scholarly journals Species Correlation Measurements in Turbulent Flare Plumes: Considerations for Field Measurements

2021 ◽  
Author(s):  
Scott P. Seymour ◽  
Matthew R. Johnson
Keyword(s):  
Measurement Uncertainty ◽  
Field Measurements ◽  
Tunable Diode Laser ◽  
Emission Rates ◽  
Bootstrap Analysis ◽  
Positive Skewness ◽  
Spatial Coverage ◽  
Sampling Protocols ◽  
Added Uncertainty ◽  
Short Time

Abstract. Field measurement of flare emissions in turbulent flare plumes is an important and complex challenge. The simplest approaches necessarily assume that combustion species are spatially and/or temporally correlated in the plume, such that simple species ratios can be used to close a carbon balance to calculate species emission rates (i.e. emission factors) and flare conversion efficiency. This study examines the veracity of this assumption and the associated implications for measurement uncertainty. A novel tunable diode laser absorption spectroscopy (TDLAS) system is used to measure the correlation between H2O and black carbon (BC) volume fractions in the plumes of a vertical, turbulent, non-premixed, buoyancy-driven lab-scale gas flare. Experiments reveal that instantaneous, path-averaged concentrations of BC and H2O can vary independently and are not necessarily well-correlated over short time intervals. The scatter in the BC / H2O ratio along a path through the plume was well beyond that which could be attributed to measurement uncertainty and was asymmetrically distributed about the mean. Consistent with previous field observations, this positive skewness toward higher BC / H2O ratios implies short, localized, and infrequent bursts of high BC production, that are not well-correlated with H2O. This demonstrates that the common assumption of fixed species ratios is not universally valid, and measurements based on limited samples, short sampling times, and/or limited spatial coverage of the plume could be subject to potentially large added uncertainty. For BC emission measurements, the positive skewness of the BC / H2O ratio also suggests that results from small numbers of samples are more likely to be biased low. However, a bootstrap analysis of the results shows how these issues should be easily avoidable with sufficient sample size and provides initial guidance for creating sampling protocols for future field measurements using analogous path-averaged techniques.

scholarly journals Species correlation measurements in turbulent flare plumes: considerations for field measurements

2021 ◽  
Vol 14 (7) ◽  
pp. 5179-5197
Author(s):  
Scott P. Seymour ◽  
Matthew R. Johnson
Keyword(s):  
Measurement Uncertainty ◽  
Black Carbon ◽  
Field Measurement ◽  
Field Measurements ◽  
Tunable Diode Laser ◽  
Bootstrap Analysis ◽  
Positive Skewness ◽  
Spatial Coverage ◽  
Sampling Protocols ◽  
Added Uncertainty

Abstract. Field measurement of flare emissions in turbulent flare plumes is an important and complex challenge. Incomplete combustion from these processes results in emissions of black carbon, unburnt fuels (methane), CO2, and other pollutants. Many field measurement approaches necessarily assume that combustion species are spatially and/or temporally correlated in the plume, such that simple species ratios can be used to close a carbon balance to calculate species emission factors and flare conversion efficiency. This study examines the veracity of this assumption and the associated implications for measurement uncertainty. A novel tunable diode laser absorption spectroscopy (TDLAS) system is used to measure the correlation between H2O and black carbon (BC) volume fractions in the plumes of a vertical, turbulent, non-premixed, buoyancy-driven lab-scale gas flare. Experiments reveal that instantaneous, path-averaged concentrations of BC and H2O can vary independently and are not necessarily well correlated over short time intervals. The scatter in the BC/H2O ratio along a path through the plume was well beyond that which could be attributed to measurement uncertainty and was asymmetrically distributed about the mean. Consistent with previous field observations, this positive skewness toward higher BC/H2O ratios implies short, localized, and infrequent bursts of high BC production that are not well correlated with H2O. This demonstrates that the common assumption of fixed species ratios is not universally valid, and measurements based on limited samples, short sampling times, and/or limited spatial coverage of the plume could be subject to potentially large added uncertainty. For BC emission measurements, the positive skewness of the BC/H2O ratio also suggests that results from small numbers of samples are more likely to be biased low. However, a bootstrap analysis of the results shows how these issues can be avoided with sufficient sample size and provides initial guidance for creating sampling protocols for future field measurements using analogous path-averaged techniques.

