Steps, waves and turbulence in the stably stratified planetary boundary layer

The stably-stratified planetary boundary layer contains small-vertical-scale, step-like structures, waves on a multitude of scales, large horizontal eddies and small-scale turbulence, all of which constantly interact with, and modify, one another. Current knowledge of how the various components act in the vicinity of the step-like structures is surveyed. It is concluded that packets of internal waves are the main conduit for interaction within and across the boundary layer, and low-intensity critical-level absorption at the fringes of their spectrum probably maintains the step-like structures. Further investigation of the processes requires intensive observations of the four-dimensional structure of the region, but such an investigation will need a new generation of high-resolution sensing systems.