Improving Regional Estimates of Surface Emissions Using Geostationary and Polar Orbit Satellite Observations: A Proof of Concept for GeoCARB and ASCENDS

Two future satellite missions propose to measure total column CO₂ in different ways. The Active Sensing of CO₂ Emissions over Days, Nights and Seasons will be an active measurement that employs a lidar with online and offline frequencies in the portion of spectrum for which CO₂ is strongly absorbing. The narrow beam width will provide low biases and full earth coverage every 16 days. By comparison, the GeoCARB platform will provide a geostationary view of the total column CO₂ over a limited area domain, about a quarter of the globe. This limited area, high time resolution measurement is ideally suited for improved estimation of regional fluxes.

Past studies have shown that the results of a regional flux estimation are sensitive to boundary conditions, which must be provided to the inversion system to fully specify the problem. The combination of these two measurement platforms would allow researchers for the first time to simultaneously estimate both the global and regional emissions in a consistent way.

In this paper, the authors will describe a series of Observing Systems Simulation Experiments that point out the promise of these two instruments being used in tandem for flux estimation. Different metrics will show the impact of each instrument alone in terms of reducing the posterior uncertainty, as well as their impact when used simultaneously for better understanding smaller scale sources and sinks, such as megacities and terrestrial biomes.