Air Masses - Definition, Types, Formation

By : Neha Dhyani

Updated : Mar 10, 2022, 9:11

Air masses constitute a significant concept in meteorological studies. The boundaries of such a mass are defined, and it can span hundreds or thousands of kilometres horizontally and as high as the top of the troposphere, about 10-18 km above the Earth's surface.

Several types of air mass are formed and classified based on distinct parameters like temperature and humidity.

Air Masses Definition

An air mass is described as an enormous mass of air with low horizontal temperature and moisture variance. The physical attributes of air masses, such as temperature, pressure, and humidity, exhibit a reasonably equitable distribution of vertical gradients.

Air Masses Formation

Air masses arise in specific surfaces and atmospheric conditions that are found only in a few parts of the world. The following conditions lead to the formation of air masses:

  • Physiographic homogeneity needs to be maintained, i.e. the surface should be either oceanic or a continental plane.
  • Atmospheric conditions must be steady with no significant movement in the air.
  • The air should sustain long-term contact with a consistent surface area.
  • The air should be allowed to settle on a particular surface for two to three days to counteract the characteristics of the surface.

Such environmental characteristics can be observed in a few places around the world when the air sinks gradually with time over a uniform surface, such as

  • Polar and subpolar regions because of the prevalence of polar high-pressure belts and simultaneous air sinking.
  • Subtropical high-pressure zones are caused by air sinking from the upper to the lower troposphere.

Types of Air Mass

Air masses are classified by meteorologists according to the regions of their origination.

The classification is as follows:

  • Arctic- Extremely cold air masses form in the Arctic region.
  • Tropical- These originate at lower altitudes and heat up to a reasonable temperature.
  • Polar- These are chilly air masses that originate at high latitudes.
  • Equatorial- These tend to appear over the equatorial region and are warmer.

Apart from this categorisation, meteorologists also divide air masses into two groupings: those that form over the water and those that form over land. These are the variations:

  • Maritime- These form above water bodies and are saturated with moisture.
  • Continental- These originate over land and are arid.

As a result, they get classified according to their latitudinal orientation. Their symbol denotation is as follows-

  1. Maritime tropical (mT)
  2. Continental tropical (cT)
  3. Maritime polar (mP)
  4. Continental polar (cP)
  5. Continental arctic (cA)

Effect of Air Masses on Global Climate

Air masses have a significant effect on their regions of action.

  • Subtropical Marine Air Masses, for example, have fully constituted the climate of Western Europe.
  • The confluence of two opposing air masses, the continental polar and maritime tropical air masses, is required for the formation of temperate cyclones.
  • The Indian monsoon, which is crucial to Indian agriculture, is an example of the tropical marine air mass.

All types of air mass combined stretch out over a large area, covering up to 1600 km or more. They significantly impact the climatic conditions of the region in which they are active and bring exceptional climatic attributes from their source region along with them.

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FAQs on Air Masses

Q.1. What is a source region?

According to the air masses definition, the source region is where an air mass derives its temperature and humidity parameters.

Q.2. What type of air mass is present in the Indian region?

The maritime tropical air mass that is humid and warm forms over the Indian region.

Q.3. What are superior air masses?

These types of air masses arise when the atmosphere motions downward, causing dry air to form.

Q.4. What are the origins of the world's major air masses?

Polar or subtropical latitudes are the origins of the Earth's major air masses.