Revisiting the global atmospheric glyoxal budget: updates in secondary production pathways and evaluations against satellite observations

Glyoxal (CHOCHO) serves as a critical marker for the oxidation capacities of volatile organic compounds (VOCs) and acts as a precursor to secondary organic aerosols. Nonetheless, the sources and chemical reaction pathways of glyoxal have not been updated, which results in global simulations underestimating the observed concentrations of glyoxal. We have enhanced the representation of glyoxal sources and sinks through laboratory experiments, a comprehensive MCM chemical scheme, and diverse observational data. Within the GEOS-Chem chemical transport model, the revised glyoxal parameterizations reduced the model's underestimation from 80% (72%~85%) to 17% (5%~32%), compared with TROPOMI satellite retrievals. This advancement is attributed to the increased glyoxal yield from isoprene photooxidation (from 5% to 15%) and the incorporation of a glyoxal source over the marine boundary layer (78 Tg/yr). Following the inclusion of the marine source, the global burden of glyoxal augmented by a factor of 1.4, signifying enhanced oxidation over the remote ocean. This investigation elucidates an improved global budget of glyoxal, underscoring the necessity to refine the photochemical processes of biogenic OVOCs and to address the oxidation states of OVOCs in remote oceanic regions.