Global simulations of monoterpene-derived peroxy radical fates and the distributions of highly oxygenated organic molecules (HOMs) and accretion products

Abstract. We evaluate monoterpene-derived peroxy radical (MT-RO2) unimolecular autoxidation and self- cross-reactions with other RO2 species in the GEOS-Chem global chemical transport model. The formation of associated highly oxygenated organic molecules (HOMs) accretion products are tracked competition bimolecular reactions. Autoxidation is dominant fate up to 6–8 km for first-generation MT-RO2, which can undergo H shifts. Reaction NO be a more common H-shift rate constants < 0.1 s−1 or at altitudes higher than 8 due imposed Arrhenius temperature dependence For MT-derived HOM-RO2, generated by multistep reaction predicted major throughout most boreal tropical forest regions, whereas dominates temperate subtropical forests Northern Hemisphere. newly added reactions result an approximate 4 % average decrease HO2 RO2, mainly faster self-/cross-reactions but impact upon HO2, OH, NOx abundances only important planetary boundary layer (PBL) over portions forests. Predicted HOM concentrations MT-rich regions seasons exceed total aerosol standard version model depending on parameters used. Comparisons observations reveal that large uncertainties remain key processes, especially respect photochemical lifetime volatility HOMs as well rates branching products. Further laboratory studies related MT-RO2-derived gas-phase product kinetics – their atmospheric fate, such gas–particle partitioning, multiphase chemistry, net secondary needed.