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Dernière mise à jour : Mai 2018

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WIND-O-V

WIND-O-V's 2017 field experiment

The WIND-O-V's 2017 experiment took place from March 1st to May 15th 2017 in South Tunisia, in the experimental range (Dar Dhaoui) of the Institut des Régions Arides (IRA) of Médenine close to Médenine/Zarzis (Tunisia). The site approximates a flat half-circle plot of 150 m radius where measurements were performed at the centre of the circle in order to ensure a fetch of at least 150 m for westerly, northerly to easterly winds (see Figure). Before the experiment, the surface had been tilled with a disc plough and levelled with a wood board in order to meet the conditions of an ideal flat bare soil without soil crust or ridges.

Three types of measures were carried out.

Meteorology: on a 9 m high mast erected at the center of the plot, turbulent velocity components and air temperature fluctuations were measured simultaneously at 1.0, 1.9, 3.0, and 4.1 m height using four 3D sonic anemometers sampling at 60, 50, 50, and 20 Hz, respectively. On the same mast, 7 cup anemometers (0.2, 0.6, 1.3, 1.8, 3.0, 4.0, 5.2 m) and 4 thermocouples (0.4, 1.6, 3.7, 5.0 m) were also installed to measure simultaneously at 0.1 Hz the mean horizontal wind velocity and temperature profiles, respectively.

Saltation flux: one vertical array of 5 sediment traps like Big Spring Number Eight (BSNE) was deployed to quantify the saltation flux and its size distribution. The modified BSNE had a 5 times wider opening area to collect larger sediment quantities, allowing sequential (in time) sampling of individual erosive events and guarantying the possibility of applying size resolved analyses. Saltation flux measurements with a better temporal resolution were thus associated with more stable friction velocity conditions. A Saltiphone and a camera gave information on the beginning, end, and duration of erosive events.

Dust flux: for the first time size-resolved dust fluxes were estimated from both the traditional flux-gradient approach and the eddy covariance approach. For the first approach, mass and size resolved number concentrations were measured at two levels (2 and 4 m). To that purpose, two TEOM microbalances and two optical particle counters (WELAS Promo 2300) were used. Both sensor-types were connected to omnidirectional air sampling inlets. The WELAS monitored at 1 Hz the dust concentrations per size class (32 classes between 0.3 and 17 μm). For the second approach, a third WELAS was coupled to the 3 m high sonic anemometer in order to correlate the size-resolved dust concentration and the vertical wind velocity fluctuations. Finally, the chemical composition of dust fluxes was estimated from the sequential sampling of dust particles at two levels (2 and 4 m) with online filters equipped with inlets of different size cut-offs (20, 10, 2.5 and 1 μm).

(1) In the below attached file, the 15-min average wind statistics obtained during 3 main erosion events (7-9 March, 14-15 March, and 20 April) are available. Roughness lengths of the surface and friction velocities deduced from both the Law-of-the-wall and Eddy-Covariance methods, are also available.

Excel DATA FILE
(Thanks for informing us if you plan to use these data: sylvain.dupont @ inra.fr)

(2) In the below attached file, the time series of the friction velocity and size-resolved dust fluxes as estimated from the Eddy Covariance and Wavelet Transform approches at 15 min, 1 min and 10 s time resolution, are available for the 8 March, 9 March, and 20 April 2017 events.

Excel DATA FILE
(Thanks for informing us if you plan to use these data: sylvain.dupont @ inra.fr)

For more information on these data see the papers:

Dupont, S., J.-L. Rajot, M. Labiadh, G. Bergametti, S. Alfaro, C. Bouet, R. Fernandes, B. Khalfallah, E. Lamaud,B. Marticorena, J.-M. Bonnefond, S. Chevaillier, D. Garrigou, T. Henry-des-Tureaux, S. Sekrafi, and P. Zapf (2018). Aerodynamic parameters over an eroding bare surface: reconciliation of the Law-of-the-wall and Eddy-Covariance determinations, Journal of Geophysical Research - Atmospheres, 123 (9), 4490-4508.

Dupont, S., Rajot, J.-L., Labiadh, M., Bergametti, G., Alfaro, S. C., Bouet, C., Fernandes, R., Khalfallah, Lamaud, E., Marticorena, Bonnefond, J.-M., Chevaillier, Garrigou, D., Henry-des-Tureaux, T., Sekrafi, S., Zapf (2019). Dissimilarity between dust, heat, and momentum turbulent transports during aeolian soil erosion. Journal of Geophysical Research: Atmospheres, 124. https://doi.org/10.1029/2018JD029048.

Dupont, S. (2019). Scaling of dust flux with friction velocity: time resolution effects. Journal of Geophysical Research: Atmospheres, submitted.