1. New Data-Driven Estimation of Terrestrial CO2 Fluxes in Asia Using a Standardized Database of Eddy Covariance Measurements, Remote Sensing Data, and Support Vector Regression
- Author
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Ichii, Kazuhito, Ueyama, Masahito, Kondo, Masayuki, Saigusa, Nobuko, Kim, Joon, Alberto, Ma. Carmelita, Ardö, Jonas, Euskirchen, Eugénie S, Kang, Minseok, Hirano, Takashi, Joiner, Joanna, Kobayashi, Hideki, Marchesini, Luca Belelli, Merbold, Lutz, Miyata, Akira, Saitoh, Taku M, Takagi, Kentaro, Varlagin, Andrej, Bret-Harte, M. Syndonia, Kitamura, Kenzo, Kosugi, Yoshiko, Kotani, Ayumi, Kumar, Kireet, Li, Sheng-Gong, Machimura, Takashi, Matsuura, Yojiro, Mizoguchi, Yasuko, Ohta, Takeshi, Mukherjee, Sandipan, Yanagi, Yuji, Yasuda, Yukio, Zhang, Yiping, and Zhao, Fenghua
- Subjects
Earth Resources And Remote Sensing - Abstract
The lack of a standardized database of eddy covariance observations has been an obstacle for data-driven estimation of terrestrial carbon dioxide fluxes in Asia. In this study, we developed such a standardized database using 54 sites from various databases by applying consistent postprocessing for data-driven estimation of gross primary productivity (GPP) and net ecosystem carbon dioxide exchange (NEE). Data-driven estimation was conducted by using a machine learning algorithm: support vector regression (SVR), with remote sensing data for 2000 to 2015 period. Site-level evaluation of the estimated carbon dioxide fluxes shows that although performance varies in different vegetation and climate classifications, GPP and NEE at 8 days are reproduced (e.g., r (exp 2) =0.73 and 0.42 for 8 day GPP and NEE). Evaluation of spatially estimated GPP with Global Ozone Monitoring Experiment 2 sensor-based Sun-induced chlorophyll fluorescence shows that monthly GPP variations at subcontinental scale were reproduced by SVR (r (exp 2)=1.00, 0.94, 0.91, and 0.89 for Siberia, East Asia, South Asia, and Southeast Asia, respectively). Evaluation of spatially estimated NEE with net atmosphere-land carbon dioxide fluxes of Greenhouse Gases Observing Satellite (GOSAT) Level 4A product shows that monthly variations of these data were consistent in Siberia and East Asia; meanwhile, inconsistency was found in South Asia and Southeast Asia. Furthermore, differences in the land carbon dioxide fluxes from SVR-NEE and GOSAT Level 4A were partially explained by accounting for the differences in the definition of land carbon dioxide fluxes. These data-driven estimates can provide a new opportunity to assess carbon dioxide fluxes in Asia and evaluate and constrain terrestrial ecosystem models.
- Published
- 2017
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