Nitrogen Oxides in the Arctic Marine Boundary Layer during the Polar Sunrise Experiment-2000

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Honrath abstract Photochemical reactions of halogen compounds in the Arctic springtime atmosphere cause depletion of boundary-layer ozone, deposition of mercury to the arctic ecosystem, and halogen-mediated decomposition of organic compounds. However, key aspects of these processes are inadequately understood. The Polar Sunrise Experiment-2000 (PSE-2000) is designed to improve understanding of springtime boundary layer halogen chemistry and the role of surface snow as a source and sink of photochemically active compounds. Measurements and analyses of nitrogen oxides mixing ratios are proposed here as part of the PSE-2000 project. NO, NO2, and NOy will be determined at the PSE-2000 site near Alert, Nunavut, Canada, with gradient measurements of NOx and ancillary measurements of the N02 photodissociation rate constant and spectral actinic flux. The proposed N02 measurements will be used with measurements of BrO and other compounds by collaborating researchers to investigate the importance of these reactions to O3-depletion chemistry. Analyses of the NO-NO2 photostationary state will provide further insight into the importance of the BrO + NO2 = BrONO2 reaction and other NOx-sink reactions. Measurements of the vertical gradient of NOx and analysis of expected post-sunrise diurnal cycles in NOx and NOy will be used to investigate the role of the snow surface as a source and sink for photochemically active nitrogen oxide compounds.