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Volume 51 Supplement 7-8

Special Issue: Dynamics and Structure of the Mesopause Region (DYSMER)

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Modulation of the mesospheric semiannual oscillation by the quasibiennial oscillation

Abstract

Recent satellite and radar observations suggest that the semiannual oscillation (SAO) in the mesosphere is modulated by the stratospheric quasibiennial oscillation (QBO). The modulation is only apparent during the SAO easterly phase, which is considerably stronger when QBO winds are westerly than when they are easterly. We use an equatorial beta-plane model to demonstrate how such a modulation could come about through selective damping of the equatorial wave spectrum excited by deep convection. The waves affected most strongly are easterly inertia-gravity waves of phase speeds slower than −40 m s−1. This is close to the zonal wind speed during the easterly phase of the QBO (−30 to −35 m s−1), so the waves suffer strong thermal damping or even absorption as they propagate through the stratosphere. Because these waves are important for driving the easterly phase of the mesopause SAO in the model, that phase is weaker when the stratospheric QBO winds are easterly. A similar modulation of the westerly phase of the SAO does not occur for two reasons: (1) QBO westerlies are only half as strong as QBO easterlies, and (2) much of the driving of the westerly phase of the SAO is accomplished by Kelvin waves of phase speed 40–60 m s−1. As a consequence, the QBO winds have negligible influence on the vertical propagation of waves with westerly phase velocity and hence on the westerly phase of the modeled SAO.

References

  • Andrews, D. G., J. R. Holton, and C. B. Leovy, Middle Atmosphere Dynamics, 489 pp., Academic Press Inc., 1987.

  • Bergman, J. W. and M. L. Salby, Equatorial wave activity generated by fluctuations in observed convection, J. Atmos. Sci., 51, 3791–3806, 1994.

    Article  Google Scholar 

  • Boville, B. A. and W. J. Randel, Equatorial waves in a stratospheric GCM: Effects of vertical resolution, J. Atmos. Sci., 49, 785–801, 1992.

    Article  Google Scholar 

  • Burrage, M. D., R. A. Vincent, H. G. Mayr, W. R. Skinner, N. F. Arnold, and P. B. Hays, Long term variability in the equatorial mesosphere and lower thermosphere zonal winds, J. Geophys. Res., 101, 12847–12854, 1996.

    Article  Google Scholar 

  • Garcia, R. R. and M. L. Salby, Transient response to localized episodic heating in the tropics. Part II: Far-field behavior, J. Atmos. Sci., 44, 499–530, 1987.

    Article  Google Scholar 

  • Garcia, R. R., T. J. Dunkerton, R. S. Lieberman, and R. Vincent, Climatology of the semiannual oscillation of the tropical middle atmosphere, J. Geophys. Res., 102, 26019–26032, 1997.

    Article  Google Scholar 

  • Hayashi, Y., D. G. Golder, and J. D. Mahlman, Stratospheric and mesospheric Kelvin waves simulated by the GFDL “SKYHI” general circulation model, J. Atmos. Sci., 41, 1971–1984, 1984.

    Article  Google Scholar 

  • Hirota, I., Equatorial waves in the upper stratosphere and mesosphere in relation to the semiannual oscillation of the zonal mean wind, J. Atmos. Sci., 35, 714–722, 1978.

    Article  Google Scholar 

  • Hitchman, M. H. and C. B. Leovy, Estimation of the Kelvin wave contribution to the semiannual oscillation, J. Atmos. Sci., 45, 1462–1475, 1988.

    Article  Google Scholar 

  • Holton, J. R., Waves in the equatorial stratosphere generated by tropospheric heat sources, J. Atmos. Sci., 29, 368–375, 1972.

    Article  Google Scholar 

  • Holton, J. R., On the frequency distribution of atmospheric Kelvin waves, J. Atmos. Sci., 30, 499–501, 1973.

    Article  Google Scholar 

  • Manzini, E. and K. P. Hamilton, Middle atmospheric traveling waves forced by latent and convective heating, J. Atmos. Sci., 50, 2180–2200, 1993.

    Article  Google Scholar 

  • Mayr, H. G., J. G. Mengel, C. O. Hines, K. L. Chan, N. F. Arnold, and C. A. Reddy, The gravity wave Doppler spread theory applied in a numerical spectral model of the middle atmosphere. 2. Equatorial oscillations, J. Geophys. Res., 102, 26093–26105, 1997.

    Article  Google Scholar 

  • Reed, R. J., Some features of the annual temperature regime in the tropical stratosphere, Mon. Weather Rev., 90, 211–215, 1962.

    Article  Google Scholar 

  • Reed, R. J., Zonal wind behavior in the equatorial stratosphere and lower mesosphere, J. Geophys. Res., 71, 4223–4233, 1966.

    Article  Google Scholar 

  • Salby, M. L. and R. R. Garcia, Transient response to localized episodic heating in the tropics. Part I: excitation and short-term near field behavior, J. Atmos. Sci., 44, 458–498, 1987.

    Article  Google Scholar 

  • Salby, M. L., H. H. Hendon, K. Woodberry, and K. Tanaka, Analysis of global cloud imageries from multiple satellites, Bull. Am. Meteor. Soc., 72, 467–480, 1991.

    Article  Google Scholar 

  • Sassi, F. and R. R. Garcia, The role of equatorial waves forced by convection in the tropical semiannual oscillation, J. Geophys. Res., 54, 1925–1942, 1997.

    Google Scholar 

  • Tsuda, T., Y. Maruyama, H. Wiryosumarto, S. W. B. Harijono, and S. Kato, Radiosonde observations of equatorial atmosphere dynamics over Indonesia, 1, Equatorial waves and diurnal tides, J. Geophys. Res., 99, 10491–10506, 1994.

    Article  Google Scholar 

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Correspondence to Rolando R. Garcia.

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Garcia, R.R., Sassi, F. Modulation of the mesospheric semiannual oscillation by the quasibiennial oscillation. Earth Planet Sp 51, 563–569 (1999). https://doi.org/10.1186/BF03353215

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