• Ackerman, B., 1958: Turbulence around tropical cumuli. J. Meteor., 15 , 6974.

  • Bluestein, H. W., and C. C. Weiss, 2004: Doppler radar observations of dust devils in Texas. Mon. Wea. Rev., 132 , 209224.

  • Blyth, A. M., 1993: Entrainment in cumulus clouds. J. Appl. Meteor., 32 , 626641.

  • Blyth, A. M., W. A. Cooper, and J. B. Jensen, 1988: A study of the source of entrained air in Montana cumuli. J. Atmos. Sci., 45 , 39443964.

    • Search Google Scholar
    • Export Citation
  • Carpenter, R. L. J., K. K. Droegemeier, and A. M. Blyth, 1998: Entrainment and detrainment in numerically simulated cumulus congestus clouds. Part III: Parcel analysis. J. Atmos. Sci., 55 , 34403455.

    • Search Google Scholar
    • Export Citation
  • Carroll, J. J., and J. A. Ryan, 1970: Atmospheric vorticity and dust devil rotation. J. Geophys. Res., 75 , 51795184.

  • Chang, Y. K., and A. D. Vakili, 1995: Dynamics of vortex rings in crossflow. Phys. Fluids, 7 , 15831597.

  • Church, C. R., J. T. Snow, and J. Dessens, 1980: Intense atmospheric vortices associated with a 1000 MW fire. Bull. Amer. Meteor. Soc., 61 , 682694.

    • Search Google Scholar
    • Export Citation
  • Cortese, T., and S. Balachandar, 1993: Vortical nature of thermal plumes in turbulent convection. Phys. Fluids, 5 , 32263232.

  • Cunningham, P., S. L. Goodrick, M. Y. Hussaini, and R. R. Linn, 2005: Coherent vortical structures in numerical simulations of buoyant plumes from wildland fires. Int. J. Wildland Fire, 14 , 6175.

    • Search Google Scholar
    • Export Citation
  • Damiani, R., and S. Haimov, 2006: A high-resolution dual-Doppler technique for fixed multi-antenna airborne radar. IEEE Trans. Geosci. Remote Sens., 42 , 34753489.

    • Search Google Scholar
    • Export Citation
  • Damiani, R., S. Haimov, and G. Vali, 2005: High-resolution airborne radar dual-Doppler technique. Preprints, 32d Conf. on Radar Meteorology, Albuquerque, NM, Amer. Meteor. Soc., CD-ROM, P1R.4.

  • Damiani, R., G. Vali, and S. Haimov, 2006: The structure of thermals in cumulus from airborne dual-Doppler radar observations. J. Atmos. Sci., 63 , 14321450.

    • Search Google Scholar
    • Export Citation
  • Davies-Jones, R., 1984: Streamwise vorticity: The origin of updraft rotation in supercell storms. J. Atmos. Sci., 41 , 29913006.

  • Diez, F. J., L. P. Bernal, and G. M. Faeth, 2003: Round turbulent thermals, puffs, starting plumes and starting jets in uniform crossflow. ASME J. Heat Transfer, 125 , 10461057.

    • Search Google Scholar
    • Export Citation
  • Emmitt, G. D., 1978: Tropical cumulus interaction with and modification of the subcloud region. J. Atmos. Sci., 35 , 14851502.

  • Etling, D., 1985: Some aspects of helicity in atmospheric flows. Beitr. Phys. Atmos., 58 , 88100.

  • Fernando, H. J. S., and D. C. I. Smith, 2001: Vortex structure in geophysical convection. Eur. J. Mech., 20B , 437470.

  • Fric, T. F., and A. Roshko, 1994: Vortical structure in the wake of a transverse jet. J. Fluid Mech., 279 , 147.

  • Hauf, T., 1985: Rotating clouds within cloud streets. Beitr. Phys. Atmos., 58 , 380398.

  • Kanak, K. M., D. K. Lilly, and J. T. Snow, 2000: The formation of vertical vortices in the convective boundary layer. Quart. J. Roy. Meteor. Soc., 126 , 27892810.

    • Search Google Scholar
    • Export Citation
  • Kelso, R. M., T. T. Lim, and A. E. Perry, 1996: An experimental study of round jets in cross-flow. J. Fluid Mech., 306 , 111144.

  • Kitchen, M., and S. J. Caughey, 1981: Tethered-balloon observations of the structure of small cumulus clouds. Quart. J. Roy. Meteor. Soc., 107 , 853874.

    • Search Google Scholar
    • Export Citation
  • Klemp, J. B., 1987: Dynamics of tornadic thunderstorms. Annu. Rev. Fluid Mech., 19 , 369402.

  • Lilly, D. K., 1986: The structure, energetics, and propagation of rotating convective storms. Part II: Helicity and storm stabilization. J. Atmos. Sci., 43 , 126140.

    • Search Google Scholar
    • Export Citation
  • Lim, T. T., T. H. New, and S. C. Luo, 2001: On the development of large-scale structures of a jet normal to a cross flow. Phys. Fluids, 13 , 770775.

    • Search Google Scholar
    • Export Citation
  • Malkus, J. S., 1954: Some results of a trade-cumulus cloud investigation. J. Atmos. Sci., 11 , 220237.

  • Maxworthy, T., 1973: A vorticity source for large-scale dust devils and other comments on naturally occurring columnar vortices. J. Atmos. Sci., 30 , 17171722.