Evaluation of S-N curves including failure probabilities using short-time procedures

2021 ◽  
Vol 63 (8) ◽  
pp. 705-713
Author(s):  
Ruth Acosta ◽  
Christian Boller ◽  
Markus Doktor ◽  
Haoran Wu ◽  
Hanna Jost ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Treatment ◽  
Fatigue Life ◽  
Statistical Evaluation ◽  
Field Measurements ◽  
Treatment Conditions ◽  
Evaluation Strategies ◽  
Magnetic Field Measurements ◽  
Short Time ◽  
Experimental Effort

Abstract In recent years, different short-time procedures have been developed that significantly reduce the experimental effort required to generate S-N curves and thus S-N databases. Methods like StressLife, StrainLife, and SteBLife are some of those which have shown enormous potential in this respect. In this contribution, the practicability of the SteBLife method is shown. Two S-N curve evaluation strategies based on temperature and magnetic field measurements are presented. These take statistical evaluation into account, describing a material’s scatter in terms of fatigue life. In order to demonstrate the versatility of the approach and to underline the advantages in terms of effort saved when compared to conventional procedures, the process on how to get the required information obtained is shown for three unalloyed and low-alloyed steels under different heat treatment conditions.

scholarly journals The fluxgate magnetometer of the Low Orbit Pearl Satellites (LOPS): overview of in-flight performance and initial results

2021 ◽  
Vol 10 (2) ◽  
pp. 227-243
Author(s):  
Ye Zhu ◽  
Aimin Du ◽  
Hao Luo ◽  
Donghai Qiao ◽  
Ying Zhang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Current System ◽  
Field Measurements ◽  
Stray Field ◽  
Fluxgate Magnetometer ◽  
General Description ◽  
Flight Performance ◽  
Spatial Coverage ◽  
Magnetic Field Measurements ◽  
Initial Results

Abstract. The Low Orbit Pearl Satellite series consists of six constellations, with each constellation consisting of three identical microsatellites that line up just like a string of pearls. The first constellation of three satellites were launched on 29 September 2017, with an inclination of ∼ 35.5∘ and ∼ 600 km altitude. Each satellite is equipped with three identical fluxgate magnetometers that measure the in situ magnetic field and its low-frequency fluctuations in the Earth's low-altitude orbit. The triple sensor configuration enables separation of stray field effects generated by the spacecraft from the ambient magnetic field (e.g., Zhang et al., 2006). This paper gives a general description of the magnetometer including the instrument design, calibration before launch, in-flight calibration, in-flight performance, and initial results. Unprecedented spatial coverage resolution of the magnetic field measurements allow for the investigation of the dynamic processes and electric currents of the ionosphere and magnetosphere, especially for the ring current and equatorial electrojet during both quiet geomagnetic conditions and storms. Magnetic field measurements from LOPS could be important for studying the method to separate their contributions of the Magnetosphere-Ionosphere (M-I) current system.

scholarly journals Evaluation of single and multiple Doppler lidar techniques to measure complex flow during the XPIA field campaign

2017 ◽  
Vol 10 (1) ◽  
pp. 247-264 ◽  
Author(s):  
Aditya Choukulkar ◽  
W. Alan Brewer ◽  
Scott P. Sandberg ◽  
Ann Weickmann ◽  
Timothy A. Bonin ◽  
...  
Keyword(s):  
Measurement Uncertainty ◽  
Measurement Techniques ◽  
Vertical Plane ◽  
Complex Flow ◽  
Field Campaign ◽  
Velocity Statistics ◽  
Spatial Coverage ◽  
Stable Conditions ◽  
Sonic Anemometers ◽  
Measurement Uncertainties

