Evaluation of an Algebraic Turbulence Closure Scheme for the Simulations of Dry and Moist Atmospheric Boundary Layers

It is a challenge to parameterize the effects of subfilter-scale (SFS) turbulence in the terra incognita (TI), which refers to a range of grid spacing that can only partially resolve the most energetic eddies in a simulation. Traditional turbulence schemes in large-eddy simulations (LES) assume the energetic eddies are mostly resolved, while the schemes in mesoscale and global models assume they are mostly unresolved. TI does not satisfy either of these assumptions and thus may require different designs. Here we evaluate an implicit generalized linear algebraic subfilter-scale model (iGLASS) of turbulence for the simulations at LES and TI resolutions. iGLASS derives from the conservation equations of SFS stresses and scalar fluxes, with the time tendency and higher-order terms neglected and some of the remaining terms, such as dissipation and pressure redistribution, parameterized. SFS stresses and scalar fluxes are coupled in the resulting algebraic equations and are solved simultaneously. iGLASS has been tested at LES resolutions for dry stable, neutral, and convective boundary-layer flows and showed promising performance compared with traditional LES turbulence schemes (Enriquez 2013). This study addresses the choice of pressure-strain term parameters in iGLASS and its performance in the TI for both dry and moist flows. Multiple parameter sets are tested in the simulations of a dry neutral boundary layer (NBL) and a stratocumulus-capped boundary layer (SCBL). At standard LES resolutions, iGLASS with properly chosen parameters can perform significantly better than traditional LES turbulence schemes and slightly better than the dynamic reconstruction model (DRM; Chow et al. 2005) in both the NBL and the SCBL cases. At TI resolutions, the quality of the simulations using iGLASS deteriorates. However, if the reconstruction approach used in DRM is combined with iGLASS, satisfying results are still achievable in the TI.