Horizontal Patterns of CO2 Concentrations in Global Inversion Models, as Evaluated Against ACT-America Aircraft Data

CO2 concentrations can show substantial horizontal variability in the troposphere, up to 50 ppm in the daytime boundary layer. One contributor to this variability near the surface is that biogenic and anthropogenic fluxes of CO2 vary temporally and spatially, leading to, for example, seasonally-dependent latitudinal gradients of CO2 concentration. Another contributor to variability on the regional scale are synoptic weather systems, which can create regions of enhanced horizontal concentration gradients along frontal zones, but also can lead to both vertical and horizontal mixing, which tend to reduce gradients. Atmospheric inversions are a valuable tool for estimating CO2 surface fluxes on the regional scale. Inverse systems use prior flux models and tower or satellite CO2 mole fraction measurements to solve for an optimized posterior flux. Generally global inversion systems have horizontal grid spacings of 1-4°, limiting their ability to reproduce regional-scale CO2 gradients. Furt