Instantaneous streamwise velocity profiles at very high Reynolds number in the neutrally stable atmospheric surface

We present instantaneous streamwise velocity profiles from the neutrally stable atmospheric surface layer, which we consider as a model for a very high Reynolds number canonical zero pressure gradient boundary layer with $Re_\tau = O(10^6)$. The data were acquired at the SLTEST site in Utah's western desert using 31 logarithmically-spaced single normal hot wires and 9 sonic anemometers spanning $0.001 \le z \le 26$m ($2 < z^+ < 10^5$). Low- and high-pass filters applied to the instantaneous velocity field reveal the relationship between the ``footprint" of large-scale motions (which are thought to originate in the logarithmic overlap layer) reaching down through the buffer layer and the spatial and temporal extent of periods of intense small-scale activity.