Inhomogeneous Mixing in Stratocumulus: Effects on Microphysics and Entrainment
Abstract
The mixing of cloudy and free-tropospheric air is essential to understand the microphysical structure of stratocumulus. Since the relevant scales involved in this process are typically smaller than the grid spacing of frequently applied large-eddy simulations (LES), their correct representation is difficult and, usually, error-prone. Recently, we developed a new approach which allows the explicit representation of subgrid-scale mixing in LES with Lagrangian cloud microphysics, based on the so-called linear eddy model, an accurate one-dimensional, representation of turbulent mixing in high Reynolds number flows.
Using this new approach, we are able to show that the inhomogeneous mixing represented by the linear eddy model enhances the diffusional growth of droplets at the stratocumulus top significantly, which might initiate rain and, therefore, trigger the breakup of closed stratocumulus decks. Furthermore, the new approach enables a much more detailed representation of holes of free-tropospheric air within the stratocumulus deck. The mixing of these holes into the cloud layer is significantly delayed by the new approach. As a result, entrainment rates are reduced. All in all, this study not only provides new process-level insights into the mixing of stratocumulus but also emphasizes the difficulties in simulating these clouds.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A31J2983H
- Keywords:
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- 0320 Cloud physics and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSESDE: 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCESDE: 4548 Ocean fog;
- OCEANOGRAPHY: PHYSICAL