WorldWideScience

Sample records for ground-based reflectance measurements

  1. Quantifying the Uncertainty in High Spatial and Temporal Resolution Synthetic Land Surface Reflectance at Pixel Level Using Ground-Based Measurements

    Science.gov (United States)

    Kong, J.; Ryu, Y.

    2017-12-01

    Algorithms for fusing high temporal frequency and high spatial resolution satellite images are widely used to develop dense time-series land surface observations. While many studies have revealed that the synthesized frequent high spatial resolution images could be successfully applied in vegetation mapping and monitoring, validation and correction of fused images have not been focused than its importance. To evaluate the precision of fused image in pixel level, in-situ reflectance measurements which could account for the pixel-level heterogeneity are necessary. In this study, the synthetic images of land surface reflectance were predicted by the coarse high-frequency images acquired from MODIS and high spatial resolution images from Landsat-8 OLI using the Flexible Spatiotemporal Data Fusion (FSDAF). Ground-based reflectance was measured by JAZ Spectrometer (Ocean Optics, Dunedin, FL, USA) on rice paddy during five main growth stages in Cheorwon-gun, Republic of Korea, where the landscape heterogeneity changes through the growing season. After analyzing the spatial heterogeneity and seasonal variation of land surface reflectance based on the ground measurements, the uncertainties of the fused images were quantified at pixel level. Finally, this relationship was applied to correct the fused reflectance images and build the seasonal time series of rice paddy surface reflectance. This dataset could be significant for rice planting area extraction, phenological stages detection, and variables estimation.

  2. Ground-based measurements of ionospheric dynamics

    Science.gov (United States)

    Kouba, Daniel; Chum, Jaroslav

    2018-05-01

    Different methods are used to research and monitor the ionospheric dynamics using ground measurements: Digisonde Drift Measurements (DDM) and Continuous Doppler Sounding (CDS). For the first time, we present comparison between both methods on specific examples. Both methods provide information about the vertical drift velocity component. The DDM provides more information about the drift velocity vector and detected reflection points. However, the method is limited by the relatively low time resolution. In contrast, the strength of CDS is its high time resolution. The discussed methods can be used for real-time monitoring of medium scale travelling ionospheric disturbances. We conclude that it is advantageous to use both methods simultaneously if possible. The CDS is then applied for the disturbance detection and analysis, and the DDM is applied for the reflection height control.

  3. Biomass burning aerosols characterization from ground based and profiling measurements

    Science.gov (United States)

    Marin, Cristina; Vasilescu, Jeni; Marmureanu, Luminita; Ene, Dragos; Preda, Liliana; Mihailescu, Mona

    2018-04-01

    The study goal is to assess the chemical and optical properties of aerosols present in the lofted layers and at the ground. The biomass burning aerosols were evaluated in low level layers from multi-wavelength lidar measurements, while chemical composition at ground was assessed using an Aerosol Chemical Speciation Monitor (ACSM) and an Aethalometer. Classification of aerosol type and specific organic markers were used to explore the potential to sense the particles from the same origin at ground base and on profiles.

  4. Observing Tsunamis in the Ionosphere Using Ground Based GPS Measurements

    Science.gov (United States)

    Galvan, D. A.; Komjathy, A.; Song, Y. Tony; Stephens, P.; Hickey, M. P.; Foster, J.

    2011-01-01

    Ground-based Global Positioning System (GPS) measurements of ionospheric Total Electron Content (TEC) show variations consistent with atmospheric internal gravity waves caused by ocean tsunamis following recent seismic events, including the Tohoku tsunami of March 11, 2011. We observe fluctuations correlated in time, space, and wave properties with this tsunami in TEC estimates processed using JPL's Global Ionospheric Mapping Software. These TEC estimates were band-pass filtered to remove ionospheric TEC variations with periods outside the typical range of internal gravity waves caused by tsunamis. Observable variations in TEC appear correlated with the Tohoku tsunami near the epicenter, at Hawaii, and near the west coast of North America. Disturbance magnitudes are 1-10% of the background TEC value. Observations near the epicenter are compared to estimates of expected tsunami-driven TEC variations produced by Embry Riddle Aeronautical University's Spectral Full Wave Model, an atmosphere-ionosphere coupling model, and found to be in good agreement. The potential exists to apply these detection techniques to real-time GPS TEC data, providing estimates of tsunami speed and amplitude that may be useful for future early warning systems.

  5. Ground-based observations coordinated with Viking satellite measurements

    International Nuclear Information System (INIS)

    Opgenoorth, H.J.; Kirkwood, S.

    1989-01-01

    The instrumentation and the orbit of the Viking satellite made this first Swedish satellite mission ideally suited for coordinated observations with the dense network of ground-based stations in northern Scandinavia. Several arrays of complementing instruments such as magnetometers, all-sky cameras, riometers and doppler radars monitored on a routine basis the ionosphere under the magnetospheric region passed by Viking. For a large number of orbits the Viking passages close to Scandinavia were covered by the operation of specially designed programmes at the European incoherent-scatter facility (EISCAT). First results of coordinated observations on the ground and aboard Viking have shed new light on the most spectacular feature of substorm expansion, the westward-travelling surge. The end of a substorm and the associated decay of a westward-travelling surge have been analysed. EISCAT measurements of high spatial and temporal resolution indicate that the conductivities and electric fields associated with westward-travelling surges are not represented correctly by the existing models. (author)

  6. Ground-based SMART-COMMIT Measurements for Studying Aerosol and Cloud Properties

    Science.gov (United States)

    Tsay, Si-Chee

    2008-01-01

    From radiometric principles, it is expected that the retrieved properties of extensive aerosols and clouds from reflected/emitted measurements by satellite (and/or aircraft) should be consistent with those retrieved from transmitted/emitted radiance observed at the surface. Although space-borne remote sensing observations cover large spatial domain, they are often plagued by contamination of surface signatures. Thus, ground-based in-situ and remote-sensing measurements, where signals come directly from atmospheric constituents, the sun, and/or the Earth-atmosphere interactions, provide additional information content for comparisons that confirm quantitatively the usefulness of the integrated surface, aircraft, and satellite data sets. The development and deployment of SMARTCOMMIT (Surface-sensing Measurements for Atmospheric Radiative Transfer - Chemical, Optical & Microphysical Measurements of In-situ Troposphere) mobile facilities are aimed for the optimal utilization of collocated ground-based observations as constraints to yield higher fidelity satellite retrievals and to determine any sampling bias due to target conditions. To quantify the energetics of the surface-atmosphere system and the atmospheric processes, SMART-COMMIT instruments fall into three categories: flux radiometer, radiance sensor and in-situ probe. In this paper, we will demonstrate the capability of SMART-COMMIT in recent field campaigns (e.g., CRYSTAL-FACE, UAE 2, BASEASIA, NAMMA) that were designed and executed to study the compelling variability in temporal scale of both anthropogenic and natural aerosols (e.g., biomass-burning smoke, airborne dust) and cirrus clouds. We envision robust approaches in which well-collocated ground-based measurements and space-borne observations will greatly advance our knowledge of extensive aerosols and clouds.

  7. Ground-Based VIS/NIR Reflectance Spectra of 25143 Itokawa: What Hayabusa will See and How Ground-Based Data can Augment Analyses

    Science.gov (United States)

    Vilas, Faith; Abell, P. A.; Jarvis, K. S.

    2004-01-01

    Planning for the arrival of the Hayabusa spacecraft at asteroid 25143 Itokawa includes consideration of the expected spectral information to be obtained using the AMICA and NIRS instruments. The rotationally-resolved spatial coverage the asteroid we have obtained with ground-based telescopic spectrophotometry in the visible and near-infrared can be utilized here to address expected spacecraft data. We use spectrophotometry to simulate the types of data that Hayabusa will receive with the NIRS and AMICA instruments, and will demonstrate them here. The NIRS will cover a wavelength range from 0.85 m, and have a dispersion per element of 250 Angstroms. Thus, we are limited in coverage of the 1.0 micrometer and 2.0 micrometer mafic silicate absorption features. The ground-based reflectance spectra of Itokawa show a large component of olivine in its surface material, and the 2.0 micrometer feature is shallow. Determining the olivine to pyroxene abundance ratio is critically dependent on the attributes of the 1.0- and 2.0 micrometer features. With a cut-off near 2,1 micrometer the longer edge of the 2.0- feature will not be obtained by NIRS. Reflectance spectra obtained using ground-based telescopes can be used to determine the regional composition around space-based spectral observations, and possibly augment the longer wavelength spectral attributes. Similarly, the shorter wavelength end of the 1.0 micrometer absorption feature will be partially lost to the NIRS. The AMICA filters mimic the ECAS filters, and have wavelength coverage overlapping with the NIRS spectral range. We demonstrate how merging photometry from AMICA will extend the spectral coverage of the NIRS. Lessons learned from earlier spacecraft to asteroids should be considered.

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

    Directory of Open Access Journals (Sweden)

    T. Manninen

    2012-11-01

    Full Text Available Ground-based pyranometer measurements of the (clear-sky broadband surface albedo are affected by the atmospheric conditions (mainly by aerosol particles, water vapour and ozone. A new semi-empirical method for estimating the magnitude of the effect of atmospheric conditions on surface albedo measurements in clear-sky conditions is presented. Global and reflected radiation and/or aerosol optical depth (AOD at two wavelengths are needed to apply the method. Depending on the aerosol optical depth and the solar zenith angle values, the effect can be as large as 20%. For the cases we tested using data from the Cabauw atmospheric test site in the Netherlands, the atmosphere caused typically up to 5% overestimation of surface albedo with respect to corresponding black-sky surface albedo values.

  9. Ground-based spectral measurements of solar radiation, (2)

    International Nuclear Information System (INIS)

    Murai, Keizo; Kobayashi, Masaharu; Goto, Ryozo; Yamauchi, Toyotaro

    1979-01-01

    A newly designed spectro-pyranometer was used for the measurement of the global (direct + diffuse) and the diffuse sky radiation reaching the ground. By the subtraction of the diffuse component from the global radiation, we got the direct radiation component which leads to the spectral distribution of the optical thickness (extinction coefficient) of the turbid atmosphere. The measurement of the diffuse sky radiation reveals the scattering effect of aerosols and that of the global radiation allows the estimation of total attenuation caused by scattering and absorption of aerosols. The effects of the aerosols are represented by the deviation of the real atmosphere measured from the Rayleigh atmosphere. By the combination of the measured values with those obtained by theoretical calculation for the model atmosphere, we estimated the amount of absorption by the aerosols. Very strong absorption in the ultraviolet region was recognized. (author)

  10. Ground-based intercomparison of two isoprene measurement techniques

    Directory of Open Access Journals (Sweden)

    E. Leibrock

    2003-01-01

    Full Text Available An informal intercomparison of two isoprene (C5H8 measurement techniques was carried out during Fall of 1998 at a field site located approximately 3 km west of Boulder, Colorado, USA. A new chemical ionization mass spectrometric technique (CIMS was compared to a well-established gas chromatographic technique (GC. The CIMS technique utilized benzene cation chemistry to ionize isoprene. The isoprene levels measured by the CIMS were often larger than those obtained with the GC. The results indicate that the CIMS technique suffered from an anthropogenic interference associated with air masses from the Denver, CO metropolitan area as well as an additional interference occurring in clean conditions. However, the CIMS technique is also demonstrated to be sensitive and fast. Especially after introduction of a tandem mass spectrometric technique, it is therefore a candidate for isoprene measurements in remote environments near isoprene sources.

  11. Exploration of a Polarized Surface Bidirectional Reflectance Model Using the Ground-Based Multiangle SpectroPolarimetric Imager

    Directory of Open Access Journals (Sweden)

    David J. Diner

    2012-12-01

    Full Text Available Accurate characterization of surface reflection is essential for retrieval of aerosols using downward-looking remote sensors. In this paper, observations from the Ground-based Multiangle SpectroPolarimetric Imager (GroundMSPI are used to evaluate a surface polarized bidirectional reflectance distribution function (PBRDF model. GroundMSPI is an eight-band spectropolarimetric camera mounted on a rotating gimbal to acquire pushbroom imagery of outdoor landscapes. The camera uses a very accurate photoelastic-modulator-based polarimetric imaging technique to acquire Stokes vector measurements in three of the instrument’s bands (470, 660, and 865 nm. A description of the instrument is presented, and observations of selected targets within a scene acquired on 6 January 2010 are analyzed. Data collected during the course of the day as the Sun moved across the sky provided a range of illumination geometries that facilitated evaluation of the surface model, which is comprised of a volumetric reflection term represented by the modified Rahman-Pinty-Verstraete function plus a specular reflection term generated by a randomly oriented array of Fresnel-reflecting microfacets. While the model is fairly successful in predicting the polarized reflection from two grass targets in the scene, it does a poorer job for two manmade targets (a parking lot and a truck roof, possibly due to their greater degree of geometric organization. Several empirical adjustments to the model are explored and lead to improved fits to the data. For all targets, the data support the notion of spectral invariance in the angular shape of the unpolarized and polarized surface reflection. As noted by others, this behavior provides valuable constraints on the aerosol retrieval problem, and highlights the importance of multiangle observations.

  12. Ground-Based Observations and Modeling of the Visibility and Radar Reflectivity in a Radiation Fog Layer

    NARCIS (Netherlands)

    Boers, R.; Baltink, K.H.; Hemink, H.J.; Bosveld, F.C.; Moerman, M.

    2013-01-01

    The development of a radiation fog layer at the Cabauw Experimental Site for Atmospheric Research(51.97°N, 4.93°E) on 23 March 2011 was observed with ground-based in situ and remote sensing observationsto investigate the relationship between visibility and radar reflectivity. The fog layer thickness

  13. Overview of Boundary Layer Clouds Using Satellite and Ground-Based Measurements

    Science.gov (United States)

    Xi, B.; Dong, X.; Wu, P.; Qiu, S.

    2017-12-01

    A comprehensive summary of boundary layer clouds properties based on our few recently studies will be presented. The analyses include the global cloud fractions and cloud macro/micro- physical properties based on satellite measurements using both CERES-MODIS and CloudSat/Caliposo data products,; the annual/seasonal/diurnal variations of stratocumulus clouds over different climate regions (mid-latitude land, mid-latitude ocean, and Arctic region) using DOE ARM ground-based measurements over Southern great plain (SGP), Azores (GRW), and North slope of Alaska (NSA) sites; the impact of environmental conditions to the formation and dissipation process of marine boundary layer clouds over Azores site; characterizing Arctice mixed-phase cloud structure and favorable environmental conditions for the formation/maintainess of mixed-phase clouds over NSA site. Though the presentation has widely spread topics, we will focus on the representation of the ground-based measurements over different climate regions; evaluation of satellite retrieved cloud properties using these ground-based measurements, and understanding the uncertainties of both satellite and ground-based retrievals and measurements.

  14. Characterizing GEO Titan IIIC Transtage Fragmentations Using Ground-based and Telescopic Measurements

    Science.gov (United States)

    Cowardin, H.; Anz-Meador, P.; Reyes, J. A.

    In a continued effort to better characterize the geosynchronous orbit (GEO) environment, NASA’s Orbital Debris Program Office (ODPO) utilizes various ground-based optical assets to acquire photometric and spectral data of known debris associated with fragmentations in or near GEO. The Titan IIIC Transtage upper stage is known to have fragmented four times. Two of the four fragmentations were in GEO while the Transtage fragmented a third time in GEO transfer orbit. The forth fragmentation occurred in low Earth orbit. To better assess and characterize these fragmentations, the NASA ODPO acquired a Titan Transtage test and display article previously in the custody of the 309th Aerospace Maintenance and Regeneration Group (AMARG) in Tucson, Arizona. After initial inspections at AMARG demonstrated that it was of sufficient fidelity to be of interest, the test article was brought to NASA Johnson Space Center (JSC) to continue material analysis and historical documentation. The Transtage has undergone two separate spectral measurement campaigns to characterize the reflectance spectroscopy of historical aerospace materials. These data have been incorporated into the NASA Spectral Database, with the goal of using telescopic data comparisons for potential material identification. A Light Detection and Ranging (LIDAR) system scan also has been completed and a scale model has been created for use in the Optical Measurement Center (OMC) for photometric analysis of an intact Transtage, including bidirectional reflectance distribution function (BRDF) measurements. An historical overview of the Titan IIIC Transtage, the current analysis that has been done to date, and the future work to be completed in support of characterizing the GEO and near GEO orbital debris environment will be discussed in the subsequent presentation.

  15. Validation of OMI UV measurements against ground-based measurements at a station in Kampala, Uganda

    Science.gov (United States)

    Muyimbwa, Dennis; Dahlback, Arne; Stamnes, Jakob; Hamre, Børge; Frette, Øyvind; Ssenyonga, Taddeo; Chen, Yi-Chun

    2015-04-01

    We present solar ultraviolet (UV) irradiance data measured with a NILU-UV instrument at a ground site in Kampala (0.31°N, 32.58°E), Uganda for the period 2005-2014. The data were analyzed and compared with UV irradiances inferred from the Ozone Monitoring Instrument (OMI) for the same period. Kampala is located on the shores of lake Victoria, Africa's largest fresh water lake, which may influence the climate and weather conditions of the region. Also, there is an excessive use of worn cars, which may contribute to a high anthropogenic loading of absorbing aerosols. The OMI surface UV algorithm does not account for absorbing aerosols, which may lead to systematic overestimation of surface UV irradiances inferred from OMI satellite data. We retrieved UV index values from OMI UV irradiances and validated them against the ground-based UV index values obtained from NILU-UV measurements. The UV index values were found to follow a seasonal pattern similar to that of the clouds and the rainfall. OMI inferred UV index values were overestimated with a mean bias of about 28% under all-sky conditions, but the mean bias was reduced to about 8% under clear-sky conditions when only days with radiation modification factor (RMF) greater than 65% were considered. However, when days with RMF greater than 70, 75, and 80% were considered, OMI inferred UV index values were found to agree with the ground-based UV index values to within 5, 3, and 1%, respectively. In the validation we identified clouds/aerosols, which were present in 88% of the measurements, as the main cause of OMI inferred overestimation of the UV index.

  16. The SPARC water vapor assessment II: intercomparison of satellite and ground-based microwave measurements

    Science.gov (United States)

    Nedoluha, Gerald E.; Kiefer, Michael; Lossow, Stefan; Gomez, R. Michael; Kämpfer, Niklaus; Lainer, Martin; Forkman, Peter; Christensen, Ole Martin; Oh, Jung Jin; Hartogh, Paul; Anderson, John; Bramstedt, Klaus; Dinelli, Bianca M.; Garcia-Comas, Maya; Hervig, Mark; Murtagh, Donal; Raspollini, Piera; Read, William G.; Rosenlof, Karen; Stiller, Gabriele P.; Walker, Kaley A.

    2017-12-01

    As part of the second SPARC (Stratosphere-troposphere Processes And their Role in Climate) water vapor assessment (WAVAS-II), we present measurements taken from or coincident with seven sites from which ground-based microwave instruments measure water vapor in the middle atmosphere. Six of the ground-based instruments are part of the Network for the Detection of Atmospheric Composition Change (NDACC) and provide datasets that can be used for drift and trend assessment. We compare measurements from these ground-based instruments with satellite datasets that have provided retrievals of water vapor in the lower mesosphere over extended periods since 1996. We first compare biases between the satellite and ground-based instruments from the upper stratosphere to the upper mesosphere. We then show a number of time series comparisons at 0.46 hPa, a level that is sensitive to changes in H2O and CH4 entering the stratosphere but, because almost all CH4 has been oxidized, is relatively insensitive to dynamical variations. Interannual variations and drifts are investigated with respect to both the Aura Microwave Limb Sounder (MLS; from 2004 onwards) and each instrument's climatological mean. We find that the variation in the interannual difference in the mean H2O measured by any two instruments is typically ˜ 1%. Most of the datasets start in or after 2004 and show annual increases in H2O of 0-1 % yr-1. In particular, MLS shows a trend of between 0.5 % yr-1 and 0.7 % yr-1 at the comparison sites. However, the two longest measurement datasets used here, with measurements back to 1996, show much smaller trends of +0.1 % yr-1 (at Mauna Loa, Hawaii) and -0.1 % yr-1 (at Lauder, New Zealand).

  17. The SPARC water vapor assessment II: intercomparison of satellite and ground-based microwave measurements

    Directory of Open Access Journals (Sweden)

    G. E. Nedoluha

    2017-12-01

    Full Text Available As part of the second SPARC (Stratosphere–troposphere Processes And their Role in Climate water vapor assessment (WAVAS-II, we present measurements taken from or coincident with seven sites from which ground-based microwave instruments measure water vapor in the middle atmosphere. Six of the ground-based instruments are part of the Network for the Detection of Atmospheric Composition Change (NDACC and provide datasets that can be used for drift and trend assessment. We compare measurements from these ground-based instruments with satellite datasets that have provided retrievals of water vapor in the lower mesosphere over extended periods since 1996. We first compare biases between the satellite and ground-based instruments from the upper stratosphere to the upper mesosphere. We then show a number of time series comparisons at 0.46 hPa, a level that is sensitive to changes in H2O and CH4 entering the stratosphere but, because almost all CH4 has been oxidized, is relatively insensitive to dynamical variations. Interannual variations and drifts are investigated with respect to both the Aura Microwave Limb Sounder (MLS; from 2004 onwards and each instrument's climatological mean. We find that the variation in the interannual difference in the mean H2O measured by any two instruments is typically  ∼  1%. Most of the datasets start in or after 2004 and show annual increases in H2O of 0–1 % yr−1. In particular, MLS shows a trend of between 0.5 % yr−1 and 0.7 % yr−1 at the comparison sites. However, the two longest measurement datasets used here, with measurements back to 1996, show much smaller trends of +0.1 % yr−1 (at Mauna Loa, Hawaii and −0.1 % yr−1 (at Lauder, New Zealand.

  18. Intercomparison of ground-based ozone and NO2 measurements during the MANTRA 2004 campaign

    Directory of Open Access Journals (Sweden)

    K. Strong

    2007-11-01

    Full Text Available The MANTRA (Middle Atmosphere Nitrogen TRend Assessment 2004 campaign took place in Vanscoy, Saskatchewan, Canada (52° N, 107° W from 3 August to 15 September, 2004. In support of the main balloon launch, a suite of five zenith-sky and direct-Sun-viewing UV-visible ground-based spectrometers was deployed, primarily measuring ozone and NO2 total columns. Three Fourier transform spectrometers (FTSs that were part of the balloon payload also performed ground-based measurements of several species, including ozone. Ground-based measurements of ozone and NO2 differential slant column densities from the zenith-viewing UV-visible instruments are presented herein. They are found to partially agree within NDACC (Network for the Detection of Atmospheric Composition Change standards for instruments certified for process studies and satellite validation. Vertical column densities of ozone from the zenith-sky UV-visible instruments, the FTSs, a Brewer spectrophotometer, and ozonesondes are compared, and found to agree within the combined error estimates of the instruments (15%. NO2 vertical column densities from two of the UV-visible instruments are compared, and are also found to agree within combined error (15%.

  19. On mean wind and turbulence profile measurements from ground-based wind lidars

    DEFF Research Database (Denmark)

    Mikkelsen, Torben

    2009-01-01

    Two types of wind lidar?s have become available for ground-based vertical mean wind and turbulence profiling. A continuous wave (CW) wind lidar, and a pulsed wind lidar. Although they both are build upon the same recent 1.55 μ telecom fibre technology, they possess fundamental differences between...... their temporal and spatial resolution capabilities. A literature review of the two lidar systems spatial and temporal resolution characteristics will be presented, and the implication for the two lidar types vertical profile measurements of mean wind and turbulence in the lower atmospheric boundary layer...

  20. Ground based mobile isotopic methane measurements in the Front Range, Colorado

    Science.gov (United States)

    Vaughn, B. H.; Rella, C.; Petron, G.; Sherwood, O.; Mielke-Maday, I.; Schwietzke, S.

    2014-12-01

    Increased development of unconventional oil and gas resources in North America has given rise to attempts to monitor and quantify fugitive emissions of methane from the industry. Emission estimates of methane from oil and gas basins can vary significantly from one study to another as well as from EPA or State estimates. New efforts are aimed at reconciling bottom-up, or inventory-based, emission estimates of methane with top-down estimates based on atmospheric measurements from aircraft, towers, mobile ground-based vehicles, and atmospheric models. Attributing airborne measurements of regional methane fluxes to specific sources is informed by ground-based measurements of methane. Stable isotopic measurements (δ13C) of methane help distinguish between emissions from the O&G industry, Confined Animal Feed Operations (CAFO), and landfills, but analytical challenges typically limit meaningful isotopic measurements to individual point sampling. We are developing a toolbox to use δ13CH4 measurements to assess the partitioning of methane emissions for regions with multiple methane sources. The method was applied to the Denver-Julesberg Basin. Here we present data from continuous isotopic measurements obtained over a wide geographic area by using MegaCore, a 1500 ft. tube that is constantly filled with sample air while driving, then subsequently analyzed at slower rates using cavity ring down spectroscopy (CRDS). Pressure, flow and calibration are tightly controlled allowing precise attribution of methane enhancements to their point of collection. Comparisons with point measurements are needed to confirm regional values and further constrain flux estimates and models. This effort was made in conjunction with several major field campaigns in the Colorado Front Range in July-August 2014, including FRAPPÉ (Front Range Air Pollution and Photochemistry Experiment), DISCOVER-AQ, and the Air Water Gas NSF Sustainability Research Network at the University of Colorado.

  1. Nighttime Aerosol Optical Depth Measurements Using a Ground-based Lunar Photometer

    Science.gov (United States)

    Berkoff, Tim; Omar, Ali; Haggard, Charles; Pippin, Margaret; Tasaddaq, Aasam; Stone, Tom; Rodriguez, Jon; Slutsker, Ilya; Eck, Tom; Holben, Brent; hide

    2015-01-01

    In recent years it was proposed to combine AERONET network photometer capabilities with a high precision lunar model used for satellite calibration to retrieve columnar nighttime AODs. The USGS lunar model can continuously provide pre-atmosphere high precision lunar irradiance determinations for multiple wavelengths at ground sensor locations. When combined with measured irradiances from a ground-based AERONET photometer, atmospheric column transmissions can determined yielding nighttime column aerosol AOD and Angstrom coefficients. Additional demonstrations have utilized this approach to further develop calibration methods and to obtain data in polar regions where extended periods of darkness occur. This new capability enables more complete studies of the diurnal behavior of aerosols, and feedback for models and satellite retrievals for the nighttime behavior of aerosols. It is anticipated that the nighttime capability of these sensors will be useful for comparisons with satellite lidars such as CALIOP and CATS in additional to ground-based lidars in MPLNET at night, when the signal-to-noise ratio is higher than daytime and more precise AOD comparisons can be made.

  2. Exploring the relationship between monitored ground-based and satellite aerosol measurements over the City of Johannesburg

    CSIR Research Space (South Africa)

    Garland, Rebecca M

    2012-09-01

    Full Text Available This project studied the relationship between aerosol optical depth (AOD) from the Multi-angle Imaging SpectroRadiometer (MISR) instrument on the Terra satellite, and ground-based monitored particulate matter (PM) mass concentrations measured...

  3. The Holy Grail of Resource Assessment: Low Cost Ground-Based Measurements with Good Accuracy

    Energy Technology Data Exchange (ETDEWEB)

    Marion, Bill; Smith, Benjamin

    2017-06-22

    Using performance data from some of the millions of installed photovoltaic (PV) modules with micro-inverters may afford the opportunity to provide ground-based solar resource data critical for developing PV projects. The method used back-solves for the direct normal irradiance (DNI) and the diffuse horizontal irradiance (DHI) from the micro-inverter ac production data. When the derived values of DNI and DHI were then used to model the performance of other PV systems, the annual mean bias deviations were within +/- 4%, and only 1% greater than when the PV performance was modeled using high quality irradiance measurements. An uncertainty analysis shows the method better suited for modeling PV performance than using satellite-based global horizontal irradiance.

  4. An evaluation of IASI-NH3 with ground-based Fourier transform infrared spectroscopy measurements

    Directory of Open Access Journals (Sweden)

    E. Dammers

    2016-08-01

    Full Text Available Global distributions of atmospheric ammonia (NH3 measured with satellite instruments such as the Infrared Atmospheric Sounding Interferometer (IASI contain valuable information on NH3 concentrations and variability in regions not yet covered by ground-based instruments. Due to their large spatial coverage and (bi-daily overpasses, the satellite observations have the potential to increase our knowledge of the distribution of NH3 emissions and associated seasonal cycles. However the observations remain poorly validated, with only a handful of available studies often using only surface measurements without any vertical information. In this study, we present the first validation of the IASI-NH3 product using ground-based Fourier transform infrared spectroscopy (FTIR observations. Using a recently developed consistent retrieval strategy, NH3 concentration profiles have been retrieved using observations from nine Network for the Detection of Atmospheric Composition Change (NDACC stations around the world between 2008 and 2015. We demonstrate the importance of strict spatio-temporal collocation criteria for the comparison. Large differences in the regression results are observed for changing intervals of spatial criteria, mostly due to terrain characteristics and the short lifetime of NH3 in the atmosphere. The seasonal variations of both datasets are consistent for most sites. Correlations are found to be high at sites in areas with considerable NH3 levels, whereas correlations are lower at sites with low atmospheric NH3 levels close to the detection limit of the IASI instrument. A combination of the observations from all sites (Nobs = 547 give a mean relative difference of −32.4 ± (56.3 %, a correlation r of 0.8 with a slope of 0.73. These results give an improved estimate of the IASI-NH3 product performance compared to the previous upper-bound estimates (−50 to +100 %.

  5. Method for validating cloud mask obtained from satellite measurements using ground-based sky camera.

    Science.gov (United States)

    Letu, Husi; Nagao, Takashi M; Nakajima, Takashi Y; Matsumae, Yoshiaki

    2014-11-01

    Error propagation in Earth's atmospheric, oceanic, and land surface parameters of the satellite products caused by misclassification of the cloud mask is a critical issue for improving the accuracy of satellite products. Thus, characterizing the accuracy of the cloud mask is important for investigating the influence of the cloud mask on satellite products. In this study, we proposed a method for validating multiwavelength satellite data derived cloud masks using ground-based sky camera (GSC) data. First, a cloud cover algorithm for GSC data has been developed using sky index and bright index. Then, Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data derived cloud masks by two cloud-screening algorithms (i.e., MOD35 and CLAUDIA) were validated using the GSC cloud mask. The results indicate that MOD35 is likely to classify ambiguous pixels as "cloudy," whereas CLAUDIA is likely to classify them as "clear." Furthermore, the influence of error propagations caused by misclassification of the MOD35 and CLAUDIA cloud masks on MODIS derived reflectance, brightness temperature, and normalized difference vegetation index (NDVI) in clear and cloudy pixels was investigated using sky camera data. It shows that the influence of the error propagation by the MOD35 cloud mask on the MODIS derived monthly mean reflectance, brightness temperature, and NDVI for clear pixels is significantly smaller than for the CLAUDIA cloud mask; the influence of the error propagation by the CLAUDIA cloud mask on MODIS derived monthly mean cloud products for cloudy pixels is significantly smaller than that by the MOD35 cloud mask.

  6. Validation of OMI erythemal doses with multi-sensor ground-based measurements in Thessaloniki, Greece

    Science.gov (United States)

    Zempila, Melina Maria; Fountoulakis, Ilias; Taylor, Michael; Kazadzis, Stelios; Arola, Antti; Koukouli, Maria Elissavet; Bais, Alkiviadis; Meleti, Chariklia; Balis, Dimitrios

    2018-06-01

    The aim of this study is to validate the Ozone Monitoring Instrument (OMI) erythemal dose rates using ground-based measurements in Thessaloniki, Greece. In the Laboratory of Atmospheric Physics of the Aristotle University of Thessaloniki, a Yankee Environmental System UVB-1 radiometer measures the erythemal dose rates every minute, and a Norsk Institutt for Luftforskning (NILU) multi-filter radiometer provides multi-filter based irradiances that were used to derive erythemal dose rates for the period 2005-2014. Both these datasets were independently validated against collocated UV irradiance spectra from a Brewer MkIII spectrophotometer. Cloud detection was performed based on measurements of the global horizontal radiation from a Kipp & Zonen pyranometer and from NILU measurements in the visible range. The satellite versus ground observation validation was performed taking into account the effect of temporal averaging, limitations related to OMI quality control criteria, cloud conditions, the solar zenith angle and atmospheric aerosol loading. Aerosol optical depth was also retrieved using a collocated CIMEL sunphotometer in order to assess its impact on the comparisons. The effect of total ozone columns satellite versus ground-based differences on the erythemal dose comparisons was also investigated. Since most of the public awareness alerts are based on UV Index (UVI) classifications, an analysis and assessment of OMI capability for retrieving UVIs was also performed. An overestimation of the OMI erythemal product by 3-6% and 4-8% with respect to ground measurements is observed when examining overpass and noontime estimates respectively. The comparisons revealed a relatively small solar zenith angle dependence, with the OMI data showing a slight dependence on aerosol load, especially at high aerosol optical depth values. A mean underestimation of 2% in OMI total ozone columns under cloud-free conditions was found to lead to an overestimation in OMI erythemal

  7. Ozone ground-based measurements by the GASCOD near-UV and visible DOAS system

    Science.gov (United States)

    Giovanelli, G.; Bonasoni, P.; Cervino, M.; Evangelisti, F.; Ravegnani, F.

    1994-01-01

    GASCOD, a near-ultraviolet and visible differential optical spectrometer, was developed at CNR's FISBAT Institute in Bologna, Italy, and first tested at Terra Nova Bay station in Antarctica (74.6 deg S, 164.6 deg E) during the summer expeditions 1988-1990 of PNRA (PNRA is the national research program in Antarctica, 'Programma Nazionale di Ricerche in Atartide'). A comparison with coincident O3 total column measurements taken in the same Antarctic area is presented, as is another comparison performed in Italy. Also introduced is an updated model for solar zenith measurements taken from a ground-based, upward-looking GASCOD spectrometer, which was employed for the 1991-92 winter campaign at Aer-Ostersund in Sweden (63.3 deg N, 13.1 deg E) during AESOE (European Arctic Stratospheric Ozone Experiment). The GASCOD can examine the spectra from 300 to 700 nm, in 50 nm steps, by moving the spectrometer's grating. At present, it takes measurements of solar zenith radiation in the 310-342 nm range for O3 and in the 405-463 nm range for NO2.

  8. Evaluation of the National Solar Radiation Database (NSRDB) Using Ground-Based Measurements

    Science.gov (United States)

    Xie, Y.; Sengupta, M.; Habte, A.; Lopez, A.

    2017-12-01

    Solar resource is essential for a wide spectrum of applications including renewable energy, climate studies, and solar forecasting. Solar resource information can be obtained from ground-based measurement stations and/or from modeled data sets. While measurements provide data for the development and validation of solar resource models and other applications modeled data expands the ability to address the needs for increased accuracy and spatial and temporal resolution. The National Renewable Energy Laboratory (NREL) has developed and regular updates modeled solar resource through the National Solar Radiation Database (NSRDB). The recent NSRDB dataset was developed using the physics-based Physical Solar Model (PSM) and provides gridded solar irradiance (global horizontal irradiance (GHI), direct normal irradiance (DNI), and diffuse horizontal irradiance) at a 4-km by 4-km spatial and half-hourly temporal resolution covering 18 years from 1998-2015. A comprehensive validation of the performance of the NSRDB (1998-2015) was conducted to quantify the accuracy of the spatial and temporal variability of the solar radiation data. Further, the study assessed the ability of NSRDB (1998-2015) to accurately capture inter-annual variability, which is essential information for solar energy conversion projects and grid integration studies. Comparisons of the NSRDB (1998-2015) with nine selected ground-measured data were conducted under both clear- and cloudy-sky conditions. These locations provide a high quality data covering a variety of geographical locations and climates. The comparison of the NSRDB to the ground-based data demonstrated that biases were within +/- 5% for GHI and +/-10% for DNI. A comprehensive uncertainty estimation methodology was established to analyze the performance of the gridded NSRDB and includes all sources of uncertainty at various time-averaged periods, a method that is not often used in model evaluation. Further, the study analyzed the inter

  9. The high-resolution extraterrestrial solar spectrum (QASUMEFTS determined from ground-based solar irradiance measurements

    Directory of Open Access Journals (Sweden)

    J. Gröbner

    2017-09-01

    Full Text Available A high-resolution extraterrestrial solar spectrum has been determined from ground-based measurements of direct solar spectral irradiance (SSI over the wavelength range from 300 to 500 nm using the Langley-plot technique. The measurements were obtained at the Izaña Atmospheric Research Centre from the Agencia Estatal de Meteorología, Tenerife, Spain, during the period 12 to 24 September 2016. This solar spectrum (QASUMEFTS was combined from medium-resolution (bandpass of 0.86 nm measurements of the QASUME (Quality Assurance of Spectral Ultraviolet Measurements in Europe spectroradiometer in the wavelength range from 300 to 500 nm and high-resolution measurements (0.025 nm from a Fourier transform spectroradiometer (FTS over the wavelength range from 305 to 380 nm. The Kitt Peak solar flux atlas was used to extend this high-resolution solar spectrum to 500 nm. The expanded uncertainties of this solar spectrum are 2 % between 310 and 500 nm and 4 % at 300 nm. The comparison of this solar spectrum with solar spectra measured in space (top of the atmosphere gave very good agreements in some cases, while in some other cases discrepancies of up to 5 % were observed. The QASUMEFTS solar spectrum represents a benchmark dataset with uncertainties lower than anything previously published. The metrological traceability of the measurements to the International System of Units (SI is assured by an unbroken chain of calibrations leading to the primary spectral irradiance standard of the Physikalisch-Technische Bundesanstalt in Germany.

  10. TEMIS UV product validation using NILU-UV ground-based measurements in Thessaloniki, Greece

    Science.gov (United States)

    Zempila, Melina-Maria; van Geffen, Jos H. G. M.; Taylor, Michael; Fountoulakis, Ilias; Koukouli, Maria-Elissavet; van Weele, Michiel; van der A, Ronald J.; Bais, Alkiviadis; Meleti, Charikleia; Balis, Dimitrios

    2017-06-01

    This study aims to cross-validate ground-based and satellite-based models of three photobiological UV effective dose products: the Commission Internationale de l'Éclairage (CIE) erythemal UV, the production of vitamin D in the skin, and DNA damage, using high-temporal-resolution surface-based measurements of solar UV spectral irradiances from a synergy of instruments and models. The satellite-based Tropospheric Emission Monitoring Internet Service (TEMIS; version 1.4) UV daily dose data products were evaluated over the period 2009 to 2014 with ground-based data from a Norsk Institutt for Luftforskning (NILU)-UV multifilter radiometer located at the northern midlatitude super-site of the Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki (LAP/AUTh), in Greece. For the NILU-UV effective dose rates retrieval algorithm, a neural network (NN) was trained to learn the nonlinear functional relation between NILU-UV irradiances and collocated Brewer-based photobiological effective dose products. Then the algorithm was subjected to sensitivity analysis and validation. The correlation of the NN estimates with target outputs was high (r = 0. 988 to 0.990) and with a very low bias (0.000 to 0.011 in absolute units) proving the robustness of the NN algorithm. For further evaluation of the NILU NN-derived products, retrievals of the vitamin D and DNA-damage effective doses from a collocated Yankee Environmental Systems (YES) UVB-1 pyranometer were used. For cloud-free days, differences in the derived UV doses are better than 2 % for all UV dose products, revealing the reference quality of the ground-based UV doses at Thessaloniki from the NILU-UV NN retrievals. The TEMIS UV doses used in this study are derived from ozone measurements by the SCIAMACHY/Envisat and GOME2/MetOp-A satellite instruments, over the European domain in combination with SEVIRI/Meteosat-based diurnal cycle of the cloud cover fraction per 0. 5° × 0. 5° (lat × long) grid cells. TEMIS

  11. TEMIS UV product validation using NILU-UV ground-based measurements in Thessaloniki, Greece

    Directory of Open Access Journals (Sweden)

    M.-M. Zempila

    2017-06-01

    Full Text Available This study aims to cross-validate ground-based and satellite-based models of three photobiological UV effective dose products: the Commission Internationale de l'Éclairage (CIE erythemal UV, the production of vitamin D in the skin, and DNA damage, using high-temporal-resolution surface-based measurements of solar UV spectral irradiances from a synergy of instruments and models. The satellite-based Tropospheric Emission Monitoring Internet Service (TEMIS; version 1.4 UV daily dose data products were evaluated over the period 2009 to 2014 with ground-based data from a Norsk Institutt for Luftforskning (NILU-UV multifilter radiometer located at the northern midlatitude super-site of the Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki (LAP/AUTh, in Greece. For the NILU-UV effective dose rates retrieval algorithm, a neural network (NN was trained to learn the nonlinear functional relation between NILU-UV irradiances and collocated Brewer-based photobiological effective dose products. Then the algorithm was subjected to sensitivity analysis and validation. The correlation of the NN estimates with target outputs was high (r = 0. 988 to 0.990 and with a very low bias (0.000 to 0.011 in absolute units proving the robustness of the NN algorithm. For further evaluation of the NILU NN-derived products, retrievals of the vitamin D and DNA-damage effective doses from a collocated Yankee Environmental Systems (YES UVB-1 pyranometer were used. For cloud-free days, differences in the derived UV doses are better than 2 % for all UV dose products, revealing the reference quality of the ground-based UV doses at Thessaloniki from the NILU-UV NN retrievals. The TEMIS UV doses used in this study are derived from ozone measurements by the SCIAMACHY/Envisat and GOME2/MetOp-A satellite instruments, over the European domain in combination with SEVIRI/Meteosat-based diurnal cycle of the cloud cover fraction per 0. 5° × 0. 5

  12. Radiometric modeling and calibration of the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) ground based measurement experiment

    Science.gov (United States)

    Tian, Jialin; Smith, William L.; Gazarik, Michael J.

    2008-12-01

    The ultimate remote sensing benefits of the high resolution Infrared radiance spectrometers will be realized with their geostationary satellite implementation in the form of imaging spectrometers. This will enable dynamic features of the atmosphere's thermodynamic fields and pollutant and greenhouse gas constituents to be observed for revolutionary improvements in weather forecasts and more accurate air quality and climate predictions. As an important step toward realizing this application objective, the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) Engineering Demonstration Unit (EDU) was successfully developed under the NASA New Millennium Program, 2000-2006. The GIFTS-EDU instrument employs three focal plane arrays (FPAs), which gather measurements across the long-wave IR (LWIR), short/mid-wave IR (SMWIR), and visible spectral bands. The GIFTS calibration is achieved using internal blackbody calibration references at ambient (260 K) and hot (286 K) temperatures. In this paper, we introduce a refined calibration technique that utilizes Principle Component (PC) analysis to compensate for instrument distortions and artifacts, therefore, enhancing the absolute calibration accuracy. This method is applied to data collected during the GIFTS Ground Based Measurement (GBM) experiment, together with simultaneous observations by the accurately calibrated AERI (Atmospheric Emitted Radiance Interferometer), both simultaneously zenith viewing the sky through the same external scene mirror at ten-minute intervals throughout a cloudless day at Logan Utah on September 13, 2006. The accurately calibrated GIFTS radiances are produced using the first four PC scores in the GIFTS-AERI regression model. Temperature and moisture profiles retrieved from the PC-calibrated GIFTS radiances are verified against radiosonde measurements collected throughout the GIFTS sky measurement period. Using the GIFTS GBM calibration model, we compute the calibrated radiances from data

  13. Evidence of Urban Precipitation Anomalies from Satellite and Ground-Based Measurements

    Science.gov (United States)

    Shepherd, J. Marshall; Manyin, M.; Negri, Andrew

    2004-01-01

    Urbanization is one of the extreme cases of land use change. Most of world's population has moved to urban areas. Although currently only 1.2% of the land is considered urban, the spatial coverage and density of cities are expected to rapidly increase in the near future. It is estimated that by the year 2025, 60% of the world's population will live in cities. Human activity in urban environments also alters weather and climate processes. However, our understanding of urbanization on the total Earth-weather-climate system is incomplete. Recent literature continues to provide evidence that anomalies in precipitation exist over and downwind of major cities. Current and future research efforts are actively seeking to verify these literature findings and understand potential cause-effect relationships. The novelty of this study is that it utilizes rainfall data from multiple satellite data sources (e.g. TRMM precipitation radar, TRMM-geosynchronous-rain gauge merged product, and SSM/I) and ground-based measurements to identify spatial anomalies and temporal trends in precipitation for cities around the world. Early results will be presented and placed within the context of weather prediction, climate assessment, and societal applications.

  14. Spatio-temporal representativeness of ground-based downward solar radiation measurements

    Science.gov (United States)

    Schwarz, Matthias; Wild, Martin; Folini, Doris

    2017-04-01

    Surface solar radiation (SSR) is most directly observed with ground based pyranometer measurements. Besides measurement uncertainties, which arise from the pyranometer instrument itself, also errors attributed to the limited spatial representativeness of observations from single sites for their large-scale surrounding have to be taken into account when using such measurements for energy balance studies. In this study the spatial representativeness of 157 homogeneous European downward surface solar radiation time series from the Global Energy Balance Archive (GEBA) and the Baseline Surface Radiation Network (BSRN) were examined for the period 1983-2015 by using the high resolution (0.05°) surface solar radiation data set from the Satellite Application Facility on Climate Monitoring (CM-SAF SARAH) as a proxy for the spatiotemporal variability of SSR. By correlating deseasonalized monthly SSR time series form surface observations against single collocated satellite derived SSR time series, a mean spatial correlation pattern was calculated and validated against purely observational based patterns. Generally decreasing correlations with increasing distance from station, with high correlations (R2 = 0.7) in proximity to the observational sites (±0.5°), was found. When correlating surface observations against time series from spatially averaged satellite derived SSR data (and thereby simulating coarser and coarser grids), very high correspondence between sites and the collocated pixels has been found for pixel sizes up to several degrees. Moreover, special focus was put on the quantification of errors which arise in conjunction to spatial sampling when estimating the temporal variability and trends for a larger region from a single surface observation site. For 15-year trends on a 1° grid, errors due to spatial sampling in the order of half of the measurement uncertainty for monthly mean values were found.

  15. Ultraviolet radiation modelling from ground-based and satellite measurements on Reunion Island, southern tropics

    Directory of Open Access Journals (Sweden)

    K. Lamy

    2018-01-01

    Full Text Available Surface ultraviolet radiation (SUR is not an increasing concern after the implementation of the Montreal Protocol and the recovery of the ozone layer Morgenstern et al.(2008. However, large uncertainties remain in the prediction of future changes of SUR Bais et al.(2015. Several studies pointed out that UV-B impacts the biosphere Erickson et al.(2015, especially the aquatic system, which plays a central part in the biogeochemical cycle Hader et al.(2007. It can affect phytoplankton productivity Smith and Cullen(1995. This influence can result in either positive or negative feedback on climate (Zepp et al., 2007. Global circulation model simulations predict an acceleration of the Brewer-Dobson circulation over the next century (Butchart, 2014, which would lead to a decrease in ozone levels in the tropics and an enhancement at higher latitudes (Hegglin and Shepherd, 2009. Reunion Island is located in the tropics (21° S, 55° E, in a part of the world where the amount of ozone in the ozone column is naturally low. In addition, this island is mountainous and the marine atmosphere is often clean with low aerosol concentrations. Thus, measurements show much higher SUR than at other sites at the same latitude or at midlatitudes. Ground-based measurements of SUR have been taken on Reunion Island by a Bentham DTMc300 spectroradiometer since 2009. This instrument is affiliated with the Network for the Detection of Atmospheric Composition Change (NDACC. In order to quantify the future evolution of SUR in the tropics, it is necessary to validate a model against present observations. This study is designed to be a preliminary parametric and sensitivity study of SUR modelling in the tropics. We developed a local parameterisation using the Tropospheric Ultraviolet and Visible Model (TUV; Madronich, 1993 and compared the output of TUV to multiple years of Bentham spectral measurements. This comparison started in early 2009 and continued until 2016

  16. Ultraviolet radiation modelling from ground-based and satellite measurements on Reunion Island, southern tropics

    Science.gov (United States)

    Lamy, Kévin; Portafaix, Thierry; Brogniez, Colette; Godin-Beekmann, Sophie; Bencherif, Hassan; Morel, Béatrice; Pazmino, Andrea; Metzger, Jean Marc; Auriol, Frédérique; Deroo, Christine; Duflot, Valentin; Goloub, Philippe; Long, Charles N.

    2018-01-01

    Surface ultraviolet radiation (SUR) is not an increasing concern after the implementation of the Montreal Protocol and the recovery of the ozone layer (Morgenstern et al., 2008). However, large uncertainties remain in the prediction of future changes of SUR (Bais et al., 2015). Several studies pointed out that UV-B impacts the biosphere (Erickson et al., 2015), especially the aquatic system, which plays a central part in the biogeochemical cycle (Hader et al., 2007). It can affect phytoplankton productivity (Smith and Cullen, 1995). This influence can result in either positive or negative feedback on climate (Zepp et al., 2007). Global circulation model simulations predict an acceleration of the Brewer-Dobson circulation over the next century (Butchart, 2014), which would lead to a decrease in ozone levels in the tropics and an enhancement at higher latitudes (Hegglin and Shepherd, 2009). Reunion Island is located in the tropics (21° S, 55° E), in a part of the world where the amount of ozone in the ozone column is naturally low. In addition, this island is mountainous and the marine atmosphere is often clean with low aerosol concentrations. Thus, measurements show much higher SUR than at other sites at the same latitude or at midlatitudes. Ground-based measurements of SUR have been taken on Reunion Island by a Bentham DTMc300 spectroradiometer since 2009. This instrument is affiliated with the Network for the Detection of Atmospheric Composition Change (NDACC). In order to quantify the future evolution of SUR in the tropics, it is necessary to validate a model against present observations. This study is designed to be a preliminary parametric and sensitivity study of SUR modelling in the tropics. We developed a local parameterisation using the Tropospheric Ultraviolet and Visible Model (TUV; Madronich, 1993) and compared the output of TUV to multiple years of Bentham spectral measurements. This comparison started in early 2009 and continued until 2016. Only

  17. Airborne and Ground-Based Measurements Using a High-Performance Raman Lidar

    Science.gov (United States)

    Whiteman, David N.; Rush, Kurt; Rabenhorst, Scott; Welch, Wayne; Cadirola, Martin; McIntire, Gerry; Russo, Felicita; Adam, Mariana; Venable, Demetrius; Connell, Rasheen; hide

    2010-01-01

    A high-performance Raman lidar operating in the UV portion of the spectrum has been used to acquire, for the first time using a single lidar, simultaneous airborne profiles of the water vapor mixing ratio, aerosol backscatter, aerosol extinction, aerosol depolarization and research mode measurements of cloud liquid water, cloud droplet radius, and number density. The Raman Airborne Spectroscopic Lidar (RASL) system was installed in a Beechcraft King Air B200 aircraft and was flown over the mid-Atlantic United States during July August 2007 at altitudes ranging between 5 and 8 km. During these flights, despite suboptimal laser performance and subaperture use of the telescope, all RASL measurement expectations were met, except that of aerosol extinction. Following the Water Vapor Validation Experiment Satellite/Sondes (WAVES_2007) field campaign in the summer of 2007, RASL was installed in a mobile trailer for groundbased use during the Measurements of Humidity and Validation Experiment (MOHAVE-II) field campaign held during October 2007 at the Jet Propulsion Laboratory s Table Mountain Facility in southern California. This ground-based configuration of the lidar hardware is called Atmospheric Lidar for Validation, Interagency Collaboration and Education (ALVICE). During theMOHAVE-II field campaign, during which only nighttime measurements were made, ALVICE demonstrated significant sensitivity to lower-stratospheric water vapor. Numerical simulation and comparisons with a cryogenic frost-point hygrometer are used to demonstrate that a system with the performance characteristics of RASL ALVICE should indeed be able to quantify water vapor well into the lower stratosphere with extended averaging from an elevated location like Table Mountain. The same design considerations that optimize Raman lidar for airborne use on a small research aircraft are, therefore, shown to yield significant dividends in the quantification of lower-stratospheric water vapor. The MOHAVE

  18. Simultaneous Retrieval of Aerosol and Surface Optical Properties from Combined Airborne- and Ground-Based Direct and Diffuse Radiometric Measurements

    Science.gov (United States)

    Gatebe, C. K.; Dubovik, O.; King, M. D.; Sinyuk, A.

    2010-01-01

    This paper presents a new method for simultaneously retrieving aerosol and surface reflectance properties from combined airborne and ground-based direct and diffuse radiometric measurements. The method is based on the standard Aerosol Robotic Network (AERONET) method for retrieving aerosol size distribution, complex index of refraction, and single scattering albedo, but modified to retrieve aerosol properties in two layers, below and above the aircraft, and parameters on surface optical properties from combined datasets (Cloud Absorption Radiometer (CAR) and AERONET data). A key advantage of this method is the inversion of all available spectral and angular data at the same time, while accounting for the influence of noise in the inversion procedure using statistical optimization. The wide spectral (0.34-2.30 m) and angular range (180 ) of the CAR instrument, combined with observations from an AERONET sunphotometer, provide sufficient measurement constraints for characterizing aerosol and surface properties with minimal assumptions. The robustness of the method was tested on observations made during four different field campaigns: (a) the Southern African Regional Science Initiative 2000 over Mongu, Zambia, (b) the Intercontinental Transport Experiment-Phase B over Mexico City, Mexico (c) Cloud and Land Surface Interaction Campaign over the Atmospheric Radiation Measurement (ARM) Central Facility, Oklahoma, USA, and (d) the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) over Elson Lagoon in Barrow, Alaska, USA. The four areas are dominated by different surface characteristics and aerosol types, and therefore provide good test cases for the new inversion method.

  19. NO2 DOAS measurements from ground and space: comparison of ground based measurements and OMI data in Mexico City

    Science.gov (United States)

    Rivera, C.; Stremme, W.; Grutter, M.

    2012-04-01

    The combination of satellite data and ground based measurements can provide valuable information about atmospheric chemistry and air quality. In this work we present a comparison between measured ground based NO2 differential columns at the Universidad Nacional Autónoma de México (UNAM) in Mexico City, using the Differential Optical Absorption Spectroscopy (DOAS) technique and NO2 total columns measured by the Ozone Monitoring Instrument (OMI) onboard the Aura satellite using the same measurement technique. From these data, distribution maps of average NO2 above the Mexico basin were constructed and hot spots inside the city could be identified. In addition, a clear footprint was detected from the Tula industrial area, ~50 km northwest of Mexico City, where a refinery, a power plant and other industries are located. A less defined footprint was identified in the Cuernavaca basin, South of Mexico City, and the nearby cities of Toluca and Puebla do not present strong enhancements in the NO2 total columns. With this study we expect to cross-validate space and ground measurements and provide useful information for future studies.

  20. Solar energy prediction and verification using operational model forecasts and ground-based solar measurements

    International Nuclear Information System (INIS)

    Kosmopoulos, P.G.; Kazadzis, S.; Lagouvardos, K.; Kotroni, V.; Bais, A.

    2015-01-01

    The present study focuses on the predictions and verification of these predictions of solar energy using ground-based solar measurements from the Hellenic Network for Solar Energy and the National Observatory of Athens network, as well as solar radiation operational forecasts provided by the MM5 mesoscale model. The evaluation was carried out independently for the different networks, for two forecast horizons (1 and 2 days ahead), for the seasons of the year, for varying solar elevation, for the indicative energy potential of the area, and for four classes of cloud cover based on the calculated clearness index (k_t): CS (clear sky), SC (scattered clouds), BC (broken clouds) and OC (overcast). The seasonal dependence presented relative rRMSE (Root Mean Square Error) values ranging from 15% (summer) to 60% (winter), while the solar elevation dependence revealed a high effectiveness and reliability near local noon (rRMSE ∼30%). An increment of the errors with cloudiness was also observed. For CS with mean GHI (global horizontal irradiance) ∼ 650 W/m"2 the errors are 8%, for SC 20% and for BC and OC the errors were greater (>40%) but correspond to much lower radiation levels (<120 W/m"2) of consequently lower energy potential impact. The total energy potential for each ground station ranges from 1.5 to 1.9 MWh/m"2, while the mean monthly forecast error was found to be consistently below 10%. - Highlights: • Long term measurements at different atmospheric cases are needed for energy forecasting model evaluations. • The total energy potential at the Greek sites presented ranges from 1.5 to 1.9 MWh/m"2. • Mean monthly energy forecast errors are within 10% for all cases analyzed. • Cloud presence results of an additional forecast error that varies with the cloud cover.

  1. Confronting remote sensing product with ground base measurements across time and scale

    Science.gov (United States)

    Pourmokhtarian, A.; Dietze, M.

    2015-12-01

    Ecosystem models are essential tools in forecasting ecosystem responses to global climate change. One of the most challenging issues in ecosystem modeling is scaling while preserving landscape characteristics and minimizing loss of information, when moving from point observation to regional scale. There is a keen interest in providing accurate inputs for ecosystem models which represent ecosystem initial state conditions. Remote sensing land cover products, such as Landsat NLCD and MODIS MCD12Q1, provide extensive spatio-temporal coverage but do not capture forest composition and structure. Lidar and hyperspectral have the potential to meet this need but lack sufficient spatial and historical coverage. Forest inventory measurements provide detailed information on the landscape but in a very small footprint. Combining inventory and land cover could improve estimates of ecosystem state and characteristic across time and space. This study focuses on the challenges associated with fusing and scaling the US Forest Service FIA database and NLCD across regional scales to quantify ecosystem characteristics and reduce associated uncertainties. Across Southeast of U.S. 400 stratified random samples of 10x10 km2 landscapes were selected. Data on plant density, species, age, and DBH of trees in FIA plots within each site were extracted. Using allometry equations, the canopy cover of different plant functional types (PFTs) was estimated using a PPA-style canopy model and used to assign each inventory plot to a land cover class. Inventory and land cover were fused in a Bayesian model that adjusts the fractional coverage of inventory plots while accounting for multiple sources of uncertainty. Results were compared to estimates derived from inventory alone, land cover alone, and model spin-up alone. Our findings create a framework of data assimilation to better interpret remote sensing data using ground-based measurements.

  2. Snowfall retrieval at X, Ka and W bands: consistency of backscattering and microphysical properties using BAECC ground-based measurements

    Science.gov (United States)

    Tecla Falconi, Marta; von Lerber, Annakaisa; Ori, Davide; Silvio Marzano, Frank; Moisseev, Dmitri

    2018-05-01

    Radar-based snowfall intensity retrieval is investigated at centimeter and millimeter wavelengths using co-located ground-based multi-frequency radar and video-disdrometer observations. Using data from four snowfall events, recorded during the Biogenic Aerosols Effects on Clouds and Climate (BAECC) campaign in Finland, measurements of liquid-water-equivalent snowfall rate S are correlated to radar equivalent reflectivity factors Ze, measured by the Atmospheric Radiation Measurement (ARM) cloud radars operating at X, Ka and W frequency bands. From these combined observations, power-law Ze-S relationships are derived for all three frequencies considering the influence of riming. Using microwave radiometer observations of liquid water path, the measured precipitation is divided into lightly, moderately and heavily rimed snow. Interestingly lightly rimed snow events show a spectrally distinct signature of Ze-S with respect to moderately or heavily rimed snow cases. In order to understand the connection between snowflake microphysical and multi-frequency backscattering properties, numerical simulations are performed by using the particle size distribution provided by the in situ video disdrometer and retrieved ice particle masses. The latter are carried out by using both the T-matrix method (TMM) applied to soft-spheroid particle models with different aspect ratios and exploiting a pre-computed discrete dipole approximation (DDA) database for rimed aggregates. Based on the presented results, it is concluded that the soft-spheroid approximation can be adopted to explain the observed multi-frequency Ze-S relations if a proper spheroid aspect ratio is selected. The latter may depend on the degree of riming in snowfall. A further analysis of the backscattering simulations reveals that TMM cross sections are higher than the DDA ones for small ice particles, but lower for larger particles. The differences of computed cross sections for larger and smaller particles are

  3. Investigation of tropical cirrus cloud properties using ground based lidar measurements

    Science.gov (United States)

    Dhaman, Reji K.; Satyanarayana, Malladi; Krishnakumar, V.; Mahadevan Pillai, V. P.; Jayeshlal, G. S.; Raghunath, K.; Venkat Ratnam, M.

    2016-05-01

    Cirrus clouds play a significant role in the Earths radiation budget. Therefore, knowledge of geometrical and optical properties of cirrus cloud is essential for the climate modeling. In this paper, the cirrus clouds microphysical and optical properties are made by using a ground based lidar measurements over an inland tropical station Gadanki (13.5°N, 79.2°E), Andhra Pradesh, India. The variation of cirrus microphysical and optical properties with mid cloud temperature is also studied. The cirrus clouds mean height is generally observed in the range of 9-17km with a peak occurrence at 13- 14km. The cirrus mid cloud temperature ranges from -81°C to -46°C. The cirrus geometrical thickness ranges from 0.9- 4.5km. During the cirrus occurrence days sub-visual, thin and dense cirrus were at 37.5%, 50% and 12.5% respectively. The monthly cirrus optical depth ranges from 0.01-0.47, but most (<80%) of the cirrus have values less than 0.1. Optical depth shows a strong dependence with cirrus geometrical thickness and mid-cloud height. The monthly mean cirrus extinction ranges from 2.8E-06 to 8E-05 and depolarization ratio and lidar ratio varies from 0.13 to 0.77 and 2 to 52 sr respectively. A positive correlation exists for both optical depth and extinction with the mid-cloud temperature. The lidar ratio shows a scattered behavior with mid-cloud temperature.

  4. On reconciling ground-based with spaceborne normalized radar cross section measurements

    DEFF Research Database (Denmark)

    Baumgartner, Francois; Munk, Jens; Jezek, K C

    2002-01-01

    This study examines differences in the normalized radar cross section, derived from ground-based versus spaceborne radar data. A simple homogeneous half-space model, indicates that agreement between the two improves as 1) the distance from the scatterer is increased; and/or 2) the extinction...

  5. Validation of GOME (ERS-2) NO2 vertical column data with ground-based measurements at Issyk-Kul (Kyrgyzstan)

    Science.gov (United States)

    Ionov, D.; Sinyakov, V.; Semenov, V.

    Starting from 1995 the global monitoring of atmospheric nitrogen dioxide is carried out by the measurements of nadir-viewing GOME spectrometer aboard ERS-2 satellite. Continuous validation of that data by means of comparisons with well-controlled ground-based measurements is important to ensure the quality of GOME data products and improve related retrieval algorithms. At the station of Issyk-Kul (Kyrgyzstan) the ground-based spectroscopic observations of NO2 vertical column have been started since 1983. The station is located on the northern shore of Issyk-Kul lake, 1650 meters above the sea level (42.6 N, 77.0 E). The site is equipped with grating spectrometer for the twilight measurements of zenith-scattered solar radiation in the visible range, and applies the DOAS technique to retrieve NO2 vertical column. It is included in the list of NDSC stations as a complementary one. The present study is focused on validation of GOME NO2 vertical column data, based on 8-year comparison with correlative ground-based measurements at Issyk-Kul station in 1996-2003. Within the investigation, an agreement of both individual and monthly averaged GOME measurements with corresponding twilight ground-based observations is examined. Such agreement is analyzed with respect to different conditions (season, sun elevation), temporal/spatial criteria choice (actual overpass location, correction for diurnal variation) and data processing (GDP version 2.7, 3.0). In addition, NO2 vertical columns were integrated from simultaneous stratospheric profile measurements by NASA HALOE and SAGE-II/III satellite instruments and introduced to explain the differences with ground-based observations. In particular cases, NO2 vertical profiles retrieved from the twilight ground-based measurements at Issuk-Kul were also included into comparison. Overall, summertime GOME NO2 vertical columns were found to be systematicaly lower than ground-based data. This work was supported by International Association

  6. Comparison of GOME tropospheric NO2 columns with NO2 profiles deduced from ground-based in situ measurements

    Science.gov (United States)

    Schaub, D.; Boersma, K. F.; Kaiser, J. W.; Weiss, A. K.; Folini, D.; Eskes, H. J.; Buchmann, B.

    2006-08-01

    Nitrogen dioxide (NO2) vertical tropospheric column densities (VTCs) retrieved from the Global Ozone Monitoring Experiment (GOME) are compared to coincident ground-based tropospheric NO2 columns. The ground-based columns are deduced from in situ measurements at different altitudes in the Alps for 1997 to June 2003, yielding a unique long-term comparison of GOME NO2 VTC data retrieved by a collaboration of KNMI (Royal Netherlands Meteorological Institute) and BIRA/IASB (Belgian Institute for Space Aeronomy) with independently derived tropospheric NO2 profiles. A first comparison relates the GOME retrieved tropospheric columns to the tropospheric columns obtained by integrating the ground-based NO2 measurements. For a second comparison, the tropospheric profiles constructed from the ground-based measurements are first multiplied with the averaging kernel (AK) of the GOME retrieval. The second approach makes the comparison independent from the a priori NO2 profile used in the GOME retrieval. This allows splitting the total difference between the column data sets into two contributions: one that is due to differences between the a priori and the ground-based NO2 profile shapes, and another that can be attributed to uncertainties in both the remaining retrieval parameters (such as, e.g., surface albedo or aerosol concentration) and the ground-based in situ NO2 profiles. For anticyclonic clear sky conditions the comparison indicates a good agreement between the columns (n=157, R=0.70/0.74 for the first/second comparison approach, respectively). The mean relative difference (with respect to the ground-based columns) is -7% with a standard deviation of 40% and GOME on average slightly underestimating the ground-based columns. Both data sets show a similar seasonal behaviour with a distinct maximum of spring NO2 VTCs. Further analysis indicates small GOME columns being systematically smaller than the ground-based ones. The influence of different shapes in the a priori and

  7. Comparison of GOME tropospheric NO2 columns with NO2 profiles deduced from ground-based in situ measurements

    Directory of Open Access Journals (Sweden)

    D. Schaub

    2006-01-01

    Full Text Available Nitrogen dioxide (NO2 vertical tropospheric column densities (VTCs retrieved from the Global Ozone Monitoring Experiment (GOME are compared to coincident ground-based tropospheric NO2 columns. The ground-based columns are deduced from in situ measurements at different altitudes in the Alps for 1997 to June 2003, yielding a unique long-term comparison of GOME NO2 VTC data retrieved by a collaboration of KNMI (Royal Netherlands Meteorological Institute and BIRA/IASB (Belgian Institute for Space Aeronomy with independently derived tropospheric NO2 profiles. A first comparison relates the GOME retrieved tropospheric columns to the tropospheric columns obtained by integrating the ground-based NO2 measurements. For a second comparison, the tropospheric profiles constructed from the ground-based measurements are first multiplied with the averaging kernel (AK of the GOME retrieval. The second approach makes the comparison independent from the a priori NO2 profile used in the GOME retrieval. This allows splitting the total difference between the column data sets into two contributions: one that is due to differences between the a priori and the ground-based NO2 profile shapes, and another that can be attributed to uncertainties in both the remaining retrieval parameters (such as, e.g., surface albedo or aerosol concentration and the ground-based in situ NO2 profiles. For anticyclonic clear sky conditions the comparison indicates a good agreement between the columns (n=157, R=0.70/0.74 for the first/second comparison approach, respectively. The mean relative difference (with respect to the ground-based columns is −7% with a standard deviation of 40% and GOME on average slightly underestimating the ground-based columns. Both data sets show a similar seasonal behaviour with a distinct maximum of spring NO2 VTCs. Further analysis indicates small GOME columns being systematically smaller than the ground-based ones. The influence of different shapes in the a

  8. Analysis of polarization characteristics of plant canopies using ground-based remote sensing measurements

    International Nuclear Information System (INIS)

    Sid’ko, A.F.; Botvich, I.Yu.; Pisman, T.I.; Shevyrnogov, A.P.

    2014-01-01

    The paper presents results and analysis of a study on polarized characteristics of the reflectance factor of different plant canopies under field conditions, using optical remote sensing techniques. Polarization characteristics were recorded from the elevated work platform at heights of 10–18 m in June and July. Measurements were performed using a double-beam spectrophotometer with a polarized light filter attachment, within the spectral range from 400 to 820 nm. The viewing zenith angle was below 20 degree. Birch (Betila pubescens), pine (Pinus sylvestris L.), wheat (Triticum acstivum) [L.] crops, corn (Zea mays L. ssp. mays) crops, and various grass canopies were used in this study. The following polarization characteristics were studied: the reflectance factor of the canopy with the polarizer adjusted to transmit the maximum and minimum amounts of light (R max and R min ), polarized component of the reflectance factor (R q ), and the degree of polarization (P). Wheat, corn, and grass canopies have higher R max and R min values than forest plants. The R q and P values are higher for the birch than for the pine within the wavelength range between 430 and 740 nm. The study shows that polarization characteristics of plant canopies may be used as an effective means of decoding remote sensing data. - Highlights: • The reflection and polarization properties of plant were studied. • The compiled electronic database of the spectrophotometric information of plant. • Polarization characteristics are a source of useful data on the state of plants

  9. Atmospheric greenhouse gases retrieved from SCIAMACHY: comparison to ground-based FTS measurements and model results

    Directory of Open Access Journals (Sweden)

    O. Schneising

    2012-02-01

    Full Text Available SCIAMACHY onboard ENVISAT (launched in 2002 enables the retrieval of global long-term column-averaged dry air mole fractions of the two most important anthropogenic greenhouse gases carbon dioxide and methane (denoted XCO2 and XCH4. In order to assess the quality of the greenhouse gas data obtained with the recently introduced v2 of the scientific retrieval algorithm WFM-DOAS, we present validations with ground-based Fourier Transform Spectrometer (FTS measurements and comparisons with model results at eight Total Carbon Column Observing Network (TCCON sites providing realistic error estimates of the satellite data. Such validation is a prerequisite to assess the suitability of data sets for their use in inverse modelling.

    It is shown that there are generally no significant differences between the carbon dioxide annual increases of SCIAMACHY and the assimilation system CarbonTracker (2.00 ± 0.16 ppm yr−1 compared to 1.94 ± 0.03 ppm yr−1 on global average. The XCO2 seasonal cycle amplitudes derived from SCIAMACHY are typically larger than those from TCCON which are in turn larger than those from CarbonTracker. The absolute values of the northern hemispheric TCCON seasonal cycle amplitudes are closer to SCIAMACHY than to CarbonTracker and the corresponding differences are not significant when compared with SCIAMACHY, whereas they can be significant for a subset of the analysed TCCON sites when compared with CarbonTracker. At Darwin we find discrepancies of the seasonal cycle derived from SCIAMACHY compared to the other data sets which can probably be ascribed to occurrences of undetected thin clouds. Based on the comparison with the reference data, we conclude that the carbon dioxide data set can be characterised by a regional relative precision (mean standard deviation of the differences of about 2.2 ppm and a relative accuracy (standard deviation of the mean differences

  10. A comparison of ground-based hydroxyl airglow temperatures with SABER/TIMED measurements over 23° N, India

    Science.gov (United States)

    Parihar, Navin; Singh, Dupinder; Gurubaran, Subramanian

    2017-03-01

    Ground-based observations of OH (6, 2) Meinel band nightglow were carried out at Ranchi (23.3° N, 85.3° E), India, during January-March 2011, December 2011-May 2012 and December 2012-March 2013 using an all-sky imaging system. Near the mesopause, OH temperatures were derived from the OH (6, 2) Meinel band intensity information. A limited comparison of OH temperatures (TOH) with SABER/TIMED measurements in 30 cases was performed by defining almost coincident criterion of ±1.5° latitude-longitude and ±3 min of the ground-based observations. Using SABER OH 1.6 and 2.0 µm volume emission rate profiles as the weighing function, two sets of OH-equivalent temperature (T1. 6 and T2. 0 respectively) were estimated from its kinetic temperature profile for comparison with OH nightglow measurements. Overall, fair agreement existed between ground-based and SABER measurements in the majority of events within the limits of experimental errors. Overall, the mean value of OH-derived temperatures and SABER OH-equivalent temperatures were 197.3 ± 4.6, 192.0 ± 10.8 and 192.7 ± 10.3 K, and the ground-based temperatures were 4-5 K warmer than SABER values. A difference of 8 K or more is noted between two measurements when the peak of the OH emission layer lies in the vicinity of large temperature inversions. A comparison of OH temperatures derived using different sets of Einstein transition probabilities and SABER measurements was also performed; however, OH temperatures derived using Langhoff et al. (1986) transition probabilities were found to compare well.

  11. An In Depth Look at Lightning Trends in Hurricane Harvey using Satellite and Ground-Based Measurements

    Science.gov (United States)

    Ringhausen, J.

    2017-12-01

    This research combines satellite measurements of lightning in Hurricane Harvey with ground-based lightning measurements to get a better sense of the total lightning occurring in the hurricane, both intra-cloud (IC) and cloud-to-ground (CG), and how it relates to the intensification and weakening of the tropical system. Past studies have looked at lightning trends in hurricanes using the space based Lightning Imaging Sensor (LIS) or ground-based lightning detection networks. However, both of these methods have drawbacks. For instance, LIS was in low earth orbit, which limited lightning observations to 90 seconds for a particular point on the ground; hence, continuous lightning coverage of a hurricane was not possible. Ground-based networks can have a decreased detection efficiency, particularly for ICs, over oceans where hurricanes generally intensify. With the launch of the Geostationary Lightning Mapper (GLM) on the GOES-16 satellite, researchers can study total lightning continuously over the lifetime of a tropical cyclone. This study utilizes GLM to investigate total lightning activity in Hurricane Harvey temporally; this is augmented with spatial analysis relative to hurricane structure, similar to previous studies. Further, GLM and ground-based network data are combined using Bayesian techniques in a new manner to leverage the strengths of each detection method. This methodology 1) provides a more complete estimate of lightning activity and 2) enables the derivation of the IC:CG ratio (Z-ratio) throughout the time period of the study. In particular, details of the evolution of the Z-ratio in time and space are presented. In addition, lightning stroke spatiotemporal trends are compared to lightning flash trends. This research represents a new application of lightning data that can be used in future study of tropical cyclone intensification and weakening.

