Wind erosion flux, meteorology, soil roughness, and crop characteristics collected on a barley field in Dar Dhaoui (Tunisia) during 2015-2016

After accounting for the collection efficiency of the sand traps (assumed to be 100% as suggested by Goossens et al. (2000)), the saltation flux was computed by vertical integration of the cumulative masses collected at the 4 heights using the exponential formula proposed by Williams (1964). (2) meteorological parameters: wind speed and direction were measured at 2 m agl using a 2 dimensional (2D) sonic anemometer (WindSonicTM Gill Instruments Ltd), and rainfall using an ARG100 Tipping Bucket rain gauge (Campbell® Scientific company).

Data were acquired using a CR200X data logger (Campbell® Scientific company), with a nominal data acquisition time of 5-min for all parameters measured with a frequency of 0.1 Hz. Given the high variability of both wind speed and direction on a 5-min time step, the maximum and mean values of wind speed, and the mean and standard deviation of wind direction measured over this interval were recorded. 5-min rainfall corresponds to the accumulated bucket tippings over this interval with one tipping corresponding to 0.2 mm of rainfall.

(3) aerodynamic roughness length (15-min. averages): aerodynamic roughness length, z0, was estimated by fitting the logarithmic law of the wind speed vertical profile. This profile was determined using 7 cup anemometers (A100R Vector Instrument®) positioned at 0.285 m, 0.825 m, 1.395 m, 1.920 m, 2.965 m, 4.060 m, and 5.005 m (agl). The mast was located at the eastern edge of the plot.

Data were acquired using a CR1000 data logger (Campbell® Scientific company), with a nominal data acquisition time of 1-min. (4) barley features: five plots of 2 m x 1.5 m were delimited in the field to weekly follow the barley height and cover rate using photographs and eye estimate. Barley height was measured by using a meter tape.

The mean maximum height of the barley tufts was measured for each plot. Barley cover rate was always estimated by the same observer on site. When barley was green, its cover rate was also estimated following Mougin et al. (2014) by a numerical treatment (CAN-EYE© software) to corroborate eye estimates.

Vertical and horizontal photographs were used to check the estimates.