A field-based parameterization of wind flow recovery in the lee of dryland plants
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- 作者：Jerome R. Mayaud ; Giles F.S. Wiggs and Richard M. Bailey
- 刊名：Earth Surface Processes and Landforms
- 出版年：2017
- 出版时间：February 2017
- 年：2017
- 卷：42
- 期：2
- 页码：378-386
- 全文大小：1170K
- ISSN：1096-9837
文摘
Wind erosion is a key component of land degradation in vulnerable dryland regions. Despite a wealth of studies investigating the impact of vegetation and windbreaks on windflow in controlled wind-tunnel and modelling environments, there is still a paucity of empirical field data for accurately parameterizing the effect of vegetation in wind and sediment transport models. The aim of this study is to present a general parameterization of wind flow recovery in the lee of typical dryland vegetation elements (grass clumps and shrubs), based on their height (m>h m>) and optical porosity (mathematics">m>θ m>). Spatial variations in mean wind velocity around eight isolated vegetation elements in Namibia (three grass clumps and five shrubs) were recorded at 0.30 m height, using a combination of sonic and cup anemometry sampled at a temporal frequency of 10 seconds. Wind flow recovery in the lee of the elements was parameterized in an exponential form, math-equation-construct">mage="true" class="math-equation-image">mathml="true" class="math-equation-mathml" style="display:none"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mfenced xmlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML" open="(" close=")" separators=","><mrow><msub><mi>umi><mi>refmi>msub><mo>−mo><msub><mi>umi><mn>0mn>msub>mrow>mfenced><mo xmlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">.mo><mfenced xmlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML" open="(" close=")" separators=","><mrow><mn>1mn><mo>−mo><msup><mi>emi><mrow><mo>−mo><mi>bmi><mfrac><mi>xmi><mi>hmi>mfrac>mrow>msup>mrow>mfenced><mo xmlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">+mo><msub xmlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML"><mi>umi><mn>0mn>msub>mml:math>. The best-fit parameters derived from the field data were mathematics">m>u m>0 = m>u m>ref(0.0146m>θ m> − 0.4076) and mathematics">m>b m> = 0.0105m>θ m> + 0.1627. By comparing this parameterization to existing models, it is shown that wind recovery curves derived from two-dimensional wind fence experiments may not be suitable analogues for describing airflow around more complex, three-dimensional forms. Field-derived parameterizations such as the one presented here are a crucial step for connecting plant-scale windflow behaviour to dryland bedform development at landscape scales.