These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Design of a differential radiometer for atmospheric radiative flux measurements  

SciTech Connect

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.

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

1994-11-01

2

Measuring Longwave Radiative Flux Divergence in an Urban Canyon  

NASA Astrophysics Data System (ADS)

There has been very little measurement of longwave radiation divergence since the urban studies of Fuggle, Oke and Nunez in the mid 1970's or the rural work of Funk in the early 1960's. Although radiative divergence has been widely ignored for sometime there is the belief that it may play an important role in balancing nocturnal energy budgets in a range of environments. For example, in urban environments surface temperature relates well to the energy balance whereas air temperature does not, even in non-turbulent conditions. This is probably due at least in part to the effects of longwave divergence. To help answer issues related to longwave divergence a new dual-channel infrared radiometer (DCIR) has been developed. The DCIR, as the name implies, measures the directional infrared radiation in two wavebands and can, through differencing of the signals and further signal processing, give a direct measurement of longwave radiative flux divergence. The DCIR was deployed for the first time as part of a larger study (BUBBLE) of the urban boundary layer of Basel, Switzerland. The objective is to further study the thermal regime of a city at the canyon scale. To this end, a street canyon was carefully selected, in the city of Basel. The canyon surface and air volume were instrumented, including turbulent and conductive fluxes, and standard meteorological variables in addition to radiation. A unique data set was obtained to allow the complete energy balance of the canyon system to be evaluated without the need to resort to using residuals to quantify the magnitude of the longwave radiative flux divergence. Measured values of longwave flux-divergence are converted to cooling rates to compare with measured air temperature cooling. Preliminary results show that at the onset of canyon air-volume cooling, measured cooling rates are slightly lower than radiative cooling rates. The differences are less than 0.5° C. This contrasts sharply with previously measured above roof level and rural differences of greater than 5° C. The difference between the rural and above-canyon case and the in-canyon case is most likely a result of differences in radiative environments and wind and temperature fields. The differences illustrate the strong role of urbanization on the surface energy budget.

Soux, A.; Oke, T. R.; Nunez, M.; Wilson, M.

2003-12-01

3

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

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

4

Measuring Radiation Heat Fluxes from a Jet Fire Using a Lumped Capacitance Model  

Microsoft Academic Search

This paper presents an experimental methodology for measuring the incident radiation heat flux distribution surrounding a\\u000a jet fire. The methodology uses a line of surface thermocouples attached to a steel bar. The thermocouples measure the temperature\\u000a time history of the steel bar in response to an imposed incident radiation heat flux. The theoretical basis of the methodology\\u000a is an energy

Peter S. Cumber

2011-01-01

5

Determination of solar proton fluxes and energies at high solar latitudes by UV radiation measurements  

NASA Technical Reports Server (NTRS)

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.

Witt, N.; Blum, P. W.; Ajello, J. M.

1981-01-01

6

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

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

7

Characterisation of radiation and flux measurements on a neutraliser plate of the Tore Supra ergodic divertor  

Microsoft Academic Search

A recent extensive experimental study of impurity production and penetration for various density regimes is described. Deuterium and carbon emissions near a neutraliser plate (NP) of the Tore Supra Ergodic Divertor (ED) has been measured with an absolutely calibrated visible endoscope, for high- and low-density plasma regimes. From these radiation measurements, we have deduced an effective carbon flux, and at

Y. Corre; R. Giannella; C. De Michelis; R. Guirlet; A. Azeroual; E. Chareyre; L. Costanzo; A. Escarguel; E. Gauthier; P. Ghendrih; J. Gunn; J. Hogan; P. Monier-Garbet; B. Pégourié; A. Pospieszczyk; E. Tsitrone

2001-01-01

8

Radiative transfer in cirrus clouds from airborne flux and microphysical measurements during FIRE 86  

NASA Technical Reports Server (NTRS)

Microphysical and radiation measurements from three case studies during FIRE 86 are presented and analyzed. Calculated solar and infrared flux profiles are compared to measured flux values for the studies. The flux comparison shows that the modeled cirrus cloud underestimates cloud extinction, especially near the cloud base, where modeled extinctions are largest. The large downward solar attenuation near the cloud base cannot be matched, while the modeled solar reflection is too small. Most of this difference is attributed to an underestimation of cloud optical depth in the model. Modeling difficulties and difficulties in the measurements are discussed. It is proposed that, in order to assure a more useful flux comparison, field experiment set-ups and instrumentation as well as the modeling of cirrus clouds need to be improved.

Kinne, S.; Ackerman, T.; Heymsfield, A.; Miller, K.

1990-01-01

9

Temperature and Radiative Heat Flux Measurements in Microgravity Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

The objective of this project is to provide detailed measurements and modeling analyses of local soot concentration, temperature and radiation heat flux distributions in laminar and turbulent jet diffusion flames under normal (1-g) and reduced gravity (0-g) conditions. Results published to date by these co-PI's and their co-workers include: 1. thermophoretic sampling and size and morphological analyses of soot aggregates in laminar flames under normal and reduced gravity conditions; 2. full-field absorption imaging for soot volume fraction maps in laminar and turbulent flames under normal and reduced gravity conditions; 3. an accurate solver module for detailed radiation heat transfer in nongray nonhomogeneous media; 4. a complete model to include flame structure, soot formation and an energy equation to couple with radiation solver.

Ku, Jerry C.; Greenberg, Paul S.

1997-01-01

10

Heat flux microsensor measurements  

NASA Technical Reports Server (NTRS)

A thin-film heat flux sensor has been fabricated on a stainless steel substrate. The thermocouple elements of the heat flux sensor were nickel and nichrome, and the temperature resistance sensor was platinum. The completed heat flux microsensor was calibrated at the AEDC radiation facility. The gage output was linear with heat flux with no apparent temperature effect on sensitivity. The gage was used for heat flux measurements at the NASA Langley Vitiated Air Test Facility. Vitiated air was expanded to Mach 3.0 and hydrogen fuel was injected. Measurements were made on the wall of a diverging duct downstream of the injector during all stages of the hydrogen combustion tests. Because the wall and the gage were not actively cooled, the wall temperature reached over 1000 C (1900 F) during the most severe test.

Terrell, J. P.; Hager, J. M.; Onishi, S.; Diller, T. E.

1992-01-01

11

Surface Measurements of Solar Spectral Radiative Flux in the Cloud-Free Atmosphere  

NASA Technical Reports Server (NTRS)

Recent studies (Charlock, et al.; Kato, et. al) have indicated a potential discrepancy between measured solar irradiance in the cloud-free atmosphere and model derived downwelling solar irradiance. These conclusions were based primarily on broadband integrated solar flux. Extinction (both absorption and scattering) phenomena, however, typically have spectral characteristics that would be present in moderate resolution (e.g., 10 nm) spectra, indicating the need for such measurements to thoroughly investigate the cause of any discrepancies. The 1996 Department of Energy Atmospheric Radiation Measurement Program (ARM) Intensive Observation Period (IOP), held simultaneously with the NASA Subsonic Aircraft: Contrail and Cloud Effects Special Study (SUCCESS) Program, provided an opportunity for two simultaneous but independent measurements of moderate resolution solar spectral downwelling irradiance at the surface. The instruments were the NASA Ames Solar Spectral Flux Radiometer and the Analytical Spectral Devices, Inc., FieldSpecT-FR. Spectral and band integrated quantities from both sets of measurements will be presented, along with estimates of the downwelling solar irradiance from band model and line by line calculations, in an effort to determine the compatibility between measured and calculated solar irradiance in the cloud-free atmosphere.

Pilewskie, Peter; Goetz, A. F. H.; Bergstrom, R.; Beal, D.; Gore, Warren J. Y. (Technical Monitor)

1997-01-01

12

GEWEX Radiative Flux Assessment  

Atmospheric Science Data Center

... detail and accuracy to diagnose the causes of recent climate variations in terms of the energy and water exchanges among the main ... project will provide a forum for consistent analysis of long-term radiative flux products, primarily top-of-atmosphere (TOA) and ...

2013-06-27

13

On the estimation of the forest fire front position by radiative flux measurement.  

E-print Network

of the radiative flux obtained by sensors to estimate the fire front position. The inverse method developed the study. Some models of forest fire propagation at large scale are reaction diffusion systems, see [1 from flames, evT T! = is the characteristic function of the zone of evaporation. This model supposes

Bergmann, Michel

14

A non-water-cooled heat flux measurement system under concentrated solar radiation conditions  

Microsoft Academic Search

This paper presents a brief description of a direct heat flux measurement system to measure the concentrated solar power delivered by a heliostat field onto the flat aperture of solar central receiver prototypes. The main advantages of this device are the low measurement uncertainty and the non-requirement of water-cooling. This system has been designed, mounted and used successfully on top

Jesus Ballestrin

2002-01-01

15

The uncertainty of UTCI due to uncertainties in the determination of radiation fluxes derived from measured and observed meteorological data  

Microsoft Academic Search

In the present study, we investigate the determination accuracy of the Universal Thermal Climate Index (UTCI). We study especially\\u000a the UTCI uncertainties due to uncertainties in radiation fluxes, whose impacts on UTCI are evaluated via the mean radiant\\u000a temperature (Tmrt). We assume “normal conditions”, which means that usual meteorological information and data are available but no special\\u000a additional measurements. First,

Philipp Weihs; Henning Staiger; Birger Tinz; Ekaterina Batchvarova; Harald Rieder; Laurent Vuilleumier; Marion Maturilli; Gerd Jendritzky

2011-01-01

16

Measuring surface fluxes in CAPE  

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

17

Conical electromagnetic radiation flux concentrator  

NASA Technical Reports Server (NTRS)

Concentrator provides method of concentrating a beam of electromagnetic radiation into a smaller beam, presenting a higher flux density. Smaller beam may be made larger by sending radiation through the device in the reverse direction.

Miller, E. R.

1972-01-01

18

Radiative Flux Changes by Aerosols from North America, Europe, and Africa over the Atlantic Ocean: Measurements and Calculations from TARFOX and ACE-2  

NASA Technical Reports Server (NTRS)

Aerosol effects on atmospheric radiative fluxes provide a forcing function that is a major source of uncertainty in understanding the past climate and predicting climate change. To help reduce this uncertainty, the 1996 Tropospheric Aerosol Radiative Forcing Experiment (TARFOX) and the 1997 second Aerosol Characterization Experiment (ACE-2) measured the properties and radiative effects of American, European, and African aerosols over the Atlantic. In TARFOX, radiative fluxes and microphysics of the American aerosol were measured from the UK C-130 while optical depth spectra, aerosol composition, and other properties were measured by the University of Washington C-131A and the CIRPAS Pelican. Closure studies show that the measured flux changes agree with those derived from the aerosol measurements using several modelling approaches. The best-fit midvisible single-scatter albedos (approx. 0.89 to 0.93) obtained from the TARFOX flux comparisons are in accord with values derived by independent techniques. In ACE-2 we measured optical depth and extinction spectra for both European urban-marine aerosols and free-tropospheric African dust aerosols, using sunphotometers on the R/V Vodyanitskiy and the Pelican. Preliminary values for the radiative flux sensitivities (Delta Flux / Delta Optical depth) computed for ACE-2 aerosols (boundary layer and African dust) over ocean are similar to those found in TARFOX. Combining a satellite-derived optical depth climatology with the aerosol optical model validated for flux sensitivities in TARFOX provides first-cut estimates of aerosol-induced flux changes over the Atlantic Ocean.

Russell, P. B.; Hignett, P.; Livingston, J. M.; Schmid, B.; Chien, A.; Bergstrom, R.; Durkee, P. A.; Hobbs, P. V.; Bates, T. S.; Quinn, P. K.; Condon, Estelle (Technical Monitor)

1998-01-01

19

Heat flux measurements  

SciTech Connect

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.

Liebert, C.H.; Weikle, D.H.

1989-01-01

20

Fast Longwave and Shortwave Radiative Flux (FLASHFlux) Products from CERES and MODIS Measurements  

NASA Technical Reports Server (NTRS)

The Clouds and the Earth s Radiant Energy Systems (CERES) project is currently producing world-class climatological data products derived from measurements taken aboard the Terra and Aqua spacecrafts (Wielicki et al., 1996). While of exceptional fidelity, these data products require a considerable amount of processing to assure quality and verify accuracy and precision. Obtaining such high quality assurance, however, means that the CERES data is typically released more than six months after the acquisition of the initial measurements. For climate studies, such delays are of little consequence, especially considering the improved quality of the released data products. There are, however, many uses for the CERES data products on a near real-time basis. These include: CERES instrument calibration and subsystem quality checks, CLOUDSAT operations, seasonal predictions, agricultural and ocean assimilations, support of field campaigns, and outreach programs such as S'Cool. The FLASHflux project was envisioned as a conduit whereby CERES data could be provided to the community within a week of the initial measurements, with the trade-off that some degree of fidelity would be exacted to gain speed. In this paper, we will report on some very encouraging initial results from the FLASHflux project in which we compared the FLASHflux instantaneous surface fluxes to the CERES surface-only flux algorithm data products.

Stackhouse, Paul W., Jr.; Kratz, David P.; McGarragh, Greg R.; Gupta, Shashi K.; Geier, Erika B.

2006-01-01

21

Fast Longwave and Shortwave Radiative Fluxes (FLASHFlux) From CERES and MODIS Measurements  

Microsoft Academic Search

The Clouds and the Earth's Radiant Energy System (CERES) project is currently producing highly accurate surface and top-of-atmosphere (TOA) radiation budget datasets from measurements taken by CERES broadband radiometers and a subset of imaging channels on the Moderate-resolution Imaging Spectroradiometer (MODIS) instrument operating onboard Terra and Aqua satellites. The primary objective of CERES is to produce highly accurate and stable

Paul Stackhouse; Shashi Gupta; David Kratz; Erika Geier; Anne Edwards; Anne Wilber

2008-01-01

22

Atmospheric State, Cloud Microphysics and Radiative Flux  

DOE Data Explorer

Atmospheric thermodynamics, cloud properties, radiative fluxes and radiative heating rates for the ARM Southern Great Plains (SGP) site. The data represent a characterization of the physical state of the atmospheric column compiled on a five-minute temporal and 90m vertical grid. Sources for this information include raw measurements, cloud property and radiative retrievals, retrievals and derived variables from other third-party sources, and radiative calculations using the derived quantities.

Mace, Gerald

23

Atmospheric State, Cloud Microphysics and Radiative Flux  

SciTech Connect

Atmospheric thermodynamics, cloud properties, radiative fluxes and radiative heating rates for the ARM Southern Great Plains (SGP) site. The data represent a characterization of the physical state of the atmospheric column compiled on a five-minute temporal and 90m vertical grid. Sources for this information include raw measurements, cloud property and radiative retrievals, retrievals and derived variables from other third-party sources, and radiative calculations using the derived quantities.

Mace, Gerald

2008-01-15

24

Measured and calculated clear-sky solar radiative fluxes during the Subsonic Aircraft Contrail and Cloud Effects Special Study (SUCCESS)  

SciTech Connect

Modeled and measured surface insolations are compared with the purpose of evaluating the ability of a radiative transfer model to predict the amount of solar radiation reaching the surface under clear-sky conditions. Model uncertainties are estimated by performing sensitivity studies for variations in aerosol optical depth, aerosol optical properties, water vapor profiles, ozone content, solar irradiance at the top of the atmosphere, and surface albedo. In this fashion, a range of possible calculated values is determined and compared to observations. Experimental errors are evaluated by comparison with independent, simultaneous measurements performed using two World Radiation Reference instrument arrays that were operational for a limited period during SUCCESS. Assuming a mineral aerosol, it is found that there is agreement between calculated and measured fluxes, with differences approximately equal to and within one standard deviation. Such agreement improves further if a layer containing a small amount of carbonaceous aerosol is added. The presence of carbonaceous aerosols is likely because occasional biomass burning activities took place during SUCCESS in the area around the experimental site (the clouds and radiation test bed operated by the Department of Energy in Oklahoma). (c) 2000 American Geophysical Union.

Valero, Francisco P. J. [Atmospheric Research Laboratory, Center for Atmospheric Sciences, Scripps Institution of Oceanography, University of California, San Diego, California (United States)] [Atmospheric Research Laboratory, Center for Atmospheric Sciences, Scripps Institution of Oceanography, University of California, San Diego, California (United States); Bush, Brett C. [Atmospheric Research Laboratory, Center for Atmospheric Sciences, Scripps Institution of Oceanography, University of California, San Diego, California (United States)] [Atmospheric Research Laboratory, Center for Atmospheric Sciences, Scripps Institution of Oceanography, University of California, San Diego, California (United States)

1999-11-27

25

A method for continuous estimation of clear-sky downwelling longwave radiative flux developed using ARM surface measurements  

NASA Astrophysics Data System (ADS)

We present an improved self-adaptive methodology for the continuous estimation of downwelling clear-sky longwave (LW) radiative flux based on analysis of surface irradiance, air temperature, and humidity measurements that includes a term to account for near surface optically thin haze. Comparison between our estimations and clear-sky LW measurements for many years of data from the Atmospheric Radiation Measurement (ARM) Climate Research Facility's Southern Great Plains (SGP), Tropical Western Pacific (TWP), and North Slope of Alaska (NSA) sites show agreement at about the 4 W m-2 level, with 75%, 94%, and 68% of the data falling within that range for the SGP, TWP, and NSA sites, respectively. Although there is no exact means of determining the uncertainty associated with the clear-sky LW estimations, our analyses and comparison with detailed radiative transfer (RT) model calculations suggest our estimations on average are no worse than model calculations that require temporally and spatially averaged input information. Our technique exhibits a high degree of repeatability for the downwelling LW cloud effect, with agreement at about the 3 W m-2 level. Applying our technique and that of Long and Ackerman (2000) to 15 years of data from the ARM SGP site shows the maximum all-sky and clear-sky SW and LW occurs during summer, with the greatest year-to-year clear-sky SW variability occurring in fall. The downwelling LW cloud effect is fairly constant across the seasons, but the greatest SW cloud effect occurs in spring. The downwelling net cloud effect is dominated by the SW, with the largest effect occurring in spring (-64 W m-2) and the smallest occurring during winter (-21 W m-2).

Long, C. N.; Turner, D. D.

2008-09-01

26

Development of a balloon-borne stabilized platform for measuring radiative flux profiles in the atmospheric boundary layer  

SciTech Connect

A stabilized platform has been developed to carry broadband short-wave and long-wave radiometric sensors on the tether line of a small tethered balloon that ascends through atmospheric depths of up to 1.5 km to obtain vertical profiles of radiative flux and flux divergence for evaluating atmospheric radiative transfer models. The Sky Platform was designed to keep the radiometers level despite unpredictable movements of the balloon and tether line occasioned by turbulence and wind shear. The automatic control loop drives motors, gears, and pulleys located on two of the vertices of the triangular frame to climb the harness lines to keep the platform level. Radiometric sensors, an electronic compass, and an on-board data acquisition system make up the remainder of the Sky Platform. Because knowledge of the dynamic response of the tether line-platform system is essential to properly close the automatic control loop on the Sky Platform, a Motion Sensing Platform (MSP) was developed to fly in place of the Sky Platform on the tether line to characterize the Sky Platform`s operating environment. This unstabilized platform uses an array of nine solid-state linear accelerometers to measure the lateral and angular accelerations, velocities, and displacements that the Sky Platform will experience. This paper presents field performance tests of the Sky and Motion Sensing Platforms, as conducted at Richland, Washington, on February 17, 1993. The tests were performed primarily to characterize the stabilization system on the Sky Platform. Test flights were performed on this cold winter day from 1400 to 1800 Pacific Standard Time (PST). During this period, temperature profiles were near the dry adiabatic lapse rate. Flights were made through a jet wind speed profile having peak wind speeds of 7 m/s at a height of 100 m AGL. Wind directions were from the northwest. All flights were performed as continuous ascents, rather than ascending in discrete steps with halts at set altitudes.

Whiteman, C.D.; Alzheimer, J.M.; Anderson, G.A.; Shaw, W.J.

1993-03-01

27

Development of a balloon-borne stabilized platform for measuring radiative flux profiles in the atmospheric boundary layer  

SciTech Connect

A stabilized platform has been developed to carry broadband short-wave and long-wave radiometric sensors on the tether line of a small tethered balloon that ascends through atmospheric depths of up to 1.5 km to obtain vertical profiles of radiative flux and flux divergence for evaluating atmospheric radiative transfer models. The Sky Platform was designed to keep the radiometers level despite unpredictable movements of the balloon and tether line occasioned by turbulence and wind shear. The automatic control loop drives motors, gears, and pulleys located on two of the vertices of the triangular frame to climb the harness lines to keep the platform level. Radiometric sensors, an electronic compass, and an on-board data acquisition system make up the remainder of the Sky Platform. Because knowledge of the dynamic response of the tether line-platform system is essential to properly close the automatic control loop on the Sky Platform, a Motion Sensing Platform (MSP) was developed to fly in place of the Sky Platform on the tether line to characterize the Sky Platform's operating environment. This unstabilized platform uses an array of nine solid-state linear accelerometers to measure the lateral and angular accelerations, velocities, and displacements that the Sky Platform will experience. This paper presents field performance tests of the Sky and Motion Sensing Platforms, as conducted at Richland, Washington, on February 17, 1993. The tests were performed primarily to characterize the stabilization system on the Sky Platform. Test flights were performed on this cold winter day from 1400 to 1800 Pacific Standard Time (PST). During this period, temperature profiles were near the dry adiabatic lapse rate. Flights were made through a jet wind speed profile having peak wind speeds of 7 m/s at a height of 100 m AGL. Wind directions were from the northwest. All flights were performed as continuous ascents, rather than ascending in discrete steps with halts at set altitudes.

Whiteman, C.D.; Alzheimer, J.M.; Anderson, G.A.; Shaw, W.J.

1993-03-01

28

Remote sounding of surface radiative fluxes in cirrus cloudy conditions  

NASA Technical Reports Server (NTRS)

It has been long recognized that radiation and radiation perturbations play a critical role in the climate system. Surface radiative fluxes are useful parameters for monitoring global change, for understanding of the effects of clouds on the radiation field, and for improving parameterization of surface sensible and latent heat fluxes. Monitoring of the radiation budget at the top of the atmosphere has been one of the prime satellite programs for the last 30 years. However, monitoring radiative fluxes at the surface over the globe from space cannot be performed in a direct way at the present time. In particular, since clouds are the prime regulators of the radiative fluxes, uncertainties in the retrieved cloud parameters, which are inputs to radiative transfer models, can introduce significant errors in the computed radiative fluxes. Thus, remote sounding of surface radiative fluxes in cloudy conditions requires the development of both satellite cloud retrieval scheme and radiation models. In this paper, we present results of computed surface radiative fluxes in cirrus cloudy conditions using a cirrus cloud retrieval scheme and a detailed radiative transfer program. Comparisons have been made between the computed surface radiative fluxes and the ground-based radiometer measurements obtained during FIRE-II-IFO, which was carried out near Coffeyville, Kansas, during November and December, 1991.

Ou, S. C.; Liou, K. N.

1995-01-01

29

Ionization chamber for measuring the exposure dose rate of intense pulsed fluxes of X rays and ?-radiation  

Microsoft Academic Search

Measurements of the exposure dose rate of powerful pulsed sources of bremsstrahlung xrays and y-radiation are very difficult because a standard of pulsed radiation is not available. The presently employed measuring means are based on scintillation, semiconductor, and pyroelectric devices [1-3] and are characterized by adequate resolution on the time scale and a satisfactory dynamic range, but cannot be successfully

N. D. Villeval'de; N. N. Morozov; A. V. Oborin; B. M. Stepanov; V. I. Fominykh

1981-01-01

30

Measuring Radiation  

MedlinePLUS

... or beta particles, gamma rays, x-rays, or neutrons, a quantity of radioactive material is expressed in ... larger than the absorbed dose for alpha and neutron radiation, because these types of radiation are more ...

31

Angular Distribution Models for Top-of-Atmosphere Radiative Flux Estimation from the Clouds and the Earth’s Radiant Energy System Instrument on the Tropical Rainfall Measuring Mission Satellite  

Microsoft Academic Search

Abstract Top-of-atmosphere (TOA) radiative fluxes from ,the Clouds and the Earth’s Radiant Energy System (CERES) are estimated by applying empirical Angular Distribution Models (ADMs) that convert instantaneous radiance measurements to TOA fluxes. This paper evaluates the accuracy of CERES TOA fluxes from ,a new ,set of ADMs ,developed ,for the CERES instrument on board ,the Tropical Rainfall Measuring Mission (TRMM).

Norman G. Loeb; Konstantin Loukachine; Natividad Manalo-smith; Bruce A. Wielicki; David F. Young

32

Errors in airborne flux measurements  

NASA Astrophysics Data System (ADS)

We present a general approach for estimating systematic and random errors in eddy correlation fluxes and flux gradients measured by aircraft in the convective boundary layer as a function of the length of the flight leg, or of the cutoff wavelength of a highpass filter. The estimates are obtained from empirical expressions for various length scales in the convective boundary layer and they are experimentally verified using data from the First ISLSCP (International Satellite Land Surface Climatology Experiment) Field Experiment (FIFE), the Air Mass Transformation Experiment (AMTEX), and the Electra Radome Experiment (ELDOME). We show that the systematic flux and flux gradient errors can be important if fluxes are calculated from a set of several short flight legs or if the vertical velocity and scalar time series are high-pass filtered. While the systematic error of the flux is usually negative, that of the flux gradient can change sign. For example, for temperature flux divergence the systematic error changes from negative to positive about a quarter of the way up in the convective boundary layer.

Mann, Jakob; Lenschow, Donald H.

1994-07-01

33

Radiation from Kinetic Poynting Flux Acceleration  

E-print Network

We derive analytic formulas for the power output and critical frequency of radiation by electrons accelerated by relativistic kinetic Poynting flux, and validate these results with Particle-In-Cell plasma simulations. We find that the in-situ radiation power output and critical frequency are much below those predicted by the classical synchrotron formulae. We discuss potential astrophysical applications of these results.

Edison Liang; Koichi Noguchi

2007-11-18

34

Aerosol-Induced Radiative Flux Changes Off the United States Mid-Atlantic Coast: Comparison of Values Calculated from Sunphotometer and In Situ Data with Those Measured by Airborne Pyranometer  

NASA Technical Reports Server (NTRS)

The Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) measured a variety of aerosol radiative effects (including flux changes) while simultaneously measuring the chemical, physical, and optical properties of the responsible aerosol particles. Here we use TARFOX-determined aerosol and surface properties to compute shortwave radiative flux changes for a variety of aerosol situations, with midvisible optical depths ranging from 0.06 to 0.55. We calculate flux changes by several techniques with varying degrees of sophistication, in part to investigate the sensitivity of results to computational approach. We then compare computed flux changes to those determined from aircraft measurements. Calculations using several approaches yield downward and upward flux changes that agree with measurements. The agreement demonstrates closure (i.e. consistency) among the TARFOX-derived aerosol properties, modeling techniques, and radiative flux measurements. Agreement between calculated and measured downward flux changes is best when the aerosols are modeled as moderately absorbing (midvisible single-scattering albedos between about 0.89 and 0.93), in accord with independent measurements of the TARPOX aerosol. The calculated values for instantaneous daytime upwelling flux changes are in the range +14 to +48 W/sq m for midvisible optical depths between 0.2 and 0.55. These values are about 30 to 100 times the global-average direct forcing expected for the global-average sulfate aerosol optical depth of 0.04. The reasons for the larger flux changes in TARFOX include the relatively large optical depths and the focus on cloud-free, daytime conditions over the dark ocean surface. These are the conditions that produce major aerosol radiative forcing events and contribute to any global-average climate effect.

Russell, P. B.; Livingston, J. M.; Hignett, P.; Kinne, S.; Wong, J.; Chien, A.; Bergstrom, R.; Durkee, P.; Hobbs, P. V.

2000-01-01

35

Spectral estimates of net radiation and soil heat flux  

USGS Publications Warehouse

Conventional methods of measuring surface energy balance are point measurements and represent only a small area. Remote sensing offers a potential means of measuring outgoing fluxes over large areas at the spatial resolution of the sensor. The objective of this study was to estimate net radiation (Rn) and soil heat flux (G) using remotely sensed multispectral data acquired from an aircraft over large agricultural fields. Ground-based instruments measured Rn and G at nine locations along the flight lines. Incoming fluxes were also measured by ground-based instruments. Outgoing fluxes were estimated using remotely sensed data. Remote Rn, estimated as the algebraic sum of incoming and outgoing fluxes, slightly underestimated Rn measured by the ground-based net radiometers. The mean absolute errors for remote Rn minus measured Rn were less than 7%. Remote G, estimated as a function of a spectral vegetation index and remote Rn, slightly overestimated measured G; however, the mean absolute error for remote G was 13%. Some of the differences between measured and remote values of Rn and G are associated with differences in instrument designs and measurement techniques. The root mean square error for available energy (Rn - G) was 12%. Thus, methods using both ground-based and remotely sensed data can provide reliable estimates of the available energy which can be partitioned into sensible and latent heat under nonadvective conditions. ?? 1990.

Daughtry, C.S.T.; Kustas, W.P.; Moran, M.S.; Pinter, P. J., Jr.; Jackson, R. D.; Brown, P.W.; Nichols, W.D.; Gay, L.W.

1990-01-01

36

EOS Terra Aerosol and Radiative Flux Validation: An Overview of the Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) Experiment  

Microsoft Academic Search

NASA developed an Earth Observing System (EOS) to study global change and reduce uncertainties associated with aerosols and other key parameters controlling climate. The first EOS satellite, Terra ,w as launched in December 1999. The Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) field campaign was conducted from 10 July to 2 August 2001 to validate several Terra data products,

W. L. Smith; T. P. Charlock; R. Kahn; J. V. Martins; L. A. Remer; P. V. Hobbs; J. Redemann; C. K. Rutledge

2005-01-01

37

Radiant Flux of Near Field in Temperature Measurements  

SciTech Connect

In this work we present a calculation of the radiant flux exiting from an object which is at a constant temperature. The flux calculation is based in the propagation model of irradiance and it permit to predict the small variations in measurements of infrared radiation sources when the pyrometer is going far from the source, this variation is known as distance effect. The classical radiometry defines the quantity radiance, which is used in temperature measurements of objects through the infrared radiation they emit. Unfortunately the radiance does not permit to take into account the variations of the radiant flux measured by the pyrometer due to the wave propagation of the radiation given that the radiance definition is based in ray propagation, the geometrical model. Due to the anterior in this work we present a radiant flux calculation using wave model and considering the approximation of the near field or Fresnel approximation. We show experimental results that confirm our proposal.

Suarez-Romero, J. G.; Resendiz Barron, A. J. [Instituto Tecnologico de Queretaro, Av. Tecnologico SN, esq. Escobedo, Centro, Queretaro, Qro. 76000. MEXICO (Mexico); Farias Arguello, J. O. [Centro de Ingenieria y Desarrollo Industrial, Av. Playa Pie de la Cuesta 702, Desarrollo San Pablo, Queretaro, Qro. 76130 (Mexico)

2008-04-15

38

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...

39

Airborne Solar Radiant Flux Measurements During ACE-2  

NASA Technical Reports Server (NTRS)

Aerosol effects on atmospheric radiative fluxes provide a forcing function that can change the climate in potentially significant ways. This aerosol radiative forcing is a major source of uncertainty in understanding the climate change of the past century and predicting future climate. To help reduce this uncertainty, the 1996 Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) and the 1997 Aerosol Characterization Experiment (ACE-2) measured the properties and radiative effects of aerosols over the Atlantic Ocean. In the ACE 2 program the solar radiant fluxes were measured on the Pelican aircraft and the UK Met Office C130. This poster will show results from the measurements for the aerosol effects during the clear column days. We will compare the results with calculations of the radiant fluxes.

Bergstrom, Robert W.; Russell, Philip B.; Jonsson, Haflidi

2000-01-01

40

Radiation measuring instrumentation  

NASA Technical Reports Server (NTRS)

Four radiation measuring instruments were developed. These are: (1) improved detector probe, (2) neutron spectrometer--dosimeter, (3) portable ultraviolet spectro-radiometer; and (4) pocket ionization chamber radiation dosimeter. A brief description of each of these devices is presented.

Piltingsrud, H. V.

1975-01-01

41

LDEF radiation measurements: preliminary results  

NASA Technical Reports Server (NTRS)

The Long Duration Exposure Facility (LDEF), retrieved by the Space Shuttle mission STS-32 after nearly 6 yr in orbit, is the focus of a broad-based study of the radiation environment in low Earth orbit (LEO) and its effects on materials. A combination of passive techniques has been used to study this environment via detectors which were contained in experiments aboard the LDEF spacecraft and through analysis of induced radioactivities. Preliminary results for absorbed dose measurements and for induced activities in various materials are presented. A number of effects have been observed which reflect the anisotropy of the charged particle flux in low Earth orbit. Quantitative results from these measurements should provide an accurate means of confirming environmental flux models and techniques for predicting radiation encountered in future LEO missions, particularly those of extended duration.

Harmon, B. A.; Fishman, G. J.; Parnell, T. A.; Benton, E. V.; Frank, A. L.

1992-01-01

42

Flux gradient measurements from a catamaran buoy in SEMAPHORE  

SciTech Connect

During the SEMAPHORE Structure des Echanges Mer Atmosphere Proprietes des Heterogeneities de L`Ocean leur Repartition (Structure of Exchanges with the Marine Atmosphere, Properties of Heterogeneities of the Ocean and their Repartition) experiment in the fall of 1993, a large catamaran buoy, the MENTOR, was set adrift in the Azores region. The purpose of the buoy was to provide measurements for testing flux-profile relations over the sea, and to measure the influence of sea state on the turbulent fluxes and atmospheric profiles and the effects of atmospheric and radiative fluxes on near surface temperature structure in the ocean. In addition, the buoy measurements were to provide an anchor point for calibrating mesoscale bulk surface flux estimates over the SEMAPHORE domain and to provide intercomparison data for dissipation estimates of fluxes from the R/V Le Suroit.

Katsaros, K.B. [Univ. of Washington, Seattle, WA (United States). Dept. of Atmospheric Sciences; Drennan, W.M.; Donelan, M.A. [Canada Centre for Inland Waters, Burlington, Ontario (Canada)

1994-12-31

43

Earth Radiation Measurement Science  

NASA Technical Reports Server (NTRS)

This document is the final report for NASA Grant NAG1-1959, 'Earth Radiation Measurement Science'. The purpose of this grant was to perform research in this area for the needs of the Clouds and Earth Radiant Energy System (CERES) project and for the Earth Radiation Budget Experiment (ERBE), which are bing conducted by the Radiation and Aerosols Branch of the Atmospheric Sciences Division of Langley Research Center. Earth Radiation Measurement Science investigates the processes by which measurements are converted into data products. Under this grant, research was to be conducted for five tasks: (1) Point Response Function Measurements; (2) Temporal Sampling of Outgoing Longwave Radiation; (3) Spatial Averaging of Radiation Budget Data; (4) CERES Data Validation and Applications; and (5) ScaRaB Data Validation and Application.

Smith, G. Louis

2000-01-01

44

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

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

45

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

PubMed

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. PMID:11537894

Barnes, C; Tibbitts, T; Sager, J; Deitzer, G; Bubenheim, D; Koerner, G; Bugbee, B

1993-12-01

46

Determination of longwave heat flux at the air-sea interface using measurements from buoy platforms  

Microsoft Academic Search

A theory for pyrgeometer operation is utilized for determining downwelling longwave radiation. Errors in downwelling longwave radiation measurements are due to differences in pyrgeometer body and dome temperatures compared to that of the atmosphere. Additionally, incident shortwave radiation fluxes may be important. Using the present theory along with laboratory and field observations, it appears that downwelling longwave heat fluxes can

T. D. Dickey; D. V. Manov; R. A. Weller; D. A. Siegel

1994-01-01

47

Modelling radiation fluxes in simple and complex environments: basics of the RayMan model.  

PubMed

Short- and long-wave radiation flux densities absorbed by people have a significant influence on their energy balance. The heat effect of the absorbed radiation flux densities is parameterised by the mean radiant temperature. This paper presents the physical basis of the RayMan model, which simulates the short- and long-wave radiation flux densities from the three-dimensional surroundings in simple and complex environments. RayMan has the character of a freely available radiation and human-bioclimate model. The aim of the RayMan model is to calculate radiation flux densities, sunshine duration, shadow spaces and thermo-physiologically relevant assessment indices using only a limited number of meteorological and other input data. A comparison between measured and simulated values for global radiation and mean radiant temperature shows that the simulated data closely resemble measured data. PMID:19756771

Matzarakis, Andreas; Rutz, Frank; Mayer, Helmut

2010-03-01

48

Infrared calorimeter for time-resolved plasma energy flux measurement  

SciTech Connect

An infrared calorimeter system for measuring energy flux in a noisy electromagnetic environment has been developed. A thin (13 ..mu..) oxidized stainless-steel foil is heated by energy flux and its temperature is determined by measuring the infrared emission from the back surface of the foil. The radiation is transported to the detector, which is located inside a double-shielded enclosure, through a nylon-tube infrared telescope. The calculated response time is 12 ..mu..s, and the measured peak-to-peak noise is equivalent to 0.4 mJ/cm/sup 2/ deposited energy.

Ingraham, J.C.; Miller, G.

1983-06-01

49

Eddy Correlation Flux Measurement System (ECOR) Handbook  

SciTech Connect

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.

Cook, DR

2011-01-31

50

How Well are Recent Climate Variability Signals Resolved by Satellite Radiative Flux Estimates?  

NASA Technical Reports Server (NTRS)

One notable aspect of Earth s climate is that although the planet appears to be very close to radiative balance at top-of-atmosphere (TOA), the atmosphere itself and underlying surface are not. Profound exchanges of energy between the atmosphere and oceans, land and cryosphere occur over a range of time scales. Recent evidence from broadband satellite measurements suggests that even these TOA fluxes contain some detectable variations. Our ability to measure and reconstruct radiative fluxes at the surface and at the top of atmosphere is improving rapidly. Understanding the character of radiative flux estimates and relating them to variations in other energy fluxes and climate state variables is key to improving our understanding of climate. In this work we will evaluate several recently released estimates of radiative fluxes, focusing primarily on surface estimates. The International Satellite Cloud Climatology Project FD radiative flux profiles are available from rnid-1983 to near present and have been constructed by driving the radiative transfer physics from the Goddard Institute for Space Studies (GISS) global model with ISCCP clouds and HlRS operational soundings profiles. Full and clear sky SW and LW fluxes are produced. A similar product from the NASA/GEWEX Surface Radiation Budget Project using different radiative flux codes and thermodynamics from the NASA/Goddard Earth Observing System assimilation model makes a similar calculation of surface fluxes. However this data set currently extends only through 1995. Several estimates of downward LW flux at the surface inferred from microwave data are also examined. Since these products have been evaluated with Baseline Surface Radiation Network data over land we focus over ocean regions and use the DOE/NOAA/NASA Shipboard Ocean Atmospheric Radiation (SOAR) surface flux measurements to characterize performance of these data sets under both clear and cloudy conditions. Some aspects of performance are stratified according to SST and vertical motion regimes. Comparisons to the TRMM/CERES SRB data in 1998 are also interpreted. These radiative fluxes are then analyzed to determine how surface (and TOA) radiative exchanges respond to interannual signals of ENS0 warm and cold events. Our analysis includes regional changes as well as integrated signals over land, ocean and various latitude bands. Changes in water vapor and cloud forcing signatures are prominent on interannual time scales. Prominent signals are also found in the SW fluxes for the Pinatubo volcanic event. These systematic changes in fluxes are related to changes in large-scale circulations and energy transport in the atmosphere and ocean. Some estimates of signal-to-noise and reliability are discussed to place our results in context.

Robertson, Franklin R.; Lu, H.-L.

2004-01-01

51

4, 66036643, 2004 Flux measurements  

E-print Network

deciduous forest site in North-Western Germany using the eddy covari- ance (EC) technique. The measurement site was characterised by a forest of inho-5 mogeneous composition, complex canopy structure, limited this forest, with average emissions10 (normalised to 30 C and 1000 µmoles m-2 s-1 PAR) of 1.5 and 0.39 µg m-2

Boyer, Edmond

52

ATMOSPHERIC RADIATION MEASUREMENT PROGRAM  

EPA Science Inventory

The Atmospheric Radiation Measurement Program (ARM) is the largest global change research program supported by the U.S. Department of Energy (DOE). ARM scientists focus on obtaining field measurements and developing models to better understand the processes that control solar and...

53

Radiative flux opens new window on climate research  

NASA Technical Reports Server (NTRS)

For several decades, global satellite observations have been made of the rate at which electromagnetic energy (radiative flux) is emerging from the top of the atmosphere of our planet in the spectral range of about 0.2-50.0 microns. At the same time, models have been developed to infer the radiative flux at the surface from the values observed by the satellites at the upper boundary. The balance of incoming and outgoing radiative flux (radiation budget) at both boundaries, determines the net gain or loss of the radiative energy within an atmospheric column. Climate researchers can use the radiative flux as a tool to validate climate models, separate the radiative impact of clouds from surface and atmosphere contributions, and to understand the global hydrological cycle. When applied to physical processes occurring at the surface, information on the radiative flux has the potential to substantially advance our understanding of the transport of heat, moisture, and momentum across the surface/atmosphere interface. Geophysicists of many disciplines stand to benefit from efforts to improve the use of this latter untapped resource. Oceanographers can improve the representation of the selective absorption of radiation in the oceans; biologists and ecologists can improve their models for carbon dioxide exchange and biological heating in oceans; agronomists can model more realistically biomass and crop yields; and environmentalists can obtain better assessment of natural resources of radiation.

Pinker, R. T.; Laszlo, I.; Whitlock, C. H.; Charlock, T. P.

1995-01-01

54

Experimental flux measurements on a network scale  

SciTech Connect

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.

Schwender, J.

2011-10-11

55

Dual neutron flux/temperature measurement sensor  

DOEpatents

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.

Mihalczo, John T. (Oak Ridge, TN); Simpson, Marc L. (Knoxville, TN); McElhaney, Stephanie A. (Oak Ridge, TN)

1994-01-01

56

Dual neutron flux/temperature measurement sensor  

DOEpatents

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. 3 figs.

Mihalczo, J.T.; Simpson, M.L.; McElhaney, S.A.

1994-10-04

57

Radon flux maps for the Netherlands and Europe using terrestrial gamma radiation derived from soil radionuclides  

NASA Astrophysics Data System (ADS)

Naturally occurring radioactive noble gas, radon (222Rn) is a valuable tracer to study atmospheric processes and to validate global chemical transport models. However, the use of radon as a proxy in atmospheric and climate research is limited by the uncertainties in the magnitude and distribution of the radon flux density over the Earth's surface. Terrestrial gamma radiation is a useful proxy for generating radon flux maps. A previously reported radon flux map of Europe used terrestrial gamma radiation extracted from automated radiation monitoring networks. This approach failed to account for the influence of local artificial radiation sources around the detector, leading to under/over estimation of the reported radon flux values at different locations. We present an alternative approach based on soil radionuclides which enables us to generate accurate radon flux maps with good confidence. Firstly, we present a detailed comparison between the terrestrial gamma radiation obtained from the National Radiation Monitoring network of the Netherlands and the terrestrial gamma radiation calculated from soil radionuclides. Extending further, we generated radon flux maps of the Netherlands and Europe using our proposed approach. The modelled flux values for the Netherlands agree reasonably well with the two observed direct radon flux measurements (within 2? level). On the European scale, we find that the observed radon flux values are higher than our modelled values and we introduce a correction factor to account for this difference. Our approach discussed in this paper enables us to develop reliable and accurate radon flux maps in countries with little or no information on radon flux values.

Manohar, S. N.; Meijer, H. A. J.; Herber, M. A.

2013-12-01

58

Regional airborne flux measurements in Europe  

NASA Astrophysics Data System (ADS)

The problem of identifying the spatial and temporal distribution of sources and sinks of atmospheric CO2 is the subject of considerable scientific and political debate. Even if it is now possible to estimate within reasonable accuracy the sink strength of European forests at the local scale, difficulties still exist in determining the partitioning of the sinks at the global and regional scales. The aim of the EU-project RECAB (Regional Assessment of the Carbon Balance in Europe) that is coordinated by Alterra, Wageningen (NL), is to bridge the gap between local scale flux measurements and continental scale inversion models by a generic modelling effort and measurement program, focussing on a limited number of selected regions in Europe for which previous measurements exists. This required the establishment of a European facility for airborne measurement of surface fluxes of CO2 at very low altitude, and a research aircraft capable of performing airborne eddy covariance measurements has been acquired by this project and used on several occasions at the different RECAB sites. The aircraft is the italian Sky Arrows ERA (Environmental Research Aircraft) equipped with the NOAA/ARA Mobile Flux Platform (MFP), and a commercial open-path infrared gas analyser. Airborne eddy covariance measurements were made from June 2001 onwards in Southern Spain near Valencia (June and December 2001), in Central Germany near Jena (July 2001), in Sweden near Uppsala (August 2001), in The Netherlands near Wageningen (January and July 2002) and in Italy near Rome (June 2002). Flux towers were present at each site to provide a validation of airborne eddy covariance measurements. This contribution reports some validation results based on the comparison between airborne and ground based flux measurements and some regional scale results for different locations and different seasons, in a wide range of meteorological and ecological settings.

Gioli, B.; Miglietta, F.; Vaccari, F. P.; Zaldei, A.; Hutjes, R. W. A.

2003-04-01

59

An Apparatus for Absolute Neutron Flux Measurement  

NASA Astrophysics Data System (ADS)

A fully-absorbing neutron detector is being developed to measure the absolute flux (s-1) of a cold neutron beam at the level of 0.1,%. The device will be used to calibrate a neutron flux monitor used in an in-beam neutron lifetime measurement performed at NIST (?n= (886.3 ±3.4) s). The precision of the measurement was limited by the uncertainty in the efficiency of the neutron flux monitor (0.3,%). The flux monitor operates by counting charged particles produced when neutrons impinge on a ^6Li (or ^10B) foil. Its efficiency was calculated from the cross section, the solid angle subtended by the charged particle detectors, and the amount of neutron-absorbing material present on the foil. Successful calibration would reduce the neutron lifetime uncertainty to approximately 0.25,%. In addition, using the measured solid angle and amount of material on the deposit, a new experimental value for the ^6Li or (^10B) capture cross section will be obtained. Details of the apparatus and the measurement technique along with the status of the experiment will be discussed.

