• Atlas, D., , Matrosov S. Y. , , Heysmfield A. J. , , Chou M. , , and Wolff D. B. , 1995: Radar and radiation properties of clouds. J. Appl. Meteor., 34 , 23292345.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Brown, P. R. A., , Illingworth A. J. , , Heymsfield A. J. , , McFarquhar G. M. , , Browning K. A. , , and Gosset M. , 1995: The role of spaceborne millimeter-wave radar in the global monitoring of ice clouds. J. Appl. Meteor., 34 , 23462366.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Charlock, T., , Rose F. , , Yang S-K. , , Alberta T. , , and Smith G. , 1992: An observational study of the interaction of clouds, radiation, and the general circulation. Proceedings IRS'92: Current Problems in Atmospheric Radiation, S. Keevallik and O. Karner, Eds., A. Deepak Publishing, 151–154.

    • Search Google Scholar
    • Export Citation
  • ——,, ——, , Albert T. , , Smith G. L. , , Rutan D. , , Manola-Smith N. , , Minnis P. , , and Wielicki B. , 1994: Cloud profiling radar requirements: Perspective from retrievals of the surface and atmospheric radiation budget and studies of atmospheric energetics. Utility and Feasibility of a Cloud of Profiling Radar, Report of the GEWEX Topical Workshop, Pasadena, CA, IGPO Publication Series 10, WMO/TD-593, WCRP-84, 46 pp.

    • Search Google Scholar
    • Export Citation
  • Clothiaux, E. E., , Miller M. A. , , Albrecht B. A. , , Ackerman T. P. , , Verlinde J. , , Babb D. M. , , Peters R. M. , , and Syrett W. J. , 1995: An evaluation of a 94-GHz radar for remote sensing of cloud properties. J. Atmos. Oceanic Technol., 12 , 201228.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Fox, N. I., , and Illingworth A. J. , 1997: The potential of spaceborne cloud radar for the detection of stratocumulus clouds. J. Appl. Meteor., 36 , 676687.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • IGPO, 1994: Utility and Feasibility of a Cloud Profiling Radar, Report of the GEWEX Topical Workshop,. Pasadena, CA, IGPO Publication Series 10, WMO/TD-593, WCRP-84, 46 pp.

    • Search Google Scholar
    • Export Citation
  • Kropfli, R. A., , and Kelly R. D. , 1996: Meteorological research applications of MM-wave radar. Meteorol. Atmos. Phys., 59 , 105121.

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

  • Lemke, H., , Danne O. , , Quanta M. , , Raschke E. , , Girard R. A. , , and Park P. S. , 1997: Study on critical requirements for a cloud profiling radar. Executive Summary, ESTEC Contract No. 11327/94/NL/CN, GKSS Research Center, 10 pp.

    • Search Google Scholar
    • Export Citation
  • Lhermitte, R. M., 1987: A 94-GHz Doppler radar for cloud observations. J. Atmos. Oceanic Technol., 4 , 3648.

  • Liang, X-Z., , and Wang W-C. , 1997: Effect of cloud overlap on GCM climate simulations. J. Geophys. Res., 102 , 11 03911 047.

  • Mace, G. G., , Ackerman T. P. , , and Clothiaux E. E. , 1997: A study of composite cirrus morphology using data from a 94 Ghz radar and correlations with temperature and large-scale vertical motion. J. Geophys. Res., 102 , (D12),. 13 58113 593.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • ——, ——, Minnis, P., , and Young D. F. , 1998: Cirrus layer microphysical properties derived from surface based millimeter radar and infrared interferometer data, 1998. J. Geophys. Res., 103 , (D18),. 2320723216.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Martner, B. E., , and Moran K. P. , 2001: Using cloud radar polarization measurements to evaluate stratus cloud and insect echoes. J. Geophys. Res., in press.

    • Search Google Scholar
    • Export Citation
  • Moran, K. P., , Martner B. E. , , Post M. J. , , Kropfli R. A. , , Welsh D. C. , , and Widener K. B. , 1998: An unattended cloud profiling radar for use in climate research. Bull. Amer. Meteor. Soc., 79 , 443455.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Schneider, T. L., , and Stephens G. L. , 1996: Climatically relevant clouds as sensed by spaceborne cloud radar. Proceedings of the International Radiation Symposium, Deepak Publishing, 651–654.

    • Search Google Scholar
    • Export Citation
  • Sekelsky, S. M., , and McIntosh R. E. , 1996: Cloud observations with a polarimetric 33 Ghz and 95 Ghz radar. Meteor. Atmos. Phys., 59 , 123140.

