• Ashendon, R., , and Marwitz J. D. , 1997: Turboprop aircraft performance response to various environmental conditions. J. Aircraft, 34 , 278287.

  • Ashendon, R., , Lindberg W. , , Marwitz J. D. , , and Hoxie B. , . 1996: Airfoil performance degradation by supercooled cloud, drizzle, and rain drop icing. J. Aircraft, 33 , 10401046.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Brunkow, K. V., , Kennedy P. C. , , Rutledge S. A. , , Bringi V. N. , , and Chandrasekar V. , 1997: CSU–CHILL radar status and comparison of available operating modes. Preprints, 28th Conf. on Radar Meteorology, Austin, TX, Amer. Meteor. Soc., 43–44.

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

  • Doviak, R. J., , Bringi V. , , Ryzhkov A. , , Zahrai A. , , and Zrnić D. , . 2000: Considerations for polarimetric upgrades to operational WSR-88D radars. J. Atmos. Oceanic Technol., 17 , 257278.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hendry, A., , and Antar Y. M. M. , 1984: Precipitation particle identification with centimeter wavelength dual-polarization radar. Radio Sci., 19 , 132140.

    • Search Google Scholar
    • Export Citation
  • Hill, G. E., 1989: Laboratory calibration of a vibrating wire device for measuring concentrations of supercooled liquid water. J. Atmos. Oceanic Technol., 6 , 961970.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hill, G. E., . 1994: Analysis of supercooled liquid water measurements using microwave radiometer and vibrating wire devices. J. Atmos. Oceanic Technol., 11 , 12421252.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kajikawa, M., 1976: Observation of falling motion of columnar snow crystals. J. Meteor. Soc. Japan, 54 , 276283.

  • Kropfli, R. A., , and Kelly R. D. , 1996: Meteorological research applications of mm-wave radar. Meteor. Atmos. Phys., 59 , 105121.

  • Kropfli, R. A., and Coauthors. 1995: Cloud physics studies with 8 mm wavelength radar. Atmos. Res., 35 , 299313.

  • Lawson, R. P., , and Jensen T. L. , 1998: Improved microphysical observations in mixed phase clouds. Preprints, Conf. on Cloud Physics, Everett, WA, Amer. Meteor. Soc., 451–454.

    • Search Google Scholar
    • Export Citation
  • Lawson, R. P., , Korolev A. V. , , Cober S. G. , , Huang T. , , Strapp J. W. , , and Isaac G. A. , . 1998: Improved measurements of the drop size distribution of a freezing drizzle event. Atmos. Res., 47–48 , 181191.

    • Search Google Scholar
    • Export Citation
  • Liu, H., , and Chandrasekar V. , 2000: Classification of hydrometeors based on polarimetric radar measurements: Developments of fuzzy logic and neuro-fuzzy systems, and in situ verification. J. Atmos. Oceanic Technol., 17 , 140164.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Magono, C., , and Lee C. W. , 1966: Meteorological classification of natural snow crystals. J. Fac. Sci. Hokkaido Univ., 2 , 321335.

  • Mallman, A. J., , Hock J. L. , , and Greenler R. G. , 1998: Comparison of sun pillars with light pillars from nearby light sources. Appl. Opt., 37 , 14411449.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Martner, B. E., , and Kropfli R. A. , 1989: TRACIR: A radar technique for observing the exchange of air between clouds and their environment. Atmos. Environ., 23 , 27152721.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Matrosov, S. Y., 1991: Theoretical study of radar polarization parameters obtained from cirrus clouds. J. Atmos. Sci., 48 , 10621070.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Matrosov, S. Y., , and Kropfli R. A. , 1993: Cirrus cloud studies with elliptically polarized Ka-band radar signals: A suggested approach. J. Atmos. Oceanic Technol., 10 , 684692.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Matrosov, S. Y., , Reinking R. F. , , Kropfli R. A. , , and Bartram B. W. , . 1996: Estimation of ice hydrometeor types and shapes from radar polarization measurements. J. Atmos. Oceanic Technol., 13 , 8596.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Matrosov, S. Y., , Reinking R. F. , , Kropfli R. A. , , Martner B. E. , , and Bartram B. W. , . 2001: On the use of radar depolarization ratios for estimating shapes of ice hydrometeors. J. Appl. Meteor., 40 , 479490.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Politovich, M. K., 1996: Response of a research aircraft to icing and evaluation of severity indices. J. Aircraft, 33 , 291297.

