• Abma, D., T. Heus, and J. P. Mellado, 2013: Direct numerical simulation of evaporative cooling at the lateral boundary of shallow cumulus clouds. J. Atmos. Sci., 70, 20882102, doi:10.1175/JAS-D-12-0230.1.

    • Search Google Scholar
    • Export Citation
  • Betts, A., 1973: Non-precipitating cumulus convection and its parameterization. Quart. J. Roy. Meteor. Soc., 99, 178196, doi:10.1002/qj.49709941915.

    • Search Google Scholar
    • Export Citation
  • Gerber, H., B. G. Arends, and A. S. Ackerman, 1994: New microphysics sensor for aircraft use. Atmos. Res., 31, 235252, doi:10.1016/0169-8095(94)90001-9.

    • Search Google Scholar
    • Export Citation
  • Gerber, H., G. M. Frick, J. B. Jensen, and J. G. Hudson, 2008: Entrainment, mixing, and microphysics in trade-wind cumulus. J. Meteor. Soc. Japan, 86A, 87106, doi:10.2151/jmsj.86A.87.

    • Search Google Scholar
    • Export Citation
  • Haman, K. E., A. Makulski, S. P. Malinowski, and R. Busen, 1997: A new ultrafast thermometer for airborne measurements in clouds. J. Atmos. Oceanic Technol., 14, 217227, doi:10.1175/1520-0426(1997)014<0217:ANUTFA>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Heus, T., and H. J. J. Jonker, 2008: Subsiding shells around shallow cumulus clouds. J. Atmos. Sci., 65, 10031018, doi:10.1175/2007JAS2322.1.

    • Search Google Scholar
    • Export Citation
  • Heus, T., J. Pols, C. Freek, J. Jonker, J. Harm, A. V. den Akker, E. Harry, and D. H. Lenschow, 2009: Observational validation of the compensating mass flux through the shell around cumulus clouds. Quart. J. Roy. Meteor. Soc., 135, 101112, doi:10.1002/qj.358.

    • Search Google Scholar
    • Export Citation
  • Jonas, P. R., 1990: Observations of cumulus cloud entrainment. Atmos. Res., 25, 105127, doi:10.1016/0169-8095(90)90008-Z.

  • Jonker, H. J. J., T. Heus, and P. P. Sullivan, 2008: A refined view of vertical mass transport by cumulus convection. Geophys. Res. Lett.,35, L07810, doi:10.1029/2007GL032606.

  • Kain, J. S., and J. M. Fritsch, 1990: A one-dimensional entraining/detraining plume model and its application in convective parameterization. J. Atmos. Sci., 47, 27842802, doi:10.1175/1520-0469(1990)047<2784:AODEPM>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Knight, C. A., and L. J. Miller, 1998: Early radar echoes from small, warm cumulus: Bragg and hydrometeor scattering. J. Atmos. Sci., 55, 29742992, doi:10.1175/1520-0469(1998)055<2974:EREFSW>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Rodts, S. M. A., P. G. Dnynkerke, and H. J. J. Jonker, 2003: Size distributions and dynamical properties of shallow cumulus clouds from aircraft observations and satellite data. J. Atmos. Sci., 60, 18951912, doi:10.1175/1520-0469(2003)060<1895:SDADPO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Siebert, H., and A. Muschinski, 2001: Relevance of a tuning-fork effect for temperature measurements with the Gill Solent HS ultrasonic anemometer–thermometer. J. Atmos. Oceanic Technol., 18, 13671376, doi:10.1175/1520-0426(2001)018<1367:ROATFE>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Siebert, H., M. Wendisch, T. Conrath, U. Teichmann, and J. Heintzenberg, 2003: A new tethered balloon-borne payload for fine-scale observations in the cloudy boundary layer. Bound.-Layer Meteor., 106, 461482, doi:10.1023/A:1021242305810.

    • Search Google Scholar
    • Export Citation
  • Siebert, H., H. Franke, K. Lehmann, R. Maser, E. W. Saw, D. Schell, R. A. Shaw, and M. Wendisch, 2006a: Probing fine-scale dynamics and microphysics of clouds with helicopter-borne measurements. Bull. Amer. Meteor. Soc., 87, 17271738, doi:10.1175/BAMS-87-12-1727.

    • Search Google Scholar
    • Export Citation
  • Siebert, H., K. Lehmann, and M. Wendisch, 2006b: Observations of small scale turbulence and energy dissipation rates in the cloudy boundary layer. J. Atmos. Sci., 63, 14511466, doi:10.1175/JAS3687.1.

    • Search Google Scholar
    • Export Citation
  • Siebert, H., K. Lehmann, and R. A. Shaw, 2007: On the use of hot-wire anemometers for turbulence measurements in clouds. J. Atmos. Oceanic Technol., 24, 980993, doi:10.1175/JTECH2018.1.

    • Search Google Scholar
    • Export Citation
  • Siebert, H., and Coauthors, 2013: The fine-scale structure of the trade wind cumuli over barbados—An introduction to the CARRIBA project. Atmos. Chem. Phys., 13, 10 06110 077, doi:10.5194/acp-13-10061-2013.

    • Search Google Scholar
    • Export Citation
  • Small, J. D., P. Y. Chuang, G. Feingold, and H. Jiang, 2009: Can aerosol decrease cloud lifetime? Geophys. Res. Lett.,36, L16806, doi:10.1029/2009GL038888.