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

2007-10-01

60

Suggestions for the measurement and derivation of fluxes and flux divergences from a satellite  

NASA Technical Reports Server (NTRS)

Consideration is given to the determination of the optimal bands for measuring and deriving the total outgoing longwave radiation (OLR), surface downward flux (SDF), and cooling rates (CRs) using linear regression. The optimal bands are determined from scatter plots of total fluxes and cooling rates associated with the various bands. It is found that the best band for OLR is between 800 and 1200/cm, while the best band for SDF is between 500 and 660/cm or between 660 and 800/cm. For CRs, it is shown that the best band is also between 660 and 800/cm. It is noted that the AVHRR OLR is damped compared with the Nimbus-7 earth radiation budget (ERB) OLR derived from the broadband, narrow FOV ERB instrument.

Wu, Man-Li C.

1990-01-01

61

Atmospheric radiative flux divergence from Clouds and Earth Radiant Energy System (CERES)  

NASA Technical Reports Server (NTRS)

A major objective of the Clouds and Earth Radiant Energy System (CERES) is the computation of vertical profiles through the atmosphere of the divergence of radiation flux, with global coverage. This paper discusses the need for radiation divergence and presents some options for its inference from CERES measurements and other data from the Earth Observating System.

Smith, Louis G.; Charlock, Thomas P.; Crommelynk, D.; Rutan, David; Gupta, Shashi

1990-01-01

62

Instruments for measuring radiant thermal fluxes  

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

63

Plasma momentum meter for momentum flux measurements  

DOEpatents

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.

Zonca, Fulvio (Rome, IT); Cohen, Samuel A. (Hopewell, NJ); Bennett, Timothy (Princeton, NJ); Timberlake, John R. (Allentown, NJ)

1993-01-01

64

Near-Core and In-Core Neutron Radiation Monitors for Real Time Neutron Flux Monitoring and Reactor Power Level Measurements  

SciTech Connect

MPFDs are a new class of detectors that utilize properties from existing radiation detector designs. A majority of these characteristics come from fission chamber designs. These include radiation hardness, gamma-ray background insensitivity, and large signal output.

Douglas S. McGregor; Marvin L. Adams; Igor Carron; Paul Nelson

2006-06-12

65

Evaluation of Arctic Broadband Surface Radiation Measurements  

SciTech Connect

The Arctic is a challenging environment for making in-situ radiation measurements. A standard suite of radiation sensors is typically designed to measure the total, direct and diffuse components of incoming and outgoing broadband shortwave (SW) and broadband thermal infrared, or longwave (LW) radiation. Enhancements can include various sensors for measuring irradiance in various narrower bandwidths. Many solar radiation/thermal infrared flux sensors utilize protective glass domes and some are mounted on complex mechanical platforms (solar trackers) that rotate sensors and shading devices that track the sun. High quality measurements require striking a balance between locating sensors in a pristine undisturbed location free of artificial blockage (such as buildings and towers) and providing accessibility to allow operators to clean and maintain the instruments. Three significant sources of erroneous data include solar tracker malfunctions, rime/frost/snow deposition on the instruments and operational problems due to limited operator access in extreme weather conditions. In this study, a comparison is made between the global and component sum (direct [vertical component] + diffuse) shortwave measurements. The difference between these two quantities (that theoretically should be zero) is used to illustrate the magnitude and seasonality of radiation flux measurement problems. The problem of rime/frost/snow deposition is investigated in more detail for one case study utilizing both shortwave and longwave measurements. Solutions to these operational problems are proposed that utilize measurement redundancy, more sophisticated heating and ventilation strategies and a more systematic program of operational support and subsequent data quality protocols.

Matsui, N.; Long, Charles N.; Augustine, J. A.; Halliwell, D.; Uttal, Taneil; Longenecker, D.; Niebergale, J.; Wendell, J.; Albee, R.

2012-02-24

66

Solar UVA and UV-B radiation fluxes at two Alpine stations at different altitudes  

Microsoft Academic Search

Daily totals of UV-A and UV-B radiation fluxes and global radiation were measured since 1981 at Jungfraujoch (3576 m) a.s.l.) and in Innsbruck (577 m a.s.l.) in their seasonal course. The altitude effect of annual totals yields 19%\\/1000 m (UV-B), 11%\\/1000 m (UV-A) and 9%\\/1000 m (global radiation) with reference to Innsbruck station. The ratio of the daily totals of

M. Blumthaler; W. Ambach; W. Rehwald

1992-01-01

67

Micrometeorological flux measurements at a coastal site  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

68

Cosmic matter flux may turn Hawking radiation off  

NASA Astrophysics Data System (ADS)

An astrophysical (cosmological) black hole forming in a cosmological context will be subject to a flux of infalling matter and radiation, which will cause the outer apparent horizon (a marginal trapping surface) to be spacelike spacelike (Ellis et al., arXiv:1407.3577). As a consequence the radiation emitted close to the apparent horizon no longer arrives at infinity with a diverging redshift. Standard calculations of the emission of Hawking radiation then indicate that no blackbody radiation is emitted to infinity by the black hole in these circumstances, hence there will also then be no black hole evaporation process due to emission of such radiation as long as the matter flux is significant. The essential adiabatic condition (eikonal approximation) for black hole radiation gives a strong limit to the black holes that can emit Hawking radiation. We give the mass range for the black holes that can radiate, according to their cosmological redshift, for the special case of the cosmic blackbody radiation (CBR) influx (which exists everywhere in the universe). At a very late stage of black hole formation when the CBR influx decays away, the black hole horizon becomes first a slowly evolving horizon and then an isolated horizon; at that stage, black hole radiation will start. This study suggests that the primordial black hole evaporation scenario should be revised to take these considerations into account.

Firouzjaee, Javad T.; Ellis, George F. R.

2015-02-01

69

Angular Distribution Models for Top-of-Atmosphere Radiative Flux Estimation from the Clouds and the Earth's Radiant Energy System Instrument on the Tropical Rainfall Measuring Mission Satellite. Part I: Methodology  

Microsoft Academic Search

Clouds and the Earth's Radiant Energy System (CERES) investigates the critical role that clouds and aerosols play in modulating the radiative energy flow within the Earth-atmosphere system. CERES builds upon the foundation laid by previous missions, such as the Earth Radiation Budget Experiment, to provide highly accurate top-of-atmosphere (TOA) radiative fluxes together with coincident cloud and aerosol properties inferred from

Norman G. Loeb; Natividad Manalo-Smith; Seiji Kato; Walter F. Miller; Shashi K. Gupta; Patrick Minnis; Bruce A. Wielicki

2003-01-01

70

Combining the effect of crops surface albedo variability on the radiative forcing together with crop GHG budgets calculated from in situ flux measurements in a life cycle assessment approach: methodology and results  

NASA Astrophysics Data System (ADS)

The carbon and GHG budgets (GHGB) of the 2 crop sites with contrasted management located in South West France was estimated over a complete rotation by combining a classical LCA approach with on site CO2 flux measurements. At both sites, carbon inputs (organic fertilization, seeds), carbon exports (harvest) and net ecosystem production (NEP), measured with the eddy covariance technique, were estimated. The variability of the different terms and their relative contributions to the net ecosystem carbon budget (NECB) were analyzed for all site-years, and the effect of management on NECB was assessed. To account for GHG fluxes that were not directly measured on site, we estimated the emissions caused by field operations (EFO) for each site using emission factors from the literature. The EFO were added to the NECB to calculate the total GHGB for a range of cropping systems and management regimes. N2O emissions were calculated following the IPCC (2007) guidelines or and CH4 emissions were assumed to be negligible. Albedo was calculated continuously using the short wave incident and reflected radiation measurements in the field from CNR1 sensors. Rapid changes in surface albedo typical from those ecosystems and resulting from management and crop phenology were analysed. The annual radiative forcing for each plot was estimated by calculating the difference between a mean annual albedo for each crop and a reference bare soil albedo value calculated over 5 years for each plot. To finalize the radiative forcing calculation, the method developed by Muñoz et al (2010) using up and down atmospheric transmittance had to be corrected so it would only account for up-going atmospheric transmittance. Annual differences in radiative forcing between crops were then converted in g C equivalent m-2 in order to add this effect to the GHG budget of each crop within a rotation. This methodology could be applied to all ICOS/NEON cropland sites. We found that the differences in radiative forcing between crops (ranging from -1800 to 750 g C-eq for rapeseed and sunflower, respectively) largely exceeded the NEP, the NECB and the GHGB of those crops. Also, as increasing the length of the vegetative period is considered as one of the main levers for improving the NECB and the GHGB of crop ecosystems, we tested the effect of adding intermediate crops on the NECB, GHGB and the radiative forcing resulting from changes in mean annual surface albedo. We showed that the NEP was improved and as a consequence NECB and GHGB too. Intermediate crops also increased the mean annual surface albedo and therefore caused a negative radiative forcing (cooling effect) expressed in g C equivalent m-2 (sink). The use of an intermediate crop could in some cases switch the crop from a positive NEP (source) to a negative one (sink) and the change in radiative forcing (up to -110 g C-eq m-2 yr-1) could overwhelm the NEP term and it improves the GHG budget.

Ceschia, E.; Ferlicoq, M.; Brut, A.; Tallec, T.

2013-12-01

71

Measurement of the Meteoroid Flux at Mars  

NASA Astrophysics Data System (ADS)

In the fall of 2005, a dedicated meteor observing campaign was carried out by the Panoramic Camera (Pancam) onboard the Mars Exploration Rover (MER) Spirit to determine the viability of using MER cameras as meteor detectors and to obtain the first experimental estimate of the meteoroid flux at Mars. Our observing targets included both the sporadic meteoroid background and two predicted martian meteor showers: one associated with comet 1P/Halley and a potential stream associated with 2001/R1 LONEOS. A total of 353 images covering 2.7 h of net exposure time were analyzed with no conclusive meteor detections. From these data, we estimate the upper limit to the background meteoroid flux at Mars to be < 4.4 x 10-6 meteoroids km-2hr-1 for meteoroids with mass larger than 4 g. The estimated flux to this same mass limit at the Earth is 10-6 meteoroids km-2hr-1(Grün et al. 1985). This result is qualitatively consistent, within error bounds, with theoretical models predicting martian fluxes of 50% that at Earth for meteoroids of mass 10-3-101 g (Adolfsson et al. 1996). Our analysis also suggests that the event reported as the first martian meteor (Selsis et al. 2005) is more likely to be a grazing cosmic ray impact, which we found to be a major source of confusion with potential meteors in all Pancam images. Domokos, A., Bell III, J.F., Brown, P., Lemmon, M.T., Suggs, R., Vaubaillon, J., 2007. Measurement of the Meteoroid Flux at Mars. Icarus, in press. doi: 10.1016/j.icarus.2007.04.017

Domokos, Andrea; Bell, J. F., III; Brown, P.; Lemmon, M. T.; Suggs, R.; Vaubaillon, J.; Cooke, W.

2007-12-01

72

Indication of increasing solar ultraviolet-B radiation flux in alpine regions  

Microsoft Academic Search

Measurements at the Jungfraujoch High Mountain Station (Swiss Alps, 47°N, 3,576 meters above sea level) indicate that there has been a slight increase of about 1% per year in the flux of solar ultraviolet-B radiation (290 to 330 nanometers) since 1981. A Robertson-Berger detector was used to measure solar erythemal radiation. The increase can be related to a long-term ozone

M. Blumthaler; W. Ambach

1990-01-01

73

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...

74

Radiation detection and measurement  

Microsoft Academic Search

Introductory material covers radiation sources, radiation interactions, general properties of radiation detectors, and counting statistics and error prediction. This is followed by detailed sections on gas-filled detectors, scintillation counters, semiconductor detectors, neutron detectors and spectroscopy, detector electronics and pulse processing, and miscellaneous radiation detectors and applications.

Glenn F. Knoll

1979-01-01

75

Radiation flux tables for ICRCCM using the GLA GCM radiation codes  

NASA Technical Reports Server (NTRS)

Tabulated values of longwave and shortwave radiation fluxes and also cooling and heating rates in the atmosphere for standard atmospheric profiles are presented. The radiation codes used in the Goddard general circulation model were employed for the computations. These results were obtained for an international intercomparison projected called Intercomparison of Radiation Codes in Climate Models (ICRCCM).

HARSHVARDHAN

1986-01-01

76

Electron and proton flux models for Jupiter's radiation belts  

NASA Technical Reports Server (NTRS)

Estimates of the energetic particle distribution in Jupiter's radiation belts are presented and are compared with previous estimates. Mathematical expressions are developed for the equatorial electron and proton fluxes, shielded electron and proton dose rates, and radiation lifetimes of electronic circuits. It is calculated that a 1 g/sq cm aluminum shield will screen out all protons of energy less than 27.5 MeV, and a 2 g/sq cm shield will screen out protons less than 40.6 MeV. The radiation lifetimes are based on a maximum permissible dose value of 10 million rads, a value 1/2 to 1/3 of the flux at which electronic circuits begin to fail. Estimated increases in lifetimes by using a 3 x 50 orbit instead of a 3 x 3 orbit, and going from 1 to 2 g/sq cm are given.

Klopp, D. A.

1972-01-01

77

Measurements of the radiation environment on the APEX satellite  

Microsoft Academic Search

The Cosmic Radiation Environment and Dosimetry experiment was built to accompany the CRUX (Cosmic Ray Upset) experiment on the USAF APEX satellite, launched in August 1994. Results of measurements of the space radiation environment are presented here whilst a companion paper presents CRUX measurements of upsets correlated with proton flux

A. J. Sims; C. S. Dyer; C. J. Watson; C. L. Peerless

1995-01-01

78

Saharan Airborne Dust Flux Measurements from the Fennec Campaign  

NASA Astrophysics Data System (ADS)

The Fennec campaign of 2011involved deployment of the Facility for Airborne Atmospheric Measurements BAe 146 (FAAM Bae 146) scientific research aircraft to Fuerteventura with research flights over the remote Saharan desert in Mali and Mauritania. The aims of the Fennec campaign were to characterise the dynamics, radiation and dust environment in this inaccessible region. The FAAM BAe 146 operated a suite of instruments which measured size distributions of dust including a Passive Cavity Aerosol Spectrometer Probe, a Cloud Droplet Probe and a Cloud Imaging Probe (part of a Cloud, Aerosol and Precipitation Spectrometer). These instruments were able to reliably generate particle size distributions over the approximate range 0.1 to 200 ?m and for the first time were simultaneously operated at high temporal resolution of at least 10 Hz. Combining these dust measurements with the measured 3D wind vectors has allowed size resolved dust flux estimates to be derived using the eddy covariance method. To the authors' knowledge this is the first time such estimates have been successfully derived from aircraft data. Although the FAAM BAe 146 is capable of low level flying with straight and level runs at minimum altitudes of ~100 m (higher in poor visibility), this is still significantly higher than mast based flux measurements making comparison of the total flux with surface based observations difficult. However, these observations give useful measures of the size dependence of the particle flux and the spectral signature of the dynamics of vertical dust transport. The size resolved measurements show that dust mass flux includes significant contributions up to particle diameters ~100 ?m. This is much larger than the limit seen by other studies and is even more surprising given that the measurements were made at heights so far above the saltation layer. Spectral analysis shows three distinct dynamical regimes. The first appears to be linked to chaotic turbulence with horizontal scales of ~100 m. The second seems to be linked to features on scales ~1 km, similar to the order of the boundary layer depth. Finally, in the third regime, the concentration and wind measurements have a very asymmetric cross correlation series in the along flight direction which may indicate a preferred orientation for turbulent eddies caused buy e.g. shear. These characteristics are linked to the weather conditions and dust uplift mechanisms for each case.

Rosenberg, Phil; Parker, Doug; Ryder, Claire; Garcia-Carreras, Luis; Marsham, John; Dorsey, James; Brooks, Ian; Dean, Angela; Crosier, Jonathan; McQuaid, Jim; Washington, Richard

2013-04-01

79

Plasma momentum meter for momentum flux measurements  

DOEpatents

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.

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

1993-08-24

80

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...

81

Kilometric radiation power flux dependence on area of discrete aurora  

NASA Technical Reports Server (NTRS)

Kilometer wavelength radiation, measured from distant positions over the North Pole and over the Earth's equator, was compared to the area of discrete aurora imaged by several low-altitude spacecraft. Through correlative studies of auroral kilometric radiation (AKR) with about two thousand auroral images, a stereoscopic view of the average auroral acceleration region was obtained. A major result is that the total AKR power increases as the area of the discrete auroral oval increases. The implications are that the regions of parallel potentials or the auroral plasma cavities, in which AKR is generated, must possess the following attributes: (1) they are shallow in altitude and their radial position depends on wavelength, (2) they thread flux tubes of small cross section, (3) the generation mechanism in them reaches a saturation limit rapidly, and (4) their distribution over the discrete auroral oval is nearly uniform. The above statistical results are true for large samples collected over a long period of time (about six months). In the short term, AKR frequently exhibits temporal variations with scales as short as three minutes (the resolution of the averaged data used). These fluctuations are explainable by rapid quenchings as well as fast starts of the electron cyclotron maser mechanism. There were times when AKR was present at substantial power levels while optical emissions were below instrument thresholds. A recent theoretical result may account for this set of observations by predicting that suprathermal electrons, of energies as low as several hundred eV, can generate second harmonic AKR. The indirect observations of second harmonic AKR require that these electrons have mirror points high above the atmosphere so as to minimize auroral light emissions. The results provide evidence supporting the electron cyclotron maser mechanism.

Saflekos, N. A.; Burch, J. L.; Gurnett, D. A.; Anderson, R. R.; Sheehan, R. E.

1989-01-01

82

Measurement of local high-level, transient surface heat flux  

SciTech Connect

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.

Liebert, C.H.

1988-09-01

83

Measurement of local high-level, transient surface heat flux  

NASA Technical Reports Server (NTRS)

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.

Liebert, Curt H.

1988-01-01

84

Measurement of aerosol particles, gases and flux radiation in the Pico de Orizaba National Park, and its relationship to air pollution transport  

NASA Astrophysics Data System (ADS)

Continuous atmospheric measurements were carried out at the Pico de Orizaba National Park (PONP), Mexico, in order to evaluate the characteristics and sources of air quality. This action allowed one to identify specific threats for the effective protection of natural resources and biodiversity. Results show the presence of particles and polluted gases transported by winds from the urban zones nearby (cities of Mexico, Puebla and Tlaxcala), as well as their measurable influence on the optical properties of the park environment. Nitrogen dioxide, carbon monoxide and sulfur dioxide show a daily pattern suggesting an influence of pollution generated by anthropogenic processes. Average concentration of SO 2 was higher than recorded at the southern part of Mexico City. Ozone concentrations ranging from 0.035 to 0.06 ppm suggest residual or background ozone character. Back trajectory analysis of air parcels arriving at the site confirm pollution caused by biomass burning and mass transport from urban zones. The SO 42-/TC ratio exhibited values (0.88±0.33) similar to urban areas. Ratios BC/TC and OC/BC for PONP are similar to those reported as influenced by burning emissions of fossil fuels. Typical rural aerosols were also found at the site, and sulfate and ammonium concentrations were correlated. The most predominating mode in surface particles size distribution was at 0.32 ?m with no significant presence of coarse particles. Total carbon (OC+BC) content of fine particle mass (PM less than 1 ?m) comprised, on average, 75%. Optical properties retrieved from photometric data show intermittent influence from urban pollution. Time periods with low absorbing particles, great visibility and abundance of small particles alternating with short times with bigger particles and high turbidity indicated by the optical depth.

Márquez, C.; Castro, T.; Muhlia, A.; Moya, M.; Martínez-Arroyo, A.; Báez, A.

85

Effects of Clouds on Cross-Atmospheric Radiative Flux Divergence: Case Studies in Different Cloud Conditions  

NASA Astrophysics Data System (ADS)

Clouds have a profound effect on the amount of radiation absorbed across the atmospheric column. The amount of absorption mainly depends on the location and type of the clouds, the albedo of the surface and profile of water vapor mixing ratio in the atmospheric column. In this study we have used the data collected during the deployment of Atmospheric Radiation Measurement (ARM)'s first Mobile Facility (AMF#1) at the island of Graciosa in the North Atlantic and at the Niamey, Niger to assess the impact of different cloud types on the cross-atmospheric radiative flux divergence. The cloud structure was retrieved using the data collected by a vertically pointing w-band cloud radar, a micro-pulse lidar, laser ceilometer among other instruments. The profiles of temperature, moisture and winds were measured by balloon borne radiosondes. The radiation at the surface were measured by broadband radiometers, while the radiation at the top of the atmosphere were measured by the Geostationary Earth Radiation Budget (GERB) radiometers onboard the Meteosat Second Generation (MSG) satellite. Simulations of a 1-dimensional radiative transfer model called as Rapid Radiative Transfer Model (RRTM) having representation of cloud and aerosol properties are made to assess the relative impact of different cloud types and water vapor on spectral bands both in the shortwave and longwave radiation spectrum. Results from four case-studies which had cloud free conditions, single layered stratocumulus clouds, broken shallow cumulus clouds and high level cirrus clouds respectively will be presented.

Ghate, V. P.; Miller, M. A.

2013-12-01

86

Total aerosol effect: forcing or radiative flux perturbation?  

SciTech Connect

Uncertainties in aerosol forcings, especially those associated with clouds, contribute to a large extent to uncertainties in the total anthropogenic forcing. The interaction of aerosols with clouds and radiation introduces feedbacks which can affect the rate of rain formation. Traditionally these feedbacks were not included in estimates of total aerosol forcing. Here we argue that they should be included because these feedbacks act quickly compared with the time scale of global warming. We show that for different forcing agents (aerosols and greenhouse gases) the radiative forcings as traditionally defined agree rather well with estimates from a method, here referred to as radiative flux perturbations (RFP), that takes these fast feedbacks and interactions into account. Thus we propose replacing the direct and indirect aerosol forcing in the IPCC forcing chart with RFP estimates. This implies that it is better to evaluate the total anthropogenic aerosol effect as a whole.

Lohmann, Ulrike; Storelvmo, Trude; Jones, Andy; Rotstayn, Leon; Menon, Surabi; Quaas, Johannes; Ekman, Annica; Koch, Dorothy; Ruedy, Reto

2009-09-25

87

Trapped Proton Fluxes at Low Earth Orbits Measured by the PAMELA Experiment  

NASA Astrophysics Data System (ADS)

We report an accurate measurement of the geomagnetically trapped proton fluxes for kinetic energy above ~70 MeV performed by the PAMELA mission at low Earth orbits (350 ÷ 610 km). Data were analyzed in the frame of the adiabatic theory of charged particle motion in the geomagnetic field. Flux properties were investigated in detail, providing a full characterization of the particle radiation in the South Atlantic Anomaly region, including locations, energy spectra, and pitch angle distributions. PAMELA results significantly improve the description of the Earth's radiation environment at low altitudes, placing important constraints on the trapping and interaction processes, and can be used to validate current trapped particle radiation models.

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

2015-01-01

88

Trapped proton fluxes at low Earth orbits measured by the PAMELA experiment  

E-print Network

We report an accurate measurement of the geomagnetically trapped proton fluxes for kinetic energy above > 70 MeV performed by the PAMELA mission at low Earth orbits (350-610 km). Data were analyzed in the frame of the adiabatic theory of charged particle motion in the geomagnetic field. Flux properties were investigated in detail, providing a full characterization of the particle radiation in the South Atlantic Anomaly region, including locations, energy spectra and pitch angle distributions. PAMELA results significantly improve the description of the Earth's radiation environment at low altitudes placing important constraints on the trapping and interaction processes, and can be used to validate current trapped particle radiation models.

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

2014-01-01

89

Overview of observations from the RADAGAST experiment in Niamey, Niger. Part 2: Radiative fluxes and divergences  

SciTech Connect

Broadband shortwave and longwave radiative fluxes observed both at the surface and from space during the RADAGAST experiment in Niamey, Niger in 2006 are presented. The surface fluxes were measured by the Atmospheric Radiation Measurement (ARM) Program Mobile Facility (AMF) at Niamey airport, while the fluxes at the top of the atmosphere (TOA) are from the Geostationary Earth Radiation Budget (GERB) instrument on the Meteosat-8 satellite. The data are analyzed as daily averages, in order to minimise sampling differences between the surface and top of atmosphere instruments, while retaining the synoptic and seasonal changes that are the main focus of this study. A cloud mask is used to identify days with cloud from those with predominantly clear skies. The influence of temperature, water vapor, aerosols and clouds is investigated. Aerosols are ubiquitous throughout the year and have a significant impact on both the shortwave and longwave fluxes. The large and systematic seasonal changes in temperature and column integrated water vapor (CWV) through the dry and wet seasons are found to exert strong influences on the longwave fluxes. These influences are often in opposition to each other, because the highest temperatures occur at the end of the dry season when the CWV is lowest, while in the wet season the lowest temperatures are associated with the highest values of CWV. Apart from aerosols, the shortwave fluxes are also affected by clouds and by the seasonal changes in CWV. The fluxes are combined to provide estimates of the divergence of radiation across the atmosphere throughout 2006. The longwave divergence is remarkably constant through the year, because of a compensation between the seasonal variations in the outgoing longwave radiation (OLR) and surface net longwave radiation. A simple model of the greenhouse effect is used to interpret this result in terms of the dependence of the normalized greenhouse effect at the TOA and of the effective emissivity of the atmosphere at the surface on the CWV. It is shown that, as the CWV increases, the atmosphere loses longwave energy to the surface with about the same increasing efficiency with which it traps the OLR, thus keeping the atmospheric longwave divergence roughly constant. The shortwave divergence is mainly determined by the CWV and aerosol loadings and the effect of clouds is much smaller than on the component fluxes.

Slingo, A.; White, H. E.; Bharmal, N.; Robinson, G. J.

2009-02-25

90

Flux-based environmental management: the future of integrated passive flux measurements in groundwater  

NASA Astrophysics Data System (ADS)

The measurement and interpretation of parameter mass fluxes and discharges is gaining more and more importance. Especially in the frame of soil and groundwater contamination, remediation and related environmental risks, water management and ecosystem management, the interpretation of mass fluxes is essential. Current legislation already includes a mass flux approach today (e.g. EU Water Framework Directive and Groundwater Daughter Directive). Environmental management actions regarding groundwater pollutions and ecosystem research and management are mostly driven by parameter concentrations. Since concentration estimates are highly uncertain and do not include the fluctuations caused by spatially and temporally varying conditions, decisions about these actions can be improved by also considering parameter mass fluxes (mass of parameter passing per unit time per unit area, or flow rate of these parameters per unit area) and parameter mass discharges (sum of all mass flux measures across an entire plume). The mass that effectively reaches a downgradient receptor, determines the actual situation and risks, and should therefore be monitored. It is essential to determine mass fluxes directly instead of estimating mass flux based on concentration data and estimates of groundwater velocity. The direct determination of contaminant mass fluxes in soil and groundwater systems is possible with the Passive Flux Meter (PFM) technology. The PFM is a recently developed passive sampling device that provides simultaneous in situ point measurements of a time-averaged contaminant mass flux and water flux. The device, with a suite of tracers, is placed in a monitoring well or borehole for a known exposure period, where it intercepts the groundwater flow and captures contaminants from it. The measurements of the contaminants and the remaining resident tracer can then be used to estimate groundwater and contaminant fluxes. Today, an increasing demand from different sectors for the combined determination of multiple parameter mass fluxes, has stimulated us to optimize the technology and develop an integrated flux measurement device which targets the combined mass flux determination of multiple parameter types. The principles of flux-based environmental management will be presented, with a special focus on the application and future of integrated passive flux measurements in groundwater.

Verreydt, Goedele; Struyf, Eric; Van Keer, Ilse; Meire, Patrick; Bronders, Jan; Seuntjens, Piet

2014-05-01

91

Comparison of surface fluxes and boundary-layer measurements at Arctic terrestrial sites  

NASA Astrophysics Data System (ADS)

Observational evidence suggests that atmospheric energy fluxes are a major contributor to the decrease of the Arctic pack ice, seasonal land snow cover and the warming of the surrounding land areas and permafrost layers. To better understand the atmosphere-surface exchange mechanisms, improve models, and to diagnose climate variability in the Arctic, accurate measurements are required of all components of the net surface energy budget and the carbon dioxide cycle over representative areas and over multiple years. This study analyzes and discusses variability of surface fluxes and basic meteorological parameters based on measurements made at several long-term research observatories near the coast of the Arctic Ocean located in USA (Barrow), Canada (Eureka), and Russia (Tiksi). Tower-based eddy covariance and solar radiation measurements provide a long-term near continuous temporal record of hourly average mass and energy fluxes respectively. The turbulent fluxes of the momentum, sensible heat, water vapor, and carbon dioxide are supported by additional atmospheric and surface/snow/permafrost measurements (mean wind speed, air temperature and humidity, upwelling and downwelling short-wave and long-wave atmospheric and surface radiation, snow depth, surface albedo, soil heat flux, active layer temperature profiles etc.) In this study we compare annual cycles of surface fluxes including solar radiation and other ancillary data to describe four seasons in the Arctic including spring onset of melt and fall onset of snow accumulation. Particular interest is a transition through freezing point, i.e. during transition from winter to spring and from summer to fall, when the carbon dioxide and/or water vapor turbulent fluxes change their direction. According to our data, in a summer period observed temporal variability of the carbon dioxide flux was generally in anti-phase with water vapor flux (downward CO2 flux and upward H2O flux). On average the turbulent flux of carbon dioxide was mostly negative (uptake by the surface) in summer indicating that the Arctic terrestrial sites are generally net sinks for atmospheric CO2 during the growing season when surface is extensively covered with vegetation. This study also shows that the sensible heat flux, water vapor, and carbon dioxide fluxes as well as air temperature exhibit clear diurnal cycles during the Arctic summer. During the Polar winter and cold seasons, the sensible heat flux, water vapor and carbon dioxide fluxes were small and mostly irregular when the ground is covered with snow and air temperatures are sufficiently below freezing. The work is supported by the U.S. National Science Foundation (NSF) with award ARC 11-07428 and by the U.S. Civilian Research & Development Foundation (CRDF) with award RUG1-2976-ST-10.

Grachev, Andrey; Uttal, Taneil; Persson, Ola; Stone, Robert; Crepinsek, Sara; Albee, Robert; Makshtas, Alexander; Kustov, Vasily; Repina, Irina; Artamonov, Arseniy

2014-05-01

92

Balloon-borne measurement of energetic electron fluxes inside thunderclouds  

NASA Astrophysics Data System (ADS)

High-energy radiation is routinely produced by thunderclouds and lightning. This radiation is in the form of x-rays and gamma-rays with timescales ranging from sub-microsecond (x-rays associated with lightning leaders), to sub-millisecond (Terrestrial Gamma-ray Flashes), to minute long glows (Gamma-ray Glows from thunderclouds seen on the ground and in or near the cloud by aircrafts and balloons). It is generally accepted that these emissions originate from bremsstrahlung interactions of relativistic runaway electrons with air, which can be accelerated in the thundercloud/lightning electric fields and gain up to multi-MeV energies. However, the exact physical details of the mechanism that produces these runaway electrons are still unknown. In order to better understand the source of energetic radiation inside thunderclouds, we have begun a campaign of balloon-borne instruments to directly measure the flux of energetic electrons inside thunderclouds. In the current configuration, each balloon carries Geiger counters to record the energetic particles. Geiger counters are well suited for directly measuring energetic electrons and positrons and have the advantage of being lightweight and dependable. We transmit data at 900MHz, ISM band, with 115.2 kb/s transmission rate. This would provide us a high resolution radiation profile over a relatively large distance. Due to the nature of the thunderstorm environment, the campaign has many design, communication, and safety challenges. In this presentation we will report on the status of the campaign and some of the physical insights gained from the data collected by our instruments. This work was supported in part by the NASA grant NNX12A002H and by DARPA grant HR0011-1-10-1-0061.

Arabshahi, Shahab; Vodopiyanov, Igor; Dwyer, Joseph; Rassoul, Hamid

2014-05-01

93

Heat flux measurements on ceramics with thin film thermocouples  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

94

Measurement of trace gas fluxes over an unfertilized agricultural field using the flux-gradient technique.  

PubMed

Trace gas fluxes exhibit extensive spatial and temporal variability that is dependent on a number of factors, including meteorology, ambient concentration, and emission source size. Previous studies have found that agricultural fertilization contributes to higher fluxes of certain gases. The magnitude of trace gas fluxes over unfertilized crops is still uncertain. In the present study, deposition of ammonia (NH), nitric acid (HNO), and sulfur dioxide (SO) was measured over unfertilized soybean using the flux-gradient technique. The eddy diffusivity was estimated from eddy covariance measurements of temperature fluxes, resulting in K of 0.64 ± 0.30 m s. Flux means and standard deviations were -0.14 ± 0.13, -0.22 ± 0.19, and -0.38 ± 0.54 ?g m s for NH, HNO, and SO, respectively. Low concentrations of NH and HNO increased the relative uncertainties in the deposition velocities estimated from measured fluxes. This contributed to dissimilarities between deposition velocities estimated from the resistance analogy and deposition velocities estimated from fluxes. However, wet canopy conditions during the study may have led to an underestimation of deposition by the resistance analogy because the resistance method does not accurately describe the enhanced deposition rates that occur after dew formation. Quantification of vegetation characteristics, such as leaf wetness and apoplast chemistry, would be beneficial in future studies to more accurately determine stomatal resistance and its influence on fluxes. PMID:21869497

Myles, Latoya; Kochendorfer, John; Heuer, Mark W; Meyers, Tilden P

2011-01-01

95

The accuracy of oxygen flux measurements using microelectrodes  

Microsoft Academic Search

An electrochemical analog of a biofilm was constructed to test the accuracy of oxygen flux measurements using microelectrodes. We used a cathodically polarized graphite felt attached to the bottom of a flat plate open channel reactor as the reactive surface consuming oxygen. The oxygen flux to the felt was calculated from the polarization current. Microelectrodes were used to measure the

Kjetil Rasmussen; Zbigniew Lewandowski

1998-01-01

96

Heat flux measurement in SSME turbine blade tester  

SciTech Connect

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.

Liebert, C.H.

1990-11-01

97

Heat flux measurement in SSME turbine blade tester  

NASA Technical Reports Server (NTRS)

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.

Liebert, Curt H.

1990-01-01

98

Measurements for the JASPER Program Flux Monitor Experiment  

SciTech Connect

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.

Muckenthaler, F.J.; Spencer, R.R.; Hunter, H.T.; Hull, J.L. [Oak Ridge National Lab., TN (United States); Shono, A. [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center

1993-02-01

99

Sensitivity of shortwave radiative flux density, forcing, and heating rates to the aerosol vertical profile  

SciTech Connect

The effect of the aerosol vertical distribution on the solar radiation profiles, for idealized and measured profiles of optical properties (extinction and single-scattering albedo (SSA)) during the May 2003 Atmospheric Radiation Measurement (ARM) Aerosol Intensive Observation Period (AIOP), has been investigated using the Rapid Radiative Transfer Model Shortwave (RRTM_SW) code. Calculated profiles of down-welling and up-welling solar fluxes during the AIOP have been compared with the data measured by up- and down-looking solar broadband radiometers aboard a profiling research aircraft. The measured profiles of aerosol extinction, SSA, and water vapor obtained from the same aircraft that carried the radiometers served as the inputs for the model calculations. It is noteworthy that for this study, the uplooking radiometers were mounted on a stabilized platform that kept the radiometers parallel with respect to the earth’s horizontal plane. The results indicate that the shape of the aerosol extinction profiles has very little impact on direct radiative forcings at the top of atmosphere and surface in a cloud-free sky. However, as long as the aerosol is not purely scattering, the shape of the extinction profiles is important for forcing profiles. Identical extinction profiles with different absorption profiles drastically influence the forcing and heating rate profiles. Using aircraft data from 19 AIOP profiles over the Southern Great Plains (SGP), we are able to achieve broadband down-welling solar flux closure within 0.8% (bias difference) or 1.8% (rms difference), well within the expected measurement uncertainty of 1 to 3%. The poorer agreement in up-welling flux (bias -3.7%, rms 10%) is attributed to the use of inaccurate surface albedo data. The sensitivity tests reveal the important role accurate, vertically resolved aerosol extinction data plays in tightening flux closure. This study also suggests that in the presence of a strongly absorbing substance, aircraft flux measurements from a stabilized platform have the potential to determine heating rate profiles. These measurement-based heating rate profiles provide useful data for heating rate closure studies and indirect estimates of single scattering albedo assumed in radiative transfer calculations.

Guan, Hong; Schmid, Beat; Bucholtz, Anthony; Bergstrom, Robert

2010-03-31

100

In Situ Measurement of Energetic Electron Fluxes Inside Thunderclouds  

NASA Astrophysics Data System (ADS)

It is now well established that high-energy radiation is routinely produced by thunderclouds and lightning. This radiation is in the form of x-rays and gamma-rays with timescales ranging from sub-microsecond (x-rays associated with lightning leaders), to sub-millisecond (Terrestrial Gamma-ray Flashes), to minute long glows (Gamma-ray Glows from thunderclouds seen on the ground and in or near the cloud by aircrafts and balloons). It is generally accepted that these emissions originate from bremsstrahlung interactions of relativistic runaway electrons with air, which can be accelerated in the thundercloud/lightning electric fields and gain up to multi-MeV energies. However, the exact physical details of the mechanism that produces these runaway electrons are still unknown. In order to better understand the source of energetic radiation inside thunderclouds, we have begun a campaign of balloon-borne instruments to directly measure the flux of energetic electrons inside thunderclouds. In the current configuration, each balloon carries Geiger counters to record the energetic particles. Geiger counters are well suited for directly measuring energetic electrons and positrons and have the advantage of being lightweight and dependable. Due to the nature of the thunderstorm environment, the campaign has many design, communication, and safety challenges. In this presentation we will report on the status of the campaign and some of the physical insights gained from the data collected by our instruments. This work was supported in part by the NASA grant NNX12A002H and by DARPA grant HR0011-1-10-1-0061.

Arabshahi, S.; Vodopiyanov, I. B.; Dwyer, J. R.; Rassoul, H.

2013-12-01

101

Uncertainty analysis of steady state incident heat flux measurements in hydrocarbon fuel fires.  

SciTech Connect

The objective of this report is to develop uncertainty estimates for three heat flux measurement techniques used for the measurement of incident heat flux in a combined radiative and convective environment. This is related to the measurement of heat flux to objects placed inside hydrocarbon fuel (diesel, JP-8 jet fuel) fires, which is very difficult to make accurately (e.g., less than 10%). Three methods will be discussed: a Schmidt-Boelter heat flux gage; a calorimeter and inverse heat conduction method; and a thin plate and energy balance method. Steady state uncertainties were estimated for two types of fires (i.e., calm wind and high winds) at three times (early in the fire, late in the fire, and at an intermediate time). Results showed a large uncertainty for all three methods. Typical uncertainties for a Schmidt-Boelter gage ranged from {+-}23% for high wind fires to {+-}39% for low wind fires. For the calorimeter/inverse method the uncertainties were {+-}25% to {+-}40%. The thin plate/energy balance method the uncertainties ranged from {+-}21% to {+-}42%. The 23-39% uncertainties for the Schmidt-Boelter gage are much larger than the quoted uncertainty for a radiative only environment (i.e ., {+-}3%). This large difference is due to the convective contribution and because the gage sensitivities to radiative and convective environments are not equal. All these values are larger than desired, which suggests the need for improvements in heat flux measurements in fires.

Nakos, James Thomas

2005-12-01

102

Quantitative Comparison of Measured Plasma Sheet Electron Energy Flux and Remotely Sensed Auroral Electron Energy Flux  

NASA Astrophysics Data System (ADS)

In situ plasma sheet observations and auroral images give us two views of magnetospheric dynamics. With in situ observations, we get a detailed point measurement; auroral images give us a global view. Previous studies have shown an excellent correlation between dynamic plasma behavior in the plasma sheet and auroral activity. Here we extend the previous work with quantitative comparisons between the two regions. We directly compare the electron energy flux measured in the plasma sheet with the electron energy flux into the ionosphere inferred from auroral images. We find that during quiet times, the plasma sheet is able to supply the aurora with nearly all of the observed energy flux. During intervals of intense auroral emission, the electron spectrum in the conjugate region of the plasma sheet changes, increasing the amount of energy flux incident on the ionosphere. However, the increases in the plasma sheet energy flux is not enough to account for the inferred energy flux into the ionosphere from the images by nearly an order of magnitude. This implies that additional energy flux must be entering the loss cone through pitch angle diffusion or through the presence of parallel electric fields between the plasma sheet and the ionosphere during intervals of intense auroral emission. A likely source of this additional energy flux is the low altitude auroral acceleration region. >http://www.ess.washington.edu/People/Students/matt/AGU2001/

Fillingim, M. O.; Parks, G. K.; Chua, D.; Germany, G. A.; Lin, R. P.; McCarthy, M.

2001-12-01

103

Solar cycle variations of trapped proton flux in the inner radiation belt  

NASA Astrophysics Data System (ADS)

Trapped proton population in the inner radiation belt is highly dense, posing a potential danger to astronauts and man-made space assets traversing through this region. While being significantly stable within timescales up to hundreds of days, inner zone proton fluxes can exhibit considerable solar cycle variations, which has not been investigated comprehensively yet. To analyze the long-term variation of the South Atlantic Anomaly (SAA), we adopt the proton flux data measured by NOAA 15 from 1999 through 2009 and perform statistical analyses on the basis of reasonable Gaussian fits. We report that the variation of the peak proton flux in the SAA is anticorrelated with that of F10.7 during a solar cycle. There also exists a phase lag of 685 days between the solar F10.7 flux and the proton flux. Similar features are seen for changes of the SAA distribution area, which in addition shows a rapid decrease during the solar maximum and a slow increase during the solar minimum. We also find that the region where the proton flux peaks drifts westward year by year with larger drift rates during the solar minimum. The peak region shifts southward during the solar maximum but in the opposite direction during the solar minimum with higher shift speed. Enhancements in solar wind dynamic pressure can favor the north-south drift of the SAA.

Qin, Murong; Zhang, Xianguo; Ni, Binbin; Song, Hongqiang; Zou, Hong; Sun, Yueqiang

2014-12-01

104

Measurements of muon flux in the Pyhäsalmi underground laboratory  

NASA Astrophysics Data System (ADS)

The cosmic-ray induced muon flux was measured at several depths in the Pyhäsalmi mine (Finland) using a plastic scintillator telescope mounted on a trailer. The flux was determined at four different depths underground at 400 m (980 m.w.e), at 660 m (1900 m.w.e), at 990 m (2810 m.w.e) and at 1390 m (3960 m.w.e) with the trailer, and also at the ground surface. In addition, previously measured fluxes from depths of 90 m (210 m.w.e) and 210 m (420 m.w.e) are shown. A relation was obtained for the underground muon flux as a function of the depth. The measured flux follows well the general behaviour and is consistent with results determined in other underground laboratories.

Enqvist, T.; Mattila, A.; Föhr, V.; Jämsén, T.; Lehtola, M.; Narkilahti, J.; Joutsenvaara, J.; Nurmenniemi, S.; Peltoniemi, J.; Remes, H.; Sarkamo, J.; Shen, C.; Usoskin, I.

2005-12-01

105

Measurements of muon flux in the Pyhäsalmi underground laboratory  

E-print Network

The cosmic-ray induced muon flux was measured at several depths in the Pyh\\"asalmi mine (Finland) using a plastic scintillator telescope mounted on a trailer. The flux was determined at four different depths underground at 400 m (980 m.w.e), at 660 m (1900 m.w.e), at 990 m (2810 m.w.e) and at 1390 m (3960 m.w.e) with the trailer, and also at the ground surface. In addition, previously measured fluxes from depths of 90 m (210 m.w.e) and 210 m (420 m.w.e) are shown. A relation was obtained for the underground muon flux as a function of the depth. The measured flux follows well the general behaviour and is consistent with results determined in other underground laboratories.

T. Enqvist; A. Mattila; V. Föhr; T. Jämsén; M. Lehtola; J. Narkilahti; J. Joutsenvaara; S. Nurmenniemi; J. Peltoniemi; H. Remes; J. Sarkamo; C. Shen; I. Usoskin

2005-06-13

106

Quantifying the "chamber effect" in CO2 flux measurements  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

107

EXOMARS IRAS (DOSE) radiation measurements.  

NASA Astrophysics Data System (ADS)

The characterization and the study of the radiations on their interaction with organic matter is of great interest in view of the human exploration on Mars. The Ionizing RAdiation Sensor (IRAS) selected in the frame of the ExoMars/Pasteur ESA mission is a lightweight particle spectrometer combining various techniques of radiation detection in space. It characterizes the first time the radiation environment on the Mars surface, and provide dose and dose equivalent rates as precursor information absolutely necessary to develop ways to mitigate the radiation risks for future human exploration on Mars. The Martian radiation levels are much higher than those found on Earth and they are relatively low for space. Measurements on the surface will show if they are similar or not to those seen in orbit (modified by the presence of ``albedo'' neutrons produced in the regolith and by the thin Martian atmosphere). IRAS consists of a telescope based on segmented silicon detectors of about 40\\userk\\milli\\metre\\user;k diameter and 300\\user;k\\micro\\metre\\user;k thickness, a segmented organic scintillator, and of a thermoluminescence dosimeter. The telescope will continuously monitor temporal variation of the particle count rate, the dose rate, particle and LET (Linear Energy Transfer) spectra. Tissue equivalent BC430 scintillator material will be used to measure the neutron dose. Neutrons are selected by a criteria requiring no signal in the anti-coincidence. Last, the passive thermoluminescence dosimeter, based on LiF:Mg detectors, regardless the on board operation timing, will measure the total dose accumulated during the exposure period and due to beta and gamma radiation, with a responsivity very close to that of a human tissue.

Federico, C.; Di Lellis, A. M.; Fonte, S.; Pauselli, C.; Reitz, G.; Beaujean, R.

108

FLUX MEASUREMENTS FROM A TALL TOWER IN A COMPLEX LANDSCAPE  

SciTech Connect

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.

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

2010-07-22

109

Estimating shortwave solar radiation using net radiation and meteorological measurements  

Technology Transfer Automated Retrieval System (TEKTRAN)

Shortwave radiation has a wide variety of uses in land-atmosphere interactions research. Actual evapotranspiration estimation that involves stomatal conductance models like Jarvis and Ball-Berry require shortwave radiation to estimate photon flux density. However, in most weather stations, shortwave...

