|BACKYARD METEOROLOGY: LATENT HEAT
METEOROLOGIST JEFF HABY
Latent heat is energy that is transferred when a substance goes through a phase change. For water, 6 phase changes can occur. 3 go in
one direction while the other three go in the opposite direction. The pairs of phase changes are melting and freezing, evaporation
and condensation, and sublimation and deposition. These phase change occur while the water is at a constant temperature but the energy
transfer results in a warming or cooling of the surrounding environment. The cooling processes are melting, evaporation and sublimation
while the warming processes are freezing, condensation and deposition.
Many of these processes can be witnessed in the backyard. Examples of each are below:
Freezing: When the temperature drops of 32 F, liquid water will begin freezing. It will often start as ice crystals and lines of ice
crystals that fan out and gradually freeze all the water.
Melting: The thawing of snow, dripping of melting icicles, melting of frost and snow melting as it hits the
ground are examples.
Evaporation: Evaporation can be seen indirectly as rain, dew or other water on the ground that dries up. Virga is precipitation
that evaporates before reaching the ground. This can be seen as streaks of rain in the sky that do not reach ground level.
Condensation: Condensation can be witnessed as clouds develop. The moisture in the air becomes visible as it
is turned into cloud droplets.
Deposition: Deposition is the conversion from vapor to ice. This can be seen when frost develops at
temperatures below freezing.
Sublimation: Sublimation is the conversion from ice to vapor. This can be seen when frost or any other ice goes from ice to vapor
without going through the melting process first.