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Sand Dune Albedo Feedback

机译：沙丘反照率反馈

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Sand dunes cover substantial parts of desert areas. Fully active dunes are bare, while fixed dunes are stabilized by vegetation and biogenic crust, and the dune activity is affected by the wind. Here we suggest the following atmosphere-sand dune feedback: spatial differences in the dunes’ vegetation and biogenic crust cover lead to differences in albedo as the albedo of bare sand is larger than that of vegetation and biogenic crust. This leads to a higher temperature over the vegetated area, resulting in air flow from the bare dune area to the vegetated dune area, thus increasing the wind activity over the vegetated dune area. In turn, this leads to enhanced stress on the vegetation and enhanced dune activity and thus to a decrease in vegetation. These changes in vegetation cover affect the surface albedo, leading to a change in wind activity. We examined this feedback using an atmospheric general circulation model, Weather Research and Forecasting (WRF), in selected regions of the northwestern Negev Desert and the Sahara/Sahel region, and we show that changes in surface albedo do indeed lead to significantly enhanced wind activity over the lower albedo region. We then incorporated this feedback into a simple vegetated dune model, showing that the multiple states associated with active and fixed dunes can be obtained for a larger range of parameters and that the stables states become more extreme (i.e., the fixed dune state becomes more vegetated and the active dune state becomes less vegetated).
机译：沙丘覆盖了沙漠地区的大部分地区。完全活跃的沙丘是裸露的，而固定的沙丘则由植被和生物成因的外壳稳定，沙丘的活动受风的影响。在这里，我们提出以下大气沙丘反馈：沙丘植被和生物成因地壳的空间差异会导致反照率的差异，因为裸砂的反照率大于植被和生物成因地壳的反照率。这导致植被区温度升高，导致空气从裸露的沙丘区流向植被沙丘区，从而增加了植被沙丘区的风活动。反过来，这导致对植被的压力增加和沙丘活动增强，从而导致植被减少。植被覆盖的这些变化影响了地表反照率，导致风活动发生变化。我们在西北内盖夫沙漠和撒哈拉/萨赫勒地区的选定区域中使用大气总循环模型“天气研究与预报（WRF）”检查了此反馈，并表明表面反照率的确确实导致风活动显着增强在较低的反照率地区。然后，我们将此反馈合并到一个简单的植被沙丘模型中，表明对于较大范围的参数，可以获得与活动和固定沙丘关联的多个状态，并且稳定状态变得更加极端（即，固定沙丘状态变得更加植被化）并且活跃的沙丘状态变得植被减少）。

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