Abstract. Accurate three-dimensional information of wind flow fields can be an important tool in not only visualizing complex flow but also understanding the underlying physical processes and improving flow modeling. However, a thorough analysis of the measurement uncertainties is required to properly interpret results. The XPIA (eXperimental Planetary boundary layer Instrumentation Assessment) field campaign conducted at the Boulder Atmospheric Observatory (BAO) in Erie, CO, from 2 March to 31 May 2015 brought together a large suite of in situ and remote sensing measurement platforms to evaluate complex flow measurement strategies. In this paper, measurement uncertainties for different single and multi-Doppler strategies using simple scan geometries (conical, vertical plane and staring) are investigated. The tradeoffs (such as time–space resolution vs. spatial coverage) among the different measurement techniques are evaluated using co-located measurements made near the BAO tower. Sensitivity of the single-/multi-Doppler measurement uncertainties to averaging period are investigated using the sonic anemometers installed on the BAO tower as the standard reference. Finally, the radiometer measurements are used to partition the measurement periods as a function of atmospheric stability to determine their effect on measurement uncertainty. It was found that with an increase in spatial coverage and measurement complexity, the uncertainty in the wind measurement also increased. For multi-Doppler techniques, the increase in uncertainty for temporally uncoordinated measurements is possibly due to requiring additional assumptions of stationarity along with horizontal homogeneity and less representative line-of-sight velocity statistics. It was also found that wind speed measurement uncertainty was lower during stable conditions compared to unstable conditions.

scholarly journals Robust, spatially scanning, open-path TDLAS hygrometer using retro-reflective foils for fast tomographic 2-D water vapour concentration field measurements

2014 ◽  
Vol 7 (12) ◽  
pp. 12827-12849 ◽  
Author(s):  
A. Seidel ◽  
S. Wagner ◽  
A. Dreizler ◽  
V. Ebert
Keyword(s):  
Water Vapour ◽  
Single Channel ◽  
Greenhouse Gas Emission ◽  
Concentration Field ◽  
Field Measurements ◽  
Tunable Diode Laser ◽  
Environmental Research ◽  
Soil Physics ◽  
Water Vapour Concentration ◽  
Vapour Concentration

Abstract. We have developed a fast, spatially direct scanning tunable diode laser absorption spectrometer (dTDLAS) that combines four polygon-mirror based scanning units with low-cost retro-reflective foils. With this instrument, tomographic measurements of absolute 2-D water vapour concentration profiles are possible without any calibration using a reference gas. A spatial area of 0.8 m × 0.8 m was covered, which allows for application in soil physics, where greenhouse gas emission from certain soil structures shall be monitored. The whole concentration field was measured with up to 2.5 Hz. In this paper, we present the setup and spectroscopic performance of the instrument regarding the influence of the polygon rotation speed and mode on the absorption signal. Homogeneous H2O distributions were measured and compared to a single channel, bi-static reference TDLAS spectrometer for validation of the instrument. Good accuracy and precision with errors of less than 6% of the absolute concentration and length and bandwidth normalized detection limits of up to 1.1 ppmv · m · √Hz−1 were achieved. The spectrometer is a robust and easy to set up instrument for tomographic reconstructions of 2-D-concentration fields that can be considered a good basis for future field measurements in environmental research.

scholarly journals Stochastic marine ice sheet variability

2018 ◽  
Vol 843 ◽  
pp. 748-777 ◽  
Author(s):  
T. E. Mulder ◽  
S. Baars ◽  
F. W. Wubs ◽  
H. A. Dijkstra
Keyword(s):  
Transition Probabilities ◽  
Accumulation Rate ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Field Measurements ◽  
Multiple Equilibrium ◽  
Short Time Scale ◽  
Two Dimensional ◽  
Grounding Line ◽  
Short Time

