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Entrainment in Unbroken Stratocumulus During POST

Hermann Gerber
Gerber Scientific, Inc.

In July and August of 2008 the CIRPAS Twin Otter aircraft was used during the POST (Physics of Stratocumulus Top) field study for 17 flights in unbroken Sc found off the coast of California in the vicinity of Monterey. The main goal of POST was to improve the understanding of the physical processes associated with entrainment and to permit its more accurate parameterization. Most Twin Otter flights were quasi-Lagrangian following the air flow in Sc, and most flight time was spent porpoising +/- 100-m on either side of Sc top. The fully instrumented Twin Otter included fast response microphysics and thermodynamic probes clustered closely around the aircraft’s gust probe producing 1-m resolution in cloud data.

This presentation includes the following topics based on POST data analysis: comparison of POST and DYCOMS II Sc; limitations of the classic equation for entrainment velocity; entrainment flux and velocity measurements; role of wind shear, mixing, and droplet evaporation at Sc top; entrained-parcel cooling due to IR flux divergence vs droplet evaporation; physical process of entrainment/detrainment; accuracy of CTEI and mixture fraction- analysis predictions, and recommendations for additional Sc studies.

Monday July 16, 2012, 3:30 PM - 4:30PM
Refreshments 3:15 PM
NCAR-Foothills Laboratory
3450 Mitchell Lane
Bldg 1 EOL Atrium (2198)

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Tuesday, July 10, 2012
Monday, July 16, 2012