Air Mass

An air mass is a large body of air that has relatively uniform characteristics of temperature and humidity. These properties are largely determined by the characteristics of the surface over which the air mass forms, typically over large land or water bodies. Air masses can cover hundreds or thousands of square miles and can cause significant weather changes as they move from one region to another. The classification of an air mass is based on its source region, which can be polar or tropical, and its moisture content, which can be maritime (wet) or continental (dry). Examples include Continental Polar (cP), Maritime Polar (mP), Continental Tropical (cT), and Maritime Tropical (mT).