110

Development of a radiative flux evaluation program with a 3-D Monte Carlo radiative transfer code  

NASA Astrophysics Data System (ADS)

In this paper, we have developed a three-dimensional (3D) Monte Carlo radiative transfer code that can treat a broadband solar flux calculation implemented with k-distribution parameters [1]. We used this code for generating the radiative flux profile and heating rate profile in the atmosphere including broken clouds. In order to construct 3-D extinction coefficient fields, we tried following three methods: 1) Minimum cloud Information Deviation Profiling Method (MIDPM), 2) numerical simulations by a non-hydrostatic model with bin cloud microphysics model and 3) idealized stochastic clouds generated by randomized extinction coefficient distribution and regularly-distributed tiled clouds. Using these constructed 3-D cloud systems, we calculated the radiation field by our Monte Carlo radiative transfer code at wavelengths of 0.5, 1.6 and 2.1 microns. We then compared the results with Plane Parallel Approximation (PPA) and a reflectivity of 3-D with Independent Pixel Approximation (IPA). In the case of wavelength 0.5 microns, as expected, all the discrepancies between 3-D clouds and equivalent IPA clouds are smaller than the discrepancies between 3-D clouds and equivalent PPA clouds. At maximum the reflectivity difference for the PPA and IPA is about equal to fluxes of 30 Wm-2 and 10 Wm-2, respectively.

Okata, Megumi; Nakajima, Teruyuki; Barker, Howard W.; Donovan, David P.

2013-05-01

111

Eddy Covariance Measurements Of CO2 Fluxes Above Lake Superior  

NASA Astrophysics Data System (ADS)

Lake Superior has been reported to be seasonally supersaturated with respect to atmospheric CO2, and fluxes estimated from measured pCO2 would be regionally significant. Comparison of pCO2 within the lake and atmospheric CO2 measured 400 m above ground at a site 100 km south of the lake suggest that ?pCO2 (difference between air and water) is 0-400 ?atm. Application of empirical gas exchange models suggests that the flux out of the lake is 0.1-0.4 g C m-2 d-1. While these fluxes are small compared to daily or monthly averages over nearby terrestrial systems (-8 to +4 g C m-2 d-1), the annual fluxes for the lake (~140 g C m-2 yr-1) are comparable in magnitude but opposite in direction to fluxes over nearby forests (-120 to -300 g C m-2 yr-1). Given the large surface area of Lake Superior, annual emissions of CO2 from the lake (~11 Tg C yr-1) may be regionally significant. To better assess the magnitude of the flux, eddy covariance (EC) measurements of the CO2 flux above the lake were made on six occasions between August 2007 and October 2008. Measurements were made at fixed stations that were 1-20 km from shore in the central region of the lake. EC instrumentation was mounted on top of a 10-m pneumatic mast on board the R/V Agassiz. A Crossbow AHRS300CA was mounted level with the sonic anemometer to enable measured wind vectors to be corrected for ship motion. The adequacy of the motion correction was verified by power spectral analysis of vertical wind speeds, comparison of EC fluxes with bulk aerodynamic calculations, and comparison of latent and sensible heat fluxes with other estimates of these fluxes. Measurements were conducted for an hour at each station; 10-minute average fluxes were computed, and these were then averaged to yield hourly means. The EC CO2 fluxes were in the range of 0.15 to 0.63 g C m-2 d-1 which is similar to the range of estimates cited above, though all measurements were made at times of low wind speeds (1 - 6 m s-1). The mean (± 95% CI) of all measured fluxes (0.28 ± 0.15 g C m-2 d-1 or 100 g C m-2 yr-1) supports the conclusion that Lake Superior is a regionally significant source of CO2 to the atmosphere.

Mwangi, J. M.; Urban, N. R.; Perlinger, J. A.; Bariteau, L.; Fairall, C. W.

2008-12-01

112

Measured and parameterized energy fluxes estimated for Atlantic transects of RV Polarstern  

NASA Astrophysics Data System (ADS)

Even to date energy fluxes over the oceans are difficult to assess. As an example the relative paucity of evaporation observations and the uncertainties of currently employed empirical approaches lead to large uncertainties of evaporation products over the ocean (e.g. Large and Yeager, 2009). Within the frame of OCEANET (Macke et al., 2010) we performed such measurements on Atlantic transects between Bremerhaven (Germany) and Cape Town (South Africa) or Punta Arenas (Chile) onboard RV Polarstern during the recent years. The basic measurements of sensible and latent heat fluxes are inertial-dissipation (e.g. Dupuis et al., 1997) flux estimates and measurements of the bulk variables. Turbulence measurements included a sonic anemometer and an infrared hygrometer, both mounted on the crow's nest. Mean meteorological sensors were those of the ship's operational measurement system. The global radiation and the down terrestrial radiation were measured on the OCEANET container placed on the monkey island. At least about 1000 time series of 1 h length were analyzed to derive bulk transfer coefficients for the fluxes of sensible and latent heat. The bulk transfer coefficients were applied to the ship's meteorological data to derive the heat fluxes at the sea surface. The reflected solar radiation was estimated from measured global radiation. The up terrestrial radiation was derived from the skin temperature according to the Stefan-Boltzmann law. Parameterized heat fluxes were compared to the widely used COARE-parameterization (Fairall et al., 2003), the agreement is excellent. Measured and parameterized heat and radiation fluxes gave the total energy budget at the air sea interface. As expected the mean total flux is positive, but there are also areas, where it is negative, indicating an energy loss of the ocean. It could be shown that the variations in the energy budget are mainly due to insolation and evaporation. A comparison between the mean values of measured and parameterized sensible and latent heat fluxes shows that the data are suitable to validate satellite derived fluxes at the sea surface and re-analysis data. References Dupuis, H., P. K. Taylor, A. Weill, and K. Katsaros, 1997: Inertial dissipation method applied to derive turbulent fluxes over the ocean during the surface of the ocean. J. Geophys. Res., 102 (C9), 21 115-21 129. Fairall, C. W., E. F. Bradley, J. E. Hare, A. A. Grachev, J. B. Edson, 2003: Bulk Parameterization of Air-Sea Fluxes: Updates and Verification for the COARE Algorithm. J. Climate, 16, 571-591. Large, W.G., and S.G. Yeager, 2009: The global climatology of an interannually varying air-sea flux data set. Climate Dynamics 33, 341-364. Macke, A., Kalisch, J., Zoll, Y., and Bumke, K., 2010: Radiative effects of the cloudy atmosphere from ground and satellite based observations, EPJ Web of Conferences, 5 9, 83-94

Bumke, Karl; Macke, Andreas; Kalisch, John; Kleta, Henry

2013-04-01

113

Radiation measurements on the Mir Orbital Station  

NASA Technical Reports Server (NTRS)

Radiation measurements made onboard the MIR Orbital Station have spanned nearly a decade and covered two solar cycles, including one of the largest solar particle events, one of the largest magnetic storms, and a mean solar radio flux level reaching 250 x 10(4) Jansky that has been observed in the last 40 years. The cosmonaut absorbed dose rates varied from about 450 microGy day-1 during solar minimum to approximately half this value during the last solar maximum. There is a factor of about two in dose rate within a given module, and a similar variation from module to module. The average radiation quality factor during solar minimum, using the ICRP-26 definition, was about 2.4. The drift of the South Atlantic Anomaly was measured to be 6.0 +/- 0.5 degrees W, and 1.6 +/- 0.5 degrees N. These measurements are of direct applicability to the International Space Station. This paper represents a comprehensive review of Mir Space Station radiation data available from a variety of sources. c2002 Elsevier Science Ltd. All rights reserved.

Badhwar, G. D.; Atwell, W.; Reitz, G.; Beaujean, R.; Heinrich, W.

2002-01-01

114

Radiation measurements on the Mir Orbital Station.  

PubMed

Radiation measurements made onboard the MIR Orbital Station have spanned nearly a decade and covered two solar cycles, including one of the largest solar particle events, one of the largest magnetic storms, and a mean solar radio flux level reaching 250 x 10(4) Jansky that has been observed in the last 40 years. The cosmonaut absorbed dose rates varied from about 450 microGy day-1 during solar minimum to approximately half this value during the last solar maximum. There is a factor of about two in dose rate within a given module, and a similar variation from module to module. The average radiation quality factor during solar minimum, using the ICRP-26 definition, was about 2.4. The drift of the South Atlantic Anomaly was measured to be 6.0 +/- 0.5 degrees W, and 1.6 +/- 0.5 degrees N. These measurements are of direct applicability to the International Space Station. This paper represents a comprehensive review of Mir Space Station radiation data available from a variety of sources. PMID:12440430

Badhwar, G D; Atwell, W; Reitz, G; Beaujean, R; Heinrich, W

2002-10-01

115

Flux Measurements of Volatile Organic Compounds from an Urban Landscape  

SciTech Connect

Direct measurements of volatile organic compound (VOC) emissions that include all anthropogenic and biogenic emission sources in urban areas are a missing requirement to evaluate emission inventories and constrain current photochemical modelling practices. Here we demonstrate the use of micrometeorological techniques coupled with fast-response sensors to measure urban VOC fluxes from a neighborhood of Mexico City, where the spatial variability of surface cover and roughness is high. Fluxes of olefins, methanol, acetone, toluene and C2-benzenes were measured and compared with the local gridded emission inventory. VOC fluxes exhibited a clear diurnal pattern with a strong relationship to vehicular traffic. Recent photochemical modeling results suggest that VOC emissions are significantly underestimated in Mexico City1, but the measured VOC fluxes described here indicate that the official emission inventory2 is essentially correct. Thus, other explanations are needed to explain the photochemical modelling results.

Velasco, E.; Lamb, Brian K.; Pressley, S.; Allwine, Eugene J.; Westberg, Halvor; Jobson, B Tom T.; Alexander, M. Lizabeth; Prazeller, Peter; Molina, Luisa; Molina, Mario J.

2005-10-19

116

Impact of biomass burning aerosols on the clear-sky shortwave radiative fluxes  

NASA Astrophysics Data System (ADS)

Aerosol radiative forcing is recognized as a key climate change component, and biomass burning is one of the largest sources of anthropogenic tropospheric aerosols. Biomass burning aerosols have both a direct radiative impact by scattering and absorbing solar radiation and an indirect radiative impact by serving as cloud condensation nuclei. Although our knowledge of the optical properties of smoke aerosols has been significantly improved during the past decade through field experiments, there still exists large uncertainty in both direct and indirect smoke radiative forcings at the Top-of-Atmosphere (TOA) and at the surface. Using satellite measurements, direct shortwave radiative forcings of smoke aerosols are estimated both at the TOA and at the surface. Optical thickness (?) and single scattering albedo (?0) are the two most important optical parameters of smoke aerosols in determining their radiative impact. A look-up table approach is applied to retrieve these parameters using Advanced Very High Resolution Radiometer (AVHRR) imagery from the NOAA platform. Using NOAA-14 AVHRR visible reflectances and ground-based ? measurements, the ?0 values of smoke aerosols are estimated for selected days during both the Smoke, Clouds and Radiation-Brazil (SCAR-B) experiment held in Brazil during 1995 and for selected days during the Zambian International Biomass Burning Emission Experiment (ZIBBEE) held in Africa in 1997. The results indicate that when ground-based values of aerosol ? are available, reasonable estimates of ?0 can be retrieved from AVHRR imagery which, in turn, then can be used to characterize biomass burning aerosols in radiative transfer calculations. Surface SW fluxes can be estimated from the TOA observed SW fluxes using the radiative transfer model. In this study, a ?-four stream radiative transfer model has been modified to account for the biomass burning aerosols so that it can be used over biomass burning regions. Finally, one month of VIRS and CERES data in August 1998 over biomass burning regions in South America and Africa have been processed to study the instantaneous and diurnally-averaged smoke radiative forcings both at the TOA and at the surface. The results from one month of data indicate that smoke aerosols have significant cooling effect at both the TOA and the surface. (Abstract shortened by UMI.)

Li, Xiang

117

Reconstruction of charged particle fluxes detected by the Radiation Assessment Detector onboard of MSL  

NASA Astrophysics Data System (ADS)

One of the main science objectives of the Mars Science Laboratory (MSL) is to help planning future human exploration to Mars by constraining the radiation environment during the cruise phase and on the planet's surface. During the 253-day, 560 million km cruise to Mars, the Radiation Assessment Detector, RAD made detailed measurements of the energy spectrum deposited by energetic particles from space and scattered within the spacecraft. Two types of radiation pose potential health risks to astronauts in deep space: a prolonged low-dose exposure to Galactic Cosmic Rays (GCRs) and short-term exposures to the Solar Energetic Particles (SEPs). On the surface of Mars such energetic particles penetrate through its thin atmosphere and generate secondary particles that can also result harms to humans. In order to interpret the energetic charged particle flux coming into the detector, we have developed the Detector Response Function (DRF) using GEANT 4 simulations and employed a Maximum likelihood inversion technique to invert the detected energy spectrum. This method has been applied to RAD detection of GCRs and secondary charged particles on the Martian surface, giving us an unique insight into their energy fluxes. The spectra of the stopping particle fluxes (hydrogen and helium) are also directly obtained from RAD observations and compared with the inversion results.

Guo, J.; Wimmer-Schweingruber, R. F.; Hassler, D.; Zeitlin, C. J.; Ehresmann, B.; Kohler, J.; Boehm, E.; Appel, J. K.; Lohf, H.; Boettcher, S.; Burmeister, S.; Rafkin, S. C.; Kharytonov, A.; Martin-Garcia, C.; Matthiae, D.; Reitz, G.

2013-12-01

118

Heat flux measurement from vertical temperature profile and thermal infrared imagery in low-flux fumarolic zones  

NASA Astrophysics Data System (ADS)

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 illumination, wind, or rainfalls. It has been successfully tested during 5 months with a permanent station built on the Ty fault on La Soufrière volcano (Guadeloupe, Lesser Antilles). Results show that the diurnal cycle has a significant influence on the temperature up to ca. 30 cm depth, hindering the use of the thermal gradient in this zone, while the STA has a negligible variation. Rain has a more dramatic influence: the surface temperature and the STA are significantly affected, even for small rains. The model shows that the drop of temperature and the affected thickness are mainly controlled by the amount of rain, while the relaxation time is primarily a function of the heat flux. These results have strong implications in the interpretation and the reliability of the temperature surveys, and could be used to correct them from the climate fluctuations.

Gaudin, Damien; Finizola, Anthony; Beauducel, François; Brothelande, Elodie; Allemand, Pascal; Delacourt, Christophe; Delcher, Eric; Peltier, Aline

2014-05-01

119

Intercalibration of benthic flux chambers I. Accuracy of flux measurements and influence of chamber hydrodynamics  

Microsoft Academic Search

The hydrodynamic properties and the capability to measure sediment–water solute fluxes, at assumed steady state conditions, were compared for three radically different benthic chamber designs: the “Microcosm”, the “Mississippi” and the “Göteborg” chambers. The hydrodynamic properties were characterized by mounting a PVC bottom in each chamber and measuring mixing time, diffusive boundary layer thickness (DBL thickness) shear velocity (u?), and

A. Tengberg; H. Stahl; G. Gust; V. Müller; U. Arning; H. Andersson; P. O. J. Hall

2004-01-01

120

ADcp Measurements of Suspended Sediment Fluxes in Banat Rivers, Romania  

E-print Network

ADcp Measurements of Suspended Sediment Fluxes in Banat Rivers, Romania Eugenia Rotaru1 , Jérôme Le sediment, aDcp, river discharge measurement, hydrometry Introduction Suspended load represents a huge used to perform river discharge measurements. Water velocity profiles are computed from the Doppler

Paris-Sud XI, Université de

121

Hybrid heat flux measurement system for solar central receiver evaluation  

Microsoft Academic Search

A hybrid heat flux measurement system has been designed, built and mounted on top of the SSPS-CRS tower at the Plataforma Solar de Almería (PSA) to measure the incident solar power that is concentrated by a heliostat field on the flat aperture of a central receiver. This device is composed of two measurement systems, one direct and the other indirect.

J. Ballestrín; R. Monterreal

2004-01-01

122

Inaccuracies in soil heat flux measurement and modeling: a matter of vertical and temporal resolution?  

NASA Astrophysics Data System (ADS)

We here demonstrate with a conceptual model of the land-atmosphere interaction and a high vertical resolution Soil Vegetation Atmosphere Transfer model that the high daily frequencies of incoming radiation play a fundamental role in the soil heat flux signal. These high frequencies remain concentrated in a very shallow layer at the surface of about 1cm, which precludes the use of deeper measurement to accurately describe the surface soil heat flux signal. Current measurement techniques lead to important errors in the surface energy budget. In addition the currently-used calorimetric method is demonstrated to be unable to characterize the variability, magnitude and phase in the surface soil heat flux. In consequence, these results call for a higher-resolution sampling of soil heat flux, both in time and vertically near the surface, in order to accurately quantify the surface soil heat flux and to account for its rapid variations, especially in cloudy situations. In addition those results demonstrate the need for high vertical and temporal resolution in the modeling of the soil surface in order to describe the diurnal course of the surface soil heat flux. Coarser resolutions are shown to miss most of the soil heat flux signal since it acts as a high-pass filter of incoming radiation. Finally this works points out important limitations of the assimilation of infrared surface temperature because of the rapid fluctuations in solar radiation (weather noise). Comparison of the soil heat flux at different depth obtained with SVAT (continuous line) and conceptual land-atmosphere model (dashed line) over 135 days of data from the SUDMED project. The conceptual model captures the emergent behavior of the soil heat flux response. Soil heat flux at the surface is mostly influenced by high frequencies, whereas the high-frequency component of the signal has almost disappeared at typical soil heat flux measurement depth (2.5 or 5cm). This shows the limitation of current soil heat flux methodology since they do not capture most of the surface signal and cannot therefore close the surface energy partitioning.

Gentine, P.; Entekhabi, D.

2010-12-01

123

Airborne flux measurements of biogenic volatile organic compounds over California  

NASA Astrophysics Data System (ADS)

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 coniferous forests were extremely low, high concentrations of methanol and monoterpenes were found above some of these regions. These observations demonstrate the ability to measure fluxes from specific sources by eddy covariance from an aircraft, and suggest the utility of measurements using fast response chemical sensors to constrain emission inventories and map out source distributions for a much broader array of trace gases than was observed in this study. This paper reports the first regional direct eddy covariance fluxes of isoprene. The emissions of VOCs measured from aircraft with 2 km spatial resolution can quantify the distribution of major sources providing the observations required for testing statewide emission inventories of these important trace gases. These measurements will be used in a future study to assess BVOC emission models and their driving variable datasets.

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

2014-03-01

124

Studies of the net surface radiative flux from satellite radiances during FIFE  

NASA Technical Reports Server (NTRS)

Studies of the net surface radiative flux from satellite radiances during First ISLSCP Field Experiment (FIFE) are presented. Topics covered include: radiative transfer model validation; calibration of VISSR and AVHRR solar channels; development and refinement of algorithms to estimate downward solar and terrestrial irradiances at the surface, including photosynthetically available radiation (PAR) and surface albedo; verification of these algorithms using in situ measurements; production of maps of shortwave irradiance, surface albedo, and related products; analysis of the temporal variability of shortwave irradiance over the FIFE site; development of a spectroscopy technique to estimate atmospheric total water vapor amount; and study of optimum linear combinations of visible and near-infrared reflectances for estimating the fraction of PAR absorbed by plants.

Frouin, Robert

1993-01-01

125

A Simple Method for Estimating the Latent Heat Flux over Grass from Radiative Bowen Ratio.  

NASA Astrophysics Data System (ADS)

The evaluation of crop evapotranspiration from infrared temperature is usually calculated as the residual component of the surface energy balance. This method has given good results over a full grass canopy cover with unstressed transpiration, in spite of the not well understood meaning of the aerodynamic resistance needed. A simple and more accurate method, which determines the Bowen ratio () and the latent heat flux (E) over a reference grass area without knowledge of surface resistances, is proposed. The proportionality between and a radiative Bowen ratio s is shown. The radiative Bowen ratio is derived from surface and air temperatures and vapor pressure. This relationship allows the estimation of E from temperatures, vapor pressure, and solar radiation measurements at one reference level. The new method gives an estimated error of around 10% in front of the residual one, where the wind speed has to be known, with an error of above 20%. The proposed method requires further verification for different climatological conditions.

Ibañez, M.; Pérez, P. J.; Caselles, V.; Castellvi, F.

1998-04-01

126

Standard Test Method for Measuring Heat Flux Using a Copper-Constantan Circular Foil, Heat-Flux Transducer  

E-print Network

1.1 This test method describes the measurement of radiative heat flux using a transducer whose sensing element (1,2 ) is a thin circular metal foil. These sensors are often called Gardon Gauges. 1.2 The values stated in SI units are to be regarded as the standard. The values stated in parentheses are provided for information only. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

American Society for Testing and Materials. Philadelphia

2007-01-01

127

Simulation of the outer radiation belt electron flux decrease during the March 26, 1995, magnetic storm  

Microsoft Academic Search

In this paper we study the variation of the relativistic electron fluxes in the Earth's outer radiation belt during the March 26, 1995, magnetic storm. Using observations by the radiation environment monitor (REM) on board the space technology research vehicle (STRV-1b), we discuss the flux decrease and possible loss of relativistic electrons during the storm main phase. In order to

L. Desorgher; P. Bühler; A. Zehnder; E. O. Flückiger

2000-01-01

128

Radiation budget measurement/model interface research  

NASA Technical Reports Server (NTRS)

The NIMBUS 6 data were analyzed to form an up to date climatology of the Earth radiation budget as a basis for numerical model definition studies. Global maps depicting infrared emitted flux, net flux and albedo from processed NIMBUS 6 data for July, 1977, are presented. Zonal averages of net radiation flux for April, May, and June and zonal mean emitted flux and net flux for the December to January period are also presented. The development of two models is reported. The first is a statistical dynamical model with vertical and horizontal resolution. The second model is a two level global linear balance model. The results of time integration of the model up to 120 days, to simulate the January circulation, are discussed. Average zonal wind, meridonal wind component, vertical velocity, and moisture budget are among the parameters addressed.

Vonderhaar, T. H.

1981-01-01

129

Benthic primary productivity on the Georgia midcontinental shelf: Benthic flux measurements and high-resolution, continuous in situ PAR records  

Microsoft Academic Search

Continuous, 7 year records of above-water, near-surface water column and near-bottom measurements of photosynthetically active radiation (PAR) were used in conjunction with in situ chamber measurements to estimate magnitude and seasonal variations in benthic primary productivity (BPP) on the Georgia continental shelf. Correlation between BPP and PAR flux was established with 19 light\\/dark benthic chamber and PAR flux measurements at

R. A. Jahnke; J. R. Nelson; M. E. Richards; C. Y. Robertson; A. M. F. Rao; D. B. Jahnke

2008-01-01

130

Cosmic muon flux measurements at the Kimballton Underground Research Facility  

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

131

FAST NEUTRON FLUX MEASUREMENTS FOR SHIELDING APPLICATIONS  

Microsoft Academic Search

Pressed sulfur pellets, irradiated for two hours at 10 w yielded ;\\u000a satisfactory counting rates on an internal proportional counter for measuring ;\\u000a fast neutrons. The pellets were counted in their original form and an equation ;\\u000a applicable to thick sources was applied to obtain disintegration rates. Decay ;\\u000a data and beta energy analyses indicated that the induced activity was

Roy

1959-01-01

132

Interannual variability of surface radiative fluxes and rainfall in the semi-arid Sahel  

NASA Astrophysics Data System (ADS)

In the Sahel, interannual variability of rainfall is known to be strong, from meso- to continental spatial scales. This is associated with changes in surface radiative fluxes. The actual role played by surface fluxes on the interannual variability of rainfall has been much debated, especially within the context of the major regional scale, multi-decadal West African drought which started at the end of the 1960's (e.g. changes in surface albedo, Charney et al. Science 1975). The significance of conclusions that have been drawn, essentially from modelling approaches, is however limited because of weaknesses in models (e.g. parametrizations of rainfall and clouds, vegetation and aerosols) coupled to a lack of data for assessing the relevance of theories or hypotheses put forward on such bases. The present study aims to quantify and to analyse the interannual variability of surface radiative fluxes and rainfall measured with ground-based automatic weather stations (AWS) for seven years. The AWS are located in the Malian Gourma, from the semi-arid Central Sahel (15°N, 1.5°W) to Northern Sahel (17°N, 1°W), on the border of the Sahara, over the dominant Sahelian surface type (sandy soil). The variability displayed by satellite estimates SRB over this area is also presented and discussed. This study is linked to another one presented in the session AS1.14, African Monsoon Multidisciplinary Analysis (AMMA) by Guichard et al. "Couplings between the seasonal cycles of surface thermodynamics and radiative fluxes in the semi-arid Sahel" (see also Guichard et al. J. Hydrology 2009, AMMA-Catch special issue, http://dx.doi.org/10.1016/j.jhydrol.2008.09.007) The large interannual variability of annual rainfall sampled by AWS (less than 200 mm to more than 400 mm) is associated with an equally significant variability of surface net radiation Rnet. It is the more pronounced during the core of the monsoon season. More rainy monsoon seasons are characterized by higher Rnet; the difference can reach up to 30 W.m-2 on average over the month of August. This difference in Rnet is not related to an enhancement of the incoming longwave flux, LWin actually fluctuates by less than 5 W.m-2. More rain in August is associated with less incoming shortwave radiation, with a difference of about 10W.m-2. At this monthly time scale, variations of Rnet are more largely explained by changes in surface properties. This involves the vegetation dynamics, which accounts for large interannual fluctuations of albedo (Samain et al., J. Geophys. Res. 2008, http://www.agu.org/pubs/crossref/2008/2007JD009174.shtml). However, the processes accounting for the interannual variability of the upwelling longwave flux, LWup, are found to be at least as important as albedo effects when accounting for changes in Rnet. LWup decreases sharply in response to the succession of rainfall events in this region where soil temperature reaches very high values in Spring. At larger time scale (June to September average), LWup and rainfall are also found to be strongly and consistently related. As the interannual variability of shortwave incoming and upwelling flux partly balance each other, the upwelling longwave flux LWup appears as a major driver of the interannual variability of Rnet. These results emphasize the strong couplings taking place in the Sahelian climate between surface radiation, energy fluxes and the water cycle. They point to the significance of a variety of processes, among which aerosols and vegetation-related processes cannot be neglected. Finally, they provide valuable guidance for models over an area where interactions among processes are complex and climate projections currently very uncertain.

Guichard, F.; Grippa, M.; Kergoat, L.; Hiernaux, P.; Mougin, E.; Timouk, F.; Delbart, N.

2009-04-01

133

Measurement and modelling of methane fluxes from UK peatlands  

NASA Astrophysics Data System (ADS)

Nearly 5000 chamber measurements of CH4 flux were collated from 21 sites across the UK, covering a range of soil and vegetation types, to derive a parsimonious model that explains as much of the variability as possible, with the least input requirements. Less than half of the observed variability in instantaneous fluxes could be explained by the independent variables measured. Measurement error is one reason for this, and here we analyse several of the uncertainties inherent in these measurements, including the choice of model used to calculate the flux. Other reasons include the stochastic nature of some of the transport processes and the poor correspondence between the independent variables measured and the actual variables influencing the processes underlying methane production, transport and oxidation. Alternative measurement methods are considered which may circumvent some of these problems. When temporal variation was removed, and the fluxes averaged at larger spatial scales, simple models explained up to ~75 % of the variance in CH4 fluxes. Soil carbon, peat depth, soil moisture and pH together provided the best sub-set of explanatory variables. To estimate the impact of changes in peatland water table on CH4 emissions in the UK, an emission factor of +0.4 g CH4 m-2 y-1 per cm increase in water table was derived from the data. As an alternative approach, vegetation species composition provides a long-term integrator of environmental conditions, which may correlate with methane flux. Here, we used a "weighted averaging" approach to predict methane flux from plant species composition at a range of sites in the UK, continental Europe and Canada. Species were classified into functional groups, defined by a number of qualitative traits considered relevant to methane dynamics. We compared the results based on this functional classification with those based on the original species composition data with a purely taxonomic classification.

Levy, P. E.; Gray, A.

2012-12-01

134

The Airborne Measurements of Methane Fluxes (AIRMETH) Arctic Campaign (Invited)  

NASA Astrophysics Data System (ADS)

One of the most pressing questions with regard to climate feedback processes in a warming Arctic is the regional-scale methane release from Arctic permafrost areas. The Airborne Measurements of Methane Fluxes (AIRMETH) campaign is designed to quantitatively and spatially explicitly address this question. Ground-based eddy covariance (EC) measurements provide continuous in-situ observations of the surface-atmosphere exchange of methane. 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. Here, we present the potential of environmental response functions (ERFs) for quantitatively linking methane flux observations in the atmospheric surface layer to meteorological and biophysical drivers in the flux footprints. For this purpose thousands of kilometers of AIRMETH data across the Alaskan North Slope are utilized, with the aim to extrapolate the airborne EC methane flux observations to the entire North Slope. The data were collected aboard the research aircraft POLAR 5, using its turbulence nose boom and fast response methane and meteorological sensors. After thorough data pre-processing, Reynolds averaging is used to derive spatially integrated fluxes. To increase spatial resolution and to derive ERFs, we then use wavelet transforms of the original high-frequency data. This enables much improved spatial discretization of the flux observations, and the quantification of continuous and biophysically relevant land cover properties in the flux footprint of each observation. A machine learning technique is then employed to extract and quantify the functional relationships between the methane flux observations and the meteorological and biophysical drivers in the flux footprints. Lastly, the resulting ERFs are used to extrapolate the methane release over spatio-temporally explicit grids of the Alaskan North Slope. Metzger et al. (2013) have demonstrated the efficacy of this technique for regionalizing airborne EC heat flux observations to within an accuracy of ?18% and a precision of ?5%. Here, we show for the first time results from applying the ERF procedure to airborne methane EC measurements, and report its potential for spatio-temporally explicit inventories of the regional-scale methane exchange. References: Metzger, S., Junkermann, W., Mauder, M., Butterbach-Bahl, K., Trancón y Widemann, B., Neidl, F., Schäfer, K., Wieneke, S., Zheng, X. H., Schmid, H. P., and Foken, T.: Spatially explicit regionalization of airborne flux measurements using environmental response functions, Biogeosciences, 10, 2193-2217, doi:10.5194/bg-10-2193-2013, 2013.

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

2013-12-01

135

Flux measurement and modeling in a typical mediterranean vineyard  

NASA Astrophysics Data System (ADS)

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.

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

136

Long-term radiation effects on fibre Bragg grating temperature sensors in a low flux nuclear reactor  

Microsoft Academic Search

Fibre Bragg grating (FBG) temperature sensors have already shown short-term radiation tolerance in nuclear environments. However, the effect of long-term irradiation needed to be investigated. We therefore characterized multiplexed FBG temperature sensors inserted early 2000 in an irradiation channel of a low flux nuclear reactor. After 50 months, we show that the sensors still operate satisfactorily and that the measured

A. Fernandez Fernandez; A. Gusarov; B. Brichard; M. Decréton; F. Berghmans; P. Mégret; A. Delchambre

2004-01-01

137

Comparison of Different Global Information Sources Used in Surface Radiative Flux Calculation: Radiative Properties of the Surface  

NASA Technical Reports Server (NTRS)

Direct estimates of surface radiative fluxes that resolve regional and weather-scale variabilty over the whole globe with reasonable accuracy have only become possible with the advent of extensive global, mostly satellite, datasets within the past couple of decades. The accuracy of these fluxes, estimated to be about 10-15 W per square meter is largely limited by the accuracy of the input datasets. The leading uncertainties in the surface fluxes are no longer predominantly induced by clouds but are now as much associated with uncertainties in the surface and near-surface atmospheric properties. This study presents a fuller, more quantitative evaluation of the uncertainties for the surface albedo and emissivity and surface skin temperatures by comparing the main available global datasets from the Moderate-Resolution Imaging Spectroradiometer product, the NASA Global Energy and Water Cycle Experiment Surface Radiation Budget project, the European Centre for Medium-Range Weather Forecasts, the National Aeronautics and Space Administration, the National Centers for Environmental Prediction, the International Satellite Cloud Climatology Project (ISCCP), the Laboratoire de Meteorologie Dynamique, NOAA/NASA Pathfinder Advanced Very High Resolution Radiometer project, NOAA Optimum Interpolation Sea Surface Temperature Analysis and the Tropical Rainfall Measuring Mission (TRMM) Microwave Image project. The datasets are, in practice, treated as an ensemble of realizations of the actual climate such that their differences represent an estimate of the uncertainty in their measurements because we do not possess global truth datasets for these quantities. The results are globally representative and may be taken as a generalization of our previous ISCCP-based uncertainty estimates for the input datasets. Surface properties have the primary role in determining the surface upward shortwave (SW) and longwave (LW) flux. From this study, the following conclusions are obtained. Although land surface albedos in the near near-infrared remain poorly constrained (highly uncertain), they do not cause too much error in total surface SW fluxes; the more subtle regional and seasonal variations associated with vegetation and snow are still on doubt. The uncertainty of the broadband black-sky SW albedo for land surface from this study is about 7%, which can easily induce 5-10 W per square meter uncertainty in (upwelling) surface SW flux estimates. Even though available surface (broadband) LW emissivity datasets differ significantly (3%-5% uncertainty), this disagreement is confined to wavelengths greater than 20 micrometers so that there is little practical effect (1-3 W per square meters) on the surface upwelling LW fluxes. The surface skin temperature is one of two leading factors that cause problems with surface LW fluxes. Even though the differences among the various datasets are generally only 2-4 K, this can easily cause 10-15 W per square meter uncertainty in calculated surface (upwelling) LW fluxes. Significant improvements could be obtained for surface LW flux calculations by improving the retrievals of (in order of decreasing importance): (1) surface skin temperature, (2) surface air and near-surface-layer temperature, (3) column precipitable water amount and (4) broadband emissivity. And for surface SW fluxes, improvements could be obtained (excluding improved cloud treatment) by improving the retrievals of (1) aerosols (from our sensitivity studies but not discussed in this work), and (2) surface (black-sky) albedo, of which, NIR part of the spectrum has much larger uncertainty.

Zhang, Yuanchong; Rossow, William B.; Stackhouse, Paul W., Jr.

2007-01-01

138

Comparison of different global information sources used in surface radiative flux calculation: Radiative properties of the surface  

NASA Astrophysics Data System (ADS)

Direct estimates of surface radiative fluxes that resolve regional and weather-scale variability over the whole globe with reasonable accuracy have only become possible with the advent of extensive global, mostly satellite, data sets within the past couple of decades. The accuracy of these fluxes, estimated to be about 10-15 W/m2, is largely limited by the accuracy of the input data sets. The leading uncertainties in the surface fluxes are no longer predominantly induced by clouds but are now as much associated with uncertainties in the surface and near-surface atmospheric properties. This study presents a fuller, more quantitative evaluation of the uncertainties for the surface albedo and emissivity and surface skin temperatures by comparing the main available global data sets from the Moderate-Resolution Imaging Spectroradiometer product, the NASA Global Energy and Water Cycle Experiment Surface Radiation Budget project, the European Centre for Medium-Range Weather Forecasts, the National Aeronautics and Space Administration, the National Centers for Environmental Prediction, the International Satellite Cloud Climatology Project (ISCCP), the Laboratoire de Météorologie Dynamique, NOAA/NASA Pathfinder Advanced Very High Resolution Radiometer project, and the NOAA Optimum Interpolation Sea Surface Temperature Analysis and the Tropical Rainfall Measuring Mission (TRMM) Microwave Image project. The data sets are, in practice, treated as an ensemble of realizations of the actual climate such that their differences represent an estimate of the uncertainty in their measurements because we do not possess global "truth" data sets for these quantities. The results are globally representative and may be taken as a generalization of our previous ISCCP-based uncertainty estimates for the input data sets. Surface properties have the primary role in determining the surface upward shortwave (SW) and longwave (LW) flux.From this study the following conclusions are obtained. Although land surface albedos in the near-infrared remain poorly constrained (highly uncertain), they do not cause too much error in total surface SW fluxes; the more subtle regional and seasonal variations associated with vegetation and snow are still in doubt. The uncertainty of the broadband black-sky SW albedo for land surface from this study is about 7%, which can easily induce 5-10 W/m2 uncertainty in (upwelling) surface SW flux estimates. Even though available surface (broadband) LW emissivity data sets differ significantly (3-5% uncertainty), this disagreement is confined to wavelengths >20 ?m so that there is little practical effect (1-3 W/m2) on the surface upwelling LW fluxes. The surface skin temperature is one of two leading factors that cause problems with surface LW fluxes. Even though the differences among the various data sets are generally only 2-4 K, this can easily cause 10-15 W/m2 uncertainty in calculated surface (upwelling) LW fluxes. Significant improvements could be obtained for surface LW flux calculations by improving the retrievals of (in order of decreasing importance): (1) surface skin temperature, (2) surface air and near-surface-layer temperature, (3) column precipitable water amount, and (4) broadband emissivity. In addition, for surface SW fluxes, improvements could be obtained (excluding improved cloud treatment) by improving the retrievals of (1) aerosols (from our sensitivity studies but not discussed in this work) and (2) surface (black-sky) albedo, of which the NIR part of the spectrum has much larger uncertainty.

Zhang, Yuanchong; Rossow, William B.; Stackhouse, Paul W., Jr.

2007-01-01

139

HONO Flux Measurement at a Forested Site in Northern Michigan  

NASA Astrophysics Data System (ADS)

Nitrous acid (HONO) is an important precursor of hydroxyl radical and plays an important role in the terrestrial boundary layer photochemistry. HONO is produced from various heterogeneous processes on surfaces, including photo-induced reactions involving NOx and HNO3. To quantitatively assess the HONO source strength at the forest canopy surface, we have deployed a Relaxed Eddy Accumulation (REA) method coupled with 2 LOng Path Absorption Photometers (LOPAP) for the measurement of HONO flux on PROPHET tower in the University of Michigan Biological Station during summer of 2008. Overall positive fluxes were observed, in consistent with our understanding that canopy surface is mainly a HONO source. A composite plot based on all measurement data shows a distinct diurnal variation pattern in HONO flux, with a low exchange rate (0.1 "Ýmoles m-2 hr-1) during the night and a maximum upward flux (0.7 "Ýmoles m-2 hr- 1) during noontime and early afternoon, suggesting that HONO production on canopy surface is photochemically related. The daytime upward HONO flux may counter a significant fraction of the NOy downward flux, a maximum of ~1.5 "Ýmoles m-2 hr-1 measured in August 2005. Some strong downward fluxes (up to 2 "Ýmoles m-2 hr-1) were found to be associated with rain and dew events, as a result of enhanced HONO dry deposition on wet surfaces. We will further examine the relationship between HONO flux and other parameters, such as ambient NOx, HNO3/nitrate loading on leaves, light intensity, relative humidity, and air mass back trajectories.

Zhou, X.; Zhang, N.; Tang, D.; Bertman, S.; Teravest, M.; Alaghmand, M.; Shepson, P.; Carroll, M.

2008-12-01

140

Measuring flux of soil fumigants using the aerodynamic and dynamic flux chamber methods.  

PubMed

Methods for measuring and estimating flux density of soil fumigants under field conditions are important for the purpose of providing inputs to air dispersion models and for comparing the effects of management practices on emission reduction. The objective of this study was to measure the flux of 1,3-dichloropropene (1,3-D) and chloropicrin at a site in Georgia (GA) using the aerodynamic method and the dynamic flux chamber (FC) method. A secondary objective was to compare the effects of high density polyethylene (HDPE), and virtually impermeable film (VIF) tarps on fumigant flux at a site in Florida (FL). Chloropicrin and 1,3-D were applied by surface drip application of In-Line soil fumigant on vegetable beds covered by low density polyethylene (LDPE), HDPE, or VIF. The surface drip fumigation using In-Line and LDPE tarp employed in this study resulted in volatilization of 26.5% of applied 1,3-D and 11.2% of the applied chloropicrin at the GA site, as determined using the aerodynamic method. Estimates of mass loss obtained from dynamic FCs were 23.6% for 1,3-D and 18.0% for chloropicrin at the GA site. Flux chamber trials at the FL site indicate significant additional reduction in flux density, and cumulative mass loss when VIF tarp is used. This study supports the use of dynamic FCs as a valuable tool for estimating gas flux density from agricultural soils, and evaluating best management practices for reducing fumigant emissions to the atmosphere. PMID:17412897

van Wesenbeeck, I J; Knuteson, J A; Barnekow, D E; Phillips, A M

2007-01-01

141

Jupiter's radiation belts. [electron and proton flux computations for radio generations  

NASA Technical Reports Server (NTRS)

Fluxes of electrons and protons in Jupiter's radiation belts are calculated with the source (radial diffusion inward from the solar wind) and the loss (synchroton radiation). The calculations are tested against the measured radio-wave wavelength distribution, the radio-wave distribution with distance from Jupiter, and the degree of polarization of the radio waves. The Fokker-Planck equation is solved by using the method of Farley and Walt (1971) with the fixed flux at the outer boundary and the zero flux at Jupiter's surface. It is found, in agreement with Brice and McDonough (1973), Jacques and Davis (1973), and Birmingham et al. (1974), that the usual magnetic and electric diffusions, which vary as L to the 10th power and L to the 6th power, respectively, are insufficient to furnish the required electrons and that the diffusion driven by ionospheric winds of Brice and McDonough is strong enough to furnish Jupiter's belts. An additional loss mechanism close to Jupiter is required to remove the electrons, particularly those at low energies.

Stansberry, K. G.; White, R. S.

1974-01-01

142

Flux measurements of biogenic VOCs during ECHO 2003  

NASA Astrophysics Data System (ADS)

Within the framework of the AFO 2000 project ECHO, two PTR-MS instruments were operated in combination with sonic anemometers to determine biogenic VOC fluxes from a mixed deciduous forest site in North-Western Germany using the eddy covariance (EC) technique. The measurement site was characterised by a forest of inhomogeneous composition, complex canopy structure, limited extension in certain wind directions and frequent calm wind conditions during night time. As a consequence, a considerable fraction of the measurements did not qualify for flux calculations by EC and had to be discarded. The validated results show light and temperature dependent emissions of isoprene and monoterpenes from this forest, with average emissions (normalised to 30°C and 1000 µmoles m-2 s-1 PAR) of 1.5 and 0.39 µg m-2 s-1, respectively. Emissions of methanol reached on average 0.087 µg m-2 s-1 during daytime, but fluxes were too small to be detected during night time. Upward fluxes of the isoprene oxidation products methyl vinyl ketone (MVK) and methacrolein (MACR) were also found, being two orders of magnitude lower than those of isoprene. The observed fluxes are consistent with upscalings from leaf-level emission measurements of representative tree species in this forest and, in the case of MVK and MACR, can plausibly be explained by chemical production through oxidation of isoprene within the canopy. Calculations with an analytical footprint model indicate that the observed isoprene fluxes correlate with the fraction of oaks within the footprints of the flux measurement.

Spirig, C.; Neftel, A.; Ammann, C.; Dommen, J.; Grabmer, W.; Thielmann, A.; Schaub, A.; Beauchamp, J.; Wisthaler, A.; Hansel, A.

2004-10-01

143

Analysis of actinic flux profiles measured from an ozone sonde balloon  

NASA Astrophysics Data System (ADS)

A green light sensor has been developed at KNMI to measure actinic flux profiles using an ozone sonde balloon. In total, 63 launches with ascending and descending profiles were performed between 2006 and 2010. The measured uncalibrated actinic flux profiles are analyzed using the Doubling Adding KNMI (DAK) radiative transfer model. Values of the cloud optical thickness (COT) along the flight track were taken from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) Cloud Physical Properties (CPP) product. The impact of clouds on the actinic flux profile is evaluated on the basis of the cloud modification factor (CMF) at the cloud top and cloud base, which is the ratio between the actinic fluxes for cloudy and clear-sky scenes. The impact of clouds on the actinic flux is clearly detected: the largest enhancement occurs at the cloud top due to multiple scattering. The actinic flux decreases almost linearly from cloud top to cloud base. Above the cloud top the actinic flux also increases compared to clear-sky scenes. We find that clouds can increase the actinic flux to 2.3 times of the clear-sky value at cloud top and decrease it to about 0.05 at cloud base. The relationship between CMF and COT agrees well with DAK simulations, except for a few outliers. Good agreement is found between the DAK simulated actinic flux profiles and the observations for single layer clouds in fully overcast scenes. The instrument is suitable for operational balloon measurements because of its simplicity and low cost. It is worth to further develop the instrument and launch it together with atmospheric chemistry composition sensors.

Wang, P.; Allaart, M.; Knap, W. H.; Stammes, P.

2014-12-01

144

Uncertainty of calorimeter measurements at NREL's high flux solar furnace  

NASA Astrophysics Data System (ADS)

The uncertainties of the calorimeter and concentration measurements at the High Flux Solar Furnace (HFSF) at the National Renewable Energy Laboratory (NREL) are discussed. Two calorimeter types have been used to date. One is an array of seven commercially available circular foil calorimeters (gardon or heat flux gages) for primary concentrator peak flux (up to 250 W/sq cm). The second is a cold-water calorimeter designed and built by the University of Chicago to measure the average exit power of the reflective compound parabolic secondary concentrator used at the HFSF (over 3.3 kW across a 1.6/sq cm) exit aperture, corresponding to a flux of about 2 kW/sq cm. This paper discussed the uncertainties of the calorimeter and pyrheliometer measurements and resulting concentration calculations. The measurement uncertainty analysis is performed according to the ASME/ANSI standard PTC 19.1 (1985). Random and bias errors for each portion of the measurement are analyzed. The results show that as either the power or the flux is reduced, the uncertainties increase. Another calorimeter is being designed for a new, refractive secondary which will use a refractive material to produce a higher average flux (5 kW/sq cm) than the reflective secondary. The new calorimeter will use a time derivative of the fluid temperature as a key measurement of the average power out of the secondary. A description of this calorimeter and test procedure is also presented, along with a pre-test estimate of major sources of uncertainty.

Bingham, C. E.

1991-12-01

145

A comparison between spectrally derived vegetation indices and CO2 fluxes measured over a hardwood forest  

NASA Astrophysics Data System (ADS)

A dual channel, narrow-band spectroradiometer was mounted at 34 m (1.6 x canopy ht) on the University of Michigan Biological Station AmeriFlux tower over the course of 10 days during the period of rapid leaf expansion in late May and early June 2006. Spectral scans of various locations of the plant canopy surrounding the flux tower were collected at one minute intervals during daylight hours within the sampling period. These spectral data were processed to obtain reflectance values from which a scaled Photochemical Reflectance Index (sPRI) and Normalized Difference Vegetation Index (NDVI) were calculated using reflectance values at 531nm and 570nm, and 670nm and 800nm respectively. The sPRI corresponds with xanthophyll cycle activity and thus radiation use efficiency, whereas the NDVI corresponds with absorbed photosynthetically active radiation (APAR). Midday measures of NDVI and sPRI were combined and compared with daily summed CO2 flux measurements from the eddy covariance system associated with the UMBS flux tower for the 10 day sampling period. Correlations between the combined NDVI/sPRI values and daily summed CO2 fluxes were found to vary with species, with r-square values ranging from 0.69 (p <0.1) for birch (Betula papyrifera) dominated pixels to 0.45 (p <0.1) for red pine (Pinus resinosa) dominated pixels.

