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Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
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Volume 7, issue 6
Geosci. Model Dev., 7, 2581-2597, 2014
https://doi.org/10.5194/gmd-7-2581-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Geosci. Model Dev., 7, 2581-2597, 2014
https://doi.org/10.5194/gmd-7-2581-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Development and technical paper 10 Nov 2014

Development and technical paper | 10 Nov 2014

Model–data fusion across ecosystems: from multisite optimizations to global simulations

S. Kuppel1,2, P. Peylin1, F. Maignan1, F. Chevallier1, G. Kiely3, L. Montagnani4, and A. Cescatti5 S. Kuppel et al.
  • 1Laboratoire des Sciences du Climat et de l'Environnement, UMR 8212 CEA-CNRS-UVSQ, 91191 Gif-sur-Yvette CEDEX, France
  • 2Grupo de Estudios Ambientales, IMASL – CONICET/Universidad Nacional de San Luis, Ejército de los Andes 950, D5700HHW San Luis, Argentina
  • 3Civil and Environmental Engineering Department, and Environmental Research Institute, University College Cork, Cork, Ireland
  • 4Forest Services, Autonomous Province of Bolzano, 39100 Bolzano, Italy
  • 5European Commission, Joint Research Center, Institute for Environment and Sustainability, Ispra, Italy

Abstract. This study uses a variational data assimilation framework to simultaneously constrain a global ecosystem model with eddy covariance measurements of daily net ecosystem exchange (NEE) and latent heat (LE) fluxes from a large number of sites grouped in seven plant functional types (PFTs). It is an attempt to bridge the gap between the numerous site-specific parameter optimization works found in the literature and the generic parameterization used by most land surface models within each PFT. The present multisite approach allows deriving PFT-generic sets of optimized parameters enhancing the agreement between measured and simulated fluxes at most of the sites considered, with performances often comparable to those of the corresponding site-specific optimizations. Besides reducing the PFT-averaged model–data root-mean-square difference (RMSD) and the associated daily output uncertainty, the optimization improves the simulated CO2 balance at tropical and temperate forests sites. The major site-level NEE adjustments at the seasonal scale are reduced amplitude in C3 grasslands and boreal forests, increased seasonality in temperate evergreen forests, and better model–data phasing in temperate deciduous broadleaf forests. Conversely, the poorer performances in tropical evergreen broadleaf forests points to deficiencies regarding the modelling of phenology and soil water stress for this PFT. An evaluation with data-oriented estimates of photosynthesis (GPP – gross primary productivity) and ecosystem respiration (Reco) rates indicates distinctively improved simulations of both gross fluxes. The multisite parameter sets are then tested against CO2 concentrations measured at 53 locations around the globe, showing significant adjustments of the modelled seasonality of atmospheric CO2 concentration, whose relevance seems PFT-dependent, along with an improved interannual variability. Lastly, a global-scale evaluation with remote sensing NDVI (normalized difference vegetation index) measurements indicates an improvement of the simulated seasonal variations of the foliar cover for all considered PFTs.

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A consistent calibration of an advanced land surface model was performed by grouping in situ information on land-atmosphere exchanges of carbon and water using broad ecosystem and climate classes. Signatures of improved carbon cycle simulations were found across spatial and temporal scales, along with insights into current model limitations. These results hold promising perspectives within the ongoing efforts towards building robust model-data fusion frameworks for earth system models.
A consistent calibration of an advanced land surface model was performed by grouping in situ...
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