The aeolian dust accumulation curve

This article presents a simple physical concept of aeolian dust accumulatio n, based on the behaviour of the subprocesses of dust deposition and dust e rosion. The concept is tested in an aeolian dust wind tunnel. The agreement between the accumulation curve predicted by the model and the accumulation curve obtained in the experiments is close to perfect and shows that it is necessary to discriminate between the processes of aeolian dust deposition and aeolian dust accumulation. Two important thresholds determine the accu mulation process. For wind speeds below the deflation threshold, the aeolia n accumulation of dust increases linearly with the wind speed. For wind vel ocities between the deflation threshold and the accumulation limit, the sed imentation balance is above unity and there is still accumulation, though i t rapidly drops once the deflation threshold has been exceeded. At wind spe eds beyond the accumulation limit, the sedimentation balance is below unity and there will no longer be an accumulation of dust. The thresholds have b een determined in a wind tunnel test at friction velocity u(*) = 0.34 m s(- 1) (deflation threshold) and u(*) = 0.43 in s(-1) (accumulation limit), but these values are only indicative since they depend heavily on the characte ristics of the accumulation surface and of the airborne grains. Copyright ( C) 2001 John Wiley & Sons, Ltd.