Air Masses and Fronts

Air masses form when a body of air comes to rest over an area large enough for it to take on the temperature and humidity of the land or water below it. Certain locations on the Earth's surface possess the topographical characteristics that favor the development of air masses. The two most important of these characteristics are topographic regularity and atmospheric stability. Deserts, plains, and oceans typically cover very wide areas with relatively few topographical irregularities. In such regions, large masses of air can accumulate without being broken apart by mountains, land/water interfaces, and other features that would break up the air mass.

The absence of consistent wind movements also favors the development of an air mass. In regions where cyclonic or anticyclonic storms are common, air masses obviously cannot develop easily.