Garrity, S. R.; Vierling, L. A.; Turnipseed, A.; Vogel, C. S.; Martins, D. K.; Shepson, P. B.

2006-12-01

146

Aerosol flux measurements above a mixed forest at Borden, Ontario  

NASA Astrophysics Data System (ADS)

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.

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

2010-10-01

147

Densitometric tomography using the measurement of muon flux  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

148

High heat flux measurements and experimental calibrations/characterizations  

NASA Technical Reports Server (NTRS)

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.

Kidd, Carl T.

1992-01-01

149

Thermal neutron flux measurements in the STAR experimental hall  

NASA Astrophysics Data System (ADS)

We report measurements of thermal neutron fluxes at different locations in the STAR experimental hall during RHIC Run 13 with proton-proton collisions at ?{s}=510 GeV. We compare these measurements to calculations based on PYTHIA as a minimum bias event generator, detailed GEANT3 simulation of the STAR detector and experimental hall, and with GCALOR as the neutron transport code. A fairly good agreement was found between simulation and measurements.

Fisyak, Yuri; Tsai, Oleg; Videbæk, Flemming; Xu, Zhangbu

2014-08-01

150

Long Term Isoprene Flux Measurements Above a Northern Hardwood Forest  

NASA Astrophysics Data System (ADS)

Canopy scale emissions of isoprene from a northern hardwood forest in Michigan were measured using the eddy covariance technique during the summer growing periods from 1999 through 2001. The goal of this work was to improve our understanding of isoprene emissions from forest ecosystems to better describe the role of isoprene in local and regional atmospheric chemical cycles. A second objective of this work was to contribute to the Program for Research on Oxidants: PHotochemistry, Emissions, and Transport (PROPHET) goal of characterizing the role of biogenic emissions in processing atmospheric nitrogen. Isoprene is one of the most abundant hydrocarbons in the atmosphere, and it is very reactive in the atmosphere. Long-term flux measurements are important for investigating the interannual variability in emissions due to interannual variability in climate. In addition, continuous flux data are useful for verifying canopy scale models that are used to generate emission inventories for regional photochemical models. Measurements were made in collaboration with the AmeriFlux site located at the University of Michigan Biological Station (UMBS) and the (PROPHET) site located within 100 m of the AmeriFlux Tower. The site is a 90-year old stand classified as mid-aged conifer and deciduous, with aspen and oak two of the dominant species. Fluxes of isoprene, CO2, H2O, and sensible heat were measured using a fast response isoprene sensor (FIS), an open-path infrared gas analyzer, and a 3-D sonic anemometer. Concurrent measurements of these canopy scale fluxes are useful for understanding the physiological controls on isoprene emissions and potential links between isoprene emissions and other forest ecosystem dynamics. The multi-year data set will be presented and year-to-year variations in isoprene emissions will be explored in the context of interannual variations among the other canopy scale parameters.

Pressley, S. N.; Lamb, B.; Westberg, H.; Hatten, G.; Flaherty, J.

2002-12-01

151

Comparison of different global information sources used in surface radiative flux calculation: Radiative properties of the near-surface atmosphere  

NASA Astrophysics Data System (ADS)

Direct estimates of surface radiative fluxes that resolve regional and weather-scale variability over the whole globe with reasonable accuracy have only become possible with the advent of extensive global, mostly satellite, data sets within the past couple of decades. The accuracy of these fluxes, estimated to be about 10-15 W/m2, is largely limited by the uncertainties of the input data sets. This study presents a fuller, more quantitative evaluation of these uncertainties, mainly for the near-surface air temperature and humidity, by comparing the main available global data sets from the European Centre for Medium-Range Weather Forecasts, NASA, the National Centers for Environmental Prediction, the International Satellite Cloud Climatology Project (ISCCP) and the Laboratoire de Météorologie Dynamique that are treated as ensemble realizations of actual climate such that their differences represent an estimate of the uncertainty in their measurements (because we do not know the absolute truth). The results are globally representative and may be taken as a generalization of our previous ISCCP-based uncertainty estimates for the input data sets. Near-surface atmospheric properties have the primary role in determining the surface downward longwave (LW) flux. From this study, the most important quantity, the surface air temperature, has a uncertainty of about 2-4 K (3 K on average), which would easily induce about 15 W/m2 uncertainty for surface downward LW flux. The humidity profile comparison suggests an uncertainty of 20-25% for the atmospheric column precipitable water below the 300 hPa level, which would cause ?10 W/m2 uncertainty for surface downward LW flux, making it the second largest source of uncertainty. The comparison for the difference between surface skin and air temperature shows its uncertainty is about 2-3 K, which translates into 10-15 W/m2 uncertainty for surface net LW flux. The used atmospheric data set from ISCCP represents the diurnal variations better than the other available sources (as it was designed to do) and the synoptic variations only slightly better than the other sources, but it still has notable clear-cloudy sky biases and interannual variations that are dominated by spurious changes introduced by methodology changes in the original TOVS product. In a companion paper, the work is extended to evaluate the uncertainties of surface radiative properties.

Zhang, Yuanchong; Rossow, William B.; Stackhouse, Paul W.

2006-07-01

152

Urban greenhouse gas mole fraction in-situ measurements: Results from the Indianapolis Flux Experiment (INFLUX)  

NASA Astrophysics Data System (ADS)

The Indianapolis Flux Experiment (INFLUX) was designed to develop and evaluate methods for the measurement and modeling of greenhouse gas fluxes from urban environments. Determination of greenhouse gas fluxes and uncertainty bounds is essential for the evaluation of the effectiveness of mitigation strategies. The current INFLUX observation network includes twelve in-situ tower-based, continuous measurements of CO2, CO, and CH4, flask sampling of 14CO2 and other trace gases, and periodic aircraft sampling of greenhouse gases and meteorological conditions. Eddy covariance and radiative flux are measured at four of the tower sites, and a scanning Doppler lidar was installed in April 2013; both are used to quantify key boundary layer meteorological properties and evaluate model performance. Additionally, a total carbon column observing network (TCCON) column remote sensing station was deployed August - December 2012. The data from the towers, TCCON, and aircraft measurements are being used in an inverse-modeling approach to yield estimates of the urban area flux at 1 km2 resolution. Very high space/time resolution estimates of fossil fuel carbon emissions (Hestia project) offer state-of-the-art "bottom up" emissions estimates for the city and its surroundings. Here we present an overview of the progress from INFLUX, with a focus on tower-based results. With this high density of urban tower-based greenhouse gas measurements, we will quantify horizontal and vertical spatial patterns in atmospheric mole fractions of CO2, CO, and CH4 in Indianapolis. The consistency of the observed horizontal gradients with that expected based on differences in land-cover contributions according to footprint analysis will be evaluated. The ability to correctly model transport and mixing in the atmospheric boundary layer, responsible for carrying greenhouse gases from their source to the point of measurement, is essential. Thus we investigate differences between the modeled and observed sensible heat flux, latent heat flux, air temperature, and wind speed.

Miles, Natasha; Lauvaux, Thomas; Davis, Kenneth; Richardson, Scott; Sarmiento, Daniel; Sweeney, Colm; Karion, Anna; Hardesty, Robert Michael; Turnbull, Jocelyn; Iraci, Laura; Gurney, Kevin; Razlivanov, Igor; Obiminda Cambaliza, Maria; Shepson, Paul; Whetstone, James

2014-05-01

153

Flux measurements of volatile organic compounds from an urban landscape  

NASA Astrophysics Data System (ADS)

Direct measurements of volatile organic compound (VOC) emissions that include all sources in urban areas are a missing requirement to evaluate emission inventories and constrain current photochemical modelling practices. Here we demonstrate the use of micrometeorological techniques coupled with fast-response sensors to measure urban VOC fluxes from a neighbourhood of Mexico City, where the spatial variability of surface cover and roughness is high. Fluxes of olefins, methanol, acetone, toluene and C2-benzenes were measured and compared with the local gridded emissions inventory. VOC fluxes exhibited a clear diurnal pattern with a strong relationship to vehicular traffic. Recent photochemical modelling results suggest that VOC emissions are significantly underestimated in Mexico City, but for the olefin class, toluene, C2-benzenes, and acetone fluxes measured in this work, the results show general agreement with the gridded emissions inventory. While these measurements do not address the full suite of VOC emissions, the comparison with the inventory suggests that other explanations may be needed to explain the photochemical modelling results.

Velasco, E.; Lamb, B.; Pressley, S.; Allwine, E.; Westberg, H.; Jobson, B. T.; Alexander, M.; Prazeller, P.; Molina, L.; Molina, M.

2005-10-01

154

Direct Aerosol Radiative Forcing: Calculations and Measurements from the Tropospheric  

NASA Technical Reports Server (NTRS)

Radiative forcing is defined as the change in the net (downwelling minus upwelling) radiative flux at a given level in the atmosphere. This net flux is the radiative power density available to drive climatic processes in the earth-atmosphere system below that level. Recent research shows that radiative forcing by aerosol particles is a major source of uncertainty in climate predictions. To reduce those uncertainties, TARFOX was designed to determine direct (cloud-free) radiative forcing by the aerosols in one of the world's major industrial pollution plumes--that flowing from the east coast of the US over the Atlantic Ocean. TARFOX measured a variety of aerosol radiative effects (including direct forcing) while simultaneously measuring the chemical, physical, and optical properties of the aerosol particles causing those effects. The resulting data sets permit a wide variety of tests of the consistency, or closure, among the measurements and the models that link them. Because climate predictions use the same or similar model components, closure tests help to assess and reduce prediction uncertainties. In this work we use the TARFOX-determined aerosol, gas, and surface properties to compute radiative forcing for a variety of aerosol episodes, with inadvisable optical depths ranging from 0.07 to 0.6. We calculate forcing by several techniques with varying degrees of sophistication, in part to test the range of applicability of simplified techniques--which are often the only ones feasible in climate predictions by general circulation models (GCMs). We then compare computed forcing to that determined from: (1) Upwelling and downwelling fluxes (0.3-0.7 mm and 0.7-3.0 mm) measured by radiometers on the UK MRF C-130. and (2) Daily average cloud-free absorbed solar and emitted thermal radiative flux at the top of the atmosphere derived from the AVHRR radiometer on the NOAA- 14 satellite. The calculations and measurements all yield aerosol direct radiative forcing in the range -50 to -190 W sq m per unit inadvisable optical depth. The magnitudes are about 15 to 100 times larger than the global-average direct forcing expected for the global-average sulfate aerosol optical depth of 0.04. The reasons for the larger forcing in TARFOX include the relatively large optical depths and the focus on cloud-free, daytime conditions over the dark ocean surface. These are the conditions that produce the actual major radiative forcing events that contribute to any global-average climate effect. Detailed comparisons of calculated and measured forcings for specific events are used for more refined tests of closure.

Russell, P. B.; Hignett, P.; Stowe, L. L.; Livingston, J. M.; Kinne, S.; Wong, J.; Chan, K. Roland (Technical Monitor)

1997-01-01

155

Primary Cosmic Ray Proton Flux Measured by AMS-02  

E-print Network

The Alpha Magnetic Spectrometer (AMS-02) is a high energy particle detector designed to study origin and nature of cosmic rays up to a few TV from space. It was installed on the International Space Station (ISS) on May 19, 2011. During the first two years of operation AMS-02 performed precise measurements of the proton flux. In the low rigidity range, from 1 GV to 20 GV, the proton flux was daily measured with a statistical error less than 1%. In the same rigidity range a gradual decrease due to Solar modulation effect and transit variations due to Solar Flares and Coronal Mass Ejection were also observed. In the rigidity range from 20 GV up to 100 GV instead, AMS-02 data show no drastic variation and the results are consistent with other experiments. Above 100 GV, AMS-02 proton flux exhibits a single power low behavior with no fine structures nor brakes.

C. Consolandi; on Behalf of the AMS-02 Collaboration

2014-02-03

156

Photocatalytic Active Radiation Measurements and Use  

NASA Technical Reports Server (NTRS)

Photocatalytic materials are being used to purify air, to kill microbes, and to keep surfaces clean. A wide variety of materials are being developed, many of which have different abilities to absorb various wavelengths of light. Material variability, combined with both spectral illumination intensity and spectral distribution variability, will produce a wide range of performance results. The proposed technology estimates photocatalytic active radiation (PcAR), a unit of radiation that normalizes the amount of light based on its spectral distribution and on the ability of the material to absorb that radiation. Photocatalytic reactions depend upon the number of electron-hole pairs generated at the photocatalytic surface. The number of electron-hole pairs produced depends on the number of photons per unit area per second striking the surface that can be absorbed and whose energy exceeds the bandgap of the photocatalytic material. A convenient parameter to describe the number of useful photons is the number of moles of photons striking the surface per unit area per second. The unit of micro-einsteins (or micromoles) of photons per m2 per sec is commonly used for photochemical and photoelectric-like phenomena. This type of parameter is used in photochemistry, such as in the conversion of light energy for photosynthesis. Photosynthetic response correlates with the number of photons rather than by energy because, in this photochemical process, each molecule is activated by the absorption of one photon. In photosynthesis, the number of photons absorbed in the 400 700 nm spectral range is estimated and is referred to as photosynthetic active radiation (PAR). PAR is defined in terms of the photosynthetic photon flux density measured in micro-einsteins of photons per m2 per sec. PcAR is an equivalent, similarly modeled parameter that has been defined for the photocatalytic processes. Two methods to measure the PcAR level are being proposed. In the first method, a calibrated spectrometer with a cosine receptor is used to measure the spectral irradiance. This measurement, in conjunction with the photocatalytic response as a function of wavelength, is used to estimate the PcAR. The photocatalytic response function is determined by measuring photocatalytic reactivity as a function of wavelength. In the second method, simple shaped photocatalytic response functions can be simulated with a broad-band detector with a cosine receptor appropriately filtered to represent the spectral response of the photocatalytic material. This second method can be less expensive than using a calibrated spectrometer.

Davis, Bruce A.; Underwood, Lauren W.

2011-01-01

157

Radiation-induced swelling and softening in magnesium aluminate spinel irradiated with high-flux Cu - ions  

NASA Astrophysics Data System (ADS)

Magnesium aluminate spinel of single crystal was irradiated with 60 keV Cu - at a flux up to 6.2 × 10 18 ions/m 2 s, to a total fluence of 3 × 10 20 ions/m 2, in order to study changes in hardness and step-height swelling by high-flux implantation. Hardness determined by nano-indentation measurements steeply decreased with implantation. There is a strong negative correlation between flux dependences of the hardness and the step-height swelling: the former decreases as the latter increases. The Rutherford backscattering spectrometry (RBS)/channeling measurements showed that the spinel is not completely amorphized over the flux range in this study, and the radiation-induced softening observed is not due to amorphization. Results of optical absorbance suggested that radiation-induced point defects and their clusters on the anion sublattices of the spinel played an important role in the radiation-induced swelling under high-flux ion implantation.

Lee, C. G.; Ohmura, T.; Takeda, Y.; Matsuoka, S.; Kishimoto, N.

2004-03-01

158

Next-generation angular distribution models for top-of-atmosphere radiative flux calculation from the CERES instruments: methodology  

NASA Astrophysics Data System (ADS)

The top-of-atmosphere (TOA) radiative fluxes are critical components to advancing our understanding of the Earth's radiative energy balance, radiative effects of clouds and aerosols, and climate feedback. The Clouds and Earth's Radiant Energy System (CERES) instruments provide broadband shortwave and longwave radiance measurements. These radiances are converted to fluxes by using scene type dependent Angular Distribution Models (ADMs). This paper describes the next-generation ADMs that are developed for Terra and Aqua using all available CERES rotating azimuth plane radiance measurements. Coincident cloud and aerosol retrievals, and radiance measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS), and meteorological parameters from Goddard Earth Observing System (GEOS) data assimilation version 5.4.1 are used to define scene type. CERES radiance measurements are stratified by scene type and by other parameters that are important for determining the anisotropy of the given scene type. Anisotropic factors are then defined either for discrete intervals of relevant parameters or as a continuous functions of combined parameters, depending on the scene type. Compared to the existing ADMs, the new ADMs change the monthly mean instantaneous fluxes by up to 5 W m-2 on a regional scale of 1° latitude × 1° longitude, but the flux changes are less than 0.5 W m-2 on a global scale.

Su, W.; Corbett, J.; Eitzen, Z.; Liang, L.

2014-08-01

159

A new measurement of proton fluxes in low Earth orbits by the PAMELA satellite experiment  

NASA Astrophysics Data System (ADS)

The satellite-borne experiment PAMELA has been used to make a new measurement of proton fluxes in low Earth orbits, including geomagnetically trapped particles in the South Atlantic Anomaly and the re-entrant albedo radiation below and around the local geomagnetic cutoff. The work is based on an accurate analysis of detected particle trajectories in the magnetosphere by using a tracing program with a realistic description of the geomagnetic field.

Bruno, Alessandro

160

A PROBLEM WITH FLUX CHAMBER MEASUREMENTS OF BIOGENIC SULFUR EMISSIONS  

EPA Science Inventory

Problems associated with identifying and quantifying factors that influence liquid-phase controlled evolution of hydrogen sulfide and organic sulfides through the air-water interface are briefly reviewed. It was found that at present flux chamber measurements of the release of th...

161

Corer–Reactors for Contaminant Flux Measurement in Sediments  

Microsoft Academic Search

disturbance to the sediment. This apparatus has been used in our laboratory for a number of years (Jones and Design details and operating instructions are provided for a sedi- Jung, 1996; Jung et al., 1997) and has generated useful ment corer that can be converted into a reactor for the measurement of the fluxes of contaminants from sediments to overlying

R. F. Jung; D. R. Jones; G. E. Batley

2003-01-01

162

Estimation of wet surface evaporation from sensible heat flux measurements  

Microsoft Academic Search

A new method is proposed to estimate wet surface evaporation by means of measurements of sensible heat flux and of air temperature, relative humidity, and wind speed at one level only. This formulation is made possible by the linearization of the Bowen ratio, a common assumption in other methods, such as Penman's model and its derivatives. The method will be

Nikki Vercauteren; Elie Bou-Zeid; Hendrik Huwald; Marc B. Parlange; Wilfried Brutsaert

2009-01-01

163

Estimating terrestrial uranium and thorium by antineutrino flux measurements  

E-print Network

Estimating terrestrial uranium and thorium by antineutrino flux measurements Stephen T. Dye, and approved November 16, 2007 (received for review July 11, 2007) Uranium and thorium within the Earth produce of uranium and thorium concentrations in geological reservoirs relies largely on geochemi- cal model

Mcdonough, William F.

164

Airborne flux measurements of Biogenic Isoprene over California  

SciTech Connect

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 coniferous forests were extremely low, high concentrations of methanol and monoterpenes were found above some of these regions. These observations demonstrate the ability to measure fluxes from specific sources by eddy covariance from an aircraft, and suggest the utility of measurements using fast response chemical sensors to constrain emission inventories and map out source distributions for a much broader array of trace gases than was observed in this study. This paper reports the first regional direct eddy covariance fluxes of isoprene. The emissions of VOCs measured from aircraft with 2 km spatial resolution can quantify the distribution of major sources providing the observations required for testing statewide emission inventories of these important trace gases. These measurements will be used in a future study to assess BVOC emission models and their driving variable datasets.

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

2014-10-10

165

Advances in Air-Sea Flux Measurement by Eddy Correlation  

NASA Astrophysics Data System (ADS)

Eddy-correlation measurements of the oceanic flux are useful for the development and validation of air-sea gas exchange models and for analysis of the marine carbon cycle. Results from more than a decade of published work and from two recent field programs illustrate the principal interferences from water vapour and motion, demonstrating experimental approaches for improving measurement precision and accuracy. Water vapour cross-sensitivity is the greatest source of error for flux measurements using infrared gas analyzers, often leading to a ten-fold bias in the measured flux. Much of this error is not related to optical contamination, as previously supposed. While various correction schemes have been demonstrated, the use of an air dryer and closed-path analyzer is the most effective way to eliminate this interference. This approach also obviates density corrections described by Webb et al. (Q J R Meteorol 106:85-100, 1980). Signal lag and frequency response are a concern with closed-path systems, but periodic gas pulses at the inlet tip provide for precise determination of lag time and frequency attenuation. Flux attenuation corrections are shown to be 5 % for a cavity ring-down analyzer (CRDS) and dryer with a 60-m inlet line. The estimated flux detection limit for the CRDS analyzer and dryer is a factor of ten better than for IRGAs sampling moist air. While ship-motion interference is apparent with all analyzers tested in this study, decorrelation or regression methods are effective in removing most of this bias from IRGA measurements and may also be applicable to the CRDS.

Blomquist, Byron W.; Huebert, Barry J.; Fairall, Christopher W.; Bariteau, Ludovic; Edson, James B.; Hare, Jeffrey E.; McGillis, Wade R.

2014-09-01

166

Research concerning the net flux of radiation in the atmosphere of Jupiter  

NASA Technical Reports Server (NTRS)

The plan of the NFR (Net Flux of Radiation) team is for the data from the two solar channels (B and E) of NFR to be reduced with the goal of determining the solar heating rate. In order to determine the solar heating rate from the NFR measurements, effects due to the instrument's spatial and spectral response functions, to the temperature variation of the instrument (and associated drift of calibration), to the setting sun, and to the rotation of the probe (initially at a rate comparable to the NFR sampling frequency), all must be well modelled. In the past year, a forward modeling routine was created to simulate NFR data return in the B and E channels. The effects of varying parameters describing the atmospheric model (such as cloud location and thickness) and the descent profile (such as rotation rate) were investigated and an inversion routine was developed. For the forward modeling, existing radiative transfer codes were used to determine intensity fields within the Jovian atmosphere. A routine was developed to determine instantaneous instrument response by integrating the intensity field over the instrument response functions. A second routine was developed to determine the actual output of the NFR by integrating along an arbitrary descent trajectory. Near the top of the atmosphere, the upflux data alone are used to constrain the cloud structure of he atmosphere. To accomplish this, models are used to describe the variation in up flux between consecutive measurements in terms of variations of cloud opacity and variations in known parameters such as the solar zenith angle. This allows us to develop a zero-order model of cloud structure. Lower in the atmosphere, at levels where there is little or no azimuthal structure to the net flux measurements, both the up flux and net flux are used to derive layer transmission and reflection functions, which then determine layer opacity and single scattering albedo. A preliminary analysis of the data began in December 1995. In these data we could see the rapid oscillations expected at the beginning of the data due to probe rotation and the sun passing through the edge of the field of view. In addition, the time when this oscillation stopped was clearly visible. This sets the rough optical depth above the probe at this time.

Tomasko, M. G.

1996-01-01

167

A Novel Detector for High Neutron Flux Measurements  

SciTech Connect

Measuring alpha particles from a neutron induced break-up reaction with a mass spectrometer can be an excellent tool for detecting neutrons in a high neutron flux environment. Break-up reactions of {sup 6}Li and {sup 12}C can be used in the detection of slow and fast neutrons, respectively. A high neutron flux detection system that integrates the neutron energy sensitive material and helium mass spectrometer has been developed. The description of the detector configuration is given and it is soon to be tested at iThemba LABS, South Africa.

Singo, T. D.; Wyngaardt, S. M. [Department of Physics, University of Stellenbosch, Private bag X1, Matieland, Stellenbosch (South Africa); Papka, P. [Department of Physics, University of Stellenbosch, Private bag X1, Matieland, Stellenbosch (South Africa); Nuclear Physics group, iThemba labs, P. O. Box 722, Somerset West 7129 (South Africa); Dobson, R. T. [Department of Mechanical and Mechatronic Engineering, University of Stellenbosch, Private bag X1, Matieland, Stellenbosch (South Africa)

2010-01-05

168

Infrared Camera Diagnostic for Heat Flux Measurements on NSTX  

SciTech Connect

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.

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

2003-03-25

169

Ecosystem photosynthesis inferred from measurements of carbonyl sulphide flux  

NASA Astrophysics Data System (ADS)

Limited understanding of carbon dioxide sinks and sources on land is often linked to the inability to distinguish between the carbon dioxide taken up by photosynthesis, and that released by respiration. Carbonyl sulphide, a sulphur-containing analogue of carbon dioxide, is also taken up by plants, and could potentially serve as a powerful proxy for photosynthetic carbon dioxide uptake, which cannot be directly measured above the leaf scale. Indeed, variations in atmospheric concentrations of carbonyl sulphide are closely related to those of carbon dioxide at regional, local and leaf scales. Here, we use eddy covariance and laser spectroscopy to estimate the net exchange of carbon dioxide and carbonyl sulphide across three pine forests, a cotton field and a wheat field in Israel. We estimate gross primary productivity--a measure of ecosystem photosynthesis--directly from the carbonyl sulphide fluxes, and indirectly from carbon dioxide fluxes. The two estimates agree within an error of +/-15%. The ratio of carbonyl sulphide to carbon dioxide flux at the ecosystem scale was consistent with the variability in mixing ratios observed on seasonal timescales in the background atmosphere. We suggest that atmospheric measurements of carbonyl sulphide flux could provide an independent constraint on estimates of gross primary productivity, key to projecting the response of the land biosphere to climate change.

Asaf, David; Rotenberg, Eyal; Tatarinov, Fyodor; Dicken, Uri; Montzka, Stephen A.; Yakir, Dan

2013-03-01

170

Simulation of high-energy radiation belt electron fluxes using NARMAX-VERB coupled codes  

NASA Astrophysics Data System (ADS)

This study presents a fusion of data-driven and physics-driven methodologies of energetic electron flux forecasting in the outer radiation belt. Data-driven NARMAX (Nonlinear AutoRegressive Moving Averages with eXogenous inputs) model predictions for geosynchronous orbit fluxes have been used as an outer boundary condition to drive the physics-based Versatile Electron Radiation Belt (VERB) code, to simulate energetic electron fluxes in the outer radiation belt environment. The coupled system has been tested for three extended time periods totalling several weeks of observations. The time periods involved periods of quiet, moderate, and strong geomagnetic activity and captured a range of dynamics typical of the radiation belts. The model has successfully simulated energetic electron fluxes for various magnetospheric conditions. Physical mechanisms that may be responsible for the discrepancies between the model results and observations are discussed.

Pakhotin, I. P.; Drozdov, A. Y.; Shprits, Y. Y.; Boynton, R. J.; Subbotin, D. A.; Balikhin, M. A.

2014-10-01

171

Structure of Earth's outer radiation belt inferred from long-term electron flux dynamics  

E-print Network

flux of 2­6 MeV electrons, je (t; L) log Je (t; L), at equally spaced L shells over the year 1993Structure of Earth's outer radiation belt inferred from long-term electron flux dynamics D September 2003; published 15 October 2003. [1] We map the spatial structure of the electron belts over

172

Electron Flux of Radiation Belts Animation - Duration: 0:31.  

NASA Video Gallery

This animation shows meridional (from north-south) plane projections of the REPT-A and REPT-B electron flux values. The animation first shows the expected two-belt Van Allen zone structure; from Se...

173

Martian Radiation Environment: Model Calculations and Recent Measurements with "MARIE"  

NASA Technical Reports Server (NTRS)

The Galactic Cosmic Ray spectra in Mars orbit were generated with the recently expanded HZETRN (High Z and Energy Transport) and QMSFRG (Quantum Multiple-Scattering theory of nuclear Fragmentation) model calculations. These model calculations are compared with the first eighteen months of measured data from the MARIE (Martian Radiation Environment Experiment) instrument onboard the 2001 Mars Odyssey spacecraft that is currently in Martian orbit. The dose rates observed by the MARIE instrument are within 10% of the model calculated predictions. Model calculations are compared with the MARIE measurements of dose, dose-equivalent values, along with the available particle flux distribution. Model calculated particle flux includes GCR elemental composition of atomic number, Z = 1-28 and mass number, A = 1-58. Particle flux calculations specific for the current MARIE mapping period are reviewed and presented.

Saganti, P. B.; Cucinotta, F. A.; zeitlin, C. J.; Cleghorn, T. F.

2004-01-01

174

A relaxed eddy accumulation system for measuring vertical fluxes of nitrous acid  

NASA Astrophysics Data System (ADS)

A relaxed eddy accumulation (REA) system combined with a nitrous acid (HONO) analyzer was developed to measure atmospheric HONO vertical fluxes. The system consists of three major components: (1) a fast-response sonic anemometer measuring both vertical wind velocity and air temperature, (2) a fast-response controlling unit separating air motions into updraft and downdraft samplers by the sign of vertical wind velocity, and (3) a highly sensitive HONO analyzer based on aqueous long path absorption photometry that measures HONO concentrations in the updrafts and downdrafts. A dynamic velocity threshold (±0.5?w, where ?w is a standard deviation of the vertical wind velocity) was used for valve switching determined by the running means and standard deviations of the vertical wind velocity. Using measured temperature as a tracer and the average values from two field deployments, the flux proportionality coefficient, ?, was determined to be 0.42 ± 0.02, in good agreement with the theoretical estimation. The REA system was deployed in two ground-based field studies. In the California Research at the Nexus of Air Quality and Climate Change (CalNex) study in Bakersfield, California in summer 2010, measured HONO fluxes appeared to be upward during the day and were close to zero at night. The upward HONO flux was highly correlated to the product of NO2 and solar radiation. During the Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX 2009) at Blodgett Forest, California in July 2009, the overall HONO fluxes were small in magnitude and were close to zero. Causes for the different HONO fluxes in the two different environments are briefly discussed.

Ren, X.; Sanders, J. E.; Rajendran, A.; Weber, R. J.; Goldstein, A. H.; Pusede, S. E.; Browne, E. C.; Min, K.-E.; Cohen, R. C.

2011-10-01

175

A relaxed eddy accumulation system for measuring vertical fluxes of nitrous acid  

NASA Astrophysics Data System (ADS)

A relaxed eddy accumulation (REA) system combined with a nitrous acid (HONO) analyzer was developed to measure atmosperhic HONO vertical fluxes. The system consists of three major components: (1) a fast-response sonic anemometer measuring vertical wind velocity and air temperature, (2) a fast-response controlling unit separating air motions into updraft and downdraft samplers by the sign of vertical wind velocity, and (3) a highly sensitive HONO analyzer based on aqueous long path absorption photometry measuring HONO concentations in these updrafts and downdrafts. A dynamic velocity threshold (±0.5?w, where ?w is a standard deviation of the vertical wind velocity) was used for valve switching determined by the running means and standard deviations of the vertical wind velocity. Using measured temperature as a tracer and the average values from two field deployments, the flux proportionality coefficient, ?, was determined to be 0.42 ± 0.02, in good agreement with the theoretical estimation. The REA system was deployed in two ground-based field studies. In the California Research at the Nexus of Air Quality and Climate Change (CalNex) study in Bakersfield, California in summer 2010, measured HONO fluxes appeared to be upward during the day and were close to zero at night. The upward HONO flux was highly correlated to the product of NO2 and solar radiation. During the Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX 2009) at Blodgett Forest, California in July 2009, the overall HONO fluxes were small in magnitude and were close to zero. Causes for the differences in HONO fluxes in the two different environments are briefly discussed.

Ren, X.; Sanders, J. E.; Rajendran, A.; Weber, R. J.; Goldstein, A. H.; Pusede, S. E.; Browne, E. C.; Min, K.-E.; Cohen, R. C.

2011-06-01

176

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

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

177

Airborne flux measurements of biogenic isoprene over California  

NASA Astrophysics Data System (ADS)

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 the residual layer above the valley and mix down into the valley in the morning. Thus, the isoprene emissions surrounding the valley have relevance for the regional photochemistry that is not immediately apparent solely from the direct emission flux distribution. This paper reports the first regional observations of fluxes from specific sources by eddy covariance from an aircraft which can finally constrain statewide isoprene emission inventories used for ozone simulations by state agencies. While previously there was no available means to constrain the biogenic models, our results provide a good understanding of what the major sources of isoprene are in California, their magnitude, and how they are distributed. This data set on isoprene fluxes will be particularly useful for evaluating potential model alternatives which will be dealt with in a separate paper to assess isoprene emission models and their driving variable data sets.

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

2014-10-01

178

Integral measurements of neutron and gamma-ray leakage fluxes from the Little Boy replica  

SciTech Connect

This report presents integral measurements of neutron and gamma-ray leakage fluxes from a critical mockup of the Hiroshima bomb Little Boy at Los Alamos National Laobratory with detector systems developed by Oak Ridge National Laboratory. Bonner ball detectors were used to map the neutron fluxes in the horizontal midplane at various distances from the mockup and for selected polar angles, keeping the source-detector separation constant. Gamma-ray energy deposition measurements were made with thermoluminescent detectors at several locations on the iron shell of the source mockup. The measurements were performed as part of a larger progam to provide benchmark data for testing the methods used to calculate the radiation released from the Little Boy bomb over Hiroshima. 3 references, 10 figures.

Muckenthaler, F.J.

1984-03-01

179

An investigation of the consistency of the ionospheric measurements of the photoelectron flux and solar EUV flux  

NASA Technical Reports Server (NTRS)

This paper demonstrates that there is an inconsistency between ionospheric measurements of the photoelectron flux and the solar EUV flux. The problem which occurs for EUV wavelengths near 250 A or photoelectron energies near 35 eV has serious implications for theoretical photoelectron flux calculations and could help to explain up to 40 percent of the difference between calculated and measured photoelectron fluxes for electron energies below 35 eV. It is also shown that: (1) only photons with wavelengths shorter than 310 A are of importance in producing photoelectrons; (2) above 20 eV, the photoelectron flux is controlled by the production of primary photoelectrons, while below 20 eV the flux is controlled by degraded photoelectrons; (3) the calculated cascading production rate is insensitive to the cross sections used for the calculation; and (4) the photoelectron flux is inversely proportional to the total inelastic cross sections.

Richards, P. G.; Torr, D. G.

1984-01-01

180

Estimating terrestrial uranium and thorium by antineutrino flux measurements  

PubMed Central

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

Dye, Stephen T.; Guillian, Eugene H.

2008-01-01

181

An Alpha-Gamma Counter for Absolute Neutron Flux Measurement  

NASA Astrophysics Data System (ADS)

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.

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

2012-03-01

182

A method to measure cardiac autophagic flux in vivo.  

PubMed

Autophagy, a highly conserved cellular mechanism wherein various cellular components are broken down and recycled through lysosomes, has been implicated in the development of heart failure. However, tools to measure autophagic flux in vivo have been limited. Here, we tested whether monodansylcadaverine (MDC) and the lysosomotropic drug chloroquine could be used to measure autophagic flux in both in vitro and in vivo model systems. Using HL-1 cardiac-derived myocytes transfected with GFP-tagged LC3 to track changes in autophagosome formation, autophagy was stimulated by mTOR inhibitor rapamycin. Administration of chloroquine to inhibit lysosomal activity enhanced the rapamycin-induced increase in the number of cells with numerous GFP-LC3-positive autophagosomes. The chloroquine-induced increase of autophagosomes occurred in a dose-dependent manner between 1 microM and 8 microM, and reached a maximum 2 hour after treatment. Chloroquine also enhanced the accumulation of autophagosomes in cells stimulated with hydrogen peroxide, while it attenuated that induced by Bafilomycin A1, an inhibitor of V-ATPase that interferes with fusion of autophagosomes with lysosomes. The accumulation of autophagosomes was inhibited by 3-methyladenine, which is known to inhibit the early phase of the autophagic process. Using transgenic mice expressing 3 mCherry-LC3 exposed to rapamycin for 4 hr, we observed an increase in mCherry-LC3-labeled autophagosomes in myocardium, which was further increased by concurrent administration of chloroquine, thus allowing determination of flux as a more precise measure of autophagic activity in vivo. MDC injected 1 hr before sacrifice colocalized with mCherry-LC3 puncta, validating its use as a marker of autophagosomes. This study describes a method to measure autophagic flux in vivo even in non-transgenic animals, using MDC and chloroquine. PMID:18216495

Iwai-Kanai, Eri; Yuan, Hua; Huang, Chengqun; Sayen, M Richard; Perry-Garza, Cynthia N; Kim, Lucy; Gottlieb, Roberta A

2008-04-01

183

On Sensitivity of Spectral Radiative Fluxes to Atmospheric Water Vapor in the 940 nm Region (Numerical Simulation)  

SciTech Connect

Water vapor is well known to be a critical component in many aspects of atmospheric research, such as radiative transfer and cloud and aerosol processes. This requires both improved measurements of the columnar water vapor and its profiles in the atmosphere in a wide range of conditions, and adjustment of water vapor parameterizations in radiation codes including the perfection of spectroscopic parameters. In this paper we will present the results of comparison of our calculations and downward solar fluxes measured with Rotating Shadowband Spectroradiometer under conditions of horizontally homogeneous clouds. We also will discuss the sensitivity of atmospheric radiation characteristics to variations of water vapor in the band 940 nm: these results may be useful for development of new methods of retrieval of the total column water vapor content (WVC) in the atmosphere from data of radiation observations.

Zhuravleva, T.B.; Firsov, K.M.

2005-03-18

184

Preliminary energy-flux measurements on ZT-40M  

SciTech Connect

Bolometer measurements indicate that 15 to 20% of the plasma losses from ZT-40M are due to radiation for a 190-kA, 1.6-mtorr discharge. The fraction of radiation losses increases slightly as the current is decreased. Thermistor measurements of the bellows temperature rise following a 190-kA discharge show large shot-to-shot variation on bellows peaks (relative to the plasma), with bellows peaks at large major radii being heated considerably more than bellows peaks at small major radii.

Ingraham, J.C.; Miller, G.

1982-05-01

185

DIRECT MEASUREMENT OF HEAT FLUX FROM COOLING LAKE THERMAL IMAGERY  

SciTech Connect

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.

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

2007-12-19

186

Measurement of diffusive flux of ammonia from water.  

PubMed

An instrument was developed for the measurement of gaseous ammonia concentration, NH(3(sw,eq)), in equilibrium with surface waters, notably ocean water. The instrument measures the ammonia flux from a flowing water surface under defined conditions and allows the calculation of NH(3(sw,eq)) from the principles of Fickian diffusion. The flux collector resembles a wetted parallel plate denuder previously developed for air sampling. The sample under study runs on one plate of the device; the ammonia released from the sample is collected by a slow flow of a receptor liquid on the other plate. The NH(3) + NH(4)(+) (hereinafter called N(T)) in the effluent receptor liquid is preconcentrated on a silica gel column and subsequently measured by a fluorometric flow injection analysis (FIA) system. With a 6-min cycle (4-min load, 2-min inject), the analytical system can measure down to 0.3 nM N(T) in the receptor liquid. Coupled with the flux collector, it is sufficiently sensitive to measure the ammonia flux from seawater. The instrument design is such that it is little affected by ambient ammonia. In both laboratory (N(T) 0.2-50 ?M), and field investigations (N(T) 0.18-1.7 ?M) good linearity between the ammonia flux and the N(T) concentration in seawater (spiked, synthetic, natural) was observed, although aged seawater, with depleted N(T) content, behaves in an unusual fashion upon N(T) addition, showing the existence of an "ammonia demand". NH(3(sw,eq)) levels from ocean water measured in the Coconut Island Laboratory, HI, ranged from 6.6 to 33 nmol/m(3) with an average of 17.4 ± 6.9 nmol/m(3), in comparison to 2.8-21 nmol/m(3) (average 10 ± 7 nmol/m(3)) NH(3(sw,eq)) values previously reported for the Central Pacific Ocean (Quinn, P. K.; et al. J. Geophys. Res. 1990, 95, 16405-16416). PMID:21644712

Genfa, Z; Uehara, T; Dasgupta, P K; Clarke, A D; Winiwarter, W

1998-09-01

187

Multi-element silicon detector for x-ray flux measurements  

SciTech Connect

A 30-element Si(Li) detector has been fabricated to measure the one-dimensional flux profile of 33 KeV x-rays from a synchrotron radiation beam. The device, which is fabricated from a single 39 mm x 15 mm silicon wafer, is a linear array of 0.9 mm x 7 mm elements with a 1 mm center-to-center spacing. It is 5 mm thick and when operated at room temperature has an average leakage current of 10 nA/element. The x-ray flux in each element is determined by measuring the current with a high quality operational amplifier followed by a current digitizer. This detector is being used to study the use of synchrotron radiation for non-invasive imaging of coronary arteries. The experiment uses the difference in the transmitted flux of a monochromatized x-ray beam above and below the iodine K-edge. Measurements have been made on plastic phantoms and on excised animal hearts with iodinated arteries. The images obtained indicate that a 256-element device with similar properties, but with 0.6 mm element spacing, will make a very effective detector for high-speed medical imaging.

Thompson, A.C.; Goulding, F.S.; Sommer, H.A.; Walton, J.T.; Hughes, E.B.; Rolfe, J.; Zeman, H.D.

1981-10-01

188

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

NASA Astrophysics Data System (ADS)

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 information content of micrometeorological flux measurements.

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

189

Momentum Flux Measuring Instrument for Neutral and Charged Particle Flows  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

190

Controlling quantum flux through measurement: An idealised example  

NASA Astrophysics Data System (ADS)

Classically, no transfer occurs between two equally filled reservoirs, no matter how one looks at them, but the situation can be different quantum-mechanically. This paradoxically surprising phenomenon rests on the distinctive property of the quantum world that one cannot stare at a system without disturbing it. It was recently discovered that this seemingly annoying feature could be harnessed to control small quantum systems using weak measurements. Here we present one of the simplest models —an idealised double quantum dot—where by toying with the dot measurement strength, i.e. the intensity of the look, it is possible to create a particle flux in an otherwise completely symmetric system. The basic property underlying this phenomena is that measurement disturbances are very different on a system evolving unitarily and a system evolving dissipatively. This effect shows that adaptive measurements can have dramatic effects enabling transport control but possibly inducing biases in the measurement of macroscopic quantities if not handled with care.

Tilloy, A.; Bauer, M.; Bernard, D.

2014-07-01

191

Light Flux Density Threshold at Which Protein Denaturation is Induced by Synchrotron Radiation Circula Dichroism Beamlines  

SciTech Connect

New high-flux synchrotron radiation circular dichroism (SRCD) beamlines are providing important information for structural biology, but can potentially cause denaturation of the protein samples under investigation. This effect has been studied at the new CD1 dedicated SRCD beamline at ISA in Denmark, where radiation-induced thermal damage effects were observed, depending not only on the radiation flux but also on the focal spot size of the light. Comparisons with similar studies at other SRCD facilities worldwide has lead to the estimation of a flux density threshold under which SRCD beamlines should be operated when samples are to be exposed to low-wavelength vacuum ultraviolet radiation for extended periods of time.

Miles,A.; Janes, R.; Brown, A.; Clarke, D.; Sutherland, J.; Tao, Y.; Wallace, B.; Hoffmann, S.

2008-01-01

192

Intercomparison of surface energy flux measurement systems used during the HiWATER-MUSOEXE  

NASA Astrophysics Data System (ADS)

among instruments is very important for the Multi-Scale Observation Experiment on Evapotranspiration over heterogeneous land surfaces of The Heihe Watershed Allied Telemetry Experimental Research (HiWATER-MUSOEXE), particularly in regard to radiation and turbulent flux measurements. Before HiWATER-MUSOEXE was conducted, 20 eddy covariance (EC) system sets, 18 radiometer sets, and seven large aperture scintillometers (LASs) sets were intercompared over the Gobi desert between 14 and 24 May 2012. For radiometers, the four-component radiation measurements exhibited good agreement—the average root-mean-square error (RMSE) and mean relative error (MRE) for the net radiation were 10.38 W m-2 and 1.24%, respectively. With regard to the EC systems, the best consistency for sensible heat fluxes was found among CSAT3 sonic anemometers and Li7500A/Li7500/EC150 combinations (average RMSE, 12.30 W m-2 and MRE, -1.36%), followed by Gill sonic anemometers and Li7500A/Li7500 combinations when a proper angle of attack correction method was applied (average RMSE, 16.75 W m-2 and MRE, -5.52%). The sensible heat flux measured using different LASs agreed well with high correlation coefficients—the average RMSE and MRE values were 10.26 W m-2 and 5.48% for boundary layer scintillometer (BLS) 900, 16.32 W m-2 and 10.47% for BLS450, and 14.38 W m-2 and -3.72% for ZZLAS, respectively. The EC and LAS measurements were compared and agreed well over homogeneous underlying surfaces, which also indicated that the EC and LAS measurements would be comparable in the follow-up experiment. The intercomparison results can be used to determine instrument placement and are very helpful for subsequent data analysis.

Xu, Ziwei; Liu, Shaomin; Li, Xin; Shi, Shengjin; Wang, Jiemin; Zhu, Zhongli; Xu, Tongren; Wang, Weizhen; Ma, Mingguo

2013-12-01

193

Measuring Radiation Damage from Heavy Energetic Ions in Aluminum  

SciTech Connect

An intense beam of 122 MeV/u (9.3 GeV) 76Ge ions was stopped in aluminum samples at the Coupled Cyclotron Facility at NSCL, MSU. Attempts were made at ORNL to measure changes in material properties by measuring changes in electrical resistivity and microhardness, and by transmission electron microscopy characterization, for defect density caused by radiation damage, as a function of depth and integrated ion flux. These measurements are relevant for estimating damage to components at a rare isotope beam facility.

Kostin, M., PI-MSU; Ronningen, R., PI-MSU; Ahle, L., PI-LLNL; Gabriel, T., Scientific Investigation and Development; Mansur, L., PI-ORNL; Leonard, K., ORNL; Mokhov, N., FNAL; Niita, K., RIST, Japan

2009-02-21

194

Radiation dose measurements in coronary CT angiography  

PubMed Central

Coronary computed tomography (CT) angiography is associated with high radiation dose and this has raised serious concerns in the literature. Awareness of various parameters for dose estimates and measurements of coronary CT angiography plays an important role in increasing our understanding of the radiation exposure to patients, thus, contributing to the implementation of dose-saving strategies. This article provides an overview of the radiation dose quantity and its measurement during coronary CT angiography procedures. PMID:24392190

Sabarudin, Akmal; Sun, Zhonghua

2013-01-01

195

Momentum Flux Measurements Using an Impact Thrust Stand  

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

196

Eddy covariance measurements of the sea spray aerosol flux over the open ocean  

E-print Network

Eddy covariance measurements of the sea spray aerosol flux over the open ocean Sarah J. Norris,1 eddy covariance measurements of size-segregated sea spray aerosol fluxes over the open Atlantic Ocean the high variability in sea spray aerosol flux compared with other air-sea fluxes, both between individual

Brooks, Ian M.

197

Method for radiation detection and measurement  

DOEpatents

Dose of radiation to which a body of crystalline material has been exposed is measured by exposing the body to optical radiation at a first wavelength, which is greater than about 540 nm, and measuring optical energy emitted from the body by luminescence at a second wavelength, which is longer than the first wavelength. 9 figures.

Miller, S.D.

