scholarly journals FIELD MEASUREMENTS OF DUNE EROSION

1986 ◽  
Vol 1 (20) ◽  
pp. 82 ◽  
Author(s):  
J.S. Fisher ◽  
M.F. Overton ◽  
T. Chisholm
Keyword(s):  
Linear Relationship ◽  
Field Experiments ◽  
Field Measurements ◽  
Specific Force ◽  
Force Term ◽  
Force Parameter ◽  
Dune Erosion ◽  
Specific Erosion

A series of field experiments was made to evaluate the use of a laboratory derived relationship between the force in the wave uprush and the erosion of beach dunes. Measurements of the swash velocity and height at the dune face were used to compute a specific force parameter. This force term was correlated with the specific erosion of the dune. A linear relationship similar to that found in the laboratory was determined with a R squared value of .87.

scholarly journals Field Measurements of Surface and Near-Surface Turbulence in the Presence of Breaking Waves

2015 ◽  
Vol 45 (4) ◽  
pp. 943-965 ◽  
Author(s):  
Peter Sutherland ◽  
W. Kendall Melville
Keyword(s):  
Field Experiments ◽  
North Pacific Ocean ◽  
Large Fraction ◽  
Field Measurements ◽  
Breaking Waves ◽  
Sea Surface ◽  
Near Surface ◽  
Wave Energy Dissipation ◽  
Eddy Simulation ◽  
The North

AbstractWave breaking removes energy from the surface wave field and injects it into the upper ocean, where it is dissipated by viscosity. This paper presents an investigation of turbulent kinetic energy (TKE) dissipation beneath breaking waves. Wind, wave, and turbulence data were collected in the North Pacific Ocean aboard R/P FLIP, during the ONR-sponsored High Resolution Air-Sea Interaction (HiRes) and Radiance in a Dynamic Ocean (RaDyO) experiments. A new method for measuring TKE dissipation at the sea surface was combined with subsurface measurements to allow estimation of TKE dissipation over the entire wave-affected surface layer. Near the surface, dissipation decayed with depth as z−1, and below approximately one significant wave height, it decayed more quickly, approaching z−2. High levels of TKE dissipation very near the sea surface were consistent with the large fraction of wave energy dissipation attributed to non-air-entraining microbreakers. Comparison of measured profiles with large-eddy simulation results in the literature suggests that dissipation is concentrated closer to the surface than previously expected, largely because the simulations did not resolve microbreaking. Total integrated dissipation in the water column agreed well with dissipation by breaking for young waves, (where cm is the mean wave frequency and is the atmospheric friction velocity), implying that breaking was the dominant source of turbulence in those conditions. The results of these extensive measurements of near-surface dissipation over three field experiments are discussed in the context of observations and ocean boundary layer modeling efforts by other groups.

scholarly journals Characterising optical array particle imaging probes: implications for small-ice-crystal observations

2021 ◽  
Vol 14 (3) ◽  
pp. 1917-1939
Author(s):  
Sebastian O'Shea ◽  
Jonathan Crosier ◽  
James Dorsey ◽  
Louis Gallagher ◽  
Waldemar Schledewitz ◽  
...  
Keyword(s):  
Field Experiments ◽  
Field Measurements ◽  
Sample Volume ◽  
Ice Crystal ◽  
Cloud Particle ◽  
Ice Clouds ◽  
Cloud Properties ◽  
Imaging Probes ◽  
New Methodologies ◽  
Particle Imaging

Abstract. The cloud particle concentration, size, and shape data from optical array probes (OAPs) are routinely used to parameterise cloud properties and constrain remote sensing retrievals. This paper characterises the optical response of OAPs using a combination of modelling, laboratory, and field experiments. Significant uncertainties are found to exist with such probes for ice crystal measurements. We describe and test two independent methods to constrain a probe's sample volume that remove the most severely mis-sized particles: (1) greyscale image analysis and (2) co-location using stereoscopic imaging. These methods are tested using field measurements from three research flights in cirrus. For these cases, the new methodologies significantly improve agreement with a holographic imaging probe compared to conventional data-processing protocols, either removing or significantly reducing the concentration of small ice crystals (< 200 µm) in certain conditions. This work suggests that the observational evidence for a ubiquitous mode of small ice particles in ice clouds is likely due to a systematic instrument bias. Size distribution parameterisations based on OAP measurements need to be revisited using these improved methodologies.

scholarly journals Depression storage and infiltration effects on overland flow depth-velocity-friction at desert conditions: field plot results and model

