Measuring the erosivity of the wind

Measuring wind erosion is difficult as it requires the coincidence of a rare wind event with soil conditions that allow erosion. The measure must include a scale and an indication of the force of the wind on the ground, usually the dynamic roughness and the Rouse Number. There is not necessarily a distinct ‘threshold velocity’; the relative force of the wind and the ‘fluffiness’ of the soil determine whether erosion will occur. Grain sizes, density and shape should be characterised by mass-mean fall velocity. The relative importance of stable/unstable surface elements may be determined by analysing the wind profile. Lastly, a model of suspension with saltation has evolved; it suggests that saltation is not distinctly different from suspension and that there is no distinct ‘saltation layer’.