1993-12-21

198

Fetch effects of forest canopy on flux measurements  

NASA Astrophysics Data System (ADS)

The flux measured above a canopy often deviates from the source strength due to the consequence of limited fetch. Any natural surface is commonly more or less heterogeneous, which violates the assumption of horizontal homogeneity for most micrometeorological measurement methods. This affects methods such as the eddy covariance technique where fluxes are measured in situ from a mast and the source area (or footprint) of the measurements lies upwind from the mast. Hence, in order to understand how the horizontal scale of heterogeneity influences scalar transport as well as the footprint of the measurements, we study the effects of the scale of surface heterogeneity to the measurements conducted at different measurement heights. Numerical simulations of flow over forest canopy with varying scales of heterogeneity were performed using a large eddy simulation (LES) model PALM. LES provides us a means of studying detailed and highly resolved turbulence and understanding the combined effects of forest terrain. The results show that the flow over canopy is sensitive to the size of homogenous fetch and the complexity of terrain. In particular, when the size of fetch is getting smaller and more complex, the local turbulence affects scalar transportation strongly. This has implications for the transport of scalars in the forest canopy. The blending height of scalar in relation to the scale of heterogeneity, measurement height and site location are also discussed. Furthermore, these results show great potential of LES for a wide range of applications in the field of micrometeorology including the determination of placing of instruments and the interpretation of measurements in complex forest terrain.

Tu, Sofia M.; Nordbo, Annika; Kanani, Farah; Rinne, Janne; Raasch, Siegfried; Vesala, Timo; Hellsten, Antti

2014-05-01

199

[Research on reducing mold flux's radiative heat transfer based on FTIR and XRD].  

PubMed

The mold fluxes samples containing transition metal oxides TiO2 were designed based on the composition of commercial mold fluxes in continuous casting of steel, and the relation between radiative heat transfer and the content of TiO2 was obtained through FTIR spectrum analysis and XRD analysis. The result of FTIR analysis indicates that TiO2 has a great negative effect on infrared transmittance of flux samples in the wavelength range of 1-6 microm. The result of XRD analysis indicates that crystallization of cuspidine was restrained with addition of TiO2, and CaTiO3 and other phases were found in the samples. The decrease in cuspidine phase is beneficial to strand lubrication in the mold. Radiation heat flux from the strand to the mold was calculated using a radiative heat transfer model concluded in previous study. Addition of TiO2 was found to result in a remarkable decrease in radiation heat flux for both glassy and crystalline samples, and the heat flux tended to decrease with increasing TiO2, with the maximal decrease reaching 30%. As a result of great refraction and scatter at surface and grain boundaries of samples, the negative effect of crystalline samples was much larger than that of the glassy ones. PMID:19445198

Diao, Jiang; Xie, Bing

2009-02-01

200

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

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

201

Progress on a Rayleigh Scattering Mass Flux Measurement Technique  

NASA Technical Reports Server (NTRS)

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.

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

2010-01-01

202

An Ensemble Forecast for Geosynchronous Radiation Belt Fluxes  

NASA Astrophysics Data System (ADS)

Steven Nelson1, 2, Shawn Young1, Kara Perry1, 3, Alan Ling1, 4, Xinlin Li5 1. Air Force Research Laboratory Space Vehicles Division 2. University of New Mexico 3. Institute of Scientific Research, Boston College 4. Atmosphere and Environmental Research Inc. 5. University of Colorado An ensemble model composed of three functional forecasting models has been developed to forecast >2 MeV electron flux at geosynchronous (GEO) orbit. The REFM model is based on a statistical link between electron flux and solar wind speed using empirically derived linear filter coefficients, the Li model solves a radial diffusion equation with a diffusion coefficient that is a function of the solar wind velocity and interplanetary magnetic field, and the fluxpred model is a multi-layer feed-forward neural network with electron flux and Kp as input. A multivariate regression is done on these three independent forecasting methods to produce significantly better predictive results than any of the individual models alone. We will discuss our regression technique, our efforts to optimize it, and we will discuss our calculation of forecast probability.

Nelson, S. G.; Young, S. L.; Ling, A.; Perry, K. L.; Li, X.

2010-12-01

203

On gravitational radiation and the energy flux of matter  

E-print Network

A suitable derivative of Einstein's equations in the framework of the teleparallel equivalent of general relativity (TEGR) yields a continuity equation for the gravitational energy-momentum. In particular, the time derivative of the total gravitational energy is given by the sum of the total fluxes of gravitational and matter fields energy. We carry out a detailed analysis of the continuity equation in the context of Bondi and Vaidya's metrics. In the former space-time the flux of the gravitational energy is given by the well known expression in terms of the square of the news function. It is known that the energy definition in the realm of the TEGR yields the ADM (Arnowitt-Deser-Misner) energy for appropriate boundary conditions. Here we show that the same definition also describes the Bondi energy. The analysis of the continuity equation in Vaidya's space-time shows that the variation of the total gravitational energy is given by the energy flux of matter only.

J. W. Maluf; F. F. Faria

2004-05-28

204

Offline GCSS Intercomparison of Cloud-Radiation Interaction and Surface Fluxes  

NASA Technical Reports Server (NTRS)

Simulations of deep tropical clouds by both cloud-resolving models (CRMs) and single-column models (SCMs) in the GEWEX Cloud System Study (GCSS) Working Group 4 (WG4; Precipitating Convective Cloud Systems), Case 2 (19-27 December 1992, TOGA-COARE IFA) have produced large differences in the mean heating and moistening rates (-1 to -5 K and -2 to 2 grams per kilogram respectively). Since the large-scale advective temperature and moisture "forcing" are prescribed for this case, a closer examination of two of the remaining external types of "forcing", namely radiative heating and air/sea hear and moisture transfer, are warranted. This paper examines the current radiation and surface flux of parameterizations used in the cloud models participating in the GCSS WG4, be executing the models "offline" for one time step (12 s) for a prescribed atmospheric state, then examining the surface and radiation fluxes from each model. The dynamic, thermodynamic, and microphysical fluids are provided by the GCE-derived model output for Case 2 during a period of very active deep convection (westerly wind burst). The surface and radiation fluxes produced from the models are then divided into prescribed convective, stratiform, and clear regions in order to examine the role that clouds play in the flux parameterizations. The results suggest that the differences between the models are attributed more to the surface flux parameterizations than the radiation schemes.

Tao, W.-K.; Johnson, D.; Krueger, S.; Zulauf, M.; Donner, L.; Seman, C.; Petch, J.; Gregory, J.

2004-01-01

205

Atmospheric Radiation Measurement Climate Research Facility (ACRF) Annual Report 2008  

SciTech Connect

The Importance of Clouds and Radiation for Climate Change: The Earth’s surface temperature is determined by the balance between incoming solar radiation and thermal (or infrared) radiation emitted by the Earth back to space. Changes in atmospheric composition, including greenhouse gases, clouds, and aerosols, can alter this balance and produce significant climate change. Global climate models (GCMs) are the primary tool for quantifying future climate change; however, there remain significant uncertainties in the GCM treatment of clouds, aerosol, and their effects on the Earth’s energy balance. In 1989, the U.S. Department of Energy (DOE) Office of Science created the Atmospheric Radiation Measurement (ARM) Program to address scientific uncertainties related to global climate change, with a specific focus on the crucial role of clouds and their influence on the transfer of radiation in the atmosphere. To reduce these scientific uncertainties, the ARM Program uses a unique twopronged approach: • The ARM Climate Research Facility, a scientific user facility for obtaining long-term measurements of radiative fluxes, cloud and aerosol properties, and related atmospheric characteristics in diverse climate regimes; and • The ARM Science Program, focused on the analysis of ACRF and other data to address climate science issues associated with clouds, aerosols, and radiation, and to improve GCMs. This report provides an overview of each of these components and a sample of achievements for each in fiscal year (FY) 2008.

LR Roeder

2008-12-01

206

First air-sea flux mooring measurements in the Southern Ocean  

NASA Astrophysics Data System (ADS)

The Southern Ocean is a key component of the global climate system: insulating the Antarctic polar region from the subtropics, transferring climate signals throughout the world's oceans and forming the southern component of the global overturning circulation. However, the air-sea fluxes that drive these processes are severely under-observed due to the harsh and remote location. This paucity of reference observations has resulted in large uncertainties in ship-based, numerical weather prediction, satellite and derived flux products. Here, we report observations from the Southern Ocean Flux Station (SOFS); the first successful air-sea flux mooring deployment in this ocean. The mooring was deployed at 47°S, 142°E for March 2010 to March 2011 and returned measurements of near surface meteorological variables and radiative components of the heat exchange. These observations enable the first accurate quantification of the annual cycle of net air-sea heat exchange and wind stress from a Southern Ocean location. They reveal a high degree of variability in the net heat flux with extreme turbulent heat loss events, reaching -470 Wm-2 in the daily mean, associated with cold air flowing from higher southern latitudes. The observed annual mean net air-sea heat flux is a small net ocean heat loss of -10 Wm-2, with seasonal extrema of 139 Wm-2 in January and -79 Wm-2 in July. The novel observations made with the SOFS mooring provide a key point of reference for addressing the high level of uncertainty that currently exists in Southern Ocean air-sea flux datasets.

Schulz, E. W.; Josey, S. A.; Verein, R.

2012-08-01

207

Numerical study of the effects of boundary conditions on the measurement and calibration of gardon type heat flux sensors  

NASA Astrophysics Data System (ADS)

To monitor the high-intensity heat flux conditions that occur in the space shuttle main engine (SSME), it is necessary to use specifically designed heat flux sensors. These sensors, which are of the Gardon-type, are exposed on the measuring face to high-intensity radiative and convective heat fluxes and on the other face to convective cooling. To improve the calibration and measurement accuracy of these gauges, researchers are studing the effect that the thermal boundary conditions have on gauge performance. In particular, they are studying how convective cooling effects the field inside the sensor and the measured heat flux. The first phase of this study involves a numerical study of these effects. Subsequent phases will involve experimental verification. A computer model of the heat transfer around a Garden-type heat flux sensor was developed. Two specific geometries are being considered are: (1) heat flux sensor mounted on a flat-plate; and (2) heat flux sensor mounted at the stagnation point of a circular cylinder. Both of these configurations are representative of the use of heat flux sensors in the components of the SSME. The purpose of the analysis is to obtain a temperature distribution as a function of the boundary conditions.

Krane, M.; Dybbs, A.

208

Consistency Between Divergent Circulations from Reanalysis Data Sets and Satellite-Derived Precipitation, Radiation, and Surface Fluxes  

NASA Technical Reports Server (NTRS)

Large-scale divergent circulations are part of the atmospheric dynamic response to diabatic heating from condensation, radiative processes, and surface heat fluxes. Vertical motion and the associated divergent wind is thus intimately tied to the hydrologic cycle and the global heat balance. Despite its importance, the divergent circulation is too small in comparison to the rotational flow to measure directly with any accuracy. Vertical motions are recovered diagnostically from reanalyses and, as such, are subject to shortcomings in model physics, numerics, and data availability. We use several GEWEX pre-EOS data sets derived from satellite data to assess interannual divergent flow anomalies in the NCEP, GSFC, and GSFC DAO analyse. Among the data sets are monthly, 2.5 degree gridded precipitation (MSU and SSM/I-based), TOA radiative fluxes from ERBS, surface radiative fluxes from the SRB project, and surface latent and sensible flux estimates from SSM/I. Most of these data sets can be considered as independent of the reanalysis fields. We focus largely on the period 1987-1989 encompassing a strong El Nino / la Nina couplet. Consequently we emphasize interannual changes rather than climatological aspects of the reanalyses. In the processes of this study we use simple integral constraints enforced through the satellite-derived data sets to derive corrections to the divergent circulation produced from the reanalyses. We examine the implications of these corrections in describing how perturbations to the tropical heat balance evolve during a warm / cool couplet. In particular the perturbations to the planetary scale water vapor transport, and the resulting changes in TOA and surface radiative fluxes are considered.

Robertson, Franklin R.; Fitzjarrald, Dan; McCaul, Eugene W.

1997-01-01

209

Radiation: Physical Characterization and Environmental Measurements  

NASA Technical Reports Server (NTRS)

In this session, Session WP4, the discussion focuses on the following topics: Production of Neutrons from Interactions of GCR-Like Particles; Solar Particle Event Dose Distributions, Parameterization of Dose-Time Profiles; Assessment of Nuclear Events in the Body Produced by Neutrons and High-Energy Charged Particles; Ground-Based Simulations of Cosmic Ray Heavy Ion Interactions in Spacecraft and Planetary Habitat Shielding Materials; Radiation Measurements in Space Missions; Radiation Measurements in Civil Aircraft; Analysis of the Pre-Flight and Post-Flight Calibration Procedures Performed on the Liulin Space Radiation Dosimeter; and Radiation Environment Monitoring for Astronauts.

1997-01-01

210

First-wall heat-flux measurements during ELMing H-mode plasma  

NASA Astrophysics Data System (ADS)

We present measurements of the diverter heat flux in DIII-D for ELMing H-mode and radiative diverter conditions. In previous work, we have examined heat flux profiles in lower single-null diverted plasmas and measured the scaling of the peak heat flux with plasma current and beam power. One problem with those results was our lack of good power accounting. This situation has been improved to better than 80-90% accountability with the installation of new bolometer arrays, and the operation of the entire complement of 5 Infrared (IR) TV cameras using the DAPS (Digitizing Automated Processing System) video processing system for rapid inter-shot data analysis. We also have expanded the scope of our measurements to include a wider variety of plasma shapes (e.g., double-null diverters (DND), long and short single-null diverters (SND), and inside-limited plasmas), as well as more diverse discharge conditions. Double-null discharges are of particular interest because that shape has proven to yield the highest confinement (VH-mode) and beta of all DIII-D plasmas, so any future diverter modifications for DIII-D will have to support DND operation. In addition, the proposed TPX tokamak is being designed for double-null operation, and information on the magnitude and distribution of diverter heat flux is needed to support the engineering effort on that project. So far, we have measured the DND power sharing at the target plates and made preliminary tests of heat flux reduction by gas injection.

Lasnier, C. J.; Allen, S. L.; Hill, D. N.; Leonard, A. W.; Petrie, T. W.

1994-01-01

211

Greenhouse effect and altitude gradients over the Alps – by surface longwave radiation measurements and model calculated LOR  

Microsoft Academic Search

Summary The greenhouse effect has been investigated predominantly with satellite measurements, but more than 90% of the greenhouse radiative flux affecting Earth’s surface temperature and humidity originates from a 1000 meter layer above the surface. Here we show that substantial improvements on surface longwave radiation measurements and very good agreement with radiative transfer model calculations allow the clear-sky greenhouse effect

R. Philipona; B. Dürr; C. Marty

2004-01-01

212

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

SciTech Connect

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.

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

2003-05-20

213

Simulation of solar radiation heat flux data for energy calculation  

Microsoft Academic Search

The global (or total) and diffuse solar irradiation data are not always available in many areas of the world and they have to be estimated using some sort of empirical models. This paper describes how the sequence of hourly irradiation data can be simulated using some statistical parameters of the global solar radiation intensity such as the monthly average and

A. Panek; Y. Lee; H. Tanaka

1996-01-01

214

Comparisons of downwelling radiation to model predictions based on groundbased measurements during FIRE 1991  

NASA Technical Reports Server (NTRS)

Surface radiation measurements and simultaneous ground-based measurements of the atmosphere during the FIRE'91 cirrus field experiment provided an opportunity to identify crucial measurements and parameterization deficiencies in current cloud-radiation models. Comparisons between measured and calculated broadband surface fluxes with only a small data subset already reveal these needs: accurate humidity and aerosol vertical profiles for clear cases, accurate vertical extinction profiles and dimensions for clouds, and understanding of the (solar) scattering properties of cirrus.

Kinne, S.; Bergstrom, R.; Ackerman, T.; Deluisi, J.

1993-01-01

215

System having unmodulated flux locked loop for measuring magnetic fields  

DOEpatents

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.

Ganther, Jr., Kenneth R. (Olathe, KS); Snapp, Lowell D. (Blue Springs, MO)

2006-08-15

216

Measurement of autophagy flux in the nervous system in vivo  

PubMed Central

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

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

217

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...

218

Estimation of surface heat and moisture fluxes over a prairie grassland. I - In situ energy budget measurements incorporating a cooled mirror dew point hygrometer  

NASA Technical Reports Server (NTRS)

Attention is focused on in situ measurements taken during FIFE required to support the development and validation of a biosphere model. Seasonal time series of surface flux measurements obtained from two surface radiation and energy budget stations utilized to support the FIFE surface flux measurement subprogram are examined. Data collection and processing procedures are discussed along with the measurement analysis for the complete 1987 test period.

Smith, Eric A.; Crosson, William L.; Tanner, Bertrand D.

1992-01-01

219

Instantaneous Radiation Energy Flux and Radiation Power Near the Event Horizon of Slowly Changing Vaidya Black Hole  

NASA Astrophysics Data System (ADS)

By the thin film model of the black hole and the assumption of the local thermal equilibrium, the instantaneous radiation energy flux and radiation power of the slowly changing Vaidya black hole have been studied. The result has been obtained that the thermal radiation of the Vaidya black hole satisfies the generalized Stefan-Boltzmann law. When the cut-off distance and the thin film thickness are both fixed, the instantaneous radiation energy flux of the scalar field near the event horizon of the Vaidya black hole is not only related to the black hole mass, but also to the rate of the change of its event horizon and the average effusion velocity of the radiation particles in the thin film. While its instantaneous radiation power is related to the rate of the change of the event horizon and the average radial effusion velocity of the radiation particles in the thin film. These results indicate that the gravitational field around the black hole and the change of its event horizon will both affect the thermal radiation of the black hole.

Jiang, Ji-Jian

2013-01-01

220

Heat flux measurements for use in physiological and clothing research.  

PubMed

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

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

2014-08-01

221

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...

222

UV RADIATION MEASUREMENTS/ATMOSPHERIC CHARACTERIZATION  

EPA Science Inventory

Because exposure to ultraviolet (UV) radiation is an ecosystem stressor and poses a human health risk, the National Exposure Research Laboratory (NERL) has undertaken a research program to measure the intensity of UV-B radiation at various locations throughout the U.S. In Septem...

223

Measurements of human body microwave radiation  

Microsoft Academic Search

Major problems of registering microwave radiation of human body have been considered. It is pointed out that they are caused by at least three factors which may considerably influence the experimental results and their interpretation, namely: (1) properties of the radiation (their low intensity primarily); (2) features of measurements that implement waveguide techniques; (3) peculiar features of the emission medium

G. V. Ponezha; S. G. Ponezha; A. I. Nizhelskaya

2003-01-01

224

Measurement of Turbulent Water Vapor Fluxes from Lightweight Unmanned Aircraft Systems  

NASA Astrophysics Data System (ADS)

Scientists at the Center for Clouds, Chemistry and Climate (C4) at the Scripps Institution of Oceanography have successfully used Unmanned Aircraft Systems (UASs) for measurements of radiation fluxes, aerosol concentrations and cloud microphysical properties. Building on this success, a payload to measure water vapor fluxes using the eddy covariance (EC) technique has been recently developed and tested. To our knowledge this is the first UAS turbulent flux system to incorporate high-frequency water vapor measurements. The driving aim of the water vapor flux system’s development is to investigate ‘atmospheric rivers’ in the north-western Pacific Ocean, these can lead to sporadic yet extreme rainfall and flooding events upon landfall in California. Such a flux system may also be used to investigate other weather events (e.g. the formation of hurricanes) and offers a powerful aerosol-cloud-radiative forcing investigative tool when combined with the existing aerosol/radiation and cloud microphysics UAS payloads. The atmospheric vertical wind component (w) is derived by this system at up to 100Hz using data from a GPS/Inertial Measurement Unit (GPS/IMU) combined with a fast-response gust probe mounted on the UAV. Measurements of w are then combined with equally high frequency water vapor data (collected using a Campbell Scientific Krypton Hygrometer) to calculate latent heat fluxes (?E). Two test flights were conducted at the NASA Dryden test facility on 27th May 2010, located in the Mojave Desert. Horizontal flight legs were recorded at four altitudes between 1000-2500 masl within the convective boundary layer. Preliminary data analysis indicates averaged spectral data follow the theoretical -5/3 slope , and extrapolation of the flux profile to the surface resulted in ?E of 1.6 W m-2; in good agreement with 1.0 W m-2 ?E measured by NOAA from a surface tower using standard flux techniques. The system performance during the Dryden test, as well as subsequent wind tunnel investigations and the outcomes from test flights planned for September 2010 at a marine location are discussed. Acknowledgments We would like to acknowledge the significant contributions to this system made by the late Katrin Lehmann whose life was tragically cut short by a hiking accident. Katrin was responsible for the initial design, construction and programming of the UAS elements, and in doing so laid solid foundations for the system. We are indebted to NOAA, for funding this project through the research grant NOAA NA17RJ1231. Thank you also to Mike Marston of NASA, the BAE systems crew Phillip Corcoran and Rafael Gaytan, and Mike Rizen of UCSD Physics workshop for their mission roles. We would also like to thank NSF for long term support of the C4 UAS Program.

Thomas, R. M.; Ramanathan, V.; Nguyen, H.; Lehmann*, K.

2010-12-01

225

Absolute Measurement Of EUV Radiation From An Undulator  

SciTech Connect

Driven by the needs for microlithography, powerful sources for extreme ultraviolet (EUV) radiation at wavelengths around 13 nm are currently under development. For absolute photon flux measurements of highly intense and extremely pulsed radiation in the VUV and EUV spectral range, a detector system based on the photoionization of rare gases has been developed. Due to its extended dynamic range, the device can be calibrated with spectrally dispersed synchrotron radiation at low photon intensities, but applied for high power sources like recently at the VUV-FEL of the TESLA test facility at DESY. The detector is free of degradation and almost transparent, and therefore suitable for intensity monitoring. Here we describe the application of the detector for flux measurements at a beamline for undispersed, deflected undulator radiation in the PTB Radiometry Laboratory at the electron storage ring BESSY II. This beamline is used for development and lifetime testing of components for EUV lithography, where accurate determination of the incident radiant power is needed, e.g. for exposure dose control. Taking advantage of the characteristic photoionization cross sections for different rare gases in the soft x-ray wavelength range, contributions of higher undulator harmonics could be determined and suppressed for EUV (13 nm) power measurements. While in normal operation the BESSY II radiation can be seen as quasi-continuous (500 MHz repetition rate), in single-bunch operation mode (1.25 MHz) measurements of the power for single EUV pulses have been performed. This demonstrates the capability of the gas detector for a broad range of applications with pulsed EUV sources.

Gottwald, A.; Klein, R.; Mueller, R.; Richter, M.; Sorokin, A.A.; Ulm, G. [Physikalisch-Technische Bundesanstalt, Abbestr. 2-12, 10587 Berlin (Germany)

2004-05-12

226

Sound power flux measurements in strongly exited ducts with flow  

NASA Astrophysics Data System (ADS)

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.

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

2002-12-01

227

Sound power flux measurements in strongly exited ducts with flow.  

PubMed

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

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

2002-12-01

228

Radiation damages and flux pinning in YBa 2Cu 3O 7 thin films  

NASA Astrophysics Data System (ADS)

We were able to increase the critical current density ( Jc) and implicitly, enhance the flux pinning in high quality epitaxial YBCO thin films by 200 keV proton irradiation. The critical temperature ( Tc) of the film does not change until radiation-induced localized defects begin to overlap over distances to the extent of a coherence length. The point defect induced by radiation damage or the radiation induced weak center (RWC) is believed to be responsible for the observed flux pinning enhancement. The self-field of the transport current transforms the RWCs into pinning centers. Compared to the bulk materials, the much lower Jc enhancement factor observed after irradiation of the thin films is due to the already very strong pinning force of the pinning defects in thin films. The extra pinning force of radiation defects is just a small perturbation on top of a large background.

Zhao, Y. J.; Chu, W. K.; Davis, M. F.; Wolfe, J. C.; Deshmukh, S. C.; Economou, D. J.; Mcguire, Anne

1991-12-01

229

Solar-Radiation Measuring Equipment and Glossary  

NASA Technical Reports Server (NTRS)

1976 listing of commercially available solar-radiation measuring equipment is presented in 50-page report. Sensor type, response time, cost data, and comments concerning specifications and intended usage are listed for 145 instruments from 38 manufactures.

Carter, E. A.; Patel, A. M.; Greenbaum, S. A.

1982-01-01

230

Critical radiation fluxes and luminosities of black holes and relativistic stars  

NASA Technical Reports Server (NTRS)

The critial luminosity at which the outward force of radiation balances the inward force of gravity plays an important role in many astrophysical systems. We present expressions for the radiation force on particles with arbitrary cross sections and analyze the radiation field produced by radiating matter, such as a disk, ring, boundary layer, or stellar surface, that rotates slowly around a slowly rotating gravitating mass. We then use these results to investigate the critical radiation flux and, where possible, the critical luminosity of such a system in genral relativity. We demonstrate that if the radiation source is axisymmetric and emission is back-front symmetric with repect to the local direction of motion of the radiating matter, as seen in the comoving frame, then the radial component of the radiation flux and the diagonal components of the radiation stress-energy tensor outside the source are the same, to first order in the rotation rates, as they would be if the radiation source and gravitating mass were not rotating. We argue that the critical radiation flux for matter at rest in the locally nonrotating frame is often satisfactory as an astrophysical benchmark flux and show that if this benchmark is adopted, many of the complications potentially introduced by rotation of the radiation source and the gravitating mass are avoided. We show that if the radiation field in the absence of rotation would be spherically symmetric and the opacity is independent of frequency and direction, one can define a critical luminosity for the system that is independent of frequency and direction, one can define a critical luminosity for the system that is independent of the spectrum and angular size of the radiation source and is unaffected by rotation of the source and mass and orbital motion of the matter, to first order. Finally, we analyze the conditions under which the maximum possible luminosity of a star or black hole powered by steady spherically symmetric radial accretion is the same in general relativity as in the Newtonian limit.

Lamb, Frederick K.; Miller, M. Coleman

1995-01-01

231

Visualization of Radiation Environment on Mars: Assessment with MARIE Measurements  

NASA Technical Reports Server (NTRS)

For a given GCR (Galactic Cosmic Ray) environment at Mars, particle flux of protons, alpha particles, and heavy ions, are also needed on the surface of Mars for future human exploration missions. For the past twelve months, the MARJE (Martian Radiation Environment Experiment) instrument onboard the 200J Mars Odyssey has been providing the radiation measurements from the Martian orbit. These measurements are well correlated with the HZETRN (High Z and Energy Transport) and QMSFRG (Quantum Multiple-Scattering theory of nuclear Fragmentation) model calculations. These model calculations during these specific GCR environment conditions are now extended and transported through the CO2 atmosphere onto the Martian surface. These calculated pa11icle flux distributions are presented as a function of the Martian topography making use of the MOLA (Mars Orbiter Laser Altimeter) data from the MGS (Mars Global Surveyor). Also, particle flux calculations are presented with visualization in the human body from skin depth to the internal organs including the blood-forming organs.

Saganti, P.; Cucinotta, F.; Zeitlin, C.; Cleghorn, T.; Flanders, J.; Riman, F.; Hu, X.; Pinsky, L.; Lee, K.; Anderson, V.; Atwell, W.; Turner, R.

2003-01-01

232

Universal measurement of quantum correlations of radiation  

E-print Network

A measurement technique is proposed which, in principle, allows one to observe the general space-time correlation properties of a quantized radiation field. Our method, called balanced homodyne correlation measurement, unifies the advantages of balanced homodyne detection with those of homodyne correlation measurements.

E. Shchukin; W. Vogel

2006-05-16

233

Local Heat Flux Measurements with Single Element Coaxial Injectors  

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

234

Scrape-off layer modeling of radiative divertor and high heat flux experiments on D3-D  

NASA Astrophysics Data System (ADS)

We use a new multispecies 1-D fluid code, NEWT-1D, to model DIII-D scrape-off layer (SOL) behavior during radiative divertor and high heat flux experiments. The separatrix location and the width of the SOL are uncertain, and affect the comparison of the data in important ways. The model agrees with many of the experimental measurements for a particular prescription for the separatrix location. The model cannot explain the recent data on the separatrix T(sub i) with a conventional picture of ion and electron power flows across the separatrix. Radial transport of particles and heat in some form is required to explain the peak heat flux data before and after gas puffing. For argon puffing in the private flux region, entrainment is poor in the steady state. The calculations suggest that strike point argon puffing in a slot divertor geometry results in substantially better entrainment. Self-consistent, steady-state solutions with radiated powers up to 80 percent of the SOL power input are obtained in 1-D. We discuss significant radial effects which warrant the development of a code which can treat strongly radiating impurities in 2-D geometries.

Campbell, R. B.; Petrie, T. W.; Hill, D. N.

1992-03-01

235

Scrape-off layer modeling of radiative divertor and high heat flux experiments on DIII-D  

NASA Astrophysics Data System (ADS)

We use a new multispecies 1D fluid code, NEWT-ID, to model DIII-D scrape-off layer (SOL) behavior during radiative divertor and high heat flux experiments. The separatrix location and the width of the SOL are uncertain, and affect the comparison of the data in important ways. The model agrees with many of the experimental measurements for a particular prescription for the separatrix location. The model cannot explain the recent data on the separatrix Ti with a conventional picture of ion and electron power flows across the separatrix. Radial transport of particles and heat in some form is required to explain the peak heat flux data before and after gas puffing. For argon puffing in the private flux region, entrainment is poor in the steady state. The calculations suggest that strike point argon puffing in a slot divertor geometry results in substantially better entrainment. Self-consistent, steady-state solutions with radiated powers up to 80% of the SOL power input are obtained in 1D. We discuss significant radial effects which warrant the development of a code which can treat strongly radiating impurities in 2D geometries.

Campbell, R. B.; Petrie, T. W.; Hill, D. N.

1992-12-01

236

Spatial variability of shortwave radiative fluxes in the context of snowmelt  

NASA Astrophysics Data System (ADS)

Snow-covered mountain ranges are a major source of water supply for run-off and groundwater recharge. Snowmelt supplies as much as 75% of surface water in basins of the western United States. Factors that affect the rate of snow melt include incoming shortwave and longwave radiation, surface albedo, snow emissivity, snow surface temperature, sensible and latent heat fluxes, ground heat flux, and energy transferred to the snowpack from deposited snow or rain. The net radiation generally makes up about 80% of the energy balance and is dominated by the shortwave radiation. Complex terrain poses a great challenge for obtaining the needed information on radiative fluxes from satellites due to elevation issues, spatially-variable cloud cover, rapidly changing surface conditions during snow fall and snow melt, lack of high quality ground truth for evaluation of the satellite based estimates, as well as scale issues between the ground observations and the satellite footprint. In this study we utilize observations of high spatial resolution (5-km) as available from the Moderate Resolution Imaging Spectro-radiometer (MODIS) to derive surface shortwave radiative fluxes in complex terrain, with attention to the impact of slopes on the amount of radiation received. The methodology developed has been applied to several water years (January to July during 2003, 2004, 2005 and 2009) over the western part of the United States, and the available information was used to derive metrics on spatial and temporal variability in the shortwave fluxes. It is planned to apply the findings from this study for testing improvements in Snow Water Equivalent (SWE) estimates.

Pinker, Rachel T.; Ma, Yingtao; Hinkelman, Laura; Lundquist, Jessica

2014-05-01

237

Array Of Sensors Measures Broadband Radiation  

NASA Technical Reports Server (NTRS)

Multiple broadband radiation sensors aimed at various portions of total field of view. All sensors mounted in supporting frame, serving as common heat sink and temperature reference. Each sensor includes heater winding and differential-temperature-sensing bridge circuit. Power in heater winding adjusted repeatedly in effort to balance bridge circuit. Intended to be used aboard satellite in orbit around Earth to measure total radiation emitted, at various viewing angles, by mosaic of "footprint" areas (each defined by its viewing angle) on surface of Earth. Modified versions of array useful for angle-resolved measurements of broadband radiation in laboratory and field settings on Earth.

Hoffman, James W.; Grush, Ronald G.

1994-01-01

238

Interplanetary dust fluxes measurements using the Waves instrument on STEREO  

NASA Astrophysics Data System (ADS)

Dust particles provide an important fraction of the matter composing the interplanetary medium, their mass density at 1 A.U. being comparable to the one of the solar wind. The impact of a dust particle on a spacecraft produces a plasma cloud whose associated electric field is detected by the on-board electric antennas. The signal measured by the wave instruments thus reveals the dust properties. We analyse the dust particle impacts on the STEREO spacecraft during the 2007-2010 period. We use the TDS waveform sampler of the STEREO/WAVES instrument, which enables us to deduce considerably more informations than in a previous study based on the LFR spectral analyzer [Meyer-Vernet et al., 2009]. We observe two distinct populations of dust that we infer to be nano and micron sized dust particles and we derive their fluxes at 1 AU and the evolution of these fluxes with time (and solar longitude). The observations are also in accord with the dynamics of nanometer-sized and micrometer-sized dust particles in the interplanetary medium.

Zaslavsky, A.; Meyer-Vernet, N.; Mann, I.; Czechowski, A.; Issautier, K.; Le Chat, G.; Maksimovic, M.; Kasper, J. C.

2010-12-01

239

Would be the photon a composed particle? quantization of field fluxes in electromagnetic radiation  

E-print Network

[En] Here it is made a comparative analysis between the classical and the quantum expressions for the energy of electromagnetic radiation (ER). The comparison points to the possibility of the quantization of the magnetic and the electric field fluxes in the ER.

Celso de Araujo Duarte

2013-12-02

240

PERIODIC MODULATIONS OF THE ENERGETIC ELECTRON FLUXES IN THE DISTANT RADIATION ZONE  

Microsoft Academic Search

Periodic modulations of the energetic (>45 key) electron fluxes are observed throughout the distant radiation zone by Geiger counters aboard Imp I and 2. These modu- lations have periods from a few minutes to half an hour, and coherent trains of these modu- lations are observed lasting as long as several hours. The peak-to-valley ratios are often an order of

R. P. Lin; K. A. Anderson

1966-01-01

241

Inversion of Multi-Angle Radiation Measurement  

SciTech Connect

Our need to reconcile models and measurements in an efficient manner that allows for the operational retrieval of particle sizes for a two layer cloud led us to develop a new method for calculating the Green's functions for radiative transfer. The method uses the fact that doubling/adding codes can be easily used to calculate internal radiation fields at arbitrarily high resolution. We have also determined that the adjoint downwelling and upwelling vector radiation fields are simply related to the usual downwelling and upwelling vector radiation fields so that the entire Green's function can be determined from a single calculation. The Green's functions have then been used to calculate the particle sizes in a two layer cloud that are consistent with both the reflectance and polarization measurements. This approach may be of use in other applications where adjoint calculations are used, particularly if multiangle measurements are being analyzed.

Cairns, B.; Alexandrov, M. Lacis, A.; Carlson, B.

2005-03-18

242

Simulation of the outer radiation belt electron flux decrease during the March 26, 1995, magnetic storm  

NASA Astrophysics Data System (ADS)

In this paper we study the variation of the relativistic electron fluxes in the Earth's outer radiation belt during the March 26, 1995, magnetic storm. Using observations by the radiation environment monitor (REM) on board the space technology research vehicle (STRV-Ib), we discuss the flux decrease and possible loss of relativistic electrons during the storm main phase. In order to explain the observations we have performed fully adiabatic and guiding center simulations for relativistic equatorial electrons in the nonstationary Tsygarienko96 magnetospheric magnetic field model. In our simulations the drift of electrons through the magnetopause was considered as a loss process. We present our model results and discuss their dependence on the magnetospheric magnetic and electric field model, as well as on the prestorm fluxes used in the simulations.

Desorgher, L.; Bühler, P.; Zehnder, A.; Flückiger, E. O.

2000-09-01

243

Solar Modulation of Inner Trapped Belt Radiation Flux as a Function of Atmospheric Density  

NASA Technical Reports Server (NTRS)

No simple algorithm seems to exist for calculating proton fluxes and lifetimes in the Earth's inner, trapped radiation belt throughout the solar cycle. Most models of the inner trapped belt in use depend upon AP8 which only describes the radiation environment at solar maximum and solar minimum in Cycle 20. One exception is NOAAPRO which incorporates flight data from the TIROS/NOAA polar orbiting spacecraft. The present study discloses yet another, simple formulation for approximating proton fluxes at any time in a given solar cycle, in particular between solar maximum and solar minimum. It is derived from AP8 using a regression algorithm technique from nuclear physics. From flux and its time integral fluence, one can then approximate dose rate and its time integral dose.

Lodhi, M. A. K.

2005-01-01

244

The measurable heat flux that accompanies active transport Dick Bedeauxw and Signe Kjelstrupw  

E-print Network

The measurable heat flux that accompanies active transport by Ca2+ -ATPase Dick Bedeauxw and Signe of the fluxes far from global equilibrium. An asymmetric set of transport coefficients is obtained, by assuming how the measurable heat flux and the heat production under isothermal conditions, as well

Kjelstrup, Signe

245

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...

246

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

NASA Astrophysics Data System (ADS)

This study develops an algorithm for representing detailed spectral features of vegetation albedo based on Moderate Resolution Imaging Spectrometer (MODIS) observations at 7 discrete channels, referred to as the MODIS Enhanced Vegetation Albedo (MEVA) algorithm. The MEVA algorithm empirically fills spectral gaps around the vegetation red edge near 0.7 ?m and vegetation water absorption features at 1.48 and 1.92 ?m which cannot be adequately captured by the MODIS 7 channels. We then assess the effects of applying MEVA in comparison to four other traditional approaches to calculate solar fluxes and aerosol direct radiative forcing (DRF) at the top of atmosphere (TOA) based on the MODIS discrete reflectance bands. By comparing the DRF results obtained through the MEVA method with the results obtained through the other four traditional approaches, we show that filling the spectral gap of the MODIS measurements around 0.7 ?m based on the general spectral behavior of healthy green vegetation leads to significant improvement in the instantaneous aerosol DRF at TOA (up to 3.02 W m-2 difference or 48% fraction of the aerosol DRF, -6.28 W m-2, calculated for high spectral resolution surface reflectance from 0.3 to 2.5 ?m for deciduous vegetation surface). The corrections of the spectral gaps in the vegetation spectrum in the near infrared, again missed by the MODIS reflectances, also contributes to improving TOA DRF calculations but to a much lower extent (less than 0.27 W m-2, or about 4% of the instantaneous DRF). Compared to traditional approaches, MEVA also improves the accuracy of the outgoing solar flux between 0.3 to 2.5 ?m at TOA by over 60 W m-2 (for aspen 3 surface) and aerosol DRF by over 10 W m-2 (for dry grass). Specifically, for Amazon vegetation types, MEVA can improve the accuracy of daily averaged aerosol radiative forcing in the spectral range of 0.3 to 2.5 ?m at equator at the equinox by 3.7 W m-2. These improvements indicate that MEVA can contribute to regional climate studies over vegetated areas and can help to improve remote sensing-based studies of climate processes and climate change.

Zhu, L.; Martins, J. V.; Yu, H.

2012-12-01

247

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...

248

Development and Application of the Delta-DM Method for Computing Shortwave Radiative Fluxes in a Vertically Inhomogeneous Atmosphere  

Microsoft Academic Search

This study describes the development and application of the Delta-DM method for computing shortwave radiative fluxes planetary albedo and heating rates in vertically inhomogeneous atmospheres. Delta-DM was designed to minimize computer time requirements, furnish accurate flux estimates and permit a wide range of shortwave radiative transfer problems to be studied. Phase function approximation is variable and there is no restriction

Allan M. Sawchuk

1983-01-01

249

Two-Flux Green's Function Analysis for Transient Spectral Radiation in a Composite  

NASA Technical Reports Server (NTRS)

An analysis is developed for obtaining transient temperatures in a two-layer semitransparent composite with spectrally dependent properties. Each external boundary of the composite is subjected to radiation and convection. The two-flux radiative transfer equations are solved by deriving a Green's function. This yields the local radiative heat source needed to numerically solve the transient energy equation. An advantage of the two-flux method is that isotropic scattering is included without added complexity. The layer refractive indices are larger than one. This produces internal reflections at the boundaries and the internal interface; the reflections are assumed diffuse. Spectral results using the Green's function method are verified by comparing with numerical solutions using the exact radiative transfer equations. Transient temperature distributions are given to illustrate the effect of radiative heating on one side of a composite with external convective cooling. The protection of a material from incident radiation is illustrated by adding scattering to the layer adjacent to the radiative source.

Siegel, Robert

1996-01-01

250

The Design of a Calorimeter to Measure Concentrated Solar Flux  

NASA Astrophysics Data System (ADS)

A water-cooled, cavity calorimeter was designed to accurately measure concentrated solar thermal power produced by the University of Minnesota's solar simulator. The cavity is comprised of copper tubing bent into spiral and helical coils for the base and cylindrical walls, respectively. Insulation surrounds the cavity to reduce heat transfer to the ambient, and a water- cooled aperture cover is positioned at the open end of the cavity. The calorimeter measures the heat gain of water flowing through the system as radiant energy is passed through the aperture. Chilled water flows through the tubing, and the energy incident on the cavity surface is conducted through the wall and convected to the flowing water. The energy increase in the water can be observed by an increase in fluid temperature. A Monte Carlo ray tracing method is used to predict the incident flux distribution and corresponding power on the surfaces of the cavity. These values are used to estimate the thermal losses of the system, and it is found that they account for less that 1% of the total power passed through the aperture. The overall uncertainty of the calorimeter is found by summing the measured uncertainty and the estimated heat loss and is found to be +/-2.5% for 9.2 kW of power output and +/-3.4% for 3 kW.

Sefkow, Elizabeth Anne Bennett

251

Measuring neutron fluences and gamma/x-ray fluxes with CCD cameras  

SciTech Connect

The capability to measure bursts of neutron fluences and gamma/x-ray fluxes directly with charge coupled device (CCD) cameras while being able to distinguish between the video signals produced by these two types of radiation, even when they occur simultaneously, has been demonstrated. Volume and area measurements of transient radiation-induced pixel charge in English Electric Valve (EEV) Frame Transfer (FT) charge coupled devices (CCDs) from irradiation with pulsed neutrons (14 MeV) and Bremsstrahlung photons (4--12 MeV endpoint) are utilized to calibrate the devices as radiometric imaging sensors capable of distinguishing between the two types of ionizing radiation. Measurements indicate {approx}.05 V/rad responsivity with {ge}1 rad required for saturation from photon irradiation. Neutron-generated localized charge centers or ``peaks`` binned by area and amplitude as functions of fluence in the 10{sup 5} to 10{sup 7} n/cm{sup 2} range indicate smearing over {approx}1 to 10% of CCD array with charge per pixel ranging between noise and saturation levels.

Yates, G.J. [Los Alamos National Lab., NM (United States); Smith, G.W. [Ministry of Defense, Aldermaston (United Kingdom). Atomic Weapons Establishment; Zagarino, P.; Thomas, M.C. [EG and G Energy Measurements, Inc., Goleta, CA (United States). Santa Barbara Operations

1991-12-01

252

Measuring neutron fluences and gamma/x-ray fluxes with CCD cameras  

SciTech Connect

The capability to measure bursts of neutron fluences and gamma/x-ray fluxes directly with charge coupled device (CCD) cameras while being able to distinguish between the video signals produced by these two types of radiation, even when they occur simultaneously, has been demonstrated. Volume and area measurements of transient radiation-induced pixel charge in English Electric Valve (EEV) Frame Transfer (FT) charge coupled devices (CCDs) from irradiation with pulsed neutrons (14 MeV) and Bremsstrahlung photons (4--12 MeV endpoint) are utilized to calibrate the devices as radiometric imaging sensors capable of distinguishing between the two types of ionizing radiation. Measurements indicate {approx}.05 V/rad responsivity with {ge}1 rad required for saturation from photon irradiation. Neutron-generated localized charge centers or peaks'' binned by area and amplitude as functions of fluence in the 10{sup 5} to 10{sup 7} n/cm{sup 2} range indicate smearing over {approx}1 to 10% of CCD array with charge per pixel ranging between noise and saturation levels.

Yates, G.J. (Los Alamos National Lab., NM (United States)); Smith, G.W. (Ministry of Defense, Aldermaston (United Kingdom). Atomic Weapons Establishment); Zagarino, P.; Thomas, M.C. (EG and G Energy Measurements, Inc., Goleta, CA (United States). Santa Barbara Operations)

1991-01-01

253

Measuring neutron fluences and gamma/x ray fluxes with CCD cameras  

NASA Astrophysics Data System (ADS)

The capability to measure bursts of neutron fluences and gamma/x-ray fluxes directly with charge coupled device (CCD) cameras while being able to distinguish between the video signals produced by these two types of radiation, even when they occur simultaneously, has been demonstrated. Volume and area measurements of transient radiation-induced pixel charge in English Electric Valve (EEV) Frame Transfer (FT) charge coupled devices (CCD's) from irradiation with pulsed neutrons (14 MeV) and Bremsstrahlung photons (4-12 MeV endpoint) are utilized to calibrate the devices as radiometric imaging sensors capable of distinguishing between the two types of ionizing radiation. Measurements indicate approx. = .05 V/rad responsivity with greater than or = 1 rad required for saturation from photon irradiation. Neutron-generated localized charge centers or 'peaks' binned by area and amplitude as functions of fluence in the 105 to 107 n/cc range indicate smearing over approx. 1 to 10 percent of the CCD array with charge per pixel ranging between noise and saturation levels.

Yates, G. J.; Smith, G. W.; Zagarino, P.; Thomas, M. C.

254

Spatially explicit surface energy budget and partitioning with remote sensing and flux measurements in a boreal region of Interior Alaska  

NASA Astrophysics Data System (ADS)

Extrapolating energy fluxes between the ground surface and the atmospheric boundary layer from point-based measurements to spatially explicit landscape estimation is critical to understand and quantify the energy balance components and exchanges in the hydrosphere, atmosphere, and biosphere. This information is difficult to quantify and are often lacking. Using a Landsat image (acquired on 5 August 2004), the flux measurements from three eddy covariance flux towers (a 1987 burn, a 1999 burn, and an unburned control site) and a customized satellite-based surface energy balance model of Mapping Evapotranspiration at High Resolution with Internalized Calibration (METRIC), we estimated net radiation, sensible heat flux ( H), latent heat flux (LE), and soil heat flux ( G) for the boreal Yukon River Basin of Interior Alaska. The model requires user selection of two extreme conditions present within the image area to calibrate and anchor the sensible flux output. One is the "hot" condition which refers to a bare soil condition with specified residual evaporation rates. Another one is the "cold" condition which refers to a fully transpiring vegetation such as full-cover agricultural crops. We selected one bare field as the "hot" condition while we explored three different scenarios for the "cold" pixel because of the absence of larger expanses of agricultural fields within the image area. For this application over boreal forest, selecting agricultural fields whose evapotranspiration was assumed to be 1.05 times the alfalfa-based reference evapotranspiration as the "cold" pixel could result in large errors. Selecting an unburned flux tower site as the "cold" pixel could achieve acceptable results, but uncertainties remain about the energy balance closure of the flux towers. We found that METRIC performs reasonably well in partitioning energy fluxes in a boreal landscape.

