A numerical study of turbulence, dispersion, and chemistry within and above forest canopies

TitleA numerical study of turbulence, dispersion, and chemistry within and above forest canopies
Publication TypeThesis
Year of Publication2009
AuthorsEdburg SLee
AdvisorStock D, Lamb BK, VanReken T, Sparks JP
Academic DepartmentCollege of Engineering and Architecture
DegreeDoctor of Philosophy
Number of Pages222 pp.
UniversityWashington State University
CityPullman, WA
Thesis TypePhD Dissertation
KeywordsVOLATILE ORGANIC COMPOUNDS
Abstract

This research focused on understanding turbulence, dispersion, and chemistry within and above forest canopies. In the first study, we used a onedimensional turbulence model to calculate turbulent diffusivities for a three dimensional scalar transport model. The goal was to provide forest managers with quantitative data to guide them in the placement of synthetic pheromone traps for combating bark beetle infestations. The model is requires low computational resources, and thus is well suited for use in a web-based portal. In the second study, we developed two reduced chemical mechanisms for use in large eddy simulations (LES) of NOx-O3-VOC chemistry within and above a forest canopy. In the third study, we used LES to study the effect of vertical scalar source/sink distribution on scalar concentration moments, fluxes, and correlation coefficients within and above an ideal forest canopy. All scalar concentration moments, fluxes, and correlation coefficients were affected by the source location. In the final study, we used large eddy simulation (LES) to study nonlinear effects of turbulent mixing on in-canopy NOx-O3-VOC chemistry for a northern hardwood forest located at the University of Michigan Biological Station (UMBS). We found that under daytime conditions at UMBS, non-linear effects of mixing on chemistry were not significant. However, simulations for a high radical environment showed that mixing significantly altered VR-BVOC oxidation, and NOx-O3 chemistry. As the canopy absorbed more momentum and/or O3 deposition to the canopy increased, the non-linear effect of mixing on chemistry increased, which suggests that the effect of non-linear mixing on chemistry is greater in tall, dense canopies as compared to shorter, less dense canopies.