Cloud turbulence is different from `normal' turbulence

We ask whether cloud turbulence differs from typical fluid turbulence, and answer in the affirmative: we show a clear enhancement in the small scales in clouds with a significant load of inertial droplets. The difference in time scales between vortex evacuation and condensation provides the mechanism. Inertial cloud droplets grow by condensation in a supersaturated environment, leading to the local release of latent heat. In turbulent clouds, these droplets are centrifuged out of vortical regions in extremely short time compared to the time for phase change, resulting in preferential temperature increase due to latent heat in regions outside vortices, i.e., regions of strain. Our simulations on show a significant co-location of colder temperatures and higher moisture content within vortical regions. This leads to density interfaces at the boundary of vortical regions, and the creation of small-scale turbulence by baroclinic torque. Enhancement in turbulent kinetic energy is evident over a range of inertial small scales, which makes this mechanism a relevant player in rapid raindrop growth, as well as in industrial settings of relevance.