Environmental & Climate Sciences Department Seminar

Ice nucleation is the crucial step for ice formation in atmospheric clouds, and therefore underlies climatologically-relevant precipitation and radiative properties. Progress has been made in understanding the roles of temperature, supersaturation and material properties, but an explanation for the efficient ice nucleation occurring when a particle contacts a supercooled water drop (contact nucleation) has been elusive for over half a century. This work considers what other factors can affect ice nucleation, e.g., can electric fields or the dynamics of multi-phase contact lines affect ice nucleation? I have investigated these questions using conceptually-simple laboratory experiments in which the nucleation and freezing of supercooled water droplets resting on a substrate are observed with high-speed video. Two serendipitous and surprising results suggest that ice nucleation is strongly related to the contact line motion and distortion and a possible mechanism is proposed. It might interpret long-mysterious observations related to contact nucleation and its efficiency relative to immersion nucleation.