scholarly journals Aeolian mass flux characterization: uncertainties from a wind-tunnel perspective and implications for field studies

2014 ◽  
Author(s):  
Ate Poortinga ◽  
Joep GS Keijsers ◽  
Jerry Maroulis ◽  
Saskia M. Visser
Keyword(s):  
Wind Tunnel ◽  
Mass Flux ◽  
Shear Velocity ◽  
Field Studies ◽  
Sediment Traps ◽  
Sediment Flux ◽  
Cumulative Probability ◽  
Surface Moisture ◽  
The North ◽  
Specific Configuration

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

scholarly journals Measurement uncertainties in quantifying aeolian mass flux: Evidence from wind tunnel and field site data

2014 ◽  
Author(s):  
Ate Poortinga ◽  
Joep GS Keijsers ◽  
Jerry Maroulis ◽  
Saskia M. Visser
Keyword(s):  
Wind Tunnel ◽  
Mass Flux ◽  
Meteorological Data ◽  
Shear Velocity ◽  
Field Studies ◽  
Sediment Traps ◽  
Sediment Flux ◽  
Cumulative Distribution ◽  
Surface Moisture ◽  
Specific Configuration

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

scholarly journals Measurement uncertainties in quantifying aeolian mass flux: Evidence from wind tunnel and field site data

2014 ◽  
Author(s):  
Ate Poortinga ◽  
Joep GS Keijsers ◽  
Jerry Maroulis ◽  
Saskia M. Visser
Keyword(s):  
Wind Tunnel ◽  
Mass Flux ◽  
Meteorological Data ◽  
Shear Velocity ◽  
Field Studies ◽  
Sediment Traps ◽  
Sediment Flux ◽  
Cumulative Distribution ◽  
Surface Moisture ◽  
Specific Configuration

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

The effect of dry aggregation and percentage clay on sediment flux as measured by a portable field wind tunnel

Soil Research ◽  
1996 ◽  
Vol 34 (6) ◽  
pp. 849 ◽  
Author(s):  
J Leys ◽  
T Koen ◽  
G McTainsh
Keyword(s):  
Wind Tunnel ◽  
Erosion Rate ◽  
Clay Content ◽  
Temporal Variations ◽  
Sediment Flux ◽  
Erosion Rates ◽  
The North ◽  
South Wales ◽  
Wind Velocities ◽  
Soil Clay Content

The effect of dry aggregation levels >0.85 mm and the percentage clay content of 9 soils from south-western New South Wales on erosion rate is evaluated using a portable field wind tunnel. Standard soil preparations and wind velocities are used based on conventions established in the North American wind erosion literature. For the prediction of erosion rate on both cultivated and uncultivated soils, 2 highly significant empirical relationships for percentage soil clay content and percentage mass dry aggregation >0.85 mm are presented. These spatial and temporal variations in erosion rates have significance for our understanding of soil erodibility. The concept of erodibility continuum is introduced.

scholarly journals Anomalous azimuthal variations with 360° periodicity of Rayleigh phase velocities observed in Scandinavia

2020 ◽  
Vol 224 (3) ◽  
pp. 1684-1704
Author(s):  
Alexandra Mauerberger ◽  
Valérie Maupin ◽  
Ólafur Gudmundsson ◽  
Frederik Tilmann
Keyword(s):  
Seismic Anisotropy ◽  
Broad Band ◽  
Shear Velocity ◽  
Velocity Variation ◽  
The South ◽  
Study Region ◽  
Lithospheric Thickness ◽  
Phase Velocities ◽  
The North ◽  
Southern Norway

SUMMARY We use the recently deployed ScanArray network of broad-band stations covering most of Norway and Sweden as well as parts of Finland to analyse the propagation of Rayleigh waves in Scandinavia. Applying an array beamforming technique to teleseismic records from ScanArray and permanent stations in the study region, in total 159 stations with a typical station distance of about 70 km, we obtain phase velocities for three subregions, which collectively cover most of Scandinavia (excluding southern Norway). The average phase dispersion curves are similar for all three subregions. They resemble the dispersion previously observed for the South Baltic craton and are about 1 per cent slower than the North Baltic shield phase velocities for periods between 40 and 80 s. However, a remarkable sin(1θ) phase velocity variation with azimuth is observed for periods >35 s with a 5 per cent deviation between the maximum and minimum velocities, more than the overall lateral variation in average velocity. Such a variation, which is incompatible with seismic anisotropy, occurs in northern Scandinavia and southern Norway/Sweden but not in the central study area. The maximum and minimum velocities were measured for backazimuths of 120° and 300°, respectively. These directions are perpendicular to a step in the lithosphere–asthenosphere boundary (LAB) inferred by previous studies in southern Norway/Sweden, suggesting a relation to large lithospheric heterogeneity. In order to test this hypothesis, we carried out 2-D full-waveform modeling of Rayleigh wave propagation in synthetic models which incorporate a steep gradient in the LAB in combination with a pronounced reduction in the shear velocity below the LAB. This setup reproduces the observations qualitatively, and results in higher phase velocities for propagation in the direction of shallowing LAB, and lower ones for propagation in the direction of deepening LAB, probably due to the interference of forward scattered and reflected surface wave energy with the fundamental mode. Therefore, the reduction in lithospheric thickness towards southern Norway in the south, and towards the Atlantic ocean in the north provide a plausible explanation for the observed azimuthal variations.

