Effects of Wind Field Inhomogeneities on Doppler Beam Swinging Revealed by an Imaging Radar

B. L. Cheong School of Meteorology, University of Oklahoma, Norman, Oklahoma

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R. D. Palmer School of Meteorology, University of Oklahoma, Norman, Oklahoma

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T-Y. Yu School of Electrical and Computer Engineering, University of Oklahoma, Norman, Oklahoma

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K-F. Yang Institute of Space Science, National Central University, Jhongli, Taiwan

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M. W. Hoffman Department of Electrical Engineering, University of Nebraska, Lincoln, Nebraska

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S. J. Frasier Department of Computer and Electrical Engineering, University of Massachusetts—Amherst, Amherst, Massachusetts

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F. J. Lopez-Dekker Department of Computer and Electrical Engineering, University of Massachusetts—Amherst, Amherst, Massachusetts

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Abstract

In this work, the accuracy of the Doppler beam-swinging (DBS) technique for wind measurements is studied using an imaging radar—the turbulent eddy profiler (TEP) developed by the University of Massachusetts, with data collected in summer 2003. With up to 64 independent receivers, and using coherent radar imaging (CRI), several hundred partially independent beams can be formed simultaneously within the volume defined by the transmit beam. By selecting a subset of these beams, an unprecedented number of DBS configurations with varying zenith angle, azimuth angle, and number of beams can be investigated. The angular distributions of echo power and radial velocity obtained by CRI provide a unique opportunity to validate the inherent assumption in the DBS method of homogeneity across the region defined by the beam directions. Through comparison with a reference wind field, calculated as the optimal uniform wind field derived from all CRI beams with sufficient signal-to-noise ratio (SNR), the accuracy of the wind estimates for various DBS configurations is statistically analyzed. It is shown that for a three-beam DBS configuration, although the validity of the homogeneity assumption is enhanced at smaller zenith angles, the root-mean-square (RMS) error increases because of the ill-conditioned matrix in the DBS algorithm. As expected, inhomogeneities in the wind field produce large bias for the three-beam DBS configuration for large zenith angles. An optimal zenith angle, in terms of RMS error, of approximately 9°–10° was estimated. It is further shown that RMS error can be significantly reduced by increasing the number of off-vertical beams used for the DBS processing.

Corresponding author address: Dr. Boon Leng Cheong, School of Meteorology, University of Oklahoma, 120 David L. Boren Blvd., Suite 5900, Norman, OK 73072. Email: boonleng@ou.edu

This article included in the Fifth International Symposium on Tropospheric Profiling (ISTP) special collection.

Abstract

In this work, the accuracy of the Doppler beam-swinging (DBS) technique for wind measurements is studied using an imaging radar—the turbulent eddy profiler (TEP) developed by the University of Massachusetts, with data collected in summer 2003. With up to 64 independent receivers, and using coherent radar imaging (CRI), several hundred partially independent beams can be formed simultaneously within the volume defined by the transmit beam. By selecting a subset of these beams, an unprecedented number of DBS configurations with varying zenith angle, azimuth angle, and number of beams can be investigated. The angular distributions of echo power and radial velocity obtained by CRI provide a unique opportunity to validate the inherent assumption in the DBS method of homogeneity across the region defined by the beam directions. Through comparison with a reference wind field, calculated as the optimal uniform wind field derived from all CRI beams with sufficient signal-to-noise ratio (SNR), the accuracy of the wind estimates for various DBS configurations is statistically analyzed. It is shown that for a three-beam DBS configuration, although the validity of the homogeneity assumption is enhanced at smaller zenith angles, the root-mean-square (RMS) error increases because of the ill-conditioned matrix in the DBS algorithm. As expected, inhomogeneities in the wind field produce large bias for the three-beam DBS configuration for large zenith angles. An optimal zenith angle, in terms of RMS error, of approximately 9°–10° was estimated. It is further shown that RMS error can be significantly reduced by increasing the number of off-vertical beams used for the DBS processing.

Corresponding author address: Dr. Boon Leng Cheong, School of Meteorology, University of Oklahoma, 120 David L. Boren Blvd., Suite 5900, Norman, OK 73072. Email: boonleng@ou.edu

This article included in the Fifth International Symposium on Tropospheric Profiling (ISTP) special collection.

