Mixing in Shallow Cumulus Clouds Studied by Lagrangian Particle Tracking

Mixing between shallow cumulus clouds and their environment is studied using large-eddy simulations. The origin of in-cloud air is studied by two distinct methods: 1) by analyzing conserved variable mixing diagrams (Paluch diagrams) and 2) by tracing back cloud-air parcels represented by massless La...

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Bibliographic Details
Published in:Journal of the atmospheric sciences 2008-08, Vol.65 (8), p.2581-2597
Main Authors: HEUS, Thijs, VAN DIJK, Gertjan, JONKER, Harm J. J, VAN DEN AKKER, Harry E. A
Format: Article
Language:English
Subjects:
Buoyancy
Clouds
Earth, ocean, space
Exact sciences and technology
External geophysics
Meteorology
Physics of the high neutral atmosphere
Variables
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Summary:Mixing between shallow cumulus clouds and their environment is studied using large-eddy simulations. The origin of in-cloud air is studied by two distinct methods: 1) by analyzing conserved variable mixing diagrams (Paluch diagrams) and 2) by tracing back cloud-air parcels represented by massless Lagrangian particles that follow the flow. The obtained Paluch diagrams are found to be similar to many results in the literature, but the source of entrained air found by particle tracking deviates from the source inferred from the Paluch analysis. Whereas the classical Paluch analysis seems to provide some evidence for cloud-top mixing, particle tracking shows that virtually all mixing occurs laterally. Particle trajectories averaged over the entire cloud ensemble also clearly indicate the absence of significant cloud-top mixing in shallow cumulus clouds.
ISSN:0022-4928
1520-0469
DOI:10.1175/2008jas2572.1