• Briggs, B. H., 1984: The analysis of spaced sensor records by correlation techniques. Handbook for the Middle Atmosphere Program, R. A. Vincent, Ed., Vol. 13, SCOSTEP Secrt., Univ. of Illinois, Urbana, IL, 166–186.

  • Browning, K. A., D. Jerrett, J. Nash, T. Oakley, and N. M. Roberts, 1998: Cold frontal structure derived from radar wind profilers. Meteor. Appl.,5, 67–174.

    • Crossref
    • Export Citation
  • Caccia, J.-L., and J.-P. Cammas, 1998: VHF–ST radar observations of an upper-level front using vertical and oblique-beam C2 N measurements. Mon. Wea. Rev.,126, 483–501.

    • Crossref
    • Export Citation
  • Crochet, M., F. Cuq, F. M. Ralph, and S. V. Venkateswaren, 1990: Clear-air radar observations of the great October storm of 1987. Dyn. Atmos. Oceans,14, 443–461.

    • Crossref
    • Export Citation
  • Griffiths, M., M. J. Reeder, D. J. Low, and R. A. Vincent, 1998: Observations of a cut-off low over southern Australia. Quart. J. Roy. Meteor. Soc.,124, 1109–1132.

    • Crossref
    • Export Citation
  • Hanstrum, B. N., K. J. Wilson, and S. L. Barrell, 1990: Pre-frontal troughs over southern Australia. Wea. Forecasting,5, 22–31.

    • Crossref
    • Export Citation
  • Keyser, D., and M. A. Shapiro, 1986: A review of the structure and dynamics of upper-level frontal zones. Mon. Wea. Rev.,114, 452–499.

    • Crossref
    • Export Citation
  • Larsen, M. F., and J. Röttger, 1982: VHF and UHF Doppler radars as tools for synoptic research. Bull. Amer. Meteor. Soc.,63, 996–1008.

    • Crossref
    • Export Citation
  • ——, and ——, 1983: Comparison of tropopause height and frontal boundary locations based on radar and radiosonde data. Geophys. Res. Lett.,10, 325–328.

  • ——, and ——, 1985: Observations of frontal zone and tropopause structures with a VHF Doppler radar and radiosondes. Radio Sci.,20, 1223–1232.

    • Crossref
    • Export Citation
  • May, P. T., K. J. Wilson, and B. F. Ryan, 1990: VHF radar studies of cold fronts traversing southern Australia. Beitr. Phys. Atmos.,63, 257–269.

  • ——, M. Yamamoto, S. Fukao, T. Sato, S. Kato, and T. Tsuda, 1991:Wind and reflectivity fields around fronts observed with a VHF radar. Radio Sci.,26, 1245–1249.

    • Crossref
    • Export Citation
  • Neiman, P. J., and M. A. Shapiro, 1989: Retrieving horizontal temperature gradients and advections from single-station wind-profiler observations. Wea. Forecasting,4, 222–233.

    • Crossref
    • Export Citation
  • ——, P. T. May, and M. A. Shapiro, 1992: Radio Acoustic Sounding System (RASS) and wind profiler observations of lower- and mid-tropospheric weather systems. Mon. Wea. Rev.,120, 2298–2313.

    • Crossref
    • Export Citation
  • Newton, C. W., 1958: Variations in frontal structure of upper-level troughs. Geophysica,6, 357–375.

  • Palmén, E., and C. W. Newton, 1969: Atmospheric Circulation Systems. Academic Press, 603 pp.

  • Puri, K., G. S. Dietachmayer, G. A. Mills, N. E. Davidson, R. A. Bowen, and L. W. Logan, 1998: The new BMRC Limited Area Prediction System, LAPS. Aust. Meteor. Mag.,47, 203–223.

  • Reid, I. M., B. H. Johnson, D. A. Holdsworth, A. D. MacKinnon, J. Strickland, R. A. Vincent, and F. Zink, 1998: A new VHF radar for use in operational meteorology. Extended Abstracts, Fourth Int. Symp. on Tropospheric Profiling: Needs and Technologies, Snowmass, CO, University of Colorado, 264–266.

  • Shapiro, M. A., and D. Keyser, 1990: Fronts, jet streams and the tropopause. Extratropical Cyclones: The Erik Palmén Memorial Volume, C. W. Newton and E. O. Holopainen, Eds., Amer. Meteor. Soc., 167–191.

    • Crossref
    • Export Citation
  • ——, T. Hampel, D. Rotzoll, and F. Mosher, 1985: The frontal hydraulic head: A microscale (1 km) triggering mechanism for mesoconvective weather systems. Mon. Wea. Rev.,113, 1166–1183.

    • Crossref
    • Export Citation
  • Tsuda, T., P. T. May, T. Sato, S. Kato, and S. Fukao, 1988: Simultaneous observations of reflection echoes and refractive index gradient in the troposphere and lower stratosphere. Radio Sci.,23, 655–665.

    • Crossref
    • Export Citation
  • Vincent, R. A., P. T. May, W. K. Hocking, W. G. Elford, B. H. Candy, and B. H. Briggs, 1987: First results with the Adelaide VHF radar: Spaced antenna studies of tropospheric winds. J. Atmos. Terr. Phys.,49, 353–366.

