Constraining Sector-specific CO2 Fluxes using Space-based XCO2 Observations over the Los Angeles Basin

The concentration of carbon dioxide (CO2) in the Earth’s atmosphere is rising due to anthropogenic activity, leading to significant concerns regarding climate change. In re- cent years, policy-driven carbon reduction efforts have been implemented at a variety of scales. Ensuring the effectiveness of such policies requires the monitoring of CO2 from urban areas, as they are responsible for roughly 70% of anthropogenic emissions globally. This work incorporated snapshot area maps (SAMs) from NASA’s Orbiting Car- bon Observatory-3 (OCO-3) within a Bayesian inversion framework to optimize sector- specific flux information from the Vulcan 3.0 emission inventory over the Los Angeles megacity between January 2020 and December 2021. Results demonstrate that the dense space-based observations of total column CO2 (XCO2) are capable of constraining temporal trends in multiple emission sectors and optimizing high-resolution emission inventories. Recording these trends provides a means to update the inventories used in policy-driven work. Specifically, reductions in the on-road transportation and industrial sectoral emissions were evident during the COVID-19 lockdown period and increases in the marine sector from 2020 to 2021 were also present. Conversely, other sectors were not optimized by the inversion. The characteristics of sectors that were favorable to optimization are discussed followed by suggestions for improvements and a framework for an operational carbon monitoring system.