• Balasubramanian, G., and S. T. Garner, 1997a: The role of momentum fluxes in shaping the life cycle of a baroclinic wave. J. Atmos. Sci., 54 , 510533.

    • Search Google Scholar
    • Export Citation
  • Balasubramanian, G., and S. T. Garner, 1997b: The equilibrium of short baroclinic waves. J. Atmos. Sci., 54 , 28502871.

  • Berbery, E. H., and C. S. Vera, 1996: Characteristics of the Southern Hemisphere winter storm track with filtered and unfiltered data. J. Atmos. Sci., 53 , 468481.

    • Search Google Scholar
    • Export Citation
  • Chang, E. K. M., 1993: Downstream development of baroclinic waves as inferred from regression analysis. J. Atmos. Sci., 50 , 20382053.

    • Search Google Scholar
    • Export Citation
  • Chang, E. K. M., and I. Orlanski, 1993: On the dynamics of a storm track. J. Atmos. Sci., 50 , 9991015.

  • Clough, S. A., N. S. Grahame, and A. O'Neill, 1985: Potential vorticity in the stratosphere derived using data from satellites. Quart. J. Roy. Meteor. Soc., 111 , 335358.

    • Search Google Scholar
    • Export Citation
  • Dowling, T. E., 1993: A relationship between potential vorticity and zonal wind on Jupiter. J. Atmos. Sci., 50 , 1422.

  • Gross, B. D., 1997: The effect of compressibility on barotropic and baroclinic instability. J. Atmos. Sci., 54 , 2431.

  • Held, I. M., cited 2000: The general circulation of the atmosphere. Lecture Notes: Woods Hole GFD Summer School 2000. [Available online at http://gfd.whoi.edu/proceedings/2000/PDF/lectures2000.pdf.].

    • Search Google Scholar
    • Export Citation
  • Held, I. M., S. W. Lyons, and S. Nigam, 1989: Transients and the extratropical response to El Niño. J. Atmos. Sci., 46 , 163174.

  • Horel, J. D., and J. M. Wallace, 1981: Planetary scale atmospheric phenomena associated with the Southern Oscillation. Mon. Wea. Rev., 109 , 813829.

    • Search Google Scholar
    • Export Citation
  • Hoskins, B. J., 1971: Atmospheric frontogenesis models: Some solutions. Quart. J. Roy. Meteor. Soc., 97 , 139153.

  • Hoskins, B. J., and D. J. Karoly, 1981: The steady linear response of a spherical atmosphere to thermal and orographic forcing. J. Atmos. Sci., 38 , 11791196.

    • Search Google Scholar
    • Export Citation
  • Hoskins, B. J., and P. J. Valdes, 1990: On the existence of storm-tracks. J. Atmos. Sci., 47 , 18541864.

  • Lau, N-C., 1985: Modeling the seasonal dependence of the atmospheric response to observed El Niños in 1962–1976. Mon. Wea. Rev., 113 , 19701996.

    • Search Google Scholar
    • Export Citation
  • Lee, S., and I. M. Held, 1993: Baroclinic wave packets in models and observations. J. Atmos. Sci., 50 , 14131428.

  • Lim, G. H., and J. M. Wallace, 1991: Structure and evolution of baroclinic waves as inferred from regression analysis. J. Atmos. Sci., 48 , 17181732.

    • Search Google Scholar
    • Export Citation
  • McIntyre, M. E., and T. N. Palmer, 1984: The “surf zone” in the stratosphere. J. Atmos. Terr. Phys., 46 , 825849.

  • Nakamura, H., M. Nakamura, and J. L. Anderson, 1997: The role of high- and low-frequency dynamics in blocking formation. Mon. Wea. Rev., 125 , 20742093.

    • Search Google Scholar
    • Export Citation
  • Orlanski, I., 1998: On the poleward deflection of storm tracks. J. Atmos. Sci., 55 , 128154.

  • Orlanski, I., and J. J. Katzfey, 1991: The life cycle of a cyclone wave in the Southern Hemisphere. J. Atmos. Sci., 48 , 19721998.

