Partner: S.P. Malinowski


Recent publications
1.Korczyk P.M., Kowalewski T.A., Malinowski Sz.P., Turbulent mixing of clouds with the environment: Small scale two phase evaporating flow investigated in a laboratory by particle image velocimetry, PHYSICA D-NONLINEAR PHENOMENA, ISSN: 0167-2789, DOI: 10.1016/j.physd.2011.11.003, Vol.241, pp.288-296, 2012
Abstract:

In this report, experiments mimicking some aspects of cloud-clear-air mixing in a laboratory chamber are discussed. A saturated plume containing small droplets of water (a surrogate of an atmospheric cloud) is mixed with unsaturated environmental air in order to study effect of evaporative cooling at the interfaces between cloudy and clear air filaments on small-scale turbulence. Two components of the turbulent velocity at a small scale are determined using particle imaging velocimetry of the cloud droplets. Enhanced velocity fluctuations between the Kolmogorov (η ≈ 0.8 mm) and Taylor (λ ≈ 8 mm) microscales are observed.
The characteristic feature of these microscales is anisotropy with a preferred vertical direction. A straightforward dependence of the observed effects on the relative humidity of the environment indicates the importance of buoyancy production by evaporative cooling. This conclusion is in agreement with previous numerical experiments described in the literature and suggests that, under certain conditions, effects similar to the above may influence the smallest scales of turbulence in natural clouds.

Keywords:

Small-scale turbulence, Atmospheric turbulence, Evaporative cooling, Cloud-clear-air mixing

Affiliations:
Korczyk P.M.-IPPT PAN
Kowalewski T.A.-IPPT PAN
Malinowski Sz.P.-other affiliation
2.Malinowski Sz., Andrejczuk M., Grabowski W., Korczyk P., Smolarkiewicz P., Kowalewski T.A., Laboratory and modeling studies of cloud-clear air interfacial mixing: anisotropy of small-scale turbulence due to evaporative cooling, NEW JOURNAL OF PHYSICS, ISSN: 1367-2630, DOI: 10.1088/1367-2630/10/7/075020, Vol.10, pp.75020-15, 2008
Abstract:

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.

Keywords:

laboratory cloud formation, TKE of cloud air, microscale cloud turbulence

Affiliations:
Malinowski Sz.-other affiliation
Andrejczuk M.-other affiliation
Grabowski W.-other affiliation
Korczyk P.-IPPT PAN
Smolarkiewicz P.-other affiliation
Kowalewski T.A.-IPPT PAN
3.Korczyk P., Malinowski S.P., Kowalewski T.A., Mixing of cloud and clear air in centimeter scales observed in laboratory by means of Particle Image Velocimetry, ATMOSPHERIC RESEARCH, ISSN: 0169-8095, DOI: 10.1016/j.atmosres.2005.09.009, Vol.82, pp.173-182, 2006
Abstract:

Cloudy air, containing small water droplets, undergoes mixing with the unsaturated environment inside the cloud chamber in the process resembling smallest scales of entrainment and mixing in real clouds. Particle Image Velocimetry (PIV) applied to images from the chamber interior is used to investigate dynamics of the process in scales from 1.2 mm to few centimeters. A special algorithm, allowing for investigation of droplets motion, is developed, tested and adapted to the experimental data. Two velocity components retrieved in the vertical cross-section through the chamber interior indicate anisotropy of small-scale turbulent motions, with the preferred vertical direction. This result confirms earlier numerical studies, indicating that evaporation of cloud droplets at the cloud – clear air interface may substantially influence the small-scale turbulence in clouds.

Keywords:

Atmospheric turbulence, Turbulence in clouds, Small-scale turbulence, Laboratory investigations of atmospheric turbulence, Particle Image Velocimetry

Affiliations:
Korczyk P.-IPPT PAN
Malinowski S.P.-other affiliation
Kowalewski T.A.-IPPT PAN

Conference papers
1.Malinowski S.P., Górska A., Kowalewski T.A., Korczyk P., Błoński S., Kumala W., Small-scale mixing at cloud top observed in a laboratory cloud chamber - preliminary results, 13th AMS Conference on Cloud Physics, 2010-06-28/07-02, Portland (US), Vol.P1.22, pp.1-4, 2010
Keywords:

small-scale turbulence, cloud, cloud droplets, evaporation

Affiliations:
Malinowski S.P.-other affiliation
Górska A.-other affiliation
Kowalewski T.A.-IPPT PAN
Korczyk P.-IPPT PAN
Błoński S.-IPPT PAN
Kumala W.-University of Warsaw (PL)