Hydrogen peroxide in the marine atmospheric boundary layer during the Atlantic Stratocumulus Transition Experiment/Marine Aerosol and Gas Exchange experiment in the eastern subtropical North Atlantic

Gas phase H₂O₂ was measured in surface air on the NOAA ship Malcolm Baldrige from June 8 to 27, 1992 (Julian days 160-179), during the Atlantic Stratocumulus Transition Experiment/Marine Aerosol and Gas Exchange experiment in the eastern subtropical North Atlantic region. Average H₂O₂ mixing ratios observed were 0.63 ± 0.28 ppbv, ranging between detection limit and 1.5 ppbv. For the entire experiment, only weak or no correlation was found between H₂O₂ mixing ratio and meteorological parameters (pressure, temperature, humidity, or UV radiation flux) as well as with tracers of continental air masses (CO, black carbon, radon). The average daily H₂O₂ cycle for the entire period exhibits a maximum of 0.8 ± 0.3 ppbv near sunset and a minimum of 0.4 ± 0.2 ppbv 4-5 hours after sunrise. Several clear H₂O₂ diurnal variations have been observed, from which a first-order removal rate of about 1 × 10^-5 s^-1 for H₂O₂ can be inferred from nighttime measurements. This rate compares well with those deduced from measurements taken at Cape Grim (Tasmania, 41°S) and during the Soviet-American Gas and Aerosol III experiment (equatorial Pacific Ocean).