• Hitchman, M. H., , and A. S. Huesmann, 2007: A seasonal climatology of Rossby wave breaking in the 320–2000-K layer. J. Atmos. Sci., 64 , 19221940.

    • Search Google Scholar
    • Export Citation
  • Hoskins, B. J., 1997: A potential vorticity view of synoptic development. Meteor. Appl., 4 , 325334.

  • Hoskins, B. J., , and P. D. Sardeshmukh, 1987: A diagnostic study of the dynamics of the Northern Hemisphere winter of 1985/86. Quart. J. Roy. Meteor. Soc., 113 , 759778.

    • Search Google Scholar
    • Export Citation
  • Hoskins, B. J., , and P. Berrisford, 1988: A potential vorticity perspective of the storm of 15–16 October 1987. Weather, 43 , 122129.

    • Search Google Scholar
    • Export Citation
  • Hoskins, B. J., , and T. Ambrizzi, 1993: Rossby wave propagation on a realistic longitudinally varying flow. J. Atmos. Sci., 50 , 16611671.

    • Search Google Scholar
    • Export Citation
  • Hoskins, B. J., , M. E. McIntyre, , and A. W. Robertson, 1985: On the use and significance of isentropic potential vorticity maps. Quart. J. Roy. Meteor. Soc., 111 , 877946.

    • Search Google Scholar
    • Export Citation
  • Hsu, H. H., , and S. Lin, 1992: Global teleconnections in the 250-mb streamfunction field during the Northern Hemisphere winter. Mon. Wea. Rev., 120 , 11691190.

    • Search Google Scholar
    • Export Citation
  • Kallberg, P., , P. Berrisford, , B. Hoskins, , A. Simmons, , S. Uppala, , S. Lamy-Thepaut, , and R. Hine, 2005: ERA-40 Atlas. ECMWF ERA-40 Project Rep. Series 19, 199 pp.

  • Kiladis, G. N., , and K. C. Mo, 1999: Interannual and intraseasonal variability in the Southern Hemisphere. Meteorology of the Southern Hemisphere, Meteor. Monogr., No. 49, Amer. Meteor. Soc., 307–336.

  • McIntyre, M. E., , and T. Palmer, 1983: Breaking planetary waves in the stratosphere. Nature, 305 , 593600.

  • Mo, K. C., , and R. W. Higgins, 1998: The Pacific–South American modes and tropical convection during the Southern Hemisphere winter. Mon. Wea. Rev., 126 , 15811596.

    • Search Google Scholar
    • Export Citation
  • Pelly, J. L., , and B. J. Hoskins, 2003: A new perspective on blocking. J. Atmos. Sci., 60 , 743755.

  • Peters, D., , and D. W. Waugh, 1996: Influence of barotropic shear on the poleward advection of upper-tropospheric air. J. Atmos. Sci., 53 , 30133031.

    • Search Google Scholar
    • Export Citation
  • Peters, D., , and D. W. Waugh, 2003: Rossby wave breaking in the Southern Hemisphere wintertime upper troposphere. Mon. Wea. Rev., 131 , 26232634.

    • Search Google Scholar
    • Export Citation
  • Postel, G. A., , and M. H. Hitchman, 1999: A climatology of Rossby wave breaking along the subtropical tropopause. J. Atmos. Sci., 56 , 359373.

    • Search Google Scholar
    • Export Citation
  • Renwick, J. A., 1998: ENSO-related variability in the frequency of South Pacific blocking. Mon. Wea. Rev., 126 , 31173123.

  • Renwick, J. A., , and M. J. Revell, 1999: Blocking over the South Pacific and Rossby wave propagation. Mon. Wea. Rev., 127 , 22332247.

  • Shutts, G. J., 1983: The propagation of eddies in diffluent jetstreams: Eddy vorticity forcing of “blocking” flow fields. Quart. J. Roy. Meteor. Soc., 109 , 737761.

    • Search Google Scholar
    • Export Citation
  • Sinclair, M. R., 1996: A climatology of anticyclones and blocking for the Southern Hemisphere. Mon. Wea. Rev., 124 , 245263.

  • Swanson, K. L., 2000: Stationary wave accumulation and the generation of low-frequency variability on zonally varying flows. J. Atmos. Sci., 57 , 22622280.

    • Search Google Scholar
    • Export Citation
  • Thompson, D. W. J., , and J. M. Wallace, 2000: Annular modes in the extratropical circulation. Part I: Month-to-month variability. J. Climate, 13 , 10001016.

