also present in Leptomonas seymouri and this may represent the ancestral copy of these Leishmania-genus specific sequences. The L. braziliensis HASP-like proteins (named the orthologous (o HASPs are predominantly expressed on the plasma membrane in amastigotes and are recognised by immune sera taken from 4 out of 6 leishmaniasis patients tested in an endemic region of Brazil. Analysis of the repetitive domains of the oHASPs has shown considerable genetic variation in parasite isolates taken from the same patients, suggesting that antigenic change may play a role in immune recognition of this protein family.These findings confirm that antigenic hydrophilic acylated proteins are expressed from genes in the same chromosomal region in species across the genus Leishmania. These proteins are

  13. Genetic diversity and antigenicity variation of Babesia bovis merozoite surface antigen-1 (MSA-1) in Thailand.

    Science.gov (United States)

    Tattiyapong, Muncharee; Sivakumar, Thillaiampalam; Takemae, Hitoshi; Simking, Pacharathon; Jittapalapong, Sathaporn; Igarashi, Ikuo; Yokoyama, Naoaki

    2016-07-01

    Babesia bovis, an intraerythrocytic protozoan parasite, causes severe clinical disease in cattle worldwide. The genetic diversity of parasite antigens often results in different immune profiles in infected animals, hindering efforts to develop immune control methodologies against the B. bovis infection. In this study, we analyzed the genetic diversity of the merozoite surface antigen-1 (msa-1) gene using 162 B. bovis-positive blood DNA samples sourced from cattle populations reared in different geographical regions of Thailand. The identity scores shared among 93 msa-1 gene sequences isolated by PCR amplification were 43.5-100%, and the similarity values among the translated amino acid sequences were 42.8-100%. Of 23 total clades detected in our phylogenetic analysis, Thai msa-1 gene sequences occurred in 18 clades; seven among them were composed of sequences exclusively from Thailand. To investigate differential antigenicity of isolated MSA-1 proteins, we expressed and purified eight recombinant MSA-1 (rMSA-1) proteins, including an rMSA-1 from B. bovis Texas (T2Bo) strain and seven rMSA-1 proteins based on the Thai msa-1 sequences. When these antigens were analyzed in a western blot assay, anti-T2Bo cattle serum strongly reacted with the rMSA-1 from T2Bo, as well as with three other rMSA-1 proteins that shared 54.9-68.4% sequence similarity with T2Bo MSA-1. In contrast, no or weak reactivity was observed for the remaining rMSA-1 proteins, which shared low sequence similarity (35.0-39.7%) with T2Bo MSA-1. While demonstrating the high genetic diversity of the B. bovis msa-1 gene in Thailand, the present findings suggest that the genetic diversity results in antigenicity variations among the MSA-1 antigens of B. bovis in Thailand. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Variations in global land surface phenology: a comparison of satellite optical and passive microwave data

    Science.gov (United States)

    Tong, X.; Tian, F.; Brandt, M.; Zhang, W.; Liu, Y.; Fensholt, R.

    2017-12-01

    Changes in vegetation phenological events are among the most sensitive biological responses to climate change. In last decades, facilitating by satellite remote sensing techniques, land surface phenology (LSP) have been monitored at global scale using proxy approaches as tracking the temporal change of a satellite-derived vegetation index. However, the existing global assessments of changes in LSP are all established on the basis of leaf phenology using NDVI derived from optical sensors, being responsive to vegetation canopy cover and greenness. Instead, the vegetation optical depth (VOD) parameter from passive microwave sensors, which is sensitive to the aboveground vegetation water content by including as well the woody components in the observations, provides an alternative, independent and comprehensive means for global vegetation phenology monitoring. We used the unique long-term global VOD record available for the period 1992-2012 to monitoring the dynamics of LSP metrics (length of season, start of season and end of season) in comparison with the dynamics of LSP metrics derived from the latest GIMMS NDVI3G V1. We evaluated the differences in the linear trends of LSP metrics between two datasets. Currently, our results suggest that the level of seasonality variation of vegetation water content is less than the vegetation greenness. We found significant phenological changes in vegetation water content in African woodlands, where has been reported with little leaf phenological change regardless of the delays in rainfall onset. Therefore, VOD might allow us to detect temporal shifts in the timing difference of vegetation water storage vs. leaf emergence and to see if some ecophysiological thresholds seem to be reached, that could cause species turnover as climate change-driven alterations to the African monsoon proceed.

  15. Occurrence, distribution and seasonal variation of organophosphate flame retardants and plasticizers in urban surface water in Beijing, China

    International Nuclear Information System (INIS)

    Shi, Yali; Gao, Lihong; Li, Wenhui; Wang, Yuan; Liu, Jiemin; Cai, Yaqi

    2016-01-01

    The occurrence, spatial distribution and seasonal variation of 14 organophosphate esters (OPEs) were investigated in urban surface water (river and lake water) from July 2013 to June 2014 in Beijing, China. Sewage influent and effluent samples, as well as rainwater and road runoff samples were also analyzed as the potential sources of OPEs in surface water. Tris(2-chloro-1-methylethyl) phosphate (TCPP) and tris(2-chloroethyl) phosphate (TCEP) were the most abundant OPEs with the average concentrations of 291 ng L"−"1 and 219 ng L"−"1, respectively. Relatively high concentrations of OPEs were detected in rivers located at southern and eastern urban of Beijing, which was probably attributed to the treated and untreated sewage discharge. Besides, higher levels of OPEs were observed in urban surface water in the summer, and the wet deposition (rainfall) was confirmed to be an important factor for this observation. Risk assessment showed low or medium risk of OPEs for the organisms (algae, crustacean and fish). - Highlights: • High levels of OPEs were detected in urban surface water of Beijing, China. • Seasonal variation revealed higher levels of OPEs in the summer. • Wastewater, rainwater and road runoff samples were analyzed as sources of OPEs. • The risks of OPEs to the organisms (algae, crustacean and fish) were assessed. - The occurrence, spatial distribution and seasonal variation of OPEs in urban surface water were investigated from densely populated big city (Beijing, China).

  16. Effect of land albedo, CO2, orography, and oceanic heat transport on extreme climates

    Directory of Open Access Journals (Sweden)

    V. Romanova

    2006-01-01

    Full Text Available Using an atmospheric general circulation model of intermediate complexity coupled to a sea ice – slab ocean model, we perform a number of sensitivity experiments under present-day orbital conditions and geographical distribution to assess the possibility that land albedo, atmospheric CO2, orography and oceanic heat transport may cause an ice-covered Earth. Changing only one boundary or initial condition, the model produces solutions with at least some ice-free oceans in the low latitudes. Using some combination of these forcing parameters, a full Earth's glaciation is obtained. We find that the most significant factor leading to an ice-covered Earth is the high land albedo in combination with initial temperatures set equal to the freezing point. Oceanic heat transport and orography play only a minor role for the climate state. Extremely low concentrations of CO2 also appear to be insufficient to provoke a runaway ice-albedo feedback, but the strong deviations in surface air temperatures in the Northern Hemisphere point to the existence of a strong nonlinearity in the system. Finally, we argue that the initial condition determines whether the system can go into a completely ice covered state, indicating multiple equilibria, a feature known from simple energy balance models.

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

    Science.gov (United States)

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

    1994-01-01

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

  18. Trade-offs between three forest ecosystem services across the state of New Hampshire, USA: timber, carbon, and albedo.

    Science.gov (United States)

    Lutz, David A; Burakowski, Elizabeth A; Murphy, Mackenzie B; Borsuk, Mark E; Niemiec, Rebecca M; Howarth, Richard B

    2016-01-01

    Forests are more frequently being managed to store and sequester carbon for the purposes of climate change mitigation. Generally, this practice involves long-term conservation of intact mature forests and/or reductions in the frequency and intensity of timber harvests. However, incorporating the influence of forest surface albedo often suggests that long rotation lengths may not always be optimal in mitigating climate change in forests characterized by frequent snowfall. To address this, we investigated trade-offs between three ecosystem services: carbon storage, albedo-related radiative forcing, and timber provisioning. We calculated optimal rotation length at 498 diverse Forest Inventory and Analysis forest sites in the state of New Hampshire, USA. We found that the mean optimal rotation lengths across all sites was 94 yr (standard deviation of sample means = 44 yr), with a large cluster of short optimal rotation lengths that were calculated at high elevations in the White Mountain National Forest. Using a regression tree approach, we found that timber growth, annual storage of carbon, and the difference between annual albedo in mature forest vs. a post-harvest landscape were the most important variables that influenced optimal rotation. Additionally, we found that the choice of a baseline albedo value for each site significantly altered the optimal rotation lengths across all sites, lowering the mean rotation to 59 yr with a high albedo baseline, and increasing the mean rotation to 112 yr given a low albedo baseline. Given these results, we suggest that utilizing temperate forests in New Hampshire for climate mitigation purposes through carbon storage and the cessation of harvest is appropriate at a site-dependent level that varies significantly across the state.

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

    Science.gov (United States)

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

    2014-07-01

    Expanding high-elevation and high-latitude forest has contrasting climate feedbacks through carbon sequestration (cooling) and reduced surface reflectance (warming), which are yet poorly quantified. Here, we present an empirically based projection of mountain birch forest expansion in south-central Norway under climate change and absence of land use. Climate effects of carbon sequestration and albedo change are compared using four emission metrics. Forest expansion was modeled for a projected 2.6 °C increase in summer temperature in 2100, with associated reduced snow cover. We find that the current (year 2000) forest line of the region is circa 100 m lower than its climatic potential due to land-use history. In the future scenarios, forest cover increased from 12% to 27% between 2000 and 2100, resulting in a 59% increase in biomass carbon storage and an albedo change from 0.46 to 0.30. Forest expansion in 2100 was behind its climatic potential, forest migration rates being the primary limiting factor. In 2100, the warming caused by lower albedo from expanding forest was 10 to 17 times stronger than the cooling effect from carbon sequestration for all emission metrics considered. Reduced snow cover further exacerbated the net warming feedback. The warming effect is considerably stronger than previously reported for boreal forest cover, because of the typically low biomass density in mountain forests and the large changes in albedo of snow-covered tundra areas. The positive climate feedback of high-latitude and high-elevation expanding forests with seasonal snow cover exceeds those of afforestation at lower elevation, and calls for further attention of both modelers and empiricists. The inclusion and upscaling of these climate feedbacks from mountain forests into global models is warranted to assess the potential global impacts. © 2013 John Wiley & Sons Ltd.

  20. A Synthetical Estimation of Northern Hemisphere Sea-ice Albedo Radiative Forcing and Feedback between 1982 and 2009

    Science.gov (United States)

    Cao, Y.