scholarly journals Particulate barium tracing of significant mesopelagic carbon remineralisation in the North Atlantic

2018 ◽  
Vol 15 (8) ◽  
pp. 2289-2307 ◽  
Author(s):  
Nolwenn Lemaitre ◽  
Hélène Planquette ◽  
Frédéric Planchon ◽  
Géraldine Sarthou ◽  
Stéphanie Jacquet ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
North Atlantic ◽  
Deep Convection ◽  
Sediment Traps ◽  
Heterotrophic Activity ◽  
Physical Forcing ◽  
The North ◽  
Poc Export ◽  
Order Of Magnitude ◽  
The North Atlantic

Abstract. The remineralisation of sinking particles by prokaryotic heterotrophic activity is important for controlling oceanic carbon sequestration. Here, we report mesopelagic particulate organic carbon (POC) remineralisation fluxes in the North Atlantic along the GEOTRACES-GA01 section (GEOVIDE cruise; May–June 2014) using the particulate biogenic barium (excess barium; Baxs) proxy. Important mesopelagic (100–1000 m) Baxs differences were observed along the transect depending on the intensity of past blooms, the phytoplankton community structure, and the physical forcing, including downwelling. The subpolar province was characterized by the highest mesopelagic Baxs content (up to 727 pmol L−1), which was attributed to an intense bloom averaging 6 mg chl a m−3 between January and June 2014 and by an intense 1500 m deep convection in the central Labrador Sea during the winter preceding the sampling. This downwelling could have promoted a deepening of the prokaryotic heterotrophic activity, increasing the Baxs content. In comparison, the temperate province, characterized by the lowest Baxs content (391 pmol L−1), was sampled during the bloom period and phytoplankton appear to be dominated by small and calcifying species, such as coccolithophorids. The Baxs content, related to oxygen consumption, was converted into a remineralisation flux using an updated relationship, proposed for the first time in the North Atlantic. The estimated fluxes were of the same order of magnitude as other fluxes obtained using independent methods (moored sediment traps, incubations) in the North Atlantic. Interestingly, in the subpolar and subtropical provinces, mesopelagic POC remineralisation fluxes (up to 13 and 4.6 mmol C m−2 d−1, respectively) were equalling and occasionally even exceeding upper-ocean POC export fluxes, deduced using the 234Th method. These results highlight the important impact of the mesopelagic remineralisation on the biological carbon pump of the studied area with a near-zero, deep (> 1000 m) carbon sequestration efficiency in spring 2014.

scholarly journals The impact of Saharan dust on the particulate export in the water column of the North Western Mediterranean Sea

2010 ◽  
Vol 7 (3) ◽  
pp. 809-826 ◽  
Author(s):  
E. Ternon ◽  
C. Guieu ◽  
M.-D. Loÿe-Pilot ◽  
N. Leblond ◽  
E. Bosc ◽  
...  
Keyword(s):  
Atmospheric Deposition ◽  
Mass Flux ◽  
Total Mass ◽  
Spring Bloom ◽  
Western Mediterranean ◽  
Saharan Dust ◽  
The North ◽  
Western Mediterranean Sea ◽  
Total Mass Flux ◽  
North Western