  12. Ion cyclotron waves: Direct compariosn between ground-based measurements and observations in the source region

    International Nuclear Information System (INIS)

    Perraut, S.; Gendrin, R.; Roux, A.; de Villedary, C.

    1984-01-01

    Simultaneous measurements of ion cyclotron waves (ICW's) were performed on GEOS spacecraft and in the vicinity of their magnetic footprints with the French Mobile station. The detailed comparison between the two sets of data shown that while ICW's having F + gyrofrequency at the equator, generally propagate to the ground, only 50% of those generated above F/sub He/ can reach the ground station. It is shown that these results are in good agreement with the conclusions that Rauch and Roux [1982] drew on the basis of measurements reported by Young et al 1981]. In an He + -rich plasma, ICW's with F>F/sub He/ suffer a reflection where the frequency locally matches the local bi-ion hybrid frequency. We extend the calculations of Rauch and Roux and calculate, as a function of the He + concentration, the tunneling of ICW's through the stopband induced by the presence of minor He + ions. It is shown that the transmission coefficient strongly depends upon the wave frequency for a given He + abundance ratio. The results obtained are shown to be supported by existing observations

  13. Development of ground-based lidars for measuring H2O and O3 profiles in the troposphere

    Science.gov (United States)

    Sakai, T.; Abo, M.; Pham, L. H. P.; Uchino, O.; Nagai, T.; Izumi, T.; Morino, I.; Ohyama, H.; Nagasawa, C.

    2015-12-01

    Water vapor is the strongest natural greenhouse gas and a highly variable atmospheric constituent. It plays an important role of the energy transfer and the meteorological phenomena such as evaporation, vapor transport, cloud formation, and rainfall in the troposphere. Ozone is an important air pollutant that at high concentrations impacts on human health and ecosystem including crops and also a greenhouse gas that plays an important role in climate change. Aerosol is an important climate parameter and also one of the largest error sources (causes) in retrieval from solar reflected short wavelength infrared radiances observed with greenhouse gases observing satellites such as the GOSAT and OCO-2. Therefore, we have been developing ground-based differential absorption lidars (DIALs) for measuring the tropospheric water vapor, ozone and aerosols.The water vapor DIAL employs two distributed Bragg reflector (DBR) lasers operating at 829.054 nm for the online wavelength and 829.124 nm for the offline wavelength with tapered semiconductor optical amplifier (TSOA) in a master oscillator power amplifier (MOPA) configuration, and utilizes pseudorandom coded pulse modulation technique.It has started to measure the vertical distribution of lower tropospheric water vapor in order to improve accuracy and lead time of numerical weather prediction of local heavy rainfalls. Well-organized and regularly spaced convective cells of which vertical thickness were 200 m and the periods were 10 minutes were observed in the top of planetary boundary layer at 2.5 km altitude over Tokyo (35.66°N, 139.37°E) on 22 June 2015.The ozone DIAL employs a Nd:YAG laser and a 2 m long Raman cell filled with CO2 gas which generates four Stokes lines (276.2, 287.2, 299.1, and 312.0 nm) of stimulated Raman scattering, and two receiving telescopes with diameters of 49 and 10 cm.It has started to measure the vertical distributions of the tropospheric ozone as well as aerosols and thin cirrus cloud in

  14. Measurements of total and tropospheric ozone from IASI: comparison with correlative satellite, ground-based and ozonesonde observations

    Directory of Open Access Journals (Sweden)

    A. Boynard

    2009-08-01

    Full Text Available In this paper, we present measurements of total and tropospheric ozone, retrieved from infrared radiance spectra recorded by the Infrared Atmospheric Sounding Interferometer (IASI, which was launched on board the MetOp-A European satellite in October 2006. We compare IASI total ozone columns to Global Ozone Monitoring Experiment-2 (GOME-2 observations and ground-based measurements from the Dobson and Brewer network for one full year of observations (2008. The IASI total ozone columns are shown to be in good agreement with both GOME-2 and ground-based data, with correlation coefficients of about 0.9 and 0.85, respectively. On average, IASI ozone retrievals exhibit a positive bias of about 9 DU (3.3% compared to both GOME-2 and ground-based measurements. In addition to total ozone columns, the good spectral resolution of IASI enables the retrieval of tropospheric ozone concentrations. Comparisons of IASI tropospheric columns to 490 collocated ozone soundings available from several stations around the globe have been performed for the period of June 2007–August 2008. IASI tropospheric ozone columns compare well with sonde observations, with correlation coefficients of 0.95 and 0.77 for the [surface–6 km] and [surface–12 km] partial columns, respectively. IASI retrievals tend to overestimate the tropospheric ozone columns in comparison with ozonesonde measurements. Positive average biases of 0.15 DU (1.2% and 3 DU (11% are found for the [surface–6 km] and for the [surface–12 km] partial columns respectively.

  15. Helicopter-borne observations of the continental background aerosol in combination with remote sensing and ground-based measurements

    Science.gov (United States)

    Düsing, Sebastian; Wehner, Birgit; Seifert, Patric; Ansmann, Albert; Baars, Holger; Ditas, Florian; Henning, Silvia; Ma, Nan; Poulain, Laurent; Siebert, Holger; Wiedensohler, Alfred; Macke, Andreas

    2018-01-01

    This paper examines the representativeness of ground-based in situ measurements for the planetary boundary layer (PBL) and conducts a closure study between airborne in situ and ground-based lidar measurements up to an altitude of 2300 m. The related measurements were carried out in a field campaign within the framework of the High-Definition Clouds and Precipitation for Advancing Climate Prediction (HD(CP)2) Observational Prototype Experiment (HOPE) in September 2013 in a rural background area of central Europe.The helicopter-borne probe ACTOS (Airborne Cloud and Turbulence Observation System) provided measurements of the aerosol particle number size distribution (PNSD), the aerosol particle number concentration (PNC), the number concentration of cloud condensation nuclei (CCN-NC), and meteorological atmospheric parameters (e.g., temperature and relative humidity). These measurements were supported by the ground-based 3+2 wavelength polarization lidar system PollyXT, which provided profiles of the particle backscatter coefficient (σbsc) for three wavelengths (355, 532, and 1064 nm). Particle extinction coefficient (σext) profiles were obtained by using a fixed backscatter-to-extinction ratio (also lidar ratio, LR). A new approach was used to determine profiles of CCN-NC for continental aerosol. The results of this new approach were consistent with the airborne in situ measurements within the uncertainties.In terms of representativeness, the PNSD measurements on the ground showed a good agreement with the measurements provided with ACTOS for lower altitudes. The ground-based measurements of PNC and CCN-NC are representative of the PBL when the PBL is well mixed. Locally isolated new particle formation events on the ground or at the top of the PBL led to vertical variability in the cases presented here and ground-based measurements are not entirely representative of the PBL. Based on Mie theory (Mie, 1908), optical aerosol properties under ambient conditions for

  16. Helicopter-borne observations of the continental background aerosol in combination with remote sensing and ground-based measurements

    Directory of Open Access Journals (Sweden)

    S. Düsing

    2018-01-01

    Full Text Available This paper examines the representativeness of ground-based in situ measurements for the planetary boundary layer (PBL and conducts a closure study between airborne in situ and ground-based lidar measurements up to an altitude of 2300 m. The related measurements were carried out in a field campaign within the framework of the High-Definition Clouds and Precipitation for Advancing Climate Prediction (HD(CP2 Observational Prototype Experiment (HOPE in September 2013 in a rural background area of central Europe.The helicopter-borne probe ACTOS (Airborne Cloud and Turbulence Observation System provided measurements of the aerosol particle number size distribution (PNSD, the aerosol particle number concentration (PNC, the number concentration of cloud condensation nuclei (CCN-NC, and meteorological atmospheric parameters (e.g., temperature and relative humidity. These measurements were supported by the ground-based 3+2 wavelength polarization lidar system PollyXT, which provided profiles of the particle backscatter coefficient (σbsc for three wavelengths (355, 532, and 1064 nm. Particle extinction coefficient (σext profiles were obtained by using a fixed backscatter-to-extinction ratio (also lidar ratio, LR. A new approach was used to determine profiles of CCN-NC for continental aerosol. The results of this new approach were consistent with the airborne in situ measurements within the uncertainties.In terms of representativeness, the PNSD measurements on the ground showed a good agreement with the measurements provided with ACTOS for lower altitudes. The ground-based measurements of PNC and CCN-NC are representative of the PBL when the PBL is well mixed. Locally isolated new particle formation events on the ground or at the top of the PBL led to vertical variability in the cases presented here and ground-based measurements are not entirely representative of the PBL. Based on Mie theory (Mie, 1908, optical aerosol properties under ambient

  17. Aerosol optical properties over the Svalbard region of Arctic: ground-based measurements and satellite remote sensing

    Science.gov (United States)

    Gogoi, Mukunda M.; Babu, S. Suresh

    2016-05-01

    In view of the increasing anthropogenic presence and influence of aerosols in the northern polar regions, long-term continuous measurements of aerosol optical parameters have been investigated over the Svalbard region of Norwegian Arctic (Ny-Ålesund, 79°N, 12°E, 8 m ASL). This study has shown a consistent enhancement in the aerosol scattering and absorption coefficients during spring. The relative dominance of absorbing aerosols is more near the surface (lower single scattering albedo), compared to that at the higher altitude. This is indicative of the presence of local anthropogenic activities. In addition, long-range transported biomass burning aerosols (inferred from the spectral variation of absorption coefficient) also contribute significantly to the higher aerosol absorption in the Arctic spring. Aerosol optical depth (AOD) estimates from ground based Microtop sun-photometer measurements reveals that the columnar abundance of aerosols reaches the peak during spring season. Comparison of AODs between ground based and satellite remote sensing indicates that deep blue algorithm of Moderate Resolution Imaging Spectroradiometer (MODIS) retrievals over Arctic snow surfaces overestimate the columnar AOD.

  18. The thermal signature of Aso Volcano during unrest episodes detected from space and ground-based measurements

    Science.gov (United States)

    Cigolini, Corrado; Coppola, Diego; Yokoo, Akihiko; Laiolo, Marco

    2018-04-01

    The thermal signature of Aso Volcano (Nakadake) during unrest episodes has been analyzed by combining the MODIS-MIROVA data set (2000-2017) with high-resolution images (LANDSAT 8 OLI and Sentinel 2) and ground-based thermal observations (2013-2017). The site of major activity (crater 1) is located at the summit of the volcano and is composed by a fumarole field (located in the South Area) and an acidic lake (replaced by a Central Pit during Strombolian phases). The volcanic radiative power (VRP) obtained by nighttime satellite data during the reference period was mainly below 3 MW. This thermal threshold marks the transition from high fumarole activity (HFA) to Strombolian eruptions (SE). However, periods characterized by sporadic phreatic eruptions (PE, eventually bearing phreatomagmatic episodes), which is the prevalent phase during unrest episodes, exhibit very low VRP values, being around 0.5 MW, or below. The statistical analysis of satellite data shows that the transition from HFA to Strombolian activity (which started on August 2014 and ceased in May 2015) occurs when VRP values are above the cited 3 MW threshold. In particular during marked Strombolian phases (November-December 2014), the radiative power was higher than 4 MW, reaching peak values up to 15.6 MW (on December 7, 2014, i.e., 10 days after the major Strombolian explosion of November 27). Conversely, ground-based measurements show that heat fluxes recorded by FLIR T440 Thermo-camera on the fumarole field of the South Area has been relatively stable around 2 MW until February 2015. Their apparent temperatures were fluctuating around 490-575 °C before the major Strombolian explosive event, whereas those recorded at the active vent, named Central Pit, reached their maxima slightly above 600 °C; then both exhibited a decreasing trend in the following days. During the Strombolian activity, the crater lake dried out and was then replenished by early July, 2016. Then, volcanic activity shifted back to

  19. The retrieval of profile and chemical information from ground-based UV-visible spectroscopic measurements

    International Nuclear Information System (INIS)

    Schofield, R.; Connor, B.J.; Kreher, K.; Johnston, P.V.; Rodgers, C.D.

    2004-01-01

    An algorithm has been developed to retrieve altitude information at different diurnal stages for trace gas species by combining direct-sun and zenith-sky UV-visible differential slant column density (DSCD) measurements. DSCDs are derived here using differential optical absorption spectroscopy. Combining the complementary zenith-sky measurements (sensitive to the stratosphere) with direct-sun measurements (sensitive to the troposphere) allows this vertical distinction. Trace gas species such as BrO and NO 2 have vertical profiles with strong diurnal dependence. Information about the diurnal variation is simultaneously retrieved with the altitude distribution of the trace gas. The retrieval is a formal optimal estimation profile retrieval, allowing a complete assessment of information content and errors

  20. Temperature profiles by ground-based remote sensing and in situ measurements

    Energy Technology Data Exchange (ETDEWEB)

    Argentini, S; Pietroni, I; Conidi, A; Mastrantonio, G; Petenko, I; Viola, A [ISAC-CNR, Via del Fosso del Cavaliere, 100, 00133 Roma (Italy); Gariazzo, C; Pelliccioni, A; Amicarelli, A [ISPESL Dipartimento Insediamenti Produttivi e Interazione con l' Ambiente, Via Fontana Candida, 1, 00040 Monteporzio Catone (RM) (Italy)], E-mail: s.argentini@isac.cnr.it

    2008-05-01

    This study focuses on the accuracy of the temperature profiles measured with a Doppler Radio-Acoustic Sounding System and a Microwave Temperature Profiler during a period of about 3 months in winter 2007-2008. The experiment was carried on at the experimental facility of the Institute of Atmospheric Sciences and Climate (ISAC) of the Italian National Research Council (CNR). The temperature data measured with remote sensors were verified with in situ measurements on a mast as well as with tethered balloon data. The facsimile echograms obtained with the ISAC Doppler SODAR were analysed to understand to which extent the RASS and Radiometer temperature profiles behaviour can represent the real thermal structure of the atmosphere.

  1. Temperature profiles by ground-based remote sensing and in situ measurements

    International Nuclear Information System (INIS)

    Argentini, S; Pietroni, I; Conidi, A; Mastrantonio, G; Petenko, I; Viola, A; Gariazzo, C; Pelliccioni, A; Amicarelli, A

    2008-01-01

    This study focuses on the accuracy of the temperature profiles measured with a Doppler Radio-Acoustic Sounding System and a Microwave Temperature Profiler during a period of about 3 months in winter 2007-2008. The experiment was carried on at the experimental facility of the Institute of Atmospheric Sciences and Climate (ISAC) of the Italian National Research Council (CNR). The temperature data measured with remote sensors were verified with in situ measurements on a mast as well as with tethered balloon data. The facsimile echograms obtained with the ISAC Doppler SODAR were analysed to understand to which extent the RASS and Radiometer temperature profiles behaviour can represent the real thermal structure of the atmosphere

  2. Ground-based lidar measurements from Ny-Ålesund during ASTAR 2007

    Directory of Open Access Journals (Sweden)

    A. Herber

    2009-11-01

    Full Text Available During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR in March and April 2007, measurements obtained at the AWIPEV Arctic Research Base in Ny-Ålesund, Spitsbergen at 78.9° N, 11.9° E (operated by the Alfred Wegener Institute for Polar and Marine Research – AWI and the Institut polaire français Paul-Emile Victor – IPEV, supported the airborne campaign. This included lidar data from the Koldewey Aerosol Raman Lidar (KARL and the Micro Pulse Lidar (MPL, located in the atmospheric observatory as well as photometer data and the daily launched radiosonde. The MPL features nearly continuous measurements; the KARL was switched on whenever weather conditions allowed observations (145 h in 61 days. From 1 March to 30 April, 71 meteorological balloon soundings were performed and compared with the concurrent MPL measurements; photometer measurements are available from 18 March. For the KARL data, a statistical overview of particle detection based on their optical properties backscatter ratio and volume depolarization can be given. The altitudes of the occurrence of the named features (subvisible and visible ice and water as well as mixed-phase clouds, aerosol layers as well as their dependence on different air mass origins are analyzed. Although the spring 2007 was characterized by rather clean conditions, diverse case studies of cloud and aerosol occurrence during March and April 2007 are presented in more detail, including temporal development and main optical properties as depolarization, backscatter and extinction coefficients. Links between air mass origins and optical properties can be presumed but need further evidence.

  3. Tracking atmospheric boundary layer in tehran using combined lidar remote sensing and ground base measurements

    Science.gov (United States)

    Panahifar, Hossein; Khalesifard, Hamid

    2018-04-01

    The vertical structure of the atmospheric boundary layer (ABL) has been studied by use of a depolarized LiDAR over Tehran, Iran. The boundary layer height (BLH) remains under 1km, and its retrieval from LiDAR have been compared with sonding measurements and meteorological model outputs. It is also shown that the wind speed and direction as well as topography lead to the persistence of air pollution in Tehran. The situation aggravate in fall and winter due to temperature inversion.

  4. Surface energy budget and thermal inertia at Gale Crater: Calculations from ground-based measurements.

    Science.gov (United States)

    Martínez, G M; Rennó, N; Fischer, E; Borlina, C S; Hallet, B; de la Torre Juárez, M; Vasavada, A R; Ramos, M; Hamilton, V; Gomez-Elvira, J; Haberle, R M

    2014-08-01

    The analysis of the surface energy budget (SEB) yields insights into soil-atmosphere interactions and local climates, while the analysis of the thermal inertia ( I ) of shallow subsurfaces provides context for evaluating geological features. Mars orbital data have been used to determine thermal inertias at horizontal scales of ∼10 4  m 2 to ∼10 7  m 2 . Here we use measurements of ground temperature and atmospheric variables by Curiosity to calculate thermal inertias at Gale Crater at horizontal scales of ∼10 2  m 2 . We analyze three sols representing distinct environmental conditions and soil properties, sol 82 at Rocknest (RCK), sol 112 at Point Lake (PL), and sol 139 at Yellowknife Bay (YKB). Our results indicate that the largest thermal inertia I  = 452 J m -2  K -1  s -1/2 (SI units used throughout this article) is found at YKB followed by PL with I  = 306 and RCK with I  = 295. These values are consistent with the expected thermal inertias for the types of terrain imaged by Mastcam and with previous satellite estimations at Gale Crater. We also calculate the SEB using data from measurements by Curiosity's Rover Environmental Monitoring Station and dust opacity values derived from measurements by Mastcam. The knowledge of the SEB and thermal inertia has the potential to enhance our understanding of the climate, the geology, and the habitability of Mars.

  5. Soil water content and evaporation determined by thermal parameters obtained from ground-based and remote measurements

    Science.gov (United States)

    Reginato, R. J.; Idso, S. B.; Jackson, R. D.; Vedder, J. F.; Blanchard, M. B.; Goettelman, R.

    1976-01-01

    Soil water contents from both smooth and rough bare soil were estimated from remotely sensed surface soil and air temperatures. An inverse relationship between two thermal parameters and gravimetric soil water content was found for Avondale loam when its water content was between air-dry and field capacity. These parameters, daily maximum minus minimum surface soil temperature and daily maximum soil minus air temperature, appear to describe the relationship reasonably well. These two parameters also describe relative soil water evaporation (actual/potential). Surface soil temperatures showed good agreement among three measurement techniques: in situ thermocouples, a ground-based infrared radiation thermometer, and the thermal infrared band of an airborne multispectral scanner.

  6. Calibrating a ground-based backscatter lidar for continuous measurements of PM2.5

    Science.gov (United States)

    Pesch, Markus; Oderbolz, Daniel

    2007-10-01

    One of the main issues of atmospheric research and air quality control is the reduction of harmful particulate matter (PM) in the atmosphere. Small particles can enter the human airways and cause serious health problems such as COPD (Chronic Obstructive Pulmonary Disease), asthma or even lung cancer. Recently, interest has shifted from PM10 to finer fractions of particulate matter, e.g. PM2.5, because the health impact of finer particles is considered to be more severe. Up to now measurements of particulate matter were carried out mainly at ground level. However important atmospheric processes, i.e. particle formation, transport and vertical mixing processes, take place predominantly at higher altitudes in the planetary boundary layer. Lidar in principle provides the ability to observe these processes where they occur. The new method outlined in this paper demonstrates the use of a small sized and quite inexpensive lidar in stand-alone operation to investigate transport processes of particulate matter, and PM2.5 in particular. Continuous measurements of PM2.5 as a reference are gained with a conventional in-situ monitor, installed on a tower at an altitude of 325 m in the North of Berlin (Frohnauer Turm). These PM2.5 measurements will be compared with backscatter Lidar data (1064 nm) taken from approx. 60 m over ground up to an altitude of 15 km with a spatial resolution of 15 m. The vertical backscatter profiles at 325 m will be correlated to the concentrations obtained by the PM2,5 monitor on the tower. Both measurements have a time resolution of 180 s to observe also processes that take place at short time scales. The objective is to gain correlation functions for estimating PM2.5 concentrations from backscatter Lidar data. Such a calibrated Lidar system is a valuable instrument for environmental agencies and atmospheric research groups to observe and investigate causes of high level PM concentrations. First results show a reasonably good linear correlation

  7. Assessment of surface solar irradiance derived from real-time modelling techniques and verification with ground-based measurements

    Science.gov (United States)

    Kosmopoulos, Panagiotis G.; Kazadzis, Stelios; Taylor, Michael; Raptis, Panagiotis I.; Keramitsoglou, Iphigenia; Kiranoudis, Chris; Bais, Alkiviadis F.

    2018-02-01

    This study focuses on the assessment of surface solar radiation (SSR) based on operational neural network (NN) and multi-regression function (MRF) modelling techniques that produce instantaneous (in less than 1 min) outputs. Using real-time cloud and aerosol optical properties inputs from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board the Meteosat Second Generation (MSG) satellite and the Copernicus Atmosphere Monitoring Service (CAMS), respectively, these models are capable of calculating SSR in high resolution (1 nm, 0.05°, 15 min) that can be used for spectrally integrated irradiance maps, databases and various applications related to energy exploitation. The real-time models are validated against ground-based measurements of the Baseline Surface Radiation Network (BSRN) in a temporal range varying from 15 min to monthly means, while a sensitivity analysis of the cloud and aerosol effects on SSR is performed to ensure reliability under different sky and climatological conditions. The simulated outputs, compared to their common training dataset created by the radiative transfer model (RTM) libRadtran, showed median error values in the range -15 to 15 % for the NN that produces spectral irradiances (NNS), 5-6 % underestimation for the integrated NN and close to zero errors for the MRF technique. The verification against BSRN revealed that the real-time calculation uncertainty ranges from -100 to 40 and -20 to 20 W m-2, for the 15 min and monthly mean global horizontal irradiance (GHI) averages, respectively, while the accuracy of the input parameters, in terms of aerosol and cloud optical thickness (AOD and COT), and their impact on GHI, was of the order of 10 % as compared to the ground-based measurements. The proposed system aims to be utilized through studies and real-time applications which are related to solar energy production planning and use.

  8. Information operator approach applied to the retrieval of vertical distributions of atmospheric constituents from ground-based FTIR measurements

    Science.gov (United States)

    Senten, Cindy; de Mazière, Martine; Vanhaelewyn, Gauthier; Vigouroux, Corinne; Delmas, Robert

    2010-05-01

    The retrieval of information about the vertical distribution of an atmospheric absorber from high spectral resolution ground-based Fourier Transform infrared (FTIR) solar absorption spectra is an important issue in remote sensing. A frequently used technique at present is the optimal estimation method. This work introduces the application of an alternative method, namely the information operator approach (Doicu et al., 2007; Hoogen et al., 1999), for extracting the available information from such FTIR measurements. This approach has been implemented within the well-known retrieval code SFIT2, by adapting the optimal estimation method such as to take into account only the significant contributions to the solution. In particular, we demonstrate the feasibility of the method when applied to ground-based FTIR spectra taken at the southern (sub)tropical site Ile de La Réunion (21° S, 55° E) in 2007. A thorough comparison has been made between the retrieval results obtained with the original optimal estimation method and the ones obtained with the information operator approach, regarding profile and column stability, information content and corresponding full error budget evaluation. This has been done for the target species ozone (O3), methane (CH4), nitrous oxide (N2O), and carbon monoxide (CO). It is shown that the information operator approach performs well and is capable of achieving the same accuracy as optimal estimation, with a gain of stability and with the additional advantage of being less sensitive to the choice of a priori information as well as to the actual signal-to-noise ratio. Keywords: ground-based FTIR, solar absorption spectra, greenhouse gases, information operator approach References Doicu, A., Hilgers, S., von Bargen, A., Rozanov, A., Eichmann, K.-U., von Savigny, C., and Burrows, J.P.: Information operator approach and iterative regularization methods for atmospheric remote sensing, J. Quant. Spectrosc. Radiat. Transfer, 103, 340-350, 2007

  9. Ground based measurements of particulate emissions from supersonic transports. Concorde olympus engine

    Energy Technology Data Exchange (ETDEWEB)

    Whitefield, Ph D; Hagen, D E [Missouri Univ., Rolla, MO (United States). Cloud and Aerosol Sciences Lab.; Lilenfeld, H V [McDonnell Douglas Corp., St. Louis, MO (United States)

    1998-12-31

    The application of a mobile aerosol monitoring facility, the Mobile Aerosol Sampling System (MASS) is described to characterize engine aerosol emissions from the Rolls Royce Olympus Engine. The multi-configurational MASS has been employed in both ground and airborne field operations. It has been successfully flown on research aircrafts. In ground tests the MASS has participated in numerous jet engine related ground tests, and has been deployed to resolve aerosol generation problems in a high power chemical laser system. In all cases the measurements were made on samples taken from a harsh physical and chemical environment, with both high and low temperature and pressure, and in the presence of highly reactive gases. (R.P.) 9 refs.

  10. Ground based measurements of particulate emissions from supersonic transports. Concorde olympus engine

    Energy Technology Data Exchange (ETDEWEB)

    Whitefield, Ph.D.; Hagen, D.E. [Missouri Univ., Rolla, MO (United States). Cloud and Aerosol Sciences Lab.; Lilenfeld, H.V. [McDonnell Douglas Corp., St. Louis, MO (United States)

    1997-12-31

    The application of a mobile aerosol monitoring facility, the Mobile Aerosol Sampling System (MASS) is described to characterize engine aerosol emissions from the Rolls Royce Olympus Engine. The multi-configurational MASS has been employed in both ground and airborne field operations. It has been successfully flown on research aircrafts. In ground tests the MASS has participated in numerous jet engine related ground tests, and has been deployed to resolve aerosol generation problems in a high power chemical laser system. In all cases the measurements were made on samples taken from a harsh physical and chemical environment, with both high and low temperature and pressure, and in the presence of highly reactive gases. (R.P.) 9 refs.

  11. Strategy of thunderstorm measurement with super dense ground-based observation network

    Science.gov (United States)

    Takahashi, Y.; Sato, M.

    2014-12-01

    It's not easy to understand the inside structure and developing process of thunderstorm only with existing meteorological instruments since its horizontal extent of the storm cell is sometimes smaller than an order of 10 km while one of the densest ground network in Japan, AMEDAS, consists of sites located every 17 km in average and the resolution of meteorological radar is 1-2 km in general. Even the X-band radar realizes the resolution of 250 m or larger. Here we suggest a new super dense observation network with simple and low cost sensors that can be used for measurement both of raindrop and vertical electric field change caused by cloud-to-ground lightning discharge. This sensor consists of two aluminum plates with a diameter of 10-20 cm. We carried out an observation campaign in summer of 2013 in the foothills of Mt. Yastugatake, Yamanashi and Nagano prefectures in Japan, installing 6 plate-type sensors at a distance of about 4 km. Horizontal location, height and charge amount of each lightning discharge are estimated successfully based on the information of electric field changes at several observing sites. Moreover, it was found that the thunderstorm has a very narrow structure well smaller than 300 m that cannot be measured by any other ways, counting the positive and negative pulses caused by attachment of raindrop to the sensor plate, respectively. We plan to construct a new super dense observation network in the north Kanto region, Japan, where the lightning activity is most prominent in summer Japan, distributing more than several tens of sensors at every 4 km or shorter, such as an order of 100 m at minimum. This kind of new type network will reveal the unknown fine structures of thunderstorms and open the door for constructing real time alert system of torrential rainfall and lightning stroke especially in the city area.

  12. Aircraft and ground-based measurements of hydroperoxides during the 2006 MILAGRO field campaign

    Directory of Open Access Journals (Sweden)

    L. J. Nunnermacker

    2008-12-01

    Full Text Available Mixing ratios of hydrogen peroxide and hydroxymethyl hydroperoxide were determined aboard the US Department of Energy G-1 Research Aircraft during the March, 2006 MILAGRO field campaign in Mexico. Ground measurements of total hydroperoxide were made at Tecámac University, about 35 km NW of Mexico City. In the air and on the ground, peroxide mixing ratios near the source region were generally near 1 ppbv. Strong southerly flow resulted in transport of pollutants from Mexico City to two downwind surface sites on several flight days. On these days, it was observed that peroxide concentrations slightly decreased as the G-1 flew progressively downwind. This observation is consistent with low or negative net peroxide production rates calculated for the source region and is due to the very high NOx concentrations in the Mexico City plateau. However, relatively high values of peroxide were observed at takeoff and landing near Veracruz, a site with much higher humidity and lower NOx concentrations.

  13. Comparison of OMI NO2 Observations and Their Seasonal and Weekly Cycles with Ground-Based Measurements in Helsinki

    Science.gov (United States)

    Ialongo, Iolanda; Herman, Jay; Krotkov, Nick; Lamsal, Lok; Boersma, Folkert; Hovila, Jari; Tamminen, Johanna

    2016-01-01

    We present the comparison of satellite-based OMI (Ozone Monitoring Instrument) NO2 products with ground-based observations in Helsinki. OMI NO2 total columns, available from standard product (SP) and DOMINO algorithm, are compared with the measurements performed by the Pandora spectrometer in Helsinki in 2012. The relative difference between Pandora 21 and OMI SP retrievals is 4 and 6 for clear sky and all sky conditions, respectively. DOMINO NO2 retrievals showed slightly lower total columns with median differences about 5 and 14 for clear sky and all sky conditions, respectively. Large differences often correspond to cloudy autumn-winter days with solar zenith angles above 65. Nevertheless, the differences remain within the retrieval uncertainties. Furthermore, the weekly and seasonal cycles from OMI, Pandora and NO2 surface concentrations are compared. Both satellite- and ground-based data show a similar weekly cycle, with lower NO2 levels during the weekend compared to the weekdays as result of reduced emissions from traffic and industrial activities. Also the seasonal cycle shows a similar behavior, even though the results are affected by the fact that most of the data are available during spring-summer because of cloud cover in other seasons. This is one of few works in which OMI NO2 retrievals are evaluated in an urban site at high latitudes (60N). Despite the city of Helsinki having relatively small pollution sources, OMI retrievals have proved to be able to describe air quality features and variability similar to surface observations. This adds confidence in using satellite observations for air quality monitoring also at high latitudes.

  14. First measurements of a carbon dioxide plume from an industrial source using a ground based mobile differential absorption lidar.

    Science.gov (United States)

    Robinson, R A; Gardiner, T D; Innocenti, F; Finlayson, A; Woods, P T; Few, J F M

    2014-08-01

    The emission of carbon dioxide (CO2) from industrial sources is one of the main anthropogenic contributors to the greenhouse effect. Direct remote sensing of CO2 emissions using optical methods offers the potential for the identification and quantification of CO2 emissions. We report the development and demonstration of a ground based mobile differential absorption lidar (DIAL) able to measure the mass emission rate of CO2 in the plume from a power station. To our knowledge DIAL has not previously been successfully applied to the measurement of emission plumes of CO2 from industrial sources. A significant challenge in observing industrial CO2 emission plumes is the ability to discriminate and observe localised concentrations of CO2 above the locally observed background level. The objectives of the study were to modify our existing mobile infrared DIAL system to enable CO2 measurements and to demonstrate the system at a power plant to assess the feasibility of the technique for the identification and quantification of CO2 emissions. The results of this preliminary study showed very good agreement with the expected emissions calculated by the site. The detection limit obtained from the measurements, however, requires further improvement to provide quantification of smaller emitters of CO2, for example for the detection of fugitive emissions. This study has shown that in principle, remote optical sensing technology will have the potential to provide useful direct data on CO2 mass emission rates.

  15. Ground based measurements of SO2 and NO2 emissions from the oil refinery 'la Teja' in Montevideo city

    International Nuclear Information System (INIS)

    Frins, Erna; Casaballe, Nicolas; Osorio, Matias; Arismendi, Federico; Ibrahim, Ossama; Wagner, Thomas; Platt, Ulrich

    2011-01-01

    We present preliminary results of ground based measurements of SO 2 and NO 2 emissions from 'La Teja' oil refinery located in the northern part of Montevideo Bay. Our study is part of a long term effort to localize and monitor relevant emission sources in the city area of Montevideo. These measurements were performed with a Miniature Multi AXis Differential Optical Absorption Spectrometry (MiniMAX-DOAS) instrument, which is basically a temperature controlled medium-resolution spectrometer (∼ 0.5 nm) equipped with a small telescope and a stepper motor allowing automatic scans in one dimension. We present a discussion about the evolution and transformation of both above species in the atmosphere. Our observation site was approximately 1.9 km away from the oil refinery and we were able to perform vertical and horizontal scans of the plume emitted (during our measurements) almost horizontally from its stacks. The maximum value of the SO 2 slant column density (SCD) was found to be ∼ 4x10 17 molec cm -2 directly over the oil refinery, decreasing as the plume disperses. In contrast, the NO 2 SCD peaks at ∼ 1x10 16 molec cm -2 directly over the source and increases continuously as the plume disperses. The SO 2 flux measured immediately downwind of the refinery was found to be about 1200 kg h -1 (±40% uncertainty).

  16. Ground-based measurements of the vertical E-field in mountainous regions and the "Austausch" effect

    Science.gov (United States)

    Yaniv, Roy; Yair, Yoav; Price, Colin; Mkrtchyan, Hripsime; Lynn, Barry; Reymers, Artur

    2017-06-01

    Past measurements of the atmospheric vertical electric field (Ez or potential gradient) at numerous land stations showed a strong response of the daily electric field to a morning local effect known as ;Austausch; - the transport of electrical charges due to increased turbulence. In mountainous regions, nocturnal charge accumulation, followed by an attachment process to aerosols near the surface in valleys, known as the electrode effect, is lifted as a charged aerosol layer by anabatic (upslope) winds during the morning hours due to solar heating. Ground-based measurements during fair weather days were conducted at three mountain stations in Israel and Armenia. We present results of the mean diurnal variation of Ez and make comparisons with the well-known Carnegie curve and with past measurements of Ez on mountains. We report a good agreement between the mean diurnal curves of Ez at various mountain stations and the time of local sunrise when the Ez is found to increase. We attribute this morning maximum to the Austausch (or exchange) layer effect. We support our findings with conduction and turbulent current measurements showing high values of ions and charged aerosols being transported by winds from morning to noon local time, and by model simulations showing the convergence of winds in the early morning hours toward the mountain peak.

  17. COMPARATIVE RESEARCH OF VARIOUS METHODS FOR DETERMINING THE CHARACTERISTICS OF AN ELECTROMAGNETIC WAVE REFLECTED FROM A SCATTERING DIFFRACTION SCREEN IN THE PROPAGATION OF A RADIO SIGNAL IN THE EARTH-IONOSPHERE CHANNEL IN THE SHORT-WAVE RANGE OF RADIO WAVES WITH USE OF THE EXPERIMENTAL EQUIPMENT OF COHERENT RECEPTION OF A GROUND-BASED MEASURING COMPLEX

    Directory of Open Access Journals (Sweden)

    S.Yu. Belov

    2017-12-01

    Full Text Available Monitoring of the earth’s surface by remote sensing in the short-wave band can provide quick identification of some characteristics of natural systems. This band range allows one to diagnose subsurface aspects of the earth, as the scattering parameter is affected by irregularities in the dielectric permittivity of subsurface structures. The new method is suggested. This method based on the organization of the monitoring probe may detect changes in these environments, for example, to assess seismic hazard, hazardous natural phenomena, changes ecosystems, as well as some man-made hazards and etc. The problem of measuring and accounting for the scattering power of the earth’s surface in the short-range of radio waves is important for a number of purposes, such as diagnosing properties of the medium, which is of interest for geological, environmental studies. In this paper, we propose a new method for estimating the parameters of incoherent signal/noise ratio. The paper presents the results of comparison of the measurement method from the point of view of their admissible relative analytical errors. A comparative analysis and shows that the analytical (relative accuracy of the determination of this parameter new method on the order exceeds the widely-used standard method. Analysis of admissible relative analytical error of estimation of this parameter allowed to recommend new method instead of standard method

  18. The ground based plan

    International Nuclear Information System (INIS)

    1989-01-01

    The paper presents a report of ''The Ground Based Plan'' of the United Kingdom Science and Engineering Research Council. The ground based plan is a plan for research in astronomy and planetary science by ground based techniques. The contents of the report contains a description of:- the scientific objectives and technical requirements (the basis for the Plan), the present organisation and funding for the ground based programme, the Plan, the main scientific features and the further objectives of the Plan. (U.K.)

  19. Electron and ion temperatures: a comparison of ground-based incoherent scatter and AE-C satellite measurements

    International Nuclear Information System (INIS)

    Benson, R.F.; Bauer, P.; Brace, L.H.; Carlson, H.C.; Hagen, J.; Hanson, W.B.; Hoegy, W.R.; Torr, M.R.; Wickwar, V.B.

    1977-01-01

    The Atmosphere Exploere-C satellite (AE-C) is uniquely suited for correlative studies with ground-based stations because its on-board propulsion system enables a desired ground station overflight condition to be maintained for a period of several weeks. It also provides the first low-altitude (below 260 km) comparison of satellite and incoherent scatter electron and ion temperatures. More than 40 comparisons of remote and in situ measurements were made by using data from AE-C and four incoherent scatter stations (Arecibo, Chatanika, Millstone Hill, and St. Santin). The results indicate very good agreement between satellite and ground measurements of the ion temperature, the average satellite retarding potential analyzer temperatures differing from the average incoherent scatter temperatures by -2% at St. Santin, +3% at Millstone Hill, and +2% at Arecibo. The electron temperatures also agree well, the average satellite temperatures exceeding the average incoherent scatter temperatures by 3% at St. Santin, 2% at Arecibo, and 11% at Millstone Hill. Several temperature comparisons were made between AE-C and Chatanika. In spite of the highly variable ionosphere often encountered at this high-latitude location, good agreement was obtained between the in situ and remote measurements of electron and ion temperatures. Longitudinal variations are found to be very important in the comparisons of electron temperature in some locations. The agreement between the electron temperatures is considerably better than that found in some earlier comparisons involving satellities at higher altitudes

  20. Optical and geometrical properties of cirrus clouds in Amazonia derived from 1 year of ground-based lidar measurements

    Science.gov (United States)

    Gouveia, Diego A.; Barja, Boris; Barbosa, Henrique M. J.; Seifert, Patric; Baars, Holger; Pauliquevis, Theotonio; Artaxo, Paulo

    2017-03-01

    Cirrus clouds cover a large fraction of tropical latitudes and play an important role in Earth's radiation budget. Their optical properties, altitude, vertical and horizontal coverage control their radiative forcing, and hence detailed cirrus measurements at different geographical locations are of utmost importance. Studies reporting cirrus properties over tropical rain forests like the Amazon, however, are scarce. Studies with satellite profilers do not give information on the diurnal cycle, and the satellite imagers do not report on the cloud vertical structure. At the same time, ground-based lidar studies are restricted to a few case studies. In this paper, we derive the first comprehensive statistics of optical and geometrical properties of upper-tropospheric cirrus clouds in Amazonia. We used 1 year (July 2011 to June 2012) of ground-based lidar atmospheric observations north of Manaus, Brazil. This dataset was processed by an automatic cloud detection and optical properties retrieval algorithm. Upper-tropospheric cirrus clouds were observed more frequently than reported previously for tropical regions. The frequency of occurrence was found to be as high as 88 % during the wet season and not lower than 50 % during the dry season. The diurnal cycle shows a minimum around local noon and maximum during late afternoon, associated with the diurnal cycle of precipitation. The mean values of cirrus cloud top and base heights, cloud thickness, and cloud optical depth were 14.3 ± 1.9 (SD) km, 12.9 ± 2.2 km, 1.4 ± 1.1 km, and 0.25 ± 0.46, respectively. Cirrus clouds were found at temperatures down to -90 °C. Frequently cirrus were observed within the tropical tropopause layer (TTL), which are likely associated to slow mesoscale uplifting or to the remnants of overshooting convection. The vertical distribution was not uniform, and thin and subvisible cirrus occurred more frequently closer to the tropopause. The mean lidar ratio was 23.3 ± 8.0 sr. However, for

  1. Comparing multiple model-derived aerosol optical properties to spatially collocated ground-based and satellite measurements

    Science.gov (United States)

    Ocko, Ilissa B.; Ginoux, Paul A.

    2017-04-01

    Anthropogenic aerosols are a key factor governing Earth's climate and play a central role in human-caused climate change. However, because of aerosols' complex physical, optical, and dynamical properties, aerosols are one of the most uncertain aspects of climate modeling. Fortunately, aerosol measurement networks over the past few decades have led to the establishment of long-term observations for numerous locations worldwide. Further, the availability of datasets from several different measurement techniques (such as ground-based and satellite instruments) can help scientists increasingly improve modeling efforts. This study explores the value of evaluating several model-simulated aerosol properties with data from spatially collocated instruments. We compare aerosol optical depth (AOD; total, scattering, and absorption), single-scattering albedo (SSA), Ångström exponent (α), and extinction vertical profiles in two prominent global climate models (Geophysical Fluid Dynamics Laboratory, GFDL, CM2.1 and CM3) to seasonal observations from collocated instruments (AErosol RObotic NETwork, AERONET, and Cloud-Aerosol Lidar with Orthogonal Polarization, CALIOP) at seven polluted and biomass burning regions worldwide. We find that a multi-parameter evaluation provides key insights on model biases, data from collocated instruments can reveal underlying aerosol-governing physics, column properties wash out important vertical distinctions, and improved models does not mean all aspects are improved. We conclude that it is important to make use of all available data (parameters and instruments) when evaluating aerosol properties derived by models.

  2. Impact of Alternative Jet Fuels on Engine Exhaust Composition During the 2015 ECLIF Ground-Based Measurements Campaign.

    Science.gov (United States)

    Schripp, Tobias; Anderson, Bruce; Crosbie, Ewan C; Moore, Richard H; Herrmann, Friederike; Oßwald, Patrick; Wahl, Claus; Kapernaum, Manfred; Köhler, Markus; Le Clercq, Patrick; Rauch, Bastian; Eichler, Philipp; Mikoviny, Tomas; Wisthaler, Armin

    2018-04-17

    The application of fuels from renewable sources ("alternative fuels") in aviation is important for the reduction of anthropogenic carbon dioxide emissions, but may also attribute to reduced release of particles from jet engines. The present experiment describes ground-based measurements in the framework of the ECLIF (Emission and Climate Impact of Alternative Fuels) campaign using an Airbus A320 (V2527-A5 engines) burning six fuels of chemically different composition. Two reference Jet A-1 with slightly different chemical parameters were applied and further used in combination with a Fischer-Tropsch synthetic paraffinic kerosene (FT-SPK) to prepare three semi synthetic jet fuels (SSJF) of different aromatic content. In addition, one commercially available fully synthetic jet fuel (FSJF) featured the lowest aromatic content of the fuel selection. Neither the release of nitrogen oxide or carbon monoxide was significantly affected by the different fuel composition. The measured particle emission indices showed a reduction up to 50% (number) and 70% (mass) for two alternative jet fuels (FSJF, SSJF2) at low power settings in comparison to the reference fuels. The reduction is less pronounced at higher operating conditions but the release of particle number and particle mass is still significantly lower for the alternative fuels than for both reference fuels. The observed correlation between emitted particle mass and fuel aromatics is not strict. Here, the H/C ratio is a better indicator for soot emission.

  3. Reflection measurements for luminescent powders

    Science.gov (United States)

    Kroon, R. E.

    2018-04-01

    Luminescent materials are useful in applications varying from lighting and display technologies to document security features and medical research, amongst many others. Measurement of the excitation range is an important consideration, and absorption bands are often determined from a decrease in the measured diffuse reflectance of the material using a ultraviolet-visible (UV-vis) spectrophotometer with an integrating sphere. Such a system may provide questionable results when used to measure the reflectance of a luminescence material, which is demonstrated for a Tb doped silica phosphor, because the system cannot differentiate between the reflected light and luminescence. It is shown that more reliable results are achieved for this phosphor by measuring the reflectance using a synchronous zero-offset scan in a fluorescence spectrometer equipped with an integrating sphere. This method is therefore recommended instead of traditional reflectance measurements using a UV-vis spectrophotometer for luminescent powders.

  4. Airborne and ground-based measurements of the trace gases and particles emitted by prescribed fires in the United States

    Directory of Open Access Journals (Sweden)

    I. R. Burling

    2011-12-01

    Full Text Available We have measured emission factors for 19 trace gas species and particulate matter (PM2.5 from 14 prescribed fires in chaparral and oak savanna in the southwestern US, as well as conifer forest understory in the southeastern US and Sierra Nevada mountains of California. These are likely the most extensive emission factor field measurements for temperate biomass burning to date and the only published emission factors for temperate oak savanna fuels. This study helps to close the gap in emissions data available for temperate zone fires relative to tropical biomass burning. We present the first field measurements of the biomass burning emissions of glycolaldehyde, a possible precursor for aqueous phase secondary organic aerosol formation. We also measured the emissions of phenol, another aqueous phase secondary organic aerosol precursor. Our data confirm previous observations that urban deposition can impact the NOx emission factors and thus subsequent plume chemistry. For two fires, we measured both the emissions in the convective smoke plume from our airborne platform and the unlofted residual smoldering combustion emissions with our ground-based platform. The smoke from residual smoldering combustion was characterized by emission factors for hydrocarbon and oxygenated organic species that were up to ten times higher than in the lofted plume, including high 1,3-butadiene and isoprene concentrations which were not observed in the lofted plume. This should be considered in modeling the air quality impacts for smoke that disperses at ground level. We also show that the often ignored unlofted emissions can significantly impact estimates of total emissions. Preliminary evidence suggests large emissions of monoterpenes in the residual smoldering smoke. These data should lead to an improved capacity to model the impacts of biomass burning in similar temperate ecosystems.

  5. Elevated aerosol layers modify the O2–O2 absorption measured by ground-based MAX-DOAS

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, Ivan; Berg, Larry K.; Ferrare, Richard A.; Hair, Johnathan W.; Hostetler, Chris A.; Volkamer, Rainer

    2016-06-01

    The oxygen collisional complex (O2-O2, or O4) is a greenhouse gas, and a calibration trace gas used to infer aerosol and cloud properties by Differential Optical Absorption Spectroscopy (DOAS). Recent reports suggest the need for an O4 correction factor (CFO4) when comparing simulated and measured O4 differential slant column densities (dSCD) by passive DOAS. We investigate the sensitivity of O4 dSCD simulations at ultraviolet (360 nm) and visible (477 nm) wavelengths towards separately measured aerosol extinction profiles. Measurements were conducted by the University of Colorado 2D-MAX-DOAS instrument and NASA’s multispectral High Spectral Resolution Lidar (HSRL-2) during the Two Column Aerosol Project (TCAP) at Cape Cod, MA in July 2012. During two case study days with (1) high aerosol load (17 July, AOD ~ 0.35 at 477 nm), and (2) near molecular scattering conditions (22 July, AOD < 0.10 at 477 nm) the measured and calculated O4 dSCDs agreed within 6.4±0.4% (360 nm) and 4.7±0.6% (477 nm) if the HSRL-2 profiles were used as input to the calculations. However, if in the calculations the aerosol is confined to the surface layer (while keeping AOD constant) we find 0.53ground-based MAX-DOAS. Opportunities to identify and better characterize these layers are also discussed.

  6. An Analysis of Conjugate Ground-based and Space-based Measurements of Energetic Electrons during Substorms

    Science.gov (United States)

    Sivadas, N.; Semeter, J. L.

    2015-12-01

    Substorms within the Earth's magnetosphere release energy in the form of energetic charged particles and several kinds of waves within the plasma. Depending on their strength, satellite-based navigation and communication systems are adversely affected by the energetic charged particles. Like many other natural phenomena, substorms can have a severe economic impact on a technology-driven society such as ours. Though energization of charged particles is known to occur in the magnetosphere during substorms, the source of this population and its relation to traditional acceleration region dynamics, are not completely understood. Combining measurements of energetic charged particles within the plasmasheet and that of charged particles precipitated in to the ionosphere will provide a better understanding of the role of processes that accelerate these charged particles. In the current work, we present energetic electron flux measured indirectly using data from ground-based Incoherent Scatter Radar and that measured directly at the plasmasheet by the THEMIS spacecraft. Instances of low-altitude-precipitation observed from ground suggest electrons of energy greater than 300 keV, possibly arising from particle injection events during substorms at the magnetically conjugate locations in the plasmasheet. The differences and similarities in the measurements at the plasmasheet and the ionosphere indicate the role different processes play in influencing the journey of these energetic particles form the magnetosphere to the ionosphere. Our observations suggest that there is a lot more to be understood of the link between magnetotail dynamics and energetic electron precipitation during substorms. Understanding this may open up novel and potentially invaluable ways of diagnosing the magnetosphere from the ground.

  7. Simulations of the Holuhraun eruption 2014 with WRF-Chem and evaluation with satellite and ground based SO2 measurements

    Science.gov (United States)

    Hirtl, Marcus; Arnold-Arias, Delia; Flandorfer, Claudia; Maurer, Christian; Mantovani, Simone; Natali, Stefano

    2016-04-01

    Volcanic eruptions, with gas or/and particle emissions, directly influence our environment, with special significance when they either occur near inhabited regions or are transported towards them. In addition to the well-known affectation of air traffic, with large economic impacts, the ground touching plumes can lead directly to an influence of soil, water and even to a decrease of air quality. The eruption of Holuhraun in August 2014 in central Iceland is the country's largest lava and gas eruption since the Lakagígar eruption in 1783. Nevertheless, very little volcanic ash was produced. The main atmospheric threat from this event was the SO2 pollution that frequently violated the Icelandic National Air Quality Standards in many population centers. However, the SO2 affectation was not limited to Iceland but extended to mainland Europe. The on-line coupled model WRF-Chem is used to simulate the dispersion of SO2 for this event that affected the central European regions. The volcanic emissions are considered in addition to the anthropogenic and biogenic ground sources at European scale. A modified version of WRF-Chem version 4.1 is used in order to use time depending injection heights and mass fluxes which were obtained from in situ observations. WRF-Chem uses complex gas- (RADM2) and aerosol- (MADE-SORGAM) chemistry and is operated on a European domain (12 km resolution), and a nested grid covering the Alpine region (4 km resolution). The study is showing the evaluation of the model simulations with satellite and ground based measurement data of SO2. The analysis is conducted on a data management platform, which is currently developed in the frame of the ESA-funded project TAMP "Technology and Atmospheric Mission Platform": it provides comprehensive functionalities to visualize and numerically compare data from different sources (model, satellite and ground-measurements).

  8. First middle-atmospheric zonal wind profile measurements with a new ground-based microwave Doppler-spectro-radiometer

    Science.gov (United States)

    Rüfenacht, R.; Kämpfer, N.; Murk, A.

    2012-11-01

    We report on the wind radiometer WIRA, a new ground-based microwave Doppler-spectro-radiometer specifically designed for the measurement of middle-atmospheric horizontal wind by observing ozone emission spectra at 142.17504 GHz. Currently, wind speeds in five levels between 30 and 79 km can be retrieved which makes WIRA the first instrument able to continuously measure horizontal wind in this altitude range. For an integration time of one day the measurement error on each level lies at around 25 m s-1. With a planned upgrade this value is expected to be reduced by a factor of 2 in the near future. On the altitude levels where our measurement can be compared to wind data from the European Centre for Medium-Range Weather Forecasts (ECMWF) very good agreement in the long-term statistics as well as in short time structures with a duration of a few days has been found. WIRA uses a passive double sideband heterodyne receiver together with a digital Fourier transform spectrometer for the data acquisition. A big advantage of the radiometric approach is that such instruments can also operate under adverse weather conditions and thus provide a continuous time series for the given location. The optics enables the instrument to scan a wide range of azimuth angles including the directions east, west, north, and south for zonal and meridional wind measurements. The design of the radiometer is fairly compact and its calibration does not rely on liquid nitrogen which makes it transportable and suitable for campaign use. WIRA is conceived in a way that it can be operated remotely and does hardly require any maintenance. In the present paper, a description of the instrument is given, and the techniques used for the wind retrieval based on the determination of the Doppler shift of the measured atmospheric ozone emission spectra are outlined. Their reliability was tested using Monte Carlo simulations. Finally, a time series of 11 months of zonal wind measurements over Bern (46°57' N

  9. First middle-atmospheric zonal wind profile measurements with a new ground-based microwave Doppler-spectro-radiometer

    Directory of Open Access Journals (Sweden)

    R. Rüfenacht

    2012-11-01

    Full Text Available We report on the wind radiometer WIRA, a new ground-based microwave Doppler-spectro-radiometer specifically designed for the measurement of middle-atmospheric horizontal wind by observing ozone emission spectra at 142.17504 GHz. Currently, wind speeds in five levels between 30 and 79 km can be retrieved which makes WIRA the first instrument able to continuously measure horizontal wind in this altitude range. For an integration time of one day the measurement error on each level lies at around 25 m s−1. With a planned upgrade this value is expected to be reduced by a factor of 2 in the near future. On the altitude levels where our measurement can be compared to wind data from the European Centre for Medium-Range Weather Forecasts (ECMWF very good agreement in the long-term statistics as well as in short time structures with a duration of a few days has been found.

    WIRA uses a passive double sideband heterodyne receiver together with a digital Fourier transform spectrometer for the data acquisition. A big advantage of the radiometric approach is that such instruments can also operate under adverse weather conditions and thus provide a continuous time series for the given location. The optics enables the instrument to scan a wide range of azimuth angles including the directions east, west, north, and south for zonal and meridional wind measurements. The design of the radiometer is fairly compact and its calibration does not rely on liquid nitrogen which makes it transportable and suitable for campaign use. WIRA is conceived in a way that it can be operated remotely and does hardly require any maintenance.

    In the present paper, a description of the instrument is given, and the techniques used for the wind retrieval based on the determination of the Doppler shift of the measured atmospheric ozone emission spectra are outlined. Their reliability was tested using Monte Carlo simulations. Finally, a time series of 11

  10. Investigating aerosol properties in Peninsular Malaysia via the synergy of satellite remote sensing and ground-based measurements

    Science.gov (United States)

    Kanniah, Kasturi Devi; Lim, Hui Qi; Kaskaoutis, Dimitris G.; Cracknell, Arthur P.

    2014-03-01

    Spatio-temporal variation and trends in atmospheric aerosols as well as their impact on solar radiation and clouds are crucial for regional and global climate change assessment. These topics are not so well-documented over Malaysia, the fact that it receives considerable amounts of pollutants from both local and trans-boundary sources. The present study aims to analyse the spatio-temporal evolution and decadal trend of Aerosol Optical Depth (AOD) from Terra and Aqua MODIS sensors, to identify different types and origin of aerosols and explore the link between aerosols and solar radiation. AOD and fine-mode fraction (FMF) products from MODIS, AOD and Ångström Exponent (AE) values from AERONET stations along with ground-based PM10 measurements and solar radiation recordings at selected sites in Peninsular Malaysia are used for this scope. The MODIS AODs exhibit a wide spatio-temporal variation over Peninsular Malaysia, while Aqua AOD is consistently lower than that from Terra. The AOD shows a neutral-to-declining trend during the 2000s (Terra satellite), while that from Aqua exhibits an increasing trend (~ 0.01 per year). AERONET AODs exhibit either insignificant diurnal variation or higher values during the afternoon, while their short-term availability does not allow for a trend analysis. Moreover, the PM10 concentrations exhibit a general increasing trend over the examined locations. The sources and destination of aerosols are identified via the HYSPLIT trajectory model, revealing that aerosols during the dry season (June to September) are mainly originated from the west and southwest (Sumatra, Indonesia), while in the wet season (November to March) they are mostly associated with the northeast monsoon winds from the southern China Sea. Different aerosol types are identified via the relationship of AOD with FMF, revealing that the urban and biomass-burning aerosols are the most abundant over the region contributing to a significant reduction (~- 0.21 MJ m- 2) of

  11. Long-range transport of dust aerosols over the Arabian Sea and Indian region – A case study using satellite data and ground-based measurements

    Digital Repository Service at National Institute of Oceanography (India)

    Badarinath, K.V.S.; Kharol, S.K.; Kaskaoutis, D.G.; Sharma, A; Ramaswamy, V.; Kambezidis, H.D.

    The present study addresses an intense dust storm event over the Persian Gulf and the Arabian Sea (AS) region and its transport over the Indian subcontinent using multi-satellite observations and ground-based measurements. A time series of Indian...

  12. A study of electron density profiles in relation to ionization sources and ground-based radio wave absorption measurements, part 1

    Science.gov (United States)

    Gnanalingam, S.; Kane, J. A.

    1973-01-01

    An extensive set of ground-based measurements of the diurnal variation of medium frequency radio wave adsorption and virtual height is analyzed in terms of current understanding of the D- and lower E-region ion production and loss process. When this is done a gross discrepancy arises, the source of which is not known.

  13. Reflection measurements of microwave absorbers

    Science.gov (United States)

    Baker, Dirk E.; van der Neut, Cornelis A.

    1988-12-01

    A swept-frequency interferometer is described for making rapid, real-time assessments of localized inhomogeneities in planar microwave absorber panels. An aperture-matched exponential horn is used to reduce residual reflections in the system to about -37 dB. This residual reflection is adequate for making comparative measurements on planar absorber panels whose reflectivities usually fall in the -15 to -25 dB range. Reflectivity measurements on a variety of planar absorber panels show that multilayer Jaumann absorbers have the greatest inhomogeneity, while honeycomb absorbers generally have excellent homogeneity within a sheet and from sheet to sheet. The test setup is also used to measure the center frequencies of resonant absorbers. With directional couplers and aperture-matched exponential horns, the technique can be easily applied in the standard 2 to 40 GHz waveguide bands.

  14. VESPA-22: a ground-based microwave spectrometer for long-term measurements of polar stratospheric water vapor

    Directory of Open Access Journals (Sweden)

    G. Mevi

    2018-02-01

    Full Text Available The new ground-based 22 GHz spectrometer, VESPA-22 (water Vapor Emission Spectrometer for Polar Atmosphere at 22 GHz measures the 22.23 GHz water vapor emission line with a bandwidth of 500 MHz and a frequency resolution of 31 kHz. The integration time for a measurement ranges from 6 to 24 h, depending on season and weather conditions. Water vapor spectra are collected using the beam-switching technique. VESPA-22 is designed to operate automatically with little maintenance; it employs an uncooled front-end characterized by a receiver temperature of about 180 K and its quasi-optical system presents a full width at half maximum of 3.5°. Every 30 min VESPA-22 measures also the sky opacity using the tipping curve technique. The instrument calibration is performed automatically by a noise diode; the emission temperature of this element is estimated twice an hour by observing alternatively a black body at ambient temperature and the sky at an elevation of 60°. The retrieved profiles obtained inverting 24 h integration spectra present a sensitivity larger than 0.8 from about 25 to 75 km of altitude during winter and from about 30 to 65 km during summer, a vertical resolution from about 12 to 23 km (depending on altitude, and an overall 1σ uncertainty lower than 7 % up to 60 km altitude and rapidly increasing to 20 % at 75 km. In July 2016, VESPA-22 was installed at the Thule High Arctic Atmospheric Observatory located at Thule Air Base (76.5° N, 68.8° W, Greenland, and it has been operating almost continuously since then. The VESPA-22 water vapor mixing ratio vertical profiles discussed in this work are obtained from 24 h averaged spectra and are compared with version 4.2 of concurrent Aura/Microwave Limb Sounder (MLS water vapor vertical profiles. In the sensitivity range of VESPA-22 retrievals, the intercomparison from July 2016 to July 2017 between VESPA-22 dataset and Aura/MLS dataset

  15. VESPA-22: a ground-based microwave spectrometer for long-term measurements of polar stratospheric water vapor

    Science.gov (United States)

    Mevi, Gabriele; Muscari, Giovanni; Bertagnolio, Pietro Paolo; Fiorucci, Irene; Pace, Giandomenico

    2018-02-01

    The new ground-based 22 GHz spectrometer, VESPA-22 (water Vapor Emission Spectrometer for Polar Atmosphere at 22 GHz) measures the 22.23 GHz water vapor emission line with a bandwidth of 500 MHz and a frequency resolution of 31 kHz. The integration time for a measurement ranges from 6 to 24 h, depending on season and weather conditions. Water vapor spectra are collected using the beam-switching technique. VESPA-22 is designed to operate automatically with little maintenance; it employs an uncooled front-end characterized by a receiver temperature of about 180 K and its quasi-optical system presents a full width at half maximum of 3.5°. Every 30 min VESPA-22 measures also the sky opacity using the tipping curve technique. The instrument calibration is performed automatically by a noise diode; the emission temperature of this element is estimated twice an hour by observing alternatively a black body at ambient temperature and the sky at an elevation of 60°. The retrieved profiles obtained inverting 24 h integration spectra present a sensitivity larger than 0.8 from about 25 to 75 km of altitude during winter and from about 30 to 65 km during summer, a vertical resolution from about 12 to 23 km (depending on altitude), and an overall 1σ uncertainty lower than 7 % up to 60 km altitude and rapidly increasing to 20 % at 75 km. In July 2016, VESPA-22 was installed at the Thule High Arctic Atmospheric Observatory located at Thule Air Base (76.5° N, 68.8° W), Greenland, and it has been operating almost continuously since then. The VESPA-22 water vapor mixing ratio vertical profiles discussed in this work are obtained from 24 h averaged spectra and are compared with version 4.2 of concurrent Aura/Microwave Limb Sounder (MLS) water vapor vertical profiles. In the sensitivity range of VESPA-22 retrievals, the intercomparison from July 2016 to July 2017 between VESPA-22 dataset and Aura/MLS dataset convolved with VESPA-22 averaging kernels shows an average difference

  16. Comparison of stratospheric NO2 profiles above Kiruna, Sweden retrieved from ground-based zenith sky DOAS measurements, SAOZ balloon measurements and SCIAMACHY limb observations

    Science.gov (United States)

    Gu, Myojeong; Enell, Carl-Fredrik; Hendrick, François; Pukite, Janis; Van Roozendael, Michel; Platt, Ulrich; Raffalski, Uwe; Wagner, Thomas

    2015-04-01

    Stratospheric NO2 not only destroys ozone but acts as a buffer against halogen catalyzed ozone loss by converting halogen species into stable nitrates. These two roles of stratospheric NO2 depend on the altitude. Hence, the objective of this study is to investigate the vertical distribution of stratospheric NO2. We compare the NO2 profiles derived from the zenith sky DOAS with those obtained from, SAOZ balloon measurements and satellite limb observations. Vertical profiles of stratospheric NO2 are retrieved from ground-based zenith sky DOAS observations operated at Kiruna, Sweden (68.84°N, 20.41°E) since 1996. To determine the profile of stratospheric NO2 measured from ground-based zenith sky DOAS, we apply the Optimal Estimation Method (OEM) to retrieval of vertical profiles of stratospheric NO2 which has been developed by IASB-BIRA. The basic principle behind this profiling approach is the dependence of the mean scattering height on solar zenith angle (SZA). We compare the retrieved profiles to two additional datasets of stratospheric NO2 profile. The first one is derived from satellite limb observations by SCIAMACHY (Scanning Imaging Absorption spectrometer for Atmospheric CHartographY) on EnviSAT. The second is derived from the SAOZ balloon measurements (using a UV/Visible spectrometer) performed at Kiruna in Sweden.

  17. Retrieval and satellite intercomparison of O3 measurements from ground-based FTIR Spectrometer at Equatorial Station: Addis Ababa, Ethiopia

    Directory of Open Access Journals (Sweden)

    T. von Clarmann

    2013-02-01

    Full Text Available Since May 2009, high-resolution Fourier Transform Infrared (FTIR solar absorption spectra have been recorded at Addis Ababa (9.01° N latitude, 38.76° E longitude, 2443 m altitude above sea level, Ethiopia. The vertical profiles and total column amounts of ozone (O3 are deduced from the spectra by using the retrieval code PROFFIT (V9.5 and regularly determined instrumental line shape (ILS. A detailed error analysis of the O3 retrieval is performed. Averaging kernels of the target gas shows that the major contribution to the retrieved information comes from the measurement. The degrees of freedom for signals is found to be 2.1 on average for the retrieval of O3 from the observed FTIR spectra. The ozone Volume Mixing Ratio (VMR profiles and column amounts retrieved from FTIR spectra are compared with the coincident satellite observations of Microwave Limb Sounding (MLS, Michelson Interferometer for Passive Atmospheric Sounding (MIPAS, Tropospheric Emission Spectrometer (TES, Ozone Monitoring Instrument (OMI, Atmospheric Infrared Sounding (AIRS and Global Ozone Monitoring Experiment (GOME-2 instruments. The mean relative differences in ozone profiles of FTIR from MLS and MIPAS are generally lower than 15% within the altitude range of 27 to 36 km, whereas difference from TES is lower than 1%. Comparisons of measurements of column amounts from the satellite and the ground-based FTIR show very good agreement as exhibited by relative differences within +0.2% to +2.8% for FTIR versus MLS and GOME-2; and −0.9 to −9.0% for FTIR versus OMI, TES and AIRS. The corresponding standard deviations are within 2.0 to 2.8% for FTIR versus MLS and GOME-2 comparisons whereas that of FTIR versus OMI, TES and AIRS are within 3.5 to 7.3%. Thus, the retrieved O3 VMR and column amounts from a tropical site, Addis Ababa, is found to exhibit very good agreement with all coincident satellite observations over an approximate 3-yr period.

  18. Integration of Remote Sensing Products with Ground-Based Measurements to Understand the Dynamics of Nepal's Forests and Plantation Sites

    Science.gov (United States)

    Gilani, H.; Jain, A. K.

    2016-12-01

    This study assembles information from three sources - remote sensing, terrestrial photography and ground-based inventory data, to understand the dynamics of Nepal's tropical and sub-tropical forests and plantation sites for the period 1990-2015. Our study focuses on following three specific district areas, which have conserved forests through social and agroforestry management practices: 1. Dolakha district: This site has been selected to study the impact of community-based forest management on land cover change using repeat photography and satellite imagery, in combination with interviews with community members. The study time period is during the period 1990-2010. We determined that satellite data with ground photographs can provide transparency for long term monitoring. The initial results also suggests that community-based forest management program in the mid-hills of Nepal was successful. 2. Chitwan district: Here we use high resolution remote sensing data and optimized community field inventories to evaluate potential application and operational feasibility of community level REDD+ measuring, reporting and verification (MRV) systems. The study uses temporal dynamics of land cover transitions, tree canopy size classes and biomass over a Kayar khola watershed REDD+ study area with community forest to evaluate satellite Image segmentation for land cover, linear regression model for above ground biomass (AGB), and estimation and monitoring field data for tree crowns and AGB. We study three specific years 2002, 2009, 2012. Using integration of WorldView-2 and airborne LiDAR data for tree species level. 3. Nuwakot district: This district was selected to study the impact of establishment of tree plantation on total barren/fallow. Over the last 40 year, this area has went through a drastic changes, from barren land to forest area with tree species consisting of Dalbergia sissoo, Leucaena leucocephala, Michelia champaca, etc. In 1994, this district area was registered

  19. Illumination compensation in ground based hyperspectral imaging

    Science.gov (United States)

    Wendel, Alexander; Underwood, James

    2017-07-01

    Hyperspectral imaging has emerged as an important tool for analysing vegetation data in agricultural applications. Recently, low altitude and ground based hyperspectral imaging solutions have come to the fore, providing very high resolution data for mapping and studying large areas of crops in detail. However, these platforms introduce a unique set of challenges that need to be overcome to ensure consistent, accurate and timely acquisition of data. One particular problem is dealing with changes in environmental illumination while operating with natural light under cloud cover, which can have considerable effects on spectral shape. In the past this has been commonly achieved by imaging known reference targets at the time of data acquisition, direct measurement of irradiance, or atmospheric modelling. While capturing a reference panel continuously or very frequently allows accurate compensation for illumination changes, this is often not practical with ground based platforms, and impossible in aerial applications. This paper examines the use of an autonomous unmanned ground vehicle (UGV) to gather high resolution hyperspectral imaging data of crops under natural illumination. A process of illumination compensation is performed to extract the inherent reflectance properties of the crops, despite variable illumination. This work adapts a previously developed subspace model approach to reflectance and illumination recovery. Though tested on a ground vehicle in this paper, it is applicable to low altitude unmanned aerial hyperspectral imagery also. The method uses occasional observations of reference panel training data from within the same or other datasets, which enables a practical field protocol that minimises in-field manual labour. This paper tests the new approach, comparing it against traditional methods. Several illumination compensation protocols for high volume ground based data collection are presented based on the results. The findings in this paper are

  20. A large-scale intercomparison of stratospheric vertical distributions of NO2 and BrO retrieved from the SCIAMACHY limb measurements and ground-based twilight observations

    Science.gov (United States)

    Rozanov, Alexei; Hendrick, Francois; Lotz, Wolfhardt; van Roozendael, Michel; Bovensmann, Heinrich; Burrows, John P.

    This study is devoted to the intercomparison of NO2 and BrO vertical profiles obtained from the satellite and ground-based measurements. Although, the ground-based observations are performed only at selected locations, they have a great potential to be used for the validation of satellite measurements since continuous long-term measurement series performed with the same instruments are available. Thus, long-term trends in the observed species can be analyzed and intercompared. Previous intercomparisons of the vertical distributions of NO2 and BrO retrieved from SCIAMACHY limb measurements at the University of Bremen and obtained at IASB-BIRA by applying a profiling technique to ground-based zenith-sky DOAS observations have shown a good agreement between the results of completely different measurement techniques. However, only a relatively short time period of one year was analyzed so far which do not allow investigating seasonal variations and trends. Furthermore, some minor discrepancies are still to be analyzed. In the current study, several years datasets obtained at Observatoire de Haute-Provence (OHP) in France and in Harestua in Norway will be compared to the retrievals of SCIAMACHY limb measurements. Seasonal and annual variations will be analyzed and possible reasons for the remaining discrepancies will be discussed.

  1. Empirical model for mean temperature for Indian zone and estimation of precipitable water vapor from ground based GPS measurements

    Directory of Open Access Journals (Sweden)

    C. Suresh Raju

    2007-10-01

    Full Text Available Estimation of precipitable water (PW in the atmosphere from ground-based Global Positioning System (GPS essentially involves modeling the zenith hydrostatic delay (ZHD in terms of surface Pressure (Ps and subtracting it from the corresponding values of zenith tropospheric delay (ZTD to estimate the zenith wet (non-hydrostatic delay (ZWD. This further involves establishing an appropriate model connecting PW and ZWD, which in its simplest case assumed to be similar to that of ZHD. But when the temperature variations are large, for the accurate estimate of PW the variation of the proportionality constant connecting PW and ZWD is to be accounted. For this a water vapor weighted mean temperature (Tm has been defined by many investigations, which has to be modeled on a regional basis. For estimating PW over the Indian region from GPS data, a region specific model for Tm in terms of surface temperature (Ts is developed using the radiosonde measurements from eight India Meteorological Department (IMD stations spread over the sub-continent within a latitude range of 8.5°–32.6° N. Following a similar procedure Tm-based models are also evolved for each of these stations and the features of these site-specific models are compared with those of the region-specific model. Applicability of the region-specific and site-specific Tm-based models in retrieving PW from GPS data recorded at the IGS sites Bangalore and Hyderabad, is tested by comparing the retrieved values of PW with those estimated from the altitude profile of water vapor measured using radiosonde. The values of ZWD estimated at 00:00 UTC and 12:00 UTC are used to test the validity of the models by estimating the PW using the models and comparing it with those obtained from radiosonde data. The region specific Tm-based model is found to be in par with if not better than a

  2. Searching for reflected light from τ Bootis b with high-resolution ground-based spectroscopy: Approaching the 10-5 contrast barrier

    Science.gov (United States)

    Hoeijmakers, H. J.; Snellen, I. A. G.; van Terwisga, S. E.

    2018-02-01

    Context. It is challenging to measure the starlight reflected from exoplanets because of the extreme contrast with their host stars. For hot Jupiters, this contrast is in the range of 10-6 to 10-4, depending on their albedo, radius and orbital distance. Searches for reflected light have been performed since the first hot Jupiters were discovered, but with very limited success because hot Jupiters tend to have low albedo values due to the general absence of reflective cloud decks. Aim. The aim of this study is to search for reflected light from τ Boo b, a hot Jupiter with one of the brightest host stars. Since its discovery in 1997, it has been the subject of several reflected-light searches using high-dispersion spectroscopy. Here we aim to combine these data in to a single meta-analysis. Methods: We analysed more than 2000 archival high-dispersion spectra obtained with the UVES, ESPaDOnS, NARVAL UES and HARPS-N spectrographs during various epochs between 1998 and 2013. Each spectrum was first cleaned of the stellar spectrum and subsequently cross-correlated with a PHOENIX model spectrum. These were then Doppler shifted to the planet rest-frame and co-added in time, weighted according to the expected signal-to-noise of the planet signal. Results: We reach a 3σ upper limit of the planet-to-star contrast of 1.5 × 10-5. Assuming a planet radius of 1.15 RJ, this corresponds to an optical albedo of between 400-700 nm. A low albedo is in line with secondary eclipse and phase curve observations of other hot Jupiters using space-based observatories, as well as theoretical predictions of their reflective properties.

