Crystallization in melts; exploration of atmospheric ice formation and snowfall

Spontaneous crystal nucleation in melts is considered employing a method which uses equilibration between the cohesive and the destructive energies of the nucleated crystals (EBDE). This method has been originally developed for explaining solution crystal nucleation; now, it is purposely redefined. Using it, the one-component system ice/H2O is considered as an example of spontaneous melt crystallization in nature. The number of the H2O molecules that constitute the completely stable ice crystal nucleus (which is predestined to grow steadily) on the actual undercooling is calculated. The result shows that this number decreases abruptly in the temperature range from 0 degrees C till -4 to-5 degrees C. This finding can explain the nucleation of ice in clouds and snowfall readiness at temperatures in the said temperature range: the smaller the crystal nucleus (i.e., the smaller the interphase fluctuation that is needed for its formation), the easier its appearance. Growing further the nucleated ice crystals break some of the particles on which they arise; this increases the number of such particles and may lead to snowfall intensification.