Low-Frequency Variability and Evolution of North American Cold Air Outbreaks

Diane H. Portis Department of Atmospheric Sciences, University of Illinois at Urbana–Champaign, Urbana, Illinois

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Michael P. Cellitti Department of Atmospheric Sciences, University of Illinois at Urbana–Champaign, Urbana, Illinois

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William L. Chapman Department of Atmospheric Sciences, University of Illinois at Urbana–Champaign, Urbana, Illinois

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John E. Walsh Department of Atmospheric Sciences, University of Illinois at Urbana–Champaign, Urbana, Illinois

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Abstract

Hourly data from 17 relatively evenly distributed stations east of the Rocky Mountains during 54 winter seasons (1948/49 through 2001/02) are used to evaluate the low-frequency variability of extreme cold air outbreaks (CAOs). The results show no overall trend in CAO frequency, despite an increase in mean temperature over the Midwest and especially upstream into the CAO formation regions of high-latitude North America. However, there are regionally based trends in the intensity of long-duration (5 day) CAOs.

Daily heat budgets from reanalysis data are also used to investigate the thermodynamic and dynamic processes involved in the evolution of a subset of the major CAOs. The cooling of the air masses can be generally traced in the heat budget analysis as the air masses track southward along the Rocky Mountains into the Midwest. The earliest cooling begins in northwestern Canada more than a week before the cold air mass reaches the Midwest. Downstream in southwestern Canada, both diabatic and advective processes contribute to the cumulative cooling of the air mass. At peak intensity over the Midwest, diabatic processes and horizontal advection cool the air mass, but warming by subsidence offsets this cooling. By contrast, to the west of the CAO track into the Midwestern United States, vertical advection by orographic lifting cumulatively cools the air in the upslope flow regime associated with the low-level airflow around a cold air mass, and this cooling is offset by diabatic warming. Diabatic processes have strong positive correlations with temperature change over all regions (especially in central Canada) except for the mountainous regions in the United States that are to the west of the track of the cold air mass. Correlations of vertical advection with horizontal advection and diabatic processes are physically consistent and give credibility to the vertical advection field.

Corresponding author address: Diane Portis, Dept. of Atmospheric Sciences, University of Illinois at Urbana–Champaign, 105 S. Gregory Ave., Urbana, IL 61801. Email: portis@atmos.uiuc.edu

Abstract

Hourly data from 17 relatively evenly distributed stations east of the Rocky Mountains during 54 winter seasons (1948/49 through 2001/02) are used to evaluate the low-frequency variability of extreme cold air outbreaks (CAOs). The results show no overall trend in CAO frequency, despite an increase in mean temperature over the Midwest and especially upstream into the CAO formation regions of high-latitude North America. However, there are regionally based trends in the intensity of long-duration (5 day) CAOs.

Daily heat budgets from reanalysis data are also used to investigate the thermodynamic and dynamic processes involved in the evolution of a subset of the major CAOs. The cooling of the air masses can be generally traced in the heat budget analysis as the air masses track southward along the Rocky Mountains into the Midwest. The earliest cooling begins in northwestern Canada more than a week before the cold air mass reaches the Midwest. Downstream in southwestern Canada, both diabatic and advective processes contribute to the cumulative cooling of the air mass. At peak intensity over the Midwest, diabatic processes and horizontal advection cool the air mass, but warming by subsidence offsets this cooling. By contrast, to the west of the CAO track into the Midwestern United States, vertical advection by orographic lifting cumulatively cools the air in the upslope flow regime associated with the low-level airflow around a cold air mass, and this cooling is offset by diabatic warming. Diabatic processes have strong positive correlations with temperature change over all regions (especially in central Canada) except for the mountainous regions in the United States that are to the west of the track of the cold air mass. Correlations of vertical advection with horizontal advection and diabatic processes are physically consistent and give credibility to the vertical advection field.

Corresponding author address: Diane Portis, Dept. of Atmospheric Sciences, University of Illinois at Urbana–Champaign, 105 S. Gregory Ave., Urbana, IL 61801. Email: portis@atmos.uiuc.edu

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  • Bell, G. D., and L. F. Bosart, 1988: Appalachian cold-air damming. Mon. Wea. Rev, 116 , 137161.

  • Bodurtha, F. T., 1952: An investigation of anticyclogenesis in Alaska. J. Meteor, 9 , 118125.

  • Colle, B. A., and C. F. Mass, 1995: The structure and evolution of cold surges east of the Rocky Mountains. Mon. Wea. Rev, 123 , 25772610.

    • Search Google Scholar
    • Export Citation
  • Colucci, S. J., and J. C. Davenport, 1987: Rapid surface anticyclogenesis: Surface climatology and attendant large-scale circulation changes. Mon. Wea. Rev, 115 , 822836.

    • Search Google Scholar
    • Export Citation
  • Colucci, S. J., D. P. Baumhefner, and C. E. Konrad II, 1999: Numerical prediction of a cold-air outbreak: A case study with ensemble forecasts. Mon. Wea. Rev, 127 , 15381550.

    • Search Google Scholar
    • Export Citation
  • Curry, J., 1987: The contribution of radiative cooling to the formation of cold-core anticyclones. J. Atmos. Sci, 44 , 25752592.

  • Downton, M. W., and K. A. Miller, 1993: The freeze risk to Florida citrus. Part II: Temperature variability and circulation patterns. J. Climate, 6 , 364372.

    • Search Google Scholar
    • Export Citation
  • Hartjenstein, G., and R. Bleck, 1991: Factors affecting cold-air outbreaks east of the Rocky Mountains. Mon. Wea. Rev, 119 , 22802292.

