Large-eddy simulation of stably stratified canopy turbulence

Annual net ecosystem carbon exchange results from a small difference between large seasonal plant uptake and respiration. Nighttime and cold season respiration are difficult to measure at common flux network sites due to the spatial and temporal intermittency of stable boundary layers. Stable stratification tends to reduce turbulence length scales, and when using large-eddy simulation (LES) to investigate stably stratified environments this length scale reduction places undue reliance on the subgrid model. This problem is exacerbated near the ground, where the length scales are further limited by the presence of the rigid surface. In a canopy a fixed length scale is imposed on the turbulent flow and the important sink for momentum is elevated above the surface. This lessens the importance of the interactions with the underlying surface making it feasible to use LES. We will present an investigation of stably stratified turbulence interacting with a plant canopy using a set of large-eddy simulations.