South Pole Antarctica observations and modeling results: New insights on HOx radical and sulfur chemistry |
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| Authors: | Roy Mauldin Edward Kosciuch Fred Eisele Greg Huey David Tanner Steve Sjostedt Don Blake Gao Chen Jim Crawford Douglas Davis |
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| Affiliation: | 1. National Center for Atmospheric Research, Atmospheric Chemistry Division, 1850 Table Mesa, Boulder, CO 80305, USA;2. School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA;3. University of California, Irvine, CA 92697, USA;4. National Aeronautics and Space Administration, Langley Research Center, Hampton, VA 23681, USA;1. Finnish Meteorological Institute, Atmospheric Composition Research, Erik Palménin aukio 1, FIN-00560 Helsinki, Finland;2. Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremenhaven, Germany;1. LISA, UMR-CNRS 7583, Université Paris Est Créteil (UPEC), Université Paris Diderot (UPD), Institut Pierre Simon Laplace (IPSL), Créteil, France;2. Laboratoire de Météorologie Physique (LaMP), CNRS, UMR-6016, Université Blaise Pascal, F-63171, Aubière, France;3. Emissions, Measurements & Modeling of the Atmosphere Laboratory, Unité Environnement, Génomique Fonctionnelle et Études Mathématiques, Centre d''Analyses et de Recherche, Faculty of sciences, Université Saint Joseph, Beirut, Lebanon;4. CNRS/UJF–Grenoble 1, Laboratoire de Glaciologie et Géophysique de l''Environnement, UMR 5183, Grenoble, France |
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| Abstract: | Measurements of OH, H2SO4, and MSA at South Pole (SP) Antarctica were recorded as a part of the 2003 Antarctic Chemistry Investigation (ANTCI 2003). The time period 22 November, 2003–2 January, 2004 provided a unique opportunity to observe atmospheric chemistry at SP under both natural conditions as well as those uniquely defined by a solar eclipse event. Results under natural solar conditions generally confirmed those reported previously in the year 2000. In both years the major chemical driver leading to large scale fluctuations in OH was shifts in the concentration levels of NO. Like in 2000, however, the 2003 observational data were systematically lower than model predictions. This can be interpreted as indicating that the model mechanism is still missing a significant HOx sink reaction(s); or, alternatively, that the OH calibration source may have problems. Still a final possibility could involve the integrity of the OH sampling scheme which involved a fixed building site. As expected, during the peak in the solar eclipse both NO and OH showed large decreases in their respective concentrations. Interestingly, the observational OH profile could only be approximated by the model mechanism upon adding an additional HOx radical source in the form of snow emissions of CH2O and/or H2O2. This would lead one to think that either CH2O and/or H2O2 snow emissions represent a significant HOx radical source under summertime conditions at SP. Observations of H2SO4 and MSA revealed both species to be present at very low concentrations (e.g., 5 × 105 and 1 × 105 molec cm?3, respectively), but similar to those reported in 2000. The first measurements of SO2 at SP demonstrated a close coupling with the oxidation product H2SO4. The observed low concentrations of MSA appear to be counter to the most recent thinking by glacio-chemists who have suggested that the plateau's lower atmosphere should have elevated levels of MSA. We speculate here that the absence of MSA may reflect efficient atmospheric removal mechanisms for this species involving either dynamical and/or chemical processes. |
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