Abstract. Simultaneous measurements of atmospheric deposition and of sinking particles at 200 and 1000 m depth, were performed in the Ligurian Sea (North-Western Mediterranean) between 2003 and 2007, along with phytoplanktonic activity derived from satellite images. Atmospheric deposition of Saharan dust particles was very irregular and confirmed the importance of sporadic high magnitude events over the annual average (11.4 g m−2 yr−1 for the 4 years). The average marine total mass flux was 31 g m−2 yr−1, the larger fraction being the lithogenic one (~37%). The marine total mass flux displayed a seasonal pattern with a maximum in winter, occurring before the onset of the spring bloom. The highest POC fluxes did not occur during the spring bloom nor could they be directly related to any noticeable increase in the surface phytoplanktonic biomass. Over the 4 years of the study, the strongest POC fluxes were concomitant with large increases of the lithogenic marine flux, which had originated from either recent Saharan fallout events (February 2004 and August 2005), from "old" Saharan dust "stored" in the upper water column layer (March 2003 and February 2005), or alternatively from lithogenic material originating from Ligurian riverine flooding (December 2003, Arno, Roya and Var rivers). Those associated export fluxes defined as "lithogenic events", are believed to result from a combination of forcing (winter mixing or Saharan events, in particular extreme ones), biological (zooplankton) activity, and also organic-mineral aggregation inducing a ballast effect. By fertilising the surface layer, mixed Saharan dust events were shown to be able to induce "lithogenic events" during the stratification period. These events would be more efficient in transferring POC to the deeper layers than the spring bloom itself. The extreme Saharan event of February 2004 exported ~45% of the total annual POC, compared to an average of ~25% for the bloom period. This emphasises the role played by these "lithogenic events", and in particular those that are induced by the more extreme Saharan events, in the carbon export efficiency in the North-western Mediterranean Sea.

scholarly journals Vitality Structure of the Populations of Vegetative Motile Plants of Forest Ecosystems of the North-East of Ukraine

2019 ◽  
Vol 13 (1) ◽  
pp. 125-132
Author(s):  
Kovalenko Ihor ◽  
Skliar Iurii ◽  
Klymenko Hanna ◽  
Kovalenko Nataliia
Keyword(s):  
Quality Index ◽  
Forest Ecosystems ◽  
Morphological Structure ◽  
Field Studies ◽  
Complete Analysis ◽  
Individual Plant ◽  
North East ◽  
The North ◽  
Motile Species ◽  
Two Populations

Background: The vitality level of the populations has turned out to be statistically reliably associated with such coenotic factors: age and density of forest stand. In general, the vitality spectra vary widely: the quality index Q of the populations ranges from 0,00 to 0,50, that is, it fully covers the theoretically possible scale of the values of this coefficient, which indicates the sensitivity of the vitality structure of the populations to the ecological-coenotic conditions and determines high informative value of the vitality analysis. Objective: The aim of the study is to assess the vitality structure of the populations of vegetative motile plant species – typical representatives of the grassy layer of forest ecosystems of the North-East of Ukraine as a factor that determines their stability and dynamics. Methods: The analysis of the vitality structure is based on the field studies of the populations of 4 vegetative motile species of plants – Aegopodium podagraria L., Asarum europaeum L., Carex pilosa Scop. and Stellaria holostea L. in forest ecosystems of the North-East of Ukraine. Vitality analysis was carried out according to Yu. A. Zlobin’s methodology. Vitality analysis procedure, classically, is carried out in three stages: 1) Selection of quantitative features that characterize the vital status of the individual plant; 2) Evaluation of vitality of individual plants that were included in the sample; 3) Integral assessment of the population’s vitality. Depending on the ratio in the population of plants of classes a, b and c, the population belongs to one of three vitality types: prosperous, equilibrium or depressive. Results: The obtained estimates of the vitality structure of populations of the clone-forming plants in the grass-shrub layer of forests of the North-East of Ukraine can be considered quite reliable, because they are based, in general, on a complete analysis of the morphological structure of about 13 thousand ramets of the studied species of plants. The statistical reliability of estimates of the population’s vitality structure is predominantly between 70 and 99% and only in some cases lower than 70%. As the clone grows older, its ramet’s vitality decreases and the clone degrades. New young clones, that start to form on the basis of genets, replace old ones. Such ramets have increased vitality, greater stress and competitive resistance. Due to the mechanisms of clone substitution in the living cover, the dominance of nemoralis herbs persists for a long time. Conclusion: The vitality spectra of the populations of the studied species of plants vary widely: the quality index Q of the populations ranges from 0,00 to 0,50, that is, it covers full theoretically possible scale of the values of this coefficient, which indicates the sensitivity of the vitality structure of the populations to the ecological-coenotic conditions and determines high informative value of vitality analysis. Prosperous populations: two populations A. europaeum of the associations Quercetum (roboris) coryloso (avellanae) – convallariosum (majalis) and Quercetum (roboris) coryloso (avellanae) – convallariosum (majalis), two populations A. podagraria of the associations – Pinetum (sylvestris) vacciniosum (myrtilli) and Querceto (roboris) – Pinetum (sylvestris) convallarioso (majalis) – vacciniosum (myrtilli), one population S. holostea of the association Querceto (roboris) – Pinetum (sylvestris) vacciniosum (myrtilli) and one population C. pilosa of the association Querceto (roboris) – Pinetum (sylvestris) vaccinioso (myrtilli) – convallariosum (majalis).