  3. Snowfall retrieval at X, Ka and W bands: consistency of backscattering and microphysical properties using BAECC ground-based measurements

    Directory of Open Access Journals (Sweden)

    M. T. Falconi

    2018-05-01

    Full Text Available Radar-based snowfall intensity retrieval is investigated at centimeter and millimeter wavelengths using co-located ground-based multi-frequency radar and video-disdrometer observations. Using data from four snowfall events, recorded during the Biogenic Aerosols Effects on Clouds and Climate (BAECC campaign in Finland, measurements of liquid-water-equivalent snowfall rate S are correlated to radar equivalent reflectivity factors Ze, measured by the Atmospheric Radiation Measurement (ARM cloud radars operating at X, Ka and W frequency bands. From these combined observations, power-law Ze–S relationships are derived for all three frequencies considering the influence of riming. Using microwave radiometer observations of liquid water path, the measured precipitation is divided into lightly, moderately and heavily rimed snow. Interestingly lightly rimed snow events show a spectrally distinct signature of Ze–S with respect to moderately or heavily rimed snow cases. In order to understand the connection between snowflake microphysical and multi-frequency backscattering properties, numerical simulations are performed by using the particle size distribution provided by the in situ video disdrometer and retrieved ice particle masses. The latter are carried out by using both the T-matrix method (TMM applied to soft-spheroid particle models with different aspect ratios and exploiting a pre-computed discrete dipole approximation (DDA database for rimed aggregates. Based on the presented results, it is concluded that the soft-spheroid approximation can be adopted to explain the observed multi-frequency Ze–S relations if a proper spheroid aspect ratio is selected. The latter may depend on the degree of riming in snowfall. A further analysis of the backscattering simulations reveals that TMM cross sections are higher than the DDA ones for small ice particles, but lower for larger particles. The differences of computed cross sections for larger and

  4. Temporal Variability of Total Ozone in the Asian Region Inferred from Ground-Based and Satellite Measurement Data

    Science.gov (United States)

    Visheratin, K. N.; Nerushev, A. F.; Orozaliev, M. D.; Zheng, Xiangdong; Sun, Shumen; Liu, Li

    2017-12-01

    This paper reports investigation data on the temporal variability of total ozone content (TOC) in the Central Asian and Tibet Plateau mountain regions obtained by conventional methods, as well as by spectral, cross-wavelet, and composite analyses. The data of ground-based observation stations located at Huang He, Kunming, and Lake Issyk-Kul, along with the satellite data obtained at SBUV/SBUV2 (SBUV merged total and profile ozone data, Version 8.6) for 1980-2013 and OMI (Ozone Monitoring Instrument) and TOU (Total Ozone Unit) for 2009-2013 have been used. The average relative deviation from the SBUV/SBUV2 data is less than 1% in Kunming and Issyk-Kul for the period of 1980-2013, while the Huang He Station is characterized by an excess of the satellite data over the ground-based information at an average deviation of 2%. According to the Fourier analysis results, the distribution of amplitudes and the periods of TOC oscillations within a range of over 14 months is similar for all series analyzed. Meanwhile, according to the cross-wavelet and composite analyses results, the phase relationships between the series may considerably differ, especially in the periods of 5-7 years. The phase of quasi-decennial oscillations in the Kunming Station is close to the 11-year oscillations of the solar cycle, while in the Huang He and Issyk-Kul stations the TOC variations go ahead of the solar cycle.

  5. Tropospheric and total ozone columns over Paris (France measured using medium-resolution ground-based solar-absorption Fourier-transform infrared spectroscopy

    Directory of Open Access Journals (Sweden)

    C. Viatte

    2011-10-01

    Full Text Available Ground-based Fourier-transform infrared (FTIR solar absorption spectroscopy is a powerful remote sensing technique providing information on the vertical distribution of various atmospheric constituents. This work presents the first evaluation of a mid-resolution ground-based FTIR to measure tropospheric ozone, independently of stratospheric ozone. This is demonstrated using a new atmospheric observatory (named OASIS for "Observations of the Atmosphere by Solar absorption Infrared Spectroscopy", installed in Créteil (France. The capacity of the technique to separate stratospheric and tropospheric ozone is demonstrated. Daily mean tropospheric ozone columns derived from the Infrared Atmospheric Sounding Interferometer (IASI and from OASIS measurements are compared for summer 2009 and a good agreement of −5.6 (±16.1 % is observed. Also, a qualitative comparison between in-situ surface ozone measurements and OASIS data reveals OASIS's capacity to monitor seasonal tropospheric ozone variations, as well as ozone pollution episodes in summer 2009 around Paris. Two extreme pollution events are identified (on the 1 July and 6 August 2009 for which ozone partial columns from OASIS and predictions from a regional air-quality model (CHIMERE are compared following strict criteria of temporal and spatial coincidence. An average bias of 0.2%, a mean square error deviation of 7.6%, and a correlation coefficient of 0.91 is found between CHIMERE and OASIS, demonstrating the potential of a mid-resolution FTIR instrument in ground-based solar absorption geometry for tropospheric ozone monitoring.

  6. Ground-based measurement of column-averaged mixing ratios of methane and carbon dioxide in the Sichuan Basin of China by a desktop optical spectrum analyzer

    Science.gov (United States)

    Qin, Xiu-Chun; Nakayama, Tomoki; Matsumi, Yutaka; Kawasaki, Masahiro; Ono, Akiko; Hayashida, Sachiko; Imasu, Ryoichi; Lei, Li-Ping; Murata, Isao; Kuroki, Takahiro; Ohashi, Masafumi

    2018-01-01

    Remote sensing of the atmospheric greenhouse gases, methane (CH4) and carbon dioxide (CO2), contributes to the understanding of global warming and climate change. A portable ground-based instrument consisting of a commercially available desktop optical spectrum analyzer and a small sun tracker has been applied to measure the column densities of atmospheric CH4 and CO2 at Yanting observation station in a mountainous paddy field of the Sichuan Basin from September to November 2013. The column-averaged dry-air molar mixing ratios, XCH4/XCO2, are compared with those retrieved by satellite observations in the Sichuan Basin and by ground-based network observations in the same latitude zone as the Yanting observation station.

  7. Ground based remote sensing and physiological measurements provide novel insights into canopy photosynthetic optimization in arctic shrubs

    Science.gov (United States)

    Magney, T. S.; Griffin, K. L.; Boelman, N.; Eitel, J.; Greaves, H.; Prager, C.; Logan, B.; Oliver, R.; Fortin, L.; Vierling, L. A.

    2014-12-01

    Because changes in vegetation structure and function in the Arctic are rapid and highly dynamic phenomena, efforts to understand the C balance of the tundra require repeatable, objective, and accurate remote sensing methods for estimating aboveground C pools and fluxes over large areas. A key challenge addressing the modelling of aboveground C is to utilize process-level information from fine-scale studies. Utilizing information obtained from high resolution remote sensing systems could help to better understand the C source/sink strength of the tundra, which will in part depend on changes in photosynthesis resulting from the partitioning of photosynthetic machinery within and among deciduous shrub canopies. Terrestrial LiDAR and passive hyperspectral remote sensing measurements offer an effective, repeatable, and scalable method to understand photosynthetic performance and partitioning at the canopy scale previously unexplored in arctic systems. Using a 3-D shrub canopy model derived from LiDAR, we quantified the light regime of leaves within shrub canopies to gain a better understanding of how light interception varies in response to the Arctic's complex radiation regime. This information was then coupled with pigment sampling (i.e., xanthophylls, and Chl a/b) to evaluate the optimization of foliage photosynthetic capacity within shrub canopies due to light availability. In addition, a lab experiment was performed to validate evidence of canopy level optimization via gradients of light intensity and leaf light environment. For this, hyperspectral reflectance (photochemical reflectance index (PRI)), and solar induced fluorescence (SIF)) was collected in conjunction with destructive pigment samples (xanthophylls) and chlorophyll fluorescence measurements in both sunlit and shaded canopy positions.

  8. Estimation of leaf area index using ground-based remote sensed NDVI measurements: validation and comparison with two indirect techniques

    International Nuclear Information System (INIS)

    Pontailler, J.-Y.; Hymus, G.J.; Drake, B.G.

    2003-01-01

    This study took place in an evergreen scrub oak ecosystem in Florida. Vegetation reflectance was measured in situ with a laboratory-made sensor in the red (640-665 nm) and near-infrared (750-950 nm) bands to calculate the normalized difference vegetation index (NDVI) and derive the leaf area index (LAI). LAI estimates from this technique were compared with two other nondestructive techniques, intercepted photosynthetically active radiation (PAR) and hemispherical photographs, in four contrasting 4 m 2 plots in February 2000 and two 4m 2 plots in June 2000. We used Beer's law to derive LAI from PAR interception and gap fraction distribution to derive LAI from photographs. The plots were harvested manually after the measurements to determine a 'true' LAI value and to calculate a light extinction coefficient (k). The technique based on Beer's law was affected by a large variation of the extinction coefficient, owing to the larger impact of branches in winter when LAI was low. Hemispherical photographs provided satisfactory estimates, slightly overestimated in winter because of the impact of branches or underestimated in summer because of foliage clumping. NDVI provided the best fit, showing only saturation in the densest plot (LAI = 3.5). We conclude that in situ measurement of NDVI is an accurate and simple technique to nondestructively assess LAI in experimental plots or in crops if saturation remains acceptable. (author)

  9. Estimation of leaf area index using ground-based remote sensed NDVI measurements: validation and comparison with two indirect techniques

    Energy Technology Data Exchange (ETDEWEB)

    Pontailler, J.-Y. [Univ. Paris-Sud XI, Dept. d' Ecophysiologie Vegetale, Orsay Cedex (France); Hymus, G.J.; Drake, B.G. [Smithsonian Environmental Research Center, Kennedy Space Center, Florida (United States)

    2003-06-01

    This study took place in an evergreen scrub oak ecosystem in Florida. Vegetation reflectance was measured in situ with a laboratory-made sensor in the red (640-665 nm) and near-infrared (750-950 nm) bands to calculate the normalized difference vegetation index (NDVI) and derive the leaf area index (LAI). LAI estimates from this technique were compared with two other nondestructive techniques, intercepted photosynthetically active radiation (PAR) and hemispherical photographs, in four contrasting 4 m{sup 2} plots in February 2000 and two 4m{sup 2} plots in June 2000. We used Beer's law to derive LAI from PAR interception and gap fraction distribution to derive LAI from photographs. The plots were harvested manually after the measurements to determine a 'true' LAI value and to calculate a light extinction coefficient (k). The technique based on Beer's law was affected by a large variation of the extinction coefficient, owing to the larger impact of branches in winter when LAI was low. Hemispherical photographs provided satisfactory estimates, slightly overestimated in winter because of the impact of branches or underestimated in summer because of foliage clumping. NDVI provided the best fit, showing only saturation in the densest plot (LAI = 3.5). We conclude that in situ measurement of NDVI is an accurate and simple technique to nondestructively assess LAI in experimental plots or in crops if saturation remains acceptable. (author)

  10. observation and analysis of the structure of winter precipitation-generating clouds using ground-based sensor measurements

    Science.gov (United States)

    Menéndez José Luis, Marcos; Gómez José Luis, Sánchez; Campano Laura, López; Ortega Eduardo, García; Suances Andrés, Merino; González Sergio, Fernández; Salvador Estíbaliz, Gascón; González Lucía, Hermida

    2015-04-01

    In this study, we used a 28-day database corresponding to December, January and February of 2011/2012 and 2012/2013 campaigns to analyze cloud structure that produced precipitation in the Sierra Norte near Madrid, Spain. We used remote sensing measurements, both active type like the K-band Micro Rain Radar (MRR) and passive type like the Radiometrics MP-3000A multichannel microwave radiometer. Using reflectivity data from the MRR, we determined the important microphysical parameters of Ice Water Content (IWC) and its integrated value over the atmospheric column, or Ice Water Path (IWP). Among the measurements taken by the MP-3000A were Liquid Water Path (LWP) and Integrated Water Vapor (IWV). By representing these data together, sharp declines in LWP and IWV were evident, coincident with IWP increases. This result indicates the ability of a K-band radar to measure the amount of ice in the atmospheric column, simultaneously revealing the Wegener-Bergeron-Findeisen mechanism. We also used a Present Weather Sensor (VPF-730; Biral Ltd., Bristol, UK) to determine the type and amount of precipitation at the surface. With these data, we used regression equations to establish the relationship between visibility and precipitation intensity. In addition, through theoretical precipitation visibility-intensity relationships, we estimated the type of crystal, degree of accretion (riming), and moisture content of fallen snow crystals.

  11. A 25-month database of stratus cloud properties generated from ground-based measurements at the Atmospheric Radiation Measurement Southern Great Plains Site

    International Nuclear Information System (INIS)

    Dong, Xiquan; Minnis, Patrick; Ackerman, Thomas P.; Clothiaux, Eugene E.; Mace, Gerald G.; Long, Charles N.; Liljegren, James C.

    2000-01-01

    A 25-month database of the macrophysical, microphysical, and radiative properties of isolated and overcast low-level stratus clouds has been generated using a newly developed parameterization and surface measurements from the Atmospheric Radiation Measurement central facility in Oklahoma. The database (5-min resolution) includes two parts: measurements and retrievals. The former consist of cloud base and top heights, layer-mean temperature, cloud liquid water path, and solar transmission ratio measured by a ground-based lidar/ceilometer and radar pair, radiosondes, a microwave radiometer, and a standard Eppley precision spectral pyranometer, respectively. The retrievals include the cloud-droplet effective radius and number concentration and broadband shortwave optical depth and cloud and top-of-atmosphere albedos. Stratus without any overlying mid or high-level clouds occurred most frequently during winter and least often during summer. Mean cloud-layer altitudes and geometric thicknesses were higher and greater, respectively, in summer than in winter. Both quantities are positively correlated with the cloud-layer mean temperature. Mean cloud-droplet effective radii range from 8.1 μm in winter to 9.7 μm during summer, while cloud-droplet number concentrations during winter are nearly twice those in summer. Since cloud liquid water paths are almost the same in both seasons, cloud optical depth is higher during the winter, leading to greater cloud albedos and lower cloud transmittances. (c) 2000 American Geophysical Union

  12. Dust events in Beijing, China (2004–2006: comparison of ground-based measurements with columnar integrated observations

    Directory of Open Access Journals (Sweden)

    Z. J. Wu

    2009-09-01

    Full Text Available Ambient particle number size distributions spanning three years were used to characterize the frequency and intensity of atmospheric dust events in the urban areas of Beijing, China in combination with AERONET sun/sky radiometer data. Dust events were classified into two types based on the differences in particle number and volume size distributions and local weather conditions. This categorization was confirmed by aerosol index images, columnar aerosol optical properties, and vertical potential temperature profiles. During the type-1 events, dust particles dominated the total particle volume concentration (<10 μm, with a relative share over 70%. Anthropogenic particles in the Aitken and accumulation mode played a subordinate role here because of high wind speeds (>4 m s−1. The type-2 events occurred in rather stagnant air masses and were characterized by a lower volume fraction of coarse mode particles (on average, 55%. Columnar optical properties showed that the superposition of dust and anthropogenic aerosols in type-2 events resulted in a much higher AOD (average: 1.51 than for the rather pure dust aerosols in type-1 events (average AOD: 0.36. A discrepancy was found between the ground-based and column integrated particle volume size distributions, especially for the coarse mode particles. This discrepancy likely originates from both the limited comparability of particle volume size distributions derived from Sun photometer and in situ number size distributions, and the inhomogeneous vertical distribution of particles during dust events.

  13. CO Seasonal Variability and Trend over Paris Megacity Using Ground-Based QualAir FTS and Satellite IASI-MetOp Measurements

    Science.gov (United States)

    Te, Yao; Jeseck, Pascal; Hadji-Lazaro, Juliette

    2012-11-01

    In a growing world with more than 7 billion inhabitants and big emerging countries such as China, Brazil and India, emissions of anthropogenic pollutants are increasing continuously. Monitoring and control of atmospheric pollutants in megacities have become a major challenge for scientists and public health authorities in environmental research area. The QualAir platform at University Pierre et Marie Curie (UPMC), is an innovating experimental research platform dedicated to survey urban atmospheric pollution and air quality. A Bruker Optics IFS 125HR Fourier transform spectrometer belonged to the Laboratoire de Physique Moléculaire pour l'Atmosphère et l'Astrophysique (LPMAA), was adapted for ground-based atmospheric measurements. As one of the major instruments of the QualAir platform, this ground-based Fourier transform spectrometer (QualAir FTS) analyses the composition of the urban atmosphere of Paris, which is the third largest European megacity. The continuous monitoring of atmospheric pollutants is essential to improve the understanding of urban air pollution processes. Associated with a sun-tracker, the QualAir remote sensing FTS operates in solar infrared absorption and enables to monitor many trace gases, and to follow up their variability in the Ile-de-France region. Concentrations of atmospheric pollutants are retrieved by the radiative transfer model PROFFIT. These ground-based remote sensing measurements are compared to ground in-situ measurements and to satellite data from IASI-MetOp (Infrared Atmospheric Sounding Interferometer). The remote sensing total column of the carbon monoxide (CO) obtained from January 2009 to June 2012, has a seasonal variability with a maximum in April and a minimum in October. While, after 2008, the mean CO level is quite stable (no significant decrease as before 2008).

  14. Evaluating precipitation in a regional climate model using ground-based radar measurements in Dronning Maud Land, East Antarctica

    Science.gov (United States)

    Gorodetskaya, Irina; Maahn, Maximilan; Gallée, Hubert; Souverijns, Niels; Gossart, Alexandra; Kneifel, Stefan; Crewell, Susanne; Van Lipzig, Nicole

    2017-04-01

    Occasional very intense snowfall events over Dronning Maud Land (DML) region in East Antarctica, contributed significantly to the entire Antarctic ice sheet surface mass balance (SMB) during the last years. The meteorological-cloud-precipitation observatory running at the Princess Elisabeth station (PE) in the DML escarpment zone since 2009 (HYDRANT/AEROCLOUD projects), provides unique opportunity to estimate contribution of precipitation to the local snow accumulation and new data for evaluating precipitation in climate models. Our previous work using PE measurements showed that occasional intense precipitation events determine the total local yearly SMB and account for its large interannual variability. Here we use radar measurements to evaluate precipitation in a regional climate model with a special focus on intense precipitation events together with the large-scale atmospheric dynamics responsible for these events. The coupled snow-atmosphere regional climate model MAR (Modèle Atmosphérique Régional) is used to simulate climate and SMB in DML at 5-km horizontal resolution during 2012 using initial and boundary conditions from the European Centre for Medium-range Weather Forecasts (ECMWF) Interim re-analysis atmospheric and oceanic fields. Two evaluation approaches are used: observations-to-model and model-to-observations. In the first approach, snowfall rate (S) is derived from the MRR (vertically profiling 24-GHz precipitation radar) effective reflectivity factor (Ze) at 400 m agl using various Ze-S relationships for dry snow. The uncertainty in Ze-S relationships is constrained using snow particle size distribution from Snow Video Imager - Precipitation Imaging Package (SVI/PIP) and information about particle shapes. For the second approach we apply the Passive and Active Microwave radiative TRAnsfer model (PAMTRA), which allows direct comparison of the radar-measured and climate model-based vertical profiles of the radar Ze and Doppler velocity. In MAR

  15. Prototype of a Laser-Induced Fluorescence Ground-Based Instrument for Measurements of Atmospheric Iodine Monoxide (IO)

    Science.gov (United States)

    Thurlow, M. E.; Co, D. T.; Hanisco, T. F.; Lapson, L. B.; Anderson, J. G.

    2008-12-01

    High abundances of iodine monoxide (IO) are known to exist and to participate in local photochemistry of the marine boundary layer: (1) IO participates in depletion episodes of O3 and in the removal of mercury in the Arctic polar spring by enhancing atomic Br mixing ratios. Recent observations and computer simulations suggest that mercury sequestration is closely tied to halogen photochemistry and that gaseous atomic Hg depletion can be enhanced significantly by the presence of small amounts of iodine-containing compounds. (2) IO and higher- order iodine oxides are involved in the formation of new particles in coastal marine environments. Studies using smog chamber experiments simulating coastal atmospheric conditions have demonstrated that new particles can form from condensable iodine-containing vapors and that their concentrations over the open ocean are sufficient to influence marine particle formation. (3) IO has also been shown to affect the oxidizing capacity of the troposphere by altering the partitioning of NO2/NO and HO2/HO and by activating chlorine and bromine in sea salt aerosols. In the stratosphere, these same processes can lead to enhanced ozone loss rates. Detailed photochemical models that include iodine photochemistry, however, are hampered by the lack of observational data. The distribution of IO in vertical, horizontal, and temporal coordinates is unknown, so the impact of IO on global photochemistry cannot be predicted. The resolution of these important scientific issues requires an in situ IO instrument. A fully functional nanosecond Nd:YAG-pumped Ti:Sapphire laser system and a prototype IO ground-based instrument have been built in our lab. With the current setup, the laser system was situated 10 m from the field station, and the laser light was coupled via an optical fiber. With the use of highly efficient fluorescence detection optics and photon counting techniques, sensitivities of better than 0.1 ppt in 1 s for IO was achieved in the

  16. Error threshold inference from Global Precipitation Measurement (GPM) satellite rainfall data and interpolated ground-based rainfall measurements in Metro Manila

    Science.gov (United States)

    Ampil, L. J. Y.; Yao, J. G.; Lagrosas, N.; Lorenzo, G. R. H.; Simpas, J.

    2017-12-01

    The Global Precipitation Measurement (GPM) mission is a group of satellites that provides global observations of precipitation. Satellite-based observations act as an alternative if ground-based measurements are inadequate or unavailable. Data provided by satellites however must be validated for this data to be reliable and used effectively. In this study, the Integrated Multisatellite Retrievals for GPM (IMERG) Final Run v3 half-hourly product is validated by comparing against interpolated ground measurements derived from sixteen ground stations in Metro Manila. The area considered in this study is the region 14.4° - 14.8° latitude and 120.9° - 121.2° longitude, subdivided into twelve 0.1° x 0.1° grid squares. Satellite data from June 1 - August 31, 2014 with the data aggregated to 1-day temporal resolution are used in this study. The satellite data is directly compared to measurements from individual ground stations to determine the effect of the interpolation by contrast against the comparison of satellite data and interpolated measurements. The comparisons are calculated by taking a fractional root-mean-square error (F-RMSE) between two datasets. The results show that interpolation improves errors compared to using raw station data except during days with very small amounts of rainfall. F-RMSE reaches extreme values of up to 654 without a rainfall threshold. A rainfall threshold is inferred to remove extreme error values and make the distribution of F-RMSE more consistent. Results show that the rainfall threshold varies slightly per month. The threshold for June is inferred to be 0.5 mm, reducing the maximum F-RMSE to 9.78, while the threshold for July and August is inferred to be 0.1 mm, reducing the maximum F-RMSE to 4.8 and 10.7, respectively. The maximum F-RMSE is reduced further as the threshold is increased. Maximum F-RMSE is reduced to 3.06 when a rainfall threshold of 10 mm is applied over the entire duration of JJA. These results indicate that

  17. Aerosol and Cloud Properties during the Cloud Cheju ABC Plume -Asian Monsoon Experiment (CAPMEX) 2008: Linking between Ground-based and UAV Measurements

    Science.gov (United States)

    Kim, S.; Yoon, S.; Venkata Ramana, M.; Ramanathan, V.; Nguyen, H.; Park, S.; Kim, M.

    2009-12-01

    Cheju Atmospheric Brown Cloud (ABC) Plume-Monsoon Experiment (CAPMEX), comprehsensive ground-based measurements and a series of data-gathering flights by specially equipped autonomous unmanned aerial vehicles (AUAVs) for aerosol and cloud, had conducted at Jeju (formerly, Cheju), South Korea during August-September 2008, to improve our understanding of how the reduction of anthropogenic emissions in China (so-called “great shutdown” ) during and after the Summer Beijing Olympic Games 2008 effcts on the air quliaty and radiation budgets and how atmospheric brown clouds (ABCs) influences solar radiation budget off Asian continent. Large numbers of in-situ and remote sensing instruments at the Gosan ABC observatory and miniaturized instruments on the aircraft measure a range of properties such as the quantity of soot, size-segregated aerosol particle numbers, total particle numbers, size-segregated cloud droplet numbers (only AUAV), aerosol scattering properties (only ground), aerosol vertical distribution, column-integrated aerosol properties, and meteorological variables. By integrating ground-level and high-elevation AUAV measurements with NASA-satellite observations (e.g., MODIS, CALIPSO), we investigate the long range transport of aerosols, the impact of ABCs on clouds, and the role of biogenic and anthropogenic aerosols on cloud condensation nuclei (CCN). In this talk, we will present the results from CAPMEX focusing on: (1) the characteristics of aerosol optical, physical and chemical properties at Gosan observatory, (2) aerosol solar heating calculated from the ground-based micro-pulse lidar and AERONET sun/sky radiometer synergy, and comparison with direct measurements from UAV, and (3) aerosol-cloud interactions in conjunction with measurements by satellites and Gosan observatory.

  18. Quality assessment of ground-based microwave measurements of chlorine monoxide, ozone, and nitrogen dioxide from the NDSC radiometer at the Plateau de Bure

    Directory of Open Access Journals (Sweden)

    P. Ricaud

    2004-06-01

    Full Text Available A ground-based microwave radiometer dedicated to chlorine monoxide (ClO measurements around 278GHz has been in operation from December 1993-June 1996 at the Plateau de Bure, France (45° N, 5.9° E, 2500m altitude. It belongs to the international Network for the Detection of Stratospheric Change. A detailed study of both measurements and retrieval schemes has been undertaken. Although dedicated to the measurements of ClO, simultaneous profiles of O3, ClO and NO2, together with information about the instrumental baseline, have been retrieved using the optimal estimation method. The vertical profiles have been compared with other ground-based microwave data, satellite-borne data and model results. Data quality shows: 1 the weak sensitivity of the instrument that obliges to make time averages over several hours; 2 the site location where measurements of good opacities are possible for only a few days per year; 3 the baseline undulation affecting all the spectra, an issue common to all the microwave instruments; 4 the slow drift of some components affecting frequencies by 3-4MHz within a couple of months. Nevertheless, when temporally averaging data over a few days, ClO temporal variations (diurnal and over several weeks in winter 1995 from 35-50km are consistent with model results and satellite data, particularly at the peak altitude around 40km, although temporal coincidences are infrequent in winter 1995. In addition to ClO, it is possible to obtain O3 information from 30-60km whilst the instrument is not optimized at all for this molecule. Retrievals of O3 are reasonable when compared with model and another ground-based data set, although the lowermost layers are affected by the contamination of baseline remnants. Monthly-averaged diurnal variations of NO2 are detected at 40km and appear in agreement with photochemical model results and satellite zonally-averaged data, although the amplitude

  19. Ground-Based Remote or In Situ Measurement of Vertical Profiles of Wind in the Lower Troposphere

    Energy Technology Data Exchange (ETDEWEB)

    Clifton, Andrew; Newman, Jennifer

    2017-02-24

    Knowledge of winds in the lower troposphere is essential for a range of applications, including weather forecasting, transportation, natural hazards, and wind energy. This presentation focuses on the measurement of vertical profiles of wind in the lower troposphere for wind energy applications. This presentation introduces the information that wind energy site development and operations require, how it used, and the benefits and problems of current measurements from in-situ measurements and remote sensing. The development of commercial Doppler wind lidar systems over the last 10 years are shown, along with the lessons learned from this experience. Finally, potential developments in wind profiling aimed at reducing uncertainty and increasing data availability are introduced.

  20. Correlation of ground-based on topside photometric observations with auroral electron spectra measurements at rocket altitudes

    International Nuclear Information System (INIS)

    Arnoldy, R.L.; Lewis, P.B. Jr.

    1977-01-01

    Spectroscopic measurements of the auroral lines 5577, 4278, and 6300 A made at Fort Yukon, Alaska, are used in the model computations of Rees and Luckey (1974) to predict the energy influx and the characteristic energy of an assumed Maxwellian primary electron spectrum for two auroral displays. Simultaneous with the ground observations, electron detectors aboard a sounding rocket directly measured the primary electron spectrum and energy flux on the field lines which contained the auroral light in the E region observed by the ground photometers (magnetically conjugate in the local sense). For the two auroras studied, the in situ particle measurements show that the model (1) correctly predicts changes in spectral parameters. (2) predicts a precipitated energy flux in good agreement with measured values, and (3) assumes a spectral shape (Maxwellian) not typical of the peaked spectra measured above discrete auroras.One of the rocket flights also carried photometers sensitive to 5577 and 3914 A. Every 0.2 s the photometers sampled the auroral light from the E region magnetically conjugate to the rocket, and they have reaffirmed the very close correlation between emission at 3914 A and that at 5577 A. Finally, by using the measured electron precipitation and current ionospheric models the emissions at 3914, 4278, and 5577 A are calculated. The model computations closely predict the measured light at 3914 and 4278 A. However, the 5577-A emission calculated from dissociative recombination of O 2 + and direct excitation of atomic oxygen using a measured secondary spectrum accounts for only about one third of the observed emission

  1. Ground-based FTIR measurements of CO from the Jungfraujoch: characterisation and comparison with in situ surface and MOPITT data

    Directory of Open Access Journals (Sweden)

    B. Barret

    2003-01-01

    Full Text Available CO vertical profiles have been retrieved from solar absorption FTIR spectra recorded at the NDSC station of the Jungfraujoch (46.5º N, 8º E and 3580 m a.s.l. for the period from January 1997 to May 2001. The characterisation of these profiles has been established by an information content analysis and an estimation of the error budgets. A partial validation of the profiles has been performed through comparisons with correlative measurements. The average volume mixing ratios (vmr in the 3 km layer above the station have been compared with coincident surface measurements. The agreement between monthly means from both measurement techniques is very good, with a correlation coefficient of 0.87, and no significant bias observed. The FTIR total columns have also been compared to CO partial columns above 3580 m a.s.l. derived from the MOPITT (Measurement Of Pollution In The Troposphere instrument for the period March 2000 to May 2001. Relative to the FTIR columns, the MOPITT partial columns exhibit a positive bias of 8±8% for daytime and of 4±7% for nighttime measurements.

  2. Comparison of ground-based and Viking Orbiter measurements of Martian water vapor - Variability of the seasonal cycle

    Science.gov (United States)

    Jakosky, B. M.; Barker, E. S.

    1984-01-01

    Earth-based observations of Mars atmospheric water vapor are presented for the 1975-1976, 1977-1978, and 1983 apparitions. Comparisons are made with near-simultaneous spacecraft measurements made from the Viking Orbiter Mars Atmospheric Water Detection experiment during 1976-1978 and with previous earth-based measurements. Differences occur between the behavior in the different years, and may be related to the Mars climate. Measurements during the southern summer in 1969 indicate a factor of three times as much water as is present at this same season in other years. This difference may have resulted from the sublimation of water from the south polar residual cap upon removal of most or all of the CO2 ice present; sublimation of all of the CO2 ice during some years could be a result of a greater thermal load being placed on the cap due to the presence of differing amounts of atmospheric dust.

  3. EVALUATION OF OPPORTUNITIES OF SOLAR ENERGETICS ON THE BASIS OF ACCURATE GROUND-BASED MEASUREMENTS OF SOLAR RADIATION

    Directory of Open Access Journals (Sweden)

    Aculinin A.

    2008-04-01

    Full Text Available Expected quantity of a solar energy received by solar panel is estimated on the basis of accurate measurements of solar radiation in Kishinev. Optimal orientation of solar panels and apparent volume of the electric power generated by solar panels are determined.

  4. Optical Properties of the Urban Aerosol Particles Obtained from Ground Based Measurements and Satellite-Based Modelling Studies

    Directory of Open Access Journals (Sweden)

    Genrik Mordas

    2015-01-01

    Full Text Available Applications of satellite remote sensing data combined with ground measurements and model simulation were applied to study aerosol optical properties as well as aerosol long-range transport under the impact of large scale circulation in the urban environment in Lithuania (Vilnius. Measurements included the light scattering coefficients at 3 wavelengths (450, 550, and 700 nm measured with an integrating nephelometer and aerosol particle size distribution (0.5–12 μm and number concentration (Dpa > 0.5 μm registered by aerodynamic particle sizer. Particle number concentration and mean light scattering coefficient varied from relatively low values of 6.0 cm−3 and 12.8 Mm−1 associated with air masses passed over Atlantic Ocean to relatively high value of 119 cm−3 and 276 Mm−1 associated with South-Western air masses. Analysis shows such increase in the aerosol light scattering coefficient (276 Mm−1 during the 3rd of July 2012 was attributed to a major Sahara dust storm. Aerosol size distribution with pronounced coarse particles dominance was attributed to the presence of dust particles, while resuspended dust within the urban environment was not observed.

  5. Comparison of Cloud Base Height Derived from a Ground-Based Infrared Cloud Measurement and Two Ceilometers

    Directory of Open Access Journals (Sweden)

    Lei Liu

    2015-01-01

    Full Text Available The cloud base height (CBH derived from the whole-sky infrared cloud-measuring system (WSIRCMS and two ceilometers (Vaisala CL31 and CL51 from November 1, 2011, to June 12, 2012, at the Chinese Meteorological Administration (CMA Beijing Observatory Station are analysed. Significant differences can be found by comparing the measurements of different instruments. More exactly, the cloud occurrence retrieved from CL31 is 3.8% higher than that from CL51, while WSIRCMS data shows 3.6% higher than ceilometers. More than 75.5% of the two ceilometers’ differences are within ±200 m and about 89.5% within ±500 m, while only 30.7% of the differences between WSIRCMS and ceilometers are within ±500 m and about 55.2% within ±1000 m. These differences may be caused by the measurement principles and CBH retrieval algorithm. A combination of a laser ceilometer and an infrared cloud instrument is recommended to improve the capability for determining cloud occurrence and retrieving CBHs.

  6. MAX-DOAS measurements in southern China: retrieval of aerosol extinctions and validation using ground-based in-situ data

    Directory of Open Access Journals (Sweden)

    X. Li

    2010-03-01

    Full Text Available We performed MAX-DOAS measurements during the PRiDe-PRD2006 campaign in the Pearl River Delta region 50 km north of Guangzhou, China, for 4 weeks in June 2006. We used an instrument sampling at 7 different elevation angles between 3° and 90°. During 9 cloud-free days, differential slant column densities (DSCDs of O4 (O2 dimer absorptions between 351 nm and 389 nm were evaluated for 6 elevation angles. Here, we show that radiative transfer modeling of the DSCDS can be used to retrieve the aerosol extinction and the height of the boundary layer. A comparison of the aerosol extinction with simultaneously recorded, ground based nephelometer data shows excellent agreement.

  7. Measurements of O3, NO2 and BrO during the INDOEX campaign using ground based DOAS and GOME satellite data

    Directory of Open Access Journals (Sweden)

    A. Ladstätter-Weißenmayer

    2007-01-01

    Full Text Available The INDian Ocean EXperiment (INDOEX was an international, multi-platform field campaign to measure long-range transport of air masses from South and South-East-(SE Asia towards the Indian Ocean. During the dry monsoon season between January and March 1999, local measurements were carried out from ground based platforms and were compared with satellite based data. The objective of this study was to characterise stratospheric and tropospheric trace gas amounts in the equatorial region, and to investigate the impact of air pollution at this remote site. For the characterisation of the chemical composition of the outflow from the S-SE-Asian region, we performed ground based dual-axis-DOAS (Differential Optical Absorption Spectroscopy measurements at the KCO (Kaashidhoo Climate Observatory in the Maldives (5.0° N, 73.5° E. The measurements were conducted using two different observation modes (off-axis and zenith-sky. This technique allows the separation of the tropospheric and stratospheric columns for different trace gases like O3 and NO2. These dual-axis DOAS data were compared with O3-sonde measurements performed at KCO and satellite based GOME (Global Ozone Measuring Experiment data during the intensive measuring phase of the INDOEX campaign in February and March 1999. From GOME observations, tropospheric and stratospheric columns for O3 and NO2 were retrieved. In addition, the analysis of the O3-sonde measurements allowed the determination of the tropospheric O3 amount. The comparison shows that the results of all three measurement systems agree within their error limits. During the INDOEX campaign, mainly background conditions were observed, but in a single case an increase of tropospheric NO2 during a short pollution event was observed from the ground and the impact on the vertical columns was calculated. GOME measurements showed evidence for small tropospheric contributions to the BrO budget, probably located in the free troposphere and

  8. Prediction of post-sunset ESF based on the strength and asymmetry of EIA from ground based TEC measurements

    Science.gov (United States)

    Thampi, S. V.; Ravindran, S.; Devasia, C. V.; Pant, T. K.; Sreelatha, P.; Sridharan, R.

    The Coherent Radio Beacon Experiment (CRABEX) is aimed at investigating the equatorial ionospheric processes like the Equatorial Ionization Anomaly (EIA) and Equatorial Spread F (ESF) and their inter relationships. As a part of CRABEX program, a network of six stations covering the region from Trivandrum (8.5°N) to Nainital (29.3°N) is set up along the 77-78° E meridian. These ground receivers basically measure the slant Total Electron Content (TEC) along the line of sight from the Low Earth Orbiting satellites (NIMS). These simultaneous TEC measurements are inverted to obtain the tomographic image of the latitudinal distribution of electron densities in the meridional plane. In this paper, the tomographic images of the equatorial ionosphere along the 77-78°E meridian are presented. The crest intensities in the southern and northern hemispheres also show significant differences with seasons, showing the variability in the EIA asymmetry. The evening images give an indication of the prevailing electrodynamical conditions on different days, preceding the occurrence/non-occurrence of ESF. Apart from this, the single station TEC measurements from the Trivandrum station itself is used to estimate the EIA strength and asymmetry. Since this station is situated at the trough of the EIA, right over the dip equator, the latitudinal gradients on both northern (N) and southern (S) sides can be used to compute the EIA strength and asymmetry. These two parameters, obtained well ahead of the onset time of ESF, are shown to have a definite role on the subsequent ESF activity. Hence, both these factors are combined to define a new `forecast parameter' for the generation of ESF. It has been shown that this parameter can uniquely define the state of the `background ionosphere' conducive for the generation of ESF irregularities as early as 1600 IST. A critical value for the `forecast parameter' has been identified such that when the estimated value for `forecast parameter' exceeds

  9. Net Surface Shortwave Radiation from GOES Imagery—Product Evaluation Using Ground-Based Measurements from SURFRAD

    Directory of Open Access Journals (Sweden)

    Anand K. Inamdar

    2015-08-01

    Full Text Available The Earth’s surface net radiation controls the energy and water exchanges between the Earth’s surface and the atmosphere, and can be derived from satellite observations. The ability to monitor the net surface radiation over large areas at high spatial and temporal resolution is essential for many applications, such as weather forecasting, short-term climate prediction or water resources management. The objective of this paper is to derive the net surface radiation in the shortwave domain at high temporal (half-hourly and spatial resolution (~1 km using visible imagery from Geostationary Operational Environmental Satellite (GOES. The retrieval algorithm represents an adaptation to GOES data of a standard algorithm initially developed for the NASA-operated Clouds and Earth’s Radiant Energy System (CERES scanner. The methodology relies on: (1 the estimation of top of atmosphere shortwave radiation from GOES spectral measurements; and (2 the calculation of net surface shortwave (SW radiation accounting for atmospheric effects. Comparison of GOES-retrieved net surface shortwave radiation with ground-measurements at the National Oceanic and Atmospheric Administration’s (NOAA Surface Radiation (SURFRAD stations yields very good agreement with average bias lower than 5 W·m−2 and root mean square difference around 70 W·m−2. The algorithm performance is usually higher over areas characterized by low spatial variability in term of land cover type and surface biophysical properties. The technique does not involve retrieval and assessment of cloud properties and can be easily adapted to other meteorological satellites around the globe.

  10. The reflection seismology measurement method

    International Nuclear Information System (INIS)

    Sprecher, C.

    1987-01-01

    Even though data acquisition and data processing procedures have become more and more complex in recent decades, the end products of a reflection seismic survey have remained simple and illustrative. A seismic section resembles a geological cross-section and can be interpreted without in-depth knowledge provided that the basic principles behind the method are understood. This article attempts to convey some insight into the methodology without claiming to be scientifically exact or complete. (author)

  11. GreenNet: A Global Ground-Based Network of Instruments Measuring Greenhouse Gases in the Atmosphere

    Science.gov (United States)

    Floyd, M.; Grunberg, M.; Wilson, E. L.

    2017-12-01

    Climate change is the most important crisis of our lifetime. For policy makers to take action to combat the effects of climate change, they will need definitive proof that it is occurring globally. We have developed a low-cost ground instrument - a portable miniaturized laser heterodyne radiometer (mini-LHR) - capable of measuring concentrations of two of the most potent anthropogenic greenhouse gases, CO2 and methane, in columns in the atmosphere. They work by combining sunlight that has undergone absorption by gases with light from a laser. This combined light is detected by a photoreciever and a radio frequency beat signal is produced. From this beat signal, concentrations of these gases throughout the atmospheric column can be determined. A network of mini-LHR instruments in locations around the world will give us the data necessary to significantly reduce uncertainty in greenhouse gas sinks and sources contributing to climate change. Each instrument takes one reading per minute while the sun is up. With a goal to establish up to 500 instrument sites, the estimated total data per day will likely exceed 1GB. Every piece of data must be sorted as it comes in to determine whether it is a good or bad reading. The goal of the citizen science project is to collaborate with citizen scientists enrolled with Zooniverse.org to cycle through our data and help sort it, while also learning about the mini-LHR, greenhouse gases and climate change. This data will be used to construct an algorithm to automatically sort data that relies on statistical analyses of the previously sorted data.

  12. Dust impact on surface solar irradiance assessed with model simulations, satellite observations and ground-based measurements

    Science.gov (United States)

    Kosmopoulos, Panagiotis G.; Kazadzis, Stelios; Taylor, Michael; Athanasopoulou, Eleni; Speyer, Orestis; Raptis, Panagiotis I.; Marinou, Eleni; Proestakis, Emmanouil; Solomos, Stavros; Gerasopoulos, Evangelos; Amiridis, Vassilis; Bais, Alkiviadis; Kontoes, Charalabos

    2017-07-01

    This study assesses the impact of dust on surface solar radiation focussing on an extreme dust event. For this purpose, we exploited the synergy of AERONET measurements and passive and active satellite remote sensing (MODIS and CALIPSO) observations, in conjunction with radiative transfer model (RTM) and chemical transport model (CTM) simulations and the 1-day forecasts from the Copernicus Atmosphere Monitoring Service (CAMS). The area of interest is the eastern Mediterranean where anomalously high aerosol loads were recorded between 30 January and 3 February 2015. The intensity of the event was extremely high, with aerosol optical depth (AOD) reaching 3.5, and optical/microphysical properties suggesting aged dust. RTM and CTM simulations were able to quantify the extent of dust impact on surface irradiances and reveal substantial reduction in solar energy exploitation capacity of PV and CSP installations under this high aerosol load. We found that such an extreme dust event can result in Global Horizontal Irradiance (GHI) attenuation by as much as 40-50 % and a much stronger Direct Normal Irradiance (DNI) decrease (80-90 %), while spectrally this attenuation is distributed to 37 % in the UV region, 33 % in the visible and around 30 % in the infrared. CAMS forecasts provided a reliable available energy assessment (accuracy within 10 % of that obtained from MODIS). Spatially, the dust plume resulted in a zonally averaged reduction of GHI and DNI of the order of 150 W m-2 in southern Greece, and a mean increase of 20 W m-2 in the northern Greece as a result of lower AOD values combined with local atmospheric processes. This analysis of a real-world scenario contributes to the understanding and quantification of the impact range of high aerosol loads on solar energy and the potential for forecasting power generation failures at sunshine-privileged locations where solar power plants exist, are under construction or are being planned.

  13. Dust impact on surface solar irradiance assessed with model simulations, satellite observations and ground-based measurements

    Directory of Open Access Journals (Sweden)

    P. G. Kosmopoulos

    2017-07-01

    Full Text Available This study assesses the impact of dust on surface solar radiation focussing on an extreme dust event. For this purpose, we exploited the synergy of AERONET measurements and passive and active satellite remote sensing (MODIS and CALIPSO observations, in conjunction with radiative transfer model (RTM and chemical transport model (CTM simulations and the 1-day forecasts from the Copernicus Atmosphere Monitoring Service (CAMS. The area of interest is the eastern Mediterranean where anomalously high aerosol loads were recorded between 30 January and 3 February 2015. The intensity of the event was extremely high, with aerosol optical depth (AOD reaching 3.5, and optical/microphysical properties suggesting aged dust. RTM and CTM simulations were able to quantify the extent of dust impact on surface irradiances and reveal substantial reduction in solar energy exploitation capacity of PV and CSP installations under this high aerosol load. We found that such an extreme dust event can result in Global Horizontal Irradiance (GHI attenuation by as much as 40–50 % and a much stronger Direct Normal Irradiance (DNI decrease (80–90 %, while spectrally this attenuation is distributed to 37 % in the UV region, 33 % in the visible and around 30 % in the infrared. CAMS forecasts provided a reliable available energy assessment (accuracy within 10 % of that obtained from MODIS. Spatially, the dust plume resulted in a zonally averaged reduction of GHI and DNI of the order of 150 W m−2 in southern Greece, and a mean increase of 20 W m−2 in the northern Greece as a result of lower AOD values combined with local atmospheric processes. This analysis of a real-world scenario contributes to the understanding and quantification of the impact range of high aerosol loads on solar energy and the potential for forecasting power generation failures at sunshine-privileged locations where solar power plants exist, are under construction or are

  14. Measurements of CO2 Column Abundance in the Low Atmosphere Using Ground Based 1.6 μm CO2 DIAL

    Science.gov (United States)

    Abo, M.; Shibata, Y.; Nagasawa, C.

    2017-12-01

    Changes in atmospheric carbon dioxide (CO2) concentration are believed to produce the largest radiative forcing for the current climate system. Accurate predictions of atmospheric CO2 concentration rely on the knowledge of its sinks and sources, transports, and its variability with time. Although this knowledge is currently unsatisfactory, numerical models use it as a way in simulating CO2 fluxes. Validating and improving the global atmospheric transport model, therefore, requires precise measurement of the CO2 concentration profile. There are two further variations on Lidar: the differential absorption Lidar (DIAL) and the integrated path differential absorption (IPDA) Lidar. DIAL/IPDA are basically for profile/total column measurement, respectively. IPDA is a special case of DIAL and can measure the total column-averaged mixing ratio of trace gases using return signals from the Earth's surface or from thick clouds based on an airborne or a satellite. We have developed a ground based 1.6 μm DIAL to measure vertical CO2 mixing ratio profiles from 0.4 to 2.5 km altitude. The goals of the CO2 DIAL are to produce atmospheric CO2 mixing ratio measurements with much smaller seasonal and diurnal biases from the ground surface. But, in the ground based lidar, return signals from around ground surface are usually suppressed in order to handle the large dynamic range. To receive the return signals as near as possible from ground surface, namely, the field of view (FOV) of the telescope must be wide enough to reduce the blind range of the lidar. While the return signals from the far distance are very weak, to enhance the sensitivity and heighten the detecting distance, the FOV must be narrow enough to suppress the sky background light, especially during the daytime measurements. To solve this problem, we propose a total column measurement method from the ground surface to 0.4 km altitude. Instead of strong signals from thick clouds such as the IPDA, the proposed method uses

  15. Measurement of Precipitation in the Alps Using Dual-Polarization C-Band Ground-Based Radars, the GPM Spaceborne Ku-Band Radar, and Rain Gauges

    Directory of Open Access Journals (Sweden)

    Marco Gabella

    2017-11-01

    Full Text Available The complex problem of quantitative precipitation estimation in the Alpine region is tackled from four different points of view: (1 the modern MeteoSwiss network of automatic telemetered rain gauges (GAUGE; (2 the recently upgraded MeteoSwiss dual-polarization Doppler, ground-based weather radar network (RADAR; (3 a real-time merging of GAUGE and RADAR, implemented at MeteoSwiss, in which a technique based on co-kriging with external drift (CombiPrecip is used; (4 spaceborne observations, acquired by the dual-wavelength precipitation radar on board the Global Precipitation Measuring (GPM core satellite. There are obviously large differences in these sampling modes, which we have tried to minimize by integrating synchronous observations taken during the first 2 years of the GPM mission. The data comprises 327 “wet” overpasses of Switzerland, taken after the launch of GPM in February 2014. By comparing the GPM radar estimates with the MeteoSwiss products, a similar performance was found in terms of bias. On average (whole country, all days and seasons, both solid and liquid phases, underestimation is as large as −3.0 (−3.4 dB with respect to RADAR (GAUGE. GPM is not suitable for assessing what product is the best in terms of average precipitation over the Alps. GPM can nevertheless be used to evaluate the dispersion of the error around the mean, which is a measure of the geographical distribution of the error inside the country. Using 221 rain-gauge sites, the result is clear both in terms of correlation and in terms of scatter (a robust, weighted measure of the dispersion of the multiplicative error around the mean. The best agreement was observed between GPM and CombiPrecip, and, next, between GPM and RADAR, whereas a larger disagreement was found between GPM and GAUGE. Hence, GPM confirms that, for precipitation mapping in the Alpine region, the best results are obtained by combining ground-based radar with rain-gauge measurements using

  16. A long-term study of aerosol–cloud interactions and their radiative effect at the Southern Great Plains using ground-based measurements

    Directory of Open Access Journals (Sweden)

    E. T. Sena

    2016-09-01

    Full Text Available Empirical estimates of the microphysical response of cloud droplet size distribution to aerosol perturbations are commonly used to constrain aerosol–cloud interactions in climate models. Instead of empirical microphysical estimates, here macroscopic variables are analyzed to address the influence of aerosol particles and meteorological descriptors on instantaneous cloud albedo and the radiative effect of shallow liquid water clouds. Long-term ground-based measurements from the Atmospheric Radiation Measurement (ARM program over the Southern Great Plains are used. A broad statistical analysis was performed on 14 years of coincident measurements of low clouds, aerosol, and meteorological properties. Two cases representing conflicting results regarding the relationship between the aerosol and the cloud radiative effect were selected and studied in greater detail. Microphysical estimates are shown to be very uncertain and to depend strongly on the methodology, retrieval technique and averaging scale. For this continental site, the results indicate that the influence of the aerosol on the shallow cloud radiative effect and albedo is weak and that macroscopic cloud properties and dynamics play a much larger role in determining the instantaneous cloud radiative effect compared to microphysical effects. On a daily basis, aerosol shows no correlation with cloud radiative properties (correlation = −0.01 ± 0.03, whereas the liquid water path shows a clear signal (correlation = 0.56 ± 0.02.

  17. A differential optical absorption spectroscopy method for retrieval from ground-based Fourier transform spectrometers measurements of the direct solar beam

    Science.gov (United States)

    Huo, Yanfeng; Duan, Minzheng; Tian, Wenshou; Min, Qilong

    2015-08-01

    A differential optical absorption spectroscopy (DOAS)-like algorithm is developed to retrieve the column-averaged dryair mole fraction of carbon dioxide from ground-based hyper-spectral measurements of the direct solar beam. Different to the spectral fitting method, which minimizes the difference between the observed and simulated spectra, the ratios of multiple channel-pairs—one weak and one strong absorption channel—are used to retrieve from measurements of the shortwave infrared (SWIR) band. Based on sensitivity tests, a super channel-pair is carefully selected to reduce the effects of solar lines, water vapor, air temperature, pressure, instrument noise, and frequency shift on retrieval errors. The new algorithm reduces computational cost and the retrievals are less sensitive to temperature and H2O uncertainty than the spectral fitting method. Multi-day Total Carbon Column Observing Network (TCCON) measurements under clear-sky conditions at two sites (Tsukuba and Bremen) are used to derive xxxx for the algorithm evaluation and validation. The DOAS-like results agree very well with those of the TCCON algorithm after correction of an airmass-dependent bias.

  18. Retrieval of NO2 stratospheric profiles from ground-based zenith-sky uv-visible measurements at 60°N

    Science.gov (United States)

    Hendrick, F.; van Roozendael, M.; Lambert, J.-C.; Fayt, C.; Hermans, C.; de Mazière, M.

    2003-04-01

    Nitrogen dioxide (NO_2) plays an important role in controlling ozone abundances in the stratosphere, either directly through the NOx (NO+NO_2) catalytic cycle, either indirectly by reaction with the radical ClO to form the reservoir species ClONO_2. In this presentation, NO_2 stratospheric profiles are retrieved from ground-based UV-visible NO_2 slant column abundances measured since 1998 at the complementary NDSC station of Harestua (Norway, 60^oN). The retrieval algorithm is based on the Rodgers optimal estimation inversion method and a forward model consisting in the IASB-BIRA stacked box photochemical model PSCBOX coupled to the radiative transfer package UVspec/DISORT. This algorithm has been applied to a set of about 50 sunrises and sunsets for which spatially and temporally coincident NO_2 measurements made by the HALOE (Halogen Occultation Experiment) instrument on board the Upper Atmosphere Research Satellite (UARS) are available. The consistency between retrieved and HALOE profiles is discussed in term of the different seasonal conditions investigated which are spring with and without chlorine activation, summer, and fall.

  19. Applying spaceborne reflectivity measurements for calculation of the solar ultraviolet radiation at ground level

    Directory of Open Access Journals (Sweden)

    P. N. den Outer

    2012-12-01

    Full Text Available Long-term analysis of cloud effects on ultraviolet (UV radiation on the ground using spaceborne observations requires the use of instruments that have operated consecutively. The longest data record can be built from the reflectivity measurements produced by the instruments Total Ozone Mapping Spectrometers (TOMS flown on Nimbus 7 from 1979 to 1992, TOMS on Earth Probe from 1996 to 2005, and the Ozone Monitoring Instrument (OMI flown on EOS Aura since 2004. The reflectivity data produced by TOMS on Earth Probe is only included until 2002. A comparison is made with cloud effects inferred from ground-based pyranometer measurements at over 83 World Radiation Data Centre stations. Modelled UV irradiances utilizing the standard reflectivity are compared with measurements of UV irradiances at eight European low-elevation stations. The reflectivity data of the two TOMS instruments shows a consistent agreement, and the required corrections are of low percentage, i.e. 2–3%. In contrast, the reflectivity product of OMI requires correction of 7–10%, and a solar angle dependency therein is more pronounced. These corrections were inferred from a comparison with pyranometer data, and tested using the UV measurements. The average reduction of UV radiation due to clouds for all sites together indicates a small trend: a diminishing cloudiness, in line with ground-based UV observations. Uncorrected implementation of the reflectivity data would have indicated the opposite.

    An optimal area was established for reflectivity data for the calculation of daily sums of UV radiation. It measures approximately 1.25° in latitudinal direction for square-shaped areas overhead the ground-based UV stations. Such an area can be traversed within 5 to 7 h at the average wind speeds found for the West European continent.

  20. CO measurements from the ACE-FTS satellite instrument: data analysis and validation using ground-based, airborne and spaceborne observations

    Directory of Open Access Journals (Sweden)

    C. Clerbaux

    2008-05-01

    Full Text Available The Atmospheric Chemistry Experiment (ACE mission was launched in August 2003 to sound the atmosphere by solar occultation. Carbon monoxide (CO, a good tracer of pollution plumes and atmospheric dynamics, is one of the key species provided by the primary instrument, the ACE-Fourier Transform Spectrometer (ACE-FTS. This instrument performs measurements in both the CO 1-0 and 2-0 ro-vibrational bands, from which vertically resolved CO concentration profiles are retrieved, from the mid-troposphere to the thermosphere. This paper presents an updated description of the ACE-FTS version 2.2 CO data product, along with a comprehensive validation of these profiles using available observations (February 2004 to December 2006. We have compared the CO partial columns with ground-based measurements using Fourier transform infrared spectroscopy and millimeter wave radiometry, and the volume mixing ratio profiles with airborne (both high-altitude balloon flight and airplane observations. CO satellite observations provided by nadir-looking instruments (MOPITT and TES as well as limb-viewing remote sensors (MIPAS, SMR and MLS were also compared with the ACE-FTS CO products. We show that the ACE-FTS measurements provide CO profiles with small retrieval errors (better than 5% from the upper troposphere to 40 km, and better than 10% above. These observations agree well with the correlative measurements, considering the rather loose coincidence criteria in some cases. Based on the validation exercise we assess the following uncertainties to the ACE-FTS measurement data: better than 15% in the upper troposphere (8–12 km, than 30% in the lower stratosphere (12–30 km, and than 25% from 30 to 100 km.

  1. Ground-based photo monitoring

    Science.gov (United States)

    Frederick C. Hall

    2000-01-01

    Ground-based photo monitoring is repeat photography using ground-based cameras to document change in vegetation or soil. Assume those installing the photo location will not be the ones re-photographing it. This requires a protocol that includes: (1) a map to locate the monitoring area, (2) another map diagramming the photographic layout, (3) type and make of film such...

  2. Validation of the Atmospheric Chemistry Experiment (ACE version 2.2 temperature using ground-based and space-borne measurements

    Directory of Open Access Journals (Sweden)

    R. J. Sica

    2008-01-01

    Full Text Available An ensemble of space-borne and ground-based instruments has been used to evaluate the quality of the version 2.2 temperature retrievals from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS. The agreement of ACE-FTS temperatures with other sensors is typically better than 2 K in the stratosphere and upper troposphere and 5 K in the lower mesosphere. There is evidence of a systematic high bias (roughly 3–6 K in the ACE-FTS temperatures in the mesosphere, and a possible systematic low bias (roughly 2 K in ACE-FTS temperatures near 23 km. Some ACE-FTS temperature profiles exhibit unphysical oscillations, a problem fixed in preliminary comparisons with temperatures derived using the next version of the ACE-FTS retrieval software. Though these relatively large oscillations in temperature can be on the order of 10 K in the mesosphere, retrieved volume mixing ratio profiles typically vary by less than a percent or so. Statistical comparisons suggest these oscillations occur in about 10% of the retrieved profiles. Analysis from a set of coincident lidar measurements suggests that the random error in ACE-FTS version 2.2 temperatures has a lower limit of about ±2 K.

  3. Ground-based measurements of the 1.3 to 0.3 millimeter spectrum of Jupiter and Saturn, and their detailed calibration.

    Science.gov (United States)

    Pardo, Juan R; Serabyn, Eugene; Wiedner, Martina C; Moreno, Raphäel; Orton, Glenn

    2017-07-01

    One of the legacies of the now retired Caltech Submillimeter Observatory (CSO) is presented in this paper. We measured for the first time the emission of the giant planets Jupiter and Saturn across the 0.3 to 1.3 mm wavelength range using a Fourier Transform Spectrometer mounted on the 10.4-meter dish of the CSO at Mauna Kea, Hawaii, 4100 meters above sea level. A careful calibration, including the evaluation of the antenna performance over such a wide wavelength range and the removal of the Earth's atmosphere effects, has allowed the detection of broad absorption lines on those planets' atmospheres. The calibrated data allowed us to verify the predictions of standard models for both planets in this spectral region, and to confirm the absolute radiometry in the case of Jupiter. Besides their physical interest, the results are also important as both planets are calibration references in the current era of operating ground-based and space-borne submillimeter instruments.

  4. Aerosol backscatter measurements at 10.6 microns with airborne and ground-based CO2 Doppler lidars over the Colorado High Plains. II - Backscatter structure

    Science.gov (United States)

    Bowdle, David A.; Rothermel, Jeffry; Vaughan, J. Michael; Post, Madison J.

    1991-01-01

    Measurements of tropospheric aerosol volume backscatter coefficients at 10.6-microns wavelength were obtained with airborne continuous wave and ground-based pulsed CO2 Doppler lidars over the Colorado High Plains during a 20-day period in summer 1982. A persistent 'background' layer was found between 6- and 10-km altitude, with a generally uniform backscatter mixing ratio of about 10 to the -10th sq m/kg per sr. The upper boundary of this background layer varied with the tropopause height; the lower boundary varied with the strength and diurnal cycle of convective mixing in the planetary boundary layer (PBL). For quiescent meteorological conditions, the transition from the PBL to the background layer was usually very sharp, with backscatter decreases sometimes as large as 3 decades in about 70 m. Sharp gradients were also found at the boundaries of shallow (tens of meters) subvisible cirrus clouds. For less stable conditions, associated with vertical aerosol transport by deep cumuliform clouds, backscatter tended to decrease exponentially with altitude.

  5. Aerosol backscatter measurements at 10.6 microns with airborne and ground-based CO2 Doppler lidars over the Colorado High Plains. I - Lidar intercomparison

    Science.gov (United States)

    Bowdle, David A.; Rothermel, Jeffry; Vaughan, J. Michael; Brown, Derek W.; Post, Madison J.

    1991-01-01

    An airborne continuous-wave (CW) focused CO2 Doppler lidar and a ground-based pulsed CO2 Doppler lidar were to obtain seven pairs of comparative measurements of tropospheric aerosol backscatter profiles at 10.6-micron wavelength, near Denver, Colorado, during a 20-day period in July 1982. In regions of uniform backscatter, the two lidars show good agreement, with differences usually less than about 50 percent near 8-km altitude and less than a factor of 2 or 3 elsewhere but with the pulsed lidar often lower than the CW lidar. Near sharp backscatter gradients, the two lidars show poorer agreement, with the pulsed lidar usually higher than the CW lidar. Most discrepancies arise from a combination of atmospheric factors and instrument factors, particularly small-scale areal and temporal backscatter heterogeneity above the planetary boundary layer, unusual large-scale vertical backscatter structure in the upper troposphere and lower stratosphere, and differences in the spatial resolution, detection threshold, and noise estimation for the two lidars.

  6. A Chronology of Annual-Mean Effective Radii of Stratospheric Aerosols from Volcanic Eruptions During the Twentieth Century as Derived From Ground-based Spectral Extinction Measurements

    Science.gov (United States)

    Strothers, Richard B.; Hansen, James E. (Technical Monitor)

    2001-01-01

    Stratospheric extinction can be derived from ground-based spectral photometric observations of the Sun and other stars (as well as from satellite and aircraft measurements, available since 1979), and is found to increase after large volcanic eruptions. This increased extinction shows a characteristic wavelength dependence that gives information about the chemical composition and the effective (or area weighted mean) radius of the particles responsible for it. Known to be tiny aerosols constituted of sulfuric acid in a water solution, the stratospheric particles at midlatitudes exhibit a remarkable uniformity of their column-averaged effective radii r(sub eff) in the first few months after the eruption. Considering the seven largest eruptions of the twentieth century, r(sub eff) at this phase of peak aerosol abundance is approx. 0.3 micrometers in all cases. A year later, r(sub eff) either has remained about the same size (almost certainly in the case of the Katmai eruption of 1912) or has increased to approx. 0.5 micrometers (definitely so for the Pinatubo eruption of 1991). The reasons for this divergence in aerosol growth are unknown.

  7. Ground-based measurements of the 1.3 to 0.3 mm spectrum of Jupiter and Saturn, and their detailed calibration

    Science.gov (United States)

    Pardo, Juan R.; Serabyn, Eugene; Wiedner, Martina C.; Moreno, Raphäel; Orton, Glenn

    2017-07-01

    One of the legacies of the now retired Caltech Submillimeter Observatory (CSO) is presented in this paper. We measured for the first time the emission of the giant planets Jupiter and Saturn across the 0.3 to 1.3 mm wavelength range using a Fourier Transform Spectrometer mounted on the 10.4 m dish of the CSO at Mauna Kea, Hawaii, 4100 m above sea level. A careful calibration, including the evaluation of the antenna performance over such a wide wavelength range and the removal of the Earth's atmosphere effects, has allowed the detection of broad absorption lines on those planets' atmospheres. The calibrated data allowed us to verify the predictions of standard models for both planets in this spectral region, and to confirm the absolute radiometry in the case of Jupiter. Besides their physical interest, the results are also important as both planets are calibration references in the current era of operating ground-based and space-borne submillimeter instruments.

  8. Glue Film Thickness Measurements by Spectral Reflectance

    International Nuclear Information System (INIS)

    Marshall, B.R.

    2010-01-01

    Spectral reflectance was used to determine the thickness of thin glue layers in a study of the effect of the glue on radiance and reflectance measurements of shocked-tin substrates attached to lithium fluoride windows. Measurements based on profilometry of the components were found to be inaccurate due to flatness variations and deformation of the tin substrate under pressure during the gluing process. The accuracy of the spectral reflectance measurements were estimated to be ±0.5 (micro)m, which was sufficient to demonstrate a convincing correlation between glue thickness and shock-generated light.

  9. Glue Film Thickness Measurements by Spectral Reflectance

    Energy Technology Data Exchange (ETDEWEB)

    B. R. Marshall

    2010-09-20

    Spectral reflectance was used to determine the thickness of thin glue layers in a study of the effect of the glue on radiance and reflectance measurements of shocked-tin substrates attached to lithium fluoride windows. Measurements based on profilometry of the components were found to be inaccurate due to flatness variations and deformation of the tin substrate under pressure during the gluing process. The accuracy of the spectral reflectance measurements were estimated to be ±0.5 μm, which was sufficient to demonstrate a convincing correlation between glue thickness and shock-generated light.

  10. Calibration of Ground -based Lidar instrument

    DEFF Research Database (Denmark)

    Villanueva, Héctor; Yordanova, Ginka

    This report presents the result of the lidar calibration performed for the given Ground-based Lidar at DTU’s test site for large wind turbines at Høvsøre, Denmark. Calibration is here understood as the establishment of a relation between the reference wind speed measurements with measurement...

  11. Constraining Aerosol Optical Models Using Ground-Based, Collocated Particle Size and Mass Measurements in Variable Air Mass Regimes During the 7-SEAS/Dongsha Experiment

    Science.gov (United States)

    Bell, Shaun W.; Hansell, Richard A.; Chow, Judith C.; Tsay, Si-Chee; Wang, Sheng-Hsiang; Ji, Qiang; Li, Can; Watson, John G.; Khlystov, Andrey

    2012-01-01

    During the spring of 2010, NASA Goddard's COMMIT ground-based mobile laboratory was stationed on Dongsha Island off the southwest coast of Taiwan, in preparation for the upcoming 2012 7-SEAS field campaign. The measurement period offered a unique opportunity for conducting detailed investigations of the optical properties of aerosols associated with different air mass regimes including background maritime and those contaminated by anthropogenic air pollution and mineral dust. What appears to be the first time for this region, a shortwave optical closure experiment for both scattering and absorption was attempted over a 12-day period during which aerosols exhibited the most change. Constraints to the optical model included combined SMPS and APS number concentration data for a continuum of fine and coarse-mode particle sizes up to PM2.5. We also take advantage of an IMPROVE chemical sampler to help constrain aerosol composition and mass partitioning of key elemental species including sea-salt, particulate organic matter, soil, non sea-salt sulphate, nitrate, and elemental carbon. Our results demonstrate that the observed aerosol scattering and absorption for these diverse air masses are reasonably captured by the model, where peak aerosol events and transitions between key aerosols types are evident. Signatures of heavy polluted aerosol composed mostly of ammonium and non sea-salt sulphate mixed with some dust with transitions to background sea-salt conditions are apparent in the absorption data, which is particularly reassuring owing to the large variability in the imaginary component of the refractive indices. Extinctive features at significantly smaller time scales than the one-day sample period of IMPROVE are more difficult to reproduce, as this requires further knowledge concerning the source apportionment of major chemical components in the model. Consistency between the measured and modeled optical parameters serves as an important link for advancing remote

  12. Arctic Atmospheric Measurements Using Manned and Unmanned Aircraft, Tethered Balloons, and Ground-Based Systems at U.S. DOE ARM Facilities on the North Slope Of Alaska

    Science.gov (United States)

    Ivey, M.; Dexheimer, D.; Roesler, E. L.; Hillman, B. R.; Hardesty, J. O.

    2016-12-01

    The U.S. Department of Energy (DOE) provides scientific infrastructure and data to the international Arctic research community via research sites located on the North Slope of Alaska and an open data archive maintained by the ARM program. In 2016, DOE continued investments in improvements to facilities and infrastructure at Oliktok Point Alaska to support operations of ground-based facilities and unmanned aerial systems for science missions in the Arctic. The Third ARM Mobile Facility, AMF3, now deployed at Oliktok Point, was further expanded in 2016. Tethered instrumented balloons were used at Oliktok to make measurements of clouds in the boundary layer including mixed-phase clouds and to compare measurements with those from the ground and from unmanned aircraft operating in the airspace above AMF3. The ARM facility at Oliktok Point includes Special Use Airspace. A Restricted Area, R-2204, is located at Oliktok Point. Roughly 4 miles in diameter, it facilitates operations of tethered balloons and unmanned aircraft. R-2204 and a new Warning Area north of Oliktok, W-220, are managed by Sandia National Laboratories for DOE Office of Science/BER. These Special Use Airspaces have been successfully used to launch and operate unmanned aircraft over the Arctic Ocean and in international airspace north of Oliktok Point.A steady progression towards routine operations of unmanned aircraft and tethered balloon systems continues at Oliktok. Small unmanned aircraft (DataHawks) and tethered balloons were successfully flown at Oliktok starting in June of 2016. This poster will discuss how principal investigators may apply for use of these Special Use Airspaces, acquire data from the Third ARM Mobile Facility, or bring their own instrumentation for deployment at Oliktok Point, Alaska.

  13. Physical and optical properties of 2010 Eyjafjallajökull volcanic eruption aerosol: ground-based, Lidar and airborne measurements in France

    Directory of Open Access Journals (Sweden)

    M. Hervo

    2012-02-01

    Full Text Available During the Eyjafjallajökull eruption (14 April to 24 May 2010, the volcanic aerosol cloud was observed across Europe by several airborne in situ and ground-based remote-sensing instruments. On 18 and 19 May, layers of depolarizing particles (i.e. non-spherical particles were detected in the free troposphere above the Puy de Dôme station, (PdD, France with a Rayleigh-Mie LIDAR emitting at a wavelength of 355 nm, with parallel and crossed polarization channels. These layers in the free troposphere (FT were also well captured by simulations with the Lagrangian particle dispersion model FLEXPART, which furthermore showed that the ash was eventually entrained into the planetary boundary layer (PBL. Indeed, the ash cloud was then detected and characterized with a comprehensive set of in situ instruments at the Puy de Dôme station (PdD. In agreement with the FLEXPART simulation, up to 65 μg m−3 of particle mass and 2.2 ppb of SO2 were measured at PdD, corresponding to concentrations higher than the 95 percentile of 2 yr of measurements at PdD. Moreover, the number concentration of particles increased to 24 000 cm−3, mainly in the submicronic mode, but a supermicronic mode was also detected with a modal diameter of 2 μm. The resulting optical properties of the ash aerosol were characterized by a low scattering Ångström exponent (0.98, showing the presence of supermicronic particles. For the first time to our knowledge, the combination of in situ optical and physical characterization of the volcanic ash allowed the calculation of the mass-to-extinction ratio (η with no assumptions on the aerosol density. The mass-to-extinction ratio was found to be significantly different from the background boundary layer aerosol (max: 1.57 g m−2 as opposed to 0.33 ± 0.03 g m−2. Using this ratio, ash mass concentration in the volcanic plume derived from LIDAR measurements was found to be 655 ± 23

  14. Optical Reflectance Measurements for Commonly Used Reflectors

    Science.gov (United States)

    Janecek, Martin; Moses, William W.

    2008-08-01

    When simulating light collection in scintillators, modeling the angular distribution of optical light reflectance from surfaces is very important. Since light reflectance is poorly understood, either purely specular or purely diffuse reflectance is generally assumed. In this paper we measure the optical reflectance distribution for eleven commonly used reflectors. A 440 nm, output power stabilized, un-polarized laser is shone onto a reflector at a fixed angle of incidence. The reflected light's angular distribution is measured by an array of silicon photodiodes. The photodiodes are movable to cover 2pi of solid angle. The light-induced current is, through a multiplexer, read out with a digital multimeter. A LabVIEW program controls the motion of the laser and the photodiode array, the multiplexer, and the data collection. The laser can be positioned at any angle with a position accuracy of 10 arc minutes. Each photodiode subtends 6.3deg, and the photodiode array can be positioned at any angle with up to 10 arc minute angular resolution. The dynamic range for the current measurements is 10 5:1. The measured light reflectance distribution was measured to be specular for several ESR films as well as for aluminum foil, mostly diffuse for polytetrafluoroethylene (PTFE) tape and titanium dioxide paint, and neither specular nor diffuse for Lumirrorreg, Melinexreg and Tyvekreg. Instead, a more complicated light distribution was measured for these three materials.

  15. Comparisons of the error budgets associated with ground-based FTIR measurements of atmospheric CH4 profiles at Île de la Réunion and Jungfraujoch.

