Details
| Original language | English |
|---|---|
| Pages (from-to) | 1-17 |
| Number of pages | 17 |
| Journal | Boundary-Layer Meteorology |
| Volume | 164 |
| Issue number | 1 |
| Publication status | Published - 2017 |
Abstract
By means of large-eddy simulation, we investigate the transport of a passive scalar in the lee of forest patches under neutral atmospheric conditions in flat terrain. We found a pronounced local enhancement of scalar concentration and scalar flux in the lee zone of the forest, while further downstream above the unforested surface, the scalar transport adjusted to an equilibrium with the underlying surface conditions. By means of a term-by-term analysis of the scalar transport equation, we determined the local accumulation of the scalar to be caused by the convergence of: (1) mean and turbulent streamwise transport, (2) mean vertical transport. However, the relative importance of each transport mechanism for the accumulation process was found to depend strongly on forest density. Based on systematic parameter changes, we found concentrations to significantly increase with increasing forest density and with decreasing wind speed, while fluxes were invariant to wind speed and showed a similar relation to forest density as for the concentrations. Despite the scalar sources—ground and/or canopy sources—a local flux enhancement was present in the lee zone. Finally, we provide a first step towards localizing enhanced concentrations and fluxes at micrometeorological sites.
Keywords
- Enhanced scalar fluxes, Forest-edge flow, Large-eddy simulation, Lee recirculation, Scalar accumulation
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Atmospheric Science
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In: Boundary-Layer Meteorology, Vol. 164, No. 1, 2017, p. 1-17.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Enhanced Scalar Concentrations and Fluxes in the Lee of Forest Patches: A Large-Eddy Simulation Study
AU - Kanani-Sühring, Farah
AU - Raasch, Siegfried
N1 - Funding information: This study was supported by the German Research Foundation (DFG) under Grant RA 617/23-1. All simulations were performed on the SGI Altix ICE and CRAY XC30 at The North-German Supercomputing Alliance (HLRN) in Hannover and Berlin. NCL (The NCAR Command Language (Version 6.1.2) [Software]. (2013). Boulder, Colorado: UCAR/NCAR/CISL/VETS. http://dx.doi.org/10.5065/D6WD3XH5 ) was used for data analysis and visualization. We appreciate the constructive comments of the two reviewers.
PY - 2017
Y1 - 2017
N2 - By means of large-eddy simulation, we investigate the transport of a passive scalar in the lee of forest patches under neutral atmospheric conditions in flat terrain. We found a pronounced local enhancement of scalar concentration and scalar flux in the lee zone of the forest, while further downstream above the unforested surface, the scalar transport adjusted to an equilibrium with the underlying surface conditions. By means of a term-by-term analysis of the scalar transport equation, we determined the local accumulation of the scalar to be caused by the convergence of: (1) mean and turbulent streamwise transport, (2) mean vertical transport. However, the relative importance of each transport mechanism for the accumulation process was found to depend strongly on forest density. Based on systematic parameter changes, we found concentrations to significantly increase with increasing forest density and with decreasing wind speed, while fluxes were invariant to wind speed and showed a similar relation to forest density as for the concentrations. Despite the scalar sources—ground and/or canopy sources—a local flux enhancement was present in the lee zone. Finally, we provide a first step towards localizing enhanced concentrations and fluxes at micrometeorological sites.
AB - By means of large-eddy simulation, we investigate the transport of a passive scalar in the lee of forest patches under neutral atmospheric conditions in flat terrain. We found a pronounced local enhancement of scalar concentration and scalar flux in the lee zone of the forest, while further downstream above the unforested surface, the scalar transport adjusted to an equilibrium with the underlying surface conditions. By means of a term-by-term analysis of the scalar transport equation, we determined the local accumulation of the scalar to be caused by the convergence of: (1) mean and turbulent streamwise transport, (2) mean vertical transport. However, the relative importance of each transport mechanism for the accumulation process was found to depend strongly on forest density. Based on systematic parameter changes, we found concentrations to significantly increase with increasing forest density and with decreasing wind speed, while fluxes were invariant to wind speed and showed a similar relation to forest density as for the concentrations. Despite the scalar sources—ground and/or canopy sources—a local flux enhancement was present in the lee zone. Finally, we provide a first step towards localizing enhanced concentrations and fluxes at micrometeorological sites.
KW - Enhanced scalar fluxes
KW - Forest-edge flow
KW - Large-eddy simulation
KW - Lee recirculation
KW - Scalar accumulation
UR - http://www.scopus.com/inward/record.url?scp=85011835506&partnerID=8YFLogxK
U2 - 10.1007/s10546-017-0239-0
DO - 10.1007/s10546-017-0239-0
M3 - Article
AN - SCOPUS:85011835506
VL - 164
SP - 1
EP - 17
JO - Boundary-Layer Meteorology
JF - Boundary-Layer Meteorology
SN - 0006-8314
IS - 1
ER -