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| Titel |
Quantifying the coupling degree between land surface and the atmospheric boundary layer with the coupled vegetation-atmosphere model HIRVAC |
| VerfasserIn |
V. Goldberg, Ch. Bernhofer |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 19, no. 5 ; Nr. 19, no. 5, S.581-587 |
| Datensatznummer |
250014256
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| Publikation (Nr.) |
 copernicus.org/angeo-19-581-2001.pdf |
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| Zusammenfassung |
In the present study, the
ability of different indices to quantify the coupling degree between a vegetated
surface and the atmospheric boundary layer is tested. For this purpose, a
one-and-a-half dimensional atmospheric boundary layer model, including a high
resolved vegetation canopy, was applied (HIRVAC) and indices, such as the
decoupling factor Ω, as well as other measures derived from model
out-put were used. The aim of the study was to show that the quite complex
coupling and feedback mechanisms can be described with these relatively simple
measures. Model results illustrate that the vegetation and the atmosphere are
well coupled (expressed by a lower Ω) under conditions of a tall and
dense canopy, as well as under strong dynamic forcing. This better aerodynamic
coupling leads to an increase in evapotranspiration, as well as an increase in
the evaporative fraction. This fact was also shown by the second coupling
measure: the relative changes in daily model evapotranspiration. This measure
was inspired by the assumption that these changes are primarily dependent on the
coupling degree between the surface and the atmosphere, if the other boundary
conditions in the model are fixed. A third sensitivity measure was used
according to Jacobs and de Bruin (1992). It shows that the sensitivity of
evaporative fraction to stomata resistance is much higher with a better
aerodynamic coupling. The results of the factor Ω; are in a good
agreement with the findings of Jacobs and de Bruin: they stress that it is a
valuable strategy to group vegetation into two simple categories (smooth and
rough) for the understanding of vegetation-atmosphere coupling.
Key words. Atmospheric composition
and structure (biosphere- atmosphere interactions) – Hydrology (evapotranspiration;
hydroclimatology) |
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