  • Pruppacher, H. R., , and Klett J. D. , 1997: Microphysics of Clouds and Precipitation. 2d ed. D. Reidel, 954 pp.

  • Rasmussen, R., and Coauthors. 1992: Winter Icing and Storms Project (WISP). Bull. Amer. Meteor. Soc., 73 , 951974.

  • Reinking, R. F., , Matrosov S. Y. , , Bruintjes R. T. , , and Martner B. E. , 1997a: Identification of hydrometeors with elliptical and linear polarization Ka-band radar. J. Appl. Meteor., 36 , 322339.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Reinking, R. F., , Matrosov S. Y. , , Martner B. E. , , and Kropfli R. A. , . 1997b: Dual-polarization radar to identify drizzle, with applications to aircraft icing avoidance. J. Aircraft, 34 , 778784.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Reinking, R. F., , Matrosov S. Y. , , Ryerson C. C. , , Kropfli R. A. , , and Bartram B. W. , . 2000: Verified detection of supercooled large droplets with dual-polarized, millimeter-wave radar. Preprints, Ninth Conf. on Aviation, Range, and Aerospace Meteorology, Orlando, FL, Amer. Meteor. Soc., 537–542.

    • Search Google Scholar
    • Export Citation
  • Reinking, R. F., and Coauthors. 2001: Concept and design for a pilot demonstration ground-based remote icing detection system. Preprints, 30th Int. Conf. on Radar Meteorology, Munich, Germany, Amer. Meteor. Soc., 199–201.

    • Search Google Scholar
    • Export Citation
  • Ryerson, C. C., , Politovich M. K. , , Rancourt K. L. , , Koenig G. G. , , and Reinking R. F. , 2000: Mt. Washington Icing Sensors Project: Conduct and preliminary results. Proc. 38th AAIA Aerospace Science Meeting and Exhibit, Paper No. AAIA-2000-0488, Reno, NV, AIAA, 10 pp.

    • Search Google Scholar
    • Export Citation
  • Sassen, K., 1980: Remote sensing of planar ice crystal fall attitudes. J. Meteor. Soc. Japan, 58 , 422430.

  • Sturniolo, O., , Battaglia A. , , and Prodi F. , 2000: Depolarization ratios for partially aligned populations of hydrometeors with axially symmetric shapes. Proc. 13th Int. Conf. Clouds and Precipitation, Reno, NV, 276–279.

    • Search Google Scholar
    • Export Citation
  • Zikmunda, J., , and Vali G. , 1972: Fall patterns and fall velocities of rimed ice crystals. J. Atmos. Sci., 29 , 13341347.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zrnić, D. S., , and Ryzhkov A. V. , 1999: Polarimetry for weather surveillance radars. Bull. Amer. Meteor. Soc., 80 , 398406.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 171 171 18
PDF Downloads 104 104 11

Evaluation of a 45° Slant Quasi-Linear Radar Polarization State for Distinguishing Drizzle Droplets, Pristine Ice Crystals, and Less Regular Ice Particles

View More View Less
  • 1 NOAA/OAR/Environmental Technology Laboratory, Boulder, Colorado
  • | 2 Cooperative Institute for Research in the Environmental Sciences, University of Colorado, NOAA/Environmental Technology Laboratory, Boulder, Colorado
  • | 3 NOAA/OAR/Environmental Technology Laboratory, Boulder, Colorado
© Get Permissions Rent on DeepDyve
Restricted access

Abstract

A remote sensing capability is needed to detect clouds of supercooled, drizzle-sized droplets, which are a major aircraft icing hazard. Discrimination among clouds of differing ice particle types is also important because both the presence and type of ice influence the survival of liquid in a cloud and the chances for occurrence of these large, most hazardous droplets. This work shows how millimeter-wavelength dual-polarization radar can be used to identify these differing hydrometeors. It also shows that by measuring the depolarization ratio (DR), the estimation of the hydrometeor type can be accomplished deterministically for drizzle droplets; ice particles of regular shapes; and to a considerable extent, the more irregular ice particles, and that discrimination is strongly influenced by the polarization state of the transmitted microwave radiation. Thus, appropriate selection of the polarization state is emphasized.

