Theory of metamorphism of dry snow

The growth of ice particles in dry seasonal snow is caused by vapor diffusion among particles due to temperature gradients imposed on the snow cover. The diffusion is calculated by using the potential field solutions for electrostatically charged particles. The stereography of snow is represented by using a log‐normal distribution function for a geometrical enhancement factor defined here. Reasonable crystal growth rates and supersaturations are found. The transition between the growth of highly faceted crystals and the growth of highly rounded crystals is determined by the critical supersaturation for the onset of dislocation aided growth. Thermal convection and the continuous movement of vapor around the particles due to the imposed temperature gradient are accommodated in the theory, although both have little effect relative to the interparticle diffusion. The growth of a layer of faceted crystals just below semi‐permeable crusts is explained by showing that crusts can cause the local supersaturation to exceed the critical value. Faceted crystals are shown to grow most rapidly in the lower, warmer portions of the snow cover because of temperature effects on growth rate.