This work describes the use of the Direct Numerical Simulation (DNS) technique to model the evolution of turbulence in the boundary layer. Although the DNS method is restricted to flows with much lower Reynolds numbers than found in the atmosphere, recent work has suggested that Reynolds number similarity may be valid even at the low Reynolds numbers characteristic of DNS. With this realization, DNS becomes a promising tool for understanding turbulence in atmospheric flows.

Our DNS model handles thermal stratification and can currently simulate flows with Reynolds number of about 600. We initially tested the model’s performance by driving the model with a diurnal sinusoid for the surface heat flux, and the qualitative behavior of flow matched well-known characteristics of flow scales and turbulence distribution in the atmosphere. We have now driven the model with properly scaled observations of surface heat flux taken during the VTMX field campaign in October 2000 in Salt Lake City. In this paper we compare the structure of kinetic energy, dissipation rate, and other boundary layer variables in the DNS with observations of these variables in the real atmosphere. We focus on the period of turbulence decay that occurs during the evening transition from daytime convection to more stable conditions at night.