Science.gov

Sample records for flux measurement sites

  1. Micrometeorological flux measurements at a coastal site

    NASA Astrophysics Data System (ADS)

    Song, Guozheng; Meixner, Franz X.; Bruse, Michael; Mamtimin, Buhalqem

    2014-05-01

    The eddy covariance (EC) technique is the only direct measurement of the momentum, heat, and trace gas (e.g. water vapor, CO2 and ozone) fluxes. The measurements are expected to be most accurate over flat terrain where there is an extended homogenous surface upwind from the tower, and when the environmental conditions are steady. Additionally, the one dimensional approach assumes that vertical turbulent exchange is the dominant flux, whereas advective influences should be negligible. The application of EC method under non-ideal conditions, for example in complex terrain, has yet to be fully explored. To explore the possibilities and limitations of EC technique under non-ideal conditions, an EC system was set up at Selles beach, Crete, Greece (35.33°N, 25.71°E) in the beginning of July 2012. The dominant wind direction was west, parallel to the coast. The EC system consisted of a sonic anemometer (CSAT3 Campbell Scientific), an infrared open-path CO2/H2O gas analyzer (LI-7500, Li-COR Biosciences) and a fast chemiluminescence ozone analyzer (enviscope GmbH). All the signals of these fast response instruments were sampled at 10 Hz and the measurement height was 3 m. Besides, another gradient system was setup. Air temperature, relative humidity (HYGROMER MP 103 A), and wind speed (WMT700 Vaisala) were measured every 10 seconds at 3 heights (0.7, 1.45, 3 m). Air intakes were set up at 0.7m and 3m. A pump drew the air through a flow system and a telflon valve alternately switched between the two heights every 30 seconds. H2O, CO2 (LI-840A, Li-COR Biosciences) and ozone mixing ratio s (model 205, 2BTechnologies) were measured every 10 seconds. Momentum, heat, CO2 and ozone fluxes were evaluated by both EC and gradient technique. For the calculation of turbulent fluxes, TK3 algorithm (Department of Micrometeorology, University Bayreuth, Germany) was applied. We will present the measured fluxes of the two systems and assess the data quality under such non-ideal condition.

  2. Passive hyporheic flux meter - measuring nitrate flux to the reactive sites in the river bed

    NASA Astrophysics Data System (ADS)

    Kunz, Julia Vanessa; Borchardt, Dietrich; Rode, Michael; Annable, Michael

    2015-04-01

    Most European lowland rivers are afflicted by high nitrate loads, modified morphology and discharge regulations, resulting in restricted capacity to retain nitrate. In those nutrient saturated rivers, sediment bound denitrification is the only process by which nitrate is removed from the system. Despite the importance of the hyporheic zone in nutrient reduction we are lacking detailed information on the transport to and retention at those reactive sites. Passive flux meters have successfully been used to measure contaminant transport to aquifers (eg Cho and Annable 2007). Here we present how a modification of those samplers can be used to quantify nitrate flux to and intermediate storage patterns in the interstices of an agriculturally impacted river. Installed in the river bed sediments, water flux and nutrient quantities passing through the device are recorded. While the amount of water flux serves as an index for connectivity of the hyporheic zone (exchange surface-subsurface water) the nitrate flux through the device can be seen as the portion of nitrate subjected to denitrification. The generated data on solute behavior in hyporheic zones are the missing puzzle to in-stream nitrate dynamics. Complementing flume and tracer experiments our approach depicts how discharge, morphology and sediment characteristics control the denitrification rate via the connectivity of the hyporheic zone. Passive hyporheic flux meter are a novel method to directly asses the quantity of removed nitrate by an in situ experiment.

  3. Recommended Procedures for Measuring Radon Fluxes from Disposal Sites of Residual Radioactive Materials

    SciTech Connect

    Young, J. A.; Thomas, V. W.; Jackson, P. O.

    1983-03-01

    This report recommends instrumentation and methods suitable for measuring radon fluxes emanating from covered disposal sites of residual radioactive materials such as uranium mill tailings. Problems of spatial and temporal variations in radon flux are discussed and the advantages and disadvantages of several instruments are examined. A year-long measurement program and a two month measurement methodology are then presented based on the inherent difficulties of measuring average radon flux over a cover using the recommended instrumentation.

  4. Footprint prediction of scalar fluxes - Reliability and implications for airborne flux measurements over the FIFE site

    NASA Technical Reports Server (NTRS)

    Schuepp, P. H.; Desjardins, R. L.; Macpherson, J. I.; Leclerc, M. Y.

    1990-01-01

    Estimates of the location and extension of the upwind ground area that affects flux observations most directly are examined to determine the reliability of airborne versus near-ground flux measurements. The theoretical issues regarding the 'footprint' are examined, and specific observations are analyzed by studying the data over a grid regarding sensible heat, latent heat, CO2, and greenness. The grid is footprint-corrected to correlate better with independently observed surface characteristics, and an optimized footprint is developed that satisfies the relationships between the observed variables. Optimized mapping of the surface flux is given which demonstrates the importance of considering local advection to correlate airborne and ground-based flux observations. The technique is particularly applicable to situations in which significant variations in the surface flux density exist.

  5. A comparison of measured and modeled turbulent fluxes over snow based on site characteristics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sensible and latent heat and mass flux represent a significant component of the snowcover energy and mass balance in mountain environments. Though these fluxes are computed in energy balance snow models, limited measurements exist for comparison or validation in complex, mountainous sites. Sensibl...

  6. A mobile detector for measurements of the atmospheric muon flux in underground sites

    NASA Astrophysics Data System (ADS)

    Mitrica, Bogdan; Margineanu, Romul; Stoica, Sabin; Petcu, Mirel; Brancus, Iliana; Jipa, Alexandru; Lazanu, Ionel; Sima, Octavian; Haungs, Andreas; Rebel, Heinigerd; Petre, Marian; Toma, Gabriel; Saftoiu, Alexandra; Stanca, Denis; Apostu, Ana; Gomoiu, Claudia

    2011-10-01

    Muons comprise an important contribution of the natural radiation dose in air (approx. 30 nSv/h of a total dose rate of 65-130 nSv/h), as well as in underground sites even when the flux and relative contribution are significantly reduced. The flux of muons observed underground can be used as an estimator for the depth in mwe (meter water equivalent) of the underground site. The water equivalent depth is important information to devise physics experiments feasible for a specific site. A mobile detector for performing measurements of the muon flux was developed in IFIN-HH, Bucharest. Consisting of two scintillator plates (approx. 0.9 m2) which measure in coincidence, the detector is installed on a van which facilitates measurements at different locations at the surface or underground. The detector was used to determine muon fluxes at different sites in Romania. In particular, data were taken and the values of meter water equivalents were assessed for several locations at the salt mine in Slanic-Prahova, Romania. The measurements have been performed in two different galleries of the Slanic mine at different depths. In order to test the stability of the method, also measurements of the muon flux at the surface at different elevations were performed. The results were compared with predictions of Monte-Carlo simulations using the CORSIKA and MUSIC codes.

  7. Measuring and modeling near surface reflected and emitted radiation fluxes at the FIFE site

    NASA Technical Reports Server (NTRS)

    Blad, Blaine L.; Norman, John M.; Walter-Shea, Elizabeth; Starks, Patrick; Vining, Roel; Hays, Cynthia

    1988-01-01

    Research was conducted during the four Intensive Field Campaigns (IFC) of the FIFE project in 1987. The research was done on a tall grass prairie with specific measurement sites on and near the Konza Prairie in Kansas. Measurements were made to help meet the following objectives: determination of the variability in reflected and emitted radiation fluxes in selected spectral wavebands as a function of topography and vegetative community; development of techniques to account for slope and sun angle effects on the radiation fluxes; estimation of shortwave albedo and net radiation fluxes using the reflected and emitted spectral measurements described; estimation of leaf and canopy spectral properties from calculated normalized differences coupled with off-nadir measurements using inversion techniques; estimation of plant water status at several locations with indices utilizing plant temperature and other environmental parameters; and determination of relationships between estimated plant water status and measured soil water content. Results are discussed.

  8. A Carbon Flux Super Site. New Insights and Innovative Atmosphere-Terrestrial Carbon Exchange Measurements and Modeling

    SciTech Connect

    Leclerc, Monique Y.

    2014-11-17

    This final report presents the main activities and results of the project “A Carbon Flux Super Site: New Insights and Innovative Atmosphere-Terrestrial Carbon Exchange Measurements and Modeling” from 10/1/2006 to 9/30/2014. It describes the new AmeriFlux tower site (Aiken) at Savanna River Site (SC) and instrumentation, long term eddy-covariance, sodar, microbarograph, soil and other measurements at the site, and intensive field campaigns of tracer experiment at the Carbon Flux Super Site, SC, in 2009 and at ARM-CF site, Lamont, OK, and experiments in Plains, GA. The main results on tracer experiment and modeling, on low-level jet characteristics and their impact on fluxes, on gravity waves and their influence on eddy fluxes, and other results are briefly described in the report.

  9. Integration of Flux-Based Methods and Triad Principles for DNAPL Site Management, Part II: Review of Flux Measurement Methods

    EPA Science Inventory

    Managing dense nonaqueous phase liquid (DNAPL) contaminated sites continues to be among the most pressing environmental problems currently faced. One approach that has recently been investigated for use in DNAPL site characterization and remediation is mass flux (mass per unit ar...

  10. A site-level comparison of lysimeter and eddy-covariance flux measurements of evapotranspiration

    NASA Astrophysics Data System (ADS)

    Hirschi, Martin; Michel, Dominik; Lehner, Irene; Seneviratne, Sonia I.

    2015-04-01

    Accurate measurements of evapotranspiration are required for many meteorological, climatological, ecological and hydrological research applications and developments. Here we examine and compare two widely used methods to measure evapotranspiration at the site level: lysimeter-based measurements (EL) and eddy-covariance (EC) flux measurements (EEC). The analyses are based on parallel measurements at the research catchment Rietholzbach in northeastern Switzerland and focuses on the period June 2009 to December 2013. The measurements are compared on the yearly, monthly, daily, and hourly time scales, and with respect to an over 35-year lysimeter evapotranspiration time series. Overall, the two measurement techniques agree well, especially on the annual time scale. They also agree well with an independent catchment water-balance estimate of evapotranspiration. The good agreement of these independent methods emphasizes the representativeness of the lysimeter and EC measurements for the entire catchment despite their comparatively small source areas. The study also discusses different possibilities to close the energy balance of the EC flux measurements. From the comparison of EL and EEC, the closure of the energy balance according to the Bowen ratio is found to be reasonable.

  11. Lead precipitation fluxes at tropical oceanic sites determined from /sup 210/Pb measurements

    SciTech Connect

    Settle, D.M.; Patterson, C.C.; Turekian, K.K.; Cochran, J.K.

    1982-02-20

    Concentrations of lead, /sup 210/Pb, and /sup 210/Po were measured in rain selected for least influence by local sources of contamination at several tropical and subtropical islands (Enewetak; Pigeon Key, Florida; and American Samoa) and shipboard stations (near Bermuda and Tahiti). Ratios expressed as ng Pb/dpm /sup 210/Pb in rain were 250--900 for Pigeon Key (assuming 12% adsorption for /sup 210/Pb and no adsorption for lead), depending on whether the air masses containing the analyzed rain came from the Caribbean or from the continent, respectively; about 390 for the northern Sargasso Sea downwind from emissions of industrial lead in North America; 65 for Enewetak, remote from continental emissions of industrial lead in the northern hemisphere; and 14 near Tahiti, a remote location in the southern hemisphere where industrial lead emissions to the atmosphere are much less than in the northern hemisphere. (The American Samoa sample yielded a higher ratio than Tahiti; the reason for this is not clear but may be due to local Pb sources). The corresponding fluxes of lead to the oceans, based on measured or modeled /sup 210/Pb precipitation fluxes, are about 4 ng Pb/cm/sup 2/y for Tahiti, 10 for Enewetak, and 270 for the Sargasso Sea site, and between 110 to 390 at Pigeon Key.

  12. Enhancing the precision and accuracy within and among AmeriFlux site measurements

    SciTech Connect

    Law, Bev

    2013-11-25

    This is the final report for AmeriFlux QA/QC at Oregon State University. The major objective of this project is to contribute to the AmeriFlux network by continuing to build consistency in AmeriFlux measurements by addressing objectives stated in the AmeriFlux strategic plan and self evaluation, the North American Carbon Program, and the US Carbon Cycle Science Program. The project directly contributes to NACP and CCSP goals to establish an integrated, near-real time network of observations to inform climate change science.

  13. Measuring Methane Emissions from Industrial and Waste Processing Sites Using the Dual Tracer Flux Ratio Method

    NASA Astrophysics Data System (ADS)

    Herndon, S.; Floerchinger, C.; Roscioli, J. R.; Yacovitch, T.; Franklin, J. P.; Shorter, J. H.; Kolb, C. E.; Subramanian, R.; Robinson, A. L.; Molina, L. T.; Allen, D.

    2013-12-01

    In order to directly quantify facility scale methane emissions during recent multi-state measurement campaigns we have deployed novel tracer release emission characterization approaches to investigate a wide variety of facility types. The development and application of a dual tracer flux ratio methodology will be discussed. Using known release rates of two (or more) inert tracer species, downwind methane plume measurements can be used to quantify and evaluate the uncertainty in known releases and unknown emissions of methane. Results from experiments designed to challenge the experimental methodology will be presented, which determined that for downwind sampling distances in excess of ~200 m, the dual tracer release method is quite robust (<20% emission rate error) under many atmospheric conditions and landscape variations. At downwind distances less than ~200 m, the assumption of equivalent dispersion between spatially separated release points can break down. For some facilities, this can be used to distinguish and estimate the magnitude of methane emissions taking place at different spatial points within the facility. Measured emissions for selected facilities will be presented and, where possible, the accurate quantification of the episodic releases during specific activities, as well as continuous fugitive emissions are identified and will be discussed . Collaboration with on-site operators allows these measurements to inform the design and implementation of effective mitigation strategies.

  14. Measurement uncertainties in quantifying aeolian mass flux: evidence from wind tunnel and field site data.

    PubMed

    Poortinga, Ate; Keijsers, Joep G S; Maroulis, Jerry; Visser, Saskia M

    2014-01-01

    Aeolian sediment traps are widely used to estimate the total volume of wind-driven sediment transport, but also to study the vertical mass distribution of a saltating sand cloud. The reliability of sediment flux estimations from such measurements are dependent upon the specific configuration of the measurement compartments and the analysis approach used. In this study, we analyse the uncertainty of these measurements by investigating the vertical cumulative distribution and relative sediment flux derived from both wind tunnel and field studies. Vertical flux data was examined using existing data in combination with a newly acquired dataset; comprising meteorological data and sediment fluxes from six different events, using three customized catchers at Ameland beaches in northern Netherlands. Fast-temporal data collected in a wind tunnel shows that the median transport height has a scattered pattern between impact and fluid threshold, that increases linearly with shear velocities above the fluid threshold. For finer sediment, a larger proportion was transported closer to the surface compared to coarser sediment fractions. It was also shown that errors originating from the distribution of sampling compartments, specifically the location of the lowest sediment trap relative to the surface, can be identified using the relative sediment flux. In the field, surface conditions such as surface moisture, surface crusts or frozen surfaces have a more pronounced but localized effect than shear velocity. Uncertainty in aeolian mass flux estimates can be reduced by placing multiple compartments in closer proximity to the surface. PMID:25071984

  15. Measurement uncertainties in quantifying aeolian mass flux: evidence from wind tunnel and field site data

    PubMed Central

    Keijsers, Joep G.S.; Maroulis, Jerry; Visser, Saskia M.

    2014-01-01

    Aeolian sediment traps are widely used to estimate the total volume of wind-driven sediment transport, but also to study the vertical mass distribution of a saltating sand cloud. The reliability of sediment flux estimations from such measurements are dependent upon the specific configuration of the measurement compartments and the analysis approach used. In this study, we analyse the uncertainty of these measurements by investigating the vertical cumulative distribution and relative sediment flux derived from both wind tunnel and field studies. Vertical flux data was examined using existing data in combination with a newly acquired dataset; comprising meteorological data and sediment fluxes from six different events, using three customized catchers at Ameland beaches in northern Netherlands. Fast-temporal data collected in a wind tunnel shows that the median transport height has a scattered pattern between impact and fluid threshold, that increases linearly with shear velocities above the fluid threshold. For finer sediment, a larger proportion was transported closer to the surface compared to coarser sediment fractions. It was also shown that errors originating from the distribution of sampling compartments, specifically the location of the lowest sediment trap relative to the surface, can be identified using the relative sediment flux. In the field, surface conditions such as surface moisture, surface crusts or frozen surfaces have a more pronounced but localized effect than shear velocity. Uncertainty in aeolian mass flux estimates can be reduced by placing multiple compartments in closer proximity to the surface. PMID:25071984

  16. Measuring surface fluxes in CAPE

    NASA Technical Reports Server (NTRS)

    Kanemasu, E. T.; D-Shah, T.; Nie, Dalin

    1992-01-01

    Two stations (site 1612 and site 2008) were operated by the University of Georgia group from 6 July 1991 to 18 August 1991. The following data were collected continuously: surface energy fluxes (i.e., net radiation, soil heat fluxes, sensible heat flux and latent heat flux), air temperature, vapor pressure, soil temperature (at 1 cm depth), and precipitation. Canopy reflectance and light interception data were taken three times at each site between 6 July and 18 August. Soil moisture content was measured twice at each site.

  17. A New Tool for Automated Data Collection and Complete On-site Flux Data Processing for Eddy Covariance Measurements

    NASA Astrophysics Data System (ADS)

    Begashaw, I. G.; Kathilankal, J. C.; Li, J.; Beaty, K.; Ediger, K.; Forgione, A.; Fratini, G.; Johnson, D.; Velgersdyk, M.; Hupp, J. R.; Xu, L.; Burba, G. G.

    2014-12-01

    The eddy covariance method is widely used for direct measurements of turbulent exchange of gases and energy between the surface and atmosphere. In the past, raw data were collected first in the field and then processed back in the laboratory to achieve fully corrected publication-ready flux results. This post-processing consumed significant amount of time and resources, and precluded researchers from accessing near real-time final flux results. A new automated measurement system with novel hardware and software designs was developed, tested, and deployed starting late 2013. The major advancements with this automated flux system include: 1) Enabling logging high-frequency, three-dimensional wind speeds and multiple gas densities (CO2, H2O and CH4), low-frequency meteorological data, and site metadata simultaneously through a specially designed file format 2) Conducting fully corrected, real-time on-site flux computations using conventional as well as user-specified methods, by implementing EddyPro Software on a small low-power microprocessor 3) Providing precision clock control and coordinate information for data synchronization and inter-site data comparison by incorporating a GPS and Precision Time Protocol. Along with these innovations, a data management server application was also developed to chart fully corrected real-time fluxes to assist remote system monitoring, to send e-mail alerts, and to automate data QA/QC, transfer and archiving at individual stations or on a network level. Combination of all of these functions was designed to help save substantial amount of time and costs associated with managing a research site by eliminating the post-field data processing, reducing user errors and facilitating real-time access to fully corrected flux results. The design, functionality, and test results from this new eddy covariance measurement tool will be presented.

  18. Ground-Based Optical Measurements at European Flux Sites: A Review of Methods, Instruments and Current Controversies

    PubMed Central

    Balzarolo, Manuela; Anderson, Karen; Nichol, Caroline; Rossini, Micol; Vescovo, Loris; Arriga, Nicola; Wohlfahrt, Georg; Calvet, Jean-Christophe; Carrara, Arnaud; Cerasoli, Sofia; Cogliati, Sergio; Daumard, Fabrice; Eklundh, Lars; Elbers, Jan A.; Evrendilek, Fatih; Handcock, Rebecca N.; Kaduk, Joerg; Klumpp, Katja; Longdoz, Bernard; Matteucci, Giorgio; Meroni, Michele; Montagnani, Lenoardo; Ourcival, Jean-Marc; Sánchez-Cañete, Enrique P.; Pontailler, Jean-Yves; Juszczak, Radoslaw; Scholes, Bob; Martín, M. Pilar

    2011-01-01

    This paper reviews the currently available optical sensors, their limitations and opportunities for deployment at Eddy Covariance (EC) sites in Europe. This review is based on the results obtained from an online survey designed and disseminated by the Co-cooperation in Science and Technology (COST) Action ESO903—“Spectral Sampling Tools for Vegetation Biophysical Parameters and Flux Measurements in Europe” that provided a complete view on spectral sampling activities carried out within the different research teams in European countries. The results have highlighted that a wide variety of optical sensors are in use at flux sites across Europe, and responses further demonstrated that users were not always fully aware of the key issues underpinning repeatability and the reproducibility of their spectral measurements. The key findings of this survey point towards the need for greater awareness of the need for standardisation and development of a common protocol of optical sampling at the European EC sites. PMID:22164055

  19. Estimating Energy Expenditure Using Heat Flux Measured at Single Body Site

    PubMed Central

    Lyden, Kate; Swibas, Tracy; Catenacci, Victoria; Guo, Ruixin; Szuminsky, Neil; Melanson, Edward L.

    2014-01-01

    Introduction The Personal Calorie Monitor (PCM) is a portable direct calorimeter that estimates energy expenditure (EE) from measured heat flux (i.e. the sum of conductive, convective, radiative, and evaporative). Purpose The primary aim of this study was to compare EE estimated from measures of heat flux to indirect calorimetry in a thermoneutral environment (26°C). A secondary aim was to determine if exposure to ambient temperature below thermoneutral (19°C) influences the accuracy of the PCM. Methods 34 Adults (mean±SD, age = 28±5 y, body mass index = 22.9±2.6 kg.m2) were studied for 5 h in a whole-room indirect calorimeter (IC) in thermoneutral and cool conditions. Participants wore the PCM on their upper arm and completed two, 20-minute treadmill-walking bouts (0% grade, 3 mph). The remaining time was spent sedentary (e.g., watching television, using a computer). Results In thermoneutral, EE (mean (95% CI)) measured by IC and PCM was 560.0 (526.5, 593.5) and 623.3 (535.5, 711.1) kcals, respectively. In cool, EE measured by IC and PCM was 572.5 (540.9, 604.0) and 745.5 (668.1, 822.8) kcals, respectively. Under thermoneutral conditions, mean PCM minute-by-minute EE tracked closely with IC, resulting in a small, non-significant bias (63 kcals (−5.8, 132.4)). During cool conditions, mean PCM minute-by-minute EE did not track IC, resulting in a large bias (173.0 (93.9, 252.1)) (p<0.001). Conclusion This study demonstrated the validity of using measured heat flux to estimate EE. However, accuracy may be impaired in cool conditions, possibly due to excess heat loss from the exposed limbs. PMID:24811326

  20. Measuring and modeling near-surface reflected and emitted radiation fluxes at the FIFE site

    NASA Technical Reports Server (NTRS)

    Blad, Blaine L.; Walter-Shea, Elizabeth A.; Starks, Patrick J.; Vining, Roel C.; Hays, Cynthia J.; Mesarch, Mark A.

    1990-01-01

    Information is presented pertaining to the measurement and estimation of reflected and emitted components of the radiation balance. Information is included about reflectance and transmittance of solar radiation from and through the leaves of some grass and forb prairie species, bidirectional reflectance from a prairie canopy is discussed and measured and estimated fluxes are described of incoming and outgoing longwave and shortwave radiation. Results of the study showed only very small differences in reflectances and transmittances for the adaxial and abaxial surfaces of grass species in the visible and infrared wavebands, but some differences in the infrared wavebands were noted for the forbs. Reflectance from the prairie canopy changed as a function of solar and view zenith angles in the solar principal plane with definite asymmetry about nadir. The surface temperature of prairie canopies was found to vary by as much as 5 C depending on view zenith and azimuth position and on the solar azimuth. Aerodynamic temperature calculated from measured sensible heat fluxes ranged from 0 to 3 C higher than nadir-viewed temperatures. Models were developed to estimate incoming and reflected shortwave radiation from data collected with a Barnes Modular Multiband Radiometer. Several algorithms for estimating incoming longwave radiation were evaluated and compared to actual measures of that parameter. Net radiation was calculated using the estimated components of the shortwave radiation streams, determined from the algorithms developed, and from the longwave radiation streams provided by the Brunt, modified Deacon, and the Stefan-Boltzmann models. Estimates of net radiation were compared to measured values and found to be within the measurement error of the net radiometers used in the study.

  1. Controls on the seasonality of photosynthesis across the Amazon basin -A cross-site analysis of eddy flux tower measurements from the Brasil flux network

    NASA Astrophysics Data System (ADS)

    Restrepo-Coupe, N.; Saleska, S. R.; Da Rocha, H. R.

    2009-04-01

    The Amazon Basin is categorized as a terrestrial biogeochemical "hotspot" where climate change and deforestation can trigger substantial changes on atmospheric CO. However, model skill at predicting seasonality of photosynthetic metabolism and ecosystem productivity in the Amazon is limited. To enhance our understanding of these processes, we investigated the seasonal and spatial patterns of Amazonian forest photosynthetic activity by integrating data from a network of ground-based eddy flux towers in Brazil established as part of the ‘Large-Scale Biosphere Atmosphere Experiment in Amazonia' project. We present the results of a simple model of leaf-flush for two central Amazon BrasilFlux sites, based on the eddy covariance estimates of canopy photosynthetic capacity (Pc) and measured canopy structure parameters. We found that in contrast to studies of Amazon evapotranspiration, which is highly correlated with available energy, Amazon ecosystem photosynthetic flux surprisingly showed no simple relationship with measures of available energy. We hypothesize that the seasonality of Amazon photosynthesis is controlled by the interaction of adaptive mechanisms (which biologically determine photosynthetic capacity through leaf flush and litter fall seasonality) and sunlight availability (which determines the fraction of photosynthetic capacity utilized). Equatorial climates advantage vegetation that can grow leaves in the dry season, when surface solar radiation peaks, but southerly sites may not because of reduced seasonality in surface radiation.

  2. Evaluation and application of anion exchange resins to measure groundwater uranium flux at a former uranium mill site.

    PubMed

    Stucker, Valerie; Ranville, James; Newman, Mark; Peacock, Aaron; Cho, Jaehyun; Hatfield, Kirk

    2011-10-15

    Laboratory tests and a field validation experiment were performed to evaluate anion exchange resins for uranium sorption and desorption in order to develop a uranium passive flux meter (PFM). The mass of uranium sorbed to the resin and corresponding masses of alcohol tracers eluted over the duration of groundwater installation are then used to determine the groundwater and uranium contaminant fluxes. Laboratory based batch experiments were performed using Purolite A500, Dowex 21K and 21K XLT, Lewatit S6328 A resins and silver impregnated activated carbon to examine uranium sorption and extraction for each material. The Dowex resins had the highest uranium sorption, followed by Lewatit, Purolite and the activated carbon. Recoveries from all ion exchange resins were in the range of 94-99% for aqueous uranium in the environmentally relevant concentration range studied (0.01-200 ppb). Due to the lower price and well-characterized tracer capacity, Lewatit S6328 A was used for field-testing of PFMs at the DOE UMTRA site in Rifle, CO. The effect on the flux measurements of extractant (nitric acid)/resin ratio, and uranium loading were investigated. Higher cumulative uranium fluxes (as seen with concentrations>1 ug U/gram resin) yielded more homogeneous resin samples versus lower cumulative fluxes (<1 ug U/gram resin), which caused the PFM to have areas of localized concentration of uranium. Resin homogenization and larger volume extractions yield reproducible results for all levels of uranium fluxes. Although PFM design can be improved to measure flux and groundwater flow direction, the current methodology can be applied to uranium transport studies. PMID:21798572

  3. BOREAS RSS-17 Xylem Flux Density Measurements at the SSA-OBS Site

    NASA Technical Reports Server (NTRS)

    Zimmerman, Reiner; Way, JoBea; McDonald, Kyle; Nickeson, Jaime (Editor); Hall, Forrest G. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    As part of its efforts to determine environmental and phenological states from radar imagery, the Boreal Ecosystem-Atmosphere Study (BOREAS) Remote Sensing Science (RSS)-17 team collected in situ tree xylem flow measurements for one growing season on five Picea mariana (black spruce) trees. The data were collected to obtain information on the temporal and spatial variability in water uptake by trees in the Southern Study Area-Old Black Spruce (SSA-OBS) stand in the BOREAS SSA. Temporally, the data were collected in 30-minute intervals for 120 days from 31 May 1994 until 27 September 1994. The data are stored in tabular ASCII files. The xylem flux data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  4. Eddy Covariance Measurements of Methane Flux at Remote Sites with New Low-Power Lightweight Fast Gas Analyzer

    NASA Astrophysics Data System (ADS)

    Xu, Liukang; Burba, George; Schedlbauer, Jessica; Zona, Donatella; McDermitt, Dayle K.; Anderson, Tyler; Oberbauer, Steven; Oechel, Walter; Komissarov, Anatoly; Riensche, Brad

    2010-05-01

    Majority of natural methane production happens at remote unpopulated areas in ecosystems with little or no infrastructure or easily available grid power, such as arctic and boreal wetlands, tropical mangroves, etc. Present approaches for direct measurements of CH4 fluxes rely on fast closed-path analyzers, which have to work under significantly reduced pressures, and require powerful pumps and grid power. Power and labor demands may be reasons why CH4 flux is often measured at locations with good infrastructure and grid power, and not with high CH4 production. An instrument was developed to allow Eddy Covariance measurements of CH4 flux with power consumption 30-150 times below presently available technologies. This instrument, LI-7700, uses <10W of power, and can easily be run on solar panel, or with small portable generator, while present technologies require 300-1500 Watts of the grid power. The proposed extremely low-power technology would allows placing methane Eddy Covariance stations in the middle of the source (wetland, rice paddy, forest, etc.) in the absence of the grid power. This could significantly expand the Eddy Covariance CH4 flux measurements coverage, and possibly, significantly improve the budget estimates of world CH4 emissions and budget. Various prototypes of the LI-7700 were field-tested for three seasons at the remote site in middle of Everglades National Park (Florida, USA) using solar panels, at three stationary and several mobile sites during three seasons at remote Arctic wetlands near Barrow (Alaska, USA), in the tropical mangroves near La Paz (Mexico) using portable generator, and in bare agricultural field near Mead (Nebraska, USA) during 2005 through 2010. Latest data on CH4 concentration, co-spectra and fluxes, and latest details of instrumental design are examined in this presentation. Overall, hourly methane fluxes ranged from near-zero at night to about 4 mg m-2 h-1 in midday in arctic tundra. Observed fluxes were within the

  5. Heat flux measurements

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.; Weikle, Donald H.

    1989-01-01

    A new automated, computer controlled heat flux measurement facility is described. Continuous transient and steady-state surface heat flux values varying from about 0.3 to 6 MW/sq m over a temperature range of 100 to 1200 K can be obtained in the facility. An application of this facility is the development of heat flux gauges for continuous fast transient surface heat flux measurement on turbine blades operating in space shuttle main engine turbopumps. The facility is useful for durability testing at fast temperature transients.

  6. Can we distinguish autotrophic respiration from heterotrophic respiration in a field site using high temporal resolution CO2 flux measurements?

    NASA Astrophysics Data System (ADS)

    Biro, Beatrice; Berger, Sina; Praetzel, Leandra; Blodau, Christian

    2016-04-01

    The processes behind C-cycling in peatlands are important to understand for assessing the vulnerability of peatlands as carbon sinks under changing climate conditions. Especially boreal peatlands are likely to underlie strong alterations in the future. It is expected that C-pools that are directly influenced by vegetation and water table fluctuations can be easily destabilized. The CO2 efflux through respiration underlies autotrophic and heterotrophic processes that show different feedbacks on changing environmental conditions. In order to understand the respiration fluxes better for more accurate modelling and prognoses, the determination of the relative importance of different respiration sources is necessary. Earlier studies used e.g. exfoliation experiments, incubation experiments or modelling approaches to estimate the different respiration sources for the total ecosystem respiration (Reco). To further the understanding in this topic, I want to distinguish autotrophic and heterotrophic respiration using high temporal resolution measurements. The study site was selected along a hydrological gradient in a peatland in southern Ontario (Canada) and measurements were conducted from May to September 2015 once per month. Environmental controls (water table, soil temperature and soil moisture) that effect the respiration sources were recorded. In my study I used a Li-COR 6400XT and a Los Gatos greenhouse gas analyzer (GGA). Reco was determined by chamber flux measurements with the GGA, while simultaneously CO2 respiration measurements on different vegetation compartments like roots, leaves and mosses were conducted using the Li-COR 6400XT. The difference between Reco and autotrophic respiration equals heterotrophic respiration. After the measurements, the vegetation plots were harvested and separated for all compartments (leaves, roots, mosses, soil organic matter), dried and weighed. The weighted respiration rates from all vegetation compartments sum up to

  7. Eddy correlation measurements of methane fluxes using a tunable diode laser at the Kinosheo Lake tower site during the Northern Wetlands Study (NOWES)

    NASA Technical Reports Server (NTRS)

    Edwards, G. C.; Neumann, H. H.; Den Hartog, G.; Thurtell, G. W.; Kidd, G.

    1994-01-01

    As part of the Canadian Northern Wetlands Study (NOWES) measurements of methane flux were made at the Kinosheo Lake tower site for a 1-month period during the 1990 summer intensive. The measurements were made with a diode-laser-based methane sensor using the eddy correlation technique. Measurements of the methane fluxes were made at two levels, 5 or 18 m. Approximately 900 half-hour average methane flux measurements were obtained. Weak temporal and diurnal trends were observed in the data. Fluxes averaged over the study period showed an overall methane emission of 16 mg CH4 m(exp -2)/d with a daytime average of 20 mg CH4 m(exp -2)/d and a nighttime average of 9 mg CH4 m(exp -2)/d. The effect of emission footprint was evident in the data. A strong relationship between the daily average methane flux and wet bog temperature at 20-cm depth was observed.

  8. Inter-annual comparison of measured turbulent fluxes over snow at a wind-sheltered and wind-exposed site using eddy covariance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Measurements of sensible and latent heat fluxes using eddy covariance (EC) instrumentation over snow in complex terrain have become more common in the past decade. Analysis of EC measurements at two sites, wind-exposed and wind-protected, for three consecutive years is presented. The analysis focu...

  9. Inter-annual comparision of measured turbulent fluxes over snow at a wind-sheltered and wind-exposed site using eddy covariance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Measurements of sensible and latent heat fluxes using eddy covariance (EC) instrumentation over snow in complex terrain have become more common in the past decade. Analysis of EC measurements at two sites, wind-exposed and wind-protected, for three consecutive years is presented. The analysis focuse...

  10. Eddy correlation measurements of methane fluxes using a tunable diode laser at the Kinosheo Lake tower site during the Northern Wetlands Study (NOWES)

    SciTech Connect

    Edwards, G.C.; Kidd, G.; Thurtell, G.W.; Neumann, H.H.; Hartog, G. den

    1994-01-20

    As part of the Canadian Northern Wetlands Study (NOWES) measurements of methane flux were made at the Kinosheo Lake tower site for a 1-month period during the 1990 summer intensive. The measurements were made with a diode-laser-based methane sensor using the eddy correlation technique. Measurements of the methane fluxes were made at two levels, 5 or 18 m. Approximately 900 half-hour average methane flux measurements were obtained. Weak temporal and diurnal trends were observed in the data. Fluxes averaged over the study period showed an overall methane emission of 16 mg CH{sub 4} m{sup {minus}2} d{sup {minus}1} with a daytime average of 20 mg CH{sub 4} m{sup {minus}2} d{sup {minus}1} and a nighttime average of 9 mg CH{sub 4} m{sup {minus}2} d{sup {minus}1}. The effect of emission footprint was evident in the data. A strong relationship between the daily average methane flux and wet bog temperature at 20-cm depth was observed. 41 refs., 6 figs.

  11. Combined measurement and modeling of the hydrological impact of hydraulic redistribution using CLM4.5 at eight AmeriFlux sites

    DOE PAGESBeta

    Fu, Congsheng; Wang, Guiling; Goulden, Michael L.; Scott, Russell L.; Bible, Kenneth; G. Cardon, Zoe

    2016-05-17

    Effects of hydraulic redistribution (HR) on hydrological, biogeochemical, and ecological processes have been demonstrated in the field, but the current generation of standard earth system models does not include a representation of HR. Though recent studies have examined the effect of incorporating HR into land surface models, few (if any) have done cross-site comparisons for contrasting climate regimes and multiple vegetation types via the integration of measurement and modeling. Here, we incorporated the HR scheme of Ryel et al. (2002) into the NCAR Community Land Model Version 4.5 (CLM4.5), and examined the ability of the resulting hybrid model to capture themore » magnitude of HR flux and/or soil moisture dynamics from which HR can be directly inferred, to assess the impact of HR on land surface water and energy budgets, and to explore how the impact may depend on climate regimes and vegetation conditions. Eight AmeriFlux sites with contrasting climate regimes and multiple vegetation types were studied, including the Wind River Crane site in Washington State, the Santa Rita Mesquite savanna site in southern Arizona, and six sites along the Southern California Climate Gradient. HR flux, evapotranspiration (ET), and soil moisture were properly simulated in the present study, even in the face of various uncertainties. Our cross-ecosystem comparison showed that the timing, magnitude, and direction (upward or downward) of HR vary across ecosystems, and incorporation of HR into CLM4.5 improved the model-measurement matches of evapotranspiration, Bowen ratio, and soil moisture particularly during dry seasons. Lastly, our results also reveal that HR has important hydrological impact in ecosystems that have a pronounced dry season but are not overall so dry that sparse vegetation and very low soil moisture limit HR.« less

  12. Combined measurement and modeling of the hydrological impact of hydraulic redistribution using CLM4.5 at eight AmeriFlux sites

    NASA Astrophysics Data System (ADS)

    Fu, Congsheng; Wang, Guiling; Goulden, Michael L.; Scott, Russell L.; Bible, Kenneth; Cardon, Zoe G.

    2016-05-01

    Effects of hydraulic redistribution (HR) on hydrological, biogeochemical, and ecological processes have been demonstrated in the field, but the current generation of standard earth system models does not include a representation of HR. Though recent studies have examined the effect of incorporating HR into land surface models, few (if any) have done cross-site comparisons for contrasting climate regimes and multiple vegetation types via the integration of measurement and modeling. Here, we incorporated the HR scheme of Ryel et al. (2002) into the NCAR Community Land Model Version 4.5 (CLM4.5), and examined the ability of the resulting hybrid model to capture the magnitude of HR flux and/or soil moisture dynamics from which HR can be directly inferred, to assess the impact of HR on land surface water and energy budgets, and to explore how the impact may depend on climate regimes and vegetation conditions. Eight AmeriFlux sites with contrasting climate regimes and multiple vegetation types were studied, including the Wind River Crane site in Washington State, the Santa Rita Mesquite savanna site in southern Arizona, and six sites along the Southern California Climate Gradient. HR flux, evapotranspiration (ET), and soil moisture were properly simulated in the present study, even in the face of various uncertainties. Our cross-ecosystem comparison showed that the timing, magnitude, and direction (upward or downward) of HR vary across ecosystems, and incorporation of HR into CLM4.5 improved the model-measurement matches of evapotranspiration, Bowen ratio, and soil moisture particularly during dry seasons. Our results also reveal that HR has important hydrological impact in ecosystems that have a pronounced dry season but are not overall so dry that sparse vegetation and very low soil moisture limit HR.

  13. Heat-Flux-Measuring Facility

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.; Weikle, Donald H.

    1990-01-01

    Apparatus simulates conditions in turbine engines. Automated facility generates and measures transient and steady-state heat fluxes at flux densities from 0.3 to 6 MW/m(Sup2) and temperatures from 100 to 1,200 K. Positioning arm holds heat-flux gauge at focal point of arc lamp. Arm previously chilled gauge in liquid nitrogen in Dewar flask. Cooling water flows through lamp to heat exchanger. Used to develop heat-flux gauges for turbine blades and to test materials for durability under rapidly changing temperatures.

  14. Radiation fluxes at the FIFE site

    NASA Technical Reports Server (NTRS)

    Walter-Shea, Elizabeth A.; Blad, Blaine L.; Zara, Pedro; Vining, Roel; Hays, Cynthia J.; Mesarch, Mark A.

    1993-01-01

    The main objective of the International Satellite Land Surface Climatology Project (ISLSCP) has been stated as 'the development of techniques that may be applied to satellite observations of the radiation reflected and emitted from the Earth to yield quantitative information concerning land surface climatological conditions'. The major field study, FIFE (the First ISLSCP Field Experiment), was conducted in 1987-89 to accomplish this objective. Four intensive field campaigns (IFC's) were carried out in 1987 and one in 1989. Factors contributing to observed reflected radiation from the FIFE site must be understood before the radiation observed by satellites can be used to quantify surface processes. Our last report (Walter-Shea et al., 1992b) focused on slope effects on incoming and outgoing shortwave radiation and net radiation from data collected in 1989. We report here on the final analysis of the slope data as well as results from thermal radiation studies conducted during the FIFE experiment. The specific areas reported are the following: (1) analysis of slope effects on measured reflectance values and estimates of surface albedo; (2) using remotely-measured surface temperatures as a means of estimating sensible heat flux from the Konza Prairie; (3) extracting canopy temperatures from remotely-measured composite surface temperatures; (4) modeling the measured composite temperature of partially vegetated surfaces; and (5) estimating gap distribution in partially vegetated surfaces from reflectance measurements.

  15. Eddy Correlation Flux Measurement System Handbook

    SciTech Connect

    Cook, D. R.

    2016-01-01

    The eddy correlation (ECOR) flux measurement system provides in situ, half-hour measurements of the surface turbulent fluxes of momentum, sensible heat, latent heat, and carbon dioxide (CO2) (and methane at one Southern Great Plains extended facility (SGP EF) and the North Slope of Alaska Central Facility (NSA CF). The fluxes are obtained with the eddy covariance technique, which involves correlation of the vertical wind component with the horizontal wind component, the air temperature, the water vapor density, and the CO2 concentration. The instruments used are: • a fast-response, three-dimensional (3D) wind sensor (sonic anemometer) to obtain the orthogonal wind components and the speed of sound (SOS) (used to derive the air temperature) • an open-path infrared gas analyzer (IRGA) to obtain the water vapor density and the CO2 concentration, and • an open-path infrared gas analyzer (IRGA) to obtain methane density and methane flux at one SGP EF and at the NSA CF. The ECOR systems are deployed at the locations where other methods for surface flux measurements (e.g., energy balance Bowen ratio [EBBR] systems) are difficult to employ, primarily at the north edge of a field of crops. A Surface Energy Balance System (SEBS) has been installed collocated with each deployed ECOR system in SGP, NSA, Tropical Western Pacific (TWP), ARM Mobile Facility 1 (AMF1), and ARM Mobile Facility 2 (AMF2). The surface energy balance system consists of upwelling and downwelling solar and infrared radiometers within one net radiometer, a wetness sensor, and soil measurements. The SEBS measurements allow the comparison of ECOR sensible and latent heat fluxes with the energy balance determined from the SEBS and provide information on wetting of the sensors for data quality purposes. The SEBS at one SGP and one NSA site also support upwelling and downwelling PAR measurements to qualify those two locations as Ameriflux sites.

  16. Shortwave flux profile analysis at the Cabauw BSRN site

    NASA Astrophysics Data System (ADS)

    Wang, P.; Baltink, H. Klein; Knap, W. H.; Stammes, P.

    2013-05-01

    The vertical distribution of the shortwave flux in the atmosphere is important for understanding the energy budget and the validation of climate models. We calculated shortwave flux profiles for cloudy cases by using the Doubling-Adding KNMI radiative transfer model with water vapour and cloud liquid water profiles derived from the Integrated Profiling Technique (IPT). As an example, we will show the approach for 3 March 2012. The calculated downward flux at the surface for this day compares well with measurements made at the Cabauw Baseline Surface Radiation Network (BSRN) site (51.97°N, 4.93°E), the Netherlands.

  17. Using model analyses and surface-atmosphere exchange measurements from the Howland AmeriFlux Site in Maine, USA, to improve understanding of forest ecosystem C cycling

    SciTech Connect

    Hollinger, David Y.; Davidson, Eric A.; Richardson, Andrew D.; Dail, D. B.; Scott, N.

    2013-03-25

    Summary of research carried out under Interagency Agreement DE-AI02-07ER64355 with the USDA Forest Service at the Howland Forest AmeriFlux site in central Maine. Includes a list of publications resulting in part or whole from this support.

  18. Measurements of OVOC fluxes by eddy covariance using a proton-transfer-reaction mass spectrometer - method development at a coastal site

    NASA Astrophysics Data System (ADS)

    Yang, M.; Beale, R.; Smyth, T.; Blomquist, B.

    2013-07-01

    We present here vertical fluxes of oxygenated volatile organic compounds (OVOCs) measured with eddy covariance (EC) during the period of March to July 2012 near the southwest coast of the United Kingdom. The performance of the proton-transfer-reaction mass spectrometer (PTR-MS) for flux measurement is characterized, with additional considerations given to the homogeneity and stationarity assumptions required by EC. Observed mixing ratios and fluxes of OVOCs (specifically methanol, acetaldehyde, and acetone) vary significantly with time of day and wind direction. Higher mixing ratios and fluxes of acetaldehyde and acetone are found in the daytime and from the direction of a forested park, most likely due to light-driven emissions from terrestrial plants. Methanol mixing ratio and flux do not demonstrate consistent diel variability, suggesting sources in addition to plants. We estimate air-sea exchange and photochemical rates of these compounds, which are compared to measured vertical fluxes. For acetaldehyde, the mean (1σ) mixing ratio of 0.13 (0.02) ppb at night may be maintained by oceanic emission, while photochemical destruction outpaces production during the day. Air-sea exchange and photochemistry are probably net sinks of methanol and acetone in this region. Their nighttime mixing ratios of 0.46 (0.20) and 0.39 (0.08) ppb appear to be affected more by terrestrial emissions and long-distance transport, respectively.

  19. BOREAS TGB-1 CH4 Concentration and Flux Data from NSA Tower Sites

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Conrad, Sara K. (Editor); Crill, Patrick; Varner, Ruth K.

    2000-01-01

    The BOREAS TGB-1 team made numerous measurements of trace gas concentrations and fluxes at various NSA sites. This data set contains half-hourly averages of ambient methane (CH4) measurements and calculated fluxes for the NSA-Fen in 1996 and the NSA-BP and NSA-OJP tower sites in 1994. The purpose of this study was to determine the CH4 flux from the study area by measuring ambient CH 4 concentrations. This flux can then be compared to the chamber flux measurements taken at the same sites. The data are provided in tabular ASCII files.

  20. Spatial Representativeness of Flux Tower Sites: A Comparison Between Tower and Aircraft Eddy-Covariance Fluxes

    NASA Astrophysics Data System (ADS)

    Caulton, D.; Shepson, P. B.; Munger, J. W.; Hollinger, D. Y.; Saatchi, S. S.; Moghaddam, M.; Stirm, B. H.

    2013-12-01

    Development and testing of regional and global scale ecosystem models rely on analysis of data from flux towers that have footprint scales (~1 km2) that are much smaller and contain relatively homogeneous land use types. This approach tends to assume that the patchwork approach appropriately represents regions that are, especially on larger scale, much more heterogeneous in terms of land cover, soil moisture, topography and climatology, etc. While aircraft platforms provide snapshot views of NEE, they have access to essentially any environment and can access difficult and heterogeneous environments. We used an instrumented aircraft platform equipped with a 50 Hz wind probe and GPS/INS and a 10 Hz Picarro CO2/H2O analyzer to measure eddy covariance fluxes over larger spatial scales (~20 km2) over and near Howland Forest, ME, Harvard Forest, MA and Duke Forest, NC, as part of the Airborne Observatory of Subcanopy and Subsurface (AirMOSS) mission campaigns. Flux measurements were conducted for varying land cover types in these forests in July, 2012 and June-August, 2013. Measured fluxes will be compared with tower fluxes from each of the three sites to investigate the quality of the aircraft data, and the ability to assess local-regional scale variability and the spatial representativeness of these towers, with respect to the larger scale fluxes. In addition, soil moisture data from a NASA G-III aircraft will be used to investigate spatial representativeness and the soil moisture dependence of the fluxes.

  1. AmeriFlux Measurement Network: Science Team Research

    SciTech Connect

    Law, B E

    2012-12-12

    Research involves analysis and field direction of AmeriFlux operations, and the PI provides scientific leadership of the AmeriFlux network. Activities include the coordination and quality assurance of measurements across AmeriFlux network sites, synthesis of results across the network, organizing and supporting the annual Science Team Meeting, and communicating AmeriFlux results to the scientific community and other users. Objectives of measurement research include (i) coordination of flux and biometric measurement protocols (ii) timely data delivery to the Carbon Dioxide Information and Analysis Center (CDIAC); and (iii) assurance of data quality of flux and ecosystem measurements contributed by AmeriFlux sites. Objectives of integration and synthesis activities include (i) integration of site data into network-wide synthesis products; and (ii) participation in the analysis, modeling and interpretation of network data products. Communications objectives include (i) organizing an annual meeting of AmeriFlux investigators for reporting annual flux measurements and exchanging scientific information on ecosystem carbon budgets; (ii) developing focused topics for analysis and publication; and (iii) developing data reporting protocols in support of AmeriFlux network goals.

  2. Carbon Dioxide Flux Measurement Systems (CO2Flux) Handbook

    SciTech Connect

    Fischer, M

    2005-01-01

    The Southern Great Plains (SGP) carbon dioxide flux (CO2 flux) measurement systems provide half-hour average fluxes of CO2, H2O (latent heat), and sensible heat. The fluxes are obtained by the eddy covariance technique, which computes the flux as the mean product of the vertical wind component with CO2 and H2O densities, or estimated virtual temperature. A three-dimensional sonic anemometer is used to obtain the orthogonal wind components and the virtual (sonic) temperature. An infrared gas analyzer is used to obtain the CO2 and H2O densities. A separate sub-system also collects half-hour average measures of meteorological and soil variables from separate 4-m towers.

  3. Latent Heat in Soil Heat Flux Measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The surface energy balance includes a term for soil heat flux. Soil heat flux is difficult to measure because it includes conduction and convection heat transfer processes. Accurate representation of soil heat flux is an important consideration in many modeling and measurement applications. Yet, the...

  4. Apparatus for measuring a flux of neutrons

    DOEpatents

    Stringer, James L.

    1977-01-01

    A flux of neutrons is measured by disposing a detector in the flux and applying electronic correlation techniques to discriminate between the electrical signals generated by the neutron detector and the unwanted interfering electrical signals generated by the incidence of a neutron flux upon the cables connecting the detector to the electronic measuring equipment at a remote location.

  5. AmeriFlux US-Bo2 Bondville (companion site)

    SciTech Connect

    Bernacchi, Carl

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-Bo2 Bondville (companion site). Site Description - Located 400m north of Tilden Meyer's site and planted with opposite crop in corn/soybean rotation

  6. Neutrino flux predictions for cross section measurements

    SciTech Connect

    Hartz, Mark

    2015-05-15

    Experiments that measure neutrino interaction cross sections using accelerator neutrino sources require a prediction of the neutrino flux to extract the interaction cross section from the measured neutrino interaction rate. This article summarizes methods of estimating the neutrino flux using in-situ and ex-situ measurements. The application of these methods by current and recent experiments is discussed.

  7. Hydrothermal Fluxes at the Turtle Pits Vent Site, southern MAR

    NASA Astrophysics Data System (ADS)

    Köhler, J.; Walter, M.; Mertens, C.; Sültenfuß, J.; Rhein, M.

    2009-04-01

    The Turtle Pits vent fields are located in a north-south orientated rift valley at the Mid-Atlantic Ridge (MAR) near 5oS. The site consists of three known hydrothermal fields: Turtle Pits, Comfortless Cove, and Red Lion. Data collected during a Meteor cruise in May 2006 and a L' Atalante cruise in January 2008 are used to calculate the total emission of volume, heat, and helium of the site. The data sets consist of vertical profiles and towed transsects of temperature, salinity, and turbidity, as well as direct velocity measurements with a lowered acoustic Doppler current profiler (LADCP) and water samples for Helium isotope analysis. Vent fluid samples for noble gas analysis where taken with an ROV. The particle plume is confined to the rift valley since the depth of the valley exceeds the rise height of the plume. Therefore the fluxes of heat and volume can be estimated from the helium fluxes at the vent sites in comparison with the horizontal helium transport in the valley. The comparison of the 3He concentration measured south of the hydrothermal vents with the 3He signal north of the hydrothermal vents suggests a rather strong northward flow. This is confirmed by the tide corrected velocities observed with the LADCP during the Meteor cruise. The northward volume transport has been calculated using the local bathymetry and tide corrected velocities from the Meteor cruise. In combination with the 3He concentrations and an average 3He end member concentration a flux of 900 l/s is estimated, which corresponds to a heat flux of 450 MW. The rise height of the particle plume estimated from the turbidity data combined with the known background stratification yields an estimate of the total flux of the hydrothermal vents which is one order of magnitude lower.

  8. Eddy covariance measurements of methane fluxes over grazed native and improved prairies in Oklahoma

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although several studies have reported eddy covariance (EC) measurements at several tallgrass prairie sites to investigate the dynamics of carbon and water vapor fluxes, the EC measurements of methane (CH4) fluxes over grazed tallgrass prairie sites are lacking. CH4 fluxes were measured during the 2...

  9. Pyrolytic graphite gauge for measuring heat flux

    NASA Technical Reports Server (NTRS)

    Bunker, Robert C. (Inventor); Ewing, Mark E. (Inventor); Shipley, John L. (Inventor)

    2002-01-01

    A gauge for measuring heat flux, especially heat flux encountered in a high temperature environment, is provided. The gauge includes at least one thermocouple and an anisotropic pyrolytic graphite body that covers at least part of, and optionally encases the thermocouple. Heat flux is incident on the anisotropic pyrolytic graphite body by arranging the gauge so that the gauge surface on which convective and radiative fluxes are incident is perpendicular to the basal planes of the pyrolytic graphite. The conductivity of the pyrolytic graphite permits energy, transferred into the pyrolytic graphite body in the form of heat flux on the incident (or facing) surface, to be quickly distributed through the entire pyrolytic graphite body, resulting in small substantially instantaneous temperature gradients. Temperature changes to the body can thereby be measured by the thermocouple, and reduced to quantify the heat flux incident to the body.

  10. Diamagnetic flux measurement in Aditya tokamak

    SciTech Connect

    Kumar, Sameer; Jha, Ratneshwar; Lal, Praveen; Hansaliya, Chandresh; Gopalkrishna, M. V.; Kulkarni, Sanjay; Mishra, Kishore

    2010-12-15

    Measurements of diamagnetic flux in Aditya tokamak for different discharge conditions are reported for the first time. The measured diamagnetic flux in a typical discharge is less than 0.6 mWb and therefore it has required careful compensation for various kinds of pick-ups. The hardware and software compensations employed in this measurement are described. We introduce compensation of a pick-up due to plasma current of less than 20 kA in short duration discharges, in which plasma pressure gradient is supposed to be negligible. The flux measurement during radio frequency heating is also presented in order to validate compensation.

  11. Water, energy and carbon flux observations from ARS watersheds and agro-ecosystem experimental sites

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Several ARS watershed locations and long term experimental/monitoring sites have been measuring water, energy and carbon fluxes using the eddy covariance technique. Several sites have been collecting flux data for 5 to 10 years, while other locations have recently started a monitoring program. The...

  12. Uncertainties Associated with Flux Measurements Due to Heterogeneous Contaminant Distributions

    EPA Science Inventory

    Mass flux and mass discharge measurements at contaminated sites have been applied to assist with remedial management, and can be divided into two broad categories: point-scale measurement techniques and pumping methods. Extrapolation across un-sampled space is necessary when usi...

  13. Spatially averaged heat flux and convergence measurements at the ARM regional flux experiment

    SciTech Connect

    Porch, W.; Barnes, F.; Buchwald, M.; Clements, W.; Cooper, D.; Hoard, D. ); Doran, C.; Hubbe, J.; Shaw, W. ); Coulter, R.; Martin, T. ); Kunkel, K. )

    1991-01-01

    Cloud formation and its relation to climate change is the greatest weakness in current numerical climate models. Surface heat flux in some cases causes clouds to form and in other to dissipate and the differences between these cases are subtle enough to make parameterization difficult in a numerical model. One of the goals of the DOE Atmospheric Radiation Measurement program is to make long term measurements at representative sites to improve radiation and cloud formation parameterization. This paper compares spatially averaged optical measurements of heat flux and convergence with a goal of determining how point measurements of heat fluxes scale up to the larger scale used for climate modeling. It was found that the various optical techniques used in this paper compared well with each other and with independent measurements. These results add confidence that spatially averaging optical techniques can be applied to transform point measurements to the larger scales needed for mesoscale and climate modeling. 10 refs., 6 figs. (MHB)

  14. Eddy Correlation Flux Measurement System (ECOR) Handbook

    SciTech Connect

    Cook, DR

    2011-01-31

    The eddy correlation (ECOR) flux measurement system provides in situ, half-hour measurements of the surface turbulent fluxes of momentum, sensible heat, latent heat, and carbon dioxide (CO2) (and methane at one Southern Great Plains extended facility (SGP EF) and the North Slope of Alaska Central Facility (NSA CF). The fluxes are obtained with the eddy covariance technique, which involves correlation of the vertical wind component with the horizontal wind component, the air temperature, the water vapor density, and the CO2 concentration.

  15. FLUXNET. Database of fluxes, site characteristics, and flux-community information

    SciTech Connect

    Olson, R. J.; Holladay, S. K.; Cook, R. B.; Falge, E.; Baldocchi, D.; Gu, L.

    2004-02-28

    FLUXNET is a “network of regional networks” created by international scientists to coordinate regional and global analysis of observations from micrometeorological tower sites. The flux tower sites use eddy covariance methods to measure the exchanges of carbon dioxide (CO2), water vapor, and energy between terrestrial ecosystems and the atmosphere. FLUXNET’S goals are to aid in understanding the mechanisms controlling the exchanges of CO2, water vapor, and energy across a range of time (0.5 hours to annual periods) and space scales. FLUXNET provides an infrastructure for the synthesis and analysis of world-wide, long-term flux data compiled from various regional flux networks. Information compiled by the FLUXNET project is being used to validate remote sensing products associated with the National Aeronautics and Space Administration (NASA) Terra and Aqua satellites. FLUXNET provides access to ground information for validating estimates of net primary productivity, and energy absorption that are being generated by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors. In addition, this information is also used to develop and validate ecosystem models.

  16. AmeriFlux US-MOz Missouri Ozark Site

    SciTech Connect

    Gu, Lianhong

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-MOz Missouri Ozark Site. Site Description - The site is located in the University of Missouri Baskett Wildlife Research area, situated in the Ozark region of central Missouri. The site is uniquely located in the ecologically important transitional zone between the central hardwood region and the central grassland region of the US. The land has been publically owned since the 1930s, and is on a land tract that was forested with the same dominant species before settlement in the early 1800s.

  17. AmeriFlux Measurement Component (AMC) Handbook

    SciTech Connect

    Reichl, K.; Biraud, S. C.

    2016-01-01

    An AMC system was installed at the Atmospheric Radiation Measurement (ARM) Climate Research Facility’s North Slope Alaska (NSA) Barrow site, also known as NSA C1 at the ARM Data Archive, in August 2012. A second AMC system was installed at the third ARM Mobile Facility deployment at Oliktok Point, also known as NSA M1. This in situ system consists of 12 combination soil temperature and volumetric water content (VWC) reflectometers and one set of upwelling and downwelling PAR sensors, all deployed within the fetch of the Eddy Correlation Flux Measurement System. Soil temperature and VWC sensors placed at two depths (10 and 30 cm below the vegetation layer) at six locations (or microsites) allow soil property inhomogeneity to be monitored across a landscape. The soil VWC and temperature sensors used at NSA C1 are the Campbell Scientific CS650L and the sensors at NSA M1 use the Campbell Scientific CS655. The two sensors are nearly identical in function, and vendor specifications are based on the CS650 unless otherwise stated.

  18. Contaminant discharge and uncertainty estimates from passive flux meter measurements

    NASA Astrophysics Data System (ADS)

    Klammler, Harald; Hatfield, Kirk; GuimarãEs da Luz, Joana AngéLica; Annable, Michael D.; Newman, Mark; Cho, Jaehyun; Peacock, Aaron; Stucker, Valerie; Ranville, James; Cabaniss, Steven A.; Rao, P. S. C.

    2012-02-01

    The passive flux meter (PFM) measures local cumulative water and contaminant fluxes at an observation well. Conditional stochastic simulation accounting for both spatial correlation and data skewness is introduced to interpret passive flux meter observations in terms of probability distributions of discharges across control planes (transects) of wells. An estimator of the effective number of independent data is defined and applied in the development of two significantly simpler approximate methods for estimating discharge distributions. One method uses a transformation of the t statistic to account for data skewness and the other method is closely related to the classic bootstrap. The approaches are demonstrated with passive flux meter data from two field sites (a trichloroethylene [TCE] plume at Ft. Lewis, WA, and a uranium plume at Rifle, CO). All methods require that the flux heterogeneity is sufficiently represented by the data and maximum differences in discharge quantile estimates between methods are ˜7%.

  19. Gas flux estimates at the LUSI eruption site.

    NASA Astrophysics Data System (ADS)

    Sciarra, Alessandra; Mazzini, Adriano; Husein, Alwii; Hadi J., Soffian; Etiope, Giuseppe

    2015-04-01

    The spectacular Indonesian Lusi mud eruption started in May 2006 following to a 6.3 M earthquake striking the island of Java (Mazzini et al., 2007). Previous studies investigated the mechanisms of reactivation of the Watukosek fault system that crosses Lusi locality (Mazzini et al., 2009) and continues to the NE of Java. Results show that the quake triggered lateral movement of this strike-slip system resulting in several aligned eruptions sites including Lusi. Geochemical studies of the erupted fluids reveal a mantle signature and point to a connection with the neighboring Arjuno-Welirang volcanic complex (Mazzini et al., 2012) indicating that Lusi is a sedimentary hosted geothermal system. In order to estimate the amount of gas that is being released around the Lusi crater (~7 km2), we recently conducted a survey of over 300 stations (CO2 and CH4 flux measurements) using a closed-chamber flux-meter system and collected gas samples to analyze the composition of the seeps. In addition 20 soil gas concentrations were collected using a steel probe driven into the ground to a depth of 0.7-0.8 m to avoid the major influence of meteorological variables. Results show that the highest CO2 flux is present along the NE-SW oriented Watukosek fault (with peaks up to 400 g/m2day) and along the ~E-W oriented Siring antithetic fault (with peaks up to 110 g/m2day). The pools have overall a CH4-dominated composition, while the dry fault-related fractures are CO2-dominated which is in agreement with higher recorded temperatures at these sites. Flux measurements in the seeping pools reveal that CO2 flux is an order of magnitude higher than that measured in the fault zones, and two order of magnitude for CH4 flux. C02 and CH4 microseepage is occurring in significant amount throughput the mud-covered area with average values of 297 and 95 g/m2day, respectively. CH4 flux shows the highest values in the W and NW sector of the Lusi area, while CO2 flux highlights the presence of three

  20. Experimental flux measurements on a network scale

    SciTech Connect

    Schwender, J.

    2011-10-11

    Metabolic flux is a fundamental property of living organisms. In recent years, methods for measuring metabolic flux in plants on a network scale have evolved further. One major challenge in studying flux in plants is the complexity of the plant's metabolism. In particular, in the presence of parallel pathways in multiple cellular compartments, the core of plant central metabolism constitutes a complex network. Hence, a common problem with the reliability of the contemporary results of {sup 13}C-Metabolic Flux Analysis in plants is the substantial reduction in complexity that must be included in the simulated networks; this omission partly is due to limitations in computational simulations. Here, I discuss recent emerging strategies that will better address these shortcomings.

  1. Fundamentals of heat measurement. [heat flux transducers

    NASA Technical Reports Server (NTRS)

    Gerashchenko, O. A.

    1979-01-01

    Various methods and devices for obtaining experimental data on heat flux density over wide ranges of temperature and pressure are examined. Laboratory tests and device fabrication details are supplemented by theoretical analyses of heat-conduction and thermoelectric effects, providing design guidelines and information relevant to further research and development. A theory defining the measure of correspondence between transducer signal and the measured heat flux is established for individual (isolated) heat flux transducers subject to space and time-dependent loading. An analysis of the properties of stacked (series-connected) transducers of various types (sandwich-type, plane, and spiral) is used to derive a similarity theory providing general governing relationships. The transducers examined are used in 36 types of derivative devices involving direct heat loss measurements, heat conduction studies, radiation pyrometry, calorimetry in medicine and industry and nuclear reactor dosimetry.

  2. Radiative flux measurements in the troposphere

    NASA Technical Reports Server (NTRS)

    Valero, F. P. J.; Gore, W. J. Y.; Giver, L. P. M.

    1982-01-01

    A new airborne radiometric system with a time resolution as high as 60 msec has been designed for measuring radiative fluxes in the atmosphere. To verify the instrument performance, the solar constant at the top of the atmosphere has been calculated using the radiative flux densities measured in the troposphere, and the result obtained has been found to agree with the standard value to within 4%. Total heating rates of 0.175 and 0.377 K/h have been determined for hazy and foggy atmospheres, respectively, and aerosol heating rates of 0.065 and 0.235 K/h have been deduced from the total heating rates.

  3. Dual neutron flux/temperature measurement sensor

    DOEpatents

    Mihalczo, John T.; Simpson, Marc L.; McElhaney, Stephanie A.

    1994-01-01

    Simultaneous measurement of neutron flux and temperature is provided by a single sensor which includes a phosphor mixture having two principal constituents. The first constituent is a neutron sensitive 6LiF and the second is a rare-earth activated Y203 thermophosphor. The mixture is coated on the end of a fiber optic, while the opposite end of the fiber optic is coupled to a light detector. The detected light scintillations are quantified for neutron flux determination, and the decay is measured for temperature determination.

  4. Intercomparison of gas analyzers for methane flux measurements

    NASA Astrophysics Data System (ADS)

    Haapanala, S.; Rinne, J.; Vesala, T.

    2010-12-01

    Four gas analyzers, capable of measuring methane concentration at a response time necessary for eddy covariance flux measurements, were operated in parallel for about six months between March and August 2010. Their reliability, need of maintenance, user friendliness, data coverage, and data quality were evaluated. The primary aim of this campaign was to provide an instrumentation suggestion for the European Research Infrastructure ICOS (Integrated Carbon Observation System). The instruments used were TGA100A (Campbell Scientific Inc.), RMT-200 (Los Gatos Research Inc.) , G1301-f (Picarro Inc.), and LI-7700 (Li-Cor Inc.). The last one, LI-7700, was a prototype of a later commercialized open path analyzer. The other instruments were closed path analyzers. The measurement site is an oligotrophic open fen Siikaneva, located in southern Finland. The site provides spatially quite uniform methane flux within the footprint. The methane flux rises in the spring, peaks in early August and falls down during the autumn. This provides excellent opportunity to study the performance of the analyzers at different CH4 flux levels from near zero up to about 5 mg m-2 h-1. The preliminary results show great similarity among the instruments in both concentrations and fluxes. Detailed numbers of the measurement characteristics will be provided later. The reliability and need of maintenance are difficult to evaluate quantitatively during that short period.

  5. AmeriFlux US-MRf Mary's River (Fir) site

    DOE Data Explorer

    Law, Bev [Oregon State University

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-MRf Mary's River (Fir) site. Site Description - The Marys River Fir site is part of the "Synthesis of Remote Sensing and Field Observations to Model and Understand Disturbance and Climate Effects on the Carbon Balance of Oregon and Northern California (ORCA)". Located in the western region of Oregon the Marys River site represents the western extent of the climate gradient that spans eastward into the semi-arid basin of central Oregon. The sites that make up the eastern extent of the ORCA climate gradient is the Metolius site network (US-Me1, US-ME2, US-ME4, US-Me5) all of which are part of the TERRA PNW project at Oregon State University.

  6. Instruments for measuring radiant thermal fluxes

    NASA Technical Reports Server (NTRS)

    Gerashenko, O. A.; Sazhina, S. A.

    1974-01-01

    An absolute two-sided radiometer, designed on the principle of replacing absorbed radiant energy with electrical energy, is described. The sensitive element of the detector is a thermoelectric transducer of thermal flux. The fabrication technology, methods of measurement, technical characteristics, and general operation of the instrument are presented.

  7. AmeriFlux US-Wrc Wind River Crane Site

    SciTech Connect

    Bible, Ken; Wharton, Sonia

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-Wrc Wind River Crane Site. Site Description - Wind River Field Station flux tower site is located in the T.T. Munger Research Area of the Wind River Ranger District in the Gifford Pinchot National Forest. Protected since 1926, the T.T. Munger Research Natural Area (RNA) is administered by the USDA Forest Service Pacific Northwest Research Station and Gifford Pinchot National Forest. The Douglas-fir/western hemlock dominant stand is approximately 500 years old and represents end points of several ecological gradients including age, biomass, structural complexity, and density of the dominant overstory species. A complete stand replacement fire, approximately 450-500 years ago, resulted in the initial establishment. No significant disturbances have occurred since the fire aside from those confined to small groups of single trees, such as overturn from high wind activity and mechanical damage from winter precipitation.

  8. Interplanetary magnetic flux - Measurement and balance

    NASA Technical Reports Server (NTRS)

    Mccomas, D. J.; Gosling, J. T.; Phillips, J. L.

    1992-01-01

    A new method for determining the approximate amount of magnetic flux in various solar wind structures in the ecliptic (and solar rotation) plane is developed using single-spacecraft measurements in interplanetary space and making certain simplifying assumptions. The method removes the effect of solar wind velocity variations and can be applied to specific, limited-extent solar wind structures as well as to long-term variations. Over the 18-month interval studied, the ecliptic plane flux of coronal mass ejections was determined to be about 4 times greater than that of HFDs.

  9. Plasma momentum meter for momentum flux measurements

    DOEpatents

    Zonca, Fulvio; Cohen, Samuel A.; Bennett, Timothy; Timberlake, John R.

    1993-01-01

    Invention comprises an instrument in which momentum flux onto a biasable target plate is transferred via a suspended quartz tube onto a sensitive force transducer--a capacitance-type pressure gauge. The transducer is protected from thermal damage, arcing and sputtering, and materials used in the target and pendulum are electrically insulating, rigid even at elevated temperatures, and have low thermal conductivity. The instrument enables measurement of small forces (10.sup.-5 to 10.sup.3 N) accompanied by high heat fluxes which are transmitted by energetic particles with 10's of eV of kinetic energy in a intense magnetic field and pulsed plasma environment.

  10. Distributed Sensible Heat Flux Measurements for Wireless Sensor Networks

    NASA Astrophysics Data System (ADS)

    Huwald, H.; Brauchli, T.; Lehning, M.; Higgins, C. W.

    2015-12-01

    The sensible heat flux component of the surface energy balance is typically computed using eddy covariance or two point profile measurements while alternative approaches such as the flux variance method based on convective scaling has been much less explored and applied. Flux variance (FV) certainly has a few limitations and constraints but may be an interesting and competitive method in low-cost and power limited wireless sensor networks (WSN) with the advantage of providing spatio-temporal sensible heat flux over the domain of the network. In a first step, parameters such as sampling frequency, sensor response time, and averaging interval are investigated. Then we explore the applicability and the potential of the FV method for use in WSN in a field experiment. Low-cost sensor systems are tested and compared against reference instruments (3D sonic anemometers) to evaluate the performance and limitations of the sensors as well as the method with respect to the standard calculations. Comparison experiments were carried out at several sites to gauge the flux measurements over different surface types (gravel, grass, water) from the low-cost systems. This study should also serve as an example of spatially distributed sensible heat flux measurements.

  11. The AmeriFlux Network of Long-Term CO{sub 2} Flux Measurement Stations: Methodology and Intercomparability

    SciTech Connect

    Hollinger, D. Y.; Evans, R. S.

    2003-05-20

    A portable flux measurement system has been used within the AmeriFlux network of CO{sub 2} flux measurement stations to enhance the comparability of data collected across the network. No systematic biases were observed in a comparison between portable system and site H, LE, or CO{sub 2} flux values although there were biases observed between the portable system and site measurement of air temperature and PPFD. Analysis suggests that if values from two stations differ by greater than 26% for H, 35% for LE, and 32% for CO{sub 2} flux they are likely to be significant. Methods for improving the intercomparability of the network are also discussed.

  12. Estimating terrestrial uranium and thorium by antineutrino flux measurements

    PubMed Central

    Dye, Stephen T.; Guillian, Eugene H.