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  • Adachi, A., Kobayashi T. , Gage K. S. , Carter D. A. , Hartten L. M. , Clark W. L. , and Fukuda M. , 2005: Evaluation of three-beam and four-beam profiler wind measurement techniques using a five-beam wind profiler and collocated meteorological tower. J. Atmos. Oceanic Technol., 22 , 11671180.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Capon, J., 1969: High-resolution frequency-wavenumber spectrum analysis. Proc. IEEE, 57 , 14081419.

  • Cheong, B. L., Hoffman M. W. , Palmer R. D. , Frasier S. J. , and López-Dekker F. J. , 2004: Pulse pair beamforming and the effects of reflectivity field variations on imaging radars. Radio Sci., 39 .RS3014, doi:10.1029/2002RS002843.

    • Search Google Scholar
    • Export Citation
  • Cheong, B. L., Hoffman M. W. , Palmer R. D. , Frasier S. J. , and López-Dekker F. J. , 2006: Phase-array design for biological clutter rejection: Simulation and experimental validation. J. Atmos. Oceanic Technol., 23 , 585598.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gage, K. S., 1990: Radar observations of the free atmosphere: Structure and dynamics. Radar in Meteorology: Battan Memorial and 40th Anniversary Radar Meteorology Conference, D. Atlas, Ed., Amer. Meteor. Soc., 534–565.

    • Search Google Scholar
    • Export Citation
  • Hélal, D., Crochet M. , Luce H. , and Spano E. , 2001: Radar imaging and high-resolution array processing applied to a classical VHF-ST profiler. J. Atmos. Solar-Terr. Phys., 63 , 263274.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Koscielny, A. J., Doviak R. J. , and Zrnić D. S. , 1984: An evaluation of the accuracy of some radar wind profiling techniques. J. Atmos. Oceanic Technol., 1 , 309320.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kudeki, E., and Sürücü F. , 1991: Radar interferometric imaging of field-aligned plasma irregularities in the equatorial electrojet. Geophys. Res. Lett., 18 , 4144.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lopez-Dekker, P., and Frasier S. J. , 2004: Radio acoustic sounding with a UHF volume imaging radar. J. Atmos. Oceanic Technol., 21 , 766776.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Mead, J. B., Hopcraft G. , Frasier S. J. , Pollard B. D. , Cherry C. D. , Schaubert D. H. , and McIntosh R. E. , 1998: A volume-imaging radar wind profiler for atmospheric boundary layer turbulence studies. J. Atmos. Oceanic Technol., 15 , 849859.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Palmer, R. D., Larsen M. F. , and Sheppard E. L. , 1993: Poststatistic steering wind estimation in the troposphere and lower stratosphere. Radio Sci., 28 , 261271.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Palmer, R. D., Gopalam S. , Yu T. , and Fukao S. , 1998: Coherent radar imaging using Capon’s method. Radio Sci., 33 , 15851598.

  • Palmer, R. D., Cheong B. L. , Hoffman M. W. , Frasier S. J. , and López-Dekker F. J. , 2005: Observation of the small-scale variability or precipitation using an imaging radar. J. Atmos. Oceanic Technol., 22 , 11221137.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Röttger, J., and Larsen M. F. , 1990: UHF/VHF radar techniques for atmospheric research and wind profiler applications. Radar in Meteorology: Battan Memorial and 40th Anniversary Radar Meteorology Conference, D. Atlas, Ed., Amer. Meteor. Soc., 235–281.

    • Search Google Scholar
    • Export Citation
  • Strauch, R. G., Merritt D. A. , Moran K. P. , Earnshaw K. B. , and Kamp D. V. , 1984: The Colorado wind-profiling network. J. Atmos. Oceanic Technol., 1 , 3749.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Strauch, R. G., Weber B. L. , Frisch A. S. , Little C. G. , Merritt D. A. , Moran K. P. , and Welsh D. C. , 1987: The precision and relative accuracy of profiler wind measurements. J. Atmos. Oceanic Technol., 4 , 563571.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Thorsen, D., Franke S. J. , and Kudeki E. , 1997: A new approach to MF radar interferometry for estimating mean winds and momentum flux. Radio Sci., 32 , 707726.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Yu, T-Y., Palmer R. D. , and Hysell D. L. , 2000: A simulation study of coherent radar imaging. Radio Sci., 35 , 11291141.

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