Diagram gives
terminal fall speeds for CCN, droplets and raindrops. NOTE logarithmic
ordinate. It also give the updraft speed required to keep the particle
suspended.
CCN are easy to
suspend via turbulent motions; just 0.1 microns per second updraft is
needed.
Small cloud
droplets need 1.0 cm/s, easily achievable by winter storms.
Large raindrops
(5mm diameter) require a fast updraft 1.0 m/s.