| The structure of turbulence near a tall forest edge: the backward-facing step flow analogy revisited. | |
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MedLine Citation:
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PMID: 18767620 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Flow disturbances near tall forest edges are receiving significant attention in diverse disciplines including ecology, forest management, meteorology, and fluid mechanics. Current theories suggest that near a forest edge, when the flow originates from a forest into a large clearing, the flow retains its forest canopy turbulence structure at the exit point. Here, we propose that this framework is not sufficiently general for dense forested edges and suggest that the flow shares several attributes with backward-facing step (BFS) flow. Similar analogies, such as rotor-like circulations, have been proposed by a number of investigators, though the consequences of such circulations on the primary terms in the mean momentum balance at the forest clearing edge have rarely been studied in the field. Using an array of three triaxial sonic anemometers positioned to measure horizontal and vertical gradients of the velocity statistics near a forest edge, we show that the flow structure is more consistent with an intermittent recirculation pattern, rather than a continuous rotor, whose genesis resembles the BFS flow. We also show that the lateral velocity variance, v'2, is the moment that adjusts most slowly with downwind distance as the flow exits from the forest into the clearing. Surprisingly, the longitudinal and vertical velocity variances (u'2 and w'2) at the forest edge were comparable in magnitude to their respective values at the center of a large grass-covered forest clearing, suggesting rapid adjustment at the edge. Discussions on how the forest edge modifies the spectra and co-spectra of momentum fluxes, effective mixing length, and static pressure are also presented. |
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Authors:
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Matteo Detto; Gabriel G Katul; Mario Siqueira; Jehn-Yih Juang; Paul Stoy |
Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, Non-P.H.S. |
Journal Detail:
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Title: Ecological applications : a publication of the Ecological Society of America Volume: 18 ISSN: 1051-0761 ISO Abbreviation: Ecol Appl Publication Date: 2008 Sep |
Date Detail:
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Created Date: 2008-09-04 Completed Date: 2008-12-31 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 9889808 Medline TA: Ecol Appl Country: United States |
Other Details:
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Languages: eng Pagination: 1420-35 Citation Subset: IM |
Affiliation:
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Dipartimento di Ingegneria Idraulica, Ambientale e del Rilevamento, Politecnico di Milano, Italy. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Air Movements* Ecosystem* Models, Statistical Poaceae Trees* |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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