    2008-01-01

    Uranium and thorium within the Earth produce a major portion of terrestrial heat along with a measurable flux of electron antineutrinos. These elements are key components in geophysical and geochemical models. Their quantity and distribution drive the dynamics, define the thermal history, and are a consequence of the differentiation of the Earth. Knowledge of uranium and thorium concentrations in geological reservoirs relies largely on geochemical model calculations. This article describes the methods and criteria to experimentally determine average concentrations of uranium and thorium in the continental crust and in the mantle by using site-specific measurements of the terrestrial antineutrino flux. Optimal, model-independent determinations involve significant exposures of antineutrino detectors remote from nuclear reactors at both a midcontinental and a midoceanic site. This would require major, new antineutrino detection projects. The results of such projects could yield a greatly improved understanding of the deep interior of the Earth. PMID:18172211

  13. Novel Sensor for the In Situ Measurement of Uranium Fluxes

    SciTech Connect

    Hatfield, Kirk

    2015-02-10

    The goal of this project was to develop a sensor that incorporates the field-tested concepts of the passive flux meter to provide direct in situ measures of flux for uranium and groundwater in porous media. Measurable contaminant fluxes [J] are essentially the product of concentration [C] and groundwater flux or specific discharge [q ]. The sensor measures [J] and [q] by changes in contaminant and tracer amounts respectively on a sorbent. By using measurement rather than inference from static parameters, the sensor can directly advance conceptual and computational models for field scale simulations. The sensor was deployed in conjunction with DOE in obtaining field-scale quantification of subsurface processes affecting uranium transport (e.g., advection) and transformation (e.g., uranium attenuation) at the Rifle IFRC Site in Rifle, Colorado. Project results have expanded our current understanding of how field-scale spatial variations in fluxes of uranium, groundwater and salient electron donor/acceptors are coupled to spatial variations in measured microbial biomass/community composition, effective field-scale uranium mass balances, attenuation, and stability. The coupling between uranium, various nutrients and micro flora can be used to estimate field-scale rates of uranium attenuation and field-scale transitions in microbial communities. This research focuses on uranium (VI), but the sensor principles and design are applicable to field-scale fate and transport of other radionuclides. Laboratory studies focused on sorbent selection and calibration, along with sensor development and validation under controlled conditions. Field studies were conducted at the Rifle IFRC Site in Rifle, Colorado. These studies were closely coordinated with existing SBR (formerly ERSP) projects to complement data collection. Small field tests were conducted during the first two years that focused on evaluating field-scale deployment procedures and validating sensor performance under

  14. Observational biases in flux magnification measurements

    NASA Astrophysics Data System (ADS)

    Hildebrandt, H.

    2016-02-01

    Flux magnification is an interesting complement to shear-based lensing measurements, especially at high redshift where sources are harder to resolve. One measures either changes in the source density (magnification bias) or in the shape of the flux distribution (e.g. magnitude shift). The interpretation of these measurements relies on theoretical estimates of how the observables change under magnification. Here, we present simulations to create multiband photometric mock catalogues of Lyman-break galaxies in a CFHTLenS (Canada France Hawaii Telescope Lensing Survey)-like survey that include several observational effects that can change these relations, making simple theoretical estimates unusable. In particular, we show how the magnification bias can be affected by photometric noise, colour selection, and dust extinction. We find that a simple measurement of the slope of the number-counts is not sufficient for the precise interpretation of virtually all observations of magnification bias. We also explore how sensitive the shift in the mean magnitude of a source sample in different photometric bands is to magnification including the same observational effects. Again we find significant deviations from simple analytical estimates. We also discover a wavelength-dependence of the magnitude-shift effect when applied to a colour-selected noisy source sample. Such an effect can mimic the reddening by dust in the lens. It has to be disentangled from the dust extinction before the magnitude shift/colour-excess can be used to measure the distribution of either dark matter or extragalactic dust. Using simulations like the ones presented here these observational effects can be studied and eventually removed from observations making precise measurements of flux magnification possible.

  15. AmeriFlux US-ARc ARM Southern Great Plains control site- Lamont

    SciTech Connect

    Torn, Margaret

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-ARc ARM Southern Great Plains control site- Lamont. Site Description - The ARM SGP Control site is located in the native tallgrass prairies of the USDA Grazinglands Research Laboratory near El Reno, OK. One of two adjacent 35 ha plots with identical towers, measurements at the US-ARc unburned plot are used as the experimental control. The second plot, US-Arb, was burned on 2005/03/08. Measurement comparisons between the control and burn plot are used to address questions regarding the effects of burning activities on carbon fluxes. The region evaded burning activities for at least 15 years. Current disturbances consist of only light grazing activities.

  16. Comparison of surface fluxes and conductances at two contrasting sites within the FIFE area

    NASA Technical Reports Server (NTRS)

    Stewart, J. B.; Verma, S. B.

    1992-01-01

    Surface flux measurements from two contrasting sites within the FIFE study area are analyzed. The seasonal variation of midday latent heat fluxes and surface conductances at the two sites was found to be very similar even though the ratio of their average total leaf area indices was greater than two to one. Concurrent measurements made at another six flat sites within the FIFE area confirmed the independence of latent heat flux with respect to leaf area index. The surface conductance stress function related to specific humidity deficit was the same for the two sites, whereas the solar radiation stress function showed a difference of 30 percent at a solar radiation input of 300 W/sq m and the soil moisture stress function showed a difference of 16 percent when half the extractable soil moisture had been taken up. However, when the stress functions were combined to determine the surface conductance, these differences virtually canceled out.

  17. A mobile detector for measurements of the atmospheric muon flux

    NASA Astrophysics Data System (ADS)

    Mitrica, B.; Brancus, I. M.; Margineanu, R.; Petcu, M.; Dima, M.; Sima, O.; Haungs, A.; Rebel, H.; Petre, M.; Toma, G.; Saftoiu, A.; Apostu, A.

    2011-04-01

    Measurements of the underground atmospheric muon flux are important in order to determine accurately the overburden in mwe (meter water equivalent) of an underground laboratory for appreciating which kind of experiments are feasible for that location. Slanic- Prohava is one of the 7 possible locations for the European large underground experiment LAGUNA (Large Apparatus studying Grand Unification and Neutrino Astrophysics). A mobile device consisting of 2 scintillator plates (≍0.9 m2, each) one above the other and measuring in coincidence, was set-up for determining the muon flux. The detector it is installed on a van which facilitates measurements on different positions at the surface or in the underground and it is in operation since autumn 2009. The measurements of muon fluxes presented in this contribution have been performed in the underground salt mine Slanic-Prahova, Romania, where IFIN-HH has built a low radiation level laboratory, and at the surface on different sites of Romania, at different elevations from 0 m a.s.l up to 655 m a.s.l. Based on our measurements we can say that Slanic site is a feasible location for LAGUNA in Unirea salt mine at a water equivalent depth of 600 mwe. The results have been compared with Monte-Carlo simulations performed with the simulation codes CORSIKA and MUSIC.

  18. Comparison of measured and modeled radiation, heat and water vapor fluxes: FIFE pilot study

    NASA Technical Reports Server (NTRS)

    Blad, Blaine L.; Hubbard, Kenneth G.; Verma, Shashi B.; Starks, Patrick; Norman, John M.; Walter-Shea, Elizabeth

    1987-01-01

    The feasibility of using radio frequency receivers to collect data from automated weather stations to model fluxes of latent heat, sensible heat, and radiation using routine weather data collected by automated weather stations was tested and the estimated fluxes were compared with fluxes measured over wheat. The model Cupid was used to model the fluxes. Two or more automated weather stations, interrogated by radio frequency and other means, were utilized to examine some of the climatic variability of the First ISLSCP (International Satellite Land-Surface Climatology Project) Field Experiment (FIFE) site, to measure and model reflected and emitted radiation streams from various locations at the site and to compare modeled latent and sensible heat fluxes with measured values. Some bidirectional reflected and emitted radiation data were collected from 23 locations throughout the FIFE site. Analysis of these data along with analysis of the measured sensible and latent heat fluxes is just beginning.

  19. ACCURACY OF SOIL HEAT FLUX MEASUREMENTS MADE WITH FLUX PLATES OF CONTRASTING PROPERTIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Flux plate measurements of soil heat flux (G) may include significant errors unless the plates are carefully installed and known errors accounted for. The objective of this research was to quantify potential errors in G when using soil heat flux plates of contrasting designs. Five flux plates with...

  20. Low Permafrost Methane Emissions from Arctic Airborne Flux Measurements

    NASA Astrophysics Data System (ADS)

    Sachs, T.; Serafimovich, A.; Metzger, S.; Kohnert, K.; Hartmann, J.

    2014-12-01

    One of the most pressing questions with regard to climate feedback processes in a warming Arctic is the regional-scale greenhouse gas release from Arctic permafrost areas. Ground-based eddy covariance (EC) measurements provide continuous in-situ observations of the surface-atmosphere exchange of energy and matter. However, these observations are rare in the Arctic permafrost zone and site selection is bound by logistical constraints among others. Consequently, these observations cover only small areas that are not necessarily representative of the region of interest. Airborne measurements can overcome this limitation by covering distances of hundreds of kilometers over time periods of a few hours. The Airborne Measurements of Methane Fluxes (AIRMETH) campaigns are designed to quantitatively and spatially explicitly address this question. During the AIRMETH-2012 and AIRMETH-2013 campaigns aboard the research aircraft POLAR 5 we measured turbulent exchange of energy, methane, and (in 2013) carbon dioxide along thousands of kilometers covering the North Slope of Alaska and the Mackenzie Delta, Canada. Time-frequency (wavelet) analysis, footprint modeling, and machine learning techniques are used to (i) determine spatially resolved turbulence statistics, fluxes, and contributions of biophysical surface properties, and (ii) extract regionally valid functional relationships between environmental drivers and the observed fluxes. These environmental response functions (ERF) are used to explain spatial flux patterns and - if drivers are available in temporal resolution - allow for spatio-temporal scaling of the observations. This presentation will focus on 2012 methane fluxes on the North Slope of Alaska and the relevant processes on the regional scale and provide an updated 100 m resolution methane flux map of the North Slope of Alaska.

  1. An ecosystem-scale perspective of the net land methanol flux. Synthesis of micrometeorological flux measurements

    SciTech Connect

    Wohlfahrt, G.; Amelynck, C.; Ammann, C.; Arneth, A.; Bamberger, I.; Goldstein, A. H.; Gu, L.; Guenther, A.; Hansel, A.; Heinesch, B.; Holst, T.; Hörtnagl, L.; Karl, T.; Laffineur, Q.; Neftel, A.; McKinney, K.; Munger, J. W.; Pallardy, S. G.; Schade, G. W.; Seco, R.; Schoon, N.

    2015-07-09

    Methanol is the second most abundant volatile organic compound in the troposphere and plays a significant role in atmospheric chemistry. While there is consensus about the dominant role of living plants as the major source and the reaction with OH as the major sink of methanol, global methanol budgets diverge considerably in terms of source/sink estimates, reflecting uncertainties in the approaches used to model and the empirical data used to separately constrain these terms. Here we compiled micrometeorological methanol flux data from eight different study sites and reviewed the corresponding literature in order to provide a first cross-site synthesis of the terrestrial ecosystem-scale methanol exchange and present an independent data-driven view of the land–atmosphere methanol exchange. Our study shows that the controls of plant growth on production, and thus the methanol emission magnitude, as well as stomatal conductance on the hourly methanol emission variability, established at the leaf level, hold across sites at the ecosystem level. Unequivocal evidence for bi-directional methanol exchange at the ecosystem scale is presented. Deposition, which at some sites even exceeds methanol emissions, represents an emerging feature of ecosystem-scale measurements and is likely related to environmental factors favouring the formation of surface wetness. Methanol may adsorb to or dissolve in this surface water and eventually be chemically or biologically removed from it. Management activities in agriculture and forestry are shown to increase local methanol emission by orders of magnitude; however, they are neglected at present in global budgets. While contemporary net land methanol budgets are overall consistent with the grand mean of the micrometeorological methanol flux measurements, we caution that the present approach of simulating methanol emission and deposition separately is prone to opposing systematic errors and does not allow for full advantage to be taken of

  2. An ecosystem-scale perspective of the net land methanol flux. Synthesis of micrometeorological flux measurements

    DOE PAGESBeta

    Wohlfahrt, G.; Amelynck, C.; Ammann, C.; Arneth, A.; Bamberger, I.; Goldstein, A. H.; Gu, L.; Guenther, A.; Hansel, A.; Heinesch, B.; et al

    2015-07-09

    Methanol is the second most abundant volatile organic compound in the troposphere and plays a significant role in atmospheric chemistry. While there is consensus about the dominant role of living plants as the major source and the reaction with OH as the major sink of methanol, global methanol budgets diverge considerably in terms of source/sink estimates, reflecting uncertainties in the approaches used to model and the empirical data used to separately constrain these terms. Here we compiled micrometeorological methanol flux data from eight different study sites and reviewed the corresponding literature in order to provide a first cross-site synthesis ofmore » the terrestrial ecosystem-scale methanol exchange and present an independent data-driven view of the land–atmosphere methanol exchange. Our study shows that the controls of plant growth on production, and thus the methanol emission magnitude, as well as stomatal conductance on the hourly methanol emission variability, established at the leaf level, hold across sites at the ecosystem level. Unequivocal evidence for bi-directional methanol exchange at the ecosystem scale is presented. Deposition, which at some sites even exceeds methanol emissions, represents an emerging feature of ecosystem-scale measurements and is likely related to environmental factors favouring the formation of surface wetness. Methanol may adsorb to or dissolve in this surface water and eventually be chemically or biologically removed from it. Management activities in agriculture and forestry are shown to increase local methanol emission by orders of magnitude; however, they are neglected at present in global budgets. While contemporary net land methanol budgets are overall consistent with the grand mean of the micrometeorological methanol flux measurements, we caution that the present approach of simulating methanol emission and deposition separately is prone to opposing systematic errors and does not allow for full advantage to be

  3. An ecosystem-scale perspective of the net land methanol flux: synthesis of micrometeorological flux measurements

    PubMed Central

    Wohlfahrt, G.; Amelynck, C.; Ammann, C.; Arneth, A.; Bamberger, I.; Goldstein, A. H.; Gu, L.; Guenther, A.; Hansel, A.; Heinesch, B.; Holst, T.; Hörtnagl, L.; Karl, T.; Laffineur, Q.; Neftel, A.; McKinney, K.; Munger, J. W.; Pallardy, S. G.; Schade, G. W.; Seco, R.; Schoon, N.

    2015-01-01

    Methanol is the second most abundant volatile organic compound in the troposphere and plays a significant role in atmospheric chemistry. While there is consensus about the dominant role of living plants as the major source and the reaction with OH as the major sink of methanol, global methanol budgets diverge considerably in terms of source/sink estimates reflecting uncertainties in the approaches used to model, and the empirical data used to separately constrain these terms. Here we compiled micrometeorological methanol flux data from eight different study sites and reviewed the corresponding literature in order to provide a first cross-site synthesis of the terrestrial ecosystem-scale methanol exchange and present an independent data-driven view of the land–atmosphere methanol exchange. Our study shows that the controls of plant growth on the production, and thus the methanol emission magnitude, and stomatal conductance on the hourly methanol emission variability, established at the leaf level, hold across sites at the ecosystem-level. Unequivocal evidence for bi-directional methanol exchange at the ecosystem scale is presented. Deposition, which at some sites even exceeds methanol emissions, represents an emerging feature of ecosystem-scale measurements and is likely related to environmental factors favouring the formation of surface wetness. Methanol may adsorb to or dissolve in this surface water and eventually be chemically or biologically removed from it. Management activities in agriculture and forestry are shown to increase local methanol emission by orders of magnitude; they are however neglected at present in global budgets. While contemporary net land methanol budgets are overall consistent with the grand mean of the micrometeorological methanol flux measurements, we caution that the present approach of simulating methanol emission and deposition separately is prone to opposing systematic errors and does not allow taking full advantage of the rich

  4. An ecosystem-scale perspective of the net land methanol flux: synthesis of micrometeorological flux measurements

    NASA Astrophysics Data System (ADS)

    Wohlfahrt, G.; Amelynck, C.; Ammann, C.; Arneth, A.; Bamberger, I.; Goldstein, A. H.; Gu, L.; Guenther, A.; Hansel, A.; Heinesch, B.; Holst, T.; Hörtnagl, L.; Karl, T.; Laffineur, Q.; Neftel, A.; McKinney, K.; Munger, J. W.; Pallardy, S. G.; Schade, G. W.; Seco, R.; Schoon, N.

    2015-01-01

    Methanol is the second most abundant volatile organic compound in the troposphere and plays a significant role in atmospheric chemistry. While there is consensus about the dominant role of living plants as the major source and the reaction with OH as the major sink of methanol, global methanol budgets diverge considerably in terms of source/sink estimates reflecting uncertainties in the approaches used to model, and the empirical data used to separately constrain these terms. Here we compiled micrometeorological methanol flux data from eight different study sites and reviewed the corresponding literature in order to provide a first cross-site synthesis of the terrestrial ecosystem-scale methanol exchange and present an independent data-driven view of the land-atmosphere methanol exchange. Our study shows that the controls of plant growth on the production, and thus the methanol emission magnitude, and stomatal conductance on the hourly methanol emission variability, established at the leaf level, hold across sites at the ecosystem-level. Unequivocal evidence for bi-directional methanol exchange at the ecosystem scale is presented. Deposition, which at some sites even exceeds methanol emissions, represents an emerging feature of ecosystem-scale measurements and is likely related to environmental factors favouring the formation of surface wetness. Methanol may adsorb to or dissolve in this surface water and eventually be chemically or biologically removed from it. Management activities in agriculture and forestry are shown to increase local methanol emission by orders of magnitude; they are however neglected at present in global budgets. While contemporary net land methanol budgets are overall consistent with the grand mean of the micrometeorological methanol flux measurements, we caution that the present approach of simulating methanol emission and deposition separately is prone to opposing systematic errors and does not allow taking full advantage of the rich

  5. An ecosystem-scale perspective of the net land methanol flux: synthesis of micrometeorological flux measurements

    NASA Astrophysics Data System (ADS)

    Wohlfahrt, G.; Amelynck, C.; Ammann, C.; Arneth, A.; Bamberger, I.; Goldstein, A. H.; Gu, L.; Guenther, A.; Hansel, A.; Heinesch, B.; Holst, T.; Hörtnagl, L.; Karl, T.; Laffineur, Q.; Neftel, A.; McKinney, K.; Munger, J. W.; Pallardy, S. G.; Schade, G. W.; Seco, R.; Schoon, N.

    2015-07-01

    Methanol is the second most abundant volatile organic compound in the troposphere and plays a significant role in atmospheric chemistry. While there is consensus about the dominant role of living plants as the major source and the reaction with OH as the major sink of methanol, global methanol budgets diverge considerably in terms of source/sink estimates, reflecting uncertainties in the approaches used to model and the empirical data used to separately constrain these terms. Here we compiled micrometeorological methanol flux data from eight different study sites and reviewed the corresponding literature in order to provide a first cross-site synthesis of the terrestrial ecosystem-scale methanol exchange and present an independent data-driven view of the land-atmosphere methanol exchange. Our study shows that the controls of plant growth on production, and thus the methanol emission magnitude, as well as stomatal conductance on the hourly methanol emission variability, established at the leaf level, hold across sites at the ecosystem level. Unequivocal evidence for bi-directional methanol exchange at the ecosystem scale is presented. Deposition, which at some sites even exceeds methanol emissions, represents an emerging feature of ecosystem-scale measurements and is likely related to environmental factors favouring the formation of surface wetness. Methanol may adsorb to or dissolve in this surface water and eventually be chemically or biologically removed from it. Management activities in agriculture and forestry are shown to increase local methanol emission by orders of magnitude; however, they are neglected at present in global budgets. While contemporary net land methanol budgets are overall consistent with the grand mean of the micrometeorological methanol flux measurements, we caution that the present approach of simulating methanol emission and deposition separately is prone to opposing systematic errors and does not allow for full advantage to be taken of

  6. Untangling Autophagy Measurements: All Fluxed Up

    PubMed Central

    Gottlieb, Roberta A.; Andres, Allen M.; Sin, Jon; Taylor, David

    2015-01-01

    Autophagy is an important physiological process in the heart, and alterations in autophagic activity can exacerbate or mitigate injury during various pathological processes. Methods to assess autophagy have changed rapidly as the field of research has expanded. As with any new field, methods and standards for data analysis and interpretation evolve as investigators acquire experience and insight. The purpose of this review is to summarize current methods to measure autophagy, selective mitochondrial autophagy (mitophagy), and autophagic flux. We will examine several published studies where confusion arose in in data interpretation, in order to illustrate the challenges. Finally we will discuss methods to assess autophagy in vivo and in patients. PMID:25634973

  7. Measuring fast calcium fluxes in cardiomyocytes.

    PubMed

    Golebiewska, Urszula; Scarlata, Suzanne

    2011-01-01

    Cardiomyocytes have multiple Ca(2+) fluxes of varying duration that work together to optimize function (1,2). Changes in Ca(2+) activity in response to extracellular agents is predominantly regulated by the phospholipase Cβ- Gα(q;) pathway localized on the plasma membrane which is stimulated by agents such as acetylcholine (3,4). We have recently found that plasma membrane protein domains called caveolae(5,6) can entrap activated Gα(q;)(7). This entrapment has the effect of stabilizing the activated state of Gα(q;) and resulting in prolonged Ca(2+) signals in cardiomyocytes and other cell types(8). We uncovered this surprising result by measuring dynamic calcium responses on a fast scale in living cardiomyocytes. Briefly, cells are loaded with a fluorescent Ca(2+) indicator. In our studies, we used Ca(2+) Green (Invitrogen, Inc.) which exhibits an increase in fluorescence emission intensity upon binding of calcium ions. The fluorescence intensity is then recorded for using a line-scan mode of a laser scanning confocal microscope. This method allows rapid acquisition of the time course of fluorescence intensity in pixels along a selected line, producing several hundreds of time traces on the microsecond time scale. These very fast traces are transferred into excel and then into Sigmaplot for analysis, and are compared to traces obtained for electronic noise, free dye, and other controls. To dissect Ca(2+) responses of different flux rates, we performed a histogram analysis that binned pixel intensities with time. Binning allows us to group over 500 traces of scans and visualize the compiled results spatially and temporally on a single plot. Thus, the slow Ca(2+) waves that are difficult to discern when the scans are overlaid due to different peak placement and noise, can be readily seen in the binned histograms. Very fast fluxes in the time scale of the measurement show a narrow distribution of intensities in the very short time bins whereas longer Ca(2+) waves

  8. Reducing measurement scale mismatch to improve surface energy flux estimation

    NASA Astrophysics Data System (ADS)

    Iwema, Joost; Rosolem, Rafael; Rahman, Mostaquimur; Blyth, Eleanor; Wagener, Thorsten

    2016-04-01

    Soil moisture importantly controls land surface processes such as energy and water partitioning. A good understanding of these controls is needed especially when recognizing the challenges in providing accurate hyper-resolution hydrometeorological simulations at sub-kilometre scales. Soil moisture controlling factors can, however, differ at distinct scales. In addition, some parameters in land surface models are still often prescribed based on observations obtained at another scale not necessarily employed by such models (e.g., soil properties obtained from lab samples used in regional simulations). To minimize such effects, parameters can be constrained with local data from Eddy-Covariance (EC) towers (i.e., latent and sensible heat fluxes) and Point Scale (PS) soil moisture observations (e.g., TDR). However, measurement scales represented by EC and PS still differ substantially. Here we use the fact that Cosmic-Ray Neutron Sensors (CRNS) estimate soil moisture at horizontal footprint similar to that of EC fluxes to help answer the following question: Does reduced observation scale mismatch yield better soil moisture - surface fluxes representation in land surface models? To answer this question we analysed soil moisture and surface fluxes measurements from twelve COSMOS-Ameriflux sites in the USA characterized by distinct climate, soils and vegetation types. We calibrated model parameters of the Joint UK Land Environment Simulator (JULES) against PS and CRNS soil moisture data, respectively. We analysed the improvement in soil moisture estimation compared to uncalibrated model simulations and then evaluated the degree of improvement in surface fluxes before and after calibration experiments. Preliminary results suggest that a more accurate representation of soil moisture dynamics is achieved when calibrating against observed soil moisture and further improvement obtained with CRNS relative to PS. However, our results also suggest that a more accurate

  9. Flux measurements using the BATSE spectroscopic detectors

    NASA Technical Reports Server (NTRS)

    Mcnamara, Bernard

    1993-01-01

    Among the Compton Gama-Ray Observatory instruments, the BATSE Spectroscopic Detectors (SD) have the distinction of being able to detect photons of energies less than about 20 keV. This is an interesting energy range for the examination of low mass X-ray binaries (LMXB's). In fact, Sco X-1, the prototype LMXB, is easily seen even in the raw BATSE spectroscopic data. The all-sky coverage afforded by these detectors offers a unique opportunity to monitor this source over time periods never before possible. The aim of this investigation was to test a number of ways in which both continous and discrete flux measurements can be obtained using the BATSE spectroscopic datasets. A instrumental description of a SD can be found in the Compton Workshop of Apr. 1989, this report will deal only with methods which can be used to analyze its datasets. Many of the items discussed below, particularly in regard to the earth occultation technique, have been developed, refined, and applied by the BATSE team to the reduction of BATSE LAD data. Code written as part of this project utilizes portions of that work. The following discussions will first address issues related to the reduction of SD datasets using the earth occultation technique. It will then discuss methods for the recovery of the flux history of strong sources while they are above the earth's limb. The report will conclude with recommended reduction procedures.

  10. Plasma momentum meter for momentum flux measurements

    DOEpatents

    Zonca, F.; Cohen, S.A.; Bennett, T.; Timberlake, J.R.

    1993-08-24

    An apparatus is described for measuring momentum flux from an intense plasma stream, comprising: refractory target means oriented normal to the flow of said plasma stream for bombardment by said plasma stream where said bombardment by said plasma stream applies a pressure to said target means, pendulum means for communicating a translational displacement of said target to a force transducer where said translational displacement of said target is transferred to said force transducer by an elongated member coupled to said target, where said member is suspended by a pendulum configuration means and where said force transducer is responsive to said translational displacement of said member, and force transducer means for outputting a signal representing pressure data corresponding to said displacement.

  11. Evaluation of the Community Land Model simulated carbon and water fluxes against observations over ChinaFLUX sites

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Mao, J.; Shi, X.; Ricciuto, D. M.; He, H.; Thornton, P. E.; Yu, G.; Han, S.; Li, Y.; Yan, J.; Hao, Y.; Wang, H.

    2014-12-01

    The Community Land Model (CLM) is an advanced process-based land surface model that simulates the complicated carbon, water vapor and energy exchanges between the terrestrial ecosystem and the atmosphere at various spatial-temporal scales. We for the first time use eddy-covariance observations of CO2 and water vapor exchange and soil respiration measurements at five representative Chinese Terrestrial Ecosystem Flux Observational Network (ChinaFLUX) tower sites to systematically evaluate the latest versions of CLM, the CLM4.0 and CLM4.5, and comprehensively examine the similarities and differences between the observational and simulated results. The CLM4.5 underestimates annual carbon sink at three forest sites and one alpine grassland site but overestimates the carbon sink at a semi-arid grassland site. The underestimation in annual carbon sink at a deciduous dominated forest site is resulted from underestimated daytime carbon sequestration in summer and overestimated nighttime carbon emission in spring and autumn. Compared with the CLM4.0, the bias of annual Gross Primary Production (GPP) is reduced by 24% and 28% in CLM4.5 at two subtropical forest sites. However, CLM4.5 still has a large positive bias in annual GPP. The improvement in NEE is limited, although the bias of soil respiration decreases by 16%-43% at three forest sites. The CLM4.5 has lower soil water content in dry season than this simulated by the CLM4.0 at two grassland sites. These lead to the significant drop in leaf area index and GPP, and the increase in respiration for the CLM4.5. The new fire parameterization in CLM4.5 causes incorrect fire estimation at Changbaishan forest site, which results in unexpected underestimation of NEE, vegetation carbon, and soil organic carbon by 46%, 95%, and 87%, respectively. Our study with the ChinaFLUX sites indicates a significant improvement of the CLM4.5 than the CLM4, and suggests further developments on the parameterization of seasonal GPP and

  12. Large Area Lunar Dust Flux Measurement Instrument

    NASA Technical Reports Server (NTRS)

    Corsaro, R.; Giovane, F.; Liou, Jer-Chyi; Burchell, M.; Stansbery, Eugene; Lagakos, N.

    2009-01-01

    The instrument under development is designed to characterize the flux and size distribution of the lunar micrometeoroid and secondary ejecta environment. When deployed on the lunar surface, the data collected will benefit fundamental lunar science as well as enabling more reliable impact risk assessments for human lunar exploration activities. To perform this task, the instrument requirements are demanding. It must have as large a surface area as possible to sample the very sparse population of the larger potentially damage-inducing micrometeorites. It must also have very high sensitivity to enable it to measure the flux of small (<10 micron) micrometeorite and secondary ejecta dust particles. To be delivered to the lunar surface, it must also be very low mass, rugged and stow compactly. The instrument designed to meet these requirements is called FOMIS. It is a large-area thin film under tension (i.e. a drum) with multiple fiber optic displacement (FOD) sensors to monitor displacements of the film. This sensor was chosen since it can measure displacements over a wide dynamic range: 1 cm to sub-Angstrom. A prototype system was successfully demonstrated using the hypervelocity impact test facility at the University of Kent (Canterbury, UK). Based on these results, the prototype system can detect hypervelocity (approx.5 km/s) impacts by particles as small as 2 microns diameter. Additional tests using slow speeds find that it can detect secondary ejecta particles (which do not penetrate the film) with momentums as small as 15 pico-gram 100m/s, or nominally 5 microns diameter at 100 m/s.

  13. Establishment of a New, Cooperative ARM and AmeriFlux Site on the Alaskan North Slope

    NASA Astrophysics Data System (ADS)

    Billesbach, D. P.; Fischer, M. L.; Cook, D. R.; Torn, M. S.; Castanha, C.

    2011-12-01

    We report here on the establishment of a new research facility on the Alaskan North Slope. The experiment, located near Barrow, AK will be operated by the US Department of Energy (US DOE) as a permanent facility at the North Slope of Alaska (NSA) site of the Atmospheric Radiation Measurement (ARM) Climate Research Facility. The instrumentation at the site as well as on-going vegetation and soil measurements will also constitute the core data set for a new AmeriFlux site. Data will be made available through both the ARM and the AmeriFlux data centers. The experiment will be centered around an eddy covariance flux tower that will generated measurements of carbon dioxide, methane, water vapor, and energy fluxes. Additionally, surface radiation, meteorological, and soil instruments will provide ancillary data needed for gap filling, quality control, and climate quantification. Destructive and non-destructive sampling, according to the AmeriFlux biometric sampling protocols will quantify plant biomass, species, leaf area and nitrogen, and soil carbon stocks. Our goal is to assess both the impact that the Arctic costal region might have on the carbon cycle as well as climatic feedbacks that could affect this vulnerable ecosystem.

  14. Latent heat sink in soil heat flux measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The surface energy balance includes a term for soil heat flux. Soil heat flux is difficult to measure because it includes conduction and convection heat transfer processes. Accurate representation of soil heat flux is an important consideration in many modeling and measurement applications. Yet, the...

  15. Measurement of local high-level, transient surface heat flux

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.

    1988-01-01

    This study is part of a continuing investigation to develop methods for measuring local transient surface heat flux. A method is presented for simultaneous measurements of dual heat fluxes at a surface location by considering the heat flux as a separate function of heat stored and heat conducted within a heat flux gage. Surface heat flux information is obtained from transient temperature measurements taken at points within the gage. Heat flux was determined over a range of 4 to 22 MW/sq m. It was concluded that the method is feasible. Possible applications are for heat flux measurements on the turbine blade surfaces of space shuttle main engine turbopumps and on the component surfaces of rocket and advanced gas turbine engines and for testing sensors in heat flux gage calibrators.

  16. A highly portable, rapidly deployable system for eddy covariance measurements of CO2 fluxes

    SciTech Connect

    Billesbach, David P.; Fischer, Marc L.; Torn, Margaret S.; Berry, Joe A.

    2001-09-19

    To facilitate the study of flux heterogeneity within a region, the authors have designed, built, and field-tested a highly portable, rapidly deployable, eddy covariance CO{sub 2} flux measurement system. The system is built from off-the-shelf parts and was assembled at a minimal cost. The unique combination of features of this system allow for a very rapid deployment with a minimal number of field personnel. The system is capable of making high precision, unattended measurements of turbulent CO{sub 2} fluxes, latent heat (LE) fluxes, sensible heat fluxes (H), and momentum transfer fluxes. In addition, many of the meteorological and ecosystem variables necessary for quality control of the fluxes and for running ecosystem models are measured. A side-by-side field comparison of the system at a pair of established AmeriFlux sites has verified that, for single measurements, the system is capable of CO{sub 2} flux accuracy of about {+-} 1.2 {micro}mole/m{sup 2}/sec, LE flux accuracy of about {+-} 15 Watts/m{sup 2}, H flux accuracy of about {+-} 7 Watts/m{sup 2}, and momentum transfer flux accuracy of about {+-} 11 gm-m/sec/sec. System deployment time is between 2 and 4 hours by a single person. The system was measured to draw between 30 and 35 Watts of power and may be run from available line power, storage batteries, or solar panels.

  17. Use of single-well tracer dilution tests to evaluate LNAPL flux at seven field sites.

    PubMed

    Mahler, Nicholas; Sale, Tom; Smith, Tim; Lyverse, Mark

    2012-01-01

    Petroleum liquids, referred to as light non-aqueous phase liquids (LNAPLs), are commonly found beneath petroleum facilities. Concerns with LNAPLs include migration into clean soils, migration beyond property boundaries, and discharges to surface water. Single-well tracer dilution techniques were used to measure LNAPL fluxes through 50 wells at 7 field sites. A hydrophobic tracer was mixed into LNAPL in a well. Intensities of fluorescence associated with the tracer were measured over time using a spectrometer and a fiber optic cable. LNAPL fluxes were estimated using observed changes in the tracer concentrations over time. Measured LNAPL fluxes range from 0.006 to 2.6 m/year with a mean and median of 0.15 and 0.064 m/year, respectively. Measured LNAPL fluxes are two to four orders of magnitude smaller than a common groundwater flux of 30 m/year. Relationships between LNAPL fluxes and possible governing parameters were evaluated. Observed LNAPL fluxes are largely independent of LNAPL thickness in wells. Natural losses of LNAPL through dissolution, evaporation, and subsequent biodegradation, were estimated using a simple mass balance, measured LNAPL fluxes in wells, and an assumed stable LNAPL extent. The mean and median of the calculated loss rates were found to be 24.0 and 5.0 m3/ha/year, respectively. Mean and median losses are similar to values reported by others. Coupling observed LNAPL fluxes to observed rates of natural LNAPL depletion suggests that natural losses of LNAPL may be an important parameter controlling the overall extent of LNAPL bodies. PMID:23289131

  18. Design and operation - Surface flux measurements in FIFE

    NASA Technical Reports Server (NTRS)

    Kanemasu, E. T.; Verma, Shashi B.; Fritschen, L. J.; Gurney, R. J.; Hsu, A. T.

    1990-01-01

    A general overview of the structure, technology, and methodology of the investigation of surface flux is presented for the First International Satellite Land-Surface Climatology Project Field Experiment. The paper examines the placement of stations, choice of constants, instruments, and micrometeorological techniques, the information system, and comparisons between the data from the sensors and data from different sites. The differences between sites are generally small, and a similarity is noted in the magnitude of fluxes across all sites.

  19. Productivity and carbon dioxide exchange of the leguminous crops: Estimates from flux tower measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Net CO2 exchange data on legume crops at 17 flux tower sites in North America and 3 sites in Europe representing 29 site-years of measurements were partitioned into gross photosynthesis and ecosystem respiration using a light-response function method, resulting in new estimates of ecosystem-scale ec...

  20. Integrated Cropland and Grassland Flux Tower Observation Sites over Grazinglands for Quantifying Surface-Atmosphere Exchange

    NASA Astrophysics Data System (ADS)

    Mahan, H. R.; Wagle, P.; Bajgain, R.; Zhou, Y.; Basara, J. B.; Xiao, X.; Duckles, J. M.; Steiner, J. L.; Starks, P. J.; Northup, B. K.

    2014-12-01

    Quantifying methane (CH4), carbon dioxide (CO2), and water vapor fluxes between land surface and boundary layer using the eddy covariance method have many applicable uses across several disciplines. Three eddy flux towers have been established over no-till winter wheat (Triticum aestivum L.), and native and improved pastures at the USDA ARS Grazinglands Research Laboratory, El Reno, OK. An additional tower will be established in fall 2014 over till winter wheat. Each flux site is equipped with an eddy covariance system, PhenoCam, COSMOS, and in-situ observations of soil and atmospheric state variables. The objective of this research is to measure, compare, and model the land-atmosphere exchange of CO2, water vapor, and CH4 in different land cover types and management practices (till vs no-till, grazing vs no-grazing, native vs improved pasture). Models that focus on net ecosystem CO2 exchange (NEE), gross primary production (GPP), evapotranspiration (ET), and CH4 fluxes can be improved by the cross verification of these measurements. Another application will be to link the in-situ measurements with satellite remote sensing in order to scale-up flux measurements from small spatial scales to local and regional scales. Preliminary data analysis from the native grassland site revealed that CH4 concentration was negligible (~ 0), and it increased significantly when cattle were introduced into the site. In summer 2014, daily ET magnitude was about 4-5 mm day-1 and the NEE magnitude was 4-5 g C day-1 at the native grassland site. Further analysis of data for all the sites for longer temporal periods will enhance understanding of biotic and abiotic factors that govern carbon, water, and energy exchanges between the land surface and atmosphere under different land cover and management systems. The research findings will help predict the responses of these ecosystems to management practices and global environmental change in the future.

  1. Seasonal radiolarian flux at the VERTEX North Pacific time-series site

    NASA Astrophysics Data System (ADS)

    Gowing, Marcia M.

    1993-03-01

    Fluxes of radiolarians were measured at several depths from 50 to 2000 m at 33°N. 139°W with free-floating particle interceptor traps in a series of 3-month collections from October 1986 to May 1988. Fluxes of spumellarians, nassellarians and phaeodarians were generally highest and were most variable in the upper 100 m. Patterns of flux differed among the three groups, and no clear seasonal patterns were evident, within the resolution of the methods. Standing stocks, sampled with large-volume water samples, varied little during the study period. Fluxes of each group from the base of the euphotic zone (150 m) were similar throughout the study period, as generally were fluxes from 150 to 2000 m. Flux patterns of two species of nassellarians and of several species of phacodarians were examined. Flux of the symbiont-bearing nassellarian Lithopera bacca from the euphotic zone peaked in summer, but at 2000 m there was no seasonal pattern to its flux. Among the phacodarians. Lirella bullata showed spring peaks in flux at 2000 m. The lack of clear seasonal patterns for the groups and for many individual species suggests that the seasonal variability in factors, such as primary productivity and nitrogen dynamics, at this oligotrophic site was too weak to affect radiolarians, which are at least one trophic step removed from these factors. Variability in radiolarian fluxes at all depths over the 18 month period ranged from undetectable to a factor of 10; this probably represents normal variability at this oligotrophic site. The majority of polycystines trapped in the upper 100 m were alive at the time of capture, and the percentage of living specimens decreased rapidly as depth increased. In contrast, living phacodarians dominated the fluxes of phacodarians at all depths. Several species of phacodarians with shallower depth distributions were absent from the deepest traps, whereas species with deeper distributions were present in the 2000 m traps. Carbon flux of living

  2. Measurement of Integrated Low Frequency Flux Noise in Superconducting Flux/Phase Qubits

    SciTech Connect

    Mao Bo; Qiu Wei; Han Siyuan

    2008-11-07

    We measured the integrated low frequency flux noise ({approx}1 m{phi}{sub 0}) of an rf SQUID as a flux qubit by fitting the resonant peaks from photon assistant tunneling (PAT). The energy relaxation time Tl between the ground and first excited states in the same potential well, measured directly in time domain, is 3 ns. From these results we identified low frequency flux noise as the dominant source of decoherence. In addition, we found that the measured values of integrated flux noise in three qubits of various sizes differ more than an order of magnitude.

  3. Anthropogenic and biogenic influence on VOC fluxes at an urban background site in Helsinki, Finland

    NASA Astrophysics Data System (ADS)

    Rantala, Pekka; Järvi, Leena; Taipale, Risto; Laurila, Terhi K.; Patokoski, Johanna; Kajos, Maija K.; Kurppa, Mona; Haapanala, Sami; Siivola, Erkki; Petäjä, Tuukka; Ruuskanen, Taina M.; Rinne, Janne

    2016-07-01

    We measured volatile organic compounds (VOCs), carbon dioxide (CO2) and carbon monoxide (CO) at an urban background site near the city centre of Helsinki, Finland, northern Europe. The VOC and CO2 measurements were obtained between January 2013 and September 2014 whereas for CO a shorter measurement campaign in April-May 2014 was conducted. Both anthropogenic and biogenic sources were identified for VOCs in the study. Strong correlations between VOC fluxes and CO fluxes and traffic rates indicated anthropogenic source of many VOCs. The VOC with the highest emission rate to the atmosphere was methanol, which originated mostly from traffic and other anthropogenic sources. The traffic was also a major source for aromatic compounds in all seasons whereas isoprene was mostly emitted from biogenic sources during summer. Some amount of traffic-related isoprene emissions were detected during other seasons but this might have also been an instrumental contamination from cycloalkane products. Generally, the observed VOC fluxes were found to be small in comparison with previous urban VOC flux studies. However, the differences were probably caused by lower anthropogenic activities as the CO2 fluxes were also relatively small at the site.

  4. A comparison of new measurements of total monoterpene flux with improved measurements of speciated monoterpene flux

    NASA Astrophysics Data System (ADS)

    Lee, A.; Schade, G. W.; Holzinger, R.; Goldstein, A. H.

    2005-02-01

    Many monoterpenes have been identified in forest emissions using gas chromatography (GC). Until now, it has been impossible to determine whether all monoterpenes are appropriately measured using GC techniques. We used a proton transfer reaction mass spectrometer (PTR-MS) coupled with the eddy covariance (EC) technique to measure mixing ratios and fluxes of total monoterpenes above a ponderosa pine plantation. We compared PTR-MS-EC results with simultaneous measurements of eight speciated monoterpenes, β-pinene, α-pinene, 3-carene, d-limonene, β-phellandrene, α-terpinene, camphene, and terpinolene, made with an automated, in situ gas chromatograph with flame ionization detectors (GC-FID), coupled to a relaxed eddy accumulation system (REA). Monoterpene mixing ratios and fluxes measured by PTR-MS averaged 30±2.3% and 31±9.2% larger than by GC-FID, with larger mixing ratio discrepancies between the two techniques at night than during the day. Two unidentified peaks that correlated with β-pinene were resolved in the chromatograms and completely accounted for the daytime difference and reduced the nighttime mixing ratio difference to 20±2.9%. Measurements of total monoterpenes by PTR-MS-EC indicated that GC-FID-REA measured the common, longer-lived monoterpenes well, but that additional terpenes were emitted from the ecosystem that represented an important contribution to the total mixing ratio above the forest at night.

  5. A comparison of new measurements of total monoterpene flux with improved measurements of speciated monoterpene flux

    NASA Astrophysics Data System (ADS)

    Lee, A.; Schade, G. W.; Holzinger, R.; Goldstein, A. H.

    2004-12-01

    Many monoterpenes have been identified in forest emissions using gas chromatography (GC). Until now, it has been impossible to determine whether all monoterpenes are appropriately measured using GC techniques. We used a proton transfer reaction mass spectrometer (PTR-MS) coupled with the eddy covariance (EC) technique to measure mixing ratios and fluxes of total monoterpenes above a ponderosa pine plantation. We compared PTR-MS-EC results with simultaneous measurements of eight speciated monoterpenes, β-pinene, α-pinene, 3-carene, d-limonene, β-phellandrene, α-terpinene, camphene, and terpinolene, made with an automated, in situ gas chromatograph with flame ionization detectors (GC-FID), coupled to a relaxed eddy accumulation system (REA). Monoterpene mixing ratios and fluxes measured by PTR-MS averaged 30±2.3% and 31±9.2% larger than by GC-FID, with larger differences at night than during the day. Four unidentified peaks that correlated with β-pinene were resolved in the chromatograms and completely accounted for the daytime difference and reduced the nighttime difference to 19±3.4%. Measurements of total monoterpenes by PTR-MS-EC indicated that GC-FID-REA measured the common, longer-lived monoterpenes well, but that additional monoterpenes were emitted from the ecosystem that represented an important contribution to the total mixing ratio above the forest at night, and that must have been oxidized during the day before they escaped the forest canopy.

  6. Heat flux microsensor measurements and calibrations

    NASA Technical Reports Server (NTRS)

    Terrell, James P.; Hager, Jon M.; Onishi, Shinzo; Diller, Thomas E.

    1992-01-01

    A new thin-film heat flux gage has been fabricated specifically for severe high temperature operation using platinum and platinum-10 percent rhodium for the thermocouple elements. Radiation calibrations of this gage were performed at the AEDC facility over the available heat flux range (approx. 1.0 - 1,000 W/cu cm). The gage output was linear with heat flux with a slight increase in sensitivity with increasing surface temperature. Survivability of gages was demonstrated in quench tests from 500 C into liquid nitrogen. Successful operation of gages to surface temperatures of 750 C has been achieved. No additional cooling of the gages is required because the gages are always at the same temperature as the substrate material. A video of oxyacetylene flame tests with real-time heat flux and temperature output is available.

  7. Seasonal spectral dynamics and carbon fluxes at core EOS sites using EO-1 Hyperion images

    NASA Astrophysics Data System (ADS)

    Lagomasino, D.; Campbell, P.; Price, R. M.

    2010-12-01

    Fluxes of water and carbon into the atmosphere are critical components in order to monitor and predict climate change. Spatial heterogeneity and seasonal changes in vegetation contribute to ambiguities in regional and global CO2 and water cycle dynamics. Satellite remote sensing is essential for monitoring the spatial and temporal dynamics of various vegetation types for the purposes of determining carbon and water fluxes. Satellite data from the EO-1 Hyperion sensor was acquired for five Earth Observing Satellite (EOS) sites, Mongu (Zambia, Africa), Konza Prairie (Kansas, USA), Duke Forest (North Carolina, USA), Barrow (Alaska, USA) and Sevilleta (New Mexico, USA). Each EOS site represented a distinct vegetative ecosystem type; hardwood forest, grassland, evergreen forest, lichens, and shrubland/grassland respectively. Satellite data was atmospherically corrected using the Atmosphere CORrection Now (ACORN) model and subsequently, the spectral reflectance data was extracted in the vicinity of existing flux towers. The EO-1 Hyperion sensor proved advantageous because of its high and continuous spectral resolution (10 nm intervals from 355 to 2578 nm wavelengths). The high spectral resolution allowed us calculate biophysical indices based on specific wavelengths in the electromagnetic spectrum that are associated with alterations in foliar chemistry and plant membrane structure (i.e., vegetation stress) brought upon by many environmental factors. Previous studies have focused on relationships within a specific site or vegetation community. This study however, incorporated many sites with different vegetation types and various geographic locations throughout the world. Monitoring the fluctuations in vegetation stress with contemporaneous environmental conditions and carbon flux measurements from each site will provide better insight into water and carbon flux dynamics in many different biomes. Noticeable spectral signatures were identified based on site specific

  8. Soil Flux Chamber Measurements with Five Species CRDS and New Realtime Chamber Flux Processor

    NASA Astrophysics Data System (ADS)

    Saad, N.; Alstad, K. P.; Arata, C.; Franz, P.

    2014-12-01

    Continuous soil flux chamber measurements remains a key tool for determining production and sequestration of direct and indirect greenhouse gases. The Picarro G2508 Cavity Ring-down Spectrometer has radically simplified soil flux studies by providing simultaneous measurements of five gases: CO2, CH4, N2O, NH3, and H2O, and by lending itself to field deployment. Successful use of the Picarro G2508 for continuous soil flux measurements in a variety of ecosystem types has already been demonstrated. Most recently, Picarro is developing a real-time processing software to simplify chamber measurements of soil flux with the G2508 CRDS. The new Realtime Chamber Flux Processor is designed to work with all chamber types and sizes, and provides real-time flux values of N2O, CO2 & CH4. The software features include chamber sequence table, flexible data tagging feature, ceiling concentration measurement shut-off parameter, user-defined run-time interval, temperature/pressure input for field monitoring and volumetric conversion, and manual flux measurement start/stop override. Realtime Chamber Flux Processor GUI interface is presented, and results from a variety of sampling designs are demonstrated to emphasize program flexibility and field capability.

  9. AmeriFlux US-Br1 Brooks Field Site 10- Ames

    DOE Data Explorer

    Parkin, Tim [USDA; Prueger, John [National Laboratory for Agriculture and the Environment

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-Br1 Brooks Field Site 10- Ames. Site Description - The Brooks Field Site 10 - Ames Site is one of three sites (Brooks Field Site 11 and Brooks Field Site 1011) located in a corn/soybean agricultural landscape of central Iowa. The farming systems, associated tillage, and nutrient management practices for soybean/corn production are typical of those throughout Upper Midwest Corn Belt. All three sites are members of the AmeriFlux network. Information for all three can be found in synchronous pages of this website.

  10. AmeriFlux US-Br3 Brooks Field Site 11- Ames

    DOE Data Explorer

    Parkin, Tim [USDA; Prueger, John [National Laboratory for Agriculture and the Environment

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-Br3 Brooks Field Site 11- Ames. Site Description - The Brooks Field Site 11 - Ames Site is one of three sites (Brooks Field Site 10 and Brooks Field Site 1011) located in a corn/soybean agricultural landscape of central Iowa. The farming systems, associated tillage, and nutrient management practices for soybean/corn production are typical of those throughout Upper Midwest Corn Belt. All three sites are members of the AmeriFlux network. Information for all three can be found in synchronous pages of this website.

  11. Fluxpro As a Realtime Monitoring and Surveillance System for Eddy Covariance Flux Measurement

    NASA Astrophysics Data System (ADS)

    Kim, W.

    2014-12-01

    To understand how terrestrial ecosystems respond to global climate change, colleagues have globally measured the energy, water and carbon dioxide flux densities (F) over various vegetations by the eddy covariance (EC) method. However, the process of F calculation and the method of quality control and quality assurance (QCQA) are complex and site specific. Moreover, instantly maintaining remote EC flux measurement sites against instrumentation problems and administrative difficulties is laborious. To overcome these issues, particularly those of realtime F monitoring and prompt site management, FluxPro was created. FluxPro is consisted of three functional systems: 1) gathering system that transports EC measurements from various sites to the FluxPro management server; 2) cooking system that computes F and its frictional uncertainty (ɛ) together with micrometeorological variables (V); and 3) serving system that presents the above two results as charts to be distributed over the internet in realtime. Consequently, FluxPro could become an appropriate system in realtime-multi-site management, since it not only to automatically monitors F with ɛ and V but also continuously surveils EC sites, providing copious information and an email alert system.

  12. Heat flux measurements on ceramics with thin film thermocouples

    NASA Technical Reports Server (NTRS)

    Holanda, Raymond; Anderson, Robert C.; Liebert, Curt H.

    1993-01-01

    Two methods were devised to measure heat flux through a thick ceramic using thin film thermocouples. The thermocouples were deposited on the front and back face of a flat ceramic substrate. The heat flux was applied to the front surface of the ceramic using an arc lamp Heat Flux Calibration Facility. Silicon nitride and mullite ceramics were used; two thicknesses of each material was tested, with ceramic temperatures to 1500 C. Heat flux ranged from 0.05-2.5 MW/m2(sup 2). One method for heat flux determination used an approximation technique to calculate instantaneous values of heat flux vs time; the other method used an extrapolation technique to determine the steady state heat flux from a record of transient data. Neither method measures heat flux in real time but the techniques may easily be adapted for quasi-real time measurement. In cases where a significant portion of the transient heat flux data is available, the calculated transient heat flux is seen to approach the extrapolated steady state heat flux value as expected.

  13. Measurement of Urban fluxes of CO2 and water

    NASA Astrophysics Data System (ADS)

    Grimmond, S.; Crawford, B.; Offerle, B.; Hom, J.

    2006-05-01

    Measurements of surface-atmosphere fluxes of carbon dioxide (FCO2) and latent heat in urban environments are rare even though cities are a major source of atmospheric CO2 and users of water. In this paper, an overview of urban FCO2 measurements will be presented to illustrate how and where such measurements are being conducted and emerging results to date. Most of these studies have been conducted over short periods of time; few studies have considered annual sources/sinks. More investigations have been conducted, and are planned, in European cities than elsewhere, most commonly in areas of medium density urban development. The most dense urban sites are significant net sources of carbon. However, in areas where there is large amounts of vegetation present, there is a net sink of carbon during the summertime. In the second part of the presentation, more detailed attention will be directed to an ongoing measurement program in Baltimore, MD (part of the Baltimore Ecosystem Study). Eddy covariance instrumentation mounted on a tall-tower at 41.2 m has continuously measured local-scale fluxes of carbon dioxide from a suburban environment since 2001. Several features make this particular study unique: 1) for an urban area, the study site is extensively vegetated, 2) the period of record (2001-2005) is among the longest available for urban FCO2 measurements, 3) both closed-path and open-path infrared gas analyzers are used for observations, and 4) several unique data quality control and gap-filling methods have been developed for use in an urban environment. Additionally, detailed surface datasets and GIS software are used to perform flux source area analysis. Results from Baltimore indicate that FCO2 is very dependent on source area land-cover characteristics, particularly the proportion of vegetated and built surfaces. Over the course of a year, the urban surface is a strong net source of CO2, though there is considerable inter-annual variability depending on

  14. Eddy-covariance methane flux measurements over a European beech forest

    NASA Astrophysics Data System (ADS)

    Gentsch, Lydia; Siebicke, Lukas; Knohl, Alexander

    2015-04-01

    The role of forests in global methane (CH4) turnover is currently not well constrained, partially because of the lack of spatially integrative forest-scale measurements of CH4 fluxes. Soil chamber measurements imply that temperate forests generally act as CH4 sinks. Upscaling of chamber observations to the forest scale is however problematic, if the upscaling is not constrained by concurrent 'top-down' measurements, such as of the eddy-covariance type, which provide sufficient integration of spatial variations and of further potential CH4 flux components within forest ecosystems. Ongoing development of laser absorption-based optical instruments, resulting in enhanced measurement stability, precision and sampling speed, has recently improved the prospects for meaningful eddy-covariance measurements at sites with presumably low CH4 fluxes, hence prone to reach the flux detection limit. At present, we are launching eddy-covariance CH4 measurements at a long-running ICOS flux tower site (Hainich National Park, Germany), located in a semi natural, unmanaged, beech dominated forest. Eddy-covariance measurements will be conducted with a laser spectrometer for parallel CH4, H2Ov and CO2 measurements (FGGA, Los Gatos Research, USA). Independent observations of the CO2 flux by the FGGA and a standard Infrared Gas Analyser (LI-7200, LI-COR, USA) will allow to evaluate data quality of measured CH4 fluxes. Here, we want to present first results with a focus on uncertainties of the calculated CH4 fluxes with regard to instrument precision, data processing and site conditions. In future, we plan to compare eddy-covariance flux estimates to side-by-side turbulent flux observations from a novel eddy accumulation system. Furthermore, soil CH4 fluxes will be measured with four automated chambers situated within the tower footprint. Based on a previous soil chamber study at the same site, we expect the Hainich forest site to act as a CH4 sink. However, we hypothesize that our

  15. Heat flux measurement in SSME turbine blade tester

    SciTech Connect

    Liebert, C.H.

    1990-11-01

    Surface heat flux values were measured in the turbine blade thermal cycling tester located at NASA-Marshall. This is the first time heat flux has been measured in a space shuttle main engine turbopump environment. Plots of transient and quasi-steady state heat flux data over a range of about 0 to 15 MW/sq m are presented. Data were obtained with a miniature heat flux gage device developed at NASA-Lewis. The results from these tests are being incorporated into turbine design models. Also, these gages are being considered for airfoil surface heat flux measurement on turbine vanes mounted in SSME turbopump test bed engine nozzles at Marshall. Heat flux effects that might be observed on degraded vanes are discussed.

  16. Flux Measurements of Trace Gases, Aerosols and Energy from the Urban Core of Mexico City

    NASA Astrophysics Data System (ADS)

    Velasco, E.; Molina, L.; Lamb, B.; Pressley, S.; Grivicke, R.; Westberg, H.; Jobson, T.; Allwine, E.; Coons, T.; Jimenez, J.; Nemitz, E.; Alexander, L. M.; Worsnop, D.; Ramos, R.

    2007-05-01

    As part of the MILAGRO field campaign in March 2006 we deployed a flux system in a busy district of Mexico City surrounded by congested avenues. The flux system consisted of a tall tower instrumented with fast-response sensors coupled with eddy covariance (EC) techniques to measure fluxes of volatile organic compounds (VOCs), CO2, CO, aerosols and energy. The measured fluxes represent direct measurements of emissions that include all major and minor emission sources from a typical residential and commercial district. In a previous study we demonstrated that the EC techniques are valuable tools to evaluate emissions inventories in urban areas, and understand better the atmospheric chemistry and the role that megacities play in global change. We measured fluxes of olefins using a Fast Olefin Sensor (FOS) and the EC technique, fluxes of aromatic and oxygenated VOCs by Proton Transfer Reaction-Mass Spectroscopy (PTR-MS) and the disjunct eddy covariance (DEC) technique, fluxes of CO2 and H2O with an open path Infrared Gas Analyzer (IRGA) and the EC technique, fluxes of CO using a modified gradient method and a commercial CO instrument, and fluxes of aerosols (organics, nitrates and sulfates) using an Aerodyne Aerosol Mass Spectrometer (AMS) and the EC technique. In addition we used a disjunct eddy accumulation (DEA) system to extend the number of VOCs. This system collected whole air samples as function of the direction of the vertical wind component, and the samples were analyzed on site using gas chromatography / flame ionization detection (GC-FID). We also measured fluxes of sensible and latent heat by EC and the radiation components with a net radiometer. Overall, these flux measurements confirm the results of our previous flux measurements in Mexico City in terms of the magnitude, composition, and distribution. We found that the urban surface is a net source of CO2 and VOCs. The diurnal patterns show clear anthropogenic signatures, with important contributions from

  17. A bottom-up perspective of the net land methanol flux: synthesis of global eddy covariance flux measurements

    NASA Astrophysics Data System (ADS)

    Wohlfahrt, Georg; Amelynck, Crist; Ammann, Christof; Arneth, Almut; Bamberger, Ines; Goldstein, Allen; Hansel, Armin; Heinesch, Bernhard; Holst, Thomas; Hörtnagl, Lukas; Karl, Thomas; Neftel, Albrecht; McKinney, Karena; Munger, William; Schade, Gunnar; Schoon, Niels

    2014-05-01

    Methanol (CH3OH) is, after methane, the second most abundant VOC in the troposphere and globally represents nearly 20% of the total biospheric VOC emissions. With typical concentrations of 1-10 ppb in the continental boundary layer, methanol plays a crucial role in atmospheric chemistry, which needs to be evaluated in the light of ongoing changes in land use and climate. Previous global methanol budgets have approached the net land flux by summing up the various emission terms (namely primary biogenic and anthropogenic emissions, plant decay and biomass burning) and by subtracting dry and wet deposition, resulting in a net land flux in the range of 75-245 Tg y-1. The data underlying these budget calculations largely stem from small-scale leaf gas exchange measurements and while recently column-integrated remotely sensed methanol concentrations have become available for constraining budget calculations, there have been few attempts to contrast model calculations with direct net ecosystem-scale methanol flux measurements. Here we use eddy covariance methanol flux measurements from 8 sites in Europe and North America to study the magnitude of and controls on the diurnal and seasonal variability in the net ecosystem methanol flux. In correspondence with leaf-level literature, our data show that methanol emission and its strong environmental and biotic control (by temperature and stomatal conductance) prevailed at the more productive (agricultural) sites and at a perturbed forest site. In contrast, at more natural, less productive sites substantial deposition of methanol occurred, in particular during periods of surface wetness. These deposition processes are poorly represented by currently available temperature/light and/or production-driven modelling algorithms. A new framework for modelling the bi-directional land-atmosphere methanol exchange is proposed which accounts for the production of methanol in leaves, the regulation of leaf methanol emission by stomatal

  18. Non-contact heat flux measurement using a transparent sensor

    NASA Technical Reports Server (NTRS)

    Ng, Daniel; Spuckler, Charles M.

    1993-01-01

    A working non-contact heat flux sensor was demonstrated using a transparent material (sapphire) and a multiwavelength pyrometer. The pyrometer is used to measure the temperatures of the two surfaces of the sensor from the spectrum of radiation originating from them. The heat conducted through the material is determined from the temperature difference of the two surfaces and the thermal conductivity of the material. The measured heat flux is equal to the incident heat flux within experimental error indicating that no calibration would be necessary. A steady state heat flux of 100 kW/sq m was easily achieved.

  19. Software used with the flux mapper at the solar parabolic dish test site

    NASA Technical Reports Server (NTRS)

    Miyazono, C.

    1984-01-01

    Software for data archiving and data display was developed for use on a Digital Equipment Corporation (DEC) PDP-11/34A minicomputer for use with the JPL-designed flux mapper. The flux mapper is a two-dimensional, high radiant energy scanning device designed to measure radiant flux energies expected at the focal point of solar parabolic dish concentrators. Interfacing to the DEC equipment was accomplished by standard RS-232C serial lines. The design of the software was dicated by design constraints of the flux-mapper controller. Early attemps at data acquisition from the flux-mapper controller were not without difficulty. Time and personnel limitations result in an alternative method of data recording at the test site with subsequent analysis accomplished at a data evaluation location at some later time. Software for plotting was also written to better visualize the flux patterns. Recommendations for future alternative development are discussed. A listing of the programs used in the anaysis is included in an appendix.

  20. Sand Flux Results for Aeolian Dunes at Current and Candidate Landing Sites on Mars

    NASA Astrophysics Data System (ADS)

    Chojnacki, M.; Urso, A.; Yingling, W.

    2015-12-01

    It is now known unambiguously that wind-driven bedform activity is occurring on Mars today. It has also been demonstrated the rapid aeolian abrasion of sedimentary deposits that potentially host ancient habitable environments may provide the best mechanism for exposing samples containing relatively undegraded organics (Farley et al. 2014). Thus, current processes operating on the surface of Mars are highly relevant to our understanding of the past. Here, we discuss new sand flux results of active dune across Mars, including several current and candidate landing sites with Meridiani Planum, Gale crater, Valles Marineris, and Mawrth Vallis. For this task, we have utilized multi-temporal images acquired annually by the HiRISE camera (25 cm/pixel) along with co-located HiRISE Digital Terrain Models. Falling dunes in Coprates Chasma (Mars 2020 candidate landing site) measuring 6-10 meters in height were detected migrating on average 0.5 m per Earth year, yielding crest fluxes of 3.1 m3 m-1 yr-1 (units hereafter assumed). Barchans near the MSL rover at Gale crater have slightly lower fluxes of 1.2, while earlier work in Endeavour crater, the current site of the Opportunity Rover, showed dome dunes with fluxes as high as 13 (average of 6.8; Chojnacki et al. 2015). New results of Mawrth Vallis (Mars 2020 candidate) dunes suggest these high rates are not uncommon, as barchans there possess average fluxes of 11.5. Assuming ripple reptation rates are 1/10th that of crest fluxes, total flux (saltation plus reptation) would range 3.2 to 12.7 m3 m-1 yr-1 for all sites studied herein. Active dunes and the abrasion susceptibility (Sa) of local rocks are relevant to assess how sand fluxes modify the landscape. Using the methodology and assumptions (Sa for basalt, mean trajectory height etc.) described in Bridges et al. (2012), we estimated abrasion rates of local basaltic bedrock. For example, sand blasting at Mawrth Vallis is estimated to produce 2-8 μm/yr for flat ground and 15

  1. Multi-year estimates of plant and ecosystem 13C discrimination at AmeriFlux sites

    NASA Astrophysics Data System (ADS)

    Dang, X.; Lai, C.; Hollinger, D. Y.; Bush, S.; Randerson, J. T.; Law, B. E.; Schauer, A. J.; Ehleringer, J.

    2011-12-01

    We estimated plant and ecosystem 13C discrimination continuously at 8 AmeriFlux sites (Howland Forest, Harvard Forest, Wind River Forest, Rannells Prairie, Freeman Ranch, Chestnut Ridge, Metolius, and Marys River fir) over 8 years (2002-2009). We used an observation-based approach from weekly measurements of eddy covariance CO2 fluxes and their 13C/12C ratios to estimate photosynthetic 13C discrimination (△A) and respiration (δ13CR) on seasonal and interannual time scales. The coordinated, systematic flask sampling across the AmeriFlux subnetwork were used for cross-site synthesis of monthly flux estimates [Dang et al. Combining tower mixing ratio and community model data to estimate regional-scale net ecosystem carbon exchange by boundary layer inversion over 4 flux towers in the U.S.A., Journal of Geophysical Research-Biogeosciences, in press]. Here, we evaluated environmental factors that also influenced temporal variability in △A and δ13CR from daily to interannual time scales, comparing atmospheric 13C/12C measurements, leaf and needle organic matter, and tree ring cellulose. Across these major biomes that dominate the continent, we show differential ecophysiological responses to environmental stresses, among which water availability appeared to be a dominant factor. Our decadal measurement period provided robust estimates of atmospheric 13C discrimination by terrestrial ecosystems, but also suggest regions where enhanced monitoring efforts are required (e.g., 13C/12C emission from fire and urban metabolism; increased temporal resolution of 13C measurements in stress-sensitive ecosystems) to make atmospheric 13C/12C measurements an effective constraint for continental-scale assessments of the terrestrial carbon cycle.

  2. Heat and Volume Fluxes at the Turtle Pits Vent Site, southern Mid Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    Köhler, Janna; Walter, Maren; Mertens, Christian; Sültenfuß, Jürgen; Rhein, Monika

    2010-05-01

    The Turtle Pits vent site consists of eight known high temperature vents and several diffuse vent sites which are distributed over three hydrothermal fields: Turtle Pits, Comfortless Cove, and Red Lion. These vent fields are located in a north-south orientated rift valley at the Mid-Atlantic Ridge (MAR) near 5°S. The total volume and heat emissions of the entire Turtle Pits site have been calculated with three different approaches using data collected during a Meteor cruise in May 2006 and a L'Atalante cruise in January 2008. The data sets consist of vertical profiles and towed transects of temperature, salinity, and turbidity, as well as direct velocity measurements with a lowered acoustic Doppler current profiler (LADCP) and water samples for Helium isotope analysis. Vent fluid samples for noble gas analysis where taken with ROVs. Since the vent fluid is highly enriched in primordial 3He this noble gas can be used as a conservative tracer for vent fluid. The geographical setting of the vent site confines the particle plume to the rift valley since the depth of the valley exceeds the rise height of the plume. Therefore the fluxes of heat and volume can be estimated from the horizontal helium transport in the valley in combination with a mean 3He endmember concentration determined from the water samples taken with the ROVs. The comparison of the 3He concentrations measured south of the hydrothermal vents with the 3He signal north of the hydrothermal vents suggests a rather strong northward flow. This is confirmed by the tide corrected velocities observed with the LADCP during the Meteor cruise. The northward volume transport has been calculated using the local bathymetry and tide corrected velocities from the Meteor cruise. In combination with the 3He concentrations and the average 3He endmember concentration a flux of 1000 l/s is estimated, which corresponds to a heat flux of 1400 MW. The measured temperature anomalies within the plume combined with the known

  3. The measurement of surface heat flux using the Peltier effect

    SciTech Connect

    Shewen, E.C. ); Hollands, K.G.T., Raithby, G.D. )

    1989-08-01

    Calorimetric methods for measuring surface heat flux use Joulean heating to keep the surface isothermal. This limits them to measuring the heat flux of surfaces that are hotter than their surroundings. Presented in this paper is a method whereby reversible Peltier effect heat transfer is used to maintain this isothermality, making it suitable for surfaces that are either hotter or colder than the surroundings. The paper outlines the theory for the method and describes physical models that have been constructed, calibrated, and tested. The tested physical models were found capable of measuring heat fluxes with an absolute accuracy of 1 percent over a wide range of temperature (5-50C) and heat flux (15-500 W/m{sup 2}), while maintaining isothermality to within 0.03 K. A drawback of the method is that it appears to be suited only for measuring the heat flux from thick metallic plates.

  4. The 3He flux gauge in the Sargasso Sea: a determination of physical nutrient fluxes to the euphotic zone at the Bermuda Atlantic time series site

    NASA Astrophysics Data System (ADS)

    Stanley, R. H. R.; Jenkins, W. J.; Doney, S. C.; Lott, D. E., III

    2015-03-01

    We provide a new determination of the annual mean physical supply of nitrate to the euphotic zone in the western subtropical North Atlantic based on a three year time-series of measurements of tritiugenic 3He from 2003 to 2006 in the surface ocean at the Bermuda Atlantic Time-series Study (BATS) site. We combine the 3He data with a sophisticated noble gas calibrated air-sea gas exchange model to constrain the 3He flux across the sea-air interface, which must closely balance the upward 3He flux into the euphotic zone. The product of the 3He flux and the observed subsurface nitrate-3He relationship provides an estimate of the minimum rate of new production in the BATS region. We also applied the gas model to an earlier time series of 3He measurements at BATS in order to recalculate new production fluxes for the 1985 to 1988 time period. The observations, despite an almost three-fold difference in the nitrate-3He relationship, yield a roughly consistent estimate of nitrate flux. In particular, the nitrate flux from 2003-2006 is estimated to be 0.65 ± 0.3 mol m-2 y-1, which is ~ 40% smaller than the calculated flux for the period from 1985 to 1988. The difference between the time periods, which is barely significant, may be due to a real difference in new production resulting from changes in subtropical mode water formation. Overall, the nitrate flux is larger than most estimates of export fluxes or net community production fluxes made locally for BATS site, which is likely a reflection of the larger spatial scale covered by the 3He technique and potentially also by decoupling of 3He and nitrate during obduction of water masses from the main thermocline into the upper ocean.

  5. Real-time diamagnetic flux measurements on ASDEX Upgrade.

    PubMed

    Giannone, L; Geiger, B; Bilato, R; Maraschek, M; Odstrčil, T; Fischer, R; Fuchs, J C; McCarthy, P J; Mertens, V; Schuhbeck, K H

    2016-05-01

    Real-time diamagnetic flux measurements are now available on ASDEX Upgrade. In contrast to the majority of diamagnetic flux measurements on other tokamaks, no analog summation of signals is necessary for measuring the change in toroidal flux or for removing contributions arising from unwanted coupling to the plasma and poloidal field coil currents. To achieve the highest possible sensitivity, the diamagnetic measurement and compensation coil integrators are triggered shortly before plasma initiation when the toroidal field coil current is close to its maximum. In this way, the integration time can be chosen to measure only the small changes in flux due to the presence of plasma. Two identical plasma discharges with positive and negative magnetic field have shown that the alignment error with respect to the plasma current is negligible. The measured diamagnetic flux is compared to that predicted by TRANSP simulations. The poloidal beta inferred from the diamagnetic flux measurement is compared to the values calculated from magnetic equilibrium reconstruction codes. The diamagnetic flux measurement and TRANSP simulation can be used together to estimate the coupled power in discharges with dominant ion cyclotron resonance heating. PMID:27250425

  6. Measurements of Urban Area-Wide CO2 and CH4 Fluxes as part of the Indianapolis Flux Experiment (INFLUX)

    NASA Astrophysics Data System (ADS)

    Shepson, P.; Callahan, B.; Cambaliza, M. L.; Davis, K. J.; Hardesty, R.; Iraci, L. T.; Gurney, K. R.; Karion, A.; Lauvaux, T.; McGowan, L. E.; Miles, N. L.; Moser, B.; Newberger, T.; Possolo, A.; Razlivanov, I. N.; Richardson, S.; Samarov, D. V.; Sarmiento, D.; Stirm, B.; Sweeney, C.; Turnbull, J. C.; Whetstone, J. R.

