Detection of elevated tropospheric hydrogen peroxide (H2O2) mixing ratios in atmospheric chemistry experiment (ACE) subtropical infrared solar occultation spectra

We report measurements of hydrogen peroxide (H2O2) profiles from infrared solar occultation spectra recorded at 0.02 cm−1 resolution by the atmospheric chemistry experiment (ACE) during 2004 and 2005. Mixing ratios as high as 1.7 ppbv (1 ppbv=1×10−9 per unit volume) were measured in the subtropical troposphere. Back trajectories, fire count statistics, and simultaneous measurements of other species from the same occultation provide evidence that the elevated H2O2 mixing ratios originated from a young biomass-burning plume. The ACE time series show only a few cases with elevated H2O2 mixing ratios likely because of the short lifetime of H2O2 and the limited sampling during biomass-burning time periods.