Geosci. Model Dev. Discuss., 6, 3977-4008, 2013
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This discussion paper has been under review for the journal Geoscientific Model Development (GMD). Please refer to the corresponding final paper in GMD.
The North American Carbon Program Multi-scale synthesis and Terrestrial Model Intercomparison Project – Part 1: Overview and experimental design
D. N. Huntzinger1, C. Schwalm2, A. M. Michalak3, K. Schaefer4,5, A. W. King6, Y. Wei6, A. Jacobson4,7, S. Liu6, R. B. Cook6, W. M. Post6, G. Berthier8, D. Hayes6, M. Huang9, A. Ito10, H. Lei11,12, C. Lu13, J. Mao6, C. H. Peng14,15, S. Peng8, B. Poulter8, D. Riccuito6, X. Shi6, H. Tian13, W. Wang16, N. Zeng17, F. Zhao17, and Q. Zhu15
1School of Earth Sciences and Environmental Sustainability and the Department of Civil Engineering, Construction Management, and Environmental Engineering, Northern Arizona University, P.O. Box 5694, Flagstaff, Arizona 86011-5694, USA
2School of Earth Sciences and Environmental Sustainability, Northern Arizona University, USA
3Department of Global Ecology, Carnegie Institution for Science, Stanford, California, USA
4National Snow and Ice Data Center, Boulder, Colorado, USA
5Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA
6Earth Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
7NOAA Earth System Research Lab Global Monitoring Division, Boulder, Colorado, USA
8Laboratoire des Sciences du Climat et de l'Environnement, LSCE, Gif sur Yvette, France
9Fundamental & Computational Sciences, Pacific Northwest National Laboratory, Richland, Washington, USA
10National Institute for Environmental Studies, Tsukuba, Japan, USA
11Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, Washington, USA
12State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing, China
13International Center for Climate and Global Change Research and School of Forestry and Wildlife Sciences, Auburn University, Auburn, Alabama, USA
14Department of Biology Sciences, Institute of Environment Sciences, University of Quebec at Montreal, C.P. 8888, Succ. Centre-Ville, Montreal H3C 3P8, Canada
15Laboratory for Ecological Forecasting and Global Change, College of Forestry, Northwest A&F University, Yangling, Shaanxi 712100, China
16Ames Research Center, National Aeronautics and Space Administration, Moffett Field, California, USA
17Department of Atmospheric and Oceanic Science, University of Maryland, College Park, Maryland, USA

Abstract. Terrestrial biosphere models (TBMs) have become an integral tool for extrapolating local observations and understanding of land-atmosphere carbon exchange to larger regions. The North American Carbon Program (NACP) Multi-scale synthesis and Terrestrial Model Intercomparison Project (MsTMIP) is a formal model intercomparison and evaluation effort focused on improving the diagnosis and attribution of carbon exchange at regional and global scales. MsTMIP builds upon current and past synthesis activities, and has a unique framework designed to isolate, interpret, and inform understanding of how model structural differences impact estimates of carbon uptake and release. Here we provide an overview of the MsTMIP effort and describe how the MsTMIP experimental design enables the assessment and quantification of TBM structural uncertainty. Model structure refers to the types of processes considered (e.g. nutrient cycling, disturbance, lateral transport of carbon), and how these processes are represented (e.g. photosynthetic formulation, temperature sensitivity, respiration) in the models. By prescribing a common experimental protocol with standard spin-up procedures and driver data sets, we isolate any biases and variability in TBM estimates of regional and global carbon budgets resulting from differences in the models themselves (i.e. model structure) and model-specific parameter values. An initial intercomparison of model structural differences is represented using hierarchical cluster diagrams (a.k.a. dendrograms), which highlight similarities and differences in how models account for carbon cycle, vegetation, energy, and nitrogen cycle dynamics. We show that, despite the standardized protocol used to derive initial conditions, models show a high degree of variation for GPP, total living biomass, and total soil carbon, underscoring the influence of differences in model structure and parameterization on model estimates.

Citation: Huntzinger, D. N., Schwalm, C., Michalak, A. M., Schaefer, K., King, A. W., Wei, Y., Jacobson, A., Liu, S., Cook, R. B., Post, W. M., Berthier, G., Hayes, D., Huang, M., Ito, A., Lei, H., Lu, C., Mao, J., Peng, C. H., Peng, S., Poulter, B., Riccuito, D., Shi, X., Tian, H., Wang, W., Zeng, N., Zhao, F., and Zhu, Q.: The North American Carbon Program Multi-scale synthesis and Terrestrial Model Intercomparison Project – Part 1: Overview and experimental design, Geosci. Model Dev. Discuss., 6, 3977-4008, doi:10.5194/gmdd-6-3977-2013, 2013.
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