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| Titel |
Influence of seasonal canopy development on turbulent flow characteristics in a hedgerow vineyard |
| VerfasserIn |
Nadia Vendrame, Luca Tezza, Kyaw Tha Paw U, Andrea Pitacco |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250130948
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| Publikation (Nr.) |
 EGU/EGU2016-11280.pdf |
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| Zusammenfassung |
| Turbulence is the main driver of vegetation-atmosphere exchanges. Flow characteristics
determine the transport of energy and matter between different layers of the canopy and the
atmosphere, defining local microclimatic conditions and influencing physiological processes
of the vegetation. Therefore, studying turbulent flow dynamics inside and above the canopy is
crucial to correctly predict overall fluxes of matter and energy and to understand their nature.
Numerous studies have already investigated the characteristics of canopy turbulence over a
wide range of vegetation types, leading to a thorough description of canopy turbulence.
However, only a few studies have investigated the influence of gradual canopy
structural changes such as foliage density (on multi-day time scales) on turbulence
field properties. We hypothesize that seasonal variations of foliage density play a
crucial role modifying foliage drag and canopy roughness, determining the degree of
coupling between vegetation and the atmosphere, and changing the profiles of turbulent
moments.
The aim of this study was to follow the continuous evolution of turbulent flow
characteristics from leaf budbreak to fully developed foliage in a hedgerow vineyard in the
North East of Italy. Synchronous measurements from a vertical profile of five sonic
anemometers on a 5 m tower have been collected at 20 Hz from beginning of April to
end of July 2015.Detailed measurements of Leaf Area Density (LAD) profile and
canopy architecture were performed at regular intervals (ca. weekly) around the
tower.
The canopy bulk drag coefficient increased during the growing season, suggesting that the
coupling between the vegetation and the atmosphere increased with LAD. Vertical profiles of
turbulent statistics showed to be highly correlated to local values of LAD. The penetration of
momentum flux in the canopy decreased with the gradual increase of foliage. Most of the
drag was exerted by the part of the canopy with denser foliage, this level moving upward
during the growing season. Skewness of horizontal (Sku) and vertical (Skw) wind suggested
that momentum transport in the canopy is dominated by intermittent downward gusts
(sweeps). Without leaves the peaks of Skuand Skwwere both located in the lower part of the
canopy, while during the growing season the magnitude of both values became
larger, showing how sweep penetration decreased as LAD increased.The evolution of
geometrical structure of the canopy imposed a strong directional behavior on mean
wind, gradually increasing wind channeling effect in the lower part of the canopy. |
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