    2014-12-01

    The decreasing surface albedo caused by continously vanishing sea ice over the Arctic plays a very important role in Arctic warming amplification. However, the quantification of the change of radiative forcing at top of atmosphere (TOA) introduced by the decreasing sea ice albedo and its generated feedback to the climate remain uncertain. Two recent representative studies showed a large difference with each other: Flanner et al. (2011) used a method of synthesis of surface albedo and radiative kernels and found that the change of sea ice radiative forcing (ΔSIRF) in Northern Hemisphere (NH) from 1979 to 2008 was 0.22 (0.15 - 0.32) W m-2, and the corresponding sea ice albedo feedback (SIAF) over NH was 0.28 (0.19 - 0.41) W m-2 K-1; while Pistone et al. (2014) directly used the observed planetary albedo to estimate the NH ΔSIRF and SIAF from 1979 to 2011 and draw a NH ΔSIRF of 0.43 ± 0.07 W m-2, which was nearly twice as larger as Flanner's result, and the estimated global SIAF was 0.31 ± 0.04 W m-2 K-1. Motivated by reconciling the difference between these two studies and obtaining a more accurate qualification of the NH ΔSIRF, we used a newly released satellite-retrieved surface albedo product CLARA-A1 and made an attempt in two steps: Firstly, based on synthesising the surface albedo and raditive kernels, we calcualted the ΔSIRF from 1982 to 2009 was 0.20 ± 0.05 W m-2, and the NH SIAF was 0.25 W m-2 K-1; After comparing with TOA observed radiative flux, we found it's quite likely the kernel methods yield an underestimation for the all-sky ΔSIRF. Then, we tried to use TOA observed broadband radiative flux to adjust the estimation with kernels. After an adjustment, the NH all-sky ΔSIRF was 0.34 ± 0.09 W m-2, and the corresponding SIAF was 0.43 W m-2 K-1 over NH and 0.31 W m-2 K-1 over the entire globe.

  1. Poloidal density variation of impurities in a rotating tokamak plasma - flux surface coordinates and effect on transport coefficients

    International Nuclear Information System (INIS)

    Romanelli, M.

    1999-09-01

    The poloidal variation of impurity densities over magnetic surfaces brings about an enhancement of neoclassical transport coefficients, as shown by Romanelli and Ottaviani for impurities in the Pfirsch Schlueter regime and by Helander for particles in the banana-plateau regime, both in a large aspect ratio tokamak. The same effect will occur in a finite aspect ratio tokamak and therefore it is considered to be relevant for inclusion in transport codes for comparison with the experimental measurements of impurity transport. Here an expression for the impurity-density poloidal-variation generated by the fast toroidal rotation of the plasma column is presented in general coordinates. (author)

  2. Decadal variations in estimated surface solar radiation over Switzerland since the late 19th century

    Directory of Open Access Journals (Sweden)

    A. Sanchez-Lorenzo

    2012-09-01

    Full Text Available Our knowledge on trends in surface solar radiation (SSR involves uncertainties due to the scarcity of long-term time series of SSR, especially with records before the second half of the 20th century. Here we study the trends of all-sky SSR from 1885 to 2010 in Switzerland, which have been estimated using a homogenous dataset of sunshine duration series. This variable is shown to be a useful proxy data of all-sky SSR, which can help to solve some of the current open issues in the dimming/brightening phenomenon. All-sky SSR has been fairly stable with little variations in the first half of the 20th century, unlike the second half of the 20th century that is characterized also in Switzerland by a dimming from the 1950s to the 1980s and a subsequent brightening. Cloud cover changes seem to explain the major part of the decadal variability observed in all-sky SSR, at least from 1885 to the 1970s; at this point, a discrepancy in the sign of the trend is visible in the all-sky SSR and cloud cover series from the 1970s to the present. Finally, an attempt to estimate SSR series for clear-sky conditions, based also on sunshine duration records since the 1930s, has been made for the first time. The mean clear-sky SSR series shows no relevant changes between the 1930s to the 1950s, then a decrease, smaller than the observed in the all-sky SSR, from the 1960s to 1970s, and ends with a strong increase from the 1980s up to the present. During the three decades from 1981 to 2010 the estimated clear-sky SSR trends reported in this study are in line with previous findings over Switzerland based on direct radiative flux measurements. Moreover, the signal of the El Chichón and Pinatubo volcanic eruption visible in the estimated clear-sky SSR records further demonstrates the potential to infer aerosol-induced radiation changes from sunshine duration observations.

  3. Predicting Indian Summer Monsoon onset through variations of surface air temperature and relative humidity

    Science.gov (United States)

    Stolbova, Veronika; Surovyatkina, Elena; Kurths, Jurgen

    2015-04-01

    Indian Summer Monsoon (ISM) rainfall has an enormous effect on Indian agriculture, economy, and, as a consequence, life and prosperity of more than one billion people. Variability of the monsoonal rainfall and its onset have a huge influence on food production, agricultural planning and GDP of the country, which on 22% is determined by agriculture. Consequently, successful forecasting of the ISM onset is a big challenge and large efforts are being put into it. Here, we propose a novel approach for predictability of the ISM onset, based on critical transition theory. The ISM onset is defined as an abrupt transition from sporadious rainfall to spatially organized and temporally sustained rainfall. Taking this into account, we consider the ISM onset as is a critical transition from pre-monsoon to monsoon, which take place in time and also in space. It allows us to suggest that before the onset of ISM on the Indian subcontinent should be areas of critical behavior where indicators of the critical transitions can be detected through an analysis of observational data. First, we identify areas with such critical behavior. Second, we use detected areas as reference points for observation locations for the ISM onset prediction. Third, we derive a precursor for the ISM onset based on the analysis of surface air temperature and relative humidity variations in these reference points. Finally, we demonstrate the performance of this precursor on two observational data sets. The proposed approach allows to determine ISM onset in advance in 67% of all considered years. Our proposed approach is less effective during the anomalous years, which are associated with weak/strong monsoons, e.g. El-Nino, La-Nina or positive Indian Ocean Dipole events. The ISM onset is predicted for 23 out of 27 normal monsoon years (85%) during the past 6 decades. In the anomalous years, we show that time series analysis in both areas during the pre-monsoon period reveals indicators whether the

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

    Science.gov (United States)

    Hsu, N. Christina; Gautam, Ritesh

    2012-01-01

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

  5. High-frequency pressure variations in the vicinity of a surface CO2 flux chamber

    Science.gov (United States)

    Eugene S. Takle; James R. Brandle; R. A. Schmidt; Rick Garcia; Irina V. Litvina; William J. Massman; Xinhua Zhou; Geoffrey Doyle; Charles W. Rice

    2003-01-01

    We report measurements of 2Hz pressure fluctuations at and below the soil surface in the vicinity of a surface-based CO2 flux chamber. These measurements were part of a field experiment to examine the possible role of pressure pumping due to atmospheric pressure fluctuations on measurements of surface fluxes of CO2. Under the moderate wind speeds, warm temperatures,...

  6. Assessment of spatio-temporal variations in surface water quality of ...

    African Journals Online (AJOL)

    MANN

    2012-10-02

    Oct 2, 2012 ... 1School of Biological and Environmental Sciences, Shoolini University, Solan, H.P.- 173229, India. 2Department ... variation. Of late, multivariate statistical techniques such ..... Statistical Package for the Social Sciences 10.0.

  7. Genetic variation of hepatitis B surface antigen among acute and chronic hepatitis B virus infections in The Netherlands.

    Science.gov (United States)

    Cremer, Jeroen; Hofstraat, Sanne H I; van Heiningen, Francoise; Veldhuijzen, Irene K; van Benthem, Birgit H B; Benschop, Kimberley S M

    2018-05-24

    Genetic variation within hepatitis B surface antigen (HBsAg), in particular within the major hydrophobic region (MHR), is related to immune/vaccine and test failures and can have a significant impact on the vaccination and diagnosis of acute infection. This study shows, for the first time, variation among acute cases and compares the amino acid variation within the HBsAg between acute and chronic infections. We analyzed the virus isolated from 1231 acute and 585 chronic cases reported to an anonymized public health surveillance database between 2004 and 2014 in The Netherlands. HBsAg analysis revealed the circulation of 6 genotypes (Gt); GtA was the dominant genotype followed by GtD among both acute (68.2% and 17.4%, respectively) and chronic (34.9% and 34.2%, respectively) cases. Variation was the highest among chronic strains compared to that among acute strains. Both acute and chronic GtD showed the highest variation compared to that of other genotypes (P < .01). Substitutions within the MHR were found in 8.5% of the acute strains and 18.6% of the chronic strains. Specific MHR substitutions described to have an impact on vaccine/immune escape and/or HBsAg test failure were found among 4.1% of the acute strains and 7.0% of the chronic strains. In conclusion, we show a high variation of HBsAg among acute and chronic hepatitis B virus-infected cases in The Netherlands, in particular among those infected with GtD, and compare, for the first time, variation in frequencies between acute and chronic cases. Additional studies on the impact of these variations on vaccination and test failure need to be conducted, as well as whether HBsAg false-negative variants have been missed. © 2018 The Authors. Journal of Medical Virology Published by Wiley Periodicals, Inc.

  8. The influence of burn severity on post-fire vegetation recovery and albedo change during early succession in North American boreal forests

    Science.gov (United States)

    Jin, Y.; Randerson, J. T.; Goetz, S. J.; Beck, P. S.; Loranty, M. M.; Goulden, M.

    2011-12-01

    Severity of burning can influence multiple aspects of forest composition, carbon cycling, and climate forcing. We quantified how burn severity affected vegetation recovery and albedo change during early succession in Canadian boreal regions by combining satellite observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Canadian Large Fire Data Base (LFDB). We used the difference Normalized Burn Ratio (dNBR) and changes in spring albedo derived from MODIS 500m albedo product as measures of burn severity. We found that the most severe burns had the greatest reduction in summer EVI in first year after fire, indicating greater loss of vegetation cover immediately following fire. By 5-7 years after fire, summer EVI for all severity classes had recovered to within 90-110% of pre-fire levels. Burn severity had a positive effect on the increase of post-fire spring albedo during the first 7 years after fire, and a shift from low to moderate or moderate to severe fires led to amplification of the post-fire albedo increase by approximately 30%. Fire-induced increases in both spring and summer albedo became progressively larger with stand age from years 1-7, with the trend in spring albedo likely driven by continued losses of needles and branches from trees killed by the fire (and concurrent losses of black carbon coatings on remaining debris), and the summer trend associated with increases in leaf area of short-stature herbs and shrubs. Our results suggest that increases in burn severity and carbon losses observed in some areas of boreal forests (e.g., Turetsky et al., 2011) may be at least partly offset by increases in negative forcing associated with changes in surface albedo.

