Articles | Volume 7, issue 7
Biogeosciences, 7, 2061–2080, 2010

Special issue: CarboEastAsia

Biogeosciences, 7, 2061–2080, 2010

  02 Jul 2010

02 Jul 2010

Multi-model analysis of terrestrial carbon cycles in Japan: limitations and implications of model calibration using eddy flux observations

K. Ichii1, T. Suzuki1, T. Kato2,3, A. Ito2,4, T. Hajima2, M. Ueyama5, T. Sasai6, R. Hirata7, N. Saigusa4, Y. Ohtani8, and K. Takagi9 K. Ichii et al.
  • 1Faculty of Symbiotic Systems Science, Fukushima University, 1 Kanayagawa, Fukushima, 960-1296, Japan
  • 2Japan Agency for Marine-Earth Science and Technology, 3173-25, Showamachi, Kanazawa, Yokohama, 236-0001, Japan
  • 3QUEST, Department of Earth Science, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ, UK
  • 4National Institute for Environmental Studies, 16-2, Onogawa, Tsukuba, 305-8506, Japan
  • 5Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka, 599-8531, Japan
  • 6Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa, Nagoya, 464-8601, Japan
  • 7Graduate School of Agriculture, Hokkaido University, Kita 9 Nishi 9, Kita-ku, Sapporo, 060-8589, Japan
  • 8Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, 305-8687, Japan
  • 9Field Science Center for Northern Biosphere, Hokkaido University, Toikanbetsu, Horonobe, 098-2943, Japan

Abstract. Terrestrial biosphere models show large differences when simulating carbon and water cycles, and reducing these differences is a priority for developing more accurate estimates of the condition of terrestrial ecosystems and future climate change. To reduce uncertainties and improve the understanding of their carbon budgets, we investigated the utility of the eddy flux datasets to improve model simulations and reduce variabilities among multi-model outputs of terrestrial biosphere models in Japan. Using 9 terrestrial biosphere models (Support Vector Machine – based regressions, TOPS, CASA, VISIT, Biome-BGC, DAYCENT, SEIB, LPJ, and TRIFFID), we conducted two simulations: (1) point simulations at four eddy flux sites in Japan and (2) spatial simulations for Japan with a default model (based on original settings) and a modified model (based on model parameter tuning using eddy flux data). Generally, models using default model settings showed large deviations in model outputs from observation with large model-by-model variability. However, after we calibrated the model parameters using eddy flux data (GPP, RE and NEP), most models successfully simulated seasonal variations in the carbon cycle, with less variability among models. We also found that interannual variations in the carbon cycle are mostly consistent among models and observations. Spatial analysis also showed a large reduction in the variability among model outputs. This study demonstrated that careful validation and calibration of models with available eddy flux data reduced model-by-model differences. Yet, site history, analysis of model structure changes, and more objective procedure of model calibration should be included in the further analysis.

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