Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 7 4 2007 10.5194/acpd-7-12011-2007 http://www.atmos-chem-phys-discuss.net/7/12011/2007/ http://www.atmos-chem-phys-discuss.net/7/12011/2007/acpd-7-12011-2007.html http://www.atmos-chem-phys-discuss.net/7/12011/2007/acpd-7-12011-2007.pdf 12011 12033 2007-08-14 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 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. 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, although transport may be the dominant effect. 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-day wave and the 10-day wave between 30 and 60 km. Interannual variability of the waves is also examined. Beagley, S R., de~Grandpré, 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. Brasseur, G. and Solomon, S.: Aeronomy of the Middle Atmosphere, D. Reidel, 1986. 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. Cordero, E C. and Kawa, S R.: Ozone and tracer transport variations in the summer Northern Hemisphere stratosphere, J Geophys Res., 106, 12 227–12 240, 2001. de~Grandpré, 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. and Julian, P.: Further Evidence of Global-Scale, 5-Day Pressure Waves, J Atmos Sci., 29, 1464–1469, 1972. Madden, R A.: Further Evidence of Traveling Planetary Waves, J Atmos Sci., 35, 1605–1618, 1978. 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. McLandress, C.: Interannual variations of the diurnal tide in the mesosphere induced by zonal-mean wind oscillations in the tropics., Geophys Res Lett., 29, doi:10.1029/2001GL014 551, 2002. Michelsen, H A., Manney, G L., Gunson, M R., Rinsland, C P., and Zander, R.: Correlations of stratospheric abundances of \chemCH_4 and \chemN_2O derived from ATMOS measurements, Geophys Res Lett., 25, 2777–2780, 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. Sciremammano, F J.: A suggestion for the Presentation of Correlations and their significance levels, J Phys Ocean., 9, 1273–1276, 1979.