H₂O₂ and CH₃OOH (MHP) in the Remote Atmosphere: 2. Physical and Chemical Controls

Hydrogen peroxide (Hâ‚‚Oâ‚‚) and methyl hydroperoxide (MHP, CH₃OOH) serve as HOâ‚“ (OH and HOâ‚‚ radicals) reservoirs and therefore as useful tracers of HOâ‚“ chemistry. Both hydroperoxides were measured during the 2016–2018 Atmospheric Tomography Mission as part of a global survey of the remote troposphere over the Pacific and Atlantic Ocean basins conducted using the NASA DC-8 aircraft. To assess the relative contributions of chemical and physical processes to the global hydroperoxide budget and their impact on atmospheric oxidation potential, we compare the observations with two models, a diurnal steady-state photochemical box model and the global chemical transport model Goddard Earth Observing System (GEOS)-Chem. We find that the models systematically under-predict Hâ‚‚Oâ‚‚ by 5%–20% and over-predict MHP by 40%–50% relative to measurements. In the marine boundary layer, over-predictions of Hâ‚‚Oâ‚‚ in a photochemical box model are used to estimate Hâ‚‚Oâ‚‚ boundary-layer mean deposition velocities of 1.0–1.32 cm sâ»Â¹, depending on season; this process contributes to up to 5%–10% of HOâ‚“ loss in this region. In the upper troposphere and lower stratosphere, MHP is under-predicted and Hâ‚‚Oâ‚‚ is over-predicted by a factor of 2–3 on average. The differences between the observations and predictions are associated with recent convection: MHP is under-estimated and Hâ‚‚Oâ‚‚ is over-estimated in air parcels that have experienced recent convective influence. ; © 2022 American Geophysical Union. Issue Online: 18 March 2022; Version of Record online: 18 March 2022; Accepted manuscript online: 01 March 2022; Manuscript accepted: 27 February 2022; Manuscript revised: 11 February 2022; Manuscript received: 13 August 2021. Funding for this work was provided by NASA Grant No. NNX15AG61A. Additional support for H. M. Allen was provided by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1144469 and additional support for M. J. Kim was provided by the National Science ...