Contact nucleus

From Glossary of Meteorology

contact nucleus

A type of ice nucleating aerosol particle characterized by its ability to initiate the ice phase in a supercooled water drop when it contacts the drop surface.

Nucleation may occur at a different temperature (usually higher) than would occur for a totally immersed particle. The contact can occur through a variety of processes, including diffusion (modified by gradients of temperature and water vapor) or collection by differential fall speed.