Editorial Type:
Article
Article Type:
Research Article

A Numerical Study of a Southeast Australian Coastal Ridging Event

K. J. Tory Environmental Studies, University of Northern British Columbia, Prince George, British Columbia, Canada

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C. J. C. Reason School of Earth Sciences, University of Melbourne, Parkville, Victoria, Australia

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P. L. Jackson Environmental Studies, University of Northern British Columbia, Prince George, British Columbia, Canada

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Print Publication:
01 Mar 2001
DOI:
https://doi.org/10.1175/1520-0493(2001)129<0437:ANSOAS>2.0.CO;2
Page(s):
437–452
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Abstract

A numerical study of the 9–11 November 1982 southeast Australian coastal ridging event is presented. The mesoscale coastal features of this event have been previously described as a coastally trapped disturbance (CTD). However, the analysis presented in this paper shows that the model coastal trapping is of secondary importance in generating the coastal ridging. Given the potential controversy, particular emphasis in this paper is placed on identifying the causes of the ridging. The paper follows a previous study by the authors in which a Colorado State University Regional Atmospheric Modeling System simulation of this event was validated.

In this event, contributions to ridging along the southeastern Australian coast came from both synoptic and mesoscale phenomena in the model. A Southern Ocean anticyclone that tracked east from the Great Australian Bight toward the southern Tasman Sea led to a large-scale steady pressure increase over the entire southeast Australian region. Ridging at the Victorian coastal stations developed with the passage of a synoptic-scale wave of cooler denser air at midlevels, and the arrival of low-level cooler marine air with a wind shift from the southwest to a more southerly direction. On the east coast, the pressure change was most abrupt in the south as warm continental air was replaced with cooler marine air after strong winds passed through Bass Strait and turned left around the southeast continental corner. The flow closest to the coast continued turning left, enhanced by the daytime lowering of pressure over the continent, and pushed inland to the mountain barrier.

The most intense part of the wind surge crossed the coast during the evening near the Hunter Valley (a significant gap in the east coast mountain barrier). This led to flow splitting inland up the Hunter Valley and northward along the east coast. The coastal component developed into a CTD in the form of a wind surge that accelerated ahead of the region of onshore forcing until it encountered a reduced mountain barrier farther north, and the flow spilled inland signaling the end of the model event.

Current affiliation: Bureau of Meteorology Research Centre, Melbourne, Victoria, Australia.

* Corresponding author address: Kevin Tory, Bureau of Meteorology Research Centre, GPO Box 1289K, Melbourne, Victoria 3001, Australia.

Abstract

A numerical study of the 9–11 November 1982 southeast Australian coastal ridging event is presented. The mesoscale coastal features of this event have been previously described as a coastally trapped disturbance (CTD). However, the analysis presented in this paper shows that the model coastal trapping is of secondary importance in generating the coastal ridging. Given the potential controversy, particular emphasis in this paper is placed on identifying the causes of the ridging. The paper follows a previous study by the authors in which a Colorado State University Regional Atmospheric Modeling System simulation of this event was validated.

In this event, contributions to ridging along the southeastern Australian coast came from both synoptic and mesoscale phenomena in the model. A Southern Ocean anticyclone that tracked east from the Great Australian Bight toward the southern Tasman Sea led to a large-scale steady pressure increase over the entire southeast Australian region. Ridging at the Victorian coastal stations developed with the passage of a synoptic-scale wave of cooler denser air at midlevels, and the arrival of low-level cooler marine air with a wind shift from the southwest to a more southerly direction. On the east coast, the pressure change was most abrupt in the south as warm continental air was replaced with cooler marine air after strong winds passed through Bass Strait and turned left around the southeast continental corner. The flow closest to the coast continued turning left, enhanced by the daytime lowering of pressure over the continent, and pushed inland to the mountain barrier.

The most intense part of the wind surge crossed the coast during the evening near the Hunter Valley (a significant gap in the east coast mountain barrier). This led to flow splitting inland up the Hunter Valley and northward along the east coast. The coastal component developed into a CTD in the form of a wind surge that accelerated ahead of the region of onshore forcing until it encountered a reduced mountain barrier farther north, and the flow spilled inland signaling the end of the model event.

Current affiliation: Bureau of Meteorology Research Centre, Melbourne, Victoria, Australia.

* Corresponding author address: Kevin Tory, Bureau of Meteorology Research Centre, GPO Box 1289K, Melbourne, Victoria 3001, Australia.

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  • Baines, P. G., 1980: The dynamics of the southerly buster. Aust. Meteor. Mag.,28, 175–200.