    Science.gov (United States)

    Vanhaelewyn, Gauthier; Duchatelet, Pierre; Vigouroux, Corinne; Dils, Bart; Kumps, Nicolas; Hermans, Christian; Demoulin, Philippe; Mahieu, Emmanuel; Sussmann, Ralf; de Mazière, Martine

    2010-05-01

    The Fourier Transform Infra Red (FTIR) remote measurements of atmospheric constituents at the observatories at Saint-Denis (20.90°S, 55.48°E, 50 m a.s.l., Île de la Réunion) and Jungfraujoch (46.55°N, 7.98°E, 3580 m a.s.l., Switzerland) are affiliated to the Network for the Detection of Atmospheric Composition Change (NDACC). The European NDACC FTIR data for CH4 were improved and homogenized among the stations in the EU project HYMN. One important application of these data is their use for the validation of satellite products, like the validation of SCIAMACHY or IASI CH4 columns. Therefore, it is very important that errors and uncertainties associated to the ground-based FTIR CH4 data are well characterized. In this poster we present a comparison of errors on retrieved vertical concentration profiles of CH4 between Saint-Denis and Jungfraujoch. At both stations, we have used the same retrieval algorithm, namely SFIT2 v3.92 developed jointly at the NASA Langley Research Center, the National Center for Atmospheric Research (NCAR) and the National Institute of Water and Atmosphere Research (NIWA) at Lauder, New Zealand, and error evaluation tools developed at the Belgian Institute for Space Aeronomy (BIRA-IASB). The error components investigated in this study are: smoothing, noise, temperature, instrumental line shape (ILS) (in particular the modulation amplitude and phase), spectroscopy (in particular the pressure broadening and intensity), interfering species and solar zenith angle (SZA) error. We will determine if the characteristics of the sites in terms of altitude, geographic locations and atmospheric conditions produce significant differences in the error budgets for the retrieved CH4 vertical profiles

  16. CFC-11, CFC-12 and HCFC-22 ground-based remote sensing FTIR measurements at Réunion Island and comparisons with MIPAS/ENVISAT data

    Directory of Open Access Journals (Sweden)

    M. Zhou

    2016-11-01

    Full Text Available Profiles of CFC-11 (CCl3F, CFC-12 (CCl2F2 and HCFC-22 (CHF2Cl have been obtained from Fourier transform infrared (FTIR solar absorption measurements above the Saint-Denis (St Denis and Maïdo sites at Réunion Island (21° S, 55° E with low vertical resolution. FTIR profile retrievals are performed by the well-established SFIT4 program and the detail retrieval strategies along with the systematic/random uncertainties of CFC-11, CFC-12 and HCFC-22 are discussed in this study. The FTIR data of all three species are sensitive to the whole troposphere and the lowermost stratosphere, with the peak sensitivity between 5 and 10 km. The ground-based FTIR data have been compared with the collocated Michelson Interferometer for Passive Atmospheric Sounding (MIPAS/ENVISAT data and found to be in good agreement: the observed mean relative biases and standard deviations of the differences between the smoothed MIPAS and FTIR partial columns (6–30 km are (−4.3 and 4.4 %, (−2.9 and 4.6 % and (−0.7 and 4.8 % for CFC-11, CFC-12 and HCFC-22, respectively, which are within the combined error budgets from both measurements. The season cycles of CFC-11, CFC-12 and HCFC-22 from FTIR measurements and MIPAS data show a similar variation: concentration is highest in February–April and lowest in August–October. The trends derived from the combined St Denis and Maïdo FTIR time series are −0.86 ± 0.12 and 2.84 ± 0.06 % year−1 for CFC-11 and HCFC-22, respectively, for the period 2004 to 2016, and −0.76 ± 0.05 % year−1 for CFC-12 for 2009 to 2016. These measurements are consistent with the trends observed by the National Oceanic and Atmospheric Administration (NOAA Global Monitoring Division's (GMD Halocarbons & other Atmospheric Trace Species Group (HATS measurements at Samoa (14.2° S, 170.5° W for CFC-11 (−0.87 ± 0.04 % year−1, but slightly weaker for HCFC-22 (3.46 ± 0.05 % year−1 and

  17. Technical Note: New ground-based FTIR measurements at Ile de La Réunion: observations, error analysis, and comparisons with independent data

    Directory of Open Access Journals (Sweden)

    C. Senten

    2008-07-01

    Full Text Available Ground-based high spectral resolution Fourier-transform infrared (FTIR solar absorption spectroscopy is a powerful remote sensing technique to obtain information on the total column abundances and on the vertical distribution of various constituents in the atmosphere. This work presents results from two FTIR measurement campaigns in 2002 and 2004, held at Ile de La Réunion (21° S, 55° E. These campaigns represent the first FTIR observations carried out at a southern (subtropical site. They serve the initiation of regular, long-term FTIR monitoring at this site in the near future. To demonstrate the capabilities of the FTIR measurements at this location for tropospheric and stratospheric monitoring, a detailed report is given on the retrieval strategy, information content and corresponding full error budget evaluation for ozone (O3, methane (CH4, nitrous oxide (N2O, carbon monoxide (CO, ethane (C2H6, hydrogen chloride (HCl, hydrogen fluoride (HF and nitric acid (HNO3 total and partial column retrievals. Moreover, we have made a thorough comparison of the capabilities at sea level altitude (St.-Denis and at 2200 m a.s.l. (Maïdo. It is proved that the performances of the technique are such that the atmospheric variability can be observed, at both locations and in distinct altitude layers. Comparisons with literature and with correlative data from ozone sonde and satellite (i.e., ACE-FTS, HALOE and MOPITT measurements are given to confirm the results. Despite the short time series available at present, we have been able to detect the seasonal variation of CO in the biomass burning season, as well as the impact of particular biomass burning events in Africa and Madagascar on the atmospheric composition above Ile de La Réunion. We also show that differential measurements between St.-Denis and Maïdo provide useful information about the concentrations in the boundary layer.

  18. Integration of Ground-based Magnetics and Vertical Deformation Measurements for the Characterization of the San Andreas Fault at the Durmid Hill Region, California

    Science.gov (United States)

    Alvarez, K.; Polet, J.

    2017-12-01

    The Durmid Hill region is located near the termination of the San Andreas Fault (SAF) at Bombay Beach. This section of the fault has not experienced any major earthquakes for at least the last three centuries. During a 6 year study, Sylvester et al. (1993) collected vertical deformation measurements at Durmid Hill from monuments they installed along a 2.37 km leveling line normal to the SAF. They concluded that interseismic processes account for most of the growth at Durmid Hill and estimated more than 9 mm of uplift within the leveling line, with uniform tilt at distances greater than 500 m from the fault. Langenheim et al. (2014) created a model based on ground-based magnetic data that they collected in the same area and found a complex magnetic structure with a broad band magnetic anomaly present on the northeast side of SAF and a prominent magnetic high along the main mapped trace of the SAF. A primary objective of our study is to reoccupy the leveling line from Sylvester et al. (1993), across the SAF at Durmid Hill. Additionally, we will utilize subsurface geophysical techniques to enhance our understanding of the fault geometry along the southernmost end of the SAF and its relationship to the aseismic deformation at Durmid Hill. Elevation profiles are measured using Nikon Nivo 5C total stations and magnetic field intensity measurements are made by a GSM-19TGW v7.0 walking magnetometer, with a VLF (Very Low requency) attachment. We will present preliminary results from data sets gathered in March and May of 2017, as well as additional surveys that will be carried out in October and November. The preliminary maps produced from the results of the first magnetic surveys show two significant and distinct magnetic anomalies consistent with earlier studies. Initial monument elevation comparisons could only be made for monuments located at the north-eastern end of the leveling line, at a distance of about 1.5 km behind Bat Cave Buttes. There appear to be sections of

  19. The in situ measurement of road reflection.

    NARCIS (Netherlands)

    Schreuder, D.A.

    1994-01-01

    This paper describes a procedure that has been designed to measure P(0;0), P(2;0) and P(1;90), the three values that are the basis for the C1-C2 system for measuring road reflection of light. The system was proposed in The Netherlands, and subsequently adopted by the CIE as an alternative to the

  20. Assessment of cirrus cloud and aerosol radiative effect in South-East Asia by ground-based NASA MPLNET lidar network data and CALIPSO satellite measurements

    Science.gov (United States)

    Lolli, Simone; Campbell, James R.; Lewis, Jasper R.; Welton, Ellsworth J.; Di Girolamo, Paolo; Fatkhuroyan, Fatkhuroyan; Gu, Yu; Marquis, Jared W.

    2017-10-01

    Aerosol, together with cirrus clouds, play a fundamental role in the earth-atmosphere system radiation budget, especially at tropical latitudes, where the Earth surface coverage by cirrus cloud can easily reach 70%. In this study we evaluate the combined aerosol and cirrus cloud net radiative effects in a wild and barren region like South East Asia. This part of the world is extremely vulnerable to climate change and it is source of important anthropogenic and natural aerosol emissions. The analysis has been carried out by computing cirrus cloud and aerosol net radiative effects through the Fu-Liou-Gu atmospheric radiative transfer model, adequately adapted to input lidar measurements, at surface and top-of-the atmosphere. The aerosol radiative effects were computed respectively using the retrieved lidar extinction from Cloud-Aerosol Lidar with Orthogonal Polarization in 2011 and 2012 and the lidar on-board of Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations for the South East Asia Region (27N-12S, 77E-132E) with 5° x 5° spatial resolution. To assess the cirrus cloud radiative effect, we used the ground-based Micro Pulse Lidar Network measurements at Singapore permanent observational site. Results put in evidence that strong aerosol emission areas are related on average to a net surface cooling. On the contrary, cirrus cloud radiative effect shows a net daytime positive warming of the system earth-atmosphere. This effect is weak over the ocean where the albedo is lower and never counter-balances the net cooling produced by aerosols. The net cooling is stronger in 2011, with an associated reduction in precipitations by the four of the five rain-gauges stations deployed in three regions as Sumatra, Kalimantan and Java with respect to 2012. We can speculate that aerosol emissions may be associated with lower rainfall, however some very important phenomena as El Nino Southern Oscillation , Madden-Julian Oscillation, Monsoon and Indian Dipole are not

  1. Water Pollution Detection by Reflectance Measurements

    Science.gov (United States)

    Goolsby, A. D.

    1971-01-01

    Measurement of the intensity of light reflected from various planar liquid surfaces has been performed. The results of this brief study show that the presence of a film of foreign material floating on a reference substrate is easily detected by reflectance measurement if the two liquids possess significantly different refractive indices, for example, oil (n = 1.40) and water (n = 1.33). Additional study of various optical configurations, and the building and testing of a prototype monitoring device revealed that the method is sufficiently practical for application to continuous water quality monitoring.

  2. Measuring Light Reflectance of BGO Crystal Surfaces

    Science.gov (United States)

    Janecek, Martin; Moses, William W.

    2008-10-01

    A scintillating crystal's surface reflectance has to be well understood in order to accurately predict and optimize the crystal's light collection through Monte Carlo simulations. In this paper, we measure the inner surface reflectance properties for BGO. The measurements include BGO crystals with a mechanically polished surface, rough-cut surface, and chemically etched surface, and with various reflectors attached, both air-coupled and with coupling compound. The measurements are performed with a laser aimed at the center of a hemispherical shaped BGO crystal. The hemispherical shape eliminates any non-perpendicular angles for light entering and exiting the crystal. The reflected light is collected with an array of photodiodes. The laser can be set at an arbitrary angle, and the photodiode array is rotated to fully cover 2pi of solid angle. The current produced in the photodiodes is readout with a digital multimeter connected through a multiplexer. The two rows of photodiodes achieve 5-degree by 4-degree resolution, and the current measurement has a dynamic range of 105:1. The acquired data was not described by the commonly assumed linear combination of specular and diffuse (Lambertian) distributions, except for a very few surfaces. Surface roughness proved to be the most important parameter when choosing crystal setup. The reflector choice was of less importance and of almost no consequence for rough-cut surfaces. Pure specular reflection distribution for all incidence angles was measured for polished surfaces with VM2000 film, while the most Lambertian distribution for any surface finish was measured for titanium dioxide paint. The distributions acquired in this paper will be used to create more accurate Monte Carlo models for light reflection distribution within BGO crystals.

  3. Calibration of Ground-based Lidar instrument

    DEFF Research Database (Denmark)

    Yordanova, Ginka; Gómez Arranz, Paula

    This report presents the result of the lidar calibration performed for the given Ground-based Lidar at DTU’s test site for large wind turbines at Høvsøre, Denmark. Calibration is here understood as the establishment of a relation between the reference wind speed measurements with measurement...... uncertainties provided by measurement standard and corresponding lidar wind speed indications with associated measurement uncertainties. The lidar calibration concerns the 10 minute mean wind speed measurements. The comparison of the lidar measurements of the wind direction with that from wind vanes...

  4. Reliability of reflectance measures in passive filters

    Science.gov (United States)

    Saldiva de André, Carmen Diva; Afonso de André, Paulo; Rocha, Francisco Marcelo; Saldiva, Paulo Hilário Nascimento; Carvalho de Oliveira, Regiani; Singer, Julio M.

    2014-08-01

    Measurements of optical reflectance in passive filters impregnated with a reactive chemical solution may be transformed to ozone concentrations via a calibration curve and constitute a low cost alternative for environmental monitoring, mainly to estimate human exposure. Given the possibility of errors caused by exposure bias, it is common to consider sets of m filters exposed during a certain period to estimate the latent reflectance on n different sample occasions at a certain location. Mixed models with sample occasions as random effects are useful to analyze data obtained under such setups. The intra-class correlation coefficient of the mean of the m measurements is an indicator of the reliability of the latent reflectance estimates. Our objective is to determine m in order to obtain a pre-specified reliability of the estimates, taking possible outliers into account. To illustrate the procedure, we consider an experiment conducted at the Laboratory of Experimental Air Pollution, University of São Paulo, Brazil (LPAE/FMUSP), where sets of m = 3 filters were exposed during 7 days on n = 9 different occasions at a certain location. The results show that the reliability of the latent reflectance estimates for each occasion obtained under homoskedasticity is km = 0.74. A residual analysis suggests that the within-occasion variance for two of the occasions should be different from the others. A refined model with two within-occasion variance components was considered, yielding km = 0.56 for these occasions and km = 0.87 for the remaining ones. To guarantee that all estimates have a reliability of at least 80% we require measurements on m = 10 filters on each occasion.

  5. Analysis of Dual- and Full-Circular Polarimetric SAR Modes for Rice Phenology Monitoring: An Experimental Investigation through Ground-Based Measurements

    Directory of Open Access Journals (Sweden)

    Yuta Izumi

    2017-04-01

    Full Text Available Circularly polarized synthetic aperture radar (CP-SAR is known to be insensitive to polarization mismatch losses caused by the Faraday rotation effect and antenna misalignment. Additionally, the dual-circular polarimetric (DCP mode has proven to have more polarimetric information than that of the corresponding mode of linear polarization, i.e., the dual-linear polarimetric (DLP mode. Owing to these benefits, this paper investigates the feasibility of CP-SAR for rice monitoring. A ground-based CP-radar system was exploited, and C-band anechoic chamber data of a self-cultivated Japanese rice paddy were acquired from germination to ripening stages. Temporal variations of polarimetric observables derived from full-circular polarimetric (FCP and DCP as well as synthetically generated DLP data are analyzed and assessed with regard to their effectiveness in phenology retrieval. Among different observations, the H / α ¯ plane and triangle plots obtained by three scattering components (surface, double-bounce, and volume scattering for both the FCP and DCP modes are confirmed to have reasonable capability in discriminating the relevant intervals of rice growth.

  6. Ground-Based Global Positioning System (GPS) Meteorology Integrated Precipitable Water Vapor (IPW)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ground-Based Global Positioning System (GPS) Meteorology Integrated Precipitable Water Vapor (IPW) data set measures atmospheric water vapor using ground-based...

  7. Identifying diffraction effects in measured reflectances

    OpenAIRE

    Holzschuch , Nicolas; Pacanowski , Romain

    2015-01-01

    International audience; There are two different physical models connecting the micro-geometry of a surface and its physical reflectance properties (BRDF). The first, Cook-Torrance, assumes geometrical optics: light is reflected and masked by the micro-facets. In this model, the BRDF depends on the probability distribution of micro-facets normals. The second, Church-Takacs, assumes diffraction by the micro-geometry. In this model, the BRDF depends on the power spectral distribution of the surf...

  8. Space weather effects on ground based technology

    Science.gov (United States)

    Clark, T.

    Space weather can affect a variety of forms of ground-based technology, usually as a result of either the direct effects of the varying geomagnetic field, or as a result of the induced electric field that accompanies such variations. Technologies affected directly by geomagnetic variations include magnetic measurements made d ringu geophysical surveys, and navigation relying on the geomagnetic field as a direction reference, a method that is particularly common in the surveying of well-bores in the oil industry. The most obvious technology affected by induced electric fields during magnetic storms is electric power transmission, where the example of the blackout in Quebec during the March 1989 magnetic storm is widely known. Additionally, space weather effects must be taken into account in the design of active cathodic protection systems on pipelines to protect them against corrosion. Long-distance telecommunication cables may also have to be designed to cope with space weather related effects. This paper reviews the effects of space weather in these different areas of ground-based technology, and provides examples of how mitigation against hazards may be achieved. (The paper does not include the effects of space weather on radio communication or satellite navigation systems).

  9. The High Accuracy Measurement of CO2 Mixing Ratio Profiles Using Ground Based 1.6 μm CO2-DIAL with Temperature Measurement Techniques in the Lower-Atmosphere

    Science.gov (United States)

    Abo, M.; Shibata, Y.; Nagasawa, C.

    2017-12-01

    We have developed a ground based direct detection three-wavelength 1.6 μm differential absorption lidar (DIAL) to achieve measurements of vertical CO2 concentration and temperature profiles in the atmosphere. As the spectra of absorption lines of any molecules are influenced basically by the temperature and pressure in the atmosphere, it is important to measure them simultaneously so that the better accuracy of the DIAL measurement is realized. Conventionally, we have obtained the vertical profile of absorption cross sections using the atmospheric temperature profile by the objective analysis and the atmospheric pressure profile calculated by the pressure height equation. Comparison of atmospheric pressure profiles calculated from this equation and those obtained from radiosonde observations at Tateno, Japan is consistent within 0.2 % below 3 km altitude. But the temperature dependency of the CO2 density is 0.25 %/°C near the surface. Moreover, the CO2 concentration is often evaluated by the mixing ratio. Because the air density is related by the ideal gas law, the mixing ratio is also related by the atmospheric temperature. Therefore, the temperature affects not only accuracy of CO2 concentration but the CO2 mixing ratio. In this paper, some experimental results of the simultaneous measurement of atmospheric temperature profiles and CO2 mixing ratio profiles are reported from 0.4 to 2.5 km altitude using the three-wavelength 1.6 μm DIAL system. Temperature profiles of CO2 DIAL measurement were sometimes different from those of objective analysis below 1.5 km altitude. These differences are considered to be due to regionality at the lidar site. The temperature difference of 5.0 °C corresponds to a CO2 mixing ratio difference of 8.0 ppm at 500 m altitude. This cannot be ignored in estimates of regional sources and sinks of CO2. This three-wavelength CO2 DIAL technique can estimate accurately temporal behavior of CO2 mixing ratio profiles in the lower atmosphere

  10. Pathway to the Galactic Distribution of Planets: Combined Spitzer and Ground-Based Microlens Parallax Measurements of 21 Single-Lens Events

    Science.gov (United States)

    Novati, S. Calchi; Gould, A.; Udalski, A.; Menzies, J. W.; Bond, I. A.; Shvartzvald, Y.; Street, R. A.; Hundertmark, M.; Beichman, C. A.; Barry, R. K.

    2015-01-01

    We present microlens parallax measurements for 21 (apparently) isolated lenses observed toward the Galactic bulge that were imaged simultaneously from Earth and Spitzer, which was approximately 1 Astronomical Unit west of Earth in projection. We combine these measurements with a kinematic model of the Galaxy to derive distance estimates for each lens, with error bars that are small compared to the Sun's galactocentric distance. The ensemble therefore yields a well-defined cumulative distribution of lens distances. In principle, it is possible to compare this distribution against a set of planets detected in the same experiment in order to measure the Galactic distribution of planets. Since these Spitzer observations yielded only one planet, this is not yet possible in practice. However, it will become possible as larger samples are accumulated.

  11. MODIS GPP/NPP for complex land use area: a case study of comparison between MODIS GPP/NPP and ground-based measurements over Korea

    Science.gov (United States)

    Shim, C.

    2013-12-01

    The Moderate Resolution Imaging Radiometer (MODIS) Gross Primary Productivity (GPP)/Net Primary Productivity (NPP) has been widely used for the study on global terrestrial ecosystem and carbon cycle. The current MODIS product with ~ 1 km spatial resolution, however, has limitation on the information on local scale environment (fairly comparable values of the MODIS here however, cannot assure the quality of the MOD17 over the complex vegetation area of Korea since the ground measurements except the eddy covariance tower flux measurements are highly inconsistent. Therefore, the comprehensive experiments to represents GPP/NPP over diverse vegetation types for a comparable scale of MODIS with a consistent measurement technique are necessary in order to evaluate the MODIS vegetation productivity data over Korea, which contains a large portion of highly heterogeneous vegetation area.

  12. Measuring and manipulating audiences : A personal reflection

    NARCIS (Netherlands)

    Bulterman, Dick C A

    2016-01-01

    Understanding the emotional reactions of audiences to a wide range of content types is an important area of research. In this article, I provide a personal reflection on various approaches to modeling, quantifying and understanding audience behavior based on a broad range of evaluation techniques.

  13. Measuring and Modeling the Earth's Gravity - Introduction to Ground-Based Gravity Surveys and Analysis of Local Gravity Data

    Energy Technology Data Exchange (ETDEWEB)

    Rowe, Charlotte Anne [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-11-21

    We can measure changes in gravity from place to place on the earth. These measurements require careful recording of location, elevation and time for each reading. These readings must be adjusted for known effects (such as elevation, latitude, tides) that can bias our data and mask the signal of interest. After making corrections to our data, we can remove regional trends to obtain local Bouguer anomalies. The Bouguer anomalies arise from variations in the subsurface density structure. We can build models to explain our observations, but these models must be consistent with what is known about the local geology. Combining gravity models with other information – geologic, seismic, electromagnetic, will improve confidence in the results.

  14. Measurements of the Young's modulus of hydroxide catalysis bonds, and the effect on thermal noise in ground-based gravitational wave detectors

    Science.gov (United States)

    Phelps, Margot; van Veggel, Anna-Maria; Hough, James; Messenger, Chris; Hughes, David; Cunningham, William; Haughian, Karen; Rowan, Sheila

    2018-05-01

    With the outstanding results from the detection and observation of gravitational waves from coalescing black holes and neutron star inspirals, it is essential that pathways to further improve the sensitivities of the LIGO and VIRGO detectors are explored. There are a number of factors that potentially limit the sensitivities of the detectors. One such factor is thermal noise, a component of which results from the mechanical loss in the bond material between the silica fibre suspensions and the test mass mirrors. To calculate its magnitude, the Young's modulus of the bond material has to be known with reasonable accuracy. In this paper we present a new combination of ultrasonic technology and Bayesian analysis to measure the Young's modulus of hydroxide catalysis bonds between fused silica substrates. Using this novel technique, we measure the bond Young's modulus to be 18.5 ±2.32.0 GPa . We show that by applying this value to thermal noise models of bonded test masses with suitable attachment geometries, a reduction in suspension thermal noise consistent with an overall design sensitivity improvement allows a factor of 5 increase in event rate to be achieved.

  15. On the factors governing water vapor turbulence mixing in the convective boundary layer over land: Concept and data analysis technique using ground-based lidar measurements

    International Nuclear Information System (INIS)

    Pal, Sandip

    2016-01-01

    The convective boundary layer (CBL) turbulence is the key process for exchanging heat, momentum, moisture and trace gases between the earth's surface and the lower part of the troposphere. The turbulence parameterization of the CBL is a challenging but important component in numerical models. In particular, correct estimation of CBL turbulence features, parameterization, and the determination of the contribution of eddy diffusivity are important for simulating convection initiation, and the dispersion of health hazardous air pollutants and Greenhouse gases. In general, measurements of higher-order moments of water vapor mixing ratio (q) variability yield unique estimates of turbulence in the CBL. Using the high-resolution lidar-derived profiles of q variance, third-order moment, and skewness and analyzing concurrent profiles of vertical velocity, potential temperature, horizontal wind and time series of near-surface measurements of surface flux and meteorological parameters, a conceptual framework based on bottom up approach is proposed here for the first time for a robust characterization of the turbulent structure of CBL over land so that our understanding on the processes governing CBL q turbulence could be improved. Finally, principal component analyses will be applied on the lidar-derived long-term data sets of q turbulence statistics to identify the meteorological factors and the dominant physical mechanisms governing the CBL turbulence features. - Highlights: • Lidar based study for CBL turbulence features • Water vapor and aerosol turbulence profiles • Processes governing boundary layer turbulence profiles using lidars

  16. On the factors governing water vapor turbulence mixing in the convective boundary layer over land: Concept and data analysis technique using ground-based lidar measurements

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Sandip, E-mail: sup252@PSU.EDU

    2016-06-01

    The convective boundary layer (CBL) turbulence is the key process for exchanging heat, momentum, moisture and trace gases between the earth's surface and the lower part of the troposphere. The turbulence parameterization of the CBL is a challenging but important component in numerical models. In particular, correct estimation of CBL turbulence features, parameterization, and the determination of the contribution of eddy diffusivity are important for simulating convection initiation, and the dispersion of health hazardous air pollutants and Greenhouse gases. In general, measurements of higher-order moments of water vapor mixing ratio (q) variability yield unique estimates of turbulence in the CBL. Using the high-resolution lidar-derived profiles of q variance, third-order moment, and skewness and analyzing concurrent profiles of vertical velocity, potential temperature, horizontal wind and time series of near-surface measurements of surface flux and meteorological parameters, a conceptual framework based on bottom up approach is proposed here for the first time for a robust characterization of the turbulent structure of CBL over land so that our understanding on the processes governing CBL q turbulence could be improved. Finally, principal component analyses will be applied on the lidar-derived long-term data sets of q turbulence statistics to identify the meteorological factors and the dominant physical mechanisms governing the CBL turbulence features. - Highlights: • Lidar based study for CBL turbulence features • Water vapor and aerosol turbulence profiles • Processes governing boundary layer turbulence profiles using lidars.

  17. On the factors governing water vapor turbulence mixing in the convective boundary layer over land: Concept and data analysis technique using ground-based lidar measurements.

    Science.gov (United States)

    Pal, Sandip

    2016-06-01

    The convective boundary layer (CBL) turbulence is the key process for exchanging heat, momentum, moisture and trace gases between the earth's surface and the lower part of the troposphere. The turbulence parameterization of the CBL is a challenging but important component in numerical models. In particular, correct estimation of CBL turbulence features, parameterization, and the determination of the contribution of eddy diffusivity are important for simulating convection initiation, and the dispersion of health hazardous air pollutants and Greenhouse gases. In general, measurements of higher-order moments of water vapor mixing ratio (q) variability yield unique estimates of turbulence in the CBL. Using the high-resolution lidar-derived profiles of q variance, third-order moment, and skewness and analyzing concurrent profiles of vertical velocity, potential temperature, horizontal wind and time series of near-surface measurements of surface flux and meteorological parameters, a conceptual framework based on bottom up approach is proposed here for the first time for a robust characterization of the turbulent structure of CBL over land so that our understanding on the processes governing CBL q turbulence could be improved. Finally, principal component analyses will be applied on the lidar-derived long-term data sets of q turbulence statistics to identify the meteorological factors and the dominant physical mechanisms governing the CBL turbulence features. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Ground-based PTR-MS measurements of reactive organic compounds during the MINOS campaign in Crete, July–August 2001

    Directory of Open Access Journals (Sweden)

    G. Salisbury

    2003-01-01

    Full Text Available This study presents measurements of acetonitrile, benzene, toluene, methanol and acetone made using the proton-transfer-reaction mass spectrometry (PTR-MS technique at the Finokalia ground station in Crete during the Mediterranean INtensive Oxidant Study (MINOS in July-August 2001. Three periods during the campaign with broadly consistent back trajectories are examined in detail. In the first, air was advected from Eastern Europe without significant biomass burning influence (mean acetonitrile mixing ratio 154 pmol/mol. In the second period, the sampled air masses originated in Western Europe, and were advected approximately east-south-east, before turning south-west over the Black Sea and north-western Turkey. The third well-defined period included air masses advected from Eastern Europe passing east and south of/over the Sea of Azov, and showed significant influence by biomass burning (mean acetonitrile mixing ratio 436 pmol/mol, confirmed by satellite pictures. The mean toluene:benzene ratios observed in the three campaign periods described were 0.35, 0.37 and 0.22, respectively; the use of this quantity to determine air mass age is discussed. Methanol and acetone were generally well-correlated both with each other and with carbon monoxide throughout the campaign. Comparison of the acetone and methanol measurements with the MATCH-MPIC model showed that the model underestimated both species by a factor of 4, on average. The correlations between acetone, methanol and CO implied that the relatively high levels of methanol observed during MINOS were largely due to direct biogenic emissions, and also that biogenic sources of acetone were highly significant during MINOS (~35%. This in turn suggests that the model deficit in both species may be due, at least in part, to missing biogenic emissions.

  19. A new NDVI measure that overcomes data sparsity in cloud-covered regions predicts annual variation in ground-based estimates of high arctic plant productivity

    Science.gov (United States)

    Rune Karlsen, Stein; Anderson, Helen B.; van der Wal, René; Bremset Hansen, Brage

    2018-02-01

    Efforts to estimate plant productivity using satellite data can be frustrated by the presence of cloud cover. We developed a new method to overcome this problem, focussing on the high-arctic archipelago of Svalbard where extensive cloud cover during the growing season can prevent plant productivity from being estimated over large areas. We used a field-based time-series (2000-2009) of live aboveground vascular plant biomass data and a recently processed cloud-free MODIS-Normalised Difference Vegetation Index (NDVI) data set (2000-2014) to estimate, on a pixel-by-pixel basis, the onset of plant growth. We then summed NDVI values from onset of spring to the average time of peak NDVI to give an estimate of annual plant productivity. This remotely sensed productivity measure was then compared, at two different spatial scales, with the peak plant biomass field data. At both the local scale, surrounding the field data site, and the larger regional scale, our NDVI measure was found to predict plant biomass (adjusted R 2 = 0.51 and 0.44, respectively). The commonly used ‘maximum NDVI’ plant productivity index showed no relationship with plant biomass, likely due to some years having very few cloud-free images available during the peak plant growing season. Thus, we propose this new summed NDVI from onset of spring to time of peak NDVI as a proxy of large-scale plant productivity for regions such as the Arctic where climatic conditions restrict the availability of cloud-free images.

  20. An Examination of the Chemistry of Peroxycarboxylic Nitric Anhydrides and Related Volatile Organic Compounds During Texas Air Quality Study 2000 Using Ground-Based Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, James M.; Jobson, B Tom T.; Kuster, W. C.; Goldan, P. D.; Murphy, Paul; Williams, Eric; Frost, G. J.; Riemer, D.; Apel, Eric; Stroud, C.; Wiedinmyer, Christine; Fehsenfeld, Fred C.

    2003-08-19

    Measurements of peroxycarboxylic nitric anhydrides (PANs) along with related volatile organic compounds (VOCs) were made at the La Porte super site during the TexAQS 2000 Houston study. The PAN mixing ratios ranged up to 6.5 ppbv and were broadly correlated with O3, characteristic of a highly polluted urban environment. The anthropogenic PAN homologue concentrations were generally consistent with those found in other urban environments; peroxypropionic nitric anhydride (PPN) averaged 15%, and peroxyisobutyric nitric anhydride (PiBN) averaged 3% of PAN,. Some periods were noted where local petrochemical sources resulted in anomalous PANs chemistry. This effect was especially noticeable in the case of peroxyacrylic nitric anhydride (APAN) where local sources of 1,3-butadiene and acrolein resulted in APAN as high as 30% of PAN. Peroxymethacrylic nitric anhydride (MPAN) was a fairly minor constituent of the PANs except for two periods on 4 and 5 September when air masses from high biogenic hydrocarbons (BHC) areas were observed. BHC chemistry was not a factor in the highest ozone pollution episodes in Houston but may have an impact on daily average ozone levels in some circumstances.

  1. Near InfraRed Imaging Spectrograph (NIRIS) for ground-based mesospheric OH(6-2) and O2(0-1) intensity and temperature measurements

    Science.gov (United States)

    Singh, Ravindra P.; Pallamraju, Duggirala

    2017-08-01

    This paper describes the development of a new Near InfraRed Imaging Spectrograph (NIRIS) which is capable of simultaneous measurements of OH(6-2) Meinel and O2(0-1) atmospheric band nightglow emission intensities. In this spectrographic technique, rotational line ratios are obtained to derive temperatures corresponding to the emission altitudes of 87 and 94 km. NIRIS has been commissioned for continuous operation from optical aeronomy observatory, Gurushikhar, Mount Abu (24.6°N, 72.8°E) since January 2013. NIRIS uses a diffraction grating of 1200 lines mm^{-1} and 1024× 1024 pixels thermoelectrically cooled CCD camera and has a large field-of-view (FOV) of 80° along the slit orientation. The data analysis methodology adopted for the derivation of mesospheric temperatures is also described in detail. The observed NIRIS temperatures show good correspondence with satellite (SABER) derived temperatures and exhibit both tidal and gravity waves (GW) like features. From the time taken for phase propagation in the emission intensities between these two altitudes, vertical phase speed of gravity waves, cz, is calculated and along with the coherent GW time period `τ ', the vertical wavelength, λ z, is obtained. Using large FOV observations from NIRIS, the meridional wavelengths, λ y, are also calculated. We have used one year of data to study the possible cause(s) for the occurrences of mesospheric temperature inversions (MTIs). From the statistics obtained for 234 nights, it appears that in situ chemical heating is mainly responsible for the observed MTIs than the vertical propagation of the waves. Thus, this paper describes a novel near infrared imaging spectrograph, its working principle, data analysis method for deriving OH and O2 emission intensities and the corresponding rotational temperatures at these altitudes, derivation of gravity wave parameters (τ , cz, λ z, and λ y), and results on the statistical study of MTIs that exist in the earth's mesospheric

  2. Ground-based observations of exoplanet atmospheres

    NARCIS (Netherlands)

    Mooij, Ernst Johan Walter de

    2011-01-01

    This thesis focuses on the properties of exoplanet atmospheres. The results for ground-based near-infrared secondary eclipse observations of three different exoplanets, TrES-3b, HAT-P-1b and WASP-33b, are presented which have been obtained with ground-based telescopes as part of the GROUSE project.

  3. Column Aerosol Optical Properties and Aerosol Radiative Forcing During a Serious Haze-Fog Month over North China Plain in 2013 Based on Ground-Based Sunphotometer Measurements

    Science.gov (United States)

    Che, H.; Xia, X.; Zhu, J.; Li, Z.; Dubovik, O.; Holben, Brent N.; Goloub, P.; Chen, H.; Estelles, V.; Cuevas-Agullo, E.

    2014-01-01

    In January 2013, North China Plain experienced several serious haze events. Cimel sunphotometer measurements at seven sites over rural, suburban and urban regions of North China Plain from 1 to 30 January 2013 were used to further our understanding of spatial-temporal variation of aerosol optical parameters and aerosol radiative forcing (ARF). It was found that Aerosol Optical Depth at 500 nm (AOD500nm) during non-pollution periods at all stations was lower than 0.30 and increased significantly to greater than 1.00 as pollution events developed. The Angstrom exponent (Alpha) was larger than 0.80 for all stations most of the time. AOD500nm averages increased from north to south during both polluted and non-polluted periods on the three urban sites in Beijing. The fine mode AOD during pollution periods is about a factor of 2.5 times larger than that during the non-pollution period at urban sites but a factor of 5.0 at suburban and rural sites. The fine mode fraction of AOD675nm was higher than 80% for all sites during January 2013. The absorption AOD675nm at rural sites was only about 0.01 during pollution periods, while 0.03-0.07 and 0.01-0.03 during pollution and non-pollution periods at other sites, respectively. Single scattering albedo varied between 0.87 and 0.95 during January 2013 over North China Plain. The size distribution showed an obvious tri-peak pattern during the most serious period. The fine mode effective radius in the pollution period was about 0.01-0.08 microns larger than during nonpollution periods, while the coarse mode radius in pollution periods was about 0.06-0.38 microns less than that during nonpollution periods. The total, fine and coarse mode particle volumes varied by about 0.06-0.34 cu microns, 0.03-0.23 cu microns, and 0.03-0.10 cu microns, respectively, throughout January 2013. During the most intense period (1-16 January), ARF at the surface exceeded -50W/sq m, -180W/sq m, and -200W/sq m at rural, suburban, and urban sites

  4. Comparison of CERES-MODIS stratus cloud properties with ground-based measurements at the DOE ARM Southern Great Plains site

    Science.gov (United States)

    Dong, Xiquan; Minnis, Patrick; Xi, Baike; Sun-Mack, Sunny; Chen, Yan

    2008-02-01

    Overcast stratus cloud properties derived for the Clouds and the Earth's Radiant Energy System (CERES) project using Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) data are compared with observations taken at the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Southern Great Plains site from March 2000 through December 2004. Retrievals from ARM surface-based data were averaged over a 1-h interval centered at the time of each satellite overpass, and the CERES-MODIS cloud properties were averaged within a 30 km × 30 km box centered on the ARM SGP site. Two data sets were analyzed: all of the data (ALL), which include multilayered, single-layered, and slightly broken stratus decks and a subset, single-layered unbroken decks (SL). The CERES-MODIS effective cloud heights were determined from effective cloud temperature using a lapse rate method with the surface temperature specified as the 24-h mean surface air temperature. For SL stratus, they are, on average, within the ARM radar-lidar estimated cloud boundaries and are 0.534 ± 0.542 km and 0.108 ± 0.480 km lower than the cloud physical tops and centers, respectively, and are comparable for day and night observations. The mean differences and standard deviations are slightly larger for ALL data, but not statistically different to those of SL data. The MODIS-derived effective cloud temperatures are 2.7 ± 2.4 K less than the surface-observed SL cloud center temperatures with very high correlations (0.86-0.97). Variations in the height differences are mainly caused by uncertainties in the surface air temperatures, lapse rates, and cloud top height variability. The biases are mainly the result of the differences between effective and physical cloud top, which are governed by cloud liquid water content and viewing zenith angle, and the selected lapse rate, -7.1 K km-1. On the basis of a total of 43 samples, the means and standard deviations of the differences between the daytime

  5. Some reflections on radon and its measurement

    International Nuclear Information System (INIS)

    Becker, K.

    1991-01-01

    A brief editorial considers mainly two problems concerning radon measurement in residential buildings and its possible health effects. The first relates to the reporting in the literature of radon measurements to an accuracy which exceeds the accuracy of the measuring equipment. Secondly in radioepidemiological studies, care should be exercised in equating uranium miners and people living in houses since their working and living conditions are not comparable; this could sometimes explain an apparent lack of detectable negative health effects in residents. (UK)

  6. Ground-based measurements of ionospheric dynamics

    Czech Academy of Sciences Publication Activity Database

    Kouba, Daniel; Chum, Jaroslav

    2018-01-01

    Roč. 8 (2018), č. článku A29. ISSN 2115-7251 R&D Projects: GA ČR(CZ) GA15-24688S; GA ČR(CZ) GC15-07281J Institutional support: RVO:68378289 Keywords : ve zpracování Subject RIV: DG - Athmosphere Sciences, Meteorology OBOR OECD: Meteorology and atmospheric sciences Impact factor: 2.446, year: 2016 https://www.swsc-journal.org/articles/swsc/full_html/2018/01/swsc170047/swsc170047.html

  7. Intercomparison of unmanned aerial vehicle and ground-based narrow band spectrometers applied to crop trait monitoring in organic potato production

    NARCIS (Netherlands)

    Domingues Franceschini, Marston; Bartholomeus, Harm; Apeldoorn, van Dirk; Suomalainen, Juha; Kooistra, Lammert

    2017-01-01

    Vegetation properties can be estimated using optical sensors, acquiring data on board of different platforms. For instance, ground-based and Unmanned Aerial Vehicle (UAV)-borne spectrometers can measure reflectance in narrow spectral bands, while different modelling approaches, like regressions

  8. Analysis of climatically relevant processes in the troposphere using ground-based remote measuring methods (windprofiler/RASS). Final report; Analyse klimatisch relevanter Prozesse in der Troposphaere mit Hilfe bodengebundener Fernerkundungsmethoden (Windprofiler/RASS). Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Steinhagen, H.; Christoph, A.; Engelbart, D.; Goersdorf, U.; Hirsch, L.; Lippmann, J.; Neisser, J.; Wergen, W.

    1995-09-01

    In the framework of the present research project the Meterological Observatory of Lindenberg (MOL) was equipped with the scientific and technical means necessary for the future operational application at the German weather service of ground-based remote sounding technologies such as `windprofiler radar`, radio-acoustic sounding system (RASS). Several case studies were used to demonstrate the multifarious possibilities of analysing mesoscale tropospheric structures by means of windprofiler radar and RASS. Besides this, further information such as mixing layer thickness and heat flux were derived from windprofiler and RASS measurements and the applied algorithms were tried on case examples. (orig./AKF) [Deutsch] Im Rahmen dieses Forschungsvorhabens sind am Meteorologischen Observatorium Lindenberg (MOL) wissenschaftliche und technische Voraussetzungen fuer eine zukuenftige operationelle Anwendung aktiver bodengebundener Fernsondierungstechnologien, wie `Windprofiler-Radar` und `Radio-Akustisches-Sondierungs-System (RASS)` im Deutschen Wetterdienst geschaffen worden. An Hand mehrerer Fallstudien wurden die vielfaeltigen Moeglichkeiten zur Analyse mesoskaliger troposphaerischer Strukturen mit Windprofiler-Radar und RASS demonstriert. Darueber hinaus wurden aus Windprofiler-/RASS-Messungen weiterfuehrende Informationen, wie Mischungsschichthoehe und Waermefluss abgeleitet und die entsprechenden Algorithmen am Fallbeispielen erprobt. (orig./AKF)

  9. Measurement Development in Reflective Supervision: History, Methods, and Next Steps

    Science.gov (United States)

    Tomlin, Angela M.; Heller, Sherryl Scott

    2016-01-01

    This issue of the "ZERO TO THREE" journal provides a snapshot of the current state of measurement of reflective supervision within the infant-family field. In this article, the authors introduce the issue by providing a brief history of the development of reflective supervision in the field of infant mental health, with a specific focus…

  10. Intercomparison of XH2O Data from the GOSAT TANSO-FTS (TIR and SWIR and Ground-Based FTS Measurements: Impact of the Spatial Variability of XH2O on the Intercomparison

    Directory of Open Access Journals (Sweden)

    Hirofumi Ohyama

    2017-01-01

    Full Text Available Spatial and temporal variability of atmospheric water vapor (H2O is extremely high, and therefore it is difficult to accurately evaluate the measurement precision of H2O data by a simple comparison between the data derived from two different instruments. We determined the measurement precisions of column-averaged dry-air mole fractions of H2O (XH2O retrieved independently from spectral radiances in the thermal infrared (TIR and the short-wavelength infrared (SWIR regions measured using a Thermal And Near-infrared Sensor for carbon Observation-Fourier Transform Spectrometer (TANSO-FTS onboard the Greenhouse gases Observing SATellite (GOSAT, by an intercomparison between the two TANSO-FTS XH2O data products and the ground-based FTS XH2O data. Furthermore, the spatial variability of XH2O was also estimated in the intercomparison process. Mutually coincident XH2O data above land for the period ranging from April 2009 to May 2014 were intercompared with different spatial coincidence criteria. We found that the precisions of the TANSO-FTS TIR and TANSO-FTS SWIR XH2O were 7.3%–7.7% and 3.5%–4.5%, respectively, and that the spatial variability of XH2O was 6.7% within a radius of 50 km and 18.5% within a radius of 200 km. These results demonstrate that, in order to accurately evaluate the measurement precision of XH2O, it is necessary to set more rigorous spatial coincidence criteria or to take into account the spatial variability of XH2O as derived in the present study.

  11. Low-temperature relative reflectivity measurements of reflective and scintillating foils used in rare event searches

    Science.gov (United States)

    Langenkämper, A.; Ulrich, A.; Defay, X.; Feilitzsch, F. v.; Lanfranchi, J.-C.; Mondragón, E.; Münster, A.; Oppenheimer, C.; Potzel, W.; Roth, S.; Schönert, S.; Steiger, H.; Trinh Thi, H. H.; Wawoczny, S.; Willers, M.; Zöller, A.

    2018-03-01

    In this work we investigate the reflectivity of highly reflective multilayer polymer foils used in the CRESST experiment. The CRESST experiment searches directly for dark matter via operating scintillating CaWO4 crystals as targets for elastic dark matter-nucleon scattering. In order to suppress background events, the experiment employs the so-called phonon-light technique which is based on the simultaneous measurement of the heat signal in the main CaWO4 target crystal and of the emitted scintillation light with a separate cryogenic light detector. Both detectors are surrounded by a highly reflective and scintillating multilayer polymer foil to increase the light collection efficiency and to veto surface backgrounds. While this study is motivated by the CRESST experiment, the results are also relevant for other rare event searches using scintillating cryogenic bolometers in the field of the search of dark matter and neutrinoless double beta decay (0 νββ). In this work a dedicated experiment has been set up to determine the relative reflectivity at 300 K and 20 K of three multilayer foils ("VM2000", "VM2002", "Vikuiti") produced by the company 3M. The intensity of a light beam reflected off the foil is measured with a CCD camera. The ratio of the intensities at 300 K and 20 K corresponds to the relative reflectivity change. The measurements performed in this work show no variation of the reflectivity with temperature at a level of ∼1%.

  12. Fine-resolution repeat topographic surveying of dryland landscapes using UAS-based structure-from-motion photogrammetry: Assessing accuracy and precision against traditional ground-based erosion measurements

    Science.gov (United States)

    Gillian, Jeffrey K.; Karl, Jason W.; Elaksher, Ahmed; Duniway, Michael C.

    2017-01-01

    Structure-from-motion (SfM) photogrammetry from unmanned aerial system (UAS) imagery is an emerging tool for repeat topographic surveying of dryland erosion. These methods are particularly appealing due to the ability to cover large landscapes compared to field methods and at reduced costs and finer spatial resolution compared to airborne laser scanning. Accuracy and precision of high-resolution digital terrain models (DTMs) derived from UAS imagery have been explored in many studies, typically by comparing image coordinates to surveyed check points or LiDAR datasets. In addition to traditional check points, this study compared 5 cm resolution DTMs derived from fixed-wing UAS imagery with a traditional ground-based method of measuring soil surface change called erosion bridges. We assessed accuracy by comparing the elevation values between DTMs and erosion bridges along thirty topographic transects each 6.1 m long. Comparisons occurred at two points in time (June 2014, February 2015) which enabled us to assess vertical accuracy with 3314 data points and vertical precision (i.e., repeatability) with 1657 data points. We found strong vertical agreement (accuracy) between the methods (RMSE 2.9 and 3.2 cm in June 2014 and February 2015, respectively) and high vertical precision for the DTMs (RMSE 2.8 cm). Our results from comparing SfM-generated DTMs to check points, and strong agreement with erosion bridge measurements suggests repeat UAS imagery and SfM processing could replace erosion bridges for a more synoptic landscape assessment of shifting soil surfaces for some studies. However, while collecting the UAS imagery and generating the SfM DTMs for this study was faster than collecting erosion bridge measurements, technical challenges related to the need for ground control networks and image processing requirements must be addressed before this technique could be applied effectively to large landscapes.

  13. Simple method for measuring reflectance of optical coatings

    International Nuclear Information System (INIS)

    Wen Gui Wang; Yi Sheng Chen

    1995-01-01

    The quality of optical coatings has an important effect on the performance of optical instrument. The last few years, the requirements for super low loss dielectric mirror coatings used in low gain laser systems such as free electron laser and the ring laser etc., have given an impetus to the development of the technology of precise reflectance measurement of optical coatings. A reliable and workable technique is to measure the light intensity decay time of optical resonant cavity. This paper describes a measuring method which is dependent on direct measurement of the light intensity decay time of a resonant cavity comprised of low loss optical components. According to the evolution of a luminous flux stored inside the cavity, this method guarantees not only a quick and precise reflectance measurements of low loss highly reflecting mirror coatings but also transmittance measurements of low loss antireflection coatings and is especially effective with super los loss highly reflecting mirror. From the round-trip path length of the cavity and the speed of light, the light intensity exponential decay time of an optical cavity is easy to obtain and the cavity losses can be deduced. An optical reflectance of low loss highly mirror coatings and antireflection coatings is precisely measured as well. This is highly significant for the discrimination of the coating surface characteristics, the improvement of the performance of optical instrument and the development of high technology

  14. Direct Reflectance Measurements from Drones: Sensor Absolute Radiometric Calibration and System Tests for Forest Reflectance Characterization

    Science.gov (United States)

    Hakala, Teemu; Scott, Barry; Theocharous, Theo; Näsi, Roope; Suomalainen, Juha; Greenwell, Claire; Fox, Nigel

    2018-01-01

    Drone-based remote sensing has evolved rapidly in recent years. Miniaturized hyperspectral imaging sensors are becoming more common as they provide more abundant information of the object compared to traditional cameras. Reflectance is a physically defined object property and therefore often preferred output of the remote sensing data capture to be used in the further processes. Absolute calibration of the sensor provides a possibility for physical modelling of the imaging process and enables efficient procedures for reflectance correction. Our objective is to develop a method for direct reflectance measurements for drone-based remote sensing. It is based on an imaging spectrometer and irradiance spectrometer. This approach is highly attractive for many practical applications as it does not require in situ reflectance panels for converting the sensor radiance to ground reflectance factors. We performed SI-traceable spectral and radiance calibration of a tuneable Fabry-Pérot Interferometer -based (FPI) hyperspectral camera at the National Physical Laboratory NPL (Teddington, UK). The camera represents novel technology by collecting 2D format hyperspectral image cubes using time sequential spectral scanning principle. The radiance accuracy of different channels varied between ±4% when evaluated using independent test data, and linearity of the camera response was on average 0.9994. The spectral response calibration showed side peaks on several channels that were due to the multiple orders of interference of the FPI. The drone-based direct reflectance measurement system showed promising results with imagery collected over Wytham Forest (Oxford, UK). PMID:29751560

  15. Direct Reflectance Measurements from Drones: Sensor Absolute Radiometric Calibration and System Tests for Forest Reflectance Characterization.

    Science.gov (United States)

    Hakala, Teemu; Markelin, Lauri; Honkavaara, Eija; Scott, Barry; Theocharous, Theo; Nevalainen, Olli; Näsi, Roope; Suomalainen, Juha; Viljanen, Niko; Greenwell, Claire; Fox, Nigel

    2018-05-03

    Drone-based remote sensing has evolved rapidly in recent years. Miniaturized hyperspectral imaging sensors are becoming more common as they provide more abundant information of the object compared to traditional cameras. Reflectance is a physically defined object property and therefore often preferred output of the remote sensing data capture to be used in the further processes. Absolute calibration of the sensor provides a possibility for physical modelling of the imaging process and enables efficient procedures for reflectance correction. Our objective is to develop a method for direct reflectance measurements for drone-based remote sensing. It is based on an imaging spectrometer and irradiance spectrometer. This approach is highly attractive for many practical applications as it does not require in situ reflectance panels for converting the sensor radiance to ground reflectance factors. We performed SI-traceable spectral and radiance calibration of a tuneable Fabry-Pérot Interferometer -based (FPI) hyperspectral camera at the National Physical Laboratory NPL (Teddington, UK). The camera represents novel technology by collecting 2D format hyperspectral image cubes using time sequential spectral scanning principle. The radiance accuracy of different channels varied between ±4% when evaluated using independent test data, and linearity of the camera response was on average 0.9994. The spectral response calibration showed side peaks on several channels that were due to the multiple orders of interference of the FPI. The drone-based direct reflectance measurement system showed promising results with imagery collected over Wytham Forest (Oxford, UK).

  16. Validation of ACE-FTS v2.2 measurements of HCl, HF, CCl3F and CCl2F2 using space-, balloon- and ground-based instrument observations

    Directory of Open Access Journals (Sweden)

    C. Servais

    2008-10-01

    Full Text Available Hydrogen chloride (HCl and hydrogen fluoride (HF are respectively the main chlorine and fluorine reservoirs in the Earth's stratosphere. Their buildup resulted from the intensive use of man-made halogenated source gases, in particular CFC-11 (CCl3F and CFC-12 (CCl2F2, during the second half of the 20th century. It is important to continue monitoring the evolution of these source gases and reservoirs, in support of the Montreal Protocol and also indirectly of the Kyoto Protocol. The Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS is a space-based instrument that has been performing regular solar occultation measurements of over 30 atmospheric gases since early 2004. In this validation paper, the HCl, HF, CFC-11 and CFC-12 version 2.2 profile data products retrieved from ACE-FTS measurements are evaluated. Volume mixing ratio profiles have been compared to observations made from space by MLS and HALOE, and from stratospheric balloons by SPIRALE, FIRS-2 and Mark-IV. Partial columns derived from the ACE-FTS data were also compared to column measurements from ground-based Fourier transform instruments operated at 12 sites. ACE-FTS data recorded from March 2004 to August 2007 have been used for the comparisons. These data are representative of a variety of atmospheric and chemical situations, with sounded air masses extending from the winter vortex to summer sub-tropical conditions. Typically, the ACE-FTS products are available in the 10–50 km altitude range for HCl and HF, and in the 7–20 and 7–25 km ranges for CFC-11 and -12, respectively. For both reservoirs, comparison results indicate an agreement generally better than 5–10% above 20 km altitude, when accounting for the known offset affecting HALOE measurements of HCl and HF. Larger positive differences are however found for comparisons with single profiles from FIRS-2 and SPIRALE. For CFCs, the few coincident measurements available suggest that the differences

  17. Spin analysis and new effects in reflectivity measurements

    International Nuclear Information System (INIS)

    Fermon, C.

    1996-01-01

    We present two new effects in polarized neutron reflectivity. We show that we have a non symmetric spin-flip signal in reflectivity measurements on magnetic films when the external field is not negligible. This phenomenon is due to different Larmor precessions for the two spin states and has to be taken into account in some experiments. The second effect is still not understood but we present results indicating that the specular reflection on a non magnetic surface can induce a neutron beam depolarization or rotation. (authors)

  18. A new setup to measure bidirectional reflectance distribution functions

    NARCIS (Netherlands)

    Roosjen, P.P.J.; Clevers, J.G.P.W.; Bartholomeus, H.

    2012-01-01

    The Plant Facility, a new laboratory goniometer system, built by the Wageningen University has been tested in order to take bidirectional reflectance distribution function (BRDF) measurements. An ASD FieldSpec 3 spectroradiometer mounted on an industrial robot arm is able to measure small targets

  19. Lidar to lidar calibration of Ground-based Lidar

    DEFF Research Database (Denmark)

    Fernandez Garcia, Sergio; Courtney, Michael

    This report presents the result of the lidar to lidar calibration performed for ground-based lidar. Calibration is here understood as the establishment of a relation between the reference lidar wind speed measurements with measurement uncertainties provided by measurement standard and corresponding...... lidar wind speed indications with associated measurement uncertainties. The lidar calibration concerns the 10 minute mean wind speed measurements. The comparison of the lidar measurements of the wind direction with that from the reference lidar measurements are given for information only....

  20. Measurement of reflectance of coal macerals: its automation and significance

    Energy Technology Data Exchange (ETDEWEB)

    Davis, A.

    1978-06-01

    A prime objective of the Pennsylvania State University's DOE program is the characterization of 1,300 samples of U.S. coals. Reflectance determination plays a major role in meeting this objective, because it is used as an accurate rank index both to select coals for testing and to investigate property-behavior interrelationships using the Penn State/DOE Coal Data Base. Reflectances of coal macerals are related to their refractive and absorptive indices by the Beer equation; the refractive index of the medium and the wavelength of light need to be specified. Determinations usually are made in immersion oil at 546 nm. Properties of vitrinite make it the most suitable maceral for these measurements, but the variety of vitrinite selected may depend upon the intended application. Vitrinite reflectance is considered to be dependent upon the degree of aromatization of its structural units. Although some of the earlier investigators believed that the reflectance of coals increased in a discontinuous, stepped manner as their rank increased, the bulk of assembled data suggests that the change is continuous. Some recent results indicate that there may be more than one coalification track for coals with different geological histories, resulting in displacement from the general trend. Several techniques have been employed to determine the optical properties of coal constituents. Usual comparative method involves the use of a microscope photometer to compare the intensity of light reflected by particles within a polished pellet of coal to that of a glass or synthetic mineral standard. Because coal is anisotropic it is common to measure either maximum reflectance in polarized light or random reflectance in non-polarized light. Various eqipment modifications and accessories have been used to improve the ease of measuring maximum reflectance.

  1. Plasma density fluctuation measurements from coherent and incoherent microwave reflection

    International Nuclear Information System (INIS)

    Conway, G.D.; Schott, L.; Hirose, A.

    1996-01-01

    Using the spatial coherency present in a reflected microwave signal (Conway et al 1994 Rev. Sci. Instrum. 65 2920) it is possible to measure a coherent, Γ c , and an incoherent, Γ i , reflection coefficient (proportional to the radar cross section) from a turbulent plasma cutoff layer. Results acquired with a 17 GHz reflectometer from a STOR-M tokamak edge region (r/a ∼ 0.8) give significant Γ c and Γ i , which suggests two-dimensional structure in the reflection layer. Using a 'distorted-mirror' model for the plasma fluctuations, estimates of an effective radial width, σ, and poloidal correlation length, L p , can be derived from the reflection coefficients. STOR-M results typically give a σ of a few millimetres and an L p of a couple of centimetres. (author)

  2. High-accuracy measurements of the normal specular reflectance

    International Nuclear Information System (INIS)

    Voarino, Philippe; Piombini, Herve; Sabary, Frederic; Marteau, Daniel; Dubard, Jimmy; Hameury, Jacques; Filtz, Jean Remy

    2008-01-01

    The French Laser Megajoule (LMJ) is designed and constructed by the French Commissariata l'Energie Atomique (CEA). Its amplifying section needs highly reflective multilayer mirrors for the flash lamps. To monitor and improve the coating process, the reflectors have to be characterized to high accuracy. The described spectrophotometer is designed to measure normal specular reflectance with high repeatability by using a small spot size of 100 μm. Results are compared with ellipsometric measurements. The instrument can also perform spatial characterization to detect coating nonuniformity

  3. Measuring solar reflectance - Part II: Review of practical methods

    Energy Technology Data Exchange (ETDEWEB)

    Levinson, Ronnen; Akbari, Hashem; Berdahl, Paul [Heat Island Group, Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States)

    2010-09-15

    A companion article explored how solar reflectance varies with surface orientation and solar position, and found that clear sky air mass 1 global horizontal (AM1GH) solar reflectance is a preferred quantity for estimating solar heat gain. In this study we show that AM1GH solar reflectance R{sub g,0} can be accurately measured with a pyranometer, a solar spectrophotometer, or an updated edition of the Solar Spectrum Reflectometer (version 6). Of primary concern are errors that result from variations in the spectral and angular distributions of incident sunlight. Neglecting shadow, background and instrument errors, the conventional pyranometer technique can measure R{sub g,0} to within 0.01 for surface slopes up to 5:12 [23 ], and to within 0.02 for surface slopes up to 12:12 [45 ]. An alternative pyranometer method minimizes shadow errors and can be used to measure R{sub g,0} of a surface as small as 1 m in diameter. The accuracy with which it can measure R{sub g,0} is otherwise comparable to that of the conventional pyranometer technique. A solar spectrophotometer can be used to determine R{sub g,0}{sup *}, a solar reflectance computed by averaging solar spectral reflectance weighted with AM1GH solar spectral irradiance. Neglecting instrument errors, R{sub g,0}{sup *} matches R{sub g,0} to within 0.006. The air mass 1.5 solar reflectance measured with version 5 of the Solar Spectrum Reflectometer can differ from R{sub g,0}{sup *} by as much as 0.08, but the AM1GH output of version 6 of this instrument matches R{sub g,0}{sup *} to within about 0.01. (author)

  4. Landslide kinematics and their potential controls from hourly to decadal timescales: Insights from integrating ground-based InSAR measurements with structural maps and long-term monitoring data

    Science.gov (United States)

    Schulz, William H.; Coe, Jeffrey A.; Ricci, Pier P.; Smoczyk, Gregory M.; Shurtleff, Brett L.; Panosky, Joanna

    2017-05-01

    Knowledge of kinematics is rudimentary for understanding landslide controls and is increasingly valuable with greater spatiotemporal coverage. However, characterizing landslide-wide kinematics is rare, especially at broadly ranging timescales. We used highly detailed kinematic data obtained using photogrammetry and field mapping during the 1980s and 1990s and our 4.3-day ground-based InSAR survey during 2010 to study kinematics of the large, persistently moving Slumgullion landslide. The landslide was segregated into 11 kinematic elements using the 1980s-1990s data and the InSAR survey revealed most of these elements within a few hours. Averages of InSAR-derived displacement point measures within each element agreed well with higher quality in situ observations; averaging was deemed necessary because adverse look angles for the radar coupled with tree cover on the landslide introduced error in the InSAR results. We found that the landslide moved during 2010 at about half its 1985-1990 speed, but slowing was most pronounced at the landslide head. Gradually decreased precipitation and increased temperature between the periods likely resulted in lower groundwater levels and consequent slowing of the landslide. We used GPS survey results and limit-equilibrium modeling to analyze changing stability of the landslide head from observed thinning and found that its stability increased between the two periods, which would result in its slowing, and the consequent slowing of the entire landslide. Additionally, InSAR results suggested movement of kinematic element boundaries in the head region and our field mapping verified that they moved and changed character, likely because of the long-term increasing head stability. On an hourly basis, InSAR results were near error bounds but suggested landslide acceleration in response to seemingly negligible rainfall. Pore-pressure diffusion modeling suggested that rainfall infiltration affected frictional strength only to shallow depths

  5. High-precision reflectivity measurements: improvements in the calibration procedure

    Science.gov (United States)

    Jupe, Marco; Grossmann, Florian; Starke, Kai; Ristau, Detlev

    2003-05-01

    The development of high quality optical components is heavily depending on precise characterization procedures. The reflectance and transmittance of laser components are the most important parameters for advanced laser applications. In the industrial fabrication of optical coatings, quality management is generally insured by spectral photometric methods according to ISO/DIS 15386 on a medium level of accuracy. Especially for high reflecting mirrors, a severe discrepancy in the determination of the absolute reflectivity can be found for spectral photometric procedures. In the first part of the CHOCLAB project, a method for measuring reflectance and transmittance with an enhanced precision was developed, which is described in ISO/WD 13697. In the second part of the CHOCLAB project, the evaluation and optimization for the presented method is scheduled. Within this framework international Round-Robin experiment is currently in progress. During this Round-Robin experiment, distinct deviations could be observed between the results of high precision measurement facilities of different partners. Based on the extended experiments, the inhomogeneity of the sample reflectivity was identified as one important origin for the deviation. Consequently, this inhomogeneity is also influencing the calibration procedure. Therefore, a method was developed that allows the calibration of the chopper blade using always the same position on the reference mirror. During the investigations, the homogeneity of several samples was characterized by a surface mapping procedure for 1064 nm. The measurement facility was extended to the additional wavelength 532 nm and a similar set-up was assembled at 10.6 μm. The high precision reflectivity procedure at the mentioned wavelengths is demonstrated for exemplary measurements.

  6. Space and Ground-Based Infrastructures

    Science.gov (United States)

    Weems, Jon; Zell, Martin

    This chapter deals first with the main characteristics of the space environment, outside and inside a spacecraft. Then the space and space-related (ground-based) infrastructures are described. The most important infrastructure is the International Space Station, which holds many European facilities (for instance the European Columbus Laboratory). Some of them, such as the Columbus External Payload Facility, are located outside the ISS to benefit from external space conditions. There is only one other example of orbital platforms, the Russian Foton/Bion Recoverable Orbital Capsule. In contrast, non-orbital weightless research platforms, although limited in experimental time, are more numerous: sounding rockets, parabolic flight aircraft, drop towers and high-altitude balloons. In addition to these facilities, there are a number of ground-based facilities and space simulators, for both life sciences (for instance: bed rest, clinostats) and physical sciences (for instance: magnetic compensation of gravity). Hypergravity can also be provided by human and non-human centrifuges.

  7. Dew point measurement technique utilizing fiber cut reflection

    Science.gov (United States)

    Kostritskii, S. M.; Dikevich, A. A.; Korkishko, Yu. N.; Fedorov, V. A.

    2009-05-01

    The fiber optical dew point hygrometer based on change of reflection coefficient for fiber cut has been developed and examined. We proposed and verified the model of condensation detector functioning principle. Experimental frost point measurements on air with different frost points have been performed.

  8. An instrument for the measurement of road surface reflection properties

    DEFF Research Database (Denmark)

    Corell, Dennis Dan; Sørensen, K.

    2017-01-01

    Road surface reflection data in the form of standard r-tables serve as input for design calculations of road lighting installations on traffic roads. However, in several countries the use of the standard r-tables has not been verified by measurement in a long period of time, while the types of road...

  9. Dynamic Bidirectional Reflectance Distribution Functions: Measurement and Representation

    Science.gov (United States)

    2008-02-01

    be included in the harmonic fits. Other sets of orthogonal functions such as Zernike polynomials have also been used to characterize BRDF and could...reflectance spectra of 3D objects,” Proc. SPIE 4663, 370–378 2001. 13J. R. Shell II, C. Salvagio, and J. R. Schott, “A novel BRDF measurement technique

  10. Bidirectional reflectance distribution function measurements and analysis of retroreflective materials.

    Science.gov (United States)

    Belcour, Laurent; Pacanowski, Romain; Delahaie, Marion; Laville-Geay, Aude; Eupherte, Laure

    2014-12-01

    We compare the performance of various analytical retroreflecting bidirectional reflectance distribution function (BRDF) models to assess how they reproduce accurately measured data of retroreflecting materials. We introduce a new parametrization, the back vector parametrization, to analyze retroreflecting data, and we show that this parametrization better preserves the isotropy of data. Furthermore, we update existing BRDF models to improve the representation of retroreflective data.

  11. A new method to detect long term trends of methane (CH4 and nitrous oxide (N2O total columns measured within the NDACC ground-based high resolution solar FTIR network

    Directory of Open Access Journals (Sweden)

    M. Schneider

    2011-07-01

    Full Text Available Total columns measured with the ground-based solar FTIR technique are highly variable in time due to atmospheric chemistry and dynamics in the atmosphere above the measurement station. In this paper, a multiple regression model with anomalies of air pressure, total columns of hydrogen fluoride (HF and carbon monoxide (CO and tropopause height are used to reduce the variability in the methane (CH4 and nitrous oxide (N2O total columns to estimate reliable linear trends with as small uncertainties as possible. The method is developed at the Harestua station (60° N, 11° E, 600 m a.s.l. and used on three other European FTIR stations, i.e. Jungfraujoch (47° N, 8° E, 3600 m a.s.l., Zugspitze (47° N, 11° E, 3000 m a.s.l., and Kiruna (68° N, 20° E, 400 m a.s.l.. Linear CH4 trends between 0.13 ± 0.01-0.25 ± 0.02 % yr−1 were estimated for all stations in the 1996-2009 period. A piecewise model with three separate linear trends, connected at change points, was used to estimate the short term fluctuations in the CH4 total columns. This model shows a growth in 1996–1999 followed by a period of steady state until 2007. From 2007 until 2009 the atmospheric CH4 amount increases between 0.57 ± 0.22–1.15 ± 0.17 % yr−1. Linear N2O trends between 0.19 ± 0.01–0.40 ± 0.02 % yr−1 were estimated for all stations in the 1996-2007 period, here with the strongest trend at Harestua and Kiruna and the lowest at the Alp stations. From the N2O total columns crude tropospheric and stratospheric partial columns were derived, indicating that the observed difference in the N2O trends between the FTIR sites is of stratospheric origin. This agrees well with the N2O measurements by the SMR instrument onboard the Odin satellite showing the highest trends at Harestua, 0.98 ± 0.28 % yr−1, and considerably smaller trends at lower latitudes, 0.27 ± 0.25 % yr−1. The multiple regression model was compared with two other trend methods, the ordinary linear

  12. A Laboratory Goniometer System for Measuring Reflectance and Emittance Anisotropy

    Directory of Open Access Journals (Sweden)

    Arjan de Jong

    2012-12-01

    Full Text Available In this paper, a laboratory goniometer system for performing multi-angular measurements under controlled illumination conditions is described. A commercially available robotic arm enables the acquisition of a large number of measurements over the full hemisphere within a short time span making it much faster than other goniometers. In addition, the presented set-up enables assessment of anisotropic reflectance and emittance behaviour of soils, leaves and small canopies. Mounting a spectrometer enables acquisition of either hemispherical measurements or measurements in the horizontal plane. Mounting a thermal camera allows directional observations of the thermal emittance. This paper also presents three showcases of these different measurement set-ups in order to illustrate its possibilities. Finally, suggestions for applying this instrument and for future research directions are given, including linking the measured reflectance anisotropy with physically-based anisotropy models on the one hand and combining them with field goniometry measurements for joint analysis with remote sensing data on the other hand. The speed and flexibility of the system offer a large added value to the existing pool of laboratory goniometers.

  13. Ultraviolet reflectance spectroscopy measurements of planetary materials and their analogs

    Science.gov (United States)

    Hibbitts, C.; Stockstill-Cahill, K.

    2017-12-01

    The compositions of airless solar system objects tell us about the origin and evolutionary processes that are responsible for the current state of our solar system and that shape our environment. Spacecraft have obtained UV reflectance measurements of the surfaces of Mercury, the Moon, asteroids, comets, icy satellites, and Pluto from which composition is being inferred. Most minerals absorb in the UV making studying surface composition both informative but also challenging [e.g. 1]. The UV region is sensitive to atomic and molecular electronic absorptions such as the ligand-metal charge transfer band that is present in oxides and silicates and the conduction band at vacuum UV wavelengths. Unfortunately, limited laboratory reflectance measurements in the ultraviolet hampers the interpretation of some of these planetary UV reflectance datasets. However, several laboratory efforts have been developed [e.g. 2,3] to fill the need for laboratory UV measurements. These are difficult measurements to make, being complicated by the absorptive nature of the atmosphere, requiring measurements to be conducted under vacuum or over very short path lengths of a N2-purged system. Also, the lack of a widely accepted UV diffuse reflectance standard is problematic. At the JHU-APL, bidirectional UV reflectance measurements are obtained under vacuum from 140 nm to 570 nm. Sample temperature can be controlled from 100K to 600K, which enables the study of the interaction of water ice and other volatiles with the refractory samples. Results from our laboratory research include the development of a correlation between the spectral nature of the OMCT band and the abundance of iron in low water content lunar analog glasses [3]. Also, the spectral signature of water in the UV has been investigated. While water-ice has a known strong absorption feature near 180 nm [e.g. 4], adsorbed molecular and disassociatively adsorbed OH apparently are not optically active in this spectral region [5]. We

  14. Ground-Based Telescope Parametric Cost Model

    Science.gov (United States)

    Stahl, H. Philip; Rowell, Ginger Holmes

    2004-01-01

    A parametric cost model for ground-based telescopes is developed using multi-variable statistical analysis, The model includes both engineering and performance parameters. While diameter continues to be the dominant cost driver, other significant factors include primary mirror radius of curvature and diffraction limited wavelength. The model includes an explicit factor for primary mirror segmentation and/or duplication (i.e.. multi-telescope phased-array systems). Additionally, single variable models based on aperture diameter are derived. This analysis indicates that recent mirror technology advances have indeed reduced the historical telescope cost curve.

  15. Does the cognitive reflection test measure cognitive reflection? A mathematical modeling approach.

    Science.gov (United States)

    Campitelli, Guillermo; Gerrans, Paul

    2014-04-01

    We used a mathematical modeling approach, based on a sample of 2,019 participants, to better understand what the cognitive reflection test (CRT; Frederick In Journal of Economic Perspectives, 19, 25-42, 2005) measures. This test, which is typically completed in less than 10 min, contains three problems and aims to measure the ability or disposition to resist reporting the response that first comes to mind. However, since the test contains three mathematically based problems, it is possible that the test only measures mathematical abilities, and not cognitive reflection. We found that the models that included an inhibition parameter (i.e., the probability of inhibiting an intuitive response), as well as a mathematical parameter (i.e., the probability of using an adequate mathematical procedure), fitted the data better than a model that only included a mathematical parameter. We also found that the inhibition parameter in males is best explained by both rational thinking ability and the disposition toward actively open-minded thinking, whereas in females this parameter was better explained by rational thinking only. With these findings, this study contributes to the understanding of the processes involved in solving the CRT, and will be particularly useful for researchers who are considering using this test in their research.

  16. Chasing Small Exoplanets with Ground-Based Near-Infrared Transit Photometry

    Science.gov (United States)

    Colon, K. D.; Barentsen, G.; Vinicius, Z.; Vanderburg, A.; Coughlin, J.; Thompson, S.; Mullally, F.; Barclay, T.; Quintana, E.

    2017-11-01

    I will present results from a ground-based survey to measure the infrared radius and other properties of small K2 exoplanets and candidates. The survey is preparation for upcoming discoveries from TESS and characterization with JWST.

  17. Augmenting WFIRST Microlensing with a Ground-Based Telescope Network

    Science.gov (United States)

    Zhu, Wei; Gould, Andrew

    2016-06-01

    Augmenting the Wide Field Infrared Survey Telescope (WFIRST) microlensing campaigns with intensive observations from a ground-based network of wide-field survey telescopes would have several major advantages. First, it would enable full two-dimensional (2-D) vector microlens parallax measurements for a substantial fraction of low-mass lenses as well as planetary and binary events that show caustic crossing features. For a significant fraction of the free-floating planet (FFP) events and all caustic-crossing planetary/binary events, these 2-D parallax measurements directly lead to complete solutions (mass, distance, transverse velocity) of the lens object (or lens system). For even more events, the complementary ground-based observations will yield 1-D parallax measurements. Together with the 1-D parallaxes from WFIRST alone, they can probe the entire mass range M > M_Earth. For luminous lenses, such 1-D parallax measurements can be promoted to complete solutions (mass, distance, transverse velocity) by high-resolution imaging. This would provide crucial information not only about the hosts of planets and other lenses, but also enable a much more precise Galactic model. Other benefits of such a survey include improved understanding of binaries (particularly with low mass primaries), and sensitivity to distant ice-giant and gas-giant companions of WFIRST lenses that cannot be detected by WFIRST itself due to its restricted observing windows. Existing ground-based microlensing surveys can be employed if WFIRST is pointed at lower-extinction fields than is currently envisaged. This would come at some cost to the event rate. Therefore the benefits of improved characterization of lenses must be weighed against these costs.

  18. Determination of electromagnetic absorption parameters by reflection measurements

    International Nuclear Information System (INIS)

    Vittitoe, C.N.

