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Titel Trend and lifetime of sulfur hexafluoride at mid-latitudes deduced from ACE-FTS occultation measurements
VerfasserIn Emmanuel Mahieu, Pierre Duchatelet, Rodolphe Zander, Peter F. Bernath, Alex Brown, Chris D. Boone, Kaley A. Walker
Konferenz EGU General Assembly 2011
Medientyp Artikel
Sprache Englisch
Digitales Dokument PDF
Erschienen In: GRA - Volume 13 (2011)
Datensatznummer 250048743
 
Zusammenfassung
Sulfur hexafluoride (SF6) is one of the strongest greenhouse gases on a per molecule basis, with a global warming potential of 22800 (100-yr horizon). This is an extremely stable gas in the atmosphere, which results in a very long lifetime, with large uncertainties. The value adopted by IPCC is 3200 years, but some studies suggest shorter lifetimes, as low as 800 years. Surface concentrations are now about 7 ppt, with reported trends indicating a steady and strong increase of 0.3 ppt/yr. Most emissions are of anthropogenic origin, related to its use as an insulator in high-voltage electrical installations. Secondary contributions result from magnesium and aluminum production as well as from the manufacturing of semiconductors (see e.g. Levin et al., 2010; Rigby et al., 2010 and references therein). In this contribution, we use occultation measurements performed by the ACE-FTS (Atmospheric Chemistry Experiment Fourier Transform Spectrometer) instrument, launched in August 2003 onboard the Canadian SCISAT satellite (Bernath et al., 2005). ACE-FTS is still in operation to date, with no significant degradation in its performance. This spectrometer achieves a spectral resolution of 0.02 cm-1 in the broad 750-4400 cm-1 range which covers the unresolved ν3 band Q branch of SF6 centered at 947.9 cm-1. Signal-to-noise ratios of 200-300 are typically obtained in the spectral region of interest. Version 3 retrievals performed by University of Waterloo give volume mixing ratio profiles of SF6 in the 11-32 km altitude range. We consider all available sunrise and sunset occultation measurements obtained at mid-latitudes in both hemispheres to derive the trend of SF6 in the lower stratosphere, from late February 2004 onwards. Consistency between both hemispheres will be investigated. In addition, concurrent N2O measurements are used to evaluate the atmospheric lifetime of SF6, following a method used previously for other long-lived gases (e.g. Zander et al, 1996). Comparisons with trends derived from in situ surface measurements or from ground-based remote-sensing observations (e.g. at the Jungfraujoch station, 46.5ºN) are also included. Acknowledgments The University of Liège contribution to the present work has primarily been supported by the PRODEX program funded by the Belgian Federal Science Policy Office, Brussels. The Atmospheric Chemistry Experiment (ACE) is a Canadian-led mission mainly supported by the Canadian Space Agency (CSA) and the Natural Sciences and Engineering Research Council (NSERC) of Canada. References Bernath, P. F., McElroy, C. T., Abrams, M. C. et al., Atmospheric Chemistry Experiment (ACE): mission overview, Geophys. Res. Lett., 32, L15S01, doi:10.1029/2005GL022386, 2005. Levin, I., Naegler, T., Heinz, R., Osusko, D., Cuevas, E., Engel, A., Ilmberger, J., Langenfelds, R. L., Neininger, B., Rohden, C. V., Steele, L. P., Weller, R., Worthy, D. E., and Zimov, S. A.: The global SF6 source inferred from long-term high precision atmospheric measurements and its comparison with emission inventories, Atmos. Chem. Phys., 10, 2655-2662, doi:10.5194/acp-10-2655-2010, 2010. Rigby, M., Mühle, J., Miller, B. R., Prinn, R. G., Krummel, P. B., Steele, L. P., Fraser, P. J., Salameh, P. K., Harth, C. M., Weiss, R. F., Greally, B. R., O’Doherty, S., Simmonds, P. G., Vollmer, M. K., Reimann, S., Kim, J., Kim, K.-R., Wang, H. J., Olivier, J. G. J., Dlugokencky, E. J., Dutton, G. S., Hall, B. D., and Elkins, J. W.: History of atmospheric SF6 from 1973 to 2008, Atmos. Chem. Phys., 10, 10305-10320, doi:10.5194/acp-10-10305-2010, 2010. Zander, R., Solomon, S., Mahieu, E., Goldman, A., Rinsland, C. P., Gunson, M. R., Abrams, M. C., Chang, A. Y., Salawitch, R. J., Michelsen, H. A., Newchurch, M. J., and Stiller, G. P., Increase of stratospheric carbon tetrafluoride (CF4) based on ATMOS observations from space, Geophys. Res. Lett., 23, 2353-2356, 1996.