• Andrews, D. G., J. R. Holton, and C. B. Leovy, 1987: Middle Atmosphere Dynamics. Academic Press, 498 pp.

  • Balasubramanian, G., and S. T. Garner, 1997: The role of momentum fluxes in shaping the life cycles of a baroclinic wave. J. Atmos. Sci.,54, 510–533.

  • Baldwin, M. P., and T. J. Dunkerton, 1999: Propagation of the arctic oscillation from the stratosphere to the troposphere. J. Geophys. Res.,104, 30 937–30 946.

  • Chen, P., and W. A. Robinson, 1992: Propagation of planetary waves between the troposphere and stratosphere. J. Atmos. Sci.,49, 2533–2545.

  • DeWeaver, E., and S. Nigam, 2000a: Do stationary waves drive the zonal-mean jet anomalies of the northern winter? J. Climate,13, 2160–2176.

  • ——, and ——, 2000b: Zonal-eddy dynamics of the North Atlantic Oscillation. J. Climate,13, 3893–3914.

  • Edmon, H. J., Jr., B. J. Hoskins, and M. E. McIntyre, 1980: Eliassen–Palm cross sections for the troposphere. J. Atmos. Sci.,37, 2600–2616.

  • Gordon, C. T., and W. F. Stern, 1982: A description of the GFDL global spectral model. Mon. Wea. Rev.,110, 625–644.

  • Hartmann, D. L., 1995: A PV view of zonal flow vacillation. J. Atmos. Sci.,52, 2561–2576.

  • ——, 2000: The key role of lower-level meridional shear in baroclinic wave life cycles. J. Atmos. Sci.,57, 389–401.

  • ——, and F. Lo, 1998: Wave-driven zonal flow vacillation in the Southern Hemisphere. J. Atmos. Sci.,55, 1303–1315.

  • ——, J. M. Wallace, V. Limpasuvan, D. W. J. Thompson, and J. R. Holton, 2000: Can ozone depletion and global warming interact to produce rapid climate change? Proc. Natl. Acad. Sci.,92, 1412–1417.

  • Hoerling, M. P., M. Ting, and A. Kumar, 1995: Zonal flow-stationary wave relationship during El Niño: Implications for seasonal forecasting. J. Climate,8, 1838–1852.

  • Hurrell, J. W., 1995: Decadal trends in the North Atlantic oscillation:Regional temperatures and precipitation. Science,269, 676–679.

  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc.,77, 437–471.

  • Karoly, D. J., 1990: The role of transient eddies in low-frequency zonal variations in the Southern Hemisphere circulation. Tellus,42A, 41–50.

  • Kidson, J. W., 1988: Indices of the Southern Hemisphere zonal wind. J. Climate,1, 183–194.

  • Kodera, K., M. Chiba, K. Yamazaki, and K. Shibata, 1991: A possible influence of the polar night stratospheric jet on the subtropical tropospheric jet. J. Meteor. Soc. Japan,69, 715–721.

  • Lau, N.-C., and M. J. Nath, 1990: A general circulation model study of the atmospheric response to extratropical SST anomalies observed in 1950–79. J. Climate,3, 965–989.

  • Limpasuvan, V., and D. L. Hartmann, 1999: Eddies and the annular modes of climate variability. Geophys. Res. Lett.,26, 3133–3136.

  • Nigam, S., 1990: On the structure of variability of the observed tropospheric and stratospheric zonal-mean wind. J. Atmos. Sci.,47, 1799–1813.

  • ——, and R. S. Lindzen, 1989: The sensitivity of stationary waves to variations in the basic state zonal flow. J. Atmos. Sci.,46, 1746–1768.

  • North, G. R., T. L. Bell, R. F. Cahalan, and F. J. Moeng, 1982: Sampling errors in the estimation of empirical orthogonal functions. Mon. Wea. Rev.,110, 699–706.

  • Robinson, W. A., 1991: The dynamics of the zonal index in a simple model of the atmosphere. Tellus,43A, 295–305.

  • Rodgers, J. C., 1984: Association between the North Atlantic oscillation and the Southern Oscillation in the Northern Hemisphere. Mon. Wea. Rev.,112, 1999–2015.

  • ——, and H. van Loon, 1982: Spatial variability of sea level pressure and 500-mb height anomalies over the Southern Hemisphere. Mon. Wea. Rev.,110, 1375–1392.

  • Shiotani, M., 1990: Low-frequency variations of the zonal mean state of the Southern Hemisphere troposphere. J. Meteor. Soc. Japan,68, 461–470.

  • Thompson, D. W. J., and J. M. Wallace, 1998: The Arctic oscillation signature in the wintertime geopotential height and temperature fields. Geophys. Res. Lett.,25, 1297–1300.

  • ——, and ——, 2000: Annual modes in the extratropical circulation. Part I: Month-to-month variability. J. Climate,13, 1000–1016.