  • Orlanski, I., and B. D. Gross, 2000: On the life-cycle of baroclinic eddies in a storm track environment. J. Atmos. Sci., 57 , 34983513.

    • Search Google Scholar
    • Export Citation
  • Polvani, L. M., D. W. Waugh, and R. A. Plumb, 1995: On the subtropical edge of the stratospheric surf zone. J. Atmos. Sci., 52 , 12881309.

    • Search Google Scholar
    • Export Citation
  • Shapiro, M. A., H. Wernli, N. A. Bond, and R. Langland, 2001: The influence of the 1997–99 El Niño Southern Oscillation on extratropical baroclinic life cycles over the eastern North Pacific. Quart. J. Roy. Meteor. Soc., 127 , 331342.

    • Search Google Scholar
    • Export Citation
  • Simmons, A. J., and B. J. Hoskins, 1978: The life cycles of some nonlinear baroclinic waves. J. Atmos. Sci., 35 , 414432.

  • Simmons, A. J., and B. J. Hoskins, 1979: The downstream and upstream development of unstable baroclinic waves. J. Atmos. Sci., 36 , 12391254.

    • Search Google Scholar
    • Export Citation
  • Simmons, A. J., and B. J. Hoskins, 1980: Barotropic influences on the growth and decay of nonlinear baroclinic waves. J. Atmos. Sci., 37 , 16791684.

    • Search Google Scholar
    • Export Citation
  • Sobel, A. H., and R. A. Plumb, 1999: Quantitative diagnostics of mixing in a shallow water model of the stratosphere. J. Atmos. Sci., 56 , 28112829.

    • Search Google Scholar
    • Export Citation
  • Thorncroft, C. D., B. J. Hoskins, and M. E. McIntyre, 1993: Two paradigms of baroclinic wave life-cycle behaviour. Quart. J. Roy. Meteor. Soc., 119 , 1755.

    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., G. W. Branstator, D. Karoly, A. Kumar, N-C. Lau, and C. Ropelewski, 1998: Progress during TOGA in understanding and modeling global teleconnections associated with tropical sea surface temperatures. J. Geophys. Res., 103 , 1429114324.

    • Search Google Scholar
    • Export Citation
  • Webster, P. J., 1981: Mechanism determining the atmosphere response to sea surface anomalies. J. Atmos. Sci., 38 , 554571.

  • Whitaker, J. S., and C. Snyder, 1993: The effects of spherical geometry on the evolution of baroclinic waves. J. Atmos. Sci., 50 , 597612.

    • Search Google Scholar
    • Export Citation
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Bifurcation in Eddy Life Cycles: Implications for Storm Track Variability

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  • 1 Geophysical Fluid Dynamics Laboratory, Forrestal Campus, Princeton University, Princeton, New Jersey
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Abstract

By analyzing a number of very high resolution, nonhydrostatic experiments of baroclinic lifecycles, it was concluded that the intensity of the near-surface baroclinic development influences the upper-level wave to such an extent that it could produce cyclonic or anticyclonic wave breaking. Since the final jet position is equatorward or poleward, the position depends on whether the waves break cyclonically or anticyclonically, respectively. The low-level baroclinicity plays a very important role in the outcome of the wave and feedback to the mean circulation. Using a shallow water model the hypothesis that the intensity of the eddy forcing from the lower layers of the atmosphere can have a profound effect on the disturbances of the upper layers is tested. From these experiments the following is concluded.

For weak intensities, the strong effective beta asymmetries due to the earth's sphericity produce anticyclonic wave breaking and a poleward shift of the zonal jet will occur. For moderate forcing, anticyclonic wave breaking occurs and consequently, as before, a poleward shift of the zonal jet will occur. However, there is an important distinction between weak and moderate forcing. In the latter case, the eddy anticyclonic centers are very intense. The influence of the two anticyclones produces a difluence field that will strain the cyclonic vortex along the SW–NE direction. Consequently, the meridional vorticity flux υζ′ is positive in the north and negative in the south. This process has two effects: thinning the cyclone and producing positive vorticity fluxes on the north, negative fluxes on the south and moving the jet poleward. By increasing the forcing, the cyclone centers become considerably more intense than the anticyclones (CVC) and they are able to deform and thin the anticyclones, thus moving the jet equatorward. This transition is very abrupt; above a threshold amplitude, the life cycle bifurcates to a cyclonic wave breaking.

