Atmospheric pressure on the earth’s surface is not uniform. It varies from place to place. It is influenced by the temperature of the air at a given place.

● But on a global scale, there are a few permanent pressure belts. they are:

1. Equatorial Low-Pressure Belt

2. Subtropical high-Pressure Belt

3. Subpolar Low-Pressure Belt

4. Polar High-Pressure Belt

Equatorial Low-Pressure Belt

● The temperature is high throughout the year near the equator.

● As a result, the lower layers of the atmosphere get heated. Air expands and rises continuously in this region.

● As a result, a low-pressure belt is created in this region. It is known as the. Equatorial Low-Pressure Belt.

● Since winds are weak here the zone is also known as Doldrums

Subtropical high-Pressure Belt

● The rising air at the equator cools down after reaching the upper parts of the atmosphere.

● This air spreads out towards the poles and starts sinking near 30°N and 30°S latitudes and piles up there.

● Thus, high-pressure belts are produced in these regions. They are known as the Subtropical High-Pressure Belt or horse latitudes.

● The subsiding air is relatively dry because its moisture has already been released near the equator.

● Consequently, the world’s tropical deserts are located in this belt.

● As soon as the subsiding air reaches – the earth’s surface, it splits into two branches.

● One start flowing towards the Pole and the other towards the equator.

Subpolar Low-Pressure Belt

● In both the hemispheres, the air moving from the two high-pressure belts i.e., polar and the subtropical high-pressure belts, meet each other near 60° latitude.

● Converging air starts rising and a low-pressure belt is created named sub-polar low-pressure belt.

● Sub-polar low-pressure belts are developed near 60°N and 60°S latitudes.