Ice Crystal Process
¥Since SVP for a water droplet is higher than for ice crystal, vapor next to droplet will diffuse towards ice
¥Ice crystals grow at the expense of water drops, which freeze on contact
¥As the ice crystals grow, they begin to fall
Ahrens, Fig. 5.19
Effect maximized around -15oC
High vapor levels around droplets and lower concentrations over ice will tend to homogenize by random molecular motionsÉDIFFUSION.
Thus water vapor molecules over liquid will move towards ice crystals.
Vapor pressure over ice becomes larger than SVP over ice, smaller than SVP over liquid droplet.
Droplets will shrink as liquid evaporates to replace evacuated vapor molecules.
Supercooled water droplets will be attracted to ice crystal, where they freeze/adhere on contact.