It is well known that deterministic two-dimensional marine ice sheets can only be stable if the grounding line is positioned at a sufficiently steep, downward sloping bedrock. When bedrock conditions favour instabilities, multiple stable ice sheet profiles may occur. Here, we employ continuation techniques to examine the sensitivity of a two-dimensional marine ice sheet to stochastic noise representing short time scale variability, either in the accumulation rate or in the sea level height. We find that in unique regimes, the position of the grounding line is most sensitive to noise in the accumulation rate and can explain excursions observed in field measurements. In the multiple equilibrium regime, there is a strong asymmetry in transition probabilities between the different ice sheet states, with a strong preference to switch to the branch with a steeper bedrock slope.

Estimation of active layer thickness from modeling and InSAR deformation data at QTP

2020 ◽  
Author(s):  
Rongxing Li ◽  
Tong Hao ◽  
Ping Lu ◽  
Gang Qiao ◽  
Lemin Chen ◽  
...  
Keyword(s):  
Layer Thickness ◽  
Active Layer ◽  
Large Scale ◽  
Surface Deformation ◽  
Remote Sensing Data ◽  
Field Measurements ◽  
Active Layer Thickness ◽  
Quality Of Data ◽  
Spatial Coverage ◽  
Sbas Insar

<p>In context of global warming, permafrost, as an important component of cryosphere in the Qinghai-Tibetan Plateau (QTP) that is located in middle and low latitudes with a high radiation intensity of high Asia mountains, is particularly sensitive to climate changes. The active layer thickness (ALT) in a permafrost area is an important index to indicate its stability. Traditional methods for measuring ALT in QTP mainly rely on ground-based field surveys and accordingly are extremely time- consuming and labor-intensive. The field works provide a good quality of data at a single site, however, such measurements are limited in spatial coverage and difficult for multi-temporal acquisitions. In addition, the harsh environment in QTP is not suitable for large-scale field measurements. In this study, the ALT of permafrost in QTP is estimated using modelling and remote sensing data. Particularly, the surface deformation on permafrost, as detected by the long-term InSAR technique, is considered as an input to the inversion model of ALT. The time-series deformation results over an experimental permafrost area were obtained by the SBAS-InSAR technique. Then, combined with the soil characteristics of soil moisture and soil thermal conductivity in the Stefan model, the melting thickness was estimated. Finally, the resulting ALT was tested and verified against a set of in-situ borehole measurements of depth-temperature.</p>

scholarly journals Evaluation of Single- and Multiple-Doppler Lidar Techniques to Measure Complex Flow during the XPIA Field Campaign

2016 ◽  
Author(s):  
Aditya Choukulkar ◽  
Alan Brewer ◽  
Scott P. Sandberg ◽  
Ann Weickmann ◽  
Timothy A. Bonin ◽  
...  
Keyword(s):  
Measurement Uncertainty ◽  
Measurement Techniques ◽  
Atmospheric Stability ◽  
Complex Flow ◽  
Field Campaign ◽  
Time Space ◽  
Spatial Coverage ◽  
Stable Conditions ◽  
Sonic Anemometers ◽  
Measurement Uncertainties

Abstract. Accurate three-dimensional information of wind flow fields can be an important tool in not only visualizing complex flow, but also understanding the underlying physical processes and improving flow modeling. However, a thorough analysis of the measurement uncertainties is required to properly interpret results. The XPIA (eXperimental Planetary boundary layer Instrumentation Assessment) field campaign conducted at the Boulder Atmospheric Observatory (BAO) in Erie, CO from 2 March–31 May 2015 brought together a large suite of in-situ and remote sensing measurement platforms to evaluate complex flow measurement strategies. In this paper, measurement uncertainties for different single and multi-Doppler strategies are investigated. The tradeoffs (such as time/space resolution vs. spatial coverage) among the different measurement techniques are evaluated using co-located measurements made near the BAO tower. Sensitivity of the single/multi Doppler measurement uncertainties to averaging period are investigated using the sonic anemometers installed on the BAO tower as the standard reference. Finally, the radiometer measurements are used to partition the measurement periods as a function of atmospheric stability to determine their effect on measurement uncertainty. It was found that with increase in spatial coverage and measurement complexity, the uncertainty in the wind measurement also increased. For multi-Doppler techniques, the increase in uncertainty for temporally uncoordinated measurements is possibly due to requiring additional assumptions of stationarity and/or horizontal homogeneity. It was also found that wind speed measurement uncertainty was lower during stable conditions compared to unstable conditions.

