Preprints
https://doi.org/10.5194/egusphere-2024-1568
https://doi.org/10.5194/egusphere-2024-1568
14 Jun 2024
 | 14 Jun 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

The role of OCO-3 XCO2 retrievals in estimating global terrestrial net ecosystem exchanges

Xingyu Wang, Fei Jiang, Hengmao Wang, Zhengqi Zhang, Mousong Wu, Jun Wang, Wei He, Weimin Ju, and Jingming Chen

Abstract. Satellite-based column-averaged dry air CO2 mole fraction (XCO2) retrievals are frequently used to improve the estimates of terrestrial net carbon exchanges (NEE). The Orbiting Carbon Observatory 3 (OCO-3) satellite, launched in May 2019, was designed to address important questions about the distribution of carbon fluxes on Earth, but its role in estimating global terrestrial NEE remains unclear. Here, using the Global Carbon Assimilation System, version 2, we investigate the impact of OCO-3 XCO2 on the estimation of global NEE by assimilating the OCO-3 XCO2 retrievals alone and in combination with the OCO-2 XCO2 retrievals. The results show that when only the OCO-3 XCO2 is assimilated (Exp_OCO3), the estimated global land sink is significantly lower than that from the OCO-2 experiment (Exp_OCO2). The estimate from the joint assimilation of OCO-3 and OCO-2 (Exp_OCO3&2) is comparable on a global scale to that of Exp_OCO2. However, there are significant regional differences. Compared to the observed global annual CO2 growth rate, Exp_OCO3 has the largest bias, and Exp_OCO3&2 shows the best performance. Furthermore, validation with independent CO2 observations shows that the biases of the Exp_OCO3 are significantly larger than those of Exp_OCO2 and Exp_OCO3&2 at mid and high latitudes, probably due to the fact that OCO-3 only has observations from 52° S to 52° N. Our study indicates that assimilating OCO-3 XCO2 retrievals alone leads to an underestimation of land sinks at high latitudes, and that a joint assimilation of OCO-2 and OCO-3 XCO2 retrievals is required for a better estimation of global terrestrial NEE.

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Xingyu Wang, Fei Jiang, Hengmao Wang, Zhengqi Zhang, Mousong Wu, Jun Wang, Wei He, Weimin Ju, and Jingming Chen

Status: open (until 11 Aug 2024)

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Xingyu Wang, Fei Jiang, Hengmao Wang, Zhengqi Zhang, Mousong Wu, Jun Wang, Wei He, Weimin Ju, and Jingming Chen
Xingyu Wang, Fei Jiang, Hengmao Wang, Zhengqi Zhang, Mousong Wu, Jun Wang, Wei He, Weimin Ju, and Jingming Chen

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Short summary
The role of Orbital Carbon Observatory 3 (OCO-3) satellites in estimating the global terrestrial near-Earth environment is unclear. So we study it by assimilating OCO-3 XCO2 alone and with OCO-2 XCO2 inversion. We found that assimilation OCO-3 XCO2 underestimated land sinks at high latitudes by retrieval alone. Joint assimilation of OCO-2 and OCO-3 XCO2 needs to be retrieved to better estimate global terrestrial NEEs.