| Summary: | Approved for public release; distribution unlimited. === The objective of this thesis is to obtain a better understanding of cloud-top
entrainment through an in-depth analysis of entrainment-zone structure. In situ
aircraft measurements taken during the Atlantic Stratocumulus Transition Experiment
(ASTEX) were used for this purpose. Using data collected from multiple cloud-top
penetrations, the presence of an interfacial layer in-between the top of the cloud
mixed-layer and the base of the free atmosphere is identified and consequently defined
as the entrainment zone. The depth of the entrainment zone is on the order of tens of
meters, where turbulence and sometimes cloud droplets are detectable. Inhomogeneous
mixing was found to occur within the entrainment zone. Parcels of inversion-layer air
and boundary-layer air are identified within the entrainment zone. Analyses suggest
that turbulence intensity and cloud amount in the entrainment zone vary depending on
the distribution of entrainment mixing fraction. Furthermore, continuous mixing in the
entrainment zone appears to dissipate the upper-cloud layer. However, continuous
dissipation of the upper-cloud layer has not been observed. Further study is needed to
determine the interaction between cloud-top entrainment and the full integration of
boundary-layer dynamics.
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