Scale interactions in the stably stratified atmospheric boundary layer and impacts on the anisotropy and intermittency of turbulence

Turbulence in the stably stratified boundary layer is generated by shear, while its development is inhibited by buoyant forces. Due to this interplay, flow regimes with different physical and dynamical characteristics exist. Fully turbulent stable boundary layers, also coined as weakly stable boundary layers, are rather well described by turbulence theory, but the very stable boundary layer is home to unsteady and intermittent turbulence that is less well understood. At high stability in the atmospheric boundary layer, non-turbulent processes on sub-mesoscales (such as dirty waves, drainage flows, etc) become more important, and the flow becomes highly non-stationary. Multiscale data analyses based on different field measurement campaigns show signs of direct energy transfers between sub-mesoscales and turbulent scales, with impacts on the turbulence characteristics. On the one hand, the scale interactions are linked to anisotropic turbulence; on the other hand, turbulence intermittency becomes important when the energy content of the sub-mesoscales becomes an important percentage of the mean kinetic energy.