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Soil erosion by wind, including saltation and dust suspension, has many environmental and climatic implications. At global scale, mineral dust represents 32% of annual natural emission of aerosols in the atmosphere, impacting the Earth radiative budget and biogeochemical cycles. At local scale, wind-blown sand damages agricultural areas through abrasion, burial/uprooting, and wind-blown dust impoverishes soil in organic matters and nutrients. In semi-arid regions, fertility loss of soil due to wind erosion should be modified in the future by the combined effect of climate change and increasing human activities.

Dust emission schemes present in climate models to predict dust cycle and their local to global impacts, give different predictions from one to the other due to their poor representation of near-surface winds and vegetation, and none of them accounts for the chemical/mineralogical fractionation of erosion fluxes. To overcome these limitations, WIND-O-V attempts to develop a new generation of wind erosion models predicting the amount and composition of emitted dust from bare and sparse vegetated surfaces, typical of semiarid regions. To that purpose, WIND-O-V relies on an original modeling approach of wind erosion over vegetated surfaces, from local to regional scales, using the state of the art of high resolution turbulent airflow models. This will enable (1) to quantify soil erosion and soil fertility loss following vegetation characteristics and wind conditions, (2) to deduce optimal crop organizations for sustainable soil management, and (3) to improve emission schemes in regional dust-dispersal models. WIND-O-V responds to 4 objectives.

The 1^st objective is to develop the first wind soil erosion model at landscape scale. Saltation-suspension processes will be simulated at fine resolution from an Lagrangian-Eulerian approach, accounting for the presence of natural or cultivated vegetation, and coupled with a LES (Large-Eddy Simulation) airflow model, that explicitly simulates wind gusts. This model will be tested against dedicated experiments performed in Tunisia with and without vegetation, where wind dynamics, saltation and dust fluxes and their chemical/mineralogical composition will be measured simultaneously.

The 2^nd objective is to improve the flow modelling in the saltation layer over a bare soil by performing DNS (Direct Numerical Simulation) and wind-tunnel measurements to better characterize wind-saltation interaction and to improve the near-surface resolution of the LES model.

The 3^rd objective is to quantify the chemical fractionation of particles along the soil-saltation-suspension continuum from field measurements to deduce a simple parameterization. Knowledge of the composition of erosion fluxes is necessary to evaluate precisely soil nutriment losses and dust impact on the radiative budget.

The 4^th objective is to develop a dust emission scheme for regional models, accounting for vegetation, by applying the erosion model developed at landscape scale on different arrangements of vegetation. This scheme will be implemented in the regional model Chimere-Dust and validated in southern Tunisia.

WIND-O-V is an innovative and interdisciplinary project that (1) takes advantage of recent advances in modelling turbulent flows with particles, in presence of vegetation, to overcome difficulties in predicting wind erosion fluxes over vegetated surfaces, and that (2) brings together well-recognized partners, with a unique expertise on geophysics, sedimentology, and theoretical and environmental fluid mechanics, and covering all spatial scales between local and regional scales.

WIND-O-V is supported by the AGRI SUD-OUEST competitiveness cluster.