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| Titel |
Do we (need to) care about canopy radiation schemes in DGVMs? Caveats and potential impacts |
| VerfasserIn |
A. Loew, P. M. van Bodegom, J.-L. Widlowski, J. Otto, T. Quaife, B. Pinty, T. Raddatz |
| 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 ; 11, no. 7 ; Nr. 11, no. 7 (2014-04-08), S.1873-1897 |
| Datensatznummer |
250117347
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| Publikation (Nr.) |
 copernicus.org/bg-11-1873-2014.pdf |
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| Zusammenfassung |
Dynamic global vegetation models (DGVMs) are an essential part of current
state-of-the-art Earth system models. In recent years, the complexity of
DGVMs has increased by incorporating new important processes like,
e.g., nutrient cycling and land cover dynamics, while biogeophysical
processes like surface radiation have not been developed much further. Canopy
radiation models are however very important for the estimation of absorption
and reflected fluxes and are essential for a proper estimation of surface
carbon, energy and water fluxes.
The present study provides an overview of current implementations of canopy
radiation schemes in a couple of state-of-the-art DGVMs and assesses their
accuracy in simulating canopy absorption and reflection for a variety of
different surface conditions. Systematic deviations in surface albedo and
fractions of absorbed photosynthetic active radiation (faPAR) are identified
and potential impacts are assessed.
The results show clear deviations for both, absorbed and reflected, surface
solar radiation fluxes. FaPAR is typically underestimated, which results in
an underestimation of gross primary productivity (GPP) for the investigated
cases. The deviation can be as large as 25% in extreme cases. Deviations
in surface albedo range between −0.15 ≤ Δα ≤ 0.36,
with a slight positive bias on the order of Δα ≈ 0.04.
Potential radiative forcing caused by albedo deviations is estimated at
−1.25 ≤ RF ≤ −0.8 (W m−2), caused by neglect of the
diurnal cycle of surface albedo.
The present study is the first one that provides an assessment of canopy RT
schemes in different currently used DGVMs together with an assessment of the
potential impact of the identified deviations. The paper illustrates that
there is a general need to improve the canopy radiation schemes in DGVMs and
provides different perspectives for their improvement. |
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