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Geosciences 2018, 8(3), 82; https://doi.org/10.3390/geosciences8030082

Sand Dune Albedo Feedback

Department of Solar Energy and Environmental Physics, Blaustein Institutes for Desert Research, Sede Boqer Campus, Ben-Gurion University of the Negev, Be’er Sheva 84990, Israel
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Received: 11 December 2017 / Revised: 22 January 2018 / Accepted: 13 February 2018 / Published: 27 February 2018
(This article belongs to the Special Issue Aeolian Processes and Geomorphology)
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Abstract

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). View Full-Text
Keywords: sand dunes; albedo; atmospheric dynamics; feedback; WRF sand dunes; albedo; atmospheric dynamics; feedback; WRF
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Ashkenazy, Y.; Shilo, E. Sand Dune Albedo Feedback. Geosciences 2018, 8, 82.

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