2012 ◽  
Vol 16 (9) ◽  
pp. 3293-3307 ◽  
Author(s):  
M. J. Rossi ◽  
J. O. Ares
Keyword(s):  
Field Experiments ◽  
Overland Flow ◽  
Field Measurements ◽  
Life Forms ◽  
Water Infiltration ◽  
Soil Core ◽  
Infiltration Rates ◽  
Overland Flows ◽  
Desert Areas ◽  
Semi Arid

Abstract. Water infiltration and overland flow are relevant in considering water partition among plant life forms, the sustainability of vegetation and the design of sustainable hydrological models and management. In arid and semi-arid regions, these processes present characteristic trends imposed by the prevailing physical conditions of the upper soil as evolved under water-limited climate. A set of plot-scale field experiments at the semi-arid Patagonian Monte (Argentina) were performed in order to estimate the effect of depression storage areas and infiltration rates on depths, velocities and friction of overland flows. The micro-relief of undisturbed field plots was characterized at z-scale 1 mm through close-range stereo-photogrammetry and geo-statistical tools. The overland flow areas produced by controlled water inflows were video-recorded and the flow velocities were measured with image processing software. Antecedent and post-inflow moisture were measured, and texture, bulk density and physical properties of the upper soil were estimated based on soil core analyses. Field data were used to calibrate a physically-based, mass balanced, time explicit model of infiltration and overland flows. Modelling results reproduced the time series of observed flow areas, velocities and infiltration depths. Estimates of hydrodynamic parameters of overland flow (Reynolds-Froude numbers) are informed. To our knowledge, the study here presented is novel in combining several aspects that previous studies do not address simultaneously: (1) overland flow and infiltration parameters were obtained in undisturbed field conditions; (2) field measurements of overland flow movement were coupled to a detailed analysis of soil microtopography at 1 mm depth scale; (3) the effect of depression storage areas in infiltration rates and depth-velocity friction of overland flows is addressed. Relevance of the results to other similar desert areas is justified by the accompanying biogeography analysis of similarity of the environment where this study was performed with other desert areas of the world.

Measurement of gaseous emissions from denitrification of applied N-15 .3. Field-measurements

Soil Research ◽  
1995 ◽  
Vol 33 (1) ◽  
pp. 101 ◽  
Author(s):  
UK Avalakki ◽  
WM Strong ◽  
PG Saffigna
Keyword(s):  
Mass Balance ◽  
Field Experiments ◽  
Field Measurements ◽  
Cereal Crops ◽  
Gaseous Emissions ◽  
Gas Emission ◽  
Winter Cereal ◽  
Autumn And Winter ◽  
Balance Loss ◽  
Peak Emission

Field experiments were conducted during autumn and winter (April-July) at four locations on Vertisol or Alfisol soils on the Darling Downs of Queensland in 1988 and 1989 to determine 15N losses when soil was saturated after applications of 15N labelled nitrate-N prior to sowing winter cereal crops. Losses of applied 15N were quantified by either gas emission or mass balance measurements on microplots (0.043 m2) confined laterally to a depth of 110 or 260 mm. At each field location, two experiments were established, one on a soil containing little visible crop residue where winter cereal had been harvested the previous November and another site containing residues of a recently harvested sorghum crop. Because shallow (110 mm) confinement was found to be unsatisfactory for both gas emission and mass balance measurement of 15N losses, comparison of the two methods was not applicable at one of the four field locations. Loss estimates for the six field sites by accumulating daily gas emissions averaged 80.7 � 33.4% (range 43-132%) of that estimated by mass balance. Loss estimates from peak emission measurements were generally closer to that estimated by mass balance 100.8� 39.9% (range 56-169%). Loss of applied 15N (40 kg N ha-1) when soils were saturated in April was several-fold more (19-29 kg N ha-1)) than that lost when soils were saturated in July (3.9-6.4 kg N ha-1)). Loss of 15N following saturation during July 1988 was similar in magnitude to the quantity of 15N apparently immobilized into soil organic forms (5.8-6.0 kg N ha-1)). Sorghum residues returned in March, or wheat straw added in December prior to a long period of dry weather, promoted loss of 15N applied prior to soil saturation in April or July. Alternatively, where residues of a previous winter cereal had decomposed considerably, loss of applied 15N was much lower than where sorghum residues had been added prior to saturations in April (15.3 cf. 28.6 kg N ha-1)) or July (3.9 cf. 6.4 kg N ha-1)).

scholarly journals Field Measurements of Wind Characteristics Using LiDAR on a Wind Farm with Downwind Turbines Installed in a Complex Terrain Region