    • Crossref
    • Export Citation
  • ——, S. Dullaway, A. MacKinnon, I. M. Reid, F. Zink, P. T. May, and B. H. Johnson, 1998: A VHF boundary layer radar: First results. Radio Sci.,33, 845–860.

    • Crossref
    • Export Citation
  • Wilson, K. J., and H. Stern, 1985: The Australian summertime cool change. Part I. Synoptic and subsynoptic aspects. Mon. Wea. Rev.,113, 177–201.

    • Crossref
    • Export Citation
  • WMO, 1957: Definition of the tropopause. WMO Bull.,6, 136.

  • Wuertz, D. A., B. Weber, R. G. Strauch, A. S. Frisch, G. Little, D. A. Merritt, K. P. Moran, and D. C. Welsh, 1988: Effects of precipitation on UHF wind profiler measurements. J. Atmos. Oceanic Technol.,5, 450–465.

    • Crossref
    • Export Citation
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An Algorithm for the Detection of Fronts in Wind Profiler Data

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  • 1 Department of Physics and Mathematical Physics, University of Adelaide, Adelaide, Australia
  • | 2 Bureau of Meteorology Research Centre, Melbourne, Australia
  • | 3 Department of Physics and Mathematical Physics, University of Adelaide, Adelaide, Australia
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Abstract

An algorithm to detect frontal zones in time–height cross sections of horizontal wind from wind profiler measurements is described. The algorithm works by identifying regions with 1) a strong horizontal temperature gradient, estimated by using a quasigeostrophic thermal wind retrieval, 2) a strong temporal increase in the signal-to-noise ratio at a given range gate, and/or 3) a strong temporal shift in the horizontal winds at a given range gate. The type (e.g., cold or warm) of front is determined by examining the advection field and the characteristics of the boundary. Most weight is given to the horizontal temperature gradient component of the algorithm.

A springtime frontal system and an associated baroclinic wave over South Australia are examined using both routine synoptic observations and analyses as well as data from the profiler. Synoptic observations depict a prefrontal trough and two cold fronts at the surface and a deep trough in upper levels. The tropopause is identified at ∼6 km in one sounding. The algorithm successfully identifies the one main cold front and the lowered tropopause in the polar air. There are also hints of a prefrontal trough and a descending tropopause with the onset of the main cold front. After the passage of the upper trough, the ascending tropopause and the so-called jet front or trailing front are also identified by the algorithm. The latter represents the passage of the upper-level baroclinic wave and the reappearance of a strong jet stream.

Other regions are spuriously identified as fronts. These regions could be the reflection of some short-term meteorological phenomena, such as gravity waves; deviations from the assumed quasi-geostrophy; or simply reflections of noise in the analysis. An examination of the effect of random measurement uncertainties on the frontal analysis gives an estimate of error of around 2 K (100 km)−1 in the horizontal temperature gradient calculations for typical wind errors. The errors on the retrieved advection vary, depending on the wind speed, but are around 25 K day−1 for a ∼20 m s−1 wind speed. These values are typical of the noise in those fields, suggesting that the spuriously defined fronts likely reflect uncertainties in the data rather than actual meteorological phenomena.

Corresponding author address: Dr. Christopher Lucas, Department of Physics and Mathematical Physics, University of Adelaide, Adelaide 5005, Australia.

Email: clucas@physics.adelaide.edu.au

Abstract

An algorithm to detect frontal zones in time–height cross sections of horizontal wind from wind profiler measurements is described. The algorithm works by identifying regions with 1) a strong horizontal temperature gradient, estimated by using a quasigeostrophic thermal wind retrieval, 2) a strong temporal increase in the signal-to-noise ratio at a given range gate, and/or 3) a strong temporal shift in the horizontal winds at a given range gate. The type (e.g., cold or warm) of front is determined by examining the advection field and the characteristics of the boundary. Most weight is given to the horizontal temperature gradient component of the algorithm.

A springtime frontal system and an associated baroclinic wave over South Australia are examined using both routine synoptic observations and analyses as well as data from the profiler. Synoptic observations depict a prefrontal trough and two cold fronts at the surface and a deep trough in upper levels. The tropopause is identified at ∼6 km in one sounding. The algorithm successfully identifies the one main cold front and the lowered tropopause in the polar air. There are also hints of a prefrontal trough and a descending tropopause with the onset of the main cold front. After the passage of the upper trough, the ascending tropopause and the so-called jet front or trailing front are also identified by the algorithm. The latter represents the passage of the upper-level baroclinic wave and the reappearance of a strong jet stream.

Other regions are spuriously identified as fronts. These regions could be the reflection of some short-term meteorological phenomena, such as gravity waves; deviations from the assumed quasi-geostrophy; or simply reflections of noise in the analysis. An examination of the effect of random measurement uncertainties on the frontal analysis gives an estimate of error of around 2 K (100 km)−1 in the horizontal temperature gradient calculations for typical wind errors. The errors on the retrieved advection vary, depending on the wind speed, but are around 25 K day−1 for a ∼20 m s−1 wind speed. These values are typical of the noise in those fields, suggesting that the spuriously defined fronts likely reflect uncertainties in the data rather than actual meteorological phenomena.

Corresponding author address: Dr. Christopher Lucas, Department of Physics and Mathematical Physics, University of Adelaide, Adelaide 5005, Australia.

Email: clucas@physics.adelaide.edu.au

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