Sediment transport equations used in wind erosion and dust emission models generally incorporate a threshold for particle motion (u_*t) with a correction function to account for roughness-induced momentum reduction and aerodynamic sheltering. The prevailing approach is to adjust u_*t by the drag partition R, estimated as the ratio of the bare soil threshold (u_*ts) to that of the surface in the presence of roughness elements (u_*tr). Here, we show that application of R to adjust only the entrainment threshold (u_*t = u_*ts/R) is physically inconsistent with the effect of roughness on the momentum partition as represented in models and produces overestimates of the sediment flux density (Q). Equations for Q typically include a friction velocity scaling term (u_*ⁿ). As Q scales with friction velocity at the soil surface (u_s*), rather than total friction velocity (u_*) acting over the roughness layer, u_*ⁿ must be also adjusted for roughness effects. Modelling aeolian transport as a function of u_s* represents a different way of thinking about the application of some drag partition schemes but is consistent with understanding of aeolian transport physics. We further note that the practice of reducing Q by the vegetation cover fraction to account for the physically-protected surface area constitutes double accounting of the surface protection when R is represented through the basal-to-frontal area ratio of roughness elements (σ) and roughness density (λ). If the drag partition is implemented fully, additional adjustment for surface protection is unnecessary to produce more accurate aeolian transport estimates. These findings apply equally to models of the vertical dust flux.

在风蚀和尘埃排放模型中使用的泥沙输送方程式通常包含一个粒子运动阈值（u _{* t}），该阈值具有校正功能，以说明粗糙度引起的动量减少和空气动力学遮挡。流行的方法是通过阻力分区R来调整u _{* t}，估计为裸土阈值（u _{* ts}）与存在粗糙度元素（u _{* tr}）的表面的比率。在这里，我们表明应用R来仅调整夹带阈值（u _{* t}  =  u _{* ts} / R）在物理上与模型中表示的粗糙度对动量分配的影响不一致，并且会高估沉积物通量密度（Q）。Q的方程式通常包括摩擦速度缩放项（u _* ⁿ）。由于Q与土壤表面的摩擦速度（u _{s *}）成比例，而不是作用在粗糙层上的总摩擦速度（u _*）缩放，因此还必须针对粗糙度影响对u _* ⁿ进行调整。风沙建模作为交通工具的功能ü_小号*代表了对某些阻力分配方案的应用的另一种思考方式，但与对风沙运输物理学的理解是一致的。我们进一步注意到，当R表示为粗糙度元素的底面积与前额面积之比（σ）和R时，通过植被覆盖率降低Q来解决物理保护表面积的做法构成了对表面保护的双重考虑。粗糙度密度（λ）。如果阻力分区得到充分实施，则无需进行其他表面保护调整就可以得出更准确的风沙运输估算。这些发现同样适用于垂直尘埃通量模型。