Air Masses - Definition, Types, Formation

Air masses can be defined as a volume of air distinctly defined by parameters such as parameters like temperature and humidity. Often confused with clouds, air masses have defined boundaries, which can span hundreds or thousands of kilometres horizontally and as high as the top of the troposphere.

Air masses constitute a significant concept in meteorological studies, with their categorization and formation being some of the important topics. We have shared information about the types, and forms of air mass here.

Air Mass 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. Here are some more details about air masses -

• They can be found as high as about 10-18 km above the Earth's surface.
• They can cover hundreds of thousands of square kilometres.
• Air masses adapt to the condition of the surface below them.
• When they move away from a region, the vegetation and water bodies that lie under that specific region can change their characteristics.

Types of Air Masses

Air masses are classified by meteorologists according to the regions of their origination. They are classified into 4 major regions and we have shared the details of their classification here. The types of air masses based on regional classification are 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 water and those that form over land. These variations include Maritime air masses, which form above water bodies and are saturated with moisture, and Continental air mass, which originate over land and are arid.

As a result, they get classified according to their latitudinal orientation as well. We have shared the details of the types of air masses based on their latitudinal orientation as follows -

• Maritime Tropical (mT)
• Continental Tropical (cT)
• Maritime Polar (mP)
• Continental Polar (cP)
• Continental Arctic (cA)

Air Mass Formation

Air masses form over regions where the temperature and humidity levels are at the right levels. They remain stationary over an aerial region and low wind speeds around these air volumes can prevent them from moving. While they are stationary, the air masses acquire either the temperature or humidity of that region.

Gradually, with the increasing speed of the wind, the air masses move to different locations while still carrying the original aerial source’s temperature or humidity. Sometimes, when they clash with other air masses, they can cause storms in that region.

Condition in which Air Mass form

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 for the air mass to form.
• The air should sustain long-term contact with a consistent surface area.
• For the formation of air masses, 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 that are perfect for air mass formation can be observed in a few places around the world when the air sinks gradually with time over a uniform surface, such as the following -

• 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.

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.

FAQs on Air Masses

Q1. What are air masses?

Air masses are simple volume of air that consists of the characteristics of the region they belong to. Air masses have distinct humidity and temperature and have defined boundaries, which can span hundreds or thousands of kilometres horizontally and as high as the top of the troposphere.

Q2. What are the types of air masses?

The types of air masses can be classified based on their regional characteristics. Here are the details about the types of air masses -

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

Q3. What is in an air mass?

Air masses consist of nothing but air with specific humidity or temperature. An air mass gets its characteristics (temperature or humidity) straight from the region in which it originates. Moreover, the more time an air mass spends over a region, the more characteristics of that region it will acquire.

Q4. What are the properties of an air mass?

Air masses have distinct properties such as having the specific temperature or humidity as the region it was formed in. Its characteristics such as humidity levels and temperature stay the same, no matter what altitude it is in.