The near-bed airflow and the movement of sand dune sediments by wind are fundamental dune geomorphological processes.This research measured the wind profiles and sand mass flux on the rounded top of a transverse dune ...The near-bed airflow and the movement of sand dune sediments by wind are fundamental dune geomorphological processes.This research measured the wind profiles and sand mass flux on the rounded top of a transverse dune at the southern edge of the Tengger Desert to examine how to best predict the vertical profile of sand flux.This work also tested the accuracy of previously developed models in predicting the apparent roughness length during saltation.Results show that mass flux vertical distribution over the dune top is underestimated by an exponential function,overestimated by a power function,but closely matches the predictions made using the LgstcDoseRsp function.Given suitable values ofα,βandγaccording to the grain size composition,S?rensen equation with the peaked shape of the mass transport curve will well predict the dimensionless mass flux qg/ρu*3against dimensionless shear velocity u*/u*t.The modified Charnock model works best of the previously published models tested,with an R2of 0.783 in predicting the enhanced roughness over the moving sand surface,as opposed to an R2of0.758 for the Owen model and an R2of 0.547 for the Raupach model.For the rounded dune top in this study,C m=0.446±0.016.展开更多
The wind fetch effect is important to wind erosion and aeolian transport and controls aeolian flux.It is useful to study the wind fetch effect in determining the aeolian transport mechanism and improving our knowledge...The wind fetch effect is important to wind erosion and aeolian transport and controls aeolian flux.It is useful to study the wind fetch effect in determining the aeolian transport mechanism and improving our knowledge of aeolian physics and wind erosion.In this paper,multichannel samplers measure aeolian transport at different heights above an artificial Gobi surface in the southeastern region of the Tengger Desert.The results show that aeolian transport flux can be expressed as an exponential function of height.Wind fetch obviously affects aeolian flux and aeolian transport.The coefficients and relative decay rate of aeolian flux decrease and then increase with increasing wind fetch distance.Aeolian transport depends on the height and fetch distance;aeolian transport increases and then decreases with increasing fetch distance,reaching a maximum at a fetch distance of about 34 m at the very near surface.The fetch distance of maximum aeolian transport tends to increase with height.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41171004&40871015)
文摘The near-bed airflow and the movement of sand dune sediments by wind are fundamental dune geomorphological processes.This research measured the wind profiles and sand mass flux on the rounded top of a transverse dune at the southern edge of the Tengger Desert to examine how to best predict the vertical profile of sand flux.This work also tested the accuracy of previously developed models in predicting the apparent roughness length during saltation.Results show that mass flux vertical distribution over the dune top is underestimated by an exponential function,overestimated by a power function,but closely matches the predictions made using the LgstcDoseRsp function.Given suitable values ofα,βandγaccording to the grain size composition,S?rensen equation with the peaked shape of the mass transport curve will well predict the dimensionless mass flux qg/ρu*3against dimensionless shear velocity u*/u*t.The modified Charnock model works best of the previously published models tested,with an R2of 0.783 in predicting the enhanced roughness over the moving sand surface,as opposed to an R2of0.758 for the Owen model and an R2of 0.547 for the Raupach model.For the rounded dune top in this study,C m=0.446±0.016.
基金supported by the National Natural Science Foundation of China (Grant Nos.41101007,41130533 and 41171010)
文摘The wind fetch effect is important to wind erosion and aeolian transport and controls aeolian flux.It is useful to study the wind fetch effect in determining the aeolian transport mechanism and improving our knowledge of aeolian physics and wind erosion.In this paper,multichannel samplers measure aeolian transport at different heights above an artificial Gobi surface in the southeastern region of the Tengger Desert.The results show that aeolian transport flux can be expressed as an exponential function of height.Wind fetch obviously affects aeolian flux and aeolian transport.The coefficients and relative decay rate of aeolian flux decrease and then increase with increasing wind fetch distance.Aeolian transport depends on the height and fetch distance;aeolian transport increases and then decreases with increasing fetch distance,reaching a maximum at a fetch distance of about 34 m at the very near surface.The fetch distance of maximum aeolian transport tends to increase with height.