    2012-12-01

    The Indianapolis Flux Experiment (INFLUX) was created in order to develop and evaluate methods for the measurement of greenhouse gas emission fluxes from urban environments. Such methods are important for a variety of reasons, including that more than half the global population now resides in cities, and because it is likely that many CO2 emissions reductions strategies will be implemented on local, largely urban, scales. INFLUX is using Indianapolis as a test case for measurements of urban scale greenhouse gas fluxes, because it is a fairly isolated urban environment with tractable meteorology, and a well-developed emission inventory (Vulcan/Hestia). INFLUX aims to quantify and reduce the uncertainty limits for such flux determinations, and to define the uncertainties for individual and combined approaches. The project currently combines a network of towers (currently 10 with 12 possible by the end of 2012) at which CO, CO2 and CH4 are measured, along with periodic flask sampling for 14CO2 and ~50 other trace gases and isotopes. Aircraft-based measurements of CO2, CH4 and H2O, along with flask samples for a variety of gases including 14CO2 are conducted from a light twin aircraft that enables flux measurements using the on-board turbulence/wind measurements via mass balance or eddy covariance methods. As of August of 2012 INFLUX has a Total Carbon Column Observing Network (TCCON) Fourier Transform Spectrometer at a downwind site, measuring column total CO2, CH4, H2O (and other greenhouse gases). The data from these tower, TCCON and aircraft measurements are then used in an inverse-modeling approach, using the Weather Research and Forecast model with chemistry (WRF-Chem) and the Lagrangian Particle Dispersion Model (LDPM) to yield estimates of the urban area flux at 1 km2 resolution. When aggregated these fluxes can be compared to estimates derived from aircraft mass-balance estimates, and the 14CO2 and CO data are used to extract the fossil fuel component of the

  7. BOREAS TE-1 CO2 and CH4 Flux Data Over the SSA-OBS Site

    NASA Technical Reports Server (NTRS)

    Anderson, Darwin; Papagno, Andrea; Hall, Forrest G. (Editor); Newcomer, Jeffrey A. (Editor)

    2000-01-01

    The BOREAS TE-1 team collected various data to characterize the soil-plant systems in the BOREAS SSA. Particular emphasis was placed on nutrient biochemistry, the stores and transfers of organic carbon, and how the characteristics were related to measured methane fluxes. The overall transect in the Prince Albert National Park (Saskatchewan, Canada) included the major plant communities and related soils that occurred in that section of the boreal forest. Soil physical, chemical, and biological measurements along the transect were used to characterize the static environment, which allowed them to be related to methane fluxes. Chamber techniques were used to provide a measure of methane production/uptake. Chamber measurements coupled with flask sampling were used to determine the seasonality of methane fluxes. This particular data set contains carbon dioxide and methane flux values from the SSA-OBS site. The data were collected from 09-Jun to 04-Sep-1994. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  8. BOREAS TGB-3 CH4 and CO2 Chamber Flux Data over NSA Upland Sites

    NASA Technical Reports Server (NTRS)

    Savage, Kathleen; Hall, Forrest G. (Editor); Conrad, Sara K. (Editor); Moore, Tim R.

    2000-01-01

    The BOReal Ecosystem-Atmosphere Study Trace Gas Biogeochemistry (BOREAS TGB-3) team collected methane and carbon dioxide (CH4, CO2) chamber flux measurements at the Northern Study Area (NSA) Fen, Old Black Spruce (OBS), Young Jack Pine (YJP), and auxiliary sites along Gillam Road and the 1989 burn site. Gas samples were extracted from chambers and analyzed at the NSA lab facility approximately every 7 days during May to September 1994 and June to October 1996. The data are provided in tabular ASCII files.

  9. SkyLine and SkyGas: Novel automated technologies for automatic GHG flux measurements

    NASA Astrophysics Data System (ADS)

    Ineson, Philip; Stockdale, James

    2014-05-01

    1. Concerns for the future of the Earth's climate centre around the anthropogenically-driven continuing increases in atmospheric concentrations of the major 'greenhouse gases' (GHGs) which include CO2, CH4 and N2O. A major component of the global budgets for all three of these gases is the flux between the atmosphere and terrestrial ecosystems. 2. Currently, these fluxes are poorly quantified, largely due to technical limitations associated with making these flux measurements. Whilst eddy covariance systems have greatly improved such measurements at the ecosystem scale, flux measurements at the plot scale are commonly made using labour intensive traditional 'cover box' approaches; technical limitations have frequently been a bottle-neck in producing adequate and appropriate GHG flux data necessary for making land management decisions. For example, there are almost no night time flux data for N2O fluxes, and frequently such data are only measured over bare soil patches. 3. We have been addressing the design of novel field equipment for the automation of GHG flux measurements at the chamber and plot scale and will present here some of the technical solutions we have developed. These solutions include the development of the SkyLine and SkyGas approaches which resolve many of the common problems associated with making high frequency, sufficiently replicated GHG flux measurements under field conditions. 4. Unlike most other automated systems, these technologies 'fly' a single chamber to the measurement site, rather than have multiple replicated chambers and analysers. We will present data showing how such systems can deliver high time and spatial resolution flux data, with a minimum of operator intervention and, potentially, at relatively low per plot cost. We will also show how such measurements can be extended to monitoring fluxes from freshwater features in the landscape.

  10. Quantifying the "chamber effect" in CO2 flux measurements

    NASA Astrophysics Data System (ADS)

    Vihermaa, Leena; Childs, Amy; Long, Hazel; Waldron, Susan

    2014-05-01

    The significance of aquatic CO2 emissions has received attention in recent years. For example annual aquatic emissions in the Amazon basin have been estimated as 500 Mt of carbon1. Methods for determining the flux rates include eddy covariance flux tower measurements, flux estimates calculated from partial pressure of CO2 (pCO2) in water and the use floating flux chambers connected to an infra-red gas analyser. The flux chamber method is often used because it is portable, cheaper and allows smaller scale measurements. It is also a direct method and hence avoids problems related to the estimation of the gas transfer coefficient that is required when fluxes are calculated from pCO2. However, the use of a floating chamber may influence the flux measurements obtained. The chamber shields the water underneath from effects of wind which could lead to lower flux estimates. Wind increases the flux rate by i) causing waves which increase the surface area for efflux, and ii) removing CO2 build up above the water surface, hence maintaining a higher concentration gradient. Many floating chambers have an underwater extension of the chamber below the float to ensure better seal to water surface and to prevent any ingress of atmospheric air when waves rock the chamber. This extension may cause additional turbulence in flowing water and hence lead to overestimation of flux rates. Some groups have also used a small fan in the chamber headspace to ensure thorough mixing of air in the chamber. This may create turbulence inside the chamber which could increase the flux rate. Here we present results on the effects of different chamber designs on the detected flux rates. 1Richey et al. 2002. Outgassing from Amazonian rivers and wetlands as a large tropical source of atmospheric CO2. Nature 416: 617-620.

  11. Calibration system for measuring the radon flux density.

    PubMed

    Onishchenko, A; Zhukovsky, M; Bastrikov, V

    2015-06-01

    The measurement of radon flux from soil surface is the useful tool for the assessment of radon-prone areas and monitoring of radon releases from uranium mining and milling residues. The accumulation chambers with hollow headspace and chambers with activated charcoal are the most used devices for these purposes. Systematic errors of the measurements strongly depend on the geometry of the chamber and diffusion coefficient of the radon in soil. The calibration system for the attestation of devices for radon flux measurements was constructed. The calibration measurements of accumulation chambers and chambers with activated charcoal were conducted. The good agreement between the results of 2D modelling of radon flux and measurements results was observed. It was demonstrated that reliable measurements of radon flux can be obtained by chambers with activated charcoal (equivalent volume ~75 l) or by accumulation chambers with hollow headspace of ~7-10 l and volume/surface ratio (height) of >15 cm. PMID:25977351

  12. An inter-comparison of surface energy flux measurement systems used during FIFE, 1987

    NASA Technical Reports Server (NTRS)

    Nie, D.; Kanemasu, E. T.; Fritschen, L. J.; Weaver, H.; Smith, E. A.; Verma, S. B.; Field, R. T.; Kustas, W.; Stewart, J. B.

    1990-01-01

    During the first International Satellite Land Surface Climatology Program Field Experiment (FIFE-87), surface energy fluxes were measured at 22 flux sites by nine groups of scientists using different measuring systems. A rover Bowen ratio station was taken to nearly all the flux stations to serve as a reference for estimating the instrument related differences. The rover system was installed within a few meters from the host instrument of a site. Net radiation, Bowen ratio, and latent heat fluxes were compared between the rover and the host for the stations visited. Linear regression analysis was used to examine the relationship between rover measurements and host measurements. These inter-comparisons are needed to examine the influence of instrumentation on measurement uncertainty. Highly significant effects of instrument type were detected from these comparisons. Instruments of the same type showed average differences of less than 5 percent for net radiation, 10 percent for Bowen ratio, and 6 percent for latent heat flux. The corresponding average differences for different types of instruments can be up to 10, 30, and 20 percent respectively. The Didcot net radiometer gave higher net radiation while the Swissteco type showed lower values, as compared to the corrected REBS model. The 4-way components methed and the Thornswaite type give similar values to the REBS. The SERBS type Bowen ratio systems exhibit slightly lower Bowen ratios and thus higher latent heat fluxes, compared to the AZET systems. Eddy correlation systems showed slightly lower latent heat flux in comparison to the Bowen ratio systems.

  13. Anthropogenic and Biogenic Features of Long-Term Measured CO Flux in North Downtown Houston, Texas.

    PubMed

    Park, Changhyoun; Schade, Gunnar W

    2016-01-01

    Long-term urban carbon cycle studies remain rare despite the importance of carbon for energy, air quality, and climate change. To study spatial and temporal variations of energy and carbon fluxes in a subtropical urban environment, eddy covariance flux measurements were conducted north of downtown Houston, TX, using a tall radio-tower installation. The results of the first 2 yr of measurements show that both concentrations and fluxes of CO display typical seasonal and diurnal variations in urban areas. The seasonal variation of net CO flux is driven by steady anthropogenic emissions dominated by car traffic and human respiration, moderated by the local deciduous tree foliage. Weekday-weekend differences were observed in carbon fluxes, but not concentrations, while diurnal changes were dominated by rush-hour peaks from traffic and vegetation influences. Interestingly, CO and CO concentrations, but not CO flux, exhibited long-term declines, especially comparing pre- and post-Hurricane Ike periods. A directional analysis of CO fluxes revealed that the highest fluxes typically occurred from northwest directions, most likely due to emissions from small industrial sources. Car traffic as carbon source was revealed via correlations of CO with CO during the morning rush hours, and of CO flux with traffic counts during winter time. The influence of urban vegetation on net CO fluxes was identified via correlations with daytime photosynthetically active radiation due to photosynthesis, and with nighttime temperatures due to ecosystem respiration. The study site is a net source of CO throughout all seasons. PMID:26828181

  14. FLUX MEASUREMENTS FROM A TALL TOWER IN A COMPLEX LANDSCAPE

    SciTech Connect

    Kurzeja, R.; Weber, A.; Chiswell, S.; Parker, M.

    2010-07-22

    The accuracy and representativeness of flux measurements from a tall tower in a complex landscape was assessed by examining the vertical and sector variability of the ratio of wind speed to momentum flux and the ratio of vertical advective to eddy flux of heat. The 30-60 m ratios were consistent with theoretical predictions which indicate well mixed flux footprints. Some variation with sector was observed that were consistent with upstream roughness. Vertical advection was negligible compared with vertical flux except for a few sectors at night. This implies minor influence from internal boundary layers. Flux accuracy is a function of sector and stability but 30-60 m fluxes were found to be generally representative of the surrounding landscape. This paper will study flux data from a 300 m tower, with 4 levels of instruments, in a complex landscape. The surrounding landscape will be characterized in terms of the variation in the ratio of mean wind speed to momentum flux as a function of height and wind direction. The importance of local advection will be assessed by comparing vertical advection with eddy fluxes for momentum and heat.

  15. How errors on meteorological variables impact simulated ecosystem fluxes: a case study for six French sites

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Ciais, P.; Peylin, P.; Viovy, N.; Longdoz, B.; Bonnefond, J. M.; Rambal, S.; Klumpp, K.; Olioso, A.; Cellier, P.; Maignan, F.; Eglin, T.; Calvet, J. C.

    2011-03-01

    We analyze how biases of meteorological drivers impact the calculation of ecosystem CO2, water and energy fluxes by models. To do so, we drive the same ecosystem model by meteorology from gridded products and by ''true" meteorology from local observation at eddy-covariance flux sites. The study is focused on six flux tower sites in France spanning across a 7-14 °C and 600-1040 mm yr-1 climate gradient, with forest, grassland and cropland ecosystems. We evaluate the results of the ORCHIDEE process-based model driven by four different meteorological models against the same model driven by site-observed meteorology. The evaluation is decomposed into characteristic time scales. The main result is that there are significant differences between meteorological models and local tower meteorology. The seasonal cycle of air temperature, humidity and shortwave downward radiation is reproduced correctly by all meteorological models (average R2=0.90). At sites located near the coast and influenced by sea-breeze, or located in altitude, the misfit of meteorological drivers from gridded dataproducts and tower meteorology is the largest. We show that day-to-day variations in weather are not completely well reproduced by meteorological models, with R2 between modeled grid point and measured local meteorology going from 0.35 (REMO model) to 0.70 (SAFRAN model). The bias of meteorological models impacts the flux simulation by ORCHIDEE, and thus would have an effect on regional and global budgets. The forcing error defined by the simulated flux difference resulting from prescribing modeled instead than observed local meteorology drivers to ORCHIDEE is quantified for the six studied sites and different time scales. The magnitude of this forcing error is compared to that of the model error defined as the modeled-minus-observed flux, thus containing uncertain parameterizations, parameter values, and initialization. The forcing error is the largest on a daily time scale, for which it is

  16. Validating CERES Radiative Fluxes in the Arctic with Airborne Radiative Flux Measurements from the ARISE Campaign

    NASA Astrophysics Data System (ADS)

    Corbett, J.; Bucholtz, A.; Kato, S.; Rose, F. G.; Smith, W. L., Jr.

    2015-12-01

    The Clouds and the Earth's Radiant Energy System (CERES) instruments on board NASA's Terra, Aqua, and Soumi-NPP satellites provide the only measurements of reflected solar shortwave and emitted longwave radiative flux over the Arctic. Various methods have shown the uncertainty of CERES fluxes over sea ice to be higher than other scene types. However validation against an independent radiative flux measurement has never been attempted. We present here an attempt to better quantify the uncertainty of time-and-space averaged CERES flux measurements using airborne measurements from the Arctic Radiation - IceBridge Sea Ice Experiment (ARISE). The ARISE campaign took place during September of 2014 based out of Fairbanks, Alaska, with most of the measurements taken in the vicinity of the sea ice edge between 125°W and 150°W, and 71°N to 77°N. For six of the flights, measurements were taken in a lawnmower type pattern over either 100 x 200 km box regions at a constant altitude of >6 km, or 100 x 100 km box regions at an altitude of between 200 m to 500 m. They were designed to resemble the CERES Level 3 spatial averaging grids, and were located and timed to coincide with a high number of CERES overpasses. On board the aircraft were a set of upward and downward facing shortwave and longwave broadband radiometers (BBR), along with other instruments measuring meteorological conditions and cloud properties. We have compared the broadband radiative fluxes from BBR with those from CERES for the three days where the aircraft was flying the high altitude pattern. We use the Fu-Liou radiative transfer model to account for differences in the measurement altitude between BBR and CERES. We will present results of the comparisons between the computed fluxes and the measured longwave and shortwave radiative fluxes.

  17. Atmospheric Attenuation Of Total Solar Flux By Clouds At Six Amazonian Sites: 1999-2001

    NASA Astrophysics Data System (ADS)

    Schafer, J.; Holben, B.; Eck, T.; Artaxo, P.; Yamasoe, M.; Procopio, A.

    2002-12-01

    In Brazil, we now have a data set of pyranometer measurements at several sites distributed across the Amazon basin, with a record spanning more than 3 years at some locations. This network represents one of the few such long-term flux data bases available for this region, and provides an opportunity to characterize the nature of atmospheric effects on surface, broadband irradiance. Sufficient data are now available to assess trends in cloud attenuation on a range of timescales (diurnally, seasonally, and interannually). Cloud-induced fractional and absolute total flux reductions at the surface were evaluated for all years and sites. The fractional reduction, fB was computed as the ratio of received irradiance to the modeled clear-sky irradiance for background (low) aerosol conditions. A distinct difference was found between cloud attenuation in the wet and dry seasons, particularly in the southern Amazon. Histograms of fB for typical wet season months reveal a bi-modal distribution with a reduction peak (when the solar beam is obstructed) and an enhancement peak (produced by edge reflections from broken cloud cover). This phenomenon has been noted previously at the Abracos Hill sites during a 2 month study in 1999 (Gu et al., 2001). Our multi-year, multi-site data now suggest this is a fairly consistent feature of wet season months in the southern sites in Rondonia and northern Mato Grosso, and of most or all months at the equatorial sites (Balbina, Belterra) in Para and Amazonas.

  18. Measurements of EUV coronal holes and open magnetic flux

    SciTech Connect

    Lowder, C.; Qiu, J.; Leamon, R.; Liu, Y.

    2014-03-10

    Coronal holes are regions on the Sun's surface that map the footprints of open magnetic field lines. We have developed an automated routine to detect and track boundaries of long-lived coronal holes using full-disk extreme-ultraviolet (EUV) images obtained by SOHO/EIT, SDO/AIA, and STEREO/EUVI. We measure coronal hole areas and magnetic flux in these holes, and compare the measurements with calculations by the potential field source surface (PFSS) model. It is shown that, from 1996 through 2010, the total area of coronal holes measured with EIT images varies between 5% and 17% of the total solar surface area, and the total unsigned open flux varies between (2-5)× 10{sup 22} Mx. The solar cycle dependence of these measurements is similar to the PFSS results, but the model yields larger hole areas and greater open flux than observed by EIT. The AIA/EUVI measurements from 2010-2013 show coronal hole area coverage of 5%-10% of the total surface area, with significant contribution from low latitudes, which is under-represented by EIT. AIA/EUVI have measured much enhanced open magnetic flux in the range of (2-4)× 10{sup 22} Mx, which is about twice the flux measured by EIT, and matches with the PFSS calculated open flux, with discrepancies in the location and strength of coronal holes. A detailed comparison between the three measurements (by EIT, AIA-EUVI, and PFSS) indicates that coronal holes in low latitudes contribute significantly to the total open magnetic flux. These low-latitude coronal holes are not well measured with either the He I 10830 line in previous studies, or EIT EUV images; neither are they well captured by the static PFSS model. The enhanced observations from AIA/EUVI allow a more accurate measure of these low-latitude coronal holes and their contribution to open magnetic flux.

  19. An analytical quantification of mass fluxes and natural attenuation rate constants at a former gasworks site

    NASA Astrophysics Data System (ADS)

    Bockelmann, Alexander; Ptak, Thomas; Teutsch, Georg

    2001-12-01

    A new integral groundwater investigation approach was used for the first time to quantify natural attenuation rates at field scale. In this approach, pumping wells positioned along two control planes were operated at distances of 140 and 280 m downstream of a contaminant source zone at a former gasworks site polluted with BTEX- (benzene, toluene, ethyl-benzene, o-, p-xylene) and PAH- (polycyclic aromatic hydrocarbons) compounds. Based on the quantified changes in total contaminant mass fluxes between the control planes, first-order natural attenuation rate constants could be estimated. For BTEX-compounds, these ranged from 1.4e-02 to 1.3e-01 day -1, whereas for PAH-compounds natural attenuation rate constants of 3.7e-04 to 3.1e-02 day -1 were observed. Microbial degradation activity at the site was indicated by an increase in dissolved iron mass flux and a reduction in sulphate mass flux between the two investigated control planes. In addition to information about total contaminant mass fluxes and average concentrations, an analysis of the concentration-time series measured at the control planes also allowed to semi-quantitatively delineate the aquifer regions most likely contaminated by the BTEX- and PAH-compounds.

  20. An analytical quantification of mass fluxes and natural attenuation rate constants at a former gasworks site.

    PubMed

    Bockelmann, A; Ptak, T; Teutsch, G

    2001-12-15

    A new integral groundwater investigation approach was used for the first time to quantify natural attenuation rates at field scale. In this approach, pumping wells positioned along two control planes were operated at distances of 140 and 280 m downstream of a contaminant source zone at a former gasworks site polluted with BTEX- (benzene, toluene, ethyl-benzene, o-, p-xylene) and PAH- (polycyclic aromatic hydrocarbons) compounds. Based on the quantified changes in total contaminant mass fluxes between the control planes, first-order natural attenuation rate constants could be estimated. For BTEX-compounds, these ranged from 1.4e-02 to 1.3e-01 day(-1) whereas for PAH-compounds natural attenuation rate constants of 3.7e-04 to 3.1e-02 day(-1) were observed. Microbial degradation activity at the site was indicated by an increase in dissolved iron mass flux and a reduction in sulphate mass flux between the two investigated control planes. In addition to information about total contaminant mass fluxes and average concentrations, an analysis of the concentration-time series measured at the control planes also allowed to semi-quantitatively delineate the aquifer regions most likely contaminated by the BTEX- and PAH-compounds. PMID:11820481

  1. Design of a differential radiometer for atmospheric radiative flux measurements

    NASA Astrophysics Data System (ADS)

    LaDelfe, Peter C.; Weber, Paul G.; Rodriguez, C. William

    1995-02-01

    The hemispherical optimized net radiometer (HONER) is an instrument under development at the Los Alamos National Laboratory as part of the Atmospheric Radiation measurements/Unmanned Aerospace Vehicles (ARM/UAV) program. HONER is a radiometer which will either measure directly the difference between the total upwelling and downwelling fluxes or the individual fluxes and will provide a means of measuring the atmospheric radiative flux divergence. Unlike existing instruments which only measure the upwelling and downwelling fluxes separately, HONER will achieve an optical difference by chopping the two fluxes alternately onto a common pyroelectric detector. HONER will provide data resolved into the two relevant spectral bands; one covering the solar dominated region from less than 0.4 micrometer to approximately 4 micrometers and the other covering the region from approximately 4 micrometers to greater than 50 micrometers, dominated by thermal radiation. The means of separating the spectral regions guarantees seamless summation to calculate the total flux. The fields-of-view are near-hemispherical, upward and downward. The instrument can be converted, in flight, from the differential mode to absolute mode, measuring the upwelling and downwelling fluxes separately and simultaneously. The instrument also features continuous calibration from on-board sources. We describe the basic design and operation of the sensor head and the on-board reference sources as well as the means of the initial deployment on a UAV. This instrument can also be used in ground-based, space, or other airborne applications.

  2. Sensible heat bias in open-path eddy covariance carbon dioxide flux measurements

    NASA Astrophysics Data System (ADS)

    Sonnentag, O.; Helbig, M.; Karoline, W.; Humphreys, E.; Quinton, W. L.; Bogoev, I.

    2015-12-01

    The widely observed differences between net carbon dioxide (CO2) flux estimates derived from eddy covariance systems deploying open- and closed-path infrared gas analyzers (IRGAs) pose a major challenge for site intercomparison studies. Our limited knowledge about potential systematic biases in the derivation of CO2 flux estimates by these two types of systems hampers our ability to detect significant differences in CO2 flux measurements made at contrasting ecosystems. Here we explore potential systematic biases in CO2 fluxes measured with two open-path IRGAs. Comparison of fluxes from open- (EC150 & IRGASON, Campbell Scientific Inc.) and (en)closed-path IRGAs (LI7000 & LI7200, LI-COR Biosciences) at a northern peatland and a northern boreal forest site revealed consistent differences in CO2 flux estimates across a wide range of environmental conditions. These differences directly scaled with the magnitude of the sensible heat flux indicating a selectively systematic bias in open-path CO2 flux measurements due to the temperature sensitivity of the CO2 density measurements. We present two empirical correction procedures: the "direct" approach requires data from a limited period of concurrent CO2 flux measurements by open- and closed-path IRGA-based eddy covariance systems, whereas the second approach only requires wintertime CO2 flux data from the open-path IRGA. The "direct" approach effectively removes the bias in the open-path CO2 flux measurements and results in remaining differences with the closed-path CO2 fluxes smaller than 0.5 µmol m-2 s-1. In contrast, the "wintertime" approach seems to overcompensate for the sensible heat effects with differences remaining between 0.9 µmol m-2 s-1 and 1.8 µmol m-2 s-1. When a high-frequency air temperature is used to compensate for the temperature sensitivity of the CO2 density measurements, open- and closed-path CO2 flux agree within ±0.5 µmol m-2 s-1, similar to the "direct" post-processing correction. These

  3. Micro-scale modelling of energy fluxes over a small Fluxnet forest site in Denmark

    NASA Astrophysics Data System (ADS)

    Sogachev, A.; Dellwik, E.; Boegh, E.

    2012-12-01

    Most forests, especially in Europe, are too small to fulfil strict fetch requirements associated with idealized flux observations in undisturbed, homogeneous flow. As a consequence of limited fetch, the flux measured above the canopy will often deviate from the source strength underlying the measurements. Since representative measurements focused on heterogeneous effects are scarce because of demanding experimental arrangements the numerical modelling are often recruited for analysis of these deviations. During the last years the atmospheric boundary layer (ABL) model SCADIS (scalar distribution model; Sogachev et al., 2002, Tellus 54B, 784-819) has been successfully applied especially in the region adjacent to a forest edge in order to improve flux data interpretation. Most of the analyses were done for the neutral case and in two-dimensional mode. When analyzing the effect of a forest edge on both flow and passive scalar properties, numerical studies showed that sources located on a soil surface are major contributors to wave-like flux behavior downwind of the leading edge, and that it is important to distinguish the effects of ground sources from those of the foliage. In the present work, we apply the SCADIS model with enhanced turbulence closure including buoyancy for investigation of the daily course of energy fluxes over patchy forested terrain in Denmark, where the model is used in three-dimensional mode. The modelling results (with 50 m horizontal resolution) are in good qualitative agreement with high-resolution (60 m and 120 m) remote-sensing data of the effective surface temperature of the area near the site in focus: the forested areas are colder in daytime and warmer in night time than surrounding open areas. In contrast to the remote sensing approach, SCADIS provides the information about spatial distribution of latent and sensible heat vertical fluxes in the whole ABL. Topography and forest edge effects result in vertical turbulent fluxes that

  4. A Preliminary Study of CO2 Flux Measurements by Lidar

    NASA Technical Reports Server (NTRS)

    Gibert, Fabien; Koch, Grady J.; Beyon, Jeffrey Y.; Hilton, T.; Davis, Kenneth J.; Andrews, Arlyn; Ismail, Syed; Singh, Upendra N.

    2008-01-01

    A mechanistic understanding of the global carbon cycle requires quantification of terrestrial ecosystem CO2 fluxes at regional scales. In this paper, we analyze the potential of a Doppler DIAL system to make flux measurements of atmospheric CO2 using the eddy-covariance and boundary layer budget methods and present results from a ground based experiment. The goal of this study is to put CO2 flux point measurements in a mesoscale context. In June 2007, a field experiment combining a 2-m Doppler Heterodyne Differential Absorption Lidar (HDIAL) and in-situ sensors of a 447-m tall tower (WLEF) took place in Wisconsin. The HDIAL measures simultaneously: 1) CO2 mixing ratio, 2) atmosphere structure via aerosol backscatter and 3) radial velocity. We demonstrate how to synthesize these data into regional flux estimates. Lidar-inferred fluxes are compared with eddy-covariance fluxes obtained in-situ at 396m AGL from the tower. In cases where the lidar was not yet able to measure the fluxes with acceptable precision, we discuss possible modifications to improve system performance.

  5. Determining Maximum Glycolytic Capacity Using Extracellular Flux Measurements

    PubMed Central

    Mookerjee, Shona A.; Nicholls, David G.; Brand, Martin D.

    2016-01-01

    Measurements of glycolytic rate and maximum glycolytic capacity using extracellular flux analysis can give crucial information about cell status and phenotype during normal operation, development of pathology, differentiation, and malignant transformation. They are also of great use when assessing the effects of chemical or drug treatments. Here, we experimentally define maximum glycolytic capacity, demonstrate how it differs from glycolytic rate, and provide a protocol for determining the basal glycolytic rate and maximum glycolytic capacity in cells using extracellular flux measurements. The results illustrate the power of extracellular flux analysis to describe the energetics of adherent cells in culture in a fully quantitative way. PMID:27031845

  6. Measurement of emission fluxes from Technical Area 54, Area G and L. Final report

    SciTech Connect

    Eklund, B.

    1995-03-15

    The emission flux (mass/time-area) of tritiated water from TA-54 was measured to support the characterization of radioactive air emissions from waste sites for the Radioactive Air Emissions Management (RAEM) program and for the Area G Performance Assessment. Measurements were made at over 180 locations during the summers of 1993 and 1994, including randomly selected locations across Area G, three suspected areas of contamination at Area G, and the property surrounding TA-54. The emission fluxes of radon were measured at six locations and volatile organic compounds (VOCs) at 30 locations. Monitoring was performed at each location over a several-hour period using the U.S. EPA flux chamber approach. Separate samples for tritiated water, radon, and VOCs were collected and analyzed in off-site laboratories. The measured tritiated water emission fluxes varied over several orders of magnitude, from background levels of about 3 pCi/m{sup 2}-min to 9.69 x 10{sup 6} pCi/m{sup 2}-min near a disposal shaft. Low levels of tritiated water were found to have migrated into Pajarito Canyon, directly south of Area G. The tritium flux data were used to generate an estimated annual emission rate of 14 Curies/yr for all of Area G, with the majority of this activity being emitted from relatively small areas adjacent to several disposal shafts. The estimated total annual release is less than 1% of the total tritium release from all LANL in 1992 and results in a negligible off-site dose. Based on the limited data available, the average emission flux of radon from Area G is estimated to be 8.1 pCi/m{sup 2}-min. The measured emission fluxes of VOCs were < 100 {mu}g/m{sup 2}-min, which is small compared with fluxes typically measured at hazardous waste landfills. The air quality impacts of these releases were evaluated in a separate report.

  7. Measurement of magnetic fluctuation-induced particle flux (invited)

    SciTech Connect

    Ding, W. X.; Brower, D. L.; Yates, T. Y.

    2008-10-15

    Magnetic field fluctuation-induced particle transport has been directly measured in the high-temperature core of the MST reversed field pinch plasma. Measurement of radial particle transport is achieved by combining various interferometry techniques, including Faraday rotation, conventional interferometry, and differential interferometry. It is observed that electron convective particle flux and its divergence exhibit a significant increase during a sawtooth crash. In this paper, we describe the basic techniques employed to determine the particle flux.

  8. Uncertainty analysis of the Operational Simplified Surface Energy Balance (SSEBop) model at multiple flux tower sites

    NASA Astrophysics Data System (ADS)

    Chen, Mingshi; Senay, Gabriel B.; Singh, Ramesh K.; Verdin, James P.

    2016-05-01

    Evapotranspiration (ET) is an important component of the water cycle - ET from the land surface returns approximately 60% of the global precipitation back to the atmosphere. ET also plays an important role in energy transport among the biosphere, atmosphere, and hydrosphere. Current regional to global and daily to annual ET estimation relies mainly on surface energy balance (SEB) ET models or statistical and empirical methods driven by remote sensing data and various climatological databases. These models have uncertainties due to inevitable input errors, poorly defined parameters, and inadequate model structures. The eddy covariance measurements on water, energy, and carbon fluxes at the AmeriFlux tower sites provide an opportunity to assess the ET modeling uncertainties. In this study, we focused on uncertainty analysis of the Operational Simplified Surface Energy Balance (SSEBop) model for ET estimation at multiple AmeriFlux tower sites with diverse land cover characteristics and climatic conditions. The 8-day composite 1-km MODerate resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) was used as input land surface temperature for the SSEBop algorithms. The other input data were taken from the AmeriFlux database. Results of statistical analysis indicated that the SSEBop model performed well in estimating ET with an R2 of 0.86 between estimated ET and eddy covariance measurements at 42 AmeriFlux tower sites during 2001-2007. It was encouraging to see that the best performance was observed for croplands, where R2 was 0.92 with a root mean square error of 13 mm/month. The uncertainties or random errors from input variables and parameters of the SSEBop model led to monthly ET estimates with relative errors less than 20% across multiple flux tower sites distributed across different biomes. This uncertainty of the SSEBop model lies within the error range of other SEB models, suggesting systematic error or bias of the SSEBop model is within the

  9. The 3He flux gauge in the Sargasso Sea: a determination of physical nutrient fluxes to the euphotic zone at the Bermuda Atlantic Time-series Site

    NASA Astrophysics Data System (ADS)

    Stanley, R. H. R.; Jenkins, W. J.; Doney, S. C.; Lott, D. E., III

    2015-09-01

    Significant rates of primary production occur in the oligotrophic ocean, without any measurable nutrients present in the mixed layer, fueling a scientific paradox that has lasted for decades. Here, we provide a new determination of the annual mean physical supply of nitrate to the euphotic zone in the western subtropical North Atlantic. We combine a 3-year time series of measurements of tritiugenic 3He from 2003 to 2006 in the surface ocean at the Bermuda Atlantic Time-series Study (BATS) site with a sophisticated noble gas calibrated air-sea gas exchange model to constrain the 3He flux across the sea-air interface, which must closely mirror the upward 3He flux into the euphotic zone. The product of the 3He flux and the observed subsurface nitrate-3He relationship provides an estimate of the minimum rate of new production in the BATS region. We also apply the gas model to an earlier time series of 3He measurements at BATS in order to recalculate new production fluxes for the 1985 to 1988 time period. The observations, despite an almost 3-fold difference in the nitrate-3He relationship, yield a roughly consistent estimate of nitrate flux. In particular, the nitrate flux from 2003 to 2006 is estimated to be 0.65 ± 0.14 mol m-2 yr-1, which is ~40 % smaller than the calculated flux for the period from 1985 to 1988. The difference in nitrate flux between the time periods may be signifying a real difference in new production resulting from changes in subtropical mode water formation. Overall, the nitrate flux is larger than most estimates of export fluxes or net community production fluxes made locally for the BATS site, which is likely a reflection of the larger spatial scale covered by the 3He technique and potentially also by the decoupling of 3He and nitrate during the obduction of water masses from the main thermocline into the upper ocean. The upward nitrate flux is certainly large enough to support observed rates of primary production at BATS and more generally

  10. Measuring Regional CO2 Fluxes Using a Lagrangian Approach

    NASA Astrophysics Data System (ADS)

    Martins, D. K.; Sweeney, C.; Stirm, B. H.; Shepson, P. B.

    2008-12-01

    The difficulty of measuring regional fluxes of CO2 has limited our understanding of the global carbon budget and the processes controlling carbon exchange across politically relevant spatial scales. A Lagrangian experiment was conducted over Iowa on June 19, 2007 as part of the North American Carbon Program's Mid-Continent Intensive using a light-weight, cost-effective aircraft to measure a net drawdown of CO2 concentration within the boundary layer. The drawdown is related to photosynthetic uptake when emission footprints are considered using a combination of emission inventories from the Vulcan project and HYSPLIT source contributions. Entrainment through the top of the boundary layer is measured directly using turbulence measurements from an onboard probe capable of measuring winds in 3-dimensions. Results show a total average CO2 flux of -5.3±0.7 μmol m-2 s-1. The average flux from fossil fuels over the measurement area is 2.8±0.4 μmol m-2 s-1. Thus, the CO2 flux attributable to the vegetation is -8.1±0.8 μmol m-2 s-1. The magnitude of the vegetative flux is comparable to other studies using the Lagrangian approach, but it is smaller than tower- based eddy covariance fluxes over the same period and measurement area. Sensitivities to analysis procedures and discrepancies between aircraft and tower-based measurements are discussed. We describe an aircraft Lagrangian experiment that offers direct, reliable, and cost-effective means for measuring CO2 fluxes at regional scales that can be used to compare to ecosystem models or to satellite measurements.

  11. Error Evaluation of Methyl Bromide Aerodynamic Flux Measurements

    USGS Publications Warehouse

    Majewski, M.S.

    1997-01-01

    Methyl bromide volatilization fluxes were calculated for a tarped and a nontarped field using 2 and 4 hour sampling periods. These field measurements were averaged in 8, 12, and 24 hour increments to simulate longer sampling periods. The daily flux profiles were progressively smoothed and the cumulative volatility losses increased by 20 to 30% with each longer sampling period. Error associated with the original flux measurements was determined from linear regressions of measured wind speed and air concentration as a function of height, and averaged approximately 50%. The high errors resulted from long application times, which resulted in a nonuniform source strength; and variable tarp permeability, which is influenced by temperature, moisture, and thickness. The increase in cumulative volatilization losses that resulted from longer sampling periods were within the experimental error of the flux determination method.

  12. A simple laboratory system for diffusive radon flux measurements

    NASA Astrophysics Data System (ADS)

    Kranrod, C.; Chanyotha, S.; Tonlublao, S.; Burnett, W. C.

    2015-05-01

    This study designed a simple, custom-made system to estimate the diffusive radon flux from solid materials (e.g., sediments, soils, building materials). Determination of the radon flux is based on the measurement of the radon activity in the air over time inside a closed loop system. For sediments, the system consists of wet sediment and water inside a gas-tight flask connected in a closed loop to a drying system and a radon analyzer (Durridge RAD7). The flux is determined based on an initial slope method in which the slope of radon activities vs. time plot during the first 12 h is evaluated. The slope is then multiplied by the total air volume and divided by the exposed sediment area to obtain the radon flux. The minimal thickness or mass of wet sediment should be about 4 cm or (equivalent to approximately 150 g of wet sediment) to obtain a reliable radon diffusive flux in this study.

  13. Design of a differential radiometer for atmospheric radiative flux measurements

    SciTech Connect

    LaDelfe, P.C.; Weber, P.G.; Rodriguez, C.W.

    1994-11-01

    The Hemispherical Optimized NEt Radiometer (HONER) is an instrument under development at the Los Alamos National Laboratory for deployment on an unmanned aerospace vehicle as part of the Atmospheric Radiation Measurements (ARM/UAV) program. HONER is a differential radiometer which will measure the difference between the total upwelling and downwelling fluxes and is intended to provide a means of measuring the atmospheric radiative flux divergence. Unlike existing instruments which measure the upwelling and downwelling fluxes separately, HONER will achieve an optical difference by chopping the two fluxes alternately onto a common pyroelectric detector. HONER will provide data resolved into two spectral bands; one covering the solar dominated region from less than 0.4 micrometer to approximately 4.5 micrometers and the other covering the region from approximately 4.5 micrometers to greater than 50 micrometers, dominated by thermal radiation. The means of separating the spectral regions guarantees seamless summation to calculate the total flux. The fields-of-view are near-hemispherical, upward and downward. The instrument can be converted, in flight, from the differential mode to absolute mode, measuring the upwelling and downwelling fluxes separately and simultaneously. The instrument also features continuous calibration from on-board sources. We will describe the design and operation of the sensor head and the on-board reference sources as well as the means of deployment.

  14. Design of a differential radiometer for atmospheric radiative flux measurements

    NASA Astrophysics Data System (ADS)

    Ladelfe, P. C.; Weber, P. G.; Rodriguez, C. W.

    The Hemispherical Optimized NEt Radiometer (HONER) is an instrument under development at the Los Alamos National Laboratory for deployment on an unmanned aerospace vehicle as part of the Atmospheric Radiation Measurements (ARM/UAV) program. HONER is a differential radiometer which will measure the difference between the total upwelling and downwelling fluxes and is intended to provide a means of measuring the atmospheric radiative flux divergence. Unlike existing instruments which measure the upwelling and downwelling fluxes separately, HONER will achieve an optical difference by chopping the two fluxes alternately onto a common pyroelectric detector. HONER will provide data resolved into two spectral bands; one covering the solar dominated region from less than 0.4 micrometer to approximately 4.5 micrometers and the other covering the region from approximately 4.5 micrometers to greater than 50 micrometers, dominated by thermal radiation. The means of separating the spectral regions guarantees seamless summation to calculate the total flux. The fields-of-view are near-hemispherical, upward and downward. The instrument can be converted, in flight, from the differential mode to absolute mode, measuring the upwelling and downwelling fluxes separately and simultaneously. The instrument also features continuous calibration from on-board sources. We will describe the design and operation of the sensor head and the on-board reference sources as well as the means of deployment.

  15. Measurement of surface energy fluxes in a rangeland ecosystem and comparison with a multi-layer canopy model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rangeland ecosystems are often characterized by a patchy mosaic of vegetation types, making measurement and modeling of surface energy fluxes particularly challenging. The purpose of this study was to evaluate surface energy fluxes measured using eddy correlation at three rangeland sites, and use ...

  16. Airborne flux measurements of biogenic volatile organic compounds over California

    NASA Astrophysics Data System (ADS)

    Misztal, P. K.; Karl, T.; Weber, R.; Jonsson, H. H.; Guenther, A. B.; Goldstein, A. H.

    2014-03-01

    Biogenic Volatile Organic Compound (BVOC) fluxes were measured onboard the CIRPAS Twin Otter aircraft as part of the California Airborne BVOC Emission Research in Natural Ecosystem Transects (CABERNET) campaign during June 2011. The airborne virtual disjunct eddy covariance (AvDEC) approach used measurements from a PTR-MS and a wind radome probe to directly determine fluxes of isoprene, MVK + MAC, methanol, monoterpenes, and MBO over ∼10 000 km of flight paths focusing on areas of California predicted to have the largest emissions of isoprene. The Fast Fourier Transform (FFT) approach was used to calculate fluxes over long transects of more than 15 km, most commonly between 50 and 150 km. The Continuous Wavelet Transformation (CWT) approach was used over the same transects to also calculate "instantaneous" fluxes with localization of both frequency and time independent of non-stationarities. Vertical flux divergence of isoprene is expected due to its relatively short lifetime and was measured directly using "racetrack" profiles at multiple altitudes. It was found to be linear and in the range 5% to 30% depending on the ratio of aircraft altitude to PBL height (z / zi). Fluxes were generally measured by flying consistently at 400 ± 50 m (a.g.l.) altitude, and extrapolated to the surface according to the determined flux divergence. The wavelet-derived surface fluxes of isoprene averaged to 2 km spatial resolution showed good correspondence to Basal Emission Factor (BEF) landcover datasets used to drive biogenic VOC (BVOC) emission models. The surface flux of isoprene was close to zero over Central Valley crops and desert shrublands, but was very high (up to 15 mg m-2 h-1) above oak woodlands, with clear dependence of emissions on temperature and oak density. Isoprene concentrations of up to 8 ppb were observed at aircraft height on the hottest days and over the dominant source regions. While isoprene emissions from agricultural crop regions, shrublands, and

  17. A new low-power, open-path instrument for measuring methane flux by eddy covariance

    NASA Astrophysics Data System (ADS)

    McDermitt, D.; Burba, G.; Xu, L.; Anderson, T.; Komissarov, A.; Riensche, B.; Schedlbauer, J.; Starr, G.; Zona, D.; Oechel, W.; Oberbauer, S.; Hastings, S.

    2011-02-01

    This paper describes a new low-power instrument for measuring methane flux by eddy covariance method at sites without grid power. Design and field performance of the LI-7700 Methane Analyzer (LI-COR Biosciences) are examined in this study. The instrument uses 8 W of power in steady-state operation and employs a tunable diode laser in an open Herriott cell configuration with 0.47 m base path and 30 m optical path length. Methane number density is measured using wavelength modulation spectroscopy (WMS) with 2f detection. Typical signal noise is <5 ppb rms at 10 Hz. Corrections for variations in temperature, pressure and water vapor are described. Data losses due to mirror contamination and condensation are minimized by a radiation shield and automatic mirror cleaning system and are shown to be small. Measured spectra and co-spectra are shown to follow the Kaimal model at deployment sites meeting classical criteria, and to follow sensible heat flux co-spectra from the sonic anemometer in most other cases, including difficult ones. Measured fluxes are similar in magnitude to those expected from the literature, and zero flux was measured during both summer and winter at a site known to have fluxes at or very near zero.

  18. Radiative flux measurements in the stratosphere

    NASA Technical Reports Server (NTRS)

    Valero, Francisco P. J.

    1990-01-01

    The objective is to determine how the stratospheric tropospheric exchange of water vapor is affected by the interaction of solar (visible) and planetary (infrared) radiation with tropical cumulonimbus anvils. This research involves field measurements from the ER-2 aircraft as well as radiative transfer modelling to determine heating and cooling rates and profiles that directly affect the exchange between the troposphere and the stratosphere.

  19. Measurement of LNAPL flux using single-well intermittent mixing tracer dilution tests.

    PubMed

    Smith, Tim; Sale, Tom; Lyverse, Mark

    2012-01-01

    The stability of subsurface Light Nonaqueous Phase Liquids (LNAPLs) is a key factor driving expectations for remedial measures at LNAPL sites. The conventional approach to resolving LNAPL stability has been to apply Darcy's Equation. This paper explores an alternative approach wherein single-well tracer dilution tests with intermittent mixing are used to resolve LNAPL stability. As a first step, an implicit solution for single-well intermittent mixing tracer dilution tests is derived. This includes key assumptions and limits on the allowable time between intermittent mixing events. Second, single-well tracer dilution tests with intermittent mixing are conducted under conditions of known LNAPL flux. This includes a laboratory sand tank study and two field tests at active LNAPL recovery wells. Results from the sand tank studies indicate that LNAPL fluxes in wells can be transformed into formation fluxes using corrections for (1) LNAPL thicknesses in the well and formation and (2) convergence of flow to the well. Using the apparent convergence factor from the sand tank experiment, the average error between the known and measured LNAPL fluxes is 4%. Results from the field studies show nearly identical known and measured LNAPL fluxes at one well. At the second well the measured fluxes appear to exceed the known value by a factor of two. Agreement between the known and measured LNAPL fluxes, within a factor of two, indicates that single-well tracer dilution tests with intermittent mixing can be a viable means of resolving LNAPL stability. PMID:22489832

  20. Key to GHG fluxes from organic soils: site characteristics, agricultural practices or water table management?

    NASA Astrophysics Data System (ADS)

    Tiemeyer, Bärbel

    2015-04-01

    Drained peatlands are hotspots of greenhouse gas (GHG) emissions. Agriculture is the major land use type for peatlands in Germany and other European countries, but strongly varies in its intensity regarding the groundwater level and the agricultural management. Although the mean annual water table depth is sometimes proposed as an overall predictor for GHG emissions, there is a strong variability of its effects on different peatlands. Furthermore, re-wetting measures generally decrease carbon dioxide emissions, but may strongly increase methane emissions. We synthesized 250 annual GHG budgets for 120 different sites in 13 German peatlands. Carbon dioxide (net ecosystem exchange and ecosystem respiration), nitrous oxide and methane fluxes were measured with transparent and opaque manual chambers. Land management ranged from very intensive use with arable land or grassland with up to five cuts per year to partially or completely re-wetted peatlands. Besides the GHG fluxes, biomass yield, fertilisation, groundwater level, climatic data, vegetation composition and soil properties were measured. Overall, we found a large variability of the total GHG budget ranging from small uptakes to extremely high emissions (> 70 t CO2-equivalents/(ha yr)). At nearly all sites, carbon dioxide was the major component of the GHG budget. Site conditions, especially the nitrogen content of the unsaturated zone and the intra-annual water level distribution, controlled the GHG emissions of the agricultural sites. Although these factors are influenced by natural conditions (peat type, regional hydrology), they could be modified by an improved water management. Agricultural management such as the number of cuts had only a minor influence on the GHG budgets. At the level of individual peatlands, higher water levels always decreased carbon dioxide emissions. In nearly all cases, the trade-off between reduced carbon dioxide and increased methane emissions turned out in favour of the re

  1. Cosmological flux noise and measured noise power spectra in SQUIDs

    PubMed Central

    Beck, Christian

    2016-01-01

    The understanding of the origin of 1/f magnetic flux noise commonly observed in superconducting devices such as SQUIDs and qubits is still a major unsolved puzzle. Here we discuss the possibility that a significant part of the observed low-frequency flux noise measured in these devices is ultimately seeded by cosmological fluctuations. We consider a theory where a primordial flux noise field left over in unchanged form from an early inflationary or quantum gravity epoch of the universe intrinsically influences the phase difference in SQUIDs and qubits. The perturbation seeds generated by this field can explain in a quantitatively correct way the form and amplitude of measured low-frequency flux noise spectra in SQUID devices if one takes as a source of fluctuations the primordial power spectrum of curvature fluctuations as measured by the Planck collaboration. Our theoretical predictions are in excellent agreement with recent low-frequency flux noise measurements of various experimental groups. Magnetic flux noise, so far mainly considered as a nuisance for electronic devices, may thus contain valuable information about fluctuation spectra in the very early universe. PMID:27320418

  2. Cosmological flux noise and measured noise power spectra in SQUIDs

    NASA Astrophysics Data System (ADS)

    Beck, Christian

    2016-06-01

    The understanding of the origin of 1/f magnetic flux noise commonly observed in superconducting devices such as SQUIDs and qubits is still a major unsolved puzzle. Here we discuss the possibility that a significant part of the observed low-frequency flux noise measured in these devices is ultimately seeded by cosmological fluctuations. We consider a theory where a primordial flux noise field left over in unchanged form from an early inflationary or quantum gravity epoch of the universe intrinsically influences the phase difference in SQUIDs and qubits. The perturbation seeds generated by this field can explain in a quantitatively correct way the form and amplitude of measured low-frequency flux noise spectra in SQUID devices if one takes as a source of fluctuations the primordial power spectrum of curvature fluctuations as measured by the Planck collaboration. Our theoretical predictions are in excellent agreement with recent low-frequency flux noise measurements of various experimental groups. Magnetic flux noise, so far mainly considered as a nuisance for electronic devices, may thus contain valuable information about fluctuation spectra in the very early universe.

  3. Cosmological flux noise and measured noise power spectra in SQUIDs.

    PubMed

    Beck, Christian

    2016-01-01

    The understanding of the origin of 1/f magnetic flux noise commonly observed in superconducting devices such as SQUIDs and qubits is still a major unsolved puzzle. Here we discuss the possibility that a significant part of the observed low-frequency flux noise measured in these devices is ultimately seeded by cosmological fluctuations. We consider a theory where a primordial flux noise field left over in unchanged form from an early inflationary or quantum gravity epoch of the universe intrinsically influences the phase difference in SQUIDs and qubits. The perturbation seeds generated by this field can explain in a quantitatively correct way the form and amplitude of measured low-frequency flux noise spectra in SQUID devices if one takes as a source of fluctuations the primordial power spectrum of curvature fluctuations as measured by the Planck collaboration. Our theoretical predictions are in excellent agreement with recent low-frequency flux noise measurements of various experimental groups. Magnetic flux noise, so far mainly considered as a nuisance for electronic devices, may thus contain valuable information about fluctuation spectra in the very early universe. PMID:27320418

  4. Comparison of measured and modeled radiation, heat and water vapor fluxes: FIFE pilot study

    NASA Technical Reports Server (NTRS)

    Blad, Blaine L.; Verma, Shashi B.; Hubbard, Kenneth G.; Starks, Patrick; Hays, Cynthia; Norman, John M.; Waltershea, Elizabeth

    1988-01-01

    The primary objectives of the 1985 study were to test the feasibility of using radio frequency receivers to collect data from automated weather stations and to evaluate the use of the data collected by the automated weather stations for modeling the fluxes of latent heat, sensible heat, and radiation over wheat. The model Cupid was used to calculate these fluxes which were compared with fluxes of these entities measured using micrometeorological techniques. The primary objectives of the 1986 study were to measure and model reflected and emitted radiation streams at a few locations within the First International Satellite Land-Surface Climatology Project Field Experiment (FIFE) site and to compare modeled and measured latent heat and sensible heat fluxes from the prairie vegetation.

  5. Measurement of thermal fluxes in power plant components

    SciTech Connect

    Stradomskii, M.V.; Fedorova, O.V.; Maksimov, E.A.

    1985-12-01

    The authors present a method of recovering the thermal flux acting on a sensing element with respect to measurements of sensing element signals. The solution of such problems is prompted by the need for information on the actual values of the energy density entering parts of various power plants. The dynamics of temperatures at the sensing element surfaces in a thermal flux data unit is shown during start up from cold of a power plant. The variation in time of the thermal flux density is also shown as calculated by the proposed method.

  6. Cosmic muon flux measurements at the Kimballton Underground Research Facility

    NASA Astrophysics Data System (ADS)

    Kalousis, L. N.; Guarnaccia, E.; Link, J. M.; Mariani, C.; Pelkey, R.

    2014-08-01

    In this article, the results from a series of muon flux measurements conducted at the Kimballton Underground Research Facility (KURF), Virginia, United States, are presented. The detector employed for these investigations, is made of plastic scintillator bars readout by wavelength shifting fibers and multianode photomultiplier tubes. Data was taken at several locations inside KURF, spanning rock overburden values from ~ 200 to 1450 m.w.e. From the extracted muon rates an empirical formula was devised, that estimates the muon flux inside the mine as a function of the overburden. The results are in good agreement with muon flux calculations based on analytical models and MUSIC.

  7. Estimation of surface heat and moisture fluxes over a prairie grassland. II - Two-dimensional time filtering and site variability

    NASA Technical Reports Server (NTRS)

    Crosson, William L.; Smith, Eric A.

    1992-01-01

    The behavior of in situ measurements of surface fluxes obtained during FIFE 1987 is examined by using correlative and spectral techniques in order to assess the significance of fluctuations on various time scales, from subdiurnal up to synoptic, intraseasonal, and annual scales. The objectives of this analysis are: (1) to determine which temporal scales have a significant impact on areal averaged fluxes and (2) to design a procedure for filtering an extended flux time series that preserves the basic diurnal features and longer time scales while removing high frequency noise that cannot be attributed to site-induced variation. These objectives are accomplished through the use of a two-dimensional cross-time Fourier transform, which serves to separate processes inherently related to diurnal and subdiurnal variability from those which impact flux variations on the longer time scales. A filtering procedure is desirable before the measurements are utilized as input with an experimental biosphere model, to insure that model based intercomparisons at multiple sites are uncontaminated by input variance not related to true site behavior. Analysis of the spectral decomposition indicates that subdiurnal time scales having periods shorter than 6 hours have little site-to-site consistency and therefore little impact on areal integrated fluxes.

  8. Biogenic volatile organic compound emissions during BEARPEX 2009 measured by eddy covariance and flux-gradient similarity methods

    NASA Astrophysics Data System (ADS)

    Park, J.-H.; Fares, S.; Weber, R.; Goldstein, A. H.

    2012-09-01

    The Biosphere Effects on AeRosols and Photochemistry EXperiment (BEARPEX) took place in Blodgett Forest, a Ponderosa pine forest in the Sierra Nevada Mountains of California, during summer 2009. We deployed a Proton Transfer Reaction - Mass Spectrometer (PTR-MS) to measure fluxes and concentrations of biogenic volatile organic compounds (BVOCs). Eighteen ion species including the major BVOC expected at the site were measured sequentially at 5 heights to observe their vertical gradient from the forest floor to above the canopy. Fluxes of the 3 dominant BVOCs methanol, 2-Methyl-3-butene-2-ol (MBO), and monoterpenes, were measured above the canopy by the eddy covariance method. Canopy scale fluxes were also determined by the flux-gradient similarity method (K-theory). A universal K (Kuniv) was determined as the mean of individual K's calculated from the measured fluxes divided by vertical gradients for methanol, MBO, and monoterpenes. This Kuniv was then multiplied by the gradients of each observed ion species to compute their fluxes. The flux-gradient similarity method showed very good agreement with the Eddy Covariance method. Fluxes are presented for all measured species and compared to historical measurements from the same site, and used to test emission algorithms used to model fluxes at the regional scale. MBO was the dominant emission observed followed by methanol, monoterpenes, acetone, and acetaldehyde. The flux-gradient similarity method is shown to be a useful, and we recommend its use especially in experimental conditions when fast measurement of BVOC species is not available.

  9. Flux measurement and modeling in a typical mediterranean vineyard

    NASA Astrophysics Data System (ADS)

    Marras, Serena; Bellucco, Veronica; Pyles, David R.; Falk, Matthias; Sirca, Costantino; Duce, Pierpaolo; Snyder, Richard L.; Tha Paw U, Kyaw; Spano, Donatella

    2014-05-01

    Vineyard ecosystems are typical in the Mediterranean area, since wine is one of the most important economic sectors. Nevertheless, only a few studies have been conducted to investigate the interactions between this kind of vegetation and the atmosphere. These information are important both to understand the behaviour of such ecosystems in different environmental conditions, and are crucial to parameterize crop and flux simulation models. Combining direct measurements and modelling can obtain reliable estimates of surface fluxes and crop evapotranspiration. This study would contribute both to (1) directly measure energy fluxes and evapotranspiration in a typical Mediterranean vineyard, located in the South of Sardinia (Italy), through the application of the Eddy Covariance micrometeorological technique and to (2) evaluate the land surface model ACASA (Advanced-Canopy-Atmosphere-Soil Algorithm) in simulating energy fluxes and evapotranspiration over vineyard. Independent datasets of direct measurements were used to calibrate and validate model results during the growing period. Statistical analysis was performed to evaluate model performance and accuracy in predicting surface fluxes. Results will be showed as well as the model capability to be used for future studies to predict energy fluxes and crop water requirements under actual and future climate.

  10. Unsaturated zone carbon dioxide flux, mixing, and isotopic composition at the USGS Amargosa Desert Research Site

    NASA Astrophysics Data System (ADS)

    Conaway, C. H.; Thordsen, J. J.; Thomas, B.; Haase, K.; Moreo, M. T.; Walvoord, M. A.; Andraski, B. J.; Stonestrom, D. A.

    2015-12-01

    Elevated concentrations of tritium, radiocarbon, and volatile organic compounds at the USGS Amargosa Desert Research Site, adjacent to a low-level radioactive waste disposal facility, have stimulated research on factors affecting transport of these contaminants. This research includes an examination of unsaturated zone carbon dioxide (CO2) fluxes, mixing, and isotopic composition, which can help in understanding these factors. In late April 2015 we collected 76 soil-gas samples in multi-layer foil bags from existing 1.5-m deep tubes, both inside and outside the low-level waste area, as well as from two 110-m-deep multilevel gas-sampling boreholes and a distant background site. These samples were analyzed for carbon dioxide concentration and isotopic composition by direct injection into a cavity ring-down spectrometer. Graphical analysis of results indicates mixing of CO2 characteristic of the root zone (δ13C -18 ‰ VPDB), deep soil gas of the capillary fringe (-20‰), and CO2 produced by microbial respiration of organic matter disposed in the waste area trenches (-28‰). Land-surface boundary conditions are being constrained by the application of a novel non-dispersive infrared sensor and traditional concentration and flux measurements, including discrete CO2 flux data using a gas chamber method to complement continuous data from surface- and tower-based CO2 sensors. These results shed light on radionuclide and VOC mobilization and transport mechanisms from this and similar waste disposal facilities.

  11. Accuracy of quantum sensors measuring yield photon flux and photosynthetic photon flux

    NASA Technical Reports Server (NTRS)

    Barnes, C.; Tibbitts, T.; Sager, J.; Deitzer, G.; Bubenheim, D.; Koerner, G.; Bugbee, B.; Knott, W. M. (Principal Investigator)

    1993-01-01

    Photosynthesis is fundamentally driven by photon flux rather than energy flux, but not all absorbed photons yield equal amounts of photosynthesis. Thus, two measures of photosynthetically active radiation have emerged: photosynthetic photon flux (PPF), which values all photons from 400 to 700 nm equally, and yield photon flux (YPF), which weights photons in the range from 360 to 760 nm according to plant photosynthetic response. We selected seven common radiation sources and measured YPF and PPF from each source with a spectroradiometer. We then compared these measurements with measurements from three quantum sensors designed to measure YPF, and from six quantum sensors designed to measure PPF. There were few differences among sensors within a group (usually <5%), but YPF values from sensors were consistently lower (3% to 20%) than YPF values calculated from spectroradiometric measurements. Quantum sensor measurements of PPF also were consistently lower than PPF values calculated from spectroradiometric measurements, but the differences were <7% for all sources, except red-light-emitting diodes. The sensors were most accurate for broad-band sources and least accurate for narrow-band sources. According to spectroradiometric measurements, YPF sensors were significantly less accurate (>9% difference) than PPF sensors under metal halide, high-pressure sodium, and low-pressure sodium lamps. Both sensor types were inaccurate (>18% error) under red-light-emitting diodes. Because both YPF and PPF sensors are imperfect integrators, and because spectroradiometers can measure photosynthetically active radiation much more accurately, researchers should consider developing calibration factors from spectroradiometric data for some specific radiation sources to improve the accuracy of integrating sensors.

  12. Absolute photon-flux measurements in the vacuum ultraviolet

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Haddad, G. N.

    1974-01-01

    Absolute photon-flux measurements in the vacuum ultraviolet have extended to short wavelengths by use of rare-gas ionization chambers. The technique involves the measurement of the ion current as a function of the gas pressure in the ion chamber. The true value of the ion current, and hence the absolute photon flux, is obtained by extrapolating the ion current to zero gas pressure. Examples are given at 162 and 266 A. The short-wavelength limit is determined only by the sensitivity of the current-measuring apparatus and by present knowledge of the photoionization processes that occur in the rate gases.

  13. Auroral Energy and Energy Flux Measurements using GUVI

    NASA Astrophysics Data System (ADS)

    Holley, K. E.; McHarg, M. G.; Paxton, L.; Zhang, Y.; Morrison, D.

    2003-12-01

    We present estimates of the average characteristic energy and energy flux of energetic precipitating auroral particles. These estimates are derived from irradiance data measured on the Global Ultraviolet Imager (GUVI) flying on the TIMED satellite. We will present both the average and standard deviation of global maps of the energy and energy flux during the first year of GUVI data. We will compare results of the GUVI derived measurements to previous estimates of Hardy who used in-situ particle measurements from the Defense Meteorological Support Satellite (DMSP) program.

  14. High geothermal heat flux measured below the West Antarctic Ice Sheet.

    PubMed

    Fisher, Andrew T; Mankoff, Kenneth D; Tulaczyk, Slawek M; Tyler, Scott W; Foley, Neil

    2015-07-01

    The geothermal heat flux is a critical thermal boundary condition that influences the melting, flow, and mass balance of ice sheets, but measurements of this parameter are difficult to make in ice-covered regions. We report the first direct measurement of geothermal heat flux into the base of the West Antarctic Ice Sheet (WAIS), below Subglacial Lake Whillans, determined from the thermal gradient and the thermal conductivity of sediment under the lake. The heat flux at this site is 285 ± 80 mW/m(2), significantly higher than the continental and regional averages estimated for this site using regional geophysical and glaciological models. Independent temperature measurements in the ice indicate an upward heat flux through the WAIS of 105 ± 13 mW/m(2). The difference between these heat flux values could contribute to basal melting and/or be advected from Subglacial Lake Whillans by flowing water. The high geothermal heat flux may help to explain why ice streams and subglacial lakes are so abundant and dynamic in this region. PMID:26601210

  15. High geothermal heat flux measured below the West Antarctic Ice Sheet

    PubMed Central

    Fisher, Andrew T.; Mankoff, Kenneth D.; Tulaczyk, Slawek M.; Tyler, Scott W.; Foley, Neil

    2015-01-01

    The geothermal heat flux is a critical thermal boundary condition that influences the melting, flow, and mass balance of ice sheets, but measurements of this parameter are difficult to make in ice-covered regions. We report the first direct measurement of geothermal heat flux into the base of the West Antarctic Ice Sheet (WAIS), below Subglacial Lake Whillans, determined from the thermal gradient and the thermal conductivity of sediment under the lake. The heat flux at this site is 285 ± 80 mW/m2, significantly higher than the continental and regional averages estimated for this site using regional geophysical and glaciological models. Independent temperature measurements in the ice indicate an upward heat flux through the WAIS of 105 ± 13 mW/m2. The difference between these heat flux values could contribute to basal melting and/or be advected from Subglacial Lake Whillans by flowing water. The high geothermal heat flux may help to explain why ice streams and subglacial lakes are so abundant and dynamic in this region. PMID:26601210

  16. Estimation of water flux in urban area using eddy covariance measurements in Riverside, Southern California

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Micrometeorological methods can direct measure the sensible and latent heat flux in specific sites and provide robust estimates of the evaporative fraction (EF), which is the fraction of available surface energy contained in latent heat. Across a vegetation coverage gradient in urban area, an empir...

  17. Monitoring of MNSR operation by measuring subcritical photoneutron flux.

    PubMed

    Haddad, Kh; Alsomel, N

    2011-03-01

    Passive nondestructive assay methods are used to monitor the reactor's operation. It is required for nuclear regulatory, calculation validation and safeguards purposes. So, it plays a vital role in the safety and security of the nuclear plants. The possibility of MNSR operation monitoring by measuring the subcritical state photoneutron flux were investigated in this work. The photoneutron flux is induced by the fuels hard gamma radiation in the beryllium reflector. Theoretical formulation and experimental tests were performed. The results show that within a specified cooling time range, the photoneutron flux is induced by a single dominant hard gamma emitter such as (117)Cd (activation product) and (140)Ba ((140)La fission product). This phenomenon was utilized to monitor the cooling time and the operation neutron flux during the last campaign. Thus a passive nondestructive assay method is proposed with regard to the reactor operation's monitoring. PMID:21168337

  18. Direct measurements of CO2 flux in the Greenland Sea

    NASA Astrophysics Data System (ADS)

    Lauvset, Siv K.; McGillis, Wade R.; Bariteau, Ludovic; Fairall, C. W.; Johannessen, Truls; Olsen, Are; Zappa, Christopher J.

    2011-06-01

    During summer 2006 eddy correlation CO2 fluxes were measured in the Greenland Sea using a novel system set-up with two shrouded LICOR-7500 detectors. One detector was used exclusively to determine, and allow the removal of, the bias on CO2 fluxes due to sensor motion. A recently published correction method for the CO2-H2O cross-correlation was applied to the data set. We show that even with shrouded sensors the data require significant correction due to this cross-correlation. This correction adjusts the average CO2 flux by an order of magnitude from -6.7 × 10-2 mol m-2 day-1 to -0.61 × 10-2 mol m-2 day-1, making the corrected fluxes comparable to those calculated using established parameterizations for transfer velocity.

  19. How Well Can We Measure the Vertical Wind Speed? Implications for Fluxes of Energy and Mass

    NASA Astrophysics Data System (ADS)

    Kochendorfer, John; Meyers, Tilden P.; Frank, John; Massman, William J.; Heuer, Mark W.

    2012-11-01

    Sonic anemometers are capable of measuring the wind speed in all three dimensions at high frequencies (10-50 Hz), and are relied upon to estimate eddy-covariance-based fluxes of mass and energy over a wide variety of surfaces and ecosystems. In this study, wind-velocity measurement errors from a three-dimensional sonic anemometer with a non-orthogonal transducer orientation were estimated for over 100 combinations of angle-of-attack and wind direction using a novel technique to measure the true angle-of-attack and wind speed within the turbulent atmospheric surface layer. Corrections to the vertical wind speed varied from -5 to 37% for all angles-of-attack and wind directions examined. When applied to eddy-covariance data from three NOAA flux sites, the wind-velocity corrections increased the magnitude of CO2 fluxes, sensible heat fluxes, and latent heat fluxes by ≈11%, with the actual magnitude of flux corrections dependent upon sonic anemometer, surface type, and scalar. A sonic anemometer that uses vertically aligned transducers to measure the vertical wind speed was also tested at four angles-of-attack, and corrections to the vertical wind speed measured using this anemometer were within ±1% of zero. Sensible heat fluxes over a forest canopy measured using this anemometer were 15% greater than sensible heat fluxes measured using a sonic anemometer with a non-orthogonal transducer orientation. These results indicate that sensors with a non-orthogonal transducer orientation, which includes the majority of the research-grade three-dimensional sonic anemometers currently in use, should be redesigned to minimize sine errors by measuring the vertical wind speed using one pair of vertically aligned transducers.

  20. Continuous measurements of methane flux in two Japanese temperate forests based on the micrometeorological and chamber methods

    NASA Astrophysics Data System (ADS)

    Yoshikawa, K.; Ueyama, M.; Takagi, K.; Kominami, Y.

    2015-12-01

    Methane (CH4) budget in forest ecosystems have not been accurately quantified due to limited measurements and considerable spatiotemporal heterogeneity. In order to quantify CH4 fluxes at temperate forest at various spatiotemporal scales, we have continuously measured CH4 fluxes at two upland forests based on the micrometeorological hyperbolic relaxed eddy accumulation (HREA) and automated dynamic closed chamber methods.The measurements have been conducted at Teshio experimental forest (TSE) since September 2013 and Yamashiro forest meteorology research site (YMS) since November 2014. Three automated chambers were installed on each site. Our system can measure CH4 flux by the micrometeorological HREA, vertical concentration profile at four heights, and chamber measurements by a laser-based gas analyzer (FGGA-24r-EP, Los Gatos Research Inc., USA).Seasonal variations of canopy-scale CH4 fluxes were different in each site. CH4 was consumed during the summer, but was emitted during the fall and winter in TSE; consequently, the site acted as a net annual CH4 source. CH4 was steadily consumed during the winter, but CH4 fluxes fluctuated between absorption and emission during the spring and summer in YMS. YMS acted as a net annual CH4 sink. CH4 uptake at the canopy scale generally decreased with rising soil temperature and increased with drying condition for both sites. CH4 flux measured by most of chambers showed the consistent sensitivity examined for the canopy scale to the environmental variables. CH4 fluxes from a few chambers located at a wet condition were independent of variations in soil temperature and moisture at both sites. Magnitude of soil CH4 uptake was higher than the canopy-scale CH4 uptake. Our results showed that the canopy-scale CH4 fluxes were totally different with the plot-scale CH4 fluxes by chambers, suggesting the considerable spatial heterogeneity in CH4 flux at the temperate forests.

  1. A True Eddy Accumulation - Eddy Covariance hybrid for measurements of turbulent trace gas fluxes

    NASA Astrophysics Data System (ADS)

    Siebicke, Lukas

    2016-04-01

    Eddy covariance (EC) is state-of-the-art in directly and continuously measuring turbulent fluxes of carbon dioxide and water vapor. However, low signal-to-noise ratios, high flow rates and missing or complex gas analyzers limit it's application to few scalars. True eddy accumulation, based on conditional sampling ideas by Desjardins in 1972, requires no fast response analyzers and is therefore potentially applicable to a wider range of scalars. Recently we showed possibly the first successful implementation of True Eddy Accumulation (TEA) measuring net ecosystem exchange of carbon dioxide of a grassland. However, most accumulation systems share the complexity of having to store discrete air samples in physical containers representing entire flux averaging intervals. The current study investigates merging principles of eddy accumulation and eddy covariance, which we here refer to as "true eddy accumulation in transient mode" (TEA-TM). This direct flux method TEA-TM combines true eddy accumulation with continuous sampling. The TEA-TM setup is simpler than discrete accumulation methods while avoiding the need for fast response gas analyzers and high flow rates required for EC. We implemented the proposed TEA-TM method and measured fluxes of carbon dioxide (CO2), methane (CH4) and water vapor (H2O) above a mixed beech forest at the Hainich Fluxnet and ICOS site, Germany, using a G2301 laser spectrometer (Picarro Inc., USA). We further simulated a TEA-TM sampling system using measured high frequency CO2 time series from an open-path gas analyzer. We operated TEA-TM side-by-side with open-, enclosed- and closed-path EC flux systems for CO2, H2O and CH4 (LI-7500, LI-7200, LI-6262, LI-7700, Licor, USA, and FGGA LGR, USA). First results show that TEA-TM CO2 fluxes were similar to EC fluxes. Remaining differences were similar to those between the three eddy covariance setups (open-, enclosed- and closed-path gas analyzers). Measured TEA-TM CO2 fluxes from our physical

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

    NASA Astrophysics Data System (ADS)

    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

  3. Measurement of Decoherence Time in a Flux Qubit

    NASA Astrophysics Data System (ADS)

    Harrabi, K.; Yoshihara, F.; Nakamura, Y.; Tsai, J. S.

    2006-09-01

    We present a measurement of the relaxation and the dephasing times in a flux qubit. In order to improve coherence of the qubit, two external parameters were optimized: the applied flux through the qubit loop and the bias current of the SQUID which serves as a readout device of the qubit state. At the optimal point the dephasing time measured with spin-echo technique was twice longer than the energy relaxation time. By changing one of the two bias parameters while keeping the other at the optimal value, one can separate the contribution of the noise in each parameter to the decoherence of the qubit.

  4. Calorimeter probes for measuring high thermal flux. [in arc jets

    NASA Technical Reports Server (NTRS)

    Russell, L. D.

    1979-01-01

    Expendable, slug-type calorimeter probes were developed for measuring high heat-flux levels of 10-30 kW/sq cm in electric-arc jet facilities. The probes were constructed with thin tungsten caps mounted on Teflon bodies. The temperature of the back surface of the tungsten cap is measured, and its time rate of change gives the steady-state absorbed heat flux as the calorimeter probe heats to destruction when inserted into the arc jet. Design, construction, test, and performance data are presented.

  5. High heat flux measurements and experimental calibrations/characterizations

    NASA Technical Reports Server (NTRS)

    Kidd, Carl T.

