RESOLVED-SCALE TURBULENCE IN THE ATMOSPHERIC SURFACE-LAYER FROM A LARGE-EDDY SIMULATION

Large eddy simulation has encountered difficulties in handling turbule nce in the atmospheric surface layer due to deficiencies in sub-grid s cale models. This paper addresses the possibility of resolving the tur bulence in the upper part of the surface layer by a low-aspect ratio o f grid spacing. Results show that resolved-scale shear stresses domina te over the sub-grid scale components so that effects due to the sub-g rid scale model can be ignored in this region. The effects of the lowe r boundary condition on the resolved-scale turbulence in the upper par t of the surface layer are discussed. It is concluded that the normali zed mean velocity shear and resolved turbulence in the upper part of t he surface layer are not affected by the specification of the lower bo undary condition. In addition, the present work proposes a new indepen dent model parameter, the Smagorinsky Reynolds Number (Re-SM), and dem onstrates that this number determines the resolved turbulence in the u pper part of the surface layer.