  • ——, ——, and G. Hegerl, 2000: Annual modes in the extratropical circulation. Part II: Trends. J. Climate,13, 1018–1036.

  • Ting, M., M. P. Hoerling, T. Xu, and A. Kumar, 1996: Northern Hemisphere teleconnection patterns during extreme phases of the zonal-mean circulation. J. Climate,9, 2614–2633.

  • Trenberth, K. E., 1984: Interannual variability of the Southern Hemisphere circulation: Representativeness of the year of the Global Weather Experiment. Mon. Wea. Rev.,112, 108–125.

  • Wallace, J. M., 2000: North Atlantic oscillation/annular mode: Two paradigms—one phenomenon. Quart. J. Roy. Meteor. Soc.,126, 791–805.

  • ——, and H.-H. Hsu, 1985: Another look at the index cycle. Tellus,37A, 478–486.

  • Yoden, S., M. Shiotani, and I. Hirota, 1987: Multiple planetary flow regimes in the Southern Hemisphere. J. Meteor. Soc. Japan,65, 571–585.

  • Yu, J.-Y., and D. L. Hartmann, 1993: Zonal flow vacillation and eddy forcing in a simple GCM of the atmosphere. J. Atmos. Sci.,50, 3244–3259.

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Wave-Maintained Annular Modes of Climate Variability

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  • 1 Department of Atmospheric Sciences, University of Washington, Seattle, Washington
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Abstract

The leading modes of month-to-month variability in the Northern and Southern Hemispheres are examined by comparing a 100-yr run of the Geophysical Fluid Dynamics Laboratory GCM with the NCEP–NCAR reanalyses of observations. The model simulation is a control experiment in which the SSTs are fixed to the climatological annual cycle without any interannual variability. The leading modes contain a strong zonally symmetric or annular component that describes an expansion and contraction of the polar vortex as the midlatitude jet shifts equatorward and poleward. This fluctuation is strongest during the winter months. The structure and amplitude of the simulated modes are very similar to those derived from observations, indicating that these modes arise from the internal dynamics of the atmosphere.

Dynamical diagnosis of both observations and model simulation indicates that variations in the zonally symmetric flow associated with the annular modes are forced by eddy fluxes in the free troposphere, while the Coriolis acceleration associated with the mean meridional circulation maintains the surface wind anomalies against friction. High-frequency transients contribute most to the total eddy forcing in the Southern Hemisphere. In the Northern Hemisphere, stationary waves provide most of the eddy momentum fluxes, although high-frequency transients also make an important contribution. The behavior of the stationary waves can be partly explained with index of refraction arguments. When the tropospheric westerlies are displaced poleward, Rossby waves are refracted equatorward, inducing poleward momentum fluxes and reinforcing the high-latitude westerlies. Planetary Rossby wave refraction can also explain why the stratospheric polar vortex is stronger when the tropospheric westerlies are displaced poleward. When planetary wave activity is refracted equatorward, it is less likely to propagate into the stratosphere and disturb the polar vortex.

Corresponding author address: Varavut Limpasuvan, Department of Chemistry and Physics, Coastal Carolina University, P.O. Box 261954, Conway, SC 29528.

Email: var@coastal.edu

Abstract

The leading modes of month-to-month variability in the Northern and Southern Hemispheres are examined by comparing a 100-yr run of the Geophysical Fluid Dynamics Laboratory GCM with the NCEP–NCAR reanalyses of observations. The model simulation is a control experiment in which the SSTs are fixed to the climatological annual cycle without any interannual variability. The leading modes contain a strong zonally symmetric or annular component that describes an expansion and contraction of the polar vortex as the midlatitude jet shifts equatorward and poleward. This fluctuation is strongest during the winter months. The structure and amplitude of the simulated modes are very similar to those derived from observations, indicating that these modes arise from the internal dynamics of the atmosphere.

Dynamical diagnosis of both observations and model simulation indicates that variations in the zonally symmetric flow associated with the annular modes are forced by eddy fluxes in the free troposphere, while the Coriolis acceleration associated with the mean meridional circulation maintains the surface wind anomalies against friction. High-frequency transients contribute most to the total eddy forcing in the Southern Hemisphere. In the Northern Hemisphere, stationary waves provide most of the eddy momentum fluxes, although high-frequency transients also make an important contribution. The behavior of the stationary waves can be partly explained with index of refraction arguments. When the tropospheric westerlies are displaced poleward, Rossby waves are refracted equatorward, inducing poleward momentum fluxes and reinforcing the high-latitude westerlies. Planetary Rossby wave refraction can also explain why the stratospheric polar vortex is stronger when the tropospheric westerlies are displaced poleward. When planetary wave activity is refracted equatorward, it is less likely to propagate into the stratosphere and disturb the polar vortex.

Corresponding author address: Varavut Limpasuvan, Department of Chemistry and Physics, Coastal Carolina University, P.O. Box 261954, Conway, SC 29528.

Email: var@coastal.edu

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