Vertical profiles, size distributions, and intermittency in aeolian sediment transport: Field measurements with a novel instrument

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Project Abstract: Vertical profiles, size distributions, and intermittency in aeolian sediment transport: Field measurements with a novel instrumentIn two separate field deployments, an instrument that will be developed as part of this project will be used for the economical measurement of the rate and magnitude of the movement of sand under the influence of wind, a process referred to as eolian sand transport. The instrument, nicknamed the SANTRI will utilize inexpensive optical sensors in conjunction with wind sensors to measure the threshold winds required for the movement of sand and the magnitude of the sand flux with time resolution on the order of one second. Preliminary pilot tests indicate that in addition to aggregate sand flux, these sensors can provide valuable grain size, and possibly speed information. Compared to other instruments that are currently available, including those that use optical sensors, the SANTRI would be much more independent, requiring no external data capture, electrical power, or frequent servicing. Deployment at a field site that has been established through an existing NSF project will provide the information necessary to identify areas for improvement. A second deployment at another selected field site will provide a large dataset of sand movement under varying wind conditions. Results from this latter effort can be used for testing of physical models.Movement of sand by wind is the principal process that suspends dust, the largest atmospheric aerosol constituent on a global basis. Sand grains that are lofted by the shearing forces of the wind at the soil surface can, upon subsequent impact on the soil, cause the ejection of additional sand grains and much smaller, aerosol-sized dust particles. This saltation process has been a central subject of windblown, or eolian, sediment transport research since the first seminal writings on the topic appeared in the scientific literature. Significant progress has been made in understanding how saltation is initiated, the effect of vegetation and other surface roughness, and the influence of soil parameters such as moisture. However, the ability to accurately model the behavior of a specific soil under specific wind conditions continues to be a primary challenge, one that is made more difficult by a relative paucity of in-situ measurements, owing in part to the labor- and cost-intensive nature of these measurements.This research will result in the development of a new, economical, and transformative instrument that has the potential to open up new lines of inquiry and enable the collection of field measurements to test established models that have been relying heavily on laboratory wind tunnel experiments instead of real-world data. Through improvement of models and more robust datasets, a more thorough understanding can be obtained of local, regional, and global emissions of windblown dust, which impacts climate, rate of snow melt, land degradation, and human health.