Computer Science – Performance
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufm.p31b0990k&link_type=abstract
American Geophysical Union, Fall Meeting 2004, abstract #P31B-0990
Computer Science
Performance
5415 Erosion And Weathering, 5445 Meteorology (3346), 3307 Boundary Layer Processes, 1625 Geomorphology And Weathering (1824, 1886), 0343 Planetary Atmospheres (5405, 5407, 5409, 5704, 5705, 5707)
Scientific paper
The presence of non-erodible elements is well understood to be a reducing factor for soil erosion by wind, but the limits of its protection of the surface and erosion threshold prediction is complicated by the varying geometry, spatial organization and density of the elements. The predictive capabilities of some of the most recent models for estimating wind driven particle fluxes are reduced due to the poor representation of the effectiveness of vegetation to reduce wind erosion and dust emissions. Two approaches have been taken to account for roughness effects on sediment transport thresholds. Marticorena and Bergametti (1995) in their dust emission model parameterize the effect of roughness on threshold with the assumption that there is a relationship between roughness density and the aerodynamic roughness length of a surface and that the partitioning of shear stress can be estimated based on this relationship. Raupach et al. (1993) offer a different approach based on physical modeling of wake developments behind individual roughness elements and the partition of the surface stress and the total stress over a roughened surface. This geometric and drag coefficient based-predictive model allows the user to specify available inputs to describe most environments and generate the ratio that characterizes the erosion threshold of an initially bare erodible surface with the threshold once non-erodible elements are present. The objective of this presentation is to quantify the precision and accuracy of these two threshold wind erosion models by comparing model predictions with field and wind tunnel measurements with airflow over a range of roughness element scales, shapes, and distributions. The comparison between the models shows the partitioning approach to be a good framework to explain the effect of roughness on entrainment (and potentially transport) of sediment by wind. Both models provided very good agreement for the wind tunnel experiments using solid objects on a non-erodible surface, however their performance when tested in a field environment is less favourable. The Marticorena and Bergametti (1995) approach displays a scaling dependency when the difference between the roughness length of the surface and the overall roughness length is too great, creating a negative partition. While the Raupach et al. (1993) model requires more inputs than that of Marticorena and Bergametti (1995) its predictions are better due to the incorporation of more variations in the roughness geometry and the alterations to the flow they can cause.
Gillies J. A.
King Ji
Nickling William G.
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