What kind of water droplets lead to clear icing?

Clear icing occurs primarily due to the presence of large water droplets in the atmosphere. These droplets are typically found in supercooled cloud conditions where the temperature is below freezing, yet the water remains liquid due to the extreme pressure or the droplet size. When an aircraft encounters these large droplets, they impact the surface and spread out, forming a smooth, clear layer of ice.

In contrast, small or rapid droplets tend to freeze upon contact with cooler surfaces but do not accumulate in a way that forms clear ice. An assortment of droplet sizes could lead to mixed conditions, often producing rime ice rather than the smooth, transparent layer associated with clear icing. Lastly, while highly condensed water vapor can result in certain weather phenomena, it does not lead to icing directly as it would need to first condense into liquid droplets to contribute to icing. Therefore, the involvement of large water droplets is crucial in leading to clear icing on aircraft surfaces.