Submitted to: Sedimentology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 21, 1996
Publication Date: N/A
Interpretive Summary: Anyone who has observed wind erosion in the field will recognize that soil movement often occurs intermittent bursts interspaced with periods of relative inactivity. Often the wind velocity will fall below that necessary for soil movement producing a momentary lull or quiescent period followed immediately by strong wind gusts which produce bursts of blowing soil. These intermittent bursts contribute significantly to the total amount of soil loss from wind eroding fields. So if we wish accurately to predict soil loss and fugitive dust emissions we must properly account for these intermittent burst events. In this paper we describe a simple method for predicting intermittency in the wind erosion process.
Technical Abstract: During a typical wind erosion event, large variations in wind strength produce temporal variations of saltation activity. The focus of this paper is on a special type of unsteady behavior - intermittent saltation - a process characterized by bursts of blowing soil interspersed with periods of inactivity. We report here measurements from a field study designed to measure intermittency in saltation activity during three separate one-hour periods. Our measurements show that saltation activity during a natural wind erosion event consists of intermittent bursts of blowing soil that often occupy a small fraction of the total time. We have managed to describe the level of intermittency by a simple and universal mathematical expression. We find that intermittency is related to the relative magnitude of the mean wind speed compared with the threshold wind speed and to whether typical wind fluctuations can span the gap between the mean wind speed and threshold. We have formed a nondimensional number that expresses the ratio of these velocity scales called the relative wind strength and find that the level of intermittency can be described by a simple distribution function of the relative wind strength.