  9. Higher albedos and size distribution of large transneptunian objects

    Science.gov (United States)

    Lykawka, Patryk Sofia; Mukai, Tadashi

    2005-11-01

    Transneptunian objects (TNOs) orbit beyond Neptune and do offer important clues about the formation of our solar system. Although observations have been increasing the number of discovered TNOs and improving their orbital elements, very little is known about elementary physical properties such as sizes, albedos and compositions. Due to TNOs large distances (>40 AU) and observational limitations, reliable physical information can be obtained only from brighter objects (supposedly larger bodies). According to size and albedo measurements available, it is evident the traditionally assumed albedo p=0.04 cannot hold for all TNOs, especially those with approximately absolute magnitudes H⩽5.5. That is, the largest TNOs possess higher albedos (generally >0.04) that strongly appear to increase as a function of size. Using a compilation of published data, we derived empirical relations which can provide estimations of diameters and albedos as a function of absolute magnitude. Calculations result in more accurate size/albedo estimations for TNOs with H⩽5.5 than just assuming p=0.04. Nevertheless, considering low statistics, the value p=0.04 sounds still convenient for H>5.5 non-binary TNOs as a group. We also discuss about physical processes (e.g., collisions, intrinsic activity and the presence of tenuous atmospheres) responsible for the increase of albedo among large bodies. Currently, all big TNOs (>700 km) would be capable to sustain thin atmospheres or icy frosts composed of CH 4, CO or N 2 even for body bulk densities as low as 0.5 g cm -3. A size-dependent albedo has important consequences for the TNOs size distribution, cumulative luminosity function and total mass estimations. According to our analysis, the latter can be reduced up to 50% if higher albedos are common among large bodies. Lastly, by analyzing orbital properties of classical TNOs ( 42AUbodies. For both populations, distinct absolute magnitude distributions are maximized for an inclination threshold

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

    Science.gov (United States)

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

    2008-09-01

    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 archived MIPS observations of Phoebe reproduces Cassini results very accurately, thereby validating our method. For all targets, the geometric albedo is found to be low, probably below 10% and clearly below 15%. Irregular satellites are much darker than the large regular satellites. Their albedo is, however, quite similar to that of small bodies in the outer Solar System (such as cometary nuclei, Jupiter Trojans, or TNOs). This is consistent with color measurements as well as dynamical considerations which suggest a common origin of the said populations. There appear to be significant object-to-object albedo differences. Similar albedos found for some members of dynamical clusters support the idea that they may have originated in the breakup of a parent body. For three satellites, thermal data at two wavelengths are available, enabling us to constrain their thermal properties. Sub-solar temperatures are similar to that found from Cassini's Phoebe fly-by. This suggests a rather low thermal inertia, as expected for regolith-covered objects. This work is based on observations made with the Spitzer Space Telescope, which is operated by JPL under a contract with NASA. Support for this work was provided by NASA.

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

    International Nuclear Information System (INIS)

    Mathews, K.; Dishaw, J.

    2007-01-01

    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)

  12. What is the potential of cropland albedo management in the fight against global warming? A case study based on the use of cover crops

    Science.gov (United States)

    Carrer, Dominique; Pique, Gaétan; Ferlicoq, Morgan; Ceamanos, Xavier; Ceschia, Eric

    2018-04-01

    Land cover management in agricultural areas is a powerful tool that could play a role in the mitigation of climate change and the counterbalance of global warming. First, we attempted to quantify the radiative forcing that would increase the surface albedo of croplands in Europe following the inclusion of cover crops during the fallow period. This is possible since the albedo of bare soil in many areas of Europe is lower than the albedo of vegetation. By using satellite data, we demonstrated that the introduction of cover crops into the crop rotation during the fallow period would increase the albedo over 4.17% of Europe’s surface. According to our study, the effect resulting from this increase in the albedo of the croplands would be equivalent to a mitigation of 3.16 MtCO2-eq.year‑1 over a 100 year time horizon. This is equivalent to a mitigation potential per surface unit (m2) of introduced cover crop over Europe of 15.91 gCO2-eq.year‑1.m‑2. This value, obtained at the European scale, is consistent with previous estimates. We show that this mitigation potential could be increased by 27% if the cover crop is maintained for a longer period than 3 months and reduced by 28% in the case of no irrigation. In the second part of this work, based on recent studies estimating the impact of cover crops on soil carbon sequestration and the use of fertilizer, we added the albedo effect to those estimates, and we argued that, by considering areas favourable to their introduction, cover crops in Europe could mitigate human-induced agricultural greenhouse gas emissions by up to 7% per year, using 2011 as a reference. The impact of the albedo change per year would be between 10% and 13% of this total impact. The countries showing the greatest mitigation potentials are France, Bulgaria, Romania, and Germany.

  13. Influences of the variation in inflow to East Asia on surface ozone over Japan during 1996–2005

    Directory of Open Access Journals (Sweden)

    S. Chatani

    2011-08-01

    Full Text Available Air quality simulations in which the global chemical transport model CHASER and the regional chemical transport model WRF/chem are coupled have been developed to consider the dynamic transport of chemical species across the boundaries of the domain of the regional chemical transport model. The simulation captures the overall seasonal variations of surface ozone, but overestimates its concentration over Japanese populated areas by approximately 20 ppb from summer to early winter. It is deduced that ozone formation around Northeast China and Japan in summer is overestimated in the simulation. On the other hand, the simulation well reproduces the interannual variability and the long-term trend of observed surface ozone over Japan. Sensitivity experiments have been performed to investigate the influence of the variation in inflow to East Asia on the interannual variability and the long-term trend of surface ozone over Japan during 1996–2005. The inflow defined in this paper includes the recirculation of species with sources within the East Asian region as well as the transport of species with sources out of the East Asian region. Results of sensitivity experiments suggest that inflow to East Asia accounts for approximately 30 % of the increasing trend of surface ozone, whereas it has much less influence on the interannual variability of observed surface ozone compared to meteorological processes within East Asia.

  14. Measuring variation of indoor radon concentration using bare nuclear tracks detectors, scintillation counters and surface barrier detectors

    International Nuclear Information System (INIS)

    Ishak, I.; Mahat, R.H.; Amin, Y.M.

    1996-01-01

    Bare LRI 15 nuclear track detectors , scintillators counter and surface barrier detectors were used to measured the indoor radon concentration in various location within two rooms. Spatial variation of the radon concentration is caused by positioning of the door, windows, furniture, cracks in the building and also distances from floor, wall and ceiling. It is found that the change in temperature are causing radon concentration to increase at certain time of the day

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

    International Nuclear Information System (INIS)

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

    1991-09-01

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

  16. Seasonal and Spatial Variation of Surface Urban Heat Island Intensity in a Small Urban Agglomerate in Brazil

    Directory of Open Access Journals (Sweden)

    Elis Dener Lima Alves

    2016-12-01

    Full Text Available In recent years, SUHIs (surface urban heat islands have been greatly emphasized in urban climate studies, since it is one of the climate phenomena most influenced by human action. In this study, temporal and spatial variations of SUHIs in the cities of Ceres and Rialma (Brazil were investigated; satellite Landsat 8 TIRS/OLI images from 2013 to 2016 were used for this purpose. The results showed that in all seasons, two relationships were observed, one positive and one negative. An N D V I (Normalized Difference Vegetation Index of 0.2 is the divider of this relationship: up to this value, the relationship is positive, that is, the higher the N D V I value, the higher the surface temperature, while the relationship is negative at an N D V I greater than 0.2. There was high seasonal variation in the SUHIs, with the highest intensities recorded in the spring and summer (±12 °C, and the lowest in the winter. These temporal variations were attributed to the annual cycle of precipitation, which directly involves the robustness of the Cerrado vegetation. SUHIs occupied, on average, an area three times larger than the area of SUCIs (surface urban cool islands. The highest values of SUCIs were observed in water bodies and in valley bottoms. Overall, SUHIs showed high intensities; however, a more intense core area, such as in large cities, was not observed.

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

    International Nuclear Information System (INIS)

    Potter, G.L.; Ellsaesser, H.W.; MacCracken, M.C.; Luther, F.M.

    1978-06-01

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Martins, M.M., E-mail: marcelo@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD), Av. Salvador Allende, s/n, CEP: 22780-160, Rio de Janeiro, RJ (Brazil); Mauricio, C.L.P., E-mail: claudia@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD), Av. Salvador Allende, s/n, CEP: 22780-160, Rio de Janeiro, RJ (Brazil); Fonseca, E.S. da, E-mail: evaldo@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD), Av. Salvador Allende, s/n, CEP: 22780-160, Rio de Janeiro, RJ (Brazil); Silva, A.X. da, E-mail: ademir@con.ufrj.b [Coordenacao dos Programas de Pos-Graduacao em Engenharia, COPPE/PEN Caixa Postal 68509, CEP: 21941-972, Rio de Janeiro, RJ (Brazil)

    2010-12-15

    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 ({sup 252}Cf, {sup 252}Cf(D{sub 2}O), {sup 241}Am-Be, {sup 241}Am-B and {sup 238}Pu-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.

  19. Impact of Surface Soil Moisture Variations on Radar Altimetry Echoes at Ku and Ka Bands in Semi-Arid Areas

    Directory of Open Access Journals (Sweden)

    Christophe Fatras

    2018-04-01

    Full Text Available Radar altimetry provides information on the topography of the Earth surface. It is commonly used for the monitoring not only sea surface height but also ice sheets topography and inland water levels. The radar altimetry backscattering coefficient, which depends on surface roughness and water content, can be related to surface properties such as surface soil moisture content. In this study, the influence of surface soil moisture on the radar altimetry echo and backscattering coefficient is analyzed over semi-arid areas. A semi-empirical model of the soil’s complex dielectric permittivity that takes into account that small-scale roughness and large-scale topography was developed to simulate the radar echoes. It was validated using waveforms acquired at Ku and Ka-bands by ENVISAT RA-2 and SARAL AltiKa respectively over several sites in Mali. Correlation coefficients ranging from 0.66 to 0.94 at Ku-band and from 0.27 to 0.96 at Ka-band were found. The increase in surface soil moisture from 0.02 to 0.4 (i.e., the typical range of variations in semi-arid areas increase the backscattering from 10 to 15 dB between the core of the dry and the maximum of the rainy seasons.

  20. Albedo boundary conditions for global calculations of thermal nuclear reactors with the model of discrete ordinates to two energy groups

    International Nuclear Information System (INIS)

    Nunes, Carlos Eduardo de Araujo

    2011-01-01

    As neutron fission events do not take place in the non-multiplying regions of nuclear reactors, e.g., moderator, reflector, and structural core, these regions do not generate power and the computational efficiency of nuclear reactor global calculations can hence be improved by eliminating the explicit numerical calculations within the non-multiplying regions around the active domain. Discussed here is the computational efficiency of approximate discrete ordinates (SN) albedo boundary conditions for two-energy group eigenvalue problems in X, Y geometry. Albedo, the Latin word for w hiteness , was originally defined as the fraction of incident light reflected diffusely by a surface. This Latin word has remained the usual scientific term in astronomy and in this dissertation this concept is extended for the reflection of neutrons. The non-standard SN albedo substitutes approximately the reflector region around the active domain, as we neglect the transverse leakage terms within the non-multiplying reflector. Should the problem have no transverse leakage terms, i.e., one dimensional slab geometry, then the offered albedo boundary conditions are exact. By computational efficiency we mean analyzing the accuracy of the numerical results versus the CPU execution time of each run for a given model problem. Numerical results to two 1/4 symmetric test problems are shown to illustrate this efficiency analysis. (author)

  1. Tradeoffs between Three Forest Ecosystem Services across the State of New Hampshire, USA: Timber, Carbon, and Albedo

    Science.gov (United States)

    Lutz, D. A.; Burakowski, E. A.; Murphy, M. B.; Borsuk, M. E.; Niemiec, R. M.; Howarth, R. B.

    2014-12-01

    Albedo is an important physical property of the land surface which influences the total amount of incoming solar radiation that is reflected back into space. It is a critical ecosystem service that helps regulate the Earth's energy balance and, in the context of climate mitigation, has been shown to have a strong influence on the overall effectiveness of land management schemes designed to counteract climate change. Previously, we demonstrated that incorporating the physical effects of albedo into an ecological economic forest model of locations in the White Mountain National Forest, in New Hampshire, USA, leads to a substantially shorter optimal rotation period for forest harvest than under a carbon- and timber-only approach. In this study, we investigate similar tradeoffs at 565 sites across the entire state of New Hampshire in a variety of different forest types, latitudes, and elevations. Additionally, we use a regression tree approach to calculate the influence of biogeochemical and physical factors on the optimal rotation period. Our results suggest that in many instances, incorporating albedo may lead to optimal rotation times approaching zero, or, perpetual clear-cut. Overall, the difference between growing season and winter-time albedo for forested and harvested states was the most significant variable influencing the rotation period, followed by timber stumpage price, and biomass growth rate. These results provide an initial understanding of tradeoffs amongst these three ecosystem services and provide guidance for forest managers as to the relative important properties of their forests when these three services are incentivized economically.

