Air Masses

As air masses traverse Earth's surface, they adapt to the characteristics of the areas beneath them. For instance, a cold, dry arctic air mass moving over the ocean will become warm and moist, transforming into a maritime polar air mass.

An air mass is a vast body of air, often spanning thousands of miles, characterized by consistent temperature and moisture properties. The type of air mass is determined by its source region, where it originates.

Air masses possess one of four primary qualities: continental (dry, forming over land), maritime (moist, forming over water), tropical (warm, forming at lower latitudes), or polar (very cold, forming over polar ice caps).

Various major air masses influence weather in the United States. Maritime tropical air masses from oceans near the equator bring warm, moist conditions and rain. Maritime polar air masses cause fog on the west coast and cooler temperatures in the east during summer, but heavy snow in winter. Continental tropical air masses from Mexico bring hot, dry air to the Southwest, while continental polar masses from northern Canada result in very cold winter temperatures in the northern US.

In summary, air masses are enormous bodies of air with uniform temperature and humidity. They are classified as continental, maritime, tropical, or polar, and these qualities can merge (e.g., maritime polar or continental polar) as the air mass moves and interacts with different environments.