The selection of an optimal polarization state involves trade-offs in competing factors such as the functional dynamic range of DR, sensitivity to low-reflectivity clouds, and insensitivity to oscillations in the settling orientations of ice crystals. A 45° slant, quasi-linear polarization state, one in which only slight ellipticity is introduced, was found to offer a very good compromise, providing considerable advantages over standard horizontal and substantially elliptical polarizations. This was determined by theoretical scattering calculations that were verified experimentally in field measurements conducted during the Mount Washington Icing Sensors Project (MWISP). A selectable-dual-polarization Ka-band (8.66-mm wavelength) radar was used. A wide variety of hydrometeor types was sampled. Clear differentiation among planar crystals, columnar crystals, and drizzle droplets was achieved. Also, differentiation among crystals of fundamentally different shapes (aspect ratios) within each of the planar and columnar families was found possible. These distinctions matched calculations of DR, usually to within 1 or 2 dB. The results from MWISP and from previous experiments with other polarizations have demonstrated that the agreement between theory and measurements by this method is repeatable. Additionally, although less rigorously predicted by theory, the field measurements demonstrated substantial differentiation among the more irregular and more spherical ice particles, including aggregates, elongated aggregates, heavily rimed dendrites, and graupel. Measurable separation between these various irregular ice particle types and drizzle droplets was also verified.

Corresponding author address: Dr. Roger F. Reinking, NOAA/ETL/ET6, 325 Broadway, Boulder, CO 80305. Email: Roger.Reinking@noaa.gov

Abstract

A remote sensing capability is needed to detect clouds of supercooled, drizzle-sized droplets, which are a major aircraft icing hazard. Discrimination among clouds of differing ice particle types is also important because both the presence and type of ice influence the survival of liquid in a cloud and the chances for occurrence of these large, most hazardous droplets. This work shows how millimeter-wavelength dual-polarization radar can be used to identify these differing hydrometeors. It also shows that by measuring the depolarization ratio (DR), the estimation of the hydrometeor type can be accomplished deterministically for drizzle droplets; ice particles of regular shapes; and to a considerable extent, the more irregular ice particles, and that discrimination is strongly influenced by the polarization state of the transmitted microwave radiation. Thus, appropriate selection of the polarization state is emphasized.

The selection of an optimal polarization state involves trade-offs in competing factors such as the functional dynamic range of DR, sensitivity to low-reflectivity clouds, and insensitivity to oscillations in the settling orientations of ice crystals. A 45° slant, quasi-linear polarization state, one in which only slight ellipticity is introduced, was found to offer a very good compromise, providing considerable advantages over standard horizontal and substantially elliptical polarizations. This was determined by theoretical scattering calculations that were verified experimentally in field measurements conducted during the Mount Washington Icing Sensors Project (MWISP). A selectable-dual-polarization Ka-band (8.66-mm wavelength) radar was used. A wide variety of hydrometeor types was sampled. Clear differentiation among planar crystals, columnar crystals, and drizzle droplets was achieved. Also, differentiation among crystals of fundamentally different shapes (aspect ratios) within each of the planar and columnar families was found possible. These distinctions matched calculations of DR, usually to within 1 or 2 dB. The results from MWISP and from previous experiments with other polarizations have demonstrated that the agreement between theory and measurements by this method is repeatable. Additionally, although less rigorously predicted by theory, the field measurements demonstrated substantial differentiation among the more irregular and more spherical ice particles, including aggregates, elongated aggregates, heavily rimed dendrites, and graupel. Measurable separation between these various irregular ice particle types and drizzle droplets was also verified.

Corresponding author address: Dr. Roger F. Reinking, NOAA/ETL/ET6, 325 Broadway, Boulder, CO 80305. Email: Roger.Reinking@noaa.gov

Save