  2. Influence of the atmospheric aerosol and air pollution on solar albedo of the earth. Vol. 4

    International Nuclear Information System (INIS)

    Mayhoub, A.B.; Mohamed, K.S.

    1996-01-01

    The effect of increasing atmospheric aerosol and air pollutant concentration on the solar albedo and consequently upon the heat budget near the earth's surface is studied. The magnitude of aerosol absorption coefficient to back-scattering coefficient B ab /B bs is calculated. This study will be used to estimate atmospheric stability categories and other meteorological parameters which are affected by thermal state radiation balance of the atmosphere as mixing and inversion height of Inshas nuclear reactor site. Consequently, concentration distribution of radioactive release from Inshas can be evaluated.. 4 figs., 5 tabs

  3. Influence of the atmospheric aerosol and air pollution on solar albedo of the earth. Vol. 4

    Energy Technology Data Exchange (ETDEWEB)

    Mayhoub, A B; Mohamed, K S [Mathematics and Theoretical Physics Department, Nuclear Research Center, Atomic Energy Auhtority, Cairo, (Egypt)

    1996-03-01

    The effect of increasing atmospheric aerosol and air pollutant concentration on the solar albedo and consequently upon the heat budget near the earth`s surface is studied. The magnitude of aerosol absorption coefficient to back-scattering coefficient B{sub ab}/B{sub bs} is calculated. This study will be used to estimate atmospheric stability categories and other meteorological parameters which are affected by thermal state radiation balance of the atmosphere as mixing and inversion height of Inshas nuclear reactor site. Consequently, concentration distribution of radioactive release from Inshas can be evaluated.. 4 figs., 5 tabs.

  4. Improved streaming analysis technique: spherical harmonics expansion of albedo data

    International Nuclear Information System (INIS)

    Albert, T.E.; Simmons, G.L.

    1979-01-01

    An improved albedo scattering technique was implemented with a three-dimensional Monte Carlo transport code for use in analyzing radiation streaming problems. The improvement was based on a shifted spherical Harmonics expansion of the doubly differential albedo data base. The result of the improvement was a factor of 3 to 10 reduction in data storage requirements and approximately a factor of 3 to 6 increase in computational speed. Comparisons of results obtained using the technique with measurements are shown for neutron streaming in one- and two-legged square concrete ducts

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

    DEFF Research Database (Denmark)

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

    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-7 b based on Q0-Q4 data, published radial velocities, and asteroseismology constraints. We measure an occultation depth in the Kepler bandpass...

  6. Validation of response simulation methodology of Albedo dosemeter

    International Nuclear Information System (INIS)

    Freitas, B.M.; Silva, A.X. da

    2016-01-01

    The Instituto de Radioprotecao e Dosimetria developed and runs a neutron TLD albedo individual monitoring service. To optimize the dose calculation algorithm and to infer new calibration factors, the response of this dosemeter was simulated. In order to validate this employed methodology, it was applied in the simulation of the problem of the QUADOS (Quality Assurance of Computational Tools for Dosimetry) intercomparison, aimed to evaluate dosimetric problems, one being to calculate the response of a generic albedo dosemeter. The obtained results were compared with those of other modeling and the reference one, with good agreements. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-12-01

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

  8. Influence of spatial variations of microtopography and infiltration on surface runoff and field scale hydrological connectivity

    NARCIS (Netherlands)

    Appels, W.M.; Bogaart, P.W.; Zee, van der S.E.A.T.M.

    2011-01-01

    Surface runoff on agricultural fields arises when rainfall exceeds infiltration. Excess water ponding in and flowing through local microtopography increases the hydrological connectivity of fields. In turn, an increased level of hydrological connectivity leads to a higher surface runoff flux at the

  9. The effect of host star spectral energy distribution and ice-albedo feedback on the climate of extrasolar planets.

    Science.gov (United States)

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

    2013-08-01

    Planetary climate can be affected by the interaction of the host star spectral energy distribution with the wavelength-dependent reflectivity of ice and snow. In this study, we explored this effect with a one-dimensional (1-D), line-by-line, radiative transfer model to calculate broadband planetary albedos as input to a seasonally varying, 1-D energy balance climate model. A three-dimensional (3-D) general circulation model was also used to explore the atmosphere's response to changes in incoming stellar radiation, or instellation, and surface albedo. Using this hierarchy of models, we simulated planets covered by ocean, land, and water-ice of varying grain size, with incident radiation from stars of different spectral types. Terrestrial planets orbiting stars with higher near-UV radiation exhibited a stronger ice-albedo feedback. We found that ice extent was much greater on a planet orbiting an F-dwarf star than on a planet orbiting a G-dwarf star at an equivalent flux distance, and that ice-covered conditions occurred on an F-dwarf planet with only a 2% reduction in instellation relative to the present instellation on Earth, assuming fixed CO(2) (present atmospheric level on Earth). A similar planet orbiting the Sun at an equivalent flux distance required an 8% reduction in instellation, while a planet orbiting an M-dwarf star required an additional 19% reduction in instellation to become ice-covered, equivalent to 73% of the modern solar constant. The reduction in instellation must be larger for planets orbiting cooler stars due in large part to the stronger absorption of longer-wavelength radiation by icy surfaces on these planets in addition to stronger absorption by water vapor and CO(2) in their atmospheres, which provides increased downwelling longwave radiation. Lowering the IR and visible-band surface ice and snow albedos for an M-dwarf planet increased the planet's climate stability against changes in instellation and slowed the descent into global ice

  10. On a free-surface problem with moving contact line: From variational principles to stable numerical approximations

    Science.gov (United States)

    Fumagalli, Ivan; Parolini, Nicola; Verani, Marco

    2018-02-01

    We analyze a free-surface problem described by time-dependent Navier-Stokes equations. Surface tension, capillary effects and wall friction are taken into account in the evolution of the system, influencing the motion of the contact line - where the free surface hits the wall - and of the dynamics of the contact angle. The differential equations governing the phenomenon are first derived from the variational principle of minimum reduced dissipation, and then discretized by means of the ALE approach. The numerical properties of the resulting scheme are investigated, drawing a parallel with the physical properties holding at the continuous level. Some instability issues are addressed in detail, in the case of an explicit treatment of the geometry, and novel additional terms are introduced in the discrete formulation in order to damp the instabilities. Numerical tests assess the suitability of the approach, the influence of the parameters, and the effectiveness of the new stabilizing terms.

  11. Bacterial community diversity and variation in spray water sources and the tomato fruit surface.

    Science.gov (United States)

    Telias, Adriana; White, James R; Pahl, Donna M; Ottesen, Andrea R; Walsh, Christopher S

    2011-04-21

    Tomato (Solanum lycopersicum) consumption has been one of the most common causes of produce-associated salmonellosis in the United States. Contamination may originate from animal waste, insects, soil or water. Current guidelines for fresh tomato production recommend the use of potable water for applications coming in direct contact with the fruit, but due to high demand, water from other sources is frequently used. We sought to describe the overall bacterial diversity on the surface of tomato fruit and the effect of two different water sources (ground and surface water) when used for direct crop applications by generating a 454-pyrosequencing 16S rRNA dataset of these different environments. This study represents the first in depth characterization of bacterial communities in the tomato fruit surface and the water sources commonly used in commercial vegetable production. The two water sources tested had a significantly different bacterial composition. Proteobacteria was predominant in groundwater samples, whereas in the significantly more diverse surface water, abundant phyla also included Firmicutes, Actinobacteria and Verrucomicrobia. The fruit surface bacterial communities on tomatoes sprayed with both water sources could not be differentiated using various statistical methods. Both fruit surface environments had a high representation of Gammaproteobacteria, and within this class the genera Pantoea and Enterobacter were the most abundant. Despite the major differences observed in the bacterial composition of ground and surface water, the season long use of these very different water sources did not have a significant impact on the bacterial composition of the tomato fruit surface. This study has provided the first next-generation sequencing database describing the bacterial communities living in the fruit surface of a tomato crop under two different spray water regimes, and therefore represents an important step forward towards the development of science

  12. Bacterial community diversity and variation in spray water sources and the tomato fruit surface

    Directory of Open Access Journals (Sweden)

    Ottesen Andrea R

    2011-04-01

    Full Text Available Abstract Background Tomato (Solanum lycopersicum consumption has been one of the most common causes of produce-associated salmonellosis in the United States. Contamination may originate from animal waste, insects, soil or water. Current guidelines for fresh tomato production recommend the use of potable water for applications coming in direct contact with the fruit, but due to high demand, water from other sources is frequently used. We sought to describe the overall bacterial diversity on the surface of tomato fruit and the effect of two different water sources (ground and surface water when used for direct crop applications by generating a 454-pyrosequencing 16S rRNA dataset of these different environments. This study represents the first in depth characterization of bacterial communities in the tomato fruit surface and the water sources commonly used in commercial vegetable production. Results The two water sources tested had a significantly different bacterial composition. Proteobacteria was predominant in groundwater samples, whereas in the significantly more diverse surface water, abundant phyla also included Firmicutes, Actinobacteria and Verrucomicrobia. The fruit surface bacterial communities on tomatoes sprayed with both water sources could not be differentiated using various statistical methods. Both fruit surface environments had a high representation of Gammaproteobacteria, and within this class the genera Pantoea and Enterobacter were the most abundant. Conclusions Despite the major differences observed in the bacterial composition of ground and surface water, the season long use of these very different water sources did not have a significant impact on the bacterial composition of the tomato fruit surface. This study has provided the first next-generation sequencing database describing the bacterial communities living in the fruit surface of a tomato crop under two different spray water regimes, and therefore represents an

  13. Influence of ozone precursors and particulate matter on the variation of surface ozone at an urban site of Delhi, India

    Directory of Open Access Journals (Sweden)

    Ashima Sharma

    2016-03-01

    Full Text Available Continuous measurements of surface O3 and its precursors (NO, NO2, CO, CH4 and NMHCs at an urban site of Delhi, India during January 2012 to December 2013 are presented. In the present study, the annual average mixing ratios of surface O3, NO, NO2, CO, CH4 and NMHC were 30 ± 6 ppb, 24 ± 6 ppb, 15 ± 4 ppb, 1.5 ± 0.4 ppm, 2.4 ± 0.4 ppm and 0.4 ± 0.1 ppm, respectively. The maximum average mixing ratios of surface O3, NO and NO2 were observed during the summer, whereas, the minimum average mixing ratios of ambient NO and NO2 were during monsoon seasons. The surface O3, NO and NO2 have shown the prominent diurnal variations during all the seasons at the observational site of Delhi. The result reveals that the surface O3 was negatively correlated with NOx and CO during the study. The linear scatter plot analysis shows that the PM2.5 and PM10 present in the ambient air of Delhi influence the production of surface O3 at observational site.

