Drizzle formation in stratocumulus clouds: effects of turbulent mixing
The mechanism of drizzle formation in shallow stratocumulus clouds and the effect of turbulent mixing on this process are investigated. A Lagrangian–Eularian model of the cloud-topped boundary layer is used to simulate the cloud measured during flight RF07 of the DYCOMS-II field experiment. The m...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/1849/2016/acp-16-1849-2016.pdf |
| Summary: | The mechanism of drizzle formation in shallow stratocumulus clouds and the
effect of turbulent mixing on this process are investigated. A
Lagrangian–Eularian model of the cloud-topped boundary layer is used to
simulate the cloud measured during flight RF07 of the DYCOMS-II field experiment. The model contains ~ 2000 air parcels that are advected in a
turbulence-like velocity field. In the model all microphysical processes are
described for each Lagrangian air volume, and turbulent mixing between the
parcels is also taken into account. It was found that the first large drops
form in air volumes that are closest to adiabatic and characterized by high
humidity, extended residence near cloud top, and maximum values of liquid
water content, allowing the formation of drops as a result of efficient
collisions. The first large drops form near cloud top and initiate drizzle
formation in the cloud. Drizzle is developed only when turbulent mixing of
parcels is included in the model. Without mixing, the cloud structure is
extremely inhomogeneous and the few large drops that do form in the cloud
evaporate during their sedimentation. It was found that turbulent mixing can
delay the process of drizzle initiation but is essential for the further
development of drizzle in the cloud. |
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| ISSN: | 1680-7316 1680-7324 |