    1975-09-01

    The method described is for determining the electromagnetic absorption parameters of a material by measuring the optical reflection from a thick sample. With linearly polarized incident light (both perpendicular to and parallel to the plane of incidence), the ratio of the reflected intensities at three or more angles of incidence offers promise for determining the complex index of refraction of a material for a broad range of parameter values. The method may be applicable to molten materials, such as UO 2 , where high temperatures cause corrosion and containment difficulties. A method is given for extending the data to neighboring frequencies. Use of the method was successful for all portions of the complex index of refraction plane except for small values of the extinction coefficient

  19. First Ground-Based Infrared Solar Absorption Measurements of Free Tropospheric Methanol (CH3OH): Multidecade Infrared Time Series from Kitt Peak (31.9 deg N 111.6 deg W): Trend, Seasonal Cycle, and Comparison with Previous Measurements

    Science.gov (United States)

    Rinsland, Curtis P.; Mahieu, Emmanuel; Chiou, Linda; Herbin, Herve

    2009-01-01

    Atmospheric CH3OH (methanol) free tropospheric (2.09-14-km altitude) time series spanning 22 years has been analyzed on the basis of high-spectral resolution infrared solar absorption spectra of the strong vs band recorded from the U.S. National Solar Observatory on Kitt Peak (latitude 31.9degN, 111.6degW, 2.09-km altitude) with a 1-m Fourier transform spectrometer (FTS). The measurements span October 1981 to December 2003 and are the first long time series of CH3OH measurements obtained from the ground. The results were analyzed with SFIT2 version 3.93 and show a factor of three variations with season, a maximum at the beginning of July, a winter minimum, and no statistically significant long-term trend over the measurement time span.

  20. Evaluation of retro-reflective coating performance by reflectance and perceived relative brightness measurements

    Energy Technology Data Exchange (ETDEWEB)

    Luse, Kaiva; Pausus, Anete; Karitans, Varis; Ozolins, Maris; Tukisa, Madara, E-mail: kaiva.luse@gmail.com [University of Latvia, Optometry and Vision Science Department, Kengaraga street 8, Riga LV-1063 (Latvia)

    2011-06-23

    Retro-reflective properties of six types and five different colors or retro-reflective materials were discussed in this paper. Reflectance optical indicatrix of samples was determined and compared to obtained psychophyisical data of perceived brightness of human observer. Microscopic structure of the retro-reflective active regions of RR's was studied. Statistically significant differences in reflectivity and brightness of various types and colors of RR's were found.

  1. Evaluation of retro-reflective coating performance by reflectance and perceived relative brightness measurements

    International Nuclear Information System (INIS)

    Luse, Kaiva; Pausus, Anete; Karitans, Varis; Ozolins, Maris; Tukisa, Madara

    2011-01-01

    Retro-reflective properties of six types and five different colors or retro-reflective materials were discussed in this paper. Reflectance optical indicatrix of samples was determined and compared to obtained psychophyisical data of perceived brightness of human observer. Microscopic structure of the retro-reflective active regions of RR's was studied. Statistically significant differences in reflectivity and brightness of various types and colors of RR's were found.

  2. Diffuse Reflectance Spectroscopy for Surface Measurement of Liver Pathology.

    Science.gov (United States)

    Nilsson, Jan H; Reistad, Nina; Brange, Hannes; Öberg, Carl-Fredrik; Sturesson, Christian

    2017-01-01

    Liver parenchymal injuries such as steatosis, steatohepatitis, fibrosis, and sinusoidal obstruction syndrome can lead to increased morbidity and liver failure after liver resection. Diffuse reflectance spectroscopy (DRS) is an optical measuring method that is fast, convenient, and established. DRS has previously been used on the liver with an invasive technique consisting of a needle that is inserted into the parenchyma. We developed a DRS system with a hand-held probe that is applied to the liver surface. In this study, we investigated the impact of the liver capsule on DRS measurements and whether liver surface measurements are representative of the whole liver. We also wanted to confirm that we could discriminate between tumor and liver parenchyma by DRS. The instrumentation setup consisted of a light source, a fiber-optic contact probe, and two spectrometers connected to a computer. Patients scheduled for liver resection due to hepatic malignancy were included, and DRS measurements were performed on the excised liver part with and without the liver capsule and alongside a newly cut surface. To estimate the scattering parameters and tissue chromophore volume fractions, including blood, bile, and fat, the measured diffuse reflectance spectra were applied to an analytical model. In total, 960 DRS spectra from the excised liver tissue of 18 patients were analyzed. All factors analyzed regarding tumor versus liver tissue were significantly different. When measuring through the capsule, the blood volume fraction was found to be 8.4 ± 3.5%, the lipid volume fraction was 9.9 ± 4.7%, and the bile volume fraction was 8.2 ± 4.6%. No differences could be found between surface measurements and cross-sectional measurements. In measurements with/without the liver capsule, the differences in volume fraction were 1.63% (0.75-2.77), -0.54% (-2.97 to 0.32), and -0.15% (-1.06 to 1.24) for blood, lipid, and bile, respectively. This study shows that it is possible to manage DRS

  3. Infrared reflectance measurement for InN thin film characterization

    International Nuclear Information System (INIS)

    Fukui, K.; Kugumiya, Y.; Nakagawa, N.; Yamamoto, A.

    2006-01-01

    Infrared reflectance measurements of a series of InN thin films have been performed and attempt to derive carrier concentration and other physical constants for InN thin film characterization. Fitting calculations are performed by use of the dielectric function equation based on phonon-plasmon coupling model. Longitudinal and transverse optical phonon frequencies, plasma frequency and their damping parameters can be derived from fitting. From those results, electrical and phonon properties of InN and characterization of films are discussed. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. An instrument for the measurement of road surface reflection properties

    DEFF Research Database (Denmark)

    Corell, Dennis Dan; Sørensen, K.

    2017-01-01

    surfaces in use have changed - for instance to road surface types with less noise from wheel passages. Because of this, a co-operation between the road administrations of the Nordic countries (abbreviated NMF) decided to construct a portable instrument to be used on selections of traffic roads within......Road surface reflection data in the form of standard r-tables serve as input for design calculations of road lighting installations on traffic roads. However, in several countries the use of the standard r-tables has not been verified by measurement in a long period of time, while the types of road...

  5. Enhancing our Understanding of Snowfall Modes with Ground-Based Observations

    Science.gov (United States)

    Pettersen, C.; Kulie, M.; Petersen, W. A.; Bliven, L. F.; Wood, N.

    2016-12-01

    Snowfall can be broadly categorized into deep and shallow events based on the vertical distribution of the precipitating ice. Remotely sensed data refine these precipitation categories and aid in discerning the underlying macro- and microphysical mechanisms. The unique patterns in the remotely sensed instruments observations can potentially connect distinct modes of snowfall to specific processes. Though satellites can observe and recognize these patterns in snowfall, these measurements are limited - particularly in cases of shallow and light precipitation, as the snow may be too close to the surface or below the detection limits of the instrumentation. By enhancing satellite measurements with ground-based instrumentation, whether with limited-term field campaigns or long-term strategic sites, we can further our understanding and assumptions about different snowfall modes and how they are measured from spaceborne instruments. Presented are three years of data from a ground-based instrument suite consisting of a MicroRain Radar (MRR; optimized for snow events) and a Precipitation Imaging Package (PIP). These instruments are located at the Marquette, Michigan National Weather Service Weather Forecast Office to: a) use coincident meteorological measurements and observations to enhance our understanding of the thermodynamic drivers and b) showcase these instruments in an operational setting to enhance forecasts of shallow snow events. Three winters of MRR and PIP measurements are partitioned, based on meteorological surface observations, into two-dimensional histograms of reflectivity and particle size distribution data. These statistics improve our interpretation of deep versus shallow precipitation. Additionally, these statistical techniques are applied to similar datasets from Global Precipitation Measurement field campaigns for further insight into cloud and precipitation macro- and microphysical processes.

  6. Reflective measurement of water concentration using millimeter wave illumination

    Science.gov (United States)

    Sung, Shijun; Bennett, David; Taylor, Zachary; Bajwa, Neha; Tewari, Priyamvada; Maccabi, Ashkan; Culjat, Martin; Singh, Rahul; Grundfest, Warren

    2011-04-01

    THz and millimeter wave technology have shown the potential to become a valuable medical imaging tool because of its sensitivity to water and safe, non-ionizing photon energy. Using the high dielectric constant of water in these frequency bands, reflectionmode THz sensing systems can be employed to measure water content in a target with high sensitivity. This phenomenology may lead to the development of clinical systems to measure the hydration state of biological targets. Such measurements may be useful in fast and convenient diagnosis of conditions whose symptoms can be characterized by changes in water concentration such as skin burns, dehydration, or chemical exposure. To explore millimeter wave sensitivity to hydration, a reflectometry system is constructed to make water concentration measurements at 100 GHz, and the minimum detectable water concentration difference is measured. This system employs a 100 GHz Gunn diode source and Golay cell detector to perform point reflectivity measurements of a wetted polypropylene towel as it dries on a mass balance. A noise limited, minimum detectable concentration difference of less than 0.5% by mass can be detected in water concentrations ranging from 70% to 80%. This sensitivity is sufficient to detect hydration changes caused by many diseases and pathologies and may be useful in the future as a diagnostic tool for the assessment of burns and other surface pathologies.

  7. Variable reflectivity signal mirrors and signal response measurements

    International Nuclear Information System (INIS)

    Vine, Glenn de; Shaddock, Daniel A; McClelland, David E

    2002-01-01

    Future gravitational wave detectors will include some form of signal mirror in order to alter the signal response of the device. We introduce interferometer configurations which utilize a variable reflectivity signal mirror allowing a tunable peak frequency and variable signal bandwidth. A detector configured with a Fabry-Perot cavity as the signal mirror is compared theoretically with one using a Michelson interferometer for a signal mirror. A system for the measurement of the interferometer signal responses is introduced. This technique is applied to a power-recycled Michelson interferometer with resonant sideband extraction. We present broadband measurements of the benchtop prototype's signal response for a range of signal cavity detunings. This technique is also applicable to most other gravitational wave detector configurations

  8. Variable reflectivity signal mirrors and signal response measurements

    CERN Document Server

    Vine, G D; McClelland, D E

    2002-01-01

    Future gravitational wave detectors will include some form of signal mirror in order to alter the signal response of the device. We introduce interferometer configurations which utilize a variable reflectivity signal mirror allowing a tunable peak frequency and variable signal bandwidth. A detector configured with a Fabry-Perot cavity as the signal mirror is compared theoretically with one using a Michelson interferometer for a signal mirror. A system for the measurement of the interferometer signal responses is introduced. This technique is applied to a power-recycled Michelson interferometer with resonant sideband extraction. We present broadband measurements of the benchtop prototype's signal response for a range of signal cavity detunings. This technique is also applicable to most other gravitational wave detector configurations.

  9. Optical constants from mirror reflectivities measured at synchrotrons

    International Nuclear Information System (INIS)

    Blake, R.L.; Davis, J.C.; Burbine, T.H.; Graessle, D.E.; Gullikson, E.M.

    1992-01-01

    Improved mirror reflectivity measurement techniques have been introduced to permit more accurate determinations of optical constants δ and β in the complex index of refraction n = 1 - δ-iβ over the energy range 50 to 5000 eV. When the density has been determined by x-ray or other means, one can calculate the real and imaginary parts f' and f double-prime, of the complex atomic scattering factor f = f o + f ' + if double-prime from δ and β. Preliminary results are given for the Ni LIII edge around 852 eV, and the Au M edge region from 2150 to 3500 eV. Since these are the first experimental evaluations of δ for these element edges, they are compared with appropriate reservations to semi-empirical tabulations. There is much potential for this technique applied to synchrotron sources

  10. Features of High-Latitude Ionospheric Irregularities Development as Revealed by Ground-Based GPS Observations, Satellite-Borne GPS Observations and Satellite In Situ Measurements over the Territory of Russia during the Geomagnetic Storm on March 17-18, 2015

    Science.gov (United States)

    Zakharenkova, I. E.; Cherniak, Iu. V.; Shagimuratov, I. I.; Klimenko, M. V.

    2018-01-01

    The dynamic picture of the response of the high- and mid-latitude ionosphere to the strong geomagnetic disturbances on March 17-18, 2015, has been studied with ground-based and satellite observations, mainly, by transionospheric measurements of delays of GPS (Global Positioning System) signals. The advantages of the joint use of ground-based GPS measurements and GPS measurements on board of the Swarm Low-Earth-Orbit satellite mission for monitoring of the appearance of ionospheric irregularities over the territory of Russia are shown for the first time. The results of analysis of ground-based and space-borne GPS observations, as well as satellite, in situ measurements, revealed large-scale ionospheric plasma irregularities observed over the territory of Russia in the latitude range of 50°-85° N during the main phase of the geomagnetic storm. The most intense ionospheric irregularities were detected in the auroral zone and in the region of the main ionospheric trough (MIT). It has been found that sharp changes in the phase of the carrier frequency of the navigation signal from all tracked satellites were recorded at all GPS stations located to the North from 55° MLAT. The development of a deep MIT was related to dynamic processes in the subauroral ionosphere, in particular, with electric fields of the intense subauroral polarization stream. Analysis of the electron and ion density values obtained by instruments on board of the Swarm and DMSP satellites showed that the zone of highly structured auroral ionosphere extended at least to heights of 850-900 km.

  11. SCIENTIFIC EFFICIENCY OF GROUND-BASED TELESCOPES

    International Nuclear Information System (INIS)

    Abt, Helmut A.

    2012-01-01

    I scanned the six major astronomical journals of 2008 for all 1589 papers that are based on new data obtained from ground-based optical/IR telescopes worldwide. Then I collected data on numbers of papers, citations to them in 3+ years, the most-cited papers, and annual operating costs. These data are assigned to four groups by telescope aperture. For instance, while the papers from telescopes with an aperture >7 m average 1.29 more citations than those with an aperture of 2 to 7 m) telescopes. I wonder why the large telescopes do so relatively poorly and suggest possible reasons. I also found that papers based on archival data, such as the Sloan Digital Sky Survey, produce 10.6% as many papers and 20.6% as many citations as those based on new data. Also, the 577.2 papers based on radio data produced 36.3% as many papers and 33.6% as many citations as the 1589 papers based on optical/IR telescopes.

  12. Diffuse reflectance spectroscopy for the measurement of tissue oxygen saturation

    International Nuclear Information System (INIS)

    Sircan-Kucuksayan, A; Canpolat, M; Uyuklu, M

    2015-01-01

    Tissue oxygen saturation (StO 2 ) is a useful parameter for medical applications. A spectroscopic method has been developed to detect pathologic tissues, due to a lack of normal blood circulation, by measuring StO 2 . In this study, human blood samples with different levels of oxygen saturation have been prepared and spectra were acquired using an optical fiber probe to investigate the correlation between the oxygen saturation levels and the spectra. A linear correlation between the oxygen saturation and ratio of the intensities (760 nm to 790 nm) of the spectra acquired from blood samples has been found. In a validation study, oxygen saturations of the blood samples were estimated from the spectroscopic measurements with an error of 2.9%. It has also been shown that the linear dependence between the ratio and the oxygen saturation of the blood samples was valid for the blood samples with different hematocrits. Spectra were acquired from the forearms of 30 healthy volunteers to estimate StO 2 prior to, at the beginning of, after 2 min, and at the release of total vascular occlusion. The average StO 2 of a forearm before and after the two minutes occlusion was significantly different. The results suggested that optical reflectance spectroscopy is a sensitive method to estimate the StO 2 levels of human tissue. The technique developed to measure StO 2 has potential to detect ischemia in real time. (paper)

  13. A simple method for the measurement of reflective foil emissivity

    International Nuclear Information System (INIS)

    Ballico, M. J.; Ham, E. W. M. van der

    2013-01-01

    Reflective metal foil is widely used to reduce radiative heat transfer within the roof space of buildings. Such foils are typically mass-produced by vapor-deposition of a thin metallic coating onto a variety of substrates, ranging from plastic-coated reinforced paper to 'bubble-wrap'. Although the emissivity of such surfaces is almost negligible in the thermal infrared, typically less than 0.03, an insufficiently thick metal coating, or organic contamination of the surface, can significantly increase this value. To ensure that the quality of the installed insulation is satisfactory, Australian building code AS/NZS 4201.5:1994 requires a practical agreed method for measurement of the emissivity, and the standard ASTM-E408 is implied. Unfortunately this standard is not a 'primary method' and requires the use of specified expensive apparatus and calibrated reference materials. At NMIA we have developed a simple primary technique, based on an apparatus to thermally modulate the sample and record the apparent modulation in infra-red radiance with commercially available radiation thermometers. The method achieves an absolute accuracy in the emissivity of approximately 0.004 (k=2). This paper theoretically analyses the equivalence between the thermal emissivity measured in this manner, the effective thermal emissivity in application, and the apparent emissivity measured in accordance with ASTM-E408

  14. A simple method for the measurement of reflective foil emissivity

    Science.gov (United States)

    Ballico, M. J.; van der Ham, E. W. M.

    2013-09-01

    Reflective metal foil is widely used to reduce radiative heat transfer within the roof space of buildings. Such foils are typically mass-produced by vapor-deposition of a thin metallic coating onto a variety of substrates, ranging from plastic-coated reinforced paper to "bubble-wrap". Although the emissivity of such surfaces is almost negligible in the thermal infrared, typically less than 0.03, an insufficiently thick metal coating, or organic contamination of the surface, can significantly increase this value. To ensure that the quality of the installed insulation is satisfactory, Australian building code AS/NZS 4201.5:1994 requires a practical agreed method for measurement of the emissivity, and the standard ASTM-E408 is implied. Unfortunately this standard is not a "primary method" and requires the use of specified expensive apparatus and calibrated reference materials. At NMIA we have developed a simple primary technique, based on an apparatus to thermally modulate the sample and record the apparent modulation in infra-red radiance with commercially available radiation thermometers. The method achieves an absolute accuracy in the emissivity of approximately 0.004 (k=2). This paper theoretically analyses the equivalence between the thermal emissivity measured in this manner, the effective thermal emissivity in application, and the apparent emissivity measured in accordance with ASTM-E408.

  15. MODELING ATMOSPHERIC EMISSION FOR CMB GROUND-BASED OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Errard, J.; Borrill, J. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Ade, P. A. R. [School of Physics and Astronomy, Cardiff University, Cardiff CF10 3XQ (United Kingdom); Akiba, Y.; Chinone, Y. [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801 (Japan); Arnold, K.; Atlas, M.; Barron, D.; Elleflot, T. [Department of Physics, University of California, San Diego, CA 92093-0424 (United States); Baccigalupi, C.; Fabbian, G. [International School for Advanced Studies (SISSA), Trieste I-34014 (Italy); Boettger, D. [Department of Astronomy, Pontifica Universidad Catolica de Chile (Chile); Chapman, S. [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, B3H 4R2 (Canada); Cukierman, A. [Department of Physics, University of California, Berkeley, CA 94720 (United States); Delabrouille, J. [AstroParticule et Cosmologie, Univ Paris Diderot, CNRS/IN2P3, CEA/Irfu, Obs de Paris, Sorbonne Paris Cité (France); Dobbs, M.; Gilbert, A. [Physics Department, McGill University, Montreal, QC H3A 0G4 (Canada); Ducout, A.; Feeney, S. [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom); Feng, C. [Department of Physics and Astronomy, University of California, Irvine (United States); and others

    2015-08-10

    Atmosphere is one of the most important noise sources for ground-based cosmic microwave background (CMB) experiments. By increasing optical loading on the detectors, it amplifies their effective noise, while its fluctuations introduce spatial and temporal correlations between detected signals. We present a physically motivated 3D-model of the atmosphere total intensity emission in the millimeter and sub-millimeter wavelengths. We derive a new analytical estimate for the correlation between detectors time-ordered data as a function of the instrument and survey design, as well as several atmospheric parameters such as wind, relative humidity, temperature and turbulence characteristics. Using an original numerical computation, we examine the effect of each physical parameter on the correlations in the time series of a given experiment. We then use a parametric-likelihood approach to validate the modeling and estimate atmosphere parameters from the polarbear-i project first season data set. We derive a new 1.0% upper limit on the linear polarization fraction of atmospheric emission. We also compare our results to previous studies and weather station measurements. The proposed model can be used for realistic simulations of future ground-based CMB observations.

  16. Infrared reflection properties and modelling of in situ reflection measurements on plasma-facing materials in Tore Supra

    International Nuclear Information System (INIS)

    Reichle, R; Desgranges, C; Faisse, F; Pocheau, C; Lasserre, J-P; Oelhoffen, F; Eupherte, L; Todeschini, M

    2009-01-01

    Tore Supra has-like ITER-reflecting internal surfaces, which can perturb the machine protection systems based on infrared (IR) thermography. To ameliorate this situation, we have measured and modelled in the 3-5 μm wavelength range the bi-directional reflection distribution function (BRDF) of wall material samples from Tore Supra and conducted in situ reflection measurements and simulated them with the CEA COSMOS code. BRDF results are presented for B 4 C and carbon fibre composite (CFC) tiles. The hemispherical integrated reflection ranges from 0.12 for the B 4 C sample to 0.39 for a CFC tile from the limiter erosion zone. In situ measurements of the IR reflection of a blackbody source off an ICRH and an LHCD antenna of Tore Supra are well reproduced by the simulation.

  17. Infrared reflection properties and modelling of in situ reflection measurements on plasma-facing materials in Tore Supra

    Energy Technology Data Exchange (ETDEWEB)

    Reichle, R; Desgranges, C; Faisse, F; Pocheau, C [CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France); Lasserre, J-P; Oelhoffen, F; Eupherte, L; Todeschini, M [CEA, DAM, CESTA, F-33114 Le Barp (France)

    2009-12-15

    Tore Supra has-like ITER-reflecting internal surfaces, which can perturb the machine protection systems based on infrared (IR) thermography. To ameliorate this situation, we have measured and modelled in the 3-5 {mu}m wavelength range the bi-directional reflection distribution function (BRDF) of wall material samples from Tore Supra and conducted in situ reflection measurements and simulated them with the CEA COSMOS code. BRDF results are presented for B{sub 4}C and carbon fibre composite (CFC) tiles. The hemispherical integrated reflection ranges from 0.12 for the B{sub 4}C sample to 0.39 for a CFC tile from the limiter erosion zone. In situ measurements of the IR reflection of a blackbody source off an ICRH and an LHCD antenna of Tore Supra are well reproduced by the simulation.

  18. Biosensors for EVA: Improved Instrumentation for Ground-based Studies

    Science.gov (United States)

    Soller, B.; Ellerby, G.; Zou, F.; Scott, P.; Jin, C.; Lee, S. M. C.; Coates, J.

    2010-01-01

    During lunar excursions in the EVA suit, real-time measurement of metabolic rate is required to manage consumables and guide activities to ensure safe return to the base. Metabolic rate, or oxygen consumption (VO2), is normally measured from pulmonary parameters but cannot be determined with standard techniques in the oxygen-rich environment of a spacesuit. Our group has developed novel near infrared spectroscopic (NIRS) methods to calculate muscle oxygen saturation (SmO 2), hematocrit, and pH, and we recently demonstrated that we can use our NIRS sensor to measure VO 2 on the leg during cycling. Our NSBRI project has 4 objectives: (1) increase the accuracy of the metabolic rate calculation through improved prediction of stroke volume; (2) investigate the relative contributions of calf and thigh oxygen consumption to metabolic rate calculation for walking and running; (3) demonstrate that the NIRS-based noninvasive metabolic rate methodology is sensitive enough to detect decrement in VO 2 in a space analog; and (4) improve instrumentation to allow testing within a spacesuit. Over the past year we have made progress on all four objectives, but the most significant progress was made in improving the instrumentation. The NIRS system currently in use at JSC is based on fiber optics technology. Optical fiber bundles are used to deliver light from a light source in the monitor to the patient, and light reflected back from the patient s muscle to the monitor for spectroscopic analysis. The fiber optic cables are large and fragile, and there is no way to get them in and out of the test spacesuit used for ground-based studies. With complimentary funding from the US Army, we undertook a complete redesign of the sensor and control electronics to build a novel system small enough to be used within the spacesuit and portable enough to be used by a combat medic. In the new system the filament lamp used in the fiber optic system was replaced with a novel broadband near infrared

  19. Coordinated Ground-Based Observations and the New Horizons Fly-by of Pluto

    Science.gov (United States)

    Young, Eliot; Young, Leslie; Parker, Joel; Binzel, Richard

    2015-04-01

    The New Horizons (NH) spacecraft is scheduled to make its closest approach to Pluto on July 14, 2015. NH carries seven scientific instruments, including separate UV and Visible-IR spectrographs, a long-focal-length imager, two plasma-sensing instruments and a dust counter. There are three arenas in particular in which ground-based observations should augment the NH instrument suite in synergistic ways: IR spectra at wavelengths longer than 2.5 µm (i.e., longer than the NH Ralph spectrograph), stellar occultation observations near the time of the fly-by, and thermal surface maps and atmospheric CO abundances based on ALMA observations - we discuss the first two of these. IR spectra in the 3 - 5 µm range cover the CH4 absorption band near 3.3 µm. This band can be an important constraint on the state and areal extent of nitrogen frost on Pluto's surface. If this band depth is close to zero (as was observed by Olkin et al. 2007), it limits the area of nitrogen frost, which is bright at that wavelength. Combined with the NH observations of nitrogen frost at 2.15 µm, the ground-based spectra will determine how much nitrogen frost is diluted with methane, which is a basic constraint on the seasonal cycle of sublimation and condensation that takes place on Pluto (and similar objects like Triton and Eris). There is a fortuitous stellar occultation by Pluto on 29-JUN-2015, only two weeks before the NH closest approach. The occulted star will be the brightest ever observed in a Pluto event, about 2 magnitudes brighter than Pluto itself. The track of the event is predicted to cover parts of Australia and New Zealand. Thanks to HST and ground based campaigns to find a TNO target reachable by NH, the position of the shadow path will be known at the +/-100 km level, allowing SOFIA and mobile ground-based observers to reliably cover the central flash region. Ground-based & SOFIA observations in visible and IR wavelengths will characterize the haze opacity and vertical

  20. Measurement and application of bidirectional reflectance distribution function

    Science.gov (United States)

    Liao, Fei; Li, Lin; Lu, Chengwen

    2016-10-01

    When a beam of light with certain intensity and distribution reaches the surface of a material, the distribution of the diffused light is related to the incident angle, the receiving angle, the wavelength of the light and the types of the material. Bidirectional Reflectance Distribution Function (BRDF) is a method to describe this distribution. For an optical system, the optical and mechanical materials' BRDF are unique, and if we want to calculate stray light of the system we should know the correct BRDF data of the whole materials. There are fundamental significances in the area of space remote sensor where BRDF is needed in the precise radiation calibration. It is also important in the military field where BRDF can be used in the object identification and target tracking, etc. In this paper, 11 kinds of aerospace materials' BRDF are measured and more than 310,000 groups of BRDF data are achieved , and also a BRDF database is established in China for the first time. With the BRDF data of the database, we can create the detector model, build the stray light radiation surface model in the stray light analysis software. In this way, the stray radiation on the detector can be calculated correctly.

  1. Reflections

    Directory of Open Access Journals (Sweden)

    Joanne Embree

    2001-01-01

    Full Text Available Ideally, editorials are written one to two months before publication in the Journal. It was my turn to write this one. I had planned to write the first draft the evening after my clinic on Tuesday, September 11. It didn't get done that night or during the next week. Somehow, the topic that I had originally chosen just didn't seem that important anymore as I, along my friends and colleagues, reflected on the changes that the events of that day were likely to have on our lives.

  2. Reconstruction of Sky Illumination Domes from Ground-Based Panoramas

    Science.gov (United States)

    Coubard, F.; Lelégard, L.; Brédif, M.; Paparoditis, N.; Briottet, X.

    2012-07-01

    The knowledge of the sky illumination is important for radiometric corrections and for computer graphics applications such as relighting or augmented reality. We propose an approach to compute environment maps, representing the sky radiance, from a set of ground-based images acquired by a panoramic acquisition system, for instance a mobile-mapping system. These images can be affected by important radiometric artifacts, such as bloom or overexposure. A Perez radiance model is estimated with the blue sky pixels of the images, and used to compute additive corrections in order to reduce these radiometric artifacts. The sky pixels are then aggregated in an environment map, which still suffers from discontinuities on stitching edges. The influence of the quality of estimated sky radiance on the simulated light signal is measured quantitatively on a simple synthetic urban scene; in our case, the maximal error for the total sensor radiance is about 10%.

  3. RECONSTRUCTION OF SKY ILLUMINATION DOMES FROM GROUND-BASED PANORAMAS

    Directory of Open Access Journals (Sweden)

    F. Coubard

    2012-07-01

    Full Text Available The knowledge of the sky illumination is important for radiometric corrections and for computer graphics applications such as relighting or augmented reality. We propose an approach to compute environment maps, representing the sky radiance, from a set of ground-based images acquired by a panoramic acquisition system, for instance a mobile-mapping system. These images can be affected by important radiometric artifacts, such as bloom or overexposure. A Perez radiance model is estimated with the blue sky pixels of the images, and used to compute additive corrections in order to reduce these radiometric artifacts. The sky pixels are then aggregated in an environment map, which still suffers from discontinuities on stitching edges. The influence of the quality of estimated sky radiance on the simulated light signal is measured quantitatively on a simple synthetic urban scene; in our case, the maximal error for the total sensor radiance is about 10%.

  4. Study of the relations between cloud properties and atmospheric conditions using ground-based digital images

    Science.gov (United States)

    Bakalova, Kalinka

    The aerosol constituents of the earth atmosphere are of great significance for the radiation budget and global climate of the planet. They are the precursors of clouds that in turn play an essential role in these processes and in the hydrological cycle of the Earth. Understanding the complex aerosol-cloud interactions requires a detailed knowledge of the dynamical processes moving the water vapor through the atmosphere, and of the physical mechanisms involved in the formation and growth of cloud particles. Ground-based observations on regional and short time scale provide valuable detailed information about atmospheric dynamics and cloud properties, and are used as a complementary tool to the global satellite observations. The objective of the present paper is to study the physical properties of clouds as displayed in ground-based visible images, and juxtapose them to the specific surface and atmospheric meteorological conditions. The observations are being carried out over the urban area of the city of Sofia, Bulgaria. The data obtained from visible images of clouds enable a quantitative description of texture and morphological features of clouds such as shape, thickness, motion, etc. These characteristics are related to cloud microphysical properties. The changes of relative humidity and the horizontal visibility are considered to be representative of the variations of the type (natural/manmade) and amount of the atmospheric aerosols near the earth surface, and potentially, the cloud drop number concentration. The atmospheric dynamics is accounted for by means of the values of the atmospheric pressure, temperature, wind velocity, etc., observed at the earth's surface. The advantage of ground-based observations of clouds compared to satellite ones is in the high spatial and temporal resolution of the obtained data about the lowermost cloud layer, which in turn is sensitive to the meteorological regimes that determine cloud formation and evolution. It turns out

  5. Satellite and Ground Based Monitoring of Aerosol Plumes

    International Nuclear Information System (INIS)

    Doyle, Martin; Dorling, Stephen

    2002-01-01

    Plumes of atmospheric aerosol have been studied using a range of satellite and ground-based techniques. The Sea-viewing WideField-of-view Sensor (SeaWiFS) has been used to observe plumes of sulphate aerosol and Saharan dust around the coast of the United Kingdom. Aerosol Optical Thickness (AOT) was retrieved from SeaWiFS for two events; a plume of Saharan dust transported over the United Kingdom from Western Africa and a period of elevated sulphate experienced over the Easternregion of the UK. Patterns of AOT are discussed and related to the synoptic and mesoscale weather conditions. Further observation of the sulphate aerosol event was undertaken using the Advanced Very High Resolution Radiometer instrument(AVHRR). Atmospheric back trajectories and weather conditions were studied in order to identify the meteorological conditions which led to this event. Co-located ground-based measurements of PM 10 and PM 2.5 were obtained for 4sites within the UK and PM 2.5/10 ratios were calculated in order to identify any unusually high or low ratios(indicating the dominant size fraction within the plume)during either of these events. Calculated percentiles ofPM 2.5/10 ratios during the 2 events examined show that these events were notable within the record, but were in noway unique or unusual in the context of a 3 yr monitoring record. Visibility measurements for both episodes have been examined and show that visibility degradation occurred during both the sulphate aerosol and Saharan dust episodes

  6. Validation of a spectral correction procedure for sun and sky reflections in above-water reflectance measurements.

    Science.gov (United States)

    Groetsch, Philipp M M; Gege, Peter; Simis, Stefan G H; Eleveld, Marieke A; Peters, Steef W M

    2017-08-07

    A three-component reflectance model (3C) is applied to above-water radiometric measurements to derive remote-sensing reflectance Rrs (λ). 3C provides a spectrally resolved offset Δ(λ) to correct for residual sun and sky radiance (Rayleigh- and aerosol-scattered) reflections on the water surface that were not represented by sky radiance measurements. 3C is validated with a data set of matching above- and below-water radiometric measurements collected in the Baltic Sea, and compared against a scalar offset correction Δ. Correction with Δ(λ) instead of Δ consistently reduced the (mean normalized root-mean-square) deviation between Rrs (λ) and reference reflectances to comparable levels for clear (Δ: 14.3 ± 2.5 %, Δ(λ): 8.2 ± 1.7 %), partly clouded (Δ: 15.4 ± 2.1 %, Δ(λ): 6.5 ± 1.4 %), and completely overcast (Δ: 10.8 ± 1.7 %, Δ(λ): 6.3 ± 1.8 %) sky conditions. The improvement was most pronounced under inhomogeneous sky conditions when measurements of sky radiance tend to be less representative of surface-reflected radiance. Accounting for both sun glint and sky reflections also relaxes constraints on measurement geometry, which was demonstrated based on a semi-continuous daytime data set recorded in a eutrophic freshwater lake in the Netherlands. Rrs (λ) that were derived throughout the day varied spectrally by less than 2 % relative standard deviation. Implications on measurement protocols are discussed. An open source software library for processing reflectance measurements was developed and is made publicly available.

  7. Active Multispectral Band Selection and Reflectance Measurement System

    National Research Council Canada - National Science Library

    Rennich, Bradley

    1999-01-01

    .... To aid in the selection of these bands, a novel multispectral band selection technique is presented based on the cross-correlation of the material class reflectance spectra over a wavelength range of 1 - 5 microns...

  8. Reflections on Measuring Thinking, while Listening to Mozart's "Jupiter" Symphony.

    Science.gov (United States)

    Wasserman, Selma

    1989-01-01

    Reflects on educators' current preoccupation with assessment of higher order thinking skills. Easy-to-mark, forced-choice, pencil-and-paper tests with single numerical scores may trivialize the wonderful complexity of human capabilities. Includes 17 references. (MLH)

  9. Retrieval of reflections from seismic background?noise measurements

    NARCIS (Netherlands)

    Draganov, D.S.; Wapenaar, K.; Mulder, W.; Singer, J.; Verdel, A.

    2007-01-01

    The retrieval of the earth's reflection response from cross?correlations of seismic noise recordings can provide valuable information, which may otherwise not be available due to limited spatial distribution of seismic sources. We cross?correlated ten hours of seismic background?noise data acquired

  10. Measuring Effects of Reflection on Learning – A Physiological Study

    NARCIS (Netherlands)

    Qi, Wen; Verpoorten, Dominique; Westera, Wim

    2014-01-01

    As an economical and feasible intervention, reflection demands learners using critical thinking to examine presented information, questioning its validity, and drawing conclusions based on the resulting ideas during a learning process. The aim of this study is to gain insight into the effects

  11. Challenges in complementing data from ground-based sensors with satellite-derived products to measure ecological changes in relation to climate – lessons from temperate wetland-upland landscapes

    Science.gov (United States)

    Gallant, Alisa L.; Sadinski, Walter J.; Brown, Jesslyn F.; Senay, Gabriel B.; Roth, Mark F.

    2018-01-01

    Assessing climate-related ecological changes across spatiotemporal scales meaningful to resource managers is challenging because no one method reliably produces essential data at both fine and broad scales. We recently confronted such challenges while integrating data from ground- and satellite-based sensors for an assessment of four wetland-rich study areas in the U.S. Midwest. We examined relations between temperature and precipitation and a set of variables measured on the ground at individual wetlands and another set measured via satellite sensors within surrounding 4 km2 landscape blocks. At the block scale, we used evapotranspiration and vegetation greenness as remotely sensed proxies for water availability and to estimate seasonal photosynthetic activity. We used sensors on the ground to coincidentally measure surface-water availability and amphibian calling activity at individual wetlands within blocks. Responses of landscape blocks generally paralleled changes in conditions measured on the ground, but the latter were more dynamic, and changes in ecological conditions on the ground that were critical for biota were not always apparent in measurements of related parameters in blocks. Here, we evaluate the effectiveness of decisions and assumptions we made in applying the remotely sensed data for the assessment and the value of integrating observations across scales, sensors, and disciplines.

  12. Item Construction Using Reflective, Formative, or Rasch Measurement Models: Implications for Group Work

    Science.gov (United States)

    Peterson, Christina Hamme; Gischlar, Karen L.; Peterson, N. Andrew

    2017-01-01

    Measures that accurately capture the phenomenon are critical to research and practice in group work. The vast majority of group-related measures were developed using the reflective measurement model rooted in classical test theory (CTT). Depending on the construct definition and the measure's purpose, the reflective model may not always be the…

  13. Cross Validation of Rain Drop Size Distribution between GPM and Ground Based Polarmetric radar

    Science.gov (United States)

    Chandra, C. V.; Biswas, S.; Le, M.; Chen, H.

    2017-12-01

    Dual-frequency precipitation radar (DPR) on board the Global Precipitation Measurement (GPM) core satellite has reflectivity measurements at two independent frequencies, Ku- and Ka- band. Dual-frequency retrieval algorithms have been developed traditionally through forward, backward, and recursive approaches. However, these algorithms suffer from "dual-value" problem when they retrieve medium volume diameter from dual-frequency ratio (DFR) in rain region. To this end, a hybrid method has been proposed to perform raindrop size distribution (DSD) retrieval for GPM using a linear constraint of DSD along rain profile to avoid "dual-value" problem (Le and Chandrasekar, 2015). In the current GPM level 2 algorithm (Iguchi et al. 2017- Algorithm Theoretical Basis Document) the Solver module retrieves a vertical profile of drop size distributionn from dual-frequency observations and path integrated attenuations. The algorithm details can be found in Seto et al. (2013) . On the other hand, ground based polarimetric radars have been used for a long time to estimate drop size distributions (e.g., Gorgucci et al. 2002 ). In addition, coincident GPM and ground based observations have been cross validated using careful overpass analysis. In this paper, we perform cross validation on raindrop size distribution retrieval from three sources, namely the hybrid method, the standard products from the solver module and DSD retrievals from ground polarimetric radars. The results are presented from two NEXRAD radars located in Dallas -Fort Worth, Texas (i.e., KFWS radar) and Melbourne, Florida (i.e., KMLB radar). The results demonstrate the ability of DPR observations to produce DSD estimates, which can be used subsequently to generate global DSD maps. References: Seto, S., T. Iguchi, T. Oki, 2013: The basic performance of a precipitation retrieval algorithm for the Global Precipitation Measurement mission's single/dual-frequency radar measurements. IEEE Transactions on Geoscience and

  14. Remote measurement of surface roughness, surface reflectance, and body reflectance with LiDAR.

    Science.gov (United States)

    Li, Xiaolu; Liang, Yu

    2015-10-20

    Light detection and ranging (LiDAR) intensity data are attracting increasing attention because of the great potential for use of such data in a variety of remote sensing applications. To fully investigate the data potential for target classification and identification, we carried out a series of experiments with typical urban building materials and employed our reconstructed built-in-lab LiDAR system. Received intensity data were analyzed on the basis of the derived bidirectional reflectance distribution function (BRDF) model and the established integration method. With an improved fitting algorithm, parameters involved in the BRDF model can be obtained to depict the surface characteristics. One of these parameters related to surface roughness was converted to a most used roughness parameter, the arithmetical mean deviation of the roughness profile (Ra), which can be used to validate the feasibility of the BRDF model in surface characterizations and performance evaluations.

  15. Characterization of aerosol pollution events in France using ground-based and POLDER-2 satellite data

    Directory of Open Access Journals (Sweden)

    M. Kacenelenbogen

    2006-01-01

    Full Text Available We analyze the relationship between daily fine particle mass concentration (PM2.5 and columnar aerosol optical thickness derived from the Polarization and Directionality of Earth's Reflectances (POLDER satellite sensor. The study is focused over France during the POLDER-2 lifetime between April and October 2003. We have first compared the POLDER derived aerosol optical thickness (AOT with integrated volume size distribution derived from ground-based Sun Photometer observations. The good correlation (R=0.72 with sub-micron volume fraction indicates that POLDER derived AOT is sensitive to the fine aerosol mass concentration. Considering 1974 match-up data points over 28 fine particle monitoring sites, the POLDER-2 derived AOT is fairly well correlated with collocated PM2.5 measurements, with a correlation coefficient of 0.55. The correlation coefficient reaches a maximum of 0.80 for particular sites. We have analyzed the probability to find an appropriate air quality category (AQC as defined by U.S. Environmental Protection Agency (EPA from POLDER-2 AOT measurements. The probability can be up to 88.8% (±3.7% for the "Good" AQC and 89.1% (±3.6% for the "Moderate" AQC.

  16. BigBOSS: The Ground-Based Stage IV BAO Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Schlegel, David; Bebek, Chris; Heetderks, Henry; Ho, Shirley; Lampton, Michael; Levi, Michael; Mostek, Nick; Padmanabhan, Nikhil; Perlmutter, Saul; Roe, Natalie; Sholl, Michael; Smoot, George; White, Martin; Dey, Arjun; Abraham, Tony; Jannuzi, Buell; Joyce, Dick; Liang, Ming; Merrill, Mike; Olsen, Knut; Salim, Samir

    2009-04-01

    The BigBOSS experiment is a proposed DOE-NSF Stage IV ground-based dark energy experiment to study baryon acoustic oscillations (BAO) and the growth of structure with an all-sky galaxy redshift survey. The project is designed to unlock the mystery of dark energy using existing ground-based facilities operated by NOAO. A new 4000-fiber R=5000 spectrograph covering a 3-degree diameter field will measure BAO and redshift space distortions in the distribution of galaxies and hydrogen gas spanning redshifts from 0.2< z< 3.5. The Dark Energy Task Force figure of merit (DETF FoM) for this experiment is expected to be equal to that of a JDEM mission for BAO with the lower risk and cost typical of a ground-based experiment.

  17. KSC ADVANCED GROUND BASED FIELD MILL V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The Advanced Ground Based Field Mill (AGBFM) network consists of 34 (31 operational) field mills located at Kennedy Space Center (KSC), Florida. The field mills...

  18. LOAC: a small aerosol optical counter/sizer for ground-based and balloon measurements of the size distribution and nature of atmospheric particles - Part 2: First results from balloon and unmanned aerial vehicle flights

    Science.gov (United States)

    Renard, Jean-Baptiste; Dulac, François; Berthet, Gwenaël; Lurton, Thibaut; Vignelles, Damien; Jégou, Fabrice; Tonnelier, Thierry; Jeannot, Matthieu; Couté, Benoit; Akiki, Rony; Verdier, Nicolas; Mallet, Marc; Gensdarmes, François; Charpentier, Patrick; Mesmin, Samuel; Duverger, Vincent; Dupont, Jean-Charles; Elias, Thierry; Crenn, Vincent; Sciare, Jean; Zieger, Paul; Salter, Matthew; Roberts, Tjarda; Giacomoni, Jérôme; Gobbi, Matthieu; Hamonou, Eric; Olafsson, Haraldur; Dagsson-Waldhauserova, Pavla; Camy-Peyret, Claude; Mazel, Christophe; Décamps, Thierry; Piringer, Martin; Surcin, Jérémy; Daugeron, Daniel

    2016-08-01

    In the companion (Part I) paper, we have described and evaluated a new versatile optical particle counter/sizer named LOAC (Light Optical Aerosol Counter), based on scattering measurements at angles of 12 and 60°. That allows for some typology identification of particles (droplets, carbonaceous, salts, and mineral dust) in addition to size-segregated counting in a large diameter range from 0.2 µm up to possibly more than 100 µm depending on sampling conditions (Renard et al., 2016). Its capabilities overpass those of preceding optical particle counters (OPCs) allowing the characterization of all kind of aerosols from submicronic-sized absorbing carbonaceous particles in polluted air to very coarse particles (> 10-20 µm in diameter) in desert dust plumes or fog and clouds. LOAC's light and compact design allows measurements under all kinds of balloons, on-board unmanned aerial vehicles (UAVs) and at ground level. We illustrate here the first LOAC airborne results obtained from a UAV and a variety of scientific balloons. The UAV was deployed in a peri-urban environment near Bordeaux in France. Balloon operations include (i) tethered balloons deployed in urban environments in Vienna (Austria) and Paris (France), (ii) pressurized balloons drifting in the lower troposphere over the western Mediterranean (during the Chemistry-Aerosol Mediterranean Experiment - ChArMEx campaigns), (iii) meteorological sounding balloons launched in the western Mediterranean region (ChArMEx) and from Aire-sur-l'Adour in south-western France (VOLTAIRE-LOAC campaign). More focus is put on measurements performed in the Mediterranean during (ChArMEx) and especially during African dust transport events to illustrate the original capability of balloon-borne LOAC to monitor in situ coarse mineral dust particles. In particular, LOAC has detected unexpected large particles in desert sand plumes.

  19. Ground Based Support for Exoplanet Space Missions

    Science.gov (United States)

    Haukka, H.; Hentunen, V.-P.; Salmi, T.; Aartolahti, H.; Juutilainen, J.; Vilokki, H.; Nissinen, M.

    2011-10-01

    Taurus Hill Observatory (THO), observatory code A95, is an amateur observatory located in Varkaus, Finland. The observatory is maintained by the local astronomical association Warkauden Kassiopeia. THO research team has observed and measured various stellar objects and phenomena. Observatory has mainly focused to asteroid [1] and exoplanet light curve measurements, observing the gamma rays burst, supernova discoveries and monitoring [2] and long term monitoring projects [3]. In the early 2011 Europlanet NA1 and NA2 organized "Coordinated Observations of Exoplanets from Ground and Space"-workshop in Graz, Austria. The workshop gathered together proam astronomers who have the equipment to measure the light curves of the exoplanets. Also there were professional scientists working in the exoplanet field who attended to the workshop. The result of the workshop was to organize coordinated observation campaign for follow-up observations of exoplanets (e.g. CoRoT planets). Also coordinated observation campaign to observe stellar CME outbreaks was planned. THO has a lot of experience in field of exoplanet light curve measurements and therefore this campaign is very supported by the research team of the observatory. In next coming observing seasons THO will concentrate its efforts for this kind of campaigns.

  20. Radiative and temperature effects of aerosol simulated by the COSMO-Ru model for different atmospheric conditions and their testing against ground-based measurements and accurate RT simulations

    Science.gov (United States)

    Chubarova, Nataly; Poliukhov, Alexei; Shatunova, Marina; Rivin, Gdali; Becker, Ralf; Muskatel, Harel; Blahak, Ulrich; Kinne, Stefan; Tarasova, Tatiana

    2017-04-01

    We use the operational Russian COSMO-Ru weather forecast model (Ritter and and Geleyn, 1991) with different aerosol input data for the evaluation of radiative and temperature effects of aerosol in different atmospheric conditions. Various aerosol datasets were utilized including Tegen climatology (Tegen et al., 1997), updated Macv2 climatology (Kinne et al., 2013), Tanre climatology (Tanre et al., 1984) as well as the MACC data (Morcrette et al., 2009). For clear sky conditions we compare the radiative effects from the COSMO-Ru model over Moscow (55.7N, 37.5E) and Lindenberg/Falkenberg sites (52.2N, 14.1E) with the results obtained using long-term aerosol measurements. Additional tests of the COSMO RT code were performed against (FC05)-SW model (Tarasova T.A. and Fomin B.A., 2007). The overestimation of about 5-8% of COSMO RT code was obtained. The study of aerosol effect on temperature at 2 meters has revealed the sensitivity of about 0.7-1.1 degree C per 100 W/m2 change in shortwave net radiation due to aerosol variations. We also discuss the radiative impact of urban aerosol properties according to the long-term AERONET measurements in Moscow and Moscow suburb as well as long-term aerosol trends over Moscow from the measurements and Macv2 dataset. References: Kinne, S., O'Donnel D., Stier P., et al., J. Adv. Model. Earth Syst., 5, 704-740, 2013. Morcrette J.-J.,O. Boucher, L. Jones, eet al, J.GEOPHYS. RES.,VOL. 114, D06206, doi:10.1029/2008JD011235, 2009. Ritter, B. and Geleyn, J., Monthly Weather Review, 120, 303-325, 1992. Tanre, D., Geleyn, J., and Slingo, J., A. Deepak Publ., Hampton, Virginia, 133-177, 1984. Tarasova, T., and Fomin, B., Journal of Atmospheric and Oceanic Technology, 24, 1157-1162, 2007. Tegen, I., Hollrig, P., Chin, M., et al., Journal of Geophysical Research- Atmospheres, 102, 23895-23915, 1997.

  1. Eruption mass estimation using infrasound waveform inversion and ash and gas measurements: Evaluation at Sakurajima Volcano, Japan [Comparison of eruption masses at Sakurajima Volcano, Japan calculated by infrasound waveform inversion and ground-based sampling

    International Nuclear Information System (INIS)

    Fee, David; Izbekov, Pavel; Kim, Keehoon; Yokoo, Akihiko; Lopez, Taryn

    2017-01-01

    Eruption mass and mass flow rate are critical parameters for determining the aerial extent and hazard of volcanic emissions. Infrasound waveform inversion is a promising technique to quantify volcanic emissions. Although topography may substantially alter the infrasound waveform as it propagates, advances in wave propagation modeling and station coverage permit robust inversion of infrasound data from volcanic explosions. The inversion can estimate eruption mass flow rate and total eruption mass if the flow density is known. However, infrasound-based eruption flow rates and mass estimates have yet to be validated against independent measurements, and numerical modeling has only recently been applied to the inversion technique. Furthermore we present a robust full-waveform acoustic inversion method, and use it to calculate eruption flow rates and masses from 49 explosions from Sakurajima Volcano, Japan.

  2. Bridge Testing With Ground-Based Interferometric Radar: Experimental Results

    International Nuclear Information System (INIS)

    Chiara, P.; Morelli, A.

    2010-01-01

    The research of innovative non-contact techniques aimed at the vibration measurement of civil engineering structures (also for damage detection and structural health monitoring) is continuously directed to the optimization of measures and methods. Ground-Based Radar Interferometry (GBRI) represents the more recent technique available for static and dynamic control of structures and ground movements.Dynamic testing of bridges and buildings in operational conditions are currently performed: (a) to assess the conformity of the structure to the project design at the end of construction; (b) to identify the modal parameters (i.e. natural frequencies, mode shapes and damping ratios) and to check the variation of any modal parameters over the years; (c) to evaluate the amplitude of the structural response to special load conditions (i.e. strong winds, earthquakes, heavy railway or roadway loads). If such tests are carried out by using a non-contact technique (like GBRI), the classical issues of contact sensors (like accelerometers) are easily overtaken.This paper presents and discusses the results of various tests carried out on full-scale bridges by using a Stepped Frequency-Continuous Wave radar system.

  3. Bridge Testing With Ground-Based Interferometric Radar: Experimental Results

    Science.gov (United States)

    Chiara, P.; Morelli, A.

    2010-05-01

    The research of innovative non-contact techniques aimed at the vibration measurement of civil engineering structures (also for damage detection and structural health monitoring) is continuously directed to the optimization of measures and methods. Ground-Based Radar Interferometry (GBRI) represents the more recent technique available for static and dynamic control of structures and ground movements. Dynamic testing of bridges and buildings in operational conditions are currently performed: (a) to assess the conformity of the structure to the project design at the end of construction; (b) to identify the modal parameters (i.e. natural frequencies, mode shapes and damping ratios) and to check the variation of any modal parameters over the years; (c) to evaluate the amplitude of the structural response to special load conditions (i.e. strong winds, earthquakes, heavy railway or roadway loads). If such tests are carried out by using a non-contact technique (like GBRI), the classical issues of contact sensors (like accelerometers) are easily overtaken. This paper presents and discusses the results of various tests carried out on full-scale bridges by using a Stepped Frequency-Continuous Wave radar system.

  4. Validation of the CrIS fast physical NH3 retrieval with ground-based FTIR

    NARCIS (Netherlands)

    Dammers, E.; Shephard, M.W.; Palm, M.; Cady-Pereira, K.; Capps, S.; Lutsch, E.; Strong, K.; Hannigan, J.W.; Ortega, I.; Toon, G.C.; Stremme, W.; Grutter, M.; Jones, N.; Smale, D.; Siemons, J.; Hrpcek, K.; Tremblay, D.; Schaap, M.; Notholt, J.; Willem Erisman, J.

    2017-01-01

    Presented here is the validation of the CrIS (Cross-track Infrared Sounder) fast physical NH3 retrieval (CFPR) column and profile measurements using ground-based Fourier transform infrared (FTIR) observations. We use the total columns and profiles from seven FTIR sites in the Network for the

  5. Measurement of an Evaporating Drop on a Reflective Substrate

    Science.gov (United States)

    Chao, David F.; Zhang, Nengli

    2004-01-01

    A figure depicts an apparatus that simultaneously records magnified ordinary top-view video images and laser shadowgraph video images of a sessile drop on a flat, horizontal substrate that can be opaque or translucent and is at least partially specularly reflective. The diameter, contact angle, and rate of evaporation of the drop as functions of time can be calculated from the apparent diameters of the drop in sequences of the images acquired at known time intervals, and the shadowgrams that contain flow patterns indicative of thermocapillary convection (if any) within the drop. These time-dependent parameters and flow patterns are important for understanding the physical processes involved in the spreading and evaporation of drops. The apparatus includes a source of white light and a laser (both omitted from the figure), which are used to form the ordinary image and the shadowgram, respectively. Charge-coupled-device (CCD) camera 1 (with zoom) acquires the ordinary video images, while CCD camera 2 acquires the shadowgrams. With respect to the portion of laser light specularly reflected from the substrate, the drop acts as a plano-convex lens, focusing the laser beam to a shadowgram on the projection screen in front of CCD camera 2. The equations for calculating the diameter, contact angle, and rate of evaporation of the drop are readily derived on the basis of Snell s law of refraction and the geometry of the optics.

  6. Neutron Reflectivity Measurement for Polymer Dynamics near Graphene Oxide Monolayers

    Science.gov (United States)

    Koo, Jaseung

    We investigated the diffusion dynamics of polymer chains confined between graphene oxide layers using neutron reflectivity (NR). The bilayers of polymethylmetacrylate (PMMA)/ deuterated PMMA (d-PMMA) films and polystyrene (PS)/d-PS films with various film thickness sandwiched between Langmuir-Blodgett (LB) monolayers of graphene oxide (GO) were prepared. From the NR results, we found that PMMA diffusion dynamics was reduced near the GO surface while the PS diffusion was not significantly changed. This is due to the different strength of GO-polymer interaction. In this talk, these diffusion results will be compared with dewetting dynamics of polymer thin films on the GO monolayers. This has given us the basis for development of graphene-based nanoelectronics with high efficiency, such as heterojunction devices for polymer photovoltaic (OPV) applications.

  7. Intercomparison of Vertical Structure of Storms Revealed by Ground-Based (NMQ and Spaceborne Radars (CloudSat-CPR and TRMM-PR

    Directory of Open Access Journals (Sweden)

    Veronica M. Fall

    2013-01-01

    Full Text Available Spaceborne radars provide great opportunities to investigate the vertical structure of clouds and precipitation. Two typical spaceborne radars for such a study are the W-band Cloud Profiling Radar (CPR and Ku-band Precipitation Radar (PR, which are onboard NASA’s CloudSat and TRMM satellites, respectively. Compared to S-band ground-based radars, they have distinct scattering characteristics for different hydrometeors in clouds and precipitation. The combination of spaceborne and ground-based radar observations can help in the identification of hydrometeors and improve the radar-based quantitative precipitation estimation (QPE. This study analyzes the vertical structure of the 18 January, 2009 storm using data from the CloudSat CPR, TRMM PR, and a NEXRAD-based National Mosaic and Multisensor QPE (NMQ system. Microphysics above, within, and below the melting layer are studied through an intercomparison of multifrequency measurements. Hydrometeors’ type and their radar scattering characteristics are analyzed. Additionally, the study of the vertical profile of reflectivity (VPR reveals the brightband properties in the cold-season precipitation and its effect on the radar-based QPE. In all, the joint analysis of spaceborne and ground-based radar data increases the understanding of the vertical structure of storm systems and provides a good insight into the microphysical modeling for weather forecasts.

  8. PhotoSpec - Ground-based Remote Sensing of Solar-Induced Chlorophyll Fluorescence: First Results

    Science.gov (United States)

    Grossmann, K.; Magney, T. S.; Frankenberg, C.; Seibt, U.; Pivovaroff, A. L.; Hurlock, S. C.; Stutz, J.

    2016-12-01

    Solar-Induced Chlorophyll Fluorescence (SIF) emitted from vegetation can be used as a proxy for photosynthetic activity and is observable on a global scale from space. However, many issues on a leaf-to-canopy scale remain poorly understood, such as influences on the SIF signal from environmental conditions, water stress, or radiation. We have developed a novel ground-based spectrometer system for measuring SIF from natural ecosystems. The instrumental set-up, requirements, and measurement technique are based on decades of experience using Differential Optical Absorption Spectroscopy (DOAS), an established method to measure atmospheric trace gases. The instrument consists of three thermally stabilized commercial spectrometers that are linked to a 2D scanning telescope unit via optical fiber bundles, and also includes a commercial photosynthetic active radiation (PAR) sensor. The spectrometers cover a SIF retrieval wavelength range at high spectral resolution (670 - 780 nm, 0.1 nm FWHM), and also provide moderate resolution spectra (400 - 800 nm, 1.5 nm FWHM) to retrieve vegetation indices and the photochemical reflectance index (PRI). We report on results of the first continuous field measurements of this novel system at Stunt Ranch Santa Monica Mountains UC Reserve, where the PhotoSpec instrument was monitoring SIF of four native Californian shrubland species with different adaptations to seasonal summer drought. We report on the correlation with CO2 fluxes over both the growing season and the hot summer period in 2016. We also show detailed measurements of the diurnal cycle of the SIF signal of single broad leaves, as well as dark-light transitions, under controlled experimental conditions. In addition to demonstrating the instrumental set-up, retrieval algorithm, and instrument performance, our results illustrate that SIF measurements at the leaf to ecosystem scale are needed to understand and interpret the SIF signals retrieved at larger scales.

  9. Methods for measuring the spectral reflectivity of advanced materials at high temperature

    International Nuclear Information System (INIS)

    Salikhov, T.P.; Kan, V.V.

    1993-01-01

    For investigation in the domain of advanced materials as well as for new technologies there is an urgent need for knowledge of the spectral reflectivity of the materials specially at high temperatures. However the methods available are mostly intended for measuring the model materials with specular or diffuse reflection surface. This is not quite correct since advanced materials have mixed specular diffuse reflection surfaces. New methods for reflectivity measurements of materials in the visible, near and middle infrared range at high temperature, regardless of surface texture, have been developed. The advantages of the methods proposed are as flows: (a) the facility of performing the reflectivity measurements for materials with mixed specular diffuse reflectance; (b) wide spectral range 0,38-8 micro m; (c) wide temperature range 300-3000 K; (d) high accuracy and rapid measurements. The methods are based on the following principals (i) Diffuse irradiation of the sample surface and the use of Helkholtz reciprocity principle to determine the directional hemispherical reflectivity ii) Pulse polychromatic probing of the sample by additional light source. The first principle excludes the influence of the angular reflection distribution of sample surface on data obtained. The second principle gives the possibility of simultaneous measurements of the reflectivity. The second principle gives the possibility of simultaneous measurements of the reflectivity in wide spectral range. On the basis of these principles for high temperature reflectometers have been developed and discussed here. (author)

  10. Ground-based infrared surveys: imaging the thermal fields at volcanoes and revealing the controlling parameters.

    Science.gov (United States)

    Pantaleo, Michele; Walter, Thomas

    2013-04-01

    Temperature monitoring is a widespread procedure in the frame of volcano hazard monitoring. Indeed temperature changes are expected to reflect changes in volcanic activity. We propose a new approach, within the thermal monitoring, which is meant to shed light on the parameters controlling the fluid pathways and the fumarole sites by using infrared measurements. Ground-based infrared cameras allow one to remotely image the spatial distribution, geometric pattern and amplitude of fumarole fields on volcanoes at metre to centimetre resolution. Infrared mosaics and time series are generated and interpreted, by integrating geological field observations and modeling, to define the setting of the volcanic degassing system at shallow level. We present results for different volcano morphologies and show that lithology, structures and topography control the appearance of fumarole field by the creation of permeability contrasts. We also show that the relative importance of those parameters is site-dependent. Deciphering the setting of the degassing system is essential for hazard assessment studies because it would improve our understanding on how the system responds to endogenous or exogenous modification.

  11. Do dose area product meter measurements reflect radiation doses ...

    African Journals Online (AJOL)

    Enrique

    SA JOURNAL OF RADIOLOGY • August 2004. Abstract. This study determined the correlation between radiation doses absorbed by health care workers and dose area product meter (DAP) measurements at Universitas Hospital, Bloemfontein. The DAP is an instrument which accurately measures the radiation emitted from ...

  12. Do dose area product meter measurements reflect radiation doses ...

    African Journals Online (AJOL)

    This study determined the correlation between radiation doses absorbed by health care workers and dose area product meter (DAP) measurements at Universitas Hospital, Bloemfontein. The DAP is an instrument which accurately measures the radiation emitted from the source. The study included the interventional ...

  13. Quantifying the effect of riming on snowfall using ground-based observations

    Science.gov (United States)

    Moisseev, Dmitri; von Lerber, Annakaisa; Tiira, Jussi

    2017-04-01

    Ground-based observations of ice particle size distribution and ensemble mean density are used to quantify the effect of riming on snowfall. The rime mass fraction is derived from these measurements by following the approach that is used in a single ice-phase category microphysical scheme proposed for the use in numerical weather prediction models. One of the characteristics of the proposed scheme is that the prefactor of a power law relation that links mass and size of ice particles is determined by the rime mass fraction, while the exponent does not change. To derive the rime mass fraction, a mass-dimensional relation representative of unrimed snow is also determined. To check the validity of the proposed retrieval method, the derived rime mass fraction is converted to the effective liquid water path that is compared to microwave radiometer observations. Since dual-polarization radar observations are often used to detect riming, the impact of riming on dual-polarization radar variables is studied for differential reflectivity measurements. It is shown that the relation between rime mass fraction and differential reflectivity is ambiguous, other factors such as change in median volume diameter need also be considered. Given the current interest on sensitivity of precipitation to aerosol pollution, which could inhibit riming, the importance of riming for surface snow accumulation is investigated. It is found that riming is responsible for 5% to 40% of snowfall mass. The study is based on data collected at the University of Helsinki field station in Hyytiälä during U.S. Department of Energy Biogenic Aerosols Effects on Clouds and Climate (BAECC) field campaign and the winter 2014/2015. In total 22 winter storms were analyzed, and detailed analysis of two events is presented to illustrate the study.

  14. A Manual Transportable Instrument Platform for Ground-Based Spectro-Directional Observations (ManTIS and the Resultant Hyperspectral Field Goniometer System

    Directory of Open Access Journals (Sweden)

    Marcel Buchhorn

    2013-11-01

    Full Text Available This article presents and technically describes a new field spectro-goniometer system for the ground-based characterization of the surface reflectance anisotropy under natural illumination conditions developed at the Alfred Wegener Institute (AWI. The spectro-goniometer consists of a Manual Transportable Instrument platform for ground-based Spectro-directional observations (ManTIS, and a hyperspectral sensor system. The presented measurement strategy shows that the AWI ManTIS field spectro-goniometer can deliver high quality hemispherical conical reflectance factor (HCRF measurements with a pointing accuracy of ±6 cm within the constant observation center. The sampling of a ManTIS hemisphere (up to 30° viewing zenith, 360° viewing azimuth needs approx. 18 min. The developed data processing chain in combination with the software used for the semi-automatic control provides a reliable method to reduce temporal effects during the measurements. The presented visualization and analysis approaches of the HCRF data of an Arctic low growing vegetation showcase prove the high quality of spectro-goniometer measurements. The patented low-cost and lightweight ManTIS instrument platform can be customized for various research needs and is available for purchase.

  15. Comparison of monthly nighttime cloud fraction products from MODIS and AIRS and ground-based camera over Manila Observatory (14.64N, 121.07E)

    Science.gov (United States)

    Gacal, G. F. B.; Lagrosas, N.

    2017-12-01

    Cloud detection nowadays is primarily achieved by the utilization of various sensors aboard satellites. These include MODIS Aqua, MODIS Terra, and AIRS with products that include nighttime cloud fraction. Ground-based instruments are, however, only secondary to these satellites when it comes to cloud detection. Nonetheless, these ground-based instruments (e.g., LIDARs, ceilometers, and sky-cameras) offer significant datasets about a particular region's cloud cover values. For nighttime operations of cloud detection instruments, satellite-based instruments are more reliably and prominently used than ground-based ones. Therefore if a ground-based instrument for nighttime operations is operated, it ought to produce reliable scientific datasets. The objective of this study is to do a comparison between the results of a nighttime ground-based instrument (sky-camera) and that of MODIS Aqua and MODIS Terra. A Canon Powershot A2300 is placed ontop of Manila Observatory (14.64N, 121.07E) and is configured to take images of the night sky at 5min intervals. To detect pixels with clouds, the pictures are converted to grayscale format. Thresholding technique is used to screen pixels with cloud and pixels without clouds. If the pixel value is greater than 17, it is considered as a cloud; otherwise, a noncloud (Gacal et al., 2016). This algorithm is applied to the data gathered from Oct 2015 to Oct 2016. A scatter plot between satellite cloud fraction in the area covering the area 14.2877N, 120.9869E, 14.7711N and 121.4539E and ground cloud cover is graphed to find the monthly correlation. During wet season (June - November), the satellite nighttime cloud fraction vs ground measured cloud cover produce an acceptable R2 (Aqua= 0.74, Terra= 0.71, AIRS= 0.76). However, during dry season, poor R2 values are obtained (AIRS= 0.39, Aqua & Terra = 0.01). The high correlation during wet season can be attributed to a high probability that the camera and satellite see the same clouds

  16. Review of commonly used remote sensing and ground-based ...

    African Journals Online (AJOL)

    This review provides an overview of the use of remote sensing data, the development of spectral reflectance indices for detecting plant water stress, and the usefulness of field measurements for ground-truthing purposes. Reliable measurements of plant water stress over large areas are often required for management ...

  17. Comparison of LANDSAT-2 and field spectrometer reflectance signatures of south Texas rangeland plant communities

    Science.gov (United States)

    Richardson, A. J.; Escobar, D. E.; Gausman, H. W.; Everitt, J. H. (Principal Investigator)

    1982-01-01

    The accuracy was assessed for an atmospheric correction method that depends on clear water bodies to infer solar and atmospheric parameters for radiative transfer equations by measuring the reflectance signature of four prominent south Texas rangeland plants with the LANDSAT satellite multispectral scanner (MSS) and a ground based spectroradiometer. The rangeland plant reflectances produced by the two sensors were correlated with no significant deviation of the slope from unity or of the intercept from zero. These results indicated that the atmospheric correction produced LANDSAT MSS estimates of rangeland plant reflectances that are as accurate as the ground based spectroradiometer.

  18. Ground-Based Photometric Measurements HAES Program Support.

    Science.gov (United States)

    1979-01-31

    A3, A-, E, F (J) Spatial structure of optical irregularities from F (K) Auroral electric fields from G, (BI, 132) ( L ) Pederson and Hall...investigator on this program was Mr. R. D. Sears. Also contributing significantly to the program were D. R. Hillendahl and G. Rogers . We acknowledge the...WBM experiment 57 23 Plot of height-integrated Pederson conductivities versus horizontal distance from Chatanika zenith for WBM experiment 58 24

  19. Cavity ring-down technique for measurement of reflectivity of high ...

    Indian Academy of Sciences (India)

    Laser & Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai 400 085,. India. *Corresponding author. E-mail: gsridhar@barc.gov.in. Abstract. A simple, accurate and reliable method for measuring the reflectivity of laser- ... Keywords. Cavity ring-down method; reflectivity measurement; optical resonator.

  20. Measuring thin films using quantitative frustrated total internal reflection (FTIR)

    NARCIS (Netherlands)

    Shirota, Minori; van Limbeek, Michiel A.J.; Lohse, Detlef; Sun, Chao

    2017-01-01

    Abstract.: In the study of interactions between liquids and solids, an accurate measurement of the film thickness between the two media is essential to study the dynamics. As interferometry is restricted by the wavelength of the light source used, recent studies of thinner films have prompted the

  1. Estimation of High-Frequency Earth-Space Radio Wave Signals via Ground-Based Polarimetric Radar Observations

    Science.gov (United States)

    Bolen, Steve; Chandrasekar, V.

    2002-01-01

    Expanding human presence in space, and enabling the commercialization of this frontier, is part of the strategic goals for NASA's Human Exploration and Development of Space (HEDS) enterprise. Future near-Earth and planetary missions will support the use of high-frequency Earth-space communication systems. Additionally, increased commercial demand on low-frequency Earth-space links in the S- and C-band spectra have led to increased interest in the use of higher frequencies in regions like Ku and Ka-band. Attenuation of high-frequency signals, due to a precipitating medium, can be quite severe and can cause considerable disruptions in a communications link that traverses such a medium. Previously, ground radar measurements were made along the Earth-space path and compared to satellite beacon data that was transmitted to a ground station. In this paper, quantitative estimation of the attenuation along the propagation path is made via inter-comparisons of radar data taken from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and ground-based polarimetric radar observations. Theoretical relationships between the expected specific attenuation (k) of spaceborne measurements with ground-based measurements of reflectivity (Zh) and differential propagation phase shift (Kdp) are developed for various hydrometeors that could be present along the propagation path, which are used to estimate the two-way path-integrated attenuation (PIA) on the PR return echo. Resolution volume matching and alignment of the radar systems is performed, and a direct comparison of PR return echo with ground radar attenuation estimates is made directly on a beam-by-beam basis. The technique is validated using data collected from the TExas and Florida UNderflights (TEFLUN-B) experiment and the TRMM large Biosphere-Atmosphere experiment in Amazonia (LBA) campaign. Attenuation estimation derived from this method can be used for strategiC planning of communication systems for

  2. Procedure for measuring the solar reflectance of flat or curved roofing assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Akbari, Hashem; Levinson, Ronnen [Heat Island Group, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Stern, Stephanie [Cool Roof Rating Council, Oakland, CA 94612 (United States)

    2008-07-15

    The widely used methods to measure the solar reflectance of roofing materials include ASTM standards E903 (spectrometer), C1549 (reflectometer), and E1918 (pyranometer). Standard E903 uses a spectrometer with an integrating sphere to measure the solar spectral reflectance of an area approximately 0.1 cm{sup 2}. The solar spectral reflectance is then weighted with a solar spectral irradiance to calculate the solar reflectance. Standard C1549 uses a reflectometer to measure the solar reflectance of an area approximately 5 cm{sup 2}. Both E903 and C1549 are best suited to measurement of the solar reflectance of flat, homogeneous surfaces. Standard E1918 uses a pyranometer to measure the solar reflectance of an area approximately 10 m{sup 2}, and is best applied to large surfaces that may also be rough and/or non-uniform. We describe a technique that uses a pyranometer to measure the solar reflectance of a uniform or variegated sample with diffusely reflective surface of an area of approximately 1 m{sup 2}, and use this technique (referred to as E1918A) to measure the solar reflectances of low- and high-profile tile assemblies. For 10 large (10 m{sup 2}) tile assemblies whose E1918 solar reflectances ranged from 0.10 to 0.50, the magnitude of the difference between the E1918A and E1918 measurements did not exceed 0.02 for unicolor assemblies, and did not exceed 0.03 for multicolor assemblies. (author)

  3. Spectral reflectance measurement methodologies for TUZ Golu field campaign

    CSIR Research Space (South Africa)

    Boucher, Y

    2011-07-01

    Full Text Available panel. However, it's possible to take this into account in the uncertainty budget. 2.2. Instrumentation and sampling area All of the teams except INPE used a Fieldspec ASD spectroradiometer. In this case, the user has to choose the aperture... of the objective and the ASD configuration (the number of elementary spectra averaged to get one measurement, here typically 10, and the number of dark current acquisitions, here typically 25). The spectroradiometer must also be optimized from time to time...

  4. Ultrahigh precision nonlinear reflectivity measurement system for saturable absorber mirrors with self-referenced fluence characterization.

    Science.gov (United States)

    Orsila, Lasse; Härkönen, Antti; Hyyti, Janne; Guina, Mircea; Steinmeyer, Günter

    2014-08-01

    Measurement of nonlinear optical reflectivity of saturable absorber devices is discussed. A setup is described that enables absolute accuracy of reflectivity measurements better than 0.3%. A repeatability within 0.02% is shown for saturable absorbers with few-percent modulation depth. The setup incorporates an in situ knife-edge characterization of beam diameters, making absolute reflectivity estimations and determination of saturation fluences significantly more reliable. Additionally, several measures are discussed to substantially improve the reliability of the reflectivity measurements. At its core, the scheme exploits the limits of state-of-the-art digital lock-in technology but also greatly benefits from a fiber-based master-oscillator power-amplifier source, the use of an integrating sphere, and simultaneous comparison with a linear reflectivity standard.

  5. A New Method for Simultaneous Measurement of the Integrated Reflectivity of Crystals at Multiple Orders of Reflection and Comparison with New Theoretical Calculations

    International Nuclear Information System (INIS)

    Lee, S.G.; Bak, J.G.; Jung, Y.S.; Bitter, M.; Hill, K.W.; Hoelzer, G.; Wehrhan, O.; Foerster, E.