    • Search Google Scholar
    • Export Citation
  • Morton, B. R., 1997a: Discrete dry convective entities. I: Review. The Physics and Parameterization of Moist Atmospheric Convection, Series C: Mathematical and Physical Sciences, Vol. 505, Kluwer Academic, 143–173.

    • Search Google Scholar
    • Export Citation
  • Morton, B. R., 1997b: Discrete dry convective entities. II: Thermals and deflected jets. The Physics and Parameterization of Moist Atmospheric Convection, Series C: Mathematical and Physical Sciences, Vol. 505, Kluwer Academic, 175–210.

    • Search Google Scholar
    • Export Citation
  • Perry, K. D., and P. V. Hobbs, 1996: Influences of isolated cumulus clouds on the humidity of their surroundings. J. Atmos. Sci., 53 , 159174.

    • Search Google Scholar
    • Export Citation
  • Rogers, D. P., J. W. Telford, and S. K. Chai, 1985: Entrainment and the temporal evolution of the microphysics of convective clouds. J. Atmos. Sci., 42 , 18461858.

    • Search Google Scholar
    • Export Citation
  • Rotunno, R., 1981: On the evolution of thunderstorm rotation. Mon. Wea. Rev., 109 , 577586.

  • Scorer, R. S., 1958: Natural Aerodynamics. Vol. 1, International Series of Monographs in Aeronautics and Astronautics, Pergamon, 312 pp.

    • Search Google Scholar
    • Export Citation
  • Scorer, R. S., and F. H. Ludlam, 1953: Bubble theory of penetrative convection. Quart. J. Roy. Meteor. Soc., 79 , 94103.

  • Shapiro, A., and Y. L. Kogan, 1994: On vortex formation in multicell convective clouds in a shear-free environment. Atmos. Res., 33 , 125136.

    • Search Google Scholar
    • Export Citation
  • Shapiro, A., and M. Kanak, 2002: Vortex formation in ellipsoidal thermal bubbles. J. Atmos. Sci., 59 , 22532269.

  • Vaillancourt, P. A., M. K. Yau, and W. W. Grabowski, 1997: Upshear and downshear evolution of cloud structure and spectral properties. J. Atmos. Sci., 54 , 12031217.

    • Search Google Scholar
    • Export Citation
  • Woodward, B., 1959: The motion in and around isolated thermals. Quart. J. Roy. Meteor. Soc., 85 , 144151.

  • Zhao, M., and P. H. Austin, 2005: Life cycle of numerically simulated shallow cumulus clouds. Part II: Mixing dynamics. J. Atmos. Sci., 62 , 12911310.

    • Search Google Scholar
    • Export Citation
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Evidence for Tilted Toroidal Circulations in Cumulus

Rick DamianiDepartment of Atmospheric Science, University of Wyoming, Laramie, Wyoming

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Gabor ValiDepartment of Atmospheric Science, University of Wyoming, Laramie, Wyoming

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Abstract

Intense vortical circulations, often organized in counterrotating vortex pairs, were detected in midcontinental cumulus congestus over southeast Wyoming in July 2003. The sampled clouds developed in dry environments and at cold temperatures, and were a few kilometers in depth and width. Observations were obtained with the Wyoming Cloud Radar from aboard the Wyoming King Air research aircraft. Dual-Doppler analyses of the data yielded high-resolution (30–45 m) depictions of the horizontal components of air motions across vigorously growing clouds. The vortices found in the horizontal cross sections are interpreted as components of the toroidal circulations in thermals when those are tilted because of the effect of ambient cross flow. This configuration also leads to a partial stabilization of the vertical trajectory of the updraft, by opposing the drag by the ambient wind. Additionally, dry air intrusions were seen to accompany these features when the vortices developed near the cloud outer boundaries; recirculation of hydrometeors occurred when the vortices were adjacent to in-cloud downdrafts. These features are also evident in the radar reflectivity patterns. In general, gradients of velocities and vorticity values in horizontal planes are comparable to those found in vertical planes.

Corresponding author address: Rick Damiani, University of Wyoming, 1000 E. University Ave., Laramie, WY 82071. Email: rdamiani@cppwind.com

Abstract

Intense vortical circulations, often organized in counterrotating vortex pairs, were detected in midcontinental cumulus congestus over southeast Wyoming in July 2003. The sampled clouds developed in dry environments and at cold temperatures, and were a few kilometers in depth and width. Observations were obtained with the Wyoming Cloud Radar from aboard the Wyoming King Air research aircraft. Dual-Doppler analyses of the data yielded high-resolution (30–45 m) depictions of the horizontal components of air motions across vigorously growing clouds. The vortices found in the horizontal cross sections are interpreted as components of the toroidal circulations in thermals when those are tilted because of the effect of ambient cross flow. This configuration also leads to a partial stabilization of the vertical trajectory of the updraft, by opposing the drag by the ambient wind. Additionally, dry air intrusions were seen to accompany these features when the vortices developed near the cloud outer boundaries; recirculation of hydrometeors occurred when the vortices were adjacent to in-cloud downdrafts. These features are also evident in the radar reflectivity patterns. In general, gradients of velocities and vorticity values in horizontal planes are comparable to those found in vertical planes.

Corresponding author address: Rick Damiani, University of Wyoming, 1000 E. University Ave., Laramie, WY 82071. Email: rdamiani@cppwind.com

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