    1992-01-01

    Recent progress in techniques employed in the measurement of very high heat-transfer rates in reentry-type facilities at the Arnold Engineering Development Center (AEDC) is described. These advances include thermal analyses applied to transducer concepts used to make these measurements; improved heat-flux sensor fabrication methods, equipment, and procedures for determining the experimental time response of individual sensors; performance of absolute heat-flux calibrations at levels above 2,000 Btu/cu ft-sec (2.27 kW/cu cm); and innovative methods of performing in-situ run-to-run characterizations of heat-flux probes installed in the test facility. Graphical illustrations of the results of extensive thermal analyses of the null-point calorimeter and coaxial surface thermocouple concepts with application to measurements in aerothermal test environments are presented. Results of time response experiments and absolute calibrations of null-point calorimeters and coaxial thermocouples performed in the laboratory at intermediate to high heat-flux levels are shown. Typical AEDC high-enthalpy arc heater heat-flux data recently obtained with a Calspan-fabricated null-point probe model are included.

  6. Measuring diffuse neutrino fluxes with IceCube

    NASA Astrophysics Data System (ADS)

    Kowalski, Marek

    2005-05-01

    In this paper the sensitivity of a future kilometre-sized neutrino detector to detect and measure the diffuse flux of high energy neutrinos is evaluated. Event rates in established detection channels, such as muon events from charged current νμ interactions or cascade events from νe and ντ interaction, are calculated using a detailed Monte Carlo simulation. Neutrino fluxes as expected from prompt charm decay in the atmosphere or from astrophysical sources such as Active Galactic Nuclei are modelled assuming power laws. The ability to measure the normalization and slope of these spectra is then analysed. It is found that the cascade channel generally has a high sensitivity for the detection and characterization of the diffuse flux, when compared to what is expected for the upgoing- and downgoing-muon channels. A flux at the level of the Waxman Bahcall upper bound should be detectable in all channels separately while a combination of the information of the different channels will allow detection of a flux more than one order of magnitude lower. Neutrinos from the prompt decay of charmed mesons in the atmosphere should be detectable in future measurements for all but the lowest predictions.

  7. Aerosol flux measurements above a mixed forest at Borden, Ontario

    NASA Astrophysics Data System (ADS)

    Gordon, M.; Staebler, R. M.; Liggio, J.; Vlasenko, A.; Li, S.-M.; Hayden, K.

    2010-10-01

    Aerosol fluxes were measured above a mixed forest by Eddy Covariance (EC) with a Fast Mobility Particle Sizer (FMPS) at the Borden Forest Research Station in Ontario, Canada between 13 July and 12 August 2009. The FMPS, mounted at a height of 33 m (approximately 10 m above the canopy top) and housed in a temperature controlled enclosure, measured size-resolved particle concentrations for 3 to 410 nm at a rate of 1 Hz. For the size range 20fluxes were upward. The exchange velocity is between -0.5 and 2.0 mm s-1, with median values near 0.5 mm s-1 for all sizes between 24 and 280 nm. The net production rate of particles is highest for 75 nm particles and is near 0.4×106 m-2 s-1. Results indicate a decoupling of the above and below canopy spaces, whereby particles are stored in the canopy space at night, and are then diluted with cleaner air above during the day. Chemically speciated flux measurements from a previous study at the same location using a Quadrupole Aerosol Mass Spectrometer (Q-AMS) demonstrate a tendency towards downward fluxes, which may be due to an organic particle component which can not be resolved by the flux mode of the Q-AMS.

  8. Densitometric tomography using the measurement of muon flux

    NASA Astrophysics Data System (ADS)

    Hivert, F.; Busto, J.; Brunner, J.; Salin, P.; Gaffet, S.

    2013-12-01

    The knowledge of the subsurface properties is essentially obtained by geophysical methods, e.g. seismic imaging, electric prospection or gravimetry. The present work develops a recent method to investigate the in situ density of rocks using atmospheric the muon flux measurement , its attenuation depending on the rock density and thickness. This new geophysical technique have been mainly applied in volcanology (Lesparre N., 2011) using scintillator detectors. The present project (T2DM2) aims to realize underground muons flux measurements in order to characterizing the rock massif density variations above the LSBB underground research facility in Rustrel (France). The muon flux will be measure with a new Muon telescope instrumentation using Micromegas detectors in Time Projection Chambers (TPC) configuration. The first step of the work presented considers the muon flux simulation using the Gaisser model, for the interactions between muons and atmospheric particles, and the MUSIC code (Kudryavtsev V. A., 2008) for the muons/rock interactions. The results show that the muon flux attenuation caused by density variations are enough significant to be observed until around 500 m depth and for period of time in the order of one month. Such a duration scale and depth of investigation is compatible with the duration of the water transfer processes involved within the Karst unsaturated zone where LSBB is located. Our work now concentrates on the optimization of the spatial distribution of detectors that will be deployed in future.

  9. Carbon flux to the deep in three open sites of the Southern European Seas (SES)

    NASA Astrophysics Data System (ADS)

    Gogou, Alexandra; Sanchez-Vidal, Anna; Durrieu de Madron, Xavier; Stavrakakis, Spyros; Calafat, Antoni M.; Stabholz, Marion; Psarra, Stella; Canals, Miquel; Heussner, Serge; Stavrakaki, Ioanna; Papathanassiou, Evangelos

    2014-01-01

    In this study, we investigate the strength and efficiency of carbon sequestration in the Southern European Seas (SES), by analyzing the export of POC at three deep sites located in the Western Mediterranean Sea (WMED), the Eastern Mediterranean Sea (EMED) and the Black Sea (BS). We combine estimations of satellite and algorithm-generated primary production data, calculated POC fluxes out of the euphotic layer and POC fluxes measured by sediment traps at the mesopelagic and bathypelagic layers during a one year period, with an ultimate goal to obtain a better understanding of the functioning of the biological pump in the SES. Annual particulate primary production based on satellite estimations (SeaWiFS) at the three sites, averages 205, 145 and 225 gC m- 2 y- 1 at the WMED, EMED and BS, respectively. According to our findings, the fraction of primary production that is exported out of the euphotic zone in the SES ranges between 4.2% and 11.4%, while the fraction reaching the mesopelagic layer (1000-1400 m depth) ranges between 0.6% and 1.8%. Finally, the fraction of primary production exported at the bathypelagic layer (2000-2800 m depth) is found to be 0.6%, 0.3% and 1.4% in the WMED, EMED and BS, respectively. The role of various processes responsible for the replenishment of surface waters with nutrients, giving rise to productivity episodes and organic carbon export to depth at the three SES sites is considered.

  10. Seasonality of Overstory and Understory Fluxes in a Semi-Arid Oak Savanna: What can be Learned from Comparing Measured and Modeled Fluxes?

    NASA Astrophysics Data System (ADS)

    Raz-Yaseef, N.; Sonnentag, O.; Kobayashi, H.; Chen, J. M.; Verfaillie, J. G.; Ma, S.; Baldocchi, D. D.

    2011-12-01

    Semi-arid climates experience large seasonal and inter-annual variability in radiation and precipitation, creating natural conditions adequate to study how year-to-year changes affect atmosphere-biosphere fluxes. Especially, savanna ecosystems, that combine tree and below-canopy components, create a unique environment in which phenology dramatically changes between seasons. We used a 10-year flux database in order to define seasonal and interannual variability of climatic inputs and fluxes, and evaluate model capability to reproduce observed variability. This is based on the perception that model capability to construct the deviation, and not the average, is important in order to correctly predict ecosystem sensitivity to climate change. Our research site is a low density and low LAI (0.8) semi-arid savanna, located at Tonzi Ranch, Northern California. In this system, trees are active during the warm season (Mar - Oct), and grasses are active during the wet season (Dec - May). Measurements of carbon and water fluxes above and below the tree canopy using eddy covariance and supplementary measurements have been made since 2001. Fluxes were simulated using bio-meteorological process-oriented ecosystem models: BEPS and 3D-CAONAK. Models were partly capable of reproducing fluxes on daily scales (R2=0.66). We then compared model outputs for different ecosystem components and seasons, and found distinct seasons with high correlations while other seasons were purely represented. Comparison was much higher for ET than for GPP. The understory was better simulated than the overstory. CANOAK overestimated spring understory fluxes, probably due to the capability to directly calculated 3D radiative transfer. BEPS underestimated spring understory fluxes, following the pre-description of grass die-off. Both models underestimated peak spring overstory fluxes. During winter tree dormant, modeled fluxes were null, but occasional high fluxes of both ET and GPP were measured following

  11. Measurement of neutrino flux from neutrino-electron elastic scattering

    DOE PAGESBeta

    Park, J.; Aliaga, L.; Altinok, O.; Bellantoni, L.; Bercellie, A.; Betancourt, M.; Bodek, A.; Bravar, A.; Budd, H.; Cai, T.; et al

    2016-06-10

    In muon-neutrino elastic scattering on electrons is an observable neutrino process whose cross section is precisely known. Consequently a measurement of this process in an accelerator-based νμ beam can improve the knowledge of the absolute neutrino flux impinging upon the detector; typically this knowledge is limited to ~10% due to uncertainties in hadron production and focusing. We also isolated a sample of 135±17 neutrino-electron elastic scattering candidates in the segmented scintillator detector of MINERvA, after subtracting backgrounds and correcting for efficiency. We show how this sample can be used to reduce the total uncertainty on the NuMI νμ flux frommore » 9% to 6%. Finally, our measurement provides a flux constraint that is useful to other experiments using the NuMI beam, and this technique is applicable to future neutrino beams operating at multi-GeV energies.« less

  12. Measurement of neutrino flux from neutrino-electron elastic scattering

    NASA Astrophysics Data System (ADS)

    Park, J.; Aliaga, L.; Altinok, O.; Bellantoni, L.; Bercellie, A.; Betancourt, M.; Bodek, A.; Bravar, A.; Budd, H.; Cai, T.; Carneiro, M. F.; Christy, M. E.; Chvojka, J.; da Motta, H.; Dytman, S. A.; Díaz, G. A.; Eberly, B.; Felix, J.; Fields, L.; Fine, R.; Gago, A. M.; Galindo, R.; Ghosh, A.; Golan, T.; Gran, R.; Harris, D. A.; Higuera, A.; Kleykamp, J.; Kordosky, M.; Le, T.; Maher, E.; Manly, S.; Mann, W. A.; Marshall, C. M.; Martinez Caicedo, D. A.; McFarland, K. S.; McGivern, C. L.; McGowan, A. M.; Messerly, B.; Miller, J.; Mislivec, A.; Morfín, J. G.; Mousseau, J.; Naples, D.; Nelson, J. K.; Norrick, A.; Nuruzzaman; Osta, J.; Paolone, V.; Patrick, C. E.; Perdue, G. N.; Rakotondravohitra, L.; Ramirez, M. A.; Ray, H.; Ren, L.; Rimal, D.; Rodrigues, P. A.; Ruterbories, D.; Schellman, H.; Solano Salinas, C. J.; Tagg, N.; Tice, B. G.; Valencia, E.; Walton, T.; Wolcott, J.; Wospakrik, M.; Zavala, G.; Zhang, D.; Miner ν A Collaboration

    2016-06-01

    Muon-neutrino elastic scattering on electrons is an observable neutrino process whose cross section is precisely known. Consequently a measurement of this process in an accelerator-based νμ beam can improve the knowledge of the absolute neutrino flux impinging upon the detector; typically this knowledge is limited to ˜10 % due to uncertainties in hadron production and focusing. We have isolated a sample of 135 ±17 neutrino-electron elastic scattering candidates in the segmented scintillator detector of MINERvA, after subtracting backgrounds and correcting for efficiency. We show how this sample can be used to reduce the total uncertainty on the NuMI νμ flux from 9% to 6%. Our measurement provides a flux constraint that is useful to other experiments using the NuMI beam, and this technique is applicable to future neutrino beams operating at multi-GeV energies.

  13. Comparison of ground-derived and satellite-derived surface energy fluxes from a shrub-steppe site

    SciTech Connect

    Kirkham, R.R.; Gee, G.W.; Fritschen, L.J.

    1994-03-01

    Efforts to measure evapotranspiration (ET) remotely are common in agriculture, and the application of such data to irrigation scheduling is readily apparent. Extending this methodology to arid environments is primarily of use as a mechanism for validation of ET algorithms used in large-scale watershed and global climate change modeling efforts. To facilitate testing of the remote sensing method for ET, measurements of sensible and latent heat flux were made at four sites located on the US Department of Energy`s Hanford Site using a combination of lysimeter and Bowen Ratio Energy Balance (BREB) stations. The objective was to calibrate an aerodynamic transport equation that relates sensible heat flux to radiant surface temperature, and to map sensible heat flux using Landsat data.

  14. Comparison between elementary flux modes analysis and 13C-metabolic fluxes measured in bacterial and plant cells

    PubMed Central

    2011-01-01

    Background 13C metabolic flux analysis is one of the pertinent ways to compare two or more physiological states. From a more theoretical standpoint, the structural properties of metabolic networks can be analysed to explore feasible metabolic behaviours and to define the boundaries of steady state flux distributions. Elementary flux mode analysis is one of the most efficient methods for performing this analysis. In this context, recent approaches have tended to compare experimental flux measurements with topological network analysis. Results Metabolic networks describing the main pathways of central carbon metabolism were set up for a bacteria species (Corynebacterium glutamicum) and a plant species (Brassica napus) for which experimental flux maps were available. The structural properties of each network were then studied using the concept of elementary flux modes. To do this, coefficients of flux efficiency were calculated for each reaction within the networks by using selected sets of elementary flux modes. Then the relative differences - reflecting the change of substrate i.e. a sugar source for C. glutamicum and a nitrogen source for B. napus - of both flux efficiency and flux measured experimentally were compared. For both organisms, there is a clear relationship between these parameters, thus indicating that the network structure described by the elementary flux modes had captured a significant part of the metabolic activity in both biological systems. In B. napus, the extension of the elementary flux mode analysis to an enlarged metabolic network still resulted in a clear relationship between the change in the coefficients and that of the measured fluxes. Nevertheless, the limitations of the method to fit some particular fluxes are discussed. Conclusion This consistency between EFM analysis and experimental flux measurements, validated on two metabolic systems allows us to conclude that elementary flux mode analysis could be a useful tool to complement 13C

  15. AmeriFlux US-Bn1 Bonanza Creek, 1920 Burn site near Delta Junction

    DOE Data Explorer

    Randerson, James [University of California, Irvine

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-Bn1 Bonanza Creek, 1920 Burn site near Delta Junction. Site Description - The Delta Junction 1920 Control site is located near Delta Junction, just to the north of the Alaska Range in interior Alaska. All three Delta Junction sites are within a 15-km radius of one another. Composed of a combination of alluvial outwashes, floodplains, and low terraces dissected by glacial streams originating in the nearby Alaska Range. In 2001, total aboveground biomass consisted almost entirely of black spruce (Picea mariana).

  16. AmeriFlux US-IB1 Fermi National Accelerator Laboratory- Batavia (Agricultural site)

    SciTech Connect

    Matamala, Roser

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-IB1 Fermi National Accelerator Laboratory- Batavia (Agricultural site). Site Description - Two eddy correlation systems are installed at Fermi National Accelerator Laboratory: one on a restored prairie (established October 2004) and one on a corn/soybean rotation agricultural field (established in July 2005). The prairie site had been farmed for more than 100 years, but was converted to prairie in 1989. The agricultural site has likely been farmed for more than 100 years, but the first documented instance of agricultural activity dates back to a picture taken in 1952.

  17. Testing the Need for Replication of Eddy Covariance Carbon Dioxide Flux Measurements over Agricultural Fields

    NASA Astrophysics Data System (ADS)

    Taylor, A. M.; Amiro, B. D.; Gervais, M.

    2015-12-01

    The eddy covariance method directly measures carbon dioxide (CO2) fluxes for long periods of time and with footprints up to hundreds of meters in size. Any ecosystem process that alters how gases and energy move between the atmosphere and soil/vegetation can affect these fluxes. Eddy covariance is vulnerable to systematic errors and uncertainy, particular through relying on assumptions about surface characteristics. Additionally, spatial variation within a site can cause more uncertainty in these measurements and lack of replication in many eddy covariance studies makes statistical analysis of carbon fluxes challenging. We tested if there are significant differences between co-located and simultaneous CO2 flux measurements over a uniform crop surface, and if the differences increase if we measure different flux footprint areas over the same field. During the summer of 2014, three matched instrumented 2.5-m high towers were co-located and then periodically separated by moving at 50 m intervals along a north-south transect on an alfalfa/trefoil field and a spring wheat field in Southern Manitoba, Canada to compare CO­2 fluxes. Georeferenced leaf area index measurements were taken in 50 m grid of each field to establish uniformity of the source/sink within a footprint. Diurnal differences of similar magnitude in the CO2 ­fluxes were found in both the co-located experiment and the spatially separated intervals. Despite rigorous calibration during the experiment, some differences were caused by the measurement systems rather than by variation within the field. Interpretation of the spatial variation in leaf area index is being used to determine the contribution caused by difference in source/sink contributions to the flux footprint areas when the towers were spatially separated.

  18. CO{sub 2} flux measurements across portions of the Dixie Valley geothermal system, Nevada

    SciTech Connect

    Bergfeld, D.; Goff, F.; Janik, C.J.; Johnson, S.D.

    1998-12-31

    A map of the CO{sub 2} flux across a newly formed area of plant kill in the NW part of the Dixie Valley geothermal system was constructed to monitor potential growth of a fumarole field. Flux measurements were recorded using a LI-COR infrared analyzer. Sample locations were restricted to areas within and near the dead zone. The data delineate two areas of high CO{sub 2} flux in different topographic settings. Older fumaroles along the Stillwater range front produce large volumes of CO{sub 2} at high temperatures. High CO{sub 2} flux values were also recorded at sites along a series of recently formed ground fractures at the base of the dead zone. The two areas are connected by a zone of partial plant kill and moderate flux on an alluvial fan. Results from this study indicate a close association between the range front fumaroles and the dead zone fractures. The goals of this study are to characterize recharge to the geothermal system, provide geochemical monitoring of reservoir fluids and to examine the temporal and spatial distribution of the CO{sub 2} flux in the dead zone. This paper reports the results of the initial CO{sub 2} flux measurements taken in October, 1997.

  19. BOREAS TE-6 NPP For The Tower Flux, Carbon Evaluation, and Auxiliary Sites

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Gower, Stith T.; Vogel, Jason G.

    2000-01-01

    The BOREAS TE-6 team collected several data sets to examine the influence of vegetation, climate, and their interactions on the major carbon fluxes for boreal forest species. This data set contains estimates of the biomass produced by the plant species at the TF, CEV, and AUX sites in the SSA and NSA for a given year. Temporally, the data cover the years of 1985 to 1995. The plant biomass production (i.e., aboveground, belowground, understory, litterfall), spatial coverage, and temporal nature of measurements varied between the TF, CEV, and AUX sites as deemed necessary by BOREAS principal investigators. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distrobuted Activity Archive Center (DAAC).

  20. Multiple-Point Mass Flux Measurement System Using Rayleigh Scattering

    NASA Technical Reports Server (NTRS)

    Mielke, Amy F.; Elam, Kristie A.; Clem, Michelle M.

    2009-01-01

    A multiple-point Rayleigh scattering diagnostic is being developed to provide mass flux measurements in gas flows. Spectroscopic Rayleigh scattering is an established flow diagnostic that has the ability to provide simultaneous density, temperature, and velocity measurements. Rayleigh scattered light from a focused 18 Watt continuous-wave laser beam is directly imaged through a solid Fabry-Perot etalon onto a CCD detector which permits spectral analysis of the light. The spatial resolution of the measurements is governed by the locations of interference fringes, which can be changed by altering the etalon characteristics. A prototype system has been used to acquire data in a Mach 0.56 flow to demonstrate feasibility of using this system to provide mass flux measurements. Estimates of measurement uncertainty and recommendations for system improvements are presented

  1. Simultaneous Flux Measurements of CO2, its Stable Isotope Ratios and Trace Gases Based on Eddy Accumulation Technique for Flux Partitioning

    NASA Astrophysics Data System (ADS)

    Takahashi, Y.; Hirata, R.

    2007-12-01

    for on-site measurement. Therefore, as a first step, we are planning to measure those fluxes based on an eddy accumulation technique coupled with flask sampling and high precision lab analysis. We report current progress of the development.

  2. Long-term micrometeorological measurements of nitrous oxide fluxes from agro-ecosystems (Invited)

    NASA Astrophysics Data System (ADS)

    Wagner-Riddle, C.; Brown, S.; Snider, D.

    2013-12-01

    Year-round measurements of nitrous oxide fluxes are needed in order to better characterize emissions from agro-ecosystems, and devise mitigation strategies for emission reduction. This is particularly the case for agroecosystems in cold regions where freezing and thawing of soil often results in enhanced fluxes. In addition, nitrogen fertilizer application at crop planting in the spring will also result in emission events with high temporal variability. Micrometeorological methods do not interfere with soil conditions and hence, can be used quasi-continuously (at hourly to half-hourly intervals) to capture the highly intermittent nature of N2O emission episodes. Simultaneous flux measurements on multiple plots is desirable so that the effect of soil management practices on N2O emissions can be characterized. We have conducted several studies deploying the flux-gradient technique to measure surface N2O fluxes at a long-term in Elora, ON, Canada, a site established in 2000 with the objective of improving our understanding of how management affects N2O emissions. The experimental area consists of four 1.5-4 ha plots within a level and aerodynamically homogeneous 30-ha area, and half-hourly flux is measured sequentially providing up to 12 values per plot per day. A total of 521 monthly N2O emission rates were measured over the 2000-2013 period for a range of crops (e.g. soybeans, corn, wheat) and management (e.g. no-tillage, conventional). The aggregated analysis shows that extreme flux events tend to be concentrated in February/March and May/Jun/Jul (Fig. 1). The main thaw events tend to occur in February and March, and they events contribute on average 30% to the annual nitrous oxide emission total. Timely rains after fertilizer application at crop planting in May provide high soil water content for denitrification to take place and also lead to high emission events. Sixty-six percent of the annual emission occurred from Jan to Jun on average at this site. Emissions

  3. Using "snapshot" measurements of CH4 fluxes from peatlands to estimate annual budgets: interpolation vs. modelling.

    NASA Astrophysics Data System (ADS)

    Green, Sophie M.; Baird, Andy J.

    2016-04-01

    There is growing interest in estimating annual budgets of peatland-atmosphere carbon dioxide (CO2) and methane (CH4) exchanges. Such budgeting is required for calculating peatland carbon balance and the radiative forcing impact of peatlands on climate. There have been multiple approaches used to estimate CO2 budgets; however, there is a limited literature regarding the modelling of annual CH4 budgets. Using data collected from flux chamber tests in an area of blanket peatland in North Wales, we compared annual estimates of peatland-atmosphere CH4 emissions using an interpolation approach and an additive and multiplicative modelling approach. Flux-chamber measurements represent a snapshot of the conditions on a particular site. In contrast to CO2, most studies that have estimated the time-integrated flux of CH4 have not used models. Typically, linear interpolation is used to estimate CH4 fluxes during the time periods between flux-chamber measurements. It is unclear how much error is involved with such a simple integration method. CH4 fluxes generally show a rise followed by a fall through the growing season that may be captured reasonably well by interpolation, provided there are sufficiently frequent measurements. However, day-to-day and week-to-week variability is also often evident in CH4 flux data, and will not necessarily be properly represented by interpolation. Our fits of the CH4 flux models yielded r2 > 0.5 in 38 of the 48 models constructed, with 55% of these having a weighted rw2 > 0.4. Comparison of annualised CH4 fluxes estimated by interpolation and modelling reveals no correlation between the two data sets; indeed, in some cases even the sign of the flux differs. The difference between the methods seems also to be related to the size of the flux - for modest annual fluxes there is a fairly even scatter of points around the 1:1 line, whereas when the modelled fluxes are high, the corresponding interpolated fluxes tend to be low. We consider the

  4. Aerosol properties derived from spectral actinic flux measurements

    NASA Astrophysics Data System (ADS)

    Stark, H.; Schmidt, K. S.; Pilewskie, P.; Cozic, J.; Wollny, A. G.; Brock, C. A.; Baynard, T.; Lack, D.; Parrish, D. D.; Fehsenfeld, F. C.

    2008-12-01

    Measurement of aerosol properties is very important for understanding climate change. Aerosol optical properties influence solar radiation throughout the troposphere. According to the Working Group I report of the intergovernmental panel for climate change [IPCC, 2007], aerosols have a direct radiative forcing of - 0.5±0.4 W/m2 with a medium to low level of scientific understanding. This relatively large uncertainty indicates the need for more frequent and precise measurements of aerosol properties. We will show how actinic flux measurements can be used to derive important optical aerosol parameters such as aerosol optical thickness and depth, surface albedo, angstrom exponent, radiative forcing by clouds and aerosols, aerosol extinction, and others. The instrument used for this study is a combination of two spectroradiometers measuring actinic flux in the ultraviolet and visible radiation range from 280 to 690 nm with a resolution of 1 nm. Actinic flux is measured as the radiation incident on a spherical surface with sensitivity independent of direction. In contrast, irradiance is measured as the radiation incident on a plane surface, which depends on the cosine of the incident angle. Our goal is to assess the capabilities of using spectral actinic flux measurements to derive various aerosol properties. Here we will compare 1) actinic flux measurements to irradiance measurements from the spectral solar flux radiometer (SSFR), 2) derived aerosol size distributions with measurements from a white light optical particle counter (WLOPC) and ultra high sensitivity aerosol size spectrometer (UHSAS), and 3) derived aerosol optical extinction with measurements from a cavity ringdown aerosol extinction spectrometer (CRD-AES). These comparisons will utilize data from three recent field campaigns over New England and the Atlantic Ocean (ICARTT 2004), Texas and the Gulf of Mexico during (TexAQS/GoMACCS 2006), and Alaska and the Arctic Ocean (ARCPAC 2008) when the instruments

  5. Evapotranspiration: Mass balance measurements compared with flux estimation methods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Evapotranspiration (ET) may be measured by mass balance methods and estimated by flux sensing methods. The mass balance methods are typically restricted in terms of the area that can be represented (e.g., surface area of weighing lysimeter (LYS) or equivalent representative area of neutron probe (NP...

  6. IMPROVING EMISSION INVENTORIES USING DIRECT FLUX MEASUREMENTS AND MODELING

    EPA Science Inventory

    This project uses a novel approach to measure real-world pollutant fluxes on an extended spatial and temporal scale, and to infer from those the source-specific pollutant emissions needed for a comparison to and an improvement of current emissions inventories. Air pollutants a...

  7. Some Recent Secondary Production Measurements for Neutrino Flux Determination

    NASA Astrophysics Data System (ADS)

    Mills, Geoffrey B.

    2011-12-01

    Recent measurements of meson production in proton-nucleus interactions have made possible reliable neutrino flux determinations at modern neutrino experiments. This article discusses preliminary results from the HARP, MIP, and E910 are discussed along with some of their implications for the MINOS, K2K, and MiniBooNE neutrino experiments.

  8. Field intercomparison of four methane gas analyzers suitable for eddy covariance flux measurements

    NASA Astrophysics Data System (ADS)

    Peltola, O.; Mammarella, I.; Haapanala, S.; Burba, G.; Vesala, T.

    2013-06-01

    Performances of four methane gas analyzers suitable for eddy covariance measurements are assessed. The assessment and comparison was performed by analyzing eddy covariance data obtained during summer 2010 (1 April to 26 October) at a pristine fen, Siikaneva, Southern Finland. High methane fluxes with pronounced seasonality have been measured at this fen. The four participating methane gas analyzers are commercially available closed-path units TGA-100A (Campbell Scientific Inc., USA), RMT-200 (Los Gatos Research, USA), G1301-f (Picarro Inc., USA) and an early prototype open-path unit Prototype-7700 (LI-COR Biosciences, USA). The RMT-200 functioned most reliably throughout the measurement campaign, during low and high flux periods. Methane fluxes from RMT-200 and G1301-f had the smallest random errors and the fluxes agree remarkably well throughout the measurement campaign. Cospectra and power spectra calculated from RMT-200 and G1301-f data agree well with corresponding temperature spectra during a high flux period. None of the gas analyzers showed statistically significant diurnal variation for methane flux. Prototype-7700 functioned only for a short period of time, over one month, in the beginning of the measurement campaign during low flux period, and thus, its overall accuracy and season-long performance were not assessed. The open-path gas analyzer is a practical choice for measurement sites in remote locations due to its low power demand, whereas for G1301-f methane measurements interference from water vapor is straightforward to correct since the instrument measures both gases simultaneously. In any case, if only the performance in this intercomparison is considered, RMT-200 performed the best and is the recommended choice if a new fast response methane gas analyzer is needed.

  9. Airborne flux measurements of Biogenic Isoprene over California

    SciTech Connect

    Misztal, P.; Karl, Thomas G.; Weber, Robin; Jonsson, H. H.; Guenther, Alex B.; Goldstein, Allen H.

    2014-10-10

    Biogenic Volatile Organic Compound (BVOC) fluxes were measured onboard the CIRPAS Twin Otter aircraft as part of the California Airborne BVOC Emission Research in Natural Ecosystem Transects (CABERNET) campaign during June 2011. The airborne virtual disjunct eddy covariance (AvDEC) approach used measurements from a PTR-MS and a wind radome probe to directly determine fluxes of isoprene, MVK+MAC, methanol, monoterpenes, and MBO over ~10,000-km of flight paths focusing on areas of California predicted to have the largest emissions of isoprene. The Fast Fourier Transform (FFT) approach was used to calculate fluxes over long transects of more than 15 km, most commonly between 50 and 150 km. The Continuous Wavelet Transformation (CWT) approach was used over the same transects to also calculate "instantaneous" fluxes with localization of both frequency and time independent of non-stationarities. Vertical flux divergence of isoprene is expected due to its relatively short lifetime and was measured directly using "racetrack" profiles at multiple altitudes. It was found to be linear and in the range 5% to 30% depending on the ratio of aircraft altitude to PBL height (z/zi). Fluxes were generally measured by flying consistently 1 at 400 m ±50 m (a.g.l.) altitude, and extrapolated to the surface according to the determined flux divergence. The wavelet-derived surface fluxes of isoprene averaged to 2 km spatial resolution showed good correspondence to Basal Emission Factor (BEF) landcover datasets used to drive biogenic VOC (BVOC) emission models. The surface flux of isoprene was close to zero over Central Valley crops and desert shrublands, but was very high (up to 15 mg m-2 h-1) above oak woodlands, with clear dependence of emissions on temperature and oak density. Isoprene concentrations of up to 8 ppb were observed at aircraft height on the hottest days and over the dominant source regions. While isoprene emissions from agricultural crop regions, shrublands, and

  10. Combining two complementary micrometeorological methods to measure CH4 and N2O fluxes over pasture

    NASA Astrophysics Data System (ADS)

    Laubach, J.; Barthel, M.; Fraser, A.; Hunt, J. E.; Griffith, D. W. T.

    2015-09-01

    New Zealand's largest industrial sector is pastoral agriculture, giving rise to a large fraction of the country's emissions of methane (CH4) and nitrous oxide (N2O). We designed a system to continuously measure CH4 and N2O fluxes at the field scale on two adjacent pastures that differed with respect to management. At the core of this system was a closed-cell Fourier-transform infrared spectrometer (FTIR), measuring the mole fractions of CH4, N2O and carbon dioxide (CO2) at two heights at each site. In parallel, CO2 fluxes were measured using eddy-covariance instrumentation. We applied two different micrometeorological ratio methods to infer the CH4 and N2O fluxes from their respective mole fractions and the CO2 fluxes. The first is a variant of the flux-gradient method, where it is assumed that the turbulent diffusivities of CH4 and N2O equal that of CO2. This method was reliable when the CO2 mole-fraction difference between heights was at least 4 times greater than the FTIR's resolution of differences. For the second method, the temporal increases of mole fractions in the stable nocturnal boundary layer, which are correlated for concurrently-emitted gases, are used to infer the unknown fluxes of CH4 and N2O from the known flux of CO2. This method was sensitive to "contamination" from trace gas sources other than the pasture of interest and therefore required careful filtering. With both methods combined, estimates of mean daily CH4 and N2O fluxes were obtained for 60 % of days at one site and 77 % at the other. Both methods indicated both sites as net sources of CH4 and N2O. Mean emission rates for one year at the unfertilised, winter-grazed site were 8.2 (± 0.91) nmol CH4 m-2 s-1 and 0.40 (± 0.018) nmol N2O m-2 s-1. During the same year, mean emission rates at the irrigated, fertilised and rotationally-grazed site were 7.0 (± 0.89) nmol CH4 m-2 s-1 and 0.57 (± 0.019) nmol N2O m-2 s-1. At this site, the N2O emissions amounted to 1.19 (± 0.15) % of the

  11. Combining two complementary micrometeorological methods to measure CH4 and N2O fluxes over pasture

    NASA Astrophysics Data System (ADS)

    Laubach, Johannes; Barthel, Matti; Fraser, Anitra; Hunt, John E.; Griffith, David W. T.

    2016-03-01

    New Zealand's largest industrial sector is pastoral agriculture, giving rise to a large fraction of the country's emissions of methane (CH4) and nitrous oxide (N2O). We designed a system to continuously measure CH4 and N2O fluxes at the field scale on two adjacent pastures that differed with respect to management. At the core of this system was a closed-cell Fourier transform infrared (FTIR) spectrometer, which measured the mole fractions of CH4, N2O and carbon dioxide (CO2) at two heights at each site. In parallel, CO2 fluxes were measured using eddy-covariance instrumentation. We applied two different micrometeorological ratio methods to infer the CH4 and N2O fluxes from their respective mole fractions and the CO2 fluxes. The first is a variant of the flux-gradient method, where it is assumed that the turbulent diffusivities of CH4 and N2O equal that of CO2. This method was reliable when the CO2 mole-fraction difference between heights was at least 4 times greater than the FTIR's resolution of differences. For the second method, the temporal increases of mole fractions in the stable nocturnal boundary layer, which are correlated for concurrently emitted gases, are used to infer the unknown fluxes of CH4 and N2O from the known flux of CO2. This method was sensitive to "contamination" from trace gas sources other than the pasture of interest and therefore required careful filtering. With both methods combined, estimates of mean daily CH4 and N2O fluxes were obtained for 56 % of days at one site and 73 % at the other. Both methods indicated both sites as net sources of CH4 and N2O. Mean emission rates for 1 year at the unfertilised, winter-grazed site were 8.9 (±0.79) nmol CH4 m-2 s-1 and 0.38 (±0.018) nmol N2O m-2 s-1. During the same year, mean emission rates at the irrigated, fertilised and rotationally grazed site were 8.9 (±0.79) nmol CH4 m-2 s-1 and 0.58 (±0.020) nmol N2O m-2 s-1. At this site, the N2O emissions amounted to 1.21 (±0.15) % of the nitrogen

  12. Long-term CH3Br and CH3Cl flux measurements in temperate salt marshes

    NASA Astrophysics Data System (ADS)

    Blei, E.; Heal, M. R.; Heal, K. V.

    2010-08-01

    Fluxes of CH3Br and CH3Cl and their relationship with potential drivers such as sunlight, temperature and soil moisture, were monitored at fortnightly to monthly intervals for more than two years at two contrasting temperate salt marsh sites in Scotland. Manipulation experiments were conducted to further investigate possible links between drivers and fluxes. Mean (± 1 sd) annually and diurnally-weighted net emissions from the two sites were found to be 300 ± 44 ng m-2 h-1 for CH3Br and 662 ± 266 ng m-2 h-1 for CH3Cl. A tentative scale-up indicates that salt marshes account for 0.5-3.2% and 0.05-0.33%, respectively, of currently-estimated total global production of these two gases, in line with previous findings from this and other research groups, but consistently lower than past global scale-up estimates from Southern Californian salt marshes. Fluxes followed both seasonal and diurnal trends with highest fluxes during summer days and lowest (negative) fluxes during winter nights. Statistical analysis generally did not demonstrate a strong link between temperature or sunlight levels and methyl halide fluxes, although it is likely that temperatures have a weak direct influence on emissions, and both certainly have indirect influence via the annual and daily cycles of the vegetation. CH3Cl flux magnitudes from different measurement locations depended on the plant species enclosed whereas such dependency was not discernible for CH3Br fluxes. In 14 out of 19 collars CH3Br and CH3Cl net fluxes were significantly correlated. The CH3Cl/CH3Br net-emission mass ratio was 2.2, a magnitude lower than mass ratios of global methyl halide budgets (~22) or emissions from tropical rainforests (~60). This is likely due to preference for CH3Br production by the relatively high bromine content in the salt marsh plant material.

  13. Infrared Camera Diagnostic for Heat Flux Measurements on NSTX

    SciTech Connect

    D. Mastrovito; R. Maingi; H.W. Kugel; A.L. Roquemore

    2003-03-25

    An infrared imaging system has been installed on NSTX (National Spherical Torus Experiment) at the Princeton Plasma Physics Laboratory to measure the surface temperatures on the lower divertor and center stack. The imaging system is based on an Indigo Alpha 160 x 128 microbolometer camera with 12 bits/pixel operating in the 7-13 {micro}m range with a 30 Hz frame rate and a dynamic temperature range of 0-700 degrees C. From these data and knowledge of graphite thermal properties, the heat flux is derived with a classic one-dimensional conduction model. Preliminary results of heat flux scaling are reported.

  14. Ultra High Precision Laser Monitor for Oxygen Eddy Flux Measurements

    NASA Astrophysics Data System (ADS)

    Nelson, David; Herndon, Scott; McManus, Barry; Roscioli, Rob; Jervis, Dylan; Zahniser, Mark

    2016-04-01

    Atmospheric oxygen provides one of the most powerful tracers to study the carbon cycle through its close interaction with carbon dioxide. Keeling and co-workers demonstrated this at the global scale by using small variations in atmospheric oxygen content to disentangle oceanic and terrestrial carbon sinks. It would be very exciting to apply similar ideas at the ecosystem level to improve our understanding of biosphere-atmosphere exchange and our ability to predict the response of the biosphere and atmosphere to climate change. The eddy covariance technique is perhaps the most effective approach available to quantify the exchange of gases between these spheres. Therefore, eddy covariance flux measurements of oxygen would be extremely valuable. However, this requires a fast response (0.1 seconds), high relative precision (0.001% or 10 per meg) oxygen sensor. We report recent progress in developing such a sensor using a high resolution visible laser to probe the oxygen A-band electronic transition. We have demonstrated precision of 1 ppmv or 5 per meg for a 100 second measurement duration. This sensor will enable oxygen flux measurements using eddy covariance. In addition, we will incorporate a second laser in this instrument to simultaneously determine the fluxes of oxygen, carbon dioxide and water vapor within the same sampling cell. This will provide a direct, real time measurement of the ratio of the flux of oxygen to that of carbon dioxide. This ratio is expected to vary on short time scales and small spatial scales due to the differing stoichiometry of processes producing and consuming carbon dioxide. Thus measuring the variations in the ratio of oxygen and carbon dioxide fluxes will provide mechanistic information to improve our understanding of the crucial exchange of carbon between the atmosphere and biosphere.

  15. CO2-flux measurements above the Baltic Sea at two heights: flux gradients in the surface layer?

    NASA Astrophysics Data System (ADS)

    Lammert, A.; Ament, F.

    2015-11-01

    The estimation of CO2 exchange between the ocean and the atmosphere is essential to understand the global carbon cycle. The eddy-covariance technique offers a very direct approach to observe these fluxes. The turbulent CO2 flux is measured, as well as the sensible and latent heat flux and the momentum flux, a few meters above the ocean in the atmosphere. Assuming a constant-flux layer in the near-surface part of the atmospheric boundary layer, this flux equals the exchange flux between ocean and atmosphere. The purpose of this paper is the comparison of long-term flux measurements at two different heights above the Baltic Sea to investigate this assumption. The results are based on a 1.5-year record of quality-controlled eddy-covariance measurements. Concerning the flux of momentum and of sensible and latent heat, the constant-flux layer theory can be confirmed because flux differences between the two heights are insignificantly small more than 95 % of the time. In contrast, significant differences, which are larger than the measurement error, occur in the CO2 flux about 35 % of the time. Data used for this paper are published at http://doi.pangaea.de/10.1594/PANGAEA.808714.

  16. Automatic magnetic flux measurement of micro plastic-magnetic rotors

    NASA Astrophysics Data System (ADS)

    Wang, Qingdong; Lin, Mingxing; Song, Aiwei

    2015-07-01

    Micro plastic-magnetic rotors of various sizes and shapes are widely used in industry, their magnetic flux measurement is one of the most important links in the production process, and therefore some technologies should be adopted to improve the measurement precision and efficiency. In this paper, the automatic measurement principle of micro plastic-magnetic rotors is proposed and the integration time constant and the integrator drift’s suppression and compensation in the measurement circuit are analyzed. Two other factors influencing the measurement precision are also analyzed, including the relative angles between the rotor magnetic poles and the measurement coil, and the starting point of the rotors in the coil where the measurement begins. An instrument is designed to measure the magnetic flux of the rotors. Measurement results show that the measurement error is within  ±1%, which meets the basic requirements in industry application, and the measurement efficiency is increased by 10 times, which can cut down labor cost and management cost when compared with manual measurement.

  17. Measuring Response Of Propellant To Oscillatory Heat Flux

    NASA Technical Reports Server (NTRS)

    Strand, Leon D.; Schwartz, Ken; Burns, Shawn P.

    1990-01-01

    Apparatus for research in combustion of solid propellants measures oscillatory response of rate of burning to oscillating thermal radiation from modulated CO2 laser. Determines response to rate of burning to equivalent oscillation in pressure. Rod of propellant mounted in burner assembly including waveguide at one end and infrared window at other end. Microwave Doppler velocimeter measures motion of combustion front. Microwave, laser-current, and heat-flux signals processed into and recorded in forms useful in determining desired response of propellent.

  18. Thermal Accommodation Coefficients Based on Heat-Flux Measurements

    NASA Astrophysics Data System (ADS)

    Gallis, Michael A.; Trott, Wayne M.; Torczynski, John R.; Rader, Daniel J.

    2006-11-01

    A new method to determine the thermal accommodation coefficient of gases on solid surfaces based on heat-flux measurements is presented. An experimental chamber and supporting diagnostics have been developed that allow accurate heat-flux measurements between two parallel plates. The heat flux is inferred from temperature-difference measurements across the plates using precision thermistors, where the plate temperatures are set with two carefully controlled thermal baths. The resulting heat flux is used in a recently derived semi-empirical formula to determine the thermal accommodation coefficient. This formula has the advantage of eliminating the ˜8% discrepancy between molecular simulations and the predictions of the more approximate Sherman-Lees formula used in most studies. Nitrogen, argon, and helium on stainless steel with various finishes and on other silicon-based surfaces are examined. The thermal accommodation coefficients thus determined indicate that the Maxwell gas-surface interaction model can adequately represent all of the experimental observations. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  19. High-Fidelity Measurements of Long-Lived Flux Qubits

    NASA Astrophysics Data System (ADS)

    Hover, David; Macklin, Chris; O'Brien, Kevin; Sears, Adam; Yoder, Jonilyn; Gudmundsen, Ted; Kerman, Jamie; Bolkhovsky, Vladimir; Tolpygo, Sergey; Fitch, George; Weir, Terry; Kamal, Archana; Gustavsson, Simon; Yan, Fei; Birenbaum, Jeff; Siddiqi, Irfan; Orlando, Terry; Clarke, John; Oliver, Will

    2015-03-01

    We report on high-fidelity dispersive measurements of a long-lived flux qubit using a Josephson superconducting traveling wave parametric amplifier (JTWPA). A capacitively shunted flux qubit that incorporates high-Q MBE aluminum will have longer relaxation and dephasing times when compared to a conventional flux qubit, while also maintaining the large anharmonicity necessary for complex gate operations. The JTWPA relies on a Josephson junction embedded transmission line to deliver broadband, nonreciprocal gain with large dynamic range. This research was funded in part by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA); and by the Assistant Secretary of Defense for Research & Engineering under Air Force Contract number FA8721-05-C-0002. All statements of fact, opinion or conclusions contained herein are those of the authors and should not be construed as representing the official views or policies of

  20. CO2, CH4 and particles flux measurements in Florence, Italy

    NASA Astrophysics Data System (ADS)

    Gioli, Beniamino; Toscano, Piero; Zaldei, Alessandro; Fratini, Gerardo; Miglietta, Franco

    2013-04-01

    We report a synthesis of seven years of eddy covariance (EC) flux measurements in the city of Florence, Italy. The measurement site is located in a densely urbanized area in the central city area, where fluxes are governed by anthropogenic emissions, considering the lack of green-space in the flux footprint. EC flux measurements of CO2 are made long-term since seven years, while short-term campaigns have been aimed at measuring CH4 and particles fluxes. CO2 and CH4 densities are measured with fast open-path sensors, while particles in the range 0.32 - 7.00 µm optical diameter are measured with a custom-built optical counter. CO2 long-term fluxes are always a net source, with a small inter-annual variability associated with a high seasonality, ranging from 39 to 172% of the mean annual value in summer and winter respectively. CH4 fluxes to the atmosphere are relevant, representing about 8% of CO2-equivalent emissions, and do not exhibit any significant seasonality. Relative contributions of road traffic and domestic heating to observed emissions has been estimated through multi-variate analysis combined with inventorial data and emission proxies such as traffic counters and gas network flow rates, revealing that domestic heating accounts for more than 80% of observed CO2 fluxes. Heating and road traffic are instead responsible for only 14% of observed CH4 fluxes, while the major residual part is likely dominated by gas network leakages. Particles flux data show a smaller seasonal trend and a pronounced weekend decrease, highlighting that the contribution of heating to particle emissions is relatively small compared to road traffic. Dynamics at hourly time scales during week and week-end days allows the analysis of the coupled role of emission strength and atmospheric processes such as advection and entrainment in regulating atmospheric concentrations. This set of observations highlights the potential of urban EC flux measurements as a validation tool for

  1. AmeriFlux US-ARb ARM Southern Great Plains burn site- Lamont

    SciTech Connect

    Torn, Margaret

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-ARb ARM Southern Great Plains burn site- Lamont. Site Description - The ARM SGP Burn site is located in the native tallgrass prairies of the USDA Grazinglands Research Laboratory near El Reno, OK. One of two adjacent 35 ha plots, the US-ARb plot was burned on 2005/03/08. The second plot, US-ARc, was left unburned as the control for experimental purposes. Aside from 2005, the region evaded burning activities for at least 15 years. Current disturbances consist of only light grazing activities.

  2. AmeriFlux US-IB2 Fermi National Accelerator Laboratory- Batavia (Prairie site)

    SciTech Connect

    Matamala, Roser

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-IB2 Fermi National Accelerator Laboratory- Batavia (Prairie site). Site Description - Two eddy correlation systems are installed at Fermi National Accelerator Laboratory: one on a restored prairie (established October 2004) and one on a corn/soybean rotation agricultural field (established in July 2005). The prairie site had been farmed for more than 100 years, but was converted to prairie in 1989. April annual to bi-annual prescribed burns have taken place from 1994 - 2007.

  3. Field intercomparison of four methane gas analysers suitable for eddy covariance flux measurements

    NASA Astrophysics Data System (ADS)

    Peltola, O.; Mammarella, I.; Haapanala, S.; Burba, G.; Vesala, T.

    2012-12-01

    Performances of four methane gas analyzers suitable for eddy covariance measurements are assessed. The assessment and comparison was performed by analyzing eddy covariance data obtained during summer 2010 (1 April to 26 October) at a pristine fen, Siikaneva, Southern Finland. High methane fluxes with pronounced seasonality have been measured at this fen. The four participating methane gas analyzers are commercially available closed-path units TGA-100A (Campbell Scientific Inc., USA), RMT-200 (Los Gatos Research, USA), G1301-f (Picarro Inc., USA) and an early prototype open-path unit Prototype-7700 (LI-COR Biosciences, USA). The RMT-200 functioned most reliably throughout the measurement campaign, during low and high flux periods. Methane fluxes from RMT-200 and G1301-f had the smallest random errors and the fluxes agree remarkably well throughout the measurement campaign. Cospectra and power spectra calculated from RMT-200 and G1301-f data agree well with corresponding temperature spectra during a high flux period. None of the gas analysers showed statistically significant diurnal variation for methane flux. Prototype-7700 functioned only for a short period of time, over one month, in the beginning of the measurement campaign during low flux period, and thus, its overall accuracy and long-term performance were not assessed. Prototype-7700 is a practical choice for measurement sites in remote locations due to its low power demand, however if only the performance in this intercomparison is considered, RMT-200 performed the best and is the recommended choice if a new fast response methane gas analyser is needed.

  4. Eddy covariance methane flux measurements over a grazed pasture: effect of cows as moving point sources

    NASA Astrophysics Data System (ADS)

    Felber, R.; Münger, A.; Neftel, A.; Ammann, C.

    2015-06-01

    Methane (CH4) from ruminants contributes one-third of global agricultural greenhouse gas emissions. Eddy covariance (EC) technique has been extensively used at various flux sites to investigate carbon dioxide exchange of ecosystems. Since the development of fast CH4 analyzers, the instrumentation at many flux sites has been amended for these gases. However, the application of EC over pastures is challenging due to the spatially and temporally uneven distribution of CH4 point sources induced by the grazing animals. We applied EC measurements during one grazing season over a pasture with 20 dairy cows (mean milk yield: 22.7 kg d-1) managed in a rotational grazing system. Individual cow positions were recorded by GPS trackers to attribute fluxes to animal emissions using a footprint model. Methane fluxes with cows in the footprint were up to 2 orders of magnitude higher than ecosystem fluxes without cows. Mean cow emissions of 423 ± 24 g CH4 head-1 d-1 (best estimate from this study) correspond well to animal respiration chamber measurements reported in the literature. However, a systematic effect of the distance between source and EC tower on cow emissions was found, which is attributed to the analytical footprint model used. We show that the EC method allows one to determine CH4 emissions of cows on a pasture if the data evaluation is adjusted for this purpose and if some cow distribution information is available.

  5. Eddy covariance methane flux measurements over a grazed pasture: effect of cows as moving point sources

    NASA Astrophysics Data System (ADS)

    Felber, R.; Münger, A.; Neftel, A.; Ammann, C.

    2015-02-01

    Methane (CH4) from ruminants contributes one third to global agricultural greenhouse gas emissions. Eddy covariance (EC) technique has been extensively used at various flux sites to investigate carbon dioxide exchange of ecosystems. Since the development of fast CH4 analysers the instrumentation at many flux sites have been amended for these gases. However the application of EC over pastures is challenging due to the spatial and temporal uneven distribution of CH4 point sources induced by the grazing animals. We applied EC measurements during one grazing season over a pasture with 20 dairy cows (mean milk yield: 22.7 kg d-1) managed in a rotational grazing system. Individual cow positions were recorded by GPS trackers to attribute fluxes to animal emissions using a footprint model. Methane fluxes with cows in the footprint were up to two orders of magnitude higher than ecosystem fluxes without cows. Mean cow emissions of 423 ± 24 g CH4 head-1 d-1 (best guess of this study) correspond well to animal respiration chamber measurements reported in the literature. However a systematic effect of the distance between source and EC tower on cow emissions was found which is attributed to the analytical footprint model used. We show that the EC method allows to determine CH4 emissions of grazing cows if the data evaluation is adjusted for this purpose and if some cow distribution information is available.

  6. Luminous-flux measurements by an absolute integrating sphere

    NASA Astrophysics Data System (ADS)

    Rastello, Maria Luisa; Miraldi, Elio; Pisoni, Paolo

    1996-08-01

    We present an original implementation of the absolute-sphere method recently proposed by Ohno. The luminous-flux unit, the lumen, is realized by means of an integrating sphere with an opening calibrated by a luminous-intensity standard placed outside. The adapted experimental setup permits one to measure luminous-flux values between 5 and 2500 lm with a significant improvement with respect to the simulated performances reported in the literature. Traditionally, the luminous-flux unit, the lumen, is realized by goniophotometric techniques in which the luminous-intensity distribution is measured and integrated over the whole solid angle. Thus sphere results are compared with those obtained with the Istituto Elettrotecnico Nazionale goniophotometer. In particular, a set of standards, characterized by luminous-flux values of approximately 2000 lm, has been calibrated with both techniques. We highlight some of the problems encountered. Experimental results show that the agreement between the two methods is within the estimated uncertainty and suggest promising areas for future research.

  7. Time and Space Resolved Heat Flux Measurements During Nucleate Boiling with Constant Heat Flux Boundary Conditions

    NASA Technical Reports Server (NTRS)

    Yerramilli, Vamsee K.; Myers, Jerry G.; Hussey, Sam W.; Yee, Glenda F.; Kim, Jungho

    2005-01-01

    The lack of temporally and spatially resolved measurements under nucleate bubbles has complicated efforts to fully explain pool-boiling phenomena. The objective of this current work was to acquire time and space resolved temperature distributions under nucleating bubbles on a constant heat flux surface using a microheater array with 100x 100 square microns resolution, then numerically determine the wall to liquid heat flux. This data was then correlated with high speed (greater than l000Hz) visual recordings of The bubble growth and departure from the heater surface acquired from below and from the side of the heater. The data indicate that microlayer evaporation and contact line heat transfer are not major heat transfer mechanisms for bubble growth. The dominant heat transfer mechanism appears to be transient conduction into the liquid as the liquid rewets the wall during the bubble departure process.

  8. Measurements of Mass, Momentum and Energy fluxes over an ice/snow covered lake

    NASA Astrophysics Data System (ADS)

    Salgado, Rui; Potes, Miguel; Mammarella, Ivan; Provenzale, Maria

    2016-04-01

    A better understanding of the interactions between ice and snow and the atmosphere requires improved measurements of energy, mass and momentum fluxes, which continue to have a high degree of uncertainty. In this communication, observed near surface fluxes of momentum, heat and mass (H2O and CO2) over a boreal lake during a freezing period (winter 2015/2016) will be analysed and compared with observations over ice free lakes. Continuously measurements of near surface fluxes of momentum, heat and mass (H2O and CO2) are obtained with a new eddy covariance (EC) system, the Campbell Scientific's IRGASON Integrated Open-Path CO2/H2O Gas Analyzer and 3D Sonic Anemometer, over lake Vanajavesi in Finland. The measurement site is located in a tip of narrow peninsula on the lake (61.133935° N ; 24.259119° E), offering very good conditions for eddy covariance flux measurements. The EC system was installed at 2.5m height above the lake surface and was oriented against the prevailing wind direction in the site.

  9. Airborne flux measurements of biogenic isoprene over California

    NASA Astrophysics Data System (ADS)

    Misztal, P. K.; Karl, T.; Weber, R.; Jonsson, H. H.; Guenther, A. B.; Goldstein, A. H.

    2014-10-01

    Biogenic isoprene fluxes were measured onboard the CIRPAS Twin Otter aircraft as part of the California Airborne Biogenic volatile organic compound (BVOC) Emission Research in Natural Ecosystem Transects (CABERNET) campaign during June 2011. The airborne virtual disjunct eddy covariance (AvDEC) approach used measurements from a proton transfer reaction mass spectrometer (PTR-MS) and a wind radome probe to directly determine fluxes of isoprene over 7400 km of flight paths focusing on areas of California predicted to have the largest emissions. The fast Fourier transform (FFT) approach was used to calculate fluxes of isoprene over long transects of more than 15 km, most commonly between 50 and 150 km. The continuous wavelet transformation (CWT) approach was used over the same transects to also calculate instantaneous isoprene fluxes with localization of both frequency and time independent of non-stationarities. Fluxes were generally measured by flying consistently at 400 m ± 50 m (a.g.l.) altitude, and extrapolated to the surface according to the determined flux divergence determined in the racetrack-stacked profiles. The wavelet-derived surface fluxes of isoprene averaged to 2 km spatial resolution showed good correspondence to basal emission factor (BEF) land-cover data sets used to drive BVOC emission models. The surface flux of isoprene was close to zero over Central Valley crops and desert shrublands, but was very high (up to 15 mg m-2 h-1) above oak woodlands, with clear dependence of emissions on temperature and oak density. Isoprene concentrations of up to 8 ppb were observed at aircraft height on the hottest days and over the dominant source regions. Even though the isoprene emissions from agricultural crop regions, shrublands, and coniferous forests were extremely low, observations at the Walnut Grove tower south of Sacramento demonstrate that isoprene oxidation products from the high emitting regions in the surrounding oak woodlands accumulate at night in

  10. Measurement of a surface heat flux and temperature

    NASA Astrophysics Data System (ADS)

    Davis, R. M.; Antoine, G. J.; Diller, T. E.; Wicks, A. L.

    1994-04-01

    The Heat Flux Microsensor is a new sensor which was recently patented by Virginia Tech and is just starting to be marketed by Vatell Corp. The sensor is made using the thin-film microfabrication techniques directly on the material that is to be measured. It consists of several thin-film layers forming a differential thermopile across a thermal resistance layer. The measured heat flux q is proportional to the temperature difference across the resistance layer q= k(sub g)/delta(sub g) x (t(sub 1) - T(sub 2)), where k(sub g) is the thermal conductivity and delta (sub g) is the thickness of the thermal resistance layer. Because the gages are sputter coated directly onto the surface, their total thickness is less than 2 micrometers, which is two orders of magnitude thinner than previous gages. The resulting temperature difference across the thermal resistance layer (delta is less than 1 micrometer) is very small even at high heat fluxes. To generate a measurable signal many thermocouple pairs are put in series to form a differential thermopile. The combination of series thermocouple junctions and thin-film design creates a gage with very attractive characteristics. It is not only physically non-intrusive to the flow, but also causes minimal disruption of the surface temperature. Because it is so thin, the response time is less than 20 microsec. Consequently, the frequency response is flat from 0 to over 50 kHz. Moreover, the signal of the Heat Flux Microsensor is directly proportional to the heat flux. Therefore, it can easily be used in both steady and transient flows, and it measures both the steady and unsteady components of the surface heat flux. A version of the Heat Flux Microsensor has been developed to meet the harsh demands of combustion environments. These gages use platinum and platinum-10 percent rhodium as the thermoelectric materials. The thermal resistance layer is silicon monoxide and a protective coating of Al2O3 is deposited on top of the sensor. The

  11. Measurement of a surface heat flux and temperature

    NASA Technical Reports Server (NTRS)

    Davis, R. M.; Antoine, G. J.; Diller, T. E.; Wicks, A. L.

    1994-01-01

    The Heat Flux Microsensor is a new sensor which was recently patented by Virginia Tech and is just starting to be marketed by Vatell Corp. The sensor is made using the thin-film microfabrication techniques directly on the material that is to be measured. It consists of several thin-film layers forming a differential thermopile across a thermal resistance layer. The measured heat flux q is proportional to the temperature difference across the resistance layer q= k(sub g)/delta(sub g) x (t(sub 1) - T(sub 2)), where k(sub g) is the thermal conductivity and delta (sub g) is the thickness of the thermal resistance layer. Because the gages are sputter coated directly onto the surface, their total thickness is less than 2 micrometers, which is two orders of magnitude thinner than previous gages. The resulting temperature difference across the thermal resistance layer (delta is less than 1 micrometer) is very small even at high heat fluxes. To generate a measurable signal many thermocouple pairs are put in series to form a differential thermopile. The combination of series thermocouple junctions and thin-film design creates a gage with very attractive characteristics. It is not only physically non-intrusive to the flow, but also causes minimal disruption of the surface temperature. Because it is so thin, the response time is less than 20 microsec. Consequently, the frequency response is flat from 0 to over 50 kHz. Moreover, the signal of the Heat Flux Microsensor is directly proportional to the heat flux. Therefore, it can easily be used in both steady and transient flows, and it measures both the steady and unsteady components of the surface heat flux. A version of the Heat Flux Microsensor has been developed to meet the harsh demands of combustion environments. These gages use platinum and platinum-10 percent rhodium as the thermoelectric materials. The thermal resistance layer is silicon monoxide and a protective coating of Al2O3 is deposited on top of the sensor. The

  12. Automation of soil flux chamber measurements: potentials and pitfalls

    NASA Astrophysics Data System (ADS)

    Görres, Carolyn-Monika; Kammann, Claudia; Ceulemans, Reinhart

    2016-03-01

    Recent technological advances have enabled the wider application of automated chambers for soil greenhouse gas (GHG) flux measurements, several of them commercially available. However, few studies addressed the challenges associated with operating these systems. In this contribution we compared two commercial soil GHG chamber systems - the LI-8100A Automated Soil CO2 Flux System and the greenhouse gas monitoring system AGPS. From April until August 2014, the two systems monitored in parallel soil respiration (SR) fluxes at a recently harvested poplar (Populus) plantation, which provided a bare field situation directly after the harvest as well as a closed canopy later on. For the bare field situation (15 April-30 June 2014), the cumulated average SR obtained from the unfiltered data sets of the LI-8100A and the AGPS were 520 and 433 g CO2 m-2 respectively. For the closed canopy phase (1 July-31 August 2014), which was characterized by a higher soil moisture content, the cumulated average SR estimates were not significantly different with 507 and 501 g CO2 m-2 for the AGPS and the LI-8100A respectively. Flux quality control and filtering did not significantly alter the results obtained by the LI-8100A, whereas the AGPS SR estimates were reduced by at least 20 %. The main reasons for the observed differences in the performance of the two systems were (i) a lower data coverage provided by the AGPS due to technical problems; (ii) incomplete headspace mixing in the AGPS chambers; (iii) lateral soil CO2 diffusion below the collars during AGPS chamber measurements; and (iv) a possible overestimation of nighttime SR fluxes by the LI-8100A. Additionally, increased root growth was observed within the LI-8100A collars but not within the AGPS collars, which might have also contributed to the observed differences. In contrast to the LI-8100A, the AGPS had the gas sample inlets installed inside the collars and not the chambers. This unique design feature enabled for the first

  13. Automation of soil flux chamber measurements: potentials and pitfalls

    NASA Astrophysics Data System (ADS)

    Görres, C.-M.; Kammann, C.; Ceulemans, R.

    2015-09-01

    Recent technological advances have enabled the wider application of automated chambers for soil greenhouse gas (GHG) flux measurements, several of them commercially available. However, only few studies addressed the difficulties and challenges associated with operating these systems. In this contribution we compared two commercial soil GHG chamber systems-the LI-8100A Automated Soil CO2 Flux System and the Greenhouse Gas Monitoring System AGPS. From April 2014 until August 2014, the two systems monitored in parallel soil respiration (SR) fluxes at a recently harvested poplar plantation, which provided a bare field situation directly after the harvest as well as a closed canopy later on. For the bare field situation (15 April-30 June 2014), the cumulated average SR obtained from the unfiltered datasets of the LI-8100A and the AGPS were 520 and 433 g CO2 m-2, respectively. For the closed canopy phase (01 July-31 August 2014), which was characterized by a higher soil moisture content, the cumulated average SR estimates were not significantly different with 507 and 501 g CO2 m-2 for the AGPS and the LI-8100A, respectively. Flux quality control and filtering did not significantly alter the results obtained by the LI-8100A, whereas the AGPS SR estimates were reduced by at least 20 %. The main reasons for the observed differences in the performance of the two systems were (i) a lower data coverage provided by the AGPS due to technical problems; (ii) incomplete headspace mixing in the AGPS chambers; (iii) lateral soil CO2 diffusion below the collars during AGPS chamber measurements; (iv) increased root growth within the LI-8100A collars; and (v) a possible overestimation of nighttime SR fluxes by the LI-8100A. In contrast to the LI-8100A, the AGPS had the gas sample inlets installed inside the collars and not the chambers. This unique design feature enabled for the first time the detection of disturbed chamber measurements during nights with a stratified atmosphere

  14. Flux threshold measurements of He-ion beam induced nanofuzz formation on hot tungsten surfaces

    NASA Astrophysics Data System (ADS)

    Meyer, F. W.; Hijazi, H.; Bannister, M. E.; Unocic, K. A.; Garrison, L. M.; Parish, C. M.

    2016-02-01

    We report measurements of the energy dependence of flux thresholds and incubation fluences for He-ion induced nano-fuzz formation on hot tungsten surfaces at UHV conditions over a wide energy range using real-time sample imaging of tungsten target emissivity change to monitor the spatial extent of nano-fuzz growth, corroborated by ex situ SEM and FIB/SEM analysis, in conjunction with accurate ion-flux profile measurements. The measurements were carried out at the multicharged ion research facility (MIRF) at energies from 218 eV to 8.5 keV, using a high-flux deceleration module and beam flux monitor for optimizing the decel optics on the low energy MIRF beamline. The measurements suggest that nano-fuzz formation proceeds only if a critical rate of change of trapped He density in the W target is exceeded. To understand the energy dependence of the observed flux thresholds, the energy dependence of three contributing factors: ion reflection, ion range and target damage creation, were determined using the SRIM simulation code. The observed energy dependence can be well reproduced by the combined energy dependences of these three factors. The incubation fluences deduced from first visual appearance of surface emissivity change were (2-4) × 1023 m-2 at 218 eV, and roughly a factor of 10 less at the higher energies, which were all at or above the displacement energy threshold. The role of trapping at C impurity sites is discussed.

  15. Aerosol flux measurements above a mixed forest at Borden, Ontario

    NASA Astrophysics Data System (ADS)

    Gordon, M.; Staebler, R. M.; Liggio, J.; Vlasenko, A.; Li, S.-M.; Hayden, K.

    2011-07-01

    Aerosol fluxes were measured above a mixed forest by Eddy Covariance (EC) with a Fast Mobility Particle Sizer (FMPS) at the Borden Forest Research Station in Ontario, Canada between 13 July and 12 August 2009. Chemically speciated flux measurements were made at a height of 29 m at the same location between 19 July and 2 August, 2006 using a Quadrupole Aerosol Mass Spectrometer (Q-AMS). The Q-AMS measured an average sulphate deposition velocity of 0.3 mm s-1 and an average nitrate deposition velocity of 4.8 mm s-1. The FMPS, mounted at a height of 33 m (approximately 10 m above the canopy top) and housed in a temperature controlled enclosure, measured size-resolved particle concentrations from 3 to 410 nm diameter at a rate of 1 Hz. For the size range 18 < D < 452 nm, 60 % of fluxes were upward. The exchange velocity was between -0.5 and 2.0 mm s-1, with median values near 0.5 mm s-1 for all sizes between 22 and 310 nm. The size distribution of the apparent production rate of particles at 33 m peaked at a diameter of 75 nm. Results indicate a decoupling of the above and below canopy spaces, whereby particles are stored in the canopy space at night, and are then diluted with cleaner air above during the day.

  16. Burn site groundwater interim measures work plan.

    SciTech Connect

    Witt, Jonathan L.; Hall, Kevin A.

    2005-05-01

    This Work Plan identifies and outlines interim measures to address nitrate contamination in groundwater at the Burn Site, Sandia National Laboratories/New Mexico. The New Mexico Environment Department has required implementation of interim measures for nitrate-contaminated groundwater at the Burn Site. The purpose of interim measures is to prevent human or environmental exposure to nitrate-contaminated groundwater originating from the Burn Site. This Work Plan details a summary of current information about the Burn Site, interim measures activities for stabilization, and project management responsibilities to accomplish this purpose.

  17. AmeriFlux US-Ne3 Mead - rainfed maize-soybean rotation site

    DOE Data Explorer

    Suyker, Andy [University of Nebraska - Lincoln

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-Ne3 Mead - rainfed maize-soybean rotation site. Site Description - The study site is one of three fields (all located within 1.6 km of each other) at the University of Nebraska Agricultural Research and Development Center near Mead, Nebraska. While the other two sites are equipped with irrigation systems, this site relies on rainfall. A tillage operation (disking) was done just prior to the 2001 planting to homogenize the top 0.1 m of soil, incorporate P and K fertilizers, as well as previously accumulated surface residues. Since initiation of the study in 2001, this site has been under no-till management.

  18. AmeriFlux US-Ne2 Mead - irrigated maize-soybean rotation site

    DOE Data Explorer

    Suyker, Andy [University of Nebraska - Lincoln

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-Ne2 Mead - irrigated maize-soybean rotation site. Site Description - The study site is one of three fields (all located within 1.6 km of each other) at the University of Nebraska Agricultural Research and Development Center near Mead, Nebraska. This site is irrigated with a center pivot system. Prior to the initiation of the study, the irrigated site had a 10-yr history of maize-soybean rotation under no-till. A tillage operation (disking) was done just prior to the 2001 planting to homogenize the top 0.1 m of soil, incorporate P and K fertilizers, as well as previously accumulated surface residues. Since this tillage operation, the site has been under no-till management.

  19. AmeriFlux CA-NS4 UCI-1964 burn site wet

    SciTech Connect

    Goulden, Mike

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site CA-NS4 UCI-1964 burn site wet. Site Description - The UCI-1964 wet site is located in a continental boreal forest, dominated by black spruce trees, within the BOREAS northern study area in central Manitoba, Canada. The site is a member of a chronological series of sites that are representative secondary succession growth stages after large stand replacement fires. Black spruce trees undergo a slow growth process enabling the accurate determination of the chronosequence of stand age disturbance. Additionally, boreal forests make up approximately 25% of forest ecosystems on earth. With both of these in mind, the UCI sites provide an excellent location to study the CO2 exchange between the atmosphere and boreal forest ecosystems as a function of sequential wildfires.

  20. AmeriFlux CA-NS7 UCI-1998 burn site

    SciTech Connect

    Goulden, Mike

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site CA-NS7 UCI-1998 burn site. Site Description - The UCI-1998 site is located in a continental boreal forest, dominated by black spruce trees, within the BOREAS northern study area in central Manitoba, Canada. The site is a member of a chronological series of sites that are representative secondary succession growth stages after large stand replacement fires. Black spruce trees undergo a slow growth process enabling the accurate determination of the chronosequence of stand age disturbance. Additionally, boreal forests make up approximately 25% of forest ecosystems on earth. With both of these in mind, the UCI sites provide an excellent location to study the CO2 exchange between the atmosphere and boreal forest ecosystems as a function of sequential wildfires.

  1. AmeriFlux CA-NS2 UCI-1930 burn site

    SciTech Connect

    Goulden, Mike

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site CA-NS2 UCI-1930 burn site. Site Description - The UCI-1930 site is located in a continental boreal forest, dominated by black spruce trees, within the BOREAS northern study area in central Manitoba, Canada. The site is a member of a chronological series of sites that are representative secondary succession growth stages after large stand replacement fires. Black spruce trees undergo a slow growth process enabling the accurate determination of the chronosequence of stand age disturbance. Additionally, boreal forests make up approximately 25% of forest ecosystems on earth. With both of these in mind, the UCI sites provide an excellent location to study the CO2 exchange between the atmosphere and boreal forest ecosystems as a function of sequential wildfires.

  2. AmeriFlux CA-NS3 UCI-1964 burn site

    SciTech Connect

    Goulden, Mike

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site CA-NS3 UCI-1964 burn site. Site Description - The UCI-1964 site is located in a continental boreal forest, dominated by black spruce trees, within the BOREAS northern study area in central Manitoba, Canada. The site is a member of a chronological series of sites that are representative secondary succession growth stages after large stand replacement fires. Black spruce trees undergo a slow growth process enabling the accurate determination of the chronosequence of stand age disturbance. Additionally, boreal forests make up approximately 25% of forest ecosystems on earth. With both of these in mind, the UCI sites provide an excellent location to study the CO2 exchange between the atmosphere and boreal forest ecosystems as a function of sequential wildfires.

  3. AmeriFlux CA-NS5 UCI-1981 burn site

    SciTech Connect

    Goulden, Mike

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site CA-NS5 UCI-1981 burn site. Site Description - The UCI-1981 site is located in a continental boreal forest, dominated by black spruce trees, within the BOREAS northern study area in central Manitoba, Canada. The site is a member of a chronological series of sites that are representative secondary succession growth stages after large stand replacement fires. Black spruce trees undergo a slow growth process enabling the accurate determination of the chronosequence of stand age disturbance. Additionally, boreal forests make up approximately 25% of forest ecosystems on earth. With both of these in mind, the UCI sites provide an excellent location to study the CO2 exchange between the atmosphere and boreal forest ecosystems as a function of sequential wildfires.

  4. AmeriFlux CA-NS8 UCI-2003 burn site

    SciTech Connect

    Goulden, Mike

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site CA-NS8 UCI-2003 burn site. Site Description - The UCI-2003 site is located in a continental boreal forest, dominated by black spruce trees, within the BOREAS northern study area in central Manitoba, Canada. The site is a member of a chronological series of sites that are representative secondary succession growth stages after large stand replacement fires. Black spruce trees undergo a slow growth process enabling the accurate determination of the chronosequence of stand age disturbance. Additionally, boreal forests make up approximately 25% of forest ecosystems on earth. With both of these in mind, the UCI sites provide an excellent location to study the CO2 exchange between the atmosphere and boreal forest ecosystems as a function of sequential wildfires.

  5. AmeriFlux CA-NS6 UCI-1989 burn site

    SciTech Connect

    Goulden, Mike

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site CA-NS6 UCI-1989 burn site. Site Description - The UCI-1989 site is located in a continental boreal forest, dominated by black spruce trees, within the BOREAS northern study area in central Manitoba, Canada. The site is a member of a chronological series of sites that are representative secondary succession growth stages after large stand replacement fires. Black spruce trees undergo a slow growth process enabling the accurate determination of the chronosequence of stand age disturbance. Additionally, boreal forests make up approximately 25% of forest ecosystems on earth. With both of these in mind, the UCI sites provide an excellent location to study the CO2 exchange between the atmosphere and boreal forest ecosystems as a function of sequential wildfires.