    • Search Google Scholar
    • Export Citation
  • Hassol, S. J., 2004: Impacts of a Warming Arctic: Arctic Climate Impact Assessment. Cambridge University Press, 146 pp.

  • Houghton, J. T., Y. Ding, D. C. Griggs, M. Noguer, P. J. van der Linden, X. Dai, K. Mastell, and C. A. Johnson, 2001: Climate Change 2001: The Scientific Basis. Cambridge University Press, 944 pp.

    • Search Google Scholar
    • Export Citation
  • Jones, P. D., and A. Moberg, 2003: Hemispheric and large-scale surface air temperature variations: An extensive revision and an update to 2001. J. Climate, 16 , 206223.

    • Search Google Scholar
    • Export Citation
  • Kalkstein, L. S., P. C. Dunne, and R. S. Voss, 1990: Detection of climatic change in the western North American Arctic using a synoptic climatological approach. J. Climate, 3 , 11531167.

    • Search Google Scholar
    • Export Citation
  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc, 77 , 437471.

  • Konrad II, C. E., 1996: Relationships between the intensity of cold-air outbreaks and the evolution of synoptic and planetary-scale features over North America. Mon. Wea. Rev, 124 , 10671083.

    • Search Google Scholar
    • Export Citation
  • Konrad II, C. E., and S. J. Colucci, 1989: An examination of extreme cold-air outbreaks over eastern North America. Mon. Wea. Rev, 117 , 26872700.

    • Search Google Scholar
    • Export Citation
  • Lau, N-C., and K-A. Lau, 1984: The structure and energetics of midlatitude disturbances accompanying cold-air outbreaks over east Asia. Mon. Wea. Rev, 112 , 13091327.

    • Search Google Scholar
    • Export Citation
  • Liang, X. Z., W. C. Wang, and M. P. Dudek, 1996: Northern Hemispheric interannual teleconnection patterns and their changes due to the greenhouse effect. J. Climate, 9 , 465479.

    • Search Google Scholar
    • Export Citation
  • McBride, J. L., and K. L. McInnes, 1993: Australian southerly busters. Part II: The dynamical structure of the orographically modified front. Mon. Wea. Rev, 121 , 19211935.

    • Search Google Scholar
    • Export Citation
  • McInnes, K. L., and J. L. McBride, 1993: Australian southerly busters. Part I: Analysis of a numerically simulated case study. Mon. Wea. Rev, 121 , 19041920.

    • Search Google Scholar
    • Export Citation
  • Mecikalski, J. R., and J. S. Tilley, 1992: Cold surges along the Front Range of the Rocky Mountains: Development of a classification scheme. Meteor. Atmos. Phys, 48 , 249271.

    • Search Google Scholar
    • Export Citation
  • Miller, K. A., and M. W. Downton, 1993: The freeze risk to Florida citrus. Part I: Investment decisions. J. Climate, 6 , 354363.

  • Portis, D. H., J. E. Walsh, M. El Hamly, and P. J. Lamb, 2001: Seasonality of the North Atlantic Oscillation. J. Climate, 14 , 20692078.

    • Search Google Scholar
    • Export Citation
  • Quiroz, R. S., 1984: The climate of the 1983–84 winter—A season of strong blocking and severe cold in North America. Mon. Wea. Rev, 112 , 18941912.

    • Search Google Scholar
    • Export Citation
  • Reding, P. J., 1992: The Central American cold surge: An observational analysis of the deep southward penetration of North American cold fronts. M.S. thesis, Department of Meteorology, Texas A&M University, 177 pp. [Available from Dept. of Meteorology, Texas A&M University, College Station, TX 77843-3150.].

  • Rogers, J. C., and R. V. Rohli, 1991: Florida citrus freezes and polar anticyclones in the Great Plains. J. Climate, 4 , 11031113.

  • Schultz, D. M., W. E. Bracken, L. F. Bosart, G. J. Hakim, M. A. Bedrick, M. J. Dickinson, and K. R. Tyle, 1997: The 1993 superstorm cold surge: Frontal structure, gap flow, and tropical impact. Mon. Wea. Rev, 125 , 539. Corrigendum. 125 , 662.

    • Search Google Scholar
    • Export Citation
  • Schultz, D. M., W. E. Bracken, and L. F. Bosart, 1998: Planetary- and synoptic-scale signatures associated with Central American cold surges. Mon. Wea. Rev, 126 , 527.

    • Search Google Scholar
    • Export Citation
  • Song, Y., and W. Robinson, 2004: Dynamical mechanisms for stratospheric influences on the troposphere. J. Atmos. Sci, 61 , 17111725.

  • Tan, Y. C., and J. A. Curry, 1993: A diagnostic study of the evolution of an intense North American anticyclone during winter 1989. Mon. Wea. Rev, 121 , 961975.

    • Search Google Scholar
    • Export Citation
  • Tanaka, H. L., and M. L. Milkovich, 1990: A heat budget analysis of the polar troposphere in and around Alaska during the abnormal winter of 1988/89. Mon. Wea. Rev, 118 , 16281639.

    • Search Google Scholar
    • Export Citation
  • Thompson, D. W. J., and J. M. Wallace, 2001: Regional climate impacts of the Northern Hemisphere annular mode. Science, 293 , 8589.

  • Thompson, D. W. J., M. P. Baldwin, and J. M. Wallace, 2002: Stratospheric connection to Northern Hemisphere wintertime weather: Implications for prediction. J. Climate, 15 , 14211428.

    • Search Google Scholar
    • Export Citation
  • Walsh, J. E., A. S. Phillips, D. H. Portis, and W. L. Chapman, 2001: Extreme cold air outbreaks in the United States and Europe, 1948–99. J. Climate, 14 , 26422658.

    • Search Google Scholar
    • Export Citation
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