Aerodynamic roughness length related to non-aggregated tillage ridges

Kardous, M.; Bergametti, Gilles; Marticorena, Béatrice

doi:10.5194/angeo-23-3187-2005

Cited by 12 publications

(5 citation statements)

References 16 publications

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“…Thus an increase in non‐erodible elements decreases the emissions of dust [ Schlichting , 1936; Marshall , 1971; Marticorena and Bergametti , 1995]. Agriculture can change non‐erodible elements [e.g., Kardous et al , 2005].…”

Section: Controls On Distribution Of Atmospheric Mineral Aerosolsmentioning

confidence: 99%

Atmospheric global dust cycle and iron inputs to the ocean

Mahowald

Baker

Bergametti

et al. 2005

Global Biogeochemical Cycles

1,080

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[1] Since iron is an important micronutrient, deposition of iron in mineral aerosols can impact the carbon cycle and atmospheric CO 2 . This paper reviews our current understanding of the global dust cycle and identifies future research needs. The global distribution of desert dust is estimated from a combination of observations of dust from in situ concentration, optical depth, and deposition data; observations from satellite; and global atmospheric models. The anthropogenically influenced portion of atmospheric desert dust flux is thought to be smaller than the natural portion, but is difficult to quantify due to the poorly understood response of desert dust to changes in climate, land use, and water use. The iron content of aerosols is thought to vary by a factor of 2, while the uncertainty in dust deposition is at least a factor of 10 in some regions due to the high spatial and temporal variability and limited observations. Importantly, we have a limited understanding of the processes by which relatively insoluble soil iron (typically $0.5% is soluble) becomes more soluble (1-80%) during atmospheric transport, but these processes could be impacted by anthropogenic emissions of sulfur or organic acids. In order to understand how humans will impact future iron deposition to the oceans, we need to improve our understanding of: iron deposition to remote oceans, iron chemistry in aerosols, how desert dust sources will respond to climate change, and how humans will impact the transport of bioavailable fraction of iron to the oceans.

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Section: Controls On Distribution Of Atmospheric Mineral Aerosolsmentioning

confidence: 99%

Atmospheric global dust cycle and iron inputs to the ocean

Mahowald

Baker

Bergametti

et al. 2005

Global Biogeochemical Cycles

1,080

1,000

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“…Using the mean calculated particle diameter of 33 mm as a representative size for all the particles and assuming aerodynamic roughness of 5 mm (Kardous et al, 2005), the value of 0.36 and 0.386 m s À1 were calculated for the dimensionless parameter A and the threshold friction velocity, respectively. Bagnold had obtained the A factor in above equation equal to 0.4 for the wind speed having Reynolds number less than 3.5 (Alfaro et al, 2004) when the mean size of surface roughness is used for Reynolds number calculation as the characterization length and u* as the pertinent value for the velocity.…”

Section: Friction Velocitymentioning

confidence: 99%

Diffuse Emissions of Particles from Iron Ore Piles by Wind Erosion

Afshar-Mohajer¹,

Torkian²

2011

Environmental Engineering Science

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Industrial air pollution from point and nonpoint sources of steel complexes has drawn increasingly more public attention in the past decades. Previous research efforts have been more concentrated on point sources of particulate emissions from these complexes. However, wind-induced particulate emissions from iron ore storage piles not only result in ambient air pollution but also increase economic adverse effects to the industry by loss of process raw materials. Experiments were conducted to assess the impact of wind speed and humidity on particulate emission rates from iron ore storage piles. A wind-generating system and specific iron ore, experimental piles (L:W:H of 30:11.5:5 cm) were constructed to evaluate emission rates at four different wind velocities (4.3, 5, 7, and 11 m s À1 ). Optical and electron microscopes were used for determining size distribution of particles at various distances from emission source. Moreover, the decrease in emission rate was evaluated by changing the percentage of pile surface water content at the maximum speed. Finally, experimental results were compared with classic erosion equations and common parameters such as shearing velocity. Results indicated emission factors of 478, 1,527, 2,315, and 4,409 g m À2 for 4.3, 5, 7, and 11 m s À1 wind speeds, respectively. Pile surface moisture content variations indicated a decrease of 47%-77% in wind-induced particulate emissions for pile surface water content of 2% and 10%, respectively. However, inherent differences between natural winds with continued exerted force and experimental conditions of produced wind were attributed to relatively shorter distance transport of particulates in this study.

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“…In a previous work (Kardous et al, 2005, this issue), wind tunnel experiments involving 11 sets of simulated ridges were carried out to determine the relationships between z 0 and the geometric characteristics of tilled ridges. Depending on the tested ridge configurations, 6 to 12 wind velocity measurements, located in the log-law region, were used to fit wind profiles, in order to determine, aerodynamic roughness lengths (z 0 and D) and wind friction velocity.…”

Section: Wind Friction Velocity (U * )mentioning

confidence: 99%

Wind tunnel experiments on the effects of tillage ridge features on wind erosion horizontal fluxes

2005

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Abstract. In addition to the well-known soil factors which control wind erosion on flat, unridged surfaces, two specific processes affect the susceptibility of tillage ridged surfaces to wind erosion: ridge-induced roughness and ridge-trapping efficiency.In order to parameterize horizontal soil fluxes produced by wind over tillage ridges, eight-ridge configurations composed of sandy soil and exhibiting ridge heights to ridge spacing (RH/RS) ratios ranging from 0.18 to 0.38 were experimented in a wind tunnel. These experiments are used to develop a parameterization of the horizontal fluxes over tillage ridged surfaces based only on the geometric characteristics of the ridges. Indeed, the key parameters controlling the horizontal flux, namely the friction velocity, threshold friction velocity and the adjustment coefficient, are derived through specific expressions, from ridge heights (RH) and ridge spacing (RS). This parameterization was evaluated by comparing the results of the simulations to an additional experimental data set and to the data set obtained by Hagen and Armbrust (1992). In both cases, predicted and measured values are found to be in a satisfying agreement.This parameterization was used to evaluate the efficiency of ridges in reducing wind erosion. The results show that ridged surfaces, when compared to a loose, unridged soil surface, lead to an important reduction in the horizontal fluxes (exceeding 60%). Moreover, the effect of ridges in trapping particles contributes for more than 90% in the flux reduction while the ridge roughness effect is weak and decreases when the wind velocity increases.

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Aerodynamic roughness length related to non-aggregated tillage ridges

Cited by 12 publications

References 16 publications

Atmospheric global dust cycle and iron inputs to the ocean

Atmospheric global dust cycle and iron inputs to the ocean

Diffuse Emissions of Particles from Iron Ore Piles by Wind Erosion

Wind tunnel experiments on the effects of tillage ridge features on wind erosion horizontal fluxes

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