Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 7 7 2010 10.5194/bg-7-2061-2010 http://www.biogeosciences.net/7/2061/2010/ http://www.biogeosciences.net/7/2061/2010/bg-7-2061-2010.html http://www.biogeosciences.net/7/2061/2010/bg-7-2061-2010.pdf 2061 2080 2010-07-02 Multi-model analysis of terrestrial carbon cycles in Japan: limitations and implications of model calibration using eddy flux observations K. Ichii kazuhito.ichii@gmail.com T. Suzuki T. Kato A. Ito T. Hajima M. Ueyama T. Sasai R. Hirata N. Saigusa Y. Ohtani K. Takagi Faculty of Symbiotic Systems Science, Fukushima University, 1 Kanayagawa, Fukushima, 960-1296, Japan Japan Agency for Marine-Earth Science and Technology, 3173-25, Showamachi, Kanazawa, Yokohama, 236-0001, Japan QUEST, Department of Earth Science, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ, UK National Institute for Environmental Studies, 16-2, Onogawa, Tsukuba, 305-8506, Japan Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka, 599-8531, Japan Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa, Nagoya, 464-8601, Japan Graduate School of Agriculture, Hokkaido University, Kita 9 Nishi 9, Kita-ku, Sapporo, 060-8589, Japan Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, 305-8687, Japan Field Science Center for Northern Biosphere, Hokkaido University, Toikanbetsu, Horonobe, 098-2943, Japan 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. 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