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5135
Author(s):  
Tetsuya Kogaki ◽  
Kenichi Sakurai ◽  
Susumu Shimada ◽  
Hirokazu Kawabata ◽  
Yusuke Otake ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Farm ◽  
Field Experiments ◽  
Wind Farms ◽  
Field Measurements ◽  
Horizontal Wind ◽  
Flow Distortion ◽  
Horizontal Wind Speed ◽  
Vertical Profiling ◽  
Wind Characteristics

Downwind turbines have favorable characteristics such as effective energy capture in up-flow wind conditions over complex terrains. They also have reduced risk of severe accidents in the event of disruptions to electrical networks during strong storms due to the free-yaw effect of downwind turbines. These favorable characteristics have been confirmed by wind-towing tank experiments and computational fluid dynamics (CFD) simulations. However, these advantages have not been fully demonstrated in field experiments on actual wind farms. In this study—although the final objective was to demonstrate the potential advantages of downwind turbines through field experiments—field measurements were performed using a vertical-profiling light detection and ranging (LiDAR) system on a wind farm with downwind turbines installed in complex terrains. To deduce the horizontal wind speed, vertical-profiling LiDARs assume that the flow of air is uniform in space and time. However, in complex terrains and/or in wind farms where terrain and/or wind turbines cause flow distortion or disturbances in time and space, this assumption is not valid, resulting in erroneous wind speed estimates. The magnitude of this error was evaluated by comparing LiDAR measurements with those obtained using a cup anemometer mounted on a meteorological mast and detailed analysis of line-of-sight wind speeds. A factor that expresses the nonuniformity of wind speed in the horizontal measurement plane of vertical-profiling LiDAR is proposed to estimate the errors in wind speed. The possibility of measuring and evaluating various wind characteristics such as flow inclination angles, turbulence intensities, wind shear and wind veer, which are important for wind turbine design and for wind farm operation is demonstrated. However, additional evidence of actual field measurements on wind farms in areas with complex terrains is required in order to obtain more universal and objective evaluations.

Field Measurements of Dune Erosion

1987 ◽  
Author(s):  
J. S. Fisher ◽  
M. F. Overton ◽  
T. Chisholm
Keyword(s):  
Field Measurements ◽  
Dune Erosion

scholarly journals Adjustments for Wind-Induced Undercatch in Snowfall Measurements Based on Precipitation Intensity

2020 ◽  
Vol 21 (5) ◽  
pp. 1039-1050 ◽  
Author(s):  
Matteo Colli ◽  
Mattia Stagnaro ◽  
Luca G. Lanza ◽  
Roy Rasmussen ◽  
Julie M. Thériault
Keyword(s):  
Wind Speed ◽  
Field Experiments ◽  
Transfer Functions ◽  
Collection Efficiency ◽  
Surface Air Temperature ◽  
Field Measurements ◽  
Precipitation Intensity ◽  
Operational Conditions ◽  
Explanatory Variables ◽  
Precipitation Gauge

AbstractAdjustments for the wind-induced undercatch of snowfall measurements use transfer functions to account for the expected reduction of the collection efficiency with increasing the wind speed for a particular catching-type gauge. Based on field experiments or numerical simulation, collection efficiency curves as a function of wind speed also involve further explanatory variables such as surface air temperature and/or precipitation type. However, while the wind speed or wind speed and temperature approach is generally effective at reducing the measurement bias, it does not significantly reduce the root-mean-square error (RMSE) of the residuals, implying that part of the variance is still unexplained. In this study, we show that using precipitation intensity as the explanatory variable significantly reduces the scatter of the residuals. This is achieved by optimized curve fitting of field measurements from the Marshall Field Site (Colorado, United States), using a nongradient optimization algorithm to ensure optimal binning of experimental data. The analysis of a recent quality-controlled dataset from the Solid Precipitation Intercomparison Experiment (SPICE) campaign of the World Meteorological Organization confirms the scatter reduction, showing that this approach is suitable to a variety of locations and catching-type gauges. Using computational fluid dynamics simulations, we demonstrate that the physical basis of the reduction in RMSE is the correlation of precipitation intensity with the particle size distribution. Overall, these findings could be relevant in operational conditions since the proposed adjustment of precipitation measurements only requires wind sensor and precipitation gauge data.

