Wall Shear stress measurements in the atmosperhic surface layer

w data, valuable contributions have been made to the physical understanding of turbulence over an unprecedented range of Reynolds numbers. The shear stress measurements were made at the unique SLTEST (Surface Layer Turbulence and Environmental Science Test facility) site on the great salt lakes of Utah, pictured in figure 1. Winds over the site are known to remain strong and consistent for extended periods. Upstream of the measurement site, the surface is extremely flat and smooth over many kilometres [5]. The geophysically driven air flow is therefore thought to share important characteristics with common wind-tunnel boundary layers, albeit at three orders of magnitude higher Reynolds number. Thus, another goal was to further understand similarities that may exist between the SLTEST surface layer and the wind tunnel boundary layer. For such comparisons, neutrally buoyant conditions are required; figure 2 confirms that these conditions were present throughout the night. From extensive sonic anemometer measurements under these conditions, turbulence statistics were calculated which exhibit laboratory-boundary-layer-like behaviour. Beyond sonic anemometery, the present work followed on from that of Heuer & Marusic [3] who developed a floating-element-type shear stress sensor, specifically designed to measure τ ′