  6. AmeriFlux CA-NS1 UCI-1850 burn site

    SciTech Connect

    Goulden, Mike

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site CA-NS1 UCI-1850 burn site. Site Description - The UCI-1850 site is located in a continental boreal forest, dominated by black spruce trees, within the BOREAS northern study area in central Manitoba, Canada. The site is a member of a chronological series of sites that are representative secondary succession growth stages after large stand replacement fires. Black spruce trees undergo a slow growth process enabling the accurate determination of the chronosequence of stand age disturbance. Additionally, boreal forests make up approximately 25% of forest ecosystems on earth. With both of these in mind, the UCI sites provide an excellent location to study the CO2 exchange between the atmosphere and boreal forest ecosystems as a function of sequential wildfires.

  7. Comparison of CO2 fluxes from eddy covariance and soil chambers measurements in a vineyard

    NASA Astrophysics Data System (ADS)

    Vendrame, Nadia; Tezza, Luca; Meggio, Franco; Pitacco, Andrea

    2015-04-01

    In order to study the processes involved in the carbon balance of a vineyard, we set up a long-term monitoring station of CO2, water vapour and energyfluxes. The experimental site is located in an extensive flat vineyard in the north-east of Italy. We measure the net ecosystem exchange with the eddy covariance (EC) technique using a Campbell Scientific closed-path IRGA and sonic anemometer, and the soil CO2 flux using a Li-Cor multiplexed system connected with six automatic dynamic chambers. Ancillary meteorological and soil variables are also measured. The vineyard is planted with north-south oriented rows spaced 2.2 m apart. Floor is grass covered, and a strip 0.6 m wide on the rows is chemically treated. To represent the different soil conditions existing in the EC footprint and to study the components of the CO2 soil flux, we placed dark soil chambers both on the vineyard rows and in the inter-row space. A well-known limit of the EC technique is the underestimation of fluxes during calm wind periods, mainly occurring at night. In the autumn/winter vine dormancy period, the EC and soil chambers CO2 fluxes should be similar. We compared the CO2 fluxes measured using the two methods to evaluate the reliability of EC measurements at different atmospheric turbulent mixing conditions and stability. The EC technique underestimates the ecosystem respiration during night time periods with friction velocity lower than 0.1 m/s. The present comparison could enable the assessment of a friction velocity threshold, representing the limit above which the EC fluxes can be considered representative of the vegetation-atmosphere exchanges at our specific site.

  8. An Alpha-Gamma Counter for Absolute Neutron Flux Measurement

    NASA Astrophysics Data System (ADS)

    Yue, A.; Greene, G.; Dewey, M.; Gilliam, D.; Nico, J.; Laptev, A.

    2012-03-01

    An alpha-gamma counter was used to measure the absolute neutron flux of a monochromatic cold neutron beam to sub-0.1,% precision. Simultaneously, the counter was used to calibrate a thin neutron flux monitor based on neutron absorption on ^6Li to the same precision. This monitor was used in the most precise beam-based measurement of the neutron lifetime, where the limiting systematic effect was the uncertainty in the neutron counting efficiency (0.3,%). The counter uses a thick target of ^10B-enriched boron carbide to completely absorb the beam. The rate of absorbed neutrons is determined by counting 478 keV gamma rays from neutron capture on ^10B with calibrated high-purity germanium detectors. The calibration results and the implications for the neutron lifetime will be discussed.

  9. Using Airborne Microwave Remotely Sensed Root-Zone Soil Moisture and Flux Measurements to Improve Regional Predictions of Carbon Fluxes in a Terrestrial Biosphere Model

    NASA Astrophysics Data System (ADS)

    Zhang, K.; Antonarakis, A. S.; Medvigy, D.; Burgin, M. S.; Crow, W. T.; Milak, S.; Jaruwatanadilok, S.; Truong-Loi, M.; Moghaddam, M.; Saatchi, S. S.; Cuenca, R. H.; Moorcroft, P. R.

    2013-12-01

    North American ecosystems are critical components of the global carbon cycle, exchanging large amounts of carbon dioxide and other gases with the atmosphere. Net ecosystem exchange (NEE) of CO2 between atmosphere and ecosystems quantifies these carbon fluxes, but current continental-scale estimates contain high levels of uncertainty. Root-zone soil moisture (RZSM) and its spatial and temporal heterogeneity influences NEE and improved estimates can help reduce uncertainty in NEE estimates. We used the RZSM measurements from the Airborne Microwave Observatory of Subcanopy and Subsurface (AirMOSS) mission, and the carbon, water and energy fluxes observed by the eddy-covariance flux towers to constrain the Ecosystem Demography Model 2.2 (ED2.2) to improve its predictions of carbon fluxes. The parameters of the ED2.2 model were first optimized at seven flux tower sites in North America, which represent six different biomes, by constraining the model against a suite of flux measurements and forest inventory measurements through a Bayesian Markov-Chain Monte Carlo framework. We further applied the AirMOSS RZSM products to constrain the ED2.2 model to achieve better estimates of regional NEE. Evaluation against flux tower measurements and forest dynamics measurements shows that the constrained ED2.2 model produces improved predictions of monthly to annual carbon fluxes. The remote sensing based RZSM can further help improve the spatial patterns and temporal variations of model NEE. The results demonstrate that model-data fusion can substantially improve model performance and highlight the important role of RZSM in regulating the spatial and temporal heterogeneities of carbon fluxes.

  10. DIRECT MEASUREMENT OF HEAT FLUX FROM COOLING LAKE THERMAL IMAGERY

    SciTech Connect

    Garrett, A; Eliel Villa-Aleman, E; Robert Kurzeja, R; Malcolm Pendergast, M; Timothy Brown, T; Saleem Salaymeh, S

    2007-12-19

    Laboratory experiments show a linear relationship between the total heat flux from a water surface to air and the standard deviation of the surface temperature field, {sigma}, derived from thermal images of the water surface over a range of heat fluxes from 400 to 1800 Wm{sup -2}. Thermal imagery and surface data were collected at two power plant cooling lakes to determine if the laboratory relationship between heat flux and {sigma} exists in large heated bodies of water. The heat fluxes computed from the cooling lake data range from 200 to 1400 Wm{sup -2}. The linear relationship between {sigma} and Q is evident in the cooling lake data, but it is necessary to apply band pass filtering to the thermal imagery to remove camera artifacts and non-convective thermal gradients. The correlation between {sigma} and Q is improved if a correction to the measured {sigma} is made that accounts for wind speed effects on the thermal convection. Based on more than a thousand cooling lake images, the correlation coefficients between {sigma} and Q ranged from about 0.8 to 0.9.

  11. Corrections of Heat Flux Measurements on Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Reinarts, Thomas R.; Matson, Monique L.; Walls, Laurie K.

    2002-01-01

    Knowledge of aerothermally induced convective heat transfer is important in the design of thermal protection systems for launch vehicles. Aerothermal models are typically calibrated via the data from circular, in-flight, flush-mounted surface heat flux gauges exposed to the thermal and velocity boundary layers of the external flow. Typically, copper or aluminum Schmidt- Boelter gauges, which take advantage of the one-dimensional Fourier's law of heat conduction, are used to measure the incident heat flux. This instrumentation, when surrounded by low-conductivity insulation, has a wall temperature significantly lower than the insulation. As a result of this substantial disturbance to the thermal boundary layer, the heat flux incident on the gauge tends to be considerably higher than it would have been on the insulation had the calorimeter not been there. In addition, radial conductive heat transfer from the hotter insulation can cause the calorimeter to indicate heat fluxes higher than actual. An overview of an effort to develop and calibrate gauge correction techniques for both of these effects will be presented.

  12. Assessing and correcting spatial representativeness of tower eddy-covariance flux measurements

    NASA Astrophysics Data System (ADS)

    Metzger, S.; Xu, K.; Desai, A. R.; Taylor, J. R.; Kljun, N.; Blanken, P.; Burns, S. P.; Scott, R. L.

    2014-12-01

    Estimating the landscape-scale exchange of ecologically relevant trace gas and energy fluxes from tower eddy-covariance (EC) measurements is often complicated by surface heterogeneity. For example, a tower EC measurement may represent less than 1% of a grid cell resolved by mechanistic models (order 100-1000 km2). In particular for data assimilation or comparison with large-scale observations, it is hence critical to assess and correct the spatial representativeness of tower EC measurements. We present a procedure that determines from a single EC tower the spatio-temporally explicit flux field of its surrounding. The underlying principle is to extract the relationship between biophysical drivers and ecological responses from measurements under varying environmental conditions. For this purpose, high-frequency EC flux processing and source area calculations (≈60 h-1) are combined with remote sensing retrievals of land surface properties and subsequent machine learning. Methodological details are provided in our companion presentation "Towards the spatial rectification of tower-based eddy-covariance flux observations". We apply the procedure to one year of data from each of four AmeriFlux sites under different climate and ecological environments: Lost Creek shrub fen wetland, Niwot Ridge subalpine conifer, Park Falls mixed forest, and Santa Rita mesquite savanna. We find that heat fluxes from the Park Falls 122-m-high EC measurement and from a surrounding 100 km2 target area differ up to 100 W m-2, or 65%. Moreover, 85% and 24% of the EC flux observations are adequate surrogates of the mean surface-atmosphere exchange and its spatial variability across a 900 km2 target area, respectively, at 5% significance and 80% representativeness levels. Alternatively, the resulting flux grids can be summarized as probability density functions, and used to inform mechanistic models directly with the mean flux value and its spatial variability across a model grid cell. Lastly

  13. A new disjunct eddy-covariance system for BVOC flux measurements - validation on CO2 and H2O fluxes

    NASA Astrophysics Data System (ADS)

    Baghi, R.; Durand, P.; Jambert, C.; Jarnot, C.; Delon, C.; Serça, D.; Striebig, N.; Ferlicoq, M.; Keravec, P.

    2012-12-01

    The disjunct eddy covariance (DEC) method is an interesting alternative to the conventional eddy covariance (EC) method because it allows the estimation of turbulent fluxes of species for which fast sensors are not available. We have developed and validated a new disjunct sampling system (called MEDEE). This system is built with chemically inert materials. Air samples are taken quickly and alternately in two cylindrical reservoirs, the internal pressures of which are regulated by a moving piston. The MEDEE system was designed to be operated either on the ground or aboard an aircraft. It is also compatible with most analysers since it transfers the air samples at a regulated pressure. To validate the system, DEC and EC measurements of CO2 and latent heat fluxes were performed concurrently during a field campaign. EC fluxes were first compared to simulated DEC (SDEC) fluxes and then to actual DEC fluxes. Both the simulated and actual DEC fluxes showed a good agreement with EC fluxes in terms of correlation. The determination coefficients (R2) were 0.93 and 0.91 for DEC and SDEC latent heat fluxes, respectively. For DEC and SDEC CO2 fluxes R2 was 0.69 in both cases. The conditions of low fluxes experienced during the campaign impaired the comparison of the different techniques especially for CO2 flux measurements. Linear regression analysis showed an 14% underestimation of DEC fluxes for both CO2 and latent heat compared to EC fluxes. A first field campaign, focusing on biogenic volatile organic compound (BVOC) emissions, was carried out to measure isoprene fluxes above a downy oak (Quercus Pubescens) forest in the south-east of France. The measured standard emission rate was in the lower range of reported values in earlier studies. Further analysis will be conducted through ground-based and airborne campaigns in the coming years.

  14. Estimation of rainfall interception in grassland using eddy flux measurements

    NASA Astrophysics Data System (ADS)

    Maruyama, A.; Miyazawa, Y.; Inoue, A.

    2014-12-01

    Rainfall interception plays an important role in the water cycle in natural ecosystems. Interception by the forest canopies have been widely observed or estimated over various ecosystems, such as tropical rainforest, evergreen forest and deciduous forest. However interception by the short canopies, e.g. shrubby plant, grassland and crop, has been rarely observed since it has been difficult to obtain reliable precipitation measurements under the canopy. In this study, we estimated monthly and annual rainfall interception in grassland using evapotranspiration data of eddy flux measurements. Experiments were conducted in grassland (Italian ryegrass) from 2010 to 2012 growing season in Kumamoto, Japan. Evapotranspiration (latent heat flux) were observed throughout the year based on the eddy covariance technique. A three dimensional sonic anemometer and an open path CO2/H2O analyzer were used to calculate 30 min flux. Other meteorological factors, such as air temperature, humidity and solar radiation, were also observed. Rainfall interception was estimated as follows. 1) Using evapotranspiration data during dry period, environmental response of surface conductance (gc) was inversely calculated based on the big-leaf model. 2) Evapotranspiration without interception during precipitation period was estimated using above model and environmental response of gc. 3) Assuming that evaporation of intercepted rainfall is equal to the difference in evapotranspiration between above estimation and actual measurements, rainfall interception was estimated over experimental period. The account of rainfall interception in grassland using this technique will be presented at the meeting.

  15. AmeriFlux US-Ho3 Howland Forest (harvest site)

    SciTech Connect

    Hollinger, David; Hollinger, David

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-Ho3 Howland Forest (harvest site). Site Description - Closed conifer forest, minimal disturbance. References: Fernandez et al. (1993), Canadian Journal of Soil Science 73 317-328. Hollinger et al. (1999), Global Change Biology 5: 891-902. Savage KE, Davidson EA (2001), Global Biogeochemical Cycles 15 337-350. Scott et al. (2004), Environmental Management, Vol. 33, Supplement 1, pp. S9-S22. Hollinger et al. (2004), Global Change Biology 10: 1689-1706.

  16. A Push-Pull Test to Measure Volatilization Fluxes of Organic Pollutants without Flux Chambers

    NASA Astrophysics Data System (ADS)

    Reid, M. C.; Jaffe, P. R.

    2011-12-01

    Volatilization of organic contaminants is a potentially significant removal mechanism from wetlands, but field measurements are scarce and the physiochemical controls on volatilization from wetland soils remain poorly understood. It has been established that volatilization rates of certain pollutants are enhanced by vegetation and are strongly correlated with evapotranspiration (ET). These observations rely on flux chambers measurements, which are characterized by significant uncertainty due the chamber's effects on the meteorological variables around the plant and consequent impact on the biophysical processes governing ET and plant uptake of soil contaminants. Here we present data from a mesocosm study using a modified single-well push-pull test to measure in-situ volatilization rates from inundated soils vegetated with the wetland macrophytes Scirpus acutus and Typha latifolia, as well as from unplanted soil. This new method uses a test solution containing the volatile tracers sulfur hexafluoride (SF6), helium (He), and dichlorodifluoromethane (CFC-12) to estimate first-order volatilization rates and examine the relationship between physiochemical properties and volatilization rates. The test also yields an estimate for the volume of subsurface gas bubbles, which is used to derive a retardation factor for the effect of interphase partitioning on the estimation of kinetic parameters. We evaluate models to partition observed fluxes into different pathways for plant-mediated volatilization: transpirational uptake and consequent volatilization, and gas-phase diffusion through porous root aerenchyma. Those models are then used to scale tracer-derived volatilization fluxes to priority organic pollutants including benzene, trichloroethylene, and vinyl chloride. We also discuss the implementation of this method at field scales to estimate volatilization as a component of phytoremediation applications.

  17. CO2 uptake and ecophysiological parameters of the grain crops of midcontinent North America: estimates from flux tower measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We present net CO2 exchange data from 13 flux tower sites with 27 site-years of measurements over maize and wheat fields across midcontinent North America. A numerically robust “light-soil temperature-VPD”-based method was used to partition the data into photosynthetic assimilation and ecosystem re...

  18. High-Energy Neutron Spectra and Flux Measurements Below Ground

    NASA Astrophysics Data System (ADS)

    Roecker, Caleb; Bernstein, Adam; Marleau, Peter; Vetter, Kai

    2016-03-01

    High-energy neutrons are a ubiquitous and often poorly measured background. Below ground, these neutrons could potentially interfere with antineutrino based reactor monitoring experiments as well as other rare-event neutral particle detectors. We have designed and constructed a transportable fast neutron detection system for measuring neutron energy spectra and flux ranging from tens to hundreds of MeV. The spectrometer uses a multiplicity technique in order to have a higher effective area than traditional transportable high-energy neutron spectrometers. Transportability ensures a common detector-related systematic bias for future measurements. The spectrometer is composed of two Gd containing plastic scintillator detectors arranged around a lead spallation target. A high-energy neutron may interact in the lead producing many secondary neutrons. The detector records the correlated secondary neutron multiplicity. Over many events, the response can be used to infer the incident neutron energy spectrum and flux. As a validation of the detector response, surface measurements have been performed; results confirm agreement with previous experiments. Below ground measurements have been performed at 3 depths (380, 600, and 1450 m.w.e.); results from these measurements will be presented.

  19. Momentum Flux Measuring Instrument for Neutral and Charged Particle Flows

    NASA Technical Reports Server (NTRS)

    Chavers, Greg; Chang-Diaz, Franklin; Schafer, Charles F. (Technical Monitor)

    2002-01-01

    An instrument to measure the momentum flux (total pressure) of plasma and neutral particle jets onto a surface has been developed. While this instrument was developed for magnetized plasmas, the concept works for non-magnetized plasmas as well. We have measured forces as small as 10(exp -4) Newtons on a surface immersed in the plasma where small forces are due to ionic and neutral particles with kinetic energies on the order of a few eV impacting the surface. This instrument, a force sensor, uses a target plate (surface) that is immersed in the plasma and connected to one end of an alumina rod while the opposite end of the alumina rod is mechanically connected to a titanium beam on which four strain gauges are mounted. The force on the target generates torque causing strain in the beam. The resulting strain measurements can be correlated to a force on the target plate. The alumina rod electrically and thermally isolates the target plate from the strain gauge beam and allows the strain gauges to be located out of the plasma flow while also serving as a moment arm of several inches to increase the strain in the beam at the strain gauge location. These force measurements correspond directly to momentum flux and may be used with known plasma conditions to place boundaries on the kinetic energies of the plasma and neutral particles. The force measurements may also be used to infer thrust produced by a plasma propulsive device. Stainless steel, titanium, molybdenum, and aluminum flat target plates have been used. Momentum flux measurements of H2, D2, He, and Ar plasmas produced in a magnetized plasma device have been performed.

  20. PERFORMING QUALITY FLOW MEASUREMENTS AT MINE SITES

    EPA Science Inventory

    Accurate flow measurement data is vital to research, monitoring, and remediation efforts at mining sites. This guidebook has been prepared to provide a summary of information relating to the performance of low measurements, and how this information can be applied at mining sites....

  1. Flux measurements of energy and trace gases in urban Houston, Texas

    NASA Astrophysics Data System (ADS)

    Boedeker, I.; Schade, G. W.; Adams, S.; Park, C.

    2008-12-01

    We describe the setup and some first year results of a new flux measurements tower in an urban area. An existing radio communications tower 4 km north of downtown Houston was equipped with micrometeorological instrumentation and trace gas sampling lines in spring 2007. Wind speed, temperature and relative humidity are recorded at five levels between 12 and 60 m above ground; 3-D wind speed measurements, solar and net radiances, and trace gas sampling are established from the 60 m level. A closed path IRGA is used for CO2 and water vapor fluxes, and independent instrumentation for criteria pollutant and VOC fluxes. Two CSI data loggers and software control the measurements, and EdiRe software is used to analyze turbulence data and compute fluxes. A project description is provided at http://atmo.tamu.edu/yellowcabtower. Surface properties as calculated from the gradient measurements show the site to be surprisingly uniform, with displacement heights between 5 and 9 m and roughness lengths between 0.4 and 0.7 m, despite urban heterogeneity. The latter is investigated through visible/near IR orthoimagery and LIDAR data, which are incorporated into a local GIS. Net radiation was also only marginally affected by surface heterogeneity. At this urban location it is balanced by roughly equal amounts of sensible heat, latent heat, and storage fluxes. Latent heat flux, however, is smaller outside the growing season, with an equivalent increase in winter storage fluxes, as expected. Significant differences are also observed with direction during summer, showing decreased Bowen ratios and lower CO2 emissions from sectors with a larger urban tree canopy cover in the footprint. The largely mature, dominantly oak urban canopy cover alleviates approximately 100 W m- 2 during typical summer days. On the other hand, anthropogenic CO2 emissions dominate over photosynthetic uptake all year round. Measured carbon fluxes peak during morning rush-hour traffic, especially when increasing

  2. Development of a Passive Sensor for Measuring Water and Solute Mass Flux in the Hyporheic Zone

    NASA Astrophysics Data System (ADS)

    Annable, Michael D.; Layton, Leif; Hatfield, Kirk; Newman, Mark C.; Cho, Jaehyun; Klammler, Harald

    2014-05-01

    Measuring water, pollutant and nutrient exchange at the groundwater-surface water interface is challenging due to the dynamic nature of the hyporheic zone. Quantifying the exchange is critical to understanding mass balance across this interface. Technologies currently exist to identify groundwater discharge zones and infer estimates of contaminant mass flux based on total contaminant concentration in bulk sediment, though it is generally accepted that freely dissolved concentration in pore water is a better measure of potential exposure. Laboratory and preliminary field testing has been completed to demonstrate a new tool with potential to provide more accurate characterization of water, pollutant and nutrient flux at the groundwater-surface water interface through direct in-situ measurement. The sediment bed passive flux meter (SBPFM) was designed for passively and directly providing in-situ measurements of volumetric water flux and solute mass flux vertically through the upper surface sediment layer and into the overlying water column. The SBPFM consists of an internal permeable sorbent which is impregnated with one or more water soluble tracers (typically alcohols) and is contained in a dedicated drive-point with upper and lower screened openings for fluid intake and exhaust. This configuration generates water flow through the device proportional to the vertical gradient between the sediment bed and the water column. Once the SBPFM has been deployed, the tracers are displaced from the sorbent at rates proportional to the average vertical specific discharge. The mass loss of tracers during deployment can be used to calculate the cumulative water flux. Similarly, the cumulative mass of sorbed pollutants or nutrients provide a direct measurement of the vertical mass flux during deployment. The SBPFM prototype has been tested in controlled laboratory sediment interface models. The results show good agreement between the SBPFM calculated and the applied water and

  3. Doppler lidar measurement of profiles of turbulence and momentum flux

    NASA Technical Reports Server (NTRS)

    Eberhard, Wynn L.; Cupp, Richard E.; Healy, Kathleen R.

    1989-01-01

    A short-pulse CO2 Doppler lidar with 150-m range resolution measured vertical profiles of turbulence and momentum flux. Example measurements are reported of a daytime mixed layer with strong mechanical mixing caused by a wind speed of 15 m/sec, which exceeded the speed above the capping inversion. The lidar adapted an azimuth scanning technique previously demonstrated by radar. Scans alternating between two elevation angles allow determination of mean U-squared, V-squared, and W-squared. Expressions were derived to estimate the uncertainty in the turbulence parameters. A new processing method, partial Fourier decomposition, has less uncertainty than the filtering used earlier.

  4. Eddy covariance measurements in screenhouses: turbulence characteristics and flux gradients

    NASA Astrophysics Data System (ADS)

    Dicken, U.; Cohen, S.; Tanny, J.

    2012-04-01

    Shading banana and other orchard crops with screens is popular in arid and semi-arid regions for decreasing water use and increasing fruit quality. However, crop water use within this unique environment is much less studied than for canopies in the open. Previous studies of our research group have established the use of the Eddy Covariance (EC) technique for reliable evapotranspiration and sensible heat flux measurements within screenhouses. These studies focused on operating conditions of the system. The present paper is a comprehensive study which examined the performance of the EC system in different types of screenhouses (shading and insect-proof), different crops (banana and pepper) at different development stages (small and large plants) and different climatic regions in Israel. The main goal was to establish guidelines for optimal application of the EC technique in screenhouses. The research consisted of 6 field campaigns: in 3 campaigns two EC systems were simultaneously deployed either vertically or horizontally, and in 3 other campaigns a single EC system was deployed at one measurement height. EC systems were deployed at different normalized system heights, Zs, which define the relative measurement heights within the air gap between the canopy top and the horizontal screened roof. System performance was examined using quality tests like energy balance closure, flux variance similarity, friction velocity, footprint modeling, energy spectrum, turbulence intensity and vertical and horizontal flux gradient analyses. Resulting energy balance closure slopes averaged 0.81±0.08 and 0.91±0.08 for the smaller and larger plants, respectively. Turbulent flows were found to be marginally developed within the air gap between the top of the plants and the horizontal screened roof. Turbulence intensity, flux variance similarity test, energy spectrum decay rate and friction velocity were essentially independent of the measurement height and were within the common range

  5. Optimizing laboratory-based radon flux measurements for sediments.

    PubMed

    Chanyotha, Supitcha; Kranrod, Chutima; Kritsananuwat, Rawiwan; Lane-Smith, Derek; Burnett, William C

    2016-07-01

    Radon flux via diffusion from sediments and other materials may be determined in the laboratory by circulating air through the sample and a radon detector in a closed loop. However, this approach is complicated by the necessity of having to determine the total air volume in the system and accounting for any small air leaks that can arise if using extended measurement periods. We designed a simple open-loop configuration that includes a measured mass of wet sediment and water inside a gas-tight reaction flask connected to a drying system and a radon-in-air analyzer. Ambient air flows through two charcoal columns before entering the reaction vessel to eliminate incoming radon. After traveling through the reaction flask, the air passes the drier and the radon analyzer and is then vented. After some time, the radon activity will reach a steady state depending upon the airflow rate. With this approach, the radon flux via diffusion is simply the product of the steady-state radon activity (Bq/m(3)) multiplied by the airflow rate (mL/min). We demonstrated that this setup could produce good results for materials that produce relatively high radon fluxes. We also show that a modified closed system approach, including radon removal of the incoming air by charcoal filtration in a bypass, can produce very good results including samples with very low emission rates. PMID:27064564

  6. A measurement of the antiproton flux in the cosmic rays

    NASA Technical Reports Server (NTRS)

    Buffington, A.; Schindler, S. M.

    1981-01-01

    A balloon-borne instrument has been used to detect cosmic-ray antiprotons. These are identified topologically by the appearance of annihilation prongs in a thick lead-plate spark chamber. The initial recording of the data is enriched in potential antimatter events by a selective trigger. After a small subtraction for background, 14 identified antiprotons yield a flux of 1.7 plus or minus 0.00005 antiproton/(sq m ster sec MeV) between 130 and 320 MeV at the top of the atmosphere. When combined with higher energy antiproton flux measurements, this result indicates that the antiprotons have a spectrum whose shape is the same as that of the protons, but with a magnitude reduced by a factor of 1/3000.

  7. Momentum Flux Measurements Using an Impact Thrust Stand

    NASA Technical Reports Server (NTRS)

    Chavers, Greg; Chang-Diaz, Franklin; Breizman, Boris; Bengtson, Roger

    2004-01-01

    A device has been developed to measure the force caused by a beam of charged and neutral particles impacting a target plate. This device, an impact thrust stand, was developed to allow thrusters, during early stages of development, to be quickly and easily exhausted and compared to other thrusters. Since some thruster concepts are tested using laboratory equipment that is heavy and cumbersome, measuring the momentum flux of the particles in the plume can be much simpler than placing the entire thruster on a thrust stand. Conservation of momentum requires the momentum flux measured in the plume to be related to the thrust produced by the thruster. The impact thrust stand was designed to be placed in the plume of an electric thruster and has been tested and compared to the thrust measured from a Hall thruster placed on a pendulum thrust stand. Force measurements taken at several axial locations in the magnetic nozzle region of the Variable Specific Impulse Magnetoplasma Rocket will be presented.

  8. Momentum flux measurements using an impact thrust stand

    NASA Astrophysics Data System (ADS)

    Chavers, Greg; Chang-Diaz, Franklin; Breizman, Boris; Bengtson, Roger

    2004-11-01

    A device has been developed to measure the force caused by a beam of charged and neutral particles impacting a target plate. This device, an impact thrust stand, was developed to allow thrusters, during early stages of development, to be quickly and easily evaluated and compared to other thrusters. Since some thruster concepts are tested using laboratory equipment that is heavy and cumbersome, measuring the momentum flux of the particles in the plume can be much simpler than placing the entire thruster on a thrust stand. Conservation of momentum requires the momentum flux measured in the plume to be related to the thrust produced by the thruster. The impact thrust stand was designed to be placed in the plume of an electric thruster and has been tested and compared to the thrust measured from a Hall thruster placed on a pendulum thrust stand. Force measurements taken at several axial locations in the magnetic nozzle region of the Variable Specific Impulse Magnetoplasma Rocket will be presented.

  9. Biogenic volatile organic compound emissions during BEARPEX 2009 measured by eddy covariance and flux-gradient similarity methods

    NASA Astrophysics Data System (ADS)

    Park, J.-H.; Fares, S.; Weber, R.; Goldstein, A. H.

    2014-01-01

    The Biosphere Effects on AeRosols and Photochemistry EXperiment (BEARPEX) took place in Blodgett Forest, a Ponderosa pine forest in the Sierra Nevada of California, USA, during summer 2009. We deployed a proton transfer reaction-quadrupole mass spectrometer (PTR-QMS) to measure fluxes and concentrations of biogenic volatile organic compounds (BVOCs). Eighteen ion species, including the major BVOC expected at the site, were measured sequentially at 5 heights to observe their vertical gradient from the forest floor to above the canopy. Fluxes of the 3 dominant BVOCs methanol, 2-Methyl-3-butene-2-ol (MBO), and monoterpenes were measured above the canopy by the disjunct eddy covariance (EC) method. Canopy-scale fluxes were also determined by the flux-gradient similarity method (K-theory). A universal K (Kuniv) was determined as the mean of individual K's calculated from the measured fluxes divided by vertical gradients for methanol, MBO, and monoterpenes. This Kuniv was then multiplied by the gradients of each observed ion species to compute their fluxes. The flux-gradient similarity method showed very good agreement with the disjunct EC method. Fluxes are presented for all measured species and compared to historical measurements from the same site, and used to test emission algorithms used to model fluxes at the regional scale. MBO was the dominant emission observed, followed by methanol, monoterpenes, acetone, and acetaldehyde. The flux-gradient similarity method is shown to be tenable, and we recommend its use, especially in experimental conditions when fast measurement of BVOC species is not available.

  10. Modelling the non steady state downward flux of particles at the PAP site in 2009

    NASA Astrophysics Data System (ADS)

    Sanders, R.; Lampitt, R.; Riley, J.; Lemoigne, F.; Marsay, C.; Giering, S.; Martin, A.

    2012-04-01

    The biological carbon pump, mediated principally via the sinking of organic matter from the surface ocean, is a significant term in the global carbon cycle. It transfers annually 5-15 GT C yr-1 out of the photic zone, an amount comparable to the annual accumulation of CO2 in the atmosphere driven by anthropogenic processes, and mediates a storage of CO2 in the ocean interior without which atmospheric CO2 would be much larger than it is today. Yet most of the material exported from the photic zone does not penetrate the deep ocean, instead it is mineralised in the twilight zone with fluxes in the thin 100m thick layer under the photic zone being extremely rapidly attenuated. The shape of this attenuation varies in time and space yet appears to be a critical determinand over atmosphere - ocean CO2 partitioning. Attempts to predict this attenuation using independent measures of heterotrophic activity have often not yielded the observed pattern of attenuation implying substantial uncertainties in one or more of the terms that enter into the comparison. In this talk we will describe direct estimates of particle flux made using drifting neutrally buoyant traps at the PAP site in 2009. We show that although we can make substantial progress towards closing the mid water C budget we still have a significant excess of carbon consumption over supply. We believe that this is due to erroneous steady state assumptions, a hypothesis we explore via simple numerical models.

  11. Predicting carbon dioxide and energy fluxes across global FLUXNET sites with regression algorithms

    NASA Astrophysics Data System (ADS)

    Tramontana, Gianluca; Jung, Martin; Schwalm, Christopher R.; Ichii, Kazuhito; Camps-Valls, Gustau; Ráduly, Botond; Reichstein, Markus; Altaf Arain, M.; Cescatti, Alessandro; Kiely, Gerard; Merbold, Lutz; Serrano-Ortiz, Penelope; Sickert, Sven; Wolf, Sebastian; Papale, Dario

    2016-07-01

    Spatio-temporal fields of land-atmosphere fluxes derived from data-driven models can complement simulations by process-based land surface models. While a number of strategies for empirical models with eddy-covariance flux data have been applied, a systematic intercomparison of these methods has been missing so far. In this study, we performed a cross-validation experiment for predicting carbon dioxide, latent heat, sensible heat and net radiation fluxes across different ecosystem types with 11 machine learning (ML) methods from four different classes (kernel methods, neural networks, tree methods, and regression splines). We applied two complementary setups: (1) 8-day average fluxes based on remotely sensed data and (2) daily mean fluxes based on meteorological data and a mean seasonal cycle of remotely sensed variables. The patterns of predictions from different ML and experimental setups were highly consistent. There were systematic differences in performance among the fluxes, with the following ascending order: net ecosystem exchange (R2 < 0.5), ecosystem respiration (R2 > 0.6), gross primary production (R2> 0.7), latent heat (R2 > 0.7), sensible heat (R2 > 0.7), and net radiation (R2 > 0.8). The ML methods predicted the across-site variability and the mean seasonal cycle of the observed fluxes very well (R2 > 0.7), while the 8-day deviations from the mean seasonal cycle were not well predicted (R2 < 0.5). Fluxes were better predicted at forested and temperate climate sites than at sites in extreme climates or less represented by training data (e.g., the tropics). The evaluated large ensemble of ML-based models will be the basis of new global flux products.

  12. Modeling the impact of hydraulic redistribution on the carbon flux and storages using CLM4.5 at four AmeriFlux Sites

    NASA Astrophysics Data System (ADS)

    Fu, C.; Wang, G.; Cardon, Z. G.

    2015-12-01

    Effects of hydraulic redistribution (HR) on the hydrological cycle and ecosystem dynamics have been demonstrated in the field, but few modeling studies have compared HR's influences on the carbon cycle in different ecosystems and climate regions. The soil moisture changes associated with HR could influence plant carbon gain via two mechanisms: (1) improved plant water status supporting stomatal opening, and/or (2) enhanced nutrient availability to plants caused by enhanced soil microbial activity. In this study, using a modified version of the Community Land Model with Century-based soil carbon pool kinetics that includes the "Ryel et al. 2002" scheme for hydraulic redistribution (HR), the influence of HR on the carbon flux and storage is investigated at four Ameriflux sites where HR was detected from soil moisture measurements. The study sites include a Douglas-fir site (US-Wrc) in Washington State with a mediterranean climate, a savanna site (US-SRM) in Arizona with a semi-arid climate, an oak/pine forest site (US-SCf) in Southern California with a mediterranean climate, and an evergreen broadleaf forest site (BR-Sa1) with tropical monsoon climate. Simulations revealed that HR tended to enhance plant growth at all four sites, and incorporating HR into CLM4.5 reduces the temporal fluctuation of soil carbon storage at all four sites. Simulations with HR can capture the net carbon exchange between ecosystem and the atmosphere (NEE) at the US-Wrc, US-SRM, and BR-Sa1 sites over the annual cycle. Incorporation of HR into CLM4.5 clearly improved the weekly and sub-daily NEE simulation during dry periods at US-SCf and BR-Sa1 site. HR-induced increase in Net Primary Productivity (NPP) at the US-Wrc and US-SRM sites was driven approximately equally by the two distinct mechanisms we investigated: increased stomatal conductance and increased nutrient availability to plants.

  13. Assessment of CO2 flux measurements in different soil types

    NASA Astrophysics Data System (ADS)

    Xia, L.; Szlavecz, K.; Musaloiu, R.; Cupchup, J.; Pitz, S.

    2008-12-01

    Accurate measurements of soil CO2 efflux are extraordinarily challenging due to the very properties of CO2 transport in a porous medium of soil. The most commonly used method today is the chamber method, which provides direct measurements of CO2 efflux at the soil surface, but it can not measure the soil CO2 flux continuously. In order to develop new measurement methods in soil CO2 efflux, small solid-state CO2 sensors have been used to continuously to monitor soil CO2 profiles by burying these sensors at different soil depths. Using this method we compared soil CO2 efflux of four different soil types: forests soil, grassland soil (collected in Maryland) commercial potting soil and pure sand as control. CO2 concentration varied between 500 ppm in sand and 8000 ppm in forest soil at depth 12 cm. CO2 flux had the following order: Forest (0.3~0.4 mg CO2 m-2 s-1), potting soil (0.1~0.14 mg CO2 m-2 s-1 ), grassland (0.03~0.05 mg CO2 m-2 s-1), sand ( 0 mg CO2 m-2 s-1 ). Exponential relationship between temperature and CO2 flux was established for forest soil and potting soil only. Leaf litter, often thick layer in many terrestrial ecosystems and a significant source of CO2 production, is not part of the of the diffusivity models. We are currently conducting experiments which include the effect of leaf litter and soil invertebrates into soil respiration.

  14. Airflows and turbulent flux measurements in mountainous terrain: Part 2: Mesoscale effects

    USGS Publications Warehouse

    Turnipseed, A.A.; Anderson, D.E.; Burns, S.; Blanken, P.D.; Monson, Russell K.

    2004-01-01

    The location of the Niwot Ridge Ameriflux site within the rocky mountains subjects it to airflows which are common in mountainous terrain. In this study, we examine the effects of some of these mesoscale features on local turbulent flux measurements; most notably, the formation of valley/mountain flows and mountain lee-side waves. The valley/mountain flows created local non-stationarities in the wind flow caused by the passage of a lee-side convergence zone (LCZ) in which upslope and downslope flows met in the vicinity of the measurement tower. During June-August, 2001, possible lee-side convergences were flagged for ???26% of all half-hour daytime flux measurement periods. However, there was no apparent loss of flux during these periods. On some relatively stable, summer nights, turbulence (designated via ??w), and scalar fluctuations (temperature and CO2, for example) exhibited periodicities that appeared congruent with passage of low frequency gravity waves (?? ??? 20 min). Spectral peaks at 0.0008 Hz (20 min) in both vertical velocity and scalar spectra were observed and indicated that 25-50% of the total scalar covariances were accounted for by the low frequency waves. During some periods of strong westerly winds (predominantly in winter), large mountain gravity waves were observed to form. Typically, the flux tower resided within a region of downslope "shooting flow", which created high turbulence, but had no detrimental effect on local flux measurements based on valid turbulence statistics and nearly complete energy budget closure. Periodically, we found evidence for re-circulating, rotor winds in the simultaneous time series of wind data from the Ameriflux tower site and a second meteorological site situated 8 km upslope and to the West. Only 14% of the half-hour time periods that we examined for a 4 month period in the winter of 2000-2001 indicated the possible existence of rotor winds. On average, energy budget closure was ???20% less during periods with

  15. Progress on a Rayleigh Scattering Mass Flux Measurement Technique

    NASA Technical Reports Server (NTRS)

    Mielke-Fagan, Amy F.; Clem, Michelle M.; Elam, Kristie A.; Hirt, Stefanie M.

    2010-01-01

    A Rayleigh scattering diagnostic has been developed to provide mass flux measurements in wind tunnel flows. Spectroscopic molecular Rayleigh scattering is an established flow diagnostic tool that has the ability to provide simultaneous density and velocity measurements in gaseous flows. Rayleigh scattered light from a focused 10 Watt continuous-wave laser beam is collected and fiber-optically transmitted to a solid Fabry-Perot etalon for spectral analysis. The circular interference pattern that contains the spectral information that is needed to determine the flow properties is imaged onto a CCD detector. Baseline measurements of density and velocity in the test section of the 15 cm x 15 cm Supersonic Wind Tunnel at NASA Glenn Research Center are presented as well as velocity measurements within a supersonic combustion ramjet engine isolator model installed in the tunnel test section.

  16. Development of a laser remote sensing instrument to measure sub-aerial volcanic CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Queisser, Manuel; Burton, Mike

    2016-04-01

    A thorough quantification of volcanic CO2 fluxes would lead to an enhanced understanding of the role of volcanoes in the geological carbon cycle. This would enable a more subtle understanding of human impact on that cycle. Furthermore, variations in volcanic CO2 emissions are a key to understanding volcanic processes such as eruption phenomenology. However, measuring fluxes of volcanic CO2 is challenging as volcanic CO2 concentrations are modest compared with the ambient CO2 concentration (~400 ppm) . Volcanic CO2 quickly dilutes with the background air. For Mt. Etna (Italy), for instance, 1000 m downwind from the crater, dispersion modelling yields a signal of ~4 ppm only. It is for this reason that many magmatic CO2 concentration measurements focus on in situ techniques, such as direct sampling Giggenbach bottles, chemical sensors, IR absorption spectrometers or mass spectrometers. However, emission rates are highly variable in time and space. Point measurements fail to account for this variability. Inferring 1-D or 2-D gas concentration profiles, necessary to estimate gas fluxes, from point measurements may thus lead to erroneous flux estimations. Moreover, in situ probing is time consuming and, since many volcanoes emit toxic gases and are dangerous as mountains, may raise safety concerns. In addition, degassing is often diffuse and spatially extended, which makes a measurement approach with spatial coverage desirable. There are techniques that allow to indirectly retrieve CO2 fluxes from correlated SO2 concentrations and fluxes. However, they still rely on point measurements of CO2 and are prone to errors of SO2 fluxes due to light dilution and depend on blue sky conditions. Here, we present a new remote sensing instrument, developed with the ERC project CO2Volc, which measures 1-D column amounts of CO2 in the atmosphere with sufficient sensitivity to reveal the contribution of magmatic CO2. Based on differential absorption LIDAR (DIAL) the instrument measures

  17. Are far-IR fluxes good measures of cloud mass?

    NASA Astrophysics Data System (ADS)

    Wagle, Gururaj; Ferland, G. J.; Troland, T. H.; Abel, N.

    2014-01-01

    It is commonly assumed that the Herschel far-IR fluxes are a measure of column density, hence, mass of interstellar clouds. The Polaris Flare, a high galactic latitude cirrus cloud, with several starless molecular cores, has been previously observed with the Herschel Space Telescope. We used Cloudy version 13.02 to model a molecular cloud MCLD 123.5+24.9, one of the denser regions of the Polaris Flare. These models include a detailed calculation of far-IR grain opacities, subject to various assumptions about grain composition, and predict far-IR fluxes. The models suggest that the observed fluxes reflect the incident stellar UV radiation field rather than the column density, if N(H) > a few times 1021 cm2 (AV > 1). For higher column densities, the models show that dust temperatures decline rapidly into the cloud. Therefore, the cloud interiors contribute very little additional far-IR flux, and column densities based upon far-IR fluxes can be significantly underestimated. The Polaris Flare, 150 pc distant, is well within the Galactic disc. There are no nearby hot stars. Therefore, the stellar UV radiation field incident on the cloud should be close to the mean interstellar radiation field (ISRF). In addition, the calculated grain opacities required to reproduce the far-IR fluxes in the Cloudy models are a few factors larger than that calculated for standard ISM graphite and silicate grains. This result suggests that the grains in dense regions are coated with water and ammonia ices, increasing their sizes and opacities. The Cloudy models also predict mm-wavelength CO line strengths for comparison with published observations at the IRAM 30-m telescope. In order to reproduce the observed CO line strengths for cores in MCLD 123.5+24.9, the models require that CO molecules be partially frozen out onto the grains. This result places age constraints upon the cores. We have also modeled CO emission from inter-core regions in MCLD 123.5+24.9. For these regions, the models

  18. Initiation of methane turbulent flux measurements over a grazed grassland in Belgium

    NASA Astrophysics Data System (ADS)

    Dumortier, Pierre; Aubinet, Marc; Chopin, Henri; Debacq, Alain; Jérome, Elisabeth; Beckers, Yves; Heinesch, Bernard

    2013-04-01

    Methane fluxes emitted by a grazed meadow were measured continuously during the 2012 grazing season at the Dorinne Terrestrial Observatory (50° 18' 44" N; 4° 58' 07" E; 248 m asl.) in Belgium. Measurements were made with the eddy covariance technique, using a fast CH4 analyzer (Picarro G2311-f). Carbon dioxide fluxes (LI-7000) and various micro-meteorological and soil variables, biomass growth and stocking rate evolution were also measured at the site. The site is an intensively pastured meadow of 4.2 ha managed according to the regional usual practices where up to 30 cows are grazing simultaneously. N2O emissions are currently measured through dynamic closed chambers (Beekkerk van Ruth et al., Geophysical Research Abstracts. Vol. 15, EGU2013-3211, 2013) and the carbon budget of the site has already been investigated (Jerome et al. Geophysical Research Abstracts, Vol. 15, EGU2013-6989, 2013). As no CH4 measurements were available, CH4 fluxes were estimated on the basis of dry matter intake by the cows and a conversion factor obtained from a literature review. We want to improve this estimation by measuring CH4 fluxes, identifying their main environmental drivers and understanding diurnal and annual exchange patterns. Methane emissions were found strongly related with cattle stocking rate with a slope of 7.34±0.78 mol CH4 day-1 LSU-1. Up to now, no methane absorption has been observed, the meadow behaving as a methane emitter, even in the absence of cows. In the absence of cows, no significant relation can be established up to now between methane emissions and environmental parameters. No clear diurnal evolution is observed, neither during grazing periods nor during cow free periods. During cow presence periods, fluxes are highly variable, probably due to cow movements in and out the measurement footprint and cow digestion rhythm. Further developments are ongoing in order to improve cattle geo-localization through individual home-made GPS devices and infra

  19. Factors contributing to seasonal variations in wet deposition fluxes of trace elements at sites along Japan Sea coast

    NASA Astrophysics Data System (ADS)

    Sakata, Masahiro; Asakura, Kazuo

    In this study, we measured the wet deposition fluxes of ten trace elements (As, Cd, Cr, Cu, Mn, Ni, Pb, Sb, V and Zn) from December 2002 to March 2006 at three sites along the Japan Sea coast, which have been strongly affected by the long-range transport of air pollutants from the Asian continent. Also, factors, contributing to their seasonal variations were investigated. At the northern and central sites, the monthly wet deposition fluxes of all or most trace elements greatly increased during the cold season (typically, November-April), along with their monthly average (volume-weighted) concentrations in the precipitation. The cold/warm season ratios for the average concentrations of trace elements in precipitation were within the range of 2.7-5.1 at the northern site and 1.8-5.9 at the central site, which were similar to the average scavenging ratios (= concentration in precipitation/concentration in air) at each site. However, there were small differences (0.47-1.2 at the northern site and 0.73-1.7 at the central site) in the ratios of average concentrations in air between the two seasons. These suggest that the increase in the wet deposition fluxes of trace elements during the cold season is due to increases in their scavenging ratios. On the other hand, the result for the southern site was different from those at the other sites. The number of days when the daily maximum wind speed exceeded 10 m s -1 at the meteorological observatories near the study sites increased markedly during the cold season at the northern and central sites, showing that strong winds usually blow during the cold season at those sites, but not at the southern site. Higher wind speed transports larger amounts of constituents into the cloud system, which can result in their increased concentrations in precipitation. Thus, high scavenging ratios of trace elements during the cold season may be caused by the increase in their amounts of discharge into the cloud system owing to high wind speed

  20. SIERRA-Flux: Measuring Regional Surface Fluxes of Carbon Dioxide, Methane, and Water Vapor from an Unmanned Aircraft System

    NASA Technical Reports Server (NTRS)

    Fladeland; Yates, Emma Louise; Bui, Thaopaul Van; Dean-Day, Jonathan; Kolyer, Richard

    2011-01-01

    The Eddy-Covariance Method for quantifying surface-atmosphere fluxes is a foundational technique for measuring net ecosystem exchange and validating regional-to-global carbon cycle models. While towers or ships are the most frequent platform for measuring surface-atmosphere exchange, experiments using aircraft for flux measurements have yielded contributions to several large-scale studies including BOREAS, SMACEX, RECAB by providing local-to-regional coverage beyond towers. The low-altitude flight requirements make airborne flux measurements particularly dangerous and well suited for unmanned aircraft.

  1. AmeriFlux US-Bn3 Bonanza Creek, 1999 Burn site near Delta Junction

    SciTech Connect

    Randerson, James

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-Bn3 Bonanza Creek, 1999 Burn site near Delta Junction. Site Description - The Delta Junction 1999 Burn site is located near Delta Junction, just to the north of the Alaska Range in interior Alaska. All three Delta Junction sites are within a 15-km radius of one another. Composed of a combination of alluvial outwashes, floodplains, and low terraces dissected by glacial streams originating in the nearby Alaska Range. The Donnelly Flats fire burned ~7,600 ha of black spruce (Picea mariana) during June 1999. The boles of the black spruce remained standing 3 years after the fire. 70% of the surface was not covered by vascular plants.

  2. AmeriFlux US-Bn2 Bonanza Creek, 1987 Burn site near Delta Junction

    DOE Data Explorer

    Randerson, James [University of California, Irvine

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-Bn2 Bonanza Creek, 1987 Burn site near Delta Junction. Site Description - The Delta Junction 1987 Burn site is located near Delta Junction, just to the north of the Alaska Range in interior Alaska. All three Delta Junction sites are within a 15-km radius of one another. Composed of a combination of alluvial outwashes, floodplains, and low terraces dissected by glacial streams originating in the nearby Alaska Range. The Granite Creek fire burned ~20,000 ha of black spruce (Picea mariana) during 1987. Approximately half of the dead boles remained upright in 2004, while the other half had fallen over or had become entangled with other boles.

  3. 3D density imaging with muons flux measurements from underground galleries

    NASA Astrophysics Data System (ADS)

    Lesparre, Nolwenn; Cabrera, Justo; Marteau, Jacques

    2016-04-01

    Atmospheric muons flux measurements provide information on sub-surface density distribution, giving insights on the medium structure. We measured the muons flux from the underground galleries of the Tournemire experimental platform to image the medium between the galleries and the surface. The experiment aimed at evaluating the capacity of the method to detect the presence of discontinuities produced either by secondary strike-slip faults that present small vertical displacements or by a karstic network may be present at the level of an upper aquifer. Measurements were performed from three different sites so the trajectories of detected muons paths intersect in the medium. Such a configuration provided complementary information on the density distribution, offering the possibility to seek density variations at different depths. A specific calibration method was applied in order to interpolate the data acquired at different times with the same muons sensor. Muons flux measurements variations were then processed through a non-linear inversion, producing a 3D image of the density together with an evaluation of the different distinguished targets reliability. The density distribution showed the presence of a very low density region at the level of the upper aquifer, suggesting the presence of a karstic network hosting locally cavities. The trace of secondary strike-slip faults did not appear clearly on the image as the density contrast they produce might be too low compared to the signal to noise ratio present in the muons flux data. We propose different strategies to improve the density image accuracy.

  4. Design and measurement of improved capacitively-shunted flux qubits

    NASA Astrophysics Data System (ADS)

    Sears, Adam; Birenbaum, Jeffrey; Hover, David; Gudmundsen, Theodore; Kerman, Andrew; Welander, Paul; Yoder, Jonilyn L.; Gustavsson, Simon; Jin, Xiaoyue; Kamal, Archana; Clarke, John; Oliver, William

    2014-03-01

    The addition of a capacitive or inductive shunt across one of the junctions can alter the coherence properties of a classic flux or RF-SQUID qubit. We have studied the performance of capacitively shunted flux qubits fabricated with MBE aluminum, starting from a 2D coplanar waveguide geometry used in similar high-performance transmon qubits, and measured dispersively. We will detail the importance of design parameters that preserve the flux qubit's anharmonicity and discuss conclusions about materials quality based on calculations of the participation of junction, dielectric, and superconductor components. This research was funded in part by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA); and by the Assistant Secretary of Defense for Research & Engineering under Air Force Contract number FA8721-05-C-0002. All statements of fact, opinion or conclusions contained herein are those of the authors and should not be construed as representing the official views or policies of IARPA, the ODNI, or the U.S. Government Present address: SLAC National Accelerator Laboratory, Menlo Park, CA.

  5. Long-term CH3Br and CH3Cl flux measurements in temperate salt marshes

    NASA Astrophysics Data System (ADS)

    Blei, E.; Heal, M. R.; Heal, K. V.

    2010-11-01

    Fluxes of CH3Br and CH3Cl and their relationship with potential drivers such as sunlight, temperature and soil moisture, were monitored at fortnightly to monthly intervals for more than two years at two contrasting temperate salt marsh sites in Scotland. Manipulation experiments were conducted to further investigate possible links between drivers and fluxes. Fluxes followed both seasonal and diurnal trends with highest fluxes during summer days and lowest (negative) fluxes during winter nights. Mean (± 1 sd) annually and diurnally-weighted net emissions from the two sites were found to be 300 ± 44 ng m-2 h-1 for CH3Br and 662 ± 266 ng m-2 h-1 for CH3Cl. The fluxes from this work are similar to findings from this and other research groups for salt marshes in cooler, higher latitude climates, but lower than values from salt marshes in the Mediterranean climate of southern California. Statistical analysis generally did not demonstrate a strong link between temperature or sunlight levels and methyl halide fluxes, although it is likely that temperatures have a weak direct influence on emissions, and both certainly have indirect influence via the annual and daily cycles of the vegetation. CH3Cl flux magnitudes from different measurement locations depended on the plant species enclosed whereas such dependency was not discernible for CH3Br fluxes. In 14 out of 18 collars with vegetation CH3Br and CH3Cl net fluxes were significantly positively correlated. The CH3Cl/CH3Br net-emission mass ratio was 2.2, a magnitude lower than mass ratios of global methyl halide budgets (~22) or emissions from tropical rainforests (~60). This is likely due to preference for CH3Br production by the relatively high bromine content in the salt marsh plant material. Extrapolation based solely on data from this study yields salt marsh contributions of 0.5-3.2% and 0.05-0.33%, respectively, of currently-estimated total global production of CH3Br and CH3Cl, but actual global contributions likely

  6. Energy partitioning between latent and sensible heat flux during the warm season at FLUXNET sites

    NASA Astrophysics Data System (ADS)

    Wilson, Kell B.; Baldocchi, Dennis D.; Aubinet, Marc; Berbigier, Paul; Bernhofer, Christian; Dolman, Han; Falge, Eva; Field, Chris; Goldstein, Allen; Granier, Andre; Grelle, Achim; Halldor, Thorgeirsson; Hollinger, Dave; Katul, Gabriel; Law, B. E.; Lindroth, Anders; Meyers, Tilden; Moncrieff, John; Monson, Russ; Oechel, Walter; Tenhunen, John; Valentini, Riccardo; Verma, Shashi; Vesala, Timo; Wofsy, Steve

    2002-12-01

    The warm season (mid-June through late August) partitioning between sensible (H) and latent (LE) heat flux, or the Bowen ratio (β = H/LE), was investigated at 27 sites over 66 site years within the international network of eddy covariance sites (FLUXNET). Variability in β across ecosystems and climates was analyzed by quantifying general climatic and surface characteristics that control flux partitioning. The climatic control on β was quantified using the climatological resistance (Ri), which is proportional to the ratio of vapor pressure deficit (difference between saturation vapor pressure and atmospheric vapor pressure) to net radiation (large values of Ri decrease β). The control of flux partitioning by the vegetation and underlying surface was quantified by computing the surface resistance to water vapor transport (Rc, with large values tending to increase β). There was a considerable range in flux partitioning characteristics (Rc, Ri and β) among sites, but it was possible to define some general differences between vegetation types and climates. Deciduous forest sites and the agricultural site had the lowest values of Rc and β (0.25-0.50). Coniferous forests typically had a larger Rc and higher β (typically between 0.50 and 1.00 but also much larger). However, there was notable variability in Rc and Ri between coniferous site years, most notably differences between oceanic and continental climates and sites with a distinct dry summer season (Mediterranean climate). Sites with Mediterranean climates generally had the highest net radiation, Rc, Ri, and β. There was considerable variability in β between grassland site years, primarily the result of interannual differences in soil water content and Rc.

  7. System having unmodulated flux locked loop for measuring magnetic fields

    DOEpatents

    Ganther, Jr., Kenneth R.; Snapp, Lowell D.

    2006-08-15

    A system (10) for measuring magnetic fields, wherein the system (10) comprises an unmodulated or direct-feedback flux locked loop (12) connected by first and second unbalanced RF coaxial transmission lines (16a, 16b) to a superconducting quantum interference device (14). The FLL (12) operates for the most part in a room-temperature or non-cryogenic environment, while the SQUID (14) operates in a cryogenic environment, with the first and second lines (16a, 16b) extending between these two operating environments.

  8. A simple calculation algorithm to separate high-resolution CH4 flux measurements into ebullition and diffusion-derived components

    NASA Astrophysics Data System (ADS)

    Hoffmann, Mathias; Schulz-Hanke, Maximilian; Garcia Alba, Joana; Jurisch, Nicole; Hagemann, Ulrike; Sachs, Torsten; Sommer, Michael; Augustin, Jürgen

    2016-04-01

    Processes driving methane (CH4) emissions in wetland ecosystems are highly complex. Especially, the separation of CH4 emissions into ebullition and diffusion derived flux components, a perquisite for the mechanistic process understanding and identification of potential environmental driver is rather challenging. We present a simple calculation algorithm, based on an adaptive R-script, which separates open-water, closed chamber CH4 flux measurements into diffusion- and ebullition-derived components. Hence, flux component specific dynamics are revealed and potential environmental driver identified. Flux separation is based on a statistical approach, using ebullition related sudden concentration changes obtained during high resolution CH4 concentration measurements. By applying the lower and upper quartile ± the interquartile range (IQR) as a variable threshold, diffusion dominated periods of the flux measurement are filtered. Subsequently, flux calculation and separation is performed. The algorithm was verified in a laboratory experiment and tested under field conditions, using flux measurement data (July to September 2013) from a flooded, former fen grassland site. Erratic ebullition events contributed 46% to total CH4 emissions, which is comparable to values reported by literature. Additionally, a shift in the diurnal trend of diffusive fluxes throughout the measurement period, driven by the water temperature gradient, was revealed.

  9. Impact of hydrological variations on modeling of peatland CO2 fluxes: Results from the North American Carbon Program site synthesis

    NASA Astrophysics Data System (ADS)

    Sulman, Benjamin N.; Desai, Ankur R.; Schroeder, Nicole M.; Ricciuto, Dan; Barr, Alan; Richardson, Andrew D.; Flanagan, Lawrence B.; Lafleur, Peter M.; Tian, Hanqin; Chen, Guangsheng; Grant, Robert F.; Poulter, Benjamin; Verbeeck, Hans; Ciais, Philippe; Ringeval, Bruno; Baker, Ian T.; Schaefer, Kevin; Luo, Yiqi; Weng, Ensheng

    2012-03-01

    Northern peatlands are likely to be important in future carbon cycle-climate feedbacks due to their large carbon pools and vulnerability to hydrological change. Use of non-peatland-specific models could lead to bias in modeling studies of peatland-rich regions. Here, seven ecosystem models were used to simulate CO2fluxes at three wetland sites in Canada and the northern United States, including two nutrient-rich fens and one nutrient-poor,sphagnum-dominated bog, over periods between 1999 and 2007. Models consistently overestimated mean annual gross ecosystem production (GEP) and ecosystem respiration (ER) at all three sites. Monthly flux residuals (simulated - observed) were correlated with measured water table for GEP and ER at the two fen sites, but were not consistently correlated with water table at the bog site. Models that inhibited soil respiration under saturated conditions had less mean bias than models that did not. Modeled diurnal cycles agreed well with eddy covariance measurements at fen sites, but overestimated fluxes at the bog site. Eddy covariance GEP and ER at fens were higher during dry periods than during wet periods, while models predicted either the opposite relationship or no significant difference. At the bog site, eddy covariance GEP did not depend on water table, while simulated GEP was higher during wet periods. Carbon cycle modeling in peatland-rich regions could be improved by incorporating wetland-specific hydrology and by inhibiting GEP and ER under saturated conditions. Bogs and fens likely require distinct plant and soil parameterizations in ecosystem models due to differences in nutrients, peat properties, and plant communities.

  10. Wind tunnel measurements of pollutant turbulent fluxes in urban intersections

    NASA Astrophysics Data System (ADS)

    Carpentieri, Matteo; Hayden, Paul; Robins, Alan G.

    2012-01-01

    Wind tunnel experiments have been carried out at the EnFlo laboratory to measure mean and turbulent tracer fluxes in geometries of real street canyon intersections. The work was part of the major DAPPLE project, focussing on the area surrounding the intersection between Marylebone Road and Gloucester Place in Central London, UK. Understanding flow and dispersion in urban streets is a very important issue for air quality management and planning, and turbulent mass exchange processes are important phenomena that are very often neglected in urban modelling studies. The adopted methodology involved the combined use of laser Doppler anemometry and tracer concentration measurements. This methodology was applied to quantify the mean and turbulent flow and dispersion fields within several street canyon intersections. Vertical profiles of turbulent tracer flux were also measured. The technique, despite a number of limitations, proved reliable and allowed tracer balance calculations to be undertaken in the selected street canyon intersections. The experience gained in this work will enable much more precise studies in the future as issues affecting the accuracy of the experimental technique have been identified and resolved.

  11. Performance measurements at the fast flux test facility

    SciTech Connect

    Baumhardt, R.J.; Newland, D.J.; Praetorius, P.R.

    1987-01-01

    In 1984, Fast Flux Test Facility (FFTF) management recognized the need to develop a measurement system that would quantify the operational performance of the FFTF and the human resources needed to operate it. Driven by declining budgets and the need to safely manage a manpower rampdown at FFTF, an early warning system was developed. Although the initiating event for the early warning system was the need to safely manage a manpower rampdown, many related uses have evolved. The initial desired objective for the FFTF performance measurements was to ensure safety and control of key performance trends. However, the early warning system has provided a more quantitative, supportable basis upon which to make decisions. From this initial narrow focus, efforts in the FFTF plant and supporting organizations are leading to measurement of and, subsequently, improvements in productivity. Pilot projects utilizing statistical process control have started with longer range productivity improvement.

  12. Measurement of autophagy flux in the nervous system in vivo

    PubMed Central

    Castillo, K; Valenzuela, V; Matus, S; Nassif, M; Oñate, M; Fuentealba, Y; Encina, G; Irrazabal, T; Parsons, G; Court, F A; Schneider, B L; Armentano, D; Hetz, C

    2013-01-01

    Accurate methods to measure autophagic activity in vivo in neurons are not available, and most of the studies are based on correlative and static measurements of autophagy markers, leading to conflicting interpretations. Autophagy is an essential homeostatic process involved in the degradation of diverse cellular components including organelles and protein aggregates. Autophagy impairment is emerging as a relevant factor driving neurodegeneration in many diseases. Moreover, strategies to modulate autophagy have been shown to provide protection against neurodegeneration. Here we describe a novel and simple strategy to express an autophagy flux reporter in the nervous system of adult animals by the intraventricular delivery of adeno-associated viruses (AAV) into newborn mice. Using this approach we efficiently expressed a monomeric tandem mCherry-GFP-LC3 construct in neurons of the peripheral and central nervous system, allowing the measurement of autophagy activity in pharmacological and disease settings. PMID:24232093

  13. Quantifying Representation and Using Representation Weights to Interpolate Flux Tower Measurements across the United States

    NASA Astrophysics Data System (ADS)

    Hargrove, W. W.; Hoffman, F. M.

    2003-12-01

    We are using a new multivariate statistical technique to quantitatively divide the lower 48 United States into a series of flux-relevant ecoregions. On the basis of these flux-relevant ecoregions, we will quantify the representativeness of the existing network of AmeriFlux towers, showing how well each ecoregion is represented by the current stations in the AmeriFlux network. Quantifying AmeriFlux representation will indicate the best locations where additional AmeriFlux towers should be placed. Using a "paint-by-number" approach, we are attempting to use the flux ecoregions as the statistical basis for extrapolating measurements made at the 52 actively-reporting AmeriFlux towers into a continuous 1-km grid across the United States seasonally. We will use the similarity of the suite of flux-relevant ecosystem characteristics to modify existing flux measurements and estimate fluxes within unmeasured flux ecoregions. Weights calculated for each environmental gradient will allow us to mix new "paint-by-number" colors, extending the process beyond the palette of existing flux measurements. The map of 2000 to 5000 flux ecoregions will produce a highly-resolved national map of estimated fluxes, and will be equivalent to creating thousands of new "virtual" flux towers across the nation. Once flux ecoregions and representation weights have been determined, it may be possible to use them to obtain an interpolated grid of the estimated flux at any point in time across the United States.

  14. Signal-to-noise issues in measuring nitrous oxide fluxes by the eddy covariance method

    NASA Astrophysics Data System (ADS)

    Cowan, Nicholas; Levy, Peter; Langford, Ben; Skiba, Ute

    2016-04-01

    Recently-developed fast-response gas analysers capable of measuring atmospheric N2O with high precision (< 50 ppt) at a rate of 10 Hz are becoming more widely available. These instruments are capable of measuring N2O fluxes using the eddy covariance method, with significantly less effort and uncertainty than previous instruments have allowed. However, there are still many issues to overcome in order to obtain accurate and reliable flux data. The signal-to-noise ratio of N2O measured using these instruments is still two to three orders of magnitude smaller than that of CO2. The low signal-to-noise ratio can lead to systematic uncertainties, in the eddy covariance method, the most significant being in the calculation of the time lag between gas analyser and anemometer by maximisation of covariance (Langford et al., 2015). When signal-to-noise ratio is relatively low, as it is with many N2O measurements, the maximisation of covariance method can systematically overestimate fluxes. However, if constant time lags are assumed, then fluxes will be underestimated. This presents a major issue for N2O eddy covariance measurements. In this presentation we will focus on the signal to noise ratio for an Aerodyne quantum cascade laser (QCL). Eddy covariance flux measurements from multiple agricultural sites across the UK were investigated for potential uncertainties. Our presentation highlights some of these uncertainties when analysing eddy covariance data and offers suggestions as to how these issues may be minimised. Langford, B., Acton, W., Ammann, C., Valach, A. and Nemitz, E.: Eddy-covariance data with low signal-to-noise ratio: time-lag determination, uncertainties and limit of detection, Atmos Meas Tech, 8(10), 4197-4213, doi:10.5194/amt-8-4197-2015, 2015.

  15. Automated Soil Flux Chamber Measurements with Five Species Cavity Ring-Down Spectroscopy and New Realtime Soil Flux Processor

    NASA Astrophysics Data System (ADS)

    Alstad, Karrin; Saad, Nabil; Tan, Sze

    2015-04-01

    Continuous soil flux chamber measurements remains a key tool for determining production and sequestration of direct and indirect greenhouse gases. Cavity Ring-Down Spectroscopy has radically simplified soil flux studies by providing simultaneous measurements of five gases: CO2, CH4, N2O, NH3, and H2O in one analyzer (Picarro G2508) and by lending itself to field deployment. Successful use of the Picarro G2508 for continuous soil flux measurements in a variety of ecosystem types has already been demonstrated. Most recently, we have developed a real-time processing software to simplify chamber measurements and calculations of soil flux with the G2508 CRDS analyzer. The new Realtime Soil Flux Processor is designed to work with all chamber types and sizes, and provides a multi-option for real-time flux curve mathematical fitting and generation of flux values of N2O, CO2 & CH4 in addition to NH3 and H2O. The software features include: Sequence table Flexible data tagging feature Ceiling concentration shut-off parameter Set run-time interval Temperature/pressure input for field monitoring and volumetric conversion Manual start/stop override The Realtime Soil Flux Processor GUI interface and functionalities are presented, and results from a variety of sampling designs are demonstrated to emphasize program flexibility and field capability.

  16. Standardization of flux chamber and wind tunnel flux measurements for quantifying emissions from area sources at animal feeding operations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A variety of wind tunnels and flux chambers have been used to measure fluxes of volatile organic compounds (VOC) and ammonia (NH3) at animal feeding operations (AFO). However, there has been little regard to the extreme variation and inaccuracy caused by inappropriate air velocity or sweep air flow...

  17. Airborne boundary layer flux measurements of trace species over Canadian boreal forest and northern wetland regions

    NASA Technical Reports Server (NTRS)

    Ritter, John A.; Barrick, John D. W.; Watson, Catherine E.; Sachse, Glen W.; Gregory, Gerald L.; Anderson, Bruce E.; Woerner, Mary A.; Collins, James E., Jr.

    1994-01-01

    Airborne heat, moisture, O3, CO, and CH4 flux measurements were obtained over the Hudson Bay lowlands (HBL) and northern boreal forest regions of Canada during July - August 1990. The airborne flux measurements were an integral part of the NASA/Arctic Boundary Layer Expedition (ABLE) 3B field experiment executed in collaboration with the Canadian Northern Wetlands Study (NOWES). Airborne CH4 flux measurements were taken over a large portion of the HBL. The surface level flux of CH4 was obtained from downward extrapolations of multiple-level CH4 flux measurements. Methane source strengths ranged from -1 to 31 mg m(exp -2)/d, with the higher values occurring in relatively small, isolated areas. Similar measurements of the CH4 source strength in the boreal forest region of Schefferville, Quebec, ranged from 6 to 27 mg m(exp -2)/d and exhibited a diurnal dependence. The CH4 source strengths found during the ABLE 3B expedition were much lower than the seasonally averaged source strength of 51 mg m(exp -2)/d found for the Yukon-Kuskokwim delta region of Alaska during the previous ABLE 3A study. Large positive CO fluxes (0.31 to 0.53 parts per billion by volume (ppbv) m/s) were observed over the inland, forested regions of the HBL study area, although the mechanism for the generation of these fluxes was not identified. Repetitive measurements along the same ground track at various times of day near the Schefferville site also suggested a diurnal dependence for CO emissions. Measurements of surface resistance to the uptake of O3 (1.91 to 0.80 s/cm) for the HBL areas investigated were comparable to those observed near the Schefferville site (3.40 to 1.10 s/cm). Surface resistance values for the ABLE 3B study area were somewhat less than those observed over the Yukon-Kuskokwim delta during the previous ABLE 3A study. The budgets for heat, moisture, O3, CO, and CH4 were evaluated. The residuals from these budget studies indicated, for the cases selected, a moderate net

  18. Fluxes of polychlorinated biphenyls volatilizing from the Hudson River, New York measured using micrometeorological approaches.

    PubMed

    Sandy, Andy L; Guo, Jia; Miskewitz, Robert J; McGillis, Wade R; Rodenburg, Lisa A

    2012-01-17

    This study represents the first time that a micrometeorological technique, using turbulent transport measurements, has been used to determine the direction and magnitude of air-water exchange of polychlorinated biphenyls (PCBs). The study was conducted during July 2008 on the Hudson River estuary near the Tappan Zee Bridge, which is the site of some of the most serious PCB contamination in the world. Gas-phase ΣPCB concentrations measured at two heights above the water column averaged 1.1 ng m(-3), and concentrations were usually lower in the upper air sample, indicating net transport of PCBs from the water column to the air. Volatilization PCB fluxes were calculated using the modified Thornthwaite-Holzman equation. Values of friction velocity and atmospheric stability were calculated using the Aerodynamic Gradient and Eddy Correlation techniques. The PCB fluxes were corrected for changes in atmospheric stability using the atmospheric stability factor of water vapor (ϕ(w)) calculated from empirical formulations which ranged from 1.0 to 3.2 (neutral to stable atmospheric boundary layer conditions). Vertical ΣPCB fluxes ranged from +0.5 μg m(-2) d (-1) to +13 μg m(-2) d (-1). Mono- through tri-homologues accounted for about half of ΣPCB fluxes, with tetra- through hexa-homologue accounting for the other half. This work demonstrates the utility of a micrometeorological approach to measuring the air-water exchange of organic contaminants. PMID:22191600

  19. Heat flux measurements for use in physiological and clothing research

    NASA Astrophysics Data System (ADS)

    Niedermann, R.; Psikuta, A.; Rossi, R. M.

    2014-08-01

    Scientists use passive heat flow meters to measure body heat exchanges with the environment. In recent years, several such sensors have been developed and concerns about their proper calibration have been addressed. However, calibration methods have differed in the geometry of the heated device as well as in the heat transfer mechanism. Therefore, a comparison of calibration methods is needed in order to understand the obtained differences in calibration lines. We chose three commercially available heat flux sensors and placed them on four different heated devices: a hot plate, double hot plate, nude cylinder and a cylinder covered with a spacer material. We found differences between the calibration line of the manufacturer and our own measurements, especially when forced convection was involved as the main heat transfer mechanism. The results showed clearly that the calibration method should be chosen according to the intended purpose of use. In addition, we recommend use a thin, light heat flux sensor with good thermal conduction in human subject studies.

