Uncertainties in Plot-Scale Mass Balance Measurements Using Aeolian Sediment Traps

Abstract

Modified Wilson and Cooke (MWAC) sediment catchers are commonly used for quantifying aeolian sediment transport in the saltation layer. The accuracy of aeolian mass flux and mass balance estimates using MWAC catchers has, however, not been reported in detail so far. By combining analytical error propagation equations and Monte Carlo simulation, this study tested a random error propagation scheme that incorporates six sources of uncertainty: sediment mass, MWAC inlet diameter, vertical position of the catchers, trapping efficiency, horizontal spacing between catcher arrays, and wind direction. For a weighing uncertainty of 0.01 g, the relative uncertainty in the cumulative mass flux of sediment reached up to 140%, but this generally affected only the highest catchers. The relative error in the measured unit mass transport was much less, ranging between 2 and 20%, with an average of 10%. The relative uncertainty in the corrected cumulative unit sediment mass transport, however, was found to be 32%, on average, because of the high relative uncertainty in the trapping efficiency of 31%. The relative uncertainty in the plot-scale mass balances ranged between 32 and 80%. Uncertainty in the trapping efficiency and the measured unit mass transport contributed most to the mass balance uncertainty, but the uncertainty in the wind direction sometimes also contributed substantially. The high uncertainties that potentially affect the sediment mass transport and mass balances highlight the need for their systematic reporting in future studies. We also investigated possible pathways for reducing the uncertainty