• Banacos, P., , and H. Bluestein, 2004: Hodograph variability within analytically modeled, synoptic-scale, baroclinic systems. Mon. Wea. Rev., 132 , 14481461.

    • Search Google Scholar
    • Export Citation
  • Charney, J., , R. Fjortoft, , and J. von Neumann, 1950: Numerical integration of the barotropic vorticity equation. Tellus, 2 , 237254.

  • Hess, S., , and H. Wagner, 1948: Atmospheric waves in the north-western United States. J. Meteor., 5 , 119.

  • Holloway, G., 1986: Eddies, waves, circulation, and mixing: Statistical geofluid mechanics. Annu. Rev. Fluid Mech., 18 , 91147.

  • Killworth, P., 1992: An equivalent–barotropic mode in the fine resolution Antarctic model. J. Phys. Oceanogr., 22 , 13791387.

  • Krupitsky, A., , V. Kamenkovich, , N. Naik, , and M. Cane, 1996: A linear equivalent barotropic model of the Antarctic Circumpolar Current with realistic coastlines and bottom topography. J. Phys. Oceanogr., 26 , 18031824.

    • Search Google Scholar
    • Export Citation
  • Lau, N-C., 1979: The structure and energetics of transient disturbances in the Northern Hemisphere wintertime circulation. J. Atmos. Sci., 36 , 982995.

    • Search Google Scholar
    • Export Citation
  • Pedlosky, J., 1987: Geophysical Fluid Dynamics. 2d ed. Springer-Verlag, 710 pp.

  • Peixoto, J., , and A. Oort, 1992: Physics of Climate. AIP, 520 pp.

  • Sanders, F., 1971: Analytical solutions of the nonlinear omega and vorticity equations for a structurally simple model of disturbances in the baroclinic westerlies. Mon. Wea. Rev., 99 , 393408.

    • Search Google Scholar
    • Export Citation
  • Sun, C., 2001: The columnar structure in stratified geostrophic flows. Geophys. Astrophys. Fluid Dyn., 95 , 5565.

  • Sun, C., , and D. R. Watts, 2001: A circumpolar gravest empirical mode for the Southern Ocean hydrography. J. Geophys. Res., 106 , 28332856.

    • Search Google Scholar
    • Export Citation
  • Sun, C., , and D. R. Watts, 2002a: A view of ACC fronts in streamfunction space. Deep-Sea Res., 49 , 11411164.

  • Sun, C., , and D. R. Watts, 2002b: Heat flux carried by the Antarctic Circumpolar Current mean flow. J. Geophys. Res., 107 .3119, doi:10.1029/2001JC001187.

    • Search Google Scholar
    • Export Citation
  • Sun, C., , and D. R. Watts, 2002c: A pulsation mode in the Antarctic Circumpolar Current south of Australia. J. Phys. Oceanogr., 32 , 14791495.

    • Search Google Scholar
    • Export Citation
  • Sutcliffe, R., , and A. Forsdyke, 1950: The theory and use of upper air thickness patterns in forecasting. Quart. J. Roy. Meteor. Soc., 76 , 189217.

    • Search Google Scholar
    • Export Citation
  • Watts, D., , C. Sun, , and S. Rintoul, 2001: A two-dimensional gravest empirical mode determined from hydrographic observations in the Subantarctic Front. J. Phys. Oceanogr., 31 , 21862209.

    • Search Google Scholar
    • Export Citation
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Equivalent-Barotropic Definition of Tropospheric Mean Temperature

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  • 1 Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
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Abstract

An equivalent-barotropic (EB) description of the tropospheric temperature field is derived from the geostrophic empirical mode (GEM) in the form of a scalar function Γ(p, ϕ), where p is pressure and ϕ is 300–850-mb thickness. Baroclinic parameter ϕ plays the role of latitude at each longitudinal section. Compared with traditional Eulerian-mean methods, GEM defines a mean field in baroclinic streamfunction space with a time scale much longer than synoptic variability. It prompts an EB concept that is only based on a baroclinic field.

Monthly GEM fields are diagnosed from NCEP–NCAR reanalysis data and account for more than 90% of the tropospheric thermal variance. The circumglobal composite of GEM fields exhibits seasonal, zonal, and hemispheric asymmetries, with larger rms errors occurring in winter and in the Northern Hemisphere (NH). Zonally asymmetric features and planetary deviation from EB are seen in the NH winter GEM. Reconstruction of synoptic sections and correlation analysis reveal that the tropospheric temperature field is EB at the leading order and has a 1-day phase lag behind barotropic variations in extratropical regions.

Corresponding author address: Che Sun, Institute of Oceanology, 7 Nanhai Road, Qingdao, China. Email: csun@ms.qdio.ac.cn

Abstract

An equivalent-barotropic (EB) description of the tropospheric temperature field is derived from the geostrophic empirical mode (GEM) in the form of a scalar function Γ(p, ϕ), where p is pressure and ϕ is 300–850-mb thickness. Baroclinic parameter ϕ plays the role of latitude at each longitudinal section. Compared with traditional Eulerian-mean methods, GEM defines a mean field in baroclinic streamfunction space with a time scale much longer than synoptic variability. It prompts an EB concept that is only based on a baroclinic field.

Monthly GEM fields are diagnosed from NCEP–NCAR reanalysis data and account for more than 90% of the tropospheric thermal variance. The circumglobal composite of GEM fields exhibits seasonal, zonal, and hemispheric asymmetries, with larger rms errors occurring in winter and in the Northern Hemisphere (NH). Zonally asymmetric features and planetary deviation from EB are seen in the NH winter GEM. Reconstruction of synoptic sections and correlation analysis reveal that the tropospheric temperature field is EB at the leading order and has a 1-day phase lag behind barotropic variations in extratropical regions.

Corresponding author address: Che Sun, Institute of Oceanology, 7 Nanhai Road, Qingdao, China. Email: csun@ms.qdio.ac.cn

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