Towards Top-down Constraints on Regional Sources and Sinks of CO2 Imposed by Column Observations: a High-resolution Inverse Modeling Approach

Abstract:

Carbon dioxide is monitored around the world by a number of different observation platforms including space-based observing systems. In recent years, satellite instruments have been effectively enhanced with their spatiotemporal sampling and precision strategies, with a focus on improving the confidence levels in the source-sink estimations at spatial scales relevant for policy-makers. However, accurately identifying the regional sources and sinks of CO₂ using the available observations and techniques is highly complicated due to their insufficient spatial and temporal representativeness that misses the detailed information about the processes and the transport. Here, we will demonstrate the potential of space-borne monitoring of the CO₂ column on inferring sources and sinks of CO₂ at the regional scale. One of the main goals of this study is to assess the capability of a proposed satellite mission, Carbon Monitoring Satellite (CarbonSat), to quantify emission patterns of moderate to strong localized sources, taking into account a realistic description of the retrieval errors, the spatiotemporal distributions of CO₂ and atmospheric transport. CarbonSat will provide measurements of the column averaged mixing ratios of CO₂ and CH₄ at a high spatial resolution (2km x 3km) over the entire globe with contiguous sampling over a 200 km wide swath. In this study, we use a high-resolution modeling framework consisting of the Weather Research Forecasting model with greenhouse gas module (WRF-GHG) and the Vegetation Photosynthesis Respiration Model (VPRM), to simulate CO₂ concentrations for a domain centered on Berlin in Germany (a typical mid-scale city). An analysis is carried out for CarbonSat’s overpasses (using pseudo observations) for one reference year. A simple Bayesian inversion is performed to estimate the emission budget with associated uncertainty. Additionally, results from our preliminary analysis using observations from Orbiting Carbon Observatory-2 (OCO-2) to assess the usefulness of these column measurements to estimate the regional distribution of CO₂ surface fluxes will be presented.