Scale interactions in the atmospheric surface layer*

Near wall turbulence in the logarithmic and roughness sublayer has been observed to be influenced by large and very-large scale motions since early studies on inner-outer interactions and amplitude modulation. Here we present experimental results at the scale of the atmospheric surface layer, where the turbulent flow field has been captured by Super Large Particle Image Velocimetry  (SLPIV) sampled at 120 Hz up to 10m height, synchronized and co-located with a fixed-scan LiDAR operating at 2Hz up to 120m height. This dataset was acquired at the EOLOS Research Field in Minnesota (winter 2022), as part of the Grand-scale Atmospheric Imaging Apparatus (GAIA) collaboration. Preliminary results include i) a brief discussion on scale-dependent, height dependent convection velocities for the spatio-temporal conversion of the LiDAR data, ii) conditional averages of small-scale turbulent quantities, e.g. turbulent kinetic energy dissipation rate, vorticity, swirling strength, based on the large-scale velocity signal from the LiDAR.  Results are presented in the framework of rough wall zero pressure gradient turbulent boundary layers at high Reynolds number, and extended to near surface processes in the atmospheric surface layer.