Variability of the apparent von Karman parameter during aeolian saltation

The variability of the apparent von Karman parameter kappa(a) during aeolian saltation was evaluated in a field experiment at Jericoacoara, Brazil. To test this variability, velocity profiles, Reynolds stress and sand transport data were gathered and analyzed. We used 15 data sets with sand-laden airflow and 2 runs with clear airflow. Results indicated an inverse linear relationship between kappa(a) and bulk, gravimetric sand concentration (R-2 = 0.746) and sand transport rate (R-2 = 0.577). We found values of kappa(a) as low as 0.26. This means that using the von Karman constant, kappa (0.40) rather than the variable kappa(a) to estimate shear velocity based on the slope of the velocity profile will lead to over estimation of shear velocity, averaging about 20% in this study. This, in turn, produces an over estimation of wind-blown sand transport rates based on models that have terms with shear velocity cubed. Citation: Li, B., D. J. Sherman, E. J. Farrell, and J. T. Ellis (2010), Variability of the apparent von Karman parameter during aeolian saltation, Geophys. Res. Lett., 37, L15404, doi: 10.1029/2010GL044068.