Ross, AN and Harman, IN (2015) The impact of source distribution on scalar transport over forested hills. Boundary-Layer Meteorology, 156 (2). pp. 211-230. ISSN 0006-8314
Abstract
Numerical simulations of neutral flow over a two-dimensional, isolated, forested ridge are conducted to study the effects of scalar source distribution on scalar concentrations and fluxes over forested hills. Three different constant-flux sources are considered that span a range of idealized but ecologically important source distributions - a source at the ground, one uniformly distributed through the canopy, and one decaying with depth in the canopy. A fourth source type, where the in-canopy source depends on both the wind speed and the difference in concentration between the canopy and a reference concentration on the leaf, designed to mimic deposition, is also considered. The simulations show that the topographically-induced perturbations to the scalar concentration and fluxes are quantitatively dependent on the source distribution. The net impact is a balance of different processes affecting both advection and turbulent mixing, and can be significant even for moderate topography. Sources that have significant input in the deep canopy or at the ground exhibit a larger magnitude advection and turbulent flux-divergence terms in the canopy. The flows have identical velocity fields and so the differences are entirely due to the different tracer concentration fields resulting from the different source distributions. These in-canopy differences lead to larger spatial variations in above-canopy scalar fluxes for sources near the ground compared to cases where the source is predominantly located near the canopy top. Sensitivity tests show that the most significant impacts are often seen near to or slightly downstream of the flow separation or reattachment points within the canopy flow. The qualitative similarities to previous studies using periodic hills suggest that important processes occurring over isolated and periodic hills are not fundamentally different. The work has important implications for the interpretation of flux measurements over forests, even in relatively gentle terrain and for neutral flow. To understand fully such measurements it is necessary not only to understand the flow structure (given the site characteristics) but also to know the distribution of scalar sources and sinks in the canopy.
Metadata
Item Type: | Article |
---|---|
Authors/Creators: |
|
Copyright, Publisher and Additional Information: | © 2015 Springer Science+Business Media Dordrecht. This is an author produced version of a paper published in Boundary-Layer Meteorology and uploaded in accordance with the publisher's self-archiving policy. The final publication is available at Springer via https://dx.doi.org/10.1007/s10546-015-0029-5. |
Keywords: | Advection; Canopy; Complex terrain; FLUXNET; Scalar; Topography |
Dates: |
|
Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst for Climate & Atmos Science (ICAS) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 17 Apr 2015 08:03 |
Last Modified: | 18 Jan 2018 18:53 |
Published Version: | https://dx.doi.org/10.1007/s10546-015-0029-5 |
Status: | Published |
Publisher: | Springer Verlag |
Identification Number: | 10.1007/s10546-015-0029-5 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:85116 |