Insights on aeolian streamer dynamics from conventional and doppler lidar measurements

Abstract:

Beach environments are often characterized by complex spatial variability in surface grain size and moisture characteristics, with corresponding implications on sediment availability for wind-driven sediment transport. Unsteady coastal wind fields also play a large role on spatio-temporal variability in sediment transport rates. De-coupling the relative controls of these sediment and environmental properties on aeolian sediment transport rates in coastal beach settings is critically important for advancing predictive capabilities of wind-blown transport rates, yet has proven to be challenging, particularly from limited point-based in-situ sensors. To effectively isolate these relative controls requires more spatially and temporally comprehensive datasets of aerodynamic and transport properties.

Building off of previous proof of concept works by Nield and Wiggs (2011) and others who demonstrated that terrestrial lidar scanners (TLS) could provide insights into aeolian saltation dynamics, we utilize a Riegl VZ-2000 TLS to explore spatio-temporal fluctuations in the saltation field over an intermediate beach system on a sandy beach located on the Outer Banks of North Carolina, USA. High frequency (~20Hz), high angular resolution (θ = 0.008°) line-scanning is utilized to map the height of the saltation layer during moderate to high wind speed conditions when aeolian streamers are prevalent. These remote sensing measurements of the transport field are complemented by co-located, remotely sensed wind fields collected using a ZX TM doppler wind lidar. These detailed remote sensing measurements are validated against traditional in-situ wind and sediment transport measurements. The data are collectively used to explore (1) geometric characteristics of aeolian streamers and (2) whether the height of the saltation layer is shear invariant.