The Atmospheric Boundary Layer and the "gray zone" of turbulence: A critical review

As a result, models are starting to partially resolve the coherent overturning structures in the boundary layer. In this resolution regime, the so-called boundary layer "gray zone," neither the techniques of high-resolution atmospheric modeling (a few tens of meters resolution) nor those of traditional meteorological models (a few kilometers resolution) are appropriate because fundamental assumptions behind the parameterizations are violated.

Nonetheless, model simulations in this regime may remain highly useful. In this paper, a newly formed gray zone boundary layer community lays the basis for parameterizing gray zone turbulence, identifies the challenges in high-resolution atmospheric modeling and presents different gray zone boundary layer models. We discuss both the successful applications and the limitations of current parameterization approaches, and consider various issues in extending promising research approaches into use for numerical weather prediction.