Meridional Propagation of Planetary-Scale Waves in Vertical Shear: Implication for the Venus Atmosphere

Takeshi Imamura Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Kanagawa, Japan

Search for other papers by Takeshi Imamura in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

It is shown that planetary-scale waves are inherently accompanied by latitudinal momentum transport when they propagate vertically in vertically sheared zonal flows. Because of the dependence of the wave's latitudinal scale on the intrinsic phase speed, positive (negative) vertical shear should force prograde (retrograde) waves to focus equatorward and retrograde (prograde) waves to expand poleward in the course of upward propagation. Consequently, Eliassen–Palm (EP) flux vectors are tilted from the vertical and nonzero latitudinal momentum fluxes occur. The direction of momentum transport should always be equatorward (poleward) in positive (negative) vertical shear irrespective of the zonal propagation direction.

The idea was applied to upwardly propagating waves in the Venusian middle atmosphere, where vertical shear of strong midlatitude jets and equatorial superrotation exist. Numerical solutions showed that Kelvin and prograde inertio-gravity waves focus equatorward and mixed Rossby–gravity and Rossby waves expand poleward below the cloud top. The former is attributed primarily to the vertical shear of the superrotation, while the latter to the vertical shear beneath the midlatitude jets. Such characteristics of planetary-scale waves will cause angular momentum separation between high and low latitudes and, at least partly, contribute to the maintenance of the superrotation.

Corresponding author address: Takeshi Imamura, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1, Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan. Email: ima@isas.jaxa.jp

Abstract

It is shown that planetary-scale waves are inherently accompanied by latitudinal momentum transport when they propagate vertically in vertically sheared zonal flows. Because of the dependence of the wave's latitudinal scale on the intrinsic phase speed, positive (negative) vertical shear should force prograde (retrograde) waves to focus equatorward and retrograde (prograde) waves to expand poleward in the course of upward propagation. Consequently, Eliassen–Palm (EP) flux vectors are tilted from the vertical and nonzero latitudinal momentum fluxes occur. The direction of momentum transport should always be equatorward (poleward) in positive (negative) vertical shear irrespective of the zonal propagation direction.

The idea was applied to upwardly propagating waves in the Venusian middle atmosphere, where vertical shear of strong midlatitude jets and equatorial superrotation exist. Numerical solutions showed that Kelvin and prograde inertio-gravity waves focus equatorward and mixed Rossby–gravity and Rossby waves expand poleward below the cloud top. The former is attributed primarily to the vertical shear of the superrotation, while the latter to the vertical shear beneath the midlatitude jets. Such characteristics of planetary-scale waves will cause angular momentum separation between high and low latitudes and, at least partly, contribute to the maintenance of the superrotation.

Corresponding author address: Takeshi Imamura, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1, Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan. Email: ima@isas.jaxa.jp

Save
  • Andrews, D. G., and M. E. McIntyre, 1976a: Planetary waves in horizontal and vertical shear: Asymptotic theory for equatorial waves in weak shear. J. Atmos. Sci, 33 , 20492053.

    • Search Google Scholar
    • Export Citation
  • Andrews, D. G., and M. E. McIntyre, 1976b: Planetary waves in horizontal and vertical shear: The generalized Eliassen–Palm relation and the mean zonal acceleration. J. Atmos. Sci, 33 , 20312048.

    • Search Google Scholar
    • Export Citation
  • Andrews, D. G., and M. E. McIntyre, 1978: Generalized Eliassen–Palm and Charney–Drazin theorems for waves on axisymmetric mean flows in compressible atmospheres. J. Atmos. Sci, 35 , 175185.

    • Search Google Scholar
    • Export Citation
  • Andrews, D. G., J. R. Holton, and C. B. Loevy, 1987: Middle Atmosphere Dynamics. Academic Press, 150 pp.

  • Chen, P., and W. A. Robinson, 1992: Propagation of planetary waves between the troposphere and stratosphere. J. Atmos. Sci, 49 , 25332545.

    • Search Google Scholar
    • Export Citation
  • Collard, A. D., and Coauthors, 1993: Latitudinal distributions of carbon monoxide in the deep atmosphere of Venus. Planet. Space Sci, 41 , 487494.

    • Search Google Scholar
    • Export Citation
  • Covey, C., and G. Schubert, 1982: Planetary-scale waves in the Venus atmosphere. J. Atmos. Sci, 39 , 23972413.

  • Crisp, D., 1989: Radiative forcing of the Venus mesosphere II. Thermal fluxes, cooling rates, and radiative equilibrium temperatures. Icarus, 77 , 391413.

    • Search Google Scholar
    • Export Citation
  • Del Genio, A. D., and W. B. Rossow, 1990: Planetary-scale waves and the cyclic nature of cloud top dynamics on Venus. J. Atmos. Sci, 47 , 293318.

    • Search Google Scholar
    • Export Citation
  • Forbes, J. M., 2002: Wave coupling in terrestrial planetary atmospheres. Atmospheres in the Solar System: Comparative Aeronomy,Geophys. Monogr., Vol. 130, Amer. Geophys. Union, 171–190.