Huang, Shengli; Dahal, Devendra; Singh, Ramesh; Liu, Heping; Young, Claudia; Liu, Shuguang

2013-08-01

255

Radiation budget measurement/model interface  

NASA Technical Reports Server (NTRS)

This final report includes research results from the period February, 1981 through November, 1982. Two new results combine to form the final portion of this work. They are the work by Hanna (1982) and Stevens to successfully test and demonstrate a low-order spectral climate model and the work by Ciesielski et al. (1983) to combine and test the new radiation budget results from NIMBUS-7 with earlier satellite measurements. Together, the two related activities set the stage for future research on radiation budget measurement/model interfacing. Such combination of results will lead to new applications of satellite data to climate problems. The objectives of this research under the present contract are therefore satisfied. Additional research reported herein includes the compilation and documentation of the radiation budget data set a Colorado State University and the definition of climate-related experiments suggested after lengthy analysis of the satellite radiation budget experiments.

Vonderhaar, T. H.; Ciesielski, P.; Randel, D.; Stevens, D.

1983-01-01

256

Measurement of Emission from a Radiative Shock  

NASA Astrophysics Data System (ADS)

Radiative shocks are shock waves whose structure has been altered by radiation transport from the shock-heated matter. Such shocks are present in numerous astrophysical systems, including supernova remnants, supernovae, and accretion disks. Recent experiments have used the Omega laser to study radiative shock systems that are optically thin upstream and optically thick downstream. In these systems, a radiative precursor and high density cooling layer are formed in response to radiation lost in the upstream region. A thin slab of low-Z material is driven into a 1.1 atm. cylinder of high-Z gas at speeds > 100 km/s, producing strong radiative effects.. Measurements of radiative emission from the shocked region and the precursor region have been made using a streaked optical pyrometer. From these measurements, the temperature of the system can be inferred. Details of the experiment and results will be discussed. This work is funded by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, by the National Laser User Facility Program in NNSA-DS and by the Predictive Sciences Academic Alliances Program in NNSA-ASC. The corresponding grant numbers are DE-FG52-09NA29548, DE-FG52-09NA29034, and DE-FC52-08NA28616.

Visco, A.; Drake, R. P.; Grosskopf, M. J.

2010-11-01

257

Optical radiation measurements. Volume 1 - Radiometry  

Microsoft Academic Search

This 12-chapter book on optical radiation measurements is divided into three parts: concepts, components, and techniques. Chapters 2-4 describe the basic concepts such as radiation laws, terminology, and the transfer of radiant energy, the emphasis being on fundamentals. Chapters 5-7 survey the major components of radiometric systems; the objective is to introduce increasing amounts of specific performance data, particularly for

F. Grum; R. J. Becherer

1979-01-01

258

Nuclear radiation measuring apparatus and method  

SciTech Connect

A visually readable nuclear radiation measurement device functioning as a dose rate meter or a dosimeter. There are disclosed several embodiments allowing the user to match the brightness of a scintillating means to a reference light source thereby to ascertain the desired dose rate radiation information and allowing the user to match the brightness of light penetrating a dye type dosimeter to a reference light source to ascertain the total dose.

Bernstein, K.

1984-12-11

259

Methods of in vivo radiation measurement  

DOEpatents

Methods of and apparatus for in vivo radiation measurements relay on a MOSFET dosimeter of high radiation sensitivity with operates in both the passive mode to provide an integrated dose detector and active mode to provide an irradiation rate detector. A compensating circuit with a matched unirradiated MOSFET is provided to operate at a current designed to eliminate temperature dependence of the device. Preferably, the MOSFET is rigidly mounted in the end of a miniature catheter and the catheter is implanted in the patient proximate the radiation source.

Huffman, Dennis D. (Albuquerque, NM); Hughes, Robert C. (Albuquerque, NM); Kelsey, Charles A. (Albuquerque, NM); Lane, Richard (Galveston, TX); Ricco, Antonio J. (Albuquerque, NM); Snelling, Jay B. (Albuquerque, NM); Zipperian, Thomas E. (Albuquerque, NM)

1990-01-01

260

Role of plant-generated water vapor and VOC fluxes in shoot chamber measurements of O3 and NOx  

NASA Astrophysics Data System (ADS)

One of the processes underlying the atmospheric balance of O3 and NOx is their interaction with vegetation. Both are removed, absorbed, and NOx potentially also emitted by foliage. Uncertainties remain on relevant factors controlling O3 and NOx interactions with foliage as well as on including them in large-scale models. One reason for the uncertainty is that chamber measurements of O3 and NOx fluxes are complicated. These reactive gases are adsorbed and desorbed on the chamber walls, depending on the conditions (i.e. humidity). These artefact gas fluxes (chamber blank) must also be quantified and taken into account in the data analysis. Their importance increases when measuring in clean air, where the fluxes are generally small. At near-zero concentrations, the fluxes may not pass the detection limit of the instrumentation, which usually means it is not possible to separate the plant-related fluxes from the chamber blank. The long-term field measurements at the SMEAR II station in Hyytiälä, Southern Finland, have provided valuable insights into O3 and NOx exchange (i.e. Raivonen & al. 2009, Altimir & al. 2006). This project builds up on the expertise and conclusions from these works. The aim of this study was to improve the reliability of the measuring system by checking the role of potential measuring artefact(s). A live shoot, enclosed in a chamber, creates a water vapor in the chamber flux by transpiring. There are also biogenic VOC emissions from the shoot. In principle, these may affect the reactions of O3 and possibly NOx in the chamber. The potential interference of these fluxes created naturally during chamber closure is a main concern. Their effect on the O3 and NOx flux measurements has been tested with field calibrations in 2010-2011. In these calibrations, a controlled water vapor /VOC flux was fed into an empty shoot measurement chamber, and the H2O, CO2, O3 and NOx fluxes created in the chamber were measured. The created water vapor flux pattern was modified to either simulate shoot transpiration or to break the close connection of natural daily variation in transpiration, radiation and temperature. We will present results of this experiment. The project is funded by the Maj and Tor Nessling Foundation and the Ella and Georg Ehnrooth Foundation.

Joensuu, J.; Altimir, N.; Raivonen, M.; Kolari, P.; Keronen, P.; Vesala, T.; Bäck, J.; Hari, P.; Järvinen, E.; Nikinmaa, E.

2012-04-01

261

New Angular Distribution Models for Shortwave and Longwave Top-of-Atmosphere Radiative Flux Estimation From the Clouds and the Earth's Radiant Energy System Instrument  

NASA Astrophysics Data System (ADS)

The Clouds and the Earth's Radiant Energy System (CERES) provides highly accurate top-of-atmosphere (TOA) shortwave (SW), longwave (LW) and window (WN) radiance measurements and radiative flux estimates together with coincident cloud and aerosol properties inferred from the Moderate Resolution Imaging Spectrometer (MODIS). These data are needed to investigate the critical role that clouds and aerosols play in modulating the radiative energy flow within the Earth-atmosphere system. To estimate TOA fluxes from measured CERES radiances, one must account for the angular dependence in the radiance field, which is a strong function of the physical and optical characteristics of the scene (e.g. surface type, cloud fraction, cloud/aerosol optical depth, cloud phase), as well as the illumination angle. Because the CERES instrument can rotate in azimuth as it scans in elevation, it is acquires data over a wide range of angles. Consequently, one can construct angular distribution models (ADMs) for radiance-to-flux conversion from the CERES measurements. Furthermore, since CERES and MODIS are on the same spacecraft, the ADMs can be derived as a function of MODIS-based scene type parameters that have a strong influence on radiance anisotropy. This presentation provides a brief overview of the methodology and validation results for a new set of global CERES ADMs developed from two years of CERES measurements on the Terra spacecraft. The uncertainty in regional monthly mean SW and LW TOA fluxes from the new ADMs is less than 0.5 W m-2 based on comparisons with TOA fluxes evaluated by direct integration of the measured radiances. From multiangle CERES radiance measurements, instantaneous TOA flux errors are estimated to be < 10 W m-2 in the SW and < 3.5 W m-2 in the LW. Uncertainties in TOA fluxes from the new CERES ADMs are a factor of 2-5 smaller than those based on ADMs developed during the Earth Radiation Budget Experiment (ERBE). The improved accuracy in the Terra radiative fluxes is essential in studies that examine radiative forcing by cloud type and studies that combine TOA fluxes with surface measurements from specific locations.

Loeb, N. G.; Kato, S.; Loukachine, K.; Manalo-Smith, N.

2003-12-01

262

Plasma Lens for High Flux X-Ray Radiation  

SciTech Connect

We have developed the Scaled Thermal Explosion Experiment (STEX) to provide a database of reaction violence from thermal explosion for explosives of interest. Such data are needed to develop, calibrate, and validate predictive capability for thermal explosions using simulation computer codes. A cylinder of explosive 25, 50 or 100 mm in diameter, is confined in a steel cylinder with heavy end caps, and heated under controlled conditions until reaction. Reaction violence is quantified through non-contact micropower impulse radar measurements of the cylinder wall velocity and by strain gauge data at reaction onset. Here we describe the test concept, design and diagnostic recording, and report results with HMX- and RDX-based energetic materials.

Shlyaptsev, V N; Toor, A; Tatchyn, R O

2001-12-17

263

Weighted mean method for eddy covariance flux measurement  

NASA Astrophysics Data System (ADS)

The study to monitor the exchange of energy, water vapor and carbon dioxide between the atmosphere and terrestrial ecosystem has been carried out with eddy covariance method throughout the world. The monitored exchange quantity, named flux F , is conventionally determined by a mean of 1 hr or 30 min interval because no technique have been fortified to directly measure a momentary F itself at an instant of time. Therefore, the posterior analysis with this sampling should be paid attention to those spatial or temporal averaging and summation in the consideration of the sampling uncertainty. In particular, the averaging calcurated by arithmetic mean Fa might be inappropriate because the sample F used in this averaging has nonidentical inherent quality within one another according to different micrometeorological and ecophysiological conditions while those are observed under the same instruments. To overcome this issue, we propose the weighted mean Fw using a relative sampling error estimated by a sampling F and its error, and introduce Fw performance tested with EC measurements for 3 years at tangerine orchard.

Kim, W.; Cho, J.; Seo, H.; Oki, T.

2013-12-01

264

Tunable diode-laser-based measurements of a gas flux emanating from a two-dimensional surface  

NASA Astrophysics Data System (ADS)

Remote optical techniques are well suited for obtaining representative average values for gas fluxes emanating from a semi-infinite flat surface. Unisearch, the Alberta Reserach Council and the University of Alberta have developed a technique and methodology for making such measurements using a near-IR tunable diode laser analyzer and a set of open path optics. The technqiue uses the LasIR to measure gas concentrations at two different heights along paths which folow the perimeter of a square, flat surface. The measurements are used to calculate a concentration gradient across the height difference. These values, along with air temperature, relative humidity, soil heat flux, net radiation and wind speed/direction data, are then used to calculate the average flux emanating from the surface by applying an integrated flux gradient analysis based on Monin-Obukhov similarity theory. This method was applied to measure fluxes of methane emanating from a 50m × 50m test agricultural plot after the application of manure. Plans are underway to extend the capability of the system to measure up to four different species simultaneously.

Gamble, Heather A.; Feng, Yongsheng; Li, Xiaomei; Schiff, Harold I.; Mackay, Gervase I.

2003-02-01

265

Reconciling Models of Luminous Blazars with Magnetic Fluxes Determined by Radio Core-shift Measurements  

NASA Astrophysics Data System (ADS)

Estimates of magnetic field strength in relativistic jets of active galactic nuclei, obtained by measuring the frequency-dependent radio core location, imply that the total magnetic fluxes in those jets are consistent with the predictions of the magnetically arrested disk (MAD) scenario of jet formation. On the other hand, the magnetic field strength determines the luminosity of the synchrotron radiation, which forms the low-energy bump of the observed blazar spectral energy distribution (SED). The SEDs of the most powerful blazars are strongly dominated by the high-energy bump, which is most likely due to the external radiation Compton mechanism. This high Compton dominance may be difficult to reconcile with the MAD scenario, unless (1) the geometry of external radiation sources (broad-line region, hot-dust torus) is quasi-spherical rather than flat, or (2) most gamma-ray radiation is produced in jet regions of low magnetization, e.g., in magnetic reconnection layers or in fast jet spines.

Nalewajko, Krzysztof; Sikora, Marek; Begelman, Mitchell C.

2014-11-01

266

Measurement of Flux Density of Cas A at Low Frequencies  

NASA Astrophysics Data System (ADS)

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.

Patil, Ajinkya; Fisher, R.

2012-01-01

267

Recent measurements of coherent transition radiation  

SciTech Connect

An extended series of experiments has been used to investigate transition radiation in the x-ray spectral region. The x-rays were generated at the Lawrence Livermore National Laboratory electron-positron linear accelerator by 54 MeV electrons traversing multiple thin-foil targets. The measured angular and spectral distributions have shown excellent agreement with calculated predictions based on a simplified theoretical description of transition radiation. Recently, energy-resolved measurements of x-ray generation by targets consisting of multiple closely-spaced foils has clearly demonstrated the longitudinal coherence of transition radiation. This behavior might lead to a variety of applications such as tuneable narrow-band x-ray sources, measurement of x-ray dielectric constants, or particle beam diagnostics. These issues will be discussed, and recent results will be presented.

Moran, M.J.

1986-09-25

268

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

SciTech Connect

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.

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

2001-09-19

269

Measurements and modelling of the Jovian and Saturnian radiation belts  

NASA Astrophysics Data System (ADS)

The radiation belts regimes of the outer planets are the harshest environments in our solar system. In extremely strong internal closed magnetic field configurations energetic particles up to several hundred MeV energies are trapped and bounce back and forth along the magnetic field lines emitting waves in a whole variety of frequencies. Unlike Earth, Jupiter's and Saturn's magnetospheres are rotation dominated. Charged particle drift paths close around the whole planet to substantial planetary distances, unlike in the case of Earth (Chen et al, 1970). The combination of a strong internal magnet and quasi-stable trapping allows the fluxes of energetic ions and electrons to become very large. In this study we will review the in-situ measurements obtained onboard various spacecraft that flew by or orbited Jupiter or Saturn and compare them with existing models of the radiation belts.

Krupp, Norbert; Roussos, Elias; Paranicas, Chris; Sicard, Angelica; Hospodarsky, George; Shprits, Yuri

2014-05-01

270

Gamma radiation background measurements from Spacelab 2  

NASA Technical Reports Server (NTRS)

A Nuclear Radiation Monitor incorporating a NaI(Tl) scintillation detector was flown as part of the verification flight instrumentation on the Spacelab 2 mission, July 29 to August 6, 1985. Gamma-ray spectra were measured with better than 20 s resolution throughout most of the mission in the energy range 0.1 to 30 MeV. Knowledge of the decay characteristics and the geomagnetic dependence of the counting rates enable measurement of the various components of the Spacelab gamma-ray background: prompt secondary radiation, Earth albedo, and delayed induced radioactivity. The status of the data analysis and present relevant examples of typical background behavior are covered.

Paciesas, William S.; Gregory, John C.; Fishman, Gerald J.

1988-01-01

271

Radiation measurements from polar and geosynchronous satellites  

NASA Technical Reports Server (NTRS)

During the 1960's, radiation budget measurements from satellites have allowed quantitative study of the global energetics of our atmosphere-ocean system. A continuing program is planned, including independent measurement of the solar constant. Thus far, the measurements returned from two basically different types of satellite experiments are in agreement on the long term global scales where they are most comparable. This fact, together with independent estimates of the accuracy of measurement from each system, shows that the energy exchange between earth and space is now measured better than it can be calculated. Examples of application of the radiation budget data were shown. They can be related to the age-old problem of climate change, to the basic question of the thermal forcing of our circulation systems, and to the contemporary problems of local area energetics and computer modeling of the atmosphere.

Vonderhaar, T. H.

1973-01-01

272

MEASURED AND PREDICTED FLUXES OF BIOGENIC SILICA IN LAKE MICHIGAN  

EPA Science Inventory

Diatom production in the offshore waters of Lake Michigan is limited by silica supplies in late summer and can be predicted from the seasonal disappearance of silica from the trophogenic zone. Biogenic silica fluxes obtained from sediment trap collections were compared with fluxe...

273

The preliminary results of fast neutron flux measurements in the DULB laboratory at Baksan  

Microsoft Academic Search

One of the main sources of a background in underground physics experiments (such as the investigation of solar neutrino flux, neutrino oscillations, neutrinoless double beta decay, and the search for annual and daily Cold Dark Matter particle flux modulation) are fast neutrons originating from the surrounding rocks. The measurements of fast neutron flux in the new DULB Laboratory situated at

J. N. Abdurashitov; V. N. Gavrin; A. V. Kalikhov; A. A. Shikhin; V. E. Yants; O. S. Zaborskaya; A. A. Klimenko; S. B. Osetrov; A. A. Smolnikov; S. I. Vasiliev

2000-01-01

274

Measurements of diffusive sublayer thicknesses in the ocean by alabaster dissolution, and their implications for the measurements of benthic fluxes  

Microsoft Academic Search

Fluxes of reactive chemical species across the sediment-water interface can profoundly influence the dominant biogeochemical cycles in the worlds ocean. However, reliable in-situ measurements of benthic fluxes of many reactive species cannot be carried out without adjustments of stirring rates inside benthic flux chambers to match boundary layer conditions prevailing outside. A simple method to compare flow levels consists of

Peter H. Santschi; Robert F. Anderson; Walter Bowles

1991-01-01

275

Cloud radiative forcing on surface shortwave fluxes: A case study based on Cloud Lidar and Radar Exploratory Test  

SciTech Connect

Shortwave downward fluxes for selected stratus, cirrus, and mixed phase cloud cases are analyzed based on cloud and surface radiation measurements from the Cloud Lidar and Radar Exploratory Test conducted in the Denver-Boulder area of Colorado during September-October, 1989. A medium resolution, discrete-ordinate shortwave radiative transfer model is used to provide clear-sky conditions and to examine the cloud shortwave radiative forcing. The model simulation indicates that for stratus clouds the effective radius increases with increasing liquid water path. For cirrus cloud simulation, the model results are within 10% agreement with the surface flux measurements. However, using the one-dimensional plane-parallel model, the model results are in poor agreement for the inhomogeneous mixed phase cloud case. Over the elevated observation site, the reduction in shortwave downward flux by clouds can be as large as 40% for a small cloud water path value of 20 g m{sup {minus}2}. The variation in observed cloud shortwave forcing is highly correlated with the integrated cloud water path. The normalized (by the clear-sky value) cloud shortwave forcing increases rapidly when the cloud water path is small. The rate of increase decreases, and the normalized cloud forcing approaches saturation when cloud water path becomes large. The magnitude of the saturation value depends on cloud optical properties. The variation in observed cloud forcing is consistent with the theoretical curve for cloudy atmospheric albedo variation. At a constant value of cloud water path, the normalized cloud forcing increases with solar zenith angle. The solar zenith angle effect is less significant for larger value of cloud water path. 44 refs., 11 figs.

Shi, L. [Univ. of California, San Diego, CA (United States)] [Univ. of California, San Diego, CA (United States)

1994-12-20

276

Measurement of Global Radiation using Photovoltaic Panels  

NASA Astrophysics Data System (ADS)

The Vito Unit - Environmental and Spatial Aspects (RMA) - for many of its models makes use of global solar radiation. From this viewpoint and also from the notion that this variable is seldom measured or available at the local scale and at high multi-temporal frequencies, it can be stated that many models are fed with low quality estimates of global solar radiation at the local to regional scales. A project was initiated called SUNSPIDER with the following objective. To make use of photovoltaic solar panels to measure solar radiation at the highest spatio-temporal resolution, from the local to the regional scales and from minutes to years. To integrate the measured solar fields in different application fields like, plant systems and agriculture, agro-meteorology and hydrology and last but not least solar energy applications. In Belgium about 250.000 PV installations have been built leading to about 6% electric power supply from photovoltaics on a yearly basis. Last year in June, the supply reached a peak of more than 20% of the total power input on the Belgian grid. A database of Belgian residential solar panel sites will be compiled. The database will serve as an input to an inverted PV model to be able to perform radiation calculations specifically for each of the validated panel sites based on minutely logged power data. Data acquisition for these sites will start each time a site is validated and hence imported in the database. Keywords: Photovoltaic Panels; PV modelling; Global Radiation.

Veroustraete, Frank; Bronders, Jan; Lefevre, Filip; Mensink, Clemens

2014-05-01

277

Assessment of radiative feedback in climate models using satellite observations of annual flux variation  

PubMed Central

In the climate system, two types of radiative feedback are in operation. The feedback of the first kind involves the radiative damping of the vertically uniform temperature perturbation of the troposphere and Earth’s surface that approximately follows the Stefan–Boltzmann law of blackbody radiation. The second kind involves the change in the vertical lapse rate of temperature, water vapor, and clouds in the troposphere and albedo of the Earth’s surface. Using satellite observations of the annual variation of the outgoing flux of longwave radiation and that of reflected solar radiation at the top of the atmosphere, this study estimates the so-called “gain factor,” which characterizes the strength of radiative feedback of the second kind that operates on the annually varying, global-scale perturbation of temperature at the Earth’s surface. The gain factor is computed not only for all sky but also for clear sky. The gain factor of so-called “cloud radiative forcing” is then computed as the difference between the two. The gain factors thus obtained are compared with those obtained from 35 models that were used for the fourth and fifth Intergovernmental Panel on Climate Change assessment. Here, we show that the gain factors obtained from satellite observations of cloud radiative forcing are effective for identifying systematic biases of the feedback processes that control the sensitivity of simulated climate, providing useful information for validating and improving a climate model. PMID:23613585

Tsushima, Yoko; Manabe, Syukuro

2013-01-01

278

Wide Range Neutron Flux Measuring Channel for Aerospace Application  

SciTech Connect

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.

Cibils, R. M.; Busto, A.; Gonella, J. L.; Martinez, R.; Chielens, A. J.; Otero, J. M.; Nunez, M. [INVAP S.E., Moreno 1089, 8400 Bariloche, Rio Negro (Argentina); Tropea, S. E. [INTI, Av. Gral. Paz 5445, 1650 San Martin, Buenos Aires (Argentina)

2008-01-21

279

Results and interpretation of measurements of the light flux in the near-surface layer of the Venusian atmosphere  

NASA Technical Reports Server (NTRS)

The characteristics of the field of radiation in the near surface layer of the atmosphere and on the surface of Venus are reported. Optical measurements made during the landing of the descent vehicles are described. The relief of the surface and the amount of dust on it are examined. The spectral relationship of the albedo of the soil and the light flux incident on the surface is discussed.

Golovin, Y. M.; Moshkin, B. Y.; Ekonomov, A. P. E.

1979-01-01

280

An unmanned aircraft vehicle system for boundary-layer flux measurements over forest canopies  

Microsoft Academic Search

Describes a system design of an unmanned aircraft vehicle (UAV) system for boundary-layer measurements of carbon dioxide fluxes, particularly of those fluxes over forest canopies. The system is aircraft-based, which permits measurements that are difficult to obtain by ground-based line-of-sight instruments (e.g., lidar). The system is unmanned, which permits flux measurements to as low as 5 m above a forest

Jason M. Daida; P. B. Russell; Timothy L. Crawford; J. F. Vesecky

1994-01-01

281

Optical design of a high radiative flux solar furnace for Mexico  

SciTech Connect

In the present work, the optical design of a new high radiative flux solar furnace is described. Several optical configurations for the concentrator of the system have been considered. Ray tracing simulations were carried out in order to determine the concentrated radiative flux distributions in the focal zone of the system, for comparing the different proposals. The best configuration was chosen in terms of maximum peak concentration, but also in terms of economical and other practical considerations. It consists of an arrangement of 409 first surface spherical facets with hexagonal shape, mounted on a spherical frame. The individual orientation of the facets is corrected in order to compensate for aberrations. The design considers an intercepted power of 30 kW and a target peak concentration above 10,000 suns. The effect of optical errors was also considered in the simulations. (author)

Riveros-Rosas, D.; Perez-Rabago, C.A.; Arancibia-Bulnes, C.A.; Jaramillo, O.A.; Estrada, C.A. [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Av. Xochicalco s/n, A.P. 34, Temixco, 62580 Morelos (Mexico); Herrera-Vazquez, J.; Vazquez-Montiel, S.; Granados-Agustin, F. [Instituto Nacional de Astrofisica, Optica y Electronica, Luis Enrique Erro 1, Tonantzintla, A.P. 216, 72000 Puebla (Mexico); Sanchez-Gonzalez, M. [Centro Nacional de Energias Renovables, Calle Somera 7-9, 28026 Madrid (Spain)

2010-05-15

282

The validation of the GEWEX SRB surface longwave flux data products using BSRN measurements  

NASA Astrophysics Data System (ADS)

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-Smirnov (KS) two-sample test and Cramér-von Mises (CvM) two-sample test are used to show that the GLW is able to replicate the cumulative frequency distribution of the measurements at the 0.01 significance level.

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

2015-01-01

283

The prototype of a detector for monitoring the cosmic radiation neutron flux on ground  

SciTech Connect

This work presents a comparison between the results of experimental tests and Monte Carlo simulations of the efficiency of a detector prototype for on-ground monitoring the cosmic radiation neutron flux. The experimental tests were made using one conventional {sup 241}Am-Be neutron source in several incidence angles and the results were compared to that ones obtained with a Monte Carlo simulation made with MCNPX Code.

Lelis Goncalez, Odair; Federico, Claudio Antonio; Mendes Prado, Adriane Cristina; Galhardo Vaz, Rafael; Tizziani Pazzianotto, Mauricio [Instituto de Estudos Avancados - IEAv/DCTA - Sao Jose dos Campos, SP (Brazil); Semmler, Renato [Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP - Sao Paulo, SP (Brazil)

2013-05-06

284

COMPARISON OF FLUX MEASUREMENTS WITH OPEN-AND CLOSED-PATH GAS ANALYZERS ABOVE AN AGRICULTURAL  

E-print Network

COMPARISON OF FLUX MEASUREMENTS WITH OPEN- AND CLOSED-PATH GAS ANALYZERS ABOVE AN AGRICULTURAL 16 March, 1993) Abstract. Comparison was made of the flux measurements of a closed-path CO2/H20), the measurement can be made using the eddy correlation technique with a velocity sensor and an adjacent open

Lee, Xuhui

285

Comparison of floating chamber and eddy covariance measurements of lake greenhouse gas fluxes  

NASA Astrophysics Data System (ADS)

Fluxes of carbon dioxide (CO2) and methane (CH4) from lakes may have a large impact on the magnitude of the terrestrial carbon sink. Traditionally lake fluxes have been measured using the floating chamber (FC) technique; however, several recent studies use the eddy covariance (EC) method. We present simultaneous flux measurements using both methods at lake Tämnaren in Sweden during field campaigns in 2011 and 2012. Only very few similar studies exist. For CO2 flux, the two methods agree relatively well during some periods, but deviate substantially at other times. The large discrepancies might be caused by heterogeneity of partial pressure of CO2 (pCO2w) in the EC flux footprint. The methods agree better for CH4 fluxes. It is, however, clear that short-term discontinuous FC measurements are likely to miss important high flux events.

Podgrajsek, E.; Sahlée, E.; Bastviken, D.; Holst, J.; Lindroth, A.; Tranvik, L.; Rutgersson, A.

2014-08-01

286

A Binomial Model for Radiated Immunity Measurements  

E-print Network

1 A Binomial Model for Radiated Immunity Measurements Emmanuel Amador, Hans Georg Krauth analysis of immunity testing in EMC based on binomial distributions. This approach aims at extracting the immunity properties of a device from its probability of failure during a test. We show that under certain

Paris-Sud XI, Université de

287

SUMER - Solar Ultraviolet Measurements of Emitted Radiation  

Microsoft Academic Search

The instrument SUMER - Solar Ultraviolet Measurements of Emitted Radiation is designed to investigate structures and associated dynamical processes occurring in the solar atmosphere, from the chromosphere through the transition region to the inner corona, over a temperature range from 104 to 2 × 106K and above. These observations will permit detailed spectroscopic diagnostics of plasma densities and temperatures in

K. Wilhelm; W. Curdt; E. Marsch; U. Schühle; P. Lemaire; A. Gabriel; J.-C. Vial; M. Grewing; M. C. E. Huber; S. D. Jordan; A. I. Poland; R. J. Thomas; M. Kühne; J. G. Timothy; D. M. Hassler; O. H. W. Siegmund

1995-01-01

288

Experimental study of radiation power flux on the target surface during high heat plasma irradiation  

NASA Astrophysics Data System (ADS)

Some new data of the experimental study of visible radiation from the plasma shielding layer (SL) on the target surface during high heat plasma-material interaction are given in the report. The experiments were performed on the VIKA facility. Long pulse ( ?p=0.36 ms) high power ( Pirr˜100 GW m -2 plasma streams were used for irradiation of graphite and tungsten samples. The target inclination ( ?=0° normal irradiation; 45°; 70°) and magnetic field ( B=0 to 3 T) were varied in experiments. It is shown that the values of ( ???400 to 700 nm) visible radiation power flux (VRPF) on the target surface can be characterised by the level of PR˜1 GW m -2 for normal irradiation in the presence of a magnetic field B=2 to 3 T. Inclination of targets leads to the reduction of this flux in conformity with the corresponding decrease of the irradiation power. The material of the target does not influence sufficiently on the level of the incident radiation power flux in the performed experiments.

Litunovsky, V. N.; Ovchinnikov, I. B.; Titov, V. A.

2001-03-01

289

MSL-RAD Radiation Environment Measurements  

NASA Astrophysics Data System (ADS)

We present results from the Radiation Assessment Detector (RAD) obtained during MSL's cruise to Mars and during the first 150 sols after Curiosity's successful landing. RAD is designed to measure the energetic particle environment, which consists of Galactic Cosmic Rays (GCRs), Solar Energetic Particles (SEPs), and the secondary particles created by nuclear interactions of primary GCRs in shielding. During cruise, RAD was asymmetrically shielded inside the spacecraft. On the surface, RAD is shielded by the atmosphere, and the radiation dose rate is seen to vary slightly as the column depth of the atmosphere varies on a diurnal cycle. RAD's cruise measurements are a unique data set that provide a reasonable simulation of what might be encountered by a human crew headed for Mars or for some other destination in deep space. RAD successfully operated for 220 days of the 253 day journey to Mars. RAD has also operated stably on the surface of Mars, returning the first detailed radiation data from the surface of another planet. The data from the surface are also highly relevant for planning future crewed missions. We will present results for radiation dose and dose equivalent (the quantity most directly related to human health risk) obtained with both cruise and surface data. Dose and dose equivalent are dominated by the continuous GCR radiation, but five significant SEP events were seen during cruise and will be discussed.

Zeitlin, Cary; Hassler, Donald; Wimmer-Schweingruber, Robert; Boehm, Eckart; Boettcher, Stephan; Brinza, David; Burmeister, Soenke; Cucinotta, Francis; Ehresmann, Bent; Guo, Jingnan; Koehler, Jan; Martin, Cesar; Posner, Arik; Rafkin, Scot; Reitz, Guenther; MSL Science Team

2013-04-01

290

Measurement of photon flux with a miniature gas ionization chamber in a Material Testing Reactor  

NASA Astrophysics Data System (ADS)

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.

Fourmentel, D.; Filliatre, P.; Villard, J. F.; Lyoussi, A.; Reynard-Carette, C.; Carcreff, H.

2013-10-01

291

High Time Resolution Measurements of Methane Fluxes From Enteric Fermentation in Cattle Rumen  

NASA Astrophysics Data System (ADS)

Methane accounts for roughly 20% of the global radiative climate forcing in the last two and a half centuries. Methane emissions arise from a number of anthropogenic and biogenic sources. In some areas enteric fermentation in livestock produces over 90% of agricultural methane. In the spring of 2013, as a part of the Short Lived Climate Forcer-Mexico field campaign, the Aerodyne Mobile Laboratory in partnership with the Molina Center for the Environment studied methane production associated with enteric fermentation in the rumen of cattle. A variety of different breeds and stocks being raised in two agricultural and veterinary research facilities located in different areas of Mexico were examined. Methane fluxes were quantified using two methods: 1) an atmospherically stable gaseous tracer release was collocated with small herds in a pasture, allowing tracer ratio flux measurements; 2) respiratory CO2 was measured in tandem with methane in the breath of individual animals allowing methane production to be related to metabolism. The use of an extensive suite of very high time response instruments allows for differentiation of individual methane producing rumination events and respiratory CO2 from possible background interferences. The results of these studies will be presented and compared to data from traditional chamber experiments.

Floerchinger, C. R.; Herndon, S.; Fortner, E.; Roscioli, J. R.; Kolb, C. E.; Knighton, W. B.; Molina, L. T.; Zavala, M.; Castelán, O.; Ku Vera, J.; Castillo, E.

2013-12-01

292

Effects of tropospheric aerosols on radiative flux calculations at UV and visible wavelengths  

SciTech Connect

The surface fluxes in the wavelength range 175 to 735nm have been calculated for an atmosphere which contains a uniformly mixed aerosol layer of thickness 1km at the earth`s surface. Two different aerosol types were considered, a rural aerosol, and an urban aerosol. The visibility range for the aerosol layers was 95 to 15 km. Surface flux ratios (15km/95km) were in agreement with previously published results for the rural aerosol layer to within about 2%. The surface flux ratios vary from 7 to 14% for the rural aerosol layer and from 13 to 23% for the urban aerosol layer over the wavelength range. A tropospheric radiative forcing of about 1.3% of the total tropospheric flux was determined for the 95km to 15km visibility change in the rural aerosol layer, indicating the potential of tropospheric feedback effects on the surface flux changes. This effect was found to be negligible for the urban aerosol layer. Stratospheric layer heating rate changes due to visibility changes in either the rural or urban aerosol layer were found to be negligible.

Grossman, A.S.; Grant, K.E.

1994-08-01

293

Measurements of the atmospheric radiation environment from CREAM and comparisons with models for quiet time and solar particle events  

Microsoft Academic Search

Flight data on neutron fluxes and dose rates obtained over a wide range of latitudes and altitudes are compared with several models of atmospheric radiation for both quiet-time and solar particle events. For quiet-time, general agreement between the models and measurements is within about 25%. Geomagnetic disturbances can increase atmospheric cosmic ray fluxes by up to 10% due to suppression

Clive Dyer; Fan Lei; Alex Hands; Simon Clucas; Bryn Jones

2005-01-01

294

A Strategy to Assess Aerosol Direct Radiative Forcing of Climate Using Satellite Radiation Measurements  

NASA Technical Reports Server (NTRS)

Atmospheric aerosols have a complex internal chemical composition and optical properties. Therefore it is difficult to model their impact on redistribution and absorption of solar radiation, and the consequent impact on atmospheric dynamics and climate. The use in climate models of isolated aerosol parameters retrieved from satellite data (e.g. optical thickness) may result in inconsistent calculations, if the model assumptions differ from these of the satellite retrieval schemes. Here we suggest a strategy to assess the direct impact of aerosol on the radiation budget at the top and bottom of the atmosphere using satellite and ground based measurements of the spectral solar radiation scattered by the aerosol. This method ensures consistent use of the satellite data and increases its accuracy. For Kaufman and Tanre: Strategy for aerosol direct forcing anthropogenic aerosol in the fine mode (e.g. biomass burning smoke and urban pollution) consistent use of satellite derived optical thickness can yield the aerosol impact on the spectral solar flux with accuracy an order of magnitude better than the optical thickness itself. For example, a simulated monthly average smoke optical thickness of 0.5 at 0.55 microns (forcing of 40-50 W/sq m) derived with an error of 20%, while the forcing can be measured directly with an error of only 0-2 W/sq m. Another example, the effect of large dust particles on reflection of solar flux can be derived three times better than retrievals of optical thickness. Since aerosol impacts not only the top of the atmosphere but also the surface irradiation, a combination of satellite and ground based measurements of the spectral flux, can be the most direct mechanism to evaluate the aerosol effect on climate and assimilate it in climate models. The strategy is applied to measurements from SCAR-B and the Tarfox experiments. In SCAR-B aircraft spectral data are used to derive the 24 hour radiative forcing of smoke at the top of the atmosphere of (Delta)F(sub 24hr)/(Delta)tau = - 25 +/- 5 W/sq m. Ground based data give forcing at the surface of (Delta)F(sub 24hr)/(Delta)taur = -80 +/- 5 W/sq m. In TARFOX a mixture of maritime and regional pollution aerosol resulted in a varied forcing at the top of the atmosphere, (Delta)F(sub 24hr)/(Delta)tau, between -26 W/sq 2 and -50 W/sq m depending on mixture of coarse and accumulation modes, for Angstrom exponents of 1.0 and 0.2 respectively.

Kaufman, Yoram J.; Tanre, Didier; Einaudi, Franco (Technical Monitor)

2001-01-01

295

A Comparison of EAST Shock-Tube Radiation Measurements with a New Air Radiation Model  

NASA Technical Reports Server (NTRS)

This paper presents a comparison between the recent EAST shock tube radiation measurements (Grinstead et al., AIAA 2008-1244) and the HARA radiation model. The equilibrium and nonequilibrium radiation measurements are studied for conditions relevant to lunar-return shock-layers; specifically shock velocities ranging from 9 to 11 kilometers per second at initial pressures of 0.1 and 0.3 Torr. The simulated shock-tube flow is assumed one-dimensional and is calculated using the LAURA code, while a detailed nonequilibrium radiation prediction is obtained in an uncoupled manner from the HARA code. The measured and predicted intensities are separated into several spectral ranges to isolate significant spectral features, mainly strong atomic line multiplets. The equations and physical data required for the prediction of these strong atomic lines are reviewed and their uncertainties identified. The 700-1020 nm wavelength range, which accounts for roughly 30% of the radiative flux to a peak-heating lunar return shock-layer, is studied in detail and the measurements and predictions are shown to agree within 15% in equilibrium. The plus or minus 1.5% uncertainty on the measured shock velocity is shown to cause up to a plus or minus 30% difference in the predicted radiation. This band of predictions contains the measured values in almost all cases. For the highly nonequilibrium 0.1 Torr cases, the nonequilibrium radiation peaks are under-predicted by about half. This under-prediction is considered acceptable when compared to the order-of-magnitude over-prediction obtained using a Boltzmann population of electronic states. The reasonable comparison in the nonequilibrium regions provides validation for both the non-Boltzmann modeling in HARA and the thermochemical nonequilibrium modeling in LAURA. The N2 (+)(1-) and N2(2+) molecular band systems are studied in the 290 480 nm wavelength range for both equilibrium and nonequilibrium regimes. The non-Boltzmann rate models for these systems, which have significant uncertainties, are tuned to improve the comparison with measurements.

Johnston, Christopher O.

2008-01-01

296

Modelling radiation fluxes in simple and complex environments—application of the RayMan model  

NASA Astrophysics Data System (ADS)

The most important meteorological parameter affecting the human energy balance during sunny weather conditions is the mean radiant temperature Tmrt. It considers the uniform temperature of a surrounding surface giving off blackbody radiation, which results in the same energy gain of a human body given the prevailing radiation fluxes. This energy gain usually varies considerably in open space conditions. In this paper, the model ‘RayMan’, used for the calculation of short- and long-wave radiation fluxes on the human body, is presented. The model, which takes complex urban structures into account, is suitable for several applications in urban areas such as urban planning and street design. The final output of the model is, however, the calculated Tmrt, which is required in the human energy balance model, and thus also for the assessment of the urban bioclimate, with the use of thermal indices such as predicted mean vote (PMV), physiologically equivalent temperature (PET) and standard effective temperature (SET*). The model has been developed based on the German VDI-Guidelines 3789, Part II (environmental meteorology, interactions between atmosphere and surfaces; calculation of short- and long-wave radiation) and VDI-3787 (environmental meteorology, methods for the human-biometeorological evaluation of climate and air quality for urban and regional planning. Part I: climate). The validation of the results of the RayMan model agrees with similar results obtained from experimental studies.

Matzarakis, Andreas; Rutz, Frank; Mayer, Helmut

2007-03-01

297

CERES: The Next Generation of Earth Radiation Budget Measurements  

NASA Technical Reports Server (NTRS)

NASA's Earth Observing System (EOS) is part of an international program for studying the Earth from space using a multiple-instrument, multiple-satellite approach. The Clouds and the Earth's Radiant Energy System (CERES) experiment is designed to monitor changes in the Earth s radiant energy system and cloud systems and to provide these data with sufficient simultaneity and accuracy to examine critical cloud/climate feedback mechanisms which may play a major role in determining future changes in the climate system. The first EOS satellite (Terra), scheduled for launch this year, and the EOS-PM satellite, to be launched in late 2000, will each carry two CERES instruments. The first CERES instrument was launched in 1997 on the Tropical Rainfall Measuring Mission (TRMM) satellite. The CERES TRMM data show excellent instrument stability and a factor of 2 to 3 less error than previous Earth radiation budget missions. The first CERES data products have been validated and archived. The data consist of instantaneous longwave and shortwave broadband radiances, top-of-atmosphere fluxes, scene types, and time and space averaged fluxes and albedo. A later data product will combine CERES radiances and high- resolution imager data to produce cloud properties and fluxes throughout the atmosphere and at the surface.

Gibson, Gary G.; Wielicki, Bruce A.

1999-01-01

298

REDUCING THE UNCERTAINTY OF NORTH AMERICAN CARBON FLUX ESTIMATES USING AN EXTENDED ATMOSPHERIC CARBON DIOXIDE MEASUREMENT NETWORK.  

E-print Network

??We evaluate North American carbon fluxes using a monthly global Bayesian synthesis inversion that includes well-calibrated carbon dioxide concentrations measured at continental flux towers. We… (more)

Butler, Martha

2010-01-01

299

Radiation beam calorimetric power measurement system  

DOEpatents

A radiation beam calorimetric power measurement system for measuring the average power of a beam such as a laser beam, including a calorimeter configured to operate over a wide range of coolant flow rates and being cooled by continuously flowing coolant for absorbing light from a laser beam to convert the laser beam energy into heat. The system further includes a flow meter for measuring the coolant flow in the calorimeter and a pair of thermistors for measuring the temperature difference between the coolant inputs and outputs to the calorimeter. The system also includes a microprocessor for processing the measured coolant flow rate and the measured temperature difference to determine the average power of the laser beam.

Baker, John (Livermore, CA); Collins, Leland F. (Pleasanton, CA); Kuklo, Thomas C. (Ripon, CA); Micali, James V. (Dublin, CA)

1992-01-01

300

Remote Measurement of Heat Flux from Power Plant Cooling Lakes  

SciTech Connect

Laboratory experiments have demonstrated a correlation between the rate of heat loss q? from an experimental fluid to the air above and the standard deviation ? of the thermal variability in images of the fluid surface. These experimental results imply that q? can be derived directly from thermal imagery by computing ?. This paper analyses thermal imagery collected over two power plant cooling lakes to determine if the same relationship exists. Turbulent boundary layer theory predicts a linear relationship between q? and ? when both forced (wind driven) and free (buoyancy driven) convection are present. Datasets derived from ground- and helicopter-based imagery collections had correlation coefficients between ? and q? of 0.45 and 0.76, respectively. Values of q? computed from a function of ? and friction velocity u* derived from turbulent boundary layer theory had higher correlations with measured values of q? (0.84 and 0.89). This research may be applicable to the problem of calculating losses of heat from the ocean to the atmosphere during high-latitude cold-air outbreaks because it does not require the information typically needed to compute sensible, evaporative, and thermal radiation energy losses to the atmosphere.

Garrett, A.; Kurzeja, R.; Villa-Aleman, E.; Bollinger, J.

2013-01-01

301

Eddy covariance flux measurements of gaseous elemental mercury using cavity ring-down spectroscopy.  

PubMed

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 of 1309 ng m(-2) h(-1). This study demonstrated that a CRDS system can be used to measure GEM fluxes over Hg-enriched areas, with a conservative detection limit estimate of 32 ng m(-2) h(-1). PMID:25608027

Pierce, Ashley M; Moore, Christopher W; Wohlfahrt, Georg; Hörtnagl, Lukas; Kljun, Natascha; Obrist, Daniel

2015-02-01

302

The Sensitivity of Latent Heat Flux to Changes in the Radiative Forcing: A Framework for Comparing Models and Observations  

E-print Network

A climate model must include an accurate surface physics scheme in order to examine the interactions between the land and atmosphere. Given an increase in the surface radiative forcing, the sensitivity of latent heat flux ...

Winter, Jonathan (Jonathan Mark)

303

Diurnal Variations of Energetic Particle Radiation Dose Measured by the Mars Science Laboratory Radiation Assessment Detector  

NASA Astrophysics Data System (ADS)

The Radiation Assessment Detector (RAD) on board the Mars Science Laboratory (MSL) rover Curiosity has collected data on the interplanetary radiation environment during cruise from Earth to Mars and at the surface of Mars since its landing in August 2012. RAD's particle detection capabilities are achieved with a solid-state detector (SSD) stack (A, B, C), a CsI(Tl) scintillator (D), and a plastic scintillator (E) for neutron detection. The D and E detectors are surrounded by an anticoincidence shield (F), also made of plastic scintillator. All scintillators are optically coupled to silicon diodes which convert scintillation light to electrons. RAD is capable of measuring both Galactic Cosmic Rays (GCRs) thought to be produced by supernovae outside the heliosphere and Solar Energetic Particles (SEPs). GCRs are relativistic particles (100 MeV/nuc to >10 GeV/nuc) composed of roughly 89% protons, 10% alpha particles (He), and 1% heavier nuclei [1]. Because of their high energies and continuous nature, GCRs are the dominant source of background radiation at the Martian surface, and are responsible for the production of secondary particles (notably neutrons) via complex interactions in the atmosphere and regolith. SEPs are produced by coronal mass ejections. These intermittent storms are most likely to occur near solar maximum and typical fluxes are dominated by protons with energies lower than 100 MeV/nuc. Unlike the GCR flux, the SEP flux can vary by five or more orders of magnitude over timescales of a day. Even under a constant flux of energetic particle radiation at the top of the atmosphere, the radiation dose at the surface should vary as a function of surface elevation [2]. This variation is directly related to the change in the shielding provided by the total atmospheric mass column, which is to a very good approximation directly related to surface pressure. Thus, the flux of primary energetic particles should increase with altitude, all other things being equal. At present, MSL has been at a nearly constant altitude of ~-4.4 km MOLA so that no elevation-induced changes are expected and none have been observed. However, any process that changes the column mass of atmosphere should change the dose at the surface. On Mars there are two major processes that substantially change column atmospheric mass. The first is the seasonal condensation cycle during which ~25% of the dominant atmospheric constituent (CO2) condenses onto the winter pole. This seasonal signal is very strong and has been observed by surface pressure measurements from the Viking Landers up through MSL [3,4]. The second major process is related to the thermal tide. The direct heating of the Martian atmosphere by the Sun produces global scale waves that redistribute mass [5]. The two most dominant tidal modes are the diurnal and semidiurnal tide. Together, the thermal tide can produce a variation of 10-15% over a Martian day (sol). Here, we report on the dose measured by the RAD E detector and the variation of this dose over the diurnal cycle. Further, we show that the variation in the E dose rate is very likely due to the variation of column mass, as measured by the pressure sensor on the Rover Environmental Monitoring Station (REMS), driven by the thermal tide. While changes in dose were expected from changes in altitude or season, the discovery of a diurnal variation was not anticipated, although it should have been reasonably expected in hindsight.

