Air mass formation and its characteristics are determined by the latitudes of land and ocean. The latitudes near the equator tends to have a warm and humid-like maritime tropical air mass. In North America, this air mass forms over the Gulf of Mexico from the warm currents of the Gulf Stream. In summer it moves up north and brings rain and thunderstorms on its course. While moving toward the north, it loses much of it humidity and warmth along the way.
As the name suggests, maritime polar air mass forms in polar region, or rather in the higher latitudes over the oceans. In comparison to tropical air masses, polar air mass has low moisture content and is cooler. The weather in its course depends on the geography of the region. If moving against highlands, polar air mass can bring in heavy precipitation in the form of snow or rain.
Continental polar air mass forms over the polar continental shelf. As the formation is over land in cold climate, the air mass carries little moisture and is cold in nature. The movement of the air mass is slow toward the south, as the temperature variations are minimal on its course, making it highly stable.
Continental tropical air mass forms over the tropical continental shelf, mostly over arid landscapes during summer. Due to this, the air mass has high temperature and low humidity. In North America the air mass forms over Mexico and the Southern U.S. states. The air mass creates a clear atmosphere due to absence of humidity.
