Specific Heat vs. Latent Heat Defined: energy processes that drive our weather

Weather Glossary

Specific heat and latent heat are important processes that affect how the matter in our everyday weather behave. The two concepts are similar in that they both have to do with energy, but are slightly different in how they affect the objects around them. Here’s a breakdown on how they work.  

Specific Heat

This process refers to the amount of energy it takes to warm 1 gram of substance, 1 degree Celsius. If something has a higher specific heat, it takes longer for that substance to change its temperature because it requires more energy to do so. This is based on the material of an object since different materials take different amounts of energy to heat up or cool down.

How is this relevant to weather?

Notice in the image above just how much more energy it takes water to heat up than concrete or land does. This energy is measured in Joules per kilogram Kelvin (J/kg*K), and it roughly takes water 5 times more energy than water to heat up one degree Celsius.

The differences in the specific heat of water versus land dictate one of our biggest weather makers here in Western New York: lake effect snow!

It takes water much more energy to heat up, which means it reacts slower to temperature changes in the air from season to season. After a long summer of heating up, when colder air moves in for the winter the lake has a much slower response to it than the land does. In short, the land gets colder than the water faster, which means any cold air moving over the still warm lake waters will create instability (rising motion) for lake effect snow to form.

This process also affects our overall temperatures we experience throughout the entire year from season to season. Since the earth is covered in 75% of water, our oceans play a big role in mediating seasonal temperatures. For example, the warmest time of the year doesn’t fall when the earth is receiving its most direct rays from the sun. Our oceans create a bigger lag time in our warmest to coldest temperatures of the year, which is why it takes a month or so for our planet to react.

Latent Heat

This process refers to the energy given off by a substance due to phase changes. Energy is required to change matter from liquid to solid, or liquid to gas. For example, think about how liquid water evaporates into a gas. It takes a certain amount of energy for that water to change into that gas, and since energy can’t be created or destroyed, it has to go somewhere. This energy is released as heat and can affect certain processes we see in weather.

How is this relevant to weather?

Think about the process of freezing rain. The process is the result of liquid rain water falling into a surface that’s below freezing, and cooling to the point that the liquid changes into a solid: ice! This is what coats the ground and what makes freezing rain so slick and dangerous on roads. Energy always moves from warm objects to cold objects, so the energy used to turn the water into ice is transferred and released as heat energy. This is also why freezing rain is a self-destructing process, because this heat will end up warming the cold layer at the surface needed for freezing rain to freeze in the first place!

Latent heat is also released during any type of storm as warm air rises, cools, and condenses into a liquid (change of phase). This added heat energy can help continue to fuel the storm as it increases instability and rising motion that helps the storm gain more strength.

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