  • Slingo, A., , and Slingo J. M. , 1988: The response of a general circulation model to cloud longwave radiative forcing. I: Introduction and initial experiments. Quart. J. Roy. Meteor. Soc., 114 , 10271062.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Stackhouse Jr., P. W., , and Stephens G. L. , 1991: A theoretical and observational study of the radiative properties of cirrus: Results from FIRE 1986. J. Atmos. Sci., 48 , 20442059.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Stephens, G. L., , and Webster P. J. , 1984: Cloud decoupling of the surface and planetary radiative budgets. J. Atmos. Sci., 41 , 681686.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Stokes, G. M., , and Schwartz S. E. , 1994: The Atmospheric Radiation Measurement (ARM) Program: Programmatic background and design of the cloud and radiation test bed. Bull. Amer. Meteor. Soc., 75 , 12011221.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Uttal, T., , Clothiaux E. E. , , Ackerman T. P. , , Intrieri J. M. , , and Eberhard W. L. , 1995: Cloud boundary statistics during FIRE II. J. Atmos. Sci., 52 , 42764284.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Walter, S. J., , Stephens G. L. , , and Vane D. G. , 1998: The CLOUDSAT mission. Proc. Battle Space Atmosphere and Coud Impacts on Military Operations Conf., Hanscom AFB, MA, Air Force Research Laboratory, 139–145.

    • Search Google Scholar
    • Export Citation
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The Effect of Radar Pulse Length on Cloud Reflectivity Statistics

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  • 1 NOAA/Environmental Technology Laboratory, Boulder, Colorado
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Abstract

When observing clouds with radars, there are a number of design parameters, such as transmitted power, antenna size, and wavelength, that can affect the detection threshold. In making calculations of radar thresholds, also known as minimum sensitivities, it is usually assumed that the radar pulse volume is completely filled with targets. In this paper, the issue of partial beam filling, which results, for instance, if a cloud is thin with respect to the pulse length, or measurements are being made near cloud edges, is investigated. This study pursues this question by using measurements of radar reflectivities made with a 35-GHz, surface-based radar with 37.5-m pulse lengths, and computing how reflectivity statistics would be affected if the same clouds and/or precipitation had been observed with a radar with a 450-m pulse length. In a dataset measured during winter over a midcontinental site, partial beamfilling degraded the percentage of clouds detected by about 22% if it was assumed that the minimum detection threshold was −30 dBZ. In a second dataset collected during summer over a summertime subtropical site that was dominated by thin, boundary layer stratus, partial beam filling degraded the percentage of clouds detected by 38%, again assuming a minimum detection threshold of −30 dBZ. This study provides a preliminary indication of how radar reflectivity statistics from a spaceborne cloud radar may be impacted by design constraints, which would mandate a pulse length of around 500 m and a minimum detection threshold of around −30 dBZ.

Corresponding author address: Taneil Uttal, R/E/ET6, NOAA/Environmental Technology Laboratory, 325 Broadway, Boulder, CO, 80305-3328.Email: Taneil.Uttal@noaa.gov

Abstract

When observing clouds with radars, there are a number of design parameters, such as transmitted power, antenna size, and wavelength, that can affect the detection threshold. In making calculations of radar thresholds, also known as minimum sensitivities, it is usually assumed that the radar pulse volume is completely filled with targets. In this paper, the issue of partial beam filling, which results, for instance, if a cloud is thin with respect to the pulse length, or measurements are being made near cloud edges, is investigated. This study pursues this question by using measurements of radar reflectivities made with a 35-GHz, surface-based radar with 37.5-m pulse lengths, and computing how reflectivity statistics would be affected if the same clouds and/or precipitation had been observed with a radar with a 450-m pulse length. In a dataset measured during winter over a midcontinental site, partial beamfilling degraded the percentage of clouds detected by about 22% if it was assumed that the minimum detection threshold was −30 dBZ. In a second dataset collected during summer over a summertime subtropical site that was dominated by thin, boundary layer stratus, partial beam filling degraded the percentage of clouds detected by 38%, again assuming a minimum detection threshold of −30 dBZ. This study provides a preliminary indication of how radar reflectivity statistics from a spaceborne cloud radar may be impacted by design constraints, which would mandate a pulse length of around 500 m and a minimum detection threshold of around −30 dBZ.

Corresponding author address: Taneil Uttal, R/E/ET6, NOAA/Environmental Technology Laboratory, 325 Broadway, Boulder, CO, 80305-3328.Email: Taneil.Uttal@noaa.gov

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