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
Résumé
Gas phase H20 2 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 H20 2 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 H20 2 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 H20 2 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 H20 2 diurnal variations have been observed, from which a first-order removal rate of about 1 x 10-s s-• for H20 2 can be inferred from nighttime measurements. This rate compares well with those deduced from measurements taken at Cape Grim (Tasmania, 41øS) and during the Soviet-American Gas and Aerosol III experiment (equatorial Pacific Ocean).
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