Joint effects of subgrid-scale diffusion and truncation errors in large-eddy simulations of the convective boundary layer

Two runs of a large-eddy simulation model with Deardorff's and Schumann's subgrid parametrizations have been compared in order to analyze spurious effects at the top of the mixed layer due to a presence of a strong temperature jump. Simulations performed showed that Schumann's subgrid eddy viscosity was sufficient to spreads out sharp ripples which appeared in the numerical solution due to numerical dispersion. Deardorff's subgrid eddy viscosity was found too small near the top of the mixed layer, and as a result truncation dispersion errors caused unphysical solutions in this region.