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| Titel |
Local flux-profile relationships of wind speed and temperature in a canopy layer in atmospheric stable conditions |
| VerfasserIn |
G. Zhang, M. Y. Leclerc, A. Karipot |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 7, no. 11 ; Nr. 7, no. 11 (2010-11-12), S.3625-3636 |
| Datensatznummer |
250005060
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| Publikation (Nr.) |
 copernicus.org/bg-7-3625-2010.pdf |
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| Zusammenfassung |
| The particularities of the physics of the canopy layer pose challenges to the
determination and use of traditional universal functions so helpful in the
atmospheric surface layer. Progress toward "universal-like functions" such as
those provided by Monin-Obukhov similarity theory for the canopy layer has
been modest. One of the challenges lies in that the assumptions underlying
Monin-Obukhov similarity theory do not hold within a canopy layer. This paper
thus examines the local flux-profile relations for wind (Φm) and for
temperature (Φh). It uses three different stability parameters, i.e.,
h/L(h) at tree top, local z/L(z), and the local bulk
Richardson number (Ri), within a tall forest canopy in nighttime
stable (indicated by h/L(h) > 0) conditions. Results suggest
that the in-canopy Φm can be described using the local Richardson
number Ri. Furthermore, Φm is found to increase linearly
with Ri in the upper canopy layer for |Ri| < 1. When local |Ri| > 1, |Φm|
decreases with |Ri| in a power function, a result consistent for all
levels of measurements within the canopy. When both local Φh and
local Ri are positive, i.e., the local downward turbulent heat flux
is consistent with the local temperature gradient, the local Φh
increases with the local Ri when Ri < 1. However,
Φh does not change with Ri (or much more scattered) when
Ri > 1. The relationship between local Φh and
Ri disappears when counter-gradient heat transfer occurs in strongly
stable conditions. A self-correlation analysis is used to examine the
influence of self-correlation and the physical meaning of these
relationships. |
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