Effect of averaging time on the apparent threshold for aeolian transport

Stout, John E.

doi:10.1006/jare.1997.0370

Cited by 60 publications

(54 citation statements)

References 10 publications

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“…In addition to the difference of mean particle size and slope angle, the state of the airflow in the field is one of the main factors affecting the threshold velocity. Under the different states of the airflow, the threshold velocity fluctuated significantly (Stout and Zobeck, 1997;Stout, 1998;McKenna Neuman et al, 2000). Because we use the 1-min mean wind velocity, it is difficult to assess the fluctuation of the airflow.…”

Section: Resultsmentioning

confidence: 96%

Relations between morphology, air flow, sand flux and particle size on transverse dunes, Taklimakan Sand Sea, China

Wang

Dong

Zhang

et al. 2002

Earth Surf Processes Landf

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Field experiments on two isolated transverse dunes with different scales in the Taklimakan Sand Sea show that particle size and slope control the threshold shear velocity and sand flows on the stoss of the dunes. The decreased threshold shear velocity and the unsaturated sand flows are the main reasons why sands are not deposited at the toe of the dunes. The particle size controls sand flux through its influence on the aerodynamic roughness elements and threshold shear velocities. The sand flux is different for dune surfaces with different particle size distributions. Under the control of the medium to low stress of the drifting-sand winds, the results of the field experiments and particle size analysis showed that sand transport had little influence on the particle size distributions. The mean particle size being transported on the stoss is lower than that on the dune surface. It is difficult to determine whether or not the wind is fully saturated with sands when sand flux calculation is mainly dependent on the shear velocity and the mean particle size. The sands within some range of the particle size are transported and developed into simple transverse dunes, and then the interdune surface is coarsened and alternated with the draas in the Taklimakan Sand Sea.

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Section: Resultsmentioning

confidence: 96%

Relations between morphology, air flow, sand flux and particle size on transverse dunes, Taklimakan Sand Sea, China

Wang

Dong

Zhang

et al. 2002

Earth Surf Processes Landf

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“…Even shorter sampling intervals are necessary to arrive at the true value of erosion threshold wind speed. Calculated threshold values decrease as wind speed averaging time increases (Stout, 1998). Stout (1998) found that threshold estimates based on a 10 s averaging time were about 18 per cent less than estimates based on a 1 s averaging time.…”

Section: Sampling Intervalmentioning

confidence: 92%

“…Calculated threshold values decrease as wind speed averaging time increases (Stout, 1998). Stout (1998) found that threshold estimates based on a 10 s averaging time were about 18 per cent less than estimates based on a 1 s averaging time. The recommended sampling interval to estimate erosion threshold wind speed is 1 s.…”

Section: Sampling Intervalmentioning

confidence: 92%

Measurement and data analysis methods for field‐scale wind erosion studies and model validation

Zobeck

Sterk

Funk

et al. 2003

Earth Surf Processes Landf

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178

107

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Accurate and reliable methods of measuring windblown sediment are needed to confirm, validate, and improve erosion models, assess the intensity of aeolian processes and related damage, determine the source of pollutants, and for other applications. This paper outlines important principles to consider in conducting field-scale wind erosion studies and proposes strategies of field data collection for use in model validation and development. Detailed discussions include consideration of field characteristics, sediment sampling, and meteorological stations. The field shape used in field-scale wind erosion research is generally a matter of preference and in many studies may not have practical significance. Maintaining a clear nonerodible boundary is necessary to accurately determine erosion fetch distance. A field length of about 300 m may be needed in many situations to approach transport capacity for saltation flux in bare agricultural fields. Field surface conditions affect the wind profile and other processes such as sediment emission, transport, and deposition and soil erodibility. Knowledge of the temporal variation in surface conditions is necessary to understand aeolian processes. Temporal soil properties that impact aeolian processes include surface roughness, dry aggregate size distribution, dry aggregate stability, and crust characteristics. Use of a portable 2 tall anemometer tower should be considered to quantify variability of friction velocity and aerodynamic roughness caused by surface conditions in field-scale studies. The types of samplers used for sampling aeolian sediment will vary depending upon the type of sediment to be measured. The Big Spring Number Eight (BSNE) and Modified Wilson and Cooke (MWAC) samplers appear to be the most popular for field studies of saltation. Suspension flux may be measured with commercially available instruments after modifications are made to ensure isokinetic conditions at high wind speeds. Meteorological measurements should include wind speed and direction, air temperature, solar radiation, relative humidity, rain amount, soil temperature and moisture. Careful consideration of the climatic, sediment, and soil surface characteristics observed in future field-scale wind erosion studies will ensure maximum use of the data collected.

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“…The lower concentration of soluble solids at S6 was most probably a result of the low ground turbulence of wind speed which deposited a small volume of soluble solid into the dust fall collectors. Strong ground turbulence of wind speed can also contribute to the source of dust and fine particulates originating from exposed ground surface (Stout, 1998;Sami et al, 2006;Pandey et al, 2008). A study by Latif and Rozali (1999) in Teluk Kalung, Norela et al (2004) and Norela et al (2009) in Nilai and Serdang respectively recorded a higher concentration of soluble solids, while a study by Latif and Rozali (1999) in another sub-location in the Air Keroh industrial area and Latif and Rozali (2000) detected a lower concentration of soluble solids.…”

Section: Deposited Particulatesmentioning

confidence: 99%

Compositions of Dust Fall around Semi-Urban Areas in Malaysia

Alahmr

Othman

Wahid

et al. 2012

Aerosol Air Qual. Res.

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This study aimed to determine the amount and composition of dust fall in semi-urban areas in Selangor, Malaysia from mid-July to mid-October 2010. The dust fall samples (a combination of dry and wet deposition) through rainwater were collected using polyethylene bottles on a monthly basis so as to determine the concentration of total solids, soluble and insoluble solids from eight monitoring stations. Zn was recorded as the dominant heavy metal in rainwater followed by Fe, Al, Pb, Cd and Cr. This study suggests that sea salts, earth crust and anthropogenic activities such as motor vehicles were the main sources of dust fall in the study areas.

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Effect of averaging time on the apparent threshold for aeolian transport

Cited by 60 publications

References 10 publications

Relations between morphology, air flow, sand flux and particle size on transverse dunes, Taklimakan Sand Sea, China

Relations between morphology, air flow, sand flux and particle size on transverse dunes, Taklimakan Sand Sea, China

Measurement and data analysis methods for field‐scale wind erosion studies and model validation

Compositions of Dust Fall around Semi-Urban Areas in Malaysia

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