Sublimation from Snow and Ice

The process of ice changing directly into vapor without any intermediate liquid stage is often described by sublimation. The opposite of sublimation is “deposition,” where water vapor changes directly into ice. The sublimation of ice or snow is driven by an imbalance between the saturation vapor pressure (or vapor density) at a given temperature, and the vapor pressure in the immediate vicinity of an ice surface. Sublimation process in snow controls the grain shape and size. Snow sublimation rate can be defined as the amount of mass lost per unit time and depends on particle surface area to mass ratio, vapor pressure gradients, and rate of air exchange around the snow crystal surface. Typically, these rates are higher when large vapor pressure gradients exist and rapid air exchange occurs.

It is not easy to actually see sublimation occurring, especially for ice. Sublimation occurs more readily when certain weather conditions are present, that is, on a dry and windy day with low...