    2003-01-01

    This paper describes a new method for the simultaneous measurement of the integrated reflectivity of a crystal for multiple orders of reflection at a predefined Bragg angle. The technique is demonstrated with a mica crystal for Bragg angles of 43 o , 47 o , and 50 o . The measured integrated reflectivity for Bragg reflections up to the 24th order is compared with new theoretical predictions, which are also presented in this paper

  6. A Ground-based validation of GOSAT-observed atmospheric CO2 in Inner-Mongolian grasslands

    International Nuclear Information System (INIS)

    Qin, X; Lei, L; Zeng, Z; Kawasaki, M; Oohasi, M

    2014-01-01

    Atmospheric carbon dioxide (CO 2 ) is a long-lived greenhouse gas that significantly contributes to global warming. Long-term and continuous measurements of atmospheric CO 2 to investigate its global distribution and concentration variations are important for accurately understanding its potential climatic effects. Satellite measurements from space can offer atmospheric CO 2 data for climate change research. For that, ground-based measurements are required for validation and improving the precision of satellite-measured CO 2 . We implemented observation experiment of CO 2 column densities in the Xilinguole grasslands in Inner Mongolia, China, using a ground-based measurement system, which mainly consists of an optical spectrum analyzer (OSA), a sun tracker and a notebook controller. Measurements from our ground-based system were analyzed and compared with those from the Greenhouse gas Observation SATellite (GOSAT). The ground-based measurements had an average value of 389.46 ppm, which was 2.4 ppm larger than from GOSAT, with a standard deviation of 3.4 ppm. This result is slightly larger than the difference between GOSAT and the Total Carbon Column Observing Network (TCCON). This study highlights the usefulness of the ground-based OSA measurement system for analyzing atmospheric CO 2 column densities, which is expected to supplement the current TCCON network

  7. Long term landslide monitoring with Ground Based SAR

    Science.gov (United States)

    Monserrat, Oriol; Crosetto, Michele; Luzi, Guido; Gili, Josep; Moya, Jose; Corominas, Jordi

    2014-05-01

    In the last decade, Ground-Based (GBSAR) has proven to be a reliable microwave Remote Sensing technique in several application fields, especially for unstable slopes monitoring. GBSAR can provide displacement measurements over few squared kilometres areas and with a very high spatial and temporal resolution. This work is focused on the use of GBSAR technique for long term landslide monitoring based on a particular data acquisition configuration, which is called discontinuous GBSAR (D-GBSAR). In the most commonly used GBSAR configuration, the radar is left installed in situ, acquiring data periodically, e.g. every few minutes. Deformations are estimated by processing sets of GBSAR images acquired during several weeks or months, without moving the system. By contrast, in the D-GBSAR the radar is installed and dismounted at each measurement campaign, revisiting a given site periodically. This configuration is useful to monitor slow deformation phenomena. In this work, two alternative ways for exploiting the D-GBSAR technique will be presented: the DInSAR technique and the Amplitude based Technique. The former is based on the exploitation of the phase component of the acquired SAR images and it allows providing millimetric precision on the deformation estimates. However, this technique presents several limitations like the reduction of measurable points with an increase in the period of observation, the ambiguous nature of the phase measurements, and the influence of the atmospheric phase component that can make it non applicable in some cases, specially when working in natural environments. The second approach, that is based on the use of the amplitude component of GB-SAR images combined with a image matching technique, will allow the estimation of the displacements over specific targets avoiding two of the limitations commented above: the phase unwrapping and atmosphere contribution but reducing the deformation measurement precision. Two successful examples of D

  8. Modeling ground-based timber harvesting systems using computer simulation

    Science.gov (United States)

    Jingxin Wang; Chris B. LeDoux

    2001-01-01

    Modeling ground-based timber harvesting systems with an object-oriented methodology was investigated. Object-oriented modeling and design promote a better understanding of requirements, cleaner designs, and better maintainability of the harvesting simulation system. The model developed simulates chainsaw felling, drive-to-tree feller-buncher, swing-to-tree single-grip...

  9. The COROT ground-based archive and access system

    Science.gov (United States)

    Solano, E.; González-Riestra, R.; Catala, C.; Baglin, A.

    2002-01-01

    A prototype of the COROT ground-based archive and access system is presented here. The system has been developed at LAEFF and it is based on the experience gained at Laboratorio de Astrofisica Espacial y Fisica Fundamental (LAEFF) with the INES (IUE Newly Extracted System) Archive.

  10. Reflection measurement of waveguide-injected high-power microwave antennas.

    Science.gov (United States)

    Yuan, Chengwei; Peng, Shengren; Shu, Ting; Zhang, Qiang; Zhao, Xuelong

    2015-12-01

    A method for reflection measurements of High-power Microwave (HPM) antennas excited with overmoded waveguides is proposed and studied systemically. In theory, principle of the method is proposed and the data processing formulas are developed. In simulations, a horn antenna excited by a TE11 mode exciter is examined and its reflection is calculated by CST Microwave Studio and by the method proposed in this article, respectively. In experiments, reflection measurements of two HPM antennas are conducted, and the measured results are well consistent with the theoretical expectations.

  11. Simultaneous and synergistic profiling of cloud and drizzle properties using ground-based observations

    Science.gov (United States)

    Rusli, Stephanie P.; Donovan, David P.; Russchenberg, Herman W. J.

    2017-12-01

    Despite the importance of radar reflectivity (Z) measurements in the retrieval of liquid water cloud properties, it remains nontrivial to interpret Z due to the possible presence of drizzle droplets within the clouds. So far, there has been no published work that utilizes Z to identify the presence of drizzle above the cloud base in an optimized and a physically consistent manner. In this work, we develop a retrieval technique that exploits the synergy of different remote sensing systems to carry out this task and to subsequently profile the microphysical properties of the cloud and drizzle in a unified framework. This is accomplished by using ground-based measurements of Z, lidar attenuated backscatter below as well as above the cloud base, and microwave brightness temperatures. Fast physical forward models coupled to cloud and drizzle structure parameterization are used in an optimal-estimation-type framework in order to retrieve the best estimate for the cloud and drizzle property profiles. The cloud retrieval is first evaluated using synthetic signals generated from large-eddy simulation (LES) output to verify the forward models used in the retrieval procedure and the vertical parameterization of the liquid water content (LWC). From this exercise it is found that, on average, the cloud properties can be retrieved within 5 % of the mean truth. The full cloud-drizzle retrieval method is then applied to a selected ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques) campaign dataset collected in Cabauw, the Netherlands. An assessment of the retrieval products is performed using three independent methods from the literature; each was specifically developed to retrieve only the cloud properties, the drizzle properties below the cloud base, or the drizzle fraction within the cloud. One-to-one comparisons, taking into account the uncertainties or limitations of each retrieval, show that our results are consistent with what is derived

  12. Atomic oxygen effects on boron nitride and silicon nitride: A comparison of ground based and space flight data

    Science.gov (United States)

    Cross, J. B.; Lan, E. H.; Smith, C. A.; Whatley, W. J.

    1990-01-01

    The effects of atomic oxygen on boron nitride (BN) and silicon nitride (Si3N4) were evaluated in a low Earth orbit (LEO) flight experiment and in a ground based simulation facility. In both the inflight and ground based experiments, these materials were coated on thin (approx. 250A) silver films, and the electrical resistance of the silver was measured in situ to detect any penetration of atomic oxygen through the BN and Si3N4 materials. In the presence of atomic oxygen, silver oxidizes to form silver oxide, which has a much higher electrical resistance than pure silver. Permeation of atomic oxygen through BN, as indicated by an increase in the electrical resistance of the silver underneath, was observed in both the inflight and ground based experiments. In contrast, no permeation of atomic oxygen through Si3N4 was observed in either the inflight or ground based experiments. The ground based results show good qualitative correlation with the LEO flight results, indicating that ground based facilities such as the one at Los Alamos National Lab can reproduce space flight data from LEO.

  13. Polyethylene-reflected plutonium metal sphere : subcritical neutron and gamma measurements.

    Energy Technology Data Exchange (ETDEWEB)

    Mattingly, John K.

    2009-11-01

    Numerous benchmark measurements have been performed to enable developers of neutron transport models and codes to evaluate the accuracy of their calculations. In particular, for criticality safety applications, the International Criticality Safety Benchmark Experiment Program (ICSBEP) annually publishes a handbook of critical and subcritical benchmarks. Relatively fewer benchmark measurements have been performed to validate photon transport models and codes, and unlike the ICSBEP, there is no program dedicated to the evaluation and publication of photon benchmarks. Even fewer coupled neutron-photon benchmarks have been performed. This report documents a coupled neutron-photon benchmark for plutonium metal reflected by polyethylene. A 4.5-kg sphere of ?-phase, weapons-grade plutonium metal was measured in six reflected configurations: (1) Bare; (2) Reflected by 0.5 inch of high density polyethylene (HDPE); (3) Reflected by 1.0 inch of HDPE; (4) Reflected by 1.5 inches of HDPE; (5) Reflected by 3.0 inches of HDPE; and (6) Reflected by 6.0 inches of HDPE. Neutron and photon emissions from the plutonium sphere were measured using three instruments: (1) A gross neutron counter; (2) A neutron multiplicity counter; and (3) A high-resolution gamma spectrometer. This report documents the experimental conditions and results in detail sufficient to permit developers of radiation transport models and codes to construct models of the experiments and to compare their calculations to the measurements. All of the data acquired during this series of experiments are available upon request.

  14. Remote sensing reflectance and inherent optical properties of oceanic waters derived from above-water measurements

    Science.gov (United States)

    Lee, Zhongping; Carder, Kendall L.; Steward, Robert G.; Peacock, Thomas G.; Davis, Curtiss O.; Mueller, James L.

    1997-02-01

    Remote-sensing reflectance and inherent optical properties of oceanic properties of oceanic waters are important parameters for ocean optics. Due to surface reflectance, Rrs or water-leaving radiance is difficult to measure from above the surface. It usually is derived by correcting for the reflected skylight in the measured above-water upwelling radiance using a theoretical Fresnel reflectance value. As it is difficult to determine the reflected skylight, there are errors in the Q and E derived Rrs, and the errors may get bigger for high chl_a coastal waters. For better correction of the reflected skylight,w e propose the following derivation procedure: partition the skylight into Rayleigh and aerosol contributions, remove the Rayleigh contribution using the Fresnel reflectance, and correct the aerosol contribution using an optimization algorithm. During the process, Rrs and in-water inherent optical properties are derived at the same time. For measurements of 45 sites made in the Gulf of Mexico and Arabian Sea with chl_a concentrations ranging from 0.07 to 49 mg/m3, the derived Rrs and inherent optical property values were compared with those from in-water measurements. These results indicate that for the waters studied, the proposed algorithm performs quite well in deriving Rrs and in- water inherent optical properties from above-surface measurements for clear and turbid waters.

  15. Polyethylene-reflected plutonium metal sphere: subcritical neutron and gamma measurements

    International Nuclear Information System (INIS)

    Mattingly, John K.

    2009-01-01

    Numerous benchmark measurements have been performed to enable developers of neutron transport models and codes to evaluate the accuracy of their calculations. In particular, for criticality safety applications, the International Criticality Safety Benchmark Experiment Program (ICSBEP) annually publishes a handbook of critical and subcritical benchmarks. Relatively fewer benchmark measurements have been performed to validate photon transport models and codes, and unlike the ICSBEP, there is no program dedicated to the evaluation and publication of photon benchmarks. Even fewer coupled neutron-photon benchmarks have been performed. This report documents a coupled neutron-photon benchmark for plutonium metal reflected by polyethylene. A 4.5-kg sphere of ?-phase, weapons-grade plutonium metal was measured in six reflected configurations: (1) Bare; (2) Reflected by 0.5 inch of high density polyethylene (HDPE); (3) Reflected by 1.0 inch of HDPE; (4) Reflected by 1.5 inches of HDPE; (5) Reflected by 3.0 inches of HDPE; and (6) Reflected by 6.0 inches of HDPE. Neutron and photon emissions from the plutonium sphere were measured using three instruments: (1) A gross neutron counter; (2) A neutron multiplicity counter; and (3) A high-resolution gamma spectrometer. This report documents the experimental conditions and results in detail sufficient to permit developers of radiation transport models and codes to construct models of the experiments and to compare their calculations to the measurements. All of the data acquired during this series of experiments are available upon request.

  16. Measurement of the acoustic reflectivity of sirenia (Florida manatees) at 171 kHz.

    Science.gov (United States)

    Jaffe, Jules S; Simonet, Fernando; Roberts, Paul L D; Bowles, Ann E

    2007-01-01

    The Florida manatee (Trichechus manatus latirostris) is an endangered sirenian. At present, its adult population (approximately 2200) seems stable, but tenuous. Manatee-boat collisions are a significant proportion (approximately 25%) of mortalities. Here, the potential use of active sonar for detecting manatees by quantifying sonic reflectivity is explored. In order to estimate reflectivity two methods were used. One method measured live reflections from captive animals using a carefully calibrated acoustic and co-registered optical system. The other method consisted of the analysis of animal tissue in order to obtain estimates of the sound speed and density and to predict reflectivity. The impedance measurement predicts that for a lateral view, the tissue reflectivity is close to 0.13, with a critical grazing angle of 28 degrees. Data measured from live animals indicate that substantial reflections can be recorded, however in many instances observed "empirical target strengths" were less than an experimentally dependent -48-dB threshold. Conclusions favor the hypothesis that the animals reflect substantial amounts of sound; however, the reflections can often be specular, and therefore impractical for observation by a manatee detection sonar operating at 171 kHz.

  17. Integrating sphere based reflectance measurements for small-area semiconductor samples

    Science.gov (United States)

    Saylan, S.; Howells, C. T.; Dahlem, M. S.

    2018-05-01

    This article describes a method that enables reflectance spectroscopy of small semiconductor samples using an integrating sphere, without the use of additional optical elements. We employed an inexpensive sample holder to measure the reflectance of different samples through 2-, 3-, and 4.5-mm-diameter apertures and applied a mathematical formulation to remove the bias from the measured spectra caused by illumination of the holder. Using the proposed method, the reflectance of samples fabricated using expensive or rare materials and/or low-throughput processes can be measured. It can also be incorporated to infer the internal quantum efficiency of small-area, research-level solar cells. Moreover, small samples that reflect light at large angles and develop scattering may also be measured reliably, by virtue of an integrating sphere insensitive to directionalities.

  18. Semi-automated high-efficiency reflectivity chamber for vacuum UV measurements

    Science.gov (United States)

    Wiley, James; Fleming, Brian; Renninger, Nicholas; Egan, Arika

    2017-08-01

    This paper presents the design and theory of operation for a semi-automated reflectivity chamber for ultraviolet optimized optics. A graphical user interface designed in LabVIEW controls the stages, interfaces with the detector system, takes semi-autonomous measurements, and monitors the system in case of error. Samples and an optical photodiode sit on an optics plate mounted to a rotation stage in the middle of the vacuum chamber. The optics plate rotates the samples and diode between an incident and reflected position to measure the absolute reflectivity of the samples at wavelengths limited by the monochromator operational bandpass of 70 nm to 550 nm. A collimating parabolic mirror on a fine steering tip-tilt motor enables beam steering for detector peak-ups. This chamber is designed to take measurements rapidly and with minimal oversight, increasing lab efficiency for high cadence and high accuracy vacuum UV reflectivity measurements.

  19. LBA-ECO ND-01 Reflectance and Biophysical Measures, Grass Pastures: Rondonia, Brazil

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set provides the results of spectral reflectance (350 to 2,500 nm at 1-nm increments) and biophysical measurements on grass pastures in eight...

  20. Microwave reflection measurements of the dielectric properties of concrete : final report.

    Science.gov (United States)

    1983-01-01

    The use of microwave reflection measurements to continuously and nondestructively monitor the hydration of concrete is described. The method relies upon the influence of the free-water content on the dielectric properties of the concrete. Use of the ...

  1. Source-driven noise analysis measurements with neptunium metal reflected by high enriched uranium

    International Nuclear Information System (INIS)

    Valentine, Timothy E.; Mattingly, John K.

    2003-01-01

    Subcritical noise analysis measurements have been performed with neptunium ( 237 Np) sphere reflected by highly enriched uranium. These measurements were performed at the Los Alamos Critical Experiment Facility in December 2002 to provide an estimate of the subcriticality of 237 Np reflected by various amounts of high-enriched uranium. This paper provides a description of the measurements and presents some preliminary results of the analysis of the measurements. The measured and calculated spectral ratios differ by 15% whereas the 'interpreted' and calculated k eff values differ by approximately 1%. (author)

  2. 1.06 μm reflectivity measurements of metal optics

    International Nuclear Information System (INIS)

    Saito, T.T.

    1975-01-01

    The equipment and technique for the measurement of 1.06 μm reflectivity of diamond turned, diamond turned/polished, and polished metal mirrors is presented. From an analysis of repeatability and systematic errors it is concluded the precision of the measurements is 0.003 and the accuracy is 0.005. Diamond turned mirrors compete well with the best 1 μm reflectivity values reported and are superior to polished surfaces studied in this work. (U.S.)

  3. Measurement of multilayer mirror reflectivity and stimulated emission in the XUV spectral region

    International Nuclear Information System (INIS)

    Keane, C.; Nam, C.H.; Meixler, L.; Milchberg, H.; Skinner, C.H.; Suckewer, S.; Voorhees, D.; Barbee, T.

    1986-03-01

    We present measurements of multilayer mirror reflectivity and stimulated emission in the XUV spectral region. A molybdenum-silicon multilayer mirror with 12% measured reflectivity at 182 A was found to produce a 120% enhancement of the C VI 182 A line (3 → 2 transition) in a strongly recombining plasma. No such enhancement of the CV 186.7 A line was seen, demonstrating amplification of stimulated emission at 182 A

  4. Dose determination with nitro blue tetrazolium containing radiochromic dye films by measuring absorbed and reflected light

    DEFF Research Database (Denmark)

    Kovács, A.; Baranyai, M.; Wojnárovits, L.

    2000-01-01

    determination in a wide dose range both by absorbance and reflectance measurements. The concept of measuring reflected light from dose labels has been discussed earlier and emerged recently due to the requirement of introducing semiquantitative label dose indicators for quarantine control. The usefulness...... of the method was studied using the newly developed radiochromic dye films as well as already existing ones. (C) 2000 Elsevier Science Ltd. All rights reserved....

  5. Informing hydrological models with ground-based time-lapse relative gravimetry: potential and limitations

    DEFF Research Database (Denmark)

    Bauer-Gottwein, Peter; Christiansen, Lars; Rosbjerg, Dan

    2011-01-01

    parameter uncertainty decreased significantly when TLRG data was included in the inversion. The forced infiltration experiment caused changes in unsaturated zone storage, which were monitored using TLRG and ground-penetrating radar. A numerical unsaturated zone model was subsequently conditioned on both......Coupled hydrogeophysical inversion emerges as an attractive option to improve the calibration and predictive capability of hydrological models. Recently, ground-based time-lapse relative gravity (TLRG) measurements have attracted increasing interest because there is a direct relationship between...

  6. Testing a ground-based canopy model using the wind river canopy crane

    Science.gov (United States)

    Robert Van Pelt; Malcolm P. North

    1999-01-01

    A ground-based canopy model that estimates the volume of occupied space in forest canopies was tested using the Wind River Canopy Crane. A total of 126 trees in a 0.25 ha area were measured from the ground and directly from a gondola suspended from the crane. The trees were located in a low elevation, old-growth forest in the southern Washington Cascades. The ground-...

  7. Determining the influential depth for surface reflectance of sediment by BRDF measurements.

    Science.gov (United States)

    Zhang, H; Voss, K; Reid, R

    2003-10-20

    We measure the Bi-directional reflectance distribution function (BRDF) of ooid sand layers with three particle size distributions (0.5-1mm, 0.25-0.5mm and 0.125-0.25mm) and layer thicknesses on a reflecting mirror to determine the influential depth in the optical region at wavelengths of 658 nm (red), 570 nm (green) and 457 nm (blue). The hemispherical reflectance (albedo) was used as an indicator of BRDF changes between different layers. Measurements are carried out on both dry and water wetted grains. The results indicate that for both dry and wet and all size distributions, the influential depth is at most 2mm.

  8. Diffuse and localized reflectance measurements of hemoglobin and hematocrit in human skin

    Science.gov (United States)

    Khalil, Omar S.; Wu, Xiaomao; Yeh, Shu-Jen; Jeng, Tzyy-Wen

    2001-05-01

    We conducted visible/near infrared optical measurements on the forearm of human subjects using a commercial diffuse reflectance spectrophotometer, and a breadboard temperature- controlled localized reflectance tissue photometer. Calibration relationships were established between skin reflectance signal and reference blood hemoglobin (Hb) concentration, or hematocrit values (Hct). These were then used to predict Hb and Hct values from optical measurement in a cross validation analysis. Different linear least- squares models for the prediction of Hb and Hct are presented and shows the ability to predict both. It was possible to screen prospective blood donors with low Hb concentration. It was possible to predict anemic subjects in the limited prospective blood donor population.

  9. High Angular Resolution Measurements of the Anisotropy of Reflectance of Sea Ice and Snow

    Science.gov (United States)

    Goyens, C.; Marty, S.; Leymarie, E.; Antoine, D.; Babin, M.; Bélanger, S.

    2018-01-01

    We introduce a new method to determine the anisotropy of reflectance of sea ice and snow at spatial scales from 1 m2 to 80 m2 using a multispectral circular fish-eye radiance camera (CE600). The CE600 allows measuring radiance simultaneously in all directions of a hemisphere at a 1° angular resolution. The spectral characteristics of the reflectance and its dependency on illumination conditions obtained from the camera are compared to those obtained with a hyperspectral field spectroradiometer manufactured by Analytical Spectral Device, Inc. (ASD). Results confirm the potential of the CE600, with the suggested measurement setup and data processing, to measure commensurable sea ice and snow hemispherical-directional reflectance factor, HDRF, values. Compared to the ASD, the reflectance anisotropy measured with the CE600 provides much higher resolution in terms of directional reflectance (N = 16,020). The hyperangular resolution allows detecting features that were overlooked using the ASD due to its limited number of measurement angles (N = 25). This data set of HDRF further documents variations in the anisotropy of the reflectance of snow and ice with the geometry of observation and illumination conditions and its spectral and spatial scale dependency. Finally, in order to reproduce the hyperangular CE600 reflectance measurements over the entire 400-900 nm spectral range, a regression-based method is proposed to combine the ASD and CE600 measurements. Results confirm that both instruments may be used in synergy to construct a hyperangular and hyperspectral snow and ice reflectance anisotropy data set.

  10. Very small beam-size measurement by a reflective synchrotron radiation interferometer

    Directory of Open Access Journals (Sweden)

    T. Naito

    2006-12-01

    Full Text Available A synchrotron radiation (SR interferometer with Herschelian reflective optics has been developed for the measurement of beams of several μm in size. In a conventional refractive SR interferometer, the dispersion effect of the objective lens limits the instrument to a smaller range of beam-size measurements. To avoid this problem, we designed a Herschelian arrangement of reflective optics for the interferometer. The effectiveness of the reflective SR interferometer was confirmed at the KEK Accelerator Test Facility (ATF damping ring. The measured vertical beam size obtained using the reflective SR interferometer was 4.7   μm and the estimated vertical emittance was 0.97×10^{-11}   m.

  11. Measurement and modelization of silica opal reflection properties: Optical determination of the silica index

    Science.gov (United States)

    Avoine, Amaury; Hong, Phan Ngoc; Frederich, Hugo; Frigerio, Jean-Marc; Coolen, Laurent; Schwob, Catherine; Nga, Pham Thu; Gallas, Bruno; Maître, Agnès

    2012-10-01

    Self-assembled artificial opals (in particular silica opals) constitute a model system to study the optical properties of three-dimensional photonic crystals. The silica optical index is a key parameter to correctly describe an opal but is difficult to measure at the submicrometer scale and usually treated as a free parameter. Here, we propose a method to extract the silica index from the opal reflection spectra and we validate it by comparison with two independent methods based on infrared measurements. We show that this index gives a correct description of the opal reflection spectra, either by a band structure or by a Bragg approximation. In particular, we are able to provide explanations in quantitative agreement with the measurements for two features : the observation of a second reflection peak in specular direction, and the quasicollapse of the p-polarized main reflection peak at a typical angle of 54∘.

  12. Measurement of integrated coefficients of ultracold neutron reflection from solid surfaces

    International Nuclear Information System (INIS)

    Golikov, V.V.; Kulagin, E.N.; Nikitenko, Yu.V.

    1985-01-01

    The method of measurement of the integrated coefficients of ultracold neutrons (UCN) reflection from solid surfaces is reported. A simple formula is suggested which expresses the integrated coefficients of UCN reflection from a given sample through the measured counting rate of the detector with and without strong absorber (polyethelene). The parameters are determined describing anisotropic and inhomogeneity properties of UCN reflection from Al, Mg, Pb, Zn, Mo, stainless steel, T and V are measured. The thickness of oxide layers is determined within the 5-10A accuracy limits from the experimental coefficients of UCN reflection from metals having on their surfaces the oxides with boundary velocity larger than that for the metal. It has been determined that the density of 5000 A layer of heavy ice freezed on aluminium is 0.83 +- 0.05 from the crystal ice density

  13. Investigation of ground-based microwave radiometer calibration techniques at 530 hPa

    Directory of Open Access Journals (Sweden)

    G. Maschwitz

    2013-10-01

    Full Text Available Ground-based microwave radiometers (MWR are becoming more and more common for remotely sensing the atmospheric temperature and humidity profile as well as path-integrated cloud liquid water content. The calibration accuracy of the state-of-the-art MWR HATPRO-G2 (Humidity And Temperature Profiler – Generation 2 was investigated during the second phase of the Radiative Heating in Underexplored Bands Campaign (RHUBC-II in northern Chile (5320 m above mean sea level, 530 hPa conducted by the Atmospheric Radiation Measurement (ARM program conducted between August and October 2009. This study assesses the quality of the two frequently used liquid nitrogen and tipping curve calibrations by performing a detailed error propagation study, which exploits the unique atmospheric conditions of RHUBC-II. Both methods are known to have open issues concerning systematic offsets and calibration repeatability. For the tipping curve calibration an uncertainty of ±0.1 to ±0.2 K (K-band and ±0.6 to ±0.7 K (V-band is found. The uncertainty in the tipping curve calibration is mainly due to atmospheric inhomogeneities and the assumed air mass correction for the Earth curvature. For the liquid nitrogen calibration the estimated uncertainty of ±0.3 to ±1.6 K is dominated by the uncertainty of the reflectivity of the liquid nitrogen target. A direct comparison between the two calibration techniques shows that for six of the nine channels that can be calibrated with both methods, they agree within the assessed uncertainties. For the other three channels the unexplained discrepancy is below 0.5 K. Systematic offsets, which may cause the disagreement of both methods within their estimated uncertainties, are discussed.

  14. High energy astrophysics with ground-based gamma ray detectors

    International Nuclear Information System (INIS)

    Aharonian, F; Buckley, J; Kifune, T; Sinnis, G

    2008-01-01

    Recent advances in ground-based gamma ray astronomy have led to the discovery of more than 70 sources of very high energy (E γ ≥ 100 GeV) gamma rays, falling into a number of source populations including pulsar wind nebulae, shell type supernova remnants, Wolf-Rayet stars, giant molecular clouds, binary systems, the Galactic Center, active galactic nuclei and 'dark' (yet unidentified) galactic objects. We summarize the history of TeV gamma ray astronomy up to the current status of the field including a description of experimental techniques and highlight recent astrophysical results. We also discuss the potential of ground-based gamma ray astronomy for future discoveries and describe possible directions for future instrumental developments

  15. Ground-based Nuclear Detonation Detection (GNDD) Technology Roadmap

    International Nuclear Information System (INIS)

    Casey, Leslie A.

    2014-01-01

    This GNDD Technology Roadmap is intended to provide guidance to potential researchers and help management define research priorities to achieve technology advancements for ground-based nuclear explosion monitoring science being pursued by the Ground-based Nuclear Detonation Detection (GNDD) Team within the Office of Nuclear Detonation Detection in the National Nuclear Security Administration (NNSA) of the U.S. Department of Energy (DOE). Four science-based elements were selected to encompass the entire scope of nuclear monitoring research and development (R&D) necessary to facilitate breakthrough scientific results, as well as deliver impactful products. Promising future R&D is delineated including dual use associated with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Important research themes as well as associated metrics are identified along with a progression of accomplishments, represented by a selected bibliography, that are precursors to major improvements to nuclear explosion monitoring.

  16. Ground-based Nuclear Detonation Detection (GNDD) Technology Roadmap

    Energy Technology Data Exchange (ETDEWEB)

    Casey, Leslie A.

    2014-01-13

    This GNDD Technology Roadmap is intended to provide guidance to potential researchers and help management define research priorities to achieve technology advancements for ground-based nuclear explosion monitoring science being pursued by the Ground-based Nuclear Detonation Detection (GNDD) Team within the Office of Nuclear Detonation Detection in the National Nuclear Security Administration (NNSA) of the U.S. Department of Energy (DOE). Four science-based elements were selected to encompass the entire scope of nuclear monitoring research and development (R&D) necessary to facilitate breakthrough scientific results, as well as deliver impactful products. Promising future R&D is delineated including dual use associated with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Important research themes as well as associated metrics are identified along with a progression of accomplishments, represented by a selected bibliography, that are precursors to major improvements to nuclear explosion monitoring.

  17. 3D shape measurement of automotive glass by using a fringe reflection technique

    Science.gov (United States)

    Skydan, O. A.; Lalor, M. J.; Burton, D. R.

    2007-01-01

    In automotive and glass making industries, there is a need for accurately measuring the 3D shapes of reflective surfaces to speed up and ensure product development and manufacturing quality by using non-contact techniques. This paper describes a technique for the measurement of non-full-field reflective surfaces of automotive glass by using a fringe reflection technique. Physical properties of the measurement surfaces do not allow us to apply optical geometries used in existing techniques for surface measurement based upon direct fringe pattern illumination. However, this property of surface reflectivity can be used to implement similar ideas from existing techniques in a new improved method. In other words, the reflective surface can be used as a mirror to reflect illuminated fringe patterns onto a screen behind. It has been found that in the case of implementing the reflective fringe technique, the phase-shift distribution depends not only on the height of the object but also on the slope at each measurement point. This requires the solving of differential equations to find the surface slope and height distributions in the x and y directions and development of the additional height reconstruction algorithms. The main focus has been made on developing a mathematical model of the optical sub-system and discussing ways for its practical implementation including calibration procedures. A number of implemented image processing algorithms for system calibration and data analysis are discussed and two experimental results are given for automotive glass surfaces with different shapes and defects. The proposed technique showed the ability to provide accurate non-destructive measurement of 3D shapes of the reflective automotive glass surfaces and can be used as a key element for a glass shape quality control system on-line or in a laboratory environment.

  18. Automatic Barometric Updates from Ground-Based Navigational Aids

    Science.gov (United States)

    1990-03-12

    ro fAutomatic Barometric Updates US Department from of Transportation Ground-Based Federal Aviation Administration Navigational Aids Office of Safety...tighter vertical spacing controls , particularly for operations near Terminal Control Areas (TCAs), Airport Radar Service Areas (ARSAs), military climb and...E.F., Ruth, J.C., and Williges, B.H. (1987). Speech Controls and Displays. In Salvendy, G., E. Handbook of Human Factors/Ergonomics, New York, John

  19. Silicon carbide optics for space and ground based astronomical telescopes

    Science.gov (United States)

    Robichaud, Joseph; Sampath, Deepak; Wainer, Chris; Schwartz, Jay; Peton, Craig; Mix, Steve; Heller, Court

    2012-09-01

    Silicon Carbide (SiC) optical materials are being applied widely for both space based and ground based optical telescopes. The material provides a superior weight to stiffness ratio, which is an important metric for the design and fabrication of lightweight space telescopes. The material also has superior thermal properties with a low coefficient of thermal expansion, and a high thermal conductivity. The thermal properties advantages are important for both space based and ground based systems, which typically need to operate under stressing thermal conditions. The paper will review L-3 Integrated Optical Systems - SSG’s (L-3 SSG) work in developing SiC optics and SiC optical systems for astronomical observing systems. L-3 SSG has been fielding SiC optical components and systems for over 25 years. Space systems described will emphasize the recently launched Long Range Reconnaissance Imager (LORRI) developed for JHU-APL and NASA-GSFC. Review of ground based applications of SiC will include supporting L-3 IOS-Brashear’s current contract to provide the 0.65 meter diameter, aspheric SiC secondary mirror for the Advanced Technology Solar Telescope (ATST).

  20. Validation of CALIPSO space-borne-derived attenuated backscatter coefficient profiles using a ground-based lidar in Athens, Greece

    Directory of Open Access Journals (Sweden)

    R. E. Mamouri

    2009-09-01

    Full Text Available We present initial aerosol validation results of the space-borne lidar CALIOP -onboard the CALIPSO satellite- Level 1 attenuated backscatter coefficient profiles, using coincident observations performed with a ground-based lidar in Athens, Greece (37.9° N, 23.6° E. A multi-wavelength ground-based backscatter/Raman lidar system is operating since 2000 at the National Technical University of Athens (NTUA in the framework of the European Aerosol Research LIdar NETwork (EARLINET, the first lidar network for tropospheric aerosol studies on a continental scale. Since July 2006, a total of 40 coincidental aerosol ground-based lidar measurements were performed over Athens during CALIPSO overpasses. The ground-based measurements were performed each time CALIPSO overpasses the station location within a maximum distance of 100 km. The duration of the ground–based lidar measurements was approximately two hours, centred on the satellite overpass time. From the analysis of the ground-based/satellite correlative lidar measurements, a mean bias of the order of 22% for daytime measurements and of 8% for nighttime measurements with respect to the CALIPSO profiles was found for altitudes between 3 and 10 km. The mean bias becomes much larger for altitudes lower that 3 km (of the order of 60% which is attributed to the increase of aerosol horizontal inhomogeneity within the Planetary Boundary Layer, resulting to the observation of possibly different air masses by the two instruments. In cases of aerosol layers underlying Cirrus clouds, comparison results for aerosol tropospheric profiles become worse. This is attributed to the significant multiple scattering effects in Cirrus clouds experienced by CALIPSO which result in an attenuation which is less than that measured by the ground-based lidar.

  1. On the Meaning of Formative Measurement and How It Differs from Reflective Measurement: Comment on Howell, Breivik, and Wilcox (2007)

    Science.gov (United States)

    Bagozzi, Richard P.

    2007-01-01

    D. Howell, E. Breivik, and J. B. Wilcox (2007) have presented an important and interesting analysis of formative measurement and have recommended that researchers abandon such an approach in favor of reflective measurement. The author agrees with their recommendations but disagrees with some of the bases for their conclusions. He suggests that…

  2. Effects of phase change on reflection in phase-measuring interference microscopy

    OpenAIRE

    Dubois , Arnaud

    2004-01-01

    International audience; We show by analytical and numerical calculations that the phase change on reflection that occurs in interference microscopy is almost independent of the numerical aperture of the objective. The shift of the microscope interferogram response due to the phase change on reflection, however, increases with the numerical aperture. Measurements of the interferogram shift are made with a Linnik interference microscope equipped with various numerical-aperture objectives and ar...

  3. Density-independent algorithm for sensing moisture content of sawdust based on reflection measurements

    Science.gov (United States)

    A density-independent algorithm for moisture content determination in sawdust, based on a one-port reflection measurement technique is proposed for the first time. Performance of this algorithm is demonstrated through measurement of the dielectric properties of sawdust with an open-ended haft-mode s...

  4. Assessment of NASA airborne laser altimetry data using ground-based GPS data near Summit Station, Greenland

    Science.gov (United States)

    Brunt, Kelly M.; Hawley, Robert L.; Lutz, Eric R.; Studinger, Michael; Sonntag, John G.; Hofton, Michelle A.; Andrews, Lauren C.; Neumann, Thomas A.

    2017-03-01

    A series of NASA airborne lidars have been used in support of satellite laser altimetry missions. These airborne laser altimeters have been deployed for satellite instrument development, for spaceborne data validation, and to bridge the data gap between satellite missions. We used data from ground-based Global Positioning System (GPS) surveys of an 11 km long track near Summit Station, Greenland, to assess the surface-elevation bias and measurement precision of three airborne laser altimeters including the Airborne Topographic Mapper (ATM), the Land, Vegetation, and Ice Sensor (LVIS), and the Multiple Altimeter Beam Experimental Lidar (MABEL). Ground-based GPS data from the monthly ground-based traverses, which commenced in 2006, allowed for the assessment of nine airborne lidar surveys associated with ATM and LVIS between 2007 and 2016. Surface-elevation biases for these altimeters - over the flat, ice-sheet interior - are less than 0.12 m, while assessments of measurement precision are 0.09 m or better. Ground-based GPS positions determined both with and without differential post-processing techniques provided internally consistent solutions. Results from the analyses of ground-based and airborne data provide validation strategy guidance for the Ice, Cloud, and land Elevation Satellite 2 (ICESat-2) elevation and elevation-change data products.

  5. Applying measured reflection from the ground to simulations of thermal perfromance of solar collectors

    DEFF Research Database (Denmark)

    Dragsted, Janne; Furbo, Simon

    2009-01-01

    representation of the reflection from the ground. In this study a more accurate description of the albedo is obtained based on detailed measurements from a solar hat, installed at ASIAQ’s climate station in Sisimiut, Greenland. The solar hat measures the global radiation on horizontal, the total radiation......Solar radiation on tilted and vertical surfaces in the Arctic is, in large parts of the year, strongly influenced by reflection from snow. In connection with planning and optimization of energy efficient buildings and solar energy systems in the Arctic, it is important to have an accurate...... on vertical surfaces facing north, south, east and west, and radiation reflected from the ground on vertical surfaces facing north, south, east and west. Based on measured data from 2004-2007 the albedo is determined for each month of the year as a function of the difference between the solar azimuth...

  6. Detection of greenbug infestation on wheat using ground-based radiometry

    Science.gov (United States)

    Yang, Zhiming

    Scope of methods of study. The purpose of this greenhouse study was to characterize stress in wheat caused by greenbugs using ground-based radiometry. Experiments were conducted to (a) identify spectral bands and vegetation indices sensitive to greenbug infestation; (b) differentiate stress caused due to greenbugs from water stress; (c) examine the impacts of plant growth stage on detection of greenbug infestation; and (d) compare infestations due to greenbug and Russian wheat aphid. Wheat (variety-TAM 107) was planted (seed spacing 1 in. x 3 in.) in plastic flats with dimension 24 in. x 16 in. x 8.75 in. Fifteen days after sowing, wheat seedlings were infested with greenbugs (biotype-E). Nadir measurement of canopy reflectance started the day after infestation and lasted until most infested plants were dead. Using a 16-band Cropscan radiometer, spectral reflectance data were collected daily (between 13:00--14:00 hours) and 128 vegetation indices were derived in addition to greenbug counts per tiller. Using SAS PROC MIXED, sensitivity of band and vegetation indices was identified based on Threshold Day. Subsequent to Threshold Day there was a consistent significant spectral difference between control and infested plants. Sensitivity of band and vegetation indices was further examined using correlation and relative sensitivity analyses. Findings and conclusions. Results show that it is possible to detect greenbug-induced stress on wheat using hand-held radiometers, such as Cropscan. Band 694 nm and the ratio-based vegetation index (RVI) derived from the band 694 nm and 800 nm were identified as most sensitive to greenbug infestation. Landsat TM bands and their derived vegetation indices also show potential for detecting wheat stress caused by greenbug infestation. Also, RVIs particularly derived using spectral band 694 nm and 800 nm were found useful in differentiating greenbug infestation from water stress. Furthermore, vegetation indices such as Normalized total

  7. Implant Monitoring Measurements On Ultra Shallow Implants Before And After Anneal Using Photomodulated Reflection And Junction Photovoltage Measurement Techniques

    Science.gov (United States)

    Tallian, M.; Pap, A.; Mocsar, K.; Somogyi, A.; Nadudvari, Gy.; Kosztka, D.; Pavelka, T.

    2011-01-01

    Ultra shallow junctions are becoming widely used in the micro- and nanoelectronic devices, and novel measurement methods are needed to monitor the manufacturing processes. Photomodulated Reflection measurements before anneal and Junction Photovoltage-based sheet resistance measurements after anneal are non-contact, nondestructive techniques suitable for characterizing both the implantation and the annealing process. Tests verify that these methods are consistent with each other and by using them together, defects originating in the implantation and anneal steps can be separated.

  8. Modeling the effect of reflection from metallic walls on spectroscopic measurements

    International Nuclear Information System (INIS)

    Zastrow, K.-D.; Keatings, S. R.; O'Mullane, M. G.; Marot, L.; Temmerman, G. de

    2008-01-01

    A modification of JET is presently being prepared to bring operational experience with ITER-like first wall (Be) and divertor (W) materials, geometry and plasma parameters. Reflectivity measurements of JET sample tiles have been performed and the data are used within a simplified model of the JET and ITER vessels to predict additional contributions to quantitative spectroscopic measurements. The most general method to characterize reflectivity is the bidirectional reflection distribution function (BRDF). For extended sources however, such as bremsstrahlung and edge emission of fuel and intrinsic impurities, the results obtained in the modeling are almost as accurate if the total reflectivity with ideal Lambertian angular dependence is used. This is in contrast to the experience in other communities, such as optical design, lighting design, or rendering who deal mostly with pointlike light sources. This result is so far based on a very limited set of measurements and will be reassessed when more detailed BRDF measurements of JET tiles have been made. If it is true it offers the possibility of in situ monitoring of the reflectivity of selected parts of the wall during exposure to plasma operation, while remeasurement of the BRDF is performed during interventions. For a closed vessel structure such as ITER, it is important to consider multiple reflections. This makes it more important to represent the whole of the vessel reasonably accurately in the model, which on the other hand is easier to achieve than for the more complex internal structure of JET. In both cases the dominant contribution is from the first reflection, and a detailed model of the areas intersected by lines of sight of diagnostic interest is required.

  9. Reflectance Measures from Infant Ears With Normal Hearing and Transient Conductive Hearing Loss.

    Science.gov (United States)

    Voss, Susan E; Herrmann, Barbara S; Horton, Nicholas J; Amadei, Elizabeth A; Kujawa, Sharon G

    2016-01-01

    The objective is to develop methods to utilize newborn reflectance measures for the identification of middle-ear transient conditions (e.g., middle-ear fluid) during the newborn period and ultimately during the first few months of life. Transient middle-ear conditions are a suspected source of failure to pass a newborn hearing screening. The ability to identify a conductive loss during the screening procedure could enable the referred ear to be either (1) cleared of a middle-ear condition and recommended for more extensive hearing assessment as soon as possible, or (2) suspected of a transient middle-ear condition, and if desired, be rescreened before more extensive hearing assessment. Reflectance measurements are reported from full-term, healthy, newborn babies in which one ear referred and one ear passed an initial auditory brainstem response newborn hearing screening and a subsequent distortion product otoacoustic emission screening on the same day. These same subjects returned for a detailed follow-up evaluation at age 1 month (range 14 to 35 days). In total, measurements were made on 30 subjects who had a unilateral refer near birth (during their first 2 days of life) and bilateral normal hearing at follow-up (about 1 month old). Three specific comparisons were made: (1) Association of ear's state with power reflectance near birth (referred versus passed ear), (2) Changes in power reflectance of normal ears between newborn and 1 month old (maturation effects), and (3) Association of ear's newborn state (referred versus passed) with ear's power reflectance at 1 month. In addition to these measurements, a set of preliminary data selection criteria were developed to ensure that analyzed data were not corrupted by acoustic leaks and other measurement problems. Within 2 days of birth, the power reflectance measured in newborn ears with transient middle-ear conditions (referred newborn hearing screening and passed hearing assessment at age 1 month) was significantly

  10. Measurement of multilayer reflectivities from 8 keV to 130 keV

    DEFF Research Database (Denmark)

    Hoeghoej, P.; Joensen, K. D.; Christensen, Finn Erland

    1993-01-01

    This paper presents measurements of specular and non-specular reflectivities of a W/Si multilayer with period d=135.1 A. Angular dispersive measurements were performed at 8.05 keY and 59.3 keY, while energy dispersive measurements were made in the range of 17 keV to 130 keY. At an incidence angle...

  11. State-dependent cellular activity patterns of the cat paraventricular hypothalamus measured by reflectance imaging

    DEFF Research Database (Denmark)

    Kristensen, Morten Pilgaard; Rector, D M; Poe, G R

    1996-01-01

    Activity within the cat paraventricular hypothalamus (PVH) during sleep and waking states was measured by quantifying intrinsic tissue reflectivity. A fiber optic probe consisting of a 1.0 mm coherent image conduit, surrounded by plastic fibers which conducted 660 nm source light, was attached...... to a charge-coupled device camera, and positioned over the PVH in five cats. Electrodes for assessing state variables, including electroencephalographic activity, eye movement, and somatic muscle tone were also placed. After surgical recovery, reflected light intensity was measured continuously at 2.5 Hz...

  12. Remote sensing of high-latitude ionization profiles by ground-based and spaceborne instrumentation

    International Nuclear Information System (INIS)

    Vondrak, R.R.

    1981-01-01

    Ionospheric specification and modeling are now largely based on data provided by active remote sensing with radiowave techniques (ionosondes, incoherent-scatter radars, and satellite beacons). More recently, passive remote sensing techniques have been developed that can be used to monitor quantitatively the spatial distribution of high-latitude E-region ionization. These passive methods depend on the measurement, or inference, of the energy distribution of precipitating kilovolt electrons, the principal source of the nighttime E-region at high latitudes. To validate these techniques, coordinated measurements of the auroral ionosphere have been made with the Chatanika incoherent-scatter radar and a variety of ground-based and spaceborne sensors

  13. Standardization of reflectance measurements in dispersed organic matter: results of an exercise to improve interlaboratory agreement

    Science.gov (United States)

    Hackley, Paul C.; Araujo, Carla Viviane; Borrego, Angeles G.; Bouzinos, Antonis; Cardott, Brian; Cook, Alan C.; Eble, Cortland; Flores, Deolinda; Gentzis, Thomas; Gonçalves, Paula Alexandra; Filho, João Graciano Mendonça; Hámor-Vidó, Mária; Jelonek, Iwona; Kommeren, Kees; Knowles, Wayne; Kus, Jolanta; Mastalerz, Maria; Menezes, Taíssa Rêgo; Newman, Jane; Pawlewicz, Mark; Pickel, Walter; Potter, Judith; Ranasinghe, Paddy; Read, Harold; Reyes, Julito; Rodriguez, Genaro De La Rosa; de Souza, Igor Viegas Alves Fernandes; Suarez-Ruiz, Isabel; Sýkorová, Ivana; Valentine, Brett J.

    2015-01-01

    Vitrinite reflectance generally is considered the most robust thermal maturity parameter available for application to hydrocarbon exploration and petroleum system evaluation. However, until 2011 there was no standardized methodology available to provide guidelines for vitrinite reflectance measurements in shale. Efforts to correct this deficiency resulted in publication of ASTM D7708: Standard test method for microscopical determination of the reflectance of vitrinite dispersed in sedimentary rocks. In 2012-2013, an interlaboratory exercise was conducted to establish precision limits for the D7708 measurement technique. Six samples, representing a wide variety of shale, were tested in duplicate by 28 analysts in 22 laboratories from 14 countries. Samples ranged from immature to overmature (0.31-1.53% Ro), from organic-lean to organic-rich (1-22 wt.% total organic carbon), and contained Type I (lacustrine), Type II (marine), and Type III (terrestrial) kerogens. Repeatability limits (maximum difference between valid repetitive results from same operator, same conditions) ranged from 0.03-0.11% absolute reflectance, whereas reproducibility limits (maximum difference between valid results obtained on same test material by different operators, different laboratories) ranged from 0.12-0.54% absolute reflectance. Repeatability and reproducibility limits degraded consistently with increasing maturity and decreasing organic content. However, samples with terrestrial kerogens (Type III) fell off this trend, showing improved levels of reproducibility due to higher vitrinite content and improved ease of identification. Operators did not consistently meet the reporting requirements of the test method, indicating that a common reporting template is required to improve data quality. The most difficult problem encountered was the petrographic distinction of solid bitumens and low-reflecting inert macerals from vitrinite when vitrinite occurred with reflectance ranges overlapping

  14. Seasonal variations of leaf and canopy properties tracked by ground-based NDVI imagery in a temperate forest.

    Science.gov (United States)

    Yang, Hualei; Yang, Xi; Heskel, Mary; Sun, Shucun; Tang, Jianwu

    2017-04-28

    Changes in plant phenology affect the carbon flux of terrestrial forest ecosystems due to the link between the growing season length and vegetation productivity. Digital camera imagery, which can be acquired frequently, has been used to monitor seasonal and annual changes in forest canopy phenology and track critical phenological events. However, quantitative assessment of the structural and biochemical controls of the phenological patterns in camera images has rarely been done. In this study, we used an NDVI (Normalized Difference Vegetation Index) camera to monitor daily variations of vegetation reflectance at visible and near-infrared (NIR) bands with high spatial and temporal resolutions, and found that the infrared camera based NDVI (camera-NDVI) agreed well with the leaf expansion process that was measured by independent manual observations at Harvard Forest, Massachusetts, USA. We also measured the seasonality of canopy structural (leaf area index, LAI) and biochemical properties (leaf chlorophyll and nitrogen content). We found significant linear relationships between camera-NDVI and leaf chlorophyll concentration, and between camera-NDVI and leaf nitrogen content, though weaker relationships between camera-NDVI and LAI. Therefore, we recommend ground-based camera-NDVI as a powerful tool for long-term, near surface observations to monitor canopy development and to estimate leaf chlorophyll, nitrogen status, and LAI.

  15. Ground-based Polarization Remote Sensing of Atmospheric Aerosols and the Correlation between Polarization Degree and PM2.5

    International Nuclear Information System (INIS)

    Cheng, Chen; Zhengqiang, Li; Weizhen, Hou; Yisong, Xie; Donghui, Li; Kaitao, Li; Ying, Zhang

    2014-01-01

    The ground-based polarization remote sensing adds the polarization dimension information to traditional intensity detection, which provides a new method to detect atmospheric aerosols properties. In this paper, the polarization measurements achieved by a new multi-wavelength sun photometer, CE318-DP, are used for the ground-based remote sensing of atmospheric aerosols. In addition, a polarized vector radiative transfer model is introduced to simulate the DOLP (Degree Of Linear Polarization) under different sky conditions. At last, the correlative analysis between mass density of PM 2.5 and multi-wavelength and multi-angular DOLP is carried out. The result shows that DOLP has a high correlation with mass density of PM 2.5 , R 2 >0.85. As a consequence, this work provides a new method to estimate the mass density of PM 2.5 by using the comprehensive network of ground-based sun photometer

  16. Strong Sporadic E Occurrence Detected by Ground-Based GNSS

    Science.gov (United States)

    Sun, Wenjie; Ning, Baiqi; Yue, Xinan; Li, Guozhu; Hu, Lianhuan; Chang, Shoumin; Lan, Jiaping; Zhu, Zhengping; Zhao, Biqiang; Lin, Jian

    2018-04-01

    The ionospheric sporadic E (Es) layer has significant impact on radio wave propagation. The traditional techniques employed for Es layer observation, for example, ionosondes, are not dense enough to resolve the morphology and dynamics of Es layer in spatial distribution. The ground-based Global Navigation Satellite Systems (GNSS) technique is expected to shed light on the understanding of regional strong Es occurrence, owing to the facts that the critical frequency (foEs) of strong Es structure is usually high enough to cause pulse-like disturbances in GNSS total electron content (TEC), and a large number of GNSS receivers have been deployed all over the world. Based on the Chinese ground-based GNSS networks, including the Crustal Movement Observation Network of China and the Beidou Ionospheric Observation Network, a large-scale strong Es event was observed in the middle latitude of China. The strong Es shown as a band-like structure in the southwest-northeast direction extended more than 1,000 km. By making a comparative analysis of Es occurrences identified from the simultaneous observations by ionosondes and GNSS TEC receivers over China middle latitude statistically, we found that GNSS TEC can be well employed to observe strong Es occurrence with a threshold value of foEs, 14 MHz.

  17. Reflectance measurements of leaves for detecting visible and non-visible ozon damage to crops

    International Nuclear Information System (INIS)

    Kraft, M.; Weigel, H.-J.; Mejer, G.-J.; Brandes, F.

    1996-01-01

    Spring wheat (Triticum aestivum cv. Turbo), white clover (Trifolium repens cv. Karina) and maize (Zea mays cv. Bonny) plants were exposed for 20–30 days in open top chambers to charcoal-filtered air (CF, control) and CF air supplied with O 3 for 8–12 h/per day in the concentration range of 180–240 μg O 3 /m 3 (8–12 h/day treatment mean). At the end of the O 3 treatment spectral reflectance measurements were made on single leaves of all 3 species and on canopies of wheat and clover using a CCD (Charged Coupled Device) camera and wavelength filters with 11 wavelength bands ranging from 450 nm to 950 nm. Different vegetation indices such as the normalized difference vegetation index (NDVI) and the ≪main inflection point≫ (MIP) were calculated. Based on these results it was shown that visible O 3 damages were correlated to the spectral reflectance changes: Both leaves and canopies showed an increased reflectance of visible light after ozone treatment. While clover and maize leaves as well as clover and wheat canopies showed a decreased near infrared (NIR) reflectance, the NIR reflectance of wheat leaves did not change, even if the leaves had visible symptoms. A decreased infrared reflectance was detectable for all clover leaves after O 3 treatment although for part of the leaves no visible foliar damage symptoms could be observed

  18. A comparison of hair colour measurement by digital image analysis with reflective spectrophotometry.

    Science.gov (United States)

    Vaughn, Michelle R; van Oorschot, Roland A H; Baindur-Hudson, Swati

    2009-01-10

    While reflective spectrophotometry is an established method for measuring macroscopic hair colour, it can be cumbersome to use on a large number of individuals and not all reflective spectrophotometry instruments are easily portable. This study investigates the use of digital photographs to measure hair colour and compares its use to reflective spectrophotometry. An understanding of the accuracy of colour determination by these methods is of relevance when undertaking specific investigations, such as those on the genetics of hair colour. Measurements of hair colour may also be of assistance in cases where a photograph is the only evidence of hair colour available (e.g. surveillance). Using the CIE L(*)a(*)b(*) colour space, the hair colour of 134 individuals of European ancestry was measured by both reflective spectrophotometry and by digital image analysis (in V++). A moderate correlation was found along all three colour axes, with Pearson correlation coefficients of 0.625, 0.593 and 0.513 for L(*), a(*) and b(*) respectively (p-values=0.000), with means being significantly overestimated by digital image analysis for all three colour components (by an average of 33.42, 3.38 and 8.00 for L(*), a(*) and b(*) respectively). When using digital image data to group individuals into clusters previously determined by reflective spectrophotometric analysis using a discriminant analysis, individuals were classified into the correct clusters 85.8% of the time when there were two clusters. The percentage of cases correctly classified decreases as the number of clusters increases. It is concluded that, although more convenient, hair colour measurement from digital images has limited use in situations requiring accurate and consistent measurements.

  19. A fiber-coupled displacement measuring interferometer for determination of the posture of a reflective surface

    International Nuclear Information System (INIS)

    Mao, Shuai; Hu, Peng-Cheng; Ding, Xue-Mei; Tan, Jiu-Bin

    2016-01-01

    A fiber-coupled displacement measuring interferometer capable of determining of the posture of a reflective surface of a measuring mirror is proposed. The newly constructed instrument combines fiber-coupled displacement and angular measurement technologies. The proposed interferometer has advantages of both the fiber-coupled and the spatially beam-separated interferometer. A portable dual-position sensitive detector (PSD)-based unit within this proposed interferometer measures the parallelism of the two source beams to guide the fiber-coupling adjustment. The portable dual PSD-based unit measures not only the pitch and yaw of the retro-reflector but also measures the posture of the reflective surface. The experimental results of displacement calibration show that the deviations between the proposed interferometer and a reference one, Agilent 5530, at two different common beam directions are both less than ±35 nm, thus verifying the effectiveness of the beam parallelism measurement. The experimental results of angular calibration show that deviations of pitch and yaw with the auto-collimator (as a reference) are less than ±2 arc sec, thus proving the proposed interferometer’s effectiveness for determination of the posture of a reflective surface.

  20. Release path temperatures of shock-compressed tin from dynamic reflectance and radiance measurements

    Energy Technology Data Exchange (ETDEWEB)

    La Lone, B. M., E-mail: lalonebm@nv.doe.gov; Stevens, G. D.; Turley, W. D. [National Security Technologies, LLC, Special Technologies Laboratory, Santa Barbara, California 93111 (United States); Holtkamp, D. B. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Iverson, A. J. [National Security Technologies, LLC, Los Alamos Operations, Los Alamos, New Mexico 87544 (United States); Hixson, R. S.; Veeser, L. R. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); National Security Technologies, LLC, Los Alamos Operations, Los Alamos, New Mexico 87544 (United States)

    2013-08-14

    Dynamic reflectance and radiance measurements were conducted for tin samples shock compressed to 35 GPa and released to 15 GPa using high explosives. We determined the reflectance of the tin samples glued to lithium fluoride windows using an integrating sphere with an internal xenon flashlamp as an illumination source. The dynamic reflectance (R) was determined at near normal incidence in four spectral bands with coverage in visible and near-infrared spectra. Uncertainties in R/R{sub 0} are <2%, and uncertainties in absolute reflectance are <5%. In complementary experiments, thermal radiance from the tin/glue/lithium fluoride interface was recorded with similar shock stress and spectral coverage as the reflectance measurements. The two sets of experiments were combined to obtain the temperature history of the tin surface with an uncertainty of <2%. The stress at the interface was determined from photonic Doppler velocimetry and combined with the temperatures to obtain temperature-stress release paths for tin. We discuss the relationship between the experimental release paths and release isentropes that begin on the principal shock Hugoniot.

  1. Retrieval of optical properties of skin from measurement and modeling the diffuse reflectance

    Science.gov (United States)

    Douven, Lucien F. A.; Lucassen, Gerald W.

    2000-06-01

    We present results on the retrieval of skin optical properties obtained by fitting of measurements of the diffuse reflectance of human skin. Reflectance spectra are simulated using an analytical model based on the diffusion approximation. This model is implemented in a simplex fit routine. The skin optical model used consists of five layers representing epidermis, capillary blood plexus, dermis, deep blood plexus and hypodermis. The optical properties of each layer are assumed homogeneously distributed. The main optical absorbers included are melanin in epidermis and blood. The experimental setup consists of a HP photospectrometer equipped with a remote fiber head. Total reflectance spectra were measured in the 400 - 820 nm wavelength range on the volar underarm of 19 volunteers under various conditions influencing the blood content and oxygenation degree. Changes in the reflectance spectra were observed. Using the fit routine changes in blood content in the capillary blood plexus and in the deep blood plexus could be quantified. These showed different influences on the total reflectance. The method can be helpful to quantitatively assess changes in skin color appearance such as occurs in the treatment of port wine stains, blanching, skin irritation and tanning.

  2. Polarised Multiangular Reflectance Measurements Using the Finnish Geodetic Institute Field Goniospectrometer

    Directory of Open Access Journals (Sweden)

    Jouni Peltoniemi

    2009-05-01

    Full Text Available The design, operation, and properties of the Finnish Geodetic Institute Field Goniospectrometer (FIGIFIGO are presented. FIGIFIGO is a portable instrument for the measurement of surface Bidirectional Reflectance Factor (BRF for samples with diameters of 10 – 50 cm. A set of polarising optics enable the measurement of linearly polarised BRF over the full solar spectrum (350 – 2,500 nm. FIGIFIGO is designed mainly for field operation using sunlight, but operation in a laboratory environment is also possible. The acquired BRF have an accuracy of 1 – 5% depending on wavelength, sample properties, and measurement conditions. The angles are registered at accuracies better than 2°. During 2004 – 2008, FIGIFIGO has been used in the measurement of over 150 samples, all around northern Europe. The samples concentrate mostly on boreal forest understorey, snow, urban surfaces, and reflectance calibration surfaces.

  3. Measurement of collisional self broadening of atomic resonance lines in selective reflection experiment

    International Nuclear Information System (INIS)

    Papoyan, A.V.

    1998-01-01

    A method is developed to measure directly the collisional self broadening rate for a dense atomic vapor from selective reflection spectra. Experimental realization for the atomic D 1 and D 2 resonance lines of Rb confirms a validity of the proposed technique. The deflection of experimentally measured values is not more than 20% from theoretically predicted ones in the atomic number density range of 7· 10 16 - 7· 10 17 cm - 3 . 10 refs

  4. Simulation study of the aerosol information content in OMI spectral reflectance measurements

    Directory of Open Access Journals (Sweden)

    B. Veihelmann

    2007-06-01

    Full Text Available The Ozone Monitoring Instrument (OMI is an imaging UV-VIS solar backscatter spectrometer and is designed and used primarily to retrieve trace gases like O3 and NO2 from the measured Earth reflectance spectrum in the UV-visible (270–500 nm. However, also aerosols are an important science target of OMI. The multi-wavelength algorithm is used to retrieve aerosol parameters from OMI spectral reflectance measurements in up to 20 wavelength bands. A Principal Component Analysis (PCA is performed to quantify the information content of OMI reflectance measurements on aerosols and to assess the capability of the multi-wavelength algorithm to discern various aerosol types. This analysis is applied to synthetic reflectance measurements for desert dust, biomass burning aerosols, and weakly absorbing anthropogenic aerosol with a variety of aerosol optical thicknesses, aerosol layer altitudes, refractive indices and size distributions. The range of aerosol parameters considered covers the natural variability of tropospheric aerosols. This theoretical analysis is performed for a large number of scenarios with various geometries and surface albedo spectra for ocean, soil and vegetation. When the surface albedo spectrum is accurately known and clouds are absent, OMI reflectance measurements have 2 to 4 degrees of freedom that can be attributed to aerosol parameters. This information content depends on the observation geometry and the surface albedo spectrum. An additional wavelength band is evaluated, that comprises the O2-O2 absorption band at a wavelength of 477 nm. It is found that this wavelength band adds significantly more information than any other individual band.

  5. Methane Emissions from Bangladesh: Bridging the Gap Between Ground-based and Space-borne Estimates

    Science.gov (United States)

    Peters, C.; Bennartz, R.; Hornberger, G. M.

    2015-12-01

    Gaining an understanding of methane (CH4) emission sources and atmospheric dispersion is an essential part of climate change research. Large-scale and global studies often rely on satellite observations of column CH4 mixing ratio whereas high-spatial resolution estimates rely on ground-based measurements. Extrapolation of ground-based measurements on, for example, rice paddies to broad region scales is highly uncertain because of spatio-temporal variability. We explore the use of ground-based river stage measurements and independent satellite observations of flooded area along with satellite measurements of CH4 mixing ratio to estimate the extent of methane emissions. Bangladesh, which comprises most of the Ganges Brahmaputra Meghna (GBM) delta, is a region of particular interest for studying spatio-temporal variation of methane emissions due to (1) broadscale rice cultivation and (2) seasonal flooding and atmospheric convection during the monsoon. Bangladesh and its deltaic landscape exhibit a broad range of environmental, economic, and social circumstances that are relevant to many nations in South and Southeast Asia. We explore the seasonal enhancement of CH4 in Bangladesh using passive remote sensing spectrometer CH4 products from the SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) and the Atmospheric Infrared Sounder (AIRS). The seasonal variation of CH4 is compared to independent estimates of seasonal flooding from water gauge stations and space-based passive microwave water-to-land fractions from the Tropical Rainfall Measuring Mission Microwave Imager (TRMM-TMI). Annual cycles in inundation (natural and anthropogenic) and atmospheric CH4 concentrations show highly correlated seasonal signals. NOAA's HYSPLIT model is used to determine atmospheric residence time of ground CH4 fluxes. Using the satellite observations, we can narrow the large uncertainty in extrapolation of ground-based CH4 emission estimates from rice paddies

  6. X-ray reflectivity measurements of liquid/solid interfaces under high hydrostatic pressure conditions.

    Science.gov (United States)

    Wirkert, Florian J; Paulus, Michael; Nase, Julia; Möller, Johannes; Kujawski, Simon; Sternemann, Christian; Tolan, Metin

    2014-01-01

    A high-pressure cell for in situ X-ray reflectivity measurements of liquid/solid interfaces at hydrostatic pressures up to 500 MPa (5 kbar), a pressure regime that is particularly important for the study of protein unfolding, is presented. The original set-up of this hydrostatic high-pressure cell is discussed and its unique properties are demonstrated by the investigation of pressure-induced adsorption of the protein lysozyme onto hydrophobic silicon wafers. The presented results emphasize the enormous potential of X-ray reflectivity studies under high hydrostatic pressure conditions for the in situ investigation of adsorption phenomena in biological systems.

  7. Exploring the relationship between a ground-based network and airborne CCN spectra observed at the cloud level

    Science.gov (United States)

    Corrigan, C.; Roberts, G. C.; Ritchie, J.; Creamean, J.; White, A. B.

    2011-12-01

    better understanding of the ability of ground-based measurements of CCN to reflect what is happening at cloud level and if selective placement of these ground sampling sites might better capture cloud relevant data.

  8. Measuring contact angle and meniscus shape with a reflected laser beam.

    Science.gov (United States)

    Eibach, T F; Fell, D; Nguyen, H; Butt, H J; Auernhammer, G K

    2014-01-01

    Side-view imaging of the contact angle between an extended planar solid surface and a liquid is problematic. Even when aligning the view perfectly parallel to the contact line, focusing one point of the contact line is not possible. We describe a new measurement technique for determining contact angles with the reflection of a widened laser sheet on a moving contact line. We verified this new technique measuring the contact angle on a cylinder, rotating partially immersed in a liquid. A laser sheet is inclined under an angle φ to the unperturbed liquid surface and is reflected off the meniscus. Collected on a screen, the reflection image contains information to determine the contact angle. When dividing the laser sheet into an array of laser rays by placing a mesh into the beam path, the shape of the meniscus can be reconstructed from the reflection image. We verified the method by measuring the receding contact angle versus speed for aqueous cetyltrimethyl ammonium bromide solutions on a smooth hydrophobized as well as on a rough polystyrene surface.

  9. Characterizing the solar reflection from wildfire smoke plumes using airborne multiangle measurements

    Science.gov (United States)

    Gatebe, C. K.; Varnai, T.; Gautam, R.; Poudyal, R.; Singh, M. K.

    2016-12-01

    To help better understand forest fire smoke plumes, this study examines sunlight reflected from plumes that were observed over Canada during the ARCTAS campaign in summer 2008. In particular, the study analyzes multiangle and multispectral measurements of smoke scattering by the airborne Cloud Absorption Radiometer (CAR). In combination with other in-situ and remote sensing information and radiation modeling, CAR data is used for characterizing the radiative properties and radiative impact of smoke particles—which inherently depend on smoke particle properties that influence air quality. In addition to estimating the amount of reflected and absorbed sunlight, the work includes using CAR data to create spectral and broadband top-of-atmosphere angular distribution models (ADMs) of solar radiation reflected by smoke plumes, and examining the sensitivity of such angular models to scene parameters. Overall, the results help better understand the radiative properties and radiative effects of smoke particles, and are anticipated to help better interpret satellite data on smoke plumes.

  10. Influence of probe pressure on diffuse reflectance spectra of human skin measured in vivo

    Science.gov (United States)

    Popov, Alexey P.; Bykov, Alexander V.; Meglinski, Igor V.

    2017-11-01

    Mechanical pressure superficially applied on the human skin surface by a fiber-optic probe influences the spatial distribution of blood within the cutaneous tissues. Upon gradual load of weight on the probe, a stepwise increase in the skin reflectance spectra is observed. The decrease in the load follows the similar inverse staircase-like tendency. The observed stepwise reflectance spectra changes are due to, respectively, sequential extrusion of blood from the topical cutaneous vascular beds and their filling afterward. The obtained results are confirmed by Monte Carlo modeling. This implies that pressure-induced influence during the human skin diffuse reflectance spectra measurements in vivo should be taken into consideration, in particular, in the rapidly developing area of wearable gadgets for real-time monitoring of various human body parameters.

  11. Antarctic Surface Reflectivity Measurements from the ANITA-3 and HiCal-1 Experiments

    Science.gov (United States)

    Gorham, P. W.; Allison, P.; Banerjee, O.; Beatty, J. J.; Belov, K.; Besson, D. Z.; Binns, W. R.; Bugaev, V.; Cao, P.; Chen, C.; Chen, P.; Clem, J. M.; Connolly, A.; Dailey, B.; Dasgupta, P.; Deaconu, C.; Cremonesi, L.; Dowkontt, P. F.; Fox, B. D.; Gordon, J.; Hill, B.; Hupe, R.; Israel, M. H.; Jain, P.; Kowalski, J.; Lam, J.; Learned, J. G.; Liewer, K. M.; Liu, T. C.; Matsuno, S.; Miki, C.; Mottram, M.; Mulrey, K.; Nam, J.; Nichol, R. J.; Novikov, A.; Oberla, E.; Prohira, S.; Rauch, B. F.; Romero-Wolf, A.; Rotter, B.; Ratzlaff, K.; Russell, J.; Saltzberg, D.; Seckel, D.; Schoorlemmer, H.; Stafford, S.; Stockham, J.; Stockham, M.; Strutt, B.; Tatem, K.; Varner, G. S.; Vieregg, A. G.; Wissel, S. A.; Wu, F.; Young, R.

    The primary science goal of the NASA-sponsored ANITA project is measurement of ultra-high energy neutrinos and cosmic rays, observed via radio-frequency signals resulting from a neutrino or cosmic ray interaction with terrestrial matter (e.g. atmospheric or ice molecules). Accurate inference of the energies of these cosmic rays requires understanding the transmission/reflection of radio wave signals across the ice-air boundary. Satellite-based measurements of Antarctic surface reflectivity, using a co-located transmitter and receiver, have been performed more-or-less continuously for the last few decades. Our comparison of four different reflectivity surveys, at frequencies ranging from 2 to 45GHz and at near-normal incidence, yield generally consistent maps of high versus low reflectivity, as a function of location, across Antarctica. Using the Sun as an RF source, and the ANITA-3 balloon borne radio-frequency antenna array as the RF receiver, we have also measured the surface reflectivity over the interval 200-1000MHz, at elevation angles of 12-30∘. Consistent with our previous measurement using ANITA-2, we find good agreement, within systematic errors (dominated by antenna beam width uncertainties) and across Antarctica, with the expected reflectivity as prescribed by the Fresnel equations. To probe low incidence angles, inaccessible to the Antarctic Solar technique and not probed by previous satellite surveys, a novel experimental approach (“HiCal-1”) was devised. Unlike previous measurements, HiCal-ANITA constitute a bi-static transmitter-receiver pair separated by hundreds of kilometers. Data taken with HiCal, between 200 and 600MHz shows a significant departure from the Fresnel equations, constant with frequency over that band, with the deficit increasing with obliquity of incidence, which we attribute to the combined effects of possible surface roughness, surface grain effects, radar clutter and/or shadowing of the reflection zone due to Earth

  12. Retrieval and Validation of aerosol optical properties from AHI measurements: impact of surface reflectance assumption

    Science.gov (United States)

    Lim, H.; Choi, M.; Kim, J.; Go, S.; Chan, P.; Kasai, Y.

    2017-12-01

    This study attempts to retrieve the aerosol optical properties (AOPs) based on the spectral matching method, with using three visible and one near infrared channels (470, 510, 640, 860nm). This method requires the preparation of look-up table (LUT) approach based on the radiative transfer modeling. Cloud detection is one of the most important processes for guaranteed quality of AOPs. Since the AHI has several infrared channels, which are very advantageous for cloud detection, clouds can be removed by using brightness temperature difference (BTD) and spatial variability test. The Yonsei Aerosol Retrieval (YAER) algorithm is basically utilized on a dark surface, therefore a bright surface (e.g., desert, snow) should be removed first. Then we consider the characteristics of the reflectance of land and ocean surface using three visible channels. The known surface reflectivity problem in high latitude area can be solved in this algorithm by selecting appropriate channels through improving tests. On the other hand, we retrieved the AOPs by obtaining the visible surface reflectance using NIR to normalized difference vegetation index short wave infrared (NDVIswir) relationship. ESR tends to underestimate urban and cropland area, we improved the visible surface reflectance considering urban effect. In this version, ocean surface reflectance is using the new cox and munk method which considers ocean bidirectional reflectance distribution function (BRDF). Input of this method has wind speed, chlorophyll, salinity and so on. Based on validation results with the sun-photometer measurement in AErosol Robotic NETwork (AERONET), we confirm that the quality of Aerosol Optical Depth (AOD) from the YAER algorithm is comparable to the product from the Japan Aerospace Exploration Agency (JAXA) retrieval algorithm. Our future update includes a consideration of improvement land surface reflectance by hybrid approach, and non-spherical aerosols. This will improve the quality of YAER

  13. Measurement of stress-induced birefringence in glasses based on reflective laser feedback effect

    Science.gov (United States)

    Haisha, Niu; YanXiong, Niu; Jiyang, Li

    2017-02-01

    A glass birefringence measurement system utilizing the reflective laser feedback (RLF) effect is presented. The measurement principle is analyzed based on the equivalent cavity of a Fabry-Perot interferometer, and the experiments are conducted with a piece of quartz glass with applied extrusion force. In the feedback system, aluminum film used as a feedback mirror is affixed to the back of the sample. When the light is reflected back into the cavity, as the reinjected light is imprinted with the birefringence information in the sample, the gain and polarization states of the laser are modulated. The variation of optical power and polarization states hopping is monitored to obtain the magnitude of the stress. The system has advantages such as simplicity and low-cost with a precision of 1.9 nm. Moreover, by adjusting the position of the aluminum, large-area samples can be measured anywhere at any place.

  14. Retrieval of cloud droplet size distribution parameters from polarized reflectance measurements

    Directory of Open Access Journals (Sweden)

    M. Alexandrov

    2011-09-01

    Full Text Available We present an algorithm for retrieval of cloud droplet size distribution parameters (effective radius and variance from the Research Scanning Polarimeter (RSP measurements. The RSP is an airborne prototype for the Aerosol Polarimetery Sensor (APS, which is due to be launched as part of the NASA Glory Project. This instrument measures both polarized and total reflectances in 9 spectral channels with center wavelengths ranging from 410 to 2250 nm. For cloud droplet size retrievals we utilize the polarized reflectances in the scattering angle range between 140 and 170 degrees where they exhibit rainbow. The shape of the rainbow is determined mainly by single-scattering properties of the cloud particles, that simplifies the inversions and reduces retrieval uncertainties. The retrieval algorithm was tested using realistically simulated cloud radiation fields. Our retrievals of cloud droplet sizes from actual RSP measurements made during two recent field campaigns were compared with the correlative in situ observations.

