Articles | Volume 16, issue 12
Atmos. Chem. Phys., 16, 7889–7898, 2016
https://doi.org/10.5194/acp-16-7889-2016

Special issue: BACCHUS – Impact of Biogenic versus Anthropogenic emissions...

Special issue: Integrated Land Ecosystem-Atmosphere Processes Study (iLEAPS)...

Atmos. Chem. Phys., 16, 7889–7898, 2016
https://doi.org/10.5194/acp-16-7889-2016

Research article 29 Jun 2016

Research article | 29 Jun 2016

A DNS study of aerosol and small-scale cloud turbulence interaction

Natalia Babkovskaia1, Ullar Rannik1, Vaughan Phillips2, Holger Siebert3, Birgit Wehner3, and Michael Boy1 Natalia Babkovskaia et al.
  • 1University of Helsinki, Department of Physics, Helsinki, Finland
  • 2Lund University, Department of Physical Geography and Ecosystems Science, Lund, Sweden
  • 3Leibniz Institute for Tropospheric Research, Leipzig, Germany

Abstract. The purpose of this study is to investigate the interaction between small-scale turbulence and aerosol and cloud microphysical properties using direct numerical simulations (DNS). We consider the domain located at the height of about 2000 m from the sea level, experiencing transient high supersaturation due to atmospheric fluctuations of temperature and humidity. To study the effect of total number of particles (Ntot) on air temperature, activation and supersaturation, we vary Ntot. To investigate the effect of aerosol dynamics on small-scale turbulence and vertical air motion, we vary the intensity of turbulent fluctuations and the buoyant force. We find that even a small number of aerosol particles (55.5 cm−3), and therefore a small droplet number concentration, strongly affects the air temperature due to release of latent heat. The system comes to an equilibrium faster and the relative number of activated particles appears to be smaller for larger Ntot. We conclude that aerosol particles strongly affect the air motion. In a case of updraught coursed by buoyant force, the presence of aerosol particles results in acceleration of air motion in vertical direction and increase of turbulent fluctuations.

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Short summary
Turbulence, aerosol growth and microphysics of hydrometeors in clouds are intimately coupled. A new modelling approach was applied to quantify this linkage. We study the interaction in the cloud area under transient, high supersaturation conditions, using direct numerical simulations. Analysing the effect of aerosol dynamics on the turbulent kinetic energy and on vertical velocity, we conclude that the presence of aerosol has an effect on vertical motion and tends to reduce downward velocity.
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