Evaporative and Radiative Cooling in POST Stratocumulus

H. Gerber Gerber Scientific, Inc., Reston, Virginia

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Szymon P. Malinowski University of Warsaw, Warsaw, Poland

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Haflidi Jonsson Naval Postgraduate School, Monterey, California

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Abstract

Buoyancy reversal by evaporative cooling in entrainment holes has a minimal influence on stratocumulus (Sc) observed during the Physics of Stratocumulus Top (POST) aircraft field study held off the California coast in 2008. High-resolution temperature and microphysics measurements show only small differences for Sc with and without buoyancy reversal predicted by mixing fraction analysis that relates mixtures of cloudy air and free-atmospheric air to buoyancies of the mixtures. The reduction of LWC due to evaporation in the holes is a small percentage (average ~12%) of liquid water diluted in the Sc by entrainment from the entrainment interface layer (EIL) located above unbroken cloud top where most mixing, evaporation, and reduction of the large buoyancy jump between the cloud and free atmosphere occur. Entrainment is dominated by radiative cooling at cloud top.

Corresponding author address: H. Gerber, Gerber Scientific, Inc., 1643 Bentana Way, Reston, VA 20190. E-mail: hgerber6@comcast.net

Abstract

Buoyancy reversal by evaporative cooling in entrainment holes has a minimal influence on stratocumulus (Sc) observed during the Physics of Stratocumulus Top (POST) aircraft field study held off the California coast in 2008. High-resolution temperature and microphysics measurements show only small differences for Sc with and without buoyancy reversal predicted by mixing fraction analysis that relates mixtures of cloudy air and free-atmospheric air to buoyancies of the mixtures. The reduction of LWC due to evaporation in the holes is a small percentage (average ~12%) of liquid water diluted in the Sc by entrainment from the entrainment interface layer (EIL) located above unbroken cloud top where most mixing, evaporation, and reduction of the large buoyancy jump between the cloud and free atmosphere occur. Entrainment is dominated by radiative cooling at cloud top.

Corresponding author address: H. Gerber, Gerber Scientific, Inc., 1643 Bentana Way, Reston, VA 20190. E-mail: hgerber6@comcast.net
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  • Albrecht, B. A., 1991: Fractional cloudiness and cloud-top entrainment instability. J. Atmos. Sci., 48, 15191525, doi:10.1175/1520-0469(1991)048<1519:FCACTE>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Deardorff, J. W., 1980: Cloud top entrainment instability. J. Atmos. Sci., 37, 561563, doi:10.1175/1520-0469(1980)037<0131:CTEI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • de Lozar, A., and J. P. Mellado, 2013: Direct numerical simulations of a smoke cloud-top mixing layer as a model for stratocumuli. J. Atmos. Sci., 70, 23562375, doi:10.1175/JAS-D-12-0333.1.

    • Search Google Scholar
    • Export Citation
  • de Lozar, A., and J. P. Mellado, 2015a: Mixing driven by radiative and evaporative cooling at stratocumulus top. J. Atmos. Sci., 72, 46814700, doi:10.1175/JAS-D-15-0087.1.

    • Search Google Scholar
    • Export Citation
  • de Lozar, A., and J. P. Mellado, 2015b: Evaporative cooling amplification of the entrainment velocity in radiatively driven stratocumulus. Geophys. Res. Lett., 42, 72237229, doi:10.1002/2015GL065529.

    • Search Google Scholar
    • Export Citation
  • de Roode, S. R., and Q. Wang, 2007: Do stratocumulus clouds detrain? FIRE I data revisited. Bound.-Layer Meteor., 122, 479491, doi:10.1007/s10546-006-9113-1.

    • 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., S. P. Malinowski, J.-L. Brenguier, and F. Burnet, 2005: Holes and entrainment in stratocumulus. J. Atmos. Sci., 62, 443459, doi:10.1175/JAS-3399.1.

    • Search Google Scholar
    • Export Citation
  • Gerber, H., G. Frick, S. P. Malinowski, H. Jonsson, D. Khelif, and S. K. Krueger, 2013: Entrainment rates and microphysics in POST stratocumulus. J. Geophys. Res. Atmos., 118, 12 09412 109, doi:10.1002/jgrd.50878.

    • Search Google Scholar
    • Export Citation
  • Gerber, H., S. P. Malinowski, A. Bucholtz, and T. Thorsen, 2014: Radiative cooling of stratocumulus. 14th Conf. on Atmospheric Radiation, Boston, MA, Amer. Meteor. Soc., 9.3. [Available online at https://ams.confex.com/ams/14CLOUD14ATRAD/webprogram/Paper248451.html.]

