Coupling a land-surface model to large-eddy simulation to study the nocturnal boundary layer

Negatively buoyant forces in the stable boundary layer (SBL) damp turbulent motions, resulting in decreased transport of momentum, heat and water vapor. During high levels of stratification this can cause intermittent turbulence, gravity waves and weak turbulent fluxes. In some cases, decoupling between the atmospheric boundary layer (ABL) and land-atmosphere fluxes can occur. Accurately reproducing these phenomena requires detailed treatment of the physical processes that govern the two-way dynamic interaction between surface properties and the ABL. Increasingly, large-eddy simulation (LES) is used to study land-atmosphere interactions in the SBL. In these studies, the dominant treatment of surface boundary conditions is to specify a known state or flux. This research uses LES that is fully coupled to a land-surface model (LSM) to investigate the SBL. The LSM explicitly solves for the transport of heat and water in a one-dimensional column of the upper soil. Coupling to the atmosphere is achieved through a surface budget, which partitions the available radiative forcing into ground heat flux and sensible and latent heat fluxes. Turbulent boundary layer profiles and surface fluxes are compared to field data and results from simulations of the GABLS3 LES intercomparison case.