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Principal Length Scales in Second-Order Closure Models for Canopy Turbulence

Principal Length Scales in Second-Order Closure Models for Canopy Turbulence Triaxial sonic anemometer velocity measurements vertically arrayed at six levels within and above a pine forest were used to examine the performance of two second-order closure models put forth by Wilson and Shaw and by Wilson. Based on these measurements, it was demonstrated that Wilson’’s model reproduced the longitudinal velocity standard deviation σσ u better than did Wilson and Shaw’’s model. However, Wilson and Shaw’’s model reproduced the measured mean velocity ⟨⟨ u ⟩⟩ near the forest––atmosphere interface better than Wilson’’s model did. The primary mechanisms responsible for discrepancies between modeled and measured ⟨⟨ u ⟩⟩ and σσ u profiles were investigated. The conceptual formulations of these two closure models differ in the characteristic length scales and timescales used in the closure parameterizations of the mean turbulent kinetic energy dissipation rate term, the pressure––strain rate term, and the flux-transport term. These characteristic length scales were computed and compared with measured integral length scales inside the canopy. A discussion on how these length scales compare with the mixing layer analogy also is presented. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Applied Meteorology American Meteorological Society

Principal Length Scales in Second-Order Closure Models for Canopy Turbulence

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References (45)

Publisher
American Meteorological Society
Copyright
Copyright © 1998 American Meteorological Society
ISSN
1520-0450
DOI
10.1175/1520-0450(1999)038<1631:PLSISO>2.0.CO;2
Publisher site
See Article on Publisher Site

Abstract

Triaxial sonic anemometer velocity measurements vertically arrayed at six levels within and above a pine forest were used to examine the performance of two second-order closure models put forth by Wilson and Shaw and by Wilson. Based on these measurements, it was demonstrated that Wilson’’s model reproduced the longitudinal velocity standard deviation σσ u better than did Wilson and Shaw’’s model. However, Wilson and Shaw’’s model reproduced the measured mean velocity ⟨⟨ u ⟩⟩ near the forest––atmosphere interface better than Wilson’’s model did. The primary mechanisms responsible for discrepancies between modeled and measured ⟨⟨ u ⟩⟩ and σσ u profiles were investigated. The conceptual formulations of these two closure models differ in the characteristic length scales and timescales used in the closure parameterizations of the mean turbulent kinetic energy dissipation rate term, the pressure––strain rate term, and the flux-transport term. These characteristic length scales were computed and compared with measured integral length scales inside the canopy. A discussion on how these length scales compare with the mixing layer analogy also is presented.

Journal

Journal of Applied Meteorology – American Meteorological Society

Published: May 26, 1998

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