  14. The investigation of spatiotemporal variations of land surface temperature based on land use changes using NDVI in southwest of Iran

    Science.gov (United States)

    Fathizad, Hassan; Tazeh, Mahdi; Kalantari, Saeideh; Shojaei, Saeed

    2017-10-01

    Land use changes can bring about changes in land surface temperature (LST) which is influenced by climatic conditions and physical characteristics of the land surface. In this study, spatiotemporal variations of land surface temperature have been investigated in the desert area of Dasht-e-Abbas, Ilam, based on a variety of land use changes. The investigated periods for the study include 1990, 2000 and 2010 using Landsat image data. First, in mapping land use we used the Fuzzy ARTMAP Neural Network Classification method followed by determination of the NDVI Index to estimate land surface temperature. The results show an increase in LST in areas where degradation, land use and land cover changes have occurred. In 1990, 2000 and 2010, the average land surface temperature of the Fair Rangelands was 26.72 °C, 30.06 °C and 30.95 °C, respectively. This rangeland has been reduced by about 5%. For poor rangelands, the average LSTs were 26.95, 32.83 and 34.49 Cº, respectively which had a 18% reduction. In 1990, 2000 and 2010, the average land surface temperatures of agricultural lands were 24.31 °C, 27.87 °C and 28.61 °C, respectively which has been an increasing trend. The reason can be attributed to changes in cropping patterns of the study area.

  15. Validation of response simulation methodology of Albedo dosemeter; Validacao da metodologia de simulacao de resposta de dosimetro de Albedo

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, B.M.; Silva, A.X. da, E-mail: bfreitas@nuclear.ufrj.br [Coordenacao do Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear; Mauricio, C.L.P. [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2016-07-01

    The Instituto de Radioprotecao e Dosimetria developed and runs a neutron TLD albedo individual monitoring service. To optimize the dose calculation algorithm and to infer new calibration factors, the response of this dosemeter was simulated. In order to validate this employed methodology, it was applied in the simulation of the problem of the QUADOS (Quality Assurance of Computational Tools for Dosimetry) intercomparison, aimed to evaluate dosimetric problems, one being to calculate the response of a generic albedo dosemeter. The obtained results were compared with those of other modeling and the reference one, with good agreements. (author)

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

    Science.gov (United States)

    Istomina, L.; Heygster, G.; Huntemann, M.; Schwarz, P.; Birnbaum, G.; Scharien, R.; Polashenski, C.; Perovich, D.; Zege, E.; Malinka, A.; Prikhach, A.; Katsev, I.

    2014-10-01

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

  17. Variations in land surface temperature and cooling efficiency of green space in rapid urbanization

    DEFF Research Database (Denmark)

    Yu, Zhaowu; Guo, Xieying; Zeng, Yuxi

    2018-01-01

    understood. Additionally, a strategy to optimize the most significant decreased land cover type in order to maximize the cooling effect is still lacking. Therefore, in this study, we selected the rapidly urbanizing and ‘hottest’ city in China, Fuzhou, as a case study. Two algorithms were selected to compare....... This study extends the current understanding of LCC dynamics and LST variation. The concepts of the CE and TVoE are meaningful for landscape planning practice and can be used in other cases....... and obtain reliable LST data. A land use transfer matrix was used to detect critical contributions leading to the LST variations. The concept of cooling efficiency (CE) and the threshold value of efficiency (TVoE) are also proposed, defined, and calculated. The results show that LST values increased...

  18. Production of Arctic Sea-ice Albedo by fusion of MISR and MODIS data

    Science.gov (United States)

    Kharbouche, Said; Muller, Jan-Peter

    2017-04-01

    We have combined data from the NASA MISR and MODIS spectro-radiometers to create a cloud-free albedo dataset specifically for sea-ice. The MISR (Multi-Angular Spectro-Radiometer) instrument on board Terra satellite has a unique ability to create high-quality Bidirectional Reflectance (BRF) over a 7 minute time interval per single overpass, thanks to its 9 cameras of different view angles (±70°,±60°,±45°,±26°). However, as MISR is limited to narrow spectral bands (443nm, 555nm, 670nm, 865nm), which is not sufficient to mask cloud effectively and robustly, we have used the sea-ice mask MOD09 product (Collection 6) from MODIS (Moderate resolution Imaging Spectoradiometer) instrument, which is also on board Terra satellite and acquiring data simultaneously. Only We have created a new and consistent sea-ice (for Arctic) albedo product that is daily, from 1st March to 22nd September for each and every year between 2000 to 2016 at two spatial grids, 1km x 1km and 5km x 5km in polar stereographic projection. Their analysis is described in a separate report [1]. References [1] Muller & Kharbouche, Variation of Arctic's Sea-ice Albedo between 2000 and 2016 by fusion of MISR and MODIS data. This conference. Acknowledgements This work was supported by www.QA4ECV.eu, a project of European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 607405. We thank our colleagues at JPL and NASA LaRC for processing these data, especially Sebastian Val and Steve Protack.

  19. On numerical heat transfer characteristic study of flat surface subjected to variation in geometric thickness

    Science.gov (United States)

    Umair, Siddique Mohammed; Kolawale, Abhijeet Rangnath; Bhise, Ganesh Anurath; Gulhane, Nitin Parashram

    Thermal management in the looming world of electronic packaging system is the most prior and conspicuous issue as far as the working efficiency of the system is concerned. The cooling in such systems can be achieved by impinging air jet over the heat sink as jet impingement cooling is one of the cooling technologies which are widely studied now. Here the modulation in impinging and geometric parameters results in the establishment of the characteristic cooling rate over the target surface. The characteristic cooling curve actually resembles non-uniformity in cooling rate. This non-uniformity favors the area average heat dissipation rate. In order to study the non-uniformity in cooling characteristic, the present study takes an initiative in plotting the local Nusselt number magnitude against the non-dimensional radial distance of the different thickness of target surfaces. For this, the steady temperature distribution over the target surface under the impingement of air jet is being determined numerically. The work is completely inclined towards the determination of critical value of geometric thickness below which the non-uniformity in the Nusselt profile starts. This is done by numerically examining different target surfaces under constant Reynolds number and nozzle-target spacing. The occurrences of non-uniformity in Nusselt profile contributes to over a 42% enhancement in area average Nusselt magnitude. The critical value of characteristic thickness (t/d) reported in the present investigation approximate to 0.05. Below this value, the impingement of air jet generates a discrete pressure zones over the target surface in the form of pressure spots. As a result of this, the air flowing in contact with the target surface experiences a damping potential, in due of which it gets more time and contact with the surface to dissipate heat.

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

    NARCIS (Netherlands)

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

    2008-01-01

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

  1. Effective single scattering albedo estimation using regional climate model

    CSIR Research Space (South Africa)

    Tesfaye, M

    2011-09-01

    Full Text Available In this study, by modifying the optical parameterization of Regional Climate model (RegCM), the authors have computed and compared the Effective Single-Scattering Albedo (ESSA) which is a representative of VIS spectral region. The arid, semi...

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

    Czech Academy of Sciences Publication Activity Database

    Lukeš, Petr; Stenberg, P.; Mottus, M.; Manninen, T.; Rautiainen, M.

    2016-01-01

    Roč. 52, OCT (2016), s. 296-305 ISSN 0303-2434 R&D Projects: GA MŠk(CZ) LM2010007; GA MŠk(CZ) LO1415 Institutional support: RVO:67179843 Keywords : Albedo * fAPAR * LAI * NDVI * Time series * Seasonal trends * Forest structure Subject RIV: EH - Ecology, Behaviour Impact factor: 3.930, year: 2016

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

    DEFF Research Database (Denmark)

    Bhanderi, Dan

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

  4. Evidence for ice-ocean albedo feedback in the Arctic Ocean shifting to a seasonal ice zone.

    Science.gov (United States)

    Kashiwase, Haruhiko; Ohshima, Kay I; Nihashi, Sohey; Eicken, Hajo

    2017-08-15

    Ice-albedo feedback due to the albedo contrast between water and ice is a major factor in seasonal sea ice retreat, and has received increasing attention with the Arctic Ocean shifting to a seasonal ice cover. However, quantitative evaluation of such feedbacks is still insufficient. Here we provide quantitative evidence that heat input through the open water fraction is the primary driver of seasonal and interannual variations in Arctic sea ice retreat. Analyses of satellite data (1979-2014) and a simplified ice-upper ocean coupled model reveal that divergent ice motion in the early melt season triggers large-scale feedback which subsequently amplifies summer sea ice anomalies. The magnitude of divergence controlling the feedback has doubled since 2000 due to a more mobile ice cover, which can partly explain the recent drastic ice reduction in the Arctic Ocean.

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

    KAUST Repository

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

    2013-01-01

    Albedo plays an important role in land-atmosphere interactions and local climate. This study presents the impact on simulating regional climate, and the evolution of a drought, when using the default climatological albedo as is usually done

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

    Data.gov (United States)

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

  7. Arecibo Radar Observation of Near-Earth Asteroids: Expanded Sample Size, Determination of Radar Albedos, and Measurements of Polarization Ratios

    Science.gov (United States)

    Lejoly, Cassandra; Howell, Ellen S.; Taylor, Patrick A.; Springmann, Alessondra; Virkki, Anne; Nolan, Michael C.; Rivera-Valentin, Edgard G.; Benner, Lance A. M.; Brozovic, Marina; Giorgini, Jon D.

    2017-10-01

    The Near-Earth Asteroid (NEA) population ranges in size from a few meters to more than 10 kilometers. NEAs have a wide variety of taxonomic classes, surface features, and shapes, including spheroids, binary objects, contact binaries, elongated, as well as irregular bodies. Using the Arecibo Observatory planetary radar system, we have measured apparent rotation rate, radar reflectivity, apparent diameter, and radar albedos for over 350 NEAs. The radar albedo is defined as the radar cross-section divided by the geometric cross-section. If a shape model is available, the actual cross-section is known at the time of the observation. Otherwise we derive a geometric cross-section from a measured diameter. When radar imaging is available, the diameter was measured from the apparent range depth. However, when radar imaging was not available, we used the continuous wave (CW) bandwidth radar measurements in conjunction with the period of the object. The CW bandwidth provides apparent rotation rate, which, given an independent rotation measurement, such as from lightcurves, constrains the size of the object. We assumed an equatorial view unless we knew the pole orientation, which gives a lower limit on the diameter. The CW also provides the polarization ratio, which is the ratio of the SC and OC cross-sections.We confirm the trend found by Benner et al. (2008) that taxonomic types E and V have very high polarization ratios. We have obtained a larger sample and can analyze additional trends with spin, size, rotation rate, taxonomic class, polarization ratio, and radar albedo to interpret the origin of the NEAs and their dynamical processes. The distribution of radar albedo and polarization ratio at the smallest diameters (≤50 m) differs from the distribution of larger objects (>50 m), although the sample size is limited. Additionally, we find more moderate radar albedos for the smallest NEAs when compared to those with diameters 50-150 m. We will present additional trends we

  8. Variation in PAH inputs and microbial community in surface sediments of Hamilton Harbour: Implications to remediation and monitoring

    International Nuclear Information System (INIS)

    Slater, G.F.; Cowie, B.R.; Harper, N.; Droppo, I.G.