    • Search Google Scholar
    • Export Citation
  • Tibaldi, S., , and F. Molteni, 1990: On the operational predictability of blocking. Tellus, 42A , 343365.

  • Tibaldi, S., , E. Tosi, , A. Navarra, , and L. Pedulli, 1994: Northern and Southern Hemisphere seasonal variability of blocking frequency and predictability. Mon. Wea. Rev., 122 , 19712003.

    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., , and K. C. Mo, 1985: Blocking in the Southern Hemisphere. Mon. Wea. Rev., 113 , 321.

  • Uppala, S. M., and Coauthors, 2005: The ERA-40 Reanalysis. Quart. J. Roy. Meteor. Soc., 131 , 29613012.

  • Wallace, J. M., , and D. W. J. Thompson, 2002: The Pacific center of action of the Northern Hemisphere annular mode: Real or artifact? J. Climate, 15 , 19871991.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 260 260 21
PDF Downloads 251 251 15

Blocking and Rossby Wave Breaking on the Dynamical Tropopause in the Southern Hemisphere

View More View Less
  • 1 Walker Institute, and National Centre for Atmospheric Science-Climate, University of Reading, Reading, United Kingdom
  • | 2 Department of Meteorology, University of Reading, Reading, United Kingdom
© Get Permissions
Restricted access

Abstract

Rossby wave breaking on the dynamical tropopause in the Southern Hemisphere (the −2-PVU surface) is investigated using the ERA-40 dataset. The indication of wave breaking is based on reversal in the meridional gradient of potential temperature, and persistent large-scale wave breaking is taken as a strong indication that blocking may be present. Blocking in the midlatitudes is found to occur predominantly during wintertime in the Pacific and is most vigorous in the east Pacific, while during summertime, the frequency of blocking weakens and its extent becomes confined to the west Pacific. The interannual variability of blocking is found to be high. Wave breaking occurs most frequently on the poleward side of the polar jet and has some, but not all, of the signatures of blocking, so it is referred to as high-latitude blocking. In general, cyclonic wave breaking occurs on the poleward side of the polar jet, otherwise anticyclonic breaking occurs. However, at least in wintertime, wave breaking in the New Zealand/west to mid-Pacific sector between the polar and subtropical jets is a mixture between cyclonic and anticyclonic types. Together, episodes of wave breaking and enhanced westerly flow describe much of the variability in the seasonal Antarctic Oscillation (AnO) index and give a synoptic manifestation of it with a focus on the date line and Indian Ocean that is in agreement with the centers of action for the AnO. During summertime, anticyclonic wave breaking in the upper troposphere is also to be found near 30°S in both the Pacific and Atlantic, and appears to be associated with Rossby waves propagating into the subtropics from the New Zealand region.

Corresponding author address: Dr. P. Berrisford, NCAS-Climate, Department of Meteorology, University of Reading, Reading RG6 6BB, United Kingdom. Email: p.berrisford@rdg.ac.uk

Abstract

Rossby wave breaking on the dynamical tropopause in the Southern Hemisphere (the −2-PVU surface) is investigated using the ERA-40 dataset. The indication of wave breaking is based on reversal in the meridional gradient of potential temperature, and persistent large-scale wave breaking is taken as a strong indication that blocking may be present. Blocking in the midlatitudes is found to occur predominantly during wintertime in the Pacific and is most vigorous in the east Pacific, while during summertime, the frequency of blocking weakens and its extent becomes confined to the west Pacific. The interannual variability of blocking is found to be high. Wave breaking occurs most frequently on the poleward side of the polar jet and has some, but not all, of the signatures of blocking, so it is referred to as high-latitude blocking. In general, cyclonic wave breaking occurs on the poleward side of the polar jet, otherwise anticyclonic breaking occurs. However, at least in wintertime, wave breaking in the New Zealand/west to mid-Pacific sector between the polar and subtropical jets is a mixture between cyclonic and anticyclonic types. Together, episodes of wave breaking and enhanced westerly flow describe much of the variability in the seasonal Antarctic Oscillation (AnO) index and give a synoptic manifestation of it with a focus on the date line and Indian Ocean that is in agreement with the centers of action for the AnO. During summertime, anticyclonic wave breaking in the upper troposphere is also to be found near 30°S in both the Pacific and Atlantic, and appears to be associated with Rossby waves propagating into the subtropics from the New Zealand region.

Corresponding author address: Dr. P. Berrisford, NCAS-Climate, Department of Meteorology, University of Reading, Reading RG6 6BB, United Kingdom. Email: p.berrisford@rdg.ac.uk

Save