06 Dec 2022
06 Dec 2022
Status: this preprint is currently under review for the journal ACP.

The carbon sink in China as seen from GOSAT with a regional inversion system based on CMAQ and EnSRF

Xingxia Kou1, Zhen Peng2, Meigen Zhang3,4, Fei Hu3,4, Xiao Han3,4, Ziming Li5, and Lili Lei2,6 Xingxia Kou et al.
  • 1Institute of Urban Meteorology, China Meteorological Administration, Beijing, China
  • 2School of Atmospheric Sciences, Nanjing University, Nanjing, China
  • 3State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
  • 4University of Chinese Academy of Sciences, Beijing, China
  • 5Beijing Meteorological Observatory, Beijing, China
  • 6Key Laboratory of Mesoscale Severe Weather, Ministry of Education, Nanjing University, Nanjing, China

Abstract. Top-down inversions of China’s terrestrial carbon sink are known to be uncertain because of errors related to the relatively coarse resolution of global transport models and the sparseness of in situ observations. Taking advantage of regional chemistry transport models for mesoscale simulation and spaceborne sensors for spatial coverage, Greenhouse Gases Observing Satellite (GOSAT) column-mean dry mole fraction of carbon dioxide (XCO2) retrievals were introduced in the Models-3 Community Multi-scale Air Quality (CMAQ) and Ensemble Square Root Filter (EnSRF)-based regional inversion system to constrain China’s biosphere sink at a spatiotemporal resolution of 64 km and 1 h. In general, the annual, monthly and daily variation in biosphere flux was reliably delivered, attributable to the novel flux forecast model, reasonable CMAQ background simulation, well-designed observational operator, and joint data assimilation scheme (JDAS) of CO2 concentrations and fluxes. The size of the assimilated biosphere sink in China was −0.47 PgC yr−1, which was consistent with most global estimates (i.e., −0.27 to −0.68 PgC yr−1), indicating that the regional inversion system was sufficient to robustly constrain the control vectors. Furthermore, the seasonal patterns were recalibrated well, with a growing season that shifted earlier in the year over central and south China. Moreover, the provincial-scale biosphere flux was re-estimated, and the difference between the a posteriori and a priori flux ranged from −7.03 TgC yr−1 in Heilongjiang to 2.95 TgC yr−1 in Shandong. Additionally, better performance of the a posteriori flux in contrast to the a priori flux was proven when the simulation was fitted to independent observations, indicating improved results in JDAS. This study serves as a basis for future regional- and urban-scale top-down carbon assimilation.

Xingxia Kou et al.

Status: open (until 15 Feb 2023)

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  • RC1: 'Comment on acp-2022-777', Anonymous Referee #1, 19 Jan 2023 reply

Xingxia Kou et al.

Xingxia Kou et al.


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Short summary
A CMAQ EnSRF-based regional inversion system was extended to resolve satellite retrievals into biogenic source–sink changes. The size of the assimilated biosphere sink in China inferred from GOSAT was −0.47 PgC yr−1. The biosphere flux at the provincial scale was re-estimated following the refined description in the regional inversion.