Three-Body Scattering and Hail Size

D. S. Zrnic NOAA/National Severe Storms Laboratory, Norman, Oklahoma

Search for other papers by D. S. Zrnic in
Current site
Google Scholar
PubMed
Close
,
G. Zhang University of Oklahoma, Norman, Oklahoma

Search for other papers by G. Zhang in
Current site
Google Scholar
PubMed
Close
,
V. Melnikov Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, and NOAA/OAR/National Severe Storms Laboratory, Norman, Oklahoma

Search for other papers by V. Melnikov in
Current site
Google Scholar
PubMed
Close
, and
J. Andric Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, and NOAA/OAR/National Severe Storms Laboratory, Norman, Oklahoma

Search for other papers by J. Andric in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

The three-body scattering signature is an appendage seen on weather radar displays of reflectivity behind strong storm cells. It is caused by multiple scattering between hydrometeors and the ground. The radar equation for this phenomenon is reexamined and corrected to include the coherent wave component producing 3 dB more power than previously reported. Furthermore, the possibility to gauge hail size causing this phenomenon is explored. A model of forward scattering by spherical hail and accepted values of ground backscattering cross sections are used in an attempt to reconcile the reflectivity in this signature with observations. This work demonstrates that the signature can be caused by small- (<10 mm) to moderate- (20 mm) sized hail. An effort to gauge hail size by comparing the direct return from hail with the three-body scattered return is made. The theory indicates fundamental ambiguities in size retrieval resulting from resonant effects. Although theory eliminates the number of hailstones per unit volume, the shape of hail size distribution and the cross section of ground contribute additional uncertainty to the retrieval.

Corresponding author address: Dusan Zrnic, 120 David L. Boren Blvd., NOAA/NSSL, Norman, OK 73072. Email: dusan.zrnic@noaa.gov

Abstract

The three-body scattering signature is an appendage seen on weather radar displays of reflectivity behind strong storm cells. It is caused by multiple scattering between hydrometeors and the ground. The radar equation for this phenomenon is reexamined and corrected to include the coherent wave component producing 3 dB more power than previously reported. Furthermore, the possibility to gauge hail size causing this phenomenon is explored. A model of forward scattering by spherical hail and accepted values of ground backscattering cross sections are used in an attempt to reconcile the reflectivity in this signature with observations. This work demonstrates that the signature can be caused by small- (<10 mm) to moderate- (20 mm) sized hail. An effort to gauge hail size by comparing the direct return from hail with the three-body scattered return is made. The theory indicates fundamental ambiguities in size retrieval resulting from resonant effects. Although theory eliminates the number of hailstones per unit volume, the shape of hail size distribution and the cross section of ground contribute additional uncertainty to the retrieval.

Corresponding author address: Dusan Zrnic, 120 David L. Boren Blvd., NOAA/NSSL, Norman, OK 73072. Email: dusan.zrnic@noaa.gov

Save
  • Bohren, C. F., and D. R. Huffman, 1983: Absorption and Scattering of Light by Small Particles. John Wiley & Sons, 530 pp.

  • Cheng, L., 1987: An attempt to normalize the hailstorm variability for the evaluation of cloud seeding. J. Climate Appl. Meteor., 26 , 443456.

    • Search Google Scholar
    • Export Citation
  • Cheng, L., and M. English, 1983: A relationship between hailstone concentration and size. J. Atmos. Sci., 40 , 204213.

  • Depue, T. K., P. C. Kennedy, and S. A. Rutledge, 2007: Performance of the hail differential reflectivity (HDR) polarimetric radar hail indicator. J. Appl. Meteor. Climatol., 46 , 12901301.

    • Search Google Scholar
    • Export Citation
  • Doviak, R. J., and D. S. Zrnic, 2006: Doppler Radar and Weather Observations. 2nd ed. Dover, 562 pp.

  • Dumas, A., 1846: Twenty Years After. Oxford University Press, 880 pp.

  • Federer, B., and A. Waldvogel, 1975: Hail and raindrop size distributions form a Swiss multicell storm. J. Appl. Meteor., 14 , 9197.

  • Hubbert, J. C., and V. N. Bringi, 2000: The effects of three-body scattering on differential reflectivity signatures. J. Atmos. Oceanic Technol., 17 , 5161.

    • Search Google Scholar
    • Export Citation
  • Ishimaru, I., 1991: Electromagnetic Wave Propagation, Radiation and Scattering. Prentice-Hall, 656 pp.

  • Laws, J. O., and D. A. Parsons, 1943: The relationship of raindrop size to intensity. Trans. Amer. Geophys. Union, 24 , 452460.

  • Lemon, L. R., 1998: The radar “three-body scatter spike”: An operational large-hail signature. Wea. Forecasting, 13 , 327340.

  • Lindley, T. T., and L. R. Lemon, 2007: Preliminary observations of weak three-body scattering spikes associated with low-end severe hail. Electron. J. Severe Storms Meteor., 2 .[Available online at http://www.ejssm.org/ojs/index.php/ejssm/article/viewArticle/12/22].

    • Search Google Scholar
    • Export Citation
  • Long, M. W., 1975: Radar Reflectivity of Land and Sea. Lexington Books, 366 pp.

  • Marshall, J. S., and W. Palmer, 1948: The distribution of raindrops with size. J. Meteor., 5 , 165166.

  • Rasmussen, R. M., and A. J. Heymsfield, 1987: Melting and shedding of graupel and hail. Part I: Model physics. J. Atmos. Sci., 44 , 27542763.

    • Search Google Scholar
    • Export Citation
  • Seliga, T. A., and V. N. Bringi, 1976: Potential use of radar differential reflectivity measurements at orthogonal polarizations for measuring precipitation. J. Appl. Meteor., 15 , 6976.

    • Search Google Scholar
    • Export Citation
  • Ulaby, F. T., R. K. Moore, and A. K. Fung, 1990: From Theory to Applications. Vol. III, Microwave Remote Sensing Active and Passive, Artech House.

    • Search Google Scholar
    • Export Citation
  • Wilson, J. W., and D. Reum, 1988: The flare echo: Reflectivity and velocity signature. J. Atmos. Oceanic Technol., 5 , 197205.

  • Ziegler, C. L., P. S. Ray, and N. C. Knight, 1983: Hail growth in an Oklahoma multicell storm. J. Atmos. Sci., 40 , 17681791.

  • Zrnic, D. S., 1987: Three-body scattering produces precipitation signatures of special diagnostic value. Radio Sci., 22 , 7686.

  • Zrnic, D., V. Melnikov, and A. Ryzhkov, 2006: Correlation coefficients between vertically and horizontally polarized returns from ground clutter. J. Atmos. Oceanic Technol., 23 , 381394.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 611 140 19
PDF Downloads 523 131 24