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Comparison of Measured and Simulated Friction Velocity and Threshold Friction Velocity Using SWEEP

Huawei Pi, Brenton Sharratt, Gary Feng, Xiaoxiao Zhang
Soil science 2014 v.179 no.8 pp. 393-402
simulation models, loess soils, semiarid zones, model validation, wind speed, friction, environmental quality, wind erosion, prediction
Adequately simulating the occurrence and magnitude of erosion using the Wind Erosion Prediction System is critical for resource conservation and improving environmental quality in the United States and other regions of the world. Past observations indicate an insensitivity of the Wind Erosion Prediction System erosion submodel (Single-event Wind Erosion Evaluation Program (SWEEP)) to simulate the occurrence of wind erosion from loess soils during intensifying winds in the Pacific Northwest United States. This insensitivity is attributed to either underestimation of friction velocity (u*) or overestimation of threshold friction velocity (u*t), but no definitive work has been conducted to validate u* and u*t in the SWEEP. The objective of this study was to compare measured u* and u*t with those simulated by the SWEEP. The SWEEP begins to simulate erosion when u* exceeds u*t, thus we compared measured and simulated u* and u*t of agricultural fields during wind erosion events in eastern Washington. No evidence indicated that the SWEEP consistently overestimated or underestimated u*. The SWEEP was very sensitive to the stem area index, and estimation of u* was better when the SWEEP was used at field sites characterized by a lower rather than a higher stem area index. Our results, however, indicate that the SWEEP overestimated u*t during all observed erosion events. Therefore, simulating the occurrence of wind erosion of loess soils in the Pacific Northwest and other arid and semiarid regions of the world may be improved through better estimation of u*t in the SWEEP.