  20. Heat flux measurements for use in physiological and clothing research.

    PubMed

    Niedermann, R; Psikuta, A; Rossi, R M

    2014-08-01

    Scientists use passive heat flow meters to measure body heat exchanges with the environment. In recent years, several such sensors have been developed and concerns about their proper calibration have been addressed. However, calibration methods have differed in the geometry of the heated device as well as in the heat transfer mechanism. Therefore, a comparison of calibration methods is needed in order to understand the obtained differences in calibration lines. We chose three commercially available heat flux sensors and placed them on four different heated devices: a hot plate, double hot plate, nude cylinder and a cylinder covered with a spacer material. We found differences between the calibration line of the manufacturer and our own measurements, especially when forced convection was involved as the main heat transfer mechanism. The results showed clearly that the calibration method should be chosen according to the intended purpose of use. In addition, we recommend use a thin, light heat flux sensor with good thermal conduction in human subject studies. PMID:23824222

  1. AmeriFlux US-Ha2 Harvard Forest Hemlock Site

    SciTech Connect

    Munger, William

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-Ha2 Harvard Forest Hemlock Site. Site Description - The forest surrounding the Hemlock site has remained pristine with two exceptions. In the early to mid-1700s, European settlers cleared the majority of the forest for agricultural purposes. Selective harvesting of hemlock and chestnut trees occurred up until the early 1900s, when the chestnut blight killed all of the chestnut trees. In the current forest, about 83% of the total basal area of trees is hemlock. The remainder is equally divided between eastern white pine (Pinus strobus L.) and deciduous species, including red maple (Acer rubrum), red oak (Quercus rubra) and black birch (Betula lenta). A very thick organic layer (10-20 cm or more) covers the soil surface, and highly decayed coarse woody debris is abundant.

  2. Potentials and challenges associated with automated closed dynamic chamber measurements of soil CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Görres, Carolyn-Monika; Kammann, Claudia; Ceulemans, Reinhart

    2015-04-01

    the row width alternating between 1.50 m and 0.75 m, creating spatial differences in e.g. dry bulk density and soil organic carbon content. The soil CO2 flux data sets were split into four subsets each characterized by different environmental conditions, thus presenting different challenges for the measurement equipment, namely 1) daytime, calm conditions, 2) daytime, windy conditions, 3) nighttime, calm conditions, and 4) nighttime, windy conditions. In parallel to the chamber measurements, soil CO2 concentrations were manually measured in the topsoil. Soil CO2 fluxes calculated from this dataset were used as a reference range of soil CO2 fluxes at the field site. Funding support: ERC Advanced Grant agreement (# 233366) POPFULL under the EC 7th Framework Program (FP7/2007-2013), Flemish Hercules Foundation as Infrastructure contract # ZW09-06, and the Methusalem Program of the Flemish Government.

  3. Cosmic rays muon flux measurements at Belgrade shallow underground laboratory

    SciTech Connect

    Veselinović, N. Dragić, A. Maletić, D. Joković, D. Savić, M. Banjanac, R. Udovičić, V. Aničin, I.

    2015-02-24

    The Belgrade underground laboratory is a shallow underground one, at 25 meters of water equivalent. It is dedicated to low-background spectroscopy and cosmic rays measurement. Its uniqueness is that it is composed of two parts, one above ground, the other bellow with identical sets of detectors and analyzing electronics thus creating opportunity to monitor simultaneously muon flux and ambient radiation. We investigate the possibility of utilizing measurements at the shallow depth for the study of muons, processes to which these muons are sensitive and processes induced by cosmic rays muons. For this purpose a series of simulations of muon generation and propagation is done, based on the CORSIKA air shower simulation package and GEANT4. Results show good agreement with other laboratories and cosmic rays stations.

  4. Absolute measurement of the extreme UV solar flux

    NASA Technical Reports Server (NTRS)

    Carlson, R. W.; Ogawa, H. S.; Judge, D. L.; Phillips, E.

    1984-01-01

    A windowless rare-gas ionization chamber has been developed to measure the absolute value of the solar extreme UV flux in the 50-575-A region. Successful results were obtained on a solar-pointing sounding rocket. The ionization chamber, operated in total absorption, is an inherently stable absolute detector of ionizing UV radiation and was designed to be independent of effects from secondary ionization and gas effusion. The net error of the measurement is + or - 7.3 percent, which is primarily due to residual outgassing in the instrument, other errors such as multiple ionization, photoelectron collection, and extrapolation to the zero atmospheric optical depth being small in comparison. For the day of the flight, Aug. 10, 1982, the solar irradiance (50-575 A), normalized to unit solar distance, was found to be 5.71 + or - 0.42 x 10 to the 10th photons per sq cm sec.

  5. Measurement of geothermal flux through poorly consolidated sediments

    USGS Publications Warehouse

    Sass, J.H.; Munroe, R.J.; Lachenbruch, A.H.

    1968-01-01

    In many regions, crystalline rocks are covered by hundreds of meters of unconsolidated and poorly consolidated sediments. Estimates of heat flux within these sediments using standard continental techniques (temperature and conductivity measurements at intervals of 10 to 30 meters) are unreliable, mainly because of the difficulty in obtaining and preserving representative lengths of core. However, it is sometimes feasible to use what amounts to an oceanographic technique by making closely spaced temperature and conductivity measurements within short cored intervals. This is demonstrated in a borehole at Menlo Park, California (37??27???N, 122??10???W, elevation 16 meters), where heat flows determined over 12 separate 1-meter intervls al lie within 10% of their mean value; 2.2 ??cal/cm2 sec. ?? 1968.

  6. Sound power flux measurements in strongly exited ducts with flow.

    PubMed

    Holland, Keith R; Davies, Peter O A L; van der Walt, Danie C

    2002-12-01

    This contribution describes new robust procedures for the measurement of sound power flux at appropriate axial positions along a duct with flow, using pairs of flush wall mounted microphones, or pressure transducers. The technology includes the application of selective averaging, order tracking, and optimized sampling rate methods to identify the small fraction of the total fluctuating wave energy that is being propagated along the flow path in a reverberent, or highly reactive duct system. Such measurements can also be used to quantify the local acoustic characteristics that govern the generation, transfer, and propagation of wave energy in the system. Illustrative examples include the determination of the acoustic characteristics of individual silencing elements installed in IC engine intakes and exhausts both on the flow bench and during controlled acceleration or run down on a test bed, where the wave component spectral levels approached 170 dB. PMID:12509008

  7. Post-disturbance dynamics in forest-atmosphere fluxes: Observations from a windthrow site in the European Alps

    NASA Astrophysics Data System (ADS)

    Matthews, Bradley; Mayer, Mathias; Katzensteiner, Klaus; Schume, Helmut

    2015-04-01

    Natural disturbances can cause abrupt and substantial changes in ecosystem properties regulating forest-atmosphere exchange. Although forest sites disturbed by e.g. wind, fire, and insects have become important targets of micrometeorological research, investigations of intact and disturbed forests in mountainous areas remain comparatively scarce. This discrepancy is likely explained by the additional methodological challenges posed by mountainous ecosystems, especially with respect to the eddy covariance technique. Nonetheless, the lack of such experiments constitutes a significant void in global and regional flux networks, particularly in the Central European context, where the Alps are forecasted as potential hotspots of intensifying windthrow and bark beetle disturbance regimes. We therefore began a micrometeorological investigation at a forest site in the Northern Calcareous Alps of Austria disturbed by windthrow and subsequent bark beetle infestation in 2009. The objectives of the study were to determine 1) whether the eddy covariance technique provides robust measurements of turbulent surface-atmosphere exchange at the site and 2) how net exchange of carbon dioxide (CO2), water vapor, sensible heat and shortwave radiation develop over 3 subsequent growing seasons (2011 to 2013) following disturbance. According to a flux quality assessment looking at turbulence, stationarity, flux footprint and energy balance closure, eddy covariance provides defensible estimates of net turbulent exchange at the site, despite the non ideal conditions for its application. While the site remained a CO2 source in 2013, decreasing net CO2 release over the three subsequent growing seasons indicated that the ecosystem was in a state of recovery. Moreover, it appeared that this recovery also significantly influenced the net exchange of shortwave radiation and the partitioning between sensible and latent heat fluxes. Taking into account the varying climate over the three campaign

  8. Measurement of momentum flux using two meteor radars in Indonesia

    NASA Astrophysics Data System (ADS)

    Matsumoto, Naoki; Shinbori, Atsuki; Riggin, Dennis M.; Tsuda, Toshitaka

    2016-03-01

    Two nearly identical meteor radars were operated at Koto Tabang (0.20° S, 100.32° E), West Sumatra, and Biak (1.17° S, 136.10° E), West Papua, in Indonesia, separated by approximately 4000 km in longitude on the Equator. The zonal and meridional momentum flux, u'w' and v'w', where u, v, and w are the eastward, northward, and vertical wind velocity components, respectively, were estimated at 86 to 94 km altitudes using the meteor radar data by applying a method proposed by Hocking (2005). The observed u'w' at the two sites agreed reasonably well at 86, 90, and 94 km during the observation periods when the data acquisition rate was sufficiently large enough. Variations in v'w' were consistent between 86, 90, and 94 km altitudes at both sites. The climatological variation in the monthly averaged u'w' and v'w' was investigated using the long-term radar data at Koto Tabang from November 2002 to November 2013. The seasonal variations in u'w' and v'w' showed a repeatable semiannual and annual cycles, respectively. u'w' showed eastward values in February-April and July-September and v'w' was northward in June to August at 90-94 km, both of which were generally anti-phase with the mean zonal and meridional winds, having the same periodicity. Our results suggest the usefulness of the Hocking method.

  9. Comparison of buried soil sensors, surface chambers and above ground measurements of carbon dioxide fluxes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil carbon dioxide (CO2) flux is an important component of the terrestrial carbon cycle. Accurate measurements of soil CO2 flux aids determinations of carbon budgets. In this study, we investigated soil CO2 fluxes with time and depth and above ground CO2 fluxes in a bare field. CO2 concentrations w...

  10. Stable water isotope and surface heat flux simulation using ISOLSM: Evaluation against in-situ measurements

    NASA Astrophysics Data System (ADS)

    Cai, Mick Y.; Wang, Lixin; Parkes, Stephen D.; Strauss, Josiah; McCabe, Matthew F.; Evans, Jason P.; Griffiths, Alan D.

    2015-04-01

    The stable isotopes of water are useful tracers of water sources and hydrological processes. Stable water isotope-enabled land surface modeling is a relatively new approach for characterizing the hydrological cycle, providing spatial and temporal variability for a number of hydrological processes. At the land surface, the integration of stable water isotopes with other meteorological measurements can assist in constraining surface heat flux estimates and discriminate between evaporation (E) and transpiration (T). However, research in this area has traditionally been limited by a lack of continuous in-situ isotopic observations. Here, the National Centre for Atmospheric Research stable isotope-enabled Land Surface Model (ISOLSM) is used to simulate the water and energy fluxes and stable water isotope variations. The model was run for a period of one month with meteorological data collected from a coastal sub-tropical site near Sydney, Australia. The modeled energy fluxes (latent heat and sensible heat) agreed reasonably well with eddy covariance observations, indicating that ISOLSM has the capacity to reproduce observed flux behavior. Comparison of modeled isotopic compositions of evapotranspiration (ET) against in-situ Fourier Transform Infrared spectroscopy (FTIR) measured bulk water vapor isotopic data (10 m above the ground), however, showed differences in magnitude and temporal patterns. The disparity is due to a small contribution from local ET fluxes to atmospheric boundary layer water vapor (∼1% based on calculations using ideal gas law) relative to that advected from the ocean for this particular site. Using ISOLSM simulation, the ET was partitioned into E and T with 70% being T. We also identified that soil water from different soil layers affected T and E differently based on the simulated soil isotopic patterns, which reflects the internal working of ISOLSM. These results highlighted the capacity of using the isotope-enabled models to discriminate

  11. Local Heat Flux Measurements with Single Element Coaxial Injectors

    NASA Technical Reports Server (NTRS)

    Jones, Gregg; Protz, Christopher; Bullard, Brad; Hulka, James

    2006-01-01

    To support the mission for the NASA Vision for Space Exploration, the NASA Marshall Space Flight Center conducted a program in 2005 to improve the capability to predict local thermal compatibility and heat transfer in liquid propellant rocket engine combustion devices. The ultimate objective was to predict and hence reduce the local peak heat flux due to injector design, resulting in a significant improvement in overall engine reliability and durability. Such analyses are applicable to combustion devices in booster, upper stage, and in-space engines, as well as for small thrusters with few elements in the injector. In this program, single element and three-element injectors were hot-fire tested with liquid oxygen and ambient temperature gaseous hydrogen propellants at The Pennsylvania State University Cryogenic Combustor Laboratory from May to August 2005. Local heat fluxes were measured in a 1-inch internal diameter heat sink combustion chamber using Medtherm coaxial thermocouples and Gardon heat flux gauges. Injectors were tested with shear coaxial and swirl coaxial elements, including recessed, flush and scarfed oxidizer post configurations, and concentric and non-concentric fuel annuli. This paper includes general descriptions of the experimental hardware, instrumentation, and results of the hot-fire testing for three of the single element injectors - recessed-post shear coaxial with concentric fuel, flush-post swirl coaxial with concentric fuel, and scarfed-post swirl coaxial with concentric fuel. Detailed geometry and test results will be published elsewhere to provide well-defined data sets for injector development and model validatation.

  12. The Use of a Mesoscale Climate Model to Validate the Nocturnal Carbon Flux over a Forested Site

    NASA Astrophysics Data System (ADS)

    Werth, D.; Parker, M.; Kurzeja, R.; Leclerc, M.; Watson, T.

    2007-12-01

    The Savannah River National Laboratory is initiating a comprehensive carbon dioxide monitoring and modeling program in collaboration with the University of Georgia and the Brookhaven National Laboratory. One of the primary goals is to study the dynamics of carbon dioxide in the stable nocturnal boundary layer (NBL) over a forested area of the Savannah River Site in southwest South Carolina. In the nocturnal boundary layer (NBL), eddy flux correlation is less effective in determining the release of CO2 due to respiration. Theoretically, however, the flux can be inferred by measuring the build up of CO2 in the stable layer throughout the night. This method of monitoring the flux will be validated and studied in more detail with both observations and the results of a high-resolution regional climate model. The experiment will involve two phases. First, an artificial tracer will be released into the forest boundary layer and observed through an array of sensors and at a flux tower. The event will be simulated with the RAMS climate model run at very high resolution. Ideally, the tracer will remain trapped within the stable layer and accumulate at rates which will allow us to infer the release rate, and this should compare well to the actual release rate. If an unknown mechanism allows the tracer to escape, the model simulation would be used to reveal it. In the second phase, carbon fluxes will be measured overnight through accumulation in the overlying layer. The RAMS model will be coupled with the SiB carbon model to simulate the nocturnal cycle of carbon dynamics, and this will be compared to the data collected during the night. As with the tracer study, the NBL method of flux measurement will be validated against the model. The RAMS-SiB coupled model has been run over the SRS at high-resolution to simulate the NBL, and results from simulations of both phases of the project will be presented.

  13. Measurement of N{sub 2}O fluxes from fertilized grassland using a fast response tunable diode laser spectrometer

    SciTech Connect

    Wienhold, F.G.; Frahm, H.; Harris, G.W.

    1994-08-20

    Measurements of nitrous oxide flux from fertilized agricultural grasslands is important in explaining and predicting the relationship of emissions of this gas to global warming. The nitrous oxide flux from agricultural grasslands was measured using micrometeorological techniques at a site near Stirling, Scotland. Emission levels were measured using a fast response tunable diode laser spectrometer. Measurements were made by both eddy correlation and concentration gradient techniques. This paper describes the results of this experiment and discusses information obtained that may be used for the characterization of the spatial variability in nitrous oxide emissions. 20 refs., 8 figs, 1 tab.

  14. Flux measurements in the near surface layer over a non-uniform crop surface in China

    NASA Astrophysics Data System (ADS)

    Gao, Z.; Bian, L.; Liu, S.

    2005-06-01

    Eddy covariance measurements were conducted on fluxes of moisture, heat and CO2 in a near-surface layer over a non-uniform crop surface in an agricultural ecosystem in the central plain of China from 10 June to 20 July 2002. During this period, the mean canopy height was about 0.50 m. The study site consisted of grass (10% of area), bean (15%), corn (15%) and rice (60%). Based on footprint analysis, we expected >90% of the measured flux (at a height of 4 m above ground surface) to occur within the nearest 600 m of upwind area. We examined interdiurnal variations in the components of the surface energy balance and in CO2 flux. Results show that the pattern of energy partition had no obvious variation during the season. Daytime absorption of CO2 flux by the crop canopy suddenly increased after thunderstorm events. We examined the energy budget closure and found it to be around 0.85. We compared energy partitioning for all rain-free days, and found energy imbalance was more significant for the 1~3 days after rainy events and energy components almost achieve balance for the other rain-free days. It indicated that the cold or warm rainwater infiltrating into soil made problems.

  15. Improvements to measuring water flux in the vadose zone.

    PubMed

    Masarik, Kevin C; Norman, John M; Brye, Kristofor R; Baker, John M

    2004-01-01

    Evaluating the impact of land use practices on ground water quality has been difficult because few techniques are capable of monitoring the quality and quantity of soil water flow below the root zone without disturbing the soil profile and affecting natural flow processes. A recently introduced method, known as equilibrium tension lysimetry, was a major improvement but it was not a true equilibrium since it still required manual intervention to maintain proper lysimeter suction. We addressed this issue by developing an automated equilibrium tension lysimeter (AETL) system that continuously matches lysimeter tension to soil-water matric potential of the surrounding soil. The soil-water matric potential of the bulk soil is measured with a heat-dissipation sensor, and a small DC pump is used to apply suction to a lysimeter. The improved automated approach reported here was tested in the field for a 12-mo period. Powered by a small 12-V rechargeable battery, the AETLs were able to continuously match lysimeter suction to soil-water matric potential for 2-wk periods with minimal human attention, along with the added benefit of collecting continuous soil-water matric potential data. We also demonstrated, in the laboratory, methods for continuous measurement of water depth in the AETL, a capability that quantifies drainage on a 10-min interval, making it a true water-flux meter. Equilibrium tension lysimeters have already been demonstrated to be a reliable method of measuring drainage flux, and the further improvements have created a more effective device for studying water drainage and chemical leaching through the soil matrix. PMID:15224955

  16. "Influence Method" applied to measure a moderated neutron flux

    NASA Astrophysics Data System (ADS)

    Rios, I. J.; Mayer, R. E.

    2016-01-01

    The "Influence Method" is conceived for the absolute determination of a nuclear particle flux in the absence of known detector efficiency. This method exploits the influence of the presence of one detector, in the count rate of another detector when they are placed one behind the other and define statistical estimators for the absolute number of incident particles and for the efficiency. The method and its detailed mathematical description were recently published (Rios and Mayer, 2015 [1]). In this article we apply it to the measurement of the moderated neutron flux produced by an 241AmBe neutron source surrounded by a light water sphere, employing a pair of 3He detectors. For this purpose, the method is extended for its application where particles arriving at the detector obey a Poisson distribution and also, for the case when efficiency is not constant over the energy spectrum of interest. Experimental distributions and derived parameters are compared with theoretical predictions of the method and implications concerning the potential application to the absolute calibration of neutron sources are considered.

  17. Measurements for the JASPER Program Flux Monitor Experiment

    SciTech Connect

    Muckenthaler, F.J.; Spencer, R.R.; Hunter, H.T.; Hull, J.L.; Shono, A.

    1993-02-01

    The Flux Monitor Experiment was conducted at the Oak Ridge National Laboratory (ORNL) Tower Shielding Facility (TSF) during the months of May and June 1992, as part of the continuing series of eight experiments planned for the Japanese-American Shielding Program for Experimental Research (JASPER) program that was started in 1986. This series of experiments was designed to examine shielding concerns and radiation transport effects pertaining to in-vessel flux monitoring systems (FMS) in current reactor shield designs proposed for both the Advanced Liquid Metal Reactor (ALMR) design and the Japanese loop-type design. The program is a cooperative effort between the United States Department of Energy (US DOE) and the Japanese Power Reactor and Nuclear Fuel Development Corporation (PNC). The Tower Shielding Reactor H (TSR-II) neutron source was altered by the spectrum modifier (SM) used previously in the Axial Shield Experiment, and part of the Japanese Removable Radial Shield (RRS) before reaching the axial shield. In the axial shield were placed six homogeneous boron carbide (B{sub 4}C) hexagons around a center hexagon of aluminum used to represent sodium. Shield designs to be studied were placed beyond the axial shield, each design forming a void directly behind the axial shield. Measurements were made in the void and behind each slab as successive slabs were added.

  18. Estimation of water flux in urban area using eddy covariance measurements in Riverside, Southern California

    NASA Astrophysics Data System (ADS)

    Jenerette, D.; Liang, L.

    2015-12-01

    Micrometeorological methods can direct measure the sensible and latent heat flux in specific sites and provide robust estimates of the evaporative fraction (EF), which is the fraction of available surface energy contained in latent heat. Across a vegetation coverage gradient in urban area, an empirical relationship is expected between EF and vegetation coverage, which provides the opportunity to quantify regional water flux. Here we deployed three eddy covariance (EC) systems to quantify the relationship between EF and vegetation coverage. First, two continuous systems were deployed at an industrial area with very low vegetation cover and another located in the orange orchid in Riverside, CA, to quantify the temporal dynamic of EF for the endpoints. Second, a mobile EC system was deployed to quantify the spatial distribution of EF across a gradient of vegetation coverage, during the summer time in Riverside, CA. These data showed the EF in high vegetation cover is 31.16±3.99%, but at the lower vegetation cover site EF is only 16.48±5.40%, which about 2 times lower in EF than the area with high vegetation cover. These results derived from the EC measurements provide essential data to quantify the temporal and spatial water fluxes in urban area and are needed to better understand and manage urban water use in response to drought.

  19. Measurements of the total ion flux from vacuum arc cathodespots

    SciTech Connect

    Anders, Andre; Oks, Efim M.; Yushkov, Georgy Yu; Savkin,Konstantin P.; Brown, Ian G.; Nikolaev, Alexey G.

    2005-05-25

    The ion flux from vacuum arc cathode spots was measured in two vacuum arc systems. The first was a vacuum arc ion source which was modified allowing us to collect ions from arc plasma streaming through an anode mesh. The second discharge system essentially consisted of a cathode placed near the center of a spherically shaped mesh anode. In both systems, the ion current streaming through the mesh was measured by a biased collector. The mesh anodes had geometric transmittances of 60 percent and 72 percent, respectively, which were taken into account as correction factors. The ion current from different cathode materials was measured for 50-500 A of arc current. The ion current normalized by the arc current was found to depend on the cathode material, with values in the range from 5 percent to 19 percent. The normalized ion current is generally greater for elements of low cohesive energy. The ion erosion rates were determined from values of ion current and ion charge states, which were previously measured in the same ion source. The absolute ion erosion rates range from 16-173 mu g/C.

  20. Measurement of particulate matter emission fluxes from a beef cattle feedlot using Flux-gradient technique

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Data on air emissions from open-lot beef cattle feedlots are limited. This research was conducted to determine PM10 emission fluxes from a commercial beef cattle feedlot in Kansas using the flux-gradient technique, a widely-used micrometeorological method for gaseous emissions from open sources. V...

  1. Trends in long-term carbon and water fluxes - a case study from a temperate Norway spruce site

    NASA Astrophysics Data System (ADS)

    Babel, Wolfgang; Lüers, Johannes; Hübner, Jörg; Serafimovich, Andrei; Thomas, Christoph; Foken, Thomas

    2016-04-01

    In this study we analyse eddy-covariance flux measurements of carbon dioxide and water vapour from 18 years at Waldstein-Weidenbrunnen (DE-Bay), a Norway spruce forest site in the Fichtelgebirge, Germany. Standard flux partitioning algorithms have been applied for separation of net ecosystem exchange NEE into gross ecosystem uptake GEE and ecosystem respiration Reco, and gap-filling. The annual NEE shows a positive trend, which is related to a strong increase in GEE, while Reco enhances slightly. Annual evapotranspiration increases as well, while atmospheric demand, i.e. potential evapotranspiration, shows inter-annual variability, but no trend. Comparisons with studies from other warm temperate needle-leaved forests show, that NEE is at the upper range of the distribution, and evapotranspiration in Budyko space is in a similar range, but with a large inter-annual variability. While this trends are generally in agreement with findings from other locations and expectations to climate change, the specific history at this site clearly has a large impact on the results: The forest was in the first years very much affected due to forest decline and convalesced after a liming. In the last ten years the site was much affected by beetles and windthrow. Thus the more recent positive trends may be related to increased heterogeneity at the site. As FLUXNET stations, built 10-20 years ago, often started with "ideal forest sites", increasing heterogeneity might be a more general problem for trend analysis of long-term data sets.

  2. Eddy Covariance Measurements Over a Maize Field: The Contribution of Minor Flux Terms to the Energy Balance Gap

    NASA Astrophysics Data System (ADS)

    Smidt, J.; Ingwersen, J.; Streck, T.

    2015-12-01

    The lack of energy balance closure is a long-standing problem in eddy covariance (EC) measurements. The energy balance equation is defined as Rn - G = H + λE, where Rn is net radiation, G is the ground heat flux, H is the sensible heat flux and λE is the latent heat flux. In most cases of energy imbalance, either Rn is overestimated or the ground heat and turbulent fluxes are underestimated. Multiple studies have shown that calculations, incorrect instrument installation/calibration and measurement errors alone do not entirely account for this imbalance. Rather, research is now focused on previously neglected sources of heat storage in the soil, biomass and air beneath the EC station. This project examined the potential of five "minor flux terms" - soil heat storage, biomass heat storage, energy consumption by photosynthesis, air heat storage and atmospheric moisture change, to further close the energy balance gap. Eddy covariance measurements were conducted at a maize (Zea mays) field in southwest Germany during summer 2014. Soil heat storage was measured for six weeks at 11 sites around the field footprint. Biomass and air heat storage were measured for six subsequent weeks at seven sites around the field footprint. Energy consumption by photosynthesis was calculated using the CO2 flux data. Evapotranspiration was calculated using the water balance method and then compared to the flux data processed with three post-closure methods: the sensible heat flux, the latent heat flux and the Bowen ratio post-closure methods. An energy balance closure of 66% was achieved by the EC station measurements over the entire investigation period. During the soil heat flux campaign, EC station closure was 74.1%, and the field footprint soil heat storage contributed 3.3% additional closure. During the second minor flux term measurement period, closure with the EC station data was 91%. Biomass heat storage resulted in 1.1% additional closure, the photosynthesis flux closed the gap

  3. Comparative analysis of matter and energy fluxes determined by Bowen Ratio and Eddy Covariance techniques at a crop site in eastern Germany

    NASA Astrophysics Data System (ADS)

    Brust, K.; Hehn, M.; Bernhofer, C.

    2012-04-01

    The measurement of atmospheric fluxes is an important means to evaluate ecosystem exchanges. In 2009 and 2010, fluxes and gradients of heat, water vapour, and CO2 over winter barley and rapeseed were measured simultaneously at the Klingenberg cropland site in Germany. A Bowen Ratio (BR) system was employed alongside to an existing Eddy Covariance (EC) tower. The BR system is required to account for the longer response time of the chemiluminescence analysers measuring other trace gases, e.g. NOx. To test and evaluate the application of the NOx measurement setup, the two independent systems (BR/EC) are compared with respect to energy and CO2 fluxes. We show a regression and differences analysis, diurnal cycles of the obtained fluxes, and interpret their coherence to the growth stage of the crops. The regression analysis depicts that differences between the systems are largest for latent heat LE (BR detects apparently higher LE due to the forced closure of energy balance), whereby the matter fluxes of CO2 show fairly little differences. Both measurement systems are able to capture the fluctuations of fluxes adequately well. Additionally, a multiple linear regression revealed that differences between the obtained fluxes are not induced by atmospheric conditions. The results of the differences analysis for sensible and latent heat point out that the observed differences of fluxes between both systems are mainly due to deviations in the mean, while differences in variability and timing/shape are of smaller importance. The differences of CO2 fluxes between both measurement systems are particularly caused by deviations in timing and shape, which can be explained with the linear cross-correlation coefficient (R2=0.8). From the good results of the comparison of matter fluxes (CO2) we conclude that the use of the Bowen Ratio method is applicable to other matter fluxes (like NOx).

  4. Isoprene Fluxes Measured By Eddy-correlation Over A Mixed Deciduous Forest In Italy

    NASA Astrophysics Data System (ADS)

    Finco, A.; Cieslik, S.

    A measuring campaign was conducted from July to September 2001 at a mixed de- ciduous forest located at a flat site (Nonantola, 4441' N; 1107' E) in the North- ern Italian plain to determine isoprene fluxes. The measuring station, operated by the CNR-ISAO (Bologna ) and CNR-IATA (Florence) was part of the CARBOEU- ROFLUX network, whose main goal is the study of the carbon balance in European forests. The flux measuring system used the eddy-correlation technique and consisted of a Gill sonic anemometer installed at 13 m a.g.l., and a LI-COR CO2/H2O analyser. For isoprene, a Hills Fast Isoprene Sensor was used.In this forest, about 50% of the trees (oaks, poplars and willows) are isoprene emitters. The canopy is very dense and homogeneous; its average height is 8 meters a.g.l. The general daily course of isoprene concentrations consisted in an increase during morning hours, followed with a sharp maximum and a rapid decrease. Maximum val- ues were quite high (around 15 ppb) in July and August, decreasing in September. During daytime, fluxes appeared to be strongly correlated with latent heat fluxes, con- firming the hypothesis of emission through stomata. The concentration decrease ob- served in the afternoon shows exponential decay, suggesting that no emission occurs after the concentration maximum, when stomata are progressively closing. A resistance analysis confirmed the above hypothesis : the role of stomatal emission appears essential, practically excluding other pathways. A mathematical investigation of the stationarity state of the lower atmosphere dur- ing the observations was made in order to draw attention on limitations of the eddy- correlation method. During nighttime, non-stationary situations are frequent, causing apparent peaks of isoprene flux, not due to an emission from the plants. The method developed permits to eliminate these biases.

  5. AmeriFlux US-Ne1 Mead - irrigated continuous maize site

    DOE Data Explorer

    Suyker, Andy [University of Nebraska - Lincoln

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-Ne1 Mead - irrigated continuous maize site. Site Description - The study site is one of three fields (all located within 1.6 km of each other) at the University of Nebraska Agricultural Research and Development Center near Mead, Nebraska. This site is irrigated with a center pivot system. Prior to the initiation of the study, the irrigated site had a 10-yr history of maize-soybean rotation under no-till. A tillage operation (disking) was done just prior to the 2001 planting to homogenize the top 0.1 m of soil, incorporate P and K fertilizers, as well as previously accumulated surface residues. Since the tillage operation, the site has been under no-till management until the harvest of 2005. Following harvest, a conservation-plow tillage operation was initiated where a small amount of N fertilizer is sprayed on the residue immediately prior to the plow operation. Approximately 1/3 of the crop residue is left on the surface. The post-harvest conservation-plow operation continues as the current practice.

  6. Passive flux sampler for measurement of formaldehyde emission rates

    NASA Astrophysics Data System (ADS)

    Shinohara, Naohide; Fujii, Minoru; Yamasaki, Akihiro; Yanagisawa, Yukio

    A new passive flux sampler (PFS) was developed to measure emission rates of formaldehyde and to determine emission sources in indoor environments. The sampler consisted of a glass Petri dish containing a 2,4-dinitrophenyl hydrazine (DNPH)-impregnated sheet. At the start of sampling, the PFS was placed with the open face of the dish on each of the indoor materials under investigation, such as flooring, walls, doors, closets, desks, beds, etc. Formaldehyde emitted from a source material diffused through the inside of the PFS and was adsorbed onto the DNPH sheet. The formaldehyde emission rates could be determined from the quantities adsorbed. The lower determination limits were 9.2 and 2.3 μg m -2 h -1 for 2- and 8-h sampling periods. The recovery rate and the precision of the PFS were 82.9% and 8.26%, respectively. The emission rates measured by PFS were in good agreement with the emission rates measured by the chamber method ( R2=0.963). This shows that it is possible to take measurements of the formaldehyde emission rates from sources in a room and to compare them. In addition, the sampler can be used to elucidate the emission characteristics of a source by carrying out emission measurements with different air-layer thicknesses inside the PFS and at different temperatures. The dependency of the emission rate on the thickness of the air layer inside the PFS indicated whether the internal mass transfer inside the source material or the diffusion in the gas-phase boundary layer controlled the formaldehyde emission rate from a material. In addition, as a pilot study, the formaldehyde emission rates were measured, and the largest emission source of formaldehyde could be identified from among several suspected materials in a model house by using the PFS.

  7. Eddy covariance flux measurements of net ecosystem carbon dioxide exchange from a lowland peatland flux tower network in England and Wales

    NASA Astrophysics Data System (ADS)

    Morrison, Ross; Balzter, Heiko; Burden, Annette; Callaghan, Nathan; Cumming, Alenander; Dixon, Simon; Evans, Jonathan; Kaduk, Joerg; Page, Susan; Pan, Gong; Rayment, Mark; Ridley, Luke; Rylett, Daniel; Worrall, Fred; Evans, Christopher

    2016-04-01

    Peatlands store disproportionately large amounts of soil carbon relative to other terrestrial ecosystems. Over recent decades, the large amount of carbon stored as peat has proved vulnerable to a range of land use pressures as well as the increasing impacts of climate change. In temperate Europe and elsewhere, large tracts of lowland peatland have been drained and converted to agricultural land use. Such changes have resulted in widespread losses of lowland peatland habitat, land subsidence across extensive areas and the transfer of historically accumulated soil carbon to the atmosphere as carbon dioxide (CO2). More recently, there has been growth in activities aiming to reduce these impacts through improved land management and peatland restoration. Despite a long history of productive land use and management, the magnitude and controls on greenhouse gas emissions from lowland peatland environments remain poorly quantified. Here, results of surface-atmosphere measurements of net ecosystem CO2 exchange (NEE) from a network of seven eddy covariance (EC) flux towers located at a range of lowland peatland ecosystems across the United Kingdom (UK) are presented. This spatially-dense peatland flux tower network forms part of a wider observation programme aiming to quantify carbon, water and greenhouse gas balances for lowland peatlands across the UK. EC measurements totalling over seventeen site years were obtained at sites exhibiting large differences in vegetation cover, hydrological functioning and land management. The sites in the network show remarkable spatial and temporal variability in NEE. Across sites, annual NEE ranged from a net sink of -194 ±38 g CO2-C m-2 yr-1 to a net source of 784±70 g CO2-C m-2 yr-1. The results suggest that semi-natural sites remain net sinks for atmospheric CO2. Sites that are drained for intensive agricultural production range from a small net sink to the largest observed source for atmospheric CO2 within the flux tower network

  8. Yeast dynamic metabolic flux measurement in nutrient-rich media by HPLC and accelerator mass spectrometry.

    PubMed

    Stewart, Benjamin J; Navid, Ali; Turteltaub, Kenneth W; Bench, Graham

    2010-12-01

    Metabolic flux, the flow of metabolites through networks of enzymes, represents the dynamic productive output of cells. Improved understanding of intracellular metabolic fluxes will enable targeted manipulation of metabolic pathways of medical and industrial importance to a greater degree than is currently possible. Flux balance analysis (FBA) is a constraint-based approach to modeling metabolic fluxes, but its utility is limited by a lack of experimental measurements. Incorporation of experimentally measured fluxes as system constraints will significantly improve the overall accuracy of FBA. We applied a novel, two-tiered approach in the yeast Saccharomyces cerevisiae to measure nutrient consumption rates (extracellular fluxes) and a targeted intracellular flux using a (14)C-labeled precursor with HPLC separation and flux quantitation by accelerator mass spectrometry (AMS). The use of AMS to trace the intracellular fate of (14)C-glutamine allowed the calculation of intracellular metabolic flux through this pathway, with glutathione as the metabolic end point. Measured flux values provided global constraints for the yeast FBA model which reduced model uncertainty by more than 20%, proving the importance of additional constraints in improving the accuracy of model predictions and demonstrating the use of AMS to measure intracellular metabolic fluxes. Our results highlight the need to use intracellular fluxes to constrain the models. We show that inclusion of just one such measurement alone can reduce the average variability of model predicted fluxes by 10%. PMID:21062031

  9. Careful Measurements and Energy Balance Closure - The Case of Soil Heat Flux

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An area of persistent concern in micrometeorological measurements is the failure to close the energy balance at surface flux stations. While most attention has focused on corrections associated with the eddy fluxes, none of the energy balance terms are measured without error. The flux plate method i...

  10. Using passive capillary lysimeter water flux measurements to improve flow predictions in variably saturated soils.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Passive capillary lysimeters (PCLs) are uniquely suited for measuring water fluxes in variably-saturated soils. The objective of this work was to compare PCL flux measurements with simulated fluxes obtained with a calibrated unsaturated flow model. The Richards equation-based model was calibrated us...

  11. Standardization of flux chambers and wind tunnels for area source emission measurements at animal feeding operations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Researchers and practitioners have used many varied designs of wind tunnels and flux chambers to measure the flux of volatile organic compounds, odor, and ammonia from area sources at animal feeding operations. The measured fluxes are used to estimate emission factors or compare treatments. We sho...

  12. Impact of vegetation cover and stand age on scaling carbon fluxes in the upper Midwest: a multiple eddy flux site study

    NASA Astrophysics Data System (ADS)

    Desai, A. R.; Normeets, A.; Bolstad, P. V.; Chen, J.; Cook, B. D.; Curtis, P. S.; Davis, K. J.; Euskirchen, E.; Gough, C.; Martin, J.; Ricciuto, D. M.; Schmid, H. P.; Tang, J.; Su, H.; Vogel, C.; Wang, W.

    2004-12-01

    Eight permanent and three roving eddy flux towers were used to observe the exchange of carbon dioxide between the ecosystem and atmosphere at fourteen different sites in northern Wisconsin and Michigan (USA) during the growing seasons (May-Sept) of 2002 and 2003. These towers were part of the Chequamegon Ecosystem-Atmosphere Study (ChEAS), the University of Michigan Biological Station (UMBS), and the Michigan Technical University. The sites spanned a range of vegetation types typical of the region (northern hardwood, hemlock-hardwood, mixed forest, red pine, jack pine, pine barrens and shrub wetland). The hardwood and red pine sites also spanned a range of forest stand age (young, intermediate, mature and old). All sites experienced roughly similar climate; thus, comparisons among the sites allow for an examination of the impact of heterogeneous vegetation cover and stand age across a regional landscape. Carbon fluxes at different sites generally reacted similarly in response to variability in climate. Results suggest that both cover type and stand age are important variables for modeling and predicting fluxes in this region. These results have implications for developing methods of scaling carbon dioxide fluxes from sites to regions. These results will be contrasted to a flux decomposition at the WLEF tall tower.

  13. On the applicability of surrogate-based MCMC-Bayesian inversion to the Community Land Model: Case studies at Flux tower sites

    DOE PAGESBeta

    Huang, Maoyi; Ray, Jaideep; Hou, Zhangshuan; Ren, Huiying; Liu, Ying; Swiler, Laura

    2016-06-01

    The Community Land Model (CLM) has been widely used in climate and Earth system modeling. Accurate estimation of model parameters is needed for reliable model simulations and predictions under current and future conditions, respectively. In our previous work, a subset of hydrological parameters has been identified to have significant impact on surface energy fluxes at selected flux tower sites based on parameter screening and sensitivity analysis, which indicate that the parameters could potentially be estimated from surface flux observations at the towers. To date, such estimates do not exist. In this paper, we assess the feasibility of applying a Bayesianmore » model calibration technique to estimate CLM parameters at selected flux tower sites under various site conditions. The parameters are estimated as a joint probability density function (PDF) that provides estimates of uncertainty of the parameters being inverted, conditional on climatologically-average latent heat fluxes derived from observations. We find that the simulated mean latent heat fluxes from CLM using the calibrated parameters are generally improved at all sites when compared to those obtained with CLM simulations using default parameter sets. Further, our calibration method also results in credibility bounds around the simulated mean fluxes which bracket the measured data. The modes (or maximum a posteriori values) and 95% credibility intervals of the site-specific posterior PDFs are tabulated as suggested parameter values for each site. Lastly, analysis of relationships between the posterior PDFs and site conditions suggests that the parameter values are likely correlated with the plant functional type, which needs to be confirmed in future studies by extending the approach to more sites.« less

  14. On the applicability of surrogate-based Markov chain Monte Carlo-Bayesian inversion to the Community Land Model: Case studies at flux tower sites

    NASA Astrophysics Data System (ADS)

    Huang, Maoyi; Ray, Jaideep; Hou, Zhangshuan; Ren, Huiying; Liu, Ying; Swiler, Laura

    2016-07-01

    The Community Land Model (CLM) has been widely used in climate and Earth system modeling. Accurate estimation of model parameters is needed for reliable model simulations and predictions under current and future conditions, respectively. In our previous work, a subset of hydrological parameters has been identified to have significant impact on surface energy fluxes at selected flux tower sites based on parameter screening and sensitivity analysis, which indicate that the parameters could potentially be estimated from surface flux observations at the towers. To date, such estimates do not exist. In this paper, we assess the feasibility of applying a Bayesian model calibration technique to estimate CLM parameters at selected flux tower sites under various site conditions. The parameters are estimated as a joint probability density function (PDF) that provides estimates of uncertainty of the parameters being inverted, conditional on climatologically average latent heat fluxes derived from observations. We find that the simulated mean latent heat fluxes from CLM using the calibrated parameters are generally improved at all sites when compared to those obtained with CLM simulations using default parameter sets. Further, our calibration method also results in credibility bounds around the simulated mean fluxes which bracket the measured data. The modes (or maximum a posteriori values) and 95% credibility intervals of the site-specific posterior PDFs are tabulated as suggested parameter values for each site. Analysis of relationships between the posterior PDFs and site conditions suggests that the parameter values are likely correlated with the plant functional type, which needs to be confirmed in future studies by extending the approach to more sites.

  15. Heat flux measured acoustically at Grotto Vent, a hydrothermal vent cluster on the Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Xu, G.; Jackson, D. R.; Bemis, K. G.; Rona, P. A.

    2013-12-01

    Over the past several decades, quantifying the heat output has been a unanimous focus of studies at hydrothermal vent fields discovered around the global ocean. Despite their importance, direct measurements of hydrothermal heat flux are very limited due to the remoteness of most vent sites and the complexity of hydrothermal venting. Moreover, almost all the heat flux measurements made to date are snapshots and provide little information on the temporal variation that is expected from the dynamic nature of a hydrothermal system. The Cabled Observatory Vent Imaging Sonar (COVIS, https://sites.google.com/a/uw.edu/covis/) is currently connected to the Endeavour node of the NEPTUNE Canada observatory network (http://www.neptunecanada.ca) to monitor the hydrothermal plumes issuing from a vent cluster (Grotto) on the Endeavour Segment of the Juan de Fuca Ridge. COVIS is acquiring a long-term (20-months to date) time series of the vertical flow rate and volume flux of the hydrothermal plume above Grotto through the Doppler analysis of the acoustic backscatter data (Xu et al., 2013). We then estimate the plume heat flux from vertical flow rate and volume flux using our newly developed inverse method. In this presentation, we will briefly summarize the derivation of the inverse method and present the heat-flux time series obtained consequently with uncertainty quantification. In addition, we compare our heat-flux estimates with the one estimated from the plume in-situ temperatures measured using a Remotely Operative Vehicle (ROV) in 2012. Such comparison sheds light on the uncertainty of our heat flux estimation. Xu, G., Jackson, D., Bemis, K., and Rona, P., 2013, Observations of the volume flux of a seafloor hydrothermal plume using an acoustic imaging sonar, Geochemistry, Geophysics Geosystems, 2013 (in press).

  16. Measuring Total Flux of Organic Vapors From the Unsaturated Zone Under Natural Conditions: Design, Laboratory and Field Testing of a Flux Chamber Device

    NASA Astrophysics Data System (ADS)

    Tillman, F. D.; Choi, J.; Smith, J. A.

    2002-05-01

    A simple, easy-to-use, and inexpensive device for measuring VOC flux under natural conditions was designed and tested both in a controlled laboratory environment and in a natural field setting. The chamber consists of a stainless-steel right circular cylinder open on one end with a flexible, impermeable membrane allowing for chamber expansion and contraction. Air is pumped from inside the chamber through activated carbon traps and returned to the chamber maintaining a net zero pressure gradient from the inside to the outside of the chamber. The traps are analyzed using thermal desorption/GC-FID and the mass of contaminant is divided by the product of the sampled area and sample time to give VOC flux measured by the chamber. Design parameters for the chamber were selected using continuously stirred tank reactor (CSTR)-equation based modeling under step, sinusoidal and transport-model simulation flux inputs. Laboratory testing of the flux chamber under both diffusion and advection dominated conditions was performed in a device constructed to simulate unsaturated zone transport. Aqueous trichloroethene (TCE) solution was pumped through the bottom of a steel drum inside which 50-cm of fine sand was suspended. For diffusion-dominated transport experiments, the chamber was installed in the sand at the top of the simulator and operated in the same manner as would occur in the field. The flux measurement of the chamber was then compared to flux prediction based on measured linear concentration data from the simulator and Fick's law. Advective transport is initiated in the vadose zone simulator by flowing humidified, pressurized air into an input port in the bottom of the simulator below the suspended porous media. Soil-gas velocity is calculated by dividing the airflow input by the surface area of the simulator. Flux was measured with the chamber and compared to flux predicted using airflow and concentration data from the simulator. Results from both the diffusion-only and

  17. The BESS-Polar Proton & Helium flux measurements

    NASA Astrophysics Data System (ADS)

    Hams, T.; Yamamoto, A.; Mitchell, J.W.; Abe, K.; Fuke, H.; Haino, S.; Hasegawa, M.; Horikoshi, A.; Itazaki, A.; Kim, K.C.; Kumazawal, T.; Lee, M.H.; Makida, Y.; Matsuda, S.; Matsukawa, Y.; Matsumoto, K.; Moiseev, A.A.; Meyers, Z.; Nishimura, J.; Nozaki, M.; Orito, R.; Ormes, J.F.; Sakai, K.; Sasaki, M.; Seo, E.S.; Shikaze, Y.; Shinoda, R.; Streitmatter, R.E.; Suzuki, J.; Takasugi, Y.; Takeuchi, K.; Tanaka, K.; Thakur, N.; Yamagami, T.; Yoshida, T.; Yoshimura, K.

    The Balloon-borne Experiment with a Superconducting Spectrometer (BESS) instrument pro-vides precise measurements of the elemental and isotopic composition of the light Galactic cosmic radiation (GCR) component. The ability to determine the charge sign of incident par-ticles enables the instrument to search for GCR antimatter, which is a major objective of the BESS program. Since 1993, the US-Japan BESS collaboration has conducted 11 successful balloon flights, nine northern-latitude flights of 1-day duration and most recently two long-duration balloon flights (8.5 days in 2004 & 24.5 days in 2007/2008), with the BESS-Polar instrument. The BESS-Polar instrument is the current effort of BESS program specifically designed for long-duration, low-geomagnetic cutoff Antarctic flights with significantly increased transparency for incident CR particle allowing to study anti/proton down to 100 MeV and a faster data acquisition enables processing of all CR events without event selection. The first BESS-Polar flight was launched on Dec 13, 2004 from Williams Field, near McMurdo Station in Antarctica. The instrument recorded data for 8.5 days, limited by the cryogenic life time of the superconducting magnet. During this flight the BESS-Polar instrument recorded 0.9 x 109 CR events. In this paper, we present the absolute proton and helium flux for the first BESS-Polar flight as well as the time variation of the fluxes due to solar activity.

  18. Nevada Test Site seismic: telemetry measurements

    SciTech Connect

    Albright, J N; Parker, L E; Horton, E H

    1983-08-01

    The feasibility and limitations of surface-to-tunnel seismic telemetry at the Nevada Test Site were explored through field measurements using current technology. Range functions for signaling were determined through analysis of monofrequency seismic signals injected into the earth at various sites as far as 70 km (43 mi) from installations of seismometers in the G-Tunnel complex of Rainier Mesa. Transmitted signal power at 16, 24, and 32 Hz was measured at two locations in G-Tunnel separated by 670 m (2200 ft). Transmissions from 58 surface sites distributed primarily along three azimuths from G-Tunnel were studied. The G-Tunnel noise environment was monitored over the 20-day duration of the field tests. Noise-power probability functions were calculated for 20-s and 280-s seismic-record populations. Signaling rates were calculated for signals transmitted from superior transmitter sites to G-Tunnel. A detection threshold of 13 dB re 1 nm/sup 2/ displacement power at 95% reliability was demanded. Consideration of field results suggests that even for the frequency range used in this study, substantially higher signaling rates are likely to be obtained in future work in view of the present lack of information relevant to hardware-siting criteria and the seismic propagation paths at the Nevada Test Site. 12 references.

  19. Simulating Energy, Water and Carbon Fluxes at the Shortgrass Steppe Long Term Ecological Research (LTER) Site

    NASA Astrophysics Data System (ADS)

    Beltran-Przekurat, A. B.; Pielke, R. A.; Morgan, J. A.; Burke, I. C.

    2005-12-01

    Coupled atmospheric-biospheric models are a particularly valuable tool for studying the potential effects of land-use and land-cover changes on the near-surface atmosphere since the atmosphere and biosphere are allowed to dynamically interact through the surface and canopy energy balance. GEMRAMS is a coupled atmospheric-biospheric model comprised of an atmospheric model, RAMS, and an ecophysiological process-based model, GEMTM. In the first part of this study, the soil-vegetation-atmosphere-transfer (SVAT) scheme, LEAF2, from RAMS, coupled with GEMTM, are used to simulate energy, water and carbon fluxes over different cropping systems (winter wheat and irrigated corn) and over a mixed C3/C4 shortgrass prairie located at the USDA-ARS Central Plains Experimental Range near Nunn, Colorado, the LTER Shortgrass Steppe site. The new SVAT scheme, GEMLEAF, is forced with air temperature and humidity, wind speed and photosynthetic active radiation (PAR). Calculated canopy temperature and relative humidity, soil moisture and temperature and PAR are used to compute sunlit/shaded leaf photosynthesis (for C3 and C4 plant types) and respiration. Photosynthate is allocated to leaves, shoots, roots and reproductive organs with variable partition coefficients, which are functions of soil water conditions. As water stress increases, the fraction of photosynthate allocated to root growth increases. Leaf area index (LAI) is estimated from daily leaf biomass growth, using the vegetation-prescribed specific leaf area. Canopy conductance, computed and based on photosynthesis and relative humidity, is used to calculate latent heat flux. Simulated energy and CO2 fluxes are compared to observations collected using Bowen ratio flux towers during two growing seasons. Seasonality of the fluxes reflecting different plant phenologies agrees well with the observed patterns. In the second part of this study, simulations for two clear days are performed with GEMRAMS over a model domain centered at

  20. Size resolved dust emission fluxes measured in Niger during 3 dust storms of the AMMA experiment

    NASA Astrophysics Data System (ADS)

    Sow, M.; Alfaro, S. C.; Rajot, J. L.; Marticorena, B.

    2009-03-01

    During the 2006 and 2007 special observing periods of the African Monsoon Multidisciplinary Analysis campaign an original experimental system has been implemented in Banizoumbou (Niger) for measuring the size-resolved dust emission flux in natural conditions and documenting the possible influence of wind speed on its size distribution. The instrumental set-up, associated methodology, and the quality tests applied to the data set are described before the results acquired during 2 events of the Monsoon type and 1 of the convective type are analyzed in detail. In good agreement with the theory of sandblasting, it is found in all cases that saltation must take place for a vertical emission flux to be detected. During a particular erosion event, the magnitude of the vertical flux is controlled by the surface roughness, which conditions the saltation threshold, and by the wind friction velocity. The dust flux released by the high energy convective event is also found to be much richer in very fine (<2 μm) particles than those of the relatively moderate Monsoon event, which shows that aerodynamic conditions definitely influence the initial size distribution of the erosion flux as previously suggested by wind tunnel experiments. However, the size distribution of the dust released by a given event is fairly constant and insensitive to even relatively important variations of u*. This is interpreted as a possible result of the rather long duration (15') over which wind fluctuations must be averaged for computing u*, which could make it an inadequate parameter for representing the very short response-time physical processes that are at the origin of fine dust emission at the measurement sites.

  1. Size resolved dust emission fluxes measured in Niger during 3 dust storms of the AMMA experiment

    NASA Astrophysics Data System (ADS)

    Sow, M.; Alfaro, S.; Rajot, J. L.; Marticorena, B.

    2009-04-01

    During the 2006 and 2007 special observing periods of the African Monsoon Multidisciplinary Analysis campaign an original experimental system has been implemented in Banizoumbou (Niger) for measuring the size-resolved dust emission flux in natural conditions and documenting the possible influence of wind speed on its size distribution. The instrumental set-up, associated methodology, and the quality tests applied to the data set are described before the results acquired during 2 events of the Monsoon type and 1 of the convective type are analyzed in detail. In good agreement with the theory of sandblasting, it is found in all cases that saltation must take place for a vertical emission flux to be detected. During a particular erosion event, the magnitude of the vertical flux is controlled by the surface roughness, which conditions the saltation threshold, and by the wind friction velocity. The dust flux released by the high energy convective event is also found to be much richer in very fine (<2µm) particles than those of the relatively moderate Monsoon events, which shows that aerodynamic conditions definitely influence the initial size distribution of the erosion flux as previously suggested by wind tunnel experiments. However, the size distribution of the dust released by a given event is fairly constant and insensitive to even relatively important variations of u*. This is interpreted as a possible result of the rather long duration (15') over which wind fluctuations must be averaged for computing u*, which could make it an inadequate parameter for representing the very short response-time physical processes that are at the origin of fine dust emission at the measurement sites

  2. Size resolved dust emission fluxes measured in Niger during 3 dust storms of the AMMA experiment

    NASA Astrophysics Data System (ADS)

    Sow, M.; Alfaro, S. C.; Rajot, J. L.; Marticorena, B.

    2009-06-01

    During the 2006 and 2007 special observing periods of the African Monsoon Multidisciplinary Analysis campaign an original experimental system has been implemented in Banizoumbou (Niger) for measuring the size-resolved dust emission flux in natural conditions and documenting the possible influence of wind speed on its size distribution. The instrumental set-up, associated methodology, and the quality tests applied to the data set are described before the results acquired during 2 events of the Monsoon type and 1 of the convective type are analyzed in detail. In good agreement with the theory of sandblasting, it is found in all cases that saltation must take place for a vertical emission flux to be detected. During a particular erosion event, the magnitude of the vertical flux is controlled by the surface roughness, which conditions the saltation threshold, and by the wind friction velocity. The dust flux released by the high energy convective event is also found to be much richer in very fine (<2 µm) particles than those of the relatively moderate Monsoon event, which shows that aerodynamic conditions definitely influence the initial size distribution of the erosion flux as previously suggested by wind tunnel experiments. However, the size distribution of the dust released by a given event is fairly constant and insensitive to even relatively important variations of u*. This is interpreted as a possible result of the rather long duration (15 min) over which wind fluctuations must be averaged for computing u*, which could make it an inadequate parameter for representing the very short response-time physical processes that are at the origin of fine dust emission at the measurement sites.

  3. Measurement of Flux Density of Cas A at Low Frequencies

    NASA Astrophysics Data System (ADS)

    Patil, Ajinkya; Fisher, R.

    2012-01-01

    Cas A is used as a flux calibrator throughout the radio spectrum. Therefore it is important to know the spectral and secular variations in its flux density. Earlier observations by Scott et. al. (1969) and Baars et. al. (1972) suggested a secular decrease in flux density of Cas A at a rate of about 1% per year at all frequencies. However later observations by Erickson & Perley (1975) and Read (1977) indicated anomalously high flux from Cas A at 38 MHz. Also, these observations suggested that the original idea of faster decay of the flux density rate at low frequencies may be in error or that something more complex than simple decay is affecting the flux density at low frequencies. The source changes at 38 MHz still remains a mystery. We intend to present the results of follow up observations made from 1995 to 1998 with a three element interferometer in Green Bank operating in frequency range 30 to 120 MHz. We will discuss the problems at such low frequencies due to large beamwidth and unstable ionosphere. We will also discuss the strategies we have used so far to to find the flux density of Cas A by calculating the ratio of flux density of Cas A to that of Cyg A, assuming flux density of Cyg A to be constant. Above mentioned work was performed in summer student program sponsored by National Radio Astronomy Observatory.

  4. Comparison of three stationary tests for eddy covariance measurements of turbulent fluxes of different scalars

    NASA Astrophysics Data System (ADS)

    Donateo, Antonio; Cava, Daniela; Contini, Daniele

    2013-04-01

    In atmospheric turbulent flows, variables describing the motion undergo random and stochastic fluctuations. In turbulence studies the hypotheses of stationarity and ergodicity of time series is required in order to obtain estimates of ensemble averages from the temporal averages obtained from single runs. In atmosphere, however, equivalence between the two averages is just approximated because of non stationarity often inherent to atmospheric time series. Typically non-stationary conditions are driven by weather or internal boundary layer changing, for example for the presence of gravity waves or simply for the slow diurnal evolution of the boundary layer. The individuation of non-stationary cases is important for measurements of turbulent fluxes using the eddy covariance method generally applied to 30 minutes averages. Moreover it is necessary to have an analytical/parametric stationarity test, which can be used in real time determination of turbulent fluxes, for example in Fluxnet network. Nowadays different stationarity tests are proposed in literature and they are substantially used by scientific community (Foken & Wichura, 1996; Mahrt, 1998; Affre et al., 2000). In this work several time series have been analysed with the three different stationarity tests and a comparison of their performances has been developed. The stationarity tests have been applied to different scalars (temperature, ultrafine particles number concentration, carbon dioxide and water vapour concentration). All the time series come from measurements in different sites and are collected over different canopies: iced surface (in Antarctica), urban or suburban surface (Italy) and vegetal canopy over forests (both in Italy and USA). In total 6 different sites have been analysed and the performances of the stationarity tests do not seem to be site dependent. The correlation of their performances as a function of local micro-meteorological conditions have been analysed. All the three tests show

  5. Organic Carbon Inventories and Vertical Fluxes Through the Vadose Zone into Groundwater at the Rifle, Colorado River Floodplain Site

    NASA Astrophysics Data System (ADS)

    Tokunaga, T. K.; Wan, J.; Dong, W.; Williams, K. H.; Robbins, M.; Kim, Y.; Faybishenko, B.; Conrad, M. E.; Christensen, J. N.; Gilbert, B.; Dayvault, R. D.; Long, P. E.; Hubbard, S. S.

    2013-12-01

    Understanding carbon inventories and fluxes within the vadose zone and groundwater of semi-arid regions is challenging because of their typically deep profiles, moderately low soil organic carbon (SOC) inventories, low dissolved organic carbon (DOC) fluxes, and slow changes in soil inorganic carbon (SIC) inventories. The remediated uranium/vanadium mill tailings site situated on a floodplain at Rifle, Colorado possesses a number of characteristics that facilitate investigation of subsurface carbon fluxes. These include locally derived fill soil having SOC and SIC concentrations representative of the region, established vegetation cover (perennial grasses and shrubs) on the fill, boundaries between the fill and underlying alluvium distinguishable through concentrations of SIC and other chemical components, predictable groundwater flow and interaction with the adjacent Colorado River, and a clearly delineated impermeable lower boundary (Wasatch Formation shale) at depths ranging from 6 to 7.5 m. Environmental characteristics of this site permit year-round sampling of both pore water and pore gas throughout most of the moderately deep (~ 3.5 m) vadose zone. Within this well-defined hydrological system, we recently installed a suite of tensiometers, pore water (vadose zone and groundwater) samplers, gas samplers, and neutron probe access tubes at three sites along a transect aligned with the groundwater flow direction in order to determine inventories and fluxes of water, carbon, and other components. The tensiometer and piezometer measurements are revealing impacts of infiltration and groundwater recharge events, evapotranspiration, and capillary fringe-groundwater interactions. The results of pore water analyses are showing relatively high concentrations of DOC (up to 4 mM) in the vadose zone, and particulate organic carbon (POC) mobile in the capillary fringe. Differences in DOC characteristics are being determined using a variety of analytical techniques. Hydraulic

  6. Characterization of neutron flux spectra in the irradiation sites of a 37 GBq 241Am-Be isotopic source

    NASA Astrophysics Data System (ADS)

    Yücel, Haluk; Budak, Mustafa Guray; Karadag, Mustafa; Yüksel, Alptuğ Özer

    2014-11-01

    For the applicability of instrumental neutron activation analysis (NAA) technique, an irradiation unit with a 37 GBq 241Am-Be neutron source was installed at Institute of Nuclear Sciences of Ankara University. Design and configuration properties of the irradiation unit are described. It has two different sample irradiation positions, one is called site #1 having a pneumatic sample transfer system and the other is site #2 having a location for manual use. In order to characterize neutron flux spectra in the irradiation sites, the measurement results were obtained for thermal (Фth) and epithermal neutron fluxes (Фepi), thermal to epithermal flux ratio (f) and epithermal spectrum shaping factors (α) by employing cadmium ratios of gold (Au) and molybdenum (Mo) monitors. The activities produced in these foils were measured by using a p-type, 44.8% relative efficiency HPGe well detector. For the measured γ-rays, self-absorption and true coincidence summing effects were taken into account. Additionally, thermal neutron self-shielding and resonance neutron self-shielding effects were taken into account in the measured results. For characterization of site #1, the required parameters were found to be Фth = (2.11 ± 0.05) × 103 n cm-2 s-1, Фepi = (3.32 ± 0.17) × 101 n cm-2 s-1, f = 63.6 ± 1.5, α = 0.045 ± 0.009, respectively. Similarly, those parameters were measured in site #2 as Фth = (1.49 ± 0.04) × 103 n cm-2 s-1, Фepi = (2.93 ± 0.15) × 101 n cm-2 s-1, f = 50.9 ± 1.3 and α = 0.038 ± 0.008. The results for f-values indicate that good thermalization of fast neutrons on the order of 98% was achieved in both sample irradiation sites. This is because an optimum combination of water and paraffin moderator is used in the present configuration. In addition, the shielding requirements are met by using natural boron oxide powder (5.5 cm) and boron loaded paraffin layers against neutrons, and a 15 cm thick lead bricks against gamma-rays from source and its

  7. Background light measurements at the DUMAND site

    NASA Technical Reports Server (NTRS)

    Aoki, T.; Kitamura, T.; Matsuno, S.; Mitsui, K.; Ohashi, Y.; Okada, A.; Cady, D. R.; Learned, J. G.; Oconnor, D.; Mcmurdo, M.

    1985-01-01

    Ambient light intensities at the DUMAND site, west of the island of Hawaii were measured around the one photoelectron level. Throughout the water column between 1,500m and 4,700m, a substantial amount of stimulateable bioluminescence is observed with a ship suspended detector. But non-stimulated bioluminescence level is comparable, or less than, K sup 40 background, when measured with a bottom tethered detector typical of a DUMAND optical module.

  8. Forest floor leachate fluxes under six different tree species on a metal contaminated site.

    PubMed

    Van Nevel, Lotte; Mertens, Jan; De Schrijver, An; Baeten, Lander; De Neve, Stefaan; Tack, Filip M G; Meers, Erik; Verheyen, Kris

    2013-03-01

    Trees play an important role in the biogeochemical cycling of metals, although the influence of different tree species on the mobilization of metals is not yet clear. This study examined effects of six tree species on fluxes of Cd, Zn, DOC, H(+) and base cations in forest floor leachates on a metal polluted site in Belgium. Forest floor leachates were sampled with zero-tension lysimeters in a 12-year-old post-agricultural forest on a sandy soil. The tree species included were silver birch (Betula pendula), oak (Quercus robur and Q. petraea), black locust (Robinia pseudoacacia), aspen (Populus tremula), Scots pine (Pinus sylvestris) and Douglas fir (Pseudotsuga menziesii). We show that total Cd fluxes in forest floor leachate under aspen were slightly higher than those in the other species' leachates, yet the relative differences between the species were considerably smaller when looking at dissolved Cd fluxes. The latter was probably caused by extremely low H(+) amounts leaching from aspen's forest floor. No tree species effect was found for Zn leachate fluxes. We expected higher metal leachate fluxes under aspen as its leaf litter was significantly contaminated with Cd and Zn. We propose that the low amounts of Cd and Zn leaching under aspen's forest floor were possibly caused by high activity of soil biota, for example burrowing earthworms. Furthermore, our results reveal that Scots pine and oak were characterized by high H(+) and DOC fluxes as well as low base cation fluxes in their forest floor leachates, implying that those species might enhance metal mobilization in the soil profile and thus bear a potential risk for belowground metal dispersion. PMID:23376521

  9. Post processing of CO2 flux measurements from an urban landscape

    NASA Astrophysics Data System (ADS)

    Menzer, O.; Meiring, W.; Kyriakidis, P. C.; McFadden, J. P.

    2013-12-01

    Tower based measurements of CO2 fluxes by the eddy covariance method are subject to random error, systematic error, and missing data (gaps). In homogeneous ecosystems such as forests and grasslands, the post processing methods to address these problems are relatively well established. In the urban environment, however, the assumptions of most such methods are violated due to spatial heterogeneity in the tower footprint and localized CO2 sources such as traffic emission. For this reason, work is needed to develop and test methods appropriate to the urban setting. Here, we report comparisons of post processing methods for >3 years of flux measurements from the KUOM tall tower in a suburban neighborhood of Minneapolis, Minnesota, USA. Machine learning regression approaches including Artificial Neural Networks and Gaussian Processes were used to integrate observations from remote sensing, traffic and weather stations, and to extract complex underlying functional relationships, in order to improve gap-filling and minimize uncertainties. Specifically, we tested the sensitivity of the measurements to vehicle emissions by incorporating traffic counts from nearby roads and highways. Also, the selection of the friction velocity (u*) threshold was found to be sensitive to the wind direction but consistent between years. We calculated carbon flux sums for both residential and recreational land use types in the tower footprint, and assessed the random and systematic uncertainties caused by gap-filling and u*-filtering. While these post processing methods are essential for interpreting CO2 flux measurements in urban environments, they may also be useful for other inhomogeneous sites such as logged forests or ecosystems under disturbance from fire or pests.

  10. A Summary of Mass Flux Measurements in Solid 4He

    NASA Astrophysics Data System (ADS)

    Hallock, R. B.; Ray, M. W.; Vekhov, Y.

    2012-11-01

    Here we provide a summary and brief review of some of the work done with solid 4He at the University of Massachusetts Amherst below a sample pressure of 28 bar. The motivation for the work has been to attempt to pass 4He atoms through solid 4He without directly applying mechanical pressure to the solid itself. The specific technique chosen is limited to pressures near the melting curve and was initially designed to provide a yes/no answer to the question of whether or not it might be possible to observe such a mass flux. The thermo-mechanical effect and direct mass injection have been separately used to create chemical potential differences between two reservoirs of superfluid 4He connected to each other through superfluid-filled Vycor rods in series with solid 4He, which is in the hcp region of the phase diagram. The thermo-mechanical effect is a more versatile approach. And, in a particular symmetric application it is designed to provide a mass flux with little or no net increase in the density of the solid. Our observations, off but near the melting curve, have included: (1) the presence of an increasing DC flux of atoms through the solid-filled cell with decreasing temperature below ≈650 mK and no flux above this temperature; (2) the presence of a flux minimum and flux instability in the vicinity of 75-80 mK, with a flux increase at lower temperatures; (3) the temperature dependence of the flux above 100 mK and the dependence of the flux on the net driving chemical potential difference provide interesting insights on the possible mechanism that leads to the flux above 100 mK. The most recent data suggest that whatever is responsible for the flux in solid 4He, at least for T>100 mK, may be an example of a Bosonic Luttinger liquid.

  11. Modelling of the OASIS Energy Flux Measurements Using Two Canopy Concepts

    NASA Astrophysics Data System (ADS)

    Finkele, K.; Katzfey, J.J.; Kowalczyk, E.A.; McGregor, J.L.; Zhang, L.; Raupach, M.R.

    Two land surface schemes, SCAM and CSIRO9, were used to model the measured energy fluxes during the OASIS (Observations At Several Interacting Scales) field program. The measurements were taken at six sites along a 100 km rainfall gradient. Two types of simulations were conducted: (1) offline simulations forced with measured atmospheric input data at each of the six sites, and (2) regional simulations with the two land surface schemes coupled to the regional climate model DARLAM.The two land surface schemes employ two different canopy modelling concepts: in SCAM the vegetation is conceptually above the ground surface, while CSIRO9 employs the more commonly used `horizontally tiled' approach in which the vegetation cover is modelled by conceptually placing it beside bare ground. Both schemes utilize the same below-ground components (soil hydrological and thermal models) to reduce the comparison to canopy processes only. However, the ground heat flux, soil evaporation and evapotranspiration are parameterised by the two canopy treatments somewhat differently.

  12. SIERRA-Flux: measuring regional surface fluxes of carbon dioxide, methane, and water vapor from an unmanned aircraft system

    NASA Astrophysics Data System (ADS)

    Fladeland, M. M.; Yates, E. L.; Bui, T. P.; Dean-Day, J. M.; Kolyer, R.; Schiro, K.; Berthold, R.; Iraci, L. T.; Loewenstein, M.

    2011-12-01

    The Eddy-Covariance Method for quantifying surface-atmosphere fluxes is a foundational technique for measuring net ecosystem exchange and validating regional-to-global carbon cycle models. While towers or ships are the more frequent platform for measuring surface-atmosphere exchange, experiments using aircraft for flux measurements have yielded contributions to several large-scale studies including BOREAS, SMACEX, RECAB by providing local-to-regional coverage beyond towers. The low-altitude flight requirements make airborne flux measurements particularly dangerous and well suited for unmanned aircraft. In a series of flights in June of 2011, the NASA SIERRA carried a payload consisting of the NASA Ames Meteorological Measurement System (MMS) and a fast response (10Hz) CO2, CH4, and H2O vapor analyzer in order to demonstrate the feasibility of measuring fluxes from unmanned aircraft and to characterize accuracy and precision based upon ground measurements. The flights were conducted in Railroad Valley, NV in order to provide a simple model for understanding biases and uncertainties. This paper describes the system specifications, provides preliminary data compared against coincident ground measurements, and discusses future applications of the system.

  13. BOREAS RSS-8 BIOME-BGC Model Simulations at Tower Flux Sites in 1994

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Nickeson, Jaime (Editor); Kimball, John

    2000-01-01

    BIOME-BGC is a general ecosystem process model designed to simulate biogeochemical and hydrologic processes across multiple scales (Running and Hunt, 1993). In this investigation, BIOME-BGC was used to estimate daily water and carbon budgets for the BOREAS tower flux sites for 1994. Carbon variables estimated by the model include gross primary production (i.e., net photosynthesis), maintenance and heterotrophic respiration, net primary production, and net ecosystem carbon exchange. Hydrologic variables estimated by the model include snowcover, evaporation, transpiration, evapotranspiration, soil moisture, and outflow. The information provided by the investigation includes input initialization and model output files for various sites in tabular ASCII format.

  14. Flux Growth of Large Single Crystals of YFe2Al10 by Nucleation Site Reduction

    NASA Astrophysics Data System (ADS)

    Kistner-Morris, Jedediah; Wu, Liusou; Gannon, William; Aronson, Meigan

    2014-03-01

    The metallic d-electron compound YFe2Al10 is near a quantum critical point. Large single crystals of this compound are required for inelastic neutron scattering experiments. We synthesized high quality single crystals via aluminum flux growth. A number of adjustments to the growth procedure were required to optimize crystal quality and size. First, the cooling rate of the flux growth was adjusted to produce a thermodynamically favorable environment for YFe2Al10 growth, which was found to grow around 920°C. Second, initial composition of the growths were then optimized to avoid the growth of the binary phases, YAl3 and Fe4Al13, as well as to maximize crystal size and reduce site nucleation. Third, site nucleation was further reduced by polishing the alumina growth crucibles with sandpaper and then etching them with aqua regia. The result after optimization is that individual growths produced three to five polyhedral crystals with single facets up to 9mm in width, and mass of about 700mg. The implemented nucleation site reduction techniques can be applied to other flux systems to increase crystal size and mass. We acknowledge the Office of Assistant Secretary of Defense for Research and Engineering for providing the NSSEFF funds that supported this research.

  15. Using Carbonyl Sulfide Column Measurements and a Chemical Transport Model to Investigate Variability in Biospheric CO2 Fluxes

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Palm, M.; Deutscher, N. M.; Warneke, T.; Notholt, J.; Baker, I. T.; Berry, J. A.; Suntharalingam, P.; Campbell, J. E.; Wolf, A.

