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| Titel |
Turbulence parameter inside and above a tall spruce site |
| VerfasserIn |
T. Biermann, K. Staudt, A. Serafimovich, T. Foken |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250021938
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| Zusammenfassung |
| In the EGER (ExchanGE processes in mountainous Regions) project, different physical,
chemical and biological processes in the soil-vegetation-boundary-layer system
were investigated. Field experiments were performed at the BayCEER research site
Waldstein/Weidenbrunnen, a spruce site located in the Fichtelgebirge Mountains in
North-Eastern Bavaria, which are challenging for their heterogeneity and orographically
structured terrain. Turbulence structure, advection, flux gradients of meteorological and
chemical quantities were observed within the first intensive observation period (IOP 1) in
September and October 2007. Observations of turbulence structure were obtained by a
vertical profile of sonic anemometers covering all parts of the forest up to the lower part of
the roughness sub layer. Field observations are complemented by simulations of ACASA
model (Advanced Canopy-Atmosphere-Soil Algorithm).
Integral turbulence characteristics, the normalized standard deviation of a turbulent
quantity, can be used to describe the structure of turbulence. A comparison between measured
and predicted values shows whether turbulence is fully developed or not and is therefore used
in quality assessment. For this quality control and as an input for models, when
measurements are not available, parameterizations for profiles are needed. Since there is
no uniform theory for those parameterizations inside a forest available, different
approaches were tested with data collected during the EGER IOP1. In order to
parameterize the integral turbulence characteristics of the wind components inside the
roughness sub layer a dimensionless height ζ = hc L-1 should be used instead of
ζ = z L-1, which is used above short vegetation. Profiles of integral turbulence
characteristics from different ecosystems show that the decrease inside the roughness
sub layer is similar but that parameterizations of profiles can not be generalized
due to different stand structures. Selecting the profiles of the integral turbulence
characteristics by coupling situations between the atmosphere above and inside the
stand did not reveal a significant different behavior than a selection according to
stratification above the canopy. A comparison between the measured values and
model results from the ACASA model showed a good agreement for the normalized
wind speed but the integral turbulence characteristics of the wind components were
usually overestimated above the canopy and underestimated inside the trunk space. |
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