Methane Oxidation Chain Data Assimilation in GEOS-Chem Adjoint

The archive includes a frozen version of the GEOS-Chem adjoint model code used for methane oxidation chain four-dimensional variational (4D-Var) inversions. Assimilated tracers include methane, HCHO, CO, and MCF. 

For a full description see:
Yu, X., Millet, D. B., Henze, D. K., Worden, H., Vigouroux, C., Patra, P., Hill, J. D., and Jackson, R. B.: Multi-species constraints resolve methane source versus sink changes: lessons from 2020. Earth’s Future, 14, e2025EF007067, 10.1029/2025EF007067, 2026.