What are Air Masses: They large volumes of air that have generally the same temperature and pressure.
How they work: One is heated by an electrical current, the other is not. As air flows across the heated wire, it cools down.
Example of an Air Mass: The air masses in and around North America include the continental arctic, maritime polar, maritime tropical, continental tropical, and continental polar air masses. Air is not the same everywhere.
Fact: Unstable air masses have different temperatures and pressures.
How they are formed: An air mass forms whenever the atmosphere remains in contact with a large, relatively uniform land or sea surface for a time sufficiently long to acquire the temperature and moisture properties of that surface.
*** The Earth's major air masses originate in polar or subtropical latitudes.