Large eddy simulations of canopy flows in stable atmospheric conditions

The flux exchanges between canopies and atmosphere as modeled by land surface models, are usually treated using so called “big-leaf” models. However, turbulence structures within forest canopies cannot be well established in single-layer “big-leaf” models. Although some multi-layer canopy models are used in canopy flows studies, these only consider simple physical processes within canopies. Here, we incorporate a new multi-layer canopy model based on the Community Land Mode 4.5 into the Weather Research and Forecasting model with large eddy simulation to study forest canopy turbulence structures. The model consists of a multi-layer radiative transfer model, a photosynthesis model, and a scalar transfer model. It was evaluated with a single multi-level tower field experiment data from the ExchanGE processes in mountainous Regions (EGER) project. We then used this model to study mean and turbulent canopy flows in stable conditions over simple gentle sloped terrain. Particularly, the impact of different stably stratified atmospheric conditions (weakly, intermidiately, and strongly) upon mean profiles and turbulence structures were studied.