scholarly journals Drifting snow statistics from multiple-year autonomous measurements in Adelie Land, eastern Antarctica

2019 ◽  
Author(s):  
Charles Amory
Keyword(s):  
Temporal Frequency ◽  
Field Measurements ◽  
Near Surface ◽  
Continental Scale ◽  
Drifting Snow ◽  
Single Location ◽  
Antarctic Continent ◽  
Short Time ◽  
The Antarctic ◽  
Snow Transport

Abstract. Drifting snow is a widespread feature over the Antarctic ice sheet whose climatological and hydrological significances at the continental scale have been consequently investigated through modelling and satellite approaches. While field measurements are needed to evaluate and interpret model and punctual satellite products, most drifting snow observation campaigns in Antarctica involved data collected at a single location and over short time periods. With the aim of acquiring new data relevant to the observations and modelling of drifting snow in Antarctic conditions, two remote locations in coastal Adelie Land (East Antarctica) 100 km apart were instrumented in January 2010 with meteorological and second-generation IAV Engineering acoustic FlowCaptTM sensors. The data provided nearly continuously so far constitutes the longest dataset of autonomous near-surface (i.e., below 2 m) measurements of drifting snow currently available over the Antarctic continent. This paper presents an assessment of drifting snow occurrences and snow mass transport from up to 9 years (2010–2018) of half-hourly observational records collected in one of the Antarctic regions most prone to snow transport by wind. The dataset is freely available to the scientific community and can be used to complement satellite products and evaluate snow-transport models close to the surface and at high temporal frequency.

scholarly journals Current estimates of biogenic emissions from Eucalypts uncertain for Southeast Australia

2016 ◽  
Author(s):  
K. M. Emmerson ◽  
I. E. Galbally ◽  
A. B. Guenther ◽  
C. Paton-Walsh ◽  
E.-A. Guerette ◽  
...  
Keyword(s):  
Transport Model ◽  
Chemical Species ◽  
Field Measurements ◽  
Oxidation Products ◽  
Biogenic Emissions ◽  
Emission Rates ◽  
Chemical Transport Model ◽  
Southeast Australia ◽  
Unusual Position ◽  
Adult Trees

Abstract. The biogenic emissions of isoprene and monoterpenes are one of the main drivers of atmospheric photochemistry, including oxidant and secondary organic aerosol production. In this paper, the emission rates of isoprene and monoterpenes from Australian vegetation are investigated for the first time using the Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGANv2.1), the CSIRO chemical transport model, and atmospheric observations of isoprene, monoterpenes and isoprene oxidation products (methacrolein and methyl-vinyl-ketone). Observations from four field campaigns during three different seasons are used, covering urban, coastal suburban and inland forest areas. The observed concentrations of isoprene and monoterpenes were of a broadly similar magnitude, which may indicate that southeast Australia holds an unusual position where neither chemical species dominates. The model results overestimate the observed atmospheric concentrations of isoprene (up to a factor of 6) and underestimate the monoterpene concentrations (up to a factor of 4). This may occur because the emission rates currently used in MEGANv2.1 for Australia are drawn mainly from young Eucalypt trees (< 7 years), which may emit more isoprene than adult trees. There is no single increase/decrease factor for the emissions which suits all seasons and conditions studied. There is a need for further field measurements of in-situ isoprene and monoterpene emission fluxes in Australia.

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