Development and Implementation of a Carbon Data Assimilation System for the Orbiting Carbon Observatory-2 (OCO-2) Mission

The GEOS-Carb modeling system at NASA's Global Modeling and Assimilation Office leverages the GEOS family of models to deliver a consistent set of land and ocean flux estimates. Recently as part of this system, we have been developing a top-down flux estimation capability that is designed to ingest high-density atmospheric CO₂ observations to estimate fluxes at high spatiotemporal resolutions. With the preliminary L2 data available from the Orbiting Carbon Observatory-2 (OCO-2) mission, the assimilation system will be used to examine: (a) the degree to which the OCO-2 total column observations (X_CO2) are constraining global fluxes with reasonable precision and accuracy, and (b) the degree to which these data provide additional information relative to the high precision but sparse in situ observations. In this study, we will show global flux estimates based on observations from OCO-2 and the in situ network. Evaluation of the flux estimates and posterior CO₂ concentrations will initially focus on two test regions: (a) North America, and (b) a region that is poorly constrained by the existing ground-based monitoring network, such as the Tropics and/or the Southern Hemisphere. The North American test region will enable us to compare flux estimates using OCO-2 observations relative to the constraints provided by the current in-situ monitoring network. On the other hand, the second test area will focus on a current data sparse region, and aim to augment knowledge about the carbon budget in that region. With continual improvements to the retrieval algorithm and/or increased availability of the OCO-2 data, we plan to refine these test cases to target areas where we observe anomalies in the X_CO2 distribution. Such anomalies indicate the possibility of previously unobserved fluxes and/or transport variability, and will be detected by comparing the OCO-2 L2 data with existing simulations from the GEOS-5 system.