Rafkin, Scot; Zeitlin, Cary; Ehresmann, Bent; Köhler, Jan; Guo, Jingnan; Kahanpää, Henrik; Hassler, Don; -Gomez, Javier E.; Wimmer-Schweingruber, Robert; Brinza, David; Böttcher, Stephan; Böhm, Eckhard; Burmeister, Sonka; Martin, Cesar; Müller-Mellin, Robert; Appel, Jan; Posner, Arik; Reitz, Gunter; Kharytonov, Aliksandr; Cucinotta, Francis

2013-04-01

304

New Heat Transfer Correlation for an HCCI Engine Derived from Measurements of Instantaneous Surface Heat Flux  

Microsoft Academic Search

An experimental study has been carried out to provide qualitative and quantitative insight into gas to wall heat transfer in a gasoline fueled Homogeneous Charge Compression Ignition (HCCI) engine. Fast response thermocouples are embedded in the piston top and cylinder head surface to measure instantaneous wall temperature and heat flux. Heat flux measurements obtained at multiple locations show small spatial

Junseok Chang; Orgun Güralp; Zoran Filipi; Dennis Assanis; Tang-Wei Kuo; Paul Najt; Rod Rask

305

Continental Shelf Research 23 (2003) 457481 A time series of benthic flux measurements from  

E-print Network

Continental Shelf Research 23 (2003) 457­481 A time series of benthic flux measurements from September 2002; accepted 3 December 2002 Abstract In situ incubation chamber measurements of benthic. Variability in nutrient (Si, PO4 2+ , NH3, NO3 � ) and trace metal (Mn, Fe (II), Cu) fluxes correlate

Burdige, David

306

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...

307

MERCURY FLUX MEASUREMENTS OVER AIR AND WATER IN KEJIMKUJIK NATIONAL PARK, NOVA SCOTIA  

E-print Network

MERCURY FLUX MEASUREMENTS OVER AIR AND WATER IN KEJIMKUJIK NATIONAL PARK, NOVA SCOTIA F. S. BOUDALA. Mercury flux measurements were conducted at two lakes and three soil sites in Kejimkujik National Park, located in the eastern Canadian province of Nova Scotia. One of the lakes had high levels of both mercury

Folkins, Ian

308

Measurement of the cosmic ray and neutrino-induced muon flux at the Sudbury neutrino observatory  

Microsoft Academic Search

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 unoscillated portion of the neutrino

B. Aharmim; S. N. Ahmed; T. C. Andersen; A. E. Anthony; N. Barros; E. W. Beier; A. Bellerive; B. Beltran; M. Bergevin; S. D. Biller; K. Boudjemline; M. G. Boulay; T. H. Burritt; B. Cai; Y. D. Chan; M. Chen; M. C. Chon; B. T. Cleveland; G. A. Cox-Mobrand; C. A. Currat; X. Dai; F. Dalnoki-Veress; H. Deng; J. Detwiler; P. J. Doe; R. S. Dosanjh; G. Doucas; P.-L. Drouin; F. A. Duncan; M. Dunford; S. R. Elliott; H. C. Evans; G. T. Ewan; J. Farine; H. Fergani; F. Fleurot; R. J. Ford; J. A. Formaggio; N. Gagnon; J. T. M. Goon; K. Graham; D. R. Grant; E. Guillian; S. Habib; R. L. Hahn; A. L. Hallin; E. D. Hallman; C. K. Hargrove; P. J. Harvey; R. Hazama; K. M. Heeger; W. J. Heintzelman; J. Heise; R. L. Helmer; R. J. Hemingway; R. Henning; A. Hime; C. Howard; M. A. Howe; M. Huang; B. Jamieson; N. A. Jelley; J. R. Klein; M. Kos; A. Krüger; C. Kraus; C. B. Krauss; T. Kutter; C. C. M. Kyba; R. Lange; J. Law; I. T. Lawson; K. T. Lesko; J. R. Leslie; I. Levine; J. C. Loach; S. Luoma; R. MacLellan; S. Majerus; H. B. Mak; J. Maneira; A. D. Marino; R. Martin; N. McCauley; A. B. McDonald; S. McGee; C. Mifflin; M. L. Miller; B. Monreal; J. Monroe; A. J. Noble; N. S. Oblath; C. E. Okada; H. M. O'Keeffe; Y. Opachich; G. D. Orebi Gann; S. M. Oser; R. A. Ott; S. J. M. Peeters; A. W. P. Poon; G. Prior; K. Rielage; B. C. Robertson; R. G. H. Robertson; E. Rollin; M. H. Schwendener; J. A. Secrest; S. R. Seibert; O. Simard; J. J. Simpson; D. Sinclair; P. Skensved; M. W. E. Smith; T. J. Sonley; T. D. Steiger; L. C. Stonehill; N. Tagg; G. Tesic; N. Tolich; T. Tsui; R. G. van de Water; B. A. Vandevender; C. J. Virtue; D. Waller; C. E. Waltham; H. Wan Chan Tseung; D. L. Wark; P. Watson; J. Wendland; J. F. Wilkerson; J. R. Wilson; J. M. Wouters; A. Wright; M. Yeh; F. Zhang; K. Zuber

2009-01-01

309

Aerosol Fluxes over Amazon Rain Forest Measured with the Eddy Covariance Method  

Microsoft Academic Search

We present measurements of vertical aerosol fluxes over the Amazon carried out on top of K34, a 50 meter high tower in the Cuieiras Reserve about 50 km north of Manaus in northern Brazil. The turbulent fluxes were measured with the eddy covariance method. The covariance of vertical wind speed from a sonic anemometer Gill Windmaster and total aerosol number

L. Ahlm; E. D. Nilsson; R. Krejci; E. M. Mårtensson; M. Vogt; P. Artaxo

2008-01-01

310

Measuring radon flux across active faults: Relevance of excavating and possibility of satellite discharges  

E-print Network

Measuring radon flux across active faults: Relevance of excavating and possibility of satellite January 2010 Keywords: Exhalation flux Radon-222 Carbon dioxide Faults Earthquake Trench a b s t r a c on the Xidatan segment of the Kunlun Fault, Qinghai Province, China, using measurement of the radon- 222

Klinger, Yann

311

FLUX MEASUREMENTS OF OZONE AND NITRIC ACID AT COASTAL AND MID-CONTINENTAL SITES  

EPA Science Inventory

A system for measuring the turbulent fluxes of ozone, nitric acid, and other gases was operated at two sites in 1994. hese direct measurements of fluxes are for comparison with those calculated for National Dry Deposition Network sites using an inferential model approach. zone fl...

312

Methodological approach to field measurement of mercury vapor flux using portable devices in a mineralized volcanic realm: Rodalquilar (SE Spain)  

NASA Astrophysics Data System (ADS)

The measurement of mercury vapor flux is a technique that has been applied to the exploration of buried sulfide deposits. This is due to the general presence of mercury in sulfide ore deposits and the mobility of released mercury gas, that is able to ascend to the surface where can be detected and measured as an indication of the deep presence of such deposits. We tried this technique as a pilot study at the Rodalquilar Valley (Almería SE Spain), where alluvial and colluvial sedimentary deposits cover epithermal veins and strongly altered volcanic rocks. We used portable analytical devices including a LUMEX RA915+ mercury vapor analyzer and an Oxford X-MET3000TXS X Ray Fluorescence multielemental device. The pilot survey consisted in measurements of mercury emissions in the alluvial and colluvial soils, using an opaque flux chamber. The usage of opaque flux chambers minimizes the effect of different sun radiation. We also dug ~ 1.5 cm (diameter) vertical holes in the sampling area to observe whether these channels allowed enhanced rates of mercury flux. The results put forward differential emissions, in particular with the measurements corresponding to 15 cm deep holes.

Higueras, Pablo; Oyarzun, Roberto; María Esbrí, José; Martínez-Coronado, Alba

2010-05-01

313

On the Relationship Between High Speed Solar Wind Streams and Radiation Belt Electron Fluxes  

NASA Technical Reports Server (NTRS)

Both past and recent research results indicate that solar wind speed has a close connection to radiation belt electron fluxes [e.g., Paulikas and Blake, 1979; Reeves et aI., 2011]: a higher solar wind speed is often associated with a higher level of radiation electron fluxes. But the relationship can be very complex [Reeves et aI., 2011]. The study presented here provides further corroboration of this viewpoint by emphasizing the importance of a global perspective and time history. We find that all the events during years 2010 and 2011 where the >0.8 MeV integral electron flux exceeds 10(exp 5) particles/sq cm/sr/s (pfu) at GEO orbit are associated with the high speed streams (HSS) following the onset of the Stream Interaction Region (SIR), with most of them belonging to the long-lasting Corotating Interaction Region (CIR). Our preliminary results indicate that during HSS events, a maximum speed of 700 km/s and above is a sufficient but not necessary condition for the > 0.8 MeV electron flux to reach 10(exp 5) pfu. But in the exception cases of HSS events where the electron flux level exceeds the 10(exp 5) pfu value but the maximum solar wind speed is less than 700 km/s, a prior impact can be noted either from a CME or a transient SIR within 3-4 days before the arrival of the HSS - stressing the importance of time history. Through superposed epoch analysis and studies providing comparisons with the CME events and the HSS events where the flux level fails to reach the 10(exp 5) pfu, we will present the quantitative assessment of behaviors and relationships of various quantities, such as the time it takes to reach the flux threshold value from the stream interface and its dependence on different physical parameters (e.g., duration of the HSS event, its maximum or average of the solar wind speed, IMF Bz, Kp). The ultimate goal is to apply what is derived to space weather forecasting.

Zheng, Yihua

2011-01-01

314

The Atmospheric Radiation Measurement (ARM) Program  

NSDL National Science Digital Library

The Atmospheric Radiation Measurement (ARM) Program is an important part of the U.S. Department of Energy's (DOE's) strategy to understand global climate change. The ARM Program has established three outdoor research sites around the world. Scientists gather and use the data from these sites to study the effects of sunlight, radiant energy, and clouds on temperatures, weather, and climate. This site has information about ARM and global warming. It has lesson plans, a question area, and an Ask a Scientist link.

2000-04-18

315

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

NASA Astrophysics Data System (ADS)

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.

Ineson, Philip; Stockdale, James

2014-05-01

316

Area-Averaged Surface Fluxes Over the Litfass Region Based on Eddy-Covariance Measurements  

NASA Astrophysics Data System (ADS)

Micrometeorological measurements (including eddy-covariance measurements of the surface fluxes of sensible and latent heat) were performed during the LITFASS-2003 experiment at 13 field sites over different types of land use (forest, lake, grassland, various agricultural crops) in a 20 × 20 km2 area around the Meteorological Observatory Lindenberg (MOL) of the German Meteorological Service (Deutscher Wetterdienst, DWD). Significant differences in the energy fluxes could be found between the major land surface types (forest, farmland, water), but also between the different agricultural crops (cereals, rape, maize). Flux ratios between the different surfaces changed during the course of the experiment as a result of increased water temperature of the lake, changing soil moisture, and of the vegetation development at the farmland sites. The measurements over grass performed at the boundary-layer field site Falkenberg of the MOL were shown to be quite representative for the farmland part of the area. Measurements from the 13 sites were composed into a time series of the area-averaged surface flux by taking into account the data quality of the single flux values from the different sites and the relative occurrence of each surface type in the area. Such composite fluxes could be determined for about 80% of the whole measurement time during the LITFASS-2003 experiment. Comparison of these aggregated surface fluxes with area-averaged fluxes from long-range scintillometer measurements and from airborne measurements showed good agreement.

Beyrich, Frank; Leps, Jens-Peter; Mauder, Matthias; Bange, Jens; Foken, Thomas; Huneke, Sven; Lohse, Horst; Lüdi, Andreas; Meijninger, Wouter M. L.; Mironov, Dmitrii; Weisensee, Ulrich; Zittel, Peter

2006-10-01

317

MEASURING CO2 FLUX OVER NORTHERN GREAT PLAINS RANGELANDS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The role of rangelands in regulating atmospheric CO2 levels is a critical issue in global climate change research. Rangelands are complex systems occupying more than 40% of the land area in the world and USA. We studied the effects of seasonal grazing on CO2 flux on small plots located on a silty ra...

318

The effect of cumulus cloud field anisotropy on solar radiative fluxes and atmospheric heating rates  

NASA Astrophysics Data System (ADS)

The effect of fair-weather cumulus cloud field anisotropy on domain average surface fluxes and atmospheric heating profiles was studied. Causes of anisotropy were investigated using a large-eddy simulation (LES) model. Cloud formation under a variety of environmental conditions was simulated and the degree of anisotropy in the output fields was calculated. Wind shear was found to be the single greatest factor in the development of both vertically tilted and horizontally stretched cloud structures. A stochastic field generation algorithm was used to produce twenty three-dimensional liquid water content fields based on the statistical properties of the LES cloud scenes. Progressively greater degrees of tilt and stretching were imposed on each of these scenes, so that an ensemble of scenes were produced for each level of distortion. The resulting scenes were used as input to a three-dimensional Monte Carlo model. Domain-average transmission, reflection, and absorption of broadband solar radiation were computed for each scene along with the average heating rate profile. Both tilt and horizontal stretching were found to significantly affect calculated fluxes, with the amount and sign of flux differences depending strongly on sun position relative to cloud distortion geometry. For nearly all solar geometries, domain-averaged fluxes and atmospheric heating rate profiles calculated using the Independent Pixel Approximation differed substantially from the corresponding three-dimensional Monte Carlo results.

Hinkelman, Laura M.

319

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

NASA Astrophysics Data System (ADS)

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 conductance and the bi-directional methanol exchange within plant canopies as governed by surface wetness and ambient methanol concentrations.

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

320

``Designing Lagrangian experiments to measure regional-scale trace gas fluxes''  

Microsoft Academic Search

Knowledge of trace gas fluxes at the land surface is essential for understanding the impact of human activities on the composition and radiative balance of the atmosphere. An ability to derive fluxes at the regional scale (on the order of 102-104 km2), at the scale of ecosystems and political borders, is crucial for policy and management responses. Lagrangian (``air mass-following'')

J. C. Lin; C. Gerbig; S. C. Wofsy; V. Y. Chow; E. Gottlieb; B. C. Daube; D. M. Matross

2007-01-01

321

Development of the Radiation Stabilized Distributed Flux Burner, Phase II Final Report  

SciTech Connect

This report covers progress made during Phase 2 of a three-phase DOE-sponsored project to develop and demonstrate the Radiation Stabilized Distributed Flux burner (also referred to as the Radiation Stabilized Burner, or RSB) for use in industrial watertube boilers and process heaters. The goal of the DOE-sponsored work is to demonstrate an industrial boiler burner with NOx emissions below 9 ppm and CO emissions below 50 ppm (corrected to 3% stack oxygen). To be commercially successful, these very low levels of NOx and CO must be achievable without significantly affecting other measures of burner performance such as reliability, turndown, and thermal efficiency. Phase 1 of the project demonstrated that sub-9 ppm NOx emissions and sub-50 ppm CO emissions (corrected to 3% oxygen) could be achieved with the RSB in a 3 million Btu/Hr laboratory boiler using several methods of NOx reduction. The RSB was also tested in a 60 million Btu/hr steam generator used by Chevron for Thermally Enhanced Oil Recovery (TEOR). In the larger scale tests, fuel staging was demonstrated, with the RSB consistently achieving sub-20 ppm NOx and as low as 10 ppm NOx. Large-scale steam generator tests also demonstrated that flue gas recirculation (FGR) provided a more predictable and reliable method of achieving sub-9 ppm NOx levels. Based on the results of tests at San Francisco Thermal and Chevron, the near-term approach selected by Alzeta for achieving low NOx is to use FGR. This decision was based on a number of factors, with the most important being that FGR has proved to be an easier approach to transfer to different facilities and boiler designs. In addition, staging has proved difficult to implement in a way that allows good combustion and emissions performance in a fully modulating system. In Phase 3 of the project, the RSB will be demonstrated as a very low emissions burner product suitable for continuous operation in a commercial installation. As such, the Phase 3 field demonstration will represent the first installation in which the RSB will be operated continuously with a sub-9 ppm guarantee.

Webb, A.; Sullivan, J.D.

1997-06-01

322

Comparison of Two Chamber Methods for Measuring Soil Trace-gas Fluxes in Bioenergy Cropping Systems  

NASA Astrophysics Data System (ADS)

Greenhouse gas emissions from soils are often measured using trace-gas flux chamber techniques without a standardized protocol, raising concerns about measurement accuracy and consistency. To address this, we compared measurements from non-steady-state non-through-flow (NTF) chambers with a non-steady-state through-flow (TF) chamber system in three bioenergy cropping systems located in Wisconsin. Additionally, we investigated the effects of NTF flux calculation method and deployment time on flux measurements. In all cropping systems, when NTF chambers were deployed for 60 min and a linear (LR) flux calculation was used, soil CO2 and N2O fluxes were, on average, 18% and 12% lower, respectively, than fluxes measured with a 15 min deployment. Fluxes calculated with the HMR method, a hybrid of non-linear and linear approaches, showed no deployment time effects for CO2 and N2O and produced 27-32% higher CO2 fluxes and 28-33% higher N2O fluxes in all crops than the LR approach with 60 min deployment. Across all crops, CO2 fluxes measured with the TF chamber system were higher by 24.4 to 84.9 mg CO2-C m-2 h-1, than fluxes measured with NTF chambers using either flux calculation method. These results suggest NTF chamber deployment time should be shortened if the LR approach is used though detection limits should be considered, and the HMR approach may be more appropriate when long deployment times are necessary. Significant differences in absolute flux values with different chamber types highlight the need for significant effort in determining the accuracy of methods or alternative flux measurement technologies. N2O fluxes with chamber deployment time for (a) all crops (switchgrass, corn, hybrid poplar) using both linear (LR) and HMR flux calculation methods, (b) each crop individually using LR approach, and (c) each crop individually using HMR approach. Given are seasonal (May-August) means + standard error. Letters indicate significant differences among deployment times (p<0.05, Tukey-Kramer test). Because there were no significant crop x deployment time interactions, significance letters are not shown in (b) and (c).

Duran, B. E.; Kucharik, C. J.

2013-12-01

323

Improved radon-flux-measurement system for uranium-tailings pile measurement  

SciTech Connect

The Pacific Northwest Laboratory (PNL) is developing cover technology for uranium mill tailings that will inhibit the diffusion of radon to the atmosphere. As part of this cover program, an improved radon flux measurement system has been developed. The radon measurement system is a recirculating, pressure-balanced, flow-through system that uses activated carbon at ambient temperatures to collect the radon. With the system, an area of 0.93 m/sup 2/ is sampled for periods ranging from 1 to 12 h. The activated carbon is removed from the radon trap and the collected radon is determined by counting the /sup 214/Bi daughter product. Development of the system included studies to determine the efficiency of activated carbon, relative calibration measurements and field measurements made during 1980 at the inactive tailings pile in Grand Junction, Colorado. Results of these studies are presented.

Freeman, H.D.

1981-10-01

324

Quantitative method for measuring heat flux emitted from a cryogenic object  

DOEpatents

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.

Duncan, Robert V. (Tijeras, NM)

1993-01-01

325

Experimental Measurements of Temperature and Heat Flux in a High Temperature Black Body Cavity  

NASA Technical Reports Server (NTRS)

During hypersonic flight, high temperatures and high heat fluxes are generated. The Flight Loads Laboratory (FLL) at Dryden Flight Research Center (DFRC) is equipped to calibrate high heat fluxes up to 1100 kW/sq m. There are numerous uncertainties associated with these heat flux calibrations, as the process is transient, there are expected to be interactions between transient conduction, natural and forced convection, radiation, and possibly an insignificant degree of oxidation of the graphite cavity. Better understanding, of these mechanisms during the calibration process, will provide more reliable heat transfer data during either ground testing or flight testing of hypersonic vehicles.

Abdelmessih, Amanie N.

1998-01-01

326

Aerosol Fluxes over Amazon Rain Forest Measured with the Eddy Covariance Method  

NASA Astrophysics Data System (ADS)

We present measurements of vertical aerosol fluxes over the Amazon carried out on top of K34, a 50 meter high tower in the Cuieiras Reserve about 50 km north of Manaus in northern Brazil. The turbulent fluxes were measured with the eddy covariance method. The covariance of vertical wind speed from a sonic anemometer Gill Windmaster and total aerosol number concentration from a condensation particle counter (CPC) TSI 3010 provided the total number flux (diameter >0.01 ?m). The covariance of vertical wind speed and size resolved number concentrations from an optical particle counter (OPC) Grimm 1.109 provided size resolved number fluxes in 15 bins from 0.25 ?m to 2.5 ?m diameter. Additionally fluxes of CO2 and H2O were derived from Li-7500 observations. The observational period, from early March to early August, includes both wet and dry season. OPC fluxes generally show net aerosol deposition both during wet and dry season with the largest downward fluxes during midday. CPC fluxes show different patterns in wet and dry season. During dry season, when number concentrations are higher, downward fluxes clearly dominate. In the wet season however, when number concentrations are lower, our data indicates that upward and downward fluxes are quite evenly distributed during course of a day. On average there is a peak in upward flux during late morning and another peak during the afternoon. Since the OPC fluxes in the same time show net deposition, there is an indication of net source of primary aerosol particles with diameters between 10 and 250 nm emitted from the rain forest. Future data analysis will hopefully shed light on origin and formation mechanism of these particles and thus provide a deeper insight in the rain forest - atmosphere interactions. The aerosol flux measurements were carried out as a part of the AMAZE project in collaboration with University of Sao Paulo, Brazil, and financial support was provided by Swedish International Development Cooperation Agency (SIDA).

Ahlm, L.; Nilsson, E. D.; Krejci, R.; Mårtensson, E. M.; Vogt, M.; Artaxo, P.

2008-12-01

327

Atmospheric Radiation Measurement Program - unmanned aerospace vehicle: The follow-on phase  

SciTech Connect

Unmanned Aerospace Vehicle (UAV) demonstration flights (UDF) are designed to provide an early demonstration of the scientific utility of UAVs by using an existing UAV and instruments to measure broadband radiative flux profiles under clear sky conditions. UDF is but the first of three phases of ARM-UAV. The second phase significantly extends both the UAV measurement techniques and the available instrumentation to allow both multi-UAV measurements in cloudy skies and extended duration measurements in the tropopause. These activities build naturally to the third and final phase, that of full operational capability, i.e., UAVs capable of autonomous operations at 20-km altitudes for multiple days with a full suite of instrumentation for measuring radiative flux, cloud properties, and water vapor profiles.

Vitko, J. Jr. [Sandia National Labs., Livermore, CA (United States)

1995-04-01

328

A fast gauge for energy flux density measurement  

NASA Astrophysics Data System (ADS)

Herein, the design and characterization of a fast energy flux density gauge are described. The gauge is based on a thermoelectrical pair with the junction made of a thin layer of silver. High absorptivity is attained by an electrolytic deposit of platinum black on the silver coat. Dynamic calibration gives a response time below 100 microsec. Computer methods to obtain the energy flux density from temperature-time history were evaluated. The results of the tests performed with igniters of pelleted boron/potassium nitrate and black powder, used in solid propellant ignition, are shown. The gauge developed can be applied to fast processes which require small response time. The gauge does not need previous calibration, it is resistant to vibrations and accelerations, and, at the same time, it is small in size, economical, and easy to build.

Garcia, Jorge; Bana de Schor, Beatriz

1990-01-01

329

Computation of Solar Radiative Fluxes by 1D and 3D Methods Using Cloudy Atmospheres Inferred from A-train Satellite Data  

NASA Technical Reports Server (NTRS)

The main point of this study was to use realistic representations of cloudy atmospheres to assess errors in solar flux estimates associated with 1D radiative transfer models. A scene construction algorithm, developed for the EarthCARE satellite mission, was applied to CloudSat, CALIPSO, and MODIS satellite data thus producing 3D cloudy atmospheres measuring 60 km wide by 13,000 km long at 1 km grid-spacing. Broadband solar fluxes and radiances for each (1 km)2 column where then produced by a Monte Carlo photon transfer model run in both full 3D and independent column approximation mode (i.e., a 1D model).

Barker, Howard W.; Kato, Serji; Wehr, T.

2012-01-01

330

Bunch Length Measurements using Coherent Radiation  

SciTech Connect

The accelerating field that can be obtained in a beam-driven plasma wakefield accelerator depends on the current of the electron beam that excites the wake. In the E-167 experiment, a peak current above 10 kA will be delivered at a particle energy of 28 GeV. The bunch has a length of a few ten micrometers and several methods are used to measure its longitudinal profile. Among these, autocorrelation of coherent transition radiation (CTR) is employed. The beam passes a thin metallic foil, where it emits transition radiation. For wavelengths greater than the bunch length, this transition radiation is emitted coherently. This amplifies the long-wavelength part of the spectrum. A scanning Michelson interferometer is used to autocorrelate the CTR. However, this method requires the contribution of many bunches to build an autocorrelation trace. The measurement is influenced by the transmission characteristics of the vacuum window and beam splitter. We present here an analysis of materials, as well as possible layouts for a single shot CTR autocorrelator.

Ischebeck, Rasmus; Barnes, Christopher; Blumenfeld, Ian; Decker, Franz-Josef; Hogan, Mark; Iverson, Richard H.; Krejcik, Patrick; Siemann, Robert H.; Walz, Dieter; /SLAC; Kirby, Neil; /Stanford U., Phys. Dept.; Clayton, Chris; Huang, Chengkun; Johnson, Devon K.; Lu, Wei; Marsh, Ken; /UCLA; Deng, Suzhi; Oz, Erdem; /Southern California U.

2005-06-24

331

Measuring ionizing radiation with a mobile device  

NASA Astrophysics Data System (ADS)

In cases of nuclear disasters it is desirable to know one's personal exposure to radioactivity and the related health risk. Usually, Geiger-Mueller tubes are used to assess the situation. Equipping everyone with such a device in a short period of time is very expensive. We propose a method to detect ionizing radiation using the integrated camera of a mobile consumer device, e.g., a cell phone. In emergency cases, millions of existing mobile devices could then be used to monitor the exposure of its owners. In combination with internet access and GPS, measured data can be collected by a central server to get an overview of the situation. During a measurement, the CMOS sensor of a mobile device is shielded from surrounding light by an attachment in front of the lens or an internal shutter. The high-energy radiation produces free electrons on the sensor chip resulting in an image signal. By image analysis by means of the mobile device, signal components due to incident ionizing radiation are separated from the sensor noise. With radioactive sources present significant increases in detected pixels can be seen. Furthermore, the cell phone application can make a preliminary estimate on the collected dose of an individual and the associated health risks.

Michelsburg, Matthias; Fehrenbach, Thomas; Puente León, Fernando

2012-02-01

332

Evaluating the value of enhanced atmospheric measurements and models to improve interpretation of flux data  

NASA Astrophysics Data System (ADS)

Gaps in trace-gas fluxes measured via eddy-covariance occur for many reasons. One of these reasons is that many sites are equipped with flux measurements at only one height above the canopy. The optimal height for detecting fluxes, however, changes in time with the environmental conditions at the site. In some instances, a measurement such as friction velocity (u*) can indicate when data should be eliminated. When u* is high however, data are not eliminated but sensors may not actually be detecting fluxes from the ecosystem of interest. This latter scenario often occurs at night when the surface layer of the atmosphere is stably stratified and may be lower than the tower measurement height. Here, we propose that increased information about atmospheric structure near the surface and the processes occurring within the surface layer can inform an improved interpretation of fluxes as measured at a single point above the canopy. We adjusted and tuned the Advanced Canopy-Atmosphere-Soil Algorithm (ACASA) for modeling a California mediterranean oak savanna, the Tonzi AmeriFlux Site near Ione, CA, USA. We fused datasets of wind profiles, temperature profiles, and fluxes from standard eddy-covariance measurements, radiosonde launches, and upward-facing LIDAR measurements to determine surface layer depth and then drive ACASA from the top of the surface layer. By combining modeled profiles of the surface layer with flux measurements above and below the canopy, we were able to better interpret when flux signals were true indications of canopy processes, and the sources of flux anomalies.

Osuna, J. L.; Wharton, S.; Falk, M.; Pyles, R. D.; Ma, S.; Baldocchi, D. D.

2013-12-01

333

Measurement of auroral Birkeland currents and energetic particle fluxes  

Microsoft Academic Search

A rocket-borne experiment containing a vector magnetometer and a set of ; charged-particle detectors was launched from Poker Flat, Alaska, at 2217 LT on ; February 13, 1971, over a single auroral arc. Particle data in the energy range ; 0.5-20 kev, obtained during part of the night, show a peak incident flux of 4x10\\/; sup 7\\/ el\\/cm² sec ster

P. A. Cloutier; B. R. Sandel; H. R. Anderson; P. M. Pazich; R. J. Spiger

1973-01-01

334

Soil CO 2 flux measurements in volcanic and geothermal areas  

Microsoft Academic Search

The accumulation chamber methodology allows one to obtain reliable values of the soil CO2 flux, ?soil CO2, in the range 0.2 to over 10?000 g m?2 d?1, as proven by both laboratory tests and field surveys in geothermal and volcanic areas. A strong negative correlation is observed between ??soil CO2\\/?t and ?Patm\\/?t. Maps of classes of log ?soil CO2 for

G. Chiodini; R. Cioni; M. Guidi; B. Raco; L. Marini

1998-01-01

335

Long-term isoprene flux measurements above a northern hardwood forest  

Microsoft Academic Search

We report continuous whole canopy isoprene emission fluxes from a northern hardwood forest in Michigan for the 1999–2002 growing seasons. The eddy covariance fluxes of isoprene, CO2, latent heat, and sensible heat are presented along with an analysis of the seasonal and year-to-year variations. Measurements were made in collaboration with the AmeriFlux site located at the University of Michigan Biological

Shelley Pressley; Brian Lamb; Hal Westberg; Julia Flaherty; Jack Chen; Christoph Vogel

2005-01-01

336

The measurement of absolute thermal neutron flux using liquid scintillation counting techniques  

E-print Network

factor for flux depression due to a neutron absorbing indium foil. Later Tittle (2, 3) studied the same problem and extended Bothe's re- sults to a more useful form. To minimize flux depression and also the self absorption of the induced radioactivity... of the foil, the use of very thin foils has become a standard practice . Greenfield et al . (4) have described in detail the conventional techniques for measuring absolute thermal neutron flux with thin indium foils. The authors discuss the importance...

Walker, Jack Vernon

2012-06-07

337

Novel Surface Thermocouple Probes for Divertor Heat Flux Measurement  

NASA Astrophysics Data System (ADS)

An array of novel surface thermocouple probes have been installed and tested in the outer divertor of Alcator C-Mod. These sensors can, in principle, record divertor surface temperatures with fast time response (? >= 10 ? sec), allowing a direct estimate of the plasma heat flux to be inferred. The design is an adaptation of a commercially available device(``The Self-Renewing Thermocouple,'' Nanmac Corp., Framingham, MA), employing a coaxial-like geometry with a single tungsten-rhenium ribbon wire embedded inside a 6.35 mm diameter molybdenum rod. Various prototypes were tested, including probes with flush and 5^circ angles with respect to the divertor surface, and probes with and without protective surface coatings. Typical surface temperature rises are ~ 300-700 ^circC, corresponding to signals of ~ 3-9 mV. RC filters with 10 ms time constants are used to reduce noise introduced by the plasma environment. The surface temperature corresponding to typical RMS noise levels is ~ 25 ^circC. Using a one-dimensional, semi-infinite slab model, parallel heat fluxes in the range of 50-500 MW/m^2 are estimated. A comparison with heat flux estimates from Langmuir probes located adjacent to the thermocouple array will be presented. Supported by U.S. DOE Contract No. DE-AC02-78ET51013

Gangadhara, S.; Labombard, B.; Lipschultz, B.; Pierce, N.

1996-11-01

338

Fluence measurements employing iodide/iodate chemical actinometry as applied to upper-room germicidal radiation.  

PubMed

To measure the fluence distribution in the upper room of a facility equipped with germicidal UV lamps a method has been developed utilizing iodide/iodate chemical actinometry together with spherical (1 cm) quartz irradiation chambers. The use of spherical vessels allows radiation from essentially all directions to be measured. Such a measurement allows an estimate of the radiation flux at a given point in space, i.e. the fluence rate. When a battery of spheres located at various points in a room are simultaneously irradiated, a measure of the fluence distribution can be obtained. The use of the iodide/iodate chemical actinometer is uniquely qualified to measure germicidal UV radiation. The purpose of this report is to provide details on how this system can be used to measure fluence rates. In particular, it describes how a hand-held colorimeter can be used to measure the absorbance changes in irradiated spheres. PMID:23668319

Rahn, Ronald O

2013-01-01

339

Future radiation measurements in low Earth orbit  

NASA Technical Reports Server (NTRS)

The first Long Duration Exposure Facility (LDEF) mission has demonstrated the value of the LDEF concept for deep surveys of the space radiation environment. The kinds of measurements that could be done on a second LDEF mission are discussed. Ideas are discussed for experiments which: (1) capitalize on the discoveries from LDEF 1; (2) take advantage of LDEF's unique capabilities; and (3) extend the investigations begun on LDEF 1. These ideas have been gleaned from investigators on LDEF 1 and others interested in the space radiation environment. They include new approaches to the investigation of Be-7 that was discovered on LDEF 1, concepts to obtain further information on the ionic charge state of cosmic rays and other energetic particles in space and other ideas to extend the investigations begun on LDEF 1.

Adams, James H., Jr.

1993-01-01

340

Far field and energy flux caused by a radiating source in an anisotropic medium  

NASA Astrophysics Data System (ADS)

The Lighthill-Giles (1960, 1978), method is extended to evaluate the far field resulting from a moving radiating source in an anisotropic and dispersive medium, and the result thus obtained has a retardation interpretation. The radiation energy flux derived from the J-E method, only after a modification resulting from anisotropy of the medium and a correction factor resulting from retardation, is found to be compatible with that directly calculated from the far field, provided interference may be neglected. While the interference, which arises from the mixed product of any two far-field terms of different wave vectors, is demonstrated to be completely null in a uniaxial medium for a stationary source, it is shown to exist in a gyrotropic magnetoplasma, and the total Poynting vector could be substantially nonradial in certain special cases.

Lai, H. M.; Chan, P. K.

1986-06-01

341

Measurement of the Cosmic Ray and Neutrino-Induced Muon Flux at the Sudbury Neutrino Observatory  

SciTech Connect

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}.

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

342

Effect of aerosols and NO2 concentration on ultraviolet actinic flux near Mexico City during MILAGRO: Measurements and model calculations  

SciTech Connect

Ultraviolet (UV) actinic ?uxes (AF) measured with three Scanning Actinic Flux Spectroradiometers (SAFS) are compared with the Tropospheric Ultraviolet-Visible (TUV) model v.5 in order to assess the effects of aerosols and NO2 concentrations on the radiation. Measurements were made during the MILAGRO campaign near Mexico City in March 2006, at a ground-based station near Mexico City (the T1 supersite) and from the NSF/NCAR C-130 aircraft. At the surface, measurements are typically smaller by up to 25 % in the morning, 10% at noon, and 40% in the afternoon, than actinic flux modeled for clean, cloud-free conditions. When measurements of PBL height, NO2 concentration and aerosols optical properties are included in the model, the agreement improves to within ±10% in the morning and afternoon, and ±3% at noon. Based on daily averages, aerosols account for 68%, NO2 for 25%, and residual uncertainties for 7% of these AF reductions observed at the surface. Several overpasses from the C-130 aircraft provided the opportunity to examine the actinic flux perturbations aloft, and also show better agreement with the model when aerosol and NO2 effects are included above and below the flight altitude. TUV model simulations show that the vertical structure of the actinic flux is sensitive to the choice of the aerosol single scattering albedo (SSA) at UV wavelengths. Typically, aerosols caused enhanced AF above the PBL and reduced AF near the surface. However, for highly scattering aerosols (SSA > 0.95), enhancements can penetrate well into the PBL, while for strongly absorbing aerosols (SSA<0.7) reductions in AF are computed in the free troposphere as well as in the PBL. Additional measurements of the SSA at these wavelengths are needed to better constrain the effect of aerosols on the vertical structure of the actinic flux.

Palancar, Gustavo G.; Lefer, Barry; Hall, Samual R.; Shaw, William J.; Corr, Chelsea A.; Herndon, Scott C.; Slusser, J. R.; Madronich, Sasha

2013-01-24

343

Derivation of Surface Net Radiation at the Valencia Anchor Station from Top of the Atmosphere Gerb Fluxes by Means of Linear Models and Neural Networks  

NASA Astrophysics Data System (ADS)

In this work, Linear Models (LM) and Artificial Neural Networks (ANN) have been developed to estimate net radiation (RN) at the surface. The models have been developed and evaluated by using the synergy between Geostationary Earth Radiation Budget (GERB-1) and Spinning Enhanced Visible and Infrared Imager (SEVIRI) data, both instruments onboard METEOSAT-9, and ``in situ'' measurements. The data used in this work, corresponding to August 2006 and June to August 2007, proceed from Top of the Atmosphere (TOA) broadband fluxes from GERB-1, every 15 min, and from net radiation at the surface measured, every 10 min, at the Valencia Anchor Station (VAS) area, having measured independently the shortwave and the longwave radiation components (downwelling and upwelling) for different land uses and land cover. The adjustment of both temporal resolutions for the satellite and in situ data was achieved by linear interpolation that showed less standard deviation than the cubic one. The LMs were developed and validated by using satellite TOA RN and ground station surface RN measurements, only considering cloudy free days selected from the ground data. The ANN model was developed both for cloudy and cloudy-free conditions using seven input variables selected for the training/validation sets, namely, hour, day, month, surface RN, solar zenith angle and TOA shortwave and longwave fluxes. Both, LMs and ANNs show remarkably good agreement when compared to surface RN measurements. Therefore, this methodology can be successfully applied to estimate RN at surface from GERB/SEVIRI data.

Geraldo Ferreira, A.; Lopez-Baeza, Ernesto; Velazquez Blazquez, Almudena; Soria-Olivas, Emilio; Serrano Lopez, Antonio J.; Gomez Chova, Juan

2012-07-01

344

A comparison of six methods for measuring soil-surface carbon dioxide fluxes  

NASA Astrophysics Data System (ADS)

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%.

Norman, J. M.; Kucharik, C. J.; Gower, S. T.; Baldocchi, D. D.; Crill, P. M.; Rayment, M.; Savage, K.; Striegl, R. G.

1997-12-01

345

A comparison of six methods for measuring soil-surface carbon dioxide fluxes  

USGS Publications Warehouse

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%.

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

346

Charged Particle Measurements on Mars and during Cruise with the Radiation Assessment Detector (MSL/RAD)  

NASA Astrophysics Data System (ADS)

The Radiation Assessment Detector (RAD), part of the Mars Science Laboratory (MSL), has been successfully measuring the energetic particle radiation on the Martian surface since the landing of the Curiosity rover in Gale crater. Furthermore, RAD was already operating for large parts of the ~250-day cruise to Mars, measuring the radiation environment inside the spacecraft. Detailed knowledge of particle-type-dependent energy spectra is important for several reasons. E.g., for one measured differential particle fluxes can be used to validate and evaluate transport models currently used to estimate the radiation exposure on the Martian surface. Another important point of knowing the energy spectra of individual ion species is their differing biological effectiveness in terms of assessing radiation exposure risks for future manned missions to Mars. Here, we will present differential fluxes for different ion species, both for the cruise and the surface phase. As the energy range of these spectra is limited by the maximum energy with that a particle can stop in one of RAD's detectors, we will show integral fluxes for energies above these upper limits where the total energy of the detected particle is not known.

Ehresmann, B.; Hassler, D.; Zeitlin, C. J.; Wimmer-Schweingruber, R. F.; Appel, J. K.; Brinza, D.; Burmeister, S.; Boehm, E.; Boettcher, S.; Guo, J.; Kohler, J.; Lohf, H.; Martin-Garcia, C.; Rafkin, S. C.; Reitz, G.

2013-12-01

347

Field measurement of small ozone fluxes to snow, wet bare soil, and lake water  

Microsoft Academic Search

Eddy-correlation measurements over snow, wet bare soil, and lake water indicate very small vertical ozone fluxes. Adjustments to the small vertical fluxes are needed to take into account the effect of mean Stefan flow associated with evaporation at the surface and the effects of correlation between density variations and vertical wind fluctuations. For snow, the residual resistance calculated for the

M. L. Wesely; D. R. Cook; R. M. Williams

1981-01-01

348

Balloon-borne measurements of the ultraviolet flux in the Arctic stratosphere during winter  

NASA Technical Reports Server (NTRS)

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).

Schiller, Cornelius; Mueller, Martin; Klein, Erich; Schmidt, Ulrich; Roeth, Ernst-Peter

1994-01-01

349

Eddy covariance flux measurements of biogenic VOCs during ECHO 2003 using proton transfer reaction mass spectrometry  

NASA Astrophysics Data System (ADS)

Within the framework of the AFO 2000 project ECHO, two PTR-MS instruments were operated in combination with sonic anemometers to determine biogenic VOC fluxes from a mixed deciduous forest site in North-Western Germany. The measurement site was characterised by a forest of inhomogeneous composition, complex canopy structure, limited extension in certain wind directions and frequent calm wind conditions during night time. The eddy covariance (EC) technique was applied since it represents the most direct flux measurement approach on the canopy scale and is, therefore, least susceptible to these non-ideal conditions. A specific flux calculation method was used to account for the sequential multi-component PTR-MS measurements and allowing an individual delay time adjustment as well as a rigorous quality control based on cospectral analysis. The validated flux results are consistent with light and temperature dependent emissions of isoprene and monoterpenes from this forest, with average daytime emissions of 0.94 and 0.3µg m-2s-1, respectively. Emissions of methanol reached on average 0.087µg m-2s-1 during daytime, but fluxes were too small to be detected during night time. Upward fluxes of the isoprene oxidation products methyl vinyl ketone (MVK) and methacrolein (MACR) were also found, being two orders of magnitude lower than those of isoprene. Calculations with an analytical footprint model indicate that the observed isoprene fluxes correlate with the fraction of oaks within the footprints of the flux measurement.

Spirig, C.; Neftel, A.; Ammann, C.; Dommen, J.; Grabmer, W.; Thielmann, A.; Schaub, A.; Beauchamp, J.; Wisthaler, A.; Hansel, A.

2005-02-01

350

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...

351

Two years of continuous CO 2 eddy-flux measurements over a Danish beech forest  

Microsoft Academic Search

As part of the EUROFLUX network a long-term monitoring station for fluxes of CO2 and water vapour has been established in an 80-year old beech forest in Denmark. The station has been in continuous operation since June 1996 and will be so at least to the end of 2002. A primary goal of EUROFLUX is to combine flux measurements on

K Pilegaard; P Hummelshøj; N. O Jensen; Z Chen

2001-01-01

352

Measurement of advective soil gas flux: Results of field and laboratory experiments with CO2  

SciTech Connect

We modified our multi-channel, steady-state flow-through (SSFT), soil-CO2 flux monitoring system to include an array of inexpensive pyroelectric non-dispersive infrared detectors for full-range (0-100%) coverage of CO2 concentrations without dilution, and a larger-diameter vent tube. We then conducted field testing of this system from late July through mid-September 2010 at the Zero Emissions Research and Technology (ZERT) project site located in Bozeman, MT, and subsequently, laboratory testing at the Pacific Northwest National Laboratory (PNNL) in Richland, WA using a flux bucket filled with dry sand. In the field, an array of twenty-five SSFT and three non-steady-state (NSS) flux chambers was installed in a 10x4 m area, the long boundary of which was directly above a shallow (2-m depth) horizontal injection well located 0.5 m below the water table. Two additional chambers (one SSFT and one NSS) were installed 10 m from the well for background measurements. Volumetric soil moisture sensors were installed at each SSFT chamber to measure mean levels in the top 0.15 m of soil. A total flux of 52 kg CO2 d-1 was injected into the well for 27 d and the efflux from the soil was monitored by the chambers before, during, and for 27 d after the injection. Overall, the results were consistent with those from previous years, showing a radial efflux pattern centered on a known “hot spot”, rapid responses to changes in injection rate and wind power, evidence for movement of the CO2 plume during the injection, and nominal flux levels from the SSFT chambers that were up to 6-fold higher than those measured by adjacent NSS chambers. Soil moisture levels varied during the experiment from moderate to near saturation with the highest levels occurring consistently at the hot spot. The effects of wind on measured flux were complex and decreased as soil moisture content increased. In the laboratory, flux bucket testing with the SSFT chamber showed large measured-flux enhancement due to the Venturi effect on the chamber vent, but an overall decrease in measured flux when wind also reached the sand surface. Flux-bucket tests at a high flux (comparable to that at the hot spot) also showed that the measured flux levels increase linearly with the chamber-flushing rate until the actual level is reached. At the SSFT chamber-flushing rate used in the field experiment the measured flux in the laboratory was only about a third of the actual flux. The ratio of measured to actual flux increased logarithmically as flux decreased, and reached parity at low levels typical of diffusive flux systems. Taken together, our results suggest that values for advective CO2 flux measured by SSFT and NSS chamber systems are likely to be significantly lower than the actual values due to back pressure developed in the chamber that diverts flux from entering the chamber. Chamber designs that counteract the back pressure and also avoid large Venturi effects associated with vent tubes, such as the SSFT with a narrow vent tube operated at a high chamber-flushing rate, are likely to yield flux measurements closer to the true values.

Amonette, James E.; Barr, Jonathan L.; Erikson, Rebecca L.; Dobeck, Laura M.; Barr, Jamie L.; Shaw, Joseph A.