    2014-12-01

    Understanding the CO2 processes on land is of great importance, because the terrestrial exchange drives the seasonal and interannual variability of CO2 in the atmosphere. Atmospheric inversions based on CO2 concentration measurements alone can only determine net biosphere fluxes, but not differentiate between photosynthesis (uptake) and respiration (production). Carbonyl sulfide (OCS) could provide an important additional constraint: it is also taken up by plants during photosynthesis but not emitted during respiration, and therefore is a potential means to differentiate between these processes. Solar absorption Fourier Transform InfraRed (FTIR) spectrometry allows for the retrieval of the atmospheric concentrations of both CO2 and OCS. Here, we investigate co-located and nearly simultaneous measurements of OCS and CO2 measured at 3 sites via FTIR spectrometers. These northern-hemispheric sites span a wide range of latitudes and all have multiple year time-series. The sites include Ny-Alesund (79°N), Bremen (53°N) and Paramaribo (6°N). We compare these measurements to simulations of OCS and CO2 using the GEOS-Chem model. The simulations are driven by different land biospheric fluxes of OCS and CO2 to match the seasonality of the measurements. The simple biosphere model (SiB-COS) are used in the study because it simultaneously calculates the biospheric fluxes of both OCS and CO2. The CO2 simulation with SiB fluxes agrees with the measurements better than a simulation using CASA. Comparison of the OCS simulations with different fluxes indicates that the latitudinal distribution of the OCS fluxes within SiB needs to be adjusted.

  16. Using Carbonyl Sulfide column measurements and a Chemical Transport Model to investigate variability in biospheric CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Wang, Yuting; Petri, Christof; Palm, Mathias; Warneke, Thorsten; Baker, Ian; Berry, Joe; Suntharalingam, Parvadha; Campbell, Elliott; Wolf, Adam; Deutscher, Nick; Notholt, Justus

    2015-04-01

    Understanding the CO2 processes on land is of great importance, because the terrestrial exchange drives the seasonal and interannual variability of CO2 in the atmosphere. Atmospheric inversions based on CO2 concentration measurements alone can only determine net biosphere fluxes, but not differentiate between photosynthesis (uptake) and respiration (production). Carbonyl sulfide (OCS) could provide an important additional constraint: it is also taken up by plants during photosynthesis but not emitted during respiration, and therefore is a potential means to differentiate between these processes. Solar absorption Fourier Transform InfraRed (FTIR) spectrometry allows for the retrieval of the atmospheric concentrations of both CO2 and OCS. Here, we investigate co-located and nearly simultaneous measurements of OCS and CO2 measured at 3 sites via FTIR spectrometers. These northern-hemispheric sites span a wide range of latitudes and all have multiple year time-series. The sites include Ny-Alesund (79°N), Bremen (53°N) and Paramaribo (6°N). We compare these measurements to simulations of OCS and CO2 using the GEOS-Chem model. The simulations are driven by different land biospheric fluxes of OCS and CO2 to match the seasonality of the measurements. The simple biosphere model (SiB-COS) are used in the study because it simultaneously calculates the biospheric fluxes of both OCS and CO2. The CO2 simulation with SiB fluxes agrees with the measurements better than a simulation using CASA. Comparison of the OCS simulations with different fluxes indicates that the latitudinal distribution of the OCS fluxes within SiB needs to be adjusted.

  17. LOW-POWER SOLUTION FOR EDDY COVARIANCE MEASUREMENTS OF METHANE FLUX

    NASA Astrophysics Data System (ADS)

    Anderson, T.; Burba, G. G.; Komissarov, A.; McDermitt, D. K.; Xu, L.; Zona, D.; Oechel, W. C.; Schedlbauer, J. L.; Oberbauer, S. F.; Riensche, B.; Allyn, D.

    2009-12-01

    Open-path analyzers offer a number of advantages for measuring methane fluxes, including undisturbed in-situ flux measurements, spatial integration using the Eddy Covariance approach, zero frequency response errors due to tube attenuation, confident water and thermal density terms from co-located fast measurements of water and sonic temperature, and possibility of remote and mobile solar-powered or small-generator-powered deployments due to lower power demands in the absence of a pump. The LI-7700 open-path methane analyzer is a VCSEL (vertical-cavity surface-emitting laser)-based instrument. It employs an open Herriott cell and measures levels of methane with RMS noise below 5 ppb at 10 Hz sampling in controlled laboratory conditions. The power consumption of the stand-alone LI-7700 in steady-state is about 8W, so it can be deployed in any methane-generating location of interest on a portable or mobile solar-powered tower, and it does not have to have grid power or permanent industrial generator. Eddy Covariance measurements of methane flux using the LI-7700 open-path methane analyzer were conducted in 2006-2009 in five ecosystems with contrasting weather and moisture conditions: (1) sawgrass wetland in the Florida Everglades; (2) coastal wetlands in an Arctic tundra; and (3) pacific mangroves in Mexico; (4) maize field and (5) ryegrass field in Nebraska. Methane co-spectra behaved in a manner similar to that of the co-spectra of carbon dioxide, water vapor, and air temperature, demonstrating that the LI-7700 adequately measured fluctuations in methane concentration across the whole spectrum of frequencies contributing to vertical atmospheric turbulent transport at the experimental sites. All co-spectra also closely followed the Kaimal model, and demonstrated good agreement with another methane co-spectrum obtained with a TDLS (Tunable Diode Laser Spectroscope; Unisearch Associates, Inc.) over a peatland. Overall, hourly methane fluxes ranged from near-zero at

  18. Eddy covariance measurements of the net turbulent methane flux in the city centre - results of 2-year campaign in Łódź, Poland

    NASA Astrophysics Data System (ADS)

    Pawlak, Włodzimierz; Fortuniak, Krzysztof

    2016-07-01

    To investigate temporal variability of methane (CH4) fluxes in an urban environment, air-surface exchange fluxes of CH4 were continuously measured using eddy covariance techniques at a city-centre site in Łódź, Poland, from July 2013 to August 2015. In the immediate vicinity of the measurement site, potential methane sources include vehicle traffic, dense sewerage infrastructure and natural gas networks. Sensible and latent heat fluxes have also been measured since 2000 and carbon dioxide fluxes since 2007 at this site. Upward CH4 fluxes dominated during the measurement period, indicating that the city centre is a net source of CH4 to the troposphere. The highest monthly fluxes were observed in winter (2.0 to 2.7 g m-2 month-1) and the lowest in summer (0.8 to 1.0 g m-2 month-1). Fluxes on working days were around 6 % higher than on weekends. The cumulative flux indicates that the city centre emitted a net quantity of nearly 18 g m-2 of CH4 in 2014. Stable values of the FCO2/ FCH4 ratio in months (minimum 2.41 × 10-3, maximum 5.3 × 10-3) and the lack of a clear annual course suggest comparable magnitude of both fluxes.

  19. CO2 Flux Measurement Uncertainty Estimates for NACP

    NASA Astrophysics Data System (ADS)

    Barr, A.; Hollinger, D.; Richardson, A. D.

    2009-12-01

    We evaluated the uncertainties in eddy-covariance net ecosystem exchange NEE, total ecosystem respiration RE and gross primary production GPP associated with (a) random measurement error and (b) uncertainties in the u* (friction velocity) threshold u*Th for all site-years in the NACP site-level synthesis. The analyses required automated evaluation of the u*Th filter used to identify and reject bad NEE measurements during low-turbulence periods at night. The u*Th detection algorithm was adapted from Papale et al. (2006), modified to use a standard change-point detection algorithm. Uncertainty in the u*Th was estimated by bootstrapping, conducted annually with 1,000 draws per site-year, then pooling all years and calculating the lower and upper 95% confidence intervals from the median and 2.5 and 97.5 percentiles of the pooled u*Th values. Random uncertainties in NEE, RE and GPP were estimated following Richardson et al. (2007). The NEE random uncertainty characteristic curve, which characterizes random uncertainty in NEE as a function of NEE, was estimated for each site-year based on the differences between the measured data and the output of a simple and robust gap-filling model. The estimation procedure began with synthetic NEE data generated by the gap-filling model, introduced gaps (as in the measured data after u*Th filtering), added synthetic noise (defined by the NEE random uncertainty characteristic curve using a Monte-Carlo approach), then filled the gaps in the noisy, gappy synthetic data. The process was repeated 1,000 times for each site-year, and the random uncertainty was estimated from median and the 2.5 and 97.5 percentiles of the gap-filled data. The uncertainties in NEE, RE and GPP associated with uncertainties in the u*Th were evaluated by running the gap-filling routine at 1,000 u*Th values, drawn randomly from the pooled annual bootstrapping estimates. This produced 1,000 realizations of the gap-filled NEE, RE and GPP time series. The

  20. Wide Range Neutron Flux Measuring Channel for Aerospace Application

    SciTech Connect

    Cibils, R. M.; Busto, A.; Gonella, J. L.; Martinez, R.; Chielens, A. J.; Otero, J. M.; Nunez, M.; Tropea, S. E.

    2008-01-21

    The use of classical techniques for neutron flux measurements in nuclear reactors involves the switching between several detection chains as the power grows up to 10 decades. In space applications where mass and size constraints are of key significance, such volume of hardware represents a clear disadvantage. Instead of requiring different instruments for each reactor operating range (start-up, ramping-up, and nominal power), a single instrument chain should be desirable. A Wide Range Neutron Detector (WRND) system, combining a classic pulse Counting Channel with a Campbell's theorem based Fluctuation Channel can be implemented for the monitoring and control of a space nuclear reactor. Such an instrument will allow for a reduction in the complexity of space-based nuclear instrumentation and control systems. In this presentation we will discuss the criteria and tradeoffs involved in the development of such a system. We will focus particularly on the characteristics of the System On Chip (SOC) and the DSP board used to implement this instrument.

  1. Eddy Covariance Flux Measurements of Pollutant Gases in the Mexico City Urban Area: a Useful Technique to Evaluate Emissions inventories

    NASA Astrophysics Data System (ADS)

    Velasco, E.; Grivicke, R.; Pressley, S.; Allwine, G.; Jobson, T.; Westberg, H.; Lamb, B.; Ramos, R.; Molina, L.

    2007-12-01

    Direct measurements of emissions of pollutant gases that include all major and minor emissions sources in urban areas are a missing requirement to improve and evaluate emissions inventories. The quality of an urban emissions inventory relies on the accuracy of the information of anthropogenic activities, which in many cases is not available, in particular in urban areas of developing countries. As part of the MCMA-2003 field campaign, we demonstrated the feasibility of using eddy covariance (EC) techniques coupled with fast-response sensors to measure fluxes of volatile organic compounds (VOCs) and CO2 from a residential district of Mexico City. Those flux measurements demonstrated to be also a valuable tool to evaluate the emissions inventory used for air quality modeling. With the objective to confirm the representativeness of the 2003 flux measurements in terms of magnitude, composition and diurnal distribution, as well to evaluate the most recent emissions inventory, a second flux system was deployed in a different district of Mexico City during the 2006 MILAGRO field campaign. This system was located in a busy district surrounded by congested avenues close to the center of the city. In 2003 and 2006 fluxes of olefins and CO2 were measured by the EC technique using a Fast Isoprene Sensor calibrated with a propylene standard and an open path Infrared Gas Analyzer (IRGA), respectively. Fluxes of aromatic and oxygenated VOCs were analyzed by Proton Transfer Reaction-Mass Spectroscopy (PTR-MS) and the disjunct eddy covariance (DEC) technique. In 2006 the number of VOCs was extended using a disjunct eddy accumulation (DEA) system. This system collected whole air samples as function of the direction of the vertical wind component, and the samples were analyzed on site by gas chromatography / flame ionization detection (GC-FID). In both studies we found that the urban surface is a net source of CO2 and VOCs. The diurnal patterns were similar, but the 2006 fluxes

  2. Ship-board Flux Measurements made during CalNex 2010

    NASA Astrophysics Data System (ADS)

    Wolfe, D. E.; Fairall, C. W.

    2010-12-01

    Air-Sea flux measurements were made from the research vessel Atlantis during the California Air Quality Study (CalNex 2010) off the California coast from San Diego to San Francisco (Fig. 1). Measurements included sensible and latent heat fluxes in conjunction with long and short-wave incoming solar radiation, total precipitable and liquid water, remote sensing of the clouds, and thermodynamic and wind profiles from radiosonde launches to capture the boundary layer structure. As can be seen in Fig. 1 a diverse and complicated set of data were collected in such regions as the harbors of San Diego, Los Angeles, and San Francisco, the Sacramento ship channel, coastal transects, and the open ocean. These measurements combined with the large suite of air chemistry measurements being made on the Atlantis as well as the many land-base sites will attempt to provide a detailed picture of the emissions, chemical processes, transport, and meteorology as they relate to California’s air quality and climate assessment. These data will be carefully analyzed to sort out the influence of the land, ocean, micro-climates, and the continually changing air-sea temperature differences on the boundary layer. Measurements from a W-band cloud radar will be used to better understand the cloud forcing in addition to providing comparisons with several aircraft overpasses and satellite observations.

  3. Carbon, Water and Heat Fluxes Comparison between Two Subtropical Mangroves Sites, Southeastern China

    NASA Astrophysics Data System (ADS)

    Liu, F.; Lin, G., Sr.; Lu, W.; Chen, H.

    2014-12-01

    Due to the numerous ecological services provided by mangroves and its vital ecological role, the monitor of mangrove ecosystem in China receives a growing concern. We deployed eddy covariance system and meteorological instrument to continuously monitor the exchange of CO2 flux, water vapor, heat flux and meteorological factors of mangrove ecosystem on Guangdong and Fujian province in 2012, namely GDGQ and FJYX. The major species of two sites were similar, and by 2012 were on average 2.8~3.3 m in height. Climatically, temperature, net radiation and rainfall have significant seasonal difference, all reaching peak values during the summer wet season. Based on the results available, two sites were strong carbon sink in annual scale. The cumulative NEP in GDGQ (667.92 g C m-2 year-1) was lower than that in FJYX (848.31 g C m-2 year-1), but respiration (Rd) was opposite, 1433.80 g C m-2 year-1 for GDGQ and 1345.13 g C m-2 year-1 for FJYX. Tidal inundation decreased nighttime Rd by ~0.82 μ mol m-2 s-1 in GDGQ and ~0.99 μ mol m-2 s-1 in FJYX. The diurnal patterns of sensible (Hs) and latent heat fluxes (LE) of two sites were both single peak, and peak values both occurred at 12:00~14:00. Hs of GDGQ was higher than FJYX during nighttime and lower in daytime, but LE of GDGQ was lower than FJYX during nighttime. Evapotranspiration (ET) of two sites presented similar seasonal pattern, reaching highest value in July and lowest value in January. ET of whole year were 892.66 mm and 1051.76mm for GDGQ and FJYX. Daily WUE was strong negatively correlated to salinity in in FJYX, but the pattern of GDGQ was less distinct. Due to its high salinity stress and long-time inundation, water use efficiency (WUE) of GDGQ was higher than FJYX in all months. Soil heat flux (G) was quite small when compared to other heat flux, but both had obvious diurnal pattern in two sites. G was positively correlated to air temperature and G variation range of GDGQ (-8.68 ~5.51 w m-2) was greater than

  4. Long-term measurements of CO2 flux and evapotranspiration in a Chihuahuan desert grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We measured CO2 and evapotranspiration (ET) fluxes above a Chihuahuan desert grassland from 1996 through 2001. Averaged across six years, this ecosystem was a source (positive flux)of CO2 in every month. Over that period, sustained periods of carbon uptake (negative flux)were rare. Averaged across a...

  5. Improving surface energy balance closure by reducing errors in soil heat flux measurement

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The flux plate method is the most commonly employed method for measuring soil heat flux (G) in surface energy balance studies. Although relatively simple to use, the flux plate method is susceptible to significant errors. Two of the most common errors are heat flow divergence around the plate and fa...

  6. Measurements of NO(x) and NO(y) concentrations and fluxes over Arctic tundra

    NASA Technical Reports Server (NTRS)

    Bakwin, Peter S.; Wofsy, Steven C.; Fan, Song-Miao; Fitzjarrald, David R.

    1992-01-01

    Measurements of the atmospheric concentrations of NO, NO2, total NO(y), and O3 were made during the NASA Arctic Boundary Layer Expedition (ABLE 3A) at a remote location in a tundra bog ecosystem in southeastern Alaska during the growing season (July-August 1988). Concentrations of NO(x) and NO(y) were found to be very low compared to other remote continental sites, indicating that anthropogenic influences were small at this site during this time of year. The NO(y) emission rate from the soil were 0.13 +/- 0.05 x 10 exp 9 molecules/sq cm/s. Direct measurements of the flux of total NO(y) were made for the first time, indicating downward flux of NO(y) at all times of day, with maximum deposition of 2.5 +/- 0.9 x 10 exp 9 molecules/sq cm/s in the afternoon. Deposition of HNO3 appears to dominate the atmosphere/surface exchange of NO(y). The mean dry deposition rate of NO(y) to the tundra was 1.8 +/- 1.0 x 10 exp 9 molecules/sq cm/s.

  7. Real-time soil flux measurements and calculations with CRDS + Soil Flux Processor: comparison among flux algorithms and derivation of whole system error

    NASA Astrophysics Data System (ADS)

    Alstad, K. P.; Venterea, R. T.; Tan, S. M.; Saad, N.

    2015-12-01

    Understanding chamber-based soil flux model fitting and measurement error is key to scaling soils GHG emissions and resolving the primary uncertainties in climate and management feedbacks at regional scales. One key challenge is the selection of the correct empirical model applied to soil flux rate analysis in chamber-based experiments. Another challenge is the characterization of error in the chamber measurement. Traditionally, most chamber-based N2O and CH4 measurements and model derivations have used discrete sampling for GC analysis, and have been conducted using extended chamber deployment periods (DP) which are expected to result in substantial alteration of the pre-deployment flux. The development of high-precision, high-frequency CRDS analyzers has advanced the science of soil flux analysis by facilitating much shorter DP and, in theory, less chamber-induced suppression of the soil-atmosphere diffusion gradient. As well, a new software tool developed by Picarro (the "Soil Flux Processor" or "SFP") links the power of Cavity Ring-Down Spectroscopy (CRDS) technology with an easy-to-use interface that features flexible sample-ID and run-schemes, and provides real-time monitoring of chamber accumulations and environmental conditions. The SFP also includes a sophisticated flux analysis interface which offers a user-defined model selection, including three predominant fit algorithms as default, and an open-code interface for user-composed algorithms. The SFP is designed to couple with the Picarro G2508 system, an analyzer which simplifies soils flux studies by simultaneously measuring primary GHG species -- N2O, CH4, CO2 and H2O. In this study, Picarro partners with the ARS USDA Soil & Water Management Research Unit (R. Venterea, St. Paul), to examine the degree to which the high-precision, high-frequency Picarro analyzer allows for much shorter DPs periods in chamber-based flux analysis, and, in theory, less chamber-induced suppression of the soil

  8. Mass Flux Measurements of Arsenic in Groundwater (Battelle Conference)

    EPA Science Inventory

    Concentration trends of arsenic are typically used to evaluate the performance of remediation efforts designed to mitigate arsenic contamination in groundwater. A complementary approach would be to track changes in mass flux of the contaminant through the subsurface, for exampl...

  9. On Using CO2 Concentration Measurements at Mountain top and Valley Locations in Regional Flux Studies.

    NASA Astrophysics Data System (ADS)

    de Wekker, S. F.; Song, G.; Stephens, B. B.

    2007-12-01

    Data from the Regional Atmospheric Continuous CO2 Network in the Rocky Mountains (Rocky RACCOON) are used to investigate atmospheric controls on temporal and spatial variability of CO2 in mountainous terrain and the usefulness of mountain top and valley measurement for the estimation of regional CO2 fluxes. Rocky RACCOON consists of four sites installed in fall of 2005 and spring of 2006: Niwot Ridge, near Ward, Colorado; Storm Peak Laboratory near Steamboat Springs, Colorado; Fraser Experimental Forest, near Fraser Colorado; and Hidden Peak, near Snowbird, Utah. The network uses the NCAR-developed Autonomous Inexpensive Robust CO2 Analyzer. These units measure CO2 concentrations at three levels on a tower, producing individual measurements every 2.5 minutes precise to 0.1 ppm CO2 and closely tied to the WMO CO2 scale. Three of the sites are located on a mountain top while one site is located in a valley. Initial analyses show interesting relationships between CO2 concentration and atmospheric parameters, such as wind speed and direction, temperature, and incoming solar radiation. The nature of these relationships is further investigated with an atmospheric mesoscale model. Idealized and realistic simulations are able to capture the observed behavior of spatial and temporal CO2 variability and reveal the responsible physical processes. The implications of the results and the value of the measurements for providing information on local to regional scale respiration and photosynthesis rates in the Rockies are discussed.

  10. Bayesian calibration of reactor neutron flux spectrum using activation detectors measurements: Application to CALIBAN reactor

    SciTech Connect

    Cartier, J.; Casoli, P.; Chappert, F.

    2013-07-01

    In this paper, we present calibration methods in order to estimate reactor neutron flux spectrum and its uncertainties by using integral activation measurements. These techniques are performed using Bayesian and MCMC framework. These methods are applied to integral activation experiments in the cavity of the CALIBAN reactor. We estimate the neutron flux and its related uncertainties. The originality of this work is that these uncertainties take into account measurements uncertainties, cross-sections uncertainties and model error. In particular, our results give a very good approximation of the total flux and indicate that neutron flux from MCNP simulation for energies above about 5 MeV seems to overestimate the 'real flux'. (authors)

  11. Calculations of automatic chamber flux measurements of methane and carbon dioxide using short time series of concentrations

    NASA Astrophysics Data System (ADS)

    Pirk, N.; Mastepanov, M.; Parmentier, F.-J. W.; Lund, M.; Crill, P.; Christensen, T. R.

    2015-09-01

    The closed chamber technique is widely used to measure the exchange of methane (CH4) and carbon dioxide (CO2) from terrestrial ecosystems. There is, however, large uncertainty about which model should be used to calculate the gas flux from the measured gas concentrations. Due to experimental uncertainties the robust linear regression model (first order polynomial) is often applied, even though theoretical considerations of the technique suggest the application of other, curvilinear models. High-resolution automatic chamber systems which sample gas concentrations several hundred times per flux measurement make it possible to resolve the curvilinear behavior and study the information imposed by the natural variability of the temporal concentration changes. We used more than 50 000 such flux measurements of CH4 and CO2 from five field sites located in peat forming wetlands to calculate fluxes with different models. The flux differences from independent linear estimates are generally found to be smaller than the local flux variability on the plot scale. The curvilinear behavior of the gas concentrations within the chamber is strongly influenced by wind driven chamber leakage, and less so by changing gas concentration gradients in the soil during chamber closure. Such physical processes affect both gas species equally, which makes it possible to isolate biochemical processes affecting the gases differently, such as photosynthesis limitation by chamber headspace CO2 concentrations under high levels of incoming solar radiation. We assess the possibility to exploit this effect for a partitioning of the net CO2 flux into photosynthesis and ecosystem respiration and argue that high-resolution automatic chamber measurements could be used for purposes beyond the estimation of the net gas flux.

  12. Reprint of: Carbon flux to the deep in three open sites of the Southern European Seas (SES)

    NASA Astrophysics Data System (ADS)

    Gogou, Alexandra; Sanchez-Vidal, Anna; Durrieu de Madron, Xavier; Stavrakakis, Spyros; Calafat, Antoni M.; Stabholz, Marion; Psarra, Stella; Canals, Miquel; Heussner, Serge; Stavrakaki, Ioanna; Papathanassiou, Evangelos

    2014-07-01

    In this study, we investigate the strength and efficiency of carbon sequestration in the Southern European Seas (SES), by analyzing the export of POC at three deep sites located in the Western Mediterranean Sea (WMED), the Eastern Mediterranean Sea (EMED) and the Black Sea (BS). We combine estimations of satellite and algorithm-generated primary production data, calculated POC fluxes out of the euphotic layer and POC fluxes measured by sediment traps at the mesopelagic and bathypelagic layers during a one year period, with an ultimate goal to obtain a better understanding of the functioning of the biological pump in the SES. Annual particulate primary production based on satellite estimations (SeaWiFS) at the three sites, averages 205, 145 and 225 gC m- 2 y- 1 at the WMED, EMED and BS, respectively. According to our findings, the fraction of primary production that is exported out of the euphotic zone in the SES ranges between 4.2% and 11.4%, while the fraction reaching the mesopelagic layer (1000-1400 m depth) ranges between 0.6% and 1.8%. Finally, the fraction of primary production exported at the bathypelagic layer (2000-2800 m depth) is found to be 0.6%, 0.3% and 1.4% in the WMED, EMED and BS, respectively. The role of various processes responsible for the replenishment of surface waters with nutrients, giving rise to productivity episodes and organic carbon export to depth at the three SES sites is considered.

  13. Assessment of CO2 fluxes and forest productivity (NPP/GPP) estimates from eddy covariance measurement and field observations

    NASA Astrophysics Data System (ADS)

    Anić, Mislav; Marjanović, Hrvoje; Zorana Ostrogović Sever, Maša; Barcza, Zoltán; Večenaj, Željko

    2016-04-01

    Eddy covariance (EC) measurements were carried out at the Jastrebarsko site, Croatia, in lowland forest dominated by pedunculate oak. For validation of CO2 fluxes measured with EC method bi-weekly field measurements of increment of 640 trees in 24 plots set in a 100m x 100m grid, height increment and litterfall have been used. In our work we compared annual productivity (GPP and NPP) assessments from EC measurements with field measurements. The comparison was made on a seven year dataset of measurements, spanning from 2008 to 2014. Also, flux dependence on groundwater level has been investigated. Results are showing that forest productivity estimates with EC method are in good agreement with the estimates from field measurements in the dry years. Agreement is slightly lower for years with high precipitation.

  14. Direct measurements of transport properties are essential for site characterization

    SciTech Connect

    Wright, J.; Conca, J.L.

    1994-08-01

    Direct measurements of transport parameters on subsurface sediments using, the UFA method provided detailed hydrostratigraphic mapping, and subsurface flux distributions at a mixed-waste disposal site at Hanford. Seven hundred unsaturated conductivity measurements on fifty samples were obtained in only six months total of UFA run time. These data are used to provide realistic information to conceptual models, predictive models and restoration strategies. The UFA instrument consists of an ultracentrifuge with a constant, ultralow flow pump that provides fluid to the sample surface through a rotating seal assembly and microdispersal system. Effluent from the sample is collected in a transparent, volumetrically-calibrated chamber at the bottom of the sample assembly. Using a strobe light, an observer can check the chamber while the sample is being centrifuged. Materials can be run in the UFA as recomposited samples or in situ samples can be subcored directly into the sample UFA chamber.

  15. Evaluating Source Area Contributions from Aircraft Flux Measurements Over Heterogeneous Land Using Large-Eddy Simulation

    NASA Astrophysics Data System (ADS)

    Bertoldi, Giacomo; Kustas, William P.; Albertson, John D.

    2013-05-01

    The estimation of spatial patterns in surface fluxes from aircraft observations poses several challenges in the presence of heterogeneous land cover. In particular, the effects of turbulence on scalar transport and the different behaviour of passive (e.g. water vapour) versus active (e.g. temperature) scalars may lead to large uncertainties in the source area/flux-footprint estimation for sensible ( H) and latent ( LE) heat-flux fields. This study uses large-eddy simulation (LES) of the land-atmosphere interactions to investigate the atmospheric boundary-layer (ABL) processes that are likely to create differences in airborne-estimated H and LE footprints. We focus on 32~m altitude aircraft flux observations collected over a study site in central Oklahoma during the Southern Great Plains experiment in 1997 (SGP97). Comparison between the aircraft data and traditional model estimates provide evidence of a difference in source area for turbulent sensible and latent heat fluxes. The LES produces reasonable representations of the observed fluxes, and hence provides credible evidence and explanation of the observed differences in the H and LE footprints. Those differences can be quantified by analyzing the change in the sign of the spatial correlation of the H and LE fields provided by the LES model as a function of height. Dry patterns in relatively moist surroundings are able to generate strong, but localized, sensible heating. However, whereas H at the aircraft altitude is still in phase with the surface, LE presents a more complicated connection to the surface as the dry updrafts force a convergence of the surrounding moist air. Both the observational and LES model evidence support the concept that under strongly advective conditions, H and LE measured at the top of the surface layer (≈50 m) can be associated with very different upwind source areas, effectively contradicting surface-layer self-similarity theory for scalars. The results indicate that, under certain

  16. Site-specific seasonal models of carbon fluxes in terrestrial biomes

    SciTech Connect

    King, A.W.; DeAngelis, D.L.

    1986-01-01

    A set of site-specific computer simulation models of seasonal terrestrial carbon exchange has been assembled from open-literature sources. This collection is designed to facilitate the development of biome-level models for each of the principal terrestrial vegetation biomes on earth, for their integration into a global model of seasonal CO/sub 2/ variation in the atmosphere. The models are described in sufficient detail that their underlying assumptions can be compared. Descriptions include the following aspects of each model: (1) the compartments; (2) the carbon fluxes between compartments; and (3) the climatic variables that drive the carbon fluxes. In particular, the functional forms of the dependencies of respiration and photosynthesis on the driving variables are described. The methods by which these models will be extrapolated to biome-level models are also discussed.

  17. Mercury Surface-Atmosphere Flux and Speciation Measurements in Barrow, Alaska, USA during the BROMEX campaign

    NASA Astrophysics Data System (ADS)

    Moore, C.; Steffen, A.; Obrist, D.; Staebler, R.; Douglas, T.; Nghiem, S.

    2012-04-01

    Atmospheric Mercury Depletion Events (AMDEs) during which gaseous elemental mercury is oxidized to gaseous oxidized mercury and then readily deposits to underlying snow and ice surfaces are an important concern for polar mercury loads. There are many unknown factors surrounding the causes and controls of AMDEs in the polar atmosphere, including the fate of the mercury once deposited, the degree to which AMDEs relate to bromine chemistry, and how sea ice dynamics and changes thereof may affect future Hg cycling. We show an experimental set-up and provide results from a portion of a new study, the Bromine, Ozone, and Mercury Experiment (BROMEX) in Barrow, Alaska, located 515 km north of the Arctic Circle along the coast of the Arctic Ocean. Our instrumentation is designed to characterize AMDEs and quantify atmospheric mercury and ozone emissions and depositions over seasonal sea ice near open ice leads. These areas, that are known to cause intensive halogen chemistry, are expected to increase as the expanse of perennial sea ice decreases. Our unique, portable, cold-weather tested experimental set-up, called the Out On The Ice (OOTI) system, allows for the quantification of atmospheric speciated mercury concentrations, along with gaseous elemental mercury and ozone surface fluxes. These fluxes are measured with a micrometeorological surface-flux tower over the seasonal sea ice. The systems are housed in well-insulated aluminum boxes that can be deployed and retrieved readily with snow machines. A second, equivalent set of instruments is deployed near the coast at an inland location. This second site allows us to quantify the atmospheric chemical gradients from the seasonal sea ice site close to the open ice lead to the coast. Auxiliary measurements of mercury and halogen concentrations in surface snow, ice, and diamond dust along a transect from the sea ice site to the inland site and daily samplings at each site are also included. This unique campaign will be provide

  18. Intercomparison of fast response commercial gas analysers for nitrous oxide flux measurements under field conditions

    NASA Astrophysics Data System (ADS)

    Rannik, Ü.; Haapanala, S.; Shurpali, N. J.; Mammarella, I.; Lind, S.; Hyvönen, N.; Peltola, O.; Zahniser, M.; Martikainen, P. J.; Vesala, T.

    2015-01-01

    of the same magnitude as the fluxes when N2O exchange was small at the measurement site. Both instruments based on continuous-wave quantum cascade laser, CW-TILDAS-CS and N2O / CO-23d, were able to determine the same sample of low N2O fluxes with a high mutual coefficient of determination at the 30 min averaging level and with minor systematic difference over the observation period of several months. This enables us to conclude that the new-generation instrumentation is capable of measuring small N2O exchange with high precision and accuracy at sites with low fluxes.

  19. Comparison of eddy covariance and modified Bowen ratio methods for measuring gas fluxes and implications for measuring fluxes of persistent organic pollutants

    NASA Astrophysics Data System (ADS)

    Bolinius, Damien Johann; Jahnke, Annika; MacLeod, Matthew

    2016-04-01

    Semi-volatile persistent organic pollutants (POPs) cycle between the atmosphere and terrestrial surfaces; however measuring fluxes of POPs between the atmosphere and other media is challenging. Sampling times of hours to days are required to accurately measure trace concentrations of POPs in the atmosphere, which rules out the use of eddy covariance techniques that are used to measure gas fluxes of major air pollutants. An alternative, the modified Bowen ratio (MBR) method, has been used instead. In this study we used data from FLUXNET for CO2 and water vapor (H2O) to compare fluxes measured by eddy covariance to fluxes measured with the MBR method using vertical concentration gradients in air derived from averaged data that simulate the long sampling times typically required to measure POPs. When concentration gradients are strong and fluxes are unidirectional, the MBR method and the eddy covariance method agree within a factor of 3 for CO2, and within a factor of 10 for H2O. To remain within the range of applicability of the MBR method, field studies should be carried out under conditions such that the direction of net flux does not change during the sampling period. If that condition is met, then the performance of the MBR method is neither strongly affected by the length of sample duration nor the use of a fixed value for the transfer coefficient.

  20. Measurement of photon flux with a miniature gas ionization chamber in a Material Testing Reactor

    NASA Astrophysics Data System (ADS)

    Fourmentel, D.; Filliatre, P.; Villard, J. F.; Lyoussi, A.; Reynard-Carette, C.; Carcreff, H.

    2013-10-01

    Nuclear heating measurements in Material Testing Reactors (MTR) are crucial for the design of the experimental devices and the prediction of the temperature of the hosted samples. Nuclear heating in MTR materials (except fuel) is mainly due to the energy deposition by the photon flux. Therefore, the photon flux is a key input parameter for the computer codes which simulate nuclear heating and temperature reached by samples/devices under irradiation. In the Jules Horowitz MTR under construction at the CEA Cadarache, the maximal expected nuclear heating levels will be about 15 to 18 W g-1 and it will be necessary to assess this parameter with the best accuracy. An experiment was performed at the OSIRIS reactor to combine neutron flux, photon flux and nuclear heating measurements to improve the knowledge of the nuclear heating in MTR. There are few appropriate sensors for selective measurement of the photon flux in MTR even if studies and developments are ongoing. An experiment, called CARMEN-1, was conducted at the OSIRIS MTR and we used in particular a gas ionization chamber based on miniature fission chamber design to measure the photon flux. In this paper, we detail Monte-Carlo simulations to analyze the photon fluxes with ionization chamber measurements and we compare the photon flux calculations to the nuclear heating measurements. These results show a good accordance between photon flux measurements and nuclear heating measurement and allow improving the knowledge of these parameters.

  1. Solid He: Progress, Status, and Outlook for Mass Flux Measurements

    NASA Astrophysics Data System (ADS)

    Hallock, R. B.

    2015-07-01

    After a brief introduction, what is provided there is brief summary of work with solid He done at the University of Massachusetts Amherst and an outlook for future work. What is presented here is based on a presentation made at the Quantum Gases Fluids and Solids Workshop in Sao Paulo, Brazil in August of 2014. Our work with solid He is aimed at the question: Can a sample cell filled with solid He support a mass flux through the cell? The answer, as will be shown here, is yes. Evidence for this from several types of experiments will be reviewed. There will be an emphasis on more recent work, work that explores how the flux observed depends on temperature and on the He impurity level. The behavior observed suggests that solid He may be an example of a material that demonstrates Bosonic Luttinger liquid behavior. The normalized He flux has a universal temperature dependence. The presence of He at different impurity levels shows that the He blocks the flux at a characteristic temperature. The behavior appears to be consistent with the cores of dislocations as the entity that carries the flux, but it is clear that more work needs to be done to fully understand solid He.

  2. A comparison of direct measurement and model simulation of total flux of volatile organic compounds from the subsurface to the atmosphere under natural field conditions

    NASA Astrophysics Data System (ADS)

    Tillman, Fred D.; Choi, Jee-Won; Smith, James A.

    2003-10-01

    Accurate quantification of natural attenuation of volatile organic compounds (VOCs) in groundwater requires an accounting of all VOC mass-loss processes, including volatilization into soil gas with ultimate transport to land surface and the atmosphere. This paper compares two methods of estimating VOC flux to the atmosphere. The first method measures VOC flux at land surface using a vertical flux chamber (VFC). The VFC has been shown in a previous laboratory study to reliably measure organic vapor fluxes from soil to the atmosphere that are caused by either gas phase diffusion or a combination of advection plus diffusion [, 2003]. The second method simulates VOC flux using a transient, one-dimensional gas flow and transport model incorporating the effects of gas phase diffusion, equilibrium air-water partitioning of organic vapors, and unsaturated zone airflow caused by atmospheric pressure changes (i.e., barometric pumping). Flux chamber measurements were made concurrently with field data measurements required for the flow and transport model at a trichloroethene (TCE)-contaminated field site. The two methods of VOC flux estimation provided comparable results in nine sets of field comparisons with the flux chamber estimating a lower flux during most of the time periods. Sensitivity analyses of model input parameters produce upper and lower bounds on best estimate flux simulations. Average VFC measurements fall within these upper and lower bounds of combined parameter values for all nine comparison events. The ease of use, lack of a priori site knowledge and accuracy of the VFC compared with the data-intensive flow and transport model suggests that direct measurement of VOC flux from the subsurface to the atmosphere at contaminated sites could become routine practice, providing important information to decision makers about the progress of monitored natural attenuation.

  3. The validation of the GEWEX SRB surface longwave flux data products using BSRN measurements

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    The longwave downward fluxes at the Earth's surface are a significant part of the products of the NASA GEWEX SRB (Surface Radiation Budget) project which has produced and archived a 24.5-year continuous record from July 1983 to December 2007 of global shortwave (SW) and longwave (LW) radiation fluxes at TOA and the surface from satellite measurements. The data are generated on a system of grid boxes ranging from 1° latitude by 1° longitude at lower latitudes to 1° latitude by 120° longitude next to the poles. The LW datasets, which are available as 3-hourly, 3-hourly-monthly, daily and monthly means, are produced from two sets of algorithms, the GEWEX LW (GLW) algorithm which is designated as primary and the Langley Parameterized LW (LPLA) algorithm which is designated as quality-check. The inputs of the latest versions, GLW (V3.1) and LPLA (V3.0), include the Geostationary Satellite system (GEOS) Version 4.0.3 meteorological information and cloud properties derived from the International Satellite Cloud Climatology Project (ISCCP) DX data. In this paper, we compare the LW downward fluxes at the Earth's surface from both algorithms against over 4000 site-months of the Baseline Surface Radiation Network (BSRN) data from among the 59 BSRN sites. The comparisons are made for the 3-hourly, daily and monthly means each for the entire record, and on a month-by-month basis as well as a site-by-site basis. It is found that the overall daily mean bias/RMS for the GLW (V3.1) and LPLA (V3.0) algorithms are, respectively, 1.1/22.1 and 4.6/22.8 W m-2, their monthly counterparts are, respectively, 0.9/11.1 and 4.5/12.9 W m-2. Anomaly time series for a subset of more continuous BSRN measurement data sets show a standard deviation of 2.3 W m-2 and a correlation of 0.82 indicating the accurate replication of month-to-month variability. Clusters of similar surface types are analyzed showing that the uncertainties are largest over the polar regions. Finally, Kolmogorov

  4. Galileo Probe Measurements of Thermal and Solar Radiation Fluxes in the Jovian Atmosphere

    NASA Technical Reports Server (NTRS)

    Sromovsky, L. A.; Collard, A. D.; Fry, P. M.; Orton, G. S.; Lemmon, M. T.; Tomasko, M. G.; Freedman, R. S.

    1998-01-01

    The Galileo probe net flux radiometer (NFR) measured radiation fluxes in Jupiter's atmosphere from about 0.44 to 14 bars, using five spectral channels to separate solar and thermal components. Onboard calibration results confirm that the NFR responded to radiation approximately as expected. NFR channels also responded to a superimposed thermal perturbation, which can be approximately removed using blind channel measurements and physical constraints. Evidence for the expected NH3 cloud was seen in the spectral character of spin-induced modulations of the direct solar beam signals. These results are consistent with an overlying cloud of small NH3 ice particles (0.5-0.75 microns in radius) of optical depth 1.5-2 at 0.5 microns. Such a cloud would have so little effect on thermal fluxes that NFR thermal channels provide no additional constraints on its properties. However, evidence for heating near 0.45 bar in the NFR thermal channels would seem to require either an additional opacity source beyond this small-particle cloud, implying a heterogeneous-cloud structure to avoid conflicts with solar modulation results, or a change in temperature lapse rate just above the probe measurements. The large thermal flux levels imply water vapor mixing ratios that are only 6% of solar at 10 bars, but possibly increasing with depth, and significantly subsaturated ammonia at pressures less than 3 bars. If deep NH3 mixing ratios at the probe entry site are 3-4 times ground-based inferences, as suggested by probe radio signal attenuation, then only half as much water is needed to match NFR observations. No evidence of a water cloud was seen near the 5-bar level. The 5 microns thermal channel detected the presumed NH4SH cloud base near 1.35 bars. Effects of this cloud were also seen in the solar channel upflux measurements but not in the solar net fluxes, implying that the cloud is a conservative scatterer of sunlight. The minor thermal signature of this cloud is compatible with

  5. Galileo Probe Measurements of Thermal and Solar Radiation Fluxes in the Jovian Atmosphere

    NASA Technical Reports Server (NTRS)

    Sromovsky, L. A.; Collard, A. D.; Fry, P. M.; Orton, G. S.; Lemmon, M. T.; Tomasko, M. G.; Freedman, R. S.

    1998-01-01

    The Galileo probe net flux radiometer (NFR) measured radiation fluxes in Jupiter's atmosphere from about 0.44 to 14 bars, using five spectral channels to separate solar and thermal components. Onboard calibration results confirm that the NFR responded to radiation approximately as expected. NFR channels also responded to a superimposed thermal perturbation, which can be approximately removed using blind channel measurements and physical constraints. Evidence for the expected NH3 cloud was seen in the spectral character of spin-induced modulations of the direct solar beam signals. These results are consistent with an overlying cloud of small NH3 ice particles (0.5-0.75 microns in radius) of optical depth 1.5-2 at 0.5 microns. Such a cloud would have so little effect on thermal fluxes that NFR thermal channels provide no additional constraints on its properties. However, evidence for heating near 0.45 bar in the NFR thermal channels would seem to require either an additional opacity source beyond this small-particle cloud, implying a heterogeneous cloud structure to avoid conflicts with solar modulation results, or a change in temperature lapse rate just above the probe measurements. The large thermal flux levels imply water vapor mixing ratios that are only 6% of solar at 10 bars, but possibly increasing with depth, and significantly subsaturated ammonia at pressures less than 3 bars. If deep NH3 mixing ratios at the probe entry site are 3-4 times ground-based inferences, as suggested by probe radio signal attenuation, then only half as much water is needed to match NFR observations. No evidence of a water cloud was seen near the 5-bar level. The 5-microns thermal channel detected the presumed NH4SH cloud base near 1.35 bars. Effects of this cloud were also seen in the solar channel upflux measurements but not in the solar net fluxes, implying that the cloud is a conservative scatterer of sunlight. The minor thermal signature of this cloud is compatible with

  6. Significance of multidimensional radiative transfer effects measured in surface fluxes at an Antarctic coastline

    NASA Astrophysics Data System (ADS)

    Lubin, Dan; Ricchiazzi, Paul; Payton, Allison; Gautier, Catherine

    2002-10-01

    At a coastal high-latitude site, multiple reflection of photons between the high albedo surface and an overlying cloud can enhance the downwelling shortwave flux out over the adjacent open water to a distance of several kilometers. This coastal albedo effect has been predicted by theoretical radiative transfer studies and has also been measured under ideal conditions. In this study, three multispectral solar ultraviolet radiometers were deployed in the vicinity of Palmer Station, Antarctica (64° 46'S, 64° 04'W) to determine the prevalence of the coastal albedo effect under the region's natural variability in cloud cover. One radiometer was deployed near the base of a glacier, and the other two radiometers were deployed on Janus Island and Outcast Island, islets ˜2.8 km (1.5 nautical miles) and 5.6 km (3 nautical miles) distant from Palmer Station, respectively. The radiometers were operated simultaneously for 16 days during late December 1999 and January 2000. Under all cloudy sky conditions sampled by this experiment the coastal albedo effect is seen in the data 60% of the time, in the form of a decreasing gradient in surface flux from Palmer Station through Janus and Outcast Islands. During the other 40% of the cloudy sky measurements, local cloud inhomogeneity obscured the coastal albedo effect. The effect is more apparent under overcast layers that appear spatially uniform and occurs 86% of the time under the low overcast decks sampled. The presence of stratus fractus of bad weather, under higher overcast layers, obscures the coastal albedo effect such that it occurs only 43% of the time. A wavelength dependence is noted in the data under optically thin cloud cover: the ratio of a flux measured at an islet to that measured at the station increases with wavelength. This wavelength dependence can be explained by plane-parallel radiative transfer theory.

  7. So close, so different: geothermal flux shapes divergent soil microbial communities at neighbouring sites.

    PubMed

    Gagliano, A L; Tagliavia, M; D'Alessandro, W; Franzetti, A; Parello, F; Quatrini, P

    2016-03-01

    This study is focused on the (micro)biogeochemical features of two close geothermal sites (FAV1 and FAV2), both selected at the main exhalative area of Pantelleria Island, Italy. A previous biogeochemical survey revealed high CH4 consumption and the presence of a diverse community of methanotrophs at FAV2 site, whereas the close site FAV1 was apparently devoid of methanotrophs and recorded no CH4 consumption. Next-Generation Sequencing (NGS) techniques were applied to describe the bacterial and archaeal communities which have been linked to the physicochemical conditions and the geothermal sources of energy available at the two sites. Both sites are dominated by Bacteria and host a negligible component of ammonia-oxidizing Archaea (phylum Thaumarchaeota). The FAV2 bacterial community is characterized by an extraordinary diversity of methanotrophs, with 40% of the sequences assigned to Methylocaldum, Methylobacter (Gammaproteobacteria) and Bejerickia (Alphaproteobacteria); conversely, a community of thermo-acidophilic chemolithotrophs (Acidithiobacillus, Nitrosococcus) or putative chemolithotrophs (Ktedonobacter) dominates the FAV1 community, in the absence of methanotrophs. Since physical andchemical factors of FAV1, such as temperature and pH, cannot be considered limiting for methanotrophy, it is hypothesized that the main limiting factor for methanotrophs could be high NH4(+) concentration. At the same time, abundant availability of NH4(+) and other high energy electron donors and acceptors determined by the hydrothermal flux in this site create more energetically favourable conditions for chemolithotrophs that outcompete methanotrophs in non-nitrogen-limited soils. PMID:26560641

  8. Spatial source attribution of measured urban eddy covariance CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Crawford, B.; Christen, A.

    2015-02-01

    Interpretation of tower-based eddy covariance (EC) carbon dioxide flux ( F C ) measurements in urban areas is challenging because of the location bias of EC instruments. This bias results from EC point measurements taken above a complex CO2 source/sink surface that is spatially heterogeneous at scales approaching or exceeding those of the turbulent flux source areas. This makes it difficult to accomplish traditional measurement objectives such as calculating spatially unbiased ecosystem-wide cumulative F C totals or objectively comparing F C during different environmental conditions (e.g., day vs. night or seasonal differences). This study uses a multiyear F C dataset measured over a residential area of Vancouver, BC, Canada from a 30-m flux tower in close proximity to a busy traffic intersection on one side. The F C measurements are analyzed using surface geospatial data and turbulent flux source area models to exploit location bias to develop methods to statistically model individual emissions and uptake processes in terms of environmental controls and surface land cover. The empirical relations between controls and measured F C are used to spatially and temporally downscale individual CO2 emissions/uptake processes that are then used to create high-resolution maps (20 m) and calculate ecosystem-wide F C at temporal resolutions of 30 min to 1 year. At this site, the modeled ecosystem-wide annual net F C total is calculated as 6.42 kg C m-2 year-1 with traffic emissions estimated to account for 68.8 % of the total net emissions. Building sources contribute 27.9 %, respiration from soil and vegetation is 5.5 %, respiration from humans 5.0 %, and photosynthesis offsets are -7.2 % of the annual net total. The statistical models developed here are then tested by direct comparison to independent EC measurements using land cover scalings derived from 30-min source area models. Results are also scaled to ecosystem-averaged land cover to compare results to independent

  9. Uncertainties in Eddy Covariance fluxes due to post-field data processing: a multi-site, full factorial analysis

    NASA Astrophysics Data System (ADS)

    Sabbatini, S.; Fratini, G.; Arriga, N.; Papale, D.

    2012-04-01

    Eddy Covariance (EC) is the only technologically available direct method to measure carbon and energy fluxes between ecosystems and atmosphere. However, uncertainties related to this method have not been exhaustively assessed yet, including those deriving from post-field data processing. The latter arise because there is no exact processing sequence established for any given situation, and the sequence itself is long and complex, with many processing steps and options available. However, the consistency and inter-comparability of flux estimates may be largely affected by the adoption of different processing sequences. The goal of our work is to quantify the uncertainty introduced in each processing step by the fact that different options are available, and to study how the overall uncertainty propagates throughout the processing sequence. We propose an easy-to-use methodology to assign a confidence level to the calculated fluxes of energy and mass, based on the adopted processing sequence, and on available information such as the EC system type (e.g. open vs. closed path), the climate and the ecosystem type. The proposed methodology synthesizes the results of a massive full-factorial experiment. We use one year of raw data from 15 European flux stations and process them so as to cover all possible combinations of the available options across a selection of the most relevant processing steps. The 15 sites have been selected to be representative of different ecosystems (forests, croplands and grasslands), climates (mediterranean, nordic, arid and humid) and instrumental setup (e.g. open vs. closed path). The software used for this analysis is EddyPro™ 3.0 (www.licor.com/eddypro). The critical processing steps, selected on the basis of the different options commonly used in the FLUXNET community, are: angle of attack correction; coordinate rotation; trend removal; time lag compensation; low- and high- frequency spectral correction; correction for air density

  10. SIGNAL : Water vapour flux variability and local wind field investigations within five differently managed agroforestry sites across Germany

    NASA Astrophysics Data System (ADS)

    Markwitz, Christian; Siebicke, Lukas; Knohl, Alexander

    2016-04-01

    Optimising soil water uptake and ground water consumption in mono-specific agricultural systems plays an important role for sustainable land management. By including tree alleys into the agricultural landscape, called agroforestry (AF), the wind flow is modified leading to a presumably favourable microclimate behind the tree alleys. We expect that this zone is characterized by increased air temperature and atmospheric water vapour content, compared to mono-specific fields. This would extend the growing season and increase the yield production behind the tree alleys. Within the SIGNAL (Sustainable Intensification of Agriculture through Agroforestry) project the evapotranspiration (ET) variability and the local wind field of agroforestry sites compared to mono-specific agricultural systems is investigated. Our study is based on the comparison of five differently managed agroforestry sites across Germany. All site feature one agroforestry plot and one reference plot, which represents a mono-specific cropped system. Each plot is equipped with an eddy-covariance tower, including a high frequency 3D SONIC anemometer and instruments gathering standard meteorological parameter as pressure, temperature, relative humidity, precipitation, ground heat flux, net- and global radiation. The Surface Energy Budget (SEB) method will be used to calculate evapotranspiration QE as QE = ‑ QN ‑ QH ‑ QG ‑ Res by measuring the sensible heat flux, QH, with the eddy covariance method, the radiation balance, QN and the ground heat flux, QG. QH and QN will be measured continuously long-term. We will quantify site specific energy balance non-closure, Res, by temporarily measuring QE, using eddy covariance and a roving tower and then solving the SEB equation for Res. The short term Res will be used to then continuously derive QE from the SEB method. We will compare measured evapotranspiration rates from the SEB method to modelled evapotranspiration of the agroforestry systems through

  11. Methane fluxes measured by eddy covariance and static chamber techniques at a temperate forest in central ontario, Canada

    NASA Astrophysics Data System (ADS)

    Wang, J. M.; Murphy, J. G.; Geddes, J. A.; Winsborough, C. L.; Basiliko, N.; Thomas, S. C.

    2012-12-01

    Methane flux measurements were carried out at a temperate forest (Haliburton Forest and Wildlife Reserve) in central Ontario (45°17´11´´ N, 78°32´19´´ W) from June-October, 2011. Continuous measurements were made by an off-axis integrated cavity output spectrometer Fast Greenhouse Gas Analyzer (FGGA) from Los Gatos Research Inc. that measures methane (CH4) at 10 Hz sampling rates. Fluxes were calculated from the gas measurements in conjunction with wind data collected by a 3-D sonic anemometer using the eddy covariance (EC) method. Observed methane fluxes showed net uptake of CH4 over the measurement period with an average uptake flux (± standard deviation of the mean) of -2.7 ± 0.13 nmol m-2 s-1. Methane fluxes showed a seasonal progression with average rates of uptake increasing from June through September and remaining high in October. This pattern was consistent with a decreasing trend in soil moisture content at the monthly time scale. On the diurnal timescale, there was evidence of increased uptake during the day, when the mid-canopy wind speed was at a maximum. These patterns suggest that substrate supply of CH4 and oxygen to methanotrophs, and in certain cases hypoxic soil conditions supporting methanogenesis in low-slope areas, drive the observed variability in fluxes. A network of soil static chambers used at the tower site showed close agreement with the eddy covariance flux measurements. This suggests that soil-level microbial processes, and not abiological leaf-level CH4 production, drive overall CH4 dynamics in temperate forest ecosystems such as Haliburton Forest.

  12. Scaling up of Carbon Exchange Dynamics from AmeriFlux Sites to a Super-Region in the Eastern United States

    SciTech Connect

    Hans Peter Schmid; Craig Wayson

    2009-05-05

    The primary objective of this project was to evaluate carbon exchange dynamics across a region of North America between the Great Plains and the East Coast. This region contains about 40 active carbon cycle research (AmeriFlux) sites in a variety of climatic and landuse settings, from upland forest to urban development. The core research involved a scaling strategy that uses measured fluxes of CO{sub 2}, energy, water, and other biophysical and biometric parameters to train and calibrate surface-vegetation-atmosphere models, in conjunction with satellite (MODIS) derived drivers. To achieve matching of measured and modeled fluxes, the ecosystem parameters of the models will be adjusted to the dynamically variable flux-tower footprints following Schmid (1997). High-resolution vegetation index variations around the flux sites have been derived from Landsat data for this purpose. The calibrated models are being used in conjunction with MODIS data, atmospheric re-analysis data, and digital land-cover databases to derive ecosystem exchange fluxes over the study domain.

  13. New technique of the local heat flux measurement in combustion chambers of steam boilers

    NASA Astrophysics Data System (ADS)

    Taler, Jan; Taler, Dawid; Sobota, Tomasz; Dzierwa, Piotr

    2011-12-01

    A new method for measurement of local heat flux to water-walls of steam boilers was developed. A flux meter tube was made from an eccentric tube of short length to which two longitudinal fins were attached. These two fins prevent the boiler setting from heating by a thermal radiation from the combustion chamber. The fins are not welded to the adjacent water-wall tubes, so that the temperature distribution in the heat flux meter is not influenced by neighbouring water-wall tubes. The thickness of the heat flux tube wall is larger on the fireside to obtain a greater distance between the thermocouples located inside the wall which increases the accuracy of heat flux determination. Based on the temperature measurements at selected points inside the heat flux meter, the heat flux absorbed by the water-wall, heat transfer coefficient on the inner tube surface and temperature of the water-steam mixture was determined.

  14. Airborne eddy correlation gas flux measurements - Design criteria for optical techniques

    NASA Technical Reports Server (NTRS)

    Ritter, John A.; Sachse, Glen W.; Anderson, Bruce E.

    1993-01-01

    Although several methods exist for the determination of the flux of an atmospheric species, the airborne eddy correlation method has the advantage of providing direct flux measurements that are representative of regional spatial domains. The design criteria pertinent to the construction of chemical instrumentation suitable for use in airborne eddy correlation flux measurements are discussed. A brief overview of the advantages and limitations of the current instrumentation used to obtain flux measurements for CO, CH4, O3, CO2, and water vapor are given. The intended height of the measurement within the convective boundary layer is also shown to be an important design criteria. The sensitivity, or resolution, which is required in the measurement of a scalar species to obtain an adequate species flux measurement is discussed. The relationship between the species flux resolution and the more commonly stated instrumental resolution is developed and it is shown that the standard error of the flux estimate is a complicated function of the atmospheric variability and the averaging time that is used. The use of the recently proposed intermittent sampling method to determine the species flux is examined. The application of this technique may provide an opportunity to expand the suite of trace gases for which direct flux measurements are possible.

  15. Sensitivity of model parameterizations for simulated latent heat flux at the snow surface for complex mountain sites

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The snowcover energy balance is typically dominated by net radiation and sensible and latent heat fluxes. Validation of the two latter components is rare and often difficult to undertake at complex mountain sites. Latent heat flux, the focus of this paper, is the primary coupling mechanism between...

  16. Use of CMOS imagers to measure high fluxes of charged particles

    NASA Astrophysics Data System (ADS)

    Servoli, L.; Tucceri, P.

    2016-03-01

    The measurement of high flux charged particle beams, specifically at medical accelerators and with small fields, poses several challenges. In this work we propose a single particle counting method based on CMOS imagers optimized for visible light collection, exploiting their very high spatial segmentation (> 3 106 pixels/cm2) and almost full efficiency detection capability. An algorithm to measure the charged particle flux with a precision of ~ 1% for fluxes up to 40 MHz/cm2 has been developed, using a non-linear calibration algorithm, and several CMOS imagers with different characteristics have been compared to find their limits on flux measurement.

  17. Heat flux measurement from vertical temperature profile and thermal infrared imagery in low-flux fumarolic zones

    NASA Astrophysics Data System (ADS)

    Gaudin, Damien; Finizola, Anthony; Beauducel, François; Brothelande, Elodie; Allemand, Pascal; Delacourt, Christophe; Delcher, Eric; Peltier, Aline

    2014-05-01

    Hydrothermal systems are associated to most of the dormant volcanoes. Heat is transported by steam from the hot magma body in the connected porosity and the fissures of the rock to the surface. If the flux is low enough (<500 W/m²), the steam mainly condensates in the soil close to surface, and a significant proportion of the heat is transported to the surface by conduction, producing a gradient of temperature and a thermal anomaly detectable at the surface. Detecting and monitoring these fluxes is crucial for hazard management, since it reflects the state of the magma body in depth. In order to quantify this flux two methods are considered. First, a vertical profile of temperature is measured by a series of thermocouples, and the conducted flux is estimated thanks to the Fourier law. Secondly, a more recent method uses the thermal infrared imagery to monitor the surface temperature anomaly (STA) between the studied zone and an equivalent zone not affected by the geothermal flux. The heat flux from the soil to the atmosphere is computed as the sum of (1) the radiative flux, (2) the sensible flux and (3) the residual steam flux. These two methods are complementary and have an equivalent uncertainty of approximately 20%, which would allow to track the major changes in the hydrothermal system. However, the surface and sub-surface temperatures are strongly influenced by the climate. For instance, it has been widely demonstrated that the surface temperature dramatically decreases after a rainfall. In order to estimate the reliability of the measurements, a numerical model simulating the evolution of the subsurface temperature in low flux fumarolic zone has been built. In depth, the heat can be transported either by conduction, or by the rising steam, or by condensed water. In surface, both the radiative flux and the sensible flux (convection of the atmosphere) are taken into account. This model allows to estimate the changes of temperature due to a variation of solar

  18. Thermal flux measurements in hypersonic flows: A review

    NASA Astrophysics Data System (ADS)

    Wendt, J. F.; Balageas, D.; Neumann, R. D.

    1993-04-01

    This contribution reviews the papers presented in the Session on 'Heat Flux' and 'Thermography' at a NATO Advanced Research Workshop entitled 'New Trends in Instrumentation for Hypersonic Research', 27 April-1 May, 1992, Le Fauga, France. The present status and problem areas associated with specific methods are discussed and recommendations for future research and development are presented.

  19. DYNAMIC FLUX CHAMBER SYSTEMS FOR FUMIGANT EMISSION MEASUREMENTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Assessment of effective field practices on emission reductions from soil fumigation relies on continuous and reliable emission data. Dynamic (flow through) flux chambers can provide continuous sampling for fumigants volatilized from the soil surface. The objective of this project was to design and c...

  20. Long-term elemental dry deposition fluxes measured around Lake Michigan with an automated dry deposition sampler

    SciTech Connect

    Shahin, U. Yi, S.M.; Paode, R.D.; Holsen, T.M.

    2000-05-15

    Long-term measurements of mass and elemental dry deposition (MG, Al, V, Cr, Mn, Ni, Co, Cu, Zn, As, Sr, Mo, Cd, Sb, Ba, and Pb) were made with an automated dry deposition sampler (Eagle II) containing knife-edge surrogate surfaces during the Lake Michigan Mass Balance/Mass Budget Study. Measurements were made over a roughly 700-day period in Chicago, IL; in South Haven and Sleeping Bear Dunes, MI; and over Lake Michigan on the 68th Street drinking water intake cribs from December 1993 to October 1995. Average mass fluxes in Chicago, South Haven, Sleeping Bear Dunes, and the 68th Street crib were 65, 10, 3.6, and 12 mg m{sup {minus}2} day{sup {minus}1}, respectively. Primarily crustal elemental fluxes were significantly smaller than the mass fluxes but higher than primarily anthropogenic elemental fluxes. For example, the average elemental flux of Al in Chicago, South Haven, Sleeping Bear Dunes, and the 68th Street crib were 1.0, 0.34, 0.074, and 0.34 mg m{sup {minus}2}day{sup {minus}1}, respectively. The average Pb fluxes in Chicago, South Haven, Sleeping Bear Dunes, and the 68th Street crib were 0.038, 0.023, 0.035, and 0.032 mg m{sup {minus}2}day{sup {minus}1}, respectively. The measured fluxes at the various sites were used to calculate the dry deposition loadings to the lake. These estimated fluxes were highest for Mg and lowest for Cd.

  1. Eddy covariance flux measurements of gaseous elemental mercury using cavity ring-down spectroscopy.

    PubMed

    Pierce, Ashley M; Moore, Christopher W; Wohlfahrt, Georg; Hörtnagl, Lukas; Kljun, Natascha; Obrist, Daniel

    2015-02-01

    A newly developed pulsed cavity ring-down spectroscopy (CRDS) system for measuring atmospheric gaseous elemental mercury (GEM) concentrations at high temporal resolution (25 Hz) was used to successfully conduct the first eddy covariance (EC) flux measurements of GEM. GEM is the main gaseous atmospheric form, and quantification of bidirectional exchange between the Earth's surface and the atmosphere is important because gas exchange is important on a global scale. For example, surface GEM emissions from natural sources, legacy emissions, and re-emission of previously deposited anthropogenic pollution may exceed direct primary anthropogenic emissions. Using the EC technique for flux measurements requires subsecond measurements, which so far has not been feasible because of the slow time response of available instrumentation. The CRDS system measured GEM fluxes, which were compared to fluxes measured with the modified Bowen ratio (MBR) and a dynamic flux chamber (DFC). Measurements took place near Reno, NV, in September and October 2012 encompassing natural, low-mercury (Hg) background soils and Hg-enriched soils. During nine days of measurements with deployment of Hg-enriched soil in boxes within 60 m upwind of the EC tower, the covariance of GEM concentration and vertical wind speed was measured, showing that EC fluxes over an Hg-enriched area were detectable. During three separate days of flux measurements over background soils (without Hg-enriched soils), no covariance was detected, indicating fluxes below the detection limit. When fluxes were measurable, they strongly correlated with wind direction; the highest fluxes occurred when winds originated from the Hg-enriched area. Comparisons among the three methods showed good agreement in direction (e.g., emission or deposition) and magnitude, especially when measured fluxes originated within the Hg-enriched soil area. EC fluxes averaged 849 ng m(-2) h(-1), compared to DFC fluxes of 1105 ng m(-2) h(-1) and MBR fluxes

  2. MARIE Dose and Flux Measurements in Mars Orbit

    NASA Technical Reports Server (NTRS)

    Zeitlin, C.; Cleghorn, T.; Cucinotta, F. A.; Saganti, P.; Andersen, V.; Lee, K. T.; Pinsky, L. S.; Turner, R.; Atwell, W.

    2004-01-01

    We present results from the Martian Radiation Environment Experiment (MARIE), aboard the 2001 Mars Odyssey spacecraft in orbit around Mars. MARIE operated successfully from March 2002 through October 2003. At the time of this writing, the instrument is off due to a loss of communications during an extremely intense Solar Particle Event. Efforts to revive MARIE are planned for Spring 2004, when Odyssey's role as a communications relay for the MER rovers is completed. During the period of successful operation, MARIE returned the first detailed energetic charged particle data from Mars. Due to limitations of the instrument, normalizing MARIE data to flux or dose is not straightforward - several large corrections are needed. Thus normalized results (like dose or flux) have large uncertainties and/or significant model-dependence. The problems in normalization are mainly due to inefficiency in detecting high-energy protons (signal-to-noise problems force the trigger threshold to be higher than optimal), to the excessively high gains employed in the signal processing electronics (many ions deposit energy sufficient to saturate the electronics, and dE/dx information is lost), and to artifacts associated with the two trigger detectors (incomplete registration of dE/dx). Despite these problems, MARIE is efficient for detecting helium ions with kinetic energies above about 30 MeV/nucleon, and for detecting high-energy ions (energies above about 400 MeV/nucleon) with charges from 5 to 10. Fluxes of these heavier ions can be compared to fluxes obtained from the ACE/CRIS instrument, providing at least one area of direct comparison between data obtained at Earth and at Mars; this analysis will be presented as a work in progress. We will also present dose-rate data, with a detailed explanation of the many sources of uncertainty in normalization. The results for both flux and dose will be compared to predictions of the HZETRN model of the GCR.

  3. Proteome and carbon flux analysis of Pseudomonas aeruginosa clinical isolates from different infection sites.

    PubMed

    Lassek, Christian; Berger, Antje; Zühlke, Daniela; Wittmann, Christoph; Riedel, Katharina

    2016-05-01

    Pseudomonas aeruginosa is known as opportunistic pathogen frequently isolated from different infection sites. To investigate the expression rates of P. aeruginosa proteins commonly expressed by different clinical isolates, absolute protein quantities were determined employing a gel-free and data-independent LC-IMS(E) approach. Moreover, the metabolic diversity of these isolates was investigated by (13) C-metabolic flux analyses. 812 proteins were reproducibly identified and absolutely quantified for the reference strain P. aeruginosa PAO1, 363 of which were also identified and relatively quantified in all isolates. Whilst the majority of these proteins were expressed in constant amounts, expression rates of 42 proteins were highly variable between the isolates. Notably, the outer membrane protein OprH and the response regulator PhoP were strongly expressed in burned wounds isolates compared to lung/urinary tract isolates. Moreover, proteins involved in iron/amino acids uptake were found to be highly abundant in urinary tract isolates. The fluxome data revealed a conserved glycolysis, and a niche-specific divergence in fluxes through the glyoxylate shunt and the TCA cycle among the isolates. The integrated proteome/fluxome analysis did not indicate straightforward correlation between the protein amount and flux, but rather points to additional layers of regulation that mediate metabolic adaption of P. aeruginosa to different host environments. All MS data have been deposited in the ProteomeXchange with identifier PXD002373 (http://proteomecentral.proteomexchange.org/dataset/PXD002373). PMID:26959854

  4. The altitude variation of the ionospheric photoelectron flux A comparison of theory and measurement

    NASA Technical Reports Server (NTRS)

    Richards, P. G.; Torr, D. G.

    1985-01-01

    The 145 to 300-km altitude variation of the measured photoelectron flux in the 13 to 18 eV, 28 to 34 eV, and 50 to 55 eV energy regions are compared with the variations expected from theory. There is a strong linear relationship between the measured photoelectron flux and the attenuation of the solar EUV flux at these energies. Therefore, the photoelectron flux is sensitive to changes in the solar zenith angle, neutral density scale height, and total neutral density. However, contrary to previous assertions, the photoelectron flux at most energies is not sensitive to the relative densities of the neutral constituents. In addition, good agreement between theory and measurement is obtained. By using the concept of photoelectron production frequencies, the usually complex evaluation of the local equilibrium photoelectron flux is reduced to a trivial calculation so that the steps in the calculation can be readily verified.

  5. Water flux and drainage from soil measured with automated passive capillary wick samplers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Various soil water samplers are used to monitor measure and estimate drainage water, fluxes and solute transport in the soil vadose zone. Passive capillary samplers (PCAPs) have shown potential to provide better measurements and estimates of soil water drainage and fluxes than other lysimeters.Twelv...

  6. LEAF, BRANCH, STAND & LANDSCAPE SCALE MEASUREMENTS OF VOLATILE ORGANIC COMPOUND FLUXES FROM U.S. WOODLANDS

    EPA Science Inventory

    Natural volatile organic compounds (VOC) fluxes were measured in three U.S. woodlands in summer 1993. Fluxes from individual leaves and branches were estimated with enclosure techniques and used to initialize and evaluate VOC emission model estimates. Ambient measurements were us...

  7. Calculating the detection limits of chamber-based greenhouse gas flux measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Chamber-based measurement of greenhouse gas emissions from soil is a common technique. However, when changes in chamber headspace gas concentrations are small over time, determination of the flux can be problematic. Several factors contribute to the reliability of measured fluxes, including: samplin...

  8. Characterization and Remediation of Contaminated Sites:Modeling, Measurement and Assessment

    NASA Astrophysics Data System (ADS)

    Basu, N. B.; Rao, P. C.; Poyer, I. C.; Christ, J. A.; Zhang, C. Y.; Jawitz, J. W.; Werth, C. J.; Annable, M. D.; Hatfield, K.

    2008-05-01

    The complexity of natural systems makes it impossible to estimate parameters at the required level of spatial and temporal detail. Thus, it becomes necessary to transition from spatially distributed parameters to spatially integrated parameters that are capable of adequately capturing the system dynamics, without always accounting for local process behavior. Contaminant flux across the source control plane is proposed as an integrated metric that captures source behavior and links it to plume dynamics. Contaminant fluxes were measured using an innovative technology, the passive flux meter at field sites contaminated with dense non-aqueous phase liquids or DNAPLs in the US and Australia. Flux distributions were observed to be positively or negatively correlated with the conductivity distribution, depending on the source characteristics of the site. The impact of partial source depletion on the mean contaminant flux and flux architecture was investigated in three-dimensional complex heterogeneous settings using the multiphase transport code UTCHEM and the reactive transport code ISCO3D. Source mass depletion reduced the mean contaminant flux approximately linearly, while the contaminant flux standard deviation reduced proportionally with the mean (i.e., coefficient of variation of flux distribution is constant with time). Similar analysis was performed using data from field sites, and the results confirmed the numerical simulations. The linearity of the mass depletion-flux reduction relationship indicates the ability to design remediation systems that deplete mass to achieve target reduction in source strength. Stability of the flux distribution indicates the ability to characterize the distributions in time once the initial distribution is known. Lagrangian techniques were used to predict contaminant flux behavior during source depletion in terms of the statistics of the hydrodynamic and DNAPL distribution. The advantage of the Lagrangian techniques lies in their

  9. Flux measurements in a nuclear research reactor by using an aluminum nitride detector

    NASA Astrophysics Data System (ADS)

    Moon, B. S.; Yoo, D. S.; Hwang, I. K.; Chung, C. E.; Holcomb, D. E.

    2007-08-01

    A small polycrystalline aluminium nitride detector with a thickness of 381 μm was used to measure a 200,000 Ci Co 60 source and to measure the flux in a research reactor where the neutron flux is about 10 14/cm 2 s, which is nearly the same order as in the commercial power plant. If the applied voltage is greater than or equal to 2000 V and if the measurements are done in a short period of time so that the heat energy does not build up in the aluminium nitride, then the measured electric current is linearly proportional to the input flux. It is assumed of course that the energy spectrum of the input flux remains constant. This linearity relation is illustrated by the results of a measurement in which the reactor power has been controlled so that the flux becomes a step function.

  10. Effective monitoring of landfills: flux measurements and thermography enhance efficiency and reduce environmental impact

    NASA Astrophysics Data System (ADS)

    Battaglini, Raffaele; Raco, Brunella; Scozzari, Andrea

    2013-12-01

    This work presents a methodology for estimating the behaviour of a landfill system in terms of biogas release to the atmosphere. Despite the various positions towards the impact of methane on global warming, there is a general agreement about the fact that methane from landfill represents about 23% of the total anthropogenic CH4 released to the atmosphere. Despite the importance of this topic, no internationally accepted protocol exists to quantify the leakage of biogas from the landfill cover. To achieve this goal, this paper presents a field method based on accumulation chamber flux measurements. In addition, the results obtained from a nine-year-long monitoring activity on an Italian municipal solid waste (MSW) landfill are presented. The connection between such flux measurements of biogas release and thermal anomalies detected by infrared radiometry is also discussed. The main overall benefit of the presented approach is a significant increase in the recovered energy from the landfill site by means of an optimal collection of biogas, which implies a reduction of the total anthropogenic methane originated from the disposal of waste.