  • Gierasch, P. J., 1975: Meridional circulation and the maintenance of the Venus atmospheric rotation. J. Atmos. Sci, 32 , 10381044.

  • Haltiner, G. J., and R. T. Williams, 1980: Numerical Prediction and Dynamic Meteorology. 2d ed. John Wiley & Sons, 477 pp.

  • Holton, J. R., 1970: The influence of mean wind shear on the propagation of Kelvin waves. Tellus, 22 , 186193.

  • Imamura, T., 1997: Momentum balance of the Venusian midlatitude mesosphere. J. Geophys. Res, 102 , 66156620.

  • Imamura, T., T. Horinouchi, and T. J. Dunkerton, 2004: The lateral transport of zonal momentum due to Kelvin waves in a meridional circulation. J. Atmos. Sci, 61 , 19661975.

    • Search Google Scholar
    • Export Citation
  • Leroy, S. S., and A. P. Ingersoll, 1996: Radio scintillations in Venus's atmosphere: Application of a theory of gravity wave generation. J. Atmos. Sci, 53 , 10181028.

    • Search Google Scholar
    • Export Citation
  • Lindzen, R. S., 1970: Internal equatorial planetary-scale waves in shear flow. J. Atmos. Sci, 27 , 394407.

  • Lindzen, R. S., 1971: Equatorial planetary waves in shear: Part I. J. Atmos. Sci, 28 , 609622.

  • Longuet-Higgins, M. S., 1968: The eigenfunctions of Laplace's tidal equations over the sphere. Philos. Trans. Roy. Soc. London, A262 , 511607.

    • Search Google Scholar
    • Export Citation
  • Matsuno, T., 1966: Quasi-geostrophic motions in the equatorial area. J. Meteor. Soc. Japan, 44 , 2543.

  • Matsuno, T., 1970: Vertical propagation of stationary planetary waves in the winter Northern Hemisphere. J. Atmos. Sci, 27 , 871883.

  • Newman, M., and C. B. Leovy, 1992: Maintenance of strong rotational winds in Venus' middle atmosphere by thermal tides. Science, 257 , 647650.

    • Search Google Scholar
    • Export Citation
  • Rossow, W. B., and G. P. Williams, 1979: Large-scale motion in the Venus stratosphere. J. Atmos. Sci, 36 , 377389.

  • Rossow, W. B., A. D. Del Genio, and T. Eichler, 1990: Cloud-tracked winds from Pioneer Venus OCPP images. J. Atmos. Sci, 47 , 20532084.

    • Search Google Scholar
    • Export Citation
  • Schubert, G., 1983: General circulation and dynamical state of the Venus atmosphere. Venus, D. M. Hunten et al., Eds., The University of Arizona Press, 650–680.

    • Search Google Scholar
    • Export Citation
  • Schubert, G., and R. L. Walterscheid, 1984: Propagation of small-scale acoustic-gravity waves in the Venus atmosphere. J. Atmos. Sci, 41 , 12021213.

    • Search Google Scholar
    • Export Citation
  • Smith, M. D., P. J. Gierasch, and P. J. Schinder, 1993: Global-scale waves in the Venus atmosphere. J. Atmos. Sci, 50 , 40804096.

  • Takagi, M., and Y. Matsuda, 2005: Sensitivity of thermal tides in the Venus atmosphere to basic zonal flow and Newtonian cooling. Geophys. Res. Lett, 32 .L02203, doi:10.1029/2004GL022060.

    • Search Google Scholar
    • Export Citation
  • Taylor, F. W., D. Crisp, and B. Bezard, 1997: Near-infrared sounding of the lower atmosphere of Venus. Venus II, S. W. Bougher, D. M. Hunten, and R. J. Phillips, Eds., The University of Arizona Press, 325–351.

    • Search Google Scholar
    • Export Citation
  • Woo, R., and A. Ishimaru, 1981: Eddy diffusion coefficient for the atmosphere of Venus from radio scintillation measurement. Nature, 289 , 383384.

    • Search Google Scholar
    • Export Citation
  • Woo, R., J. W. Armstrong, and A. J. Kliore, 1982: Small-scale turbulence in the atmosphere of Venus. Icarus, 52 , 335345.

  • Yamamoto, M., and M. Takahashi, 2003a: The fully developed superrotation simulated by a general circulation model of a Venus-like atmosphere. J. Atmos. Sci, 60 , 561574.

    • Search Google Scholar
    • Export Citation
  • Yamamoto, M., and M. Takahashi, 2003b: Superrotation and equatorial waves in a T21 Venus-like AGCM. Geophys. Res. Lett, 30 .1449, doi:10.1029/2003GL016924.

    • Search Google Scholar
    • Export Citation
  • Yamamoto, M., and M. Takahashi, 2004: Dynamics of Venus' superrotation: the eddy momentum transport processes newly found in a GCM. Geophys. Res. Lett, 31 .L09701, doi:10.1029/2004GL019518.

    • Search Google Scholar
    • Export Citation
  • Young, R. E., H. Houben, and L. Pfister, 1984: Baroclinic instability in the Venus atmosphere. J. Atmos. Sci, 41 , 23102332.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 348 64 11
PDF Downloads 243 43 1