Taking Regional Atmospheric Inversions to the Next Level: Lessons from the ACT-America Mission

The Atmospheric Carbon and Transport (ACT) – America, a NASA Earth-Venture Suborbital-2 mission, aims to drive regional atmospheric inversions to the next level of accuracy and precision by addressing primary observational and modeling gaps limiting this methodology. From 2016 through 2019 ACT-America deployed two research aircraft across the central and eastern United States in five flight campaigns covering all four seasons to observe the greenhouse gas (GHG) and meteorological structure of midlatitude weather systems. More than 1100 hours of flight data including continuous in situ measurement of GHGs, associated trace gases, and meteorological variables, roughly 2000 flask samples, and airborne lidar measurements of atmospheric layering and column CO 2 and CH 4 mole fractions were acquired. These data are being used to evaluate both the meteorological performance and the GHG distributions in numerical models used to construct atmospheric inverse flux estimates. Transport model fidelity can be evaluated (and improved) by comparison with airborne meteorological observations, especially atmospheric boundary layer winds and depth. Given well-constrained meteorology, airborne GHG mole fraction and trace gas data can be used to evaluate and improve models of GHG fluxes. Minimization of biases in these transport and flux models will improve inverse flux estimates. Further, the airborne meteorological and GHG observations provide the basis for the construction of regionally-, seasonally-calibrated atmospheric transport and GHG flux model ensembles, a step toward more realistic transport and flux error estimates and a critical component of more realistic uncertainties in atmospheric inverse flux estimates. Finally, under-flights of both the Orbiting Carbon Observatory – 2 and the TROPOMI satellite provide unique evaluation of the spatial performance of these GHG column observing systems. This evaluation of atmospheric transport, prior GHG flux estimates, and satellite GHG remote sensing is building the scientific basis for a new generation of regional atmospheric inverse flux estimates. This presentation will outline the ACT-America scientific plan, the database of airborne observations and model results that are available to the scientific community, and highlight major results to date.