Last chapter we focused on the composition, temperature, function and effect of the atmosphere. We talked about the electromagnetic energy that comes from the sun and is transferred into heat energy when it is absorbed by objects. This week we are going to look at the interaction between the atmosphere, the lithosphere, and the hydrosphere and how sensible and latent heat transfers drive nearly all motion in the atmosphere and hydrosphere.
Hot air is at a lower pressure (less dense) than cold air (think about a hot air balloon where you must heat the air inside the balloon to make it rise). The earth is not heated equally, partially because of day and night, partially because of differing amounts of isolation received over the earth (recall seasons from the first lecture), and partially because land and water heat up differently. Therefore, air heated over warmer parts of the earth forms low pressure zones, and air cooled over colder parts of the earth forms high pressure zones. These zones of differing pressure lead to circulation of the atmosphere and ocean (hydrosphere).
K. Allison Lenkeit-Meezan (Foothill College)