Wind Erosion Terms

Definitions of common terms used to describe wind erosion processes

Aeolian – processes relating to or arising from the action of the wind.

Aerodynamic roughness length (z0) – a parameter describing the height (m) at which wind speed becomes zero above the land surface due to drag forces associated with surface roughness (e.g., vegetation, rocks, and soil clods).

Entrainment – to lift and transport (soil grains) by the flow of a fluid (the wind).

Dust emission – the entrainment of fine soil particles and aggregates (dust), typically regarded as being smaller than 62.5 μm in diameter (e.g., silt and clays).

Dust deposition – the settling of dust particles to the land surface under the force of gravity or in rainfall.

Particulate matter (PM) – solid and liquid particles in the air, comprising the particulate portion of aerosols. PM10 particles have an aerodynamic diameter <10 μm and may be inhalable.

Saltation – the movement of soil grains and aggregates along the soil surface in a leaping or hopping motion, typically larger than 62.5 μm and within ~1 m of the surface.

Sediment mass flux – the mass of soil grains in saltation and/or suspended in the air (dust) per unit length or area per unit time; often separated into saltation (g m-1 s-1) and dust  (g m-2 s-1) components.

Wind erosion – the net loss of soil from an area, considered the sum of all saltation and dust emission out of the area (loss) and deposition (gain) of sediment into the area from upwind sources (e.g., t ha-1).

Wind friction velocity (u*) – also called shear velocity, an expression of the wind shear stress (force per unit area) related to its momentum in the units of velocity (m s-1).

Threshold wind friction velocity (u*t) – the wind shear stress at which soil grains are mobilized and/or entrained from a soil surface, expressed in units of velocity (m s-1).

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