Top-Down Estimates of Regional Carbon Fluxes over East Asia for 2010-2020 Using Satellite Observations

East Asia plays a crucial role in achieving carbon neutrality due to its significant fossil fuel emissions. Developing an accurate carbon budget for this region is vital, yet the flux estimates remain highly uncertain. To address this, our study utilized a Bayesian inverse method to optimize the annual Net Ecosystem Exchange (NEE) and Ocean Exchange across the East Asia domain from 2010 to 2020. We employed the GOSAT ACOS lite L2 v9r product in conjunction with forward simulations from the GEOS-Chem model version 13.1.0. Initially, we optimized global fluxes for the same period to minimize uncertainties in other regions before focusing on East Asia with much finer spatial resolutions. The study area encompasses China, North and South Korea, Japan, Taiwan, and adjacent oceanic areas (part of the Pacific Ocean). Prior uncertainties over land were significantly reduced due to the availability of abundant observational data, while reductions over the ocean were less pronounced due to limited data. We conducted a GEOS-Chem simulation for the same period to evaluate the accuracy of the optimized fluxes obtained through inverse modeling. The results, compared with ground-based and satellite observation data, showed reduced errors and confirmed strong performance. Our top-down carbon flux estimates contribute to a better understanding of the carbon budget and support the development of carbon net-zero policies for East Asian countries.