Q: Is there energy in snow?

A: Snow is a form of solid water, and water is the only substance that occurs naturally in all three phases — solid, liquid and invisible gas — in the Earth’s atmosphere. Of course, that means that an accumulation of snow began as the equivalent amount of water in the invisible vapor (gas) phase before it was transformed into solid water.

Melting ice into liquid water requires energy. Not surprisingly, energy is also required to transform liquid water into water vapor, the familiar process of evaporation. The particular amounts of energy needed to accomplish these changes of phase are known as latent heats — the latent heat of melting for the first one and the latent heat of evaporation for the second.

Winter weather

A woman walks with skis in the snow in Sioux City, Iowa, as a winter storm blows through the area. (AP Photo/Nati Harnik)

When a cloud of invisible water vapor condenses into a puddle of liquid water, the latent heat of condensation (equal to the latent heat of evaporation) is released to the environment. Also, when that puddle freezes into ice, the latent heat of fusion (equal to the latent heat of melting) is similarly released, incoherently, to the environment.

If we know the depth of liquid-equivalent precipitation involved in delivering, for example, 35 inches of snow over a period of time, and the latent heats of condensation and fusion, we can calculate how much energy has been released to the atmosphere in the production of that much snow.

Without providing the details of the calculation, we can report that the amount of energy involved could power a medium-sized city's metro area for about 7.7 years. Clearly, there are huge amounts of energy involved.

Photos: Icy weather greets start of 2020

"Weather Guys" Steve Ackerman and Jonathan Martin are professors in the University of Wisconsin-Madison department of atmospheric and oceanic sciences.

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