Sublimation is a direct solid-to-gas phase transition that occurs when the vapour pressure of ice exceeds the partial vapour pressure of the surrounding air, even at temperatures below 0 °C. This process requires a significant amount of energy—2,830 kJ/kg, the sum of the latent heat of fusion and vaporisation—which the ice absorbs from its environment, contributing to local cooling. In nature, sublimation is responsible for the slow disappearance of snow on dry, cold days with sunshine: snow banks can reduce their volume without any visible melting or liquid water. At high altitudes, sublimation can remove up to 30–40% of accumulated snow under conditions of low humidity, strong wind, and clear skies. Tropical glaciers in the Andes lose mass primarily through sublimation, not melting. The reverse process—deposition or reverse sublimation—is equally important in meteorology: water vapour passes directly to ice, forming crystals that produce frost, cirrus clouds, and other ice crystal phenomena. Sublimation and deposition are key processes in the Bergeron mechanism for precipitation formation in mixed-phase clouds where ice crystals and supercooled droplets coexist.