Parabolic dunes are ‘U’ or ‘V’-shaped aeolian landforms that form on pre-existing sand deposits. Their morphology consists of an upwind deflation basin, bordered by often vegetated trailing arms and a downwind depositional lobe. The orientation of parabolic dunes is commonly attributed to the prevailing or resultant wind direction. Consequently, the orientation of parabolic dunes stabilised by vegetation growth has been used as a proxy for wind direction during past climates in several studies. However, the ability or extent of parabolic dune morphology to steer incident wind flow parallel to the orientation of the landform, and thus migrate in the direction of the current landform orientation rather than prevailing wind direction, is unknown. By numerically modelling wind flow within the deflation basin of eight parabolic dunes, we demonstrate for the first time that wind flow direction within the deflation basin of a parabolic dune is highly controlled by the depth and width of the deflation basin. The greater the depth–width ratio of the landform (i.e. the deeper and narrower the deflation basin), the greater the degree of flow steering relative to the axis orientation of the landform. These results demonstrate that future studies must exercise caution when using parabolic dune orientation as a direct proxy for prevailing wind direction, especially where parabolic dunes have a relatively high deflation basin depth–width ratio, as the deflation basin of these landforms may continue to migrate in an antecedent wind direction.

中文翻译：

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贪婪抛物线：抛物线沙丘的紧缩盆地内的风流方向受紧缩盆地的宽度和深度控制

抛物线沙丘是“U”形或“V”形风成地貌，形成于预先存在的沙丘上。它们的形态包括一个逆风的紧缩盆地，周围是经常有植被的拖臂和一个顺风的沉积瓣。抛物线沙丘的方向通常归因于盛行风向或合成风向。因此，在几项研究中，由植被生长稳定的抛物线沙丘的方向已被用作过去气候中风向的代理。然而，抛物线沙丘形态引导入射风流平行于地形方向的能力或范围，从而沿当前地形方向而不是盛行风向迁移，这是未知的。通过对八个抛物线沙丘的紧缩盆地内的风流进行数值模拟，我们首次证明抛物线沙丘的泄流盆内的风流方向受泄压盆的深度和宽度高度控制。地貌的深宽比越大（即紧缩盆地越深越窄），相对于地貌轴线方向的水流转向程度就越大。这些结果表明，未来的研究在使用抛物线沙丘方向作为盛行风向的直接代表时必须谨慎行事，尤其是在抛物线沙丘具有相对较高的紧缩盆地深宽比的情况下，因为这些地貌的紧缩盆地可能会继续在一个先前的风向。