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Submitted to: Earth Surface Processes and Landforms
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/3/2009 Publication Date: 3/15/2010 Citation: Stout, J.E. 2010. Diurnal patterns of blowing sand. Earth Surface Processes and Landforms. 35(3):314-318. Interpretive Summary: Early explorers of desert regions often noticed that dust storms tend to occur more frequently during the day and less frequently at night. More recent observations of blowing dust have confirmed that there is a strong tendency for dust storms to occur preferentially, but not exclusively, during the day. In the present study, attempts have been made to explore this dynamic process from a slightly different perspective. Instead of using blowing dust as an indicator of aeolian activity, direct detection of blowing sand was used to compute diurnal patterns. Blowing sand was detected using a fast responding “saltation sensor” that utilizes a piezoelectric transducer to detect the wind-induced movement of sand grains. Measurements taken over a four-month period at a site located in the Southern High Plains suggest that sand movement tends to occur more frequently during daylight hours with a peak in aeolian activity occurring in the afternoon between 2:00 and 3:00 p.m. Technical Abstract: The diurnal pattern of blowing sand results from a complex process that involves the interaction between the sun, wind, and earth. During the day, solar heating produces thermal instability, which enhances the convective mixing of high momentum winds from the upper levels of the atmosphere to the surface layer. The sun also dries the sand surface so that the critical threshold is as low as possible. Thus, in the afternoon, the combination of strong turbulent winds and a low surface threshold increases the likelihood that winds may intermittently exceed the critical threshold of the surface to produce bursts of blowing sand. Here an attempt has been made to explore this dynamic aeolian process using a new method for monitoring the diurnal pattern of blowing sand. This technique involves detecting blowing sand with a piezoelectric saltation sensor and then determining the relative proportion of time that blowing sand is detected for a given “time of day”. Measurements taken over a four-month period in the Southern High Plains suggest that sand movement tends to occur more frequently during daylight hours with a peak in aeolian activity occurring in the afternoon between 1400 and 1500 Local Standard Time (LST). |