  • Jen-La Plante, I., and Coauthors, 2016: Physics of Stratocumulus Top (POST): Turbulence characteristics. Atmos. Phys. Chem., 16, 97119725, doi:10.5194/acp-16-9711-2016.

    • Search Google Scholar
    • Export Citation
  • Kumala, W., K. E. Haman, M. K. Kopec, D. Khelif, and S. P. Malinowski, 2013: Modified ultrafast thermometer UFT-M and temperature measurements during Physics of Stratocumulus Top (POST). Atmos. Meas. Tech., 6, 20432054, doi:10.5194/amt-6-2043-2013.

    • Search Google Scholar
    • Export Citation
  • Kurowski, M. J., S. P. Malinowski, and W. W. Grabowski, 2009: A numerical investigation of entrainment and transport within a stratocumulus-topped boundary layer. Quart. J. Roy. Meteor. Soc., 135, 7792, doi:10.1002/qj.354.

    • Search Google Scholar
    • Export Citation
  • Lilly, D. K., 1968: Models of cloud-topped mixed layers under a strong inversion. Quart. J. Roy. Meteor. Soc., 94, 292309, doi:10.1002/qj.49709440106.

    • Search Google Scholar
    • Export Citation
  • Malinowski, S. P., and Coauthors, 2013: Physics of Stratocumulus Top (POST): Turbulent mixing across capping inversion. Atmos. Chem. Phys., 13, 15 23315 269, doi:10.5194/acpd-13-15233-2013.

    • Search Google Scholar
    • Export Citation
  • Martin, G. M., D. W. Johnson, and A. Spice, 1994: The measurement and parameterization of effective radius of droplets in warm stratocumulus clouds. J. Atmos. Sci., 51, 18231842, doi:10.1175/1520-0469(1994)051<1823:TMAPOE>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Mellado, J. P., B. Stevens, and H. Schmidt, 2014: Wind shear and buoyancy reversal at the top of stratocumulus. J. Atmos. Sci., 71, 10401057, doi:10.1175/JAS-D-13-0189.1.

    • Search Google Scholar
    • Export Citation
  • Nicholls, S., and J. D. Turton, 1986: An observational study of the structure of stratiform cloud sheets: Part II. Entrainment. Quart. J. Roy. Meteor. Soc., 112, 461480, doi:10.1002/qj.49711247210.

    • Search Google Scholar
    • Export Citation
  • Randall, D. A., 1980: Conditional stability of the first kind upside down. J. Atmos. Sci., 37, 125130, doi:10.1175/1520-0469(1980)037<0125:CIOTFK>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Siems, S. T., C. S. Bretherton, M. B. Baker, S. Shy, and R. E. Breidenthal, 1990: Buoyancy reversal and cloud-top entrainment instability. Quart. J. Roy. Meteor. Soc., 116, 705739, doi:10.1002/qj.49711649309.

    • Search Google Scholar
    • Export Citation
  • Stevens, B., 2002: Entrainment in stratocumulus topped mixed layers. Quart. J. Roy. Meteor. Soc., 128, 26632690, doi:10.1256/qj.01.202.

    • Search Google Scholar
    • Export Citation
  • Stevens, B., and Coauthors, 2003: On entrainment rates in nocturnal marine stratocumulus. Quart. J. Roy. Meteor. Soc., 129, 34693493, doi:10.1256/qj.02.202.

    • Search Google Scholar
    • Export Citation
  • Van Zanten, M. C., and P. G. Duynkerke, 2002: Radiative and evaporative cooling in the entrainment zone of stratocumulus—The role of longwave radiative cooling above cloud top. Bound.-Layer Meteor., 102, 253280, doi:10.1023/A:1013129713315.

    • Search Google Scholar
    • Export Citation
  • Wang, Q., and B. A. Albrecht, 1994: Observations of cloud-top entrainment in marine stratocumulus clouds. J. Atmos. Sci., 51, 15301547, doi:10.1175/1520-0469(1994)051<1530:OOCTEI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Yamaguchi, T., and D. A. Randall, 2012: Cooling of entrained parcels in a large-eddy simulation. J. Atmos. Sci., 69, 11181136, doi:10.1175/JAS-D-11-080.1.

    • Search Google Scholar
    • Export Citation
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