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

Kazuhito Ichii*, Masahito Ueyama, Masayuki Kondo, Nobuko Saigusa, Joon Kim, Ma Carmelita Alberto, Jonas Ardö, Eugénie S. Euskirchen, Minseok Kang, Takashi Hirano, Joanna Joiner, Hideki Kobayashi, Luca Belelli Marchesini, Lutz Merbold, Akira Miyata, Taku M. Saitoh, Kentaro Takagi, Andrej Varlagin, M. Syndonia Bret-Harte, Kenzo KitamuraYoshiko Kosugi, Ayumi Kotani, Kireet Kumar, Sheng Gong Li, Takashi Machimura, Yojiro Matsuura, Yasuko Mizoguchi, Takeshi Ohta, Sandipan Mukherjee, Yuji Yanagi, Yukio Yasuda, Yiping Zhang, Fenghua Zhao

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The lack of a standardized database of eddy covariance observations has been an obstacle for data-driven estimation of terrestrial CO2 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 CO2 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 CO2 fluxes shows that although performance varies in different vegetation and climate classifications, GPP and NEE at 8 days are reproduced (e.g., r2 = 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 (r2 = 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 CO2 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 CO2 fluxes from SVR-NEE and GOSAT Level 4A were partially explained by accounting for the differences in the definition of land CO2 fluxes. These data-driven estimates can provide a new opportunity to assess CO2 fluxes in Asia and evaluate and constrain terrestrial ecosystem models.

Original languageEnglish
Pages (from-to)767-795
Number of pages29
JournalJournal of Geophysical Research: Biogeosciences
Volume122
Issue number4
DOIs
Publication statusPublished - 1 Apr 2017

Keywords

  • Asia
  • data-driven model
  • eddy covariance data
  • remote sensing
  • terrestrial CO flux
  • upscaling

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