A process from which more ice particles are produced from existing ice crystals in clouds. Sometimes known as ice enhancement. The process is inferred from the observation that ice particle concentration often exceeds that of ice nuclei, sometimes by several orders of magnitude. Currently the following mechanisms are thought to be responsible for the ice multiplication phenomenon: 1) mechanical fracturing of ice crystals during evaporation; 2) shattering or partial fragmentation of large drops during freezing; and 3) ice splinter formation during the riming of ice particles (Hallett–Mossop process).