  15. Superresolution confocal technology for displacement measurements based on total internal reflection.

    Science.gov (United States)

    Kuang, Cuifang; Ali, M Yakut; Hao, Xiang; Wang, Tingting; Liu, Xu

    2010-10-01

    In order to achieve a higher axial resolution for displacement measurement, a novel method is proposed based on total internal reflection filter and confocal microscope principle. A theoretical analysis of the basic measurement principles is presented. The analysis reveals that the proposed confocal detection scheme is effective in enhancing the resolution of nonlinearity of the reflectance curve greatly. In addition, a simple prototype system has been developed based on the theoretical analysis and a series of experiments have been performed under laboratory conditions to verify the system feasibility, accuracy, and stability. The experimental results demonstrate that the axial resolution in displacement measurements is better than 1 nm in a range of 200 nm which is threefold better than that can be achieved using the plane reflector.

  16. Superresolution confocal technology for displacement measurements based on total internal reflection

    International Nuclear Information System (INIS)

    Kuang Cuifang; Hao Xiang; Wang Tingting; Liu Xu; Ali, M. Yakut

    2010-01-01

    In order to achieve a higher axial resolution for displacement measurement, a novel method is proposed based on total internal reflection filter and confocal microscope principle. A theoretical analysis of the basic measurement principles is presented. The analysis reveals that the proposed confocal detection scheme is effective in enhancing the resolution of nonlinearity of the reflectance curve greatly. In addition, a simple prototype system has been developed based on the theoretical analysis and a series of experiments have been performed under laboratory conditions to verify the system feasibility, accuracy, and stability. The experimental results demonstrate that the axial resolution in displacement measurements is better than 1 nm in a range of 200 nm which is threefold better than that can be achieved using the plane reflector.

  17. Predicting seed yield in perennial ryegrass using repeated canopy reflectance measurements and PLSR

    DEFF Research Database (Denmark)

    Gislum, René; Deleuran, Lise Christina; Boelt, Birte

    2009-01-01

    with first year seed crops using three sowing rates and three spring nitrogen (N) application rates. PLSR models were developed for each year and showed correlation coefficients of 0.71, 0.76, and 0.92, respectively. Regression coefficients showed in these experiments that the optimum time for canopy...... reflectance measurements was from approximately 600 cumulative growing degree-days (CGDD) to approximately 900 CGDD. This is the period just before and at heading of the seed crop. Furthermore, regression coefficients showed that information about N and water is important. The results support the development......Repeated canopy reflectance measurements together with partial least-squares regression (PLSR) were used to predict seed yield in perennial ryegrass (Lolium perenne L.). The measurements were performed during the spring and summer growing seasons of 2001 to 2003 in three field experiments...

  18. Ground-based transmission line conductor motion sensor

    International Nuclear Information System (INIS)

    Jacobs, M.L.; Milano, U.

    1988-01-01

    A ground-based-conductor motion-sensing apparatus is provided for remotely sensing movement of electric-power transmission lines, particularly as would occur during the wind-induced condition known as galloping. The apparatus is comprised of a motion sensor and signal-generating means which are placed underneath a transmission line and will sense changes in the electric field around the line due to excessive line motion. The detector then signals a remote station when a conditioning of galloping is sensed. The apparatus of the present invention is advantageous over the line-mounted sensors of the prior art in that it is easier and less hazardous to install. The system can also be modified so that a signal will only be given when particular conditions, such as specific temperature range, large-amplitude line motion, or excessive duration of the line motion, are occurring

  19. Development of a Ground-Based Atmospheric Monitoring Network for the Global Mercury Observation System (GMOS

    Directory of Open Access Journals (Sweden)

    Sprovieri F.

    2013-04-01

    Full Text Available Consistent, high-quality measurements of atmospheric mercury (Hg are necessary in order to better understand Hg emissions, transport, and deposition on a global scale. Although the number of atmospheric Hg monitoring stations has increased in recent years, the available measurement database is limited and there are many regions of the world where measurements have not been extensively performed. Long-term atmospheric Hg monitoring and additional ground-based monitoring sites are needed in order to generate datasets that will offer new insight and information about the global scale trends of atmospheric Hg emissions and deposition. In the framework of the Global Mercury Observation System (GMOS project, a coordinated global observational network for atmospheric Hg is being established. The overall research strategy of GMOS is to develop a state-of-the-art observation system able to provide information on the concentration of Hg species in ambient air and precipitation on the global scale. This network is being developed by integrating previously established ground-based atmospheric Hg monitoring stations with newly established GMOS sites that are located both at high altitude and sea level locations, as well as in climatically diverse regions. Through the collection of consistent, high-quality atmospheric Hg measurement data, we seek to create a comprehensive assessment of atmospheric Hg concentrations and their dependence on meteorology, long-range atmospheric transport and atmospheric emissions.

  20. Kepler and Ground-Based Transits of the exo-Neptune HAT-P-11b

    Science.gov (United States)

    Deming, Drake; Sada, Pedro V.; Jackson, Brian; Peterson, Steven W.; Agol, Eric; Knutson, Heather A.; Jennings, Donald E.; Haase, Plynn; Bays, Kevin

    2011-01-01

    We analyze 26 archival Kepler transits of the exo-Neptune HAT-P-11b, supplemented by ground-based transits observed in the blue (B band) and near-IR (J band). Both the planet and host star are smaller than previously believed; our analysis yields Rp = 4.31 R xor 0.06 R xor and Rs = 0.683 R solar mass 0.009 R solar mass, both about 3 sigma smaller than the discovery values. Our ground-based transit data at wavelengths bracketing the Kepler bandpass serve to check the wavelength dependence of stellar limb darkening, and the J-band transit provides a precise and independent constraint on the transit duration. Both the limb darkening and transit duration from our ground-based data are consistent with the new Kepler values for the system parameters. Our smaller radius for the planet implies that its gaseous envelope can be less extensive than previously believed, being very similar to the H-He envelope of GJ 436b and Kepler-4b. HAT-P-11 is an active star, and signatures of star spot crossings are ubiquitous in the Kepler transit data. We develop and apply a methodology to correct the planetary radius for the presence of both crossed and uncrossed star spots. Star spot crossings are concentrated at phases 0.002 and +0.006. This is consistent with inferences from Rossiter-McLaughlin measurements that the planet transits nearly perpendicular to the stellar equator. We identify the dominant phases of star spot crossings with active latitudes on the star, and infer that the stellar rotational pole is inclined at about 12 deg 5 deg to the plane of the sky. We point out that precise transit measurements over long durations could in principle allow us to construct a stellar Butterfly diagram to probe the cyclic evolution of magnetic activity on this active K-dwarf star.

  1. Fluororeflectometer for measuring the emission, excitation, reflection and transmission of materials doped with active ions

    Energy Technology Data Exchange (ETDEWEB)

    Ramírez-Duverger, Aldo S., E-mail: aldo@cifus.uson.mx [Departamento de Física, Universidad de Sonora, Apdo. Postal 5-88, Hermosillo, Sonora 83000, México (Mexico); García-Llamas, Raúl, E-mail: ragal@cifus.uson.mx [Departamento de Investigación en Física, Universidad de Sonora, Apdo. Postal 5-88, Hermosillo, Sonora 83000, México (Mexico); Aceves, R., E-mail: raceves@cifus.uson.mx [Departamento de Investigación en Física, Universidad de Sonora, Apdo. Postal 5-88, Hermosillo, Sonora 83000, México (Mexico)

    2013-04-15

    The design and construction of a new hybrid instrument, which is named a fluororeflectometer, for measuring the radiation from materials doped with rare earth atoms is presented. This instrument operates in two modes. In the XL-λ mode, the instrument measures the luminescence and excitation spectra of the samples. In the RT-λ mode, the instrument measures the specular reflection and transmission spectra of thick or thin films. A photomultiplier (UV-enhanced photodiode) is used when the XL-λ (RT-λ) mode is in operation. The angle of incidence on the sample and the angle of the detected emission can be changed in both modes; the first one is changed manually and the last one is changed automatically. The reflection and transmission spectra from slabs of KCl:Eu{sup 2+} were measured to test the RT-λ mode. These data were fitted using Lorentz-type dispersion for the material, and the densities for each Eu absorption bands were obtained. In the XL-λ mode, the luminescence and excitation spectra from a slab and thin film of KCl:Eu{sup 2+} were obtained. The sensitivity of the instrument enables the luminescence from thin films with thicknesses as low as 3 μm to be measured; in this case, the signal barely exceeded the noise. The emission spectra from a slab of KCl:Eu{sup 2+} for several angles of incidence were measured in the direction parallel to the interfaces of the slab. -- Highlights: ► Develops an instrument for measuring optical properties of phosphors materials. ► Emission, excitation, transmission and reflectance are measured in KCl:Eu{sup 2+} slabs. ► The angular distribution for the emission, measured in situ, is also characterized. ► Its performance was compared with other instruments and good agreement is found. ► Capabilities are found superior to those offered by commercial fluorometers.

  2. Fluororeflectometer for measuring the emission, excitation, reflection and transmission of materials doped with active ions

    International Nuclear Information System (INIS)

    Ramírez-Duverger, Aldo S.; García-Llamas, Raúl; Aceves, R.

    2013-01-01

    The design and construction of a new hybrid instrument, which is named a fluororeflectometer, for measuring the radiation from materials doped with rare earth atoms is presented. This instrument operates in two modes. In the XL-λ mode, the instrument measures the luminescence and excitation spectra of the samples. In the RT-λ mode, the instrument measures the specular reflection and transmission spectra of thick or thin films. A photomultiplier (UV-enhanced photodiode) is used when the XL-λ (RT-λ) mode is in operation. The angle of incidence on the sample and the angle of the detected emission can be changed in both modes; the first one is changed manually and the last one is changed automatically. The reflection and transmission spectra from slabs of KCl:Eu 2+ were measured to test the RT-λ mode. These data were fitted using Lorentz-type dispersion for the material, and the densities for each Eu absorption bands were obtained. In the XL-λ mode, the luminescence and excitation spectra from a slab and thin film of KCl:Eu 2+ were obtained. The sensitivity of the instrument enables the luminescence from thin films with thicknesses as low as 3 μm to be measured; in this case, the signal barely exceeded the noise. The emission spectra from a slab of KCl:Eu 2+ for several angles of incidence were measured in the direction parallel to the interfaces of the slab. -- Highlights: ► Develops an instrument for measuring optical properties of phosphors materials. ► Emission, excitation, transmission and reflectance are measured in KCl:Eu 2+ slabs. ► The angular distribution for the emission, measured in situ, is also characterized. ► Its performance was compared with other instruments and good agreement is found. ► Capabilities are found superior to those offered by commercial fluorometers

  3. Investigating Bidirectional Reflectance in the Los Angeles Megacity Using CLARS Multiangle and Hyperspectral Measurements

    Science.gov (United States)

    Zeng, Z. C.; Natraj, V.; Pongetti, T.; Shia, R. L.; Sander, S. P.; Yung, Y. L.

    2017-12-01

    The surface reflectance is a key ingredient in the remote sensing of surface and atmospheric properties from space. The determination of atmospheric composition, including greenhouse gas (GHG) and aerosol concentrations, from reflected sunlight requires accurate knowledge of the contribution from the underlying surface. Over megacity areas, such as the Los Angeles (LA) basin, which are major sources of GHGs and anthropogenic aerosols, the quantification of surface reflectance is challenging due to the associated complex land use types. In this study, we investigate the bidirectional reflectance in the Los Angeles megacity area using multiangle and hyperspectral radiance measurements from the California Laboratory for Atmospheric Remote Sensing (CLARS). The CLARS facility is located near the top of Mt. Wilson, at an altitude of 1670 m a.s.l., overlooking the LA megacity area with an FTS operating since 2011 to continuously monitor the GHGs and near-surface aerosols in the basin. The CLARS-FTS offers continuous high-resolution spectral measurements in the visible, near infrared and shortwave infrared spectral regions. The CLARS measurements mimic the off-nadir viewing of a low-Earth orbiting instrument, such as GOSAT and OCO-2, but with daily viewing capability. Eight surface targets with different land use types, including urban parks, industrial and residential areas, are selected in this study. The surface reflectance for specific solar incident and viewing angles is calculated by dividing, for non-absorbing spectral channels on clear days (such that gas and aerosol extinction can be ignored), the observed radiance reflected from surface targets by the observed irradiance. The non-linear Rahman-Pinty-Verstraete (RPV) model is used to model the Bidirectional Reflectance Distribution Function (BRDF) by fitting the multiangle and hyperspectral measurements. By evaluating the retrieved RPV parameters, we find that the RPV model provides a good representation of the

  4. Biodiversity Measurement Using Indices Based on Hyperspectral Reflectance on the Coast of Lagos

    Science.gov (United States)

    Omodanisi, E. O.; Salami, A. T.

    2013-12-01

    Hyperspectral measurements provide explicit measurements which can be used in the analysis of biodiversity change. This study was carried out in the coastal area of Lagos State, Nigeria. The objective of this study was to determine if gasoline seepage affects vegetation species distribution and reflectance; with the view to analyzing the vegetation condition. To evaluate the potential of different reflectance spectroscopy of species, the ASD Handheld2 Spectrometer was used. Three identified impacted plots of 30m by 30m were selected randomly and a control plot established in relatively undisturbed vegetated areas away from but perpendicular to the source of seepage. Each identified plot and the control consisted of five transects and measurement were taken at every 2m with about four reflectance measurement per sample point, to average out differences in reflectance as a result of different leaf angles. The radiance output of the spectrometer was converted into reflectance using the reflectance of a white reference over a standardized white spectralon panel. Indices such as Normalized Differential Vegetation Index, RedEdge Normalized Difference Vegetation Index, Soil Adjusted Vegetation Index, Ratio Vegetation Index and Volgelmann RedEdge Index 1 were calculated to accurately estimate the chlorophyll content in the vegetation within optimal band wavelength. Shannon-Weiner's index, Spearman's rank correlation and Analysis of Variance were used to analyze the data. Cocos nucifera was observed to be the most dominant species with a relative abundance of 47.27% while Ananas comosus recorded the lowest relative abundance of 21.8%. In the control plot, Cocos nucifera had the highest relative abundance of 42.3% and Mangifera indica with the least relative abundance of 16.7%. The relationship between the indices and chlorophyll content of the vegetation were significantly higher at (p>0.01) for all the indices in all the plots; however, RedEdgeNDVI and VOG1 indices had the

  5. Weighted least-square approach for simultaneous measurement of multiple reflective surfaces

    Science.gov (United States)

    Tang, Shouhong; Bills, Richard E.; Freischlad, Klaus

    2007-09-01

    Phase shifting interferometry (PSI) is a highly accurate method for measuring the nanometer-scale relative surface height of a semi-reflective test surface. PSI is effectively used in conjunction with Fizeau interferometers for optical testing, hard disk inspection, and semiconductor wafer flatness. However, commonly-used PSI algorithms are unable to produce an accurate phase measurement if more than one reflective surface is present in the Fizeau interferometer test cavity. Examples of test parts that fall into this category include lithography mask blanks and their protective pellicles, and plane parallel optical beam splitters. The plane parallel surfaces of these parts generate multiple interferograms that are superimposed in the recording plane of the Fizeau interferometer. When using wavelength shifting in PSI the phase shifting speed of each interferogram is proportional to the optical path difference (OPD) between the two reflective surfaces. The proposed method is able to differentiate each underlying interferogram from each other in an optimal manner. In this paper, we present a method for simultaneously measuring the multiple test surfaces of all underlying interferograms from these superimposed interferograms through the use of a weighted least-square fitting technique. The theoretical analysis of weighted least-square technique and the measurement results will be described in this paper.

  6. Laser Sensing of Vegetation Based on Dual Spectrum Measurements of Reflection Coefficients

    Directory of Open Access Journals (Sweden)

    M. L. Belov

    2017-01-01

    Full Text Available Currently, a promising trend in remote sensing of environment is to monitor the vegetative cover: evaluate the productivity of agricultural crops; evaluate the moisture content of soils and the state of ecosystems; provide mapping the sites of bogging, desertification, drought, etc.; control the phases of vegetation of crops, etc.Development of monitoring systems for remote detection of vegetation sites being under unfavorable conditions (low or high temperature, excess or lack of water, soil salinity, disease, etc. is of relevance. Optical methods are the most effective for this task. These methods are based on the physical features of reflection spectra in the visible and near infrared spectral range for vegetation under unfavorable conditions and vegetation under normal conditions.One of the options of optoelectronic equipment for monitoring vegetation condition is laser equipment that allows remote sensing of vegetation from the aircraft and mapping of vegetation sites with abnormal (inactive periods of vegetation reflection spectra with a high degree of spatial resolution.The paper deals with development of a promising dual-spectrum method for laser remote sensing of vegetation. Using the experimentally measured reflection spectra of different vegetation types, mathematical modeling of probability for appropriate detection and false alarms to solve a problem of detecting the vegetation under unfavorable conditions (with abnormal reflection spectra is performed based on the results of dual-spectrum measurements of the reflection coefficient.In mathematical modeling, the lidar system was supposed to provide sensing at wavelengths of 0.532 μm and 0.85 μm. The noise of the measurement was supposed to be normal with zero mean value and mean-square value of 1% -10%.It is shown that the method of laser sensing of vegetation condition based on the results of dual-spectrum measurement of the reflection coefficient at wavelengths of 0.532 μm and 0

  7. Quantitative skin color measurements in acanthosis nigricans patients: colorimetry and diffuse reflectance spectroscopy.

    Science.gov (United States)

    Pattamadilok, Bensachee; Devpura, Suneetha; Syed, Zain U; Agbai, Oma N; Vemulapalli, Pranita; Henderson, Marsha; Rehse, Steven J; Mahmoud, Bassel H; Lim, Henry W; Naik, Ratna; Hamzavi, Iltefat H

    2012-08-01

    Tristimulus colorimetry and diffuse reflectance spectroscopy (DRS) are white-light skin reflectance techniques used to measure the intensity of skin pigmentation. The tristimulus colorimeter is an instrument that measures a perceived color and the DRS instrument measures biological chromophores of the skin, including oxy- and deoxyhemoglobin, melanin and scattering. Data gathered from these tools can be used to understand morphological changes induced in skin chromophores due to conditions of the skin or their treatments. The purpose of this study was to evaluate the use of these two instruments in color measurements of acanthosis nigricans (AN) lesions. Eight patients with hyperinsulinemia and clinically diagnosable AN were seen monthly. Skin pigmentation was measured at three sites: the inner forearm, the medial aspect of the posterior neck, and anterior neck unaffected by AN. Of the three, measured tristimulus L*a*b* color parameters, the luminosity parameter L* was found to most reliably distinguish lesion from normally pigmented skin. The DRS instrument was able to characterize a lesion on the basis of the calculated melanin concentration, though melanin is a weak indicator of skin change and not a reliable measure to be used independently. Calculated oxyhemoglobin and deoxyhemoglobin concentrations were not found to be reliable indicators of AN. Tristimulus colorimetry may provide reliable methods for respectively quantifying and characterizing the objective color change in AN, while DRS may be useful in characterizing changes in skin melanin content associated with this skin condition. © 2012 John Wiley & Sons A/S.

  8. Exoplanets -New Results from Space and Ground-based Surveys

    Science.gov (United States)

    Udry, Stephane

    The exploration of the outer solar system and in particular of the giant planets and their environments is an on-going process with the Cassini spacecraft currently around Saturn, the Juno mission to Jupiter preparing to depart and two large future space missions planned to launch in the 2020-2025 time frame for the Jupiter system and its satellites (Europa and Ganymede) on the one hand, and the Saturnian system and Titan on the other hand [1,2]. Titan, Saturn's largest satellite, is the only other object in our Solar system to possess an extensive nitrogen atmosphere, host to an active organic chemistry, based on the interaction of N2 with methane (CH4). Following the Voyager flyby in 1980, Titan has been intensely studied from the ground-based large telescopes (such as the Keck or the VLT) and by artificial satellites (such as the Infrared Space Observatory and the Hubble Space Telescope) for the past three decades. Prior to Cassini-Huygens, Titan's atmospheric composition was thus known to us from the Voyager missions and also through the explorations by the ISO. Our perception of Titan had thus greatly been enhanced accordingly, but many questions remained as to the nature of the haze surrounding the satellite and the composition of the surface. The recent revelations by the Cassini-Huygens mission have managed to surprise us with many discoveries [3-8] and have yet to reveal more of the interesting aspects of the satellite. The Cassini-Huygens mission to the Saturnian system has been an extraordinary success for the planetary community since the Saturn-Orbit-Insertion (SOI) in July 2004 and again the very successful probe descent and landing of Huygens on January 14, 2005. One of its main targets was Titan. Titan was revealed to be a complex world more like the Earth than any other: it has a dense mostly nitrogen atmosphere and active climate and meteorological cycles where the working fluid, methane, behaves under Titan conditions the way that water does on

  9. GPS Multipath Fade Measurements to Determine L-Band Ground Reflectivity Properties

    Science.gov (United States)

    Kavak, Adnan; Xu, Guang-Han; Vogel, Wolfhard J.

    1996-01-01

    In personal satellite communications, especially when the line-of-sight is clear, ground specular reflected signals along with direct signals are received by low gain, almost omni-directional subscriber antennas. A six-channel, C/A code processing, GPS receiver with an almost omni-directional patch antenna was used to take measurements over three types of ground to characterize 1.575 GHz specular ground reflections and ground dielectric properties. Fade measurements were taken over grass, asphalt, and lake water surfaces by placing the antenna in a vertical position at a fixed height from the ground. Electrical characteristics (conductivity and dielectric constant) of these surfaces (grass, asphalt, lake water) were obtained by matching computer simulations to the experimental results.

  10. State-dependent cellular activity patterns of the cat paraventricular hypothalamus measured by reflectance imaging

    DEFF Research Database (Denmark)

    Kristensen, Morten Pilgaard; Rector, D M; Poe, G R

    1996-01-01

    Activity within the cat paraventricular hypothalamus (PVH) during sleep and waking states was measured by quantifying intrinsic tissue reflectivity. A fiber optic probe consisting of a 1.0 mm coherent image conduit, surrounded by plastic fibers which conducted 660 nm source light, was attached...... to a charge-coupled device camera, and positioned over the PVH in five cats. Electrodes for assessing state variables, including electroencephalographic activity, eye movement, and somatic muscle tone were also placed. After surgical recovery, reflected light intensity was measured continuously at 2.5 Hz...... changes with behavioral state in a regionally specific manner, and that overall activity increases during quiet sleep, and is even more enhanced in active sleep. PVH activation could be expected to stimulate pituitary release of adrenocorticotropic hormone (ACTH) and affect input to autonomic regulatory...

  11. Measurement of the enzymes lactate dehydrogenase and creatine kinase using reflectance spectroscopy and reagent strips.

    OpenAIRE

    Stevens, J F; Tsang, W; Newall, R G

    1983-01-01

    Two new methods for the assay of total activities of lactate dehydrogenase and creatine kinase are described, in which the enzyme activities are measured from a solid-state reagent strip during a kinetic reaction, the reaction being monitored in the ultra-violet region of the spectrum by reflectance spectroscopy. The performances of these methods are evaluated, and compared to conventional "wet" chemistry methods. The solid-phase reagent methods demonstrated precision and accuracy acceptable ...

  12. Measuring third year undergraduate nursing students' reflective thinking skills and critical reflection self-efficacy following high fidelity simulation: A pilot study.

    Science.gov (United States)

    Tutticci, Naomi; Lewis, Peter A; Coyer, Fiona

    2016-05-01

    Critical reflection underpins critical thinking, a highly desirable generic nursing graduate capability. To improve the likelihood of critical thinking transferring to clinical practice, reflective thinking needs to be measured within the learning space of simulation. This study was divided into two phases to address the reliability and validity measures of previously untested surveys. Phase One data was collected from individuals (n = 6) using a 'think aloud' approach and an expert panel to review content validity, and verbatim comment analysis was undertaken. The Reflective Thinking Instrument and Critical Reflection Self-Efficacy Visual Analogue Scale items were contextualised to simulation. The expert review confirmed these instruments exhibited content validity. Phase Two data was collected through an online survey (n = 58). Cronbach's alpha measured internal consistency and was demonstrated by all subscales and the Instrument as a whole (.849). There was a small to medium positive correlation between critical reflection self-efficacy and general self-efficacy (r = .324, n = 56, p = .048). Participant responses were positive regarding the simulation experience. The research findings demonstrated that the Reflective Thinking and Simulation Satisfaction survey is reliable. Further development of this survey to establish validity is recommended to make it viable. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Spatio-temporal monitoring of cotton cultivation using ground-based and airborne multispectral sensors in GIS environment.

    Science.gov (United States)

    Papadopoulos, Antonis; Kalivas, Dionissios; Theocharopoulos, Sid

    2017-07-01

    Multispectral sensor capability of capturing reflectance data at several spectral channels, together with the inherent reflectance responses of various soils and especially plant surfaces, has gained major interest in crop production. In present study, two multispectral sensing systems, a ground-based and an aerial-based, were applied for the multispatial and temporal monitoring of two cotton fields in central Greece. The ground-based system was Crop Circle ACS-430, while the aerial consisted of a consumer-level quadcopter (Phantom 2) and a modified Hero3+ Black digital camera. The purpose of the research was to monitor crop growth with the two systems and investigate possible interrelations between the derived well-known normalized difference vegetation index (NDVI). Five data collection campaigns were conducted during the cultivation period and concerned scanning soil and plants with the ground-based sensor and taking aerial photographs of the fields with the unmanned aerial system. According to the results, both systems successfully monitored cotton growth stages in terms of space and time. The mean values of NDVI changes through time as retrieved by the ground-based system were satisfactorily modelled by a second-order polynomial equation (R 2 0.96 in Field 1 and 0.99 in Field 2). Further, they were highly correlated (r 0.90 in Field 1 and 0.74 in Field 2) with the according values calculated via the aerial-based system. The unmanned aerial system (UAS) can potentially substitute crop scouting as it concerns a time-effective, non-destructive and reliable way of soil and plant monitoring.

  14. Application of a multilayer perceptron neural network to phytoplankton concentration using marine reflectance measures

    Science.gov (United States)

    Su, Feng-Chun; Ho, Chung-Ru; Kuo, Nan-Jung

    2005-01-01

    The multilayer perceptron (MLP) neural network have been widely used to fit non-linear transfer function and performed well. In this study, we use MLP to estimate chlorophyll-a concentrations from marine reflectance measures. The optical data were assembled from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Bio-optical Algorithm Mini-workshop (SeaBAM). Most bio-optical algorithms use simple ratios of reflectance in blue and green bands or combinations of ratios as parameters for regression analysis. Regression analysis has limitations for nonlinear function. Neural network, however, have been shown better performance for nonlinear problems. The result showed that accuracy of chlorophyll-a concentration using MLP is much higher than that of regression method. Nevertheless, using all of the five bands as input can derive the best performance. The results showed that each band could carry some useful messages for ocean color remote sensing. Only using band ratio (OC2) or band switch (OC4) might lose some available information. By preprocessing reflectance data with the principle component analysis (PCA), MLP could derive much better accuracy than traditional methods. The result showed that the reflectance of all bands should not be ignored for deriving the chlorophyll-a concentration because each band carries different useful ocean color information.

  15. Measurements of plasma mirror reflectivity and focal spot quality for tens of picosecond laser pulses

    Science.gov (United States)

    Forestier-Colleoni, Pierre; Williams, Jackson; Scott, Graeme; Mariscal, Dereck. A.; McGuffey, Christopher; Beg, Farhat N.; Chen, Hui; Neely, David; Ma, Tammy

    2017-10-01

    The Advanced Radiographic Capability (ARC) laser at the NIF (LLNL) is high-energy ( 4 kJ) with a pulse length of 30ps, and is capable of focusing to an intensity of 1018W/cm2 with a 100 μm focal spot. The ARC laser is at an intensity which can be used to produce proton beams. However, for applications such as radiography and warm dense matter creation, a higher laser intensity may be desired to generate more energetic proton beams. One possibility to increase the intensity is to decrease the focused spot size by employing a smaller f-number optic. But it is difficult to implement such an optic or to bring the final focusing parabola closer to the target within the complicated NIF chamber geometry. A proposal is to use ellipsoidal plasma mirrors (PM) for fast focusing of the ARC laser light, thereby increasing the peak intensity. There is uncertainty, however, in the survivability and reflectivity of PM at such long pulse durations. Here, we show experimental results from the Titan laser to study the reflectivity of flat PM as a function of laser pulse length. A calorimeter was used to measure the PM reflectivity. We also observed degradation of the far and near field energy distribution of the laser after the reflection by the PM for pulse-lengths beyond 10ps. Contract DE-AC52-07NA27344. Funded by the LLNL LDRD program: tracking code 17-ERD-039.

  16. Active laser radar (lidar) for measurement of corresponding height and reflectance images

    Science.gov (United States)

    Froehlich, Christoph; Mettenleiter, M.; Haertl, F.

    1997-08-01

    For the survey and inspection of environmental objects, a non-tactile, robust and precise imaging of height and depth is the basis sensor technology. For visual inspection,surface classification, and documentation purposes, however, additional information concerning reflectance of measured objects is necessary. High-speed acquisition of both geometric and visual information is achieved by means of an active laser radar, supporting consistent 3D height and 2D reflectance images. The laser radar is an optical-wavelength system, and is comparable to devices built by ERIM, Odetics, and Perceptron, measuring the range between sensor and target surfaces as well as the reflectance of the target surface, which corresponds to the magnitude of the back scattered laser energy. In contrast to these range sensing devices, the laser radar under consideration is designed for high speed and precise operation in both indoor and outdoor environments, emitting a minimum of near-IR laser energy. It integrates a laser range measurement system and a mechanical deflection system for 3D environmental measurements. This paper reports on design details of the laser radar for surface inspection tasks. It outlines the performance requirements and introduces the measurement principle. The hardware design, including the main modules, such as the laser head, the high frequency unit, the laser beam deflection system, and the digital signal processing unit are discussed.the signal processing unit consists of dedicated signal processors for real-time sensor data preprocessing as well as a sensor computer for high-level image analysis and feature extraction. The paper focuses on performance data of the system, including noise, drift over time, precision, and accuracy with measurements. It discuses the influences of ambient light, surface material of the target, and ambient temperature for range accuracy and range precision. Furthermore, experimental results from inspection of buildings, monuments

  17. Retrieval of tropospheric HCHO in El Salvador using ground based DOAS

    Science.gov (United States)

    Abarca, W.; Gamez, K.; Rudamas, C.

    2017-12-01

    Formaldehyde (HCHO) is the most abundant carbonyl in the atmosphere, being an intermediate product in the oxidation of most volatile organic compounds (VOCs). HCHO is carcinogenic, and highly water soluble [1]. HCHO can originate from biomass burning and fossil fuel combustion and has been observed from satellite and ground-based sensors by using the Differential Optical Absorption Spectroscopy (DOAS) technique [2].DOAS products can be used for air quality monitoring, validation of chemical transport models, validation of satellite tropospheric column density retrievals, among others [3]. In this study, we report on column density levels of HCHO measured by ground based Multi-Axis -DOAS in different locations of El Salvador in March, 2015. We have not observed large differences of the HCHO column density values at different viewing directions. This result points out a reasonably polluted and hazy atmosphere in the measuring sites, as reported by other authors [4]. Average values ranging from 1016 to 1017 molecules / cm2 has been obtained. The contribution of vehicular traffic and biomass burning to the column density levels in these sites of El Salvador will be discussed. [1] A. R. Garcia et al., Atmos. Chem. Phys. 6, 4545 (2006) [2] E. Peters et al., Atmos. Chem. Phys. 12, 11179 (2012) [3] T. Vlemmix, et al. Atmos. Meas. Tech., 8, 941-963, 2015 [4] A. Heckel et al., Atmos. Chem. Phys. 5, (2005)

  18. Recent successes and emerging challenges for coordinated satellite/ground-based magnetospheric exploration and modeling.

    Science.gov (United States)

    Angelopoulos, Vassilis

    With the availability of a distributed constellation of spacecraft (THEMIS, Geotail, Cluster) and increased capability ground based arrays (SuperDARN, THEMIS/GBOs), it is now pos-sible to infer simply from timing significant information regarding mapping of magnetospheric phenomena. Optical, magnetometer and radar data can pinpoint the location and nature of onset signatures. On the other hand, magnetic field modeling constrained by physical bound-aries (such as the isotropy boundary) the measured magnetic field and total pressure values at a distibuted network of satellites has proven to do a much better job at correlating ionospheric precipitation and diffuse auroral boundaries to magnetospheric phenomena, such as the inward boundary of the dipolarization fronts. It is now possible to routinely compare in-situ measured phase space densities of ion and electron distributions during ionosphere -magnetosphere con-junctions, in the absense of potential drops. It is also possible to not only infer equivalent current systems from the ground, but use reconstruction of the ionospheric current system from space to determine the full electrodynamics evolution of the ionosphere and compare with radars. Assimilation of this emerging ground based and global magnetospheric panoply into a self consistent magnetospheric model will likely be one of the most fruitful endeavors in magnetospheric exploration during the next few years.

  19. Potential use of ground-based sensor technologies for weed detection.

    Science.gov (United States)

    Peteinatos, Gerassimos G; Weis, Martin; Andújar, Dionisio; Rueda Ayala, Victor; Gerhards, Roland

    2014-02-01

    Site-specific weed management is the part of precision agriculture (PA) that tries to effectively control weed infestations with the least economical and environmental burdens. This can be achieved with the aid of ground-based or near-range sensors in combination with decision rules and precise application technologies. Near-range sensor technologies, developed for mounting on a vehicle, have been emerging for PA applications during the last three decades. These technologies focus on identifying plants and measuring their physiological status with the aid of their spectral and morphological characteristics. Cameras, spectrometers, fluorometers and distance sensors are the most prominent sensors for PA applications. The objective of this article is to describe-ground based sensors that have the potential to be used for weed detection and measurement of weed infestation level. An overview of current sensor systems is presented, describing their concepts, results that have been achieved, already utilized commercial systems and problems that persist. A perspective for the development of these sensors is given. © 2013 Society of Chemical Industry.

  20. z'-BAND GROUND-BASED DETECTION OF THE SECONDARY ECLIPSE OF WASP-19b

    Energy Technology Data Exchange (ETDEWEB)

    Burton, J. R.; Watson, C. A.; Pollacco, D. [Astrophysics Research Centre, Queen' s University Belfast, Belfast BT7 1NN (United Kingdom); Littlefair, S. P.; Dhillon, V. S. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Gibson, N. P. [Department of Physics, University of Oxford, Oxford OX1 3RH (United Kingdom); Marsh, T. R., E-mail: jburton04@qub.ac.uk [Department of Physics and Astronomy, University of Warwick, Coventry CV4 7AL (United Kingdom)

    2012-08-01

    We present the ground-based detection of the secondary eclipse of the transiting exoplanet WASP-19b. The observations were made in the Sloan z' band using the ULTRACAM triple-beam CCD camera mounted on the New Technology Telescope. The measurement shows a 0.088% {+-} 0.019% eclipse depth, matching previous predictions based on H- and K-band measurements. We discuss in detail our approach to the removal of errors arising due to systematics in the data set, in addition to fitting a model transit to our data. This fit returns an eclipse center, T{sub 0}, of 2455578.7676 HJD, consistent with a circular orbit. Our measurement of the secondary eclipse depth is also compared to model atmospheres of WASP-19b and is found to be consistent with previous measurements at longer wavelengths for the model atmospheres we investigated.

  1. Radius of curvature measurement of spherical smooth surfaces by multiple-beam interferometry in reflection

    Science.gov (United States)

    Abdelsalam, D. G.; Shaalan, M. S.; Eloker, M. M.; Kim, Daesuk

    2010-06-01

    In this paper a method is presented to accurately measure the radius of curvature of different types of curved surfaces of different radii of curvatures of 38 000,18 000 and 8000 mm using multiple-beam interference fringes in reflection. The images captured by the digital detector were corrected by flat fielding method. The corrected images were analyzed and the form of the surfaces was obtained. A 3D profile for the three types of surfaces was obtained using Zernike polynomial fitting. Some sources of uncertainty in measurement were calculated by means of ray tracing simulations and the uncertainty budget was estimated within λ/40.

  2. Simultaneous time-space resolved reflectivity and interferometric measurements of dielectrics excited with femtosecond laser pulses

    Science.gov (United States)

    Garcia-Lechuga, M.; Haahr-Lillevang, L.; Siegel, J.; Balling, P.; Guizard, S.; Solis, J.

    2017-06-01

    Simultaneous time-and-space resolved reflectivity and interferometric measurements over a temporal span of 300 ps have been performed in fused silica and sapphire samples excited with 800 nm, 120 fs laser pulses at energies slightly and well above the ablation threshold. The experimental results have been simulated in the frame of a multiple-rate equation model including light propagation. The comparison of the temporal evolution of the reflectivity and the interferometric measurements at 400 nm clearly shows that the two techniques interrogate different material volumes during the course of the process. While the former is sensitive to the evolution of the plasma density in a very thin ablating layer at the surface, the second yields an averaged plasma density over a larger volume. It is shown that self-trapped excitons do not appreciably contribute to carrier relaxation in fused silica at fluences above the ablation threshold, most likely due to Coulomb screening effects at large excited carrier densities. For both materials, at fluences well above the ablation threshold, the maximum measured plasma reflectivity shows a saturation behavior consistent with a scattering rate proportional to the plasma density in this fluence regime. Moreover, for both materials and for pulse energies above the ablation threshold and delays in the few tens of picoseconds range, a simultaneous "low reflectivity" and "low transmission" behavior is observed. Although this behavior has been identified in the past as a signature of femtosecond laser-induced ablation, its origin is alternatively discussed in terms of the optical properties of a material undergoing strong isochoric heating, before having time to substantially expand or exchange energy with the surrounding media.

  3. GNSS as a sea ice sensor - detecting coastal freeze states with ground-based GNSS-R

    Science.gov (United States)

    Strandberg, Joakim; Hobiger, Thomas; Haas, Rüdiger

    2017-04-01

    Based on the idea of using freely available signals for remote sensing, ground-based GNSS-reflectometry (GNSS-R) has found more and more applications in hydrology, oceanography, agriculture and other Earth sciences. GNSS-R is based on analysing the elevation dependent SNR patterns of GNSS signals, and traditionally only the oscillation frequency and phase have been studied to retrieve parameters from the reflecting surfaces. However, recently Strandberg et al. (2016) developed an inversion algorithm that has changed the paradigms of ground-based GNSS-R as it enables direct access to the radiometric properties of the reflector. Using the signal envelope and the rate at which the magnitude of the SNR oscillations are damped w.r.t. satellite elevation, the algorithm retrieves the roughness of the reflector surface amongst other parameters. Based on this idea, we demonstrate for the first time that a GNSS installation situated close to the coastline can detect the presence of sea-ice unambiguously. Using data from the GTGU antenna at the Onsala Space Observatory, Sweden, the time series of the derived damping parameter clearly matches the occurrence of ice in the bay where the antenna is situated. Our results were validated against visual inspection logs as well as with the help of ice charts from the Swedish Meteorological and Hydrological Institute. Our method is even sensitive to partial and intermediate ice formation stages, with clear difference in response between frazil ice and both open and solidly frozen water surfaces. As the GTGU installation is entirely built with standard geodetic equipment, the method can be applied directly to any coastal GNSS site, allowing analysis of both new and historical data. One can use the method as an automatic way of retrieving independent ground truth data for ice extent measurements for use in hydrology, cryosphere studies, and even societal interest fields such as sea transportation. Finally, the new method opens up for

  4. Spatial and Temporal Analysis of Winter Fog Episodes over South Asia by exploiting ground-based and satellite observations

    Science.gov (United States)

    Fahim Khokhar, Muhammad; Yasmin, Naila; Zaib, Naila; Murtaza, Rabia; Noreen, Asma; Ishtiaq, Hira; Khayyam, Junaid; Panday, Arnico

    2016-04-01

    The South Asian region in general and the Indo-Gangetic Plains (IGP) in particular hold about 1/6th of the world's population and is considered as one of the major hotspots with increasing air pollution. Due to growing population and globalization, South Asia is experiencing high transformations in the urban and industrial sectors. Fog is one of the meteorological/environmental phenomena which can generate significant social and economic problems especially havoc to air and road traffic. Meteorological stations provide information about the fog episodes only on the basis of point observation. Continuous monitoring as well as a spatially coherent picture of fog distribution can only be possible through the use of satellite imagery. Current study focus on winter fog episodes over South Asian region using Moderate Resolution Image Spectrometer (MODIS) Level 2 Terra Product and other MODIS Aerosol Product in addition to ground-based sampling and AERONET measurements. MODIS Corrected Reflectance RGBs are used to analyse the spatial extent of fog over study area. MOD04 level 2 Collection 6 data is used to study aerosol load and distribution which are further characterised by using aerosol type land product of MODIS. In order to study the variation of ground based observations from satellite data MODIS, AERONET and high volume air Sampler were used. Main objective of this study was to explore the spatial extent of fog, its causes and to analyse the Aerosol Optical Depth (AOD) over South Asia with particular focus over Indo-Gangetic Plains (IGP). Current studies show a descent increase in AOD from past few decades over South Asia and is contributing to poor air quality in the region due to growing population, urbanization, and industrialization. Smoke and absorbing aerosol are major constituent of fog over South Asia. Furthermore, winter 2014-15 extended span of Fog was also observed over South Asia. A significant correlation between MODIS (AOD) and AERONET Station (AOD

  5. Development and Validation of a Self-Report Measure of Mentalizing: The Reflective Functioning Questionnaire.

    Directory of Open Access Journals (Sweden)

    Peter Fonagy

    Full Text Available Reflective functioning or mentalizing is the capacity to interpret both the self and others in terms of internal mental states such as feelings, wishes, goals, desires, and attitudes. This paper is part of a series of papers outlining the development and psychometric features of a new self-report measure, the Reflective Functioning Questionnaire (RFQ, designed to provide an easy to administer self-report measure of mentalizing. We describe the development and initial validation of the RFQ in three studies. Study 1 focuses on the development of the RFQ, its factor structure and construct validity in a sample of patients with Borderline Personality Disorder (BPD and Eating Disorder (ED (n = 108 and normal controls (n = 295. Study 2 aims to replicate these findings in a fresh sample of 129 patients with personality disorder and 281 normal controls. Study 3 addresses the relationship between the RFQ, parental reflective functioning and infant attachment status as assessed with the Strange Situation Procedure (SSP in a sample of 136 community mothers and their infants. In both Study 1 and 2, confirmatory factor analyses yielded two factors assessing Certainty (RFQ_C and Uncertainty (RFQ_U about the mental states of self and others. These two factors were relatively distinct, invariant across clinical and non-clinical samples, had satisfactory internal consistency and test-retest stability, and were largely unrelated to demographic features. The scales discriminated between patients and controls, and were significantly and in theoretically predicted ways correlated with measures of empathy, mindfulness and perspective-taking, and with both self-reported and clinician-reported measures of borderline personality features and other indices of maladaptive personality functioning. Furthermore, the RFQ scales were associated with levels of parental reflective functioning, which in turn predicted infant attachment status in the SSP. Overall, this study lends

  6. Algorithm of extraction optics properties from the measurement of spatially resolved diffuse reflectance

    International Nuclear Information System (INIS)

    Cunill Rodriguez, Margarita; Delgado Atencio, Jose Alberto; Castro Ramos, Jorge; Vazquez y Montiel, Sergio

    2009-01-01

    There are several methods to obtain the optical parameters of biological tissues from the measurement of spatially resolved diffuse reflectance. One of them is well-known as Video Reflectometry in which a camera CCD is used as detection and recording system of the lateral distribution of diffuse reflectance Rd(r) when an infinitely narrow light beam impinges on the tissue. In this paper, we present an algorithm that we have developed for the calibration and application of an experimental set-up of Video Reflectometry destined to extract the optical properties of models of biological tissues with optical properties similar to the human skin. The results of evaluation of the accuracy of the algorithm for optical parameters extraction is shown for a set of proofs reflectance curves with known values of these parameters. In the generation of these curves the simulation of measurement errors was also considered. The results show that it is possible to extract the optical properties with an accuracy error of less than 1% for all the proofs curves. (Author)

  7. Biomass Burning Aerosol Absorption Measurements with MODIS Using the Critical Reflectance Method

    Science.gov (United States)

    Zhu, Li; Martins, Vanderlei J.; Remer, Lorraine A.

    2010-01-01

    This research uses the critical reflectance technique, a space-based remote sensing method, to measure the spatial distribution of aerosol absorption properties over land. Choosing two regions dominated by biomass burning aerosols, a series of sensitivity studies were undertaken to analyze the potential limitations of this method for the type of aerosol to be encountered in the selected study areas, and to show that the retrieved results are relatively insensitive to uncertainties in the assumptions used in the retrieval of smoke aerosol. The critical reflectance technique is then applied to Moderate Resolution Imaging Spectrometer (MODIS) data to retrieve the spectral aerosol single scattering albedo (SSA) in South African and South American 35 biomass burning events. The retrieved results were validated with collocated Aerosol Robotic Network (AERONET) retrievals. One standard deviation of mean MODIS retrievals match AERONET products to within 0.03, the magnitude of the AERONET uncertainty. The overlap of the two retrievals increases to 88%, allowing for measurement variance in the MODIS retrievals as well. The ensemble average of MODIS-derived SSA for the Amazon forest station is 0.92 at 670 nm, and 0.84-0.89 for the southern African savanna stations. The critical reflectance technique allows evaluation of the spatial variability of SSA, and shows that SSA in South America exhibits higher spatial variation than in South Africa. The accuracy of the retrieved aerosol SSA from MODIS data indicates that this product can help to better understand 44 how aerosols affect the regional and global climate.

  8. A design for a ground-based data management system

    Science.gov (United States)

    Lambird, Barbara A.; Lavine, David

    1988-01-01

    An initial design for a ground-based data management system which includes intelligent data abstraction and cataloging is described. The large quantity of data on some current and future NASA missions leads to significant problems in providing scientists with quick access to relevant data. Human screening of data for potential relevance to a particular study is time-consuming and costly. Intelligent databases can provide automatic screening when given relevent scientific parameters and constraints. The data management system would provide, at a minimum, information of availability of the range of data, the type available, specific time periods covered together with data quality information, and related sources of data. The system would inform the user about the primary types of screening, analysis, and methods of presentation available to the user. The system would then aid the user with performing the desired tasks, in such a way that the user need only specify the scientific parameters and objectives, and not worry about specific details for running a particular program. The design contains modules for data abstraction, catalog plan abstraction, a user-friendly interface, and expert systems for data handling, data evaluation, and application analysis. The emphasis is on developing general facilities for data representation, description, analysis, and presentation that will be easily used by scientists directly, thus bypassing the knowledge acquisition bottleneck. Expert system technology is used for many different aspects of the data management system, including the direct user interface, the interface to the data analysis routines, and the analysis of instrument status.

  9. Use of ground-based wind profiles in mesoscale forecasting

    Science.gov (United States)

    Schlatter, Thomas W.

    1985-01-01

    A brief review is presented of recent uses of ground-based wind profile data in mesoscale forecasting. Some of the applications are in real time, and some are after the fact. Not all of the work mentioned here has been published yet, but references are given wherever possible. As Gage and Balsley (1978) point out, sensitive Doppler radars have been used to examine tropospheric wind profiles since the 1970's. It was not until the early 1980's, however, that the potential contribution of these instruments to operational forecasting and numerical weather prediction became apparent. Profiler winds and radiosonde winds compare favorably, usually within a few m/s in speed and 10 degrees in direction (see Hogg et al., 1983), but the obvious advantage of the profiler is its frequent (hourly or more often) sampling of the same volume. The rawinsonde balloon is launched only twice a day and drifts with the wind. In this paper, I will: (1) mention two operational uses of data from a wind profiling system developed jointly by the Wave Propagation and Aeronomy Laboratories of NOAA; (2) describe a number of displays of these same data on a workstation for mesoscale forecasting developed by the Program for Regional Observing and Forecasting Services (PROFS); and (3) explain some interesting diagnostic calculations performed by meteorologists of the Wave Propagation Laboratory.

  10. Tissue Engineering of Cartilage on Ground-Based Facilities

    Science.gov (United States)

    Aleshcheva, Ganna; Bauer, Johann; Hemmersbach, Ruth; Egli, Marcel; Wehland, Markus; Grimm, Daniela

    2016-06-01

    Investigations under simulated microgravity offer the opportunity for a better understanding of the influence of altered gravity on cells and the scaffold-free three-dimensional (3D) tissue formation. To investigate the short-term influence, human chondrocytes were cultivated for 2 h, 4 h, 16 h, and 24 h on a 2D Fast-Rotating Clinostat (FRC) in DMEM/F-12 medium supplemented with 10 % FCS. We detected holes in the vimentin network, perinuclear accumulations of vimentin after 2 h, and changes in the chondrocytes shape visualised by F-actin staining after 4 h of FRC-exposure. Scaffold-free cultivation of chondrocytes for 7 d on the Random Positioning Machine (RPM), the FRC and the Rotating Wall Vessel (RWV) resulted in spheroid formation, a phenomenon already known from spaceflight experiments with chondrocytes (MIR Space Station) and thyroid cancer cells (SimBox/Shenzhou-8 space mission). The experiments enabled by the ESA-CORA-GBF programme gave us an optimal opportunity to study gravity-related cellular processes, validate ground-based facilities for our chosen cell system, and prepare long-term experiments under real microgravity conditions in space

  11. Ground-based detection of G star superflares with NGTS

    Science.gov (United States)

    Jackman, James A. G.; Wheatley, Peter J.; Pugh, Chloe E.; Gänsicke, Boris T.; Gillen, Edward; Broomhall, Anne-Marie; Armstrong, David J.; Burleigh, Matthew R.; Chaushev, Alexander; Eigmüller, Philipp; Erikson, Anders; Goad, Michael R.; Grange, Andrew; Günther, Maximilian N.; Jenkins, James S.; McCormac, James; Raynard, Liam; Thompson, Andrew P. G.; Udry, Stéphane; Walker, Simon; Watson, Christopher A.; West, Richard G.

    2018-04-01

    We present high cadence detections of two superflares from a bright G8 star (V = 11.56) with the Next Generation Transit Survey (NGTS). We improve upon previous superflare detections by resolving the flare rise and peak, allowing us to fit a solar flare inspired model without the need for arbitrary break points between rise and decay. Our data also enables us to identify substructure in the flares. From changing starspot modulation in the NGTS data we detect a stellar rotation period of 59 hours, along with evidence for differential rotation. We combine this rotation period with the observed ROSAT X-ray flux to determine that the star's X-ray activity is saturated. We calculate the flare bolometric energies as 5.4^{+0.8}_{-0.7}× 10^{34}and 2.6^{+0.4}_{-0.3}× 10^{34}erg and compare our detections with G star superflares detected in the Kepler survey. We find our main flare to be one of the largest amplitude superflares detected from a bright G star. With energies more than 100 times greater than the Carrington event, our flare detections demonstrate the role that ground-based instruments such as NGTS can have in assessing the habitability of Earth-like exoplanets, particularly in the era of PLATO.

  12. Depolarization ratio of polar stratospheric clouds in coastal Antarctica: comparison analysis between ground-based Micro Pulse Lidar and space-borne CALIOP observations

    Directory of Open Access Journals (Sweden)

    C. Córdoba-Jabonero

    2013-03-01

    Full Text Available Polar stratospheric clouds (PSCs play an important role in polar ozone depletion, since they are involved in diverse ozone destruction processes (chlorine activation, denitrification. The degree of that ozone reduction is depending on the type of PSCs, and hence on their occurrence. Therefore PSC characterization, mainly focused on PSC-type discrimination, is widely demanded. The backscattering (R and volume linear depolarization (δV ratios are the parameters usually used in lidar measurements for PSC detection and identification. In this work, an improved version of the standard NASA/Micro Pulse Lidar (MPL-4, which includes a built-in depolarization detection module, has been used for PSC observations above the coastal Antarctic Belgrano II station (Argentina, 77.9° S 34.6° W, 256 m a.s.l. since 2009. Examination of the MPL-4 δV feature as a suitable index for PSC-type discrimination is based on the analysis of the two-channel data, i.e., the parallel (p- and perpendicular (s- polarized MPL signals. This study focuses on the comparison of coincident δV-profiles as obtained from ground-based MPL-4 measurements during three Antarctic winters with those reported from the space-borne lidar CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization aboard the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation satellite in the same period (83 simultaneous cases are analysed for 2009–2011 austral winter times. Three different approaches are considered for the comparison analysis between both lidar profile data sets in order to test the degree of agreement: the correlation coefficient (CC, as a measure of the relationship between both PSC vertical structures; the mean differences together with their root mean square (RMS values found between data sets; and the percentage differences (BIAS, parameter also used in profiling comparisons between CALIOP and other ground-based lidar systems. All of them are examined as a function

  13. Measurement and models of bent KAP(001) crystal integrated reflectivity and resolution (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Loisel, G. P., E-mail: gploise@sandia.gov; Wu, M.; Lake, P.; Dunham, G. S.; Bailey, J. E.; Rochau, G. A. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Stolte, W. [National Security Technologies, LLC, Livermore, California 94551 (United States); Kruschwitz, C. [National Security Technologies, LLC, Los Alamos, New Mexico 87544 (United States)

    2016-11-15

    The Advanced Light Source beamline-9.3.1 x-rays are used to calibrate the rocking curve of bent potassium acid phthalate (KAP) crystals in the 2.3-4.5 keV photon-energy range. Crystals are bent on a cylindrically convex substrate with a radius of curvature ranging from 2 to 9 in. and also including the flat case to observe the effect of bending on the KAP spectrometric properties. As the bending radius increases, the crystal reflectivity converges to the mosaic crystal response. The X-ray Oriented Programs (XOP) multi-lamellar model of bent crystals is used to model the rocking curve of these crystals and the calibration data confirm that a single model is adequate to reproduce simultaneously all measured integrated reflectivities and rocking-curve FWHM for multiple radii of curvature in both 1st and 2nd order of diffraction.

  14. Intra-Cavity Total Reflection For High Sensitivity Measurement Of Optical Properties

    Science.gov (United States)

    Pipino, Andrew Charles Rule

    1999-11-16

    An optical cavity resonator device is provided for conducting sensitive murement of optical absorption by matter in any state with diffraction-limited spatial resolution through utilization of total internal reflection within a high-Q (high quality, low loss) optical cavity. Intracavity total reflection generates an evanescent wave that decays exponentially in space at a point external to the cavity, thereby providing a localized region where absorbing materials can be sensitively probed through alteration of the Q-factor of the otherwise isolated cavity. When a laser pulse is injected into the cavity and passes through the evanescent state, an amplitude loss resulting from absorption is incurred that reduces the lifetime of the pulse in the cavity. By monitoring the decay of the injected pulse, the absorption coefficient of manner within the evanescent wave region is accurately obtained from the decay time measurement.

  15. Measuring solar reflectance - Part I: Defining a metric that accurately predicts solar heat gain

    Energy Technology Data Exchange (ETDEWEB)

    Levinson, Ronnen; Akbari, Hashem; Berdahl, Paul [Heat Island Group, Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States)

    2010-09-15

    Solar reflectance can vary with the spectral and angular distributions of incident sunlight, which in turn depend on surface orientation, solar position and atmospheric conditions. A widely used solar reflectance metric based on the ASTM Standard E891 beam-normal solar spectral irradiance underestimates the solar heat gain of a spectrally selective ''cool colored'' surface because this irradiance contains a greater fraction of near-infrared light than typically found in ordinary (unconcentrated) global sunlight. At mainland US latitudes, this metric R{sub E891BN} can underestimate the annual peak solar heat gain of a typical roof or pavement (slope {<=} 5:12 [23 ]) by as much as 89 W m{sup -2}, and underestimate its peak surface temperature by up to 5 K. Using R{sub E891BN} to characterize roofs in a building energy simulation can exaggerate the economic value N of annual cool roof net energy savings by as much as 23%. We define clear sky air mass one global horizontal (''AM1GH'') solar reflectance R{sub g,0}, a simple and easily measured property that more accurately predicts solar heat gain. R{sub g,0} predicts the annual peak solar heat gain of a roof or pavement to within 2 W m{sup -2}, and overestimates N by no more than 3%. R{sub g,0} is well suited to rating the solar reflectances of roofs, pavements and walls. We show in Part II that R{sub g,0} can be easily and accurately measured with a pyranometer, a solar spectrophotometer or version 6 of the Solar Spectrum Reflectometer. (author)

  16. Measuring solar reflectance Part I: Defining a metric that accurately predicts solar heat gain

    Energy Technology Data Exchange (ETDEWEB)

    Levinson, Ronnen; Akbari, Hashem; Berdahl, Paul

    2010-05-14

    Solar reflectance can vary with the spectral and angular distributions of incident sunlight, which in turn depend on surface orientation, solar position and atmospheric conditions. A widely used solar reflectance metric based on the ASTM Standard E891 beam-normal solar spectral irradiance underestimates the solar heat gain of a spectrally selective 'cool colored' surface because this irradiance contains a greater fraction of near-infrared light than typically found in ordinary (unconcentrated) global sunlight. At mainland U.S. latitudes, this metric RE891BN can underestimate the annual peak solar heat gain of a typical roof or pavement (slope {le} 5:12 [23{sup o}]) by as much as 89 W m{sup -2}, and underestimate its peak surface temperature by up to 5 K. Using R{sub E891BN} to characterize roofs in a building energy simulation can exaggerate the economic value N of annual cool-roof net energy savings by as much as 23%. We define clear-sky air mass one global horizontal ('AM1GH') solar reflectance R{sub g,0}, a simple and easily measured property that more accurately predicts solar heat gain. R{sub g,0} predicts the annual peak solar heat gain of a roof or pavement to within 2 W m{sup -2}, and overestimates N by no more than 3%. R{sub g,0} is well suited to rating the solar reflectances of roofs, pavements and walls. We show in Part II that R{sub g,0} can be easily and accurately measured with a pyranometer, a solar spectrophotometer or version 6 of the Solar Spectrum Reflectometer.

  17. Measurement of the band gap by reflection electron energy loss spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Vos, Maarten, E-mail: maarten.vos@anu.edu.au [Electronic Materials Engineering Department, Research School of Physics and Engineering, The Australian National University, Canberra 0200 (Australia); King, Sean W. [Logic Technology Development, Intel Corporation, Hillsboro, OR 97124 (United States); French, Benjamin L. [Ocotillo Materials Laboratory, Intel Corporation, Chandler, AZ 85248 (United States)

    2016-10-15

    Highlights: • Semiconductors are measured (without surface preparation) using REELS. • At low beam energies it is difficult to measure band gap due to surface impurities. • At very high energies it is difficult to measure band gap due to recoil effect. • At intermediate energies (around 5 keV) one obtains a good estimate of the band gap. - Abstract: We investigate the possibilities of measuring the band gap of a variety of semiconductors and insulators by reflection electron energy loss spectroscopy without additional surface preparation. The band gap is a bulk property, whereas reflection energy loss spectroscopy is generally considered a surface sensitive technique. By changing the energy of the incoming electrons, the degree of surface sensitivity can be varied. Here, we present case studies to determine the optimum condition for the determination of the band gap. At very large incoming electron energies recoil effects interfere with the band gap determination, whereas at very low energies surface effects are obscuring the band gap without surface preparation. Using an incoming energy of 5 keV a reasonable estimate of the band gap is obtained in most cases.

  18. Measurement of the band gap by reflection electron energy loss spectroscopy

    International Nuclear Information System (INIS)

    Vos, Maarten; King, Sean W.; French, Benjamin L.

    2016-01-01

    Highlights: • Semiconductors are measured (without surface preparation) using REELS. • At low beam energies it is difficult to measure band gap due to surface impurities. • At very high energies it is difficult to measure band gap due to recoil effect. • At intermediate energies (around 5 keV) one obtains a good estimate of the band gap. - Abstract: We investigate the possibilities of measuring the band gap of a variety of semiconductors and insulators by reflection electron energy loss spectroscopy without additional surface preparation. The band gap is a bulk property, whereas reflection energy loss spectroscopy is generally considered a surface sensitive technique. By changing the energy of the incoming electrons, the degree of surface sensitivity can be varied. Here, we present case studies to determine the optimum condition for the determination of the band gap. At very large incoming electron energies recoil effects interfere with the band gap determination, whereas at very low energies surface effects are obscuring the band gap without surface preparation. Using an incoming energy of 5 keV a reasonable estimate of the band gap is obtained in most cases.

  19. Ground-based observation of emission lines from the corona of a red-dwarf star.

    Science.gov (United States)

    Schmitt, J H; Wichmann, R

    2001-08-02

    All 'solar-like' stars are surrounded by coronae, which contain magnetically confined plasma at temperatures above 106 K. (Until now, only the Sun's corona could be observed in the optical-as a shimmering envelope during a total solar eclipse.) As the underlying stellar 'surfaces'-the photospheres-are much cooler, some non-radiative process must be responsible for heating the coronae. The heating mechanism is generally thought to be magnetic in origin, but is not yet understood even for the case of the Sun. Ultraviolet emission lines first led to the discovery of the enormous temperature of the Sun's corona, but thermal emission from the coronae of other stars has hitherto been detectable only from space, at X-ray wavelengths. Here we report the detection of emission from highly ionized iron (Fe XIII at 3,388.1 A) in the corona of the red-dwarf star CN Leonis, using a ground-based telescope. The X-ray flux inferred from our data is consistent with previously measured X-ray fluxes, and the non-thermal line width of 18.4 km s-1 indicates great similarities between solar and stellar coronal heating mechanisms. The accessibility and spectral resolution (45,000) of the ground-based instrument are much better than those of X-ray satellites, so a new window to the study of stellar coronae has been opened.

  20. Ground-based VHE γ ray astronomy with air Cherenkov imaging telescopes

    International Nuclear Information System (INIS)

    Mirzoyan, R.

    2000-01-01

    The history of astronomy has been one of the scientific discovery following immediately the introduction of new technology. In this report, we will review shortly the basic development of the atmospheric air Cherenkov light detection technique, particularly the imaging telescope technique, which in the last years led to the firm establishment of a new branch in experimental astronomy, namely ground-based very high-energy (VHE) γ ray astronomy. Milestones in the technology and in the analysis of imaging technique will be discussed. The design of the 17 m diameter MAGIC Telescope, being currently under construction, is based on the development of new technologies for all its major parts and sets new standards in the performance of the ground-based γ detectors. MAGIC is one of the next major steps in the development of the technique being the first instrument that will allow one to carry out measurements also in the not yet investigated energy gap i.e. between 10 and 300 GeV

  1. Validation of ozone monitoring instrument ultraviolet index against ground-based UV index in Kampala, Uganda.

    Science.gov (United States)

    Muyimbwa, Dennis; Dahlback, Arne; Ssenyonga, Taddeo; Chen, Yi-Chun; Stamnes, Jakob J; Frette, Øyvind; Hamre, Børge

    2015-10-01

    The Ozone Monitoring Instrument (OMI) overpass solar ultraviolet (UV) indices have been validated against the ground-based UV indices derived from Norwegian Institute for Air Research UV measurements in Kampala (0.31° N, 32.58° E, 1200 m), Uganda for the period between 2005 and 2014. An excessive use of old cars, which would imply a high loading of absorbing aerosols, could cause the OMI retrieval algorithm to overestimate the surface UV irradiances. The UV index values were found to follow a seasonal pattern with maximum values in March and October. Under all-sky conditions, the OMI retrieval algorithm was found to overestimate the UV index values with a mean bias of about 28%. When only days with radiation modification factor greater than or equal to 65%, 70%, 75%, and 80% were considered, the mean bias between ground-based and OMI overpass UV index values was reduced to 8%, 5%, 3%, and 1%, respectively. The overestimation of the UV index by the OMI retrieval algorithm was found to be mainly due to clouds and aerosols.

  2. The Polarization-Sensitive Bolometers for SPICA and their Potential Use for Ground-Based Application

    Science.gov (United States)

    Reveret, Vincent

    2018-01-01

    CEA is leading the development of Safari-POL, an imaging-polarimeter aboard the SPICA space observatory (ESA M5). SPICA will be able to reach unprecedented sensitivities thanks to its cooled telescope and its ultra-sensitive detectors. The detector assembly of Safari-POL holds three arrays that are cooled down to 50 mK and correspond to three spectral bands : 100, 200 and 350 microns. The detectors (silicon bolometers), benefit from the Herschel/PACS legacy and are also a big step forward in term of sensitivity (improved by two orders of magnitude compared to PACS bolometers) and for polarimetry capabilities. Indeed, each pixel is intrinsically sensitive to two polarization components (Horizontal and Vertical). We will present the Safari-POL concept, the first results of measurements made on the detectors, and future plans for possible ground-based instruments using this technology. We will also present the example of the ArTéMiS camera, installed at APEX, that was developped as a ground-based conterpart of the PACS photometer.

  3. Predicting Electron Population Characteristics in 2-D Using Multispectral Ground-Based Imaging

    Science.gov (United States)

    Grubbs, Guy; Michell, Robert; Samara, Marilia; Hampton, Donald; Jahn, Jorg-Micha

    2018-01-01

    Ground-based imaging and in situ sounding rocket data are compared to electron transport modeling for an active inverted-V type auroral event. The Ground-to-Rocket Electrodynamics-Electrons Correlative Experiment (GREECE) mission successfully launched from Poker Flat, Alaska, on 3 March 2014 at 11:09:50 UT and reached an apogee of approximately 335 km over the aurora. Multiple ground-based electron-multiplying charge-coupled device (EMCCD) imagers were positioned at Venetie, Alaska, and aimed toward magnetic zenith. The imagers observed the intensity of different auroral emission lines (427.8, 557.7, and 844.6 nm) at the magnetic foot point of the rocket payload. Emission line intensity data are correlated with electron characteristics measured by the GREECE onboard electron spectrometer. A modified version of the GLobal airglOW (GLOW) model is used to estimate precipitating electron characteristics based on optical emissions. GLOW predicted the electron population characteristics with 20% error given the observed spectral intensities within 10° of magnetic zenith. Predictions are within 30% of the actual values within 20° of magnetic zenith for inverted-V-type aurora. Therefore, it is argued that this technique can be used, at least in certain types of aurora, such as the inverted-V type presented here, to derive 2-D maps of electron characteristics. These can then be used to further derive 2-D maps of ionospheric parameters as a function of time, based solely on multispectral optical imaging data.

  4. A New Technique to Observe ENSO Activity via Ground-Based GPS Receivers

    Science.gov (United States)

    Suparta, Wayan; Iskandar, Ahmad; Singh, Mandeep Singh Jit

    In an attempt to study the effects of global climate change in the tropics for improving global climate model, this paper aims to detect the ENSO events, especially El Nino phase by using ground-based GPS receivers. Precipitable water vapor (PWV) obtained from the Global Positioning System (GPS) Meteorology measurements in line with the sea surface temperature anomaly (SSTa) are used to connect their response to El Niño activity. The data gathered from four selected stations over the Southeast Asia, namely PIMO (Philippines), KUAL (Malaysia), NTUS (Singapore) and BAKO (Indonesia) for the year of 2009/2010 were processed. A strong correlation was observed for PIMO station with a correlation coefficient of -0.90, significantly at the 99 % confidence level. In general, the relationship between GPS PWV and SSTa at all stations on a weekly basis showed with a negative correlation. The negative correlation indicates that during the El Niño event, the PWV variation was in decreased trend. Decreased trend of PWV value is caused by a dry season that affected the GPS signals in the ocean-atmospheric coupling. Based on these promising results, we can propose that the ground-based GPS receiver is capable used to monitor ENSO activity and this is a new prospective method that previously unexplored.

  5. Characterizing the Vertical Distribution of Aerosols using Ground-based Multiwavelength Lidar Data

    Science.gov (United States)

    Ferrare, R. A.; Thorsen, T. J.; Clayton, M.; Mueller, D.; Chemyakin, E.; Burton, S. P.; Goldsmith, J.; Holz, R.; Kuehn, R.; Eloranta, E. W.; Marais, W.; Newsom, R. K.; Liu, X.; Sawamura, P.; Holben, B. N.; Hostetler, C. A.

    2016-12-01

    Observations of aerosol optical and microphysical properties are critical for developing and evaluating aerosol transport model parameterizations and assessing global aerosol-radiation impacts on climate. During the Combined HSRL And Raman lidar Measurement Study (CHARMS), we investigated the synergistic use of ground-based Raman lidar and High Spectral Resolution Lidar (HSRL) measurements to retrieve aerosol properties aloft. Continuous (24/7) operation of these co-located lidars during the ten-week CHARMS mission (mid-July through September 2015) allowed the acquisition of a unique, multiwavelength ground-based lidar dataset for studying aerosol properties above the Southern Great Plains (SGP) site. The ARM Raman lidar measured profiles of aerosol backscatter, extinction and depolarization at 355 nm as well as profiles of water vapor mixing ratio and temperature. The University of Wisconsin HSRL simultaneously measured profiles of aerosol backscatter, extinction and depolarization at 532 nm and aerosol backscatter at 1064 nm. Recent advances in both lidar retrieval theory and algorithm development demonstrate that vertically-resolved retrievals using such multiwavelength lidar measurements of aerosol backscatter and extinction can help constrain both the aerosol optical (e.g. complex refractive index, scattering, etc.) and microphysical properties (e.g. effective radius, concentrations) as well as provide qualitative aerosol classification. Based on this work, the NASA Langley Research Center (LaRC) HSRL group developed automated algorithms for classifying and retrieving aerosol optical and microphysical properties, demonstrated these retrievals using data from the unique NASA/LaRC airborne multiwavelength HSRL-2 system, and validated the results using coincident airborne in situ data. We apply these algorithms to the CHARMS multiwavelength (Raman+HSRL) lidar dataset to retrieve aerosol properties above the SGP site. We present some profiles of aerosol effective

  6. Formative versus reflective measurement: an illustration using work-family balance.

    Science.gov (United States)

    Ellwart, Thomas; Konradt, Udo

    2011-01-01

    The aim of this article is to propose the formative measurement approach that can be used in various constructs of applied psychology. To illustrate this approach, the authors will (a) discuss the distinction between commonly used principal-factor (reflective) measures in comparison to the composite (formative) latent variable model, which is often applied in other disciplines such as marketing or engineering, and (b) point out the advantages and limitations of formative specifications using the example of the work-family balance (WFB) construct. Data collected from 2 large cross-sectional field studies confirm the reliability and validity of formative WFB measures as well as its predictive value regarding criteria of WFB (i.e., job satisfaction, family satisfaction, and life satisfaction). Last, the specific informational value of each formative indicator will be demonstrated and discussed in terms of practical implications for the assessment in different psychological fields.

  7. Multivariate curve resolution applied to infrared reflection measurements of soil contaminated with an organophosphorus analyte.

    Science.gov (United States)

    Gallagher, Neal B; Blake, Thomas A; Gassman, Paul L; Shaver, Jeremy M; Windig, Willem

    2006-07-01

    Multivariate curve resolution (MCR) is a powerful technique for extracting chemical information from measured spectra of complex mixtures. A modified MCR technique that utilized both measured and second-derivative spectra to account for observed sample-to-sample variability attributable to changes in soil reflectivity was used to estimate the spectrum of dibutyl phosphate (DBP) adsorbed on two different soil types. This algorithm was applied directly to measurements of reflection spectra of soils coated with analyte without resorting to soil preparations such as grinding or dilution in potassium bromide. The results provided interpretable spectra that can be used to guide strategies for detection and classification of organic analytes adsorbed on soil. Comparisons to the neat DBP liquid spectrum showed that the recovered analyte spectra from both soils showed spectral features from methyl, methylene, hydroxyl, and P=O functional groups, but most conspicuous was the absence of the strong PO-(CH2)3CH3 stretch absorption at 1033 cm(-1). These results are consistent with those obtained previously using extended multiplicative scatter correction.

  8. Analysis and suppression of reflections in far-field antenna measurement ranges

    OpenAIRE

    Sierra Castañer, Manuel; Cano Facila, Francisco Jose; Foged, Lars Jacob; Saccardi, Francesco; Nader Kawassaki, Guilherme; Raimundi, Lucas dos Reis; Vilela Rezende, Stefano Albino

    2013-01-01

    This paper presents the analysis of the reflections in two kind of spherical far field ranges: one if the classical acquisition where the AUT is rotated and the second one corresponds to the systems where the AUT is fixed and the antenna probe is rotated. In large far field systems this is not possible, but this can be used to the measurement of small antennas, for instance, with the SATIMO StarGate system. In both cases, it is assumed that only one frequency is acquired and the results shoul...

  9. Measurement of the enzymes lactate dehydrogenase and creatine kinase using reflectance spectroscopy and reagent strips.

    Science.gov (United States)

    Stevens, J F; Tsang, W; Newall, R G

    1983-01-01

    Two new methods for the assay of total activities of lactate dehydrogenase and creatine kinase are described, in which the enzyme activities are measured from a solid-state reagent strip during a kinetic reaction, the reaction being monitored in the ultra-violet region of the spectrum by reflectance spectroscopy. The performances of these methods are evaluated, and compared to conventional "wet" chemistry methods. The solid-phase reagent methods demonstrated precision and accuracy acceptable for diagnostic purposes, and were easy to use by trained operators. PMID:6655069

  10. Reflective Optical Chopper Used in NIST High-Power Laser Measurements

    Directory of Open Access Journals (Sweden)

    Cromer, Chris

    2008-11-01

    Full Text Available For the past ten years, NIST has used high-reflectivity, optical choppers as beamsplitters and attenuators when calibrating the absolute responsivity and response linearity of detectors used with high-power CW lasers. The chopper-based technique has several advantages over the use of wedge-shaped transparent materials (usually crystals often used as beam splitters in this type of measurement system. We describe the design, operation and calibration of these choppers. A comparison between choppers and transparent wedge beampslitters is also discussed.

  11. Monitoring Hydraulic Fracturing Using Ground-Based Controlled Source Electromagnetics

    Science.gov (United States)

    Hickey, M. S.; Trevino, S., III; Everett, M. E.