The implications for storm track variability are quite direct. In normal years, at the entrance of the storm track, intense baroclinicity produces CVCs with a slight shift of the jet equatorward. At the last half of the storm track, due to much weaker baroclinicity, anticyclonic wave breaking occurs (AVCs) displacing the jet poleward. The eddies at the entrance of the storm track develop from the baroclinicity of the subtropical jet. Downstream fluxing and weaker surface baroclinicity make the upper-level waves more aloft and barotropic by the middle of the storm track. These waves normally break anticyclonically, enhancing the subpolar eddy-driven jet. In the warm phase of ENSO, more baroclinicity (and subtropical moisture flux) is present in the eastern Pacific Ocean. This enhanced baroclinicity could support more CVCs in the eastern basin, maintaining the subtropical jet further east.

Corresponding author address: Dr. Isidoro Orlanski, Geophysical Fluid Dynamics Lab, Princeton University, Forrestal Campus, Princeton, NJ 08542. Email: io@gfdl.noaa.gov

Abstract

By analyzing a number of very high resolution, nonhydrostatic experiments of baroclinic lifecycles, it was concluded that the intensity of the near-surface baroclinic development influences the upper-level wave to such an extent that it could produce cyclonic or anticyclonic wave breaking. Since the final jet position is equatorward or poleward, the position depends on whether the waves break cyclonically or anticyclonically, respectively. The low-level baroclinicity plays a very important role in the outcome of the wave and feedback to the mean circulation. Using a shallow water model the hypothesis that the intensity of the eddy forcing from the lower layers of the atmosphere can have a profound effect on the disturbances of the upper layers is tested. From these experiments the following is concluded.

For weak intensities, the strong effective beta asymmetries due to the earth's sphericity produce anticyclonic wave breaking and a poleward shift of the zonal jet will occur. For moderate forcing, anticyclonic wave breaking occurs and consequently, as before, a poleward shift of the zonal jet will occur. However, there is an important distinction between weak and moderate forcing. In the latter case, the eddy anticyclonic centers are very intense. The influence of the two anticyclones produces a difluence field that will strain the cyclonic vortex along the SW–NE direction. Consequently, the meridional vorticity flux υζ′ is positive in the north and negative in the south. This process has two effects: thinning the cyclone and producing positive vorticity fluxes on the north, negative fluxes on the south and moving the jet poleward. By increasing the forcing, the cyclone centers become considerably more intense than the anticyclones (CVC) and they are able to deform and thin the anticyclones, thus moving the jet equatorward. This transition is very abrupt; above a threshold amplitude, the life cycle bifurcates to a cyclonic wave breaking.

The implications for storm track variability are quite direct. In normal years, at the entrance of the storm track, intense baroclinicity produces CVCs with a slight shift of the jet equatorward. At the last half of the storm track, due to much weaker baroclinicity, anticyclonic wave breaking occurs (AVCs) displacing the jet poleward. The eddies at the entrance of the storm track develop from the baroclinicity of the subtropical jet. Downstream fluxing and weaker surface baroclinicity make the upper-level waves more aloft and barotropic by the middle of the storm track. These waves normally break anticyclonically, enhancing the subpolar eddy-driven jet. In the warm phase of ENSO, more baroclinicity (and subtropical moisture flux) is present in the eastern Pacific Ocean. This enhanced baroclinicity could support more CVCs in the eastern basin, maintaining the subtropical jet further east.

Corresponding author address: Dr. Isidoro Orlanski, Geophysical Fluid Dynamics Lab, Princeton University, Forrestal Campus, Princeton, NJ 08542. Email: io@gfdl.noaa.gov

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