    2008-01-01

    Variations in concentrations of polycyclic aromatic hydrocarbons (PAHs) and microbial community indicators were investigated in representative highly contaminated and less contaminated surface sediment sites of Hamilton Harbour. Inputs of PAH to the upper 3 cm of sediments up to four times the average upper sediment concentrations were observed. Associated PAH fingerprint profiles indicated that the source was consistent with the PAH source to the industrial region of the harbour. Increased PAH loadings were associated with decreased bacterial populations as indicated by phospholipid fatty acid (PLFA) concentrations. However, relatively minor impacts on overall community composition were indicated. Porewater methane concentrations and isotopic data indicated a difference in the occurrence of methane oxidation between the two sites. This study confirms temporally limited transport of contaminants from highly impacted regions as a vector for contaminants within the harbour and the impact on microbial carbon cycling and bed stability. - Variations in PAH inputs to harbour sediments have implications to implementation and monitoring of mitigation/remediation efforts

  9. Unusual shapes for a catenary under the effects of surface tension and gravity: A variational treatment

    International Nuclear Information System (INIS)

    Behroozi, F.; Mohazzabi, P.; McCrickard, J.

    1995-01-01

    The familiar catenary is the shape assumed by a chain or string as it hangs from two points. The mathematical equation of the catenary was first published more than three hundred years ago by Leibnitz and Huygen, among others. Here we consider the shapes assumed by a hanging string in the presence of gravity and surface tension. The surface tension is introduced by suspending the string from a thin horizontal rod while the area bounded by the string and the rod is covered with a soap film. The string then assumes new and wonderful shapes depending on the relative strength of the surface tension and the weight per unit length of the string. When surface tension dominates, the string is pulled inward, assuming a convex shape similar to the Greek letter γ. On the other hand, when gravity is dominant the string is pulled outward and assumes a concave shape best described as a distorted catenary. However, when the gravitational force normal to the string matches the surface tension, the string takes a linear configuration similar to the letter V. Under suitable conditions, the string can be made to assume any of the three configurations by adjusting the separation of its end points. The equations that describe the shape of the string are derived by minimizing the total energy of the system and are presented for the three principal configurations

  10. Spectroscopic study on variations in illite surface properties after acid-base titration.

    Science.gov (United States)

    Liu, Wen-xin; Coveney, R M; Tang, Hong-xiao

    2003-07-01

    FT-IR, Raman microscopy, XRD, 29Si and 27Al MAS NMR, were used to investigate changes in surface properties of a natural illite sample after acid-base potentiometric titration. The characteristic XRD lines indicated the presence of surface Al-Si complexes, preferable to Al(OH)3 precipitates. In the microscopic Raman spectra, the vibration peaks of Si-O and Al-O bonds diminished as a result of treatment with acid, then increased after hydroxide back titration. The varied ratio of signal intensity between (IV)Al and (VI)Al species in 27Al MAS NMR spectra, together with the stable BET surface area after acidimetric titration, suggested that edge faces and basal planes in the layer structure of illite participated in dissolution of structural components. The combined spectroscopic evidence demonstrated that the reactions between illite surfaces and acid-leaching silicic acid and aluminum ions should be considered in the model description of surface acid-base properties of the aqueous illite.

  11. Resolved spectrophotometric properties of the Ceres surface from Dawn Framing Camera images

    Science.gov (United States)

    Schröder, S. E.; Mottola, S.; Carsenty, U.; Ciarniello, M.; Jaumann, R.; Li, J.-Y.; Longobardo, A.; Palmer, E.; Pieters, C.; Preusker, F.; Raymond, C. A.; Russell, C. T.

    2017-05-01

    We present a global spectrophotometric characterization of the Ceres surface using Dawn Framing Camera (FC) images. We identify the photometric model that yields the best results for photometrically correcting images. Corrected FC images acquired on approach to Ceres were assembled into global maps of albedo and color. Generally, albedo and color variations on Ceres are muted. The albedo map is dominated by a large, circular feature in Vendimia Planitia, known from HST images (Li et al., 2006), and dotted by smaller bright features mostly associated with fresh-looking craters. The dominant color variation over the surface is represented by the presence of "blue" material in and around such craters, which has a negative spectral slope over the visible wavelength range when compared to average terrain. We also mapped variations of the phase curve by employing an exponential photometric model, a technique previously applied to asteroid Vesta (Schröder et al., 2013b). The surface of Ceres scatters light differently from Vesta in the sense that the ejecta of several fresh-looking craters may be physically smooth rather than rough. High albedo, blue color, and physical smoothness all appear to be indicators of youth. The blue color may result from the desiccation of ejected material that is similar to the phyllosilicates/water ice mixtures in the experiments of Poch et al. (2016). The physical smoothness of some blue terrains would be consistent with an initially liquid condition, perhaps as a consequence of impact melting of subsurface water ice. We find red terrain (positive spectral slope) near Ernutet crater, where De Sanctis et al. (2017) detected organic material. The spectrophotometric properties of the large Vendimia Planitia feature suggest it is a palimpsest, consistent with the Marchi et al. (2016) impact basin hypothesis. The central bright area in Occator crater, Cerealia Facula, is the brightest on Ceres with an average visual normal albedo of about 0.6 at

  12. Decomposing Shortwave Top-of-Atmosphere Radiative Flux Variability in Terms of Surface and Atmospheric Contributions Using CERES Observations

    Science.gov (United States)

    Loeb, N. G.; Wong, T.; Wang, H.

    2017-12-01

    Earth's climate is determined by the exchange of radiant energy between the Sun, Earth and space. The absorbed solar radiation (ASR) fuels the climate system, providing the energy required for atmospheric and oceanic motions, while the system cools by emitting outgoing longwave (LW) radiation to space. A central objective of the Clouds and the Earth's Radiant Energy System (CERES) is to produce a long-term global climate data record of Earth's radiation budget along with the associated atmospheric and surface properties that influence it. CERES data products utilize a number of data sources, including broadband radiometers measuring incoming and reflected solar radiation and OLR, polar orbiting and geostationary spectral imagers, meteorological, aerosol and ozone assimilation data, and snow/sea-ice maps based on microwave radiometer data. Here we use simple diagnostic model of Earth's albedo and CERES Energy Balanced and Filled (EBAF) Ed4.0 data for March 2000-February 2016 to quantify interannual variations in SW TOA flux associated with surface albedo and atmospheric reflectance and transmittance variations. Surface albedo variations account for cloud properties over the Arctic Ocean.

  13. Comparison of Surface and Column Variations of CO2 Over Urban Areas for Future Active Remote CO2 Sensors

    Science.gov (United States)

    Choi, Yonghoon; Yang, Melissa; Kooi, Susan; Browell, Edward

    2015-01-01

    High resolution in-situ CO2 measurements were recorded onboard the NASA P-3B during the DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) Field Campaign, to investigate the ability of space-based observations to accurately assess near surface conditions related to air quality. This campaign includes, Washington DC/Baltimore, MD (July 2011), San Joaquin Valley, CA (January - February 2013), Houston, TX (September 2013), and Denver, CO (July-August 2014). Each of these campaigns consisted of missed approaches and approximately two hundred vertical soundings of CO2 within the lower troposphere (surface to about 5 km). In this study, surface (0 - 1 km) and column-averaged (0 - 3.5 km) CO2 mixing ratio values from the vertical soundings in the four geographically different urban areas are used to investigate the temporal and spatial variability of CO2 within the different urban atmospheric emission environments. Tracers such as CO, CH2O, NOx, and NMHCs are used to identify the source of CO2 variations in the urban sites. Additionally, we apply nominal CO2 column weighting functions for potential future active remote CO2 sensors operating in the 1.57-microns and 2.05-microns measurement regions to convert the in situ CO2 vertical mixing ratio profiles to variations in CO2 column optical depths, which is what the active remote sensors actually measure. Using statistics calculated from the optical depths at each urban site measured during the DISCOVER-AQ field campaign and for each nominal weighting function, we investigate the natural variability of CO2 columns in the lower troposphere; relate the CO2 column variability to the urban surface emissions; and show the measurement requirements for the future ASCENDS (Active Sensing of CO2 Emissions over Nights, Days, and Seasons) in the continental U.S. urban areas.

  14. Evaluation of preindustrial to present-day black carbon and its albedo forcing from Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP

    Directory of Open Access Journals (Sweden)

    Y. H. Lee

    2013-03-01

    Full Text Available As part of the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP, we evaluate the historical black carbon (BC aerosols simulated by 8 ACCMIP models against observations including 12 ice core records, long-term surface mass concentrations, and recent Arctic BC snowpack measurements. We also estimate BC albedo forcing by performing additional simulations using offline models with prescribed meteorology from 1996–2000. We evaluate the vertical profile of BC snow concentrations from these offline simulations using the recent BC snowpack measurements. Despite using the same BC emissions, the global BC burden differs by approximately a factor of 3 among models due to differences in aerosol removal parameterizations and simulated meteorology: 34 Gg to 103 Gg in 1850 and 82 Gg to 315 Gg in 2000. However, the global BC burden from preindustrial to present-day increases by 2.5–3 times with little variation among models, roughly matching the 2.5-fold increase in total BC emissions during the same period. We find a large divergence among models at both Northern Hemisphere (NH and Southern Hemisphere (SH high latitude regions for BC burden and at SH high latitude regions for deposition fluxes. The ACCMIP simulations match the observed BC surface mass concentrations well in Europe and North America except at Ispra. However, the models fail to predict the Arctic BC seasonality due to severe underestimations during winter and spring. The simulated vertically resolved BC snow concentrations are, on average, within a factor of 2–3 of the BC snowpack measurements except for Greenland and the Arctic Ocean. For the ice core evaluation, models tend to adequately capture both the observed temporal trends and the magnitudes at Greenland sites. However, models fail to predict the decreasing trend of BC depositions/ice core concentrations from the 1950s to the 1970s in most Tibetan Plateau ice cores. The distinct temporal trend at the Tibetan

  15. Evaluation of preindustrial to present-day black carbon and its albedo forcing from Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP)

    Science.gov (United States)

    Lee, Y. H.; Lamarque, J.-F.; Flanner, M. G.; Jiao, C.; Shindell, D. T.; Bernsten, T.; Bisiaux, M. M.; Cao, J.; Collins, W. J.; Curran, M.; hide

    2013-01-01

    As part of the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP), we evaluate the historical black carbon (BC) aerosols simulated by 8 ACCMIP models against observations including 12 ice core records, long-term surface mass concentrations, and recent Arctic BC snowpack measurements. We also estimate BC albedo forcing by performing additional simulations using offline models with prescribed meteorology from 1996-2000. We evaluate the vertical profile of BC snow concentrations from these offline simulations using the recent BC snowpack measurements. Despite using the same BC emissions, the global BC burden differs by approximately a factor of 3 among models due to differences in aerosol removal parameterizations and simulated meteorology: 34 Gg to 103 Gg in 1850 and 82 Gg to 315 Gg in 2000. However, the global BC burden from preindustrial to present-day increases by 2.5-3 times with little variation among models, roughly matching the 2.5-fold increase in total BC emissions during the same period.We find a large divergence among models at both Northern Hemisphere (NH) and Southern Hemisphere (SH) high latitude regions for BC burden and at SH high latitude regions for deposition fluxes. The ACCMIP simulations match the observed BC surface mass concentrations well in Europe and North America except at Ispra. However, the models fail to predict the Arctic BC seasonality due to severe underestimations during winter and spring. The simulated vertically resolved BC snow concentrations are, on average, within a factor of 2-3 of the BC snowpack measurements except for Greenland and the Arctic Ocean. For the ice core evaluation, models tend to adequately capture both the observed temporal trends and the magnitudes at Greenland sites. However, models fail to predict the decreasing trend of BC depositions/ice core concentrations from the 1950s to the 1970s in most Tibetan Plateau ice cores. The distinct temporal trend at the Tibetan Plateau ice cores

