10.4122/1.1000000215
Avissar, Ron I
Ron I
Avissar
avissar@duke.edu
Bohrer, Gil
Gil
Bohrer
gil.bohrer@duke.edu
Avissar, Ron I
Ron I
Avissar
avissar@duke.edu
Using Large-Eddy Simulations and experiments to quantify long-range tree seed dispersal
XVI International Conference on Computational Methods in Water Resources
2006
2006
One of the key challenges to quantifying long-distance seed dispersal by wind is
describing the complex and three-dimensional eddy motion inside and above canopies.
The Large-Eddy Simulations (LES) option of the Regional Atmospheric Modeling System
(RAMS), a state-of-the-art, three-dimensional, non-hydrostatic atmospheric numerical
model was modified to simulate atmospheric turbulence within and above tree canopies.
The primary modification included a new coordinate system designed to contour the
shape of trees, thereby permitting a more faithful descriptor of the interaction
between canopy morphology and the “energetic” eddies. A detailed energy balance of
the tree canopy was also introduced in the model. The model was set up to simulate
turbulence within a second-growth 180-year old hardwood stand at Duke Forest having a
mean canopy height of 30 m and a maximum leaf area index of 6. The LES was
initialized with measured hourly mean wind speed, temperature, and humidity profiles
near a 45-m tower in this stand. The various statistical moments needed to drive seed
trajectories were compared with the corresponding moments measured at the tower. A
Lagrangian Dispersion Particle Model (LDPM) driven with the turbulent flow simulated
with the RAMS-LES was then used to quantify seed dispersal at that site. The
combined RAMS-LES and LDPM simulations adequately match the patterns of seed
dispersal as quantified by observations conducted near the tower.