Air Masses - Definition, Formation, Classification & Reading on Weather Maps

An air mass is a sizable mass of air with relatively consistent temperature and humidity. Its characteristics are derived from the region where it forms, and the longer it remains over that area, the more it adopts the underlying surface properties. Air masses are broadly divided based on moisture content. Continental air masses, denoted by "c," originate over continents and are consequently dry. Maritime air masses, indicated by "m," originate over oceans and are thus moist. The movement of air masses is typically influenced by upper atmosphere air flow. Changes in the intensity and position of the jet stream impact the motion and strength of air masses. When air masses come together, they create boundaries known as "fronts."

Gaining a comprehensive understanding of this subject is crucial for individuals preparing for competitive exams. With this in mind, we have prepared an in-depth guide on air masses, particularly for students studying for the UPSC and IAS exam . 

Air Masses covers a significant part of the Geography subject in the General Studies Paper-1 syllabus and General Studies Paper 1 of the UPSC Prelims syllabus.

Defining Air Mass

An air mass is a large volume of air with uniform temperature and moisture. These masses can stretch thousands of miles horizontally over the Earth's surface, and vertically from ground level to the stratosphere (10 miles) into the atmosphere.

Formation of Air Masses

Air masses are formed over source regions that provide them with uniform temperature and humidity. Low wind speeds prevent these large volumes from moving, allowing them to acquire the conditions of their source region, be it temperature or humidity. Once wind speeds increase, these air masses move to other areas, retaining their original characteristics.

When these air masses encounter different air masses in other regions, they can cause storms.

Classification of Air Masses

Air masses are classified by meteorologists based on their formation location. Here's a look at the classification.

Generally, there are 4 types of air masses:

• Arctic: Formed in the Arctic region, these air masses are extremely cold.
• Tropical: Formed in low-lying latitudes, these air masses are moderately warm.
• Polar: Formed in high-latitude regions, these air masses are cold.
• Equatorial: These air masses form over the Equator and are warm.

In addition to this classification, air masses can also be categorized based on whether they form over water or land. These categories include:

• Maritime: Maritime air masses form over bodies of water and are typically moist.
• Continental: Continental air masses form over land and are typically dry.

For example, an air mass formed over the interior of Asia would be a continental polar air mass, characterized by its cold and dry nature. However, an air mass formed over the Indian Ocean would be a tropical air mass, characterized by its warm and humid nature.

UPSC CSE aspirants can also refer to the following related links:

Interpreting Air Masses on Weather Maps

Air masses are classified using a notation that includes a lowercase letter, a capital letter, and another lowercase letter.

• The first lowercase letter indicates whether the air mass is dry or humid, continental or maritime.

• The second capital letter describes the temperature of the air mass.

• The third lowercase letter represents the relationship between the ground and the air mass.

Classification of Air Masses in the USA

The Classification of Air Masses in the USA are listed below.

Continental Polar

Continental Polar air masses form over large land masses like Northern Canada. These are typically stable and lack condensation forms as they originate over land. When heated or moistened from the ground, they can produce snow or rain.

Maritime Polar

Maritime Polar air masses form over large bodies of water and gather significant moisture. They move towards land in middle and high latitudes and can produce heavy rain when forced up mountain slopes or caught in cyclonic activity.

Continental Tropical

Continental Tropical air masses originate in lower latitudes over deserts or interiors of land masses. They typically develop in summer, are subject to intense heat, and are usually dry due to the lack of moisture on the ground.

Maritime Tropical

Maritime Tropical air masses form over large tropical oceans and contain a lot of moisture. They are responsible for producing rain. If they move towards the poles, they are cooled by the ground surface and produce fog. Over continental areas, they are strongly heated and can cause convectional rain or thunderstorms.

Conclusion

In conclusion, understanding air masses is crucial for UPSC aspirants as it provides a deep insight into the weather conditions in India. We hope this comprehensive guide will aid UPSC exam aspirants in their preparation. Aspirants can also refer to our extensive study materials and seek expert guidance for comprehensive preparation.

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