scholarly journals Carbonate sedimentation and effects of eutrophication observed at the Kališta subaquatic springs in Lake Ohrid (Macedonia)

2010 ◽  
Vol 7 (3) ◽  
pp. 4715-4747 ◽  
Author(s):  
M. Matter ◽  
F. S. Anselmetti ◽  
B. Jordanoska ◽  
B. Wagner ◽  
M. Wessels ◽  
...  
Keyword(s):  
Sediment Traps ◽  
Authigenic Carbonate ◽  
Sidescan Sonar ◽  
Carbonate Content ◽  
Carbonate Precipitation ◽  
Lake Ohrid ◽  
Radiocarbon Dates ◽  
North West ◽  
The North ◽  
Spring Area

Abstract. To date, little is known about the role of spring waters with respect to authigenic carbonate precipitation in the shallow lacustrine setting. Lake Ohrid, located in Southeastern Europe, is a large lake fed to over 50% by karstic springs of which half enter subaquatically and influence significantly its ecology and species distribution. In order to evaluate how sedimentological processes are influenced by such shallow-water springs, the Kališta subaquatic spring area in the north west of Lake Ohrid was investigated by a sidescan sonar survey and with sediment traps and three transects of gravity short cores. Results indicate that sedimentation in the spring area is dominated by authigenic carbonate precipitation. High sedimentation rates and evidences for bio-induced precipitation processes were observed in the water column and in the sediments. Two distinct stratigraphic units characterize the shallow subsurface, both composed of carbonate silts with high carbonate contents of up to 96%, but differing in color, carbonate content and diatom content. A chronological correlation of the cores by radiocarbon dates and 137Cs activities places the transition between the two stratigraphic units after ~1955 AD. At that time, coastal sedimentation changed drastically to significantly darker sediments with higher contents of organic matter and more abundant diatoms. This change coincides with the recent human impact of littoral eutrophication.

Life before and after implementation of an acoustic noise reduction enclosure

2005 ◽  
Vol 109 (1092) ◽  
pp. 65-74
Author(s):  
B. Timmins
Keyword(s):  
Wind Tunnel ◽  
Noise Reduction ◽  
Acoustic Noise ◽  
Financial Health ◽  
Two Phase ◽  
North West ◽  
The North ◽  
Close Proximity ◽  
Before And After ◽  
Increase Productivity

Abstract This paper looks back on the designs and ambitions of ARA in resolving a long term acoustic noise problem which threatened ARA with closure. This paper today briefly looks back to the original issues but deals more fully with the later phases of a two phase project implementation and construction. ARA is now a truly ‘silent site’, where closure was once threatened, ARA has achieved the implementation of a bespoke noise reduction enclosure where 24-hour running has proved to be a reality. This paper looks at the design and construction phases, the ‘before and after’ noise footprints and at some of the financial benefits ARA has achieved. The ARA transonic wind tunnel is sited on an industrial estate on the north west perimeter of Bedford. When it was first built it was on an original farm site with no appreciable residential houses in close proximity. Since the early 1950s there has been considerable residential development around the ARA site resulting in the local householders complaining about the wind tunnel acoustic noise. In early 1999 ARA was obliged to consider several options for noise reduction measures to reduce the noise to within UK government statutory requirements. This paper deals briefly with the original noise nuisance characteristics and footprint, the noise reduction design and method that ARA selected and shows the construction phases, the further noise treatment ARA had to do on other major ancillary equipment to make ARA a truly quiet industrial site. The paper shows how ARA has utilised the resulting benefits of these investments to increase productivity and reduce costs, and the influence it has had on ARA’s financial health.

Wind-borne sand mass flux in vegetated surfaces – Wind tunnel experiments with live plants

CATENA ◽  
2019 ◽  
Vol 172 ◽  
pp. 421-434 ◽  
Author(s):  
Abbas Miri ◽  
Deirdre Dragovich ◽  
Zhibao Dong
Keyword(s):  
Wind Tunnel ◽  
Mass Flux ◽  
Wind Tunnel Experiments ◽  
Sand Mass Flux
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