Nucleation
Nucleation is a crystallization process. Water needs a solid point to freeze into ice, so pure water drops do not freeze. Once they touch the surface, the drops start freezing immediately. Freezing rain happens when frozen raindrops pass through a warm layer of air. This causes the drops to melt. Then the drops need to go again through freezing air, where their temperature falls below freezing, but they remain liquid.
- ↑ Pruppacher, H. R. et al. (1998) Microphysics of Clouds and Precipitation. Aerosol Science and Technology. [Online] 28 (4), 381–382.
- ↑ Will it rain, sleet or snow?, Weather.Gov, webpage, available (accessed 29.2.2021): https://www.weather.gov/source/zhu/ZHU_Training_Page/winter_stuff/winter_w x/winter_wx.html