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

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Hydrogen peroxide (H2O2), methyl hydroperoxide (CH3OOH), and formaldehyde (CH2O) were measured over North America and the North Atlantic during the INTEXNA, 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. Copyright 2007 by the American Geophysical Union.

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Journal of Geophysical Research Atmospheres