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A LiDAR method of canopy structure retrieval for wind modeling of heterogeneous forests

Boudreault, Louis-Etienne; Bechmann, Andreas; Taryainen, Lasse; Klemedtsson, Leif; Shendryk, Iurii LU and Dellwik, Ebba (2015) In Agricultural and Forest Meteorology 201. p.86-97
Abstract
The difficulty of obtaining accurate information about the canopy structure is a current limitation towards higher accuracy in numerical predictions of the wind field in forested terrain. The canopy structure in computational fluid dynamics is specified through the frontal area density and this information is required for each grid point in the three-dimensional computational domain. By using raw data from aerial LiDAR scans together with the Beer-Lambert law, we propose and test a method to calculate and grid highly variable and realistic frontal area density input. An extensive comparison with ground-based measurements of the vertically summed frontal area density (or plant area index) and tree height was used to optimize the method,... (More)
The difficulty of obtaining accurate information about the canopy structure is a current limitation towards higher accuracy in numerical predictions of the wind field in forested terrain. The canopy structure in computational fluid dynamics is specified through the frontal area density and this information is required for each grid point in the three-dimensional computational domain. By using raw data from aerial LiDAR scans together with the Beer-Lambert law, we propose and test a method to calculate and grid highly variable and realistic frontal area density input. An extensive comparison with ground-based measurements of the vertically summed frontal area density (or plant area index) and tree height was used to optimize the method, both in terms of plant area index magnitude and spatial variability. The resolution of the scans was in general low (<2.5 reflections m(-2)). A decrease of the resolution produced an increasing systematic underestimation of the spatially averaged tree height, whereas the mean plant area index remained insensitive. The gridded frontal area density and terrain elevation were used at the lower boundary of wind simulations in a 5 km x 5 km area of a forested site. The results of the flow simulations were compared to wind measurements using a vertical array of sonic anemometers. A good correlation was found for the mean wind speed of two contrasting wind directions with different influences from the upstream forest. The results also predicted a high variability on the horizontal and vertical mean wind speed, in close correlation with the canopy structure. The method is a promising tool for several computational fluid dynamics applications requiring accurate predictions of the near-surface wind field. (C) 2014 The Authors. Published by Elsevier B.V. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Forest, LiDAR, 3D, CFD, RANS
in
Agricultural and Forest Meteorology
volume
201
pages
86 - 97
publisher
Elsevier
external identifiers
  • wos:000347863900009
  • scopus:84911445496
ISSN
1873-2240
DOI
10.1016/j.agrformet.2014.10.014
language
English
LU publication?
yes
id
62bfbd76-1f5a-4c79-be87-9e8155a8cd61 (old id 5069114)
date added to LUP
2015-04-23 16:10:41
date last changed
2017-04-09 03:56:30
@article{62bfbd76-1f5a-4c79-be87-9e8155a8cd61,
  abstract     = {The difficulty of obtaining accurate information about the canopy structure is a current limitation towards higher accuracy in numerical predictions of the wind field in forested terrain. The canopy structure in computational fluid dynamics is specified through the frontal area density and this information is required for each grid point in the three-dimensional computational domain. By using raw data from aerial LiDAR scans together with the Beer-Lambert law, we propose and test a method to calculate and grid highly variable and realistic frontal area density input. An extensive comparison with ground-based measurements of the vertically summed frontal area density (or plant area index) and tree height was used to optimize the method, both in terms of plant area index magnitude and spatial variability. The resolution of the scans was in general low (&lt;2.5 reflections m(-2)). A decrease of the resolution produced an increasing systematic underestimation of the spatially averaged tree height, whereas the mean plant area index remained insensitive. The gridded frontal area density and terrain elevation were used at the lower boundary of wind simulations in a 5 km x 5 km area of a forested site. The results of the flow simulations were compared to wind measurements using a vertical array of sonic anemometers. A good correlation was found for the mean wind speed of two contrasting wind directions with different influences from the upstream forest. The results also predicted a high variability on the horizontal and vertical mean wind speed, in close correlation with the canopy structure. The method is a promising tool for several computational fluid dynamics applications requiring accurate predictions of the near-surface wind field. (C) 2014 The Authors. Published by Elsevier B.V.},
  author       = {Boudreault, Louis-Etienne and Bechmann, Andreas and Taryainen, Lasse and Klemedtsson, Leif and Shendryk, Iurii and Dellwik, Ebba},
  issn         = {1873-2240},
  keyword      = {Forest,LiDAR,3D,CFD,RANS},
  language     = {eng},
  pages        = {86--97},
  publisher    = {Elsevier},
  series       = {Agricultural and Forest Meteorology},
  title        = {A LiDAR method of canopy structure retrieval for wind modeling of heterogeneous forests},
  url          = {http://dx.doi.org/10.1016/j.agrformet.2014.10.014},
  volume       = {201},
  year         = {2015},
}