  16. Surface modification induced phase transformation and structure variation on the rapidly solidified recast layer of titanium

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Ming-Hung [Department of Mechanical Engineering and Graduate Institute of Mechanical and Precision Engineering, National Kaoshiung University of Applied Sciences, Kaoshiung 807, Taiwan (China); School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Haung, Chiung-Fang [School of Dental Technology, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Division of Family and Operative Dentistry, Department of Dentistry, Taipei Medical University Hospital, Taipei 110, Taiwan (China); Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University, Taipei 110, Taiwan (China); Shyu, Shih-Shiun [Department of Dentistry, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, New Taipei City 231, Taiwan (China); Chou, Yen-Ru [Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University, Taipei 110, Taiwan (China); Graduate Institute of Biomedical Materials and Tissue Engineering, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China); Lin, Ming-Hong [Department of Mechanical Engineering and Graduate Institute of Mechanical and Precision Engineering, National Kaoshiung University of Applied Sciences, Kaoshiung 807, Taiwan (China); Peng, Pei-Wen, E-mail: apon@tmu.edu.tw [School of Dental Technology, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); and others

    2015-08-15

    In this study, neodymium-doped yttrium orthovanadate (Nd:YVO{sub 4}) as a laser source with different scanning speeds was used on biomedical Ti surface. The microstructural and biological properties of laser-modified samples were investigated by means of optical microscope, electron microscope, X-ray diffraction, surface roughness instrument, contact angle and cell cytotoxicity assay. After laser modification, the rough volcano-like recast layer with micro-/nanoporous structure and wave-like recast layer with nanoporous structure were generated on the surfaces of laser-modified samples, respectively. It was also found out that, an α → (α + rutile-TiO{sub 2}) phase transition occurred on the recast layers of laser-modified samples. The Ti surface becomes hydrophilic at a high speed laser scanning. Moreover, the cell cytotoxicity assay demonstrated that laser-modified samples did not influence the cell adhesion and proliferation behaviors of osteoblast (MG-63) cell. The laser with 50 mm/s scanning speed induced formation of rough volcano-like recast layer accompanied with micro-/nanoporous structure, which can promote cell adhesion and proliferation of MG-63 cell on Ti surface. The results indicated that the laser treatment was a potential technology to enhance the biocompatibility for titanium. - Highlights: • Laser induced the formation of recast layer with micro-/nanoporous structure on Ti. • An α → (α + rutile-TiO{sub 2}) phase transition was observed within the recast layer. • The Ti surface becomes hydrophilic at a high speed laser scanning. • Laser-modified samples exhibit good biocompatibility to osteoblast (MG-63) cell.

  17. Continuous versus discontinuous albedo representations in a simple diffusive climate model

    Science.gov (United States)

    Simmons, P. A.; Griffel, D. H.

    1988-07-01

    A one-dimensional annually and zonally averaged energy-balance model, with diffusive meridional heat transport and including icealbedo feedback, is considered. This type of model is found to be very sensitive to the form of albedo used. The solutions for a discontinuous step-function albedo are compared to those for a more realistic smoothly varying albedo. The smooth albedo gives a closer fit to present conditions, but the discontinuous form gives a better representation of climates in earlier epochs.

  18. Potential of electrical resistivity tomography and muon density imaging to study spatio-temporal variations in the sub-surface

    Science.gov (United States)

    Lesparre, Nolwenn; Cabrera, Justo; Courbet, Christelle

    2015-04-01

    We explore the capacity of electrical resistivity tomography and muon density imaging to detect spatio-temporal variations of the medium surrounding a regional fault crossing the underground platform of Tournemire (Aveyron, France). The studied Cernon fault is sub-vertical and intersects perpendicularly the tunnel of Tournemire and extends to surface. The fault separates clay and limestones layers of the Dogger from limestones layers of the Lias. The Cernon fault presents a thickness of a ten of meters and drives water from an aquifer circulating at the top of the Dogger clay layer to the tunnel. An experiment combining electrical resistivity imaging and muon density imaging was setup taking advantage of the tunnel presence. A specific array of electrodes were set up, adapted for the characterization of the fault. Electrodes were placed along the tunnel as well as at the surface above the tunnel on both sides of the fault in order to acquire data in transmission across the massif to better cover the sounded medium. Electrical resistivity is particularly sensitive to water presence in the medium and thus carry information on the main water flow paths and on the pore space saturation. At the same time a muon sensor was placed in the tunnel under the fault region to detect muons coming from the sky after their crossing of the rock medium. Since the muon flux is attenuated as function of the quantity of matter crossed, muons flux measurements supply information on the medium average density along muons paths. The sensor presents 961 angles of view so measurements performed from one station allows a comparison of the muon flux temporal variations along the fault as well as in the medium surrounding the fault. As the water saturation of the porous medium fluctuates through time the medium density might indeed present sensible variations as shown by gravimetric studies. During the experiment important rainfalls occurred leading variations of the medium properties

  19. Signal and noise in Gravity Recovery and Climate Experiment (GRACE) observed surface mass variations

    NARCIS (Netherlands)

    Schrama, E.J.O.; Wouters, B.; Lavallée, D.A.

    2007-01-01

    The Gravity Recovery and Climate Experiment (GRACE) product used for this study consists of 43 monthly potential coefficient sets released by the GRACE science team which are used to generate surface mass thickness grids expressed as equivalent water heights (EQWHs). We optimized both the smoothing

  20. Quantitative estimation of Holocene surface salinity variation in the Black Sea using dinoflagellate cyst process length

    DEFF Research Database (Denmark)

    Mertens, Kenneth Neil; Bradley, Lee R.; Takano, Yoshihito

    2012-01-01

    Reconstruction of salinity in the Holocene Black Sea has been an ongoing debate over the past four decades. Here we calibrate summer surface water salinity in the Black Sea, Sea of Azov and Caspian Sea with the process length of the dinoflagellate cyst Lingulodinium machaerophorum. We then apply ...

  1. Variation with age of anisotropy under oceans, from great circle surface waves

    International Nuclear Information System (INIS)

    Journet, B.; Jobert, N.

    1982-01-01

    Global great circle measurements of regionalized mantle Love wave phase velocities are interpreted in terms of regional models. The same study had been made by J. J. Leveque (1980) for Rayleigh waves, and the resulting models for the two oceanic regions of different ages are used as a basis for comparison: the observed Love wave dispersion cannot be explained with these models if isotropic. The models obtained by inversion of Love wave data are compared with the models mentioned; the discrepancy appearing in the 250 km depth range between the velocities β/sub H/ and β/sub V/ of respectively SH and SV waves is indicative of polarization anisotropy. Moreover, we put forward a significant variation from young to old oceans: the difference between β/sub H/, and β/sub V/ is of the order of 1% for the former, compared to 3% for the latter. This variation can bring information about the behaviour of upper mantle materials in connection with the motion of oceanic plates

  2. Remote sensing the susceptibility of cloud albedo to changes in drop concentration

    International Nuclear Information System (INIS)

    Platnick, S.E.

    1991-01-01

    The role of clouds in reflecting solar radiation to space and thereby reducing surface heating is of critical importance to climate. Combustion processes that produce greenhouse gases also increase cloud condensation nuclei (CCN) concentrations which in turn increase cloud drop concentrations and thereby cloud albedo. A calculation of cloud susceptibility, defined in this work as the increase in albedo resulting from the addition of one cloud drop per cubic centimeter (as cloud liquid water content remains constant), is made through satellite remote sensing of cloud drop radius and optical thickness. The remote technique uses spectral channels of the Advanced Very High Resolution Radiometer (AVHRR) instrument on board the NOAA polar orbiting satellites. Radiative transfer calculations of reflectance and effective surface and cloud emissivities are made for applicable sun and satellite viewing angles, including azimuth, at various radii and optical thicknesses for each AVHRR channel. Emission in channel 3 (at 3.75 microns) is removed to give the reflected solar component. These calculations are used to infer the radius and optical thickness giving the best match to the satellite measurements. The effect of the atmosphere on the signal received by the satellite is included in the analysis

  3. Significant Variation of Post-critical SsPmp Amplitude as a Result of Variation in Near-surface Velocity: Observations from the Yellowknife Array

    Science.gov (United States)

    Ferragut, G.; Liu, T.; Klemperer, S. L.

    2017-12-01

    In recent years Virtual Deep Seismic Sounding (VDSS) emerged as a novel method to image the Moho, which uses the post-critical reflection P waves at the Moho generated by teleseismic S waves at the free surface near the receivers (SsPmp). However, observed SsPmp sometimes have significantly lower amplitude than predicted, raising doubts among the seismic community on the theoretical basis of the method. With over two decades of continuous digital broadband records and major subduction zones in the range of 30-50 degrees, the Yellowknife Array in northern Canada provides a rich opportunity for observation of post-critical SsPmp. We analyze S wave coda of events with epicenter distances of 30-50°, and pay special attention to earthquakes in a narrow azimuth range that ­­­encompasses the Kamchatka Peninsula. Among 21 events with strong direct S energy on the radial components, we observe significant variation of SsPmp energy. After associating the SsPmp energy with the virtual source location of each event, we observe a general trend of decreasing SsPmp energy from NE to SW. As the trend coincides with the transition from exposed basement of the Slave Craton to Paleozoic platform covered by Phanerozoic sediment, we interpret the decreasing SsPmp energy as a result of lower S velocity at the virtual sources, which reduces S-to-P reflection coefficients. We plan to include more events from the Aleutian Islands, the virtual sources of which are primarily located in the Paleozoic platform. This will allow us to further investigate the relationship between SsPmp amplitude and near-surface velocity.

  4. Fringe projection application for surface variation analysis on helical shaped silicon breast

    Science.gov (United States)

    Vairavan, R.; Ong, N. R.; Sauli, Z.; Shahimin, M. M.; Kirtsaeng, S.; Sakuntasathien, S.; Alcain, J. B.; Paitong, P.; Retnasamy, V.

    2017-09-01

    Breast carcinoma is rated as a second collective cause of cancer associated death among adult females. Detection of the disease at an early stage would enhance the chance for survival. Established detection methods such as mammography, ultrasound and MRI are classified as non invasive breast cancer detection modality, but however they are not entire non-invasive as physical contact still occurs to the breast. Thus requirement for a complete non invasive and non contact is evident. Therefore, in this work, a novel application of digital fringe projection for early detection of breast cancer based on breast surface analysis is reported. Phase shift fringe projection technique and pixel tracing method was utilized to analyze the breast surface change due to the incidence of breast lump. Results have shown that the digital fringe projection is capable in detecting the existence of 1 cm sized lump within the breast sample.

