Abstract
High spatial resolution carbon dioxide (CO2) flux inversion systems are needed to support the global stocktake required by the Paris Agreement and to complement the bottom-up emission inventories. Based on the work of Zhang, a regional CO2 flux inversion system capable of assimilating the column-averaged dry air mole fractions of CO2 (XCO2) retrieved from Orbiting Carbon Observatory-2 (OCO-2) observations had been developed. To evaluate the system, under the constraints of the initial state and boundary conditions extracted from the CarbonTracker 2017 product (CT2017), the annual CO2 flux over the contiguous United States in 2016 was inverted (1.08 Pg C yr−1) and compared with the corresponding posterior CO2 fluxes extracted from OCO-2 model intercomparison project (OCO-2 MIP) (mean: 0.76 Pg C yr−1, standard deviation: 0.29 Pg C yr−1, 9 models in total) and CT2017 (1.19 Pg C yr−1). The uncertainty of the inverted CO2 flux was reduced by 14.71% compared to the prior flux. The annual mean XCO2 estimated by the inversion system was 403.67 ppm, which was 0.11 ppm smaller than the result (403.78 ppm) simulated by a parallel experiment without assimilating the OCO-2 retrievals and closer to the result of CT2017 (403.29 ppm). Independent CO2 flux and concentration measurements from towers, aircraft, and Total Carbon Column Observing Network (TCCON) were used to evaluate the results. Mean bias error (MBE) between the inverted CO2 flux and flux measurements was 0.73 g C m−2 d−1, was reduced by 22.34% and 28.43% compared to those of the prior flux and CT2017, respectively. MBEs between the CO2 concentrations estimated by the inversion system and concentration measurements from TCCON, towers, and aircraft were reduced by 52.78%, 96.45%, and 75%, respectively, compared to those of the parallel experiment. The experiment proved that CO2 emission hotspots indicated by the inverted annual CO2 flux with a relatively high spatial resolution of 50 km consisted well with the locations of most major metropolitan/urban areas in the contiguous United States, which demonstrated the potential of combing satellite observations with high spatial resolution CO2 flux inversion system in supporting the global stocktake.
Highlights
1.08 ± 0.03 Pg C yr−1, which was more in line with the fluxes estimated by CarbonTracker 2017 product (CT2017) and the models from Orbiting Carbon Observatory-2 (OCO-2) model intercomparison project (MIP)
A regional CO2 flux inversion system had been developed from WRF-Chem model coupled with DART using the ensemble adjustment Kalman filter (EAKF) assimilation method to invert regional CO2 flux from
The uncertainty of the inverted annual CO2 flux was reduced by 14.71%
Summary
The significant increase of carbon dioxide (CO2 ) in the atmosphere caused by anthropogenic activities is believed to be one of the main driving creativecommons.org/licenses/by/ 4.0/). The atmospheric CO2 concentration has increased from 277 parts per million (ppm) in 1750 to above 409 ppm in 2019 [2]. In order to mitigate climate change, the Paris Agreement [3], a legally binding international treaty on climate change, was adopted at the 21st Conference of the Parties of the United Nations Framework Convention on Climate Change (UNFCCC) and entered into force on November 4, 2016. The Paris Agreement [3] requires all parties to submit their emission reduction plans in the form of nationally determined contributions (NDC).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
