Scale Invariance of Albedo‐Based Wind Friction Velocity
Autor: | Adrian Chappell, Nancy P. Ziegler, Nicholas P. Webb, Sandra L. LeGrand |
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Rok vydání: | 2020 |
Předmět: |
Atmospheric Science
010504 meteorology & atmospheric sciences Fetch Wind direction Albedo Atmospheric sciences 01 natural sciences Wind speed Physics::Geophysics Geophysics Space and Planetary Science Earth and Planetary Sciences (miscellaneous) Surface roughness Environmental science Aeolian processes Astrophysics::Earth and Planetary Astrophysics Shear velocity Physics::Atmospheric and Oceanic Physics 0105 earth and related environmental sciences Wind tunnel |
Zdroj: | Journal of Geophysical Research: Atmospheres. 125 |
ISSN: | 2169-8996 2169-897X |
Popis: | Obtaining reliable estimates of aerodynamic roughness is necessary to interpret and accurately predict aeolian sediment transport dynamics. However, inherent uncertainties in field measurements and models of surface aerodynamic properties continue to undermine aeolian research, monitoring, and dust modeling. A new relation between aerodynamic shelter and land surface shadow has been established at the wind tunnel scale, enabling the potential for estimates of wind erosion and dust emission to be obtained across scales from albedo data. Here, we compare estimates of wind friction velocity (u * ) derived from traditional methods (wind speed profiles) with those derived from the albedo model at two separate scales using bare soil patch (via net radiometers) and landscape (via MODIS 500 m) datasets. Results show that profile‐derived estimates of u * are highly variable in anisotropic surface roughness due to changes in wind direction and fetch. Wind speed profiles poorly estimate soil surface (bed) wind friction velocities necessary for aeolian sediment transport research and modeling. Albedo‐based estimates of u * at both scales have small variability because the estimate is integrated over a defined, fixed area and resolves the partition of wind momentum between roughness elements and the soil surface. We demonstrate that the wind tunnel‐based calibration of albedo for predicting wind friction velocities at the soil surface (u s* ) is applicable across scales. The albedo‐based approach enables consistent and reliable drag partition correction across scales for model and field estimates of u s* necessary for wind erosion and dust emission modeling. |
Databáze: | OpenAIRE |
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