• Atlas, D., 1966: The balance level in convective storms. J. Atmos. Sci., 23 , 635651.

  • Atlas, D., and C. W. Ulbrich, 2000: An observationally based conceptual model of warm oceanic convective rain in the Tropics. J. Appl. Meteor., 39 , 21652181.

    • Search Google Scholar
    • Export Citation
  • Atlas, D., C. W. Ulbrich, F. D. Marks Jr., E. Amitai, and C. R. Williams, 1999: Systematic variations of drop size and radar–rainfall relations. J. Geophys. Res., 104 (D6) 61556169.

    • Search Google Scholar
    • Export Citation
  • Auer Jr., A. H., 1972: Inferences about ice nucleation from ice crystal observations. J. Atmos. Sci., 29 , 311317.

  • Austin, P. M., and A. C. Bemis, 1950: A quantitative study of the “bright band” in radar precipitation echoes. J. Meteor., 7 , 145151.

    • Search Google Scholar
    • Export Citation
  • Battan, L. J., 1964: Some observations of vertical velocities and precipitation sizes in a thunderstorm. J. Appl. Meteor., 3 , 415420.

    • Search Google Scholar
    • Export Citation
  • Bringi, V. N., G-J. Huang, V. Chandrasekar, and E. Gorgucci, 2002: A methodology for estimating the parameters of a gamma raindrop size distribution model from polarimetric radar data: Application to a squall-line event from the TRMM/Brazil campaign. J. Atmos. Oceanic Technol., 19 , 633645.

    • Search Google Scholar
    • Export Citation
  • Carbone, R. E., and L. D. Nelson, 1978: The evolution of raindrop spectra in warm-based convective storms as observed and numerically modeled. J. Atmos. Sci., 35 , 23022314.

    • Search Google Scholar
    • Export Citation
  • Carey, L. D., and S. A. Rutledge, 2000: The relationship between precipitation and lightning in tropical island convection: A C-band polarimetric radar study. Mon. Wea. Rev., 128 , 26872710.

    • Search Google Scholar
    • Export Citation
  • Fujiwara, M., 1965: Raindrop-size distribution from individual storms. J. Atmos. Sci., 22 , 585591.

  • Gage, K. S., C. R. Williams, P. E. Johnston, W. L. Ecklund, R. Cifelli, A. Tokay, and D. A. Carter, 2000: Doppler radar profilers as calibration tools for scanning radars. J. Appl. Meteor., 39 , 22092222.

    • Search Google Scholar
    • Export Citation
  • Gunn, K. L. S., and J. S. Marshall, 1955: The effect of wind shear on falling precipitation. J. Meteor., 12 , 339349.

  • Hildebrand, P. H., and R. S. Sekhon, 1974: Objective determination of the noise level in Doppler spectra. J. Appl. Meteor., 13 , 808811.

    • Search Google Scholar
    • Export Citation
  • Hu, Z., and R. C. Srivastava, 1995: Evolution of raindrop size distribution by coalescence, breakup, and evaporation: Theory and observations. J. Atmos. Sci., 52 , 17611783.

    • Search Google Scholar
    • Export Citation
  • Hudlow, M. D., 1979: Mean rainfall patterns for the three phases of GATE. J. Appl. Meteor., 18 , 16561669.

  • Joss, J., and A. Waldvogel, 1967: Ein spektrograph fur niederschlagstropfen mit automatisher auswertung. Pure Appl. Geophys., 68 , 240246.

    • Search Google Scholar
    • Export Citation
  • Knight, N. C., and A. J. Heymsfield, 1983: Measurement and interpretation of hailstone density and terminal velocity. J. Atmos. Sci., 40 , 15101516.

    • Search Google Scholar
    • Export Citation
  • List, R., 1988: A linear radar reflectivity–rainrate relationship for steady tropical rain. J. Atmos. Sci., 45 , 35643572.

  • List, R., N. R. Donaldson, and R. E. Stewart, 1987: Temporal evolution of drop spectra to collisional equilibrium in steady and pulsating rain. J. Atmos. Sci., 44 , 362372.

    • Search Google Scholar
    • Export Citation
  • Lucas, C., E. J. Zipser, and M. A. Lemone, 1994: Vertical velocity in oceanic convection off tropical Australia. J. Atmos. Sci., 51 , 31833193.

    • Search Google Scholar
    • Export Citation
  • May, P. T., A. R. Jameson, T. D. Keenan, and P. E. Johnston, 2001: A comparison between polarimetric radar and wind profiler observations of precipitation in tropical showers. J. Appl. Meteor., 40 , 17021717.

