Continued Evaluation of OCO-2 Small-Scale Variability Using Lidar and In Situ CO2 Observations from the ACT-America Campaign

NASA's Atmospheric Carbon and Transport - America (ACT-America) field campaign provides the unique opportunity to validate small-scale satellite column CO₂ measurements. The Orbiting Carbon Observatory 2 (OCO-2) satellite provides a robust XCO₂ dataset on a global scale, but the sparseness of ground-based networks makes validation on the finest OCO-2 resolutions, 1-10km, a challenge. After four complete ACT-America field campaigns, the Multi-functional Fiber Laser LIDAR (MFLL) instrument has completed nine underflights of OCO-2, allowing for direct spatial comparison of the two datasets over several North American regions. Comparisons show a respectable level of agreement between satellite- and LIDAR-observed XCO₂ gradients over the course of several hundred kilometers, but little agreement on smaller scales. Further comparisons to models and in situ column data, including two-dimensional CO₂ "curtains" constructed from in situ data along the flight track, show varying levels of spatial correlation and reveal idiosyncrasies in each dataset that must be considered in comparison evaluation. There is also evidence that the OCO-2 data remain contaminated to some degree by 3-D cloud effects, motivating current work by the science team on the identification and mitigation of such effects. In this work, we show key comparisons to date and attempt to draw conclusions on the fidelity of the remotely-sensed CO₂ gradients, including our ability to reconstruct these gradients using the curtain approach.