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

    Science.gov (United States)

    Harris, Alan; Mueller, Michael; Fitzsimmons, Alan

    2006-03-01

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

  6. Light-absorbing impurities enhance glacier albedo reduction in the southeastern Tibetan plateau

    Science.gov (United States)

    Zhang, Yulan; Kang, Shichang; Cong, Zhiyuan; Schmale, Julia; Sprenger, Michael; Li, Chaoliu; Yang, Wei; Gao, Tanguang; Sillanpää, Mika; Li, Xiaofei; Liu, Yajun; Chen, Pengfei; Zhang, Xuelei

    2017-07-01

    Light-absorbing impurities (LAIs) in snow of the southeastern Tibetan Plateau (TP) and their climatic impacts are of interest not only because this region borders areas affected by the South Asian atmospheric brown clouds but also because the seasonal snow and glacier melt from this region form important headwaters of large rivers. In this study, we collected surface snow and snowpit samples from four glaciers in the southeastern TP in June 2015 to investigate the comprehensive observational data set of LAIs. Results showed that the LAI concentrations were much higher in the aged snow and granular ice than in the fresh snow and snowpits due to postdepositional processes. Impurity concentrations fluctuated across snowpits, with maximum LAI concentrations frequently occurring toward the bottom of snowpits. Based on the SNow ICe Aerosol Radiative model, the albedo simulation indicated that black carbon and dust account for approximately 20% of the albedo reduction relative to clean snow. The radiative forcing caused by black carbon and dust deposition on the glaciers were between 1.0-141 W m-2 and 1.5-120 W m-2, respectively. Black carbon (BC) played a larger role in albedo reduction and radiative forcing than dust in the study area, enhancing approximately 15% of glacier melt. Analysis based on the Fire INventory from NCAR indicated that nonbiomass-burning sources of BC played an important role in the total BC deposition, especially during the monsoon season. This study suggests that eliminating anthropogenic BC could mitigate glacier melt in the future of the southeastern TP.

  7. A Combined EOF/Variational Approach for Mapping Radar-Derived Sea Surface Currents

    Science.gov (United States)

    2011-01-01

    gaps in the gridded SST images, which was successfully applied in Adriatic ( Alvera - Azcarate et al., 2005). Kondrashov and Chil (2006) developed...velocities. Similar to SST analysis (Beckers and Rixen, 2003: Alvera -Azcarate et al.. 2005), these modes are used to fill the gaps in HFR...and selection of the time interval for estimating the covariances becomes important. In the present study the sea surface velocity Alvera -Azcarate

  8. Variation in surface water-groundwater exchange with land use in an urban stream

    Science.gov (United States)

    Ryan, Robert J.; Welty, Claire; Larson, Philip C.

    2010-10-01

    SummaryA suite of methods is being utilized in the Baltimore metropolitan area to develop an understanding of the interaction between groundwater and surface water at multiple space and time scales. As part of this effort, bromide tracer experiments were conducted over two 10-day periods in August 2007 and May 2008 along two sections (each approximately 900 m long) of Dead Run, a small urban stream located in Baltimore County, Maryland, to investigate the influence of distinct zones of riparian land cover on surface-subsurface exchange and transient storage under low and high baseflow conditions. Riparian land cover varied by reach along a gradient of land use spanning parkland, suburban/residential, commercial, institutional, and transportation, and included wooded, meadow, turf grass, and impervious cover. Under summer low baseflow conditions, surface water-groundwater exchange, defined by gross inflow and gross outflow, was larger and net inflow (gross inflow minus gross outflow) had greater spatial variability, than was observed under spring high baseflow conditions. In addition, the fraction of nominal travel time attributable to transient storage ( Fmed) was lower and was more spatially variable under high baseflow conditions than under low baseflow conditions. The influence of baseflow condition on surface water-ground water exchange and transient storage was most evident in the subreaches with the least riparian forest cover and these effects are attributed to a lack of shading in reaches with little riparian forest cover. We suggest that under summer low baseflow conditions, the lack of shading allowed excess in-channel vegetation growth which acted as a transient storage zone and a conduit for outflow (i.e. uptake and evapotranspiration). Under spring high baseflow conditions the transient storage capacity of the channel was reduced because there was little in-channel vegetation.

  9. Atmospheric summer teleconnections and Greenland Ice Sheet surface mass variations: insights from MERRA-2

    International Nuclear Information System (INIS)

    Lim, Young-Kwon; Schubert, Siegfried D; Molod, Andrea M; Cullather, Richard I; Zhao, Bin; Nowicki, Sophie M J; Lee, Jae N; Velicogna, Isabella

    2016-01-01

    The relationship between leading atmospheric teleconnection patterns and Greenland Ice Sheet (GrIS) temperature, precipitation, and surface mass balance (SMB) are investigated for the last 36 summers (1979–2014) based on Modern-Era Retrospective analysis for Research and Applications version 2 reanalyses. The results indicate that the negative phase of both the North Atlantic Oscillation (NAO) and Arctic Oscillation, associated with warm and dry conditions for the GrIS, lead to SMB decreases within 0–1 months. Furthermore, the positive phase of the East Atlantic (EA) pattern often lags the negative NAO, reflecting a dynamical linkage between these modes that acts to further enhance the warm and dry conditions over the GrIS, leading to a favorable environment for enhanced surface mass loss. The development of a strong negative NAO in combination with a strong positive EA in recent years leads to significantly larger GrIS warming compared to when the negative NAO occurs in combination with a negative or weak positive EA (0.69 K versus 0.13 K anomaly). During 2009 and 2011, weakened (as compared to conditions during the severe surface melt cases of 2010 and 2012) local high pressure blocking produced colder northerly flow over the GrIS inhibiting warming despite the occurrence of a strong negative NAO, reflecting an important role for the EA during those years. In particular, the EA acts with the NAO to enhance warming in 2010 and 2012, and weaken high pressure blocking in 2009 and 2011. In general, high pressure blocking primarily impacts the western areas of the GrIS via advective temperature increases, while changes in net surface radiative fluxes account for both western and eastern GrIS temperature changes. (letter)

  10. Seasonal variation of monomethylmercury concentrations in surface sediments of the Tagus Estuary (Portugal)

    International Nuclear Information System (INIS)

    Canario, Joao; Branco, Vasco; Vale, Carlos

    2007-01-01

    Surface sediments (0-2 cm) were collected at 40 sites along the Tagus Estuary in July and December 2004. The sediments were analysed for total mercury, monomethylmercury (MMHg) and interpretative parameters (e.g. redox potential, pH, C org ). No significant differences in total Hg, pH, Al, Fe, Mn and C org were found between sediments collected in the two periods, but MMHg concentrations were higher in July. On average sediments were warmer and more reducing in summer. On the basis of these results, an increase of 7 kg of MMHg (+37%) in surface sediments of the Tagus Estuary was estimated. Presumably higher temperatures in summer promote the increase of microbial activity and higher methylation rates. The alterations observed in this study point to the potential importance of seasonal changes in MMHg production at surface sediments with eventual changes in the MMHg uptake by benthic invertebrates and other organisms in the food web. - Seasonal changes in monomethylmercury production in sediments may increase its uptake by benthic invertebrates and other organisms in the food web

  11. Causes of seasonal variations of Cs-134/137 activity concentrations in surface air

    International Nuclear Information System (INIS)

    Hoetzl, H.; Winkler, R.

    1993-01-01

    In winter months maxima of Cs-134/137 activity concentrations in air are observed at several locations in Europe. To clarify this phenomenon, from October 1991 to November 1992 we performed a program for aerosol collection on a short-term scale based on collecting intervals of 48-72 hours. The local meteorological parameters were determined simultaneously. Statistical analysis of these observations reveiled a highly significant positive correlation between Cs-137 activity concentration and the so-called 'Stagnationsindex'. Based on this relationship the seasonal variations of Cs-134/137 concentrations in ground-level air can be explained by atmospheric inversion conditions frequently occurring during fall- and wintermonths. (orig.) [de

  12. A numerical analysis of antithetic variates in Monte Carlo radiation transport with geometrical surface splitting

    International Nuclear Information System (INIS)

    Sarkar, P.K.; Prasad, M.A.

    1989-01-01

    A numerical study for effective implementation of the antithetic variates technique with geometric splitting/Russian roulette in Monte Carlo radiation transport calculations is presented. The study is based on the theory of Monte Carlo errors where a set of coupled integral equations are solved for the first and second moments of the score and for the expected number of flights per particle history. Numerical results are obtained for particle transmission through an infinite homogeneous slab shield composed of an isotropically scattering medium. Two types of antithetic transformations are considered. The results indicate that the antithetic transformations always lead to reduction in variance and increase in efficiency provided optimal antithetic parameters are chosen. A substantial gain in efficiency is obtained by incorporating antithetic transformations in rule of thumb splitting. The advantage gained for thick slabs (∼20 mfp) with low scattering probability (0.1-0.5) is attractively large . (author). 27 refs., 9 tabs

  13. The contact binary VW Cephei revisited: surface activity and period variation

    Science.gov (United States)

    Mitnyan, T.; Bódi, A.; Szalai, T.; Vinkó, J.; Szatmáry, K.; Borkovits, T.; Bíró, B. I.; Hegedüs, T.; Vida, K.; Pál, A.

    2018-05-01

    Context. Despite the fact that VW Cephei is one of the most well-studied contact binaries in the literature, there is no fully consistent model available that can explain every observed property of this system. Aims: Our aims are to obtain new spectra along with photometric measurements, to analyze what kind of changes may have happened in the system in the past two decades, and to propose new ideas for explaining them. Methods: For the period analysis we determined ten new times of minima from our light curves, and constructed a new O-C diagram of the system. Radial velocities of the components were determined using the cross-correlation technique. The light curves and radial velocities were modeled simultaneously with the PHOEBE code. All observed spectra were compared to synthetic spectra and equivalent widths (EWs) of the Hα line were measured on their differences. Results: We re-determine the physical parameters of the system according to our new light curve and spectral models. We confirm that the primary component is more active than the secondary, and there is a correlation between spottedness and the chromospheric activity. We propose that the flip-flop phenomenon occurring on the primary component could be a possible explanation of the observed nature of the activity. To explain the period variation of VW Cep, we test two previously suggested scenarios: the presence of a fourth body in the system, and the Applegate-mechanism caused by periodic magnetic activity. We conclude that although none of these mechanisms can be ruled out entirely, the available data suggest that mass transfer with a slowly decreasing rate provides the most likely explanation for the period variation of VW Cep.

  14. Surface variations affecting human dental enamel studied using nanomechanical and chemical analysis

    Science.gov (United States)

    Dickinson, Michelle Emma

    The enamel surface is the interface between the tooth and its ever changing oral environment. Cavity (caries) formation and extrinsic tooth staining are due, respectively, to degradation of the enamel structure under low pH conditions and interactions between salivary pellicle and dietary elements. Both of these occur at the enamel surface and are caused by the local environment changing the chemistry of the surface. The results can be detrimental to the enamel's mechanical integrity and aesthetics. Incipient carious lesions are the precursor to caries and form due to demineralisation of enamel. These carious lesions are a reversible structure where ions (e.g. Ca2+, F -) can diffuse in (remineralisation) to preserve the tooth's structural integrity. This investigation used controlled in vitro demineralisation and remineralisation to study artificial carious lesion formation and repair. The carious lesions were cross-sectioned and characterised using nanoindentation, electron probe micro-analysis and time of flight secondary ion mass spe