  11. Impact of surrounding environment evolution on long-term gas flux measurements in a temperate mixed forest

    NASA Astrophysics Data System (ADS)

    Hurdebise, Quentin; Rixen, Toma; De Ligne, Anne; Vincke, Caroline; Heinesch, Bernard; Aubinet, Marc

    2016-04-01

    With the development of eddy covariance networks like Fluxnet, ICOS or NEON, long-term data series of carbon dioxide, water vapor and other gas exchanges between terrestrial ecosystems and atmosphere will become more and more numerous. However, long-term analyses of such exchanges require a good understanding of measurement conditions during the investigated period. Independently of climate drivers, measurements may indeed be influenced by measurement conditions themselves subjected to long-term variability due to vegetation growth or set-up changes. The present research refers to the Vielsalm Terrestrial Observatory (VTO) where fluxes of momentum, carbon dioxide, latent and sensible heat have been continuously measured by eddy covariance during twenty years. VTO is an ICOS site installed in a mixed forest (beech, silver fir, Douglas fir, Norway spruce) in the Belgian Ardennes. A multidisciplinary approach was developed in order to investigate the spatial and temporal evolution of several site characteristics: -displacement height (d) and relative measurement height (z-d) were determined using a spectral approach that compared observed and theoretical cospectra; -turbulence statistics were analyzed in the context of Monin-Obukhov similarity theory; -tree height during the measurement period was obtained by combining tree height inventories, a LIDAR survey and tree growth models; -measurement footprint was determined by using a footprint model. A good agreement was found between the three first approaches. Results show notably that z-d was subjected to both temporal and spatial evolution. Temporal evolution resulted from continuous tree growth as well as from a tower raise, achieved in 2009. Spatial evolution, due to canopy heterogeneity, was also observed. The impacts of these changes on measurements are investigated. In particular, it was shown that they affect measurement footprint, flux spectral corrections and flux quality. All these effects must be taken into

  12. Determination of solar proton fluxes and energies at high solar latitudes by UV radiation measurements

    NASA Technical Reports Server (NTRS)

    Witt, N.; Blum, P. W.; Ajello, J. M.

    1981-01-01

    The latitudinal variation of the solar proton flux and energy causes a density increase at high solar latitudes of the neutral gas penetrating the heliosphere. Measurements of the neutral density by UV resonance radiation observations from interplanetary spacecraft thus permit deductions on the dependence of the solar proton flux on heliographic latitude. Using both the results of Mariner 10 measurements and of other off-ecliptic solar wind observations, the values of the solar proton fluxes and energies at polar heliographic latitudes are determined for several cases of interest. The Mariner 10 analysis, together with IPS results, indicate a significant decrease of the solar proton flux at polar latitudes.

  13. Measuring sand flux on Mars using HiRISE Images

    NASA Astrophysics Data System (ADS)

    Ayoub, F.; Bridges, N. T.; Avouac, J.; Leprince, S.; Lucas, A.; Mattson, S.

    2011-12-01

    As wind is the major agent of sediment transport on Mars, a quantitative estimate of aeolian processes is therefore essential to assess recent geological evolution and current climate. We adapted the Co-registration of Optically Sensed Image and Correlation (COSI-Corr) toolbox to the MRO HiRISE imager specifications to produce a dense map of the ripples migration on the surface of the Martian dunes on the Nili Patera area. The ripple migration rate, along with an estimate of the ripple height, were used to derive the sand flux, a key quantity that controls the style and rate of landscape evolution. Using the dunes shape, size, and height, which were extracted from a DEM of the dune field, we show that the dunes are near steady state, and we observe that dune migration rate varies inversely with size and position within the dune field. The time scale associated with the formation and evolution of the Nili Patera dune field, estimated from comparing the sand volume with the sand flux and the dunes migration rates with the length scale of the dune field, is on the order of 10s to 100s of thousands Earth years. However, sand fluxes at the dune crests are 0.7 - 4.8 m3 m-1 per Earth year, which is comparable to that of dunes in Victoria Valley, Antarctica. This implies that rates of landscape modification from aeolian abrasion on Mars may be comparable to that on Earth.

  14. Modeling the Impact of Hydraulic Redistribution on Carbon Cycles Using CLM4.5 at Eight AmeriFlux Sites

    NASA Astrophysics Data System (ADS)

    Fu, C.; Wang, G.; Cardon, Z. G.

    2014-12-01

    Hydraulic redistribution (HR) has significant impacts on the terrestrial hydrological, biogeochemical, and ecological processes. Accurate modeling of HR and its impact on vegetation growth and ecosystem carbon dynamics is important for accurate simulation of regional and global carbon cycles. However, how HR influences plant, soil carbon and nitrogen dynamics remains poorly understood. In this study, we incorporate a simple HR scheme into the Community Land Model Version 4.5 (CLM4.5) including the biogeochemical model BGC. We use the modified CLM4.5-BGC model to investigate the impact of HR on the terrestrial carbon cycle at eight AmeriFlux sites where HR was detected from soil moisture measurements: a Douglas-fir site (US-Wrc) in Washington State with a Mediterranean climate, a savanna site (US-SRM) in Arizona with a semi-arid climate, and six sites along the Southern California Climate Gradient with a Mediterranean climate, with coverage of coastal sage (US-SCs), grassland (US-SCg), oak/pine forest (US-SCf), pinyon and juniper woodland (US-SCw), desert chaparral (US-SCc), and desert perennials and annuals (US-SCd). Monitored net ecosystem exchange of carbon (NEE) at the US-Wrc, US-SRM, and US-SCf sites, is used in model calibration and HR sensitivity analysis. Preliminary results from the model indicate that HR tends to increase net primary production (NPP) during dry periods and increase leaf area index (LAI) throughout the year at the US-Wrc site, while HR increased NPP and LAI during growing season and reduced NPP and LAI during dry periods at the US-SCs and US-SCg sites, with corresponding modifications to carbon storage in soil layers and in plant leaf, stem, and root carbon pools. The biogeochemical processes leading to these effects will be analyzed and presented.

  15. Quantitative method for measuring heat flux emitted from a cryogenic object

    DOEpatents

    Duncan, R.V.

    1993-03-16

    The present invention is a quantitative method for measuring the total heat flux, and of deriving the total power dissipation, of a heat-fluxing object which includes the steps of placing an electrical noise-emitting heat-fluxing object in a liquid helium bath and measuring the superfluid transition temperature of the bath. The temperature of the liquid helium bath is thereafter reduced until some measurable parameter, such as the electrical noise, exhibited by the heat-fluxing object or a temperature-dependent resistive thin film in intimate contact with the heat-fluxing object, becomes greatly reduced. The temperature of the liquid helum bath is measured at this point. The difference between the superfluid transition temperature of the liquid helium bath surrounding the heat-fluxing object, and the temperature of the liquid helium bath when the electrical noise emitted by the heat-fluxing object becomes greatly reduced, is determined. The total heat flux from the heat-fluxing object is determined as a function of this difference between these temperatures. In certain applications, the technique can be used to optimize thermal design parameters of cryogenic electronics, for example, Josephson junction and infrared sensing devices.

  16. Quantitative method for measuring heat flux emitted from a cryogenic object

    DOEpatents

    Duncan, Robert V.

    1993-01-01

    The present invention is a quantitative method for measuring the total heat flux, and of deriving the total power dissipation, of a heat-fluxing object which includes the steps of placing an electrical noise-emitting heat-fluxing object in a liquid helium bath and measuring the superfluid transition temperature of the bath. The temperature of the liquid helium bath is thereafter reduced until some measurable parameter, such as the electrical noise, exhibited by the heat-fluxing object or a temperature-dependent resistive thin film in intimate contact with the heat-fluxing object, becomes greatly reduced. The temperature of the liquid helum bath is measured at this point. The difference between the superfluid transition temperature of the liquid helium bath surrounding the heat-fluxing object, and the temperature of the liquid helium bath when the electrical noise emitted by the heat-fluxing object becomes greatly reduced, is determined. The total heat flux from the heat-fluxing object is determined as a function of this difference between these temperatures. In certain applications, the technique can be used to optimize thermal design parameters of cryogenic electronics, for example, Josephson junction and infra-red sensing devices.

  17. Assessing the spatial representativeness of eddy-covariance measurements of AmeriFlux network based on remote sensing and footprint analysis

    NASA Astrophysics Data System (ADS)

    Fu, D.; Zhang, L.; Chen, B.

    2015-12-01

    The eddy-covariance towers of AmeriFlux network are important for the analysis of terrestrial ecosystem-atmosphere interactions, and they have been used to improve our understanding of the mechanism behind terrestrial carbon cycle and upscaling from site to landscape and regional scales. However, the spatial representativeness of AmeriFlux network has not been assessed, especially accounting for the effects of land cover change on it using high spatial resolution data. Here we demonstrated an approach for evaluating the spatial representativeness of flux tower measurements based on footprint climatology analyses, land cover change data and remotely sensed vegetation indices. This method was applied to 79 flux towers of AmeriFlux network located in the continental United States, covering evergreen forest, deciduous forest, mixed forest, grass, cropland, shrub, and wetland biomes. For each site, monthly and annual footprint climatologies (i.e. monthly or annual accumulative footprints) were calculated using the Simple Analytical Footprint model on Eulerian coordinates (SAFE-f). The footprint climatologies were then overlaid on the images of Normalized Difference Vegetation Index (NDVI) and National Land Cover Database (NLCD) for the years (2001, 2006 and 2011), which were used as surrogates of land surface fluxes to assess the spatial representativeness. For most sites of AmeriFlux network, the results show that (i) the percentages of the target vegetation functional type (dominant land cover) observed by the AmeriFlux towers were higher than 60%; (ii) to some extent, most of the AmeriFlux sites presented anisotropically distributed patterns of NDVI within the 90% annual footprint climatology area; (iii) the land surface heterogeneity within the flux footprint area differed among sites; and (iv) the land cover types had changed higher than 10% within 6 km*6 km area centered at the flux tower for 5 AmeriFlux sites. We conclude that the footprint modeling based on high

  18. Remote Sensing and Sea-Truth Measurements of Methane Flux to the Atmosphere (HYFLUX project)

    SciTech Connect

    Ian MacDonald

    2011-05-31

    , respectively. Based on the contemporaneous wind speeds at this site, contemporary estimates of the diffusive fluxes from the mixed layer to the atmosphere for methane, ethane, and propane are 26.5, 2.10, and 2.78 {micro}mol/m{sup 2}d, respectively. Continuous measurements of air and sea surface concentrations of methane were made to obtain high spatial and temporal resolution of the diffusive net sea-to-air fluxes. The atmospheric methane fluctuated between 1.70 ppm and 2.40 ppm during the entire cruise except for high concentrations (up to 4.01 ppm) sampled during the end of the occupation of GC600 and the transit between GC600 and GC185. Results from interpolations within the survey areas show the daily methane fluxes to the atmosphere at the three sites range from 0.744 to 300 mol d-1. Considering that the majority of seeps in the GOM are deep (>500 m), elevated CH{sub 4} concentrations in near-surface waters resulting from bubble-mediated CH4 transport in the water column are expected to be widespread in the Gulf of Mexico.

  19. Flux estimation of fugitive particulate matter emissions from loose Calcisols at construction sites

    NASA Astrophysics Data System (ADS)

    Hassan, Hala A.; Kumar, Prashant; Kakosimos, Konstantinos E.

    2016-09-01

    A major source of airborne pollution in arid and semi-arid environments (i.e. North Africa, Middle East, Central Asia, and Australia) is the fugitive particulate matter (fPM), which is a frequent product of wind erosion. However, accurate determination of fPM is an ongoing scientific challenge. The objective of this study is to examine fPM emissions from the loose Calcisols (i.e. soils with a substantial accumulation of secondary carbonates), owing to construction activities that can be frequently seen nowadays in arid urbanizing regions such as the Middle East. A two months field campaign was conducted at a construction site, at rest, within the city of Doha (Qatar) to measure number concentrations of PM over a size range of 0.25-32 μm using light scattering based monitoring stations. The fPM emission fluxes were calculated using the Fugitive Dust Model (FDM) in an iterative manner and were fitted to a power function, which expresses the wind velocity dependence. The power factors were estimated as 1.87, 1.65, 2.70 and 2.06 for the four different size classes of particles ≤2.5, 2.5-6, 6-10 and ≤10 μm, respectively. Fitted power function was considered acceptable given that adjusted R2 values varied from 0.13 for the smaller particles and up to 0.69 for the larger ones. These power factors are in the same range of those reported in the literature for similar sources. The outcome of this study is expected to contribute to the improvement of PM emission inventories by focusing on an overlooked but significant pollution source, especially in dry and arid regions, and often located very close to residential areas and sensitive population groups. Further campaigns are recommended to reduce the uncertainty and include more fPM sources (e.g. earthworks) and other types of soil.

  20. Accurate measurement of poleward microtubule flux in the spindle of Drosophila S2 cells.

    PubMed

    Munzarova, Alina; Popova, Julia; Razuvaeva, Alena; Shloma, Victor; Gatti, Maurizio; Omelyanchuk, Leonid

    2016-09-01

    The spindle microtubule (MT) flux is the continuous translocation of MTs toward the spindle poles caused by MT polymerization at plus ends coupled to depolymerization at minus ends. Poleward flux is observed in both mitotic and meiotic spindles; it is evolutionarily conserved and contributes to the regulation of spindle length and anaphase chromosome movement. MT photobleaching is a tool frequently used to measure poleward flux. Spindles containing fluorescently tagged tubulin are photobleached to generate a non-fluorescent stripe, which moves toward the spindle poles allowing a measure of the flux. However, this method only permits rapid measurements of the flux, because the fluorescence of the bleached stripe recovers rapidly due to the spindle MT turnover. Here, we describe a modification of the current photobleaching-based method for flux measurement. We photobleached two large areas at the opposite sides of the metaphase plate in spindles of Drosophila S2 cells expressing Cherry-tagged tubulin, leaving unbleached only the area near the chromosomes. We then measured the speed with which the fluorescent MTs move toward the poles. We found that this method allows a measure of the flux over a two- to threefold longer time than the "single stripe" method, providing a reliable evaluation of the flux rate. PMID:27317357

  1. Climate-driven uncertainties in modeling terrestrial energy and water fluxes: a site-level to global-scale analysis.

    PubMed

    Barman, Rahul; Jain, Atul K; Liang, Miaoling

    2014-06-01

    We used a land surface model constrained using data from flux tower sites, to analyze the biases in ecosystem energy and water fluxes arising due to the use of meteorological reanalysis datasets. Following site-level model calibration encompassing major vegetation types from the tropics to the northern high-latitudes, we repeated the site and global simulations using two reanalysis datasets: the NCEP/NCAR and the CRUNCEP. In comparison with the model simulations using observed meteorology from sites, the reanalysis-driven simulations produced several systematic biases in net radiation (Rn ), latent heat (LE), and sensible heat (H) fluxes. These include: (i) persistently positive tropical/subtropical biases in Rn using the NCEP/NCAR, and gradually transitioning to negative Rn biases in the higher latitudes; (ii) large positive H biases in the tropics/subtropics using the NCEP/NCAR; (iii) negative LE biases using the NCEP/NCAR above 40°N; (iv) high tropical LE using the CRUNCEP in comparison with observationally derived global estimates; and (v) flux-partitioning biases from canopy and ground components. Across vegetation types, we investigated the role of the meteorological drivers (shortwave and longwave radiation, atmospheric humidity, temperature, precipitation) and their seasonal biases in controlling these reanalysis-driven uncertainties. At the global scale, our site-level analysis explains several model-data differences in the LE and H fluxes when compared with observationally derived global estimates of these fluxes. Using our results, we discuss the implications of site-level model calibration on subsequent regional/global applications to study energy and hydrological processes. The flux-partitioning biases presented in this study have potential implications on the couplings among terrestrial carbon, energy, and water fluxes, and for the calibration of land-atmosphere parameterizations that are dependent on LE/H partitioning. PMID:24273011

  2. Combined FTIR-micrometeorological techniques for long term measurements of greenhouse gas fluxes from agriculture

    NASA Astrophysics Data System (ADS)

    Petersen, A. K.; Griffith, D.; Harvey, M.; Naylor, T.; Smith, M.

    2009-04-01

    The exchange of trace gases between the biosphere and the atmosphere affects the atmospheric concentrations of gases such as methane, carbon dioxide, nitrous oxide, carbon monoxide, ammonia, volatile organic compounds, nitrogen dioxide and others. The quantification of the exchange between a biogenic system and the atmosphere is necessary for the evaluation of the impact of these interactions. This is of special interest for agricultural systems which can be sources or sinks of trace gases, and the measurement of the fluxes is necessary when evaluating both the environmental impact of agricultural activities and the impact of atmospheric pollution on agricultural production and sustainability. With the exception of CO2, micrometeorological measurements of the fluxes of greenhouse gases from agricultural activities are still mostly possible only in campaign mode due to the complexity and logistical requirements of the existing measurement techniques. This limitation precludes studies of fluxes which run for longer periods, for example over full seasonal or growing cycles for both animal- and crop-based agriculture. We have developed an instrument system for long-term flux measurements through a combination of micrometeorological flux measurement techniques such as Relaxed Eddy Accumulation (REA) and Flux-Gradient (FG) with the high precision multi-species detection capabilities of FTIR spectroscopy. The combined technique is capable of simultaneous flux measurements of N2O, CH4 and CO2 at paddock to regional scales continuously, over longer terms (months, seasonal cycles, years). The system was tested on a 3 weeks field campaign in NSW, Australia on a flat, homogeneous circular grass paddock with grazing cattle. The flux of the atmospheric trace gas CO2 was measured with three different micrometeorological techniques: Relaxed Eddy Accumulation, Flux-Gradient, and Eddy Correlation. Simultaneously, fluxes of CH4 and N2O were measured by REA and FG technique.

  3. Estimation of surface energy fluxes using surface renewal and flux variance techniques over an advective irrigated agricultural site

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Estimation of surface energy fluxes over irrigated agriculture is needed to monitor crop water use. Estimates are commonly done using well-established techniques such as eddy covariance (EC) and weighing lysimetry, but implementing these to collect spatially distributed observations is complex and c...

  4. Predicting landscape-scale CO2 flux at a pasture and rice paddy with long-term hyperspectral canopy reflectance measurements

    NASA Astrophysics Data System (ADS)

    Matthes, J. H.; Knox, S. H.; Sturtevant, C.; Sonnentag, O.; Verfaillie, J.; Baldocchi, D.

    2015-03-01

    Measurements of hyperspectral canopy reflectance provide a detailed snapshot of information regarding canopy biochemistry, structure and physiology. In this study, we collected five years of repeated canopy hyperspectral reflectance measurements for a total of over 100 site visits within the flux footprints of two eddy covariance towers at a pasture and rice paddy in Northern California. The vegetation at both sites exhibited dynamic phenology, with significant inter-annual variability in the timing of seasonal patterns that propagated into inter-annual variability in measured hyperspectral reflectance. We used partial least-squares regression (PLSR) modeling to leverage the information contained within the entire continuous canopy reflectance spectra (400-900 nm) in order to investigate questions regarding the connection between measured hyperspectral reflectance and landscape-scale fluxes of net ecosystem exchange (NEE) and gross primary productivity (GPP) across multiple timescales, from instantaneous flux to monthly-integrated flux. With the PLSR models developed from this large dataset we achieved a high level of predictability for both NEE and GPP flux in these two ecosystems, where the R2 of prediction with an independent validation dataset ranged from 0.24 to 0.69. The PLSR models achieved the highest skill at predicting the integrated GPP flux for the week prior to the hyperspectral canopy reflectance collection, whereas the NEE flux often achieved the same high predictive power at the daily- through monthly-integrated flux timescales. The high level of predictability achieved by PLSR regression in this study demonstrated the potential for using repeated hyperspectral canopy reflectance measurements to help partition NEE measurements into its component fluxes, GPP and ecosystem respiration, and for using continuous hyperspectral reflectance measurements to model regional carbon flux in future analyses.

  5. Net drainage effects on CO2 fluxes of a permafrost ecosystem through eddy-covariance measurements

    NASA Astrophysics Data System (ADS)

    Kittler, Fanny; Burjack, Ina; Zimov, Nikita; Zimov, Sergey; Heimann, Martin; Göckede, Mathias

    2015-04-01

    Permafrost landscapes in the Northern high latitudes with their massive organic carbon stocks are critically important for the global carbon cycle, yet feedback processes with the atmosphere under future climate conditions are uncertain. To improve the understanding of mechanisms and drivers dominating permafrost carbon cycling, we established a continuous observation program in moist tussock tundra ecosystem near Cherskiy in North-eastern Siberia (68.75°N, 161.33°E). The experiment has been designed to monitor carbon cycle fluxes at different scales with different approaches, including e.g. the eddy-covariance technique, and their environmental drivers. Recent observations started mid July 2013 and are still ongoing, while 'historic' measurements are available for the period 2002-2005. Since 2004 part of the observation area has been disturbed by a drainage ditch ring, altering the soil water conditions in the surrounding area in a way that is expected for degrading ice-rich permafrost under a warming climate. With parallel observations over the disturbed (drained) area and a reference area nearby, respectively, we aim to evaluate the disturbance effect on the carbon cycle budgets and the dominating biogeochemical mechanisms. Here, findings based on over 1.5 years of continuous eddy-covariance CO2 flux measurements (July 2013 - March 2015) for both observation areas are presented. Results show systematic shifts in the tundra ecosystem as a result of 10 years of disturbance in the drained area, with significant effects on biotic and abiotic site conditions as well as on the carbon cycle dynamics. Comparing the net budget fluxes between both observations areas indicates a reduction of the net sink strength for CO2 of the drained ecosystem during the summer season in comparison to natural conditions, mostly caused by reduced CO2 uptake with low water levels in late summer. Regarding the long-term CO2 uptake dynamics of the disturbance regime (2005 vs. 2013/14) the

  6. Calculations of automatic chamber flux measurements of methane and carbon dioxide using short time series of concentrations

    NASA Astrophysics Data System (ADS)

    Pirk, Norbert; Mastepanov, Mikhail; Parmentier, Frans-Jan W.; Lund, Magnus; Crill, Patrick; Christensen, Torben R.

    2016-02-01

    The closed chamber technique is widely used to measure the exchange of methane (CH4) and carbon dioxide (CO2) from terrestrial ecosystems. There is, however, large uncertainty about which model should be used to calculate the gas flux from the measured gas concentrations. Due to experimental uncertainties the simple linear regression model (first-order polynomial) is often applied, even though theoretical considerations of the technique suggest the application of other, curvilinear models. High-resolution automatic chamber systems which sample gas concentrations several hundred times per flux measurement make it possible to resolve the curvilinear behavior and study the information imposed by the natural variability of the temporal concentration changes. We used more than 50 000 such flux measurements of CH4 and CO2 from five field sites located in peat-forming wetlands ranging from 56 to 78° N to quantify the typical differences between flux estimates of different models. In addition, we aimed to assess the curvilinearity of the concentration time series and test the general applicability of curvilinear models. Despite significant episodic differences between the calculated flux estimates, the overall differences are generally found to be smaller than the local flux variability on the plot scale. The curvilinear behavior of the gas concentrations within the chamber is strongly influenced by wind-driven chamber leakage, and less so by changing gas concentration gradients in the soil during chamber closure. Such physical processes affect both gas species equally, which makes it possible to isolate biochemical processes affecting the gases differently, such as photosynthesis limitation by chamber headspace CO2 concentrations under high levels of incoming solar radiation. We assess the possibility to exploit this effect for a partitioning of the net CO2 flux into photosynthesis and ecosystem respiration as an example of how high-resolution automatic chamber

  7. Direct comparison of 210Po, 234Th and POC particle-size distributions and export fluxes at the Bermuda Atlantic Time-series Study (BATS) site.

    PubMed

    Stewart, Gillian; Moran, S Bradley; Lomas, Michael W; Kelly, Roger P

    2011-05-01

    Particle-reactive, naturally occurring radionuclides are useful tracers of the sinking flux of organic matter from the surface to the deep ocean. Since the Joint Global Ocean Flux Study (JGOFS) began in 1987, the disequilibrium between (234)Th and its parent (238)U has become widely used as a technique to measure particle export fluxes from surface ocean waters. Another radionuclide pair, (210)Po and (210)Pb, can be used for the same purpose but has not been as widely adopted due to difficulty with accurately constraining the (210)Po/(210)Pb radiochemical balance in the ocean and because of the more time-consuming radiochemical procedures. Direct comparison of particle flux estimated in different ocean regions using these short-lived radionuclides is important in evaluating their utility and accuracy as tracers of particle flux. In this paper, we present paired (234)Th/(238)U and (210)Po/(210)Pb data from oligotrophic surface waters of the subtropical Northwest Atlantic and discuss their advantages and limitations. Vertical profiles of total and particle size-fractionated (210)Po and (234)Th activities, together with particulate organic carbon (POC) concentrations, were measured during three seasons at the Bermuda Atlantic Time-series Study (BATS) site. Both (210)Po and (234)Th reasonably predict sinking POC flux caught in sediment traps, and each tracer provides unique information about the magnitude and efficiency of the ocean's biological pump. PMID:21055851

  8. Calculating the diffusive flux of persistent organic pollutants between sediments and the water column on the Palos Verdes shelf superfund site using polymeric passive samplers.

    PubMed

    Fernandez, Loretta A; Lao, Wenjian; Maruya, Keith A; Burgess, Robert M

    2014-04-01

    Passive samplers were deployed to the seafloor at a marine Superfund site on the Palos Verdes Shelf, California, USA, and used to determine water concentrations of persistent organic pollutants (POPs) in the surface sediments and near-bottom water. A model of Fickian diffusion across a thin water boundary layer at the sediment-water interface was used to calculate flux of contaminants due to molecular diffusion. Concentrations at four stations were used to calculate the flux of DDE, DDD, DDMU, and selected PCB congeners from sediments to the water column. Three passive sampling materials were compared: PE strips, POM strips, and SPME fibers. Performance reference compounds (PRCs) were used with PE and POM to correct for incomplete equilibration, and the resulting POP concentrations, determined by each material, agreed within 1 order of magnitude. SPME fibers, without PRC corrections, produced values that were generally much lower (1 to 2 orders of magnitude) than those measured using PE and POM, indicating that SPME may not have been fully equilibrated with waters being sampled. In addition, diffusive fluxes measured using PE strips at stations outside of a pilot remedial sand cap area were similar to those measured at a station inside the capped area: 240 to 260 ng cm(-2) y(-1) for p,p'-DDE. The largest diffusive fluxes of POPs were calculated at station 8C, the site where the highest sediment concentrations have been measured in the past, 1100 ng cm(-2) y(-1) for p,p'-DDE. PMID:24564763

  9. Observed and Modeled Isoprene Fluxes at a Remote Michigan Forest Site

    NASA Astrophysics Data System (ADS)

    Wen, M.; Pressley, S. N.; Gu, D.; Yu, H.; Guenther, A. B.; VanReken, T. M.

    2015-12-01

    Biogenic volatile organic compounds (BVOCs) constitute a major part of global VOC emissions and can affect regional or global climate by influencing tropospheric chemistry and forming secondary organic aerosols. Isoprene is the most abundant species in global BVOC budget. The Model of Emissions of Gases and Aerosols from Nature (MEGAN) 2.1 (Guenther et al., 2006, 2012) is a state-of-art emission model that simulates BVOC emissions by considering major environmental activity factors (e.g. temperature, solar radiation). Here we compare measurements of isoprene emissions in a mixed hardwood forest at the University of Michigan Biological Station (UMBS) during 1999-2005 growing seasons (Pressley et al., 2004, 2005) with MEGAN model simulations. We investigated the seasonal variations of isoprene emissions by considering the impacts from meteorological conditions, as well as correlations between sensible heat flux, latent heat flux and isoprene flux for a model uncertainty analysis. Model simulations are in good agreement with observations during leaf full expansion periods, but the values are 3-4 times higher than observations before full leaf development and after leaf senescence periods. There are significant correlations between the variations of isoprene emissions and precipitation.

  10. Continuous atmospheric monitoring of the injected CO2 behavior over geological storage sites using flux stations: latest technologies and resources

    NASA Astrophysics Data System (ADS)

    Burba, George; Madsen, Rodney; Feese, Kristin

    2014-05-01

    Flux stations have been widely used to monitor emission rates of CO2 from various ecosystems for climate research for over 30 years [1]. The stations provide accurate and continuous measurements of CO2 emissions with high temporal resolution. Time scales range from 20 times per second for gas concentrations, to 15-minute, hourly, daily, and multi-year periods. The emissions are measured from the upwind area ranging from thousands of square meters to multiple square kilometers, depending on the measurement height. The stations can nearly instantaneously detect rapid changes in emissions due to weather events, as well as changes caused by variations in human-triggered events (pressure leaks, control releases, etc.). Stations can also detect any slow changes related to seasonal dynamics and human-triggered low-frequency processes (leakage diffusion, etc.). In the past, station configuration, data collection and processing were highly-customized, site-specific and greatly dependent on "school-of-thought" practiced by a particular research group. In the last 3-5 years, due to significant efforts of global and regional CO2 monitoring networks (e.g., FluxNet, Ameriflux, Carbo-Europe, ICOS, etc.) and technological developments, the flux station methodology became fairly standardized and processing protocols became quite uniform [1]. A majority of current stations compute CO2 emission rates using the eddy covariance method, one of the most direct and defensible micrometeorological techniques [1]. Presently, over 600 such flux stations are in operation in over 120 countries, using permanent and mobile towers or moving platforms (e.g., automobiles, helicopters, and airplanes). Atmospheric monitoring of emission rates using such stations is now recognized as an effective method in regulatory and industrial applications, including carbon storage [2-8]. Emerging projects utilize flux stations to continuously monitor large areas before and after the injections, to locate and

  11. Four-year measurement of methane flux over a temperate forest with a relaxed eddy accumulation method

    NASA Astrophysics Data System (ADS)

    Sakabe, A.; Kosugi, Y.; Ueyama, M.; Hamotani, K.; Takahashi, K.; Iwata, H.; Itoh, M.

    2013-12-01

    Forests are generally assumed to be an atmospheric methane (CH4) sink (Le Mer and Roger, 2001). However, under Asian monsoon climate, forests are subject to wide spatiotemporal range in soil water status, where forest soils often became water-saturated condition heterogeneously. In such warm and humid conditions, forests may act as a CH4 source and/or sink with considerable spatiotemporal variations. Micrometeorological methods such as eddy covariance (EC) method continuously measure spatially-representative flux at a canopy scale without artificial disturbance. In this study, we measured CH4 fluxes over a temperate forest during four-year period using a CH4 analyzer based on tunable diode laser spectroscopy detection with a relaxed eddy accumulation (REA) method (Hamotani et al., 1996, 2001). We revealed the amplitude and seasonal variations of canopy-scale CH4 fluxes. The REA method is the attractive alternative to the EC method to measure trace-gas flux because it allows the use of analyzers with an optimal integration time. We also conducted continuous chamber measurements on forest floor to reveal spatial variations in soil CH4 fluxes and its controlling processes. The observations were made in an evergreen coniferous forest in central Japan. The site has a warm temperate monsoon climate with wet summer. Some wetlands were located in riparian zones along streams within the flux footprint area. For the REA method, the sonic anemometer (SAT-550, Kaijo) was mounted on top of the 29-m-tall tower and air was sampled from just below the sonic anemometer to reservoirs according to the direction of vertical wind velocity (w). After accumulating air for 30 minutes, the air in the reservoirs was pulled into a CO2/H2O gas analyzer (LI-840, Li-Cor) and a CH4 analyzer (FMA-200, Los Gatos Research). Before entering the analyzers, the sampled air was dried using a gas dryer (PD-50 T-48; Perma Pure Inc.). The REA flux is obtained from the difference in the mean concentrations

  12. Measurement of the Cosmic Ray and Neutrino-Induced Muon Flux at the Sudbury Neutrino Observatory

    DOE R&D Accomplishments Database

    SNO collaboration; Aharmim, B.; Ahmed, S. N.; Andersen, T. C.; Anthony, A. E.; Barros, N.; Beier, E. W.; Bellerive, A.; Beltran, B.; Bergevin, M.; Biller, S. D.; Boudjemline, K.; Boulay, M. G.; Burritt, T. H.; Cai, B.; Chan, Y. D.; Chen, M.; Chon, M. C.; Cleveland, B. T.; Cox-Mobrand, G. A.; Currat, C. A.; Dai, X.; Dalnoki-Veress, F.; Deng, H.; Detwiler, J.; Doe, P. J.; Dosanjh, R. S.; Doucas, G.; Drouin, P.-L.; Duncan, F. A.; Dunford, M.; Elliott, S. R.; Evans, H. C.; Ewan, G. T.; Farine, J.; Fergani, H.; Fleurot, F.; Ford, R. J.; Formaggio, J. A.; Gagnon, N.; Goon, J. TM.; Grant, D. R.; Guillian, E.; Habib, S.; Hahn, R. L.; Hallin, A. L.; Hallman, E. D.; Hargrove, C. K.; Harvey, P. J.; Harvey, P. J.; Heeger, K. M.; Heintzelman, W. J.; Heise, J.; Helmer, R. L.; Hemingway, R. J.; Henning, R.; Hime, A.; Howard, C.; Howe, M. A.; Huang, M.; Jamieson, B.; Jelley, N. A.; Klein, J. R.; Kos, M.; Kruger, A.; Kraus, C.; Krauss, C. B.; Kutter, T.; Kyba, C. C. M.; Lange, R.; Law, J.; Lawson, I. T.; Lesko, K. T.; Leslie, J. R.; Levine, I.; Loach, J. C.; Luoma, S.; MacLellan, R.; Majerus, S.; Mak, H. B.; Maneira, J.; Marino, A. D.; Martin, R.; McCauley, N.; McDonald, A. B.; McGee, S.; Mifflin, C.; Miller, M. L.; Monreal, B.; Monroe, J.; Noble, A. J.; Oblath, N. S.; Okada, C. E.; O'Keeffe, H. M.; Opachich, Y.; Orebi Gann, G. D.; Oser, S. M.; Ott, R. A.; Peeters, S. J. M.; Poon, A. W. P.; Prior, G.; Rielage, K.; Robertson, B. C.; Robertson, R. G. H.; Rollin, E.; Schwendener, M. H.; Secrest, J. A.; Seibert, S. R.; Simard, O.; Simpson, J. J.; Sinclair, D.; Skensved, P.; Smith, M. W. E.; Sonley, T. J.; Steiger, T. D.; Stonehill, L. C.; Tagg, N.; Tesic, G.; Tolich, N.; Tsui, T.; Van de Water, R. G.; VanDevender, B. A.; Virtue, C. J.; Waller, D.; Waltham, C. E.; Wan Chan Tseung, H.; Wark, D. L.; Watson, P.; Wendland, J.; West, N.; Wilkerson, J. F.; Wilson, J. R.; Wouters, J. M.; Wright, A.; Yeh, M.; Zhang, F.; Zuber, K.

    2009-07-10

    Results are reported on the measurement of the atmospheric neutrino-induced muon flux at a depth of 2 kilometers below the Earth's surface from 1229 days of operation of the Sudbury Neutrino Observatory (SNO). By measuring the flux of through-going muons as a function of zenith angle, the SNO experiment can distinguish between the oscillated and un-oscillated portion of the neutrino flux. A total of 514 muon-like events are measured between -1 {le} cos {theta}{sub zenith} 0.4 in a total exposure of 2.30 x 10{sup 14} cm{sup 2} s. The measured flux normalization is 1.22 {+-} 0.09 times the Bartol three-dimensional flux prediction. This is the first measurement of the neutrino-induced flux where neutrino oscillations are minimized. The zenith distribution is consistent with previously measured atmospheric neutrino oscillation parameters. The cosmic ray muon flux at SNO with zenith angle cos {theta}{sub zenith} > 0.4 is measured to be (3.31 {+-} 0.01 (stat.) {+-} 0.09 (sys.)) x 10{sup -10} {micro}/s/cm{sup 2}.

  13. Measurement of the Cosmic Ray and Neutrino-Induced Muon Flux at the Sudbury Neutrino Observatory

    SciTech Connect

    SNO collaboration; Aharmim, B.; Ahmed, S.N.; Andersen, T.C.; Anthony, A.E.; Barros, N.; Beier, E.W.; Bellerive, A.; Beltran, B.; Bergevin, M.; Biller, S.D.; Boudjemline, K.; Boulay, M.G.; Burritt, T.H.; Cai, B.; Chan, Y.D.; Chen, M.; Chon, M.C.; Cleveland, B.T.; Cox-Mobrand, G.A.; Currat, C.A.; Dai, X.; Dalnoki-Veress, F.; Deng, H.; Detwiler, J.; Doe, P.J.; Dosanjh, R.S.; Doucas, G.; Drouin, P.-L.; Duncan, F.A.; Dunford, M.; Elliott, S.R.; Evans, H.C.; Ewan, G.T.; Farine, J.; Fergani, H.; Fleurot, F.; Ford, R.J.; Formaggio, J.A.; Gagnon, N.; Goon, J.TM.; Grant, D.R.; Guillian, E.; Habib, S.; Hahn, R.L.; Hallin, A.L.; Hallman, E.D.; Hargrove, C.K.; Harvey, P.J.; Harvey, P.J.; Heeger, K.M.; Heintzelman, W.J.; Heise, J.; Helmer, R.L.; Hemingway, R.J.; Henning, R.; Hime, A.; Howard, C.; Howe, M.A.; Huang, M.; Jamieson, B.; Jelley, N.A.; Klein, J.R.; Kos, M.; Kruger, A.; Kraus, C.; Krauss, C.B.; Kutter, T.; Kyba, C.C.M.; Lange, R.; Law, J.; Lawson, I.T.; Lesko, K.T.; Leslie, J.R.; Levine, I.; Loach, J.C.; Luoma, S.; MacLellan, R.; Majerus, S.; Mak, H.B.; Maneira, J.; Marino, A.D.; Martin, R.; McCauley, N.; McDonald, A.B.; McGee, S.; Mifflin, C.; Miller, M.L.; Monreal, B.; Monroe, J.; Noble, A.J.; Oblath, N.S.; Okada, C.E.; O?Keeffe, H.M.; Opachich, Y.; Orebi Gann, G.D.; Oser, S.M.; Ott, R.A.; Peeters, S.J.M.; Poon, A.W.P.; Prior, G.; Rielage, K.; Robertson, B.C.; Robertson, R.G.H.; Rollin, E.; Schwendener, M.H.; Secrest, J.A.; Seibert, S.R.; Simard, O.; Simpson, J.J.; Sinclair, D.; Skensved, P.; Smith, M.W.E.; Sonley, T.J.; Steiger, T.D.; Stonehill, L.C.; Tagg, N.; Tesic, G.; Tolich, N.; Tsui, T.; Van de Water, R.G.; VanDevender, B.A.; Virtue, C.J.; Waller, D.; Waltham, C.E.; Wan Chan Tseung, H.; Wark, D.L.; Watson, P.; Wendland, J.; West, N.; Wilkerson, J.F.; Wilson, J.R.; Wouters, J.M.; Wright, A.; Yeh, M.; Zhang, F.; Zuber, K.

    2009-02-16

    Results are reported on the measurement of the atmospheric neutrino-induced muon flux at a depth of 2 kilometers below the Earth's surface from 1229 days of operation of the Sudbury Neutrino Observatory (SNO). By measuring the flux of through-going muons as a function of zenith angle, the SNO experiment can distinguish between the oscillated and un-oscillated portion of the neutrino flux. A total of 514 muon-like events are measured between -1 {le} cos {theta}{sub zenith} 0.4 in a total exposure of 2.30 x 10{sup 14} cm{sup 2} s. The measured flux normalization is 1.22 {+-} 0.09 times the Bartol three-dimensional flux prediction. This is the first measurement of the neutrino-induced flux where neutrino oscillations are minimized. The zenith distribution is consistent with previously measured atmospheric neutrino oscillation parameters. The cosmic ray muon flux at SNO with zenith angle cos {theta}{sub zenith} > 0.4 is measured to be (3.31 {+-} 0.01 (stat.) {+-} 0.09 (sys.)) x 10{sup -10} {micro}/s/cm{sup 2}.

  14. Effects of biased CO2 flux measurements by open-path sensors on the interpretation of CO2 flux dynamics at contrasting ecosystems

    NASA Astrophysics Data System (ADS)

    Helbig, Manuel; Humphreys, Elyn; Bogoev, Ivan; Quinton, William L.; Wischnweski, Karoline; Sonnentag, Oliver

    2015-04-01

    Long-term measurements of net ecosystem exchange of CO2 (NEE) are conducted across a global network of flux tower sites. These sites are characterised by varying climatic and vegetation conditions, but also differ in the type of CO2/H2O gas analyser used to obtain NEE. Several studies have observed a systematic bias in measured NEE when comparing open-path (OP) and closed-path (CP) sensors with consistently more negative daytime NEE measurements when using OP sensors, both during the growing and non-growing season. A surface heating correction has been proposed in the literature, but seems not to be universally applicable. Systematic biases in NEE measurements are particularly problematic for synthesis papers and inter-comparison studies between sites where the 'true' NEE is small compared to the potential instrument bias. For example, NEE estimates for boreal forest sites derived from OP sensors show large, ecologically unreasonable winter CO2 uptake. To better understand the causes and the magnitude of this potential bias, we conducted a sensor inter-comparison study at the Mer Bleue peatland near Ottawa, ON, Canada. An eddy covariance system with a CP (LI7000 & GILL R3-50) and an OP sensor (EC150 & CSAT3A) was used. Measurements were made between September 2012 and January 2013 and covered late summer, fall, and winter conditions. Flux calculations were made as consistently as possible to minimise differences due to differing processing procedures (e.g. spectral corrections). The latent (LE, slope of orthogonal linear regression of LEOP on LECP: 1.02 ± 0.01 & intercept: -0.2 ± 0.6 W m-2 and sensible heat fluxes (H, slope of HCSAT3A on HGILL: 0.96 ± 0.01 & intercept: 0.1 ± 0.03 W m-2) did not show any significant bias. However, a significant bias was apparent in the NEE measurements (slope of NEEOP on NEECP: 1.36 ± 0.02 & intercept: -0.1 ± 0.05). The differences between NEEOP and NEECP were linearly related to the magnitude of HCSAT3A with a slope of -0

  15. Liner velocity, current, and symmetry measurements on the 32 MEGAMP flux compression generator experiment ALT-1

    SciTech Connect

    Anderson, B. G.; Rodriguez, G.; Stokes, J. L.; Tabaka, L. J.; Clark, D. A.

    2001-01-01

    A flux compression generator pulse power system, designed, built, and fielded by a Russian team at the All Russian Scientific Research Institute of Experimental Physics (VNIIEF), was used to successfully drive an aluminum liner to velocities greater than 12 km/sec. The experiment objective was to demonstrate performance of a precision liner implosion at an Atlas current of 30 MA or greater. Diagnostics to measure liner performance were an essential part of the experiment. An experimental team from Los Alamos National Laboratory (LANL) provided a suite of diagnostics to measure liner performance. Three diagnostics were fielded: (1) A velocity interferometer (VISAR) to continuously measure the liner innersurface velocity throughout the entire range of travel, (2) Two Faraday rotation devices to measure liner current during the implosion, and, (3) Sixteen fiber optic impact pins to record liner impact time and provide axial and azimuthal symmetry information. All diagnostics performed very well. Major results are maximum current: 32.3 MA, velocity at impact: greater than 12 km/sec, symmetry: the impact pins indicated that the liner was smooth, solid, and axially symmetric upon arrival at the diagnostic package. The LANL team fabricated, installed, and recorded the three diagnostics presented here. All necessary equipment was brought to the site in Russia. The VNIIEF team fielded other diagnostics to measure machine performance. Results of machine diagnostics are reported in other presentations.

  16. Demonstration of HNO3 Eddy Flux Measurements at the Boulder Atmospheric Observatory Using Active Passivation

    NASA Astrophysics Data System (ADS)

    Roscioli, J. R.; Herndon, S. C.; Zahniser, M. S.; Nelson, D. D.; Zaragoza, J.; Pollack, I. B.; Fischer, E. V.

    2015-12-01

    Eddy flux measurements of "sticky" molecules have historically proven difficult due to strong interactions with instrument surfaces. A novel approach has been developed to improve these response times, enabling flux measurements of nitric acid (HNO3) and and ammonia (NH3). Deliberate addition of the vapor of perfluorinated acids and bases into a sample stream serves to eject existing surface-bound sample molecules and passivate instrument surfaces. HNO3 response times for an Aerodyne quantum cascade laser absorption spectrometer (QCLAS) improve by a factor of 60-fold when actively passivating. This approach was used during field measurements of HNO3 fluxes at the Boulder Atmospheric Observatory, where an actively passivated inertial inlet at 8 m height yielded HNO3 deposition fluxes of 0.5 - 2 nmol/m2/sec. The dependence of the deposition flux upon urban vs rural outflow is discussed.

  17. A comparison of six methods for measuring soil-surface carbon dioxide fluxes

    USGS Publications Warehouse

    Norman, J.M.; Kucharik, C.J.; Gower, S.T.; Baldocchi, D.D.; Crill, P.M.; Rayment, M.; Savage, K.; Striegl, R.G.

    1997-01-01

    Measurements of soil-surface CO2 fluxes are important for characterizing the carbon budget of boreal forests because these fluxes can be the second largest component of the budget. Several methods for measuring soil-surface CO2 fluxes are available: (1) closed-dynamic-chamber systems, (2) closed-static-chamber systems, (3) open-chamber systems, and (4) eddy covariance systems. This paper presents a field comparison of six individual systems for measuring soil-surface CO2 fluxes with each of the four basic system types represented. A single system is used as a reference and compared to each of the other systems individually in black spruce (Picea mariana), jack pine (Pinus banksiana), or aspen (Populus tremuloides) forests. Fluxes vary from 1 to 10 ??mol CO2 m-2 s-1. Adjustment factors to bring all of the systems into agreement vary from 0.93 to 1.45 with an uncertainty of about 10-15%.

  18. Natural Gas Seepage Along the Edge of the Aquitaine Shelf (France): Origin and Flux Measurements

    NASA Astrophysics Data System (ADS)

    Ruffine, L.; Donval, J. P.; Battani, A.; Bignon, L.; Croguennec, C.; Caprais, J. C.; Birot, D.; Bayon, G.; Lantéri, N.; Levaché, D.; Dupré, S.

    2014-12-01

    A newly discovered and highly active seepage area has been acoustically mapped at the western edge of the Aquitaine Shelf in the Bay of Biscay [Dupré et al., 2014]. Three selected seeping sites have been investigated with a Remotely Operated Vehicle. All sites were characterized by vigorous gas emissions, and the occurrence of massive carbonate crusts and bacterial mats at the seafloor. Nine seeps have been sampled with the PEGAZ sampler. The latter allowed gas-bubble sampling and preservation at in situpressure, together with gas-flux measurement through its graduated transparent cone. The C2+ fraction of the gas samples accounts for less than 0.06 %-mol of the total composition. Both the abundance of methane and dD and d13C isotopic analyses of the hydrocarbons indicate a biogenic source generated by microbial reduction of carbon dioxide [Whiticar et al., 1986]. The analyses of the associated noble gases also provide further support for a shallow-depth generation. While sharing the same origin, the collected samples are different in other respects, such as the measured d13C values for carbon dioxide and the hydrocarbons. This is the case in particular for methane, with displays values in between -66.1 and -72.7 ‰. We hypothesized that such variations are the result of multiple gas-transport processes along with the occurrence of hydrocarbon oxidation at different rates within the sedimentary column. The measured gas fluxes are extremely heterogeneous from one seep to another, ranging from 18 to 193 m3.yr-1. These values will be discussed in detail by comparing them with values obtained from different measurement techniques at other gas-seeping sites. The GAZCOGNE study is co-funded by TOTAL and IFREMER as part of the PAMELA (Passive Margin Exploration Laboratories) scientific project. References:Dupré, S., L. Berger, N. Le Bouffant, C. Scalabrin, and J. F. Bourillet (2014), Fluid emissions at the Aquitaine Shelf (Bay of Biscay, France): a biogenic origin or

  19. Corrective measures technology for humid sites

    SciTech Connect

    Spalding, B.P.

    1983-01-01

    The corrective measures technology task for humid sites consists of three subtasks. The first subtask has the objective of demonstrating that grout injection into closed burial trenches can achieve the hydrologic isolation of buried wastes. From laboratory testing of seven grout formulations, two promising grouts, 7.6% sodium silicate and 11.7% acrylamide, were selected for field demonstration by injection into 1:10-scale burial trenches. Both grouts effected a several orders of magnitude reduction in the mean hydraulic conductivity of the trench. The trench chemical treatment subtask has the objective of demonstrating the caustic soda injection into a closed trench's backfill and surrounding soil can achieve a fixation of radiostrontium from further ground water contamination. Monitoring of ground waters in and around the treated trench indicate a continued fixation of radiostrontium from further leaching. Soil samples were taken from the trench and found to contain /sup 90/Sr coprecipitated with calcium carbonate. The final subtask has the objective of demonstrating that the detection and treatment of ground water seeps can achieve a significant reduction in radiostrontium contamination of surface water. The utility of measuring /sup 90/Sr in ground water samples by Cerenkov radiation detection was found to be analytically equivalent to but considerably less expensive and time consuming than the standard radiochemical method.

  20. Increasing fluxes of S5 1044+71 measured with RATAN-600 radio telescope

    NASA Astrophysics Data System (ADS)

    Trushkin, S. T.; Mingaliev, M. G.; Sotnikova, Yu. V.; Erkenov, A.; Udovitskij, R. Yu.; Mufakharov, T. V.

    2014-02-01

    We report about the growing fluxes of the quasar S5 1044+71, identified with the FERMI source 2FGL J1048.3+714, since detection of the high state in the rest of January 2014 (ATEL #5792). We continue measurements and again detect the increase of the flux densities at frequencies 8.2-21.7 GHz in February.

  1. Balloon-borne measurements of the ultraviolet flux in the Arctic stratosphere during winter

    NASA Technical Reports Server (NTRS)

    Schiller, Cornelius; Mueller, Martin; Klein, Erich; Schmidt, Ulrich; Roeth, Ernst-Peter

    1994-01-01

    Filter radiometers sensitive from 280 to 320 nm and from 280 to 400 nm, respectively, were used for measurements of the actinic flux in the stratosphere. Since the instruments are calibrated for absolute spectral sensitivity the data can be compared with model calculations of the actinic flux. Data were obtained during seven balloon flights during the European Arctic Stratospheric Ozone Experiment (EASOE).

  2. An assessment of corrections for eddy covariance measured turbulent fluxes over snow in mountain environments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Snow-covered complex terrain is an extremely important runoff generating landscape in high altitude and latitude environments, yet is often considered non-viable for eddy covariance measurements of turbulent fluxes. Turbulent flux data are useful for evaluating the coupled snow cover mass and energ...

  3. Absolute beam flux measurement at NDCX-I using gold-melting calorimetry technique

    SciTech Connect

    Ni, P.A.; Bieniosek, F.M.; Lidia, S.M.; Welch, J.

    2011-04-01

    We report on an alternative way to measure the absolute beam flux at the NDCX-I, LBNL linear accelerator. Up to date, the beam flux is determined from the analysis of the beam-induced optical emission from a ceramic scintilator (Al-Si). The new approach is based on calorimetric technique, where energy flux is deduced from the melting dynamics of a gold foil. We estimate an average 260 kW/cm2 beam flux over 5 {micro}s, which is consistent with values provided by the other methods. Described technique can be applied to various ion species and energies.

  4. Predicting landscape-scale CO2 flux at a pasture and rice paddy with long-term hyperspectral canopy reflectance measurements

    NASA Astrophysics Data System (ADS)

    Matthes, J. H.; Knox, S. H.; Sturtevant, C.; Sonnentag, O.; Verfaillie, J.; Baldocchi, D.

    2015-08-01

    Measurements of hyperspectral canopy reflectance provide a detailed snapshot of information regarding canopy biochemistry, structure and physiology. In this study, we collected 5 years of repeated canopy hyperspectral reflectance measurements for a total of over 100 site visits within the flux footprints of two eddy covariance towers at a pasture and rice paddy in northern California. The vegetation at both sites exhibited dynamic phenology, with significant interannual variability in the timing of seasonal patterns that propagated into interannual variability in measured hyperspectral reflectance. We used partial least-squares regression (PLSR) modeling to leverage the information contained within the entire canopy reflectance spectra (400-900 nm) in order to investigate questions regarding the connection between measured hyperspectral reflectance and landscape-scale fluxes of net ecosystem exchange (NEE) and gross primary productivity (GPP) across multiple timescales, from instantaneous flux to monthly integrated flux. With the PLSR models developed from this large data set we achieved a high level of predictability for both NEE and GPP flux in these two ecosystems, where the R2 of prediction with an independent validation data set ranged from 0.24 to 0.69. The PLSR models achieved the highest skill at predicting the integrated GPP flux for the week prior to the hyperspectral canopy reflectance collection, whereas the NEE flux often achieved the same high predictive power at daily to monthly integrated flux timescales. The high level of predictability achieved by PLSR in this study demonstrated the potential for using repeated hyperspectral canopy reflectance measurements to help partition NEE into its component fluxes, GPP and ecosystem respiration, and for using quasi-continuous hyperspectral reflectance measurements to model regional carbon flux in future analyses.

  5. Carbon fluxes and export in the northern and middle Atlantic Sea measured with drifting sediment traps

    SciTech Connect

    Miquel, J-C; Fowler, S; Hamilton, T; Heilmann, J P; LaRosa, J; Carroll, M

    2000-07-26

    In July 1993 and June 1995 drifting sediment traps were deployed near the Po outflow, in the coastal zone and in the Jabuka Pit in order to obtain quantitative information on the vertical flux of particulate material and export of organic carbon in the Northern and Middle Adriatic Sea. During these periods and in July 1994, the standing stock of carbon and nitrogen in the water column were also estimated. Carbon and nitrogen concentrations were higher in the north with a mean of 266 {micro}g C l{sup -1} in surface waters as compared to 92 {micro}g C l{sup -1} in Middle Adriatic; maximum concentrations were associated to the less-saline surface-subsurface waters in the north and to the chlorophyll a maximum in the Middle Adriatic. Organic carbon flux was roughly five times higher near the Po than in the more oligotrophic waters of the central region, with overall values (0.8 to 11.5 mg m{sup -2} d{sup -1}) being low compared to the open Northwestern Mediterranean. Comparison with primary production measurements yielded estimates of carbon export (f-ratio) of 4.7 and 3.4% in the Po and Pit stations, respectively, in 1993 and of 1.6 and 3.6% in the central part of the Adriatic in 1995. These consistently low values suggest enhanced carbon recycling in the upper water column, even in regions characterized by different production and organic flux regimes. Zooplankton fecal pellets were important conveyors of organic carbon in this region; particularly those produced by fishes in the North and coastal sites.

  6. Measurement of the Magnetic Flux Noise Spectrum in Superconducting Xmon Transmon Quantum Bits

    NASA Astrophysics Data System (ADS)

    Chiaro, Ben; Sank, D.; Kelly, J.; Chen, Z.; Campbell, B.; Dunsworth, A.; O'Malley, P.; Neill, C.; Quintana, C.; Vainsencher, A.; Wenner, J.; Barends, R.; Chen, Y.; Fowler, A.; Jeffrey, E.; Migrant, A.; Mutus, J.; Roushan, P.; White, T.; Martinis, J. M.

    Dephasing induced by magnetic flux noise limits the performance of modern superconducting quantum processors. We measure the flux noise power spectrum in planar, frequency-tunable, Xmon transmon quantum bits (qubits), with several SQUID loop geometries. We extend the Ramsey Tomography Oscilloscope (RTO) technique by rapid sampling up to 1 MHz, without state reset, to measure the flux noise power spectrum between 10-2 and 105 Hz. The RTO measurements are combined with idle gate randomized benchmarking and Ramsey decay to give a more complete picture of dephasing in SQUID-based devices.

  7. Measuring eddy covariance fluxes of ozone with a slow-response analyser

    PubMed Central

    Wohlfahrt, Georg; Hörtnagl, Lukas; Hammerle, Albin; Graus, Martin; Hansel, Armin

    2013-01-01

    Ozone (O3) fluxes above a temperate mountain grassland were measured by means of the eddy covariance (EC) method using a slow-response O3 analyser. The resultant flux loss was corrected for by a series of transfer functions which model the various sources of high- and, in particular, low-pass filtering. The resulting correction factors varied on average between 1.7 and 3.5 during night and day time, respectively. A cospectral analysis confirmed the accuracy of this approach. O3 fluxes were characterised by a comparatively large random uncertainty, which during daytime typically amounted to 60 %. EC O3 fluxes were compared against O3 flux measurements made concurrently with the flux-gradient (FG) method. The two methods generally agreed well, except for a period between sun rise and early afternoon, when the FG method was suspected of being affected by the presence of photochemical sources/sinks. O3 flux magnitudes and deposition velocities determined with the EC method compared nicely with the available literature from grassland studies. We conclude that our understanding of the causes and consequences of various sources of flux loss (associated with any EC system) has sufficiently matured so that also less-than-ideal instrumentation may be used in EC flux applications, albeit at the cost of relatively large empirical corrections. PMID:24348085

  8. Using Vapor Phase Tomography to Measure the Spatial Distribution of Vapor Concentrations and Flux for Vadose-zone VOC Sources

    PubMed Central

    Mainhagu, J.; Morrison, C.; Brusseau, M.L.

    2015-01-01

    A test was conducted at a chlorinated-solvent contaminated site in Tucson, AZ, to evaluate the effectiveness of vapor-phase tomography (VPT) for characterizing the distribution of volatile organic contaminants (VOC) in the vadose zone. A soil vapor extraction (SVE) system has been in operation at the site since 2007. Vapor concentration and vacuum pressure were measured at four different depths in each of four monitoring wells surrounding the extraction well. The test provided a 3D characterization of local vapor concentrations under induced-gradient conditions. Permeability data obtained from analysis of borehole logs were combined with the vapor-concentration data to determine VOC mass flux within the test domain. A region of higher mass flux was identified in the deepest interval of the S-SW section of the domain, indicating the possible location of a zone with greater contaminant mass. These results are consistent with the TCE-concentration distribution obtained from sediment coring conducted at the site. In contrast, the results of a standard soil gas survey did not indicate the presence of a zone with greater contaminant mass. These results indicate that the VPT test provided a robust characterization of VOC concentration and flux distribution at the site. PMID:25835545

  9. Using Vapor Phase Tomography to Measure the Spatial Distribution of Vapor Concentrations and Flux for Vadose-Zone VOC Sources

    NASA Astrophysics Data System (ADS)

    Mainhagu, J.; Brusseau, M. L. L.; Morrison, C. N.

    2015-12-01

    A test was conducted at a chlorinated-solvent contaminated site in Tucson, AZ, to evaluate the effectiveness of vapor-phase tomography (VPT) for characterizing the distribution of volatile organic contaminants (VOC) in the vadose zone. A soil vapor extraction (SVE) system has been in operation at the site since 2007. Vapor concentration and vacuum pressure were measured at four different depths in each of the four monitoring wells surrounding the extraction well. The test provided a 3D characterization of local vapor concentrations under induced-gradient conditions. Permeability data obtained from analysis of borehole logs were used along with pressure and the vapor-concentration data to determine VOC mass flux within the test domain. A region of higher mass flux was identified in the deepest interval of the S-SW section of the domain, indicating the possible location of a zone with greater contaminant mass. These results are consistent with the TCE-concentration distribution obtained from sediment coring conducted at the site. In contrast, the results of a standard soil gas survey did not indicate the presence of a zone with greater contaminant mass. These results indicate that the VPT test provided a robust characterization of VOC concentration and flux distribution at the site.

  10. Using vapor phase tomography to measure the spatial distribution of vapor concentrations and flux for vadose-zone VOC sources

    NASA Astrophysics Data System (ADS)

    Mainhagu, J.; Morrison, C.; Brusseau, M. L.

    2015-06-01

    A test was conducted at a chlorinated-solvent contaminated site in Tucson, AZ, to evaluate the effectiveness of vapor-phase tomography (VPT) for characterizing the distribution of volatile organic contaminants (VOC) in the vadose zone. A soil vapor extraction (SVE) system has been in operation at the site since 2007. Vapor concentration and vacuum pressure were measured at four different depths in each of the four monitoring wells surrounding the extraction well. The test provided a 3D characterization of local vapor concentrations under induced-gradient conditions. Permeability data obtained from analysis of borehole logs were used along with pressure and the vapor-concentration data to determine VOC mass flux within the test domain. A region of higher mass flux was identified in the deepest interval of the S-SW section of the domain, indicating the possible location of a zone with greater contaminant mass. These results are consistent with the TCE-concentration distribution obtained from sediment coring conducted at the site. In contrast, the results of a standard soil gas survey did not indicate the presence of a zone with greater contaminant mass. These results indicate that the VPT test provided a robust characterization of VOC concentration and flux distribution at the site.

  11. A 3-year dataset of sensible and latent heat fluxes from the Tibetan Plateau, derived using eddy covariance measurements

    NASA Astrophysics Data System (ADS)

    Li, Maoshan; Babel, Wolfgang; Chen, Xuelong; Zhang, Lang; Sun, Fanglin; Wang, Binbin; Ma, Yaoming; Hu, Zeyong; Foken, Thomas

    2015-11-01

    The Tibetan Plateau (TP) has become a focus of strong scientific interest due to its role in the global water cycle and its reaction to climate change. Regional flux estimates of sensible and latent heat are important variables for linking the energy and hydrological cycles at the TP's surface. Within this framework, a 3-year dataset (2008-2010) of eddy covariance measured turbulent fluxes was compiled from four stations on the TP into a standardised workflow: corrections and quality tests were applied using an internationally comparable software package. Second, the energy balance closure ( C EB) was determined and two different closure corrections applied. The four stations (Qomolangma, Linzhi, NamCo and Nagqu) represent different locations and typical land surface types on the TP (high altitude alpine steppe with sparse vegetation, a densely vegetated alpine meadow, and bare soil/gravel, respectively). We show that the C EB differs between each surface and undergoes seasonal changes. Typical differences in the turbulent energy fluxes occur between the stations at Qomolangma, Linzhi and NamCo, while Nagqu is quite similar to NamCo. Specific investigation of the pre-monsoon, the Tibetan Plateau summer monsoon, post-monsoon and winter periods within the annual cycle reinforces these findings. The energy flux of the four sites is clearly influenced by the Tibetan Plateau monsoon. In the pre-monsoon period, sensible heat flux is the major energy source delivering heat to the atmosphere, whereas latent heat flux is greater than sensible heat flux during the monsoon season. Other factors affecting surface energy flux are topography and location. Land cover type also affects surface energy flux. The energy balance residuum indicates a typically observed overall non-closure in winter, while closure (or `turbulent over-closure') is achieved during the Tibetan Plateau summer monsoon at the Nagqu site. The latter seems to depend on ground heat flux, which is higher in the

  12. Energy Balance Closure Using Eddy Covariance Above Two Different Land Surfaces and Implications for CO2 Flux Measurements

    NASA Astrophysics Data System (ADS)

    Kidston, Joe; Brümmer, Christian; Black, T. Andrew; Morgenstern, Kai; Nesic, Zoran; McCaughey, J. Harry; Barr, Alan G.

    2010-08-01

    Components of the surface energy balance of a mature boreal jack pine forest and a jack pine clearcut were analysed to determine the causes of the imbalance that is commonly observed in micrometeorological measurements. At the clearcut site (HJP02), a significant portion of the imbalance was caused by: (i) the overestimation of net radiation ( R n ) due to the inclusion of the tower in the field of view of the downward facing radiometers, and (ii) the underestimation of the latent heat flux (λ E) due to the damping of high frequency fluctuations in the water vapour mixing ratio by the sample tube of the closed-path infrared gas analyzer. Loss of low-frequency covariance induced by insufficient averaging time as well as systematic advection of fluxes away from the eddy-covariance (EC) tower were discounted as significant issues. Spatial and temporal distributions of the total surface-layer heat flux ( T), i.e. the sum of sensible heat flux ( H) and λ E, were well behaved and differences between the relative magnitudes of the turbulent fluxes for several investigated energy balance closure ( C) classes were observed. Therefore, it can be assumed that micrometeorological processes that affected all turbulent fluxes similarly did not cause the variation in C. Turbulent fluxes measured at the clearcut site should not be forced to close the energy balance. However, at the mature forest site (OJP), loss of low-frequency covariance contributed significantly to the systematic imbalance when a 30-min averaging time was used, but the application of averaging times that were long enough to capture all of the low-frequency covariance was inadequate to resolve all of the high-frequency covariance. Although we found qualitative similarity between T and the net ecosystem exchange (NEE) of carbon dioxide (CO2), forcing T to closure while retaining the Bowen ratio and applying the same factor to CO2 fluxes ( F C ) cannot be generally recommended since it remains uncertain to what

  13. A framework to utilize turbulent flux measurements for mesoscale models and remote sensing applications

    NASA Astrophysics Data System (ADS)

    Babel, W.; Huneke, S.; Foken, T.

    2011-05-01

    Meteorologically measured fluxes of energy and matter between the surface and the atmosphere originate from a source area of certain extent, located in the upwind sector of the device. The spatial representativeness of such measurements is strongly influenced by the heterogeneity of the landscape. The footprint concept is capable of linking observed data with spatial heterogeneity. This study aims at upscaling eddy covariance derived fluxes to a grid size of 1 km edge length, which is typical for mesoscale models or low resolution remote sensing data. Here an upscaling strategy is presented, utilizing footprint modelling and SVAT modelling as well as observations from a target land-use area. The general idea of this scheme is to model fluxes from adjacent land-use types and combine them with the measured flux data to yield a grid representative flux according to the land-use distribution within the grid cell. The performance of the upscaling routine is evaluated with real datasets, which are considered to be land-use specific fluxes in a grid cell. The measurements above rye and maize fields stem from the LITFASS experiment 2003 in Lindenberg, Germany and the respective modelled timeseries were derived by the SVAT model SEWAB. Contributions from each land-use type to the observations are estimated using a forward lagrangian stochastic model. A representation error is defined as the error in flux estimates made when accepting the measurements unchanged as grid representative flux and ignoring flux contributions from other land-use types within the respective grid cell. Results show that this representation error can be reduced up to 56 % when applying the spatial integration. This shows the potential for further application of this strategy, although the absolute differences between flux observations from rye and maize were so small, that the spatial integration would be rejected in a real situation. Corresponding thresholds for this decision have been estimated as

  14. Time and Space Resolved Heat Transfer Measurements Under Nucleate Bubbles with Constant Heat Flux Boundary Conditions

    NASA Technical Reports Server (NTRS)

    Myers, Jerry G.; Hussey, Sam W.; Yee, Glenda F.; Kim, Jungho

    2003-01-01

    Investigations into single bubble pool boiling phenomena are often complicated by the difficulties in obtaining time and space resolved information in the bubble region. This usually occurs because the heaters and diagnostics used to measure heat transfer data are often on the order of, or larger than, the bubble characteristic length or region of influence. This has contributed to the development of many different and sometimes contradictory models of pool boiling phenomena and dominant heat transfer mechanisms. Recent investigations by Yaddanapyddi and Kim and Demiray and Kim have obtained time and space resolved heat transfer information at the bubble/heater interface under constant temperature conditions using a novel micro-heater array (10x10 array, each heater 100 microns on a side) that is semi-transparent and doubles as a measurement sensor. By using active feedback to maintain a state of constant temperature at the heater surface, they showed that the area of influence of bubbles generated in FC-72 was much smaller than predicted by standard models and that micro-conduction/micro-convection due to re-wetting dominated heat transfer effects. This study seeks to expand on the previous work by making time and space resolved measurements under bubbles nucleating on a micro-heater array operated under constant heat flux conditions. In the planned investigation, wall temperature measurements made under a single bubble nucleation site will be synchronized with high-speed video to allow analysis of the bubble energy removal from the wall.

  15. A direct passive method for measuring water and contaminant fluxes in porous media

    NASA Astrophysics Data System (ADS)

    Hatfield, Kirk; Annable, Michael; Cho, Jaehyun; Rao, P. S. C.; Klammler, Harald

    2004-12-01

    This paper introduces a new direct method for measuring water and contaminant fluxes in porous media. The method uses a passive flux meter (PFM), which is essentially a self-contained permeable unit properly sized to fit tightly in a screened well or boring. The meter is designed to accommodate a mixed medium of hydrophobic and/or hydrophilic permeable sorbents, which retain dissolved organic/inorganic contaminants present in the groundwater flowing passively through the meter. The contaminant mass intercepted and retained on the sorbent is used to quantify cumulative contaminant mass flux. The sorptive matrix is also impregnated with known amounts of one or more water soluble 'resident tracers'. These tracers are displaced from the sorbent at rates proportional to the groundwater flux; hence, in the current meter design, the resident tracers are used to quantify cumulative groundwater flux. Theory is presented and quantitative tools are developed to interpret the water flux from tracers possessing linear and nonlinear elution profiles. The same theory is extended to derive functional relationships useful for quantifying cumulative contaminant mass flux. To validate theory and demonstrate the passive flux meter, results of multiple box-aquifer experiments are presented and discussed. From these experiments, it is seen that accurate water flux measurements are obtained when the tracer used in calculations resides in the meter at levels representing 20 to 70 percent of the initial condition. 2,4-Dimethyl-3-pentanol (DMP) is used as a surrogate groundwater contaminant in the box aquifer experiments. Cumulative DMP fluxes are measured within 5% of known fluxes. The accuracy of these estimates generally increases with the total volume of water intercepted.

  16. Eddy covariance carbonyl sulfide flux measurements with a quantum cascade laser absorption spectrometer

    NASA Astrophysics Data System (ADS)

    Gerdel, Katharina; Spielmann, Felix M.; Hammerle, Albin; Wohlfahrt, Georg

    2016-04-01

    Carbonyl sulfide (COS) is the most abundant sulfur containing trace gas present in the troposphere at concentrations of around 500 ppt. Recent interest in COS by the ecosystem-physiological community has been sparked by the fact that COS co-diffuses into plant leaves pretty much the same way as carbon dioxide (CO2) does, but in contrast to CO2, COS is not known to be emitted by plants. Thus uptake of COS by vegetation has the potential to be used as a tracer for canopy gross photosynthesis, which cannot be measured directly, however represents a key term in the global carbon cycle. Since a few years, quantum cascade laser absorption spectrometers (QCLAS) are commercially available with the precision, sensitivity and time response suitable for eddy covariance (EC) flux measurements. While there exist a handful of published reports on EC flux measurements in the recent literature, no rigorous investigation of the applicability of QCLAS for EC COS flux measurements has been carried out so far, nor have been EC processing and QA/QC steps developed for carbon dioxide and water vapor flux measurements within FLUXNET been assessed for COS. The aim of this study is to close this knowledge gap, to discuss critical steps in the post-processing chain of COS EC flux measurements and to devise best-practice guidelines for COS EC flux data processing. To this end we collected EC COS (and CO2, H2O and CO) flux measurements above a temperate mountain grassland in Austria over the vegetation period 2015 with a commercially available QCLAS. We discuss various aspects of EC data post-processing, in particular issues with the time-lag estimation between sonic anemometer and QCLAS signals and QCLAS time series detrending, as well as QA/QC, in particular flux detection limits, random flux uncertainty, the interaction of various processing steps with common EC QA/QC filters (e.g. detrending and stationarity tests), u*-filtering, etc.

  17. A preliminary evaluation of an O2/CO2 based eddy covariance theory at Missouri AmeriFlux site

    NASA Astrophysics Data System (ADS)

    Yan, B.; Gu, L.

    2013-12-01

    The eddy covariance (EC) technique has been widely used at flux sites on every continent, across most ecosystem types and climates to monitor exchanges of momentum, mass and energy between land surface and atmosphere. In an attempt to develop a self-consistent theory for the EC technique, Gu et al. (2012) reformulated the fundamental equations for EC by introducing the concept of constraining gas that has no net ecosystem sink/source. Gu (2013) expanded the theory of Gu et al. (2012) to include paired gases whose ecosystem exchange ratios are stable over an averaging period (e.g. 30 min) and therefore can be used to constrain EC flux measurements of any gases. He proposed that O2 and CO2 are an ideal pair of gases as their biological processes are coupled and their ecosystem exchange ratio (also known as oxidative ratio) is close to 1. Advantages of this new O2/CO2 based EC theory include: 1) avoidance of covariance loss in calculating dry air density induced by spatial separation of measuring instruments and use of multiple indirectly derived variables, 2) the minimum number of assumptions adopted for the derivation of the equation, and 3) avoidance of errors related to linearization of ideal gas law. In this study, we conducted a preliminary evaluation for the basic principle of Gu (2013) EC theory. We crosschecked net ecosystem exchange (NEE) estimations from different, i