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| Titel |
Towards a more detailed representation of the energy balance in a coupled land surface model |
| VerfasserIn |
J. Ryder, J. Polcher, S. Luyssaert |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250067033
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| Zusammenfassung |
| Currently, the land-surface region sequesters 25% of global CO2 emissions. In addition to
climate change, increasing atmospheric CO2 concentrations, fertilisation and nitrogen
deposition, this sink is thought to be largely due to land management. When applied
deliberately to enhance the terrestrial carbon sink strength, this land management may have
unintended effects on the energy budget, potentially offsetting the radiative effect of carbon
sequestration.
As with other land surface models, the present release of ORCHIDEE (the land surface
model of the IPSL Earth system model) has difficulties in reproducing consistently observed
energy balances (Pitman et al., 2009; Jimenez et al., 2011; de Noblet-Ducoudré et al., 2011).
Hence, the model must be improved to be better able to study the radiative effect of forest
management and land use change. This observation serves as a starting point in this
research – improving the level of detail in energy balance simulations of the surface
layer.
We here outline the structure of a new detailed and practical simulation of the energy
budget that is currently under development within the surface model ORCHIDEE, and will be
coupled to the atmospheric model LMDZ.
The most detailed simulations of the surface layer energy budget are detailed iterative
multi-layer canopy models, such as Ogeé et al. (2003), which are linked to specific
measurement sites and do not interact with the atmosphere. In this current project, we aim to
create a model that will implement the insights obtained in those previous studies and
improve upon the present ORCHIDEE parameterisation, but will run stably and efficiently
when coupled to an atmospheric model.
This work involves a replacement of the existing allocation of 14 different types
of vegetation within each surface tile (the ’Plant Functional Types’) by a more
granular scheme that can be modified to reflect changes in attributes such as vegetation
density, leaf type, distribution (clumping factors), age and height of vegetation
within the surface tile. There will be the implementation of more than one canopy
vegetation layer to simulate the effects of scalar gradients within the canopy for
determining, more accurately, the net sensible and latent heat fluxes that are passed to the
atmosphere.
The model will include representation of characteristics such as in-canopy transport,
coupling with sensible heat flux from the soil, a multilayer radiation budget and stomatal
resistance, and interaction with the bare soil flux within the canopy space (and also
with snow pack). We present how the implicit coupling approach of Polcher et al.
(1998) and Best et al. (2004) is to be extended to a multilayer scenario, present
initial sensitivity studies and outline future testing scenarios and validation plans. |
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