Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 8 7 2008 10.5194/acp-8-1925-2008 http://www.atmos-chem-phys.net/8/1925/2008/ http://www.atmos-chem-phys.net/8/1925/2008/acp-8-1925-2008.html http://www.atmos-chem-phys.net/8/1925/2008/acp-8-1925-2008.pdf 1925 1935 2008-04-03 Normal mode Rossby waves and their effects on chemical composition in the late summer stratosphere D. Pendlebury diane@atmosp.physics.utoronto.ca T. G. Shepherd M. Pritchard C. McLandress University of Toronto, Toronto, Canada now at: University of California, San Diego, USA During past MANTRA campaigns, ground-based measurements of several long-lived chemical species have revealed quasi-periodic fluctuations on time scales of several days. These fluctuations could confound efforts to detect long-term trends from MANTRA, and need to be understood and accounted for. Using the Canadian Middle Atmosphere Model, we investigate the role of dynamical variability in the late summer stratosphere due to normal mode Rossby waves and the impact of this variability on fluctuations in chemical species. Zonal wavenumber 1, westward travelling waves are considered with average periods of 5, 10 and 16 days. Time-lagged correlations between the temperature and nitrous oxide, methane and ozone fields are calculated in order to assess the possible impact of these waves on the chemical species. Using Fourier-wavelet decomposition and correlating the fluctuations between the temperature and chemical fields, we determine that variations in the chemical species are well-correlated with the 5- and 10-day waves between 30 and 60 km, although the nature of the correlations depend strongly on altitude. Interannual variability of the waves is also examined. % % % %\beginthebibliography Austin, J., Shindell, D., Brühl, C., Dameris, M., Manzini, E., Nagashima, T., Newman, P., Pawson, S., Pitari, G., Rozanov, E., C Schnadt, C., and Shepherd, T G.: Uncertainties and assessments of chemistry-climate models of the stratosphere, Atmos. Chem. Phys., 3, 1–27, 2003. Beagley, S R., de~Grandprè, J., Koshyk, J N., McFarlane, N A., and Shepherd, T G.: Radiative-dynamical climatology of the first-generation Canadian Middle Atmosphere Model, Atmos.-Ocean, 35, 293–331, 1997. Cheong, H.-B. and Kimura, R.: Excitation of the 5-day wave by Antarctica, J. Atmos. Sci., 54, 87–102, 1997. Cheong, H.-B. and Kimura, R.: Excitation of the 10-day and 14-day waves, J. Atmos. Sci., 58, 1129–1145, 2001. de~Grandprè, J., Beagley, S R., Fomichev, V I., Griffioen, E., McConnell, J C., Medvedev, A S., and Shepherd, T G.: Ozone climatology using interactive chemistry: Results from the Canadian Middle Atmosphere Model, J. Geophys. Res., 105, 26 475–26 491, 2000. Geisler, J E. and Dickinson, R E.: The five-day wave on a sphere with realistic zonal winds, J. Atmos. Sci., 33, 632–641, 1976. Hines, C O.: Doppler-spread parameterization of gravity-wave momentum deposition in the middle atmosphere. Part 1: Basic formulation, J. Atmos. and Solar-Terr. Phys., 59, 371–386, 1997. Hirooka, T.: Normal mode Rossby waves as revealed by UARS/IASMS observations, J. Atmos. Sci., 57, 1277–1285, 2000. Hirooka, T. and Hirota, I.: Further evidence of normal mode Rossby waves, Pageoph., 130, 277–289, 1989. Hirota, I. and Hirooka, T.: Normal mode Rossby waves observed in the upper stratosphere. Part I: First symmetric modes of zonal wavenumbers 1 and 2, J. Atmos. Sci., 41, 1253–1267, 1983. Madden, R. A.: Further Evidence of Traveling Planetary Waves, J. Atmos. Sci., 35, 1605–1618, 1978. Madden, R. and Julian, P.: Further evidence of global-scale, 5-day pressure waves, J. Atmos. Sci., 29, 1464–1469, 1972. McLandress, C.: Seasonal variability of the diurnal tide: Results from the Canadian middle atmosphere general circulation model, J. Geophys. Res., 102, 29,747–29,764, 1997. McLandress, C.: On the importance of gravity waves in the middle atmosphere and their parameterization in general circulation models, J. Atmos. Sol.- Terr. Phys., 60, 1357–1383, 1998. Miyoshi, Y.: Numerical simulation of the 5-day and 16-day waves in the mesopause region, Earth Planets Space, 51, 763–772, 1999. Miyoshi, Y. and Hirooka, T.: A numerical experiment of excitation of the 5-day wave by a GCM, J. Atmos. Sci., 56, 1698–1707, 1999. Prata, A J.: Observations of the 5-day wave in the stratosphere and mesosphere, J. Atmos. Sci., 46, 2473–2477, 1989. Salby, M L.: Rossby normal modes in nonuniform background configurations. Part II: Equinox and solstice conditions, J. Atmos. Sci., 38, 1827–1840, 1981. Sankey, D. and Shepherd, T G.: Correlations of long-lived chemical species in a middle atmosphere general circulation model, J. Geophys. Res., 108, 10.1029/2002JD002 799, 2003. Sciremammano, F., Jr.: A suggestion for the presentation of correlations and their significance levels, J. Phys. Ocean., 9, 1273–1276, 1979.