HKDSE Geography/M7/Heat Transfer

After sunlight enters the atmosphere, heat transfer processes will occur.

Radiation

Radiation's role in the earth's radiation budget was discussed in the last page.

When radiation hits an object, two processes may occur: reflection and absorption. The amount absorbed depends on the albedo of the object. For example, a dark-coloured rock has low albedo, so most heat is absorbed and little heat is reflected. Ice has high albedo, so most heat is reflected and little is absorbed.

Radiation transfers sensible heat.

Convection and Conduction

They also transfer sensible heat.

Conduction means heat is transferred from a hotter object to a colder object.

Convection occurs in fluids. Hot gas or liquid rises. As it rises, it cools downs and sinks again. Thus heat is transported upwards.

Evaporation

Evaporation transfers latent heat. Latent heat is absorbed when water evaporates. As it rises up, the latent heat is transferred upwards and released when the water condenses.

Advection

Advection is the horizontal movement of air. It transfers heat horizontally.