The formation of first raindrops in deep convective clouds is investigated. A combination of observational data analysis and 2D and 3D simulations of deep convective clouds suggests that the first raindrops form at the top of undiluted or slightly diluted cores. It is shown that droplet size distributions in these regions are wider and contain more large droplets than in diluted volumes.

- A. Khain,1 Thara V. Prabha,2 Nir Benmoshe,1 G. Pandithurai,2 and M. Ovchinnikov3