Droplets condensation in turbulent warm clouds

Microdroplets growth by condensation/evaporation is a question of paramount im- portance to understand warm clouds formation. We consider the problem of droplet growth by condensation in a turbulent flow of nearly saturated vapour both from a theoretical and numerical point of view. Water droplets are inertial particles, subject to gravity, transported by a turbulent flow, and whose size depends on the saturated vapour turbulent fluctuations present in the flow. Feeedback of the droplets conden- sation/evaporation on the vapour field is also taken into account. By means of high resolution 3D direct numerical simulations of a warm cloud, we show how the pres- ence of an underlying turbulent velocity field induces a correlation between droplet trajectories and supersaturation. This leads both to the enhancement of the droplet growth rate and to a fast spreading of the droplet size distribution. We conclude that the enlargement of droplet size spectrum crucially depends on the turbulent fluctua- tions that droplets experience along their lagrangian motion.