Relative Statistical Calibration of ILI Measurements

2016 ◽  
Author(s):  
Mona Abdolrazaghi ◽  
Sherif Hassanien ◽  
Karmun Cheng
Keyword(s):  
Linear Relationship ◽  
Measurement Errors ◽  
Oil And Gas ◽  
Graphical Representation ◽  
Measurement Techniques ◽  
Measurement Data ◽  
Field Measurements ◽  
True Value ◽  
Accuracy And Precision ◽  
Examination Techniques

In-Line inspection tools (ILI) including Magnetic Flux Leakage (MFL) and Ultrasonic (UT) technologies are commonly used to detect/measure potential anomalies in oil and gas pipelines. Some of ILI reported anomalies are usually selected for excavation and validated through field non-destructive examination techniques (NDE). It is a fact that both ILI and NDE readings are contaminated with measurement errors. Such errors are usually originated from inherent tool limitations and capabilities, measurement techniques, and/or human factors. The intend of this paper is to calibrate the corrosion ILI data relative to NDE measurement given estimated statistical errors from both tools. Commonly, a graphical representation is used to compare ILI versus field measurements; namely, a unity plot. Herein, a linear relationship between ILI and NDE measurements is assumed. Such an assumption leads to another assumption of having a linear relationship between the ILI measurement and true value. Similarly, NDE measurement has the same relationship with the true value. An advanced statistical approach based on linear regression and maximum likelihood is used to determine the uncertainty of both ILI and NDE measurement errors. This method is based on first quantifying the uncertainty of ILI and field measurement and then calibrating the ILI data relative to the field using the estimated tools errors. The tool error estimation is based on reducing the relative error between ILI and field measurements. The calibration methodology implements advanced statistics to improve both accuracy and precision of measurement data. The proposed process is validated through results from successive ILI programs. The proposed calibration can be easily adopted in ubiquitous computing spreadsheet environment and be applied to both corrosion and crack measurements.

scholarly journals Relationship of the Severity of Citrus Greasy Spot, Caused by Mycosphaerella citri, to Ascospore Dose, Epiphytic Growth, Leaf Age, and Fungicide Timing

Plant Disease ◽  
2006 ◽  
Vol 90 (2) ◽  
pp. 220-224 ◽  
Author(s):  
S. N. Mondal ◽  
L. W. Timmer
Keyword(s):  
Linear Relationship ◽  
Symptom Severity ◽  
Field Experiments ◽  
Rapid Development ◽  
Leaf Age ◽  
Fruit Size ◽  
Rough Lemon ◽  
Large Numbers ◽  
Relationship Of ◽  
Greenhouse Tests

Greasy spot, caused by Mycosphaerella citri, produces leaf and fruit lesions and defoliates trees, resulting in reduced yields and fruit size. Techniques now available allow production of large numbers of ascospores and the quantification of epiphytic growth. The effects of ascospore dose, leaf age, and the timing of fenbuconazole sprays on epiphytic growth and disease severity was determined primarily on rough lemon seedlings in the greenhouse. Inoculation of leaves with 104 ascospores/ml resulted in rapid development of epiphytic growth and symptoms. At lower doses, epiphytic growth and symptoms developed more slowly and were less severe. There was a linear relationship between log10 of the ascospore dose and ratings of epiphytic growth and symptoms, and a linear relationship between the amount of epiphytic growth and symptom severity in greenhouse tests. On grapefruit trees treated with different fungicides in six field experiments, there also was a significant linear relationship between epiphytic growth of M. citri measured in August and symptom severity rated in February to March of the following year, but coefficients of determination were much lower than in greenhouse experiments. Leaf age from 10 to 60 days did not affect susceptibility of leaves to M. citri. Fenbuconazole applied up to 50 days prior to inoculation still reduced epiphytic growth and greasy spot severity under greenhouse conditions, but the postinoculation treatments were effective for only 30 days.

Brine Transport in the Bedded Salt of the Waste Isolation Pilot Plant (wipp): Field Measurements and a Darcy Flow Model

1987 ◽  
Vol 112 ◽  
Author(s):  
David F. Mctigue ◽  
E. James Nowak
Keyword(s):  
Field Experiments ◽  
Flow Model ◽  
Radial Flow ◽  
Field Measurements ◽  
Darcy Flow ◽  
Waste Isolation Pilot Plant ◽  
One Dimensional ◽  
Brine Transport ◽  
Order Of Magnitude ◽  
Linearized Model

AbstractBrine flow has been measured to unheated boreholes for periods of a few days and to heated holes for two years in the WIPP facility. It is proposed that Darcy flow may dominate the observed influx of brine. Exact solutions to a linearized model for one-dimensional, radial flow are evaluated for conditions approximating the field experiments. Flow rates of the correct order of magnitude are calculated for permeabilities in the range 10−21–1020 m2 (1–10 nanodarcy) for both the unheated and heated cases.

Sign in / Sign up

Export Citation Format

Share Document