Adiabaticity, Turbulence and Drizzle in Marine Stratocumulus Clouds
Abstract
Cloud adiabaticity is defined as the ratio of the measured Liquid Water Path (LWP) to its adiabatic value, and is affected by cloud-top entrainment and drizzle effects. Thus, in the absence of drizzle, the value of adiabaticity is a measure of the degree of entrainment. In return, subadiabatic conditions greatly influence the microphysical properties of clouds, and subsequently its radiative impacts. The U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) operates at Graciosa Island (Azores) since May 2009 as part of a 21 month long field campaign to study marine stratus clouds. The ARM/AMF instrumentation and location provides a unique opportunity to observe the cloud properties of marine stratocumulus clouds utilizing a variety of active and passive remote sensors. The adiabatic LWP of the observed marine stratus clouds is estimated using the frequent radiosonde measurements, with the cloud boundaries obtained from a ceilometer (base) and a cloud radar (top). A microwave radiometer provides the observed LWP, allowing the estimation of the cloud adiabaticity. The observations are classified into day-night and into drizzling and non-drizzling periods. Retrievals of the microphysical and dynamical properties of the same clouds are being developed in parallel, using mainly the Doppler moments observed by the cloud radar. Profiles of various quantities are composited for different strength of subadiabaticity, separating night and day conditions. Results will be presented and analysed in association with turbulence, cloud entrainment mixing and drizzle presence.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.A21D0138R
- Keywords:
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- 3310 ATMOSPHERIC PROCESSES / Clouds and cloud feedbacks;
- 3379 ATMOSPHERIC PROCESSES / Turbulence;
- 3399 ATMOSPHERIC PROCESSES / General or miscellaneous