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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2018-28
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
08 Feb 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Bridging the condensation-collision size gap: a direct numerical simulation of continuous droplet growth in turbulent cloud
Sisi Chen1, Man-Kong Yau1, Peter Bartello1, and Lulin Xue2 1McGill University, Montréal, Québec, Canada
2National Center for Atmospheric Research, Boulder, Colorado, USA
Abstract. In most previous DNS studies on droplet growth in turbulence, condensational growth and collisional growth were treated separately. Studies in recent decades have postulated that small-scale turbulence may accelerate droplet collisions when droplets are still small when condensational growth is effective. This implies that both processes should be considered simultaneously to unveil the full history of droplet growth and rain formation. This paper introduces the first DNS approach to explicitly study the continuous droplet growth by condensation and collisions inside an adiabatic ascending cloud parcel. Results from the condensation-only, collision-only, and condensation-collision experiments are compared to examine the contribution to the broadening of droplet size distribution by the individual process and by the combined processes. Simulations of different turbulent intensities are conducted to investigate the impact of turbulence on each process and on the condensation-induced collisions. The results show that the condensational process promotes the collisions in a turbulent environment and reduces the collisions when in still air, indicating a positive impact of condensation on turbulent collisions. This work suggests the necessity to include both processes simultaneously when studying droplet-turbulence interaction to quantify the turbulence effect on the evolution of cloud droplet spectrum and rain formation.

Citation: Chen, S., Yau, M.-K., Bartello, P., and Xue, L.: Bridging the condensation-collision size gap: a direct numerical simulation of continuous droplet growth in turbulent cloud, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2018-28, in review, 2018.
Sisi Chen et al.
Sisi Chen et al.
Sisi Chen et al.

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Short summary
This paper introduces a sophisticated approach to incorporate the droplet hydrodynamic collision and condensation processes into a single DNS modeling framework. Arguably, this model provides a sophisticated approach to study the warm-rain initiation problem that has puzzled the cloud physics community for decades.The results show the increased condensation-mediated collisions when turbulence intensifies, indicating a positive impact of turbulence on droplet condensation-collisional growth.
This paper introduces a sophisticated approach to incorporate the droplet hydrodynamic collision...
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