Szymon P Malinowski et al 2008 New J. Phys. 10 075020 doi:10.1088/1367-2630/10/7/075020
Laboratory and modeling studies of cloud–clear air interfacial mixing: anisotropy of small-scale turbulence due to evaporative cooling
Focus on Cloud PhysicsSzymon P Malinowski1,5, Miroslaw Andrejczuk2, Wojciech W Grabowski3, Piotr Korczyk4, Tomasz A Kowalewski4 and Piotr K Smolarkiewicz3
Show affiliationsPart of Focus on Cloud Physics
Small-scale mixing between cloudy air and unsaturated clear air is investigated in numerical simulations and in a laboratory cloud chamber. Despite substantial differences in physical conditions and some differences in resolved scales of motion, results of both studies indicate that small-scale turbulence generated through cloud–clear air interfacial mixing is highly anisotropic. For velocity fluctuations, numerical simulations and cloud chamber observations demonstrate that the vertical velocity variance is up to a factor of two larger than the horizontal velocity variance. The Taylor microscales calculated separately for the horizontal and vertical directions also indicate anisotropy of turbulent eddies. This anisotropy is attributed to production of turbulent kinetic energy (TKE) by buoyancy forces due to evaporative cooling of cloud droplets at the cloud–clear air interface. Numerical simulations quantify the effects of buoyancy oscillations relative to the values expected from adiabatic and isobaric mixing, standardly assumed in cloud physics. The buoyancy oscillations result from microscale transport of liquid water due to the gravitational sedimentation of cloud droplets. In the particular modeling setup considered here, these oscillations contribute to about a fifth of the total TKE production.
- PACS
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92.60.hk Convection, turbulence, and diffusion
92.60.Jq Water in the atmosphere (humidity, clouds, evaporation, precipitation)
92.60.Gn Winds and their effects
- Subjects
- Dates
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Issue 7 (August 2008)
Received 6 February 2008
Published 31 July 2008
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Laboratory and modeling studies of cloud–clear air interfacial mixing: anisotropy of small-scale turbulence due to evaporative cooling
Szymon P Malinowski et al 2008 New J. Phys. 10 075020
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