Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 9 11 2009 10.5194/acp-9-3601-2009 http://www.atmos-chem-phys.net/9/3601/2009/ http://www.atmos-chem-phys.net/9/3601/2009/acp-9-3601-2009.html http://www.atmos-chem-phys.net/9/3601/2009/acp-9-3601-2009.pdf 3601 3612 2009-06-04 Variability and trends in stratospheric NO₂ in Antarctic summer, and implications for stratospheric NO_y P. A. Cook H. K. Roscoe hkro@bas.ac.uk British Antarctic Survey, Madingley Rd, Cambridge CB3 0ET, UK NO₂ measurements during 1990–2007, obtained from a zenith-sky spectrometer in the Antarctic, are analysed to determine the long-term changes in NO₂. An atmospheric photochemical box model and a radiative transfer model are used to improve the accuracy of determination of the vertical columns from the slant column measurements, and to deduce the amount of NO_y from NO₂. We find that the NO₂ and NO_y columns in midsummer have large inter-annual variability superimposed on a broad maximum in 2000, with little or no overall trend over the full time period. These changes are robust to a variety of alternative settings when determining vertical columns from slant columns or determining NO_y from NO₂. They may signify similar changes in speed of the Brewer-Dobson circulation but with opposite sign, i.e. a broad minimum around 2000. Multiple regressions show significant correlation with solar and quasi-biennial-oscillation indices, and weak correlation with El Nino, but no significant overall trend, corresponding to an increase in Brewer-Dobson circulation of 1.4±3.5%/decade. There remains an unexplained cycle of amplitude and period at least 15% and 17 years, with minimum speed in about 2000. Brewer, A. W.: Evidence for a world circulation provided by the measurements of helium and water vapour distribution in the stratosphere, Q. J. Roy. Meteor. Soc. 75, 351–363, 1949. Butchart, N. and Scaife, A. A.: Removal of chlorofluorocarbons by increased mass exchange between the stratosphere and troposphere in a changing climate, Nature 410, 799–802, 2001. Chipperfield, M. P.: Multiannual simulations with a three-dimensional chemical transport model, J. Geophys. Res., 104, 1781–1805, 1999. Cook, P A. and Roscoe, H K.: Does an increase in the Brewer-Dobson circulation increase or reduce the amounts of stratospheric reactive gases?, submitted, Geophys. Res. Lett., 2009. Denis, L., Roscoe, H. K., Chipperfield, M. P., Van Roozendael, M., and Goutail, F.: A new software suite for NO₂ vertical profile retrieval from ground-based zenith-sky spectrometers', J. Quant. Spectrosc. Ra., 92, 321–333, 2005. Dobson, G. M. B.: Origin and distribution of polyatomic molecules in the atmosphere, Proc. R. Soc. Lond. A, 236, 187–193, 1956. Garcia-Herrera, R., Calvo, N., Garcia, R. R., and Giorgetta, M. A.: Propagation of ENSO temperature signals into the middle atmosphere: A comparison of two general circulation models and ERA-40 reanalysis data, J. Geophys. Res., 111, D06101, doi:10.1029/2005JD006061, 2006. Lee, A. M., Roscoe, H. K., Oldham, D. J., Squires, J. A. C., Sarkissian, A., Pommereau, J.-P., and Gardiner, B. G.: Improvements to the accuracy of measurements of NO₂ by zenith-sky visible spectrometers, J. Quant. Spectrosc. Ra., 52, 649–657, 1994. Liley, J. B., Johnston, P. V., McKenzie, R. L., Thomas, A. J., and Boyd, I. S.: Stratospheric NO₂ variations from a long time series at Lauder, New Zealand, J. Geophys. Res., 105, 11633–11640, 2000. McLinden, C. A., Olsen, S. C., Prather, M. J., and Liley, J. B.: "Understanding trends in stratospheric NO_y and NO₂", J. Geophys. Res. 106, 27787–27793, 2001. Mount, G. H., Sanders, R. W., Schmeltekopf, A. L., and Solomon, S.: Visible spectroscopy at McMurdo station, Antarctica 1. Overview and daily variations of NO₂ and O₃, austral spring 1986, J. Geophys. Res., 92, 8320–8328, 1987. Platt, U., Perner, D., and Patz, H. W.: Simultaneous measurements of atmospheric CH₂O, O₃ and NO₂ by differential optical absorption, J. Geophys. Res., 84, 6329–6335, 1979. Pommereau, J.-P. and Goutail, F.: O₃ and NO₂ ground-based measurements by visible spectrometry during Arctic winter and spring 1988, Geophys. Res. Lett., 15, 8, 891–894, 1988a. Pommereau, J.-P. and Goutail, F.: Stratospheric O₃ and NO₂ observations at the southern polar circle in summer and fall 1988, Geophys. Res. Lett., 15, 895–897, 1988b. Randel, W. J., Wu, F., Vomel, H., Nedoluha, G. E., and Forster, P.: Deceases in stratospheric water vapor after 2001: Links to changes in the tropical tropopause and the Brewer-Dobson circulation, J. Geophys. Res., 111, D12312, doi:10.1029/2005JD006744, 2006. Roscoe, H. K., Drummond, J. R., and Jarnot, R. F.: Infrared measurements of stratospheric composition. III. The daytime changes of NO and NO₂', Proc. R. Soc. Lond. A 375, 507–528, 1981. Roscoe, H. K., Fish, D. J., and Jones, R. L.: Interpolation errors in UV-visible spectroscopy for stratospheric sensing: implications for sensitivity, spectral resolution and spectral range, Appl. Optics 35, 427–432, 1996. Roscoe H. K., Charlton A. J., Fish D. J., and Hill J. G. T.: Improvements to the accuracy of measurements of NO₂ by zenith-sky visible spectrometers II: errors in zero using a more complete chemical model', J. Quant. Spectrosc. Ra., 68, 337–349, 2001. Roscoe, H. K.: A review of stratospheric H₂O and NO₂, Adv. Space Res., 34, 1747–1754, 2004. Rosenlof, K. H. and Reid, G. C.: Trends in the temperature and water vapor content of the tropical lower stratosphere: Sea surface connection, J. Geophys. Res., 113, D06107, doi:10.1029/2007JD009109, 2008. Sarkissian A., Roscoe, H. K., and Fish, D. J.: Ozone measurements by zenith-sky spectrometers: an evaluation of errors in air-mass factors calculated by radiative transfer models, J. Quant. Spectrosc. Ra., 54, 3, 471–480, 1995. Slusser, J. R., Fish, D. J., Strong, E. K., Jones, R. L., Roscoe, H. K., and Sarkissian, A.: Five years of NO₂ vertical column measurements at Faraday (65° S): Evidence for the hydrolysis of BrONO₂ on Pinatubo aerosols', J. Geophys. Res., 102, 12987–12993, 1997. WMO (World Meteorological Organisation), Scientific Assessment of Ozone Depletion: 2006, Global Ozone Research and Monitoring Project – Report No. 50, Geneva, 2007. Zeng, G. and Pyle, J. A.: Influence of El Nino Southern Oscillation on stratosphere/troposphere exchange and the global tropospheric ozone budget, Geophys. Res. Lett., 32, L01814, doi:10.1029/2004GL021353, 2005.