Use of a dynamic subgrid-scale model for large-eddy simulation of the planetary boundary layer

Large-eddy simulation (LES) of the planetary boundary layer (PBL) is very sensitive to the subgrid-scale (SGS) model used when the strength of SGS motions begins to approach that of the resolved motions. This can typically occur near the ground and in strongly stable or sheared conditions. The underlying algebraic relations of Germano and least-squares local evaluation of dynamic parameters used in many dynamic SGS models require that the flow field be adequately resolved. This requirement is met throughout most of the PBL, but difficulty arises near the ground under non-convective conditions where energy-containing eddies are resolved, constrained in size due to the presence of a solid boundary. Adding grid resolution near the ground is an obvious approach, which is tried in this study. A more computationally efficient alternative is to include a parameterization that achieves a better match between the LES fields and similarity in the surface layer.