Where'd You Go, Snow?

1-31-14 SHORT HILLS: It continues to be cold, perhaps a little warmer today, with occasional snow—a flurry today, a dusting a few days ago. This snow cover is slowly disappearing even though the temperature is below the freezing point. The snow seems to evaporate, but the correct term for the phase change of solid ice or snow directly to gaseous water vapor, skipping the liquid water phase is Sublimation.

Another example of sublimation that we have all seen is the change of dry ice, frozen carbon dioxide, to that thick, white gas often used in theaters or movies for its eerie, spooky, foggy effect.

Water vapor is colorless and invisible, but sometimes we can see snow melting in a warmish rain forming a fog, a visible fog of water particles in the air. That’s melting of snow and evaporation of the melt water and condensation of the water vapor to liquid water droplets. We may see that tomorrow.

In three weeks the sun will be half way back to the Equator from its southern-most excursion, and four weeks after that, the sun will be on the Equator at the Vernal Equinox.