  • Colquhoun, J. R., 1981: The origin, evolution and structure of some southerly bursters. Australian Bureau of Meteorology Tech. Rep. 40, 57 pp. [Available from Australian Bureau of Meteorology, National Meteorological Library, GPO Box 1289K, Melbourne, Victoria 3001, Australia.].

  • Dorman, C. E., 1985: Evidence of Kelvin waves in California’s marine layer and related eddy generation. Mon. Wea. Rev.,113, 827–839.

  • ——, 1987: Possible role of gravity currents in northern California’s coastal summer wind reversals. J. Geophys. Res.,92, 1497–1506.

  • ——, 1988: Comments on “Coastal southerlies and alongshore surges of the west coast of North America: Evidence of mesoscale topographically trapped response to synoptic forcing.” Mon. Wea. Rev.,116, 2401–2406.

  • Guan, S., P. L. Jackson, and C. J. C. Reason, 1998: Numerical modeling of a coastal trapped disturbance. Part I: Comparison with observations. Mon. Wea. Rev.,126, 972–990.

  • Holland, G. J., and L. M. Leslie, 1986: Ducted coastal ridging over south east Australia. Quart. J. Roy. Meteor. Soc.,112, 731–748.

  • Jackson, P. L., C. J. C. Reason, and S. Guan, 1999: Numerical modeling of a coastal trapped disturbance. Part II: Structure and dynamics. Mon. Wea. Rev.,127, 535–550.

  • Mass, C. F., and M. D. Albright, 1987: Coastal southerlies and alongshore surges of the west coast of North America: Evidence of mesoscale topographically trapped response to synoptic forcing. Mon. Wea. Rev.,115, 1707–1738.

  • ——, and ——, 1988: Reply. Mon. Wea. Rev.,116, 2407–2410.

  • 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, 1921–1935.

  • McInnes, K. L., 1993: Australian southerly busters. Part III: The physical mechanism an synoptic conditions contributing to development. Mon. Wea. Rev.,121, 3261–3281.

  • ——, and J. L. McBride, 1993: Australian southerly busters. Part I:Analysis of a numerically simulated case study. Mon. Wea. Rev.,121, 1904–1920.

  • Pielke, R. A., and Coauthors, 1992: A comprehensive meteorological modeling system—RAMS, Meteor. Atmos. Phys.,49, 69–91.

  • Ralph, F. M., L. Armi, J. M. Bane, C. E. Dorman, W. D. Neff, P. J. Neiman, W. Nuss, and P. O. G. Persson, 1998: Observations and analysis of the 10–11 June 1994 coastally trapped disturbance. Mon. Wea. Rev.,126, 2435–2465.

  • ——, P. J. Neiman, P. O. G. Persson, J. M. Bane, M. L. Cancillo, and J. M. Wilczak, 2000: Kelvin waves and internal bores in the marine boundary layer inversion and their relationship to coastally trapped wind reversals. Mon. Wea. Rev.,128, 283–300.

  • Reason, C. J. C., 1994: Orographically trapped disturbances in the lower atmosphere: Scale analysis and simple models. Meteor. Atmos. Phys.,53, 131–136.

  • ——, and D. G. Steyn, 1992: The dynamics of coastally trapped mesoscale ridges in the lower atmosphere. J. Atmos. Sci.,49, 1677–1692.

  • ——, and R. Dunkley, 1993: Coastally trapped stratus events in British Columbia. Atmos.–Ocean,31, 235–258.

  • ——, K. J. Tory, and P. L. Jackson, 1999: Evolution of a southeast Australian coastally trapped disturbance. Meteor. Atmos. Phys.,70, 141–165.

  • Reid, H. J., 2000: Modeling coastally trapped wind surges over southeastern Australia. Part I: Intensity and depth. Wea. Forecasting,15, 174–191.

  • ——, and L. M. Leslie, 1999: Modeling coastally trapped wind surges over southeastern Australia. Part I: Timing and speed of propagation. Wea. Forecasting,14, 53–66.

  • Skamarock, W. C., R. Rotunno, and J. B. Klemp, 1999: Models of coastally trapped disturbances. J. Atmos. Sci.,56, 3349–3365.

  • Speer, M. S., and L. M. Leslie, 1997: A climatology of coastal ridging over southeastern Australia. Int. J. Climatol.,17, 831–845.

  • Thompson, W. T., T. Haack, J. D. Doyle, and S. D. Burk, 1997: A nonhydrostatic mesoscale simulation of the 10–11 June 1994 coastally trapped wind reversal. Mon. Wea. Rev.,125, 3211–3230.

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