  • Squires, P., and J. Warner, 1957: Some measurement in the orographic cloud of the island of Hawaii and of trade wind cumuli. Tellus, 9, 475494, doi:10.1111/j.2153-3490.1957.tb01909.x.

    • Search Google Scholar
    • Export Citation
  • Stith, J. L., 1992: Observations of cloud-top entrainment in cumuli. J. Atmos. Sci., 49, 13341347, doi:10.1175/1520-0469(1992)049<1334:OOCTEI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Stommel, H., 1947: Entrainment of air into a cumulus cloud. J. Meteor., 4, 9194, doi:10.1175/1520-0469(1947)004<0091:EOAIAC>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Wang, Y., and B. Geerts, 2010: Humidity variations across the edge of trade wind cumuli: Observations and dynamical implications. Atmos. Res., 97, 144156, doi:10.1016/j.atmosres.2010.03.017.

    • Search Google Scholar
    • Export Citation
  • Wang, Y., B. Geerts, and J. French, 2009: Dynamics of the cumulus cloud margin: An observational study. J. Atmos. Sci., 66, 36603677, doi:10.1175/2009JAS3129.1.

    • Search Google Scholar
    • Export Citation
  • Woodward, B., 1959: The motion in and around isolated thermals. Quart. J. Roy. Meteor. Soc., 85, 144151, doi:10.1002/qj.49708536407.

  • Wyngaard, J. C., 2010: Turbulence in the Atmosphere. Cambridge University Press, 408 pp.

  • Zhao, M., and P. H. Austin, 2005a: Life cycle of numerically simulated shallow cumulus clouds. Part I: Transport. J. Atmos. Sci., 62, 12691290, doi:10.1175/JAS3414.1.

    • Search Google Scholar
    • Export Citation
  • Zhao, M., and P. H. Austin, 2005b: Life cycle of numerically simulated shallow cumulus clouds. Part II: Mixing dynamics. J. Atmos. Sci., 62, 12911310, doi:10.1175/JAS3415.1.

    • Search Google Scholar
    • Export Citation
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Measurements of Turbulent Mixing and Subsiding Shells in Trade Wind Cumuli

Jeannine KatzwinkelLeibniz Institute for Tropospheric Research, Leipzig, Germany

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Holger SiebertLeibniz Institute for Tropospheric Research, Leipzig, Germany

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Thijs HeusUniversity of Cologne, Cologne, Germany

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Raymond A. ShawDepartment of Physics, Michigan Technological University, Houghton, Michigan

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Abstract

High-resolution measurements of the turbulent, thermodynamic, and microphysical structure of the edges of trade wind cumuli have been performed with the Airborne Cloud Turbulence Observation System. Lateral entrainment of subsaturated air into the cloud region leads to an evaporative cooling effect. The negatively buoyant air partly enhances the compensating downdraft, forming a subsiding shell at cloud edge. Based on the presented observations, the subsiding shell is divided into a turbulent and humid inner shell adjacent to the cloud interior and a nonbuoyant, nonturbulent outer shell. In the trade wind region, continuous development of shallow cumuli over the day allows for an analysis of the properties of both shells as a function of different cloud evolution stages. The shallow cumuli are divided into actively growing, decelerated, and dissolving based on cloud properties. As the cumuli evolve from actively growing to dissolving, the subsaturated environmental air is mixed deeper and deeper into the cloud region and the subsiding shell grows at the expense of the cloud. This measured evolution of the subsiding shell compares favorably with the predictions of a direct numerical simulation of an idealized subsiding shell. The thickness of the measured outer shell decreases with the evolution of the cumuli while the intensity of the downdraft is nearly constant.

Corresponding author address: Jeannine Katzwinkel, Leibniz Institute for Tropospheric Research, Permoserstraße 15, 04318 Leipzig, Germany. E-mail: jeannine.katzwinkel@tropos.de

Abstract

High-resolution measurements of the turbulent, thermodynamic, and microphysical structure of the edges of trade wind cumuli have been performed with the Airborne Cloud Turbulence Observation System. Lateral entrainment of subsaturated air into the cloud region leads to an evaporative cooling effect. The negatively buoyant air partly enhances the compensating downdraft, forming a subsiding shell at cloud edge. Based on the presented observations, the subsiding shell is divided into a turbulent and humid inner shell adjacent to the cloud interior and a nonbuoyant, nonturbulent outer shell. In the trade wind region, continuous development of shallow cumuli over the day allows for an analysis of the properties of both shells as a function of different cloud evolution stages. The shallow cumuli are divided into actively growing, decelerated, and dissolving based on cloud properties. As the cumuli evolve from actively growing to dissolving, the subsaturated environmental air is mixed deeper and deeper into the cloud region and the subsiding shell grows at the expense of the cloud. This measured evolution of the subsiding shell compares favorably with the predictions of a direct numerical simulation of an idealized subsiding shell. The thickness of the measured outer shell decreases with the evolution of the cumuli while the intensity of the downdraft is nearly constant.

Corresponding author address: Jeannine Katzwinkel, Leibniz Institute for Tropospheric Research, Permoserstraße 15, 04318 Leipzig, Germany. E-mail: jeannine.katzwinkel@tropos.de
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