    2017-12-01

    Hydraulic fracturing allows hydrocarbon production in low permeability formations. Imaging the distribution of fluid used to create a hydraulic fracture can aid in the characterization of fracture properties such as extent of plume penetration as well as fracture azimuth and symmetry. This could contribute to improving the efficiency of an operation, for example, in helping to determine ideal well spacing or the need to refracture a zone. A ground-based controlled-source electromagnetics (CSEM) technique is ideal for imaging the fluid due to the change in field caused by the difference in the conductive properties of the fluid when compared to the background. With advances in high signal to noise recording equipment, coupled with a high-power, broadband transmitter we can show hydraulic fracture extent and azimuth with minimal processing. A 3D finite element code is used to model the complete well casing along with the layered subsurface. This forward model is used to optimize the survey design and isolate the band of frequencies with the best response. In the field, the results of the modeling are also used to create a custom pseudorandom numeric (PRN) code to control the frequencies transmitted through a grounded dipole source. The receivers record the surface voltage across two grounded dipoles, one parallel and one perpendicular to the transmitter. The data are presented as the displays of amplitude ratios across several frequencies with the associated spatial information. In this presentation, we show multiple field results in multiple basins in the United States along with the CSEM theory used to create the survey designs.

  12. OBSERVATIONAL SELECTION EFFECTS WITH GROUND-BASED GRAVITATIONAL WAVE DETECTORS

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hsin-Yu; Holz, Daniel E. [University of Chicago, Chicago, Illinois 60637 (United States); Essick, Reed; Vitale, Salvatore; Katsavounidis, Erik [LIGO, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2017-01-20

    Ground-based interferometers are not perfect all-sky instruments, and it is important to account for their behavior when considering the distribution of detected events. In particular, the LIGO detectors are most sensitive to sources above North America and the Indian Ocean, and as the Earth rotates, the sensitive regions are swept across the sky. However, because the detectors do not acquire data uniformly over time, there is a net bias on detectable sources’ right ascensions. Both LIGO detectors preferentially collect data during their local night; it is more than twice as likely to be local midnight than noon when both detectors are operating. We discuss these selection effects and how they impact LIGO’s observations and electromagnetic (EM) follow-up. Beyond galactic foregrounds associated with seasonal variations, we find that equatorial observatories can access over 80% of the localization probability, while mid-latitudes will access closer to 70%. Facilities located near the two LIGO sites can observe sources closer to their zenith than their analogs in the south, but the average observation will still be no closer than 44° from zenith. We also find that observatories in Africa or the South Atlantic will wait systematically longer before they can begin observing compared to the rest of the world; though, there is a preference for longitudes near the LIGOs. These effects, along with knowledge of the LIGO antenna pattern, can inform EM follow-up activities and optimization, including the possibility of directing observations even before gravitational-wave events occur.

  13. Project management for complex ground-based instruments: MEGARA plan

    Science.gov (United States)

    García-Vargas, María. Luisa; Pérez-Calpena, Ana; Gil de Paz, Armando; Gallego, Jesús; Carrasco, Esperanza; Cedazo, Raquel; Iglesias, Jorge

    2014-08-01

    The project management of complex instruments for ground-based large telescopes is a challenge itself. A good management is a clue for project success in terms of performance, schedule and budget. Being on time has become a strict requirement for two reasons: to assure the arrival at the telescope due to the pressure on demanding new instrumentation for this first world-class telescopes and to not fall in over-costs. The budget and cash-flow is not always the expected one and has to be properly handled from different administrative departments at the funding centers worldwide distributed. The complexity of the organizations, the technological and scientific return to the Consortium partners and the participation in the project of all kind of professional centers working in astronomical instrumentation: universities, research centers, small and large private companies, workshops and providers, etc. make the project management strategy, and the tools and procedures tuned to the project needs, crucial for success. MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) is a facility instrument of the 10.4m GTC (La Palma, Spain) working at optical wavelengths that provides both Integral-Field Unit (IFU) and Multi-Object Spectrograph (MOS) capabilities at resolutions in the range R=6,000-20,000. The project is an initiative led by Universidad Complutense de Madrid (Spain) in collaboration with INAOE (Mexico), IAA-CSIC (Spain) and Universidad Politécnica de Madrid (Spain). MEGARA is being developed under contract with GRANTECAN.

  14. OBSERVATIONAL SELECTION EFFECTS WITH GROUND-BASED GRAVITATIONAL WAVE DETECTORS

    International Nuclear Information System (INIS)

    Chen, Hsin-Yu; Holz, Daniel E.; Essick, Reed; Vitale, Salvatore; Katsavounidis, Erik

    2017-01-01

    Ground-based interferometers are not perfect all-sky instruments, and it is important to account for their behavior when considering the distribution of detected events. In particular, the LIGO detectors are most sensitive to sources above North America and the Indian Ocean, and as the Earth rotates, the sensitive regions are swept across the sky. However, because the detectors do not acquire data uniformly over time, there is a net bias on detectable sources’ right ascensions. Both LIGO detectors preferentially collect data during their local night; it is more than twice as likely to be local midnight than noon when both detectors are operating. We discuss these selection effects and how they impact LIGO’s observations and electromagnetic (EM) follow-up. Beyond galactic foregrounds associated with seasonal variations, we find that equatorial observatories can access over 80% of the localization probability, while mid-latitudes will access closer to 70%. Facilities located near the two LIGO sites can observe sources closer to their zenith than their analogs in the south, but the average observation will still be no closer than 44° from zenith. We also find that observatories in Africa or the South Atlantic will wait systematically longer before they can begin observing compared to the rest of the world; though, there is a preference for longitudes near the LIGOs. These effects, along with knowledge of the LIGO antenna pattern, can inform EM follow-up activities and optimization, including the possibility of directing observations even before gravitational-wave events occur.

  15. Space- and Ground-based Coronal Spectro-Polarimetry

    Science.gov (United States)

    Fineschi, Silvano; Bemporad, Alessandro; Rybak, Jan; Capobianco, Gerardo

    This presentation gives an overview of the near-future perspectives of ultraviolet and visible-light spectro-polarimetric instrumentation for probing coronal magnetism from space-based and ground-based observatories. Spectro-polarimetric imaging of coronal emission-lines in the visible-light wavelength-band provides an important diagnostics tool of the coronal magnetism. The interpretation in terms of Hanle and Zeeman effect of the line-polarization in forbidden emission-lines yields information on the direction and strength of the coronal magnetic field. As study case, this presentation will describe the Torino Coronal Magnetograph (CorMag) for the spectro-polarimetric observation of the FeXIV, 530.3 nm, forbidden emission-line. CorMag - consisting of a Liquid Crystal (LC) Lyot filter and a LC linear polarimeter - has been recently installed on the Lomnicky Peak Observatory 20cm Zeiss coronagraph. The preliminary results from CorMag will be presented. The linear polarization by resonance scattering of coronal permitted line-emission in the ultraviolet (UV)can be modified by magnetic fields through the Hanle effect. Space-based UV spectro-polarimeters would provide an additional tool for the disgnostics of coronal magnetism. As a case study of space-borne UV spectro-polarimeters, this presentation will describe the future upgrade of the Sounding-rocket Coronagraphic Experiment (SCORE) to include the capability of imaging polarimetry of the HI Lyman-alpha, 121.6 nm. SCORE is a multi-wavelength imager for the emission-lines, HeII 30.4 nm and HI 121.6 nm, and visible-light broad-band emission of the polarized K-corona. SCORE has flown successfully in 2009. This presentation will describe how in future re-flights SCORE could observe the expected Hanle effect in corona with a HI Lyman-alpha polarimeter.

  16. Simulating the Performance of Ground-Based Optical Asteroid Surveys

    Science.gov (United States)

    Christensen, Eric J.; Shelly, Frank C.; Gibbs, Alex R.; Grauer, Albert D.; Hill, Richard E.; Johnson, Jess A.; Kowalski, Richard A.; Larson, Stephen M.

    2014-11-01

    We are developing a set of asteroid survey simulation tools in order to estimate the capability of existing and planned ground-based optical surveys, and to test a variety of possible survey cadences and strategies. The survey simulator is composed of several layers, including a model population of solar system objects and an orbital integrator, a site-specific atmospheric model (including inputs for seeing, haze and seasonal cloud cover), a model telescope (with a complete optical path to estimate throughput), a model camera (including FOV, pixel scale, and focal plane fill factor) and model source extraction and moving object detection layers with tunable detection requirements. We have also developed a flexible survey cadence planning tool to automatically generate nightly survey plans. Inputs to the cadence planner include camera properties (FOV, readout time), telescope limits (horizon, declination, hour angle, lunar and zenithal avoidance), preferred and restricted survey regions in RA/Dec, ecliptic, and Galactic coordinate systems, and recent coverage by other asteroid surveys. Simulated surveys are created for a subset of current and previous NEO surveys (LINEAR, Pan-STARRS and the three Catalina Sky Survey telescopes), and compared against the actual performance of these surveys in order to validate the model’s performance. The simulator tracks objects within the FOV of any pointing that were not discovered (e.g. too few observations, too trailed, focal plane array gaps, too fast or slow), thus dividing the population into “discoverable” and “discovered” subsets, to inform possible survey design changes. Ongoing and future work includes generating a realistic “known” subset of the model NEO population, running multiple independent simulated surveys in coordinated and uncoordinated modes, and testing various cadences to find optimal strategies for detecting NEO sub-populations. These tools can also assist in quantifying the efficiency of novel

  17. Foundation Investigation for Ground Based Radar Project-Kwajalein Island, Marshall Islands

    Science.gov (United States)

    1990-04-01

    iL_ COPY MISCELLANEOUS PAPER GL-90-5 i iFOUNDATION INVESTIGATION FOR GROUND BASED RADAR PROJECT--KWAJALEIN ISLAND, MARSHALL ISLANDS by Donald E...C!assification) Foundatioa Investigation for Ground Based Radar Project -- Kwajalein Island, Marshall Islands 12. PERSONAL AUTHOR(S) Yule, Donald E...investigation for the Ground Based Radar Project -- Kwajalein Island, Marshall Islands , are presented.- eophysical tests comprised of surface refrac- tion

  18. Tracking morphological changes and slope instability using spaceborne and ground-based SAR data

    Science.gov (United States)

    Di Traglia, Federico; Nolesini, Teresa; Ciampalini, Andrea; Solari, Lorenzo; Frodella, William; Bellotti, Fernando; Fumagalli, Alfio; De Rosa, Giuseppe; Casagli, Nicola

    2018-01-01

    Stromboli (Aeolian Archipelago, Italy) is an active volcano that is frequently affected by moderate to large mass wasting, which has occasionally triggered tsunamis. With the aim of understanding the relationship between the geomorphologic evolution and slope instability of Stromboli, remote sensing information from space-born Synthetic Aperture Radar (SAR) change detection and interferometry (InSAR) () and Ground Based InSAR (GBInSAR) was compared with field observations and morphological analyses. Ground reflectivity and SqueeSAR™ (an InSAR algorithm for surface deformation monitoring) displacement measurements from X-band COSMO-SkyMed satellites (CSK) were analysed together with displacement measurements from a permanent-sited, Ku-band GBInSAR system. Remote sensing results were compared with a preliminary morphological analysis of the Sciara del Fuoco (SdF) steep volcanic flank, which was carried out using a high-resolution Digital Elevation Model (DEM). Finally, field observations, supported by infrared thermographic surveys (IRT), allowed the interpretation and validation of remote sensing data. The analysis of the entire dataset (collected between January 2010 and December 2014) covers a period characterized by a low intensity of Strombolian activity. This period was punctuated by the occurrence of lava overflows, occurring from the crater terrace evolving downslope toward SdF, and flank eruptions, such as the 2014 event. The amplitude of the CSK images collected between February 22nd, 2010, and December 18th, 2014, highlights that during periods characterized by low-intensity Strombolian activity, the production of materials ejected from the crater terrace towards the SdF is generally low, and erosion is the prevailing process mainly affecting the central sector of the SdF. CSK-SqueeSAR™ and GBInSAR data allowed the identification of low displacements in the SdF, except for high displacement rates (up to 1.5 mm/h) that were measured following both lava

  19. Portable laser spectrometer for airborne and ground-based remote sensing of geological CO2 emissions.

    Science.gov (United States)

    Queisser, Manuel; Burton, Mike; Allan, Graham R; Chiarugi, Antonio

    2017-07-15

    A 24 kg, suitcase sized, CW laser remote sensing spectrometer (LARSS) with a ~2 km range has been developed. It has demonstrated its flexibility in measuring both atmospheric CO2 from an airborne platform and terrestrial emission of CO2 from a remote mud volcano, Bledug Kuwu, Indonesia, from a ground-based sight. This system scans the CO2 absorption line with 20 discrete wavelengths, as opposed to the typical two-wavelength online offline instrument. This multi-wavelength approach offers an effective quality control, bias control, and confidence estimate of measured CO2 concentrations via spectral fitting. The simplicity, ruggedness, and flexibility in the design allow for easy transportation and use on different platforms with a quick setup in some of the most challenging climatic conditions. While more refinement is needed, the results represent a stepping stone towards widespread use of active one-sided gas remote sensing in the earth sciences.

  20. Experimental design for reflection measurements of highly reactive liquid or solid substances with application to liquid sodium

    International Nuclear Information System (INIS)

    Chan, S.H.; Gossler, A.A.

    1980-01-01

    A versatile goniometer system with associated electronic components and mechanical instruments has been assembled. It is designed to measure spectral, specular reflectances of highly reactive liquid or solid substances over a spectral range of 0.3 to 9 μ and incidence angles of 12 to 30 0 off the normal direction. The capability of measuring reflectances of liquid substances clearly distinguishes this experimental design from conventional systems which are applicable only to solid substances. This design has been used to measure the spectral, specular reflectance of liquid sodium and preliminary results obtained are compared with those of solid sodium measured by other investigators

  1. Intercomparison of Unmanned Aerial Vehicle and Ground-Based Narrow Band Spectrometers Applied to Crop Trait Monitoring in Organic Potato Production

    Directory of Open Access Journals (Sweden)

    Marston Héracles Domingues Franceschini

    2017-06-01

    Full Text Available Vegetation properties can be estimated using optical sensors, acquiring data on board of different platforms. For instance, ground-based and Unmanned Aerial Vehicle (UAV-borne spectrometers can measure reflectance in narrow spectral bands, while different modelling approaches, like regressions fitted to vegetation indices, can relate spectra with crop traits. Although monitoring frameworks using multiple sensors can be more flexible, they may result in higher inaccuracy due to differences related to the sensors characteristics, which can affect information sampling. Also organic production systems can benefit from continuous monitoring focusing on crop management and stress detection, but few studies have evaluated applications with this objective. In this study, ground-based and UAV spectrometers were compared in the context of organic potato cultivation. Relatively accurate estimates were obtained for leaf chlorophyll (RMSE = 6.07 µg·cm−2, leaf area index (RMSE = 0.67 m2·m−2, canopy chlorophyll (RMSE = 0.24 g·m−2 and ground cover (RMSE = 5.5% using five UAV-based data acquisitions, from 43 to 99 days after planting. These retrievals are slightly better than those derived from ground-based measurements (RMSE = 7.25 µg·cm−2, 0.85 m2·m−2, 0.28 g·m−2 and 6.8%, respectively, for the same period. Excluding observations corresponding to the first acquisition increased retrieval accuracy and made outputs more comparable between sensors, due to relatively low vegetation cover on this date. Intercomparison of vegetation indices indicated that indices based on the contrast between spectral bands in the visible and near-infrared, like OSAVI, MCARI2 and CIg provided, at certain extent, robust outputs that could be transferred between sensors. Information sampling at plot level by both sensing solutions resulted in comparable discriminative potential concerning advanced stages of late blight incidence. These results indicate that optical

  2. Comparison of Measurements and FluorMOD Simulations for Solar Induced Chlorophyll Fluorescence and Reflectance of a Corn Crop under Nitrogen Treatments [SIF and Reflectance for Corn

    Science.gov (United States)

    Middleton, Elizabeth M.; Corp, Lawrence A.; Campbell, Petya K. E.

    2007-01-01

    The FLuorescence Explorer (FLEX) satellite concept is one of six semifinalist mission proposals selected in 2006 for pre-Phase studies by the European Space Agency (ESA). The FLEX concept proposes to measure passive solar induced chlorophyll fluorescence (SIF) of terrestrial ecosystems. A new spectral vegetation Fluorescence Model (FluorMOD) was developed to include the effects of steady state SIF on canopy reflectance. We used our laboratory and field measurements previously acquired from foliage and canopies of corn (Zea mays L.) under controlled nitrogen (N) fertilization to parameterize and evaluate FluorMOD. Our data included biophysical properties, fluorescence (F) and reflectance spectra for leaves; reflectance spectra of canopies and soil; solar irradiance; plot-level leaf area index; and canopy SIF emissions determined using the Fraunhofer Line Depth principal for the atmospheric telluric oxygen absorption features at 688 nm (O2-beta) and 760 nm (O2-alpha). FluorMOD simulations implemented in the default "look-up-table" mode did not reproduce the observed magnitudes of leaf F, canopy SIF, or canopy reflectance. However, simulations for all of these parameters agreed with observations when the default FluorMOD information was replaced with measurements, although N treatment responses were underestimated. Recommendations were provided to enhance FluorMOD's potential utility in support of SIF field experiments and studies of agriculture and ecosystems.

  3. TANGOO: A ground-based tilting-filter spectrometer for deriving the temperature in the mesopause region

    Science.gov (United States)

    Wildner, S.; Bittner, M.

    2009-04-01

    TANGOO (Tilting-filter spectrometer for Atmospheric Nocturnal Ground-based Oxygen & hydrOxyl emission measurements) is a passive, ground-based optical instrument for the purpose of a simultanously automatic long-term monitoring of OH(6-2) and O2 atm. Band (0-1) emissions (called "airglow"), yielding rotational temperatures in about 87 and 95 km, respectively. TANGOO, being a transportable and comparatively easy-to-use instrument, is the enhancement of the Argentine Airglow Spectrometer (Scheer, 1987) and shows significant improvements in the temporal resolution and throughput. It will be located on the German Enviromental Research Station "Schneefernerhaus", Zugspitze (47°,4 N, 11° E) and will start measurements in 2009. Objectives of TANGOO cover the analysis of dynamical processes such as gravity waves as well as the identification of climate signals. The observation method will be presented.

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

    Directory of Open Access Journals (Sweden)

    H. S. Negi

    2011-03-01

    Full Text Available In the present paper, spectral reflectance measurements of Himalayan seasonal snow were carried out and analysed to retrieve the snow albedo and effective grain size. The asymptotic radiative transfer (ART theory was applied to retrieve the plane and spherical albedo. The retrieved plane albedo was compared with the measured spectral albedo and a good agreement was observed with ±10% differences. Retrieved integrated albedo was found within ±6% difference with ground observed broadband albedo. The retrieved snow grain sizes using different models based on the ART theory were compared for various snow types and it was observed that the grain size model using two channel method (one in visible and another in NIR region can work well for the Himalayan seasonal snow and it was found consistent with temporal changes in grain size. This method can work very well for clean, dry snow as in the upper Himalaya, but sometimes, due to the low reflectances (<20% using wavelength 1.24 μm, the ART theory cannot be applied, which is common in lower and middle Himalayan old snow. This study is important for monitoring the Himalayan cryosphere using air-borne or space-borne sensors.

  5. A Method of Drusen Measurement Based on the Geometry of Fundus Reflectance

    Directory of Open Access Journals (Sweden)

    Barbazetto Irene

    2003-04-01

    Full Text Available Abstract Background The hallmarks of age-related macular degeneration, the leading cause of blindness in the developed world, are the subretinal deposits known as drusen. Drusen identification and measurement play a key role in clinical studies of this disease. Current manual methods of drusen measurement are laborious and subjective. Our purpose was to expedite clinical research with an accurate, reliable digital method. Methods An interactive semi-automated procedure was developed to level the macular background reflectance for the purpose of morphometric analysis of drusen. 12 color fundus photographs of patients with age-related macular degeneration and drusen were analyzed. After digitizing the photographs, the underlying background pattern in the green channel was leveled by an algorithm based on the elliptically concentric geometry of the reflectance in the normal macula: the gray scale values of all structures within defined elliptical boundaries were raised sequentially until a uniform background was obtained. Segmentation of drusen and area measurements in the central and middle subfields (1000 μm and 3000 μm diameters were performed by uniform thresholds. Two observers using this interactive semi-automated software measured each image digitally. The mean digital measurements were compared to independent stereo fundus gradings by two expert graders (stereo Grader 1 estimated the drusen percentage in each of the 24 regions as falling into one of four standard broad ranges; stereo Grader 2 estimated drusen percentages in 1% to 5% intervals. Results The mean digital area measurements had a median standard deviation of 1.9%. The mean digital area measurements agreed with stereo Grader 1 in 22/24 cases. The 95% limits of agreement between the mean digital area measurements and the more precise stereo gradings of Grader 2 were -6.4 % to +6.8 % in the central subfield and -6.0 % to +4.5 % in the middle subfield. The mean absolute

  6. Early Type Stars as Calibrators for Ground-Based Interferometry

    National Research Council Canada - National Science Library

    Yoon, Jinmi; Peterson, Deane M; Amstrong, Thomas; Clark III, James H; Gilbreath, Charmaine; Pauls, Thomas; Schmitt, Henrique R

    2006-01-01

    Visibility measurements with Michelson interferometers, particularly the measurement of fringe contrast, are affected by various atmospheric and instrumental effects, all of which reduce the measured contrast...

  7. A novel technique for extracting clouds base height using ground based imaging

    Directory of Open Access Journals (Sweden)

    E. Hirsch

    2011-01-01

    Full Text Available The height of a cloud in the atmospheric column is a key parameter in its characterization. Several remote sensing techniques (passive and active, either ground-based or on space-borne platforms and in-situ measurements are routinely used in order to estimate top and base heights of clouds. In this article we present a novel method that combines thermal imaging from the ground and sounded wind profile in order to derive the cloud base height. This method is independent of cloud types, making it efficient for both low boundary layer and high clouds. In addition, using thermal imaging ensures extraction of clouds' features during daytime as well as at nighttime. The proposed technique was validated by comparison to active sounding by ceilometers (which is a standard ground based method, to lifted condensation level (LCL calculations, and to MODIS products obtained from space. As all passive remote sensing techniques, the proposed method extracts only the height of the lowest cloud layer, thus upper cloud layers are not detected. Nevertheless, the information derived from this method can be complementary to space-borne cloud top measurements when deep-convective clouds are present. Unlike techniques such as LCL, this method is not limited to boundary layer clouds, and can extract the cloud base height at any level, as long as sufficient thermal contrast exists between the radiative temperatures of the cloud and its surrounding air parcel. Another advantage of the proposed method is its simplicity and modest power needs, making it particularly suitable for field measurements and deployment at remote locations. Our method can be further simplified for use with visible CCD or CMOS camera (although nighttime clouds will not be observed.

  8. How ground-based observations can support satellite greenhouse gas retrievals

    Science.gov (United States)

    Butler, J. H.; Tans, P. P.; Sweeney, C.; Dlugokencky, E. J.

    2012-04-01

    Global society will eventually accelerate efforts to reduce greenhouse gas emissions in a variety of ways. These would likely involve international treaties, national policies, and regional strategies that will affect a number of economic, social, and environmental sectors. Some strategies will work better than others and some will not work at all. Because trillions of dollars will be involved in pursuing greenhouse gas emission reductions - through realignment of energy production, improvement of efficiencies, institution of taxes, implementation of carbon trading markets, and use of offsets - it is imperative that society be given all the tools at its disposal to ensure the ultimate success of these efforts. Providing independent, globally coherent information on the success of these efforts will give considerable strength to treaties, policies, and strategies. Doing this will require greenhouse gas observations greatly expanded from what we have today. Satellite measurements may ultimately be indispensable in achieving global coverage, but the requirements for accuracy and continuity of measurements over time are demanding if the data are to be relevant. Issues such as those associated with sensor drift, aging electronics, and retrieval artifacts present challenges that can be addressed in part by close coordination with ground-based and in situ systems. This presentation identifies the information that ground-based systems provide very well, but it also looks at what would be deficient even in a greatly expanded surface system, where satellites can fill these gaps, and how on-going, ground and in situ measurements can aid in addressing issues associated with accuracy, long-term continuity, and retrieval artifacts.

  9. Methods for quantitative infrared directional-hemispherical and diffuse reflectance measurements using an FTIR and a commercial integrating sphere

    Energy Technology Data Exchange (ETDEWEB)

    Blake, Thomas A.; Johnson, Timothy J.; Tonkyn, Russell G.; Forland, Brenda M.; Myers, Tanya L.; Brauer, Carolyn S.; Su, Yin-Fong; Bernacki, Bruce E.; Hanssen, Leonard; Gonzalez, Gerardo

    2018-01-01

    Infrared integrating sphere measurements of solid samples are important in providing reference data for contact, standoff and remote sensing applications. At the Pacific Northwest National Laboratory (PNNL) we have developed protocols to measure both the directional-hemispherical ( and diffuse (d) reflectances of powders, liquids, and disks of powders and solid materials using a commercially available, matte gold-coated integrating sphere and Fourier transform infrared spectrometer. Detailed descriptions of the sphere alignment and its use for making these reflectance measurements are given. Diffuse reflectance values were found to be dependent on the bidirectional reflection distribution function (BRDF) of the sample and the solid angle intercepted by the sphere’s specular exclusion port. To determine how well the sphere and protocols produce quantitative reflectance data, measurements were made of three diffuse and two specular standards prepared by the National institute of Standards and Technology (NIST, USA), LabSphere Infragold and Spectralon standards, hand-loaded sulfur and talc powder samples, and water. The five NIST standards behaved as expected: the three diffuse standards had a high degree of “diffuseness,” d/ = D > 0.9, whereas the two specular standards had D ≤ 0.03. The average absolute differences between the NIST and PNNL measurements of the NIST standards for both directional-hemispherical and diffuse reflectances are on the order of 0.01 reflectance units. Other quantitative differences between the PNNL-measured and calibration (where available) or literature reflectance values for these standards and materials are given and the possible origins of discrepancies are discussed. Random uncertainties and estimates of systematic uncertainties are presented. Corrections necessary to provide better agreement between the PNNL reflectance values as measured for the NIST standards and the NIST reflectance values for these same standards are also

  10. Laser Guidestar Satellite for Ground-based Adaptive Optics Imaging of Geosynchronous Satellites and Astronomical Targets

    Science.gov (United States)

    Marlow, W. A.; Cahoy, K.; Males, J.; Carlton, A.; Yoon, H.

    2015-12-01

    Real-time observation and monitoring of geostationary (GEO) satellites with ground-based imaging systems would be an attractive alternative to fielding high cost, long lead, space-based imagers, but ground-based observations are inherently limited by atmospheric turbulence. Adaptive optics (AO) systems are used to help ground telescopes achieve diffraction-limited seeing. AO systems have historically relied on the use of bright natural guide stars or laser guide stars projected on a layer of the upper atmosphere by ground laser systems. There are several challenges with this approach such as the sidereal motion of GEO objects relative to natural guide stars and limitations of ground-based laser guide stars; they cannot be used to correct tip-tilt, they are not point sources, and have finite angular sizes when detected at the receiver. There is a difference between the wavefront error measured using the guide star compared with the target due to cone effect, which also makes it difficult to use a distributed aperture system with a larger baseline to improve resolution. Inspired by previous concepts proposed by A.H. Greenaway, we present using a space-based laser guide starprojected from a satellite orbiting the Earth. We show that a nanosatellite-based guide star system meets the needs for imaging GEO objects using a low power laser even from 36,000 km altitude. Satellite guide star (SGS) systemswould be well above atmospheric turbulence and could provide a small angular size reference source. CubeSatsoffer inexpensive, frequent access to space at a fraction of the cost of traditional systems, and are now being deployed to geostationary orbits and on interplanetary trajectories. The fundamental CubeSat bus unit of 10 cm cubed can be combined in multiple units and offers a common form factor allowing for easy integration as secondary payloads on traditional launches and rapid testing of new technologies on-orbit. We describe a 6U CubeSat SGS measuring 10 cm x 20 cm x

  11. Ground-based acoustic parametric generator impact on the atmosphere and ionosphere in an active experiment

    Directory of Open Access Journals (Sweden)

    Y. G. Rapoport

    2017-01-01

    Full Text Available We develop theoretical basics of active experiments with two beams of acoustic waves, radiated by a ground-based sound generator. These beams are transformed into atmospheric acoustic gravity waves (AGWs, which have parameters that enable them to penetrate to the altitudes of the ionospheric E and F regions where they influence the electron concentration of the ionosphere. Acoustic waves are generated by the ground-based parametric sound generator (PSG at the two close frequencies. The main idea of the experiment is to design the output parameters of the PSG to build a cascade scheme of nonlinear wave frequency downshift transformations to provide the necessary conditions for their vertical propagation and to enable penetration to ionospheric altitudes. The PSG generates sound waves (SWs with frequencies f1 = 600 and f2 = 625 Hz and large amplitudes (100–420 m s−1. Each of these waves is modulated with the frequency of 0.016 Hz. The novelty of the proposed analytical–numerical model is due to simultaneous accounting for nonlinearity, diffraction, losses, and dispersion and inclusion of the two-stage transformation (1 of the initial acoustic waves to the acoustic wave with the difference frequency Δf = f2 − f1 in the altitude ranges 0–0.1 km, in the strongly nonlinear regime, and (2 of the acoustic wave with the difference frequency to atmospheric acoustic gravity waves with the modulational frequency in the altitude ranges 0.1–20 km, which then reach the altitudes of the ionospheric E and F regions, in a practically linear regime. AGWs, nonlinearly transformed from the sound waves, launched by the two-frequency ground-based sound generator can increase the transparency of the ionosphere for the electromagnetic waves in HF (MHz and VLF (kHz ranges. The developed theoretical model can be used for interpreting an active experiment that includes the PSG impact on the atmosphere–ionosphere system

  12. Managing a big ground-based astronomy project: the Thirty Meter Telescope (TMT) project

    Science.gov (United States)

    Sanders, Gary H.

    2008-07-01

    TMT is a big science project and its scale is greater than previous ground-based optical/infrared telescope projects. This paper will describe the ideal "linear" project and how the TMT project departs from that ideal. The paper will describe the needed adaptations to successfully manage real world complexities. The progression from science requirements to a reference design, the development of a product-oriented Work Breakdown Structure (WBS) and an organization that parallels the WBS, the implementation of system engineering, requirements definition and the progression through Conceptual Design to Preliminary Design will be summarized. The development of a detailed cost estimate structured by the WBS, and the methodology of risk analysis to estimate contingency fund requirements will be summarized. Designing the project schedule defines the construction plan and, together with the cost model, provides the basis for executing the project guided by an earned value performance measurement system.

  13. Space situational awareness satellites and ground based radiation counting and imaging detector technology

    International Nuclear Information System (INIS)

    Jansen, Frank; Behrens, Joerg; Pospisil, Stanislav; Kudela, Karel

    2011-01-01

    We review the current status from the scientific and technological point of view of solar energetic particles, solar and galactic cosmic ray measurements as well as high energy UV-, X- and gamma-ray imaging of the Sun. These particles and electromagnetic data are an important tool for space situational awareness (SSA) aspects like space weather storm predictions to avoid failures in space, air and ground based technological systems. Real time data acquisition, position and energy sensitive imaging are demanded by the international space weather forecast services. We present how newly developed, highly miniaturized radiation detectors can find application in space in view of future SSA related satellites as a novel space application due to their counting and imaging capabilities.

  14. Compact binary coalescences in the band of ground-based gravitational-wave detectors

    International Nuclear Information System (INIS)

    Mandel, Ilya; O'Shaughnessy, Richard

    2010-01-01

    As the ground-based gravitational-wave telescopes LIGO, Virgo and GEO 600 approach the era of first detections, we review the current knowledge of the coalescence rates and the mass and spin distributions of merging neutron-star and black-hole binaries. We emphasize the bi-directional connection between gravitational-wave astronomy and conventional astrophysics. Astrophysical input will make possible informed decisions about optimal detector configurations and search techniques. Meanwhile, rate upper limits, detected merger rates and the distribution of masses and spins measured by gravitational-wave searches will constrain astrophysical parameters through comparisons with astrophysical models. Future developments necessary to the success of gravitational-wave astronomy are discussed.

  15. Coastal wind study based on Sentinel-1 and ground-based scanning lidar

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Badger, Merete; Pena Diaz, Alfredo

    Winds in the coastal zone have importance for near-shore wind farm planning. Recently the Danish Energy Agency gave new options for placing offshore wind farms much closer to the coastlines than previously. The new tender areas are located from 3 to 8 km from the coast. Ground-based scanning lidar...... located on land can partly cover this area out to around 15 km. In order to improve wind farm planning for near-shore coastal areas, the project‘Reducing the Uncertainty of Near-shore Energy estimates from meso- and micro-scale wind models’ (RUNE) is established. The measurement campaign starts October....... The various observation types have advantages and limitations; one advantage of both the Sentinel-1 and the scanning lidar is that they both observe wind fields covering a large area and so can be combined for studying the spatial variability of winds. Sentinel-1 are being processed near-real-time at DTU Wind...

  16. Perturbations of ionosphere-magnetosphere coupling by powerful VLF emissions from ground-based transmitters

    International Nuclear Information System (INIS)

    Belov, A. S.; Markov, G. A.; Ryabov, A. O.; Parrot, M.

    2012-01-01

    The characteristics of the plasma-wave disturbances stimulated in the near-Earth plasma by powerful VLF radiation from ground-based transmitters are investigated. Radio communication VLF transmitters of about 1 MW in power are shown to produce artificial plasma-wave channels (density ducts) in the near-Earth space that originate in the lower ionosphere above the disturbing emission source and extend through the entire ionosphere and magnetosphere of the Earth along the magnetic field lines. Measurements with the onboard equipment of the DEMETER satellite have revealed that under the action of emission from the NWC transmitter, which is one of the most powerful VLF radio transmitters, the generation of quasi-electrostatic (plasma) waves is observed on most of the satellite trajectory along the disturbed magnetic flux tube. This may probably be indicative of stimulated emission of a magnetospheric maser.

  17. Space situational awareness satellites and ground based radiation counting and imaging detector technology

    Energy Technology Data Exchange (ETDEWEB)

    Jansen, Frank, E-mail: frank.jansen@dlr.de [DLR Institute of Space Systems, Robert-Hooke-Str. 7, 28359 Bremen (Germany); Behrens, Joerg [DLR Institute of Space Systems, Robert-Hooke-Str. 7, 28359 Bremen (Germany); Pospisil, Stanislav [Czech Technical University, IEAP, 12800 Prague 2, Horska 3a/22 (Czech Republic); Kudela, Karel [Slovak Academy of Sciences, IEP, 04001 Kosice, Watsonova 47 (Slovakia)

    2011-05-15

    We review the current status from the scientific and technological point of view of solar energetic particles, solar and galactic cosmic ray measurements as well as high energy UV-, X- and gamma-ray imaging of the Sun. These particles and electromagnetic data are an important tool for space situational awareness (SSA) aspects like space weather storm predictions to avoid failures in space, air and ground based technological systems. Real time data acquisition, position and energy sensitive imaging are demanded by the international space weather forecast services. We present how newly developed, highly miniaturized radiation detectors can find application in space in view of future SSA related satellites as a novel space application due to their counting and imaging capabilities.

  18. Quantifying greenhouse gas emissions from coal fires using airborne and ground-based methods

    Science.gov (United States)

    Engle, Mark A.; Radke, Lawrence F.; Heffern, Edward L.; O'Keefe, Jennifer M.K.; Smeltzer, Charles; Hower, James C.; Hower, Judith M.; Prakash, Anupma; Kolker, Allan; Eatwell, Robert J.; ter Schure, Arnout; Queen, Gerald; Aggen, Kerry L.; Stracher, Glenn B.; Henke, Kevin R.; Olea, Ricardo A.; Román-Colón, Yomayara

    2011-01-01

    Coal fires occur in all coal-bearing regions of the world and number, conservatively, in the thousands. These fires emit a variety of compounds including greenhouse gases. However, the magnitude of the contribution of combustion gases from coal fires to the environment is highly uncertain, because adequate data and methods for assessing emissions are lacking. This study demonstrates the ability to estimate CO2 and CH4 emissions for the Welch Ranch coal fire, Powder River Basin, Wyoming, USA, using two independent methods: (a) heat flux calculated from aerial thermal infrared imaging (3.7–4.4 t d−1 of CO2 equivalent emissions) and (b) direct, ground-based measurements (7.3–9.5 t d−1 of CO2 equivalent emissions). Both approaches offer the potential for conducting inventories of coal fires to assess their gas emissions and to evaluate and prioritize fires for mitigation.

  19. Comparison of cloud top heights derived from FY-2 meteorological satellites with heights derived from ground-based millimeter wavelength cloud radar

    Science.gov (United States)

    Wang, Zhe; Wang, Zhenhui; Cao, Xiaozhong; Tao, Fa

    2018-01-01

    Clouds are currently observed by both ground-based and satellite remote sensing techniques. Each technique has its own strengths and weaknesses depending on the observation method, instrument performance and the methods used for retrieval. It is important to study synergistic cloud measurements to improve the reliability of the observations and to verify the different techniques. The FY-2 geostationary orbiting meteorological satellites continuously observe the sky over China. Their cloud top temperature product can be processed to retrieve the cloud top height (CTH). The ground-based millimeter wavelength cloud radar can acquire information about the vertical structure of clouds-such as the cloud base height (CBH), CTH and the cloud thickness-and can continuously monitor changes in the vertical profiles of clouds. The CTHs were retrieved using both cloud top temperature data from the FY-2 satellites and the cloud radar reflectivity data for the same time period (June 2015 to May 2016) and the resulting datasets were compared in order to evaluate the accuracy of CTH retrievals using FY-2 satellites. The results show that the concordance rate of cloud detection between the two datasets was 78.1%. Higher consistencies were obtained for thicker clouds with larger echo intensity and for more continuous clouds. The average difference in the CTH between the two techniques was 1.46 km. The difference in CTH between low- and mid-level clouds was less than that for high-level clouds. An attenuation threshold of the cloud radar for rainfall was 0.2 mm/min; a rainfall intensity below this threshold had no effect on the CTH. The satellite CTH can be used to compensate for the attenuation error in the cloud radar data.

  20. Monitoring Strategies of Earth Dams by Ground-Based Radar Interferometry: How to Extract Useful Information for Seismic Risk Assessment.

    Science.gov (United States)

    Di Pasquale, Andrea; Nico, Giovanni; Pitullo, Alfredo; Prezioso, Giuseppina

    2018-01-16

    The aim of this paper is to describe how ground-based radar interferometry can provide displacement measurements of earth dam surfaces and of vibration frequencies of its main concrete infrastructures. In many cases, dams were built many decades ago and, at that time, were not equipped with in situ sensors embedded in the structure when they were built. Earth dams have scattering properties similar to landslides for which the Ground-Based Synthetic Aperture Radar (GBSAR) technique has been so far extensively applied to study ground displacements. In this work, SAR and Real Aperture Radar (RAR) configurations are used for the measurement of earth dam surface displacements and vibration frequencies of concrete structures, respectively. A methodology for the acquisition of SAR data and the rendering of results is described. The geometrical correction factor, needed to transform the Line-of-Sight (LoS) displacement measurements of GBSAR into an estimate of the horizontal displacement vector of the dam surface, is derived. Furthermore, a methodology for the acquisition of RAR data and the representation of displacement temporal profiles and vibration frequency spectra of dam concrete structures is presented. For this study a Ku-band ground-based radar, equipped with horn antennas having different radiation patterns, has been used. Four case studies, using different radar acquisition strategies specifically developed for the monitoring of earth dams, are examined. The results of this work show the information that a Ku-band ground-based radar can provide to structural engineers for a non-destructive seismic assessment of earth dams.

  1. Vertical-type chiroptical spectrophotometer (I): instrumentation and application to diffuse reflectance circular dichroism measurement.

    Science.gov (United States)

    Harada, Takunori; Hayakawa, Hiroshi; Kuroda, Reiko

    2008-07-01

    We have designed and built a novel universal chiroptical spectrophotometer (UCS-2: J-800KCMF), which can carry out in situ chirality measurement of solid samples without any pretreatment, in the UV-vis region and with high relative efficiency. The instrument was designed to carry out transmittance and diffuse reflectance (DR) circular dichroism (CD) measurements simultaneously, thus housing two photomultipliers. It has a unique feature that light impinges on samples vertically so that loose powders can be measured by placing them on a flat sample holder in an integrating sphere. As is our first universal chiroptical spectrophotometer, UCS-1, two lock-in amplifiers are installed to remove artifact signals arising from macroscopic anisotropies which are unique to solid samples. High performance was achieved by theoretically analyzing and experimentally proven the effect of the photoelastic modulator position on the CD base line shifts, and by selecting high-quality optical and electric components. Measurement of microcrystallines of both enantiomers of ammonium camphorsulfonate by the DRCD mode gave reasonable results.

  2. Evaluating statistical cloud schemes: What can we gain from ground-based remote sensing?

    Science.gov (United States)

    Grützun, V.; Quaas, J.; Morcrette, C. J.; Ament, F.

    2013-09-01

    Statistical cloud schemes with prognostic probability distribution functions have become more important in atmospheric modeling, especially since they are in principle scale adaptive and capture cloud physics in more detail. While in theory the schemes have a great potential, their accuracy is still questionable. High-resolution three-dimensional observational data of water vapor and cloud water, which could be used for testing them, are missing. We explore the potential of ground-based remote sensing such as lidar, microwave, and radar to evaluate prognostic distribution moments using the "perfect model approach." This means that we employ a high-resolution weather model as virtual reality and retrieve full three-dimensional atmospheric quantities and virtual ground-based observations. We then use statistics from the virtual observation to validate the modeled 3-D statistics. Since the data are entirely consistent, any discrepancy occurring is due to the method. Focusing on total water mixing ratio, we find that the mean ratio can be evaluated decently but that it strongly depends on the meteorological conditions as to whether the variance and skewness are reliable. Using some simple schematic description of different synoptic conditions, we show how statistics obtained from point or line measurements can be poor at representing the full three-dimensional distribution of water in the atmosphere. We argue that a careful analysis of measurement data and detailed knowledge of the meteorological situation is necessary to judge whether we can use the data for an evaluation of higher moments of the humidity distribution used by a statistical cloud scheme.

  3. Introducing the VISAGE project - Visualization for Integrated Satellite, Airborne, and Ground-based data Exploration

    Science.gov (United States)

    Gatlin, P. N.; Conover, H.; Berendes, T.; Maskey, M.; Naeger, A. R.; Wingo, S. M.

    2017-12-01

    A key component of NASA's Earth observation system is its field experiments, for intensive observation of particular weather phenomena, or for ground validation of satellite observations. These experiments collect data from a wide variety of airborne and ground-based instruments, on different spatial and temporal scales, often in unique formats. The field data are often used with high volume satellite observations that have very different spatial and temporal coverage. The challenges inherent in working with such diverse datasets make it difficult for scientists to rapidly collect and analyze the data for physical process studies and validation of satellite algorithms. The newly-funded VISAGE project will address these issues by combining and extending nascent efforts to provide on-line data fusion, exploration, analysis and delivery capabilities. A key building block is the Field Campaign Explorer (FCX), which allows users to examine data collected during field campaigns and simplifies data acquisition for event-based research. VISAGE will extend FCX's capabilities beyond interactive visualization and exploration of coincident datasets, to provide interrogation of data values and basic analyses such as ratios and differences between data fields. The project will also incorporate new, higher level fused and aggregated analysis products from the System for Integrating Multi-platform data to Build the Atmospheric column (SIMBA), which combines satellite and ground-based observations into a common gridded atmospheric column data product; and the Validation Network (VN), which compiles a nationwide database of coincident ground- and satellite-based radar measurements of precipitation for larger scale scientific analysis. The VISAGE proof-of-concept will target "golden cases" from Global Precipitation Measurement Ground Validation campaigns. This presentation will introduce the VISAGE project, initial accomplishments and near term plans.

  4. Ground-based Observations and Atmospheric Modelling of Energetic Electron Precipitation Effects on Antarctic Mesospheric Chemistry

    Science.gov (United States)

    Newnham, D.; Clilverd, M. A.; Horne, R. B.; Rodger, C. J.; Seppälä, A.; Verronen, P. T.; Andersson, M. E.; Marsh, D. R.; Hendrickx, K.; Megner, L. S.; Kovacs, T.; Feng, W.; Plane, J. M. C.

    2016-12-01

    The effect of energetic electron precipitation (EEP) on the seasonal and diurnal abundances of nitric oxide (NO) and ozone in the Antarctic middle atmosphere during March 2013 to July 2014 is investigated. Geomagnetic storm activity during this period, close to solar maximum, was driven primarily by impulsive coronal mass ejections. Near-continuous ground-based atmospheric measurements have been made by a passive millimetre-wave radiometer deployed at Halley station (75°37'S, 26°14'W, L = 4.6), Antarctica. This location is directly under the region of radiation-belt EEP, at the extremity of magnetospheric substorm-driven EEP, and deep within the polar vortex during Austral winter. Superposed epoch analyses of the ground based data, together with NO observations made by the Solar Occultation For Ice Experiment (SOFIE) onboard the Aeronomy of Ice in the Mesosphere (AIM) satellite, show enhanced mesospheric NO following moderate geomagnetic storms (Dst ≤ -50 nT). Measurements by co-located 30 MHz riometers indicate simultaneous increases in ionisation at 75-90 km directly above Halley when Kp index ≥ 4. Direct NO production by EEP in the upper mesosphere, versus downward transport of NO from the lower thermosphere, is evaluated using a new version of the Whole Atmosphere Community Climate Model incorporating the full Sodankylä Ion Neutral Chemistry Model (WACCM SIC). Model ionization rates are derived from the Polar orbiting Operational Environmental Satellites (POES) second generation Space Environment Monitor (SEM 2) Medium Energy Proton and Electron Detector instrument (MEPED). The model data are compared with observations to quantify the impact of EEP on stratospheric and mesospheric odd nitrogen (NOx), odd hydrogen (HOx), and ozone.

  5. Determining surface coverage of ultra-thin gold films from X-ray reflectivity measurements

    International Nuclear Information System (INIS)

    Kossoy, A.; Simakov, D.; Olafsson, S.; Leosson, K.

    2013-01-01

    The paper describes usage of X-ray reflectivity for characterization of surface coverage (i.e. film continuity) of ultra-thin gold films which are widely studied for optical, plasmonic and electronic applications. The demonstrated method is very sensitive and can be applied for layers below 1 nm. It has several advantages over other techniques which are often employed in characterization of ultra-thin metal films, such as optical absorption, Atomic Force Microscopy, Transmission Electron Microscopy or Scanning Electron Microscopy. In contrast to those techniques our method does not require specialized sample preparation and measurement process is insensitive to electrostatic charge and/or presence of surface absorbed water. We validate our results with image processing of Scanning Electron Microscopy images. To ensure precise quantitative analysis of the images we developed a generic local thresholding algorithm which allowed us to treat series of images with various values of surface coverage with similar image processing parameters. - Highlights: • Surface coverage/continuity of ultra-thin Au films (up to 7 nm) was determined. • Results from X-ray reflectivity were verified by scanning electron microscopy. • We developed local thresholding algorithm to treat non-homogeneous image contrast

  6. Reflectance measurements of PTFE, Kapton, and PEEK for xenon scintillation light for the LZ detector.

    Science.gov (United States)

    Arthurs, M.; Batista, E.; Haefner, J.; Lorenzon, W.; Morton, D.; Neff, A.; Okunawo, M.; Pushkin, K.; Sander, A.; Stephenson, S.; Wang, Y.; LZ Collaboration

    2017-01-01

    LZ (LUX-Zeplin) is an international collaboration that will look for dark matter candidates, WIMPs (Weakly Interacting Massive Particles), through direct detection by dual-phase time projection chamber (TPC) using liquid xenon. The LZ detector will be located nearly a mile underground at SURF, South Dakota, shielded from cosmic background radiation. Seven tons active mass of liquid xenon will be used for detecting the weak interaction of WIMPs with ordinary matter. Over three years of operation it is expected to reach the ultimate sensitivity of 2x10-48 cm2 for a WIMP mass of 50 GeV. As for many other rare event searches, high light collection efficiency is essential for LZ detector. Moreover, in order to achieve greater active volume for detection as well as reduce potential backgrounds, thinner detector walls without significant loss in reflectance are desired. Reflectance measurements of polytetrafluoroethylene (PTFE), Kapton, and PEEK for xenon scintillation light (178 nm), conducted at the University of Michigan using the Michigan Xenon Detector (MiX) will be presented. The University of Michigan, LZ Collaboration, The US Department of Energy.

  7. Resolving meso-scale seabed variability using reflection measurements from an autonomous underwater vehicle.

    Science.gov (United States)

    Holland, Charles W; Nielsen, Peter L; Dettmer, Jan; Dosso, Stan

    2012-02-01

    Seabed geoacoustic variability is driven by geological processes that occur over a wide spectrum of space-time scales. While the acoustics community has some understanding of horizontal fine-scale geoacoustic variability, less than O(10(0)) m, and large-scale variability, greater than O(10(3)) m, there is a paucity of data resolving the geoacoustic meso-scale O(10(0)-10(3)) m. Measurements of the meso-scale along an ostensibly "benign" portion of the outer shelf reveal three classes of variability. The first class was expected and is due to horizontal variability of layer thicknesses: this was the only class that could be directly tied to seismic reflection data. The second class is due to rapid changes in layer properties and/or boundaries, occurring over scales of meters to hundreds of meters. The third class was observed as rapid variations of the angle/frequency dependent reflection coefficient within a single observation and is suggestive of variability at scales of meter or less. Though generally assumed to be negligible in acoustic modeling, the second and third classes are indicative of strong horizontal geoacoustic variability within a given layer. The observations give early insight into possible effects of horizontal geoacoustic variability on long-range acoustic propagation and reverberation. © 2012 Acoustical Society of America

  8. Ultraviolet reflectance spectroscopy measurements of carbonaceous meteorites and planetary analog materials

    Science.gov (United States)

    Hibbitts, Charles A.; Stockstill-Cahill, Karen; Takir, Driss

    2017-10-01

    The compositions of airless solar system objects tell us about the origin and evolutionary processes that are responsible for the current state of our solar system and that shape our environment. Spectral reflectance measurements in the ultraviolet are being used more frequently for providing compositional information of airless solid surfaces. Most minerals absorb in the UV making studying surface composition both informative but also challenging [e.g. 1]. The UV region is sensitive to atomic and molecular electronic absorptions such as the ligand-metal charge transfer band that is present in oxides and silicates and the conduction band at vacuum UV wavelengths. At the JHU-APL, bidirectional UV reflectance measurements are obtained under vacuum using a McPherson monochrometer with a PMT detector to achieve measurements over the range from ~ 140 nm to ~ 570 nm. Sample temperature can also be controlled from ~ 100K to ~ 600K, which enables the exploring the interaction of water ice and other volatiles with refractory samples. We have measured the UV spectra of many carbonaceous chondrites, including Mokoia, Vigarano, Warrenton, Orgueil, SaU290, and Essebi. In addition to being dark, some also possess on OMCT band. We have also obtained IR measurement of these meteorites to explore possible correlations between their UV and IR spectral signatures. In addition, we have also measured the UV spectra of low water content lunar analog glasses and have found a correlation between the spectral nature of the OMCT band and the abundance of iron [3]. Also, the spectral signature of mineralic and adsorbed water in the UV has been investigated. While water-ice has a known strong absorption feature near 180 nm (e.g. 4], adsorbed molecular and disassociatively adsorbed OH appear to not be optically active in this spectral region [5]. References: [1] Wagner et al. (1987) Icarus, 69, 14-28.1987; [2] Cloutis et al. (2008) Icarus, 197, 321-347; [3] Greenspon et al. (2012), 43rd LPSC

  9. Applicability of reflection seismic measurements in detailed characterization of crystalline bedrock

    International Nuclear Information System (INIS)

    Sireni, S.

    2011-03-01

    known geological feature had no reflector. Reflection seismic measurements can be used in detailed characterization of crystalline bedrock. Wide brittle fault zones and lithological contacts but also single fractures were detected. However, interpretation is challenging and geological and geophysical reference material is needed. All the expected features were not detected and the explanations were not always fully satisfying. (orig.)

  10. A detrimental soil disturbance prediction model for ground-based timber harvesting

    Science.gov (United States)

    Derrick A. Reeves; Matthew C. Reeves; Ann M. Abbott; Deborah S. Page-Dumroese; Mark D. Coleman

    2012-01-01

    Soil properties and forest productivity can be affected during ground-based harvest operations and site preparation. The degree of impact varies widely depending on topographic features and soil properties. Forest managers who understand site-specific limits to ground-based harvesting can alter harvest method or season to limit soil disturbance. To determine the...

  11. New optical scheme for differential measurements of diffraction reflection intensity on X-radiation sliding incidence

    International Nuclear Information System (INIS)

    Golovin, A.L.; Mas', E.T.

    1989-01-01

    An X-ray optical scheme for differential measurements of X-ray diffraction under sliding incidence conditions is proposed and an attachment design realizng this scheme, using standard equipment, is described. The main feature of the scheme is the following: collimation according to the Bragg angle is carried out for the reflected beam rather than the incident one. Goniometers can be used from DRON, TRS, GS-5 and other spectrometers. The goniometer head carrying the sample is standard, it is a part of the DRON, TRS and DTS. The crystal analyzer is fixed on the attachment. The angular position of the crystal monochromator is controlled by an inductive sensor. The experimental differential curves of X-ray diffraction under conditions of sliding incidence, taken for a silicon crystal having the 111 orientation, are given as well

  12. Determination of hot carrier energy distributions from inversion of ultrafast pump-probe reflectivity measurements.

    Science.gov (United States)

    Heilpern, Tal; Manjare, Manoj; Govorov, Alexander O; Wiederrecht, Gary P; Gray, Stephen K; Harutyunyan, Hayk

    2018-05-10

    Developing a fundamental understanding of ultrafast non-thermal processes in metallic nanosystems will lead to applications in photodetection, photochemistry and photonic circuitry. Typically, non-thermal and thermal carrier populations in plasmonic systems are inferred either by making assumptions about the functional form of the initial energy distribution or using indirect sensors like localized plasmon frequency shifts. Here we directly determine non-thermal and thermal distributions and dynamics in thin films by applying a double inversion procedure to optical pump-probe data that relates the reflectivity changes around Fermi energy to the changes in the dielectric function and in the single-electron energy band occupancies. When applied to normal incidence measurements our method uncovers the ultrafast excitation of a non-Fermi-Dirac distribution and its subsequent thermalization dynamics. Furthermore, when applied to the Kretschmann configuration, we show that the excitation of propagating plasmons leads to a broader energy distribution of electrons due to the enhanced Landau damping.

  13. Measured reflectance of graded multilayer mirrors designed for astronomical hard X-ray telescopes

    DEFF Research Database (Denmark)

    Christensen, Finn Erland; Craig, W.W.; Windt, D.L.

    2000-01-01

    Future astronomical X-ray telescopes, including the balloon-borne High-Energy Focusing Telescope (HEFT) and the Constellation-X Hard X-ray Telescope (Con-X HXT) plan to incorporate depth-graded multilayer coatings in order to extend sensitivity into the hard X-ray (10 less than or similar to E less......-graded W/Si multilayers optimized for broadband performance up to 69.5 keV (WK-edge). These designs are ideal for both the HEFT and Con-X HXT applications. We compare the measurements to model calculations to demonstrate that the reflectivity can be well described by the intended power law distribution...

  14. An Automatic System for Determining Solar Absorptance and Thermal Emittance of Surfaces from Spectral Normal Reflectance Measurements

    National Research Council Canada - National Science Library

    Teichman, Louis

    1965-01-01

    .... The system consists of two spectrophotometers used to make optical reflectance measurements, electronic digitizing equipment to record the data, and a high-speed electronic computer to calculate the desired results...

  15. Quantitative Estimation of Above Ground Crop Biomass using Ground-based, Airborne and Spaceborne Low Frequency Polarimetric Synthetic Aperture Radar

    Science.gov (United States)

    Koyama, C.; Watanabe, M.; Shimada, M.

    2016-12-01

    Estimation of crop biomass is one of the important challenges in environmental remote sensing related to agricultural as well as hydrological and meteorological applications. Usually passive optical data (photographs, spectral data) operating in the visible and near-infrared bands is used for such purposes. The virtue of optical remote sensing for yield estimation, however, is rather limited as the visible light can only provide information about the chemical characteristics of the canopy surface. Low frequency microwave signals with wavelength longer 20 cm have the potential to penetrate through the canopy and provide information about the whole vertical structure of vegetation from the top of the canopy down to the very soil surface. This phenomenon has been well known and exploited to detect targets under vegetation in the military radar application known as FOPEN (foliage penetration). With the availability of polarimetric interferometric SAR data the use PolInSAR techniques to retrieve vertical vegetation structures has become an attractive tool. However, PolInSAR is still highly experimental and suitable data is not yet widely available. In this study we focus on the use of operational dual-polarization L-band (1.27 GHz) SAR which is since the launch of Japan's Advanced Land Observing Satellite (ALOS, 2006-2011) available worldwide. Since 2014 ALOS-2 continues to deliver such kind of partial polarimetric data for the entire land surface. In addition to these spaceborne data sets we use airborne L-band SAR data acquired by the Japanese Pi-SAR-L2 as well as ultra-wideband (UWB) ground based SAR data operating in the frequency range from 1-4 GHz. By exploiting the complex dual-polarization [C2] Covariance matrix information, the scattering contributions from the canopy can be well separated from the ground reflections allowing for the establishment of semi-empirical relationships between measured radar reflectivity and the amount of fresh-weight above

  16. Determination of the optical constants of polymer light-emitting diode films from single reflection measurements

    International Nuclear Information System (INIS)

    Zhu Dexi; Shen Weidong; Ye Hui; Liu Xu; Zhen Hongyu

    2008-01-01

    We present a simple and fast method to determine the optical constant and physical thickness of polymer films from a single reflectivity measurement. A self-consistent dispersion formula of the Forouhi-Bloomer model was introduced to fit the measured spectral curves by a modified 'Downhill' simplex algorithm. Four widely used polymer light-emitting diodes materials: poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene], poly(9,9-dioctylfluoreny-2,7-diyl) (PFO), poly(N-vinyl carbazole) and poly(3,4-ethylene dioxythiophene) : poly(styrenesulfonate) were investigated by this technique. The refractive indices over the whole visible region as well as the optical band gap extracted by this method agree well with those reported in the literature. The determined physical thicknesses present a deviation less than 4% compared with the experimental values measured by the stylus profiler. The influence of scattering loss on the fitted results is discussed to demonstrate the applicability of this technology for polymer films.

  17. Study of phosphoric acid crystallization using a focused beam reflectance measurement method

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Yong [School of Chemistry and Resource Environment, Linyi Normal University, Linyi Shandong 276005 (China); Chen, Kui; Wu, Yanyang; Zhu, Jiawen [Chemical Engineering Research Center, East China University of Science and Technology, Shanghai 200237 (China); Sheng, Yong [SINOCHEN Fuling Chemical Industrial Co., Ltd, Chongqing 226005 (China)

    2010-10-15

    A way for restoring the crystal size distributions (CSD) from measured chord length distributions (CLD) was reported in this paper. The kinetics of phosphoric acid crystallization process was investigated in cooling mode using focused beam reflectance measurement (FBRM) and digital photo technique. In order to restore the CSD from measured CLD and verify the reliability of FBRM data, digital photo technique in real time and optical microscope were applied in large crystal size and small range, respectively. Results indicated a converting constant A existed between CLD and CSD when crystal growth follows size-independent growth (Mcabe's {delta}L law) law. It was verified by Malvern particles size analysis method. The converting constant A varied with crystal morphology. The crystal growth order increased with the stirring increasing speed during phosphoric acid crystallization process. The trend was especially notable at higher speed situations. It can illustrate that the state of phosphoric acid hemihydrate crystal growth was controlled by both diffusion and surface-integration with the increasing stirring speed. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Ground-based thermal imaging of stream surface temperatures: Technique and evaluation

    Science.gov (United States)

    Bonar, Scott A.; Petre, Sally J.

    2015-01-01

    We evaluated a ground-based handheld thermal imaging system for measuring water temperatures using data from eight southwestern USA streams and rivers. We found handheld thermal imagers could provide considerably more spatial information on water temperature (for our unit one image = 19,600 individual temperature measurements) than traditional methods could supply without a prohibitive amount of effort. Furthermore, they could provide measurements of stream surface temperature almost instantaneously compared with most traditional handheld thermometers (e.g., >20 s/reading). Spatial temperature analysis is important for measurement of subtle temperature differences across waterways, and identification of warm and cold groundwater inputs. Handheld thermal imaging is less expensive and equipment intensive than airborne thermal imaging methods and is useful under riparian canopies. Disadvantages of handheld thermal imagers include their current higher expense than thermometers, their susceptibility to interference when used incorrectly, and their slightly lower accuracy than traditional temperature measurement methods. Thermal imagers can only measure surface temperature, but this usually corresponds to subsurface temperatures in well-mixed streams and rivers. Using thermal imaging in select applications, such as where spatial investigations of water temperature are needed, or in conjunction with stationary temperature data loggers or handheld electronic or liquid-in-glass thermometers to characterize stream temperatures by both time and space, could provide valuable information on stream temperature dynamics. These tools will become increasingly important to fisheries biologists as costs continue to decline.

  19. Focused Beam Reflectance Measurement (FBRM) a promising tool for wet-end optimisation and web break prediction

    NARCIS (Netherlands)

    Lumpe, C.; Joore, L.; Homburg, K.; Verstraeten, E.

    2001-01-01

    The trends to increased speed and higher qualities have increased the need for wet-end control - especially for systems with on-line measuring devices and feed forward control. One possibility is the use of Focused Beam Reflectance Measurement (FBRM) to measure on-line particle counts and their

  20. Estimating atmospheric visibility using synergy of MODIS data and ground-based observations

    Science.gov (United States)

    Komeilian, H.; Mohyeddin Bateni, S.; Xu, T.; Nielson, J.

    2015-05-01

    Dust events are intricate climatic processes, which can have adverse effects on human health, safety, and the environment. In this study, two data mining approaches, namely, back-propagation artificial neural network (BP ANN) and supporting vector regression (SVR), were used to estimate atmospheric visibility through the synergistic use of Moderate Resolution Imaging Spectroradiometer (MODIS) Level 1B (L1B) data and ground-based observations at fourteen stations in the province of Khuzestan (southwestern Iran), during 2009-2010. Reflectance and brightness temperature in different bands (from MODIS) along with in situ meteorological data were input to the models to estimate atmospheric visibility. The results show that both models can accurately estimate atmospheric visibility. The visibility estimates from the BP ANN network had a root-mean-square error (RMSE) and Pearson's correlation coefficient (R) of 0.67 and 0.69, respectively. The corresponding RMSE and R from the SVR model were 0.59 and 0.71, implying that the SVR approach outperforms the BP ANN.

  1. The SPQR experiment: detecting damage to orbiting spacecraft with ground-based telescopes

    Science.gov (United States)

    Paolozzi, Antonio; Porfilio, Manfredi; Currie, Douglas G.; Dantowitz, Ronald F.

    2007-09-01

    The objective of the Specular Point-like Quick Reference (SPQR) experiment was to evaluate the possibility of improving the resolution of ground-based telescopic imaging of manned spacecraft in orbit. The concept was to reduce image distortions due to atmospheric turbulence by evaluating the Point Spread Function (PSF) of a point-like light reference and processing the spacecraft image accordingly. The target spacecraft was the International Space Station (ISS) and the point-like reference was provided by a laser beam emitted by the ground station and reflected back to the telescope by a Cube Corner Reflector (CCR) mounted on an ISS window. The ultimate objective of the experiment was to demonstrate that it is possible to image spacecraft in Low Earth Orbit (LEO) with a resolution of 20 cm, which would have probably been sufficient to detect the damage which caused the Columbia disaster. The experiment was successfully performed from March to May 2005. The paper provides an overview of the SPQR experiment.

  2. Overview of diffraction gratings technologies for spaceflight satellites and ground-based telescopes

    Science.gov (United States)

    Cotel, A.; Liard, A.; Desserouer, F.; Pichon, P.

    2017-11-01

    The diffraction gratings are widely used in Space-flight satellites for spectrograph instruments or in ground-based telescopes in astronomy. The diffraction gratings are one of the key optical components of such systems and have to exhibit very high optical performances. HORIBA Jobin Yvon S.A.S. (part of HORIBA Group) is in the forefront of such gratings development for more than 40 years. During the past decades, HORIBA Jobin Yvon (HJY) has developed a unique expertise in diffraction grating design and manufacturing processes for holographic, ruled or etched gratings. We will present in this paper an overview of diffraction grating technologies especially designed for space and astronomy applications. We will firstly review the heritage of the company in this field with the space qualification of different grating types. Then, we will describe several key grating technologies developed for specific space or astronomy projects: ruled blazed low groove density plane reflection grating, high-groove density holographic toroidal and spherical grating, and finally transmission Fused Silica Etched (FSE) grism-assembled grating. We will not present the Volume Phase Holographic (VPHG) grating type which is used in Astronomy.

  3. Composite mirror facets for ground based gamma ray astronomy

    Energy Technology Data Exchange (ETDEWEB)

    Brun, P.; Carton, P.-H.; Durand, D.; Glicenstein, J.-F.; Jeanney, C. [CEA, Irfu, Centre de Saclay, F-91191 Gif sur Yvette (France); Medina, M.C., E-mail: clementina@iar.unlp.edu.ar [CEA, Irfu, Centre de Saclay, F-91191 Gif sur Yvette (France); Micolon, P.; Peyaud, B. [CEA, Irfu, Centre de Saclay, F-91191 Gif sur Yvette (France)

    2013-06-21

    Composite mirrors for gamma-ray astronomy have been developed to fulfill the specifications required for the next generation of Cherenkov telescopes represented by CTA (Cherenkov Telescope Array). In addition to the basic requirements on focus and reflection efficiency, the mirrors have to be stiff, lightweight, durable and cost efficient. In this paper, the technology developed to produce such mirrors is described, as well as some tests that have been performed to validate them. It is shown that these mirrors comply with the needs of CTA, making them good candidates for use on a significant part of the array.

  4. A Method of Retrieving BRDF from Surface-Reflected Radiance Using Decoupling of Atmospheric Radiative Transfer and Surface Reflection

    Directory of Open Access Journals (Sweden)

    Alexander Radkevich

    2018-04-01

    Full Text Available Bi-directional reflection distribution function (BRDF defines anisotropy of the surface reflection. It is required to specify the boundary condition for radiative transfer (RT modeling used in aerosol retrievals, cloud retrievals, atmospheric modeling, and other applications. Ground based measurements of reflected radiance draw increasing attention as a source of information about anisotropy of surface reflection. Derivation of BRDF from surface radiance requires atmospheric correction. This study develops a new method of retrieving BRDF on its whole domain, making it immediately suitable for further atmospheric RT modeling applications. The method is based on the integral equation relating surface-reflected radiance, BRDF, and solutions of two auxiliary atmosphere-only RT problems. The method requires kernel-based BRDF. The weights of the kernels are obtained with a quickly converging iterative procedure. RT modeling has to be done only one time before the start of iterative process.

  5. A full-mission data set of H2O and HDO columns from SCIAMACHY 2.3 µm reflectance measurements

    Directory of Open Access Journals (Sweden)

    A. Schneider

    2018-06-01

    Full Text Available A new data set of vertical column densities of the water vapour isotopologues H2O and HDO from the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY instrument for the whole of the mission period from January 2003 to April 2012 is presented. The data are retrieved from reflectance measurements in the spectral range 2339 to 2383 nm with the Shortwave Infrared CO Retrieval (SICOR algorithm, ignoring atmospheric light scattering in the measurement simulation. The retrievals are validated with ground-based Fourier transform infrared measurements obtained within the Multi-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water (MUSICA project. A good agreement for low-altitude stations is found with an average bias of −3.6×1021 for H2O and −1.0×1018 molec cm−2 for HDO. The a posteriori computed δD shows an average bias of −8 ‰, even though polar stations have a larger negative bias. The latter is due to the large amount of sensor noise in SCIAMACHY in combination with low albedo and high solar zenith angles. To demonstrate the benefit of accounting for light scattering in the retrieval, the quality of the data product fitting effective cloud parameters simultaneously with trace gas columns is evaluated in a dedicated case study for measurements round high-altitude stations. Due to a large altitude difference between the satellite ground pixel and the mountain station, clear-sky scenes yield a large bias, resulting in a δD bias of 125 ‰. When selecting scenes with optically thick clouds within 1000 m above or below the station altitude, the bias in a posteriori δD is reduced from 125 to 44 ‰. The insights from the present study will also benefit the analysis of the data from the new Sentinel-5 Precursor mission.

  6. New intraocular pressure measurement method using reflected pneumatic pressure from cornea deformed by air puff of ring-type nozzle.

    Science.gov (United States)

    Kim, Hyung Jin; Seo, Yeong Ho; Kim, Byeong Hee

    2017-01-01

    In this study, a non-contact type intraocular pressure (IOP) measuring system using reflected pneumatic pressure is proposed to overcome the disadvantages of existing measurement systems. A ring-type nozzle, a key component in the proposed system, is designed via computational fluid analysis. It predicts the reflected pneumatic pressure based on the nozzle exit angle and inner and outer diameters of the nozzle, which are 30°, 7 mm, and 9 mm, respectively. Performance evaluation is conducted using artificial eyes fabricated using polydimethylsiloxane with the specifications of human eyes. The IOP of the fabricated artificial eyes is adjusted to 10, 30, and 50 mm Hg, and the reflected pneumatic pressure is measured as a function of the distance between the ring-type nozzle and artificial eye. The measured reflected pneumatic pressure is high when the measurement distance is short and eye pressure is low. The cornea of an artificial eye is significantly deformed at a low IOP, and the applied pneumatic pressure is more concentrated in front of the ring-type nozzle because of the deformed cornea. Thus, the reflected pneumatic pressure at a low IOP has more inflows into the pressure sensor inserted inside the nozzle. The sensitivity of the output based on the IOP at measurement distances between 3-5 mm is -0.0027, -0.0022, -0.0018, -0.0015, and -0.0012. Sensitivity decreases as the measurement distance increases. In addition, the reflected pneumatic pressure owing to the misalignment at the measurement distances of 3-5 mm is not affected within a range of 0.5 mm. Therefore, the measurement range is acceptable up to a 1 mm diameter from the center of an artificial eye. However, the accuracy gradually decreases as the reflected pneumatic pressure from a misalignment of 1 mm or more decreases by 26% or more.

  7. Automated sulcal depth measurement on cortical surface reflecting geometrical properties of sulci.

    Directory of Open Access Journals (Sweden)

    Hyuk Jin Yun

    Full Text Available Sulcal depth that is one of the quantitative measures of cerebral cortex has been widely used as an important marker for brain morphological studies. Several studies have employed Euclidean (EUD or geodesic (GED algorithms to measure sulcal depth, which have limitations that ignore sulcal geometry in highly convoluted regions and result in under or overestimated depth. In this study, we proposed an automated measurement for sulcal depth on cortical surface reflecting geometrical properties of sulci, which named the adaptive distance transform (ADT. We first defined the volume region of cerebrospinal fluid between the 3D convex hull and the cortical surface, and constructed local coordinates for that restricted region. Dijkstra's algorithm was then used to compute the shortest paths from the convex hull to the vertices of the cortical surface based on the local coordinates, which may be the most proper approach for defining sulcal depth. We applied our algorithm to both a clinical dataset including patients with mild Alzheimer's disease (AD and 25 normal controls and a simulated dataset whose shape was similar to a single sulcus. The mean sulcal depth in the mild AD group was significantly lower than controls (p = 0.007, normal [mean±SD]: 7.29±0.23 mm, AD: 7.11±0.29 and the area under the receiver operating characteristic curve was relatively high, showing the value of 0.818. Results from clinical dataset that were consistent with former studies using EUD or GED demonstrated that ADT was sensitive to cortical atrophy. The robustness against inter-individual variability of ADT was highlighted through simulation dataset. ADT showed a low and constant normalized difference between the depth of the simulated data and the calculated depth, whereas EUD and GED had high and variable differences. We suggest that ADT is more robust than EUD or GED and might be a useful alternative algorithm for measuring sulcal depth.

  8. White Paper on the Status and Future of Ground-based Gamma-Ray Astronomy - Extragalactic Science Working Group

    Science.gov (United States)

    Krawczynski, H.; Coppi, P.; Dermer, C.; Dwek, E.; Georganopoulos, M.; Horan, D.; Jones, T.; Krennrich, F.; Mukherjee, R.; Perlman, E.; Vassiliev, V.

    2007-04-01

    In fall 2006, the Division of Astrophysics of the American Physical Society requested a white paper about the status and future of ground based gamma-ray astronomy. The white paper will largely be written in the year 2007. Interested scientists are invited to join the science working groups. In this contribution, we will report on some preliminary results of the extragalactic science working group. We will discuss the potential of future ground based gamma-ray experiments to elucidate how supermassive black holes accrete matter, form jets, and accelerate particles, and to study in detail the acceleration and propagation of cosmic rays in extragalactic systems like infrared galaxies and galaxy clusters. Furthermore, we discuss avenues to constrain the spectrum of the extragalactic infrared to optical background radiation, and to measure the extragalactic magnetic fields based on gamma-ray observations. Eventually, we discuss the potential of ground based experiments for conducting gamma-ray source surveys. More information about the white paper can be found at: http://cherenkov.physics.iastate.edu/wp/

  9. Subcritical multiplication measurements with a BeO reflected 233U uranyl nitrate solution system

    International Nuclear Information System (INIS)

    Job, P.K.; Srinivasan, M.; Nargundkar, V.R.; Chandramoleshwar, K.; Pasupathy, C.S.; Das, S.; Mayankutty, P.C.

    1978-01-01

    A series of subcritical multiplication measurements were carried out in PURNIMA with 233 U uranyl nitrate solution contained in all 11 x 11 cm 2 square sectional tank and reflected