    • Search Google Scholar
    • Export Citation
  • NCAR, 1999: S-POL TRMM-LBA Brazil 1999. S-Pol data user's guide: Introduction. [Available online at http://www.atd.ucar.edu/rsf/TRMM-LBA/.].

    • Search Google Scholar
    • Export Citation
  • Proctor, F. H., 1988: Numerical simulations of an isolated microburst. Part I: Dynamics and structure. J. Atmos. Sci., 45 , 31373160.

  • Pruppacher, H. R., and J. D. Klett, 1998: Microphysics of Clouds and Precipitation. Kluwer Academic, 954 pp.

  • Rasmussen, R. M., and A. J. Heymsfield, 1987: Melting and shedding of graupel and hail. Part II: Sensitivity study. J. Atmos. Sci., 44 , 27642782.

    • Search Google Scholar
    • Export Citation
  • Reynolds, S. E., M. Brook, and M. Gourley, 1957: Thunderstorm charge separation. J. Meteor., 14 , 426436.

  • Rickenbach, T. M., R. N. Ferreira, J. B. Halverson, D. L. Herdies, and M. A. F. Silva Dias, 2002: Modulation of convection in the southwestern Amazon basin by extratropical stationary fronts. J. Geophys. Res.,107 (D20), 8040, doi: 10.1029/2000JD000263.

    • Search Google Scholar
    • Export Citation
  • Rutledge, S. A., E. R. Williams, and T. D. Keenan, 1992: The Down Under Doppler and Electricity Experiment (DUNDEE): Overview and preliminary results. Bull. Amer. Meteor. Soc., 73 , 316.

    • Search Google Scholar
    • Export Citation
  • Saunders, C. P. R., W. D. Keith, and R. P. Mitzeva, 1991: The effect of liquid water on thunderstorm charging. J. Geophys. Res., 96 , 1100711017.

    • Search Google Scholar
    • Export Citation
  • Srivastava, R. C., 1987: A model of intense downdrafts driven by the melting and evaporation of precipitation. J. Atmos. Sci., 44 , 17521774.

    • Search Google Scholar
    • Export Citation
  • Stith, J. L., J. E. Dye, A. Bansemer, A. J. Heymsfield, C. A. Grainger, W. A. Peterson, and R. Cifelli, 2002: Microphysical observations of tropical clouds. J. Appl. Meteor., 41 , 97117.

    • Search Google Scholar
    • Export Citation
  • Szoke, E. J., and E. J. Zipser, 1986: A radar study of convective cells in mesoscale systems in GATE. Part II: Life cycles of convective cells. J. Atmos. Sci., 43 , 199218.

    • Search Google Scholar
    • Export Citation
  • Takahashi, T., 1978: Riming electrification as a charge generation mechanism in thunderstorms. J. Atmos. Sci., 35 , 15361548.

  • Testud, J., S. Oury, R. A. Black, P. Amayenc, and X. Dou, 2001: The concept of “normalized” distribution to describe raindrop spectra: A tool for cloud physics and cloud remote sensing. J. Appl. Meteor., 40 , 11181140.

    • Search Google Scholar
    • Export Citation
  • Tokay, A., and D. A. Short, 1996: Evidence from tropical raindrop spectra of the origin of rain from stratiform versus convective clouds. J. Appl. Meteor., 35 , 355371.

    • Search Google Scholar
    • Export Citation
  • Tokay, A., D. A. Short, C. R. Williams, W. L. Ecklund, and K. S. Gage, 1999: Tropical rainfall associated with convective and stratiform clouds: Intercomparison of disdrometer and profiler measurements. J. Appl. Meteor., 38 , 302320.

    • Search Google Scholar
    • Export Citation
  • Ulbrich, C. W., and D. Atlas, 1978: The rain parameter diagram: Methods and applications. J. Geophys. Res., 83 , 13191325.

  • Ulbrich, C. W., and D. Atlas, 2002: On the separation of tropical convective and stratiform rains. J. Appl. Meteor., 41 , 188195.

  • Wallace, J. M., and P. V. Hobbs, 1977: Atmospheric Sciences: An Introductory Survey. Academic Press, 467 pp.

  • Williams, C. R., 2002: Simultaneous ambient air motion and raindrop size distributions retrieved from UHF vertical incident profiler observations. Radio Sci., 37, 1024, doi: 10.1029/2000RS002603.

