Hydrogen peroxide, methyl hydroperoxide, and formaldehdye over North America and the North Atlantic

Hydrogen peroxide (H₂O), methyl hydroperoxide (CH₃OOH), and formaldehyde (CH₂O) were measured over North America and the North Atlantic during the INTEX-NA, TOPSE, and SONEX aircraft campaigns. An overview of H₂O₂, CH₃OOH, and CH₂O across the geographic and temporal range of these campaigns is presented. H₂O₂, CH₃OOH, and CH₂O mixing ratios and variability were larger during INTEX-NA compared to TOPSE and SONEX. Mean H₂O₂, CH₃OOH, and CH₂O were 1390, 440, and 480 pptv, respectively, more than two times higher than TOPSE measurements and an order of magnitude higher than SONEX measurements. This is attributed to higher solar radiation levels and the more polluted conditions of INTEX-NA. Mixing ratios and variability decreased with altitude for all three gases and on all three campaigns, except for CH₃OOH during TOPSE. The impact of convection on H₂O₂, CH₃OOH, and CH₂O is also discussed. Using the ratio H₂O₂/CH₃OOH, convectively influenced air parcels were found to be enhanced in CH₃OOH, CH₂O, CO, NO, and NO₂ while H₂O₂ and HNO3 were depleted by wet removal. Biomass burning was also shown to increase H₂O₂, CH₃OOH, and CH₂O mixing ratios up to 1.5, 2, and 1 ppbv, respectively, even after 4-5 days of transit. Results from this study show considerable variability in H₂O₂, CH₃OOH, and CH₂O throughout the North American and North Atlantic troposphere. The variability in the upper troposphere is driven by local photochemical production and transport via regional convection and long-range pathways, suggesting transport mechanisms are important factors to include in photochemical models simulating H₂O₂, CH₃OOH, CH₂O, and HOx.