H₂O₂ and CH₃OOH (MHP) in the Remote Atmosphere: 1. Global Distribution and Regional Influences

Abstract

Atmospheric hydroperoxides are a significant component of the atmosphere's oxidizing capacity. Two of the most abundant hydroperoxides, hydrogen peroxide (H₂O₂) and methyl hydroperoxide (MHP, CH₃OOH), were measured in the remote atmosphere using chemical ionization mass spectrometry aboard the NASA DC-8 aircraft during the Atmospheric Tomography Mission. These measurements present a seasonal investigation into the global distribution of these two hydroperoxides, with near pole-to-pole coverage across the Pacific and Atlantic Ocean basins and from the marine boundary layer to the upper troposphere and lower stratosphere. H₂O₂ mixing ratios are highest between 2 and 4 km altitude in the equatorial region of the Atlantic Ocean basin, where they reach global maximums of 3.6–6.5 ppbv depending on season. MHP mixing ratios reach global maximums of 4.3–8.6 ppbv and are highest between 1 and 3 km altitude, but peak in different regions depending on season. A major factor contributing to the global H₂O₂ distribution is the influence of biomass burning emissions in the Atlantic Ocean basin, encountered in all four seasons, where the highest H₂O₂ mixing ratios were found to correlate strongly with increased mixing ratios of the biomass burning tracers hydrogen cyanide (HCN) and carbon monoxide (CO). This biomass burning enhanced H₂O₂ by a factor of 1.3–2.2, on average, in the Atlantic compared with the Pacific Ocean basin.