sublimation nucleus

In meteorology, a sublimation nucleus is a type of atmospheric dust particle that facilitates the conversion of water vapor directly into ice crystals within clouds, a process known as heterogeneous ice nucleation. This is crucial because, without these nuclei, ice crystals would only form spontaneously at very low temperatures (below -39°C or -38°F).12

Sublimation nuclei are essential for precipitation formation, particularly in supercooled clouds where liquid water exists below freezing temperatures. When ice crystals form on these nuclei, they can grow by collecting more water vapor through sublimation or by colliding with supercooled water droplets, eventually becoming large enough to fall as precipitation like snow. The specific temperature at which ice crystals form on these nuclei depends on their physical and chemical properties.1