Investigating neutral and stable atmospheric surface layers using computational fluid dynamics

Computational fluid dynamics (CFD) is an effective technique to investigate atmospheric processes at a local scale. For example, in near-source atmospheric dispersion applications, the effects of meteorology, air pollutant sources, and buildings can be included. A prerequisite is to establish horizontally homogeneous atmospheric conditions, prior to the inclusion of pollutant sources and buildings. This work investigates modelling of the atmospheric surface layer under neutral and stable boundary layer conditions, respectively. Steady-state numerical solutions of the Reynolds Averaged Navier-Stokes (RANS) equations were used, including the the k-ε turbulence model. Atmospheric profiles derived from the Cooperative Atmosphere-Surface Exchange Study-99 (CASES-99) were used as reference data. The results indicate that the observed profiles of velocity and potential temperature can be adequately reproduced using CFD, while turbulent kinetic energy showed less agreement with the observations under the stable conditions. The results are discussed in relation to the boundary conditions and sources, and the observational data.