Simulation and Interpretation of the Phase Data Used by the Radar Refractivity Retrieval Algorithm

Shinju Park Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Quebec, Canada

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Frédéric Fabry Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Quebec, Canada

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Abstract

The radar refractivity retrieval algorithm applied to radar phase measurements from ground targets can provide high-resolution, near-surface moisture estimates in time and space. The reliability of the retrieval depends on the quality of the returned phase measurements, which are affected by factors such as 1) the vertical variation of the refractive index along the ray path and 2) the properties of illuminated ground targets (e.g., the height and shape of the targets intercepted by radar rays over complex terrain). These factors introduce ambiguities in the phase measurement that have not yet been considered in the refractivity algorithm and that hamper its performance.

A phase measurement simulator was designed to better understand the effect of these factors. The results from the simulation were compared with observed phase measurements for selected atmospheric propagation conditions estimated from low-level radio sounding profiles. Changes in the vertical gradient of refractivity coupled with the varying heights of targets are shown to have some influence on the variability of phase fields. However, they do not fully explain the noisiness of the real phase observations because other factors that are not included in the simulation, such as moving ground targets, affect the noisiness of phase measurements.

Corresponding author address: Shinju Park, Dept. of Atmospheric and Oceanic Sciences, 805 Sherbrooke West 945, Montreal QC H3A 2K6, Canada. Email: shinju@meteo.mcgill.ca

Abstract

The radar refractivity retrieval algorithm applied to radar phase measurements from ground targets can provide high-resolution, near-surface moisture estimates in time and space. The reliability of the retrieval depends on the quality of the returned phase measurements, which are affected by factors such as 1) the vertical variation of the refractive index along the ray path and 2) the properties of illuminated ground targets (e.g., the height and shape of the targets intercepted by radar rays over complex terrain). These factors introduce ambiguities in the phase measurement that have not yet been considered in the refractivity algorithm and that hamper its performance.

A phase measurement simulator was designed to better understand the effect of these factors. The results from the simulation were compared with observed phase measurements for selected atmospheric propagation conditions estimated from low-level radio sounding profiles. Changes in the vertical gradient of refractivity coupled with the varying heights of targets are shown to have some influence on the variability of phase fields. However, they do not fully explain the noisiness of the real phase observations because other factors that are not included in the simulation, such as moving ground targets, affect the noisiness of phase measurements.

Corresponding author address: Shinju Park, Dept. of Atmospheric and Oceanic Sciences, 805 Sherbrooke West 945, Montreal QC H3A 2K6, Canada. Email: shinju@meteo.mcgill.ca

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  • Bean, B. R., and Dutton E. J. , 1968: Radio Meteorology. National Bureau of Standards Monogr., No. 92, National Bureau of Standards, 435 pp.

    • Search Google Scholar
    • Export Citation
  • Bevington, P. R., 1969: Data Reduction and Error Analysis for the Physical Sciences. McGraw-Hill, 336 pp.

  • Cheong, B. L., Palmer R. D. , Curtis C. D. , Yu T-Y. , Zrnić D. S. , and Forsyth D. , 2008: Refractivity retrieval using the phased array radar: First results and potential for multimission operation. IEEE Trans. Geosci. Remote Sens., 46 , 25272537.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Doviak, R. J., and Zrnić D. S. , 1993: Doppler Radar and Weather Observations. 2nd ed. Academy Press, 562 pp.

  • Fabry, F., 2004: Meteorological value of ground target measurements by radar. J. Atmos. Oceanic Technol., 21 , 560573.

  • Fabry, F., 2005: Peeping through the keyhole at the mesoscale variability of humidity: Some IHOP_2002 observations and future challenges of radar refractivity mapping. Preprints, 32nd Int. Conf. on Radar Meteorology, Albuquerque, NM, Amer. Meteor. Soc., J6J.1. [Available online at http://ams.confex.com/ams/pdfpapers/98313.pdf].

    • Search Google Scholar
    • Export Citation
  • Fabry, F., and Creese C. , 1999: If fine lines fail, try ground targets. Preprints, 29th Int. Conf. on Radar Meteorology, Montreal, QC, Canada, Amer. Meteor. Soc., 21–23.

    • Search Google Scholar
    • Export Citation
  • Fabry, F., Frush C. , Zawadzki I. , and Kilambi A. , 1997: On the extraction of near-surface index of refraction using radar phase measurements from ground targets. J. Atmos. Oceanic Technol., 14 , 978987.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Feltz, F., Smith W. L. , Howell H. B. , Knuteson R. O. , Woolf H. , and Revercomb H. E. , 2003: Near-continuous profiling of temperature, moisture, and atmospheric stability using the Atmospheric Emitted Radiance Interferometer (AERI). J. Appl. Meteor., 42 , 584597.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Fritz, J., and Chandrasekar V. , 2009: Implementation and analysis of networked radar refractivity retrieval. J. Atmos. Oceanic Technol., 26 , 21232135.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Heinselman, P. L., Cheong B. L. , Palmer R. D. , Bodine D. , and Hondl K. , 2009: Radar refractivity retrievals from KTLX: Insights into operational benefits and limitations. Wea. Forecasting, 24 , 13451361.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kalbfleisch, J. G., 1985: Probability. Vol. 1, Probability and Statistical Inference. 2nd ed. Springer-Verlag, 343 pp.

  • Lhermitte, R., 2002: Centimeter and Millimeter Wavelength Radars in Meteorology. Lhermitte Publications, 548 pp.

  • Montmerle, T., Caya A. , and Zawadski I. , 2002: Short-term numerical forecasting of a shallow storm complex using bi-static and single-Doppler radar data. Wea. Forecasting, 17 , 12111225.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Roberts, R. D., and Coauthors, 2008: REFRACTT-2006: Real-time retrieval of high-resolution low-level moisture fields from operational NEXRAD and research radars. Bull. Amer. Meteor. Soc., 89 , 15351538.

    • Search Google Scholar
    • Export Citation
  • Sauvageot, H., 1992: Radar Meteorology. Artech House, 366 pp.

  • Steiner, M., and Smith J. A. , 2002: Use of three-dimensional reflectivity structure for automated detection and removal of non-precipitating echoes in radar data. J. Atmos. Oceanic Technol., 19 , 673686.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Weber, R., 1997: Estimators for the standard deviation of horizontal wind direction. J. Appl. Meteor., 36 , 14031415.

  • Weckwerth, T. M., and Parsons D. B. , 2006: A review of convection initiation and motivation for IHOP_2002. Mon. Wea. Rev., 134 , 522.

  • Weckwerth, T. M., and Coauthors, 2004: An overview of the International H2O Project (IHOP_2002) and some preliminary highlights. Bull. Amer. Meteor. Soc., 85 , 253277.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Weckwerth, T. M., Pettet C. R. , Fabry F. , Park S. , LeMone M. A. , and Wilson J. W. , 2005: Radar refractivity retrieval: Validation and application to short-term forecasting. J. Appl. Meteor., 44 , 285300.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wilson, J. W., and Roberts R. D. , 2006: Summary of convective storm initiation and evolution during IHOP: Observational and modeling perspective. Mon. Wea. Rev., 134 , 2347.

    • Crossref
    • Search Google Scholar
    • Export Citation
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