    • Search Google Scholar
    • Export Citation
  • Williams, E., and Coauthors. 2002: Contrasting convective regimes over the Amazon: Implications for cloud electrication. J. Geophys. Res.,107 (D20), 8082, doi: 10.1029/2001JD000380.

    • Search Google Scholar
    • Export Citation
  • Zipser, E. J., and K. R. Lutz, 1994: The vertical profile of radar reflectivity of convective cells: A strong indicator of storm intensity and lightning probability? Mon. Wea. Rev., 122 , 17511759.

    • Search Google Scholar
    • Export Citation
  • Zrnic, D. S., and A. V. Ryzhkov, 1999: Polarimetry for weather surveillance radars. Bull. Amer. Meteor. Soc., 80 , 389406.

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The Anatomy of a Continental Tropical Convective Storm

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  • 1 NASA Goddard Space Flight Center, Greenbelt, Maryland
  • | 2 University of Colorado, and NOAA/Aeronomy Laboratory, Boulder, Colorado
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Abstract

This study provides a very clear picture of the microphysics and flow field in a convective storm in the Rondonia region of Brazil through a synthesis of observations from two unique radars, measurements of the surface drop size distribution (DSD), and particle types and sizes from an aircraft penetration. The primary findings are 1) the growth of rain by the collision–coalescence–breakup (CCB) process to equilibrium drop size distributions entirely below the 0°C level; 2) the subsequent growth of larger ice particles (graupel and hail) at subfreezing temperatures; 3) the paucity of lightning activity during the former process, and the increased lightning frequency during the latter; 4) the occurrence of strong downdrafts and a downburst during the latter phase of the storm resulting from cooling by melting and evaporation; 5) the occurrence of turbulence along the main streamlines of the storm; and 6) the confirmation of the large drops reached during the CCB growth by polarimetric radar observations. These interpretations have been made possible by estimating the updraft magnitude using the “lower bound” of the Doppler spectrum at vertical incidence, and identifying the “balance level” at which particles are supported for growth. The combination of these methods shows where raindrops are supported for extended periods to allow their growth to equilibrium drop size distributions, while smaller drops ascend and large ones descend. A hypothesis worthy of pursuit is the control of the storm motion by the winds at the balance level, which is the effective precipitation generating level. Above the 0°C level the balance level separates the small ascending ice crystals from the large descending graupel and hail. Collisions between the two cause electrical charging, while gravity and the updrafts separate the charges to cause lightning. Below the 0°C level, large downward velocities (caused by the above-mentioned cooling) in excess of the terminal fall speeds of raindrops represent the downbursts, which are manifested in the surface winds.

Distinguished visiting scientist

Corresponding author address: David Atlas, Goddard Space Flight Center, Code 912, Greenbelt, MD 20771. Email: datlas@radar.gsfc.nasa.gov

Abstract

This study provides a very clear picture of the microphysics and flow field in a convective storm in the Rondonia region of Brazil through a synthesis of observations from two unique radars, measurements of the surface drop size distribution (DSD), and particle types and sizes from an aircraft penetration. The primary findings are 1) the growth of rain by the collision–coalescence–breakup (CCB) process to equilibrium drop size distributions entirely below the 0°C level; 2) the subsequent growth of larger ice particles (graupel and hail) at subfreezing temperatures; 3) the paucity of lightning activity during the former process, and the increased lightning frequency during the latter; 4) the occurrence of strong downdrafts and a downburst during the latter phase of the storm resulting from cooling by melting and evaporation; 5) the occurrence of turbulence along the main streamlines of the storm; and 6) the confirmation of the large drops reached during the CCB growth by polarimetric radar observations. These interpretations have been made possible by estimating the updraft magnitude using the “lower bound” of the Doppler spectrum at vertical incidence, and identifying the “balance level” at which particles are supported for growth. The combination of these methods shows where raindrops are supported for extended periods to allow their growth to equilibrium drop size distributions, while smaller drops ascend and large ones descend. A hypothesis worthy of pursuit is the control of the storm motion by the winds at the balance level, which is the effective precipitation generating level. Above the 0°C level the balance level separates the small ascending ice crystals from the large descending graupel and hail. Collisions between the two cause electrical charging, while gravity and the updrafts separate the charges to cause lightning. Below the 0°C level, large downward velocities (caused by the above-mentioned cooling) in excess of the terminal fall speeds of raindrops represent the downbursts, which are manifested in the surface winds.

Distinguished visiting scientist

Corresponding author address: David Atlas, Goddard Space Flight Center, Code 912, Greenbelt, MD 20771. Email: datlas@radar.gsfc.nasa.gov

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