Entrainment and Microphysics of Stratocumulus Clouds

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The objective of this project is to study mixing processes and cloud droplet growth as part of DYCOMS-II (Dynamics and Chemistry of Marine Stratocumulus), a collaborative field program conducted off the coast of California in July 2001. The experimental program, based on the NSF C-130 research aircraft, will provide data of unprecedented high resolution on air motions, temperature, and humidity. The Particle Volume Monitor (PVM) of Dr. Gerber will also be deployed, to give information on the fine-scale variability of cloud water content. Four studies related to entrainment and mixing at cloud top will be undertaken:1. Estimation of entrainment rate using high-resolution measurements of liquid water content, humidity, and vertical air velocity.2. Investigation of the cause of an apparent "scale break" at a scale of several meters in the spectrum of liquid water content fluctuations.3. Formulation of a conceptual model of the structure of the cloud-top layer.4. Exploring the possibility of enhanced condensation near cloud top caused by the mixing of air parcels with different temperatures.The ultimate goal of the research is to improve the ability to model the development of marine stratocumulus clouds, taking into account mixing processes at cloud top. This will lead to better parameterization of cloud processes in climate models.