Air Mass: Definition and Characteristics

Definition of Air Mass: An air mass is a large body of air that has uniform temperature, humidity, and pressure. It extends horizontally over thousands of kilometers and vertically up to the troposphere. The characteristics of an air mass are determined by the region where it originates, known as the source region.

Chief Characteristics of an Air Mass:

1. Temperature and Humidity Uniformity: The most significant characteristic of an air mass is the uniformity in temperature and humidity. For example, a continental polar (cP) air mass originating from high latitudes over land is cold and dry, while a maritime tropical (mT) air mass from the tropics over oceans is warm and moist.
2. Source Region Influence: The properties of an air mass are heavily influenced by its source region. An air mass formed over the Sahara Desert will be hot and dry, while one formed over the Arctic Ocean will be cold and moist.
3. Movement and Modification: As an air mass moves away from its source region, it modifies the weather of the regions it passes over. For example, when a continental tropical (cT) air mass moves into North America, it brings hot, dry conditions.
4. Boundary Interactions: The interaction of different air masses leads to the formation of weather fronts, which are critical in determining weather patterns. The 2019 Polar Vortex over North America, caused by the interaction of polar and tropical air masses, led to extreme cold conditions.

These characteristics make air masses fundamental in understanding and predicting global weather patterns.