Editorial Type:
Article
Article Type:
Research Article

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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Print Publication:
01 Oct 2016
DOI:
https://doi.org/10.1175/JAS-D-16-0023.1
Page(s):
3877–3884
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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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