2013-10-01

353

Quantifying particle size and turbulent scale dependence of dust flux in the Sahara using aircraft measurements  

NASA Astrophysics Data System (ADS)

first size-resolved airborne measurements of dust fluxes and the first dust flux measurements from the central Sahara are presented and compared with a parameterization by Kok (2011a). High-frequency measurements of dust size distribution were obtained from 0.16 to 300 µm diameter, and eddy covariance fluxes were derived. This is more than an order of magnitude larger size range than previous flux estimates. Links to surface emission are provided by analysis of particle drift velocities. Number flux is described by a -2 power law between 1 and 144 µm diameter, significantly larger than the 12 µm upper limit suggested by Kok (2011a). For small particles, the deviation from a power law varies with terrain type and the large size cutoff is correlated with atmospheric vertical turbulent kinetic energy, suggesting control by vertical transport rather than emission processes. The measured mass flux mode is in the range 30-100 µm. The turbulent scales important for dust flux are from 0.1 km to 1-10 km. The upper scale increases during the morning as boundary layer depth and eddy size increase. All locations where large dust fluxes were measured had large topographical variations. These features are often linked with highly erodible surface features, such as wadis or dunes. We also hypothesize that upslope flow and flow separation over such features enhance the dust flux by transporting large particles out of the saltation layer. The tendency to locate surface flux measurements in open, flat terrain means these favored dust sources have been neglected in previous studies.

Rosenberg, Philip D.; Parker, Douglas J.; Ryder, Claire L.; Marsham, John H.; Garcia-Carreras, Luis; Dorsey, James R.; Brooks, Ian M.; Dean, Angela R.; Crosier, Jonathon; McQuaid, James B.; Washington, Richard

2014-06-01

354

Absolute beam flux measurement at NDCX-I using gold-melting calorimetry technique  

SciTech Connect

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.

Ni, P.A.; Bieniosek, F.M.; Lidia, S.M.; Welch, J.

2011-04-01

355

Comparisons of Radiative Flux Distributions from Satellite Observations and Global Models  

NASA Astrophysics Data System (ADS)

Radiative flux distributions at the top of the atmosphere (TOA) and at the surface are compared between typical data from satellite observations and from global modeling. Averages of CERES, ISCCP and SRB data-products (for the same 4-year period) represent satellite observations. Central values of IPCC-4AR output (over a 12-year period) represent global modeling. At TOA, differences are dominated by differences for cloud-effects, which are extracted from the differences between all-sky and clear-sky radiative flux products. As satellite data are considered as TOA reference, these differences document the poor representation of clouds in global modeling, especially for low altitude clouds over oceans. At the surface the differences, caused by the different cloud treatment are overlaid by a general offset. Satellite products suggest a ca 15Wm-2 stronger surface net-imbalance (and with it stronger precipitation). Since surface products of satellite and modeling are based on simulations and many assumptions, this difference has remained an open issue. BSRN surface monitoring is too short and too sparsely distributed for clear answers to provide a reliable basis for validation.

Raschke, Ehrhard; Kinne, Stefan; Wild, Martin; Stackhouse, Paul; Rossow, Bill

2014-05-01

356

Relativistic electron fluxes dropout in the outer radiation belt under different solar wind conditions  

NASA Astrophysics Data System (ADS)

In this study, we apply superposed epoch analysis to the 1.5-6.0 MeV electron flux dropout events observed on Solar, Anomalous, Magnetospheric Particle Explorer satellite for 110 magnetic storms related to coronal mass ejections (CMEs) associated with interplanetary shocks during 1998-2003, which can help to study one of the scientific objectives of the recently launched Van Allen Probe—to determine and quantify the mechanisms of the losses in the outer radiation belt. Results obtained in this paper show that the impact of high solar wind dynamic pressure (Pdy) on the magnetosphere would lead to much larger electron flux dropout than low dynamic pressure. Furthermore, it is shown that southward interplanetary magnetic field (IMF) condition can result in more significant dropout compared with northward IMF condition. In addition, the largest local dropout is caused by high Pdy with northward IMF at L˜5.1. Dropouts under high Pdy and southward IMF conditions are the largest, whereas dropouts under low Pdy and northward IMF conditions are the smallest. Our study tackles the problem of quantifying the dropouts of electrons by calculating the radiation belt content index and finding the spatial distribution of dropout and the location of maximum dropout. Another finding is that Pdy and IMF affect the dropouts in CME-driven storms. These new findings provide insight into which mechanisms play a more important role in different dropout events.

Yuan, Chongjing; Zong, Qiugang

2013-12-01

357

Measurements of suprathermal hydrogen flux in CASTOR tokamak  

NASA Astrophysics Data System (ADS)

A study of the non-equilibrium absorption of hydrogen particles by a plasma-facing absorption probe (AP) made of Group V metals in the CASTOR tokamak environment has been undertaken with the main purposes: (1) to investigate the role of nonmetallic coatings upon plasma-facing materials in D/T inventory and recycling and (2) to develop a method of the registration and diagnostic of the flux of suprathermal hydrogen. Two series of experiments were performed: with AP of Nb and of V. The absorption of suprathermal hydrogen particles coming from the tokamak plasma was investigated as a function of AP temperature, AP distance from the plasma, AP bias and of plasma pulse duration. The possibility of a reliable registration of suprathermal hydrogen was demonstrated in spite of the short plasma pulse duration and a relatively high background H 2 pressure. The composition of the hydrogen flux (molecules, atoms, ions) impinging on the tokamak walls was analyzed, including ion energy distribution.

Notkin, M. E.; Livshits, A. I.; Hron, M.; Stockel, J.

2006-10-01

358

Combination of ecosystem carbon flux measurements and remote sensing to estimate regional primary production in Iowa  

Technology Transfer Automated Retrieval System (TEKTRAN)

The objective of this study was to examine to test the relationship between net ecosystem fluxes and absorbed photosynthetically active radiation (PAR) as a method of estimating production at regional scales from field-scale data. The Soil Moisture Experiment 2005 was conducted in Walnut Creek Water...

359

Inaccuracies in soil heat flux measurement and modeling: a matter of vertical and temporal resolution?  

Microsoft Academic Search

We here demonstrate with a conceptual model of the land-atmosphere interaction and a high vertical resolution Soil Vegetation Atmosphere Transfer model that the high daily frequencies of incoming radiation play a fundamental role in the soil heat flux signal. These high frequencies remain concentrated in a very shallow layer at the surface of about 1cm, which precludes the use of

P. Gentine; D. Entekhabi

2010-01-01

360

Back-reaction of the Hawking radiation flux on a gravitationally collapsing star II: Fireworks instead of firewalls  

E-print Network

A star collapsing gravitationally into a black hole emits a flux of radiation, knowns as Hawking radiation. When the initial state of a quantum field on the background of the star, is placed in the Unruh vacuum in the far past, then Hawking radiation corresponds to a flux of positive energy radiation travelling outwards to future infinity. The evaporation of the collapsing star can be equivalently described as a negative energy flux of radiation travelling radially inwards towards the center of the star. Here, we are interested in the evolution of the star during its collapse. Thus we include the backreaction of the negative energy Hawking flux in the interior geometry of the collapsing star and solve the full 4-dimensional Einstein and hydrodynamical equations numerically. We find that Hawking radiation emitted just before the star passes through its Schwarzschild radius slows down the collapse of the star and substantially reduces its mass thus the star bounces before reaching the horizon. The area radius starts increasing after the bounce. Beyond this point our program breaks down due to shell crossing. We find that the star stops collapsing at a finite radius larger than its horizon, turns around and its core explodes. This study provides a more realistic investigation of the backreaction of Hawking radiation on the collapsing star, that was first presented in [1].

Laura Mersini-Houghton; Harald P. Pfeiffer

2014-09-05

361

A framework to utilize turbulent flux measurements for mesoscale models and remote sensing applications  

NASA Astrophysics Data System (ADS)

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 a minimum mean absolute deviation in modelled timeseries of the different land-use types with 35 W m-2 for the sensible heat flux and 50 W m-2 for the latent heat flux. Finally, a quality lagging scheme to classify the data with respect to representativeness for a given grid cell is proposed, based on an overall flux error estimate. This enables the data user to infer the uncertainty of mesoscale models and remote sensing products with respect to ground observations. Major uncertainty sources remaining are the lack of an adequate method for energy balance closure correction as well as model structure and parameter estimation, when applying the model for surfaces without flux measurements.

Babel, W.; Huneke, S.; Foken, T.

2011-05-01

362

Description of heat flux measurement methods used in hydrocarbon and propellant fuel fires at Sandia.  

SciTech Connect

The purpose of this report is to describe the methods commonly used to measure heat flux in fire applications at Sandia National Laboratories in both hydrocarbon (JP-8 jet fuel, diesel fuel, etc.) and propellant fires. Because these environments are very severe, many commercially available heat flux gauges do not survive the test, so alternative methods had to be developed. Specially built sensors include 'calorimeters' that use a temperature measurement to infer heat flux by use of a model (heat balance on the sensing surface) or by using an inverse heat conduction method. These specialty-built sensors are made rugged so they will survive the environment, so are not optimally designed for ease of use or accuracy. Other methods include radiometers, co-axial thermocouples, directional flame thermometers (DFTs), Sandia 'heat flux gauges', transpiration radiometers, and transverse Seebeck coefficient heat flux gauges. Typical applications are described and pros and cons of each method are listed.

Nakos, James Thomas

2010-12-01

363

Eddy covariance flux measurements of pollutant gases in urban Mexico City  

NASA Astrophysics Data System (ADS)

Eddy covariance (EC) flux measurements of the atmosphere/surface exchange of gases over an urban area are a direct way to improve and evaluate emissions inventories, and, in turn, to better understand urban atmospheric chemistry and the role that cities play in regional and global chemical cycles. As part of the MCMA-2003 study, we demonstrated the feasibility of using eddy covariance techniques to measure fluxes of selected volatile organic compounds (VOCs) and CO2 from a residential district of Mexico City (Velasco et al., 2005a, b). During the MILAGRO/MCMA-2006 field campaign, a second flux measurement study was conducted in a different district of Mexico City to corroborate the 2003 flux measurements, to expand the number of species measured, and to obtain additional data for evaluation of the local emissions inventory. Fluxes of CO2 and olefins were measured by the conventional EC technique using an open path CO2 sensor and a Fast Isoprene Sensor calibrated with a propylene standard. In addition, fluxes of toluene, benzene, methanol and C2-benzenes were measured using a virtual disjunct EC method with a Proton Transfer Reaction Mass Spectrometer. The flux measurements were analyzed in terms of diurnal patterns and vehicular activity and were compared with the most recent gridded local emissions inventory. In both studies, the results showed that the urban surface of Mexico City is a net source of CO2 and VOCs with significant contributions from vehicular traffic. Evaporative emissions from commercial and other anthropogenic activities were significant sources of toluene and methanol. The results show that the emissions inventory is in reasonable agreement with measured olefin and CO2 fluxes, while C2-benzenes and toluene emissions from evaporative sources are overestimated in the inventory. It appears that methanol emissions from mobile sources occur, but are not reported in the mobile emissions inventory.

Velasco, E.; Pressley, S.; Grivicke, R.; Allwine, E.; Coons, T.; Foster, W.; Jobson, B. T.; Westberg, H.; Ramos, R.; Hernández, F.; Molina, L. T.; Lamb, B.

2009-10-01

364

Eddy covariance flux measurements of pollutant gases in urban Mexico City  

NASA Astrophysics Data System (ADS)

Eddy covariance (EC) flux measurements of the atmosphere/surface exchange of gases over an urban area are a direct way to improve and evaluate emissions inventories, and, in turn, to better understand urban atmospheric chemistry and the role that cities play in regional and global chemical cycles. As part of the MCMA-2003 study, we demonstrated the feasibility of using eddy covariance techniques to measure fluxes of selected volatile organic compounds (VOCs) and CO2 from a residential district of Mexico City (Velasco et al., 2005a, b). During the MILAGRO/MCMA-2006 field campaign, a second flux measurement study was conducted in a different district of Mexico City to corroborate the 2003 flux measurements, to expand the number of species measured, and to obtain additional data for evaluation of the local emissions inventory. Fluxes of CO2 and olefins were measured by the conventional EC technique using an open path CO2 sensor and a Fast Isoprene Sensor calibrated with a propylene standard. In addition, fluxes of toluene, benzene, methanol and C2-benzenes were measured using a virtual disjunct EC method with a Proton Transfer Reaction Mass Spectrometer. The flux measurements were analyzed in terms of diurnal patterns and vehicular activity and were compared with the most recent gridded emissions inventory. In both studies, the results showed that the urban surface of Mexico City is a net source of CO2 and VOCs with significant contributions from vehicular traffic. Evaporative emissions from commercial and other anthropogenic activities were significant sources of toluene and methanol. The data show that the emissions inventory is in reasonable agreement with measured olefin and CO2 fluxes, while C2-benzenes and toluene emissions from evaporative sources are overestimated in the inventory. It appears that methanol emissions from mobile sources occur, but are not present in the mobile emissions inventory.

Velasco, E.; Pressley, S.; Grivicke, R.; Allwine, E.; Coons, T.; Foster, W.; Jobson, T.; Westberg, H.; Ramos, R.; Hernández, F.; Molina, L. T.; Lamb, B.

2009-03-01

365

Measuring diurnal cycles of plant transpiration fluxes in the Arctic with an automated clear chamber  

NASA Astrophysics Data System (ADS)

Evapotranspiration is an important greenhouse gas and a major component of the hydrological cycle, but methodological challenges still limit our knowledge of this flux. Measuring evapotranspiration is even more difficult when aiming to partition plant transpiration and soil evaporation. Information on this process for arctic systems is very limited. In order to decrease this gap, our objective was to directly measure plant transpiration in Barrow, Alaska (71.3°N 156.7°W). A commercial system allows measuring carbon soil respiration fluxes with an automated clear chamber connected to an infrared gas-analyzer (Licor 8100), and while it simultaneously measures water concentrations, it is not calibrated to measure vapor fluxes. We calibrated the clear chamber against a previously established method based on a Licor 6400 soil chamber, and we developed a code to calculate fluxes. We performed laboratory comparisons in New Mexico and field comparisons in the Arctic, suggesting that this is a valid tool for a large range of climates. In the field we found a strong correlation between the two instruments with R2 of 0.79. Even with 24 hours of daylight in the Arctic, the system captures a clear diurnal transpiration flux, peaking at 0.9 mmol m-2 s-1 and showing no flux at the lowest points. This new method should be a powerful approach for long term measurements of specific vegetation types or surface features. Such Data can also be used to help understand controls on larger scale eddy covariance tower measurements of evapotranspiration.

Cohen, L. R.; Raz Yaseef, N.; Curtis, J. B.; Rahn, T. A.; Young, J. M.; Newman, B. D.

2013-12-01

366

THE MEASURE OF RATES OF NUTRIENT FLUXES BETWEEN TAMPA BAY SEDIMENTS AND THE OVERLYING WATER COLUMN  

EPA Science Inventory

The project will measure rates of nutrient fluxes between Tampa Bay sediments and the ovrelying water column. This information has been lacking from previous nitrogen budgets for Tampa Bay, potentially hampering their accuracy and effectiveness. Refined nitrogen budgets based o...

367

Eddy covariance flux measurements of pollutant gases in urban Mexico City  

E-print Network

Eddy covariance (EC) flux measurements of the atmosphere/surface exchange of gases over an urban area are a direct way to improve and evaluate emissions inventories, and, in turn, to better understand urban atmospheric ...

Velasco, Erik

368

Atmospheric Radiation Measurement Program facilities newsletter, January 2000  

SciTech Connect

The subject of this newsletter is the ARM unmanned aerospace vehicle program. The ARM Program's focus is on climate research, specifically research related to solar radiation and its interaction with clouds. The SGP CART site contains highly sophisticated surface instrumentation, but even these instruments cannot gather some crucial climate data from high in the atmosphere. The Department of Energy and the Department of Defense joined together to use a high-tech, high-altitude, long-endurance class of unmanned aircraft known as the unmanned aerospace vehicle (UAV). A UAV is a small, lightweight airplane that is controlled remotely from the ground. A pilot sits in a ground-based cockpit and flies the aircraft as if he were actually on board. The UAV can also fly completely on its own through the use of preprogrammed computer flight routines. The ARM UAV is fitted with payload instruments developed to make highly accurate measurements of atmospheric flux, radiance, and clouds. Using a UAV is beneficial to climate research in many ways. The UAV puts the instrumentation within the environment being studied and gives scientists direct measurements, in contrast to indirect measurements from satellites orbiting high above Earth. The data collected by UAVs can be used to verify and calibrate measurements and calculated values from satellites, therefore making satellite data more useful and valuable to researchers.

Sisterson, D.L.

2000-02-16

369

Reconstruction of global atmospheric dust concentrations using dust flux measurements in paleoclimatic archives and dust model variables  

NASA Astrophysics Data System (ADS)

Aerosols are the second most potent agent affecting anthropogenic radiative forcing after greenhouse gases. However, despite some progress in the field, the uncertainty of aerosol impact on present and past climate remains much larger than for other species. The total atmospheric dust load is an important factor for the radiative budget of the atmosphere, and for the micronutrient supply to terrestrial and marine ecosystems. We have collected published dust flux (mass accumulation rate) measurements from marine sediment cores, ice cores, loess fields, and peat bogs. These measurements are interpolated to two global grids of average Holocene and Last Glacial Maximum (LGM) climatic conditions. The interpolation is performed using a kriging algorithm and its uncertainty shows regions where new measurements are most needed. We have developed a new method that combines observational dust flux measurements with dust depositional variables from climate models to reconstruct average Holocene and LGM atmospheric dust concentrations. Here we use dust simulations from two different coupled GCMs (CAM3-CCSM3 and SPRINTARS-MIROC) to give an idea of the uncertainties due to model variables. Our reconstructions give a different perspective on Holocene and LGM atmospheric dust loads from pure model simulations. The discrepancies between modeled and reconstructed dust concentrations and radiative forcing gives insights on regions and variables that may be improved in the models. In addition, this method allows to follow the temporal and spatial evolution of dust loads (and the resulting changes in radiative forcing and iron fertilization) through the glacial-interglacial transition. Top row: Interpolated Mass Accumulation Rates (MAR) for average Holocene (left column) and Last Glacial Maximum (right column) climatic conditions. The second and third row show simulated MAR from two different coupled climate models.

Lambert, F.; Rojas, M.; Gallardo, L.; Mahowald, N. M.; Takemura, T.; KUG, J.; Winckler, G.; Park, R.; Abe-Ouchi, A.

2013-12-01

370

Airborne Sunphotometer and Solar Spectral Flux Radiometer Measurements During INTEX/ITCT 2004  

NASA Technical Reports Server (NTRS)

During the period 12 July - 8 August 2004, the NASA Ames 14-channel Airborne Tracking Sunphotometer (MTS-14) and Solar Spectral Flux Radiometer (SSFR) were operated aboard a Jetstream 31 (J31) aircraft and acquired measurements during nineteen science flights (approx. 53 flight hours) over the Gulf of Maine in support of the INTEX-NA (INtercontinental chemical Transport Experiment-North America) and ITCT (Intercontinental Transport and Chemical Transformation of anthropogenic pollution) field studies. In this paper, we will present results from analyses of those data sets. AATS-14 measures the direct solar beam transmission at fourteen discrete wavelengths (354-2138 nm), and provides instantaneous measurements of aerosol optical depth (AOD) spectra and water vapor column content, in addition to vertical profiles of aerosol extinction and water vapor density during suitable aircraft ascents and descents. SSFR consists of separate nadir and zenith viewing hemispheric FOV sensors that yield measurements of up- and downwelling solar irradiance at a spectral resolution of approx. 8-12 nm over the wavelength range 300-1700 nm. The objectives of the J31-based measurements during INTEX/ITCT were to provide AOD data for the evaluation of MODIS (MODerate-resolution Imaging Spectroradiometer) and MISR (Multi-angle Imaging Spectro-Radiometer) AOD retrievals, quantify sea surface spectral albedo (which can contribute the largest uncertainty to satellite aerosol retrievals for low aerosol loading), test closure (consistency) among suborbital results, test chemical-transport models using AOD profiles, and assess regional radiative forcing by combining satellite and suborbital results. Specific J31 flight patterns were designed to achieve these objectives, and they included a mixture of vertical profiles (spiral and ramped ascents and descents) and constant altitude horizontal transects at a variety of altitudes. Additional information is included in the original extended abstract.

Russell, P. B.; Pilewski, P.; Redemann, J.; Schmid, B.; Kahn, R.; Livingston, J.; Chu, A.; Eilers, J.; Pommier, J.; Howard, S.

2005-01-01

371

Eddy Covariance Flux Measurements of Urban Aerosols During the MILAGRO Mexico City Field Campaign  

NASA Astrophysics Data System (ADS)

Expansive urban development in the fast growing number of megacities around the world raises concerns regarding the pollution levels in such sites. The Mexico City MILAGRO 2006 (Megacity Initiative: Local and Global Research Observations) field campaign was a worldwide initiative aiming to understand sources, chemical nature and evolution of pollution in one of the largest urban developments. As part of the MILAGRO campaign, urban fluxes of aerosols and related trace gases were measured near the centre of Mexico City at 42 m above street level. Aerosol concentrations (1 min. averages) and aerosol fluxes (10 Hz, selected ion monitoring) were measured with an Aerodyne quadrupole aerosol mass spectrometer operated in an alternating 30 minute mode of ambient concentrations and fluxes. The fluxes were derived using eddy covariance calculations. The aerosol flux data were supported by additional flux measurements of CO2 and a number of gas phase VOC species using a combination of techniques, including Proton Transfer Reaction Mass Spectrometry using a disjunct eddy covariance technique and GC-FID analysis of samples from a disjunct eddy accumulation sampler. Preliminary results of aerosol concentrations and flux measurements indicate that the urban landscape is a significant source of organic aerosols.

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

2007-12-01

372

Estimating regional methane surface fluxes: the relative importance of surface and GOSAT mole fraction measurements  

NASA Astrophysics Data System (ADS)

We use an ensemble Kalman filter (EnKF), together with the GEOS-Chem chemistry transport model, to estimate regional monthly methane (CH4) fluxes for the period June 2009-December 2010 using proxy dry-air column-averaged mole fractions of methane (XCH4) from GOSAT (Greenhouse gases Observing SATellite) and/or NOAA ESRL (Earth System Research Laboratory) and CSIRO GASLAB (Global Atmospheric Sampling Laboratory) CH4 surface mole fraction measurements. Global posterior estimates using GOSAT and/or surface measurements are between 510-516 Tg yr-1, which is less than, though within the uncertainty of, the prior global flux of 529 ± 25 Tg yr-1. We find larger differences between regional prior and posterior fluxes, with the largest changes in monthly emissions (75 Tg yr-1) occurring in Temperate Eurasia. In non-boreal regions the error reductions for inversions using the GOSAT data are at least three times larger (up to 45%) than if only surface data are assimilated, a reflection of the greater spatial coverage of GOSAT, with the two exceptions of latitudes >60° associated with a data filter and over Europe where the surface network adequately describes fluxes on our model spatial and temporal grid. We use CarbonTracker and GEOS-Chem XCO2 model output to investigate model error on quantifying proxy GOSAT XCH4 (involving model XCO2) and inferring methane flux estimates from surface mole fraction data and show similar resulting fluxes, with differences reflecting initial differences in the proxy value. Using a series of observing system simulation experiments (OSSEs) we characterize the posterior flux error introduced by non-uniform atmospheric sampling by GOSAT. We show that clear-sky measurements can theoretically reproduce fluxes within 10% of true values, with the exception of tropical regions where, due to a large seasonal cycle in the number of measurements because of clouds and aerosols, fluxes are within 15% of true fluxes. We evaluate our posterior methane fluxes by incorporating them into GEOS-Chem and sampling the model at the location and time of surface CH4 measurements from the AGAGE (Advanced Global Atmospheric Gases Experiment) network and column XCH4 measurements from TCCON (Total Carbon Column Observing Network). The posterior fluxes modestly improve the model agreement with AGAGE and TCCON data relative to prior fluxes, with the correlation coefficients (r2) increasing by a mean of 0.04 (range: -0.17 to 0.23) and the biases decreasing by a mean of 0.4 ppb (range: -8.9 to 8.4 ppb).

Fraser, A.; Palmer, P. I.; Feng, L.; Boesch, H.; Cogan, A.; Parker, R.; Dlugokencky, E. J.; Fraser, P. J.; Krummel, P. B.; Langenfelds, R. L.; O'Doherty, S.; Prinn, R. G.; Steele, L. P.; van der Schoot, M.; Weiss, R. F.

2013-06-01

373

Estimating regional methane surface fluxes: the relative importance of surface and GOSAT mole fraction measurements  

NASA Astrophysics Data System (ADS)

We use an ensemble Kalman filter (EnKF), together with the GEOS-Chem chemistry transport model, to estimate regional monthly methane (CH4) fluxes for the period June 2009-December 2010 using proxy dry-air column-averaged mole fractions of methane (XCH4) from GOSAT (Greenhouse gases Observing SATellite) and/or NOAA ESRL (Earth System Research Laboratory) and CSIRO GASLAB (Global Atmospheric Sampling Laboratory) CH4 surface mole fraction measurements. Global posterior estimates using GOSAT and/or surface measurements are between 510-516 Tg yr-1, which is less than, though within the uncertainty of, the prior global flux of 529 ± 25 Tg yr-1. We find larger differences between regional prior and posterior fluxes, with the largest changes (75 Tg yr-1) occurring in Temperate Eurasia. In non-boreal regions the error reductions for inversions using the GOSAT data are at least three times larger (up to 45%) than if only surface data are assimilated, a reflection of the greater spatial coverage of GOSAT, with the two exceptions of latitudes > 60° associated with a data filter and over Europe where the surface network adequately describes fluxes on our model spatial and temporal grid. We use CarbonTracker and GEOS-Chem XCO2 model output to investigate model error on quantifying proxy GOSAT XCH4 (involving model XCO2) and inferring methane flux estimates from surface mole fraction data and show similar resulting fluxes, with differences reflecting initial differences in the proxy value. Using a series of observing system simulation experiments (OSSEs) we characterize the posterior flux error introduced by non-uniform atmospheric sampling by GOSAT. We show that clear-sky measurements can theoretically reproduce fluxes within 5% of true values, with the exception of South Africa and Tropical South America where, due to a large seasonal cycle in the number of measurements because of clouds and aerosols, fluxes are within 17% and 19% of true fluxes, respectively. We evaluate our posterior methane fluxes by incorporating them into GEOS-Chem and sampling the model at the location and time of independent surface CH4 measurements from the AGAGE (Advanced Global Atmospheric Gases Experiment) network and column XCH4 measurements from TCCON (Total Carbon Column Observing Network). The posterior fluxes modestly improve the model agreement with AGAGE and TCCON data relative to prior fluxes, with the correlation coefficients (r2) increasing by a mean of 0.04 (range: -0.17, 0.23) and the biases decreasing by a mean of 0.4 ppb (range: -8.9, 8.4 ppb).

Fraser, A.; Palmer, P. I.; Feng, L.; Boesch, H.; Cogan, A.; Parker, R.; Dlugokencky, E. J.; Fraser, P. J.; Krummel, P. B.; Langenfelds, R. L.; O'Doherty, S.; Prinn, R. G.; Steele, L. P.; van der Schoot, M.; Weiss, R. F.

2012-12-01

374

Radiation field of cosmic rays measured in low Earth orbit by CR-39 detectors  

NASA Astrophysics Data System (ADS)

In low Earth orbit astronauts are exposed to a radiation field composed of galactic cosmic rays, solar particles, particles in the Earth’s radiation belts and albedo neutrons and protons from the Earth’s atmosphere. Linear Energy Transfer (LET) spectra have been measured for the STS-108, STS-112 and ISS-7S missions. Measurement of the radiation fields is based on accurate measurements of recoils and fragments produced in CR-39 detectors by cosmic ray primary and secondary protons and heavier nuclei and by secondary neutrons. The measured LET spectra were used to determine the corresponding absorbed dose and dose equivalent. Total flux of Z ? 2 was estimated and a charge spectrum was measured for STS-108 and STS-112 missions. Comparisons are made with the predictions of cosmic ray transport models.

Zhou, D.; O'Sullivan, D.; Semones, E.; Heinrich, W.

375

Radiation Field of Cosmic Rays Measured in Low Earth Orbit by CR-39 Detectors  

NASA Astrophysics Data System (ADS)

In low earth orbit (LEO) astronauts are exposed to a radiation field composed of galactic cosmic rays, solar particles, particles in the Earth's radiation belts and albedo neutrons and protons from the Earth's atmosphere. LET spectra have been measured for the STS-108, STS-112 and ISS-7S missions. Measurement of the radiation fields is based on accurate measurements of recoils produced in CR-39 detectors by cosmic ray primary and secondary protons and heavier nuclei and by secondary neutrons. The measured LET spectra were used to determine the corresponding absorbed dose and dose equivalent. Total flux of Z?2 was estimated and a charge spectrum was measured for STS-108 and STS-112 missions. Comparisons are made with the predictions of cosmic ray transport models.

Zhou, D.; O'Sullivan, D.; Semones, E.; Heinrich, W.

376

Simultaneous equatorial measurements of waves and precipitating electrons in the outer radiation belt  

NASA Astrophysics Data System (ADS)

Simultaneous wave and precipitating electron measurements near the equator in the outer radiation belt have been made from the CRRES satellite. The electron data of principal concern here were acquired in and about the loss cone with narrow angular resolution spectrometers covering the energy range 340 eV to 5 MeV. The wave data included electric field measurements spanning frequencies from 5 Hz to 400 kHz and magnetic field measurements from 5 Hz to 10 kHz. This paper presents examples in which the variations in electron fluxes in the loss cone and the wave intensities were correlated. These variations in electron flux were confined to pitch angles less than about 30 deg. The association between the flux enhancements and the waves is consistent with wave-induced pitch angle diffusion processes.

Imhof, W. L.; Robinson, R. M.; Collin, H. L.; Wygant, J. R.; Anderson, R. R.

1992-12-01

377

Annual sediment flux estimates in a tidal strait using surrogate measurements  

USGS Publications Warehouse

Annual suspended-sediment flux estimates through Carquinez Strait (the seaward boundary of Suisun Bay, California) are provided based on surrogate measurements for advective, dispersive, and Stokes drift flux. The surrogates are landward watershed discharge, suspended-sediment concentration at one location in the Strait, and the longitudinal salinity gradient. The first two surrogates substitute for tidally averaged discharge and velocity-weighted suspended-sediment concentration in the Strait, thereby providing advective flux estimates, while Stokes drift is estimated with suspended-sediment concentration alone. Dispersive flux is estimated using the product of longitudinal salinity gradient and the root-mean-square value of velocity-weighted suspended-sediment concentration as an added surrogate variable. Cross-sectional measurements validated the use of surrogates during the monitoring period. During high freshwater flow advective and dispersive flux were in the seaward direction, while landward dispersive flux dominated and advective flux approached zero during low freshwater flow. Stokes drift flux was consistently in the landward direction. Wetter than average years led to net export from Suisun Bay, while dry years led to net sediment import. Relatively low watershed sediment fluxes to Suisun Bay contribute to net export during the wet season, while gravitational circulation in Carquinez Strait and higher suspended-sediment concentrations in San Pablo Bay (seaward end of Carquinez Strait) are responsible for the net import of sediment during the dry season. Annual predictions of suspended-sediment fluxes, using these methods, will allow for a sediment budget for Suisun Bay, which has implications for marsh restoration and nutrient/contaminant transport. These methods also provide a general framework for estimating sediment fluxes in estuarine environments, where temporal and spatial variability of transport are large. ?? 2006 Elsevier Ltd. All rights reserved.

Ganju, N.K.; Schoellhamer, D.H.

2006-01-01

378

Longwave Radiative Flux Calculations in the TOVS Pathfinder Path A Data Set  

NASA Technical Reports Server (NTRS)

A radiative transfer model developed to calculate outgoing longwave radiation (OLR) and downwelling longwave, surface flux (DSF) from the Television and Infrared Operational Satellite (TIROS) Operational Vertical Sounder (TOVS) Pathfinder Path A retrieval products is described. The model covers the spectral range of 2 to 2800 cm in 14 medium medium spectral bands. For each band, transmittances are parameterized as a function of temperature, water vapor, and ozone profiles. The form of the band transmittance parameterization is a modified version of the approach we use to model channel transmittances for the High Resolution Infrared Sounder 2 (HIRS2) instrument. We separately derive effective zenith angle for each spectral band such that band-averaged radiance calculated at that angle best approximates directionally integrated radiance for that band. We develop the transmittance parameterization at these band-dependent effective zenith angles to incorporate directional integration of radiances required in the calculations of OLR and DSF. The model calculations of OLR and DSF are accurate and differ by less than 1% from our line-by-line calculations. Also, the model results are within 1% range of other line-by-line calculations provided by the Intercomparison of Radiation Codes in Climate Models (ICRCCM) project for clear-sky and cloudy conditions. The model is currently used to calculate global, multiyear (1985-1998) OLR and DSF from the TOVS Pathfinder Path A Retrievals.

Mehta, Amita; Susskind, Joel

1999-01-01

379

A scintillating fission detector for neutron flux measurements  

SciTech Connect

Neutron flux monitors are commonly used for a variety of nuclear physics applications. A scintillating neutron detector, consisting of a liquid scintillator loaded with fissionable material, has been developed, characterized, and tested in the beam line at the Los Alamos Neutron Science Center, and shows a significant improvement in neutron sensitivity compared with a conventional fission chamber. Recent research on nanocomposite-based scintillators for gamma-ray detection indicates that this approach can be extended to load nanoparticles of fissionable material into a scintillating matrix, with up to three orders of magnitude higher loading than typical fission chambers. This will result in a rugged, cost-efficient detector with high efficiency, a short signal rise time, and the ability to be used in low neutron-flux environments. Initial efforts to utilize the luminescence of uranyl oxide to eliminate the need for wavelength-shifting dyes were unsuccessful. Excitation of uranyl compounds has been reported at wavelengths ranging from 266 nm to 532 nm. However, neither the 300 nm emission of toluene, nor the 350 nm emission of PPO, nor the 410 nm emission of POPOP resulted in significant excitation of and emission by uranyl oxide. As indicated by UV/visible spectroscopy, light emitted at these wavelengths was absorbed by the colored solution. {sup 235}U remains the most attractive candidate for a fissionable scintillator, due to its high fission cross-section and lack of a threshold fission energy, but all solutions containing molecular uranium compounds will be colored, most more highly than the U{sup 6+} compounds used here. Research is therefore continuing toward the fabrication of uranium nanoparticles, in which, due to Rayleigh scattering, the coloration should be less pronounced. The characterization of the thorium-loaded liquid scintillator and the fabrication of the 100 mL detectors for use at LANSCE demonstrated the feasibility of loading fissionable material into a liquid scintillator. Analysis of beam line experiments using the thorium-loaded scintillator is underway to determine the fission event rate in the detector, for comparison with a conventional fission chamber as well as with an unloaded liquid scintillator.

Stange, Sy [Los Alamos National Laboratory; Esch, Ernst I [Los Alamos National Laboratory; Burgett, Eric A [Los Alamos National Laboratory; May, Iain [Los Alamos National Laboratory; Muenchausen, Ross E [Los Alamos National Laboratory; Taw, Felicia [Los Alamos National Laboratory; Tovesson, Fredrik K [Los Alamos National Laboratory

2010-01-01

380

Cluster electric current density measurements within a magnetic flux rope in the plasma sheet  

NASA Technical Reports Server (NTRS)

On August 22, 2001 all 4 Cluster spacecraft nearly simultaneously penetrated a magnetic flux rope in the tail. The flux rope encounter took place in the central plasma sheet, Beta(sub i) approx. 1-2, near the leading edge of a bursty bulk flow. The "time-of-flight" of the flux rope across the 4 spacecraft yielded V(sub x) approx. 700 km/s and a diameter of approx.1 R(sub e). The speed at which the flux rope moved over the spacecraft is in close agreement with the Cluster plasma measurements. The magnetic field profiles measured at each spacecraft were first modeled separately using the Lepping-Burlaga force-free flux rope model. The results indicated that the center of the flux rope passed northward (above) s/c 3, but southward (below) of s/c 1, 2 and 4. The peak electric currents along the central axis of the flux rope predicted by these single-s/c models were approx.15-19 nA/sq m. The 4-spacecraft Cluster magnetic field measurements provide a second means to determine the electric current density without any assumption regarding flux rope structure. The current profile determined using the curlometer technique was qualitatively similar to those determined by modeling the individual spacecraft magnetic field observations and yielded a peak current density of 17 nA/m2 near the central axis of the rope. However, the curlometer results also showed that the flux rope was not force-free with the component of the current density perpendicular to the magnetic field exceeding the parallel component over the forward half of the rope, perhaps due to the pressure gradients generated by the collision of the BBF with the inner magnetosphere. Hence, while the single-spacecraft models are very successful in fitting flux rope magnetic field and current variations, they do not provide a stringent test of the force-free condition.

Slavin, J. A.; Lepping, R. P.; Gjerloev, J.; Goldstein, M. L.; Fairfield, D. H.; Acuna, M. H.; Balogh, A.; Dunlop, M.; Kivelson, M. G.; Khurana, K.

2003-01-01

381

Application of an energy balance correction method for turbulent flux measurements based on buoyancy  

NASA Astrophysics Data System (ADS)

The energy imbalance in flux measurements between the atmosphere and the surface is a well-known problem, but unsolved due to the complexity of possible reasons and potential error sources. In order to provide unbiased budgets, however, eddy-covariance measurements of sensible and latent heat flux should be corrected according to the closure gap. Recent studies utilising turbulent flux data and LES models suggest that the transport of the missing turbulent flux is triggered by meso-scale circulations, not detected by eddy-covariance measurements within typical averaging intervals of 30 minutes. These motions on longer timescales are driven by buoyancy, suggesting that the missing turbulent flux is a missing buoyancy flux. Based on this assumption we present an energy balance closure correction method according to the buoyancy flux. The effects are compared with the results obtained by the commonly used correction according to the Bowen ratio (Twine et al., Agr. Forest Meteorol., 2000). We show that in general both correction methods could be applied to daytime fluxes and conditions with positive Bowen ratios. Finally the corrected turbulent fluxes are compared with different simulations of SVAT-type models for Tibetan grassland sites and a central European spruce forest site. The model performance with respect to the used data correction method is linked to the different mechanism of closing the energy balance within the model. Model validation requires energy balance closure correction in case the model relies on the energy balance equation. We conclude that mechanistic model development of turbulent flux parameterisations should recognize the recent hypotheses concerning the energy balance closure rather than fitting just to the uncorrected eddy-covariance data.

Babel, Wolfgang; Charuchittipan, Doojdao; Zhao, Peng; Biermann, Tobias; Gatzsche, Kathrin; Foken, Thomas

2014-05-01

382

Energetic ion diagnostics using neutron flux measurements during pellet injection  

SciTech Connect

Neutron measurements during injection of deuterium pellets into deuterium plasmas on the Tokamak Fusion Test Reactor (TFTR) indicate that the fractional increase in neutron emission about 0.5 msec after pellet injection is proportional to the fraction of beam-plasma reactions to total fusion reactions in the unperturbed plasma. These observations suggest three diagnostic applications of neutron measurements during pellet injection: (1) measurement of the beam-plasma reaction rate in deuterium plasmas for use in determining the fusion Q in an equivalent deuterium-tritium plasma, (2) measurement of the radial profile of energetic beam ions by varying the pellet size and velocity, and (3) measurement of the ''temperature'' of ions accelerated during wave heating. 18 refs., 3 figs.

Heidbrink, W.W.

1986-01-01

383

A flux-gradient system for simultaneous measurement of the CH4, CO2, and H2O fluxes at a lake-air interface.  

PubMed

Inland lakes play important roles in water and greenhouse gas cycling in the environment. This study aims to test the performance of a flux-gradient system for simultaneous measurement of the fluxes of water vapor, CO2, and CH4 at a lake-air interface. The concentration gradients over the water surface were measured with an analyzer based on the wavelength-scanned cavity ring-down spectroscopy technology, and the eddy diffusivity was measured with a sonic anemometer. Results of a zero-gradient test indicate a flux measurement precision of 4.8 W m(-2) for water vapor, 0.010 mg m(-2) s(-1) for CO2, and 0.029 ?g m(-2) s(-1) for CH4. During the 620 day measurement period, 97%, 69%, and 67% of H2O, CO2, and CH4 hourly fluxes were higher in magnitude than the measurement precision, which confirms that the flux-gradient system had adequate precision for the measurement of the lake-air exchanges. This study illustrates four strengths of the flux-gradient method: (1) the ability to simultaneously measure the flux of H2O, CO2, and CH4; (2) negligibly small density corrections; (3) the ability to resolve small CH4 gradient and flux; and (4) continuous and noninvasive operation. The annual mean CH4 flux (1.8 g CH4 m(-2) year(-1)) at this hypereutrophic lake was close to the median value for inland lakes in the world (1.6 g CH4 m(-2) year(-1)). The system has adequate precision for CH4 flux for broad applications but requires further improvement to resolve small CO2 flux in many lakes. PMID:25377990

Xiao, Wei; Liu, Shoudong; Li, Hanchao; Xiao, Qitao; Wang, Wei; Hu, Zhenghua; Hu, Cheng; Gao, Yunqiu; Shen, Jing; Zhao, Xiaoyan; Zhang, Mi; Lee, Xuhui

2014-12-16

384

Low Energy Electron Detector for Space Radiation Measurements  

NASA Astrophysics Data System (ADS)

Low Energy Electron Detector LEED is a miniature particle monitor for measurements in space. It is based on the MYTHEN Si-microstrip system made at Paul Scherrer Institut PSI for X-ray detection at the Synchrotron Light Source SLS. It was designed in collaboration with the European Space Agency ESA in order to provide a new instrument covering an unexplored energy range of space electrons below few tens of keV. A lack of measurements and realtime data both at low and high energies of particle as well as difficulties in radiation belts modeling are still persisting even after 40 years from their discovery. In particular the low energy electrons, up to few hundred keV are particularly poorly studied. Such electrons can shed a new light on the acceleration and trapping processes and on the dynamics of radiation belts. Measurements of electrons in wide range of energies can provide a link between hot plasma and trapped higher energy particles. The long term observations can probe and verify a coupling between Sun and Earth magnetosphere. On the spacecraft environment side, the electrons with energies of tens of keV can create radiation hazard for on-board instruments, induce spacecraft charging and increase the background in precise X-ray observations. Therefore the requirements put on monitors devoted for above studies are very demanding and often opposing. A special care in construction of LEED - the space version of MYTHEN was optimizing it for very high fluxes and harsh radiation environment. The device aims to monitor Space Weather, map planetary Radiation Belts and study hot plasmas and particle acceleration. It will detect electrons with energies from few up to few hundred keV with energy resolution of several keV. The detector is characterized by ability to deal with very high counting rate of up to 1.4 million counts per second per strip. Its core is a PSI developed radiation hard ASIC read-out chip serving for 128 detection channels. The main design features of LEED are small size and weight as well as minimized power consumption. This makes it also very beneficial for radiation detection at remote locations like peripheries of other planets of the solar system. The LEED demonstration model has been constructed and first qualification measurements with electron beams are being performed. In parallel, the radiation hardness tests of electronic components are prepared at the PSI Proton Irradiation Facility PIF to qualify its critical parts for the flight version. The full computer model of the detector was constructed using GEANT4 package from CERN. It allowed for improvement of the detector response and study background rejection methods. Development of LEED is supported by the Swiss Space Office and ESA. Future possible implementation on-board of the International Space Station and on micro-satellites is currently investigated.

Hajdas, Wojtek

385

Surface Catalysis and Oxidation on Stagnation Point Heat Flux Measurements in High Enthalpy Arc Jets  

NASA Technical Reports Server (NTRS)

Heat flux sensors are routinely used in arc jet facilities to determine heat transfer rates from plasma plume. The goal of this study is to assess the impact of surface composition changes on these heat flux sensors. Surface compositions can change due to oxidation and material deposition from the arc jet. Systematic surface analyses of the sensors were conducted before and after exposure to plasma. Currently copper is commonly used as surface material. Other surface materials were studied including nickel, constantan gold, platinum and silicon dioxide. The surfaces were exposed to plasma between 0.3 seconds and 3 seconds. Surface changes due to oxidation as well as copper deposition from the arc jets were observed. Results from changes in measured heat flux as a function of surface catalycity is given, along with a first assessment of enthalpy for these measurements. The use of cupric oxide is recommended for future heat flux measurements, due to its consistent surface composition arc jets.

Nawaz, Anuscheh; Driver, David M.; Terrazas-Salinas

2013-01-01

386

Analysis of field measurements of carbon dioxide and water vapor fluxes  

NASA Technical Reports Server (NTRS)

Analysis of the field measurements of carbon dioxide and water vapor fluxes is discussed. These data were examined in conjunction with reflectance obtained from helicopter mounted Modular Multiband Radiometer. These measurements are representative of the canopy scale (10 to 100 m)(exp 2) and provide a good basis for investigating the hypotheses/relationship potentially useful in remote sensing applications. All the micrometeorological data collected during FIFE-89 were processed and fluxes of CO2, water vapor, and sensible heat were calculated. Soil CO2 fluxes were also estimated. Employing these soil CO2 flux values, in conjunction with micrometeorological measurements, canopy photosynthesis is being estimated. A biochemical model of leaf photosynthesis was adapted to the prairie vegetation. The modeled leaf photosynthesis rates were scaled up to the canopy level. This model and a multiplicative stomatal conductance model are also used to calculate canopy conductance.

Verma, Shashi B.

1991-01-01

387

The great advances in radiation measurements.  

PubMed

The title of this banquet talk was selected to entertain conferees with recollections of major advances in dosimetry that have stimulated appetites for scientific progress. Recalling over fifty years of use of dosimetric instruments and concepts in the 1950-2000 era leads to an appreciation of many advances in solid state dosimetry, which others here know well and pursue vigorously. This author has been mainly a user, admirer, and interpreter of the fundamental methods of dose measurement. These advances have allowed ease of application in radiation protection and medical physics, for determining current routine and accidental exposures to workers, and for precise radiotherapeutic dose delivery. In more recent years, advances in identifying means of locating selective depositions of energy in various materials are providing ways of retrospectively assessing doses to tissue that were deposited many years ago. These methods also will allow development of quantitative theories of radiation damage once the lesions of interest are identified through further advances in molecular genetics. Yet, reflections on the past fifty years lead to increasing appreciation of the enormous achievements of our predecessors in the 1900-1950 period. Therefore, this presentation emphasises methods used by the author and some of his data interpretations during his 52 year career, with somc examination of the earlier origin of some of these methods. PMID:12382821

Brodsky, A

2002-01-01