Diurnal Patterns of Blowing Sand and Dust

The diurnal pattern of blowing sand results from a complex interaction between the sun, the atmosphere, and the sand surface. During the day, solar heating produces thermal instability, which enhances 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 seven-month period on the high plains of the Llano Estacado 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). Photo of the sampling system used to measure wind speed and detect blowing sand.