Laser particle counter validation for aeolian sand transport measurements using a highspeed camera

Duarte-Campos, Leonardo; Wijnberg, Kathelijne Mariken; Gálvez, Loreto Oyarte; Hulscher, Suzanne J.M.H.

doi:10.1016/j.aeolia.2017.02.002

Cited by 19 publications

(20 citation statements)

References 15 publications

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“…In this regard, examining images for streamers which can be reconciled with increases in measured particle counts is preferable. The increases in particle counts associated with images containing streamers are likely to be underestimated as a consequence of saturation of the Wenglor sensors (Hugenholtz and Barchyn, 2011;Sherman et al, 2011;Duarte-Campos et al, 2017). Given the unanimity in the user results, streamers offer a readily identifiable visual signal of transport.…”

Section: Discussionmentioning

confidence: 99%

Detection of aeolian transport in coastal images

2018

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A B S T R A C TOptical remote sensing provides a low cost method of documenting surface conditions over extended periods of time. Its utility in resolving large scale aeolian transport events is examined in this paper. To this end, over 1800 images taken over a three month period by a stationary camera in a coastal setting are classified as containing/ not containing aeolian transport using both a manual and automated approach. In both cases transport is inferred by the identification of aeolian streamers within a given image. With regards to the manual approach, images were visually examined by three users. There was good agreement between the different users with 77.8% of transport identifications being unanimous. Comparison of the user results with measured transport highlights that observations of transport in images coincide with increased particle counts. The particle counts indicate that transport is dominated by a series of discernible transport events. Transport is observed in images throughout the duration of these events. Manually processing the images is a laborious process. A method is presented which allows for the automated detection of images containing transport. The method utilises 2D-DFTs to exploit the linear appearance of streamers in images. Relative to the manual classifications which serve as ground truth, the method performs well in identifying images containing transport with values of precision, recall and F1 score ⩾ 0.85. address: i.a.williams@utwente.nl (I.A. Williams). Aeolian Research 35 (2018) 47-57 1875-9637/

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Section: Discussionmentioning

confidence: 99%

Detection of aeolian transport in coastal images

2018

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“…Optical sensors appear to provide intermediate sensitivity Leonard et al, 2011), though Wenglor sensors appear unable to detect small particles of <200 µm diameter (Duarte-Campos et al, 2017;Leonard et al, 2011). To overcome these issues of grain-size sensitivity bias, HF sensors should be developed in the future to directly detect airborne particle size distributions, such as through application of optical disdrometer techniques typically used for characterizing the size of rain droplets (e.g., Löffler-Mang and Joss, 2000).…”

Section: High-frequency Instrument Selectionmentioning

confidence: 99%

High-frequency measurements of aeolian saltation flux: Field-based methodology and applications

et al. 2018

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Aeolian transport of sand and dust is driven by turbulent winds that fluctuate over a broad range of temporal and spatial scales. However, commonly used aeolian transport models do not explicitly account for such fluctuations, likely contributing to substantial discrepancies between models and measurements. Underlying this problem is the absence of accurate sand flux measurements at the short time scales at which wind speed fluctuates. Here, we draw on extensive field measurements of aeolian saltation to develop a methodology for generating highfrequency (25 Hz) time series of total (vertically-integrated) saltation flux, namely by calibrating high-frequency (HF) particle counts to low-frequency (LF) flux measurements. The methodology follows four steps: (1) fit exponential curves to vertical profiles of saltation flux from LF saltation traps, (2) determine empirical calibration factors through comparison of LF exponential fits to HF number counts over concurrent time intervals, (3) apply these calibration factors to subsamples of the saltation count time series to obtain HF height-specific saltation fluxes, and (4) aggregate the calibrated HF height-specific saltation fluxes into estimates of total saltation fluxes. When coupled to high-frequency measurements of wind velocity, this methodology offers new opportunities for understanding how aeolian saltation dynamics respond to variability in driving winds over time scales from tens of milliseconds to days.

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“…The traps were housed inside a 0.4‐m cylindrical tube that was buried coplanar to the sediment surface. The funnel diameter of a trap is 0.25 m, and weight resolution is 0.003 g. Wenglor (model YH08PCT8) LPC sensors are 80‐mm fork‐like sensors that can be easily deployed on slopes and that measure sand transport intensity as saltating grains cross the 0.6‐mm laser beam between the LPC legs (Davidson‐Arnott et al, ; Duarte‐Campos et al, ; Hugenholtz & Barchyn, ). These were oriented into the incoming wind direction at each location and positioned at 0.02 m above the surface.…”

Section: Methodsmentioning

confidence: 99%

Event‐Scale Dynamics of a Parabolic Dune and Its Relevance for Mesoscale Evolution

et al. 2018

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Parabolic dunes are widespread aeolian landforms found in a variety of environments. Despite modeling advances and good understanding of how they evolve, there is limited empirical data on their dynamics at short time scales of hours and on how these dynamics relate to their medium‐term evolution. This study presents the most comprehensive data set to date on aeolian processes (airflow and sediment transport) inside a parabolic dune at an event scale. This is coupled with information on elevation changes inside the landform to understand its morphological response to a single wind event. Results are contextualized against the medium‐term (years) allowing us to investigate one of the most persistent conundrums in geomorphology, that of the significance of short‐term findings for landform evolution. Our field data suggested three key findings: (1) sediment transport rates inside parabolic dunes correlate well with wind speeds rather than turbulence; (2) up to several tonnes of sand can move through these landforms in a few hours; and (3) short‐term elevation changes inside parabolic dunes can be complex and different from long‐term net spatial patterns, including simultaneous erosion and accumulation along the same wall. Modeled airflow patterns along the basin were similar to those measured in situ for a range of common wind directions, demonstrating the potential for strong transport during multiple events. Mesoscale analyses suggested that the measured event was representative of the type of events potentially driving significant geomorphic changes over years, with supply‐limiting conditions playing an important role in resultant flux amounts.

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Laser particle counter validation for aeolian sand transport measurements using a highspeed camera

Cited by 19 publications

References 15 publications

Detection of aeolian transport in coastal images

Detection of aeolian transport in coastal images

High-frequency measurements of aeolian saltation flux: Field-based methodology and applications

Event‐Scale Dynamics of a Parabolic Dune and Its Relevance for Mesoscale Evolution

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