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

摘要

Hydrogen peroxide (H_2O_2), methyl hydroperoxide (CH_3OOH), and formaldehyde (CH_2O) were measured over North America and the North Atlantic during the INTEX-NA, TOPSE, and SONEX aircraft campaigns. An overview of H_2O_2, CH_3OOH, and CH_2O across the geographic and temporal range of these campaigns is presented. H_2O_2, CH_3OOH, and CH_2O mixing ratios and variability were larger during INTEX-NA compared to TOPSE and SONEX. Mean H_2O_2, CH_3OOH, and CH_2O 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 CH_3OOH during TOPSE. The impact of convection on H_2O_2, CH_3OOH, and CH_2O is also discussed. Using the ratio H_2O_2/CH_3OOH, convectively influenced air parcels were found to be enhanced in CH_3OOH, CH_2O, CO, NO, and NO_2 while H_2O_2 and HNO_3 were depleted by wet removal. Biomass burning was also shown to increase H_2O_2, CH_3OOH, and CH_2O 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 H_2O_2, CH_3OOH, and CH_2O 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 H_2O_2, CH_3OOH, CH_2O, and HOx.