Planetary Energy Balance

Latent Heat

Energy, or latent heat, is transported around the atmosphere as water evaporates and condenses.

	Energy is required to melt or evaporate a material. This is called latent heat of fusion (melting) or vaporization. When water is heated, it evaporates more rapidly than when it is cooled.
	A material releases energy when it condenses or becomes a solid. This is called latent heat of condensation or crystallization. Clouds are an example of condensation in the atmosphere.

During evaporation, heat is added to change the state of water, for example, without changing temperature. Thus, evaporation cools the surface from which water evaporates, and provides latent heat to the atmosphere. This thermal energy is liberated when water condenses into droplets that may form clouds or rain, thus releasing the heat to the atmosphere.