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Air Masses - The Types of Air Masses


An air mass is a huge body of air with similar temperature and moisture properties. The types of air masses formed on Earth are determined by their source region.

Air Mass Characteristics

There are two main characteristics that define air masses - temperature and moisture content. Generally, the temperature and moisture content of air masses are abbreviated as two letters. The first letter is a lower case letter and is used to symbolize the overall moisture in the air.

The second letter used to symbolize a type of air mass is capitalized. The capital letter symbolizes the temperature or thermal properties of the air.

In the horizontal plane, temperature and humidity are essentially consistent in the layers of the air mass. Vertically, the general trend in an air mass is cooling, but the temperature and moisture will remain fairly consistent. The height of the air mass is greater with warm air masses. Cooler air masses are more shallow. In addition to the temperature and humidity in an air mass, the stability of the air can change over time.

Types of Air

When each of the 4 properties above are combined, there are 4 possible choices for the types of air masses.
  1. maritime tropical (mT)
  2. continental tropical (cT)
  3. maritime polar (mP)
  4. maritime tropical (cP)

Other Temperature Symbols for an Air Mass

Arctic air is often symbolized with an A. This type of air mass is characterized by extremely cold temperatures. Equatorial air is symbolized with an E. The air is hot because it originates in the equatorial regions.

It is important to remember that the classification system for an air mass is based on source region and not the destination of the air mass. As the air mass moves over Earth, the characteristics can slowly change and the air mass itself will eventually change.

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